A microbial fuel cell with improved cathode reaction as a low biochemical oxygen demand sensor

Mediator-less microbial fuel cells (MFC) enriched with oligotrophic microbes were optimized through enhancement of cathode reaction and lowering O₂ diffusion into the anode compartment as a low BOD sensor. The optimization of the MFC has greatly improved the maximum current and coulomb yield. The oligotroph-type MFC could be used as a low BOD sensor with high operational stability, good repeatability and reproducibility.     

Improving the dynamic response of a mediator-less microbial fuel cell as a biochemical oxygen demand (BOD) sensor

The dynamic behavior of a mediator-less, microbial fuel cell (MFC) was studied as a continuous biochemical oxygen demand (BOD) sensor. The response time and the sensitivity were analyzed through the step-change testing of the fuel concentration. The MFC of 25 ml had the shortest response time of 36± 2 min at the fuel-feeding rate of 0.53 ml min^–1 and the resistance of 10 A smaller MFC of 5 ml had a response time of 5± 1 min.     

Submersible microbial fuel cell sensor for monitoring microbial activity and BOD in groundwater: Focusing on impact of anodic biofilm on sensor applicability

A sensor, based on a submersible microbial fuel cell (SUMFC), was developed for in situ monitoring of microbial activity and biochemical oxygen demand (BOD) in groundwater. Presence or absence of a biofilm on the anode was a decisive factor for the applicability of the sensor. Fresh anode was required for application of the sensor for microbial activity measurement, while biofilm‐colonized anode was needed for utilizing the sensor for BOD content measurement. The current density of SUMFC sensor equipped with a biofilm‐colonized anode showed linear relationship with BOD content, to up to 250 mg/L (～233 ± 1 mA/m²), with a response time of <0.67 h. This sensor could, however, not measure microbial activity, as indicated by the indifferent current produced at varying active microorganisms concentration, which was expressed as microbial adenosine‐triphosphate (ATP) concentration. On the contrary, the current density (0.6 ± 0.1 to 12.4 ± 0.1 mA/m²) of the SUMFC sensor equipped with a fresh anode showed linear relationship, with active microorganism concentrations from 0 to 6.52 nmol‐ATP/L, while no correlation between the current and BOD was observed. It was found that temperature, pH, conductivity, and inorganic solid content were significantly affecting the sensitivity of the sensor. Lastly, the sensor was tested with real contaminated groundwater, where the microbial activity and BOD content could be detected in <3.1 h. The microbial activity and BOD concentration measured by SUMFC sensor fitted well with the one measured by the standard methods, with deviations ranging from 15% to 22% and 6% to 16%, respectively. The SUMFC sensor provides a new way for in situ and quantitative monitoring contaminants content and biological activity during bioremediation process in variety of anoxic aquifers. Biotechnol. Bioeng. 2011;108: 2339–2347. © 2011 Wiley Periodicals, Inc.     

From microbial fuel cell (MFC) to microbial electrochemical snorkel (MES): maximizing chemical oxygen demand (COD) removal from wastewater

The paper introduces the concept of the microbial electrochemical snorkel (MES), a simplified design of a “short-circuited” microbial fuel cell (MFC). The MES cannot provide current but it is optimized for wastewater treatment. An electrochemically active biofilm (EAB) was grown on graphite felt under constant polarization in an urban wastewater. Controlling the electrode potential and inoculating the bioreactor with a suspension of an established EAB improved the performance and the reproducibility of the anodes. Anodes, colonized by an EAB were tested for the chemical oxygen demand (COD) removal from urban wastewater using a variety of bio-electrochemical processes (microbial electrolysis, MFC, MES). The MES technology, as well as a short-circuited MFC, led to a COD removal 57% higher than a 1000 Ω-connected MFC, confirming the potential for wastewater treatment.     

Sustainable power production in a membrane-less and mediator-less synthetic wastewater microbial fuel cell

Microbial fuel cells (MFCs) fed with wastewater are currently considered a feasible strategy for production of renewable electricity.     

A novel BOD sensor based on bacterial luminescence

A reagent-type BOD sensor with a new principle employing a luminous bacterium, Photobacterium phosphoreum, was developed. The increased intensity of luminescence resulting from the cellular assimilation of organic compounds in wastewater was detected by a photodiode. The BOD response of the bacterial reagent could be obtained within 15 min with +/-7% error. The temperature condition for optimal BOD response was 18 degrees to 25 degrees C at pH 7 to 8, indicating that it is possible to measure BOD at room temperature without having to stabilize the temperature of the measuring system. For practical use, two procedures for long-term preservation of the bacterial reagent, vacuum drying method and freezing method, are suggested. The metabolic characteristics of employed luminous bacteria were investigated by comparing the BOD values for several pure organic substrates estimated by the BOD sensor with conventional 5-day BOD values. In comparison with the 5-day measurement for some wastewater samples, BOD values estimated by the sensor showed comparatively good agreement with those measured by the 5-day method. (c) 1993 Wiley & Sons, Inc.     

微生物燃料电池在固体废物堆肥中的应用进展

微生物燃料电池(Microbial fuel cell,MFC)是一种近几年快速发展的废物处理与能源化技术,可以与污水处理、污染物降解、脱盐等环境技术结合。微生物燃料电池与堆肥技术结合可以在处理日益增长的固体废弃物的同时回收能量,具有很好的发展前景。文中分析了堆肥微生物燃料电池系统的微生物特征,探讨了堆肥过程中影响微生物燃料电池产电性能的因素,包括电极,隔膜,供氧和构型。最后归纳说明了堆肥微生物电池作为一种新的废弃物处理技术的特点:较高的微生物量并可产生较高的电流密度;对不同环境的适应性强;可以自身调节温度,能源利用效率高;质子从阳极向阴极的移动会受到不同堆肥原料的影响。     

纳米材料修饰微生物燃料电池阳极的研究进展

阳极作为微生物燃料电池中的重要组成部分,其性能的高低显著影响着微生物燃料电池的产电性能。纳米材料具有导电性好、表面积大等优良特性。因此,纳米材料修饰阳极能够有效减小电极内阻、增大微生物的粘附量,从而显著提高微生物燃料电池的产电性能。本文首先简要介绍了微生物燃料电池中阳极修饰纳米材料的种类,然后重点归纳了不同纳米材料修饰阳极对微生物燃料电池产电性能的影响及其原因。最后对微生物燃料电池阳极修饰纳米材料和技术进行展望。     

Oxygen availability effect on the performance of air‐breathing cathode microbial fuel cell

The effect of the oxygen availability over the performance of an air‐breathing microbial fuel cell (MFC) was studied by limiting the oxygen supply to the cathode. It was found that anodic reaction was the limiting stage in the performance of the MFC while oxygen was fully available at cathode. As the cathode was depleted of oxygen, the current density becomes limited by oxygen transport to the electrode surface. The exerted current density was maintained when oxygen mole fraction was higher than 10% due to the very good performance of the cathodic catalysts. However, the current density drastically falls when working at lower concentrations because of mass transfer limitations. In this sense it must be highlighted that the maximum exerted power, when oxygen mole fraction was higher than 10%, was almost three times higher than that obtained when oxygen mole fraction was 5%. Regarding to the wastewater treatment, a significant decrease in the COD removal was obtained when the MFC performance was reduced due to the limited availability of oxygen, which indicates the significant role of the electrogenic microorganisms in the COD removal in MFC. In addition, the low availability of oxygen at the cathode leads to a lower presence of oxygen at the anode, resulting in an increase in the coulombic efficiency. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:900–907, 2015     

Nitrilotriacetic acid degradation under microbial fuel cell environment

The removal of nitrilotriacetic acid (NTA) was studied under anaerobic conditions using oligotrophic and copiotrophic microbial fuel cells (MFCs) as a novel wastewater treatment process. Over 85% of NTA was removed from oligotrophic MFCs enriched and maintained with fuel containing NTA, whilst the value was around 20% in oligotrophic MFCs fed with NTA-free fuel, and in copiotrophic MFCs enriched with NTA containing fuel. The oligotrophic MFCs generated current with concomitant utilization of NTA when served as the sole organic compound, suggesting that NTA is oxidized its suitability as fuel in the MFCs.     

Resource recovery from paddy field using plant microbial fuel cell

The plant microbial fuel cell (PMFC) is a recently developed energy-generating technology that supports sustainable agriculture. Design configuration is the key bottleneck in optimization and upscaling of paddy based PMFCs. In this study, two designs (Type-I (horizontal) and Type-II (vertical)) of terracotta based ceramic PMFCs (C-PMFC) are incorporated into the paddy field to recover nutrients, energy, and water (“NEW”) resources. The peak voltage generated in Type-I and Type-II C-PMFC was 292.1 mV and 321.7 mV respectively. The polarisation study in the ripening phase of paddy showed a maximum power density of 9.1 mW/m² (type-I) and 16.8 mW/m² (type-II). The volume of catholyte recovered is observed to be dependent on the C-PMFC performance and growth phases of the paddy. In the entire 10 weeks of the experimental period, a total of 451 mL and 943 mL of catholyte was collected at 100Ω load in type-I and type-II, respectively. The collected catholyte is alkaline in nature and maximum catholyte recovery is achieved at the active tillering phase and declined with the advancement of the development stages of the plant. Osmotic and electro-osmotic migration of various nutrients like ammonium from the paddy field to cathode chamber of C-PMFC is observed throughout the experiment.     

Energy from algae using microbial fuel cells

Bioelectricity production from a phytoplankton, Chlorella vulgaris, and a macrophyte, Ulva lactuca was examined in single chamber microbial fuel cells (MFCs). MFCs were fed with the two algae (as powders), obtaining differences in energy recovery, degradation efficiency, and power densities. C. vulgaris produced more energy generation per substrate mass (2.5 kWh/kg), but U. lactuca was degraded more completely over a batch cycle (73 ± 1% COD). Maximum power densities obtained using either single cycle or multiple cycle methods were 0.98 W/m² (277 W/m³) using C. vulgaris, and 0.76 W/m² (215 W/m³) using U. lactuca. Polarization curves obtained using a common method of linear sweep voltammetry (LSV) overestimated maximum power densities at a scan rate of 1 mV/s. At 0.1 mV/s, however, the LSV polarization data was in better agreement with single‐ and multiple‐cycle polarization curves. The fingerprints of microbial communities developed in reactors had only 11% similarity to inocula and clustered according to the type of bioprocess used. These results demonstrate that algae can in principle, be used as a renewable source of electricity production in MFCs. Biotechnol. Bioeng. 2009;103: 1068–1076. © 2009 Wiley Periodicals, Inc.     

Development of a solar-powered microbial fuel cell

Aims: To understand factors that impact solar‐powered electricity generation by Rhodobacter sphaeroides in a single‐chamber microbial fuel cell (MFC). Methods and Results: The MFC used submerged platinum‐coated carbon paper anodes and cathodes of the same material, in contact with atmospheric oxygen. Power was measured by monitoring voltage drop across an external resistance. Biohydrogen production and in situ hydrogen oxidation were identified as the main mechanisms for electron transfer to the MFC circuit. The nitrogen source affected MFC performance, with glutamate and nitrate‐enhancing power production over ammonium. Conclusions: Power generation depended on the nature of the nitrogen source and on the availability of light. With light, the maximum point power density was 790 mW m^?2 (2·9 W m^?3). In the dark, power output was less than 0·5 mW m^?2 (0·008 W m^?3). Also, sustainable electrochemical activity was possible in cultures that did not receive a nitrogen source. Significance and Impact of the Study: We show conditions at which solar energy can serve as an alternative energy source for MFC operation. Power densities obtained with these one‐chamber solar‐driven MFC were comparable with densities reported in nonphotosynthetic MFC and sustainable for longer times than with previous work on two‐chamber systems using photosynthetic bacteria.     

微生物燃料电池利用乳酸产电性能与微生物群落分布特征

【目的】为探讨以乳酸为基质的微生物燃料电池(Microbial fuel cell,MFC)产电性能以及微生物群落在阳极膜、悬浮液、阳极沉淀污泥中的分布特征,【方法】试验建立了双室MFC,以乳酸为阳极主要碳源,研究了反应器的启动过程及产电效能,同时以电镜和PCR-变性梯度凝胶电泳(Denaturing gradient gelelectrophoresis,DGGE)技术解析了微生物群落的空间分布特征。【结果】结果表明,反应器启动第7天时外电压达到0.56 V,当外阻为80Ω时,电流密度为415 mA/m2,MFC的功率密度达到最大值82 mW/m2。电镜观察发现大量杆菌附着在阳极表面,结合较为紧密;DGGE图谱显示阳极膜表面微生物与种泥最为相似,与阳极悬浮液、底部沉淀污泥中的主要菌群一致,条带序列与睾丸酮丛毛单胞菌(Comamonas testosteroni)和布氏弓形菌(Arcobacter butzleri)等最为相似。【结论】本研究表明以乳酸为基质MFC可产生较高的功率密度,阳极附着的优势菌与接种污泥来源密切相关。     

Improvement of a microbial fuel cell performance as a BOD sensor using respiratory inhibitors

Studies were made to improve the performance of a microbial fuel cell (MFC) as a biochemical oxygen demand (BOD) sensor. The signal from MFCs decreased in the presence of electron acceptors of higher redox potential such as nitrate and oxygen. The addition of azide and cyanide did not change the signal in the absence of the electron acceptors. The respiratory inhibitors eliminated the inhibitory effects of the electron acceptors on the current generation from MFCs. Similar results were obtained using oligotrophic MFCs fed with an environmental sample that contained nitrate. The use of the respiratory inhibitors is therefore recommended for the accurate BOD measurement of environmental samples containing nitrate and/or oxygen with an MFC-type BOD sensor.     

Characterisation of organic fractions of pulp and paper mill wastewater with a manometric respirometric biochemical oxygen demand method and automatic chemical oxygen demand analyses

Abstract

The manometric respirometric method was applied to a characterisation of organic material in pulp and paper mill wastewater, which is usually high in organic content and inhibitory substances. Preliminary tests, including experiments with an extra microbial seed as well as dilution series, were carried out before the characterisation analyses in order to optimise the method. Three different physical-chemical methods were then used to characterise organic fractions. Influent organic fractions were specified with two methods in which the determination of the soluble biodegradable and the soluble inert fraction differed. In the third method, the influent fractions as well as the new metabolic products generated during the biodegradation process and an estimate of the mineralised part of the influent biodegradable fraction were determined without any hypothetical conversion factors. The results showed that a remarkable part of the detected oxygen demand was consumed for the biotransformation of biodegradable fractions into new inert organic products, not only for mineralisation. The amount of these new metabolic products, measured after biochemical oxygen demand analyses, was significant. It was also noticed that volatile organic compounds can have an influence on the chemical oxygen demand value of effluents.     

Maximizing power production in a stack of microbial fuel cells using multiunit optimization method

This study demonstrates real‐time maximization of power production in a stack of two continuous flow microbial fuel cells (MFCs). To maximize power output, external resistances of two air–cathode membraneless MFCs were controlled by a multiunit optimization algorithm. Multiunit optimization is a recently proposed method that uses multiple similar units to optimize process performance. The experiment demonstrated fast convergence toward optimal external resistance and algorithm stability during external perturbations (e.g., temperature variations). Rate of the algorithm convergence was much faster than in traditional maximum power point tracking algorithms (MPPT), which are based on temporal perturbations. A power output of 81–84 mW/L_A (A = anode volume) was achieved in each MFC. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Anode microbial communities produced by changing from microbial fuel cell to microbial electrolysis cell operation using two different wastewaters

Conditions in microbial fuel cells (MFCs) differ from those in microbial electrolysis cells (MECs) due to the intrusion of oxygen through the cathode and the release of H₂ gas into solution. Based on 16S rRNA gene clone libraries, anode communities in reactors fed acetic acid decreased in species richness and diversity, and increased in numbers of Geobacter sulfurreducens, when reactors were shifted from MFCs to MECs. With a complex source of organic matter (potato wastewater), the proportion of Geobacteraceae remained constant when MFCs were converted into MECs, but the percentage of clones belonging to G. sulfurreducens decreased and the percentage of G. metallireducens clones increased. A dairy manure wastewater-fed MFC produced little power, and had more diverse microbial communities, but did not generate current in an MEC. These results show changes in Geobacter species in response to the MEC environment and that higher species diversity is not correlated with current.     

Continuous determination of biochemical oxygen demand using microbial fuel cell type biosensor

A mediator-less microbial fuel cell (MFC) was used as a biochemical oxygen demand (BOD) sensor in an amperometric mode for real-time wastewater monitoring. At a hydraulic retention time of 1.05 h, BOD values of up to 100 mg/l were measured based on a linear relationship, while higher BOD values were measured using a lower feeding rate. About 60 min was required to reach a new steady-state current after the MFCs had been fed with different strength artificial wastewaters (Aws). The current generated from the MFCs fed with AW with a BOD of 100 mg/l was compared to determine the repeatability, and the difference was less than 10%. When the MFC was starved, the original current value was regained with a varying recovery time depending on the length of the starvation. During starvation, the MFC generated a background level current, probably due to an endogenous metabolism.