ACWA Services, part of the ACWA Group, has completed a new £1.7 million ammonia removal plant for United Utilities, at the company’s Leigh Wastewater Treatment Works (WwTW) in Greater Manchester.

The project, awarded by framework contractor KMI Plus on behalf of United Utilities, is part of an overall upgrade to sewage sludge processing capacity at Leigh WwTW to improve sludge recycling and disposal to land within Nitrate Vulnerable Zones. ACWA is providing all mechanical and electrical aspects of the standalone solution including design, construction, testing and commissioning.

The solution is centred on ACWA’s Amtreat technology, a high-rate activated sludge process designed to treat wastewater streams and sludge liquors containing high concentrations of ammonia.

Leigh WwTW, which acts as a processing centre importing sludge from outlying sites will treat the sludges utilising advanced digestion and dewatering which will generate high strength ammonia liquors. These include centrifuge liquors from both raw sludge thickening and digested sludge de-watering processes.

With a processing volume of 805m3 per day, the new Amtreat plant is designed to provide full nitrification-denitrification with a minimum 95% ammonia removal. Once operational, treated liquor will be pumped back to the head of the main treatment works, to complete the cycle.

Managing ammonia levels is an increasing issue for water companies where advanced thermal hydrolysis and digester technologies are utilised to provide an enhanced sludge suitable for recycling to land, especially in Nitrate Vulnerable Zones (NVZs).

Work on the project  is now operational - associated civil construction works are being undertaken by KMI Plus.

“The modernisation project at Leigh WwTW lead by framework contractor KMI Plus will improve quality, capacity and efficiency for sewage sludge processing including energy recovery,” explained Jane Horseman, production manager at Leigh for United Utilities. “Treating wastewater flows containing high quantities of ammonia is crucial and ACWA’s treatment process, tried and tested at a number of sites, will deliver a robust and flexible solution for ammonia removal.”

ACWA’s Amtreat solution, the UK’s first high-rate process for treating high-strength ammonia liquors, was developed in consortium with four UK water companies and is now in operation, commissioning or construction at six plants in the UK, including Anglian Water, Southern Water, Seven Trent and now United Utilities.