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26 October 2021updated 27 Oct 2021 10:50am

Why do UK water companies pump sewage into the sea?

Brexit and ageing infrastructure are two reasons the UK has sewage floating around its shores.

By Emma Haslett

The government has announced a partial u-turn on its Environment Bill after public and political uproar over its plans to make some water companies legally liable when they pump sewage into water courses.

The Bill will now include an amendment forcing companies to reduce “adverse impacts” when they release untreated sewage into water courses following a rain storm, says the government, which was taken aback by the amount of opposition to its decision.

The practice, known as storm overflow, usually takes place after heavy rain, and is permitted under current law – but after a summer of flash floods left many beaches closed to swimmers as sewage was pumped into the sea around the UK, the population has become increasingly aware of it.

Following the vote, some voiced fears that because the Environment Bill is designed to replace EU law, Brexit will give water companies the green light to ramp up the practice.

Why do water companies pump sewage into the sea?

The UK’s Victorian sewer system was built with one thing in mind: removing wastewater from homes and businesses. It’s only since the Clean Water Act of 1972 that sewage has been routinely treated to remove pollutants.

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Treating sewage is a slow biological process. Although water companies have storage tanks for overflow, these fill up fast during a storm. Southern Water, for instance, has a storage tank with a 40 million litre capacity (over 15 Olympic swimming pools), which fills up in about 40 minutes during a storm.

The problem comes when it rains heavily. Once storm tanks have filled up, companies have two choices: release a valve that lets the overflow into waterways or allow it to back up. In the latter case, it could (and occasionally does) back up through sewers into people’s sinks and showers.

These incidents are called storm overflows and combined sewer overflows, and are legally permitted – although they are only supposed to be used in exceptional circumstances.

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In these situations, it’s worth pointing out that much of what is pumped into the sea is rainwater – although the overflows also contain effluent and waste from industry.

How often do storm overflows happen?

They are on the increase. There were more than 400,000 raw sewage discharges last year, over 3.1 million hours – up 37% year-on-year, show figures from the Environment Agency.

The rise was partly because the agency has increased the number of such incidents it monitors – in 2020, it increased the number of storm overflows it monitored by almost 50 per cent, to 12,092.

Heavy rainfall incidents are expected to rise as the climate crisis worsens, and so the number of storm overflows is likely to surge. A report published in August by the Intergovernmental Panel on Climate Change shows climate change is intensifying the water cycle, creating heavier rainfall in many regions.

Did water companies really start pumping sewage into the sea after the vote?

Not really. Immediately after the MPs’ vote, a map produced by Surfers Against Sewage appeared to indicate overflows were happening in 60 locations, suggesting companies had taken it as a green light to start polluting the nation’s waters.

But as those living in coastal regions know, this isn’t new. This summer, Southern Water was fined a record £90m for illegal spills, while in August the chief executive of the Whitstable Oyster Fishery Company complained about water quality affecting his shellfish.

“If people’s perception of the water quality is that it’s not good enough to eat shellfish, that’s the end for the business,” he told the Telegraph.

What does the Environment Bill say about sewage?

The proposed amendment to the Environment Bill would have forced water companies to take “all reasonable steps” to avoid releasing untreated wastewater into rivers and seas.

Environment Secretary George Eustice recommended MPs reject the amendment: his department, the Department for Environment, Food and Rural Affairs, said it was well intentioned, but it is “already delivered through the many measures within the Environment Bill and more broadly”.  

The new measures announced last night mean water companies will be legally mandated to demonstrate a drop in overflows.

Is this happening because of Brexit?

In 2018, the then-environment minister Michael Gove promised a “green Brexit”, but campaigners have suggested the Environment Bill does not bear that out. The bill, which includes rules that will allow ministers to set targets for air pollution, waste, water quality and biodiversity, has been heavily criticised, with a cross-party committee of MPs saying in 2019 that it will “severely downgrade” EU environmental rules.

But the bill isn’t the only factor at play. This week’s vote follows a decision by the Environment Agency in September to ease rules on wastewater plants discharging effluent that has not been properly treated, because problems with supply chains means they are struggling to obtain the correct chemicals. That can be more directly attributed to Brexit – although other countries are also experiencing supply chain issues because of the pandemic.

How do we solve this?

The Environment Bill goes back to the House of Lords and then returns to the Commons this week.

There are moves afoot to solve the problem: the £4.2bn Thames Tideway “supersewer” will help to prevent storm overflows from happening as frequently, although that won’t be completed until 2024.

Developers can also help by including “soakaways”, porous surfaces such as lawns and gravel areas, in their designs to absorb water during heavy rainfall, preventing it from running into the sewers. Water companies have also agreed to invest £1.1bn to improve storm overflows, a spokesperson for Water UK, the industry body, has said.

[See also: The raw sewage dumped into the UK’s rivers reveals a broken model]

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