OA17773A - Method and device for treating an organic effluent. - Google Patents

Abstract

This is a method and a device for treating an organic effluent (2, 31). The effluent is fed in a continuous flow at a flow rate q <m3 / h), via a first enclosure <6) maintained at a first determined pressure (Pi), and / or directly through a first restriction (7), a second enclosure or container (10, 33,55) maintained at a second average pressure (P2; P '; P1 ";P2") determined by injecting air (11,31,54) into said second enclosure at a flow rate Q (Nm3 / h), to obtain an emulsion (13,57) in said second chamber, a pressure drop 1 determined in the emulsion is created, possibly modified by a second and / or a third restriction or a valve (61 ) supplying a third enclosure (22,39,62) maintained at a third determined pressure (P3; P '; P3 ") in the zone (79) 20 located immediately downstream of said second or third restriction and / or valve (61) and a flocculant (24, 45, 78) is injected into said zone of the third chamber, then said emulsion is degassed at atmospheric pressure and the emulsi is recovered. is thus degassed in a filtration or settling device

Description

PROCESS AND DEVICE FOR TREATMENT OF AN ORGANIC EFFLUENT

The present invention relates to a process for the treatment of an organic effluent, and more particularly for the treatment, conditioning, coagulation, flocculation and oxidation of emulsions, strongly colloidal water and / or liquid sludge, by bursting. , dispersion and diffusion of these inside a pressurized gas.

It also relates to a treatment device (conditioning, coagulation, flocculation and oxygenation) of emulsions, strongly colloidal water and / or liquid sludge using such a process.

The invention finds a particularly important, although not exclusive, application in the field of reducing the volume of organic or biological sludge, with a view to their treatment or subsequent use.

Methods of separating solid matter in suspension from the liquid effluent in which it is found are already known.

The techniques that exist for extracting water from the sludge are essentially compaction which increases the content (% by weight of the total mixture) of solid compound of the order of 5%, centrifugation or filtration which increase the both the solid compound content of 18 to 25%, and finally drying (by combustion or spreading for several weeks) which increases the solid compound content from 90 to 95%, knowing that the content of weight of solid compound of sewage sludge before treatment is generally between 0.1% to 1% of the total weight of the effluent.

All these treatments known from the prior art have drawbacks, either linked to the fact that the desiccation is not sufficient (compaction, centrifugation, filtration) or linked to the treatment time (drying) or to the high energy consumption ( combustion).

There is also known (FR 2 175 897) a sludge waste treatment process in which a sealed circuit comprising a tank is supplied, a circuit in which is recirculated for several tens of minutes by introducing a gas containing oxygen into the circuit by upstream of the tank.

Retention of the activated sludge in the vessel for a period of time sufficient to allow supersaturation with the oxygen-containing gas is reported to allow substantial removal of suspended solids.

Such a process, in addition to being long, implements a fairly complicated device, a source of numerous blockages.

There is also known a method for the shock-stripping of at least two flows facing each other in a small chamber in which air is bubble.

Although quite effective, this process is mainly applicable to highly mineralized sludge (that is to say having a% organic matter on 100% by weight of dry matter of less than 5 to 15%).

Also known (FR 2 966 818) is a process for separating liquid and suspended matter from a sludge, in which sludge and air are injected at a high rate into a small volume enclosure.

The process allows the separation of water bound to organic colloids.

However, such a process does not allow the removal of certain elements which contaminate the organic sludge, for example loaded with ammonia.

The dewatering of the sludge obtained with such a treatment can moreover be improved, a gain of only one% in dryness compared to the prior art leading to significant savings in transport and disposal costs.

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

The present invention aims to provide a method and a device which respond better than those previously known to the requirements of practice, in particular in that it will allow improved dehydration, in particular when it is implemented in combination with known techniques. centrifugation or pressing / filtration, and this while allowing better decontamination of sludge in particular loaded with ammonia, very quickly, the use of the process according to the invention requiring only a few seconds or minutes before obtaining a result.

In particular, this process makes it possible to obtain excellent results for very organic sludge, that is to say essentially loaded with phospholipids, polysaccharides, bacterial residues, volatile fatty acids, etc.

It is also possible to obtain an optimized yield when it is combined with an additional separation tool placed downstream of the device (belt filter or centrifugation), improving drying by more than 10%, for example by 25%.

With the invention, existing installations can be easily improved, at low cost due to low power consumption and reasonable use in quantity of utilities implemented (compressed air, reagent ...).

In addition, the method uses a simple device, the continuous operation of which has few operating constraints, unlike devices of the prior art such as centrifuges for example.

The invention also makes it possible to obtain a solid residue, in the form of a dehydrated porous cake, odorless, or with a humus odor, particularly easy to reuse and / or to spread.

To this end, the invention provides in particular a process for treating an effluent in which, said effluent is fed, in continuous flow at a flow rate q (m ³ / h), a chamber or a container maintained at an average pressure. determined by injecting air into said chamber at a flow rate Q (Nm ³ / h) to obtain an emulsion in said chamber, and a pressure drop is created before recovery of the emulsion in a filtration or settling device, characterized in that the sludge being organic sludge, the supply of effluent to the chamber or container called second chamber is effected, via a first chamber maintained at a first determined pressure (P ^ and / or directly, and in this that the determined pressure drop in the emulsion is created by at least one restriction or a supply valve to a third chamber maintained at a third determined pressure in the zone located immediately downstream of said restriction and / or valve, and we inject a flocculant in said zone of the third chamber to form at the outlet of the treatment an air emulsion in the thickened flocculated sludge, then said emulsion is degassed at atmospheric pressure before evacuation.

Advantageously, the supply of effluent to the enclosure or container is effected through a restriction, the pressure drop determined in the emulsion being created by a second and / or a third restriction. The restriction number can also be further increased.

One or more pressure / depression sequences are thus produced which, surprisingly, create a state of matter (emulsion) making it possible to ultimately obtain a higher gain in dryness.

We are not looking here for porosity but for water extraction, by playing on the interactive and / or iterative pressure / depression gradient.

More precisely, the pressure parameter is used to work the organic sludge at the level of its colloid bonds, the energy supply being brought by the pressure in particular to the right of the organs creating the pressure drop, by allowing one or more fairly strong local overpressures.

Thus by exerting a first pressure, a strong stress is produced on the mud. This being a colloidal structure made of organic matter and water, this pressure brings an energy capable of destabilizing / breaking the electrostatic (Coulomb type) or dipolar (van der waals type) bonds. It therefore causes water to escape organic fractions.

The following depression will in turn produce an acceleration movement of the sludge and an expansion / stretching towards the zone of least pressure continuing the effect of destabilization / destruction of the colloids and a breaking effect of the bonds.

Finally, again, we enter a sequence of compression then depression ... to prolong / amplify / produce the effects stated above.

Sequence after sequence, we therefore create a different state of matter (emulsion) to achieve the desired effect.

This can be further improved each time by adding one more pressure / vacuum sequence.

The flocculation is itself and simply a materialization of the separation of the phase.

By medium pressure is meant an average pressure on the volume of the enclosure.

It should also be noted that the injection of air into the stream of the effluent itself introduced with a restriction causing a pressure drop, creates a violent suction of air as the flow passes.

In essence, the emulsion is mud (dispersed phase) in the air (continuous phase) that coats it.

The emulsion of the mud in the air is therefore the result of the pressure / depression actions due to the successive restrictions as claimed.

It is also recalled that the value of the gas flow rates is conventionally given in Nm ³ / h (cubic normometer / h), the volume (in Nm ³ / h) being considered here at its value referred to a pressure of 1 bar, a temperature of 20 ° C. and 0% humidity, as is naturally accepted and understood by a person skilled in the art, an engineer in the field of chemical engineering.

Even in the presence of a slight depression, there is indeed a very good dispersion of the mud in the gas bed, knowing that when passing through the restriction zones the pressure is locally high and can lead to a reversal of the proportions.

In these areas the pressure builds up and the air penetrates the mud better, probably accentuating the exceptional porosity effect observed with the invention.

Thanks to these phenomena of emulsion and / or inversion of emulsions, the air comes into contact with the sludge intimately, the flocculation freezing the air / water couple in a way favorable to the deodorization, the flotation of the flocs of sludge and their dehydration.

It was thus possible to observe a high porosity of the sludge flocs with millimeter bubbles (from 1 to 5 mm) while, during conventional flotation, micrometric bubbles are created and serve as surfactant media for the organic matter.

In these known cases, the material rises to the surface at a speed of a few meters per hour, causing the bubbles to burst on the surface of the float, possibly letting the flocs fall in the middle zone and then at the bottom of the tank, the mud. having a density slightly higher than water.

With the invention, the flocs themselves have a density that is much lower than that of water (density of the sludge from 0.6 to 0.9 g / cm ³ ).

This very specific characteristic allows the sludge to have a high flotation quality, carried out with an improved speed which makes the phase separation sustainable.

According to one embodiment, means for providing shocks / dispersion in the gaseous fluidized bed are provided. For example each enclosure is decorated with simple hydraulic systems such as walls perpendicular to the flow, systems of springs of raschig rings etc ...

Advantageously, the effluent is introduced into a small enclosure (first or second enclosure), corresponding for example to a volume <0.5% of the volume of effluent passed per hour, (flow rate) ie 50 I for 10 m ³ / h of mud, for example 30 I, or even less than or equal to 5 I. This allows a sudden pressure drop in the flow of mud, for example supplied by pumps with a water height of 10 bars.

This first enclosure (or the second enclosure) is for example closed by a reduced outlet forming a venturi, making it possible to maintain it at an overpressure> 4 bars absolute, for example 5 bars absolute.

The exit from the first enclosure is therefore effected by a first and / or a second restriction favorable to the penetration of air into the effluent, injected downstream of the restriction, for example at 10 Nm ³ / h in the second pregnant.

Downstream, more or less immediately from this first restriction, a second restriction at the head of a third chamber and / or a third restriction at the head of a fourth chamber are for example provided.

According to the embodiment of the invention more particularly described here, and more or less immediate downstream of this second restriction (a few centimeters, 1 m or a few meters), a flocculant is also injected which makes it possible to trap micro bubbles and millimeter in contact with the suspended matter.

A very interesting phenomenon of immediate flotation of the sludge then occurs, with an upward speed of 50 or even 100 and more m / h. In comparison, conventional sludge flotation techniques allow an upward speed of 2 to 6 m / h.

This unexpected phenomenon makes it possible to constitute a self-draining material from colloidal mud.

In advantageous embodiments, one and / or the other of the following provisions is additionally and / or additionally used:

- the first chamber has a volume of less than 3200 cm ³ , or even 30 l, the first pressure being between 4 and 10 bars absolute, the flow rate q being between 5 m3 / h and 30 m3 / h, the second pressure being between between 1.2 bars and 4 bars absolute, the air flow Q being between 5 Nm3 / h and 200 Nm3 / h, and the third pressure being between 1.05 bar and 2 bars absolute;

- An intermediate chamber between the second and third chambers is supplied with emulsion;

- Air is injected a second time downstream of the first injection into said intermediate chamber, located between the second and the third chamber at a flow rate Q 'for example between 50 and 200 Nm ³ / h or more (ie> 200 Nm ³ / h, for example 500 Nm ³ / h or 1000 Nm ³ / h);

- the first, second and / or third restrictions are formed by venturis;

- the second enclosure is a column of average diameter d and height H> 10 d, for example a column> 2 m, for example 3 m for example 5 m;

- The flocculant is a polymer injected at the immediate outlet (a few centimeters, for example between 5 cm and 10 cm) from the second or third restriction;

- A part of the flocculated emulsion is recycled in the first chamber, for example in 1/10 ^th and 1/5 ^th of the flow or between 5% and 30% of the volume of sludge leaving the device, for example 10% or 20 %. This makes it possible to lower the overall consumption of polymer;

- the sludge is treated downstream of the tubular enclosure by centrifugation, filtration and / or pressing;

- the injected air can be heated.

The invention also proposes a device implementing the method as described above.

It also relates to a device for the continuous treatment of a sludge, comprising means for supplying said sludge in continuous flow at a flow rate q, to an enclosure or container maintained at a determined mean pressure, injection means d air in said chamber at a flow rate Q, to obtain an emulsion in said chamber, a restriction or valve arranged to create a determined pressure drop in the emulsion and means for recovering the emulsion thus degassed in a filtration device or settling, characterized in that, the enclosure or container being said second enclosure, and the device being arranged to treat organic sludge, the supply means of said second enclosure are arranged to supply it, via a first enclosure maintained at a first determined pressure and / or directly, and in that the device further comprises at least one restriction or a valve designed to create a determined pressure drop in the emulsion n and a third chamber maintained at a third determined pressure in the zone located immediately downstream of said restriction, as well as means for injecting a flocculant into said zone of the third chamber, and means for degassing said emulsion at atmospheric pressure.

Advantageously, the supply means comprise a first restriction upstream of the second enclosure, the pressure drop determined in the emulsion being created by a second and / or third restriction.

In an advantageous embodiment, the degassing means are located at the other end of the third enclosure relative to the zone located immediately downstream of said restriction.

Advantageously, it further comprises an intermediate enclosure between the second and third enclosures and means for injecting air downstream of the first injection into said intermediate enclosure.

Also advantageously the first and second restrictions are formed by venturis.

In another advantageous embodiment, the second enclosure is a column of average diameter d and height H> 10 d.

As a variant, a reagent improving the impacts between the sludge particles can be added. It can for example be used up to 10%, 5%, 1% of the DM content of the sludge.

This reagent is, for example, sand, calcium carbonate, slaked lime, etc. It is introduced upstream of the column, for example, in a mixing tank with the liquid sludge (not shown).

Oxygenation reagents can also be provided.

The invention will be better understood on reading the following description of embodiments given below by way of non-limiting examples. The description refers to the accompanying drawings in which:

Figure 1 is a block diagram of a device according to the embodiment of the invention more particularly described here.

Figure 2 is an embodiment of another device according to the invention.

Figure 3 shows another embodiment of a device according to the invention.

Figure 1 shows schematically a device 1 sludge thickener 2 sucked by means 3 (pump) from a reservoir or storage basin 4.

The device 1 comprises a first enclosure 5 of small volume, for example cylindrical or cubic, for example of volume 10 I, for receiving the liquid sludge, for example at a first determined pressure Pi a little lower than the outlet pressure P _o of the feed pump 3, due to the pressure drops of the feed circuit 6 (flexible tube for example). The flow rate g of the pump is for example between 5 m ³ / h and 50 m ³ / h, for example 10 m ³ / h, and the first determined pressure Pi is 2 bars absolute, P _o being for example 2, 2 bars absolute.

The enclosure 5 comprises at its outlet a restriction 7, for example formed by an orifice or nozzle 8, round, for example of 2 cm diameter, in an intermediate wall 9, separating with a second enclosure 10, of greater volume, for example 200 I.

The second chamber 10, for example cylindrical, is at a second pressure P ₂ (for example 1.8 absolute bar) and is supplied for example in the lower part with air 11 at a very high flow rate Q = 500 Nm ³ / h, and a pressure of several bars, for example 5 bars creating in the chamber 12 formed by the enclosure an emulsion 13 of droplets of mud 14 which is discharged via a second restriction 15 similar or identical to the restriction 7 .

The injection of air into the emulsion just after introducing the sludge into the chamber facilitates the mixing which takes place in the accelerating part after the nozzle (air ejector effect).

The second restriction 15 leads to an intermediate chamber 18, for example of greater volume, for example 500 I, formed by a cylinder 19 whose interior is at a third pressure P ₃ , for example of 1.6 bars absolute.

A second injection of air 20 in the lower part of this intermediate chamber further increases the fragmentation or dilution of the sludge in the air, the injection being carried out for example at a flow rate Q ′ of 200 Nm ³ / h, with for example 50 Nm3 / h <Q '<Q.

The intermediate enclosure 18 supplies for its part and in the embodiment described here, via a third restriction or nozzle 21, a third enclosure 22, also cylindrical, for example of height 3 m, at a fourth pressure P ₄ decreasing by l. entry of the enclosure at 23 to 1.2 bars up to atmospheric pressure in the upper part.

The fourth chamber comprises a supply of flocculant 24 (for example a known polymer) at a flow rate q ', for example depending on the type and flow rate of sludge, which can be appreciated by those skilled in the art in a manner known per se. to obtain good flocculation.

The sludge is then evacuated for example by gravity via a pipe 25 vented in a filter bag 26, the purified water 27 being evacuated downwards and the thickened sludge being recovered for example by shoveling to form thickened blocks 29, for example by a factor of 20 relative to the liquid sludge 2 at the inlet (τ of DM multiplied by 20 before draining into the filter bag).

Figure 2 shows another embodiment of a device 30 for treating liquid sludge 31 introduced at an end portion 32 of a container 33 elongated around an axis 34 and of determined height H, for example 1 m .

The container is maintained at an average pressure P 'for example of 2 bars absolute, and is formed by a cylinder of diameter d for example of 150 mm.

The sludge is supplied, for example by restriction, via a reduced zone 35, for example of 10 I located at the end portion 32 also supplied at the end of the container and upstream of the introduction of the sludge by an air inlet 36 for example at a pressure P "> P ', for example 2.5 bars absolute.

The air is supplied at a very high flow rate Q ', for example 100 Nm ³ / h, the sludge for its part being introduced at a flow rate Q for example of 10 m ³ / h.

The sludge 31 bursts into the air which is at an overpressure, a slight depression ΔΡ existing between the receptacle when the sludge arrives at 35 and the outlet of the sludge emulsion downstream 37 of the receptacle.

At the outlet of the container 33 there is a venturi 38 and / or a regulating valve generating a pressure drop, for example of 0.4 bar, the mud emulsion here being discharged into a tubular enclosure 39 comprising a first cylindrical part 40 of diameter d '(for example d' = d) which is at a pressure P ' ₄ <P', for example here of 1.6 bars (in the example taken), into which can be injected, downstream of the venturi , and close to the latter (for example at 10 cm to allow good mixing), a reagent at 41, and / or again air (taping 42).

In this embodiment, the tubular enclosure also comprises a second cylindrical part 43, separated from the first part 40 by a second venturi 44, said second part being of diameter d ”with for example d’ = d ”= d.

Downstream of the venturi 44, and close to the latter (1 to 10 cm), a supply 45 of flocculant is provided, with means known per se (metering pump, etc.), and a vent 46 for setting it up. to the atmosphere and / or a sludge outlet 47 open to the atmosphere, the pressure P ' ₂ in this second part therefore being very quickly brought to atmospheric pressure, for example by 1.3 bar at the outlet of the venturi for pass rapidly to 1 bar = 1 atmosphere at the outlet 47, the emulsion becoming, after the addition of the flocculant, an air emulsion in the sludge flakes, which flow by gravity at the end.

The total length of the enclosure L ₂ = h + l ₂ , is for example 10 m, with h = 3 m and l ₂ = 7 m, but other values are possible, the proportion between h and l ₂ being in general, but not limited to such that h <l ₂ .

The device 30 further comprises a filter 48 and / or a settling tank for evacuating the purified water 49 in the lower part and dehydrated sludge 50 in the upper part.

There is shown in Figure 3 a third embodiment of a device 51 according to the invention.

The device 51 comprises a receptacle 52 supplied by a nozzle 53 at the bottom then forming, for example, a restriction, in liquid sludge, and for example below (but it can also be above or at the same level) of this nozzle 53, supplied with compressed air at high flow by a second connection 54.

More specifically, the container is formed by a vertical column 55 comprising a first part forming a tank 56 for very violent mixing / stirring of air and mud, of small dimensions, for example cylindrical of height h! = 50 cm and diameter d ^ 30 cm, ie a volume of the order of 35 I, making it possible to obtain the first emulsion 57 of droplets 58 of broken mud.

This emulsion of drops in a strong upward flow of pressurized air then enters a cylindrical pipe 59, extending the reservoir 56, of smaller diameter d ₂ <d! for example 10 cm in diameter and which extends over a length h ^ for example 1 m (with L-ι = Ιη + h ₂ ).

In this column of air, the gas flow performs a stripping (stripping in English) of the gases contained and / or resulting from the sludge and in particular from the ammonia NH3, achieving surprisingly and depending on the operating conditions and treated organic sludge, almost complete elimination of unwanted gases (<a few ppm) trapped in the sludge.

The length l ₂ is advantageously dimensioned to do this by a person skilled in the art.

At the top 60 of the enclosure, a regulating valve 61 and / or a valve is provided, for evacuation to a tubular enclosure 62.

The pressure of the emulsion 57 goes from P / '(for example 3 bars) in the initial reservoir 56, to P ₂ ”(2.890 bars) a little less than P! at the top of the column 59 of the container, at the level of the valve 61, with ΔΡ ”= P ₂ ” - P-Γ = a few millibars, then at the outlet of the valve at P ₃ ”= 2 bars (due to the pressure drop of the valve).

More precisely, the enclosure 62 comprises a first section 63 of length l _3, for example 5 m, which ends in a venturi 64 passing the pressure P ₃ "'<P ₃ " at the end 65 of the first section at a pressure P ₄ ”in a second section 66 of the enclosure on a granite slope, provided with a vent 67, the section 66 being of length l _4, for example 1 m, with L ₂ = l ₃ + l ₄ .

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

According to the invention, the enclosure comprises means 72 for supplying flocculant 73 from a preparation tank 74 by mixing and mixing. A metering pump 75 brings the flocculant into the sludge emulsion which leaves the container 52 at the level of the outlet of the valve 61, or in the immediate vicinity (ie a few cm) in a fairly disturbed zone 76 due to the pressure drop generated by said valve 61. P ₃ ”is here and for example passed from P ₂ ” ~ 2 bars to P ₃ ”= 1.4 bar, P ₄ ” being for its part at atmospheric pressure, or substantially at atmospheric pressure due to the vent 67.

In this embodiment, provision has also been made for an additional air inlet 77, injected for example with the flocculant through the tapping 78, or in parallel.

The emulsion 79 at the end of the treatment with the flocculant becomes an air emulsion in the thickened flocculated sludge.

The two sections 63 and 66 are for example cylindrical with the same diameter d _3, for example equal to the average diameter of the container, for example dj_ + d ?.

For 10 m ³ / h of liquid sludge, an air flow of 60 Nm ³ / h minimum, whatever the injection mode, the container having a section of 200 mm for a height of 5 m, 10 m, 30 m or more, there is a very strong stripping effect (in English) (pulling out trapped gases), the air being intimately mixed with the mud.

As regards the flocculant, a polymer, for example cationic, will preferably be used.

Example, for a sludge containing 7 g / l of DM, 50 g of crude polymer is used, for example prepared at 5 g / l, ie an injection of 10 l of solution per m ³ of sludge. The injection takes place immediately after leaving the column of the container.

As a variant, a reagent improving the impacts between the sludge particles can be added. It can for example be used up to 10%, 5%, 1% of the DM content of the sludge, as seen above.

This reagent is, for example, sand, calcium carbonate, slaked lime, etc. It is introduced upstream of the column, for example, in a mixing tank with the liquid sludge (not shown).

Oxidation reagents can also be added.

In certain applications, for example when the sludge contains a lot of organic fatty acids or when the sludge is sludge from an methanizer, excellent results are indeed observed.

For example in proportions of 1 l of H2O2 or 1 l of S2o8 for 1 m ³ of sludge containing 40 g / l of DM.

There may also be addition of reagent to aid the coagulation of complementary organic matter.

For example, for a sludge of 11 g / l of DM and 8% of 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) either when the liquid is introduced into the column, or before the introduction of flocculant (after column).

For example, tests were carried out on biological sludge with a band filter, from sludge loaded with 26 to 30 g / l in DM with:

Q ’= 50 to 80 Nm3 / h

P = 1.7 bar pressure of the vessel / reactor

Q = 3 to 15 m3 / h

At the end of the process, sludge is obtained with a porous appearance, dry, with an accelerated drying and a dryness of 25 to 35%.

We thus observe that, surprisingly and by simple decantation, the water allows its unbound water to drain directly by gravity.

The sludge then gradually dries up, going from 100 g / l of DM after the 1st hour, to 130 g / l after 2 h, 160 g / l after 5 h, 350 g / l after 1 month, (big bag) .

Other examples of treatment according to the process implemented, by recovery on a filter bucket or filter bags (big bag in English) give:

Filter bucket; Ex 2: 130 g / l after 8 p.m. and 180 g / l after 8 days

Filter bucket; Ex 3: 100 g / l after 5 h, 130 g / l after 7 d.

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

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

Big bag; Ex 4: 120 g / l after 24 hours (while it rained all night) and 402 g / l after 1 month.

Note that the sludge treated according to the invention is initially liquid.

Up to 30 g / l a dilution is not required a priori. But if the sludge is more dense, for example beyond 40 g / l, we can proceed to a dilution at the inlet of the device to allow proper operation of the pumping of the sludge, which is remembered an organic sludge, c 'That is to say whose rate of MO (Organic Matter) on the rate of DM (Suspended Matter) is between 65% and 85%. By Organic Matter is meant essentially phospholipids, polysaccharides, proteins, alkalis, alkaline earth metals and / or metals, etc.

Another example of operation is given below, this time with reference to FIG. 2 simplified (this eliminates the need for the first portion of the enclosure).

The receptacle 33 forms a first chamber in the form of a pipe 20 cm in diameter and 50 cm in length, into which is introduced at the flow rate Q = 10 m3 / h, an organic sludge (from a clarifier of a purification station municipal) at 6 g / l of DM and compressed air at 50 Nm3 / h of air at 1.9 bar thanks to a booster.

A 5 cm2 orifice closes this chamber over a length of 10 cm.

Immediately downstream of the latter, a flocculant, for example dosed at 10 g / l, is introduced into the chamber 43.

The post orifice pressure gradually drops to reach the atmosphere after a few meters.

For example: the enclosure 43 which forms a post-orifice chamber is also a pipe 3 m in length and 20 cm in diameter.

At the end of the enclosure, all of the flows join, for example, a filter bag (filter 50) with a cut-off threshold of 500 μm, immediately giving a dryness of 10% (or 100 g / l) and a clear filtrate in 49 of 50 mg of oxygen (02) per liter (COD).

The reagents are introduced liquid by metering pumps. Conventionally, the more the sludge is concentrated, the more diluted the reagents must be prepared.

The device is released to atmosphere. However, the venting to the atmosphere can optionally be regulated in one embodiment of the invention, so as to recover the pressure of the downstream separation apparatus.

Downstream devices are classic. It can be seen that their efficiency on dehydration is improved by at least 3%, for example for a centrifuge which gives a result of 23% dryness, i.e. 230 g / l of DM, the device placed upstream makes it possible to ultimately achieve minimum 26% dryness, i.e. 260 g / l of DM.

The devices that can be used downstream are:

• Filter bags (100, 300, 500 pm or more) open or closed • Floats • Mechanical thickeners • Screw presses • Band filters • Centrifuges • Press filters

At the exit, the sludge can obviously be used for spreading on the ground, without or after composting, alone or with green or other waste. They can also be dried on single or solar drying beds.

We notice that curiously, the sludge obtained is "odorless" and does not ferment over time (anaerobic fermentation)

In fact, the enormous dilution with air allows the sludge to have a high dehydrating power, due to the presence of the air bubbles.

The results obtained with the device 1 according to the invention were shown below in Tables I, II, III, combined downstream with the devices indicated, at different mud flow rates.

TABLE I: Device + band filter

Test Dryness Mud input device Mud flow rate M ³ / h Air flow Nm ³ / h Pressure P bar Dryness filter outlet Note s Length rL ₂ 2 10 7.8 80 1.7 14 Diluted sludge 6m 3 10 7.8 95 1.2 16.5 Diluted sludge 3m

TABLE II: Device 1 + big bag

Trial Type of test Test date Immediate dryness Dryness at 1 day At 1 month TO Indicator without device only big bag filtering 04/05 8% 10% 22%

TESTS 10 DAYS Device + filtering big bag Flow rate from 3 to 12m ³ / h Half April 10 to 11% 14.5 to 15.5% 45.9% to 53.5%

It is observed that thanks to an optimized sludge concentration, obtained with the invention, for example from 70 to 130 g / l of DM, this will very favorably maximize the dehydration function by tools such as centrifuges or a filter. 5 press, allowing to considerably improve the output thereof. Indeed, the unbound water having been extracted by the process described above, this makes it possible to almost systematically improve, by at least 100 g / l, the DM content of the sludge at the outlet.

As goes without saying and as it also follows from the foregoing, the present invention is not limited to the embodiments more particularly described. On the contrary, it embraces all the variants thereof and in particular those where the number of portions and / or sections of the enclosure is different, for example greater than three, or alternatively the container is horizontal with a single section.

Claims (15)

1. A method of treating an organic sludge in which the said sludge is fed in a continuous flow at a flow rate q (m ^{3 /} h), either directly or via a first chamber (5) maintained at a first determined pressure ( P ^, a second enclosure (10, 33, 55) maintained at a second determined average pressure (P2, P ', P'j, P ”2) by injecting air (11) into said second enclosure (10, 33, 55) at a flow rate Q (Nm ³ / h) to obtain in said second chamber (10, 33, 55) a first emulsion, forming a dispersed phase of sludge in a continuous phase of air which coats it, it is creates a determined pressure drop in said first emulsion by passing it, through one or two restrictions (15, 21, 38, 44) or through a supply valve (61), into a third enclosure (22, 43, 62 ) maintained at a third determined pressure (P4, P ' ₂ , P ” ₃ ) in the zone located immediately downstream of said restriction (s) or of said valve, a flocculant (24, 45,78) is injected into said zone of the third chamber to form at the outlet of the treatment a second emulsion of air in the thickened flocculated sludge, then said second emulsion is degassed (46, 67) at atmospheric pressure before discharge, said second emulsion is recovered in a filtration or settling device (26, 48, 68), and it is filtered or decanted. 2. Method according to claim 1, characterized in that the supply of sludge to the second enclosure (10, 33, 55) is effected through a so-called first restriction restriction (7), the pressure drop determined in the 'emulsion being created by a second restriction (15, 38) and a third restriction (21, 44) or else by a valve (61). 3. Method according to any one of the preceding claims, characterized in that the first enclosure (7) has a volume of less than 3200 cm ³ , the first pressure (P4) being between 4 and 10 bars absolute, in that the flow q is between 5 m ³ / h and 30 m ³ / h, the second pressure (P2; P '; P-, ”; P” ₂ ) is between 1.2 bars and 4 bars absolute, the flow d 'air Q being between 5 Nm ³ / h and 200 Nm ³ / h, and the third pressure (P ₄ ; P'₂; P ₃ ”) is between 1.05 bar and 2 bar absolute. 4. Method according to any one of the preceding claims, characterized in that an emulsion is supplied to an intermediate chamber (18, 40) between the second (10, 33) and third chambers (22, 43). 5. Method according to claim 4, characterized in that air is injected a second time downstream of the first injection into the intermediate chamber (18, 40) located between the second chamber (10, 33, 55) and the third enclosure (22, 43, 62) at a flow rate Q '. 6. Method according to any one of the preceding claims, characterized in that the first, second and / or third restrictions (7, 15, 38, 21, 44) are formed by venturis. 7. Method according to any one of the preceding claims, characterized in that the second enclosure (10, 33, 55) is a column of average diameter d and height H> 10 d. 8. Method according to any one of the preceding claims, characterized in that the flocculant is a polymer injected immediately out of said restriction (s) (21, 44) or from the valve (61). 9. Method according to any one of the preceding claims, characterized in that a part of the flocculated emulsion is recycled in the first chamber (17). 10. Device (1) for continuous treatment of an organic sludge comprising supply means (3, 6) of said sludge in continuous flow at a rate q, either directly or via a first enclosure (5) maintainable at a first pressure (P ₄ ), of a second enclosure (10, 33, 55) maintainable at a second determined average pressure (P ₂ , P ', P "i, P" ₂ ); said second enclosure (10, 33, 55); means for injecting air (11) into said second enclosure (10, 33, 55) at a flow rate Q, to obtain a first emulsion, forming a dispersed phase of sludge in a continuous phase of air which coats it in said second enclosure (10, 33, 55), a restriction (21, 44) or valve (61) arranged to create a determined pressure drop in said first emulsion, a third enclosure (22, 43, 62) maintainable at a third determined pressure (P ₃ , P ₂ ', P'3) in the area immediately downstream of said restriction (21,44) or valve (61), means for injecting a flocculant (24, 45, 78) in said zone of the third enclosure (22, 39, 62), to form a second air emulsion in the thickened flocculated sludge, means (46, 67) for degassing said second emulsion at atmospheric pressure, means for recovering said second emulsion thus degassed in a filtration or settling device (26, 48, 68) and said filtrating device (26, 48, 68) n or settling. 11. Device according to claim 10, characterized in that the supply means comprise a first restriction (7) for introduction into the second chamber, the pressure drop in the emulsion being created by a second restriction (15, 38 ) and a third restriction (21, 44) or valve (61). 12. Device according to any one of claims 10 and 11, characterized in that the degassing means (46, 67) are located at the other end of the third enclosure (22, 43, 62) relative to the zone. located immediately downstream of the restriction (21, 44) or valve (61) arranged to create a determined pressure drop in the emulsion. 13. Device according to any one of claims 10 to 12, characterized in that it further comprises an intermediate enclosure (18, 40) between the second (10, 33) and third (22, 43) enclosures and means air injection (20, 42) downstream of the first injection into said intermediate chamber. 14. Device according to any one of claims 10 to 13, characterized in that the first, second and / or third restrictions (7, 15, 38, 21, 44) are formed by venturis. 15. Device according to any one of claims 10 to 14, characterized in that the second enclosure (10, 33, 55) is a column of average diameter d and height H> 10 d.