United Utilities has begun a £34.4M upgrade at its Crewe wastewater treatment works in which Costain, the engineering contractor on the project, has adapted techniques from industrial cooling systems to refurbish the filters.

The project aims to reduce ammonia and phosphorus levels discharged into the River Weaver.

The Cheshire site will receive technology more commonly associated with the energy sector: cooling-tower style pack media installed within two nitrifying trickling filters. The polypropylene media provide a large surface area for nitrifying bacteria to colonise, converting ammonia to nitrate as part of the treatment process. United Utilities says the approach will make the works more efficient and help it cope with projected population growth in the area.

Costain engineers manufactured and assembled the new media and brought the first phase of work forward by around 12 months, with additional phased refurbishments planned through the year. Costain is also working with local partners to recycle the removed media where possible.

United Utilities frames the Crewe upgrade as part of a much larger investment programme. The company is investing more than £13bn across the North West , a programme it describes as the biggest water and wastewater infrastructure investment in the region for a century , to protect and enhance rivers, lakes and bathing waters as well as secure drinking water supplies. The Crewe work is being delivered under United Utilities’ Enterprise model, a partnership that groups the company with seven design and construction firms to deliver a £2.5bn package of major projects; Costain is one of those partners.

Environmentally, the upgrade targets lower nutrient discharges to improve river health. Ammonia and phosphorus can contribute to oxygen depletion and algal growth in waterways; reducing them is a common objective of wastewater improvements intended to meet regulatory standards and support aquatic ecosystems.

Independent observers and regulators typically monitor such projects to ensure claimed improvements in water quality are realised in practice. United Utilities has reported similar upgrades elsewhere in its capital programme; this project adds to a broad effort across the region to modernise ageing treatment works and reduce pollution from wastewater discharges.

Costain programme director Richard Helme said: “We have an excellent working relationship as a trusted partner to United Utilities.

“Part of that trust is built on our ability to apply innovative solutions to enable for the safe and efficient treatment of wastewater. By drawing on strong practices and capabilities from our colleagues in the energy sector, we’ve been able to deliver critical upgrades for United Utilities ahead of schedule.”

United Utilities enterprise director Tony Slater said: “Through our enterprise model, we’re working with delivery partners that have a strong track record of delivering best-in-class water infrastructure solutions, supporting our ambitious plans to transform infrastructure and services across the North West.

“We’ve been impressed by the innovative solution Costain has brought to what is a complex project. The upgrades at Crewe will enhance treatment performance and help make the site more resilient for customers as demand grows.”

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