Glimpses of old Glasgow

Part I. Historical

City Sewage Purification Works

IS it possible to bring back the river Clyde to somewhat of its primitive purity, so that from Dalmarnock Bridge to Dumbarton the angler may ply his rod as successfully as of yore? It looks as though this may yet be accomplished; if the new sewage purification works at Dalmarnock fulfil expectations, and are generally adopted in the upper reaches of the river we may yet have a pure, transparent stream, fit for the return of the finny tribe.

During the last forty years many schemes have been propounded for dealing with and attempting to purify the city sewage, but either from inherent defects, or the schemes being too costly, few have been adopted or have survived. The Rivers Pollution Act of 1876, gave an impetus to the subject of river purification. Since then, it may be remarked, upwards of 500 patents have been taken out for dealing with the residual products of sewage, so as to make a profit out of them, but not one has been a commercial success.

The problem of the efficient and economical disposal of our city sewage has for nearly fifty years exercised the anxious thought of our civic rulers. No other local subject has received so much scientific attention. As early as 1853, Mr. Bateman was asked to report on the best method of dealing with the sewage: he recommended engineering works in preference to chemical treatment, but nothing was done. In 1863, Mr. Bateman and Mr. Bazalgette reported on the same subject. Again, in 1867, a remit was made to Messrs. J. F. Bateman and J. W. Bazalgette, and Prof. Anderson; their recommendation was to convey the whole sewage by a huge tunnel to the sandy soil between Saltcoats and Ayr, at an estimated cost of £1,254,000.

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In December, 1874, a Royal Commission was given to Sir John Hawkshaw, to enquire and report regarding the best means for remedying the polluted condition of the whole area of the valley of the Clyde, and the watershed of all its tributaries: he reported in 1876, and recommended intercepting sewers to be constructed, with an outfall by means of a huge sewer, to carry the whole sewage of the city, as well as the villages and burghs around Glasgow, and discharge it into the deep water of the Clyde near Farland Head. The estimated cost was to be over £2,500,000.

In 1877, a Committee of the Town Council investigated the question anew, and reported on it; and in 1878-79, Mr. Bateman again reported, while in 1880, a further examination and report was made by a Committee of the Council. Deputations visited various towns in England, and reported favourably of Mr. G. V. Alsing's system, which combines precipitation and filtration. This system was adopted by the Town Council as being economical, and most likely to meet the necessities of the whole city, and. they appointed Mr. Alsing, engineer, for constructing the works dealing with the eastern section of the city.

Circumstances became favourable for proceeding with the erection of buildings, and practically testing the scheme. The formation of the Central Underground Railway rendered imperative the reconstruction of the drains and sewers in the eastern district of the city, the cost of which (about £200,000) had to be borne by the Caledonian. Railway Company. The Corporation were thus enabled to secure the readjustment of the deviated drains and sewers on lines and levels necessary for their plan for the purification of the sewage. Thirty acres of land were acquired near Swanston Street, Bridgeton, including the site of the old Dalmarnock Waterworks, on which the various works and buildings are now erected, the whole costing £100,000.

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These were completed and inaugurated on 2nd May, 1894, by the presence of the Magistrates and Town Council, and representatives from neighbouring burghs, and other well-known citizens. In the system adopted, the sewage is dealt with as follows:-

The crude sewage is intercepted by sluices, and diverted through three four-feet channels into a deep well inside the main building. The sewage here filters through rotary travelling intercepting screens, which catch up by a series of catch-plates any floating bodies, such as pieces of wood, drowned dogs, etc.; these are collected and thrown into the destructive furnaces. The sewage then runs into what are called catch pits, in which the sand and heavier ingredients subside to the bottom by their own gravity. Worm screws drive this matter along V-shaped conduits to a cavity, called the "sump," from which it is raised by buckets as in a dredger and delivered through shoots into railway waggons conveniently arranged. The sewage that remains in the catch pits, now freed from the heavier and suspended matters, passes through an overflow into a well 31 feet deep, from which it is lifted by means of centrifugal steam pumps into the mixing chamber where sulphate of alumina and milk of lime are added. By gravitation the liquid then flows into the precipitation tanks, of which there are 24, each 40 by 50ft. by 6ft. 6in. deep, and of a capacity of 81,000 gallons. In these reservoirs the sewage is kept in total quiescence until the process of precipitation is completed. The work of separation having been effected, the fluid on the top is emitted through self-floating automatic valves, the invention of Mr. Alsing, into the aerating tanks, each 40 by 44 feet, and corresponding in number with the precipitation chambers. These tanks are constructed with small steps to facilitate the process of aerating the effluent, which next passes through sixty capacious filters containing coke and other graduated filtering materials, and occupying an area of about three acres. The effluent again passes through sand filters, where the last traces of impurity are removed, and is discharged into the river in a pure state from a sanitary point of view, being by the process perfectly clarified. Meanwhile, the precipitate or sludge remaining after the withdrawal of the liquid, flows by its own gravity through underground channels into the sludge-tank, from which it is raised by means of chain pumps into an "agitator," where it is mixed with a little additional lime. The sludge thus chemically treated gravitates into four receptacles which are under air pressure; by this means it is forced into powerful presses on the upper flat of the building, where it is pressed into the form of cakes. The catch pits, sludge-tanks, pumping machinery, and presses are concentrated in one building, in which are also the engines, boilers, workshops, and store-rooms. A siding of the Caledonian Railway runs into the works; and to facilitate transit, the sludge presses are so constructed that the cakes fall directly from them into the railway waggons, and thus save any handling or labour.

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It is expected that the sludge formed into "chemical cakes," which contain a certain amount of ammonia, will form a valuable manurial agent, and will be sold to farmers and others for "top dressing."

The works are at present arranged to deal with the sewage, on the north of the Clyde east from Mitchell Street, of about ten million gallons per day, or equal to one-fifth of the total sewage of the city. On that area there is a population larger than that of the city of Edinburgh - in all, 265,000 people. In view of probable extensions, the plans and space have been so disposed that double the quantity of sewage can readily be treated when required.

The arrangement of the buildings, precipitation tanks, catch pits, sludge chambers, and filtration beds, are the most perfect of their kind in the kingdom. The chemical treatment and various processes show the highest degree of ingenuity and skill. To witness the sewage entering - a seething stream of grey-coloured liquid - and then see it emerge into the river perfectly clear and innocuous, truly makes an uninitiated onlooker marvel.

For the many years that this important subject has been before the Health Committee of the Corporation, every one of the Conveners has given intelligent and thoughtful consideration thereto.

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It also engaged the attention of many of our Councillors; among them the late Councillor W. R. W. Smith, ex-Lord Provost Ure, and Councillor Crawford. And it is worthy of recording that, in carrying out these extensive works at Dalmarnock, ex-Councillor Mason (while Convener of the Sewage Committee), gave the benefit of his wide experience and great practical knowledge. The completion of the whole reflects the highest credit on the Sewage Committee.