Thames Water is currently carrying out a £21m upgrade to Cirencester Sewage Treatment Works (STW).

The upgrade will improve the quality of effluent released at the works and increase the site's capacity to help manage the challenges of climate change and prepare for population growth.

The STW, which currently treat up to 269 litres of wastewater per second, will almost double its capacity to 484 litres per second. This includes a new 9,000sq m HIRB, a natural filtration system which provides a final treatment of water before it is returned to the environment.

The HIRB will treat an extra 114 litres of waste per second, as part of the treatment process. Increasing this capacity will greatly reduce the risk of storm overflows during periods of heavy rainfall and return a better quality of effluent to the river.

The upgrade began last summer and is expected to be completed in spring 2025.

Paul Parfrey, project manager at Thames Water, said: "We are pleased to be working towards improving our Cirencester Sewage Treatment Works for residents and businesses in the area. Our new 9,000 square metre HIRB will treat an extra 114 litres of waste per second, to help increase capacity of the site.

"As custodians of this important infrastructure, we need to ensure our sites are resilient to the pressures of climate change and population growth, so we can continue to provide reliable services to our customers. This upgrade to our network will help protect customers and the health of the rivers and waterways."

Cllr Lisa Spivey, Cotswold: South Cerney (Lib Dem) member for Gloucestershire County Council, said: "I saw the new reed beds at Cirencester Sewage Treatment Works during a recent visit and was impressed by the size of the bed. By using this system, Thames Water should be able to increase treatment capacity which is desperately needed. All too often we are seeing storm overflows meaning sewage discharging into our local rivers and waterways. I hope that this reed bed will lead to less discharges into rivers like the Churn, Thames and Coln."

The upgrade of Cirencester STW comes as part of Thames Water's plans to improve 250 of its wastewater sites, including Fairford, Cricklade and Bourton-on-the-Water.