Impact of natural organic matter on bromate removal in the sulfite/UV-L advanced reduction process

Advanced reduction processes (ARPs) are treatment processes that involve combining reducing reagents and activating tools to produce highly reactive reducing free radicals. The process has proven effective for treating oxidized contaminants, and the effects of process variables on the degradation kinetics of various target contaminants have been investigated in our previous studies. In natural environments, natural organic matter (NOM) is found in surface or ground water. NOM absorbs UV light and can react with photochemically produced radicals, thus affecting target contaminant photochemical reactions and further influencing the efficiency of ARP. This study examines the impact of humic acid (HA) and Suwanee River NOM on bromate reduction rates with UV irradiation using a low-pressure mercury UV lamp. The effects of the sulfite dose, solution pH, and light intensity are studied and the pseudo-first-order rate constants in the presence of HA (k_obs,HA) are compared to those observed in the absence of HA (k_obs). At low HA concentrations of 1 mg L⁻¹, k_obs,HA was larger than k_obs; however, k_obs,HA was less than k_obs at higher HA concentrations. Furthermore, k_obs,HA did not increase with increasing sulfite doses in the presence of HA, which is unlike the behavior of k_obs.