Sewage bypasses happen when sewage is diverted, purposely or accidentally, around one or more units of treatment in a wastewater treatment facility. The diverted sewage can be taken back to the plant to be treated or it can outflow directly into a body of water such as a lake or river .

When do sewage bypasses occur?

Bypasses generally occur when the volume of wastewater coming into the treatment plant is more than the facility can handle. Wastewater volumes generally increase when they are combined with stormwater; therefore, when there is a storm, rapid snow melt, or flood, wastewater will be bypassed. Climate change is also causing increased and/or unseasonal rain events, which is leading to more sewage bypasses in certain municipalities.

Bypasses can also occur when the wastewater system in an urban area decays or when its infrastructure can no longer manage the volume of wastewater produced by a population.

Are there different types of bypasses?

Yes! A sewage bypass can either be primary or secondary.

A primary sewage bypass is the most harmful kind of bypass; This means the sewage completely bypasses any form of treatment and raw sewage flows directly to the waterbody.
A secondary sewage bypass consists of a bypass where the wastewater receives primary treatment. This can mean the wastewater receives basic treatment, such as large solid filtration and/or a primary chlorine treatment.

How sewage bypasses affect human health

Sewage-polluted waters can contain all kinds pathogens, heavy metals, pharmaceuticals, and chemicals that can lead to illness and infection. There are increased health risks associated with contact with water contaminated by a bypass. The bacteria, viruses,and parasites, can cause diseases and infections ranging in severity. Gastroenteritis, ear, nose, and throat infections and rashes are common risks associated with exposure to contaminated water. More severe health risks include cholera, dysentery, infectious hepatitis, and severe gastroenteritis.

Therefore, a sewage bypass can have a negative impact on human health in many ways. Health is impacted by the pathogens, heavy metals, and chemicals in the water. The pathogens can lead to contracting waterborne diseases such as Giardiasis, as well as a broad range of symptoms including respiratory and gastrointestinal problems. Heavy metals and chemicals can produce symptoms such as nausea, vomiting, and diarrhea, as well as skin, eye, ear and nose infections.

In order to protect human health during recreational water activities, chlorine is often used during wastewater treatment as a disinfecting agent to reduce or eliminate bacteria, viruses and pathogens in the water. When the water is shocked with chlorine it destroys organic matter and microorganisms such as Salmonella, Shigella, and Vibrio cholera, removes ammonia and controls odor. However, chlorine is not effective at destroying microorganisms like Cryptosporidium and Giardia or pharmaceuticals which are present in wastewater.

Plants and animals suffer too

Sewage and stormwater pollution are also harmful to aquatic life. The standards for protection of swimmers and recreational water users are identical to the standards for the protection of fish, plants, and other life in the lake. Even if humans avoid contact with recreational waters, this pollution will have an impact on the natural environment.

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