Fouling-resistant biofilter of an anaerobic electrochemical membrane reactor

Abstract

Membrane fouling is a considerable challenge for the stable operation of anaerobic membrane-based bioreactors. Membrane used as a cathode is a common measure to retard fouling growth in anaerobic electrochemical membrane bioreactors (AnEMBR), which; however, cannot avoid the fouling growth. Here we report a strategy using the membrane as an anode to resist membrane fouling in an AnEMBR. Although aggravating in the initial stage, the fouling on the anode membrane is gradually alleviated by the anode oxidation with enriching exoelectrogens to finally achieve a dynamic equilibrium between fouling growth and decomposition to maintain the operation stable. A mesh-like biofilter layer composed of cells with less extracellular polymeric substance (EPS) is formed on the membrane surface to lower the trans-membrane pressure and promote the interception of the anode membrane. The membrane has high electron storage and transfer capacities to accelerate the oxidation of the intercepted fouling materials, especially, the redundant EPSs of the biofilter layer.

Performance of Alternating-Current-Enhanced Anaerobic Membrane Bioreactor: Membrane Fouling, Wastewater Treatment, and CH4 Production

“…Then the electrochemical oxidation provided by positive charged membranes would play a role in oxidizing or mineralizing pollutants; they are also able to inactivate or impair the living bacteria adhering on the membranes by which the adhesion capability of live bacteria is lowered, eventually causing a bacterial detachment from membrane surface. 14,27 Table 1 shows the permeate flux recovery rates of membranes from the three AnMBRs at the end of each stage after the two types of backwash. For AC-AnMBR, the membranes permeate flux recovery rates after hydraulic backwash and chemical cleaning were 66%/86%, 55%/83%, and 50%/77% at the end of stages 1−3, respectively.…”

“…The electrochemical repulsion effect hindered part of pollutants with the same charges from depositing on the membranes first. Then the electrochemical oxidation provided by positive charged membranes would play a role in oxidizing or mineralizing pollutants; they are also able to inactivate or impair the living bacteria adhering on the membranes by which the adhesion capability of live bacteria is lowered, eventually causing a bacterial detachment from membrane surface. , …”

“…Among many alternative technologies, integration of electrochemistry technology and MBR has gained growing interest owing to its properties of environmentally friendliness and convenience of implementation . This approach is based on the concept that the primary foulants causing membrane fouling in MBR are always charged. , Currently, many efforts toward alleviating the membrane fouling have been proved the effect by application of intensive direct current (dc, positive or negative bias) on MBR systems. − For example, Chen et al investigated the antifouling effect of appending direct electric field into MBR. The results indicated that the appending electric field could significantly influence the membrane flux by inducing charged coarse particle and colloid (they accounted for 80% of COD Cr and BOD 5 in urban domestic sewage) away from the membranes.…”

“…It was concluded that appropriate application of the electric field could improve biomass in terms of its dewaterability and the removal of SMP, which are highly correlated to membrane fouling in MBR . When the membranes are carried out the bias, the same charge between membranes and pollutants will induce electrophoretic force to repel the foulants, such as planktonic microorganisms (sludge) and EPS, away from the separation unit. − This in turn mitigates the subsequent fouling by inhibiting such particles deposition on the membranes surface. − A positive bias higher than the oxidation potential of the pollutants endows membranes efficient ability for effluent quality improvement and membrane fouling control, since it could oxidize or mineralize various pollutants on the membrane surface or in deep pores in a timely and effectively manner. − Also, the bacteria attached on the anode could be inactive by a positive bias, − which further hinders the growth and proliferation of biofilm. Moreover, the physical movement and electrochemical reactions of charged particles induced by anode and cathode (fixing at opposite sides of the insulating membrane) or conductive membranes (as a separation unit and electrode simultaneously) are beneficial to reducing the fouling level .…”

Electrically Conductive Biofilms Assembled by Magnetite in Anaerobic Oxidation of Methane Coupled to Debromination/Denitrification

“…The region of 1700−1300 cm −1 in spectra is generally dominated by protein absorption (Figure 6). 41 A shift in the peak intensities of the protein-like region with the increased potential from −0.8 to 0.4 V was attributed to the conformational changes of the protein structure that had been described in the intracellular proton-coupled electron transport chains 53 or extracellular electrical connection components. 41 Specifically, the bands at 1684 and 1662 cm −1 are assigned to the stretching vibration of a C�O group in amide I, and the band at 1554 cm −1 is assigned to the stretching vibration of the C−N group in amide II.…”