12-04: A hetero-photoautotrophic two-stage cultivation model to improve wastewater nutrient removal and enhance algal lipid accumulation for low cost biofuel feedstock production

In this study, a hetero-photoautotrophic algal growth model was studied for improved wastewater treatment and low cost algae-based biofuel feedstock production. Microalga Auxenochlorella protothecoides UMN280 was grown heterotrophically on concentrated municipal wastewater and then autotrophically with CO2 supplementation. The strain UMN280 was harvested by self-sedimentation after the heterotrophic stage and the supernatant was aerated with CO2 to facilitate autotrophic growth in the second stage. The maximal biomass concentration and lipid content at the first stage and second stage reached up to 1.12 g/L and 28.90 %, and 1.16 g/L and 33.22%, respectively. The nutrient removal efficiencies for total phosphorus, ammonia, total nitrogen and chemical oxygen demand at the end of the two-stage cultivation were 98.48%, 100%, 90.60% and 79.10%, respectively. The above model can be used to treat organic-rich wastewaters (e.g. industrial and animal manure wastewater) to achieve dual purpose of reduced-cost wastewater treatment and biofuel feedstock production.