Final effluent compliance

As part of our permits, the water we release back into the environment after treatment must meet certain standards. This is to protect the environment and public health. To check the water we release meets these standards, samples are tested.

We publish our annual compliance figures here (last updated March 2022). The Environment Agency has not yet published the final performance data that we need to update this page, we will update as soon as we have the information, which is expected in April.


Compliance of samples

Samples are taken at the point the effluent is released into the environment. They’re tested for several indicators of the discharge's potential polluting impact. If the result for any indicator is above a set limit, the sample fails the compliance test.

The graph below shows the number of failed works per calendar year, as recorded by the Environment Agency:

We take thousands of samples each year from around 300 separate locations. As such, compared to the small proportion of samples that fail each year, the vast majority are compliant. However, we take every instance of non-compliance seriously. 

To protect the environment and public health, the indicators for the potential polluting impact of a sample are set very low. As a result, failed samples are usually only slightly above these thresholds and pose no significant risk to people or the natural world.


Our final effluent compliance data

For details of which sites have failed during each calendar year, please download the .xlsx spreadsheet or CSV data file below:

Final effluent compliance data 2017–21 – Excel

Final effluent compliance data 2017–21 – CSV