Impact of Wastewater Treatment Plant Capacity and Treatment Process on the Dynamics of Antimicrobial Resistance Determinants

The proliferation and spread of antimicrobial resistance genes (AMR) is a global health concern. Thus, it is important to understand and mitigate their fate in the environment. The removal and emergence of antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs) has not been extensively reported based on the operational capacity and treatment system. This study quantified antibiotic-resistant bacteria (ARBs), heavy metals, and antibiotic resistance genes (ARGs) that confer resistance to antibiotics such as aminoglycosides, macrolides, quinolones, tetracyclines, beta-lactams, sulphonamides, and the intI 1 and 16S rRNA genes in four different WWTPs situated along the Musi River in Hyderabad, Southern India. ARGs were present in all treated samples of WWTPs. Although the absolute abundances of ARGs were reduced by 50–99% from influents to effluents, significant levels of ARGs, notably sul2 , were still found in WWTP effluents. Seasonal differences in ARG levels between influents, effluents, and sludge were not significant, except for blaCTX-M in sludge. ARG removal efficiency was significantly higher in anaerobic/anaerobic-aerobic system than aerobic alone. Additionally, the abundance of ARBs in sludge was influenced by the treatment process, with higher absolute abundance observed in Upflow Anaerobic Sludge Blanket systems and higher relative abundance in Sequencing Batch Reactors. This research highlights the importance of plant overcapacity and treatment processes in the effective removal of ARBs and ARGs. These factors should be considered during the design and implementation of WWTPs to mitigate the risks of AMR emergence associated with WWTPs.