HK1229750B - Method and device for treating an organic effluent - Google Patents

Description

Method and equipment for treating organic emissions

Technical Field

The present invention relates to a method for treating organic effluents and more particularly to the treatment of emulsions, highly colloidal waters and/or liquid sludges by conditioning, coagulation, flocculation and oxidation by their bursting, dispersion and diffusion within a pressurized gas.

The invention also relates to an apparatus for treating (conditioning, coagulating, flocculating and oxidizing) emulsions, highly colloidal water and/or liquid sludge for carrying out this method.

The invention finds particular, but not exclusive, application in the field of volume reduction of biological or organic sludge with a view to its treatment or subsequent use.

Background Art

Methods for separating suspended solid matter from liquid effluents containing such matter are known.

The current technology for extracting water from sludge essentially consists in compacting, which increases the solid compound content (expressed as a % by weight of the total mixture) by about 5%, centrifugation or filtration, which increases the solid compound content by 18 to 25% in each case, and finally drying (by burning or scattering over a period of several weeks) which increases the solid compound content by 90 to 95%, and this is known to the fact that the weight content of solid compounds of the purified sludge before treatment is generally between 0.1 and 1% of the total weight of the effluent.

All of these processes known from the prior art have disadvantages which are either associated with insufficient drying (compaction, centrifugation, filtration), with long process times (drying) or with high energy consumption (combustion).

Also known (FR 2 175 897) is a method for treating sludge waste in which a sealed circuit comprising a cuvee is fed in which an oxygen-containing gas is recirculated for several tens of minutes by introducing it into the circuit upstream of the cuvee.

Retention of activated sludge in the lagoon for a period of time sufficient to supersaturate the oxygen-containing gas is indicated to enable significant removal of suspended solids.

In addition to being time-consuming, this method also uses rather complex equipment, which is the source of many blockages.

There is also known a decolloidation method which is carried out by causing at least two streams to collide with each other in a small container in which air bubbling is carried out.

This method, although quite effective, is essentially applied to highly mineralized sludges (ie less than 5 to 15% organic matter by weight based on 100% dry matter).

Also known (FR 2 966 818) is a method for separating suspended matter and liquid from sludge, in which a large flow of sludge and air is introduced into a small-volume container.

This method is able to separate water bound to organic colloids.

However, this method cannot remove certain components of polluting organic sludge, such as sludge loaded with ammonia.

The drainage of the sludge obtained by this treatment can be further improved; a gain in dryness of only 1% compared to the prior art results in significant economic benefits in terms of transport and disposal costs.

Thus, for users of sludge treatment plants, the return on investment in terms of operating costs very quickly justifies the effectiveness of small improvements.

Summary of the Invention

The present invention aims to provide a method and an apparatus that meet the practical needs better than previously known methods and apparatuses, and in particular, the invention will enable improved dewatering, especially when it is used in combination with known techniques of centrifugation or pressing/filtration, and this will at the same time enable better decontamination of sludge (especially sludge loaded with ammonia) in a very rapid manner, the use of the method of the invention requiring only seconds or minutes before the results are obtained.

In particular, this method can achieve excellent results with highly organic sludges, ie sludges which are substantially loaded with phospholipids, polysaccharides, bacterial residues, volatile fatty acids etc.

When combined with additional separation means (centrifuge or belt filter) arranged downstream of the apparatus, optimized yields can also be achieved, resulting in improvements in drying of more than 10%, such as 25%.

By using the present invention, existing plants can be easily retrofitted and this is done at low cost due to the low electricity consumption and the rational use of the quantities of supplies used (compressed air, reagents, etc.).

Furthermore, in contrast to prior art equipment such as centrifuges, the method uses simple equipment that operates continuously with few operational limitations.

The invention also makes it possible to obtain a solid residue in the form of a dehydrated porous cake which is odorless or has a humic odor and which can be particularly easily reused and/or spread.

To this end, the invention provides in particular a method for treating effluents, wherein said effluents are fed in a continuous stream at a flow rate q (m ³ /h) into a chamber or container, said chamber or container being kept at a defined mean pressure by injecting air into said chamber at a flow rate Q (Nm ³ /h), in order to obtain an emulsion in said chamber, and a pressure drop being generated before the emulsion is recovered in a filtration or decantation device, characterized in that

The sludge is an organic sludge supplied via the discharge of a first chamber maintained at a first determined pressure (P ₁ ) and/or directly to a chamber or container called a second chamber,

and

generating a defined pressure drop in the emulsion by means of at least one flow restrictor or valve for supplying a third chamber, said third chamber being maintained at a third defined pressure in a region immediately downstream of said flow restrictor and/or valve,

And flocculant is injected into said zone of the third chamber to form an emulsion of air in the thickened flocculent sludge at the end of the treatment, which emulsion is then degassed at atmospheric pressure before discharge.

Advantageously, the discharge supply of the chamber or container is carried out via flow restrictors, the defined pressure drop in the emulsion being generated via the second and/or third flow restrictors.The number of flow restrictors can also be increased further.

One or more pressurization/depressurization sequences are therefore implemented, which surprisingly lead to a state of matter (emulsion) which ultimately enables a greater dryness gain to be achieved.

By applying an alternating and/or iterative pressure/decompression gradient, it is not the porosity that is sought here, but rather the extraction of water.

More particularly, using the pressure parameter for acting on the organic sludge at its colloidal bonds, the supply of energy is brought about by the pressure, in particular at the location of the components generating the pressure drop, by allowing one or more relatively strong local overpressures.

Thus, by applying the first pressure, a strong stress is generated in the sludge. Since the sludge is a colloidal structure composed of organic matter and water, this pressure introduces energy that can destabilize/break electrostatic bonds (Coulomb type) or dipole bonds (van der Waals type). This causes the water to leave the organic part.

The subsequent decompression, in itself, causes the sludge to accelerate and expand/extend toward areas of lower pressure, continuing the colloid destabilization/destruction effects and bond breaking effects.

Finally, again, a sequence of compression followed by decompression… is performed to prolong/amplify/produce the effect as described above.

Through one sequence after another, different material states (emulsions) are produced that can achieve the desired effect.

This can be further improved each time by adding new additional pressurization/depressurization sequences.

Flocculation, in itself and simply put, is a manifestation of phase separation.

The term "mean pressure" is understood to mean the mean pressure for the volume of the chamber.

It is also noted that the injection of air into the exhaust stream, which itself is introduced using a flow restrictor causing a pressure drop, creates a strong suction of air as the stream passes through.

In the main part of the device, the emulsion is sludge (dispersed phase) in air (continuous phase), where the air surrounds the sludge.

The emulsion of sludge in air is thus a result of the pressurization/depressurization action due to the successive flow restrictors as claimed.

It is also recalled that gas flow values are conventionally given in Nm ³ /h (standard cubic meters per hour), the volume (Nm ³ /h) being considered here to be at its values associated with a pressure of 1 bar, a temperature of 20° C. and a humidity of 0%, as naturally accepted and understood by engineers, those skilled in the art in the field of chemical engineering.

In fact, very good dispersion of the sludge in the gas phase bed is observed even in the presence of a slight reduced pressure, it being known that in the region of the flow restrictor the pressure is locally strong and can lead to a reversal of the ratio.

In these areas, the pressure increases and air penetrates better into the sludge, likely thereby enhancing the extraordinary porosity effect observed with the present invention.

Due to these emulsion and/or emulsion inversion phenomena, the air comes into close contact with the sludge, and the flocculation fixes the air/water pairs in a manner that is favorable for deodorization, flottation of the sludge flocs and their dewatering.

Thus, large porosity of sludge flocs with millimeter-sized (1 to 5 mm) bubbles can be observed, whereas in conventional flotation, micrometer-sized bubbles are generated and act as a surfactant medium for the organic matter.

In these known cases, the material rises to the surface at a speed of several meters per hour, causing the bubbles to burst at the surface of the float, optionally causing the flocs to fall to the intermediate area and then to the bottom of the tank, the sludge having a density slightly greater than that of water.

By utilizing the present invention, the flocs themselves have a density much smaller than that of water (the density of sludge is 0.6 to 0.9 g/cm ³ ).

This highly specific characteristic enables the production of sludge at an improved rate with high flotation properties, which makes the phase separation durable.

According to one embodiment, means are provided that enable the impingement/diffusion in the gas fluidized bed. For example, each chamber is equipped with a simple hydraulic system such as walls perpendicular to the flow, a system of Raschig ring springs, and so on.

Advantageously, the effluent is introduced into a chamber (first or second chamber) of small dimensions, for example corresponding to a volume ≤ 0.5% of the effluent volume passing through per hour, i.e. 50 l for 10 m ³ /h of sludge, for example 30 l, or even less than or equal to 5 l. This makes it possible to achieve a strong pressure drop in the sludge flow supplied, for example, by a pump with a water pressure of 10 bar.

This first chamber (or second chamber) is closed, for example, by a reduced outlet forming a venturi, making it possible to keep it at an overpressure of ≧4 bar absolute, such as 5 bar absolute.

The outlet of the first chamber is thus realized by the first and/or second flow restrictor, facilitating the penetration of air into the exhaust which is injected into the second chamber downstream of the flow restrictor, for example at a flow rate of 10 Nm ³ /h.

For example, a second flow restrictor at the top of the third chamber and/or a third flow restrictor at the top of the fourth chamber is provided more or less directly downstream of this first flow restrictor.

According to the embodiment of the invention described more particularly here, and more or less directly downstream (a few centimeters, 1 m or meters) of this second flow restrictor, a flocculant is also injected which enables the capture of micrometer- and millimeter-sized bubbles in contact with the suspended matter.

Then a very advantageous immediate floating phenomenon of the sludge occurs, with a floating speed of 50 m/h or even 100 m/h and more m/h. In comparison, conventional technologies for floating sludge may have a floating speed of 2 to 6 m/h.

This unexpected phenomenon enables the formation of a self-draining mass from colloidal sludge.

In an advantageous embodiment, one and/or another of the following arrangements may further and/or additionally be present:

the first chamber has a volume of less than 3200 cm ³ , even less than 30 1, a first determined pressure of 4-10 bar absolute, a flow rate q of 5 m ³ /h-30 m ³ /h, a second determined average pressure of 1.2 bar-4 bar absolute, an air flow rate Q of 5 Nm ³ /h-200 Nm ³ /h, and a third determined pressure of 1.05 bar-2 bar absolute;

- supplying emulsion to the intermediate chamber between the second chamber and the third chamber;

a second injection of air downstream of the first injection into the intermediate chamber between the second and third chambers at a flow rate Q′, for example 50 Nm ³ /h - 200 Nm ³ /h, or even higher (ie > 200 Nm ³ /h, for example 500 Nm ³ /h or 1000 Nm ³ /h);

- the first, second and/or third flow restrictor is formed by a Venturi tube;

- the second chamber is a tower having an average diameter d and a height H ≥ 10d, for example a tower > 2 m, such as 3 m, such as 5 m;

- The flocculant is a polymer injected in the immediate vicinity (a few centimeters, for example 5 cm-10 cm) of the outlet of the second or third flow restrictor;

- a portion of the flocculated emulsion is recycled in the first chamber, for example 5% to 30% of the volume of the sludge leaving the plant, for example 10% or 20% or 1/ ^10th to 1/ ^5th of the flow rate. This makes it possible to reduce the overall polymer consumption;

- treatment of the sludge is carried out downstream of the tubular chamber by centrifugation, filtration and/or pressing;

- The injected air can be heated.

The present invention also provides an apparatus for carrying out the above-described method.

The invention also relates to an apparatus for the continuous treatment of sludge, comprising means for supplying said sludge in the form of a continuous flow at a flow rate q into a chamber or container maintained at a determined average pressure, means for injecting air into said chamber at a flow rate Q in order to obtain an emulsion in said chamber, a flow restrictor or valve arranged to produce a determined pressure drop in the emulsion, and means for recovering the emulsion thus degassed in a filtering or decanting apparatus, characterised in that said chamber or container is referred to as the second chamber and that the apparatus is arranged for the treatment of organic sludge,

the means for supplying the second chamber are arranged for supplying the second chamber via the first chamber maintained at a first determined pressure and/or directly,

and

The apparatus further comprises at least one flow restrictor or valve arranged to generate a defined pressure drop in the emulsion, and a third chamber maintained at a third defined pressure in a region situated directly downstream of said flow restrictor, and means for injecting a flocculant into said region of the third chamber, and means for degassing said emulsion at atmospheric pressure.

Advantageously, the supply device comprises a first flow restrictor upstream of the second chamber, the determined pressure drop in the emulsion being generated by means of the second and/or third flow restrictor.

In an advantageous embodiment, the degassing device is located at the other end of the third chamber relative to the region located directly downstream of the flow restrictor.

Advantageously, the device also comprises an intermediate chamber between the second and third chambers and means for injecting air into said intermediate chamber downstream of the first injection.

Advantageously still further, the first and second flow restrictors are formed by Venturi tubes.

In a further advantageous embodiment, the second chamber is a column having an average diameter d and a height H≧10d.

As a variant, an agent that increases the collisions between the sludge particles can be added. It can be used, for example, in an amount of 10%, 5%, 1% of the MS content of the sludge.

Such reagents are, for example, sand, calcium carbonate, slaked lime, etc. It is introduced upstream of the tower, for example into a sump (not shown) for mixing with the liquid sludge.

An oxidizing agent may also be introduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reading the following description of embodiments given by way of non-limiting examples. This description makes reference to the accompanying drawings, in which:

FIG1 is a schematic diagram of a principle of an apparatus according to an embodiment of the invention more particularly described herein.

FIG. 2 shows another embodiment of an apparatus according to the present invention.

FIG3 shows another embodiment of the device according to the invention.

DETAILED DESCRIPTION

FIG1 schematically shows a thickening device 1 for sludge 2 which is sucked from a tank or pond 4 by means 3 (pump).

The apparatus 1 comprises a first chamber 5 of small volume, for example in the form of a cylinder or a cube, for example with a volume of 10 1, for containing the liquid sludge, for example at a first defined pressure P1 slightly lower than the outlet pressure _P0 of the supply pump ₃ , due to the pressure drop of the supply line 6 (for example a flexible pipe). The flow rate q of the pump is for example 5 ^m3 /h-50 ^m3 /h, for example 10 ^m3 /h, and the first defined pressure _P1 is 2 bar absolute, _P0 is for example 2.2 bar absolute.

The chamber 5 comprises at its outlet a flow restrictor 7, for example formed by a circular opening or spout 8, for example 2 cm in diameter, in an intermediate wall 9 separating a second chamber 10 having a larger volume, for example 200 l.

A second chamber 10 , for example in the form of a cylinder, is at a second pressure P ₂ (for example 1.8 bar absolute) and is supplied with air 11 , for example at the bottom, at a very high flow rate Q=500 Nm ³ /h and a pressure of a few bars (for example 5 bar), forming in the chamber 12 formed by this chamber an emulsion 13 of sludge droplets 14 which is discharged by means of a second restrictor 15 similar or identical to the restrictor 7 .

The injection of air into the emulsion immediately after the introduction of the sludge into the compartment facilitates the mixing that occurs in the acceleration section after the nozzle (air ejector effect).

The second flow restrictor 15 opens into an intermediate chamber 18 , for example having a larger volume, for example 500 1, formed by a cylindrical body 19 , the interior of which is at a third pressure P ₃ , for example 1.6 bar absolute.

A second air injection 20 at the bottom of this intermediate chamber, for example with a flow rate Q' of 200 Nm ³ /h, wherein for example 50 Nm ³ /h<Q'≤Q, further increases the sludge fragmentation or dilution in the air.

The intermediate chamber 18 for its part and in the embodiment described here feeds via a third flow restrictor or nozzle 21 a third chamber 22, also of cylindrical form, for example with a height of 3 m, at a fourth pressure P ₄ which gradually decreases from 1.2 bar at the chamber inlet at 23 to atmospheric pressure at the top.

The fourth chamber comprises a flocculant 24 (e.g. a known polymer) supplied at a flow rate q', e.g. depending on the type and flow rate of the sludge, which can e.g. be assessed by a person skilled in the art in a manner known per se to obtain good flocculation.

The sludge is then discharged, for example by gravity, via a ventilation pipe 25 into filter bags 26, the purified water 27 is discharged downwards and the thickened sludge itself is recovered, for example by shoveling, to form a thickened mass 29, for example 20 times thicker than the liquid sludge 2 at the inlet (τ of MS before draining in the filter bags multiplied by 20).

FIG2 shows another embodiment of a treatment plant 30 for liquid sludge 31 , wherein the liquid sludge 31 is introduced into an end portion 32 of a container 33 , which is elongated around an axis 34 and has a determined height H, for example 1 m.

The container is maintained at a mean pressure P', for example 2 bar absolute, and is formed by a cylinder with a diameter d (for example 150 mm).

The sludge is supplied, for example, by means of a flow restrictor via a reduced area 35 (e.g. 101) at the end portion 32, which is also fed at the end of the container upstream of the introduction of the sludge by means of an air inlet 36, for example at a pressure P">P' (e.g. 2.5 bar absolute).

The air is supplied at a very high flow rate Q' (eg 100 ^Nm3 /h) and the sludge itself is supplied at a flow rate Q (eg 10 ^m3 /h).

The sludge 31 explodes in the air at overpressure, with a slight reduced pressure ΔP existing between the sludge inlet of the vessel at 35 and the sludge emulsion outlet 37 downstream of the vessel.

At the outlet of the container 33 there is a venturi 38 and/or a regulating valve generating a pressure drop (e.g. 0.4 bar), from which the sludge emulsion is discharged into a tubular chamber 39 comprising a first cylindrical portion 40 of diameter d' (e.g. d'= d' ) at a pressure _P'1 <P', e.g. 1.6 bar here (in the embodiment taken), into which reagents can be injected at 41 downstream of the venturi and close to it (e.g. 10 cm to allow good stirring), and/or air can be injected again (branch 42).

In this embodiment, the tubular chamber further comprises a second cylindrical portion 43 separated from the first portion 40 by a second venturi 44, said second portion having a diameter d", where for example d'=d"=d.

Downstream of the venturi tube 44 and in the vicinity thereof (1 to 10 cm) a flocculant supply 45 is provided using means known per se (metering pump, etc.), as well as an air vent 46 at atmospheric pressure and/or a sludge outlet 47 exposed to the atmosphere, the pressure _P'2 in this second part thus becoming atmospheric pressure very quickly, for example from 1.3 bar at the outlet of the venturi tube to 1 bar = 1 atmosphere at the outlet 47, and after the addition of the flocculant the emulsion becomes an emulsion of air in the sludge flocs, which flow to the end by gravity.

The total length L ₂ ≈ _{l 1} + l ₂ of the chamber is for example 10 m, with l ₁ =3 m and l ₂ =7 m, but other values are possible, the ratio between l ₁ and l ₂ being typically, but not restrictively, l ₁ <l ₂ .

The apparatus 30 also comprises a filter 48 and/or a decanting tank for discharging purified water 49 at the bottom and dewatered sludge 50 at the top.

FIG3 shows a third embodiment of a device 51 according to the invention.

The device 51 comprises a container 52 which is supplied with liquid sludge at the bottom via a branch 53 (thus forming, for example, a flow restrictor) and with compressed air at a high flow rate, for example below this branch 53 (but also above or at the same level) via a second branch 54 .

More particularly, the vessel is formed of a vertical tower 55 comprising a first portion forming a tank 56 for very intense stirring/mixing of air and sludge, having small dimensions, for example a cylinder with a height h ₁ =50 cm and a diameter d ₁ of 30 cm (i.e. a volume of about 35 l), making it possible to obtain a first emulsion 57 of droplets 58 of fragmented sludge.

This emulsion of droplets in a strong upward compressed air flow then enters a cylindrical conduit 59 extending from the tank 56, having a smaller diameter _d2 < _d1 , eg 10 cm, and extending over a length _h2 , eg 1 m (where _L1 = _h1 + _h2 ).

In this air tower, the gas stream strips the gases generated by and/or contained in the sludge (especially ammonia NH3), thereby achieving, in a surprising manner and depending on the operating conditions and the organic sludge being treated, an almost complete removal (< a few ppm) of the undesirable gases trapped in the sludge.

The lengths 1 and ₂ are advantageously dimensioned by a person skilled in the art.

A regulating valve 61 and/or a souppad for discharge into a tubular chamber 62 is provided at the top 60 of the chamber.

The pressure of the emulsion 57 in the initial storage tank 56 changes from P ₁ ″ (for example 3 bar) to a pressure P ₂ ″ (2.890 bar) in the top of the column 59 of the vessel at the level of the valve 61 , slightly less than the pressure P ₁ , with ΔP″=P ₂ ″-P ₁ ″=a few millibars, and then to P ₃ ″=2 bar at the outlet of this valve (due to the pressure drop of the valve).

More specifically, the chamber 62 comprises a first section 63 of length l ₃ (for example 5 m) terminating in a venturi 64 which allows the pressure P ₃ ″′<P ₃ ″ at the end 65 of the first section to become a pressure P ₄ ″ in a second section 66 of the chamber made of a granite slope equipped with a vent 67 , the section 66 having a length l ₄ , for example 1 m, where L ₂ =l ₃ +l ₄ .

The section 66 is connected to a filter 68 for separating suspended matter 69 from a liquid portion 70 which is discharged continuously at 71 in a manner known per se.

According to the invention, the chamber comprises means 72 for supplying a flocculant 73 from a tank 74 prepared by mixing and stirring. A metering pump 75 introduces the flocculant into the sludge emulsion in a zone 76 which leaves the container 52 at or in the immediate vicinity (i.e. a few centimeters) of the outlet of the valve 61 and which is substantially disturbed by the pressure drop generated by the valve 61. _P3 " here changes, for example, from _P2 "≈2 bar to _P3 "=1.4 bar, _P4 " itself being at atmospheric pressure or substantially atmospheric pressure due to the vent 67.

In this embodiment, an additional air inlet 77 is also provided, for example via a branch pipe 78 for injection together with or in parallel with the flocculant.

The emulsion 79 at the outlet of the treatment with flocculants becomes an emulsion of air in thickened flocculent sludge.

The two sections 63 and 66 are, for example, cylinders having the same diameter d ₃ , which is, for example, equal to the average diameter of the container, e.g.

For 10 ^m3 /h of liquid sludge, a minimum air flow of ⁶⁰ Nm3/h and whatever the injection method, the container has a cross section of 200 mm for heights of 5 m, 10 m, 30 m and greater, a very strong stripping effect (stripping of trapped gases) is observed, with air intimately mixed with the sludge.

As the flocculant, it is preferred to use a polymer such as a cationic polymer.

For example, for a sludge containing 7 g/l of MS, 50 g of crude polymer, prepared for example at 5 g/l, are used, ie 10 l of solution are injected per m ³ of sludge. This injection is carried out in the immediate vicinity of the outlet of the column of the vessel.

In a variant, an agent that increases the collisions between the sludge particles can be added. It can be used, for example, in an amount of 10%, 5%, 1% of the MS content of the sludge, as can be seen above.

This reagent may be, for example, sand, calcium carbonate, slaked lime, etc. It is introduced upstream of the tower into a sump (not shown) for mixing with the liquid sludge.

An oxidizing agent may also be introduced.

In some applications, for example when the sludges contain a large amount of organic fatty acids or when these sludges are sludges obtained from a methanator, excellent results are in fact observed.

For example, the ratio is: for ^1m3 of sludge containing 40g/l MS, 1l of H2O2 or 1l of S2O8.

Reagents to aid in the coagulation of additional organic matter may also be provided therein.

For example, for a sludge containing 11 g/l MS and 8% MV (volatile matter, i.e. organic matter/dry matter) (approximately organic matter/dry matter (?)) and for 500 ml of sludge, 1 ml of FeCl3 (10% solution) is introduced before the introduction of the liquid into the tower or before the introduction of the flocculant (after the tower).

For example, a test was conducted on biological sludge using a belt filter with a sludge loading of 26 to 30 g/l MS as raw material, where:

Q'＝50 to 80 Nm ³ /h

P = 1.7 bar vessel/reactor pressure

Q＝3 to 15m ³ /h

At the end of the process, a sludge having a dry, porous appearance is obtained under accelerated drying and at a degree of dryness ranging from 25 to 35%.

It was thus observed that, surprisingly and by simple decanting, the water was able to have its unbound water discharged directly by gravity.

The sludge gradually drains from 100g/l MS after the first hour to 130g/l after 2 hours, 160g/l after 5 hours, and 350g/l after 1 month. (Big bag)

Other processing embodiments according to the method used provide for recovery on a filter drum or filter bag (called "big bag" in English):

Filter tank; Example 2: 130 g/l after 20 h and 180 g/l after 8 days.

Filter tank; Example 3: 100 g/l after 5 h, 130 g/l after 7 days.

Big bag; Example 4: 100 g/l after 24 h, 115 g/l after 7 days and 221 g/l after 1 month.

Big bag; Example 5: 144 g/l after 24 h, 154 g/l after 7 days and 459 g/l after 1 month.

Big bag; Example 4: 120 g/l after 24 h (while it rained overnight) and 402 g/l after 1 month.

It is noted that the sludge treated according to the invention is initially liquid.

Up to 30 g/l, dilution is theoretically not necessary. However, if the sludge is thicker, for example above 40 g/l, dilution can be performed at the inlet of the plant to allow satisfactory sludge pumping, recalling that the sludge is organic, i.e., one with an MO (Organic Matter) ratio relative to an MS (Suspension Matter) ratio of 65% to 85%. The term "organic matter" is understood to mean essentially phospholipids, polysaccharides, proteins, alkali metals, alkaline earth metals and/or metals.

Another operating example is given below, this time with reference to a simplified FIG. 2 (omitting the first part of the chamber).

The container 33 forms a first compartment in the form of a tube of 20 cm diameter and 50 cm length, into which organic sludge (from a purifier of a municipal purification plant) with 6 g/l MS is introduced at a flow rate Q=10 ^m3 /h and compressed air is introduced by means of a pressurizer at 1.9 bar and 50 ^Nm3 /h air.

An opening of 5 ^cm2 closes this compartment over a length of 10 cm.

Directly downstream of this opening, a flocculant, for example in a dosage of 10 g/l, is introduced into the chamber 43 .

Post orifice the pressure gradually decreases to reach atmospheric pressure after a few meters.

For example: the chamber 43 forming the open rear compartment is also a tube with a length of 3 m and a diameter of 20 cm.

At the end of the chamber, all flows are combined and a filter bag (filter 50) with a cut-off threshold of 500 μm immediately gives a clear filtrate with a dryness of 10% (or 100 g/l) and 50 mg of oxygen (O2) per liter (COD) at 49, for example.

The reagent is introduced in liquid form via a metering pump. Traditionally, the thicker the sludge, the more dilute the reagent must be prepared.

The outlet of the device is operated at atmospheric pressure, but in one embodiment of the invention may optionally be adjusted to atmospheric pressure to restore the pressure of the downstream separation device.

The downstream equipment is of conventional type. It is observed that their efficiency in dehydration is at least 3% higher, for example, for a centrifuge which gives a result of 23% dryness, i.e. 230 g/l MS, this equipment placed upstream makes it possible to obtain at the end a minimum dryness of 26%, i.e. 260 g/l MS.

The devices available downstream are:

Open or closed filter bags (100, 300, 500 μm or larger)

Flotation device

Mechanical thickener

Screw press

Belt filter

Centrifuge

Filter press

At the outlet, the sludge can of course be spread on the soil without composting or after composting, alone or together with green waste or other waste.

They can also be dried using solar energy or simple drying beds.

It was noted that, surprisingly, the sludge obtained was "odorless" and did not ferment over time (anaerobic fermentation).

In fact, due to the presence of air bubbles, a great dilution with air enables a high dewatering capacity of the sludge.

Tables I, II, III present the results obtained using the apparatus 1 according to the invention, combined downstream with the indicated devices, with different sludge flow rates.

Table I: Equipment + Belt Filter

Table II: Equipment 1 + Big Bag

It has been observed that the preferred sludge concentrations obtained using the present invention, for example between 70 and 130 g/l of MS, very advantageously maximize the dewatering function by means such as centrifuges or filter presses, making it possible to significantly increase their yields. This is because, since the unbound water has already been extracted by the above-mentioned method, this makes it possible to almost systematically increase the MS content of the sludge at the outlet by at least 100 g/l.

It is clear, and also clear from the above, that the invention is not limited to the more particularly described embodiments. On the contrary, it encompasses all its alternative forms and in particular forms in which the number of chamber parts and/or sections is different, for example greater than three, or in which the container is of horizontal form with only one section.

Claims (15)

1. A method for treating organic sludge, wherein the sludge is supplied in a continuous flow at a flow rate q ( ^m³ /h) to a second chamber ( ₁₀ , 33, 55) directly or via a first chamber (5) maintained at a first predetermined pressure (P₁), the second chamber (10, 33, 55) being maintained at a second predetermined average pressure ( _P₂ , ^P ', _P₆₁ , _P₆₂ ) by injecting air (11) into the second chamber (10, 33, 55) at a flow rate Q (Nm³/h). Under the condition that a first emulsion is obtained in the second chamber (10, 33, 55), the first emulsion is formed in a sludge dispersion phase in a continuous phase of air encapsulating sludge, and a defined pressure drop is generated in the first emulsion by passing it through a third chamber (22, 43, 62) via one or two flow restrictors (15, 21, 38, 44) or via a supply valve, the third chamber (22, 43, 62) being maintained at a third defined pressure ( _P4 , _P'2 , P" ₃ ) in a region located directly downstream of the one or more flow restrictors or the valve. Flocculants (24, 45, 78) are injected into the area of the third chamber to form a second emulsion of air in the thickened flocculent sludge at the end of the treatment. The second emulsion was then degassed at atmospheric pressure (46, 67) before discharge. The second emulsion is recovered in a filtration or decanting apparatus (26, 48, 68). And then filter or decan it. 2. The method according to claim 1, characterized in that sludge is supplied to the second chamber (10, 33, 55) through a flow restrictor called the first flow restrictor (7), and a certain pressure drop in the emulsion is generated by the second flow restrictor (15, 38) and the third flow restrictor (21, 44) or by a valve (61). 3. The method according to any one of the preceding claims, characterized in that the first chamber (5) has a volume of less than 3200 ^cm³ , a first determined pressure ( _P1 ) of 4-10 bar absolute, a flow rate q of 5 ^m³ /h-30 ^m³ /h, a second determined average pressure ( _P2 ; P'; _P1 ”; P” ₂ ) of 1.2 bar-4 bar absolute, an air flow rate Q of 5 ^Nm³ /h-200 ^Nm³ /h, and a third determined pressure ( _P4 ; _P'2 ; _P3 ”) of 1.05 bar-2 bar absolute. 4. The method according to claim 1 or 2, characterized in that the emulsion is supplied to the intermediate chamber (18, 40) between the second chamber (10, 33) and the third chamber (22, 43). 5. The method according to claim 4, characterized in that, downstream of the first injection, air is injected a second time into an intermediate chamber (18, 40) located between the second chamber (10, 33, 55) and the third chamber (22, 43, 62) at a flow rate Q'. 6. The method according to claim 1 or 2, wherein the first, second and/or third current limiters (7, 15, 38, 21, 44) are formed of venturi tubes. 7. The method according to claim 1 or 2, wherein the second chamber (10, 33, 55) is a tower having an average diameter d and a height H ≥ 10d. 8. The method according to claim 1 or 2, wherein the flocculant is a polymer injected immediately adjacent to the outlet of one or more flow restrictors (21, 44) or valves (61). 9. The method according to claim 1 or 2, wherein a portion of the flocculated emulsion is recirculated in the first chamber. 10. Equipment for continuous treatment of organic sludge (1), comprising: Devices (3, 6) for supplying the sludge in a continuous flow at a flow rate q to a second chamber (10, 33, 55) directly or via a first chamber (5) which can be maintained at a first determined pressure ( _P1 ), the second chamber (10, 33, 55) being maintained at a second determined average pressure ( _P2 , P', P” ₁ , P” ₂ ); The second chamber (10, 33, 55); An apparatus for injecting air (11) at a flow rate Q into a second chamber (10, 33, 55) to obtain a first emulsion in the second chamber (10, 33, 55), the first emulsion being formed in a sludge dispersion phase within a continuous phase of air encapsulating sludge. A flow restrictor (21, 44) or valve (61) is arranged to generate a defined pressure drop in the first emulsion. A third chamber (22, 43, 62) can be maintained at a third determined pressure ( _P3 , _P2 ', P” ₃ ) in the region located directly downstream of the flow restrictor (21, 44) or valve (61). The apparatus for injecting flocculants (24, 45, 78) into the region of the third chamber (22, 39, 62) is used to form a second emulsion of air in the thickened flocculent sludge. Apparatus (46, 67) for degassing the second emulsion at atmospheric pressure. Apparatus for recovering the degassed second emulsion in a filtration or decanting apparatus (26, 48, 68), and The filtration or decanting equipment (26, 48, 68). 11. The device according to claim 10, characterized in that the supply device includes a first flow restrictor (7) for introducing into the second chamber, wherein the pressure drop in the emulsion is generated by a second flow restrictor (15, 38) and a third flow restrictor (21, 44) or a valve (61). 12. The device according to any one of claims 10 and 11, characterized in that the degassing device (46, 67) is located at the other end of a third chamber (22, 43, 62) relative to a region located directly downstream of the flow restrictor (21, 44) or valve (61), the flow restrictor (21, 44) or valve (61) being arranged to generate a defined pressure drop in the emulsion. 13. The device according to any one of claims 10-11, characterized in that the device further comprises an intermediate chamber (18, 40) between the second (10, 33) and the third (22, 43) chambers and means (20, 42) for injecting air into the intermediate chamber downstream of the first injection. 14. The device according to any one of claims 10-11, characterized in that the first, second and/or third current limiters (7, 15, 38, 21, 44) are formed of venturi tubes. 15. The device according to any one of claims 10-11, characterized in that the second chamber (10, 33, 55) is a tower having an average diameter d and a height H ≥ 10d.