Patent US3772191A successfully refreshed from Google Patents.
US3772191A
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US
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Method of digesting and further processing fresh sewage sludge or sopropel
Assignee: Individual
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Filing: 1971-04-26
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Granted: 1973-11-13
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Expires: 1991-04-26
Abstract
Abstract The method of treating sewage wherein the sludge is acidified with a mineral acid to a pH value just below 5 and then the pH value is adjusted to the isoelectrical range of the high molecular sludge substances by addition of hydrochloric acid. The floated hydrophobic substances are removed from the surface and the precipitated sludge substances are separated from the supernatent liquid. The precipitated sludge is mixed with calcium hydroxyde or calcium oxyde and dehydrated in a filter presse to a water content of 50 to 30 percent by weight. This process is less expensive than prior art processes and allows a faster sludge dehydration than up to now.
Inventors
- 👤 W Thorn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 23:41
CPC Classifications
C; C02; C02F; C02F11/00; C02F11/12; C02F11/14; C02F11/143; C02F11/145; C02F11/121; C02F11/122
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
38 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 1, wherein the pH value is adjusted to the isoelectric range of most of the high molecular substances of biological origin contained in the sludge.
Claim 2
Dependent Claim
36 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 1, wherein the sludge is acidified by addition of hydrochloric acid preferably of concentrations containing 3 to 35 percent by weight hydrogen chloride.
Claim 3
Dependent Claim
35 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 1, wherein the sludge is acidified by addition of sulphuric acid preferably of concentrations containing 20 to 98 percent by weight H2SO4.
Claim 4
Dependent Claim
26 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 1, whereiN the sludge is acidified by addition of crude concentrated sulphuric acid.
Claim 5
Dependent Claim
37 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 1, wherein the mixture of precipitated sludge and basic chemical is dehydrated down to a water content of 50 to 30 percent by weight.
Claim 6
Dependent Claim
27 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 1, wherein the sludge has an oxygen containing gas bubbled therethrough before being acidified.
Claim 7
Dependent Claim
25 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 1, wherein the sludge is acidifed by addition of fuming hydrochloric acid.
Claim 8
Dependent Claim
29 words
A method of processing pumpable putrid or fresh sewage sludge as in claim 2, wherein final fine adjustment of the pH is effected by means of fuming hydrochloric acid.
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) | 1976-11-12 | 1977-05-14 | 1977-11-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-12 | 1981-05-14 | 1981-11-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-12 | 1985-05-14 | 1985-11-13 | $7700.00 | Window Closed / Lapsed |