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Microbial electrosynthesis (MES) is an innovative technology, which can yield valuable organic chemicals with concomitant CO2 sequestration by employing microbes as biocatalysts. The mode of operation has an imperative role in the performance of MES, thus, affecting the yield of synthesized organic chemicals from the MES. However, to the best of our knowledge, the optimal mode of operation for MES has not been determined till date. Hence, in the present investigation, two MES were operated: one in batch mode (MES-B) and another in continuous mode (MES-C), and their performance was monitored. The MES-B exhibited 31%, 33.5% and 44% higher production rate of acetate, propionate and butyrate, respectively, in comparison to MES-C. Moreover, the performance of MES-B also stabilized faster, and microbiome in the cathodic chamber of MES-B was able to accept 26% more electrons supplied to it externally, which were employed as reducing equivalents to reduce CO2. The enactment of MES-B was superior to that of MES-C due to the higher retention of CO2 and hydrogen in cathodic chamber of MES-B. Therefore, operating MES in batch mode would aid in yielding more organic chemicals through CO2 sequestration. [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]

Sediment microbial fuel cells (SMFCs) are bio-electrochemical devices generating electricity from redox gradients occurring across the sediment–water interface. Sediment microbial carbon-capture cell (SMCC), a modified SMFC, uses algae grown in the overlying water of sediment and is considered as a promising system for power generation along with algal cultivation. In this study, the performance of SMCC and SMFC was evaluated in terms of power generation, dissolved oxygen variations, sediment organic matter removal and algal growth. SMCC gave a maximum power density of 22.19 mW/m2, which was 3.65 times higher than the SMFC operated under similar conditions. Sediment organic matter removal efficiencies of 77.6 ± 2.1% and 61.0 ± 1.3% were obtained in SMCC and SMFC, respectively. With presence of algae at the cathode, a maximum chemical oxygen demand and total nitrogen removal efficiencies of 63.3 ± 2.3% (8th day) and 81.6 ± 1.2% (10th day), respectively, were observed. The system appears to be favorable from a resources utilization perspective as it does not depend on external aeration or membranes and utilizes algae and organic matter present in sediment for power generation. Thus, SMCC has proven its applicability for installation in an existing oxidation pond for sediment remediation, algae growth, carbon conversion and power generation, simultaneously. [ABSTRACT FROM AUTHOR]

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]

The effect of influent chemical oxygen demand (COD), hydraulic retention time (HRT), and influent pH on COD removal efficiency and power generation was studied in a dual-chambered microbial fuel cell (MFC) having stainless-steel mesh electrodes and treating synthetic wastewater. Statistical models were formulated based on these three variables to predict the responses, namely COD removal efficiency and power generation, in MFC using a two-level full factorial design. It was observed from statistical analyses that all the three variables affected the COD removal efficiency, whereas proper combination of the operating variables was of utmost importance in enhancing power generation. Average influent COD concentration of 2200-2400 mg/L and HRT of 22-25 h was found to be optimum for achieving optimal COD removal efficiency and power. Validation of the model's predictions for treatment of synthetic wastewater revealed the efficacy of these models. Under optimal conditions when these MFCs were operated with a graphite plate cathode and using aerated distilled water and persulfate as cathodic electrolyte, respective volumetric power densities of 979 and 7,408 mW/m3 were observed. [ABSTRACT FROM AUTHOR]

A five-chamber microbial desalination cell (MDC) with anode, cathode, one central desalination chamber and two concentrate chambers separated by ion exchange membranes was operated in batch mode for more than 60 days. The performance of the MDC was evaluated for chemical oxygen demand (COD) removal, total dissolved solids (TDS) removal and energy production. An average COD removal of 81±2.1% was obtained using acetate-fed wastewater as substrate in the anodic chamber inoculated with mixed anaerobic sludge. TDS removals of 58, 70 and 78% were observed with salt concentration of 8, 20 and 30 g/L, respectively, in the middle desalination chamber. The MDC produced a maximum power output of 16.87 mW/m2 during polarization. The highest Coulombic efficiency of 12± 2.4% was observed in this system using mixed anaerobic sludge as inoculum. The system effectively demonstrated capability for simultaneous organic matter removal and desalination along with power generation. [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 performance of three sediment microbial fuel cells (SMFCs) was evaluated at different feed water pH and electrode spacing for chemical oxygen demand (COD) removal, total nitrogen (TN) removal, and power density; while offering in situ remediation of aquaculture pond water. SMFC-A was operated at the feed water pH of 6.5 and spacing between the electrodes of 100 cm. SMFC-B and SMFC-C were operated at feed water pHs of 8.5 and 6.5, respectively, and distance between electrodes of 50 cm. The anode and cathode were connected with concealed copper wire through an external load of 100 Ω. The average amount of total COD removal rate and TN removal rate, per unit area of cathode, were 1.72± 0.06 and 0.021±0.007 g/m2 d in SMFC-A, 1.03± 0.08 and 0.024± 0.005 g/m2 d in SMFC-B, and 1.14±0.01 and 0.017±0.001 g/m2 d in SMFC-C, respectively. SMFC-A, operated with higher distance between electrodes, demonstrated better removal of organic matter and highest open circuit voltage of 0.903 V. SMFCs with less feed pH (6.5) gave higher COD removal and feed pH of 8.5 gave higher TN removal. SMFCs operated with lesser distance between electrodes gave higher power density. [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]

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]

Wastewater treatment coupled with electricity recovery in microbial fuel cell (MFC) prefer mixed anaerobic sludge as inoculum in anodic chamber than pure stain of electroactive bacteria (EAB), due to robustness and syntrophic association. Genetic modification is difficult to adopt for mixed sludge microbes for enhancing power production of MFC. Hence, we demonstrated use of eco-friendly plant secondary metabolites (PSM) with sub-lethal concentrations to enhance the rate of extracellular electron transfer between EAB and anode and validated it in both bench-scale as well as pilot-scale MFCs. The PSMs contain tannin, saponin and essential oils, which are having electron shuttling properties and their addition to microbes can cause alteration in cell morphology, electroactive behaviour and shifting in microbial population dynamics depending upon concentrations and types of PSM used. Improvement of 2.1-times and 3.8-times in power densities was observed in two different MFCs inoculated with Eucalyptus-extract pre-treated mixed anaerobic sludge and pure culture of Pseudomonas aeruginosa, respectively, as compared to respective control MFCs operated without adding Eucalyptus-extract to inoculum. When Eucalyptus-extract-dose was spiked to anodic chamber (125 l) of pilot-scale MFC, treating septage, the current production was dramatically improved. Thus, PSM-dosing to inoculum holds exciting promise for increasing electricity production of field-scale MFCs. [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]

Electrosynthesis of multi-carbon compounds from the carbon dioxide present in biogas is a nascent approach towards purification of biogas. Microbial electrosynthesis (MES) cells, fabricated using different electrode materials, were operated using different electrolytes and mixed anaerobic culture as biocatalysts in the cathodic chamber under an applied cathode potential of -0.7 V vs standard hydrogen electrode (SHE). The rate of production of acetate, isobutyrate, propionate and 2-piperidinone from reduction of CO2 in the cathodic chamber of the MES was 0.81 mM/day, 0.63 mM/day, 0.44 mM/day and 0.53 mM/day, respectively. As methane was also present in the biogas, methyl derivatives of these acids were also found in traces in catholyte. It was observed that the use of nickel foam as an anode, 1 M NiSO4 solution as anolyte, graphite felt as a cathode, phosphate buffer solution as catholyte at a pH of 5.2 proved to be the best possible combination for MES for this study to get enhanced product yield at higher energy efficiency. [ABSTRACT FROM AUTHOR]

Methanogens compete with anodophiles for substrate and thus reduce the power generation and coulombic efficiency (CE) of the microbial fuel cell (MFC). Performance of a baked clayware membrane MFC inoculated with mixed anaerobic sludge pretreated with lauric acid was investigated in order to enhance power recovery by controlling methanogenesis. In the presence of lauric acid pretreated inoculum, MFC produced maximum volumetric power density of 4.8 W/m3 and the CE increased from 3.6% (for untreated inoculum) to 11.6%. Cyclic voltammetry (CV) and electro-kinetic evaluation indicated a higher bio-catalytic activity at the anode of the MFC inoculated with lauric acid pretreated sludge. With the lauric acid pretreated inoculum a higher catalytic current of 114 mA, exchange current density of 40.78 mA/m2 and lower charge transfer resistance of 0.00016 Ωm2 were observed during oxidation at the anode. Addition of lauric acid significantly achieved suppression of methanogenesis and enhanced the sustainable power generation of MFC by 3.9 times as compared with control MFC inoculated with sludge without any pretreatment. [ABSTRACT FROM AUTHOR]

The performance of dual chambered mediator-less microbial fuel cell (MFC) operated under batch mode was evaluated under different operating temperatures, ranging between 20 and 55 °C, with step increase in temperature of 5 °C. Synthetic wastewater with sucrose as carbon source having chemical oxygen demand (COD) of 519-555 mg/L was used in the study. Temperature was a crucial factor in the performance of MFCs for both COD removal and electricity production. The MFC demonstrated highest COD removal efficiency of 84% and power density normalized to the anode surface area of 34.38 mW/m2 at operating temperature of 40 °C. Higher VSS to SS ratio was observed at the operating temperature between 35 and 45 °C. Under different operating temperatures the observed sludge yield was in the range of 0.05 to 0.14 g VSS/g COD removed. The maximum Coulombic and energy efficiencies were obtained at 40 °C, with values of 7.39 and 13.14%, respectively. Internal resistance of the MFC decreased with increase in operating temperature. Maximum internal resistance of 1,150 Ω was observed when the MFC was operated at 20 °C; whereas the minimum internal resistance (552 Ω) was observed at 55°C. [ABSTRACT FROM AUTHOR]

An electrochemically active bacteria Pseudomonas aeruginosa IIT BT SS1 was isolated from a dark fermentative spent media fed anode, and a bioaugmentation technique using the isolated strain was used to improve the start-up time of a microbial fuel cell (MFC). Higher volumetric current density and lower start-up time were observed with the augmented system MFC-PM (13.7 A/m³) when compared with mixed culture MFC-M (8.72 A/m³) during the initial phase. This enhanced performance in MFC-PM was possibly due to the improvement in electron transfer ability by the augmented strain. However, pure culture MFC-P showed maximum volumetric current density (17 A/m³) due to the inherent electrogenic properties of Pseudomonas sp. An electrochemical impedance spectroscopic (EIS) study, along with matrix-assisted laser desorption/ionization-time-offlight (MALDI-TOF) analysis, supported the influence of isolated species in improving the MFC performance. The present study indicates that the bioaugmentation strategy using the isolated Pseudomonas sp. can be effectively utilized to decrease the start-up time of MFC. [ABSTRACT FROM AUTHOR]