The bacteria that help classify bathing waters
Escherichia coli (E. coli) and Intestinal Enterococci (IE) are two types of bacteria found in human and animal poo and, if ingested, cause severe tummy upsets.
Concentrations of these bacteria are used to classify a bathing water. Their presence indicates that there is faecal matter in the water, whether human or animal, and the higher their levels, the greater the risk is to bathers’ health. The bathing water classifications are based on the analysis of samples taken over a four-year period.
The bacteria can find themselves in the water for different reasons: sewage spills; road drainage; run off from areas that host agricultural livestock; and from wildlife and birds that live in and around the water.
Thresholds set by the Environment Agency
The levels of E. coli and Intestinal Enterococci are measured by the number of bacterial groups (colony forming units (cfu)) per 100ml of water tested. The number is then matched to a percentile agreed by the Environment Agency to determine the quality of bathing water at that location.
| Classification | Thresholds (percentile) |
|---|---|
| Coastal Bathing Waters | |
| Excellent | EC: ≤250 cfu/100ml ; IE: ≤100 cfu/100ml (95th percentile) |
| Good | EC: ≤500 cfu/100ml ; IE: ≤200 cfu/100ml (95th percentile) |
| Sufficient | EC: ≤500 cfu/100ml ; IE: ≤185 cfu/100ml (90th percentile) |
| Poor | means that the values are worse than the sufficient |
| Inland Bathing Waters | |
| Excellent | EC: ≤500 cfu/100ml ; IE: ≤200 cfu/100ml (95th percentile) |
| Good | EC: ≤1000 cfu/100ml ; IE: ≤400 cfu/100ml (95th percentile) |
| Sufficient | EC: ≤900 cfu/100ml ; IE: ≤330 cfu/100ml (90th percentile) |
| Poor | means that the values are worse than the sufficient |
What we do to remove them from wastewater and drinking water?
Drinking water
When we abstract raw water from rivers, there’s a lot of different bacteria in it. Our filtering removes the vast majority of bacteria. Any still left in the water are deactivated by chlorine in the final stage of treatment. By the time the water reaches your tap, these bacteria pose no risk to your health.
Upstream Thinking
We’re working with farmers across our catchment to help reduce the risk of animal faeces ending up in river and sea water. There are small changes farmers can do that make a huge difference. For example, putting up fences stops animals entering the water, and correct storage of silage and manure help prevents run off into watercourses during heavy rain. Raising awareness of where there is risk of bacteria ending up in the water has helped improve the quality of the river and sea water across 111,515 hectares.