LU82736A1 - PROCESS FOR THE PURIFICATION OF WASTEWATER CONTAINING COLORING MATERIALS - Google Patents

Description

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The present invention relates to a process for purifying waste water containing dyestuffs such as, for example, waste water from dye manufacturing plants or waste water from dye-5 · This process is intended to reduce the pollutant load of these effluents.

These waste waters are usually characterized by significant variations in the pollutant load * consisting of hardly biodegradable compounds, 1D a high content of chlorides, dyes in colloidal form, traces of heavy metals and possibly other toxic materials *

Previous work has focused on eliminating biochemical oxygen demand (BOD), but recently there has been major concern with eliminating chemical oxygen demand (COD) of suspended matter (ME5.), Color and colloidal particles.

In the process according to the present invention, it is these constituents of the polluting load which reduction has been sought by the Applicant.

Numerous treatment methods, biological, physical or chemical, have long been proposed for eliminating or reducing the pollutant load of this type of waste water.

*.

The work carried out on the biodegradability of different direct dyes, acidic, basic or pigmentary, has shown that if in certain cases a good reduction of the D.B.D. is achieved, that of the color and of the 3D D.C.O. is always weak and does not justify the direct use of biological treatment, see in particular Dennis W. Weeter and A. Gale Hodgson - Proceedings of the ^ 32nd Industrial Waste Conference - "Ann Arbor Science - j. - 9. L__ .. Among the physical processes, the use of resins Ψ t ’? -η * 2 ion exchangers has been recommended for example by | the USP 3 803 030 and that of a liquid-liquid extraction I by the USP 3 966 594 · But these processes involve modes; delicate and poorly adapted to strong operating procedures varied 5 qualitative or quantitative terms of the pollutant load of the waste water to be treated.

As a chemical process, the use of hydrogen peroxide • · in the presence of ferrous iron constitutes a known treatment process described for example by Kitao, Takane-Mizu! 10 Shori Gijutsu 1976, .17 (8), 735-40. It leads to a good elimination of the color and of the D.C, 0, at least in the case of soluble dyes but requires significant amounts of reagent and does not solve the problem of M.E.S. the content of which is even improved by the treatment, 15 Furthermore, the Applicant has found that a flocculation treatment with mineral compounds followed by decantation, if in certain cases it allows satisfactory discoloration as well as generally a strong reduction - | i tion of suspended matter, is always accompanied by the [I 20 formation of a very large amount of sludge which makes 9 this treatment unattractive, especially from the point of view of the environment (displacement of pollution from a liquid effluent I to a solid residue).

1 There was therefore an industrial need to develop B t 25 a technique for purifying waste water containing dyestuffs meeting the requirements of! various administrations controlling the quality of these waters.

4: 1 Within the framework of the studies carried out by the applicant; for the treatment of such waste waters, it has been found that results much better than those previously known were obtained by a treatment comprising an oxidation step with hydrogen peroxide and a coagulation-flocculation-dpcantation step.

ÎThe process according to the invention therefore consists of a treatment in two stages: - an oxidation stage using hydrogen peroxide, - a coagulation-flocculation-decantation stage using mineral salts associated or not with a polyelectrolyte such as an acrylamide-based copolymer and optionally comprising ionic functions.

To obtain the best reduction in D.C.O. and color, it is particularly recommended to por-10 ter, before the addition of hydrogen peroxide, if necessary the effluent at a pH below 5, and to add, if necessary, a metal salt as an oxidation catalyst such as a ferrous salt, for example ferrous sulfate FeSO 7 HO.

4 2 These 2 steps can be combined without departing from the object of the present invention any other conventional anterior or posterior treatment that the nature of the water to be treated would justify.

'Depending on the effluents treated, the oxidation step.

can be performed before the coagulation step or after it.

To obtain the best yield from the use of H 0, it is particularly recommended, according to the process of the invention, to have a reaction time of between 1 and 24 hours and preferably from 1 to 4 hours.

25 The waste water capable of being treated according to the method of the invention generally exhibits significant variations in the pollutant load. This is why, when designing the works in which the treatment is carried out, it is common to provide a pre-30 thousand tank intended to homogenize the waste water to be treated. In this case it is particularly recommended to introduce ^ 2 ^ 2 e ^ * ®ven ^ ue ^ - ^ emen ^ Ie catalyst oxidation in this basin to have the reaction time recommended, bous provided that the best yield of purification is ob-35 held by first carrying out the oxygen treatment and then ii! ri "1 '" 4 \\ I then the coagulant treatment. Otherwise, the addition of H2O2 must be done after the step of coagulation-flocculation-decantation, in an appropriate reaction tank.

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All aqueous solutions of ^ O ^ are used; 5 sands to carry out the process but it is particularly advisable, for reasons of convenience of use, to use solutions with 50 5s ^ 2 ^ * 2 in PD ^^ S #

To obtain the best yield from the coagulation-flocculation-decantation stage, it is particularly recommended to use an inorganic coagulant chosen from the metallic salts of iron or aluminum usually used in water treatment such as aluminum sulphate , aluminum chloride, basic aluminum chlorosulfates, ferric chloride, ferric chlorosulfate, ferrous sulfate or a combination thereof.

In the present process the use of massive amounts of lime, as a coagulant, is avoided which makes it possible to considerably reduce the amount of sludge formed. The contents of reagents to be used in the 2 phases of the treatment depend on the effluent. to be treated, and of the desired quality for the treated water, they can vary within very large proportions while remaining within the scope of the claimed invention. The temperature of the 2 phases of the treatment is not critical, the effluents can be treated without inconvenience at the temperature where they arrive at the treatment plant.

The following examples illustrate, without limitation, the advantage of the process developed by the applicants.

In these examples the color of the solutions, the chemical oxygen demand (DC0.) And the suspended matter (ME5.) Were measured as follows: / 5 - Color: the coloring of the water to be measured beforehand diluted (to bring it back into the measurement range) with demineralized water is compared with 'colored glass disks graduated in scale i 5 Pt - Co (see NF - T 90 - 034-).

The value thus determined is multiplied by the dilution factor to obtain the color of the water to be measured, - D.C.D. : It is determined by the potassium dichromate 10 method according to NF - T 90 - 101, - M.E.5. : It is determined by filtration on a glass fiber disc according to NF - T 9D - 105, EXAMPLE 1

Effluent: Brown waste water from the production of m 15 azo dyes containing approximately ï I - - 50 to 200 mg / 1 of dyes (certain pigments, others soluble), - 150 to 300 mg / l of phenols, - amines and various organic impurities (reaction intermediates, unreacted starting material), - NaCl; 2 to 5 g / 1, - Sulfate, carbonate, bicarbonate of Na, “etc, ·,

The characteristics of the effluent studied are: 25 - PH = 9 - Color = 60,000 tng / l Pt - D.C.O. = 757 mg 0/1 i - M.E, S. = 90 mg / 1 5 on these waste waters a conventional coagulation treatment is carried out in parallel and the treatment in 2 stages of oxidation then coagulation according to the present application.

A) Coagulation-flocculation-decantation treatment with lime and ferrous salt ‘, on the effluent as it is::! **. 6 ί - flocculation with 2.5 g of lime Ca (DH) ^ at 95% d and 1.25 g of FeSO ^, 7 H ^ O per liter of effluent, then 5 mg of non-ionic polyelectrolyte Sepiflor AH12B, brand filed '! from the company SEPPIC, per liter of effluent "D 5 After decantation for one hour and addition to the decantate of 1 ml of 80% sulfuric acid per liter, water is obtained having the following characteristics: pH = B , 5 - Color = 6,000 mg / 1 Pt i.e. a reduction of 10 90% - DC0, = 617 mg 02 / l or a reduction of 18.5% - ME5. = 70 mg / 1, i.e. a reduction of 22% m, D5 - Sludge produced ^ 2.1 g of dry matter per liter of effluent B) Treatment in 2 stages oxidation with H2O2 - flocculation - Oxidation step: 20 Effluent supplied at pH CL 3 by adding 0.36 ml of 80% sulfuric acid per liter of effluent and then adding:. Fe S04, 7 H2O: 0.2 g / l. H2O2 50%: 1.1 g / l 'After 2 h of contact time, we obtain: • pH ~ 3 • Color = 10,000 mg / 1 Pt, ie a reduction of 63.3% • D.C.0. = 677 mg 02 / l, ie a 30 'reduction of 1D »6% - Coagulation-flocculation-decantation stage î After addition of lime allowing a final pH close to 7 to be obtained, coagulation-flocculation i- i is carried out! τ non-ionic trolyte, FLOERGER, registered trademark, FA 2DH.

Depending on the mineral salt used in this step, the re-obtenus results obtained, after combined treatment, are indicated in Table I below.

5 Examination of these results shows the effectiveness of the treatment carried out according to the method of the invention which allows, alongside a significant reduction in color, to obtain a D.C.O. already low and an M.E.S. corresponding to current specifications. By increasing the content of the oxidation treatment, it is possible to obtain, as will be seen, for example, in example 3 of the D.C.O. much lower then meeting current specifications in this area.

EXAMPLE 2 Effluent: Brown waste water from the manufacture of azo dyes of the same type and coming from the same factory as in Example 1.

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Summary characteristics of the effluent studied: - pH = 7.3 20 “Color = 60,000 mg / 1 Pt - D.C.O, s 960 mg 0 ^ / 1. On these waste waters, conventional coagulation treatments are carried out in parallel with various coagu-! lants, and treatment in 2 stages according to the present invention j * 25 tion.

! A) Coagulation-flocculation-decantation treatment only ï The above waste water is treated either with Γ AlClg, or with lime and ferrous sulphate.

30 A.1 - With AlCl ^

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-P CJ L) tn 33 ffl H 0) ‘tü p 2 * C U. U_ r— / ____ 9 lution of AlCl ^ to 3D ^ and 4 mg of nonionic polyelectrolyte FLDERGER, registered trademark, FA2DH. After decanting for one hour, water with the following characteristics is obtained: 5 - pH 7.5 - Color = 9 DOD mg / l Pt, i.e. a reduction of 65 £ - D.C.O. - 466 mg O2 / I, i.e. a reduction of 52.4% jQ - Sludge produced = 0.52 g of dry matter per liter of effluent A.2 - With lime and ferrous sulphate

Addition of 2.5 g of 95% lime and coagulation-flocculation with 1.25 g of FeSO, JH ~ 0 per liter of effluent * 4 2 15 and 5 mg of non-ionic polyelectrolyte Sepiflor AH12B, registered trademark of the company SEPPIC, per liter of effluent · After decanting for one hour, the decantate is added with 0.74 ml of 80% SO SO per liter. Water is then obtained having; ... 2 4.

the following characteristics: 20 - pH = 8.9 - Color s 9,000 mg / l Pt i.e. a reduction of B5% - D.C.O. = 583 mgD ^ / l i.e. a reduction of 40.5% 25 - Sludge produced = 2.1 g of dry matter per liter of effluent B) Combined treatment: oxidation by ^ 02 - flocculation

Oxidation step; Addition of 0.2 ml of 80% Hn50 per liter of effluent 4 4 to obtain a pH 3.5.

Addition of 0.3 g FeSO, 7 H 2 0 per liter of effluent then 1.275 g Hp0 50% per liter of effluent.

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After 2 h of contact time, the flocculation is carried out.

j Flocculation step:

Al '"1 Ί - 1 Γ Γ1 1 After adding lime in quantity allowing j 5 to obtain a final pH close to 7, coagulation is carried out - flocculation with 0.8 g of basic aluminum chlorosulfate, commercial solution sold by the company Chemicals Ugine Kuhlmann under the registered trademark WAC, 0.1 g of chloride, ferric commercial solution with 41% FeCl ^ 4 mg of 10 nonionic polyelectrolyte FLDERGER, registered trademark, FA20H per liter of effluent *

After one hour of decantation, water with the following characteristics is obtained:.

- pH = 8.8 15 - Color = 3500 mg / l Pt i.e. a reduction of £ 94.1 - D.C.O. ss 431 mg D -, / 1 a reduction of 56% - Sludge produced = 0.72 g of dry matter per 20 liter of effluent | Combination treatment leads to better elimination yields than flocculation treatments.

EXAMPLE 3 I Effluent: Basic effluent for the production of 25 Bleu Foulon B.R.L.

Characteristics of the effluent studied: - pH = 12.3 - Color = 2,500 mg / l Pt dd - D.C.O. = 465 mg 0 ^ / 1 30 This example is intended to compare the results obtained during a coagulation-flocculation-decantation treatment alone (§ A) with those corresponding to a combined treatment according to the present invention, the oxidation step being performed before (§ B) or after (§ C) step ί ii rnamtl atinn_i1 nriil a + ΐ nn-rifrantati nn.

- 11 A) Coagulation-flocculation-decantation treatment only The residual water is treated either with A1C1 or 3 with a mixture of basic aluminum chloride and ferric chloride.

A.1 - With AlClg * 'Addition of 7 ml concentrated (d = 1.83) per liter of effluent then —agulation-flocculation with AlCl ^ in 30% solution and 4 cg of non-ionic polyelectrolyte ID FLOERGER, registered trademark , FA 20H per liter of effluent. The treatment rates and the results obtained after one hour of decantation are indicated in Table II below.

m A.2 - With basic aluminum chlorosulfate and ferric chloride 15 Addition of 7 ml concentrated H 5D (d = 1.83) per 2 4 - '- liter of effluent then roagulation-flocculation with a mixture of • basic aluminum chlorosulfate commercial solution (WAC) f 8 parts by weight, ferric chloride commercial solution at 41%, 1 part by weight and water, 1 part by weight 20 (this mixture is hereinafter called mixture A) and 4 mg of non-ionic polyelectrolyte FLDERGER, registered trademark, FA 20H per liter of effluent. The treatment rates expressed * 'in g of mixture per liter of effluent and the results obtained after 1 hour of settling are indicated in Table III 25 below.

B) Combined oxidation treatment then coagulation-flocculation-decantation

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Ji subjected to coagulation. · 1 d \ Coaaulation-flocculation-decantation step: 5 After adding lime in quantity allowing to obtain a final pH close to 7 ”the previously oxidized effluent is flocculated using a reagent mineral and poly-electrolyte.

The nature of the reagents, the treatment rates and the results obtained after 1 hour of decantation are indicated in Table IV below.

C) Combined coagulation-flocculation-decantation treatment then oxidation

Flocculation stage; 15 Addition of 7.6 ml concentrated (d = 1.83) per liter of effluent then coagulation-flocculation using a mineral reagent and non-ionic polyelectrolyte FLOERGER, registered trademark, FA 20H.

The decantates obtained after one hour of decanting are then oxidized according to the step below:

Oxidation stage:

Addition of 0.125 to 0.2 ml of concentrated H 2 SO 4; (d = .1.83) per liter of decantate in order to bring the pH to ci. 3.3 l, then addition of 32 mg of Fe5D4, 7 ^ 0 and 0.2 g ^ 2 ^ 2 ^ I 25 per liter of decantate. After 1.5 hours of contact time, neu-?! tralisation by D, 100 to 0.145 g of lime at B0% per liter.

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bleau V below where, for the flocculation step: - 0 ^ corresponds to a treatment with 0.15 g of mixture A and 5 mg of nonionic polyelectrolyte per liter of effluent.

- C2 corresponds to a treatment with 0.25 g of mixture A and 5 mg of non-ionic polyelectrolyte - j j l ** 15 5 ω Γ - - +3 I ω

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5 TABLE V

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Color tests,,,. D.C.O. ,,,.

From reduction reduction mg / 1 Pt of Pg / l of ^ -a 10 color D.C.O.

C 1 8.0 .10 99.6 58 87.5 --r- ----- ----- - - - - - - ................ .........

C 2 7.9 10 99.6 64 86.2. C 3 8.0 10 99.6 69 85.2

The comparison of Tables IV and V shows that whatever the order of the oxidation-coagulation treatments, or coagulation-oxidation treatments, excellent results are obtained by the patent process with regard to the elimination of the color to be which is obtained with coagulation alone (Tables II and III).

EXAMPLE 4 1 Effluent; Blue waste water from industrial dyers (direct dyeing on cotton).

Characteristics of the effluent studied: - pH »8.0! 25 - Color = 160,000 mg / 1 Pt - D.C.O. = 3 411 mg 02 / l

On these waters treatments are carried out according to. the invention either oxidation-coagulation or coagulation- * ’17 oxidation.

A) Combined oxidation treatment then coagulation-flocculation-decantation

Oxidation step: 5 Addition of 0.18 ml of concentrated H 50 (d = 1.83) 2 4 per liter of effluent to bring the pH to ^ 3.1 then addition of 1.2 g of FeSO ^ 7 1 ^ 0 and 7.54 g of $ 50> per liter of effluent.

After 3 hours of contact time, we proceed to the next step.

Coagulation-flocculation-decantation stage ï After addition of lime in quantity allowing a pH close to 7j to be obtained, the previously oxidized effluent is flocculated using a mineral reagent and an anionic polyelec-15 trolyte, FLOERGER FA 57H, registered trademark.

• / -

The nature of the reagents, the treatment rates and the results obtained after the final decantation are stated. qués in table VI below.

B) Combined coagulation-flocculation treatment 20 decantation then oxidation

Flocculation stage:

Addition of lime at 80% then coagulation-flocculation using a mineral reagent and anionic polyelec trolyte, FLOERGER FA 57H, registered trademark, under the conditions indicated in Table VI.

The decantates are then oxidized according to the step below:

Oxidation stage:

Addition of 0.12 ml of concentrated H 2 SO 4 (d = 1.83) 30 per liter of decantate in order to bring the pH to -3.3 then addition of 0.96 g of Fe5D4, 7 H20 and 5 , 52, g 50% H202 per liter of decantate.

, After a contact time of 2 h, the mixture is

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!; added with 1, B to 2.2 g of 80% lime per liter and after J decantation, the characteristics of the decantate are given I in Table VII ·

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Claims (7)

21 1. A method of purifying waste water containing coloring matter, characterized in that it consists of two stages, an oxidation stage carried out using hydrogen peroxide, a coagulation-flocculation stage- decantation carried out using a coagulating reagent. 2. Method according to claim 1 wherein the oxidation step - with 1b hydrogen peroxide is carried out before the coagulation-flocculation-decantation step. 10 3 - Process according to claim 1 wherein the step of oxidation with hydrogen peroxide is carried out after the step of coagulation-flocculation-decantation · 4. Method according to one of claims 1 to 3 where the ef-; " · · Fluent is brought to a pH lower than 5 and / or is added * J '+ * *, · 15 of a metal salt before the addition of hydrogen peroxide. 5. Method according to one of claims 1 to 4 wherein the duration of the oxidation step is between 1 and 24 hours. 6. The method of claim 5 wherein the duration of the step 2D 2D oxidation is between 1 and 4 hours. 7. Method according to one of claims 1 to 6 wherein the coagulation step is carried out by means of a coagulating metal salt such as aluminum sulfate, aluminum chloride, basic aluminum chlorosulfates, ferric chloride, ferric chlorosulfate, ferrous sulfate and combinations of these salts. \ l \ 5:, • \ / V h h v v λ.