BACTERIOLOGY OF SEWAGE 



235 



The newer bacterial processes, contact beds, and 

 trickling filters naturally show a much less satisfactory 

 bacterial removal than sand filtration beds. In the 

 Columbus experiments, Johnson (1905) found from 

 i,cxx5,ooo to 2,000.000 bacteria in the effluents of con- 

 tact beds and from 750,000 to 1,900,000 in the effluent 

 from trickling filters. 



At the experiment station of La Madeleine, in Lille, 

 Calmette (1907), reports 5,000,000 bacteria per c.c. in 

 the crude sewage, 2,900,000 in the second contact 

 effluent and 800,000 in the effluent from the trickling 

 bed. Of 20,000 B. coli per c.c. applied to the filters, 

 the contact system delivered 4000 and the trickling 

 bed 2000 per c.c. The average results of examinations 

 made three times a week at the Sewage Experiment 

 Station of the Massachusetts Institute of Technology, 

 during two different periods, were as follows: 



BACTERIA IN SEWAGE, SEPTIC EFFLUENT AND 



TRICKLING EFFLUENT AT BOSTON 



(WtNSLOW AND Phelps, 1907) 



* Jackson bile test. 



