Phycoremediation potential of Nostoc ellipsosporum and Spirulina subsalsa for pollutant removal from textile wastewater with integrated biodiesel production

The present study investigated the potential of two cyanobacterial species, namely Nostoc ellipsosporum (NE) and Spirulina subsalsa (SS), to remediate textile wastewater (TWW) while obtaining wastewater-grown biomass for biodiesel production. This study reports their multi-faceted benefits using unsterilized and undiluted (100%) TWW for the first time. Both cyanobacterial species were cultivated in TWW under greenhouse conditions, focusing on their growth, TWW decolorization, pollutant removal, phytotoxicity, lipid content, and fatty acid profile. Results demonstrated significant growth and decolorization of TWW by both species, highlighting their potential for sustainable treatment of TWW. NE-treated TWW (NE-TWW) achieved a chemical oxygen demand (COD) removal efficiency of 96.48%, while SS-treated TWW (SS-TWW) reached 93.11%. Ammonia removal efficiencies were recorded as 76.28% for NE-TWW and 96.86% for SS-TWW. NE-TWW and SS-TWW achieved nitrate removal of 69% and 73%, respectively. Phosphate removal was 81.14% for NE-TWW and 33.33% for SS-TWW. Both species exhibited more than 75% removal of heavy metals, particularly Cr, Fe, Zn, Cu, and Ni. Seed germination studies showed enhanced germination and seedling growth of green gram (Vigna radiata) when irrigated with NE-TWW and SS-TWW, indicating phytotoxicity reduction in treated TWW. Lipid yields (w/w) of 21.5% and 25% were recorded from TWW-grown biomass of NE and SS, respectively. Both species exhibited favorable fatty acid methyl ester (biodiesel) profiles, dominated by palmitic acid (C16:0), oleic acid (C18:1), stearic acid (C18:0), lauric acid (C12:0), and myristic acid (C14:0), indicating their suitability as biodiesel feedstocks. Overall, this integrated approach not only provides an eco-friendly and cost-effective strategy for TWW treatment but also offers a sustainable feedstock for biodiesel production.