Effects of carbon-nitrogen ratio on electricity generation, pollutant removal and microbial community structure of single-chamber MFCs in high salinity wastewater

Effect of nitrate on electricity generation in single-chamber air cathode microbial fuel cells

Electricity generation and microbial community analysis of alcohol powered microbial fuel cells

Due to the known problems of microbial fuel cells (MFCs), such as low electricity generation performance and high cost of operation, we modified the electrode with graphene and polyaniline (PANI) is a single-chamber air-cathode MFC and then evaluated the effects of electrode modification on MFC electricity generation performance. Carbon cloth electrodes (unmodified, CC; graphene-modified, G/CC; and polyaniline-graphene-modified, PANI-G/CC) were prepared using the impregnation method. Sulfonated cobalt phthalocyanine (CoPcS) was then introduced as a cathode catalyst. The Co-PANI-G/CC cathode showed higher catalytic activity toward oxygen reduction compared with other electrodes. The maximum power density of the MFC with Co-PANI-G/CC cathode was 32.2 mW/m2, which was 1.8 and 6.1 times higher than the value obtained with Co-G/CC and Co/CC cathodes, respectively. This indicates a significant improvement in the electricity generation of single-chamber MFCs and provides a simple, effective cathode modification method. Furthermore, we constructed single-chamber MFCs using the modified anode and cathode and analyzed electricity generation and oxytetracycline (OTC) degradation with different concentrations of OTC as the fuel. With increasing added OTC concentration, the MFC performance in both electricity generation and OTC degradation gradually decreased. However, when less than 50 mg/L OTC was added, the 5-day degradation rate of OTC reached more than 90%. It is thus feasible to process OTC-containing wastewater and produce electricity using single-chamber MFCs, which provides a new concept for wastewater treatment.

ABSTRACTThe chemical oxygen demand (COD) removal, electricity generation, and microbial communities were compared in 3 types of microbial fuel cells (MFCs) treating molasses wastewater. Single-chamber MFCs without and with a proton exchange membrane (PEM), and double-chamber MFC were constructed. A total of 10,000 mg L−1 COD of molasses wastewater was continuously fed. The COD removal, electricity generation, and microbial communities in the two types of single-chamber MFCs were similar, indicating that the PEM did not enhance the reactor performance. The COD removal in the single-chamber MFCs (89–90%) was higher than that in the double-chamber MFC (50%). However, electricity generation in the double-chamber MFC was higher than that in the single-chamber MFCs. The current density (80 mA m−2) and power density (17 mW m−2) in the double-chamber MFC were 1.4- and 2.2-times higher than those in the single-chamber MFCs, respectively. The bacterial community structures in single- and double-chamber MFCs were also distinguishable. The amount of Proteobacteria in the double-chamber MFC was 2–3 times higher than those in the single-chamber MFCs. For the archaeal community, Methanothrix (96.4%) was remarkably dominant in the single-chamber MFCs, but Methanobacterium (35.1%), Methanosarcina (28.3%), and Methanothrix (16.2%) were abundant in the double-chamber MFC.

Copper removal and microbial community analysis in single-chamber microbial fuel cell

This was the first establishment of an air-cathode single chamber microbial fuel cell (MFC) without a proton exchange membrane and with stainless steel wire as the anode. The performance of the MFC was evaluated by using glucose as the sole substrate. With an initial chemical oxygen demand (COD Cr ) concentration of 496 mg/L and the external resistance of 1000 ? under room temperature, electricity was generated continuously by the MFC. The highest voltage reached up to 235.11 mV. The open circuit voltage was measured at 461.00 mV, and the internal resistance of the system under test was calculated at 2820 ?. The MFC achieved a maximum power density of 137.1 mW/m cathode and a coulombic efficiency of 32.4% under the experimental condition. Contrastive experimental research on brewery wastewater treatment was done by using the MFC and anaerobic reactor. Under the initial COD Cr of 15900 mg/L and the hydraulic retention time of 96 hours, the MFC achieved 40% to 55 % removal rate of COD Cr The voltage at the two ends stayed stably at 220 to 250 m V. It indicated that MFCs could reclaim electric energy from the process of wastewater treatment.

Over the last couple decades, microbial fuel cells (MFCs) have become a technology of interest for renewable energy production and waste treatment/reclamation. MFCs are flexible with fuel and, for this reason, have garnered interest as biosensors, unit operations in advanced wastewater treatment, and alternative power sources. MFCs oxidize organic matter at the anode where microbes perform anaerobic respiration to convert organic matter into simpler compounds (such as carbon dioxide, methane, etc.); however, the anode electrode serves as the final electron acceptor [1, 2]. The electrons produced at the anode are used at the cathode in oxygen reduction reaction (ORR), a reaction that requires the presence of a catalyst. The system design for MFCs can vary to meet different applications [3], but one of the more popular designs is a membrane less, single chamber, air cathode microbial fuel cell [4], which has the anode submerged in an oxygen-less, nutrient solution and has an air-exposed cathode. Although promising in concept, MFCs have very low power density, making them cost inefficient. A major performance limitation in MFCs has been identified in the cathode. Overall efficiency and power density a strongly influenced by cathode design and catalyst selection for the ORR [4, 5]. Previous modeling efforts have suggested oxygen crossover to the anode, oxygen diffusion to the ORR catalyst, and the catalyst used are major factors for low power density [6-8]. In this work, improved MFC performance is demonstrated using non-platinum group catalyst material. The novel catalyst was benchmarked against a platinum group catalyst. Using the novel non-platinum catalyst results in a modest increase in open circuit potential, and a significant increase in maximum current density and power density. In addition, we have investigated the influence of non-platinum catalyst loading on the overall performance. The novel catalysts used in this work demonstrated stability over months of operation. This suggests that the non-platinum group catalyst used in this work is more efficient than platinum group catalyst, improving the cell performance while simultaneously enabling lower cost. References Jr, L.B.W., C.H. Shaw, and J.F. Castner, Bioelectrochemical fuel cells. Enzyme and Microbial Technology, 1982. 4(3): p. 6.Kim, H.J., et al., A mediator-less microbial fuel cell using a metal reducing bacterium, Shewanella putrefaciens. Enzyme and Microbial Technology, 2002. 30(2): p. 8.He, Z., S.D. Minteer, and L.T. Angenent, Electricity Generation from Artificial Wastewater Using an Upflow Microbial Fuel Cell. Environmental Science and Technology, 2006. 39: p. 6.Liu, H. and B.E. Logan, Electricity Generation Using an Air-Cathode Single Chamber Microbial Fuel Cell in the Presence and Absence of a Proton Exchange Membrane. Environmental Science and Technology, 2004. 38: p. 6.Rismani-Yazdi, H., et al., Cathodic limitations in microbial fuel cells: An overview. Journal of Power Sources, 2008. 180: p. 12.Ou, S., et al., Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell. Journal of Power Sources, 2017. 347: p. 11.Ou, S., et al., Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition. Journal of Power Sources, 2016. 328: p. 12.Ou, S., et al., Multi-variable mathematical models for the air-cathode microbial fuel cell system. Journal of Power Sources, 2016. 314: p. 9. Figure 1

Bio-electrochemical technology in form of single chamber microbial fuel cell was used to simultaneous reduce organic pollutants and electricity generation under anoxic condition. Reactor was fixed working volume 1liters. Single chamber microbial fuel cell was started with open circuit that inoculates to biofilm on anode chamber and microorganisms can be adjusted to single chamber microbial fuel cell condition. Close circuit was started with 1,000 ω. Initial COD was converted to 5,109 mg L−1 that obtained current density per area 154 mA m−2, maximum power density per area 152 mW m−2 and COD removal efficiency was 70%, respectively. Moreover, the economic feasibility was evaluated in term of net present value (NPV) was 1,746.20, payback period (PBP) was obtained 1 year 4 months, respectively. Therefore, single chamber microbial fuel cell is technology that suitable for simultaneous reduce organic pollutants and electricity generation.

Electricity generation from landfill leachate was examined by using both a dual-chamber microbial fuel cell (MFC) and a single chamber MFC. Experimental results showed that the maximum power density of 2060.19 mW/m3 in the dual-chamber MFC and that of 6817.4 mW/m3 in the single chamber MFC were obtained. It was recognized that the difference in internal resistance for two MFC systems was the main reason for resulting in the difference of power generation. Power generation as function of chemical oxygen demand (COD) in single chamber MFC showed a Monod-type relationship with P max of 5920.96 mW/m3 and Ks of 251.39 mg/L at an external resistance of 500 Ω. Cyclic voltammetry showed that electrons were directly transferred onto the anode by bacteria in biofilms, rather than self-produced mediators of bacteria in the solutions. At low COD concentration, electricity generation was limited by the anode due to kinetic limitation; while at high COD concentration, the cathode was shown to have more significant effects on the electricity generation than the anode. COD in leachate could be removed when it increases, mainly because oxygen diffused from the cathode was substantially reduced by aerobic or anoxic bacteria in the anode chamber, leading to the substrate loss. Removal of ammonium-nitrogen was not observed in the single chamber MFC. This novel technology provides an economical route for electricity energy recovery in leachate treatment.

Effect of pH on bacterial distributions within cathodic biofilm of the microbial fuel cell with maltodextrin as the substrate

<i>Harvesting Energy using Biocatalysts</i>

A waste to energy approach in pollution controls is highly desirable to create a green and sustainable environment. Microbial Fuel Cell (MFC), which converts organic to electricity via the help of microorganism is one of the examplatory approach of waste to energy concept. Here we tried to find out the influence of MFC technology to the degradation of Total Petroleum Hydrocarbon (TPH) on contaminated sediment. The research used completely randomized design with three treatments and three replications which were control, single-chamber MFC and dual-chamber MFC observed for twenty days. The result showed that the TPH content degraded around 10.26%, 46.15 and 25.64% for control, single-chamber MFC and dual-chamber MFC treatments, respectively. The electricity production for single-chamber treatments was 184.36 mV, 179.59 mA/m 2 and 50.57 W/m 2 and for dual-chamber MFC was 57.58 mV, 62.51 mA/m 2 and 5.76 W/m2. According to annova analysis at 5% significance rate, it could be concluded that the use of MFC technology had shown a significant effect to TPH degradation on contaminated sediment.

Microbial stratification structure within cathodic biofilm of the microbial fuel cell using the freezing microtome method

Effects of chemical oxygen demand/nitrogen on electrochemical performances and denitrification efficiency in single-chamber microbial fuel cells: Insights from electron transfer and bacterial communities

Optimization of a single chamber microbial fuel cell using Lactobacillus pentosus: Influence of design and operating parameters