Co-metabolism kinetics and electrogenesis change during cyanide degradation in a microbial fuel cell

Efficient biodechlorination at the Fe3O4-based silicone powder modified chlorobenzene-affinity anode

The treatment of chlorinated volatile organic compounds faces challenges of secondary pollution and less-efficiency due to the substitution of chlorine. Microbial fuel cells (MFCs) provide a promising opportunity for its abatement. In this study, a novel Fe3O4 nanoparticles and silicone-based powder (SP) were integrated and immobilized on carbon felt (CF+Fe3O4@SP), which was further used as anode in the chlorobenzene (CB) powered MFC. Owing to the cooperation between SP and Fe3O4, the anode exhibited excellent performance for both biodechlorination and power generation. The results indicated that the CF+Fe3O4@SP anode loaded MFC achieved 98.5% removal of 200 mg/L CB within 28 h, and the maximum power density was 675.9 mW/m3, which was a 45.6% increase compared to that of the bare CF anode. Microbial community analysis indicated that the genera Comamonadaceae, Pandoraea, Obscuribacteraceae, and Truepera were dominated, especially, the Comamonadaceae and Obscuribacteraceae showed outstanding affinity for Fe3O4 and SP, respectively. Moreover, the proportion of live bacteria, secretion of extracellular polymer substances, and protein content in the extracellular polymer substances were significantly increased by modifying Fe3O4@SP onto the carbon-based anode. Thus, this study provides new insights into the development of MFCs for refractory and hydrophobic volatile organic compounds removal.

Sustainable application of tubular photosynthesis microbial desalination cell for simultaneous desalination of seawater for potable water supply associated with sewage treatment and energy recovery

A sustainable approach for simultaneous desalination of actual seawater for potable water supply, and bioelectrochemical treatment of sewage associated with power generation was evaluated in a tubular photosynthesis desalination microbial fuel cell (PDMC) continually operated for 180 days. Anion exchange membrane (AEM) was used to separate the bioanode and desalination compartments, whereby, and cation exchange membrane (CEM) was used to separate the desalination and biocathode compartments. Mixed bacterial species and mixed microalgae were utilized for inoculation of the bioanode and biocathode, respectively. The results revealed that maximum and average desalination efficiencies of saline seawater fed to the desalination compartment were 80 ± 1 % and 72 ± 1.2 %, respectively. Maximum and average removal efficiencies of the sewage organic content in the anodic compartment were up to 99.3 ± 0.5 % and 91.0 ± 0.8 %, respectively associated with maximum power output of 430.7 ± 0.7 mW/m³. In spite of the heavy growth of the mixed bacterial species and microalgae as well, no fouling of AEM and CEM was observed during the entire period of operation. Kinetic study demonstrated that Blackman model described well the bacterial growth. Dense and healthy growth of biofilm and the microalgae in the anodic and cathodic compartments, respectively were clearly observed during the operation period. The promising outcomes of this investigation demonstrated that the suggested approach is a potential sustainable option for simultaneous desalination of saline seawater for potable water supply, biotreatment of sewage, and power generation.

An Overview of Emerging Cyanide Bioremediation Methods

Cyanide compounds are hazardous compounds which are extremely toxic to living organisms, especially free cyanide in the form of hydrogen cyanide gas (HCN) and cyanide ion (CN−). These cyanide compounds are metabolic inhibitors since they can tightly bind to the metals of metalloenzymes. Anthropogenic sources contribute significantly to CN− contamination in the environment, more specifically to surface and underground waters. The treatment processes, such as chemical and physical treatment processes, have been implemented. However, these processes have drawbacks since they generate additional contaminants which further exacerbates the environmental pollution. The biological treatment techniques are mostly overlooked as an alternative to the conventional physical and chemical methods. However, the recent research has focused substantially on this method, with different reactor configurations that were proposed. However, minimal attention was given to the emerging technologies that sought to accelerate the treatment with a subsequent resource recovery from the process. Hence, this review focuses on the recent emerging tools that can be used to accelerate cyanide biodegradation. These tools include, amongst others, electro-bioremediation, anaerobic biodegradation and the use of microbial fuel cell technology. These processes were demonstrated to have the possibility of producing value-added products, such as biogas, co-factors of neurotransmitters and electricity from the treatment process.

A New Model for Microbial Desalination Cells: Model Formulation and Validation under Different Operating Conditions

In this paper, a dynamic mathematical model was developed to simulate the processes in Microbial Desalination Cells (MDCs) operated in cyclic batch flow mode using ordinary differential equations found in the literature. In contrast to previous models, the proposed model was developed for fed-batch operations and considers the effects of temperature and substrate inhibition using simple equations for quick simulation. Local sensitivity analysis was performed to determine the parameters with the least impact on current, COD, and salt removal, which were then eliminated from the simplified model. These parameters were found to be the decay rates of anodophilic and methanogenic microorganisms ( $k_{d,a}$ and $k_{d,m}$ ) and the internal resistance parameters ( $R_{\text{anolyte}}$ and $R_{\text{membrane}}$ ). In addition, the best-performing parameters based on the sensitivity analysis results were selected for reestimation for model fitting. The reestimated parameters were mediator yield ( $Y$ ), membrane salt transfer coefficient ( $d$ ), maximum substrate utilization rate by methanogenic microorganisms ( ${\mu }_{\text{s}}$ , ${}_{\text{m}}$ , max), and maximum anodophilic growth rate ( ${\mu }_{\text{a}}$ , max). The predictions of the model were consistent with both our previous experimental data and experimental studies found in the literature and can be easily used by experimentalists for the rapid simulation and prediction of an MDC’s performance under different operating conditions.

Augmentation of microbial fuel cell and photocatalytic polishing technique for the treatment of hazardous dimethyl phthalate containing wastewater

In the present paper, the potentiality of integrating microbial fuel cells (MFCs) with a photocatalytic reactor to maximize the wastewater treatment efficiency with concurrent power generation was explored. Dimethyl phthalate (DMP) and acetic acid (AA) were the employed substrate and the co-substrate, respectively, using Pseudomonas aeruginosa as a biocatalyst. MFCs operated by single substrate showed the maximum power generation of 0.75-3.84 W m^-3 whereas an addition of AA as the co-substrate yielded 3-12 fold higher power generation. Pseudomonas aeruginosa produced phenazine-1-carboxylic acid in DMP-fed MFC as the metabolite whereas AA along with DMP yielded pyocyanin which reduced the charge transfer resistance. Chemical oxygen demand (COD) removal efficiency in the MFCs was circa 62% after 11 days of operation. Thereafter, it further increased albeit with a drastic reduction in power generation. Subsequently, the MFC anolyte was treated in a photocatalytic reactor under visible light irradiation and catalyzed by CuO-gC₃N₄. The performance of photocatalytic reactor was evaluated, with COD and total organic carbon (TOC) removal efficiency of 88% and 86% after 200 min of light irradiation. The present work suggests that the MFC can be integrated with photocatalysis as a sustainable wastewater treatment method with concurrent power generation.