Sewage and stormwater pump stations

Challenge
The revival of one of Britain’s largest commercially unexploited land areas called for multi-phase construction of two large pump stations. One pump station was to provide drainage for a combined flow of sewage and surface water, yet ensure separation of surface water for discharge directly into a nearby river. The other was to provide adequate drainage for stormwater for the continuing redevelopment of the area.

Solution
For the first pump station, Flygt developed a complete mechanical and electrical package that will cost-effectively pump sewage and surface water for the entire redeveloped area. Designed to separate foul and surface water flows into two drainage networks, the system consists of two Flygt CP 3300 drainage pumps and 10 Flygt CP 3500 stormwater pumps in a twin level wet well with siphonic discharge into a surge chamber. This configuration with its circular sump design provides a total station capacity of 12 m3/s (190,000 US gpm) at a pump station that is 50% smaller than standard stations. It ensures that surface water can be efficiently and economically discharged directly into the river without overloading the local sewage works as well as drastically reduced construction, installation, operating and maintenance costs. For the second pump station, we designed a circular pump station with 18 radially positioned submersible pumps that discharge siphonically into a central chamber above the inlet chamber. Installed inside a wet well 28 m (90 ft) deep in parts are 16 Flygt CP 3311 pumps for handling stormwater and two Flygt CP 3300 drainage pumps. With a total capacity of 8 m3/s (125,000 US gpm), this station is one of the world’s largest using submersible technology. For both pump station solutions, we conducted and analyzed start calculations to ensure reliable starts, long lasting equipment and optimal hydraulic performance.