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The microbial desalination cell (MDC) is a bio-electrochemical system that exhibits the ability to oxidize organic compounds, produce energy, and decrease the saline concentrations within the desalination chamber. The selective removal of ions from the desalination chamber is significantly influenced by the anion and cation exchange membranes. In this study, a three-chamber microbial desalination cell was developed to treat seawater using a synthesize Fe3O4 magnetite nanoparticle (MNP)-modified anode. The impact of different performance parameters, such as temperature, pH, and concentrations of NPs, has been investigated in order to assess the performance of three-chamber MDCs in terms of energy recovery and salt removal. The evaluation criteria of the system included multiple factors such as chemical oxygen demand (COD), Coulombic efficiency (CE), desalination efficiency, as well as system aspects including voltage generation and power density. The highest COD% removal efficiency was 74% at 37 °C, pH = 7, and 30 g/L salt concentration with an optimized NPs concentration of 2.0 mg/cm2 impregnated on anode. The maximum Coulombic efficiency was 10.3% with the maximum power density of 4.3 W/m3. The effect of the nanoparticle concentration impregnated on the anode was clarified by the primary factor of analysis. This research has revealed consistent patterns in the enhancement of voltage generation, COD, and Coulombic efficiencies when incorporating higher concentrations of nanoparticles on the anode at a certain point.

Carbon constraints, as well as the growing hazard of greenhouse gas emissions, have accelerated research into all possible renewable energy and fuel sources. Microbial electrolysis cells (MECs), a novel technology able to convert soluble organic matter into energy such as hydrogen gas, represent the most recent breakthrough. While research into energy recovery from wastewater using microbial electrolysis cells is fascinating and a carbon-neutral technology that is still mostly limited to lab-scale applications, much more work on improving the function of microbial electrolysis cells would be required to expand their use in many of these applications. The present limiting issues for effective scaling up of the manufacturing process include the high manufacturing costs of microbial electrolysis cells, their high internal resistance and methanogenesis, and membrane/cathode biofouling. This paper examines the evolution of microbial electrolysis cell technology in terms of hydrogen yield, operational aspects that impact total hydrogen output in optimization studies, and important information on the efficiency of the processes. Moreover, life-cycle assessment of MEC technology in comparison to other technologies has been discussed. According to the results, MEC is at technology readiness level (TRL) 5, which means that it is ready for industrial development, and, according to the techno-economics, it may be commercialized soon due to its carbon-neutral qualities.

Crude oil is a major energy source that is exploited globally to achieve economic growth. To meet the growing demands for oil, in an environment of stringent environmental regulations and economic and technical pressure, industries have been required to develop novel oil salvaging techniques. The remaining ~70% of the world’s conventional oil (one-third of the available total petroleum) is trapped in depleted and marginal reservoirs, and could thus be potentially recovered and used. The only means of extracting this oil is via microbial enhanced oil recovery (MEOR). This tertiary oil recovery method employs indigenous microorganisms and their metabolic products to enhance oil mobilization. Although a significant amount of research has been undertaken on MEOR, the absence of convincing evidence has contributed to the petroleum industry’s low interest, as evidenced by the issuance of 400+ patents on MEOR that have not been accepted by this sector. The majority of the world’s MEOR field trials are briefly described in this review. However, the presented research fails to provide valid verification that the microbial system has the potential to address the identified constraints. Rather than promising certainty, MEOR will persist as an unverified concept unless further research and investigations are carried out.

Due to the continuous depletion of natural resources currently used for electricity generation, it is imperative to develop alternative energy sources. Human waste is nowadays being explored as an efficient source to produce bio-energy. Human waste is renewable and can be used as a source for an uninterrupted energy supply in bioelectricity or biofuel. Annually, human waste such as urine is produced in trillions of liters globally. Hence, utilizing the waste to produce bioenergy is bio-economically suitable and ecologically balanced. Microbial fuel cells (MFCs) play a crucial role in providing an effective mode of bioelectricity production by implementing the role of transducers. MFCs convert organic matter into energy using bio-electro-oxidation of material to produce electricity. Over the years, MFCs have been explored prominently in various fields to find a backup for providing bioenergy and biofuel. MFCs involve the role of exoelectrogens which work as transducers to convert the material into electricity by catalyzing redox reactions. This review paper demonstrates how human waste is useful for producing electricity and how this innovation would be beneficial in the long term, considering the current scenario of increasing demand for the supply of products and shortages of natural resources used to produce biofuel and bioelectricity.

Considering the complexity associated with bioelectrochemical processes, the performance of a microbial fuel cell (MFC) is governed by input operating parameters. For scaled-up applications, a MFC system needs to be modeled from engineering perspectives in terms of optimum operating conditions to get higher performance and energy recovery. Several conceptual numerical models to advanced computational simulation approaches have been developed to represent simple-form of a complex MFC system. Application of mathematical and computation models are explored to establish the relationship between operating input-variables and power output. The present review discusses about the complexity of system, modeling strategies used and reality of such modeling for scaling-up applications of MFCs. Additionally, the selection of an appropriate mathematical model reduces the computational duration and provides better understanding of the system process. It also explores the possibility and progress towards commercialization of MFCs and thus the need of development of model-based optimization and process-control approaches.

Three different approaches were employed to improve single chambered microbial fuel cell (sMFC) performance using Shewanella putrefaciens as biocatalyst. Taguchi design was used to identify the key process parameter (anolyte concentration, CaCl₂ and initial anolyte pH) for maximization of volumetric power. Supplementation of CaCl₂ was found most significant and maximum power density of 4.92 W/m(3) was achieved. In subsequent approaches, effect on power output by riboflavin supplementation to anolyte and anode surface modification using nano-hematite (Fe₂O₃) was observed. Volumetric power density was increased by 44% with addition of 100 nM riboflavin to anolyte while with 0.8 mg/cm(2) nano-Fe₂O₃ impregnated anode power density and columbic efficiency increased by 40% and 33% respectively. Cyclic voltammetry revealed improvement in electrochemical activity of Shewanella with nano-Fe₂O₃ loading and electrochemical impedance depicted inverse relationship between charge transfer resistance and nano-Fe₂O₃ loading. This study suggests anodic improvement strategies for maximization of power output.

Abstract An electrochemically active bacteria Pseudomonas aeruginosa IIT BT SS1 was isolated from a dark fermentative spent media fed anode, and a bioaugmentation technique using the isolated strain was used to improve the start-up time of a microbial fuel cell (MFC). Higher volumetric current density and lower start-up time were observed with the augmented system MFC-PM (13.7 A/m3) when compared with mixed culture MFC-M (8.72 A/m3) during the initial phase. This enhanced performance in MFC-PM was possibly due to the improvement in electron transfer ability by the augmented strain. However, pure culture MFC-P showed maximum volumetric current density (17 A/m3) due to the inherent electrogenic properties of Pseudomonas sp. An electrochemical impedance spectroscopic (EIS) study, along with matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) analysis, supported the influence of isolated species in improving the MFC performance. The present study indicates that the bioaugmentation strategy using the isolated Pseudomonas sp. can be effectively utilized to decrease the start-up time of MFC.