Ammonia has been shown to minimize bromate formation during ozonation
by blocking two of three potential bromate formation pathways. It can be
hypothesized that (bi)carbonate alkalinity in the presence of ammonia would
further inhibit bromate formation since the pathway that ammonia does not block (the I/D pathway) requires the hydroxyl radical (OH.), and (bi)carbonate alkalinity
is an OH. scavenger. Experiments where (bi)carbonate alkalinity was
increased from 50 mg/L to 357mg/L NaHCO3 in the presence of excess ammonia
resulted in a 40% reduction in bromate formation, providing evidence in support
of this theory.
In addition to bromate minimization, the OH. scavenging ability of
(bi)carbonate alkalinity also results in an increased ozone residual half-life and
the formation of carbonate radicals (CO3-) which react with free bromine (OBr -)
to form OBr. This promotes bromate formation in the D and D/I pathways in the
absence of ammonia. In the presence of a constant ozone residual,
experiments where (bi)carbonate alkalinity was increased from 50 mg/L to
357mg/L NaHCO3 (with no ammonia) resulted in an increasing bromate
formation trend. This demonstrates that the principal effect of (bi)carbonate
alkalinity is the promotion of bromate formation via the carbonate radical. Includes 11 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 310 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 7 |
| Published : | 06/16/2002 |
