Sewage Dumping and Its Impact on Natural Water Quality

In this expert guide the water quality experts at Water Treatment Services review the UK practice of sewage dumping and its effect on the quality (and safety) of natural waterways including lakes, ponds, streams, rivers and the sea.

How many sewage spills occur each year?

There have been many news reports of late about the amount of sewage being released into rivers and seas around the UK. The Environment Agency confirmed that 1.75 million hours of sewage spills occurred in 2022 alone. This more than doubled in 2023, with the figure rising to 3.6 million hours. To view it another way, 2022 saw an average of 825 sewage spills per day, whereas this increased to an average of 1,271 spills the following year.

Just 15% of English, 31% of Northern Irish, and 50% of Irish river stretches reach good ecological health standards.

The water quality team at Water Treatment Services have compiled this article as the first of a two-part series about water quality issues relating to sewage spills and the impact they have on the environment. Here, we’ll look at water quality, while the second part will focus on the impact to health and water testing.

Is sewage dumping illegal?

Under general conditions, yes, it is illegal to dump sewage into waterways such as rivers and seas. However, in cases of heavy rain, water companies are permitted to release sewage to reduce the risk of nearby homes becoming flooded.

So, put simply, untreated sewage is illegal to release when the weather is dry. Water companies can release it without breaking the law in wet weather. The above figures should be considered in connection with the above average rainfall that occurred during 2023. This does go some way to explaining the increased figures. 2023 was also the first year that saw monitors installed at all combined sewer overloads (or CSOs). As such, we now have accurate data relating to all sewage discharges, rather than only having data from around half the network, which was the case in 2019. This too will push the figures up and point to worse overall water quality.

One quirk of the UK system is that when it rains, the rain goes into the same pipework as the sewage. Hence why water companies are permitted to release untreated sewage at such times, otherwise the system would become backed up and would not cope with the amount of water and sewage in it.

What are the components of raw sewage?

Raw or untreated sewage may contain all manner of things, including water, waste organic matter, wet wipes, sanitary towels, condoms, and even plastic. Various gases, microorganisms and waterborne pathogens can also be present.

That’s why sewers can become blocked, as the items within the sewage come together and clog up the pipework. In cases of heavy rain, the pipework can become overwhelmed, which risks flooding reaching our homes as the system is unable to cope.

How does the sewage discharge process work?

Ideally, when the weather is good, water companies screen the sewage received and treat it to make sure it is safe to discharge. When there is heavy rain, the companies use storm tanks, sending excess water into those until the rain abates. Then it’s back to normal, treating the sewage before releasing it.

However, as we’ve noted, heavy rain means the water companies need only partially treat the sewage before releasing it, as the law allows for this to prevent flooding. There are still strict conditions regulating this, however.

No single stretch of river in England or Northern Ireland is in good overall health.

How does the discharge of untreated sewage affect water quality?

We’ve noted that the sewage released into waterways during periods of heavy rain may not have been appropriately treated, so it does pose a risk to anyone or anything using those waterways. The amount of fresh rainwater running through the same pipework will play a role in diluting the sewage present there, but it’s typically not enough to negate the potential health risks associated with it.

Put simply, when sewage runs into waterways in bad weather, everything in it goes into rivers and into the sea. The Rivers Trust has stated that, ‘no single stretch of river in England or Northern Ireland is in good overall health.’

Monitoring river water quality

Each river is split into a series of stretches known as river waterbodies. This enables researchers to assess the health of each stretch, to see how this may change as the river goes from source to sea. It’s common for the head (or start) of a river to be the healthiest section, since the water there has yet to be exposed to any type of pollution of sewage release.

Toxic chemicals persist in every stretch of English rivers.

The Rivers Trust has noted that 23% of rivers in England are deemed to have an either poor or bad status. Rivers are examined for their ecological health, while the water is tested for all kinds of chemicals. Just 15% of rivers in England are noted to have a good ecological status or better.

Of course, all kinds of things contribute to the overall health of a river. However, the Rivers Report 2024 from The Rivers Trust notes both continuous and intermittent sewage discharges are having a considerable effect on river health.

While 62% of river waterbodies failed because of a link to farming or agriculture, a full 54% were deemed to fail because of actions taken by the water industry, including discharge of both treated and untreated sewage. This will send all kinds of waste matter into natural waterways, polluting it and potentially causing some of the wildlife and fish in those areas to die.

What does the future hold for the health and quality of the UK’s waterways?

It’s clear that pumping sewage into waterways, no matter the reason, will reduce the quality of the water in the rivers, streams, and seas around the UK… even when there is good reason to do so – i.e., the prevention of flooded homes during storms – it still damages the world around us.

Many people enjoy swimming in lakes and rivers, but you cannot always tell how safe the water is to swim in. The Rivers Trust provides advice on choosing a spot – and notably mentions sewage discharges when it does so. We’ll go into more detail about health and testing impacts in the next part of this series.

Expert water quality testing for natural water sources

Water Treatment Services offer a comprehensive range of water quality testing and laboratory analysis solutions for natural water sources.

Our experts can provide advice and support to help you identify strategies for the safe management of your natural and recreational waters.

With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained technicians, in-field specialists and consultants we can offer professional, cost effective water quality testing and laboratory analysis solutions across the whole of the UK and internationally.

Contact us today to learn how our expert water quality analysis services can help you keep your water safe.