Sewage and Sewage Effluents. 



195 



however, the combination of septic tank and double 

 contact beds produces a bacterial purification of 80 to 

 90 per cent as measured by total numbers. The fol- 

 lowing table shows the results of four examinations 

 made in 1906. 



BACTERIA IN SEWAGE, SEPTIC EFFLUENT, AND CON- 

 TACT EFFLUENT AT PLAINFIELD, N. J. 

 (N.J. STATE SEWERAGE COMMISSION, 1907.) 



It is obvious that effluents of this character cannot be 

 considered satisfactory from the standpoint of bacterial 

 purification. As Houston concluded, after a careful 

 review of the subject, "The different kinds of bacteria 

 and their relative abundance appear to be very much the 

 same in the effluents as in the crude sewage. Thus, as 

 regards undesirable bacteria, the effluents frequently con- 

 tain nearly as many B. coli, proteus-like germs, spores of 

 B. enteritidis sporogenes and streptococci, as crude sew- 

 age. In no case, seemingly, has the reduction of these 

 objectionable bacteria been so marked as to be very 



