Advances and prospects on the aquatic plant coupled with sediment microbial fuel cell system

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.

Constructed wetland microbial fuel cell as enhancing pollutants treatment technology to produce green energy

The persistent challenge of water pollution, exacerbated by slow progress in ecofriendly technologies and accumulating pollutants, underscores the need for innovative solutions. Constructed Wetland Microbial Fuel Cell (CW-MFC) emerges as an intriguing environmental technology capable of adressing this issue by eliminating contaminants from wastewater while simultaneously producing green energy as an additional bonus. In recent years, CW-MFC technology has gained attention due to its sustainability and promising prospects for a circular waste-free industry. However, due to various technological and biological challenges, it has not yet achieved wide-scale application. This review examines the current state of CW-MFC technology and identifies both biotic and abiotic strategies for optimization through operational and structural improvements affecting biocomponents. Our review highlights several key findings: (1) Plants play an important role in reducing the system's inner resistance through mechanisms such as radial oxygen loss, evapotranspiration, and high photosynthetic flow, which facilitate electroactive bacteria and affect redox potential. (2) Plant characteristics such as root porosity, phloem and aerenchyma development, chlorophyll content, and plant biomass are key indicators of CW-MFC performance and significantly impact both pollutant removal and energy harvesting. (3) We expand the criteria for selecting suitable plants to include mesophytes and C3 pollutant-tolerant species, in addition to traditional aquatic and C4 plants. Additionally, the review presents several technical approaches that enhance CW-MFC efficiency: (1) design optimization, (2) use of novel materials, and (3) application of external electrical fields, aeration, light, and temperature adjustments. CW-MFCs are capable of nearly complete elimination of a wide range of contaminants, including organic matter (84 % ± 10), total nitrogen (80 % ± 7) and phosphorus (79 % ± 18) compounds, metals (86 % ± 10), pharmaceuticals (87 % ± 7), dyes (90 % ± 8), and other complex pollutants, while generating green energy. We hope our findings will be useful in optimizing CW-MFC design and providing insights for researchers aiming to advance the technology and facilitate its future scaling.

Organic carbon compounds removal and phosphate immobilization for internal pollution control: Sediment microbial fuel cells, a prospect technology

As a current technology that can effectively remove organic carbon compounds and immobilize phosphorus in sediment, sediment microbial fuel cells (SMFCs) can combine sediment remediation with power generation. This review discusses the removal efficiency of SMFCs on organic carbon compounds, including sediment organic matter, antibiotics, oil-contaminated sediments, methane, persistent organic pollutants, and other organic pollutants in sediment, with more comprehensive and targeted summaries, and it also emphasizes the mitigation of phosphorus pollution in water from the perspective of controlling endogenous phosphorus. In this review, the microbial community is used as a starting point to explore more about its roles on phosphorus and organic carbon compounds under SMFCs. Electrode modification, addition of exogenous substances and combinations with other technologies to improve the performance of SMFCs are also reviewed. It is further demonstrated that SMFCs have the prospect of long-term sustainability, but more attention needs to be paid to the study of the mechanism of SMFCs and the continuous improvement of devices for further application in practice.

Removal of sulfur and nitrogen pollutants in a sediment microbial fuel cell coupled with Vallisneria natans: Efficiency, microbial community structure, and functional genes

The rapid development of the economy has led to an increase in the sulfur and nitrogen load in surface water, which has the potential to cause river eutrophication and the emission of malodorous gases. A lab-scale sediment microbial fuel cell coupled with Vallisneria natans (P-SMFC) was designed for surface water remediation. The enhancement of pollutant removal performance of P-SMFC was evaluated in contrast to the SMFC system without plants (SMFC), the open-circuit control system with plants (C-P), and the open-circuit control system without plants (C-S), while illustrating the mechanisms of the sulfur and nitrogen transformation process. The results demonstrated that the effluent and sediment of P-SMFC had lower concentrations of sulfide compared to other systems. Furthermore, P-SMFC exhibited higher removal efficiency for COD (73.1 ± 8.7%), NH4+-N (80.5 ± 19.8%), and NO3--N (88.5 ± 11.8%) compared to other systems. The closed-circuit conditions and growth of Vallisneria natans create a favorable ecological niche for functional microorganisms involved in power generation, sulfur oxidation, and nitrogen transformation. Additionally, metagenomic analysis revealed that multifunctional bacteria possessing both denitrification and sulfur oxidation genes, such as Thiobacillus, Dechloromonas, and Bacillus, may play simultaneous roles in metabolizing sulfur and nitrogen, thus serving as integral factors in maintaining the performance of P-SMFC. In summary, these findings provide a theoretical reference for the concurrent enhancement of sulfur and nitrogen pollutants removal in P-SMFC and will facilitate its practical application in the remediation of contaminated surface water.

Harnessing fungal bio-electricity: a promising path to a cleaner environment

Integrating fungi into fuel cell systems presents a promising opportunity to address environmental pollution while simultaneously generating energy. This review explores the innovative concept of constructing wetlands as fuel cells for pollutant degradation, offering a practical and eco-friendly solution to pollution challenges. Fungi possess unique capabilities in producing power, fuel, and electricity through metabolic processes, drawing significant interest for applications in remediation and degradation. Limited data exist on fungi's ability to generate electricity during catalytic reactions involving various enzymes, especially while remediating pollutants. Certain species, such as Trametes versicolor, Ganoderma lucidum, Galactomyces reessii, Aspergillus spp., Kluyveromyce smarxianus, and Hansenula anomala, have been reported to generate electricity at 1200 mW/m3, 207 mW/m2, 1,163 mW/m3, 438 mW/m3, 850,000 mW/m3, and 2,900 mW/m3, respectively. Despite the eco-friendly potential compared to conventional methods, fungi's role remains largely unexplored. This review delves into fungi's exceptional potential as fuel cell catalysts, serving as anodic or cathodic agents to mitigate land, air, and water pollutants while simultaneously producing fuel and power. Applications cover a wide range of tasks, and the innovative concept of wetlands designed as fuel cells for pollutant degradation is discussed. Cost-effectiveness may vary depending on specific contexts and applications. Fungal fuel cells (FFCs) offer a versatile and innovative solution to global challenges, addressing the increasing demand for alternative bioenergy production amid population growth and expanding industrial activities. The mechanistic approach of fungal enzymes via microbial combinations and electrochemical fungal systems facilitates the oxidation of organic substrates, oxygen reduction, and ion exchange membrane orchestration of essential reactions. Fungal laccase plays a crucial role in pollutant removal and monitoring environmental contaminants. Fungal consortiums show remarkable potential in fine-tuning FFC performance, impacting both power generation and pollutant degradation. Beyond energy generation, fungal cells effectively remove pollutants. Overall, FFCs present a promising avenue to address energy needs and mitigate pollutants simultaneously.

Methane emission reduction oriented extracellular electron transfer and bioremediation of sediment microbial fuel cell: A review

Sediment is the internal and external source of water environment pollution, so sediment remediation is the premise of water body purification. Sediment microbial fuel cell (SMFC) can remove the organic pollutants in sediment by electroactive microorganisms, compete with methanogens for electrons, and realize resource recycling, methane emission inhibiting and energy recovering. Due to these characteristics, SMFC have attracted wide attention for sediment remediation. In this paper, we comprehensively summarized the recent advances of SMFC in the following areas: (1) The advantages and disadvantages of current applied sediment remediation technologies; (2) The basic principles and influencing factors of SMFC; (3) The application of SMFC for pollutant removal, phosphorus transformation and remote monitoring and power supply; (4) Enhancement strategies for SMFC in sediments remediation such as SMFC coupled with constructed wetland, aquatic plant and iron-based reaction. Finally, we have summarized the drawback of SMFC and discuss the future development directions of applying SMFC for sediment bioremediation.

Electroactive Bacteria in Natural Ecosystems and Their Applications in Microbial Fuel Cells for Bioremediation: A Review

Electroactive bacteria (EAB) are natural microorganisms (mainly Bacteria and Archaea) living in various habitats (e.g., water, soil, sediment), including extreme ones, which can interact electrically each other and/or with their extracellular environments. There has been an increased interest in recent years in EAB because they can generate an electrical current in microbial fuel cells (MFCs). MFCs rely on microorganisms able to oxidize organic matter and transfer electrons to an anode. The latter electrons flow, through an external circuit, to a cathode where they react with protons and oxygen. Any source of biodegradable organic matter can be used by EAB for power generation. The plasticity of electroactive bacteria in exploiting different carbon sources makes MFCs a green technology for renewable bioelectricity generation from wastewater rich in organic carbon. This paper reports the most recent applications of this promising technology for water, wastewater, soil, and sediment recovery. The performance of MFCs in terms of electrical measurements (e.g., electric power), the extracellular electron transfer mechanisms by EAB, and MFC studies aimed at heavy metal and organic contaminant bioremediationF are all described and discussed.

Photoaging processes of polyvinyl chloride microplastics enhance the adsorption of tetracycline and facilitate the formation of antibiotic resistance

Microplastics (MPs), antibiotics and microorganism ubiquitously coexist in aquatic environments. MPs inevitably undergo photoaging processes in aquatic environments, affecting the interactions between MPs and antibiotics and the antibiotic resistance of microorganism. In this study, the impact of photoaging processes of MPs on their adsorption behavior of tetracycline (TC) and related formation of antibiotic resistance were investigated. It was found that the photoaging processes significantly increased the adsorption capacity of TC onto MPs, with the Q_e increasing from 0.387 to 0.507 mg/g at 288 K and from 0.507 to 0.688 mg/g at 308 K. The site energy distribution (SED) analysis further confirmed that the enhanced adsorption capacity was attributed to more high-energy adsorption sites acquired from MPs photoaging processes. Moreover, the enhanced adsorption of TC further facilitated the formation of seven antibiotic resistance genes (i.e., tetA, tetB, tetC, tetD, tetE, tetG, tetK) when MPs adsorbed with TC was covered by biofilm. This study helps comprehensively understand the environmental behaviors of co-existing MPs, antibiotics and microorganisms, providing a theoretical basis for evaluating and mitigating their coexistence risks.

Environmental Sensing in High-Altitude Mountain Ecosystems Powered by Sedimentary Microbial Fuel Cells

The increasing need for fresh water in a climate change scenario requires remote monitoring of water bodies in high-altitude mountain areas. This study aimed to explore the feasibility of SMFC operation in the presence of low dissolved oxygen concentrations for remote, on-site monitoring of physical environmental parameters in high-altitude mountainous areas. The implemented power management system (PMS) uses a reference SMFC (SMFC_Ref) to implement a quasi-maximum power point tracking (quasi-MPPT) algorithm to harvest energy stably. As a result, while transmitting in a point-to-point wireless sensor network topology, the system achieves an overall efficiency of 59.6%. Furthermore, the control mechanisms prevent energy waste and maintain a stable voltage despite the microbial fuel cell (MFC)'s high impedance, low time response, and low energy production. Moreover, our system enables a fundamental understanding of environmental systems and their resilience of adaptation strategies by being a low-cost, ecological, and environmentally friendly alternative to power-distributed and dynamic environmental sensing networks in high-altitude mountain ecosystems with anoxic environmental conditions.

Research progress and hotspot analysis of rhizosphere microorganisms based on bibliometrics from 2012 to 2021

Rhizosphere microorganisms are important organisms for plant growth promotion and bio-control. To understand the research hot topics and frontier trends of rhizosphere microorganisms comprehensively and systematically, we collected 6,056 publications on rhizosphere microorganisms from Web of Science and performed a bibliometric analysis by CiteSpace 6.1.3 and R 5.3.1. The results showed that the total number of references issued in this field has been on the rise in the past decades. China, India, and Pakistan are the top three countries in terms of the number of articles issued, while Germany, the United States, and Spain were the countries with the highest number of co-published papers with other countries. The core research content in this field were the bio-control, bacterial community, ACC deaminase, phytoremediation, induced systematic resistance, and plant growth promotion. Seeding growth, Bacillus velezensis, plant-growth, and biological-control were currently and may be the highlights in the field of rhizosphere microorganisms research for a long time in the future. The above study results quantitatively, objectively, and scientifically described the research status and research focus of rhizosphere microorganisms from 2012 to 2021 from the perspective of referred papers, with a view to promoting in-depth research in this field and providing reference information for scholars in related fields to refine research trends and scientific issues.

Anode modification of sediment microbial fuel cells (SMFC) towards bioremediating mariculture wastewater

Remediation of mariculture wastewater is of great practical importance. In this study, sediment microbial fuel cells (SMFCs) were adopted and carbon felt anodes were modified to enhance COD and ammonia removal in mariculture system. The results showed that the SMFC anode with 5 % (w/w) graphene oxide (GO) coating performed best in pollutants removal and electricity generation. The maximum power density approached 132 mW/m², nearly 4.5 times higher than the unmodified anode. The removal efficiency of COD and ammonia reached 82.1 % and 95.8 % respectively, both improved compared with the control and chemical modification. The modified anode effectively enriched the electrogenic Sulfurovum and Lactobacillus and thus led to a significant improvement in the electrochemical performance of SMFC. This study demonstrates the successful application of SMFCs with GO modified anodes in the in-situ removing pollutants and SMFCs present obvious remediation potential on the contaminated mariculture inhabitant.

Photocatalytic Fuel Cells for Simultaneous Wastewater Treatment and Power Generation: Mechanisms, Challenges, and Future Prospects

Technological advancement is accompanied by excessive consumption of fossil fuels and affluent uses of chemical substances in many sectors, including transportation and manufacturing companies, and so on. Being an exhaustible resource, the excessive use of fossil fuels and of chemical substances may lead to a serious energy crisis in the long run, and it may additionally impose environmental pollution. Attempts have been made in the solution of such serious issues from every nook and corner. Nonetheless, no method has been found to be a panacea in waste water treatment and subsequent beneficiaries. One of the attempts in the solution to such issues is the application of photocatalytic technology, which could serve as a dual function in environmental remediation and clean energy production. A photocatalytic fuel cell is a tool developed for the recovery of energy from organic wastes. A rational cell construction needs the fabrication of photoelectrodes, the design of a photoanode and a photocathode chamber, in addition to an ion-transport membrane for pollution treatment and electricity generation. In this review, comprehensive fundamental assessments and recent developments in the design of photocatalytic fuel cells, their applications, future prospects, and challenges are covered.

Knowledge Map of Spatial Planning and Sustainable Development: A Visual Analysis Using CiteSpace

Spatial planning has become an important measure for countries and regions to promote sustainable development. However, there remains a lack of systematic and quantitative research on spatial planning worldwide. In this study, CiteSpace was used to perform bibliometric analysis and visualization research on the Web of Science core collection and China National Knowledge Infrastructure database. It was found that: (1) The number of papers published in global spatial planning research shows an increasing trend, especially after 2018, with China showing an obvious increasing trend. (2) Globally, the United States has the largest number of relevant research results, and Italy has the most cooperation with other countries. The highest research output is from developed countries, while that of developing countries is relatively weak. (3) There is some intersection among countries, disciplines, and authors but it is not strong, indicating that cooperation should be strengthened. (4) Through keyword cluster, timeline, and time zone analysis, global development can be roughly divided into three stages: the first stage is characterized by the study of spatial planning system theory, the second stage is characterized by building green infrastructure and providing ecological services, and the third stage is characterized by an emphasis on public participation and the establishment of justice mechanisms. China’s development corresponds to three stages: the theory and experience learning stage, the spatial planning system focused on economic development stage, and the integration of multiple plans and the sustainable development exploration stage. (5) There are differences in burst words between the world and China, indicating that there are great differences in research hotspots in different countries’ periods and conditions.