Sewage Treatment Works are industrial filtration centres, used to clarify water, removing waste contaminants from the supply through chemical and material processes, before reintegrating treated water back into the water system. Interestingly, many of the material filtration processes are similar to the naturally occurring filtration seen in chalk bed aquifers. Sewage Treatment Works can be seen as a secondary water source.

Click on the images below for a detailed look at these processes.

This aspect of waste management has fallen increased public scrutiny after large numbers of swimmers in Summer 2023 were reported to have contracted water-borne illnesses. Water companies are legally permitted to dump untreated waste at times of high rainfall, but routinely do so in dry times as well, in violation of environmental regulations.

Legislation allows the discharge of raw sewage into waterways in order to avoid flooding. This is permitted when water levels exceed the capacity of storm drains across the sewage system. However, legal definitions of this threshold for rainfall are incredibly vague. Using terms like “unusually heavy rainfall”. This allows for water companies to characterise any amount of rain as unusual, and release untreated waste into waterways at any time, regardless of weather conditions.

Water companies are responsible for monitoring their own spills. Certain spills are lawful and authorised by environmental permits. While some Combined Sewage Outflows (CSO) are monitored through Event Duration Monitoring (EDM), others remain unmonitored. Water companies apply for annual waste permits, using expected rainfall and prior CSO use to calculate how much they should be allowed to spill.

Thames Water is the only company that publishes a live map of its EDMs, following sustained pressure from Windrush Against Sewage Pollution, but the status of these CSOs can sometimes be impossible to independently verify. There are multiple factors that contribute to the obscurity of CSO use, notably location and time lag.

A Thames Water worker, who preferred not to be named, explained that they too find it difficult to locate their own CSOs. Pipes entering the nearby River Darent, a Thames tributary, appear to have killed off local plant life, but it is was not listed as a “spill location” on the Thames Water EDM Map.

Since 2010, the Environment Agency's protection budget, which allows them to monitor England and Wales's waterways, has been drastically reduced by successive cuts, according to an analysis by the National Audit Office.

Since 2009, as a result of austerity budget cuts during the global financial crisis, responsibility for monitoring spillages has fallen to the water companies themselves. These self-audits are often unreliable and insufficiently scrutinized by regulatory agencies. The level of pollutants such as Coliform bacteria and uPBTs in water has increased since this change was made. The obscurity of the monitoring system and of the relations between water companies and regulatory bodies is reflected in the murkiness of the nation's rivers and coastal waters.

Although water companies are primarily responsible for the pollution in our rivers, developers and the construction industry have also had a detrimental effect on water quality. According to the Department for Environment, Food and Rural Affairs (DEFRA), there are currently between 150,000 and 500,000 houses in the UK which are misconnected to sewers. Because each sewer main has many connections, responsibility for leaks are almost impossible to determine – and so these problems go unresolved.

There is no such thing as H20, but we are all bodies of water. The abstract concept of "pure water" has led to misconceived, one-dimensional approaches to water treatment, obfuscating the slow violence of waste management that has despoiled our water systems. According to environmental theorist Stacy Alaimo, human bodies are necessarily enmeshed with the polluted systems in which they live.

As industrial and agricultural runoff and human domestic waste overload water sources, many ecosystems will approach precarious unsustainable thresholds of living. Lakes suffer from blue-green algal blooms, whilst food chains are irreversibly entangled with manufactured micro-plastics and "forever chemicals".

Water is a comprehensive concept-object that flows through multiple bodies – human, political, geographical – carrying in it the pollution of the present and past. This collective encounter could be useful in breaking down the abstraction of water. We are all already polluted, and so is the water system.

To bring this issue to the forefront of collective action, one could integrate comprehensive monitoring of the water cycle with open-access monitoring of the sewage system. What would a weather forecast that included information about polluted waterways and the reporting of sewage look like? How much would need to change from the current system of weather reporting?