Disinfection of biologically treated sewage using AlGaN-based ultraviolet-C light-emitting diodes in a novel reactor system

The application of ultraviolet (UV) disinfection systems in water and wastewater treatment plants is highly recommended due to their high inactivation efficiency and absence of disinfection by-products. UV light-emitting diodes (UV-LEDs) are alternatives for UV mercury lamps due to its longer lifetime, improved efficiency, robustness, lesser start-up time, and environment-friendly. In this research study, the log inactivation of total coliform, fecal coliform, Escherichia coli (E. coli), and fecal streptococci were determined in biologically treated sewage using AlGaN-based UVC-LED reactor system operated at a wavelength of 275 nm. A novel reactor system with a baffled arrangement of UV-LEDs was developed and evaluated to improve the inactivation efficiency. The performance of the laboratory-scale UVC-LED reactor was evaluated under batch mode. AlGaN-based UVC-LED reactor yields high log inactivation in terms of coliform removal, even in the biologically treated sewage of heterogeneous character. The experimental results showed that the log inactivation of total coliform, fecal coliform, E. coli, and fecal streptococci was 5.25, 5.45, 5.00, and 4.70 log, respectively. With improved reactor design, increased output power, and reduced cost, AlGaN-based UVC-LEDs could be scaled-up for full-scale application in sewage treatment plants.