Chhabra, Meenu

Microbial fuel cells (MFCs) are emerging wastewater treatment systems with a proven potential for denitrification. In this study, we have developed a high-rate denitrifying MFC. The anode consisted of cow manure and fruit waste and the cathode consisted of cow manure and soil. The initial chemical oxygen demand (COD)/nitrate nitrogen (NO3−-N) was varied from 2 to 40 at the cathode while keeping the anode ratio fixed at 100. NO3−-N removal rate of 7.1 ± 0.9 kg NO3−-N/m3 net cathodic compartment (NCC)/day was achieved at cathode COD/NO3−-N ratio 7.31 with the current density of 190 ± 9.1 mA/m2 and power density of 31.92 ± 4 mW/m2 of electrode surface area. We achieved an open-circuit voltage (OCV) of 410 ± 20 mV at initial cathodic NO3−-N of 0.345 g/l. The cathode COD/NO3−-N ratio had a significant influence on MFC’s OCV and nitrate removal rate. Lower OCV (<150 mV) and NO3−-N removal rates were observed at COD/NO3−-N ratio >12 and <7. Experiments done at different cathode pH values indicated that the optimum pH for denitrification was 7. Under optimized biochemical conditions, nitrate removal rate of 6.5 kg NO3−-N/m3 net cathodic compartment (NCC)/day and power density of 210 mW/m2 were achieved in a low resistance MFC. The present study thus demonstrates the utility of MFCs for the treatment of high nitrate wastes.

The photosynthetic microbial fuel cells (PMFCs) have showcased considerable potential for sustainable bioenergy and bioproduct generation while cultivating microalgae in the cathode chamber. Nevertheless, the exploration of genetically engineered microalgae as cathodic species in PMFCs is currently limited. This study systematically compares the performance of wild type (WT) and genetically modified (GM) Chlamydomonas reinhardtii in PMFCs, focusing on bioelectricity and bioproduct generation. The study showed that β-carotene productivity in MFCs with WT and GM strains has reached 1.55 ± 0.05 and 3.88 ± 0.14 mg/g DCW, respectively. Therefore, the MFC cathode environment significantly boosted the β-carotene production (2.49-fold) in microalgae compared to flask-grown cultures. Moreover, power generation in MFCs using GM strains (0.99 ± 0.15 W/m3) was not significantly different from that of WT species (1.26 ± 0.27 W/m3). The removal of anodic chemical oxygen demand (COD) reaches up to 79 % in MFCs with GM microalgae. Therefore, the current investigation presents a proof of concept for GM microalgae-based PMFCs, which may strengthen the existing bioproduct synthesis at a global scale by enhancing microalgae growth and carotenoid production.

The increasing challenge of treating saline wastewater while recovering energy highlights the need for sustainable and efficient solutions. This study presents the performance of a halophilic bacteria and Dunaliella salina-assisted photomicrobial fuel cell (PMFC) in an outdoor operation for COD removal and simultaneously energy production. The PMFCs made of inexpensive material were used for organic matter removal in saline wastewater (between the salinity range 0.5M–1.5M). Lipid-extracted algae (LEA) and starch were used as electron donors at the anode. D. salina at the cathode produces oxygen as an electron acceptor and serves as a valuable source of lipids, glycerol, and β-carotene. The PMFCs were characterized for energy recovery, algae biomass production, and microbial composition. The 0.5M LEA-fed PMFCs produced the highest operating voltage of 615 ± 79 mV across the 100 Ω register and 0.496 kWh/m3 of net energy. Further metagenomic analyses of the operating systems were analyzed to better understand microbial interactions. The comparison of the metagenomic profile of the anodic biofilm of 0.5M LEA-fed PMFC and 1.5M LEA-fed PMFC showed the dominance of the halophilic hat can use complex substrates electrogens like Pseudomonas (0.5M-13.61 %; 1.5M-1.73 %), Blastopirellula (0.5M-13.44 %; 1.5M-0.62 %), Halomonas (0.5M-1.21 %; 1.5M-33.26 %), and Lentimicrobium (0.5M-8.67 %; 1.5M-3.92 %). This work highlights the practical importance of PMFCs in the treatment of saline wastewater, offering both efficient COD removal and sustainable energy generation. The results provide insights into managing microbial communities to improve the performance of the operating PMFCs, facilitating wider applications in saline wastewater management. © 2025 Elsevier Ltd

Strengthening the existing CO2 capture technologies is crucial for averting the imminent climate crisis. The present study undertakes the algae-assisted microbial fuel cell (MFC) for indirect CO2 capture via bicarbonate utilization through natural photosynthesis process. The flue gas is first cooled using a heat exchanger and then directed to a sieve-plate absorption column where sodium carbonate supplemented wastewater absorbs CO2 generating flue gas-derived bicarbonates (FGDBs). The FGDBs are added in the plastic bag photobioreactors (PBRs) coupled with the MFC for absorption by Chlorella vulgaris. Adding FGDB at the MFC cathode increased the algae biomass productivity two times (0.677 ± 0.086 Kg/m3/d) compared to the cathode without FGDB. The algae could efficiently utilize 76.84 ± 1.23 %. More than 50 % of sodium carbonate can be recycled for the next round of CO2 capture. FGDB supplementation at the cathode improved MFC's electrical energy production (0.0066 kWh/m3) by 1.5 times through enhanced anodic and cathodic currents. Therefore, the present study offers a biochemical CO2 sequestration process that generates power, algae biomass, and treats water by utilizing algae-assisted MFC for flue gas carbon capture.