Perchlorate reduction by the sulfite/ultraviolet light advanced reduction process.

Advanced reduction processes (ARPs) are a new class of water treatment processes that combine activation methods and reducing agents to form highly reactive reducing radicals that degrade oxidized contaminants. The combination of sulfite with low-pressure ultraviolet light (UV-L) is the most effective ARP tested to date. In this study, batch kinetic experiments were conducted to characterize the kinetics of perchlorate destruction by the sulfite/UV-L ARP. Experimental variables were pH, sulfite concentration, temperature and UV-L irradiance. The rate of perchlorate degradation by sulfite/UV-L increases with increasing pH and temperature and increases with increasing sulfite concentration to a maximum and then decreases due to lack of mixing within the reactor system used. Efficiency of perchlorate degradation was measured as a quantum yield and was observed to decrease with increasing sulfite concentration. The ultimate product of perchlorate degradation by the sulfite/UV-L ARP is chloride, but chlorate was detected as an intermediate.