Davyhulme Sewage Works is the main waste water treatment works for the city of Manchester, England, and one of the largest in Europe. It was opened in 1894, and has pioneered the improvement of treatment processes.
With the growth of population in the late nineteenth century, and the proliferation of water closets, the rivers around Manchester were becoming grossly polluted, and the City of Manchester decided to build two deep level sewers to intercept existing sewers. When the first one reached Davyhulme, further extension was blocked by the Manchester Ship Canal, and so a treatment works was built there. The works used precipitation tanks, and a gauge tramway was built, to facilitate the movement of materials around the site. The first steam locomotive was acquired in 1897, and a further fourteen steam and two diesel locomotives operated on the system before its closure in 1958.
Treated sludge was loaded into ships and discharged into the Mersey estuary from 1898. Over the next hundred years, seven ships were used to transport the sludge, including one borrowed from Glasgow after another hit a mine and sank. At first, ships used the ship canal to transport sludge from the works, but later a pipeline was built to Liverpool, and the ships made a much shorter journey.
An early feature was a laboratory, where trials of various types of filter were carried out, and incoming effluent was analysed. Attempts to improve the treatment process proved successful in 1914, when two chemists, Ardern and Lockett, discovered the Activated Sludge Process, which was soon in use worldwide. A second deep level sewer, started in 1911, eventually reached the works in 1928, and to cope with the increased flows, half of the sewage was fed into a new Activated Sludge plant. Three separate operating systems were installed, so that comparisons on their efficiency could be made. A second Activated Sludge plant was built between 1955 and 1966, and the control system on the first was upgraded between 1970 and 1973.
In 1974, the Rivers Committee, which had managed the site since its inception, ceased to be, when water and sewage treatment became the responsibility of the newly formed North West Water Authority. The organisation was subsequently privatised, and became part of United Utilities in 1995. In order to meet demands for better water quality, a pilot Biostyr plant was built in 1992, and a much larger one was completed in 1998. Innovation continued, with the commissioning of the world's largest thermal hydrolysis plant in 2013, using a new process to break down sludge, which generates methane as a by-product, enabling the site to be self-sufficient for gas and electricity. An upgrade to the Activated Sludge plant began in 2014, and is expected to be completed in 2018.
History The city of Manchester experienced rapid growth during the eighteenth and nineteenth centuries, and the existing administrative bodies were not equipped to deal with such expansion. The area was managed by the court leet, which was responsible for all administration and judicial functions. The Manchester and Salford Police Act 1792 led to the establishment of a day and night watch. The night watch was mainly a guard against fire. At that time the word police was used to mean administration, rather than the handling of law and order. A group of police commissioners were established to manage cleansing and water supply. In 1797, this was formalised, by creating separate commissioners for Salford and for Manchester. The Municipal Corporations Act 1835 (5 & 6 Will. 4. c. 76) paved the way for borough councils to be established, with ratepayers electing their members. A petition to create such a council for Manchester was organised by two industrialists, Richard Cobden and Thomas Potter, but this was resisted by both the Court Leet and the Police Commissioners, who stood to lose some of their powers.
Despite the opposition, Manchester's first proper council was elected in 1838, although its area of jurisdiction was quite small, and there were independent areas within the city, such as Chorlton-on-Medlock, which had their own committees to manage local functions. The new council began the task of constructing a brick-built sewerage network within the city. In 1847, John Francis the Borough Surveyor suggested using egg-shaped clay pipes instead, and using these proved to be much quicker. However, the period also saw the introduction of the water closet, the forerunner of the modern flush toilet, and this resulted in much larger volumes of effluent entering the system. The council tried to limit their use to public buildings and the homes of the rich, as the waste was discharged in an untreated state into the rivers, which were becoming grossly polluted. This policy was not successful, and by the early 1890s, around 90 per cent of the housing in Manchester had water closets.
In an attempt to deal with river pollution, the council created the River Medlock Improvement Committee on 1 April 1863. Such problems were not limited to Manchester, and two pieces of legislation were introduced nationally to address the issues. The first was the Public Health Act 1875 (38 & 39 Vict. c. 55), and the second was the Rivers Pollution Prevention Act 1876 (39 & 40 Vict. c. 75). In the following year, the River Medlock Improvement Committee became the Rivers Committee, and proposed a combined drainage scheme for the city and 15 other authorities with responsibility for the areas around the city. All pulled out of the scheme because of the likely cost, but in 1888, the City of Manchester decided to proceed on its own. Two deep level sewers were authorised, which intercepted the existing sewers before they discharged into the rivers. When the first sewer reached Davyhulme, further progress was impeded by the Manchester Ship Canal, then being built, and the site became the location of the sewage treatment works. It had the advantage that treated water could be discharged into the ship canal to maintain water levels.
Construction Manchester Corporation bought of land at Davyhulme from the landowner, Sir Humphrey Francis de Trafford. They paid £13,333 on 14 December 1889, and in 1891, they paid £6,981 for another . All of the land was close to the ship canal, on a large loop which had formerly been the course of the River Irwell. The construction work was managed by the City Surveyor, and used direct labour, with a contract for the machinery being awarded to Manlove, Alliott & Co. Ltd. The sewage was to be treated in eleven precipitation tanks, arranged as a bank of six tanks and a bank of five, separated by a wide roadway. The complete structure measured . The main building complex included a power plant with two Lancashire steam boilers, which produced hydraulic power, compressed air and electricity. After treatment, sludge was removed from the tanks using air-powered ejectors, and was compressed using hydraulic sludge presses. There was also an office building, and a range of facilities for the workers.
An order was placed with Barningham and Co. in August 1893 for rails, sleepers and wagons for a gauge railway system, which would be used to deliver lime to the lime store and carry the compressed sludge to the old river bed for disposal. Barningham had previously supplied equipment to the Corporation for a light railway on Carrington Moss for the Cleansing Department. Track laying was carried out by the Paving Sub Committee and Highways Department. The Corporation also paid the Ship Canal company to construct Davyhulme Wharf, which would enable coal and chemicals to be delivered to the site. This required the railway to be extended and a road to be built to serve the wharf, and this work was not completed until October 1894, although the works had begun to treat sewage in January 1894.
There was a dispute with Manlove Alliot in May 1894 over the number of railway wagons to be supplied. The Corporation thought they had ordered 20 tipping wagons for the transport of the sludge cakes, but only four were supplied by Manlove Alliot, and eight extra wagons, which they had used during construction, were also being used for this purpose. The Corporation eventually ordered eight more. The wagons were moved using both manual labour and horses.
The incoming sewage ran through a catch pit, which removed large debris, and into the precipitation tanks. Liquid was removed from the top, and sludge from the bottom. The sludge was mixed with lime in three sludge pits, and then pressed into cakes. Initially, the works produced around 738 tons of pressed cake per week. Some 50 tons a day were sold as fertiliser, with the rest being carried by the railway to the old river bed for dumping. The liquid flowed along an open channel to of land, which was used for land filtration, before the treated effluent was discharged into the Ship Canal. The process was inadequate for the volumes entering the works, and the canal became increasingly polluted. Consideration was given to discharging the effluent into the tidal River Mersey, by construction of a culvert to Randall's sluices, near Warrington, or treating it by the use of septic tanks and double-contact bacteria beds. The second option was chosen, as the first would have reduced the flow in the Ship Canal.
Expansion
A small laboratory was built near the power house in mid-1896. Trials were begun with several types of filter, but none were particularly effective, although they were better than land filtration. The old river bed soon became full of sludge, and the Corporation purchased a boat, so that the sludge could be dumped at sea. The Joseph Thompson was built in Barrow in Furness at a cost of £24,837, and made its first voyage in December 1897. Loading of the sludge took around 45 minutes, the journey down the Ship Canal took six and a half hours, and the sludge was discharged near the Mersey Bar Light in five minutes.
Conversion of the treatment process from chemical precipitation to septic tanks and sedimentation tanks began in December 1900, and was completed on 4 August 1904. The tanks covered an area of . Air was excluded from them by the formation of a scum on the surface, and anaerobic microbes broke down the sewage. The 'first contact bacteria beds' covered , with a similar area used for 'second contact bacteria beds'. There were also which were used for 'storm water filters'. The bacteria beds were filled with a media of coke or granite chippings, around which microbes formed a slimy film. The oxygen-loving microbes digested the organic matter in the sewage as it passed through the media.
The railway system was heavily used in the construction of the beds. A steam locomotive had been purchased in 1897, and another four were bought as the work expanded. Once the filter beds had been completed, they needed to be emptied for the media to be washed, regraded and topped up every few years, and this became the primary function of the railway for the next 32 years. It was also used to remove rubbish from the screening chambers, moving 861 wagon loads between October 1901 and March 1902. By July 1905, the primary bacteria beds had been completed, and an extra of land had been bought at Flixton and Carrington, which was to be used for secondary bacteria beds and land filtration. By 1905, the works owned a total of , which included the route for a conduit from Davyhulme to Flixton.