Part 4
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~. =============+===========+==========+================== | 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 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.
~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 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.