Study On Optimizing Structure And Operating Parameters Of Ozonation Contact Reactor For Yellow River Water

O3-BAC (Biological Activated Carbon) treatment technology can remove odormatter and trace organics in Yellow River water, which has the properties of lowturbidity, high odor, high bromide, high algae effectively. However the reaction ofozone and bromide in Yellow River water produces a carcinogen, i.e., bromate. Ozoneutilization efficiency can be enhanced with reduced ozone dose through optimizingozone contact reactor in order to reduce bromate production. In this study, we firstconducted a statistical analysis for the quality of Yellow River water. Then withYellow River water as an example, a pilot study was conducted to research theinfluence of ozone dosing mode on ozone utilization efficiency and organics removal.Computational Fluent Dynamics (CFD) method was utilized to simulate the flowfield of ozone contactor, to evaluate its hydraulic efficiency and optimize its structureto improve the efficiency of ozone exposure. Through bench experiments, the amountof ammonium exposure was studied in ozonation process, evaluating the risk ofexcess bromate production. The results of the study show:It is feasible to implement CFD to simulate Ozone contactor’s flow field tocalculate its hydraulic efficiency in terms of t10/T. Inappropriate stucture in ozonecontactor leads to the creation of short flow and eddy current, and etc., making flowpattern deviating from the ideal push flow and low hydraulic efficiency. Flow state ofozone contactor can be improved and hydraulic efficiency can be enhanced by addingguide plate and increasing height-width ratio of contactor, among which, increasingheight-width ratio enhances hydraulic efficiency much more significantly and addingguide plate changes the contactor structure smaller.Water quality analysis shows that Yellow River water possesses suchcharacteristics as low turbidity, high algae, moderate organics and ammonia. Ozonecontacting system evaluation indicators were established by pilot experiments, whichinclude ozone utilization efficiency, organics removal efficiency and organicsremoval amoutnt of unit ozone consumption. Based on these indicators, it is foundthat ozone dose and ozone dosing proportion both affect the processing efficiency of ozone contacting system. With comprehensive consideration, the optimal operatingparameters for O3-BAC are the ozone dose of2mg/L and the dosing proportion of6:2:2, which make all those three indicators proformance well. Ozone dosingproportion influences ozone utilization efficiency more significantly than ozone dose,and the ozone dosing mode of high flow rate and low concentration achieves highozone utilization efficiency.Ammonia in Yellow River water has significant impact on bromate productionsignificantly. Ozonation of Yellow River water with low ammonia leads to a highconcentration of bromate in effluent, and the risk of excess bromate production ishigh. Bromate production in ozonation process can be reduced by supplying extraammonium. The bromate amount is the function of exponential of aquatic ammoniaconcontration approximately in certain concentration range. Ammonia in YellowRiver water can control the bromate production effectively, and with the ammoniaconcentration of0.4mg/L, bromate production concentration will not exceed10μg/Leven with a high ozone dose as large as5mg/L.