Low-pressure UV/Cl2 for advanced oxidation of taste and odor

Ultraviolet- (UV-) based methods of advanced oxidation processes (AOPs), such as UV/hydrogen peroxide (H2O2), can be used for removal of taste and odor contaminants in drinking water. However, significant disadvantages to UV/H2O2 include chemical costs associated with the addition of peroxide and quenching residual peroxide and the operational challenge of balancing peroxide quenching with secondary disinfection needs. Recent work has shown that chlorinating before UV can yield advanced oxidation of organic contaminants under certain conditions. This article uses modeling of the photochemistry of UV/H2O2 and UV/chlorine (Cl-2) to compare their relative oxidation efficiencies for geosmin and 2-methylisoborneol. Although UV/H2O2 has a decided advantage with respect to oxidation efficiency in surface waters at neutral to basic pH, UV/Cl-2 can provide a cost-effective AOP alternative at low pH. Tests in one water sample showed minimal trihalomethane and haloacetic acid formation when using UV/Cl-2.