Sludge spreading

Sewage sludge might seem an unexpected topic of discussion when it comes to the health of our oceans, but it’s actually incredibly relevant. Read on to discover the dangers and find out what action is needed.

What is sewage sludge?

The wastewater from our homes, businesses and industry goes to treatment plants to be cleaned. As the water is filtered, a solid waste product is formed. This material is known as sewage sludge and tonnes of it is generated in the UK every day.

The sludge is made up largely of organic matter and contains nutrients, such as nitrogen and phosphorus, which makes it a useful fertiliser. Once treated to reduce the health risk, the overwhelming majority of sewage sludge is spread over farmland. The water industry call this treated sewage sludge bio-solids.

Sewage sludge being spread on field Pascvii

Tractor fertilising fields

Credit: Pascvii via Pixabay

Why is that a problem?

Despite this treatment, sewage sludge often contains synthetic chemicals such as PFAS and plastic contaminants (see microplastics). These tiny particles are difficult to remove, which means harmful contaminants end up in the soil, enter our rivers and ultimately the sea.

Our research

Water treatment works are often seen as a solution to stopping microfibres and certain chemicals getting into our environment. However, our report shows that although microfibres and chemicals are captured in the sludge they are then released when spread on farmland. Our findings are being shared with policymakers, water companies and decision makers emphasising the need for stopping pollution at source.

What needs to happen

We agree that sewage sludge is a valuable resource within the circular economy, but it must be properly monitored to ensure it isn't a source of pollution. We are calling for a number of key actions to stop pollution at source:

  • For washing machine manufacturers to fit microfibre filters in all new domestic and commercial machines, by law, by 2023.
  • To restrict the use of intentionally added microplastics.
  • To ban all PFAS from all non-essential uses.