350 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The Effect of the Septic Method of Treating 

 Crude Sewage. 



A further question remains to be considered in 

 relation to the contamination of the Morecambe mussel 

 beds, viz., the extent to which the biological or septic 

 method of purification reduces the numbers of pathogenic 

 bacteria which may possibly be present in the crude 

 sewage. It will be admitted that the fact that most of the 

 Morecambe crude sewage passes through septic tanks 

 before reaching the sea must have its influence on the 

 interpretation of the bacteriological results. The question 

 of the harmful effects of contamination of the mussels by 

 the eflluent from the main sewer outfall in fact turns to 

 some extent on what really happens in the septic tanks. 

 Does the putrefactive process taking place there lead to 

 the elimination of pathogenic bacteria ? There are com- 

 paratively few observations on this subject, and I may 

 refer here to the principal results obtained. 



(1) Dr. A. C. Houston (Bacterial Treatment of Crude 

 Sewage : Third Report : London County Council, No. 

 501, 1900), inoculated small quantities of unsterilised 

 Crossness crude sewage with various pathogenic bacteria. 

 The cholera bacillus was employed in two experiments, 

 and a number of these vibrios greatly in excess of the 

 number of other micro-organisms present in the sewage 

 was added to 10 cc. of the crude liquid. In one experiment 

 the bacillus lost its vitality in less than a fortnight; and 

 in the other experiment was found in the sewage for 

 nearly four weeks. 



Tubes containing Crossness crude sewage were then 

 inoculated with pure cultures of Bacillus ffodigiosus. In 

 one experiment the bacillus was not recognised in the 

 liquid after sixteen days. Day by day the numbers of 



