Patents Examined by Peter A. Hauskoci
  • Patent number: 5403495
    Abstract: A method for removing dissolved fluoride from waste water involving a multiple stage process which includes a first step of contacting a solution comprising calcium fluoride with a calcium ion source to form a first precipitate and a second step of contacting the first precipitate comprising the calcium ion source with the fluoride-containing waste water solution to form a second precipitate. A first portion of the solution that has been treated directly with the waste water and which contains the second precipitate, is preferably recycled, along with calcium fluoride, to the first step for contact with the calcium ion source. A second portion of the solution treated with the waste water may be transported to a thickener or gravity settling step, and/or to a solids-dewatering step wherein standard filtration equipment may be used to produce a filter cake having a controlled particle size distribution.
    Type: Grant
    Filed: October 14, 1993
    Date of Patent: April 4, 1995
    Assignee: Tetra Technologies, Inc.
    Inventors: Roger N. Kust, Surendra K. Mishra, James B. Pfeiffer