Synergistic coagulation/flocculation and UV254 photo-assisted electrochemical advanced oxidation process for the efficient treatment of municipal influent wastewater.

内容摘要

This study evaluates a synergistic treatment combining coagulation-flocculation with a UV254 photo-assisted electrochemical advanced oxidation process (AOP) producing HOCl-•OH for domestic wastewater collected from the influent of a municipal wastewater treatment plant in Mexico, and fortified with ciprofloxacin (CIP), cefadroxil (CFX), sulfamethoxazole (SMX), and carbamazepine (CBZ) at 20 mg L-1 each. Coagulation/flocculation with a coagulant/biopolymer at a 1:1 ratio achieved substantial primary removal efficiencies (80.64% turbidity, 73% Chemical Oxygen Demand (COD), and 82.08% Total Organic Carbon (TOC)), with removal mechanisms strongly influenced by pharmaceutical speciation. Subsequent UV254 photo-assisted electrochemical treatment in a filter-press FM01-LC reactor equipped with a Ti/RuO2-ZrO2-Sb2O3 anode enabled active chlorine electrogeneration and photolytic radical formation. Standalone photolysis, and pure electrocatalysis (77.76% TOC elimination) resulted in negligible mineralization, confirming the necessity of the hybrid method. Optimal degradation and mineralization (99.19% turbidity, 98.36% COD, 95.65% TOC) was achieved at 30 mA cm-2, 0.2 M NaCl, 1 L min-1, and pH 4.5 (1 h) in the fortified municipal wastewater; while a TOC decrease of 94.60% was achieved in the untreated sewage influent without fortification. These results demonstrate that pH control is more critical than increasing current density, as predominance of HOCl induces UV homolysis into highly reactive •OH and Cl• radicals. Active species trapping tests confirmed the dominant role of •OH in contaminant mineralization, while energy consumption remained low (0.04-0.05 kWh m-3), indicating competitive operational performance. Complete elimination of total coliforms was achieved; while Daphnia magna bioassays revealed null toxicity at shorter treatment times than 0.5 h. Overall, this hybrid process demonstrates high mineralization efficiency for municipal wastewater conditions while identifying operational constraints relevant for pilot-scale implementation.