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IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
Department held that inasmuch as the quantity of water re- 
quired by the passengers is small the railroad companies could 
afford to furnish a better water than a city water plant. As a 
matter of fact the Treasury Department Standard is rapidly 
becoming the working standard of the waterworks operators 
in this country. In effect it requires a maximum count of 100 
bacteria per cc. on agar at 37° and not more than one positive 
tube out of five ten cc. plantings into lactose broth for the colon 
group. Acid colonies on Litmus lactose agar of typical colonies 
on Endo’s medium are given as authorized confirmatory tests 
for the colon bacillus. Of the ninety plants listed in the chart 
fourteen already claim this standard for the water they supply. 
Many of the others use a standard differing only slightly. 
The percentage standard of plant efficiency is not satisfactory 
because as the raw water becomes higher in bacteria the number 
of bacteria in a water which is up to the standard, may become 
very large. For instance 99 per cent efficiency at one time dur- 
ing the past winter (1916-17) when the raw water of our local 
plant showed 880,000 bacteria per cc. would have allowed a 
bacterial count of 8,800. Wohlman has recently proposed a 
standard based upon the ratio of the logarithms of the numbers 
of bacteria in the raw and treated water. It requires higher 
bacterial-removal efficiency. 
There are very few plants in my list which are content to 
wmrk merely with a view to the removal of the turbidity and 
color. It is very necessary, especially in connection with the 
chlorination treatment, to have as much as possible of the color 
and turbidity removed, but that is not the aim of the water 
treatment. The waterworks superintendent who “ didn’t be- 
lieves in these here bacteria, anyway” is almost extinct. 
A glance at the table will show you that in spite of the ex- 
cellent work which has been done in the preparation of our 
Standard Methods of Water Analysis, the bacteriological pro- 
cedure of the water plants is far from uniform. This is due 
in part to the changes recommended in the 2d Edition of the 
Standard Methods. It was recommended that the bacterial 
counts be made on agar at 37°, dropping the gelatine count at 
20°. In view of the great amount of work which had already 
been done on gelatine, this was objected to quite strenuously 
and gelatine has been officially reinstated in the 3d Edition 
which has just come from the press. The Confirmatory tests 
