Phycoremediation of dairy industry wastewater using Chlorella sorokiniana: a cost-effective strategy for biodiesel production.

This study explored the potential of a newly isolated strain of Chlorella sorokiniana for dairy wastewater (DWW) phycoremediation and biodiesel production. Microalgae were cultivated in various dilutions of dairy wastewater (50%, 60%, 70%, 80%, and 90%) and compared with growth in synthetic Amaral medium. The results demonstrated that C. sorokiniana exhibited robust growth across all wastewater dilutions, with the 90% dilution outperforming the synthetic medium in terms of cell concentration and biomass production (0.47 g/L/d). Chlorophyll a content increased with higher wastewater concentrations, peaking at 20.24 µg/L in 90% DWW. Lipid content analysis revealed the highest accumulation in 90% DWW, reaching 40.33% of the dry weight biomass. Fatty acid profiling revealed a predominance of palmitic acid (C16:0), oleic acid (C18:1), and linoleic acid (C18:2) across all treatments. The proportion of saturated fatty acids slightly increased with higher wastewater concentrations, while monounsaturated fatty acids decreased and polyunsaturated fatty acids remained relatively stable. The results indicated that moderate dilution of 60% wastewater resulted in the highest nitrate removal efficiency (75%). Phosphate removal remained consistently high (85-98%) across all dilutions. The biodiesel properties derived from wastewater-cultivated algae met the ASTM D6751 and EN14214 standards, with improvements in the cetane number and cloud point at higher wastewater concentrations. This study demonstrated the feasibility of using dairy wastewater as a cost-effective and sustainable medium for microalgal cultivation, offering the dual benefits of wastewater phycoremediation and high-quality biodiesel feedstock production. The findings highlight the potential for integrating algal cultivation with dairy industry waste management, contributing to circular economic principles in the biofuel sector.