Fouling in membrane bioreactors used in wastewater treatment

Microbial fuel cells (MFCs) have been used to produce electricity from different compounds, including acetate, lactate, and glucose. We demonstrate here that it is also possible to produce electricity in a MFC from domestic wastewater, while atthe same time accomplishing biological wastewater treatment (removal of chemical oxygen demand; COD). Tests were conducted using a single chamber microbial fuel cell (SCMFC) containing eight graphite electrodes (anodes) and a single air cathode. The system was operated under continuous flow conditions with primary clarifier effluent obtained from a local wastewater treatment plant. The prototype SCMFC reactor generated electrical power (maximum of 26 mW m(-2)) while removing up to 80% of the COD of the wastewater. Power output was proportional to the hydraulic retention time over a range of 3-33 h and to the influent wastewater strength over a range of 50-220 mg/L of COD. Current generation was controlled primarily by the efficiency of the cathode. Optimal cathode performance was obtained by allowing passive air flow rather than forced air flow (4.5-5.5 L/min). The Coulombic efficiency of the system, based on COD removal and current generation, was < 12% indicating a substantial fraction of the organic matter was lost without current generation. Bioreactors based on power generation in MFCs may represent a completely new approach to wastewater treatment. If power generation in these systems can be increased, MFC technology may provide a new method to offset wastewater treatment plant operating costs, making advanced wastewater treatment more affordable for both developing and industrialized nations.

Production of electricity during wastewater treatment using a single chamber microbial fuel cell.

Membrane bioreactors (MBRs), in which membranes are applied to biological wastewater treatment for biomass separation, provide many advantages over conventional treatment. However, membrane fouling in MBRs restricts their widespread application because it reduces productivity and increases maintenance and operating costs. Recently much research and development has taken place to investigate, model, and control membrane fouling processes. However, unified and well-structured theories on membrane fouling are not currently available because of the complexity of the biomass matrix, which is highly heterogeneous and includes living microorganisms. Membrane fouling in MBR systems can be reversible (i.e., removable by physical washing) or irreversible (removable by chemical cleaning only), and can take place on the membrane surface or into the membrane pores. Although establishing a general model to describe membrane fouling in such a process is made extremely difficult by the inherent heterogeneity of the syste...

Membrane Fouling in Membrane Bioreactors for Wastewater Treatment

R. Witzig

Papers

Performance of a bioreactor with submerged membranes for aerobic treatment of municipal waste water.

Microbiological aspects of a bioreactor with submerged membranes for aerobic treatment of municipal wastewater

Operation of different membrane bioreactors : experimental results and physiological state of the micro-organisms