Eco-friendly and cost-effective Fe-IDS Fenton processes for the inactivation of antibiotic-resistant bacteria in MBR effluents

Antibiotic resistance is a critical global challenge. Urban wastewater treatment plants (UWTPs) are key sources of this problem, discharging antibiotic-resistant bacteria (ARB) into the environment, highlighting the importance of effective wastewater treatment for public and environmental health. This study explores the use of the biodegradable organic complex iron iminodisuccinate (Fe-IDS) in Fenton and solar photo-Fenton processes for ARB inactivation in membrane bioreactor effluent (MBR-E). The effect of catalyst (Fe-IDS) and oxidant (H2O2) concentrations, pH (3, 6, 7, 8) and wastewater matrix were evaluated for inactivation of multidrug-resistant E. coli and enterococci, compared to conventional Fenton process under identical conditions. In real wastewater at pH 7.2, the Fe-IDS-based Fenton process achieved ∼3.8-log reduction of both E. coli and enterococci in 20 and 35 min respectively, while conventional Fenton process achieved lower inactivation (∼0.8-log and ∼0.7-log) in 20 and 30 min for E. coli and enterococci, respectively. When combined with solar light, Fe-IDS-based solar photo-Fenton achieved the same inactivation of E. coli and enterococci in 15 min and 30 min respectively, while conventional solar photo-Fenton achieved only a 1.5-log reduction of E. coli and ∼1.8-log reduction of enterococci in 15 and 30 min, respectively. After storage for 72 h, no bacterial regrowth was observed in Fe-IDS-based solar photo-Fenton-treated stored samples. In contrast, in conventional solar photo-Fenton, bacterial regrowth was observed 24 h after treatment, highlighting the superiority of the Fe-IDS-based treatments in preventing regrowth. Importantly, the cost analysis revealed that Fe-IDS-based Fenton treatment (€1.85/m3) is more economical than the conventional FeSO4-based process (€4.00/m3), mainly due to the elimination of acidification and sludge disposal steps.