Ashvini D. Chendake’s research while affiliated with Maharashtra Institute of Technology and other places

Electrochemists and ecological engineers find environmental bioelectrochemistry appealing; however, there is a big gap between expectations and actual progress in bioelectrochemical system (BES). Implementing such technology opens new opportunities for novel electrochemical reactions for resource recovery and effective wastewater treatment. Loopholes of BES exist in its scaling-up applications, and numerous attempts toward practical applications (200, 1000, and 1500 L) are key successive indicators toward its commercialization. This review emphasized the critical rethinking of standardization of performance indices i.e. current generation (A/m²), net energy recovery (kWh/kg·COD), product yield (mM), and economic feasibility ($/kWh) to make fair comparison with the existing treatment system. Therefore, directional perspectives, including modularity, energy-cost balance, energy and resource recovery, have been proposed for the sustainable market of BES. The current state of the art and up-gradation in resource recovery and contaminant removal warrants a systematic rethinking of functional worth and niches of BES for practical applications.

Application of power management system (PMS) in microbial fuel cell (MFC) for potential energy harvesting is coming up as an emerging trend for field level applications. Though the energy recovery and environment benefits of MFC are well recognized, still scaling-up challenges are confronted during onsite applications for sufficient power generation. Increasing number of research on PMS in MFC studies reveals incorporation of various power electronic components and different maximum power point tracking (MPPT) algorithm models to boost electricity generation. From the point of stacking-up of MFCs, present review focuses on use of different electronic circuits i.e. DC-DC booster, supercapacitor, Metal- Oxide Semiconductor Field- Effect Transistor (MOSFET), amplifier, transistor, etc. incorporated in PMS. Tracking of maximum power point in MFC has been described using different MPPT algorithms. Some recent field trials are described which emphasize the importance of incorporation of PMS for boosting and storage of electricity generated from MFC. A suitable electrical and hydraulic series parallel connection establishment during stack mode operation of MFC is inevitable to generate desired voltage output. Present review aims towards applications of PMS in MFC for making power output useable in realistic applications. Valuable studies providing useful information, challenges and their probable solutions regarding PMS for stacking of MFC are discussed.

Membrane is one of the important components of microbial electrochemical technologies (METs), which facilitate the proton transfer from anodic to cathodic chamber. Membrane/separator performance is governed by membrane properties, surface area, mineral composition, porosity and other characteristics. Long-term operation of MFC is restricted majorly due to bacterial mediated-biofouling of membrane over period results in proton-transfer limitation and poor efficiency. Several strategies have been proposed to develop the antimicrobial membrane, including silver nano-particles and antifouling chemicals that could control biofouling. Present review article summarizes the biofouling mechanism, biofouling development and provides an update on different strategies employed to reduce biofouling and overcome limitations of MFC for scaling-up applications. The cost of membrane replacement due to biofouling can be reduced with proper biofouling mitigation strategies and help improve the rate of electrokinetic reactions. For scalable applications, membrane pretreatment with intermittent dosing of antifouling chemicals can enhance the performance of a long-term operation.

Plant photosynthesis is one of nature’s best gifts to humankind for converting solar energy into chemical energy in the form of carbohydrates and energy. Plant microbial fuel cells (PMFCs) or photosynthetic MFCs integrate the principles of photosynthesis and fuel cell to convert such synthesized carbohydrates and organic matter into electricity by microbial oxidation in the rhizosphere of plants. Also, plants utilize nutrients from effluent streams for self-growth and metabolism, reducing the nutrient load and heavy metal concentration, and are capable to degrade contaminants. Performance of PMFC is governed by various parameters such as selection of plant species, rhizodeposits, design of MFC, electrode properties, inoculum characteristics, wastewater properties, etc. This chapter discussed the basics of PMFC to applications for real field. According to applications, PMFC designs can be varied as constructed MFC, microbial carbon capture cells, microbial solar cells, floating islands, hydroponics-MFC, and paddy field MFC. Thus, simultaneous organic matter degradation, biomass recovery, oxygen release for cathodic reduction, CO2 sequestrations, nutrient removal, and heavy metal removal along with electricity generation can be achieved in PMFC.

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 a 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.

Wastewater generated through various processes can be characterized by chemical composition, physical appearance, and biological activities. Monitoring the quality and concentration of pollutants is a determining parameter for the selection of a suitable wastewater treatment process. Conventional techniques or sensors used for the analysis of water quality parameters are time-consuming, expensive, complicated, rely on an external power source, and have reproducibility issues. Hence, the research community has focused on the application of the self-powered microbial fuel cell (MFC) system as a biosensor for sensing the contaminants from effluent streams. MFC offers online and in-situ measurement of environmental monitoring parameters such as biological oxygen demand, chemical oxygen demand, dissolved oxygen, heavy metals, volatile fatty acid, toxicity detection, gas detection, microbial activities estimation, and can power the external sensors. This chapter overviews the characteristics of biosensors and various applications of MFC-based biosensors for environmental monitoring. Such MFC system offers self-sustained, reliable, and reproducible system as a low-cost solution and warning alarm for shocking load conditions with changes in wastewater properties, and hence can be an effective alternative to the conventional sensors. However, as a bioelectrochemical system, system stability, repetitiveness, and reproducibility of results are some challenges to be overcome for the long-term use of MFC for the biosensing applications.

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 a 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.

Water-energy crisis and wastewater treatment (WWT) issues can be addressed simultaneously in microbial fuel cell (MFC). Being a microbial electrochemical technology, it provides flexible platform for both aerobic and anoxic treatment processes and hence provides efficient WWT solution. Simple substrate to complex industrial wastewater can be effectively treated in such system. Over the advancement in research, MFC is capable to harvest electricity from nW to kW/m³ with use of high redox catalysts and novel electrodes. The output electrical energy is sufficient to operate the different electronic appliances. With biostimulation approach, MFC can be a good option as biosensor to detect the concentration of heavy metals, COD dose, pH. Additionally, MFC attracts attention for by-product recovery during WWT. Valuable products and resources such as struvite from urine, manure, H2O2, NaOH, H2 and methane gas, and other chemicals can be recovered during electrochemical reactions. According to various applications, MFC can be used for carbon capture and sequestration (in microbial carbon capture cells), for desalination of saline water (in microbial desalination cells), for biohydrogen production (in MFC-electrolysis coupled cell), for utilizing sediment as carbon source (in benthic MFC), for sanitation (in bioelectric toilet), and so on. In advance WWT system, MFC can be pre-treatment or post-treatment obtain for efficient WWT. Thus, it can be solution for biological oxidation process and as a tertiary treatment for disinfection, denitrification, aeration to make effluent suitable for discharge. Thus, MFC provides efficient and effective solution for WWT along with electricity and by-product recovery for sustainable development.