The rule expressly protects all recreational waters and tributaries that may threaten these waters. Effluents to these waters must be disinfected and then dechlorinated. A site-specific review process is applied to all dischargers seeking disinfection exemptions to ensure that potential or existing recreation is protected. Animal waste is everywhere. These fecal coliforms and potential tagalong organisms enter streams and lakes by a route known as non-point source pollution.
Rainfall washes feces into the water where the bacteria persist for a time.
This prospect isn't a new problem. Imagine what happened when a thunderstorm hit after a herd of bison finished grazing next to a stream in pre-settlement Illinois. You get the picture. Fecal coliforms and the disease organisms they may be associated with aren't at all happy about being excreted into the world of sunshine because, fortunately for us, it's the beginning of the end for them. The UV light in sunlight is a very effective disinfectant - if the sunlight can get to the microorganism.