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Amsterdam Water Supply uses ozonation as a barrier for bacteria, Giardia and viruses at two of its water treatment plants: Leiduin and Weesperkarspel. In addition to being used for disinfection,ozone is also used to eliminate organic micro-pollutants and to stimulate biological activity onthe activated carbon filters following the ozone process. More stringent legislation andthe allowance to put cattle to pasture in the dune infiltration area lead to an increase ofthe required disinfection capacity. To improve the disinfection capacity, increasing theozone dose is considered (Hijnen et al, 2001). However, higher ozone doses also will leadto higher bromate concentrations (Orlandini et al, 1997). Further optimization of theozone systems is therefore required.In general, an ozone system can be divided into two parts, the dosing equipment and thereactive flow part, where the reaction with the dissolved ozone residual takes place.Ozone can be added to the water stream by bubble columns, or injection devices. The fullscale installations in the Netherlands all apply bubble columns for ozone addition. The hydraulic characteristics of the ozone system influence both parts; masstransfer and mixing in the bubble column as well as residence time distribution in thereactive flow part largely determine the disinfection performance and the byproductsformation. In the bubble column, mixing is required to get a uniform ozone residualconcentration. On the other hand plug flow is desired to get better disinfection results(prevent short residence times by short-circuiting). However, plug flow lacks mixingcapabilities.Application of Computational Fluid Dynamics (CFD) offers the possibility of accuratelydescribing the hydraulic conditions. CFD results are compared to experimental data frompilot and bench scale experiments. Also full scale experiments were done to determinethe residence time distribution of the ozone system at the Leiduin water treatment plant ofAmsterdam Water Supply. The pilot plant experiments were conducted at the Berenplaatwater treatment plant of the Evides water company. Lab-scale data were collected in aplug-flow reactor at Kiwa Water Research. Includes 10 references, table, figures.

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Edition: Vol. - No. Published: 11/01/2005 Number of Pages: 7 File Size: 1 file , 230 KB