Chlorine dioxide (ClO2) has become increasingly popular for
drinking water treatment, partly because it oxidizes rather
than chlorinates organic matter and therefore does not form
trihalomethanes or other chlorination byproducts. Its reaction
with organic matter, however, produces chlorite ion (ClO2-) and
chlorate ion (ClO3-).
This study, conducted at the Spring Hollow Water Treatment
Facility (SHWTF) in Virginia, was the first full-scale evaluation of
a chlorine gas-solid sodium chlorite ClO2 generation system. In
addition to evaluating the system, the utility wanted to determine
the efficacy of its deep-bed granular activated carbon (GAC) filters
following conventional filtration for removing ClO2-. Finally,
SHWTF wanted to determine the relationship between ClO2-
concentrations leaving the treatment plant and the levels of ClO2
that reformed following final chlorination and led to complaints
from customers of odors resembling kerosene and cat urine.
Utilities facing similar customer complaints may try reducing
the ClO2 dosage, but complaints will not be completely eliminated
until ClO2- concentrations in water leaving the treatment plant
are <0.4 mg/L. GAC contactors afford limited protection against
high ClO2- concentrations entering the distribution system if the
ClO2 dosage remains low, but the effectiveness of GAC declines
rapidly. To keep ClO2 dosages at an effective treatment level
without triggering odor complaints, water providers can either
remove ClO2- at the treatment plant or substitute chloramines for
free chlorine in the distribution system. Includes 36 references, figures.
| Edition : | Vol. 95 - No. 4 |
| File Size : | 1
file
, 350 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 04/01/2003 |
