Current approaches for disinfection process design involve application of a C*T (concentration*time) concept or the Integrated Disinfection Design Framework (IDDF). This study presents a new design approach for chorine disinfection employing computational fluid dynamics (CFD). CFD models were developed to predict flow structure, mass transport, chlorine decay and microbial inactivation in a continuous-flow reactor and associated piping. Prior CFD models for chlorine disinfection have only predicted chlorine contactor flow structure and residence time distribution. The present model incorporates experimentally derived terms for chlorine decay (free and combined) and microbial inactivation (E.coli, MS2 bacteriophage and Giardia muris) based on the work of Haas et al.. CFD predictions were in good agreement with the experimental data set over a wide range of Damkohler number (Da) for microbial inactivation. Includes 25 references, tables, figures.