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 water.