ch, Assoc. M. Am. Soc. C. E., in
the Fifty-ninth Annual Report of the Bureau of Water for the year
ending September 30th, 1909. The Hudson River water used at Albany
is quite different in character from the Potomac River water used at
Washington, as it is less turbid and contains rather more organic
matter. The results obtained in these experiments showed that during
the summer the number of bacteria in the effluent from the
experimental sand filter used in connection with a preliminary
filter did not differ widely from the number found in the effluent
of the city filter where there was no other preliminary treatment
than sedimentation. In the winter, however, the numbers of bacteria
did not increase in the effluent from the experimental filter as
they did in the effluent from the city filter. This is shown by
Table 26, taken from the report mentioned.

Apparently, therefore, at Albany the benefits of the preliminary
filter, as far as bacterial efficiency is concerned, would be
confined to a short period of three or four months in each year.
Under such circumstances it may well be questioned whether the
advantages of preliminary filtration justify its cost.

~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 | 1,80