A new solar photo-Fenton strategy for wastewater reclamation based on simultaneous supply of H2O2 and NaOCl

Abstract

This study presents, for the first time, the concurrent supply of the oxidants H2O2 and NaOCl in solar-driven Fenton-like processes at neutral pH with ferric nitrilotriacetate (Fe3+-NTA) for wastewater reclamation. Simultaneous Escherichia coli (E. coli) inactivation and the removal of the antibiotic sulfamethoxazole (SMX) at 50 μg/L in municipal effluents were investigated in 5-cm deep raceway pond reactors. First, the individual effects of reagent concentrations (1.47, 2.94 and 4.41 mM for H2O2; 0.134, 0.269 and 0.403 mM for NaOCl; 0.1 and 0.2 mM for Fe3+-NTA) on the economic efficiency (in terms of mass of SMX eliminated per Euro and per hour to attain complete E. coli inactivation and more than 50% of SMX removal) were considered. The highest economic efficiencies were 141 mgSMX/€·h with H2O2 and 222 with NaOCl, the reaction times being 105 and 60 min, respectively. Second, a new strategy for solar photo-Fenton with the combination of the most cost-effective conditions (1.47 mM H2O2 – 0.134 mM NaOCl – 0.1 mM Fe3+-NTA) was carried out in secondary effluents from two treatment plants with different technologies. Economic efficiency was substantially affected by wastewater composition, ranging from 178 to 1131 mgSMX/€·h with treatment times between 60 and 10 min, significantly improving the reported results for conventional solar photo-Fenton to date.