Two-dimensional carbon cloth and three-dimensional carbon felt perform similarly to form bioanode fed with food waste

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. a b s t r a c tTwo-dimensional carbon cloth and three-dimensional carbon felt were compared for their capacity to form bioanodes for food waste treatment. Wastewater was used as the dilution medium instead of a synthetic solution to be close to industrial conditions. In both cases, microbial cells were mainly wrapped around the fibers of the electrodes. The biofilms were around 80-120 μm thick with a 39.3% microbial volume ratio on carbon cloths. On carbon felt, the biofilms showed a lower microbial volume ratio of 16.3% on the upper layers but with a penetration depth of 200-800 μm. The biofilm patterns were different but they resulted in similar current density, around 3.5 A/m 2 .When chemically rich media have to be implemented, 2D cloth offers a worthwhile solution that can equal 3D porous materials.

The Limits of Three‐Dimensionality: Systematic Assessment of Effective Anode Macrostructure Dimensions for Mixed‐Culture Electroactive Biofilms

“…If the openings of a 3 D electrode structure become completely overgrown or clogged by biomass, the electrode will produce current densities similar to a 2 D electrode of the same footprint area. This behavior has been observed in the past for different electrode structures . A Geobacter sulfurreducens pure culture biofilm was able to overgrow a structure with pores of up to 50 μm, and mixed‐culture biofilms have been reported to overgrow structures with sizes of up to 200 μm .…”

“…This behavior has been observed in the past for different electrode structures . A Geobacter sulfurreducens pure culture biofilm was able to overgrow a structure with pores of up to 50 μm, and mixed‐culture biofilms have been reported to overgrow structures with sizes of up to 200 μm . It is to be expected that the minimum structure size will depend not only on the biological system but also on external factors such as medium flow rate and the resulting shear forces inside and outside the structure.…”

“…On the other hand, increasing biofilm thickness may cause both electron‐ and mass‐transport limitations within the biofilm and may even lead to the accumulation of inactive bacteria (i.e., bacteria that do not contribute to the electrode performance) below or on top of the metabolically active bacteria. The values that are usually reported for the biofilm thickness of Geobacter ‐dominated mixed‐culture EAB are in the range 100–200 μm . However, these values are generally reported without a discussion of the respective biofilm growth conditions.…”

“…Macrostructures with a comparatively larger size can, however, drastically increase the current density, which has been shown by several studies with specific 3 D macrostructure designs . Here, clogging of the 3 D structures during the biofilm growth represents a major obstacle that needs to be overcome . Whether a structure is susceptible to clogging because of biofilm growth depends predominately on two factors: 1) the size of the electrode structural elements relative to the biofilm thickness, and 2) the presence of shear forces resulting from medium flow inside the electrode.…”

“…[15,17,23] Here, clogging of the 3D structures during the biofilm growth represents a major obstacle that needs to be overcome. [16,24] Whether a structure is susceptible to clogging because of biofilm growth depends predominately on two factors:1 )the size of the electrode structurale lements relative to the biofilm thickness, and 2) the presence of shear forces resulting from mediumf low inside the electrode. The presence of shear forces can induce the production of exopolysaccharides (EPSs) [25] as well as detachment processesa tt he biofilm solution interface, [26,27] which leads to the formation of more compactb iofilms.…”