Continuous electricity generation from domestic wastewater and organic substrates in a flat plate microbial fuel cell

Electrode and azo dye decolorization performance in microbial-fuel-cell-coupled constructed wetlands with different electrode size during long-term wastewater treatment

Microbial-fuel-cell-coupled constructed wetlands (CW-MFCs) with various cathode layers were used for long-term azo dye wastewater treatment. Their performance was assessed using cathode diameters ranging from 20 to 27.5cm and the influence of plants at the cathode was also examined. Bioelectricity generation, ABRX3 decolorization, and chemical oxygen demand (COD) removal performances first increased and then decreased with increasing cathode diameter. The CW-MFCs with larger cathodes had an anoxic region at the cathode where ABRX3 was decolorized. This phenomenon has not been reported in previous research on MFCs using traditional air cathodes. Anode performance was influenced by the cathode. The CW-MFC with a cathode diameter of 25cm showed the best electrode performance, and the highest voltage and power density were 560mV and 0.88W/m³, respectively. The highest ABRX3 decolorization and COD removal volumes were 271.53mg/L and 312.17mg/L, respectively.

Microbial fuel cells: From fundamentals to applications. A review

In the past 10-15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described.

Chlorinated phenol treatment and in situ hydrogen peroxide production in a sulfate-reducing bacteria enriched bioelectrochemical system

Wastewaters are increasingly being considered as renewable resources for the sustainable production of electricity, fuels, and chemicals. In recent years, bioelectrochemical treatment has come to light as a prospective technology for the production of energy from wastewaters. In this study, a bioelectrochemical system (BES) enriched with sulfate-reducing bacteria (SRB) in the anodic chamber was proposed and evaluated for the biodegradation of recalcitrant chlorinated phenol, electricity generation (in the microbial fuel cell (MFC)), and production of hydrogen peroxide (H₂O₂) (in the microbial electrolysis cell (MEC)), which is a very strong oxidizing agent and often used for the degradation of complex organics. Maximum power generation of 253.5 mW/m², corresponding to a current density of 712.0 mA/m², was achieved in the presence of a chlorinated phenol pollutant (4-chlorophenol (4-CP) at 100 mg/L (0.78 mM)) and lactate (COD of 500 mg/L). In the anodic chamber, biodegradation of 4-CP was not limited to dechlorination, and further degradation of one of its metabolic products (phenol) was observed. In MEC operation mode, external voltage (0.2, 0.4, or 0.6 V) was added via a power supply, with 0.4 V producing the highest concentration of H₂O₂ (13.3 g/L-m² or 974 μM) in the cathodic chamber after 6 h of operation. Consequently, SRB-based bioelectrochemical technology can be applied for chlorinated pollutant biodegradation in the anodic chamber and either net current or H₂O₂ production in the cathodic chamber by applying an optimum external voltage.

Response of microbial community structure to pre-acclimation strategies in microbial fuel cells for domestic wastewater treatment

Microbial community structures and performance of air-cathode microbial fuel cells (MFCs) inoculated with activated sludge from domestic wastewater were investigated to evaluate the effects of three substrate pre-acclimation strategies: 1, serial pre-acclimation with acetate and glucose before supplying domestic wastewater; 2, one step pre-acclimation with acetate before supplying domestic wastewater; and 3, direct supply of domestic wastewater without any pre-acclimation. Strategy 1 showed much higher current generation (1.4mA) and Coulombic efficiency (33.5%) than strategies 2 (0.7mA and 9.4%) and 3 (0.9mA and 10.3%). Pyrosequencing showed that microbial communities were significantly affected by pre-acclimation strategy. Although Proteobacteria was the dominant phylum with all strategies, Actinobacteria was abundant when MFCs were pre-acclimated with glucose after acetate. Not only anode-respiring bacteria (ARB) in the genus Geobacter but also non-ARB belonging to the family Anaerolinaceae seemed to play important roles in air-cathode MFCs to produce electricity from domestic wastewater.

Microbial diversity structure in acetate single chamber microbial fuel cell for electricity generation

This study investigates the performance of acetate feed membrane less single chamber microbial fuel cell and physical characterization of the bio film present on the anode surface using Scanning Electron Microscope (SEM) and 16S rRNA analyzer. The performance has been investigated using Teflon treated carbon paper with 0.3 mg/cm2 Pt/C loaded as a cathode and carbon paper as an anode. The maximum open circuit potential is noticed as 791 mV, the system successfully revealed a maximum power density of 86.1 mW m-2 at stable current density of 354 mA m-2 with high coulombic efficiency of 65% at maximum degradation rate of 96%. SEM showed the dense adherence of microorganisms on the anode. 16S rRNA sequencing results indicates phylogenetic mixture in the communities of anodic biofilm and there is no single dominant bacterial species. The dominant phyla are Firmicutes, Gamma Proteobacteria, Alpha Proteobacteria, Actinobacteria, with ten dominant microbial strains: Bacillus firmus, Shewanella profunda, Bacillus isronensis, Brevundimonas bullata, Pseudomonas putida, Planococcus citreus, Micrococcus endophyticus, Acinetobacter tandoii, Bacillus safensis and Shewanella xiamenensis.

Electrobioremediation of oil spills

Annually, thousands of oil spills occur across the globe. As a result, petroleum substances and petrochemical compounds are widespread contaminants causing concern due to their toxicity and recalcitrance. Many remediation strategies have been developed using both physicochemical and biological approaches. Biological strategies are most benign, aiming to enhance microbial metabolic activities by supplying limiting inorganic nutrients, electron acceptors or donors, thus stimulating oxidation or reduction of contaminants. A key issue is controlling the supply of electron donors/acceptors. Bioelectrochemical systems (BES) have emerged, in which an electrical current serves as either electron donor or acceptor for oil spill bioremediation. BES are highly controllable and can possibly also serve as biosensors for real time monitoring of the degradation process. Despite being promising, multiple aspects need to be considered to make BES suitable for field applications including system design, electrode materials, operational parameters, mode of action and radius of influence. The microbiological processes, involved in bioelectrochemical contaminant degradation, are currently not fully understood, particularly in relation to electron transfer mechanisms. Especially in sulfate rich environments, the sulfur cycle appears pivotal during hydrocarbon oxidation. This review provides a comprehensive analysis of the research on bioelectrochemical remediation of oil spills and of the key parameters involved in the process.

Microbial fuel cell characterisation and evaluation of Lysinibacillus macroides MFC02 electrigenic capability

Microbial fuel cell (MFC) is the most prominent research field due to its capability to generate electricity by utilizing the renewable sources. In the present study, Two MFC designs namely, H type-Microbial fuel cell (HT-MFC) and U type-Microbial fuel cell (UT-MFC) were constructed based on standardized H shaped anode and cathode compartment as well as U shaped anode and cathode compartments, respectively. In order to lower the cost for MFC construction, Pencil graphite lead was used as electrode and salt agar as Proton exchange membrane. Results inferred that newly constructed UT-MFC showed high electron production when compared to the HT-MFC. UT-MFC displayed an output of about 377 ± 18.85 mV (millivolts); whereas HT-MFC rendered only 237 ± 11.85 mV (millivolts) of power generation, which might be due to the low internal resistance. By increasing the number of cathode in UT-MFC, power production was increased upto 313 ± 15.65 mV in Open circuit voltage (OCV). Electrogenic bacteria namely, Lysinibacillus macroides (Acc. No. KX011879) rendered enriched power generation. The attachment of bacteria as a biofilm on pencil graphite lead was analyzed using fluorescent microscope and Scanning Electron Microscope (SEM). Based on our findings, it was observed that UT-MFC has a tendency to produce high electron generation using pencil graphite lead as the electrode material.

Effects of electrode gap and wastewater condition on the performance of microbial fuel cell coupled constructed wetland

The effects of electrode gap, PB solution concentration and azo dye on the wastewater treatment and electricity generation of microbial fuel cell coupled constructed wetland (CW-MFC) were studied. The electrode gap had obvious influence on the decolorization, while the influence of PB concentration on the decolorization was not obvious. The best decolorization efficiency was 91.05% and was gained when the electrode gap was 13.2 cm. The smaller the electrode gap, the smaller the ohmic resistance. However, a too small electrode gap would reduce the electricity generation. The best PB concentration in this study was 50 mM. In the glucose group, when the PB concentration was 50 mM, the power density was enhanced to 0.38 W/m³, while the PB concentration was 5 mM, the power density was only 0.14 W/m³. In the ABRX3 group, when the PB concentration was 50 mM, the power density was 0.18 W/m³, while when the PB concentration was 5 mM, the power density was 0.12 W/m³. The electricity generation performance of the CW-MFC was enhanced with an increase in running time. Long-time running CW-MFC got a higher cathode potential and a smaller internal resistance.

Yeast and carbon nanotube based biocatalyst developed by synergetic effects of covalent bonding and hydrophobic interaction for performance enhancement of membraneless microbial fuel cell

Membraneless microbial fuel cell (MFC) employing new microbial catalyst formed as yeast cultivated from Saccharomyces cerevisiae and carbon nanotube (yeast/CNT) is suggested. To analyze its catalytic activity and performance and stability of MFC, several characterizations are performed. According to the characterizations, the catalyst shows excellent catalytic activities by facile transfer of electrons via reactions of NAD, FAD, cytochrome c and cytochrome a3, while it induces high maximum power density (MPD) (344mW·m^-2). It implies that adoption of yeast induces increases in catalytic activity and MFC performance. Furthermore, MPD is maintained to 86% of initial value even after eight days, showing excellent MFC stability.

Electricity generation and microbial community in response to short-term changes in stack connection of self-stacked submersible microbial fuel cell powered by glycerol

Stack connection (i.e., in series or parallel) of microbial fuel cell (MFC) is an efficient way to boost the power output for practical application. However, there is little information available on short-term changes in stack connection and its effect on the electricity generation and microbial community. In this study, a self-stacked submersible microbial fuel cell (SSMFC) powered by glycerol was tested to elucidate this important issue. In series connection, the maximum voltage output reached to 1.15 V, while maximum current density was 5.73 mA in parallel. In both connections, the maximum power density increased with the initial glycerol concentration. However, the glycerol degradation was even faster in parallel connection. When the SSMFC was shifted from series to parallel connection, the reactor reached to a stable power output without any lag phase. Meanwhile, the anodic microbial community compositions were nearly stable. Comparatively, after changing parallel to series connection, there was a lag period for the system to get stable again and the microbial community compositions became greatly different. This study is the first attempt to elucidate the influence of short-term changes in connection on the performance of MFC stack, and could provide insight to the practical utilization of MFC.

Effect of gradual transition of substrate on performance of flat-panel air-cathode microbial fuel cells to treat domestic wastewater

In order to confirm the effects of the low conductivity and biodegradability of wastewater, flat-panel air-cathode microbial fuel cells (FA-MFCs) were operated by supplying substrates with different volume ratios of domestic wastewater mixed with an artificial medium: the artificial medium only, 25% wastewater, 50% wastewater, 75% wastewater, 100% of wastewater with 500mg-COD/L by adding acetate, and raw domestic wastewater (230mg-COD/L). With the increase of wastewater ratio, the maximum power density and organic removal efficiency decreased from 187 to 60W/m³ and 51.5 to 37.4%, respectively, but the Coulombic efficiency was maintained in the range of 18.0-18.9%. The FA-MFCs could maintain their low internal resistances and overcome the decreasing conductivity. The acetate concentration was more important than the total organics for power production. This study suggests that the FA-MFC configuration has great applicability for practical applications when supplied by domestic wastewater with low conductivity and biodegradability.

Biological degradation of potato pulp waste and microbial community structure in microbial fuel cells

The syntrophic interactions between polysaccharide-degrading bacteria and exoelectrogens drove simultaneous alternative energy production and degradation of potato pulp waste in microbial fuel cells.

The potential use of glucose oxidase-imprinted polymer-coated electrodes for biofuel cells

Enzymatic biofuel cells using molecularly imprinted polymer coated electrodes.

Engineering of Microbial Electrodes

This chapter provides an overview of the current state-of-the-art in the engineering of microbial electrodes for application in microbial electrosynthesis. First, important functional aspects and requirements of basic materials for microbial electrodes are introduced, including the meaningful benchmarking of electrode performance, a comparison of electrode materials, and methods to improve microbe-electrode interaction. Suitable current collectors and composite materials that combine different functionalities are also discussed. Subsequently, the chapter focuses on the design of macroscopic electrode structures. Aspects such as mass transfer and electrode topology are touched upon, and a comparison of the performance of microbial electrodes relevant for practical application is provided. The chapter closes with an overall conclusion and outlook, highlighting the future prospects and challenges for the engineering of microbial electrodes toward practical application in the field of microbial electrosynthesis. Graphical Abstract.

Continuous treatment of high strength wastewaters using air-cathode microbial fuel cells

Treatment of low strength wastewaters using microbial fuel cells (MFCs) has been effective at hydraulic retention times (HRTs) similar to aerobic processes, but treatment of high strength wastewaters can require longer HRTs. The use of two air-cathode MFCs hydraulically connected in series was examined to continuously treat high strength swine wastewater (7-8g/L of chemical oxygen demand) at an HRT of 16.7h. The maximum power density of 750±70mW/m² was produced after 12daysof operation. However, power decreased by 85% after 185d of operation due to serious cathode fouling. COD removal was improved by using a lower external resistance, and COD removal rates were substantially higher than those previously reported for a low strength wastewater. However, removal rates were inconsistent with first order kinetics as the calculated rate constant was an order of magnitude lower than rate constant for the low strength wastewater.

Electricity generation from rice bran in microbial fuel cells

Background

Rice bran is a by-product of the rice milling process and mostly discarded in Japan. Although many studies have shown that microbial fuel cells (MFCs) are able to generate electricity from organic wastes, limited studies have examined MFCs for generating electricity from rice bran.

Findings

Laboratory-scale single-chamber MFCs were inoculated with paddy field soil and supplied with rice bran for examining electricity generation. Power outputs and microbiome compositions were compared between MFCs containing pure water as the liquid phase (MFC-W) and those containing mineral solution (MFC-M). Polarization analyses showed that both MFCs successfully generated electricity with the maximum power densities of 360 and 520 mW m⁻² (based on the projected area of anode) for MFC-W and MFC-M, respectively. Amplicon-sequencing analyses revealed that Trichococcus and Geobacter specifically occurred in anode biofilms in MFC-W and MFC-M, respectively.

Conclusions

The results suggest that rice bran is a feasible fuel by itself for generating electricity in MFCs.

Evaluating the efficiency of a mixed culture biofilm for the treatment of black liquor and molasses in a mediator-less microbial fuel cell

A microbial fuel cell (MFC) is an emerging environment-friendly technology to recover the useful energy available in waste by using microorganisms as catalyst. In this study, double chamber mediator-less MFCs separated by proton exchange membrane (PEM; Nafion) were constructed to determine the efficiency of mixed culture in using complex substrates (molasses and black liquor). It was found that activated sludge can serve as efficient source of electricigens for biofilm development on an anode. Power density of 2.425 W/m² was generated from molasses with chemical oxygen demand (COD) removal efficiency of 67% as compared to power density of 3.55 W/m² produced from black liquor along with COD removal efficiency of 78%. Moreover, it was demonstrated that surface area of PEM has a significant effect on power generation. An almost 5- to 8-fold increase in voltage was observed as the size of PEM was increased from 6.5 to 25 cm².

Treatment of seafood processing wastewater using upflow microbial fuel cell for power generation and identification of bacterial community in anodic biofilm

Tubular upflow microbial fuel cell (MFC) utilizing sea food processing wastewater was evaluated for wastewater treatment efficiency and power generation. At an organic loading rate (OLR) of 0.6 g d(-1), the MFC accomplished total and soluble chemical oxygen demand (COD) removal of 83 and 95%, respectively. A maximum power density of 105 mW m(-2) (2.21 W m(-3)) was achieved at an OLR of 2.57 g d(-1). The predominant bacterial communities of anode biofilm were identified as RB1A (LC035455), RB1B (LC035456), RB1C (LC035457) and RB1E (LC035458). All the four strains belonged to genera Stenotrophomonas. The results of the study reaffirms that the seafood processing wastewater can be treated in an upflow MFC for simultaneous power generation and wastewater treatment.

Anodic biofilms as the interphase for electroactive bacterial growth on carbon veil

The structure and activity of electrochemically active biofilms (EABs) are usually investigated on flat electrodes. However, real world applications such as wastewater treatment and bioelectrosynthesis require tridimensional electrodes to increase surface area and facilitate EAB attachment. The structure and activity of thick EABs grown on high surface area electrodes are difficult to characterize with electrochemical and microscopy methods. Here, the authors adopt a stacked electrode configuration to simulate the high surface and the tridimensional structure of an electrode for large-scale EAB applications. Each layer of the stacked electrode is independently characterized using confocal laser scanning microscopy (CLSM) and digital image processing. Shewanella oneidensis MR-1 biofilm on stacked carbon veil electrodes is grown under constant oxidative potentials (0, +200, and +400 mV versus Ag/AgCl) until a stable current output is obtained. The textural, aerial, and volumetric parameters extracted from CLSM images allow tracking of the evolution of morphological properties within the stacked electrodes. The electrode layers facing the bulk liquid show higher biovolumes compared with the inner layer of the stack. The electrochemical performance of S. oneidensis MR-1 is directly linked to the overall biofilm volume as well as connectivity between cell clusters.

Biogas generation in anaerobic wastewater treatment under tetracycline antibiotic pressure

The effect of tetracycline (TC) antibiotic on biogas generation in anaerobic wastewater treatment was studied. A lab-scale Anaerobic Baffled Reactor (ABR) with three compartments was used. The reactor was operated with synthetic wastewater in the absence of TC and in the presence of 250 μg/L TC for 90 days, respectively. The removal rate of TC, volatile fatty acids (VFAs), biogas compositions (hydrogen (H₂), methane (CH₄), carbon dioxide (CO₂)), and total biogas production in each compartment were monitored in the two operational conditions. Results showed that the removal rate of TC was 14.97–67.97% in the reactor. The presence of TC had a large negative effect on CH₄ and CO₂ generation, but appeared to have a positive effect on H₂ production and VFAs accumulation. This response indicated that the methanogenesis process was sensitive to TC presence, but the acidogenesis process was insensitive. This suggested that the presence of TC had less influence on the degradation of organic matter but had a strong influence on biogas generation. Additionally, the decrease of CH₄ and CO₂ generation and the increase of H₂ and VFAs accumulation suggest a promising strategy to help alleviate global warming and improve resource recovery in an environmentally friendly approach.

Abattoir Wastewater Treatment and Energy Recovery Using a Ferricyanide-Catholyte Microbial Fuel Cell

The capacity of Microbial fuel cells (MFCs) to produce voltage and concurrently treat abattoir waste water was investigated in MFCs that used 0.1M potassium ferricyanide (K3[Fe(CN)6] as catholytes. Physicochemical, electrochemical and Microbiological properties of the MFCs were monitored. The open circuit voltage (OCV) readings were taken at 3 hours interval and maximum OCV of 965mV was recorded. Also, The physicochemical characteristics of the MFCs revealed that the pH decreased by 0.2 after treatment; Chemical Oxygen demand, biochemical oxygen demand, total suspended solids, ammonia, and total nitrogen reduced by 88.4%, 65.56%, 43.88%, 60% and 60% respectively. However, Phosphate increased by 54%. The bacterial isolates from the raw abattoir wastewater were Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Enterobacter aerogenes, Escherichia coli and Micrococcus luteus while Enterococcus faecalis, Bacillus cereus and Escherichia coli were isolated from the biofilms on the anode. Microbial fuel cells therefore have capacities for simultaneous waste water treatment and electricity generation.

Abattoir Wastewater Treatment and Energy Recovery Using a Ferricyanide-Catholyte Microbial Fuel Cell

The capacity of Microbial fuel cells (MFCs) to produce voltage and concurrently treat abattoir waste water was investigated in MFCs that used 0.1M potassium ferricyanide (K3[Fe(CN)6] as catholytes. Physicochemical, electrochemical and Microbiological properties of the MFCs were monitored. The open circuit voltage (OCV) readings were taken at 3 hours interval and maximum OCV of 965mV was recorded. Also, The physicochemical characteristics of the MFCs revealed that the pH decreased by 0.2 after treatment; Chemical Oxygen demand, biochemical oxygen demand, total suspended solids, ammonia, and total nitrogen reduced by 88.4%, 65.56%, 43.88%, 60% and 60% respectively. However, Phosphate increased by 54%. The bacterial isolates from the raw abattoir wastewater were Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Enterobacter aerogenes, Escherichia coli and Micrococcus luteus while Enterococcus faecalis, Bacillus cereus and Escherichia coli were isolated from the biofilms on the anode. Microbial fuel cells therefore have capacities for simultaneous waste water treatment and electricity generation.

Influence of sludge age on the performance of MFC treating winery wastewater

The objective of this paper was to determine the influence of sludge age on microbial fuel cell (MFC) performance for generating electricity and removing organic matter from winery wastewater. Six Solid Retention Times (SRT) were used: 1.2, 1.4, 1.8, 2.3, 3.5 and 7.0 d. Results demonstrate that the electricity generation increases by decreasing the SRT, selecting electrogenic microorganisms, once the specific organic loading rate (SOLR) increased and the competition for substrate was reduced. Decreasing the SRT, coulombic efficiency can be increased from 3.4% to almost 42.2% and maximum power density from 58 to 890 mW m(-2). However the SRT did not influence on organic matter removal in biological treatment, because only a small part of COD was removed oscillating around 600 mg L(-1) d(-1)and it was very similar at all SRT studied.

Effect of C/N ratio and salinity on power generation in compost microbial fuel cells

In this work, compost Microbial Fuel Cells (cMFCs) were used to generate electricity from a mix of fruit and vegetable wastes, and soil with different C/N ratios and salinities. Experiments were carried out in 500mL cMFCs equipped with carbon felt anodes and manganese dioxide cathodes. The cMFCs were loaded with fresh compost and operated at 20-23°C for up to 97days. The low C/N ratio (C/N 24) had a greater power production with a maximum power density of 5.29mW/m(2) (71.43mW/m(3)), indicating a more favorable condition for microbial growth. High-saline cMFCs produced lower power, suggesting that their level of salinity (10g/L of NaCl) inhibited electricigenic microorganisms. The closed-circuit cMFC showed an improved degradation of organic matter by 6% to 8% compared to the control MFC operated in an open circuit mode (no external resistor attached).

Microwave-Assisted Synthesis of Reduced Graphene Oxide/SnO2 Nanocomposite for Oxygen Reduction Reaction in Microbial Fuel Cells

We report on an easy, fast, eco-friendly, and reliable method for the synthesis of reduced graphene oxide/SnO2 nanocomposite as cathode material for application in microbial fuel cells (MFCs). The material was prepared starting from graphene oxide that has been reduced to graphene during the hydrothermal synthesis of the nanocomposite, carried out in a microwave system. Structural and morphological characterizations evidenced the formation of nanocomposite sheets, with SnO2 crystals of few nanometers integrated in the graphene matrix. Physico-chemical analysis revealed the formation of SnO2 nanoparticles, as well as the functionalization of the graphene by the presence of nitrogen atoms. Electrochemical characterizations put in evidence the ability of such composite to exploit a cocatalysis mechanism for the oxygen reduction reaction, provided by the presence of both SnO2 and nitrogen. In addition, the novel composite catalyst was successfully employed as cathode in seawater-based MFCs, giving electrical performances comparable to those of reference devices employing Pt as catalyst.

Relieving the fermentation inhibition enables high electron recovery from landfill leachate in a microbial electrolysis cell

The energy value of the organic matter in landfill leachate can be captured with a microbial electrolysis cell (MEC), which oxidizes organic compounds at an anode and generates H₂gas at a cathode.

Harvest and utilization of chemical energy in wastes by microbial fuel cells

Energy generated from wastes by using MFC technology could be effectively stored and utilized for real-world applications.

Analysis of the effect of biofouling distribution on electricity output in microbial fuel cells

Biofouling inside the catalyst layer decreased reaction sites and oxygen diffusion which mainly impaired cathode activity.

Operational, design and microbial aspects related to power production with microbial fuel cells implemented in constructed wetlands

This work aimed at determining the amount of energy that can be harvested by implementing microbial fuel cells (MFC) in horizontal subsurface constructed wetlands (HSSF CWs) during the treatment of real domestic wastewater. To this aim, MFC were implemented in a pilot plant based on two HSSF CW, one fed with primary settled wastewater (Settler line) and the other fed with the effluent of a hydrolytic up-flow sludge blanket reactor (HUSB line). The eubacterial and archaeal community was profiled on wetland gravel, MFC electrodes and primary treated wastewater by means of 16S rRNA gene-based 454-pyrosequencing and qPCR of 16S rRNA and mcrA genes. Maximum current (219 mA/m(2)) and power (36 mW/m(2)) densities were obtained for the HUSB line. Power production pattern correlated well with water level fluctuations within the wetlands, whereas the type of primary treatment implemented had a significant impact on the diversity and relative abundance of eubacteria communities colonizing MFC. It is worth noticing the high predominance (13-16% of relative abundance) of one OTU belonging to Geobacter on active MFC of the HUSB line that was absent for the settler line MFC. Hence, MFC show promise for power production in constructed wetlands receiving the effluent of a HUSB reactor.

Impact of electrode configurations on retention time and domestic wastewater treatment efficiency using microbial fuel cells

Efficient treatment of domestic wastewater under continuous flow conditions using microbial fuel cells (MFCs) requires hydraulic retention times (HRTs) that are similar to or less than those of conventional methods such as activated sludge. Two MFCs in series were compared at theoretical HRTs of 8.8, 4.4 and 2.2 h using two different brush-electrode MFC configurations: a full brush evenly spaced between two cathodes (S2C); and trimmed brush anodes near a single cathode (N1C). The MFCs with two cathodes produced more power than the MFCs with a single cathode, with 1.72 mW for the S2C, compared to and 1.12 mW for the N1C at a set HRT = 4.4 h. The single cathode MFCs with less cathode area removed slightly more COD (54.2 ± 2.3%, N1C) than the two-cathode MFCs (48.3 ± 1.0%, S2C). However, the higher COD removal was due to the longer HRTs measured for the MFCs with the N1C configuration (10.7, 5.3 and 3.1 h) than with the S2C configuration (7.2, 3.7 and 2.2 h), despite the same theoretical HRT. The longer HRTs of the N1C MFCs also resulted in slightly higher coulombic efficiencies (≤37%) than those of the S2C MFCs (≤29%). While the S2C MFC configuration would be more advantageous based on electrical power production, the N1C MFC might be more useful on the basis of capital costs relative to COD removal efficiency due to the use of less cathode surface area per volume of reactor.

Bioelectricity generation in microbial fuel cell using natural microflora and isolated pure culture bacteria from anaerobic palm oil mill effluent sludge

A double-chambered membrane microbial fuel cell (MFC) was constructed to investigate the potential use of natural microflora anaerobic palm oil mill effluent (POME) sludge and pure culture bacteria isolated from anaerobic POME sludge as inoculum for electricity generation. Sterilized final discharge POME was used as the substrate with no addition of nutrients. MFC operation using natural microflora anaerobic POME sludge showed a maximum power density and current density of 85.11mW/m(2) and 91.12mA/m(2) respectively. Bacterial identification using 16S rRNA analysis of the pure culture isolated from the biofilm on the anode MFC was identified as Pseudomonas aeruginosa strain ZH1. The electricity generated in MFC using P. aeruginosa strain ZH1 showed maximum power density and current density of 451.26mW/m(2) and 654.90mA/m(2) respectively which were five times higher in power density and seven times higher in current density compared to that of MFC using anaerobic POME sludge.