Effect of HRT and external resistances on power generation of sidestream microbial fuel cell with CNT-coated SSM anode treating actual fermentation filtrate of municipal sludge.

A microbial fuel cell (MFC) with multiwall carbon nanotube (CNT) coated stainless steel mesh (SSM) coated anode (S-MFC) was operated with a filtrate generated by the fermentation of municipal primary sludge. The S-MFC's maximum power density (MPD: 69.8-164.9 W/m3) and energy recovery (ER: 0.15-0.60 kWh/kgCOD) were 7-21 times higher than those (3.8-27.3 W/m3 and 0.01-0.11 kWh/kgCOD) of MFC with a graphite felt as an anode (G-MFC). The microbial communities of S- and G-MFCs varied slightly depending on the electrode material. Chloroflexi (23.5%) was dominant in S-MFC, and Proteobacteria (25.3%) in G-MFC. Fermenting bacteria such as Rhodanobacter lindaniclasticus and Anaerolineaceae bacterium were dominated by continuous non-electrochemically active bacteria invasion because the actual fermentation filtrate was directly utilized as the substrate. Nevertheless, the CNT-coated SSM anode and the fermentation filtrate of primary sludge improved the power generation in MFC, which demonstrates the significant potential of this sidestream process for sludge treatment.

Power generation response to readily biodegradable COD in single-chamber microbial fuel cells.

Single-chamber microbial fuel cells (MFCs) using domestic wastewater (DWW) and milk processing wastewater (MWW) were operated at different organic loading rates (OLRs). The maximum power density (PDmax) and OLR (readily biodegradable COD [RBCOD] and soluble COD [SCOD]) followed the Lineweaver-Burk equation in all influents. The coefficients of determination were 0.9209 and 0.9975 for SCOD and RBCOD, respectively. OLR based on RBCOD showed better power generation function than that based on SCOD. PDmax (2.9-12.2 W/m(3)) in DWW was lower than that (6.9-24.9 W/m(3)) in MWW but the net energy recovery (kWh/kg-SCOD(removed)) in DWW (0.542-1.108) was larger than that in MWW (0.322-0.602). This was attributed to the higher ratio of RBCOD/SCOD (0.44) and the lower values of RBCOD (40 mg/L) in DWW, compared to RBOCD/SCOD (0.11) and RBCOD (110 mg/L) in MWW. Therefore, RBCOD is an important indicator for estimating power generation.

Electricity generation and microbial community in microbial fuel cell using low-pH distillery wastewater at different external resistances.

Single chamber MFC (SMFC) consisted of two separator-electrode assemblies (SEA) using low-pH distillery wastewater (DW) was operated under continuous mode. The electricity generation and microbial community were analyzed according to the external resistance (Rext; 0.1, 0.5, 1, and 5 kΩ). The two SEAs exhibited different electricity generations, despite sharing the same anodic chamber. The SMFC showed the largest maximum power density (PDmax) of 3.7 W/m(3) (SEA 1) and 12.9 W/m(3) (SEA 2) at 5 kΩ. These results demonstrated that low-pH wastewater could be sufficiently used as fuels for electricity generation. Pyrosequencing analysis showed that microbial communities at the phylum level were significantly different according to the Rext. The communities of SEA 1 were slightly different from those of SEA 2. In both SEAs, Firmicutes (>45%) were the most dominant at 0.1 kΩ, while Firmicutes (>34%) and Caldiserica (>34%) were dominant at 5 kΩ. Caldiserica sp. might significantly contribute to electricity generation under low-pH and high-Rext.

Computational fluid dynamics analysis in microbial fuel cells with different anode configurations.

A key criterion in microbial fuel cell (MFC) design is that the bio-electrochemical reaction between bacteria and the bulk solution should occur evenly on the electrode surface in order to improve electricity generation. However, experimental optimization of MFC design over a wide range of conditions is limited. Computational fluid dynamics (CFD) technology makes it possible to evaluate physicochemical phenomena such as fluid flows, mass transfer and chemical reaction, which can assist in system optimization. Twelve MFCs (M1-M12) with different internal structures were subjected to CFD analysis. The dead (DS) and working spaces (WS) of the anode compartment were calculated. The flow patterns of the anodic fluid varied according to the internal structures. The WS where the bio-electrochemical reaction can actually occur varied over the range of 0.14-0.57 m(2). Based on the above results, the power densities were estimated under the assumption that a monolayer biofilm was formed on the electrode. M11, with 18 rectangular-type internal structures, showed the largest WS of 0.57 m(2) and a theoretical maximum power density of 0.54 W/m(2). Although the optimization of the MFC configuration with only CFD analysis remains limited, the present study results are expected to provide fundamental data for MFC optimization.