Bioelectricity generation by natural microflora of septic tank wastewater (STWW) and biodegradation of persistent petrogenic pollutants by basidiomycetes fungi: An integrated microbial fuel cell system

The microbial fuel cell is a unique advantageous technology for the scientific community with the simultaneous generation of green energy along with bioelectroremediation of persistent hazardous materials. In this work, a novel approach of integrated system with bioelectricity generation from septic tank wastewater by native microflora in the anode chamber, while Psathyrella candolleana with higher ligninolytic enzyme activity was employed at cathode chamber for the biodegradation of polycyclic aromatic hydrocarbons (PAHs). Six MFC systems designated as MFC1, MFC2, MFC3, MFC4, MFC5, and MFC6 were experimented with different conditions. MFC1 system using natural microflora of STWW (100%) at anode chamber and K₃[Fe(CN)₆] as cathode buffer showed a power density and current density of 110 ± 10 mW/m² and 90 ± 10 mA/m² respectively. In the other five MFC systems 100% STWW was used at the anode and basidiomycetes fungi in the presence or absence of individual PAHs (naphthalene, acenaphthene, fluorene, and anthracene) at the cathode. MFC2, MFC3, MFC4, MFC5, and MFC6 had showed power density of 132 ± 17 mW/m², 138 ± 20 mW/m², 139 ± 25 mW/m², and 147 ± 10 mW/m² respectively. MFC2, MFC3, MFC4, MFC5, and MFC6 had showed current density of 497 ± 17 mA/m², 519 ± 10 mA/m², 522 ± 21 mA/m² and 525 ± 20 mA/m² respectively. In all the MFC systems, the electrochemical activity of anode biofilm was evaluated by cyclic voltammetry analysis and biofilms on all the MFC systems electrode surface were visualized by confocal laser scanning microscope. Biodegradation of PAHs during MFC experimentations in the cathode chamber was estimated by UV-Vis spectrophotometer. Overall, MFC6 system achieved maximum power density production of 525 ± 20 mA/m² with 77% of chemical oxygen demand removal and 54% of coulombic efficiency at the anode chamber and higher anthracene biodegradation (62 ± 1.13%) at the cathode chamber by the selected Psathyrella candolleana at 14th day. The present natural microflora - basidiomycetes fungal coupled MFC system offers excellent opening towards the simultaneous generation of green electricity and PAHs bioelectroremediation.

Influence of Nickel molybdate nanocatalyst for enhancing biohydrogen production in microbial electrolysis cell utilizing sugar industrial effluent

Biohydrogen production in Microbial Electrolysis Cell (MEC) had inspired the researchers to overcome the challenges associated towards sustainability. Despite microbial community and various substrates, economical cathode catalyst development is most significant factor for enhancing hydrogen production in the MEC. Hence, in this study, the performance of MEC was investigated with a sugar industry effluent (COD 4200 ± 20 mg/L) with graphite anode and modified Nickel foam (NF) cathode. Nickel molybdate (NiMoO₄) coated NF achieved a higher hydrogen production rate 0.12 ± 0.01 L.L^-1D^-1 as compared to control under favorable conditions. Electrochemical characterizations demonstrated that the improved catalytic activity of novel nanocatalyst with lower impedance favoring faster hydrogen evolution kinetics. The MEC with the novel catalyst performed with 58.2% coloumbic efficiency, 20.36% cathodic hydrogen recovery, 11.96% overall hydrogen recovery and 54.38% COD removal efficiency for a 250 mL substrate during 5 days' batch cycle. Hence, the potentiality of modified cathode was established with the real time industrial effluent highlighting the waste to wealth bio-electrochemical technology.

Fermentative hydrogen production and bioelectricity generation from food based industrial waste: An integrative approach

In the present study, isolation and identification of hydrogen producing strains from sugar and food industry wastewater were reported. From 48 isolates in both the wastewater, initial batch studies led to the use of four effective strains, which were identified using 16S rRNA gene sequencing as Bacillus thuringiensis-FH1, Comamonas testosteroni-FB1, Klebsiella pneumoniae-FA2 and Bacillus cereus-SB2, respectively. Further optimization studies were done at various pH values (5-8) and wastewater concentrations (10-100%). In the optimized batch experimentation, K. pneumoniae-FA2 excelled with the maximum cumulative hydrogen production of 880.93 ± 44.0 mL/L. A 3 L bioreactor was employed for effective hydrogen production, which conferred that K. pneumoniae-FA2, surpassed the other three with the maximum hydrogen yield of 3.79 ± 0.04 mol H₂/mol glucose. Bioelectricity production by K. pneumoniae-FA2 was also investigated in the microbial fuel cell at the optimized conditions to demonstrate its versatility in energy applications.

Bioelectricity production from kitchen wastewater using microbial fuel cell with photosynthetic algal cathode

In this study, the treatment of kitchen wastewater was demonstrated using microbial fuel cell (MFC) consisting photosynthetic microorganism as cathode catalyst. The power density and biomass generation were investigated using two photosynthetic microorganisms namely Synechococcus sp. and Chlorococcum sp., respectively. Cyclic Voltammogram analysis was performed to study the exoelectrogenic activity of mixed culture microorganisms present in the wastewater. The MFC experimental results showed that both species influenced the power production and COD removal efficiency. The MFC observed the higher power density of 41.5 ± 1.2 mW/m² with Synechococcus sp. as compared to Chlorococcum sp. (30.2 ± 0.8 mW/m²). The effect of CO₂ supply, light intensity and wastewater COD concentration on MFC performance were investigated. This study demonstrated the possibility of bioelectricity generation, CO₂ sequestration and biomass production with the algae biocatholyte during the treatment of kitchen wastewater in the MFC.