FR2464230A1 - PROCESS FOR PURIFYING WASTE WATER CONTAINING COLORING MATERIALS - Google Patents

Abstract

PROCESS FOR DEPURING WASTE WATER CONTAINING COLORING MATERIALS CHARACTERIZED IN THAT IT CONSISTS OF TWO STEPS, AN OXIDATION STEP CARRIED OUT WITH THE HELP OF HYDROGEN PEROXIDE, A COAGULATION-FLOCULATION-DECANTATION STEP PERFORMED AID OF A COAGULATING REAGENT.

Description

The present invention relates to a process for

  wastewater containing colored matter

  such as, for example, wastewater from

  manufacture of dyestuffs or wastewater dye-

  series. 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.

  consists of compounds that are difficult to biodegrade, high chloride content, dyes in colloidal form, traces of heavy metals and possibly

other toxic materials.

  Previous work has focused on

  elimination of the biochemical oxygen demand (D.B.0.) but,

  Recently, the major concern has been the elimination of

  the chemical oxygen demand (OC) of the substances

  in suspension (M.E.S.), color as well as particles

the collo dales.

  In the process according to the present invention this

  these constituents of the polluting load

  deresse has particularly sought the reduction.

  Many biological, physical or chemical treatment processes have long been proposed to eliminate or reduce the pollutant load of this type.

waste water.

  Work carried out on the biodegradability of

  different direct, acidic, basic or pigment dyes

  They have shown that, in some cases, there is a good reduction in D.B.0., that of color and D.C.0. is still weak and does not warrant the direct use of a biological treatment, see in particular Dennis W. Weeter and A. Gale Hodgson - Proceedings of the

  32nd Industrial Waste Conference - Ann Arbor Science - 1 - 9.

  Among the physical processes, the use of ion exchange resins has been recommended for example by USP 3,803,030 and that of a liquid-liquid extraction by USP 3,966,594. However, these methods involve

  delicate procedures and do not accommodate the strong variations

  qualitative or quantitative characteristics of the polluting load

wastewater to be treated.

  As a chemical process, the use of hydrogen peroxide in the presence of ferrous iron is a known method of treatment described, for example, by Kitao, Takane-Mizu Shori Gijutsu 1976, 17 (8), 735-40. It leads to a good elimination of color and 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.

  whose content is even increased by the treatment.

  Furthermore, the Applicant has found that a flocculation treatment with mineral compounds followed

  decantation, if in some cases it allows decolourisation

  satisfactorily and generally a strong reduction in

  suspended matter, is always accompanied by the formation of a very large amount of sludge which makes this treatment unattractive, especially from the point of view of the environment (displacement of the pollution of an effluent

liquid to a solid residue).

  There was therefore an industrial need to

  developed a wastewater treatment technique

  coloring matter meeting the requirements of the

  various administrations controlling the quality of these waters.

  As part of the studies carried out by the

  deresse for the treatment of such waste water he has

  has been found that results much higher than those

  previously known were obtained by treatment with

  both an oxidation step with hydrogen peroxide and

  a coagulation-flocculation-decantation step.

  The process according to the invention therefore consists of a treatment in two stages: an oxidation stage using hydrogen peroxide,

  a step of coagulation-flocculation-decantation

  with the help of mineral salts, whether or not associated with a poly-

  electrolyte such as a copolymer based on acrylamide and

  possibly carrying ionic functions.

  To obtain the best reduction of D.C.0.

  and color, it is particularly recommended to

  ter, before the addition of hydrogen peroxide, if necessary the effluent to a pH below 5, and to add, if necessary, a metal salt as oxidation catalyst such

  a ferrous salt, for example ferrous sulphate FeSO4 7H20.

  At these 2 steps can be associated without going out of the object of

  the present invention any other prior treatment or pos-

  conventional nature that the nature of the waters to be treated

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

it.

  For the best use performance

  H202 is particularly recommended, depending on the

  assigned of the invention to have a reaction time understood

  between 1 and 24 hours and preferably from 1 to 4 hours.

  Waste water which may be treated

  According to the process of the invention, there are generally significant variations in the pollutant load. Therefore, when designing works in which

  treatment, it is often necessary to

  first basin to homogenize the waste water

  b. In this case it is particularly recommended to

  troduce H 202 and possibly the oxidation catalyst in this basin to have the recommended reaction time,

  provided that the best purification performance is achieved

  held by first realizing the oxygenated treatment and then

  then the coagulant treatment. If not, ltad-

  H202 should be done after the coagulation step.

  flocculation-decantation, in a suitable reaction tank.

  All aqueous H2O2 solutions are used

  sand to carry out the process but it is particularly

  advised, for the sake of convenience of use, to

  be 50% H2O2 solutions by weight.

  To obtain the best yield of the coagulation-flocculation-decantation step, it is particularly recommended to use a mineral coagulant chosen from the

  metal salts of iron or aluminum usually used

  in the treatment of waters such as aluminum sulphate

  nium, aluminum chloride, basic aluminum chlorosulphates

  nium, ferric chloride, ferric chlorosulfate, sulphate

  ferrous or a combination thereof.

  In the present process the use of quantum

  Massive lime tins, as a coagulant, are avoided which considerably reduces the amount of sludge formed. The contents of reagents to be used in the two phases of the treatment depend on the effluent to be treated, and the desired quality for the treated water, they can vary in 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 o

  they arrive at the treatment facility.

  The following examples illustrate not only

  mitative the interest of the process developed by the

  is. In these examples the color of the solutions, the

  chemical oxygen demand (OC.O.) and the materials

  (M.E.S.) were measured as follows: - Color:

- D.C.0 .:

- M.E.S .:

  the color of the water to be measured previously diluted (to be brought back into the measuring range) with demineralized water is compared with colored glass discs graduated in scale

Pt - Co (see NF - T 90 - 034-).

  The value thus determined is multiplied by the dilution factor to obtain the color

water to measure.

  It is determined by the dichromate method

of potassium according to NF - T 90 - 101.

  It is determined by disk filtration

  fiberglass according to NF - T 90 - 105.

EXAMPLE 1

  Effluent: Brown waste water of azocolear dye manufacture containing approximately:

  - 50 to 200 mg / l of dyes (some pigment

  res, other soluble), - 150 to 300 mg / l of phenols,

  - amines and various organic impurities (inter

  reaction media, unreacted starting material), - NaCl: 2-5 g / l, - Sulfate, carbonate, Na-bicarbonate,

- etc ...

  The characteristics of the tributary studied are: - pH = 9 - Color = 60 000 mg / l Pt - D.C.0. = 757 mg O 2 / L 2 - M.E.S. = 90 mg / - M.E.S. = 90 mg / l On these waste waters is carried out parallel conventional treatment of coagulation and treatment in

  2 stages oxidation and coagulation according to the present application.

  A) Coagulation-flocculation-settling treatment with lime and ferrous salt on the tributary as it is: - flocculation with 2.5 g of 95% Ca (OH) lime and 1.25 g of FeSO 4, 7 H 2 O per liter of effluent then 5 mg of Sepiflor AH12B nonionic polyelectrolyte, registered trademark

  of the company SEPPIC, per liter of effluent.

  After decantation for one hour and addition to the decantation of 1 ml of 80% sulfuric acid per liter, a water having the following characteristics is obtained: pH = 8.5 - Color = 6000 mg / l Pt either a reduction of

90%

  - D.C.0. = 617 mg 02/1 is a reduction of

18.5%

  - M.E.S. = 70 mg / 1 ie a reduction of 22% - Mud produced = 2.1 g of dry matter per liter of tributary

  B) Treatment in 2 stages oxidation by H2O2 -

  flocculation - oxidation step: Effluent brought to pH 3 by addition of 0.36 mi

  sulfuric acid at 80% per liter of tributary and then added

  50%: 1.1 g / l After 2 hours of contact time, the following are obtained: pH 3 to Color = 10,000 mg / l Pt a reduction of 83.3% DC0. = 677 mg 02/1 is a reduction of 10.6% - Coagulation-flocculation-decantation step: After addition of lime to obtain a final pH of 7, a coagulation-flocculation is carried out

  using different mineral salts and 4 mg / l of a polyelectrolyte

  nonionic trolyte, FLOERGER, registered trademark, FA 20H.

  Depending on the mineral salt used in this step, the

  results obtained, after combined treatment, are indicated in

Table I below.

  Examination of these results shows the effectiveness of

  treatment carried out according to the process of the invention which allows

  put aside a significant lowering of the color of ob-

  a D.C.O. already low and a MoE.S. corresponding

  current specifications. By increasing the content of H202 water oxidation treatment one can get

  as will be seen for example in Example 3 D.C.O. beautiful-

  coup weaker then meeting the specifications

in this respect.

EXAMPLE 2

  Effluent: Brown waste water of azo dye manufacture of the same type and coming from the same

factory than in Example 1.

  Summary characteristics of the studied effluent:

  - pH = 7.3 - Color = 60,000 mg / l Pt - D.C.O. = 980 mg 02/1 On these waste water is carried out in parallel

  conventional coagulation treatments with various coagulants

  and 2-stage treatment according to the present invention.

tion.

  A) Coagulation-flocculation treatment-

  decantation only The wastewater above is treated either by

  AlCl3, either by lime and ferrous sulphate.

  A.1 - With AlCl3 Addition per liter of effluent of 0.25 g of lime

  Ca (OH) 2 at 95%, then coagulation-flocculation with 1 g of sodium

TABLE I

  1%> or% c) Flocculant used Results obtained after combination treatment C__Color D * C. * o M.E.S. Mud produced Nature Treatment rate pH in Reduction in Reduction in dry tires mg m / 1 tint sècheus m Pt color mg / 1 02 of the mg / i AlCl3 1 g of solution at 30% per liter 8.8 3 500 94.2 553 26.3 56 0.80 .CO l._ eflun FeCl 1 g of 41% solution per liter 7.8 3 500 94.2 518 31.6 32 0.77 FeSO4 1 g FeSO 4t 7 H2 0 7 H 2 per liter 6.9 4,000 93.3 458 39.5 10 0.91 2. 1 lution of 30% AlCl 3 and 4 mg of nonionic polyelectrolyte

  FLOERGER, registered trademark, FA20H. After decantation of a

  a water with the following characteristics is obtained

  : -pH = 7.5 - Color = 9000 mg / 1 Pt is a reduction of% - D.C.O. = 466 mg 02 / l, a reduction of

52.4%

  - 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 FeSO4, 7 H2O per liter of effluent and 5 mg of nonionic polyelectrolyte Sepiflor AH12B, brand

  deposited by the company SEPPIC, per liter of effluent. After

  For one hour, the decantate is added with 0.74 ml of 80% H 2 O 4 per liter. This gives a water having the following characteristics: - pH = 8.9 - Color = 9000 mg / 1 Pt is a reduction of% D.C.O. = 583 mgO2 / l or a reduction of .5% - Mud produced = 2.1 g of dry matter per liter of effluent

  B) Combined treatment: oxidation with H2O2 -

flocculation Oxidation step:

  Addition of 0.2 ml of 80% H2504 per liter of

fluent to obtain a pH - 3.5.

  Addition of 0.3 g Fe 504.7 H 2 O per liter of

  and then 1.275 g H 2 O 2 50% per liter of effluent.

  2464t230 After 2 hours of contact time, flocculation is carried out. Flocculation step: After addition of lime in an amount making it possible to obtain a final pH in the region of 7, the coagulation-flocculation is carried out with 0.8 g of basic aluminum chlorosulfate, a commercial solution sold by Ugine Kuhlmann Chemicals under the WAC trademark, 0.1 g ferric chloride commercial solution at 41% FeC13 and 4 mg nonionic polyelectrolyte FLOERGER, registered trademark, FA20H

per liter of effluent.

  After one hour of settling, a water having the following characteristics is obtained: - pH = 8.8 - Color = 3500 mg / l Pt is a reduction of

94.1%

  - D.C.O. = 431 mg 02/1 is a reduction of 56% - Mud produced = 0.72 g of dry matter per liter of effluent

  Combined treatment leads to better

  elimination measures than flocculation treatments.

EXAMPLE 3

  Effluent: Basic effluent from the production of

Blue Foulon B.R.L.

  Characteristics of the studied effluent: - pH = 12.3 - Color = 2500 mg / l Pt - D.C.O. = 465 mg 02/1 This example is intended to compare the results

  obtained during a coagulation-flocculation treatment-

  decantation alone (A) with those corresponding to a

  according to the present invention, the oxidation step being carried out before (B) or after (C) the step

  coagulation-flocculation-settlement.

  A) Coagulation-flocculation treatment-

  decantation only The wastewater is treated with either AlCl3 or a mixture of basic aluminum chlorosulfate and ferric chloride. A.1 - With AlC13 Addition of 7 ml concentrated H2SO4 (d = 1.83) per liter of effluent then coagulation-flocculation with AiC13 in 30% solution and 4 mg of nonionic polyelectrolyte FLOERGER, registered trademark, FA 20H by liter of effluent. Treatment rates and results after one hour

  decantation are shown in Table II below.

  A.2 - With basic aluminum chlorosulfate and ferric chloride Addition of 7 ml concentrated H2504 (d = 1.83) per

  liter of effluent then coagulation-flocculation with a mixture

  basic aluminum chlorosulfate solution commercial solution

  (WAC), 8 parts by weight, of ferric chloride solution

  mercial at 41%, 1 part by weight and water, 1 part by weight (this mixture will be referred to as mixture A) and 4 mg of nonionic polyelectrolyte FLOERGER, 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.

below.

  B) Combined oxidation and then coagulation

  flocculation-decantation Oxidation step: Addition of 7.8 ml of concentrated H2504 (d = 1.83) per liter of effluent to bring the pH to 3.2 and then add 30.8 mg of FeSO4, 7 H20 and 0 , 17 g H202 50% per liter

TABLE II

  A1C13 solution at 30% Results Mud produced

Tests Color n.c. in g of

  1 g / l of pH reduction / reduction in dry matter of mg / ml pH mg 02/1 D.C.O. by 1 of effluent

A 1 0.5 7.65 1 150 54 63 86.5 0.63

A 2 1 7.6 I 500 40 55 88.2 0.82

A 3 1.5 7.8 1,000 60 57 87.7 0.95

N N 0o

TABLE III

  Mixture of coagulants A Results Mud produced

Color Tests D.C.0. in g of

  g / i tributary pH reduction reduction dry matter mg / i Pt color mg 02/1 D.C.0. by 1 of tributary

A 4 0.5 7.7 1 400 44 63 86.5 0.55

A 5 1 7.5 1 150 54 59 87.3 0.72

A 61.5 7.6 thousand 60 59 7.3 1.66

A 6 1.5 7.6 1,000 60 59 87.3 1.66

AT,,,, . i. i iiii, u ro w 0>

-24 4230

  effluent. After 2 hours of contact time, the effluent is

subjected to coagulation.

  Step coaqulation-flocculation-decantation: After addition of lime in quantity to obtain a final pH of about 7, the effluent previously

  oxidized is flocculated with a mineral reagent and poly-

  electrolyte. The nature of the reagents, the treatment rates and the results obtained after 1 hour of settling are

  shown in Table IV below.

  C) Combined coagulation-flocculation treatment

  decantation then oxidation Flocculation step: Addition of 7.6 ml concentrated H2SO04 (d = 1.83) per liter of effluent and then coagulation-flocculation using a mineral reagent and nonionic polyelectrolyte FLOERGER,

registered trademark, FA 20H.

  The decantates obtained after one hour of decantation

  The reaction is then oxidized according to the following step: Oxidation step: Addition of 0.125 to 0.2 ml of concentrated H2504 (d = 1.83) per liter of decantate to bring the pH to 23.3 and then add 32 mg FeSO4, 7 H2O and 0.2 g H2O2 50%

  per liter of decantate. After 1 h 30 of contact time, neu-

  0.100 to 0.145 g of echoes at 80% per liter.

  The results obtained are indicated in the table

  Bleau V hereinafter o, for the flocculation step: C1 corresponds to a treatment with 0.15 g of

  mixture A and 5 mg of nonionic polyelectrolyte

per liter of effluent.

  C2 corresponds to treatment with 0.25 g of

  lange A and 5 mg of nonionic polyelectrolyte

TABLE IV

  Results obtained after combination treatment

REAGENTS

RATF%% Produced mud

  Tests (treatment rate for Color reduction COD reduction in g of

  litred'eifluen) pHColor reduction DoC.0. reduction of 1 liter of effluent) p mg / 1 Pt of the mg 02/1 of the D.C.O. by 1 dieffluent

-. -. -

  B 1 0.15 g of mixture A and 5 mg of anionic polyelectrolyte FLOERGER, 7, 7 100 96 22 95.3 0.35 trademark, FA 57H 0.25 g of mixture A and 5 mg of B 2 anionic polyelectrolyte FLOERGER , 7.2 80 96.8 32 93.1 0.40 registered trademark, FA 57H 0.25 g of mixture A and 5 mg of B 3 nonionic polyelectrolyte 7.8 100 96 44 90.5 0.39 FLOERGER , registered trademark, FA 20H 0.15 g of AlC13 solution at 30% B 4 and 5 mg of anionic polyelectrolyte 6.9 80 96.8 0.37 FLOERGER, registered trademark,

FA 57H

  0.25 g AlCl3 solution 30% B 5 and 5 mg polyelectrolyte non 7.7 50 98 28 94.0 0.37

ionic FLOERGER, trademark

se, FA 20H

-_ - -

Ln na r1j w c

only per liter of effluent.

  - C3 corresponds to treatment with 0.25 g of

30% solution of AlCl3 and 5 mg of polyelectrolyte

  nonionic trolyte per liter of effluent.

TABLE V

  The comparison of Tables IV and V shows that regardless of the order of oxidation-coagulation or coagulation-oxidation treatments, the patent process achieves excellent results that are much higher in terms of eliminating color than we get with the

  coagulation alone (Tables II and III).

EXAMPLE 4

  Effluent: Blue dyeing waste water

  industrial (dyeing direct dye on cotton).

  Characteristics of the studied effluent: - pH = 8.0 - Color = 160 000 mg / 1 Pt - D.C.0. = 3 411 mg 02/1 On these waters treatments are carried out according to

  the invention is oxidation-coagulation or coagulation-

  Results obtained after combined treatment% of% of Tests H Color reduction D.C.O. reduction mg / l Pt of the mg 02/1 of the

color D.C.0.

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

oxidation.

  A) Combined oxidation and then coagulation treatment

  flocculation-decantation Step oxidation: Addition of 0.18 ml of concentrated H2504 (d = 1.83)

  per liter of effluent to bring the pH to 3.1 and then add

  1.2 g of FeSO 4, 7 H 2 O and 7.54 g of 50% H 2 O 2

effluent.

  After 3 hours of contact time, we proceed to

next step.

  Coagulation-flocculation-decantation step: After addition of lime in an amount making it possible to obtain a pH close to 7, the previously oxidized effluent

  is flocculated with a mineral reagent and a polyelectrolyte

  anionic trolyte, FLOERGER FA 57H, registered trademark.

  The nature of the reagents, the treatment rates and

  the results obtained after final decantation are indi-

in Table VI below.

  B) Combined coagulation-flocculation treatment

  decantation then oxidation Step flocculation:

  Addition of 80% lime and then coagulation

  flocculation using a mineral reagent and polyelectrolyte

  anionic trolyte, the FLOERGER FA 57H registered, in

  the conditions given in Table VI.

  The decantates are then oxidized according to the step

  below: Oxidation step: Addition of 0.12 ml concentrated H2SO4 (d = 1.83)

  per liter of decantate to bring the pH to - 3.3 and then add

  0.96 g of FeSO 4, 7 H 2 O and 5.52 g of 50% H 2 O 2

liter of decantate.

  After a contact time of 2 h, the mixture is supplemented with 1.8 to 2.2 g of lime 80% per liter and after decantation, the characteristics of the decantate are given

in Table VII.

  Examination of Tables VI and VII shows that the eli-

  Mination of color is excellent for the 2 tests of Example 4, the reduction of D.C.0. being bigger

  for treatment coagulation followed by oxidation.

TABLE VI

  _ Results obtained after combined treatment

REAGENTS. ....

  (treatment rate for%% of tests (t dlitre deffluent) pColor reduction D.C.0 reduction mg / l Pt of mg 02 / of

color D.C.0.

  0.6 g of mixture A and 5 mg of poly-anionic electrolyte 2 0.9 g of mixture A and 5 mg of poly-6.85 400 99 75 1 366 59.95 anionic electrolyte 30 g 30% AlCl3 solution and 6.9 400 99.75 1 357 60.22 mg anionic polyelectrolyte 4 0.9 g 30% AlCl3 solution and 6.9 300 99.81 1 289 62.21 mg of anionic polyelectrolyte as seen in 4N M wt; % _

TABLE VII

  FLOCCULATION REAGENTS Results obtained after combined treatment Ee8s sai6s. %% of Emmais Treatment rate for 1 1 of the same pH Color reduction D.C.O. reduction Rate of treatment for 1 1 of tributary pH m / t dg0 / el ag / 1 Pt of mg 02/1. l

color D.C.0.

  0.2 g of 80% Ca (OH) 2, 2 g of a mixture of 6,85,300 99.81 583 and 82.91 g of A and 5 mg of anionic polyelectrolyte I T. I I .. I [I. III 1II, __ 1,, m, ........

  0.25 g of 80% Ca (OH) 2, 2.5 g of 6.95 mg of 99.94% of sodium hydroxide and 3 mg of anionic polyelectrolyte 3 0.3 g Ca (OH) 2 80%, 3 g of melanin 7.15 180 99.89 294 91.38 g and 5 mg of anionic polyelectrolyte I III. 0.1 g of Ca (OH) 2 80%, 2 g , 95 120 99t93 419 87.72..DTD: 30% AlCl and 5 mg of poly-

  anionic electrolytes 0.4 g of Ca (OH) 2 80%, 2.5 g of sodium, 7.2% 99.94 429 87.42

30% AlCi solution and 5 mg of

  anionic lylectrolyte 6 '"0.5 g of 80% Ca (OH) 2, 3 g of 80-7.35 80 99, 95 255 92.52

AlC13 30% and 5 mg poly-

  anionic electrolyte I i. i, i. i_. i ii N N ch Ma fD

Claims (5)

  1 - Process for the purification of wastewater containing dyestuffs, characterized in that it consists in   two stages, an oxidation step carried out with the help of   hydrogen oxide, a step of coagulation-flocculation-   decantation carried out using a coagulating reagent.   2 - Process according to claim 1 o the oxidation step with hydrogen peroxide is carried out before the coagulationfloculation-decantation step. 3 - Process according to claim 1 o the oxidation step with hydrogen peroxide is carried out after the coagulation-flocculation-decantation step.   4 - Process according to one of claims 1 to 3 o ef-   Fluent is brought to a pH below 5 and / or is added with a metal salt prior to the addition of hydrogen peroxide.   - Method according to one of claims 1 to 4 o the duration   the oxidation step is between 1 and 24 hours.   6 - Process according to claim 5 o the duration of the step   oxidation is between 1 and 4 hours.   7 - Method according to one of claims 1 to 6 o the step   coagulation is carried out by means of a metal salt co-   such as aluminum sulphate, aluminum chloride,   aluminum chlorosulphates, ferric chloride, ferric chlorosulphate, ferrous sulphate combinations of these salts.