ASSESSMENT OF FLUORIDE REMOVAL FROM DRINKING-WATER BY CALCIUM-PHOSPHATE SYSTEMS

Static defluoridation of high fluoride (10 - 12 ppm) wafer by sixteen different combinations of tricalcium phosphate (TCP), bone char (BC), hydroxyapatite (HAP), and related substances has been investigated. De fluoridation of 100 mt of the water by 300 mg of relatively insoluble phosphates is only 60 - 70 percent complete. Defluoridation is 30 perc ent more efficient, however, when a more soluble phosphate is present, which suggests that defluoridation by TCP, BC, and HAP could be simil arly improved. The combination of 300 mg BC plus 23 mg monocalcium pho sphate (MCP) per 100 mt of high fluoride water appears to be the most efficient, reducing the fluoride concentration from 10.4 mg/L to 0.6 m g/L by coprecipitation over 24 hr at pH 6.5 - 8.5.