Curbing per- and polyfluoroalkyl substances (PFASs): First investigation in a constructed wetland-microbial fuel cell system

Research progress on coupling and stacking systems to enhance power generation performance of microbial fuel cell

Microbial fuel cells (MFCs) face significant challenges related to low power output, which severely limits their practical applications. Coupling MFC with other technologies and stacking MFCs are feasible solutions to enhance power output. In recent years, the coupling and stacking technology of MFCs has become a research hotspot in the field of environmental energy. This paper first outlines the basic configurations of MFCs and then analyzes the advantages and disadvantages of different setups in the context of coupling and stacking. Subsequently, it discusses in detail the coupling systems of MFC with other technologies, as well as several configurations of stacked MFCs and the phenomenon of voltage reversal. Based on these investigations, the paper proposes future research directions aimed at optimizing MFC performance, thereby enhancing their potential for energy recovery from wastewater and supporting the commercialization and scaling of MFC technology.

Optimization of anode positioning in constructed wetlands coupled with microbial fuel cells based on C/O microenvironment for simultaneous removal of disinfection by-products and nitrogen

Constructed wetland coupled with microbial fuel cell (CW-MFC) has been applied for the advanced removal of emerging contaminants and nitrogen due to its sustainability potential. However, the impact of anode positioning on the synergistic removal of disinfection by-products (DBPs) and nitrogen in CW-MFC remains insufficiently understood. In this study, three CW-MFCs with different anode positions were constructed to explore the response differences in the removal of DBPs (represented by haloacetic acids-HAAs) and nitrogen. It was observed that the CW-MFC with the anode positioned centrally exhibited considerable nitrogen removal (TN removal efficiency: 56.3 ± 8.6 %) and HAAs degradation performance (dichloroacetic acid removal efficiency: 97.8 ± 1.3 %). Correlation analysis identified the advantageous carbon-oxygen environment at the anode as the most critical factor. Furthermore, this carbon-oxygen environment (CODcr-anode/DO=27.7) directly provided favorable conditions for electroactive bacteria to inhabit the anode, significantly enriching denitrifiers and HAAs-degrading bacteria at the cathode. Key genes (HAAs and carbon-nitrogen metabolic) were upregulated, clarifying the mechanisms of synergistic removal of HAAs and nitrogen in CW-MFCs with centrally positioned anodes. This study highlights the importance of CW-MFCs with anode positioning in the synergistic removal of DBPs and nitrogen, providing straightforward and feasible strategy for optimizing CW-MFC performance and scaling up.

In situ bioelectrochemical remediation of contaminated soil and groundwater: A review

Contamination of the subsurface environment poses a serious hazard to the environment and human health. Recently, the bioelectrochemical system (BES) has drawn great attention in soil and groundwater remediation as it does not necessitate the addition of chemicals and exhibits minimal energy consumption to facilitate microbial degradation of pollutants. However, the complexity of the subsurface environment and the design parameters of the BES significantly affect the remediation performance and the current literature on BES primarily concentrates on its application in wastewater treatment, with a lack of summary of that in the subsurface environment. Therefore, the purpose of this review was to provide the current status, challenges, and outlooks of BES in situ treatment of pollutants from soil and groundwater. Firstly, the principles and efficacies of BES in treating the typical pollutants from the subsurface environment were discussed. Secondly, the factors that impact the BES treatment efficiencies, especially soil properties, the distinctive and pivotal factors for BES in situ application, were discussed specifically. Finally, the challenges and outlooks of BES for the in situ remediation of the contaminated soil and groundwater were addressed. BES is a green and sustainable in situ remediation technology and future advancements may necessitate the integration with complementary technologies and innovative system configurations to advance the practical implementation of BES.

Harnessing the power of microbial consortia for the biodegradation of per- and polyfluoroalkyl substances: Challenges and opportunities

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants that pose significant risks to human health and ecosystems owing to their widespread use and resistance to degradation. This study examines the potential of microbial consortia as a sustainable and effective strategy for biodegrading PFAS. It highlights how these complex communities interact with various PFAS, including perfluorocarboxylic acids, perfluorosulfonic acids, fluorotelomer alcohols, and fluorotelomer-based precursors. Despite the potential of microbial consortia, several challenges impede their application in PFAS remediation, including effective microbial species identification, inherent toxicity of PFAS compounds, co-contaminants, complications from biofilm formation, diversity of environmental matrices, and competition with native microbial populations. Future research should focus on refining characterization techniques to enhance our understanding of microbial interactions and functions within consortia. Integrating bioinformatics and system biology will enable a comprehensive understanding of microbial dynamics and facilitate the design of tailored consortia for specific PFAS compounds. Furthermore, field applications and pilot studies are essential for assessing the real-world effectiveness of microbial remediation strategies. Ultimately, advancing our understanding and methodologies will lead to efficient biodegradation processes and positioning microbial consortia as viable solutions for PFAS-contaminated environments.

Evaluating advancements and opportunities in electro-assisted biodehalogenation of emerging halogenated contaminants

Electro-assisted biodehalogenation (EASB) as a biostimulation strategy can accelerate the slow attenuation of emerging halogenated contaminants (EHCs) in anaerobic aqueous environments. A timely review is urgent to evaluate the knowledge gaps and potential opportunities, further facilitating its design and application. Till now, EASB achieves promising progress in accelerating biohalogenation rates, promoting the detoxification of EHCs to cope with unfavourable environments and mitigating greenhouse gas emissions. However, EASB of EHCs still faces several knowledge gaps. Exploring crucial microbes and deciphering insights into dehalogenase characteristics and extracellular electron transfer (EET) pathways remain the prominent task for EASB of EHCs. Moreover, microbial ecological relationships and intricate environmental factors affecting performances and applications are largely underexplored. The emergence of emerging tools holds promises for sorting the intricate changes and addressing these knowledge gaps. Judicious use of emerging tools will rejuvenate EASB strategy, from EET to scale-up, to purposefully and effectively address cascading EHCs.

Insights into poly-and perfluoroalkyl substances (PFAS) removal in treatment wetlands: Emphasizing the roles of wetland plants and microorganisms

Poly- and perfluoroalkyl substances (PFAS) are widespread emerging contaminants in aquatic environments, raising serious concerns due to their persistence and potential toxicity to both human health and ecosystems. Treatment wetlands (TWs) provide a sustainable, low-carbon solution for PFAS removal by harnessing the combined actions of substrates, plants, and microorganisms. This review evaluates the effectiveness of TWs in PFAS treatment, emphasizing their role as a post-treatment option for conventional wastewater treatment plants. Mass balance analysis reveals that substrate adsorption was the primary pathway for PFAS removal from TWs, while plant uptake and subsequent harvesting treatments, as well as microbial degradation, contribute substantially to long-term PFAS removal. Comparisons of bioaccumulation factor (BCF) and translocation factors (TF) between wetland and terrestrial plants demonstrate that wetland plants are particularly effective at adsorbing long-chain PFAS and transferring them from roots to aboveground tissues. The diverse environmental conditions within TWs support varied microbial communities, facilitating the evolution of PFAS-degrading microorganisms. Wetland microorganisms demonstrate the capacity to break down PFAS through processes such as head group transformations (e.g., decarboxylation, desulfonation) and defluorination (e.g., elimination, reductive defluorination, hydrolysis, dealkylation). This review emphasizes the crucial role of wetland plants and microorganisms in the sustainable removal of PFAS in TWs, providing insights for the ecological remediation of PFAS-contaminated wastewater.

Evolutionary trends and development of constructed wetland coupled microbial fuel cell: A decade of development

Constructed wetland coupled microbial fuel cells (CW-MFC) have gained considerable attention as an innovative sustainable technology for simultaneous wastewater treatment and bio-electricity generation since its inception in 2012. This study, which employed bibliometrics of research articles and patent analysis, is a comprehensive investigation into the evolutionary trend and development status of CW-MFC. We analyzed 85 patents and 247 research articles using structured and unstructured data. By using the logistic model and econometric analysis, we predicted the technological life cycle and investigated the factors driving the development of CW-MFC. In addition, this study discusses the innovative hotspots, research and innovative trends, and key contributors at the forefront of this green infrastructure. The study results show that CW-MFC technology has gained greater interest under the influence of national and international policies, market demand, economic growth, and national R&D expenditure, highlighting its global impact. The study also showed that CW-MFC was predominantly distributed in Asia, with China at the forefront. The technology evolution path from both patents and papers showed the transition of research and development from the performance evaluation of CW-MFC with conventional-based technology to the current study focused on system optimization by exploring designs and component factors to enhance efficiency. Furthermore, the technological maturity (TMR) of CW-MFC was determined using the logistic model to be 50.5%, with significant potential for further development (R2 = 0.98). Overall, this study provides a comprehensive understanding of the current trends of CW-MFC development and provides forecasting and direction for future developments.

Simultaneous deep removal of nitrate and tetrabromobisphenol A in microbial electrochemical system-constructed wetland

Microbial electrochemical system-constructed wetland (MES-CW) is environmentally friendly in removing organic contaminants from wastewater. Tetrabromobisphenol A (TBBPA) is an emerging pollutant that is inefficiently removed in conventional wastewater treatment. The feasibility of deep removal of TBBPA and nitrate and the related mechanism in MES-CW remains unclear. This study demonstrated the enhanced TBBPA detoxification in MES-CW accompanied by nitrate removal. Nitrate significantly suppressed the TBBPA reductive debromination and methane generation. It altered the microbial community and enriched Acinetobacter in the electrode, stimulating the TBBPA hydrolytic debromination and metabolite oxidation. The biocathode supplied electrons for dehalogenators in TBBPA reductive debromination, while the anode served as the electron acceptor for function bacteria in TBBPA metabolite oxidation. Nitrate and anodic electricity optimized the microbial community and provided electron acceptors for TBBPA metabolites oxidation in MES-CW, guiding the deep removal of nitrate and emerging pollutants in wastewater.

Effects of perfluoroalkyl acids on nitrogen release, transformation and microbial community during the debris decomposition of Alisma orientale and Iris pseudacorus

The release of nutrients into water during debris decomposition is a serious concern, leading to severe environmental pollution. To understand the effects of extensively present emerging contaminants (such as perfluoroalkyl acids (PFAAs)) on the nitrogen (N) release and transformation, the concentration dynamics of different N species in surrounding water and changes in microbial communities on biofilm during the 70-days decomposition of two typical submerged macrophyte (Alisma orientale and Iris pseudacorus) debris were studied. The results showed that large amounts of N species (especially organic and ammonium N) were released during decomposition. PFAAs with a low concentration (1 μg/L) could stimulate total N (TN) release, whereas PFAAs with a high concentration (≥ 10 μg/L) might have inhibited TN release. Higher intensities of ammonification, nitrosification, and denitrification, but lower intensities of nitrification were observed in water in the presence of PFAAs. Microbiota associated with organic matter hydrolysis, nitrification and denitrification, as well as PFAA degrading/tolerant bacteria, were beneficial and might have occupied dominant states. Redundancy analysis showed that PFAAs were positively associated with the amounts of nitrate, denitrifiers, and azotobacteria but negatively correlated with the TN, ammonia, nitrite, organic N, and nitrosobacteria amounts (p = 0.0002). The complete N metabolism pathway was identified using PICRUSt and KEGG. Functional genes related to ammonification (0.76‰-2.16‰), N reduction (3.43‰-5.05‰), and assimilation (0.81‰-2.16‰) were more abundant than others in all treatments. This study provides a more comprehensive understanding of N cycling during debris decomposition under the increasingly intractable threat of emerging contaminants in aquatic ecosystems.

Pollutant removal and greenhouse gas emissions in horizontal subsurface flow constructed wetlands with iron ore treating ammonium-rich wastewater

Horizontal subsurface flow constructed wetlands (HFCWs) are capable of eliminating organic matter and nitrogen while emitting less methane (CH4) and nitrous oxide (N2O) than free water surface flow wetlands. However, the simultaneous removal of pollutants and reduction of greenhouse gases (GHG) emissions from high-strength wastewater containing high levels of organic matter and ammonium nitrogen (NH4+-N) has not get been investigated. The influent COD concentration affected the efficiency of nitrogen removal, GHG emissions and the presence of iron from iron ore, but the COD and TP removal efficiencies remained unaffected. CO2 and CH4 fluxes were significantly influenced by influent COD concentrations, whereas less N2O emissions were obtained during 7d. The highest CO2 and CH4 fluxes, along with the GHG emissions, were observed in HFCWs with COD concentrations of 375.6 mg/L and NH4+-N concentrations of 159.0 mg/L at a COD/N ratio of 2.4. Conversely, the lowest CH4 (-1.72 mg/m2/h) and N2O fluxes (0.13 mg/m2/h) were recorded in HFCWs with COD concentrations of 375.6 mg/L and NH4+-N concentrations of 162.4 mg/L at a COD/N of 4.5, although nitrogen removal was weak in these HFCWs. HFCWs at a COD/N ratio of 3.6 exhibited greater removal of nitrogen and other pollutants, along with a lower global warming potential (GWP). In conclusion, the concentrations of organic matter and NH4+-N in wastewater affected both pollutant removal and GHG emissions. The simultaneous enhancement of pollutant removal and the reduction of GHG emissions can be achieved in HFCWs with a COD/N ratio of 3.6.

Enhancement of PFAS stress tolerance and wastewater treatment efficiency by arbuscular mycorrhizal fungi in constructed wetlands

This study aims to explore the effects of arbuscular mycorrhizal fungi (AMF) on the growth of Iris pseudacorus L. and treatment efficacy in constructed wetlands (CWs) subjected to stress from per-and poly-fluoroalkyl substances (PFASs). The findings reveal that PFASs exposure induces oxidative damage and inhibits the growth of I. pseudacorus. However, AMF symbiosis enhances plant tolerance to PFAS stress by modulating oxidative responses. AMF treatment not only promoted plant growth but also improved photosynthetic efficiency under PFAS exposure. Compared to non-AMF treatment, those with AMF treatment exhibited significantly increased levels of peroxidases and antioxidant enzymes, including peroxidase and superoxide dismutase, along with a notable reduction in lipid peroxidation. Additionally, AM symbiosis markedly enhanced the efficacy of CWs in the remediation of wastewater under PFASs-induced stress, with removal efficiencies for COD, TP, TN, and NH4+-N increasing by 19-34%, 67-180%, 106-137%, and 25-95%, respectively, compared to the AMF- treatments. In addition, the metabolic pathways of PFASs appeared to be influenced by their carbon chain length, with long-chain PFASs like perfluorooctanoic acid (PFOA) and perfluoro anionic acid (PFNA) exhibiting more complex pathways compared to short-chain PFASs such as perfluoro acetic acid (PFPeA), and perfluoro hexanoic acid (PFHpA). These results suggest that AMF-plant symbiosis can enhance plant resilience against PFAS-induced stress and improve the pollutant removal efficiency of CWs. This study highlights the significant potential of AMF in enhancing environmental remediation strategies, providing new insights for the more effective management of PFAS-contaminated ecosystems.

A review of per- and polyfluoroalkyl substances (PFASs) removal in constructed wetlands: Mechanisms, enhancing strategies and environmental risks

PER: Polyfluoroalkyl substances (PFASs), typical persistent organic pollutants detected in various water environments, have attracted widespread attention due to their undesirable effects on ecology and human health. Constructed wetlands (CWs) have emerged as a promising, cost-effective, and nature-based solution for removing persistent organic pollutants. This review summarizes the removal performance of PFASs in CWs, underlying PFASs removal mechanisms, and influencing factors are also discussed comprehensively. Furthermore, the environmental risks of PFASs-enriched plants and substrates in CWs are analyzed. The results show that removal efficiencies of total PFASs in various CWs ranged from 21.3% to 98%. Plant uptake, substrate absorption and biotransformation are critical pathways in CWs for removing PFASs, which can be influenced by the physiochemical properties of PFASs, operation parameters, environmental factors, and other pollutants. Increasing dissolved oxygen supply and replacing traditional substrates in CWs, and combining CWs with other technologies could significantly improve PFASs removal. Further, CWs pose relatively lower ecological and environmental risks in removing PFASs, which indicates CWs could be an alternative solution for controlling PFASs in aquatic environments.

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.

Emerging eco-friendly technologies for remediation of Per- and poly-fluoroalkyl substances (PFAS) in water and wastewater: A pathway to environmental sustainability

Per- and polyfluoroalkyl substances (PFAS) are rampant, toxic contaminants from anthropogenic sources, called forever chemicals for their recalcitrance. Although banned in several parts of the world for public health implications, including liver, kidney, and testicular diseases, PFAS are abundant in water sources due to easy dispersion. With chemical properties resulting from strong hydrophobic bonds, they defile many physicochemical removal methods. Though adsorption processes such as granular activated carbon (GAC) are widely used, they are marred by several limitations, including cost and secondary contamination. Thus, eco-friendly methods involving a synergy of the removal principles have been preferred for ease of use, cost-effectiveness, and near-zero effect on the environment. We present novel eco-friendly methods as the solution to PFAS remediation towards environmental sustainability. Current eco-friendly methods of PFAS removal from water sources, including electrocoagulation, membrane/filtration, adsorption, and phytoremediation methods, were highlighted, although with limitations. Novel eco-friendly methods such as microbial fuel cells, photoelectrical cells, and plasma treatment offer solutions to PFAS remediation and are quite efficient in terms of cost, result, and environmental sustainability. Overall, the successful integration of eco-friendly techniques in a seamless manner ensures the desired result. We also present a balanced position on the ecosystem impact of these ecofriendly methods, noting the successes towards environmental sustainability while exposing the gaps for further research.

Advancement in constructed wetland microbial fuel cell process for wastewater treatment and electricity generation: a review

The constructed wetland coupled with a microbial fuel cell (CW-MFC) is a wastewater treatment process that combines contaminant removal with electricity production, making it an environmentally friendly option. This hybrid system primarily relies on anaerobic bioprocesses for wastewater treatment, although other processes such as aerobic bioprocesses, plant uptake, and chemical oxidation also contribute to the removal of organic matter and nutrients. CW-MFCs have been successfully used to treat various types of wastewater, including urban, pharmaceutical, paper and pulp industry, metal-contaminated, and swine wastewater. In CW-MFC, macrophytes such as rice plants, Spartina angalica, Canna indica, and Phragmites australis are used. The treatment process can achieve a chemical oxygen demand removal rate of between 80 and 100%. Initially, research focused on enhancing power generation from CW-MFC, but recent studies have shifted towards resource recovery from wastewater. This review paper provides an overview of the development of constructed wetland microbial fuel cell technology, from its early stages to its current applications. The paper also highlights research gaps and potential directions for future research.

Constructed wetlands as nature-based solutions in managing per-and poly-fluoroalkyl substances (PFAS): Evidence, mechanisms, and modelling

Per- and poly-fluoroalkyl substances (PFAS) have emerged as newly regulated micropollutants, characterised by extreme recalcitrance and environmental toxicity. Constructed wetlands (CWs), as a nature-based solution, have gained widespread application in sustainable water and wastewater treatment and offer multiple environmental and societal benefits. Despite CWs potential, knowledge gaps persist in their PFAS removal capacities, associated mechanisms, and modelling of PFAS fate. This study carried out a systematic literature review, supplemented by unpublished experimental data, demonstrating the promise of CWs for PFAS removal from the influents of varying sources and characteristics. Median removal performances of 64, 46, and 0 % were observed in five free water surface (FWS), four horizontal subsurface flow (HF), and 18 vertical flow (VF) wetlands, respectively. PFAS adsorption by the substrate or plant root/rhizosphere was deemed as a key removal mechanism. Nevertheless, the available dataset resulted unsuitable for a quantitative analysis. Data-driven models, including multiple regression models and machine learning-based Artificial Neural Networks (ANN), were employed to predict PFAS removal. These models showed better predictive performance compared to various mechanistic models, which include two adsorption isotherms. The results affirmed that artificial intelligence is an efficient tool for modelling the removal of emerging contaminants with limited knowledge of chemical properties. In summary, this study consolidated evidence supporting the use of CWs for mitigating new legacy PFAS contaminants. Further research, especially long-term monitoring of full-scale CWs treating real wastewater, is crucial to obtain additional data for model development and validation.

Emergence of per- and poly-fluoroalkyl substances (PFAS) and advances in the remediation strategies

A group of fluorinated organic molecules known as per- and poly-fluoroalkyl substances (PFAS) have been commonly produced and circulated in the environment. PFAS, owing to multiple strong CF bonds, exhibit exceptional stability and possess a high level of resistance against biological or chemical degradation. Recently, PFAS have been identified to cause numerous hazardous effects on the biotic ecosystem. As a result, extensive efforts have been made in recent years to develop effective methods to remove PFAS. Adsorption, filtration, heat treatment, chemical oxidation/reduction, and soil washing are a few of the physicochemical techniques that have shown their ability to remove PFAS from contaminated matrixes. However these methods also carry significant drawbacks, including the fact that they are expensive, energy-intensive, unsuitable for in-situ treatment, and requirement to be carried under dormant conditions. The metabolic products released upon PFAS degradation are largely unknown, despite the fact that thermal disintegration methods are widely used. In contrast to physical and chemical methods, biological degradation of PFAS has been regarded as efficient method. However, PFAS are difficult to instantly and completely metabolize through biological methods due to the limitations of biocatalytic mechanisms. Nevertheless, cost, easy-to-operate and environmentally safe are some of the advantages over its counterpart. The present review comprehensively discusses the occurrence of PFAS, the state-of-the science of remediation technologies and approaches applied, and the remediation challenges. The article also focuses on the future research directions toward the development of effective methods for PFAS-contaminated site in-situ treatment.

Interactions between MPs and PFASs in aquatic environments: A dual-character situation

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs) have drawn great attention as emerging threats to aquatic ecosystems. Although the literature to study the MPs and PFASs alone has grown significantly, our knowledge of the overlap and interactions between the two contaminations is scarce due to the unawareness of it. Actually, numerous human activities can simultaneously release MPs and PFASs, and the co-sources of the two are common, meaning that they have a greater potential for interactions. The direct interaction lies in the PFASs adsorption by MPs in water with integrated mechanisms including electrostatic and hydrophobic interactions, plus many influence factors. In addition, the existence and transportation of MPs and PFASs in the aquatic environment have been identified. MPs and PFASs can be ingested by aquatic organisms and cause more serious combined toxicity than exposure alone. Finally, curbing strategies of MPs and PFASs are overviewed. Wastewater treatment plants (WWTPs) can be an effective place to remove MPs from wastewater, while they are also an important point source of MPs pollution in water bodies. Although adsorption has proven to be a successful curbing method for PFASs, more technological advancements are required for field application. It is expected that this review can help revealing the unheeded relationship and interaction between MPs and PFASs in aquatic environments, thus assisting the further investigations of both MPs and PFASs as a whole.

Interactions between biofilms and PFASs in aquatic ecosystems: Literature exploration

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been detected in most aquatic environments worldwide and are referred to as "forever chemicals" because of their extreme chemical and thermal stability. Biofilms, as basic aquatic bioresources, can colonize various substratum surfaces. Biofilms in the aquatic environment have to interact with the ubiquitous PFASs and have significant implications for both their behavior and destiny, which are still poorly understood. Here, we have a preliminary literature exploration of the interaction between PFASs and biofilms in the various aquatic environments and expect to provide some thoughts on further study. In this review, the biosorption properties of biofilms on PFASs and possible mechanisms are presented. The complex impact of PFASs on biofilm systems was further discussed in terms of the composition and electrical charges of extracellular polymeric substances, intracellular microbial communities, and overall contaminant purification functions. Correspondingly, the effects of biofilms on the redistribution of PFASs in the aqueous environment were analyzed. Finally, we propose that biofilm after adsorption of PFASs is a unique ecological niche that not only reflects the contamination level of PFASs in the aquatic environment but also offers a possible "microbial pool" for PFASs biodegradation. We outline existing knowledge gaps and potential future efforts for investigating how PFASs interact with biofilms in aquatic ecosystems.

An Overview of Microbial Fuel Cell Technology for Sustainable Electricity Production

The over-exploitation of fossil fuels and their negative environmental impacts have attracted the attention of researchers worldwide, and efforts have been made to propose alternatives for the production of sustainable and clean energy. One proposed alternative is the implementation of bioelectrochemical systems (BESs), such as microbial fuel cells (MFCs), which are sustainable and environmentally friendly. MFCs are devices that use bacterial activity to break down organic matter while generating sustainable electricity. Furthermore, MFCs can produce bioelectricity from various substrates, including domestic wastewater (DWW), municipal wastewater (MWW), and potato and fruit wastes, reducing environmental contamination and decreasing energy consumption and treatment costs. This review focuses on recent advancements regarding the design, configuration, and operation mode of MFCs, as well as their capacity to produce bioelectricity (e.g., 2203 mW/m2) and fuels (i.e., H2: 438.7 mg/L and CH4: 358.7 mg/L). Furthermore, this review highlights practical applications, challenges, and the life-cycle assessment (LCA) of MFCs. Despite the promising biotechnological development of MFCs, great efforts should be made to implement them in a real-time and commercially viable manner.

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.