Application fuzzy DEMATEL methodology to investigate some technical parameters of biochemical methane potential (BMP) test produced vegetable waste anaerobic biogas.

As the transition to renewable energy systems is accelerating, anaerobic digestion, which is one of the methods of energy recovery from organic substrates, continues to be studied with great interest by scientists. Anaerobic digestion research and applications are mostly carried out with biochemical methane potential (BMP) tests to decide the methane potency of sewage sludge, energy crops, and organic wastes. Unlike long and costly continually reactor experiments, actually, BMP tests are cumulative and can be performed with a relatively low investment of materials, technical labor, and also time. For the BMP to give accurate results, the effect of all the tools and technical parameters used in the implementation of the BMP should be well understood. In such situations, it is very useful to apply fuzzy logic methods in multi-criteria decision-making stages when more than one parameter changes at the same time. Therefore, in this study, fifteen parameters were determined and analyzed with the fuzzy DEMATEL (decision-making trial and evaluation laboratory) method to understand the cause-effect mechanism of the technical parameters of BMP. As a result of these analyses, it was seen that the material of the reactor (ri-cj value of 0.55), the particle size (ri-cj value of 0.43), the effect of mixing (ri-cj value of 0.32), and the amount of the total solids (TSA) (ri-cj value of 0.25) had a high effect in the causal sense. It was observed that the first-order parameter (material of reactor) was 27% stronger than the second-order (the particle size) parameter in terms of causality. Likewise, the second-order parameter is 34% stronger than the third-order parameter (the effect of mixing) in terms of cause effect. In addition, it was understood that the most effective parameters in the mechanism of effect were pH (ri + cj value of 3.41), C/N ratio (ri + cj value of 3.26), and temperature (ri + cj value of 3.07), respectively. Besides, high methane yield is seen in mesophilic conditions. The average cumulative biogas yield of the reactor is 282.1 NmL/g VS. The highest percentage of methane formed in the biogas occurred on the 21st day. Briefly, this study is important to provide a facilitating way for researchers working on BMP to understand the cause-effect mechanism of system technical requirements.

Development of an MFC-biosensor for determination of Pb+2: an assessment from computational fluid dynamics and life cycle assessment perspectives.

Microbial fuel cell (MFC)-based biosensor sensing has emerged as an innovative approach to in situ and immediate monitoring of substrate concentration. MFC-biosensor uses bioanode as a sensing element. In this study, the performance of MFC-biosensor, operated with Pb+2, was studied at different hydraulic retention times (HRTs). The HRT ranges were 0.5, 1, and 2 days. The power density generation increased with the decreasing HRT. The highest achievable power density was obtained at HRT of 1 days with the density value of 597 mW/m2. The power density produced in the MFC system was stored in the energy storage system. The computational fluid dynamics (CFD) method simulates detailed three-dimensional flow and heat transfer properties in reactors and provides information about potential reactor design. CFD was chosen to simulate the concentration distribution of the substrate in the MFC in different reactor type and different HRTs. It was observed that there was good turbulence in the reactor in a two day HRT and the reactor volume was used effectively. Life cycle assessment (LCA) was performed at 1 day with the highest power density. An LCA was implemented to the production and operation processes of a microbial fuel cell. According to the results, these two processes caused 4.23 × 10-6 loss of healthy years, extinction of 1.3 × 10-8 species in a year and loss of $ 0.33 source availability. The emissions to air, water, and soil were also calculated. These results showed that MFC-biosensor provided information on the rate of biodegradation processes.

Removal of Cu(II) ions from aqueous solutions using membrane system and membrane capacitive deionization (MCDI) technology.

Copper ion removal with nanofiltration membranes has accelerated in recent years. In this study, Cu2+ ion removal was investigated with nanofiltration membrane and a membrane capacitive deionization (MCDI) system; consequently, it was observed that the highest performance was seen when these two systems worked in an integrated system (99% Cu2+ ion removal) MCDI system is a purification technology through ion exchange membranes based on applying an electric field between two opposed electrodes. The flow rate, direct current voltage, and the operation time at which the Cu2+ ion removal rate was the highest were 50 mL/min, 1.2 V, and 15 min. respectively. Here, we report the application of the life cycle assessment (LCA) method to evaluate the environmental performance of the membrane system in different operating conditions. In the sensitivity analysis component of the study, different materials used in the membrane system and MCDI ststem were compared. Results from the LCA analysis showed that the MCDI system has far worse environmental impacts in all aspects particularly in material and energy-related effects.

Life cycle assessment of environmental effects and nitrate removal for membrane capacitive deionization technology.

Nitrate is among the important types of pollutant sources in drinking water worldwide, and there are a number of methods to remove it from water. New treatment methods are being developed as an alternative to traditional treatment methods. One of them is membrane capacitive deionization (MCDI). In this study, the removal of nitrate ions with MCDI system was investigated. Nitrate solutions were treated via MCDI at different operating conditions. The obtained nitrate removal efficiency reached 83.07% at a flow rate of 2.5 L/min and a potential of 0.8 V was applied. In addition, during the nitrate removal of the MCDI system, the environmental effects were evaluated by life cycle analysis. As a result of these analyses, MCDI system offered advantages of low energy demand and low-energy environmental effects during operation. The results showed that the improved MCDI technology holds a great potential to be an energy-efficient process for nitrate removal. Life cycle assessment was applied to the experimental study. According to the assessment, water consumption had the highest effect in all damage assessment categories.

Electricity Production and Characterization of High-Strength Industrial Wastewaters in Microbial Fuel Cell.

Microbial fuel cells (MFCs) convert electrochemical energy into electrical energy immediately and have a big potential usage for the same time wastewater treatment and energy recovery via electro-active microorganisms. However, MFCs must be efficiently optimized due to its limitations such as high cost and low power production. Finding new materials to increase the cell performance and reduce cost for MFC anodes is mandatory. In the first step of this study, different inoculation sludges such as anaerobic gum industry wastewater, anaerobic brewery wastewater and anaerobic phosphate were tested, and MFC that was set up with anaerobic gum industry wastewater inoculation sludge exhibited the highest performance. In the second step of this study, various wastewaters such as chocolate industry, gum industry and slaughterhouse industry were investigated for anode bacteria sources. Several electrochemical techniques have been employed to elucidate how wastewaters affect the MFCs' performance. Among all the mentioned wastewaters, the best performance was achieved by the MFCs fed with slaughterhouse wastewater; this device produced a maximum power density of 267 mW·m-2.

Simultaneous production of bioelectricity and treatment of membrane concentrate in multitube microbial fuel cell.

The performance of upflow multitube microbial fuel cell (UM2FC) from membrane concentrate of domestic wastewater (50% concentrate or a volume to concentration ratio of 2) has been investigated in a laboratory test. The test found that the UM2FC with the tin-coated copper mesh and coil spring under different hydraulic retention times (HRTs) produced maximum electricity of 916 ± 200 mW/m3 (61 mW/m2) at an HRT of 0.75 day with a 78% soluble chemical oxygen demand (sCOD) removal efficiency and 3% and 20% Coulombic efficiencies (CEs). The whole-cell resistance as calculated from the Nyquist plot and equivalent circuit were approximately 134 and 255 Ω for HRTs of 0.5 and 0.75 days, respectively. Considering HRT, the current increase with longer HRT could be due to longer contact time between organic material and biofilm, which results in a higher electrical efficiency. The results showed that UM2FC could represent an effective system for simultaneous membrane concentrate treatment and electricity production after further improvements on MFC and operating conditions.

The development of catalytic performance by coating Pt-Ni on CMI7000 membrane as a cathode of a microbial fuel cell.

Performance of cathode materials in microbial fuel cell (MFC) from dairy wastewater has been investigated in laboratory tests. Both cyclic voltammogram experiments and MFC tests showed that Pt-Ni cathode much better than pure Pt cathode. MFC with platinum cathode had the maximum power density of 0.180 W m(-2) while MFC with Pt:Ni (1:1) cathode produced the maximum power density of 0.637 W m(-2), even if the mass mixing ratio of Pt is lower in the alloy were used. The highest chemical oxygen demand (COD) removal efficiency was around 82-86% in both systems. The cyclic voltammogram (CV) analyses show that Pt:Ni (1:1) offers higher specific surface area than Pt alone does. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) results showed that entire Pt:Ni (1:1) alloys can reduce the oxygen easily than pure platinum, even though less precious metal amount. The main outcome of this study is that Pt-Ni, may serve as a alternative catalyst in MFC applications.