TREATMENT METHOD OF FLUORINE-CONTAINING WASTEWATER

摘要

PROBLEM TO BE SOLVED: To eliminate the concn. irregularity of fluorine after the treatment of wastewater and to certainly complete the treatment by setting the concn. of calcium fluoride and that of an iron (III) compd. in a liquid of a sludge forming process and the content of calcium fluoride in the solid of return sludge to predetennined values or more. SOLUTION: A treatment method of fluorine-containing wastewater has a sludge forming process wherein a calcium compd. 3b is added to fluorine- containing wastewater to adjust the pH of wastewater to 7 or more and an iron (III) compd. (ferric chloride) 3b is added thereto to form sludge 7b, a sedimentation and removal process for sedimenting and removing the sludge 7b formed in the sludge forming process to remove a fluorine component from wastewater and a process for returning at least a part of the sludge 7b removed in the sedimentation and removal process to the sludge forming process by a return sludge piping 8. The concn. of calcium fluoride in the wastewater of the sludge forming process is set to 200 mg/l or more and the concn. of the iron (III) compd. therein is set to 100 mg/l or more and the content of calcium fluoride in the solid of return sludge 7b is set to 8 wt.% or more.