Project Summary
Coffey delivered the expansion of the Enfield Wastewater Treatment Plant, increasing its capacity from 3,600 PE to 9,600 PE. The project involved major upgrades to treatment and sludge-handling infrastructure to support future growth, improve environmental performance, and ensure compliance with regulations. The works included new final settlement tanks, pumping stations, trenchless river crossings, and the construction of 11 sludge drying reed beds that provide a sustainable, chemical-free sludge treatment solution.
Project Description
The Enfield WWTP Upgrade involved extensive civil, mechanical, electrical, and environmental works to increase plant capacity and future-proof its operations. Key infrastructure delivered included the construction of settlement tanks, sludge holding tank, and a new MLSS Pumping Station. A Sludge Import Facility and Sludge Transfer Pumping System were also constructed as part of the overall sludge treatment strategy.
Scope of Works
The works included:
- Expansion of WWTP capacity from 3,600 PE to 9,600 PE.
- Construction of Final Settlement Tanks (FSTs).
- Construction of Sludge Holding Tank.
- Construction of MLSS Pumping Station.
- Trenchless crossings of the River Blackwater.
- Upgrade and installation of MCCs.
- Construction of a Sludge Import Facility.
- Construction of Sludge Drying Reed Beds (SDRBs) and sludge transfer pump system.
- Construction of scour protection and flood defence walls.
- Deep excavations, trenchless pipe installation, and large-scale earthworks.
- Electrical, instrumentation, and control system installation across the new works.
Technical Highlights
- Use of trenchless technology to install crossings beneath the River Blackwater without disturbing the riverbed.
- Construction of SDRBs to naturally treat and dewater sludge, reducing operational power needs and HGV sludge transport.
- Strip and raft foundations constructed in challenging ground conditions.
- Integration of advanced mechanical equipment, including rotating scraper bridges, progressive cavity pumps, and a sludge import screen.
- Installation of VSDs, MCCs, and full site electrical commissioning.
- Advanced instrumentation, including radar and ultrasonic level sensors, suspended solids meters, and loss of rotation sensors.
Environmental and Community
- Implemented 11 Sludge Drying Reed Beds (SDRBs), eliminating the need for chemicals, dewatering equipment, and sludge transport.
- Achieved significant sustainability gains:
– Removed over 155 annual HGV trips (~17,763 km/year).
– Saved 3,744 kWh annually; projected 231,400 km and 48,750 kWh over SDRB lifecycle. - Used SuDS-based drainage (swales and planting) to promote infiltration and reduce runoff to the River Blackwater.
- Conducted otter surveys and scheduled works around breeding seasons to protect local ecology.
- SDRBs enhance biodiversity and produce nutrient-rich material usable as soil conditioner.
- Continued strong local engagement, building on past collaboration from the Enfield
- Treated Water Storage Project.
- Phased works and clear communication minimised community disruption.
Added Value
- Selected mechanical and electrical components were upsized to accommodate Phase 2 (9,600 PE) flows, avoiding costly retrofits later.
- SDRBs removed the need for over 155 HGV sludge disposal trips annually, reducing emissions and operational costs.
- Over 3,744 kWh of electricity saved annually by eliminating sludge dewatering equipment.
- SDRBs promote ecological treatment processes and end-product reuse as natural fertilizer.
- Sustainable drainage swales used instead of petrol interceptors and hard kerbing, encouraging water infiltration and habitat development.
- Built on Coffey’s history of successful community engagement in Enfield during previous infrastructure projects.
To learn more about Coffey’s work in water and wastewater management, or to discuss future opportunities, please contact us at 091 844356 or info@coffeygroup.com.
