Manoj Kumar, Rajesh Singh

Environmental Science: Water Research & Technology • 0

<p>In the present study, we investigated the role of constructed wetlands (CWs) integrated with a bioelectrochemical system (BES), which can concurrently treat wastewater effectively with energy recovery.</p>

Jing Wang, Ming Li, Fangtai Liu et al.

Journal of Nanomaterials • 2016

<jats:p>We proposed a self-connected carbon nanofiber design for electrode in microbial bioelectrochemical system. This design was realized by direct growth of carbon nanofibers (CNFs) onto stainless steel (SSM) via a chemical vapor deposition process without addition of any external catalysts. In the CNFs-SSM composite electrode, the SSM acted as the conductive network and ensured efficient substrate and proton transfer, and the CNFs layer served as highly porous habitats for thick biofilm propagation. The current generated by the CNFs-SSM was 200 times higher than the bare SSM under the same experimental conditions. This provided a simple and promising method for preparation of electrode material with high performance and low-cost in bioelectrochemical system.</jats:p>

Hui Wang, Ying Du, XiangHua Wang et al.

Fuel Cells • 2024

<jats:title>ABSTRACT</jats:title><jats:p>Refractory organic pollutant removal can be enhanced by a bioelectrochemical system via the addition of electron donors/acceptors. In this study, a single‐chamber soil microbial fuel cell (MFC) was constructed, and electricity production and atrazine removal efficiency were assessed using different co‐substrates and phosphate buffer concentrations. The co‐substrates compensated for the lack of soil organic matter and provided a sufficient carbon source for microorganisms to facilitate MFC electricity generation and efficient atrazine removal. The maximum voltage (94 mV), power density (39.41 mW m<jats:sup>−2</jats:sup>), removal efficiency (85.30%), and degradation rate (1.68 mg kg<jats:sup>−1</jats:sup> d<jats:sup>−1</jats:sup>) were highest in the soil MFCs with sodium acetate when compared with the other groups. Phosphate buffer significantly alleviated the dramatic soil pH change. The electricity generation and atrazine removal efficiency increased with the buffer concentration (0–0.10 g L<jats:sup>−1</jats:sup>). The maximum voltage (144 mV) and power density (89.35 mW m<jats:sup>−2</jats:sup>) were highest, total internal resistance (652 Ω) was lowest, and atrazine removal efficiency (90.95%) and degradation rate (1.54 mg kg<jats:sup>−1</jats:sup> d<jats:sup>−1</jats:sup>) were determined in the soil MFCs with the phosphate buffer concentration of 0.10 g L<jats:sup>−1</jats:sup>, and. These results indicate that the co‐substrate and phosphate buffer can enhance the electricity generation of soil MFCs and atrazine removal.</jats:p>

Philipp Arbter, Niklas Widderich, Tyll Utesch et al.

Microbial Cell Factories • 0

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>Electro-fermentation (EF) is an emerging tool for bioprocess intensification. Benefits are especially expected for bioprocesses in which the cells are enabled to exchange electrons with electrode surfaces directly. It has also been demonstrated that the use of electrical energy in BES can increase bioprocess performance by indirect secondary effects. In this case, the electricity is used to alter process parameters and indirectly activate desired pathways. In many bioprocesses, oxidation-reduction potential (ORP) is a crucial process parameter. While <jats:italic>C. pasteurianum</jats:italic> fermentation of glycerol has been shown to be significantly influenced electrochemically, the underlying mechanisms are not clear. To this end, we developed a system for the electrochemical control of ORP in continuous culture to quantitatively study the effects of ORP alteration on <jats:italic>C. pasteurianum</jats:italic> by metabolic flux analysis (MFA), targeted metabolomics, sensitivity and regulation analysis.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>In the ORP range of −462 mV to −250 mV, the developed algorithm enabled a stable anodic electrochemical control of ORP at desired set-points and a fixed dilution rate of 0.1 h<jats:sup>−1</jats:sup>. An overall increase of 57% in the molar yield for 1,3-propanediol was observed by an ORP increase from −462 to −250 mV. MFA suggests that <jats:italic>C. pasteurianum</jats:italic> possesses and uses cellular energy generation mechanisms in addition to substrate-level phosphorylation. The sensitivity analysis showed that ORP exerted its strongest impact on the reaction of pyruvate-ferredoxin-oxidoreductase. The regulation analysis revealed that this influence is mainly of a direct nature. Hence, the observed metabolic shifts are primarily caused by direct inhibition of the enzyme upon electrochemical production of oxygen. A similar effect was observed for the enzyme pyruvate-formate-lyase at elevated ORP levels.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The results show that electrochemical ORP alteration is a suitable tool to steer the metabolism of <jats:italic>C. pasteurianum</jats:italic> and increase product yield for 1,3-propanediol in continuous culture. The approach might also be useful for application with further anaerobic or anoxic bioprocesses. However, to maximize the technique's efficiency, it is essential to understand the chemistry behind the ORP change and how the microbial system responds to it by transmitted or direct effects.</jats:p> </jats:sec>

Manoj Kumar, Rajesh Singh

Environmental Science: Water Research &amp; Technology • 0

<p>In this study, two-phase continuous vertical flow constructed wetlands were installed with a pre-cleaner bioelectrochemical system for the removal of NH₄⁺-N (60.41–85.78%), NO₃⁻-N (25.55–35.18%), TN (57.80–84.65%), TKN (37.24–70.08%), PO₄³⁻-P (38.89–63.40%), SO₄²⁻ (49.53–76.06%), and COD (25.83–74.70%) from municipal wastewater.</p>

Young Eun Song, Changman Kim, Jiyun Baek et al.

Sustainable Energy &amp; Fuels • 0

<p>The high CODH activity appears to have a synergistic effect with an electrode-assisted electron transfer, and thus maximize the conversion of acetate and VFAs from electrosynthesis with CO.</p>

Anna Weimer, Jens Krömer, Bin Lai et al.

Microbial Biotechnology • 2025

<jats:title>ABSTRACT</jats:title><jats:p>Mediator‐based extracellular electron transfer (EET) in a bioelectrochemical system is a unique approach to regulate the microbial redox and energy metabolism of <jats:styled-content style="fixed-case"><jats:italic>Pseudomonas putida</jats:italic></jats:styled-content> KT2440, which enables a new‐to‐nature high product yield under anaerobic conditions. Previous studies identified respiratory complex III in the inner membrane as a key redox protein involved in mediator (ferricyanide) interactions, but the exact mechanism through which the mediator crosses the outer membrane to extract electrons from membrane‐bound redox proteins and transfer them to the anode remains unclear. In this study, we demonstrated the critical role of the TonB‐dependent system, a widespread transportation system in gram‐negative bacteria, in the mediator‐based EET process. Transcriptomic analyses revealed significant upregulation of TonB‐dependent receptors in response to ferricyanide exposure, suggesting their involvement in mediator uptake. Deletion of the TonB complex resulted in <jats:italic>a</jats:italic> &gt; 50% decrease in the mediator reduction rate and current output, confirming the role of the TonB‐dependent system in mediator transport. Additionally, increasing passive diffusion through the overexpression of the general porin OprF increased cell permeability and the mediator reduction rate, but it failed to compensate for the absence of TonB‐dependent transport. These findings suggest that both systems act in a complementary manner: the TonB‐dependent system is likely the primary mechanism for periplasmic mediator uptake, whereas OprF is likely involved mainly in mediator efflux. Further bioelectrochemical system experiments demonstrated that, with a functional TonB‐dependent system, OprF overexpression increased current output, glucose consumption, and 2‐ketogluconate production, suggesting a viable strategy for enhancing the efficacy of mediator‐based EET. This work reveals the major mediator transport mechanism in <jats:styled-content style="fixed-case"><jats:italic>P. putida</jats:italic></jats:styled-content> and deepens the understanding of the mediator‐based EET pathway, laying the basis for future rational engineering of EET kinetics and facilitating the integration of mediator‐based electron transfer into industrial biotechnology to push its process boundaries.</jats:p>

Christy M. Dykstra, Spyros G. Pavlostathis

Biotechnology and Bioengineering • 2017

<jats:title>ABSTRACT</jats:title><jats:sec><jats:label /><jats:p>Bioelectrochemical systems (BESs) may be used to upgrade anaerobic digester biogas by directly converting CO<jats:sub>2</jats:sub> to CH<jats:sub>4</jats:sub>. The objective of this study was to evaluate gas (N<jats:sub>2</jats:sub>, CO<jats:sub>2</jats:sub>, CH<jats:sub>4</jats:sub>, and H<jats:sub>2</jats:sub>) and carbon transport within a methanogenic BES. Four BES configurations were evaluated: abiotic anode with abiotic cathode (AAn‐ACa), bioanode with abiotic cathode (BAn‐ACa), abiotic anode with biocathode (AAn‐BCa), and bioanode with biocathode (BAn‐BCa). Transport of N<jats:sub>2</jats:sub>, a gas commonly used for flushing anoxic systems, out of the anode headspace ranged from 3.7 to 6.2 L/d‐atm‐m<jats:sup>2</jats:sup>, normalized to the proton exchange membrane (PEM) surface area and net driving pressure (NDP). CO<jats:sub>2</jats:sub> was transported from the cathode to the anode headspace at rates from 3.7 to 5.4 L/d‐atm‐m<jats:sup>2</jats:sup>. The flux of H<jats:sub>2</jats:sub> from cathode to anode headspace was 48% greater when the system had a biocathode (AAn‐BCa) than when H<jats:sub>2</jats:sub> was produced at an abiotic cathode (BAn‐ACa), even though the abiotic cathode headspace had 75% more H<jats:sub>2</jats:sub> than the AAn‐BCa biocathode at the end of 1 day. A 7‐day carbon balance of a batch‐fed BAn‐BCa BES showed transient microbial carbon storage and a net transport of carbon from anode to cathode. After a 7‐day batch incubation, the CH<jats:sub>4</jats:sub> production in the biocathode was 27% greater on a molar basis than the initial CO<jats:sub>2</jats:sub> supplied to the biocathode headspace, indicating conversion of CO<jats:sub>2</jats:sub> produced in the anode. This research expands the current understanding of methanogenic BES operation, which may be used in improving the assessment of BES performance and/or in the development of alternative BES designs and mathematical models. Biotechnol. Bioeng. 2017;114: 961–969. © 2016 Wiley Periodicals, Inc.</jats:p></jats:sec>

M. Zeppilli, A. Mattia, M. Villano et al.

Fuel Cells • 2017

<jats:title>Abstract</jats:title><jats:p>Here, an innovative three‐chamber bioelectrochemical system configuration is proposed to combine COD, CO<jats:sub>2</jats:sub> and NH<jats:sub>4</jats:sub><jats:sup>+</jats:sup> removal into a single device. In the proposed process, while COD oxidation and CO<jats:sub>2</jats:sub> reduction occurred, respectively, in the anodic and cathodic chamber, the consequent current generation promoted the migration of target ionic species towards an intermediate accumulation chamber, across cation and anion exchange membranes, respectively. Under this configuration, COD removal proceeded in the anode chamber with an average removal rate of 841 mgCOD L<jats:sup>−1</jats:sup> d<jats:sup>−1</jats:sup> while the cathode was able to remove 2.1 gCO<jats:sub>2</jats:sub> L<jats:sup>−1</jats:sup> d<jats:sup>−1</jats:sup> and produce 60 meq L<jats:sup>−1</jats:sup> d<jats:sup>−1</jats:sup> of CH<jats:sub>4</jats:sub>. Around 90% of the removed CO<jats:sub>2</jats:sub> was contained in the concentrated spill (at around 20 g L<jats:sup>−1</jats:sup> of bicarbonate), which was recovered from the intermediate accumulation chamber and also contained the removed nitrogen as ammonium ion (around 32% removal and around 4‐fold concentration with respect to the anode influent). Methane generation allowed a partial recovery of energy of overall energy consumption costs of both COD and CO<jats:sub>2</jats:sub> removal. This study confirms the possibility to combine three processes into a single bioelectrochemical device.</jats:p>

Gowthami Palanisamy, Sadhasivam Thangarasu, Tae Hwan Oh

Polymers • 0

<jats:p>Microbial fuel cells (MFCs) provide considerable benefits in the energy and environmental sectors for producing bioenergy during bioremediation. Recently, new hybrid composite membranes with inorganic additives have been considered for MFC application to replace the high cost of commercial membranes and improve the performances of cost-effective polymers, such as MFC membranes. The homogeneous impregnation of inorganic additives in the polymer matrix effectively enhances the physicochemical, thermal, and mechanical stabilities and prevents the crossover of substrate and oxygen through polymer membranes. However, the typical incorporation of inorganic additives in the membrane decreases the proton conductivity and ion exchange capacity. In this critical review, we systematically explained the impact of sulfonated inorganic additives (such as (sulfonated) sSiO2, sTiO2, sFe3O4, and s-graphene oxide) on different kinds of hybrid polymers (such as PFSA, PVDF, SPEEK, SPAEK, SSEBS, and PBI) membrane for MFC applications. The membrane mechanism and interaction between the polymers and sulfonated inorganic additives are explained. The impact of sulfonated inorganic additives on polymer membranes is highlighted based on the physicochemical, mechanical, and MFC performances. The core understandings in this review can provide vital direction for future development.</jats:p>

Axel Rous, G. Santa-Catalina, E. D. Quéméner et al.

• 2023

The production of nitrogen fertilizers in modern agriculture is mostly based on the Haber-Bosch process, representing nearly 2% of the total energy consumed in the world. Low-energy bioelectrochemical fixation of N2 to microbial biomass was previously observed but the mechanisms of microbial interactions in N2-fixing electroactive biofilms are still poorly understood. The present study aims to develop a new method of enrichment of autotrophic and diazotrophic bacteria from soil samples with a better electron source availability than using H2 alone. The enrichment method was based on a multi-stage procedure. The first enrichment step was specifically designed for the selection of N2-fixing bacteria from soil samples with organic C as electron and carbon source. Then, a polarized cathode was used for the enrichment of autotrophic bacteria using H2 (hydrogenotrophic) or the cathode as electron source. This enrichment was compared with an enrichment culture of pure diazotrophic hydrogenotrophic bacteria without the use of a microbial electrochemical system. Interestingly, both methods showed comparable results for N2 fixation rates at day 340 of the enrichment with an estimated average of approximately 0.2 mgNfixed/L.d. Current densities up to −15 A/m2 were observed in the polarized cathode enrichments and a significant increase of the microbial biomass on the cathode was shown between 132 and 214 days of enrichment.These results confirmed an enrichment in autotrophic and diazotrophic bacteria on the polarized cathode. It was hypothesied that autotrophic bacteria were able to use either the H2 produced at the cathode or directly the cathode through direct electron transfer (DET) as more biomass was produced than with H2 alone. Finally, the analysis of the enriched communities suggested that Desulforamulus ruminis mediated microbial interactions between autotrophic anaerobic and heterotrophic aerobic bacteria in polarized cathode enrichment. These interactions could play a key role in the development of biomass in these systems and on N2 fixation. Based on these findings, a conceptual model on the functioning of mixed cultures N2-fixing electroactive biofilms was proposed.

D. Pant, Suman Bajracharya, G. Mohanakrishna et al.

Qatar Foundation Annual Research Conference Proceedings Volume 2016 Issue 1 • 2016

Microbial Electrosynthesis (MES) comprises electro-reduction of carbon dioxide (CO2) to multi-carbon organic compounds by chemolithotrophs using electrons from a cathode. Reduction of CO2 to chemicals through microbial electrocatalysis was investigated by using a mixed culture of acetogenic and carboxydotrophic bacteria forming a microbial biofilm supported on a carbon based electrode, as biocathode, in a two chamber reactor. The biofilm was developed after a start-up phase with fructose and later on, growing on bicarbonate as substrate at sufficiently negative cathode potential (hydrogen evolution) in a couple of subsequent fed-batch operations. CO2 reduction could occur via direct electron transfer from the electrode or indirectly via mediators or via hydrogen at more reductive potential. Predominantly, Acetic acid was produced along with other volatile fatty acids (VFAs) while applying − 1.1 V/Ag/AgCl cathode potential, along with hydrogen evolution. At the initial stage of fed-batch operation, higher carbon recovery up to 60% was observed from bicarbonate (dissolved CO2) to acetic acid while after accumulation of acetate, the recovery rate went down to 12% as acetate degradation/conversion started or other unmeasured products formed. Maximum acetate production rate achieved during the operation was 40 g m− 2 day− 1 corresponding to coulumbic efficiency of 41%. Microbial analysis of catholyte at the end of the experiment showed that the bacterial community was dominated by Cellulomonas, Stappia and Pseudomonas spp. These results suggest that the mixed culture enriched with acetogenic bacteria can catalyze the electro-reduction of CO2 into a number of chemicals like VFAs through direct or indirect electron transfer mechanisms. While using gaseous CO2 as carbon source, the dissolution and mass transfer of CO2 to the biocatalyst limit the biological reduction process. In addition, the bacterial attachment and retention of reducing equivalent specially hydrogen also restrict the process at the cathode. In order to deal with these issues, a gas diffusion cathode (GDC) (VITO Core™) and a flow-through porous carbon felt cathode were separately tested in MES for CO2 reduction. In principal, the porous activated carbon with hydrophobic binder layer in GDC creates a three-phase interface that makes CO2 and reducing equivalents available to the bacteria. Flow-through graphite felt cathode retains the suspended biomass and electrochemically produced hydrogen when the catholyte is forced to flow through it. An enriched inoculum of acetogenic bacteria, isolated from wastewater sludge was used as biocatalyst. The cathode potentials were maintained at − 0.9 to − 1.1 V vs Ag/AgCl to facilitate CO2 reduction also via the hydrogen evolved at the cathode. On average, CO2 reduction to acetate was achieved with the production rate ∼35 to 43 mg/L/d supplying 20% (v/v) CO2 gas mixture in both the reactors. In the reactors without GDCs or modified cathode, CO2 reduction was never steady for a long period of operation. Acetate was the primary product of CO2 reduction but ethanol and butyrate were also produced concurrently at pH lower than 6. The highest acetate production rate reached in GDC reactor was ∼550 mg/L/d supplying 80% (v/v) CO2 mixture over the GDC. In conclusion, gas diffusion and flow-through cathodes were useful to develop stable CO2 reducing biocathodes and also to operate in continuous mode. Keywords: Microbial electrosynthesis, CO2 reduction, Gas diffusion cathode, Flow-through biocathode, Biocathode, Autotrophic Bioproduction.

Kengo Sasaki, Daisuke Sasaki, Yota Tsuge et al.

Biotechnology for Biofuels • 2021

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>It is desirable to improve the anaerobic digestion processes of recalcitrant materials, such as cellulose. Enhancement of methane (CH<jats:sub>4</jats:sub>) production from organic molecules was previously accomplished through coupling a bioelectrochemical system (BES); however, scaling-up BES-based production is difficult. Here, we developed a two-stage process consisting of a BES using low-cost and low-reactive carbon sheets as the cathode and anode, and a fixed film reactor (FFR) containing conductive material, i.e., carbon fiber textiles (CFTs) (:BES → FFR). By controlling the cathodic current at 2.7 μA/cm<jats:sup>2</jats:sup> without abiotic H<jats:sub>2</jats:sub> production, the three-electrode BES system was operated to mimic a microbial electrolysis cell.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>The thermophilic BES (inlet pH: 6.1) and FFR (inlet pH: 7.5) were operated using hydraulic retention times (HRTs) of 2.5 and 4.2 days, respectively, corresponding to a cellulose load of 3555.6 mg-carbon (C)/(L day). The BES → FFR process achieved a higher CH<jats:sub>4</jats:sub> yield (37.5%) with 52.8 vol% CH<jats:sub>4</jats:sub> in the product gas compared to the non-bioelectrochemical system (NBES) → FFR process, which showed a CH<jats:sub>4</jats:sub> yield of 22.1% with 46.8 vol% CH<jats:sub>4</jats:sub>. The CH<jats:sub>4</jats:sub> production rate (67.5 mM/day) obtained with the BER → FFR process was much higher than that obtained using electrochemical methanogenesis (0.27 mM/day). Application of the electrochemical system or CFTs improved the yields of CH<jats:sub>4</jats:sub> with the NBES → FFR or BES → non-fixed film reactor process, respectively. Meta 16S rRNA sequencing revealed that putative cellulolytic bacteria (identified as <jats:italic>Clostridium</jats:italic> species) were present in the BES and NBES, and followed (BES→ and NBES→) FFR. Notably, H<jats:sub>2</jats:sub>-consuming methanogens, <jats:italic>Methanobacterium</jats:italic> sp. and <jats:italic>Methanosarcina</jats:italic> sp., showed increased relative abundances in the suspended fraction and attached fraction of (BES→) FFR, respectively, compared to that of (NBES→) FFR, although these methanogens were observed at trace levels in the BES and NBES.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>These results indicate that bioelectrochemical preprocessing at a low current effectively induces interspecies H<jats:sub>2</jats:sub> transfer in the FFR with conductive material. Sufficient electrochemical preprocessing was observed using a relatively short HRT. This type of two-stage process, BES → FFR, is useful for stabilization and improvement of the biogas (CH<jats:sub>4</jats:sub>) production from cellulosic material, and our results imply that the two-stage system developed here may be useful with other recalcitrant materials.</jats:p> </jats:sec>

Diya Novarina, Eko Swistoro, M. Firdaus et al.

PENDIPA Journal of Science Education • 2018

ABSTRACT[Innovation of microbial fuel cell stack system using cow rumen waste substrate and its implementation as a learning media]. The aims of this study are to: 1) describe the difference of Electric Motion (GGL), 2) describe the difference of electric power per unit area of the anode (Pa) which is produced between the series design MFC type series, parallel, mixed type 1 and mixed type 2, and 3) describe the significant difference of learning outcomes between the PBL learning model using MFC media with PBL learning model by using the electrical kit medium on dynamic electrical concept in SMA Muhammadiyah 4 Bengkulu. The free variable of this research are MFC stack system design (series, parallel, mixed types 1 and 2) and the dependent variable is GGL and electric power per unit of anode surface area. The results are obtained difference GGL and Pa between series design, parallel, mixed types 1 and 2 by comparison are 3: 1: 1,5: 2 whereas Pa ratio is 1: 10: 6: 2 with maximum GGL is obtained in series design of 3,29 V and Pa maximum in parallel circuit 21,76 mW / m2. Implementation of MFC series as a learning media used Problem Based Learning model on physics learning Implementation of MFC circuit with research design using one group pretest-posttest design. The testing of hypothesis with t-test shows tcount 2.739> ttable 2,001 and 95% significant level so it can be concluded there are significant differences in learning outcomes of PBL learning model by using MFC media with PBL learning model by using media Electric Kit on dynamic electrical concept in SMA Muhammadiyah 4 Bengkulu. Keywords: Stack Microbial Fuel Cell (MFC) Sistem; Rumen Cow Liquid Waste; Learning Media.

Shujie Fan, M. Mahmoud, Biao Wen et al.

BioResources • 2018

The bioelectric activity of two lab scale microbial fuel cell (MFC) designs, MFCI (1,500 cm3) and MFCII (12,000 cm3) were examined using old corrugated containerboard (OCC) discharge for simultaneous effective treatment with greater power production. The decrease of MFC internal resistance (MFC-Rin) resulted in increased generated power output. The different parameters used in MFC included electrode conducting area (ECA), cathodic redox solution (CRS), MFC volume capacity, and MFCs connections. The generated current densities (CD) and power densities output (PD) at variables of external resistances (Rex) that ranged from 10 Ω to 20,000 Ω were calculated to estimate the MFC-Rin. In MFCI, using potassium ferri-cyanide as CRS, the change of ECA from 16 cm2 to 64 cm2 decreased the MFCI-Rin from 130 Ω to 110 Ω, and it was further decreased to 65 Ω when manganese dioxide was used as the CRS. Using Rex 100 Ω, MFCII exhibited lower Rin 18.46%, enhanced voltage 37.5%, and greater chemical oxygen demand removal 4.77% compared with MFCI. Series and parallel connections between four MFCI increased the generated PD by 286% and 258%, respectively, compared with that obtained by single MFCI.

K R S Pamintuan, J A A Clomera, K V Garcia et al.

IOP Conference Series: Earth and Environmental Science • 2018

Plant-microbial fuel cells (PMFCs) are a sub-branch of a class of promising bioelectrochemical systems which are capable of simultaneously supplying biomass and renewable energy from photosynthesis and root exudation. In this study, the possibility of power amplification through stacking was tested. Ipomoea aquatica and Pistia stratiotes were used as model plants in this study because their biomass is valued as food for humans and livestock, respectively. In a brief 7-day experiment, maximum power densities of 6.35 mW / m2 for I. aquatica and 3.54 mW/m2 for P. stratiotes were obtained from aquatic PMFC assemblies. No significant difference in voltage was observed between the two plants, although the current and power output of I. aquatica were significantly higher than that of P. stratiotes. Connecting three cells in series resulted to three times higher voltage but the same current, and connecting three cells in parallel resulted to three times higher current but the same voltage for both plants. Power was also amplified by stacking. There is no significant difference in the power produced by the cells connected in series or parallel. Power density remained constant due to the increase in surface area of electrodes used upon stacking. These results are consistent with the rules of electric circuits and would become a valuable tool in the computational design of larger systems with numerous cells that can supply a large part of our electricity demands. For future studies, assemblies with more cells are recommended to establish the upper limit of the validity of the series/parallel models and can be tested with other plants.

G. Zhu, Shan Huang, Yongze Lu et al.

Environmental Technology • 2019

ABSTRACT A multi-anode microbial fuel cell (MA-MFC) was developed to investigate simultaneous nitrification and denitrification (SND) in the bio-cathode. As the chemical oxygen demand to nitrogen (COD/N) ratio of the cathode was increased from 0 to 4.5, the electricity-producing quantity ranged between 498 and 543 C and the attained total nitrogen (TN) removal rate reached 12.07 g TN·m−3·d−1, resulting in a TN removal efficiency of 78.8% under the target COD/N ratio of 3.5. The removal of pollutants in series and parallel, open-circuit and closed-circuit were compared, respectively. The removal rates of TN, , and cathode and anode COD were all higher in the parallel connection configuration than in the series configuration. In parallel connection, the TN removal rate reached 14.4 g TN·m−3·d−1, which was 1.9 times that in series connection. Compared with the open-circuit system, the removal rate of TN in the closed-circuit system was improved by 17.8%, which could be ascribed to electrochemical denitrification. The results of high-throughput sequencing confirmed and clarified the presence of autotrophic denitrification and heterotrophic denitrification, including aerobic denitrification, when the MA-MFC had been operated for 18 months. GRAPHICAL ABSTRACT

K. Pamintuan, Arnie Jantzen G. Ancheta, S. Robles

E3S Web of Conferences • 2020

Plant-Microbial Fuel Cells (PMFCs) are an emerging type of renewable energy that generates an electric current through the consumption of rhizodeposits by exoelectrogenic bacteria that lives in the rhizosphere of the plant. Since the plant is not harmed by the energy-harvesting process, PMFC technology has the potential to simultaneously produce food (biomass) and generate electricity. As of now, power densities of PMFCs have remained low and commercialization is not yet possible. To achieve higher power densities, the stacking behaviour of PMFCs needs to be studied. In this study, several cells growing Ocimum basilicum (basil) and Origanum vulgare (oregano) were constructed and evaluated. Upon stacking, it was shown that the constructed PMFCs did indeed behave like batteries, where the voltage of cells connected in series are additive, and that the voltage of cells connected in parallel are constant. The actual values of voltage of stacked cells are similar to the expected value (α=0.05). Cumulative stacking tests revealed that there is no apparent loss in voltage upon stacking up to 9 cells growing O. basilicum. Further computation of power and power densities have proven that stacking is a viable method of amplifying electricity generation in PMFCs, as both increased with increasing number of cells connected in series.

M. Halim, Md. Owaleur Rahman, I. Eti et al.

Energy Sources, Part A: Recovery, Utilization, and Environmental Effects • 2020

ABSTRACT The present study examined optimized anodic electrode materials microbial fuel cells (MFCs) with Jashore Municipal Wastewater (JMW) as substrate in series and parallel connections. Three anodic materials, Iron plate (Fe), Carbon felt (CF), and Graphite rod (GR), were used to get green energy from waste biomass in microbial fuel cells. The output voltage, current, and power density of MFC were measured to investigate the preeminent anodic electrode material. The optimized anodic electrode material was Fe owing to high voltage generation followed by CF and GR. Results further indicated that the output voltage increased, but current density, as well as power density, decreased in series connection due to the increase of internal resistance compared to parallel at Fe-Cu combination. The maximum voltage, current density, and power density in series connection were 2238 mV, 79.98 mA/m2, and 108.850 mW⁄m2, respectively. On the other hand, in parallel connection, those values were 793 mV, 248.272 mA/m2, and 115.943 mW⁄m2, respectively. Most small electrical devices need high currents rather than high voltage imply parallel connections are preferred in this regard. Moreover, Fe-Cu combination is better to remove (87%) organic matter regarding COD removal efficiency from wastewater of MFCs.

Kumar Sonu, Z. Syed, M. Sogani

International Journal of Environmental Studies • 2020

ABSTRACT In this work the energy recovery in microbial fuel cell was studied by electrically stacking its three individual units into series and parallel arrangements. The power output was higher in parallel stacking by 2.07 and 14.77 times than series and individual units respectively. The rate of degradation of dye wastewater was in order of individual Microbial Fuel Cell (MFC) < series stack < parallel stack. The corn cob biochar was used as an additive in the MFC to improve the efficiency of the individual MFC unit. The addition of 0.5 g corn cob biochar enhanced the power output to 38.6 mW/m2 from 0.47 mW/m2 in the MFC individual unit without the biochar additive. The simultaneous COD reduction, TDS reduction and decolourisation of dye wastewater achieved are 82.14%, 68% and 74.8% respectively. The current work demonstrates that the dose of biochar and parallel stacking are a framework to achieve enhanced dye removal and bioenergy recovery via microbial fuel cell.

S. Mehrotra, N. K. Singh, Anusha Vempaty et al.

Environmental Technology • 2022

ABSTRACT A bioelectrochemical reactor is an assembly, which facilitates energy generation and resource recovery using electrochemically active microorganisms. To maximise energy production from wastewater in this bioreactor system special design is required. Therefore, in the present study, continuous flow auto dripping bioelectrochemical reactors (AutoDriBERs) were developed as a single and multi-electrode assembly for urine treatment. Further, their performance was assessed by connecting reactors in series and parallel arrangements. AutoDriBER configured in series connection showed the highest 93.64 ± 1.57% chemical oxygen demand removal rate with the 1.38 ± 0.64 V voltage and 2.54 W m−3 polarisation power density. The optimum flow rate for maximum voltage production was tested with various models i.e. the linear, exponential, Sweibull-1, and Sweibull-2 models to confirm voltage prediction and its validity. The Linear and exponential models were found best fitted for voltage production with R2 value of 0.999. These findings infer a novel approach toward optimisation of the complex, inexpensive and self-sufficient design for electricity generation from energy-rich urine wastewater in rural areas. GRAPHICAL ABSTRACT

Gabriela Marcano, Colleen Josephson, P. Pannuto

2022 IEEE International Symposium on Circuits and Systems (ISCAS) • 2022

This paper discusses experiments on soil-based microbial fuel cells (MFCs) as energy scavenging sources. We explain the mechanism of operation for MFCs, perform controlled laboratory experiments of MFCs, and deploy a small-scale insitu pilot in an active farm. We find that traditional energy harvester ICs draw power too aggressively, which reduces overall energy capture. We show that isolated MFCs can be combined in series or parallel to improve the voltage or current output of the harvesting source. Lastly, we observe that under a real-world, drip-irrigated agricultural setting, MFC output is appreciably lower, but consistent at 0.5-2 microwatts.

K. Pamintuan, Hazelle Jae Abanilla, Luis Alfonso Dañez

2023 International Conference on Power and Renewable Energy Engineering (PREE) • 2023

Plant microbial fuel cells (PMFCs) are bio-electrochemical systems that show promise in electricity generation via the plant-microorganism reactions occurring at the rhizosphere of the plant roots. The study aims to determine the scalability of this technology by the stacking of fifteen (15) 3D-printed hexagonal multi-anode/cathode cells growing water hyacinth (Pontederia crassipes); the cells are stacked to determine the extent of power amplification when multiple connections and configurations are employed. In a 30-day experiment, a branched series pattern generated the highest power (1.52 µW) and power density (5.34 µW/m2) among all arrangements. Voltage losses were more prevalent in cells stacked in series than in parallel. Power densities were much higher for cells stacked in series. Still, stacking cells in both series and parallel improved the power-generating capacity of PMFCs compared to an individual cell. Combining series and parallel connections in a clumped stack resulted in a much lower power density than the value generated by an individual cell. Differences were observed when cells were rotated to change the orientation of the connections, as switching from series to parallel caused a consistent deterioration in performance. Polarization tests revealed this clustered pattern to have the highest internal resistance, contributing to internal losses and decreased exerted power. It is hoped that the results of this study will have a significant contribution to the efforts of optimizing PMFC performance, particularly by stacking.

Yumi Kimura, Gabrielle Angela Magdaluyo, K. Pamintuan

2023 International Conference on Power and Renewable Energy Engineering (PREE) • 2023

Plant microbial fuel cell (PMFC), a green energy source, is a bioelectrochemical system that converts rhizodeposits to bioelectricity. This paper investigated the stacking efficiency of PMFCs with USB connectivity using 3D-printed conductive PLA electrodes with Vigna radiata as the model plant. The stacking techniques successfully connected 16 PMFCs in pure and varying combinations of series and parallel. Stacking all cells in pure parallel obtained a maximum voltage of 98.4 mV. However, due to voltage reversal, cumulative stacking of PMFCs in pure series or parallel is inefficient and not an ideal strategy for scale-up. Further evaluation of the overall performance was done by stacking the cells in series-parallel and parallel-series configurations. The results revealed that stacking 6 (3P-S), 8 (4P-S), and 12 (4P-2S) cells in parallel-series correspondingly amplified the power and power densities of the system. Essentially, it was reported that stacking two sets of two parallel cells in series (2P-S) collected the highest power and power density of 0.42 µW and 13.76 µW/m2, respectively. Despite optimizing the power and power density, PMFC still faces a challenge in retaining the power and power density while connecting stacked cells. The scale-up potential of this system, the optimal power density of PMFCs could be improved by design optimization of electrodes and further analysis of the factors influencing the power generation capacity of this environmentally benign technology.

Muhammad Lutfan Aiman Zamri, S. Z. Makhtar, Mohamad Farhan Mohamad Sobri et al.

IOP Conference Series: Earth and Environmental Science • 2023

Microbial fuel cell (MFC) is an outstanding technology recently creating the headlines relating to energy and environment field that been discovered since the earlier 20th century. It has been furthered implemented for energy renewable through simultaneous bioremediation of wastes. MFC works by converting chemical energy store in the waste into electrical energy with the help of selected microorganisms. Regarding to this, the principle of bioremediation was applied using MFC as the renewable energy where the microorganisms consume the substrate thus generating electrical energy. Many studies done by researches are mostly focusing on MFC utilizing waste and measuring the power generation on different type of MFC but lack of studies on the effect of series and parallel circuit in MFC setup and how does it differentiate the outcome of the studies. This paper reviews the history, working principle, design of MFC, classification of different substrates and its power output and the effect of series and parallel circuit of MFC setup for simultaneous bioremediation and energy recovery.

Alexiane Godain, Timothy M. Vogel, Jean-Michel Monnier et al.

Microorganisms • 0

<jats:p>MFCs represent a promising sustainable biotechnology that enables the direct conversion of organic matter from wastewater into electricity using bacterial biofilms as biocatalysts. A crucial aspect of MFCs is how electroactive bacteria (EAB) behave and their associated mechanisms during extracellular electron transfer to the anode. A critical phase in the MFC start-up process is the initial colonization of the anode by EAB. Two MFCs were operated with an external resistance of 1000 ohms, one with an applied electrical voltage of 500 mV during the initial four days of biofilm formation and the other without any additional applied voltage. After stabilization of electricity production, total DNA and protein were extracted and sequenced from both setups. The combined metaproteomic/metagenomic analysis revealed that the application of voltage during the colonization step predominantly increased direct electron transfer via cytochrome c, mediated primarily by Geobacter sp. Conversely, the absence of applied voltage during colonization resulted in a broader diversity of bacteria, including Pseudomonas and Aeromonas, which participated in electricity production via mediated electron transfer involving flavin family members.</jats:p>

Eduardo Leiva, Enzo Leiva-Aravena, Ignacio Vargas

Water • 0

<jats:p>Acid mine drainage (AMD) is a complex environmental problem, which has adverse effects on surface and ground waters due to low pH, high toxic metals, and dissolved salts. New bioremediation approach based on microbial fuel cells (MFC) can be a novel and sustainable alternative for AMD treatment. We studied the potential of MFC for acidic synthetic water treatment through pH neutralization in batch-mode and continuous-flow operation. We observed a marked pH increase, from ~3.7 to ~7.9 under batch conditions and to ~5.8 under continuous-flow operation. Likewise, batch reactors (non-MFC) inoculated with different MFC-enriched biofilms showed a very similar pH increase, suggesting that the neutralization observed for batch operation was due to a synergistic influence of these communities. These preliminary results support the idea of using MFC technologies for AMD remediation, which could help to reduce costs associated with conventional technologies. Advances in this configuration could even be extrapolated to the recovery of heavy metals by precipitation or adsorption processes due to the acid neutralization.</jats:p>

Anna Sekrecka-Belniak, Renata Toczyłowska-Mamińska

Energies • 0

<jats:p>Fungi are among the microorganisms able to generate electricity as a result of their metabolic processes. Throughout the last several years, a large number of papers on various microorganisms for current production in microbial fuel cells (MFCs) have been published; however, fungi still lack sufficient evaluation in this regard. In this review, we focus on fungi, paying special attention to their potential applicability to MFCs. Fungi used as anodic or cathodic catalysts, in different reactor configurations, with or without the addition of an exogenous mediator, are described. Contrary to bacteria, in which the mechanism of electron transfer is pretty well known, the mechanism of electron transfer in fungi-based MFCs has not been studied intensively. Thus, here we describe the main findings, which can be used as the starting point for future investigations. We show that fungi have the potential to act as electrogens or cathode catalysts, but MFCs based on bacteria–fungus interactions are especially interesting. The review presents the current state-of-the-art in the field of MFC systems exploiting fungi.</jats:p>

A. Mukherjee, R. Patel, P. Zaveri et al.

Letters in Applied Microbiology • 2022

<jats:title>Abstract</jats:title> <jats:p>Microbial fuel cell (MFC) is an emerging technology which has been immensely investigated for wastewater treatment along with electricity generation. In the present study, the treatment efficiency of MFC was investigated for hydrocarbon containing wastewater by optimizing various parameters of MFC. Mediator-less MFC (1·2 l) was constructed, and its performance was compared with mediated MFC with Escherichia coli as a biocatalyst. MFC with electrode having biofilm proved to be better compared with MFC inoculated with suspended cells. Analysis of increasing surface area of electrode by increasing their numbers indicated increase in COD reduction from 55 to 75%. Catholyte volume was optimized to be 750 ml. Sodium benzoate (0·721 g l–1) and actual common effluent treatment plant (CETP) wastewater as anolyte produced 0·8 and 0·6 V voltage and 89 and 50% COD reduction, respectively, when a novel consortium of four bacterial strains were used. Twenty MFC systems with the developed consortium when electrically connected in series-parallel connection were able to generate 2·3 V and 0·5 mA current. This is the first report demonstrating the application of CETP wastewater in the MFC system, which shows potential of the system towards degradation of complex organic components present in industrial wastewater.</jats:p>

A. Afify, A. M. Abd, El Gwad et al.

Journal of Agricultural Chemistry and Biotechnology • 2023

Microbial electrolysis cells (MECs) are important for environment and renewable energy source. They were used for bio-hydrogen production by bacteria from organic matters, which is biological method to treat wastewater. Therefore, in this study MEC was used for bio-hydrogen producing by two bacterial strains: Escherichia coli NRRL B-3008 and Pseudomonas aeruginosa ATCC 27853 in MEC 1 (300ml), MEC 2 (400ml) and MEC 3 (500ml) were applied from domestic wastewater. Volumes of MEC refer to anode chamber. Applied voltage of 0.4V, 0.6V and 0.8V was used as an external electrical circuit in MECs (1, 2 & 3). The lowest value of Bio-Hydrogen production rate (Bio-HPR) 112.28 cm 3 was obtained by domestic wastewater without bacteria in MEC 3 (500ml) at applied voltage 0.8V. While highest values of Bio-HPR 235.87 and 268.08 cm 3 were obtained by E. coli NRRL B-3008 and P. aeruginosa ATCC 27853 in MEC 3 (500ml) at applied voltage 0.8V from domestic wastewater respectively.

Rahma El-Sayad, Ahmed Khalil, Ali M. Basha

Journal of Contemporary Technology and Applied Engineering • 2023

. The rapid increase in human activity in recent years has increased energy demand and waste output. Although wastewater is frequently seen as a problem, it has the potential to be seen as a rich source of resources and energy. An appealing approach to lowering environmental pollution and supplying alternative energy sources is the treatment of contaminants found in wastewater combined with energy recovery. Microbial electrolysis cell (MEC) is one of the most effective waste-to-product conversion technologies available today. There are other methods for wastewater treatment and the production of hydrogen as dark fermentation and photo fermentation. This paper explores the interconnected fields of wastewater treatment and hydrogen production, highlighting their significance in addressing environmental challenges and promoting sustainable development. Various technologies and processes employed in wastewater treatment, such as microbial electrolysis cells (MECs), dark fermentation, and photo fermentation, are discussed in detail. Also, this paper compares MEC, photo fermentation, and dark fermentation for hydrogen production and wastewater treatment. Moreover, it shows some benefits and drawbacks of these technologies. In addition, the integration between these technologies is discussed in this review. Additionally, it provides some descriptive statistics about the outcomes. Finally, some recommendations are presented in the review for future work.

Ibdal Satar, M. Sirajuddin, Adidiya Permadi et al.

Indonesian Journal of Environmental Management and Sustainability • 2023

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.

Yunjeong Choi, Danbee Kim, Hyun-Rock Choi et al.

Bioengineered • 2023

ABSTRACT Fermentation effluents from organic wastes contain simple organic acids and ethanol, which are good electron sources for exoelectrogenic bacteria, and hence are considered a promising substrate for hydrogen production in microbial electrolysis cells (MECs). These fermentation products have different mechanisms and thermodynamics for their anaerobic oxidation, and therefore the composition of fermentation effluent significantly influences MEC performance. This study examined the microbial electrolysis of a synthetic fermentation effluent (containing acetate, propionate, butyrate, lactate, and ethanol) in two-chamber MECs fitted with either a proton exchange membrane (PEM) or an anion exchange membrane (AEM), with a focus on the utilization preference between the electron sources present in the effluent. Throughout the eight cycles of repeated batch operation with an applied voltage of 0.8 V, the AEM-MECs consistently outperformed the PEM-MECs in terms of organic removal, current generation, and hydrogen production. The highest hydrogen yield achieved for AEM-MECs was 1.26 L/g chemical oxygen demand (COD) fed (approximately 90% of the theoretical maximum), which was nearly double the yield for PEM-MECs (0.68 L/g COD fed). The superior performance of AEM-MECs was attributed to the greater pH imbalance and more acidic anodic pH in PEM-MECs (5.5–6.0), disrupting anodic respiration. Although butyrate is more thermodynamically favorable than propionate for anaerobic oxidation, butyrate was the least favored electron source, followed by propionate, in both AEM- and PEM-MECs, while ethanol and lactate were completely consumed. Further research is needed to better comprehend the preferences for different electron sources in fermentation effluents and enhance their microbial electrolysis.

Cong Wang, Dongdong Chang, Qi Zhang et al.

Bioresources and Bioprocessing • 2024

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

Jieyi Peng, Shuo Zhao, Ying Li et al.

Fermentation • 2024

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.

A. Tremouli, G. Kanellos, Evangelia Monokrousou et al.

Global NEST International Conference on Environmental Science &amp; Technology • 2024

This study deals with the treatment of a potent two-phase olive mill waste (TPOMW) through the degradation of its phenolic content, with simultaneous bio-electrochemical reduction of CO2 to CH4, using a dual-chamber Microbial Electrolysis Cell (MEC). The MEC operated for 120 days and the effects of different dilutions (1:10, 1:5 and no dilution) and applied potentials (0.5 V and 1 V) on its performance were studied. The results showed that decreasing the dilution (from 1:10 to 1:5 and to no dilution) led to an increase of the COD removal (from 74%, to 77% and to 87%, respectively), of the total phenolic content removal (from 73%, to 76% and to 79%, respectively), as well as of the produced CH4 (from 0.08, to 0.48 and to 2.33 mmols, respectively). Increasing the applied potential (from 0.5 V to 1 V), while the TPOMW was employed in the anode with no dilution, resulted in further increase of both the COD and the total phenolic content removal to 91%, while the produced CH4 further increased to 2.88 mmols. The results indicate that the MEC technology can be potentially exploited for the treatment of the potent TPOMW and produce CH4 as a waste-to-energy source.

Hyungwon Chai, Bonyoung Koo, S. Son et al.

Energies • 2024

The electrode is a key component in a microbial electrolysis cell (MEC) that needs significant improvement for practical implementation. Accurate and reproducible analytical methods are substantial for the effective development of electrode technology. Linear sweep voltammetry (LSV) is an essential analytical method for evaluating electrode performance. In this study, inoculated carbon brush (IB), abiotic brush (AB), Pt wire (PtW), stainless steel wire (SSW), and mesh (SSM) were tested to find the most suitable counter electrode under different medium conditions. The coefficient of variation (Cv) of maximum current (Imax) was the most decisive indicator of the reproducibility test. This study shows that (i) the electrode used in operation is an appropriate counter electrode in an acetate-added condition, (ii) the anode LSV test should avoid the use of Pt wire as counter electrodes, and (iii) PtW is an appropriate counter electrode in cathode LSV in all conditions.

Y. Liu, Mohan Qin, Shuai Luo et al.

Scientific Reports • 2016

We report an integrated experimental and simulation study of ammonia recovery using microbial electrolysis cells (MECs). The transport of various species during the batch-mode operation of an MEC was examined experimentally and the results were used to validate the mathematical model for such an operation. It was found that, while the generated electrical current through the system tends to acidify (or basify) the anolyte (or catholyte), their effects are buffered by a cascade of chemical groups such as the NH3/NH4+ group, leading to relatively stable pH values in both anolyte and catholyte. The transport of NH4+ ions accounts for ~90% of the total current, thus quantitatively confirming that the NH4+ ions serve as effective proton shuttles during MEC operations. Analysis further indicated that, because of the Donnan equilibrium at cation exchange membrane-anolyte/catholyte interfaces, the Na+ ion in the anolyte actually facilitates the transport of NH4+ ions during the early stage of a batch cycle and they compete with the NH4+ ions weakly at later time. These insights, along with a new and simple method for predicting the strength of ammonia diffusion from the catholyte toward the anolyte, will help effective design and operation of bioeletrochemical system-based ammonia recovery systems.

Zhihong Liu, Aijuan Zhou, Zhang Jiaguang et al.

ACS Sustainable Chemistry &amp; Engineering • 2018

Due to the limited hydrolysis rate of particulate organics and suitable substrates for hydrogen-producing bacteria in raw waste activated sludge (WAS), traditional fermentative hydrogen production has low hydrogen yield and energy recovery efficiency. The role of free nitrous acid (FNA) pretreatment on WAS and hydrogen recovery was investigated in a prefermentation–microbial electrolysis cells (MECs) system. The results demonstrated that WAS hydrolysis and acidification were enhanced by FNA pretreatment. Notably, the accumulation of acetic acid and propionic acid eventually reached to 55% and 22% during prefermentation. During MECs cascade utilization, volatile fatty acids (VFAs) were exhausted and the utilization efficiencies of soluble carbohydrates and proteins reached 62% and 41.5%, respectively. The hydrogen yield from FNA-pretreated sludge was 1.44 mL/g of volatile suspended solids, which was approximately 3 times than that of the control. High-throughput sequencing and canonical correspondence anal...

Wenzong Liu, Zhangwei He, Chunxue Yang et al.

Biotechnology for Biofuels • 2016

BackgroundBioelectrochemical systems have been considered a promising novel technology that shows an enhanced energy recovery, as well as generation of value-added products. A number of recent studies suggested that an enhancement of carbon conversion and biogas production can be achieved in an integrated system of microbial electrolysis cell (MEC) and anaerobic digestion (AD) for waste activated sludge (WAS). Microbial communities in integrated system would build a thorough energetic and metabolic interaction network regarding fermentation communities and electrode respiring communities. The characterization of integrated community structure and community shifts is not well understood, however, it starts to attract interest of scientists and engineers.ResultsIn the present work, energy recovery and WAS conversion are comprehensively affected by typical pretreated biosolid characteristics. We investigated the interaction of fermentation communities and electrode respiring communities in an integrated system of WAS fermentation and MEC for hydrogen recovery. A high energy recovery was achieved in the MECs feeding WAS fermentation liquid through alkaline pretreatment. Some anaerobes belonging to Firmicutes (Acetoanaerobium, Acetobacterium, and Fusibacter) showed synergistic relationship with exoelectrogens in the degradation of complex organic matter or recycling of MEC products (H2). High protein and polysaccharide but low fatty acid content led to the dominance of Proteiniclasticum and Parabacteroides, which showed a delayed contribution to the extracellular electron transport leading to a slow cascade utilization of WAS.ConclusionsEfficient pretreatment could supply more short-chain fatty acids and higher conductivities in the fermentative liquid, which facilitated mass transfer in anodic biofilm. The overall performance of WAS cascade utilization was substantially related to the microbial community structures, which in turn depended on the initial pretreatment to enhance WAS fermentation. It is worth noting that species in AD and MEC communities are able to build complex networks of interaction, which have not been sufficiently studied so far. It is therefore important to understand how choosing operational parameters can influence reactor performances. The current study highlights the interaction of fermentative bacteria and exoelectrogens in the integrated system.