Pilot-scale photocatalytic detoxification and disinfection of hazardous medical wastewater

BACKGROUND: Treatment of liquid hazardous medical wastewater produced by healthcare laboratories is a global matter that has been inadequately addressed. In this study, the potential of heterogeneous and homogeneous photocatalytic oxidation to detoxify and disinfect such effluents was investigated. Experiments were performed using two toxic effluents and one of simultaneous toxic and infectious composition in pilot scale, in a novel photocatalytic inactivation system. RESULTS: Photocatalytic experimental runs performed with both toxic effluents showed that photo-Fenton-assisted TiO2 photocatalytic oxidation under optimal conditions was the most efficient process among the tested ones, when the initial dissolved organic carbon values (DOC0) ranged from 100 to 1000 mg L-1. Furthermore, the potential of catalyst reuse was examined and verified for five sequential runs. Moreover, phytotoxicity was either eliminated or significantly reduced after photocatalytic processing under optimal conditions in the case of the second wastewater of toxic composition, while ecotoxicity showed a similar trend, highlighting the importance of extended mineralization for the removal of toxicity. The performance of the pilot photocatalytic inactivation system concerning the inactivation of bio-pollutants was tested on five different types of microbes. Four of them were completely inactivated in relatively short periods, while survival of the more resistant bacterial endospores was found to be decreased to >99% after 5 h of treatment. CONCLUSION: Toxic and infectious hazardous medical effluents are highly recalcitrant targets in terms of mineralization, detoxification and inactivation. However, photocatalytic oxidation may serve as an efficient processing tool, providing alternative or complementary solutions to this highly challenging issue. (C) 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).