Carbon nano-onions enhancing anaerobic membrane bioreactor for chloramphenicol wastewater treatment
To address the problem of difficult biodegradation of chloramphenicol(CAP),carbon nano-onions(CNOs)were used as a conductive material for the removal of CAP from wastewater by an anaerobic membrane bioreactor(AnMBR).The anaerobic degradation pathways of CAP and the distribution of antibiotic resistance genes(ARGs)were investigated,and the enhanced effect of CNOs on CAP removal was analyzed.Mass spectrometry data indicated that the esterification reactions occurred between CAP and substances involved in the tricarboxylic acid cycle,and these degradation products were less toxic than CAP.Moreover,the addition of CNOs promoted the up-regulation of some tricarboxylic acid cycle enzymes,which further reduced the biotoxicity of CAP.It was also found that CNOs enhanced horizontal gene transfer of ARGs,of which the relative abundance of intIl gene significantly increased.On the other hand,the membrane module of AnMBR effectively sequestered ARGs.Sequential batch experiments were used to further investigate the enhanced effect of CNOs on CAP removal,and the results showed that the CAP removal rate in the experimental group with the addition of CNOs was 90.4％(10 h),which was much higher than that in the control group without CNOs(59.4％).Besides,the methane production of the anaerobic biological system with the addition of CNOs was 46.1 mL in 24 h,which was much higher than that of the control group,and the lag time for methane production was shorter.These results indicated that CNOs strengthened the removal effect of anaerobic biotic system on CAP wastewater and reduced the biotoxicity of CAP,which provided a certain theoretical basis for the treatment of antibiotic wastewater by AnMBR.
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