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Novel Anaerobic Electrochemical Membrane Bioreactor with a CNTs Hollow Fiber Membrane Cathode to Mitigate Membrane Fouling and Enhance Energy Recovery

Yang, Yue, Qiao, Sen, Jin, Ruofei, Zhou, Jiti, Quan, Xie
Environmental science & technology 2018 v.53 no.2 pp. 1014-1021
Methanomicrobia, anaerobic treatment, carbon nanotubes, cathodes, chemical oxygen demand, electric potential, electrochemistry, electrostatic interactions, energy recovery, fouling, gels, membrane bioreactors, methane, methanogens, microfiltration, pollutants, temperature, thermoplastics, water quality
A novel anaerobic treatment system that combines the impact of applied voltage with membrane filtration over carbon nanotubes hollow fiber membranes (CNTs-HFMs) was developed at low temperature (15–20 °C) to mitigate membrane fouling, treat wastewater, and recover energy (CH₄). Herein, electro-assisted CNTs-HFMs served a dual function as the cathode and membrane filtration. In contrast with other two anaerobic membrane bioreactors (AnMBRs; polyvinylidene fluoride hollow fiber membranes and CNTs-HFMs without electro-assistance), the CNTs-HFMs with electro-assistance (−1.2 V applied voltage) had slower transmembrane pressure (TMP) increasing rates and better TMP recovery with a more than 95% effluent chemical oxygen demand (COD) removal rate during an almost 100-day operation period. This result can be attributed to the presence of an electrostatic repulsion force pushing pollutants (mainly extracellular polymeric substances, EPS) away from the membrane surface, thereby hindering the formation of a gel layer and mitigating membrane pore blocking in the anaerobic electro-assisted membrane bioreactor (AnEMBR). Due to the almost two-times higher Methanomicrobia content and more H₂-utilizing methanogens than the other two AnMBRs, approximately more than 111.12 mL/gVSS d of CH₄ was obtained in the AnEMBR with electro-assistance. This work provides an efficient strategy for mitigating membrane fouling, improving water quality, and enhancing CH₄ yield.