EP2342165A2

EP2342165A2 - Method and device for the biological treatment of a contaminated liquid feedstock containing a dispersible and digestible organic liquid phase such as an oil or a toxic solvent

Info

Publication number: EP2342165A2
Application number: EP09760538A
Authority: EP
Inventors: William Everett
Original assignee: Dewdrops SAS
Current assignee: Dewdrops SAS
Priority date: 2008-10-27
Filing date: 2009-10-23
Publication date: 2011-07-13
Also published as: CA2741616A1; WO2010049629A2; WO2010049629A3; FR2937646B1; KR20110095872A; US20110253626A1; JP2012506713A; US8758618B2; FR2937646A1

Abstract

The plant of the present invention includes three reaction vats (100, 200, 300) in series, each containing an aqueous phase and a specific bacterial population. The vats are used for sequentially solubilising the liquid feedstock to be treated by enzymatic hydrolysis, and biodegrading the resulting effluent by biological digestion, and finally reducing the residual bacterial components. The vats are isolated from each other by tangential filters (108, 208, 308) and centrifugal separators (212, 312) for filtering the biomass from the reaction products. The result is an essentially inorganic final liquid effluent (EFF/N), and the biomass filtered downstream is an ultimate organic waste (DU) having a reduced volume.

Description

Process and device for the biological treatment of a contaminated liquid charge comprising a dispersible and digestible organic liquid phase such as an oil or toxic solvent

The invention relates to a method and a plant for the biological treatment of a contaminated liquid feed comprising a dispersible and digestible organic liquid phase. The invention is particularly applicable to toxic oils and solvents contaminated in particular by radioactive substances. These oils or solvents must be destroyed or decomposed into acceptable effluents for the site. The invention is, however, applicable to the treatment of other products than oils or solvents, since these are dispersible organic liquids (unlike tars, for example) and digestible, that is to say - say who can undergo the enzymatic action of microorganisms that will use the organic liquid as a carbon source for their aerobic metabolism. The oxidation of the liquid to be treated by the micro-organisms is accompanied by a discharge of carbon dioxide and water.

The invention is also applicable to the treatment of fillers comprising fine particles suspended in an organic liquid phase, for example spent catalyst particles suspended in oil, in order to be able to regenerate these catalyst particles. In the remainder of the description, the terms "oils" and "oils or solvents" will be used for convenience, but everything that will be described can be generalized to other types of organic liquid fillers, provided that they have the properties indicated. above. There are several techniques for removing toxic oils. The simplest technique is to burn these oils in an incinerator, but this technique has several disadvantages. Firstly, the oil must generally be mixed with other waste, and this type of disposal is difficult to implement continuously. In addition, there is a risk of producing toxic volatile compounds during the incineration, which must be carefully filtered before being discharged into the atmosphere.

Another technique involves subjecting the oils to wet oxidation in supercritical water. This technique is very effective and well controlled, however it is very difficult to implement (pressures of at least 221 bar and temperatures of at least 376 ° C) Consequently this technique requires a significant initial investment, entails a high operating cost and involves drastic safety measures related to very high pressures.

The third technique, which is that of the invention, consists in oxidizing the oils biologically in the presence of microorganisms, at a temperature of the order of 30 to 37 ^° C. for optimal bacterial metabolism. The supply of oxygen is obtained by continuous aeration of the system, and the oxidation of the oils simply produces carbon dioxide and water, without danger. In addition, the treatment pressure does not exceed 3 bars, and this technique is adaptable to highly variable streams to be treated. WO 96/24937 A1 describes a method and an installation for removing contaminated oils or solvents of this type. However, this process does not allow a satisfactory degradation of the fillers such as contaminated oils, which consist of a mixture of several tens of different constituents and structurally very diverse: cyclic, branched, linear, etc., with for each category a large number of distinct molecules. Indeed, a given bacterial population ensures a preferential digestion of a specific category of molecules, but not of all the molecules. As a result, bacteria will tend to degrade the most digestible molecules, that is, to "eat what is easier to eat". However, because of the continuous supply of the treatment tank, there will be permanent renewal of the easily digestible fraction, which will ultimately be the only or almost the only degraded by biomass. This phenomenon will lead to an accumulation of difficult-to-digest molecules, whose bacteria will never begin to decay. This accumulation will be a factor of intoxication of the biomass, leading rapidly to the cessation of the process of degradation of the liquid charge and / or to autolysis (self-digestion) of the bacterial mass at the expense of the digestion of the oil, more long and more difficult. As digestion by biomass is not sufficient to produce an acceptable effluent, this effluent must be subjected to a relatively complex and expensive post-treatment (evaporation, activated carbon filtration, etc.). which results in the production of additional waste, in particular activated charcoal, which must be renewed regularly. In addition, the technique described in this document requires a permanent injection of biomass into the plant, implying that this additional biomass is removed downstream.

In addition, this process is essentially designed for continuous waste treatment, with the most constant flow possible, insofar as any significant variation in the quantity or nature of the charge to be treated is likely to substantially modify the process. general equilibrium of the process.

Finally, this process requires continuous monitoring of the various reactions and treatments implemented, with almost permanent presence of an operator to monitor the evolution of the process and take the appropriate adjustment and adjustment actions. One of the aims of the invention is to remedy these various drawbacks by proposing a method and a facility for the biological elimination of organic waste such as toxic oils or solvents, with a high yield, an adaptability to flows very varied (and without interruption of operation) and the capacity to handle large quantities of waste, thus allowing exploitation on an industrial scale.

More specifically, the subject of the present invention is such a method and such an installation that makes it possible to reduce costs of any kind, be they:

- initial investment costs, - operating costs incurred by the day-to-day operation of the installation, and

- future costs ("inheritance costs") of dismantling the machine when it is expected to become itself a waste, as in the case of facilities for the treatment of radioactive substances.

Another aim of the invention is to propose such a technique that, without complex post-treatment, it is possible to obtain, directly at the outlet of the process, a liquid effluent that is acceptable for the site (legal standards), with a minimized quantity of reject, and producing a minimum of ultimate waste. The invention also aims to provide such an installation that can be regulated simply and automatically, so as to avoid the use of an operator permanently present on site for monitoring and implementation of treatment. Another object of the invention is to provide a very great flexibility in terms of the quantities and variety of waste to be treated, including the possibility of treating this waste in batches, unlike systems previously proposed, essentially designed for continuous treatment. Another aspect of the flexibility of the method of the installation of the invention resides, as will be seen, in the fact that the system as a whole is a very stable system, with a relatively predictable and calculable behavior, which makes it possible to limit initial trial and error adjustments to each change in the nature of the waste to be treated. The method of the invention, which is of the general type already disclosed by the aforementioned WO 96/24937 A1, is characterized by the successive steps of: a) feeding with the liquid feedstock to be treated a first vessel containing an aqueous phase and a first bacterial population; b) solubilizing the liquid charge to be treated in the first tank by enzymatic hydrolysis with the first bacterial population; c) withdrawing from the first tank a first liquid reaction product; d) filtering the first reaction product biomass contained therein, to give a first effluent; e) feeding with the first effluent a second tank containing an aqueous phase and a second bacterial population, different from the first; f) biodegrading the first effluent in the second tank by biological digestion with the second bacterial population; g) withdrawing from the second tank a second liquid reaction product; h) filtering the second reaction product from the biomass contained therein, to give a second effluent; i) adjust the bacterial concentration in the second tank by extracting surplus biomass; j) supply with the second effluent a third tank containing an aqueous phase and a third bacterial population, different from the first and the second; k) reducing the residual bacterial components of the second effluent in the third vessel by biological action of the third bacterial population;

I) withdrawing from the third tank a third liquid reaction product; m) filtering the third reaction product biomass contained therein, to give a third effluent, the third effluent constituting a substantially inorganic final liquid effluent, and the separated biomass constituting an ultimate organic waste of reduced volume.

Thanks to this process, by the multiplication and isolation of the tanks (which prevents the bacteria from migrating from one tank to the next), it is possible to specialize the bacterial populations in the three tanks according to the different molecules of the charge. to digest: the easily digested fraction will be degraded in the first tank, while the molecules for which the biomass of the first tank will not have begun the digestion will be concentrated in the second tank, where the bacteria (whose specificity will be function of the fraction to be digested) will have to digest the remaining fraction, and the same for the third tank. The evolution of the biomass metabolism can thus be done, over time, in the sense of an optimization of the digestion of the most difficult molecules. In addition, the adjustment of the bacterial concentration in the second tank avoids a phenomenon of "self-digestion" of the bacterial mass at the expense of digestion of the oil, longer and more difficult, Advantageously, in this process :

steps d), h) and / or m) further comprise recycling, to the vessel from which the reaction product subjected to filtration has been withdrawn, separated biomass; this makes it possible to adapt the bacterial populations at each stage and avoids the risks of contamination between the different tanks;

- The method further comprises recycling to the first tank of the final liquid effluent obtained in step m); and step h) further comprises a chemical oxidation of the second effluent after filtering, and / or the excess of biomass resulting from the filtering;

step k) comprises a reduction of the biomass in the third reactor; - It is further provided, prior to step a), an oxidation pretreatment by Fenton reaction of the liquid feed to be treated;

- It is further provided a step of withdrawing excess biomass in the first, second and / or third tanks, and digestion of the excess biomass with separation of a liquid phase and a solid mineral waste;

a further post-treatment step, by combined UV irradiation and ozonation, of the final liquid effluent resulting from the filtration of the third reaction product and / or the liquid phase resulting from the digestion is also provided; excess biomass. The invention also relates to a corresponding installation, comprising means for implementing the various process steps indicated above. Advantageously, this installation can further provide that:

the means for filtering the first, the second and / or the third product comprise a tangential membrane filter;

- The means for filtering the second and / or the third product further comprises a centrifugal separator and / or a flotation system;

the second tank comprises mechanical stirring and anti-foaming means capable of sucking the foam formed during the biodegradation process and incorporating this foam into the aqueous phase contained in the tank;

the second tank comprises means for pumping and recirculating the contents of the tank, as well as means for thermal regulation, aeration means for the liquid phase, calibrated homogenization means, and / or means measurement and / or sampling, these various means being arranged in the recirculation circuit outside the volume of the tank.

0 An embodiment of the invention will now be described with reference to the accompanying drawings in which the same reference numerals designate identical or functionally similar elements from one figure to another. Figure 1 is a schematic view of the installation according to the invention, illustrating the various elements for the implementation of the successive steps of the method.

Figure 2 illustrates in more detail the structure of the central reactor for biodegradation of oils. Figure 3 is a top view of the same reactor, taken according to HI-III of Figure 2.

Figure 4 schematically describes a complete system integrating the various components of the installation described Figure 1.

0

As illustrated in FIG. 1, the installation according to the invention essentially comprises three distinct reactors 100, 200, 300 in the form of three respective tanks of determined volume connected in series. The first reactor 100 is intended to solubilize the oils by enzymatic hydrolysis. The toxic oils H are introduced into the reactor 100 by a dosing pump 102 of determined flow. The same pump injects a minimum industrial MMI medium composed of purified water and mineral salts essential for the development of microorganisms. The whole is mixed with the aqueous phase 104 contained in the first reactor 100, where the microorganisms will solubilize the oils by hydrolysis by specific enzymatic action of a selected population of bacterial microorganisms. The residence time depends on the type of oil to be treated and the choice of microorganisms. In general, the flow of oil typically varies, depending on the type of oil, from 20 to 200 μl per liter of reaction volume and per hour.

This phase of solubilization of the oils is critical for the implementation of the process of the invention, because it considerably increases the bioavailability of these oils. Indeed for an effective biodegradation it is necessary that the microorganisms have access to the organic substrate, and this is simpler when the oil is soluble in the aqueous phase. The bath containing the solubilized oils is drawn off at the bottom of the reactor by a pump 106, leaving on the surface the oils not yet solubilized. In this way, only the solubilized oils are transferred to the reactor 200. The solubilized oils thus withdrawn are subjected to the action of a tangential filter 108 making it possible to separate the biomass BM from a part of the liquid effluent EFF (permeate or filtrate). The retentate (biomass) returns to the reactor 100 via a pipe 110, which thus prevents the microorganisms of the first reactor 100 from mixing with the microorganisms of the reactor 200. This separation step between the effluent and the biomass also makes it possible to to optimize the bacterial population of each reactor according to its function, with a selection of microorganisms specific to the first reactor 100, optimized for hydrolysis, which is different from that of the second reactor 200, optimized for the biodegradation of the oil .

The same remark obviously applies to the insulation between the second reactor 200 and the third reactor 300, made by implementing a tangential membrane filter, as will be explained above. The use of a tangential membrane filter is preferred to a simple decantation, because such a filter makes it possible to exactly adjust the quantity of effluent desired, while ensuring that the biomass does not pass into this effluent.

The insulation provided by the use of a tangential membrane filter also provides a biologically additional safety, for example in case of death of the bacteria due to the presence of protozoa in the aqueous phase of one of the reactors. Insofar as it can be ensured that the biomass does not pass the filter, this contamination will not extend to the downstream reactor. After the etching treatment (solubilization of the oils) carried out by the first reactor 100, the effluent containing the oil to be treated is fed via line 202 to the second reactor 200, which is the one implementing the main biodegradation step. oils. This second reactor has for example a capacity of 100 liters, and the residence time is typically 343 hours. The second reactor 200, which will be described in more detail below with reference to FIGS. 2 and 3, ensures the digestion of the oils in the aqueous phase 204, under the effect of microorganisms specifically chosen to optimize this biological digestion function. , and which are different from those contained in the other two reactors 100 and 300.

The passage to the third and last reactor 300 is provided in the same way as the passage of the first reactor 100 to the second reactor 200: the fluid is withdrawn at the bottom of the reactor 200 by a pump 206 and then passes through a filter tangential 208 where the biomass BM (retentate) is separated from a part of the liquid effluent EFF. The effluent produced by the tangential filter 208 via line 218 is directed to a chemical oxidation device 220 operating by ozonation or oxygen peroxide treatment, to complete the oxidation of the biodegradation products. After this oxidation step, the effluent is sent to the reactor 300 via line 302.

The biomass 210, which leaves the tangential filter 208 via a pipe 210 is recycled to the second reactor 200 via a pipe 214. The possible surplus of biomass formed in the second reactor 200 during the biodegradation of the oils can be extracted by a centrifugal separator 212 and / or by a flotation system, via line 216. The excess biomass can also be directed to the chemical oxidation device 220 via line 216 before being fed to reactor 300 via line 302. It is important effect of adjusting the bacterial concentration in the reagent 200, avoiding that it becomes excessive (typically a maximum limit of 10 ⁹ cells / ml). In fact, excessive concentration leads to the death of a large proportion of bacteria, resulting in the production of organic matter that is easily digested by living bacteria. This phenomenon of "self-digestion" of the bacterial mass occurs at the expense of digestion of the oil, longer and more difficult. To avoid this phenomenon, instead of recycling the biomass of the reactor (via line 214) this biomass at the outlet of the separator 212 is extracted and destroyed by oxidation (line 216 to the device 220). The effluent thus oxidized by the device 220 is delivered via the line 302 to the third reactor 300, which ensures the reduction of the excess biomass formed during the metabolism of the toxic oils or solvents in the reactor 200. Indeed, the effluent conveyed by the tube 302 contains the constituents of bacterial cells lysed during the chemical oxidation step by the device 220, constituents which serve as nutrients for the bacteria of this third reactor, by action in the aqueous phase 304 of a third bacterial population specifically chosen to optimize this final degradation function, which is generally different from that of the other two reactors 100 and 200.

The third reactor 300 has for example a capacity of 20 liters, and the residence time is typically 68 hours. It makes it possible to mineralize and therefore considerably reduce the excess biomass produced in the second reactor 200. Moreover, it adds an additional residence time to possibly degrade the most recalcitrant molecules with the enzymatic action of the microparticles. organizations. The effluent is withdrawn from the third reactor 300 by a pump 306 and then applied to a third and last tangential filtration system 308: the separated biomass BM is applied via line 310 to a centrifugal separator 312 and / or to a flotation system, of the same type as the separator 212 associated with the second reactor. The solid effluent thus separated, which constitutes the totality of the organic part produced by the process, constitutes an ultimate waste DU which can then be dried. This non-mineralized solid effluent (rot-proof, sterile and thus dangerous) has, however, an extremely small volume, which is not a constraint for the process.

The liquid effluent EFF at the outlet of the tangential filter 308 is delivered via line 318 and constitutes a EFF / N effluent that is acceptable for the site, typically an effluent whose main characteristic is a COD (chemical oxygen demand) strictly less than 150 mg / l. If the discharge standards allow it, it is possible to dilute in the effluent EFF / N all or part of the organic waste resulting from the separation by the filter 312, as shown by the arrow 320. If the dilution is total, only the liquid effluent remains, which is simpler for waste management. It should be noted that the flow rates are regulated so as to maintain the levels in the reactors, so that the volume in the reactors does not vary and that the material balance is balanced between the inlet and the outlet of the installation (which facilitates the traceability). Eventually, and without this having any influence on the material balance, part of the effluent obtained at the outlet of the installation can be recycled to the first reactor 100 (arrow 320), according to the results of the analysis of this effluent. . Incidentally, the invention advantageously makes it possible to batch process oils of different natures by adapting the bacterial populations of the different reactors, and with the possibility of starting the treatment of a batch before that of the previous batch. be completed. For example, at the end of the treatment of a first batch, when the oil has been completely solubilized and is being processed in the reactants 200 and 300, it is possible to begin solubilizing the oil of the second batch. batch in the reactor 100, without this having any impact on the end of the treatment of the first batch. This is actually made possible by the separation of the biological treatments in the three tanks 100, 200 and 300, whose respective reaction conditions (choice of microorganism populations, various operating conditions, etc.) can be adjusted separately for each reactor. , independently of the other two.

The structure of the second reactor 200 intended to ensure the actual biodegradation of the toxic oils will now be described in more detail with reference to FIGS. 2 and 3.

This biodegradation reactor has a number of original elements to simultaneously perform several functions, while simplifying the device so as to reduce maintenance operations. The air required for oxidation can be injected by a ramp 222 at the bottom of the reactor, fed by a pipe 224 located outside the reactor vessel. Alternatively or in addition, there is provided a venturi air incorporation system 242 mounted on the pipe 230, and a calibrated homogenizer 244, based on the ultrasonic molecular agitation property: according to the frequency of ultrasound emitted, particles in solution (bacteria, micelles, air bubbles, etc.) can be destroyed selectively according to their size, by vibratory effect. It is thus possible to choose, for example, to destroy particles larger than 100 μm in order to save bacteria, which generally measure 1 μm. An anti-foam function is provided by means of an assembly including in particular a flexible rotor pump 226 sucking the contents of the reactor 200 continuously from below, at 228, and delivering this content via a pipe 230, 232, to The mouths 234 are oriented tangentially (FIG. 3) so as to create inside the vat a vortex preventing the accumulation of foam on the surface of the contents of the reactor. The foam that forms during the process may indeed trap the oils, which makes it unavailable for bacteria. The system described here allows, in a purely mechanical way, to disperse and homogenize the foam, which is reincorporated in the aqueous phase, thus increasing the biodegradability of the oils and therefore the efficiency of the process, without the need to add any chemical defoaming agent, as is often the case.

It is furthermore provided at the lowest point, in 236, a pipe for evacuating and emptying the liquid phase. The reactor 200 also provides a thermal regulation function, by means of a sleeve 238 surrounding the portion 240 of the pipe 230 of the loop recirculation system described above, and traversed by a heating or cooling heat transfer fluid. The liquid phase contained in the reactor is thus thermoregulated, and this by an element located outside the tank, so requiring a minimum of intervention in case of maintenance (unlike conventional underwater heating systems). To this must be added the advantage of this so-called "soft" heating method which is safer and which, unlike resistance heating systems, does not create a hot spot, lethal for microorganisms.

Note that all the elements that have just been described are arranged outside the reactor vessel, thus greatly simplifying maintenance operations. In addition, the only moving part of this assembly is the flexible rotor pump 226, which gives a very high good robustness to the installation, which will be able to work continuously during very long periods without particular intervention. Finally, the reactor comprises a measurement cell 246 mounted in a bypass on the sampling line located at the bottom of the reactor in order to allow taking representative samples and analyzing these samples (pH, temperature, dissolved oxygen, etc. .) by appropriate sensors. The data provided by these sensors, as well as the measurement of the CO ₂ released by the reaction, will provide almost in real time an indication of the activity of the bath contained in the reactor, and therefore the efficiency of the biomass, thus allowing a very powerful piloting of the whole installation.

Figure 4 schematically illustrates a complete system derived from the installation described in Figure 1. This system makes it possible to transform toxic oils or solvents, in particular radioactive waste, into an acceptable liquid effluent for disposal in a station. treatment.

This system implements a biodegradation module M2 corresponding to the installation described in Figure 1, with the three specialized reactors 100, 200, 300 for metabolizing organic matter into water, carbon dioxide and biomass from specialized bacterial populations, different, which are contained in the respective bins 104, 204, 304.

As explained above, a certain class of molecules will be destroyed in the first reactor 100 (the simplest molecules to be degraded), then another class in the second reactor 200 and so on in the third reactor 300, the bacterial populations of each tank adapting themselves under the pressure of natural selection according to the organic molecules present in their environment. The first reactor 100 is fed with organic matter (oil H) and also with inorganic salts MMI necessary for biological growth. The three reactors 100, 200, 300 are supplied with air, are stabilized at a temperature of about 30 ⁰ C and their pH at a value between 6.5 and 7.5. Each reactor has at its exit a tangential filter which makes it possible to obtain an effluent without biomass designated EFF / N. On the other hand, during biodegradation, bacterial growth will generate biological sludge, resulting in an XBM excess biomass separated from the liquid phase.

The pre- and post-treatments applied to the different H, EFF / N and XBM fluxes of this biodegradation module M2 will now be described.

Very advantageously, the toxic oils or solvents are pretreated by reaction of Fenton in a chemical oxidation module M1. The Fenton reaction, itself well known, improves the biodegradability of organic oils and solvents and eliminates the antioxidants generally present in synthetic oils, which tend to inhibit biological activity. This reaction is based on a chemical oxidation at ambient temperature and pressure (therefore under very advantageous conditions), which uses the oxidizing power of the hydroxyl radical OH ^' , obtained by chemical reaction between hydrogen peroxide (hydrogen peroxide) H ₂ O ₂ and ferrous Fe ²⁺ ions in an acid medium, the hydroxyl radical reacting with the organic material to transform it into water and carbon dioxide. In this reaction, oxygenated water is a consumable, while ferrous ions are catalysts, because during the reaction the ferrous ion is transformed into Fe ³⁺ ferric ion which can be converted back into Fe ²⁺ ion by UV irradiation.

Concretely, this pretreatment can be performed in "batch": in a first step, the organic matter MO to destroy is introduced into the reactor already containing Fe ²⁺ ions, then the pH is lowered to 3.5 by sulfuric acid ratio, and the hydrogen peroxide is then added dropwise in stoichiometric proportions relative to the amount of organic material to be destroyed. The contents of the reactor are circulated throughout the reaction through a tube containing a UV lamp for transforming the Fe ³⁺ ion into Fe ²⁺ . Once the reaction is complete, the pH is raised to 10 by adding NaOH, which has the effect of precipitating the iron, which will sediment at the bottom of the reactor. The supernatant, which contains the partially oxidized organic material (without iron, which has sedimented at the bottom of the reactor and can be reused), is withdrawn and placed in a tank until it is transferred to the module M2, after its pH has been reached. readjusted to 7. Any gases formed during the reaction may be washed using a wash column of gas. The liquid used for this washing, which has captured the toxic products, can also be oxidized later, by a Fenton-type reaction.

With regard to the M2 module, the biodegradation of the oils H produces, on the one hand, an EFF / N effluent and, on the other hand, an excess of XBM biomass.

The excess XBM biomass generated during biodegradation in the M2 module is digested in an M3 module, so as to produce a solid mineral waste MIN concentrating the radioactivity of the organic material MO. In fact, the bacterial cells accumulate on their surface the heavy metals as well as the radioactive elements present in the medium, so that the excess of biomass concentrates the radioactivity resulting from the organic matter MO, and it is then necessary to mineralize this concentrate to be able to store it. The M3 module digester is a conventional anaerobic digester, the liquid phase of which is taken by tangential filtration to keep the biomass in the digester. The filtered aqueous phase can be subjected to a post-treatment with an M4 module (see below), while the contaminated biomass is extracted to constitute the final solid waste MIN, possibly after a chemical oxidation by reaction of Fenton.

The EFF / N effluent resulting from the biodegradation by the M2 module, and / or the LIQ liquid effluent resulting from the digestion of the biomass by the M3 module, is advantageously subjected to an oxidation post-treatment by a module M4, so as to give, respectively, a effluent EFF1 acceptable for the site and complies with standards (COD strictly less than 150 mg / l), and a effluent EFF2 recyclable.

The oxidation, which aims to destroy the soluble organic matter possibly present in these effluents, is advantageously carried out in the M4 modules by treatment combined with ozone and with UV rays, for example by means of an apparatus such as the UVOX-250 system from Wapure International GmbH, whose principle is to irradiate air with ultraviolet light in order to convert oxygen from the air to ozone, then inject the air / ozone mixture into the liquid to be treated via a Venturi system, the liquid to be treated being also irradiated by a light ultraviolet light. The ozone in solution is converted into OH ^' radicals with a very high oxidation power, thus eliminating a very large variety of residual substances. In particular, such a treatment makes it possible to do without a post-treatment by means of an activated carbon filter, which is not necessary. Irradiation with ultraviolet light also makes it possible to destroy almost all the microorganisms possibly present in the effluent to be treated.

Claims

1. A method of biological treatment of a toxic liquid charge comprising a dispersible and digestible organic liquid phase such as an oil or toxic solvent, characterized by the successive steps of: a) feeding with the liquid charge to be treated a first vat (100) containing an aqueous phase and a first bacterial population; b) solubilizing the liquid charge to be treated in the first tank by enzymatic hydrolysis with the first bacterial population; c) withdrawing from the first tank a first liquid reaction product; d) filtering the first reaction product biomass contained therein, to give a first effluent; e) feeding with the first effluent a second tank (200) containing an aqueous phase and a second bacterial population, different from the first; f) biodegrading the first effluent in the second tank by biological digestion with the second bacterial population; g) withdrawing from the second tank a second liquid reaction product; h) filtering the second reaction product from the biomass contained therein, to give a second effluent; i) adjust the bacterial concentration in the second tank by extracting surplus biomass; j) supplying with the second effluent a third tank (300) containing an aqueous phase and a third bacterial population, different from the first and second; k) reducing the residual bacterial components of the second effluent in the third vessel by biological action of the third bacterial population;

I) withdrawing from the third tank a third liquid reaction product; m) filtering the third reaction product from the biomass contained therein, to give a third effluent, the third effluent constituting an essentially inorganic final effluent effluent (EFF / N), and the separated biomass constituting an ultimate organic waste; (DU) of reduced volume.

2. The process of claim 1 wherein steps d), h) and / or m) further comprise recycling to the vessel from which the filtered reaction product has been withdrawn separate biomass. .

3. The process of claim 1, further comprising recycling to the first tank the final liquid effluent obtained in step m).

4. The method of claim 1, wherein step h) further comprises a chemical oxidation of the second effluent after filtering and / or excess biomass from the filtering.

The process of claim 1 wherein step k) comprises reducing the biomass in the third reactor (300).

The process of claim 1, further comprising, prior to step a), a Fenton reaction oxidation pretreatment (M1) of the liquid feed to be treated.

7. The method of claim 1, further comprising a step of withdrawing excess biomass in the first, second and / or third tanks, and digestion (M3) of this excess biomass with separation of a liquid phase. (LIQ) and a solid mineral waste (MIN).

The method of claim 1 or claim 7, further comprising a post-treatment step (M4), by combined UV irradiation and ozonation, of the final liquid effluent (EFF / N) from filtration of the third reaction product, and / or the liquid phase (LIQ) resulting from the digestion of the excess biomass.

9. An installation for implementing the method according to one of the preceding claims, characterized in that it comprises:

a first tank (100) containing an aqueous phase and a first bacterial population;

means (102) for feeding the first tank with a contaminated liquid charge comprising a dispersed organic liquid phase; ble and digestible such as an oil or toxic solvent, the liquid charge being able to be solubilized in the first tank by enzymatic hydrolysis with the first bacterial population;

means (106) for withdrawing from the first tank a first liquid reaction product;

means (108) for filtering from the first reaction product the biomass contained therein, to give a first effluent;

- a second tank (200) containing an aqueous phase and a second bacterial population, different from the first; means (202) for feeding the second tank with the first effluent, this first effluent being able to be biodegraded in the second tank by biological digestion with the second bacterial population;

means (206) for withdrawing from the second tank a second liquid reaction product;

means (208, 212) for filtering from the second reaction product the biomass contained therein, to give a second effluent;

means (216, 220) for adjusting the bacterial concentration in the second vessel by extracting the excess biomass; - a third tank (300) containing an aqueous phase and a third bacterial population, different from the first and the second;

means (302) for feeding the third tank with the second effluent, this second effluent being able to see its residual bacterial components reduced by the biological action of the third bacterial population;

means (306) for withdrawing a third liquid reaction product from the third tank;

means (308, 316) for filtering the third reaction product from the biomass contained therein, to give a third effluent, the third effluent constituting an essentially non-organic final effluent (EFF / N), and the separated biomass; constituting an ultimate organic waste (DU) of reduced volume.

The installation of claim 9, wherein said means for filtering the first, second and / or third product comprises a tangential membrane filter (108, 208, 308).

The installation of claim 9, wherein said means for filtering the second and / or third product further comprises a centrifugal separator (212, 312) and / or a flotation system.

12. The installation of claim 9, wherein the second tank (200) comprises means (226-234) for agitation and anti-foam mechanical clean suction of the foam formed during the biodegradation process and to incorporate this foam in the aqueous phase (204) contained in the tank.

13. The installation of claim 9, wherein the second tank (200) comprises, arranged in the recirculation circuit outside the volume of the tank: means (226-234) for pumping and recirculating the contents of the tank, as well as means (238, 240) for thermal regulation, means (222, 224, 242) for aeration of the liquid phase, means (244) for calibrated homogenization, and / or means ( 246) for measuring and / or sampling.

14. The installation of claim 9, further comprising a module (M1) prior oxidation by Fenton reaction of the liquid feed to be treated.

15. The plant of claim 9, further comprising means for withdrawing excess biomass in the first, second and / or third tanks, and a module (M3) for digestion of this biomass into exs with separation. a liquid phase (LIQ) and a solid mineral waste (MIN).

The installation of claim 9 or claim 15, further comprising a post-treatment module (UV), by combined UV irradiation and ozonation, of the final liquid effluent (EFF / N) from the filtration the third reaction product, and / or the liquid phase (LIQ) resulting from the digestion of the excess biomass.