WO2015114254A1

WO2015114254A1 - Method for treating water

Info

Publication number: WO2015114254A1
Application number: PCT/FR2015/050200
Authority: WO
Inventors: Laura CROWTHER-ALWYN; Tamara Putois; Medhi CARRE
Original assignee: Roquette Frères
Priority date: 2014-01-29
Filing date: 2015-01-29
Publication date: 2015-08-06
Also published as: FR3016877A1

Abstract

The invention relates to a method for treating an aqueous solution containing suspended matter, said method containing a step of coagulation-flocculation, which comprises: a) a step of adding coagulants to the aqueous solution to be treated, followed by; b) a step of stirring the aqueous solution to which the coagulants have been added; c) a step of separating the coagulated solids by decanting or flotation; and d) a step of recovering purified water; characterised in that the coagulants added in step a) comprise at least a tannin which is modified or not, and an amylaceous liquid composition containing a solubilised cationic starch. The invention also relates to a liquid composition of cationic starch and tannin that can be used in the method.

Description

PROCESS FOR TREATING WATER

The subject of the invention is a method for treating water, in particular a method comprising a coagulation-flocculation step using, together with at least one tannin, a solubilized cationic starch liquid starch composition. This process is very useful for the treatment of effluents. The invention also relates to a liquid composition comprising both a solubilized cationic starch and at least one tannin. In the field of water, the treatment processes are very diverse: for example, before being released into the environment, the wastewater (or effluents) are not treated identically according to the nature of the water . It is for the treatment of these effluents to comply with the regulations regarding water released after treatment, the purity of this water may be more or less important depending on the case. On the contrary, as far as drinking water is concerned, regulations require very high purity water at the end of the process.

The waters to be treated are aqueous solutions that include suspended solids that must be removed by treatment.

For larger particles, generally greater than 1 mm, they can be removed in a preliminary step by passing the aqueous solution through grids. This step is also called "screening step".

The finer particles in suspension can also be removed by separating them from the aqueous solution to be treated, for example by decantation or by flotation.

Decantation consists of allowing the solution to settle in a settling tank, also called a "settling tank", so that the suspended particles are deposited at the bottom of this tank. The purified water is thus recovered by overflow.

Flotation has the principle of mixing in a float the aqueous solution with air, in order to recover the particles on the surface. The water thus treated is recovered at the outlet of the float.

In order to separate these fine particles more easily and more quickly, a coagulation and / or flocculation step is carried out beforehand. In a schematic manner, these steps consist in the agglomeration of the particles in suspension, these larger agglomerated particles are then separated more easily and more quickly by the separation treatments mentioned above. To achieve coagulation and flocculation, coagulants and flocculants are used alone or in mixture. These agents may be, for example, chosen from iron or aluminum salts, poly (diallyldimethylammonium) polychlorides (polyDADMAC), anionic or cationic polyacrylamides and nonionic, anionic or cationic starches.

Generally, the coagulating agent and the flocculating agent are mixed in two distinct stages with the aqueous solution to be treated in a tank, called coagulation-flocculation tank in the present application. This tank is generally composed of a first pool called "coagulation basin" and a second basin called "flocculation basin", in which are introduced respectively coagulant and flocculant. These coagulation phenomena are generally explained by a destabilization of the particles, in particular colloids, and of flocculation by the aggregation of these destabilized particles. Then, the aqueous solution comprising agglomerates of particles or colloids, called flocs, undergoes a separation step: sludge consisting of agglomerated flocs and purified water are thus recovered.

However, the coagulants and flocculants can be introduced simultaneously as described for example in the document WO 201 1/123970 A1 where it is a method of treating a contaminated water with algae which comprises a step of addition a treatment composition comprising a metal inorganic coagulant and a cationic polymer, which may be a water-soluble cationic starch, a water-soluble mixture of starch and cationic gum, or a modified tannin soluble in water; water.

One of the problems of this process is that the use of inorganic metal coagulant generates large quantities of sludge that must be reprocessed, which generates an additional cost for the operator. In addition, following the publication of several studies on the health risk of certain coagulants, including aluminum salts, these coagulants have a bad image with public authorities and consumers.

Document CN 101602553 A describes a process for treating a water contaminated with cyanobacteria, comprising a flocculation step. This flocculation step can be done using tannin, starch and polyacrylamide. In this case, proceed as follows: A first addition of a tannin is carried out,

Followed by stirring of the solution thus added,

• then a second addition without stirring of a mixture of a starch and a polyacrylamide is made in order to agglomerate and separate the formed flocs.

No indication of the form of the starch is given in this document.

Although generally very effective, tannins are also products whose cost still remains high today. This is partly due to extraction processes that are expensive and difficult.

Since coagulation and flocculation are two phenomena that can not always be clearly distinguished, these steps are grouped together under the term "coagulation-flocculation" step for the present invention.

Other types of aqueous solution to be treated include emulsions such as paints or paper coating sauces. This is usually referred to as "emulsion breaking process" in which the object is to destabilize the emulsion by coalescing the oil phase by adding a coagulant and / or a flocculant. This may be, for example, cationic starch as described in US Pat. No. 4,088,600.

To measure the effectiveness of this coagulation-flocculation step, it is possible to measure the Chemical Oxygen Demand (COD) of the purified water, which is an indirect measure of the concentration of organic or inorganic matter, dissolved or suspended in this water: the quantity of oxygen necessary for the total chemical oxidation of these materials is measured. Measurement of the amount of organic carbon dissolved in the treated water can also be achieved.

Alternatively, it is also possible to measure the turbidity level of the aqueous solution, or turbidity, before and after this coagulation-flocculation step.

This turbidity is measured by a nephelometer (also called a turbidimeter) and is measured in Nephelometric Turbidity Units (NTU or NTU for

Nephelometric Turbidity Unit).

The reduction of turbidity that can be expressed as a percentage is thus determined.

Another means is also to measure the absorbance of the aqueous solution treated at a given wavelength to estimate a color abatement. There is still a need for new water treatment processes. In particular, it is of interest that this method can be achieved by using a fast treatment time, using a small amount of chemicals, and this without modifying the facilities conventionally used for these treatments. It must be able to significantly reduce the turbidity of the treated water. It must also generate small amounts of sludge.

This is what the Applicant was able to implement by carrying out work on water treatment processes.

Indeed, the Applicant has found that a water treatment method using as a coagulant cationic starch associated with a tannin was particularly advantageous in reducing the turbidity of many effluents in comparison with the processes using these coagulants alone, or to propose a solution presenting a particularly advantageous cost / performance compromise. This process has been particularly interesting for example when it comes to breaking an emulsion.

In particular, the invention relates to a method of treating an aqueous solution having suspended solids, containing a coagulation-flocculation step which comprises:

a) a step of adding coagulants in the aqueous solution to be treated, followed;

b) a stirring step of the aqueous solution thus added;

c) a step of separating the coagulated solids by decantation or flotation;

d) a step of recovering a purified water;

characterized in that the coagulants added in step a) comprise at least one modified or unmodified tannin and a starchy liquid composition containing a solubilized cationic starch.

This process is made particularly effective by the flocculation coagulation step using the addition of two coagulants: a tannin and a starchy liquid composition containing a solubilized cationic starch. In contrast to the process described in document CN101602553 A, a stirring step of the two coagulants, and in particular of the starchy liquid composition, must be carried out before carrying out the separation step. The process according to the invention can be used for the treatment of any type of aqueous solution but is particularly useful for the treatment of effluent. This effluent can be of any type, for example a refinery effluent, a dairy effluent, a slaughterhouse effluent, an ink factory effluent, an ink formulator or an ink user, an effluent of brewery, a paint factory effluent, paint formulator or paint user, a stationery effluent, a textile industry effluent, in particular an effluent from a dyeing plant or a laundry effluent.

According to one variant, the process according to the invention is not a water purification process.

The aqueous solution may also be an emulsion. The process according to the invention is particularly effective for separating an organic phase from an aqueous phase and thus for treating and breaking an emulsion. It may be for example a paint emulsion, a coating color emulsion, a cutting fluid, also called "cutting oil", or an ink emulsion. The emulsion may have water-in-oil phases, oil-in-water phases, water-in-oil phases or oil-in-oil phases.

An emulsion breaking process is described in the examples below.

The aqueous solution comprising suspended solids to be treated may have a very high turbidity, which may be greater than or equal to 50 NTU, for example greater than 100 NTU, or even greater than 500 NTU, especially greater than 1200 NTU.

According to a first variant of the process according to the invention, the tannin and the starchy liquid composition are added separately in step a). Advantageously, the time between the introduction of the tannin and the introduction of the liquid starchy composition during step a) is less than 120 seconds, for example less than 90 seconds, advantageously less than 60 seconds.

According to the process of the invention, the order of introduction of the tannin and the liquid starchy composition does not matter. According to a second variant of the process according to the invention, the tannin and the starchy liquid composition are added simultaneously to step a). According to this variant, the tannin and the starchy liquid composition can be added in step a) via a liquid composition M comprising both the solubilized cationic starch and the tannin, which simplifies the process and requiring a single dosage unit to introduce the two coagulants in step a) of the method.

The total quantity of cationic starch and tannin in the aqueous solution to be treated, that is to say the amount of these two coagulants, can range from 1 to 500 mg / L of water to be treated. This quantity is in particular adapted to the turbidity of the initial water and may be from 5 to 350 mg / l, advantageously from 8 to 250 mg / l, preferably from 10 to 200 mg / l, most preferably from 12 to 190 mg / l. L.

When several tannins and / or several cationic starches are added during step a), it is specified that the amounts of tannin are the total amounts in these different tannins and that the amounts of cationic starch are the total amounts in these different tannins. cationic starches. It is also specified that the mass quantities of each of the coagulants are in dry mass.

The tannin may be added during step a) in the form of a liquid solution, for example having a concentration ranging from 0.01 to 60 g / l.

The tannin used in the process of the invention may be modified or unmodified. Preferably, the tannin is a modified tannin, most preferably a cationic tannin.

By unmodified tannin is meant according to the present invention phenolic compounds having a molar mass ranging from 300 to 20000 Da, preferably from 500 to 3000 Da. Preferably, these unmodified tannins are water soluble.

Among the tannins, mention may be made of the products of the esterification of the hydroxyl functions of glucose or of a polyol derived from glucose by acids such as gallic acid, cinnamic acid and, more generally, polyphenolic acids. More particularly, mention may be made of gall tannins which may come from plants of the Ericaceae family, geraniaceae, aceraceae, ellagic tannins resulting from the reaction of glucose with hexahydroxydiphenic acid, which may be derived from oak gall, dihydroellagic tannin resulting from oxidation of tannin ellagic, oligomeric tannins, formed of gallic acid, ellagic acid and 2000 to 5000 oses, for example the rugosin of the meadow-queen, and the hamamelitannin of witch hazel. It may also be complex tannins that are constructed by a gallotannin or ellagitannin unit with catechin binding.

Another type of tannin useful for the invention may be condensed tannins also called catechin tannins or proanthocyanidols, which include polymers of flavones-3-ol and / or anthocyanidins. By way of example, mention may be made of procyanidols generally derived from fruits such as catechol, epicatechol, gallocatechol and epigallocatechol. Type B procyanidols comprise a single interflavanic bond (C4 and C8) and type A procyanidols comprise two flavanic bonds (C4 and C8 and C2 and C1). These tannins, in particular proanthocyanidols, may be derived from horse chestnut and cinnamon, the anthocyanidins (generally from cypress) may be for example delphinidol and cyanidol. Most condensed tannins are anthocyanidins or proanthocyanidols.

The tannin useful for the invention may also be a modified tannin. By modified tannin is meant a polymer comprising in its polymer backbone at least one unit derived from a tannin.

According to a first variant, the modified tannin may be a copolymer of a tannin and a cationic monomer. According to another variant, the modified tannin may be a copolymer of a tannin, a cationic monomer and an additional monomer, which may be an anionic monomer or a nonionic monomer. Such tannins are described for example in US Patent 5,614,103.

The cationic monomer may be chosen from monomers carrying an ethylenic unsaturated bond of quaternary ammonium, phosphonium or sulphonium type, preferably of quaternary ammonium type. These monomers may in particular be ammonium salts of dialkylaminoalkyl (meth) acrylamide, ammonium salts of dialkylaminoalkyl (meth) acrylates or diallyl dialkyl ammonium salts. Examples of these monomers are methylaminoethyl methacrylate, Ν, Ν-dimethylaminoethyl methacrylate, acryloyloxyethyltrimethylammonium chloride (AETAC), methacryloyloxyethyltrimethylammonium chloride (METAC), acryloyloxyethyltrimethylammonium methosulfate (AETAMS), methosulphate of methacryloyloxyethyltrimethylammonium (METAMS) and acryloyloxyethyldiethylmethyl ammonium chloride.

The anionic monomer may be chosen from monomers carrying an ethylenic unsaturated bond of carboxylic acid or sulphonic acid type. These monomers may be (meth) acrylic acid, itaconic acid, maleic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropanesulphonic acid (AMPS), 3-allyloxy acid, and the like. 2-hydroxypropanesulphonic acid or a salt thereof.

The nonionic monomer may be, for its part, chosen from nonionic monomers carrying an ethylenic unsaturated bond, such as, for example, (meth) acrylamide, N-methylolacrylamide, Ν, Ν-dimethylacrylamide, vinyl esters. such as vinyl acetate or propionate, (meth) acrylic esters such as alkyl (meth) acrylates, hydroxylated alkyl (meth) acrylates, allyl and glycidyl ether, ethoxylated allyl of polyethylene glycol or polypropylene glycol and propoxylated acrylates.

The modified tannin useful for the invention may especially be obtained by copolymerization of 10 to 80% by weight of tannin, 20 to 90% by weight of cationic monomer, 0 to 30% by weight of nonionic monomer and from 0 to 30% by weight. 20% by weight of anionic monomer, the sum of the monomers being 100%.

Typical examples of modified tannins that can be used according to the invention are copolymers of tannin and cationic monomer in which the proportions of cationic monomer range from 50 to 90% by weight, the balance being tannin.

The modified tannin can be prepared by mixing the various monomers with the tannin and initiating the polymerization using a radical initiator, using for example the solution or emulsion polymerization techniques. Azo, persulfate and peroxide compounds can be used as initiator. These initiators can also be used at the end of the reaction in order to polymerize the residual monomer. A chain transfer agent may also be used to regulate the molecular weight of the modified tannin. The weight average molar mass can vary widely and range from 500 to 2,000,000 g / mol, for example from 5,000 to 200,000 g / mol. The polymer can be separated by precipitation or it can also directly use the aqueous solution obtained after the polymerization. The reaction temperature can vary widely and can range in particular from 20 to 100 ° C, preferably 40 to 70 The pH may also vary widely and may be between 2 and 8.

A first example of modified tannin is a copolymer of tannin and acryloyloxyethyltrimethylammonium chloride (AETAC).

Another example of modified tannin relates to a copolymer of tannin and acryloyloxyethyltrimethylammonium chloride (METAC).

Another example of modified tannin is a cationic copolymer of tannin and Ν, Ν-dimethylaminoethyl methacrylate. This copolymer can be produced by a process comprising a step of polymerizing N, N-dimethylaminoethyl methacrylate followed by a step of cationizing the polymethacrylate with hydrochloric acid, followed by a step of copolymerizing the cationized polymethacrylate with tannin.

According to a preferred variant, the modified tannin is obtained by reacting a tannin, an amine and an aldehyde, such as those described in US Pat. No. 4,558,080. According to the latter, the constituents react at acidic pH in an amine / tannin molar ratio ranging from about 1.5: 1 to 3: 1. These modified tannins can be tannin / melamine / formaldehyde or tannin / monoethanolamine / formaldehyde type.

Preferably, the modified tannin is a cationic tannin. The level of cationicity can be measured in several ways, for example by ionicity measurement by titration using sodium polyethylenesulphonate and a Streaming Current Detector (SCD) type flow detector. Preferably, the ionicity of the cationic tannin ranges from 100 to 5000, most preferably from 500 to 3500 μeq per gram of tannin.

According to the process of the invention, the mass ratio cationic starch / tannin is advantageously from 5/95 to 44/56, preferably from 10/90 to 40/60, most preferably from 15/85 to 30/70.

The Applicant has indeed found that the coagulation-flocculation step is particularly effective when these coagulants are introduced in the ratios above.

The starchy cationic starch liquid composition introduced in step a) advantageously has a cationic starch concentration ranging from 0.01 to 50 g / l. The liquid of the composition may be any solvent of the cationic starch and is preferably water. The starchy liquid composition useful in the invention comprises a solubilized cationic starch.

The cationic starch used in the context of the invention can be obtained from any type of native starch of natural or hybrid origin, including starch derived from plant organisms having undergone genetic mutations or manipulations. Said starches may in particular be derived from potato, high amylopectin potato (waxy potato), wheat, high amylopectin wheat (waxy wheat), corn, high grade corn amylopectin (waxy corn), high amylose maize, rice, peas, barley or cassava, cuts or fractions thereof, and any mixtures of any two or more of the products above.

The cationic starch used in the process of the invention may advantageously be obtained from a pea starch, wheat, corn or potato starch. According to a first preferred variant, it is a potato starch. According to a second preferred variant, it is a waxy starch, it may in particular be derived from waxy corn, waxy potato, waxy wheat, waxy barley, most preferably from waxy corn. Waxy starches have the advantage of having a lower retrograde capacity than other starches.

The selection of this native starch has in particular an influence on the final molecular weight and on its branching rate, related to the amylose and amylopectin content.

The cationization reaction can be carried out according to one of the methods well known to those skilled in the art, using cationic reagents as described for example in "Starch Chemistry and Technology" - Vol. He - Chapter XVI - R. L. WHISTLER and E. F. PASCHALL - Academy Press (1967). The starch is introduced into a reactor in the presence of these reagents.

The starch used in the cationization reaction may be in a granular form, for example when used in the native state.

The reaction may be conducted in the milk phase, wherein the granular starch suspended in a solvent is cationized using the conditions of temperature, time and catalysis well known to those skilled in the art.

At the end of the reaction, the starch thus cationized can be recovered by filtration, this cationic starch can then be washed and then dried. Alternatively, the reaction can be carried out in the dry phase, that is to say in the presence of quantities of water added to the starch considered as low, for example in amounts of water of less than 20%. the starch mass introduced for the cationization reaction, preferably less than 10%.

Preferably, the cationization reaction is carried out with nitrogen-containing reagents based on tertiary amines or quaternary ammonium salts. Among these reagents, it is preferred to use 2-dialkylaminochlorethane hydrochlorides such as 2-diethylaminochloroethane hydrochloride or glycidyltrimethylammonium halides and their halohydrins, such as N- (3-chloro-2-hydroxypropyl) trimethylammonium chloride. this latter reagent being preferred. This reaction is carried out in an alkaline medium, at a pH greater than 8, or even 10, the pH being adjustable for example by sodium hydroxide.

The levels of reagent used are chosen such that the resulting cationic starches have the degree of substitution (DS) of desired cationicity, the DS being the average number of OH groups included on the anhydroglucose of the starch which have been substituted with a cationic group.

The cationic starch may be soluble at room temperature in water. By soluble at room temperature is meant according to the invention that, when the cationic starch is introduced at 10% by weight in water at 25 ° and is stirred for 1 hour, the starch solution thus obtained has a Brookfield viscosity greater than or equal to 100 mPa.s.

According to a first variant, the starch soluble at room temperature in water is a cationic granular starch having a degree of cationic substitution (DS) greater than or equal to 0.10. According to a second variant, it is a pregelatinized cationic starch. This pregelatinization treatment of cationic starch can be carried out for example on a drying drum.

To make the starchy composition useful for the invention, any type of cationic starch can be solubilized in a solvent, the liquid starchy composition generally being an aqueous composition.

In order to manufacture the liquid starchy composition useful in the invention, the cationic starch in the solvent can be rendered soluble by a cooking step. This cooking is generally carried out in water by suspending cationic starch and thus forming a starch milk. The cooking temperature is example in the temperature range of 40 to 95 ° C, preferably 60 to 90 ° C. The cooking time can range from 5 minutes to 60 minutes. The mass quantity of cationic starch in this milk may be in the range of between 10 and 50%, for example between 20 and 40%.

According to one variant, said starchy composition is prepared by using a soluble cationic starch at room temperature and by putting it in solution in water, preferably with stirring. This variant is advantageous because the starch is thus easily solubilized in the liquid composition without cooking. The starchy composition useful for the invention can thus easily be used on the site carrying out the treatment process.

The cationic starch may have a degree of cationic substitution (DS) greater than or equal to 0.03, advantageously ranging from 0.035 to 0.2.

According to an advantageous variant of the invention, a cationic starch-free liquid cationic starch composition containing a preservative is used.

When the cationic starch is in liquid form, degradation can be observed during storage and transportation of the product. To limit this phenomenon, it is generally necessary to add a biocidal agent, which may be chosen from phthalates, for example one of those marketed by the Dow Chemical Company under the trademark VINYZENE ™. However, although the concentration of biocidal agent necessary for the storage of the starch in the form of a liquid solution is low, these biocidal agents may constitute unwanted constituents for the treatment of a water and particularly for the production of water. drinking water. The fact that the starch is stored and transported in solid form limits the problems of degradation. This makes it possible to dispense with the addition of a preservative, which may be particularly advantageous in a water treatment process.

Thus, according to a variant of the process, a preservative-free cationic starch solution is prepared less than twenty-four hours before the addition step a) from a cationic starch in solid form. for example in the form of a powder.

Although other coagulating or flocculating agents may be used during the coagulation-flocculation step, the latter may be carried out without any additional coagulant agent, in particular without polyacrylamide and without metal salt. Although other coagulants or flocculants may be used in the water treatment process, this may be done without any additional coagulant, particularly without polyacrylamide and without metal salt. Preferably, the cationic starch has a viscosity, when in the form of an aqueous composition, greater than or equal to 100 mPa.s and less than 1000 mPa.s under the conditions of Test A described below.

Test A consists in measuring the Brookfield viscosity at 25 ° C. of the cationic starch when it is in solubilized form in an aqueous 10% dry matter composition. In other words, the aqueous composition useful for test A is a composition made up of 10% solubilized cationic starch and 90% water. Thus, to carry out the test A on an aqueous composition comprising a solubilized cationic starch, it is sufficient to quantify, by any conventional method within the reach of those skilled in the art, the dry matter cationic starch of said aqueous composition and, as the case may be, diluting it with distilled water or concentrating it by any appropriate means which is not likely to significantly modify the cationic starch it contains, so as to adjust the dry matter to cationic starch of said composition at a value of 10%. As a result, the viscosity of the resulting composition is measured in a manner known per se. To concentrate the composition without modifying the starchy material comprising it, it is possible, for example, to use a rotary evaporator.

One advantage is that this starch can easily be converted into an aqueous composition concentrated in cationic starch while remaining liquid, which facilitates its transport but also its handling during the implementation of the method according to the invention.

The viscosity of the cationic starch is directly related to the cationic starch used and to the process for preparing the amylaceous composition.

As regards the cationic starch, its viscosity depends on three main characteristics, in descending order of importance: its molecular weight, its branching rate and its degree of cationic substitution (DS). These characteristics are readily selected by those skilled in the art by choosing the botanical source of the native starch and the conditions of preparation of this cationic starch. For this cationic starch which has a Brookfield viscosity, measured according to test A, greater than or equal to 100 mPa.s and less than 1000 mPa.s, it is generally necessary to also perform a step of reducing the molar mass of the starch in addition to a cationization step of the starch as described above.

These two steps of molar mass reduction and cationization can be done in any order. Thus, the cationic starch useful in the invention can be obtained in a process comprising a first cationization step followed by a second step of reducing the molar mass of the cationic starch obtained in the first step. Alternatively, the cationic starch useful in the invention can be obtained in a process comprising a first step of reducing the molar mass of the starch followed by a second step of cationization of the starch of reduced mass obtained in the first step. It is also possible to use a process in which the cationization step and the step of reducing the molar mass of the starch take place simultaneously.

The step of reducing the molar mass of the starch can be carried out by any means, in particular chemical, enzymatic and / or physical, known to those skilled in the art and suitable for obtaining directly or indirectly cationic starch having the appropriate viscosity according to test A. This step can be carried out in the solvent phase or in the dry phase. This step can be carried out continuously or discontinuously, in one or more substeps, according to a multitude of variants as to the botanical nature of the starch, the amount or the form of presentation of the modifying means, the temperature of the medium. reaction, the reaction time, the water content or the cationicity of the starch (material already cationized or not yet cationized).

It may be in particular a fluidification treatment by chemical means, in aqueous medium or in the dry phase, such as those mentioned or described in patent EP902037 in the name of the Applicant.

It may also advantageously be an enzymatic fluidification treatment (also called enzymatic conversion or liquefaction), which can be carried out, for example, according to the teachings of patent FR 2,149,640 in the name of Applicant. These enzymatic means include enzymes, thermostable or not, of alpha-amylase type of bacterial origin, fungal or other.

It may also be, in another advantageous manner, a treatment for efficiently converting the cationic starchy material in an aqueous medium, using enzymes selected from the group comprising the branching enzymes (EC 2.4. 1 .18) and cyclodextrin glycosyltransferases or "CGTases" (EC 2.4.1.19). The branching enzymes may especially consist of starch or glycogen branching enzymes, isolated from algae or bacteria, such as those whose use is described in patents WO 00/18893 and WO 00/66633. in the name of the Claimant.

The Applicant Company has observed that the cationic starches treated, before, during or after cationization, with a branching enzyme generally have an improved storage stability compared with those treated with an alpha amylase. Without wishing to be bound by any theory, the Applicant believes that this remarkable result is due, at least in part, to the fact that a branching enzyme treatment makes it possible to obtain hydrolyzed starchy materials which are more homogeneous, ie especially of which the saccharides The resulting constituents have molecular weights distributed over a generally more uniform, symmetrical and narrower Gaussian curve than that obtained with alpha amylase. Preferably, the branching enzyme treatment is carried out after the cationization step and it is moreover remarkable and surprising that the presence of relatively large cationic groups does not interfere with the action of oligomeric chain transfer. or polysaccharide of such enzymes.

The use of thermostable enzymes allows, if desired, the practice of enzymatic liquefaction at temperatures of the order of 90 - 100 ° C, particularly advantageous conditions for obtaining liquid starchy compositions having a good stability of the viscosity over time.

The modifying treatment may also, by way of nonlimiting examples, use a fluidification associating acidic and enzymatic route.

All the aforementioned means are applied to the starch, already cationized or not, to obtain the preferred viscosity of the cationic starch.

According to a preferred embodiment, a cationization of the starch is carried out in a first step, for example in the milk phase or in the dry phase, followed by second step of reducing the molecular mass obtained during the first step by enzymatic conversion, this second step can be carried out in the solvent phase, preferably in water. According to this preferred embodiment, a liquid starchy composition useful for the invention can be obtained directly.

Those skilled in the art will be able to adjust the reaction conditions of the steps for reducing the molar mass and of the cationization of the starch in order to obtain cationic starches making it possible to obtain the liquid starchy composition useful for the invention. Indeed, it is necessary that, during its manufacturing process, the molecular weight of the starch is not reduced too much or, on the contrary, insufficiently: in other words, it is necessary that the The molecular mass of the cationic starch is reduced to have the appropriate viscosity, ie a viscosity greater than or equal to 100 mPa.s and less than 1000 mPa.s according to test A.

The Applicant markets aqueous liquid starchy compositions comprising such starches.

Preferably, the viscosity of the cationic starch, measured according to test A, is between 100 and 950 mPa.s, most preferably between 300 and 800 mPa.s. According to one of the variants of the process which is the subject of the invention, the tannin and the cationic starch are introduced simultaneously via a composition M comprising these two constituents. Thus, the liquid amylaceous composition comprising the cationic starch may also comprise one or more tannins. Another subject of the invention thus relates to a liquid composition, which may be useful for the treatment method according to the invention.

Preferably, the liquid composition is an aqueous liquid composition.

The liquid composition according to the invention comprises at least one tannin as defined above as well as at least one solubilized cationic starch having the viscosity measured according to test A greater than or equal to 100 mPa.s and less than 1000 mPa.s.

Preferably, the viscosity of the cationic starch, measured according to test A, is between 100 and 950 mPa.s, preferably 300 to 800 mPa.s. Advantageously, the mass ratio of cationic starch / tannin ranges from 6/94 to 44/56, preferably from 10/90 to 40/60, most preferably from 15/85 to 30/70.

Advantageously, the tannin is a modified tannin, preferably a cationic tannin.

The liquid composition may take the form of a concentrated liquid composition, that is to say that the dry matter of said composition ranges from 10 to 80%, preferably from 15 to 40%.

An advantage of this composition is that it is liquid at 25 ° C while having a high solids content. This allows it to be easily transported and / or stored before use. It can be introduced directly into water treatment plants or sludge, this introduction is usually carried out using metering devices. However, some proportioners do not allow an optimal dosage when the dry matter is high, so it is sometimes difficult to directly use the composition according to the invention in said facilities. Because of its liquid form, the dilution of this high dry matter composition is very easily by simple mixing with water. It is thus possible to easily form the liquid composition M after preliminary dilution of this concentrated liquid composition, it being recalled that the said liquid composition M can, according to a variant of the treatment method of the invention, be added during step a) of the coagulation-flocculation step.

The preferred variants described above, which relate to cationic starch and tannin useful in the process, and which detail the characteristics of these two coagulants and their preferred relative proportions, are applicable to the composition according to the invention.

Thus, the dry matter of the starchy composition according to the invention may consist exclusively or almost exclusively of at least one tannin and at least one cationic starch having the appropriate viscosity; it may also contain one or more other components such as, for example, a biocidal agent or other constituents.

Although other coagulants or flocculants may be included in the composition according to the invention, the latter is advantageously essentially free or even free of polyacrylamide and metal salt. The composition is, more generally, preferably substantially free or even free, other additional coagulating and flocculating agents.

By composition substantially free of a constituent means amounts less than 5% of the total dry matter of the composition.

The coagulation-flocculation step of the process according to the invention can be carried out in a conventional manner.

The water or aqueous solution to be treated may optionally undergo pretreatment adjustment of its pH.

During the first steps a) and b) of the coagulation-flocculation step, the particles are coagulated to form the flocs.

These steps a) and b) can be carried out in a coagulation-flocculation tank. This tank may comprise a first pool called "coagulation basin" and a second pool called "flocculation basin", where the stirring speed is greater in the first than in the second. Advantageously, the starch composition and the tannin are introduced into the coagulation basin. In the case of a continuous process, the aqueous solution to be treated is introduced into said vessel via a pump, which thus makes it possible to adjust the feed rate. The duration of the coagulation-flocculation step then depends on this flow rate and the volume of the tanks used. The tannin and starch useful in the invention may be mixed with the aqueous solution to be treated either before the introduction of this solution into the coagulation-flocculation tank, or directly into the tank by a second inlet provided for this purpose . The duration of this coagulation-flocculation step depends directly on the volume of the tank and the flow rate chosen.

According to the invention, the process can be continuous or discontinuous. Thus, in the case where it is a continuous process, the durations of steps b) and c) are respectively the average residence time of the aqueous solution to be treated in the coagulation-flocculation tank and in the decanter.

The duration of stirring step b) may be greater than or equal to 0.5 minutes or more, preferably ranging from 1 to 30 minutes, most preferably ranging from 1.5 to 15 minutes. This stirring step may comprise a coagulation sub-step and / or a flocculation sub-step. The coagulation step, during which stirring is rapid, has a duration that generally ranges from 0.5 to 10 minutes, in particular from 1 to 5 minutes. The flocculation step, during which stirring is slow, has a duration that generally ranges from 1 to 30 minutes, in particular from 5 to 15 minutes.

The separation step c) may be a decantation step. This decantation step preferably has a duration ranging from 0.25 to 1000 minutes, preferably from 1 to 120 minutes, most preferably from 3 to 90 minutes, for example from 5 to 60 minutes.

To eliminate the flocs and thus be able to recover the treated water and carry out the separation step c), it is possible to use a decantation or flotation technique. These techniques, well known to those skilled in the art, may be implemented in standard water treatment facilities.

When this separation step is carried out by decantation, it is also possible to introduce into the coagulation-flocculation tank an agent capable of ballasting formed flocs, such as micrometric sand. These weighted flocs are transferred with the aqueous solution into the decanter, which makes it possible to improve the separation rate in the subsequent decantation stage.

The decanter may be a static settler or a lamellar clarifier. The decanter can be equipped with bottom wiper for better capture of sludge.

The static decanter is the most conventional decanter: it consists of a single tank in which the coagulated particles are deposited at the bottom of the tank to form sludge and recovering the purified water having undergone decantation by overflow. The lamellar decanters also make it possible to accelerate the decantation of the coagulated particles in comparison with the static decanters. The purified aqueous solution is recovered after step d).

The turbidity of the purified aqueous solution thus obtained at the end of step d) has a lower turbidity than the aqueous solution comprising the suspended materials which have been treated by the coagulation-flocculation step. This turbidity is generally greater than or equal to 2 NTU, in particular greater than 3 NTU, for example greater than 4 NTU and particularly between 5 and 50 NTU.

The process according to the invention makes it possible to greatly reduce the turbidity. According to the process of the invention, the reduction in turbidity may be greater than 50%, advantageously greater than 75%, most preferably greater than 80%.

It should be noted, however, that the reduction in turbidity depends on the initial turbidity: using the process for low turbidity water, the reduction will obviously not be as important as for water with higher turbidity. It also depends on the type of aqueous solution to be treated.

Turbidity can be measured using a WTW Turb 555IR device sold by WTW.

Following this coagulation-flocculation step, it is advantageous to carry out a subsequent purification step.

Embodiments will now be detailed in the following examples. It is pointed out that these illustrative examples in no way limit the scope of the present invention.

Examples

EXAMPLE 1 Emulsion Break Process - Study of the Viscosity of the Cationic Starch and of the Cationic Starch / Tannin Ratio

This example describes a coagulation-flocculation treatment of an effluent from stationery, which is a diluted coating color emulsion. This effluent has a turbidity greater than 2000 NTU. The objective is to study the influence of the mass ratio of coagulants in the mixture of tannin and cationic starch on the turbidity of the supernatant obtained after treatment.

Products used:

Tannin modified cationic charge. "A": An aqueous composition of cationic starch, potato starch base, having a viscosity of 430 mPa.s according to test A and comprising 1.2% of fixed nitrogen (expressed in dry weight / sec), or a degree of substitution of 0.16.

"B": aqueous cationic starch composition, potato starch base, having a viscosity of 1 1000 mPa.s according to test A and comprising 1.2% of fixed nitrogen (expressed in dry weight / sec), a degree of substitution of 0.16.

Protocol:

Aqueous mixtures of cationic starch and tannin are prepared according to the mass ratio given in Table 1 below, these aqueous mixtures having a mass concentration of coagulating agent of 3.1 g / l.

The beaker emulsion breaking process is then carried out in the following manner: a) 100 milligrams of dry matter of coagulant per liter of effluent are added to the effluent;

b) then stirred (magnetic stirring) for 3 minutes;

c) then the solution is allowed to settle for 10 minutes;

d) then the supernatant is recovered.

Its turbidity is then measured using a WTW Turb 555IR device sold by WTW. The results obtained are listed in Table 1.

Table 1

The mixtures of cationic starch A and tannin show that it is possible to propose a solution presenting a compromise cost / performance particularly advantage: in fact, the cationic starch is, relative to the tannin, less expensive and the combination mixture allows to present in all cases an improved turbidity compared to the cationic starch. These mixtures are particularly effective in a cationic starch / tannin ratio ranging from 6/94 to 44/56, since they have an efficiency that is even greater than that of tannin alone.

The mixtures of tannin with starch B also lead to very low turbidities on the effluents. The turbidity of the supernatant is lower than with the application of tannin alone.

However, the turbidity is slightly higher than that obtained with the starch A. In addition, this cationic starch B has a higher viscosity, which makes its implementation more difficult. On the contrary, cationic starch A has a lower viscosity and is therefore more easily handled. This starch makes it possible to form concentrated compositions which remain liquid even when the cationic starch solids content in the composition is high. This is particularly advantageous for forming liquid aqueous compositions according to the invention, which comprise a tannin and this solubilized cationic starch.

EXAMPLE 2 Emulsion Breakage - Optimization of the Dosage

This example is based on the same effluent from paper mill (diluted coating sauce) and illustrates the economic gain provided by the use of a starch / tannin mixture compared to tannin alone.

The mixture of coagulants studied is the mixture of cationic starch "A" and tannin, used in Example 1, which is applied for different dosages, at a weight ratio of 25/75 (dry / dry) optimized during the test. of Example 1.

Except for coagulant assays, the emulsion breaking protocol is the same as for Example 1. The results are summarized in Table 2. Table 2

The use of the mixture of cationic starch "A" and tannin (25/75) (dry / dry) at a dosage of 25 mg / l of emulsion makes it possible to obtain a turbidity similar to the application of tannin alone. at 100 mg / L. Thus, the use of this mixture makes it possible to divide the total dose of coagulant applied by 4. The amount of tannin being 75% in the mixture, the dose of tannin added in the emulsion is then 18.75 mg / L a 81% reduction in the tannin dose, which has an undeniable economic advantage.

Example 3: Treatment of a refinery effluent

This example describes a coagulation-flocculation treatment of a refinery effluent. Its purpose is to show the effectiveness of different starches studied mixed with a tannin as a coagulant.

Solution A: solution used in Examples 1 & 2.

Solution C: Aqueous solution of potato starch with a DS of 0.075.

Solution D: Aqueous solution of potato starch with a DS of 0.32. Solution E: A fluidized waxy corn starch solution with a DS of 0.05.

The different cationic starches are listed in Table 3.

The tannin used is identical to that used in Examples 1 and 2.

The additional flocculant is a polymeric flocculant.

Protocol: An aqueous mixture of cationic starch and tannin is prepared according to the 25/75 mass ratio (dry / dry) at a coagulant concentration of 0.55 g / l.

Then the method of treating the effluent in Jar-test is carried out as follows:

a) 12 milligrams of dry matter of coagulant per liter of effluent are added to the effluent;

b) then

Stirring (stirring at 200 rpm) for 1 minute;

After which the additional flocculant (0.78 mg / L of effluent) is added, keeping stirring at 200 rpm for 10 seconds;

• then the stirring speed is lowered to 60 rpm for 5 minutes; c) then the solution is allowed to settle for 10 minutes;

d) then the supernatant is recovered.

The turbidities measured for each of the supernatants are listed in Table 3.

The results obtained are reported in Table 3.

Table 3

Whatever the starches used in mixture with the tannin, the turbidities obtained are slightly lower than the application of tannin alone. Starches with lower costs than tannins, the cost of treatment will be lower.

Example 4: Treatment of municipal mud

This example describes a dewatering treatment of a municipal sludge. Products used:

"F": cationic starch solution whose Brookfield viscosity is, according to test A, 17500 mPa.s. This solution "F" is obtained from a cationic potato starch having a DS of 0.16. This starch is soluble in water at 20%.

"G": cationic starch solution whose Brookfield viscosity is, according to test A, 53000 mPa.s. This "G" solution is obtained from a cationic starch (waxy corn base) having a DS of 0.05. This starch is insoluble in water at 20 ° C, the solution is prepared by baking a solution at 95 ° C for 15 minutes.

These first two liquid starchy compositions A and B have a high viscosity which can not be in the form of an easily pumpable or dilutable high dry matter composition.

"H": Comparative cationic starch solution whose Brookfield viscosity is, according to test A, 50 mPa.s. This "H" solution is obtained from a cationic starch (waxy corn base), which has undergone acid hydrolysis treatment, having a DS of 0.16. The solution is prepared by baking a 95% solution for 15 minutes.

"I": cationic starch solution whose Brookfield viscosity is, according to test A, 350 mPa.s. This solution "I" is obtained from a potato starch, which has undergone an enzymatic hydrolysis treatment, having a DS of 0.16. This starch is soluble in water at 20%.

"J": cationic starch solution whose Brookfield viscosity is, according to test A, 780 mPa.s. This solution "J" is obtained from a potato starch, which has undergone enzymatic hydrolysis treatment, having a DS of 0.20. This starch is soluble in water at 20%.

"K": cationic starch solution according to the invention, the Brookfield viscosity of which, according to test A, is 210 mPa.s. This "K" solution is obtained from a cationic starch (waxy corn base), which has undergone an enzymatic hydrolysis treatment, having a DS of 0.05. This starch is soluble in water at 20%.

The starchy compositions H to K have a much lower viscosity. They have the advantage of being in the form of a high dry matter composition easily pumpable or dilutable.

The tannin used is identical to that used in Examples 1 to 3. The coagulants are added at a dose of 32 g / kg of sludge (dry / dry). The mass ratio starch / tannin is 40/60.

The Jar-Test protocol consists of adding the coagulants in 500 ml of sludge, with stirring at 45 rpm for one minute. The flocculation results are then expressed in floc size in the beaker (score from 0 to 10: 0 = no visible flocs, 10 = very large flocs). Then, the flocculated sludge is filtered on a screen of mesh 500μηι; we then evaluate:

the rate of filtration through the sieve (in volume collected over time, in ml / s);

the quantity of flocs passing through the sieve (mass% of flocs in the filtrate); the turbidity of the filtrate (in UTN).

The mode of addition of coagulants has also been studied in the case where the two coagulants (tannin and cationic starch) are used. According to a first mode, the addition of the coagulants is done by introducing the mixture of the cationic starch solution and tannin into the test jar and the stirring lasts one minute (addition mode: mixing). According to a second mode, the addition of the coagulants is done with stirring by a first introduction of the tannin in the test jar and then a second introduction, 30 seconds after the first introduction of the tannin, of the solution. cationic starch, the stirring also taking place for one minute (addition mode: separated).

The results are listed in Table 4.

Table 4

The process according to the invention is effective for the treatment of a municipal sludge. Whatever starch is used, are improved:

• filtration rate as shown by filtrate volumes versus time • the efficiency of dehydration as indicated by reductions in the amount of floc in the filtrate and decreases in turbidity of the filtrate.

However, it may be noted that, for compositions I, J and K which comprise a cationic starch having a viscosity greater than or equal to 100 mPa.s and less than 1000 mPa.s, the dehydration efficiency is even greater because the reductions the amount of floc in the filtrate and the turbidity of the filtrate are exceptionally low.

It is also noted that the simultaneous addition mode, in particular by the addition of a composition comprising the two coagulants, makes it possible to further improve the dehydration efficiency and the filtration rate of the process in comparison with the mode of filtration. separate addition in which the tannin is introduced first, the solution is stirred, then the cationic starch is introduced. This is particularly true for cationic starches I, J and K.

Claims

1. Process for treating an aqueous solution having suspended matter, containing a coagulation-flocculation step which comprises:

a) a step of adding coagulants to the aqueous solution to be treated, followed;

b) a step of stirring the aqueous solution thus added;

c) a step of separating the coagulated solids by decantation or flotation;

d) a step of recovering purified water;

2. Method according to claim 1 characterized in that the tannin and the liquid starchy composition are added separately in step a).

3. Method according to claim 1, characterized in that the tannin and the liquid starchy composition are added simultaneously in step a).

4. Method according to one of claims 1 or 3, characterized in that the tannin and the liquid starchy composition are added in step a) via a liquid composition M comprising both cationic starch solubilized and tannin.

5. Method according to one of claims 1 and 2, characterized in that the time between the addition of the tannin and the addition of the liquid starchy composition is less than 120 seconds.

6 Method according to one of the preceding claims, characterized in that the process is not a purification process.

7 Method according to one of the preceding claims characterized in that it is an effluent treatment process.

8 Method according to one of the preceding claims characterized in that the aqueous solution to be treated is an emulsion.

9. Method according to one of the preceding claims, characterized in that the total quantity of cationic starch and tannin in the aqueous solution to be treated ranges from 1 to 500 mg/L of water to be treated, preferably from 10 to 200 mg/L.

10. Method according to one of the preceding claims, characterized in that the tannin is a modified tannin, preferably a cationic tannin.

1 1 Method according to one of the preceding claims, characterized in that the cationic starch / tannin mass ratio ranges from 6/94 to 44/56, preferably from 10/90 to 40/60, most preferably from 15/85 to 30 /70.

12. Method according to one of the preceding claims characterized in that said cationic starch has a viscosity, measured according to a test A, greater than or equal to 100 mPa.s and less than 1000 mPa.s, this test A consisting of measuring the Brookfield viscosity at 25°C of cationic starch when it is in solubilized form in an aqueous composition with 10% dry matter.

13. Method according to the preceding claim, characterized in that the viscosity of the cationic starch, measured according to test A, is between 100 and 950 mPa.s, preferably from 300 to 800 mPa.s.

14. Method according to one of the preceding claims, characterized in that the turbidity of the purified water obtained at the end of step d) is greater than or equal to 2 UTN.

15. Liquid composition comprising a solubilized cationic starch and at least one tannin, modified or not, characterized in that said cationic starch has a viscosity, measured according to an A test, greater than or equal to 100 mPa.s and less than 1000 mPa. s, this test A consisting of measuring the Brookfield viscosity at 25^ of the starch cationic when it is in solubilized form in an aqueous composition with 10% dry matter.

16. Composition according to the preceding claim, characterized in that the viscosity of the cationic starch, measured according to test A, is between 100 and

950 mPa.s, preferably included in the range from 300 to 800 mPa.s.

17. Composition according to claim 15 or 16, characterized in that the cationic starch/tannin mass ratio ranges from 6/94 to 44/56, preferably from 10/90 to 40/60, most preferably from 15/85 to 30/ 70.

18. Composition according to one of claims 15 to 17, characterized in that the tannin is a modified tannin, preferably a cationic tannin.

19. Composition according to one of claims 15 to 18, characterized in that the dry matter of the composition ranges from 10 to 80%, preferably from 15 to 40%.