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Our waste water responsibility

It may not be glamorous, but treating sewage is as important to us as supplying you with wonderful drinking water. Sewage is everything that goes into our drains and sewers, from inside your property and rainwater. From everything that goes down your sink, waste from flushing your loo, dirty water from your washing machine, pollution from businesses and rainwater - it's a massive list. Our sewage works manage and clean 2.5 billions litres of dirty water every single day.

Cleaning up

As you might expect, sewage contains bacteria, organic waste matter and a whole host of potentially harmful materials. This is why the Environment Agency set such strict standards for waste water quality to help keep streams and rivers protected. Before dirty water is fit to return to the environment, we clean it in many extensive and detailed ways.

Our hard work has paid off though. During the 1990's we improved river water quality by 38%, while our treatment works met more than 99.01% of the standards needed to maintain this. We aim to continuosly improve and exceed these measure, meaning that streams and rivers across our region are kept lovely and clean for generations to come.

Men at work, digging up pipes in the road
How is sewage treated?

While we're always looking for new ways to streamline and improve our treatment process, here's a quick breakdown of how we do it at our sewage works.


  • Incoming waste passes through screens that remove large debris.
  • Liquid flows through a number of channels to remove smaller debris and grit.
  • Sewage settles in closed tanks, where even finer particles sink to form sludge.
  • Sludge is stored and mixed in the tanks, where it’s digested by friendly bacteria at 35°C for at least 12 days, turning organic matter into gas (which is then used for electricity at some of our plants).
  • The remaining treated solids are then safely returned to the environment.


Around 660,000 dry tonnes of treated sewage sludge is returned to the environment every year. It’s surprisingly popular too. As it’s packed with nitrogen and phosphorus it’s ideal for farmers looking for organic manure.

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