Impact of alternative oxidants on the formation of disinfection by‐products and assimilable organic carbon

Abstract

Pilot scale studies were conducted to investigate the effect of oxidation at various stages of water treatment process. Impact of pre‐ and postoxidation (before coagulation and after filtration, respectively), on the formation of disinfection by‐products (DBPs) and assimilable organic carbon (AOC) was investigated. Based upon the oxidant (ozone or ozone + hydrogen peroxide) dosages evaluated, no consistently significant differences, in terms of DBP reduction and AOC formation, were observed in pre‐ vs. postoxidation scenarios. The ozone dosage required in postoxidation was found to be less than half of that required in preoxidation to achieve similar DBP reductions and AOC results. Addition of hydrogen peroxide along with ozone did not result in consistently improved treatment performance. Bench and pilot scale studies were conducted to investigate the effect of ozone oxidation pathway on the reduction of DBPs. It was found that, while ozone alone was not particularly effective for long term reduction of DBPs, ozonation in the presence of radical scavenging bicarbonate resulted in statistically significant higher reduction of DBP precursors.

Keywords:

• Assimilable organic carbon
• disinfection by‐products
• ozone
• bicarbonate