Degradation Characteristics Of COD And Coupling Effects Of Mass Transfer In Vortex Membrane Bioreactors

The vortex wave is a special flow phenomenas, which a series of vorticies can be periodically formed near the walls of the channel and the core fluid flows through the vorticies here. Vortex wave can generate very effective mixing under laminar flow conditions. Compared with traditional mass transfer method by using turbulent flow, its shear rate and power dissipation are rather low. Combined with between the votex wave fluid and membrane technique, it becomes a novel membrane bioreactor that can efficiently enhance mass transfer. So it is worth to study in details. In this paper, we study the characteristics of vortex wave by testing the dissolved oxygen concentration and degradation of COD in vortex membrane bioreactor. Then we study the effect of the operation parameters and the structure on the performance of the bioreactor . The following contents are discussed:An experimental set-up is established. The aeration experiment of water and wastewater are carried out. In the aeration test of water, we change the pressure and gas flux respectively and analyze their influence on vortex wave with volumetric mass transfer coefficient. The results show that volumetric mass transfer coefficient curve with pressure and gas flux arc the same as a sinusoid, but the changing range of pressure curve is larger.We change the Reynold number, pressure, gas flux and liquid flux in the aeration test of wastewater respectively, and analyze their influence on the performance of the bioreactor by evaluating degradation of COD. It shows that the removal rate of COD gets larger basically when the Reynold number and pressure get larger. The change of gas flux has little influence on the removal rate of COD.The removal rate of COD in the oscillatory flow is higher than that of the steady flow. Compared with the oscillatory flow, the removal rates of COD under the oscillatory flow plusing the steady flow conditions are the highest.In addition, we investigate the change between the removal rate of COD and different deflector spacings in the channel of the membrane bioreactor. The results show that the smaller deflector spacing has a better influence on the oxygen mass transfer capability. At last, we present the kinetics model of the membrane bioreactor based on the experiment datas.