Design, construction and efficiency analysis of bagasse-based charcoal packed horizontal lab-scale wetland for the removal of antibiotic-resistant bacteria

Antibiotic-resistant bacteria (ARB) pose a significant and growing threat to public health, particularly in wastewater environments where they can persist and propagate, exacerbating the global antibiotic resistance crisis. Conventional wastewater treatment methods often fall short in effectively removing ARB and associated contaminants, creating an urgent need for innovative and sustainable solutions. This research addresses this critical gap by investigating the use of a lab-scale horizontal subsurface flow constructed wetland (CW) planted with Typha latifolia and Phragmites australis to enhance domestic wastewater treatment. Biochar was selected as the substrate medium due to its high adsorption capacity and ability to support microbial communities that contribute to contaminant degradation. The CW system was operated at a flow rate of 3.8 US gallons/day and a moderate organic loading rate, with influent concentrations of 698 mg/L for chemical oxygen demand (COD), 376 mg/L for biological oxygen demand (BOD), 43 mg/L for nitrogen and 51 mg/L for sulfate. The results showed that the removal efficiencies of various physiochemical parameters were 53%, 57%, 81%, 80%, and 81% for total dissolved solids (TDS), COD, BOD, total nitrogen and total sulphate, respectively. Importantly, antibiotic-resistant bacteria were reduced by 99%, highlighting the system's capability to mitigate the spread of multidrug-resistant (MDR) strains. Screening for antibiotic-resistant β-lactamase genes revealed that blaTEM was detected in 50% of MDR isolates from influent samples, while blaCTX-M was absent in both influent and effluent. These findings emphasize the potential of constructed wetlands with biochar as a sustainable and cost-effective solution for addressing the dual challenges of environmental pollution and antibiotic resistance. This study provides critical insights into the development of advanced wastewater treatment technologies to combat emerging public health threats.