USGS Ohio Water Science Center
OWML: Current ProjectsProject Title: Evaluating the effectiveness of chlorine dioxide as a wastewater disinfection agent. Project chief: Christopher Kephart Project support: Don Stoeckel Cooperators: The Ohio State University, Columbus, Ohio Project duration: 2006-2008 Introduction and
problem:
After its introduction in the 1950’s, chlorine dioxide has recently re-emerged as a disinfection agent. Chlorine dioxide has different activity than free chlorine or hypochlorite. Unlike free chlorine and hypochlorite, chlorine dioxide is active over a wide range of pH and its use does not result in the creation of byproducts such as trihalomethanes. Microbial disinfection with chlorine dioxide has been shown to be just as effective or superior to free chlorine – inactivation of viruses is much more effective with chlorine dioxide than free chlorine. A dry-packet delivery system developed by Avantec Technologies Inc., has recently made the chemistry behind chlorine dioxide generation economically and safely available to small systems. Widespread use of a newly developed chlorine dioxide disinfection system would depend, in part, upon its ability to effectively kill pathogenic microorganisms in a sewage effluent matrix. Goals and
objectives:
The specific objectives of this study are to (1) develop the Ct relation at bench scale against fecal indicator bacteria and viruses which will describe the inactivation kinetics of chlorine dioxide against multiple targets in a wastewater matrix, and (2) determine the effectiveness of the chlorine dioxide system against indicator organisms in a field-scale operational setting – an onsite, single-family household sewage treatment system. Approach: An initial, bench-scale recovery control experiment will be done in the absence of chlorine dioxide treatment in order to calculate the natural die-off or reproduction rates of the indicator organisms in the artificial effluent. The Ct relation will then be developed at bench-scale by exposing the artificial effluent to a single concentration of chlorine dioxide. Indicator organism concentrations will be plotted versus time so that a dose response curve can be constructed. The dose response will be normalized to accommodate the natural die-off and a Ct relation will be developed. A final experiment will be done to confirm the chlorine dioxide Ct relation when applied in a large-volume field setting. This experiment will be done in an onsite septic tank/wastewater stabilization pond/spray irrigation system at the OSU Molly Caren Agricultural Center.
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