US4267057A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Water treatment for selective removal of nitrates
Assignee: Alcoa Separations Technology Inc
•
Filing: 1980-01-18
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Granted: 1981-05-12
•
Expires: 2000-01-18
Abstract
Abstract Water is treated to selectively remove substantially all of the nitrates present. This selective removal of nitrates is accomplished by adjusting the pH of the water to be treated, if necessary, to a pH of less than 8, and then passing the pH-controlled water through activated carbon. In one of the preferred embodiments, the spent activated carbon is substantially completely regenerated by backwashing to permit reuse of the carbon.
Inventors
- 👤 Donald G. Hager
- 👤 Frederick Rubel, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 12:00
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/28; C02F1/283; Y; Y10; Y10S; Y10S210/00; Y10S210/902; Y10S210/903
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
59 words
A method for treating nitrate-containing potable water for selectively removing substantially all of the nitrate present in the water comprising the steps of: (a) controlling the pH of nitrate-containing water such that the pH is less than 8; and (b) passing the pH-controlled water through activated carbon to remove substantially all of the nitrate initially present in the water.
Claim 2
Independent Claim
59 words
A method for treating nitrate-containing potable water for selectively removing substantially all of the nitrate present in the water comprising the steps of: (a) controlling the pH of nitrate-containing water such that the pH is less than 8; and (b) passing the pH-controlled water through activated carbon to remove substantially all of the nitrate initially present in the water.
Claim 3
Independent Claim
88 words
A method for treating nitrate-containing potable water for selectively removing substantially all of the nitrate present in the water comprising the steps of: (a) controlling the pH of nitrate-containing water such that the pH is less than 8; (b) passing the pH-controlled water through activated carbon to remove substantially all of the nitrate initially present in the water; (c) removing the treated water; and (d) periodically backwashing the activated carbon having nitrates present thereon with a dilute alkaline solution to regenerate the activated carbon and permit its reuse.
Claim 4
Independent Claim
88 words
A method for treating nitrate-containing potable water for selectively removing substantially all of the nitrate present in the water comprising the steps of: (a) controlling the pH of nitrate-containing water such that the pH is less than 8; (b) passing the pH-controlled water through activated carbon to remove substantially all of the nitrate initially present in the water; (c) removing the treated water; and (d) periodically backwashing the activated carbon having nitrates present thereon with a dilute alkaline solution to regenerate the activated carbon and permit its reuse.
Claim 5
Dependent Claim
31 words
The method of claim 2 wherein the activated carbon is washed with a dilute inorganic acid solution other than nitric acid before the nitrate-containing water is passed through the activated carbon.
Claim 6
Dependent Claim
27 words
The method of claim 3 wherein the acid solution used to pretreat the activated carbon is a mineral acid having a concentration of 1 to 10 wt.%.
Claim 7
Dependent Claim
22 words
The method of claim 2 in which the dilute alkaline solution used to regenerate the activated carbon is reused in subsequent regenerations.
Claim 8
Dependent Claim
25 words
The method of claim 2 in which the dilute alkaline solution is selected from the group consisting of sodium hydroxide, ammonium hydroxide and potassium hydroxide.
Claim 9
Dependent Claim
19 words
The method of claim 6 in which the dilute alkaline solution has a concentration of 0.25 to 2.0 wt.%.
Claim 10
Dependent Claim
26 words
The method of claim 2 in which the backwashing of the activated carbon is followed by a rinsing of the backwashed carbon with essentially nitrate-free water.
Claim 11
Dependent Claim
24 words
The method of claim 2 in which the pH of the water to be treated is adjusted to a pH between 2.0 and 4.5.
Claim 12
Dependent Claim
16 words
The method of claim 2 wherein the pH of the nitrate-containing water is less than 6.
Claim 13
Dependent Claim
14 words
The method of claim 3 in which the dilute inorganic acid is sulfuric acid.
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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) | 1984-05-11 | 1984-11-10 | 1985-05-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-05-11 | 1988-11-10 | 1989-05-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-05-11 | 1992-11-10 | 1993-05-12 | $7700.00 | Window Closed / Lapsed |