Application Of Bioelectrochemical Systems Research Articles

Reduction of organic compounds in petro-chemical industry effluent and desalination using Scenedesmus abundans algal microbial desalination cell

Water and energy shortages are considered to be very serious global issue. As a consequence, it is necessary to develop an alternative water resource such as desalination and wastewater treatment etc. Microbial desalination cell (MDC) is the new, green and environment–friendly technology that desalinates seawater and produces bioelectricity. This study integrate desalination with wastewater treatment and bioelectricity production in MDC by utilizing microalgae as bio-cathode and the results were compared with the chemical cathode. Recently, microalgae have received a high attention for application in bio-electrochemical systems due to its potential to be used for oxygen generation and biodiesel production. The study utilizes petroleum wastewater in the anode chamber and microalgae Scenedesmus abundans in the cathode chamber. The results have highlighted that microalgae bio-cathodes perform better than chemical cathode and increases COD removal and produce a considerable amount of bioelectricity. It also proved that high initial salt concentration 35gNacl L−1desalinates well when compared with low initial salt concentration 20g NaCl L−1 .The maximum voltage and desalination efficiency of MDC 1 (35gNaCl L−1) and MDC 2(20gNaCl L−1) is found to be 654mv and 55.3%; 506mv and 42.6% with the volumetric ratio of 1:0.5:1(anode, desalination chamber and microalgae cathode). Thus the experimental results reveal that utilizing bio-cathode MDC proved to be a promising platform for effective desalination of sea water.

Heat-Treated Stainless Steel Felt as a New Cathode Material in a Methane-Producing Bioelectrochemical System.

Methane-producing bioelectrochemical systems (BESs) are a promising technology to convert renewable surplus electricity into the form of storable methane. One of the key challenges for this technology is the search for suitable cathode materials with improved biocompatibility and low cost. Here, we study heat-treated stainless steel felt (HSSF) for its performance as biocathode. The HSSF had superior electrocatalytic properties for hydrogen evolution compared to untreated stainless steel felt (SSF) and graphite felt (GF), leading to a faster start-up of the biocathodes. At cathode potentials of −1.3 and −1.1 V, the methane production rates for HSSF biocathodes were higher than the SSF, while its performance was similar to GF biocathodes at −1.1 V and lower than GF at −1.3 V. The HSSF biocathodes had a current-to-methane efficiency of 60.8% and energy efficiency of 21.9% at −1.3 V. HSSF is an alternative cathode material with similar performance compared to graphite felt, suited for application in methane-producing BESs.

Corrugated stainless-steel mesh as a simple engineerable electrode module in bio-electrochemical system: Hydrodynamics and the effects on decolorization performance

The application of bio-electrochemical system (BESs) is strongly depended on the development of the engineering applicable electrode. Here we described an economical and readily processable electrode module with three-dimensional structure, the corrugated stainless-steel mesh electrode module (c-SMEM). This novel developed electrode module was demonstrated to provide a good hydrodynamic characteristic and significantly enhanced the decolorization performance of the BES when serving for treating azo dye (acid orange 7, AO7) containing wastewater. Compared to the conventional planar electrodes module (p-SMEM), c-SMEM was found to prolong the mean residence time (MRTθ) of AO7 and change the flow pattern closer to the plug flow. As a result, the maximum enhancement of the volumetric decolorization rate (vDR) can reach to 255%, even when the c-SMEM and p-SMEM have the same electrode surface area. In addition, a techno-economic analysis model was established to elucidated the effects of the decolorization performance and the material cost on the initial capital cost, which revealed the BES with c-SMEM could be economically comparable to or even better than the traditional bio-decolorization technologies. These results suggest c-SMEM holds great potential for engineering application, which may help paving the way of applying BES at large-scale.

High-pressure thermophilic electromethanogenic system producing methane at 5 MPa, 55°C

Toward applications of bio-electrochemical systems in industrial processes and extreme environments, electromethanogenesis under high-pressure conditions was examined. Stainless-steel single-chamber reactors specifically designed to examine bio-electrochemical reactions under pressurized conditions were inoculated with thermophilic microorganisms originated from an oilfield formation water. The reactors were incubated at 5MPa, 55°C in fed-batch operational mode with an applied voltage of 0.7V. In the first few fed-batch cycles, hydrogen was mainly produced. After the third cycle, however, the reactors produced only methane simultaneously with current generation. The methane-production rate of the reactors showed an applied-voltage dependence and increased from 34.9 to 168.4mmolm-2day-1 with an increase in the applied voltage from 0.4 to 0.9V. The efficiency of capturing electrons in the produced methane on average exceeded 70% with the applied voltage of 0.4V or higher. Cyclic voltammetry further confirmed abilities of the bioelectrodes to catalyze electrochemical reactions at 5MPa. Performance of the electromethanogenesis system was not altered under lower pressure conditions (1.2 and 2.5MPa). An exoelectrogenic bacterium affiliated with the genus Thermincola and a methanogen belonging to the genus Methanothermobacter were detected as the dominant species in the bioanode and biocathode microbiotas, respectively. Thus, our results indicated that electromethanogenesis systems could be developed and operated under highly-pressurized conditions, suggesting that applications of the bio-electrochemical system in high-pressure environments (including high-temperature subsurface reservoirs) can be technically feasible.

Microbial fuel cell as a free-radical scavenging tool

ABSTRACTMicrobial fuel cells (MFCs) are known for their capability to directly convert organic substrates into electricity by the biochemical activity of specific microorganisms. Availability of a proper terminal electron acceptor is crucial for this process. Free radicals, with their one or more unpaired electrons, are extremely reducible and could be considered as electron acceptors in terms of cathodic processes in MFC. During this reduction, free radicals could be transformed in the same manner as they are transformed by antioxidants. The present study investigated this opportunity by utilization of 2,2-diphenyl-1-picrylhydrazyl (150 μmol/dm3 methanol solution) as a free-radical molecule. During the studied process, over 90% radical neutralization was observed in less than 16 hours. The results obtained demonstrate for the first time the potential of MFC type bio-electrochemical systems to serve as a free-radical scavenging tool and to provide antioxidant and anti-radical activity. In this way, this study opens a completely new field of research and application of bio-electrochemical systems.

Effects of electrolyte conductivity on power generation in bio-electrochemical systems

Bio-electrochemical systems (BESs) have recently attracted considerable attention as a promising technology for sustainable wastewater treatment. However, the practical applications of BESs remain limited partly because the conductivity of actual wastewater can vary from 0.2 to 40 ms/cm which is out of the appropriate range for power generation. Herein, we investigated the effect of anolyte and catholyte conductivities on power generation. The maximum current density (0.73 mA/cm2) was achieved by reactors using an anolyte solution with a conductivity of 14.93 ± 0.02 ms/cm; this was four times higher than the minimum current density (0.13 mA/cm2), obtained using a solution with a conductivity of 2.61 ± 0.04 ms/cm. Anolyte conductivity was found to be the primary rate-limiting factor for power generation and had a greater effect than the conductivity of the catholyte. Furthermore, an anolyte conductivity range of 6.45–14.93 ms/cm was found to be most appropriate for superior BES performance.

Mixed Culture Biocathodes for Production of Hydrogen, Methane, and Carboxylates.

Formation of hydrogen, methane, and organics at biocathodes is an attractive new application of bioelectrochemical systems (BESs). Using mixed cultures, these products can be formed at certain cathode potentials using specific operating conditions, of which pH is important. Thermodynamically, the reduction of CO2 to methane is the most favorable reaction, followed by reduction of CO2 to acetate and ethanol, and hydrogen. In practice, however, the cathode potential at which these reactions occur is more negative, meaning that more energy is required to drive the reaction. Therefore, hydrogen is often found as a second product or intermediate in the conversion of CO2 to both methane and carboxylates. In this chapter we summarize the inocula used for biocathode processes and discuss the achieved conversion rates and cathode potentials for formation of hydrogen, methane, and carboxylates. Although this overview reveals that BESs offer new opportunities for the bioproduction of different compounds, there are still challenges that need to be overcome before these systems can be applied on a larger scale. Graphical Abstract.

Electricity generation, desalination and microalgae cultivation in a biocathode-microbial desalination cell

Recently, microalgae has received a high attention for application in bioelectrochemical systems due to its potential to be used for oxygen generation and biodiesel production. In this study performance of algal biocathode in a microbial desalination cell (MDC) was evaluated against air cathode and biocathode microbial fuel cell (MFC). Effluent of a dairy wastewater treatment plant with COD of 1000mgl−1 was utilized as substrate in the anode and the microalgae Chlorella vulgaris was inoculated in the cathode using a synthetic culture media. Experiments were conducted using two different saline water concentrations including 15gl−1 (MDC-1) and 35gl−1 (MDC-2) in a desalination cell and produced power density, salt removal rate and algae growth were monitored. Maximum power density of 20.25mWm−2 was observed in MDC-2 which was over two-times higher than that for MDC-1. This indicates the positive effect of using more concentrated saline solution on power generation due to higher conductivity and less internal resistance in the middle chamber. Moreover, salinity removal rate of 0.341gl−1day−1 in MDC-2 (1.5 times higher than MDC-1) as well as higher algal growth (38%) in MDC-2 proved the higher performance of the MDC when more concentrated saline solution was used. Maximum power density generated by MDC-2 was comparable to that for MFC with air cathode (19.80mWm−2), however the MDC used in this work has the advantage of simultaneous saline removal and algae growth in a bioelectrochemical system.

Editorial: Current Challenges and Future Perspectives on Emerging Bioelectrochemical Technologies.

Editorial: Current Challenges and Future Perspectives on Emerging Bioelectrochemical Technologies.

Enrichment of Dehalococcoides mccartyi spp. from a municipal activated sludge during AQDS-mediated bioelectrochemical dechlorination of 1,2-dichloroethane to ethene

The application of bioelectrochemical systems (BES) for the treatment of chloroethanes has been so far limited, in spite of the high frequency that these contaminants are detected at contaminated sites. This work studied the biodegradation of 1,2-dichloroethane (1,2-DCA) in a lab-scale BES, inoculated with a municipal activated sludge and operated under a range of conditions, spanning from oxidative to reductive, both in the presence and in the absence of the humic acid analogue anthraquinone-2,6-disulfonate (AQDS) as a redox mediator. The results showed stable dechlorination of 1,2-DCA to ethene (up to 65±5μmol/Ld), when the BES was operated at a set potential of −300mV vs. SHE, in the presence of AQDS. Sustained filled-and-draw operation resulted in the enrichment of Dehalococcoides mccartyi. The results of this work provide new insights into the applicability of BES for groundwater remediation and the potential interaction between biogeochemistry and 1,2-DCA in humics-rich contaminated aquifers.

In situ monitoring of Shewanella oneidensis MR-1 biofilm growth on gold electrodes by using a Pt microelectrode

Much attention has been focused on electrochemically active bacteria (EAB) in the application of bioelectrochemical systems (BESs). Studying the EAB biofilm growth mechanism as well as electron transfer mechanism provides a route to upgrade BES performance. But an effective bacterial growth monitoring method on the biofilm scale is still absent in this field. In this work, electrode-attached bacterial biofilms formed by Shewanella oneidensis MR-1 were dynamically monitored through a microelectrode method. For S. oneidensis MR-1, a respiratory electron transport chain is associated with the secretion of riboflavin, severing as the cofactor to the outer membrane c-type cytochromes. The biofilm growth was monitored through adopting riboflavin as an electrochemical probe during the approach of the microelectrode to the biofilm external surface. This method allows in vivo and in situ biofilm monitoring at different growth stages without destructive manipulation. Furthermore, the biofilm growth monitoring results have been proved to be relatively accurate through observation under confocal laser scanning microscopy. We further applied this method to investigate the effects of four environmental factors (the concentrations of dissolved oxygen, sodium lactate, riboflavin as well as the electrode potential) on S. oneidensis MR-1 biofilm development.

A Bibliometric Review of Research Trends on Bioelectrochemical Systems

Bioelectrochemical systems (BES) have received widespread attention for their capability of simultaneous wastewater treatment and electricity or fuels/chemicals production. The present study was performed to evaluate the global scientific output of BES-related research based on the Science Citation Index-Expanded database from 1991 to 2014. The publication outputs, journals, subject categories, countries and institutes were analysed to identify the world research on BES. In addition, 'word cluster analysis' was applied to give an insight into the research trends on BES. The results indicate that the annual publications on BES increased steadily, especially after 2004. China, with 7 institutes included among the 15 most productive institutes, is the largest contributor on BES research during the past 24 years. Microbial fuel cell is the most frequently studied reactor, and 'electricity generation' and 'wastewater treatment' are two dominant applications of BES. The use of two nanostructured materials - carbon nanotubes and grapheme - is increasingly studied in the BES field.

Biodegradation of phenolic compounds and their metabolites in contaminated groundwater using microbial fuel cells

This is the first study demonstrating the biodegradation of phenolic compounds and their organic metabolites in contaminated groundwater using bioelectrochemical systems (BESs). The phenols were biodegraded anaerobically via 4-hydroxybenzoic acid and 4-hydroxy-3-methylbenzoic acid, which were retained by electromigration in the anode chamber. Oxygen, nitrate, iron(III), sulfate and the electrode were electron acceptors for biodegradation. Electro-active bacteria attached to the anode, producing electricity (~1.8mW/m2), while utilizing acetate as an electron donor. Electricity generation started concurrently with iron reduction; the anode was an electron acceptor as thermodynamically favorable as iron(III). Acetate removal was enhanced by 40% in the presence of the anode. However, enhanced removal of phenols occurred only for a short time. Field-scale application of BESs for in situ bioremediation requires an understanding of the regulation and kinetics of biodegradation pathways of the parent compounds to relevant metabolites, and the syntrophic interactions and carbon flow in the microbial community.

Development of Bioelectrochemical Systems to Promote Sustainable Agriculture

Bioelectrochemical systems (BES) are a newly emerged technology for energy-efficient water and wastewater treatment. Much effort as well as significant progress has been made in advancing this technology towards practical applications treating various types of waste. However, BES application for agriculture has not been well explored. Herein, studies of BES related to agriculture are reviewed and the potential applications of BES for promoting sustainable agriculture are discussed. BES may be applied to treat the waste/wastewater from agricultural production, minimizing contaminants, producing bioenergy, and recovering useful nutrients. BES can also be used to supply irrigation water via desalinating brackish water or producing reclaimed water from wastewater. The energy generated in BES can be used as a power source for wireless sensors monitoring the key parameters for agricultural activities. The importance of BES to sustainable agriculture should be recognized, and future development of this technology should identify proper application niches with technological advancement.

Encapsulation of a living bioelectrode by a hydrogel for bioelectrochemical systems in alkaline media.

The electroactive biofilms in the bioelectrodes of traditional bioelectrochemical systems (BES) directly interact with the aqueous solution and usually require a mild aqueous solution environment (e.g. 20 mM acetate and pH = 7.0) to exert their optimum bioelectrocatalytic activity. In this communication, we present a concept of encapsulation of a bioelectrode by a hydrogel for a BES in an alkaline solution environment. A hydrogel-bioelectrode (HBE) was prepared by encapsulating a living electroactive biofilm pre-grown in the bioelectrode with a poly(vinyl alcohol) hydrogel through a freezing/thawing process. Under the protection of the hydrogel, the HBE could keep a high bioelectrocatalytic activity in an alkaline feeding solution with an acetate concentration of over 80 mM and a pH value of 11.0. Moreover it was very stable and tolerated low-frequency ultrasonic vibration. These results imply the extended applications of BESs in the area of high-strength wastewater treatment, portable and implantable devices.

Membranes for bioelectrochemical systems: challenges and research advances

Increasing energy demand has been a big challenge for current society, as the fossil fuel sources are gradually decreasing. Hence, development of renewable and sustainable energy sources for the future is considered one of the top priorities in national strategic plans. Bioenergy can meet future energy requirements – renewability, sustainability, and even carbon-neutrality. Bioenergy production from wastes and wastewaters is especially attractive because of dual benefits of energy generation and contaminant stabilization. There are several bioenergy technologies using wastes and wastewaters as electron donor, which include anaerobic digestion, dark biohydrogen fermentation, biohydrogen production using photosynthetic microorganisms, and bioelectrochemical systems (BESs). Among them BES seems to be very promising as we can produce a variety of value-added products from wastes and wastewaters, such as electric power, hydrogen gas, hydrogen peroxide, acetate, ethanol etc. Most of the traditional BES uses a membrane to separate the anode and cathode chamber, which is essential for improving microbial metabolism on the anode and the recovery of value-added products on the cathode. Performance of BES lacking a membrane can be seriously deteriorated, due to oxygen diffusion or substantial loss of synthesized products. For this reason, usage of a membrane seems essential to facilitate BES performance. However, a membrane can bring several technical challenges to BES application compared to membrane-less BES. These challenges include poor proton permeability, substrate loss, oxygen back diffusion, pH gradient, internal resistance, biofouling, etc. This paper aims to review the major technical barriers associated with membranes and future research directions for their application in BESs.

High current density via direct electron transfer by the halophilic anode respiring bacterium Geoalkalibacter subterraneus

In this study the characterization of Geoalkalibacter subterraneus is presented, which is a novel halophilic anode respiring bacterium (ARB) previously selected and identified in a potentiostatically controlled bioelectrochemical system (BES) inoculated with sediments from a salt plant. Pure culture electroactive biofilms of Glk. subterraneus were grown during chronoamperometric batch experiments at a graphite electrode poised at +200 mV (vs. SCE) with 10 mM acetate as the electron donor. These biofilms exhibited the highest current density (4.68 ± 0.54 A m(-2)) reported on a planar material with a pure culture under saline conditions (3.5% NaCl). To investigate possible anodic electron transfer (ET) mechanisms, cyclic voltammetry (CV) of mature visible apparent reddish biofilms was performed under bioelectrocatalytic substrate consumption (turnover) and in the absence of the substrate (non-turnover). CV evidenced a well defined typical sigmoidal shape and a pair of clear redox couples under turnover and non-turnover conditions, respectively. Moreover, the calculation of their formal potentials indicated the presence of a common ET mechanism present in both CV conditions between -427.6 ± 0.5 (Ef,2) and -364.8 ± 4.5 mV (Ef,3). Confocal laser scanning microscopy inspection showed a biofilm structure composed of several layers of metabolically active bacteria that spread all over the electrode material within a biofilm up to 76 ± 7 μm thick. Such high value compared to the thickness values normally reported in the literature for pure culture electroactive bacteria justifies further investigations. Taken together, these results suggest that Glk. subterraneus performs a direct ET mechanism in contact with the electrode material. Furthermore, direct current generation from saline wastewater significantly expands the application of BESs.

Bioelectrochemical Systems: An Outlook for Practical Applications

Bioelectrochemical systems (BESs) hold great promise for sustainable production of energy and chemicals. This review addresses the factors that are essential for practical application of BESs. First, we compare benefits (value of products and cleaning of wastewater) with costs (capital and operational costs). Based on this, we analyze the maximum internal resistance (in mΩ m(2) ) and current density that is required to make microbial fuel cells (MFCs) and hydrogen-producing microbial electrolysis cells (MECs) cost effective. We compare these maximum resistances to reported internal resistances and current densities with special focus on cathodic resistances. Whereas the current densities of MFCs still need to be increased considerably (i.e., internal resistance needs to be decreased), MECs are closer to application as their current densities can be increased by increasing the applied voltage. For MFCs, the production of high-value products in combination with electricity production and wastewater treatment is a promising route.

New applications and performance of bioelectrochemical systems

Bioelectrochemical systems (BESs) are emerging technologies which use microorganisms to catalyze the reactions at the anode and/or cathode. BES research is advancing rapidly, and a whole range of applications using different electron donors and acceptors has already been developed. In this mini review, we focus on technological aspects of the expanding application of BESs. We will analyze the anode and cathode half-reactions in terms of their standard and actual potential and report the overpotentials of these half-reactions by comparing the reported potentials with their theoretical potentials. When combining anodes with cathodes in a BES, new bottlenecks and opportunities arise. For application of BESs, it is crucial to lower the internal energy losses and increase productivity at the same time. Membranes are a crucial element to obtain high efficiencies and pure products but increase the internal resistance of BESs. The comparison between production of fuels and chemicals in BESs and in present production processes should gain more attention in future BES research. By making this comparison, it will become clear if the scope of BESs can and should be further developed into the field of biorefineries.