US4038181A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for dewatering sewage sludge
Assignee: Agway Inc
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Filing: 1976-03-23
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Granted: 1977-07-26
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Expires: 1996-03-23
Abstract
Abstract A process for dewatering sewage sludge having a water content on the order of 75% to 95% and previously untreated for the release of such water. The sludge is mixed with a chemical selected from the group consisting of urea and the common ammonium and potassium salts in relative quantities which produce a desired degree of phase separation. The hygroscopic qualities of the chemical operate to remove water from the sludge to form a separate liquid phase of the chemical dissolved in water removed from the sludge, and a solid or semi-solid phase of the sludge solids with any remaining water. The phases may then easily be separated with great simplification of subsequent handling, disposal or further processing of each.
Inventors
- 👤 Norwood K. Talbert
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 04:29
CPC Classifications
C; C02; C02F; C02F11/00; C02F11/12
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
122 words
A process for dewatering previously unprocessed sewage sludge initially containing at least 75% water comprising: a. contacting a quantity of unprocessed sludge with at least as great a quantity, by weight, of a chemical selected from the group consisting of urea and the common salts of ammonium and potassium; b. allowing said sludge and chemical to remain in contact for a time sufficient for substantially all of said chemical to dissolve in water extracted thereby from the sludge to produce separation of said sludge and chemical into a liquid phase consisting of said chemical dissolved in water, and a solid or semi-solid phase of sludge solids with any remaining water; and c. physically separating said phases by decantation of said liquid phase.
Claim 2
Dependent Claim
122 words
A process for dewatering previously unprocessed sewage sludge initially containing at least 75% water comprising: a. contacting a quantity of unprocessed sludge with at least as great a quantity, by weight, of a chemical selected from the group consisting of urea and the common salts of ammonium and potassium; b. allowing said sludge and chemical to remain in contact for a time sufficient for substantially all of said chemical to dissolve in water extracted thereby from the sludge to produce separation of said sludge and chemical into a liquid phase consisting of said chemical dissolved in water, and a solid or semi-solid phase of sludge solids with any remaining water; and c. physically separating said phases by decantation of said liquid phase.
Claim 3
Dependent Claim
19 words
The invention according to claim 1 wherein said chemical is in dry crystalline form when mixed with the sludge.
Claim 4
Dependent Claim
26 words
The invention according to claim 2 wherein said salts are selected from the group consisting of ammonium sulfate, ammonium sulfite, diammonium phosphate, and potassium dihydrogen phosphate.
Claim 5
Dependent Claim
14 words
The invention according to claim 1 wherein said chemical is in concentrated water solution.
Claim 6
Dependent Claim
37 words
The invention according to claim 1 wherein said unprocessed sludge and chemical are mutually contacted by thorough mixing thereof in a vessel, and the mixture is allowed to stand in said vessel until separated into said phases.
Claim 7
Dependent Claim
61 words
The invention according to claim 1 wherein said sludge and chemical are mutually contacted in a continuous, counter-flow process wherein said unprocessed sludge is introduced at one end and caused to flow in a first direction, and said chemical at its highest concentration is introduced at the opposite end and caused to flow in a direction opposite to said first direction.
References Cited (Backward Citations)
US2300693A
Cited
US3794582A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-07-25 | 1981-01-24 | 1981-07-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-25 | 1985-01-24 | 1985-07-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-25 | 1989-01-24 | 1989-07-26 | $7700.00 | Window Closed / Lapsed |