Fluoride removal system
US5403495A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 14, 1993 |
| Grant date | Apr 4, 1995 |
| Priority date | — |
| Expiry date | Oct 14, 2013 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S210/915
- WIPO fieldEnvironmental technology
- WIPO sectorChemistry
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. Where flocculant is added, a pH of 8 is preferred in both the calcium-addition step and the waste water-addition step.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.