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US4159945A
Expired / Lapsed
US
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Method for denitrification of treated sewage
Assignee: TETRA RESOURCES Inc A CORP OF
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Filing: 1974-01-31
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Granted: 1979-07-03
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Expires: 1994-01-31
Abstract
Abstract A method for denitrification of aqueous nitrate-containing solutions is disclosed. Specifically the invention provides for denitrification of the effluent from an activated sludge sewage treatment process. Effluent from the settling zone of an activated sludge sewage treatment process containing nitrogen compounds such as nitrates and nitrites, is passed through a deep bed filter, the filter media of which has been innoculated with bacteria that converts the nitrogen compounds to nitrogen gas. The filter, in addition to removing the nitrogen compounds, also removes suspended solids from the settling zone effluent, so that the final effluent from the filter is concurrently clarified and denitrified. By controlling the backwash of the filter, bacteria is retained thereon so as to enable continuous use of the filter for denitrification.
Inventors
- 👤 Elton S. Savage
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:00
CPC Classifications
C; C02; C02F; C02F3/00; C02F3/28; C02F3/2806; C02F3/30; C02F3/302
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
200 words
The process for treating wastewater which contains nitrates in solution and also suspended solids, which comprises flowing the wastewater downwardly through a deep bed filter having a filter media comprising hard, gravel-like material comprised of particles in the size range between 1 mm and 6 mm providing between them voids capable of releasably entrapping bubbles of nitrogen gas and thereby provide additional filtering media to said bed, said deep bed filter being innoculated with bacteria capable of decomposing the dissolved nitrates and releasing nitrogen gas into the bed and thereby generate nitrogen bubbles that are so entrapped in said media and which thereby effectively reduces the nitrate content of said water while solid particles in the wastewater are at the same time being trapped in the filter, intermittently backwashing the filter with clean water to remove entrapped bubbles and the gas contained therein and wash away solid particles arrested in the passage of the wastewater through the filter and also removing some of said bacteria while still maintaining in the filter bed at all times, both during normal filtering operations and during backwashing, adequate denitrifying bacteria to sustain denitrification activity and nitrogen gas generation upon startup after each backwashing operation.
Claim 2
Dependent Claim
200 words
The process for treating wastewater which contains nitrates in solution and also suspended solids, which comprises flowing the wastewater downwardly through a deep bed filter having a filter media comprising hard, gravel-like material comprised of particles in the size range between 1 mm and 6 mm providing between them voids capable of releasably entrapping bubbles of nitrogen gas and thereby provide additional filtering media to said bed, said deep bed filter being innoculated with bacteria capable of decomposing the dissolved nitrates and releasing nitrogen gas into the bed and thereby generate nitrogen bubbles that are so entrapped in said media and which thereby effectively reduces the nitrate content of said water while solid particles in the wastewater are at the same time being trapped in the filter, intermittently backwashing the filter with clean water to remove entrapped bubbles and the gas contained therein and wash away solid particles arrested in the passage of the wastewater through the filter and also removing some of said bacteria while still maintaining in the filter bed at all times, both during normal filtering operations and during backwashing, adequate denitrifying bacteria to sustain denitrification activity and nitrogen gas generation upon startup after each backwashing operation.
Claim 3
Dependent Claim
37 words
The process of claim 1 wherein the backwashing is of sufficiently short duration as to retain denitrifying bacteria in the filter bed in adequate amounts to assure denitrification of the nitrates upon start-up of the filtering cycle.
Claim 4
Dependent Claim
59 words
The process of claim 2 wherein the backwashing water, after backwashing the filter bed, is transferred along with the materials which it has removed from the filter bed to a backwash container from which some of it is returned along with incoming wastewater to the filter bed to thereby restore some of the anaerobic bacteria to the filter bed.
Claim 5
Dependent Claim
63 words
The process defined in claim 3 wherein the wastewater which is supplied to the filter for denitrification and removal of solids is supplied from a preceding step of activated sewage process in which raw sewage is first activated wherein a major portion of the backwash water removed from the filter into the backwash receiving vessel is combined with the raw sewage undergoing activation.
Claim 6
Dependent Claim
71 words
The process of claim 1 wherein at least a major portion of the clean water supplied to the filter bed is introduced into the filter bed at a level intermediate the top and bottom of said bed but closer to the bottom to thereby spare removal of most of the denitrifying bacteria in the lower portion of the bed where the accumulation of solids removed from the downflowing liquid is lowest.
Claim 7
Dependent Claim
35 words
The process defined in claim 5 wherein only a minor portion of the clean backwash water enters the lowermost portion of the filter bed as the major portion enters the bed at said intermediate level.
Claim 8
Dependent Claim
77 words
The process of claim 1 wherein the wastewater which enters the filter is derived from first subjecting raw sewage to an activation sewage treating process and carbon is required in the filter bed for sustaining the denitrification bacteria and enabling them to accomplish the biological decomposition of nitrates which comprises introducing a small regulated flow of raw sewage into the treated wastewater entering the filter to supply carbon available in the raw sewage to the filter bed.
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) | 1982-07-02 | 1983-01-01 | 1983-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-07-02 | 1987-01-01 | 1987-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-07-02 | 1991-01-01 | 1991-07-03 | $7700.00 | Window Closed / Lapsed |