Why can turbidity make disinfection less effective?

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Diagram of a water treatment plant showing the process from water inlet through mixing, coagulation, flocculation, settling, filtering, chemical treatment with chlorine, storage, and high-lift pumping to the distribution system. — water purification Water from inlets located in the water supply, such as a lake, is sent to be mixed, coagulated, and flocculated and is then sent to the waterworks for purification by filtering and chemical treatment. After being treated, the water is pumped into water mains for storage or distribution.

Turbidity refers to the cloudiness of water caused by suspended particles. It can make disinfection less effective because these particles can physically shield harmful bacteria, viruses, and protozoa from disinfectant chemicals or ultraviolet radiation.

When microbes are protected by suspended matter, they may survive the treatment process, posing a significant risk to public health. To ensure the efficacy of disinfection, water treatment facilities must first remove these particles through processes such as coagulation, flocculation, sedimentation, and filtration.1