CA2149796A1 - Method and an installation for dehydrating liquid effluent by composting - Google Patents
Method and an installation for dehydrating liquid effluent by compostingInfo
- Publication number
- CA2149796A1 CA2149796A1 CA 2149796 CA2149796A CA2149796A1 CA 2149796 A1 CA2149796 A1 CA 2149796A1 CA 2149796 CA2149796 CA 2149796 CA 2149796 A CA2149796 A CA 2149796A CA 2149796 A1 CA2149796 A1 CA 2149796A1
- Authority
- CA
- Canada
- Prior art keywords
- substrate
- liquid effluent
- reactor
- composting
- air
- 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.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/16—Treatment of sludge; Devices therefor by de-watering, drying or thickening using drying or composting beds
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
- C05F17/40—Treatment of liquids or slurries
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
- C05F17/70—Controlling the treatment in response to process parameters
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
- C05F17/90—Apparatus therefor
- C05F17/964—Constructional parts, e.g. floors, covers or doors
- C05F17/971—Constructional parts, e.g. floors, covers or doors for feeding or discharging materials to be treated; for feeding or discharging other material
- C05F17/986—Constructional parts, e.g. floors, covers or doors for feeding or discharging materials to be treated; for feeding or discharging other material the other material being liquid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
- F28D21/0001—Recuperative heat exchangers
- F28D21/0014—Recuperative heat exchangers the heat being recuperated from waste air or from vapors
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/141—Feedstock
- Y02P20/145—Feedstock the feedstock being materials of biological origin
-
- 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
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/40—Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse
Abstract
The liquid effluent dehydration method is particularly suitable for effluent having low dry matter content and consists in distributing the liquid effluent in the form of a regulated drip feed throughout a composting substrate comprising a porous and carbon-containing medium disposed inside a reactor. The method also consists in causing a flow of air to circulate through the medium in order to perform a fermentation reaction on the substrate and to remove the gases produced thereby, and in particular water vapor, by entraining them in the flow of air. The liquid effluent feed rate is preferably regulated as a function of the moisture content of the substrate, in particular so as to maintain it in the range 40% to 80%, and the air flow rate is preferably regulated as a function of the temperature of the substrate, in particular so as to keep it in the range 55C to 65C.
Description
-A METHOD AND AN INSTALLATION FOR DEHYDRATING LIQUID
EFFLUENT BY COMPOSTING
FIELD OF THE INVENTION
The present invention relates to treating liquid effluent, in particular effluent having low dry matter content, such as liquid sludge, which comprises a residue made up of matter in suspension and microorganisms collected during the process of purifying waste water.
The invention relates more particularly to a method of dehydrating such liquid effluent by using composting type fermentation. The invention also relates to an installation specially designed for implementing the method.
BACKGROUND OF THE INVENTION
Composting is aerobic decomposition of organic waste by mixed populations of indigenous microorganisms under controlled conditions that gives rise to an organic residue which is partially stabilized. This technique is commonly used in the field of sludge treatment insofar as the resulting organic residue can be used in agriculture.
In conventional m~nner~ sludge composting is performed by mixing said sludge with a porous carbon-cont~;n;~g medium. The carbon is contained in such a manner as to enable the mixture to be brought back into chemical balance during the fermentation reaction, by supplying additional carbon. The medium is porous so as to allow air to circulate, thereby facilitating evacuation of the gases produced during the fermentation reaction.
In a known technique, composting is performed in a reactor which is constituted by a generally closed enclosure in which the mixture of sludge and composting medium is inserted. Under such circumstances, the sludge is previously dehydrated so as to restrict the amount of water contained in the mixture. The sludge may also have been subjected to prior conditioning by means of a flocculating agent, possibly followed by filtering.
Prior to being inserted in the reactor, the mixture is made up in a measuring and mixing device designed to obtain as uniform as possible a distribution of sludge and of medium. The fermentation reaction is allowed to run in the reactor. This reaction is exothermal and it consumes the oxygen contained in the surrounding air to produce carbon dioxide gas and water vapor. A flow of air through the mixture serves firstly to renew the oxygen of the air and secondly to evacuate the gases produced. When the fermentation reaction has come to an end, the mixture may optionally be treated mechanically to separate the portion of the medium which is suitable for recycling from the dehydrated and stabilized sludge.
According to the Applicant, that technique suffers from the main drawback that it is necessary to subject liquid sludge to prior treatment or dehydration in order to prepare the mixture for feeding to the reactor.
Document GB-A-1 498 938 describes a method of that type, but which uses liquid sludge having low dry matter content. In that method, a composting bed is made by placing a plant matter medium in a reactor so as to provide a matrix that is porous and permeable to air and that is sufficiently incompressible to obtain aerobic composting conditions, said plant matter medium being sprayed with the liquid sludge.
The liquor from the liquid sludge thus drains from the composting bed; the drained liquor, which has a dry matter content that is smaller than that of the liquid sludge, is recycled over the composting bed; a fraction of the liquor is absorbed by the composting material and is eliminated by evaporation.
However, according to the Applicant, that method suffers from the major drawback of giving rise to a steep gradient of concentration and moisture in the composting bed, the upper portion of the bed being richer in dry matter and more moist, thereby causing a crust to form on the surface and leading to fermentation that is non-~1~979~
uniform. To mitigate that drawback, it is necessary toturn over the composting bed frequently.
OBJECTS AND SUMMARY OF THE INVENTION
The aim of the Applicant is to propose a method of treating liquid effluent, in particular effluent having low dry matter content, in which the effluent is dehydrated and if liquid sludge is used, in which said sludge is also composted, while avoiding the above-mentioned drawbacks.
In addition to liquid sludge coming from waterworks, or industrial sludge, the method may also be applied to other types of effluent, e.g.: liquid manufacturing residue; industrial w~shing water; animal slurry; ullage;
liquid effluent cont~i~;ng fats or bird droppings.
In a manner known from document GB-A-1 498 938, the method of the invention implements a porous and carbon-containing medium disposed in a reactor, and a flow of air passing through said medium, the method consisting in adding the liquid effluent to a composting substrate including said medium so as to perform a fermentation reaction on said substrate and so as to remove, with the flow of air, the gases produced and in particular water vapor.
In a manner characteristic of the invention, the liquid effluent is added in the form of a regulated drip feed in such a manner as to obtain non-saturating impregnation of the medium.
Thus the medium is not prior mixed with the effluent; the effluent is added progressively to all of the medium by a drip feed so as to obtain impregnation that is not saturating but that is sufficient to allow the fermentation reaction to take place. The flow of air which also serves to remove the fermentation gases also serves to accelerate dehydration. The term "composting substrate" is used herein to mean a porous and carbon-containing medium impregnated with liquid effluent and capable of developing a composting type fermentation -reaction. When the liquid effluent is sludge with matter in suspension and microorganisms, the composting substrate may be constituted solely by a porous and carbon-cont~i ni ng medium. However, when the liquid effluent contains dry matter that is unsuitable for developing this type of fermentation reaction, then the composting substrate includes not only the porous and carbon-containing medium, but also other ingredients, including fermentable agents for enabling a fermentation reaction to develop.
The effluent and/or the flow of air passing through the composting substrate are preferably at a temperature greater than air temperature, so as to enhance dehydration.
Advantageously, the method of the invention further consists in monitoring the moisture content and the temperature of the substrate and in regulating the liquid effluent feed rate as a function of the substrate moisture content and regulating the air flow rate as a function of the substrate temperature.
Preferably, the liquid effluent flow rate is adjusted to maintain the substrate moisture content in the range 40% to 80%.
Preferably, the air flow rate is adjusted to maintain the substrate temperature in the range 55C to 65C.
In order to accelerate dehydration and also composting, it is possible to add fermentable agents either to the liquid effluent or as an additive in the composting substrate. In addition, in order to facilitate fermentation, it is possible to add inorganic matter either to the liquid effluent or as an additive to the composting substrate.
The method of the invention is particularly, but not exclusively, applicable to liquid effluent having low dry matter content. It may be implemented, in particular, with effluent having a high dry matter content, up to 21~9796 80~, providing said effluent is in a liquid state suitable for drip feeding. This applies, for example, to hot effluent having a high fat content, in particular effluent from wool wAshi ng. For waterworks sludge containing about 20% dry matter, after passing through a strip filter or a centrifugal filter, prior treatment is required to give said sludge an adequately liquid consistency; for example the sludge may be liquidized in a high speed mixer, operating at more than 1000 revolutions per minute (rpm).
Another object of the invention is to provide an installation for dehydrating liquid effluent, in particular effluent having low dry matter content, the installation being specially designed for implementing the above method.
The dehydration installation comprises a reactor suitable for containing a composting substrate, and means for establishing a forced circulation of air flow through said substrate. It also includes means for providing a regulated feed of liquid effluent, said means being disposed in the reactor in such a manner as to distribute the liquid effluent throughout the volume of the substrate in the form of a drip feed.
Preferably, the liquid effluent feed means consists in at least one tube pierced by orifices and disposed inside the reactor so as to pass through the composting substrate.
The installation includes a permeable support of the grating type which is disposed in the bottom portion of the reactor; in addition, the air circulation means comprise a first duct opening out into the reactor in a zone lying between said permeable support and the bottom of the reactor, and a second duct opening out into the top portion of the reactor at a level higher than the composting substrate.
Advantageously, the installation includes a heat exchanger in which the flow of air leaving the reactor heats the air entering the reactor. Given that the fermentation reaction is exothermal, the outgoing flow of air is at a higher temperature than the incoming flow of air; and the above-specified disposition using the heat exchanger makes it possible to recover a fraction of the heat produced by the fermentation to heat the air entering the reactor, thereby increasing the efficiency of the resulting dehydration.
Preferably, the installation includes means for measuring the temperature of the composting substrate, means for measuring the moisture content of the composting substrate, means for adjusting the liquid effluent feed rate, means for adjusting the air flow rate, and regulator means suitable for regulating the liquid effluent flow rate as a function of the measured moisture content and for regulating the air flow rate as a function of the measured temperature.
By these various means, it is possible for the user to control the various operating parameters of the installation effectively so as to obtain better efficiency of dehydration and better effectiveness of composting.
Advantageously, for the purpose of removing the composting substrate at the end of the cycle with the help of appropriate equipment, e.g. a mechanical shovel mounted on crawler tracks, the installation of the invention includes two paths on the bottom of the reactor so as to enable the mechanical shovel to enter the reactor and move about inside it. The grating type permeable support is disposed on either side of the two running tracks and together they define the bottom portion of the reactor. The first air flow duct opens out into said bottom portion beneath the permeable support on either side of the running tracks. If the running tracks are structures made of concrete, they may include passages for said duct.
In a particular disposition, it is preferable for the installation to include a plurality of tubes in an array, the tubes in each array extending in a generally vertical direction, and being interconnected by a horizontal coupling line, which horizontal coupling line is fitted with a lifting handle.
BRIEF DESCRIPTION OF THE DRAWING
The present invention will be better understood on reading the following description of embodiments of an installation for dehydrating liquid sludge by composting, and as shown in the accompanying drawing, in which:
Figure 1 is a diagrammatic section view of a first embodiment of the installation; and Figure 2 is a simplified view of a second embodiment of the installation.
MORE DETAILED DESCRIPTION
In the present text, the general term "liquid effluent" is used to cover any kind of waste liquid coming from any source whatsoever, the liquid usually containing a small quantity of residue of any kind whatsoever, at a concentration that may lie in the range a few grams per liter to several tens of grams per liter.
In the context of measures taken to protect the environment, it will be understood that this type of liquid effluent presents problems of disposal if it cannot be used for some other purpose, and in particular for agriculture. It it then necessary to proceed with various kinds of treatment to eliminate the waste contained in the effluent, e.g. by filtering, or to concentrate said effluent in such a manner as to have a larger quantity of residue, in particular by flocculation, evaporation, etc.
In particular when the liquid effluent is of the kind commonly known as liquid sludge, i.e. effluents in which the residue is made up of matter in suspension and microorganisms as obtained during sewage processing, it is important for the concentration to be high enough to prevent said sludge being liquid and to make it suitable for mixing with a porous carbon-containing medium that enables composting to take place.
A particular feature of the method of the present invention is that it dehydrates liquid effluent while composting is actually taking place. The Applicant has observed that independently of the advantage of composting per se, the conditions that apply to the fermentation reaction are favorable for dehydration, i.e.
there is a rise in temperature because fermentation is an exothermal reaction, and the circulation of air for removing the gases produced by the reaction also serves to remove the water vapor.
The Applicant has been able to verify that these conditions enable liquid effluent to be dehydrated, including effluent having low dry matter content, providing the fermentation reaction takes place on a composting substrate that is fed with said effluent in a regulated manner, by means of a drip feed so as to avoid saturating the porous carbon-containing medium, while enabling optimum development of the fermentation reaction.
The installation 1 shown in Figure 1 comprises a reactor 2 which is a chamber in the form of a rectangular parallelepiped whose floor 3 is provided with a permeable support, in particular a grating 4, thereby defining a bottom zone 5.
In the portion of the reactor 2 that is situated above the grating 6 there is an array 5 of tubes 6. The array 5 is fed with liquid effluent by a feed pipe 7.
Each tube 6 is pierced by small holes enabling the liquid effluent to pass through in the form of a drip feed.
The reactor is filled with a composting substrate 8 that completely covers the array 5 of tubes 6. This ensures that the tubes 6 are buried in the mass of substrate 8.
The number of tubes 6, their distribution within the reactor, and the number and size of the holes therethrough, are all parameters that are determined so as to ensure that the liquid effluent coming from the feed pipe 7 diffuses throughout the composting substrate 8 in the form of a drip feed suitable for impregnating said substrate 8 but without saturating it, thereby establishing moisture conditions that are favorable for development of the fermentation reaction.
The top portion 9 of the reactor is left empty, i.e.
it is not filled with composting substrate 8.
Forced air circulation is obtained through the reactor 2 by means of an inlet first duct 10 opening out into the reactor 2 in the bottom portion 5 thereof beneath the grating 4, and by means of an outlet second duct 11 opening out into the top portion 9 of the reactor 2.
In the example shown, the installation 1 includes a heat exchanger 12 enabling a certain amount of the heat produced by the fermentation reaction to be recovered.
The heat exchanger 12 is constituted by a tank 13 through which the outlet duct 11 passes. The tank 13 is itself connected to the inlet duct 10 and is fed with air taken from a feed system (not shown).
The composition of the composting substrate 8 varies depending on the type of liquid effluent that is to be dehydrated. In any event it is constituted by a porous carbon-containing medium which is a composting medium as normally used for composting concentrated sludge. In general, use is made of wood waste, e.g. sawdust, or bark chips, or wood shavings, or chopped straw, or reeds, or wood chippings, ... .
When the liquid sludge contains matter in suspension together with microorganisms, the composting substrate of the invention may be constituted solely by the absve-specified composting medium since the presence of the microorganisms enables the fermentation reaction to 21~9796 develop providing the temperature and moisture conditions are appropriate.
Under such circumstances, the installation operates as follows. The composting substrate 8 is placed inside the reactor so that the array 5 of tubes 6 is completely covered. In this case the substrate is constituted solely by a wood chippings type medium. The liquid sludge is fed in via the feed pipe 7 and the array 5.
The liquid sludge passes through the holes formed in the tubes 6 and thus establishes a drip feed to the substrate 8. A flow of air is fed via the duct 10 to penetrate into the bottom portion 5 of the reactor 2, to pass through the gaps in the grating 4, to pass through the porous substrate 8, to penetrate into the top portion 9 of the reactor 2, and to be exhausted via the outlet duct 11 .
The fermentation reaction, i.e. the decomposition of the organic waste by the microorganisms, takes place in the bulk of the substrate. This reaction causes a certain amount of the wasté to be progressively eliminated by producing a corresponding amount of carbon dioxide gas and water vapor, and it also gives off heat which raises the temperature of the substrate. The flow of air passing through the substrate enables the gases produced, including the water vapor, to be removed by being entrained. In addition, the temperature of the flow of air leaving via the duct 11 is higher than the temperature of the flow of air entering via the duct 10 because the flow of air is heated as it passes through the substrate by the heat given off by the exothermal fermentation reaction. Part of this heat is recovered in the heat exchanger 12 by heat exchange between the feed air flow and the outlet duct 11. This extra heat serves to increase the temperature of the inlet flow of air and thus to increase the efficiency of dehydration insofar as better evaporation occurs when the temperature of the air flowing through the substrate 8 is higher.
The installation 1 preferably includes regulation means enabling its operation to be optimized. These means may be constituted, in particular, by temperature sensors 14 measuring the temperature in the bulk of the composting substrate 8, and moisture sensors 15 measuring the moisture content of the bulk of the substrate 8.
These sensors 14 and 15 are connected to an electronic control circuit which is also connected to valves 16 and 17 mounted respectively on the liquid effluent feed pipe 7 and on the air inlet duct 10, possibly upstream from the heat exchanger 12. The electronic circuit 18 is programmed to use the valve 16 to adjust the flow rate of liquid effluent, i.e. the drip feed rate within the composting substrate 8, as a function of the moisture content within the bulk of said substrate 8 as measured by the sensor 15. This regulation of the liquid effluent flow rate is preferably performed so that the moisture content of the composting substrate 8 lies in the range 40% to 80~.
The electronic circuit 18 is programmed so as to adjust the flow of air entering the reactor 2 and passing through the substrate 8 by means of the valve 17 as a function of the temperature within the bulk of the substrate 8 as measured by the sensor 14. This regulation of the air flow is performed in such a manner that the temperature of the substrate lies in the range 55C to 65C.
In a non-limiting example of dehydrating liquid sludge that includes 30 grams per liter of residue, of which 75% was organic matter, the liquid sludge was fed at a rate of 12 m3 per day, the air flow rate was 2000 m3 per hour, the temperature of the air entering the reactor was 30C, and the temperature of the liquid sludge was 15C. The composting substrate 8 was constituted by wood chippings. In the above example, the reactor 2 contained about 80 m3 of composting substrate 8. The residue that was not decomposed in the form of gas remained on the 214979~
substrate 8. That caused the porosity of the substrate to change progressively and degrade operating conditions for fermentation. It was therefore necessary to renew the substrate 8. In the above example, the substrate needed to be renewed after operating for 111 days; i.e.
after dehydrating more than 1300 m3 of sludge. Naturally the substrate must subsequently be treated like any ordinary composting medium.
When the dry residue of the liquid effluent does not include any organic matter suitable for developing a fermentation reaction, it is necessary for fermentable agents and possibly also inorganic matter to be added or directly included in the porous carbon-containing medium or indeed to be mixed in with the liquid effluent prior to it being inserted into the reactor. Thus, the porous carbon-containing medium together with the fermentable agents added in this way constitutes the composting substrate 8 suitable for developing the fermentation reaction.
For example, if the effluent is a purely chemical effluent, then it is possible to add sugar. Such fermentable agents may also be added to the effluent or to the porous carbon-containing medium in order to dehydrate liquid sludge, thereby improving the efficiency of the method. It is also possible to improve said efficiency by feeding a hot liquid effluent to the reactor 2, preferably at a temperature of not more than 60C, and as mentioned above, by feeding a flow of hot air, likewise up to a maximum of 60C.
In an installation of this type, a problem can arise when the residue contained in the liquid effluent comprises lipids. Since the reaction is exothermal, there is a danger of the lipids being subject to spontaneous combustion in the event of an excessive local rise in temperature. To remedy this difficulty, a branch connection 19 is provided on the liquid effluent feed pipe 7 for the purpose of receiving pure water under pressure, and the branch connection is controlled by an electrically controlled valve 20 which is connected to the electronic circuit 18. Thus, when the temperature sensors 14 detect an abnormal rise in temperature in the substrate 8, the electronic circuit 18 causes the liquid effluent feed valve 16 to be shut off and the pressurized pure water feed valve 20 to be opened.
The installation 21 shown in Figure 2 constitutes a second variant embodiment of the invention that enables the composting substrate 8 to be removed from the reactor 22 by means of appropriate equipment such as a mechanical shovel fitted with two crawler tracks.
The installation 21 is characterized by two running paths 23 and 24, one for each crawler track, and disposed on the floor 25 of the reactor 22.
The grids 26 are disposed on either side of both running paths 23 and 24 to co-operate with the two paths 23 and 24 to define the bottom portion 27 of the reactor 22. Ducting 28 is installed in this bottom portion 27 to remove the flow of air that passes through the composting substrate 8. This ducting 28 includes manifolds 29 disposed parallel to the paths 23 and 24 and on either side thereof, extending along the entire length of the reactor 22. The set of manifolds 29 is connected via ducting 28a to a main manifold 30 outside the reactor 22 and connected to a source of suction.
Since the running paths 23 and 24 are made of concrete, they include gaps through which the ducting 28 interconnecting the manifolds 29 can pass. Each manifold 29 situated in the bottom portion 27 of the reactor is provided with orifices for sucking in the air that exists in this bottom portion.
Liquid effluent is fed by means of a plurality of tubes 31 mounted in an array, each tube 31 of the array extending in a generally vertical direction. The tubes 31 are connected together by means of a coupling line 32 which is horizontal and which occupies the top portion of 21~9796 the composting substrate 8. In the middle of the coupling line 32 there is a lifting handle 33. At one end 32a, the line 32 includes a coupling 34 enabling said line 32 to be coupled to a pipe 35 coming from the outside.
The top portion 36 of the reactor contains an air feed duct 37.
The installation 21 operates identically to the first variant. To remove the composting substrate, the operator opens a door that disengages the front face of the reactor 22, thus giving access to the two running paths 23 and 24. Using an access ramp, the mechanical shovel can progressively clear away the composting substrate 8 and penetrate into the reactor so as to empty it completely. For this purpose, it is also necessary to remove all of the tubes 31 of the array as that becomes necessary. The operator can do this merely by uncoupling each coupling 34 and using the mechanical shovel to take hold of the lifting handle 33 and lift the corresponding array of tubes 31. Since the tubes extend generally vertically through the composting substrate they are easily removed without entraining the substrate.
It will be understood that by having the running paths 23 and 24 it is possible for the mechanical shovel to gain direct access to the composting substrate inside the reactor without it being necessary to remove the gratings 26.
The method and the installation of the present invention are particularly intended for dehydrating liquid effluent having low dry matter content.
Nevertheless, as can clearly be seen from the above description, the essential aspect is not dry matter content but ability of the effluent to diffuse drop by drop throughout the volume of the substrate. Thus, it is also possible to treat liquid effluents having a high dry mater content, even up to 80%, providing said effluents are in a liquid state that is suitable for performing such drop by drop diffusion. This applies in particular to hot effluents containing fats, and in particular water that has been used for washing wool, which may have a suint content of the order of 70~.
When the effluent to be treated is not in the liquid state as is required for implementing the method, it may be possible to subject it to prior treatment for the purpose of imparting the liquid state thereto. For example, sewage sludge containing 20% dry matter after passing through a strip filter or a centrifugal filter, may be subjected to prior treatment consisting in liquidizing in a mixer having a speed of rotation that is high, greater than 1000 rpm. This prior treatment has the effect of breaking up polymers and of imparting the required liquid state to the sludge.
EFFLUENT BY COMPOSTING
FIELD OF THE INVENTION
The present invention relates to treating liquid effluent, in particular effluent having low dry matter content, such as liquid sludge, which comprises a residue made up of matter in suspension and microorganisms collected during the process of purifying waste water.
The invention relates more particularly to a method of dehydrating such liquid effluent by using composting type fermentation. The invention also relates to an installation specially designed for implementing the method.
BACKGROUND OF THE INVENTION
Composting is aerobic decomposition of organic waste by mixed populations of indigenous microorganisms under controlled conditions that gives rise to an organic residue which is partially stabilized. This technique is commonly used in the field of sludge treatment insofar as the resulting organic residue can be used in agriculture.
In conventional m~nner~ sludge composting is performed by mixing said sludge with a porous carbon-cont~;n;~g medium. The carbon is contained in such a manner as to enable the mixture to be brought back into chemical balance during the fermentation reaction, by supplying additional carbon. The medium is porous so as to allow air to circulate, thereby facilitating evacuation of the gases produced during the fermentation reaction.
In a known technique, composting is performed in a reactor which is constituted by a generally closed enclosure in which the mixture of sludge and composting medium is inserted. Under such circumstances, the sludge is previously dehydrated so as to restrict the amount of water contained in the mixture. The sludge may also have been subjected to prior conditioning by means of a flocculating agent, possibly followed by filtering.
Prior to being inserted in the reactor, the mixture is made up in a measuring and mixing device designed to obtain as uniform as possible a distribution of sludge and of medium. The fermentation reaction is allowed to run in the reactor. This reaction is exothermal and it consumes the oxygen contained in the surrounding air to produce carbon dioxide gas and water vapor. A flow of air through the mixture serves firstly to renew the oxygen of the air and secondly to evacuate the gases produced. When the fermentation reaction has come to an end, the mixture may optionally be treated mechanically to separate the portion of the medium which is suitable for recycling from the dehydrated and stabilized sludge.
According to the Applicant, that technique suffers from the main drawback that it is necessary to subject liquid sludge to prior treatment or dehydration in order to prepare the mixture for feeding to the reactor.
Document GB-A-1 498 938 describes a method of that type, but which uses liquid sludge having low dry matter content. In that method, a composting bed is made by placing a plant matter medium in a reactor so as to provide a matrix that is porous and permeable to air and that is sufficiently incompressible to obtain aerobic composting conditions, said plant matter medium being sprayed with the liquid sludge.
The liquor from the liquid sludge thus drains from the composting bed; the drained liquor, which has a dry matter content that is smaller than that of the liquid sludge, is recycled over the composting bed; a fraction of the liquor is absorbed by the composting material and is eliminated by evaporation.
However, according to the Applicant, that method suffers from the major drawback of giving rise to a steep gradient of concentration and moisture in the composting bed, the upper portion of the bed being richer in dry matter and more moist, thereby causing a crust to form on the surface and leading to fermentation that is non-~1~979~
uniform. To mitigate that drawback, it is necessary toturn over the composting bed frequently.
OBJECTS AND SUMMARY OF THE INVENTION
The aim of the Applicant is to propose a method of treating liquid effluent, in particular effluent having low dry matter content, in which the effluent is dehydrated and if liquid sludge is used, in which said sludge is also composted, while avoiding the above-mentioned drawbacks.
In addition to liquid sludge coming from waterworks, or industrial sludge, the method may also be applied to other types of effluent, e.g.: liquid manufacturing residue; industrial w~shing water; animal slurry; ullage;
liquid effluent cont~i~;ng fats or bird droppings.
In a manner known from document GB-A-1 498 938, the method of the invention implements a porous and carbon-containing medium disposed in a reactor, and a flow of air passing through said medium, the method consisting in adding the liquid effluent to a composting substrate including said medium so as to perform a fermentation reaction on said substrate and so as to remove, with the flow of air, the gases produced and in particular water vapor.
In a manner characteristic of the invention, the liquid effluent is added in the form of a regulated drip feed in such a manner as to obtain non-saturating impregnation of the medium.
Thus the medium is not prior mixed with the effluent; the effluent is added progressively to all of the medium by a drip feed so as to obtain impregnation that is not saturating but that is sufficient to allow the fermentation reaction to take place. The flow of air which also serves to remove the fermentation gases also serves to accelerate dehydration. The term "composting substrate" is used herein to mean a porous and carbon-containing medium impregnated with liquid effluent and capable of developing a composting type fermentation -reaction. When the liquid effluent is sludge with matter in suspension and microorganisms, the composting substrate may be constituted solely by a porous and carbon-cont~i ni ng medium. However, when the liquid effluent contains dry matter that is unsuitable for developing this type of fermentation reaction, then the composting substrate includes not only the porous and carbon-containing medium, but also other ingredients, including fermentable agents for enabling a fermentation reaction to develop.
The effluent and/or the flow of air passing through the composting substrate are preferably at a temperature greater than air temperature, so as to enhance dehydration.
Advantageously, the method of the invention further consists in monitoring the moisture content and the temperature of the substrate and in regulating the liquid effluent feed rate as a function of the substrate moisture content and regulating the air flow rate as a function of the substrate temperature.
Preferably, the liquid effluent flow rate is adjusted to maintain the substrate moisture content in the range 40% to 80%.
Preferably, the air flow rate is adjusted to maintain the substrate temperature in the range 55C to 65C.
In order to accelerate dehydration and also composting, it is possible to add fermentable agents either to the liquid effluent or as an additive in the composting substrate. In addition, in order to facilitate fermentation, it is possible to add inorganic matter either to the liquid effluent or as an additive to the composting substrate.
The method of the invention is particularly, but not exclusively, applicable to liquid effluent having low dry matter content. It may be implemented, in particular, with effluent having a high dry matter content, up to 21~9796 80~, providing said effluent is in a liquid state suitable for drip feeding. This applies, for example, to hot effluent having a high fat content, in particular effluent from wool wAshi ng. For waterworks sludge containing about 20% dry matter, after passing through a strip filter or a centrifugal filter, prior treatment is required to give said sludge an adequately liquid consistency; for example the sludge may be liquidized in a high speed mixer, operating at more than 1000 revolutions per minute (rpm).
Another object of the invention is to provide an installation for dehydrating liquid effluent, in particular effluent having low dry matter content, the installation being specially designed for implementing the above method.
The dehydration installation comprises a reactor suitable for containing a composting substrate, and means for establishing a forced circulation of air flow through said substrate. It also includes means for providing a regulated feed of liquid effluent, said means being disposed in the reactor in such a manner as to distribute the liquid effluent throughout the volume of the substrate in the form of a drip feed.
Preferably, the liquid effluent feed means consists in at least one tube pierced by orifices and disposed inside the reactor so as to pass through the composting substrate.
The installation includes a permeable support of the grating type which is disposed in the bottom portion of the reactor; in addition, the air circulation means comprise a first duct opening out into the reactor in a zone lying between said permeable support and the bottom of the reactor, and a second duct opening out into the top portion of the reactor at a level higher than the composting substrate.
Advantageously, the installation includes a heat exchanger in which the flow of air leaving the reactor heats the air entering the reactor. Given that the fermentation reaction is exothermal, the outgoing flow of air is at a higher temperature than the incoming flow of air; and the above-specified disposition using the heat exchanger makes it possible to recover a fraction of the heat produced by the fermentation to heat the air entering the reactor, thereby increasing the efficiency of the resulting dehydration.
Preferably, the installation includes means for measuring the temperature of the composting substrate, means for measuring the moisture content of the composting substrate, means for adjusting the liquid effluent feed rate, means for adjusting the air flow rate, and regulator means suitable for regulating the liquid effluent flow rate as a function of the measured moisture content and for regulating the air flow rate as a function of the measured temperature.
By these various means, it is possible for the user to control the various operating parameters of the installation effectively so as to obtain better efficiency of dehydration and better effectiveness of composting.
Advantageously, for the purpose of removing the composting substrate at the end of the cycle with the help of appropriate equipment, e.g. a mechanical shovel mounted on crawler tracks, the installation of the invention includes two paths on the bottom of the reactor so as to enable the mechanical shovel to enter the reactor and move about inside it. The grating type permeable support is disposed on either side of the two running tracks and together they define the bottom portion of the reactor. The first air flow duct opens out into said bottom portion beneath the permeable support on either side of the running tracks. If the running tracks are structures made of concrete, they may include passages for said duct.
In a particular disposition, it is preferable for the installation to include a plurality of tubes in an array, the tubes in each array extending in a generally vertical direction, and being interconnected by a horizontal coupling line, which horizontal coupling line is fitted with a lifting handle.
BRIEF DESCRIPTION OF THE DRAWING
The present invention will be better understood on reading the following description of embodiments of an installation for dehydrating liquid sludge by composting, and as shown in the accompanying drawing, in which:
Figure 1 is a diagrammatic section view of a first embodiment of the installation; and Figure 2 is a simplified view of a second embodiment of the installation.
MORE DETAILED DESCRIPTION
In the present text, the general term "liquid effluent" is used to cover any kind of waste liquid coming from any source whatsoever, the liquid usually containing a small quantity of residue of any kind whatsoever, at a concentration that may lie in the range a few grams per liter to several tens of grams per liter.
In the context of measures taken to protect the environment, it will be understood that this type of liquid effluent presents problems of disposal if it cannot be used for some other purpose, and in particular for agriculture. It it then necessary to proceed with various kinds of treatment to eliminate the waste contained in the effluent, e.g. by filtering, or to concentrate said effluent in such a manner as to have a larger quantity of residue, in particular by flocculation, evaporation, etc.
In particular when the liquid effluent is of the kind commonly known as liquid sludge, i.e. effluents in which the residue is made up of matter in suspension and microorganisms as obtained during sewage processing, it is important for the concentration to be high enough to prevent said sludge being liquid and to make it suitable for mixing with a porous carbon-containing medium that enables composting to take place.
A particular feature of the method of the present invention is that it dehydrates liquid effluent while composting is actually taking place. The Applicant has observed that independently of the advantage of composting per se, the conditions that apply to the fermentation reaction are favorable for dehydration, i.e.
there is a rise in temperature because fermentation is an exothermal reaction, and the circulation of air for removing the gases produced by the reaction also serves to remove the water vapor.
The Applicant has been able to verify that these conditions enable liquid effluent to be dehydrated, including effluent having low dry matter content, providing the fermentation reaction takes place on a composting substrate that is fed with said effluent in a regulated manner, by means of a drip feed so as to avoid saturating the porous carbon-containing medium, while enabling optimum development of the fermentation reaction.
The installation 1 shown in Figure 1 comprises a reactor 2 which is a chamber in the form of a rectangular parallelepiped whose floor 3 is provided with a permeable support, in particular a grating 4, thereby defining a bottom zone 5.
In the portion of the reactor 2 that is situated above the grating 6 there is an array 5 of tubes 6. The array 5 is fed with liquid effluent by a feed pipe 7.
Each tube 6 is pierced by small holes enabling the liquid effluent to pass through in the form of a drip feed.
The reactor is filled with a composting substrate 8 that completely covers the array 5 of tubes 6. This ensures that the tubes 6 are buried in the mass of substrate 8.
The number of tubes 6, their distribution within the reactor, and the number and size of the holes therethrough, are all parameters that are determined so as to ensure that the liquid effluent coming from the feed pipe 7 diffuses throughout the composting substrate 8 in the form of a drip feed suitable for impregnating said substrate 8 but without saturating it, thereby establishing moisture conditions that are favorable for development of the fermentation reaction.
The top portion 9 of the reactor is left empty, i.e.
it is not filled with composting substrate 8.
Forced air circulation is obtained through the reactor 2 by means of an inlet first duct 10 opening out into the reactor 2 in the bottom portion 5 thereof beneath the grating 4, and by means of an outlet second duct 11 opening out into the top portion 9 of the reactor 2.
In the example shown, the installation 1 includes a heat exchanger 12 enabling a certain amount of the heat produced by the fermentation reaction to be recovered.
The heat exchanger 12 is constituted by a tank 13 through which the outlet duct 11 passes. The tank 13 is itself connected to the inlet duct 10 and is fed with air taken from a feed system (not shown).
The composition of the composting substrate 8 varies depending on the type of liquid effluent that is to be dehydrated. In any event it is constituted by a porous carbon-containing medium which is a composting medium as normally used for composting concentrated sludge. In general, use is made of wood waste, e.g. sawdust, or bark chips, or wood shavings, or chopped straw, or reeds, or wood chippings, ... .
When the liquid sludge contains matter in suspension together with microorganisms, the composting substrate of the invention may be constituted solely by the absve-specified composting medium since the presence of the microorganisms enables the fermentation reaction to 21~9796 develop providing the temperature and moisture conditions are appropriate.
Under such circumstances, the installation operates as follows. The composting substrate 8 is placed inside the reactor so that the array 5 of tubes 6 is completely covered. In this case the substrate is constituted solely by a wood chippings type medium. The liquid sludge is fed in via the feed pipe 7 and the array 5.
The liquid sludge passes through the holes formed in the tubes 6 and thus establishes a drip feed to the substrate 8. A flow of air is fed via the duct 10 to penetrate into the bottom portion 5 of the reactor 2, to pass through the gaps in the grating 4, to pass through the porous substrate 8, to penetrate into the top portion 9 of the reactor 2, and to be exhausted via the outlet duct 11 .
The fermentation reaction, i.e. the decomposition of the organic waste by the microorganisms, takes place in the bulk of the substrate. This reaction causes a certain amount of the wasté to be progressively eliminated by producing a corresponding amount of carbon dioxide gas and water vapor, and it also gives off heat which raises the temperature of the substrate. The flow of air passing through the substrate enables the gases produced, including the water vapor, to be removed by being entrained. In addition, the temperature of the flow of air leaving via the duct 11 is higher than the temperature of the flow of air entering via the duct 10 because the flow of air is heated as it passes through the substrate by the heat given off by the exothermal fermentation reaction. Part of this heat is recovered in the heat exchanger 12 by heat exchange between the feed air flow and the outlet duct 11. This extra heat serves to increase the temperature of the inlet flow of air and thus to increase the efficiency of dehydration insofar as better evaporation occurs when the temperature of the air flowing through the substrate 8 is higher.
The installation 1 preferably includes regulation means enabling its operation to be optimized. These means may be constituted, in particular, by temperature sensors 14 measuring the temperature in the bulk of the composting substrate 8, and moisture sensors 15 measuring the moisture content of the bulk of the substrate 8.
These sensors 14 and 15 are connected to an electronic control circuit which is also connected to valves 16 and 17 mounted respectively on the liquid effluent feed pipe 7 and on the air inlet duct 10, possibly upstream from the heat exchanger 12. The electronic circuit 18 is programmed to use the valve 16 to adjust the flow rate of liquid effluent, i.e. the drip feed rate within the composting substrate 8, as a function of the moisture content within the bulk of said substrate 8 as measured by the sensor 15. This regulation of the liquid effluent flow rate is preferably performed so that the moisture content of the composting substrate 8 lies in the range 40% to 80~.
The electronic circuit 18 is programmed so as to adjust the flow of air entering the reactor 2 and passing through the substrate 8 by means of the valve 17 as a function of the temperature within the bulk of the substrate 8 as measured by the sensor 14. This regulation of the air flow is performed in such a manner that the temperature of the substrate lies in the range 55C to 65C.
In a non-limiting example of dehydrating liquid sludge that includes 30 grams per liter of residue, of which 75% was organic matter, the liquid sludge was fed at a rate of 12 m3 per day, the air flow rate was 2000 m3 per hour, the temperature of the air entering the reactor was 30C, and the temperature of the liquid sludge was 15C. The composting substrate 8 was constituted by wood chippings. In the above example, the reactor 2 contained about 80 m3 of composting substrate 8. The residue that was not decomposed in the form of gas remained on the 214979~
substrate 8. That caused the porosity of the substrate to change progressively and degrade operating conditions for fermentation. It was therefore necessary to renew the substrate 8. In the above example, the substrate needed to be renewed after operating for 111 days; i.e.
after dehydrating more than 1300 m3 of sludge. Naturally the substrate must subsequently be treated like any ordinary composting medium.
When the dry residue of the liquid effluent does not include any organic matter suitable for developing a fermentation reaction, it is necessary for fermentable agents and possibly also inorganic matter to be added or directly included in the porous carbon-containing medium or indeed to be mixed in with the liquid effluent prior to it being inserted into the reactor. Thus, the porous carbon-containing medium together with the fermentable agents added in this way constitutes the composting substrate 8 suitable for developing the fermentation reaction.
For example, if the effluent is a purely chemical effluent, then it is possible to add sugar. Such fermentable agents may also be added to the effluent or to the porous carbon-containing medium in order to dehydrate liquid sludge, thereby improving the efficiency of the method. It is also possible to improve said efficiency by feeding a hot liquid effluent to the reactor 2, preferably at a temperature of not more than 60C, and as mentioned above, by feeding a flow of hot air, likewise up to a maximum of 60C.
In an installation of this type, a problem can arise when the residue contained in the liquid effluent comprises lipids. Since the reaction is exothermal, there is a danger of the lipids being subject to spontaneous combustion in the event of an excessive local rise in temperature. To remedy this difficulty, a branch connection 19 is provided on the liquid effluent feed pipe 7 for the purpose of receiving pure water under pressure, and the branch connection is controlled by an electrically controlled valve 20 which is connected to the electronic circuit 18. Thus, when the temperature sensors 14 detect an abnormal rise in temperature in the substrate 8, the electronic circuit 18 causes the liquid effluent feed valve 16 to be shut off and the pressurized pure water feed valve 20 to be opened.
The installation 21 shown in Figure 2 constitutes a second variant embodiment of the invention that enables the composting substrate 8 to be removed from the reactor 22 by means of appropriate equipment such as a mechanical shovel fitted with two crawler tracks.
The installation 21 is characterized by two running paths 23 and 24, one for each crawler track, and disposed on the floor 25 of the reactor 22.
The grids 26 are disposed on either side of both running paths 23 and 24 to co-operate with the two paths 23 and 24 to define the bottom portion 27 of the reactor 22. Ducting 28 is installed in this bottom portion 27 to remove the flow of air that passes through the composting substrate 8. This ducting 28 includes manifolds 29 disposed parallel to the paths 23 and 24 and on either side thereof, extending along the entire length of the reactor 22. The set of manifolds 29 is connected via ducting 28a to a main manifold 30 outside the reactor 22 and connected to a source of suction.
Since the running paths 23 and 24 are made of concrete, they include gaps through which the ducting 28 interconnecting the manifolds 29 can pass. Each manifold 29 situated in the bottom portion 27 of the reactor is provided with orifices for sucking in the air that exists in this bottom portion.
Liquid effluent is fed by means of a plurality of tubes 31 mounted in an array, each tube 31 of the array extending in a generally vertical direction. The tubes 31 are connected together by means of a coupling line 32 which is horizontal and which occupies the top portion of 21~9796 the composting substrate 8. In the middle of the coupling line 32 there is a lifting handle 33. At one end 32a, the line 32 includes a coupling 34 enabling said line 32 to be coupled to a pipe 35 coming from the outside.
The top portion 36 of the reactor contains an air feed duct 37.
The installation 21 operates identically to the first variant. To remove the composting substrate, the operator opens a door that disengages the front face of the reactor 22, thus giving access to the two running paths 23 and 24. Using an access ramp, the mechanical shovel can progressively clear away the composting substrate 8 and penetrate into the reactor so as to empty it completely. For this purpose, it is also necessary to remove all of the tubes 31 of the array as that becomes necessary. The operator can do this merely by uncoupling each coupling 34 and using the mechanical shovel to take hold of the lifting handle 33 and lift the corresponding array of tubes 31. Since the tubes extend generally vertically through the composting substrate they are easily removed without entraining the substrate.
It will be understood that by having the running paths 23 and 24 it is possible for the mechanical shovel to gain direct access to the composting substrate inside the reactor without it being necessary to remove the gratings 26.
The method and the installation of the present invention are particularly intended for dehydrating liquid effluent having low dry matter content.
Nevertheless, as can clearly be seen from the above description, the essential aspect is not dry matter content but ability of the effluent to diffuse drop by drop throughout the volume of the substrate. Thus, it is also possible to treat liquid effluents having a high dry mater content, even up to 80%, providing said effluents are in a liquid state that is suitable for performing such drop by drop diffusion. This applies in particular to hot effluents containing fats, and in particular water that has been used for washing wool, which may have a suint content of the order of 70~.
When the effluent to be treated is not in the liquid state as is required for implementing the method, it may be possible to subject it to prior treatment for the purpose of imparting the liquid state thereto. For example, sewage sludge containing 20% dry matter after passing through a strip filter or a centrifugal filter, may be subjected to prior treatment consisting in liquidizing in a mixer having a speed of rotation that is high, greater than 1000 rpm. This prior treatment has the effect of breaking up polymers and of imparting the required liquid state to the sludge.
Claims (11)
1/ A method of dehydrating liquid effluent, implementing a porous and carbon-containing medium disposed in a reactor, and a flow of air passing through said medium, the method consisting in adding the liquid effluent to a composting substrate including said medium so as to perform a fermentation reaction on said substrate and so as to remove, with the flow of air, the gases produced and in particular water vapor, wherein the liquid effluent is added in the form of a regulated drip feed in such a manner as to obtain non-saturating impregnation of the medium.
2/ A method according to claim 1, consisting in monitoring the moisture content and the temperature of the substrate and in regulating the liquid effluent feed rate as a function of the substrate moisture content and in regulating the air flow rate as a function of the substrate temperature.
3/ A method according to claim 2, wherein the liquid effluent flow rate is adjusted to maintain the substrate moisture content in the range 40% to 80%.
4/ A method according to claim 2, wherein the air flow rate is adjusted to maintain the substrate temperature in the range 55°C to 65°C.
5/ A method according to one of claims 1 to 4, wherein fermentable agents are added either to the liquid effluent or to the composting substrate.
6/ An installation for dehydrating liquid effluent having low dry matter content, the installation comprising a reactor suitable for containing a composting substrate, and means for establishing forced air circulation through said substrate, the installation including liquid effluent feed means disposed inside the reactor in such a manner as to distribute the liquid effluent throughout the volume of the substrate in the form of a drip feed.
7/ An installation according to claim 6 or 7, including a heat liquid effluent feed means consists in at least one tube pierced by orifices and disposed inside the reactor so as to pass through the composting substrate.
8/ An installation according to claim 6, including a heat exchanger in which the flow of air leaving the reactor heats the air entering it.
9/ An installation according to claim 6, including means for measuring the temperature of the composting substrate, means for measuring the moisture content of the composting substrate, means for adjusting the liquid effluent feed rate, means for adjusting the air flow rate, and regulator means suitable for regulating the liquid effluent flow rate as a function of the measured moisture content, and for regulating the air flow rate as a function of the measured temperature.
10/ An installation according to claim 6, including two running paths disposed on the floor of the reactor, and a grid type permeable support disposed on either side of said running paths, thereby defining a bottom portion of the reactor, wherein the air circulation means comprise first duct opening out into the reactor in said bottom portion beneath the permeable support on either side of the running paths, and second duct opening out into the top portion of the reactor above the top level of the composting substrate.
11/ An installation according to claim 10, including a plurality of tubes in an array, the tubes in each array extending in a generally vertical direction, and being interconnected by a horizontal coupling line, which horizontal coupling line is fitted with a lifting handle.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9406425A FR2720389B1 (en) | 1994-05-20 | 1994-05-20 | Process and installation for dewatering by composting liquid effluents. |
| FR9406425 | 1994-05-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2149796A1 true CA2149796A1 (en) | 1995-11-21 |
Family
ID=9463557
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2149796 Abandoned CA2149796A1 (en) | 1994-05-20 | 1995-05-19 | Method and an installation for dehydrating liquid effluent by composting |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0683144A1 (en) |
| CA (1) | CA2149796A1 (en) |
| FR (1) | FR2720389B1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GR1003486B (en) * | 1997-02-26 | 2000-11-30 | Method of useful exploitation of liquid effluents of a high organic load by co-processing composting-topsoil formation with solid organic waste and agricultural by-products | |
| DE10230671A1 (en) * | 2002-07-04 | 2004-01-22 | Markgraf, Hannelore | Method and device for guiding sludge from a waste water treatment plant |
| ES2258930B1 (en) * | 2005-02-28 | 2007-05-16 | Agrotech Biotecnologia Aplicada, S.A. | PROCEDURE FOR COMPOST PRODUCTION. |
| FR2886287B1 (en) * | 2005-05-25 | 2007-08-24 | Michel Drevet | PROCESS FOR THE TREATMENT OF LIQUID EFFLUENTS BY EVAPORATION AND DEGRADATION OF THE ORGANIC LOAD, INSTALLATION AND CONTAINER THEREFOR |
| CZ303821B6 (en) | 2010-10-26 | 2013-05-15 | Manetech, A.S. | Organic fertilizer and process for preparing thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2252188B2 (en) * | 1972-10-25 | 1975-05-28 | Franz 6450 Hanau Kneer | Process for composting organic waste |
| GB1498938A (en) * | 1973-10-11 | 1978-01-25 | Nat Res Dev | Composting |
| JPS60161385A (en) * | 1984-02-02 | 1985-08-23 | 杉浦 栄市 | Compost manufacture acceleration device |
| DE3811399A1 (en) * | 1987-04-03 | 1988-10-13 | Hermann Hofmann | Process for the aerobic fermentative hydrolysis, in particular composting, of organic substances and apparatus for carrying out this process |
| WO1990009964A1 (en) * | 1989-03-02 | 1990-09-07 | La Trobe University | Biological treatment of sewage sludge or similar waste matter |
-
1994
- 1994-05-20 FR FR9406425A patent/FR2720389B1/en not_active Expired - Fee Related
-
1995
- 1995-05-18 EP EP19950490020 patent/EP0683144A1/en not_active Withdrawn
- 1995-05-19 CA CA 2149796 patent/CA2149796A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| FR2720389B1 (en) | 1996-08-14 |
| EP0683144A1 (en) | 1995-11-22 |
| FR2720389A1 (en) | 1995-12-01 |
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