POSTSCRIPT.Since the foregoing remarks were written, I have been somewhat struck with the views expressed at one or two meetings by some of those who ought to have the full facts of the case at their fingers’ ends. There seems to be a considerable vagueness as to the sanitary results to be obtained by either the natural or one of the artificial methods of sewage treatment, and with a view to making this point quite clear I have prepared the following comparative statement (see next page), which, I trust, will show at a glance what one may expect from either system.This statement has not been prepared from experimental installations, where, as a rule, better results are obtained than in actual every-day work; but it refers to fairly large works dealing from day to day with the whole town’s sewage. It has further been assumed, that the plant both for the natural as well as for the artificial treatment is suitable, and managed carefully and on intelligent lines.As in all sewage treatments the sanitary results have first to be considered, I have only dealt with them in the statement, but even if I had extended it to economic considerations the result would have been practically the same.From a careful examination of the facts recorded in the statement it follows that with natural treatment we get five distinct advantageous results, against which we have to place only two on the side of the artificial treatments; but this means, that if we wish to bring up the results of these treatments to those obtained by the natural treatment, we have to supplement them by threefurther treatments for the extraction of pathogenic germs, and of the manurial elements, and for the reduction of the liquid.It is these facts which ought to be carefully considered by all those who wish to study the comparative advantages of these two systems, or who have to decide on a definite method to be employed in a particular case, and no step ought to be taken before every one of these five points has been very carefully weighed. Generally speaking, that system will be preferred which confers the greatest number of advantages.Statement.Results to be obtained from(A)Natural Treatment.(B)Artificial Treatment.1.Removal of suspended matters.1.Removal of suspended matters.2.Removal of from 75 to 95 per cent. of the dissolved organic matters.2.Removal of from 50 to 75 per cent. of the dissolved organic matters.3.Removal of pathogenic germs.3.Nil. Effluent bacterially practically raw sewage.4.Utilisation of large portion of manurial elements.4.Nil. All manurial elements escape into the rivers.5.Great reduction of quantity of liquid.5.No appreciable reduction of quantity of liquidLONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,GREAT WINDMILL STREET, W., AND DUKE STREET, STAMFORD STREET, S.E.
Since the foregoing remarks were written, I have been somewhat struck with the views expressed at one or two meetings by some of those who ought to have the full facts of the case at their fingers’ ends. There seems to be a considerable vagueness as to the sanitary results to be obtained by either the natural or one of the artificial methods of sewage treatment, and with a view to making this point quite clear I have prepared the following comparative statement (see next page), which, I trust, will show at a glance what one may expect from either system.
This statement has not been prepared from experimental installations, where, as a rule, better results are obtained than in actual every-day work; but it refers to fairly large works dealing from day to day with the whole town’s sewage. It has further been assumed, that the plant both for the natural as well as for the artificial treatment is suitable, and managed carefully and on intelligent lines.
As in all sewage treatments the sanitary results have first to be considered, I have only dealt with them in the statement, but even if I had extended it to economic considerations the result would have been practically the same.
From a careful examination of the facts recorded in the statement it follows that with natural treatment we get five distinct advantageous results, against which we have to place only two on the side of the artificial treatments; but this means, that if we wish to bring up the results of these treatments to those obtained by the natural treatment, we have to supplement them by threefurther treatments for the extraction of pathogenic germs, and of the manurial elements, and for the reduction of the liquid.
It is these facts which ought to be carefully considered by all those who wish to study the comparative advantages of these two systems, or who have to decide on a definite method to be employed in a particular case, and no step ought to be taken before every one of these five points has been very carefully weighed. Generally speaking, that system will be preferred which confers the greatest number of advantages.
LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,GREAT WINDMILL STREET, W., AND DUKE STREET, STAMFORD STREET, S.E.