US3617540A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Removal of nitrogen and phosphorus from waste waters
Assignee: United States Department of the Interior
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Filing: 1970-05-13
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Granted: 1971-11-02
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Expires: 1990-05-13
Abstract
Abstract Nitrogen and phosphorus are removed from waste waters by a process including the steps of biological nitrification, chemical precipitation of phosphorus and biological dentrification. Buffering capacity of the water is substantially reduced and in some cases nearly eliminated by reaction of acid, produced in the nitrification step, with bicarbonate ion contained in the waste water. A precipitate containing phosphate in high concentration is recovered at low chemical cost.
Inventors
- 👤 John B Stamberg
- 👤 Dolloff F Bishop
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 23:15
CPC Classifications
C; C02; C02F; C02F3/00; C02F3/02; C02F3/12; C02F3/1205; C02F3/1215; C02F1/00; C02F1/52; C02F1/5236; C02F3/30; C02F3/308; Y; Y02; Y02W; Y02W10/00; Y02W10/10; Y10; Y10S; Y10S210/00; Y10S210/902; Y10S210/903
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
22 words
The process of claim 1 wherein the water stream is subjected to biological denitrification after separation of the insolubilized calcium phosphate product.
Claim 2
Dependent Claim
22 words
The process of claim 2 wherein sufficient lime is added to raise the pH of the nitrified effluent to above about 9.5
Claim 3
Dependent Claim
14 words
The process of claim 2 wherein the water stream is a domestic sewage stream.
Claim 4
Dependent Claim
17 words
The process of claim 4 wherein the sewage stream is subjected to carbonaceous oxidation prior to nitrification.
Claim 5
Dependent Claim
29 words
The process of claim 5 wherein the sewage stream contains more than about 5 mg./l. of nitrogen and of phosphorus compounds and less than about 150 mg./l. bicarbonate hardness.
Claim 6
Dependent Claim
31 words
The process of claim 6 wherein sufficient lime is added to raise the pH of the nitrified effluent to above about 10 and wherein the calcium phosphate product comprises calcium hydroxylapatite.
Claim 7
Dependent Claim
15 words
The process of claim 5 wherein the denitrified effluent is further treated by carbon adsorption.
Claim 8
Dependent Claim
11 words
The process of claim 5 wherein the nitrogen compounds comprise ammonia.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |