Fluorides are found in the waste discharges from process streams in a
number of industries. Significant amounts of fluoride come from the
following: glass manufacturers, electroplating operations, steel and
aluminum, pesticides and fertilizer, groundwater and the semiconductor
industry. The original fluoride effluent levels can vary over a large
range, and restrictions on final effluent level depend on place of
disposal. When there is any risk of fluoride seeping back to water
supplies, a limitation of about one ppm fluoride is normal. Apart from
treatment of industrial waste streams, the other main application of
fluoride removal is the treatment of municipal water supplies to reduce
the fluoride content to 1 ppm or less.
Fluoride added to city water supplies is a particularly American
dilemma. Most of the modern industrial world has already tried and
rejected fluoridation. Fluoridation of drinking water was originally
proposed as a solution to the toxic waste dilemma of the aluminum
manufacturing industry. Rationale for adding it to tap water has been a
claimed but never really proven protection against dental caries.
Fluoride is a fairly common element that does not occur in the
elemental state in nature because of its high reactivity. It accounts
for about 0.3 g/kg of the earth's crust and exists in the form of
fluorides in a number of minerals, of which fluorspar, cryolite, and
fluorapatite are the most common. The oxidation state of the fluoride
ion is -1.
Most people are aware that there is a controversy surrounding public
fluoridation of drinking water. To explain a bit about fluoride removal,
there are some really good and a few not-too-bad ways to go about it.
The best technologies are reverse osmosis and distillation. Both remove
fluoride handily. Activated alumina cartridges have some advantages and
some problems. Their effective lifespan is fairly short, they are
relatively expensive, and people don't like the word alumina in the name
because it sounds too much like aluminum. We can find no evidence (and
we've looked hard) that activated alumina adds anything objectionable to
the water it treats.
Filters with activated alumina are popular. They are most often used
in conjunction with other filters, usually carbon, since activated
alumina alone does little for water except remove fluoride and arsenic.
It does not improve the taste or remove chemical contaminants like
pesticides. By using an activated alumina cartridge combined with a
carbon cartridge, you get a good, broad-range water filter.
Municipal water treatment plants commonly add fluoride to the water
for various reasons, one of them common belief in prevention of tooth
decay. Water fluoridation is controversial, and Fluoride is considered
to be a poison in all but one European country. Concentrations above 5
mg/l are detrimental to tooth structure. High concentrations are
contained in waste water from the manufacture of glass, steel and
aluminum as well as from foundry operations. Organic fluorine is present
in vegetables, fruits, and nuts. Inorganic fluorine, under the name of
sodium fluoride, is a waste product of aluminum industry. Because of the
controversy in laws, we recommend that you do not drink fluoridated