Q._________ is/are an ideal disinfectant for waste water.

U-V Rays are the ideal disinfectant for waste water: UV irradiation kills/inactivates microorganisms without altering water quality and without leaving any chemical residue.

Disinfection is the final step in waste-water treatment, meant to destroy disease-causing microorganisms before the treated water is reused or released. Comparing the options: boiling is impractical for the very large volumes of municipal waste water; chlorination is effective but chlorine can react with organic matter to form harmful residual by-products and leaves a chemical residue; ozonisation is also effective but is comparatively costly and its effect does not persist. UV irradiation, by contrast, is regarded as the ideal disinfectant because it is a chemical-free physical p …