Owing to the highly variable nature of flows and water quality of CSOs for centralized as well as satellite CSO treatment, specialized methodologies and technologies have been developed to provide effective disinfection; most important has been the introduction of high-rate mixers in combination with dosing equipment to achieve disinfection in much shorter contact times than conventionally accomplished for dry-weather flows. High-rate disinfection or kill is defined as the application of high-rate mixing in combination with a chemical disinfectant to achieve disinfection within five minutes. The effectiveness is typically expressed in terms of log removal. High-rate disinfection utilizes mixing as a substitute for an additional component of time that would otherwise be required. This mixing is expressed as velocity gradient or “G”. These principals were first advanced through field scale applications during U.S. EPA demonstrations in Syracuse and Rochester, New York in the late 1970s (EPA 600/2-79-134, 600/2-79-031B).