Experiments were conducted at the bench scale to determine the effects of pH, total
organic carbon (TOC), alkalinity, temperature, and H<sub>2</sub>O<sub>2</sub> dose on the removal rate of atrazine
(ATZ) using ultraviolet light (UV) emitted from a medium-pressure mercury lamp. Simulated
natural water was used to control these parameters independently. Initial experiments showed
very little effect of alkalinity alone, and the effect of TOC was ascribable solely to light
screening since TOC had no effect on the UV dose-based rate constants (which account for light
screening by the water matrix). On the other hand, increasing temperature and H<sub>2</sub>O<sub>2</sub> dose
positively affected the removal rates while increasing the pH had a small but negative effect both
with and without H<sub>2</sub>O<sub>2</sub> that was most discernable at higher temperatures. These three parameters
(H<sub>2</sub>O<sub>2</sub>, T, and pH) were therefore selected for further study to design a dose-response model of
ATZ removal.
Other experiments examined whether nitrate (NO<sub>3</sub>
<sup>-</sup>) has a photosensitizing effect on ATZ
degradation (via <sup>.</sup>OH production during NO<sub>3</sub>
<sup>-</sup> photolysis). Nitrate concentrations up to 7 mg-N/L
enhanced the ATZ removal rates (s<sup>-1</sup>) in deionized water but decreased the rates slightly in
synthetic natural water. This latter effect is due to a combination of light screening and <sup>.</sup>OH
scavenging by natural organic matter. Nonetheless, the rates remain higher than expected on the
basis of light screening alone indicating that a large fraction of ATZ reacts with <sup>.</sup>OH even in the
presence of <sup>.</sup>OH scavengers. Includes 19 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 220 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 11/02/2003 |
