Discover insights from thousands of peer-reviewed papers on microbial electrochemical systems
Changsomba Chang, Pratima Gupta
Fuel Cells · 2022
Abstract To boost growth and global competitiveness, a growing number of industries and sewage treatment plants are making “sustainability” and “cost‐effectiveness” key goals in their strategy and vision. This movement is also spreading far beyond the small group of people who recognize as “green”. This is the first study to demonstrate that domestic sewage water can be utilized as anodic feed for the electrochemical production of H 2 O 2 in the catholyte with simultaneous wastewater treatment in a microbial peroxide‐producing cell (MPPC) designed cost‐effectively utilizing a variety of catholyte and few electrode materials. The electrochemical output utilizing domestic wastewater resulted in maximum production of 62 mM H 2 O 2 in a 37‐day batch in the MPPC with 50 mM H 2 SO 4 catholyte having a bare activated charcoal electrode. The constantly rising H 2 O 2 production during the 37‐day hydraulic retention time demonstrated the system's sustainability and efficiency in contrast to other reported studies. Cyclic voltammetry analysis of the catholyte with the Fenton process showed excellent redox peaks, indicating its applicability for in‐situ pollutant degradation. The MPPCs had an overall 40%–60% and 65%–85% removal efficiency of biochemical oxygen demand and chemical oxygen demand. This study shows that a simple MPPC design with no extensive modifications can be efficient at producing H 2 O 2 and simultaneously treating wastewater.
Violeta Martínez, Francisco Rosales, Karen Amaya et al.
Afinidad. Journal of Chemical Engineering Theoretical and Applied Chemistry · 2024
Despite the extensive literature on the effects of implementing aeration in the electrocoagulation (EC) treatment of industrial wastewater, few studies evaluate the performance of this technique at high aeration rates. In this work, we present the outcomes derived from EC treatment of pharmaceutical and synthetic textile wastewater effluents in two lab-scale reactors with and without aeration, each equipped with different electrode combinations of aluminium and iron (Al/Al, Al/Fe, and Fe/Fe). In the non-aerated EC reactor, maximum chemical oxygen demand (COD) reductions of 56% and 80% were achieved for the pharmaceutical and textile effluents, respectively, with up to 100% removal of turbidity and colour with the Al/Al combination. The installation of high-rate aeration to prevent sludge accumulation on the electrode surface markedly reduced residence times and enhanced the COD removal in the pharmaceutical effluent. However, this implementation potentially reduced the process efficiency for thesynthetic textile effluent as prolonged operation led to flocculation breakdown and subsequent re-dissolution of the contaminants in the water.
Qi Liu, Boxun Zhou, Shici Zhang et al.
Polish Journal of Environmental Studies · 2018
Constructed wetlands have been extensively applied for treating drinking water sources and other water bodies that are not severely polluted due to their low construction and operation costs. In this regard, microbial fuel cells (MFC) could potentially achieve both energy generation and wastewater purification, though the construction cost is high. Based on the bio-electrochemical theory, a novel device of the integrated vertical flow constructed wetland (IVCW) embedded with MFC (IVCW-MFC) was designed and built for treating the slightly-polluted source waters with relatively high nitrogen and low carbon, where denitrification was usually hindered. Both water purification performance and electrical characteristics were examined in this system. It was observed that the maximum output voltage and power density could reach 777 mV and 8.05 mWm -2 , respectively, when the external resistance was 6000 . With a better denitrification effect, the system exhibited a more effective removal of chemical oxygen demand (COD) and nitrate. The maximum efficiency of total nitrogen (TN) removal was as high as 97.35%, while the average removal efficiency was around 70%, even with a load of TN, 3.3 mg/L on average, in the influent. Furthermore, the macrophytes grew normally in the constructed wetland without any influence.
Enea Gino Di Domenico, Gianluca Petroni, Daniele Mancini et al.
BioMed Research International · 2015
Microbial Fuel cells (MFCs) have been proposed for nutrient removal and energy recovery from different wastes. In this study the anaerobic digestate was used to feed H-type MFC reactors, one with a graphite anode preconditioned with Geobacter sulfurreducens and the other with an unconditioned graphite anode. The data demonstrate that the digestate acts as a carbon source, and even in the absence of anode preconditioning, electroactive bacteria colonise the anodic chamber, producing a maximum power density of 172.2 mW/m². The carbon content was also reduced by up to 60%, while anaerobic ammonium oxidation (anammox) bacteria, which were found in the anodic compartment of the reactors, contributed to nitrogen removal from the digestate. Overall, these results demonstrate that MFCs can be used to recover anammox bacteria from natural sources, and it may represent a promising bioremediation unit in anaerobic digestor plants for the simultaneous nitrogen removal and electricity generation using digestate as substrate.
Mariella Belén Galeano, Mira Sulonen, Zainab Ul et al.
Chemical Engineering Journal · 2023
Due to the anticipated rise in demand for ammonia, the search for viable methods to recover it has grown in recent years, as traditional ammonia production is a high energy intensive process. Among the different, bioelectrochemical systems (BESs) offer an alternative solution for ammonia recovery since they have shown lower energy demand (in terms of kJ g−1N recovered) at lab-scale than other methodologies. In BESs, the bioelectrochemically generated current drives the transport of NH4+ from the influent to a concentration chamber through a cation exchange membrane before its subsequent recovery. This paper describes the fundamentals and opportunities for bioelectrochemical ammonia recovery (either by stripping. absorption or precipitation) in different BES devices such as microbial fuel cells, microbial electrolysis cells, microbial desalination cells and bioelectroconcentration cells and compares the performance of all the reported experimental works so far. Moreover, the most critical challenges for its scale-up (low current density, nature and quantity of the carbon source, inlet ammonium concentration, use of membranes, energy yield and recovery efficiency) have been detailed and discussed in view of better understanding the current bottlenecks for its scale-up and, thus, for its prompt industrial adoption.
Xiaofei Wang, Federico Aulenta, Sebastià Puig et al.
Environmental Science and Ecotechnology · 2020
Lack of suitable electron donors or acceptors is in many cases the key reason for pollutants to persist in the environment. Externally supplementation of electron donors or acceptors is often difficult to control and/or involves chemical additions with limited lifespan, residue formation or other adverse side effects. Microbial electrochemistry has evolved very fast in the past years - this field relates to the study of electrochemical interactions between microorganisms and solid-state electron donors or acceptors. Current can be supplied in such so-called bioelectrochemical systems (BESs) at low voltage to provide or extract electrons in a very precise manner. A plethora of metabolisms can be linked to electrical current now, from metals reductions to denitrification and dechlorination. In this perspective, we provide an overview of the emerging applications of BES and derived technologies towards the bioremediation field and outline how this approach can be game changing.
Souichiro Kato
Microbial Biotechnology · 2016
Extracellular electron transfer (EET) is a microbial metabolism that enables efficient electron transfer between microbial cells and extracellular solid materials. Microorganisms harbouring EET abilities have received considerable attention for their various biotechnological applications, including bioleaching and bioelectrochemical systems. On the other hand, recent research revealed that microbial EET potentially induces corrosion of iron structures. It has been well known that corrosion of iron occurring under anoxic conditions is mostly caused by microbial activities, which is termed as microbiologically influenced corrosion (MIC). Among diverse MIC mechanisms, microbial EET activity that enhances corrosion via direct uptake of electrons from metallic iron, specifically termed as electrical MIC (EMIC), has been regarded as one of the major causative factors. The EMIC-inducing microorganisms initially identified were certain sulfate-reducing bacteria and methanogenic archaea isolated from marine environments. Subsequently, abilities to induce EMIC were also demonstrated in diverse anaerobic microorganisms in freshwater environments and oil fields, including acetogenic bacteria and nitrate-reducing bacteria. Abilities of EET and EMIC are now regarded as microbial traits more widespread among diverse microbial clades than was thought previously. In this review, basic understandings of microbial EET and recent progresses in the EMIC research are introduced.
Philipp Kuntke, Tom Sleutels, Mariana Rodríguez Arredondo et al.
Applied Microbiology and Biotechnology · 2018
In recent years, (bio)electrochemical systems (B)ES have emerged as an energy efficient alternative for the recovery of TAN (total ammonia nitrogen, including ammonia and ammonium) from wastewater. In these systems, TAN is removed or concentrated from the wastewater under the influence of an electrical current and transported to the cathode. Subsequently, it can be removed or recovered through stripping, chemisorption, or forward osmosis. A crucial parameter that determines the energy required to recover TAN is the load ratio: the ratio between TAN loading and applied current. For electrochemical TAN recovery, an energy input is required, while in bioelectrochemical recovery, electric energy can be recovered together with TAN. Bioelectrochemical recovery relies on the microbial oxidation of COD for the production of electrons, which drives TAN transport. Here, the state-of-the-art of (bio)electrochemical TAN recovery is described, the performance of (B)ES for TAN recovery is analyzed, the potential of different wastewaters for BES-based TAN recovery is evaluated, the microorganisms found on bioanodes that treat wastewater high in TAN are reported, and the toxic effect of the typical conditions in such systems (e.g., high pH, TAN, and salt concentrations) are described. For future application, toxicity effects for electrochemically active bacteria need better understanding, and the technologies need to be demonstrated on larger scale.
Yu Kong, Jing Hu, Xiwu Lü et al.
Water · 2023
The tail wastewater from sewage treatment facilities usually lacks carbon sources, and its subsequent treatment for deep nitrogen removal is difficult in natural conditions. In this study, the constructed wetland (CW) was integrated with microbial fuel cell (MFC) with high-density polyethylene (HDPE) fillers as the main matrix to improve nitrogen removal under inefficient carbon source conditions. Compared with the regular MFC and CW systems, MFC-CW attained higher nitrogen removal under low-carbon source conditions. The influence of influent carbon/nitrogen ratio (C/N) on the denitrification and electricity-generation performance was explored. Although the increase of carbon source simultaneously improved chemical oxygen demand (COD), ammonia (NH4+-N), nitrate (NO3−-N) and TN removal, the power generation during the carbon source adjustment showed low relation with the variation of influent COD in the range of 40–120 mg/L. CW was more dependent on carbon sources, and the addition of bioelectrochemical systems into MFC-CW could reduce the dependence of nitrogen removal on carbon sources, especially under low carbon source conditions. These findings offer valuable insights into the potential applications of MFC-CW for tail water treatment, and its parameters for utilization in real CWs should be explored in future studies.
Jinfeng Hu, Longjun Xu, Qi Jing et al.
Kemija u industriji · 2017
The effect of cathode type on contaminant removal efficiency and electricity production in disposing leachate was investigated in a self-assembled microbial fuel cell (MFC). When the landfill leachate was treated with the chemical-cathode MFC (CMFC) and aerobic bio-cathode MFC (ABMFC), the maximum output voltages were 699.0 mV and 459.4 mV, the maximum output powers were 197.7 mW m -3 and 147.6 mW m -3 , and the internal resistances were 900 and 700 , respectively. After running the MFCs for 45 days, the COD removal ratios of CMFC and ABMFC were 56.5 % and 64.3 %, the Coulombic efficiencies were 14.3 % and 17.1 %, and the ammonia nitrogen removal ratios were 53.8 % and 58.1 %, respectively.
Jing Guo, Jianping Cheng, Jiaquan Wang et al.
Processes · 2021
A rectangular double chamber with trivalent arsenic as the electron donor of the biological anode was constructed by microbial fuel cells (MFC), and the feasibility of the MFC simultaneous degradation of trivalent arsenic and nitrate was studied. Experimental results show that the co-matrix-coupled MFC reactor oxidizes trivalent arsenic in an anode chamber and degrades nitrate in the cathode chamber. The removal rate of trivalent arsenic is about 63.35%, and the degradation rate of nitrate is about 55.95% during the complete and stable operation period. MFC can continuously output electric energy, and the maximum output voltage is 388 mV. We compared and analyzed the main functional microflora of biofilm microorganisms in an anode chamber. In the long-term arsenic-polluted environment, the activity of Acinetobacter, Pseudomonas bacteria with arsenic resistance, was improved. It is inferred that a fraction of trivalent arsenic was oxidized to pentavalent arsenic by electrode-attached microorganisms. While remaining trivalent, arsenic was taken up by the suspended bacterial biomass and converted into stable arsenide. The results of this study have theoretical reference value for the expansion of the MFC application scope.
Jianqiang Zhao, Jinna Wu, Xiaoling Li et al.
Frontiers in Microbiology · 2017
Microbial fuel cells (MFCs) have attracted much attention due to their ability to generate electricity while treating wastewater. The performance of a double-chamber MFC with simultaneous nitrification and denitrification (SND) in the cathode for treating synthetic high concentration ammonia wastewater was investigated at different dissolved oxygen (DO) concentrations and high temperatures. The results showed that electrode denitrification and traditional heterotrophic denitrification co-existed in the cathode chamber. Electrode denitrification by aerobic denitrification bacterium (ADB) is beneficial for achieving a higher voltage of the MFC at high DO concentrations (3.0-4.2 mg/L), while traditional heterotrophic denitrification is conducive to higher total nitrogen (TN) removal at low DO (0.5-1.0 mg/L) concentrations. Under high DO conditions, the nitrous oxide production and TN removal efficiency were higher with a 50 Ω external resistance than with a 100 Ω resistance, which demonstrated that electrode denitrification by ADB occurred in the cathode of the MFC. Sufficient electrons were inferred to be provided by the electrode to allow ADB survival at low carbon:nitrogen ratios (≤0.3). Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) results showed that increasing the DO resulted in a change of the predominant species from thermophilic autotrophic nitrifiers and facultative heterotrophic denitrifiers at low DO concentrations to thermophilic ADB at high DO concentrations. The predominant phylum changed from Firmicutes to Proteobacteria , and the predominant class changed from Bacilli to Alpha, Beta , and Gamma Proteobacteria .
Edoardo Dell’Armi, Marco Zeppilli, Maria Letizia Di Franca et al.
Journal of Water Process Engineering · 2022
In the present study, the sequential reductive/oxidative bioelectrochemical process has been tested with real groundwater from a contaminated site in Northern Italy for chlorinated aliphatic hydrocarbons (CAHs) removal. The sequential system was developed by connecting in series two membrane-less microbial electrolysis cells (MECs) equipped with an internal graphite counter electrode. The first MEC aimed at the CAHs reductive dechlorination (RD) and was constituted of a granular graphite working electrode. In the second MEC, a mixed metal oxide working electrode stimulated the oxidative dechlorination of the low chlorinated RD's by-products through oxygen production. The sequential process allowed complete mineralization of the CAHs contained in the real groundwater. A complete reduction of the perchloroethylene into vinyl chloride (VC) was observed in the first MEC polarized at −450 mV vs SHE, while the resulting VC was oxidized with a 92 ± 2 % efficiency in the second MEC due to the HRT increment from 0.7 to 1.7 days. Biomarkers of the reductive (Dehalococcoides mccartyi 16S rRNA and reductive dehalogenase genes) and oxidative (etnE, etnC genes) dechlorination have been monitored in the two MECs along with the ecotoxicity tests. Overall, they provide information on the efficiency of the applied technology and allow to assess the potential adverse effects. According to the Tetrahymena pyriformis reproduction inhibition test and Panagrellus redivivus mortality tests, showed a significant ecotoxicity reduction with respect its initial inhibitory effect at the tested concentrations.
Krishnaveni Venkidusamy, Mallavarapu Megharaj
Frontiers in Microbiology · 2016
An electrophototrophic, hydrocarbonoclastic bacterium Rhodopseudomonas palustris stain RP2 was isolated from the anodic biofilms of hydrocarbon fed microbial electrochemical remediation systems (MERS). Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments. In acetate fed microbial electrochemical cells, a maximum current density of 305 ± 10 mA/m² (1000Ω) was generated (power density 131.65 ± 10 mW/m²) by strain RP2 with a coulombic efficiency of 46.7 ± 1.3%. Cyclic voltammetry studies showed that anaerobically grown cells of strain RP2 is electrochemically active and likely to transfer electrons extracellularly to solid electron acceptors through membrane bound compounds, however, aerobically grown cells lacked the electrochemical activity. The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m²; power density 720 ± 7 μW/m², 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l⁻¹ of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS. Here, we also report the first study that shows an initial evidence for the existence of a hydrocarbonoclastic behavior in the strain RP2 when grown in different electron accepting and illuminated conditions (anaerobic and MERS degradation). Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments. Identification of such novel petrochemical hydrocarbon degrading electricigens, not only expands the knowledge on the range of bacteria known for the hydrocarbon bioremediation but also shows a biotechnological potential that goes well beyond its applications to MERS.
Ru Zheng, Kuo Zhang, Lingrui Kong et al.
Frontiers of Environmental Science & Engineering · 2024
Abstract Wastewater treatment plants are the major energy consumers and significant sources of greenhouse gas emissions, among which biological nitrogen removal of wastewater is an important contributor to carbon emissions. However, traditional heterotrophic denitrification still has the problems of excessive residual sludge and the requirement of external carbon sources. Consequently, the development of innovative low-carbon nitrate removal technologies is necessary. This review outlines the key roles of sulfur autotrophic denitrification and hydrogen autotrophic denitrification in low-carbon wastewater treatment. The discovered nitrate/nitrite dependent anaerobic methane oxidation enables sustainable methane emission reduction and nitrogen removal by utilizing available methane in situ . Photosynthetic microorganisms exhibited a promising potential to achieve carbon-negative nitrate removal. Specifically, the algal-bacterial symbiosis system and photogranules offer effective and prospective low-carbon options for nitrogen removal. Then, the emerging nitrate removal technology of photoelectrotrophic denitrification and the underlying photoelectron transfer mechanisms are discussed. Finally, we summarize and prospect these technologies, highlighting that solar-driven biological nitrogen removal technology is a promising area for future sustainable wastewater treatment. This review has important guiding significance for the design of low-carbon wastewater treatment systems.
Valeria Agostino, Miriam A. Rosenbaum
Frontiers in Energy Research · 2018
Electroautotrophs are microbes able to perform different biocathodic reactions by using CO2 as sole carbon source and electrochemical reducing power as a sole energy source. Electroautotrophy has been discovered in several groups of microorganisms, including iron-oxidizing bacteria, iron-reducing bacteria, nitrate-reducing bacteria, acetogens, methanogens and sulfate-reducing bacteria. The high diversity of electroautrophs results in a wide range of Bioelectrochemical Systems (BES) applications, ranging from bioproduction to bioremediation. In the last decade, particular research attention has been devoted towards the discovery, characterization and application of acetogenic and methanogenic electroautotrophs. Less attention has been given to autotrophic sulfate-reducing microorganisms, which are extremely interesting biocatalysts for multiple BES technologies, with concomitant CO2 fixation. They can accomplish water sulfate removal, hydrogen production and, in some case, even biochemicals production. This mini-review gives a journey into electroautotrophic ability of sulfate-reducing bacteria and highlights their possible importance for biosustainable applications. More specifically, general metabolic features of autotrophic sulfate reducers are introduced. Recently discovered strains able to perform extracellular electron uptake and possible molecular mechanisms behind this electron transfer capacity are explored. Finally, BES technologies based on sulfate-reducing electroautotrophs are illustrated.
A. S. Vishwanathan, Kartik Aiyer, L. A. Avinash Chunduri et al.
3 Biotech · 2016
Electrodes based on graphite, graphene, and carbon nanomaterials have been used in the anode chamber of microbial fuel cells (MFCs). Carbon quantum dots (C-dots) are a class of versatile nanomaterials hitherto not reported in MFCs. C-dots previously synthesized from coconut husk were reported to possess hydroxyl and carboxyl functional groups on their surface. The presence of these functional groups on a carbon matrix conferred on the C-dots the ability to conduct and transfer electrons. Formation of silver nanoparticles from silver nitrate upon addition of C-dots confirmed their reducing ability. DREAM assay using a mixed microbial culture containing C-dots showed a 172% increase in electron transfer activity and thus confirmed the involvement of C-dots in supplementing redox activity of a microbial culture. Addition of C-dots as a suspension in the anode chamber of an MFC resulted in a 22.5% enhancement in maximum power density. C-dots showed better performance as electron shuttles than methylene blue, a conventional electron shuttle used in MFCs.
Angelov, Bratkova, Ivanov et al.
Bulgarian Chemical Communications · 2023
In a two-section bioelectrochemical system (BES), the processes of biomethanation of ethanol stillage in the anode zone and oxygenic photosynthesis in the cathodic zone are combined.There is a reduction of ammonium ions and removal of H2S in the anode zone, and at the same time, there is a positive impact on the process of biomethanation from ethanol stillage in parallel to the anode anaerobic bioreactor.Chemical oxygen demand (COD) reductions ranging from 71.2% to 89.5% were achieved in the 3 BES operating modes studied.The dynamics of the main technological parameters in the bioanode and biocathode area of the BES during continuous operation of the anaerobic bioreactor and photobioreactor (PBR) at a contact time of 10 days is established.Depending on the selected variant of operation of BES -microbial fuel cell (MFC), microbial electrolysis cell (MEC) with 0.6V and 0.9V, a decrease in the ammonium concentration is found to varying degrees, as in the MEC mode with an external electrical voltage of 0.9V the highest degree of 76.5% is reached.At the same time, complete removal of H2S is found, in the liquid and gas phases in MEC -mode and partially (78 -84 %) in MFC -mode.The influence of the photosynthetic phases on the electrochemical parameters of MFC was also investigated, with maximum values for power and current densities of 29 W/m 2 and 115 mA/m 2 , respectively.
Alicia A. Mier, Ruth Belinda Domínguez-Espíndola, Hugo Olvera‐Vargas et al.
BioEnergy Research · 2025
Abstract This study evaluated the potential of mixed microalgae-bacteria cultures as electroactive microorganisms to enhance electricity production while simultaneously treating wastewater in emerging biophotovoltaic (BPV) systems. Graphite felt decorated with TiO₂ nanotubes (TiO₂-NTs) was used as the anode, supporting the growth of a biofilm composed of mixed microalgae-bacterial cultures. Batch BPV reactors treated real domestic-industrial wastewater and were compared with BPV systems using bare graphite felt anodes, both with and without microalgae-bacteria cultures. All BPVs operated under a 12-h light/dark cycle, with continuous current monitoring and water quality assessments performed at the beginning and end of the experiments. The TiO₂-NT BPV exhibited the highest power output, reaching 2.37 mW/m 2 . BPVs with bare graphite felt anodes achieved power densities of 1.48 mW/m 2 and 0.41 mW/m 2 with and without microalgae, respectively. Systems inoculated with microalgae-bacteria cultures also showed lower ohmic losses, reaching open circuit voltages between 0.125 and 0.130 V, whereas systems without microalgae reached only 0.050 V and exhibited faster potential drops. In terms of wastewater treatment, TiO₂-NT BPVs achieved the highest removal efficiencies for chemical oxygen demand (COD) and nitrogen, exceeding 90% COD removal and over 80% removal of total ammoniacal nitrogen and nitrate. This study demonstrates that integrating mixed microalgae-bacteria cultures with TiO₂ nanostructured anodes in multifunctional BPV systems significantly enhances both wastewater treatment performance and power generation.
Qianhao Zeng, Wenhui An, Dayuan Peng et al.
Catalysts · 2025
Photocatalytic-coupled microbial electrochemical systems (MESs) represent an emerging wastewater treatment technology which aims to address the limitations of traditional methods, such as the inadequate removal of refractory pollutants and excessive energy consumption. This technology realizes the simultaneous degradation of refractory pollutants in wastewater and bioenergy recovery, demonstrating significant potential for development. However, the practical application of this technology is currently hindered by challenges including insufficient electrical power output, poor stability of photoelectric electrodes, and the design of amplified application systems. This review comprehensively examines the common coupling methods and principles of photocatalytic-coupled microbial electrochemical systems. Compared to previous studies, it provides a detailed analysis of the optimal configurations for treating wastewater containing various components, such as recalcitrant organic compounds, heavy metals, and nitrates, to achieve maximum efficiency. Moreover, it summarizes the synergistic effects observed between photocatalysis and MES that enhance the degradation efficiency of pollutants through various pathways, including increasing the potential difference of cytochromes, promoting the formation of conductive nanowires, accelerating the electron transfer rates, and inhibiting electron–hole recombination. Finally, this review highlights the challenges in practical applications and proposes future research directions to facilitate the further development of this technology.
Marco Zeppilli, Ilaria Ceccarelli, Marianna Villano et al.
IRIS Research product catalog (Sapienza University of Rome) · 2016
A microbial electrolysis cell (MEC) was operated in continuous-flow condition to obtain cathodic CO2 reduction into acetate and methane along with COD anodic oxidation. Under steady-state conditions, most of the electron equivalents produced by COD anodic oxidation (866 mgCOD/Ld) were diverted into current rather than microbial growth, with an average Coulombic efficiency of 95 ± 8 %. In the cathodic chamber, acetate and methane formation from CO2 reduction accounted for 76% of the equivalents generated in the anodic oxidation reaction. Because a spill of cathodic liquid phase was necessary in order to counterbalance osmotic diffusion across the PEM, it was also possible to spill from the cathodic chamber a concentrated stream of acetate (248 ± 16meq/L). Moreover, as an additional effect, cation transport across the proton exchange membrane (PEM) and the consequent alkalinity generation made it possible to accumulate ammoniumnitrogen (242 ± 19 mgN/L) and bicarbonate (22.49 ± 1.45 gHCO3-/L). Hence, the MEC combined COD andCO2 removal in addition to nutrients and energy recovery from an anodic influent that simulated an urban wastewater.
Lola Gonzalez Olias, Alba Rodríguez-Otero, Petra J. Cameron et al.
The 1st International Electronic Conference on Biosensors · 2020
The increasing use of fertilisers rises the risk of eutrophication, a sudden algal bloom that seriously damage ecosystems due to critical oxygen depletion. Continuous monitoring of oxygen in environmental waters could improve the detection of eutrophication and prevent anoxic conditions. However, online and in situ dissolved oxygen sensors are yet to be implemented due to poor portability and power requirements. Here, we propose a ceramic soil microbial fuel cell as a self-powered sensor for algal growth detection via monitoring of dissolved oxygen in water. The sensor signal follows the characteristic photosynthetic cycle, with a maximum day current of 0.18 ± 0.2 mA and a minimum night current of 0.06 ± 0.34 mA, which correlates with dissolved oxygen (R2 = 0.85 (day); R2= 0.5 (night)) and algal concentration (R2 = 0.63). A saturated design of experiments on seven factors suggests that temperature, dissolved oxygen, nitrates, and pH are the most influential operational factors in the voltage output. Moreover, operating the system at maximum power point (Rext = 2 kΩ) improves the sensor sensitivity. To the best of our knowledge, this is the first proposed MFC-based biosensor for in-field, early detection of eutrophic events.
Haiquan Zhan, Hong Wang, Yanzeng Li et al.
Water · 2026
Photosynthetic algae–microbial fuel cells (PAMFCs) are attractive for energy-positive wastewater treatment and carbon mitigation. However, PAMFC performance under continuous flow is often constrained by limited cathodic electron-acceptor supply and unstable photosynthetic biofilms, while the extent to which cathode interfacial engineering can stabilize diurnal power output and assimilative NH4+–N removal remains unclear. In this study, the sponge-like and petal-like ZnO0.2-NiO@rGO-modified carbon fibers (ZnO0.2-NiO@rGO-pCFs and ZnO0.2-NiO@rGO-pCFp) and pre-fabricated carbon felt (pCF) were used as cathode materials to construct three sets of PAMFC systems. Under light–dark cycling, the engineered cathodes reached steady operation within about 6.5 d and increased the steady-state voltage to approximately 0.35 V, compared with approximately 0.08 V for pCF. Under continuous-flow conditions, cathodic NH4+–N removal exhibited a stable diurnal rhythm, with higher removal during illumination at about 43–51% than in the dark at about 29–30%, consistent with algal assimilation as the primary nitrogen sink, while cathode modification mainly improved the cathodic microenvironment and response stability. Compared with pCF, the ZnO0.2–NiO@rGO cathode enriched a more even, Chlorophyta-dominated algal biofilm with an approximate relative abundance of 80%, indicating that its selective interfacial environment favors biofilm stabilization and sustains in situ oxygen production and cathodic electron-acceptor supply. Consequently, the composite cathode enhanced voltage output and stabilized light-enhanced, assimilative NH4+–N removal under aeration-free operation, while establishing an interpretable link between electrochemical performance and 18S rDNA-derived community assembly features, thereby providing a low-cost cathode design basis for nitrogen removal in wastewater treatment.
Gaofeng Ni, Sebastian Canizales, Elias Broman et al.
Frontiers in Microbiology · 2018
Thiocyanate is a toxic compound produced by the mining and metallurgy industries that needs to be remediated prior to its release into the environment. If the industry is situated at high altitudes or near the poles, economic factors require a low temperature treatment process. Microbial fuel cells are a developing technology that have the benefits of both removing such toxic compounds while recovering electrical energy. In this study, simultaneous thiocyanate degradation and electrical current generation was demonstrated and it was suggested that extracellular electron transfer to the anode occurred. Investigation of the microbial community by 16S rRNA metatranscriptome reads supported that the anode attached and planktonic anolyte consortia were dominated by a Thiobacillus -like population. Metatranscriptomic sequencing also suggested thiocyanate degradation primarily occurred via the 'cyanate' degradation pathway. The generated sulfide was metabolized via sulfite and ultimately to sulfate mediated by reverse dissimilatory sulfite reductase, APS reductase, and sulfate adenylyltransferase and the released electrons were potentially transferred to the anode via soluble electron shuttles. Finally, the ammonium from thiocyanate degradation was assimilated to glutamate as nitrogen source and carbon dioxide was fixed as carbon source. This study is one of the first to demonstrate a low temperature inorganic sulfur utilizing microbial fuel cell and the first to provide evidence for pathways of thiocyanate degradation coupled to electron transfer.
Melany Ruiz-Urigüen, Daniel A. Steingart, Peter R. Jaffé
Environmental Science Water Research & Technology · 2019
Schematic of a biotic MEC with Feammox bacterium Acidimicrobiaceae sp. A6 culture. NH 4 + is oxidized to NO 2 − at the anode and H + is reduced to form H 2 at the cathode.
Fei Zhong, Chunmei Yu, Yanhong Chen et al.
Frontiers in Microbiology · 2020
An integrated vertical-flow constructed wetland-microbial fuel cell system (CW-MFC), consisting of an up-flow chamber and a down-flow chamber, was constructed to treat synthetic sewage wastewater. The performance of CW-MFCs filled with different substrates [i.e., ceramsite (CM-A), quartz (CM-B), and zeolite (CM-C) granules] under various hydraulic retention times (HRTs, 7.6, 4.0, and 2.8 d) was evaluated. Efficient and stable nitrogen (N) and phosphorus (P) removals were observed in CM-A under different HRTs, while the voltage outputs of the CW-MFCs was greatly reduced as the HRTs decreased. With an HRT of 2.8 d, the ammonium (NH 4 + -N) and orthophosphate (PO 4 3- -P) removal efficiencies in CM-A were as high as 93.8 and 99.6%, respectively. Bacterial community analysis indicates that the N removal in the cathode area of CM-A could potentially benefit from the appearance of nitrifying bacteria (e.g., Nitrosomonas and Nitrospira ) and relatively high abundance of denitrifiers involved in simultaneous nitrification and denitrification (e.g., Hydrogenophaga , Zoogloea , and Dechloromonas ) and denitrifying sulfide removal (e.g., Thauera ). Additionally, the difference in N removal efficiency among the CW-MFCs could be partly explained by higher iron (Fe) content in milled ceramsite granules and higher abundance of denitrifiers with nitrate reduction and ferrous ions oxidation capabilities in CM-A compared with that in CM-B and CM-C. Efficient PO 4 3- -P removal in CM-A was mainly ascribed to substrate adsorption and denitrifying phosphorus (P) removal. Concerning the substantial purification performance in CM-A, ceramsite granules could be used to improve the nutrient removal efficiency in integrated vertical-flow CW-MFC.
Longmian Wang, Qingqing Pang, Fuquan Peng et al.
Frontiers in Microbiology · 2020
This study explores nitrogen removal performance, bioelectricity generation, and the response of microbial community in two novel tidal flow constructed wetland-microbial fuel cells (TFCW-MFCs) when treating synthetic wastewater under two different chemical oxygen demand/total nitrogen (COD/TN, or simplified as C/N) ratios (10:1 and 5:1). The results showed that they achieved high and stable COD, NH 4 + -N, and TN removal efficiencies. Besides, TN removal rate of TFCW-MFC was increased by 5-10% compared with that of traditional CW-MFC. Molecular biological analysis revealed that during the stabilization period, a low C/N ratio remarkably promoted diversities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in the cathode layer, whereas a high one enhanced the richness of nitrite-oxidizing bacteria (NOB) in each medium; the dominant genera in AOA, AOB, and NOB were Candidatus Nitrosotenuis , Nitrosomonas , and Nitrobacter . Moreover, a high C/N ratio facilitated the growth of Nitrosomonas , while it inhibited the growth of Candidatus Nitrosotenuis . The distribution of microbial community structures in NOB was separated by space rather than time or C/N ratio, except for Nitrobacter . This is caused by the differences of pH, dissolved oxygen (DO), and nitrogen concentration. The response of microbial community characteristics to nitrogen transformations and bioelectricity generation demonstrated that TN concentration is significantly negatively correlated with AOA-shannon, AOA-chao, 16S rRNA V4-V5-shannon, and 16S rRNA V4-V5-chao, particularly due to the crucial functions of Nitrosopumilus , Planctomyces , and Aquicella . Additionally, voltage output was primarily influenced by microorganisms in the genera of Nitrosopumilus, Nitrosospira , Altererythrobacter , Gemmata , and Aquicella. This study not only presents an applicable tool to treat high nitrogen-containing wastewater, but also provides a theoretical basis for the use of TFCW-MFC and the regulation of microbial community in nitrogen removal and electricity production.
Yaohuan Gao, Jangho Lee, Josh D. Neufeld et al.
Scientific Reports · 2017
Anaerobic oxidation of methane (AOM) is an important process for understanding the global flux of methane and its relation to the global carbon cycle. Although AOM is known to be coupled to reductions of sulfate, nitrite, and nitrate, evidence that AOM is coupled with extracellular electron transfer (EET) to conductive solids is relatively insufficient. Here, we demonstrate EET-dependent AOM in a biofilm anode dominated by Geobacter spp. and Methanobacterium spp. using carbon-fiber electrodes as the terminal electron sink. The steady-state current density was kept at 11.0 ± 1.3 mA/m 2 in a microbial electrochemical cell, and isotopic experiments supported AOM-EET to the anode. Fluorescence in situ hybridization images and metagenome results suggest that Methanobacterium spp. may work synergistically with Geobacter spp. to allow AOM, likely by employing intermediate (formate or H 2 )-dependent inter-species electron transport. Since metal oxides are widely present in sedimentary and terrestrial environments, an AOM-EET niche would have implications for minimizing the net global emissions of methane.
Shaohua Chen, Wenliang Chen, Xiufang Wang et al.
Polish Journal of Environmental Studies · 2020
Microbial fuel cell (MFC) is regarded as a promising technology to treat waste water and generate electricity simultaneously. MFCs usually work in the water-soluble medium, but the performance of the MFC which works in the porous medium is still unclear. Therefore, in this paper, a sand box was used to construct a dual-chamber MFC to investigate its performance. The MFC was used in porous medium to simulate the environment of groundwater, which was used to investigate the nitrate removal rate and the performance of electricity generation under different pH values. The performance of the MFC electrode was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the maximum power density was 0.003 mW/m 3 (pH = 7.0) and the lowest nitrate concentration was 0.49 mg/L (pH = 8.5). The dominant microbial communities were Comamonadaceae bacterium, Xanthomonas axonopodis et al. Although the MFC was weak in electricity generation, it could offer valuable reference to further experiment.
Yamini Jangir, Sarah French, Lily Momper et al.
Frontiers in Microbiology · 2016
Continental subsurface environments can present significant energetic challenges to the resident microorganisms. While these environments are geologically diverse, potentially allowing energy harvesting by microorganisms that catalyze redox reactions, many of the abundant electron donors and acceptors are insoluble and therefore not directly bioavailable. Extracellular electron transfer (EET) is a metabolic strategy that microorganisms can deploy to meet the challenges of interacting with redox-active surfaces. Though mechanistically characterized in a few metal-reducing bacteria, the role, extent, and diversity of EET in subsurface ecosystems remains unclear. Since this process can be mimicked on electrode surfaces, it opens the door to electrochemical techniques to enrich for and quantify the activities of environmental microorganisms in situ. Here, we report the electrochemical enrichment of microorganisms from a deep fractured-rock aquifer in Death Valley, CA, USA. In experiments performed in mesocosms containing a synthetic medium based on aquifer chemistry, four working electrodes (WEs) were poised at different redox potentials (272, 373, 472, 572 mV vs. SHE) to serve as electron acceptors, resulting in anodic currents coupled to the oxidation of acetate during enrichment. The anodes were dominated by Betaproteobacteria from the families Comamonadaceae and Rhodocyclaceae. A representative of each dominant family was subsequently isolated from electrode-associated biomass. The EET abilities of the isolated Delftia strain (designated WE1-13) and Azonexus strain (designated WE2-4) were confirmed in electrochemical reactors using WEs poised at 522 mV vs. SHE. The rise in anodic current upon inoculation was correlated with a modest increase in total protein content. Both genera have been previously observed in mixed communities of microbial fuel cell enrichments, but this is the first direct measurement of their electrochemical activity. While alternate metabolisms (e.g., nitrate reduction) by these organisms were previously known, our observations suggest that additional 'hidden' interactions with external electron acceptors are also possible. Electrochemical approaches are well positioned to dissect such extracellular interactions that may be prevalent in the subsurface.
Cynthia J. Castro, Kamal Ziad Taha, Itzé Kenney et al.
Water · 2022
Bioelectrochemical systems with denitrifying biocathodes have been of interest for the removal of nitrate in decentralized wastewater treatment applications. Only a few studies have directly focused on this application, but the removal rates have been very low. This study evaluated the operational parameters that affect the nitrate removal of two-chambered microbial fuel cells (MFCs) with a biocathode, particularly, the carbon to nitrogen ratio (C:N) and proton diffusivity across electrode chambers. The results show that proton diffusion across a proton exchange membrane is not a limiting step in nitrogen removal performance. At C:N ratios of 4 and 8, biocathodes with a continuously supplied carbon source at the anode were able to achieve complete nitrogen removal at a rate of 0.97 ± 0.21 and 1.15 ± 0.13 mg N L−1 d−1, respectively. However, as the C:N ratio increased from 4, 8, 16, and 32, the electrode potentials decreased accordingly. Ratio 4 C:N had a cathodic reduction potential of +66.1 ± 5.3 mV vs. SHE and dropped to −78.6 ± 9.8 mV vs. SHE at 32 C:N. The cathode electrode potential can be controlled by way of the carbon concentrations at the anode, which can have major indirect implications on the evolution of cathodic microbial communities that have preference to particular ranges of reduction potentials. The cathodic biofilms in this study were dominated by the phyla Proteobacteria, Acidobacteria, Bacteroidetes and Nitrospirae, which are known to have key denitrifying microorganisms. The genus Stenotrophomonas was found in abundance within the attached cathode biofilm and to a lesser extent in the suspended biomass. Vibrio, Acidobacteria_Gp4, Nitrosomonas, and Candidatus Competibacter were also cultivated in both the suspended and attached biomass. Nitrospira was only found in the attached biofilm. Regardless of operational scheme, nitrogen removal was improved at low C:N ratios, with 8 C:N having the best performance overall. This indicates that higher C:N ratios than were previously explored (>4 C:N) provide sufficient coulombs to facilitate denitrification at the cathode even while the anodic CEs remain low. Reactor design modifications should be considered to fully support robust denitrifying communities, enhancing the overall nitrogen removal for decentralized wastewater treatment applications.
Daniele Cecconet, Silvia Bolognesi, Arianna Callegari et al.
Heliyon · 2019
Bioelectrochemical systems (BES) application was proposed for a variety of specific uses, due to these systems' characteristics: electrodes can act as virtually inexhaustible electron acceptors/donors, offering a growth-support surface for microorganisms, and stimulating naturally-occurring microbial degradation activities. In situ, groundwater denitrification therefore seems to be a potential candidate for their use. In this study, buried biocathodes were operated in laboratory settings for the simulation of in situ groundwater denitrification. Two alternative configurations were tested: biocathode buried in sand, and biocathode buried in gravel. A control test with a biocathode in absence of sand/gravel was also performed. In all the cases, biocathodes were driven by power supply or potentiostat to guarantee a steady electron flux to the cathode. The presence of sand and gravel strongly influenced the denitrification process: in both configurations, accumulation of intermediate N-forms was detected, suggesting that the denitrification process was only partially achieved. In addition, a significant decrease (in the 20-36% range) in nitrate removal rates was measured in sand and gravel setups compared to the control reactor; this issue could be attributed to lack of recirculation that limited contact between substrate and electrode-adherent biofilm. Biocathodes buried in gravel obtained better results than those buried in sand due to the lower packing of the medium. The results of this study suggest that, in order to achieve successful in situ treatment, special design of submerged-biocathodic BESs is necessary.
Matteo Tucci, David Fernández‐Verdejo, Marco Resitano et al.
Chemosphere · 2023
Subsurface co-contamination by multiple pollutants can be challenging for the design of bioremediation strategies since it may require promoting different and often antagonistic degradation pathways. Here, we investigated the simultaneous degradation of toluene and chloroform (CF) in a continuous-flow anaerobic bioelectrochemical reactor. As a result, 47 μmol L -1 d -1 of toluene and 60 μmol L -1 d -1 of CF were concurrently removed, when the anode was polarized at +0.4 V vs. Standard Hydrogen Electrode (SHE). Analysis of the microbial community structure and key functional genes allowed to identify the involved degradation pathways. Interestingly, when acetate was supplied along with toluene, to simulate the impact of a readily biodegradable substrate on process performance, toluene degradation was adversely affected, likely due to competitive inhibition effects. Overall, this study proved the efficacy of the developed bioelectrochemical system in simultaneously treating multiple groundwater contaminants, paving the way for the application in real-world scenarios.
Nguyễn Hoàng Đạt Đặng, Hữu Thùy Đoàn, Văn Tuấn Đoàn et al.
Science & Technology Development Journal - Engineering and Technology · 2021
Global challenges on water and energy crisis have pressurized on water treatment industry to put into practice advanced technologies for ensuring a suitable supply of either water or energy services. Compared with other biological treatment technologies, constructed wetland (CW) is widely considered as an efficient eco-technology for wastewater treatment with the advantages of low cost, simple operation and maintenance. Microbial fuel cell (MFC) technology is the recently emerging approach in environmental engineering. The integration of MFCs within vertical up-flow CW systems (VSF-CW) as a sustainable technology, therefore, could provide dual benefits in nitrogen removal of wastewaters and energy recovery simultaneously. This study has preliminarily evaluated the acclimation performance of VSF-CW-MFC systems at the high loading rate (4.2 mg COD/h.L; COD:N = 10:1) of domestic wastewaters containing ammonia. Results demonstrated the potential of VSF-CW-MFC systems in achieving electricity generation and ammonia removal of domestic wastewaters at the high loading rate. The plant presence and influent pH of 7.0 could improve the performance efficiency. Average removal efficiencies of NH4+ and COD in planted microcosms with the influent pH of 7.0 were 43.4% and 79%, respectively.
Feng Liu, Lei Sun, Jinbao Wan et al.
RSC Advances · 2019
A novel approach, combining a microbial fuel cell (MFC) with an integrated vertical flow constructed wetland (IVCW), was developed, and its ability to simultaneously produce electrical energy while treating swine wastewater was verified. The system combined the singular water flow path of a traditional vertical flow constructed wetland (upflow and downflow)-microbial fuel cell (CW-MFC), which demonstrates better characteristics in the aerobic, anoxic, and anaerobic regions. It not only enhanced the anti-pollution load ability and the organic compound removal effect, but also improved the gradient difference in the redox potential of the system. The results showed that the structure and substrate distribution in the device could both improve swine wastewater treatment and increase bioelectricity generation capabilities. The average chemical oxygen demand (COD) and ammonia nitrogen (NH 4 + -N) removal efficiencies were as high as 79.65% and 77.5%, respectively. Long-term and stable bioelectricity generation was achieved under continuous flow conditions. The peak values of the output voltage and power density were 713 mV and 456 mW m -3 . The activated carbon layer at the bottom of this system provided a larger surface for the growth of microbes. It showed significant promotion of the relative abundance of electrochemically active bacteria, which might result in the increase of bioelectricity generation in integrated vertical flow constructed wetland-microbial fuel cells (IVCW-MFCs). The electrochemically active bacteria, Geobacter and Desulfuromonas , were detected in the anodic biofilm by high-throughput sequencing analysis.
Yun Wu, Qing Yang, Qingnan Zeng et al.
Chemical Engineering Journal · 2016
Enza Palma, Matteo Daghio, Andrea Franzetti et al.
Microbial Biotechnology · 2017
Groundwater contamination by petroleum hydrocarbons (PHs) is a widespread problem which poses serious environmental and health concerns. Recently, microbial electrochemical technologies (MET) have attracted considerable attention for remediation applications, having the potential to overcome some of the limiting factors of conventional in situ bioremediation systems. So far, field-scale application of MET has been largely hindered by the limited availability of scalable system configurations. Here, we describe the 'bioelectric well' a bioelectrochemical reactor configuration, which can be installed directly within groundwater wells and can be applied for in situ treatment of organic contaminants, such as PHs. A laboratory-scale prototype of the bioelectric well has been set up and operated in continuous-flow regime with phenol as the model contaminant. The best performance was obtained when the system was inoculated with refinery sludge and the anode potentiostatically controlled at +0.2 V versus SHE. Under this condition, the influent phenol (25 mg l -1 ) was nearly completely (99.5 ± 0.4%) removed, with an average degradation rate of 59 ± 3 mg l -1 d and a coulombic efficiency of 104 ± 4%. Microbial community analysis revealed a remarkable enrichment of Geobacter species on the surface of the graphite anode, clearly pointing to a direct involvement of this electro-active bacterium in the current-generating and phenol-oxidizing process.
Svetlana Fernandes, Aninda Mazumdar, Sabyasachi Bhattacharya et al.
Scientific Reports · 2018
Biogeochemistry of oxygen minimum zone (OMZ) sediments, which are characterized by high input of labile organic matter, have crucial bearings on the benthic biota, gas and metal fluxes across the sediment-water interface, and carbon-sulfur cycling. Here we couple pore-fluid chemistry and comprehensive microbial diversity data to reveal the sedimentary carbon-sulfur cycle across a water-depth transect covering the entire thickness of eastern Arabian Sea OMZ, off the west coast of India. Geochemical data show remarkable increase in average total organic carbon content and aerial sulfate reduction rate (J SO4 2- ) in the sediments of the OMZ center coupled with shallowing of sulfate methane transition zone and hydrogen sulfide and ammonium build-up. Total bacterial diversity, including those of complex organic matter degraders, fermentative and exoelectrogenic bacteria, and sulfate-reducers (that utilize only simple carbon compounds) were also found to be highest in the same region. The above findings indicate that higher organic carbon sequestration from the water-columns (apparently due to lower benthic consumption, biodegradation and biotransformation) and greater bioavailability of simple organic carbon compounds (apparently produced by fermetative microflora of the sediments) are instrumental in intensifying the carbon-sulfur cycle in the sediments of the OMZ center.
Peng Xu, Enrong Xiao, Dan Xu et al.
PLoS ONE · 2017
Sediment internal nitrogen release is a significant pollution source in the overlying water of aquatic ecosystems. This study aims to remove internal nitrogen in sediment-water microcosms by coupling sediment microbial fuel cells (SMFCs) with submerged aquatic plants. Twelve tanks including four treatments in triplicates were designed: open-circuit (SMFC-o), closed-circuit (SMFC-c), aquatic plants with open-circuit (P-SMFC-o) and aquatic plants with closed-circuit (P-SMFC-c). The changes in the bio-electrochemical characteristics of the nitrogen levels in overlying water, pore water, sediments, and aquatic plants were documented to explain the migration and transformation pathways of internal nitrogen. The results showed that both electrogenesis and aquatic plants could facilitate the mineralization of organic nitrogen in sediments. In SMFC, electrogenesis promoted the release of ammonium from the pore water, followed by the accumulation of ammonium and nitrate in the overlying water. The increased redox potential of sediments due to electrogenesis also contributed to higher levels of nitrate in overlying water when nitrification in pore water was facilitated and denitrification at the sediment-water interface was inhibited. When the aquatic plants were introduced into the closed-circuit SMFC, the internal ammonium assimilation by aquatic plants was advanced by electrogenesis; nitrification in pore water and denitrification in sediments were also promoted. These processes might result in the maximum decrease of internal nitrogen with low nitrogen levels in the overlying water despite the lower power production. The P-SMFC-c reduced 8.1%, 16.2%, 24.7%, and 25.3% of internal total nitrogen compared to SMFC-o on the 55th, 82th, 136th, and 190th days, respectively. The smaller number of Nitrospira and the larger number of Bacillus and Pseudomonas on the anodes via high throughput sequencing may account for strong mineralization and denitrification in the sediments under closed-circuit. The coupled P-SMFC system has shown good potential for the efficient removal of internal nitrogen.
Tyler Arbour, Benjamin Gilbert, Jillian F. Banfield
Frontiers in Microbiology · 2020
Extracellular electron transfer (EET) between microbes and iron minerals, and syntrophically between species, is a widespread process affecting biogeochemical cycles and microbial ecology. The distribution of this capacity among microbial taxa, and the thermodynamic controls on EET in complex microbial communities, are not fully known. Microbial electrochemical cells (MXCs), in which electrodes serve as the electron acceptor or donor, provide a powerful approach to enrich for organisms capable of EET and to study their metabolism. We used MXCs coupled with genome-resolved metagenomics to investigate the capacity for EET in microorganisms present in a well-studied aquifer near Rifle, CO. Electroactive biofilms were established and maintained for almost four years on anodes poised mostly at -0.2 to -0.25 V vs. SHE, a range that mimics the redox potential of iron-oxide minerals, using acetate as the sole carbon source. Here we report the metagenomic characterization of anode-biofilm and planktonic microbial communities from samples collected at timepoints across the study period. From two biofilm and 26 planktonic samples we reconstructed draft-quality and near-complete genomes for 84 bacteria and 2 archaea that represent the majority of organisms present. A novel Geobacter sp. with at least 72 putative multiheme c-type cytochromes (MHCs) was the dominant electrode-attached organism. However, a diverse range of other electrode-associated organisms also harbored putative MHCs with at least 10 heme-binding motifs, as well as porin-cytochrome complexes and e-pili, including Actinobacteria, Ignavibacteria, Chloroflexi, Acidobacteria, Firmicutes, Beta- and Gammaproteobacteria. Our results identify a small subset of the thousands of organisms previously detected in the Rifle aquifer that may have the potential to mediate mineral redox transformations.