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IOWA ACADEMY OF SCIENCES. 
BACTERIOLOGICAL INVESTIGATION OF THE IOWA 
STATE COLLEGE SEWAGE. 
L. R. WALKER. 
INTRODUCTION. 
As an introduction to the consideration of the Iowa 
State College sewage, the kinds of sewage, the necessity of 
disposal, and several of the most important methods with 
their merits and disadvantages will be discussed. 
It has been my object in the following paper to bring 
together the data obtained from the bacteriological 
analysis of the college sewage, including daily samples 
from the effluent and weekly samples from the manhole 
and tank. Together with this data are given the daily 
temperatures of the air and of the sewage, at the time of 
taking samples; also, the soil temperatures, which were 
taken once a week. 
Besides this data it has seemed desirable to give the 
methods employed in the determination of the number of 
bacteria per cubic centimeter of the sewage. 
And lastly, a partial interpretation of the results 
obtained, has been attempted, special attention having 
been given to the percentage of gas producers present in 
the manhole, tank, and effluent, and to the fluctuations, 
during the different days and seasons, of the number of 
bacteria per cubic centimeter in the samples from the 
manhole, tank, and effluent. The determination of the 
species of bacteria present in the sewage has not been 
attempted, only incidentally. 
From a sanitary point of view there is no question of 
more vital importance than the proper disposal of sewage. 
The lack of such disposal brings a multitude of evils, 
