Pilot-scale sulfate radical-based advanced oxidation for wastewater reuse: simultaneous disinfection, removal of contaminants of emerging concern, and antibiotic resistance genes

Wastewater reuse addresses water scarcity, but contaminants of emerging concern (CECs), pathogens and antibiotic resistance genes (ARGs) pose health and environmental risks. The European Union (EU) has enacted Regulation (EU) 2020/741, establishing wastewater reuse standards for agriculture. This study evaluates for the first time the effectiveness of four sulfate radical-based advanced oxidation processes (SR-AOPs), based on the combination of peroxymonosulfate (PMS) with O3 and H2O2, applied at pilot plant, for the simultaneous elim-ination of microorganisms, CECs, and ARGs, in actual urban wastewater treatment plant (UWWTP) effluents. The system PMS/H2O2/UV-A improved the disinfection effectiveness, compared to PMS/UV-A, especially using a molar ratio 1:3 (0.5 mM PMS:1.5 mM H2O2), achieving complete elimination of total aerobic microorganisms in 90 min. However, this double oxidation system, does not improve CECs removal compared to PMS/UV-A in neither of the two molar ratios studied (1:1 or 1:3), and none of these treatments significantly reduced the prevalence of ARGs. However, the PMS/O3 system demonstrated the ability to remove total aerobic microorganisms in 20 min and Escherichia coli in 5 min, 94 % of CECs, and 6 out of the 8 ARGs, demonstrating to be the most effective treatment. However, the system showed phytotoxicity, inhibiting seed growth by 10-30 %, probably associated with the by-products formed in the reaction between organic matter and ozone. This result highlights that SR-AOPs are promising processes with the capability to achieve the simultaneous removal of different contaminant groups, reducing the risks associated with wastewater reuse. Their application at larger scales is increasingly closer.

Automated summary

This study evaluates the effectiveness of four sulfate radical-based advanced oxidation processes (SR-AOPs) in removing microorganisms, contaminants of emerging concern (CECs), and antibiotic resistance genes (ARGs) in wastewater treatment plants. The PMS/O3 system is found to be the most effective treatment, while also exhibiting phytotoxicity.