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The microbial fuel cell (MFC) is one of the sustainable technologies, which alongside treating wastewater, can generate electricity. However, its performance is limited by factors like methanogenesis where methanogens compete with the anode respiring bacteria for substrate, reducing the power output. Thus, sodium nitrate, which has been previously reported to target the hydrogenotrophic methanogens, was used as a methanogenic suppressor in this study. The performance of MFC with and without sodium nitrate was studied during the treatment of rice mill wastewater. A significantly higher power density and coulombic efficiency (CE) were noted in the MFC with sodium nitrate (MFCT) (271.26 mW/m3) as compared to the control MFC (MFCC) (107.95 mW/m3). Polarization studies showed lower internal resistance for the MFCT (330 Ω) as compared to MFCC (390 Ω). Linear sweep voltammetry and cyclic voltammetry indicated a higher electron discharge on the anode surface due to enhancement of electrogenic activity. Considerable reduction (76.8%) in specific methanogenic activity was also observed in anaerobic sewage sludge mixed with sodium nitrate compared to the activity of anaerobic sewage sludge without any treatment. Due to the inhibition of methanogens, a lower chemical oxygen demand (COD) and phenol removal efficiency were observed in MFCT as compared to MFCC. The COD balance study showed an increase in substrate conversion to electricity despite the increase in nitrate concentration. Therefore, selective inhibition of methanogenesis had been achieved with the addition of sodium nitrate, thus enhancing the power generation by MFCs.

Chloroform is a commonly found solvent in industrial wastewater and is very toxic if present in high concentration. Chloroform degradation in anaerobic processes has been reported earlier and it has also been used as a methanogenesis suppressor in rumen and rice fields. Methanogenesis is undesirable in a microbial fuel cell (MFC) operation, as it results in substrate competition between methanogens and exoelectrogens, thereby reducing the electricity output. Hence, an attempt has been made in this research work to study the effect of chloroform on the performance of MFCs and its effectiveness as methanogenesis suppressor. MFCs with different chloroform dosages in batch as well as continuous mode (0 mM, 8 mM, 16 mM and 22 mM; 0 mM and 22 mM) were operated. High open circuit voltages in batch MFC22 (781 mV) and 53 % higher peak power densities in dosed continuous MFC confirmed its efficiency as a methanogenesis suppressor. Further experimentations showed 74 % lower internal resistance in dosed MFCs. Higher coulombic efficiencies of 31.2 % (MFC22) and 18 % (MFCC22) were noted in dosed reactors than the control reactors (MFC0 – 23.8 % and MFCC0 - 8%). At the end of batches, chloroform concentration was found to be negligible, confirming its degradation in MFC.

Microbial fuel cell (MFC) provides a one-stop solution to wastewater treatment and depletion of existing energy resources. One of the major performance limitations of MFC is pH splitting that results in decreased pH of the anolyte affecting the growth of anaerobes. Hence an attempt was made in this study, to provide a suitable pH-controlled environment for microorganisms by recirculating the wastewater fed to the anode chamber. Four MFCs were fabricated allowing anolyte recirculation with different anolyte pH, viz, MFC-1 (pH 5, R.R. 1:2), MFC-2 (pH 5, R.R. 0), MFC-3 (pH 9, R.R. 1:2) and MFC-4 (pH 9, R.R. 0), where R.R. is recirculation ratio. MFC-3 and MFC-4 showed higher power generation and organics removal in comparison to MFC-1 and MFC-2. Anolyte recirculation in combination with alkaline pH improved the overall performance of the MFCs because of better substrate availability and suitable growth conditions provided to the microorganisms.

A study was conducted to introduce an efficient alternative such as bioelectrochemical degradation of pharmaceuticals. Six earthen pot MFCs were operated in batch mode, in which the pharma...

Circular bioeconomy aims at strengthening the resource efficiency by recycling materials that substitute fossil by the carbon present in biomass to obtain sustainable neutral energy as well as chemical sources. The concept of utilization of biomass as a source of renewable energy and other commercially important products is very much overlapping with the concept of circular economy and this intersection of circular economy and bioeconomy can be termed as circular bioeconomy. These biomass resources can be classified into agricultural residue, forest biomass, energy crops, algal biomass, and urban waste. Their conversion to biofuels and chemicals can be accomplished through different thermochemical, physiological, and biological pathways. While thermochemical processes involve the application of high temperature, physicochemical and biological processes employ chemicals and microorganisms, respectively, to obtain value-added products. The bioproducts produced are classified into four generations depending based on the source. The most commonly derived biofuels and chemicals are syngas, bioethanol, bio-oil, hydrogen, etc. However, the cost related to the biomass collection, segregation, transportation, and storage is still a concern. But, with reform in the biomass management system and forming laws encouraging the re-utilization of generated waste, the concept of circular bioeconomy can be implemented to address the issues of climate change, environmental pollution, and fossil fuel depletion. Comparative evaluation of large-scale projects is necessary to identify the best available technology for biofuel production. Furthermore, the existing sustainability issues of the biomass supply chain should be addressed to ensure all-year-round delivery of feedstock to the conversion facility. A robust business model would attract investors and accelerate the commercialization of biomass-derived biofuel.

Global industrialization has led to an alarming level of release of hazardous and toxic metals in water bodies. Disposal of wastewater containing heavy metals can have adverse impacts on h...

The release of untreated or partially treated pharmaceutical wastewater into water bodies has become a serious concern these days as the drugs and their intermediates present affect living...

Microbial fuel cell (MFC), one of the emerging topics of research, suffers from two chief limitations, low power generation and high cost of reactor materials. These problems limit its possibility of field scale implementation and commercialization. Hence, an attempt has been made in this study to highlight the utilization of lost cost ceramic material modified with mineral cation exchanger with various concentrations (10–50%) as separator along with studying the role of thickness and surface area in improving the overall performance of an MFC. The performance of the membranes with different thickness and kaolin concentrations was studied based on their proton exchange, ion transfer and oxygen diffusion capabilities. While, proton transfer coefficient was found to be highest in membrane of thickness 4 mm containing 30% kaolin, oxygen transfer coefficient was found to be lowest in the membrane of thickness 6 mm containing 50% kaolin. Thus, MFCs of optimised parameters with concentric anode chamber made with ceramic material were used to study the effect of membrane surface area on their performances. MFC with the highest membrane surface area showed highest power density, highest organics removal efficiency and least internal resistance. Thus, it was concluded from the results that high membrane surface area increases the performance efficiency of the MFCs by maintaining proper proton concentration on both side of the membranes. The results thus highlight the importance of a membrane in an MFC and how the presence of a cation exchanger can enhance the electricity generation.

Pharmaceutical wastewater (PW), owing to its complex and varied composition, is recalcitrant in nature. Thus treatment of PW requires a technology that can degrade not only organics but also the complex drug molecules. Antibiotics are one of the chief components of PW, which if released untreated into the water bodies, will heavily affect the aquatic life, and create antibiotic resistant microorganisms. While the conventional treatment techniques are expensive, microbial fuel cells (MFCs) are an inexpensive energy generating technology. The dual oxidative/reductive environment of MFCs allows the degradation of a wide range of compounds, while modifying operating conditions or electrode materials such as composition of anolyte, anode catalyst, preacclimation of biocatalyst, physicochemical pretreatment, and electric stimulation can further increase the degradability of real PW in MFCs. Thus MFCs can prove to be a promising technology by degrading trace organic material such as pharmaceuticals removal and generating simultaneous renewable energy.

Pseudomonas aeruginosa is a gram-negative bacterial specie well-known for pyocyanin production, which is a naturally produced mediator responsible for enhanced extracellular electron transport. However, pyocyanin production requires the presence of oxygen. Thus, in the present study, an approach of intermittent aeration was investigated to enhance pyocyanin production by P. aeruginosa, which was used for bioaugmentation of microbial fuel cells (MFCs). Two MFCs were augmented by seeding anaerobic sludge inoculum with P. aeruginosa (MFCP) and the performance was compared with a control MFC seeded with mixed anaerobic sludge (MFCC). One of the bioaugmented MFCs was intermittently aerated (MFCP+A) and was noted to produce more electricity than the MFCP (without aeration. MFCP+A generated 4% and 31% more power than MFCP and MFCC, respectively. The organic degradation efficiency was found to be higher in the MFCC denoting suppression of competitive microbial communities channelizing more electrons towards electricity generation in bioaugmented MFCs. Overall, MFCP+A showed a coulombic efficiency of 10.4%, followed by MFCP (9.7%) and MFCC (4.41%). Hence, the approach of intermittent aeration has proved to be feasible way of improving mediator production and enhancement in generation of electricity.