Chopper pump and mixing system helps prevents sewage blockages

Vaughan Pumps has announced that a combination of its chopper pump and mixing system has helped to prevent blockages at a sewage treatment works (STW) in Peterborough, UK.

Pump failures at STW are often caused by a lack of reliable mixing of unscreened sludge before it enters pumping systems, a problem that was evident at Flag Fen STW, one of Anglian Water’s main sites in Peterborough.

Unscreened sludge was being imported into the Flag Fen plant, which contained large accumulations of rag and surface crust, needing reliable mixing.

P&M Pumps, which distributes Vaughan Pumps in the UK, provided a self-priming chopper pump on a sale or return basis for a four-week trial.

The Vaughan model SP4C pump was set up to work alongside a new Gorman Rupp (GR) T4 trash pump with belt drive and 11kW motor to evaluate the two solutions on a head-to-head basis.

The results showed that the Vaughan chopper pump exceeded the performance of the GR pump in handling the unscreened, rag-laden sludge with fewer blockages.

However, it was still susceptible to large masses of reweaved material entering the pump suction line, with Anglian Water recognising the need to condition the sludge on a permanent, continuous basis.

In addition to the strain press feed pumps, P&M Pumps installed a mixing and conditioning solution, which comprised a Vaughan model SE8N chopper pump powered by an 18.5kW motor.

Following a short period of operation and a recirculation flow of 360 cubic metres per hour, the imported sludge was effectively mixed and the surface accumulation was removed, except for a large floating mass that was static in the centre of the tank.

This resulted in a period of five days without a single strain press feed pump blockage. The performance of the sludge centrifuge also improved, resulting in increased throughput due to higher feed solids being achieved.