Reduction of metronidazole in municipal wastewater and protection of activated sludge system using a novel immobilized Aspergillus tabacinus LZ-M

Metronidazole (MNZ) accumulation inhibits municipal wastewater treatment bio-systems, and an effective so-lution to augment anaerobic activated sludge (AAS) is required. This research discovered that Aspergillus taba-cinus LZ-M could degrade 77.39% of MNZ at 5 mg/L. MNZ was metabolized into urea, and the enzymes involved in its degradation were aminotransferase, methyltransferase, monooxygenase, and -C-N- cleavage hydrolase. The strain was immobilized in polyurethane foam and used in AAS for the treatment of MNZ-containing municipal wastewater. The results showed that, using immobilized LZ-M, MNZ was completely removed, and the degradation efficiency of wastewater's chemical oxygen demand (COD) was increased from 11.7% to 83.31%. The extracellular polymer and ROS levels indicated that MNZ's toxicity on AAS was reduced. Furthermore, bioaugmentation stabilized its microbial community, and decreased MNZ resistance genes. These observations confirm that the immobilized fungi are effective in protecting AAS against antibiotic contamination in the treatment process of municipal wastewater.

Automated summary

This research found that Aspergillus tabacinus LZ-M could degrade 77.39% of MNZ at 5 mg/L. The strain was immobilized in polyurethane foam and used in anaerobic activated sludge (AAS) for the treatment of MNZ-containing municipal wastewater, resulting in complete removal of MNZ and increased degradation efficiency of the wastewater's chemical oxygen demand (COD) from 11.7% to 83.31%. The immobilized fungi also reduced MNZ's toxicity on AAS, stabilized its microbial community, and decreased MNZ resistance genes.