Final effluent compliance

After treatment, the final effluent we release into the environment must meet the standards set by the Environment Agency.

Download our data sheet

What is final effluent?

Final effluent simply refers to the wastewater that has been through the treatment process at one of our wastewater treatment works. 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, we take and test samples.

Compliance of samples

Samples are taken at the point where 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. We publish our annual compliance figures here.

The figures will be updated with the performance data for 2024, following publication of the data by the Environmental Agency.

Compliance failures

This graph 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.

Compliance failures

What's the impact of compliance failures?

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.