A Novel Anaerobic Electrochemical Membrane Bioreactor (AnEMBR) with Conductive Hollow-fiber Membrane for Treatment of Low-Organic Strength Solutions

Abstract

A new anaerobic treatment system that combined a microbial electrolysis cell (MEC) with membrane filtration using electrically conductive, porous, nickel-based hollow-fiber membranes (Ni-HFMs) was developed to treat low organic strength solution and recover energy in the form of biogas. This new system is called an anaerobic electrochemical membrane bioreactor (AnEMBR). The Ni-HFM served the dual function as the cathode for hydrogen evolution reaction (HER) and the membrane for filtration of the effluent. The AnEMBR system was operated for 70 days with synthetic acetate solution having a chemical oxygen demand (COD) of 320 mg/L. Removal of COD was >95% at all applied voltages tested. Up to 71% of the substrate energy was recovered at an applied voltage of 0.7 V as methane rich biogas (83% CH4; <1% H2) due to biological conversion of the hydrogen evolved at the cathode to methane. A combination of factors (hydrogen bubble formation, low cathode potential and localized high pH at the cathode surface) contributed to reduced membrane fouling in the AnEMBR compared to the control reactor (open circuit voltage). The net energy required to operate the AnEMBR system at an applied voltage of 0.7 V was significantly less (0.27 kWh/m3) than that typically needed for wastewater treatment using aerobic membrane bioreactors (1-2 kWh/m3).

Integrating membrane filtration into bioelectrochemical systems as next generation energy-efficient wastewater treatment technologies for water reclamation: A review

“…Although the bioelectrochemical performance of such an MFC was inferior to a regular MFC with Pt/C as a cathode catalyst, its permeate had a turbidity <0.1 NTU and 91% of bacterial cells removed. Katuri et al (2014) synthesized conductive hollow-fiber membranes with nickel and used in a single-chamber microbial electrolysis cell (MEC), in which aeration was eliminated and energy was recovered as H 2 and CH 4 . The system removed >95% of the soluble COD and showed reduced fouling compared to a control reactor operated under an open circuit mode.…”

“…In addition to the benefit that BES could alleviate membrane fouling as previously discussed, membranes modified with conductivity materials can function as electrode materials, thereby benefiting BES performance. For example, an BES with conductive nickel-based hollow-fiber membranes as both filtration component and cathode electrode can recover energy in the form of biogas (CH 4 and H 2 ) (Katuri et al, 2014). However, energy neutrality could not be achieved in such a system because of the relatively low conversion efficiency by combustion.…”

The Effect of Membrane Material and Surface Pore Size on the Fouling Properties of Submerged Membranes

“…Hollow fibers are mostly used in large plants (>10,000 m 3 /d) because of their high surface areas and excellent mass transfer properties, while flat sheet membranes are employed for small plants (<5000 m 3 /d). Thus, the use of hollow fiber membranes in MBR processes has grown recently [3,4]. 2 of 11 For these reasons, the use of MBRs for research, technology, and commercial applications is rapidly advancing across the world.…”

Sustainable Route to Inorganic Porous Hollow Fibers with Superior Properties

“…As a result these fibers are applied in a vast array of applications, for example: photocatalysis, 1,2 bio-reactor and sensors 3,4 , gas-liquid contactors, [5][6][7] membranes for demanding separations [8][9][10] , and for combined chemical reaction and molecular separation in harsh environments. [11][12][13] The small radial dimensions of the fibers are generally achieved by using the dry-wet spinning method, in which a mixture of a polymer, solvent and inorganic particles is spun into a coagulation bath.…”