Evaluation of Ozone Disinfection Systems: Characteristic Concentration C

Abstract

The U.S. Environmental Protection Agency (EPA) has recently promulgated drinking water regulations known as the surface water treatment rule (SWTR) to control viruses, \IGiardia lamblia, Legionella\N, and heterotrophic bacteria. The SWTR specifies overall minimum removal and inactivation efficiencies by filtration and disinfection for \IGiardia lamblia\N and viruses. The \ICT\N concept is used to predict inactivation efficiencies. \ICT\N stands for the product of characteristic exposure time (\IT\N) and the characteristic concentration (\IC\N) of the disinfectant in the disinfection chamber. This paper presents an analysis of ways to characterize ozone concentration in water disinfection systems for the purpose of calculating ozone inactivation efficiencies. Guidelines to predict the characteristic (or average) ozone concentration are developed for four types of ozone reactors, including rigorously mixed systems, cocurrent and countercurrent contractors, and flow segments (i.e., where no ozone gas is introduced but where residuals in a water phase remains).