Computational fluid dynamics analysis of Trichosporon fermentans flocculation in refined soybean oil wastewater and flocculation rate prediction method.

Trichosporon fermentans can be used to treat refined soybean oil wastewater (RSOW) and produce microbial lipids. Bioflocculation is an effective method to recover Trichosporon fermentans which accumulates intracellular oils from wastewater. During the flocculation, the hydrodynamic distribution and parameters in the reactor are important limiting factors of yeast flocculation performance. In a 0.25 L flocculation device, it was found that the appropriate range of turbulence kinetic energy was within 0.00065-0.00073 m/s, the dissipation rate was within 0.119-0.317 m/s, and the shear force was less than 0.433 Pa by computational fluid dynamics. In this case, the flocculation rate (Fr) of Trichosporon fermentans could reach more than 90%. The empirical formula associated Fr of Trichosporon fermentans with hydrodynamic parameters was obtained by Matlab, and improved in the enlargement of flocculation device, displaying an error of less than 3.03%. A conical draft tube airlift circulating reactor for flocculation was designed based on the empirical formula, and the Fr reached 91.3%. The study shows that it is feasible to predict Fr of Trichosporon fermentans according to hydrodynamic parameters by numerical simulation, and design the industrial reactor for flocculation harvesting yeasts. It is also helpful for large-scale treatment of RSOW in a safe environment.