Ammonia-mediated iron cycle for oxidizing agent activation in advanced oxidation process

Abstract

Removing ammonia (NH4+-N) and recalcitrant organics from low carbon/nitrogen wastewater requires a large amount of chemical reagents and energy. This work reports a new advanced oxidation process to remove recalcitrant organics with the assistant of NH4+-N in low carbon/nitrogen wastewater. Specifically, NH4+-N in wastewater mediated Fe(II)/Fe(III) cycle for the activation of oxidation reagent (e.g., H2O2) (ammonia-mediated AOP) to improve the removal of recalcitrant organics. In ammonia-mediated AOP, NH4+-N, recalcitrant organics, and PO4-P in wastewater were removed by 88.2%, 80.5% and 84%, respectively, with a low H2O2 consuming of only 5 mg/L. The removal efficiency of recalcitrant organics in the ammonia-mediated AOP increased as the concentration of NH4+-N in wastewater increased. Recalcitrant organics can be removed with an efficiency of 74∼82%, when the influent pH was 6∼6.8. This work provides a new and cost-effective approach to drive the iron cycle in Fenton treatment using NH4+-N from wastewater as mediator.