Enhancing ceftriaxone sodium degradation in anaerobic sludge through co-metabolic sludge addition without supplementary substrates

Bioaugmentation can effectively improve biodegradation of recalcitrant compounds through adding specific substances or microbial consortia. In this study, a small quantity of co-metabolic sludge was introduced to conventional anaerobic sludge system (with a ratio of 1:4 between co-metabolic sludge to conventional anaerobic sludge), and enhancement effect on ceftriaxone sodium (CTX) biodegradation was investigated. The addition of co-metabolic sludge significantly improved CTX removal efficiency in anaerobic sludge system (with an average increase of 20.6 %), and the maximum removal of CTX reached 60.8 %. Co -metabolic sludge also elevated extracellular polymeric substance (EPS) secretion, increasing protein and polysaccharide contents by 34.66 % and 40.64 %, respectively, which mitigated CTX toxicity. Compared to conventional sludge, the system after bioaugmentation exhibited 4.3 % and 2.5 % increases in enzyme diversity and microbial population, respectively. Relative abundances of resistance genes evgS, NmcR, and Burkholderia pseudomallei Omp38 increased by 2.8 %, 7.6 %, and 2.5 %, respectively, which benefited improving CTX degradation. Furthermore, the abundances of pathways Two-component system (TCS) and Quorum sensing (QS) increased by 20.0 % and 21.7 %, respectively, indicating their involvement in bioaugmentation-mediated CTX degradation. Overall, this study strengthens CTX degradation in conventional sludge system with addition of some co-metabolic sludge, which provided a novel strategy for CTX wastewater treatment.