AWWA JAW31622

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is a preemergent herbicide found frequently in Midwestern drinking water supplies at concentrations near or exceeding the recently promulgated maximum contaminant level of 3 ug/L. In water treatment plants that use ozone, oxidation breaks atrazine down into several different ozonation by-products. In the research described in this article, the effects of aqueous ozone concentration, pH, total carbonate alkalinity, and temperature on the ozonation of atrazine were examined, and an empirical model based on these parameters was developed. The model was tested in a continuous-flow recycle reactor using five different natural waters fortified with atrazine to concentrations of up to 11.4 ug/L. The correlation coefficient (r) between measured and predicted effluent atrazine concentration values (n = 53) was 0.95. Tests performed on synthetic waters showed that the model underpredicts removal in the presence of high ozone demand; thus, in waters having high ozone demand, the model's predictions are conservative and represent minimum removals that may be expected for a given set of conditions. This research provides quantitative insight into the effects of key process parameters and water characteristics on the oxidation rate by ozone of atrazine at micrograms per liter concentrations. The model does not eliminate the need for laboratoryor pilot-scale testing, but it is a useful tool for designers and operators of water treatment plants. Includes 38 references, tables, figures.