Simultaneous degradation of contaminants of emerging concern and disinfection by solar photoelectro-Fenton process at circumneutral pH in a solar electrochemical raceway pond reactor

Abstract

Simultaneous contaminants of emerging concern (CECs) removal and wild microorganisms' inactivation was evaluated by applying solar photoelectro-Fenton (SPEF) process in actual secondary effluent collected from a real municipal wastewater treatment plant (MWWTP). 20 L of a mixture of four CECs was used as model pollutants (200 μg/L of acetaminophen, caffeine, sulfamethazine, and sulfamethoxazole each one). The SPEF process was carried out on fully sunny days, at circumneutral pH using the complex Fe³⁺-EDDS, in a solar electrochemical - raceway pond reactor (SEC-RPR). Initially, the optimal conditions for CECs degradation were determined using a response surface model based on current density, iron complex concentration and Fe³⁺-EDDS addition time (to allow previous accumulation of H₂O₂) as model inputs. A current density of 24.6 mA/cm², a Fe³⁺-EDDS complex concentration of 0.089 mM and 3.8 min of previous H₂O₂ accumulation were the resulting optimum conditions that were afterwards applied for the simultaneous degradation of the CECs synthetic mixture and wild microorganisms inactivation in actual secondary effluent. About 85% CECs removal and complete E. coli inactivation were achieved in 30 min, approximately, while E. faecalis and total coliforms could be inactivated under detection limit in 60 min and 75 min, respectively.

Keywords: Circumneutral pH; Pilot plant; Real secondary effluent; Response surface model; Solar wastewater treatment.