FR2824752A1 - COMPOSITION FOR USE IN THE CONDITIONING OF SLUDGE - Google Patents

Abstract

The present invention relates to a composition, usable for conditioning sludge, obtained by mixing an aqueous solution containing a cationic polyelectrolyte with an aqueous solution containing an inorganic cation of charge greater than or equal to 2 and with an aqueous solution containing a surfactant. - anionic or amphoteric active.

Description

incident.

  COMPOSITION FOR USE IN THE CONDITIONING OF SLUDGE

  The present invention relates to a new composition which can be used in particular for conditioning sludge prior to its dewatering operation. The treatment of waste water, urban or industrial, in particular by blological way, leads to the production of sludge. This sludge o generally undergoes a mechanical dewatering operation (in particular filtration (for example filter press, belt filter), centrifugation), before being transported to a site of discharge, agricultural spreading or incineration. For example, sludge from the paper industry represents a very large part of the industrial sludge produced. These sludges from the paper industry, like those from the food industry, include, on the one hand, sludges of a biological nature (that is to say coming from a treatment of waste water by blological route) , and, on the other hand, sludge of a non-biological nature generally formed, in particular in the case of the paper industry, by sludge of physico-chemical origin or fibrous sludge containing mineral fillers, cellulose fibers,

  possibly coating latex.

  The sludge to be treated consists mainly of water in which biomass is dispersed. The treatments therefore aim to concentrate

  maximum dry matter and remove water.

  The current methods of sludge treatment are distinct according to the technique of water / biomass separation chosen (filter press, belt filter, centrifuge ...)). In addition, they generally require the successive addition of several reagents; it is indeed difficult to formulate, in a single composition and at significant concentrations, these different reagents, without leading to the formation of gels which can prove to be detrimental in terms of

  fluidity with the corresponding mixtures.

  The object of the present invention is to propose a new composition which can be used effectively in the conditioning of sludge, in particular making it possible to increase their dryness, that is to say to increase the dry extracts.

  obtained during the subsequent dehydration operation.

  s The object of the invention is also to propose a universal composition, that is to say one which can be used indifferently for the treatment of sludge prior to one or the other of the techniques of

  dehydration mentioned above.

  Furthermore, the composition according to the invention preferably has the advantage of not being subject to the gelling phenomenon mentioned above. More specifically, the main object of the present invention is a composition, usable for conditioning sludge, obtained by mixing (reaction) of at least one aqueous solution containing at least one cationic polyelectrolyte and at least one inorganic cation of higher charge or equal to 2 with at least one aqueous solution containing at least one agent

  surfactant, preferably anionic or amphoteric.

  The subject of the invention is also a composition, which can be used for the conditioning of sludge, obtained by mixing (reaction) of at least one aqueous solution or one containing at least one cationic polyelectrolyte only with at least one aqueous solution containing minus one mineral cation with a charge greater than or equal to 2 and at least one aqueous solution containing at least

  a surfactant, preferably anionic or amphoteric.

  It extends to a composition which can be used for the conditioning of sludges, being in the form of an aqueous solution comprising at least one inorganic cation with a charge greater than or equal to 2, at least one cationic polyelectrolyte and at least a surfactant, preferably

anionic or amphoteric.

  The mineral cation has a charge greater than or equal to 2. It is usually chosen from Mg2 +, Al3 +, Fe3 +, La3 +, Zr4 + and their polymerized forms when they exist. Preferably, said mineral cation is Al3 + or one of its polymerized forms. In general, the mineral cation is used

in non-polymerized form.

  This mineral cation is usually in the form of a water-soluble salt. Mention may be made, as water-soluble salts, of chlorides, nitrates, sulfates and acetates. In general, a soluble salt is used, free of the nitrogen element, which makes it possible to overcome any problems linked to its presence. Preferably, a chloride is used. The mineral cation can then be in the form of an aluminum chloride or one of its polymerized forms; more

  o preferably, it is then in the form of an aluminum chloride.

  The amount of mineral cation used is preferably between 0.05 and 2 moles, in particular between 0.49 and 1.8 moles, per kg of composition. The pH of the solution can be adjusted to prevent precipitation of the corresponding mineral salt. This adjustment is the responsibility of

one skilled in the art.

  As regards the cationic polyelectrolyte, it is preferably

  high molecular weight, in particular molecular weight of at least 1. 106.

  Said cationic polyelectrolyte advantageously has a weight

  o molecular from 1.1 o6 to 20.1 o6, in particular from 1.1 o6 to 10.1 o6.

  The cationic polyelectrolyte used can be in a linear form or, preferably, in a branched form; indeed, it was noted that the ramifications generally had a beneficial effect on the kinetics of

coagulation and flocculation.

  Polyacrylamides, polyethylene oxides, polyvinylpyrrolidones, and also polymers of natural origin, such as starch and its derivatives or gum, such as cationic polyelectrolyte, are particularly suitable as cationic polyelectrolyte.

  guar gum, as long as they are cationic.

  Preferably, the cationic polyelectrolyte is a polyacrylamide.

  o Said polyacrylamide can be cationic up to 100% in charge and, from

  preferably between 0.1 and 25%, for example between 0.1 and 15%, under load.

  The cationic polyacrylamide can be chosen from copolymers of polyacrylamide with cationic monomers or polyacrylamides

  modified according to Mannich resection.

  As examples of polyacrylamide cationic copolymers, there may be mentioned the acrylamide / ha logénu re copolymers preferably ch diallyldialkylammonium orure, the diaminoalkylmethacrylate / acrylamide copolymers and the dia l kylami noa lkyl methacrylate / acryl amide copolymers, the group

  alkyl preferably being C '- C6.

  The amount of cationic polyelectrolyte used is preferably at most 10%, in particular 0.1 to 6%, by weight of the composition. Advantageously, the polyelectrolyte cati on iq ue is a polyacrylamide copolymer, and preferably a polyacrylamide / chloride chloride copolymer.

  diallyldimethylammonium, in particular of molecular weight of the order of 3.106.

  It is then more preferably associated with an aluminum chloride in the composition. Generally, the mineral cation with a charge greater than or equal to 2, for example in the case of aluminum chloride, and the cationic polyelectrolyte, for example in the case of a high molecular weight amide polyacryl amide, are used. o in work in such a way that the molar ratio (mineral cation with a charge greater than or equal to 2) / (cationic polyelectrolyte) is between 1.102 and 8.1 o6 in particular between 1.103 and 8.1 o6. In the particular case of a composition comprising aluminum chloride and a polyacrylamide consisting of an acrylamide / diallyldialkylammonium chloride copolymer, especially of high molecular weight, a polyacrylamide / aluminum weight ratio of between 0.01 and 15, more particularly between 0.1 and 10; this relationship can be understood for example between

  0.2 and 6, especially between 0.25 and 4.5.

  The surfactant used in the invention is. preferably

so anionic or amphoteric.

  Very preferably, this surfactant is an ionic. Its non-ionic part (which can be formed of a hydrocarbon chain of hydrophobic character :: 5 and, optionally, of a polyalkoxylated chain of hydrophilic character, in particular polyethoxylated) can for example have an HLB value ("Hydrophilic Balance / Lipophilicity ") of not more than 10, in particular not more than 8,

or at most 4.

  The surfactant is preferably a surfactant which remains

  inert with respect to the mineral cation with a charge greater than or equal to 2.

  This tenlo-active agent provides a hydrophobic function

  especially vis-à-vis the application environment.

  By way of illustration of water-soluble surfactants which can be used as surfactant in the composition, mention may in particular be made of water-soluble lecithins, sucrose esters, aci esters of g ras (including Tweens), polyoxyethylenated alkylamides, triglyceride sulfetes, alkyl sulfetes (including sodium dodecyl sulfate (SDS)), alkyl ether sulfates, alkyl sulfonates, alkylamine salts, fatty amines, lipoamino acids, modified polyesters, silicone polymeric surfactants. The amount of surfactant used is preferably between 0.005 and 0.5 mole, in particular between 0.005 and 0.3 mole, per kg of composition; it can for example be between 0.01 and 0.2 mole,

  o in particular between 0.01 and 0.1 mole, per kg of composition.

  The composition according to the invention can be prepared by mixing at least one aqueous solution containing at least one cationic polyelectrolyte with at least one aqueous solution containing at least one mineral cation of charge greater than or equal to 2 and at least one aqueous solution containing at least one surfactant. The pHs of the three solutions are such, or adjusted (for example by adding an acid solution, in particular hydrochloric acid)) so that the pH of the composition according to the invention is preferably

  less than 2, in particular equal to 1 0.2.

  However, the composition according to the invention is advantageously prepared by mixing at least one aqueous solution A containing at least one cationic polyelectrolyte and at least one inorganic cation of charge greater than or equal to 2 with at least one aqueous solution B containing at minus a surfactant. Preferably, the aqueous solution A is obtained by adding, generally with stirring, the cationic polyelectrolyte to an aqueous solution containing said mineral cation; the aqueous solution then obtained is generally kept under stirring until the viscosity stabilizes. The aqueous solution B is usually prepared by mixing the surfactant.

  active in solid form with water.

  The pH of the aqueous solution A and that of the aqueous solution B are such, or adjusted (for example by adding an acid solution, in particular hydrochloric acid)) so that the pH of the composition according to the invention is preferably less than 2, in particular equal to 1 + 0.2. The pH of the aqueous solution B used is for example understood or adjusted to a value

between 1.3 and 1.9.

  The aqueous solution A generally provides the largest part (for example at least 80%, in particular at least 90%) of the total volume of water

  contained in the composition according to the invention.

  The mixtures are generally carried out between 10 and 75 ° C., for example at the amblage temperature, and with stirring. Preferably, the preparation conditions are such that the composition according to the invention is presented under

  form of a homogeneous solution, in particular monophasic.

  o The compositions according to the invention find a particularly advantageous application in the chemical conditioning of sludge, in particular of sludge from sewage treatment plants or wastewater, urban or industrial: its incorporation in sludge, which can be subjected prior to an anaerobic digestion treatment, it is possible to structure them in such a way that the water contained in these sludges is better exuded during the following dehydration operation. The efficiency of the mechanical dehydration operation such as filtration or centrifugation can thus be improved, the volumes produced after this dehydration being

  reduced by obtaining a high dryness cake.

  o The amount of composition according to the invention used during the conditioning of a sludge is such that it generally corresponds from 0.05 to 3 times, preferably from 0.1 to 2 times, the amount of filler theoretical cationic necessary to neutralize the quantity of anionic charge of the sludge to be treated; in other words, the quantity of this composition used is such that it has, in absolute value, a cationicity generally equal from 0.05 to 3 times, preferably from 0.1 to 2 times, the anionicity of the sludge to be treated. The composition according to the invention can be diluted before use. The compositions according to the invention are especially suitable in the case of sludge from the paper industry, or from the food-processing industry, and containing, on the one hand, sludges of a biological nature, and, d on the other hand, sludge of a non-biological nature (sludge of physico-chemical origin or sludge

o fibrous).

  In addition, it has been found that the products constituted by sludge of biological nature and by that of non-biological nature are often incompatible. Thus, the sludge of biological nature usually exhibits a dissimilar, even divergent, behavior from that of other sludges of different nature, when all of this sludge undergoes conditioning and dewatering treatment. It has been observed that, in general, these biological sludges have a slow sedimentation rate, give rise to fermentation reactions and their dehydration is not

not easy.

  o In this context, the invention also aims to provide a process for dewatering sludge from the paper industry or sludge from the food industry, this sludge containing sludge of biological nature and sludge from non-biological nature, process in which said biological sludge is pretreated separately with at least one composition according to the invention, then mixed after said pretreatment with non-biological sludge, the mixture of sludges thus formed then being subjected (optionally after another conditioning step) to a dehydration operation. This can make it possible in particular, by making, prior to the dewatering operation, compatible / assimilable the so sludge of biological nature with the other sludge of different nature, to obtain a good behavior of all of the sludge in dewatering and a dryness

high finish.

  In general, the composition according to the invention can be used in the treatment of aqueous media, for example waste water or industrial aqueous effluents, and more particularly in the clarification of waste water of urban or industrial origin. It can also be used for the detoxification of effluents loaded with polluting species (in particular arsenates, chromates, leadates) and for the decantation of port or lagoon vessels. It can be used as an aid in the filtration of mineral oxides or in the treatment or manufacturing processes of

  paper. It can also be used for mineral processing.

Claims (24)

  1. Composition obtained by mixing at least one aqueous solution containing at least one cationic polyelectrolyte and at least one mineral cation of charge greater than or equal to 2 with at least one aqueous solution containing at least one surfactant, preferably anlonic or amphoteric. 2. Composition obtained by mixing at least one aqueous solution o containing at least one cationic polyelectrolyte with at least one aqueous solution containing at least one mineral cation of higher charge or   equal to 2 and at least one aqueous solution containing at least one surfactant   active, preferably anionic or amphoteric.   3. Composition in the form of an aqueous solution comprising at least one inorganic cation of charge greater than or equal to 2, at least one cationic polyelectrolyte and at least one surfactant, of   preferably anionic or amphoteric.   4. Salt composition in one of the res ications 1 to 3, characterized in that said mineral cation is chosen from Mg2 +, La3 +, Fe3 +, Al3 +, Zr4 + and their   o polymerized forms when they exist.   5. Composition according to resale icati on 4, characterized in that led it   mineral cation is Al3 + or one of its polymerized forms.   6. Composition according to one of claims 1 to 5, characterized in   that said general cation is in the form of a hydrosol ub le. of   preferably chosen from chlorides, nitrates, sulfates and acetates.   7. Composition according to one of claims 1 to 6, characterized in   that said mineral cation is in the form of an aluminum chloride.   8. Composition according to one of claims 1 to 7, characterized in   that said mineral cation is used in an amount of 0.05 to 2 moles,   so particular from 0.49 to 1.8 moles, per kg of said composition.   9. Composition according to one of claims 1 to 8, characterized in   that said cationic polyelectrolyte has a molecular weight of at least 1.106.   10. Composition according to one of claims 1 to 9, characterized in   that said cationic polyelectrolyte is chosen from polyacrylamides, polyethylene oxides, polyvinylpyrrolidones, polymers of origin natural cationic.   11. Composition according to one of claims 1 to 10, characterized in   that said cationic polyelectrolyte is a polyacrylamide, preferably   with between 0.1 and 25% cationic charge.   12. Composition according to one of claims 1 to 11, characterized in   that said cationic polyelectrolyte is chosen from copolymers of polyacrylamide with cationic monomers or polyacrylamides   modified according to the Mannich reaction.   13. Composition according to one of claims 1 to 12, characterized in   that said cationic polyelectrolyte is a cationic polyacrylamide copolymer chosen from acrylamide / halogen copolymers, preferably diallyldialkylammonium chloride, diaminoalkylmethacrylate copolymers I   acrylamide and dialkylaminoalkylmethacrylate / acrylamide copolymers.   14. Composition according to one of claims 1 to 13, characterized in   that said cationic polyelectrolyte is used at a rate of at most 10%,   preferably 0.1 to 6%, by weight of said composition.   o 15. Composition according to one of claims 1 to 14, characterized in   what said mineral cation is in the form of an aluminum chloride and it is polyelectro lyte cation i which is a copolymer of acryl amide / ch loride   diallyldimethyllammonium, in particular of molecular weight of the order of 3.106.   16. Composition according to one of claims 1 to 15, characterized in   s that the mineral ed it cati on and led it polyelectro lyte cation iq ue are implemented in such a way that the ratio of mineral cation to cationic polyelectrolyte   is between 1.102 and 8.106, in particular between 1.103 and 8.106.   17. Composition according to claim 16, characterized in that when, on the one hand, said mineral cation is in the form of an aluminum chloride so, and, on the other hand, said cationic polyelectrolyte is an acrylamide copolymer / diallyldimethyllammonium chloride, the polyelectrolyte / aluminum weight ratio is between 0.01 and 15, more particularly between 0.1 and 10.   18. Composition according to one of claims 1 to 17, characterized in   that said surfactant is an ionic.   s 19. Composition according to one of claims 1 to 18, characterized in   that said surfactant is used in an amount of 0.005 to 0.5 mole,   particular from 0.005 to 0.3 mole, per kg of said composition.   20. Application of at least one composition according to one of   Claims 1 to 19 for the conditioning of sludge.   21. Application according to claim 20, characterized in that the sludge comes from the purification of waste or waste water, with a view to their dehydration. 22. Application according to claim 20, characterized in that the   sludge comes from the paper or food industry.   23. Process for dewatering sludge from the paper industry or sludge from the food industry, this sludge containing sludge of biological nature and sludge of non-biological nature, process in which said sludge of biological nature are pre-processed separately   with at least one composition according to one of claims 1 to 19, then   mixed after said pre-treatment with non-biological sludge, the sludge mixture thus formed is then subjected to a dewatering operation. 24. Application of at least one composition according to one of   Claims 1 to 19 for the treatment of aqueous media.