Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
  • C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F1/5272—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using specific organic precipitants
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
  • C02F2103/26—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof
  • C02F2103/28—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof from the paper or cellulose industry

Definitions

• the invention relates to a water purification process, in particular a method comprising a coagulation-flocculation step using, together with a metal salt, a liquid cationic solubilized particular starch composition.
• aqueous solution of ground water or surface water that you will treat, such as water from a lake or watercourse.
• This aqueous solution always comprises a greater or lesser amount of suspended particles which it is necessary to eliminate.
• 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 bottom of the float.
• the aqueous solution generally comprises fine particles whose separation is particularly difficult, in particular colloidal particles of very small size, generally ranging from 1 nm to 1 ⁇ .
• a coagulation-flocculation step is first carried out. This step consists 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.
• coagulants and flocculating agents are used alone or in mixture. These agents may be chosen from iron or aluminum salts, anionic or cationic polyacrylamides and nonionic, anionic or cationic starches.
• 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.
• COD Chemical Oxygen Demand
• turbidity level of the aqueous solution, or turbidity is measured by a nephelometer (also called turbidimeter) and is measured in Nephelometric Turbidity Unit (NTU or NTU for Nephelometric Turbidity Unit).
• NTU Nephelometric Turbidity Unit
• Another means is also to measure the absorbance of the aqueous solution treated at a given wavelength.
• the water thus purified is generally subjected to a "filtration step” of passing the water through one or more filters to remove some residual pollutants. It is also possible to carry out a disinfection step, consisting of adding an agent or using a treatment capable of eliminating the bacteria present in this water. These latter treatments are particularly useful in a potabilization process.
• Water treatment processes are generally continuous processes.
• a filtration step takes place to make the drinking water, the last particles remaining in suspension are removed from the aqueous solution by passing through the filters.
• the particles accumulate inside the filters and they clog up.
• There is then a "loss of charge” that is to say a loss of flow of filtered water at constant pressure applied to the filter.
• the aqueous solution to which this filtration step is subjected must present a turbidity low, generally less than 1.5 NTU, preferably less than 1 NTU.
• the turbidity reduction obtained during the coagulation-flocculation step is very important during a process for water purification.
• cationic starch-based agents Processes for treating drinking water using cationic starch-based agents have already been described. Indeed, these cationic starches have the advantage of being made from renewable plant resources and being available in large volumes.
• this method can be achieved by using a fast treatment time, using a small amount of chemicals, without having to modify the facilities conventionally used for these treatments. It must be able to significantly reduce the turbidity of the treated water.
• the Applicant has already found a process of potabilization to solve the aforementioned problems, this process is the subject of the French application FR1 156702 and International Application PCT / FR2012 / 051714, these two requests being unpublished to date; said method uses as coagulants useful in the invention a metal salt and a particular liquid starchy composition.
• the amylaceous composition useful to the invention must have a relatively high viscosity, since it must have a Brookfield viscosity at 25 ° C at least equal to 1000 mPa.s, this viscosity being measured at 10% dry matter.
• coagulants are generally supplied to the user-users in the form of concentrated liquid solutions of high solids, in particular solutions with solids content of up to 80%. . Since the solids content of these solutions is high and the amounts of solvent are low, this allows the manufacturer to provide solutions that can be easily stored and / or transported. As for the user client, he only has to use these concentrated solutions, possibly after simple dilution.
• a starchy liquid composition one of the problems is that by increasing the dry matter to starch, the viscosity of the composition increases. It can even take a paste or gelled consistency that makes it difficult to handle and therefore dilute. It is therefore necessary that this concentrated composition is in liquid form low viscosity.
• the disadvantage of the process that was the subject of the application PCT / FR2012 / 051714 is that the starchy composition useful to the invention has a relatively high viscosity.
• the viscosity according to test A described in this application exceeds 500,000 mPa.s, it is necessary that it has a solids content which must be well below 5% to be liquid and can thus be easily handled for example by pumping, or to be able to dilute it.
• the Applicant has been able to implement, by carrying out work on water purification processes, a new water purification process that drastically reduces the turbidity of an aqueous solution comprising suspended solids.
• a liquid composition of cationic starch having specific characteristics when used in a coagulation-flocculation step together with a ferric salt and / or an aluminum salt, to reduce particularly interestingly the turbidity of the aqueous solution to be treated in comparison with the cationic starches conventionally used in this field.
• This particular starch must be, when it is introduced into the water to be treated, in the form solubilized in a liquid composition.
• This composition has the advantage of being able to present a high solids content while remaining liquid and easy to handle. It can be used, with a metal salt, in any type of water or sludge treatment process, and in particular in a process for obtaining a drinking water comprising a coagulation-flocculation step.
• the subject of the invention is a method for potabilizing an aqueous solution having suspended solids, containing a coagulation-flocculation step, characterized in that said step comprises:
• the coagulants added in step a) comprise metal salts selected from ferric salts and aluminum salts and a liquid starch composition comprising a cationic waxy starch, said cationic starch having, when it is set in the form of an aqueous composition, a viscosity, measured according to an A test, greater than 100 mPa.s and less than 1000 mPa.s, this test A consisting in adjusting the dry mass to cationic starch of the 10% aqueous composition and then to measure the Brookfield viscosity at 25% of the resulting composition.
• Test A used to measure the viscosity of the cationic waxy starch, is applicable regardless of the form of presentation of the aqueous composition comprising it, liquid or pasty.
• the test A consists in measuring the viscosity of the cationic waxy starch and therefore of course measuring the viscosity of a liquid composition constituted 90% by weight of water and 10% by weight of cationic waxy starch solubilized.
• a liquid composition constituted 90% by weight of water and 10% by weight of cationic waxy starch solubilized.
• a rotary evaporator To concentrate the aqueous composition without modifying the starchy material comprising it, it is possible, for example, to use a rotary evaporator.
• a liquid starchy composition comprising a cationic waxy starch having a viscosity greater than 100 mPa.s and less than 1000 mPa.s when it is in the form of an aqueous composition, for a concentration of cationic waxy starch, based on 10% of the total mass of the aqueous composition, made it possible to obtain an exceptional reduction in the turbidity of a solution having solids in suspension. This reduction could not be observed by the Applicant when using, instead of the above-mentioned starchy composition, a cationic starch composition of the same viscosity but not waxy.
• the salts and the liquid starchy composition useful for the invention are added separately in step a).
• the salts and the liquid starchy composition useful for the invention are added simultaneously to step a).
• This addition can be done via a liquid composition M comprising both the solubilized cationic starch and the salts.
• the viscosity of the cationic starch is between 150 and 990 mPa.s, preferably between 200 and 500 mPa.s, most preferably between 205 and 450 mPa.s.
• a waxy starch generally comprises amounts of amylopectin ranging from 90 to 100% by weight, for example ranging from 95 to 100%, very often ranging from 98 to 100%. This percentage can be determined by colorimetry using an iodine assay.
• the cationic waxy starch can in particular be obtained from maize, wheat, barley or potato. Most preferably, waxy starch is a waxy corn starch.
• the metal salt is a sulfate, a polysulfate, a chloride, a polychloride or a polychlorosulphate.
• the metal salt is chosen from polyaluminium chloride and ferric chloride.
• a liquid solution for example having a concentration ranging from 0.01 to 1000 g / l, for example ranging from 0.01 to 150 g / l.
• the liquid of the solution may be any solvent of the metal salt, this solvent may for example be water.
• the pH of the liquid solution can range from 0 to 7, for example from 1 to 5.
• the amounts of metal salt are the total amounts of these various metal salts.
• the process of the invention can be carried out with a total amount by mass of cationic waxy starch and metal salt in the aqueous solution ranging from 1 to 500 mg / L of water to be treated.
• This amount is adapted to the turbidity of the initial water and may advantageously be from 5 to 20 mg / L of water to be treated, preferably from 5 to 10 mg / L.
• the weight ratio waxy cationic starch / metal salt can range from 15/85 to 70/30, for example from 15/85 to 60/40, advantageously from 15/85 to 55/45, preferentially from 20/80 to 50/50, most preferably from 25/75 to 40/60.
• the Applicant has found that the coagulation-flocculation step is particularly effective when these coagulants are introduced in the ratios above.
• the cationic starch may have a degree of cationic substitution greater than or equal to 0.01, advantageously ranging from 0.018 to 0.3, preferably from 0.04 to 0.2.
• the liquid amylaceous cationic waxy starch composition introduced in step a) advantageously has a cationic starch concentration ranging from 0.01 to 350 g / l, for example 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 agitation step b) can be carried out in the presence of an additional treatment agent which can be selected from algae, activated carbons and potassium permanganate.
• the treatment agent is preferably activated carbon or potassium permanganate.
• the duration of stirring step b) may be greater than or equal to 1.5 minutes or more, preferably ranging from 2 to 30 minutes, most preferably ranging from 2.5 to 5 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 0.33 to 120 minutes, most preferably from 0.5 to 12 minutes, for example from 1 to 5 minutes.
• the flocs can be ballasted, for example using micro sand.
• Another advantage of the invention is therefore that the coagulation-flocculation step can thus be performed in a very short time.
• the process can be continuous or discontinuous.
• 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 potabilization process according to the invention is particularly well suited when it comprises, after the coagulation-flocculation step, a step of filtering the purified water.
• the aqueous solution comprising suspended solids to be treated may have a turbidity less than or equal to 1000 NTU, preferably ranging from 2 to 300 NTU, preferably ranging from 2.5 to 150 NTU, for example ranging from 3 to 100 NTU.
• This aqueous solution may be surface water, for example river or river lake water or groundwater which are the water conventionally used to transform water into drinking water.
• the process is very advantageous for removing particles in suspension in the aqueous solution having a size ranging from 0.001 to 500 ⁇ m, in particular those ranging from 0.001 to 1 ⁇ m.
• the turbidity of the purified aqueous solution thus obtained at the end of step e) has a low turbidity, for example less than or equal to 1.5 NTU, preferably less than 1 NTU.
• the turbidity reduction may be greater than 98%, advantageously greater than 98.5%, most preferably greater than 99%.
• the method according to the invention makes it possible to greatly reduce turbidity, which is very advantageous in a process of potabilization. These exceptional turbidity reductions have been obtained particularly from surface waters still of groundwater.
• Turbidity can be measured using a WTW Turb 555IR device sold by WTW.
• the liquid amylaceous composition useful for the invention comprises a cationic waxy starch which has a viscosity greater than 100 mPa.s and less than 1000. mPa.s according to test A described above. As will be explained below, this particular viscosity is directly related to the cationic waxy starch used and the method of preparation of the composition that is to say the solubilization of this cationic waxy starch.
• the viscosity of the aqueous composition of the test A comprising it after solubilization depends on two main characteristics, in descending order of importance: its molecular mass and its degree of cationicity. These characteristics are readily selected by those skilled in the art by choosing the botanical source of native waxy starch and the conditions of preparation of this cationic waxy starch.
• the cationic waxy starch used in the context of the invention can be obtained from any type of native waxy starch of natural or hybrid origin, including starch derived from plant organisms having undergone mutations or genetic manipulations. .
• the waxy starch may in particular be derived from waxy corn, waxy potato, waxy wheat, waxy barley, preferably from waxy corn.
• This native starch has for example an influence on the final molecular weight and also the content of amylose and amylopectin.
• cationic starch useful for the manufacture of the starchy composition, in addition to a cationization step of the starch, it is generally necessary to also perform a step of reducing the molar mass of the starch.
• 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.
• 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 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 - RL WHISTLER and EF PASCHALL - Academy Press (1967).
• the starch is introduced into a reactor in the presence of these reagents.
• the starch used during the cationization reaction is in a granular form.
• 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.
• the starch thus cationized can be recovered by filtration, this cationic starch can then be washed and then dried.
• 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%.
• glue phase is meant that the starch is at least partially solubilized, generally completely solubilized, in a solvent phase, said solvent phase generally being an aqueous phase or a hydroalcoholic phase.
• a cationic starch is obtained in the form of a liquid starchy composition. It is also possible to obtain the cationic starch in solid form by drying the composition or else by precipitation in alcohol or a hydroalcoholic solvent.
• the cationization reaction is carried out with nitrogen-containing reagents based on tertiary amines or quaternary ammonium salts.
• 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 greater than 10, the pH being adjusted 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.
• DS degree of substitution
• 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 man the art and capable of allowing to obtain directly or not a starchy composition having the appropriate viscosity according to the test A.
• This step can be carried out in the solvent phase or in the dry phase.
• This step may be carried out continuously or discontinuously, in one or more substeps, according to a multitude of variants as to the nature of the starch, the amount or the form of presentation of the modifying means, the temperature and the duration reaction, the water content of the reaction medium or the nature 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.
• enzymatic fluidification treatment also called enzymatic conversion or liquefaction
• enzymatic means include enzymes, heat-stable or not, of alpha-amylase type of bacterial, fungal or other origin.
• 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 starchy materials treated, before, during or after cationization, with a branching enzyme generally have an improved storage stability compared to 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 Gaussian curve that is generally more regular, more symmetrical and narrower than that obtained with an alpha amylase.
• 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.
• 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.
• 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 a second step of reduction of 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.
• a liquid starchy composition useful for the invention can be obtained directly.
• the cationic starch may be soluble at room temperature in water.
• soluble at room temperature is meant according to the invention that, when the cationic starch is introduced at 10% by weight of the water at 25 ° and is stirred for 1 hour. hour, the starch solution thus obtained has a Brookfield viscosity greater than 100 mPa.s.
• the liquid starchy composition is generally an aqueous composition, which may comprise mainly water and possibly small amounts of organic solvents miscible with water, such as alcohols such as methanol and ethanol, for example in amounts of organic solvent less than 10% by weight of all the solvents.
• the cationic starch in the solvent can be rendered soluble by a cooking step if this starch is not soluble in cold water. This cooking is generally carried out in water or an aqueous-alcoholic solution, by suspending cationic starch and thus forming a starch milk.
• said liquid starchy composition is prepared by using a soluble cationic starch at ambient 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 composition useful to the invention can thus easily be implemented on the site carrying out the treatment process.
• liquid starchy compositions comprising the cationic starch useful for the invention, that is to say said cationic starch has a viscosity, measured according to test A, which is greater than 100 mPa.s and less than 1000 mPa.s.
• a viscosity measured according to test A, which is greater than 100 mPa.s and less than 1000 mPa.s.
• a liquid starchy composition comprising a solubilized waxy cationic starch and one or more metal salts chosen from ferric salts and aluminum salts, and the viscosity of said cationic waxy starch, measured according to test A, is greater than 100 mPa.s and less than 1000 mPa.s.
• This new composition is another aspect of the present invention.
• the viscosity of the cationic waxy starch is advantageously between 150 and 990 mPa.s, preferably between 200 and 500 mPa.s, most preferably between 205 and 450 mPa.s.
• the cationic waxy starch has, according to test A, a viscosity ranging from 505 to 990 mPa.s, for example from 550 to 950 mPa.s.
• the pH of the composition according to the invention is between 0 and 7, for example between 1 and 5.
• the composition advantageously has a mass ratio cationic starch / metal salt ranging from 15/85 to 70/30, for example from 15/85 to 60/40, advantageously from 15/85 to 55/45, preferentially from 20/80 to 50/50. / 50, most preferably 25/75 to 40/60.
• the metal salt is advantageously polyaluminium chloride or ferric chloride.
• ferric chloride it is preferred that the cationic starch / metal salt ratio be 25/75 to 50/50, or even 30/70 to 45/55.
• polyaluminium chloride it is preferred that the cationic starch / metal salt ratio be 20/80 to 45/55, or even 25/75 to 35/65.
• the metal salt is an aluminum salt, especially a polyaluminium chloride.
• the pH of the composition is very preferably between 2 and 5.
• the liquid composition according to the invention advantageously comprises as solvent water or an aqueous-alcoholic solution, preferably water.
• the solvent is preferably water.
• a cationic starch liquid composition containing preservative is used.
• the cationic starch 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 Rohm & Haas under the trademark VINYZENE TM.
• a biocidal agent which may be chosen from phthalates, for example one of those marketed by Rohm & Haas under the trademark VINYZENE TM.
• these biocidal agents may constitute unwanted constituents for the treatment of a water and particularly for the production of water. drinking water.
• the composition according to the invention has a stability in time quite correct, even in the absence of these conventionally used biocidal agents. This stability is particularly good in the case where one or more aluminum salts are used as metal salts.
• Useful cationic waxy starch to the invention has a Brookfield viscosity greater than 100 mPa ⁇ s and less than 1000 mPa ⁇ s under the conditions of test A.
• the measurement of the viscosity, achieved by a Brookfield ® brand, is well known to those skilled in the art.
• test A can be carried out using module RV1 at 20 rpm for a viscosity of greater than 100 mPa ⁇ s and less than or equal to 1000 mPa ⁇ s.
• the liquid composition of the invention 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%.
• This composition 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 dosers do not allow an optimal dosage when the dry matter is high, so it is sometimes difficult to use directly the composition according to the invention in said installations. Due to its liquid form, the dilution of this high dry matter composition is very easily, by simple mixing with a solvent, especially by simple mixing with water.
• liquid composition M after prior dilution of this concentrated liquid composition, it being recalled that the said liquid composition M can, according to a variant of the purification process of the invention, be added during step a) of the coagulation-flocculation step.
• the composition according to the invention is useful for treating water or sludge, for example for dewatering or thickening sludge.
• water to be treated is generally meant an aqueous composition comprising water and suspended solids, the amount of suspended matter being less than 0.2% of the mass of the aqueous composition.
• mud to be treated is meant on the contrary an aqueous composition comprising water and suspended solids, the amount of suspended matter being greater than or equal to 0.2% of the mass of the aqueous composition.
• the terms "water to be treated” and "sludge to be treated” include all types of urban effluents or effluents from various industries, including effluents from paper mills or starch plants.
• the effluents from paper mills include, for example, coating colors, which are polymer emulsions dispersed in an aqueous phase.
• emulsion breaking In addition, it is necessary that this break is effective because the coating sauces disrupt the biological treatment of sludge ("activated sludge"). It is therefore necessary to break these emulsions before performing a biological treatment, especially if the levels are high.
• composition according to the invention makes it possible, for the treatment of water or sludge, to reduce the turbidity of the water recovered at the end of the treatment, to reduce the COD or still the phosphorus level. This makes it possible to either reject the water recovered in the natural environment or to reuse it in the process.
• composition according to the invention is particularly effective for the clarification of water, that is to say to reduce the amount of suspended solids of an aqueous solution.
• the use of the mixture according to the invention for the treatment of water or sludge also has the advantage of greatly limiting the residual amount of metal salt compared to conventional metal salt treatments used alone. Indeed, the Applicant has found that, even dose of metal salt introduced, the treated water contained three times less residual salt in the water obtained after treatment. The sludge volume produced is also lower using the composition of the invention.
• composition according to the invention can be used for the treatment of water or sludge, together with at least one other coagulating agent or with at least one flocculating agent.
• coagulants may be used in the process, the latter may be carried out without any additional coagulant and / or flocculant, particularly without polyacrylamide and without clay.
• the coagulation-flocculation step can be carried out in a conventional manner.
• the particles are coagulated to then form the flocs 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.
• the starch composition and the metal salt are introduced into the coagulation basin.
• the aqueous solution to be treated is introduced into said vessel via a pump, which thus makes it possible to regulate the flow rate introduction.
• the duration of the flocculation coagulation step then depends on this flow rate and the volume of the tanks used.
• the salt 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.
• the water to be treated may optionally undergo pretreatment adjustment of its pH.
• the pH of the aqueous solution comprising suspended solids ranges from 5 to 8.5.
• step c) a settling of the formed flocs is carried out.
• 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.
• an agent capable of ballasting formed flocs such as micrometric sand.
• 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.
• This may be for example a filtration step.
• the coagulation-flocculation step used in the process according to the invention is then particularly advantageous.
• This water filtration step may be a microfiltration, ultrafiltration or nanofiltration step.
• filters such as filters comprising sand, anthracite or even activated carbons are used.
• membranes of organic polymers in particular polypropylene, polyacrylamide or polysulfone. Reverse osmosis water filtration can also be performed using a semipermeable membrane to remove solutes.
• a drinking water is obtained, the turbidity of which is advantageously less than 1 NTU.
• “B” Comparative cationic starch solution whose Brookfield viscosity is, according to test A, 53000 mPa.s. This "B” solution is obtained from a cationic starch (waxy corn base) having a DS of 0.05. This starch is insoluble in 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. They can not be in the form of a high dry matter composition easily pumpable or dilutable.
• C Comparative cationic starch solution whose Brookfield viscosity is, according to test A, 50 mPa.s. This solution “C” 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.
• This third starchy composition has a much lower viscosity. It has the advantage of being in the form of a high dry matter composition easily pumpable or dilutable.
• FeCl 3 ferric chloride in solution.
• the mixtures are evaluated by Jar-Test in order to make a water taken from the Lys drinkable (initial turbidity 65UTN). 5 grams of sand (diameter ⁇ 100 ⁇ ) are added to 1 L of water with stirring, and the mixture of coagulants is added, with stirring at 200 rpm for 3 minutes. The stirring is then stopped and the turbidity of the supernatant is measured after 3 minutes of decantation.
• the dose of coagulant used is 10 milligrams of active ingredient per liter of water to be treated (mg / L).
• This example illustrates the invention by using together with a starch solution an iron salt as a metal salt.
• “D” Comparative cationic starch solution whose Brookfield viscosity is, according to test A, 350 mPa.s. This "D” solution is obtained from a non-waxy cationic starch (potato base), which has undergone an enzymatic hydrolysis treatment, having a DS of 0.16. This starch is soluble in water at 20%.
• E Cationic starch solution according to the invention, the Brookfield viscosity of which, according to test A, is 210 mPa.s.
• This "E” 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%.
• “F” cationic starch solution according to the invention, the Brookfield viscosity of which, according to test A, is 810 mPa.s.
• This "F” 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 test protocol is identical to Example 1.
• the water used here is initially 13UTN, doped with 100UTN by addition of calcium carbonate (Mikhart 5).
• This example illustrates the invention by using together with a starch solution an aluminum salt as a metal salt.
• the mixture H is as effective as the mixture G.
• the mixture H After storage for 2 months, the mixture H has a stable viscosity and is also effective in the process. It should be noted that, as in the case of starch solutions useful in the invention of Example 2, the mixture of metal salt and solution E has a viscosity which allows it to be in the form of dry matter composition high, easily pumpable or dilutable.
• This example illustrates the invention by using together with solution G previously described for the treatment of an effluent from yeast production.
• Coagulation and flocculation treatments are carried out following an anaerobic digestion and activated sludge treatment, in order to ensure the dephosphatation of the effluent. This treatment is then followed by a settling of the formed flocs.
• COD Chemical Oxygen Demand
• P phosphorus content
• the water before treatment has a turbidity of 7UTN, a color of 0.45 measured at 254nm, a chemical oxygen demand (COD) of 60mg / L and a phosphorus content (P) of 0.27mg / L.
• COD chemical oxygen demand
• P phosphorus content
• coagulation is carried out by adding to the effluent 40 ppm (in sec) FeCl3 while the flocculation is carried out using an anionic polyacrylamide (A-PAM 1, 4 ppm).
• A-PAM 1, 4 ppm an anionic polyacrylamide
• the process is identical with the difference that the coagulation is carried out by substituting the 40 ppm of FeCl 3 (in dry) with 40 ppm of the PAC / cationic starch mixture of the H solution.
• the water obtained by treatment with the reference products is compared with that obtained by treatment with solution H described in the previous example, supplemented with A-PAM, at the same dosages as the reference test.
• solution H provides lower turbidity, COD and phosphorus, and an equivalent color.
• This example illustrates the invention in the treatment of an effluent resulting from a production of coated paper, for the breaking of the emulsion.
• the coagulation-flocculation treatment is usually performed by a PAC in order to obtain the lowest possible turbidity and Chemical Oxygen Demand (COD).
• COD Chemical Oxygen Demand
• the solution E used alone is not effective and does not break the emulsion, unlike PAC alone.
• the joint use of the two coagulating agents particularly in a mass ratio of cationic starch / metal salt ranging from 15/85 to 70/30, in particular from 20/80 to 50/50, gives better results than the use of the CAP alone, folds especially with regard to turbidity.

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