Treatment and Disinfection of Municipal Wastewater Using Synergy of Ultrasound, LEDs-UVC, and Oxidants

Treatment of municipal wastewater (MWW) is one of the potential challenges in developing/underdeveloping countries. The present work demonstrates treatment of MWW using the irradiation effect of ultrasound (US) and light-emitting diode ultraviolet (UVC). The process was further intensified using the combined effect of irradiation with H2O2/O3. MWW consisted of elevated pathogen concentrations of Enterobacter aerogenes, Escherichia coli, and other coliforms with a total coliform concentration of 12 x 103 CFU/mL. The efficiency of processes was analyzed on complete inactivation of total coliform, pseudo-first-order kinetic rate constant, synergy analysis, COD removal, and process economics. Nearly complete elimination of pathogen was observed for the US+UVC effect in 20 min, whereas 83 and 98.6% of removal were observed for US and UVC effects, respectively. Further combination of US and UVC with H2O2 showed an enhanced inactivation rate for total coliforms. The least treatment time of 10 min was required for US-UVC-H2O2 for complete inactivation with a pseudo-first-order kinetic rate constant of 3.56 +/- 0.3 min-1. The synergy coefficient for UVC-H2O2 (1.9) was much higher as compared with other effects. The operational cost for the UVC-H2O2 process was 12.6 times higher than that for the UVC-O3 process, with a synergy coefficient of 1.1. Synergy of US/UVC with H2O2/O3 reduced the initial oxidant requirement. It was reduced by 50% compared to nonsynergy studies. Based on process analysis, UVC-O3 was observed as the most suitable combination for the inactivation of pathogens present in MWW with a COD removal of 91.1% and an operational cost of 0.3$/m3. The synergy of UVC-O3 has potential beneficial effects to overcome the limitation of individual processes and development of large-scale processes.