WATERWORKS LABORATORIES 
50: 
of the treatment. In small plants and those using water from 
unchanging sources laboratory control has, for the most part 
received little attention. Reliance has been placed upon the 
examinations made by the state laboratories at irregular inter- 
vals. For constant supplies this will probably continue to be 
sufficient. But plants of all sizes which treat the water of rivers 
and the other variable waters will have increasing difficulty in 
keeping the water supplied for their consumers satisfactory ac- 
cording to the accepted standards of efficiency. 
That these standards, are constantly becoming more rigid can 
easily be shown. To be sure, when bacterial standards came 
into vogue, the old arbitrary standard of 100 bacteria per ec. 
was almost universally used for all supplies, treated and un- 
treated. Then it became customary to set a certain per cent 
removal of bacteria when treating water. Then it was said 
that in addition, the colon bacillus should be constantly absent 
in one cc. of the treated water. A few years ago the Treasury 
Department issued a bacterial standard for water supplied to 
passengers in interstate traffic. The standard which was adopted 
— not by the unanimous consent of the committee appointed to 
draft the standard — is now regarded as a very rigid one. The 
