AWWA JAW57844

Chlorine dioxide (ClO2) has become increasingly popular fordrinking water treatment, partly because it oxidizes ratherthan chlorinates organic matter and therefore does not formtrihalomethanes or other chlorination byproducts. Its reactionwith organic matter, however, produces chlorite ion (ClO2-) andchlorate ion (ClO3-).This study, conducted at the Spring Hollow Water TreatmentFacility (SHWTF) in Virginia, was the first full-scale evaluation ofa chlorine gas-solid sodium chlorite ClO2 generation system. Inaddition to evaluating the system, the utility wanted to determinethe efficacy of its deep-bed granular activated carbon (GAC) filtersfollowing conventional filtration for removing ClO2-. Finally,SHWTF wanted to determine the relationship between ClO2-concentrations leaving the treatment plant and the levels of ClO2that reformed following final chlorination and led to complaintsfrom customers of odors resembling kerosene and cat urine.Utilities facing similar customer complaints may try reducingthe ClO2 dosage, but complaints will not be completely eliminateduntil ClO2- concentrations in water leaving the treatment plantare <0.4 mg/L. GAC contactors afford limited protection againsthigh ClO2- concentrations entering the distribution system if theClO2 dosage remains low, but the effectiveness of GAC declinesrapidly. To keep ClO2 dosages at an effective treatment levelwithout triggering odor complaints, water providers can eitherremove ClO2- at the treatment plant or substitute chloramines forfree chlorine in the distribution system. Includes 36 references, figures.

Product Details

Edition:

Vol. 95 - No. 4

Published:

04/01/2003

Number of Pages:

10

File Size:

1 file , 350 KB