CA1196738A - Process and apparatus for biological treatment of sludge - Google Patents
Process and apparatus for biological treatment of sludgeInfo
- Publication number
- CA1196738A CA1196738A CA000420145A CA420145A CA1196738A CA 1196738 A CA1196738 A CA 1196738A CA 000420145 A CA000420145 A CA 000420145A CA 420145 A CA420145 A CA 420145A CA 1196738 A CA1196738 A CA 1196738A
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- sludge
- residual sludge
- fermentation
- washing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/28—Anaerobic digestion processes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Abstract
ABSTRACT OF THE DISCLOSURE
Organic sludges are treated biologically by fermentation under acid anaerobic conditions, withdrawing the fermentation liquid and the residual sludge from the fermentation, washing the sludge to remove entrained fermentation liquid, combining the washings with the withdrawn fermentation liquid and subjecting the combined liquid to a digestion. The digested fermentation liquid may be used as the washing liquid.
Apparatus for carrying out this process comprises a fermentation reactor, a residual sludge washing tank, a digestion tank, means for conveying the residual sludge to the washing tank, for conveying the fermentation liquid to the digestion tank, for supplying a washing liquid to the washing tank, for withdrawing the washing liquid from the residual sludge and for conveying the washing liquid to the digestion tank. The apparatus may include means for conveying liquid from the digestion tank to the residual sludge washing tank.
Organic sludges are treated biologically by fermentation under acid anaerobic conditions, withdrawing the fermentation liquid and the residual sludge from the fermentation, washing the sludge to remove entrained fermentation liquid, combining the washings with the withdrawn fermentation liquid and subjecting the combined liquid to a digestion. The digested fermentation liquid may be used as the washing liquid.
Apparatus for carrying out this process comprises a fermentation reactor, a residual sludge washing tank, a digestion tank, means for conveying the residual sludge to the washing tank, for conveying the fermentation liquid to the digestion tank, for supplying a washing liquid to the washing tank, for withdrawing the washing liquid from the residual sludge and for conveying the washing liquid to the digestion tank. The apparatus may include means for conveying liquid from the digestion tank to the residual sludge washing tank.
Description
7~
TITLE OF THE INVEI~TION
PROCESS AND APPARATUS FOR
BIOLOGICAL TREATMENT OF SLUDGE
1 BACKGRO~ND OF THE INVENTION
Field of the Invention This invention relates to the biological treatment of sludge and more particularly to the treatment of sludge containing organic materials by hydrolysis and fermentation.
Description of the Prior Art In processes of the type disclosed in German Patent 26 21 524 hydrolysis and acid fermentation take place in a reactor~ The effluent from this reactor enters a setting tank, from which precipitated residual sludge is removed as one of two components and the fermentation liquid is removed as the other component~ Both components separately undergo a digestion process in a second step~ In the case of ordinary sludge the digestion of the residual sludge provides only about 20% of the total gas formed by the digestion stage. The relatively large apparatus cost for this small benefit makes this process for 73j~
1 converting the residual sludge to a form suitable for disposal uneconomical. The digestion of the residual sludge appears unavoidable because it is loaded with foul-smelling noxious materials.
Accordingly, a need has con-tinued to exist for an economical process of treating residual sludge to prepare it for disposal.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to lo provide an economical method for treating sewage sludge~
A further object is to provide a digestion process for the treatment of residual sludge.
A further object is to provide a method of treating sewage sludge to prepare it for disposal.
Further objects of the invention will become apparent from the description which follows:
The objects of the invention are attained by a process comprising:
20(a) fermenting said sludge anaerobically whereby a fermentation liquid and a residual sludge are produced;
(b) continuously withdrawing said fermentation liquid and subjecting said liquid to a digestion;
(c) continuously withdrawing said residual sludge;
1 (d~ washing said residual sludge with a washing liquid;
(e) adding said washing liquid from step (d) to said fermentation liquid in step (b).
An apparatus for carrying out the process of the invention comprises a fermentation reactor wherein said sludge is fermented, producing a fermentation liquid and a residual sludge;
lo a residual sludge washing tank;
means for withdrawing said residual sludge from said fermentation reactor and conveying it to said residual sludge washing tank;
a digestion tank;
means for withdrawing said fermentation liquid from said fermentation reactor and conveying it to said digestion tank;
means for supplying a washing liquid to said residual sludge washing tank;
means for withdrawing said washing liquid from said residual sludge washing tank and conveying said washing liquid to said digestion tank.
_4_ A more complete appreciation of the invention and many of the attendant advantages thereof will be readily attained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The sole figure is a schematic diagram of an installation suitable for carrying out the process of lo this invention.
DETAILED DESCRIPTION OF THE INVENTION AND
THE PREFERRED EM~ODIMENTS
According to the invention, the residual sludge withdrawn from the fermentation reactor is washed and thereby leached and then discarded. The washing step frees the residual sludge from the fermentation liquid which makes a significant contribution the the bad odor. The wash liquid con~aining the fermentation liquid washings is added to the fermentation liquid withdrawn from the fermentation reactor and subjected to a digestion process along with it.
Fresh water can be used as the wash liquid.
However, it is preferred to use for this purpose the digested fermentation liquid (referred to as the digested liquid in the following~, which, on the one hand, is already at the current process temperature, ~6~
1 and, on the other hand, is sliyhtly alkaline, while the sludge liquid is acid. Thus, in the washing, a neutralization ta~es place.
~ Iydrolysis and acid fermentation take piace in the same tank, and the residual sludge settles out. Only after the residual sludge remains in this tank for a long time is the fermentation essentially complete, i.e., the coatiny of the sludge particles which can be biologically removed by microbes, becomes completely lo removed from the particles, leaving as little residue as possible. The known process, referred to above, is inconsistent with this experience. Thus, it produces a residual sludge, before the sludge digestion, which is only incompletely washable even if it were to be washed. A washed sludge of this type according to the invention could in any case be prepared by addition of chemical-s such as, e.g., calcium carbonate, or the residual sludge could even be aerobically fermented.
Although such a post-treatment would already provide a more economical process, this post-treatment can be entirely or almost entirely omitted for the usual sludges, if the sludge withdrawn from the fermentation reactor is already thoroughly fermented there~
The biological treatment of sludge proceeds very slowly. Accordingly, in order to obtain a sufficient residence time of the sludge in the fermentation 1 reactor, the controlling apparatus need only be actuated on an hourly cycle~ Therefore, it is suffi-cient to withdraw samples of the sludge being processed at rather large intervals and to determine its degree of decomposition by measuring its digestion. According to the results of this analysis, the residence time of the sludge in the fermentation reactor is shortened or lengthened by increasing or decreasing the amount of sludge continuously withdrawn. The labor of handling lo the samples is conveniently shortened by determining only the initial digestion rate of the samples and taking this rate as representative. Thus, the incubation of the samples with bacterial cultures from the digestion reactor for the fermentation liquid makes it possible to keep the time lag short in order to attain precise process control.
An example of an apparatus for carrying out the process conveniently is shown in the drawing. It shows the plan of an installation for complete treatment of sludge containing organic material wherein digested fermentation liquid capable of being discharged into streams is produced and discardable sludge and digestion gas is produced.
Sludge tank 1 contains sludge, e.g., from a common clarification apparatus. The sludge is continuously withdrawn by a pump 2, warmed to about 37C in heater 3~
1 3, adjusted to a p~l of 5 to 6 by addition of chemicals 4, and fed into a fermentation reactor 5, After an average hydraulic residence time in fermentation reactor 5 of about 12 hours, during which the fermentation gases C02 + H2 are evolved, the mobile liquid portion of the acid fermented sludge is with-drawn at the top of the fermentation reactor 5 as fermentation liquid and sent via pump 6 to a decanter 7. In the decanter 7 the turbidity of the mobile lo liquid is reduced. The sludge residue is returned to the fermentation reactor through a pipe 8. Addition of chemicals 9 neutralizes the moderately turbid fermen-tation liquid so that its further treatment takes place under neutral or slightly alkaline conditions. At a temperature of 37C, controlled by heater 10, the digestion liquid is taken to a fermentation reactor 11. The liquid is continuously digested therein with evolution of digestion gas C~4 + CO2, and after an average residence time of 12 hours, leaves tank 11 as digestion liquid. The greater portion of the dis-charged material 12 is post clarified until it is dis-chargeable into a stream or, e~g., sprinkled on fields.
The residual sludge which precipitates directly in fermentation reactor 5 and which is composed for the most part of non-decomposable solids, is taken via pipe 14 to a sludge container 15 in which it is mixed with a '73~
portion of the digestion liquid supplied throuyh pipe 13 and is thoroughl~ mixed with a stirring apparatus 16, and is thus washed. During the washing most of the granular solid particles are freed from the Eermenta-tion liquid which surrounds them. From the tank 15 the mixture goes to a precipitator or thickener apparatus 17. The treated and thickened sludge (discharge stream 18) is buried or used in some other way. The wash liquid 19 which contains fatty acids and odoriferous lo materials goes to the inlet side of pump 6 and is Eurther treated together with the fermentation liquid which is drawn off at the top of tank 5.
Samples are withdrawn from the sludge discharge stream 18 at intervals of several hours and incubated in laboratory 20 with bacterial cultures from the digestion tank 11. The initial fermentation rate is measured. If it is too large, that is if the sludge has been withdrawn too soon from the fermentation reactor 5, the inactive interval of the intermittently activated pump 22 is increased via the control indicated by line 21. Thus, in a cycle of one to several hours the adjustment operation is performed to regulate the variable amount withdrawn in the described control loop.
Because of the relatively short residence time, the reactors 5 and 11 are small relative to the tanks 3~
g 1 used in conventional apparatus. In a conventional single-step apparatus for the treatment of sludye from 100,000 inhabitants it is necessary to have a reactor volume of about 2,500 cubic meters. In this case, an installation according to the process of the prior art mentioned above requires three reactors with a total volume of about 700 m3. On the contrary, in the process of the invention only two reactors are needed having a total volume of about 400 m3. Installation costs are correspondingly decreased, and thus the economics are also improved without any decrease in environmental protection.
Having now fully described the invention, it will be apparent to one of ordlnary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.
TITLE OF THE INVEI~TION
PROCESS AND APPARATUS FOR
BIOLOGICAL TREATMENT OF SLUDGE
1 BACKGRO~ND OF THE INVENTION
Field of the Invention This invention relates to the biological treatment of sludge and more particularly to the treatment of sludge containing organic materials by hydrolysis and fermentation.
Description of the Prior Art In processes of the type disclosed in German Patent 26 21 524 hydrolysis and acid fermentation take place in a reactor~ The effluent from this reactor enters a setting tank, from which precipitated residual sludge is removed as one of two components and the fermentation liquid is removed as the other component~ Both components separately undergo a digestion process in a second step~ In the case of ordinary sludge the digestion of the residual sludge provides only about 20% of the total gas formed by the digestion stage. The relatively large apparatus cost for this small benefit makes this process for 73j~
1 converting the residual sludge to a form suitable for disposal uneconomical. The digestion of the residual sludge appears unavoidable because it is loaded with foul-smelling noxious materials.
Accordingly, a need has con-tinued to exist for an economical process of treating residual sludge to prepare it for disposal.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to lo provide an economical method for treating sewage sludge~
A further object is to provide a digestion process for the treatment of residual sludge.
A further object is to provide a method of treating sewage sludge to prepare it for disposal.
Further objects of the invention will become apparent from the description which follows:
The objects of the invention are attained by a process comprising:
20(a) fermenting said sludge anaerobically whereby a fermentation liquid and a residual sludge are produced;
(b) continuously withdrawing said fermentation liquid and subjecting said liquid to a digestion;
(c) continuously withdrawing said residual sludge;
1 (d~ washing said residual sludge with a washing liquid;
(e) adding said washing liquid from step (d) to said fermentation liquid in step (b).
An apparatus for carrying out the process of the invention comprises a fermentation reactor wherein said sludge is fermented, producing a fermentation liquid and a residual sludge;
lo a residual sludge washing tank;
means for withdrawing said residual sludge from said fermentation reactor and conveying it to said residual sludge washing tank;
a digestion tank;
means for withdrawing said fermentation liquid from said fermentation reactor and conveying it to said digestion tank;
means for supplying a washing liquid to said residual sludge washing tank;
means for withdrawing said washing liquid from said residual sludge washing tank and conveying said washing liquid to said digestion tank.
_4_ A more complete appreciation of the invention and many of the attendant advantages thereof will be readily attained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The sole figure is a schematic diagram of an installation suitable for carrying out the process of lo this invention.
DETAILED DESCRIPTION OF THE INVENTION AND
THE PREFERRED EM~ODIMENTS
According to the invention, the residual sludge withdrawn from the fermentation reactor is washed and thereby leached and then discarded. The washing step frees the residual sludge from the fermentation liquid which makes a significant contribution the the bad odor. The wash liquid con~aining the fermentation liquid washings is added to the fermentation liquid withdrawn from the fermentation reactor and subjected to a digestion process along with it.
Fresh water can be used as the wash liquid.
However, it is preferred to use for this purpose the digested fermentation liquid (referred to as the digested liquid in the following~, which, on the one hand, is already at the current process temperature, ~6~
1 and, on the other hand, is sliyhtly alkaline, while the sludge liquid is acid. Thus, in the washing, a neutralization ta~es place.
~ Iydrolysis and acid fermentation take piace in the same tank, and the residual sludge settles out. Only after the residual sludge remains in this tank for a long time is the fermentation essentially complete, i.e., the coatiny of the sludge particles which can be biologically removed by microbes, becomes completely lo removed from the particles, leaving as little residue as possible. The known process, referred to above, is inconsistent with this experience. Thus, it produces a residual sludge, before the sludge digestion, which is only incompletely washable even if it were to be washed. A washed sludge of this type according to the invention could in any case be prepared by addition of chemical-s such as, e.g., calcium carbonate, or the residual sludge could even be aerobically fermented.
Although such a post-treatment would already provide a more economical process, this post-treatment can be entirely or almost entirely omitted for the usual sludges, if the sludge withdrawn from the fermentation reactor is already thoroughly fermented there~
The biological treatment of sludge proceeds very slowly. Accordingly, in order to obtain a sufficient residence time of the sludge in the fermentation 1 reactor, the controlling apparatus need only be actuated on an hourly cycle~ Therefore, it is suffi-cient to withdraw samples of the sludge being processed at rather large intervals and to determine its degree of decomposition by measuring its digestion. According to the results of this analysis, the residence time of the sludge in the fermentation reactor is shortened or lengthened by increasing or decreasing the amount of sludge continuously withdrawn. The labor of handling lo the samples is conveniently shortened by determining only the initial digestion rate of the samples and taking this rate as representative. Thus, the incubation of the samples with bacterial cultures from the digestion reactor for the fermentation liquid makes it possible to keep the time lag short in order to attain precise process control.
An example of an apparatus for carrying out the process conveniently is shown in the drawing. It shows the plan of an installation for complete treatment of sludge containing organic material wherein digested fermentation liquid capable of being discharged into streams is produced and discardable sludge and digestion gas is produced.
Sludge tank 1 contains sludge, e.g., from a common clarification apparatus. The sludge is continuously withdrawn by a pump 2, warmed to about 37C in heater 3~
1 3, adjusted to a p~l of 5 to 6 by addition of chemicals 4, and fed into a fermentation reactor 5, After an average hydraulic residence time in fermentation reactor 5 of about 12 hours, during which the fermentation gases C02 + H2 are evolved, the mobile liquid portion of the acid fermented sludge is with-drawn at the top of the fermentation reactor 5 as fermentation liquid and sent via pump 6 to a decanter 7. In the decanter 7 the turbidity of the mobile lo liquid is reduced. The sludge residue is returned to the fermentation reactor through a pipe 8. Addition of chemicals 9 neutralizes the moderately turbid fermen-tation liquid so that its further treatment takes place under neutral or slightly alkaline conditions. At a temperature of 37C, controlled by heater 10, the digestion liquid is taken to a fermentation reactor 11. The liquid is continuously digested therein with evolution of digestion gas C~4 + CO2, and after an average residence time of 12 hours, leaves tank 11 as digestion liquid. The greater portion of the dis-charged material 12 is post clarified until it is dis-chargeable into a stream or, e~g., sprinkled on fields.
The residual sludge which precipitates directly in fermentation reactor 5 and which is composed for the most part of non-decomposable solids, is taken via pipe 14 to a sludge container 15 in which it is mixed with a '73~
portion of the digestion liquid supplied throuyh pipe 13 and is thoroughl~ mixed with a stirring apparatus 16, and is thus washed. During the washing most of the granular solid particles are freed from the Eermenta-tion liquid which surrounds them. From the tank 15 the mixture goes to a precipitator or thickener apparatus 17. The treated and thickened sludge (discharge stream 18) is buried or used in some other way. The wash liquid 19 which contains fatty acids and odoriferous lo materials goes to the inlet side of pump 6 and is Eurther treated together with the fermentation liquid which is drawn off at the top of tank 5.
Samples are withdrawn from the sludge discharge stream 18 at intervals of several hours and incubated in laboratory 20 with bacterial cultures from the digestion tank 11. The initial fermentation rate is measured. If it is too large, that is if the sludge has been withdrawn too soon from the fermentation reactor 5, the inactive interval of the intermittently activated pump 22 is increased via the control indicated by line 21. Thus, in a cycle of one to several hours the adjustment operation is performed to regulate the variable amount withdrawn in the described control loop.
Because of the relatively short residence time, the reactors 5 and 11 are small relative to the tanks 3~
g 1 used in conventional apparatus. In a conventional single-step apparatus for the treatment of sludye from 100,000 inhabitants it is necessary to have a reactor volume of about 2,500 cubic meters. In this case, an installation according to the process of the prior art mentioned above requires three reactors with a total volume of about 700 m3. On the contrary, in the process of the invention only two reactors are needed having a total volume of about 400 m3. Installation costs are correspondingly decreased, and thus the economics are also improved without any decrease in environmental protection.
Having now fully described the invention, it will be apparent to one of ordlnary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.
Claims (10)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for biological treatment of organic sludge comprising (a) fermenting said sludge anaerobically whereby a fermentation liquid and a residual sludge are produced;
(b) continuously withdrawing said fermentation liquid and subjecting said liquid to a digestion;
(c) continuously withdrawing said residual sludge (d) washing said residual sludge with a washing liquid;
(e) adding said washing liquid from step (d) to said fermentation liquid in step (b).
(b) continuously withdrawing said fermentation liquid and subjecting said liquid to a digestion;
(c) continuously withdrawing said residual sludge (d) washing said residual sludge with a washing liquid;
(e) adding said washing liquid from step (d) to said fermentation liquid in step (b).
2. The process of Claim 1, characterized in that digested fermentation liquid from step (b) is used as the washing liquid.
3. The process of Claim 1 wherein said residual sludge comprises the product of essentially complete fermentation of said organic sludge.
4. An apparatus for biological treatment of sludge comprising a fermentation reactor wherein said sludge is fermented, producing a fermentation liquid and a residual sludge;
a residual sludge washing tank;
means for withdrawing said residual sludge from means for withdrawing said residual sludge from said fermentation reactor and conveying it to said residual sludge washing tank;
a digestion tank;
means for withdrawing said fermentation liquid from said fermentation reactor and conveying it to said digestion tank;
means for supplying a washing liquid to said residual sludge washing tank;
means for withdrawing said washing liquid from said residual sludge washing tank and conveying said washing liquid to said digestion tank.
a residual sludge washing tank;
means for withdrawing said residual sludge from means for withdrawing said residual sludge from said fermentation reactor and conveying it to said residual sludge washing tank;
a digestion tank;
means for withdrawing said fermentation liquid from said fermentation reactor and conveying it to said digestion tank;
means for supplying a washing liquid to said residual sludge washing tank;
means for withdrawing said washing liquid from said residual sludge washing tank and conveying said washing liquid to said digestion tank.
5. The apparatus of Claim 4 wherein said means for withdrawing said residual sludge from said fermentation reactor and conveying it to said residual sludge washing tank comprises fluid transmissive communication means between said fermentation reactor and said residual sludge washing tank.
6. The apparatus of Claim 5 wherein said fluid transmissive communication means comprises a pump having an inlet and an outlet, said inlet being in fluid transmissive communication with said fermentation reactor and said outlet being in fluid transmissive communication with said residual sludge washing tank.
7. The apparatus of Claim 6 wherein said fluid transmissive communication is effected by a pipe inlet and a pipe connecting said pump outlet with said residual sludge washing tank.
8. The apparatus of Claim 4 wherein said means for supplying a washing liquid to said residual sludge washing tank comprises fluid transmissive communication means between said digestion tank and said residual sludge washing tank.
9. The apparatus of Claim 8 wherein said fluid transmissive communication means comprises a pump having an inlet and an outlet, said inlet being in fluid transmissive communication with said digestion tank and said outlet being in fluid transmissive communication with said residual sludge washing tank.
10. The apparatus of Claim 9 wherein said fluid transmissive communication is effected by a pipe connecting said inlet with said digestion tank and a pipe connecting said outlet with said residual sludge washing tank.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3203445.8 | 1982-02-02 | ||
| DE19823203445 DE3203445A1 (en) | 1982-02-02 | 1982-02-02 | METHOD AND DEVICE FOR BIOLOGICAL SLUDGE TREATMENT |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1196738A true CA1196738A (en) | 1985-11-12 |
Family
ID=6154569
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000420145A Expired CA1196738A (en) | 1982-02-02 | 1983-01-25 | Process and apparatus for biological treatment of sludge |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0085421B1 (en) |
| JP (1) | JPS58174298A (en) |
| AT (1) | ATE13511T1 (en) |
| BR (1) | BR8300506A (en) |
| CA (1) | CA1196738A (en) |
| DE (2) | DE3203445A1 (en) |
| DK (1) | DK156558C (en) |
| ES (1) | ES8403091A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07200B2 (en) * | 1985-07-04 | 1995-01-11 | 株式会社西原環境衛生研究所 | Settling method |
| DE19613373A1 (en) * | 1996-04-03 | 1997-10-09 | Ml Entsorgungs Und Energieanla | Domestic waste treatment process |
| JPH1048517A (en) * | 1996-08-07 | 1998-02-20 | Nikon Corp | Projection optical system |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1999973A (en) * | 1933-08-21 | 1935-04-30 | Albert L Genter | Sewage purification |
| US2528649A (en) * | 1948-04-27 | 1950-11-07 | Albert L Genter | Sewage treatment process |
| NL296691A (en) * | 1962-08-15 | |||
| US3468794A (en) * | 1968-02-23 | 1969-09-23 | Bird Machine Co | Anaerobic digestion process |
| US4067801A (en) * | 1975-05-14 | 1978-01-10 | Hitachi, Ltd. | Process and system for anaerobic treatment of biochemical waste |
| FR2380227A1 (en) * | 1977-02-14 | 1978-09-08 | Inst Francais Du Petrole | Anaerobic fermentation to purify effluent contg. biological pollutants - at half the cost of activated sludge process |
| IE772633L (en) * | 1977-12-29 | 1979-06-29 | Sweeney J J Newell P J | Treating waste products |
-
1982
- 1982-02-02 DE DE19823203445 patent/DE3203445A1/en not_active Withdrawn
-
1983
- 1983-01-25 CA CA000420145A patent/CA1196738A/en not_active Expired
- 1983-01-29 EP EP19830100842 patent/EP0085421B1/en not_active Expired
- 1983-01-29 DE DE8383100842T patent/DE3360215D1/en not_active Expired
- 1983-01-29 AT AT83100842T patent/ATE13511T1/en not_active IP Right Cessation
- 1983-02-01 DK DK40283A patent/DK156558C/en not_active IP Right Cessation
- 1983-02-01 ES ES519452A patent/ES8403091A1/en not_active Expired
- 1983-02-02 BR BR8300506A patent/BR8300506A/en not_active IP Right Cessation
- 1983-02-02 JP JP58014679A patent/JPS58174298A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ES519452A0 (en) | 1984-03-16 |
| ATE13511T1 (en) | 1985-06-15 |
| JPS58174298A (en) | 1983-10-13 |
| ES8403091A1 (en) | 1984-03-16 |
| BR8300506A (en) | 1983-11-08 |
| DK156558B (en) | 1989-09-11 |
| DK40283A (en) | 1983-08-03 |
| DE3360215D1 (en) | 1985-07-04 |
| DE3203445A1 (en) | 1983-08-11 |
| EP0085421A1 (en) | 1983-08-10 |
| DK40283D0 (en) | 1983-02-01 |
| EP0085421B1 (en) | 1985-05-29 |
| DK156558C (en) | 1990-01-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |