Quenching H2O2 residuals after UV/H2O2 oxidation using GAC in drinking water treatment

Abstract

Pilot-scale and lab-scale experiments were performed to evaluate the ability of granular activated carbon (GAC) to quench hydrogen peroxide (H₂O₂). The GAC was harvested from 5 drinking water treatment plants and included two GACs that were specifically designed for this purpose (“catalytic”), and 3 that were used solely to adsorb taste and odour compounds (“normal”). All GACs indicated very little change in performance with time for GAC up to 9 years old (the oldest tested). Batch kinetic tests revealed that the catalytic GACs had a higher reaction rate with H₂O₂ than the normal GACs, but under typical conditions (e.g. 4+ minute EBCT) the difference may not be important in practice. The observed first order decomposition rate of H₂O₂ increased linearly with the spherical surface area of the GAC particles, providing evidence that effectiveness is governed by particle size, implying that smaller GAC would be more effective for quenching H₂O₂.