Treatment of phosphate-containing wastewater
US4698163A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 12, 1985 |
| Grant date | Oct 6, 1987 |
| Priority date | — |
| Expiry date | Nov 12, 2005 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S210/915
- WIPO fieldEnvironmental technology
- WIPO sectorChemistry
Abstract
A method is provided for treating contaminated wastewater of pH ranging from about 1.5 to 3 containing phosphate ions and fluoride ions. The method comprises treating the said wastewater with an amount of alkaline agent selected from the group consisting of limestone (CaCO.sub.3) and lime [CaO or Ca(OH).sub.2 ] sufficient to raise and maintain the pH at a level of about 3.5 to 6.5 following uniform mixing thereof in a first stage precipitation step to effect substantial precipitation of the contaminants. The treated wastewater is passed to a first stage settler to effect solid/liquid separation and provide a sludge of the precipitated contaminants which is removed and separated to provide an effluent substantially impoverished in the aforementioned contaminants, following which the contaminant-impoverished effluent is treated in a second stage precipitation step with lime in an amount sufficient to raise and maintain the pH of the effluent at a level of at least about 10.5 to effect further precipitation of said contaminants having improved settling properties, which precipitate is separated and removed to provide a clear effluent characterized in that further precipitation of soli…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.