The drinking water disinfection performances and mechanisms of UVA-LEDs promoted by electrolysis

In this study, the UVA (Ultraviolet A) drinking water disinfection was promoted by electrolysis. The influences of the UVA, electrolysis current, bubbling and temperature were investigated. The disinfection mechanisms and bacterial reactivation had been studied. The results revealed that the treatment time needed to reach the DL (detection limit, about 5.4 log removal) was shortened from 180 to 80 min by the electrolysis. The total electricity consumption decreased from about 126-57.0 kJ/L. Compared with increasing the UVA irradiation, increasing the electrolysis current in a certain range was more preferred to improve the disinfection rate. Oxygen bubbling or higher temperature could enhance the E. coli inactivation. The quenching experiment and EPR (Electron paramagnetic resonance) detection confirmed that ROSs (¹O₂, ·O₂^- and ·OH) played important roles for the disinfection. Compared with the treatment with UVA alone, the cell membrane damage was more severe by the promoting method. In addition to the dramatically reduced enzyme activity, the synergistic process degraded most of the bacterial genomic DNA, and the bacteria were completely killed. Therefore, hybrid with electrolysis is a better way for the application of the UVA-LED disinfection.