Microbial Fuel Cell Biosensor with Capillary Carbon Source Delivery for Real-Time Toxicity Detection.

A microbial fuel cell (MFC) biosensor with an anode as a sensing element is often unreliable at low or significantly fluctuating organic matter concentrations. To remove this limitation, this work demonstrates capillary action-aided carbon source delivery to an anode-sensing MFC biosensor for use in carbon-depleted environments, e.g., potable water. First, different carbon source delivery configurations using several thread types, silk, nylon, cotton, and polyester, are evaluated. Silk thread was determined to be the most suitable material for passive delivery of a 40 g L-1 acetate solution. This carbon source delivery system was then incorporated into the design of an MFC biosensor for real-time detection of toxicity spikes in tap water, providing an organic matter concentration of 56 ± 15 mg L-1. The biosensor was subsequently able to detect spikes of toxicants such as chlorine, formaldehyde, mercury, and cyanobacterial microcystins. The 16S sequencing results demonstrated the proliferation of Desulfatirhabdium (10.7% of the total population), Pelobacter (10.3%), and Geobacter (10.2%) genera. Overall, this work shows that the proposed approach can be used to achieve real-time toxicant detection by MFC biosensors in carbon-depleted environments.

Bioelectrochemical systems-based metal removal and recovery from wastewater and polluted soil: Key factors, development, and perspective.

Bioelectrochemical systems (BES) are considered efficient and sustainable technologies for bioenergy generation and simultaneously removal/recovery metal (loid)s from soil and wastewater. However, several current challenges of BES-based metal removal and recovery, especially concentrating target metals from complex contaminated wastewater or soil and their economic feasibility of engineering applications. This review summarized the applications of BES-based metal removal and recovery systems from wastewater and contaminated soil and evaluated their performances on electricity generation and metal removal/recovery efficiency. In addition, an in depth review of several key parameters (BES configurations, electrodes, catalysts, metal concentration, pH value, substrate categories, etc.) of BES-based metal removal and recovery was carried out to facilitate a deep understanding of their development and to suggest strategies for scaling up their specific application fields. Finally, the future intervention on multifunctional BES to improve their performances of mental removal and recovery were revealed.

On-line monitoring of water quality with a floating microbial fuel cell biosensor: field test results.

Real-time biomonitoring using microbial fuel cell (MFC) based biosensors have been demonstrated in several laboratory studies, but field validation is lacking. This study describes the long-term performance of an MFC based biosensor developed for real-time monitoring of changes in the water quality of a metal-contaminated stream. After a startup in the laboratory, biosensors were deployed in a stream close to an active mining complex in Sudbury, ON, Canada. Three sites within the stream were selected for biosensors installation based on their positions relative to the mining complex discharge points - upstream (lowest heavy metals concentration), midpoint and downstream. The biosensors installed at these sites were able to detect, in real-time, temporal changes in the water quality over a 2-month period. The biosensor response was confirmed by the results of a conventional toxicity assay (48-h acute Daphnia magna) as well as analytical measurements of heavy metals concentration in the stream. We conclude that the biosensor could detect changes in the overall water quality of the stream despite the uncontrolled situations typical for field operations as compared to laboratory conditions. To further explain the results observed during the field test, the rapid Microtox bioassay and D. magna assay were used to investigate the possible contributions of the two dominant mining metals (Nickel and Copper) to water toxicity in the test area.

Online monitoring of heavy metal-related toxicity using flow-through and floating microbial fuel cell biosensors.

Elevated concentrations of heavy metals in water caused by mining activities create significant risks to the environment. Traditional biological methods used to assess heavy metal-related toxicity in aquatic environments are lengthy and labor intensive. Real-time biomonitoring approaches eliminate some of these limitations and provide a more accurate indication of toxicity. This study describes the performance of a flow-through and floating design microbial fuel cell (MFC) biosensors for real-time detection of copper (Cu) and other heavy metal-related toxicity in aquatic environments. Several biomonitoring tests were carried out using Cu and mining effluents as toxicants. The biosensors were able to detect, in real-time, Cu-related toxicity at concentrations as low as 35 - 40 µg L-1, as confirmed by a Daphnia assay. A comparison of the floating biosensor's outputs with Daphnia magna survival rates showed a linear correlation with a coefficient of determination (R2) higher than 0.9. In addition, the flow-through biosensor was shown to be able to detect  differences in the quality of two mining effluents with different compositions of heavy metals. Finally, the biosensor's real-time field performance was investigated in two aquatic environments in the Sudbury, Ontario region of Canada.

Evaluation of the suitability and performance of cassava waste (peel) extracts in a microbial fuel cell for supplementary and sustainable energy production.

In a number of energy-poor nations, peel from cassava processing represents one of the most abundant sources of lignocellulosic biomass. This peel is mostly discarded indiscriminately and eventually constitutes a problem to the environment. However, energy can be extracted from this peel in a microbial fuel cell. In this study, the viability of cassava peel extract as a substrate in a single-chamber air cathode microbial fuel cell is demonstrated, and optimum performance conditions are explored. The effects of different pretreatments on the extract are also discussed in the context of observed changes in the internal resistances, conductivity and Coulombic efficiencies. At the best conditions examined, the extract from cassava peel fermented for 168 h and adjusted to a pH of 7.63 attained a peak voltage of 687 mV ± 21 mV, a power density of 155 mW m-3 of reactor volume and a Coulombic efficiency of 11 %. Although this energy is limited to direct use, systems exist that can effectively harvest and boost the energy to levels sufficient for supplementary energy usage in cassava producing regions.

The exploitation of bio-electrochemical system and microplastics removal: Possibilities and perspectives.

Microplastic (MP) pollution has caused severe concern due to its harmful effect on human beings and ecosystems. Existing MP removal methods face many obstacles, such as high cost, high energy consumption, low efficiency, release of toxic chemicals, etc. Thus, it is crucial to find appropriate and sustainable methods to replace common MP removal approaches. Bio-electrochemical system (BES) is a sustainable clean energy technology that has been successfully applied to wastewater treatment, seawater desalination, metal removal, energy production, biosensors, etc. However, research reports on BES technology to eliminate MP pollution are limited. This paper reviews the mechanism, hazards, and common treatment methods of MP removal and discusses the application of BES systems to improve MP removal efficiency and sustainability. Firstly, the characteristics and limitations of common MP removal techniques are systematically summarized. Then, the potential application of BES technology in MP removal is explored. Furthermore, the feasibility and stability of the potential BES MP removal application are critically evalauted while recommendations for further research are proposed.

Effective and Economical 3D Carbon Sponge with Carbon Nanoparticles as Floating Air Cathode for Sustainable Electricity Production in Microbial Fuel Cells.

The effective and economical 3D floating air cathodes were fabricated by a simple dipping-drying method with carbon black (CB), ethanol, and PTFE solution. Pristine Type I polyurethane sponge (5 pores/mm) and Pristine Type II polyurethane sponge (3 pores/mm) were used as the support. The deposition of CB on the Pristine Type I and Pristine Type II materials was detected by scanning electron microscopy and Fourier transform infrared spectroscopy. The carbon loss rate test exhibited good CB adhesive stability on both floating air cathodes. Besides, Type I/CB floating air cathode displayed 3.7 times higher tensile strength, 10.58 times higher elongation at break, and 3.3 times lower cost than carbon felt. The electricity production ability of carbon cloth (CC) anode with carbon felt, Type I/CB, and Type II/CB cathode MFCs (CC-CF-MFC, CC-I-MFC, and CC-II-MFC) was evaluated. After 130 days, the CC-I-MFC showed a maximum power density (PD) of 92.58 mW/m3, which was 4.6 times higher than the CC-CF-MFC. Compared with Type II/CB, Type I/CB cathode improved the maximum power density by 160% due to the smaller pores, rougher surface, and higher surface wettability. Further, CC-I-MFC exhibited the best overall oxidation-reduction performance and chemical oxygen demand removal efficiency. Consequently, Type I/CB floating air cathode opens a new opportunity for scaling up simple, inexpensive, and high-performance MFCs for energy production.

Microbial fuel cell soft sensor for real-time toxicity detection and monitoring.

Real-time toxicity detection and monitoring using a microbial fuel cell (MFC) is often based on observing current or voltage changes. Other methods of obtaining more information on the internal state of the MFC, such as electrochemical impedance spectroscopy (EIS), are invasive, disruptive, time consuming, and may affect long-term MFC performance. This study proposes a soft sensor approach as a non-invasive real-time method for evaluating the internal state of an MFC biosensor during toxicity monitoring. The proposed soft sensor approach is based on estimating the equivalent circuit model (ECM) parameters in real time. A flow-through MFC biosensor was operated at several combinations of carbon source (acetate) and toxicant (copper) concentrations. The ECM parameters, such as internal resistance, capacitance, and open-circuit voltage, were estimated in real time using a numerical parameter estimation procedure. The soft sensor approach proved to be an adequate replacement for EIS measurements in quantifying changes in the biosensor internal parameters. The approach also provided additional information, which could lead to earlier detection of the toxicity onset.

On-line monitoring of heavy metals-related toxicity with a microbial fuel cell biosensor.

This study describes an environmental biosensor for real time toxicity monitoring, which exploits high sensitivity of a microbial fuel cell (MFC) to variations in concentrations of electron donors and acceptors. Fast biosensor response to changes in total heavy metal concentration of a mining rock drainage was observed in laboratory tests with acceptable repeatability and a coefficient of determination (R2) of 0.95-0.97. The biosensor response is attributed to interference of heavy metals with the activity of electroactive microorganisms. Biomolecular analysis of the anodic electroactive biofilms showed significant population differences between microbial populations of the biosensor exposed to heavy metals and a non-exposed (control) biosensor. Furthermore, the biosensor outputs were highly correlated (R2 = 0.92) with the results of the Microtox toxicity assay. The results of this study contribute towards the development of a simple MFC-based biosensor capable of detecting, in real-time, changes in environmental conditions and providing a tool for on-site toxicity monitoring.

A comparison of microbial fuel cell and microbial electrolysis cell biosensors for real-time environmental monitoring.

This study compares the biosensing performance of a microbial fuel cell (MFC) and a microbial electrolysis cell (MEC). Initial tests provided a qualitative comparison of MFC and MEC currents after the anode compartment liquid (anolyte) was spiked with acetate, or sulphates of NH4+, Na+, Mg2+, Fe2+, or a fertilizer solution. Current measurements showed that the MFC sensor had a faster response time, higher sensitivity, and faster recovery time after the spike. Following the spike tests, the MFC and MEC were operated in a continuous flow mode at several influent concentrations of acetate, and sulphates of NH4+, Na+, and Fe2+. The continuous flow tests confirmed the better performance of the MFC sensor, which was selected for further experiments. Two MFC sensors were used for real-time (on-line) COD measurements of brewery wastewater. Regression analysis showed a strong correlation between the MFC power output and COD concentrations in the anode compartment with a coefficient of determination (R2) of 0.97. Overall, results of this study suggest that an MFC-based sensor can be successfully used as a simple and cost-efficient real-time monitoring tool.

Fibrinogen concentration: A marker of cardiovascular disorders in Nigerians.

Fibrinogen, one of the most hemorheologically active plasma proteins, is associated with several cardiovascular risk factors, and the plasma concentration can alter dramatically during acute phase response and in a wide variety of clinical conditions. We have assessed fibrinogen levels in some known cardiovascular disorders, during usage of contraceptive pills, acute phase conditions and pregnancy. Our results from patients with various disease conditions indicate that fibrinogen levels are in the pathological range and are significantly higher than in healthy controls (p<0.001). It is concluded that although Africans have low predisposition to thrombosis, they may well be pre-disposed to abnormal fibrin formation which could lead to various thromboembolic complications.

Body mass index, fibrinogen and factor VII activity in male smokers and non-smokers living in an Urban industrialized.

Differences in haemostatic parameters have been reported among smokers and non-smokers. However the relationships of these parameters with other risk factors of cardiovascular diseases have not been fully determined in Nigerians. We therefore aimed at assessing the relationship between fibrinogen, factor VII (FVII), age, body mass indeks (BMI), systolic blood pressure (SBP) and diastolic blood pressure (DBP) in smokers and non-smokers living in an Urban Nigerian city. We studied 104 male Nigerians grouped into non-smokers (n= 74) and smokers (n= 30). Fibrinogen was measured using the clot weight method of Ingram and FVII was assayed by the bioassay method. Mean fibrinogen and FVII were found to be higher in smokers than non-smokers. There was no relationship between FVII and age (r= -0.0458) in non-smokers and a weak association was found between FVII and age in smokers (r= 0.3191). Both SBP and DBP were significantly associated with BMI in smokers (r= 0.6332, p= 0.0002) for DBP and (r= 0.4869, p= 0.0064) for SBP. Fibrinogen was only associated with DBP in non-smokers (r= 0.3273, p= 0.0047). FVII and fibrinogen were found to be higher in smokers compared to non- smokers, the difference was not statistically significant (p= 0.1965). The strength of the association of BMI and fibrinogen with blood pressure is higher for DBP in Nigerians. Extensive population studies should be conducted on smokers and non-smokers to confirm these associations.