What is the purpose of disinfection or chlorination of sewage effluent?

Disinfection or chlorination of sewage effluent serves as an added safeguard against disease. This process is crucial in reducing or eliminating pathogenic microorganisms that may remain in wastewater even after primary and secondary treatment processes. The goal is to protect public health and the environment by ensuring that the treated effluent is safe for discharge into water bodies or for reuse in irrigation and other applications.

While disinfection through chlorination is an important step, it should not be relied upon as the only form of treatment, which differentiates it from the idea that it can be a substitute for adequate treatment. Additionally, the notion that it is "always necessary" may not apply to all treatment situations, as certain methods of sewage treatment may effectively reduce pathogens to a safe level without the need for chlorination. The option regarding toxicity reflects concerns, but disinfection methods are often chosen for their effectiveness while minimizing risk, not solely based on a safety measure of toxicity. Thus, the primary role of disinfection is to enhance the safety of treated effluent and help prevent the spread of waterborne diseases.