Sewage is regularly being released into rivers and seas in England in part because of ageing wastewater systems that can’t cope with modern population numbers, according to researchers.
Raw sewage was released into English rivers in 2021. Water firms in England are only meant to discharge raw discharge into water during unusually high rainfall when there is a risk the system may be overwhelmed and effluent could back up into people’s homes. However, a compiled by conservation charity Surfers Against Sewage in November 2022 found that sewage overflows routinely occur during dry weather.
To investigate why so many sewage overflows are occurring, Ěý˛ą˛Ô»ĺ at Imperial College London analysed overspill data released by water companies in England in 2020 and 2021.
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They estimated the total amount of time that sewage was discharged into water for each wastewater treatment works each year. They then looked at how much volume each wastewater system could handle using figures provided by water firms to the Environment Agency. Wastewater systems include treatment works, pumping stations, sewers and storm tanks.
“It becomes pretty obvious that there’s much more wastewater produced than these systems were built to handle,” says Voulvoulis. The researchers found that this was the case throughout the year – even during dry weather.
About 80 per cent of wastewater systems in England appear to be regularly working beyond the capacity they were designed to handle, says Voulvoulis. Sewage overflows are simply a symptom of an overwhelmed wastewater system, he says.
Vouloulis says this is due to a variety of reasons, including England’s rising population. Most wastewater systems in England were designed decades ago and were built for a far smaller population, he says. Increasing urbanisation has also led to some wastewater systems being put under more acute pressure, and the infrastructure hasn’t received the investment needed to keep up with demand.
It is difficult to know how bad the problem is as it isn’t clear whether the figures provided by water firms on sewage overflows are accurate, says Voulvoulis. “We are probably underestimating the issue,” he says.
Sewage discharge into rivers affects both marine life and human health, says Voulvoulis. Just 16 per cent of bodies of water in England have a “good ecological status” under the .
at Imperial College London, who wasn’t involved in the study, says sewage overflows are only one part of the reason why river quality in England is rated badly. Treated wastewater that flows into waters during normal operation also plays a role, as does agricultural run-off. “Fixing overflows does not suddenly mean we can swim in all of England’s rivers,” he says.
at Wildlife and Countryside Link, a coalition of environmental organisations, says: “Population growth has put more strain on our sewers, but water companies have been failing to invest in sewage infrastructure for decades at the expense of customer service and the environment. We also need to see a more holistic approach to cleaning up our water, with nature-based solutions – like creating wetlands that naturally filter pollution, and sustainable drainage to reduce overloading of sewers – that are both cost-effective and good for wildlife.”
A spokesperson for Water UK, which represents water companies, said in a statement: “Our analysis of root causes suggests that population increase, changing weather patterns and urbanisation all contribute towards the problem. Even though the Environment Agency says that overflows are only responsible for 4 per cent of the reasons that rivers do not achieve good ecological status, it is right that we accelerate action to stop them.
“Water companies will remove a quarter of spills by 2025, before tackling the rest with a new £56 billion programme of investment. This represents one of the largest infrastructure programmes ever undertaken by the UK.”
Enviromental Science: Water Research & Technology
