Abundance of Antibiotic Resistance Genes in Two Municipal Wastewater Treatment Plants and Receiving Water in Atlantic Canada

Abstract

Antibiotic resistance genes (ARGs) in pathogenic bacteria confer resistance to many clinically important antibiotics and will, if found in treated wastewater and the environment, threaten public health. Using quantitative (qPCR), ARGs were assessed throughout two municipal wastewater treatment plants (WWTPs) that use different types of biological treatment (aerated lagoons (AL) vs. biological nutrient removal (BNR)). Furthermore, ARG presence was assessed in the receiving river of the AL plant upstream and downstream of the effluent discharge location. Both WWTPs reduced ARG levels, however ARGs persisted through the treatment. Relative abundance of ARGs (per 16s rRNA gene) was slightly decreased at the BNR plant, suggesting this treatment type improved removal of resistant bacterial populations. ARGs were detected both upstream and downstream of the AL WWTP, however higher levels were detected downstream. Overall results suggested that these WWTPs cannot remove total ARGs and are impacting ARG levels in the receiving environment.