Electromyographic and mechanomyographic responses of the biceps brachii during concentric and eccentric muscle actions to failure at high and low relative loads.

PURPOSE: This study examined neuromuscular responses of the biceps brachii (BB) for concentric and eccentric muscle actions during bilateral, dynamic constant external resistance (DCER), reciprocal forearm flexions and extensions to failure at high (80% 1 repetition maximum [1RM]) and low (30% 1RM) relative loads. METHODS: Nine women completed 1RM testing and repetitions to failure (RTF) at 30 and 80% 1RM. Electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) signals were measured from the BB. Analyses included repeated measures ANOVAs (p < 0.05) and post-hoc pairwise comparisons with Bonferroni corrected alpha of p < 0.008 and p < 0.01 for between and within factor pairwise comparisons, respectively. RESULTS: EMG AMP and MPF were significantly greater for concentric than eccentric muscle actions, regardless of load or time. However, time course of change analysis revealed parallel increases in EMG AMP for concentric and eccentric muscle actions during the RTF trials at 30% 1RM, but no change at 80% 1RM. There were significant increases in MMG AMP during concentric muscle actions, but decreases or no change during eccentric muscle actions. EMG and MMG MPF decreased over time, regardless of muscle action type and loading condition. CONCLUSION: The greater EMG AMP and MPF values during concentric compared to eccentric muscle actions may reflect the difference in the efficiency characteristic of these muscle actions. The neuromuscular responses suggested that fatigue may be mediated by recruitment of additional motor units with lower firing rates during concentric muscle actions, and changes in motor unit synchronization during eccentric muscle actions.

External resistance acclimation regulates bio-anode: new perspective from biofilm structure and its correlation with anode performance.

External resistance is important for the anode and cell performance. However, little attentions were paid on the effect of external resistance on the variation of biofilm structure. Here, we used external resistance ranged from 4000 to 500 Ω for anodic acclimation to investigate the correlation between anode performance and biofilm structure. With the reduce of external resistance, the maximum current density of anode increased from 1.0 to 3.4 A/m2, which was resulted from a comprehensive effect of reduced charge transfer resistance and increased diffusion resistance. Biological analysis showed that with the reduce of external resistance, biomass and extracellular polymeric substances content increased by 109 and 286%, cell viability increased by 22.7%, which contributed to the reduced charge transfer resistance. But the porosity of anodic biofilm decreased by 27.8%, which led to an increased diffusion resistance of H+. This work provided a clear correlation between the electrochemical performance and biofilm structure.

Insights into microbial community in microbial fuel cells simultaneously treating sulfide and nitrate under external resistance.

The effect of electricity, induced by external resistance, on microbial community performance is investigated in Microbial Fuel Cells (MFCs) involved in simultaneous biotransformation of sulfide and nitrate. In the experiment, three MFCs were operated under different external resistances (100 Ω, 1000 Ω and 10,000 Ω), while one MFC was operated with open circuit as control. All MFCs demonstrate good capacity for simultaneous sulfide and nitrate biotransformation regardless of external resistance. MFCs present similar voltage profile; however, the output voltage has positive relationship with external resistance, and the MFC1 with lowest external resistance (100 Ω) generated highest power density. High-throughput sequencing confirms that taxonomic distribution of suspended sludge in anode chamber encompass phylum level to genus level, while the results of principal component analysis (PCA) suggest that microbial communities are varied with external resistance, which external resistance caused the change of electricity generation and substrate removal at the same, and then leads to the change of microbial communities. However, based on Pearson correlation analyses, no strong correlation is evident between community diversity indices (ACE index, Chao index, Shannon index and Simpson index) and the electricity (final voltage and current density). It is inferred that the performance of electricity did not significantly affect the diversity of microbial communities in MFCs biotransforming sulfide and nitrate simultaneously.

Enhancing sensitivity of microbial fuel cell sensors for low concentration biodegradable organic matter detection: Regulation of substrate concentration, anode area and external resistance.

The relatively low sensitivity is an important reason for restricting the microbial fuel cell (MFC) sensors' application in low concentration biodegradable organic matter (BOM) detection. The startup parameters, including substrate concentration, anode area and external resistance, were regulated to enhance the sensitivity of MFC sensors. The results demonstrated that both the substrate concentration and anode area were positively correlated with the sensitivity of MFC sensors, and an external resistance of 210 Ω was found to be optimal in terms of sensitivity of MFC sensors. Optimized MFC sensors had lower detection limit (1 mg/L) and higher sensitivity (Slope value of the linear regression curve was 1.02), which effectively overcome the limitation of low concentration BOM detection. The essential reason is that optimized MFC sensors had higher coulombic efficiency, which was beneficial to improve the sensitivity of MFC sensors. The main impact of the substrate concentration and anode area was to regulate the proportion between electrogens and nonelectrogens, biomass and living cells of the anode biofilm. The external resistance mainly affected the morphology structure and the proportion of living cells of the anode. This study demonstrated an effective way to improve the sensitivity of MFC sensors for low concentration BOM detection.

Influence of Altered Knee Angle and Muscular Contraction Type on Electromyographic Activity of Hamstring Muscles during 45° Hip Extension Exercise.

In this study, we investigated differences in electromyographic activity in the biceps femoris long head (BFl), semitendinosus, and semimembranosus muscles during 45° hip extension with different knee angles during eccentric, concentric, and isometric hip 0°, and isometric hip 45° conditions with non-external resistance and 5-kg load. Twenty-two male volunteers performed 45° hip extension with knee flexion angles of 0°, 45° and 90° with non-external resistance and 5-kg load eccentric, concentric, isometric hip 0°, and isometric hip 45° conditions. The electromyographic data obtained during each condition were normalized with the values collected during maximal voluntary isometric contraction of each muscle. A multivariate analysis of variance with repeated measures using syntax was used to compare the normalized electromyography of each muscle across different knee joint angles in each weight condition. Electromyographic activities of the BFl, semitendinosus, and semimembranosus at 45° and 90° knee flexion angles were significantly greater than at 0° in the eccentric, concentric, isometric hip 0°, and in isometric hip 45° conditions with both non-external resistance and 5-kg load (p<0.05), except for that of the BFl and semitendinosus in isometric hip 45° with 5-kg load. The electromyographic activity of the BFl was significantly higher than that of the semimembranosus at 90° knee flexion in all conditions (p < 0.05), except during eccentric with non-external resistance. There was no significant difference in electromyographic activity in the hamstring muscles among different knee angles and muscular contraction conditions. This study showed that 45° hip extension with 45° and 90° knee flexion might be better in terms of the recruiting hamstring activity compared to 0° knee flexion, regardless of the training intensity. We recommend 45° hip extension exercises with knee flexion angles of 45° and 90° to activate the BFl, in preventing hamstring strain.

Dynamic evolution of anodic biofilm when maturing under different external resistive loads in microbial fuel cells. Electrochemical perspective.

Appropriate inoculation and maturation may be crucial for shortening the startup time and maximising power output of Microbial Fuel Cells (MFCs), whilst ensuring stable operation. In this study we explore the relationship between electrochemical parameters of MFCs matured under different external resistance (Rext) values (50â€¯Ω - 10 kΩ) using non-synthetic fuel (human urine). Maturing the biofilm under the lower selected Rext results in improved power performance and lowest internal resistance (Rint), whereas using higher Rext results in increased ohmic losses and inferior performance. When the optimal load is applied to the MFCs following maturity, dependence of microbial activity on original Rext values does not change, suggesting an irreversible effect on the biofilm, within the timeframe of the reported experiments. Biofilm microarchitecture is affected by Rext and plays an important role in MFC efficiency. Presence of water channels, EPS and precipitated salts is distinctive for higher Rext and open circuit MFCs. Correlation analysis reveals that the biofilm changes most dynamically in the first 5 weeks of operation and that fixed Rext lefts an electrochemical effect on biofilm performance. Therefore, the initial conditions of the biofilm development can affect its long-term structure, properties and activity.

Optimized microbial fuel cell-powered electro-Fenton processes to enhance electricity and bisphenol A removal by varying external resistance and electrolyte concentrations.

This study is the first to investigate the effects of external resistance and electrolyte concentration on the performance of a bioelectro-Fenton (BEF) system, involving measurements of power density, H2O2 generation, and bisphenol A (BPA) removal efficiency. With optimized operating conditions (external resistance of 1.12 kΩ and cathodic NaCl concentration of 1,657 mg/L), the BEF system achieved a maximum power density of 38.59 mW/m2, which is about 3.5 times higher than with 1 kΩ external resistance and no NaCl. This system featured a 71.7 % reduction in total internal resistance. The optimized BEF also accelerated the oxygen reduction reaction rate, increasing H2O2 generation by 4.4 times compared to the unoptimized system. Moreover, it exhibited superior BPA degradation performance, removing over 99 % of BPA within 14 hs, representing a 1.1 to 3.3-fold improvement over the unoptimized BEF. By the fifth cycle (70 h), the optimized BEF still removed 70 % of BPA. Optimizing the operating conditions significantly increased the abundance of electrochemically active bacteria (Pseudomonadaceae) from 2.2 % to 20 %, facilitating rapid acclimation. The study demonstrates the strong potential of an optimized BEF system for removing persistent pollutants.

Acclimation of electroactive biofilms under different operating conditions: comprehensive analysis from architecture, composition, and metabolic activity.

Electroactive biofilms (EABs) have aroused wide concern in waste treatment due to their unique capability of extracellular electron transfer with solid materials. The combined effect of different operating conditions on the formation, microbial architecture, composition, and metabolic activity of EABs is still unknown. In this study, the impact of three different factors (anode electrode, substrate concentration, and resistance) on the acclimation and performance of EABs was investigated. The results showed that the shortest start-up time of 127.3 h and highest power density of 0.84 W m-2 were obtained with carbon brush as electrode, low concentration of substrate (1.0 g L-1), and 1000 Ω external resistance (denoted as N1). The EABs under N1 condition also represented strongest redox capacity, lowest internal resistance, and close arrangement of bacteria. Moreover, the EABs cultured under different conditions both showed similar results, with direct electron transfer (DET) dominated from EABs to anode. Microbial community compositions indicated that EABs under N1 condition have lowest diversity and highest abundance of electroactive bacteria (46.68%). Higher substrate concentration (3.0 g L-1) promoted the proliferation of some other bacteria without electroactivity, which was adverse to EABs. The metabolic analysis showed the difference of genes related to electron transfer (cytochrome C and pili) and biofilm formation (xap) of EABs under different conditions, which further demonstrated the higher electroactivity of EABs under N1. These results provided a comprehensive understanding of the effect of different operating conditions on EABs including biofilm formation and electrochemical activity.

Stimulation of atrazine degradation by activated carbon and cathodic effect in soil microbial fuel cell.

Soil microbial fuel cells (MFCs) have been increasingly studied in recent years and have attracted significant attention as an environmentally sustainable bioelectrochemical technology. However, the poor conductivity of the soil matrix and the neglect of the cathodic function have limited its application. In this study, quartz sand and activated carbon were subjected to investigation on their influence on atrazine degradation. Atrazine was introduced in different layers (cathode, upper layer) to explore the cathodic effect on atrazine removal. The results revealed that activated carbon could reduce the internal resistance (693 Ω) and generate the highest power density (25.51 mW/m2) of the soil MFCs, and thus increase the removal efficiency (97.92%) of atrazine. The dynamic degradation profiles of atrazine were different for different adding layers. The cathode electrode acted as an electron donor could increase the distance of the effective influence of the soil MFCs' cathode from the middle to the cathode layer. The cathode (region) and the region close to the cathode could degrade atrazine with the atrazine removal efficiencies ranging from 60.67% to 92.79%, and the degradation ability of the cathode was stronger than that of other layers. The degradation effect followed the order: cathode > upper > lower > middle). Geobacter, Desulfobulbus, and Desulfuromonas belonging to the δ-Proteobacteria class were identified as the dominant electroactive microorganisms in the anode layer, while their relative abundances are quite low in the upper and cathode layers. Pseudomonas is an atrazine-degrading bacterium, but its relative abundance was only 0.13-0.51%. Thus, bioelectrochemistry rather than microbial degradation was the primary driving force.

Application of Magnetite-Nanoparticles and Microbial Fuel Cell on Anaerobic Digestion: Influence of External Resistance.

In this paper, the application of magnetite-nanoparticles and a microbial fuel cell (MFC) was studied on the anaerobic digestion (AD) of sewage sludge. The experimental set-up included six 1 L biochemical methane potential (BMP) tests with different external resistors: (a) 100 Ω, (b) 300 Ω, (c) 500 Ω, (d) 800 Ω, (e) 1000 Ω, and (f) a control with no external resistor. The BMP tests were carried out using digesters with a working volume of 0.8 L fed with 0.5 L substrate, 0.3 L inoculum, and 0.53 g magnetite-nanoparticles. The results suggested that the ultimate biogas generation reached 692.7 mL/g VSfed in the 500 Ω digester, which was substantially greater than the 102.6 mL/g VSfed of the control. The electrochemical efficiency analysis also demonstrated higher coulombic efficiency (81.2%) and maximum power density (30.17 mW/ m2) for the 500 Ω digester. The digester also revealed a higher maximum voltage generation of 0.431 V, which was approximately 12.7 times the 0.034 V of the lowest-performing MFC (100 Ω digester). In terms of contaminants removed, the best-performing digester was the digester with 500 Ω, which reduced contaminants by more than 89% on COD, TS, VS, TSS and color. In terms of cost-benefit analysis, this digester produced the highest annual energy profit (48.22 ZAR/kWh or 3.45 USD/kWh). This infers the application of magnetite-nanoparticles and MFC on the AD of sewage sludge is very promising for biogas production. The digester with an external resistor of 500 Ω showed a high potential for use in bioelectrochemical biogas generation and contaminant removal for sewage sludge.

Electrobiochemical skills of Pseudomonas aeruginosa species that produce pyocyanin or pyoverdine for glycerol oxidation in a microbial fuel cell.

Pseudomonas aeruginosa can produce pigments, which mediate external electron transfer (EET). Depending on the mediator, this species can be explored in bioelectrosystems to harvest energy or to obtain chemicals from residual organic compounds. This study has compared the performance of microbial fuel cells (MFCs) inoculated with a Pseudomonas aeruginosa isolate, namely EW603 or EW819, which produce pyocyanin and pyoverdine, respectively. The efficiency of these MFCs in glycerol, a typical residue of biodiesel production, were also compared. The MFCs exhibited different performances. The maximum voltage was 411 and 281 mV m2, the power density was 40.1 and 21.3 mW m-2, and the coulombic efficiency was 5.16 and 1.49% for MFC-EW603 and MFC-EW819, respectively. MFC-EW603 and MFC-EW819 achieved maximum current at 560 and 2200 Ω, at 141.2 and 91.3 mA m-2, respectively. When the system was operated at the respective maximum current output, MFC-EW603 consumed the total glycerol content (11 mmol L-1), and no products could be detected after 50 h. In turn, acetic and butyric acids were detected at the end of MFC-EW819 operation (75 h). The results suggested that P. aeruginosa metabolism can be steered in the MFC to generate current or microbial products depending on the pigment-producing strain and the conditions applied to the system, such as the external resistance. In addition, gene cluster pathways related to phenazine production (phzA and phzB) and other electrogenic-related genes (mexGHI-opmB) were identified in the strain genomes, supporting the findings. These results open new possibilities for using glycerol in bioelectrochemical systems.

Converting synthetic azo dye and real textile wastewater into clean energy by using synthesized CuO/C as photocathode in dual-photoelectrode photocatalytic fuel cell.

Cathode in photocatalytic fuel cell (PFC) plays a crucial role in degradation of organic contaminants. In this study, synthesized copper oxide (CuO) was loaded on carbon plate and used as photocathode in PFC for degradation of synthetic azo dye Reactive Black 5 (RB5) and real textile wastewater. Morphology and structural phase of the synthesized CuO were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Several operating parameters had been investigated such as light irradiation, initial dye concentration, and pH of azo dye solution within 6 h of irradiation time. The lowest initial concentration of RB5 (10 mg L-1) achieved 100% color removal compared to the highest initial concentration (40 mg L-1) which only achieved 77.1% color removal within 6 h of irradiation time. The influence of external resistance was significant in electricity generation but trivial in dye degradation efficiency. The external resistance of 6000 Ω yielded highest maximum power density, with Pmax of 0.2631 µW cm-2, followed by 1000 Ω (0.2196 µW cm-2) and 8000 Ω (0.1587 µW cm-2), respectively. The real textile wastewater with dilution ratio (DR) 1:6 yielded the highest energy conversion efficiency, η (3.62%), followed by DR 1:4 (3.19%) and DR 1:2 (1.96%), respectively.

Enhancement of energy recovery from caffeine wastewater in constructed wetland-microbial fuel cell through operating conditions.

The enhancement of up-flow constructed wetland-microbial fuel cell (UFCW-MFC) performance in energy retrieval from caffeine containing wastewater has been explored via various operating conditions (hydraulic retention time (HRT), multianode (MA), multicathode current collector (MC), external resistance). The anaerobic decaffeination and COD removal improved by 37 and 12% as the HRT extended from 1 to 5 d. The increment in contact time between the microbes and organic substrates promoted the degradation and contributed to higher power output (3.4-fold), CE (eightfold), and NER (14-16-fold). The MA and MC connections facilitated the electron transfer rate and the degradation rate of organic substrates in the multiple anodic zones, which enhanced the removal efficiency in the anaerobic compartment (Caffeine: 4.2%; COD: 7.4%) and led to higher electricity generation (Power: 4.7-fold) and energy recovery (CE: 1.4-fold; NER: 2.3-2.5-fold) compared to SA. The lower external resistance favored the growth of electrogens and induced higher electron flux, where the best treatment performance and electricity production was obtained when the external resistance approached the internal resistance. Overall, it was noteworthy that the optimum operating conditions were achieved with 5 d HRT, MA, and MC connection along with external resistance of 200 Ω, which significantly outperformed the initial conditions (1 d HRT, SA connection, and 1000 Ω) by 43.7 and 29.8% of caffeine and COD removal in the anaerobic compartment, respectively as well as 14-fold of power generation.

Enhancing bio-cathodic nitrate removal through anode-cathode polarity inversion together with regulating the anode electroactivity.

Bio-cathodic nitrate removal uses autotrophic nitrate-reducing bacteria as catalysts to realize the nitrate removal process and has been considered as a cost-effective way to remove nitrate contamination. However, the present bio-cathodic nitrate removal process has problems with long start-up time and low performance, which are urgently required to improve for its application. In this study, we investigated an anode-cathode polarity inversion method for rapidly cultivating high-performance nitrate-reducing bio-cathode by regulating bio-anodic bio-oxidation electroactivities under different external resistances and explored at the first time the correlation between the oxidation performance and the reduction performance of one mixed-bacteria bioelectrode. A high bio-electrochemical nitrate removal rate of 2.74 ± 0.03 gNO3--N m-2 d-1 was obtained at the bioelectrode with high bio-anodic bio-oxidation electroactivity, which was 4.0 times that of 0.69 ± 0.03 gNO3--N m-2 d-1 at the bioelectrode with low bio-oxidation electroactivity, and which was 1.3-7.9 times that of reported (0.35-2.04 gNO3--N m-2 d-1). 16S rRNA gene sequences and bacterial biomass analysis showed higher bio-cathodic nitrate removal came from higher bacterial biomass of electrogenic bacteria and nitrate-reducing bacteria. A good linear correlation between the bio-cathodic nitrate removal performance and the reversed bio-anodic bio-oxidation electroactivity was presented and likely implied that electrogenic biofilm had either action as autotrophic nitrate reduction or promotion to the development of autotrophic nitrate removal system. This study provided a novel strategy not only to rapidly cultivate high-performance bio-cathode but also to possibly develop the bio-cathode with specific functions for substance synthesis and pollutant detection.

Applications of the Critical Power Model to Dynamic Constant External Resistance Exercise: A Brief Review of the Critical Load Test.

The study and application of the critical power (CP) concept has spanned many decades. The CP test provides estimates of two distinct parameters, CP and W', that describe aerobic and anaerobic metabolic capacities, respectively. Various mathematical models have been used to estimate the CP and W' parameters across exercise modalities. Recently, the CP model has been applied to dynamic constant external resistance (DCER) exercises. The same hyperbolic relationship that has been established across various continuous, whole-body, dynamic movements has also been demonstrated for upper-, lower-, and whole-body DCER exercises. The asymptote of the load versus repetition relationship is defined as the critical load (CL) and the curvature constant is L'. The CL and L' can be estimated from the same linear and non-linear mathematical models used to derive the CP. The aims of this review are to (1) provide an overview of the CP concept across continuous, dynamic exercise modalities; (2) describe the recent applications of the model to DCER exercise; (3) demonstrate how the mathematical modeling of DCER exercise can be applied to further our understanding of fatigue and individual performance capabilities; and (4) make initial recommendations regarding the methodology for estimating the parameters of the CL test.

The influence of external resistance on the performance of microbial fuel cell and the removal of sulfamethoxazole wastewater.

Microbial fuel cells (MFCs) are promising equipment for simultaneous treatment of sewage and power generation. External resistance (Rext) plays a crucial impact in the performance of MFCs in antibiotic wastewater treatment and antibiotic resistance genes (ARGs) reduction. In this study, Rext and whether to add 20 mg/L sulfamethoxazole (SMX) as variables, it was observed that the performance of several chemical properties of MFCs was optimal when Rext was 1000 Ω. The power density before and after addition of SMX was 1220.5 ± 24.5 mW/m2 and 1186.2 ± 9.2 mW/m2, respectively; Furthermore, the degradation rate of SMX was as high as 87.52 ± 1.97% within 48 h. High-throughput sequencing results showed that both Rext and SMX affected the microbial community and relative abundance of the phylum and genera. Meanwhile, the MFCs with 1000 Ω Rext generated less the targeted ARGs. Experimental results showed that 1000 Ω was the most suitable Rext for MFCs in the treatment of antibiotic wastewater.

Effect of external resistance on substrate removal and electricity generation in microbial fuel cell treating sulfide and nitrate simultaneously.

The effect of external resistance on substrate removal and electricity generation was explored in microbial fuel cells (MFCs) simultaneously treating sulfide and nitrate. The MFCs were operated under three different conditions keeping open-circuit MFC as control. In batch mode, all the MFCs showed good capacity of simultaneously removing sulfide and nitrate regardless of external resistance. The voltage profile could be divided into rapid descent zone, bulge zone, and stability zone, which represents typical polarization behavior. Taking open circuit as control, low external resistance promoted the production of sulfate and nitrogen gas, while a strong link between product production and external resistance was evident based on Pearson correlation analyses. In addition, low external resistance improved the amount of transferred electrons, while the peak electronic quantity was noticed when the external resistance was equivalent to internal resistance. Moreover, the mechanism of substrate removal and electricity generation was hypothesized for the MFCs simultaneously treating sulfide and nitrate which explained the results well.

The effect of start-up on energy recovery and compositional changes in brewery wastewater in bioelectrochemical systems.

Start-up of bioelectrochemical systems (BESs) fed with brewery wastewater was compared at different adjusted anode potentials (-200 and 0 mV vs. Ag/AgCl) and external resistances (50 and 1000 Ω). Current generation stabilized faster with the external resistances (9 ± 3 and 1.70 ± 0.04 A/m3 with 50 and 1000 Ω, respectively), whilst significantly higher current densities of 76 ± 39 and 44 ± 9 A/m3 were obtained with the adjusted anode potentials of -200 and 0 mV vs. Ag/AgCl, respectively. After start-up, when operated using 47 Ω external resistance, the current densities and Coulombic efficiencies of all BESs stabilized to 9.5 ± 2.9 A/m3 and 12 ± 2%, respectively, demonstrating that the start-up protocols were not critical for long-term BES operation in microbial fuel cell mode. With adjusted anode potentials, two times more biofilm biomass (measured as protein) was formed by the end of the experiment as compared to start-up with the fixed external resistances. After start-up, the organics in the brewery wastewater, mainly sugars and alcohols, were transformed to acetate (1360 ± 250 mg/L) and propionate (610 ± 190 mg/L). Optimized start-up is required for prompt BES recovery, for example, after process disturbances. Based on the results of this study, adjustment of anode potential to -200 mV vs. Ag/AgCl is recommended for fast BES start-up.

The influence of incorporating microbial fuel cells on greenhouse gas emissions from constructed wetlands.

Microbial fuel cells (MFCs) were incorporated into constructed wetlands (CWs) in recent years aiming to enhance the wastewater treatment of CWs while simultaneously produce electricity. However, currently no information is available about the greenhouse gas (GHG) emissions from integrated CW-MFC systems during wastewater treatment. Therefore, this study investigated the influence of incorporating MFCs on GHG (especially CH4 and N2O) emissions from CWs under different external resistances, influent organic loadings and seasons. Results showed that incorporating the MFC significantly reduced the GHG emissions (by 5.9%-32.4% CO2 equivalents) from CWs by reducing 17.9%-36.9% CH4 and 7.2%-38.7% N2O emissions. The CH4 and N2O emissions from CW-MFCs significantly increased with increasing external resistance (above 500 Ω), while the CO2 emission showed the opposite trend. However, the CH4 and N2O emissions at external resistances below 500â€¯Ω did not differ significantly. There was a significant positive correlation between the CO2 and CH4 emissions and influent organic loadings in CW-MFCs, but a significant negative correlation between the N2O emission and influent organic loadings. Influent chemical oxygen demand/total nitrogen (COD/TN) = 3 could result in a TN removal of ≥90% as well as the minimum CO2 equivalents emission in CW-MFCs. The GHG emissions from CW-MFCs showed significant seasonal variations.

Effect of external resistance on the sensitivity of microbial fuel cell biosensor for detection of different types of pollutants.

The relatively poor sensitivity is the main bottleneck restricting the application of microbial fuel cell biosensor (MFC-biosensor) for toxicity monitoring. Previous studies have shown that external resistance (Rext) had an obvious effect on sensor sensitivity. However, these studies reported different results and the reason of this discrepancy was not clear. The objective of this research was to observe the effect of Rext on sensor sensitivity when detecting different types of pollutants and reveal its microbiological mechanism. Results demonstrated that the optimal Rext of MFC-biosensor varied with the type of pollutants. The optimal values for detecting avermectins, tetracyclines and heavy metals were 100 Ω, 330â€¯Ω and 680 Ω, respectively. This discrepancy was mainly due to the visible differences in anodic microbial communities at different Rext settings. Both Azospirillum and Acinetobacter were susceptible to Cd and Pb, occuping 19.20% of the anodic microbial population in 680â€¯Ω MFC-biosensor. Pseudomonas accounted for 10.73% in 330â€¯Ω MFC-biosensor and possessed the sensitivity to tetracyclines. As for 100â€¯Ω MFC-biosensor, the avermectin-intolerant Ocillibacter made up 2.55% of the anodic microbial community. This study indicated that the Rext of MFC-biosensor should be optimized according to the potential pollutants.