NL8004924A - METHOD FOR PURIFYING COLORING MATERIALS CONTAINING WASTE WATERS. - Google Patents

Description

VO 616

Method for purifying waste waters containing coloring materials.

The invention relates to a process for purifying waste waters containing coloring materials such as e.g. the ~ waste waters from dye factories or waste waters from dyers. The method is intended to reduce the pollutant charge of these ef-5 fluents.

These waste waters are usually characterized by important variations in the pollutant charge, consisting of compounds that are difficult to biodegrade, a high content of chlorides, colloidal dyes, traces of heavy metals and possibly other toxic materials.

Previous studies have emphasized the elimination of the Biochemical Oxygen Demand (DBO), but recent efforts have been made to reduce the Chemical Oxygen Demand (DCO) of the Suspended Materials (MES) of the color as well as the colloidal particles. to eliminate.

In the present process, it is these constituents of the pollutant batch that are particularly targeted for reduction.

Many biological, physical or chemical treatments have long been proposed to eliminate or reduce the pollutant charge of this type of wastewater.

Studies conducted on the biodegradability of various direct, acidic, basic or pigment dyes have shown that if in some cases a good reduction of the DBO is achieved, this of the color and the DCO is still small and not the direct justifies application of a biological treatment, see in particular Dennis W. Wester and A. Gale Hodgson - Proceedings of the 32nd Industrial Waste Conference - Ann Arbor Science - 1 - 9.

8004924 - 2 -

As physical methods, the use of ion exchange resins has been proposed, e.g. in U.S. Patent 3,803,030 as well as a liquid-liquid extraction in U.S. Patent 3,966,594. However, these methods require complicated methods and are poorly adapted to the strong qualitative or. quantitative variations of the pollutant charge of the wastewater to be treated.

As a chemical process, the use of hydrogen peroxide in the presence of divalent iron constitutes a known treatment described e.g. by Kitao, Takane-Mizu Shori Gijutsu, 1976, 17 CS3, 735 - 740 ,. It leads to good color and DCQ removal, at least in the case of soluble dyes, but requires significant amounts of reagent and does not solve the problem of MES, the content of which has even increased due to the treatment. On the other hand, the Applicant has found that a flocculation treatment by mineral compounds followed by decanting, although in some cases providing satisfactory decolorization as well as generally strong reduction of the suspended material, is always accompanied by the formation of a very significant amount of sludge which makes this treatment less interesting, in particular from an environmental point of view (displacement: from contamination of a liquid effluent to a solid residue].

There was therefore an industrial need to develop a purification technique of wastewater containing coloring materials that meets the requirements of the various bodies controlling the quality of these waters.

In studies conducted by the Applicant for the treatment of such wastewater, it was found that very much better than the known results were obtained by a treatment comprising an oxidation step by hydrogen peroxide and a coagulation flocculation decant step.

The process according to the invention therefore consists of a treatment in two stages: - an oxidation stage with hydrogen peroxide, - a coagulation flocculation quench stage with mineral 8004924 f * - 3 - salts, whether or not combined with a polyelectrolyte, such as a copolymer on the basis of acrylamide and which optionally contains ionic functions.

In order to obtain the best reduction of the DCO and of the color, it is particularly recommended before the addition of the hydrogen peroxide to bring the effluent to a pH below 5 if possible and, if necessary, pen metal salt as an oxidation catalyst such as an ironCII] salt, e.g. iron (II) sulfate FeSO ^ H ^ O. With these two steps, without departing from the scope of the present invention, any other classic pre- or post-treatment that justifies the nature of the waters to be treated can be combined.

Depending on the treated effluents, the oxidation step can be carried out before or after the coagulation step.

According to the invention, in order to obtain the best use efficiency of the H 2 O 2, it is particularly recommended to work with a reaction time between 1 and 24 hours and preferably between 1-4 hours.

The waste waters that can be treated with the method of the invention generally provide important variations of the pollutant charge. Therefore, when designing the plants in which the treatment is to be carried out, it is customary to provide a first basin for homogenizing the waste water to be treated. In that case, it is especially recommended that H 2 O and possibly the oxidation catalyst be introduced into this basin to utilize the proposed reaction time, provided that the best purification efficiency is obtained by first carrying out the oxygenation treatment and then the - coagulation treatment. Conversely, the addition of the 1 2 2 content after the coagulation flocculation decantation step should be in a suitable reaction vessel.

All aqueous H 2 O 2 solutions are useful for carrying out the process, but it is especially recommended to use 50 wt% h 2 O solutions for reasons of ease of use.

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In order to obtain the best efficiency from the coagulation flocculation quench step, it is particularly recommended to use a mineral coagulant selected from metal salts of iron or aluminum commonly used in the treatment of waters such as aluminum sulfate, aluminum chloride, basic aluminum chlorosulfates, ironCIII) chloride ,. iron (III) chlorosulfate, iron (II) sulfate or a combination thereof.

In the present process, the use of very large amounts of lime as a coagulant is avoided, whereby the amount of sludge formed can be considerably reduced.

The amounts of the reagents to be used in both treatment steps depend on the effluent to be treated and on the quality desired for the treated water.

They can vary over very large ratios without departing from the invention. The temperature of the two treatment phases is not critical; the effluents can be treated without any problem at the temperature at which they enter the treatment device.

The invention is further elucidated by means of the examples below.

In these examples, the color of the solutions, the chemical oxygen demand (DCO) and the suspended material (ΓΈΞ) were determined in the following manner: color: the color of the water to be determined, which has been pre-diluted 25 Com it within the measuring range ) with demineralized water is compared with graded colored glass disks on the scale Pt - Co Czie NF - T90-034 -).

The value thus determined is multiplied by 30. dilution factor to obtain the color of the water to be determined.

DCO: it is determined by the potassium dichromate method according to NF - T 90 - 101.

MES: it is determined by filtration on a glass fiber disc according to NF-T 90-105.

8004924 - 5 ->>

Example I

Effluent: Wastewater from the preparation of azo Dyes approximately containing: 3 50 - 200 mg / dm Dyes (some as pigment, others soluble) 3; 5 150-30 mg / dm phenols, amines and various organic impurities (reaction intermediates, starting reacted product),

NaCl: 2-5 g / dm3. sodium sulfate, sodium carbonate, sodium bicarbonate, 10 etc »

The characteristics of the studied effluent are: pH * 9 color * 60,000 mg / dm3 Pt DCD = 757 mg 02 / dm3 15 MES = 90 mg / dm3

In parallel with these waste waters, a conventional coagulation treatment and the two-stage treatment are carried out, oxidation then coagulation according to the present application.

A) Coagulation flocculation decantation treatment lime and 20 iron (II) salt on the effluent as such: flocculation with 2.5 g lime CaCOHJ 95% and 1.25 g FeSD / HO per dm 5 effluent, then 5 mg of nonionic polyelectrolyte Sepiflor AH12B, Trademark Sac. SEPPIC, per dm3 effluent.

After decantation for 1 hour and addition to the decantate 3 of 1 cm of 80% sulfuric acid per dm, a water is obtained with the following characteristics: pH = 8.5 3 color = 6,000 mg / dm Pt being a reduction of 90 % 3 30 DC0 = 617 mg Oj / dm being a reduction of 18.5% MES »70 mg / dm3 being a reduction of 22% 3 sludge produced * 2.1 g dry matter per dm effluent.

B) Treatment_in_two_traggen_oxydation_dogr_H202_j_uitvlQkking

Oxidation stage: 35 effluent adjusted to pH of about 3 by addition of 3 3 0.36 cm 80% sulfuric acid per dm effluent then added. Q? * - 6 - added:

FeS04.7H20: 0.2 g / dm3 H2Q2 50¾: 1.1 g / dm3

After 2 h contact time, the following is obtained: 5 pH about 3 3 color * 10,000 mg / dm Pt being a reduction of 83.3% 3 DCO = 677 mg O 2 / dm being a reduction of 10.6%. Coagulation flocculation quench step:

After adding lime to obtain a final pH .10 near 7, a coagulation flocculation is carried out using 3 different mineral salts and 4 mg / dm of a nonionic polyelectrolyte FL0ERGER, trademark FA 20H. As a function of the mineral salt used in this step, the results obtained in combination treatment are shown in Table A below.

The examination of these results shows the effectiveness of the treatment carried out according to the invention, with which it is possible to obtain an already weak DCO in addition to a significant reduction of the color and a content of MES corresponding to the usual specifications. By increasing the content of H 2 O 2 in the oxidation treatment, one can, e.g. in Example III, obtain much lower DCO values than meet the usual specifications in this field.

Example II

Effluent: Brown wastewater from the manufacture of azo dyes of the same type and from the same factory as in Example I.

Summary characteristics of the studied effluent: pH = 7.3 3 30 color = 60,000 mg / dm Pt 3 DCO = 980 mg 02 / dm

On these waste waters, classical coagulation treatments with different coagulants and the two-stage treatment according to the invention are carried out in parallel.

8004924 = 7 - A3 CQaolation solution leaching treatment only.

The above wastewater is treated either with AlClg or with lime and iron (II3 sulfate.

A.1 - With A1C1, J 3 5 Addition per dm effluent of Q, 25 g lime CaCOH ^ 95%, then coagulation flocculation with 1 g 30% A1C13 solution and 4 mg nonionic polyelectrolyte Floerger , trademark, FA20H3. After decanting for 1 hour, a water with the following characteristics is obtained: 10 pH = 7.5 3 color = 9,000 mg / dm Pt being a reduction of 85% 3 DCO = 466 mg 0_ / dm being a reduction of 52.4% ^ 3 sludge produced * 0.52 g of dry material per dm of effluent.

A.2 - With lime and iron (II) sulfate: 15 Addition of 2.5 g of 95% lime and coagulation flocculation with 3 1.25 g FeSO..7H70.per dm effluent and 5 mg nonionic polyelectrolyte Sepiflor AH12B, trademark, Soc. SEPPIC, per dm effluent.

3

After decanting for 1 hour, 0.74 cm 80% 3 H2SQ4 per dm is added to the decantate. A water with the following characteristics is then obtained: pH = 8.9 3 color = 9,000 mg / dm Pt being a reduction of 85% 3 DCO = 583 mg 0_ / dm being a reduction of 40.5% ^ 3 sludge produced = 2.1 g of dry material per dm of effluent.

25 B3 Combined treatment2 oxidation with H292 flocculation

Oxidation stage: 3 3

Addition of 0.2 cm 80% H ^ SG ^ per dm effluent to obtain a pH of about 3.5.

3

Addition of 0.3 g FeS0..7H-Q per dm effluent and then 30 g of 1.275 g 50% per dm effluent.

The flocculation is started after 2 hours of contact time. Flocculation stage:

After adding lime in amounts to obtain a final pH near 7, the coagulation flocculation is carried out with 0.8 g of basic aluminum chlorosulfate in the form of the 8004924-a commercial solution of the Fa.Produits Chimlques Ugins Kuhlmann under the trademark WAC, 0.1 g of commercial ironCl chloride solution of 41% FeCl 2 and 4 mg of nonionic polyelskyl trolyte Floerger, trademark J 3, FA20H per dm effluent.

After decanting for 1 hour, a water with the following characteristics is obtained: pH = 8.8.

3 color * 3,500 mg / dm Pt being a reduction of 94.1% 3 DCO * 431 mg 0 / dm being a reduction of 56% ^ 3 10 produced sludge * 0.72 g of dry material per dm effluent.

The combined treatment results in better removal efficiencies than flocculation * treatments.

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Example III

Effluent: basic effluent from the preparation of Bleu Foulon B.R.L.

Characteristics of the studied effluent: 5 pH * 12.3 3 color * 2,500 mg / dm Pt 3 □ CO = 465 mg G ^ / dm

This. example is for comparing the results obtained with only a coagulation flocculation decantation treatment C paragraph A) with that corresponding to a combined treatment according to the invention, the oxidation step being carried out before (paragraph B) or after (paragraph C) ) the coagula-

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ring flocculation end step.

Al Coagulation Flocculation Decantation Treatment Only: Wastewater is treated either with AlCl3 or with a mixture of basic aluminum chlorosulfate and iron (III chloride).

A..1 - With A1C1-: 3

Addition of 7 cm concentrated H_S0. Cd - * 1.63] per 3 2 4 20 dm effluent followed by coagulation and smoothing with AlCl 3 as 30% solution and 4 mg of nonionic polyelectrolyte Floerger, 3 trademark, FA20H per dm effluent. Treatment results and results obtained after one hour of decantation are shown in Table B.

25 A.2 - With basic aluminum chlorosulphate and iron (III) chloride: 3 3

Addition of 7 cm concentrated H2SO4 (d * 1.83] per dm effluent and then coagulation flocculation with a mixture of a commercial solution of basic aluminum chlorosulfate (WAC], 8 parts, 41% iron CHI] chloride commercial solution, 1 wt .dl, water, 1 part by weight (this mixture is hereinafter referred to as mixture A] and 4 mg of nonionic polyelectrolyte Floerger, trademark, 3 FA20H per dm effluent. Treatment results expressed in g 3 mixture per dm effluent and the results obtained after decanting for 1 hour are shown in Table C.

35 B] Combined oxidation treatment, then coagulation flocculation flocculation.

8004924 - 11 -

Oxidation stage: 3

Addition of 7.8 to concentrated F ^ SQ ^ Cd = 1.83) per dm effluent to adjust the pH to about 3.2 followed by addition of 30.8 mg FeSO4. 71-1 ^ 0 and 0.17 g of 50% Cs per dm 5 effluent.

After 2 hours of contact time, the effluent is subjected to coagulation.

Coagulation flocculation quench step:

After adding lime in an amount of 10 to a pH near 7, the pre-oxidized effluent is flocculated using a mineral reagent and polyelectrolyte.

The nature of the reagents, the treatment amounts and the results obtained after decantation are shown in Table D.

C) Combined treatment of ooagulation, flattening and decanting 15. S®yolgd_by-oxidation.

Flocculation stage: 3

Addition of 7.6 cm concentrated sulfuric acid Cd = 1.83) per dm effluent followed by coagulation flocculation with a reactive mineral substance and a nonionic polyelectrolyte Floerger, 20 trademark, FA20H,

The decantates obtained after 1 hour of decantation were then oxidized according to the following step:

Oxidation stage: 3

Addition of 0.125-0.2 cm concentrated sulfuric acid Cd-3 1.83) per dm decantate to adjust the pH to about 3.3 followed by addition of 32 mg FeSO4 .TH2 O and 0.2 g 50 % 's H ^ Dj per dm ^ decantate. After 1 hour of contact time, it is neutralized with 0.100 to 0.145 g of 80% lime per dm.

The results obtained are set forth in Table E30 below for the flocculation step: C, corresponds to a treatment with 0.15 g of mixture A and 5 mg of * 3 nonionic polyelectrolyte per dm of effluent; C7 corresponds to a treatment with 0.25 g mixture A and 5 mg z 3 non-ionic polyelectrolyte per dm effluent.

35 C corresponds to a treatment with 0.25 g of 30% AlClq solution and 3 mg of nonionic polyelectrolyte per dm effluent.

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Table E

Test 'Results obtained after combined treatment pH color% color decrease- DCO% reduced-

mg / drrr daring mg EL / drn ring DCO

-Pt 5 __; ____ _ _ C.1 8.0 10 99.6 58 87.5 C.2 7.9 10 99.6 64 86.2 C.3 8.0 10 99.6 69 85.2 10 Comparison of Tables D and E shows that irrespective of the order of the treatments oxidation coagulation, or coagulation oxidation, excellent results are obtained with the process according to the invention, which are very much better in elimination of the color compared to what the single coagulation gives 15 (Tables B and C).

Example IV

Effluent: blue wastewater from industrial dyeing (dyeing with direct dye on cotton).

20 Characteristics of the studied effluent: pH = 8.0 3 color * 160,000; -. Mg / dm Pt DCO = 3,411 mg 02 / dm3

The treatments according to the invention are carried out on these waters, either an oxidation coagulation or a coagulation

Oxidation.

A) Combined treatment of oxidation followed by coagulation flocculation.

Oxidation Step: Addition of 0.18 cm concentrated H_S0 (d - 1.83) per 3 i dm effluent to adjust the pH to about 3.1 and then add 1.2 g FeSO..7H_0 and 7.54 g of 50% H 2 O per dm

4 Z Z Z

effluent.

After 3 hours of contact time, the next step is carried out.

35 8004924 - 15 -

Coagulation flocculation quench stage:

After adding lime in an amount to obtain a pH of about 7, the pre-oxidized effluent is flocculated with a reactive mineral and an anionic polyelectrolyte Het Floerger FA57H, Chandelsmerkï►

The nature of the reagents, the treatment amounts and the results obtained after the final decantation are shown in Table F.

B 3 Combined _ treatment_ coagulation; u ^ flocculation2department_ followed by oxidation »• IQ: Flocculation stage:

Addition of 80% lime followed by coagulation flocculation with a reactive mineral and an anionic polyelectrolyte Floerger FA57H [trademark] under the conditions listed in Table. F.

15 The decantates are then oxidized according to the steps below:

Oxidation stage: 3

Addition of 0.12 cm concentrated H 2 SO 4 (d * 1.83) per dm decantate to adjust the pH to about 3.3 and then addition of 0.96 g FeSO 4. 7H ^ 0 and 5.52 g 50% 1 ^ 2 per dm decantate »

After a contact time of 2 hours, 1.8-3.2 g of 80% lime per dm are added to the mixture and after decanting the decantate characteristics are as shown in Table G.

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OQ} ÖÜ pH (D O. "·" n £ + j Ο E +> O 0 bO 0 O 0 ^ >> in Ct> »- C -CJ— ω -h, £ M ω o ma ba o (- □ cm 3d o cn · »0_ cn

0 N h 03 CO (U CM -H CM Ή CO-H

Ό +3 1 rH + J C C C

0 ... * £ «0 'y £ * 0 * a' °

JZ 00 -> 0 0 0 * H 0 τΗ 0-H

1 — I “rH oV> rH“ rH "£" »£" = 0 oV »CD a □ e \ ° 03 o \ ° CO eV» <0 <£? <0 0 a> 03a a> a 2 „„ ° nn

0> fflrH fflr — I C0ÖD 03 BO Ο M

• HQ3 □ CM 0 O E E E

+30 na ~ j = cm a cm cm cm c £ <—ixa / —1 r- »m rr m / -> in 030 XCD Q0 X £ £ _ Sr · nr ωώ a .cw ή oj3 ac oc ο c ( nr- wU (OC w ¢ 3 w0 w0 χΦ

mi-} (Π £ fl fj O Ü CO <0 iO GJ

£ 3 +. u “u 5 U-Η uco u m u m _v / m c- CÖflC C» —ί μ 1—1

g * q qj üflQ fü bflO üflCJ & OO & 0CJ

iHC3 * HU1 · Η rH iHrH

> oh CMC cm ω m c cn <xj n + »0> e ίο i +3 * +5 * -p ÏJ05. a a a a 0> a0> a0> X rn 0 00 in bO - <- »*“ Γί m. g ·. £ · o \ ® O. o \ ° p o \ ° p 0 (OC (0 0 C3 £ - <0 C3 t-i 0 Q Ch uin oca oin ο n + ocn + 30cn + 3 1) -

a rH CM CT3 Ό "in CQ

u a.

.80 0 4 9 2 4 - 18 -

An examination of Tables F and G shows that the elimination of the color is excellent for the two tests of Example IV, the reduction of the DCO being greater by the treatment of coagulation followed by oxidation.

t 8004924

Claims (7)

A process for the purification of waste waters containing coloring materials, characterized in that it comprises two steps, one oxidation step carried out with hydrogen peroxide and one coagulation flocculation decant step carried out with a coagulation. 5 reagent. 2. Process according to claim 1, characterized in that the oxidation step with the hydrogen peroxide is carried out before the coagulation flocculation decantation step. Γ. 3, Process according to claim 1, characterized in that the oxidation step with the hydrogen peroxide is carried out after the coagulation flocculation decantation step. 4. Process according to claims 1-3, characterized in that the v effluent is brought to a pH below 5 and / or a metal salt is added thereto before the addition of the hydrogen peroxide. Process according to claims 1-4, characterized in that the duration of the oxidation step is 1-24 hours. Process according to claim 5, characterized in that the duration of the oxidation step is 1-4 hours. 7. Process according to claims 1-6, characterized in that the coagulation step is carried out with a coagulating metal salt such as aluminum sulphate, aluminum chloride, basic aluminum chlorosulfates, iron III chloride, iron CI chlorosulfate, iron CI sulfate and combinations of said salts . 8004924