To minimize disinfection byproduct (DBP) formation three optimization options are
available to conventional treatment plants that chlorinate prior to or at the rapid mix and include:
lower the level of chlorine dosed at the rapid mix and re-chlorinate; move the point of
chlorination to after the sedimentation basin; or, switch to a different pre-
disinfectant/oxidant. However, implementing these optimization objectives cannot
compromise the pathogenic barrier achieved by effective filters. The objectives of this
study are to: assess and evaluate the conditions under which optimizing preoxidation is
effective in controlling DBPs; and, determine the conditions under which preoxidation
impacts filter performance. Tests were conducted with a pilot-scale system. Results
indicated that lowering the pre-chlorination dose and re-chlorinating after the
sedimentation basin such that a target distribution system residual (1 mg/L at 24 hours) is
maintained, yielded lower chlorine consumed (up to 50%) and lower total
trihalomethanes (TTHMs) formed after 24 hours (up to 29%). Two aspects of filter
performance were monitored: the ripening period; and, steady-state turbidity. For all dose
scenarios, steady-state turbidity averaged 0.06 ntu. Trends in increasing steady-state
turbidities were observed as the preoxidant dose location for chlorine was moved from
the rapid mix to mid-flocculation to post sedimentation. Chlorine also yielded lower
steady state turbidities compared with chlorine dioxide and potassium permanganate
dosed at the rapid mix.
Includes 11 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 420 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 20 |
| Published : | 06/16/2002 |
