Occurrence and Removal Efficiency of Multiple Antibiotic-Resistant Bacteria in Rajshahi’s Water Supply System

Abstract

Multiple antibiotic-resistant (MAR) bacteria have recently been detected in Dhaka’s municipal water, prompting concerns about water safety in Bangladesh’s other cities. Rajshahi Water Supply & Sewerage Authority (RWASA) meets 91 % of its demand from groundwater and 9 % from the Padma River, into which untreated urban drains discharge. In this study, we first identified the thirteen most commonly used antibiotics in Rajshahi, then collected water samples from the raw river intake, each treatment‐ plant unit process, finished surface water ready for distribution, the groundwater pumping station, and household taps served by both networks. Bacterial isolation was performed via membrane filtration, and antibiotic susceptibility was assessed by the disk diffusion method following CLSI guidelines. Isolates from raw-river and intermediate treatment stages exhibited resistance to all selected antibiotics, whereas finished surface water and stagnant river samples were uniformly susceptible. Notably, no culturable bacteria were detected at the intake from Padma after repeated sampling, and post-chlorination groundwater samples showed negligible MAR presence. These findings demonstrate that RWASA’s multi-step surface-water treatment train.