FLUORIDE REMOVAL FROM POTABLE WATER SUPPLIES

FLUORIDE REMOVAL FROM POTABLE WATER SUPPLIES The objective of this project was to determine whether or not the fluoride level in waters with moderate fluoride content (2 to 10 mg/1) could be reduced to acceptable levels by chemical treatment. The optimum concen-tration for dental health is from 1.1 to 1.8 mg/1. A variety of methods for the removal of fluoride have been reported in the literature. In this study, we compared the methods which appeared to have some possibility of success. Coagulation with alum at pH levels of 6.2 to 6.4 was one of the more effective methods tested. Fluoride was also found to be adsorbed by magnesium hydroxide. This occurs in the softening process with magnesium-containing waters, and could be increased by adding both magnesium salts and lime. The formation of fluorapatite by the reaction of fluoride with phosphoric acid and lime was found to be very effective for the removal of fluoride. Flocculation with iron salt