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For successful field-scale application of microbial fuel cell (MFC), the power recovery from field-scale MFC needs to be improved considerably with simultaneous reduction in its fabrication cost. These problems can be addressed by applying low-cost and efficient cathode catalyst in MFCs. In this regard, Cu0.5Mn0.5Fe2O4 (CuMnFe) was synthesized and applied as cathode catalyst in lab and field-scale MFCs with capacity of 150 ml and 25 l, respectively. Lab-scale MFC having CuMnFe as cathode catalyst demonstrated power density of 176.0 ± 8.2 mW m-2, which was competitive with MFC having Pt as cathode catalyst (183.0 ± 12.6 mW m-2) and it was about seven times higher than control MFC (25.5 ± 4.5 mW m-2) having no catalyst. Application of CuMnFe as cathode catalyst in field-scale MFC produced power density of 7.74 mW m-2, which was three-times higher than the power produced by the field-scale MFC operated without any cathode catalyst (2.58 mW m-2). The cathode catalyst CuMnFe also demonstrated excellent anti-biofouling properties, which in turn improved the power production of field-scale MFC. Therefore, low-cost CuMnFe can be anticipated as an efficacious cathode catalyst for application in MFCs that would produce long term stable higher power, while offering simultaneous treatment to wastewater. [ABSTRACT FROM AUTHOR]

Proton exchange membranes (PEMs) were synthesized in polyvinyl alcohol (PVA) matrix by impregnating TiO2-Si or SrTiO3-Si as proton exchanger for microbial fuel cells (MFCs). These PEMs were physically characterized, which approved the presence of hygroscopic oxides like SiO2 to increase the proton transfer due to the formation of Si-H along with the water channelling through TiO2 or SrTiO3 induced microstructural modifications. Chemical characterization techniques further illustrated their comparable performance to the commercially available Nafion-117 and superior performance than bare PVA membrane. Polarization curves for MFCs using TiO2-Si- or SrTiO3-Si-based PVA membranes exhibited a power density of 6.16 ± 0.31 W m−3 and 5.39 ± 0.27 W m−3, respectively. Power density of MFC with TiO2-Si membrane was comparable to that of the MFC using Nafion-117 (6.50 ± 0.33 W m−3). Thus, comparable properties and 30-folds less synthesis cost of the fabricated TiO2-Si-impregnated PVA membrane in comparison to Nafion, demonstrate its potential for real-life applications in MFC. [ABSTRACT FROM AUTHOR]

Waste generation from healthcare facilities now has become a concerning issue as it contain plastic and metals. Medicine wrappers are one of the major portions of healthcare solid waste, which impel intensive solid waste management practice due to fewer possibilities of deriving by-products. However, it can be recycled and used as an electrode material in microbial fuel cells (MFCs). An electrode material for application in MFCs is a crucial component, which governs total fabrication cost as well as power recovery, thus a cost-effective, stable and durable electrode is essential. In this endeavour, a new metallic (aluminium) waste material, a waste medicine wrapper (WMW), was evaluated for feasibility to be used as anode/cathode in MFCs. Based on the stability test under corrosive environment (1 N KCl), the WMW electrode sustained a maximum current of 46 mA during cyclic voltammetry (CV) and noted only 14% reduction in current at an applied voltage of +0.4 V after 2500 s in chronoamperometry, indicating its good stability. Power recovery from MFC using WMW was higher than the MFC using bare carbon felt as an anode (27 vs. 21 mW/m2). The entire analytical test results viz. CV, electrochemical impedance spectroscopy and power performance established WMW as an excellent anode rather than cathode material. [ABSTRACT FROM AUTHOR]

An appropriate current collector (CC) is crucial for harvesting substantial power in a microbial fuel cell (MFC). In the present study, stainless steel (SS) and titanium wires were used as the CCs for both the anode and cathode of MFC-1 and MFC-2, respectively. Tungsten wire (TW) was used as the anode CC in MFC-3, with SS wire as the cathode CC. In MFC-4, TW was used as the cathode CC with SS wire as the anode CC, and in MFC-5 both electrode CCs were TW. The power density, current density, oxidation current and bio-capacitance were compared to select the best and most cost effective CC material to enhance the power output of MFCs. Maximum power densities (mW/m²) of 32.28, 93.10, 225.38, 210.74, and 234.88 were obtained inMFC-1,MFC-2,MFC-3,MFC-4, and MFC-5, respectively. The highest current density (639.86mA/m²) and coulombic efficiency (23.12±1.5%) achieved in MFC-5 showed TW to be the best CC for both electrodes. Themaximum oxidation current of 7.4 mA and 7 mA and bio-capacitance of 10.3 mF/cm² and 9.7 mF/cm² were achieved in MFC-3 and MFC-5, respectively, suggesting TW is the best as the anode CC and SS wire as the cathode CC to reduce MFC fabrication costs. [ABSTRACT FROM AUTHOR]

A hybrid upflow anaerobic sludge blanket (UASB)–moving bed biofilm (MBB) and rope bed biofilm (RBB) reactor was designed for treatment of sewage. Possibility of enhancing granulation in an UASB reactor using moving media to improve sludge retention was explored while treating low-strength wastewater. The presence of moving media in the top portion of the UASB reactor allowed a high solid retention time even at very short hydraulic retention times and helped in maintaining selection pressure in the sludge bed to promote formation of different sized sludge granules with an average settling velocity of 67 m/h. These granules were also found to contain plenty of extracellular polymeric substance (EPS) such as 58 mg of polysaccharides (PS) per gram of volatile suspended solids (VSS) and protein (PN) content of 37 mg/g VSS. Enriched sludge of nitrogen-removing bacteria forming a porous biofilm on the media in RBB was also observed in a concentration of around 894 g/m2. The nitrogen removing sludge also had a high EPS content of around 22 mg PS/g VSS and 28 mg PN/g VSS. This hybrid UASB-MBB-RBB reactor with enhanced anaerobic granular sludge treating both carbonaceous and nitrogenous matter may be a sustainable solution for decentralized sewage treatment. [ABSTRACT FROM PUBLISHER]

Contamination of water and sediment in water bodies is caused by the runoff from agriculture fields, and release of untreated/ partially treated domestic and industrial wastewaters. Polluted water can affect the health of humans and aquatic organisms, and nutrient discharge can lead to algal blooms. A sustainable solution is required to treat these pollutants to protect future populations from environmental hazards. Sediment microbial fuel cells (SMFCs) is a new technology that has the potential to remediate sediment and water from sluggish water bodies and ponds, and generate some electricity as a byproduct. This critical review discusses types of SMFCs, factors affecting performance of the SMFCs, its capability to offer in situ treatment of sediment and wastewater, and challenges to overcome to make this technology efficient for remediating water quality and harvesting electricity. [ABSTRACT FROM AUTHOR]

While performing in situ water quality remediation of aquaculture water using sediment microbial fuel cell, the present study provides effect of operating pH, distance between electrodes, and external resistance on organic matter and nitrogen removal as well as on power generation. Chemical oxygen demand (COD) removal was observed to be directly proportional to the distance between electrodes and inversely proportional to the influent pH as well as external resistance. However, total nitrogen (TN) removal increased with increase in pH and distance between electrodes; whereas it decreased with increase in external resistance. Power production reduced with decrease in pH, but increased with decrease in external resistance and distance between electrodes. Two factor and three factor interactions were observed to be less significant for COD, TN removal and power density. From the statistical correlation among these parameters, feed pH of 7.6-8.5, distance between electrode of 90-100cm and external resistance of 0-52Ω were found to be optimum for achieving optimal COD removal, TN removal and power density. Validation of model predictions for treatment of aquaculture water conceded that the SMFC exhibited acceptable COD and TN removal efficiencies which in turn facilitate its use for in situ aquaculture water remediation effectively. [ABSTRACT FROM AUTHOR]

Two different binder materials of varying water affinity, viz. poly vinyl alcohol (PVA) and polytetrafluoroethylene (PTFE), and biocide vanillin were tested for cathode fouling in a single chamber air-cathode microbial fuel cell (MFC) constructed with a low-cost baked clayware cylinder and operated under fed-batch mode. PVA and PTFE loadings of 0.5 mg/cm2 were used for MFC-1 and MFC-2, respectively as a binder; and a 1:1 mixture of PVAþ PTFE was used as binder in MFC-3 with same binder loading. Vanillin was mixed with PVA and also applied at a loading of 0.5 mg/cm2 for MFC-4. Results showed organic matter removal efficiencies around 90% for all MFCs both before and after fouling. Coulombic efficiency was, however, found to decrease 50% after fouling in the MFC-3 coated with both PVA and PTFE. After 5 weeks of operation, due to fouling 56, 40 and 69% reduction in power densities were observed in MFC-1, MFC-2 and MFC-3, respectively. In the MFC-4 having PVA and vanillin, the least fouling was observed. A consistent volumetric power of 233 mW/m3 was observed for MFC-4, thus potentially offering a suitable solution to alleviate the problem of fouling in the making of single-chamber air-cathode MFCs. [ABSTRACT FROM AUTHOR]

The concept of an electro-active biofilm (EAB) has recently emerged from a few studies that discovered that certain bacteria which form biofilms on conductive materials can achieve a direct electrochemical connection with the electrode surface using it as electron exchanger, without the aid of mediators. This electro-catalytic property of biofilms has been clearly related to the presence of some specific strains that are able to exchange electrons with solid substrata (eg Geobacter sulfurreducens and Rhodoferax ferrireducens). EABs can be obtained principally from natural sites such as soils or seawater and freshwater sediments or from samples collected from a wide range of different microbially rich environments (sewage sludge, activated sludge, or industrial and domestic effluents). The capability of some microorganisms to connect their metabolisms directly in an external electrical power supply is very exciting and extensive research is in progress on exploring the possibilities of EABs applications. Indeed, the best known application is probably the microbial fuel cell technology that is capable of turning biomass into electrical energy. Nevertheless, EABs coated onto electrodes have recently become popular in other fields like bioremediation, biosynthesis processes, biosensor design, and biohydrogen production. [ABSTRACT FROM AUTHOR]

The benefits of treating sewage by pond systems offer, through a simple and low-cost technology, social and commercial benefits, from the waste raw materials. The objective of this work was to demonstrate an effective treatment of the sewage by using natural treatment systems, and use of treated wastewater for aquaculture. The study was conducted for the sewage generated from the IIT Kharagpur campus. After characterization of the sewage, laboratory scale experiments were conducted for treatment using oxidation pond and duckweed pond. Survival and growth of fishes were observed in the experimental ponds using treated sewage. Based on the experimental results, full-scale treatment plant was designed to meet the aquaculture water quality. From the economics of the proposed full-scale plant, and utilization of the treated sewage for aquaculture, it is estimated that, the amount of Rs. 20,0000 can be generated every year. This amount recovered from the aquaculture will be more than the operating cost of the treatment plant, hence, making the operation of sewage treatment plant self sufficient. Use of a UASB reactor as the first stage treatment before sewage passes to the oxidation pond, can be a more attractive alternative because of less land requirement as compared to the oxidation pond alone, and additional land can be made available for aquaculture to increase revenue. [ABSTRACT FROM AUTHOR]