Performance of a single chamber microbial fuel cell at different organic loads and pH values using purified terephthalic acid wastewater

Microbial fuel cells for mineralization and decolorization of azo dyes: Recent advances in design and materials

Microbial fuel cells (MFCs) exhibit tremendous potential in the sustainable management of dye wastewater via degrading azo dyes while generating electricity. The past decade has witnessed advances in MFC configurations and materials; however, comprehensive analyses of design and material and its association with dye degradation and electricity generation are required for their industrial application. MFC models with high efficiency of dye decolorization (96-100%) and a wide variation in power generation (29.4-940 mW/m²) have been reported. However, only 28 out of 104 studies analyzed dye mineralization - a prerequisite to obviate dye toxicity. Consequently, the current review aims to provide an in-depth analysis of MFCs potential in dye degradation and mineralization and evaluates materials and designs as crucial factors. Also, structural and operation parameters critical to large-scale applicability and complete mineralization of azo dye were evaluated. Choice of materials, i.e., bacteria, anode, cathode, cathode catalyst, membrane, and substrate and their effects on power density and dye decolorization efficiency presented in review will help in economic feasibility and MFCs scalability to develop a self-sustainable solution for treating azo dye wastewater.

Advancement in Benthic Microbial Fuel Cells toward Sustainable Bioremediation and Renewable Energy Production

Anthropogenic activities are largely responsible for the vast amounts of pollutants such as polycyclic aromatic hydrocarbons, cyanides, phenols, metal derivatives, sulphides, and other chemicals in wastewater. The excess benzene, toluene and xylene (BTX) can cause severe toxicity to living organisms in wastewater. A novel approach to mitigate this problem is the benthic microbial fuel cell (BMFC) setup to produce renewable energy and bio-remediate wastewater aromatic hydrocarbons. Several mechanisms of electrogens have been utilized for the bioremediation of BTX through BMFCs. In the future, BMFCs may be significant for chemical and petrochemical industry wastewater treatment. The distinct factors are considered to evaluate the performance of BMFCs, such as pollutant removal efficiency, power density, and current density, which are discussed by using operating parameters such as, pH, temperature and internal resistance. To further upgrade the BMFC technology, this review summarizes prototype electrode materials, the bioremediation of BTX, and their applications.

Bioanodes containing catalysts from onion waste and Bacillus subtilis for energy generation from pharmaceutical wastewater in a microbial fuel cell

Performance of the FAOW8 + B. subtilis bioanode in an MFC (a 14-day test) using pharmaceutical wastewater (pH = 9.2) as a substrate.

Bioelectricity generation using microalgal biomass as electron donor in a bio-anode microbial fuel cell

In this study, microalgal biomass waste (Chlorella regularis) was treated while simultaneously producing bioelectricity in a microbial fuel cell (MFC). Algal biomass was the sole electron donor and was enriched with easily biodegradable proteins (46%) and carbohydrates (22%). The generated power density was 0.86 W/m² and the columbic efficiency reached ∼61.5%.The power generation could be further increased to 1.07 W/m² by using a biomass waste concentration enhancement strategy with maximum chemical oxygen demand (COD) removal of ∼65.2%. Via direct comparison, the power generation and COD removal capability of the algal-fed MFC was close to that of the commercial acetate-fed MFC. The algae-fed MFC presented superior electrochemical characteristics that were attributed to the complicated composition of the biomass anolyte. It possessed a multiple anode respiring bacterial group and diverse microbial community. Hence, this study provides a new strategy for the utilization of microalgal biomass as a bioresource.

Engineering rheology of electrolytes using agar for improving the performance of bioelectrochemical systems

The present study is focused on enhancing the rheological properties of the electrolyte and eliminating sedimentation of microorganisms/flocs without affecting the electron transfer kinetics for improved bioelectricity generation. Agar derived from polysaccharide agarose (0.05-0.2%, w/v) was chosen as a rheology modifying agent. Electroanalytical investigations showed that electrolytes modified with 0.15% agar display a nine-fold increase in current density (1.2 mA/cm²) by a thermophilic strain (Geobacillus sp. 44C, 60 °C) when compared with the control. Sodium phosphate buffer (0.1 M, pH 7) electrolyte with riboflavin (0.1 mM) was used as the control. Electrolytes modified with 0.15% agar significantly improved chemical oxygen demand removal rates. This developed electrolyte will aid in improving bioelectricity generation in Bioelectrochemical Systems (BES). The developed strategy avoids the use of peristaltic pumps and magnetic stirrers, thereby improving the energy efficiency of the process.

Bioanode as a limiting factor to biocathode performance in microbial electrolysis cells

The bioanode is important for a microbial electrolysis cell (MEC) and its robustness to maintain its catalytic activity affects the performance of the whole system. Bioanodes enriched at a potential of +0.2V (vs. standard hydrogen electrode) were able to sustain their oxidation activity when the anode potential was varied from -0.3 up to +1.0V. Chronoamperometric test revealed that the bioanode produced peak current density of 0.36A/m² and 0.37A/m² at applied potential 0 and +0.6V, respectively. Meanwhile hydrogen production at the biocathode was proportional to the applied potential, in the range from -0.5 to -1.0V. The highest production rate was 7.4L H₂/(m² cathode area)/day at -1.0V cathode potential. A limited current output at the bioanode could halt the biocathode capability to generate hydrogen. Therefore maximum applied potential that can be applied to the biocathode was calculated as -0.84V without overloading the bioanode.

Impacts of process parameters optimization on the performance of the annular single chamber microbial fuel cell in wastewater treatment

Energy harvest from optimized annular single chamber microbial fuel cell (ASCMFC) with novel configuration, which treats chocolate industry wastewater, was investigated. In this study, optimization of operational parameters of the ASCMFC in terms of efficiency water-soluble organic matter reduction and capability of electricity generation was evaluated. During the experiment, effluent from the anode compartment was examined through current and power density curves for variation in temperature and pH, chemical oxygen demand (COD), and turbidity removal, and substrate concentration. The performance analyzed at different temperature ranges such as 25, 30, 35, and 40°C, which showed 88% increase by uprising temperature from 25 to 35°C. The ASCMFC was used to produce electricity by adjusting pH between 5 and 9 at resistance of 100 Ω. Under the condition of pH 7 power density (16.75 W/m³) was highest, which means natural pH is preferred to maximize microbial activities. Wastewater concentration with COD of 700 and 1400 mg/L were investigated to determine its affection on current production. Reduction of current density was observed due to decrease in wastewater concentration. Significant reduction in COD and turbidity of effluent were 91 and 78%, respectively. The coulombic efficiency of 45.1% was achieved.