Sediment Microbial Fuel Cells Research Articles

Diffusion and filamentous bacteria jointly govern the spatiotemporal process of sulfide removal in sediment microbial fuel cells

Bioelectrochemical systems (BESs) have been recognized as a promising method for many bioremediation and degradation processes. However, very few studies reported the spatiotemporal diffusion and degradation processes of pollutants in anodic scope, which is fundamentally and practically important for BES application. In this study, the spatiotemporal removal processes of acidic volatile sulfide (AVS) around the anodes of sediment microbial fuel cells (SMFCs) with different external resistances were investigated. The results showed that SMFC current generation caused significant gradients of different variables in anodic sediments. Removal efficiencies of AVS (REAVS) decreased with increased external resistance and distance from the anode. A mathematical prediction based on Fick’s second law suggested diffusion-governed REAVS in different layers within the first 15 days, but the availability of the predication decreased along with both time and distance. Microbial community analysis revealed that a sulfur-reducing microorganism Caldisericum and a fermentation microorganism Anaerolineaceae, both were filamentous, were enriched and became keystone species in SMFCs over time. Our study indicated that the sulfide diffusion dynamic and the filamentous keystone bacteria jointly governed the anodic scopes of SMFCs for sediment AVS removal, providing novel insight for understanding the sulfide removal process drive by solid electron acceptors.

Impact of light/dark cycle on electrical and electrochemical characteristics of algal cathode sediment microbial fuel cells

In the present study, microalgae strain Chlorella sp. is used in catholyte of sediment microbial fuel cells (SMFCs) to provide oxygen for reduction reaction. Effect of different light/dark cycles on SMFC performance is investigated. Six light (h)/dark (h) cycles of 4/20, 8/16, 12/12, 16/8, 20/4 and 24/0 are applied. SMFC with a light/dark cycle of 12/12 (SMFC-12) produces the highest maximum power density of 19.6 mW m−2 and open circuit voltage of 442.3 mV, which are remarkably higher than those with other cycles. Individual electrode potentials and electrochemical impedance spectroscopy (EIS) are used to give an in-depth perspective of the observed trends. The anode open circuit potential (OCP) of the cells are approximately the same, whereas the cathode OCPs significantly differ with the most positive value of −23 mV for SMFC-12. Based on EIS analysis total resistance of SMFC-12 is 146.7 Ω that is remarkably lower than those of SMFC-4 (246.4 Ω) and SMFC-24 (214.4 Ω). Findings of this study suggest that the light/dark cycle has a substantial effect on the performance of algal SMFCs and an optimum photoperiod improves the electrical functioning of SMFCs by direct influence on algal growth and sufficient oxygen production at cathode.

Effect of sediment microbial fuel cell stacks on 9 V/12 V DC power supply

Sediment microbial fuel cell (SMFC) is a bio-electrochemical device that uses anaerobic bacteria to produce renewable energy. The voltage generated by SMFC is very low, so directly it cannot be applied to modern electronic devices. But, it is feasible to raise the output voltage of SMFC by connecting them in series-parallel combinations. In the present work, four SMFC modules are developed in the laboratory and by connecting in four different ways the output voltage as well as the output current are raised to the utility levels. The primary cause to avoid the practical application of series and parallel connected SMFC is voltage reversal problem. To do away with this problem, in this work each group of SMFCs is first used to charge a super-capacitor (4 F, 5.5 V) and then it has been used to power the dc boost converter. Moreover, in this research work, the effects of charging and discharging times of super capacitors for each module are also investigated. In the final stage, a dc boost converter is presented to step-up the voltage of stacked SMFCs which provides a regulated output voltage (9 V/12 V) at the load. The results obtained, show that module-4 connected boost converter provides higher output current for a longer duration as compared to other super capacitor connected modules. This technique of energy harvesting from SMFCs can be used as a power source (either of 9 V or 12 V) in practical electronic devices.

Electroactivity of the Gram-positive bacterium Paenibacillus dendritiformis MA-72

Whilst most of the microorganisms recognized as exoelectrogens are Gram-negative bacteria, the electrogenicity of Gram-positive bacteria has not been sufficiently explored. In this study, the putative electroactivity of the Gram-positive Paenibacillus dendritiformis MA-72 strain, isolated from the anodic biofilm of long-term operated Sediment Microbial Fuel Cell (SMFC), has been investigated. SEM observations show that under polarization conditions P. dendritiformis forms a dense biofilm on carbon felt electrodes. A current density, reaching 5 mA m−2, has been obtained at a prolonged applied potential of −0.195 V (vs. SHE), which represents 35% of the value achieved with the SMFC. The voltammetric studies confirm that the observed Faradaic current is associated with the electrochemical activity of the bacterial biofilm and not with a soluble redox mediator. The results suggest that a direct electron transfer takes place through the conductive extracellular polymer matrix via pili/nanowires and multiple cytochromes. All these findings demonstrate for the first time that the Gram-positive Paenibacillus dendritiformis MA-72 is a new exoelectrogenic bacterial strain.

Simultaneous bioelectricity generation and remediation of sulfide-contaminated tidal flat through sediment microbial fuel cell (SMFC)

(2020). Simultaneous bioelectricity generation and remediation of sulfide-contaminated tidal flat through sediment microbial fuel cell (SMFC). Energy Sources, Part A: Recovery, Utilization, and Environmental Effects. Ahead of Print.

On-line monitoring of repeated copper pollutions using sediment microbial fuel cell based sensors in the field environment

Most microbial fuel cells (MFCs) based sensors rely on exoelectrogenic bacteria to sense contaminants. However, these sensors cannot monitor repeated pollutions unless the exoelectrogenic bacteria are recovered or re-inoculated. To overcome this drawback, a novel sediment microbial fuel cell (SMFC) based sensor was developed for online and in situ monitoring of repeated Cu2+ shocks to the overlaying water of paddy soil. The SMFC sensor was operated for a period of eight months in the field environment and a group of CuCl2 solutions ranging from 12.5 to 400 mg L−1 Cu2+ were repeatedly applied on sunny and rainy days in different seasons. Results show that the SMFC sensor generates one voltage peak in less than 20 s after each Cu2+ shock, regardless of the seasons and weather conditions, and the voltage increments from baseline to peak exhibit linear correlation (R2 > 0.92) with the logarithm of Cu2+ concentrations. Repeated Cu2+ pollutions do not decrease the baseline voltage, indicating that the activity of exoelectrogenic bacteria was not significantly inhibited. Soil adsorbed and inactivated approximately 99% of total Cu2+. Only 1% of total Cu2+ was the toxic exchangeable fraction, of which the concentrations were 0.73, 0.23, and 0.22 mg kg−1 in the surface (0–3 cm), middle (3–6 cm), and bottom (6–11 cm) layers, respectively. The abundance of 16S rRNA gene transcripts of exoelectrogenic bacteria-associated genera is the lowest in the surface layer (2.86 × 1011 copies g−1) and the highest in the bottom layer (7.99 × 1011 copies g−1). Geobacter, Clostridium, Anaeromyxobacter, and Bacillus are the most active exoelectrogenic bacteria-associated genera in the soil. This study suggests that the SMFC sensor could be applied in wetlands to monitor the repeated discharge of Cu2+ and other heavy metals.

Sediment microbial fuel cells as a barrier to sulfide accumulation and their potential for sediment remediation beneath aquaculture pens

Sediment microbial fuel cells (SMFCs) generate electricity through the oxidation of reduced compounds, such as sulfide or organic carbon compounds, buried in anoxic sediments. The ability to remove sulfide suggests their use in the remediation of sediments impacted by point source organic matter loading, such as occurs beneath open pen aquaculture farms. However, for SMFCs to be a viable technology they must remove sulfide at a scale relevant to the environmental contamination and their impact on the sediment geochemistry as a whole must be evaluated. Here we address these issues through a laboratory microcosm experiment. Two SMFCs placed in high organic matter sediments were operated for 96 days and compared to open circuit and sediment only controls. The impact on sediment geochemistry was evaluated with microsensor profiling for oxygen, sulfide, and pH. The SMFCs had no discernable effect on oxygen profiles, however porewater sulfide was significantly lower in the sediment microcosms with functioning SMFCs than those without. Depth integrated sulfide inventories in the SMFCs were only 20% that of the controls. However, the SMFCs also lowered pH in the sediments and the consequences of this acidification on sediment geochemistry should be considered if developing SMFCs for remediation. The data presented here indicate that SMFCs have potential for the remediation of sulfidic sediments around aquaculture operations.

MnO2/tourmaline composites as efficient cathodic catalysts enhance bioelectroremediation of contaminated river sediment and shape biofilm microbiomes in sediment microbial fuel cells

The efficient degradation of pollutants in river sediments is essential for the bioremediation of contaminated rivers. In the present study, sediment microbial fuel cells (SMFCs) with manganese dioxide/tourmaline composite modified cathodes (MnO2/T-SMFCs) were developed to simultaneously produce electricity and degrade organic matter in contaminated river sediment and water. The MnO2/T-SMFCs exhibited a higher power density of 368.99 mW/m3, which was 1.26 and 2.06 times that of SMFCs with MnO2 cathode and open-circuit SMFCs (OC-SMFCs), respectively. Moreover, MnO2/T-SMFCs exhibited the highest total organic carbon (TOC) removal of 55.7 %, which was 1.76 times that of the OC-SMFCs. It also obtained the highest NH4+-N removal of 93.7 %, 40 % higher than OC-SMFCs. The high oxidation reduction reaction (ORR) associated with the MnO2/T cathode is partly attributed to the synergetic effect between MnO2 and tourmaline to change the electronic structure of MnO2 electrode and modify its adsorption/desorption behaviors. PacBio sequencing of 16S rRNA gene amplicons showed that volatile fatty acid- and alcohol-oxidizing Syntrophus and Smithella, and electroactive Geobacter dominated the anode biofilms in the MnO2/T-SMFCs. These results indicated that MnO2/T-SMFCs are effective for sediment bioelectroremediation in contaminated rivers.

Electrical current generation from a continuous flow macrophyte biocathode sediment microbial fuel cell (mSMFC) during the degradation of pollutants in urban river sediment.

A new type of sediment microbial fuel cell (SMFC) with floating macrophyte Limnobium laevigatum, Pistia stratiotes, or Lemna minor L. biocathode was constructed and assessed in three phases at different hydraulic retention time (HRT) for electrical current generation during the degradation of urban river sediment. The results showed a highest voltage output of 0.88 ± 0.1V, maximum power density of 80.22mWm-3, highest columbic efficiency of 15.3%, normalized energy recovery of 0.030kWhm-3, and normalized energy production of 0.005kWhm-3 in the Lemna minor L. SMFC during phase 3 at HRT of 48h, respectively. Highest removal efficiencies of total chemical oxygen demand of 80%, nitrite of 99%, ammonia of 93%, and phosphorus of 94% were achieved in Lemna minor L. system, and 99% of nitrate removal and 99% of sulfate removal were achieved in Pistia stratiotes and Limnobium laevigatum system during the SMFC operation, respectively. Pistia stratiotes exhibited the highest growth in terms of biomass and tap root system of 29.35g and 12.2cm to produce the maximum dissolved oxygen of 16.85 ± 0.2mgL-1 compared with other macrophytes. The predominant bacterial phylum Proteobacteria of 62.86% and genus Exiguobacterium of 17.48% were identified in Limnobium laevigatum system, while the class Gammaproteobacteria of 28.77% was observed in the control SMFC. The integration of technologies with the continuous flow operation shows promising prospect in the remediation of polluted urban river sediments along with the generation of electrical current.

Response of sediment microbial communities to crude oil contamination in marine sediment microbial fuel cells under ferric iron stimulation

In this study, response of the microbial communities associated with the bioremediation of crude oil contaminated marine sediments was addressed using sediment microbial fuel cells (SMFCs). Crude oil was spiked into marine sediments at 1 g/kg of dry sediment to simulate a heavily contaminated marine environment. Conventional SMFCs were used with carbon fiber brushes as the electrode components and were enhanced with ferric iron to stimulate electrochemically active bacteria. Controls were operated under open circuit with and without ferric iron stimulation, with the latter condition simulating natural attenuation. Crude oil removal in the Fe enhanced SMFCs reached 22.0 ± 5.5% and was comparable to the measured removal in the control treatments (19.2 ± 7.4% in natural attenuation SMFCs and 15.2 ± 2.7% in Fe stimulated open circuit SMFCs), indicating no major enhancement to biodegradation under the applied experimental conditions. The low removal efficiency could be due to limitations in the mass transfer of the electron donor to the microbes and the anodes. The microbial community structure showed similarity between the iron stimulated SMFCs operated under the open and closed circuit. Natural attenuation SMFCs showed a unique profile. All SMFCs showed high relative abundances of hydrocarbon degrading bacteria rather than anode reducers, such as Marinobacter and Arthrobacter in the case of the natural attenuation SMFCs, and Gordonia in the case of iron stimulated SMFCs. This indicated that the microbial structure during the bioremediation process was mainly determined by the presence of petroleum contamination and to a lesser extent the presence of the ferric iron, with no major involvement of the anode as a terminal electron acceptor. Under the adopted experimental conditions, the absence of electrochemically active microbes throughout the biodegradation process indicates that the use of SMFCs in crude oil bioremediation is not a successful approach. Further studies are required to optimize SMFCs systems for this aim.

Chlorella vulgaris on the cathode promoted the performance of sediment microbial fuel cells for electrogenesis and pollutant removal

The lack of electron acceptors in cathode has limited the widespread application of sediment microbial fuel cells (SMFCs). In this study, Chlorella vulgaris (C. vulgaris) was added to the cathode to produce oxygen as an electron acceptor. The synergistic effects between C. vulgaris and electrogenic microorganisms in SMFCs were investigated, and were shown to enhance biodegradation of organic matter in sediments and convert chemical energy into electrical energy. Results showed that the addition of C. vulgaris on the cathode of SMFCs significantly reduced their internal resistance. The low algae concentration SMFC group reduced the initial internal resistance by 67.4% under illumination and produced a maximum power density of 5.17 W/m3, which was 6 times higher than that of SMFCs without addition of C. vulgaris. We also obtained organic matter removal efficiencies 37.2% higher after 16 days, which accelerated the startup time for three times. It was demonstrated that IEF-N and OP, respectively, were forms of nitrogen and phosphorus removed by SMFCs. Additionally, high-throughput sequencing of microbial communities indicated that C. vulgaris increased the abundance of electrogenic bacteria (Geobacter and Desulfobulbaceae) in the anode and types of photosynthetic bacteria that support oxygen production in the cathode. The combined application of microalgae- and SMFC-based technologies offer a promising remediation approach for organically-contaminated sediments.

Electricity generation potential of sewage sludge in sediment microbial fuel cell using Ti–TiO2 electrode

AbstractThe aim of this study is to increase the electricity generation capacity of sediment microbial fuel cell (SMFC) using sewage sludge as a substrate source in anode media via an attractive electrode material. For this purpose, several electrochemical and molecular techniques have been employed to evaluate the performance of SMFC. The max power density and charge transfer resistance of SMFC running on sewage sludge were 187 mW/m2 and 84.7 Ω, respectively. The polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) analysis indicated that bacteria in anode biofilm belonged to the Clostridia, d‐proteobacteria, g‐proteobacteria, and b‐proteobacteria. Scanning electron microscopy and fluorescence in situ hybridization observations demonstrated that a viable biofilm was formed on the anode surface and the abundance of bacteria was significantly higher than archaea. Consequently, this study showed that sewage sludge could be used as a substrate in the anode media of SMFC for producing high power density.

Optimization of electricity generation from marine sediment of Kendari Bay using stacked sediment microbial fuel cell

Marine sediments of Kendari Bay has the potential as an alternative source of electrical energy through sediment microbial fuel cell (SMFC) due to the high level of sedimentation. This study aims to optimize the amount of electrical voltage that can be generated through the SMFC system using stacked SMFC in the form of a series connection. The research methods include determining the sampling location, physical-chemical properties measurement of sediments, SMFC assembly (single and stacked SMFC), and electrical voltage measurement. Three station points representing the overall condition of Kendari Bay are determined as sampling locations. The result shows that there was a decrease in the organic matter content of the sediment substrate after the use of SMFC namely organic carbon from 2.78 percent to be 2.68 percent due to microbial activity in sediments. The single SMFC from station 2 (S2) can produce the maximum electrical voltage of 438 mV which then optimized using stacked SMFC in series connection. The maximum electrical voltage of 2.174V can be obtained using stacked SMFC. These results show that marine sediments of Kendari Bay is interesting as an alternative energy source through SMFC and stacked SMFC could optimize the amount of electrical voltage from single SMFC.

Voltage control of sediment microbial fuel cell to power the AC load

This paper presents an innovative method for green energy generation by sediment microbial fuel cell (SMFC). SMFC has low output voltage and current, which can be extended for applications in modern electronic devices. In this paper, the different connection of SMFC (four modules: module1, module2, module3 and module4) is used to increase the output voltage as well as current. All modules are tested to the required time for charging four super capacitors (5.5 V, 4 F). Module4 (7 Parallel × 5 series connected SMFCs) charges a super capacitor from 2.76 V to 4.5 V in 30 min which takes less charging time as compared to other modules. The boost converter steps up input voltage super capacitor connected module4 at a constant voltage of 13.5 V to charge a 12 V battery for the time of 6.5 min. Further, module4 is expanded in six similar SMFC modules which are connected to charge the battery continuously. After 100% charging the battery, astable multi-vibrator inverter circuit is used to convert the direct current (battery) into alternating current for LED bulb lighting (7 W, 230 V, 50 Hz). This technique is useful for SMFC application as a power source in the practical AC load.

Carbon nanomaterial-modified graphite felt as an anode enhanced the power production and polycyclic aromatic hydrocarbon removal in sediment microbial fuel cells

Sediment microbial fuel cells (SMFCs) can be used to generate electricity and remove organic contaminants. For electricity generation and contaminant removal, the anode material is one of important factors influencing the performance of SMFCs. In this study, graphene (GR), graphene oxide (GO) and carbon nanotubes (CNTs) were applied to modify the graphite felt (GF) anode in SMFCs during 110 d operation. An economical and easy modification method with the carbon nanomaterials was applied. The carbon nanomaterials increased the electrochemically active surface areas and biomass content of the anodes and correspondingly effectively enhanced the generation of electricity and the removal rates of loss on ignition (LOI) and polycyclic aromatic hydrocarbons (phenanthrene and pyrene). During the steady period from 50 d to 110 d, the GO-SMFCs favored the enrichment of EAB and thus output the highest voltages of 30.60–48.61 mV. The GR-SMFCs and GO-SMFCs generated high electric power of approximate 0.98 ± 0.14 kJ and 0.87 ± 0.04 kJ, followed by CNT-SMFCs (0.57 ± 0.06 kJ) and GF-SMFCs (0.49 ± 0.07 kJ) during the 110 d operation. The PAH degradation was not directly related to the electric current in the SMFCs. Near the anodes, the order of the phenanthrene removal rates was CNT-SMFCs (78.1%) > GR-SMFCs (73.0%) ≈ GO-SMFCs (71.2%) > GF-SMFCs (45.6%), and the order of the pyrene removal rates was GO-SMFCs (69.6%) ≈ GR-SMFCs (68.2%) ≈ CNT-SMFCs (66.7%) > GF-SMFCs (42.3%). The three carbon nanomaterials increased the microbial community diversity and slightly changed the microbial community distribution of biofilms on the anodes. Correlation analysis indicated that the degradation of phenanthrene was positively correlated with the abundances of Pseudomonas, Thauera, Diaphorobacter, Tumebacillus and Lysobacter. Pyrene degradation was strongly correlated with LOI degradation.

Performance Enhancement of Single-Chamber Sediment-Microbial Fuel Cell with Variation in Cathode Surface Area

This study investigates the impact of cathode surface area on single chamber sediment-microbial fuel cell (S-MFC). A fixed graphite anode surface area of 0.000471m 2 has been used on four S-MFCs coupled with four carbon fiber cloth cathode electrodes with variation of surface area. Pond sediment has been used as the anode medium that inoculated with acetate as substrate to ramp up the amount of electrochemical-active bacteria (EAB). The S-MFCs has been operated and monitored for 120 hours using Arduino based data logger. The outcomes of this observation period have indicated the S-MFC with larger cathode surface area (0.01m 2 ) possess smaller internal resistance (123.96±2.68 I©) and thus performed significantly better than other S-MFC with the smaller cathode surface area, resulting with average voltage and current of 0.598±0.008V and 4.827±0.124mA respectively, where a maximum power density of 2.867mW with a coulombic efficiency of 64.63% was achieved. Successful performance increase suggests enlargement of the cathode area could be the alternative to reduce the internal resistance in traditional MFCs for electricity generation.

Enhanced power performance of an in situ sediment microbial fuel cell with steel-slag as the redox catalyst: I. electricity generation

Steel-slag was added as a catalyst to sediment microbial fuel cells (SMFCs) in an in situ sediment biodegradation experiment to determine the benefits to long-term power production of the cells and to elucidate the external factors affecting power production.

Control Strategy for Adaptive Active Energy Harvesting in Sediment Microbial Fuel Cells

AbstractSediment microbial fuel cells (SMFCs) are an alternative renewable power supply for sensors and communication. However, their low power outputs limit their practical applications. Maximum p...

Burial depth of anode affected the bacterial community structure of sediment microbial fuel cells

Sediment microbial fuel cells (SMFCs) are attractive devices to in situ power environmental monitoring sensors and bioremediate contaminated soils/sediments. Burial depth of the anode was verified to affect the performance of SMFCs. The present research evaluated the differences in microbial community structure of anodic biofilms located at different depth. It was demonstrated that both microbial diversity and community structure of anodic biofilms were influenced by the depth of anode location. Microbial diversity decreased with increased anodic depth. The number of the operational taxonomic units (OTUs) was determined as 1438 at the anode depth of 5 cm, which reduced to 1275 and 1005 at 10 cm and 15 cm, respectively. Cluster analysis revealed that microbial communities of 5 cm and 10 cm were clustered together, separated from the original sediment and 15 cm. Proteobacteria was the predominant phylum in all samples, followed by Bacteroidetes and Firmicutes. Beta-and Gamma-proteobacteria were the most abundant classes. A total of 23 OTUs showed high identity to 16S rRNA gene of exoelectrogens such as Geobacter and Pseudomonas. The present results provided insights into the effects of anode depth on the performance of SMFC from the perspectives of microbial community structure.

A Study on Mechanism of Sediment Bioremediation by Sediment Microbial Fuel Cells

A Study on Mechanism of Sediment Bioremediation by Sediment Microbial Fuel Cells