Sustainable treatment of dairy wastewater using a selective microalgal consortium of Chlorella vulgaris, Scenedesmus obliquus, and Chlorococcus minutus

Abstract

Dairy effluents are characterised by high concentrations of organic matter, nitrogen, phosphorus, suspended solids, and chemical additives, making them among the most challenging industrial wastewaters to treat. This study evaluates the potential of indigenous microalgae Chlorella vulgaris, Scenedesmus obliquus, and Chlorococcus minutus for the phycoremediation of dairy wastewater. The untreated wastewater, characterised by high biological oxygen demand (BOD: 768 mg/L) and chemical oxygen demand (COD: 945 mg/L), as well as nitrate (9.31 mg/L), phosphate (4.13 mg/L), and ammonium (0.68 mg/L), was subjected to microalgal treatment. All cultures significantly improved water quality, with the consortium consistently outperforming monocultures. By day 15, BOD and COD reductions exceeded 90%, nitrate removal reached 99.5%, phosphate removal reached 98.1%, and ammonium removal reached 92.6%. Biomass productivity increased steadily, with the consortium achieving the highest yield (1.70 g/L DW), indicating synergistic nutrient assimilation and enhanced growth stability. The findings demonstrate that native microalgal consortia provide an eco-friendly, cost-effective, and scalable approach for dairy wastewater treatment, while generating biomass suitable for biofuel and biofertilizer applications.