Chhabra, Meenu

Textile effluent is characterized by high colour, chemical oxygen demand and conductivity due to presence of a large number of recalcitrant compounds. The effluent is often discharged without an effective treatment leading to contamination of water bodies. In the present study, a combination of mediator assisted laccase and chemical treatment was used for decolorization of effluent from a local textile mill in a continuous enzyme membrane reactor (EMR). Treatment of the effluent first with laccase and ABTS (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) lead to about 60% decolorization but was accompanied by membrane fouling. Addition of alum further coagulated 90% of the residual colour but the process was associated with dye sludge formation and ABTS could not be recovered from the treated effluent. Reversal of the treatment sequence was effective in that 85% decolorization was achieved in the EMR and the process could be operated for over a period of 15 days. No sludge formation was noticed and membrane fouling was negligible. Most importantly, about 60% ABTS could be recovered from the treated effluent. Analysis of the treated effluent by mass spectrometery indicated extensive breakdown of the dye molecules by laccase and ABTS and the breakdown products were neither toxic nor mutagenic as assessed by measurement of the oxygen consumption rate and the standard Ames test.

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