IOWA ACADEMY OF SCIENCES. 253 



Average number of bacteria per c.c. in manhole and tank. 



August, 1899 



September. 1899. 

 October, 1899 ... 

 November. 1899. 

 December. 1899. 

 January. 1900 . . . , 

 February, 1900.. 



March, 1900 



April, 1900 



May, 1900 



June, 190:- 



July, 1900 



August, 1900 



September. 1900 



2.392,600 



8,8i5,oco 



6,064,800 



4,537.333 



816,333 



848.000 



345,533 



132, 125 

 2, 121,000 

 1, 021, coo 

 1,318,100 

 3,908,700 



403, 118 

 1,181.533 



1,358-300 



3,24s, 000 



4,941,000 



3,014,000 



848,000 



726. 000 



233, 8to 

 112. 500 



1.392,800 

 783, 300 



1,391,300 



4,578,333 

 215.700 



383.733 



BACTERIOLOGICAL ANALYSIS OF THE COLLEGE SEWAGE FROM 

 SEPT. 1, 1899, TO SEPT. 1, 1900. 



The college sewage system is a combination of several 

 systems combined into one. It combines the system of 

 the septic tank with that of intermittent filtration. For a 

 very excellent and (^20) detailed description, see the article 

 in Centralblatt No. 15, on the Iowa State College Sewage 

 D'sposal Plant, by Drs. Pammel, Weems, and Professor 

 Marston, and Contribution No. I of the Iowa State Col- 

 lege (19). 



Bacteriological analysis have been made of the effluent 

 each day, while once each week samples have been 

 taken from the manhole and the tank, as well as the efflu- 

 ent, of which both bacterological and chemical analyses 

 have been made. The chemical analyses have been under 

 the direction of Dr. Weems, who has from time to time 

 published some very interesting results, but as it is my 

 intention to deal with the bacteriological side only, no 

 chemical results will be given, only as they may serve to 

 elucidate some point in connection with the bacteriological 

 analyses. 



In making the cultures, petri dishes of a standard size 

 have been used. The dilution method has been employed 

 with the manhole and tank samples, it having been found 

 on trial that without dilution it was practically impossible 



