Thames Water is set to carry out a £21million upgrade of sewage treatment works near Swindon. 

The utility company has confirmed that it will be upgrading Cirencester Sewage Treatment Works (STW) to improve the quality of effluent released at the works and increase the site’s capacity to help manage the challenges of climate change and population growth.  

This upgrade comes as part of Thames Water’s plans to improve 250 of their wastewater sites including in the Cotswolds, such as Fairford, Cricklade and Bourton-on-the-Water. 

The Cirencester site can currently treat up to 269 litres of wastewater per second, but the upgrade will almost double its capacity to 484 litres per second.

This includes a new 9000 square metre natural filtration system called a HIRB that 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.   

Having started the upgrade in Summer 2023, work is currently ongoing 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. 

“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.” 

Councillor Lisa Spivey, Executive member for communities and public safety at Cotswold District 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.”