Low concentration peroxymonosulfate and UVA-LED combination for E. coli inactivation and wastewater disinfection from recirculating aquaculture systems

Under Minamata Convention restrictions, mercury-free UV source was in need for ultraviolet disinfection in recirculating aquaculture systems (RAS). Ultraviolet emitting diodes (UV-LEDs) seemed a potential mercury-free UV source and had gained increasing attention in water disinfection. In this study, a mercury-free UVA-LED and low concentration peroxymonosulfate (PMS) combination was proposed for E. coli (CGMCC 1.3373) inactivation and real RAS wastewater disinfection. Results showed that UVA-LED and low concentration PMS combination enhanced E. coli inactivation over UVA-LED alone. A synergistic effect on E. coli inactivation with synergy factor of 58.7 % was found when combining UVA-LED irradiation with 1 mg/L PMS. Kinetic rate constant increased by up to 139 % by UVA-LED and 1 mg/L PMS combination, which implied the required UV fluence to 2-log E. coli inactivation was saved up to 42 %. Also, UVA-LED and 1 mg/L PMS combination showed disinfection potential for real RAS wastewater treatment. Mechanism study revealed that the Cl−, ·OH and SO4·- played important roles and ·OH was dominant radical in saline solution by UVA-LED/PMS process compared to that in phosphate buffered solution(PBS). The E. coli inactivation was caused by UVA-LED irradiation and reactive species generated in UVA-LED/PMS system. Our study provided a potential strategy to introduce the mercury-free UV-LED into RAS and a better understanding of UVA-LED/PMS disinfection process.