Methods for treating fluoride-containing water

Abstract

A method for treating fluoride-containing water comprises: a first reaction step, receiving fluoride-containing wastewater and sludge containing calcium compounds, and reacting the fluoride with the calcium compounds at pH 7 to pH 11; a second reaction step, adding an aluminum-based coagulant to the first reaction solution from the first reaction step and reacting at pH 6 to pH 8; a coagulation step, adding a polymeric coagulant to the second reaction solution from the second reaction step to perform coagulation; a sedimentation step, performing solid-liquid separation on the coagulated treatment liquid from the coagulation step; and a return step, returning a portion of the sludge separated in the sedimentation step to the first reaction step, wherein the method involves adding a calcium compound in at least one of the first reaction step and the return step. In the second reaction step, the aluminum-based coagulant is added at a concentration of 7 mg / L to 30 mg / L (calculated as aluminum).

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