US3649531A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dewatering of digested sludge
Assignee: NAT RES DEV
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Filing: 1970-04-15
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Granted: 1972-03-14
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Expires: 1990-04-15
Abstract
Abstract THE DEWATERING TIME OF A SLUDGE OBTAINED BY ANAEROBIC DIGESTION OF A PRIMARY SEWAGE SLUDGE IS REDUCED SUBSTANTIALLY BY SUBJECTING THE DIGESTED SLUDGE TO AERATION WITH AIR OR OTHER SUITABLE OXYGEN CONTAINING GAS. TYPICALLY, AERATION IS CARRIED OUT FOR AT LEAST 4 HOURS, THE SLUDGE IS ALLOWED TO SETTLE, AND THEN DEWATERED WITHIN TWO DAYS. AERATION MAY BE CARRIED OUT BY MEANS OF DIFFUSED AIR OR, PREFERABLY, BY MECHANICAL MEANS USING A SURFACE AERATOR.
Inventors
- 👤 Basil Reginald Brown
- 👤 Leslie Ballentyne Wood
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 04:30
CPC Classifications
C; C02; C02F; C02F11/00; C02F11/12; C10; C10L; C10L1/00; C10L1/10; C10L1/14; C10L1/22; C10L1/222; C10L1/2222; C10L1/224; C10L1/26; C10L1/2633; C10L1/2658
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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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) | 1975-03-14 | 1975-09-13 | 1976-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-14 | 1979-09-13 | 1980-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-14 | 1983-09-13 | 1984-03-14 | $7700.00 | Window Closed / Lapsed |