In November 1935, a decision was made to convert the entire works to use the Activated Sludge system.
Renewal of the media in the primary and secondary bacteria beds ceased, and by September 1936, both of the media washing plants had been dismantled.
Railway tracks around the primary beds were removed during 1937.
Rolling stock on the railway consisted of one steam locomotive and two diesels, bought in 1935 from Hudswell Clarke.
Construction of a new sludge digestion plant and two secondary sludge digestion tanks was finished in June 1939, and two new settlement tanks were completed in 1940.
Five large lagoons were built at Flixton in 1941, which could be used to store sludge in an emergency.
The Mancunium sank after hitting a mine in the Mersey estuary in January 1941, but all of the crew were rescued.
Parts of the works were damaged by bombs in March and May 1941 and in January 1942.
Transport of sludge to the sea was maintained by borrowing the Shieldhall from Glasgow Corporation, until a new Mancunium was built by Ferguson Bros. of Glasgow.
It arrived at the works on 27 December 1946.

After a public enquiry held at Manchester Town Hall on 23 August 1955, plans for the second Activated Sludge plant were finally approved.
The nine-year project was expected to cost £5.5 million.
After slow progress, the first contractor became bankrupt in February 1957, and the contract was transferred to Percy Trentham Ltd., but progress remained slow.
The railway ceased to be used in June 1958.
Some rails, wagons and the two diesel locomotives were sold for further use, while the rest of the system was scrapped.
In 1960, the design of the Activated Sludge plant was changed to use the 'Simplex' system rather than the bio-aeration process.
It was completed in 1966, at a cost of £6.5 million, and a celebration luncheon  was held at Manchester Town Hall on 17 May.
Upgrading of the first Activated Sludge plant to use the 'Simplex' system took place between 1970 and 1973.
Because of the proximity of the M60 motorway and the risk that deep excavations might damage it, seven of the final settling tanks were built above ground.
Effluent from the Activated Sludge plant was raised up to the level of the tanks by screw pumps, and the increased hydraulic head improved their performance.
The upgrade also included five primary settlement tanks and eight sludge consolidation tanks.
Two new sludge boats were purchased in 1971 and 1972, and a new dock was constructed on land which had formerly been used for secondary beds.
In November 1935, a decision was made to convert the entire works to use the Activated Sludge system. Renewal of the media in the primary and secondary bacteria beds ceased, and by September 1936, both of the media washing plants had been dismantled. Railway tracks around the primary beds were removed during 1937. Rolling stock on the railway consisted of one steam locomotive and two diesels, bought in 1935 from Hudswell Clarke. Construction of a new sludge digestion plant and two secondary sludge digestion tanks was finished in June 1939, and two new settlement tanks were completed in 1940. Five large lagoons were built at Flixton in 1941, which could be used to store sludge in an emergency. The Mancunium sank after hitting a mine in the Mersey estuary in January 1941, but all of the crew were rescued. Parts of the works were damaged by bombs in March and May 1941 and in January 1942. Transport of sludge to the sea was maintained by borrowing the Shieldhall from Glasgow Corporation, until a new Mancunium was built by Ferguson Bros. of Glasgow. It arrived at the works on 27 December 1946.
After a public enquiry held at Manchester Town Hall on 23 August 1955, plans for the second Activated Sludge plant were finally approved. The nine-year project was expected to cost £5.5 million. After slow progress, the first contractor became bankrupt in February 1957, and the contract was transferred to Percy Trentham Ltd., but progress remained slow. The railway ceased to be used in June 1958. Some rails, wagons and the two diesel locomotives were sold for further use, while the rest of the system was scrapped. In 1960, the design of the Activated Sludge plant was changed to use the 'Simplex' system rather than the bio-aeration process. It was completed in 1966, at a cost of £6.5 million, and a celebration luncheon  was held at Manchester Town Hall on 17 May.
Upgrading of the first Activated Sludge plant to use the 'Simplex' system took place between 1970 and 1973. Because of the proximity of the M60 motorway and the risk that deep excavations might damage it, seven of the final settling tanks were built above ground. Effluent from the Activated Sludge plant was raised up to the level of the tanks by screw pumps, and the increased hydraulic head improved their performance. The upgrade also included five primary settlement tanks and eight sludge consolidation tanks. Two new sludge boats were purchased in 1971 and 1972, and a new dock was constructed on land which had formerly been used for secondary beds.
Davyhulme Sewage Works