Investigation of Microalgae Co-Cultures for Nutrient Recovery and Algal BiomassProduction from Dairy Manure

Abstract. Treatment of waste streams using algae can minimize eutrophication by removing inorganic nutrients while producing biomass which can be used for biofuels, animal feed, and fertilizer production. While there are many studies that report the growth of individual algal strains in different media, there are relatively few studies that examine the performance of algae coculture. The objective of this research was to determine the growth parameters and nutrient sequestration profiles of Chlorella vulgaris, Scenedesmus dimorphus, and their coculture in wastewater from a dairy facility at two dilutions (10% and 25%).

Average specific growth rates (and biomass concentrations) the S. dimorphus, C. vulgaris, and their coculture were 0.263 d^-1 (0.290±0.059 g/L), 0.063 d^-1 (0.145±0.011 g/L), and 0.250 d^-1 (0.400±0.060 g/L) d^-1 at 10% manure, and 0.232 d^-1 (0.543±0.149 g/L), 0.234 d^-1 (0.364±0.113 g/L), and 0.289 d^-1(0.612±0.255 g/L) at 25% manure, respectively. Based on the results it was evident that the strains S. dimorphus and C. vulgaris have different capacities for accumulation of biomass production (S. dimorphus is higher), lipid accumulation (S. dimorphus is higher), chlorophyll (C. vulgaris is higher), total suspended solids (TSS) (C. vulgaris is higher), and volatile suspended solids (VSS) (S. dimorphus is higher). It was found that mixed coculture had higher biomass growth, specific growth rate, and removal efficiency of nitrogen, phosphorous, and TSS for the 25% dairy wastewater. The results were similar for 10% dairy wastewater except for the specific growth rate and nitrogen removal efficiency which were higher for the S. dimorphus monoculture. These capacities can be leveraged in mixed coculture to achieve higher treatment efficiencies compared to monocultures. The results can inform managers of agricultural and municipal wastewater facilities as they make decisions about whether to include algal technology in future upgrades and expansion.