Interaction of flow turbulence and nitrogen nutrients on the growth of Scenedesmu Quadricanda

The effects of hydrodynamics and nutrients on algae growth have received considerable attention. In this study, the research of the interaction of flow turbulence and nitrogen nutrients on the growth of Scenedesmu Quadricanda was investigated. Scenedesmu Quadricanda was cultured under different turbulence intensities and nutrients conditions. Furthermore, the improved logistic model was used to unify the effect of nutrient flux and hydraulic diffusion flux on algal growth. Algae cell integrity, chlorophyll-a concentration, and polysaccharide content were determined to represent the algal growth. Results showed that the high turbulence intensity (turbulent energy dissipation rate 3.25 × 10−3 fm2/s3–8.93 × 10−3 m2/s3) and total nitrogen (TN) concentration increased algal density and chlorophyll-a. However, there was no significant correlation between the concentration of TN and turbulence intensity and the growth rate of algae. The polysaccharide determination results showed that the increase of TN concentration would reduce extracellular polymeric substances (EPS), which would reduce the aggregation of algal cells. Moreover, high turbulence intensity promoted the production and accumulation of intracellular polysaccharides (IPS) and inhibited the secretion of EPS. The analysis of the improved logistic model verified that the increase of both TN concentration and turbulent intensity increased the production of chlorophyll-a, maximum biomass, and the intrinsic rate of increase. The findings indicate that flow turbulence and nitrogen nutrients have a synergistic effect on algal growth, chlorophyll-a content, polysaccharide secretion, and nutrient uptake, which can foster further investigations on the control of algal bloom and harvest of microalgae biomass.