Integrated biodigestion and phycoremediation of dairy farm wastewater using an Argentinian Tetradesmus obliquus strain
摘要
The growth capacity of microalgae and their tolerance to high pollutant concentrations in agricultural and livestock effluents represent the first step in evaluating their potential as phycoremediation agents. This study aimed to isolate and characterise a native chlorophyte from wastewater in the semi-arid Pampa region of Argentina and to assess its capacity for nutrient removal, biomass productivity, and biochemical composition when cultivated in dairy farm wastewater (DFW) post-anaerobic digestion (AD). The strain was morphologically and molecularly identified as Tetradesmus obliquus. Cultures were carried out in photobioreactors for 10 days using 50% pretreated digestate and compared to growth in Bold's Basal Medium (BBM). Biomass productivity in digestate (104 ± 0.73 mg L⁻1 day⁻1) was significantly higher than in BBM (74 ± 1.05 mg L⁻1 day⁻1), demonstrating the strain’s ability to grow in a turbid (115 NTU), NH₄⁺-rich medium (N/P ratio = 108.5). Removal efficiencies for NH₄⁺, NO₃⁻, and PO₄3⁻ were ≥ 80%, indicating strong potential for wastewater remediation and reuse. The recovered biomass showed high protein (37% DW) and lipid (22.4% DW) contents. Amino acid profiles were comparable between treatments, with digestate-grown biomass rich in arginine, asparagine, and glutamine (≥ 3 g per 100 g biomass). Sterol content increased by 83% in digestate cultures, with phytosterols comprising 99.2 ± 6.4% of total sterols. These results suggest that the native T. obliquus strain is a promising alternative for treating and valorising farm digestates using simple, low-cost methods. Future large-scale studies should evaluate the technical, economic, and environmental feasibility of this integrated bioprocess.
Graphical Abstract