The impact of bottom water light exposure on electrical and sediment remediation performance of sediment microbial fuel cells.

Sediment microbial fuel cells (SMFCs) generate bioelectricity from benthic sediments and thus providing both bioelectricity generation and sediment remediation. However, the high internal resistance of the cathode leads to a low power output, which requires research on cathode treatment. In this study, we explored the influence of light irradiation on bioelectricity production and nutrient removal in the SMFC system. The microcosm experiment of the SMFC system was designed with artificial illumination of 500 lux (light-SMFC) and compared with dark conditions of 15 lux (dark-SMFC), which showed that the current increases during photoperiods. The study reveals that light-illuminated SMFC consistently produced the highest voltage, with the highest voltage (553 mV) being 1.3 times higher than the dark-SMFC (440 mV). The polarization curves show a significant reduction in internal cathodic resistance under light condition, resulting in increased voltage generation. The light-SMFC exhibits the highest maximum power density of 35.93 mW/m2, surpassing the dark SMFC of 31.13 mW/m2. It was found that light illumination in the SMFC system increases oxygen availability in the cathodic region, which supports the oxygen reduction reaction (ORR) process. At the same time, the high bioelectricity output contributes to the highest sediment remediation by greatly reducing the chemical oxygen demand (COD) and phosphate (PO4-P) concentrations. The study highlights the potential of light illumination in mitigating cathodic limitation to improve SMFC performance and nutrient removal.

Sediment microbial fuel cell coupled floating treatment wetland for enhancing non-reactive phosphorus removal.

The presence of non-reactive phosphorus (NRP) in environmental waters presents a potential risk of eutrophication and poses challenges for the removal of all phosphorus (P) fractions. This study presents the first investigation on the removal performance and mechanism of three model NRP compounds, sodium tripolyphosphate (STPP), adenosine 5'-monophosphate (AMP) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), in the sediment microbial fuel cell-floating treatment wetland (SMFC-FTW). Coupling SMFC with plants proved to be effective at removing NRP via electrochemical oxidation and plant uptake, particularly the challenging-to-degrade phosphonates that contain C-P bonds. Compared with the control group, the removal efficiencies of the model NRP in SMFC were observed to increase by 11.9%-20.8%. SMFC promoted the conversion of NRP to soluble reactive phosphorus (sRP) and the transfer of P to sediment. Furthermore, the electrochemical process enhanced both plant growth and P uptake, and increased P assimilation by 72.6%. The presence of plants in the bioelectrochemical system influenced the occurrence and fate of P by efficiently assimilating sRP and supporting microbial transformation of NRP. Consequently, plants enhanced the removal efficiencies of all P fractions in the overlying water. This study demonstrated that SMFC-FTW is a promising technology to remove various NRP species in environmental waters.

Optimized combination of zero-valent iron and oxygen-releasing biochar as cathodes of microbial fuel cells to enhance copper migration in sediment.

Membrane-less single-medium sediment microbial fuel cells (single-SMFC) can remove Cu2+ from sediment through electromigration. However, the high mass transfer resistance of the sediment and amount of oxygen at the cathode of the SMFC limit its Cu2+ removal ability. Therefore, this study used an oxygen-releasing bead (ORB) for slow oxygen release to increase oxygen at the SMFC cathode and improve the mass transfer property of the sediment. Resultantly, the copper removal efficiency of SMFC increased significantly. Response surface methodology was used to optimize the nano zero-valent iron (nZVI)-modified biochar as the catalyst to enhance the ability of the modified ORB (ORBm) to remove Cu2+ and slow release of O2. The maximum Cu2+ removal (95 %) and the slowest O2 release rate (0.41 mg O2/d·g ORBm) were obtained when the CaO2 content and ratio of nZVI-modified biochar to unmodified biochar were 0.99 g and 4.95, respectively. When the optimized ORBm was placed at the single-SMFC cathode, the voltage output and copper removal increased by 4.6 and 2.1 times, respectively, compared with the system without ORBm. This shows that the ORBm can improve the migration of Cu2+ in the sediment, providing a promising remediation method for Cu-contaminated sediments.

Solar-enhanced bio-electro-Fenton driven by sediment microbial fuel cell for ametryn degradation in simulated seawater.

In marine aquaculture areas, herbicides have been used to inhibit the wild growth of seaweed, which may seriously affect the ecological environment and food safety. Here the commonly applied ametryn was used as the representative pollutant, and solar enhanced bio-electro-Fenton driven in situ by sediment microbial fuel cell (SMFC) was proposed to degrade ametryn in simulated seawater. SMFC with γ-FeOOH-coated carbon felt cathode was operated under the simulated solar light (γ-FeOOH-SMFC), where two-electron oxygen reduction and activation of H2O2 occurred to promote the production of hydroxyl radicals at the cathode. Hydroxyl radicals, photo-generated holes, and anodic microorganism worked together to degrade ametryn with an initial concentration of 2 mg/L in the self-driven system. The removal efficiency of ametryn in γ-FeOOH-SMFC was 98.7 % during the operation period of 49 days, which was 6 times higher than that under natural degradation condition. When γ-FeOOH-SMFC was in the steady phase, oxidative species were continuously and efficiently generated. The maximum power density (Pmax) of γ-FeOOH-SMFC was 44.6 W/m3. According to the intermediate products of ametryn degradation in γ-FeOOH-SMFC, four possible pathways of ametryn degradation were proposed. This study provides an effective, cost-saving, and in situ treatment for refractory organics in seawater.

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.

Functional Prediction of Microbial Communities in Sediment Microbial Fuel Cells.

Sediment microbial fuel cells (MFCs) were developed in which the complex substrates present in the sediment could be oxidized by microbes for electron production. In this study, the functional prediction of microbial communities of anode-associated soils in sediment MFCs was investigated based on 16S rRNA genes. Four computational approaches, including BugBase, Functional Annotation of Prokaryotic Taxa (FAPROTAX), the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2), and Tax4Fun2, were applied. A total of 67, 9, 37, and 38 functional features were statistically significant. Among these functional groups, the function related to the generation of precursor metabolites and energy was the only one included in all four computational methods, and the sum total of the proportion was 93.54%. The metabolism of cofactor, carrier, and vitamin biosynthesis was included in the three methods, and the sum total of the proportion was 29.94%. The results suggested that the microbial communities usually contribute to energy metabolism, or the metabolism of cofactor, carrier, and vitamin biosynthesis might reveal the functional status in the anode of sediment MFCs.

Simultaneous treatment of chromium-containing wastewater and electricity generation using a plant cathode-sediment microbial fuel cell: investigation of associated mechanism and influencing factors.

A novel plant cathode-sediment microbial fuel cell (P-SMFC) was constructed to treat Cr-containing wastewater, and the effects of the plants used, initial concentrations of Cr(VI) employed, and the external resistance on the treatment of wastewater and generation of electricity were investigated. The results showed that the system achieved the best performance when Acorus calamus was the cathode plant, the external resistance was 2000 Ω, and the initial Cr (VI) concentration of the overlying water of is 230 mg/L. A maximum power density of 40.16 mW/m2 was reached, and Cr (VI) and COD removal efficiencies in the overlying water were 99.94% and 98.21%, respectively. The closed-circuit installation promoted the attachment of many microorganisms to the cathode, anode and sediment, increased species abundance, and reduced species diversity. The P-SMFC is inexpensive to construct, it consumes no energy, and it can generate bioelectricity; it thus has great application development value as a chromium-containing wastewater treatment method.

Microbial electrochemical system: an emerging technology for remediation of polycyclic aromatic hydrocarbons from soil and sediments.

Worldwide industrialization and other human activities have led to a frightening stage of release of hazardous, highly persistent, toxic, insoluble, strongly adsorbed to the soil and high molecular weight ubiquitous polycyclic aromatic hydrocarbons (PAHs) in soils and sediments. The various conventional remediation methods are being used to remediate PAHs with certain drawbacks. Time taking process, high expenditure, excessive quantities of sludge generation, and various chemical requirements do not only make these methods outdated but produce yet much resistant and toxic intermediate metabolites. These disadvantages may be overcome by using a microbial electrochemical system (MES), a booming technology in the field of bioremediation. MES is a green remediation approach that is regulated by electrochemically active microorganisms at the electrode in the system. The key advantage of the system over the conventional methods is it does not involve any additional chemicals, takes less time, and generates minimal sludge or waste during the remediation of PAHs in soils. However, a comprehensive review of the MES towards bioremediation of PAHs adsorbed in soil and sediment is still lacking. Therefore, the present review intended to summarize the recent information on PAHs bioremediation, application, risks, benefits, and challenges based on sediment microbial fuel cell and microbial fuel cell to remediate mount-up industrial sludge, soil, and sediment rich in PAHs. Additionally, bio-electrochemically active microbes, mechanisms, and future perspectives of MES have been discussed.

Winogradsky Bioelectrochemical System as a Novel Strategy to Enrich Electrochemically Active Microorganisms from Arsenic-Rich Sediments.

Bioelectrochemical systems (BESs) have been extensively studied for treatment and remediation. However, BESs have the potential to be used for the enrichment of microorganisms that could replace their natural electron donor or acceptor for an electrode. In this study, Winogradsky BES columns with As-rich sediments extracted from an Andean watershed were used as a strategy to enrich lithotrophic electrochemically active microorganisms (EAMs) on electrodes (i.e., cathodes). After 15 months, Winogradsky BESs registered power densities up to 650 µWcm-2. Scanning electron microscopy and linear sweep voltammetry confirmed microbial growth and electrochemical activity on cathodes. Pyrosequencing evidenced differences in bacterial composition between sediments from the field and cathodic biofilms. Six EAMs from genera Herbaspirillum, Ancylobacter, Rhodococcus, Methylobacterium, Sphingomonas, and Pseudomonas were isolated from cathodes using a lithoautotrophic As oxidizers culture medium. These results suggest that the tested Winogradsky BES columns result in an enrichment of electrochemically active As-oxidizing microorganisms. A bioelectrochemical boost of centenarian enrichment approaches, such as the Winogradsky column, represents a promising strategy for prospecting new EAMs linked with the biogeochemical cycles of different metals and metalloids.

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%.

Effect of starch-derived organic acids on the removal of polycyclic aromatic hydrocarbons in an aquaculture-sediment microbial fuel cell.

This study constructed sediment microbial fuel cells (SMFCs) for polycyclic aromatic hydrocarbons (PAHs) removal in contaminated aquaculture sediment. Starch, a waste deposited in aquaculture sediment, was employed as the co-substrate for electricity generation and PAHs removal, and the effect of starch-derived organic acids on SMFC performance was assessed. The results indicated that sufficient starch promoted PAHs removal (69.9% for naphthalene, 55.6% for acenaphthene, and 46.8% for pyrene) in dual-chamber SMFC, whereas excessive starch attenuated SMFC performance because the organic acids accumulation reduced anode pH, decreased species diversity, and changed the microbial communities. The electricity generation and PAHs removal were positively correlated (R > 0.96), and both of them were related to Macellibacteroides belonging to Bacteroidetes. However, a larger single-chamber SMFC device did not obtain enhanced PAHs removal owing to the restricted "effective range" of the anode. Hence, more challenges need to be addressed to realize the practical application of SMFC.

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

Energy resource scarcity and sediment pollution perniciousness have become enormous challenges, to which research has been focused on energy recovery and recycle technologies to solve both above problems. The organic matter stored in anoxic sediments of freshwater ecosystem represents a tremendous potential energy source. The system of aquatic plant coupled with sediment microbial fuel cell (AP-SMFC) has attracted much attention as a more feasible, economical and eco-friendly way to remediate sediment and surface water and generate electricity. However, the research on AP-SMFC has only been carried out in the last decade, and relevant studies have not been well summarized. In this review, the advances and prospects on AP-SMFC were systematically introduced. Firstly, the annual publication counts and keywords co-occurrence cluster of AP-SMFC were identified and visualized by resorting to the CiteSpace software, and the result showed that the research on AP-SMFC increased significantly in the last decade on the whole and will continue to increase. The bibliometric results provided valuable references and information on potential research directions for future studies. And then, the research progress and reaction mechanism of AP-SMFC were systematically described. Thirdly, the performance of AP-SMFC, including nutrients removal, organic contaminants removal, and electricity generation, was systematically summarized. AP-SMFC can enhance the removal of pollutants and electricity generation compared with SMFC without AP, and is considered to be an ideal technology for pollutants removal and resource recovery. Finally, the current challenges and future perspectives were summarized and prospected. Therefore, the review could serve as a guide for the new entrants to the field and further development of AP-SMFC application.

Dynamic Changes in Soil Microbial Communities with Glucose Enrichment in Sediment Microbial Fuel Cells.

To investigate soil microbial community dynamics in sediment microbial fuel cells (MFCs), this study applied nonhydric (D) and hydric (S) soils to single-chamber and mediator-free MFCs. Glucose was also used to enrich microorganisms in the soils. The voltage outputs of both the D and S sediment MFCs increased over time but differed from each other. The initial open circuit potentials were 345 and 264 mV for the D and S MFCs. The voltage output reached a maximum of 503 and 604 mV for D and S on days 125 and 131, respectively. The maximum power densities of the D and S MFCs were 2.74 and 2.12 mW m-2, analyzed on day 50. Clustering results revealed that the two groups did not cluster after glucose supplementation and 126 days of MFC function. The change in Geobacter abundance was consistent with the voltage output, indicating that these bacteria may act as the main exoelectrogens on the anode. Spearman correlation analysis demonstrated that, in the D soils, Geobacter was positively correlated with Dialister and negatively correlated with Bradyrhizobium, Kaistobacter, Pedomicrobium, and Phascolarctobacterium; in the S soils, Geobacter was positively correlated with Shewanella and negatively correlated with Blautia. The results suggested that different soil sources in the MFCs and the addition of glucose as a nutrient produced diverse microbial communities with varying voltage output efficiencies. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12088-021-00959-x.

On-line monitoring of minor oil spills in natural waters using sediment microbial fuel cell sensors equipped with vertical floating cathodes.

Oil spills near natural water bodies pose considerable threats to aquatic ecosystem and drinking water system. Various detection techniques have been developed to identify the oil pollution in natural waters. These techniques mainly focus on large and major oil spills involving significant changes in environmental characteristics. However, monitoring of minor oil spills (from seepage and dripping) in waters remains a bottleneck, allowing inconspicuous and persistent oil contamination. To overcome this drawback, a sediment microbial fuel cell (SMFC) sensor equipped with a vertical floating cathode is developed for on-line and in-situ monitoring of minor oil spills in natural waters. The vertical floating cathode was intended for recognizing oil on water surface. Oil on the cathode will trigger current drop. Two kinds of natural sediments were adopted in two sensors (SMFC1 from a lake and SMFC2 from an urban stream) for comparison. Both showed linear relationship between net steady-state current decrease and oil dose (30.78 and 27.29 µA/mL of sensitivity, respectively). The current change process was fitted well to a pseudo-first order kinetic equation. A one-point/two-point dynamic identification methods were derived from the kinetic equation. Therefore, the detection time was shortened from 10 h to 10/30 min. The triggered current decrease was mainly attributed to the increase in internal resistance related to charge and mass transfer. Despite the power loss after oil contamination, results implied SMFC sensor could still achieve self-sustainability. This study shows that the SMFC sensor with vertical floating cathodes is applicable to monitoring the unnoticeable minor oil pollutions in natural waters.

Simultaneous PAHs degradation, odour mitigation and energy harvesting by sediment microbial fuel cell coupled with nitrate-induced biostimulation.

The study investigates a bioremediation process of polycyclic aromatic hydrocarbons (PAHs) removal and odour mitigation combined with energy harvesting. Sediment microbial fuel cells (SMFCs) were constructed with the addition of nitrate in the sediment to simultaneously remove acid-volatile sulphide (AVS) and PAHs. With the combined nitrate-SMFC treatment, over 90% of the AVS was removed from the sediment in 6 weeks of the SMFC operation and a maximum of 94% of AVS removal efficiency was reached at Week 10. The highest removal efficiencies of phenanthrene, pyrene, and benzo[a]pyrene was 93%, 80%, and 69%, respectively. The maximum voltage attained for the combined nitrate-SMFC treatment was 341 mV. Illumina HiSeq sequencing revealed that the autotrophic denitrifiers Thiobacillus are the dominant genus. In electricity generation, both sulphide-oxidation and PAH-oxidation are the possible pathways. Besides, the addition of nitrate stimulated the growth of Pseudomonas which is responsible for the electricity generation and direct biodegradation of the PAHs, indicating a synergistic effect. The developed bioremediation process demonstrated the potential in the in-situ bioremediation process utilizing SMFC combined with nitrate-induced bioremediation.

Microorganisms in sediment microbial fuel cells: Ecological niche, microbial response, and environmental function.

A sediment microbial fuel cell (SMFC) is a device that harvests electrical energy from sediments rich in organic matter. SMFCs have been attracting increasing amounts of interest in environmental remediation, since they are capable of providing a clean and inexhaustible source of electron donors or acceptors and can be easily controlled by adjusting the electrochemical parameters. The microorganisms inhabiting sediments and the overlying water play a pivotal role in SMFCs. Since the SMFC is applied in an open environment rather than in an enclosed chamber, the effects of the environment on the microbes should be intense and the microbial community succession should be extremely complex. Thus, this review aims to provide an overview of the microorganisms in SMFCs, which few previous review papers have reported. In this study, the anodic and cathodic niches for the microorganisms in SMFCs are summarized, how the microbial population and community interact with the SMFC environment is discussed, a new microbial succession strategy called the electrode stimulation succession is proposed, and recent developments in the environmental functions of SMFCs are discussed from the perspective of microorganisms. Future studies are needed to investigate the electrode stimulation succession, the environmental function and the electron transfer mechanism in order to boost the application of SMFCs for power generation and environmental remediation.

Scale-up and control the voltage of sediment microbial fuel cell for charging a cell phone.

In this research, a power management system (PMS) has been developed to charge a cell phone battery based on sediment microbial fuel cells (SMFCs). The single SMFC produces a voltage of 1.16 V, which is too low for practical application. The voltage is increased by connecting several SMFCs in series or parallel, but the voltage reversal occurs when it is directly connected to the load. To prevent the voltage reversal, the super capacitor is first charged by the five different stack SMFCs and the charged super capacitor is used to provide the input power to a PMS. This PMS increases and regulates the input voltage of stack SMFCs up to 5.02 V for charging a cell phone battery. The charging and discharging times of the super capacitors have been investigated with five different stack SMFCs. In all five stack SMFCs, only module-5 provides power to PMS for long periods (13 min). Further, the cell phone battery is continuously charged using the two parallel-connected stack SMFCs similar to the module-5. The battery has been fully charged in 26 h using 72 SMFCs. The charged battery is used to perform for three purposes; voice calling, music playing and LED strip lighting. This study is informative for the application of SMFC in an off-grid location.

Electrical current generation from a continuous flow macrophyte biocathode sediment microbial fuel cell (mSMFC) during the degradation of pollutants in urban river sediment.

A new type of sediment microbial fuel cell (SMFC) with floating macrophyte Limnobium laevigatum, Pistia stratiotes, or Lemna minor L. biocathode was constructed and assessed in three phases at different hydraulic retention time (HRT) for electrical current generation during the degradation of urban river sediment. The results showed a highest voltage output of 0.88 ± 0.1 V, maximum power density of 80.22 mW m-3, highest columbic efficiency of 15.3%, normalized energy recovery of 0.030 kWh m-3, and normalized energy production of 0.005 kWh m-3 in the Lemna minor L. SMFC during phase 3 at HRT of 48 h, respectively. Highest removal efficiencies of total chemical oxygen demand of 80%, nitrite of 99%, ammonia of 93%, and phosphorus of 94% were achieved in Lemna minor L. system, and 99% of nitrate removal and 99% of sulfate removal were achieved in Pistia stratiotes and Limnobium laevigatum system during the SMFC operation, respectively. Pistia stratiotes exhibited the highest growth in terms of biomass and tap root system of 29.35 g and 12.2 cm to produce the maximum dissolved oxygen of 16.85 ± 0.2 mg L-1 compared with other macrophytes. The predominant bacterial phylum Proteobacteria of 62.86% and genus Exiguobacterium of 17.48% were identified in Limnobium laevigatum system, while the class Gammaproteobacteria of 28.77% was observed in the control SMFC. The integration of technologies with the continuous flow operation shows promising prospect in the remediation of polluted urban river sediments along with the generation of electrical current.

Novel chitosan based smart cathode electrocatalysts for high power generation in plant based-sediment microbial fuel cells.

Smart electrocatalysts are synthesized from chitosan polymer and magnetic particles to enhance power by plant based sediment microbial fuel cell (P-SMFC). Cross-linked procedure is performed gelatinous microspheres as supporting metals (Cu, Pd, Mn, Pt, and Ni) and magnetic particles which create a porous structure on smart catalysts for increase ORR activity. A high and quick OCV rising is achieved with addition of Mag-Pd-Ch in reactor, and OCV value immediately increase from 0.408 V to 0.819 V within 10 minutes. The highest power density is also obtained as 1298 mW m-2 for reactor with Mag-Pd-Ch, which was 15 times higher than control. Significant metal leaching is observed using plant growth for smart catalyst containing Cu. Consequently, high power production, good stabilization, easy separation from water environment due to magnetic property, and relatively low cost make use of Mag-Pd-Ch both economic and environment friendly tools to enhance power generation in P-SMFC.

Carbon nanomaterial-modified graphite felt as an anode enhanced the power production and polycyclic aromatic hydrocarbon removal in sediment microbial fuel cells.

Sediment microbial fuel cells (SMFCs) can be used to generate electricity and remove organic contaminants. For electricity generation and contaminant removal, the anode material is one of important factors influencing the performance of SMFCs. In this study, graphene (GR), graphene oxide (GO) and carbon nanotubes (CNTs) were applied to modify the graphite felt (GF) anode in SMFCs during 110 d operation. An economical and easy modification method with the carbon nanomaterials was applied. The carbon nanomaterials increased the electrochemically active surface areas and biomass content of the anodes and correspondingly effectively enhanced the generation of electricity and the removal rates of loss on ignition (LOI) and polycyclic aromatic hydrocarbons (phenanthrene and pyrene). During the steady period from 50 d to 110 d, the GO-SMFCs favored the enrichment of EAB and thus output the highest voltages of 30.60-48.61 mV. The GR-SMFCs and GO-SMFCs generated high electric power of approximate 0.98 ± 0.14 kJ and 0.87 ± 0.04 kJ, followed by CNT-SMFCs (0.57 ± 0.06 kJ) and GF-SMFCs (0.49 ± 0.07 kJ) during the 110 d operation. The PAH degradation was not directly related to the electric current in the SMFCs. Near the anodes, the order of the phenanthrene removal rates was CNT-SMFCs (78.1%) > GR-SMFCs (73.0%) ≈ GO-SMFCs (71.2%) > GF-SMFCs (45.6%), and the order of the pyrene removal rates was GO-SMFCs (69.6%) ≈ GR-SMFCs (68.2%) ≈ CNT-SMFCs (66.7%) > GF-SMFCs (42.3%). The three carbon nanomaterials increased the microbial community diversity and slightly changed the microbial community distribution of biofilms on the anodes. Correlation analysis indicated that the degradation of phenanthrene was positively correlated with the abundances of Pseudomonas, Thauera, Diaphorobacter, Tumebacillus and Lysobacter. Pyrene degradation was strongly correlated with LOI degradation.