WATER PURIFICATION PLANT, WASHINGTON, D. C. RESULTS OF OPERATION.1
Reading edition
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 filtration plant had been in operation for only about 1 year. It has now been in continuous operation for 5 years, and many data on the cost, efficiency, and methods of operation, have accumulated in the various records and books which have been kept. It is thought that a brief review of the results, and a summary of the records in tabular form, will be of interest to the members of the Society, and it is also hoped that the discussion of this paper will bring out the comparative results of operation of other filter plants. As a matter of convenience, the following general description of the plant is given.
Description of the Filtration Plant.—The Washington filtration plant was completed and put in operation in October, 1905. It consists of a pumping station for raising the water from the McMillan Park Reservoir to the filter beds; 29 filters of the slow sand type, having an effective area of 1 acre each; the filtered-water reservoir, having a capacity of about 15,000,000 gal.; and the necessary piping and valves for carrying water, controlling rates of filtration, etc.
In the pumping station, there are three centrifugal pumps, which are directly connected to tandem compound engines; two sand‑washer pumps; three small electric generating sets for furnishing electric light; and four 200‑h.p., water-tube boilers.
Each of the centrifugal pumps has a nominal capacity of 40,000,000 gal. per day when pumping against a head of 21 ft., and each sand‑washer pump has a capacity of 2,500,000 gal. when pumping against a head of 250 ft. The electric light engines and generators supply the current for lighting the pumping station, the office and laboratory and other buildings, and also the courts and interior of the filter beds, and for operating a machine‑shop.
The filters and filtered‑water reservoir are built entirely of concrete masonry. The floors are of inverted groined arches on which rest the piers for supporting the groined arch vaulting. All this concrete work is similar to that in the Albany, Philadelphia, and Pittsburg 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; the lower and coarser part acts as part of the under‑drain system, and the upper and finest layer supports the filter sand. The raw water from the pumps is carried to the filters through riveted steel rising mains which have 20‑in. cast‑iron branches for supplying the individual filters. The filtered water is collected in the under‑drainage system of the several filter beds, and is carried through 20‑in., cast‑iron pipes to the regulator‑houses. These regulator‑houses contain the necessary valves, registering apparatus, etc., for regulating the rate of filtration, showing the loss of head, shutting down a filter, filling a filter with filtered water from the under‑drains, and for turning the water back into the raw‑water reservoir, or wasting it into the sewer. From the regulator‑houses, the filtered water flows directly to thefiltered‑water reservoir. Generally, five filters are controlled from one house, but there are two cases where the regulator‑houses are smaller, and only two filters are controlled from each.
The dirty sand removed from the filters is carried by a portable ejector through one or more lengths of 3‑in. hose and a fixed line of 4‑in. pipe, to the sand washers. From the sand washers, the washed sand is carried to the reinforced concrete storage bins, each of which has a capacity of 250 cu. yd., and is at such an elevation that carts may be driven under it and loaded through a gate.
Until April, 1909, the sand was replaced in the filters by carts which were filled through the gates in the sand bins. It was then hauled to the top of the filter beds and dumped through the manholes on the chutes, which could be revolved in any direction. These chutes were used to prevent the sand from being unduly compacted in the vicinity of the manholes, and to facilitate spreading it in the filters. Since April, 1909, all the sand has been replaced by the hydraulic method. An ejector is placed under the gate in the sand bin, and the sand is carried in a reverse direction from the bin through the 4‑in. piping and one or more lengths of hose to the filter bed. This process has lowered the cost of re‑sanding considerably, and present indications are that it will prove entirely satisfactory in every way.
The average effective size and uniformity coefficient of the filters are shown in Table 1.
Table 1—Filter Sand as Originally Placed.
Filter No. Average effective size, in millimeters. Average uniformity coefficient. Depth of sand, in inches. Average turbidity.
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 of Washington is taken from the Potomac River, at Great Falls, about 16 miles above the city. At that place, a dam has been built across the river, which holds the water at an elevation of 150.5 ft. above mean tide at Washington. From Great Falls the water flows by gravity for a 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 the filters. After passing through the filters, it flows to the filtered‑water reservoir, and later to the city mains. In its passage from Great Falls to the filters, the water flows through three settling reservoirs, which have already been referred to. These reservoirs are known as the Dalecarlia, the Georgetown, and the McMillan Park Reservoirs, and have available capacities of 141,000,000, 140,000,000, and 180,000,000 gal., respectively.
Turbidity.—The Potomac River water is rather turbid, the turbidity being caused by very fine particles of clay. The river is subject to sudden fluctuations, it being no uncommon thing to have a turbidity of 100 one day, and 1,000 the next. The high turbidity usually disappears about as rapidly as it comes, and is seldom higher than 500 for more than 5 days at a time. It is frequently the case, however, that a succession of waves of high turbidity will appear so close together that the effect of one has not disappeared before that of another is felt.
The clarification of the water supply begins at the dam at Great Falls. Here it is a clarification by exclusion, for when an excessive quantity of mud appears in the river water, the gates are closed, and the muddy water is allowed to flow over the dam and form mud‑bars in the Lower Potomac, while the city is supplied from the water stored in the three settling reservoirs. Until a comparatively recent date, the excessively muddy water was never excluded, having been taken, like other decrees of Providence, as it came.
During the summer of 1907, the practice of shutting out water with a turbidity of 500 or more was established for the warm months. This practice was discontinued during the cold months, as it was feared that a very high consumption of water might occur at the time of low water in the reservoirs, and so cause a partial famine. During the winter of 1909‑10, however, the gates were closed, as was the practice throughout the summer months.
When the reservoirs are well filled, and the consumption of water is less than 70,000,000 gal. per day, it is safe to close the gates at Great Falls for a period of about 4 days.
Figure 1—Plan and Profile of Washington Aqueduct.
While a considerable reduction in turbidity is effected in each of the reservoirs, the bulk of the mud is deposited at the upper end of Dalecarlia Reservoir. This reservoir had become so completely filled, that, in 1905, it was necessary to dredge a channel through the deposit, in order to allow the water to pass it. During the summers of 1907 and 1908, a 10‑in. hydraulic dredge removed more than 100,000 cu. yd. of mud which had been deposited in this reservoir. The mud deposited in Georgetown and McMillan Park Reservoirs is so fine that the accumulation of many years is not very noticeable in its effect on the depth of water.
The particles of clay which remain in the water after its passage through the three reservoirs, are so exceedingly small that they do not settle out in any reasonable length of time. Even the filtration of the water through one or more slow sand filters occasionally fails to remove the last trace of turbidity. This is especially true in the colder months, and not a winter has passed when the water supply 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 that removed 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 which otherwise would have entered the system.
The turbidities, bacterial counts, and chemical analyses of numerous samples of water are shown in Tables 3, 4, 5, and 6. The amount of work done in the pumping station, average consumption of water, death rate from typhoid fever, and filter runs are shown in Tables 7, 8, 9, and 10.
Raking.—At the time the filters were first put in service, the sand bins had not been completed, and, consequently, the work of cleaning the filters was carried on in the old‑fashioned way of scraping by hand and wheeling out the sand in barrows. This method of cleaning was used from October, 1905, to April, 1906; then the regular sand‑handling system was commenced.
At times, during the first two summers the filters were in operation, considerable difficulty was experienced in keeping them cleaned as fast as was necessary to provide an ample supply of filtered water. For a short period in each summer it was found necessary to organize night shifts, and keep the work of cleaning in progress for from 16 to 24 hours per day.
Figure 2—General Plan of Washington Filtration Plant Showing Finished Surfaces.
Table 2—Tons of Suspended Matter Entering System, Etc.
Month. Amount that would have entered the system if the gates had been left continuously open. Number of hours gates were closed. Amount shut out. Amount deposited in Dalecarlia Reservoir. Amount deposited in Georgetown Reservoir. Amount deposited in McMillan Park Reservoir. Amount entering filtration plant. 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 2,212 515 611 661 6,522
In order to relieve the situation at such times, the expedient of raking was tried. This was first attempted with the filters filled with water; the effluent was first shut off in order to prevent a downward flow of water, and the filter was then raked or harrowed from boats. This method was not satisfactory, however, as the work was neither as uniform nor as thorough as necessary. Later, the filters were drained to the necessary depth, and the surface of the sand was thoroughly stirred with iron garden rakes. The filters were then filled with filtered water through the under‑drains and put in service.
This latter method proved so satisfactory that it has been resorted to at all times when the work was at all pressing. When the runs were of short duration, and the depth to which the mud had penetrated the filter sand was slight, a raking seemed to be nearly as effective in restoring the filter capacity as a scraping; it could be done in 8 hours by 3 laborers, and there seemed to be no ill effects from lowered efficiency.
Table 3—Turbidities.
Average by Months.
(United States Geological Survey Standard.)
Month. Great Falls. Reservoirs:
Dalecarlia Outlet. Gerogetown Outlet. McMillan Park Outlet. Filtered water.
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
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
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
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 02
May 300 33 55 19 50 17 28 13 1 02
June 1,500 246 180 42 110 37 50 16 1 02
Fiscal years.
1905-062 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
Table 4—Bacteria.
Averages by Months.
Month. Reservoirs:
Dalecarlia Inlet. Dalecarlia Outlet. Georgetown Outlet. McMillan Park Outlet. Filtered 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:
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
Table 5—Results of Tests for
Bacillus Coli
.
Percentage Positive.
Month. Great Falls, or Dalecarlia Reservoir Inlet. Dalecarlia Reservoir Outlet. Georgetown Reservoir. McMillan Park Reservoir (applied water). Filtered water reservoir. Tap water from various parts of city.
10 c.c. 1 c.c. 0.1 c.c. 10 c.c. 1 c.c. 0.1 c.c. 10 c.c. 1 c.c. 0.1 c.c. 10 c.c. 1 c.c. 0.1 c.c. 10 c.c. 1 c.c. 10 c.c. 1 c.c.
1906.
January1 55.6 38.9 22.2 69.2 23.1 7.7 56.0 40.0 8.0 55.6 22.2 0 7.2 0 ... ...
February 33.3 26.7 6.7 26.1 17.4 8.7 30.4 13.0 4.4 8.3 4.2 0 0 0 ... ...
March 50.0 12.5 0 45.5 18.2 0 20.8 8.3 0 18.5 7.4 3.7 0 0 0 0
April 72.2 33.3 16.7 95.5 50.0 4.6 59.1 22.7 4.6 32.0 8.0 0 4.0 0 0 0
May 20.0 8.0 4.0 20.0 12.0 0 7.8 0 0 0 0 0 0 0 0 0
June 57.7 38.5 19.2 40.0 32.0 8.0 50.0 34.6 0 23.1 7.7 3.8 0 0 3.1 0
July 65.0 50.0 5.0 60.0 25.0 10.0 15.0 5.0 5.0 9.5 0 0 4.8 0 ... ...
August 84.6 69.2 61.5 88.5 65.4 34.6 80.0 57.7 23.1 63.0 33.3 0 7.4 3.7 11.9 5.1
September 50.0 10.0 0 30.0 10.0 10.0 40.0 10.0 0 32.0 12.0 0 8.0 0 3.1 0
October 60.0 30.0 10.0 55.5 33.3 0 80.0 60.0 20.0 48.1 22.2 3.7 3.7 0 13.0 3.7
November 37.5 0 0 25.0 12.5 12.5 37.5 25.0 0 20.0 12.0 0 8.0 0 0 0
December 55.5 44.5 0 66.7 44.5 22.2 66.7 22.2 0 20.8 8.3 4.2 16.7 8.3 7.5 0
1907.
January 77.8 33.3 22.2 66.7 33.3 0 55.5 55.5 22.2 69.3 34.6 3.8 19.2 11.5 14.0 0
February 37.5 25.0 0 12.5 0 0 37.5 12.5 0 17.4 4.4 0 0 0 2.9 0
March 87.5 50.0 0 75.0 37.5 0 50.0 25.0 0 30.8 7.7 0 0 0 2.1 0
April 44.5 11.1 11.1 66.7 22.2 11.1 77.8 11.1 11.1 46.1 19.2 3.8 3.8 0 3.2 0
May 91.3 65.2 17.4 88.9 33.3 0 87.5 50.0 12.5 23.1 0 0 0 0 1.4 0
June 80.0 68.0 24.0 87.5 62.5 0 66.7 44.5 11.1 40.0 8.0 0 0 0 0 0
July 42.3 30.8 19.2 25.0 12.5 0 22.2 22.2 0 3.8 0 0 0 0 1.4 1.4
August 48.1 29.6 3.7 33.3 16.7 16.7 36.4 18.2 0 14.8 3.7 0 0 0 0 0
September 62.5 54.1 25.0 ... ... ... 41.7 33.3 16.7 16.0 4.0 0 4.0 0 1.7 0
October 51.9 40.8 7.4 ... ... ... 53.3 40.0 6.7 38.7 25.8 9.7 6.5 0 12.5 2.8
November 80.0 64.0 24.0 ... ... ... 72.7 54.5 0 58.6 17.3 3.5 0 0 4.9 0
December 56.0 48.0 16.0 ... ... ... 46.2 38.5 7.7 45.2 29.0 0 19.3 3.2 12.9 4.3
1908.
January 46.2 30.8 15.4 50.0 12.5 0 33.3 0 0 22.6 9.7 3.2 3.2 0 1.9 1.9
February 12.5 0 0 25.0 0 0 12.5 0 0 0 0 0 0 0 0 0
March 38.5 19.2 7.7 44.4 11.1 0 11.1 0 0 9.7 0 0 0 0 0 0
April 15.4 7.7 0 0 0 0 0 0 0 6.7 3.3 0 0 0 0 0
May 76.0 52.0 40.0 87.5 50.0 12.5 33.3 22.2 0 45.1 16.2 0 0 0 0 0
June 7.7 0 0 0 0 0 11.1 0 0 0 0 0 0 0 0 0
July 26.9 15.4 11.5 22.2 22.2 0 11.1 0 0 6.4 6.4 0 0 0 0 0
August 46.2 26.9 3.9 44.4 33.3 0 62.5 25.0 12.5 12.9 3.2 0 0 0 1.6 0
September 20.0 8.0 4.0 42.9 28.6 1.4 22.2 11.1 0 16.7 10.0 0 0 0 4.3 0
October 18.4 3.7 0 0 0 0 9.1 0 0 9.7 6.4 3.2 0 0 0 0
November 13.0 0 0 28.6 0 0 11.1 0 0 6.6 0 0 0 0 0 0
December 11.5 7.7 3.8 0 0 0 12.5 0 0 3.2 0 0 0 0 0 0
1909.
January 12.0 8.0 0 30.0 10.0 0 0 0 0 3.2 3.2 0 3.2 0 0 0
February 52.1 47.8 47.8 28.6 14.3 0 37.5 0 0 7.1 3.6 3.6 0 0 3.4 3.4
March 69.4 34.6 3.8 50.0 25.0 0 44.5 11.1 0 32.3 19.4 3.2 6.5 0 2.8 1.4
April 42.3 15.4 3.9 33.3 22.2 11.1 44.4 22.2 11.1 36.6 10.0 0 0 0 0 0
May 88.4 26.1 4.3 50.0 12.5 0 33.3 0 0 12.9 3.2 0 0 0 0 0
June 85.0 60.0 25.0 60.0 40.0 10.0 44.4 33.3 11.1 53.3 20.0 0 0 0 1.4 0
July 34.8 8.7 4.4 ... ... ... 33.3 11.1 0 25.8 12.9 0 0 0 0 0
August 50.0 15.4 7.7 ... ... ... 40.0 10.0 0 22.6 6.5 3.2 0 0 0 0
September 43.5 21.8 8.7 25.0 25.0 12.5 0 0 0 13.3 3.3 0 0 0 0 0
October 36.4 13.6 0 18.2 0 0 0 0 0 3.2 0 0 0 0 0 0
November 4.5 0 0 10.0 0 0 0 0 0 0 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 29.0 22.6 0 9.7 6.5 7.3 1.5
1910.
January 72.0 48.0 24.0 44.5 33.3 11.1 75.0 25.0 0 61.3 35.5 9.7 5.8 3.2 15.9 3.2
February 47.8 43.5 17.4 63.2 21.1 5.3 40.0 30.0 5.0 32.2 7.1 0 3.6 0 0 0
March 33.3 14.8 0 30.8 11.1 3.7 29.6 22.2 7.4 12.9 3.2 0 0 0 0 0
April 41.7 33.3 20.8 40.0 32.0 16.0 38.5 23.1 15.4 23.3 13.3 0 0 0 0 0
May 47.8 17.4 0 52.0 20.0 0 36.0 16.0 4.0 16.1 12.9 0 0 0 0 0
June 95.5 86.4 31.8 80.8 46.2 19.2 64.0 28.0 8.0 43.3 6.7 0 0 0 1.4 0
Fiscal years:
1905-06 35.2 19.4 9.3 0.0 3.2 5.2 6.4 4.9 1.7 4.3 8.3 .8 .3 1.8 1.3 0
1906-07 61.5 43.6 9.2 7.7 9.2 2.3 1.1 9.8 0.7 2.5 3.0 .4 .5 2.1 5.4 1.0
1907-08 44.6 31.3 3.0 2.3 2.3 3.1 4.4 2.1 4.1 2.2 9.4 .4 .8 0.3 3.1 0.9
1908-09 38.9 20.3 8.4 0.0 5.0 0 7.4 8.5 2.8 6.7 7.1 .8 .8 0 1.2 0.4
1909-10 45.5 26.9 0.1 5.3 4.0 8.8 7.9 9.8 6.2 3.6 0.4 .1 .3 0.8 2.2 0.4
Table 6—Summary of Sanitary Chemicals Analyses of Weekly Samples, July 1st, 1909, to June 30th, 1910.
(Results in Parts per Million.)
(
A
)
Maximum.
Reservoirs. Turbidity1 Ammonia. Nitrogen as: Hardness Alkalinity Chlorine
Free Albuminoid Total Nitrites Nitrates
Dalecarlia inlet 2,100 0.034 0.264 0.280 0.0070 0.45 120.0 106.0 5.4
Dalecarlia outlet2 200 0.034 0.180 0.206 0.0050 0.70 115.0 105.8 5.7
Georgetown outlet3 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.
Reservoirs. Turbidity1 Ammonia. Nitrogen as: Hardness Alkalinity Chlorine
Free Albuminoid Total Nitrites Nitrates
Dalecarlia inlet 7 0.000 0.016 0.016 0.0000 0.00 52.9 39.5 1.0
Dalecarlia outlet2 7 0.000 0.040 0.040 0.0000 0.00 54.3 38.2 0.9
Georgetown outlet3 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.
Reservoirs. Turbidity1 Ammonia. Nitrogen as: Hardness Alkalinity Chlorine
Free Albuminoid Total Nitrites Nitrates
Dalecarlia inlet 86 0.006 0.167 0.113 0.0027 0.19 93.2 81.4 2.9
Dalecarlia outlet2 30 0.008 0.106 0.114 0.0023 0.18 95.5 79.5 3.4
Georgetown outlet3 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
Table 7—Daily Results at Pumping Station.
(
A
)
Month. Million gallons pumped: Lift to filters. Pressure at sandwasher pumps, per square inche. Coal consumed per day in tons. Station duty, per 100 lb. of coal consumed.
To filters. To sand washers.
Max. Min. Ave. Max. Min. Ave. Max. Min. Ave. Max. Min. Ave.
1909.
July 76.16 57.65 64.05 1.140 0.298 0.730 24.18 110.0 13.4 8.4 10.8 67.8 52.3 61.4
August 69.31 54.44 61.42 0.629 0.157 0.441 22.18 110.0 12.4 8.0 10.1 64.2 49.5 56.6
September 66.02 52.82 69.32 0.831 0.207 0.572 22.26 110.0 12.7 8.7 10.5 61.0 48.9 55.1
October 78.50 48.12 59.18 0.761 0.060 0.467 21.84 110.0 13.4 8.0 10.3 59.6 49.1 53.6
November 64.92 49.83 55.25 0.468 0.141 0.272 20.49 110.0 11.3 7.9 9.2 55.6 45.7 51.1
December 67.83 48.32 56.77 0.307 0.039 0.174 20.54 110.0 10.3 8.5 9.5 61.0 45.4 50.4
1910.
January 70.04 51.02 62.49 0.499 0.008 0.156 22.43 110.0 12.7 9.1 10.4 59.6 49.8 54.9
February 70.79 55.19 60.28 0.284 0.041 0.173 21.44 112.3 12.3 8.7 10.2 57.4 44.8 51.5
March 59.11 51.64 56.04 0.409 0.063 0.171 19.76 120.0 10.5 7.8 9.2 53.2 45.2 49.8
April 66.53 53.79 58.32 0.715 0.167 0.474 20.78 120.0 11.1 8.1 9.7 58.7 47.2 53.7
May 61.93 54.55 57.76 0.525 0.059 0.251 20.30 120.0 10.1 7.4 8.8 60.7 48.1 54.9
June 70.49 50.42 58.37 0.281 0.124 0.207 21.19 117.3 12.3 7.4 9.1 60.1 49.9 54.4
Fiscal years:
1909-10 78.50 48.12 59.19 1.140 0.008 0.373 21.45 113.3 13.4 7.4 9.8 67.8 44.8 54.0
1905-061 80.59 57.18 66.07 2.062 0.089 0.747 21.71 107.4 14.8 6.4 8.9 79.6 48.2 62.8
1906-07 80.29 57.44 66.89 2.120 0.023 0.580 21.60 120.8 15.0 7.0 10.0 71.6 46.5 58.6
1907-08 80.38 54.35 64.91 0.735 0.017 0.347 22.20 125.0 12.0 7.2 9.6 70.7 51.3 60.3
1908-09 78.93 47.83 61.47 0.875 0.060 0.453 22.52 122.3 13.2 7.0 10.0 74.0 45.7 57.7
Table 7
—(
Continued.
)
(
B
)
Fiscal Year. Name of coal used. Cost per ton. Duty per 100 lb. of coal consumed. Cost of coal per 1,000,000 ft-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 3.152 54.0 0.00255
Table 8.—Average Consumption of Water for Twenty-Four Hours, Per Million Gallons.
Month. Fiscal years.
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 or raking, are shown in Tables 10 and 11.
Sand Handling.—For the first three years of operation, the sand was carried from the sand bins in carts and dumped through the numerous manholes of the filters on chutes which could be revolved in various directions, in order to facilitate the spreading of the sand evenly over the surface of the filter.
About a year ago, however, this method was changed, by substituting sand ejectors for the carts. By this method, an ejector is either attached to, or placed directly under, the outlet gate of the sand bin, the gate is opened, and the ejector is started. From this ejector, the sand is carried back through the line of 4‑in. fixed pipe, and one or more lengths of 3‑in. hose, to the point of discharge in the filter bed which is being re‑sanded.
Table 9.
(
A
)
Number of Deaths from Typhoid Fever, by Months, in the District of Columbia for the Last Fourteen Fiscal Years.
Fiscal year. July. August. September. October. November. December. January. February. March. April. May. June. 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
1905‑061 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.
)
(
B
)
Number of Deaths from Typhoid Fever Reduced to Death Rates per 100,000 Inhabitants per Year.
Fiscal year. July. August. September. October. November. December. January. February. March. April. May. June. Annual death rate.
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 death rate. 59 99 89 84 65 53 38 24 22 26 24 30 ...
Figure 3—Washington Aqueduct, D. C., Filtration Plant. Sand Handling, System.
Figure 4—Washington Aqueduct, D. C., Filtration Plant. Washer Sand‑Handling, System.
Figure 5—Washington Aqueduct, D. C., Filtration Plan. Ejector Sand‑Handling, System.
Table 10—Periods of Operation, and Quantities Filtered.
Month. Number of filter runs ended after: Number of days since previous: Million gallons filtered since previous:
Scraping. Raking Scraping. Raking
Scraping. Raking. Max. Min. Ave. Max. Min. Ave. Max. Min. Ave. Max. Min. Ave.
1909.
July 14 0 89 44 67.4 0 0 0 229.01 106.27 163.289 0 0 0
August 8 0 74 51 60.4 0 0 0 175.54 124.94 152.581 0 0 0
September 13 0 98 53 68.3 0 0 0 237.52 114.37 161.702 0 0 0
October 18 5 81 32 59.9 43 33 39.4 206.09 78.78 132.359 96.50 71.51 82.708
November 8 2 79 44 53.4 47 37 42.0 168.19 82.32 112.603 99.00 90.23 94.615
December 3 4 62 61 61.3 63 50 57.3 135.77 128.33 132.647 144.35 106.11 125.940
1910.
January 9 4 95 79 88.0 88 72 77.0 204.38 146.58 178.461 189.48 152.33 170.735
February 1 4 99 99 99.0 93 51 71.0 205.73 205.73 205.730 192.98 118.85 158.890
March 3 4 120 110 113.7 108 101 104.3 275.96 257.36 265.493 249.68 224.49 238.993
April 10 12 126 62 84.8 129 21 65.3 295.96 104.13 181.972 307.57 45.22 142.448
May 3 2 86 38 69.7 55 32 43.5 186.64 81.66 150.230 102.15 69.79 85.978
June 13 2 100 61 79.7 129 78 103.5 213.70 130.85 171.059 181.25 167.84 174.540
Year 1909‑10 103 39 126 32 71.1 129 21 66.6 295.96 81.66 159.151 307.57 45.22 143.832
Fiscal years:
1905-06 71 0 195 38 91.1 0 0 0 497.45 116.66 240.379 0 0 0
1906-07 101 4 199 24 77.0 32 14 21.7 466.12 69.76 220.693 103.28 32.13 76.870
1907-08 143 77 180 11 54.9 63 7 28.6 477.19 28.20 146.912 165.25 17.08 75.775
1908-09 128 50 135 11 49.9 93 13 34.2 298.08 39.26 125.617 244.19 41.41 88.439
In re‑sanding a filter, it is first filled with water to the proposed depth of the sand layer. The outlet end of the hose is connected to a 3‑in. pipe which is supported on a boat, and the sand is discharged through this pipe at the point required. Work is first begun at the far end of the filter, and it is gradually filled by swinging the boat from side to side and backing it by degrees to the front end.
At first it was feared that a small quantity of mud would be deposited on the surface of the old sand, and that this mud would ultimately cause subsurface clogging. For this reason, when this method was first adopted, a man was required to rake the sand very thoroughly in front of the discharge. Later, it was found that by giving the end of the discharge pipe a slope of about 45° downward from the horizontal, the force of the current of sand and water could be depended on to cut the old surface of sand to any required depth, and move it ahead together with the new sand, thus completely breaking up the possible mud layer between the old and new sand layers. After having used this method almost exclusively for 15 months, in which time eleven filters have been re‑sanded, and 24,531 cu. yd. of sand have been replaced, there seems to be no indication of an increased initial loss of head. The sand is very compact, and has no apparent tendency to separate into different sizes. The general appearance is similar to that of very fine sand on the seashore. The filters re‑sanded in this way have been considerably more efficient than those in which the sand was replaced with carts, and as yet, no harmful results have been noted. The rate at which the sand is replaced is shown in Table 12, and the cost of labor for sand handling is given in detail in Table 14, which shows that quite a perceptible saving has been effected by the hydraulic method.
The figures showing the cost for sand handling do not include any charge for the quantity of water used, that item having been carried on the pumping‑station account.
Table 11—Quantities of Sand Removed.
Month. No. of filters scraped when last treatment was: Cubic yards when last treatment was: Depth, in inches, when last treatment was:
Scraping. Raking. Scraping. Raking. Scraping. Raking.
Max. Min. Ave. Max. Min. Ave. Max. Min. Ave. Max. Min. Ave.
1909.
July 14 0 338 121 190.6 0 0 0 2.51 0.90 1.415 0 0 0
August 8 0 356 149 218.5 0 0 0 2.65 1.11 1.631 0 0 0
September 8 0 524 97 178.6 0 0 0 3.90 0.72 1.330 0 0 0
October 9 5 150 93 115.8 301 121 169.0 1.12 0.69 0.862 2.24 0.90 1.256
November 2 2 134 88 111.0 132 81 106.5 1.00 0.65 0.825 0.98 0.60 0.790
December 0 2 0 0 0 133 126 129.5 0 0 0 0.99 0.94 0.965
1910.
January 2 4 155 112 133.5 195 121 147.8 1.15 0.83 0.990 1.45 0.90 1.100
February 0 4 0 0 0 390 160 225.8 0 0 0 2.90 1.19 1.678
March 1 4 489 489 489.0 262 179 214.3 3.64 3.64 3.640 1.95 1.33 1.593
April 4 12 172 84 119.3 230 146 178.8 1.28 0.62 0.885 1.71 1.09 1.331
May 1 2 320 320 320.0 249 241 245.0 2.38 2.38 2.380 1.85 1.79 1.820
June 0 2 0 0 0 203 190 196.5 0 0 0 1.51 1.41 1.460
Year 1909-10 49 37 524 84 176.7 390 81 181.0 3.90 0.62 1.314 2.90 0.60 1.373
Fiscal Years:
1905-06 71 0 600 71 250.0 0 0 0 4.47 0.53 1.799 0 0 0
1906-07 94 2 536 52 259.0 398 276 337.0 4.00 0.56 1.931 2.95 2.05 2.500
1907-08 81 53 527 46 190.2 411 35 118.4 3.92 0.21 1.507 3.06 0.21 0.881
1908-09 92 50 580 55 169.5 472 81 177.5 4.31 0.41 1.259 3.51 0.60 1.317
Table 12—Rates of Sand Handling.
Date Sand removed from filters. Sand replaced in filters.
Ejector hours. Cubic yards of sand removed Average rate in cubic yards per hour Ejector hours. Cubic yards of sand removed Average rate in cubic 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 ejected and washed, and $0.03 per cu. yd. for replacing.
In addition to the water used for carrying the sand which is being replaced, it is customary to keep a slight upward flow in the filter, thus using about 500,000 gal. of filtered water per day for this purpose. Assuming the value of this water to be the total cost for pumping, filtering, etc., or $3.80 per 1,000,000 gal., the cost per cubic yard of sand replaced would be about $0.02 when one ejector is used, and $0.01 when two are in operation.
It is not considered absolutely necessary to have an upward flow of water in the filter which is being re‑sanded, and it is not always done. It was used, however, as an additional safeguard against the formation of a stratum of mud between the old and new layers of sand while the hydraulic method was in an experimental stage.
The quantities of sand removed from the filters per scraping and the rates of sand handling are shown in Tables 11 and 12.
Cost of Operation.—It is frequently difficult to compare the relative cost of corresponding items for different plants, because of the different methods of dividing the cost and the varying opinions of the officials as to what should properly be charged to each item.
In order that the data may be in sufficient detail to permit it to be rearranged to compare with other plants, a list of employees and charges for supplies is given in Table 13. This list accounts for the entire appropriation for the care and maintenance of the filtration 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 to the filters is shown in Table 14, and the cost per cubic yard of sand handled in Table 15.
Preliminary Treatment.—Before the present filtration plant was designed, Rudolph Hering, George W. Fuller, and Allen Hazen, Members, Am. Soc. C. E., made an investigation and report. This report was dated February 18th, 1901, and contained the following paragraph:
"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 among the citizens of Washington against the use of a coagulant, and, as finally passed, the bill providing for the construction of the filters 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 to justify the conclusions in the report referred to, an experimental plant was constructed for the purpose of studying the efficiency of various methods of preliminary treatment of the water. This plant consisted of three cylindrical concrete filter tanks, each 10 ft. in diameter. These tanks were filled with the layers of gravel and sand necessary to make them represent as accurately as possible the large slow sand units of the main filtration plant. Means were also provided for giving a preliminary treatment to the water supplying each of these experimental slow sand filters. In two cases, the preliminary treatment was rapid filtration, while the third consisted of sedimentation and coagulation. The sedimentation tank was of sufficient size, when compared with the area of the experimental slow sand filter, to represent the Georgetown and McMillan Park Reservoirs when used in connection with the large filters. The first preliminary filter was very similar in construction and operation to a mechanical filter. The sand for this filter was taken from the main filters, and, consequently, was finer than is generally used in mechanical filters. The second preliminary filter was a Maignen scrubber. It consisted of a cylindrical concrete tank, 4 ft. in diameter and 8‑1/2 ft. deep, which contained 12 in. of cobble‑stones on the bottom, then, successively, 12 in. of egg‑size coke, 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.
Month. Office and laboratory. Pumping station. Filter Operations: Parking (care of grounds). Experimental filters. Main office. Total.
Sand handling. Repairs, etc.
1909.
July $0.73 $0.57 $0.86 ... $0.31 ... $0.15 $2.62
August 0.75 0.64 0.59 ... 0.71 ... 0.14 2.83
September 0.83 0.67 0.80 ... 0.51 ... 0.17 2.98
October 0.72 0.66 0.73 ... 0.34 ... 0.08 2.53
November 0.87 0.76 0.42 ... 0.38 ... 0.18 2.61
December 0.90 0.69 0.27 ... 0.40 ... 0.12 2.38
1910.
January 0.81 0.63 0.33 ... 0.14 ... 0.10 2.01
February 0.94 0.74 0.35 $0.07 0.11 ... 0.16 2.37
March 0.92 0.81 0.30 0.07 0.18 ... 0.13 2.41
April 0.93 0.83 0.49 0.03 0.36 ... 0.13 2.77
May 0.86 0.72 0.36 0.03 0.55 ... 0.18 2.70
June 0.88 0.67 0.38 ... 0.38 ... 0.12 2.43
Average 0.84 0.70 0.27 10.25 0.36 ... 0.14 2.56
Fiscal years:
1905‑1906 0.45 0.45 0.47 0.02 0.01 ... 0.09 1.49
1906‑1907 0.57 0.57 0.58 0.21 0.07 $0.03 0.04 2.07
1907‑1908 0.70 0.56 0.42 0.32 0.15 0.09 0.09 2.36
1908‑1909 0.72 0.61 0.41 0.34 0.22 0.01 0.13 2.44
Table 14
—(
Continued.
)
(
B
)
Materials.
Month. Office and laboratory. Pumping station. Filter Operations: Parking (care of grounds). Experimental filters. Main office. Total.
Sand handling. Repairs, etc.
1909.
July ... ... $0.01 ... ... ... ... $0.01
August $0.01 ... ... ... $0.07 ... $0.01 0.09
September 0.05 $0.31 0.04 ... 0.01 ... 0.03 0.44
October 0.08 0.11 0.13 ... 0.46 ... 0.02 0.80
November 0.13 0.78 0.10 ... 0.34 ... 0.02 1.37
December 0.03 0.17 0.05 ... 0.01 ... 0.05 0.31
1910.
January 0.12 0.74 0.14 ... 0.01 ... ... 1.01
February 0.07 1.88 0.18 ... 0.01 ... 0.01 2.15
March 0.26 0.28 0.01 ... ... ... ... 0.55
April 0.18 1.22 0.10 ... 0.29 ... 0.02 1.81
May 0.06 0.72 0.02 ... 0.11 ... 0.02 0.98
June 0.54 2.23 ... 2$2.16 0.46 ... 0.04 5.43
Average 0.13 0.69 0.02 30.21 0.17 ... 0.02 1.24
Fiscal years.
1905‑1906 0.04 0.59 0.02 ... ... ... ... 0.65
1906‑1907 0.03 0.67 0.08 0.20 0.02 ... ... 1.00
1907‑1908 0.05 0.54 0.04 0.07 0.06 ... 0.01 0.77
1908‑1909 0.10 0.69 0.05 0.18 0.18 ... 0.02 1.22
Table 14
—(
Continued.
)
(
C
)
Totals.
Month. Office and laboratory. Pumping station. Filter Operations: Parking (care of grounds). Experimental filters. Main office. Total.
Sand handling. Repairs, etc.
1909.
July $0.73 $0.57 $0.87 ... $0.31 ... $0.15 $2.63
August 0.76 0.64 0.59 ... 0.78 ... 0.15 2.92
September 0.88 0.98 0.84 ... 0.52 ... 0.20 3.42
October 0.80 0.77 0.86 ... 0.80 ... 0.10 3.33
November 1.00 1.54 0.52 ... 0.72 ... 0.20 3.98
December 0.93 0.86 0.32 ... 0.41 ... 0.17 2.69
1910.
January 0.93 1.37 0.47 ... 0.15 ... 0.10 3.02
February 1.01 2.62 0.53 $0.07 0.12 ... 0.17 4.52
March 1.18 1.09 0.31 0.07 0.18 ... 0.13 2.96
April 1.11 2.05 0.59 0.03 0.65 ... 0.15 4.58
May 0.92 1.44 0.38 0.03 0.66 ... 0.20 3.63
June 1.42 2.90 0.38 2.16 0.84 ... 0.16 7.86
Average. 0.97 1.39 0.29 0.46 0.58 ... 0.16 3.80
Fiscal years:
1905‑1906 0.49 1.04 0.49 0.02 0.01 ... 0.09 2.14
1906‑1907 0.60 1.24 0.66 0.41 0.09 $0.03 0.04 3.07
1907‑1908 0.75 1.13 0.46 0.39 0.21 0.09 0.10 3.13
1908‑1909 0.82 1.30 0.46 0.52 0.40 0.01 0.15 3.66
The two preliminary filters were operated at a rate of about 50,000,000 gal. per acre per day, and the three slow sand filters at 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 end of July, 1908.
Figure 6—Washington Aqueduct, D. C. Experimental Filters Below Dalecarlia Reservoir Coagulating Basins and Apparatus.
Table 15—Average Cost for Labor for Sand Handling.
(
A
)
Per Million Gallons Pumped To Filter.
Month. Scraping. Ejecting. Washing. Smoothing. Raking. Re-Sanding. Total.
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. Scraping. Ejecting. Washing. Smoothing. Raking. Re-Sanding. Total.
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 combined rapid and slow sand filter will be designated as Filter Plant No. 1, the combined Maignen scrubber and slow sand filter as Filter Plant No. 2, and the combined coagulating basin and slow sand basin as Filter Plant No. 3.
The length of run of Filter Plant No. 1 was relatively long at first. The rapid rate of filtration, however, tended to carry the clay, which was suspended in the applied water, to a considerable depth in the filtering material, so that the runs gradually decreased 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, and wash them.
Although this preliminary filter was operated at a high rate, its efficiency was quite satisfactory. In fact, at times when the applied water was comparatively good, very little work was left for the slow sand filter. At times of high turbidity, however, some of the exceedingly fine mud in the applied water passed through this filter, as well as the slow sand filter connected with it, and it proved to be absolutely impossible to produce a clear effluent at all times with this combination.
Filter Plant No. 2 proved more economical and convenient in operation, but somewhat less efficient than Filter Plant No. 1. Neither filter could be depended on to give a clear effluent when the applied water was turbid.
In the operation of Filter Plant No. 3, sulphate of alumina was used when the applied water contained too much turbidity to be treated satisfactorily by slow sand filters.
When the water was comparatively clear, either one of the three systems, or slow sand filtration alone, was entirely satisfactory. At times of high turbidity, however, Filter Plant No. 3 was the only one which could be depended on to produce a clear effluent.
A fair comparison between the results of the three systems when treating 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, while No. 3 could be depended on under all conditions. The results of operation are shown in detail in Tables 17, 18, and 19. It will be noticed in Table 17, that on March 10th, 1908, Filter Plant No. 1 was put out of service and a Puech system of preliminary filters was substituted for it.
The Puech preliminary filters consisted of five units containing gravel of varying sizes through which the water was filtered successively before it was finally applied to the final slow sand filter. A general idea of this system may be obtained by referring to Figure 8.
Table 16—Turbidity Results with Experimental Filters, During Period of High Turbidity, January, 1908.
Date. Raw water. Filter No. 1 Filter No. 2 Filter No. 3
Effluent preliminary filter. Effluent sand filter. Effluent preliminary filter. Effluent sand filter. Effluent coagulant basin. Effluent sand filter.
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 cleaning ... 5 0
January 20th 72 31 6 sand filter ... cleaning 0
January 21st 55 20 4 25 4 sand filter ...
January 22d 49 17 3 21 4 sand 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 Filter Plant No. 1 or No. 2.
Experimental Rate Studies.—In September, 1908, an experimental plant consisting of six small filters was put in operation. The object of these experiments was to study the relative efficiencies and cost for the operation of slow sand filters when operated at different rates.
The units of the plant consisted of cylindrical galvanized‑iron tanks 4 ft. in diameter and 9 ft. high. The filter sand in these tanks was taken from the supply for the main filters. It was supported on gravel layers and supplied with under‑drains of suitable 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 at rates 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 the filters, with the exception of Nos. 5 and 6. For these, the rates were found to be higher than could be maintained for any great length of time, owing to the deeper penetration of the mud in the filter sand, which caused high initial losses of head, short runs, and deep scrapings. A rate of about 30,000,000 gal. was maintained in the case of Filter No. 5 from the time it was started on September 9th, 1908, until November 8th, 1909, when it was reduced to about 17,000,000 gal., which rate was maintained thereafter until the filter was shut down in February, 1910.
Figure 7—Plan of Filter‑House and Equipment.
In the case of Filter No. 6, it was found impossible to maintain a rate of 100,000,000 gal. for more than a very few days at a time. It was started at about this rate, however, at the beginning of each run, and kept as high as possible for the remainder of the time during the first seven runs. At the end of the seventh run, on October 17th, 1908, the filter was given a very deep scraping and re‑sanded.
Figure 8—Diagrammatic Sketch Showing Arrangements for Testing "Puech" System of Water Filtration at Washington D. C., U. S. A.
The layer of clean sand restored the original capacity, and the filter was operated as before, but with gradually decreasing rates until December, 1908, when the rate was reduced to about 40,000,000 gal. Even this lower rate was too high to be maintained without removing and replacing a large part of the sand. The rates, therefore, gradually decreased to about 23,000,000 gal. on March 13th, 1909, when the filter was again re‑sanded. After this re‑sanding the rate was reduced to about 20,000,000 gal., and the filter was operated at approximately that rate until it was again re‑sanded on November 13th, 1909, when the rate was again reduced to about 14,000,000 gal., which was maintained until the filter was put out of service on February 28th, 1910.
This experimental plant was in service from September, 1908, to the latter part of February, 1910, or for about 1‑1/2 years, and the leading results are summarized in Table 20.
Table 17—Record of Experimental Filter Plant No. 1.
Date. Preliminary Filter. Final Filter. Turbidity. Bacteria.
Rate, millions of gallons per acre daily. Loss of head. Rate, millions of gallons per acre daily. Loss of head. Applied water. Effluent preliminary filter. Effluent final filter. Applied water. Effluent preliminary filter. Effluent final filter.
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 from outlet to inlet. 1,400 800 450
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 1700 41
Washed.
Apr. 13 50.00 0.95 4.00 0.14 80 21 2 13,000 1300 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 Plateslost.
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 Lost. Lost. Lost.
Dec. 21 46.40 6.68 3.99 0.32 26 6 1 Lost. Lost. Lost.
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.
)
Date. Puech system: Final filter. Turbidity. Bacteria.
Rates, millions of gallons per acre daily. Rate, millions of gallons per acre daily. Loss of head. Applied water. Effluent, preliminary filter. Effluent, final filter. Applied water. Effluent, preliminary filter. Effluent, final filter.
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
April 1 265 170 90 53 18 3.00 1.48 44 9 1 750 60 41
April 2 265 170 90 53 18 2.99 1.56 42 9 1 1,100 140 26
April 3 318 204 108 64 22 2.99 1.63 41 8 1 1,500 47 11
April 4 294 189 100 59 20 2.99 1.70 54 13 1 700 80 35
April 5 279 179 95 56 19 3.00 1.73 50 13 1 Sunday.
April 6 279 179 95 56 19 2.99 1.76 41 9 1 440 65 17
April 7 265 170 90 53 18 3.00 1.78 35 6 1 650 65 34
April 8 265 170 90 53 18 3.00 1.79 39 6 1 550 44 10
April 9 265 170 90 53 18 3.00 1.79 40 6 1 390 30 25
April 10 265 170 90 53 18 3.00 1.77 40 6 1 500 27 16
April 11 265 170 90 53 18 3.00 1.78 45 7 1 430 28 28
April 12 265 170 90 53 18 2.99 1.80 52 11 1 Sunday.
April 13 265 170 90 53 18 ... 1.81 50 10 1 490 17 26
April 14 Shut down on account of losing water when aqueduct was drained; also cleaned coarse sand filter. Started April 22d.
April 23 241 155 82 48 16 ... 1.82 29 4 1 140 600 38
April 24 241 155 82 48 16 3.00 1.87 21 3 1 200 1,000 13
April 25 241 155 82 48 16 2.99 1.95 20 3 1 85 180 25
April 26 252 162 86 50 17 3.00 1.95 24 3 1 Sunday.
April 27 241 155 82 48 16 3.00 1.93 18 2 1 95 35 23
April 28 241 155 82 48 16 3.00 1.96 20 2 1 70 24 18
April 29 241 155 82 48 16 2.99 1.97 24 3 1 110 21 24
April 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 ... ... ...