~Table 17~--(_Continued._) ~Tests for~ _B. Coli._ ==================+====================== |~Percentage of Samples Quantity of water |Containing~ _B. Coli_. tested. +--------+------------- | Raw. | Filtered. ------------------+--------+------------- 0.1 cu. cm. | 0 | 0 1.0 cu. cm. | 20 | 0 10.0 cu. cm. | 40 | 0 ==================+========+============= As a matter of record, the results of a series of analyses made at Peekskill, N. Y., during 1910 are presented in Table 27. A sand filter was constructed for the water supply of this city in 1909, and put in operation in December. The filter has a capacity of 4,000,000 gal. per day. The supply is taken from Peekskill Creek, and the water receives about one week's nominal storage before flowing to the filters. An aerator is used before filtration during the summer, when algae are likely to develop in the reservoir. The filter was installed after an epidemic of typhoid which was apparently caused by an infection of the water supply. Normally, the water has been little contaminated, but the supply is subject to accidental contamination at any time, among other possible sources of infection being the camps of workmen now engaged in constructing the Catskill Aqueduct for New York City. ~Table 28--Average Results of Chemical Analysis at Peekskill, N. Y., Made at Intervals of Six Weeks During 1910.~ =====================+=================+================+================= | ~Parts per | | ~Parts per | Million.~ | | Million.~ |--------+--------| |--------+-------- | Raw |Filtered| | Raw |Filtered | water. | water. | | water. | water. ---------------------+--------+--------+----------------+--------+-------- Turbidity | 2. | 0 |Total residue | 70. | 76.00 Color | 25. | 20. |Loss on ignition| 19.00 | 17.00 Nitrogen as albumi- | | |Fixed residue | 50.00 | 59.00 noid ammonia | 0.112 | 0.076 |Iron | 0.17 | 0.13 Nitrogen as free | | |Total hardness | 38.70 | 45.10 ammonia | 0.024 | 0.006 |Alkalinity | 33.90 | 42.60 Nitrogen as nitrites | 0.001 | 0.001 |Incrustants | 4.60 | 4.50 Nitrogen as nitrates | 0.06 | 0.06 |Chlorine | 2.60 | 2.70 =====================+========+========+================+========+========