Indigenous microalgae for sustainable wastewater sanitation and biorefinery integration: A translational path to resilient resource recovery

Abstract

The improper wastewater management and overdependence on fossil fuels pose significant challenges to ecosystem stability and lead to water scarcity. In this context, the objective of the study is the strategic utilization and cultivation of indigenous microalgae as a potent resource for integrated water sanitation and bioenergy production. Correspondingly contributing to the achievement of Sustainable Development Goals (SDGs), particularly SDG 6 and SDG 7. Strategic cultivation of microalgae in wastewater improved water quality by significantly reducing nitrates (99%), phosphates (100%), heavy metals (92–98%), and pathogenic loads (100%), rendering it suitable for both potable and non-potable applications. Utilization of indigenous microalgae enables effective adaptation to stress environmental conditions by reducing their cell size, as evidenced by phase contrast microscopy, and an enhancement in metabolites. This facilitated enhanced nutrient uptake, accelerated cell division, and boosted biomass productivity to 93.750 ± 0.002 mg L⁻¹/day and 90.925 ± 0.004 mg L⁻¹/day for Chlorella sp., (RCSS-1) and Desmodesmus sp., (RCSS-2), respectively. Furthermore, the diminished cell size optimizes light absorption by minimizing internal shading and thereby increasing photosynthetic efficiency and carbon fixation rates (4.50 and 6.03%), approximately 50%. In addition, the dominance of fatty acids, hydrocarbons, and other active metabolites reveals its potential as biofuels feed additives, antimicrobials, and surfactants. Thus, low-cost cultivation strategy integrated with existing wastewater treatment systems demonstrates strong economic feasibility and scalability potential. Moreover, this study offers a translational approach for generating low-cost biomass for carbon-neutral bioproducts along with clean water for a circular bioeconomy and sustainable environment.