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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
noticeable during the winters of 1907 and 1908 when the water was
taken from the new intake. It will be interesting to compare the
results after the preliminary filters have been operated for a long
period to ascertain their normal effect on efficiency and on the
increased yield.

[Illustration: ~Figure 11--Filters at Albany, N. Y. Results of
Operation. 1899-1909. Compiled from data in Annual Reports.~]

Another fact to be drawn from the plotted Albany data is the
increase in the cost of filtration, both in capital charges and in
operation. From 1899 until 1906 the cost of operation, including the
cost of low-lift pumping, was approximately $5 per million gallons
of water filtered; and the total cost of filtration, including
capital charges, was about $10 per million gallons. During the