The Experimental Study And Numerical Simulation On Flocculent Kinetics For Drinking Water Treatment

The hydraulic condition of equipment is an importment factor to flocculation. In order to investigate the effect of hydraulic turbulence conditions on the flocculation, the study conducted jar test, CFD numerical simulation. The results can be extended to find an effective way to optimize the design and operation, to improve the efficiency of flocculation. The main work of this paper is shown as follows:1. Conducting jar test by changing the hydraulic conditions such as rotating speed of flocculation, different shape of jars, the impeller's geometry, the hight of impellers located in the vessel to investigate their effects on the flocculation. The suitable hydraulic conditions under different situations are obtained by tests.2. Based on the analysis and summarization of study results on velocity fields in stirred tanks, the CFD (Computational Fluid Dynamics) software-FLUENT is used to simulate the flow pattern. The effective energy dissipation ε and Kolmogoroff microvortexes scale λ are introduced to be the criterions to evalutate flocculation effects and interpret the complex phenomenons in the course of flocculation.The main conclusions of tests and simulations are shown as follows:1. The shape of jars is found to be the most important factor affecting slow rotating speed throughout coagulation process. In the circular vessels, the residual tuibidity of water sample reaches lowest under the suitable rotating speed. Increasing impeller area and setting impeller in the appropriate hight can provide the better hydraulic conditions and optimize effect of flocculation.2. The influences of hydraulic conditions on flocculation can be interpreted by computational results. Under the same rotating speed the circular jar produced the better mixing conditions and more effective energy dissipation. Because of the special boundary conditions, square vessels would prevent fluid in it to rotate with the impellers. The dead zones are generated around the corners in the square vessels, they reduce mass flow and localize the mixing, and eventually cause poor opportunities of collision and contact between flocs. Blending at the suitable speed in the circular jar is advantaged for...