THE IMPACT OF CHLORINE DIOXIDE AS AN ALTE RNATIVE DRINKING-WATER TREATMENT ON OXIDATION BY-PRODUCTS

The use of chlorine dioxide as a disinfectant in the treatment of drin king water constitutes a good alternative to limit the formation of ch lorinated by-products, However, chlorine dioxide reactions produce chl orites and chlorates which may be a health risk. This paper studies th e impact of several drinking-water treatments on chlorine dioxide dema nd and on chlorite and chlorate formation, The treatments investigated were: direct sand filtration, ozonation, and second stage biological activated carbon (BAG) filtration. The results showed a decrease in ch lorine dioxide demand and chlorite formation following these treatment s, However. only ozonation and second stage biological activated carbo n (BAG) filtration were able to lower chlorate formation. Interestingl y, the decrease in chlorine dioxide demand by BAC filtration was more pronounced when a lower chlorine dioxide dosage was applied, while the chlorine dioxide dosage did not seem to influence chlorite formation. This study shows the analytical difficulties associated with chlorine dioxide demand measurements as opposed to chlorite and chlorate measu rements by ionic chromatography. However, it also shows that chlorite and chlorate measurements could not replace chlorine dioxide demand me asurements. Finally, this study proves the applicability of a second o rder model to describe short-term chlorine dioxide demand.