Advanced disinfecting and post-treating the biologically treated hospital wastewater in the UVC/H2O2 and VUV/H2O2 processes: performance comparison and detoxification efficiency

Abstract The present study compares the ultraviolet (UV)-based AOPs for the disinfection and the post-treatment of the biologically-treated hospital wastewater (BHW). It was found that the vacuum UV (VUV) photoreactor was much more efficient than the UVC photoreactor in inactivation of E. coli . A 6.4 and 3.7 log E. coli inactivation (from an initial concentration of 1.09 × 10 10 CFU/mL) was achieved in the VUV and UVC photoreactors, respectively, operated under similar conditions at the neutral pH of water. In the case of continuous-flow operation, the complete inactivation of E. coli was achieved in the VUV photoreactor in hydraulic retention time (HRT) of 3 min. However, the UVC photoreactor could not attain the same performance even at the longer HRT of 10 min. Adding H 2 O 2 to the VUV photoreactor improved the removal of total organic carbon (TOC) from the BHW. The TOC removal in the recirculated VUV photoreactor improved from 10.8%–61.7% in the reaction time of 10 min at the presence of the optimum H 2 O 2 amount of 3 mM whereas the TOC removal in the UVC/H 2 O 2 operated at the similar conditions was only 13.1%. When operated under flow-through condition, 93.6% of TOC could be removed from the BHW in the VUV/H 2 O 2 process at the HRT of 10 min where the complete bacterial inactivation and detergent removal was also achieved. The electrical energy consumption was 52.9, 12.2, and 6.5 kW h/m 3 in the UVC/H 2 O 2 , VUV and VUV/H 2 O 2 processes, respectively, when operated at the HRT of 10 min under identical conditions for TOC removal. The VUV/H 2 O 2 process could also degrade most of the residual substances in the BHW thus efficiently detoxified the BHW to the level sufficient for discharging into the water environment. Accordingly, the VUV/H 2 O 2 process is an efficient, energy-effective, and thus emerging method for the disinfection and the post-treatment of the hospital wastewater.