Combining UV and Free Chlorine in Pilot-Scale Experiments: Disinfection Efficacy, Byproducts, and Microconstituents

Chlorine and UV are the most common disinfectants used for wastewater treatment, and combining them may provide advantages such as better disinfection efficacy, improved reliability, and fewer disinfection byproducts. Previous bench-scale experiments showed that free chlorine and UV provided effective disinfection of MS2 coliphage, poliovirus, adenovirus, and total coliform. This study continued that work by investigating combined UV/free chlorine in a continuous-flow pilot system. Results confirmed effective disinfection of MS2 coliphage and total coliform. The combined disinfection scheme also maintained trihalomethanes, cyanide, and N-nitrosodimethylamine at acceptable levels, and decreased concentrations of some pharmaceuticals and other microconstituents. Overall, these results confirm the benefits of using multiple disinfectants and indicate that combined UV/free chlorine is a promising disinfection technology for disinfection of wastewater effluents and recycled water.