Chlorination and ultraviolet disinfection of antibiotic-resistant bacteria and antibiotic resistance genes in drinking water

Abstract

This study determined the effectiveness of chlorine, UV and combination of UV/chlorine in inactivating antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG), as well as potential repair of these bacteria following disinfection processes in drinking water. Previous studies have assessed the efficacy of UV disinfection in inactivating ARBs, however, most of these studies have focused on wastewater treatment applications. The use of chlorine and UV disinfection at typical drinking water industry doses was found to not completely eliminate the resistance genes. Using 30 mg/min/L of chlorine, the inactivation of tet(A), bla-TEM1, sul1, mph(A) was 1.7-log, while a UV fluence of 200 mJ/cm2 only resulted in a reduction of up to 1.2-log of these genes. This suggests that these genes can continue to be present in distribution systems even following disinfection. On the other hand, the application of sequential UV disinfection followed by chlorination significantly reduced the ARGs and had synergistic effects compared to single disinfectant use, with a resulting synergy in the inactivation achieved (log units) ranging between 0.01 and 0.62-log across the tested ARGs. The ARBs also demonstrated the potential for re-growth following chlorination up to 5 mg/L and UV disinfection of up to 10 mJ/cm2 under the conditions of this study.