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Researchers are still trying to achieve desirable results while treating actual wastewater at the field size when scaling up a microbial fuel cell (MFC). This pilot-scale project aimed to create a decentralised system for treating domestic wastewater and concurrent energy generation that may be used as a model for the decentralisation process. In this investigation, a cylindrical-shaped earthen membrane was utilized. The arrangement was deployed on-site at a residence for the treatment of domestic wastewater as well as simultaneous generation of power. From August until November 2021, the 36 L pilot-scale setup was operational for a period of 92 days. The setup's performance was affected by seasonal temperature variations during the operation period. The system's performance was measured in terms of COD, nitrate, and NH

Astaxanthin (3,3-dihydroxy-β, β-carotene-4,4-dione) is a ketocarotenoid synthesized by Haematococcus pluvialis/lacustris, Chromochloris zofingiensis, Chlorococcum, Bracteacoccus aggregatus, Coelastrella rubescence, Phaffia rhodozyma, some bacteria (Paracoccus carotinifaciens), yeasts, and lobsters, among others However, it is majorly synthesized by Haematococcus lacustris alone (about 4%). The richness of natural astaxanthin over synthetic astaxanthin has drawn the attention of industrialists to cultivate and extract it via two stage cultivation process. However, the cultivation in photobioreactors is expensive, and converting it in soluble form so that it can be easily assimilated by our digestive system requires downstream processing techniques which are not cost-effective. This has made the cost of astaxanthin expensive, prompting pharmaceutical and nutraceutical companies to switch over to synthetic astaxanthin. This review discusses the chemical character of astaxanthin, more inexpensive cultivating techniques, and its bioavailability. Additionally, the antioxidant character of this microalgal product against many diseases is discussed, which can make this natural compound an excellent drug to minimize inflammation and its consequences.

Bioelectrochemical hydrogen production via microbial electrolysis cells (MECs) has attracted attention as the next generation of technology for the hydrogen economy. MECs work by electrochemically active bacteria reducing organic compounds at the anode. However, the hydrophobic nature of carbon-based anodes suppresses the release of the produced gas and water penetration, which significantly reduces the possibility of microbial attachment. Consequently, a limited surface area of the anode is used, which decreases hydrogen production efficiency. In this study, the bifunctional material poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) was applied to the surface of a three-dimensional carbon felt anode to enhance the hydrogen production efficiency of an MEC owing to the high conductivity of PEDOT and super-hydrophilicity of PSS. In experiments, the PEDOT:PSS-modified anode almost doubled the hydrogen production efficiency of the MEC compared with the control anode owing to the increased capacitance current (239.3 %) and biofilm formation (220.7 %). The modified anode reduced the time required for the MEC to reach a steady state of hydrogen production by 14 days compared to the control anode. Microbial community profiles demonstrated that the modified anode had a greater abundance of electrochemically active bacteria than the control anode. This simple method could be widely applied to various bioelectrochemical systems (e.g., microbial fuel cells and solar cells) and to scaling up MECs.

Methyl red, a synthetic azo dye, was reported for not only being mutagenic but also its persistence has severe consequences on human health, such as cancer, alongside detrimental environmental effects. In the present study, the Pseudomonas putida OsEnB_HZB_G20 strain was isolated from the soil sample to study the catalytic activity for the degradation of methyl red dye. Another isolated strain, the Pseudomonas aeruginosa PA 1_NCHU strain was used as an electroactive anodophile and mixed with the Pseudomonas putida OsEnB_HZB_G20 strain to see the effect of co-culturing on the power generation in single-chambered microbial fuel cells (MFCs). The Pseudomonas putida OsEnB_HZB_G20 and Pseudomonas aeruginosa PA 1_NCHU strains were used as co-culture inoculum in a 1:1 ratio in MFCs. This work uses isolated bacterial strains in a co-culture to treat wastewater with varying methyl red dye concentrations and anolyte pH to investigate its effect on power output in MFCs. This co-culture produced up to 7.3 W/m3 of power density with a 250 mgL−1 of dye concentration, along with 95% decolorization, indicating that the symbiotic relationship between these bacteria resulted in improved MFC performance simultaneous to dye degradation. Furthermore, the co-culture of Pseudomonas putida and Pseudomonas aeruginosa in a 1:1 ratio demonstrated improved power generation in MFCs at an optimized pH of 7.

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/resource 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.

Membrane cost, long-term stability, and sustainability are major concerns when selecting membranes in mi-crobial fuel cells (MFCs) for scaling-up applications. In recent years, efforts have been made to improve reactor architectural designs and to explore ceramic membrane materials, aiming to achieve techno-economical sus-tainability and efficiency. Furthermore, ceramics have recently emerged as low-cost separators, electrodes, and chassis materials for MFC applications. The introduction of cation exchange minerals into ceramic membranes promotes high proton transfer with improved membrane characteristics. High cationic transfer, proton exchange rate, stability against thermochemical conditions, structural strength to withstand high hydraulic load, and long-term stability with easy biofouling mitigation support the utilization of such membranes for scaling-up use. Successful field trials of Pee-power MFC, stacked urinal MFC, bioelectric toilet, and others showed the feasibility of ceramic membranes for practical applications. Therefore, this review emphasized the membrane character-istics, substantial effect of mineral additives, scaling-up applications, recent developments, and perspectives toward the practical utilization of MFC-based ceramic membranes.

Microbial fuel cell (MFC) would be a standalone solution for clean, sustainable energy and rural electrification. It can be used in addition to wastewater treatment for bioelectricity generation. Materials chosen for the membrane and electrodes are of low cost with suitable conducting ions and electrical properties. The prime objective of the present work is to enhance redox reactions by using novel and low-cost cathode catalysts synthesized from waste castor oil. Synthesized graphene has been used as an anode, castor oil-emitted carbon powder serves as a cathode, and clay material acts as a membrane. Three single-chambered MFC modules developed were used in the current study, and continuous readings were recorded. The maximum voltage achieved was 0.36 V for a 100 mL mixture of domestic wastewater and cow dung for an anodic chamber of 200 mL. The maximum power density obtained was 7280 mW/m2. In addition, a performance test was evaluated for another MFC with inoculums slurry, and a maximum voltage of 0.78 V and power density of 34.4093 mW/m2 with an anodic chamber of 50 mL was reported. The present study’s findings show that such cathode catalysts can be a suitable option for practical applications of microbial fuel cells.

This chapter contains sections titled: Introduction -- Fundamentals of SMFC and CW‐MFC -- Factors Affecting the Performance of SMFC and CW‐MFC -- Electricity Generation as a Function of Substrate Degradation -- Applications of SMFC and CW‐MFC -- Scaling Up of SMFC and CW‐MFC -- Conclusion

Constructed wetlands (CWs) have gained a lot of attention for wastewater treatment due to robustness and natural pollutant mitigation characteristics. This widely acknowledged technology possesses enough merits to derive direct electricity in collaboration with microbial fuel cell (MFC), thus taking advantage of microbial metabolic activities in the anoxic zone of CWs. In the present study, two identical lab-scale CWs were selected, each having 56 L capacity. One of the CW integrated with MFC (CW-MFC) contains two pairs of electrodes, i.e., carbon felt and graphite plate. The first pair of CW-MFC consists of a carbon felt cathode with a graphite plate anode, and the second pair contains a graphite plate cathode with a carbon felt anode. The other CW was not integrated with MFC and operated as a traditional CW for evaluating the performance. CW-MFC and CW were operated in continuous up-flow mode with a hydraulic retention time of 3 days and at different organic loading rates (OLRs) per unit surface area, such as 1.45 g m

Highlights • Electron transfer mechanism elaborated for various fungal species. • Application of fungi as a cathode and anode catalyst is discussed. • Different factors affecting on performance of fungi based MES are reviewed. • Fungi are classified based on their electron transfer mechanism., Microbial fuel cells (MFCs) that generate bioelectricity from biodegradable waste have received considerable attention from biologists. Fungi play a significant role as both anodic and cathodic catalysts in MFCs. Saccharomyces cerevisiae is a fungus with an ability to transfer electrons through mediators such as methylene blue (MB), neutral red (NR) or even without a mediator. This unique role of fungal cells in exocellular electron transfer (EET) and their interactions with electrodes hold a lot of promise in areas such as wastewater treatment where yeast cell-based MFCs can be used. The present article highlights the physico-chemical factors affecting the performance of fungal-mediated MFCs in terms of power output and degradation of organic pollutants, along with the challenges associated with fungal MFCs. In addition, to this comparative assessment of fungal-mediated bio-electrochemical systems, their development, possible applications and potential challenges are also discussed., Graphical abstract Image, graphical abstract

Microbial electrosynthesis (MES) has emerged out with immense potential as by means of microorganisms, we now can, not only produce a variety of chemicals and fuels sustainably but also accelerate or enhance bioremediation. Microbial electrolysis cells and the microbial fuel cells (MFCs) are obvious in this particular context as they mutually utilize microorganisms so as to oxidize inorganic and/or organic matter at the anode and create electrical power and/or H2, correspondingly. The revelation that metabolism in microorganisms could also be run with the help of electrical current has freshly directed to a surfeit of supplementary applications in the production of biochemicals as well as biofuels which are thought to be extremely electron exhaustive. Remarkably, the microbial production of certain biochemicals, termed MES, provides a highly enticing, novel track for the generation of beneficial goods from electricity and/ or even wastewater. This review addresses the principles of this process, challenges faced by this process at present and its possibility in the future, and opportunities that the process has promised to bring in the near future of MES. This review, in the end, proposes a side-by-side comparison between carbon dioxide and organic substrate, and glucose and electricity as a source of reducing power correspondingly.

Waste is the refuse generated by almost every human activity that gets worse when dissolved in water. Wastewater has a considerable amount of complex biological and chemical materials that can cause serious safety, sanitation, and environmental problems. However, these complex biological and chemical materials of wastewater also encourage the growth of countless microbial flora that can survive even in extreme environments. The development of a pathway to generate electricity from this microbial flora’s ability to degrade these biological and chemical materials is the driving force for the development of microbial fuel cells (MFCs). MFCs are bioelectrochemical systems that convert the chemical energy of wastewaters into electrical energy by metabolic (catalytic) activity of microorganisms. This chapter discusses the wastewater treatment potentials of MFCs.

This chapter is focused on the preparation of low-cost and effective electrode materials which may facilitate the Volmer step of hydrogen evolution reaction to produce more hydrogen through a microbial electrolysis cell (MEC). Simultaneously the solid e-waste management for a better environmental scenario and wastewater treatment through the same MEC could be addressed. In most of the MECs, various operating parameters govern the performance in terms of rate of hydrogen evolution. The threat for e-waste generation has been alarming due to the inefficient reuse and recycle process. It has resulted in very crucial environmental problems and disposal issues. To overcome this problem, investigations into e-waste generated activated carbon with nitrogen doping for effective electrode material has been outlined, along with its use in MEC as an electrode material. Moreover, the wastewater containing organic waste will be the source for the hydrogen, thus resulting in simultaneous wastewater treatment and energy recovery through the proposed cost-effective MEC with e-waste utilization, as well as the production of the source of clean energy.

Heavy metals removal and recovery from wastewater is a sustainable approach for wastewater treatment and environmental sustainability. This is also helpful to meet the strict effluent discharge norms. Acknowledging that wastewater presents a useful resource and the value of precious, semiprecious, and heavy metals has made it interesting to recover metals from wastewater. This chapter describes the sources, importance, and toxicity of heavy metals and the need to remove them before discharging effluents. The popular physical and chemical technologies, such as isolation, immobilization, toxicity and/or mobility reduction, physical separation, and extraction, used for the removal of heavy metals have been discussed along with their limitations. Finally, the configuration and application of bioelectrochemical systems (BES)-based systems present a sustainable alternative for the removal and recovery of heavy metals. Therefore in this chapter a general account of the process, principle, and BES that have been used for heavy metal removal and recovery has been covered.

Metals are extensively used by many industries such as real estate, mining, construction, and transport. These heavy metals are detrimental to the environment as most of the heavy metals are carcinogenic. Without treatment of heavy metal-containing wastewater, these may accumulate in the fishes and other aquatic flora and fauna. Upon human consumption of those fishes, it may cause carcinogenic or mutagenic conditions such as skin irritation, allergies, or dermatitis. Adsorption and other existing waste treatment technologies are unable to remove heavy metals efficiently. Conventional remediation techniques are expensive and not eco-friendly. Microbial fuel cell (MFC) is a promising technology where electroactive bacteria can be used for removal of heavy metals with simultaneous electricity generation. Heavy metals can be removed via bioelectrochemical reduction at cathode chamber using the reduction capabilities of bacteria. This chapter highlighted the principle of MFCs for heavy metal removal, microbes associated with heavy metal reduction, catabolic pathway responsible for microbial oxidation of substrate, and heavy metal reduction. The different types of heavy metals, their structure, and effects along with the advantages and disadvantages of the heavy metals removal methods of MFC compared to other existing methods. This chapter discussed different case studies for heavy metal removal from groundwater using MFCs, the factors affecting metal recovery, and challenges in MFC operation during metal reduction at the cathode. The present chapter will help the readers to understand the fundamentals of microbial electrochemical heavy metal recovery.

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.

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.

An increase in urbanization and industrialization has not only contributed to an improvement in the lifestyle of people, but it has also contributed to a surge in the generation of wastewater. To date, conventional physico-chemical and biological treatment methods are widely used for the treatment of wastewater. However, the efficient operation of these systems require substantial operation and maintenance costs, and the application of novel technologies for the treatment and disposal of sludge/residues. This review paper focuses on the application of different treatment options such as chemical, catalyst-based, thermochemical and biological processes for wastewater or sludge treatment and membrane-based technologies (i.e. pressure-driven and non-pressure driven) for the separation of the recovered products from wastewater and its residues. As evident from the literature, a wide variety of treatment and resource recovery options are possible, both from wastewater and its residues; however, the lack of planning and selecting the most appropriate design (treatment train) to scale up from pilot to the field scale has limited its practical application. The economic feasibility of the selected technologies was critically analyzed and the future research prospects of resource recovery from wastewater have been outlined in this review.

Performance of clayware Biophotovoltaics (BPVs) with three variants of inocula namely anoxygenic photosynthetic bacteria (APB) rich Effective microbes (EM), Up-flow anaerobic sludge blanket reactor (UASB) sludge, SUPER-MIX the blend of EM and UASB inoculum were evaluated on the basis of electrical output and pollutant removal. SUPER-MIX inocula with microbial community comprising of 28.42% APB and 71.58% of other microbes resulted in peak power density of 275 mW/m2, 69.3 ± 1.74% Coulombic efficiency and 91 ± 3.96% organic matter removal. The higher performance of the SUPER-MIX than EM and UASB inocula was due to the syntrophic associations of the various APBs and other heterogenous microorganisms in perfect blend which improved biocatalytic electron transfer, electro-kinetic activities with higher redox current and bio-capacitance. The promising performance of clayware BPVs with SUPER-MIX inocula indicate the possibility of BPVs to move towards the scale-up process to minimize the investment towards pure culture by effective blending strategies of inocula.

Electro-fermentation (EF) is an upcoming technology that can control the metabolism of exoelectrogenic bacteria (i.e., bacteria that transfer electrons using an extracellular mechanism). The fermenter consists of electrodes that act as sink and source for the production and movement of electrons and protons, thus generating electricity and producing valuable products. The conventional process of fermentation has several drawbacks that restrict their application and economic viability. Additionally, metabolic reactions taking place in traditional fermenters are often redox imbalanced. Almost all metabolic pathways and microbial strains have been studied, and EF can electrochemically control this. The process of EF can be used to optimize metabolic processes taking place in the fermenter by controlling the redox and pH imbalances and by stimulating carbon chain elongation or breakdown to improve the overall biomass yield and support the production of a specific product. This review briefly discusses microbe-electrode interactions, electro-fermenter designs, mixed-culture EF, and pure culture EF in industrial applications, electro methanogenesis, and the various products that could be hence generated using this process.

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.

Microbial fuel cells (MFC) is an emergent source of renewable energy technology, where the microbes are incorporated in an electrochemical system with organic loads, for controlled production of electricity from wastewater due to the catalytic action of anode respiring microbes under the anaerobic condition. Considering the redox potential of electrochemical reactions, MFC with oxygen as terminal electron acceptor is capable to produce the potential of 1.2 V theoretically However, in real practice, the obtained voltage from MFC is too low s(500–650 mV) due to various electrochemical losses encountered in the MFC, which further affects the power density. The state of the art review focused in this chapter is on the electrochemical losses related hurdles and its role in power generation in the MFCs, which is limiting this technology to be adopted widely and considerably efficient. Though the power production from MFC is being impelled by various governing aspects such as the selection of microbial strains, substrate conditions, electrodes materials, and operating conditions, researchers have attempted various studies to overcome the electrochemical losses thus making MFCs ideal for real-time applications.

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.