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Microbial fuel cells (MFCs) have attracted widespread interest due to their capability to generate power while treating wastewater. In the present investigation, rice mill wastewater (RMW) was treated in a dual-chamber MFC with a biological cathode (MFC

The microbial fuel cell (MFC) is one of the sustainable technologies, which alongside treating wastewater, can generate electricity. However, its performance is limited by factors like methanogenesis where methanogens compete with the anode respiring bacteria for substrate, reducing the power output. Thus, sodium nitrate, which has been previously reported to target the hydrogenotrophic methanogens, was used as a methanogenic suppressor in this study. The performance of MFC with and without sodium nitrate was studied during the treatment of rice mill wastewater. A significantly higher power density and coulombic efficiency (CE) were noted in the MFC with sodium nitrate (MFCT) (271.26 mW/m3) as compared to the control MFC (MFCC) (107.95 mW/m3). Polarization studies showed lower internal resistance for the MFCT (330 Ω) as compared to MFCC (390 Ω). Linear sweep voltammetry and cyclic voltammetry indicated a higher electron discharge on the anode surface due to enhancement of electrogenic activity. Considerable reduction (76.8%) in specific methanogenic activity was also observed in anaerobic sewage sludge mixed with sodium nitrate compared to the activity of anaerobic sewage sludge without any treatment. Due to the inhibition of methanogens, a lower chemical oxygen demand (COD) and phenol removal efficiency were observed in MFCT as compared to MFCC. The COD balance study showed an increase in substrate conversion to electricity despite the increase in nitrate concentration. Therefore, selective inhibition of methanogenesis had been achieved with the addition of sodium nitrate, thus enhancing the power generation by MFCs.

In this study, an acidogenic compartment was attached to a dual-chambered MFC. Rice mill wastewater was acidified in the acidogenic chamber to enhance the biodegradation of complex organics before feeding to MFC. The system was operated under HRT of 12 h (A-MFC12) and 15 h (A-MFC15). The performance of the acidogenic chamber-MFC unit was compared with a conventional dual-chambered MFC (C-MFC15). The maximum total volatile fatty acid (VFA) accumulation was found to be mg 991.21 mg COD/L for A-MFC12, and 560 mg COD/L for A-MFC15, which corresponds to the acidification yield of 78.35 ± 1.19 % and 55.94 ± 1.36 %, respectively. The maximum volumetric power density achieved in A-MFC12 (4.08 ± 0.08 W/m3) was higher than that of A-MFC15 (2.34 ± 0.07 W/m3), and C-MFC15 (2.11 ± 0.04 W/m3). The findings suggest that integrating acidogenic pre-treatment induced a positive effect on bioelectricity generation and substrate removal efficiency of the MFC.

Chloroform is a commonly found solvent in industrial wastewater and is very toxic if present in high concentration. Chloroform degradation in anaerobic processes has been reported earlier and it has also been used as a methanogenesis suppressor in rumen and rice fields. Methanogenesis is undesirable in a microbial fuel cell (MFC) operation, as it results in substrate competition between methanogens and exoelectrogens, thereby reducing the electricity output. Hence, an attempt has been made in this research work to study the effect of chloroform on the performance of MFCs and its effectiveness as methanogenesis suppressor. MFCs with different chloroform dosages in batch as well as continuous mode (0 mM, 8 mM, 16 mM and 22 mM; 0 mM and 22 mM) were operated. High open circuit voltages in batch MFC22 (781 mV) and 53 % higher peak power densities in dosed continuous MFC confirmed its efficiency as a methanogenesis suppressor. Further experimentations showed 74 % lower internal resistance in dosed MFCs. Higher coulombic efficiencies of 31.2 % (MFC22) and 18 % (MFCC22) were noted in dosed reactors than the control reactors (MFC0 – 23.8 % and MFCC0 - 8%). At the end of batches, chloroform concentration was found to be negligible, confirming its degradation in MFC.

Microbial fuel cell (MFC) provides a one-stop solution to wastewater treatment and depletion of existing energy resources. One of the major performance limitations of MFC is pH splitting that results in decreased pH of the anolyte affecting the growth of anaerobes. Hence an attempt was made in this study, to provide a suitable pH-controlled environment for microorganisms by recirculating the wastewater fed to the anode chamber. Four MFCs were fabricated allowing anolyte recirculation with different anolyte pH, viz, MFC-1 (pH 5, R.R. 1:2), MFC-2 (pH 5, R.R. 0), MFC-3 (pH 9, R.R. 1:2) and MFC-4 (pH 9, R.R. 0), where R.R. is recirculation ratio. MFC-3 and MFC-4 showed higher power generation and organics removal in comparison to MFC-1 and MFC-2. Anolyte recirculation in combination with alkaline pH improved the overall performance of the MFCs because of better substrate availability and suitable growth conditions provided to the microorganisms.

In this study, simultaneous nitrification and denitrification-sequencing batch reactor (SND-SBR) process was investigated to treat greywater. The effect of three process parameters, including hydraulic retention time (HRT), volumetric exchange ratio (VER) and sludge retention time (SRT), was optimised using a 2

A study was conducted to introduce an efficient alternative such as bioelectrochemical degradation of pharmaceuticals. Six earthen pot MFCs were operated in batch mode, in which the pharma...

Lignin, the second-most abundant plant/lignocellulosic biomass component, is a polymer of phenolic monomers embedded within polysaccharide polymers forming the cell wall. Lignin provides rigidity to plants and protection from pathogenic attack and has significant potential as a bioresource; however, it is recalcitrant toward degradation. Lignin can be degraded in nature through two stages: depolymerization and mineralization. Microbial enzymes related to lignin depolymerization could be an enticing tool for biomass pretreatment whereas, the enzymes involved in mineralization are important for the lignin valorization by generating value-added byproducts (vanillin, dicarboxylic acids, and polyhydroxyalkanoates). This chapter summarizes the latest work on fungal and bacterial lignin degradation, emphasizing enzymes involved, and factors responsible for their regulation. Stimulatory components such as minerals, low molecular weight phenolic compounds, and nutrient balance (C/N ratio) can directly influence the production of ligninolytic enzymes. Furthermore, the current barriers to lignin degradation are examined, and alternative strategies are presented for future research.

An innovative design approach was employed in the present study to enhance the electricity generation and wastewater treatment in a microbial fuel cell (MFC). A dual-chambered MFC with a ceramic separator was coupled with an acidogenic chamber. Acidogenic bioconversion of rice mill wastewater into volatile fatty acid (VFA) represents an interesting approach for wastewater valorization. The VFA containing effluent could be used as an effective substrate for bioelectricity generation in MFCs. A short hydraulic retention time (HRT) can be used for the two-stage anaerobic process (acidogenesis and electrogenesis), thus preventing the proliferation of methanogens. The effect of pH (5.5–7.5) and HRT (0.5 d–0.75 d) were investigated to understand the influence of operational parameters on the performance of the integrated system. The maximum VFA concentration of 1065.15 ± 5.08 mg COD/L was achieved at pH 7.5 and HRT 0.5 d. Under these operating conditions, the general activity of acid-forming microorganisms and exoelectrogens improved remarkably, and the power density obtained from the system was 4.72 ± 0.10 W/m3. The current research indicates excellent potential for simultaneous treatment and electricity production from rice mill wastewater. The use of low-cost, locally manufactured, and customized membranes and the two-stage treatment can pave the way for the practical application of this technology.

This study assessed the groundwater vulnerability of the Rana groundwater basin, Odisha, India. The study attempts to optimize the DRASTIC method by modifying the weights and ratings assig...

The present study investigated the solar photocatalytic treatment of greywater using modified TiO2 catalysts, viz., M-TiO2, U–TiO2, NP-TiO2, and NT-TiO2 synthesized through ultrasonication, microwave, and sol-gel method with/without doping respectively. X-ray dispersive spectroscopy (XRD) results indicated a negligible change in the crystallinity of the modified catalysts compared to commercial TiO2 catalyst, Degussa P-25 (P-25). Scanning electron microscopy (SEM) analysis depicted the lowest particle size of 88.89 nm for U–TiO2. The calculated band gap energy for P-25, U–TiO2, M-TiO2, NP-TiO2, and NT-TiO2 were 3.65, 3.1, 3.5, 3.35, and 2.7 eV, respectively. The mineralization efficiency was in the order of NT-TiO2>U–TiO2>NP-TiO2∼M-TiO2>P-25, with the highest mineralization efficiency of about 75% within 3 h using NT-TiO2. The nitrate removal was in the order of NT-TiO2>U–TiO2∼NP-TiO2>M-TiO2>P-25, with the nitrate removal of 92.5%. Simultaneous oxidation of organic matter and reduction of ammonia were observed during the solar photocatalytic treatment of greywater. The comparison of sunlight NT-TiO2system with other photocatalytic treatment employed for greywater reveals that the NT-TiO2 system was highly energy efficient (∼31.86 kWh (kgCOD)−1) compared to other systems.

Circular bioeconomy aims at strengthening the resource efficiency by recycling materials that substitute fossil by the carbon present in biomass to obtain sustainable neutral energy as well as chemical sources. The concept of utilization of biomass as a source of renewable energy and other commercially important products is very much overlapping with the concept of circular economy and this intersection of circular economy and bioeconomy can be termed as circular bioeconomy. These biomass resources can be classified into agricultural residue, forest biomass, energy crops, algal biomass, and urban waste. Their conversion to biofuels and chemicals can be accomplished through different thermochemical, physiological, and biological pathways. While thermochemical processes involve the application of high temperature, physicochemical and biological processes employ chemicals and microorganisms, respectively, to obtain value-added products. The bioproducts produced are classified into four generations depending based on the source. The most commonly derived biofuels and chemicals are syngas, bioethanol, bio-oil, hydrogen, etc. However, the cost related to the biomass collection, segregation, transportation, and storage is still a concern. But, with reform in the biomass management system and forming laws encouraging the re-utilization of generated waste, the concept of circular bioeconomy can be implemented to address the issues of climate change, environmental pollution, and fossil fuel depletion. Comparative evaluation of large-scale projects is necessary to identify the best available technology for biofuel production. Furthermore, the existing sustainability issues of the biomass supply chain should be addressed to ensure all-year-round delivery of feedstock to the conversion facility. A robust business model would attract investors and accelerate the commercialization of biomass-derived biofuel.

Nutrient removal and recovery have gained much attention to achieve pollution control and sustainable resource management. Bioelectrochemical systems (BESs) have been extensively explored for the recovery of energy, metals, and intermediate chemicals, and lately, research has focused on the recovery of valuable nutrients. It can avoid the complex and energy-intensive nutrient removal process in downstream wastewater treatment facilities. Nitrogen removal and/or recovery in BES can be achieved via nitrification and cathodic denitrification, anaerobic ammonium oxidation process, and ammonia transport across the membrane. Simultaneous nitrogen and phosphorous recovery can occur via struvite precipitation, electromigration and concentration, and algal uptake. This chapter summarizes the basic principles of nutrient removal and recovery from various waste streams in BES, the influential factors, and the key issues to be addressed in further research. Future development and industrialization of the BES can establish a nexus between nutrient, energy, and water recovery.

The global municipal solid waste (MSW) generation rate is 0.74 kg/capita/day, with an estimated annual waste generated to be 2.0 billion tonnes. It is poised to increase up to 3.4 billion tonnes by 2050 (Kaza et al., 2018). The composition of waste broadly comprises biodegradable and non-biodegradable fractions that depend on regional geography, economy, climate, lifestyle, social awareness and regulations. The biodegradable fraction majorly contributes between 40% and 50%, across the globe, dominated by kitchen waste, i.e., food, fruits and vegetables (Gerlagh et al., 1999; Futures, 2009; Yap and Nixon, 2015; Kaza et al., 2018). Fundamentally, these components are made up of carbohydrates, fats, proteins, lipids, inorganic salts and trace elements that led to a 40–70% bioenergy conversion efficiency (Ma et al., 2018). This high energy potential can be recovered by disintegrating waste into simpler compounds by anaerobic digestion (AD). The AD comprises hydrolysis, acidogenesis, acetogenesis and methanogenesis. It is considered as an effective technique to treat high moisture content waste (McKendry, 2002). Conventionally, the energy potential of organic waste has been used to obtain biogas and manure. The main component of biogas is methane (a GHG), posing a high risk to the environment. Also, the treatment of high moisture waste in thermal technologies reduces combustion efficiency drastically. Therefore, obtaining valuable products having a high commercial value such as ethanol, hydrogen, electricity and chemicals, broadens the waste to energy (WTE) concept.

The increasing water demand has been one of the major global issues for the past decades. An enormous amount of potable water is required for household, industrial and agricultural activities, which led the water authorities to look-out for suitable alternatives. Treated greywater reuse and recycling is an economically viable and attractive option for meeting a portion of future water demand. The feasibility of a continuous mode solar photocatalytic system in greywater treatment was explored in this study. The solar photocatalytic tests were employed with graphite-supported nitrogen-doped titanium dioxide (N-TiO2). The effect of flow rate (20–70 mL/min) was investigated under pH-3, H2O2 dosage-1 g/L, catalyst dosage-5 g/L in a continuous reactor. These tests revealed that the maximum removal efficiency in terms of COD, TOC and NH4-N was accomplished at 20 mL/min, while the lowest removal efficiencies were found at 70 mL/min. The removal efficiencies of COD, TOC, and NH4-N were progressively reduced from a flow rate of 20 to 50 mL/min, followed by a sharp drop at a flow rate of 70 mL/min. The reactor operation at the lowest flowrate i.e. 20 mL/min showed the removal efficiencies of 71.8, 65.1 and 63.7% for COD, TOC and NH4-N, respectively. The result showed that a solar photocatalytic system with GT-NTiO2 could be effectively used for greywater treatment under continuous mode operation.

Global industrialization has led to an alarming level of release of hazardous and toxic metals in water bodies. Disposal of wastewater containing heavy metals can have adverse impacts on h...

The review discusses the transformation of waste to energy (WTE) through bioelectrochemical systems (BESs) treating organic waste, which makes up 47% of the total municipal solid waste gen...

The release of untreated or partially treated pharmaceutical wastewater into water bodies has become a serious concern these days as the drugs and their intermediates present affect living...

In the last couple of decades, microbial fuel cells (MFCs) have gained importance because of its ability to generate electricity from renewable and carbon-neutral energy sources, such as w...

Microbial fuel cell (MFC), one of the emerging topics of research, suffers from two chief limitations, low power generation and high cost of reactor materials. These problems limit its possibility of field scale implementation and commercialization. Hence, an attempt has been made in this study to highlight the utilization of lost cost ceramic material modified with mineral cation exchanger with various concentrations (10–50%) as separator along with studying the role of thickness and surface area in improving the overall performance of an MFC. The performance of the membranes with different thickness and kaolin concentrations was studied based on their proton exchange, ion transfer and oxygen diffusion capabilities. While, proton transfer coefficient was found to be highest in membrane of thickness 4 mm containing 30% kaolin, oxygen transfer coefficient was found to be lowest in the membrane of thickness 6 mm containing 50% kaolin. Thus, MFCs of optimised parameters with concentric anode chamber made with ceramic material were used to study the effect of membrane surface area on their performances. MFC with the highest membrane surface area showed highest power density, highest organics removal efficiency and least internal resistance. Thus, it was concluded from the results that high membrane surface area increases the performance efficiency of the MFCs by maintaining proper proton concentration on both side of the membranes. The results thus highlight the importance of a membrane in an MFC and how the presence of a cation exchanger can enhance the electricity generation.

Implementing biomaterials instead of synthetic materials and non-renewable resources that lead to pollution is becoming popular. These biomaterials are naturally derived polymers from plants and microbes and are termed as biopolymers. Their production can be carried out by utilizing food processing industries, lignocellulosic and organic fraction of municipal wastes, thereby developing a clean waste management system. This chapter mainly discusses the types of biopolymers such as polyhydroxyalkanoates, xylooligosaccharides, lipid wax, exopolysaccharides, and succinic acid, to be obtained from eco-friendly bio-chemical processes carried out in biorefineries. However, strict and enriched conditions are required for producing biopolymers. Therefore, a detailed discussion on the effect of various operating parameters and their range that can be used to maximize biopolymer yield is also included. Biopolymers have been used in numerous fields’ especially biomedics, pharmaceutical, and food packaging industries. The chapter gives an overview of biopolymer production and challenges faced in developing large scale production unit that will enable biopolymer as a product of circular economy.

Pharmaceutical wastewater (PW), owing to its complex and varied composition, is recalcitrant in nature. Thus treatment of PW requires a technology that can degrade not only organics but also the complex drug molecules. Antibiotics are one of the chief components of PW, which if released untreated into the water bodies, will heavily affect the aquatic life, and create antibiotic resistant microorganisms. While the conventional treatment techniques are expensive, microbial fuel cells (MFCs) are an inexpensive energy generating technology. The dual oxidative/reductive environment of MFCs allows the degradation of a wide range of compounds, while modifying operating conditions or electrode materials such as composition of anolyte, anode catalyst, preacclimation of biocatalyst, physicochemical pretreatment, and electric stimulation can further increase the degradability of real PW in MFCs. Thus MFCs can prove to be a promising technology by degrading trace organic material such as pharmaceuticals removal and generating simultaneous renewable energy.

Microbial fuel cells (MFCs) are gaining much attention in recent years because they produce energy in the form of electricity, while simultaneously treating wastewater. In this study, the organic compounds obtained from the pretreatment of kitchen waste were used as a substrate in MFC. In order to enhance the rate of hydrolysis, parameters such as pH, solid-to-liquid ratio, and solid retention time under anaerobic conditions were studied and optimized. Two MFCs (1 and 2) having earthen separators and an anode volume of 450 mL and 630 mL, were employed, respectively. The maximum power density for MFC-1 and MFC-2 was 0.040 W/m2 and 0.044 W/m2 and maximum volumetric power density of 3.80 W/m3 and 3.40 W/m3 were, respectively obtained for a hydraulic retention time of 10 days. The study concludes that earthenware as a cation exchange membrane and kitchen waste as an anolyte were found effective for power generation.

Pseudomonas aeruginosa is a gram-negative bacterial specie well-known for pyocyanin production, which is a naturally produced mediator responsible for enhanced extracellular electron transport. However, pyocyanin production requires the presence of oxygen. Thus, in the present study, an approach of intermittent aeration was investigated to enhance pyocyanin production by P. aeruginosa, which was used for bioaugmentation of microbial fuel cells (MFCs). Two MFCs were augmented by seeding anaerobic sludge inoculum with P. aeruginosa (MFCP) and the performance was compared with a control MFC seeded with mixed anaerobic sludge (MFCC). One of the bioaugmented MFCs was intermittently aerated (MFCP+A) and was noted to produce more electricity than the MFCP (without aeration. MFCP+A generated 4% and 31% more power than MFCP and MFCC, respectively. The organic degradation efficiency was found to be higher in the MFCC denoting suppression of competitive microbial communities channelizing more electrons towards electricity generation in bioaugmented MFCs. Overall, MFCP+A showed a coulombic efficiency of 10.4%, followed by MFCP (9.7%) and MFCC (4.41%). Hence, the approach of intermittent aeration has proved to be feasible way of improving mediator production and enhancement in generation of electricity.

Ceramic membranes have been widely used as an affordable cation exchange membrane in microbial fuel cells (MFCs). This study deals with the fabrication of low-cost ceramic membranes by blending rice husk ash (RHA) with soil for its application in MFCs. Ceramic membrane having 10% RHA exhibited higher proton mass transfer and lower oxygen diffusion. The presence of silica in RHA enhanced the hydration properties of the membrane and aided proton mobility form anode to cathode chamber. Performance of the MFCs using modified (with RHA, MFCT) and unmodified (without RHA, MFCC) membrane was evaluated for the treatment of rice mill wastewater under continuous mode operation. The maximum volumetric power densities were 2.14 W mˉ3 and 1.33 W mˉ3, and COD removal efficiencies were 70.7 ± 1.24% and 63.8 ± 1.08% for MFCT and MFCC, respectively. Form the electrochemical impedance spectroscopy (EIS) study, ohmic resistance (RΩ) of MFCC and MFCT was found to be 91.3 Ω and 47.1 Ω, respectively. The RHA composite membrane displayed less tendency of membrane fouling, making it more favorable for long-term operation. This study reveals that the RHA composite membrane could serve as a suitable alternative to expensive polymeric membranes in MFC with higher power performance and minimum oxygen diffusion.