Transcriber's Notes:

1. Tildes are used to denote text in small caps. 

AMERICAN SOCIETY OF CIVIL ENGINEERSINSTITUTED 1852

TRANSACTIONS

Paper No. 1191

WATER PURIFICATION PLANT, WASHINGTON, D. C. RESULTS OF OPERATION. [1]

~By E. D. Hardy, M. Am. Soc. C. E. ~

~With Discussion by Messrs. Allen Hazen, George A. Johnson, Morris Knowles, George C. Whipple, F. F. Longley, and E. D. Hardy. ~

The Washington filtration plant has already been fully described. [2]At the time that paper was written (November, 1906), the filtrationplant had been in operation for only about 1 year. It has now beenin continuous operation for 5 years, and many data on the cost, efficiency, and methods of operation, have accumulated in thevarious records and books which have been kept. It is thought that abrief review of the results, and a summary of the records in tabularform, will be of interest to the members of the Society, and it isalso hoped that the discussion of this paper will bring out thecomparative results of operation of other filter plants. As a matterof convenience, the following general description of the plant isgiven. 

_Description of the Filtration Plant. _--The Washington filtrationplant was completed and put in operation in October, 1905. Itconsists of a pumping station for raising the water from theMcMillan Park Reservoir to the filter beds; 29 filters of the slowsand type, having an effective area of 1 acre each; thefiltered-water reservoir, having a capacity of about 15, 000, 000gal. ; and the necessary piping and valves for carrying water, controlling rates of filtration, etc. 

 [Footnote 1: Presented at the meeting of February 15th, 1911. ]

 [Footnote 2: "Works for the Purification of the Water Supply of Washington, D. C. , " by Allen Hazen and E. D. Hardy, Members, Am. Soc. C. E. , _Transactions_, Am. Soc. C. E. , Vol. LVII, p. 307. ]

In the pumping station, there are three centrifugal pumps, which aredirectly connected to tandem compound engines; two sand-washerpumps; three small electric generating sets for furnishing electriclight; and four 200-h. P. , water-tube boilers. 

Each of the centrifugal pumps has a nominal capacity of 40, 000, 000gal. Per day when pumping against a head of 21 ft. , and eachsand-washer pump has a capacity of 2, 500, 000 gal. When pumpingagainst a head of 250 ft. The electric light engines and generatorssupply the current for lighting the pumping station, the office andlaboratory and other buildings, and also the courts and interior ofthe filter beds, and for operating a machine-shop. 

The filters and filtered-water reservoir are built entirely ofconcrete masonry. The floors are of inverted groined arches on whichrest the piers for supporting the groined arch vaulting. All thisconcrete work is similar to that in the Albany, Philadelphia, andPittsburg filters. 

The filters contain, on an average, 40 in. Of filter sand and 12 in. Of filter gravel. The gravel is graded from coarse to fine; thelower and coarser part acts as part of the under-drain system, andthe upper and finest layer supports the filter sand. The raw waterfrom the pumps is carried to the filters through riveted steelrising mains which have 20-in. Cast-iron branches for supplying theindividual filters. The filtered water is collected in theunder-drainage system of the several filter beds, and is carriedthrough 20-in. , cast-iron pipes to the regulator-houses. Theseregulator-houses contain the necessary valves, registeringapparatus, etc. , for regulating the rate of filtration, showing theloss of head, shutting down a filter, filling a filter with filteredwater from the under-drains, and for turning the water back into theraw-water reservoir, or wasting it into the sewer. From theregulator-houses, the filtered water flows directly to thefiltered-water reservoir. Generally, five filters are controlledfrom one house, but there are two cases where the regulator-housesare smaller, and only two filters are controlled from each. 

The dirty sand removed from the filters is carried by a portableejector through one or more lengths of 3-in. Hose and a fixed lineof 4-in. Pipe, to the sand washers. From the sand washers, thewashed sand is carried to the reinforced concrete storage bins, eachof which has a capacity of 250 cu. Yd. , and is at such an elevationthat carts may be driven under it and loaded through a gate. 

Until April, 1909, the sand was replaced in the filters by cartswhich were filled through the gates in the sand bins. It was thenhauled to the top of the filter beds and dumped through the manholeson the chutes, which could be revolved in any direction. Thesechutes were used to prevent the sand from being unduly compacted inthe vicinity of the manholes, and to facilitate spreading it in thefilters. Since April, 1909, all the sand has been replaced by thehydraulic method. An ejector is placed under the gate in the sandbin, and the sand is carried in a reverse direction from the binthrough the 4-in. Piping and one or more lengths of hose to thefilter bed. This process has lowered the cost of re-sandingconsiderably, and present indications are that it will proveentirely satisfactory in every way. 

The average effective size and uniformity coefficient of the filtersare shown in Table 1. 

 ~Table 1--Filter Sand as Originally Placed. ~ =======+===============+============+========+========== Filter | Average | Average |Depth of| Average No. |effective size, | uniformity |sand, in|turbidity. |in millimeters. |coefficient. | inches. | -------+---------------+------------+--------+---------- 1 | 0. 32 | 1. 88 | 35. 3 | 2, 600 2 | 0. 30 | 1. 78 | 37. 7 | 2, 200 3 | 0. 32 | 1. 77 | 40. 2 | 3, 000 4 | 0. 29 | 1. 80 | 42. 5 | 1, 800 5 | 0. 34 | 1. 74 | 44. 9 | 2, 700 6 | 0. 31 | 1. 78 | 37. 7 | 2, 300 7 | 0. 29 | 1. 72 | 40. 1 | 2, 300 8 | 0. 32 | 1. 75 | 40. 2 | 2, 800 9 | 0. 32 | 1. 78 | 42. 5 | 2, 900 10 | 0. 30 | 1. 69 | 39. 5 | 2, 500 11 | 0. 34 | 1. 93 | 37. 1 | 2, 600 12 | 0. 29 | 1. 66 | 34. 7 | 2, 100 13 | 0. 32 | 1. 83 | 33. 6 | 3, 500 14 | 0. 29 | 1. 66 | 33. 6 | 2, 600 15 | 0. 33 | 1. 75 | 39. 0 | 2, 400 16 | 0. 33 | 1. 78 | 42. 3 | 3, 000 17 | 0. 33 | 1. 86 | 45. 5 | 3, 300 18 | 0. 34 | 1. 80 | 48. 7 | 3, 100 19 | 0. 34 | 1. 80 | 52. 0 | . . . . . 20 | 0. 34 | 1. 87 | 39. 0 | 2, 700 21 | 0. 32 | 1. 82 | 42. 3 | 2, 400 22 | 0. 33 | 1. 74 | 45. 5 | 2, 200 23 | 0. 33 | 1. 81 | 48. 7 | 2, 300 24 | 0. 35 | 1. 80 | 52. 0 | 2, 600 25 | 0. 29 | 1. 64 | 39. 5 | 2, 400 26 | 0. 31 | 1. 71 | 37. 1 | 2, 100 27 | 0. 31 | 1. 71 | 34. 7 | 1, 900 28 | 0. 33 | 1. 93 | 33. 6 | 2, 300 29 | 0. 34 | 1. 93 | 33. 6 | 3, 000 -------+---------------+------------+--------+---------- Maximum| 0. 36 | 1. 93 | 52. 0 | 3, 300 Minimum| 0. 29 | 1. 64 | 33. 6 | 1, 800 Average| 0. 32 | 1. 77 | 40. 4 | 2, 600 =======+===============+============+========+==========

_Description of Washington Aqueduct. _--The water supply ofWashington is taken from the Potomac River, at Great Falls, about 16miles above the city. At that place, a dam has been built across theriver, which holds the water at an elevation of 150. 5 ft. Above meantide at Washington. From Great Falls the water flows by gravity fora distance of 16 miles through a 9-ft. Conduit, three reservoirs, and a tunnel. From McMillan Park Reservoir, the last of the three, the water is lifted by centrifugal pumps about 21 ft. To thefilters. After passing through the filters, it flows to thefiltered-water reservoir, and later to the city mains. In itspassage from Great Falls to the filters, the water flows throughthree settling reservoirs, which have already been referred to. These reservoirs are known as the Dalecarlia, the Georgetown, andthe McMillan Park Reservoirs, and have available capacities of141, 000, 000, 140, 000, 000, and 180, 000, 000 gal. , respectively. 

_Turbidity. _--The Potomac River water is rather turbid, theturbidity being caused by very fine particles of clay. The river issubject to sudden fluctuations, it being no uncommon thing to have aturbidity of 100 one day, and 1, 000 the next. The high turbidityusually disappears about as rapidly as it comes, and is seldomhigher than 500 for more than 5 days at a time. It is frequently thecase, however, that a succession of waves of high turbidity willappear so close together that the effect of one has not disappearedbefore that of another is felt. 

The clarification of the water supply begins at the dam at GreatFalls. Here it is a clarification by exclusion, for when anexcessive quantity of mud appears in the river water, the gates areclosed, and the muddy water is allowed to flow over the dam and formmud-bars in the Lower Potomac, while the city is supplied from thewater stored in the three settling reservoirs. Until a comparativelyrecent date, the excessively muddy water was never excluded, havingbeen taken, like other decrees of Providence, as it came. 

During the summer of 1907, the practice of shutting out water with aturbidity of 500 or more was established for the warm months. Thispractice was discontinued during the cold months, as it was fearedthat a very high consumption of water might occur at the time of lowwater in the reservoirs, and so cause a partial famine. During thewinter of 1909-10, however, the gates were closed, as was thepractice throughout the summer months. 

When the reservoirs are well filled, and the consumption of wateris less than 70, 000, 000 gal. Per day, it is safe to close the gatesat Great Falls for a period of about 4 days. 

[Illustration: ~Figure 1--Plan and Profile of Washington Aqueduct. ~]

While a considerable reduction in turbidity is effected in each ofthe reservoirs, the bulk of the mud is deposited at the upper end ofDalecarlia Reservoir. This reservoir had become so completelyfilled, that, in 1905, it was necessary to dredge a channel throughthe deposit, in order to allow the water to pass it. During thesummers of 1907 and 1908, a 10-in. Hydraulic dredge removed morethan 100, 000 cu. Yd. Of mud which had been deposited in thisreservoir. The mud deposited in Georgetown and McMillan ParkReservoirs is so fine that the accumulation of many years is notvery noticeable in its effect on the depth of water. 

The particles of clay which remain in the water after its passagethrough the three reservoirs, are so exceedingly small that they donot settle out in any reasonable length of time. Even the filtrationof the water through one or more slow sand filters occasionallyfails to remove the last trace of turbidity. This is especially truein the colder months, and not a winter has passed when the watersupply has not been noticeably turbid at some time. 

A general idea of the quantity of mud contained in the river water, the quantity excluded by closing the gates at Great Falls, and thatremoved by sedimentation and filtration, may be gained from Table 2, which is, of course, only a rough approximation. 

Table 2 also shows that the gates were closed 10. 50% of the time, thereby excluding 40. 06% of the total suspended matter whichotherwise would have entered the system. 

The turbidities, bacterial counts, and chemical analyses of numeroussamples of water are shown in Tables 3, 4, 5, and 6. The amount ofwork done in the pumping station, average consumption of water, death rate from typhoid fever, and filter runs are shown in Tables7, 8, 9, and 10. 

_Raking. _--At the time the filters were first put in service, thesand bins had not been completed, and, consequently, the work ofcleaning the filters was carried on in the old-fashioned way ofscraping by hand and wheeling out the sand in barrows. This methodof cleaning was used from October, 1905, to April, 1906; then theregular sand-handling system was commenced. 

At times, during the first two summers the filters were inoperation, considerable difficulty was experienced in keeping themcleaned as fast as was necessary to provide an ample supply offiltered water. For a short period in each summer it was foundnecessary to organize night shifts, and keep the work of cleaningin progress for from 16 to 24 hours per day. 

[Illustration: ~Figure 2--General Plan of Washington Filtration PlantShowing Finished Surfaces. ~]

 ~Table 2--Tons of Suspended Matter Entering System, Etc. ~

 Columns: A - Amount that would have entered the system if the gates had been left continuously open. B - Number of hours gates were closed. C - Amount shut out. D - Amount deposited in Dalecarlia Reservoir. E - Amount deposited in Georgetown Reservoir. F - Amount deposited in McMillan Park Reservoir. G - Amount entering filtration plant. =========+=======+=======+=======+=======+=====+=====+=====+======== Month. | A | B | C | D | E | F | G | Total. ---------+-------+-------+-------+-------+-----+-----+-----+-------- 1909. ---------+-------+-------+-------+-------+-----+-----+-----+-------- July | 318 | 32. 0 | 3 | 0 | 125 | 74 | 116 | 318 August | 146 | 47. 0 | 1 | 0 | 78 | 38 | 29 | 146 September| 97 | 57. 0 | 7 | 21 | 13 | 38 | 18 | 97 October | 61 | 90. 5 | 8 | 7 | 9 | 25 | 12 | 61 November | 50 | 60. 0 | 4 | 13 | 5 | 17 | 11 | 50 December | 370 | 99. 0 | 126 | 108 | 33 | 59 | 44 | 370 ---------+-------+-------+-------+-------+-----+-----+-----+-------- 1910. ---------+-------+-------+-------+-------+-----+-----+-----+-------- January | 2, 410 | 136. 0 | 1, 109 | 1, 020 | 67 | 117 | 97 | 2, 410 February | 839 | 117. 5 | 481 | 126 | 56 | 75 | 101 | 839 March | 208 | 7. 5 | 13 | 43 | 15 | 13 | 124 | 208 April | 321 | 65. 0 | 17 | 195 | 43 | 43 | 23 | 321 May | 197 | 84. 5 | 58 | 54 | 22 | 24 | 39 | 197 June | 1, 505 | 124. 0 | 786 | 535 | 49 | 88 | 47 | 1, 505 ---------+-------+-------+-------+-------+-----+-----+-----+-------- Total | 6, 522 | 920. 0 | 2, 613 | 2, 122 | 515 | 611 | 661 | 6, 522 =========+=======+=======+=======+=======+=====+=====+=====+========

In order to relieve the situation at such times, the expedient ofraking was tried. This was first attempted with the filters filledwith water; the effluent was first shut off in order to prevent adownward flow of water, and the filter was then raked or harrowedfrom boats. This method was not satisfactory, however, as the workwas neither as uniform nor as thorough as necessary. Later, thefilters were drained to the necessary depth, and the surface of thesand was thoroughly stirred with iron garden rakes. The filters werethen filled with filtered water through the under-drains and put inservice. 

This latter method proved so satisfactory that it has been resortedto at all times when the work was at all pressing. When the runswere of short duration, and the depth to which the mud hadpenetrated the filter sand was slight, a raking seemed to be nearlyas effective in restoring the filter capacity as a scraping; itcould be done in 8 hours by 3 laborers, and there seemed to be noill effects from lowered efficiency. 

 ~Table 3--Turbidities. ~ Average by Months. (United States Geological Survey Standard. ) ==========+============+============================================= | | ~Reservoirs:~ | +-----------+-----------+------------+-------- Month. |Great Falls. | Dalecarlia| Georgetown| McMillan |Filtered | | Outlet. | Outlet. | Park. | water. | | | | Outlet. | +------+-----+-----+-----+-----+-----+------+-----+----+--- | Max. | Ave. | Max. | Ave. | Max. | Ave. | Max. |Ave. |Max. |Ave ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- 1905. ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- October | 100 | 36 | 40 | 21 | 32 | 18 | 20 | 11 | 4 | 1 November | 35 | 19 | 34 | 19 | 22 | 14 | 14 | 11 | 3 | 1 December |1, 500 | 199 | 250 | 84 | 150 | 74 | 95 | 39 | 14 | 6 ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- 1906. ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- January | 700 | 94 | 180 | 60 | 120 | 60 | 85 | 52 | 20 | 12 February | 120 | 45 | 85 | 41 | 55 | 29 | 35 | 22 | 5 | 3 March |1, 750 | 272 | 350 | 181 | 120 | 56 | 90 | 46 | 8 | 6 April |1, 270 | 167 | 180 | 72 | 95 | 58 | 75 | 46 | 12 | 7 May | 600 | 56 | 50 | 20 | 45 | 16 | 34 | 10 | 3 | 2 June |1, 700 | 303 | 500 | 125 | 450 | 94 | 180 | 41 | 13 | 2 July |1, 000 | 130 | 180 | 54 | 150 | 47 | 250 | 43 | 13 | 3 August |1, 530 | 375 | 250 | 112 | 95 | 66 | 65 | 45 | 5 | 2 September | 120 | 33 | 180 | 34 | 95 | 28 | 75 | 25 | 7 | 2 October |1, 025 | 127 | 110 | 37 | 60 | 24 | 55 | 21 | 1 | 1 November | 160 | 27 | 75 | 20 | 45 | 16 | 24 | 13 | 1 | 1 December | 600 | 69 | 110 | 31 | 80 | 28 | 80 | 26 | 8 | 2 ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- 1907. ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- January | 400 | 135 | 150 | 70 | 110 | 75 | 70 | 53 | 11 | 7 February | 55 | 26 | 26 | 15 | 36 | 16 | 40 | 17 | 5 | 2 March | 950 | 248 | 180 | 77 | 130 | 70 | 90 | 57 | 7 | 4 April | 200 | 47 | 80 | 33 | 60 | 30 | 45 | 24 | 4 | 2 May | 130 | 29 | 40 | 18 | 26 | 15 | 14 | 9 | 1 | 1 June | 400 | 104 | 160 | 48 | 75 | 32 | 40 | 18 | 1 | 1 July | 600 | 114 | 130 | 61 | 78 | 47 | 45 | 31 | 1 | 1 August | 800 | 73 | 130 | 35 | 85 | 26 | 30 | 14 | 1 | 0 September | 600 | 129 | [1] | [1] | 150 | 51 | 70 | 28 | 1 | 0 October | 75 | 32 | [1] | [1] | 65 | 28 | 75 | 26 | 4 | 0 November | 300 | 97 | [1] | [1] | 100 | 45 | 45 | 23 | 2 | 1 December | 680 | 135 | [1] | [1] | 180 | 61 | 100 | 46 | 10 | 4 ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- 1908. ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- January |2, 100 | 202 | 340 | 73 | 250 | 82 | 160 | 65 | 20 | 7 February |3, 000 | 302 | 300 | 52 | 150 | 52 | 75 | 32 | 7 | 4 March | 300 | 91 | 150 | 78 | 100 | 68 | 65 | 42 | 5 | 4 April | 75 | 23 | 65 | 41 | 37 | 27 | 26 | 20 | 3 | 2 May |2, 000 | 172 | 130 | 48 | 85 | 37 | 50 | 20 | 1 | 1 June | 400 | 40 | 70 | 29 | 40 | 24 | 30 | 18 | 1 | 1 July |1, 500 | 149 | . . . | 74 | 170 | 44 | 75 | 15 | 0 | 0 August | 900 | 129 | 200 | [1] | 150 | 56 | 85 | 39 | 2 | 1 September | 75 | 24 | [1] | [1] | 50 | 19 | 35 | 18 | 0 | 0 October | 95 | 20 | [1] | [1] | 55 | 18 | 28 | 15 | 0 | 0 November | 24 | 11 | [1] | [1] | 20 | 11 | 19 | 10 | 0 | 0 December | 20 | 9 | 17 | 11 | 14 | 9 | 10 | 7 | 0 | 0 ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- 1909. ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- January | 400 | 72 | 95 | 32 | 60 | 23 | 25 | 16 | 4 | 1 February | 650 | 194 | 120 | 64 | 90 | 51 | 55 | 35 | 4 | 3 March | 250 | 51 | [1] | [1] | 90 | 44 | 60 | 37 | 8 | 4 April | 750 | 98 | [1] | [1] | 130 | 42 | 76 | 31 | 2 | 1 May | 480 | 57 | [1] | [1] | 30 | 19 | 30 | 12 | 2 | 1 June | 650 | 141 | [1] | [1] | 120 | 51 | 80 | 30 | 1 | 0 July | 400 | 48 | [1] | [1] | 215 | 46 | 120 | 35 | 2 | 1 August | 180 | 23 | [1] | [1] | 50 | 17 | 18 | 9 | 0 | 0 September | 26 | 16 | 24 | 14 | [1] | [1] | 25 | 6 | 0 | 0 October | 14 | 10 | 15 | 10 | 11 | 9 | 8 | 4 | 0 | 0 November | 11 | 9 | 11 | 8 | 10 | 8 | 6 | 4 | 0 | 0 December | 600 | 63 | 110 | 31 | 80 | 28 | 50 | 15 | 3 | 0 ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- 1910. ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- January |3, 000 | 357 | 200 | 58 | 150 | 53 | 115 | 30 | 5 | 2 February |3, 000 | 143 | 150 | 55 | 120 | 50 | 100 | 36 | 7 | 4 March | 210 | 36 | 100 | 35 | 95 | 38 | 100 | 43 | 9 | 5 April | 350 | 55 | 100 | 25 | 55 | 18 | 25 | 8 | 1 | 0[2] May | 300 | 33 | 55 | 19 | 50 | 17 | 28 | 13 | 1 | 0[2] June |1, 500 | 246 | 180 | 42 | 110 | 37 | 50 | 16 | 1 | 0[2] ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- Fiscal years: ----------+------+-----+-----+-----+-----+-----+------+-----+----+--- 1905-06[2]|1, 750 | 133 | 500 | 70 | 450 | 47 | 180 | 31 | 20 | 5 1906-07 |1, 530 | 114 | 250 | 46 | 150 | 37 | 250 | 29 | 13 | 2 1907-08 |3, 000 | 117 | 340 | 53 | 250 | 45 | 160 | 31 | 20 | 2 1908-09 |1, 500 | 79 | 200 | 50 | 170 | 32 | 85 | 22 | 8 | 1 1909-10 |2, 100 | 86 | 200 | 30 | 215 | 29 | 120 | 18 | 9 | 1 ==========+======+=====+=====+=====+=====+=====+======+=====+====+=====

 [Footnote 1: Reservoirs out of service. ]

 [Footnote 2: October to June 30th. ]

 ~Table 4--Bacteria. ~ Averages by Months. =============+======================================================= | ~Reservoirs:~ +----------+----------+----------+-------------+-------- Month. | | | | | |Dalecarlia|Dalecarlia|Georgetown|McMillan Park|Filtered | Inlet. | Outlet. | Outlet. | Outlet. | water. -------------+----------+----------+----------+-------------+-------- 1905. -------------+----------+----------+----------+-------------+-------- October | . . . | . . . | . . . | 210 | 80 November | . . . | . . . | . . . | 150 | 27 December | . . . | 15, 500 | . . . | 3, 800 | 60 -------------+----------+----------+----------+-------------+-------- 1906. -------------+----------+----------+----------+-------------+-------- January | . . . | 2, 800 | . . . | 1, 500 | 39 February | 2, 900 | 4, 100 | 1, 800 | 550 | 16 March | 1, 800 | 1, 100 | 900 | 650 | 19 April | 3, 300 | 1, 700 | 700 | 400 | 22 May | 425 | 210 | 95 | 65 | 17 June | 7, 900 | 4, 600 | 325 | 220 | 17 July | 13, 500 | 600 | 475 | 160 | 26 August | 8, 700 | 1, 100 | 1, 200 | 190 | 14 September | 425 | 250 | 140 | 135 | 14 October | 2, 300 | 950 | 650 | 270 | 16 November | 1, 800 | 1, 100 | 1, 200 | 220 | 12 December | 6, 900 | 3, 800 | 3, 600 | 700 | 45 -------------+----------+----------+----------+-------------+-------- 1907. -------------+----------+----------+----------+-------------+-------- January | 4, 400 | 2, 400 | 2, 200 | 950 | 70 February | 1, 000 | 950 | 1, 000 | 700 | 45 March | 11, 500 | 8, 300 | 7, 200 | 3, 600 | 65 April | 3, 700 | 2, 100 | 1, 400 | 475 | 21 May | 750 | 350 | 325 | 130 | 26 June | 2, 300 | 1, 000 | 600 | 100 | 18 July | 2, 700 | 575 | 350 | 160 | 17 August | 3, 000 | 275 | 425 | 80 | 17 September | 6, 200 | [1] | 1, 900 | 230 | 32 October | 1, 400 | [1] | 950 | 275 | 27 November | 8, 900 | [1] | 6, 600 | 1, 500 | 27 December | 16, 000 | [1] | 9, 600 | 4, 300 | 190 -------------+----------+----------+----------+-------------+-------- 1908. -------------+----------+----------+----------+-------------+-------- January | 11, 000 | 8, 700 | 9, 400 | 3, 700 | 190 February | 11, 500 | 6, 000 | 5, 000 | 2, 800 | 75 March | 4, 600 | 4, 000 | 2, 900 | 1, 300 | 30 April | 700 | 450 | 250 | 120 | 13 May | 9, 500 | 1, 100 | 650 | 325 | 17 June | 750 | 120 | 110 | 95 | 12 July | 4, 900 | . . . | 400 | 150 | 8 August | 1, 600 | 325 | 300 | 100 | 12 September | 325 | [1] | 200 | 80 | 11 October | 375 | [1] | 325 | 140 | 8 November | 550 | [1] | 300 | 200 | 12 December | 800 | 750 | 375 | 170 | 23 -------------+----------+----------+----------+-------------+-------- 1909. -------------+----------+----------+----------+-------------+-------- January | 11, 000 | 2, 700 | 1, 600 | 700 | 31 February | 8, 000 | 3, 500 | 2, 400 | 1, 300 | 60 March | 3, 800 | [1] | 2, 600 | 1, 000 | 39 April | 2, 200 | [1] | 1, 400 | 550 | 12 May | 900 | [1] | 350 | 140 | 16 June | 3, 400 | [1] | 1, 200 | 170 | 21 July | 550 | [1] | 500 | 250 | 33 August | 400 | [1] | 325 | 55 | 18 September | 325 | 240 | [1] | 70 | 18 October | 350 | 275 | 250 | 130 | 20 November | 600 | 500 | 500 | 180 | 13 December | 21, 000 | 9, 100 | 5, 900 | 4, 500 | 250 -------------+----------+----------+----------+-------------+-------- 1910. -------------+----------+----------+----------+-------------+-------- January | 76, 000 | 78, 000 | 88, 000 | 52, 000 | 800 February | 45, 000 | 35, 500 | 31, 000 | 17, 500 | 350 March | 9, 900 | 7, 600 | 7, 400 | 4, 800 | 80 April | 7, 900 | 4, 100 | 3, 500 | 650 | 29 May | 1, 230 | 810 | 830 | 448 | 28 June | 3, 660 | 930 | 800 | 324 | 27 -------------+----------+----------+----------+-------------+-------- Fiscal years: -------------+----------+----------+----------+-------------+-------- 1905-06 | 3, 300[2]| 4, 300[3]| 750[4]| 850[2]| 33[2] 1906-07 | 4, 900 | 1, 900 | 1, 700 | 650 | 31 1907-08 | 6, 360 | 2, 700 | 2, 900 | 1, 300 | 55 1908-09 | 3, 400 | 2, 000 | 950 | 400 | 21 1909-10 | 14, 300 | 13, 900 | 10, 900 | 6, 890 | 143 =============+==========+==========+==========+=============+========

 [Footnote 1: Reservoirs out of service. ]

 [Footnote 2: October to June 30th. ]

 [Footnote 3: December to June 30th. ]

 [Footnote 4: February to June 30th. ]

 ~Table 5--Results of Tests for~ _Bacillus Coli_. Percentage Positive. =============+==============+==============+=============== | Great Falls, | Dalecarlia | |or Dalecarlia | Reservoir | Georgetown | Reservoir | Outlet. | Reservoir. Month. | Inlet. | | +----+----+----+----+----+----+----+----+----- | 10 | 1 |0. 1 | 10 | 1 |0. 1 | 10 | 1 |0. 1 |c. C. |c. C. |c. C. |c. C. |c. C. |c. C. |c. C. |c. C. |c. C. -------------+----+----+----+----+----+----+----+----+----- 1906. -------------+----+----+----+----+----+----+----+----+----- January[1] |55. 6|38. 9|22. 2|69. 2|23. 1| 7. 7|56. 0|40. 0| 8. 0 February |33. 3|26. 7| 6. 7|26. 1|17. 4| 8. 7|30. 4|13. 0| 4. 4 March |50. 0|12. 5| 0|45. 5|18. 2| 0|20. 8| 8. 3| 0 April |72. 2|33. 3|16. 7|95. 5|50. 0| 4. 6|59. 1|22. 7| 4. 6 May |20. 0| 8. 0| 4. 0|20. 0|12. 0| 0| 7. 8| 0| 0 June |57. 7|38. 5|19. 2|40. 0|32. 0| 8. 0|50. 0|34. 6| 0 July |65. 0|50. 0| 5. 0|60. 0|25. 0|10. 0|15. 0| 5. 0| 5. 0 August |84. 6|69. 2|61. 5|88. 5|65. 4|34. 6|80. 0|57. 7|23. 1 September |50. 0|10. 0| 0|30. 0|10. 0|10. 0|40. 0|10. 0| 0 October |60. 0|30. 0|10. 0|55. 5|33. 3| 0|80. 0|60. 0|20. 0 November |37. 5| 0| 0|25. 0|12. 5|12. 5|37. 5|25. 0| 0 December |55. 5|44. 5| 0|66. 7|44. 5|22. 2|66. 7|22. 2| 0 -------------+----+----+----+----+----+----+----+----+----- 1907. -------------+----+----+----+----+----+----+----+----+----- January |77. 8|33. 3|22. 2|66. 7|33. 3| 0|55. 5|55. 5|22. 2 February |37. 5|25. 0| 0|12. 5| 0| 0|37. 5|12. 5| 0 March |87. 5|50. 0| 0|75. 0|37. 5| 0|50. 0|25. 0| 0 April |44. 5|11. 1|11. 1|66. 7|22. 2|11. 1|77. 8|11. 1|11. 1 May |91. 3|65. 2|17. 4|88. 9|33. 3| 0|87. 5|50. 0|12. 5 June |80. 0|68. 0|24. 0|87. 5|62. 5| 0|66. 7|44. 5|11. 1 July |42. 3|30. 8|19. 2|25. 0|12. 5| 0|22. 2|22. 2| 0 August |48. 1|29. 6| 3. 7|33. 3|16. 7|16. 7|36. 4|18. 2| 0 September |62. 5|54. 1|25. 0| . . . | . . . | . . . |41. 7|33. 3|16. 7 October |51. 9|40. 8| 7. 4| . . . | . . . | . . . |53. 3|40. 0| 6. 7 November |80. 0|64. 0|24. 0| . . . | . . . | . . . |72. 7|54. 5| 0 December |56. 0|48. 0|16. 0| . . . | . . . | . . . |46. 2|38. 5| 7. 7 -------------+----+----+----+----+----+----+----+----+----- 1908. -------------+----+----+----+----+----+----+----+----+----- January |46. 2|30. 8|15. 4|50. 0|12. 5| 0|33. 3| 0| 0 February |12. 5| 0| 0|25. 0| 0| 0|12. 5| 0| 0 March |38. 5|19. 2| 7. 7|44. 4|11. 1| 0|11. 1| 0| 0 April |15. 4| 7. 7| 0| 0| 0| 0| 0| 0| 0 May |76. 0|52. 0|40. 0|87. 5|50. 0|12. 5|33. 3|22. 2| 0 June | 7. 7| 0| 0| 0| 0| 0|11. 1| 0| 0 July |26. 9|15. 4|11. 5|22. 2|22. 2| 0|11. 1| 0| 0 August |46. 2|26. 9| 3. 9|44. 4|33. 3| 0|62. 5|25. 0|12. 5 September |20. 0| 8. 0| 4. 0|42. 9|28. 6| 1. 4|22. 2|11. 1| 0 October |18. 4| 3. 7| 0| 0| 0| 0| 9. 1| 0| 0 November |13. 0| 0| 0|28. 6| 0| 0|11. 1| 0| 0 December |11. 5| 7. 7| 3. 8| 0| 0| 0|12. 5| 0| 0 -------------+----+----+----+----+----+----+----+----+----- 1909. -------------+----+----+----+----+----+----+----+----+----- January |12. 0| 8. 0| 0|30. 0|10. 0| 0| 0| 0| 0 February |52. 1|47. 8|47. 8|28. 6|14. 3| 0|37. 5| 0| 0 March |69. 4|34. 6| 3. 8|50. 0|25. 0| 0|44. 5|11. 1| 0 April |42. 3|15. 4| 3. 9|33. 3|22. 2|11. 1|44. 4|22. 2|11. 1 May |88. 4|26. 1| 4. 3|50. 0|12. 5| 0|33. 3| 0| 0 June |85. 0|60. 0|25. 0|60. 0|40. 0|10. 0|44. 4|33. 3|11. 1 July |34. 8| 8. 7| 4. 4| . . . | . . . | . . . |33. 3|11. 1| 0 August |50. 0|15. 4| 7. 7| . . . | . . . | . . . |40. 0|10. 0| 0 September |43. 5|21. 8| 8. 7|25. 0|25. 0|12. 5| 0| 0| 0 October |36. 4|13. 6| 0|18. 2| 0| 0| 0| 0| 0 November | 4. 5| 0| 0|10. 0| 0| 0| 0| 0| 0 December |38. 5|23. 1| 7. 7|36. 4|36. 4|18. 2|33. 3|22. 2|11. 1 -------------+----+----+----+----+----+----+----+----+----- 1910. -------------+----+----+----+----+----+----+----+----+----- January |72. 0|48. 0|24. 0|44. 5|33. 3|11. 1|75. 0|25. 0| 0 February |47. 8|43. 5|17. 4|63. 2|21. 1| 5. 3|40. 0|30. 0| 5. 0 March |33. 3|14. 8| 0|30. 8|11. 1| 3. 7|29. 6|22. 2| 7. 4 April |41. 7|33. 3|20. 8|40. 0|32. 0|16. 0|38. 5|23. 1|15. 4 May |47. 8|17. 4| 0|52. 0|20. 0| 0|36. 0|16. 0| 4. 0 June |95. 5|86. 4|31. 8|80. 8|46. 2|19. 2|64. 0|28. 0| 8. 0 -------------+----+----+----+----+----+----+----+----+---- Fiscal years: -------------+----+----+----+----+----+----+----+----+----- 1905-06 |35. 2|19. 4|9. 3 |0. 0 |3. 2 |5. 2 |6. 4 |4. 9 |1. 7 1906-07 |61. 5|43. 6|9. 2 |7. 7 |9. 2 |2. 3 |1. 1 |9. 8 |0. 7 1907-08 |44. 6|31. 3|3. 0 |2. 3 |2. 3 |3. 1 |4. 4 |2. 1 |4. 1 1908-09 |38. 9|20. 3|8. 4 |0. 0 |5. 0 | 0 |7. 4 |8. 5 |2. 8 1909-10 |45. 5|26. 9|0. 1 |5. 3 |4. 0 |8. 8 |7. 9 |9. 8 |6. 2 =============+====+====+====+====+====+====+====+====+=====

 =============+==============+=========+========== |McMillan Park |Filtered-|Tap water | Reservoir | water |from var- | (applied | reser- |ious parts Month. | water). | voir. |of city. +----+----+----+----+----+----+----- | 10 | 1 |0. 1 | 10 | 1 | 10 | 1 |c. C. |c. C. |c. C. |c. C. |c. C. |c. C. |c. C. -------------+----+----+----+----+----+----+----- 1906. -------------+----+----+----+----+----+----+----- January[1] |55. 6|22. 2| 0 | 7. 2| 0| . . . | . . . February | 8. 3| 4. 2| 0 | 0| 0| . . . | . . . March |18. 5| 7. 4|3. 7 | 0| 0| 0| 0 April |32. 0| 8. 0| 0 | 4. 0| 0| 0| 0 May | 0| 0| 0 | 0| 0| 0| 0 June |23. 1| 7. 7|3. 8 | 0| 0| 3. 1| 0 July | 9. 5| 0| 0 | 4. 8| 0| . . . | . . . August |63. 0|33. 3| 0 | 7. 4| 3. 7|11. 9| 5. 1 September |32. 0|12. 0| 0 | 8. 0| 0| 3. 1| 0 October |48. 1|22. 2|3. 7 | 3. 7| 0|13. 0| 3. 7 November |20. 0|12. 0| 0 | 8. 0| 0| 0| 0 December |20. 8| 8. 3|4. 2 |16. 7| 8. 3| 7. 5| 0 -------------+----+----+----+----+----+----+----- 1907. -------------+----+----+----+----+----+----+----- January |69. 3|34. 6|3. 8 |19. 2|11. 5|14. 0| 0 February |17. 4| 4. 4| 0 | 0| 0| 2. 9| 0 March |30. 8| 7. 7| 0 | 0| 0| 2. 1| 0 April |46. 1|19. 2|3. 8 | 3. 8| 0| 3. 2| 0 May |23. 1| 0| 0 | 0| 0| 1. 4| 0 June |40. 0| 8. 0| 0 | 0| 0| 0| 0 July | 3. 8| 0| 0 | 0| 0| 1. 4| 1. 4 August |14. 8| 3. 7| 0 | 0| 0| 0| 0 September |16. 0| 4. 0| 0 | 4. 0| 0| 1. 7| 0 October |38. 7|25. 8|9. 7 | 6. 5| 0|12. 5| 2. 8 November |58. 6|17. 3|3. 5 | 0| 0| 4. 9| 0 December |45. 2|29. 0| 0 |19. 3| 3. 2|12. 9| 4. 3 -------------+----+----+----+----+----+----+----- 1908. -------------+----+----+----+----+----+----+----- January |22. 6| 9. 7|3. 2 | 3. 2| 0| 1. 9| 1. 9 February | 0| 0| 0 | 0| 0| 0| 0 March | 9. 7| 0| 0 | 0| 0| 0| 0 April | 6. 7| 3. 3| 0 | 0| 0| 0| 0 May |45. 1|16. 2| 0 | 0| 0| 0| 0 June | 0| 0| 0 | 0| 0| 0| 0 July | 6. 4| 6. 4| 0 | 0| 0| 0| 0 August |12. 9| 3. 2| 0 | 0| 0| 1. 6| 0 September |16. 7|10. 0| 0 | 0| 0| 4. 3| 0 October | 9. 7| 6. 4|3. 2 | 0| 0| 0| 0 November | 6. 6| 0| 0 | 0| 0| 0| 0 December | 3. 2| 0| 0 | 0| 0| 0| 0 -------------+----+----+----+----+----+----+----- 1909. -------------+----+----+----+----+----+----+----- January | 3. 2| 3. 2| 0 | 3. 2| 0| 0| 0 February | 7. 1| 3. 6|3. 6 | 0| 0| 3. 4| 3. 4 March |32. 3|19. 4|3. 2 | 6. 5| 0| 2. 8| 1. 4 April |36. 6|10. 0| 0 | 0| 0| 0| 0 May |12. 9| 3. 2| 0 | 0| 0| 0| 0 June |53. 3|20. 0| 0 | 0| 0| 1. 4| 0 July |25. 8|12. 9| 0| 0| 0| 0| 0 August |22. 6| 6. 5| 3. 2| 0| 0| 0| 0 September |13. 3| 3. 3| 0| 0| 0| 0| 0 October | 3. 2| 0| 0| 0| 0| 0| 0 November | 0| 0| 0| 0| 0| 0| 0 December |29. 0|22. 6| 0| 9. 7| 6. 5| 7. 3| 1. 5 -------------+----+----+----+----+----+----+----- 1910. -------------+----+----+----+----+----+----+----- January |61. 3|35. 5|9. 7 | 5. 8| 3. 2|15. 9| 3. 2 February |32. 2| 7. 1| 0 | 3. 6| 0| 0| 0 March |12. 9| 3. 2| 0 | 0| 0| 0| 0 April |23. 3|13. 3| 0 | 0| 0| 0| 0 May |16. 1|12. 9| 0 | 0| 0| 0| 0 June |43. 3| 6. 7| 0 | 0| 0| 1. 4| 0 -------------+----+----+----+----+----+----+----- Fiscal years: -------------+----+----+----+----+----+----+----- 1905-06 |4. 3 |8. 3 |. 8 | . 3| 1. 8| 1. 3| 0 1906-07 |2. 5 |3. 0 |. 4 | . 5| 2. 1| 5. 4| 1. 0 1907-08 |2. 2 |9. 4 |. 4 | . 8| 0. 3| 3. 1| 0. 9 1908-09 |6. 7 |7. 1 |. 8 | . 8| 0| 1. 2| 0. 4 1909-10 |3. 6 |0. 4 |. 1 | . 3| 0. 8| 2. 2| 0. 4 =============+====+====+====+====+====+====+=====

 [Footnote 1: Presumptive tests. ]

 ~Table 6--Summary of Sanitary Chemicals Analyses of Weekly Samples, July 1st, 1909, to June 30th, 1910. ~ (Results in Parts per Million. )

 Columns: A - Turbidity[1] B - Free C - Albuminoid D - Total E - Nitrites F - Nitrates G - Hardness H - Alkalinity I - Chlorine

 (_A_) ~Maximum. ~ ====================+=====+=================+===========+=====+=====+==== | | Ammonia. | Nitrogen | | | | | | as: | | | Reservoirs. | A +-----+-----+-----+-----------+ G | H | I | | B | C | D | E | F | | | --------------------+-----+-----+-----+-----+------+----+-----+-----+---- Dalecarlia inlet |2, 100|0. 034|0. 264|0. 280|0. 0070|0. 45|120. 0|106. 0|5. 4 Dalecarlia outlet[2]| 200|0. 034|0. 180|0. 206|0. 0050|0. 70|115. 0|105. 8|5. 7 Georgetown outlet[3]| 215|0. 030|0. 182|0. 182|0. 0060|0. 60|115. 0|105. 0|4. 9 McMillan Park outlet| 120|0. 028|0. 126|0. 154|0. 0060|0. 65|118. 0|104. 4|4. 2 Filtered water | 9|0. 016|0. 078|0. 086|0. 0010|0. 70|119. 5|106. 3|4. 5 --------------------+-----+-----+-----+-----+------+----+-----+-----+---

 ~Table 6~--(_Continued. _) (_B_) ~Minimum. ~ ====================+=====+=================+===========+=====+=====+==== | | Ammonia. | Nitrogen | | | | | | as: | | | Reservoirs. | A +-----+-----+-----+-----------+ G | H | I | | B | C | D | E | F | | | --------------------+-----+-----+-----+-----+------+----+-----+-----+---- Dalecarlia inlet | 7|0. 000|0. 016|0. 016|0. 0000|0. 00| 52. 9| 39. 5| 1. 0 Dalecarlia outlet[2]| 7|0. 000|0. 040|0. 040|0. 0000|0. 00| 54. 3| 38. 2| 0. 9 Georgetown outlet[3]| 7|0. 000|0. 044|0. 044|0. 0000|0. 00| 51. 4| 40. 6| 0. 7 McMillan Park outlet| 2|0. 000|0. 010|0. 010|0. 0010|0. 00| 51. 4| 38. 5| 0. 2 Filtered water | 0|0. 000|0. 000|0. 000|0. 0000|0. 00| 52. 9| 40. 3| 0. 4 --------------------+-----+-----+-----+-----+------+----+-----+-----+----

 ~Table 6~--(_Continued. _) (_C_) ~Average. ~ ====================+=====+=================+===========+=====+=====+==== | | Ammonia. | Nitrogen | | | | | | as: | | | Reservoirs. | A +-----+-----+-----+-----------+ G | H | I | | B | C | D | E | F | | | --------------------+-----+-----+-----+-----+------+----+-----+-----+---- Dalecarlia inlet | 86 |0. 006|0. 167|0. 113|0. 0027|0. 19| 93. 2| 81. 4| 2. 9 Dalecarlia outlet[2]| 30 |0. 008|0. 106|0. 114|0. 0023|0. 18| 95. 5| 79. 5| 3. 4 Georgetown outlet[3]| 29 |0. 005|0. 101|0. 106|0. 0027|0. 18| 93. 4| 80. 9| 2. 9 McMillan Park outlet| 18 |0. 004|0. 077|0. 081|0. 0027|0. 17| 94. 0| 83. 0| 2. 7 Filtered water | 1 |0. 002|0. 027|0. 029|0. 0000|0. 19| 94. 9| 84. 0| 2. 8 ====================+=====+=====+=====+=====+======+====+=====+=====+====

 [Footnote 1: Summary of daily samples of water. ]

 [Footnote 2: Reservoir out of service from July 1st to September 13th, 1909. ]

 [Footnote 3: Reservoir out of service from September 10th to October 4th, 1909. ]

 No chemical determinations were made during February, March, April, and May, 1910, on account of the rearrangement of the laboratory and equipment. 

 ~Table 7--Daily Results at Pumping Station~. (_A_) =============+===================================+========+========== | ~Million gallons pumped:~ | | Pressure +-----------------+-----------------+ | at sand- | | | Lift | washer | To filters. | To sand washers. | to | pumps, Month. | | |filters. | per |-----+-----+-----+-----+-----+-----| | square | Max. | Min. |Ave. | Max. | Min. | Ave. | | inch. -------------+-----+-----+-----+-----+-----+-----+--------+---------- 1909. -------------+-----+-----+-----+-----+-----+-----+--------+---------- July |76. 16|57. 65|64. 05|1. 140|0. 298|0. 730| 24. 18 | 110. 0 August |69. 31|54. 44|61. 42|0. 629|0. 157|0. 441| 22. 18 | 110. 0 September |66. 02|52. 82|69. 32|0. 831|0. 207|0. 572| 22. 26 | 110. 0 October |78. 50|48. 12|59. 18|0. 761|0. 060|0. 467| 21. 84 | 110. 0 November |64. 92|49. 83|55. 25|0. 468|0. 141|0. 272| 20. 49 | 110. 0 December |67. 83|48. 32|56. 77|0. 307|0. 039|0. 174| 20. 54 | 110. 0 -------------+-----+-----+-----+-----+-----+-----+--------+---------- 1910. -------------+-----+-----+-----+-----+-----+-----+--------+---------- January |70. 04|51. 02|62. 49|0. 499|0. 008|0. 156| 22. 43 | 110. 0 February |70. 79|55. 19|60. 28|0. 284|0. 041|0. 173| 21. 44 | 112. 3 March |59. 11|51. 64|56. 04|0. 409|0. 063|0. 171| 19. 76 | 120. 0 April |66. 53|53. 79|58. 32|0. 715|0. 167|0. 474| 20. 78 | 120. 0 May |61. 93|54. 55|57. 76|0. 525|0. 059|0. 251| 20. 30 | 120. 0 June |70. 49|50. 42|58. 37|0. 281|0. 124|0. 207| 21. 19 | 117. 3 -------------+-----+-----+-----+-----+-----+-----+--------+---------- Fiscal years: -------------+-----+-----+-----+-----+-----+-----+--------+---------- 1909-10 |78. 50|48. 12|59. 19|1. 140|0. 008|0. 373| 21. 45 | 113. 3 -------------+-----+-----+-----+-----+-----+-----+--------+---------- 1905-06[1] |80. 59|57. 18|66. 07|2. 062|0. 089|0. 747| 21. 71 | 107. 4 1906-07 |80. 29|57. 44|66. 89|2. 120|0. 023|0. 580| 21. 60 | 120. 8 1907-08 |80. 38|54. 35|64. 91|0. 735|0. 017|0. 347| 22. 20 | 125. 0 1908-09 |78. 93|47. 83|61. 47|0. 875|0. 060|0. 453| 22. 52 | 122. 3 -------------+-----+-----+-----+-----+-----+-----+--------+----------

 =============+==============+=============== |~Coal consumed|~Station duty, | per day in |per 100 lb. Of Month. | tons. ~ |coal consumed. ~ |----+----+----+----+----+----- |Max. |Min. |Ave. |Max. |Min. |Ave. -------------+----+----+----+----+----+----- 1909. -------------+----+----+----+----+----+----- July |13. 4| 8. 4|10. 8|67. 8|52. 3|61. 4 August |12. 4| 8. 0|10. 1|64. 2|49. 5|56. 6 September |12. 7| 8. 7|10. 5|61. 0|48. 9|55. 1 October |13. 4| 8. 0|10. 3|59. 6|49. 1|53. 6 November |11. 3| 7. 9| 9. 2|55. 6|45. 7|51. 1 December |10. 3| 8. 5| 9. 5|61. 0|45. 4|50. 4 -------------+----+----+----+----+----+----- 1910. -------------+----+----+----+----+----+----- January |12. 7| 9. 1|10. 4|59. 6|49. 8|54. 9 February |12. 3| 8. 7|10. 2|57. 4|44. 8|51. 5 March |10. 5| 7. 8| 9. 2|53. 2|45. 2|49. 8 April |11. 1| 8. 1| 9. 7|58. 7|47. 2|53. 7 May |10. 1| 7. 4| 8. 8|60. 7|48. 1|54. 9 June |12. 3| 7. 4| 9. 1|60. 1|49. 9|54. 4 -------------+----+----+----+----+----+----- Fiscal years: -------------+----+----+----+----+----+----- 1909-10 |13. 4| 7. 4| 9. 8|67. 8|44. 8|54. 0 -------------+----+----+----+----+----+---- 1905-06[1] |14. 8| 6. 4| 8. 9|79. 6|48. 2|62. 8 1906-07 |15. 0| 7. 0|10. 0|71. 6|46. 5|58. 6 1907-08 |12. 0| 7. 2|9. 6 |70. 7|51. 3|60. 3 1908-09 |13. 2| 7. 0|10. 0|74. 0|45. 7|57. 7 -------------+----+----+----+----+----+----

 [Footnote 1: Raw water shut off from city supply on October 5th. ]

 ~Table 7~--(_Continued. _) (_B_) ========+=======================+=========+==========+============= | | | Duty per | Cost of | | | 100 lb. | coal per Fiscal | Name of coal used. |Cost per | of coal |1, 000, 000 ft- Year. | | ton. | consumed. |lb. Of work | | | | performed --------+-----------------------+---------+----------+------------- 1905-06 |George's Creek Big Vein| $3. 34 | 62. 8 | $0. 00238 1906-07 |George's Creek Big Vein| 3. 43 | 58. 6 | 0. 00261 1907-08 |George's Creek Big Vein| 3. 75 | 60. 3 | 0. 00278 1908-09 |Orenda | 3. 47 | 57. 7 | 0. 00268 1909-10 |Orenda |[1]3. 15 | 54. 0 | 0. 00255 ========+=======================+=========+==========+=============

 [Footnote 1: Corrected for increase or decrease in ash and British thermal units, as determined by United States Geological Survey. ]

 ~Table 8--Average Consumption of Water for Twenty-four Hours, Per Million Gallons. ~ ==========+================================================ | ~Fiscal years. ~ Month. +-----+-----+-----+-----+-----+-----+-----+------ |1903. |1904. |1905. |1906. |1907. |1908. |1909. |1910. ----------+-----+-----+-----+-----+-----+-----+-----+------ July |59. 80|61. 50|63. 20|69. 80|69. 18|68. 64|71. 08|64. 05 August |59. 00|59. 70|67. 70|71. 40|68. 03|67. 74|68. 14|61. 42 September |56. 50|61. 10|67. 90|71. 30|69. 82|68. 93|65. 83|60. 32 October |58. 70|59. 10|63. 90|68. 40|69. 14|66. 46|65. 89|59. 18 November |54. 70|58. 60|62. 10|66. 10|65. 51|61. 54|60. 06|55. 25 December |60. 70|60. 10|70. 30|67. 20|65. 71|62. 29|57. 99|56. 77 January |60. 10|65. 30|75. 10|65. 30|67. 62|63. 36|57. 72|62. 49 February |59. 30|67. 80|86. 00|68. 70|74. 68|68. 17|55. 42|60. 28 March |55. 30|60. 00|67. 60|64. 30|64. 23|59. 63|55. 31|56. 04 April |55. 10|57. 20|63. 10|62. 70|63. 45|61. 51|58. 19|58. 32 May |57. 70|60. 80|66. 30|65. 60|62. 47|62. 96|59. 25|57. 76 June |59. 50|62. 30|70. 60|67. 80|63. 53|67. 96|60. 12|58. 37 ----------+-----+-----+-----+-----+-----+-----+-----+------ Average |58. 03|61. 10|68. 70|67. 40|66. 90|64. 91|61. 47|59. 19 ==========+=====+=====+=====+=====+=====+=====+=====+======

The length of runs, depth of scraping, etc. , after the scraping orraking, are shown in Tables 10 and 11. 

_Sand Handling. _--For the first three years of operation, the sandwas carried from the sand bins in carts and dumped through thenumerous manholes of the filters on chutes which could be revolvedin various directions, in order to facilitate the spreading of thesand evenly over the surface of the filter. 

About a year ago, however, this method was changed, by substitutingsand ejectors for the carts. By this method, an ejector is eitherattached to, or placed directly under, the outlet gate of the sandbin, the gate is opened, and the ejector is started. From thisejector, the sand is carried back through the line of 4-in. Fixedpipe, and one or more lengths of 3-in. Hose, to the point ofdischarge in the filter bed which is being re-sanded. 

 ~Table 9. ~

 Columns: A - July. B - August. C - September. D - October. E - November. F - December. G - January. H - February. I - March. J - April. K - May. L - June. 

 (_A_) ~Number of Deaths from Typhoid Fever, by Months, in the District of Columbia for the Last Fourteen Fiscal Years. ~ ==========+====+====+====+====+====+====+===+===+===+===+===+===+====== Fiscal | | | | | | | | | | | | | year. | A | B | C | D | E | F | G | H | I | J | K | L |Total. ----------+----+----+----+----+----+----+---+---+---+---+---+---+------ 1896-97 | 8 |15 |25 |25 |18 |16 |13 | 4 | 4 | 4 | 6 | 9 | 147 1897-98 |10 |16 |18 |10 | 9 |18 | 8 | 4 | 2 | 9 | 6 |20 | 130 1898-99 |24 |22 |22 |28 |21 |16 |10 | 4 | 7 | 6 | 3 | 6 | 169 1899-1900 | 9 |38 |30 |28 |27 |26 |17 | 6 | 8 |10 | 5 |12 | 193 1901-02 |16 |33 |28 |21 |22 |16 |19 | 8 |12 | 9 |13 | 9 | 206 1902-03 |21 |39 |25 |32 |19 |20 | 9 | 5 | 9 | 6 | 6 | 3 | 194 1903-04 |17 |26 |18 |19 | 8 |14 | 5 | 5 | 6 |10 | 8 | 8 | 144 1904-05 |16 |22 |25 |14 |11 | 9 |11 | 1 | 5 | 7 | 1 | 3 | 125 1905-06[1]|15 |30 |23 |26 |14 | 6 | 6 | 4 | 5 | 4 |10 | 9 | 152 1906-07 |21 |32 |21 |25 |17 | 4 | 7 | 6 | 4 | 6 | 7 | 2 | 152 1907-08 |10 |18 |17 |19 |11 | 7 | 4 | 1 | 1 | 8 | 8 | 3 | 107 1908-09 |15 |13 |23 |17 |16 |13 |16 | 8 | 3 | 8 | 7 | 7 | 146 1909-10 |12 |12 |17 |12 |12 | 2 | 3 | 4 | 7 | 5 | 5 | 4 | 95 ----------+----+----+----+----+----+----+---+---+---+---+---+---+------ Average |15. 3|25. 5|22. 9|21. 5|16. 6|13. 1|9. 6|4. 4|5. 8|6. 7|6. 4|7. 5|155. 4 ----------+----+----+----+----+----+----+---+---+---+---+---+---+------

 ~Table 9~--(_Continued. _)

 Columns: A - July. B - August. C - September. D - October. E - November. F - December. G - January. H - February. I - March. J - April. K - May. L - June. M - Annual death rate. 

 (_B_) ~Number of Deaths from Typhoid Fever Reduced to Death Rates per 100, 000 Inhabitants per Year. ~ ==========+===+===+===+===+===+===+===+===+===+===+===+===+==== Fiscal | | | | | | | | | | | | | year. | A | B | C | D | E | F | G | H | I | J | K | L | M ----------+---+---+---+---+---+---+---+---+---+---+---+---+---- 1896-97 | 35| 65|109|109| 78| 70| 56| 17| 17| 17| 26| 39| 53 1897-98 | 43| 69| 78| 43| 39| 78| 31| 17| 8| 38| 25| 85| 46 1898-99 |102| 93| 93|119| 89| 68| 42| 17| 29| 25| 12| 26| 59 1899-1900 | 37|158|125|116|112|108| 69| 24| 33| 41| 20| 49| 74 1900-01 | 82|167|118|102|114| 69| 28| 8| 32| 8| 16| 40| 65 1901-02 | 64|132|112| 84| 88| 64| 75| 31| 47| 35| 51| 35| 68 1902-03 | 83|153| 98|126| 75| 79| 35| 19| 35| 23| 23| 12| 63 1903-04 | 66|100| 69| 73| 31| 54| 19| 19| 23| 38| 30| 30| 46 1904-05 | 61| 83| 95| 53| 42| 34| 41| 4| 19| 26| 4| 11| 39 1905-06 | 56|111| 85| 97| 52| 22| 22| 15| 18| 15| 36| 33| 47 1906-07 | 69|105| 69| 82| 56| 13| 24| 20| 13| 20| 24| 7| 42 1907-08 | 35| 64| 60| 67| 39| 25| 14| 4| 4| 28| 28| 11| 32 1908-09 | 53| 45| 80| 60| 56| 45| 56| 28| 10| 28| 24| 24| 43 1909-10 | 42| 42| 60| 42| 42| 7| 11| 14| 24| 17| 17| 14| 28 ----------+---+---+---+---+---+---+---+---+---+---+---+---+---- Average | | | | | | | | | | | | | monthly | 59| 99| 89| 84| 65| 53| 38| 24| 22| 26| 24| 30|. . . Death | | | | | | | | | | | | | rate. | | | | | | | | | | | | | ==========+===+===+===+===+===+===+===+===+===+===+===+===+====

 [Footnote 1: Filtered water supplied since October, 1905. ]

[Illustration: ~Figure 3--Washington Aqueduct, D. C. , FilterationPlant. Sand Handling, System. ~]

[Illustration: ~Figure 4--Washington Aqueduct, D. C. , FiltrationPlant. Washer Sand-Handling, System. ~]

[Illustration: ~Figure 5--Washington Aqueduct, D. C. , FiltrationPlant. Ejector Sand-Handling, System. ~]

 ~Table 10--Periods of Operation, and Quantities Filtered. ~ =============+=============+============================================ | Number of | ~Number of days since previous~: | filter runs +---------------------+---------------------- |ended after: | Scraping. | Raking. Month. +------+------+------+------+-------+-------+------+------- |Scrap-| Rak- | Max. | Min. | Ave. | Max. | Min. | Ave. | ing. | ing. | | | | | | -------------+------+------+------+------+-------+-------+------+------- 1909. -------------+------+------+------+------+-------+-------+------+------- July | 14 | 0 | 89 | 44 | 67. 4 | 0 | 0 | 0 August | 8 | 0 | 74 | 51 | 60. 4 | 0 | 0 | 0 September | 13 | 0 | 98 | 53 | 68. 3 | 0 | 0 | 0 October | 18 | 5 | 81 | 32 | 59. 9 | 43 | 33 | 39. 4 November | 8 | 2 | 79 | 44 | 53. 4 | 47 | 37 | 42. 0 December | 3 | 4 | 62 | 61 | 61. 3 | 63 | 50 | 57. 3 -------------+------+------+------+------+-------+-------+------+------- 1910. -------------+------+------+------+------+-------+-------+------+------- January | 9 | 4 | 95 | 79 | 88. 0 | 88 | 72 | 77. 0 February | 1 | 4 | 99 | 99 | 99. 0 | 93 | 51 | 71. 0 March | 3 | 4 | 120 | 110 | 113. 7 | 108 | 101 | 104. 3 April | 10 | 12 | 126 | 62 | 84. 8 | 129 | 21 | 65. 3 May | 3 | 2 | 86 | 38 | 69. 7 | 55 | 32 | 43. 5 June | 13 | 2 | 100 | 61 | 79. 7 | 129 | 78 | 103. 5 -------------+------+------+------+------+-------+-------+------+------ Year 1909-10 | 103 | 39 | 126 | 32 | 71. 1 | 129 | 21 | 66. 6 -------------+------+------+------+------+-------+-------+------+------ Fiscal years:| | | | | | | | -------------+------+------+------+------+-------+-------+------+------- 1905-06 | 71 | 0 | 195 | 38 | 91. 1 | 0 | 0 | 0 1906-07 | 101 | 4 | 199 | 24 | 77. 0 | 32 | 14 | 21. 7 1907-08 | 143 | 77 | 180 | 11 | 54. 9 | 63 | 7 | 28. 6 1908-09 | 128 | 50 | 135 | 11 | 49. 9 | 93 | 13 | 34. 2 =============+======+======+======+======+=======+=======+======+=======

 =============+======================================================== | ~Million gallons filtered since previous:~ +-------------------------------------------------------- Month. | Scraping. | Raking. +--------+--------+---------+--------+--------+---------- | Max. | Min. | Ave. | Max. | Min. | Ave. -------------+--------+--------+---------+--------+--------+---------- 1909. -------------+--------+--------+---------+--------+--------+---------- July | 229. 01 | 106. 27 | 163. 289 | 0 | 0 | 0 August | 175. 54 | 124. 94 | 152. 581 | 0 | 0 | 0 September | 237. 52 | 114. 37 | 161. 702 | 0 | 0 | 0 October | 206. 09 | 78. 78 | 132. 359 | 96. 50 | 71. 51 | 82. 708 November | 168. 19 | 82. 32 | 112. 603 | 99. 00 | 90. 23 | 94. 615 December | 135. 77 | 128. 33 | 132. 647 | 144. 35 | 106. 11 | 125. 940 -------------+--------+--------+---------+--------+--------+---------- 1910. -------------+--------+--------+---------+--------+--------+---------- January | 204. 38 | 146. 58 | 178. 461 | 189. 48 | 152. 33 | 170. 735 February | 205. 73 | 205. 73 | 205. 730 | 192. 98 | 118. 85 | 158. 890 March | 275. 96 | 257. 36 | 265. 493 | 249. 68 | 224. 49 | 238. 993 April | 295. 96 | 104. 13 | 181. 972 | 307. 57 | 45. 22 | 142. 448 May | 186. 64 | 81. 66 | 150. 230 | 102. 15 | 69. 79 | 85. 978 June | 213. 70 | 130. 85 | 171. 059 | 181. 25 | 167. 84 | 174. 540 -------------+--------+--------+---------+--------+--------+---------- Year 1909-10 | 295. 96 | 81. 66 | 159. 151 | 307. 57 | 45. 22 | 143. 832 -------------+--------+--------+---------+--------+--------+---------- Fiscal years: -------------+--------+--------+---------+--------+--------+---------- 1905-06 | 497. 45 | 116. 66 | 240. 379 | 0 | 0 | 0 1906-07 | 466. 12 | 69. 76 | 220. 693 | 103. 28 | 32. 13 | 76. 870 1907-08 | 477. 19 | 28. 20 | 146. 912 | 165. 25 | 17. 08 | 75. 775 1908-09 | 298. 08 | 39. 26 | 125. 617 | 244. 19 | 41. 41 | 88. 439 =============+========+========+=========+========+========+===========

In re-sanding a filter, it is first filled with water to theproposed depth of the sand layer. The outlet end of the hose isconnected to a 3-in. Pipe which is supported on a boat, and the sandis discharged through this pipe at the point required. Work is firstbegun at the far end of the filter, and it is gradually filled byswinging the boat from side to side and backing it by degrees to thefront end. 

At first it was feared that a small quantity of mud would be depositedon the surface of the old sand, and that this mud would ultimately causesubsurface clogging. For this reason, when this method was firstadopted, a man was required to rake the sand very thoroughly in front ofthe discharge. Later, it was found that by giving the end of thedischarge pipe a slope of about 45 degrees downward from the horizontal, the force of the current of sand and water could be depended on to cutthe old surface of sand to any required depth, and move it aheadtogether with the new sand, thus completely breaking up the possible mudlayer between the old and new sand layers. After having used this methodalmost exclusively for 15 months, in which time eleven filters have beenre-sanded, and 24, 531 cu. Yd. Of sand have been replaced, there seems tobe no indication of an increased initial loss of head. The sand is verycompact, and has no apparent tendency to separate into different sizes. The general appearance is similar to that of very fine sand on theseashore. The filters re-sanded in this way have been considerably moreefficient than those in which the sand was replaced with carts, and asyet, no harmful results have been noted. The rate at which the sand isreplaced is shown in Table 12, and the cost of labor for sand handlingis given in detail in Table 14, which shows that quite a perceptiblesaving has been effected by the hydraulic method. 

The figures showing the cost for sand handling do not include anycharge for the quantity of water used, that item having been carriedon the pumping-station account. 

 ~Table 11--Quantities of Sand Removed. ~ ==============+=================+================================ |~No. Of filters | ~Cubic yards when last |scraped when last| treatment was:~ |treatment was:~ | Month. +---------+-------+---------------+---------------- | | | Scraping. | Raking. |Scraping. |Raking. |----+----+-----+----+----+------ | | |Max. |Min. |Ave. |Max. |Min. |Ave. --------------+---------+-------+----+----+-----+----+----+------ 1909. --------------+---------+-------+----+----+-----+----+----+------ July | 14 | 0 |338 |121 |190. 6| 0 | 0 | 0 August | 8 | 0 |356 |149 |218. 5| 0 | 0 | 0 September | 8 | 0 |524 | 97 |178. 6| 0 | 0 | 0 October | 9 | 5 |150 | 93 |115. 8|301 |121 |169. 0 November | 2 | 2 |134 | 88 |111. 0|132 | 81 |106. 5 December | 0 | 2 | 0 | 0 | 0 |133 |126 |129. 5 --------------+---------+-------+----+----+-----+----+----+------ 1910. --------------+---------+-------+----+----+-----+----+----+------ January | 2 | 4 |155 |112 |133. 5|195 |121 |147. 8 February | 0 | 4 | 0 | 0 | 0 |390 |160 |225. 8 March | 1 | 4 |489 |489 |489. 0|262 |179 |214. 3 April | 4 | 12 |172 | 84 |119. 3|230 |146 |178. 8 May | 1 | 2 |320 |320 |320. 0|249 |241 |245. 0 June | 0 | 2 | 0 | 0 | 0 |203 |190 |196. 5 --------------+---------+-------+----+----+-----+----+----+------ Year 1909-10 | 49 | 37 |524 | 84 |176. 7|390 | 81 |181. 0 --------------+---------+-------+----+----+-----+----+----+------ Fiscal Years: --------------+---------+-------+----+----+-----+----+----+------ 1905-06 | 71 | 0 |600 | 71 |250. 0| 0 | 0 | 0 1906-07 | 94 | 2 |536 | 52 |259. 0|398 |276 |337. 0 1907-08 | 81 | 53 |527 | 46 |190. 2|411 | 35 |118. 4 1908-09 | 92 | 50 |580 | 55 |169. 5|472 | 81 |177. 5 ==============+=========+=======+====+====+=====+====+====+======

 ==============+================================ | ~Depth, in inches, when | last treatment was:~ +---------------+---------------- Month. | Scraping. | Raking. +----+----+-----+----+----+------ |Max. |Min. |Ave. |Max. |Min. |Ave. --------------+----+----+-----+----+----+------ 1909. --------------+----+----+-----+----+----+------ July |2. 51|0. 90|1. 415|0 |0 |0 August |2. 65|1. 11|1. 631|0 |0 |0 September |3. 90|0. 72|1. 330|0 |0 |0 October |1. 12|0. 69|0. 862|2. 24|0. 90|1. 256 November |1. 00|0. 65|0. 825|0. 98|0. 60|0. 790 December |0 |0 |0 |0. 99|0. 94|0. 965 --------------+----+----+-----+----+----+------ 1910. --------------+----+----+-----+----+----+------ January |1. 15|0. 83|0. 990|1. 45|0. 90|1. 100 February |0 |0 |0 |2. 90|1. 19|1. 678 March |3. 64|3. 64|3. 640|1. 95|1. 33|1. 593 April |1. 28|0. 62|0. 885|1. 71|1. 09|1. 331 May |2. 38|2. 38|2. 380|1. 85|1. 79|1. 820 June |0 |0 |0 |1. 51|1. 41|1. 460 --------------+----+----+-----+----+----+------ Year 1909-10 |3. 90|0. 62|1. 314|2. 90|0. 60|1. 373 --------------+----+----+-----+----+----+------ Fiscal Years: --------------+----+----+-----+----+----+------ 1905-06 |4. 47|0. 53|1. 799|0 |0 |0 1906-07 |4. 00|0. 56|1. 931|2. 95|2. 05|2. 500 1907-08 |3. 92|0. 21|1. 507|3. 06|0. 21|0. 881 1908-09 |4. 31|0. 41|1. 259|3. 51|0. 60|1. 317 ==============+====+====+=====+====+====+======

 ~Table 12--Rates of Sand Handling. ~ =========+================================+============================ | ~Sand removed from filters. ~ |~Sand replaced in filters. ~ +-----------+--------+-----------+---------+--------+--------- | Ejector | Cubic | Average | Ejector | Cubic |Average Date. | hours. |yards of| rate in | hours. |yards of|rate in | | sand |cubic yards| | sand | cubic | |removed | per hour | |removed | yards | | | | | |per hour ---------+-----------+--------+-----------+---------+--------+--------- 1906. ---------+-----------+--------+-----------+---------+--------+--------- April | 49 | 253 | 5. 2 | . . . | . . . | . . . May | 380 | 2, 511 | 6. 6 | . . . | . . . | . . . June | 567 | 3, 280 | 5. 8 | . . . | . . . | . . . July | 931 | 5, 376 | 5. 8 | . . . | . . . | . . . August | 105 | 533 | 5. 1 | . . . | . . . | . . . September| 315 | 1, 892 | 6. 0 | . . . | . . . | . . . October | 1, 067 | 5, 173 | 5. 8 | . . . | . . . | . . . November | 168 | 935 | 5. 6 | . . . | . . . | . . . December | 203 | 1, 073 | 5. 3 | . . . | . . . | . . . ---------+-----------+--------+-----------+---------+--------+--------- 1907. ---------+-----------+--------+-----------+---------+--------+--------- January | 399 | 2, 974 | 7. 3 | . . . | . . . | . . . February | 140 | 1, 139 | 8. 1 | . . . | . . . | . . . March | 115 | 878 | 7. 6 | . . . | . . . | . . . April | 427 | 3, 103 | 7. 3 | . . . | . . . | . . . May | 133 | 939 | 7. 0 | . . . | . . . | . . . June | 105 | 674 | 6. 4 | . . . | . . . | . . . July | 7 | 46 | 6. 6 | . . . | . . . | . . . August | 90 | 574 | 6. 4 | . . . | . . . | . . . September| 306 | 1, 396 | 6. 5 | . . . | . . . | . . . October | 273 | 1, 701 | 6. 2 | . . . | . . . | . . . November | 202 | 1, 258 | 6. 8 | . . . | . . . | . . . December | 304 | 2, 138 | 5. 9 | . . . | . . . | . . . ---------+-----------+--------+-----------+---------+--------+--------- 1908. ---------+-----------+--------+-----------+---------+--------+--------- January | 546 | 3, 708 | 6. 8 | . . . | . . . | . . . February | 98 | 776 | 7. 9 | . . . | . . . | . . . March | 315 | 2, 832 | 9. 0 | . . . | . . . | . . . April | 469 | 3, 775 | 8. 1 | . . . | . . . | . . . May | 182 | 1, 414 | 7. 8 | . . . | . . . | . . . June | 280 | 2, 057 | 7. 4 | . . . | . . . | . . . July | 280-1/2 | 2, 683 | 9. 6 | . . . | . . . | . . . August | 327-1/2 | 2, 808 | 8. 6 | . . . | . . . | . . . September| 402 | 3, 371 | 8. 4 | . . . | . . . | . . . October | 308 | 2, 696 | 8. 7 | . . . | . . . | . . . November | 47-1/2 | 333 | 7. 0 | . . . | . . . | . . . December | 153-3/4 | 1, 268 | 8. 3 | . . . | . . . | . . . ---------+-----------+--------+-----------+---------+--------+--------- 1909. ---------+-----------+--------+-----------+---------+--------+--------- January | 119-1/2 | 1, 055 | 8. 8 | . . . | . . . | . . . February | 161-1/2 | 1, 479 | 9. 2 | . . . | . . . | . . . March | 144 | 1, 465 | 10. 2 | . . . | . . . | . . . April | 214-3/4 | 2, 260 | 10. 5 | 188 | 2, 405 | 12. 8 May | 219-3/4 | 2, 223 | 10. 1 | 190 | 2, 196 | 11. 5 June | 355 | 3, 096 | 8. 7 | 243 | 3, 054 | 12. 6 July | 312-1/4 | 2, 707 | 8. 7 | 425-1/2 | 4, 050 | 9. 5 August | 218-3/4 | 1, 955 | 9. 0 | 64-1/2 | 620 | 9. 6 September| 172-1/2 | 1, 360 | 7. 9 | 408 | 2, 842 | 7. 0 October | 203 | 1, 870 | 9. 2 | 261-1/4 | 2, 350 | 9. 0 November | 54 | 397 | 7. 4 | 0 | 0 | . . . December | 62 | 382 | 6. 2 | 0 | 0 | . . . ---------+-----------+--------+-----------+---------+--------+--------- 1910. ---------+-----------+--------+-----------+---------+--------+--------- January | 104 | 703 | 6. 8 | 0 | 0 | . . . February | 106-1/2 | 1, 058 | 9. 9 | 28-1/4 | 371 | 13. 1 March | 98 | 985 | 10. 0 | 72 | 1, 008 | 14. 0 April | 268-3/4 | 2, 852 | 10. 7 | 134-1/4 | 2, 159 | 16. 1 May | 58-3/4 | 693 | 11. 8 | 171-3/4 | 3, 042 | 17. 7 June | 58-3/4 | 642 | 10. 9 | 9-3/4 | 166 | 17. 0 =========+===========+========+===========+=========+========+========

The cost for pumping water for sand handling, including all labor, materials, and repairs, amounts to $0. 06 per cu. Yd. Of sand ejectedand washed, and $0. 03 per cu. Yd. For replacing. 

In addition to the water used for carrying the sand which is beingreplaced, it is customary to keep a slight upward flow in thefilter, thus using about 500, 000 gal. Of filtered water per day forthis purpose. Assuming the value of this water to be the total costfor pumping, filtering, etc. , or $3. 80 per 1, 000, 000 gal. , the costper cubic yard of sand replaced would be about $0. 02 when oneejector is used, and $0. 01 when two are in operation. 

It is not considered absolutely necessary to have an upward flow ofwater in the filter which is being re-sanded, and it is not alwaysdone. It was used, however, as an additional safeguard against theformation of a stratum of mud between the old and new layers of sandwhile the hydraulic method was in an experimental stage. 

The quantities of sand removed from the filters per scraping and therates of sand handling are shown in Tables 11 and 12. 

_Cost of Operation. _--It is frequently difficult to compare therelative cost of corresponding items for different plants, becauseof the different methods of dividing the cost and the varyingopinions of the officials as to what should properly be charged toeach item. 

In order that the data may be in sufficient detail to permit it tobe rearranged to compare with other plants, a list of employees andcharges for supplies is given in Table 13. This list accounts forthe entire appropriation for the care and maintenance of thefiltration plant, including pumping the water to the filters, parking and caring for the grounds, buildings, roads, sidewalks, etc. The cost for the various items per million gallons pumped tothe filters is shown in Table 14, and the cost per cubic yard ofsand handled in Table 15. 

_Preliminary Treatment. _--Before the present filtration plant wasdesigned, Rudolph Hering, George W. Fuller, and Allen Hazen, Members, Am. Soc. C. E. , made an investigation and report. Thisreport was dated February 18th, 1901, and contained the followingparagraph:

 "In consideration of the full evidence, we recommend the construction of a complete system of slow or sand filters, with such auxiliary works as may be necessary for preliminary sedimentation, and the use of a coagulant for part of the time. There is no reason to believe that the use of this coagulant will in any degree affect the wholesomeness of the water. "

Notwithstanding this opinion, considerable prejudice existed amongthe citizens of Washington against the use of a coagulant, and, asfinally passed, the bill providing for the construction of thefilters did not include an appropriation for the coagulant. 

 ~Table 13--List of Employees, Rates of Pay, and Approximate Cost for Supplies. ~ ========================================================+=========== 1 Superintendent | $3, 000. 00 1 Chief Chemist and Assistant Superintendent | 2, 100. 00 1 First Assistant Chemist | 1, 500. 00 1 Second Assistant Chemist | 1, 000. 00 1 Stenographer and Clerk | 1, 200. 00 1 Surveyor | 1, 200. 00 1 Laboratory Helper | 720. 00 1 Janitor | 600. 00 1 Chief Steam Engineer | 1, 800. 00 1 First Assistant Steam Engineer | 1, 440. 00 1 Second Assistant Steam Engineer | 1, 080. 00 3 Oilers, at $900 each | 2, 700. 00 3 Firemen, at $900 each | 2, 700. 00 3 Laborers, at $540 each | 1, 620. 00 1 Filter Foreman | 1, 200. 00 2 Foremen, at $900 each | 1, 800. 00 1 Timekeeper | 900. 00 3 Watchmen and Gauge Tenders, at $900 each | 2, 700. 00 1 Machinist | 1, 140. 00 1 Blacksmith | 900. 00 1 Storekeeper | 900. 00 1 Painter | 900. 00 1 Mechanic | 900. 00 1 Electrician | 900. 00 4 Skilled Laborers at $600 each | 2, 400. 00 1 Watchman and Special Officer | 900. 00 1 Recorder | 720. 00 27 Laborers, at $1. 50 per day for 300 days | 12, 150. 00 3 Teams, at $2. 00 per day for 200 days | 1, 200. 00 Laboratory and office supplies | 2, 700. 00 Filter supplies, tools, hose, repair of | roads, parks, shrubs, etc. | 8, 820. 00 Pumping station supplies, oil, waste, | packing, repairs, etc. | 3, 570. 00 3, 600 tons of coal, at $3. 15 per ton | 11, 340. 00 Charges in U. S. Engineer Office, labor | 2, 900. 00 Charges in U. S. Engineer Office, materials | 400. 00 --------------------------------------------------------+----------- Total | $82, 000. 00 ========================================================+===========

The results obtained from operating the filters being such as tojustify the conclusions in the report referred to, an experimentalplant was constructed for the purpose of studying the efficiency ofvarious methods of preliminary treatment of the water. This plantconsisted of three cylindrical concrete filter tanks, each 10 ft. Indiameter. These tanks were filled with the layers of gravel and sandnecessary to make them represent as accurately as possible the largeslow sand units of the main filtration plant. Means were alsoprovided for giving a preliminary treatment to the water supplyingeach of these experimental slow sand filters. In two cases, thepreliminary treatment was rapid filtration, while the thirdconsisted of sedimentation and coagulation. The sedimentation tankwas of sufficient size, when compared with the area of theexperimental slow sand filter, to represent the Georgetown andMcMillan Park Reservoirs when used in connection with the largefilters. The first preliminary filter was very similar in constructionand operation to a mechanical filter. The sand for this filter wastaken from the main filters, and, consequently, was finer than isgenerally used in mechanical filters. The second preliminary filterwas a Maignen scrubber. It consisted of a cylindrical concrete tank, 4 ft. In diameter and 8-1/2 ft. Deep, which contained 12 in. Ofcobble-stones on the bottom, then, successively, 12 in. Of egg-sizecoke, 12 in. Of stove-size coke, 24 in. Of nut-size coke, and 24 in. Of sponge clippings as the final or top layer. 

 ~Table 14--Cost Per Million Gallons Filtered. ~ (_A_) ~Labor~. =============+===========+==========+================== | Office | | ~Filter~ | and | Pumping | ~operations~: Month. |laboratory. | station. +------------------ | | | Sand |Repairs | | |handling. | etc. -------------+-----------+----------+---------+-------- 1909. -------------+-----------+----------+---------+-------- July | $0. 73 | $0. 57 | $0. 86 | . . . August | 0. 75 | 0. 64 | 0. 59 | . . . September | 0. 83 | 0. 67 | 0. 80 | . . . October | 0. 72 | 0. 66 | 0. 73 | . . . November | 0. 87 | 0. 76 | 0. 42 | . . . December | 0. 90 | 0. 69 | 0. 27 | . . . -------------+-----------+----------+---------+-------- 1910. -------------+-----------+----------+---------+-------- January | 0. 81 | 0. 63 | 0. 33 | . . . February | 0. 94 | 0. 74 | 0. 35 | $0. 07 March | 0. 92 | 0. 81 | 0. 30 | 0. 07 April | 0. 93 | 0. 83 | 0. 49 | 0. 03 May | 0. 86 | 0. 72 | 0. 36 | 0. 03 June | 0. 88 | 0. 67 | 0. 38 | . . . -------------+-----------+----------+---------+-------- Average | 0. 84 | 0. 70 | 0. 27 |[1]0. 25 -------------+-----------+----------+---------+-------- Fiscal years: -------------+-----------+----------+---------+-------- 1905-1906 | 0. 45 | 0. 45 | 0. 47 | 0. 02 1906-1907 | 0. 57 | 0. 57 | 0. 58 | 0. 21 1907-1908 | 0. 70 | 0. 56 | 0. 42 | 0. 32 1908-1909 | 0. 72 | 0. 61 | 0. 41 | 0. 34 -------------+-----------+----------+---------+--------

 =============+===========+==============+==========+========= | Parking | | | Month. | (care of | Experimental | Main | Total. | grounds). | filters. | Office. | -------------+-----------+--------------+----------+--------- 1909. -------------+-----------+--------------+----------+--------- July | $0. 31 | . . . | $0. 15 | $2. 62 August | 0. 71 | . . . | 0. 14 | 2. 83 September | 0. 51 | . . . | 0. 17 | 2. 98 October | 0. 34 | . . . | 0. 08 | 2. 53 November | 0. 38 | . . . | 0. 18 | 2. 61 December | 0. 40 | . . . | 0. 12 | 2. 38 -------------+-----------+--------------+----------+--------- 1910. -------------+-----------+--------------+----------+--------- January | 0. 14 | . . . | 0. 10 | 2. 01 February | 0. 11 | . . . | 0. 16 | 2. 37 March | 0. 18 | . . . | 0. 13 | 2. 41 April | 0. 36 | . . . | 0. 13 | 2. 77 May | 0. 55 | . . . | 0. 18 | 2. 70 June | 0. 38 | . . . | 0. 12 | 2. 43 -------------+-----------+--------------+----------+---------- Average | 0. 36 | . . . | 0. 14 | 2. 56 -------------+-----------+--------------+----------+---------- Fiscal years: -------------+-----------+--------------+----------+--------- 1905-1906 | 0. 01 | . . . | 0. 09 | 1. 49 1906-1907 | 0. 07 | $0. 03 | 0. 04 | 2. 07 1907-1908 | 0. 15 | 0. 09 | 0. 09 | 2. 36 1908-1909 | 0. 22 | 0. 01 | 0. 13 | 2. 44 -------------+-----------+--------------+----------+----------

 ~Table 14~--(_Continued. _) (_B_) ~Materials~. =============+===========+==========+================== | Office | | ~Filter~ | and | Pumping | ~operations~: Month. |laboratory. | station. +------------------ | | | Sand |Repairs | | |handling. | etc. -------------+-----------+----------+---------+-------- 1909. -------------+-----------+----------+---------+-------- July | . . . | . . . | $0. 01 | . . . August | $0. 01 | . . . | . . . | . . . September | 0. 05 | $0. 31 | 0. 04 | . . . October | 0. 08 | 0. 11 | 0. 13 | . . . November | 0. 13 | 0. 78 | 0. 10 | . . . December | 0. 03 | 0. 17 | 0. 05 | . . . -------------+-----------+----------+---------+-------- 1910. -------------+-----------+----------+---------+-------- January | 0. 12 | 0. 74 | 0. 14 | . . . February | 0. 07 | 1. 88 | 0. 18 | . . . March | 0. 26 | 0. 28 | 0. 01 | . . . April | 0. 18 | 1. 22 | 0. 10 | . . . May | 0. 06 | 0. 72 | 0. 02 | . . . June | 0. 54 | 2. 23 | . . . |$[2]2. 16 -------------+-----------+----------+---------+-------- Average | 0. 13 | 0. 69 | 0. 02 | [3]0. 21 -------------+-----------+----------+---------+-------- Fiscal years: -------------+-----------+----------+---------+-------- 1905-1906 | 0. 04 | 0. 59 | 0. 02 | . . . 1906-1907 | 0. 03 | 0. 67 | 0. 08 | 0. 20 1907-1908 | 0. 05 | 0. 54 | 0. 04 | 0. 07 1908-1909 | 0. 10 | 0. 69 | 0. 05 | 0. 18 -------------+-----------+----------+---------+--------

 =============+===========+==============+==========+========= | Parking | | | Month. | (care of | Experimental | Main | Total. | grounds), | filters. | Office. | -------------+-----------+--------------+----------+--------- 1909. -------------+-----------+--------------+----------+--------- July | . . . | . . . | . . . | $0. 01 August | $0. 07 | . . . | $0. 01 | 0. 09 September | 0. 01 | . . . | 0. 03 | 0. 44 October | 0. 46 | . . . | 0. 02 | 0. 80 November | 0. 34 | . . . | 0. 02 | 1. 37 December | 0. 01 | . . . | 0. 05 | 0. 31 -------------+-----------+--------------+----------+--------- 1910. -------------+-----------+--------------+----------+--------- January | 0. 01 | . . . | . . . | 1. 01 February | 0. 01 | . . . | 0. 01 | 2. 15 March | . . . | . . . | . . . | 0. 55 April | 0. 29 | . . . | 0. 02 | 1. 81 May | 0. 11 | . . . | 0. 02 | 0. 98 June | 0. 46 | . . . | 0. 04 | 5. 43 -------------+-----------+--------------+----------+---------- Average | 0. 17 | . . . | 0. 02 | 1. 24 -------------+-----------+--------------+----------+---------- Fiscal years: -------------+-----------+--------------+----------+--------- 1905-1906 | . . . | . . . | . . . | 0. 65 1906-1907 | 0. 02 | | . . . | 1. 00 1907-1908 | 0. 06 | . . . | 0. 01 | 0. 77 1908-1909 | 0. 18 | . . . | 0. 02 | 1. 22 -------------+-----------+--------------+----------+----------

 [Footnote 1: $0. 02 for new sand-handling system. ]

 [Footnote 2: $2. 02 for new sand-handling system. ]

 [Footnote 3: $0. 16 for new sand-handling system. ]

 ~Table 14~--(_Continued. _) (_C_) ~Totals. ~ =============+===========+==========+=================== | Office | | ~Filter~ | and | Pumping | ~operations~: Month. |laboratory. | station. +------------------- | | | Sand |Repairs | | |handling. | etc. -------------+-----------+----------+---------+--------- 1909. -------------+-----------+----------+---------+--------- July | $0. 73 | $0. 57 | $0. 87 | . . . August | 0. 76 | 0. 64 | 0. 59 | . . . September | 0. 88 | 0. 98 | 0. 84 | . . . October | 0. 80 | 0. 77 | 0. 86 | . . . November | 1. 00 | 1. 54 | 0. 52 | . . . December | 0. 93 | 0. 86 | 0. 32 | . . . -------------+-----------+----------+---------+--------- 1910. -------------+-----------+----------+---------+--------- January | 0. 93 | 1. 37 | 0. 47 | . . . February | 1. 01 | 2. 62 | 0. 53 | $0. 07 March | 1. 18 | 1. 09 | 0. 31 | 0. 07 April | 1. 11 | 2. 05 | 0. 59 | 0. 03 May | 0. 92 | 1. 44 | 0. 38 | 0. 03 June | 1. 42 | 2. 90 | 0. 38 | 2. 16 -------------+-----------+----------+---------+--------- Average. | 0. 97 | 1. 39 | 0. 29 | 0. 46 -------------+-----------+----------+---------+--------- Fiscal years: -------------+-----------+----------+---------+--------- 1905-1906 | 0. 49 | 1. 04 | 0. 49 | 0. 02 1906-1907 | 0. 60 | 1. 24 | 0. 66 | 0. 41 1907-1908 | 0. 75 | 1. 13 | 0. 46 | 0. 39 1908-1909 | 0. 82 | 1. 30 | 0. 46 | 0. 52 =============+===========+==========+=========+=========

 =============+===========+==============+==========+========= | Parking | | | Month. | (care of | Experimental | Main | Total. | grounds), | filters. | Office. | -------------+-----------+--------------+----------+--------- 1909. -------------+-----------+--------------+----------+--------- Jul | $0. 31 | . . . | $0. 15 | $2. 63 August | 0. 78 | . . . | 0. 15 | 2. 92 September | 0. 52 | . . . | 0. 20 | 3. 42 October | 0. 80 | . . . | 0. 10 | 3. 33 November | 0. 72 | . . . | 0. 20 | 3. 98 December | 0. 41 | . . . | 0. 17 | 2. 69 -------------+-----------+--------------+----------+--------- 1910. -------------+-----------+--------------+----------+--------- January | 0. 15 | . . . | 0. 10 | 3. 02 February | 0. 12 | . . . | 0. 17 | 4. 52 March | 0. 18 | . . . | 0. 13 | 2. 96 April | 0. 65 | . . . | 0. 15 | 4. 58 May | 0. 66 | . . . | 0. 20 | 3. 63 June | 0. 84 | . . . | 0. 16 | 7. 86 -------------+-----------+--------------+----------+--------- Average. | 0. 58 | . . . | 0. 16 | 3. 80 -------------+-----------+--------------+----------+--------- Fiscal years: -------------+-----------+--------------+----------+--------- 1905-1906 | 0. 01 | . . . | 0. 09 | 2. 14 1906-1907 | 0. 09 | $0. 03 | 0. 04 | 3. 07 1907-1908 | 0. 21 | 0. 09 | 0. 10 | 3. 13 1908-1909 | 0. 40 | 0. 01 | 0. 15 | 3. 66 =============+===========+==============+==========+=========

The two preliminary filters were operated at a rate of about50, 000, 000 gal. Per acre per day, and the three slow sand filtersat rates of from 3, 000, 000 to 4, 000, 000 gal. Per day. 

This plant was put in service during the early part of February, 1907, and was kept in practically continuous operation until the endof July, 1908. 

[Illustration: ~Figure 6--Washington Aqueduct, D. C. , ExperimentalFilters Below Dalecarlia Reservoir Coagulating Basins and Apparatus. ~]

 ~Table 15--Average Cost for Labor for Sand Handling. ~ (_A_) ~Per Million Gallons Pumped To Filter. ~ =============+=======+=======+=======+=======+=======+========+======== Month. | Scrap-| Eject-| Wash- |Smooth-|Raking. | Re- | Total. | ing. | ing. | ing. | ing. | |sanding. | -------------+-------+-------+-------+-------+-------+--------+-------- 1909. -------------+-------+-------+-------+-------+-------+--------+-------- July | $0. 10 | $0. 21 | $0. 03 | $0. 02 | . . . | $0. 21 | $0. 57 August | 0. 07 | 0. 16 | 0. 03 | 0. 01 | . . . | 0. 04 | 0. 31 September | 0. 05 | 0. 13 | 0. 02 | 0. 01 | $0. 01 | 0. 27 | 0. 49 October | 0. 06 | 0. 15 | 0. 03 | 0. 01 | 0. 02 | 0. 12 | 0. 39 November | 0. 02 | 0. 06 | . . . | . . . | 0. 02 | . . . | 0. 70 December | 0. 02 | 0. 04 | 0. 01 | . . . | 0. 01 | 0. 01 | 0. 09 -------------+-------+-------+-------+-------+-------+--------+-------- 1910. -------------+-------+-------+-------+-------+-------+--------+-------- January | 0. 04 | 0. 07 | . . . | 0. 01 | 0. 02 | . . . | 0. 14 February | 0. 04 | 0. 10 | . . . | 0. 01 | . . . | 0. 02 | 0. 17 March | 0. 04 | 0. 06 | . . . | 0. 01 | 0. 01 | 0. 05 | 0. 17 April | 0. 10 | 0. 15 | 0. 04 | 0. 01 | 0. 02 | 0. 06 | 0. 38 May | 0. 02 | 0. 03 | 0. 01 | . . . | 0. 01 | 0. 11 | 0. 18 June | 0. 02 | 0. 04 | . . . | . . . | 0. 02 | 0. 01 | 0. 09 -------------+-------+-------+-------+-------+-------+--------+-------- Average | 0. 05 | 0. 10 | 0. 01 | 0. 01 | 0. 01 | 0. 08 | 0. 26 -------------+-------+-------+-------+-------+-------+--------+-------- Fiscal years:| | | | | | | -------------+-------+-------+-------+-------+-------+--------+-------- 1905-06 | 0. 06 | 0. 29 | 0. 02 | 0. 06 | . . . | 0. 04 | 0. 47 1906-07 | 0. 07 | 0. 20 | 0. 05 | 0. 02 | . . . | 0. 24 | 0. 58 1907-08 | 0. 09 | 0. 14 | 0. 03 | 0. 01 | 0. 02 | 0. 13 | 0. 42 1908-09 | 0. 07 | 0. 15 | 0. 03 | 0. 01 | 0. 01 | 0. 14 | 0. 41 -------------+-------+-------+-------+-------+-------+--------+--------

 ~Table 15~--(_Continued. _) (_B_) ~Per Cubic Yard of Sand. ~ =============+=======+=======+=======+=======+=======+=======+========= Month. | Scrap-| Eject-| Wash- |Smooth-|Raking. | Re- | Total. | ing. | ing. | ing. | ing. | |sanding. | -------------+-------+-------+-------+-------+-------+--------+-------- 1909. -------------+-------+-------+-------+-------+-------+--------+-------- July | $0. 08 | $0. 15 | $0. 03 | $0. 01 | . . . | $0. 10 | $0. 37 August | 0. 07 | 0. 15 | 0. 03 | 0. 01 | . . . | 0. 11 | 0. 37 September | 0. 07 | 0. 17 | 0. 03 | 0. 01 | . . . | 0. 17 | 0. 45 October | 0. 06 | 0. 15 | 0. 03 | 0. 01 | . . . | 0. 09 | 0. 34 November | 0. 10 | 0. 23 | 0. 02 | 0. 02 | . . . | . . . | 0. 37 December | 0. 12 | 0. 25 | 0. 04 | 0. 02 | . . . | 0. 08 | 0. 51 -------------+-------+-------+-------+-------+-------+--------+-------- 1910. -------------+-------+-------+-------+-------+-------+--------+-------- January | 0. 10 | 0. 19 | . . . | 0. 02 | . . . | . . . | 0. 31 February | 0. 07 | 0. 15 | . . . | 0. 01 | . . . | 0. 09 | 0. 32 March | 0. 06 | 0. 11 | . . . | 0. 02 | . . . | 0. 08 | 0. 27 April | 0. 07 | 0. 09 | 0. 03 | 0. 01 | . . . | 0. 05 | 0. 25 May | 0. 06 | 0. 09 | 0. 03 | 0. 01 | . . . | 0. 06 | 0. 25 June | 0. 06 | 0. 12 | . . . | 0. 01 | . . . | 0. 10 | 0. 29 -------------+-------+-------+-------+-------+-------+--------+-------- Average | 0. 07 | 0. 14 | 0. 02 | 0. 01 | . . . | 0. 10 | 0. 34 -------------+-------+-------+-------+-------+-------+--------+-------- Fiscal years: -------------+-------+-------+-------+-------+-------+--------+-------- 1905-06 | 0. 07 | 0. 35 | 0. 04 | 0. 07 | . . . | 0. 14 | 0. 67 1906-07 | 0. 06 | 0. 19 | 0. 03 | 0. 02 | . . . | 0. 17 | 0. 47 1907-08 | 0. 09 | 0. 15 | 0. 03 | 0. 01 | . . . | 0. 14 | 0. 42 1908-09 | 0. 06 | 0. 14 | 0. 03 | 0. 01 | . . . | 0. 13 | 0. 37 =============+=======+=======+=======+=======+=======+=======+=========

For convenience in referring to the different systems, the combinedrapid and slow sand filter will be designated as Filter Plant No. 1, the combined Maignen scrubber and slow sand filter as Filter PlantNo. 2, and the combined coagulating basin and slow sand basin asFilter Plant No. 3. 

The length of run of Filter Plant No. 1 was relatively long atfirst. The rapid rate of filtration, however, tended to carry theclay, which was suspended in the applied water, to a considerabledepth in the filtering material, so that the runs graduallydecreased in length until they were reduced to about three days. Unfortunately, it was necessary to use unfiltered water for washing, which, together with the great penetration from the applied water, finally made it necessary to remove all the filtering materials, andwash them. 

Although this preliminary filter was operated at a high rate, itsefficiency was quite satisfactory. In fact, at times when theapplied water was comparatively good, very little work was left forthe slow sand filter. At times of high turbidity, however, some ofthe exceedingly fine mud in the applied water passed through thisfilter, as well as the slow sand filter connected with it, and itproved to be absolutely impossible to produce a clear effluent atall times with this combination. 

Filter Plant No. 2 proved more economical and convenient inoperation, but somewhat less efficient than Filter Plant No. 1. Neither filter could be depended on to give a clear effluent whenthe applied water was turbid. 

In the operation of Filter Plant No. 3, sulphate of alumina was usedwhen the applied water contained too much turbidity to be treatedsatisfactorily by slow sand filters. 

When the water was comparatively clear, either one of the threesystems, or slow sand filtration alone, was entirely satisfactory. At times of high turbidity, however, Filter Plant No. 3 was the onlyone which could be depended on to produce a clear effluent. 

A fair comparison between the results of the three systems whentreating turbid water in January, 1908, is given in Table 16. 

Table 16 shows very clearly that neither Filter Plant No. 1 nor No. 2 would prove at all satisfactory when treating turbid water, whileNo. 3 could be depended on under all conditions. The results ofoperation are shown in detail in Tables 17, 18, and 19. It will benoticed in Table 17, that on March 10th, 1908, Filter Plant No. 1was put out of service and a Puech system of preliminary filters wassubstituted for it. 

The Puech preliminary filters consisted of five units containinggravel of varying sizes through which the water was filteredsuccessively before it was finally applied to the final slow sandfilter. A general idea of this system may be obtained by referringto Figure 8. 

 ~Table 16--Turbidity Results with Experimental Filters, During Period of High Turbidity, January, 1908. ~

 Columns: A - Effluent preliminary filter. B - Effluent sand filter. C - Effluent preliminary filter. D - Effluent sand filter. E - Effluent coagulant basin. F - Effluent sand filter. 

 ============+======+=============+=============+============== | Raw |Filter No. 1. |Filter No. 2. |Filter No. 3. Date. |water. |------+------+------+------+------+------- | | A | B | C | D | E | F ------------+------+------+------+------+------+------+------- January 12th| 40 | 10 | 1 | 12 | 1 | 2 | 0 January 13th| 110 | 45 | 2 | 51 | 2 | 2 | 0 January 14th| 210 | 95 | 3 | 113 | 4 | 2 | 0 January 15th| 325 | 190 | 12 | 222 | 15 | 3 | 0 January 16th| 360 | 210 | 37 | 247 | 42 | 5 | 0 January 17th| 242 | 122 | 24 | 147 | 26 | 6 | 0 January 18th| 137 | . . . | . . . | 73 | 7 | 6 | 0 January 19th| 117 | 40 | 12 |clean-| . . . | 5 | 0 | | | | ing | | | January 20th| 72 | 31 | 6 | sand | . . . |clean-| 0 | | | |filter| | ing | January 21st| 55 | 20 | 4 | 25 | 4 | sand | . . . January 22d | 49 | 17 | 3 | 21 | 4 |filter| . . . January 23d | 40 | 12 | 3 | 15 | 3 | 3 | 0 January 24th| 40 | 11 | 3 | 13 | 3 | 3 | 0 ============+======+======+======+======+======+======+=======

It is unfortunate that this system was not in operation in January, 1908, when the water was cold and turbid. The results, however, indicate that it would be no more successful than either FilterPlant No. 1 or No. 2. 

_Experimental Rate Studies. _--In September, 1908, an experimentalplant consisting of six small filters was put in operation. Theobject of these experiments was to study the relative efficienciesand cost for the operation of slow sand filters when operated atdifferent rates. 

The units of the plant consisted of cylindrical galvanized-irontanks 4 ft. In diameter and 9 ft. High. The filter sand in thesetanks was taken from the supply for the main filters. It wassupported on gravel layers and supplied with under-drains ofsuitable sizes for the proposed rate of flow in each case. 

The units of the experimental plant were designated as Nos. 1, 2, 3, 4, 5, and 6, and it was the original intention to operate them atrates of 1, 000, 000, 3, 000, 000, 6, 000, 000, 10, 000, 000, 30, 000, 000, and 100, 000, 000 gal. Per acre daily, respectively. 

This schedule of rates was carried out in a general way with all thefilters, with the exception of Nos. 5 and 6. For these, the rateswere found to be higher than could be maintained for any greatlength of time, owing to the deeper penetration of the mud in thefilter sand, which caused high initial losses of head, short runs, and deep scrapings. A rate of about 30, 000, 000 gal. Was maintainedin the case of Filter No. 5 from the time it was started onSeptember 9th, 1908, until November 8th, 1909, when it was reducedto about 17, 000, 000 gal. , which rate was maintained thereafter untilthe filter was shut down in February, 1910. 

[Illustration: ~Figure 7--Plan of Filter-House and Equipment. ~]

In the case of Filter No. 6, it was found impossible to maintain arate of 100, 000, 000 gal. For more than a very few days at a time. Itwas started at about this rate, however, at the beginning of eachrun, and kept as high as possible for the remainder of the timeduring the first seven runs. At the end of the seventh run, onOctober 17th, 1908, the filter was given a very deep scraping andre-sanded. 

[Illustration: ~Figure 8--Diagrammatic Sketch Showing Arrangements forTesting "Puech" System of Water Filtration at Washington D. C. , U. S. A. ~]

The layer of clean sand restored the original capacity, and thefilter was operated as before, but with gradually decreasing ratesuntil December, 1908, when the rate was reduced to about 40, 000, 000gal. Even this lower rate was too high to be maintained withoutremoving and replacing a large part of the sand. The rates, therefore, gradually decreased to about 23, 000, 000 gal. On March13th, 1909, when the filter was again re-sanded. After thisre-sanding the rate was reduced to about 20, 000, 000 gal. , and thefilter was operated at approximately that rate until it was againre-sanded on November 13th, 1909, when the rate was again reduced toabout 14, 000, 000 gal. , which was maintained until the filter was putout of service on February 28th, 1910. 

This experimental plant was in service from September, 1908, to thelatter part of February, 1910, or for about 1-1/2 years, and theleading results are summarized in Table 20. 

 ~Table 17--Record of Experimental Filter Plant No. 1. ~

 Columns: A - Rate, millions of gallons per acre daily. B - Loss of head. C - Rate, millions of gallons per acre daily. D - Loss of head. E - Applied water. F - Effluent preliminary filter. G - Effluent final filter. H - Applied water. I - Effluent preliminary filter. J - Effluent final filter. 

 =======+===========+===========+=================+==================== |Preliminary| Final | Turbidity. | Bacteria. | Filter. | Filter. | | Date. |-----+-----+-----+-----+-----+-----+-----+------+------+------ | A | B | C | D | E | F | G | H | I | J -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ 1907. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Feb. 8|19. 40| 0. 71| 3. 10| 0. 17 | . . . | . . . | . . . | 1, 100| 2, 000|2, 500 Feb. 9|21. 50| 0. 81| 3. 11| 0. 16 | . . . | . . . | . . . | 200| 950| 500 Feb. 10|20. 60| 0. 95| 3. 04| 0. 14 | . . . | . . . | . . . | . . . | . . . | . . . Feb. 11|20. 10| 1. 08| 3. 03| 0. 12 | 12 | 3 | 2 | 600| 900|1, 300 Feb. 12|19. 80| 1. 23| 3. 02| 0. 13 | 14 | 4 | 2 | 650| 650| 650 Feb. 13|19. 50| 1. 38| 2. 96| 0. 12 | 15 | 6 | 2 | 600| 600| 950 Feb. 14|21. 20| 1. 67| 3. 21| 0. 11 | 15 | 4 | 2 | 650| 700| 800 Feb. 15|25. 40| 2. 03| 3. 90| 0. 13 | 12 | 4 | 2 | 600| 550| 800 Feb. 16|25. 00| 2. 23| 3. 89| 0. 12 | 14 | 3 | 2 | 850| 550| 500 Feb. 17| Shut down for changes in size of meter and piping. | Feb. 18| . . . | . . . | . . . | . . . | . . . | . . . | . . . | 1, 200| . . . | 650 Feb. 21|38. 60| 1. 59| 3. 93| 0. 18 | 20 | 4 | 2 | 1, 800| 1, 100| 700 Feb. 22|38. 00| 1. 84| 3. 92| 0. 15 | 15 | 3 | 2 | Holiday. Feb. 23|42. 10| 2. 36| 3. 95| 0. 14 | 20 | 5 | 2 | 1, 600| 600| 220 Feb. 24|47. 90| 3. 04| 3. 93| 0. 13 | 20 | 6 | 3 | Sunday. Feb. 25| Shut down change meter | 1, 400| 800| 450 | from outlet to inlet. | | | Feb. 27| . . . | 2. 24| . . . | 0. 13 | 17 | 6 | 3 | 700| 550| 280 Feb. 28|49. 80| 2. 55| 3. 90| 0. 13 | 15 | 6 | 3 | 800| 470| 230 -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Mar. 1|50. 00| 2. 90| 3. 93| 0. 13 | 15 | 5 | 3 | 650| 450| 140 Mar. 2|50. 20| 3. 21| 3. 93| 0. 13 | 15 | 5 | 3 | 1, 000| 650| 200 Mar. 3|38. 80| 3. 09| 3. 89| 0. 13 | 31 | 8 | 3 | Sunday. Mar. 4|50. 00| 3. 54| 3. 93| 0. 12 | 35 | 10 | 5 | 1, 200| . . . | . . . Mar. 5|50. 00| 4. 01| 3. 90| 0. 13 |135 | 39 | 8 |13, 000| 3, 700| 600 Mar. 6|50. 00| 4. 82| 3. 90| 0. 13 |135 | 39 | 8 |18, 000| 4, 500| . . . Mar. 7|50. 00| 5. 89| 3. 90| 0. 13 |102 | 34 | 6 |24, 000| 5, 000|2, 000 Mar. 8|50. 00| 6. 58| 3. 90| 0. 13 |100 | 25 | 4 |22, 000| 5, 000|1, 400 Mar. 9|50. 00| 7. 21| 3. 93| 0. 13 | 90 | 25 | 4 |24, 000| 4, 000| 650 Mar. 10|50. 00| 7. 52| 3. 90| 0. 13 | 82 | 22 | 5 | Sunday. |Washed. Mar. 11|50. 00| 0. 84| 3. 90| 0. 13 | 68 | 19 | 6 |18, 000| 2, 100| 350 Mar. 12|50. 00| 0. 95| 3. 96| 0. 13 | 46 | 19 | 4 |11, 000| 6, 000| 310 Mar. 13|50. 00| 1. 17| 3. 99| 0. 13 | 40 | 19 | 4 | 9, 000| 4, 900| 300 Mar. 14|50. 00| 1. 53| 4. 01| 0. 13 | 39 | 17 | 4 | 5, 500| 1, 300| 130 Mar. 15|50. 00| 2. 27| 4. 05| 0. 13 | 35 | 15 | 4 | 6, 500| 1, 500| 60 Mar. 16|50. 00| 3. 08| 4. 03| 0. 13 | 60 | 20 | 4 | 5, 000| 1, 200| 100 Mar. 17|50. 00| 4. 26| 4. 03| 0. 13 |135 | 35 | 4 | Sunday. Mar. 18|50. 00| 5. 65| 4. 00| 0. 13 |170 | 49 | 7 | 9, 000| 1, 200| 95 Mar. 19|50. 00| 7. 02| 4. 01| 0. 13 |125 | 37 | 6 | 7, 000| 600| 100 |Washed. Mar. 20|50. 00| 1. 08| 3. 98| 0. 13 |102 | 30 | 5 | 4, 800| 300| 75 Mar. 21|50. 00| 1. 23| 3. 98| 0. 12 |125 | 32 | 4 | 8, 500| 1, 000| 85 Mar. 22|50. 00| 1. 46| 4. 00| 0. 13 |190 | 65 | 4 | 7, 500| 1, 100| 45 Mar. 23|50. 00| 1. 76| 3. 99| 0. 13 |180 | 65 | 6 | 7, 500| 600| 55 Mar. 24|50. 00| 2. 11| 3. 99| 0. 12 |140 | 52 | 7 | Sunday. Mar. 25|50. 00| 2. 46| 4. 00| 0. 11 | 88 | 30 | 5 | 4, 400| 500| 85 Mar. 26|50. 00| 2. 75| 4. 00| 0. 12 | 62 | 22 | 4 | 3, 600| 300| 65 Mar. 27|50. 00| 3. 04| 4. 08| 0. 13 | 47 | 18 | 4 | 2, 200| 160| 60 Mar. 28|50. 00| 3. 38| 3. 94| 0. 11 | 35 | 10 | 3 | 1, 300| 100| 55 Mar. 29|50. 00| 3. 70| 4. 00| 0. 11 | 26 | 8 | 3 | 700| 80| 29 Mar. 30|50. 00| 4. 42| 4. 00| 0. 11 | 25 | 6 | 3 | 310| 70| 35 Mar. 31|50. 00| 5. 25| 3. 99| 0. 11 | 21 | 5 | 2 | Sunday. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Apr. 1|50. 00| 6. 14| 4. 00| 0. 12 | 20 | 5 | 2 | 600| 25| 30 |Washed. Apr. 2|50. 00| 2. 10| 4. 00| 0. 12 | 24 | 5 | 2 | 270| 28| 32 Apr. 3|50. 00| 3. 00| 4. 00| 0. 12 | 24 | 5 | 2 | 460| 26| 43 Apr. 4|50. 00| 4. 01| 4. 00| 0. 12 | 20 | 5 | 2 | 280| 20| 26 Apr. 5|50. 00| 5. 15| 4. 00| 0. 12 | 20 | 4 | 2 | 450| 37| 41 |Washed. Apr. 6|50. 00| O. 76| 3. 59| 0. 12 | 20 | 4 | 2 | 320| 6| 34 Apr. 7|50. 00| O. 99| 3. 47| 0. 12 | 20 | 4 | 2 | Sunday. Apr. 8|50. 00| 1. 39| 4. 03| 0. 14 | 18 | 3 | 2 | 330| 10| 20 Apr. 9|50. 00| 2. 04| 4. 01| 0. 13 | 18 | 3 | 2 | 140| 9| 35 Apr. 10|50. 00| 3. 03| 4. 02| 0. 13 | 30 | 2 | 1 | 750| 43| 29 Apr. 11|50. 00| 4. 45| 4. 02| 0. 14 | 66 | 1 | 1 | 4, 000| 900| 26 Apr. 12|50. 00| 6. 14| 4. 01| 0. 13 | 72 | 11 | 2 |14, 000| 1 700| 41 |Washed. Apr. 13|50. 00| 0. 95| 4. 00| 0. 14 | 80 | 21 | 2 |13, 000| 1 300| 70 Apr. 14|50. 00| 1. 18| 4. 00| 0. 13 | 77 | 25 | 3 | Sunday. Apr. 15|50. 00| 1. 57| 4. 00| 0. 14 | 62 | 21 | 3 | 7, 000| 380| 55 Apr. 16|50. 00| 2. 33| 4. 00| 0. 15 | 47 | 20 | 3 | 3, 600| 160| 33 Apr. 17|50. 00| 3. 33| 4. 00| 0. 15 | 39 | 15 | 2 | 1, 600| 70| 39 Apr. 18|50. 00| 4. 81| 4. 00| 0. 16 | 30 | 10 | 2 | 1, 810| 130| 34 Apr. 19|50. 00| 6. 29| 3. 99| 0. 16 | 25 | 7 | 2 | 790| 50| 32 |Washed. Apr. 20|50. 00| 0. 93| 4. 01| 0. 16 | 20 | 5 | 2 | 540| 24| 28 Apr. 21|50. 00| 1. 36| 3. 97| 0. 16 | 20 | 3 | 2 | Sunday. Apr. 22|50. 00| 2. 22| 4. 02| 0. 16 | 18 | 2 | 1 | 235| 15| 28 Apr. 23|50. 00| 3. 33| 3. 99| 0. 14 | 15 | 2 | 1 | 170| 14| 16 Apr. 24|50. 00| 4. 78| 3. 97| 0. 15 | 19 | 1 | 1 | 150| 32| 14 Apr. 25|50. 00| 6. 43| 3. 90| 0. 15 | 34 | 1 | 1 | 700| 20| 18 |Washed. Apr. 26|50. 00| O. 97| 3. 97| 0. 14 | 46 | 2 | 1 | 1, 200| 16| 16 Apr. 27|50. 00| 2. 37| 4. 00| 0. 14 | 52 | 3 | 1 | 1, 700| 25| 17 Apr. 28|50. 00| 5. 33| 3. 99| 0. 14 | 45 | 4 | 1 | Sunday. |Washed. Apr. 29|50. 00| 0. 81| 3. 99| 0. 14 | 44 | 5 | 1 | 600| 16| 17 Apr. 30|50. 00| 1. 75| 3. 99| 0. 14 | 39 | 6 | 1 | 550| 27| 12 -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ May 1|50. 00| 0. 80| 3. 99| 0. 14 | 31 | 5 | 1 | 500| 24| 11 |Washed. May 2|50. 00| 1. 13| 4. 00| 0. 14 | 24 | 4 | 1 | 500| 12| 16 May 3|50. 00| 2. 09| 4. 00| 0. 14 | 19 | 3 | 1 | 280| 30| 25 May 4|50. 00| 3. 80| 4. 00| 0. 14 | 16 | 2 | 1 | 400| 20| 12 May 5|50. 00| 5. 38| 4. 00| 0. 14 | 15 | 1 | 1 | Sunday. |Washed. May 6|50. 00| 0. 91| 3. 90| 0. 14 | 13 | 1 | 1 | 390| 50| 40 May 7|50. 00| 1. 56| 3. 90| 0. 14 | 12 | 1 | 1 | 190| 19| 80 May 8|50. 00| 2. 25| 3. 99| 0. 14 | 10 | 1 | 1 | . . . | . . . | . . . May 9|50. 00| 3. 37| 4. 00| 0. 14 | 10 | 1 | 1 | 390| 21| 38 May 10|50. 00| 5. 16| 4. 00| 0. 14 | 10 | 1 | 1 | 300| 14| 13 |Washed. May 11|50. 00| 1. 03| 4. 00| 0. 14 | 12 | 1 | 1 | 390| 13| 12 May 12|50. 00| 1. 89| 4. 00| 0. 14 | 17 | 1 | 1 | Sunday. May 13|50. 00| 3. 82| 4. 00| 0. 14 | 35 | 2 | 1 | 600| 33| 15 May 14|50. 00| 6. 31| 4. 00| 0. 14 | 39 | 3 | 1 | 500| 27| 7 |Washed. May 15|50. 00| 0. 85| 4. 00| 0. 14 | 17 | 2 | 1 | 500| 20| 29 May 16|50. 00| 1. 42| 3. 99| 0. 14 | 24 | 2 | 1 | 290| 19| 40 May 17|50. 00| 2. 47| 3. 99| 0. 14 | 18 | 2 | 1 | 260| 19| 16 May 18|50. 00| 4. 31| 4. 00| 0. 13 | 15 | 1 | 1 | 190| 16| 20 |Washed. May 19|50. 00| 0. 83| 3. 99| 0. 13 | 12 | 1 | 1 | Sunday. May 20|50. 00| 1. 66| 4. 00| 0. 13 | 12 | 1 | 1 | 260| 17| 41 May 21|50. 00| 3. 83| 4. 00| 0. 13 | 16 | 1 | 1 | 260| 26| 25 |Washed. May 22|50. 00| 0. 82| 3. 99| 0. 13 | 20 | 1 | 1 | 280| 16| 19 May 23|50. 00| 1. 64| 4. 00| 0. 13 | 15 | 1 | 1 | 130| 20| 22 May 24|50. 00| 3. 85| 4. 00| 0. 13 | 15 | 1 | 1 | 170| 17| 32 |Washed. May 25|50. 00| 0. 84| 4. 00| 0. 13 | 15 | 1 | 1 | 340| 25| 55 May 26|50. 00| 1. 67| 3. 99| 0. 13 | 18 | 1 | 1 | Sunday. May 27|50. 00| 3. 03| 4. 00| 0. 13 | 13 | 1 | 1 | 210| 10| 40 |Washed. May 28|50. 00| 0. 87| 4. 01| 0. 13 | 16 | 1 | 1 | 260| 26| 55 May 29|50. 00| 1. 43| 4. 01| 0. 13 | 16 | 1 | 1 | 500| 19| 50 May 30|50. 00| 2. 55| 4. 00| 0. 13 | 14 | 1 | 1 | Holiday. May 31|50. 00| 4. 19| 4. 00| 0. 13 | 17 | 1 | 1 | 380| 22| 50 -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ June 1|50. 00| 6. 26| 3. 99| 0. 13 | 15 | 1 | 1 | 900| 27| 50 |Washed. June 2|50. 00| 0. 78| 3. 98| 0. 13 | 17 | 1 | 1 | Sunday. June 3|50. 00| 1. 19| 4. 00| 0. 13 | 24 | 1 | 1 | 550| 41| 50 June 4|50. 00| 2. 15| 4. 00| 0. 13 | 37 | 2 | 1 | 6, 500| 150| 60 June 5|50. 00| 3. 67| 4. 01| 0. 13 | 65 | 4 | 1 | 3, 200| 150| 46 June 6|50. 00| 6. 06| 4. 00| 0. 14 | 77 | 12 | 1 | 1, 500| 60| 27 |Washed. June 7|50. 00| 0. 86| 4. 00| 0. 14 | 64 | 19 | 1 | 2, 100| 68| 45 June 8|50. 00| 1. 41| 4. 00| 0. 14 | 46 | 16 | 1 | 600| 35| 44 June 9|50. 00| 2. 62| 4. 01| 0. 14 | 44 | 12 | 1 | Sunday. June 10|50. 00| 4. 79| 4. 00| 0. 14 | 36 | 8 | 1 | 240| 31| 35 |Washed. June 11|50. 00| 0. 77| 4. 00| 0. 14 | 30 | 6 | 1 | 280| 47| 47 June 12|50. 00| 1. 20| 4. 01| 0. 14 | 34 | 6 | 1 | 330| 70| 55 June 13|50. 00| 2. 42| 4. 00| 0. 14 | 35 | 8 | 1 | 480| 43| 75 June 14|50. 00| 4. 44| 4. 00| 0. 15 | 31 | 7 | 1 | 440| 55| 45 |Washed. June 15|50. 00| 0. 80| 3. 99| 0. 15 | 32 | 6 | 1 | 420| 17| 34 June 16|50. 00| 1. 15| 4. 00| 0. 15 | 26 | 5 | 1 | Sunday. June 17|50. 00| 2. 15| 3. 99| 0. 14 | 26 | 5 | 1 | 340| 55| 37 June 18|50. 00| 4. 36| 4. 00| 0. 14 | 31 | 6 | 1 | 440| 14| 140 |Washed. June 19|50. 00| 0. 79| 4. 01| 0. 15 | 37 | 8 | 1 | 500| 70| 24 June 20|50. 00| 1. 19| 4. 00| 0. 15 | 30 | 7 | 1 | 330| 49| 27 June 21|50. 00| 2. 65| 3. 98| 0. 14 | 25 | 5 | 1 | 170| 30| 18 June 22|50. 00| 5. 58| 4. 00| 0. 14 | 20 | 4 | 1 | 100| 18| 13 |Washed. June 23|50. 00| 0. 85| 3. 62| 0. 13 | 26 | 3 | 1 | Sunday. June 24|50. 00| 2. 02| 3. 99| 0. 13 |140 | 11 | 1 | 1, 700| 27| 36 June 25|50. 00| 4. 77| 3. 99| 0. 13 |130 | 26 | 1 | 400| 70| 23 |Washed. June 26|50. 00| 0. 73| 4. 01| 0. 13 | 82 | 27 | 1 | 750| 200| 41 June 27|50. 00| 1. 17| 4. 01| 0. 13 | 65 | 18 | 1 | . . . | . . . | . . . June 28|50. 00| 3. 10| 3. 99| 0. 13 | 47 | 16 | 1 | . . . | 20| . . . |Washed. June 29|50. 00| 0. 67| 3. 99| 0. 13 | 37 | 7 | 1 | 220| 35| 29 June 30|50. 00| 1. 02| 4. 00| 0. 13 | 30 | 6 | 1 | Sunday. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ July 1|50. 00| 2. 70| 3. 99| 0. 13 | 30 | 6 | 1 | 400| 46| 3 |Washed. July 2|50. 00| 0. 69| 4. 00| 0. 13 | 32 | 7 | 1 | 180 | 80| 38 July 3|50. 00| 1. 21| 3. 99| 0. 13 | 36 | 8 | 1 | 350 | 70| 90 July 4|50. 00| 3. 40| 3. 99| 0. 13 | 44 | 10 | 1 | Holiday. |Washed. July 5|50. 00| 0. 77| 3. 99| 0. 13 | 44 | 11 | 1 | 550 | 180| 34 July 6|50. 00| 1. 19| 4. 01| 0. 13 | 39 | 10 | 1 | 250 | 60| 26 July 7|50. 00| 3. 72| 3. 99| 0. 13 | 34 | 8 | 1 | Sunday. |Washed. July 8|50. 00| 0. 78| 3. 97| 0. 13 | 25 | 5 | 1 | 220 | 31| 21 July 9|50. 00| 1. 27| 3. 98| 0. 13 | 22 | 4 | 1 | 50 | 10| 9 July 10|50. 00| 3. 11| 4. 09| 0. 13 | 47 | 9 | 1 | Lost. |Washed. July 11|50. 00| 0. 83| 3. 99| 0. 13 | 90 | 19 | 1 | 150 | 19| 8 July 12|50. 00| 1. 47| 3. 99| 0. 13 | 97 | 25 | 1 | 300 | 40| 23 July 13|50. 00| 3. 61| 4. 00| 0. 13 | 96 | 29 | 1 | 220 | 47| 16 |Washed. July 14|50. 00| 0. 84| 3. 99| 0. 13 | 90 | 30 | 1 | Sunday. July 15|50. 00| 1. 30| 4. 00| 0. 13 | 95 | 30 | 1 | 375 | 55| 21 July 16|50. 00| 2. 72| 3. 99| 0. 14 |120 | 35 | 1 | Lost. | 90| 13 July 17|50. 00| 5. 08| 3. 99| 0. 14 | 85 | 32 | 1 | 270 | 2| 11 |Washed. July 18|50. 00| 0. 85| 3. 99| 0. 14 | 56 | 22 | 1 |1, 675 | 70| 50 July 19|50. 00| 1. 43| 4. 00| 0. 14 | 41 | 12 | 1 | 450 | 95| 22 July 20|50. 00| 3. 23| 3. 99| 0. 14 | 62 | 19 | 1 | 300 | 38| 11 |Washed. July 21|50. 00| 0. 80| 3. 99| 0. 14 | 62 | 21 | 1 | Sunday. July 22|50. 00| 1. 06| 3. 98| 0. 14 | 80 | 26 | 1 |1, 400 | 150| 7 July 23|50. 00| 2. 18| 3. 99| 0. 14 |105 | 30 | 1 |3, 700 | Lost. | 11 July 24|50. 00| 4. 95| 3. 98| 0. 15 | 95 | 30 | 1 | 770 | Lost. | 22 |Washed. July 25|50. 00| 0. 84| 3. 98| 0. 15 | 77 | 22 | 1 | 250 | 33| 11 July 26|50. 00| 1. 22| 3. 98| 0. 15 | 67 | 19 | 1 | 140 | 100| 4 July 27|50. 00| 2. 36| 4. 00| 0. 16 | 54 | 15 | 1 | 300 | 95| 7 July 28|50. 00| 4. 74| 3. 98| 0. 16 | 46 | 12 | 1 | Sunday. |Washed. July 29|50. 00| 0. 83| 3. 99| 0. 17 | 36 | 10 | 1 | 470 | 110 | 18 July 30|50. 00| 1. 02| 4. 00| 0. 17 | 29 | 7 | 1 | Plates lost. July 31|50. 00| 1. 66| 4. 00| 0. 17 | 21 | 5 | 1 | Plates lost. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Aug. 1|48. 20| 2. 95| 4. 00| 0. 17 | 16 | 4 | 1 | Plates lost. Aug. 2|46. 40| 4. 96| 4. 00| 0. 17 | 15 | 2 | 1 | 130 | 42| 13 |Washed. Aug. 3|42. 60| 0. 79| 4. 00| 0. 17 | 16 | 1 | 1 | 120 | 4| 16 Aug. 4|49. 10| 0. 91| 4. 00| 0. 17 | 21 | 1 | 1 | Sunday. Aug. 5|49. 10| 1. 59| 4. 00| 0. 17 | 29 | 1 | 1 | 230 | 160| 11 Aug. 6|48. 20| 3. 16| 4. 00| 0. 17 | 34 | 2 | 1 | 85 | 200| 12 Aug. 7|45. 60| 5. 65| 3. 99| 0. 17 | 21 | 2 | 1 | 200 | Lost | 4 |Washed. Aug. 8|50. 00| 0. 80| 3. 99| 0. 17 | 19 | 2 | 1 | 100 | 70| 11 Aug. 9|49. 10| 0. 94| 4. 00| 0. 17 | 16 | 1 | 1 | 75 | 44| 9 Aug. 10|48. 20| 1. 51| 4. 00| 0. 17| 24 | 1 | 1 | 60 | 13| 6 Aug. 11|48. 20| 3. 32| 4. 00| 0. 17| 62 | 3 | 1 | Sunday. |Washed. Aug. 12|41. 90| 0. 83| 3. 99| 0. 17| 120 | 14 | 1 | 620 | 110| 5 Aug. 13|49. 10| 1. 14| 3. 99| 0. 17| 107 | 29 | 1 | 820 | 53| 36 Aug. 14|49. 10| 1. 72| 4. 00| 0. 18| 82 | 30 | 1 | 850 | 160| 110 Aug. 15|48. 20| 3. 30| 4. 00| 0. 18| 65 | 22 | 1 | 150 | 37| 4 Aug. 16|46. 40| 0. 84| 4. 00| 0. 19| 45 | 15 | 1 | 270 | 110| 13 Aug. 17|48. 20| 1. 05| 4. 00| 0. 19| 35 | 10 | 1 | 340 | 110| 6 Aug. 18|50. 00| 1. 54| 4. 00| 0. 19| 21 | 5 | 1 | Sunday. Aug. 19|49. 10| 2. 29| 4. 00| 0. 19| 18 | 4 | 1 | 180 | 85| 13 Aug. 20|49. 10| 3. 74| 3. 99| 0. 19| 20 | 2 | 1 | 210 | 85| 8 |Washed. Aug. 21|44. 10| 1. 01| 3. 98| 0. 19| 20 | 2 | 1 | 1300 | 115| 9 Aug. 22|45. 60| 1. 86| 4. 00| 0. 19| 27 | 2 | 1 | 3800 | 265| 1 Aug. 23|47. 30| 4. 08| 3. 99| 0. 19| 49 | 2 | 1 | 2500 | 70| 13 |Washed. Aug. 24|41. 30| 1. 29| 3. 97| 0. 19| 36 | 6 | 1 | 3900 | 46| 6 Aug. 25|44. 10| 2. 11| 3. 98| 0. 20| 34 | 7 | 1 | Sunday. Aug. 26|48. 20| 3. 42| 3. 99| 0. 20| 21 | 5 | 1 | 700 | 140| 0 Aug. 27|48. 20| 5. 10| 4. 00| 0. 20| 19 | 4 | 1 | 470 | 100| 4 |Washed. Aug. 28|46. 40| 1. 28| 4. 00| 0. 20| 18 | 3 | 1 | 500 | 49| 3 Aug. 29|41. 90| 1. 90| 4. 02| 0. 20| 17 | 2 | 1 | 360 | 80| 0 Aug. 30|45. 60| 3. 23| 4. 00| 0. 20| 15 | 1 | 1 | 320 | 190| 1 Aug. 31|46. 40| 4. 57| 4. 00| 0. 20| 13 | 1 | 1 | 200 | 20| 3 -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Sept. 1|50. 00| 5. 17| 3. 65| 0. 20| 14 | 1 | 1 | Sunday. Sept. 2|48. 20| 5. 97| 4. 00| 0. 20| 12 | 1 | 1 | Holiday. |Washed. Sept. 3|47. 30| 1. 13| 4. 00| 0. 20| 12 | 1 | 1 | 300 | 9| 1 Sept. 4|48. 20| 2. 01| 4. 00| 0. 20| 16 | 1 | 1 | 600 | 60| 2 Sept. 5|46. 40| 5. 41| 3. 67| 0. 20| 34 | 1 | 0 | 360 | 72| . . . |Washed. Sept. 6|40. 60| 1. 42| 3. 98| 0. 20| 160 | 12 | 0 |15000 | 140| 0 Sept. 7|42. 60| 5. 19| 3. 99| 0. 20| 64 | 18 | 1 | 2000 | 130| 1 |Washed. Sept. 8|42. 60| 1. 25| 4. 00| 0. 20| 56 | 18 | 1 | Sunday. Sept. 9|46. 40| 3. 07| 4. 00| 0. 22| 59 | 18 | 1 | 220 | 80| 4 |Washed. Sept. 10|45. 60| 1. 02| 3. 99| 0. 23| 57 | 16 | 1 |18000 | 57| 8 Sept. 11|48. 20| 2. 36| 4. 00| 0. 23| 65 | 18 | 1 | 2700 | 90| 1 |Washed. Sept. 12|44. 10| 1. 14| 3. 99| 0. 24| 72 | 18 | 1 | 1000 | 47| 4 Sept. 13|46. 40| 3. 61| 3. 99| 0. 25| 87 | 20 | 1 | 2300 | 77| 5 |Washed. Sept. 14|38. 20| 1. 42| 3. 97| 0. 26| 72 | 19 | 1 | 2400 | 80| 5 Sept. 15|45. 60| 4. 27| 4. 00| 0. 27| 65 | 18 | 1 | Sunday. |Washed. Sept. 16|40. 00| 1. 06| 3. 99| 0. 28| 65 | 18 | 1 | Lost. | 22|Lost. Sept. 17|46. 40| 2. 48| 4. 01| 0. 28| 52 | 16 | 1 | 420 | 75| 1 |Washed. Sept. 18|46. 40| 1. 11| 4. 00| 0. 28| 60 | 13 | 1 | 900 | 37| 3 Sept. 19|46. 40| 2. 76| 4. 00| 0. 28| 85 | 16 | 1 | 2000 | 186| 0 |Washed. Sept. 20|44. 10| 1. 12| 4. 00| 0. 31| 100 | 19 | 1 | 4200 | 110| 7 Sept. 21|48. 20| 2. 07| 3. 99| 0. 33| 120 | 24 | 1 | 1100 | 110| 3 |Washed. Sept. 22|44. 10| 1. 30| 3. 67| 0. 34| 137 | 29 | 1 | Sunday. Sept. 23|45. 60| 3. 79| 3. 99| 0. 39| 112 | 25 | 1 | 2400 | 50| 2 |Washed. Sept. 24|45. 60| 1. 15| 3. 97| 0. 40| 100 | 25 | 1 | 4000 | 69| 4 Sept. 25|48. 20| 2. 06| 4. 00| 0. 42| 432 | 53 | 1 |56000 | 680| 0 Sept. 26| Stopped, unable to wash preliminary. Sept. 28|50. 00| 1. 74| 4. 00| 0. 71| 127 | 35 | 1 | . . . | . . . | 37 |Washed. Sept. 29|44. 10| 2. 85| 3. 99| 0. 82| 105 | 31 | 1 | Sunday. Sept. 30|44. 90| 3. 78| 3. 97| 1. 04| 115 | 32 | 1 | Lost. | Lost. | 160 |Washed. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Oct. 1|44. 10| 1. 20| 3. 98| 1. 34| 82 | 26 | 1 | 600| 180| 55 Oct. 2|49. 10| 3. 22| 3. 97| 1. 54| 65 | 19 | 1 | 4, 400| 120| 5 |Washed. Oct. 3|44. 10| 1. 31| 3. 97| 1. 56| 59 | 17 | 1 | 900| 55| 10 Oct. 4|49. 10| 2. 97| 3. 97| 1. 65| 55 | 15 | 1 | 850| 60| 6 |Washed. Oct. 5|44. 90| 1. 31| 3. 98| 1. 75| 59 | 16 | 1 | 2, 000| 110| 38 Oct. 6|46. 40| 3. 65| 3. 99| 1. 89| 59 | 17 | 1 | Sunday. |Washed. Oct. 7|44. 90| 1. 34| 3. 98| 1. 99| 52 | 13 | 1 | 1, 250| 70| 15 Oct. 8|49. 10| 3. 49| 3. 98| 2. 17| 54 | 13 | 1 |11, 000| 65| 6 |Washed. Oct. 9|44. 10| 1. 20| 3. 97| 2. 33| 51 | 13 | 1 | 2, 000| 85| 4 Oct. 10|49. 10| 2. 22| 3. 98| 2. 55| 50 | 12 | 1 | 800| 36| 10 Oct. 11|46. 40| 4. 59| 4. 00| 2. 51| 47 | 11 | 1 | 2, 000| 57| 10 Oct. 12| Shut off to remove sand in preliminary filter in order to | clean out the under-drains. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Nov. 5|50. 00| 1. 38| 3. 97| 3. 49| 185 | 50 | 1 | . . . | . . . | . . . Nov. 6|48. 20| 3. 25| 3. 98| 3. 79| 170 | 52 | 1 | 5, 000| 1, 500| 240 |Washed. Nov. 7|45. 60| 1. 18| 3. 98| 4. 05| 100 | 35 | 1 |14, 000| 1, 000| 220 Nov. 8|48. 20| 4. 08| 3. 99| 4. 37| 95 | 32 | 1 | 1, 900| 270| 160 Nov. 9|42. 00| 6. 58| 3. 98| 4. 39| 80 | 27 | 1 | 4, 000| 500| 190 Nov. 10| Shut down for scraping. Removed 266, 000 cu. Cm. Of sand. Nov. 12|50. 00| 0. 98| 3. 99| 0. 25| 40 | 10 | 1 | . . . | . . . | . . . Nov. 13|50. 00| 1. 51| 4. 00| 0. 22| 36 | 8 | 1 | 1, 600| 750| 85 Nov. 14|48. 20| 2. 60| 4. 00| 0. 21| 42 | 11 | 1 | 2, 700| 700| 210 Nov. 15|47. 30| 3. 80| 4. 00| 0. 20| 35 | 9 | 1 | 1, 800| 350| 180 Nov. 16|47. 30| 4. 87| 4. 00| 0. 19| 26 | 5 | 1 | 1, 100| 200| 34 Nov. 17|50. 00| 5. 75| 4. 00| 0. 19| 20 | 4 | 1 | Sunday. Nov. 18|50. 00| 6. 41| 4. 00| 0. 19| 17 | 3 | 1 | 1, 600| 290| 55 |Washed. Nov. 19|48. 20| 1. 06| 3. 99| 0. 20| 16 | 2 | 1 | 1, 300| 480| 60 Nov. 20|48. 20| 2. 05| 3. 99| 0. 20| 45 | 3 | 1 | 6, 500| 3, 700| 800 Nov. 21|48. 20| 3. 48| 3. 99| 0. 20| 52 | 9 | 1 | 9, 900| 4, 000| 300 Nov. 22|47. 30| 4. 85| 3. 99| 0. 20| 65 | 17 | 1 |10, 000| 1, 000| 380 Nov. 23|48. 20| 6. 11| 3. 99| 0. 20| 49 | 15 | 1 |18, 000| 1, 000| 320 |Washed. Nov. 24|46. 40| 3. 71| 3. 98| 0. 20| 134 | 24 | 1 | Sunday. Nov. 25| Shut down for fear of washing preliminary | with such muddy water. Nov. 29|50. 00| 1. 55| 4. 00| 0. 21| 80 | 25 | 1 | . . . | . . . | . . . Nov. 30|47. 30| 3. 14| 3. 98| 0. 22| 54 | 16 | 1 | 3, 800| 950| 160 -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Dec. 1|47. 30| 4. 48| 3. 98| 0. 23| 37 | 10 | 1 | Sunday. Dec. 2|47. 30| 5. 63| 3. 98| 0. 25| 36 | 6 | 1 | 2, 900| 550| 90 |Washed. Dec. 3|46. 40| 0. 98| 3. 99| 0. 25| 29 | 6 | 1 | 2, 900| 480| 75 Dec. 4|50. 00| 1. 15| 3. 99| 0. 26| 20 | 4 | 1 | 2, 000| 270| 70 Dec. 5|50. 00| 1. 48| 4. 00| 0. 25| 18 | 3 | 1 | 1, 100| 270| 50 Dec. 6|48. 20| 2. 04| 3. 63| 0. 25| 16 | 2 | 1 | 3, 000| . . . | . . . Dec. 7|48. 20| 2. 80| 4. 00| 0. 26| 14 | 1 | 1 | 2, 400| 190| 10 Dec. 8|50. 00| 3. 40| 3. 72| 0. 27| 12 | 1 | 1 | Sunday. Dec. 9|49. 10| 3. 93| 4. 00| 0. 27| 11 | 1 | 1 | 1, 200| 170| 7 Dec. 10|49. 10| 4. 50| 4. 00| 0. 27| 12 | 1 | 1 | 800| 90| 55 Dec. 11|48. 20| 5. 52| 4. 00| 0. 27| 255 | 44 | 1 | 6, 500| --- | --- Dec. 12| Shut down 12/11 at 6 P. M. Turbidity too high to wash. Dec. 15| --- | --- | --- | --- | --- | --- | --- | Sunday. Dec. 16|50. 00| 4. 02| 3. 99| 0. 28| 90 | 35 | 2 | --- | --- | --- |Washed. Dec. 17|40. 00| 1. 90| 3. 97| 0. 30| 70 | 25 | 2 |21, 000|10, 000|1, 200 |Washed. Dec. 18|44. 10| 1. 08| 3. 97| 0. 31| 49 | 15 | 2 | 6, 500| 4, 200| 800 Dec. 19|48. 20| 1. 88| 3. 98| 0. 31| 39 | 10 | 1 | Lost. | Lost. |Lost. Dec. 20|46. 40| 4. 77| 3. 99| 0. 31| 42 | 13 | 1 | " | " | " Dec. 21|46. 40| 6. 68| 3. 99| 0. 32| 26 | 6 | 1 | " | " | " |Washed. Dec. 22|49. 10| 1. 14| 3. 99| 0. 32| 20 | 4 | 1 | Sunday. Dec. 23|49. 10| 2. 17| 4. 00| 0. 31| 34 | 7 | 1 | 1, 400| 300| 100 Dec. 24|49. 10| 3. 76| 4. 00| 0. 31| 195 | 56 | 1 | 9, 000| 950| 70 Dec. 25|Shut down 12/24 at 9 P. M. Turbidity too high to wash. Holiday Dec. 30|50. 00| 2. 61| 3. 97| 0. 33| 56 | 19 | 2 | --- | --- | --- Dec. 31|44. 80| 5. 57| 3. 98| 0. 36| 39 | 12 | 1 | --- | --- | --- |Washed. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ 1908. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Jan. 1|46. 40| 1. 30| 3. 98| 0. 36| 31 | 6 | 1 | Holiday. Jan. 2|48. 20| 3. 36| 4. 00| 0. 36| 39 | 9 | 1 | --- | --- | --- Jan. 3|47. 30| 4. 95| 3. 99| 0. 35| 36 | 9 | 1 | 3, 100| 490| 90 Jan. 4|50. 00| 5. 28| 3. 99| 0. 35| 32 | 7 | 1 | 2, 400| 240| 43 Jan. 5|49. 10| 6. 26| 4. 00| 0. 35| 26 | 5 | 1 | Sunday. |Washed. Jan. 6|49. 10| 0. 99| 3. 98| 0. 35| 20 | 4 | 1 | 600| 200| 37 Jan. 7|50. 00| 1. 15| 4. 00| 0. 35| 20 | 4 | 1 | 1, 100| 150| 47 Jan. 8|50. 00| 1. 41| 4. 00| 0. 35| 22 | 4 | 1 | 1, 900| 160| 30 Jan. 9|49. 10| 1. 92| 4. 00| 0. 35| 45 | 11 | 1 |13, 000| 1, 300| 70 Jan. 10|49. 10| 2. 56| 4. 00| 0. 36| 70 | 25 | 1 |10, 000| 3, 500| 170 Jan. 11|50. 00| 3. 17| 3. 99| 0. 37| 56 | 18 | 1 |16, 000| 4, 000| 240 Jan. 12|49. 10| 3. 73| 4. 00| 0. 37| 40 | 10 | 1 | Sunday. Jan. 13|50. 00| 4. 14| 4. 00| 0. 37| 110 | 45 | 2 | 8, 500| 1, 200| 840 Jan. 14|49. 10| 4. 65| 3. 99| 0. 38| 210 | 95 | 3 |16, 000| 3, 900| 500 Jan. 15|49. 10| 5. 23| 3. 99| 0. 41| 325 | 190 | 12 |24, 000| 7, 000| 550 Jan. 16|50. 00| 5. 75| 3. 99| 0. 43| 360 | 210 | 37 |28, 000| 8, 500|1, 200 Jan. 17|49. 10| 6. 34| 4. 00| 0. 45| 242 | 122 | 24 |65, 000|15, 000|1, 700 Jan. 18| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- Jan. 19|50. 00| 1. 17| 4. 00| 0. 46| 117 | 40 | 12 | Sunday. Jan. 20|50. 00| 1. 38| 4. 00| 0. 46| 72 | 31 | 6 | 1, 600| 1, 800| 320 Jan. 21|50. 00| 1. 68| 3. 57| 0. 37| 55 | 20 | 4 | 5, 000| 450| Jan. 22|49. 10| 2. 04| 4. 00| 0. 44| 49 | 17 | 3 | 3, 600| 600| 100 Jan. 23|50. 00| 2. 47| 3. 24| 0. 33| 40 | 12 | 3 | 1, 800| 290| 130 Jan. 24|49. 10| 3. 03| 3. 00| 0. 34| 40 | 11 | 2 | 2, 300| 270| 65 Jan. 25|50. 00| 3. 61| 3. 00| 0. 35| 39 | 10 | 2 | 1, 100| 180| 60 Jan. 26|49. 10| 4. 18| 2. 99| 0. 35| 32 | 7 | 2 | Sunday. Jan. 27|50. 00| 4. 81| 3. 00| 0. 35| 32 | 7 | 2 | 300| 40| 24 Jan. 28|48. 20| 5. 45| 2. 99| 0. 35| 45 | 12 | 2 | 1, 200| 90| 31 Jan. 29|49. 10| 6. 01| 2. 99| 0. 35| 60 | 21 | 2 | 1, 000| 230| 50 Jan. 30|49. 10| 6. 62| 2. 99| 0. 36| 57 | 22 | 2 | 1, 400| 170| 48 |Washed. Jan. 31|50. 00| 1. 30| 2. 99| 0. 36| 42 | 15 | 2 | 1, 100| 190| 23 -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Feb. 1|50. 00| 1. 51| 2. 99| 0. 37| 39| 11 | 2 | 750| 40| 31 Feb. 2|50. 00| 1. 78| 3. 00| 0. 37| 27| 7 | 2 | Sunday. Feb. 3|49. 10| 2. 13| 3. 00| 0. 37| 29| 6 | 2 | 1, 300| 200| 7 Feb. 4|50. 00| 2. 69| 3. 00| 0. 37| 25| 5 | 1 | 600| 160| 18 Feb. 5|49. 10| 3. 31| 2. 99| 0. 37| 24| 5 | 1 | 750| 140| 41 Feb. 6|50. 00| 3. 89| 2. 99| 0. 37| 20| 4 | 1 | 2, 000| 180| 29 Feb. 7|48. 20| 4. 50| 2. 99| 0. 37| 17| 3 | 1 | . . . | 38| 15 Feb. 8|49. 10| 5. 11| 2. 99| 0. 37| 15| 3 | 1 | 900| 95| 24 Feb. 9|49. 10| 5. 65| 3. 00| 0. 38| 14| 3 | 1 | Sunday. Feb. 10|49. 10| 6. 43| 2. 99| 0. 38| 11| 3 | 1 | 850| 85| 21 Feb. 11|50. 00| 6. 90| 3. 00| 0. 38| 10| 3 | 1 | 1, 000| 70| 20 |Washed. Feb. 12|49. 10| 1. 29| 2. 99| 0. 38| 8| 2 | 1 | 750| 20| 16 Feb. 13|50. 00| 1. 50| 2. 99| 0. 39| 9| 2 | 1 | 700| 40| 11 Feb. 14|50. 00| 1. 80| 2. 99| 0. 39| 9| 2 | 1 | 1, 200| 39| 7 Feb. 15|49. 10| 2. 35| 3. 00| 0. 39| 61| 13 | 1 | 5, 500| 600| 7 Feb. 16|49. 10| 3. 28| 2. 99| 0. 39| 80| 30 | 2 | Sunday. Feb. 17|48. 20| 4. 85| 2. 99| 0. 39| 80| 29 | 3 |33, 000| 3, 800| 130 Feb. 18|47. 30| 6. 39| 2. 99| 0. 39| 130| 44 | 3 | --- | 2, 600| 160 Feb. 19|45. 50| 7. 32| 2. 98| 0. 40| 320| 143 | 6 |28, 000| 6, 000| 180 |Washed. Feb. 22|50. 00| 1. 40| 3. 00| 0. 41| 85| 30 | 5 | Holiday. Feb. 23|50. 00| 1. 77| 3. 00| 0. 41| 60| 21 | 4 | Sunday. Feb. 24|49. 10| 2. 25| 2. 99| 0. 41| 46| 14 | 3 | 3, 600| 2, 800| 90 Feb. 25|50. 00| 2. 61| 3. 00| 0. 41| 31| 7 | 2 | 2, 300| 140| 47 Feb. 26|50. 00| 3. 06| 3. 00| 0. 41| 30| 6 | 2 | 3, 800| 140| 45 Feb. 27|48. 20| 3. 65| 2. 99| 0. 41| 30| 5 | 1 | 1, 300| 100| 22 Feb. 28|50. 00| 4. 24| 3. 00| 0. 41| 37| 6 | 1 | 1, 400| 100| 40 Feb. 29|48. 20| 5. 28| 2. 99| 0. 41| 123| 52 | 2 |13, 500| 420| 40 |Washed. -------+-----+-----+-----+-----+-----+-----+-----+------+------+------ Mar. 1|44. 60| 1. 56| 2. 99| 0. 42| 97| 39 | 5 | Sunday. Mar. 2|48. 20| 2. 90| 2. 99| 0. 42| 82| 30 | 4 | 8, 000| 320| 60 Mar. 3|46. 40| 4. 69| 2. 98| 0. 42| 87| 33 | 4 |11, 000| 750| 30 Mar. 4|47. 30| 6. 13| 2. 99| 0. 42| 67| 24 | 3 | 6, 000| 290| 34 Mar. 5|48. 20| 7. 31| 2. 99| 0. 42| 59| 19 | 3 | 4, 400| 220| 41 |Washed. Mar. 6|49. 10| 1. 53| 2. 99| 0. 42| 72| 24 | 2 | 7, 000| 170| 41 Mar. 7|50. 00| 1. 95| 3. 00| 0. 43| 82| 30 | 2 | 9, 500| 210| 34 Mar. 8|49. 10| 2. 62| 2. 99| 0. 43| 92| 37 | 3 | Sunday. Mar. 9|50. 00| 3. 19| 3. 00| 0. 43| 125| 56 | 4 |11, 000| 700| 65 Mar. 10|Preliminary filter discontinued and the Puech system started. =======+=====+=====+=====+=====+=====+=====+=====+======+======+======

 ~Table 17--Record of Experimental Filter, Puech system~. --(_Continued. _)

 Columns: A - Rates, millions of gallons per acre daily. B - Rate, millions of gallons per acre daily. C - Loss of head. D - Applied water. E - Effluent, preliminary filter. F - Effluent, final filter. G - Applied water. H - Effluent, preliminary filter. I - Effluent, final filter. 

 =======+===================+=========+============+=================== | ~Puech system~: | ~Final |~Turbidity. ~| ~Bacteria. ~ | | filter~. | | Date. +-------------------+----+----+---+---+----+------+------+----- | A | B | C | D | E | F | G | H | I -------+---+---+---+---+---+----+----+---+---+----+------+------+----- 1908. -------+---+---+---+---+---+----+----+---+---+----+------+------+----- Mar. 11|265|170| 90| 53| 18|2. 99|0. 53|155| 80| 7 | 6, 500| 8, 500| 490 Mar. 12|265|170| 90| 53| 18|2. 99|0. 60|135| 70| 7 | 5, 900| 6, 000| 360 Mar. 13|265|170| 90| 53| 18|3. 00|0. 60|122| 52| 6 | 1, 900| 1, 700| 140 Mar. 14|265|170| 90| 53| 18|3. 00|0. 61| 97| 40| 5 | 1, 800| 1, 600| 130 Mar. 15|265|170| 90| 53| 18|2. 99|0. 64| 77| 31| 4 | Sunday. Mar. 16|265|170| 90| 53| 18|3. 00|0. 69| 65| 26| 3 | 1, 400| 1, 200| 50 Mar. 17|241|155| 82| 48| 16|2. 99|0. 71| 59| 19| 3 | 900| 200| 45 Mar. 18|252|162| 86| 50| 17|2. 99|0. 75| 67| 22| 2 | 1, 000| 700| 33 Mar. 19|241|155| 82| 48| 16|2. 99|0. 78| 60| 21| 2 | . . . | 800| 44 Mar. 20|294|189|100| 59| 20|2. 99|0. 85| 57| 18| 2 | 1, 300| 650| 37 Mar. 21|279|179| 95| 56| 19|2. 99|0. 92| 67| 21| 2 | 800| 600| 34 Mar. 22|265|170| 90| 53| 18|2. 99|0. 99| 80| 27| 2 | Sunday. Mar. 23|265|170| 90| 53| 18|2. 99|1. 06| 90| 32| 2 | 4, 600| 1, 300| 33 Mar. 24|265|170| 90| 53| 18|2. 99|1. 12| 82| 34| 3 | 2, 500| 950| 38 Mar. 25|265|170| 90| 53| 18|2. 99|1. 18| 67| 27| 3 | 1, 600| . . . | 30 Mar. 26|265|170| 90| 53| 18|2. 99|1. 22| 60| 20| 3 | 550| 400| 24 Mar. 27|265|170| 90| 53| 18|3. 00|1. 23| 59| 18| 2 | 950| 360| 28 Mar. 28|265|170| 90| 53| 18|3. 00|1. 25| 51| 14| 2 | 650| 230| 18 Mar. 29|265|170| 90| 53| 18|2. 99|1. 28| 31| 6| 2 | Sunday. Mar. 30|265|170| 90| 53| 18|2. 99|1. 36| 30| 5| 1 | 500| 160| 25 Mar. 31|265|170| 90| 53| 18|2. 99|1. 43| 39| 7| 1 | 750| 140| 26 -------+---+---+---+---+---+----+----+---+---+----+------+------+----- Apr. 1|265|170| 90| 53| 18|3. 00|1. 48| 44| 9| 1 | 750| 60| 41 Apr. 2|265|170| 90| 53| 18|2. 99|1. 56| 42| 9| 1 | 1, 100| 140| 26 Apr. 3|318|204|108| 64| 22|2. 99|1. 63| 41| 8| 1 | 1, 500| 47| 11 Apr. 4|294|189|100| 59| 20|2. 99|1. 70| 54| 13| 1 | 700| 80| 35 Apr. 5|279|179| 95| 56| 19|3. 00|1. 73| 50| 13| 1 | Sunday. Apr. 6|279|179| 95| 56| 19|2. 99|1. 76| 41| 9| 1 | 440| 65| 17 Apr. 7|265|170| 90| 53| 18|3. 00|1. 78| 35| 6| 1 | 650| 65| 34 Apr. 8|265|170| 90| 53| 18|3. 00|1. 79| 39| 6| 1 | 550| 44| 10 Apr. 9|265|170| 90| 53| 18|3. 00|1. 79| 40| 6| 1 | 390| 30| 25 Apr. 10|265|170| 90| 53| 18|3. 00|1. 77| 40| 6| 1 | 500| 27| 16 Apr. 11|265|170| 90| 53| 18|3. 00|1. 78| 45| 7| 1 | 430| 28| 28 Apr. 12|265|170| 90| 53| 18|2. 99|1. 80| 52| 11| 1 | Sunday. Apr. 13|265|170| 90| 53| 18| . . . |1. 81| 50| 10| 1 | 490| 17| 26 Apr. 14| Shut down on account of losing water when aqueduct was |drained; also cleaned coarse sand filter. Started April 22d. Apr. 23|241|155| 82| 48| 16| . . . |1. 82| 29| 4| 1 | 140| 600| 38 Apr. 24|241|155| 82| 48| 16|3. 00|1. 87| 21| 3| 1 | 200| 1, 000| 13 Apr. 25|241|155| 82| 48| 16|2. 99|1. 95| 20| 3| 1 | 85| 180| 25 Apr. 26|252|162| 86| 50| 17|3. 00|1. 95| 24| 3| 1 | Sunday. Apr. 27|241|155| 82| 48| 16|3. 00|1. 93| 18| 2| 1 | 95| 35| 23 Apr. 28|241|155| 82| 48| 16|3. 00|1. 96| 20| 2| 1 | 70| 24| 18 Apr. 29|241|155| 82| 48| 16|2. 99|1. 97| 24| 3| 1 | 110| 21| 24 Apr. 30|241|155| 82| 48| 16|2. 99|2. 03| 21| 2| 1 | 70| 25| 6 -------+---+---+---+---+---+----+----+---+---+----+------+------+----- May 1|241|155| 82| 48| 16|3. 00|2. 07| 32| 4| 1 | 130| 20| 18 May 2|241|155| 82| 48| 16|2. 99|2. 12| 26| 3| 1 | 140| 16| 12 May 3|241|155| 82| 48| 16|2. 99|2. 17| 22| 3| 1 | Sunday. May 4|241|155| 82| 48| 16|3. 00|2. 19| 19| 2| 1 | 85| 30| 17 May 5|241|155| 82| 48| 16|3. 00|2. 20| 18| 2| 1 | 130| 33| 9 May 6|241|155| 82| 48| 16|2. 99|2. 23| 18| 2| 1 | 230| 55| 6 May 7|252|162| 86| 50| 17|3. 00|2. 24| 19| 2| 1 | 160| 75| 10 May 8|241|155| 82| 48| 16|3. 00|2. 25| 19| 2| 1 | 375| 55| 8 May 9|318|204|108| 64| 22|2. 99|2. 29| 18| 2| 1 | 1, 200| 12| 9 May 10|318|204|108| 64| 22|2. 99|2. 30| 30| 3| 1 | Sunday. May 11|265|170| 90| 53| 18|2. 99|2. 33| 60| 10| 1 | 2, 800| 130| 11 May 12|252|162| 86| 50| 17|2. 99|2. 39| 70| 15| 1 | 2, 900| 135| 9 May 13|241|155| 82| 48| 16|3. 00|2. 41| 66| 14| 1 | 1, 800| 110| 16 May 14|265|170| 90| 53| 18|3. 00|2. 38| 45| 7| 1 | 2, 700| 65| 18 May 15|252|162| 86| 50| 17|3. 00|2. 41| 39| 5| 1 | 950| 45| 14 May 16|241|155| 82| 48| 16|3. 00|2. 41| 49| 7| 1 | 800| 32| 10 May 17|241|155| 82| 48| 16|3. 01|2. 34| 46| 7| 1 | Sunday. May 18|241|155| 82| 48| 16|3. 00|2. 31| 31| 4| 1 | 700| 26| 6 May 19|252|162| 86| 50| 17|3. 00|2. 26| 36| 4| 1 | 375| 28| 17 May 20|252|162| 86| 50| 17|3. 00|2. 20| 41| 5| 1 | 425| 38| 11 May 21|344|221|117| 69| 23|3. 00|2. 18| 30| 3| 1 | 300| 25| 9 May 22|241|155| 82| 48| 16|3. 01|2. 17| 53| 7| 1 | 950| 220| 18 May 23|265|170| 90| 53| 18|2. 99|2. 25|127| 38| 1 | 2, 400| 600| 21 May 24|331|212|112| 66| 22|3. 00|2. 19|110| 39| 3 | Sunday. May 25|318|204|108| 64| 22|3. 01|2. 02| 90| 25| 3 | 600| 300| 40 May 26|279|179| 95| 56| 19|3. 02|1. 87|135| 45| 3 | 3, 200| 110| 34 May 27|265|170| 90| 53| 18|3. 01|1. 63|110| 39| 3 |14, 500| 320| 45 May 28|252|162| 86| 50| 17|3. 01|1. 41| 90| 27| 3 | 1, 000| 95| 28 May 29|252|162| 86| 50| 17|3. 01|1. 24| 70| 17| 3 | 1, 100| 150| 26 May 30|252|162| 86| 50| 17|3. 01|1. 07| 50| 9| 2 | Holiday. May 31|241|155| 82| 48| 16|3. 01|1. 03| 34| 4| 2 | Sunday. -------+---+---+---+---+---+----+----+---+---+----+------+------+----- June 1|252|162| 86| 50| 17|3. 00|0. 83| 35| 4| 1 | . . . | . . . | . . . June 2|241|155| 82| 48| 16|3. 00|0. 74| 39| 5| 1 | . . . | . . . | . . . June 3|252|162| 86| 50| 17|3. 00|0. 68| 35| 4| 1 | . . . | . . . | . . . June 4|241|155| 82| 48| 16|3. 00|0. 63| 30| 3| 1 | . . . | . . . | . . . June 5|252|162| 86| 50| 17|2. 99|0. 60| 30| 3| 1 | . . . | . . . | . . . June 6|241|155| 82| 48| 16|3. 00|0. 56| 27| 3| 1 | . . . | . . . | . . . June 7|241|155| 82| 48| 16|2. 99|0. 53| 22| 2| 1 | . . . | . . . | . . . June 8|241|155| 82| 48| 16|3. 00|0. 49| 20| 1| 1 | . . . | . . . | . . . June 9|241|155| 82| 48| 16|2. 99|0. 46| 20| 1| 1 | . . . | . . . | . . . June 10|241|155| 82| 48| 16|3. 00|0. 44| 17| 1| 1 | . . . | . . . | . . . June 11|331|212|112| 66| 22|2. 98|0. 42| 12| 1| 1 | . . . | . . . | . . . June 12|318|204|108| 64| 22|2. 98|0. 42| 11| 1| 1 | . . . | . . . | . . . June 13|265|170| 90| 53| 18|3. 00|0. 40| 36| 3| 1 | . . . | . . . | . . . June 14|252|162| 86| 50| 17|2. 99|0. 40| 39| 5| 1 | . . . | . . . | . . . June 15|241|155| 82| 48| 16|2. 99|0. 39| 25| 3| 1 | . . . | . . . | . . . June 16|241|155| 82| 48| 16|2. 99|0. 40| 34| 3| 1 | . . . | . . . | . . . June 17|252|162| 86| 50| 17|2. 99|0. 41| 64| 11| 1 | . . . | . . . | . . . June 18|241|155| 82| 48| 16|2. 99|0. 42| 57| 11| 1 | . . . | . . . | . . . June 19|241|155| 82| 48| 16|2. 99|0. 42| 46| 8| 1 | . . . | . . . | . . . June 20|241|155| 82| 48| 16|2. 99|0. 42| 40| 5| 1 | . . . | . . . | . . . June 21|241|155| 82| 48| 16|3. 00|0. 43| 28| 4| 1 | . . . | . . . | . . . June 22|241|155| 82| 48| 16|2. 99|0. 43| 25| 3| 1 | . . . | . . . | . . . June 23|241|155| 82| 48| 16|2. 99|0. 43| 25| 3| 1 | . . . | . . . | . . . June 24|241|155| 82| 48| 16|2. 99|0. 43| 29| 4| 1 | . . . | . . . | . . . June 25|241|155| 82| 48| 16|2. 99|0. 43| 18| 2| 1 | . . . | . . . | . . . June 26|241|155| 82| 48| 16|2. 80|0. 42| 15| 1| 1 | . . . | . . . | . . . June 27|241|155| 82| 48| 16|2. 99|0. 44| 12| 1| 1 | . . . | . . . | . . . June 28|241|155| 82| 48| 16|2. 99|0. 44| 9| 1| 1 | . . . | . . . | . . . June 29|241|155| 82| 48| 16|2. 99|0. 44| 8| 1| 1 | . . . | . . . | . . . June 30|241|155| 82| 48| 16|2. 99|0. 44| 10| 1| 1 | . . . | . . . | . . . -------+---+---+---+---+---+----+----+---+---+----+------+------+----- July 1|241|155| 82| 48| 16|3. 00|0. 45| 8| 1| 1 | 80| 10| 4 July 2|241|155| 82| 48| 16|3. 00|0. 46| 8| 1| 0 | 290| 24| 5 July 3|241|155| 82| 48| 16|3. 00|0. 47| 8| 1| 0 | 350| 45| 6 July 4|241|155| 82| 48| 16|2. 99|0. 49| 9| 1| 0 | . . . | . . . | . . . July 5|305|195|103| 61| 21|3. 00|0. 51| 10| 1| 0 | . . . | . . . | . . . July 6|241|155| 82| 48| 16|3. 00|0. 51| 9| 1| 0 | 300| 36| 7 July 7|241|155| 82| 48| 16|2. 99|0. 53| 8| 1| 0 | 110| 10| 3 July 8|252|162| 86| 50| 17|3. 00|0. 53| 9| 1| 0 | 85| 22| 2 July 9|241|155| 82| 48| 16|3. 00|0. 54| 8| 1| 0 | 85| 26| 2 July 10|. . . |. . . |. . . |. . . |. . . | . . . | . . . | | | | 200| 3| 5 July 11|305|195|103| 61| 21|3. 00|0. 56| 12| 1| 0 | 145| 7| 3 July 12|241|155| 82| 48| 16|2. 99|0. 58| 11| 1| 0 | . . . | . . . | . . . July 13|241|155| 82| 48| 16|3. 00|0. 60| 10| 1| 0 | 115| 34| 55 July 14|241|155| 82| 48| 16|2. 99|0. 62| 16| 1| 0 | 300| 55| 30 July 15|241|155| 82| 48| 16|2. 99|0. 64| 17| 1| 0 | 180| 32| 23 July 16|241|155| 82| 48| 16|3. 00|0. 67| 13| 1| 0 | 100| 115| 3 July 17|241|155| 82| 48| 16|2. 99|0. 71| 10| 1| 0 | 65| 275| 5 July 18|241|155| 82| 48| 16|2. 99|0. 73| 11| 1| 0 | 38| 425| 10 July 19|241|155| 82| 48| 16|3. 00|0. 76| 12| 1| 0 | . . . | . . . | . . . July 20|241|155| 82| 48| 16|2. 99|0. 79| 10| 1| 0 | 95| 90| 70 July 21|252|162| 86| 50| 17|2. 99|0. 83| 10| 1| 1 | 70| 17| 4 July 22|241|155| 82| 48| 16|2. 99|0. 87| 13| 1| 1 | 440| 8| 5 July 23|305|195|103| 61| 21|2. 99|0. 92| 54| 4| 1 | 650| 26| 5 July 24|331|212|111| 66| 22|2. 98|0. 99|305| 61| 1 | 1, 650| . . . | . . . July 25|265|170| 90| 53| 18|2. 98|1. 08|330| 85| 1 | 2, 600| 115| 15 July 26|252|162| 86| 50| 17|2. 98|1. 21|290| 77| 2 | . . . | . . . | . . . July 27|305|195|103| 61| 21|2. 98|1. 40|335| 87| 2 |35, 000| 250| . . . July 28|252|162| 86| 50| 17|2. 98|1. 68|170| 52| 2 | 1, 200| 1, 350| 15 July 29|252|162| 86| 50| 17|2. 97|2. 14|180| 52| 2 | 2, 000| 600| 13 July 30|252|162| 86| 50| 17|2. 97|2. 65|237| 56| 2 | 800| 1, 300| 12 July 31|241|155| 82| 48| 16|2. 95|3. 01|250| 60| 2 | 1, 000| 310| 7 =======+===+===+===+===+===+====+====+===+===+====+======+======+=====

 ~Table 18--Record of Experimental Filter Plant No. 2. ~ ========+=====================+===================== |~Preliminary Filter. ~| ~Final Filter. ~ +-----------+---------+-----------+--------- Date. | Rate, | | Rate, | |millions of| Loss of |millions of| Loss of |gallons per| head. |gallons per| head. |acre daily. | |acre daily. | --------+-----------+---------+-----------+--------- 1907. --------+-----------+---------+-----------+--------- Feb. 8| 21. 50 | 0. 04 | 2. 81 | 0. 17 Feb. 9| 21. 60 | 0. 04 | 1. 09 | 0. 06 Feb. 10| 20. 90 | 0. 05 | 1. 59 | 0. 08 Feb. 11| 19. 80 | 0. 05 | 3. 01 | 0. 15 Feb. 12| 19. 70 | 0. 06 | 3. 01 | 0. 14 Feb. 13| 19. 60 | 0. 06 | 3. 01 | 0. 12 Feb. 14| 24. 70 | 0. 07 | 2. 65 | 0. 13 Feb. 15| 37. 20 | . . . | 3. 40 | 0. 12 Feb. 16| 37. 30 | . . . | 3. 40 | 0. 11 Feb. 17|Shut down for changes in meters and piping. Feb. 18| . . . | . . . | . . . | . . . Feb. 21| 44. 50 | . . . | 4. 36 | 0. 19 Feb. 22| 48. 60 | . . . | 4. 37 | 0. 16 Feb. 23| 48. 40 | . . . | 4. 20 | 0. 15 Feb. 24| 48. 30 | . . . | 4. 02 | 0. 13 Feb. 25| Shut down several hours. | 0. 14 Feb. 26| 48. 60 | 0. 04 | 4. 12 | 0. 14 Feb. 27| 53. 20 | 0. 04 | 4. 08 | 0. 15 Feb. 28| 52. 80 | 0. 04 | 4. 09 | 0. 15 --------+-----------+---------+-----------+--------- Mar. 1| 53. 00 | 0. 04 | 4. 10 | 0. 16 Mar. 2| 53. 30 | 0. 04 | 4. 11 | 0. 16 Mar. 3| 50. 60 | 0. 05 | 4. 11 | 0. 16 Mar. 4| 42. 40 | 0. 05 | 4. 12 | 0. 17 Mar. 5| 42. 70 | 0. 05 | 4. 11 | 0. 17 Mar. 6| 48. 60 | 0. 07 | 4. 13 | 0. 17 Mar. 7| 50. 50 | 0. 08 | 4. 12 | 0. 18 Mar. 8| 51. 80 | 0. 09 | 4. 12 | 0. 18 Mar. 9| 53. 00 | 0. 10 | 4. 12 | 0. 18 Mar. 10| 54. 40 | 0. 12 | 4. 11 | 0. 19 Mar. 11| 51. 00 | 0. 12 | 4. 12 | 0. 19 Mar. 12| 51. 20 | 0. 12 | 4. 07 | 0. 19 Mar. 13| 50. 50 | 0. 12 | 4. 00 | 0. 19 Mar. 14| 46. 50 | 0. 12 | . . . | 0. 20 Mar. 15| 45. 80 | 0. 12 | 3. 98 | 0. 20 Mar. 16| 42. 50 | 0. 12 | 3. 97 | 0. 19 Mar. 17| 49. 30 | 0. 14 | 3. 98 | 0. 19 Mar. 18| 52. 60 | 0. 16 | 3. 98 | 0. 20 Mar. 19| 53. 50 | 0. 17 | 4. 01 | 0. 19 Mar. 20| 52. 90 | 0. 17 | 3. 99 | 0. 18 Mar. 21| 48. 20 | 0. 16 | 4. 00 | 0. 19 Mar. 22| 51. 80 | 0. 18 | 4. 01 | 0. 20 Mar. 23| 51. 60 | 0. 19 | 4. 01 | 0. 20 Mar. 24| 48. 20 | 0. 17 | 4. 01 | 0. 20 Mar. 25| 48. 50 | 0. 18 | 4. 01 | 0. 20 Mar. 26| 45. 90 | 0. 18 | 3. 98 | 0. 20 Mar. 27| 50. 50 | 0. 20 | 4. 04 | 0. 20 Mar. 28| 49. 60 | 0. 20 | 3. 92 | 0. 19 Mar. 29| 42. 20 | 0. 17 | 3. 98 | 0. 19 Mar. 30| 48. 00 | 0. 22 | 4. 01 | 0. 19 Mar. 31| 49. 10 | 0. 22 | 3. 99 | 0. 20 --------+-----------+---------+-----------+--------- Apr. 1| 49. 10 | 0. 24 | 4. 00 | 0. 20 Apr. 2| 49. 70 | 0. 25 | 4. 00 | 0. 20 Apr. 3| 51. 40 | 0. 27 | 4. 00 | 0. 21 Apr. 4| 48. 70 | 0. 27 | 4. 00 | 0. 22 Apr. 5| 48. 10 | 0. 27 | 4. 00 | 0. 22 Apr. 6| Shut down awaiting Mr. Maiguen | to apply bone-charcoal. Apr. 7| Removed 1. 06 in. Of sand. Apr. 8| 52. 20 | 0. 33 | 4. 05 | 0. 27 Apr. 9| 46. 90 | 0. 29 | 4. 02 | 0. 29 Apr. 10| 47. 60 | 0. 31 | 4. 03 | 0. 28 Apr. 11| 46. 00 | 0. 30 | 4. 04 | 0. 28 Apr. 12| 45. 40 | 0. 31 | 4. 03 | 0. 29 Apr. 13| 45. 10 | 0. 32 | 3. 99 | 0. 32 Apr. 14| 49. 00 | 0. 34 | 4. 00 | 0. 32 Apr. 15| 47. 80 | 0. 35 | 3. 99 | 0. 33 Apr. 16| 47. 40 | 0. 36 | 3. 99 | 0. 34 Apr. 17| 45. 60 | 0. 36 | 4. 00 | 0. 34 Apr. 18| 45. 70 | 0. 36 | 4. 00 | 0. 34 Apr. 19| 45. 60 | 0. 37 | 4. 00 | 0. 34 Apr. 20| 45. 30 | 0. 40 | 4. 00 | 0. 36 Apr. 21| 47. 20 | 0. 44 | 3. 99 | 0. 38 Apr. 22| 45. 20 | 0. 42 | 3. 99 | 0. 38 Apr. 23| 44. 90 | 0. 44 | 4. 05 | 0. 40 Apr. 24| 40. 50 | 0. 41 | 4. 02 | 0. 44 Apr. 25| 39. 60 | 0. 41 | 4. 03 | 0. 45 Apr. 26| 40. 70 | 0. 44 | 4. 05 | 0. 45 Apr. 27| 39. 30 | 0. 44 | 4. 00 | 0. 44 Apr. 28| 34. 70 | 0. 43 | 4. 05 | 0. 44 Apr. 29| 37. 20 | 0. 45 | 4. 00 | 0. 42 Apr. 30| 43. 00 | 0. 49 | 4. 00 | 0. 41 --------+-----------+---------+-----------+--------- May 1| 41. 30 | 0. 49 | 4. 00 | 0. 41 May 2| 42. 40 | 0. 49 | 4. 00 | 0. 41 May 3| 40. 70 | 0. 48 | 4. 00 | 0. 40 May 4| 33. 80 | 0. 47 | 4. 00 | 0. 39 May 5| 26. 20 | 0. 43 | 4. 00 | 0. 39 May 6| 29. 00 | 0. 38 | 3. 99 | 0. 37 May 7| 27. 60 | 0. 36 | . . . | 0. 37 May 8| 24. 70 | 0. 31 | 3. 99 | 0. 37 |Washed. | | | May 9| 24. 40 | 0. 03 | 3. 98 | 0. 39 May 10| 24. 80 | 0. 04 | 4. 00 | 0. 42 May 11| 50. 00 | 0. 06 | 4. 00 | 0. 44 May 12| 50. 00 | 0. 08 | 4. 00 | 0. 48 May 13| 50. 00 | 0. 09 | 4. 00 | 0. 47 May 14| 50. 00 | 0. 10 | 4. 00 | 0. 46 May 15| 48. 50 | 0. 15 | 4. 00 | 0. 45 May 16| 47. 00 | 0. 16 | 4. 00 | 0. 46 May 17| 47. 00 | 0. 16 | 3. 99 | 0. 47 May 18| 47. 00 | 0. 19 | 4. 00 | 0. 48 May 19| 47. 00 | 0. 21 | 3. 99 | 0. 51 May 20| 46. 60 | 0. 24 | 4. 00 | 0. 53 May 21| 46. 40 | 0. 24 | 4. 00 | 0. 55 May 22| 46. 40 | 0. 27 | 4. 00 | 0. 58 May 23| 46. 40 | 0. 29 | 4. 00 | 0. 61 May 24| 46. 40 | 0. 30 | 4. 00 | 0. 63 May 25| 46. 40 | 0. 32 | 4. 00 | 0. 66 May 26| 46. 40 | 0. 34 | 3. 99 | 0. 70 May 27| 46. 40 | 0. 86 | 3. 99 | 0. 74 May 28| 46. 40 | 0. 38 | 3. 15 | 0. 76 May 29| 46. 00 | 0. 44 | 3. 88 | 0. 78 May 30| 45. 60 | 0. 46 | 3. 99 | 0. 86 May 31| 45. 60 | 0. 46 | 4. 00 | 0. 92 --------+-----------+---------+-----------+--------- June 1| 45. 60 | 0. 46 | 4. 00 | 0. 98 June 2| 45. 60 | 0. 48 | 4. 00 | 1. 09 June 3| 45. 60 | 0. 51 | 4. 00 | 1. 20 June 4| 45. 60 | 0. 54 | 4. 00 | 1. 32 June 5| 45. 60 | 0. 55 | 4. 00 | 1. 48 June 6| 45. 60 | 0. 56 | 4. 01 | 3. 66 June 7| 45. 00 | 0. 57 | 4. 00 | 1. 80 June 8| 45. 00 | 0. 57 | 4. 00 | 1. 90 June 9| 45. 00 | 0. 55 | 4. 01 | 2. 00 June 10| 45. 00 | 0. 56 | 4. 00 | 2. 09 June 11| 45. 00 | 0. 58 | 4. 00 | 2. 17 June 12| 45. 00 | 0. 60 | 4. 01 | 2. 27 June 13| 45. 00 | 0. 62 | 4. 00 | 2. 36 June 14| 45. 00 | 0. 63 | 3. 99 | 2. 49 June 15| 45. 00 | 0. 64 | 3. 99 | 2. 56 June 16| 44. 70 | 0. 65 | 4. 00 | 2. 63 June 17| 44. 40 | 0. 64 | 4. 00 | 2. 67 June 18| 45. 00 | 0. 63 | 3. 98 | 2. 69 June 19| 45. 00 | 0. 63 | 4. 00 | 2. 73 June 20| 45. 00 | 0. 62 | 4. 01 | 2. 72 June 21| 45. 00 | 0. 61 | 4. 01 | 2. 68 June 22| Shut down to scrape and apply asbestos | and coke; removed 0. 79 in. Of sand. June 23| Applied 8 lb. Of asbestos and | 10 lb. Of bone-charcoal. June 25| 50. 00 | 0. 54 | 4. 00 | 0. 27 June 26| 50. 00 | 0. 57 | 4. 01 | 0. 46 June 27| 50. 00 | 0. 63 | 4. 01 | 0. 55 June 28| 50. 00 | 0. 65 | 3. 99 | 0. 63 June 29| 50. 00 | 0. 70 | 4. 00 | 0. 73 June 30| 50. 00 | 0. 77 | 3. 99 | 0. 82 --------+-----------+---------+-----------+--------- July 1| 50. 00 | 0. 87 | 4. 00 | 0. 80 July 2| 50. 00 | 0. 95 | 4. 01 | 0. 73 July 3| 50. 00 | 1. 01 | 4. 00 | 0. 66 July 4| 50. 00 | 1. 03 | 4. 00 | 0. 58 July 5| 50. 00 | 1. 07 | 3. 99 | 0. 54 July 6| 50. 00 | 1. 10 | 4. 00 | 0. 52 July 7| 50. 00 | 1. 14 | 4. 00 | 0. 50 July 8| 50. 00 | 1. 16 | 4. 00 | 0. 48 July 9| 50. 00 | 1. 18 | 4. 00 | 0. 46 July 10| 50. 00 | 1. 20 | 3. 99 | 0. 45 July 11| 50. 00 | 1. 20 | 3. 99 | 0. 45 July 12| 50. 00 | 1. 20 | 4. 01 | 0. 44 July 13| 50. 00 | 1. 15 | 4. 00 | 0. 47 July 14| 50. 00 | 1. 15 | 4. 00 | 0. 48 July 15| 50. 00 | 1. 14 | 3. 99 | 0. 48 July 16| 50. 00 | 1. 19 | 4. 00 | 0. 48 July 17| 50. 00 | 1. 21 | 4. 00 | 0. 48 July 18| 50. 00 | 1. 19 | 3. 99 | 0. 50 July 19| 50. 00 | 1. 16 | 3. 99 | 0. 52 July 20| 50. 00 | 1. 16 | 3. 99 | 0. 56 July 21| 50. 00 | 1. 19 | 3. 99 | 0. 63 July 22| 50. 00 | 1. 20 | 3. 99 | 0. 77 July 23| 50. 00 | 1. 21 | 3. 99 | 0. 93 July 24| 50. 00 | 1. 38 | 3. 99 | 1. 07 July 25| 50. 00 | 1. 17 | 3. 99 | 1. 22 July 26| 50. 00 | 1. 07 | 4. 00 | 1. 37 July 27| 50. 00 | 1. 11 | 4. 00 | July 28| 50. 00 | 1. 22 | 3. 98 | 1. 65 July 29| 50. 00 | 1. 21 | 4. 00 | 1. 82 July 30| 50. 00 | 1. 20 | 3. 99 | 1. 98 July 31| 50. 00 | 1. 20 | 3. 99 | 2. 11 --------+-----------+---------+-----------+--------- Aug. 1| 51. 00 | 1. 21 | 3. 99 | 2. 27 Aug. 2| 51. 00 | 1. 21 | 3. 99 | 2. 43 Aug. 3| 51. 00 | 1. 21 | 4. 00 | 2. 66 Aug. 4| 50. 00 | 1. 21 | 3. 99 | 2. 95 Aug. 5| 50. 00 | 1. 21 | 3. 98 | 3. 22 Aug. 6| 50. 00 | 1. 22 | 3. 98 | 3. 50 Aug. 7| 50. 00 | 1. 21 | 3. 99 | 3. 74 Aug. 8| 48. 20 | 1. 20 | . . . | 4. 09 Aug. 9| 50. 00 | 1. 18 | . . . | 4. 45 Aug. 10| 47. 30 | 1. 16 | . . . | 4. 67 Aug. 11| Shut down to drain and scrape sand filter; | O. 9 in. Depth over all. Aug. 16|Out of service all the rest of month washing | sponge and asbestos. --------+-----------+---------+-----------+--------- Sept. 3| 50. 00 | 0. 02 | 4. 00 | 0. 16 Sept. 4| 50. 00 | 0. 02 | 3. 99 | 0. 14 Sept. 5| 50. 00 | 0. 02 | 4. 01 | 0. 13 Sept. 6| 46. 40 | 0. 02 | 4. 00 | 0. 12 Sept. 7| 50. 00 | 0. 03 | 4. 00 | 0. 11 Sept. 8| 46. 40 | 0. 04 | 3. 99 | 0. 11 Sept. 9| 50. 00 | 0. 05 | 4. 90 | 0. 11 Sept. 10| 50. 00 | 0. 05 | 4. 00 | 0. 11 Sept. 11| 50. 00 | 0. 06 | 4. 00 | 0. 11 Sept. 12| 50. 00 | 0. 07 | 4. 00 | 0. 12 Sept. 13| 50. 00 | 0. 08 | 4. 00 | 0. 12 Sept. 14| 50. 00 | 0. 09 | 4. 01 | 0. 12 Sept. 15| 48. 20 | 0. 11 | 4. 00 | 0. 12 Sept. 16| 51. 00 | 0. 13 | 4. 00 | 0. 12 Sept. 17| 50. 00 | 0. 14 | 4. 00 | 0. 12 Sept. 18| 49. 10 | 0. 14 | 4. 00 | 0. 13 Sept. 19| 50. 00 | 0. 15 | 4. 00 | 0. 13 Sept. 20| 49. 10 | 0. 17 | 4. 00 | 0. 13 Sept. 21| 49. 10 | 0. 18 | 4. 00 | 0. 13 Sept. 22| 48. 20 | 0. 20 | 4. 00 | 0. 13 Sept. 23| 49. 10 | 0. 19 | 4. 00 | 0. 13 Sept. 24| 46. 40 | 0. 19 | 3. 99 | 0. 14 Sept. 25| 46. 40 | 0. 20 | 4. 00 | 0. 14 Sept. 26| 45. 60 | 0. 24 | 4. 00 | 0. 15 Sept. 27| 44. 80 | 0. 27 | 4. 00 | 0. 16 Sept. 28| 46. 40 | 0. 30 | 3. 99 | 0. 16 Sept. 29| 46. 40 | 0. 31 | 3. 99 | 0. 16 Sept. 30| 46. 40 | 0. 31 | 4. 00 | 0. 17 --------+-----------+---------+-----------+--------- Oct. 1| 48. 20 | 0. 33 | 4. 00 | 0. 18 Oct. 2| 50. 00 | 0. 33 | 4. 01 | 0. 19 Oct. 3| 48. 20 | 0. 33 | 4. 00 | 0. 19 Oct. 4| 48. 20 | 0. 34 | 4. 00 | 0. 19 Oct. 5| 50. 00 | 0. 38 | 4. 00 | 0. 19 Oct. 6| 48. 20 | 0. 41 | 4. 00 | 0. 19 Oct. 7| 48. 20 | 0. 42 | 4. 00 | 0. 19 Oct. 8| 50. 00 | 0. 42 | 4. 00 | 0. 19 Oct. 9| 44. 80 | 0. 40 | 4. 00 | 0. 19 Oct. 10| 48. 20 | 0. 42 | 4. 00 | 0. 19 Oct. 11| 48. 20 | 0. 43 | 4. 00 | 0. 20 |Washed. | | | Oct. 12| 50. 00 | 0. 14 | 4. 00 | 0. 20 Oct. 13| 47. 30 | 0. 15 | 4. 00 | 0. 21 Oct. 14| 50. 00 | 0. 18 | 4. 00 | 0. 22 Oct. 15| 53. 00 | 0. 20 | 4. 00 | 0. 23 Oct. 16| 50. 00 | 0. 20 | 4. 00 | 0. 24 Oct. 17| 50. 00 | 0. 21 | 4. 00 | 0. 25 Oct. 18| 50. 00 | 0. 21 | 4. 00 | 0. 25 Oct. 19| 50. 00 | 0. 21 | 4. 00 | 0. 25 Oct. 20| 50. 00 | 0. 22 | 4. 00 | 0. 25 Oct. 21| 50. 00 | 0. 23 | 4. 00 | 0. 25 Oct. 22| 50. 00 | 0. 24 | 4. 00 | 0. 26 Oct. 23| 50. 00 | 0. 25 | 4. 00 | 0. 26 Oct. 24| 50. 00 | 0. 26 | 4. 00 | 0. 26 Oct. 25| 50. 00 | 0. 27 | 4. 00 | 0. 27 Oct. 26| 50. 00 | 0. 28 | 4. 00 | 0. 27 Oct. 27| 50. 00 | 0. 29 | 4. 00 | 0. 27 Oct. 28| 50. 00 | 0. 30 | 4. 00 | 0. 27 Oct. 29| 50. 00 | 0. 31 | 4. 00 | 0. 27 Oct. 30| 50. 00 | 0. 32 | 4. 00 | 0. 27 Oct. 31|Out of commission. 4-in supply pipe stopped up. --------+-----------+---------+-----------+--------- Nov. 4| 50. 00 | 0. 16 | 4. 00 | 0. 28 Nov. 5| 50. 00 | 0. 17 | 4. 00 | 0. 28 Nov. 6| 50. 00 | 0. 18 | 4. 00 | 0. 29 Nov. 7| 50. 00 | 0. 20 | 4. 00 | 0. 30 Nov. 8| 50. 00 | 0. 21 | 4. 00 | 0. 32 Nov. 9| 50. 00 | 0. 22 | 4. 00 | 0. 34 Nov. 10| 50. 00 | 0. 23 | 4. 00 | 0. 36 Nov. 11| 50. 00 | 0. 24 | 3. 46 | 0. 38 Nov. 12| 50. 00 | 0. 26 | 3. 99 | 0. 40 Nov. 13| 50. 00 | 0. 27 | 4. 00 | 0. 44 Nov. 14| 50. 00 | 0. 28 | 4. 00 | 0. 49 Nov. 15| 50. 00 | 0. 29 | 4. 00 | 0. 55 Nov. 16| 50. 00 | 0. 30 | 4. 00 | 0. 65 Nov. 17| 50. 00 | 0. 31 | 3. 98 | 0. 80 Nov. 18| 50. 00 | 0. 32 | 3. 99 | 0. 98 Nov. 19| 50. 00 | 0. 34 | 3. 99 | 1. 26 Nov. 20| 50. 00 | 0. 35 | 3. 98 | 1. 64 Nov. 21| 50. 00 | 0. 36 | 3. 99 | 2. 03 Nov. 22| 50. 00 | 0. 37 | 3. 98 | 2. 33 Nov. 23| 50. 00 | 0. 38 | 3. 99 | 2. 60 Nov. 24| 50. 00 | 0. 40 | 3. 98 | 2. 85 Nov. 25| 48. 20 | 0. 45 | 3. 98 | 3. 10 Nov. 26| 50. 00 | 0. 49 | 3. 98 | 3. 62 Nov. 27| 50. 00 | 0. 51 | 3. 99 | 4. 15 Nov. 28| 50. 00 | 0. 54 | 3. 84 | 4. 44 Nov. 29| 50. 00 | 0. 55 | 3. 67 | 4. 55 Nov. 30| 50. 00 | 0. 56 | 3. 44 | 4. 65 --------+-----------+---------+-----------+--------- Dec. 2| Shut down to scrape sand filter. | Dec. 6| 50. 00 | 0. 64 | 4. 00 | 0. 46 Dec. 7| 50. 00 | 0. 64 | 4. 00 | 0. 39 Dec. 8| 50. 00 | 0. 64 | 4. 01 | 0. 35 Dec. 9| 50. 00 | 0. 65 | 4. 01 | 0. 33 Dec. 10| 50. 00 | 0. 65 | 4. 00 | 0. 33 Dec. 11| 47. 30 | 0. 64 | 4. 00 | 0. 35 Dec. 12| 46. 40 | 0. 70 | 3. 98 | 0. 39 Dec. 13| 50. 00 | 0. 79 | 3. 98 | 0. 49 Dec. 14| 52. 00 | 0. 84 | 3. 97 | 0. 65 Dec. 15| 49. 10 | 0. 84 | 3. 98 | 0. 77 Dec. 16| 49. 10 | 0. 86 | 3. 97 | 0. 84 Dec. 17| 49. 10 | 0. 88 | 3. 98 | 0. 91 Dec. 18| 48. 20 | 0. 89 | 3. 98 | 0. 94 Dec. 19| 50. 00 | 0. 91 | 3. 98 | 0. 97 Dec. 20| 49. 10 | 0. 92 | 3. 98 | 1. 03 Dec. 21| 50. 00 | 0. 94 | 3. 98 | 1. 08 Dec. 22| 50. 00 | 0. 97 | 3. 98 | 1. 13 Dec. 23| 50. 00 | 0. 95 | 3. 98 | 1. 19 Dec. 24| 47. 30 | 0. 93 | 3. 98 | 1. 28 Dec. 25| 44. 10 | 0. 91 | 3. 97 | 1. 47 Dec. 26| 46. 40 | 1. 01 | 3. 97 | 1. 63 Dec. 27| 50. 00 | 1. 11 | 3. 98 | 1. 81 Dec. 28| 48. 20 | 1. 12 | 3. 99 | 1. 87 Dec. 29| 50. 00 | 1. 14 | 3. 99 | 1. 85 Dec. 30| 49. 10 | 1. 15 | 3. 98 | 1. 86 Dec. 31| 50. 00 | 1. 17 | 4. 00 | 1. 87 --------+-----------+---------+-----------+--------- 1908. --------+-----------+---------+-----------+--------- Jan. 1| 50. 00 | 1. 18 | 3. 98 | 1. 90 Jan. 2| 50. 00 | 1. 18 | 3. 99 | 1. 94 Jan. 3| 50. 00 | 1. 19 | 3. 98 | 1. 98 |Washed. | | | Jan. 4| 50. 00 | 0. 17 | 3. 97 | 2. 09 Jan. 5| 50. 00 | 0. 18 | 3. 98 | 2. 22 Jan. 6| 50. 00 | 0. 19 | 3. 98 | 2. 28 Jan. 7| 50. 00 | 0. 20 | 3. 98 | 2. 37 Jan. 8| 50. 00 | 0. 21 | 3. 99 | 2. 43 Jan. 9| 50. 00 | 0. 23 | 3. 98 | 2. 52 Jan. 10| 50. 00 | 0. 24 | 3. 99 | 2. 66 Jan. 11| 50. 00 | 0. 27 | 3. 98 | 2. 74 Jan. 12| 50. 00 | 0. 28 | 3. 98 | 2. 83 Jan. 13| 49. 10 | 0. 30 | 3. 98 | 2. 93 Jan. 14| 48. 20 | 0. 33 | 3. 99 | 3. 04 Jan. 15| 46. 40 | 0. 35 | 3. 98 | 3. 21 Jan. 16| 50. 00 | 0. 40 | 3. 98 | 3. 49 Jan. 17| 50. 00 | 0. 43 | 3. 98 | 3. 86 Jan. 18| 50. 00 | 0. 46 | 3. 91 | 3. 99 Jan. 19| . . . | . . . | . . . | . . . Jan. 20| Scraped. | | | Jan. 21| 50. 00 | 0. 48 | 3. 00 | 0. 76 Jan. 22| 50. 00 | 0. 48 | 3. 01 | 0. 60 Jan. 23| 50. 00 | 0. 49 | 3. 00 | 0. 57 Jan. 24| 50. 00 | 0. 49 | 2. 99 | 0. 60 Jan. 25| 50. 00 | 0. 50 | 2. 99 | 0. 65 Jan. 26| 50. 00 | 0. 50 | 2. 98 | 0. 69 Jan. 27| 50. 00 | 0. 51 | 2. 99 | 0. 76 Jan. 28| 50. 00 | 0. 52 | 2. 99 | 0. 82 Jan. 29| 50. 00 | 0. 55 | 2. 99 | 0. 90 Jan. 30| 50. 00 | 0. 57 | 2. 98 | 0. 98 Jan. 31| 50. 00 | 0. 58 | 2. 98 | 1. 08 --------+-----------+---------+-----------+--------- Feb. 1| 50. 00 | 0. 59 | 2. 99 | 1. 16 Feb. 2| 49. 10 | 0. 60 | 2. 99 | 1. 22 Feb. 3| 49. 10 | 0. 61 | 2. 98 | 1. 30 Feb. 4| 50. 00 | 0. 64 | 2. 99 | 1. 40 Feb. 5| 50. 00 | 0. 66 | 2. 99 | 1. 50 Feb. 6| 50. 00 | 0. 67 | 2. 99 | 1. 55 Feb. 7| 50. 00 | 0. 68 | 3. 00 | 1. 56 Feb. 8| 50. 00 | 0. 69 | 3. 00 | 1. 53 Feb. 9| 50. 00 | 0. 71 | 3. 00 | 1. 54 Feb. 10| 50. 00 | 0. 72 | 2. 99 | 1. 60 Feb. 11| 50. 00 | 0. 74 | 2. 99 | 1. 62 Feb. 12| 50. 00 | 0. 75 | 2. 98 | 1. 68 Feb. 13| 50. 00 | 0. 76 | 2. 99 | 1. 74 Feb. 14| 48. 20 | 0. 76 | 2. 99 | 1. 77 Feb. 15| 51. 80 | 0. 79 | 2. 99 | 1. 89 Feb. 16| 48. 20 | 0. 79 | 2. 99 | 2. 08 Feb. 17| 48. 20 | 0. 81 | 2. 99 | 2. 24 Feb. 18| 47. 30 | 0. 82 | 2. 99 | 2. 31 Feb. 19| 51. 80 | 0. 92 | 2. 99 | 2. 45 Feb. 20| 52. 70 | 0. 99 | 2. 99 | 2. 61 Feb. 21| 51. 80 | 1. 03 | 2. 99 | 2. 68 Feb. 22| 50. 90 | 1. 07 | 2. 99 | 2. 72 Feb. 23| 50. 00 | 1. 09 | 2. 99 | 2. 76 Feb. 24| 51. 80 | 1. 12 | 2. 99 | 2. 80 Feb. 25| 50. 00 | 1. 14 | 2. 99 | 2. 84 Feb. 26| 50. 00 | 1. 17 | 3. 00 | 2. 87 Feb. 27| 48. 20 | 1. 18 | 2. 99 | 2. 90 Feb. 28| 47. 30 | 1. 19 | 2. 99 | 2. 94 Feb. 29| 51. 80 | 1. 23 | 2. 99 | 3. 01 --------+-----------+---------+-----------+--------- Mar. 1| 48. 20 | 1. 20 | 2. 98 | 2. 99 Mar. 2| 50. 00 | 1. 28 | 2. 99 | 3. 12 Mar. 3| 50. 90 | 1. 32 | 2. 98 | 3. 22 Mar. 4| 50. 00 | 1. 33 | 2. 99 | 3. 28 Mar. 5| 50. 00 | 1. 35 | 2. 99 | 3. 32 Mar. 6| Discontinued; sand filter being used | for sedimentation experiments. ========+===========+=========+===========+=========

 ~Table 18~--(_Continued. _) ========+===========================+=========================== | ~Turbidity. ~ | ~Bacteria. ~ +-------+---------+---------+-------+---------+--------- Date. |Applied|Effluent, |Effluent, |Applied|Effluent, |Effluent, | water. | pre- | final | water. | pre- | final | |liminary | filter. | |liminary | filter. | filter | | | filter. | --------+-------+---------+---------+-------+---------+--------- 1907. --------+-------+---------+---------+-------+---------+--------- Feb. 8| . . . | . . . | . . . | 1, 100 | 2, 100 | . . . Feb. 9| . . . | . . . | . . . | 200 | 550 | 2, 100 Feb. 10| . . . | . . . | . . . | . . . | . . . | . . . Feb. 11| 12 | 6 | 2 | 600 | 1, 160 | 1, 100 Feb. 12| 12 | 5 | 2 | 650 | 400 | 700 Feb. 13| 15 | 5 | 2 | 660 | 900 | 700 Feb. 14| 15 | 6 | 2 | 650 | 1, 100 | 900 Feb. 15| 12 | 5 | 2 | 600 | 800 | 850 Feb. 16| 14 | 4 | 2 | 850 | 950 | 600 Feb. 17| Shut down for changes in meters and piping. Feb. 18| . . . | . . . | . . . | 1, 200 | . . . | 600 Feb. 21| 20 | 6 | 2 | 1, 800 | 1, 400 | 800 Feb. 22| 15 | 4 | 2 | Holiday. Feb. 23| 20 | 7 | 2 | 1, 600 | 750 | 380 Feb. 24| 20 | 10 | 3 | Sunday. Feb. 25| 20 | 10 | 3 | 1, 400 | 1, 000 | 450 Feb. 26| 20 | 10 | 3 | 700 | 800 | 260 Feb. 27| 17 | 8 | 3 | 700 | 700 | 290 Feb. 28| 15 | 8 | 3 | 800 | 650 | 500 --------+-------+---------+---------+-------+---------+--------- Mar. 1| 15 | 8 | 3 | 650 | 550 | 200 Mar. 2| 15 | 7 | 3 | 1, 000 | 800 | 300 Mar. 3| 31 | 11 | 3 | Sunday. Mar. 4| 35 | 15 | 6 | 1, 200 | 1, 500 | 360 Mar. 5| 135 | 52 | 10 |13, 000 | 850 | . . . Mar. 6| 135 | 54 | 12 |18, 000 | 8, 000 | . . . Mar. 7| 102 | 46 | 8 |24, 000 | 6, 500 | 1, 800 Mar. 8| 100 | 40 | 6 |22, 000 | 6, 000 | 1, 600 Mar. 9| 90 | 40 | 5 |24, 000 | 6, 000 | 800 Mar. 10| 82 | 39 | 6 | Sunday. Mar. 11| 68 | 32 | 7 |18, 000 | 4, 300 | 240 Mar. 12| 46 | 25 | 5 |11, 000 | 4, 600 | 210 Mar. 13| 40 | 20 | 5 | 9, 000 | 1, 500 | 200 Mar. 14| 39 | 20 | 4 | 5, 500 | 1, 200 | 90 Mar. 15| 35 | 18 | 4 | 6, 500 | 1, 100 | 150 Mar. 16| 60 | 24 | 4 | 5, 000 | 800 | 160 Mar. 17| 135 | 45 | 5 | Sunday. Mar. 18| 170 | 59 | 9 | 9, 000 | 1, 700 | 100 Mar. 19| 125 | 51 | 8 | 7, 000 | 1, 000 | 120 Mar. 20| 102 | 40 | 6 | 4, 800 | 700 | 75 Mar. 21| 125 | 42 | 5 | 8, 500 | 1, 100 | 90 Mar. 22| 190 | 82 | 5 | 7, 500 | 1, 100 | 55 Mar. 23| 180 | 75 | 6 | 7, 500 | 1, 300 | 90 Mar. 24| 140 | 68 | 7 | Sunday. Mar. 25| 88 | 40 | 5 | 4, 400 | 900 | 75 Mar. 26| 62 | 32 | 4 | 3, 600 | 750 | 90 Mar. 27| 47 | 25 | 4 | 2, 200 | 400 | 60 Mar. 28| 35 | 16 | 3 | 1, 300 | 350 | 55 Mar. 29| 26 | 12 | 3 | 700 | 180 | 20 Mar. 30| 25 | 7 | 3 | 310 | 220 | 39 Mar. 31| 21 | 6 | 2 | Sunday. --------+-------+---------+---------+-------+---------+--------- Apr. 1| 20 | 6 | 2 | 600 | 110 | 38 Apr. 2| 24 | 6 | 2 | 270 | 110 | 29 Apr. 3| 24 | 6 | 2 | 460 | 85 | 31 Apr. 4| 20 | 6 | 2 | 280 | 60 | 22 Apr. 5| 20 | 5 | 2 | 450 | 70 | 40 Apr. 6|Shut down awaiting Mr. Maiguen to apply bone-charcoal. Apr. 7|Removed 1. 06 in. Of sand. Sunday. Apr. 8| 18 | 4 | 3 | 330 | . . . | . . . Apr. 9| 18 | 4 | 2 | 140 | 60 | 32 Apr. 10| 30 | 4 | 1 | 750 | 120 | 28 Apr. 11| 66 | 7 | 2 | 4, 000 | . . . | 32 Apr. 12| 72 | 20 | 3 |14, 000 | 2, 900 | 85 Apr. 13| 80 | 30 | 3 |13, 000 | 2, 500 | 95 Apr. 14| 77 | 35 | 4 | Sunday. Apr. 15| 62 | 31 | 4 | 7, 000 | 1, 100 | 60 Apr. 16| 47 | 27 | 4 | 3, 600 | 650 | 31 Apr. 17| 39 | 21 | 3 | 1, 600 | 160 | 38 Apr. 18| 30 | 13 | 2 | 1, 810 | 210 | 42 Apr. 19| 25 | 9 | 2 | 790 | 190 | 34 Apr. 20| 20 | 6 | 2 | 540 | 87 | 23 Apr. 21| 20 | 4 | 2 | Sunday. Apr. 22| 18 | 3 | 1 | 235 | 55 | 22 Apr. 23| 15 | 3 | 1 | 170 | 45 | 16 Apr. 24| 19 | 2 | 1 | 150 | 14 | 14 Apr. 25| 34 | 3 | 1 | 700 | 12 | 23 Apr. 26| 46 | 4 | 1 | 1, 200 | 80 | 16 Apr. 27| 52 | 4 | 1 | 1, 700 | 160 | 23 Apr. 28| 45 | 5 | 1 | Sunday. Apr. 29| 44 | 6 | 1 | 600 | 60 | 10 Apr. 30| 39 | 7 | 1 | 550 | 55 | 15 --------+-------+---------+---------+-------+---------+--------- May 1| 31 | 6 | 1 | 500 | 80 | 17 May 2| 24 | 5 | 1 | 500 | 80 | 19 May 3| 19 | 4 | 1 | 280 | 75 | 48 May 4| 16 | 3 | 1 | 400 | 80 | 9 May 5| 15 | 1 | 1 | Sunday. May 6| 13 | 2 | 1 | 390 | 100 | 65 May 7| 12 | 2 | 1 | 190 | 60 | 19 May 8| 10 | 2 | 1 | . . . | . . . | . . . |Washed. | | | | May 9| 10 | 2 | 1 | 390 | 65 | 10 May 10| 10 | 2 | 1 | 300 | 80 | 18 May 11| 12 | 2 | 1 | 390 | 110 | 12 May 12| 17 | 2 | 1 | Sunday. May 13| 35 | 3 | 1 | 600 | 100 | 18 May 14| 39 | 4 | 1 | 500 | 65 | 15 May 15| 17 | 3 | 1 | 500 | 70 | 16 May 16| 24 | 3 | 1 | 290 | 70 | 16 May 17| 18 | 3 | 1 | 260 | 40 | 9 May 18| 15 | 2 | 1 | 190 | . . . | 17 May 19| 12 | 2 | 1 | Sunday. May 20| 12 | 2 | 1 | 260 | 40 | 13 May 21| 16 | 2 | 1 | 260 | 65 | 9 May 22| 20 | 2 | 1 | 280 | 35 | 12 May 23| 15 | 2 | 1 | 130 | 35 | 10 May 24| 15 | 2 | 1 | 170 | 26 | 6 May 25| 15 | 2 | 1 | 340 | 80 | 13 May 26| 18 | 2 | 1 | Sunday. May 27| 13 | 2 | 1 | 210 | 80 | 7 May 28| 16 | 2 | 1 | 260 | 70 | 10 May 29| 16 | 2 | 1 | 500 | 55 | 12 May 30| 14 | 2 | 1 | Holiday. May 31| 17 | 2 | 1 | 380 | 65 | 11 --------+-------+---------+---------+-------+---------+--------- June 1| 15 | 2 | 1 | 900 | 48 | 10 June 2| 17 | 2 | 1 | Sunday. June 3| 24 | 2 | 1 | 550 | 75 | 16 June 4| 37 | 3 | 1 | 6, 500 | . . . | 22 June 5| 65 | 5 | 1 | 3, 200 | 140 | 19 June 6| 77 | 16 | 1 | 1, 500 | 210 | 14 June 7| 64 | 27 | 1 | 2, 100 | 230 | 20 June 8| 46 | 22 | 1 | 600 | 240 | 33 June 9| 44 | 18 | 1 | Sunday. June 10| 36 | 12 | 1 | 240 | 110 | 43 June 11| 30 | 8 | 1 | 280 | 130 | 60 June 12| 34 | 8 | 1 | 330 | 150 | 60 June 13| 35 | 10 | 1 | 480 | . . . | 120 June 14| 31 | 9 | 1 | 440 | . . . | 65 June 15| 32 | 8 | 1 | 420 | . . . | 49 June 16| 26 | 7 | 1 | Sunday. June 17| 26 | 6 | 1 | 340 | 270 | 55 June 18| 31 | 7 | 1 | 440 | 140 | 65 June 19| 37 | 10 | 1 | 500 | 110 | 24 June 20| 30 | 9 | 1 | 330 | 70 | 34 June 21| 25 | 7 | 1 | 170 | 130 | 60 June 22| Shut down to scrape and apply asbestos and coke; | removed 0. 79 in. Of sand. June 23|Applied 8 lb. Of asbestos and 10 lb. Of bone-charcoal. June 25| 130 | 45 | 1 | 400 | . . . | . . . June 26| 82 | 37 | 1 | 750 | 550 | 35 June 27| 65 | 26 | 1 | . . . | 1, 200 | 140 June 28| 47 | 21 | 1 | . . . | 1, 200 | 26 June 29| 37 | 9 | 1 | 220 | 800 | 22 June 30| 30 | 8 | 1 | Sunday. --------+-------+---------+---------+-------+---------+--------- July 1| 30 | 8 | 1 | 400 | 90 | 37 July 2| 32 | 9 | 1 | 180 | 230 | 25 July 3| 36 | 10 | 1 | 350 | 80 | 58 July 4| 44 | 12 | 1 | Holiday. July 5| 24 | 14 | 1 | 550 | 130 | 47 July 6| 39 | 12 | 1 | 250 | 110 | 33 July 7| 34 | 10 | 1 | Sunday. July 8| 25 | 7 | 1 | 220 | 190 | 14 July 9| 22 | 5 | 1 | 50 | 30 | 3 July 10| 47 | 11 | 1 | Lost. | Lost. | Lost. July 11| 90 | 30 | 1 | 150 | 140 | 12 July 12| 97 | 35 | 1 | 300 | 110 | 20 July 13| 90 | 39 | 1 | 220 | 120 | 14 July 14| 90 | 40 | 1 | Sunday. July 15| 95 | 40 | 1 | 375 | 320 | 19 July 16| 120 | 45 | 1 | Lost. | 150 | 12 July 17| 85 | 42 | 1 | 270 | 60 | 5 July 18| 56 | 32 | 1 | 1, 675 | 23 | 39 July 19| 41 | 20 | 1 | 450 | 200 | 13 July 20| 62 | 29 | 1 | 300 | 220 | 8 July 21| 62 | 31 | 1 | Sunday. July 22| 80 | 36 | 1 | 1, 400 | 700 | 9 July 23| 105 | 40 | 1 | 3, 700 | 370 | 25 July 24| 95 | 40 | 1 | 770 | 260 | 31 July 25| 77 | 32 | 1 | 250 | 230 | 3 July 26| 67 | 29 | 1 | 140 | 90 | 12 July 27| 54 | 25 | 1 | 300 | 180 | 6 July 28| 46 | 19 | 1 | Sunday. July 29| 36 | 16 | 1 | 470 | 230 | 18 July 30| 29 | 11 | 1 | Plates lost. July 31| 21 | 9 | 1 | July " --------+-------+---------+---------+-------+---------+--------- Aug. 1| 16 | 6 | 1 | Plates lost. Aug. 2| 15 | 4 | 1 | 130 | 130 | 4 Aug. 3| 16 | 3 | 1 | 120 | 80 | 4 Aug. 4| 21 | 3 | 1 | Sunday. Aug. 5| 29 | 3 | 1 | 230 | 210 | 4 Aug. 6| 34 | 4 | 1 | 85 | 320 | 19 Aug. 7| 21 | 4 | 1 | 200 | Lost. | 19 Aug. 8| 19 | 4 | 1 | 100 | 150 | 17 Aug. 9| 16 | 3 | 1 | 75 | 220 | 9 Aug. 10| 24 | 3 | 1 | 60 | 250 | 10 Aug. 11| Shut down to drain and scrape sand filter; | O. 9 in. Depth over all. Aug. 16| Out of service all the rest of month washing | sponge and asbestos. --------+-------+---------+---------+-------+---------+--------- Sept. 3| 12 | 5 | 1 | 300 | . . . | . . . Sept. 4| 16 | 6 | 1 | 600 | 260 | 370 Sept. 5| 34 | 6 | 1 | 360 | 71 | 165 Sept. 6| 160 | 52 | 1 |15, 000 | 1, 900 | 120 Sept. 7| 64 | 26 | 1 | 2, 000 | 170 | 62 Sept. 8| 56 | 25 | 1 | Sunday. Sept. 9| 59 | 25 | 1 | 220 | 13 | 19 Sept. 10| 57 | 21 | 1 |18, 000 | 100 | 24 Sept. 11| 65 | 25 | 1 | 2, 700 | 150 | 25 Sept. 12| 72 | 26 | 1 | 1, 000 | 190 | 36 Sept. 13| 87 | 30 | 1 | 2, 300 | . . . | 35 Sept. 14| 72 | 27 | 1 | 2, 400 | 130 | 230 Sept. 15| 65 | 25 | 1 | Sunday. Sept. 16| 65 | 25 | 1 | Lost. | Lost. | 27 Sept. 17| 52 | 21 | 1 | 420 | 60 | 29 Sept. 18| 60 | 18 | 1 | 900 | 80 | 41 Sept. 19| 85 | 22 | 1 | 2, 000 | . . . | 19 Sept. 20| 100 | 29 | 1 | 4, 200 | 300 | 28 Sept. 21| 120 | 34 | 1 | 1, 100 | 160 | 30 Sept. 22| 137 | 41 | 1 | Sunday. Sept. 23| 112 | 37 | 1 | 2, 400 | 90 | 34 Sept. 24| 100 | 35 | 1 | 4, 000 | 210 | 12 Sept. 25| 432 | 80 | 1 |56, 000 | 510 | 27 Sept. 26| 385 | 80 | 4 | 1, 300 | 450 | 55 Sept. 27| 245 | 70 | 3 | 4, 000 | 240 | 41 Sept. 28| 127 | 46 | 2 |15, 000 | 430 | 37 Sept. 29| 105 | 41 | 2 | Sunday. Sept. 30| 115 | 42 | 1 | Lost. | 1, 600 | 110 --------+-------+---------+---------+-------+---------+--------- Oct. 1| 82 | 36 | 1 | 600 | 600 | 120 Oct. 2| 65 | 27 | 1 | 4, 400 | 170 | 47 Oct. 3| 59 | 34 | 1 | 900 | 210 | 44 Oct. 4| 55 | 20 | 1 | 850 | 200 | 37 Oct. 5| 9 | 21 | 1 | 2, 000 | 150 | 34 Oct. 6| 59 | 24 | 1 | Sunday. Oct. 7| 552 | 17 | 1 | 1, 250 | 200 | 28 Oct. 8| 54 | 16 | 1 |11, 000 | 210 | 28 Oct. 9| 51 | 16 | 1 | 2, 000 | 310 | 29 Oct. 10| 50 | 15 | 1 | 800 | 220 | 16 Oct. 11| 47 | 13 | 1 | 2, 000 | 310 | 46 |Washed. | | | | | Oct. 12| 36 | 11 | 1 | 1, 200 | 370 | 25 Oct. 13| 40 | 15 | 1 | Sunday. Oct. 14| 47 | 19 | 1 | 1, 200 | 390 | 22 Oct. 15| 41 | 16 | 1 | 900 | 140 | 16 Oct. 16| 35 | 12 | 1 | Lost. | 310 | 18 Oct. 17| 30 | 8 | 1 | 550 | 180 | 7 Oct. 18| 25 | 6 | 1 | 260 | 100 | 33 Oct. 19| 25 | 6 | 1 | 750 | 220 | 15 Oct. 20| 20 | 5 | 1 | Sunday. Oct. 21| 19 | 5 | 1 | 480 | 120 | 11 Oct. 22| 18 | 4 | 1 | 230 | 70 | 7 Oct. 23| 15 | 3 | 1 | 250 | 120 | 12 Oct. 24| 15 | 3 | 1 | 300 | 80 | 12 Oct. 25| 15 | 2 | 1 | 450 | 60 | 15 Oct. 26| 15 | 2 | 1 | 450 | Lost. | 14 Oct. 27| 13 | 2 | 0 | Sunday. Oct. 28| 13 | 2 | 0 | 190 | 110 | 9 Oct. 29| 25 | 2 | 0 | 380 | . . . | . . . Oct. 30| 21 | 3 | 0 | . . . | . . . | . . . Oct. 31| Out of commission. 4-in. Supply pipe stopped up. --------+-------+---------+---------+-------+---------+--------- Nov. 4| 125 | 11 | 1 | . . . | . . . | . . . Nov. 5| 185 | 61 | 1 | 6, 000 | 3, 000 | 220 Nov. 6| 170 | 66 | 1 | 5, 000 | 1, 100 | 150 Nov. 7| 100 | 45 | 1 |14, 000 | 1, 600 | 120 Nov. 8| 95 | 42 | 1 | 1, 900 | 2, 000 | 29 Nov. 9| 80 | 36 | 1 | 4, 000 | 2, 000 | 110 Nov. 10| 67 | 29 | 1 | Sunday. Nov. 11| 52 | 20 | 1 | 1, 900 | 460 | 160 Nov. 12| 40 | 13 | 1 | 7, 500 | 1, 100 | 110 Nov. 13| 36 | 10 | 1 | 1, 600 | 550 | 50 Nov. 14| 42 | 13 | 1 | 2, 700 | 950 | 48 Nov. 15| 35 | 11 | 1 | 1, 800 | 900 | 49 Nov. 16| 26 | 7 | 1 | 1, 100 | 360 | 35 Nov. 17| 20 | 5 | 1 | Sunday. Nov. 18| 17 | 4 | 1 | 1, 600 | 200 | 35 Nov. 19| 16 | 3 | 1 | 1, 300 | 400 | 55 Nov. 20| 45 | 4 | 1 | 6, 500 | 3, 500 | 200 Nov. 21| 52 | 12 | 1 | 9, 900 | 4, 500 | 130 Nov. 22| 65 | 24 | 1 |10, 000 | 5, 500 | 220 Nov. 23| 49 | 19 | 1 |18, 000 | 3, 500 | 100 Nov. 24| 134 | 32 | 1 | Sunday. Nov. 25| 225 | 87 | 2 |50, 000 | 19, 000 | 340 Nov. 26| 237 | 90 | 2 |40, 000 | 11, 000 | 220 Nov. 27| 185 | 77 | 2 |16, 000 | 7, 500 | 310 Nov. 28| 130 | 57 | 2 Holiday. Nov. 29| 80 | 36 | 1 |10, 000 | 2, 200 | 80 Nov. 30| 54 | 25 | 1 | 3, 800 | 2, 200 | 55 --------+-------+---------+---------+-------+---------+--------- Dec. 2|Shut down to scrape sand filter. Dec. 6| 16 | 3 | 1 | | | Dec. 7| 14 | 3 | 1 | 2, 400 | 1, 200 | 490 Dec. 8| 12 | 2 | 1 | Sunday. Dec. 9| 11 | 2 | 1 | 1, 200 | 420 | 60 Dec. 10| 12 | 2 | 1 | 800 | 950 | 66 Dec. 11| 255 | 84 | 3 | 6, 500 | 1, 600 | 140 Dec. 12| 212 | 100 | 6 |48, 000 | 15, 000 | 1, 800 Dec. 13| 495 | 217 | 9 |42, 000 | 20, 000 | 1, 600 Dec. 14| 357 | 167 | 9 |49, 000 | 9, 500 | 1, 200 Dec. 15| 157 | 76 | 6 | Sunday. Dec. 16| 90 | 42 | 4 |19, 000 | 800 | 700 Dec. 17| 70 | 31 | 2 |21, 000 | 18, 000 | 1, 600 Dec. 18| 49 | 21 | 2 | 6, 500 | 7, 000 | 600 Dec. 19| 39 | 13 | 1 | Lost. | Lost. | Lost. Dec. 20| 42 | 16 | 1 | Dec. | Dec. | " Dec. 21| 26 | 7 | 1 | Dec. | Dec. | " Dec. 22| 20 | 5 | 1 | Sunday. Dec. 23| 34 | 9 | 1 | 1, 400 | 500 | 160 Dec. 24| 195 | 75 | 2 | 9, 000 | 1, 700 | 130 Dec. 25| 445 | 210 | 9 | Holiday. Dec. 26| 370 | 172 | 7 |51, 000 | 8, 000 | 250 Dec. 27| 245 | 110 | 5 |55, 000 | 5, 600 | 210 Dec. 28| 102 | 46 | 3 |10, 000 | 4, 500 | 140 Dec. 29| 75 | 32 | 2 | Sunday. Dec. 30| 56 | 24 | 2 | 4, 400 | 1, 900 | 190 Dec. 31| 39 | 15 | 1 |14, 000 | 1, 300 | 60 --------+-------+---------+---------+-------+---------+--------- 1908. --------+-------+---------+---------+-------+---------+--------- Jan. 1| 31 | 8 | 1 | . . . | . . . | . . . Jan. 2| 39 | 11 | 1 | 4, 400 | 750 | 45 Jan. 3| 36 | 11 | 1 | 3, 100 | 1, 600 | 70 |Washed. | | | | | Jan. 4| 32 | 9 | 1 | 2, 400 | 1, 200 | 43 Jan. 5| 26 | 6 | 1 | Sunday. Jan. 6| 20 | 5 | 1 | 600 | 600 | 49 Jan. 7| 20 | 5 | 1 | 1, 100 | 330 | 49 Jan. 8| 22 | 5 | 1 | 1, 900 | 900 | 43 Jan. 9| 45 | 13 | 1 |13, 000 | 3, 400 | 50 Jan. 10| 70 | 30 | 1 |10, 000 | 8, 000 | 50 Jan. 11| 56 | 22 | 1 |16, 000 | 220 | 200 Jan. 12| 40 | 12 | 1 | Sunday. Jan. 13| 110 | 51 | 2 | 8, 500 | 1, 200 | 43 Jan. 14| 210 | 113 | 4 |16, 000 | 6, 000 | 280 Jan. 15| 325 | 222 | 15 |24, 000 | 9, 500 | 700 Jan. 16| 360 | 247 | 42 |28, 000 | 14, 000 | 900 Jan. 17| 242 | 147 | 26 |65, 000 | 20, 000 | 1, 200 Jan. 18| 137 | 73 | 7 | 7, 000 | 6, 500 | 400 Jan. 19| . . . | . . . | . . . | Sunday. Jan. 20|Scraped. | | | | Jan. 21| 55 | 25 | 4 | . . . | . . . | . . . Jan. 22| 49 | 21 | 4 | 3, 600 | 1, 900 | 150 Jan. 23| 40 | 15 | 3 | 1, 800 | 700 | 170 Jan. 24| 40 | 13 | 3 | 2, 300 | 950 | 90 Jan. 25| 39 | 12 | 3 | 1, 100 | 800 | 95 Jan. 26| 32 | 9 | 2 | Sunday. Jan. 27| 32 | 9 | 2 | 300 | 700 | 70 Jan. 28| 45 | 15 | 2 | 1, 200 | 900 | 70 Jan. 29| 60 | 26 | 2 | 1, 000 | 1, 400 | 95 Jan. 30| 57 | 27 | 2 | 1, 400 | 210 | 33 Jan. 31| 42 | 18 | 2 | 1, 100 | 750 | 45 --------+-------+---------+---------+-------+---------+--------- Feb. 1| 39 | 14 | 2 | 750 | 1, 000 | 70 Feb. 2| 27 | 9 | 2 | Sunday. Feb. 3| 29 | 8 | 2 | 1, 300 | 750 | 20 Feb. 4| 25 | 6 | 2 | 600 | 900 | 60 Feb. 5| 24 | 6 | 2 | 750 | 200 | 75 Feb. 6| 20 | 5 | 2 | 2, 000 | 800 | 60 Feb. 7| 17 | 4 | 1 | . . . | 600 | 34 Feb. 8| 15 | 4 | 1 | 900 | 220 | 35 Feb. 9| 14 | 4 | 1 | Sunday. Feb. 10| 11 | 4 | 1 | 850 | 500 | 28 Feb. 11| 10 | 4 | 1 | 1, 000 | 500 | 23 Feb. 12| 8 | 4 | 1 | 750 | 290 | 18 Feb. 13| 9 | 4 | 1 | 700 | 260 | 10 Feb. 14| 9 | 4 | 1 | 1, 200 | 250 | 27 Feb. 15| 61 | 18 | 1 | 5, 500 | 4, 800 | 13 Feb. 16| 80 | 40 | 2 | Sunday. Feb. 17| 80 | 40 | 3 |33, 000 | 1, 300 | 60 Feb. 18| 130 | 65 | 3 | . . . | 950 | 120 Feb. 19| 320 | 200 | 7 |28, 000 | 22, 000 | 360 Feb. 20| 177 | 97 | 9 |22, 000 | 16, 300 | 350 Feb. 21| 105 | 52 | 6 |10, 600 | 3, 800 | 270 Feb. 22| 85 | 42 | 5 | Holiday. Feb. 23| 60 | 30 | 4 | Sunday. Feb. 24| 46 | 19 | 3 | 3, 600 | 1, 700 | 120 Feb. 25| 31 | 9 | 2 | 2, 300 | 1, 300 | 60 Feb. 26| 30 | 8 | 2 | 3, 800 | 1, 300 | 43 Feb. 27| 30 | 7 | 1 | 1, 300 | 900 | 42 Feb. 28| 37 | 7 | 1 | 1, 400 | 800 | 31 Feb. 29| 123 | 49 | 2 |13, 500 | 750 | 35 --------+-------+---------+---------+-------+---------+--------- Mar. 1| 97 | 44 | 5 | Sunday. Mar. 2| 82 | 35 | 4 | 8, 000 | 2, 500 | 70 Mar. 3| 87 | 38 | 4 |11, 000 | 6, 000 | 55 Mar. 4| 67 | 29 | 3 | 6, 000 | 1, 400 | 38 Mar. 5| 59 | 23 | 3 | 4, 400 | 2, 500 | 37 Mar. 6| Discontinued; sand filter being used | for sedimentation experiments. ========+=======+=========+=========+=======+=========+==========

[Illustration: ~Figure 9--Detail of Strainer System. ~]

~Table 19--Record of Experimental Filter Plant. No. 3. ~ ========+===============+============================ | ~Sand Filter. ~| ~Turbidity. ~ +---------------+-------+----------+--------- Date. | Rate. |Loss of|Applied| Effluent, |Effluent, | | head. | water. |coagulant. | sand. --------+-------+-------+-------+----------+--------- 1907. --------+-------+-------+-------+----------+--------- Feb. 12| 2. 99 | 0. 18 | 14 | . . . | 2 Feb. 13| 3. 00 | 0. 17 | 15 | . . . | 2 Feb. 14| 3. 19 | 0. 18 | 15 | . . . | 2 Feb. 15| 3. 86 | 0. 22 | 12 | . . . | 2 Feb. 16| 3. 84 | 0. 29 | 14 | . . . | 2 Feb. 17| . . . | . . . | . . . | . . . | . . . Feb. 18| . . . | . . . | . . . | . . . | . . . Feb. 21| 3. 91 | 0. 32 | 20 | . . . | 2 Feb. 22| 3. 95 | 0. 39 | 15 | . . . | 2 Feb. 23| 3. 94 | 0. 43 | 20 | . . . | 3 Feb. 24| 3. 89 | 0. 47 | 20 | . . . | 3 Feb. 25| 4. 19 | 0. 52 | 20 | . . . | 3 Feb. 26| 4. 13 | 0. 57 | 20 | . . . | 3 Feb. 27| 3. 32 | 0. 62 | 17 | . . . | 3 Feb. 28| 4. 41 | 0. 67 | 15 | . . . | 3 --------+-------+-------+-------+----------+--------- Mar. 1| 3. 91 | 0. 72 | 15 | . . . | 3 Mar. 2| 3. 93 | 0. 79 | 15 | . . . | 3 Mar. 3| 3. 90 | 0. 82 | 31 | . . . | 3 Mar. 4| 3. 92 | 0. 80 | 35 | . . . | 3 Mar. 5| 3. 96 | 0. 98 | 135 | . . . | 4 Mar. 6| 4. 05 | 1. 25 | 135 | 29 | 2 Mar. 7| 3. 95 | 1. 52 | 102 | 15 | 1 Mar. 8| 3. 90 | 1. 67 | 100 | 15 | 1 Mar. 9| 3. 93 | 1. 80 | 90 | 15 | 1 Mar. 10| 3. 95 | 1. 91 | 82 | 16 | 1 Mar. 11| 3. 96 | 2. 08 | 68 | 18 | 1 Mar. 12| 4. 02 | 2. 19 | 46 | 18 | 1 Mar. 13| 4. 02 | 2. 31 | 40 | 15 | 1 Mar. 14| 3. 96 | 2. 44 | 39 | 16 | 1 Mar. 15| 4. 07 | 2. 42 | 35 | 20 | 1 Mar. 16| 3. 85 | 2. 20 | 60 | 29 | 1 Mar. 17| 3. 95 | 2. 21 | 135 | 25 | 1 Mar. 18| 3. 88 | 2. 86 | 170 | 25 | 1 Mar. 19| 3. 82 | 3. 31 | 125 | 21 | 1 Mar. 20| 3. 78 | 3. 47 | 102 | 20 | 1 Mar. 21| 3. 71 | 3. 70 | 125 | 20 | 1 Mar. 22| 3. 64 | 3. 81 | 190 | 25 | 1 Mar. 23| 3. 58 | 3. 95 | 180 | 26 | 1 Mar. 24| 3. 46 | 4. 18 | 140 | 19 | 1 Mar. 25|Scraped, 1. 03 in. Of sand removed. Mar. 27| 4. 06 | 0. 22 | 47 | 8 | 1 Mar. 28| 4. 02 | 0. 37 | 35 | . . . | 0 Mar. 29| 4. 02 | 0. 46 | 26 | . . . | . . . Mar. 30|Shut down to fill coagulant basin. | . . . | . . . | 25 | . . . | . . . Mar. 31| 4. 00 | 0. 45 | 21 | 15 | 1 --------+-------+-------+-------+----------+--------- Apr. 1| 3. 39 | 0. 42 | 20 | 15 | 1 Apr. 2| 3. 06 | 0. 46 | 24 | 17 | 1 Apr. 3| 3. 01 | 0. 49 | 24 | 17 | 1 Apr. 4| 2. 95 | 0. 50 | 20 | 15 | 1 Apr. 5| 2. 95 | 0. 51 | 20 | 13 | 1 Apr. 6| 2. 96 | 0. 49 | 20 | 12 | 1 Apr. 7| 2. 99 | 0. 48 | 20 | 12 | 1 Apr. 8| 3. 01 | 0. 49 | 18 | 12 | 1 Apr. 9| 3. 01 | 0. 55 | 18 | 12 | 1 Apr. 10| 3. 02 | 0. 57 | 30 | 15 | 0 Apr. 11| 3. 04 | 0. 61 | 66 | 16 | 0 Apr. 12| 3. 09 | 0. 72 | 72 | 13 | 0 Apr. 13| 3. 07 | 0. 88 | 80 | 19 | 0 Apr. 14| 2. 98 | 1. 04 | 77 | 18 | 1 Apr. 15| 2. 97 | 1. 20 | 62 | 18 | 1 Apr. 16| 3. 01 | 1. 32 | 47 | 17 | 1 Apr. 17| 3. 05 | 1. 44 | 39 | 19 | 0 Apr. 18| 3. 04 | 1. 41 | 30 | 20 | 1 Apr. 19| 3. 04 | 1. 35 | 25 | 18 | 1 Apr. 20| 3. 07 | 1. 30 | 20 | 15 | 1 Apr. 21| 3. 07 | 1. 26 | 20 | 15 | 1 Apr. 22| 3. 04 | 1. 21 | 18 | 12 | 0 Apr. 23| 3. 06 | 1. 22 | 15 | 10 | 0 Apr. 24| 2. 99 | 1. 26 | 19 | 10 | 0 Apr. 25| 3. 04 | 1. 27 | 34 | 12 | 0 Apr. 26| 3. 07 | 1. 28 | 46 | 12 | 0 Apr. 27| 2. 94 | 1. 49 | 52 | . . . | 0 Apr. 28| 2. 96 | 1. 88 | 45 | . . . | 1 Apr. 29| 2. 99 | 2. 40 | 44 | 33 | 1 Apr. 30| 3. 00 | 2. 83 | 39 | 29 | 1 --------+-------+-------+-------+----------+--------- May 1| 3. 01 | 2. 71 | 31 | 21 | 1 May 2| 3. 01 | 2. 51 | 24 | 15 | 1 May 3| 3. 00 | 2. 36 | 19 | 12 | 1 May 4| 3. 01 | 2. 29 | 16 | 10 | 0 May 5| 3. 01 | 2. 25 | 15 | 9 | 0 May 6| 3. 06 | 2. 32 | 13 | 8 | 0 May 7| 2. 96 | 2. 46 | 12 | 7 | 0 May 8| 3. 00 | 2. 51 | 10 | 5 | 0 May 9| 3. 00 | 2. 77 | 10 | 5 | 0 May 10| 3. 01 | 2. 87 | 10 | 5 | 0 May 11| 2. 99 | 3. 16 | 12 | 6 | 0 May 12| 3. 00 | 3. 34 | 17 | 7 | 0 May 13| 3. 00 | 3. 44 | 35 | 9 | 0 May 14| 3. 01 | 3. 46 | 39 | 12 | 0 May 15| 3. 01 | 3. 56 | 17 | . . . | 0 May 16| 2. 93 | 4. 07 | 24 | . . . | 0 May 17| 3. 01 | 4. 34 | 18 | . . . | 0 May 18| 2. 93 | 4. 25 | 15 | 8 | 0 May 19| 2. 97 | 4. 36 | 12 | 8 | 0 May 20| 3. 01 | 4. 64 | 12 | 8 | 0 May 21| 2. 99 | 4. 55 | 16 | 8 | 0 May 22| 3. 01 | 4. 57 | 20 | 8 | 0 May 23| 3. 00 | 4. 51 | 15 | 8 | 0 May 24| 2. 98 | 4. 44 | 15 | 8 | 0 May 25| 3. 00 | 4. 38 | 15 | 8 | 0 May 26| 3. 00 | 4. 38 | 18 | 8 | 0 May 27| Shut down to scrape sand filter; | 1. 09 in. Of sand removed. May 28| Cleaning coagulant basin and | treating coagulant basin with | 1:2, 000, 000 solution of copper sulphate. May 29| | | 16 | . . . | . . . May 30| 3. 00 | 0. 11 | 14 | 8 | 1 May 31| 3. 01 | 0. 10 | 17 | 8 | 1 --------+-------+-------+-------+----------+--------- June 1| 3. 01 | 0. 09 | 15 | 8 | 1 June 2| 3. 01 | 0. 10 | 17 | 8 | 1 June 3| 3. 01 | 0. 10 | 24 | 10 | 1 June 4| 3. 04 | 0. 11 | 37 | 13 | 1 June 5| 3. 00 | 0. 11 | 65 | 29 | 1 June 6| 3. 00 | 0. 11 | 77 | 46 | 1 June 7| 2. 99 | 0. 12 | 64 | 21 | 1 June 8| 2. 98 | 0. 17 | 46 | 22 | 1 June 9| 3. 00 | 0. 18 | 44 | 30 | 1 June 10| 3. 01 | 0. 18 | 36 | 26 | 1 June 11| 3. 00 | 0. 17 | 30 | 20 | 1 June 12| 3. 00 | 0. 17 | 34 | 22 | 1 June 13| 2. 99 | 0. 17 | 35 | 25 | 1 June 14| 2. 98 | 0. 17 | 31 | 22 | 1 June 15| 2. 99 | 0. 19 | 32 | 22 | 1 June 16| 3. 02 | 0. 21 | 26 | 18 | 1 June 17| 2. 99 | 0. 23 | 26 | 16 | 1 June 18| 3. 02 | 0. 25 | 31 | 20 | 1 June 19| 3. 02 | 0. 29 | 37 | 27 | 1 June 20| 3. 00 | 0. 32 | 30 | 21 | 1 June 21| 3. 01 | 0. 36 | 25 | 16 | 1 June 22| 3. 00 | 0. 40 | 20 | 12 | 1 June 23| 2. 97 | 0. 43 | 26 | 11 | 1 June 24| 2. 97 | 0. 44 | 140 | 36 | 1 June 25| 3. 02 | 0. 45 | 130 | 27 | 1 June 26| Interrupted, defective meter. June 27| 3. 00 | 0. 43 | 65 | 15 | 0 June 28| 3. 00 | 0. 44 | 47 | 19 | 0 June 29| 2. 99 | 0. 44 | 37 | 20 | 0 June 30| 2. 97 | 0. 42 | 30 | 19 | 0 --------+-------+-------+-------+----------+--------- July 1| 2. 99 | 0. 37 | 30 | 18 | 0 July 2| 3. 01 | 0. 33 | 32 | 19 | 0 July 3| 3. 00 | 0. 31 | 36 | 21 | 0 July 4| 3. 00 | 0. 30 | 44 | 30 | 0 July 5| 3. 00 | 0. 29 | 44 | 35 | 0 July 6| 3. 00 | 0. 28 | 39 | 30 | 0 July 7| 3. 00 | 0. 28 | 34 | 24 | 0 July 8| 3. 00 | 0. 28 | 25 | 16 | 0 July 9| 3. 00 | 0. 27 | 22 | 13 | 0 July 10| 2. 98 | 0. 27 | 47 | 27 | 1 July 11| 3. 00 | 0. 27 | 90 | 41 | 1 July 12| 3. 00 | 0. 29 | 97 | 21 | 1 July 13| 3. 00 | 0. 34 | 90 | 20 | 0 July 14| 3. 00 | 0. 40 | 90 | 19 | 0 July 15| 3. 00 | 0. 54 | 95 | 18 | 0 July 16| 3. 00 | 0. 59 | 120 | 20 | 0 July 17| 3. 00 | 0. 58 | 85 | 16 | 0 July 18| 2. 99 | 0. 61 | 56 | 13 | 0 July 19| 3. 01 | 0. 61 | 41 | 18 | 0 July 20| 2. 99 | 0. 51 | 62 | 27 | 0 July 21| 3. 00 | 0. 47 | 62 | 32 | 0 July 22| 3. 00 | 0. 47 | 80 | 34 | 0 July 23| 3. 01 | 0. 49 | 105 | 21 | 0 July 24| 3. 01 | 0. 60 | 95 | 19 | 0 July 25| 3. 00 | 0. 68 | 77 | 16 | 0 July 26| 2. 99 | 0. 68 | 67 | 17 | 0 July 27| 3. 00 | 0. 69 | 54 | 20 | 0 July 28| 3. 00 | 0. 72 | 46 | 27 | 0 July 29| 3. 00 | 0. 74 | 36 | 26 | 0 July 30| 2. 99 | 0. 76 | 29 | 19 | 0 July 31| 2. 99 | 0. 77 | 21 | 12 | 0 --------+-------+-------+-------+----------+--------- Aug. 1| 3. 00 | 0. 75 | 16 | 9 | 0 Aug. 2| 3. 00 | 0. 74 | 15 | 8 | 0 Aug. 3| 3. 00 | 0. 74 | 16 | 7 | 0 Aug. 4| 3. 00 | 0. 75 | 21 | 6 | 0 Aug. 5| 3. 00 | 0. 76 | 29 | 8 | 0 Aug. 6| 3. 00 | 0. 79 | 34 | 12 | 0 Aug. 7| 2. 99 | 1. 01 | 21 | 12 | 0 Aug. 8| 3. 00 | 1. 31 | 19 | 11 | 0 Aug. 9| 2. 98 | 1. 44 | 16 | 9 | 0 Aug. 10| 3. 00 | 1. 44 | 24 | 9 | 0 Aug. 11| 3. 00 | 1. 49 | 62 | 22 | 0 Aug. 12| 3. 00 | 1. 62 | 120 | 39 | 0 Aug. 13| 2. 97 | 2. 06 | 107 | 22 | 0 Aug. 14| 2. 97 | 3. 06 | 82 | 19 | 0 Aug. 15| 2. 81 | 3. 91 | 65 | 15 | 0 Aug. 16| 3. 00 | 4. 29 | 45 | 18 | 0 Aug. 17| 3. 00 | 3. 86 | 35 | 22 | 0 Aug. 18| 3. 00 | 3. 47 | 21 | 13 | 0 Aug. 19| 3. 00 | 3. 49 | 18 | 10 | 0 Aug. 20| 3. 00 | 3. 56 | 20 | 8 | 0 Aug. 21| 3. 00 | 3. 58 | 20 | 10 | 0 Aug. 22| 2. 99 | 3. 73 | 27 | 13 | 0 Aug. 23| 3. 00 | 4. 00 | 49 | 34 | 0 Aug. 24| 3. 00 | 4. 05 | 36 | 26 | 0 Aug. 25| 2. 98 | 4. 06 | 34 | 24 | 0 Aug. 26| 3. 00 | 4. 20 | 21 | 13 | 0 Aug. 27| 3. 00 | 4. 31 | 19 | 11 | 0 Aug. 28| 2. 99 | 4. 40 | 18 | 10 | 0 Aug. 29| 3. 01 | 4. 41 | 17 | 9 | 0 Aug. 30| 2. 98 | 4. 46 | 15 | 8 | 0 Aug. 31| Scraped. | 13 | . . . | . . . | 1. 88 in. Of | | | | sand removed. | | | --------+-------+-------+-------+----------+--------- Sept. 5| 3. 00 | 0. 10 | 34 | 4 | 0 Sept. 6| 3. 00 | 0. 10 | 160 | 3 | 0 Sept. 7| 3. 00 | 0. 09 | 64 | 3 | 0 Sept. 8| 3. 00 | 0. 08 | 56 | 4 | 0 Sept. 9| 3. 00 | 0. 08 | 59 | 3 | 0 Sept. 10| 2. 97 | 0. 07 | 57 | 3 | 0 Sept. 11| 2. 98 | 0. 07 | 65 | 2 | 0 Sept. 12| 2. 98 | 0. 08 | 72 | 2 | 0 Sept. 13| 3. 00 | 0. 08 | 87 | 3 | 0 Sept. 14| 3. 00 | 0. 08 | 72 | 3 | 0 Sept. 15| 3. 00 | 0. 08 | 65 | 3 | 0 Sept. 16| 3. 00 | 0. 08 | 65 | 2 | 0 Sept. 17| 3. 00 | 0. 08 | 52 | 2 | 0 Sept. 18| 3. 00 | 0. 08 | 60 | 2 | 0 Sept. 19| 2. 98 | 0. 08 | 85 | 2 | 0 Sept. 20| 2. 98 | 0. 09 | 100 | 2 | 0 Sept. 21| 2. 99 | 0. 09 | 120 | 3 | 0 Sept. 22| 3. 00 | 0. 09 | 137 | 3 | 0 Sept. 23| 3. 02 | 0. 09 | 112 | 4 | 0 Sept. 24| 3. 00 | 0. 10 | 100 | 4 | 0 Sept. 25| 3. 00 | 0. 11 | 432 | 3 | 0 Sept. 26| 2. 99 | 0. 11 | 385 | 2 | 0 Sept. 27| 3. 00 | 0. 12 | 245 | 4 | 0 Sept. 28| 2. 98 | 0. 13 | 127 | 4 | 0 Sept. 29| 2. 98 | 0. 14 | 105 | 4 | 0 Sept. 30| 2. 99 | 0. 15 | 115 | 3 | 0 --------+-------+-------+-------+----------+--------- Oct. 1| 3. 00 | 0. 15 | 82 | 3 | 0 Oct. 2| 2. 98 | 0. 16 | 65 | 3 | 0 Oct. 3| 3. 00 | 0. 17 | 59 | 2 | 0 Oct. 4| 2. 99 | 0. 17 | 55 | 2 | 0 Oct. 5| 2. 99 | 0. 19 | 59 | 2 | 0 Oct. 6| 2. 98 | 0. 20 | 59 | 2 | 0 Oct. 7| 2. 98 | 0. 21 | 52 | 2 | 0 Oct. 8| 2. 97 | 0. 21 | 54 | 2 | 0 Oct. 9| 2. 98 | 0. 22 | 51 | 2 | 0 Oct. 10| 2. 98 | 0. 24 | 50 | 2 | 0 Oct. 11| 2. 98 | 0. 25 | 47 | 2 | 0 Oct. 12| 2. 97 | 0. 26 | 36 | 3 | 0 Oct. 13| 2. 98 | 0. 27 | 40 | 4 | 0 Oct. 14| 2. 98 | 0. 29 | 47 | 5 | 0 Oct. 15| 2. 99 | 0. 31 | 41 | 5 | 0 Oct. 16| 2. 99 | 0. 32 | 35 | 4 | 0 Oct. 17| 2. 98 | 0. 34 | 30 | 4 | 0 Oct. 18| 3. 00 | 0. 35 | 25 | 4 | 0 Oct. 19| 3. 00 | 0. 35 | 25 | 4 | 0 Oct. 20| 3. 00 | 0. 35 | 20 | 3 | 0 Oct. 21| 3. 00 | 0. 35 | 19 | 3 | 0 Oct. 22| 2. 99 | 0. 36 | 18 | 3 | 0 Oct. 23| 2. 99 | 0. 37 | 15 | 3 | 0 Oct. 24| 2. 98 | 0. 38 | 15 | 3 | 0 Oct. 25| 2. 99 | 0. 39 | 15 | 3 | 0 Oct. 26| 2. 99 | 0. 40 | 15 | 3 | 0 Oct. 27| 2. 99 | 0. 41 | 13 | 2 | 0 Oct. 28| 2. 99 | 0. 43 | 13 | 2 | 0 Oct. 29| 2. 98 | 0. 44 | 25 | 2 | 0 Oct. 30| 2. 99 | 0. 46 | 21 | 2 | 0 Oct. 31| 2. 96 | 0. 48 | 25 | 3 | 0 --------+-------+-------+-------+----------+--------- Nov. 4| 3. 00 | 0. 51 | 125 | 2 | 0 Nov. 5| 3. 00 | 0. 53 | 185 | 2 | 0 Nov. 6| 2. 99 | 0. 56 | 170 | 2 | 0 Nov. 7| 2. 99 | 0. 60 | 100 | 3 | 0 Nov. 8| 2. 99 | 0. 64 | 95 | 3 | 0 Nov. 9| 2. 99 | 0. 70 | 80 | 4 | 0 Nov. 10| 2. 99 | 0. 79 | 67 | 4 | 0 Nov. 11| 2. 99 | 1. 00 | 52 | 6 | 0 Nov. 12| 2. 99 | 1. 46 | 40 | 9 | 0 Nov. 13| 2. 98 | 2. 09 | 36 | 10 | 0 Nov. 14| 2. 99 | 2. 74 | 42 | 9 | 0 Nov. 15| 2. 99 | 2. 98 | 35 | 8 | 0 Nov. 16| 2. 99 | 3. 03 | 26 | 8 | 0 Nov. 17| 3. 00 | 3. 07 | 20 | 6 | 0 Nov. 18| 3. 00 | 3. 09 | 17 | 5 | 0 Nov. 20| 2. 99 | 3. 17 | 45 | 3 | 0 Nov. 21| 2. 99 | 3. 22 | 52 | 3 | 0 Nov. 22| 2. 99 | 3. 27 | 65 | 5 | 0 Nov. 23| 2. 99 | 3. 33 | 49 | 8 | 0 Nov. 24| 2. 99 | 3. 41 | 134 | 11 | 0 Nov. 25| 2. 98 | 3. 54 | 225 | 12 | 1 Nov. 26| 2. 98 | 3. 68 | 237 | 13 | 1 Nov. 27| 2. 99 | 3. 96 | 185 | 16 | 1 Nov. 28| 2. 98 | 4. 29 | 130 | 18 | 1 Nov. 29| 2. 97 | 4. 48 | 80 | 19 | 1 Nov. 30| 2. 97 | 4. 54 | 54 | 15 | 1 --------+-------+-------+-------+----------+--------- Dec. 6| Scraped, 1. 62 in. Of sand removed. Dec. 8| 2. 97 | 0. 16 | 12 | 3 | 0 Dec. 9| 2. 98 | 0. 16 | 11 | 3 | 0 Dec. 10| 2. 98 | 0. 15 | 12 | 3 | 0 Dec. 11| 2. 99 | 0. 15 | 255 | 3 | 0 Dec. 12| 3. 00 | 0. 13 | 212 | 2 | 0 Dec. 13| 2. 98 | 0. 13 | 495 | 4 | 0 Dec. 14| 2. 99 | 0. 14 | 357 | 5 | 0 Dec. 15| 2. 99 | 0. 15 | 157 | 6 | 0 Dec. 16| 2. 98 | 0. 16 | 90 | 9 | 0 Dec. 17| 2. 98 | 0. 20 | 70 | 12 | 0 Dec. 18| 2. 98 | 0. 24 | 49 | 12 | 1 Dec. 19| 2. 98 | 0. 29 | 39 | 9 | 1 Dec. 20| 2. 98 | 0. 36 | 42 | 7 | 1 Dec. 21| 2. 97 | 0. 45 | 26 | 5 | 0 Dec. 22| 2. 98 | 0. 57 | 20 | 4 | 0 Dec. 23| 2. 98 | 0. 71 | 34 | 3 | 0 Dec. 24| 2. 98 | 0. 83 | 195 | 2 | 0 Dec. 25| 2. 98 | 0. 97 | 445 | 2 | 0 Dec. 26| 2. 98 | 1. 11 | 370 | 2 | 0 Dec. 27| 2. 98 | 1. 27 | 245 | 3 | 0 Dec. 28| 2. 98 | 1. 40 | 102 | 4 | 0 Dec. 29| 2. 98 | 1. 60 | 75 | 3 | 0 Dec. 30| 2. 97 | 1. 85 | 56 | 3 | 0 Dec. 31| 2. 98 | 2. 07 | 39 | 2 | 0 --------+-------+-------+-------+----------+--------- 1908. --------+-------+-------+-------+----------+--------- Jan. 1| 2. 99 | 2. 11 | 31 | 2 | 0 Jan. 2| 2. 98 | 2. 17 | 39 | 2 | 0 Jan. 3| 2. 98 | 2. 26 | 36 | 2 | 0 Jan. 4| 2. 98 | 2. 34 | 32 | 2 | 0 Jan. 5| 2. 98 | 2. 41 | 26 | 2 | 0 Jan. 6| 2. 98 | 2. 49 | 20 | 2 | 0 Jan. 7| 2. 98 | 2. 58 | 20 | 2 | 0 Jan. 8| 2. 99 | 2. 61 | 22 | 2 | 0 Jan. 9| 2. 99 | 2. 63 | 45 | 2 | 0 Jan. 10| 2. 98 | 2. 67 | 70 | 2 | 0 Jan. 11| 2. 98 | 2. 72 | 56 | 2 | 0 Jan. 12| 2. 98 | 2. 78 | 40 | 2 | 0 Jan. 13| 2. 98 | 2. 84 | 110 | 2 | 0 Jan. 14| 2. 98 | 2. 95 | 210 | 2 | 0 Jan. 15| 2. 98 | 3. 07 | 325 | 3 | 0 Jan. 16| 2. 98 | 3. 23 | 360 | 5 | 6 Jan. 17| 2. 97 | 3. 73 | 242 | 6 | 0 Jan. 18| 2. 98 | 4. 42 | 137 | 6 | 0 Jan. 19| 2. 99 | 4. 75 | 117 | 5 | 0 Jan. 21| Scrape, 1. 45 in. Of sand removed. Jan. 23| 3. 00 | 0. 14 | 40 | 3 | 0 Jan. 24| 3. 00 | 0. 14 | 40 | 3 | 0 Jan. 25| 3. 00 | 0. 13 | 39 | 3 | 0 Jan. 26| 3. 00 | 0. 13 | 32 | 3 | 0 Jan. 27| 3. 00 | 0. 13 | 32 | 2 | 0 Jan. 28| 2. 99 | 0. 15 | 45 | 3 | 0 Jan. 29| 2. 99 | 0. 20 | 69 | 6 | 1 Jan. 30| 2. 99 | 0. 24 | 57 | 8 | 1 Jan. 31| 2. 99 | 0. 30 | 42 | 6 | 1 --------+-------+-------+-------+----------+--------- Feb. 1| 2. 99 | 0. 34 | 39 | 5 | 1 Feb. 2| 2. 99 | 0. 41 | 27 | 4 | 1 Feb. 3| 2. 99 | 0. 51 | 29 | 3 | 0 Feb. 4| 2. 99 | 0. 56 | 25 | 3 | 0 Feb. 5| 2. 99 | 0. 58 | 24 | 4 | 0 Feb. 6| 2. 99 | 0. 61 | 20 | 6 | 0 Feb. 7| 3. 00 | 0. 64 | 17 | 8 | 1 Feb. 8| 2. 99 | 0. 66 | 15 | 8 | 1 Feb. 9| 3. 00 | 0. 67 | 14 | 8 | 1 Feb. 10| 2. 99 | 0. 67 | 11 | 8 | 1 Feb. 11| 3. 00 | 0. 66 | 10 | 7 | 1 Feb. 12| 3. 01 | 0. 64 | 8 | 6 | 1 Feb. 13| 3. 00 | 0. 62 | 9 | 5 | 1 Feb. 14| 3. 00 | 0. 61 | 9 | 5 | 1 Feb. 15| 3. 00 | 0. 60 | 61 | 5 | 1 Feb. 16| 3. 00 | 0. 60 | 80 | 6 | 1 Feb. 17| 3. 00 | 0. 62 | 80 | 14 | 1 Feb. 18| 2. 99 | 0. 67 | 130 | 20 | 1 Feb. 19| 2. 99 | 0. 76 | 320 | 18 | 2 Feb. 20| 2. 99 | 0. 83 | 177 | 15 | 2 Feb. 29| 3. 00 | 0. 85 | 123 | 8 | 1 --------+-------+-------+-------+----------+--------- Mar. 1| 3. 00 | 0. 87 | 97 | 9 | 1 Mar. 2| 2. 99 | 0. 92 | 82 | 13 | 1 Mar. 3| 2. 98 | 0. 96 | 87 | 19 | 1 Mar. 4| 2. 99 | 1. 02 | 67 | 21 | 1 Mar. 5| 2. 99 | 1. 08 | 59 | 25 | 1 Mar. 6| 2. 99 | 1. 15 | 72 | 25 | 2 Mar. 7| 2. 98 | 1. 21 | 82 | 25 | 2 Mar. 8| 2. 99 | 1. 25 | 92 | 29 | 2 Mar. 9| 2. 99 | 1. 30 | 125 | 34 | 2 Mar. 10| 2. 99 | 1. 35 | 142 | 39 | 2 Mar. 11| 2. 99 | 1. 39 | 155 | 35 | 2 Mar. 12| 2. 99 | 1. 42 | 135 | 29 | 2 Mar. 13| 2. 99 | 1. 46 | 122 | 19 | 2 Mar. 14| 2. 99 | 1. 47 | 97 | 12 | 1 Mar. 15| 2. 99 | 1. 48 | 77 | 8 | 1 Mar. 16| 3. 00 | 1. 52 | 65 | 9 | 0 Mar. 17| 2. 99 | 1. 66 | 59 | 7 | 0 Mar. 18| 2. 99 | 1. 72 | 67 | 11 | 1 Mar. 19| 2. 99 | 1. 75 | 60 | 24 | 1 Mar. 20| 2. 99 | 1. 81 | 57 | 25 | 1 Mar. 21| 2. 99 | 1. 89 | 67 | 22 | 1 Mar. 22| 2. 99 | 1. 95 | 80 | 21 | 1 Mar. 23| 3. 00 | 2. 00 | 90 | 26 | 1 Mar. 24| 2. 98 | 2. 06 | 82 | 32 | 1 Mar. 25| 2. 99 | 2. 17 | 67 | 39 | 1 Mar. 26| 2. 99 | 2. 24 | 60 | 36 | 1 Mar. 27| 2. 99 | 2. 29 | 59 | 30 | 1 Mar. 28| 3. 00 | 2. 32 | 51 | 21 | 1 Mar. 29| 2. 99 | 2. 35 | 31 | 18 | 1 Mar. 30| 3. 00 | 2. 38 | 30 | 14 | 1 Mar. 31| 2. 99 | 2. 43 | 39 | 9 | 1 --------+-------+-------+-------+----------+--------- Apr. 1| 2. 99 | 2. 50 | 44 | 7 | 1 Apr. 2| 2. 99 | 2. 58 | 42 | 8 | 1 Apr. 3| 2. 99 | 2. 65 | 41 | 11 | 1 Apr. 4| 2. 99 | 2. 74 | 54 | 12 | 1 Apr. 5| 3. 00 | 2. 82 | 50 | 12 | 1 Apr. 6| 2. 99 | 2. 88 | 41 | 14 | 1 Apr. 7| 2. 99 | 2. 98 | 35 | 13 | 1 Apr. 8| 2. 98 | 3. 15 | 39 | 11 | 1 Apr. 9| 2. 99 | 3. 35 | 40 | 8 | 1 Apr. 10| 2. 98 | 3. 50 | 40 | 8 | 1 Apr. 11| 2. 99 | 3. 65 | 45 | 7 | 0 Apr. 12| 2. 99 | 3. 79 | 52 | 5 | 0 Apr. 13| 2. 99 | 3. 92 | 50 | 4 | 0 Apr. 14| 2. 99 | 4. 05 | 45 | 4 | 0 Apr. 15| 2. 99 | 4. 16 | 45 | 3 | 0 Apr. 16| . . . | 4. 24 | 45 | 3 | 0 Apr. 21| Scraped, 0. 12 in. Of sand removed. Apr. 23| . . . | 0. 13 | 25 | 2 | 0 Apr. 24| 3. 00 | 0. 12 | 21 | 2 | 0 Apr. 25| 3. 00 | 0. 10 | 20 | 2 | 0 Apr. 26| 3. 00 | 0. 10 | 21 | 3 | 0 Apr. 27| 3. 00 | 0. 10 | 18 | 3 | 0 Apr. 28| 3. 00 | 0. 10 | 20 | 3 | 0 Apr. 29| 3. 00 | 0. 09 | 24 | 3 | 0 Apr. 30| 3. 00 | 0. 09 | 21 | 3 | 0 --------+-------+-------+-------+----------+--------- May 1| 3. 00 | 0. 09 | 32 | 3 | 0 May 2| 3. 00 | 0. 09 | 26 | 3 | 0 May 3| 3. 00 | 0. 11 | 22 | 5 | 0 May 4| 3. 00 | 0. 11 | 19 | 4 | 0 May 5| 3. 00 | 0. 11 | 18 | 4 | 0 May 6| 2. 99 | 0. 12 | 18 | 3 | 0 May 7| 3. 00 | 0. 13 | 19 | 3 | 0 May 8| 3. 00 | 0. 14 | 19 | 3 | 0 May 9| 2. 99 | 0. 14 | 18 | 3 | 0 May 10| 3. 00 | 0. 14 | 30 | 3 | 0 May 11| 3. 00 | 0. 13 | 60 | 3 | 0 May 12| 3. 00 | 0. 13 | 70 | 3 | 0 May 13| 3. 00 | 0. 13 | 66 | 7 | 0 May 14| 3. 00 | 0. 14 | 45 | 9 | 0 May 15| 2. 99 | 0. 14 | 39 | 7 | 0 May 16| 2. 99 | 0. 22 | 49 | 6 | 0 May 17| 2. 99 | 0. 33 | 46 | 4 | 0 May 18| 2. 99 | 0. 44 | 31 | 3 | 0 May 19| 2. 98 | 0. 62 | 36 | 3 | 0 May 20| 2. 99 | 0. 75 | 41 | 3 | 0 May 21| 2. 99 | 0. 89 | 31 | 4 | 0 May 22| 2. 99 | 1. 01 | 50 | 5 | 0 May 23| 2. 99 | 1. 12 | 127 | 5 | 0 May 24| 2. 99 | 1. 20 | 110 | 6 | 0 May 25| 2. 99 | 1. 24 | 90 | 9 | 0 May 26| 2. 98 | 1. 31 | 135 | 11 | 0 May 27| 2. 97 | 1. 54 | 110 | 12 | 0 May 28| 2. 97 | 1. 81 | 90 | 10 | 0 May 29| 2. 97 | 2. 08 | 70 | 7 | 0 May 30| 2. 97 | 2. 36 | 50 | 5 | 0 May 31| 2. 98 | 2. 63 | 34 | 4 | 0 --------+-------+-------+-------+----------+--------- June 1| 2. 98 | 2. 77 | 35 | 2 | 0 June 2| 2. 98 | 2. 84 | 39 | 2 | 0 June 3| 2. 98 | 3. 02 | 35 | 3 | 0 June 4| 3. 00 | 3. 01 | 30 | 4 | 0 June 5| 3. 00 | 2. 97 | 30 | 5 | 0 June 6| 3. 01 | 2. 81 | 27 | 5 | 0 June 7| 3. 01 | 2. 62 | 22 | 5 | 0 June 8| 3. 01 | 2. 38 | 20 | 4 | 0 June 9| 3. 00 | 2. 19 | 20 | 3 | 0 June 10| 3. 01 | 2. 02 | 17 | 3 | 0 June 11| 2. 99 | 1. 89 | 12 | 3 | 0 June 12| 2. 98 | 1. 92 | 11 | 2 | 0 June 13| 2. 98 | 1. 99 | 36 | 2 | 0 June 14| 2. 98 | 2. 08 | 39 | 2 | 0 June 15| 2. 98 | 2. 25 | 25 | 4 | 0 June 16| 2. 98 | 2. 54 | 34 | 5 | 0 June 17| 2. 97 | 2. 85 | 64 | 5 | 0 June 18| 2. 97 | 3. 20 | 57 | 5 | 0 June 19| 2. 98 | 3. 47 | 46 | 7 | 0 June 20| 2. 99 | 3. 73 | 37 | 8 | 0 June 21| 2. 99 | 4. 10 | 29 | 8 | 0 June 22| 2. 99 | 4. 44 | 25 | 6 | 0 June 23| 2. 99 | 4. 61 | 25 | 5 | 0 June 26| 3. 01 | 0. 09 | 15 | 2 | 0 June 27| 3. 00 | 0. 09 | 12 | 2 | 0 June 28| 3. 00 | 0. 09 | 9 | 2 | 0 June 29| 3. 00 | 0. 08 | 8 | 2 | 0 June 30| 3. 00 | 0. 07 | 10 | 2 | 0 --------+-------+-------+-------+----------+--------- July 1| 3. 00 | 0. 07 | 6 | 2 | 0 July 2| 3. 00 | 0. 07 | 8 | 2 | 0 July 3| 3. 00 | 0. 07 | 8 | 2 | 0 July 4| 3. 00 | 0. 07 | 9 | 2 | 0 July 5| 3. 00 | 0. 07 | 10 | 2 | 0 July 6| 3. 00 | 0. 07 | 9 | 2 | 0 July 7| 3. 00 | 0. 07 | 8 | 2 | 0 July 8| 3. 00 | 0. 07 | 9 | 2 | 0 July 9| 3. 00 | 0. 07 | 8 | 2 | 0 July 10| . . . | . . . | . . . | . . . | . . . July 11| 3. 00 | 0. 08 | 12 | 2 | 0 July 12| 3. 00 | 0. 08 | 11 | 2 | 0 July 13| 3. 00 | 0. 08 | 10 | 2 | 0 July 14| 3. 00 | 0. 09 | 16 | 2 | 0 July 15| 3. 00 | 0. 09 | 17 | 2 | 0 July 16| 3. 00 | 0. 10 | 14 | 2 | 6 July 17| 3. 00 | 0. 10 | 10 | 2 | 0 July 18| 3. 00 | 0. 11 | 11 | 2 | 0 July 19| 3. 00 | 0. 11 | 12 | 2 | 0 July 20| 3. 00 | 0. 12 | 10 | 2 | 0 July 21| 3. 00 | 0. 12 | 10 | 2 | 0 July 22| 3. 00 | 0. 13 | 13 | 2 | 0 July 23| 2. 99 | 0. 13 | 54 | 2 | 0 July 24| 2. 99 | 0. 14 | 305 | 2 | 0 July 25| 3. 00 | 0. 15 | 330 | 4 | 0 July 26| 3. 00 | 0. 15 | 290 | 9 | 0 July 27| 3. 00 | 0. 16 | 335 | 11 | 0 July 28| 2. 99 | 0. 17 | 170 | 10 | 0 July 29| 3. 00 | 0. 17 | 180 | 8 | 0 July 30| 2. 99 | 0. 18 | 237 | 7 | 0 July 31| 3. 00 | 0. 19 | 250 | 6 | 0 ========+=======+=======+=======+==========+=========

 ~Table 19~--(_Continued. _) ========+==============================+============ | ~Bacteria. ~ |~Coagulant. ~ +---------+----------+---------+------------ Date. | Applied | Effluent, |Effluent, |Grains, per | water. |coagulant. | sand. | gallon. --------+---------+----------+---------+------------ 1907. --------+---------+----------+---------+------------ Feb. 12| . . . | . . . | . . . | . . . Feb. 13| 600 | . . . | . . . | . . . Feb. 14| 650 | . . . | . . . | . . . Feb. 15| 600 | . . . | 2, 500 | . . . Feb. 16| 850 | . . . | 1, 600 | . . . Feb. 17| . . . | . . . | . . . | . . . Feb. 18| 1, 200 | . . . | 300 | . . . Feb. 21| 1, 800 | . . . | 550 | . . . Feb. 22| 2 | | Holiday. | Feb. 23| 1, 600 | . . . | 1, 100 | . . . Feb. 24| 3 | | Sunday. | Feb. 25| 1, 400 | . . . | 600 | . . . Feb. 26| 700 | . . . | 650 | . . . Feb. 27| 700 | . . . | 2, 300 | . . . Feb. 28| 800 | . . . | 550 | . . . --------+---------+----------+---------+------------ Mar. 1| 650 | . . . | 300 | . . . Mar. 2| 1, 000 | . . . | 270 | . . . Mar. 3| | Sunday. | | Mar. 4| 1, 200 | . . . | 140 | 1. 45 Mar. 5| 13, 000 | . . . | 190 | 1. 94 Mar. 6| 18, 000 | 2, 100 | 160 | 2. 03 Mar. 7| 24, 000 | 3, 500 | 160 | 1. 50 Mar. 8| 22, 000 | 1, 800 | 130 | 1. 38 Mar. 9| 24, 000 | 3, 500 | 130 | 1. 37 Mar. 10| | Sunday. | | 1. 26 Mar. 11| 18, 000 | 6, 000 | 120 | 1. 24 Mar. 12| 11, 000 | 9, 000 | 140 | 1. 08 Mar. 13| 9, 000 | 5, 000 | 120 | 0. 94 Mar. 14| 5, 500 | 3, 600 | 90 | 0 Mar. 15| 6, 500 | 3, 800 | 85 | 0 Mar. 16| 5, 000 | 3, 500 | 100 | 1. 26 Mar. 17| | Sunday. | | 1. 52 Mar. 18| 9, 000 | 1, 900 | 85 | 1. 75 Mar. 19| 7, 000 | 700 | 65 | 1. 57 Mar. 20| 4, 800 | 1, 500 | 60 | 1. 31 Mar. 21| 8, 500 | 1, 500 | 70 | 1. 38 Mar. 22| 7, 500 | 1, 100 | 35 | 1. 57 Mar. 23| 7, 500 | 470 | 55 | 1. 68 Mar. 24| | Sunday. | | 1. 52 Mar. 25|Scraped, 1. 03 in. Of sand removed. Mar. 27| 2, 200 | 480 | 60 | 1. 08 Mar. 28| 1, 300 | 250 | 80 | 1. 00 Mar. 29| 700 | 240 | 65 | 0 Mar. 30|{Shut down to fill coagulant basin. |{ 310 | . . . | . . . | 0 Mar. 31| | Sunday. | | 0 --------+---------+----------+---------+------------ Apr. 1| 600 | 1, 000 | 43 | 0 Apr. 2| 270 | Lost. | 35 | 0 Apr. 3| 460 | Apr. | 41 | 0 Apr. 4| 280 | 550 | 27 | 0 Apr. 5| 450 | 1, 000 | 60 | 0 Apr. 6| 320 | 50 | 35 | 0 Apr. 7| Sunday. | 0 | | Apr. 8| 330 | 650 | 22 | 0 Apr. 9| 140 | 750 | 21 | 0 Apr. 10| 750 | 5, 000 | 29 | 0 Apr. 11| 4, 000 | 550 | 25 | 1. 11 Apr. 12| 14, 000 | 2, 200 | 17 | 1. 15 Apr. 13| 13, 000 | 3, 900 | 25 | 1. 14 Apr. 14| | Sunday. | | 1. 17 Apr. 15| 7, 060 | 2, 200 | 19 | 1. 09 Apr. 16| 3, 600 | 900 | 22 | 1. 08 Apr. 17| 1, 600 | 1, 100 | 12 | 0 Apr. 18| 1, 810 | 1, 870 | 14 | 0 Apr. 19| 790 | 910 | 14 | 0 Apr. 20| 540 | 480 | 15 | 0 Apr. 21| | Sunday. | | . . . Apr. 22| 235 | 420 | 21 | 0 Apr. 23| 170 | 420 | 8 | 0 Apr. 24| 150 | 250 | 17 | 0 Apr. 25| 700 | 260 | 19 | 0 Apr. 26| 1, 200 | 320 | 80 | 0 Apr. 27| 1, 700 | 1, 500 | 70 | 0 Apr. 28| | Sunday. | | 0 Apr. 29| 600 | 1, 400 | 19 | 0 Apr. 30| 550 | 1, 200 | 14 | 0 --------+---------+----------+---------+------------ May 1| 500 | 1, 300 | 20 | 0 May 2| 500 | 850 | 16 | 0 May 3| 280 | 650 | 34 | 0 May 4| 400 | 550 | 24 | 0 May 5| | Sunday. | | 0 May 6| 390 | 460 | 80 | 0 May 7| 190 | . . . | 18 | 0 May 8| . . . | . . . | . . . | 0 May 9| 390 | 1, 100 | 14 | 0 May 10| 300 | 500 | 21 | 0 May 11| 390 | 650 | 16 | 0 May 12| | Sunday. | | 0 May 13| 600 | 470 | 27 | 0 May 14| 500 | 550 | 25 | 0 May 15| 500 | 900 | 23 | 0 May 16| 290 | 2, 500 | 25 | 0 May 17| 260 | 2, 000 | 16 | 0 May 18| 190 | 600 | 19 | 0 May 19| | Sunday. | | 0 May 20| 260 | 450 | 15 | 0 May 21| 260 | 330 | 14 | 0 May 22| 280 | 390 | 22 | 0 May 23| 130 | 240 | 19 | 0 May 24| 170 | 240 | 30 | 0 May 25| 340 | 400 | 41 | 0 May 26| | Sunday. | | 0 May 27| Shut down to scrape sand filter; | 1. 09 in. Of sand removed. Cleaning May 28| coagulant basin and treating coagulant | basin with 1:2, 000, 000 May 29| solution of copper sulphate. May 30| | Holiday. | | 0 May 31| 380 | 18, 000 | 150 | 0 --------+---------+----------+---------+------------ June 1| 900 | 7, 000 | 150 | 0 June 2| | Sunday. | | 0 June 3| 550 | 8, 000 | 130 | 0 June 4| 6, 500 | 7, 500 | 140 | 0 June 5| 3, 200 | 3, 600 | 110 | 0 June 6| 1, 500 | 800 | 60 | 1. 17 June 7| 2, 100 | 1, 500 | 90 | 1. 18 June 8| 660 | 1, 000 | 60 | 0 June 9| | Sunday. | | 0 June 10| 240 | 400 | 32 | 0 June 11| 280 | 300 | 31 | 0 June 12| 330 | . . . | 28 | 0 June 13| 480 | 480 | 39 | 0 June 14| 440 | 550 | 32 | 0 June 15| 420 | 450 | 27 | 0 June 16| | Sunday. | | 0 June 17| 340 | 750 | 14 | 0 June 18| 440 | 750 | 21 | 0 June 19| 500 | 460 | 35 | 0 June 20| 330 | 440 | 88 | 0 June 21| 170 | 370 | 23 | 0 June 22| 100 | 300 | 17 | 0 June 23| | Sunday. | | 0 June 24| 1, 700 | 350 | 22 | 1. 59 June 25| 400 | 250 | 16 | 1. 55 June 26| 750 | 330 | . . . | 0 June 27| . . . | 1, 400 | . . . | 0 June 28| . . . | 1, 400 | 120 | 0 June 29| 220 | 300 | . . . | 0 June 30| | Sunday. | | 0 --------+---------+----------+---------+------------ July 1| 400 | 600 | 85 | 0 July 2| 180 | 1, 000 | 50 | 0 July 3| 350 | 310 | 21 | 0 July 4| | Holiday. | | July 5| 550 | 400 | 41 | 0 July 6| 250 | 280 | 22 | 0 July 7| | Sunday. | | 0 July 8| 220 | 260 | 27 | 0 July 9| 50 | 40 | 19 | 0 July 10| Lost. | Lost. | Lost. | 0 July 11| 150 | 50 | 8 | 1. 27 July 12| 300 | 200 | 13 | 1. 27 July 13| 220 | 160 | 17 | 1. 27 July 14| | Sunday. | | 1. 27 July 15| 375 | 150 | | 1. 27 July 16| Lost. | 50 | Lost. | 1. 36 July 17| 270 | 60 | 3 | 1. 26 July 18| 1, 675 | 70 | | 1. 17 July 19| 450 | 700 | 11 | 0 July 20| 300 | 720 | 8 | 0 July 21| | Sunday. | | 0 July 22| 1, 400 | 560 | 14 | 1. 17 July 23| 3, 700 | 490 | 40 | 1. 25 July 24| 770 | 110 | 80 | 1. 27 July 25| 250 | 80 | 5 | 1. 22 July 26| 140 | 40 | 4 | 0 July 27| 300 | 130 | 21 | 0 July 28| | Sunday. | | 0 July 29| 470 | 290 | 100 | 0 July 30| Lost. | Lost. | Lost. | 0 July 31| July | July | July | 0 --------+---------+----------+---------+------------ Aug. 1| Lost. | Lost. | Lost. | 0 Aug. 2| 130 | 140 | 4 | 0 Aug. 3| 120 | 180 | 6 | 0 Aug. 4| | Sunday. | | Aug. 5| 230 | 100 | 44 | 0 Aug. 6| 85 | 470 | . . . | 0 Aug. 7| 200 | 450 | . . . | 0 Aug. 8| 100 | 180 | 45 | 0 Aug. 9| 75 | 80 | 16 | 0 Aug. 10| 60 | 90 | 11 | 0 Aug. 11| | Sunday. | | Aug. 12| 620 | 260 | 16 | 1. 45 Aug. 13| 820 | 520 | 10 | 1. 38 Aug. 14| 850 | 120 | 26 | 1. 22 Aug. 15| 150 | 260 | 6 | 1. 17 Aug. 16| 270 | 340 | 17 | 0 Aug. 17| 340 | 200 | 13 | 0 Aug. 18| | Sunday. | | Aug. 19| 180 | 220 | 17 | 0 Aug. 20| 210 | 180 | 16 | 0 Aug. 21| 1, 300 | 650 | 8 | 0 Aug. 22| 3, 800 | 360 | 6 | 0 Aug. 23| 2, 500 | 700 | 10 | 0 Aug. 24| 3, 900 | 630 | 12 | 0 Aug. 25| | Sunday. | | Aug. 26| 700 | 310 | 16 | 0 Aug. 27| 470 | 250 | 12 | 0 Aug. 28| 500 | 160 | 18 | 0 Aug. 29| 360 | 110 | 9 | 0 Aug. 30| 320 | 310 | 14 | 0 Aug. 31| 200 | 100 | . . . | 0 --------+---------+----------+---------+------------ Sept. 5| 360 | 950 | . . . | 1. 04 Sept. 6| 15, 000 | 1, 500 | 190 | 1. 35 Sept. 7| 2, 000 | 260 | 100 | 1. 20 Sept. 8| | Sunday. | . . . | 1. 04 Sept. 9| 220 | 180 | 38 | 1. 04 Sept. 10| 18, 000 | 150 | 29 | 1. 06 Sept. 11| 2, 700 | 200 | 37 | 1. 04 Sept. 12| 1, 000 | 125 | 19 | 1. 04 Sept. 13| 2, 300 | 200 | 72 | 1. 20 Sept. 14| 2, 400 | 360 | 36 | 1. 12 Sept. 15| | Sunday. | | 1. 04 Sept. 16| Lost. | Lost. | 38 | 1. 04 Sept. 17| 420 | 200 | 38 | 1. 07 Sept. 18| 900 | 200 | 17 | 1. 07 Sept. 19| 2, 000 | 220 | 25 | 1. 12 Sept. 20| 4, 200 | 320 | 31 | 1. 24 Sept. 21| 1, 100 | 160 | 19 | 1. 33 Sept. 22| | Sunday. | | 1. 45 Sept. 23| 2, 100 | 190 | 15 | 1. 41 Sept. 24| 4, 000 | 620 | 13 | 1. 33 Sept. 25| 56, 000 | 290 | 7 | 1. 83 Sept. 26| 1, 300 | 950 | 19 | 2. 34 Sept. 27| 4, 000 | Lost. | 20 | 1. 91 Sept. 28| 15, 000 | 1, 000 | 8 | 1. 54 Sept. 29| | Sunday. | | 1. 34 Sept. 30| Lost. | Lost. | 46 | 1. 35 --------+---------+----------+---------+------------ Oct. 1| 600 | 1, 700 | 22 | 1. 24 Oct. 2| 4, 400 | 550 | 8 | 1. 09 Oct. 3| 900 | 330 | 15 | 1. 04 Oct. 4| 850 | 250 | 11 | 1. 03 Oct. 5| 2, 000 | 450 | 25 | 1. 04 Oct. 6| | Sunday. | | 1. 04 Oct. 7| 1, 250 | 2, 300 | 42 | 1. 04 Oct. 8| 11, 000 | 100 | 15 | 1. 04 Oct. 9| 2, 000 | 1, 600 | 7 | 1. 04 Oct. 10| 800 | Lost. | 24 | 1. 04 Oct. 11| 2, 000 | 1, 200 | 21 | 0 Oct. 12| 1, 200 | 1, 200 | 19 | 0 Oct. 13| | Sunday. | | 0 Oct. 14| 1, 200 | 830 | 25 | 0 Oct. 15| 900 | Lost. | 105 | 0 Oct. 16| Lost. | 550 | 19 | 0 Oct. 17| 550 | 800 | 21 | 0 Oct. 18| 260 | 350 | 9 | 0 Oct. 19| 750 | 310 | 35 | 0 Oct. 20| | Sunday. | | 0 Oct. 21| 480 | 540 | 35 | 0 Oct. 22| 230 | 440 | 17 | 0 Oct. 23| 250 | 440 | 39 | 0 Oct. 24| 300 | 500 | 60 | 0 Oct. 25| 450 | 410 | 65 | 0 Oct. 26| 450 | 500 | 44 | 0 Oct. 27| | Sunday. | | 0 Oct. 28| 190 | 500 | 50 | 0 Oct. 29| 380 | 60 | 75 | 0 Oct. 30| 450 | 180 | 3 | 0 Oct. 31| 2, 300 | 390 | 75 | 0 --------+---------+----------+---------+------------ Nov. 4| . . . | . . . | . . . | 0 Nov. 5| 6, 000 | 1, 600 | 90 | 1. 70 Nov. 6| 5, 000 | 3, 900 | 6 | 1. 70 Nov. 7| 14, 000 | 300 | 9 | 1. 48 Nov. 8| 1, 900 | 230 | 2 | 1. 27 Nov. 9| 4, 000 | 2, 700 | 200 | 0 Nov. 10| | Sunday. | | 0 Nov. 11| 1, 900 | 2, 000 | 200 | 0 Nov. 12| 7, 500 | 2, 300 | 160 | 0 Nov. 13| 1, 600 | 1, 100 | 170 | 0 Nov. 14| 2, 700 | 950 | 130 | 0 Nov. 15| 1, 800 | 800 | 11 | 0 Nov. 16| 1, 100 | 800 | 90 | 0 Nov. 17| | Sunday. | | 0 Nov. 18| 1, 600 | 700 | 100 | 0 Nov. 20| 6, 500 | 120 | 120 | 0 Nov. 21| 9, 900 | 1, 000 | 80 | 0 Nov. 22| 10, 000 | 3, 200 | 90 | 0 Nov. 23| 18, 000 | 2, 400 | 100 | 0 Nov. 24| | Sunday. | | 0 Nov. 25| 50, 000 | 2, 100 | 65 | 1. 68 Nov. 26| 40, 000 | 2, 400 | 95 | 1. 76 Nov. 27| 16, 000 | 2, 600 | 60 | 1. 74 Nov. 28| | Holiday. | | 1. 57 Nov. 29| 10, 000 | 2, 500 | 65 | 1. 50 Nov. 30| 3, 800 | 1, 900 | 85 | 0 --------+---------+----------+---------+------------ Dec. 6| Scraped, 1. 62 in. Of sand removed. Dec. 8| | Sunday. | | 1. 17 Dec. 9| 1, 200 | 410 | 10 | 1. 17 Dec. 10| 800 | 550 | 150 | 1. 17 Dec. 11| 6, 500 | 600 | 130 | 1. 52 Dec. 12| 48, 000 | 500 | 130 | 1. 99 Dec. 13| 42, 000 | 500 | 120 | 2. 06 Dec. 14| 49, 000 | 750 | 150 | 2. 12 Dec. 15| | Sunday. | | 1. 69 Dec. 16| 19, 000 | 900 | 20 | 1. 28 Dec. 17| 21, 000 | 400 | 170 | 1. 17 Dec. 18| 6, 500 | 7, 000 | 350 | 1. 17 Dec. 19| Lost. | Lost. | Lost. | 1. 17 Dec. 20| Dec. | Dec. | Dec. | 1. 17 Dec. 21| Dec. | Dec. | Dec. | 1. 17 Dec. 22| | Sunday. | | 1. 17 Dec. 23| 1, 400 | 1, 300 | 220 | 1. 17 Dec. 24| 9, 000 | 1, 000 | 140 | 1. 49 Dec. 25| | Holiday. | | 2. 43 Dec. 26| 51, 000 | 1, 000 | 39 | 2. 15 Dec. 27| 55, 000 | 1, 600 | 70 | 1. 91 Dec. 28| 10, 000 | 1, 000 | 80 | 1. 50 Dec. 29| | Sunday. | | 1. 21 Dec. 30| 4, 400 | 700 | 80 | 1. 17 Dec. 31| 14, 000 | 1, 200 | 65 | 1. 17 --------+---------+----------+---------+------------ 1908. --------+---------+----------+---------+------------ Jan. 1| | Holiday. | | 1. 17 Jan. 2| 4, 400 | 700 | 19 | 1. 17 Jan. 3| 3, 100 | 1, 000 | 13 | 1. 17 Jan. 4| 2, 400 | 550 | 19 | 1. 17 Jan. 5| | Sunday. | | 1. 17 Jan. 6| 600 | 230 | 18 | 1. 17 Jan. 7| 1, 100 | 370 | 12 | 1. 17 Jan. 8| 1, 900 | 1, 100 | 20 | 1. 17 Jan. 9| 13, 000 | 1, 200 | 22 | 1. 21 Jan. 10| 10, 000 | 700 | 16 | 1. 17 Jan. 11| 16, 000 | 1, 200 | 11 | 1. 17 Jan. 12| | Sunday. | | 1. 17 Jan. 13| 8, 500 | 90 | 6 | 1. 27 Jan. 14| 16, 000 | 150 | 23 | 1. 56 Jan. 15| 24, 000 | 1, 100 | 19 | 1. 92 Jan. 16| 28, 000 | 1, 000 | 14 | 2. 10 Jan. 17| 65, 000 | 490 | 23 | 1. 91 Jan. 18| 7, 000 | 1, 600 | 14 | 1. 66 Jan. 19| | Sunday. | | 1. 50 Jan. 21| Scrape, 1. 45 in. Of sand removed. Jan. 23| . . . | . . . | . . . | 1. 17 Jan. 24| 2, 300 | 550 | 55 | 1. 17 Jan. 25| 1, 100 | 850 | 95 | 0 Jan. 26| | Sunday. | | 0 Jan. 27| 300 | 280 | 60 | 0 Jan. 28| 1, 200 | 700 | 70 | 0 Jan. 29| 1, 000 | 900 | 75 | 0 Jan. 30| 1, 400 | 650 | 50 | 0 Jan. 31| 1, 100 | 600 | 36 | 0 --------+---------+----------+---------+------------ Feb. 1| 750 | 50 | 25 | 0 Feb. 2| | Sunday. | | 0 Feb. 3| 1, 300 | 220 | 16 | 0 Feb. 4| 600 | 370 | 10 | 0 Feb. 5| 750 | 700 | 21 | 0 Feb. 6| 2, 000 | 650 | 4 | 0 Feb. 7| . . . | 410 | 26 | 0 Feb. 8| 900 | 160 | 42 | 0 Feb. 9| Sunday. | 0 Feb. 10| 850 | 450 | 18 | 0 Feb. 11| 1, 000 | 600 | 26 | 0 Feb. 12| 750 | 350 | 16 | 0 Feb. 13| 700 | 120 | 10 | 0 Feb. 14| 1, 200 | 950 | 43 | 0 Feb. 15| 5, 500 | 1, 000 | 23 | 0 Feb. 16| | Sunday. | | 0 Feb. 17| 33, 000 | 6, 100 | 36 | 0 Feb. 18| . . . | 2, 000 | 11 | 0 Feb. 19| 28, 000 | 9, 000 | 120 | 0 Feb. 20| 22, 000 | 8, 500 | 190 | 0 Feb. 29| . . . | . . . | . . . | 0 --------+---------+----------+---------+------------ Mar. 1| | Sunday. | | 0 Mar. 2| 8, 000 | 4, 400 | 50 | 0 Mar. 3| 11, 000 | 2, 100 | 26 | 0 Mar. 4| 6, 000 | 4, 700 | 7 | 0 Mar. 5| 4, 400 | 10, 000 | 36 | 0 Mar. 6| 7, 000 | 7, 400 | 50 | 0 Mar. 7| 9, 500 | 6, 500 | 28 | 0 Mar. 8| | Sunday. | | 0 Mar. 9| 11, 000 | 4, 800 | 25 | 0 Mar. 10| 8, 500 | 1, 200 | 23 | 0 Mar. 11| 6, 500 | 2, 400 | 20 | 0 Mar. 12| 5, 900 | 1, 500 | 11 | 0 Mar. 13| 1, 900 | 1, 100 | 12 | 0 Mar. 14| 1, 800 | 700 | 6 | 0 Mar. 15| | Sunday. | | 0 Mar. 16| 1, 400 | 700 | 8 | 0 Mar. 17| 900 | 800 | 11 | 0 Mar. 18| 1, 000 | 650 | 8 | 0 Mar. 19| . . . | 600 | 18 | 0 Mar. 20| 1, 300 | 750 | 20 | 0 Mar. 21| 800 | 480 | 18 | 0 Mar. 22| | Sunday. | | 0 Mar. 23| 4, 600 | 440 | 19 | 0 Mar. 24| 2, 500 | 1, 200 | 10 | 0 Mar. 25| 1, 600 | 650 | 20 | 0 Mar. 26| 550 | 410 | 7 | 0 Mar. 27| 900 | 900 | 29 | 0 Mar. 28| 650 | 250 | 42 | 0 Mar. 29| | Sunday. | | 0 Mar. 30| 500 | 650 | 28 | 0 Mar. 31| 750 | 290 | 30 | 0 --------+---------+----------+---------+------------ Apr. 1| 750 | 390 | 32 | 0 Apr. 2| 1, 100 | 280 | 47 | 0 Apr. 3| 1, 500 | 550 | 70 | 0 Apr. 4| 700 | 380 | 4 | 0 Apr. 5| | Sunday. | | 0 Apr. 6| 440 | 150 | 4 | 0 Apr. 7| 650 | 270 | 42 | 0 Apr. 8| 550 | 210 | 65 | 0 Apr. 9| 390 | 160 | 95 | 0 Apr. 10| 500 | 130 | 130 | 0 Apr. 11| 430 | 145 | 100 | 0 Apr. 12| | Sunday. | | 0 Apr. 13| 490 | 160 | 80 | 0 Apr. 14| 550 | 170 | 90 | 0 Apr. 15| 420 | 160 | 12 | 0 Apr. 16| 360 | 130 | 90 | 0 Apr. 21| Scraped, 0. 12 in. Of sand removed. Apr. 23| 140 | 140 | . . . | 0 Apr. 24| 200 | Lost. | 150 | 0 Apr. 25| 85 | 550 | 45 | 0 Apr. 26| | Sunday. | | 0 Apr. 27| 95 | 850 | 50 | 0 Apr. 28| 70 | 220 | 48 | 0 Apr. 29| 110 | 210 | 95 | 0 Apr. 30| 70 | 140 | 29 | 0 --------+---------+----------+---------+------------ May 1| 130 | 210 | 65 | 0 May 2| 140 | 140 | 55 | 0 May 3| | Sunday. | | 0 May 4| 85 | 210 | 75 | 0 May 5| 130 | 150 | 48 | 0 May 6| 230 | 430 | 50 | 0 May 7| 160 | 90 | 40 | 0 May 8| 375 | 425 | 7 | 0 May 9| 1, 209 | 180 | 6 | 0 May 10| | Sunday. | | 0 May 11| 2, 800 | 150 | 12 | 0 May 12| 2, 900 | 225 | 26 | 0 May 13| 1, 800 | 450 | 53 | 0 May 14| 2, 700 | 550 | 10 | 0 May 15| 950 | 300 | 65 | 0 May 16| 800 | 250 | 49 | 0 May 17| | Sunday. | | 0 May 18| 700 | 1, 700 | 80 | 0 May 19| 375 | 950 | 53 | 0 May 20| 425 | 700 | 46 | 0 May 21| 300 | 600 | 6 | 0 May 22| 950 | 230 | 17 | 0 May 23| 2, 400 | 32 | 28 | 0 May 24| | Sunday. | | 0 May 25| 1, 100 | 850 | 9 | 0 May 26| 3, 200 | 150 | 17 | 0 May 27| 1, 450 | 175 | 8 | 0 May 28| 1, 000 | 132 | 7 | 0 May 29| 1, 100 | 230 | 8 | 0 May 30| | Holiday. | | 0 May 31| | Sunday. | | 0 --------+---------+----------+---------+------------ June 1| . . . | . . . | . . . | 0 June 2| . . . | . . . | . . . | 0 June 3| . . . | . . . | . . . | 0 June 4| . . . | . . . | . . . | 0 June 5| . . . | . . . | . . . | 0 June 6| . . . | . . . | . . . | 0 June 7| . . . | . . . | . . . | 0 June 8| . . . | . . . | . . . | 0 June 9| . . . | . . . | . . . | 0 June 10| . . . | . . . | . . . | 0 June 11| . . . | . . . | . . . | 0 June 12| . . . | . . . | . . . | 0 June 13| . . . | . . . | . . . | 0 June 14| . . . | . . . | . . . | 0 June 15| . . . | . . . | . . . | 0 June 16| . . . | . . . | . . . | 0 June 17| . . . | . . . | . . . | 0 June 18| . . . | . . . | . . . | 0 June 19| . . . | . . . | . . . | 0 June 20| . . . | . . . | . . . | 0 June 21| . . . | . . . | . . . | 0 June 22| . . . | . . . | . . . | 0 June 23| . . . | . . . | . . . | 0 June 26| . . . | . . . | . . . | 0 June 27| . . . | . . . | . . . | 0 June 28| . . . | . . . | . . . | 0 June 29| . . . | . . . | . . . | 0 June 30| . . . | . . . | . . . | 0 --------+---------+----------+---------+------------ July 1| 80 | 75 | 3 | 0 July 2| 290 | 20 | 3 | 0 July 3| 350 | 140 | 4 | 0 July 4| | Holiday. | | 0 July 5| | Sunday. | | 0 July 6| 300 | 52 | 4 | 0 July 7| 110 | 35 | 2 | 0 July 8| 85 | 105 | 2 | 0 July 9| 85 | 80 | 3 | 0 July 10| 300 | 65 | 1 | 0 July 11| 145 | 95 | 11 | 0 July 12| | Sunday. | | 0 July 13| 115 | 105 | 7 | 0 July 14| 800 | 34 | 1 | 0 July 15| 180 | 165 | 3 | 0 July 16| 100 | 95 | 2 | 0 July 17| 65 | 65 | 1 | 0 July 18| 38 | 200 | 24 | 0 July 19| | Sunday. | | 0 July 20| 95 | 31 | 1 | 0 July 21| 70 | 100 | 2 | 0 July 22| 450 | 13 | 4 | 0 July 23| 650 | 325 | 4 | 0 July 24| 1, 650 | 325 | . . . | 0 July 25| 2, 600 | 55 | 2 | 0 July 26| | Sunday. | | 0 July 27| 35, 000 | 1, 200 | 6 | 0 July 28| 1, 200 | 675 | 6 | 0 July 29| 2, 000 | 270 | 11 | 0 July 30| 800 | 190 | 2 | 0 July 31| 1, 000 | 310 | 6 | 0 ========+=========+==========+=========+============

 ~Table 20--Summary of Results of Experimental Filters. ~ ==================+========+========+========+=========+=========+======== Filter number. . . . . | 1 | 2 | 3 | 4 | 5 | 6 | | | | | | Number of runs. . . . | 3 | 6 | 11 | 12 | 25 | 28 ------------------+--------+--------+--------+---------+---------+-------- Rate, million gallons per acre per day: Maximum. . . . . . . | 1. 35 | 3. 95 | 7. 96 | 12. 60 | 37. 5 | 118. 9 Minimum. . . . . . . | 0. 62 | 2. 30 | 3. 73 | 5. 77 | 6. 68 | 7. 1 Average. . . . . . . | 1. 06 | 3. 26 | 6. 69 | 10. 17 | 26. 1 | 38. 54 ------------------+--------+--------+--------+---------+---------+-------- Length of run, in days: Maximum. . . . . . . | 233. 5 | 150. 5 | 75. 2 | 90. 9 | 48. 71 | 39. 83 Minimum. . . . . . . | 181. 7 | 42. 0 | 14. 5 | 10. 1 | 0. 67 | 0. 62 Average. . . . . . . | 206. 4 | 109. 6 | 48. 89 | 40. 5 | 14. 41 | 12. 61 ------------------+--------+--------+--------+---------+---------+-------- Million gallons filtered per acre per run: Maximum. . . . . . . | 242. 61 | 484. 46 | 534. 67 | 960. 72 |1, 463. 35 |1, 022. 27 Minimum. . . . . . . | 202. 60 | 135. 66 | 93. 79 | 92. 57 | 19. 53 | 53. 32 Average. . . . . . . | 218. 58 | 302. 82 | 326. 76 | 417. 23 | 374. 14 | 361. 92 ------------------+--------+--------+--------+---------+---------+-------- Cubic yards of sand removed per acre at end of each run: Maximum. . . . . . . | 269 | 269 | 672 |1, 612 |2, 420 |3, 360 Minimum. . . . . . . | 269 | 134 | 101 | 134 | 134 | 101 Average. . . . . . . | 269 | 213 | 272 | 392 | 583 | 635 ------------------+--------+--------+--------+---------+---------+-------- Cubic yards of | | | | | | sand removed | | | | | | per acre per | | | | | | million gallons | | | | | | filtered. . . . . . . . | 1. 23 | 0. 70 | 0. 83 | 0. 94 | 1. 55 | 1. 72 ------------------+--------+--------+--------+---------+---------+-------- Average initial | | | | | | loss of head. . . . | 0. 07 | 0. 19 | 0. 51 | 0. 78 | 3. 88 | 5. 38 ------------------+--------+--------+--------+---------+---------+-------- Turbidity, influent: Maximum. . . . . . . | 120 | 120 | 120 | 120 | 90 | 100 Minimum. . . . . . . | 2 | 2 | 2 | 2 | 2 | 2 Average. . . . . . . | 20 | 20 | 21 | 22 | 18 | 19 ------------------+--------+--------+--------+---------+---------+-------- Turbidity, effluent: Maximum. . . . . . . | 11 | 13 | 17 | 18 | 30 | 30 Minimum. . . . . . . | 0 | 0 | 0 | 0 | 0 | 0 Average. . . . . . . | 1 | 1 | 2 | 2 | 4 | 3 ------------------+--------+--------+--------+---------+---------+-------- Percentage | | | | | | reduction | 95. 0 | 95. 0 | 90. 5 | 90. 9 | 77. 8 | 84. 3 ------------------+--------+--------+--------+---------+---------+-------- Bacteria, influent: Maximum. . . . . . . |180, 000 |180, 000 |180, 000 | 110, 000 | 180, 000 | 37, 500 Minimum. . . . . . . | 22 | 20 | 22 | 20 | 25 | 24 Average. . . . . . . | 4, 800 | 5, 100 | 4, 500 | 4, 200 | 6, 900 | 5, 900 ------------------+--------+--------+--------+---------+---------+-------- Bacteria, effluent: Maximum. . . . . . . | 4, 000 | 1, 300 | 3, 200 | 5, 400 | 12, 800 | 2, 400 Minimum. . . . . . . | 2 | 3 | 1 | 1 | 2 | 2 Average. . . . . . . | 160 | 85 | 110 | 120 | 190 | 180 ------------------+--------+--------+--------+---------+---------+-------- Percentage, | | | | | | Reduction. . . . . . . | 96. 7 | 98. 3 | 97. 6 | 97. 3 | 97. 3 | 97. 0 ------------------+--------+--------+--------+---------+---------+-------- Number of samples examined for _bacillus coli_ in influent: 10 c. C. . . . . . . . | 549 | 478 | 476 | 436 | 325 | 336 1 c. C. . . . . . . . | 560 | 492 | 486 | 445 | 335 | 342 0. 1 c. C. . . . . . | 525 | 459 | 452 | 413 | 318 | 317 0. 01 c. C. . . . . | 511 | 443 | 439 | 405 | 308 | 304 0. 001 c. C. . . . | 500 | 434 | 429 | 394 | 299 | 294 ------------------+--------+--------+--------+---------+---------+-------- Number of samples examined for _bacillus coli_ in effluent: 10 c. C. . . . . . . . | 512 | 452 | 454 | 404 | 296 | 309 1 c. C. . . . . . . . | 513 | 454 | 457 | 406 | 299 | 311 0. 1 c. C. . . . . . | 480 | 419 | 426 | 383 | 271 | 286 0. 01 c. C. . . . . | 478 | 406 | 410 | 367 | 261 | 276 0. 001 c. C. . . . | 478 | 406 | 410 | 367 | 261 | 276 ------------------+--------+--------+--------+---------+---------+-------- Number samples positive, influent: 10 c. C. . . . . . . . | 226 | 211 | 201 | 258 | 136 | 152 1 c. C. . . . . . . . | 127 | 123 | 116 | 108 | 81 | 93 0. 1 c. C. . . . . . | 55 | 59 | 54 | 51 | 43 | 42 0. 01 c. C. . . . . | 26 | 34 | 33 | 33 | 27 | 25 0. 001 c. C. . . . | 6 | 6 | 5 | 6 | 3 | 3 ------------------+--------+--------+--------+---------+---------+-------- Number samples positive, effluent: 10 c. C. . . . . . . . | 100 | 109 | 134 | 98 | 94 | 106 1 c. C. . . . . . . . | 51 | 61 | 55 | 56 | 46 | 50 0. 1 c. C. . . . . . | 9 | 13 | 16 | 16 | 4 | 13 0. 01 c. C. . . . . | 0 | 0 | 0 | 0 | 0 | 0 0. 001 c. C. . . . | 0 | 0 | 0 | 0 | 0 | 0 ------------------+--------+--------+--------+---------+---------+-------- Percentage of samples showing _bacillus coli_ in influent: 10 c. C. . . . . . . . | 41. 2 | 44. 2 | 42. 2 | 59. 2 | 41. 9 | 45. 2 1 c. C. . . . . . . . | 22. 7 | 25. 0 | 23. 9 | 24. 3 | 24. 2 | 27. 2 0. 1 c. C. . . . . . | 10. 5 | 12. 8 | 11. 9 | 12. 3 | 13. 5 | 13. 2 0. 01 c. C. . . . . | 5. 1 | 7. 7 | 7. 5 | 8. 2 | 8. 8 | 8. 2 0. 001 c. C. . . . | 1. 2 | 1. 4 | 1. 2 | 1. 5 | 1. 0 | 1. 0 ------------------+--------+--------+--------+---------+---------+-------- Percentage of samples showing _bacillus coli_ in effluent: 10 c. C. . . . . . . . | 19. 5 | 24. 1 | 29. 5 | 24. 2 | 31. 7 | 34. 3 1 c. C. . . . . . . . | 10. 0 | 13. 4 | 12. 0 | 13. 8 | 15. 4 | 16. 1 0. 1 c. C. . . . . . | 1. 9 | 3. 1 | 3. 8 | 4. 2 | 1. 5 | 4. 5 0. 01 c. C. . . . . | 0 | 0 | 0 | 0 | 0 | 0 0. 001 c. C. . . . | 0 | 0 | 0 | 0 | 0 | 0 ------------------+--------+--------+--------+---------+---------+-------- Cost per million | | | | | | gallons for | | | | | | sand handling. . . . . | $0. 43 | $0. 25 | $0. 29 | $0. 33 | $0. 54 | $0. 60 ------------------+--------+--------+--------+---------+---------+-------- Interest charges | | | | | | at 3%. . . . . . . . . . . | 6. 85 | 2. 25 | 1. 12 | 0. 73 | 0. 32 | 0. 22 ------------------+--------+--------+--------+---------+---------+-------- Total. . . . . . . . . | 7. 28 | 2. 50 | 1. 41 | 1. 06 | 0. 86 | . 82 ==================+========+========+========+=========+=========+========= _Coli_ tests presumptive. 

DISCUSSION

~Allen Hazen, M. Am. Soc. C. E. ~ (by letter). --This paper contains amost interesting and instructive record of the actual operation of alarge filter plant, and also a record of a number of experiments. The author has described some useful arrangements for improving theefficiency or reducing the cost. 

The utility of raking, as an intermediate treatment betweenscrapings, seems to have been clearly demonstrated. Its practicaleffect is to allow a greater quantity of water to be passed betweenscrapings, thereby saturating--if the term may be used--the surfacelayer with clay and other fine matter before removing it, instead oftaking it off when only a thin surface layer of it has been thussaturated. 

The large proportion of the total purification that takes place inpassing through three reservoirs successively, holding in theaggregate a quantity of water equal to about 7 days' use, is verystriking. Taking all the records, the percentage remaining afterpassing through these reservoirs, is as follows:

 Sediment for the year, 1909-1910, Table 2. . . . . . . . . . . . . . . . . . . . 17% Turbidities, 5-year average, Table 3. . . . . . . . . . . . . . . . . . . . . . . . . 25% Bacteria, 5-year average, Table 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . 24% Bacteria, selected winter months with high numbers in the raw water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20% Bacteria, selected summer months with high numbers in the raw water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 5%

There is considerable seasonal fluctuation in the results ofsettling and filtering, as is shown in Table 21. 

 ~Table 21--Average Removal of Turbidity and Bacteria by Washington Filters for Whole Period, Arranged by Seasons~. ===========================+========+========+========+========+======== | Winter. | Spring. | Summer. | Fall. | Year. ----------------+----------+--------+--------+--------+--------+-------- Turbidity, in | raw | 135 | 96 | 144 | 42 | 105 parts per | settled | 33 | 28 | 27 | 15 | 26 million: | filtered | 4 | 3 | 1 | 0. 5 | 2 ----------------+----------+--------+--------+--------+--------+-------- Percentage | settling | 24 | 29 | 19 | 36 | 25 left from: | filtering| 12 | 10 | 4 | 3 | 8 | both | 3 | 1 | 0. 3 | 1 | 2 ----------------+----------+--------+--------+--------+--------+-------- Bacteria per | raw | 16, 600 | 4, 150 | 4, 100 | 1, 960 | 6, 700 cubic | settled | 6, 300 | 980 | 160 | 270 | 1, 940 centimeter: | filtered | 149 | 29 | 18 | 22 | 54 ----------------+----------+--------+--------+--------+--------+-------- Percentage | settling | 38 | 24 | 4 | 14 | 29 left from: | filtering| 2. 4 | 3. 0 | 11. 2 | 8. 2 | 2. 8 | both | 0. 90 | 0. 79 | 0. 44 | 1. 12 | 0. 81 ================+==========+========+========+========+========+========

The fluctuation in the efficiency of the plant as a whole by seasonsis greater with the turbidity than with the bacteria. During thewinter the effluent contains 3% of the turbidity of the raw water, and in summer only 0. 3 per cent. Most of this difference isrepresented by the increased efficiency of the filters in summer, and only a little of it by the increased efficiency of settling. With bacteria, on the other hand, the seasonal fluctuation of theplant as a whole is comparatively small, but the settling andstorage processes are much more efficient in summer than in winter, the filters being apparently less efficient. The writer believesthat they are only apparently less efficient, and not really so, theexplanation being that some bacteria always grow in the under-drainsand lower parts of the filter, and are washed away by the effluent. The average number of bacteria in summer in the settled water is 160per cu. Cm. And in the filtered water 18. These are very lownumbers. It is the writer's view that nearly all of these 18represent under-drain bacteria, and practically bear no relation tothose in the applied water, and, if this view is correct, the numberof bacteria actually passing through the various processes is at alltimes less than the figures indicate. In the warmer part of the yearthe difference is a wide one, and the hygienic efficiency of theprocess is much greater than is indicated by the gross numbers ofbacteria. 

The reduction of the typhoid death rate has not been as great withthe change in water supply as was the case at Lawrence, Albany, andother cities, apparently because the Potomac water before it wasfiltered was not the cause of a large part of the typhoid fever. 

The sewage pollution of the Potomac is much less than that of theMerrimac and the Hudson, and it is perhaps not surprising that thisrelatively small amount of pollution was less potent in causingtyphoid fever than the greater pollution of rivers draining moredensely populated areas. 

The method of replacing the washed sand hydraulically seems to haveworked better than could have been reasonably anticipated, and thewriter believes that this was due, in part, to the excellent methodof manipulation described in the paper. It is his feeling, however, that part of the success is attributable to the very low uniformitycoefficient of the sand. In other words, the sand grains are nearlyall of the same size, due to the character of the stock from whichthe filter sand was prepared; and, therefore, there is much lessopportunity for separation of the sand according to grain sizes thanthere would be with the filter sand which has been available in mostother cases. Filter sand with a uniformity coefficient as low asthat obtained at Washington has been rarely available for theconstruction of sand filters, and while the method of hydraulicreturn should certainly be considered, it will not be safe to assumethat equally favorable results may be obtained with it with sands ofhigh uniformity coefficients until actual favorable experience isobtained. 

The writer believes that in calculating the cost of the water usedin the plant itself the price chosen by the author, covering onlythe actual operating expenses of pumping and filtering, is too low. The capacity of the whole Washington Aqueduct system is reduced bywhatever quantity is used in this way, and, in calculating the costof sand handling, the value of the water used should be calculatedon a basis which will cover the whole cost of the water, includingall capital charges, depreciation, operating expenses, and all costsof every description. On this basis the water used in thesand-handling operations would probably be worth five or more timesthe sum mentioned by the author. 

The cost of operation of the plant has come within the estimatesmade in advance, and has certainly been most reasonable. The cost offilter operations has averaged only about 50 cents per milliongallons, and is so low that it is obvious that the savings which maybe made by introducing further labor-saving appliances would berelatively small. It will be remembered that ten or fifteen yearsago the cost of operating such filters under American conditions wascommonly from $2 to $5 per million gallons. 

The experiments represented by Tables 17 to 19, inclusive, serve toshow that preliminary filtration, or multiple filtration, or anysystem of mechanical separation is incapable of entirely removingthe finer clay particles which cause the residual turbidity in theeffluent. They also show that this turbidity may be easily andcertainly removed by the application of coagulant to the raw waterduring the occasional periods when its character is such as torequire it. 

These general propositions were understood by those responsible forthe original design of the plant, as is shown by the author'squotations. These experiments, however, were necessary in order todemonstrate and bring home the conditions to those who thoughtdifferently, and who believed that full purification could beobtained by filtration alone, or by double filtration, withoutrecourse to the occasional use of coagulant. 

The experiments briefly summarized in Table 20 are of the greatestinterest and importance. Six small filters, otherwise alike and likethe large filters, all received the same raw water and were operatedat different rates to determine the effect of rate on efficiency. 

That the experimental results from the filter operating at the samerate as the large filters were on the whole somewhat inferior tothose from the large filters for approximately the same period, maybe attributed to the fact that the experimental filter was new whilethe large filters had been in service for some time and had therebygained in efficiency. The greatest difference was in the _coli_results in Table 20, where it is shown that 24% of the 10-cu. Cm. Effluent samples from the experimental filter contained _coli_, incomparison with only from 1 to 3% of such samples from the mainfilters. 

The results from the experimental filter operating at a rate of1, 000, 000 gal. Per acre daily may fairly be excluded, as theeffluent probably contained more under-drain bacteria in proportionthan filters operated at higher rates. The number of bacteria in thefilter operating at a 3, 000, 000-gal. Rate were 1. 7% of those in theapplied water; for the filter operating twice as fast, thepercentage was 2. 4; and, for the one operating more than ten timesas fast, was only 3. 0; thus indicating a surprisingly small increasein the number of bacteria with increase in rate. 

Further and more detailed study by the writer of the unpublishedindividual results, briefly summarized in Table 20, confirms thesubstantial accuracy of the comparison based on the average figuresas stated in that table. 

It must be kept in mind, in considering these results, that thenumber of bacteria in each case is made up of two parts, namely, those coming through the filter--which number is presumably greateras the rate is greater--and, second, those coming from harmlessgrowths in the under-drains and lower parts of the filter--thenumbers of which per cubic centimeter are presumably less as therate is greater--and these two parts, varying in oppositedirections, may balance each other, as they seem to do in this case, through a considerable range. It may thus be that the number ofbacteria really passing the filter varies much more with the ratethan is indicated by the gross results. 

It is also of interest to note that the sand filter (called apreliminary filter) in Table 18, filled with the same kind of sand, when operated at an average rate of 50, 000, 000 gal. Per acre dailyfor a year, allowed 18% of the applied bacteria to pass, incomparison with 3% found in Filter No. 6 of Table 20, operated at anaverage rate of 38, 000, 000 gal. Per acre daily. 

There was one point of difference in the manipulation: thepreliminary filter was washed by a reversed current of water, asmechanical filters are washed, while Filter No. 6 was cleaned byscraping off the surface layer, as is usual with sand filters. Whether the great difference in bacterial results with a relativelysmall difference in rate is to be attributed to this difference inmanipulation the writer will not undertake to state. 

If the experimental results of Table 20 indicate correctly theconditions which obtain in filtering Potomac water, then increasingthe rate of filtration so as to double it, or more than double it, would make but little difference in the quality of the effluent asmeasured by the usual bacterial methods. If the increase in ratewere accompanied by the preliminary filtration of the water, then, presumably, there would be little change in the quality of theeffluent, and the maintenance of excellent results might beincorrectly attributed to the influence of the preliminary filter. 

It would also seem that the apparatus which is sometimes used fordetermining and controlling the rate with more than the ordinarydegree of precision is hardly justified by such experimental resultsas those presented by the author. 

In contrast to these results may be mentioned those obtained by Mr. H. W. Clark, [1] for experimental filters operated with MerrimacRiver water, at rates ranging from 3, 000, 000 to 16, 000, 000 gal. Peracre daily. The results are the average of nearly two years ofexperimental work, the period having been nearly coincident withthat covered by the author's experiments, and of many hundreds ofbacterial analyses of each effluent, and form, with the author'sexperiments, the most thorough-going studies of the effect of rateon efficiency that have come to the writer's attention. 

Mr. Clark's results are given in Table 22. 

 ~Table 22. ~ ===========+============+===========+=============+===========+============ | | | | | _B. Coli_ | | | | |in 1 cu. Cm. Effective | | Rate | Bacteria per| |(percentage size of | | in gallons| cubic | Bacterial |of positive sand. | Filter No. |acre daily. |centimeter in|efficiency. | tests). -----------+------------+-----------+-------------+-----------+------------ 0. 28 | A | 3, 000, 000 | 48 | 99. 1 | 5. 0 0. 25 | B | 5, 000, 000 | 85 | 98. 4 | 24. 0 0. 22 | C | 7, 500, 000 | 105 | 98. 1 | 25. 0 0. 22 | D |10, 000, 000 | 110 | 98. 0 | 25. 0 0. 22 | E |16, 000, 000 | 280 | 95. 0 | 38. 0 ===========+============+===========+=============+===========+============

It will be seen that the number of bacteria passing increasesrapidly with the rate, and whether the total number of bacteria isconsidered or the _B. Coli_ results, the number passing isapproximately in proportion to the rate. In other words, doublingthe rate substantially doubles the number of bacteria in theeffluent. 

This is entirely in harmony with all the Lawrence experimentalresults extending over a period of 20 years. There have beenoccasional apparent exceptions, but, on the whole, experience withMerrimac River water has uniformly been that more bacteria pass asthe rates are higher. 

The theory sometimes advanced, that the efficiency of filtration iscontrolled to a certain extent by gelatinous films, and that, as faras thus controlled, is less dependent on rate, would not seem to beborne out by these results. The Merrimac River water, carrying largeamounts of organic matter, would certainly seem better adapted tothe formation of such films than the clay-bearing Potomac water, comparatively free from organic matter; but it is the Potomac waterwhich seems to show the least influence of rate on efficiency. 

 [Footnote 1: _Journal_, New England Water-Works Association, Vol. 24, p. 589. ]

The experiments show that turbidity passes more freely at the higherrates with the Potomac water, as has also been found to be the casewith other clay-bearing waters. 

In the last lines of Table 20 are given cost per million gallons forfiltering at various rates. There is no discussion of these figures, and as they differ considerably from those which the writer has beenaccustomed to use, the calculation in Table 23, made three years agofor a particular case, may be of interest. 

 ~Table 23--Relative Cost of Filtering at Different Rates. ~ ======================+=================================================== |Nominal rate, in millions of gallons per acre daily: +------------+------------+------------+------------ | 3 | 5 | 10 | 20 ----------------------+------------+------------+------------+------------ Percentage which | | | | average yield is of | | | | nominal rate. . . . . . . . . . | 85 | 80 | 75 | 65 ----------------------+------------+------------+------------+------------ Average output per | | | | acre, in millions of | | | | gallons per day. . . . . . . | 2. 55 | 4. 00 | 7. 5 | 13. 0 ----------------------+------------+------------+------------+------------ Cost of that part of | | | | filters per acre | | | | dependent on rate. . . . . | $12, 000 | $20, 000 | $40, 000 | $80, 000 ----------------------+------------+------------+------------+------------ Cost of that part of | | | | filters per acre not | | | | dependent on rate. . . . . | 50, 000 | 50, 000 | 50, 000 | 50, 000 ----------------------+------------+------------+------------+------------ Total cost of filters | | | | per acre. . . . . . . . . . . . . . | 60, 000 | 70, 000 | 90, 000 | 130, 000 ----------------------+------------+------------+------------+------------ Cost per million | | | | gallons of capacity. . . | 20, 600 | 14, 000 | 9, 000 | 6, 500 ----------------------+------------+------------+------------+------------ Cost per million | | | | gallons of average | | | | daily output. . . . . . . . . . | 24, 400 | 17, 500 | 12, 000 | 10, 000 ----------------------+------------+------------+------------+------------ Capital charges and | | | | depreciation at 6% on | | | | cost per million | | | | gallons. . . . . . . . . . . . . . . | 4. 00 | 2. 87 | 1. 97 | 1. 64 ----------------------+------------+------------+------------+------------ Operating expenses, | | | | the same at all | | | | rates. . . . . . . . . . . . . . . . . | 1. 00 | 1. 00 | 1. 00 | 1. 00 ----------------------+------------+------------+------------+------------ Total cost of | | | | filtering, excluding | | | | pumping, storage, and | | | | all auxiliaries. . . . . . . | 5. 00 | 3. 87 | 2. 97 | 2. 64 ----------------------+------------+------------+------------+------------ Relative cost. . . . . . . . . | 1. 29 | 1. 00 | 0. 77 | 0. 68 ======================+============+============+============+============

When the costs of pumping, pure-water reservoirs usually necessary, etc. , are taken into account (which add equally to the cost at allrates), the cost of filtering will vary less with the rate than isindicated. 

The effect of rate on cost, as calculated in Table 23, and also thepercentages of the bacteria of the raw water found in the effluentsby the author and by Mr. Clark, are shown on Figure 10. 

Considering all these results together, and also all the otherevidence known to the writer bearing on this point, it seems clearthat filters are not as sensitive to changes in rate, withinreasonable limits, as has been frequently assumed; but, on the otherhand, there is usually a substantial increase in the percentage ofbacteria passing through a filter with increased rate. 

Filters furnish relative, not absolute, protection againstinfectious matter in the raw water. The higher the bacterialefficiency, the more complete is this relative protection. 

The cost of filtering does not decrease in inverse ratio to therate, but at a much slower rate. This is especially true with ratesof more than 5, 000, 000 or 6, 000, 000 gal. Per acre daily. 

In general, a rate of filtration may rationally be selected at whichthe value of the possible danger resulting from an increase in rateis equal to the saving that may be made in cost by its use. Thispoint must be a matter of individual judgment. The tendency of thelast few years has been to use higher rates, or, in other words, tocheapen the process and to tolerate a larger proportion of bacteriain the effluent. The use of auxiliary processes has been favorableto this, especially the use of chloride of lime, in connection witheither the raw water or the effluent. 

[Illustration: ~Figure 10--Rate Million Gallons Per Acre Daily. ~]

By the judicious use of this substance, efficiency may be maintainedwhile using higher rates than would otherwise have been desirable. 

The writer believes that there will be many cases where the addedrisk of using too high a rate is not worth the relatively smallsaving in cost that accompanies it. 

~George A. Johnson, Assoc. M. Am. Soc. C. E~. --This paper containsinformation of an exceedingly interesting nature. There iscomparatively little difficulty in obtaining accurate figures on thecost of construction of water purification works, but, with costs ofoperation of such works, it is different. The data available inpublished reports and papers are usually more or less fragmentary, and unexplained local conditions with reference to the character ofthe raw water, the cost of labor and supplies, and methods ofapportioning these costs, introduce variables so wide as frequentlyto render the published figures almost useless for purposes ofcomparison. 

Mr. Hardy's paper is noteworthy in that it presents certainrelatively new features of slow sand filter operation which havebeen only lightly touched on in water purification literature up tothe present time. These refer particularly to means whereby a filtermay be continued in service without removing a portion of thesurface layer of the filter surface itself when the available headhas become exhausted, and to methods whereby washed sand may beexpeditiously and more economically restored to the filter than hasbeen the case hitherto. 

Sand handling is the most important item of expense in the operationof a slow sand filter. Quite recently a charge of $1. 50 per cu. Yd. For sand scraping, transportation to sand washers, washing, andrestoring to the filter, was not considered exorbitant, but theimproved methods developed during recent years at Washington, Philadelphia, Albany, and more recently at Pittsburg (at all ofwhich places hydraulic ejection plays an important part), haveshown the feasibility of reducing this figure by nearly, if notquite, two-thirds. 

The practice observed at Washington of raking over the surface ofthe sand layer when the available head becomes exhausted, in orderto avoid the cost and loss of time necessitated by shutting down thefilter and scraping off the surface layer, is unquestionably one ofthe most striking advances in slow sand filter operation in recentyears. In rapid sand filter operation, to prolong the period ofservice between washings, agitation of the filter surface has beenused to advantage for many years. The full value of surface rakingmay not be generally appreciated, but the results which havefollowed a trial of this procedure at Washington, Philadelphia, andPittsburg have shown that the output of filtered water betweenscrapings may be doubled or trebled thereby, with no injury to thefilter itself or to the quality of the filtered water. The cost ofraking over the surface of a 1-acre slow sand filter unit is lessthan $10 at all the above-mentioned places, which fact in itselfshows the great saving in money and time effected by periodicallysubstituting surface raking for scraping. Under ordinary conditionsit has been found that a filter can be raked to advantage at leasttwice between scrapings. 

In the case of filters thus raked, a deeper penetration of suspendedmatter into the sand layer is inevitable, but at Pittsburg, as atWashington, such penetration does not extend more than about 2 in. Below the filter surface. When the filter is finally scraped, adeeper layer is removed, of course, but it is clearly moreeconomical to remove a deep layer at one operation than to removeseparately several thinner layers of an equal total thickness. 

The lost-time element is an important one, and at Washington thiswas the main reason for trying surface raking. It became necessaryto increase the output of the filters, and the ordinary scrapingconsumed so much time that the sand-handling force was increased, working day and night. The raking expedient introduced at this timeovercame this, and Mr. Hardy states that it is still followed whenthe work is at all pressing. The speaker has found at Pittsburg, asMr. Hardy has found at Washington, that raking is nearly if notquite as effective as scraping in restoring the filter capacity. 

Eleven years ago the speaker was connected with the preliminaryinvestigations into the best methods of purifying the Potomac Riverwater for Washington. It then appeared that while for the greaterpart of the time during an average year the Potomac River could beclassed among the clear waters of the East, there were periods whenexcessive turbidity made it necessary to consider carefully methodsof preparatory treatment before this water could be filteredeffectively and economically. As Mr. Hardy has said, considerableprejudice existed against the use of a coagulating chemical, and theexpedient was therefore adopted of giving the water a long period ofsedimentation in order to remove enough of the suspended matter toallow the clarified water to be treated on slow sand filters. Theexpert commission, consisting of Messrs. Hering, Fuller, and Hazen, recommended the occasional use of a coagulating chemical, but thisrecommendation was not carried out. 

The Potomac River is somewhat peculiar, in that the turbidity of itswaters, as shown by the results presented in Mr. Hardy's paper, ranges from 3, 000 to practically nothing. The bacterial content alsovaries widely, and Mr. Hardy's tables show this variation to be from76, 000 to 325 per cu. Cm. Such a water as this requires particularlycareful preparatory treatment. The Dalecarlia Reservoir has acapacity of something like 2 days' storage, the Georgetown Reservoirthe same, and the McMillan Park Reservoir nearly 3 days, making atotal sedimentation of more than 7 days. Without the use of acoagulant, it is significant that during a period of five years, even with 7 days' sedimentation, the average maximum turbidity ofthe water delivered to the filters was 106 parts per million, andthe maximum average turbidity in one month was 250 parts permillion. The water filtration engineer can readily understand thatwaters as turbid as this cannot be treated economically andefficiently in slow sand filters. It would appear that coagulatingworks might advantageously have been installed at the entrance tothe Dalecarlia Reservoir. If this had been done, and coagulant hadbeen added to the water at times when it was excessively turbid, aconsiderably shorter period of subsequent sedimentation than nowexists would in all probability have rendered the water at all timesamenable to efficient and economical slow sand filter treatment. 

The prejudice in Washington against the use of coagulants has alsomanifested itself in other localities, but the results which havebeen obtained during the past twenty years from rapid sand filtersand from slow sand filters, treating waters previously coagulatedwith salts of iron or alumina, have shown how thoroughlyunreasonable were these objections. In this connection it isinteresting to note that there are in the United States more than350 rapid sand filter plants, and that nearly 12% of the urbanpopulation of Continental United States is being supplied with waterfiltered through rapid sand filters, in connection with all of whicha coagulating chemical is used in the preparatory treatment. 

 ~Table 24--Typhoid Fever Death Rates in Cities of the United States with Populations in 1910 of 100, 000, or More. ~

 Statistics gathered by correspondence and from Reports of the Bureau of the Census, Department of Commerce and Labor, Mortality Statistics. 

~Note~. --Statistics from Birmingham, Ala. , Dayton, Ohio, Fall River, Mass. , Louisville, Ky. , Memphis, Tenn. , Oakland, Cal. , and Providence, R. I. , are not included, as they are incomplete. 

 Columns: A - Average for six years, 1900-05, inclusive. B - Average for five years, 1906-10, inclusive. C - Average for 11 years, 1900-11, inclusive. 

 ====================+=============================================== | ~ Typhoid Fever Death Rate City. | per 100, 000 Population~. +-----+-----+-----+-----+-----+-----+-----+----- | 1906| 1907| 1908| 1909| 1910| A | B | C --------------------+-----+-----+-----+-----+-----+-----+-----+----- Albany, N. Y. | 20 | 20 | 11 | 19 | 15 | 25 | 17 | 21 Atlanta, Ga. | 50 | 64 | 47 | 44 | 43 | 65 | 50 | 58 Baltimore, Md. | 34 | 41 | 31 | 23 | 41 | 36 | 34 | 35 Boston, Mass. | 22 | 10 | 26 | 14 | 11 | 23 | 16 | 20 Bridgeport, Conn. | 10 | 13 | 13 | 13 | 9 | 15 | 12 | 14 Buffalo, N. Y. | 24 | 29 | 21 | 23 | 20 | 29 | 23 | 26 Cambridge, Mass. | 18 | 10 | 10 | 9 | 12 | 18 | 12 | 15 Chicago, Ill. | 18 | 18 | 15 | 12 | 14 | 27 | 16 | 22 Cincinnati, Ohio | 71 | 46 | 19 | 13 | 6 | 54 | 31 | 44 Cleveland, Ohio | 20 | 19 | 13 | 12 | 19 | 51 | 17 | 36 Columbus, Ohio | 45 | 38 | 110 | 17 | 13 | 61 | 45 | 54 Denver, Colo. | 68 | 67 | 58 | 24 | 30 | 37 | 49 | 42 Detroit, Mich. | 22 | 28 | 22 | 19 | 16 | 17 | 22 | 19 Grand Rapids, Mich. | 39 | 30 | 30 | 17 | 27 | 34 | 28 | 31 Indianapolis, Ind. | 39 | 29 | 26 | 22 | 31 | 76 | 30 | 55 Jersey City, N. J. | 20 | 14 | 10 | 8 | 10 | 19 | 12 | 16 Kansas City, Mo. | 38 | 40 | 35 | 23 | 38 | 48 | 35 | 42 Los Angeles, Cal. | 18 | 23 | 19 | 18 | 12 | 35 | 18 | 27 Lowell, Mass. | 7 | 9 | 24 | 11 | 21 | 19 | 14 | 17 Milwaukee, Wis. | 31 | 26 | 17 | 21 | 45 | 19 | 28 | 23 Minneapolis, Minn. | 33 | 26 | 18 | 20 | 58 | 38 | 29 | 34 Nashville, Tenn. | 66 | 85 | 62 | 53 | 48 | 54 | 58 | 56 Newark, N. J. | 18 | 24 | 12 | 11 | 13 | 17 | 16 | 17 New Haven, Conn. | 54 | 30 | 34 | 20 | 17 | 44 | 31 | 38 New York, N. Y. | 15 | 17 | 12 | 12 | 12 | 19 | 14 | 17 New Orleans, La. | 30 | 56 | 31 | 25 | 28 | 40 | 34 | 37 Omaha, Nebr. | 28 | 24 | 22 | 31 | 75 | 20 | 36 | 27 Paterson, N. J. | 4 | 11 | 10 | 5 | 7 | 25 | 7 | 17 Philadelphia, Pa. | 74 | 60 | 36 | 22 | 17 | 47 | 42 | 45 Pittsburg, Pa. | 141 | 135 |53[1]|13[1]|12[1]| 132 | 71 | 104 Richmond, Va. | 44 | 41 | 50 | 24 | 22 | 66 | 36 | 53 Rochester, N. Y. | 17 | 16 | 12 | 9 | 13 | 15 | 13 | 14 St Louis, Mo. | 18 | 16 | 15 | 15 | 14 | 33 | 16 | 25 St Paul, Minn. | 21 | 17 | 12 | 20 | 20 | 14 | 18 | 16 San Francisco, Cal. | . . . | 57 | 27 | 17 | 15 | 20 | 29 | 24 Scranton, Pa. | 11 | 76 | 11 | 11 | 14 | 18 | 35 | 26 Syracuse, N. Y. | 10 | 16 | 15 | 12 | 30 | 14 | 17 | 15 Toledo, Ohio | 45 | 36 | 40 | 31 | 32 | 36 | 37 | 36 Worcester, Mass. | 12 | 14 | 10 | 8 | 16 | 17 | 12 | 15 Washington, D. C. | 52 | 36 | 39 | 33 | 23 | 59 | 37 | 49 ====================+=====+=====+=====+=====+=====+=====+=====+=====

 [Footnote 1: Filtered water section. Allegheny District not included. ]

Attention has repeatedly been called to the fact that the relativelyhigh typhoid death rate in Washington, since the filter plant wasinstalled, was a possible indication that the filters wereinefficient. It is true that there has not been the marked reductionin the typhoid death rate in Washington, following the installationof the water filtration works, that has been observed in othercities in America. For the six years prior to the date on whichfiltered water was supplied to the citizens of Washington, theaverage typhoid fever death rate was 59 per 100, 000 population, asagainst 37 per 100, 000 for the five years following, a reduction of37 per cent. At Albany, N. Y. , where the first modern slow sandfilter was built in 1899, the typhoid death rate has been reduced by75 per cent. At Cincinnati, Ohio, the average death rate fromtyphoid ranged around 50 per 100, 000 for years, but since theinstallation of the filtration plant it has been reduced to a pointwhich places that city, with respect to freedom from typhoid fever, at the head of all the large cities in America; in 1910 the deathrate from typhoid in Cincinnati was 6 per 100, 000. Similarly, atColumbus, Ohio, where the typhoid death rate before the installationof the filtration plant in 1906 was even higher than at Cincinnati, it was reduced to less than 13 per 100, 000 in 1910, whereas, for theprevious five years, it was 61 per 100, 000. Philadelphia, before theinstallation of the filtration works, had a typhoid death rate of 60or more per 100, 000, and in 1910 the death rate from this diseasewas 17. Pittsburg, at least that part of it now supplied withfiltered water, for years had a typhoid death rate of more than 130per 100, 000, but the present rate is about 12 per 100, 000. 

 ~Table 25--Average Monthly Results for the Period, 1905-1910. ~

 Columns: A - Period of sedimentation in days. B - Turbidity in parts per million. C - Bacteria per cubic centimeter. ============+=====+=====+=======+===================== | | | |~Percentage Removed~ Reservoirs. | A | B | C |----------+---------- | | | | Turbidity| Bacteria ------------+-----+-----+-------+----------+---------- River | . . . | 106 | 6, 400 | . . . | . . . Dalecarlia | 2. 2 | 50 | 5, 000 | 53 | 22 Georgetown | 2. 2 | 38 | 3, 400 | 24 | 32 McMillan | 2. 8 | 26 | 2, 000 | 31 | 41 ------------+-----+-----+-------+----------+---------- Totals and | | | | | averages | 7. 2 | . . . | . . . | 75 | 69 ============+=====+=====+=======+==========+==========

While it may perhaps seem unreasonable to single out Washington as aparticular sufferer in this respect, it is highly probable that alarge share of the typhoid is still caused by secondary infection, flies, impure milk, and private and public wells. The speakerremembers distinctly that ten years ago, when he made aninvestigation into the purity of the water of about 100 public wellsin that city, a large number of them showed unmistakable evidence ofbeing polluted with sewagic matter. Conclusive evidence would besecured to dispel any doubt as to the sanitary quality of thefiltered product if hypochlorite of lime were added to the filteredwater throughout one year or throughout the typhoid months. It seemsstrange to the speaker, that for this, if for no other reason, thissafe and non-injurious germicide has not as yet been used atWashington, in view of the fact that at the present time it is beingused continuously or intermittently in the treatment of the watersupplies of scores of the most important cities of this country, among which may be mentioned New York, Philadelphia, Cincinnati, Pittsburg, St. Louis, and Minneapolis. 

~Morris Knowles, M. Am. Soc. C. E~. (by letter). --This descriptionof the operation of the Washington Filtration Works is timely and ofgreat interest. It is ten years since the writer, in collaborationwith Charles Gilman Hyde, M. ~Am. Soc~. C. E. , presented a similarrecord for the Lawrence, Mass. , filter. That paper was the firstcomplete, detailed, and continuous history of the actions andresults obtained for a long period of time with such a purificationworks. [1] Since then, the art of filtration has advanced in manyways, particularly in regard to the methods of cleaning slow sandfilters and in the accompanying processes. It is well, therefore, again to take account of stock and see really what progress has beenmade. Therefore, Mr. Hardy's paper, giving a description of theoperations of a system thoughtfully designed, after longconsideration of the problem, and of operations carried on underefficient and economical administration, with thorough record of alldetails, should furnish a groundwork for the careful considerationof the question stated above. 

The writer, using as a text some of the ideas given in the paper, but more particularly some of those becoming prevalent elsewhere, desires to discuss methods and costs of operation, especially inrelation to sand handling; and to offer suggestions looking towardgreater efficiency, as well as economy, in carrying out the standardand well-tried methods. 

_Theory of Slow Sand Filtration. _--First, what is the process of slowsand filtration? The answer to this question involves many factors, someof which are even yet but imperfectly understood. In the early historyof filtration, at the time of the construction of the London filters, only the straining capacity of the sand bed, to remove gross particles, was known. Later, when the organic contents of water had become betterunderstood, the chemical or oxidizing powers of the process wererecognized as performing an important part. Finally, co-existent withthe discovery of the so-called "germ theory of disease, " a study of thebacterial action of filters resulted in the recognition of itsimportance. It is now universally thought that each of these factorsperforms its useful function; that the size of the sand, the amount oforganic matter remaining on the surface of the bed, the turbidity of theapplied water, and the bacterial content of the influent, are some ofthe things on which depends the determination of the relative importanceof each. 

 [Footnote 1: _Transactions_, Am. Soc. C. E. , Vol. XLVI, p. 258. ]

Engineers have been taught to believe, by the German school ofthought, that the film of organic matter on the surface of the sandplays a very important role in filtration. This _Schmutzdecke_, asit is called, has been considered so precious that stress has beenplaced on treating it with great care. It was not to be whollyremoved at the time of cleaning, and it was not to be walked on, orindented, or in any other way consolidated or destroyed. In fact, insome cases, the wasting of the first water after cleaning has beenadvocated, for the reason that not a sufficient amount of thisorganic film would be left on top of the sand to begin thefiltration process properly immediately after the cleaning. 

In late years, however, there has been a tendency to depart fromthis fundamental doctrine of slow sand filtration. Various newprocesses for cleaning the sand surface have been advocated; some ofthese partly destroy and others completely exterminate any semblanceof a bacterial film on the sand bed. These ideas, advanced withoutany real and serious discussion of their intrinsic merits, or theireffects on the public health, are not founded on long continuousrecords of such results as are necessary to establish confidence inthe final value of any of these methods. 

Rapid advances along this line have been made more recently, notwithstanding the occurrence of notable instances of trouble andthe resultant need of complete repair of filtration beds. Because ofthe rough treatment of the sand surface, a penetration of organicmatter and filth into the bed had taken place. This caused deepclogging, prevented the usual yield of water, and brought about alessened bacterial efficiency, due to the attempt to force waterthrough the filters, and because some organic matter and growths inthe lower part of the bed had furnished a breeding place for morebacteria. 

All these endeavors to reduce the work of cleaning have beencommendable, because scraping and sand handling are the items ofgreatest expense in slow sand filter maintenance. Every one has beendesirous of minimizing this cost. However, as the writer willendeavor to show, it seems that attempts along this line should bewith the idea of doing more economically, as well as efficiently, the things which one knows will accomplish the proper results, rather than unwisely to adopt new methods which have not been triedfor a long enough period to determine their effect on the publichealth. 

_Pittsburg Methods. _--When first taking up the problem of design inPittsburg, in 1902, the writer had presented to him forconsideration and adoption, a suggestion that a certain method ofcleaning sand filters, which would involve the washing of the sandin place (similar to that recently tried at the Jerome ParkExperiment Station, New York City), would be advisable andeconomical. The decision then made has never been regretted. As thisplan involved such a complete departure from those principles whichhad been well tried and had proven successful, it was believed thatit was not safe to adopt such a method on the municipal filtrationworks, from which the people were to derive their drinking water. There is more to be considered in such a problem than mere economyof operation; the economy of human life, the effect on whichrequires far longer than a few months of trial to determine, is amuch more important factor. Believing that no one should depart, until after a long period of conclusive experimentation, from thatprinciple which is known to be safe (viz. , to take off a smallportion of the clogging surface), the writer studied to determinemore efficient and economical methods of accomplishing this end. 

A device for scraping the material, in just the same way as withshovels, but more efficiently and more exactly, was developed byGeorge P. Baldwin, M. Am. Soc. C. E. , under the general supervisionof the Bureau of Filtration, of which the writer was in charge. However, on account of the unfortunate and earlier arrangement ofother constructive matters, which the City's Legal Departmentadvised could not be changed without upsetting the contract, theentrance doors to the original forty-six filters were not builtlarge enough to permit the rapid and economical transfer of thesemachines, and, as this act takes so large a proportion of the totaltime of operation, it has not been found economical to use them. Theadditional ten filters, recently constructed, with doors especiallydesigned and large enough to pass the machines, have not yet beenplaced in operation. This is said to be on account of lack of fundsand of employees. Therefore, there has been no opportunity todemonstrate what the scraping machines can do, under the conditionsfor which they were designed to operate. The restoring machine, acomplementary device in mechanical operation, which simply replacesthe sand in the same condition that it would be if wheeled back, but, with a small percentage of moisture, has accomplished itspurpose well and economically. The sand is placed in the filters sothat there is no further settling; with a smooth surface, needing noadditional adjustment; with absolutely no possibility of sub-surfaceclogging; and with the filters starting off exceedingly well inoperative results. 

_Washington Methods. _--In Washington, it is stated that the filtersare still cleaned by the old-fashioned method of scraping withshovels, throwing the sand into piles, and afterward removing itwith a movable ejector. Between scrapings there is also anoccasional mid-period action of raking the unwatered sand surface, for the purpose of stirring up the dirty film. This process does notremove any of the clogging material from the bed, but it is saidthat no injurious effects are produced, and that it is economical. It is stated that the so-called "Brooklyn method, " of stirring thesurface of the sand while the water is on the bed, has been tried atWashington, but with unsatisfactory results. It seems to have beenadvocated with greater fervor in some other places. 

The method of dry raking does not remove the dirty material, butloosens up the pores of the surface, and through this porositypermits clogging to penetrate deeper into the filter. The method ofraking with water on the bed, although it removes some of theorganic dirt, also permits deeper penetration of the remainder. Thelatest devised system of washing the sand in place, by upwardspraying with water, called the "Blaisdell method, " thoroughlydestroys the _Schmutzdecke_ above, and, at the same time, mustpermit the formation of a subsidiary one below. In the Nicholsmethod, the material removed by shovel scraping is conveyed by anejector to a portable separator, where it receives a single washing;the dirty water overflows to the sewer, while the washed sand isdischarged through a hose and deposited on the recently scrapedsurface. As the latter is partly impregnated with impurities, thereis, by this process, a tendency toward sub-surface clogging. 

All these processes are marked and serious departures from thewell-tried method of cleaning slow sand filters, which, it is wellknown, will operate successfully to purify polluted river waters andmake them safe to drink. In all there is the danger that they havenot been sufficiently and carefully tried, under scientificobservation, as to results and possible effects on the publichealth, to be sure that the bacterial efficiency can long continueto be satisfactory, with the application of specifically infectedwaters. It is dangerous, and may even jeopardize the safety of humanlives, to experiment on water which is furnished for drinkingpurposes. There is also the added danger, well known from pastexperience, that in a few years (it may be more or less, dependingon the extent and intensity of the new workings) the filters willneed renovation, partly, if not wholly, throughout the entire bed. Thus, considering the total cost during a long term of years, theapparently cheaper method may become the most expensive. 

There is also an interesting query in regard to the Washingtonmethod of replacing sand in the filters, and it is worthy of mostcareful thought and attention. If the process described can becarried on with success and safety, it will prove to be a long andprogressive step in the methods of operation. The difficulty, however, is in determining from any short-term runs whether such aprocess can be continued permanently without impairing theefficiency of the sand bed. Apparently good conditions may change, after a few years' trial, and be followed by unsafe results andpredicaments. This replacing of sand with whatever dirt and detritusmay travel with it in the carrying water is certainly not equivalentto the care with which it has been understood that sand should bedeposited in filters. It is not comparable with the care with whichit is placed, when wheeled from a washer, where dirty wateroverflows the lip, or where it is placed by a machine restorer inthe filter, where the transporting water also overflows the weir andis carried to the sewer. 

These cheap and rapid methods of doing the work, advanced in theinterests of economy, and the idea that sand filters, receivingpolluting waters, can operate at higher rates than those which wehave demonstrated, and, therefore, have been led to believe aresafe, is a speeding up of the whole organization and of operatingconditions. It is like speeding up a machine for the purpose ofgetting a greater output, with the usual result that fast runningmeans quicker wearing out of both man and machine. Quickeroperations generally mean carelessness in doing the work, especiallyin municipal service. Carelessness is engendered by the thought thatsuch work can be handled in a rough and rapid way, and, further, bythe ridicule of all these things, which we have learned to becareful about, as old-fogyish, out-of-fashion, and archaic. Carelessness in operation breeds contempt for the art. Some of theless efficient filter plants, from the standpoint of effect on thepublic health, may reflect such ill-considered methods

_Economy with Efficiency in Operation. _--It is particularly important tofind out whether one can secure the desired economy, and, at the sametime, the required efficiency. The development of efficiency in everyline of human endeavor is receiving much attention at present, and notthe least cause for this is the growing recognition of the demand for ahigh standard of service for the expense caused. One of the firstrequirements is to have well-defined ideals and standards. When oneknows how to secure a good and safe result, it is unwise to departtherefrom for a mere whim, or to secure a supposedly lessened expense, unless other facts be also determined favorably. The desire for economymust be tempered by good sense, which means that one should be willingto change a method only when the wisdom of such has been clearlydemonstrated. Efficient service can only be secured by strictdiscipline, accompanied by fair dealing. This means employing no moremen than are actually necessary, paying them on the basis of thestandard of service and output produced, taking an interest in theworking conditions, and providing for their health and welfare. 

About twelve years ago, the writer made some investigations of theefficiency of laboring gangs in scraping and handling sand at filterbeds, [1] and found that ten men was the most economical number touse in scraping the surface of the Lawrence filter, as then builtand operated. This result was determined by numerous studies of theoutput per man per minute, with different numbers of men workingunder different conditions. This same sort of study has been carriedfurther by adepts in the art, in reference to shop and similarmanagement, but one fails to find corresponding development alongthis line in municipal organization except by a few of the scatteredBureaus of Municipal Research. These results, also, have related toa few of the more common and general factors, such as determiningthe cost per mile, or per square yard, of street cleaned, or permillion gallons of water pumped. 

 [Footnote 1: _Transactions, _ Am. Soc. C. E. , Vol. XLVI, p. 291. ]

The cost of the management of water-works, one of the largestfactors of public enterprise, has never been investigatedextensively and thoroughly. There is much possibility in planningfor greater efficiency and in determining what can be accomplishedunder economical administration. Every one is aware of themultiplicity of men in municipal service. Some of these are entirelyincompetent, others partly so; the recent appointees may be moreefficient, but the majority of them gradually deteriorate under thesubtle influence of the prevailing atmosphere, and each new incomingadministration places more and more men on the work, without reasonor necessity. All these tendencies have made the cost andmaintenance of public work greater and greater, and, at the sametime, have resulted in frequently and steadily decreasing the outputand efficiency per employee. 

The Washington situation, however, presents an admirable contrast tothis, because of the methods of administration of the public worksof the District of Columbia and their freedom from petty politicalinfluence. The limited number of employees has tended towardeconomy, and rendered this plant the envy of all who have desired toobtain good management. Its cost items have been looked on as aresult long hoped for, but seldom obtained. It is to be regretted, therefore, that such an abrupt change in methods of removingclogging material and replacing sand has taken place without yearsof experimental trial on filters not furnishing drinking water tothe public, and without an attempt, under such excellent conditions, to maintain the efficiency by a better labor output and by improvedworking and machine methods in the performance of the older andestablished order of doing things. 

In preparing water for the use of the people, the realms of theunknown are so much larger than those which have been investigatedand developed that there may be many undiscovered factors affectingthe public health, and many ways in which it is dangerous to departfrom well-known and surely safe methods. Who can say that in somesubtle and, at present, unknown manner, the failure in some places, where filtration is practiced, to reduce the death rate from typhoidfever may not be due to the introduction of radical departures fromthe older, slower, safer, and more efficient methods which haveproduced such excellent results, both in America and in Europe?Further, in cases where there has been a falling off in the typhoiddeath rate, the failure to secure an accompanying improvement ingeneral health conditions, which follows so closely in communitiessupplied by water filtered in accordance with the more conservativeprinciples, may be due to the introduction of some of these notthoroughly tried processes. Some day full information may beavailable as to the influence of these methods of plant operation onthe health of the community. Until that time, is it not a muchbetter policy to follow the principles which have been proven bymany years of experience to produce safe results, and to make theforemost object the improvement of the methods of operation inaccordance with these established truths?

There is opportunity for the upbuilding of greater efficiency in theconduct of employees and in securing the maximum output, byestablishing more comfortable and healthful conditions than usuallyexist. The elimination of political influence from municipal serviceis also a task which challenges the people of to-day, and theoperating and managing engineer is in a position to perform animportant part in accomplishing this end. The number of employeescan be reduced to those actually needed, and the way opened for theemployment of men who thoroughly understand the necessities ofhonesty and efficiency in the conduct of public affairs. It shouldbe remembered that to design and construct well is only half thejob; to operate economically and efficiently is even more of aproblem than to build, and requires just as good talent, just askeen appreciation of the various problems, and is even moreessential to public welfare. It seems to the writer that the logicaldevelopment of the art of obtaining economy as well as efficiencyshould be along these lines, rather than to revolutionize methods, without having a long-period test of their value, and at the sametime allow political influences to control, to a large extent, thelabor item. 

_Preliminary Treatment. _--The decision as to the preliminarytreatment of the Potomac River water before filtration is ofinterest, particularly because various other conclusions have beenreached in different sections of the country. However, in the main, these decisions have been due to differences in the character of thewaters, but it must be evident that they have sometimes been theresult of ill-considered action, or the desire to promote somespecial interest. The use of preliminary filters, which involves alarge investment, is not always to be commended, particularlybecause at times of reasonably good water the removal of some of theorganic matter is really injurious and lessens the effect of thefinal filters. 

For a long time, the writer has believed that, where other thingsare equal, and where there is no important reason for double orpreliminary filtration, long periods of storage, accompanied by theuse of coagulant at times of severe and extreme muddiness, asplanned at Washington, solves the problem in the most practical andeconomical way. It is true that the investment for a large storagebasin may equal, or even exceed, that required for preliminaryfilters; but the influence of storage on the quality of raw water isnever injurious, and, by ripening the condition of the water, may begreatly beneficial in the process of filtration. 

The storage available in such a basin makes it possible to shut offthe supply from the river during the worst conditions of the water. The duration of the most troublesome spells ordinarily does notexceed a few days, and it is usually possible to secure sufficientcapacity in the basin to tide over these periods. Then again, longperiods of storage, in addition to assisting in breaking up organicmatter, permit the dying out of bacteria, particularly many of thepathogenic kind, and, therefore, the water is rendered much saferfrom this standpoint. In other words, there is additional insurancein long storage against the faulty and careless operation ofincompetent filter employees. The addition of coagulant, especiallythe fact that only a very small investment of capital is requiredfor the necessary apparatus for dosing the water, and that the costof the coagulating materials has to be met only when used, seems togive the process, in a most satisfactory manner, the requirement foreconomical management and thoroughness in preparing the water forfinal filtration. 

_Parking Public Works. _--It is disappointing that the author has notmentioned some of the steps contemplated in reference to thelandscape treatment of the Washington filtration area. Probablyevery one has been impressed by the barren aspect of the works asthey are approached, and as one looks over them. Recently, however, it is stated that some steps have been taken to lay out the grounds, treat the surface in an attractive manner, and make a park of thearea. The writer has a firm opinion that when an investment is madefor public works, it costs but little in addition to constructbuildings along appropriate architectural lines, to treat thegrounds in a pleasing manner, and to make the entire works a creditto the municipality from an artistic standpoint. When treated onbroad lines, such areas become public parks, and afford openbreathing places for the residents, and, if near centers ofpopulation, may well be equipped with playground facilities for thechildren. When thus developed they should have care, that theplanting and equipment should not deteriorate and the last statebecome worse than the first. 

The influence which these ever-present examples of attractivenesshave on the community is becoming better recognized by students ofsocial progress, and there seems to be no doubt that spending moneyon such features is not only desirable from the artistic standpoint, but is justified on practical grounds as well. It is cheaper than tocreate parks, when necessity and demand can no longer be resisted, by buying property and occasionally tearing down buildings andconstructing _de novo. _ That this work is now being done inWashington, even after construction, is certainly a recognition ofthe advisability of original efforts in this direction. 

~George C. Whipple, M. Am. Soc. C. E. ~ (by letter). --Mr. Hardy'spaper is an excellent presentation of the results of the operationof the Washington water filtration plant from the time of itsconstruction in 1905 until June, 1910. Papers of this character arealtogether too infrequent, and the actual results from the filtersnow in use are not readily accessible in detailed form. Yet it isonly by studying the results obtained by filters in actual use thatimprovements can be made and the art advanced. 

Among the many important facts brought out by Mr. Hardy, only a fewcan be selected for discussion. One of these is the operation offilters under winter conditions. It is well known that theefficiency of sedimentation basins and filters is lower duringwinter than at other times, yet it is just at this season of theyear that there is the greatest danger of typhoid fever and similarwater-borne diseases being transmitted by water. Most of the greattyphoid epidemics have occurred during cold weather, and the veryuse of the term "winter cholera" is of significance. Apparently, typhoid bacilli and similar bacteria are capable of living andretaining their vitality longest during that season of the year. Just why this is so, bacteriologists have not satisfactorilyexplained. Doubtless many factors are involved. Because of theincreased viscosity of the water, sedimentation takes place lessreadily at lower temperatures, and inasmuch as sand filtration ispartly dependent on sedimentation, the efficiency tends to fall offin cold weather. During winter some of the external destroyingagencies are less potent, such as the sterilizing effect ofsunlight, and the presence and activity of some of the larger formsof microscopic organisms which prey on the bacteria. Another factormay be the greater amount of dissolved oxygen normally present inwater during cold weather, as experiments have shown that dissolvedoxygen favors longevity. 

Still another reason for the larger numbers of bacteria that passthrough a water filter during cold weather may be the effect thatthe low temperature has on the size of the bacteria themselves. Afew experiments made recently by the writer appear to indicate thatat low temperatures the gelatinous membrane which surrounds thebacterial cells tends to become somewhat contracted, thus decreasingthe apparent size of the bacteria as seen under the microscope. Either this contraction occurs, or the cells themselves are smallerwhen they develop in the cold. It is possible also that lowtemperature affects the flagella of the organisms in the same way. It is not unreasonable to suppose that the effect of low temperatureis to form what may be, in effect, a protective coating around thecells, which tends to make them smaller, less sticky, and lesssubject to outside influences. This would tend to make them passthrough a filter more readily. In line with this idea also is thewell-known fact that disinfection is less efficient in cold waterthan in warm water. 

Another way of viewing the matter is that cold retards the growth ofbacteria on the filter, thus reducing the effect of the_Schmutzdecke_. Still another view of the greater danger frombacterial contamination in winter is the theory that cold prolongsthe life of the bacteria by merely preventing them from livingthrough their life cycle and reaching natural old age and death asrapidly as in warm weather. 

Another topic in Mr. Hardy's paper which has interested the writeris that of preliminary filters. The experiments described at lengthindicate clearly that such devices would prove of little or nobenefit under the conditions existing in Washington, and that whenthe river contains considerable amounts of suspended clay nothingless than chemical coagulation will suffice to treat the water sothat the effluent will be perfectly clear. Preliminary filters havebeen used for a number of years at various places and with varyingsuccess. In few instances have they been operated for a sufficientlength of time or been studied with sufficient care to determinefully their economy and efficiency as compared with other possiblemethods of preliminary treatment. 

Among other experiments on this matter are those made at Albany, N. Y. , and published by Wallace Greenalch, Assoc. M. Am. Soc. C. E. , inthe Fifty-ninth Annual Report of the Bureau of Water for the yearending September 30th, 1909. The Hudson River water used at Albanyis quite different in character from the Potomac River water used atWashington, as it is less turbid and contains rather more organicmatter. The results obtained in these experiments showed that duringthe summer the number of bacteria in the effluent from theexperimental sand filter used in connection with a preliminaryfilter did not differ widely from the number found in the effluentof the city filter where there was no other preliminary treatmentthan sedimentation. In the winter, however, the numbers of bacteriadid not increase in the effluent from the experimental filter asthey did in the effluent from the city filter. This is shown byTable 26, taken from the report mentioned. 

Apparently, therefore, at Albany the benefits of the preliminaryfilter, as far as bacterial efficiency is concerned, would beconfined to a short period of three or four months in each year. Under such circumstances it may well be questioned whether theadvantages of preliminary filtration justify its cost. 

 ~Table 26--Results of Experiments with Preliminary Filter at Albany, N. Y. ~ ==========+==========+==========+============+============= Month, | Bacteria | Bacteria | Bacteria in|Bacteria in 1906. | in raw | in pre- | effluent | effluent | water. | liminary | from | from | | filter |experimental|city filter. | | effluent. |sand filter. | ----------+----------+----------+------------+------------- March | 133, 480 | 36, 000 | 151 | 706 April | 77, 420 | 4, 810 | 72 | 155 May | 15, 800 | 2, 250 | 48 | 37 June | 4, 520 | 358 | 38 | 34 July | 2, 090 | 163 | 25 | 22 August | 2, 740 | 121 | 36 | 22 September | 8, 280 | 445 | 20 | 24 October | 38, 350 | 4, 235 | 67 | 227 November | 67, 910 | 15, 570 | 337 | 341 December | 645, 500 | 25, 440 | 144 | 2, 783 ----------+----------+----------+------------+------------- 1907. | | | | January | 127, 560 | 4, 660 | 48 | 443 February | 28, 000 | 1, 800 | 13 | 116 ==========+==========+==========+============+=============

On the diagram, Figure 11, will be found various data taken from thepublished records of the Albany filter, from 1899 to 1909. Thesedata include: The numbers of bacteria before and after filtration;the percentage of bacteria remaining in the effluent; the averagequantity of water filtered, in millions of gallons per day; thequantities of water filtered between scrapings; the turbidity of theraw water; the cost of filtration, including capital charges andcost of operation; and the typhoid death rates of the city permonth. Several points are brought out conspicuously by this diagram. One is the uniformly low death rate from typhoid throughout theentire period. The filter was operated from 1899 until the fall of1907 with raw water taken from what is known as the "Back Channel. "Since then it has been taken from a new intake which extends intothe Hudson River itself. Until the fall of 1908 the preliminarytreatment consisted merely of sedimentation, but since then thewater has received an additional preliminary treatment in mechanicalfilters operated without coagulant, along the lines of theexperiments just mentioned. During this time the average rate offiltration of the sand filter has not changed materially, althoughit is said that the maximum rate has been increased since thepreliminary filters were put in service. The study of thebacteriological analyses shows that the best results were obtainedduring 1902, 1903, and 1904. Since then the numbers of bacteria inboth the raw and filtered water have increased. This was especiallynoticeable during the winters of 1907 and 1908 when the water wastaken from the new intake. It will be interesting to compare theresults after the preliminary filters have been operated for a longperiod to ascertain their normal effect on efficiency and on theincreased yield. 

[Illustration: ~Figure 11--Filters at Albany, N. Y. Results ofOperation. 1899-1909. Compiled from data in Annual Reports. ~]

Another fact to be drawn from the plotted Albany data is theincrease in the cost of filtration, both in capital charges and inoperation. From 1899 until 1906 the cost of operation, including thecost of low-lift pumping, was approximately $5 per million gallonsof water filtered; and the total cost of filtration, includingcapital charges, was about $10 per million gallons. During the yearending September 30th, 1909, the cost of operation had increased to$7. 63 per million gallons, and the total cost of filtration to$15. 92 per million gallons, or approximately 50% in three years. 

 ~Table 27--Results of Bacteriological Analyses of Samples of Water at Peekskill, N. Y. , Before and After Filtration. ~

 ~Bacteria per cubic centimeter. ~ ==============+=======+=======+========+========+========+========+======== | Raw | Clear |Effluent|Effluent|Effluent|Effluent| Tap in Date. | water. | reser-| No. 1. | No. 2. | No. 3. | No. 4. | city. | | voir. | | | | | --------------+-------+-------+--------+--------+--------+--------+-------- 1909. --------------+-------+-------+--------+--------+--------+--------+-------- December 29th | 190 | 100 | . . . | . . . | . . . | . . . | . . . --------------+-------+-------+--------+--------+--------+--------+-------- 1910. --------------+-------+-------+--------+--------+--------+--------+-------- February 15th | 135 | 10 | 10 | 30 | 20 | . . . | 265 March 31st | 225 | 50 | 25 | 45 | 60 | . . . | 35 May 18th | 300 | 29 | 22 | 26 | 35 | 43 | 36 July 6th | 300 | 44 | 9 | 3 | 41 | 10 | 31 August 16th | 60 | 5 | 0 | 4 | 1 | 13 | 15 October 3d | 550 | 14 | 12 | 14 | 38 | . . . | . . . November 21st | 315 | 22 | 26 | 17 | 6 | . . . | . . . --------------+-------+-------+--------+--------+--------+--------+-------- 1911. --------------+-------+-------+--------+--------+--------+--------+-------- January 25th | 415 | 7 | 8 | 4 | 6 | . . . | 7 --------------+-------+-------+--------+--------+--------+--------+-------- Average | 277 | 30 | 14 | 16 | 26 | 22 | 65 ==============+=======+=======+========+========+========+========+========

 ~Table 17~--(_Continued. _) ~Tests for~ _B. Coli. _ ==================+====================== |~Percentage of Samples Quantity of water |Containing~ _B. Coli_. Tested. +--------+------------- | Raw. | Filtered. ------------------+--------+------------- 0. 1 cu. Cm. | 0 | 0 1. 0 cu. Cm. | 20 | 0 10. 0 cu. Cm. | 40 | 0 ==================+========+=============

As a matter of record, the results of a series of analyses made atPeekskill, N. Y. , during 1910 are presented in Table 27. A sandfilter was constructed for the water supply of this city in 1909, and put in operation in December. The filter has a capacity of4, 000, 000 gal. Per day. The supply is taken from Peekskill Creek, and the water receives about one week's nominal storage beforeflowing to the filters. An aerator is used before filtration duringthe summer, when algae are likely to develop in the reservoir. Thefilter was installed after an epidemic of typhoid which wasapparently caused by an infection of the water supply. Normally, thewater has been little contaminated, but the supply is subject toaccidental contamination at any time, among other possible sourcesof infection being the camps of workmen now engaged in constructingthe Catskill Aqueduct for New York City. 

 ~Table 28--Average Results of Chemical Analysis at Peekskill, N. Y. , Made at Intervals of Six Weeks During 1910. ~ =====================+=================+================+================= | ~Parts per | | ~Parts per | Million. ~ | | Million. ~ |--------+--------| |--------+-------- | Raw |Filtered| | Raw |Filtered | water. | water. | | water. | water. ---------------------+--------+--------+----------------+--------+-------- Turbidity | 2. | 0 |Total residue | 70. | 76. 00 Color | 25. | 20. |Loss on ignition| 19. 00 | 17. 00 Nitrogen as albumi- | | |Fixed residue | 50. 00 | 59. 00 noid ammonia | 0. 112 | 0. 076 |Iron | 0. 17 | 0. 13 Nitrogen as free | | |Total hardness | 38. 70 | 45. 10 ammonia | 0. 024 | 0. 006 |Alkalinity | 33. 90 | 42. 60 Nitrogen as nitrites | 0. 001 | 0. 001 |Incrustants | 4. 60 | 4. 50 Nitrogen as nitrates | 0. 06 | 0. 06 |Chlorine | 2. 60 | 2. 70 =====================+========+========+================+========+========

~F. F. Longley, Assoc. M. Am. Soc. C. E. ~ (by letter). --In thispaper the author has presented a mass of data which will be welcomedby engineers engaged in water purification work, because completeoperating records form a substantial basis for improvement in theart, and are often the inspiration for interesting discussions andthe exchange of experiences of different observers whose views aremutually appreciated. 

Recent tendencies in filtration engineering have been largely in thedirection of reducing the cost of operation. A comparison of theoperating costs of the earlier American plants of about a decadeago, with those here presented of the Washington plant, is verygratifying to those who have been intimately connected with thelatter work. Through perfection in design and reasonable care inoperation, the cost of filter cleaning, which is a very considerablepart of the total cost, has been reduced to an unusually low figure, without any sacrifice in efficiency, and in the interests of thepublic health. 

Table 14 shows that, from the first year, there has been aprogressive increase in the total cost of operation per milliongallons filtered, but this has not meant an increase in the annualtotal expenditure. The largest percentage of increase in any itemhas been in "Care of Grounds and Parking, " and covers much-desiredlandscape improvements. Aside from this, the principal factoraffecting the table of costs has been the reduction in waterconsumption in the District of Columbia. Nothing pertaining to thisreduction has produced any corresponding reduction in the forcerequired for the maintenance and operation of the filtration plant, office and laboratory, and pumping station, though probably therehas been some reduction in filter cleaning. Obviously, then, thetotal cost per million gallons would increase. 

This decrease in consumption has been brought about by theelimination of waste in the distribution system, which is not in thesame department as the filtration plant, but with regard to which aword may not be amiss in connection with this discussion. 

The Washington Aqueduct was built half a century ago on lines whichat that time were considered extraordinarily generous. Untilrecently, therefore, there has been no occasion for concern over thehigh rate of consumption. During recent years, however, the use andwaste of water have increased, reaching a climax under unusualconditions in the winter of 1904-05. The maximum capacity of theaqueduct system is about 90, 000, 000 gal. The maximum dailyconsumption at the time mentioned arose almost to 100, 000, 000 gal. , with the result that, before normal conditions were restored, thereservoirs of the system were almost depleted. 

This had a beneficial effect, as provision was made for an activecampaign for reducing the waste of water, which was known to be verylarge. These investigations, using the pitometer, were begun inJuly, 1906, and have been pursued continuously since that time, withmost excellent results. Up to January, 1909, leaks aggregating about12, 000, 000 gal. Per day were detected and eliminated, and about halfthe house services had still to be covered by the pitometer bureau. 

Although this reduction in waste has brought about an apparentincrease in the cost of filtration, its economical results have beenfar-reaching. The causes which brought about this investigation alsoresulted in securing an appropriation for the study of the questionof increased supply. The writer was in charge of these studies, andthe most significant conclusion was that, owing to the excellentresults of the efforts for waste restriction, the total consumptionand waste of water in the district during the next few years wouldbe far enough below the safe working capacity of the existingaqueduct system to make it entirely safe to postpone theconstruction of new works, involving the expenditure of severalmillion dollars, in spite of the threatening conditions of a fewyears ago. 

There has been so much controversy over typhoid fever in theDistrict of Columbia that the writer hesitates to discuss thissubject. Viewing the situation through the perspective of severalyears, however, it does not seem to be as hopeless as the criticismsof four or five years ago would lead one to believe. 

In Table 9, showing the typhoid death rates, out of nine years givenprior to 1905-06, when the filters were started in operation, onlyone shows an annual death rate as low as the highest one since thatyear. Further than this, the annual average typhoid death rate forthe period since that year has been one-third lower than for acorresponding period before the filters were started. 

The exhaustive researches of the Public Health and Marine HospitalService into this whole question, covering a period of about fouryears, have raised the present filtered water supply of the Districtof Columbia above any well-founded criticism. There has long been astrong and growing feeling that the water supply, before filtrationwas introduced, had been blamed for more than its share of thetyphoid, and this is borne out by much evidence that has beenpresented from time to time. 

It is not an unreasonable conjecture, therefore, that perhaps thereduction of one-third in the total typhoid death rate may representa much larger reduction in that part of the total which was due topolluted water alone; and that, as the authorities in the Districtof Columbia and in certain other cities, particularly in the South, are now recognizing, the fight against much of the remaining typhoidmust be in the direction of the improvement of milk supplies, precautions against secondary infection, and attention to a largenumber of details surrounding the individual, which may effectivelyprotect him against the insidious attack of the disease favored byunknown agencies. 

~Experiments in Filter Cleaning~. 

The author refers to the difficulty encountered during the first twosummers in keeping the filters cleaned fast enough to maintain thecapacity of the plant. The real seriousness of this may be judgedfrom the following facts. The average increase in loss of head onall the filters for the entire year, July 1st, 1906, to July 1st, 1907, was about 0. 053 ft. Per day. During the 1906 period of lowcapacity under discussion, the loss of head on twelve of the filtersincreased for a period of eight days at the average rate of 0. 45 ft. Per day, or about nine times the normal rate of increase. Thisdifficulty was caused by the presence of large numbers ofmicro-organisms in the applied water. During the first summer (1906)this fact was not recognized, but the sudden decrease in capacitywas supposed to have been caused by the unusually high andlong-continued turbidity which prevailed during that summer in thePotomac River, and persisted in the water supplied to the filterseven after about four days of sedimentation in the reservoirs. During the second summer (1907) the same phenomenon of suddenly andrapidly increasing losses of head appeared again, but without anyunusual turbidity in the applied water. Investigation, however, showed the presence of large quantities of organisms, particularly_melosira_ and _synedra_, in the applied water, and examinations insubsequent years have shown a periodic recurrence of these forms inquantities sufficient to cause the trouble mentioned. In June, 1907, examination showed repeatedly more than 1, 000 and 1, 500 standardunits of _melosira_ per cu. Cm. , and one count showed nearly 3, 000standard units. 

Several expedients were tried in an effort to restore the rapidlydecreasing capacity of the filters. One of the earlier conjecturesas to the cause of the trouble was that it might be due to theaccumulation of large quantities of air under the surface of thesand, as air had been observed bubbling up through the sand, especially in filters which had been in service for some time. Theexpedient was tried, therefore, of draining the water out of thesand and then re-filling the filter in the usual manner from below, in the hope of driving out the entrained air. Presumably thistreatment got rid of the air, but it did not restore the capacity ofthe filter, as the point of maximum resistance was in the surface ofthe sand and not below it. 

As the author states, raking the filters was tried and found to giveresults which were satisfactory enough to meet the emergenciesalready referred to. When the filters were first put in operation, in the fall of 1905, the method of bringing back the capacity of afilter after the end of a run was to remove all the dirty sand to adepth determined by the marked discoloration caused by thepenetration of the clay turbidity. This sometimes necessitated theremoval of large quantities of sand at a cleaning, as the turbiditywas exceedingly fine, and penetrated at times to a depth of 3 or 4in. 

With the idea of effecting an economy in the cost of cleaning thefilters, a schedule of experiments was arranged shortly before July1st, 1907. The general object of the experiments was to determine, first, the relative costs of all different methods tried; second, whether the removal of only a thin layer of sand, or the merebreaking up of the surface of the sand by thorough raking, wouldgive the filter its proper capacity for the succeeding run; third, whether the filters under these treatments would maintain a highstandard of quality in the effluents; fourth, whether the continuedapplication of any less thorough method than the one then in usemight materially affect the future capacity of the filters. 

To this end the filters were divided into four groups which, duringa period of about six months, were subjected to treatments asfollows:

 Group _A. _--Filters scraped deep at the end of each run; Group _B. _--Filters scraped light at the end of each run; Group _C. _--Filters raked at the end of each run, until raking failed to bring back the proper capacity; then they were scraped light, and at the end of the next run the raking was resumed; Group _D. _--Light scrapings and rakings alternate at ends of runs. 

The term "deep scraping" means the removal of practically all thediscolored sand, in accordance with the usual practice prior to thebeginning of these experiments; "light scraping" means the removalof only a thin surface layer of sand. This depth has usuallyaveraged about 3/8 in. "Raking" means the thorough breaking up ofthe clogged surface of the filter by iron-toothed rakes, to a depthof about 1 or 2 in. 

_Results. _--A general summary of the results of these experiments isgiven in Table 29, which also shows the relative costs of thedifferent methods per million gallons of water filtered. A normalperiod of 9 months just prior to the beginning of these experimentsshows a labor cost (corresponding to that in Table 29) of $0. 29-1/4per million gallons filtered. 

 ~Table 29--Average Results. ~

 Columns: A - Group. B - Number of filters. C - Number of days of service. D - Million gallons filtered. E - Cost of labor per treatment. F - Sand removed in cubic yards. G - Sand removed in cubic yards. H - Cost of labor. I - Bacteria per cu. Cm. In effluent. J - Turbidity in effluent. 

 =========================================+===============+============== | Per Million | | Per Run: | Gallons | | | Filtered | I | J -----+-----+-----+-------+-------+-------+-------+-------+ | A | B | C | D | E | F | G | H | | -----+-----+-----+-------+-------+-------+-------+-------+-------+------ _A_ | 5 | 82 | 221. 2 |$68. 44 | 215 | 1. 11 |$0. 309 | 13 | 1 _B_ | 9 | 36 | 101. 4 | 29. 25 | 84 | 0. 83 | 0. 288 | 16 | 1 _C_ | 5 | 21 | 60. 0 | 10. 92 | 24 | 0. 40 | 0. 182 | 18 | 1 _D_ | 10 | 32 | 86. 0 | 20. 10 | 46 | 0. 54 | 0. 234 | 22 | 1 =====+=====+=====+=======+=======+=======+=======+=======+=======+======

_Capacity of Filters. _--The capacity of the filters under thedifferent methods of treatment are shown in a general way in Table29 for days of service and millions of gallons filtered per run. This element by itself is decidedly in favor of the deep scrapings, and least in favor of the repeated rakings. 

A clearer conception of the capacities of the filters under thesedifferent conditions may be obtained from the four diagrams, Figure12, showing, for the four different groups, the average number ofdays of service of the successive runs. The diagram for Group _A_shows that the variations in the period of service of the filtersscraped each time to clean sand follow a more or less definite curvefrom year to year. For the period covered by this curve, thetendency seems to be toward a slight decrease in capacity from yearto year, as shown by the lower average maximum and minimum in thesecond year than in the first. Group _B_ shows a sudden decrease incapacity following the first light scrapings and, since that time, alow but quite constant capacity. Group _C_ shows a constantlydecreasing capacity with successive rakings. The only significanceattaching to the curve after the first raking is the prohibitivelylow capacity indicated, and the ineffectiveness of the measurestaken to restore the capacity after the sixth raking. Group _D_, after the first raking, shows a prohibitively low and constantlydecreasing capacity. The diagrams for _C_ and _D_ indicate adangerous reduction in capacity if long persisted in. The methodfollowed with Group _C_ may be dismissed with the statement that itis entirely insufficient, and would be of use only in the rarestemergencies. 

As far as the question of capacity is concerned, these diagrams indicatethat a filter in normal condition may safely be raked once. It isbelieved that the constantly decreasing capacity shown in Group _D_ isnot due so much to the rakings as to the small quantities of sandremoved at the alternate scrapings, and therefore it would not be properto condemn this method of treatment without a further trial in whichthis defect was remedied. This view seems to be supported by the resultsof Group _B_. The low but approximately constant capacity there shownwould undoubtedly have been higher if a greater depth of sand had beenremoved each time. 

[Illustration: ~Figure 12--Average Number of Days of Service ofSuccessive Runs for Groups _A_, _B_, _C_, and _D_. ~]

_Quality of the Effluent. _--The averages given in Table 29 show butlittle difference in the bacterial contents of the effluents fromthe four groups of filters. All are entirely satisfactory, and thedifferences in favor of one method or another are small. In lookingfor possible differences in the quality of the effluents from thefour groups, it was thought that such differences might be mostapparent at a time when the entire plant was working under the mostadverse conditions. The bacterial counts, therefore, were summarizedfor the period from December 23d, 1907, to January 6th, 1908, inclusive, following a period of high turbidity and high bacteria inthe raw water, with results as follows:

 Group. . . . . . . _A_ _B_ _C_ _D_ Maximum. . . . . 204 178 189 206 Minimum. . . . . 61 45 62 57 Average. . . . . 120 107 104 155

The following is a summary of the turbidity results for a similarperiod:

 Group. . . . . . . _A_ _B_ _C_ _D_ Maximum. . . . . 10. 8 11. 7 8. 7 9. 3 Minimum. . . . . 6. 7 4. 7 6. 2 5. 7 Average. . . . . 8. 7 8. 3 7. 2 7. 9

These numbers, though high, do not show any significant differences. All the averages for each group are less than the lowest maximum, and all are greater than the highest minimum, and therefore varyless than do the individual filters, from other causes, within thedifferent groups. 

_Future Capacity of the Filters. _--An indication of the dangerswhich might affect the future capacity of the filters was shown inthe above discussion of the present capacity. A more effective wayof showing this was obtained by a study of the initial resistancesor losses of head in the four groups. A filter kept in idealcondition would show no increase in this initial loss of head fromone run to the next. If there is such an increase, it means that atsome future time measures more heroic than ordinarily used would benecessary to restore the proper capacity. 

The average initial losses of head for the different groups areplotted on the diagram, Figure 13. Group _A_ shows an initial loss ofhead, increasing gradually but slightly during more than two yearsof service. In Group _B_ the initial loss of head increased in amanner similar to that in Group _A, _ up to the time of the beginningof these experiments; after which the increase becomes more rapid. Groups _C_ and _D_ show conditions generally similar to Group _B_, with some variations which are self-explanatory. 

_Conclusions. _--The quality of the effluents from all four groupswas satisfactory, and no consistent difference was apparent in favorof one or another method of treatment. The method pursued with Group_C_ was entirely insufficient to maintain the capacity indefinitely. The methods pursued in Groups _B_ and _D_ were both insufficient, but would have been more effective if a greater depth of sand hadbeen removed. The costs of treatment of Groups _B_ and _D_ were lessthan for Group _A_. It appears, then, that a treatment which wouldbe more economical than the old method of Group _A_, and would stillmaintain the proper capacity, would be one similar to that of Groups_B_ or _D_, with the removal of a quantity of sand greater than wasdone in the case of these two groups, but less than in the oldmethod. 

[Illustration: ~Figure 13--Average Initial Losses of Head for Groups_A_, _B_, _C_, and _D_ for Successive Runs. ~]

At the time the above results were summarized, it was proposed toproceed with the filter treatment along the lines just mentioned. The writer did not have an opportunity to study the subsequentresults, as he was transferred to other work. A statement by theauthor of any new facts that may have come to light in thisconnection would be of interest. 

Mention should be made, too, of another expedient that was used tohasten the restoration of the capacity of a filter, which proved tobe a most useful one. The removal of the scraped sand from a filterwas a matter of a good many hours' work, under the most favorableconditions. To get the filters quickly into service again, the dirtysand in a number of them was simply scraped from the surface, heapedinto piles, and left there; then the water was turned in, and thefilter was started again. This was done with some hesitation atfirst for fear the presence of the piles of dirty sand might causehigh bacterial counts in the effluents of those filters. No sucheffect was observed, however, the counts being entirely normalthroughout. The writer subsequently found the same treatment beingapplied as an emergency measure at the Torresdale plant, inPhiladelphia, and, through the courtesy of the Chief Engineer of theBureau of Filtration, was furnished with the bacterial countsthrough a number of runs made under these conditions, and there, too, the results were entirely normal. 

There was practically no economy in this method, as the sand hadultimately to be ejected and washed. The piling up of the sand hadthe effect of reducing the effective filtering area by a smallpercentage, with a corresponding increase in the actual rate offiltration, but this was of trifling importance. The great benefitderived from the method was the saving of time in getting a filterback into service after scraping, and in this respect it was veryvaluable. 

~Physical Theory of Purification of Water by Slow Sand Filters~. 

The first and most natural conception of the action of a sand filteris that the removal of impurities is effected by a straining action. This, of course, is perfectly true as far as it relates to a largepart of the visible impurities. Much of this is gross enough to beintercepted and held at the surface of the sand. This very strainingaction is an accumulative one. After a quantity of suspended matterthus strained out mats itself on the surface of the sand, it in turnbecomes a strainer, even better adapted than the clean sand surfacewhich supports it for the removal of suspended matter from thewater. 

This, however, cannot explain certain features of the purificationof water by a layer of sand. The removal of color, the reduction ofnitrates, and certain other changes in the organic content of thewater have for a long time been recognized as due to a bio-chemicalaction carried on by certain bacteria in the sand. Both thestraining action and this bio-chemical action are not all-sufficientfor the explanation of certain phenomena, and it has beenrecognized, too, that sedimentation in the pores of the sand playeda large part in the purification process in those cases in which itwas apparent that the biological agencies were not the chief ones. 

In the purification of water containing only insignificantquantities of suspended matter, but a relatively large amount ofunstable organic matter, it will be conceded at once that the chieffactor in the purification is the nitrification produced by thebacteria in the upper layers of the sand. On the other hand, thepurification by sand filters of a hypothetical water containing noorganic matter, but only finely-divided mineral matter insuspension, could take place only by the physical deposition of theparticles upon the sand grains. Between these two extremes lie allclasses of water. In all problems of water purification byfiltration through sand, both these factors--biological action andsedimentation--play their parts, assisting and supplementing eachother, the relative importance of one factor or the other dependingon the place of the particular water in question on the scalebetween the two extreme conditions just mentioned. 

In Mr. Hazen's paper on "Sedimentation"[1] there is an interestingdevelopment of the theory of the removal of suspended matter bysedimentation in the pores of a layer of sand. The factors influencingthis removal are the rate of filtration, the effective size of the sand, and the temperature of the water. For the conditions at the Washingtonplant, it may be assumed that the first two of these factors areconstant. The third factor, however, varies through wide limits, and theobservations on the turbidity removal, and on the different phases ofthe filter operation of which the turbidity of the water is a factorunder varying temperature conditions, together with the known relationsbetween hydraulic values and temperatures of water, furnished goodsubstantiative evidence that this highly-induced sedimentation may be aconsiderable factor in the purification of the water as effected at thisplant. This temperature relation, briefly stated, is as follows: Forparticles of a size so small that the viscosity of the water is thecontrolling factor in determining the velocity of their subsidence instill water, that velocity will vary directly as (T + 10) / 60, in whichT is the temperature, in degrees, Fahrenheit. That is, when thetemperature of the water is between 70 deg. And 80 deg. Fahr. , aparticle will settle with twice the velocity it would have if the waterwere near the freezing point. 

 [Footnote 1: _Transactions_, Am. Soc. C. E. , Vol. LIII, p. 59. ]

The layer of sand in a slow sand filter may be considered as a verygreat number of small sedimentation basins communicating one withanother, not in the manner of basins connected in series, butrather, as Mr. Hazen has expressed it, as a long series ofcompartments connected at one side only with a passageway in which acurrent is maintained. In any section of the sand layer there areareas through which the water passes with a velocity much greaterthan its mean velocity through the total area of voids, while thereare other areas in which the velocity is very much less, perhaps inan almost quiescent state from time to time, greatly favoring thedeposition of particles, but with a gentle intermittent circulation, displacing the settled or partly-settled water and supplying fromthe main currents water containing more suspended matter particlesto be removed. There is thus a considerable percentage of the totalvolume of voids in which the water is subjected to very favorableconditions for sedimentation, almost perfect stillness and anexceedingly small distance for a particle to settle before itstrikes bottom on the surface of a grain of sand. 

If sedimentation were the predominating factor in the purificationof the water, we would then expect to find the following phenomenain the operation of the filters: A more rapid deposition of a givenamount of sediment under summer temperature conditions than underwinter, as the water passes through the sand, and therefore, for theformer condition of higher temperature:

 (a) A greater concentration of this turbidity-producing material in the top layer of sand, or, in other words, a thinner sand layer to be removed in scraping if all the dirty sand is removed;

 (b) Because of the greater concentration, a greater rate of Increase of the loss of head, and consequently shorter periods of service between scrapings;

 (c) A higher limit for turbidity in the water applied to the filter to produce a given turbidity in the effluent. 

 ~Table 30--Service Periods and Scraping Depths for Runs Ending In Various Months; Covering Entire Period, October 1st, 1905, To March 1st, 1907. ~ ==========+=========+===========+===============+============= | | Average | Average | Mean | Number | period of | depth of sand | temperature, Month. | of | service | removed, in | in degrees, | filters. | in days. | inches. | Fahrenheit. ----------+---------+-----------+---------------+------------- January | 13 | 75 | 2. 09 | 39 February | 6 | 98 | 2. 46 | 37 March | 5 | 130 | 2. 66 | 41 April | 8 | 149 | 2. 96 | 53 May | 7 | 130 | 2. 80 | 67 June | 11 | 124 | 2. 35 | 77 July | 17 | 70 | 2. 12 | 81 August | 2 | 49 | 1. 98 | 80 September | 5 | 73 | 2. 48 | 76 October | 37 | 70 | 1. 56 | 64 November | 20 | 42 | 0. 81 | 49 December | 14 | 57 | 0. 94 | 40 ==========+=========+===========+===============+=============

The operation of this plant during the first year and a half offered anexcellent opportunity for the study of sedimentation in the sand, andthe data in Table 30 are presented to show that certain of the phenomenaof filter operation observed during this period seem to be fairlyexplicable by the physical theory of purification. These data are givenonly for the period of operation before the summer of 1907. At that timethe experiments in filter cleaning already described were begun. Beforethat time, whenever a filter had been cleaned, all the discolored sandhad been removed, leaving for the following run a new sand surfacesubstantially in the perfect condition of a newly-constructed filter. After that time the experimental methods of cleaning, and the newroutine adopted as a result thereof, interfered with the tracing of theevidence as clearly as during the earlier periods. 

[Illustration: ~Figure 14--Periods of Service and Depths of Scrapingfor Runs Ending in Various Months Covering Entire Period Oct. 1, 1905, to Mar. 1 1907. ~]

Table 30 and the corresponding diagram, Figure 14, show the generalvariations in the length of runs and depth of penetration, with theseasonal temperature changes. The increase in length of runs andquantity of sand removed under low temperature conditions is verymarked. There is, however, a secondary maximum which appears, as thediagram shows, where a minimum for the year would be expected. Thismay have been an irregularity occurring this one year, which willnot appear in the average of several years, and caused by somefactor which has escaped observation. A careful analysis of the dataat hand fails to show any explanation for it. It may exist in someof the little-understood biological actions which have their maximumeffect under warm-water conditions, or it may be due--in someobscure way--to the liberation of air under the surface of the sand, accumulating with pressure enough to break the surface atinnumerable points, thereby reducing the loss of head and extendingthe period of service. Some evidence was observed pointing to thisexplanation, but it was never conclusively proven. 

The general effect of temperature changes on the rapidity of removalof the sediment and its consequent concentration in the sand layer, however, seems plainly evident. 

In corroboration of the third point mentioned in the theoreticalconsideration of turbidity removal in the filters, the dailyturbidities of the filtered water have been classified andsummarized for different turbidities in the applied water, and alsofor different temperatures. The average turbidities thus obtainedare given in Table 31. 

 ~Table 31--Turbidity in Filtered Water at Different Temperatures Produced by Given Turbidity in Applied Water. ~ ==========+================================================= Turbidity | of | ~Temperature, in Degrees, Fahrenheit. ~ applied |---------+---------+---------+---------+--------- water. | 40 | 40 - 50 | 50 - 60 | 60 - 70 | 70 ----------+---------+---------+---------+---------+--------- 20 | 1. 8 | 1. 3 | 1. 2 | 1. 5 | 1. 7 20-40 | 4. 8 | 5. 0 | 3. 5 | 3. 0 | 2. 6 40-60 | 7. 9 | 6. 9 | 5. 4 | . . . | 3. 7 60-80 | 10. 7 | 7. 7 | . . . | . . . | 5. 4 80-100 | 11. 3 | . . . | . . . | . . . | . . . 100 | . . . | . . . | . . . | . . . | 12. 0[1] ==========+=========+=========+=========+=========+=========

 [Footnote 1: For an average turbidity = 150. Approximately. ]

The influence of the temperature of the water on the turbidity ofthe effluent is very pronounced. For a temperature of less than 40 deg. Fahr. (actual average temperature about 35 deg. ), the turbidity of thefiltered water for a given turbidity of the applied water ispractically twice as great as for a temperature greater than 70 deg. (actual average temperature about 75 deg. ). This fact fits in verynicely with the influence of temperature on sedimentation. Referringagain to this temperature relation, as set forth on a previous page, the hydraulic subsiding value of a particle in water, of a size sosmall that viscosity is the controlling factor in its downwardvelocity, is approximately twice as great at 75 deg. As at 35 degrees. We would then expect to find that, in order to obtain a giventurbidity in the filtered water, a raw water may be applied at 75 deg. , having twice the turbidity of the water applied at 35 deg. , to producethe same turbidity; and further, as the turbidity of the filteredwater, for a given temperature condition, varies quite directly inproportion to the turbidity in the applied water, it follows that anapplied water of given turbidity will produce an effluent at 35 deg. With a turbidity twice as great as at 75 degrees. This is quite inaccordance with the facts obtained in actual operation, as indicatedon the diagram, Figure 15. 

_Preliminary Treatment of the Water. _--The most striking features ofthe bacterial results given in Table 4 are, first, the uniformly lownumbers of bacteria in the filtered water during perhaps 8 or 9months of the year, and the increase in numbers each winter. This isshown clearly in the analysis of bacterial counts in Table 32. 

 ~Table 32--Classification of Daily Bacterial Counts in the Filtered-Water Reservoir During the Period, November 1st, 1905, to February 1st, 1908. ~ ==========================+==============+====================== Bacterial count between: | No. Of days. | Percentage of whole. --------------------------+--------------+---------------------- 0 and 20 per cu. Cm. | 291 | 41. 0 20 and 40 per " " | 245 | 34. 6 40 and 60 per " " | 63 | 8. 9 60 and 80 per " " | 30 | 4. 2 80 and 100 per " " | 28 | 4. 0 92. 7 --------------------------+--------------+---------------------- 100 and 200 per " " | 29 | 4. 1 200 and 300 per " " | 13 | 1. 8 300 and 500 per " " | 5 | 0. 7 500 and 1000 per " " | 5 | 0. 7 7. 3 --------------------------+--------------+---------------------- | | 100. 0 ==========================+==============+======================

The tests for _Bacillus Coli_ in Table 5 show results whichcorrespond closely to these, with this organism detected onlyinfrequently, except during the periods of high bacteria, and bothof these are parallel to the turbidity variations in the filteredwater. These variations follow closely the variations in theturbidity and in the bacterial content of the water applied to thefilters. 

By all standards of excellence, the sanitary quality of the waterduring the greater part of the time is beyond criticism. In view ofthe close parallelism of turbidity and bacterial results in theapplied and in the filtered water, it is entirely logical toconclude that, if the quality of the applied water could bemaintained continually through the winter as good as, or betterthan, it is during the summer, then the filtered water would be ofthe perfect sanitary quality desired throughout the entire year. 

This was all foreseen ten years ago, when Messrs. Hering, Fuller, and Hazen recommended auxiliary works for preliminary treatment ofthe supply, although, as the author states, these works were notprovided for in the original construction. As prejudice against theuse of a coagulant seemed to be at the bottom of the opposition tothe preliminary treatment, a campaign of education bearing on thispoint was instituted, in addition to the systematic studies ofdifferent preliminary methods to which the author refers. As aresult of the combined efforts of all those interested in promotingthis improvement, an appropriation was finally made for the work in1910. The coagulating plant has since been built, and the writer isinformed that coagulation was tried on a working scale a short timeago during a period of high turbidity. A statement of the results ofthis treatment on the purification of the water in the reservoirsystem and in the filter plant would be of great interest. 

[Illustration: ~Figure 15-- Turbidity in Applied Water. ~]

_Hydraulic Replacing of Filter Sand. _--The author has adopted amethod of replacing clean sand in the filters which will commenditself to engineers as containing possibilities of economy inoperation. The first experiments in the development of this methodat the Washington plant were carried out some three years ago, whilethe writer was still there. Substantially the same methods were usedthen as are described in this paper, but examination of the sandlayer by cutting vertically downward through it after re-sanding inthis manner showed such a persistent tendency toward the segregationof the coarse material as to hold out rather discouraging promisesof success. The greatest degree of separation seemed to be caused bythe wash of the stream discharging sand on the surface. It wasobserved that, near the point where the velocity of the stream waspractically destroyed, there seemed to be a tendency to scour awaythe fine sand and leave the coarse material by itself, and pocketsof this kind were found at many points throughout the sand layer. The author states that, in the recent treatment of the filters bythis method, there has been no apparent tendency for the materialsto separate into different sizes, and it is fortunate if this workcan be done in such a manner as to avoid this separation entirely. 

It may be questioned whether a certain amount of segregation of thematerials will make any practical difference in the efficiency of afilter. In all probability this depends on the degree of thesegregation, the quantity of pollution in the water to be filtered, the rate of filtration, and the uniformity of methods followed inthe operation, etc. For an applied water as excellent in quality asthat of the Washington City Reservoir during favorable summerconditions, a considerable degree of segregation might exist withoutproducing any diminution in efficiency. For a badly polluted water, however, such as the applied water at this plant during certainwinter periods, or the water of a great many other pollutedsupplies, it might be found that even a slight lack of homogeneityin the sand might make an appreciable difference in the results offiltration. 

As a result of the experiments herein described, however, thismethod may be applied at other plants where conditions seem towarrant it, with a largely increased measure of confidence;although, as in the case of the adoption of any new or radicaldeparture, that confidence must not be permitted to foster contemptof the old and tried methods, but its operation must be watched withthe utmost caution, until long experience shall have demonstratedits perfect suitability and defined its limitations. 

~E. D. Hardy, M. Am. Soc. C. E. ~ (by letter). --It was not thewriter's original intention to enter into a discussion of either thetheory of water purification or of the experimental work on sandhandling, but simply to present the main results of operationlargely in tabular form. He is gratified, however, to have thesesides of the question so ably brought out in Mr. Longley'sdiscussion. 

Mr. Hazen referred to the inferior efficiencies of the experimentalfilters for rate studies (as shown in Table 20) in the removal of the_B. Coli_ from the water tested. This inferiority is really less thanthe figures in the table would indicate, as the tests for theexperimental filters were presumptive only (as shown by the note at thefoot of Table 20), while those for the main filters were carried throughall the confirmatory steps. 

From experiments[1] made by Messrs. Longley and Baton in thewriter's office, it would seem reasonable to assume that aboutone-half of the positive results, would have been eliminated had theconfirmatory steps been taken. In other words, the figures showingthe number of positive tests for _B. Coli_ in Table 20 should bedivided by two when comparing them with corresponding ones for themain filters. 

 [Footnote 1: Published in the _Journal of Infectious Diseases_, Vol. 4, No. 3, June, 1907. ]

Mr. Knowles seems somewhat apprehensive regarding the methods describedin the paper of restoring the capacity of the filters by raking, andreplacing sand by the hydraulic method, and yet, from Mr. Johnson'sdiscussion, it would seem that the practice of raking filters betweenscrapings had recently been adopted at the Pittsburg plant. 

Before the practice of raking was finally adopted as a part of theroutine filter operation, the subject was given a great deal ofthought and study, as may be seen by referring to Mr. Longley'sdiscussion. 

The re-sanding has been done by the hydraulic method, for nearly twoyears, and, as far as the writer is able to judge, this method hasbeen more economical and also more satisfactory in every way thanthe old one. As Mr. Hazen states, this does not prove that thehydraulic method would be as satisfactory for other filter plantsand other grades of sand. The elevated sand bins at the Washingtonplant fit in well with this scheme, and save the expense of oneshoveling of the sand; and the low uniformity coefficient of thesand is favorable in decreasing its tendency to separate intopockets or strata of coarse and fine sand. The method of washing isalso well adapted to this method of re-sanding, as the sand is madevery clean in its passage through the washers and storage bins. Thehydraulic method of replacing sand tends to make it cleaner still, because any clay which may be left in the sand is constantly beingcarried away over the weir and out of the bed, to the sewer. Sandreplaced by the hydraulic method is much more compact than whenreplaced by other methods, and consequently the depth of penetrationof mud in a filter thus re-sanded is less. Careful tests of theeffluents from filters which have been re-sanded by the two methodshave invariably shown the superiority of the hydraulic method. 

The experiment of replacing sand by water, referred to by Mr. Longley, was not considered a success at the time, and the methodwas abandoned for about a year. At that time an attempt was made tocomplete the re-sanding of a filter which had been nearly completedby the old method. The precaution of filling the filter with waterwas not taken, nor was any special device used for distributing thesand. When this method was again taken up, various experiments weretried before the present method was adopted. 

Mr. Whipple's remarks on the results from the operation of filtersunder winter conditions are very interesting, and, considering hisstanding as an authority in such matters, they are worth carefulconsideration. 

In the operation of the Washington plant, it has always beennoticeable that the results were much poorer in winter than insummer. In fact, nearly all the unsatisfactory water which has beendelivered to the city mains has been supplied during the wintermonths. On the other hand, the typhoid death rate has always beencomparatively low in cold weather. These facts would seem toindicate that the water supply was not responsible for the typhoidconditions.