Improving UV/H2O2 performance following tertiary treatment of municipal wastewater

Abstract

The ability of UV/AOP to treat trace organic contaminants (TOrCs) in wastewater is inhibited by (1) UV light-absorbing species and (2) hydroxyl radical (˙OH) scavenging species. We address these challenges by investigating four diverse technologies, single-stage biofiltration, sequential biofiltration, coagulation–flocculation–sedimentation–filtration (CFSF), and nanofiltration, as options for improving water quality conditions just prior to UV treatment, with and without added hydrogen peroxide (H₂O₂). By evaluating UV₂₅₄ transmittance (UVT), ˙OH scavengers, and ˙OH steady-state concentrations, we found nanofiltration treatment to produce the most favorable pre-UV and UV/H₂O₂ water quality conditions. In comparing CFSF, single-stage biofiltration and sequential biofiltration treatment, CFSF treatment resulted in the highest increase in UVT and all three technologies reduced the scavenging capacity by ∼24% despite differences in removal of typical ˙OH scavengers. UV and UV/H₂O₂ performance were evaluated by tracking the degradation rates of 11 targeted TOrCs for each pre-UV/H₂O₂ treatment scenario. Applying the additional treatment, average pseudo first-order degradation rates of TOrCs under UV/H₂O₂ increased by 20 to 92%, informing potential strategies to increase the oxidation potential of UV/AOP systems applied to wastewater.