Magnetic coconut shell biochar driven leachate activated sludge system treatment efficiency, antibiotic resistance...

Explored the effects of magnetic coconut shell biochar (MCSB) with different concentrations (5 and 8 g/L) on the anaerobic/aerobic (A/O) biodegradation performance, antibiotic resistance genes (ARGs), and bacterial community of landfill leachate. The optimal concentration of MCSB (5 g/L) promoted the degradation of total organic carbon (80.01 % and 76.36 % removal rates in A/O systems), total nitrogen (65.27 % and 50.26 % removal rates in A/O systems), and tetracycline antibiotics (TCs, including tetracycline, oxytetracycline, and chlortetracycline, with removal rates of 81-88 %), while 8 g/L MCSB had a more significant degradation effect on total phosphorus. 5 g/L MCSB effectively stimulated the secretion of extracellular polymers in sludge (with concentrations reaching 449.46 and 434.23 mg/g VSS in A/O systems), while 8 g/L MCSB increased the deposition of heavy metals in sludge. It was worth noting that the 8 g/L MCSB (anaerobic reactor) reduced the relative abundance of ARGs in the leachate by 28.22 % (compared to the 5 g/L anaerobic reactor), reflected in the decrease in the abundance of tetA, tetB, tetM, and tetQ, but increased the reproductive risk of ARGs in anaerobic sludge microorganisms. TCs induction and environmental factor pressure regulated the proliferation of dominant bacterial species in microbial communities, which might alter the composition of ARGs in bacteria through a co selection mechanism. MCSB provided growth space for functional microorganisms and became a vital factor in shaping the spread of ARGs and host microbial transmission by stimulating microbial metabolism, increasing their activity, and altering the abundance of functional microorganisms. From a practical application perspective, the continuous flow A-O combination process was the preferred solution. This study proposes promising magnetic biochar material, which provides technical reference for promoting A/O biodegradation of TCs containing leachate and controlling the environmental pressure of ARGs.