Inactivation of bacteria and helminth in wastewater treatment plant effluent using oxidation processes

The contamination of bodies of water by raw and even treated sewage is worrying because pathogens that affect public health and the environment are not fully eliminated in wastewater treatment systems. The disinfection step is an important barrier to adopt to reduce this contamination. However, widely used disinfectants such as chlorine do not guarantee the inactivation of resistant organisms such as spore-forming bacteria and helminth eggs. This study evaluated the effectiveness of processes of peroxidation (H₂O₂), ultraviolet radiation (UV) and peroxidation assisted by ultraviolet radiation (H₂O₂/UV) in terms of reduction and inactivation of total coliform bacteria, Escherichia coli, helminth eggs and larvae present in a treated sewage. Doses of UV radiation of 70 mJ cm⁻² and hydrogen peroxide concentration of 30 mg L⁻¹ were used. The number of bacteria reduced after UV and H₂O₂/UV processes was 3 and 4 log, respectively. An average reduction of 59% in the number of eggs was verified when using H₂O₂, UV, and H₂O₂/UV processes. Helminth larvae were reduced by 24% after H₂O₂ and UV; the process H₂O₂/UV did not reduce the number of larvae. Statistically significant differences between the processes for both organisms were not observed.