An innovative filtering unit is ready to be switched on for the first time in Cirencester as part of Thames Water’s ongoing work to protect homes from sewer flooding.

The mobile sewage filter unit, which was set up on in the town on Friday, is one of 10 purchased by Thames Water following the record wet winter two years ago.

It is designed to protect the environment by biologically filtering out the most harmful elements of sewage if, in extreme circumstances, sewers are overwhelmed and the excess water has to be diverted away from properties into water courses or fields. 

 The £20,000 unit is currently on standby as volumes in the sewer network are manageable, but with river levels on the up following the weekend’s rain Thames Water teams are on high alert.

 Thames Water’s head of waste water control, Anthony Crawford, said:

“We hope we don’t need to put it into action but, should the worst happen, we’re ready to do all we can to protect customers and the environment.”

“This proactive approach is based on careful monitoring of our own information and that from organisations such as the Environment Agency and the Met Office, and enables us to put measures in place before flooding happens. Using the filter unit will be a last resort as we want to operate normally for as long as possible by pumping everything from the sewers away for treatment.”

Councillor Sue Coakley added:

“I have been impressed with the proactive approach taken by Thames Water during the recent heavy rain. I welcome the provision of the filtration system as a further precautionary measure although I, like Thames Water, hope that it will not be necessary to put it into use.”

During and after heavy rain, especially if groundwater levels are already high, pumps which send sewage to a treatment works can get overwhelmed by extreme volumes of water. Previously in these circumstances, with permission from the Environment Agency, sewage was diverted into watercourses or to fields to stop it flooding streets and homes.

In addition to the filter units, Thames Water’s wet weather supplies include:

• 65,000 sandbags and 15,000 flood sacks to keep pumping and treatment sites working by protecting them from surface flooding and river flooding
• 300 tonnes of grit for use in cold weather to keep sites safe and accessible
• 30 extra 4x4 vehicles hired in for use during cold or wet weather to enable crews to access sites and customers in hard to reach areas
• 120 tankers available to pump away excess water from the sewer network and pumping sites

The water company said the new equipment means that if the situation arises again the most harmful elements in the sewage will be filtered out by the unit before the water enters the environment. It will stay in place for as long as there is a risk of flooding.