AWWA WQTC65844

The number of water treatment facilities using ozone as a primary disinfectant is growing in places where surface waters are used as a source. Ozone disinfection in drinking water treatment facilities is often carried out in an ozone contactor that consists of multiple vertical or horizontal chambers to which ozone is fed by fine bubble diffusers (FBD). The hydrodynamics of an ozone contactor strongly affect the overall conversion of all the chemical and biological reactions (Roustan, et al, 1993; Henry & Freeman, 1995; Do-Quang, et al, 2000). Its effect is more pronounced for reactions with a relatively higher conversion (e.g., inactivation of C. parvum oocysts up to 99 to 99.9 percent) compared to reactions with a lower conversion (e.g., bromate formation from bromide is typically below 30 percent). Consequently, the reactor hydrodynamics could be optimized to minimize bromate formation while achieving target inactivation efficiency for C. parvum oocysts (Tang, et al, 2005; Kim, et al, 2006; Kim, et al, 2007). The impact of hydrodynamic conditions determined by such design variables on inactivation efficiency, which is a primary concern in ozone contactor design, was investigated. In particular, a three-dimensional laser-induced fluorescence (3D-LIF) was developed in this study to visualize the mixing condition inside the ozone contactor by quantifying the entire instantaneous tracer concentration field at very high resolution in three-dimensional space (Tian & Roberts, 2003) without disturbing the flow conditions (i.e. due to sampling). Various hydrodynamic conditions within an ozone contactor including the non-ideal flow pattern, the effects of flow rate, and the baffle opening size, were examined. Includes 9 references, figures.