AWWA WQTC71618

This powerpoint presentation begins by providing a brief overview of drinking water disinfection and emerging challenges for water treatment. Ultraviolet (UV) irradiation is presented as a promisingalternative, along with photolysis of chlorine, the role of bromide during UV/chlorineprocess, and concerns for halate formation duringUV/chlorine process. Study objectives were to: explore the effects of bromide ion on the photolysisof free chlorine; characterize halate formation during UV/chlorinecoexposure process with the presence of bromide; and, evaluate contamination level of halate in simulated drinking water after UV/chlorine process. Materials and methods included: natural organic matter (NOM) source - Suwannee River NOM (SNOM solution); free halogen source - NaOCl: Cl₂(gas) + 0.01M NaOH. UV system configuration is presented, along with analytical methods. Conclusions indicate that: the presence of bromide did not significantly changethe observed photolysis free chlorine; upon UVirradiation, chlorine is always far more efficient inachieving higher [OH]_SS than bromine;BrO• and BrO₂^- may serve as decisive intermediatesduring bromate formation; the scavenging of BrO₂^-by excessive free chlorine could hinder the bromateformation from •OH-dominated multistep oxidation; and, from a practical point of view, when the bromide ionconcentration in raw water exceeding 1 mg/L, theUV/chlorine process may induce the potential risk ofbromate exposure by breaking its MCL of 10 µg/L;on the other hand, the chlorate formation was minorconsidering the provisional guideline value of 700µg/L. Includes figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2009

Number of Pages:

29

File Size:

1 file , 1.3 MB