Disinfection of secondary treated sewage using chitosan beads coated with ZnO ‐Ag nanoparticles to facilitate reuse of treated water

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BACKGROUND Reuse of treated wastewater is necessary to augment supply of fresh water. Secondary effluent from a sewage treatment plant was disinfected using novel synthesized ZnO–Ag–chitosan beads under visible light. RESULTS Final most probable number (MPN)/100 mL after 1 h contact time under direct sunlight was 920 with a loading of chitosan, Zn and Ag of 0.4 mg L−1 each. Disinfection resulted from the generation of reactive oxygen species. Disinfection efficiency reduced by 10% and 20%, when the total suspended solids (TSS) concentrations in the sewage were 50 mg L−1 and 100 mg L−1, respectively, compared with that with 30 mg L−1. A 5% and 10% reduction in disinfection efficiency was observed when sulphide concentration in sewage was increased from 10 mg L−1 to 20 mg L−1 and 50 mg L−1, respectively. Disinfection efficiency of the beads decreased by 10% when nitrate concentration in the sewage increased to 30 mg L−1 from zero. These novel beads had residual disinfection ability even after removal of beads from wastewater and these beads were successfully used for disinfection in four consecutive cycles. CONCLUSION Successful disinfection of secondary sewage using chitosan beads coated with ZnO–Ag nanoparticles was established for the first time in this study to facilitate reuse of treated water.