~Table 26--Results of Experiments with Preliminary Filter at Albany, N. Y.~ ==========+==========+==========+============+============= Month, | Bacteria | Bacteria | Bacteria in|Bacteria in 1906. | in raw | in pre- | effluent | effluent | water. | liminary | from | from | | filter |experimental|city filter. | | effluent.|sand filter.| ----------+----------+----------+------------+------------- March | 133,480 | 36,000 | 151 | 706 April | 77,420 | 4,810 | 72 | 155 May | 15,800 | 2,250 | 48 | 37 June | 4,520 | 358 | 38 | 34 July | 2,090 | 163 | 25 | 22 August | 2,740 | 121 | 36 | 22 September | 8,280 | 445 | 20 | 24 October | 38,350 | 4,235 | 67 | 227 November | 67,910 | 15,570 | 337 | 341 December | 645,500 | 25,440 | 144 | 2,783 ----------+----------+----------+------------+------------- 1907. | | | | January | 127,560 | 4,660 | 48 | 443 February | 28,000 | 1,800 | 13 | 116 ==========+==========+==========+============+============= On the diagram, Figure 11, will be found various data taken from the published records of the Albany filter, from 1899 to 1909. These data include: The numbers of bacteria before and after filtration; the percentage of bacteria remaining in the effluent; the average quantity of water filtered, in millions of gallons per day; the quantities of water filtered between scrapings; the turbidity of the raw water; the cost of filtration, including capital charges and cost of operation; and the typhoid death rates of the city per month. Several points are brought out conspicuously by this diagram. One is the uniformly low death rate from typhoid throughout the entire period. The filter was operated from 1899 until the fall of 1907 with raw water taken from what is known as the "Back Channel." Since then it has been taken from a new intake which extends into the Hudson River itself. Until the fall of 1908 the preliminary treatment consisted merely of sedimentation, but since then the water has received an additional preliminary treatment in mechanical filters operated without coagulant, along the lines of the experiments just mentioned. During this time the average rate of filtration of the sand filter has not changed materially, although it is said that the maximum rate has been increased since the preliminary filters were put in service. The study of the bacteriological analyses shows that the best results were obtained during 1902, 1903, and 1904. Since then the numbers of bacteria in both the raw and filtered water have increased. This was especially