Microbial Electrolysis Cell System Research Articles

Strengthening the cathodic CO2 adsorption on the MIL-88B(Fe) to enhance methane production

Direct interspecies electron transfer (DIET), as a new metabolic pathway for methanogenesis, is difficult to establish in common anaerobic digesters due to the lack of electroactive methanogens, syntrophic electroactive bacteria, and conductive proteins. In this study, a synthetic CC/MIL-88B electrode was used to accelerate the establishment of DIET in a microbial electrolysis cell (MEC)-based anaerobic digester. Results showed that the CC/MIL-88B electrode had a strong dispersive attraction generated by its three-dimensional aromatic ring structure, which benefited the capture of CO2 in the biofilm attached to the electrode and further increased the reduction of CO2 to produce methane via DIET. Electrochemical and metaproteomics analysis indicated that the MIL-88B(Fe) stimulated the secretion of conductive proteins (such as e-pili and cytochrome C). The abundances of electroactive methanogen Methanosarcina and other electroactive bacteria increased to 4.89 and 1.37 times, respectively. In addition, the expression of the key enzymes related to DIET-based methanogenesis (Fpo and Rnf) of Methanosarcina and the pathway of CO2-reduction methanogenesis were enhanced significantly. These results indicated that the synthetic CC/MIL-88B electrode helped the establishment of DIET in the MEC system, which provided a new perspective to establish DIET during anaerobic digestion by accelerating the utilization of CO2.

Potential mechanisms of propionate degradation and methanogenesis in anaerobic digestion coupled with microbial electrolysis cell system: Importance of biocathode

Microbial electrolysis cells (MEC) have the potential for enhancing the efficiency of anaerobic digestion (AD). In this study, microbiological and metabolic pathways in the biocathode of anaerobic digestion coupled with microbial electrolysis cells system (AD-MEC) were revealed to separate bioanode. The biocathode efficiently degraded 90 % propionate within 48 h, leading to a methane production rate of 3222 mL·m−2·d-1. The protein and heme-rich cathodic biofilm enhanced redox capacity and facilitated interspecies electron transfer. Key acid-degrading bacteria, including Dechloromonas agitata, Ignavibacteriales bacterium UTCHB2, and Syntrophobacter fumaroxidans, along with functional proteins such as cytochrome c and e-pili, established mutualistic relationships with Methanothrix soehngenii. This synergy facilitated a multi-pathway metabolic process that converted acetate and CO2 into methane. The study sheds light on the intricate microbial dynamics within the biocathode, suggesting promising prospects for the scalable integration of AD-MEC and its potential in sustainable energy production.

Microbial electrolysis cells designed for BioH2 production: Potential improvements with carbon dioxide and nitrogen

The long-term feasibility and efficiency of microbial electrolysis cells (MECs) depend primarily upon several crucial parameters. However, they show promise for sustainably producing biohydrogen (bioH2). This study investigates a newly designed biohydrogen reactor by studying the effects of several variables on the production of bioH2, including applied voltage, electrode material, and gas sparging with CO2 and N2. The study aims to optimize the system for improved efficiency and production performance. The results of this study show that both electrode type and applied voltage affect bioH2 production where choosing the right inoculum has a significant impact on the catalytic efficiency. The aluminum electrodes significantly help produce the most bioH2 production at 2.0 V with 884 mL/L in 11.25 min, while emphasizing the significance of material characteristics. The reduced partial pressure from CO2 sparging, up to a point, improves bioH2 generation. The N2 gas sparging further demonstrates an increased efficiency where the ideal flow rates are dependent on the size of the MEC system. The highest bioH2 production rates for CO2 and N2 sparging are measured as 821 mL/L and 813 mL/L in 4.25 min and 11.50 min at a volume of 400 mL/min and 300 mL/min, respectively. The results of this study further advance our knowledge of and ability to optimize MEC systems for long-term, sustainable bioH2 production.

Enhanced Succinic Acid Production and Electronic Utilization Efficiency by Actinobacillus succinogenes 130Z in an ORP-Controlled Microbial Electrolysis Cell System

Microbial electrochemical systems have shown great value as a means of enhancing the efficiency of fermentation reactions, but at present, there is no reliable means to balance the extracellular electron supply and corresponding intracellular demands in these systems. The current work describes the unique use of an oxidation–reduction-potential (ORP)-level-controlled microbial electrolysis cell (MEC) system to successfully balance the extracellular electron supply and succinic acid fermentation via A. succinogenes (130Z). The ORP-controlled MEC system with neutral red (NR) yielded a significant increase in succinic acid production (17.21%). The utilization of NR in this MEC system improved the ORP regulatory sensitivity. The optimal approach to the ORP level control was the use of a −400 mV high-voltage electric pulse-based strategy, which increased the yield of succinic acid by 13.08% compared to the control group, and reduced the energy consumption to 52.29% compared to the potentiostatic method. When compared to the −1 V constant potential MEC system, the high-voltage electric pulse-based ORP strategy for the MEC system control provided sufficient electrons to this system while using less electricity (11.96%) and producing 12.48% (74.43 g/L) more succinic acid during fed-batch fermentation. The electronic utilization efficiency of the ORP-controlled MEC system was 192.02%, which was 15.19 times that of the potentiostatic system. The electronic utilization efficiency is significantly increased in the ORP-controlled MEC system. Succinic acid production is ensured by a high-voltage electric pulse-based method, while the influence on cell growth and power consumption are minimized. Fed-batch fermentation with the high-voltage electric pulse-based ORP strategy for MEC system control is noted to be ideal to achieve a further increase in succinic acid concentration and electronic utilization efficiency.

Exogenous electric field as a biochemical driving factor for extracellular electron transfer: Increasing power output of microbial fuel cell

Although microbial fuel cells (MFCs) offer a promising avenue for clean power production, they are hindered by inefficient extracellular electron transfer (EET), thereby resulting in a low power output. This study focused on augmenting MFC power by boosting the EET rate using an exogenous electric field (EEF). By leveraging the dual benefits of microbial electrolysis cells (MECs) in organic waste treatment and energy recovery, we developed an MFC–MEC system that utilizes the EEF from MEC as a connecting link. Two configurations, EEF in the same direction (SD-MFC–MEC) and EEF in the reverse direction (RD-MFC–MEC), were used to examine the EET kinetic rate at the MFC anode in the EEF environment using various electrochemical methods for quantitative evaluation. Our findings revealed that EEF significantly enhanced MFC anode biofilm formation and electrochemical activity, leading to a prominent improvement in electrode reaction rates. The EET rate constants in the SD-MFC–MEC and RD-MFC–MEC were more than double those in the control R-MFC, with power density increases of 117.8% and 108.4%, respectively. The formation of electrochemically active sites within the biofilm induced by EEF has emerged as a crucial factor in amplifying the EET rate, and consequently, the MFC power output. Additionally, the variation in EET rate constants between the SD-MFC–MEC and RD-MFC–MEC was minimal, thereby indicating the negligible impact of the EEF orientation on the EET efficiency. This study provides a novel method for quantitatively examining EET rates, opens up new avenues for further facilitating microbe-to-electrode electron transfer, and promotes the application of MFC–MEC systems in energy recovery, CO2 emission reduction, and waste treatment.

Enhanced bioethanol production by evolved Escherichia coli LGE2-H in a microbial electrolysis cell system

Lignocellulose pretreated using pyrolysis can yield clean energy (such as bioethanol) via microbial fermentation, which can significantly contribute to waste recycling, environmental protection, and energy security. However, the acids, aldehydes, and phenols present in bio-oil with inhibitory effects on microorganisms compromise the downstream utilization and conversion of lignocellulosic pyrolysates. In this study, we constructed a microbial electrolysis cell system for bio-oil detoxification and efficient ethanol production using evolved Escherichia coli to overcome the bioethanol production and utilization challenges highlighted in previous studies. In electrically treated bio-oil media, the E. coli-H strain exhibited significantly higher levoglucosan consumption and ethanol production capacities compared with the control. In undetoxified bio-oil media containing 1.0% (w/v) levoglucosan, E. coli-H produced 0.54 g ethanol/g levoglucosan, reaching 94% of the theoretical yield. Our findings will contribute to developing a practical method for bioethanol production from lignocellulosic substrates, and provide a scientific basis and technical demonstration for its industrialized application.Graphical abstract

Elucidating applied voltage on the fate of antibiotic resistance genes in microbial electrolysis cell: Focusing on its transmission between anolyte and biofilm microbes

Microbial electrolysis cell (MEC) system to treat wastewater containing antibiotics has been researched actively in past years. However, the fate of antibiotic resistant genes (ARGs) in MEC is not fully revealed. The effect of applied voltage on the migration of ARGs between anolyte and biofilm microbes via examining the microbial physiology and abundances of macrolide resistance genes (MRGs) and mobile genetic elements (MGEs) was elucidated in this research. Results showed that the abundance of MRGs and MGEs was decreased in the anolyte, but their abundances were increased on the electrode biofilm, indicating their transmission from anolyte to biofilm microbes. Increased applied voltage enhanced adenosine triphosphate (ATP), reactive oxygen species (ROS), and cell membrane permeability of electrode microorganisms. The structure of the electrode microbial community was shifted through applied voltage, and the abundance of electroactive microorganisms (Geobacter, Azospirillum and Dechlorobacter) was significantly improved. Network analysis revealed that Geobacter and Geothrix were potential hosts for MRGs. Therefore, the horizontal and vertical gene transfer of ARGs could be increased by the applied voltage, leading to the enriched ARGs at the electrode biofilm. This study provides evidence and insights into the transmission of ARGs between anolyte and biofilm microbes in MEC system. SynopsisThis study revealed the effect of applied voltage on ARGs in MEC and the potential migration mechanism of ARGs.

Model-based optimal and robust control of renewable hydrogen gas production in a fed-batch microbial electrolysis cell

Microbial electrolysis cell (MEC) is a fundamental type of bio-electrochemical system. MEC is a novel and emerging renewable energy technology that is based on biomass. The behavior of the MEC system is highly nonlinear due to the complexity of its dynamics. For the desired optimal production of hydrogen, feedback control of MEC processes is necessary. Due to the novelty of MEC, limited research is available on its control. Studies on linear model-based robust control of MEC processes are missing. In this article, we develop a nonlinear dynamic model for MEC, linearize this model, and calculate a linear time-invariant transfer function. Based on this linearization, a fixed-structure, optimal and robust controller is proposed to achieve a fast-settling time exhibiting no overshoot and having zero steady-state error. The robustness of the developed controller is evaluated for parameter uncertainty, measurement noise, and disturbance rejection. Batch biomass processes are fed only at the start of each process cycle. The output does not follow the desired response when the substrate or biomass is consumed. Then, the error accumulates, and it causes the control effort to increase unboundedly. The existing literature on control of fed-batch MEC processes does not consider this integral windup phenomenon. In this article, we also develop an anti-windup control strategy to eliminate the integral windup error and to avoid any possible instability or destruction. The overall conclusion of our study is that the developed robust controller achieves a faster and more robust response than the existing controllers. We provide an anti-integral windup solution to eliminate windup errors in feedback control of fed-batch MEC processes.

Nitrogen removal enhanced by its migration and transformation in a three-chamber microbial electrolysis cell

In this study, a three-chamber microbial electrolysis cell (MEC) was established for the simultaneous migration, transformation and removal of NH4+-N, NO2−-N, and NO3−-N under different applied voltages. The results showed that higher applied voltages accelerated the migration rate of NH4+-N while had little effect on NO2−-N and NO3−-N. The highest total nitrogen (TN) removal efficiency was achieved in the MEC system at 1.0 V (61.40 ± 19.58 %). At the optimal voltage of 1.0 V, nitrogen removal performance at different carbon to nitrogen (C/N) ratios was also discussed. Under different C/N ratios, TN removal efficiencies maintained stable, which suggested that the migration of nitrogen species by applied voltages combined with nitrogen transformation was beneficial for nitrogen removal in MEC systems. Also, different denitrification pathways could be influenced by reasonably allocating carbon sources. Meanwhile, the whole system was enriched with autotrophic and heterotrophic denitrifiers (e.g. Proteobacteria, Patescibacteria, Thermomonas, and Ferruginibacter), implying that heterotrophic denitrification, hydrogenotrophic denitrification and electroactive autotrophic denitrification coexisted and collaborated in this MEC system for nitrogen removal. The “migration-transformation-removal” model of nitrogen was innovatively proposed and meanwhile this proof-of concept study provided a new insight into nitrogen removal in low C/N ratio wastewater.

Tofu Wastewater (TWW) Treatment and Hydrogen (H2) Production by Using A Microbial Electrolysis Cell (MEC) System

High organic pollutant in tofu wastewater (TWW) raises a negative impact on environmental sustainability and health. Therefore, the TWW must be treated before it is discharged into the environment. Microbial electrolysis cell (MEC) is one of the green technologies that can be used to treat wastewater and generate hydrogen as well. This work tries to investigate the performance of MEC based on the decrement of organic pollutants in TWW. Some important parameters of organic pollutants in TWW such as chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solids (TSS), total dissolved solids (TDS), total solid (TS), and pH were evaluated before and after MEC operation. The results showed that the COD and BOD levels decreased around 56% and 35% while pH increased from 7.90 to 7.16. Additionally, the TSS, TDS, and TS decreased by around 35.0%, 45.5%, and 33.2%. In addition, the optimum hydrogen yield (YH2) and hydrogen production rate (QH2) were obtained at 114 ± 0.1 mL H2/g COD 360 ± 20 mL H2/L/d. Overall, the MEC system could be used to reduce the level of organic pollutants in TWW and generated H2 at the same time.

Efficient elimination of nonylphenol and 4-tert-octylphenol by weak electrical stimulated anaerobic microbial processes

The investigation into the degradation of alkylphenol pollutants (APs) has become a hotspot due to their harmful effects on the environment and human health. In this study, microbial electrolysis cells (MECs) were used to degrade nonylphenol (NP) and 4-tert-octylphenol (4-tert-OP). The study found that the degradation rates of NP and 4-tert-OP for a 6-day period were 83.6% and 96.3%, respectively, which were 30.53% and 26.7% higher than those of the group without applied voltage. The double layer area in the degradation of 4-tert-OP was larger than that of NP, and the resistance exhibited by 4-tert-OP (87.47 Ω) in MEC was lower than that of NP (99.42 Ω). Meanwhile, NP had a greater effect on the bioenzyme activity than 4-tert-OP. GC-MS analysis showed that the degradation pathways of both pollutants mainly included oxidation and hydroxylation reactions. Furthermore, the microbial community analysis indicated that the main functional bacteria in NP degradation were Citrobacter, Desulfovibrio and Advenella, and those in 4-tert-OP degradation were Stenotrophomonas, Chryseobacterium, Dokdonella, and the key microbiomes underlying the cooperative relationship. The biotoxicity test indicated that the toxicity of residual substances was significantly reduced. Therefore, the MEC system is efficient and environmentally friendly and has broad application prospects in phenol refractory organics.

The microbial synergy and response mechanisms of hydrolysis-acidification combined microbial electrolysis cell system with stainless-steel cathode for textile-dyeing wastewater treatment

Microbial electrolysis cell (MEC) has been existing problems such as poor applicability to real wastewater and lack of cost-effective electrode materials in the practical application of refractory wastewater. A hydrolysis-acidification combined MEC system (HAR-MECs) with four inexpensive stainless-steel and conventional carbon cloth cathodes for the treatment of real textile-dyeing wastewater, which was fully evaluated the technical feasibility in terms of parameter optimization, spectral analysis, succession and cooperative/competition effect of microbial. Results showed that the optimum performance was achieved with a 12 h hydraulic retention time (HRT) and an applied voltage of 0.7 V in the HAR-MEC system with a 100 μm aperture stainless-steel mesh cathode (SSM-100 μm), and the associated optimum BOD5/COD improvement efficiency (74.75 ± 4.32 %) and current density (5.94 ± 0.03 A·m−2) were increased by 30.36 % and 22.36 % compared to a conventional carbon cloth cathode. The optimal system had effective removal of refractory organics and produced small molecules by electrical stimulation. The HAR segment could greatly alleviate the imbalance between electron donors and electron acceptors in the real refractory wastewater and reduce the treatment difficulty of the MEC segment, while the MEC system improved wastewater biodegradability, amplified the positive and specific interactions between degraders, fermenters and electroactive bacteria due to the substrate complexity. The SSM-100 μm-based system constructed by phylogenetic molecular ecological network (pMEN) exhibited moderate complexity and significantly strong positive correlation between electroactive bacteria and fermenters. It is highly feasible to use HAR-MEC with inexpensive stainless-steel cathode for textile-dyeing wastewater treatment.

Life Cycle Assessment of Microbial Electrolysis Cells for Hydrogen Generation Using TRACI Methodology

Bioelectrochemical systems (BESs) use electrochemically active microorganisms to convert the chemical energy of organic matter into electrical energy, hydrogen, or other useful products through redox reactions. Microbial electrolysis cell (MEC) is one of the most common BESs which are able to convert organic substrate into energy (such as hydrogen and methane) through the catalytic action of electrochemically active bacteria in the presence of electric current and absence of oxygen. In the past decades, BESs have gained growing attention because of their potential, but there is still a limited amount of research is done for the environmental effects of BESs. This study initially provides an update review for MECs including general historical advancement, design properties, and operation mechanisms. Later, a life cycle assessment (LCA) study was conducted using a midpoint approach, which is TRACI methodology with EIO-LCA model to identify the potential impacts to the environment whether adverse or beneficial using the MECs to produce hydrogen with domestic wastewater as a substrate. The results show that the cumulative negative impacts were substantially larger than the positive impacts by contrast with the expectations, and the cumulative output data show that human health non-cancer impact provides the highest environmental effects than others mainly because of the inorganic chemicals, pumping and wastewater recycling equipment step. In addition, global warming potential and smog creation potential are also elevated mainly due to electricity usage, inorganic chemical and glassware reactor production. Later we are externally normalized each impact category to compare the results at the normalization level, and we again found that human health (cancer or non-cancer) potential provides the most negative impact on the environment in the MEC system originates on human health indicators.

A Catalytic Effectiveness Factor for a Microbial Electrolysis Cell Biofilm Model

The aim of this work is to propose a methodology to obtain an effectiveness factor for biofilm in a microbial electrolysis cell (MEC) system and use it to reduce a partial differential equation (PDE) biofilm MEC model to an ordinary differential equation (ODE) MEC model. The biofilm mass balances of the different species are considered. In addition, it is considered that all the involved microorganisms are attached to the anodic biological film. Three effectiveness factors are obtained from partial differential equations describing the spatial distributions of potential and substrate in the biofilm. Then, a model reduction is carried out using the global mass balances of the different species in the system. The reduced model with three uncertain but bounded effectiveness factors is evaluated numerically and analyzed in the sense of stability and parametric sensibility to demonstrate its applicability. The reduced ODE model is compared with a validated model taken from the literature, and the results are in good agreement. The biofilm effectiveness factor in MEC systems can be extended to the reduction of PDE models to obtain ODE models that are commonly used in optimization and control problems.

Early activated quorum sensing enhanced a nosZ-deficient strain of Pseudomonas aeruginosa for stably recovering nitrous oxide from incineration leachate in microbial electrolysis cell

In this study, a quorum sensing (QS) signal molecule, 3-oxo-C12-HSL, was supplied into ΔnosZ Pseudomonas microbial electrolysis cell system for strengthening the N2O recovery from incineration leachate. The resistance for high nitrite loading was strongly improved with nitrite removal efficiency of 80.35% compared to 67.07% from the control on day 13 due to the increasing biomass through early activated QS. Higher N2O proportion in biogas (85.85% on average) was achieved in the QS early activated reactor, which indicated the better potential for N2O recovery. Bacterial community analysis showed the purity of ΔnosZ strain with the abundance of 100% in the anode chamber at the end of the operation. This was plausibly related to the increased synthesis of phenazine derivatives by the early activated QS system. These results show a more promising way for N2O recovery by a single engineering bacteria from the high nitrogen contained actual wastewater.

Performance optimization of microbial electrolysis cell (MEC) for palm oil mill effluent (POME) wastewater treatment and sustainable Bio-H2 production using response surface methodology (RSM)

Microbial electrolysis cells (MECs) are a new bio-electrochemical method for converting organic matter to hydrogen gas (H2). Palm oil mill effluent (POME) is hazardous wastewater that is mostly formed during the crude oil extraction process in the palm oil industry. In the present study, POME was used in the MEC system for hydrogen generation as a feasible treatment technology. To enhance biohydrogen generation from POME in the MEC, an empirical model was generated using response surface methodology (RSM). A central composite design (CCD) was utilized to perform twenty experimental runs of MEC given three important variables, namely incubation temperature, initial pH, and influent dilution rate. Experimental results from CCD showed that an average value of 1.16 m3 H2/m3 d for maximum hydrogen production rate (HPR) was produced. A second-order polynomial model was adjusted to the experimental results from CCD. The regression model showed that the quadratic term of all variables tested had a highly significant effect (P < 0.01) on maximum HPR as a defined response. The analysis of the empirical model revealed that the optimal conditions for maximum HPR were incubation temperature, initial pH, and influent dilution rate of 30.23 ∘C, 6.63, and 50.71%, respectively. Generated regression model predicted a maximum HPR of 1.1659 m3 H2/m3 d could be generated under optimum conditions. Confirmation experimentation was conducted in the optimal conditions determined. Experimental results of the validation test showed that a maximum HPR of 1.1747 m3 H2/m3 d was produced.

Enhanced straw fermentation process based on microbial electrolysis cell coupled anaerobic digestion

The low quality and yield of methane severely hinder the industrial application of straw biogas fermentation, and no effective solution has been found so far. In this study, a novel method was developed when a microbial electrolysis cell (MEC) was coupled with normal anaerobic fermentation to enhance methane yield and purity. The fermentation process achieved a methane purity of more than 85%, which is considerably higher than that of previously published reports. With microbial stimulation and an electric current, the degradation of fibers has been greatly enhanced. The MEC system substantially improved the yield and purity of biogas, bringing a new path to the synthesis of methane by carbon dioxide and hydrogen ions in solution under electron irradiation. Electrochemical index analysis showed extra methane synthesis, due to the external circuit electron transfer. The results of the gas chromatography and solid degradation rate showed that the carbon source of extra methane was CO 2 produced during normal fermentation and additional volatile solid degradation. These results show that the MEC considerably enhanced the quality and yield of methane in the straw fermentation process, providing insights into normal anaerobic fermentation.

The Microbial Synergy and Response Mechanisms of Hydrolysis-Acidification Combined Microbial Electrolysis Cell System with Stainless-Steel Cathode for Textile-Dyeing Wastewater Treatment

The Microbial Synergy and Response Mechanisms of Hydrolysis-Acidification Combined Microbial Electrolysis Cell System with Stainless-Steel Cathode for Textile-Dyeing Wastewater Treatment

Fuzzy logic controller implementation on a microbial electrolysis cell for biohydrogen production and storage

This work presents the implementation of fuzzy logic control (FLC) on a microbial electrolysis cell (MEC). Hydrogen has been touted as a potential alternative source of energy to the depleting fossil fuels. MEC is one of the most extensively studied method of hydrogen production. The utilization of biowaste as its substrate by MEC promotes the waste to energy initiative. The hydrogen production within the MEC system, which involves microbial interaction contributes to the system’s nonlinearity. Taking into account of the high complexity of MEC system, a precise process control system is required to ensure a well-controlled biohydrogen production flow rate and storage application inside a tank. Proportional-derivative-integral (PID) controller has been one of the pioneer control loop mechanism. However, it lacks the capability to adapt properly in the presence of disturbance. An advanced process control mechanism such as the FLC has proven to be a better solution to be implemented on a nonlinear system due to its similarity in human-natured thinking. The performance of the FLC has been evaluated based on its implementation on the MEC system through various control schemes progressively. Similar evaluations include the performance of Proportional-Integral (PI) and PID controller for comparison purposes. The tracking capability of FLC is also accessed against another advanced controller that is the model predictive controller (MPC). One of the key findings in this work is that the FLC resulted in a desirable hydrogen output via MEC over the PI and PID controller in terms of shorter settling time and lesser overshoot.

Continuous and efficient uranium recovery in a bioelectrochemical system

Microbial fuel cell (MFC) is a feasible technology for uranium removal and recovery from uranium-containing wastewater. However, the accumulation of reductive product (UO2) on the cathode surface hindered the continuous removal of uranium due to the increase of over-potential. In this study, we developed a microbial electrolysis cell (MEC) system in a mixed microbial consortium with a low energy input that can continuously remove uranium on the UO2-coated cathode. Thermodynamic calculation results demonstrated that the cathode potential controls U(VI) removal in the MEC system, and U(VI) removal was the contribution of the microbial process and the applied voltage (Eap). Experimental results indicated that the cathode potential for the electrochemical reduction of U(VI) on the UO2-coated cathode was about –0.64 V vs. Ag/AgCl, whereas the microbial species in the anode of MEC can provide an Ecathode of –0.47 V vs. Ag/AgCl. Therefore, only a small Eap (about 150 mV) can trigger the continuous U(VI) removal in the MEC. The continuous removal capacity of the UO2-coated cathode was evaluated over 15,830.86 μmol m−2, and the removal efficiencies were higher than 94.0% after all the 22 cyclic tests. Furthermore, over 98.0% of uranium can be recovered from the cathode by acid or alkali method, and the recovery process does not affect the electrode itself. The excellent continuous removal capacity and reusability of the electrode demonstrate that MEC is a promising technology for U(VI) removal from wastewater.