Temporary System Successfully Removes Suspended Solids Whilst Humus Settlement Tanks are Out-Of-Service

Ongoing upgrades are being implemented to improve a Waste Water Treatment facility performance

Sewage Treatment Works (STW) at Chobham, Surrey Heath is involved in the treatment of sewage effluent, utilising biological filtration systems for secondary treatment.

Ongoing upgrades are being implemented to improve the facilities performance and a leading UK contractor were appointed to undertake some remedial works as part of this.

Challenge

Remedial works required both humus settlement tanks (HSTs) at the facility to be taken temporarily out-of-service. As HSTs are essential components for the separation of solids from treated sewage before discharge, taking them both offline posed a clear risk to suspended solids compliance.

Chobham STW also treats peak flows of approximately 107L/s, meaning any temporary system implemented would need to minimise the risk to hydraulic capacity, without impacting the effectiveness of a temporary solid removal system in place and ensuring treatment continuity during construction works.

The contractor reached out to RVT Group for a temporary hire solution that would successfully navigate the strict compliance requirements of the wastewater treatment facility, so their team could focus on the remedial works at hand.

Solution

RVT Group supplied the contractor with mobile lamella clarification systems to provide interim settlement whilst HSTs were out-of-service. These systems were made up of 3 key parts:

• Flow diversion from the HST distribution chamber via duty/standby pumping
• Nine HL50 lamella clarifiers in parallel, each rated at 14 L/s (50 m³/h), delivering full peak-flow coverage with headroom
• Gravity return of clarified effluent to final effluent distribution and automatic sludge return to the site wet well

Treatment performance and throughput were maintained throughout the works, protecting compliance, minimising programme risk, and avoiding disruption to site operations.