Report to the corporation of Belfast on a bacterial investigation of the experimental contact beds for the treatment of sewage / [J. Lorrain Smith].

  • Smith, J. Lorrain (James Lorrain), 1862-1931.
Date:
1901
Catalogue details

Licence: In copyright

Credit: Report to the corporation of Belfast on a bacterial investigation of the experimental contact beds for the treatment of sewage / [J. Lorrain Smith]. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    In Professor Boyce’s Report on the action of the contact beds at West Derby, he gives the following average :— The reduction in the numbers of bacteria in Dr. Houston’s table is still more striking than that observed in the table I have given. The lowest figure which he obtained was a fall from 7,000,000 .to 400,000, a decrease of 94 per cent, of the total number. The largest reduction in mj table is that of March 22nd, when the numbers fell from 112 millions to 19'6 millions per c.c., implying a loss of over 80 per cent. In Professor Boyce’s observations the fall on the average is 44 per cent. The total number of microbes in the Liverpool sewage is approximately 1 million, n the London sewage 7 millions, and in the Belfast sewage, after sedi- mentation, 43 millions. The average fall in Houston’s series implies a loss of about 80 per cent, of the total bacteria, and at the period corresponding to these observations the percentage purification as estimated by the oxygen absorbed test was on the average 85 per cent. (Clowes). In my series in Table I. the fall in bacteria implies a loss of nearly 60 per cent., and for this period the percentage purification according to the oxygen absorbed test was 69 per cent. (Letts). There is not yet, however, a sufficient number of results published to show decisively in how far the reduction in bacteria may be regarded as a measure of the efficiency in purification by the contact beds. The results I have given show how the brick beds now examined compare with the coke beds examined for the London County Council, and the coke beds of the Liverpool Corporation, in regard to this point. It is clear that to arrive at a true conception of the process which brings about purification, it is necessary to consider how far the decrease of bacteria, observed as a result of the contact, is due to the multiplication of bacteria themselves, and their demands for food supply. This might conceivably lead to an exhaustion of the pabulum, and subsequent decrease Number of Bacteria in Crude Sewage. (Average of 29 Analyses.) 1,090,726 Number of Bacteria in the Effluent from the Final Contact Beds. (Average of 36 Analyses.) 614,158