Biodegradation of acetonitrile by adapted biofilm in a membrane-aerated biofilm reactor |
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Authors: | Tinggang Li Renbi Bai Dieudonné-Guy Ohandja Junxin Liu |
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Institution: | (1) Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, People’s Republic of China;(2) Institute of Environmental Science and Engineering, Nanyang Technological University, Singapore, Singapore, 637723;(3) Division of Environmental Science and Engineering, National University of Singapore, Singapore, Singapore, 117576;(4) Centre for Environmental Policy, Imperial College London, Prince Consort Road, London, SW7 2AZ, UK |
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Abstract: | A membrane-aerated biofilm reactor (MABR) was developed to degrade acetonitrile (ACN) in aqueous solutions. The reactor was
seeded with an adapted activated sludge consortium as the inoculum and operated under step increases in ACN loading rate through
increasing ACN concentrations in the influent. Initially, the MABR started at a moderate selection pressure, with a hydraulic
retention time of 16 h, a recirculation rate of 8 cm/s and a starting ACN concentration of 250 mg/l to boost the growth of
the biofilm mass on the membrane and to avoid its loss by hydraulic washout. The step increase in the influent ACN concentration
was implemented once ACN concentration in the effluent showed almost complete removal in each stage. The specific ACN degradation
rate achieved the highest at the loading rate of 101.1 mg ACN/g-VSS h (VSS, volatile suspended solids) and then declined with
the further increases in the influent ACN concentration, attributed to the substrate inhibition effect. The adapted membrane-aerated
biofilm was capable of completely removing ACN at the removal capacity of up to 21.1 g ACN/m2 day, and generated negligible amount of suspended sludge in the effluent. Batch incubation experiments also demonstrated
that the ACN-degrading biofilm can degrade other organonitriles, such as acrylonitrile and benzonitrile as well. Denaturing
gradient gel electrophoresis studies showed that the ACN-degrading biofilms contained a stable microbial population with a
low diversity of sequence of community 16S rRNA gene fragments. Specific oxygen utilization rates were found to increase with
the increases in the biofilm thickness, suggesting that the biofilm formation process can enhance the metabolic degradation
efficiency towards ACN in the MABR. The study contributes to a better understanding in microbial adaptation in a MABR for
biodegradation of ACN. It also highlights the potential benefits in using MABRs for biodegradation of organonitrile contaminants
in industrial wastewater. |
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Keywords: | Acetonitrile Adapted biofilm Biodegradation Haldane kinetics Membrane-aerated biofilm reactor Substrate inhibition |
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