South West Water
83 week - Programme
South West Water provides water and sewerage to 1.6 million customers in Devon, Cornwall and parts of Dorset and Somerset. The region attacts over 8 million holiday makers to the 625 miles of scenic coastline and countryside. The company is part of Pennon Group Plc.
The Client's Needs
Countess Wear wastewater treatment works is quietly nestled on an island bound by the M5 Motorway, the Exeter Canal and the River Exe, within three (3) miles of the Exeter city centre.
The original works were constructed in 1905, and consisted of natural terraced reed beds to take wastewater from the city. In 1933 major improvements were undertaken when aerating lanes and settling tanks were constructed to allow the works to take 100% of the sewage from Exeter City (PE 50,000).
In 2000, an enhanced ammonia standard was required at the existing works, which comprised primary settlement and conventional activated sludge secondary treatment. The lack of suitable land for the plant extension, required a nitrification plant with a compact footprint.
The VWS package of works consisted of the design, construction, installation and commissioning of a five-cell BAFF BiostyrTM plant to undertake tertiary treatment for ammonia removal to meet the new EA consent levels of 10 mg/l AmmN. Each BiostyrTM cell provided a filter surface area of 113 m2.
VWS started work on site and achieved successful completion seven weeks ahead of programme and well within budget. The early completion of the plant was also achieved with zero reportable accidents.
Subsequent to the original contract, VWS were awarded a further two significant packages of works: the installation of a UV disinfection plant and replacement of 4 primary settlement tank scraper bridges and controls, achieving savings for South West Water in all three schemes.
The Project Team consists of the following partners: South West Water (Purchaser), M J Gleeson plc (Principle Civil Contractor), VWS (Process, M & E Contractor), Pell Frischmann (Civil Designer).