Wessex Water needed to arrange for a specialist contractor to re-line the concrete MCERTS channel at Shepton Mallett STW in Somerset. Temporary overpumping was required to keep the work area dry for the contractors personnel whilst keeping the sewage treatment works live.
The requirement was to overpump incoming dry weather flows of up to 120 lts/sec into the high rate splitter chamber. This flow had to be restricted to ensure the works would not become overwhelmed in storm conditions. A secondary overpumping regime was required in addition, to deliver excess storm flows of a further 240 lts/sec to a fixed storm 400mm flow overpumping point.
The Selwood Solution
Nick Hayes, the Project Engineer assigned to this scheme, contacted Selwood’s Framework Manager Phil Ingleheart to arrange a meeting on site to discuss the overpumping part of the scheme. As Nick was able to explain in detail how this part of the site operated, this information allowed Phil to design bespoke overpumping solutions that would ensure that the contractors could work safely and keep the site performing at its optimum levels without disruption.
Selwood provided a combination of diesel and electric submersible pumps, pipes and fittings, including electronic mag flow metres and specialist super flexible flanged composite pipes placed where traditional bends would not have worked. All the equipment was delivered and installed by Selwood’s specialist installations team with all the electrical work undertaken by Selwood’s own electricians.
In a duty, assist and standby configuration, Selwood S150 Super Silent diesel pumps were controlled automatically by float switches and used to deal with the dry weather flows.These pumps are capable of handling up to 100mm solids with their vortex impeller design ensuring a robust trouble-free operation. Meanwhile, the latest Flygt N series non-clog electric submersible pumps controlled by ultrasonic control panels and inverter drives were installed to deal with the excess storm flows.
Efficiencies were made by Selwood with their latest control panels to help reduce the size of generation equipment. With the pumps’ capability to match incoming flows, fuel consumption was reduced as the units drew purely on the power required at any given time.
All the equipment was provided with Selwood’s remote telemetry to provide live information in the unlikely event of any failures. This gave the client confidence that everything was working as expected. The overpumping worked faultlessly for the entire period, day and night, ensuring no disruption to the sewage treatment process.
Nick Hayes commented: “Contacting our framework pump supplier at the start of the scheme and strategic collaboration from all parties ensured this challenging project went smoothly, The approach kept the contractors safe and the site operating seamlessly for the duration of the works”.