Ultraviolet-chlorine combination disinfection and formation of disinfection by-products: A review

Disinfection is a key technique to kill pathogenic microorganisms in water treatment process. Dozens of disinfection treatment technologies have been developed during the past hundred years. The ultraviolet-chlorine combination disinfection possesses advantages of both UV irradiation and chlorination in killing pathogens. However, there are plenty of chemical substances in water, and more toxic disinfection by-products may be produced owing to complex chemical reactions during the combination disinfection of UV irradiation and chlorination comparing with separate UV or chlorination disinfection. Based on the collection and analysis of previous references on UV-chlorine combination disinfection treatment, the principles of UV-chlorine combination disinfection, the formation mechanisms of major toxic disinfection by-products and related influencing factors, and the optimization of operational parameters are summarized. In addition, the issues and potential challenges in future disinfection are explored as well.