KR20020080327A - Cationic polymers for sludge dewatering - Google Patents

Abstract

The present invention relates to a composition and method for sludge dewatering. The sludge dewatering method includes the step of treating the sludge with a tangle aid and a tangle agent after dewatering the sludge. In this method, the entanglement aid is an inorganic compound; The entanglement aid and the entanglement agent are provided as a solid composition comprising 0.1 to 10 parts by weight of the entanglement per weight part of the entanglement; Water is added to the composition to provide an aqueous solution or dispersion of the composition; The aqueous composition is added to the sludge; It is characterized in that the sludge is dewatered. The sludge dewatering composition is characterized in that it comprises a mixture of 0.1 to 10 parts by weight of agglomeration aid and a solid inorganic agglomeration agent per weight part of the flocculation agent.

Description

Cationic polymer for sludge dewatering {CATIONIC POLYMERS FOR SLUDGE DEWATERING}

Cationic charged water soluble or water dispersible polymers have been utilized in methods related to dehydrating aqueous suspensions. The sludge dewatering amount is increased by mixing the chemical reagent with the sludge in order to agglomerate or clump, thereby facilitating the water separation process. To this end, different synthetic high polymers have been used in large quantities to chemically treat sludge. Polymeric polyacrylamides are generally used. These polymer electrolytes are used alone or in combination with an inorganic flocculant or a strong ion organic polymerizable flocculant. The most frequently used inorganic and organic flocculants are generally iron salts, such as ferric chloride, and polymers of diallyl dimethyl ammonium chloride (DADMAC) and epichlorohydrin dimethyl amine (epi-DMA). It is generally accepted that each individual sludge has different properties and treatment methods, thereby determining the use of suitable flocculants and flocculating agents to be added.

It is known that it is often desirable to first add a conditioning agent or flocculant before tangling the suspension, which may be inorganic polyvalent salts such as iron salts or aluminum salts, or relatively low molecular cationic polymers. For example, JP-B-5133867 discloses a method for treating sewage sludge with polyvalent metal salts, low molecular cationic polymers and high molecular cationic polymers, which are preferably added last. WO 94/02424 describes a process for purifying sludge containing mainly water, which first comprises adding a water-containing flocculation mixture containing iron salts and low molecular organic polymers and adding a polymer electrolyte. Include. US 5,846,435 describes a chemical method for dehydrating biological sludge digested by thermophilic bacteria, which method comprises polyquaternary polys with polyquaternary amines and cationic polyacrylamides as part of the polymer chain. Continuously adding acrylamide.

According to JP 56058598 (extracted from Derwent and PAJ), the mud phase was prepared by directly adding in a powder state a treatment agent comprising 1 part by weight of a polymer flocculant and 1 to 100 parts by weight of a water-soluble inorganic Ca, Mg or Fe (II) salt. It is known to treat water-containing suspension clays. The treating agent does not contain any tangles.

On the other hand, EP 479 616 patent discloses an organic flocculant polymer, preferably diallyl dimethyl ammonium chloride (DADMAC) and agglomerate polymer, as a single treatment solution containing both a treated aqueous solution or a cationic flocculant polymer and a cationic flocculant polymer. A dewatering method is disclosed in which all are added simultaneously to the sludge. US 3,642,619 discloses a method of simultaneously adding iron salts and high polymers, prepared as a solid mixture consisting of 0.05 to 5 parts by weight of a polymer and a residue of iron-containing salts.

From these references, it can be seen that bicomponent treatment results in better performance compared to this sludge dewatering method using only polyvalent metal ion conditioners, low molecular cationic organic polymers or polymeric cationic entanglement polymers. In most cases, it is preferable to add the flocculant and the flocculant continuously rather than simultaneously, which involves a more complex method than the work-product treatment.

In conventional sludge dewatering systems using either a tangle or a combination of flocculants and tangles, there is a desire to prevent the continuous production and overdose of large amounts of gelatinous aggregates that can impede the optimal release of water. This results in a small amount of processed sludge and a small amount of dry solids sludge cake. The gelatinous sticky agglomerate also tends to form cakes that do not release well from the filter press cloth (when pressing the belt and filter). In addition, variants are often produced in the sludge from sludge support, which causes various special types to be removed. In addition, it may sometimes be necessary to treat sludge which is not entangled by any of the known polymerizable flocculants.

The present invention aims to minimize or overcome the above problems while increasing the dewatering efficiency of current sludge dewatering systems.

The present invention relates to a method for dewatering sludge from municipal and industrial waste and a composition for carrying out such a method.

With the present invention, sludge from urban or industrial waste-water is crushed and then dewatered. It is effectively entangled by a solid mixture of entanglement aid and entangled polymer, prepared as a treatment solution of both components.

In general and in connection with the present invention, the term "entanglement agent" means a polymeric material having the ability to agglomerate by attaching and crosslinking adjacent suspending particles of an aqueous suspension. The molecular weight of the flocculant generally exceeds 1 × 10 ⁶ and is usually 5 to 20 × 10 ⁶ or more. The tangle agent may be nonionic or ionic, for example a polymer electrolyte.

In addition, the term "entanglement aid" as used herein means either conventional flocculants or minerals. The term "coagulant" refers to a strong ionic low molecular material (MW <1 * 10 ⁶ ), which absorbs on the suspended particle surface and changes its surface charge mainly to achieve the effect, while the term "mineral" refers to sludge It means an inorganic material that has the ability to react with impurities in the interior, and also forms a network by combining with a tangle agent.

The choice of suitable tangle agents and tangle aids depends on the particular method and the special suspension to be dehydrated.

The dehydration efficiency is surprisingly improved by mixing the tangle and tangle adjuvant ingredients in the solid state, preparing a corresponding aqueous solution and simultaneously adding these ingredients to the sludge, i.e. using a new composition. Unexpected synergistic results are obtained that improve the sludge dewatering rate compared to treatment by prior art methods.

Accordingly, the present invention provides a sludge dewatering method for dewatering sludge by treating sludge with a tangle agent and a tangle aid.

The entanglement aid is an inorganic compound;

The entanglement aid and the entanglement agent are provided as a solid composition comprising 0.1 to 10 parts by weight of the entanglement aid per weight part of the entanglement agent;

Adding water to the composition to provide an aqueous solution or dispersion of the composition;

Adding the aqueous composition to the sludge; And

It is characterized by dewatering the sludge.

The present invention also provides a composition for dewatering sludge, the composition comprising

A proportion of 0.1 to 10 parts by weight of agglomeration aid per weight part of agglomeration agent, characterized in that it comprises a mixture of a solid agglomeration agent and a solid inorganic agglomeration aid.

Further features and advantages of the present invention will become apparent from the following description and the appended claims.

The novel composition comprises a particulate mixture of water soluble or water dispersible inorganic tangle aids and tangle polymers.

According to one aspect of the present invention, agglomeration of sludge from industrial or municipal waste comprises dissolving or dispersing the particulate mixture in water to form a treatment solution and mixing the treatment solution with sludge to slit the sludge. And dewatering.

Solid inorganic agglomeration aids of the present invention are water-soluble or water-dispersible iron or aluminum containing salts, minerals or mixtures thereof. Preferred solid iron salts are ferric chloride, ferric sulfate, iron hydroxide, iron nitrate and iron nitrate sulfate. Preferred aluminum salts are aluminum sulfate, aluminum hydrate and for example polyaluminum chloride hydroxide, polyaluminum chloride hydroxide sulphate, polyaluminum chloride silicate, polyaluminum hydroxide sulphate, polyaluminum hydroxide sulphate Prepolymerized polyaluminum compounds such as phosphate and the like. Suitable minerals are silicon-containing compounds such as silica (SiO ₂ ), alkali metal metasilicates, aluminum silicates, alkali metal silicates, alkali metal aluminum silicates or mixtures thereof. Preferred silicon containing compounds are talc, kaolin, natural or synthetic zeolites and bentonite.

Inorganic alkali metal salts or alkaline earth metal salts may coexist with the entanglement aid or the entanglement polymer. Suitably the salt carries a cation which is sodium, calcium, magnesium, ammonium, potassium or mixtures thereof. Suitable salts are sodium chloride, sodium sulfate, calcium sulfate, magnesium sulfate, ammonium sulfate and potassium sulfate.

The flocculant polymer used in the present invention may be nonionic, cation or mixtures thereof. Preferred nonionic flocculating agents are water-soluble high molecular polyacrylamides comprising homopolymers of (meth) acrylamide and copolymers of (meth) acrylamide, which are up to about 25% of other nonionic comonomers. Some nonionic comonomers are diacetone acrylamide, hydroxy ethyl acrylate, hydroxy ethyl methacrylate, ethylene oxide, n-butyl acrylamide and methacrylamide. Preferred cationic entanglements include (meth) acrylamides with quaternary or acid salts of dialkylaminoalkyl (meth) -acrylamides or -acrylamides, especially quaternized dimethyl or diethyl aminoethyl (meth) acrylates. Homopolymers or copolymers are included. As examples of other tangle polymers, mention may be made of polyimines, polyimides, polyethylene oxides and phenolic resins.

The composition is a dry particulate solid. For example, it is possible to form a particulate containing both types of components, obtained by drying a film of mixed component solution and then flaking the film, but preferably the composition is agglomerating aid together with the agglomerating polymer particles. It is formed by mixing the particles. In such cases, it is desirable to maintain each component at a similar particle size as a substantially uniform mixture that facilitates uniform administration of the components in the treatment solution.

If the entanglement aid has properties that make it difficult to form a homogeneous stable mixture, the entanglement aid can be mixed with the carrier. Thus, the flocculant can be dispersed through the matrix material on the beads to release the entanglement aid when in contact with water. Suitable matrix materials are carbohydrates such as starch, or inorganic carrier materials.

The weight of the tangle aid per weight part of the tangle polymer is 0.1 part by weight or more per weight part of the tangle agent, which may be as large as 10 parts by weight, but is preferably 0.1 to 1.5 parts by weight, more preferably 0.2 to 1 part by weight. to be.

Treatable sludges have various properties for effective dewatering with the new composition. This includes industrial waste, municipal sludge or combinations thereof, which may be mainly sludge, activated sludge, waste-activated sludge, chemically precipitated sludge or mixtures thereof. It also includes untreated raw sludge, anaerobic or aerobic digested sludge, air-lift sludge or digested suspended sludge. Special sludges with varying dehydration properties and solids content are also known. Examples of such sludges are those containing from about 1% to about 5% by weight of solids.

The new composition must be dissolved or dispersed in water, and the sludge is usually formed by adding an aqueous solution or dispersion of the composition, preferably at a concentration of 0.01 to 1.5% by weight, more preferably at a concentration of 0.1 to 0.2% by weight. Added effectively. The total amount of the added composition may vary considerably depending on the sludge to be treated and the required degree of dehydration. Typical addition rates for sewage sludge will range from about 0.1 to 0.5% by weight of the composition, based on the total weight of the sludge solids. It can be added effectively by conventional methods, and it is essential to stir the mixture of the sludge and the composition to some extent. The solid separated from the liquid can then be effectively separated by conventional methods such as filtration, centrifugation or precipitation.

Compared with dual or bicomponent systems, the present invention has the advantage of facilitating the use of single dry compositions.

The novel composition added to the sludge as the treatment solution is surprisingly when one of its components is used alone, surprisingly when it is added sequentially to the sludge as a solution carried out in any order, or as a treatment solution. It is much better than those obtained by first mixing the components of and then adding them to the sludge or by adding the composition directly to the sludge in solid form.

With the addition of the separation solution to the sludge continuously or simultaneously, the process of the invention is much more cost effective compared to the process using either low molecular flocculant or high polymer flocculant polymers, or a combination of both. Provide treatment. In addition, gelatinous clumps tend not to form well, are drained better, and a large amount of dry sludge cake is obtained. Finally, the pH of the corresponding aqueous solution prepared from the new composition is about 3 to about 5 for a polymer concentration of 0.05 to 1% by weight, which prevents potential basic or acidic hydrolysis of the tangle polymer of the composition to this extent. do.

The present invention will be described in more detail with reference to the following Examples, which are not intended to limit the present invention. Parts and percentages are parts by weight and weight percent, respectively, unless otherwise noted.

Free drainage tests (by gravity) were used to evaluate the conditioning properties of the polymer for different municipal and industrial sludges. The free drainage test was used to determine the amount of water drained from the polymer treated sludge sample. The test was carried out using the following general procedure:

1. Measure 200-500 ml of well mixed raw sludge. List suspended solids (SS) and volatile suspended solids (VSS) for each tested sludge.

2. Prepare an aqueous solution or dispersion of the composition having a concentration of 0.2% by weight.

3. Add the polymer solution to the sludge and mix it thoroughly (5 seconds at 500 rpm, then 15 seconds at 50 rpm).

4. Pour the treated sludge into a funnel pre-loaded with a filter.

5. Record drainage (filtrate weight) in grams for 1 minute and measure the turbidity of the filtrate. In the examples below, turbidity is measured with a Hach device, which is expressed in nephelometric turbidity units (NTU).

The transparency of the filtrate, as well as the weight of water exiting the agglomerate mixture, is used to distinguish performance differences between polymers. In general, if a high water drainage is obtained at a low polymer dosage, this represents a very efficient and effective polymer.

Example 1

Cationic polyacrylamide (filling amount: 70 mol%; molecular weight 9 to 10 x 10 ⁶ ) in different amounts (the weight of the tangle aid per weight part of the tangle is 0, 0.11, 0.25, 0.43 and 0.66) of solid ferric sulfate ( 20.7% Fe) and mechanically mixed. The particle size of each component was about the same, which was in the range of 100 to 600 μm. A free drain test was performed on 500 ml anaerobic digested municipal sludge samples (SS = 2.97 wt%; VSS = 47 wt% of SS). Table 1 shows the weight of water discharged and turbidity of the filtrate for each test.

Dosage Tangle Aids / Tangle Polymers (w / w) 0 0.11 0.25 0.43 0.66 ppm Drain-NTU age (g) Drain-NTU age (g) Drain-NTU age (g) Drain-NTU age (g) Drain-NTU age (g) 180 316 14.9 358 11.0 353 15.2 422 22.0 322 11.7 160 213 25.5 351 9.37 321 12.9 408 20.8 305 11.1 140 115 46.6 325 8.01 317 12.2 399 19.0 277 12.1 120 43 383 260 8.54 284 12.3 229 11.6 211 59.6 100 -- 69 80.6 131 33 132 35.3 118 103

From Table 1, it is demonstrated that the use of the composition of the present invention significantly increases the drainage amount compared to using only the flocculant. Best results are obtained with a composition containing 0.43 parts by weight of a tangle aid per weight of flocculant, but also 120 ppm by weight of a composition containing 0.11 part by weight of a tangle aid per part by weight of flocculant. Remarkably good results, such as a high drainage (284 g vs. 43 g) of more than five times, are obtained for the amount of composition. In addition to the improved drainage, turbidity is also improved compared to using only the flocculant.

Example 2

70 parts of cationic polyacrylamide (35 mol% charge; molecular weight 6.5 × 10 ⁶ ) were mixed with 30 parts ferric sulfate (20.7% Fe; particle size less than 0.5 mm) according to the following method:

Method (A): Polyacrylamide and ferric sulfate were mechanically mixed in the solid state, and then an aqueous solution of a mixture having a concentration of 0.2% by weight was prepared.

Method (B): 0.2% by weight of an aqueous solution of polyacrylamide and ferric sulfate was prepared separately and then 70 ml of polyacrylamide solution was mixed with 30 ml of ferric sulfate solution.

Method (C): 0.2% by weight of an aqueous solution of polyacrylamide and ferric sulfate was prepared separately. In the free drain test, the polyacrylamide solution was first added to the sludge, stirred for 5 seconds (500 rpm), and then ferric sulfate solution was added. The weight of ferric sulfate per weight part of polyacrylamide was maintained at 0.43.

Method (D): 0.2% by weight of an aqueous solution of polyacrylamide and ferric sulfate was prepared separately. In the free drain test, the ferric sulfate solution was first added to the sludge, stirred for 5 seconds (500 rpm) and then polyacrylamide was added. The weight of ferric sulfate per weight part of polyacrylamide was maintained at 0.43.

Free drainage tests were performed on 200 ml samples (SS = 2.54 wt%; VSS = 53 wt% of SS) of municipal sludge, with the addition of a conditioning agent in accordance with the above four methods. Table 2 shows the weight in grams of water discharged for each test and the turbidity of the filtrate. Dosage means the total amount of both components (polyacrylamide and ferric sulfate):

Exam 1 2 3 4 5 Dosage / ppm hour / s Pure PAM200 A200 B200 C200 D200 0 0 0 0 0 5 46.6 112.7 106.78 84.13 10 63.45 121.54 114.12 93.54 15 74.13 126.61 118.6 98.62 20 81.28 129.71 121.02 101.47 30 88.07 133.73 124.63 106.21 60 98.26 143.44 130.43 111.94 Turbidity / NTU 2133 2180 2836 2380

From the above results, addition of pure polyacrylamide, continuous addition of polyacrylamide and iron salt (methods C and D), or addition of a mixture of two treatment solutions of polyacrylamide and ferric sulfate (method B; such As compared to no entanglement in this case), the unexpected synergistic effect of the new composition (method A) is clearly demonstrated.

Example 3

70 parts by weight of nonionic polyacrylamide (molecular weight 8 × 10 ⁶ ) was prepared by 30 parts by weight of talc [PE 8418, manufactured by Ruzenac; Method E] was mixed mechanically. The particle size of each component was about the same, which ranged from 100 to 600 μm. Free drain test was performed on a 200 ml primary sludge sample (SS = 4.5 wt%; VSS = 50 wt% of SS) from a paper mill. The drainage capacity of the novel compositions was determined using pure nonionic polyacrylamide and 70 parts of identical nonionic polyacrylamide and 30 parts of cationic poly DADMAC (Magnafloc 369, manufactured from Allied Colloids Limited); Method F] was compared to the mixture prepared by mechanically mixing. Table 3 shows the weight of water discharged and turbidity of the filtrate for each test:

Exam 1 2 3 Dosage, ppm hours / s PAM E F200 200 200 Drained water / ml 0 0 0 0 5 47.2 56.1 34.99 10 80.3 86.3 53.57 15 96.0 102.4 69.75 20 103.7 111.1 77.67 30 111.7 119.5 89.79 60 120.5 129.6 101.5 Turbidity / NTU 809 905 655

From this example, the improved cost-effective drainage of the new composition, again compared to pure polyacrylamide or a mixture of organic flocculents such as polyacrylamide and poly DADMAC, was again demonstrated.

By studying in more depth the data in Table 3, it is practically better to use a composition containing a tangle with an organic flocculant (composition F) as compared to using a tangle alone (composition PAM). It was found that poor drainage was obtained. This fact can be regarded as an indicator for using a combination of flocculants and flocculants to dewater the sludge. However, on the contrary, a composition according to the invention comprising a tangle agent together with an inorganic tangle aid (composition E) very surprisingly comprises a composition comprising only a tangle agent and a combination of an organic flocculant and a tangle agent (composition F). Both compositions provide significantly better drainage.

Example 4

70 parts of cationic polyacrylamide (35 mole% charge, molecular weight 6.5 × 10 ⁶ ) were mechanically mixed with 30 parts of aluminum hydroxide (62% Al ₂ O ₃ ; Method G). A free drain test was performed on 200 ml of activated industrial waste sample (SS = 4.05 wt%; VSS = 52 wt% of SS). The drainability of the new composition was compared to pure cationic polyacrylamide. Table 4 shows the weight of water discharged and turbidity of the filtrate for each test:

Exam 1 2 Method PAM G Dose Kg / tDS 4.4 4.4 Dose, ppm 200 200 hours / s Drained water / ml 0 0 0 5 116.6 119.9 10 119.8 124.0 15 122.3 126.0 20 123.8 127.7 25 124.7 128.8 30 125.5 129.6 45 126.9 130.8 60 128.0 131.7 Turbidity, NTU 9.85 10.3

From this example, it can be seen that the drainage is slightly increased when using the composition of the present invention compared to pure polyacrylamide (PAM). In addition, the compositions of the present invention are slightly more cost effective than the critically pure polyacrylamides.

Example 5

Plant tests were conducted in municipal sewage treatment plants with anaerobic digested sludge (SS = 3.0 wt%; VSS = 48 wt% of SS). Dehydrated using centrifugation. In order to operate the plant normally, a dry material of 5.8 kg / ton of cationic polyacrylamide (70 mole% charge, molecular weight 9 to 10 x 10 ⁶ ) in which the sludge cake has a dryness of approximately 17.4 wt% is required.

70 parts of the same cationic polyacrylamide and 30 parts of ferric sulfate were mechanically mixed. Then 0.2% by weight of an aqueous solution was prepared and added to the sludge. In this case, the sludge cake dryness of the new composition dry material of 4.8 kg / ton was 19.16%, while significantly increasing the performance of pure polyacrylamide at low cost.

Example 6

According to the following method, 70 parts of cationic polyacrylamide (35 mole% charge; molecular weight 6.5 × 10 ⁶ ) were mixed with 30 parts of solid ferric sulfate (20.7% Fe; particle size less than 0.5 mm):

A. Polyacrylamide and ferric sulfate were mechanically mixed in the solid state, and then an aqueous solution of a mixture having a concentration of 0.2% by weight was prepared.

B. Polyacrylamide and ferric sulfate were mechanically mixed in the solid state and then the solid mixture was added directly to the sludge.

C. An aqueous solution of 0.2% by weight of polyacrylamide and ferric sulfate was separately prepared. In the free drain test, after stirring for 5 seconds (500 rpm), the polyacrylamide solution was first added to the sludge and the ferric sulfate solution was added. The weight of ferric sulfate per weight part of polyacrylamide was maintained at 0.43.

D. An aqueous solution of 0.2% by weight of polyacrylamide and ferric sulfate was separately prepared. In the free drain test, after stirring for 5 seconds (500 rpm), the ferric sulfate solution sludge was added first and polyacrylamide was added. The weight of ferric sulfate per weight part of polyacrylamide was maintained at 0.43.

Free drainage tests were conducted on 200 ml of primary and secondary mixture samples (SS = 2.59 wt%; VSS = 55 wt% of SS) of municipal sludge with the addition of a conditioning agent in accordance with the above four methods. Table 5 shows the weight in grams of water discharged for each test and the turbidity of the filtrate. Dosage means the total amount of both components (polyacrylamide and ferric sulfate):

exam One 2 3 4 5 Tangle Pure PAM A B C D Dose / ppm 200 200 200 200 200 Time / s 0 0 0 0 0 5 39.32 109.55 102.43 79.42 10 55.23 117.74 110.76 87.38 15 66.41 125.56 115.45 94.79 20 75.98 128.54 118.34 99.32 30 81.36 134.34 121.83 102.42 60 83.11 142.48 123.53 104.43 Turbidity / NTU 1518 2759 2569 1915 Tangle (1-5) 4 5 5 5 color Y Y Y Y obs. F F NF F F

Tangle: 1-bad, 5-very good.

Color: Y-Yellow.

obs .: F-tangled. NF-not tangled.

From this result, addition of pure polyacrylamide, continuous addition of polyacrylamide and iron salt (methods C and D), or addition of the mixture in the solid state (method B; no entanglement in this case is identified) In comparison, the unexpected synergistic effect of the composition (method A) according to the invention is clearly demonstrated.

Claims (10)

A sludge dewatering method for dewatering sludge after treating sludge with flocculant aid and flocculant, The entanglement aid is an inorganic compound; The entanglement aid and the entanglement agent are provided as a solid composition comprising 0.1 to 10 parts by weight of the entanglement aid per weight part of the entanglement agent; Adding water to the composition to provide an aqueous solution or dispersion of the composition; Adding the aqueous composition to the sludge; And The sludge is dewatered. The method of claim 1, wherein the entanglement aid and the entanglement agent are provided as a composition comprising 0.1 to 1.5 parts by weight of the entanglement aid per weight part of the entanglement. 3. Process according to claim 1 or 2, characterized in that the composition comprises agglomeration aids and solid particles of agglomeration agents having a particle size of 100 to 600 [mu] m. The method of claim 1, wherein water is added to the composition to provide an aqueous solution or dispersion having a concentration of 0.01 to 1.5% by weight. 5. The sludge according to claim 1, wherein the aqueous composition is added to the sludge in a proportion of 0.1 to 0.5% by weight of the total weight of the agglomeration aid solids and the agglomerate solids, based on the weight of the sludge solids. Way. A composition for sludge dewatering, characterized in that it comprises a mixture of a solid agglomerate and a solid inorganic agglomeration aid at a ratio of 0.1 to 10 parts by weight of agglomeration aids per weight part of agglomeration agents. 7. The composition of claim 6, wherein the inorganic entanglement aid is selected from the group consisting of iron containing salts, aluminum containing salts, minerals or mixtures thereof. The method of claim 7, wherein the iron-containing salt is selected from the group consisting of ferric chloride, ferric sulfate, iron hydroxide, iron nitrate and iron nitrate sulfate; Aluminum containing salts are the group consisting of aluminum sulfate, aluminum hydrate, polyaluminum chloride hydroxide, polyaluminum chloride hydroxide sulphate, polyaluminum hydroxide sulphate, polyaluminum hydroxide phosphate and polyaluminum chloride silicate Is selected from; And the mineral is selected from the group consisting of silica, alkali metal metasilicates, aluminum silicates, alkali metal silicates or mixtures thereof. 9. A composition according to claim 8 wherein the mineral is selected from the group consisting of talc, kaolin, zeolites and bentonite. 10. The composition according to any one of claims 6 to 9, wherein the flocculating agent is selected from the group consisting of nonionic and cationic homopolymers and copolymers of (meth) acryl amides.