Fluoride-Removal Process Utilizing Lime and Phosphoric Acid
Original Publication Date: 1985-Sep-01
Included in the Prior Art Database: 2005-Feb-19
By combining in series two wastewater treatment processes, fluoride ion concentration may be effectively reduced from 800 ppm to 2 ppm. The two-step fluoride-removal process involves the use of lime precipitation followed by phosphoric acid addition and precipitation. In the lime precipitation step, the fluoride wastewater is mixed with lime in a saturated solution to produce a precipitate containing calcium fluoride. The precipitate is settled in a clarification step. Sludge is discharged to a sludge blend tank. The clarified effluent from the lime precipitation step is mixed with phosphoric acid with the precipitate formed being settled in a second clarifier discharged to the sludge blend tank. The clarified effluent from this step is the final product.