Sustainable photolyzers for activation of peroxosulfuric acids in the reclaiming treatment of municipal wastewater

In this work, a photolytic reactor has been developed for the activation of oxidants by ultraviolet radiation, resulting in the generation of radical species. It has been integrated with a specially designed electrolyzer to efficiently generate oxidants from the electrolysis of sulfuric acid solutions. The photoreactor is made from low-cost materials (mainly PVC pipes and fittings) to ensure it can be easily replicated, even in low-income countries. It achieves a plug flow of the water being treated, resulting in very effective irradiation with results superior to those achieved by laboratory systems that use several times more specific energy. The integrated system has been validated in the treatment of effluents from a municipal wastewater treatment plant that has previously undergone a nanofiltration process. Results demonstrate that it can completely eliminate the presence of pathogens such as E. coli, resistant genes such as sul1, and emerging contaminants like iopromide, diclofenac, sulfamethoxazole, and venlafaxine, with oxidant doses like those proposed in other studies on the subject. This research highlights some of the problems presented by using sulfate-based oxidants for the treatment of these effluents and warns that future work will need to consider process intensification in order to minimize the problem of secondary saline contamination, which results from the accumulation of sulfate from the electrochemical generation and the subsequent dosing of peroxosulfuric acids to wastewater effluents.