ON LINE CONTROL STRATEGIES FOR DISINFECTION SYSTEMS: SUCCESS AND FAILURE Edmund A. Kobylinski, Gary L. Hunter, Andrew R. Shaw Black & Veatch 8400 Ward Parkway Kansas City, Missouri 64114 ABSTRACT There are many levels of automation for control of chlorination systems. To select the best control approach for a facility, both control strategies and chlorination chemistry must be understood. Permit conditions including organism concentrations and operating data must also be fully identified. Many States require compliance with organism concentrations, as well as residual chlorine and disinfection byproduct concentrations. Breakpoint chlorination chemistry will play a role in most disinfection systems. This paper discusses combining on-line monitoring and automated control with chlorine chemistry to develop several levels of process control that will result in effective disinfection. Another factor must be considered while developing a process control strategy is disinfection byproduct formation. Disinfection byproducts (DBPs) in wastewater effluent are being regulated and the limits being imposed are much stricter than SDWA standards. Data from a recent disinfection study is presented to examine DBP formation and other selected chemical properties. KEYWORDS Breakpoint Chlorination, On-line Analyzers, Flow-paced Control INTRODUCTION Many attempts have been made to automate chlorine-based disinfection systems. Two basic problems are always encountered when controlling chlorination systems: the lag time inherent in the feedback control of plug flow systems and interpreting the impacts of chlorine chemistry on process control. Until these two issues are properly addressed in the control system logic, the control system will have serious limitations and may be more trouble to operate than the money spent to install the equipment. Strict nutrient limits are forcing many chlorine disinfection systems to vacillate between monochloramines and free chlorine. Both will effectively disinfect a wastewater, but each has its 6371 WEFTEC®.06 Copyright 2006 Water Environment Foundation. All Rights Reserved ©