We test water samples for a bacteria called enterococci. Enterococci is found in the intestines of warm blooded animals and excreted in faeces and rarely present in unpolluted waters. The bacteria is found in very high numbers in raw sewage which makes it a good indicator of sewage pollution.
Studies have shown a strong relationship between elevated levels of enterococci and illness rates in swimmers. It’s important to note that enterococci doesn’t cause illness, but its presence means there’s sewage in the water and, therefore, possibly pathogens, which do cause illness.
Indicator organisms are used to test for sewage pollution because:
- they are easily detectable by simple laboratory tests
- they are generally not present in unpolluted waters
- results are available relatively quickly.
The National health and Medical Research Council (2008) Guidelines for Managing Risks in Recreational Waters recommend enterococci as the single preferred indicator organism for the detection of faecal pollution. Prior to 2009, we also tested for the bacterial indicator faecal coliforms . While this bacteria is also present in high numbers in raw sewage, it dies off more rapidly than enterococci in marine waters and has been found to correlate poorly with illness rates in swimmers.