University of California Water Resources Center

The dynamics of breakpoint chlorination were examined in three continuous dispersed flow reactors. The reactors were comprised of 1/2, 2 and 3 inch PVC pipe, which were 730, 41, and 23 feet long, respectively. Chlorination of ammonia a various chlorine to ammonia ratios were investigated over the pH range of 6.5 to 7.5.

Seventeen experiments were performed in the three reactors over the course of the experimental investigations. Chlorine residuals, including free, monochloramine, dichloramine, and nitrogen trichloride, and ammonia were analyzed simultaneously.

To quantitatively characterize the breakpoint reactions, a mathematical model, consisting of eight simultaneous, quasi-linear, partial differential equations was developed. The model was solved using an implicit finite difference technique. The reaction rate coefficients were treated as parameters, and were estimated using a search technique to minimize the sum of squares of the difference between the expected and measured values.

The model can now be used to simulated continuous flow chlorination processes in order to develop process operating strategies to maximize of minimize any given experimental objectives.