Numerical simulation and response surface optimization of micro-vortex flocculation process for high turbidity water treatment

The optimization of continuous process was conducted for the treatment of high turbidity water by micro-vortex flocculation process. The computational fluid dynamics (CFD) numerical simulation software was applied to explore the changes of liquid flow state in the flocculation area under different flow rate (flow velocity) so as to determine the optimal flocculation time. By using response surface Box-Behnken design method, the effects of flow rate, coagulant dosing and reflux ratio and their interactions on the treatment effectiveness of high turbidity water by micro-vortex flocculation process were studied. The research showed that as the flow rate (flow velocity) increased, the turbulent kinetic energy, effective energy consumption, G-value and its rate of change in the flocculation zone gradually increased, but too excessive flow velocity could lead to insufficient flocculation time, and thus the optimal flow rate range was 4.2-7.0 m³/h. or the optimal flow velocity was 0.41-0.67 m/s. The reflux ratio was a highly significant factor affecting the micro-vortex flocculation process, followed by the coagulant dosage and flow rate, with a synergistic effect between the three. The best process parameters of micro-vortex flocculation process for treating high turbidity water were: flow rate 5.9 m³/h, coagulant dosage 34.8 mg/L, and reflux ratio 0.8; the removal rates of turbidity, UV₂₅₄ and COD_Mn were 99.23%, 95.03%, and 71.42%, respectively. The optimized micro-vortex flocculation process could provide a new way for high turbidity water treatment technology with certain application prospects.