Modified photo-Fenton for degradation of emerging contaminants in municipal wastewater effluents

Abstract

As normal municipal wastewater treatment plants (MWTP) are not able to entirely degrade xenobiotic substances, this study focuses on modified solar photo-Fenton treatment (5 mg L −1 Fe, initial pH ≈ 7) of a municipal wastewater treatment plant (MWTP) effluent. However, effluents do not contain compounds which could form photoactive Fe 3+ complexes. The use of ferrioxalate, humic substances (HA) and mixing the MWTP effluent with small amounts of influent could be justified to form photoactive Fe 3+ complexes. All experiments were done in MWTP effluent spiked (5 or 100 μg/L) with 15 emerging contaminants (ECs) using a pilot compound parabolic collector (CPC) solar plant designed for solar photocatalytic applications. Dissolved organic carbon and UPLC–UV (with prior solid phase extraction) were applied for evaluating the results. The oxalate-enhanced process provided satisfactory EC degradation results but low residual pH of the treated water. HA (10 mg L −1) enhanced the process, balancing degradation time and residual pH. Mixing of MWTP influent and effluent delivered rather disappointing results, as EC degradation was unsuccessful in all cases tested.