Reducing disinfection byproducts using cyanuric acid: Relative reactivity of hypochlorite ion, hypochlorous acid, monochlorocyanuric acid, and dichlorocyanuric acid with dichlorohydroxybenzoic acid

CHED 1137

David M. Robinson and Gordon H. Purser. Department of Chemistry and Biochemistry, University of Tulsa, 600 S. College Ave, Tulsa, OK 74104
Due to the potential health risks associated with chlorinated organic species, controlling the formation of disinfection byproducts (DBPs) during water treatment is of great importance. In the mid 1980s, it was reported that cyanuric acid, “probably holds little promise for THM control in drinking water treatment” (Feldstein, C. M.; Rickabaugh, J.; Miltner, R. J. EPA-600/D-884-167; Order No. PB84-209105). In that work, no attempt was made to differentiate the effects of the various chlorinating species in solution. Furthermore, preliminary work in our laboratory contradicts their stated conclusion. The subject of this presentation is the analysis of the rate of reaction between the chlorinating species present in solution and dichlorohydroxybenzoic acid, a model THM precursor. The rate of the reaction was followed by stopped-flow techniques. Our evidence suggests that with appropriate concentrations of cyanuric acid, the rate of DBP formation may be greatly reduced.