A new integrated constructed wetland (ICW) has been completed at Staplefield Wastewater Treatment Works in West Sussex, marking a significant step toward sustainable, nature-based water treatment in the UK. The wetland will further purify wastewater before it is released into the River Ouse, supporting biodiversity, carbon storage, and local flood resilience.
The project was delivered by Solutions by Nature — a joint venture between Binnies and Salix (both part of the RSK Group) — with design expertise from VESI Environmental. It forms part of the AMP7 capital programme for Southern Water, delivered through the Galliford Try Binnies Joint Venture.
Located across an eight-acre site, the new wetland comprises four connected cells planted with more than 80,000 native wetland plants, shrubs and trees. These cells naturally filter phosphorus, metals, microplastics, and other contaminants before the water is discharged back into the River Ouse.
Figure 1 credit to VESI Environmental
Russell Spencer, Technical Director at Binnies and representative of Solutions by Nature, said: “This project represents one of the first initiatives of its kind in England. After water has been through Staplefield Wastewater Treatment Works, it is diverted into the wetland, where natural processes remove pollutants, nutrients, and microplastics. The result is cleaner water and a thriving new ecosystem.”
As well as improving water quality, the wetland will contribute to carbon sequestration, habitat creation and flood management. According to Natural England, the UK has lost around 90% of its wetland habitats over the past 500 years — making this project a valuable ecological restoration effort. When fully mature, the Staplefield ICW is expected to sequester approximately eight tonnes of CO₂ per year.
Construction began in May 2025 following a detailed feasibility study, groundwater risk assessments, and environmental reviews. The existing on-site clay was reused to line the wetland cells, reducing cost and minimising the project’s carbon footprint by avoiding imported materials.
Spencer added: “The site’s natural slope was ideal for enabling gravity-fed water flow between the wetland cells. The design maximises hydraulic retention time to optimise treatment efficiency. In addition, excavation of the lowest area created a dedicated stormwater retention zone, adding 3,500 m² of flood storage capacity.”
Cecile Stanford, Project Manager at Southern Water, commented: “Wetlands are a natural alternative to traditional concrete and mechanical processes. They use nature to assist water treatment while attracting wildlife. This project will deliver clear benefits for water quality, biodiversity, and local communities — and we’re already seeing swifts and other species thriving in the new environment.”
