Impacts of nano-zero-valent iron on antibiotic removal by anaerobic membrane bioreactor for swine wastewater treatment

Abstract

This study investigated the impact of nano-zero-valent iron (nZVI) on the removal of veterinary antibiotics by an anaerobic membrane bioreactor (AnMBR) for swine wastewater treatment. Ten veterinary antibiotics belonged to three commonly used groups, namely tetracyclines, fluoroquinolones, and sulfonamides, were evaluated. Results show that nZVI addition could improve AnMBR performance for the removal of both phosphorus and ammonium. Moreover, nZVI addition to AnMBR could improve the biodegradation of antibiotics to enhance their overall removal. Of the three groups of antibiotics, the enhancement was most obvious for sulfonamides with an increase in the removal rate from 32 – 62% to 64–97% when 2.6 g L−1 nZVI was added to AnMBR. Further microbial and redundancy analyses indicate that the removal of sulfonamides was closely and positively correlated to the relative abundance of the genera Lentimicrobium and Methanomethylovorans. By contrast, nZVI reduced the removal of tetracycline, ciprofloxacin, and norfloxacin by AnMBR. Microbial analysis showed that nZVI dosage slightly reduced methane yield by promoting the growth of Mesotoga but reducing the proliferation of Methanomassiliicoccus to potentially disrupt the hydrogenotrophic pathway. In addition, adding nZVI reduced the ratios of protein to polysaccharide in both extracellular polymeric substances and soluble microbial products, thereby mitigating membrane fouling.