Many utilities are challenged by problems associated with disinfection byproduct (DBP) control. Alternative
strategies available for reaching goals include: moving the point of chlorine application downstream; splitting
the overall chlorine dose between two points of application; or, utilizing alternative oxidants. Both potassium
permanganate and chlorine dioxide have shown to reduce DBP formation. More specifically, as an effective
oxidant and a successful disinfectant for Cryptosporidium, chlorine dioxide (ClO<sub>2</sub>) has shown especially
promising results. Though ClO<sub>2</sub> doses are limited by the formation of inorganic DBPs, ClO<sub>2</sub> forms fewer
regulated organic DBPs compared to chlorine. The primary objectives of this study were to systematically test:
the impact on DBP formation under alternative strategies and oxidants at the pilot scale level; and, evaluate
the use of ClO<sub>2</sub> under preoxidant and primary disinfectant scenarios by the quantification of organic DBP
formation at the bench scale.
Generally, both alternative strategies in chlorine dosing resulted in a decrease in DBP formation measured at the
24-hour sample point. Moreover, as the chlorine dose was reduced, DBP formation decreased as well. Total trihalomethane (TTHM)
and haloacetic acid (HAA5) formation were reduced by an average of 27 and 16 percent, respectively, when splitting the chlorine
dose and by 11 and 7 percent, respectively when moving the point of chlorination downstream from the rapid
mix to mid-flocculation. When moving the entire dose of chlorine to post sedimentation, the TTHM and HAA5
formation was reduced by about 50 percent. The alternative oxidants were also successful at reducing DBP
formation: 36 and 53 percent for TTHM under preoxidation with KMnO<sub>4</sub> and ClO<sub>2</sub> respectively, and 39 and 55
for HAA5 formation, respectively.
The impact of ClO<sub>2</sub> as a preoxidant or primary disinfectant on TTHM and HAA5 formation was evaluated on
four source waters. Under the primary disinfection condition, TTHM and HAA5 formation at the 24-hour
sample point was reduced by an average of 50 and 34 percent, respectively. Under preoxidation, the TTHM
formation was reduced by an average of 33 percent, while the HAA5 formation actually showed an average
increase of 27 percent. Includes 20 references, tables, figure.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 19 |
| Published : | 11/15/2004 |
