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In the process of flue gas desulfurization and denitrification, the generation of high-sulfate wastewater containing nitrogen is a significant challenge for biological wastewater treatment. In this study, halophilic activated sludge was inoculated in a Sequencing Batch Reactor to remove nitrogen from wastewater with a high sulfate concentration (60 g/L). With the influent concentration of 180 mg/L, the removal rate of total nitrogen was more than 96.7%. The effluent ammonium nitrogen concentration was lower than 1.94 mg/L, and the effluent nitrate nitrogen and nitrite nitrogen concentrations were even lower than 0.77 mg/L. The salt tolerance of activated sludge is mainly related to the increase in the content of ectoine in microbial cells. The Specific Nitrite Oxidation Rate is quite low, while the Specific Nitrite Reduction Rate and Specific Nitrate Reduction Rate are relatively strong. In the system, there are various nitrogen metabolic processes, including aerobic nitrification, anaerobic denitrification, and simultaneous nitrification–denitrification processes. By analyzing the nitrogen metabolic mechanisms and microbial community structure of the reaction system, dominate bacteria can be identified, such as Azoarcus, Thauera, and Halomonas, which have significant nitrogen removal capabilities. [ABSTRACT FROM AUTHOR]

Microbial electrolysis cell (MEC) is gaining importance not only for effectively treating wastewater but also for producing hydrogen. The up‐flow microbial electrolysis cell (UPMEC) is an innovative approach to enhance the efficiency, and substrate degradation. In this study, a baffled UPMEC with an anode divided into three regions by inserting the baffle (sieve) plates at varying distances from the cathode was designed. The effect of process parameters, such as flow rate (10, 15, and 20 mL/min), electrode area (50, 100, and 150 cm2), and catholyte buffer concentration (50, 100, and 150 mM) were investigated using distillery wastewater as substrate. The experimental results showed a maximum of 0.6837 ± 0.02 mmol/L biohydrogen at 150 mM buffer, with 49 ± 1.0% COD reduction using an electrode of area 150 cm2. The maximum current density was 1335.94 mA/m2 for the flow rate of 15 mL/min and surface area of 150 cm2. The results showed that at optimized flow rate and buffer concentration, maximum hydrogen production and effective treatment of wastewater were achieved in the baffled UPMEC. Practitioner Points: Biohydrogen production from distillery wastewater was investigated in a baffled UPMEC.Flowrate, concentration and electrode areas significantly influenced the hydrogen production.Maximum hydrogen (0.6837±0.02mmol/L.day) production and COD reduction (49±1.0%) was achieved at 15 mL/min.Highest CHR of 95.37±1.9 % and OHR of 4.6±0.09 % was observed at 150 mM buffer concentration. [ABSTRACT FROM AUTHOR]

This study aims to improve the performance of microbial desalination cell (MDC) using Vigna mungo (Black gram) wash water, reported for the first time as an anolyte utilizing a graphite plate and carbon brush as the anode. Power generation was facilitated by the exoelectrogen, Shewanella putrefaciens MTCC 8104. Polarization studies revealed that the graphite plate MDC attained a high power density of 2720 ± 50 μW/m2 compared to carbon brush for two electrode pairs. The COD removal and desalination efficiency were better for carbon brush MDC, achieving 58.17 ± 2% and 38.14 ± 2% removal, respectively. Power production can be enhanced by increasing the cathode's ability to accept the electrons, reducing the ageing of biofilm and promoting complete oxidation of the substrates. Upon improving its performance, MDC can act as a sustainable technology, collaborating with industries seeking solutions for wastewater treatment, energy generation and agricultural sectors on a large scale. Highlights: MDC integrates wastewater treatment, power generation and desalination.Vigna mungo wash water was reported for the first time as an anolyte in MDC.Graphite plate showcases a better power density, 2720 ± 50 μW/m2.Carbon brush establishes better COD removal and desalination efficiency. [ABSTRACT FROM AUTHOR]

In recent years, research on Microbial Electrolytic Cell (MEC) systems, such as wastewater treatment, has shown growing potential. The present research work is based on a study of water purification potential, microbial sustainability, and electrochemical characterization of a two-chambered MEC system, with Aluminium-PANI (Polyaniline) -graphene-oxide based electrode and salt-bridge based proton exchange membrane (PEM)., using the process parameters, optimized for corresponding MFC system. The present research indicates the purification of rice mill wastewater with a MEC-based treatment system with controlled voltage drop (<0.8 Volt) and augmented active microbial activity, as supported by the spectroscopic, biochemical, and carbon-dioxide emission profile assessment. [ABSTRACT FROM AUTHOR]

Aerobic granules are small, dense aggregates of microbial cells that form naturally in aerobic wastewater treatment systems. They are characterized by their spherical shape, strong structural integrity, and ability to rapidly settle. These granules are formed through a self-immobilization process where different microbial species coalesce to degrade organic and inorganic compounds in wastewater. This study summarizes the development of aerobic granulation technology in wastewater treatment and the mechanism of aerobic granules' formation, analyzes the characteristics and the factors affecting the aerobic granules' formation, and presents practical engineering examples of its application from pilot-scale to full-scale operation. [ABSTRACT FROM AUTHOR]

In this study, nickel–cobalt co-modified stainless steel mesh (Ni-Co@SSM) was prepared and used as the biocathode in microbial electrolysis cell (MEC) for sulfamethazine (SMT) degradation. The optimal electrochemical performance of the Ni-Co@SSM was obtained at the electrodeposition time of 600 s, electrodeposition current density of 20 mA cm−2, and nickel–cobalt molar ratio of 1:2. The removal of SMT in MEC with the Ni-Co@SSM biocathode (MEC-Ni-Co@SSM) was 82%, which increased by 30% compared with the conventional anaerobic reactor. Thirteen intermediates were identified and the potential degradation pathways of SMT were proposed. Proteobacteria, Firmicutes, Patescibacteria, Chloroflexi, Bacteroidetes, and Euryarchaeota are the dominant bacteria at the phylum level in the MEC-Ni-Co@SSM, which are responsible for SMT metabolism. Due to the electrical stimulation, there was an increase in the abundance of the metabolic function and the genetic information processing. This work provides valuable insight into utilizing MECs for effective treatment of antibiotic-containing wastewater. [ABSTRACT FROM AUTHOR]

BACKGROUND: Microbial desalination cell (MDC) is a new technology in the use of electrical energy for water desalination and wastewater treatment. RESULTS: Open circuit (OC) and closed circuit (CC) modes were successfully simulated with initial TDS concentrations of 10 g/L and 10–15 g/L, respectively (an external resistance of only 150 Ω was applied for CC). After 160 h of operation, the maximum OC voltage, desalination efficiency and COD removal efficiency were 809 mV, 32.2% and 79.2%, respectively. The maximum voltage was also obtained when the external resistances were 150 Ω (423.4 and 438 mV) for the initial NaCl concentrations (10 and 15 g/L) in the central chamber, respectively. Moreover, the maximal desalting and COD removal efficiencies after 24 h run‐time were (30% and 28%) and (24% and 25%) for initial NaCl concentrations (10 or 15 g/L) in the central chamber, respectively. Maintaining pH (8.61, 7.01) to (7.85, 7.8) in anode and cathode chambers was studied. This research accurately depicted microbial desalination's efficiency in generating OC voltages and CC electrical energy via Box–Behnken Design Distribution (BBD). Investigated factors' interactions (initial salt/COD concentrations, time) on CC system's energy efficiency. Resulted in peak productivity at (1.85 mW), OC reaching (1100 mV). CONCLUSION: Finally, the research paper gave exciting results in improving the efficiency of the microbial desalination cell to increase the ability to produce electrical energy and desalinate water. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The treatment of cooking oil wastewater is an urgent issue need to be solved. We aimed to screen for efficient oil-degrading bacteria and develop a new microbial agent for degrading waste cooking oil in oily wastewater. Three extremely effective oil-degrading bacteria, known as YZQ-1, YZQ-3, and YZQ-4, were found by the enrichment and acclimation of samples from various sources and separation using oil degradation plates. The 16S rRNA sequencing analysis and phylogenetic tree construction showed that the three strains were Bacillus tropicus, Pseudomonas multiresinivorans, and Raoultella terrigena. Under optimal degradation conditions, the maximal degradation rates were 67.30 ± 3.69%, 89.65 ± 1.08%, and 79.60 ± 5.30%, respectively, for YZQ-1, YZQ-3, and YZQ-4. Lipase activity was highest for YZQ-3, reaching 94.82 ± 12.89 U/L. The best bacterial alliance was obtained by adding equal numbers of microbial cells from the three strains. Moreover, when this bacterial alliance was applied to oily wastewater, the degradation rate of waste cooking oil was 61.13 ± 7.30% (3.67% ± 2.13% in the control group), and COD removal was 62.4% ± 5.65% (55.60% ± 0.71% in the control group) in 72 h. Microbial community analysis results showed YZQ-1 and YZQ-3 were adaptable to wastewater and could coexist with local bacteria, whereas YZQ-4 could not survive in wastewater. Therefore, the combination of YZQ-1 and YZQ-3 can efficiently degrade oil and shows great potential for oily wastewater treatment. [ABSTRACT FROM AUTHOR]

This research aims to assess the microbial electrolysis cell (MEC) fed with petroleum refinery wastewater (PRW) to produce power density and bio-electrochemical hydrogen. The MEC produces a maximum bio-electricity of 21.4 mA and a power density of 1200123.90 W/m2 with a loading of chemical oxygen demand (COD) of 17000 mg/L. Due to catalyzed oxidation of complex compounds in PRW with a maintained microbial biofilm growth was observed after 90 d of operation of MEC. Results showed that the oxidation of organic substances in PRW enhanced the size in the growth of microbial film which further increased the generation of electrons leading to current density of 5890 mA/m2. The COD removal efficiency of MEC was found to be 89.9%. The bio-electricity and hydrogen production of the MEC was estimated to be 24.5 mA and 19.2 L respectively when loaded with PRW having a COD of 17500 mg/L after 130 d. Present experiments demonstrate the efficiency of MEC technology efficiency in treating petroleum wastewater with the help of microbial biofilm. [ABSTRACT FROM AUTHOR]

The increase in the population and rapid industrialization generates a significant amount of wastewater which should be treated economically. Microbial desalination cell (MDC) is a kind of technology that can treat wastewater and generate power simultaneously. It was observed that many experimental studies were lacking in findings of the variation of basic input conditions on the MDC efficiencies. The aim of the present study was to explore the impact of external resistance, electrolyte solutions and substrate concentration on power generation in an MDC system. The experimental study was conducted by using medium to high strength wastewater from distillery and brewery industry in batch-wise operation. The analysis of which resulted in medium to high-strength wastewater. The data was collected based on the experimental setup conditions. Application of different resistances on the MDC, best resulted in 82% COD removal and 57% TDS removal with 500 O external resistance. A COD and TDS removal efficiency of 83% and 61% was identified with an electrolyte concentration of 35,000 mg/L. The variation of substrate concentration reported a maximum COD removal of 86%, TDS removal of 62%, and current, and voltage of 1.872 mA and 628 mV with 1,500 and 8,000 mg/L, respectively. [ABSTRACT FROM AUTHOR]

BACKGROUND: The increase in energy and water demand due to industrialization and urbanization requires prioritized solutions for a sustainable future. Microbial electrolysis cells (MECs) have shown huge potential for biohydrogen production along with wastewater treatment. This study examined the effectiveness of employing nickel foam as an anode material for biohydrogen production from the widely available potato industry effluent. RESULTS: Hydrogen production rate increases exponentially with the increase in applied voltage. A maximum hydrogen production rate of 0.69 ± 0.02 m3 H2 m−3 reactor volume d−1 was achieved at 0.9 V with a maximum chemical oxygen demand removal efficiency of 97% at 0.8 V. The effluent of the 0.8 V cycle had the least salinity, low total dissolved solids, 84% reduced total hardness, highest effluent clarity (4.30 NTU, and negligible quantity of heavy metals. CONCLUSION: This study successfully produced biohydrogen from potato wastewater within 5 days of operation along with wastewater treatment of the substrate. The improved performance of the system can be attributed to the unique characteristics of nickel foam, such as high porosity, large surface area and excellent conductivity. The findings of this study have implications for the sustainable treatment of domestic and agro‐industrial wastewater and the development of efficient and low‐cost bio‐electrochemical systems for renewable energy production. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The selection of better electrode material and studies of the electrocatalytic activities of the electrodes are crucial to increasing biohydrogen production in a microbial electrolysis cells (MEC). In the present work, we studied biohydrogen production and electrocatalytic activities using a membraneless single-chamber MEC fed with high-strength wastewater, using different electrode materials (metal and carbon electrode), configurations and electrode distance. The electro-fermentation (EF) process showed a significantly higher biohydrogen production and COD removal, compared to conventional dark fermentation reactor (DF). The maximum hydrogen production rate (HPR) obtained was 314 m3 H 2 /m3 R.d with an overall biohydrogen recovery (r H2) of 340% using the electrode configuration stainless steel 304 pleated mesh 60 as anode and stainless steel 304 flat mesh 60 as cathode at 4 cm of electrode distance. The onset potential for the hydrogen evolution reaction (HER) with metal electrode was significantly lower than carbon electrode. [Display omitted] • Hydrogen production in MEC was investigated using high-strength wastewater. • Various combinations of electrode materials were tested in MEC. • The maximum HPR of 314 m3 H 2 /m3 R.d was observed in MEC using metal electrodes. • Electrocatalytic activities in MEC with different electrode materials were done. [ABSTRACT FROM AUTHOR]

Recalcitrant chemicals in the environment not only present obstacles to living organisms but also contribute to the degradation of natural resources. One contribution to environmental pollution is the discharge of synthetic dyes from the textile sector. This study investigates the combined effect of microbial cells and biochar on eliminating methyl orange (MO) dye. The immobilization of Aeromonas veronii on peanut shell biochar (APSB) was conducted to investigate its efficacy in removing MO dye from water. PSB synthesized by pyrolysis at 300 °C for 120 min showed maximum bacterial immobilization potential. The highest degradation rate of 96.19 % was achieved in APSB within 96 h using MO dye concentration of 100 mg L−1, incubation temperature of 37 °C, pH 7, and biocatalyst dosage of 1g L−1. In comparison, free cells achieved degradation rates of 72.53 % and 61.56 % for PSB. Moreover, the adsorption process was primarily controlled by PSB, with subsequent dye mineralization by A. veronii, as supported by FTIR and LC-MS studies. Moreover, this innovative approach exhibited the reusability of the biocatalyst, giving 76.23 % removal after fifth cycle, suggesting sustainable alternative in dye remediation and potential option for real-time applications. [Display omitted] • Immobilization of Aeromonas veronii on peanut shell biochar. • 96.19% methyl orange removal achieved using the bacteria immobilized biochar. • APSB showed maximum dye removal compared to free cell and PSB. • Reusability of APSB studied for five cycles. • Mechanism showcasing the synergistic effect of biochar and bacteria for dye removal. [ABSTRACT FROM AUTHOR]

Coal gasification wastewater (CGW) contains a range of refractory and toxic organic pollutants with low biodegradability and significant biological toxicity. This study synthesized a hemin-graphene (H-graphene) catalyst for permonosulfate (PMS) activation. The MEC-AD (Microbial electrolysis cell- Anaerobic digestion) reactor (K1) was designated as the control group. The experimental groups were the MEC-AD reactor (K2) with PMS and H-graphene, and the MEC-AD reactor (K3) with advanced oxidation as a synthetic CGW pretreatment. The results demonstrated that the COD removal rates of K1, K2 and K3 reactors were 76.7 %, 79.5 % and 87.4 %, while the total phenol removal rates were 74.1 %, 90.1 % and 100 %, respectively. Quinoline and indole were removed at rates greater than 90 % in the microbial electrolytic cell reactors K2 and K3, and 100 % in the K3 reactor. In K2 and K3, there was a considerable decrease in the abundance of unclassified _ f _ Alcaligenaceae, Arenimonas and unclassified _ f _ Gracilibacteraceae as compared to K1. The abundance of unclassified _ p _ Zixibacteria, Candidatus _ Caldatribacterium, unclassified _ c _ JS1 and JGI-0000079-D21, which are responsible for promoting the anaerobic degradation of long-chain fatty acids and anaerobic fermentation of acid production increased. [Display omitted] • Treatment of CGW by advanced oxidation process combined with MEC-AD was investigated. • The removal rates of quinoline and indole exceeded 90 % in MEC-AD by advanced oxidation. • Advanced oxidation opens the ring of nitrogen heterocyclic compounds. [ABSTRACT FROM AUTHOR]

• Microplastics (MPs) undergo aging and leaching behavior during sludge dewatering. • The concentration of MP leachates in sludge is higher than that in water. • Increasing pH value and ion strengths by dewatering agents promote the MP leaching. • MP leachates come from the release of plastic additives and polymer derivatives. • The reflux of MP leachates generates adverse effect on the activated sludge. Dewatering is an indispensable link in sludge treatment, but its effect on the microplastics (MPs) remains inadequately understood. This study investigated the physicochemical changes and leaching behavior of MPs during the mechanical dewatering of sludge, as well as the impact of MP leachates on activated sludge (AS). After sludge dewatering, MPs exhibit rougher surfaces, decreased sizes and altered functional groups due to the addition of dewatering agents and the application of mechanical force. Meanwhile, plastic additives, depolymerization products, and derivatives of their interactions are leached from MPs during sludge dewatering process. The concentration of MP-based leachates in sludge is 2–25 times higher than that in water. The enhancement of pH and ionic strength caused by dewatering agents induces the release of MP leachates enriched with protein-like, fulvic acid-like, and soluble microbial by-product-like substances. The reflux of MP leachates in sludge dewatering liquor to the wastewater treatment system negatively impacts AS, leading to a decrease in COD removal rate and inhibition of the extracellular polymeric substances secretion. More importantly, MP leachates cause oxidative stress to microbial cells and alter the microbial community structure of AS at the phylum and genus levels. These findings confirm that MPs undergo aging and leaching during sludge dewatering process, and MP leachates may negatively affect the wastewater treatment system. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents an extended mathematical model for a microbial desalination cell (MDC), integrating Haldane kinetics for substrate inhibition and proton translocation theory for substrate dissociation under dynamic flow. The model is capable of predicting exoelectrogenic and methanogenic biomass dynamics, acetate removal efficiencies, salt concentration changes, and current production. Notably, it can be used to explore the influence of operational parameters such as dilution rates, temperatures, and external resistances. Our simulations reveal the optimal conditions for maximizing exoelectrogen concentration (500 mg/L) with minimal methanogen presence (50 mg/L) in the anode chamber at an anolyte dilution rate of 0.5 d−1, a temperature of 20 °C, and an influent acetate concentration of 1500 mg/L. The model accurately predicts the salt reduction in the middle chamber (from 0.2 to 0.09 mol/L) with a salt dilution rate of 0.5 d−1 and an external resistance of 20 Ohm. The model predicts a peak power output of 2.5 mW at external resistances between 20 and 50 Ohm. The model was validated against a suite of experimental literature data, including our previously published lab-scale studies, verifying its accuracy in predicting organic and salt removal rates, current production, and desalination efficiency. This extended model is a valuable tool for understanding the complex interactions between factors that influence MDC performance and can guide the optimization of MDC design for wastewater treatment and desalination. [Display omitted] • The extended MDC model can stimulate oxidizied mediator and substrate inhibition concentrations. • Exoelectrogens and methanogens concentrations are predicted at different anolyte dilution rates. • Hydrolysis of soluble organic substrate indicates the pH effect on MDC performance. • Acetate and salt removal can be efficiently detected using an extended model. • Cell power and Coulombic efficiency can be optimized at MDC external resistance. [ABSTRACT FROM AUTHOR]

The utilization of autotrophic microorganisms in microbial electrolysis cell (MEC) is promising for the treatment of industrial wastewater that lacks carbon source and electron donor. However, constructing an autotrophic biocathode is time-consuming, and the population induction technologies may alleviate this challenge. In this study, N-butyryl-L-Homoserine lactone (C4-HSL) was added to the MEC biocathode run for 60 cycles to investigate quorum sensing effects on sulfate reduction efficiency, electrochemical properties, microbial community structure and functional genes. The results showed that the addition of C4-HSL significantly expedited the startup of the MEC cathode with a 47.1 % reduction. Its electrochemical performance was also improved, with the cyclic voltammetry area averaging 1.19 times higher than that without the addition of the signaling molecule. Under the regulation of C4-HSL, the biodiversity in the initiation phase became richer. The relative abundance of Desulfobacterota and sulfate reduction-related functional genes increased to 4 times and 1.43 times of the control, respectively. This discovery reveals the potential of signaling molecules in enhancing the construction of sulfate wastewater treatment reactors and improving the performance of autotrophic microorganisms, aiming to improve wastewater treatment efficiency and broaden the practical possibilities of MEC. [Display omitted] • Quorum sensing addition facilitated the start-up of the MEC biocathode. • The efficiency of sulfate-reducing biocathode in autotrophic MEC was enhanced. • MEC's electrochemical performance was improved by quorum sensing addition. • The relative abundance of key functional genes were promoted by quorum sensing. [ABSTRACT FROM AUTHOR]

Microbial electrolysis cells (MECs) are considered as green technologies for H2 production with simultaneously wastewater treatment. Low H2 recovery and production rate are two key bottlenecks of MECs fed with real H2 fermentation effluent of biomass wastes. This work established a 1 L cylindrical single chamber MEC and enriched electroactive anodic biofilms from cow dung compost to overcome the bottlenecks. These MEC components (platinum-coated cylindrical titanium mesh cathode and cylindrical graphite felt anode) were arranged in a concentric configuration. A high H2 production rate of 6.26 ± 0.23 L L−1 day−1 with H2 yield of 5.75 ± 0.16 L H2 L−1 fermentation effluent was achieved at 0.8 V. The degradation of acetate and butyrate (main components of H2 fermentation effluent) could reach to 95.3 ± 2.1% and 78.4 ± 3.6%, respectively. The microbial community analysis for anode showed the abundance of Geobacter (22.6%), Syntrophomonas (8.7%), and Dysgonomonas (6.3%) which are responsible to complex substrate oxidation, electrical current generation, and H2 production. These results prove the feasibility of cylindrical single-chamber MEC for high H2 production rate and high acetate and butyrate removal from H2 fermentation effluent. [ABSTRACT FROM AUTHOR]

Ammonia removal from wastewater was successfully achieved by simultaneous nitrification and denitrification (SND) in a double-chamber microbial electrolysis cell (MEC). The MEC operations at different applied voltages (0.7 to 1.5 V) and initial ammonia concentrations (30 to 150 mg/L) were conducted in order to evaluate their effects on MEC performance in batch mode. The maximum nitrification efficiency of 96.8% was obtained in the anode at 1.5 V, followed by 94.11% at 1.0 V and 87.05% at 0.7. At 1.5 V, the initial ammonia concentration considerably affected the nitrification rate, and the highest nitrification rate constant of 0.1601/h was determined from a first-order linear regression at 30 mg/L ammonium nitrogen. The overall total nitrogen removal efficiency was noted to be 85% via the SND in the MEC operated at an initial ammonium concentration of 50 mg/L and an applied cell voltage of 1.5 V. The MEC operation in continuous mode could remove ammonia (50 mg/L) in a series of anode and cathode chambers at the nitrogen removal rate of 170 g-N/m3.d at an HRT of 15. This study suggests that a standalone dual-chamber MEC can efficiently remove ammonia via the SND process without needing additional organic substrate and aeration, which makes this system viable for field applications. [ABSTRACT FROM AUTHOR]

Seawater might serve as a fresh‐water supply for future generations to help meet the growing need for clean drinking water. Desalination and waste management using newer and more energy intensive processes are not viable options in the long term. Thus, an integrated and sustainable strategy is required to accomplish cost‐effective desalination via wastewater treatment. A microbial desalination cell (MDC) is a new technology that can treat wastewater, desalinate saltwater, and produce green energy simultaneously. Bio‐electrochemical oxidation of wastewater organics creates power using this method. Desalination and the creation of value‐added by‐products are expected because of this ionic movement. According to assessments, recent investigations on MDC configurations have led to significant changes in their operating characteristics, as well as their design and operational factors. Additionally, the study notes the expanding uses of MDC in bioremediation, nutrient recovery, water softening, and value‐added chemical manufacturing. Significant results show that the MDC system produced outstanding desalination without the need for external power, in addition to achieving wastewater treatment and energy recovery without the need for intermediary processes. When it comes to its practical application, some of the technical obstacles include keeping pH stable in cathodic and anodic fluids, increasing internal resistance using catalysts as electrode fillers, along with issues of biofouling and durability. Although MDC technology is currently being developed and scaled up, additional research on membrane fouling avoidance, material feasibility, electron transport kinetics, growth of microorganisms, and catalyst durability is needed. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

To boost growth and global competitiveness, a growing number of industries and sewage treatment plants are making "sustainability" and "cost‐effectiveness" key goals in their strategy and vision. This movement is also spreading far beyond the small group of people who recognize as "green". This is the first study to demonstrate that domestic sewage water can be utilized as anodic feed for the electrochemical production of H2O2 in the catholyte with simultaneous wastewater treatment in a microbial peroxide‐producing cell (MPPC) designed cost‐effectively utilizing a variety of catholyte and few electrode materials. The electrochemical output utilizing domestic wastewater resulted in maximum production of 62 mM H2O2 in a 37‐day batch in the MPPC with 50 mM H2SO4 catholyte having a bare activated charcoal electrode. The constantly rising H2O2 production during the 37‐day hydraulic retention time demonstrated the system's sustainability and efficiency in contrast to other reported studies. Cyclic voltammetry analysis of the catholyte with the Fenton process showed excellent redox peaks, indicating its applicability for in‐situ pollutant degradation. The MPPCs had an overall 40%–60% and 65%–85% removal efficiency of biochemical oxygen demand and chemical oxygen demand. This study shows that a simple MPPC design with no extensive modifications can be efficient at producing H2O2 and simultaneously treating wastewater. [ABSTRACT FROM AUTHOR]

A vast quantity of untreated wastewater is discharged into the environment, resulting in contamination of receiving waters. A microbial electrolysis cell (MEC) is a promising bioelectrochemical system (BES) for wastewater treatment and energy production. However, poor design and control of MEC variables may lead to inhibition in the system. This study explored the utilization of Response Surface Methodology (RSM) on the synergistic aspects of MEC and magnetite nanoparticles for wastewater treatment. Influences of temperature (25–35 °C), voltage supply (0.3–1.3 V) and magnetite nanoparticle dosage (0.1–1.0 g) on the biochemical methane potentials (BMPs) were investigated with the aim of optimizing biogas yield, chemical oxygen demand removal and current density. The analysis of variance (ANOVA) technique verified that the quadratic models obtained were substantial, with p-values below 0.05 and high regression coefficients (R2). The optimum biogas yield of 563.02 mL/g VSfed, chemical oxygen demand (COD) removal of 97.52%, and current density of 26.05 mA/m2 were obtained at 32.2 °C, 0.77 V and 0.53 g. The RSM revealed a good comparison between the predicted and actual responses. This study revealed the effective utilization of statistical modeling and optimization to improve the performance of the MEC to achieve a sustainable and eco-friendly situation. [ABSTRACT FROM AUTHOR]

Summary: Increasing populations and urbanization put a lot of pressure on freshwater supplies and use. The increased demand for drinking water can be met by using seawater as a source of freshwater. Desalination and wastewater treatment have been energy‐ and time‐consuming processes in recent years. Microbial desalination cells (MDCs) have gained considerable attention as an emerging technology because of their ability to treat wastewater, desalinate seawater, and produce electricity and value‐added products. The efficiency and performance of this technology are affected by numerous factors. In this study, the effect of membranes on the efficiency and performance of this technology is examined. Anionic and cationic, carbon nanotube (CNT), bipolar and osmotic membranes were investigated. Anionic and cationic membranes, as well as their modifications, significantly influence microbial desalination cells. CNT‐based membranes have shown significant improvements in water permeability, desalination capacity, strength, anti‐fouling, and energy efficiency compared to other membranes. Bipolar membranes prevent the pH of the anode chamber from decreasing, which is essential for MDC operation. The use of FO membranes in microbial desalination cells still faces challenges; for instance, fouling is more likely in FO membranes than ion‐exchange membranes, resulting in higher internal resistance and decreased water flux. MDC technology will require research into membrane fouling, electron transfer kinetics, material feasibility, microbial growth, and catalyst durability to be scaled and sustainable. As part of the feasibility study, the performance and stability of the reactor must also be examined. [ABSTRACT FROM AUTHOR]

The current need for the upgradation of biohydrogen generation and contaminant removal in two-chambered microbial electrolysis cells (MECs) compels the design of alternatives i.e. bioelectrochemical systems (BESs) to conventional reactors. In this study, a novel three-chambered design of MEC (BES-1) was developed with a common anodic chamber and a two-cathodic chambers at both ends of the anodic chamber, separated by a membrane (MEC–MEC). To facilitate electricity recovery, a microbial fuel cell (MFC) was integrated with an MEC in BES-2. Cathodic hydrogen recovery of 8.89 and 4.81 mL/L.day, and organic matter removal of 82% and 76% were obtained in BES-1 and BES-2, respectively, demonstrating their capabilities for bioremediation. Electrochemical analyses also revealed that cathodic reduction reactions improved with the effective utilization of protons during integration. Our design regulates H 2 /O 2 -associated electrochemical reactions and is beneficial for maintaining pH equilibrium. From cost and energy perspectives, the integrated BES provides a platform for two different reactions simultaneously and is capable of boosting overall hydrogen recovery and organic matter removal. Moreover, the compactness and competitiveness of such an integrated BES increase its scope for real-world applications. • Novel 3-chamber bioelectrochemical system (BES) was designed to boost H 2 /O 2 -reaction. • Accelerated proton consumption helps to maintain pH balance of integrated BES. • Achieved BioH 2 recovery of 8.89 mL/L.day and organics removal of 82% in BES-1. • Integration of MFC–MEC/MEC–MEC promotes effective H+ utilization and equilibrium. • Electrochemical analyses support boost in hydrogen evolution in 3-chambered design. [ABSTRACT FROM AUTHOR]

Considering the removal of pollutants and the resource recovery in wastewater, it is crucial to address the conflict between phosphorus pollution and phosphorus resources during wastewater treatment. This study investigated the transformation law of phosphorus in an up-flow anaerobic sludge bed reactor using different phosphorus source substrates. In addition, metagenomics sequencing was used to analyze microbial community succession and changes in the key functional genes in the reactor. Results showed that when sodium hypophosphite and sodium phosphite were used as the phosphorus sources, the average removal efficiency of total phosphorus was 6.43 % and 5.69 %, respectively. The resulting average phosphine concentrations were 109.76 mg/m3 and 72.77 mg/m3, respectively. Sodium hypophosphite was the more effective phosphorus source for Proteobacteria growth. The ppa , ppk , ppx and gcd genes were all up-regulated when exposed to the two phosphorus sources. On day 90 of the experiment, the relative abundances of these four genes in the reactor with sodium hypophosphite as phosphorus source were 0.0046 %, 0.0025 %, 0.0036 %, and 0.0014 %, respectively. In contrast, in the reactor with sodium phosphite as a phosphorus source, the relative abundances of the ppa , ppk , ppx and gcd genes were 0.0009 %, 0.0005 %, 0.0014 %, and 0.0001 %, respectively. Sodium hypophosphite was more effective than sodium phosphite in promoting the dissolution of inorganic phosphorus in microbial cells. [Display omitted] • Sodium hypophosphite was more easily reduced into phosphine. • Conversion of IP to OP in sludge can be promoted by using sodium hypophosphite. • Sodium hypophosphite was more conducive to the growth of Proteobacteria. • ppa , ppk , ppx and gcd genes were all up-regulated under the two phosphorus sources. [ABSTRACT FROM AUTHOR]

• Basic principles and affecting parameters of electrospinning process are overviewed. • Summary of application of electrospinning biohybrid technology. • Applications of electrospinning biohybrid technology targeting different pollutants. • Microbial selection, fabricating routes of electrospinning biohybrid composites. • Bioremediation capacity of electrospinning biohybrid technology in water treatment. • The actual state and future challenges of electrospinning biohybrid technology. With the rapid development of nanotechnology and additive manufacturing industries, electrospinning for the fabrication of high-performance nanofibers has attracted increasing attention. The rapid development of biohybrid environmental remediation technology has led to sustainable water treatment materials aimed at different pollutants and application scenarios. The coupling of biohybrid materials with electrospinning technology further addresses potential drawbacks of traditional biomaterials, such as low activity, poor diffusion, and loss of biological activity. In recent years, advanced techniques for constructing biohybrid fibers have been achieved through electrospinning methods such as fiber encapsulation, microtube encapsulation, and co-electrospinning, utilizing microbial cells (bacteria, algae, yeast, etc.). In this review, we firstly introduce the basic principle of electrospinning technology and parameters affecting spinning process. Then systematically analyze the microbial selection, material synthesis routes, and degradation efficiency of electrospinning biohybrid technology in water treatment processes targeting different pollutants, while assessing the application prospects or drawbacks of each case. Finally, we summarize and prospect the technical characteristics, current issues, and industrial prospects of electrospinning biohybrid technology. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems (BESs) use electrochemically active microorganisms to convert the chemical energy of organic matter into electrical energy, hydrogen, or other useful products through redox reactions. Microbial electrolysis cell (MEC) is one of the most common BESs which are able to convert organic substrate into energy (such as hydrogen and methane) through the catalytic action of electrochemically active bacteria in the presence of electric current and absence of oxygen. In the past decades, BESs have gained growing attention because of their potential, but there is still a limited amount of research is done for the environmental effects of BESs. This study initially provides an update review for MECs including general historical advancement, design properties, and operation mechanisms. Later, a life cycle assessment (LCA) study was conducted using a midpoint approach, which is TRACI methodology with EIO-LCA model to identify the potential impacts to the environment whether adverse or beneficial using the MECs to produce hydrogen with domestic wastewater as a substrate. The results show that the cumulative negative impacts were substantially larger than the positive impacts by contrast with the expectations, and the cumulative output data show that human health non-cancer impact provides the highest environmental effects than others mainly because of the inorganic chemicals, pumping and wastewater recycling equipment step. In addition, global warming potential and smog creation potential are also elevated mainly due to electricity usage, inorganic chemical and glassware reactor production. Later we are externally normalized each impact category to compare the results at the normalization level, and we again found that human health (cancer or non-cancer) potential provides the most negative impact on the environment in the MEC system originates on human health indicators. [ABSTRACT FROM AUTHOR]

Microbial electrolysis cells (MECs) are a new bio-electrochemical method for converting organic matter to hydrogen gas (H 2). Palm oil mill effluent (POME) is hazardous wastewater that is mostly formed during the crude oil extraction process in the palm oil industry. In the present study, POME was used in the MEC system for hydrogen generation as a feasible treatment technology. To enhance biohydrogen generation from POME in the MEC, an empirical model was generated using response surface methodology (RSM). A central composite design (CCD) was utilized to perform twenty experimental runs of MEC given three important variables, namely incubation temperature, initial pH, and influent dilution rate. Experimental results from CCD showed that an average value of 1.16 m3 H 2 /m3 d for maximum hydrogen production rate (HPR) was produced. A second-order polynomial model was adjusted to the experimental results from CCD. The regression model showed that the quadratic term of all variables tested had a highly significant effect (P < 0.01) on maximum HPR as a defined response. The analysis of the empirical model revealed that the optimal conditions for maximum HPR were incubation temperature, initial pH, and influent dilution rate of 30.23 ∘C, 6.63, and 50.71%, respectively. Generated regression model predicted a maximum HPR of 1.1659 m3 H 2 /m3 d could be generated under optimum conditions. Confirmation experimentation was conducted in the optimal conditions determined. Experimental results of the validation test showed that a maximum HPR of 1.1747 m3 H 2 /m3 d was produced. [Display omitted] • POME used in MEC for H 2 as a feasible method and effective treatment technology. • To enhance H 2 production from POME, an empirical model was generated using RSM. • Results from CCD showed 1.16 m3 H 2 /m3 d for maximum HPR was produced. • The confirmation test results showed a maximum HPR of 1.1747 m3 H 2 /m3 d. [ABSTRACT FROM AUTHOR]

Microbial electrolysis cells (MECs) have been explored for various applications, including the removal of industrial pollutants, wastewater treatment chemical synthesis, and biosensing. On the other hand, MEC technology is still in its early stages and faces significant obstacles regarding practical large-scale implementations. MECs are used for energy generation and hydrogen peroxide, methane, hydrogen/biohydrogen production, and pollutant removal. This review aimed to investigate the aforementioned uses in order to better understand the different applications of MECs in the following scenarios: MECs for energy generation and recycling, such as hydrogen, methane, and hydrogen peroxide; contaminant removal, particularly complex organic and inorganic contaminants; and resource recovery. MEC technology was examined in terms of new concepts, configuration optimization, electron transfer pathways in biocathodes, and coupling with other technologies for value-added applications, such as MEC anaerobic digestion, combined MEC–MFC, and others. The goal of the review was to help researchers and engineers understand the most recent developments in MEC technologies and applications. [ABSTRACT FROM AUTHOR]

Background and Objective: With increasing population growth and water pollution, fresh water supply sources are declining and can not meet today's human needs. Thus, energy conversion systems with high efficiency and low pollution such as desalination microbial cell have been considered. Therefore the aim of this research was to investigation the efficiency of microbial desalination cell (MDC) for desalination and treatment of salt wastewater. Materials and Methods: To address this issue, the decision was taken to use saline synthetic wastewater with different initial salt concentrations (2, 5, 7 and 10 g/L NaCl) and, different hydraulic retention times (1, 2, 3 and 72 h) in open circuit voltage (OCV) and zlosed circuit voltage (CCV) continuous mode. Results: The results showed that highest EC removal was 11.2% and 14.3% with 10 g/L NaCl in open and closed circuit mode, respectively. Maximum COD removal of 68.7% was achieved in CCV mode that was obtained at 10 g/L NaCl. Additionally, Escherichia coli, Bacillus, Enterobacter, Staphylococcus aureus, Pseudomonas and Citrobacter were diagnose as effective bacteria in decomposing wastewater. Conclusion: The obtained results proved that MDC desalination microbial cell technology is Emerging technology that has many unknown aspects; however, it is expected to be an appropriate technique for wastewater treatment and desalination. [ABSTRACT FROM AUTHOR]

The ability of microorganisms to carry out interspecies electron transfer during the degradation of organic substances under anaerobic conditions opens up new possibilities for a controlled increase in the efficiency of the methanogenic decomposition of organic waste. This review presents the main principles of the effects of a direct electric current on the anaerobic degradation of organic substances, process parameters, changes in the composition of the microbial community, and factors affecting the optimization of the hybrid systems comprising microbial electrolysis cell (MEC) and anaerobic digester (AD), i.e., the performance of the MEC-AD system. The research in this field has been analyzed for the subsequent application of electromethanogenesis, which represents a new energy-efficient biotechnology for anaerobic wastewater treatment and organic waste digestion. [ABSTRACT FROM AUTHOR]

Summary: In this study, a CoNi/CoFe2O4 electrocatalyst with durian‐like structure was in‐suit fabricated on the conductive substrate of nickel foam using a hydrothermal method followed by a unipolar pulse electrodeposition (UPED), which was further applied for the production of hydrogen in a microbial electrolysis cell. The CoNi/CoFe2O4/NF electrode prepared with a pulse voltage of −1.2 V by the UPED exhibited the outstanding electrocatalytic activity and durability with the rate of hydrogen production achieved as high as 1.25 ± 0.0625 m3/(m3 day). The excellent performance of the electrocatalyst is attributed to the unique multilayer layered structure, which consisted of macroscopic porous NF, CoFe2O4 nanosheets, and CoNi double hydroxide nanosheets. The hierarchical architecture is binder‐free and beneficial for exposing catalytic active sites, enhancing mass transport, and large specific surface area for MEC hydrogen production. It is expected to the CoNi/CoFe2O4/NF composite electrode application in the practical microbial electrolysis cells to produce hydrogen during the treatment of wastewater. Highlights: A CoNi/CoFe2O4 electrocatalyst was prepared for microbial electrolysis cell.The electrocatalysts had unique multilevel hierarchical architecture.The electrocatalysts exhibited a high H2 production rate of 1.25 ± 0.0625 m3/(m3 day). [ABSTRACT FROM AUTHOR]

Industrial development owes its pace to the continued supply of energy; however, this development is also associated with a consequent consumption of water, climate change and environmental degradation. The increased concentration of carbon in the atmosphere and the dwindling clean water resources are posing another potent challenge to the sustained industrial development. The intermittent nature of the renewable energy resources particularly wind and solar energy make their storage difficult. Power‐to‐gas is perceived to solve this issue of storage of renewable energy through the production of synthetic natural gas. Production of economically viable hydrogen gas and carbon collection and utilization (CCU) are two energy‐intensive processes that are essential for the Sabatier reaction in the scheme of power‐to‐gas. This study proposes a novel model that employs low energy consuming microbial electrolysis cell along with carbon collectors for the production of synthetic natural gas through the Sabatier reaction. Renewable energy resources are proposed to power the MEC as well as the carbon collectors. The model uses the wastewater stream as input to the MEC ultimately delivering hydrogen to the Sabatier reactor. A successful model would be able to treat the wastewater, generate energy in the form of SNG, mitigate climate change and contribute to the achievement of Sustainable Development Goals (SDG 6, 7, 12, 13 & 14). [ABSTRACT FROM AUTHOR]

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Microbial Desalination Cells (MDCs) are an electrochemical process that harnesses microbial reactions to simultaneously treat wastewater, generate power, and desalinate water. By utilizing microbial decomposition of organic pollutants in wastewater, MDCs offer a sustainable and energy-efficient alternative to conventional desalination technologies. The technical framework of MDCs emphasizes the integration of water-electricity principles, making them promising for future applications in seawater desalination, wastewater treatment, resource recovery, and water softening. This study investigates the impact of acclimation resistance, represented by four different domesticated resistors values of 1 kΩ, 100Ω, 51Ω, and 10Ω, on the performance of MDCs. Larger acclimation resistors exhibit higher power performance, with the case of 100Ω achieving a power density of 0.33 mA/m2 and the case of 1 kΩ achieving the highest current density of 1.90 mA/m2. Furthermore, the case with an acclimation resistance of 1 kΩ exhibits superior performance in terms of chemical oxygen demand (COD) removal, achieving a removal rate of 76.3% on day 1. Conversely, the case with an acclimation resistance of 10Ω demonstrates the best desalination performance, achieving a desalination rate of 9.0%. It should be noted that the optimal performance in terms of COD removal and desalination capacity varies due to the various operational mechanisms involved.. The findings of this study provide valuable insights for enhancing the performance of MDCs in future applications, enabling further improvements in their efficiency and effectiveness. [Display omitted] • Influence of external load on water and energy production is explained. • MDCs offer energy-efficient substitutes by harnessing microbial reactions. • 1 KΩ resistor enhances power output and improves COD degradation. • For desalination performance, a 10Ω resistor achieves the best results. [ABSTRACT FROM AUTHOR]

Biofouling is inevitable in the membrane process, particularly in membrane bioreactors (MBR) combined with activated sludge processes. Regulating microbial signaling systems with diffusible signal factors such as cis -2-Decenoic acid (CDA) can control biofilm formation without microbial death or growth inhibition. This study assessed the effectiveness of CDA in controlling biofouling in membrane bioreactors (MBRs), essential for wastewater treatment. By modulating microbial signaling, CDA mitigated biofilm formation without hindering microbial growth. Analysis using Confocal Laser Scanning Microscopy (CLSM) revealed structural alterations in the biofilm, reducing biomass and thickness upon CDA application. Moreover, examination of extracellular polymeric substances (EPS) highlighted a decrease in total EPS, particularly effective polysaccharides. In addition, the possibility of shifting from high molecular weight EPS to low molecular weight EPS was revealed through the change in dispersion activity. The 56% extension of MBR operational lifespan resulting from the reduction in EPS is anticipated to offer potential cost savings and improved performance. Despite these results, further investigation is crucial to validate any potential environmental risks associated with CDA and to comprehend its long-term effects at various conditions. [Display omitted] • Regulation of DSF expression controls biofilm formation behavioral patterns of microbial cells. • CDA application has contributed to the extension of the operational period of lab-scale MBR. • Biofilm dispersion increased and total EPS concentration decreased as CDA was dosed. • CDA addition yields biofilms with less total biomass and more rough structures. • Dispersion by CDA can be a biofouling abatement technology in membrane bioreactors. [ABSTRACT FROM AUTHOR]

• Pilot-scale MEC yielding 19.07 ± 0.46 L H 2 m−2 d−1 with industrial wastewater. • Up to 3.0-fold increase in hydrogen production using Ni-foam cathodes. • Energy efficiency of the process up to 133 % using Ni-foam cathodes. • Cathode configuration significantly affected the anodic microbial communities. Microbial electrolysis cells (MECs) have garnered significant attention as a promising solution for industrial wastewater treatment, enabling the simultaneous degradation of organic compounds and biohydrogen production. Developing efficient and cost-effective cathodes to drive the hydrogen evolution reaction is central to the success of MECs as a sustainable technology. While numerous lab-scale experiments have been conducted to investigate different cathode materials, the transition to pilot-scale applications remains limited, leaving the actual performance of these scaled-up cathodes largely unknown. In this study, nickel-foam and stainless-steel wool cathodes were employed as catalysts to critically assess hydrogen production in a 150 L MEC pilot plant treating sugar-based industrial wastewater. Continuous hydrogen production was achieved in the reactor for more than 80 days, with a maximum COD removal efficiency of 40 %. Nickel-foam cathodes significantly enhanced hydrogen production and energy efficiency at non-limiting substrate concentration, yielding the maximum hydrogen production ever reported at pilot-scale (19.07 ± 0.46 L H 2 m−2 d−1 and 0.21 ± 0.01 m3 m−3 d−1). This is a 3.0-fold improve in hydrogen production compared to the previous stainless-steel wool cathode. On the other hand, the higher price of Ni-foam compared to stainless-steel should also be considered, which may constrain its use in real applications. By carefully analysing the energy balance of the system, this study demonstrates that MECs have the potential to be net energy producers, in addition to effectively oxidize organic matter in wastewater. While higher applied potentials led to increased energy requirements, they also resulted in enhanced hydrogen production. For our system, a conservative applied potential range from 0.9 to 1.0 V was found to be optimal. Finally, the microbial community established on the anode was found to be a syntrophic consortium of exoelectrogenic and fermentative bacteria, predominantly Geobacter and Bacteroides , which appeared to be well-suited to transform complex organic matter into hydrogen. [Display omitted] [ABSTRACT FROM AUTHOR]

This study describes the use of a microbial electrolysis cells for the production of gaseous biofuels sustained by the oxidation of a synthetic wastewater. During the overall experimental investigation, the MEC's bioanode removed on average 855 ± 57 mgCOD/d producing an average electric current of 66 ± 7 mA which was diverted into gaseous biofuels like biomethane, biohydrogen and biohythane. Three different MEC cathodic configurations were investigated selecting the electrodic materials (graphite granules GG, and mixed metal oxide MMO) and operating conditions (pH of the catholyte, additional sorption chamber). Biomethane production increased from 26 ± 4–102 ± 8 meq/d when the MMO electrode was used with respect to GG electrodic material. In contrast, the MMO electrode in combination with a CO 2 sorption chamber was successfully utilized for simultaneous H 2 production and CO 2 sorption from a N 2 /CO 2 mixture which simulates an anaerobic digestion biogas. The combination of H 2 production and CO 2 sorption allowed to obtain a gaseous mixture composed of 9% H 2 , 5% CO 2 , and 80% N 2 that according to the assumption of replacing the N 2 /CO 2 mixture with real biogas corresponded to a commercial-grade biohythane. Overall, the results highlight the potential of MECs as an efficient approach for biogas upgrading, allowing biohythane production increasing CH 4 content and lowering CO 2 concentration. [Display omitted] • 55% of removed COD was diverted into current during the microbial electrolysis cell operation • BioCH 4 production using the MMO electrode allowed for a 102% coulombic efficiency • MMO cathode promoted higher nitrogen removal (58 ± 4%) compared to GG (40 ± 3%) • Using a 6 h gas retention time biohythane was obtained (5% CO 2 - 10% H 2) • Under optimized conditions, energy consumption of the reactor reached 7 Wh/d. [ABSTRACT FROM AUTHOR]

Origin of the humic substances formed in biological wastewater treatment system (abbreviated as bio-HS) still remains inconclusive. In this study, the bio-HS that contained humic acid (HA) and fulvic acid (FA) from effluent and activated sludge were isolated and purified with XAD-8 resin and ion exchange resin, and then the molecular weight, functional groups, contents and forms of phosphorus (P) using gel permeation chromatography (GPC), fourier transform infrared (FTIR), element analysis and P nuclear magnetic resonance (31P-NMR) were investigated. The results showed that HS was formed in biological wastewater treatment systems, and had a lower degree of humification than soil, peat, or marine HS, and mainly comprised diester and monoester P fragments. Specific signal peaks of intracellular materials and cell membranes (nucleic acid, phospholipids, and sugar phosphate) showed that microbial cell debris was the precursor of bio-HS. HA comprised diester P fragments and monoester P fragments that formed when diester P fragments degraded, while FA contained only diester P fragments. The monoester P fragments in HA may result from microbial degradation of diester P fragments, and FA may simultaneously condense into HA. These results show that microbial cell debris was first transformed into FA and then into HA. [ABSTRACT FROM AUTHOR]

Commercial textiles such as Decolor Stop (Eau Écarlate, France) were characterized, and their ability for adsorbing the dyes Congo red and methylene blue in an aqueous solution was investigated. The adsorption steps of equilibrium time and velocity for both dyes in textile commercial were determined. To describe adsorption mechanisms of Congo red and methylene blue, the kinetic adsorption data were treated with pseudo-first order and pseudo-second order. The experimental data of isotherms adsorption were examined using the Langmuir and Freundlich models, showing more affinity of material toward Congo red. Besides, an attempt toward biological regeneration of polluted textile was undertaken by integrating a bacterial biofilm into the process. In effect, the polluted textile was therefore regenerated by yeast microbial fuel cell in which it was consumed and used as a mediator for oxidizing the organic matter available. As a result, the produced electrons were transferred from the substrate (organic matter) to the anode via the dye, giving rise to the value of generated electromotive force. Then, the bio-energy harvested from this microbial fuel cell was exploited for removal of traces of lead contained in diluted aqueous solution. Accordingly, two processes were used: microbial desalination cell and conventional electro-dialysis for comparison. Although the desalination rates of the two processes were relatively close to each other, the electro-dialysis required some energy to spend for imposing the current, while in microbial desalination cell, the biological system provided the energy for removing traces of lead. [ABSTRACT FROM AUTHOR]

• The microbial electrolysis cell with MoS 2 -graphene oxide cathode was developed. • Decolorization of AYR and hydrogen production were simultaneously achieved. • Effects of various operation conditions on MEC performances were evaluated. • NaAc + glucose co-substrate improved hydrogen production and COD removal. A single-chamber microbial electrolysis cell (MEC) constructed with MoS 2 -GO nickel foam (NF) cathode was established for alizarin yellow R (AYR) decolorization and hydrogen production, and influences of AYR initial concentration, co-substrate and buffer on MECs performances were determined. The cathode was obtained by in-situ growing MoS 2 -GO on NF. Physico-chemical and electrochemical characterizations showed that MoS 2 -GO NF cathode exhibited superior performance towards catalytic hydrogen evolution. The decolorization efficiency of ∼ 90 % within 10 h was achieved with AYR initial concentrations ranging from 30 to 150 mg/L (PBS + NaAc medium), indicating that MECs performances were not severely inhibited as the mutual impact between electrochemically active bacteria (EAB) and azo dye decolorization. Improved hydrogen production (0.183 m3/d/m3) and COD removal (92.44 %) were obtained with NaAc + glucose co-substrate and PBS buffer, owing to lower cathodic potential, desired solution conductivity for charge transfer, and better growth of microbial communities under neutral condition. Besides, better MECs performances were obtained when using NaHCO 3 as buffer, compared to Na 2 CO 3 , as milder environment could be provided for microbial growth by NaHCO 3. Findings in this study could promote application potential of MECs for synchronous dye removal and clean energy production with proper operations. [ABSTRACT FROM AUTHOR]

Bio‐electro‐Fenton processes use biological electrons produced from bioelectrochemical systems to treat wastewater. The most significant advantages of bio‐electro‐Fenton systems are high effectiveness, low toxicity, gentle operation conditions, environmentally friendly treatment without sludge accumulation and energy conservation. Though promising, bio‐electro‐Fenton systems still face several challenges, such as high power density, H2O2 concentration, cathode materials, Fe2+ concentration and pH. This review comprehensively discusses the mechanisms of bio‐electro‐Fenton systems. Then, structural configurations are critically reviewed, including microbial fuel cells coupled with electro‐Fenton systems, microbial electrolysis cells coupled with electro‐Fenton systems and other bioelectrochemical systems coupled with electro‐Fenton systems. Furthermore, recent advances in bio‐electro‐Fenton systems for wastewater treatment are introduced, including dye solution, pharmaceuticals and personal care products, oily wastewater, landfill leachate and other pollutants. In addition, the current challenges and specific future prospects of bio‐electro‐Fenton, such as possible mechanisms for improving the power output, electrode materials that are potentially useful, self‐designed electrodes and methods of maintaining circumneutral pH values, are also explored. Heretofore, great progress in bio‐electro‐Fenton has been made, but further improvements are still needed in order to make this system more economical and practical. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The objective of the present study was to construct a compact retrofit design of Microbial Electrolysis Cell (MEC) within an anaerobic digester. In this design, the cathode chamber is inserted in the anodic chamber for compactness, improved hydrogen production and wastewater treatment efficiency. The performance of the new design is compared with that of a conventional (dual chamber) MEC. A cumulative hydrogen of 40.05 ± 0.5 mL and 30.12 ± 0.5 mL were produced at the current density of 811.7 ± 20 and 908.3 ± 25 mA/m2 respectively for conventional and modified MEC system. The cathodic hydrogen recovery (CHR) defined as the recovery of electrons as hydrogen which was observed a maximum of 46.5 ± 0.8 and 38.8 ± 0.5% in conventional and modified MEC. The Coulombic efficiency (CE) defined as the recovery of total electrons in acetate as current was observed as 17.25 ± 0.15 and 16.82 ± 0.1% for conventional and modified MEC. In addition, the wastewater COD removal efficiency was observed to be 77.5 ± 1.0% and 75.6 ± 1.5 in 70 h for conventional and modified MEC designs. As shown in the work below, the modified compact design worked effectively to produce hydrogen under different COD concentrations; anolyte and catholyte concentrations; and applied potentials. Thus the modified compact MEC which is also a retrofit to an existing anaerobic digester can extend the use of anaerobic digesters and improve their economics in waste water treatment. • New design of MEC was constructed and compared for hydrogen generation. • MEC has achieved maximum hydrogen production of 30.2 ± 1.2 mL (@ 811.33 ± 20 mA/m2. • Applied potential and Electrolyte concentration significantly affected the MEC performance. • Distillery wastewater was tested as substrate for hydrogen production in MEC. [ABSTRACT FROM AUTHOR]

• Hydraulic connection between MEC and TEG enhances hydrogen production in MEC. • MEC can act as a cooling unit for improve TEG voltage output that then benefits MEC. • Higher anolyte recirculation rate creates a stronger cooling effect for better performance. • Lower anolyte retention time increases hydrogen production with more organic supply. • Hydrogen production is further enhanced with adding more TEG units. Using alternative power sources to drive hydrogen production in microbial electrolysis cells (MECs) is important to implementation of MEC technology. Herein, thermoelectric generators (TEG) were to power MECs using simulated waste heat. With the MEC anolyte as a cold source for TEG, current generation of the MEC increased to 2.46 ± 0.06 mA and hydrogen production reached 0.14 m3 m−3 d-1, higher than those of the TEG-MEC system without hydraulic connection (1.16 ± 0.07 mA and 0.07 ± 0.01 m3 m−3 d-1). A high recirculation rate of 30 mL min-1 doubled both current generation and hydrogen production with 10 mL min-1, benefited from a stronger cooling effect that increased the TEG voltage output. However, the optimal recirculation rate was determined as 20 mL min-1 because of comparable performance but potentially less energy requirement. Reducing anolyte hydraulic retention time to 4 h has increased hydrogen production to 0.25 ± 0.05 m3 m−3 d-1 but decreased organic removal efficiency to 69 ± 2%. Adding three more TEG units that captured more heat energy further enhanced hydrogen production to 0.36 m3 m−3 d-1. Those results have demonstrated a successful integration of TEG with MEC through both electrical and hydraulic connections for simultaneous wastewater treatment and energy recovery. [ABSTRACT FROM AUTHOR]

Biofilm reactors retain microbial cells in the form of biofilm which is attached to free moving or fixed carrying materials, thus providing a high active biomass concentration and automatic liquid and solid separation. Nowadays, microbial biofilm reactors have been widely used in high-strength wastewater treatment where very high pollutant removal efficiency is required, which usually requires excessive space and aeration energy for conventional activated sludge-based treatment. This paper provides an overview of microbial biofilm reactors developed over the last half-century, including moving bed biofilm reactor (MBBR), trickling filter (TF) reactor, rotating biological contactor (RBC), membrane biofilm reactor (MBfR), passive aeration simultaneous nitrification and denitrification (PASND) biofilm reactor, for their applications in high-strength wastewater treatment of not only removing carbon, nitrogen, sulphur but also a variety of oxidized contaminants including perchlorate and bromate. Despite the advance of biofilm reactor that exhibits high resistance to excessive pollutants loading, its drawbacks both from engineering and microbiological point of view are reviewed. The future prospects of biofilm reactor are also discussed in this review paper. [ABSTRACT FROM AUTHOR]

A new approach for easy synthesis of Bacillus pseudomycoides immobilized polyvinyl alcohol (PVA)/glutaraldehyde (GA) hydrogel for application in a wastewater treatment system is reported. Optimization studies revealed that GA/PVA mass ratio of 0.03 and acidic pH of 2 were required for hydrogel synthesis and eventually for bacterial cell immobilization. The synthesized crosslinked matrix possessed a pore size suitable for microbial cell entrapment while maintaining cell accessibility to external environment for bioremediation. Possible crosslinking and bacterial cell immobilization in the hydrogel were evidenced by FTIR, XRD, and SEM studies, respectively. Further, the extent of crosslinking of GA with PVA was investigated and confirmed by transmittance and permeability experiments. The viability and proliferation of hydrogel embedded cells (after 25 days) was confirmed by confocal fluorescence microscopy which also indicated that acidic pH of polymer solution did not affect the immobilized live cells. B. pseudomycoides immobilized hydrogel were demonstrated to be effective for treatment of municipal wastewater and reduced biochemical oxygen demand (BOD), chemical oxygen demand (COD), and protein content below the recommended levels. Overall, the results from this bench-scale work show that employing bacteria-embedded PVA/GA hydrogel for the treatment of municipal wastewater yield promising results which should be further explored in pilot/field-scale studies. [ABSTRACT FROM AUTHOR]

Domestic and industrial wastewaters are subject to the biological treatment process before discharged to environment. In that process, organic substances contained in the wastewater are degraded by microorganisms. Microbial electrolysis cells (MECs) are suitable technology for wastewater treatment, simultaneously producing hydrogen. In most case, however, a significant amount of methane instead of hydrogen is produced when the wastewater is used for MECs. Here we show that hydrogen is the main product when Makgeolli wastewater (MW) is used as a substrate in a single‐chamber MEC which was operated using acetate and MW. Although current generation profiles vary according to the substrate type and the applied voltage, hydrogen portions were maintained over 90% at −0.6 V and −0.8 V with production rates of 0.95 and 1.55 m3H2/m3/d, respectively. This result shows a possibility of implementing MECs in the real wastewater treatment and hydrogen production. [ABSTRACT FROM AUTHOR]

Antibiotic resistance genes (ARG) are prevalent in aquatic environments. Discharge from wastewater treatment plants is an important point source of ARG release into the environment. It has been reported that biological treatment processes may enhance rather than remove ARG because of their presence in sludge. Attenuation of ARG in biotechnological processes has been studied in depth, showing that many microorganisms can secrete complex extracellular polymeric substances (EPS). These EPS can serve as multifunctional elements of microbial communities, involving aspects, such as protection, structure, recognition, adhesion, and physiology. These aspects can influence the interaction between microbial cells and extracellular ARG, as well as the uptake of extracellular ARG by microbial cells, thus changing the transformative capability of extracellular ARG. However, it remains unclear whether EPS can affect horizontal ARG transfer, which is one of the main processes of ARG dissemination. In light of this knowledge gap, this review provides insight into the role of EPS in the transmission of ARGs; furthermore, the mechanism of ARG spread is analyzed, and the molecular compositions and functional properties of EPS are summarized; also, how EPS influence ARG mitigation is addressed, and factors impacting how EPS facilitate ARG during wastewater treatment are summarized. This review provides comprehensive insights into the role of EPS in controlling the transport and fate of ARG during biodegradation processes at the mechanistic level. [Display omitted] • The focus is the impact of EPS on the spread of antibiotic resistance genes (ARG). • Polysaccharides can be generated extracellularly for specific functions. • Certain ARG can be transferred to other bacteria of the same or different species. • EPS-associated ARG have a higher transformation capacity than cell-free ARG. • Nutrient increases are generally positively correlated with ARG abundance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical analyses revealed better catalytic behavior of Sn-BaTiO 3 vs control. • Sol-gel method was used to synthesize an effective and Sn-doped BaTiO 3 catalyst. • 1 mg/cm2 catalyst achieved organics removal- 88% in reactor (Power- 7.1 W/m3). • High desalination rate was achieved with increase in salt dose from 10 to 20 g/L. • Sn-doped BaTiO 3 as low-cost cathode catalyst to boost performance for upscaling use. Microbial desalination cells (MDCs) have been employed for dissolved salts and contaminant removal along with electricity production. Although oxygen depletion is a momentous reaction in the electrochemical energy transformation, its sluggish kinetics prevent it from being accustomed to fuel cells. Oxygen reduction reactions (ORR) in alkaline environments and perovskite oxide catalysts for converting energy electrochemically have emerged as excellent and promising alternatives. Various concentration of Sn-doped oxygen-deficient BaTiO 3 was incorporated to study ORR behavior and effect on MDC performance. This perovskite catalyst contains a considerable percentage of cubic BaTiO 3 (with 100 nm size) confirmed by material characterization studies. Power density obtained in the absence of the catalyst was 4.7 W/m3 which increased to 6.7 W/m3 upon utilization of BaTiO 3 with salt removal of 76.7%. Catalyst loading of 1 mg/cm2 and initial total dissolved solid (TDS) concentration of 20 g/L was found to be effective for improving the desalination rate in MDC. Electrochemical analyses also revealed enhancement in electrocatalytic behavior of cathodic kinetics under such operating conditions. Thus, Sn-doped BaTiO 3 catalyst can be a suitable candidate for upscaling of MDC to meet the sustainable development goals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wastewater treatment and hydrogen production has attracted researchers globally. • MFC and MEC are preferred for hydrogen production from wastewater. • Catalysts, reactor design, anode and cathode materials influence the process. • Hydrogen storage, transport mechanism needs to be identified for usage. Hydrogen is the green fuel with higher eco-friendly and efficient vehicular fuel. In past hydrogen gas is derived from non-renewable resources. In recent years renewable resources are utilized for generation of bio-hydrogen gas. Hydrogen gas is preferably produced via electrochemical, photochemical, thermochemical and biochemical processes. Microbial fuel cell (MFC) and microbial electrolysis cell (MEC) are the notable systems used for hydrogen production from organic wastes and wastewater. This review mainly focuses on bio-hydrogen production from both MFC and MEC from wastewater. The mechanism, factors influencing the process, different types of MFCs, energy harvesting ways are signposted in this review. This review addresses on the difficulties in harvesting the energy as well as the economic aspect of harvested energy in detail. In MEC, microbial activity happens at anode and in electrode the hydrogen evolution occurs. Upscaling of the process is mainly influenced by the reactor design and microbiology. Performance of various catalysts on hydrogen evolution are discussed in detail. The scalability of integrating MFC and MEC needs to be decoded in near future for the better of hydrogen production and achieving sustainable development goals (SDGs). [ABSTRACT FROM AUTHOR]