The works form part of an integrated £7.8 million investment in tertiary treatment at Raunds Water Recycling Centre near Wellingborough. Barhale also upgraded the site’s ammonia treatment systems to ensure compliance with more stringent legislation.

Cypermethrin is one of several emerging contaminants now detected in trace quantities in watercourses. The pesticide is widely used in agricultural, domestic and veterinary products. Although its use is legal, concerns remain that it can enter the wider environment and harm insects and other invertebrates.

Civil engineering, infrastructure and tunnelling specialist Barhale worked through Anglian Water’s @one Alliance in collaboration with the water company and the Environment Agency to design a treatment process capable of removing Cypermethrin to very low concentrations. It includes a purpose-designed cloth filter supported by a ferric dosing package with a 30m³ storage tank and downstream dosing pumps.

To meet the new 1.5mg/l ammonia consent, Barhale installed 12 modular nitrifying SAF (Submerged Aerated Filter) units to provide flexible and scalable ammonia removal capacity. The SAF units were supported by dedicated blowers and a new motor control cabinet to ensure reliable aeration and process control. A new interstage pumping station helps manage flows to the tertiary process.

Barhale’s team of specialists also completed all necessary structural bases and pipework and constructed dedicated maintenance access routes across the site.

Anglian Water’s @one Alliance is a collaboration of consultants and contractors delivering more than half of the company’s capital investment programme.

According to Szadrach Peplowski, Site Manager, Barhale, the tertiary treatment upgrades at Raunds demonstrate how Anglian Water and the @one Alliance are responding to the twin challenges of tightening environmental regulation and emerging contaminants.

“The works provide robust compliance today while introducing new technology to address contaminants such as Cypermethrin in watercourses,” he said.

“The @one Alliance has delivered a solution that keeps Raunds resilient and meeting requirements while providing the technology needed to protect Northamptonshire’s rivers and wildlife for many years.”