Membrane-less Microbial Fuel Cell Research Articles

A novel membrane-less microbial fuel cell reactor using wood as container and separator to prevent air–cathode deterioration and biofouling

In this study, we introduce a novel application of wood as the construction material for Microbial Fuel Cell (MFC) containers, developing what we term the Wooden Membrane-less Microbial Fuel Cell (WML-MFC). This innovative approach leverages the natural properties of wood to enhance the sustainability and cost-effectiveness of MFCs. Employing three different types of wood—pine, oak, and black locust—the WML-MFC design incorporates a carbon felt anode inside the wooden container and a carbon cloth cathode wrapped externally. This configuration not only protects the cathode from biofouling but also utilizes the inherent moisture management capabilities of wood to maintain operational stability. The performance of these wooden MFCs was assessed in terms of electricity generation and water treatment efficacy. Pine and oak containers achieved maximum power densities (MPD) of 35 mW/m^2 and 4 mW/m^2, respectively, with corresponding maximum open-circuit voltages of 551 mV and 269 mV. Black locust showed the least effective bioelectricity generation. COD removal efficiency was observed between 18 and 48% for pine and 3% to 39% for oak over hydraulic retention times of 24–48 h. Notable water loss due to moisture diffusion was recorded at 20%/day in pine and 6%/day in oak. Durability assessments through DMA and SEM analyses confirmed the suitability of wood as a container material, emphasizing the dual environmental and economic benefits of this WML-MFC design.

The effect of different temperature in membrane-less microbial fuel cell under series and parallel circuit mode for power generation and bioremediation

Demand for energy resources is increasing rapidly, leading to excessive exploitation of fossil fuels. The production of chicken, which is a popular source of protein, generates a huge amount of waste. Microbial fuel cells (MFC) have the potential to generate clean, sustainable, and environmentally benign electricity by utilizing electrogenic bacteria present in chicken manure (CM), while also decreasing the amount of waste. The present study was conducted to assess the effect of different temperatures and numbers of chambers in series and parallel circuits on the performance of membrane-less MFCs (ML-MFCs). The central composite design (CCD) based on response surface methodology (RSM) was applied to optimize the performance of ML-MFCs in series and parallel circuits, with a focus on chemical oxygen demand (COD) removal efficiency (R2 = 0.958 and 0.967), biomass (R2 = 0.995 and 0.836), and power density (R2 = 0.958 and 0.825). The study revealed that the highest COD removal (series: 89.554%, parallel: 84.994%), biomass (series: 1.095 mg/L, parallel: 2.267 mg/L), and power density (series: 0.551 W/m2, parallel: 0.360 W/m2) were achieved when the pre-treatment temperature was 40 °C. The best ML-MFC condition was plotted on the polarization curve in order to analyze the nature of ML-MFC. Findings of this study suggest that ML-MFCs have great potential for electricity generation and waste reduction, and the optimization of operating conditions can enhance their performance.

Effect of Using Various Cathode Materials (Carbon Felt, Ni-Co, Cu-B, and Cu-Ag) on the Operation of Microbial Fuel Cell

Wastewater has high potential as an energy source. Therefore, it is important to recover even the smallest part of this energy, e.g., in microbial fuel cells (MFCs). The obtained electricity production depends on the process rate of the electrodes. In MFC, the microorganisms are the catalyst of anode, and the cathode is usually made of carbon material. To increase the MFC efficiency it is necessary to search the new cathode materials. In this work, the electricity production from yeast wastewater in membrane-less microbial fuel cells with a carbon felt, Ni-Co, Cu-B, and Cu-Ag cathodes has been analyzed. In the first place, the measurements of the stationary potential of the electrodes (with Cu-Ag catalyst obtained by the electrochemical deposition technique) were performed. Next, the analysis of the electric energy production during the operation of the membrane-less microbial fuel cell (ML-MFC). The highest parameters were obtained for the Ni-Co and Cu-Ag catalysts. The cell voltage of 607 mV for Ni-Co and 605 mV for Cu-Ag was obtained. Additionally, the power of 4.29 mW for both cathodes - Ni-Co and Cu-Ag was obtained. Moreover, Ni-Co and Cu-Ag allow the shortest time of COD reduction. Based on the test results (with selected MFC design, wastewater, temperature, etc.), it can be concluded that of all the analyzed electrodes, Cu-Ag and Ni-Co electrodes have the best parameters for use as cathodes in ML-MFC. However, based on the results of this study, it can be concluded that all the tested electrodes can be used as cathode material in MFC.

Feeding a Membrane-less Microbial Fuel Cell by Mixed Municipal and Industrial Wastewater

Due to the constant growth of the world's population, the amount of generated wastewater is also constantly increasing. One of the devices that can use wastewater as a raw material for energy production is a microbial fuel cell (MFC). MFCs technology is constantly evolving. However, to increase its use, it is necessary to improve its efficiency. There are various possibilities to ensure this, such as the use of new electrode materials, new cell designs, or the use of wastewaters from different sources. In this paper the analysis of MFC operation (cell voltage, power, and current density) fed by mixed municipal and industrial wastewaters was shown. Moreover, the change in time of COD was analyzed. Due to cost reduction the membrane-less microbial fuel cell (ML-MFC) was chosen. It was noted that the addition of concentrated process wastewater increases the COD reduction time in the ML-MFC. An increase of generated bioelectricity during fed ML-MFC by mixed municipal and industrial (process wastewater from yeast production) wastewater was demonstrated. The highest values of average cell voltage (598 mV), maximum power (4.47 mW) and maximum current density (0.26 mA·cm-2) were obtained for a 10% share of yeast process wastewater in the mixed wastewater, which fed the ML-MFC.

Effect of Electrode Spacing on the Performance of a Membrane-Less Microbial Fuel Cell with Magnetite as an Additive.

A microbial fuel cell (MFC) is a bioelectrochemical system that can be employed for the generation of electrical energy under microbial activity during wastewater treatment practices. The optimization of electrode spacing is perhaps key to enhancing the performance of an MFC. In this study, electrode spacing was evaluated to determine its effect on the performance of MFCs. The experimental work was conducted utilizing batch digesters with electrode spacings of 2.0 cm, 4.0 cm, 6.0 cm, and 8.0 cm. The results demonstrate that the performance of the MFC improved when the electrode spacing increased from 2.0 to 6.0 cm. However, the efficiency decreased after 6.0 cm. The digester with an electrode spacing of 6.0 cm enhanced the efficiency of the MFC, which led to smaller internal resistance and greater biogas production of 662.4 mL/g VSfed. The electrochemical efficiency analysis demonstrated higher coulombic efficiency (68.7%) and electrical conductivity (177.9 µS/cm) for the 6.0 cm, which was evident from the enrichment of electrochemically active microorganisms. With regards to toxic contaminant removal, the same digester also performed well, revealing removals of over 83% for chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), and volatile solids (VS). Therefore, these results indicate that electrode spacing is a factor affecting the performance of an MFC, with an electrode spacing of 6.0 cm revealing the greatest potential to maximize biogas generation and the degradability of wastewater biochemical matter.

Electricity Production from Yeast Wastewater in Membrane-Less Microbial Fuel Cell with Cu-Ag Cathode

Wastewater has high potential as an energy source. Therefore, it is important to recover even the smallest part of this energy, e.g., in microbial fuel cells (MFCs). The obtained electricity production depends on the process rate of the electrodes. In MFC, the microorganisms are the catalyst, and the cathode is usually made of carbon material (e.g., with the addition of Pt). To increase the MFC efficiency (and reduce costs by reducing use of the noble metals), it is necessary to search the new cathode materials. In this work, the electricity production from yeast wastewater in membrane-less microbial fuel cells with Cu-Ag cathode was analyzed. In the first place, the measurements of the stationary potential of the electrodes (with Cu-Ag catalyst obtained by the electrochemical deposition technique) were performed. Because the cathode is constantly oxidized during the operation of ML-MFC, it was necessary to pre-oxidize the cathodes. Without pre-oxidation, there is a risk of changing the catalytic properties of the electrodes (along with the level of oxidation of the cathodes’ surface) throughout their operation in the ML-MFC. These measurements allowed to assess the oxidation activity of the Cu-Ag cathodes. Additionally, the influence of anodic charge on the catalytic activity of the Cu-Ag cathodes was measured. Next, the analysis of the electric energy production during the operation of the membrane-less microbial fuel cell (ML-MFC) fed by process yeast wastewater was performed. The highest parameters (the power of 6.38 mW and the cell voltage of 1.09 V) were obtained for a Cu-Ag catalyst with 5% of Ag, which was oxidized over 6 h, and after 3 anodic charges. This research proved that it is feasible to obtain the bio-electricity in the ML-MFC with Cu-Ag cathode (fed by yeast wastewater).

On the Stable Operation of a Membraneless Microbial Fuel Cell for More Than One Hundred Days

The development of alternative energy sources is one of the most important areas of modern science. The processes of energy generation are studied in a membraneless mediatorless microbial fuel cell fueled by the Gluconobacter oxydans microorganism using synthetic wastewater with phototrophic Chlorella vulgaris microalgae in the cathode chamber. The operation of the fuel cell is compared with different catholytes, including microalgae with and without illumination, a nutrient medium for growing microalgae, and a K-phosphate buffer. This microbial fuel cell shows stable operation with a slight decrease in power over 113 days of the experiment. This result is due to the formation of biofilms and is confirmed by scanning-electron-microscopy images. Thus, the studied microbial fuel cell is promising for further study in the field of wastewater treatment.

Impact of feedstock dilution on the performance of urine-fed ceramic and membrane-less microbial fuel cell cascades designs

Recent advancements in the microbial fuel cell (MFC) field have led to the deployment of pilot-scale autonomous sanitation systems converting the organic content of urine into electricity to power lights in decentralised areas. Two designs have been deployed successfully, namely ceramic cylinder based MFCs (c-MFC) and membrane-less self-stratifying MFCs (s-MFC), but only one research has tested simultaneously these two designs under similar conditions. To complement this single study, the present work investigated the response of these two designs to the dilution of feedstock. Both designs were assembled as cascades, a configuration close to the conditions of implementation. The tested conditions were 100%, 75%, 50%, 25% urine diluted with tap water. Results have shown that under the 100% condition (neat urine), the s-MFC had a higher energy output (2.29 ± 0.04 kJ d−1) and treatment (4.16 ± 0.15 gCOD.d−1; 1.39 ± 0.15 gNH4.d−1) than thec-MFC. Under the 25% condition, the c-MFC had a higher energy output (0.75 ± 0.04 kJ d−1) but a lower treatment (0.40 ± 0.05 gCOD.d−1; 0.01 ± 0.02 gNH4.d−1) than thes-MFC. Both type of cascade designs could be fed a 75% concentration feedstock for a week without a significant performance decrease. Overall, the c-MFC cascade had higher energy conversion efficiency and thes-MFC had higher power generating performance.

The Effect of Different Pretreatment of Chicken Manure for Electricity Generation in Membrane-Less Microbial Fuel Cell

The need for energy resources is growing all the time, which means that more fossil fuels are needed to provide them. People prefer to consume chicken as a source of protein, and this creates an abundance of waste. Thus, microbial fuel cells represent a new technological approach with the potential to generate electricity through the action of electrogenic bacteria toward chicken manure, while reducing the abundance of chicken manure. This study investigated the effect of different pretreatment (thermal, alkaline, and sonication pretreatment) of chicken manure to improve the performance of a membrane-less microbial fuel cell (ML-MFC). Statistical response surface methodology (RSM) through a central composite design (CCD) under a quadratic model was conducted for optimization of the ML-MFC performance focusing on the COD removal efficiency (R2 = 0.8917), biomass (R2 = 0.9101), and power density response (R2 = 0.8794). The study demonstrated that the highest COD removal (80.68%), biomass (7.8539 mg/L), and power density (220 mW/m2) were obtained when the pretreatment conditions were 140 °C, 20 kHz, and pH 10. The polarization curve of the best condition of ML-MFC was plotted to classify the behavior of the ML-MFC. The kinetic growth of Bacillus subtillis (BS) showed that, in treated chicken manure, the specific growth rate µ = 0.20 h−1 and doubling time Td = 3.43 h, whereas, in untreated chicken manure, µ = 0.11 h−1 and Td = 6.08.

Mixture of Sludge and Chicken Manure in Membrane-Less Microbial Fuel Cell for Simultaneous Waste Treatment and Energy Recovery

In addition to disposal issues, the abundance of sludge and chicken manure has been a rising issue in Malaysia. Membrane-less microbial fuel cell (ML-MFC) technology can be considered as one of the potential solutions to the issues of disposal and electricity generation. However, there is still a lack of information on the performance of an ML-MFC powered by sludge and chicken manure. Hence, with this project, we studied the performance of an ML-MFC supplemented with sludge and chicken manure, and its operating parameters were optimized using response surface methodology (RSM) through central composite design (CCD). The optimum operating parameters were determined to be 35 °C, 75% moisture content, and an electrode distance of 3 cm. Correspondingly, the highest power density, COD removal efficiency, and biomass acquired through this study were 47.2064 mW/m2, 98.0636%, and 19.6730 mg/L, respectively. The obtained COD values for dewatered sludge and chicken manure were 708 mg/L and 571 mg/L, respectively. COD values were utilized as a standard value for the substrate degradation by Bacillus subtilis in the ML-MFC. Through proximate analyses conducted by elemental analysis and atomic absorption spectrometry (AAS), the composition of carbon and magnesium for sludge and chicken manure was23.75% and 34.20% and 78.1575 mg/L and 71.6098 mg/L, respectively. The proposed optimal RSM parameters were assessed and validated to determine the ML-MFC operating parameters to be optimized by RSM (CCD).

Impact of cathodic biofouling on the uneven performance of individual units and scale-up power efficiency in parallel-connected air-cathode microbial fuel cells

Membrane-less air-cathode microbial fuel cell (MFC), as one of the low-cost and potentially scalable modules in the bioelectrochemical technology, can treat wastewater and produce electricity without additional membrane and aeration cost. Nevertheless, the formation of biofilm (i.e., biofouling) on cathodes is observed to deteriorate the cathode performance. This study constructs an eight-unit membrane-less air-cathode MFC and aims to evaluate effects of cathodic biofouling on the performance of individual unit and the scale-up power efficiency during parallel connection. Results indicate cathodic biofoulings affect the cathodic performance by deteriorating both voltage and current output, further causing the performance variation among different cathodes. Moreover, the decrease of power densities by increasing the number of parallel-connected units is observed. Cyclic voltammetry demonstrates the onset potential decreases from 0.4 V to 0.1 V after cathodic biofouling. Electrochemical impedance spectroscopy reveals the polarization resistance of the biofouling cathode increases around two folds. In addition, we also find correlation between cathodic performance and microbial community and association between cathodic performance and unit position in the eight-unit MFC. Overall, our results suggest cathodic biofouling can be the key factor to limit the performance of parallel connection and warrant the need for further research to improve scale-up power efficiency.

Mainstreaming microfluidic microbial fuel cells: a biocompatible membrane grown in situ improves performance and versatility.

A recent trend in microfluidic microbial fuel cells (MFCs) is to exclude a separation membrane, instead, relying on the physics of laminar flow to maintain isolation between anode and cathode compartments. To avoid solution crossover, the electrodes may be separated by distances of several millimeters, but this negatively affects the internal resistance and undermines a prime advantage of microscale MFCs. Therefore, we propose a facile method for in situ synthesis of a micromembrane that supports sub-millimeter electrode spacing. Membrane synthesis in situ reduces device fabrication complexity, and the proposed design avoids electrode contamination during its synthesis. Comparing results to a state-of-the-art membraneless MFC with 6 mm inter-electrode distances, the sub-millimeter membrane MFC under comparable flow conditions had an internal resistance that was 60% lower, power and current densities that were respectively 45% and 290% higher, and acetate conversion efficiencies that were 8 times higher. The enhanced flow stability provided stable operation under imbalanced flow conditions and delivered continuous increases to power density of up to 30% for flow rate increases of 100 times over baseline levels. As a result, maximum outputs obtained were 660 mW m-1 and 3.5 A m-1. These are the highest reported for microfluidic MFCs using pure culture bacteria, which advances the goal of competing with mainstream MFC formats.

Impact of Feedstock Dilution on the Performance of Urine-Fed Ceramic and Membrane-Less Microbial Fuel Cell Cascades Designs

Impact of Feedstock Dilution on the Performance of Urine-Fed Ceramic and Membrane-Less Microbial Fuel Cell Cascades Designs

Desalination and acid-base recovery in a novel design of microbial desalination and chemical recovery cell

Microbial desalination cell (MDC) is deemed as an environmentally friendly technology for water treatment using organic matters present in wastewater for the desalination process. Microbial desalination and chemical recovery cell (MDCC) is a modified version of MDC that desalinates saline water using wastewater as fuel, generates electricity, and concurrently produces value-added products. However, several factors have limited the MDCC performance and its development, e.g., pH imbalance, ions accumulation and high internal resistance. MDCCs, so far, are fabricated through modifying the dual-chamber microbial fuel cell (MFC) by placing the desalination and recovery chambers between the anodic and cathodic chambers, which not only increases the distance between two electrodes, but also brings different types of membranes between them leading to high internal resistance. This research, for the first time, demonstrated a novel design of MDCC, which is a modified version of a single chamber membrane-less MFC, named as SMDCC; with the focus of removing barriers between the anode and cathode while upholding desalination and chemical recovery features of MDCC. The study focused on assessment of SMDCC performance in terms of electrolyte pH, acid and base recovery and desalination rate at different salt concentrations and in absence and presence of applied power supply.

Effect of different yeast extract concentration in membrane-less microbial fuel cell (ML-MFC) for electricity generation using food waste as carbon sources

Electricity constitutes one of the basic energies of our everyday life and approximately 14 % of the global population does not have the access to electricity. An abundance of waste is generated daily wherein food waste constitutes 45 % of the composition. A mediator-less and membrane-less single-chambered microbial fuel cell (ML-MFC) has the potential to serve as a cost-effective solution for food waste treatment and electricity power generation at no additional cost for the substrate. Food waste from E-Idaman Sdn. Bhd. Kedah was utilised in this study to generate electrical energy while focusing on the effect of different yeast extract concentrations on the performance of the ML-MFC. Electrogenic bacterial (EB) culture employed in this study acted as a catalyst for the power generation and was isolated from a previous ML-MFC study. The proximate analysis of food waste observed carbon constituting the greatest composition at 30.02 %. From the conducted preliminary study which compared three different strains of EB to be introduced in the ML-MFC, Bacillus subtillis sp. exhibited the highest specific growth rate, μ, (0.117 g. L−1/h) and shortest doubling time, Td, (5.93 h). One-factor-at-a-time (OFAT) method was utilised to evaluate the performance of the ML-MFC. 15 g/L yeast extract concentration obtained the greatest power density (628.05 × 106 mW/m2), substrate degradation efficiency (12.3 %), COD removal (99 mg/L) and biomass (44.32 mg/L). This showcased that the addition of extra yeast extract concentration into the food waste had boosted the efficiency of EB’s growth resulting in greater consumption of carbon source (removed COD value; bioremediation) in the food waste.

Membrane-less microbial fuel cell: effect of pH on the electricity generation powered by municipal food waste

Fossil fuels have supported the industrialization and economic growth of countries during the past centuries and it is clear that they cannot indefinitely sustain in a longer time. In this study, membrane-less microbial fuel cell (ML-MFC) with mediators-less and air cathode had potential solution to generate electricity power and at the same time could reduce the abundant of food waste (1.64 kg/daily, around 8 tonnes/year) which dumped in the landfill and it’s cost effective device. The ML-MFC operated electrochemically incorporate electrogenic bacteria (EB) acted as a biocatalyst in order to produce electricity. The performance and optimization performance of food waste was evaluated using one-factor-at-a-time (OFAT) method and it was focused to pH for power generation. To determine the generated electricity the polarization curve was used to evaluate the performance of ML-MFC. The chemical oxygen demand (COD) of food waste was studied. The optimization of pH condition in ML-MFC was ranging from 7 to 9. Results showed that pH 8 was the optimum pH for EB strain, Bacillus Subtilis, with the high voltage (807 mV), EB biomass (15.46 mg/L), and power density (373.3 mW/m2) generated. Clearly the pH environment condition affected the efficiency of ML-MFC performance. The increase in EB biomass also increased the voltage in the ML-MFC, proving that EB biomass and voltage were associated with growth.

The Implications of Membranes Used as Separators in Microbial Fuel Cells.

Microbial fuel cells (MFCs) are electrochemical devices focused on bioenergy generation and organic matter removal carried out by microorganisms under anoxic environments. In these types of systems, the anodic oxidation reaction is catalyzed by anaerobic microorganisms, while the cathodic reduction reaction can be carried out biotically or abiotically. Membranes as separators in MFCs are the primary requirements for optimal electrochemical and microbiological performance. MFC configuration and operation are similar to those of proton-exchange membrane fuel cells (PEMFCs)—both having at least one anode and one cathode split by a membrane or separator. The Nafion® 117 (NF-117) membrane, made from perfluorosulfonic acid, is a membrane used as a separator in PEMFCs. By analogy of the operation between electrochemical systems and MFCs, NF-117 membranes have been widely used as separators in MFCs. The main disadvantage of this type of membrane is its high cost; membranes in MFCs can represent up to 60% of the MFC’s total cost. This is one of the challenges in scaling up MFCs: finding alternative membranes or separators with low cost and good electrochemical characteristics. The aim of this work is to critically review state-of-the-art membranes and separators used in MFCs. The scope of this review includes: (i) membrane functions in MFCs, (ii) most-used membranes, (iii) membrane cost and efficiency, and (iv) membrane-less MFCs. Currently, there are at least 20 different membranes or separators proposed and evaluated for MFCs, from basic salt bridges to advanced synthetic polymer-based membranes, including ceramic and unconventional separator materials. Studies focusing on either low cost or the use of natural polymers for proton-exchange membranes (PEM) are still scarce. Alternatively, in some works, MFCs have been operated without membranes; however, significant decrements in Coulombic efficiency were found. As the type of membrane affects the performance and total cost of MFCs, it is recommended that research efforts are increased in order to develop new, more economic membranes that exhibit favorable properties and allow for satisfactory cell performance at the same time. The current state of the art of membranes for MFCs addressed in this review will undoubtedly serve as a key insight for future research related to this topic.

Evaluating the application ability of membrane-less microbial fuel cells in shrimp farming wastewater recirculation

Microbial fuel cell (MFC) was considerable as a promising saline wastewater treatment which using microorganism to convert organic compounds to electrical energy. Most of wastewater generated from aquaculture farming contained highly saline effluents. In addition, the maintenance of good water quality was essential for optimum growth and survival of shrimp. This study aimed to evaluate the ability of Membrane-less Microbial Fuel Cells (MFCs) to treat wastewater for recirculation of shrimp culture wastewater, and improvement in the growth performance of Penaeus vannamei (White Leg Shrimp). Six MFCs models were built with locally available materials such as: polyvinyl chloride (PVC), anaerobic sludge, carbon cloth anode and cathode electrodes, granular graphite, glass wool and glass bead. This study compared two different treatments including: control (cultivation with no MFCs models) and MFCs models (application models with shrimp culture), run in continuous mode at room temperature (250C – 30oC). Each treatment was run in triplicate with shrimp at size PL30-PL45, average initial weight of 0.91 +/- 0 (g) and average initial length of 3.03 +/- 0.6 (cm). Experiments were set up using the 120 L tanks (working volume of 90 L), input with seawater at 20 ppt salinity, temperatures range of 22◦C to 26◦C, pH range of 7.5 to 9.4, and dissolve oxygen range of 5.5 to 7.2. The density of shrimp was 5 post larvae (PL) per liter. Research results achieved the removal of chemical oxygen demand, ammonia, nitrite and nitrate were up to 58.83%, 76.1%, 56.33% and 70.90%, respectively. The survival rate of shrimp was maintained, and growth rate was enhanced significantly compared with control treatment. The obtained results in this study presented that MFCs has ability to treat pre-circulation of shrimp culture wastewater and improved in the growth performance of Penaeus vannamei (White Leg Shrimp).

Low-Cost Single Chamber MFC Integrated With Novel Lignin-Based Carbon Fiber Felt Bioanode for Treatment of Recalcitrant Azo Dye

A flow through anaerobic microbial fuel cell (MFC) was designed and optimized for efficient treatment of recalcitrant textile wastewater. The membrane-less MFC was first time fabricated with a unique combination of electrodes, a novel bioanode of synthesized lignin-based electrospun carbon fiber supporting a biofilm ofGeobacter sulfurreducensfor acetate oxidation and an air-breathing cathode, consisting of a pyrolyzed macrocycle catalyst mixture on carbon bonded by polytetrafluoroethylene (PTFE). The effects of different organic loadings of acetate along with Acid Orange (AO5), operation time and ionic strength of auxiliary salts (conductivity enhancers) were investigated and responses in terms of polarization and degradation were studied. In addition, the decomposition of the organic species and the degradation of AO5 along with its metabolites and degraded products (2-aminobenzenesulfonic acid) were determined by chemical oxygen demand (COD) analysis, UV-Vis spectrophotometry and high-performance liquid chromatography (UV-HPLC) techniques. SEM and TEM images were also used to find out the biocompatibility of the microbes on lignin-based electrospun carbon felt anode and the morphology of the cathode. Reduction and breakage of the azo bond of AO5 occurs presumably as a side reaction, resulting in the formation of 2-aminobenzenesulfonic acid and unidentified aromatic amines. Maximum current density of anode 0.59 Am−2and power density of 0.12 Wm−2were obtained under optimized conditions. As a result, decolouration of AO5 and chemical oxygen demand (COD) removal efficiency was 81 and 58%, respectively. These results revealed that the low-cost MFC assembly can offer significant potential for anaerobic decolouration of recalcitrant textile wastewater.

Membrane-less microbial fuel cell: Monte Carlo simulation and sensitivity analysis for COD removal in dewatered sludge

Dewatered sludge is redundantly found in a municipal wastewater treatment plant, and the amount is increasing every year. However, the dewatered sludge could be used to power the membrane-less microbial fuel cell (ML-MFC), which is operated electrochemically via incorporation of electricity producing micro-organisms. The dewatered sludge normally acts as an electron donating substrate. Results showed that the ML-MFC produced voltage at about 927.7 ± 11.24 mV whereby 178.7 mg/L of chemical oxygen demand (COD) was removed after 240 h of incubation period. Nonetheless, voltage and COD removal values obtained from the dewatered sludge in the ML-MFC might differ every time the study is repeated because the availability of maximum biomass of electrogenic bacteria (EB) will be different due to the heterogeneous properties and EB performance inside the ML-MFC. The parametric uncertainty analysis of COD removal was then assessed using Monte Carlo simulation (stochastic variable) to determine the distribution probability affected by the fluctuation and variation of kinetic model parameters. From the study of 100 000 samples tested (simulation), the results show that the substrate removal (S) value ranged from 172.58 to 185.02 mg/L. The impact of each kinetic parameter on the ML-MFC performance was evaluated via sensitivity analysis. It is found that the ML-MFC performance significantly relied on the growth of EB present.