DISINFECTION BY-PRODUCT REDUCTION USING ON-SITE GENERATED MIXED OXIDANTS

The US EPA Stage 1 Disinfectants and Disinfection By-Product Rule (D/DBP) is driving utilities to look for methods to reduce by-product formation, particularly formation of Total Trihalomethanes (TTHMs) and the five Haloacetic Acids (HAA5). Conventional chlorination, the most commonly used water disinfectant, is notorious for its tendency to form these byproducts in surface water, whether applied in gaseous, liquid, or solid form. Additionally, each form of chlorination has its own safety or handling issues. Alternatives to chlorination, such as ozone, chlorine dioxide and UV, do not provide the chlorine residual required by the EPA. Moreover, ozone and chlorine dioxide present their own by-product concerns with the possibility of bromate and chlorite formation. On-site generated mixed oxidants have a demonstrated track record of reducing both TTHMs and HAA5 without the attendant problems associated with bromates, chlorites, or safe handling. Contributing factors to reduced by-product formation with mixed oxidants may include the presence of non-chlorine oxidants, chlorine residual maintenance with a reduced oxidant dose, elimination of biofilms, and enhanced microflocculation effects.