Anglian Water’s Chelmsford Wastewater Recycling Centre (WRC) was operating normally until a problem with their Archimedes screws arose.

These screws are responsible for transporting Return Activated Sludge (RAS) from a lower chamber to a high chamber to be treated further down the treatment process.

Both screws failed at the same time leading to an emergency, a flow of 500 l/sec needed to be over pumped to the next stage in the treatment process. If the over pumping didn’t happen quickly there was a risk of an environmental spillage.

Selwood were promptly contacted to find and execute an effective solution.

The challenge

1. High duty flow of 500 l/sec.

2. Need for quick installation as there was a high spill risk.

3. Pump system needed to effectively replicate the Archimedes screws.

4. Spillages and environmental risk must be taken into consideration.

The solution

The initial, short-term solution saw the installation of three S200 diesel pumps and two BBA pumps, combined with five 8” 100m pump lines. The longer-term solution involved two H12 pumps coupled with two 300 kVA generators in a duty/standby configuration and 150m of 12” flanged pipework.

The H12 pumps were capable of 500 l/sec, also allowing better flow control and eliminating flow fluctuation. The flanged pipework both prevented spillages and supported the high flow.

The emergency solution was set up and running within the day, the longer-term, more robust solution was set up within the week. The S200s and BBAs were kept on site as standby pumps, to ensure the system’s resilience.

The powerful H12 system, coupled with the generators enabled the effective replication of the Archimedes screws whilst repairs were carries out.

The flanged pipework both prevented spillages and supported the high flow.

The result

Selwood provided a short-and long-term solution in a week, eliminated the risk of a pollution incident and negated the need for tankers for waste disposal, whilst achieving the desired flow rate.

The robust solution brought the security of success, meaning Anglian Alliance Partners could carry on repairs without concern of any possible incident.

By the time the longer-term solution had been on site for six weeks, Selwood saved Anglian water £9,000 in running costs and 5,000L of fuel.