Synergistic role of active chlorine species and hydroxyl radicals during disinfection and mineralization of carwash wastewater

The effect of UVC light (λ = 254 nm) on chlorine generation through a sequential combination of three wastewater treatments was evaluated to disinfect and mineralize carwash wastewater. Electrocoagulation, electrooxidation, and catalysis processes were sequentially performed in the presence and absence of UVC radiation. Toxicity changes during the photoEC process were detected using Artemia salina as a model organism, which improves the LD 50 of the raw carwash effluent from 13.4 to 52.1. Disinfection trials showed a colony-forming unit decrease by approximately 90%; however, the mineralization degree was only 7%. The subsequent electrooxidation treatment showed that the IrO 2 -RuO 2 anode generated the highest concentration of active chlorine species (400 mg L −1 at pH = 3). However, during UVC irradiation, a better efficiency in producing • OH radicals was observed. Thus, the total organic carbon abatement using photoelectrocoagulation followed by photoelectrooxidation of carwash wastewater was 57%. As a final step, photocatalysis using crystalline TiO 2 increased the mineralization degree, reaching 80% at the end of the tandem protocol. Thus, it was proposed that the sequential UVC-based treatments degrade organic matter and reduce pathogens in a raw carwash effluent in the presence of chloride ions.