Neutral (Fe3+-NTA) and acidic (Fe2+) pH solar photo-Fenton Vs chlorination: Effective urban wastewater disinfection does not mean control of antibiotic resistance

Abstract

Solar photo-Fenton (SPF) process in raceway pond reactors was investigated at neutral pH by Fe3+-NTA complex and at acidic pH by Fe2+and compared with chlorination process in E. coli inactivation, antibiotic Trimethoprim (TMP) and antibiotic resistance genes (ARGs) removal from secondary treated urban wastewater. E. coli inactivation below the detection limit (DL) was achieved in less than 15 min under acidic pH. At neutral pH, the DL was reached in 60 min treatment with 0.2 mM of Fe3+-NTA and 4.41 mM of H2O2. In contrast, the removal of TMP (50 µg/L) by SPF was higher at neutral pH (95%) compared to the acidic pH condition (80%). Although chlorination (10 mg/L chlorine dose) inactivated E. coli below the DL between 2.5 and 5 min, no degradation of TMP was observed. Target ARGs (quinolone, sulphonamides, β-lactams, cephalosporins and tetracycline classes), class 1 integron integrase (intI1) and the 16 S rRNA gene, were only slightly removed under realistic conditions (32% and 23% as max removals of intl1 by chlorination and SPF at acidic pH, respectively) and may not effectively control the potential of antibiotic resistant spread under the mild oxidation conditions investigated in this study.