Semi-continuous bacterial leaching process
US5454948A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 23, 1993 |
| Grant date | Oct 3, 1995 |
| Priority date | — |
| Expiry date | Aug 23, 2013 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S210/912
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention relates to a semi-continuous process for removing heavy metals, substantially reducing volatile suspended solids and substantially destroying indicator bacteria from municipal sludges, which comprises: a) adding 1 to 3 g of sulphur per liter to a volume of municipal sludge and allowing the sulphur oxidizing thiobacilli initially present in said sludge to proliferate under aerobic conditions in said sludge being agitated until the pH of said sludge is lowered to about 1.5 to 2.5 which causes heavy metals present in said sludge to be substantially solubilized, the concentration of volatile suspended solids is substantially reduced and the concentration of indicator bacteria to be lowered to a non-toxic level; b) removing about 90% of said low pH sludge and recovering the solubilized heavy metals therefrom; c) adding about 90% of municipal sludge to the remaining low pH sludge of step b), thereby resulting in a sludge mixture having a pH of about 7 to 8; and d) repeating steps a) to c); whereby the thiobacilli are adapted when the time required for lowering the pH of the sludge to 1.5 to 2.5 is about the same in two successive operations.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.