SOIL AND SEWAGE 73 



The fate of pathogenic organisms in sewage. 



The organisms of chief interest are B. typhosns and Sp. cholerae 

 and a number of investigations have been undertaken to study 

 their viability in sewage. 



Klein 1 studied the viability of both organisms in sterile 

 sewage kept at room temperatures. The typhoid bacillus after 

 some preliminary multiplication rapidly diminished in numbers, 

 some bacilli being alive, however, after eight weeks. The 

 cholera vibrio died out at periods varying from the eighth 

 to the twenty-fifth day. 



Horrocks found typhoid bacilli alive after 60 days in sterile 

 sewage kept at 16 22 C. 



When the sewage is not sterilized the life of the typhoid 

 bacillus is very much shorter, and MacConkey could only recover 

 the bacilli after thirteen days in one series and not after six 

 days in another, while Russell and Fuller found that when this 

 bacillus was exposed directly to the action of sewage bacteria 

 its longevity was greatly diminished, three to five days being 

 the longest time for which the organism could be recovered. 

 The difficulties of isolating typhoid bacilli from crude unsterilized 

 sewage are considerable, even with recent greatly improved 

 technique and bacilli actually present may easily be overlooked 

 and not isolated. After making due allowance for this it is 

 clear that the typhoid bacillus has a hard struggle to live in 

 raw sewage and dies out after a fairly short period. 



The bacteriological examination of seivage and sewage effluents. 



At the present day this is not often required for practical 

 administrative work. The bacteriological examination of sewage 

 effluents is occasionally valuable when the question of pollution 

 of a stream subsequently used for drinking purposes or the 

 possibility of shellfish pollution is under consideration. The 

 general methods are quite similar to those described under 

 water. The chief determinations which will be required are 

 the number of B. coli group organisms, the number of spores 



1 Local Govt. Board Medical Officer's Report, 1894-5, p. 407. 



