What Is the Purpose of Wastewater Disinfection?

Wastewater can carry bacteria, viruses, protozoa, and other organisms. Some can cause illness. Earlier treatment steps remove many of them, but some may remain. Disinfection provides another barrier before the water reaches a river, lake, ocean, groundwater system, or reuse system.

Disinfection does not make wastewater into drinking water. It also does not remove every chemical or every solid. Its main purpose is to inactivate, or make unable to cause infection, the target organisms required by the facility’s permit.

For example, clear-looking effluent can still contain organisms too small to see. An operator cannot judge disinfection by appearance alone. Equipment readings, samples, lab results, and plant records are needed to show whether the process is working.

Think of disinfection as a controlled barrier. The operator cannot see the organisms being inactivated. Instead, the operator proves that the barrier is working by keeping the process inside its required conditions and checking the final water with an approved test.