The Design And Optimization Of Equipment For Ozone Disinfection Of Drinking Water Based On CFD

The drinking water is unsafe both in urban and rural of our country. There is only13.8%drinking water meted to the drinking water standard in the poor rural. Sort of waterborne pathogens exist in water distribution system and secondary water supply system, which are needed to upgrade and maintain. So the drinking water is unqualified in the point of user, and also causes the plan of direct drinking water failed in our nation. The equipment designed in this paper can effectively deal with the problem.Ozone is used in our equipment to inactivate micro-organism. The equipment includes four parts:generation of ozone, mass transfer, reaction, and treatment of tail gas. The design parameters (such as C, T) will be changed along with different water quality, and all will be changed. Through searching related information in some books and manuals, we define the values of C, T, and Q as2mg/L,10min, and40L/min. According to the above three parameters, we can calculate and design the parts, such as ozone generator, ozone-water mixing bump, ozone-water reactor, and so on.The inactivation of waterborne pathogens during disinfection of drinking water is specified in the terms of CT which is numeric product of the ozone disinfection concentration and contact time. The larger value of CT, the better disinfection of water, but the larger value of C wills product more toxic disinfection by-products (DBPs) which is limited. We also usually use CTio to substitute CT to value the efficiency of disinfection. T10is the time required for10%of a pulse of a tracer introduced at the disinfectant dosing point to have reached the residual sampling point. Disinfection of water is typically carried out in a reactor. We can increase the value of Tio and improve hydraulic efficiency by optimizing the internal structure. The reactor is divided into two zones, where zone one be called the zone of plug flow, and zone two be called the zone of circuit flow. We improve the plug flow in the zone one by reducing the distance between two partitions. A plug flow in the reactor has a large improvement on the residence time distribution, and also improves the disinfection capacity. We improve the vortex flow in the zone two by increasing the distance between two partitions. A vortex flow will cut down the concentration gradient of ozone, and improve its dispersion. Computational fluid dynamics (CFD) modeling is applied to analyze the hydraulic efficiency of reactor, and obtain several conclusions as follows.(1)The regions of C1～C4is primarily with plug flow, and have the problem of short circuit flow.(2)We can not observe apparent vortex flow, and also have the problem of short circuit flow.According the above analysis, I designed two optimization proposals. Using the CFD to analyze them, and obtain the following conclusions.(1)The first proposal is better than the second proposal for the regions of C5～C9.(2)The second proposal is better than the first proposal for the regions of C1～C4.(3)It is better than the above two single proposals to combine the first with the second. In the regions of C1～C4, we use the second one; In the regions of C5～C9, we use the first one.