Antimicrobial resistance control in wastewater treatment plants: from removal efficiency to resistance-risk reduction

Abstract

ABSTRACT Flow diagram showing AMR-related constituents moving from municipal, hospital-influenced, and industrial or pha rmaceutical wastewater through primary treatment, biological treatment, solids separation, and disinfection or advanced polishi ng. Outputs include treated effluent, reclaimed water, sludge or biosolids, and residual streams. These connect to receiving wat ers, irrigation or reuse, land application or further handling, and return-to-treatment or separate management pathways. Resista nce-risk endpoints include reduced viable antibiotic-resistant bacteria, reduced ARG burden, reduced MGE dissemination pote ntial, reduced antibiotic and co-selective pressure, and safer discharge or reuse. The diagram emphasizes target-specific treat ment, pathway-based monitoring, and management of effluent, sludge, and residual streams. Wastewater treatment plants (WWTPs) receive antibiotic-resistant ba cteria, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), antibiotic residues, disinfectants, metals, and oth er co-selective pressures from municipal wastewater and high-risk hospital, industrial, and pharmaceutical streams. Conventio nal performance indicators do not capture viability, gene persistence, mobility, selection pressure, or exposure relevance. Perce ntage removal or single-gene log reduction may therefore misrepresent resistance-risk reduction because resistance-related tar gets and residual streams respond differently across treatment processes. This structured critical review evaluates conventiona l and advanced WWTP processes and develops a pathway-specific framework for effluent, sludge, biosolids, reclaimed water, concentrate, and backwash. In a representative full-scale study of three Dutch WWTPs, conventional treatment produced avera ge reductions of 1.86 log10 for selected ARGs and 2.31 log10 for Escherichia coli; in a separate representative study, ozone-bas ed advanced treatment exceeded 3 log10 inactivation of resistant bacteria under favorable conditions. Biological treatment can reduce biomass-associated AMR while transferring part of the burden to sludge, whereas disinfection can reduce viable organis ms without fully removing DNA-based ARG signals. WWTP assessment therefore combines target identity, absolute and relati ve abundance, load reduction, gene mobility, residual selection pressure, regrowth potential, and exposure context..