(644c) Electrolysis for Bromide Removal and Reduction In Formation Potential of Brominated Disinfection Byproducts From Drinking Water

Meeting the disinfectant and disinfection by-product rules is a balancing act for water utilities as they are required to decrease health risks due to microorganisms with disinfectants, while simultaneously reducing potential the health risks attributed to disinfection byproducts (DBPs), such as trihalomethanes (THMs) and haloacetic acids (HAAs). A recent concern is that water from sources impacted by salt water intrusion (e.g., in coastal regions) contain a significant concentration of bromides (210-500 ug/L), which typically leads to the formation of brominated disinfection byproducts in chlorinated and ozonated water. Studies have suggested that brominated DBPs are more toxic than their chlorinated analogs. Accordingly, bromide removal from source water prior to disinfection is essential. In the present study, the effectiveness of electrolysis for bromide removal from drinking water, as well as the formation potential of brominated DBPs in the electrolyzed water, were investigated experimentally in a specially constructed electrolysis reactor. In principle, as water is allowed to pass through electrode pairs in the reactor, negatively charged bromide ions are attracted to the anode and undergo oxidation at the anode surfaces. As a result, the bromide ion is converted into bromine which can then volatilize from the treated water source. The design and operational criteria of the proposed process were optimized by testing electrolytic reactors of different designs under various hydraulic retention times and electric current settings. The results illustrated significant reduction in bromide concentration (44%) and formation potential of brominated THMs (up to 85%) and bromated (up to 73%) at an applied current as low as 1 A. Subsequently, the proposed process was scaled up to a 2.5-gpm reactor in which a similar bromide reduction level was achieved.