Analysis of microbial fuel cell operation in acidic conditions using the flocculating agent ferric chloride

Abstract

BACKGROUND Ferric chloride (FeCl3) is widely used as a flocculating agent during wastewater treatment but can detrimentally lower pH and increase iron concentration. Microbial fuel cells (MFCs) are a promising technology for treating waste while concomitantly producing electricity and so were tested under the extreme conditions imposed by the addition of FeCl3. MFCs were fed eight concentrations of FeCl3 over two 8‐week periods and the effects on power, pH, conductivity, metal content and COD were examined. RESULTS MFCs generated highest power (3.58 W m‐3) at 1.6 mmol L‐1 FeCl3 (pH 3.46), however cells reversed when fed 2 mmol L‐1 (pH 3.29). During the second run, power almost doubled and MFCs were more resilient at higher loadings up to 2.8 mmol L‐1 (pH 3.02). Conductivity and pH increased following treatment while soluble phosphorus, sulphur and iron levels decreased significantly in all feedstock up to 1.6 mmol L‐1 FeCl3. COD reduction was observed but efficiency may have been affected by the presence of alternative electron donors such as hydrogen sulphide. CONCLUSION These findings demonstrate the robustness and versatility of MFCs in hostile conditions. They also confirm that MFCs can complement current wastewater treatment processes, even downstream from FeCl3 dosing where conditions might be deemed unsuitable for operation. © 2014 Society of Chemical Industry

Sulfur-Mediated Electron Shuttling Sustains Microbial Long-Distance Extracellular Electron Transfer with the Aid of Metallic Iron Sulfides

“…Recently, beside the energy sources, iron sulfides have been highlighted to act as naturally occurring electrical wires − and electrocatalysts − by virtue of their metallic and/or semiconductive properties and, thus, facilitate microbial metabolism and electron-transfer reactions. For example, the chemolithotrophic microbial communities in hydrothermal mounds appear to directly use electrons transported from hydrothermal fluids via iron sulfides as energy sources for carbon assimilation. ,,− An electrical current passing across iron sulfides and Fe oxides may also facilitate intercellular and interspecies energy transfer ,,− and bridge spatially discrete redox environments. ,,, An iron-sulfide-mediated electrical current may also be generated in microbial communities involved in microbial fuel cells, − bioremediation of industrial acid mine water, , pipeline corrosion, , and direct and indirect bioleaching …”

Impact of Ferrous Iron on Microbial Community of the Biofilm in Microbial Fuel Cells

“…However, a higher pH has been demonstrated to enhance the electrochemical activity of riboflavin which is a metabolite responsible for extracellular electron transfer in some species ( Yuan et al, 2011 ; Yong et al, 2013 ). By contrast, MFCs have also been operated at pH less than 4.0 and produced high current densities by acidophilic bacterium ( Malki et al, 2008 ; Winfield et al, 2016 ). Previous studies proved that temperate substantially affected the performances of MECs or MFCs by shaping microbial community ( Lu et al, 2011 , 2012 ).…”

Response of ceramic microbial fuel cells to direct anodic airflow and novel hydrogel cathodes

“…MFCs have demonstrated in numerous studies over the last decade that wastewater with diverse and complex compositions can be utilised as fuel [12]. The MFCs adapt and can deal with different types of waste that vary considerably in parameters such as organic loading [18], pH [35], conductivity [43], sulphide content [27], toxicity [26] and other factors. Given that the fuel can be any organic waste liquid, which is treated whilst electricity is generated, there is a real focus on scaling up the technology for wastewater treatment.…”