Mechanisms for TTHM and HAA5 Reduction using an On-Site Generated Oxidant Solution

On-site generation of mixed oxidants may reduce the formation of Total Trihalomethanes (TTHM) and Haloacetic Acids (HAA5) to acceptable levels for compliance with the US EPA Stage 1 Disinfectants and Disinfection By-Product Rule (DBPR). Superior disinfection efficacy and disinfection by-product (DBP) reductions ranging from 30% to 50% at existing sites give evidence for the presence of other oxidants beyond chlorine in the mixed-oxidant solution. These other oxidants are responsible for elimination of biofilm, a longer-lasting chlorine residual at a reduced dose, and removal of precursors in pretreatment. All three of these factors contribute to the reduced formation of DBPs with use of mixed oxidants.