20 4 AIDS TO BACTERIOLOGY 



presence of decomposable organic matter, and such an 

 effluent might give rise to a nuisance). 



2. Place a goldfish or two in a bowl of the effluent. 

 The fish will live in, and be unaffected by, a satisfactory 

 effluent. In the eyes of the law a fish is an animal, and 

 this test may only be performed by a licensee under the 

 Vivisection Act. 



An effluent of sewage treated by land filtration should 

 show a considerable reduction in the total number of 

 bacteria, and in the number of B. coli, compared with the 

 original sewage ; but an effluent from a bacterial system 

 of treatment may contain as many bacteria as, or actually 

 more bacteria than, the original sewage. 



Apart from the nitrifying organisms, very little of 

 practical value is known of the bacteria concerned in 

 sewage treatment, and their ability. Especially is this 

 true of those acting in septic tanks and contact beds. 

 With further enlightenment there will be fewer failures. 



Houston, in his capacity of bateriologist to the Royal 

 Commission on Sewage Disposal, while recommending as 

 ' counsel of perfection ' the ' complete sterilisation of 

 sewage effluents ' in the case of drinking-water streams, 

 suggested as a ' practicable standard ' ' partial sterilisation 

 (absence of B. coli from 1 c.c. of the effluent).' Houston 

 also suggested ' provisional ' standards to apply to sewage 

 effluents for non-drinking-water streams, as follows : 



Total number ^ Gelatin at 20 C., less than 100,000 per c.c. 



of bacteria / Agar at 37 C., less than 10,000 per c.c. 

 JB. coli, less than 1,000 per c.c. 

 B. ertteritidissporogenc-stcst . . . . . . \Negative results 



' Gas ' test (twenty-four hours at 20 C. ) . . J with 0*1 c.c. 



Indol test (five days at 37 C. ) ] 



Neutral red broth test (two days at 37 C. ) . . (Negative results 

 Bile-silt broth test (two days at 37 C.) . . j with 0-001 c.c. 



Litmus milk (modified) test ( two days at 37 C. ) J 



These are primary standards; Houston's secondary 

 standards are arrived at by rendering the primary stan- 

 dards ten times more lenient. He does not suggest these 

 standards in an administrative sense; they are merely 

 arbitrary, and designed solely for comparative purposes. 



Prescott and Winslow think even the above primary 

 standard is far too lenient, and argue that ' either organic 



