First resultsHalf-cell experiments with flat membranes show that filtrationand current production at the same time are possible.Therefore sintered stainless steel filters with average poresizes of 0.5μm and 1μm were tested as filtration activeanodes. Geobacter sulfurreducens was used as exo-electrogenic organism together with a growth mediumcontaining acetate.With the 1μm membrane a high permeate flow of 3500 lm-2h-1

at 3 bars can be reached (Fig. 2A), while the current densitiesare 11Am-² at 0 V vs. NHE (Fig. 2B). The 0.5μm membraneyields lower permeate flows of 1700 lm-2h-1 but higher currentdensities of up to 16 Am-² at 0 V vs. NHE.

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ConclusionsIt has been demonstrated, that membrane filtration andmicrobial fuel cells can be combined by simultaneously usingthe anode of a MFC as filter in a membrane bioreactor.Further work will be focused on the characterization ofcomplete fuel cells operating on real waste waters.

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AcknowledgementsWe gratefully acknowledge financial support from the Baden-Württemberg Stiftung

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References[1] Janicek, A.(2014): Biofuels n. 1, 5, pp. 79–92

Summary Microbial fuel cells (MFC) are a promising new technology todirectly convert wastewater’s chemically stored energy intoelectrical energy. Our work shows that a conductivemembrane filter can simultaneously be used as anode of aMFC so that part of the needed energy for the filtration unit ofa membrane bioreactor (MBR) can be supplied by the MFC.

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MotivationMFCs are promising, but are not yet economically feasibledue to little power outputs (0.002 - 2 Wm-²) in real systems[1]. At the same time membrane bioreactors are increasinglyused all over the world but still have a high energy demand.Combining those two systems in one structure promises toreduce the energy demand of a membrane bioreactor withoutsignificantly increasing the investment costs.In our concept (Fig. 1) for the first time the anode of amicrobial fuel cell is used simultaneously as membrane filter.This has several advantages:

• Active proton transport from anode to cathode, whichprevents the formation of a detrimental pH gradientbetween the electrodes

• Compact design which leads to smaller internalresistances

• Negatively charged membrane which may help toreduce fouling

Combining membrane bioreactors with microbial fuel cells for energy efficient wastewater treatment

Laboratory for MEMS Applications, Department of Microsystems Engineering - IMTEK, University of Freiburg, Germany

J. Danzer, A. Götze, S. Kerzenmacher

Figure 2: (A) Filtration and (B) bioelectrochemical performance of stainless steelmembranes of the pore sizes 1μm and 0.5μm. Solid symbols ( ) showdata while increasing the TMP, open symbols ( ) while decreasing TMP.Current densities are shown at 0 V vs. NHE (Normal Hydrogen Electrode).

Figure 1: Concept of a membrane filter used as microbial fuel cell

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