AWWA WQTC58816

Experiments were conducted at the bench scale to determine the effects of pH, totalorganic carbon (TOC), alkalinity, temperature, and H₂O₂ dose on the removal rate of atrazine(ATZ) using ultraviolet light (UV) emitted from a medium-pressure mercury lamp. Simulatednatural water was used to control these parameters independently. Initial experiments showedvery little effect of alkalinity alone, and the effect of TOC was ascribable solely to lightscreening since TOC had no effect on the UV dose-based rate constants (which account for lightscreening by the water matrix). On the other hand, increasing temperature and H₂O₂ dosepositively affected the removal rates while increasing the pH had a small but negative effect bothwith and without H₂O₂ that was most discernable at higher temperatures. These three parameters(H₂O₂, T, and pH) were therefore selected for further study to design a dose-response model ofATZ removal.Other experiments examined whether nitrate (NO₃^-) has a photosensitizing effect on ATZdegradation (via ^.OH production during NO₃^- photolysis). Nitrate concentrations up to 7 mg-N/Lenhanced the ATZ removal rates (s^-1) in deionized water but decreased the rates slightly insynthetic natural water. This latter effect is due to a combination of light screening and ^.OHscavenging by natural organic matter. Nonetheless, the rates remain higher than expected on thebasis of light screening alone indicating that a large fraction of ATZ reacts with ^.OH even in thepresence of ^.OH scavengers. Includes 19 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/02/2003

Number of Pages:

13

File Size:

1 file , 220 KB