Application of sediment microbial fuel cell for in situ reclamation of aquaculture pond water quality

Aquatic plants combined with microbial fuel cells promote sulfamethoxazole and sul genes removal from aquaculture pond sediments via bioelectrochemistry

Antibiotics and antibiotic resistance genes (ARGs) in the aquaculture environment are receiving increasing public attention as emerging contaminants. In this study, aquatic plant (P) and sediment microbial fuel cells (SMFC) were used individually and in combination (P-SMFC) to simulate in situ remediation of sulfamethoxazole (SMX) and sul genes in aquaculture environments. The results showed that the average power densities of SMFC and P-SMFC were 622.18 mW m-2 and 565.99 mW m-2, respectively. The addition of 5 mg kg-1 of SMX to the sediment boosted the voltages of SMFC and P-SMFC by 36.3% and 51.5%, respectively. After 20 days of treatment, the removal efficiency of SMX from the sediment was 86.17% and 89.60% for SMFC and P-SMFC group, respectively, which were significantly higher than the control group (P < 0.05). However, removal of SMX by plants was not observed. P-SMFC group significantly reduced the biotoxicity of SMX to Staphylococcus aureus and Escherichia coli in the overlying water (P < 0.05). P and P-SMFC groups significantly reduced the abundance of ARGs intl1 and sul1 (P < 0.05). The removal rate of ARGs intl1, sul1 and sul2 from sediments by P-SMFC ranged from 94.22% to 97.08%. However, SMFC increased the abundance of sul3. SMFC and P-SMFC increased the relative abundance of some of sulfate-reducing bacteria such as Desulfatiglans, Thermodesulfovibrionia and Sva0485 in sediments. These results showed that aquatic plants promoted the removal of ARGs and SMFC promoted the removal of antibiotics, and the combination with aquatic plants and SMFC achieved a synergistic removal of both SMX and ARGs. Therefore, current study provides a promising approach for the in situ removal of antibiotics and ARGs in the aquaculture environment.

Biomass and domestic waste: a potential resource combination for bioenergy generation and water treatment via benthic microbial fuel cell

The benthic microbial fuel cell (BMFC) is one of the most efficient types of bioelectrochemical fuel cell systems. Modern bioelectrochemical fuel cells have several drawbacks, including an unstable organic substrate and a microorganism-unfriendly atmosphere. The recent literature to encounter such issues is one of the emerging talks. Researchers are focusing on the utilization of biomass and waste to encounter such challenges and make the technique more feasible at the pilot scale. This study investigated the combination of local bakery waste as an organic substrate with lignocellulosic biomass material. The whole experiment was conducted for 45 days. At an external resistance of 1000 ῼ and an internal resistance of 677 ῼ, the power density was found to be 3.51 mW/m2. Similarly, for Pb2+, Cd2+, Cr3+, Ni2+, and Co2+, the degradation efficiency was 84.40%, 81.21%, 80%, 89.50%, and 86.0%, respectively. The bacterial identification results showed that Liquorilactobacillus nagelii, Proteus mirabilis, Pectobacterium punjabense, and Xenorhabdus thuongxuanensis are the most prominent species found on anode biofilm. The method of electron generation in this study, which includes the degradation of metal ions, is also well described. Lastly, optimising the parameters showed that pH 7 provides a feasible environment for operation. A few future suggestions for practical steps are enclosed for the research community.

The race between classical microbial fuel cells, sediment-microbial fuel cells, plant-microbial fuel cells, and constructed wetlands-microbial fuel cells: Applications and technology readiness level

Microbial fuel cell (MFC) is an interesting technology capable of converting the chemical energy stored in organics to electricity. It has raised high hopes among researchers and end users as the world continues to face climate change, water, energy, and land crisis. This review aims to discuss the journey of continuously progressing MFC technology from the lab to the field so far. It evaluates the historical development of MFC, and the emergence of different variants of MFC or MFC-associated other technologies such as sediment-microbial fuel cell (S-MFC), plant-microbial fuel cell (P-MFC), and integrated constructed wetlands-microbial fuel cell (CW-MFC). This review has assessed primary applications and challenges to overcome existing limitations for commercialization of these technologies. In addition, it further illustrates the design and potential applications of S-MFC, P-MFC, and CW-MFC. Lastly, the maturity and readiness of MFC, S-MFC, P-MFC, and CW-MFC for real-world implementation were assessed by multicriteria-based assessment. Wastewater treatment efficiency, bioelectricity generation efficiency, energy demand, cost investment, and scale-up potential were mainly considered as key criteria. Other sustainability criteria, such as life cycle and environmental impact assessments were also evaluated.

Almukhlifi H, Ahmad A, Yaqoob AA. Dual Role of Sugarcane Waste in Benthic Microbial Fuel to Produce Energy with Degradation of Metals and Chemical Oxygen Demand

One of the most advanced systems of microbial fuel cells is the benthic microbial fuel cell (BMFC). Despite several developments, this strategy still has a number of significant flaws, such as instable organic substrate. Waste material (sugarcane) is used as a substrate in this work to address the organic substrate instability. The process was operated continuously for 70 days. A level of 300 mV was achieved after 33 days of operation, while the degradation efficiencies of Pb (II), Cd (II), and Cr (III) were more than 90%. More than 90% of the removed chemical oxygen demand (COD) was also recorded. The measured power density was 3.571 mW/m2 at 1000 external resistance with 458 internal resistance. This demonstrates that electrons are effectively transported throughout the operation. The Bacillus strains are the most dominant bacterial community on the surface of the anode. This research’s mechanism, which involves metal ion degradation, is also explained. Finally, parameter optimization indicated that pH 7 works efficiently. In addition to that, there are some future perspectives and concluding remarks enclosed.

Degradation of Metal Ions with Electricity Generation by Using Fruit Waste as an Organic Substrate in the Microbial Fuel Cell

A potential and developing green technology for producing renewable energy and treating wastewater is the microbial fuel cell (MFC). Despite several advancements, there are still several serious problems with this approach. In the present work, we addressed the problem of the organic substrate in MFC, which is necessary for the degradation of metal ions in conjunction with the production of energy. The utilization of fruit waste as a carbon source was strongly suggested in earlier research. Hence, the mango peel was used as a substrate in the current study. Within 25 days of operation, a 102-mV voltage was achieved in 13 days, while the degradation efficiency of Cr3+ was 69.21%, Co2+ was 72%, and Ni2+ was 70.11%. The procedure is carried out in the batch mode, and there is no continuous feeding of the organic substrate. In addition, a detailed explanation of the hypothesized mechanism for this investigation is provided, which focuses on the process of metal ion degradation. Lastly, future and concluding remarks are also enclosed.

Removal effect of enrofloxacin from mariculture sediments by bioelectrochemical system and analysis of microbial community structure

Based on the application of sediment microbial fuel cell (SMFC) in the bioremediation of sediment, this study used the sediment microbial fuel cell technology as the leading reactor. Modification of anode carbon felts (CF) by synthesis of PANI/MnO₂ composited to improve the electrical performance of the sediment microbial fuel cell. This study investigated the degradation effects, degradation pathways of the specific contaminant enrofloxacin and microbial community structure in sediment microbial fuel cell systems. The results showed that the sediment microbial fuel cell system with modified anode carbon felt (PANI-MnO₂/CF) prepared by in-situ chemical polymerization had the best power production performance. The maximum output voltage was 602 mV and the maximum power density was 165.09 mW m^-2. The low concentrations of enrofloxacin (12.81 ng g^-1) were effectively degraded by the sediment microbial fuel cell system with a removal rate of 59.52%.

Utilizing Biomass-Based Graphene Oxide-Polyaniline-Ag Electrodes in Microbial Fuel Cells to Boost Energy Generation and Heavy Metal Removal

Although regarded as environmentally stable, bioelectrochemical fuel cells or, microbial fuel cells (MFCs) continue to face challenges with sustaining electron transport. In response, we examined the performance of two graphene composite-based anode electrodes—graphene oxide (GO) and GO–polymer–metal oxide (GO–PANI–Ag)—prepared from biomass and used in MFCs. Over 7 days of operation, GO energy efficiency peaked at 1.022 mW/m² and GO–PANI–Ag at 2.09 mW/m². We also tested how well the MFCs could remove heavy metal ions from synthetic wastewater, a secondary application of MFCs that offers considerable benefits. Overall, GO–PANI–Ag had a higher removal rate than GO, with 78.10% removal of Pb(II) and 80.25% removal of Cd(II). Material characterizations, electrochemical testing, and microbial testing conducted to validate the anodes performance confirmed that using new materials as electrodes in MFCs can be an attractive approach to improve the electron transportation. When used with a natural organic substrate (e.g., sugar cane juice), they also present fewer challenges. We also optimized different parameters to confirm the efficiency of the MFCs under various operating conditions. Considering those results, we discuss some lingering challenges and potential possibilities for MFCs.

Microbial Electrochemical Technologies for Sustainable Nitrogen Removal in Marine and Coastal Environments

For many years, the world's coastal marine ecosystems have received industrial waste with high nitrogen concentrations, generating the eutrophication of these ecosystems. Different physicochemical-biological technologies have been developed to remove the nitrogen present in wastewater. However, conventional technologies have high operating costs and excessive production of brines or sludge which compromise the sustainability of the treatment. Microbial electrochemical technologies (METs) have begun to gain attention due to their cost-efficiency in removing nitrogen and organic matter using the metabolic capacity of microorganisms. This article combines a critical review of the environmental problems associated with the discharge of the excess nitrogen and the biological processes involved in its biogeochemical cycle; with a comparative analysis of conventional treatment technologies and METs especially designed for nitrogen removal. Finally, current METs limitations and perspectives as a sustainable nitrogen treatment alternative and efficient microbial enrichment techniques are included.

Constructed sediment microbial fuel cell for treatment of fat, oil, grease (FOG) trap effluent: Role of anode and cathode chamber amendment, electrode selection, and scalability

For wastewater treatment, sediment microbial fuel cells (SMFCs) have advantages over traditional microbial fuel cells in cost (due to their membrane-less structure) and operation (less intensive maintenance). Nevertheless, the technical obstacles of SMFCs include their high internal electrical resistance due to sediment in the anode chamber and slow oxygen reduction reaction (ORR) in the cathode chamber, which is responsible for their low power density (PD) (0.2-50 mW/m²). This study evaluated several SMFC improvements, including anode and cathode chamber amendment, electrode selection, and scaling the chamber size up to obtain optimally constructed single-chamber SMFCs to treat fat, oil, and grease (FOG) trap effluent. The chemical oxygen demand (COD) removal efficiency, PD, and electrical energy conversion efficiency concerning theoretically available chemical energy from FOG trap effluent treatment (%EC^WW) were examined. Packing biochar in the anode chamber reduced its electrical resistance by 5.76 times, but the improvement in PD was trivial. Substantial improvement occurred when packing the cathode chamber with activated carbon (AC), which presumably catalyzed the ORR, yielding a maximum PD of 109.39 mW/m², 959 times greater than without AC in the cathode chamber. This SMFC configuration resulted in a COD removal efficiency of 85.80 % and a %EC^WW of 99.74 % in 30 days. Furthermore, using the most appropriate electrode pair and chamber volume increased the maximum PD to 1787.26 mW/m², around 1.7 times greater than the maximum PD by SMFCs reported thus far. This optimally constructed SMFC is low cost and applicable for household wastewater treatment.

Green approach and strategies for wastewater treatment using bioelectrochemical systems: A critical review of fundamental concepts, applications, mechanism, and future trends

Millions of litters of multifarious wastewater are directly disposed into the environment annually to reduce the processing costs leading to eutrophication and destroying the clean water sources. The bioelectrochemical systems (BESs) have recently received significant attention from researchers due to their ability to convert waste into energy and their high efficiency of wastewater treatment. However, most of the performed researches of the BESs have focused on energy generation, which created a literature gap on the utilization of BESs for wastewater treatment. The review highlights this gap from various aspects, including the BESs trends, fundamentals, applications, and mechanisms. A different review approach has followed in the present work using a bibliometric review (BR) which defined the literature gap of BESs publications in the degradation process section and linked the systematic review (SR) with it to prove and review the finding systematically. The degradation mechanisms of the BESs have been illustrated comprehensively in the current work, and various suggestions have been provided for supporting future studies and cooperation.

Bioelectricity production and xylene biodegradation through double chamber benthic microbial fuel cells fed with sugarcane waste as a substrate

Xylene, a recalcitrant compound present in wastewater from activities of petrochemical and chemical industries causes chronic problems for living organisms and the environment. Xylene contaminated wastewater may be biodegraded through a benthic microbial fuel cell (BMFC) as seen in this study. Xylene was oxidized into intermediate 3-methyl benzoic acid and entirely converted into non-toxic carbon dioxide. The highest voltage of the BMFC reactor was generated at 410 mV between 23 and 90 days when cell potential was 1 kΩ. The reactor achieved a maximum power density of about 63 mW/m², and a current of 0.4 mA which was optimized from variable resistance (20 Ω - 1 kΩ). However, the maximum biodegradation efficiency of the BMFC was at 87.8%. The cyclic voltammetry curve helped to determine that the specific capacitance was 0.124 F/g after 30 days of the BMFC operation. Furthermore, the fitting equivalent circuit was observed with the help of Nyquist plot for calculating overall internal resistance of 65.82 Ω on 30th day and 124.5 Ω on 80th day. Staphylococcus edaphicus and Staphylococcus sparophiticus were identified by 16S rRNA sequencing as the dominant species in the control and BMFC electrode, presumably associated with xylene biodegradation.

Cellulose Derived Graphene/Polyaniline Nanocomposite Anode for Energy Generation and Bioremediation of Toxic Metals via Benthic Microbial Fuel Cells

Benthic microbial fuel cells (BMFCs) are considered to be one of the eco-friendly bioelectrochemical cell approaches nowadays. The utilization of waste materials in BMFCs is to generate energy and concurrently bioremediate the toxic metals from synthetic wastewater, which is an ideal approach. The use of novel electrode material and natural organic waste material as substrates can minimize the present challenges of the BMFCs. The present study is focused on cellulosic derived graphene-polyaniline (GO-PANI) composite anode fabrication in order to improve the electron transfer rate. Several electrochemical and physicochemical techniques are used to characterize the performance of anodes in BMFCs. The maximum current density during polarization behavior was found to be 87.71 mA/m² in the presence of the GO-PANI anode with sweet potato as an organic substrate in BMFCs, while the GO-PANI offered 15.13 mA/m² current density under the close circuit conditions in the presence of 1000 Ω external resistance. The modified graphene anode showed four times higher performance than the unmodified anode. Similarly, the remediation efficiency of GO-PANI was 65.51% for Cd (II) and 60.33% for Pb (II), which is also higher than the unmodified graphene anode. Furthermore, multiple parameters (pH, temperature, organic substrate) were optimized to validate the efficiency of the fabricated anode in different environmental atmospheres via BMFCs. In order to ensure the practice of BMFCs at industrial level, some present challenges and future perspectives are also considered briefly.

Sediment microbial fuel cells as a barrier to sulfide accumulation and their potential for sediment remediation beneath aquaculture pens

Sediment microbial fuel cells (SMFCs) generate electricity through the oxidation of reduced compounds, such as sulfide or organic carbon compounds, buried in anoxic sediments. The ability to remove sulfide suggests their use in the remediation of sediments impacted by point source organic matter loading, such as occurs beneath open pen aquaculture farms. However, for SMFCs to be a viable technology they must remove sulfide at a scale relevant to the environmental contamination and their impact on the sediment geochemistry as a whole must be evaluated. Here we address these issues through a laboratory microcosm experiment. Two SMFCs placed in high organic matter sediments were operated for 96 days and compared to open circuit and sediment only controls. The impact on sediment geochemistry was evaluated with microsensor profiling for oxygen, sulfide, and pH. The SMFCs had no discernable effect on oxygen profiles, however porewater sulfide was significantly lower in the sediment microcosms with functioning SMFCs than those without. Depth integrated sulfide inventories in the SMFCs were only 20% that of the controls. However, the SMFCs also lowered pH in the sediments and the consequences of this acidification on sediment geochemistry should be considered if developing SMFCs for remediation. The data presented here indicate that SMFCs have potential for the remediation of sulfidic sediments around aquaculture operations.

Community level physiological profiling of microbial electrochemical-based constructed wetlands

The performance of constructed wetlands (CW) can be enhanced through the use of microbial electrochemical technologies like METland systems. Given its novelty, uncertainties exist regarding processes responsible for the pollutant removal and microbial activity within the systems. Genetic characterization of microbial communities of METlands is desirable, but it is a time and resource consuming. An alternative, is the functional analysis based on community-level physiological profile (CLPP), which allows to evaluate the diversity of microbial communities based on the carbon consumption patterns and derived indexes (average well color development - AWCD -, richness, and diversity). This study aimed to characterize the microbial community function of laboratory-scale METlands using the CLPP method. It encompassed the analysis of planted and non-planted set-ups of two carbon-based electroconductive materials (Coke-A and Coke-LSN) colonized with electroactive biofilms, and compared to Sand-filled columns. Variations in the microbial metabolic activity were found to depend on the characteristics of the material rather than to the presence of plants. Coke-A systems showed lower values of AWCD, richness, and diversity than Sand and Coke-LSN systems. This suggests that Coke-A systems provided more favorable conditions for the development of relatively homogeneous microbial biofilms. Additionally, typical parameters of water quality were measured and correlations between utilization of carbon sources and removal of pollutants were established. The results provide useful insight into the spatial dynamics of the microbial activity of METland systems.

Microbial Electrochemical Technologies for Wastewater Treatment: Principles and Evolution from Microbial Fuel Cells to Bioelectrochemical-Based Constructed Wetlands

Microbial electrochemical technologies (MET) rely on the presence of the metabolic activity of electroactive bacteria for the use of solid-state electrodes for oxidizing different kinds of compound that can lead to the synthesis of chemicals, bioremediation of polluted matrices, the treatment of contaminants of interest, as well as the recovery of energy. Keeping these possibilities in mind, there has been growing interest in the use of electrochemical technologies for wastewater treatment, if possible with simultaneous power generation, since the beginning of the present century. In the last few years, there has been growing interest in exploring the possibility of merging MET with constructed wetlands offering a new option of an intensified wetland system that could maintain a high performance with a lower footprint. Based on that interest, this paper explains the general principles of MET, and the different known extracellular electron transfer mechanisms ruling the interaction between electroactive bacteria and potential solid-state electron acceptors. It also looks at the adoption of those principles for the development of MET set-ups for simultaneous wastewater treatment and power generation, and the challenges that the technology faces. Ultimately, the most recent developments in setups that merge MET with constructed wetlands are presented and discussed.

Electricity generation through a photo sediment microbial fuel cell using algae at the cathode

Sediment microbial fuel cells (SMFCs) are bio-electrochemical devices generating electricity from redox gradients occurring across the sediment–water interface. Sediment microbial carbon-capture cell (SMCC), a modified SMFC, uses algae grown in the overlying water of sediment and is considered as a promising system for power generation along with algal cultivation. In this study, the performance of SMCC and SMFC was evaluated in terms of power generation, dissolved oxygen variations, sediment organic matter removal and algal growth. SMCC gave a maximum power density of 22.19 mW/m2, which was 3.65 times higher than the SMFC operated under similar conditions. Sediment organic matter removal efficiencies of 77.6 ± 2.1% and 61.0 ± 1.3% were obtained in SMCC and SMFC, respectively. With presence of algae at the cathode, a maximum chemical oxygen demand and total nitrogen removal efficiencies of 63.3 ± 2.3% (8th day) and 81.6 ± 1.2% (10th day), respectively, were observed. The system appears to be favorable from a resources utilization perspective as it does not depend on external aeration or membranes and utilizes algae and organic matter present in sediment for power generation. Thus, SMCC has proven its applicability for installation in an existing oxidation pond for sediment remediation, algae growth, carbon conversion and power generation, simultaneously.

Internal nitrogen removal from sediments by the hybrid system of microbial fuel cells and submerged aquatic plants

Sediment internal nitrogen release is a significant pollution source in the overlying water of aquatic ecosystems. This study aims to remove internal nitrogen in sediment-water microcosms by coupling sediment microbial fuel cells (SMFCs) with submerged aquatic plants. Twelve tanks including four treatments in triplicates were designed: open-circuit (SMFC-o), closed-circuit (SMFC-c), aquatic plants with open-circuit (P-SMFC-o) and aquatic plants with closed-circuit (P-SMFC-c). The changes in the bio-electrochemical characteristics of the nitrogen levels in overlying water, pore water, sediments, and aquatic plants were documented to explain the migration and transformation pathways of internal nitrogen. The results showed that both electrogenesis and aquatic plants could facilitate the mineralization of organic nitrogen in sediments. In SMFC, electrogenesis promoted the release of ammonium from the pore water, followed by the accumulation of ammonium and nitrate in the overlying water. The increased redox potential of sediments due to electrogenesis also contributed to higher levels of nitrate in overlying water when nitrification in pore water was facilitated and denitrification at the sediment-water interface was inhibited. When the aquatic plants were introduced into the closed-circuit SMFC, the internal ammonium assimilation by aquatic plants was advanced by electrogenesis; nitrification in pore water and denitrification in sediments were also promoted. These processes might result in the maximum decrease of internal nitrogen with low nitrogen levels in the overlying water despite the lower power production. The P-SMFC-c reduced 8.1%, 16.2%, 24.7%, and 25.3% of internal total nitrogen compared to SMFC-o on the 55th, 82th, 136th, and 190th days, respectively. The smaller number of Nitrospira and the larger number of Bacillus and Pseudomonas on the anodes via high throughput sequencing may account for strong mineralization and denitrification in the sediments under closed-circuit. The coupled P-SMFC system has shown good potential for the efficient removal of internal nitrogen.

Assessing the suitability of sediment-type bioelectrochemical systems for organic matter removal from municipal wastewater: a column study

This study examines the use of bioelectrochemical systems (BES) as an alternative to rock filters for polishing wastewater stabilisation ponds (WSPs) effluent, which often contains soluble chemical oxygen demand (SCOD) and suspended solids mainly as algal biomass. A filter type sediment BES configuration with graphite granules (as the surrogate for rocks in a rock filter) was examined. Three reactor columns were set up to examine three different treatments: (i) open-circuit without current generation; (ii) close-circuit - with current generation; and (iii) control reactor without electrode material. All columns were continuously operated for 170 days with real municipal wastewater at a hydraulic retention time of 5 days. Compared to the control reactor, the two experimental reactors showed significant improvement of SCOD removal (from approximately 25% to 66%) possibly due to retention of biomass on the graphite media. However, substantial amount of SCOD (60%) was removed via non-current generation pathways, and a very low Coulombic efficiency (6%) was recorded due to a poor cathodic oxygen reduction kinetics and a large electrode spacing. Addressing these challenges are imperative to further develop BES technology for WSP effluent treatment.

All ecosystems potentially host electrogenic bacteria

Instead of requiring metal catalysts, MFCs utilize bacteria that oxidize organic matter and either transfer electrons to the anode or take electrons from the cathode. These devices are thus based on a wide microbial diversity that can convert a large array of organic matter components into sustainable and renewable energy. A wide variety of explored environments were found to host electrogenic bacteria, including extreme environments. In the present review, we describe how different ecosystems host electrogenic bacteria, as well as the physicochemical, electrochemical and biological parameters that control the currents from MFCs. We also report how using new molecular techniques allowed characterization of electrochemical biofilms and identification of potentially new electrogenic species. Finally we discuss these findings in the context of future research directions.

Sediment microbial fuel cells as a new source of renewable and sustainable energy: present status and future prospects

SMFCs are a bioelectricity production technology for low power applications. Recent advances in SMFCs are investigated to enhance their performance. Power improvement and organic matter reduction in SMFCs enlarge their range of applications.