Combined AOPs for potential wastewater reuse or safe discharge based on multi-barrier treatment (microfiltration-H2O2/UV-catalytic wet peroxide oxidation)

•Equation for estimation of UVC dose accumulated by the water was proposed.•Filtration, H2O2/UVC and H2O2/GAC as multiple-barrier treatment (MBT) was suggested.•The water toxicity was increased after H2O2/UVC step and reduced after H2O2/GAC.•Complete removal of H2O2 was achieved during the multiple treatments.•The quality of the wastewater after multiple barrier treatment allows its reuse.

The viability of a multi-barrier treatment (MBT) for safe discharge or potential reuse of synthetic industrial wastewater was evaluated in this study. The proposed MBT consists of microfiltration membrane pre-treatment (MF), followed by hydrogen peroxide photolysis (H2O2/UVC) using a medium pressure Hg lamp (MP) and granulate activated carbon (GAC). The synthetic wastewater (SIWW) obtained by addition of different industrial organic pollutant (orange II, phenol, 4-chlorophenol and phenanthrene) to the effluent taken from a municipal wastewater treatment plant was used in this study.At optimal operational conditions complete degradation of added contaminants, about 85% of total mineralization and total disinfection were achieved after MBT treatment. Toxicity tests with Vibrio fischeri and Paracentrotus lividus sea-urchin (fertilization and embryo-larval development assays) were conducted with water after each treatment step and drastic decrease of toxicity was observed after applied process. However, it was demonstrated that after H2O2/UVC step toxicity of water significantly increased and was even higher than that of SIWW. Novel equation for estimation of UVC dose was introduced as one of the most important scaling parameter. The main operational and maintenance cost (O&M) of MBT process was evaluated in this work. Thus, the high quality of the obtained effluent suggests its suitability for water reuse or safe discharge.