Sewage and Sewage Effluents. 



197 



effluents smaller amounts of chlorine proved efficient. 

 The primary effluent required 20 parts per million, the 

 secondary effluent 10.6 parts per million and the tertiary 

 effluent 2.5 parts per million to reduce the number of 

 B. coli so that this organism could not be isolated in 5 c.c. 

 In this country Phelps and Carpenter (1906) demon- 

 strated the practical usefulness of bleaching powder 

 disinfection, at the Sewage Experiment Station of the 

 Massachusetts Institute of Technology. As indicated in 

 the table below, smaller amounts of chlorine than were 

 used by Rideal will give good results with more dilute 

 American sewages. 



BACTERIA IN TRICKLING FILTER EFFLUENT BEFORE 

 AND AFTER TREATMENT WITH CHLORIDE OF LIME 

 (5 PARTS PER MILLION AVAILABLE CHLORINE). 

 (PHELPS AND CARPENTER, 1906.) 



Average removal 99.96 per cent. 99-993 per cent. 



