Development of chlorine dioxide-related by-product models for drinking water treatment

Factorial experiments were conducted using source waters from seven drinkin g water treatment plants in Ontario, Canada to develop statistically based model equations capable of predicting chlorine dioxide consumption and chlo rite and chlorate formation upon chlorine dioxide application. The equation s address raw water quality and operational parameters including pH, temper ature, chlorine dioxide concentration, reaction time and water organic cont ent (as described by non-purgeable organic carbon x ultraviolet absorbance measured at 254 nm, NPOC x UV254). Terms describing two-factor interaction effects were also included, improving the accuracy of the predictive equati ons in fitting measured response concentrations as evaluated through intern al and external validations. Nearly 80% of the predictions for chlorine dio xide consumption and chlorite formation were observed to be within 20% of t he measured levels. Over 90% of the predicted chlorate levels were within /- 0.1 mg,/L of the measured levels. Chlorine dioxide concentration and NPO C x UV254 were key parameters when developing the predictive models. (C) 20 01 Elsevier Science Ltd. All rights reserved.