Total Dissolved Solids
Fluoride (F+) is a common constituent of many minerals. Municipal water treatment plants commonly add fluoride to the water for prevention of tooth decay, and maintain a level of 1.5 - 2.5 mg/l. Concentrations above 5 mg/l are detrimental to tooth structure. High concentrations are contained in waste water from the manufacture of glass and steel, 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 and is used in some rat poisons. The MCL established for drinking water by the US EPA is 4 mg/l.
Fluoride can be reduced by anion exchange. Adsorption by calcium phosphate, magnesiumiydroxide or activated carbon will also reduce the fluoride content of drinking water. Reverse osmosis will remove 93 - 95% of the fluoride.