Part 3

~Table 8--Average Consumption of Water for Twenty-four Hours, Per Million Gallons.~ ==========+================================================ | ~Fiscal years.~ Month. +-----+-----+-----+-----+-----+-----+-----+------ |1903.|1904.|1905.|1906.|1907.|1908.|1909.|1910. ----------+-----+-----+-----+-----+-----+-----+-----+------ July |59.80|61.50|63.20|69.80|69.18|68.64|71.08|64.05 August |59.00|59.70|67.70|71.40|68.03|67.74|68.14|61.42 September |56.50|61.10|67.90|71.30|69.82|68.93|65.83|60.32 October |58.70|59.10|63.90|68.40|69.14|66.46|65.89|59.18 November |54.70|58.60|62.10|66.10|65.51|61.54|60.06|55.25 December |60.70|60.10|70.30|67.20|65.71|62.29|57.99|56.77 January |60.10|65.30|75.10|65.30|67.62|63.36|57.72|62.49 February |59.30|67.80|86.00|68.70|74.68|68.17|55.42|60.28 March |55.30|60.00|67.60|64.30|64.23|59.63|55.31|56.04 April |55.10|57.20|63.10|62.70|63.45|61.51|58.19|58.32 May |57.70|60.80|66.30|65.60|62.47|62.96|59.25|57.76 June |59.50|62.30|70.60|67.80|63.53|67.96|60.12|58.37 ----------+-----+-----+-----+-----+-----+-----+-----+------ Average |58.03|61.10|68.70|67.40|66.90|64.91|61.47|59.19 ==========+=====+=====+=====+=====+=====+=====+=====+======

The length of runs, depth of scraping, etc., after the scraping 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.~

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

(_A_) ~Number of Deaths from Typhoid Fever, by Months, in the District of Columbia for the Last Fourteen Fiscal Years.~ ==========+====+====+====+====+====+====+===+===+===+===+===+===+====== Fiscal | | | | | | | | | | | | | year. | A | B | C | D | E | F | G | H | I | J | K | L |Total. ----------+----+----+----+----+----+----+---+---+---+---+---+---+------ 1896-97 | 8 |15 |25 |25 |18 |16 |13 | 4 | 4 | 4 | 6 | 9 | 147 1897-98 |10 |16 |18 |10 | 9 |18 | 8 | 4 | 2 | 9 | 6 |20 | 130 1898-99 |24 |22 |22 |28 |21 |16 |10 | 4 | 7 | 6 | 3 | 6 | 169 1899-1900 | 9 |38 |30 |28 |27 |26 |17 | 6 | 8 |10 | 5 |12 | 193 1901-02 |16 |33 |28 |21 |22 |16 |19 | 8 |12 | 9 |13 | 9 | 206 1902-03 |21 |39 |25 |32 |19 |20 | 9 | 5 | 9 | 6 | 6 | 3 | 194 1903-04 |17 |26 |18 |19 | 8 |14 | 5 | 5 | 6 |10 | 8 | 8 | 144 1904-05 |16 |22 |25 |14 |11 | 9 |11 | 1 | 5 | 7 | 1 | 3 | 125 1905-06[1]|15 |30 |23 |26 |14 | 6 | 6 | 4 | 5 | 4 |10 | 9 | 152 1906-07 |21 |32 |21 |25 |17 | 4 | 7 | 6 | 4 | 6 | 7 | 2 | 152 1907-08 |10 |18 |17 |19 |11 | 7 | 4 | 1 | 1 | 8 | 8 | 3 | 107 1908-09 |15 |13 |23 |17 |16 |13 |16 | 8 | 3 | 8 | 7 | 7 | 146 1909-10 |12 |12 |17 |12 |12 | 2 | 3 | 4 | 7 | 5 | 5 | 4 | 95 ----------+----+----+----+----+----+----+---+---+---+---+---+---+------ Average |15.3|25.5|22.9|21.5|16.6|13.1|9.6|4.4|5.8|6.7|6.4|7.5|155.4 ----------+----+----+----+----+----+----+---+---+---+---+---+---+------

~Table 9~--(_Continued._)

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

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

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

~Table 10--Periods of Operation, and Quantities Filtered.~ =============+=============+============================================ | Number of | ~Number of days since previous~: | filter runs +---------------------+---------------------- |ended after: | Scraping. | Raking. Month. +------+------+------+------+-------+-------+------+------- |Scrap-| Rak- | Max. | Min. | Ave. | Max. | Min. | Ave. | ing. | ing. | | | | | | -------------+------+------+------+------+-------+-------+------+------- 1909. -------------+------+------+------+------+-------+-------+------+------- July | 14 | 0 | 89 | 44 | 67.4 | 0 | 0 | 0 August | 8 | 0 | 74 | 51 | 60.4 | 0 | 0 | 0 September | 13 | 0 | 98 | 53 | 68.3 | 0 | 0 | 0 October | 18 | 5 | 81 | 32 | 59.9 | 43 | 33 | 39.4 November | 8 | 2 | 79 | 44 | 53.4 | 47 | 37 | 42.0 December | 3 | 4 | 62 | 61 | 61.3 | 63 | 50 | 57.3 -------------+------+------+------+------+-------+-------+------+------- 1910. -------------+------+------+------+------+-------+-------+------+------- January | 9 | 4 | 95 | 79 | 88.0 | 88 | 72 | 77.0 February | 1 | 4 | 99 | 99 | 99.0 | 93 | 51 | 71.0 March | 3 | 4 | 120 | 110 | 113.7 | 108 | 101 | 104.3 April | 10 | 12 | 126 | 62 | 84.8 | 129 | 21 | 65.3 May | 3 | 2 | 86 | 38 | 69.7 | 55 | 32 | 43.5 June | 13 | 2 | 100 | 61 | 79.7 | 129 | 78 | 103.5 -------------+------+------+------+------+-------+-------+------+------ Year 1909-10 | 103 | 39 | 126 | 32 | 71.1 | 129 | 21 | 66.6 -------------+------+------+------+------+-------+-------+------+------ Fiscal years:| | | | | | | | -------------+------+------+------+------+-------+-------+------+------- 1905-06 | 71 | 0 | 195 | 38 | 91.1 | 0 | 0 | 0 1906-07 | 101 | 4 | 199 | 24 | 77.0 | 32 | 14 | 21.7 1907-08 | 143 | 77 | 180 | 11 | 54.9 | 63 | 7 | 28.6 1908-09 | 128 | 50 | 135 | 11 | 49.9 | 93 | 13 | 34.2 =============+======+======+======+======+=======+=======+======+=======

=============+======================================================== | ~Million gallons filtered since previous:~ +-------------------------------------------------------- Month. | Scraping. | Raking. +--------+--------+---------+--------+--------+---------- | Max. | Min. | Ave. | Max. | Min. | Ave. -------------+--------+--------+---------+--------+--------+---------- 1909. -------------+--------+--------+---------+--------+--------+---------- July | 229.01 | 106.27 | 163.289 | 0 | 0 | 0 August | 175.54 | 124.94 | 152.581 | 0 | 0 | 0 September | 237.52 | 114.37 | 161.702 | 0 | 0 | 0 October | 206.09 | 78.78 | 132.359 | 96.50 | 71.51 | 82.708 November | 168.19 | 82.32 | 112.603 | 99.00 | 90.23 | 94.615 December | 135.77 | 128.33 | 132.647 | 144.35 | 106.11 | 125.940 -------------+--------+--------+---------+--------+--------+---------- 1910. -------------+--------+--------+---------+--------+--------+---------- January | 204.38 | 146.58 | 178.461 | 189.48 | 152.33 | 170.735 February | 205.73 | 205.73 | 205.730 | 192.98 | 118.85 | 158.890 March | 275.96 | 257.36 | 265.493 | 249.68 | 224.49 | 238.993 April | 295.96 | 104.13 | 181.972 | 307.57 | 45.22 | 142.448 May | 186.64 | 81.66 | 150.230 | 102.15 | 69.79 | 85.978 June | 213.70 | 130.85 | 171.059 | 181.25 | 167.84 | 174.540 -------------+--------+--------+---------+--------+--------+---------- Year 1909-10 | 295.96 | 81.66 | 159.151 | 307.57 | 45.22 | 143.832 -------------+--------+--------+---------+--------+--------+---------- Fiscal years: -------------+--------+--------+---------+--------+--------+---------- 1905-06 | 497.45 | 116.66 | 240.379 | 0 | 0 | 0 1906-07 | 466.12 | 69.76 | 220.693 | 103.28 | 32.13 | 76.870 1907-08 | 477.19 | 28.20 | 146.912 | 165.25 | 17.08 | 75.775 1908-09 | 298.08 | 39.26 | 125.617 | 244.19 | 41.41 | 88.439 =============+========+========+=========+========+========+===========

In re-sanding a filter, it is first filled with water to 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 degrees 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.~ ==============+=================+================================ |~No. of filters | ~Cubic yards when last |scraped when last| treatment was:~ |treatment was:~ | Month. +---------+-------+---------------+---------------- | | | Scraping. | Raking. |Scraping.|Raking.|----+----+-----+----+----+------ | | |Max.|Min.|Ave. |Max.|Min.|Ave. --------------+---------+-------+----+----+-----+----+----+------ 1909. --------------+---------+-------+----+----+-----+----+----+------ July | 14 | 0 |338 |121 |190.6| 0 | 0 | 0 August | 8 | 0 |356 |149 |218.5| 0 | 0 | 0 September | 8 | 0 |524 | 97 |178.6| 0 | 0 | 0 October | 9 | 5 |150 | 93 |115.8|301 |121 |169.0 November | 2 | 2 |134 | 88 |111.0|132 | 81 |106.5 December | 0 | 2 | 0 | 0 | 0 |133 |126 |129.5 --------------+---------+-------+----+----+-----+----+----+------ 1910. --------------+---------+-------+----+----+-----+----+----+------ January | 2 | 4 |155 |112 |133.5|195 |121 |147.8 February | 0 | 4 | 0 | 0 | 0 |390 |160 |225.8 March | 1 | 4 |489 |489 |489.0|262 |179 |214.3 April | 4 | 12 |172 | 84 |119.3|230 |146 |178.8 May | 1 | 2 |320 |320 |320.0|249 |241 |245.0 June | 0 | 2 | 0 | 0 | 0 |203 |190 |196.5 --------------+---------+-------+----+----+-----+----+----+------ Year 1909-10 | 49 | 37 |524 | 84 |176.7|390 | 81 |181.0 --------------+---------+-------+----+----+-----+----+----+------ Fiscal Years: --------------+---------+-------+----+----+-----+----+----+------ 1905-06 | 71 | 0 |600 | 71 |250.0| 0 | 0 | 0 1906-07 | 94 | 2 |536 | 52 |259.0|398 |276 |337.0 1907-08 | 81 | 53 |527 | 46 |190.2|411 | 35 |118.4 1908-09 | 92 | 50 |580 | 55 |169.5|472 | 81 |177.5 ==============+=========+=======+====+====+=====+====+====+======

==============+================================ | ~Depth, in inches, when | last treatment was:~ +---------------+---------------- Month. | Scraping. | Raking. +----+----+-----+----+----+------ |Max.|Min.|Ave. |Max.|Min.|Ave. --------------+----+----+-----+----+----+------ 1909. --------------+----+----+-----+----+----+------ July |2.51|0.90|1.415|0 |0 |0 August |2.65|1.11|1.631|0 |0 |0 September |3.90|0.72|1.330|0 |0 |0 October |1.12|0.69|0.862|2.24|0.90|1.256 November |1.00|0.65|0.825|0.98|0.60|0.790 December |0 |0 |0 |0.99|0.94|0.965 --------------+----+----+-----+----+----+------ 1910. --------------+----+----+-----+----+----+------ January |1.15|0.83|0.990|1.45|0.90|1.100 February |0 |0 |0 |2.90|1.19|1.678 March |3.64|3.64|3.640|1.95|1.33|1.593 April |1.28|0.62|0.885|1.71|1.09|1.331 May |2.38|2.38|2.380|1.85|1.79|1.820 June |0 |0 |0 |1.51|1.41|1.460 --------------+----+----+-----+----+----+------ Year 1909-10 |3.90|0.62|1.314|2.90|0.60|1.373 --------------+----+----+-----+----+----+------ Fiscal Years: --------------+----+----+-----+----+----+------ 1905-06 |4.47|0.53|1.799|0 |0 |0 1906-07 |4.00|0.56|1.931|2.95|2.05|2.500 1907-08 |3.92|0.21|1.507|3.06|0.21|0.881 1908-09 |4.31|0.41|1.259|3.51|0.60|1.317 ==============+====+====+=====+====+====+======

~Table 12--Rates of Sand Handling.~ =========+================================+============================ | ~Sand removed from filters.~ |~Sand replaced in filters.~ +-----------+--------+-----------+---------+--------+--------- | Ejector | Cubic | Average | Ejector | Cubic |Average Date. | hours. |yards of| rate in | hours. |yards of|rate in | | sand |cubic yards| | sand | cubic | |removed | per hour | |removed | yards | | | | | |per hour ---------+-----------+--------+-----------+---------+--------+--------- 1906. ---------+-----------+--------+-----------+---------+--------+--------- April | 49 | 253 | 5.2 | ... | ... | ... May | 380 | 2,511 | 6.6 | ... | ... | ... June | 567 | 3,280 | 5.8 | ... | ... | ... July | 931 | 5,376 | 5.8 | ... | ... | ... August | 105 | 533 | 5.1 | ... | ... | ... September| 315 | 1,892 | 6.0 | ... | ... | ... October | 1,067 | 5,173 | 5.8 | ... | ... | ... November | 168 | 935 | 5.6 | ... | ... | ... December | 203 | 1,073 | 5.3 | ... | ... | ... ---------+-----------+--------+-----------+---------+--------+--------- 1907. ---------+-----------+--------+-----------+---------+--------+--------- January | 399 | 2,974 | 7.3 | ... | ... | ... February | 140 | 1,139 | 8.1 | ... | ... | ... March | 115 | 878 | 7.6 | ... | ... | ... April | 427 | 3,103 | 7.3 | ... | ... | ... May | 133 | 939 | 7.0 | ... | ... | ... June | 105 | 674 | 6.4 | ... | ... | ... July | 7 | 46 | 6.6 | ... | ... | ... August | 90 | 574 | 6.4 | ... | ... | ... September| 306 | 1,396 | 6.5 | ... | ... | ... October | 273 | 1,701 | 6.2 | ... | ... | ... November | 202 | 1,258 | 6.8 | ... | ... | ... December | 304 | 2,138 | 5.9 | ... | ... | ... ---------+-----------+--------+-----------+---------+--------+--------- 1908. ---------+-----------+--------+-----------+---------+--------+--------- January | 546 | 3,708 | 6.8 | ... | ... | ... February | 98 | 776 | 7.9 | ... | ... | ... March | 315 | 2,832 | 9.0 | ... | ... | ... April | 469 | 3,775 | 8.1 | ... | ... | ... May | 182 | 1,414 | 7.8 | ... | ... | ... June | 280 | 2,057 | 7.4 | ... | ... | ... July | 280-1/2 | 2,683 | 9.6 | ... | ... | ... August | 327-1/2 | 2,808 | 8.6 | ... | ... | ... September| 402 | 3,371 | 8.4 | ... | ... | ... October | 308 | 2,696 | 8.7 | ... | ... | ... November | 47-1/2 | 333 | 7.0 | ... | ... | ... December | 153-3/4 | 1,268 | 8.3 | ... | ... | ... ---------+-----------+--------+-----------+---------+--------+--------- 1909. ---------+-----------+--------+-----------+---------+--------+--------- January | 119-1/2 | 1,055 | 8.8 | ... | ... | ... February | 161-1/2 | 1,479 | 9.2 | ... | ... | ... March | 144 | 1,465 | 10.2 | ... | ... | ... April | 214-3/4 | 2,260 | 10.5 | 188 | 2,405 | 12.8 May | 219-3/4 | 2,223 | 10.1 | 190 | 2,196 | 11.5 June | 355 | 3,096 | 8.7 | 243 | 3,054 | 12.6 July | 312-1/4 | 2,707 | 8.7 | 425-1/2 | 4,050 | 9.5 August | 218-3/4 | 1,955 | 9.0 | 64-1/2 | 620 | 9.6 September| 172-1/2 | 1,360 | 7.9 | 408 | 2,842 | 7.0 October | 203 | 1,870 | 9.2 | 261-1/4 | 2,350 | 9.0 November | 54 | 397 | 7.4 | 0 | 0 | ... December | 62 | 382 | 6.2 | 0 | 0 | ... ---------+-----------+--------+-----------+---------+--------+--------- 1910. ---------+-----------+--------+-----------+---------+--------+--------- January | 104 | 703 | 6.8 | 0 | 0 | ... February | 106-1/2 | 1,058 | 9.9 | 28-1/4 | 371 | 13.1 March | 98 | 985 | 10.0 | 72 | 1,008 | 14.0 April | 268-3/4 | 2,852 | 10.7 | 134-1/4 | 2,159 | 16.1 May | 58-3/4 | 693 | 11.8 | 171-3/4 | 3,042 | 17.7 June | 58-3/4 | 642 | 10.9 | 9-3/4 | 166 | 17.0 =========+===========+========+===========+=========+========+========

The cost for pumping water for sand handling, including all labor, materials, and repairs, amounts to $0.06 per cu. yd. of sand 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.