I 9 



Elements of Water Bacteriology. 



BACTERIA IN SEWAGE AND SAND FILTER EFFLUENTS 



AT LAWRENCE. 



(CLARK, 1906.) 



Bacteria per c.c. 



The Septic Tank and Intermittent Sand Filter at Iowa 

 State College gave the following bacterial results in 1899 

 and 1900, the averages representing daily examinations 

 of the sand effluent and weekly examinations of crude 

 and septic sewage. 



BACTERIA IN SEWAGE SEPTIC EFFLUENT AND SAND 



FILTER EFFLUENT AT IOWA STATE COLLEGE. 



(WALKER, 1901.) 



Bacteria per c.c. 



Monthly Averages. 



