Glucose and Nitrogen Amendments Can Mitigate Wastewater-Borne Bacteria Competition Effect Against Algal Growth in Wastewater-Based Systems.

The reuse of wastewater is important for reducing costs involved with algal lipid production. However, nutrient limitations, wastewater-borne microbes, and mixotrophic growth can significantly affect biomass yields and lipid/biomass ratios. This research compared the growth performances of both Chlorella vulgaris and Pseudokirchneriella subcapitata on domestic wastewater effluent. The experiments were conducted in the presence and absence of wastewater-borne bacteria, while additionally assessing the impact of distinct nitrate and glucose supplementations. When compared to the sterilized controls, the presence of wastewater-borne bacteria in the effluent reduced C. vulgaris and P. subcapitata total biomass production by 37% and 46%, respectively. In the corresponding treatments supplemented with glucose and nitrate, total biomass production increased by 12% and 61%, respectively. The highest biomass production of 1.11 and 0.72 g · L was, however, observed in the sterilized treatments with both glucose and nitrate supplementations for C. vulgaris and P. subcapitata, respectively. Lipid to biomass ratios were, on average, threefold higher when only nitrate was introduced in the sterilized treatments for both species (0.4 and 0.5, respectively). Therefore, the combination of nitrate and glucose supplementation is shown to be an important strategy for enhancing algal lipid and biomass production when those algae are grown in the presence of wastewater-borne bacteria. On the other hand, in the absence of wastewater-borne bacteria, only nitrate supplementation can significantly improve lipid/biomass ratios.