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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]

Sodium dodecyl sulfate (SDS) is a widely used anionic surfactant, which finds its way to the receiving water body due to the incapability of conventional wastewater treatment systems to completely remove it. A hybrid treatment system consisting of upflow microbial fuel cell (MFC) with titanium dioxide (TiO2) as a photocathode catalyst was developed for treating synthetic wastewater spiked with SDS (10.00 ± 0.46 mg L−1). Effluent from anodic chamber of MFC was passed through raw laterite soil filter followed by the photo-cathodic chamber with TiO2-coated cathode irradiated with the UV spectrum. This hybrid system was operated under varying hydraulic retention time (HRT) in anodic chamber of MFC. The SDS removal efficiency of more than 96% along with organic matter removal efficiency of more than 71% was obtained by this hybrid system at different HRTs. The MFC having cathode coated with TiO2 could generate a maximum power density of 0.73 W m−3 and 0.46 W m−3 at the HRT of 12 h and 8 h, respectively, showing the adverse effect of increased SDS loading rate on the electrical performance of MFC. This investigation highlighted the importance of HRT in anodic chamber of MFC and offered solution for effective removal of surfactant from wastewater. [ABSTRACT FROM AUTHOR]

Catalysts play an essential role in various electrochemical reactions followed during the synthesis of hydrogen peroxide (H2O2). Plenty of investigations on the role of catalysts in the synthesis of H2O2 have been made in recent times. In this regard, palladium (Pd) is the most favored catalyst used by the researchers for the production of H2O2; however, monometallic Pd catalysts hydrogenate H2O2 if no acids or halide stabilizers are used. Nowadays, direct synthesis of H2O2 is mainly furnished by active metal-based catalysts such as gold, palladium, nickel, platinum, iron, silver, or manganese. However, the alloys of Au-Pd/C, Ni-Pd/C, and Au-Pd/TiO2 are also being encouraged because of their increased electrochemical activity. The efficacy of H2O2 production is highly dependent upon the type of cathode catalyst used and the pH of the solution. The electro-Fenton process, which uses Fenton reagents (dissolved Fe+2 and H2O2) to produce hydroxyl ions, is also an effective method for the degradation of biorefractory organic pollutants present in wastewater. This novel process can be made feasible if H2O2 can be produced in situ. In situ H2O2 production can be particularly important and attractive for tertiary treatment of sewage and for the removal of emerging contaminants. Thus, this mini review focuses on the effectiveness of various metal-based catalysts and the application of bioelectrochemical systems for the synthesis of H2O2. [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]

Fermentation distilleries produce a considerable volume of high-strength wastewater, known as stillage, having unconvertible organic fractions, lower pH and high percentage of dissolved organic and inorganic matters. Molasses stillage comprises higher level of chemical oxygen demand of 80-140 g/l, biochemical oxygen demand of 40-65 g/l, inorganic impurities and dark brown colour. Grain stillage contains comparatively lower chemical oxygen demand of 40-60 g/l. This stillage is acidic in nature (pH of 3.4-4.1) and exhibits considerable pollution potential upon discharge of untreated or partially treated wastewater into water body. Physical, chemical, biological and integrated processes for treatment of distillery stillage, which have been established by several researchers, are discussed in this review article. These treatment methods are discussed with focus on process details and current challenges, prospect and opportunities of future research and development. By utilizing distillery stillage as substrate in microbial fuel cell or integrated or combined fungal aerobic treatment followed by microbial fuel cell system, encouraging observations are demonstrated recently in terms of achieving the required treatment efficiency to meet the discharge standards, simultaneous bioelectricity generation and value-added products recovery. Such treatment system can offer a suitable solution for treatment of distillery wastewater in coming days. [ABSTRACT FROM AUTHOR]

Methanogenic substrate loss is reported to be a major bottleneck in microbial fuel cell (MFC), which significantly reduces the power production capacity and coulombic efficiency (CE) of this system. Nitroethane is found to be a potent inhibitor of hydrogenotrophic methanogens in rumen fermentation process. Influence of nitroethane pre-treated sewage sludge inoculum on suppressing the methanogenic activity and enhancing the electrogenesis in MFC was evaluated. MFC inoculated with nitroethane pre-treated anodic inoculum demonstrated a maximum operating voltage of 541 mV, with CE and maximum volumetric power density of 39.85% and 20.5 W/m3, respectively. Linear sweep voltammetry indicated a higher electron discharge on the anode surface due to enhancement of electrogenic activity while suppressing methanogenic activity. A 63% reduction in specific methanogenic activity was observed in anaerobic sludge pre-treated with nitroethane, emphasizing the significance of this pre-treatment for suppressing methanogenesis and its utility for enhancing electricity generation in MFC. [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]

A pilot-scale upflow anaerobic sludge blanket-moving bed biofilm (UASB-MBB) reactor followed by a high-rate algal pond (HRAP) was designed and operated to remove organic matter, nutrients and pathogens from sewage and to facilitate reuse. For an influent chemical oxygen demand (COD) concentration of 233±20 mg/L, final effluent COD was 50± 6 mg/L. Successful biomass granulation was observed in the sludge bed of the upflow anaerobic sludge blanket (UASB) reactor after 5 months of operation. Ammonia removal in HRAP was 85.1± 2.4% with average influent and effluent ammonia nitrogen concentrations of 20± 3 mg/L and 3 ±1 mg/L, respectively. Phosphate removal after treatment in the HRAP was 91±1%. There was a 2-3 log scale pathogen removal after treatment in HRAP with most probable number (MPN) of the final effluent being 600-800 per 100 mL, which is within acceptable standards for surface irrigation. The blackwater after treatment in UASBMBBR-HRAP is being reused for gardening and landscaping. This proper hydro-dynamically designed UASB reactor demonstrated successful granulation and moving bed media improved sludge retention in UASB reactor. This combination of UASB-MBB reactor followed by HRAP demonstrated successful sewage treatment for a year covering all seasons. [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]

Performance of four microbial fuel cells (MFC-1, MFC-2, MFC-3 and MFC-4) made up of earthen pots with wall thicknesses of 3, 5, 7 and 8.5 mm, respectively, was evaluated. The MFC5 were operated in fed batch mode with synthetic wastewater having sucrose as the carbon source. The power generation decreased with increase in the thickness of the earthen pot which was used to make the anode chamber. MFC-1 generated highest sustainable power density of 24.32 mW/rn2 and volumetric power of 1.04 W/m3 (1.91 mA, 0.191 V) at 100Q external resistance. The maximum Coulombic efficiencies obtained in MFC-1, MFC-2, MFC-3 and MFC-4 were 7.7, 7.1, 6.8 and 6.1%, respectively. The oxygen mass transfer and oxygen diffusion coefficients measured for earthen plate of 3mm thickness were 1.79x 105 and 5.38x 10-6 cm2/s, respectively, which implies that earthen plate is permeable to oxygen as other polymeric membranes. The internal resistance increased with increase in thickness of the earthen pot MFCs. The thickness of the earthen material affected the overall performance of 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]

Long term performance of mediator-less and membrane-less microbial fuel cell (ML-MFC) was evaluated for treatment of synthetic and actual sewage and electricity harvesting. The anode chamber of ML-MFC was inoculated with pre-heated mixed anaerobic sludge collected from a septic tank. The ML-MFC was operated by feeding synthetic wastewater for first 244 days, under different organic loading rates, and later with actual sewage for next 30 days. Maximum chemical oxygen demand (COD) removal efficiency of 91.4% and 82.7% was achieved while treating synthetic wastewater and actual sewage, respectively. Maximum current of 0.33mA and 0.17mA was produced during synthetic and actual sewage treatment, respectively. Maximum power density of 6.73mW/m² (13.65mW/m³) and maximum current density of 70.74mA/m² was obtained in this membrane-less MFC with successful organic matter removal from wastewater. [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]