DE3032831A1 - METHOD FOR THE CLEANING OF DRAINAGE CONTAINING DYE - Google Patents

Description

The invention relates to a method for purifying Wastewater that contains dyes, e.g. from wastewater from dye factories or wastewater from dye works. This Process serves to reduce the pollution of this waste water with impurities.

The mentioned wastewater are usually due to strong fluctuations in the pollution with impurities that come from biological difficult to break down compounds, a high content of chlorides, colloidal dyes, traces of heavy metals and possibly other toxic substances, marked.

Previous work has focused on eliminating the biochemical oxygen demand (BOD) , but more recently the greater concern has been on eliminating the chemical oxygen demand (COD) of suspended and suspended matter, color and colloidal particles.

In the method according to the invention, these are the components the contamination with impurities, the reduction of which was the particular aim of the applicant.

Numerous biological, physical or chemical treatment processes have long been used to remove or reduce the burden of contaminants of this type proposed by sewage.

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The work that deals with the biodegradability of various direct dyes, acidic dyes, more basic Dyes or pigments deal have shown that if one can get to a good one in certain cases Reduction in BOD occurs, the reduction in color and COD is always small and not the direct application justifies biological treatment; see in particular Dennis W. Weeter and A. Gale Hodgson - Proceedings of the 32nd Industrial Waste Conference - Ann Arbor Science - 1-9.

Of the physical methods, the use of ion exchange resins has been disclosed, for example, in US Pat and liquid-liquid extraction in U.S. Patent 3,966,594. However, these procedures require complicated ones Work stages and poorly adapt to the strong qualitative or quantitative fluctuations in the load of the wastewater to be treated with impurities.

As a chemical process, the use of hydrogen peroxide is made in the presence of iron (II) is a well-known treatment process, for example by Kitao, Takane-Mizu Shori Gijutsu 17 (8) (1976) 735-740. It leads to a good removal of the paint and COD reduction, at least in cases of soluble dyes, but requires large amounts of reagents and does not solve the problem of suspended and suspended matter, the content of which even increases as a result of the treatment.

It was also found by the applicant that a Flocculation treatment with mineral compounds followed by In certain cases, decanting results in a satisfactory discoloration and, in general, a strong one Reduction of the suspended matter or suspended matter allows, however, always of the formation of a very large one Amount of sludge is accompanied by this treatment

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especially from the point of view of the environment (transformation of pollution a liquid wastewater into a solid residue) of little interest.

There was thus a technical need for a cleaning process for the purification of waste water containing dyes to develop that meets the requirements of the various authorities that determine the quality of this wastewater.

In the context of studies that were carried out by the applicant on the treatment of such wastewater, was found that results that are far superior to the previously known results are achieved by treatment be that an oxidation stage with hydrogen peroxide and comprises a step consisting of coagulation, flocculation and decantation.

The method according to the invention thus consists of a treatment in two stages, namely an oxidation stage with the help of hydrogen peroxide and a coagulation-flocculation-decantation stage with the help of mineral salts, possibly in conjunction with a polyelectrolyte, for example a copolymer based on acrylamide and optionally has ionic functions.

To achieve the best reduction in COD and color, it is particularly useful to bring the wastewater to a pH value below 5 before adding the hydrogen peroxide and, if necessary, to add a metal salt, e.g. an iron (II) as a catalyst. salt, such as iron (II) sulfate FeSO, * 7 H ₂ O, added. Within the scope of the invention, these two stages can be combined with any other classic pretreatment or aftertreatment that would justify the nature of the wastewater to be treated.

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Depending on the treated wastewater, the oxidation level can be be carried out before or after the coagulation stage.

In order to achieve the best efficiency of the use of HO ₂ , it is particularly expedient in the process according to the invention to work with a reaction time between 1 and 24 hours, preferably between 1 and 4 hours.

The wastewater that can be treated by the method according to the invention generally has great fluctuations in the pollution load. For this reason, when designing the systems in which the treatment takes place, a first basin or pre-basin is often provided, which is intended to homogenize the water to be treated. In this case, it is particularly useful to use H ₃ O ₂ and. optionally introducing the oxidation catalyst into this basin in order to have the appropriate reaction time, provided that the best cleaning efficiency is obtained when the oxidation treatment is carried out first and then the coagulation treatment. In the opposite case, the H «O- must be added after the coagulation-flocculation-decantation stage in a suitable reaction vessel.

Any aqueous H ₂ O ₂ solutions are suitable for carrying out the process, but for reasons of simplicity of use it is particularly expedient to use solutions with 50 percent by weight of H ₃ O ₂ .

To achieve the best efficiency of the coagulation-flocculation-decantation stage it is particularly useful to use an inorganic coagulant made from metal salts of iron or aluminum, commonly used for the

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Treatment of wastewater, e.g. aluminum sulphate, Aluminum chloride, basic aluminum chlorosulfates. Iron (III) chloride, iron (III) chlorosulphate, iron (II) sulphate or combinations of these salts.

In the method according to the invention, the use becomes large Avoided amounts of lime as a coagulant, so that it is possible to reduce the amount of sludge formed considerably.

The quantities of reagents to be used in the two stages of treatment depend on the wastewater to be treated and on the desired quality of the treated water. They can vary within very wide limits and remain within the range prescribed according to the invention. The temperature of the two preparation stages is not critically important. The wastewater can be treated without any disadvantage at the temperature _t at which it reaches the treatment plant.

The advantages of the method according to the invention are illustrated by the following examples. With those in these Experiments described in the examples were the color of the solutions, the chemical oxygen demand (COD) and the content measured on suspended matter or suspended matter according to the following methods:

Color: The color of the water to be measured, which has previously been diluted with demineralized water (in order to get into the measuring range), is compared with colored glass panes that are graded according to the Pt-Co scale (see NF-T 90 -034-). The value determined in this way is multiplied by the dilution factor to obtain the color of the water to be measured.

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COD: The value can be calculated according to the potassium dichromate method NF-T 90-101 can be determined.

Suspended substances or suspended solids: The proportion is determined by filtration with a glass fiber filter disc according to NF-T 90-105.

example 1

Wastewater: Brown wastewater from the production of azo dyes, containing approximately per liter

50 to 2 00 mg of dyes (including certain pigment dyes and other soluble dyes), 150 to 300 mg phenols,

Amines and various organic impurities (intermediate products of the reaction, unreacted starting product), 2 to 5 g NaCl / 1,

Sodium sulphate, sodium carbonate, sodium bicarbonate, etc. The wastewater examined has the following key figures:
pH 9
Color 60,000 mg / 1 pt
COD 757 mg 0 ₂ / l

suspended substances 90 mg / 1

With this waste water, a classic coagulation treatment is carried out at the same time and the two-stage treatment consisting of oxidation and subsequent coagulation according to FIG Invention made.

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_ Q -

A) Processing by coagulation-flocculation-decantation with lime and iron (II) salt on wastewater as such:

Flocculation with 2.5 g of 95% lime Ca (OH) ₂ and 1.25 g

FeSO- * 7 H "0 / l wastewater and then with 5 g non-

ionic polyelectrolyte "Sepiflor AH12B" (manufacturer SEPPIC) per liter of wastewater.

After decanting for one hour and adding 1 ml of 80% sulfuric acid per liter of decantate, it becomes waste water with the following key figures:

pH 8.5

Color: 6000 mg / 1 pt corresponding to one

90% reduction;

COD: 617 mg 0 ~ / l corresponding to one

Decrease by 18.5%;

suspended substances :. 70 mg / l corresponding to a reduction of 22%;

Sludge formed: 2.1 g dry matter per liter of waste water

B) Two-stage processing: oxidation with Η ^, Ο ^ and flocculation oxidation stage

The wastewater is brought to a pH of about 3 by adding 0.36 ml of 80% sulfuric acid per liter of wastewater, whereupon the following compounds are added:

FeSO ₄ * 7 H ₂ O: 0.2 g / l
50% H ₂ O ₃ : 1.1 g / l

after a contact time of 2 hours, the following key figures are obtained:

pH value around 3

Color: 10,000 mg / 1 pt corresponding to one

Decrease by 83.3%;

COD: 677 mg 0 ₂ / l according to a ver

reduction of 10.6%.

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Coagulation-Flocculation-Decantation

After adding lime to adjust to a final pH value of about 7, coagulation and flocculation take place With the help of various inorganic salts and 4 mg / 1 of a non-ionic polyelectrolyte with the trade name "FLOERGER FA 2OH" carried out. Which depends on the inorganic salt used in this stage Results obtained from the combined treatment are shown in Table I below.

Examination of these results illustrates the effect of those carried out according to the method according to the invention Treatment that, in addition to a strong reduction in color, has an already low COD and a content of suspended Substances according to the applicable regulations. By increasing the H-O ^ -content during the oxidation treatment As Example 3 shows, a much lower COD can be achieved, which also complies with the applicable regulations corresponds in this regard.

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co O O

T a b e 1 1 e 1 pH colour
in
mg / 1 pt Diminish
tion of the
Colour, % COD
in mg
O ₂ A Diminish
tion of the
COD,% Levitation
fabrics,
mg / 1 formed sludge
in g dry matter
per / 1 wastewater Flocculant used 8.8 3,500 94.2 558 26.3 56 0.80 Amount of treatment agent 7.8 3,500 94.2 518 31.6 32 0.77 Aid, 1 g of 30% solution per liter 6.9 4,000 . 93.3 458 39.5 10 0.91 FeCl ₃ 1 g 41% solution per liter FeSO ₄ * 1 g FeSO ₄ * 7 H ₃ O. per liter
7H ₂ O results obtained after combined treatment

O OO NJ OO

Example 2

Wastewater: Brown wastewater from the production of azo dyes of the same type and from the same plant as in Example 1.
Key figures of the examined wastewater:

pH 7.3 000 mg / 1 Pt colour 60 mg o ₂ / i COD 980

Classic coagulation treatments with various coagulants and the two-stage treatment are carried out in parallel on this waste water Processing carried out according to the invention.

A) Processing by coagulation-flocculation-decantation alone

The wastewater described above is either with AlCl-. or treated with lime and ferrous sulfate.

A.1 - with AlCl ₃

0.25 g of 95% lime Ca (OH) _{2 are} added to the waste water per liter, whereupon it is treated by coagulation-flocculation with 1 g of 30% AlCl -.- solution and 4 mg of the nonionic polyelectrolyte of the trade name "FLOERGER FA20H" will. After sitting for an hour, a water with the following indicators is obtained:

pH 7.5

Color: 9,000 mg Pt / 1 according to a ver

reduction by 85%

COD: 466 mg 0- / 1 according to a ver

reduction by 52.4%

sludge formed: 0. 52 g dry matter per liter of wastewater

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A.2 - with lime and iron (II) sulfate

2.5 g of 95% lime per liter are added to the wastewater, whereupon coagulation and flocculation with 1.25 g FeSO. per liter of wastewater follows. After allowing it to settle for one hour, 0.74 ml of 80% H ₃ SO ₄ per liter are added to the decantate. Here, a water with the following key figures is obtained:

pH 8.9

Color: 9,000 mg Pt / 1 corresponding to one

Reduction of 85% COD: 583 mg O “/ l corresponding to one

40.5% reduction

Sludge formed: 2.1 g dry matter per liter of waste water

B) Combined treatment: oxidation with H ₃ O ₂ and flocculation

Oxidation level

The waste water is adjusted to a pH of about 3.5 with 0.2 ml of 80% H ₂ SO _{4. Then 0.3 g FeSO 4} 7 H ₂ O and then 1.275 g 50% H ₂ O _{3 are} added per liter of waste water. After a contact time of 2 hours, the flocculation is carried out.

Flocculation stage

After setting to a final pH value of about 7 by adding lime, the coagulation flocculation is treated with 0.8 g of basic aluminum chlorosulfate as a commercial solution ("WAC", manufacturer Produits Chimiques Ugine Kuhlmann), 0.1 g of commercial iron ( III) solution with 41% FeCl ₃ and 4 mg of the nonionic polyelectrolyte of the trade name "FLOERGER FA20H" per liter of waste water. After a settling time of one hour, a water with the following key figures is obtained:

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pH value 8.8

Color: 3,500 mg Pt / 1 corresponding to one

94.1% reduction

COD: 431 mg O ₂ / l according to a ver

reduction by 56%

Sludge formed: 0.72 g dry matter per liter of waste water

The combined treatment gives better results in terms of removal than the flocculation treatments.

Example 3

Wastewater: alkaline wastewater from the production of bleu

Foulon B.R.L.

Characteristics of the treated wastewater:

pH 12.3

Colour: · . 2,500 mg Pt / 1

COD: 465 mg _0.9 / l

This example serves to compare the results obtained with the treatment by coagulation-flocculation-settling alone (Section A) with the results obtained with a combined treatment according to the invention
correspond, the oxidation stage taking place before (section B) or after (section C) the coagulation-flocculation-settling stage.

A) Processing by coagulation-flocculation-settling alone

The wastewater is either with AlCl., Or with a mixture treated by basic aluminum chlorosulphate and ferric chloride.

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A.1 - with

7 ml of concentrated H-SO ₄ (d - 1.83) are added to the wastewater per liter, followed by coagulation and flocculation with AlCl-. in 3 0% solution and 4 mg of the non-ionic polyelectrolyte "FOERGER FA 2OH" per liter of waste water. The conditions of treatment and the results obtained after 1 hour of settling are given in Table II below.

Table II

attempt A 1 A 2 A 3 3 0% AlCl ₃ solution, g / l wastewater 0.5 1 1.5 Results PH value 7.65 7.6 7.8 Color, mg Pt / l 1150 1500 1000 Diminution of color, % 54 40 60 COD, mg 0 ₂ / l 63 55 57 COD reduction,% 86.5 88.2 87.7

formed sludge,

g dry matter / liter

Wastewater 0.63 0.82 0.95

A.2 - with basic aluminum chlorosulphate and ferric chloride

After adding 7 ml of concentrated H ₃ SO ₄ (d = 1.83) per liter of wastewater, coagulation and flocculation takes place with a mixture of 8 parts by weight of a commercial solution of basic aluminum chlorosulfate (WAC), 1 part by weight of commercial 41% iron (III) chloride solution, 1 part by weight of water (this mixture is hereinafter referred to as mixture A) and 4 mg of the nonionic polyelectrolyte

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"FLOERGER FA 2OH" per liter of wastewater. The amounts of treatment agents in grams mixed per liter of waste water and the results obtained after one hour of settling are below mentioned in Table III.

Table III Experiment A4 A 5 A 6

Mixture A of the coagulants,
g / l wastewater 0.5 1 1.5 Results PH value 7.7 7.5 7.6 Color, mg Pt / l 1400 1150 1000 Color reduction,% 44 54 60 COD, mg O ₂ / l 63 59 59 COD reduction,% 86.5 87.3 87.3

formed sludge, in ",

g dry matter per liter

Wastewater 0.55 0.72 1.66

B) Combined processing by oxidation and subsequent coagulation-flocculation-settling

Oxidation level :

The pH is adjusted to about 3.21 by adding 7.8 ml of concentrated H ₃ SO ₄ (d = 1.83) per liter of waste water, whereupon 30.8 mg of FeSO ₄ '7 H ₃ O and 0.17 g of 50% H ₃ O ₂ per liter of waste water are added. After a contact time, the waste water is subjected to coagulation.

Coagulation-flocculation-settling

After setting a final pH value of about 7 by adding a sufficient amount of lime, what was previously oxidized Water flocculated with an inorganic reagent and a polyelectrolyte. The type of reagents, their amounts and the results obtained after one hour of settling are shown in Table IV below.

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Reagents
(Type and amount per liter of wastewater) T a b e lie IV PH colour
mg Pt / 1 reduction
the color,% ¹ COD
mg 0-1 reduction
of COD,% formed sludge
g dry matter / l waste
water attempt 0.15 g mixture A and 5 mg anion
active polyelectrolyte "FLOERGER
FA 57H " 7.7 100 96 22nd 95.3 0.35 B 1 0.25 g mixture A and 5 mg anion
active polyelectrolyte "FLOERGER
FA 57 H " 7.2 80 96.8 32 93.1 0.40 B 2 0.25 g mixture A and 5 mg non-
ionic polyelectrolyte
"FLOERGER FA 2OH" 7.8 100 4th
96 44 90.5 0.39 B 3 0.15 g of 30% AlCU solution and
5 mg of anion-active polyelectro
lyt "FLOERGER FA 57 H" Results after the combined treatment 6.9 80 96.8 0.37 B 4 0.25 g of 30% AlCl ₃ solution and
5 mg non-ionic polyelectro
lyt "FLOERGER FA 20 H" 7.7 50 98 28 94.0 0.37 B 5

C) Combined processing by coagulation-flocculation-settling and subsequent oxidation

Flocculation stage:

After adding 7.6 ml of concentrated H ₅ SO ₄ (d = 1.83) per liter of waste water, coagulation and flocculation with an inorganic reagent and the non-ionic polyelectrolyte "FLOERGER FA 2OH" follow. The decantates obtained after settling for one hour are then oxidized as follows:

Oxidation level:

The decantate is adjusted to a pH of about 3.3 by adding 0.125 to 0.2 ml of concentrated H ₂ SO _{4 (d = 1.83) per liter.} Then 32 mg FeSO.7 HO and 0.2 g 50% HO per liter of decantate are added. After a contact time of 1.5 hours, neutralization with 0.100 to 0.145 g of 80% lime per liter follows.

The results obtained are shown in Table V below. Treatment was with the following reagents carried out per liter of wastewater:

Experiment C ₁ : 0.15 g of mixture A and 5 mg of nonionic poly-

electrolyte;

Experiment C ₃ : 0.25 g of mixture A and 5 mg of nonionic poly

electrolyte;

Experiment C ₃ : 0.25 g of 30% AlCl ₃ solution and 5 mg of nonionic polyelectrolyte.

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Table V

Trial results after combined treatment

1 pH O colour
mg Pt / 1 reduction
the color, % COD
mg O Reduction of the
COD,% 5 C. 2 8th, 9 10 99.6 58 87 2 C. 3 7, O 10 99.6 64 86 2 C. 8th, 10 99.6 69 85

A comparison of Tables IV and V shows that regardless of the order of treatments, i.e., oxidation-coagulation and coagulation-oxidation, excellent results are obtained by the method according to the invention, which with regard to the removal of the color far superior to the results obtained by coagulation alone (Tables II and III) are =

Example 4

Sewage; Blue wastewater from a large-scale dye works (dyeing cotton with direct dye).
Key figures of the examined wastewater:

pH 8.0

Color: 160,000 mg Pt / 1

COD: 3,411 mg O ₂ / l

This wastewater is treated according to the invention subjected to either oxidation-coagulation or coagulation-oxidation.

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A) Combined processing by oxidation and subsequent coagulation-flocculation-settling

Oxidation level:

After adjusting the pH to about 3.1 by adding 0.18 ml of concentrated H ~ SO. (d = 1.83) per liter of wastewater, 1.2 g of FeSO.7 H ₃ O and 7.54 g of 50% H ₃ O ₂ per liter of wastewater are added. After a contact time of 3 hours, the following step is carried out :

Coagulation-flocculation-settling treatment

After adjusting the pH to about 7 by adding a sufficient amount of lime, the previously oxidized wastewater becomes flocculated with an inorganic reagent and the anion-active polyelectrolyte "FLOERGER FA 57H". The type of used Reagents, their amounts and the results obtained after the final settling treatment are shown below in Table VI mentioned.

B) Combined treatment by coagulation-flocculation-settling treatment and subsequent oxidation

Flocculation stage:

After the addition of 80% lime, coagulation and flocculation follow with the aid of an inorganic reagent and the anion-active polyelectrolyte "FLOERGER FA 57H" under the conditions listed in Table VI mentioned conditions.

The decantates are then oxidized as follows: Oxidation level:

After adjusting the pH to about 3.3 by adding 0.12 ml of concentrated H-SO. (d = 1.83) 0.96 g FeSO ₄ * 7 H ₃ O and 5.52 g 50% H ₃ O ₂ per liter of decantate are added per liter of decantate. After a contact time of 2 hours, 1.8 to 2.2 g of 80% lime per liter are added to the mixture. The properties of the decantate after the settling treatment are given in Table VII below.

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The results in Tables VI and VII show that the removal of color in the two experiments of the example 4 is excellent, the reduction in COD in the coagulation treatment with subsequent oxidation is bigger.

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Table VI

co

approx

CO O

Reagents
(Type and amount per liter of wastewater) Results after the cobminized treatment PH colour
mg Pt / 1 reduction
the color, % COD
mg 0 ₂ / l Reduction of the
COD,% 0.6 g mixture A and 5 mg
anion-active polyelectrolyte 6.8 500 99.69 1366 59.95 attempt 0.9 g mixture A and 5 mg
anion-active polyelectrolyte 6.85 400 99.75 1366 59.95 1 0.6 g of 30% MCl ₃ solution
and 5 mg anionaktxver
Polyelectrolyte 6.9 400 99.75 1357 60.22 2 0.9g 30% AlClj solution
and 5 mg more anion active
Polyelectrolyte 6.9 300 99.81 1289 62.21 3 4th

to to

O CJ fS) 00 GJ

co σ ο

CO

CO O

cn

go

03 T3

m α

Flocculation reagents T a b e lie VII PH colour
mg Pt / 1 reduction
the color, % COD
mg O _2/1 Reduction of the
COD,% Type and quantity of reagents
per liter of wastewater 6.85 300 99.81 583 82.91 attempt about 0.2 g of 80% Ca (OH) ₂ ,
2 g mixture A and 5 mg anion
active electrolyte 6.95 220 99.86 592 82.64 1 about 0.25 g of 80% Ca (OH) ₂ ,
2.5g mixture A and 5 mg anion
active polyelectrolyte 7.15 180 99.89 294 91.38 2 about 0.3 g of 80% Ca (OH) ₂ ,
3 g mixture A and 5 mg anion
active polyelectrolyte Results after the combined treatment 6.95 120 99.93 419 I.
87.72 3 about 0.3 g of 80% Ca (OH) ₂ ,
2 g of 30% AlCU solution and 5 mg
anion-active polyelectrolyte 7.2 100 99.94 429 87.42 4th about 0.4 g of 80% Ca (OH) ₂ ,
2.5 g of 30% AlCl ₃ solution and 5 mg
anion-active polyelectrolyte 7.35 80 99.95 255 92.52 5 about 0.5 g of 80% Ca (OH) ₂ ,
3 g of 30% AlC ^ solution and 5 mg
anion-active electrolyte 6th

NJ U)

O CO ro oo oo

Claims (7)

Claims 1. Process for the purification of dyes containing Wastewater, characterized in that the treatment is carried out in two stages, namely one with the aid of hydrogen peroxide and one with the aid of a coagulant performed stage of coagulation-flocculation-settling treatment. 2. The method according to claim 1, characterized in that the oxidation stage with hydrogen peroxide performed prior to the coagulation-flocculation-settling treatment stage. 3. The method according to claim 1, characterized in that the oxidation stage with hydrogen peroxide after the coagulation-flocculation-settling treatment stage. 4. The method according to claims 1 to 3, characterized in that that the waste water before the addition of hydrogen peroxide to a pH value below 5 130013/1305 brings and / or adds a metal salt to it. 5. Process according to claims 1 to 4, characterized in that the oxidation is carried out for 1 to 24 hours. 6. The method according to claim 5, characterized in that the oxidation is carried out for 1 to 4 hours. 7. The method according to claim 1 to 6, characterized in that the coagulation with a coagulating metal salt such as aluminum sulfate, aluminum chloride, basic aluminum chlorosulfate, iron (III) chloride, iron (III) chlorosulfate, Iron (II) sulfate and combinations of these salts performs. 130013/1305