London Labour and the London Poor, volume 2
Of the Quantity of Metropolitan Sewage.
HAVING estimated the gross quantity of wet houserefuse produced throughout London in the course of the year, and explained the modes of removing it from the immediate vicinity of the house, I will now proceed to set forth the of wet house-refuse matter which it has been is removed with the contents of London sewers.
An experiment was made on the average discharge of sewage from the outlets of Churchlane and , , Ranelagh, King's Scholar's-pond, Grosvenor-wharf, Horseferry-road, , , , Durham-yard, , and (the last-mentioned places running from the Strand). The experiments were made "under ordinary and extraordinary circumstances," in the months of May, June, and , but the system is still the same, so that the result in the investigation as to the sewage of the year may be taken as a near criterion of the present, as regards the localities specified and the general quantity.
The surface drained into the outlets before enumerated covers, in its total area, about acres, of which nearly may be classed as urban. The observations, moreover, were made generally during fine weather.
I cannot do better by way of showing the reader the minuteness with which these observations were made, than by quoting the following results, being those of the fullest and smallest discharges of issues into the river. I must premise that these experiments were made on occasions, from to inclusive, and made at different times, but generally about hours after high water. In the sewer, from which was the largest issue, the width of the sewer at the outlet was feet. In the sewer (the smallest discharge, as given in the table) the width of the sewer was feet. The width, however, does not affect the question, as there was a greater issue from the sewer of feet, than from the sewer of feet in width.
Here we find that the mean discharge per was, from the sewer, . cubic feet per hours, and from the sewer, cubic feet per hours.
The discharge from the principal outlets in the district "being the mean of observations taken during the summer," was cubic feet in hours; the number of acres drained was .
The sewage, from the discharge of which this calculation was derived—and the dryness of the weather must not be lost sight of—may be fairly assumed as derived (in a dry season) almost entirely from artificial sources or house drainage, as there was no rain-fall, or but little. "," the Report states, " If, however, the average be taken of the outlets, viz., from to Grosvenor-wharf inclusive, which drain a surface wholly urban, the result is cubic feet per acre in the hours. This excess may be attributed to the number of manufactories, and the densely-populated nature of the locality drained; but, as indicative of the general amount of sewage due to ordinary urban districts, the former ought perhaps to be considered the fairer average."
It is then assumed—I may say officially—that the average discharge of the urban and suburban sewage from the several districts included within an area of square miles, is equal to cubic feet per acre.
Or a quantity equivalent to a surface of more than acres in extent, and feet in depth.
This mass of sewage, it must be borne in mind, is but the product of the sewage of the more populous part of the districts included within the jurisdiction of the commissions of sewers.
The foregoing observations, calculations, and deductions have supplied the basis of many scientific and commercial speculations, but it must be remembered that they were taken between and years ago. The observations were made, moreover, during fine summer weather, generally, while the greatest discharge is during rainy weather. There has been, also, an increase of sewers in the metropolis, because an increase of streets and inhabited houses. The approximate proportion of the increase of sewers (and there is no precise account of it) is pretty nearly that of the streets, lineally. Another matter has too, of late years, added to the amount of sewage— the abolition of cesspoolage in a considerable degreee, owing to the late Building and Sanitary Acts, so that fœcal and culinary matters, which were drained into the cesspool (to be removed by the nightmen), are now drained into the sewer. Altogether, I am assured, on good authority, the daily discharge of the sewers extending over square miles of the metropolis may be now put at cubic feet, instead of rather more than and a half millions. And this gives, as
So that the cubic feet of sewage annually removed from square miles of the metropolis refer to only -half of the entire area of the metropolis; but it refers, at the same time, to that part of London which is the most crowded with houses, and since, in the suburbs, the buildings average about to the acre, and, in the densest parts of London, about , it is but fair to assume that the refuse would be, at least, in the same proportion, and this is very nearly the fact; for if we suppose the miles of the suburban districts to yield times less sewage than the miles of the urban districts, we shall have cubic feet to add to the cubic feet before given, or for the sewage of the entire metropolis.
It does not appear that the sewage has ever been weighed so as to give any definite result, but calculating from the weight of water (a gallon, or lbs. of water, comprising . cubic inches, and ton of liquid comprising cubic feet) the total, from the returns of the investigation in , would be
In , Mr. Banfield, at time a Commissioner of Sewers, put the yearly quantity of sewage discharged into the Thames at tons; but this is widely at variance with the returns as to quantity.