Stockport wastewater treatment works
Stockport Wastewater Treatment Works (WwTW) is our 12th largest wastewater facility in the north west of England, serving a population equivalent of approx 195,000. We completed a £37 million upgrade in early 2009 which was in response to and saw improvements in final effluent quality and odour reduction as well as a much needed operational upgrade.
Quality improvements
The EC Freshwater Fish Directive has a principle aim to protect and improve the sustainability of fish populations by setting physical and chemical water quality objectives. To achieve this, the Environment Agency has stipulated that biochemical oxygen demand (BOD), suspended solids (SS) and ammonia (NH3) concentrations in the final wastewater effluent had to be reduced to prescribed levels by 2007, in order to improve the quality of the River Mersey, where Stockport wastewater treatment effluent is discharged to. The final effluent quality limits have been changed from 40mg/l BOD, 60mg/l SS to a consent of 20mg/l BOD, 30mg/l SS and 10mg/l NH3.
Maintenance requirements
There were two main wastewater process plants in operation at Stockport WwTW, the “Haworth” plant and the “Simplex” plant. The Haworth plant was constructed in the 1920’s and was operating beyond its asset life, was in poor structural condition and was in need of replacement so it could meet new quality objectives.
Odour improvements
The works had a history of significant odour issues. To improve the local environment for our customers a need was identified to reduce odour emission rates.
To address the issues and achieve the aims of these drivers, the proposal involved replacing the existing activated sludge plant with a new nitrifying activated sludge plant and to extend the works within the existing footprint. This integrated solution addressed the maintenance, quality and odour issues highlighted above. The successful completion of this project has meant that the works continues to take wastewater from thousands of homes and businesses, treat it and then safely returns it to the River Mersey. The water being returned to the river is the cleanest it has ever been. There have also been no odour complaints from local residents during 2008 ensuring we continue to be a responsible company and neighbour.
Keith Dyall, match secretary of Cheadle Angling Club said he was delighted with the latest efforts to ensure the River Mersey was kept clean for users. He explained “Some of our members fish a stretch of the Mersey and have caught chub, roach, dace, gudgeon, trout and even barbell, and that’s a fish that only likes clean water”.
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