Because fluoride is so effective in
reducing dental caries, many US
water suppliers add the chemical
during the treatment process, with
the result that some 62% of the American
population currently receives fluoridated
water. But few utilities may be aware that the
point at which fluoride is added can have a
deleterious effect on the treatment process,
particularly with respect to removal of particles
and natural organic matter.
Generally, fluoride is added after the
source water has passed through a plant's
physicochemical process train and shortly
before the water enters a clearwell or finished
water reservoir. When added this way, fluoride
is likely to have no influence on the
treatment processes occurring upstream.
However, a review of data compiled for the
Information Collection Rule found that
many utilities add fluoride near the beginning
of the treatment process.
Results from bench- and pilot-scale studies
involving conventional water treatment
found that under conditions typical for
treatment plants practicing enhanced coagulation,
application of fluoride to the raw
water significantly reduced removal of total
organic carbon, decreased clarifier performance
and increased filtered turbidity
breakthrough, shortened filter run times, led
to a tenfold increase in finished water aluminum
concentration, and resulted in a loss
of up to 40% of the applied fluoride dose
because of sorption to flocs. Given these
findings, utilities that practice prefluoridation
may need to assess whether fluoride
addition is exerting a negative influence on
treatment performance and finished water
quality. Includes 28 references, figures.
| Edition : | Vol. 94 - No. 2 |
| File Size : | 1
file
, 480 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 02/01/2002 |
