Study On The Removal Efficiency Of Turbidity Using Stub Tube Fillers Under Advectional Flow Conditions

Stub tube fillers have practical significance for the removal of turbidity. The removal efficiency of turbidity is the main research content when studying the characteristics of the fillers. According to shallow pond theory, the packed bed and the experimental plan under advectional flow conditions used in this paper were designed.The main research contents are as follows: (1) the removal efficiency of turbidity using stub tube fillers and its contributing factors; (2) the effects of coagulant addition on the removal efficiency of turbidity; (3) the effects of stub tube fillers on the resistance of flow and dissolved oxygen (DO) in water. Through our study on these points, the following results were achieved:1.Under advectional flow conditions, the stub tube fillers could improve the removal of turbidity.2.The main removal efficiency of turbidity using stub tube fillers are amount of fillers, retention time of water, shapes and the turbidity of influent.(l)The removal rate of turbidity using stub tube fillers increased with the increasing of the addition amount of fillers.(2) Under the same conditions, the removal efficiencies of turbidity when the fillers were immobilized and suspended were compared.(3) The removal rate of turbidity using stub tube fillers increased with the increasing of retention time of water. When the retention time was within one hour, it is increased significantly with the increasing of retention time. But when the retention time was more than one hour, there were no transparent changes of the removal rate with further increment of retention time.(4) The removal rate of turbidity using stub tube fillers increased with the decreasing of the turbidity of influen. When the turbidity of influent was low, addition of coagulant could improve its removal efficiency.3. Two basic characteristic parameters of stub tube fillers, the effective horizontal projective surface area ratio ( @e) and its multiplicational time (Ke), were presented in this paper. One numerical model was developed, and the calculated effective surface area @e equal to 0.5 when the fillers were filled up into the packed bed at random. The calculation formula for the multiplicational time of effective surface area (X) was also deduced. The two parameters provide basis for the theoretical analysis of the removal of turbidity using stub tube fillers.4. Through regressive analysis of the measured results, the empirical equation for the removal rate of turbidity under advectional flow conditions of the packed bed was presented. The range of influent turbidity and retention time were 50NTU-300NTU and 0.02h-12h, respectively. The calculated results were fit well with the measured results. Furthermore, other two general formulae, the calculation equation for residual turbidity at the outlet point and the calculation equation for the integrated removal rate of turbidity, were established. These two formulae can be used for three different conditions of the packed bed: randomly filled up, filled with different amounts of fillers and immobilized, and without fillers.5.When the turbidity of influent was low, addition of coagulant could improve its removal efficiency. Through the experiments .results as the addition of aluminium sulphate (25-30mg/L) and the optimal position of chemical addition.6.The stub tube fillers generated resistance of water flow. And the resistance increased with the increment of flow rate, the length of packed beds and the proportion of fillers.7.Under advectional flow conditions, flow cascade could increase DO in water significantly.This research provides experimental basis for the application of stub tube fillers to the removal of turbidity and has significant practical values. The two basic characteristic parameters of stub tube fillers (Xe and Ke), their calculation methods and the responsible calculation equations for the removal rate of turbidity have theoretical meanings for the further study of the related topics.