Changing Hydrogen Peroxide Quenching in an AOP to Reduce Chlorate Levels in Purified Recycled Water

The Gibson Island AWTP experienced elevated levels of chlorate in its treated water due to high sodium hypochlorite dose required to quench hydrogen peroxide residual from the advanced oxidation process and to breakpoint chlorinate monochloramine. Chlorate is formed as sodium hypochlorite degrades over time. Measures to minimize chlorate levels in the sodium hypochlorite solution resulted in some improvement in the treated water chlorate levels, however to ensure the plant consistently achieved the operational target of 0.8 mg/L of chlorate significant reduction in sodium hypochlorite dose was required. Implementation of a sodium bisulfite quenching system provided for reduction in sodium hypochlorite dose and resulted in chlorate levels in the treated water consistently below the operational target.