BACTERIA OCCURRING IN SEWAGE 85 



present in the crude sewage will not only survive, but may 

 possibly multiply, and so cause the effluent to be dangerous to 

 health. It is important, however, to remember that the 

 bacterial processes are not novel, but are identical with those 

 which obtain in Nature, so that effluents from sewage farms are 

 strictly comparable with filtrates obtained after either a "coarse 

 bed " or a tank treatment. 



It must be recollected that hitherto little attention has been 

 paid to the study of land effluents from this point of view, and 

 until sewage-farm drainage waters have been investigated in a 

 similar manner to those derived from continuous well-aerated 

 filters, no definite conclusion on this point can be formed. 



It seems to be accepted that the treatment of sewage on 

 land, though formerly urged to be more satisfactory from the 

 bacteriological point of view than its treatment in bacterial 

 beds, would not seem to by any means entirely remove the 

 danger arising from the discharge of effluents into potable 

 rivers. Experiments on the subcutaneous inoculation with 

 crude sewage and with effluents for the Royal Commission 

 show that " the pathogenic qualities of most effluents point to 

 the improbability of sewage being so modified by treatment on 

 land or by artificial processes as to be other than a liquid 

 potentially dangerous to human beings. The absence of any 

 pathogenic result when sewage is rendered germ-free by filtra- 

 tion, on the other hand, tends to show that the chemical 

 products of the vital activity of the bacteria in sewage are not 

 of a markedly poisonous nature." 



Although with any new scheme it is difficult to obtain direct 

 evidence as to its ultimate effect upon a river water which is 

 subsequently to be used as a drinking supply, one must recollect 

 that under existing circumstances the removal of all kinds of 

 bacteria from the river water is attempted by those who desire 

 to use such water for drinking purposes, so that, even assuming 

 that bacterial systems tend to increase the bacteria in the 

 river, they do not make any new departure necessitating a 

 reconsideration of our methods of water purification. Even if 

 an anaerobic treatment alone resulted in an effluent which 

 possessed toxic properties disastrous to a small river, it must 

 be recollected that no process is at present suggested which 

 does not involve a full and efficient aerating filtration as a final 

 method of purification, and it is the pathogenicity of such 

 filtrates upon which information is wanted. Satisfactory 



