US5062956A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bioremediation of chromium (VI) contaminated aqueous systems by sulfate reducing bacteria
Assignee: Honeywell International Inc
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Filing: 1990-03-20
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Granted: 1991-11-05
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Expires: 2010-03-20
Abstract
Abstract A method of reducing soluble Cr(VI) levels in aqueous wastes from 200 ppm or more to less than 1 ppm, particularly to less than 0.05 ppm, preferably to less than 0.01 ppm, uses fermentative sulfate-reudcing anaerobic bacteria to reduce Cr(VI) to Cr(III) and immobilize the latter as the extememly insoluble hydroxide. The process is readily adapted to operate continuously using a bioreactor containing sludge with sulfate-reducing anaerobic bacteria and operated as a chemostat.
Inventors
- 👤 F. Stephen Lupton
- 👤 Louis J. DeFilippi
- 👤 James R. Goodman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:45
CPC Classifications
C; C22; C22B; C22B3/00; C22B3/18; C02; C02F; C02F3/00; C02F3/28; C02F2101/00; C02F2101/10; C02F2101/20; C02F2101/22; Y; Y02; Y02P; Y02P10/00; Y02P10/20; Y10; Y10S; Y10S210/00; Y10S210/902; Y10S210/911; Y10S210/912; Y10S210/913; Y10S423/00; Y10S423/09; Y10S423/17
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
172 words
A method of reducing levels of Cr(VI) dissolved in a liquid aqueous residue resulting from chromium processing in amounts up to in excess of 200 ppm Cr(VI) said aqueous residue containing up to 5-10 wt. percent of dissolved salts comprising a) adjusting the pH of said aqueous residue to a value between about 6.5 and 9.5 by adding a neutralizing agent and thereby increasing the content of dissolved salts; b) adding to the pH adjusted residue (a) (1) a carbon source sufficient to sustain microbial growth, (2) a sulfate source sufficient to provide at least 10 millimoles sulfate per liter of said residue and (3) nutrients for sulfate-reducing anaerobic bacteria; c) diluting the aqueous residue of (b) to provide no more than 200 ppm of Cr(VI) per liter of diluted residue; d) contacting said diluted residue of (c) in the substantial absence of oxygen with sulfate-reducing anaerobic bacteria for a period of time sufficient to reduce the concentration of Cr(VI) to below about 0.05 ppm as chromium and to precipitate Cr(III) hydroxides.
Claim 2
Independent Claim
172 words
A method of reducing levels of Cr(VI) dissolved in a liquid aqueous residue resulting from chromium processing in amounts up to in excess of 200 ppm Cr(VI) said aqueous residue containing up to 5-10 wt. percent of dissolved salts comprising a) adjusting the pH of said aqueous residue to a value between about 6.5 and 9.5 by adding a neutralizing agent and thereby increasing the content of dissolved salts; b) adding to the pH adjusted residue (a) (1) a carbon source sufficient to sustain microbial growth, (2) a sulfate source sufficient to provide at least 10 millimoles sulfate per liter of said residue and (3) nutrients for sulfate-reducing anaerobic bacteria; c) diluting the aqueous residue of (b) to provide no more than 200 ppm of Cr(VI) per liter of diluted residue; d) contacting said diluted residue of (c) in the substantial absence of oxygen with sulfate-reducing anaerobic bacteria for a period of time sufficient to reduce the concentration of Cr(VI) to below about 0.05 ppm as chromium and to precipitate Cr(III) hydroxides.
Claim 3
Dependent Claim
21 words
The method of claim 1 where the pH is adjusted in (a) to a value between about 7.0 and about 8.5.
Claim 4
Dependent Claim
27 words
The method of claim 1 where the amount of Cr(VI) dissolved in the treated aqueous residue is less than about 0.01 ppm measured as chromium in (d).
Claim 5
Dependent Claim
140 words
A process for the continuous immobilization of Cr(VI) dissolved in resulting from chromium liquid aqueous residues processing resulting from chromium processing in amounts up to about 2000 ppm comprising transferring a portion of the liquid aqueous residue to a reservoir which maintains the pH of said aqueous residue at a value between about 6.5 and about 9.5, adding to the pH adjusted residue (a) a carbon source sufficient to sustain microbial growth, (b) a sulfate source sufficient to provide at least 10 millimols sulfate per liter of said residue, and optionally (c) nutrients for sulfate-reducing anaerobic bacteria, continuously delivering a portion of the pH adjusted liquid aqueous residue to a chemostat containing fermentative sulfate-reducing anaerobic bacteria in a sludge, and continuously removing as effluent an equal portion of treated aqueous residue containing less dissolved Cr(VI) than in the initial reside.
Claim 6
Dependent Claim
140 words
A process for the continuous immobilization of Cr(VI) dissolved in resulting from chromium liquid aqueous residues processing resulting from chromium processing in amounts up to about 2000 ppm comprising transferring a portion of the liquid aqueous residue to a reservoir which maintains the pH of said aqueous residue at a value between about 6.5 and about 9.5, adding to the pH adjusted residue (a) a carbon source sufficient to sustain microbial growth, (b) a sulfate source sufficient to provide at least 10 millimols sulfate per liter of said residue, and optionally (c) nutrients for sulfate-reducing anaerobic bacteria, continuously delivering a portion of the pH adjusted liquid aqueous residue to a chemostat containing fermentative sulfate-reducing anaerobic bacteria in a sludge, and continuously removing as effluent an equal portion of treated aqueous residue containing less dissolved Cr(VI) than in the initial reside.
Claim 7
Dependent Claim
22 words
The process of claim 4 where the pH is adjusted in said reservoir to a value between about 7.0 and about 8.5.
Claim 8
Dependent Claim
20 words
The process of claim 4 where the amount of Cr(VI) dissolved in said effluent is less than about 0.05 ppm.
Claim 9
Dependent Claim
20 words
The process of claim 4 where the amount of Cr(VI) dissolved in said effluent is less than about 0.01 ppm.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-11-04 | 1995-05-06 | 1995-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-11-04 | 1999-05-06 | 1999-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-11-04 | 2003-05-06 | 2003-11-05 | $7700.00 | Window Closed / Lapsed |