CHAPTER XVIII
SAVING THE SEWAGE SLUDGE
In matters pertaining to sanitation and the movement of sewage Great Britain undoubtedly leads the world. There our conquest ends. From that point onwards we can only point to lamentable inefficiency. For instance, the lay-out of the main drainage system of London, undoubtedly the finest illustration of such engineering in the world, has involved a capital expenditure of £12,514,606—$62,573,030. By the provision of enormous conduits and feeders the excrementitious matter from residences, offices, workshops, and factories of the metropolis is borne for miles to central stations. In this manner those natural and trade wastes, construed as being inimical to health, are removed swiftly and hygienically, and we compliment ourselves upon our prowess, which certainly is justifiable so far as it goes.
But when we come to the treatment of this material we fail miserably. At the central station the solid matter, in reality a mud or sludge, is separated from the free liquid. The disposal of the latter offers little or no difficulty. It can be rendered innocuous, and is therefore permitted to resume its part in the scheme of Nature. But the sludge: that is a different proposition. A few figures concerning the situation in regard to London may prove illuminating. Certainly they will serve to demonstrate the magnitude of the volume of this waste. During the year over 100,000,000,000 million gallons of sewage are received from approximately 5,350,000 people occupying 95,000 acres. Each million gallons of sewage yields about 25 tons of sludge. The total quantity of solid matter is approximately 200,000 tons. It costs about 30s.—$7.50—to treat and dispose of each million gallons of raw sewage.
The total yield of sludge exceeds 2,600,000 tons a year. It is an incubus having no ostensible commercial value, so is transferred to vessels to be carried out to sea where it is thrown overboard. Seeing that it costs about £17 13s.—$88—to run each vessel out and back again, and that some 111,000 journeys are made during the year, dumping the sludge costs the ratepayers of London nearly £2,000,000—$10,000,000—a year. The crime incidental to London is repeated throughout the country, and in this way, as Sir William Crookes pointed out, the nation is deliberately discarding 16,000,000 tons of valuable nitrogenous material which, were it subject to proper treatment, might be reclaimed to participate in the nourishment of our broad acres. Estimating the value of this potential fertilizing agent at the modest figure of one ¹⁄₂d.—1 cent—per pound we are, of malice aforethought, throwing away a round £35,000,000—$175,000,000—per annum. But this is not the most disturbing feature. For the most part the sludge, and in the case of seaside towns the crude sewage, is discharged upon potential valuable fishing grounds, to the destruction or infection of the fish, especially shell-fish. Furthermore, one must not imagine because the objectionable and dangerous refuse is abandoned well out to sea its serious dangers are removed. Tides and currents play strange tricks, the result being that much of this filth is thrown back upon the coasts, perhaps at a distant point, to wreak possible havoc.
Civilization breeds a strange fastidiousness. The idea of reclaiming sewage for exploitation is repulsive to the average individual, although he does not turn a hair at the use of the comparative material derived from the animal kingdom for the nourishment of the soil, and the feeding of produce cultivated essentially for the table. The argument often raised against any exploitation of excrement is that it has become associated with many other deleterious substances, which have been thrown or allowed to run down the drain, as the readiest avenue for their disposal. But the very circumstance that such waste has become compounded with other residues, many of which are worth reclamation, should be sufficient to induce us to regard sewage not as an incubus or danger, but as a mine worthy of development to its fullest extent.
Fortunately, the objection to the exploitation of sewage for its commercial contents is in process of being over-ruled by the growth of a more enlightened attitude towards the whole issue, although it is to be feared, in accordance with the precept that what the eye does not see the heart does not grieve, the more progressive policy is being sanctioned unconsciously. It is safe to assert that, but for the war, which retarded the hands of progress very pronouncedly, the new movement in regard to the handling of this material would have made a material advance. Even to-day the outlook is not hopeless, inasmuch as the accentuated need to make every use possible of waste products may result in the sewage exploitation problem being attacked with enhanced energy.
What can be done with sewage is revealed by the action of one or two towns which have taken their courage into their own hands, notably Bradford and Oldham. In these two instances the modern handling of sewage was assumed before the war, so that the experience gathered during the past six years may prove sufficiently convincing to permit the whole subject to be attacked more in consonance with contemporary thought, which views all wastes in one light—potential raw materials for other industries.
Changing conditions and the need to cope with this residue along more comprehensive lines, in accordance with the growth of the population and the quantity of material to be handled, were responsible for the change from the old method to the new in both instances. In the case of Bradford the Corporation found it necessary to establish new works about six miles distant from the centre of the city, and was faced with the necessity to expend £1,250,000—$6,250,000—in connection with the undertaking. In view of such a heavy capital committal perhaps it was only logical to consider the possibility of rendering the sewage more remunerative in the future than it had been in the past. Any revenue to be derived from exploitation in such a field must react to the advantage of the community affected, more especially when such action does not jeopardize the health of the citizens to the slightest degree.
Of course, the situation in so far as it concerns Bradford was somewhat unusual. The city is the hub of the wool-scouring trade of the country, and in treating the sewage much of the wealth allowed to slip down the drains from cleaning the wool is open to reclamation. The one great mistake, if such it may be called, of which Bradford has been guilty, in view of the volume of grease contained in the effluents, is ever to have permitted these wastes to pass into the drains and sewers. They should have been collected and treated as a separate entity. But, as this would have entailed combination of the interests concerned, an admittedly difficult undertaking under voluntary conditions, the city authorities decided to repair the sins of omission upon the part of its industrial citizens and to assume the recovery of the valuable materials which were being allowed to escape.
This manifestation of commendable enterprise and initiative owes its origin mainly to the activity of Mr. Joseph Garfield, A.M.I.C.E., the sewage engineer. Many years ago the idea of turning the sewage of the city to industrial account occurred to him, and he embarked upon a prolonged series of exhaustive experiments. These were sufficiently conclusive and sufficiently promising of profit as to persuade the adoption of the methods he advocated at the critical moment, which arrived when the provision of a new sewage station became imperative.