KR101849803B1 - Method and device for anaerobically treating wastewater containing terephthalic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently decompose and remove terephthalic acid by efficiently anaerobically treating refractory terephthalic acid-containing wastewater at a low cost without complicated apparatus equipment or troublesome operation.
(Solution) In anaerobic treatment of wastewater containing terephthalic acid, sulfuric acid radicals are added to the drain water so that the concentration of the sulfate ion in the anaerobic treatment water is 5 to 200 mg / l. In the anaerobic treatment of the wastewater containing terephthalic acid, when a predetermined amount of sulfuric acid is added, the decomposition efficiency of terephthalic acid in the anaerobic treatment is dramatically improved. The sulfuric acid radical is preferably added so as to have a content of 10 mass% or more with respect to terephthalic acid in the drainage.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an anaerobic treatment method for treating terephthalic acid-containing wastewater and an apparatus for treating anaerobic terephthalic acid-

The present invention relates to a method and an apparatus for anaerobic treatment of wastewater containing terephthalic acid, and more particularly, to a method and apparatus for efficiently decomposing and removing poorly decomposable terephthalic acid in wastewater by anaerobic treatment.

The wastewater from the production process of polyethylene terephthalate usually contains terephthalic acid, paratoluene acid, benzoic acid and the like.

When anaerobic treatment of wastewater, nutrient salts, trace metals, etc. are required in the anaerobic treatment system for bacterial synthesis. For example, sulfate ions require about 1.5% of SO ₄ ^{2 -} for COD _Cr in wastewater. In the drainage of the chemical system and the drainage of the electronic industry, the components necessary for synthesis of these microorganisms are hardly contained. In the anaerobic treatment of these wastewater, a mineral component is added. Sulfate ions are decomposed by sulfuric acid reducing bacteria in the methane fermentation tank to generate hydrogen sulfide gas, thereby increasing the load of the exhaust gas treatment. Hydrogen sulfide inhibits methane fermentation and decreases treatment efficiency, so that sulfate ions are added so as not to be equal to or higher than the concentration required for bacterial cell synthesis.

Terephthalic acid and paratoluene acid are resistant to anaerobic treatment.

In anaerobic treatment, drainage containing poorly decomposable organic matter is treated aerobic. The anaerobic treatment is advantageous in that it can be treated at a higher load than the aerobic treatment, thereby lowering running cost and CO ₂ emission. Therefore, it is desired to treat anaerobic wastewater containing terephthalic acid or para-toluene acid.

Patent Literature 1 discloses a method in which terephthalic acid-containing wastewater is subjected to ozone treatment and anaerobic treatment in order to increase the decomposition efficiency of terephthalic acid in the anaerobic treatment. However, this method has a high treatment efficiency, but the apparatus for ozone treatment is complicated and the treatment cost is also high.

Patent Document 2 discloses a method in which ferrous sulfate and a sulfate ion source are added to waste water to prevent floatation and outflow of granular sludge to produce iron (FeS) by reaction between iron salt and sulfate ion, A method of treating anaerobic wastewater is disclosed. In this method, since the added sulfuric acid ion source is precipitated as FeS, the concentration of the sulfate ion in the anaerobic treatment tank is not increased.

As described above, in the anaerobic treatment of wastewater, hydrogen sulfide gas is generated when the sulfuric acid ion concentration in the system is increased. In the conventional anaerobic treatment method of wastewater for suppressing the generation of hydrogen sulfide gas, the concentration of the sulfate ion is not made higher than the concentration required for bacterial cell synthesis.

Japanese Patent Application Laid-Open No. 6-269797 Japanese Patent No. 3814851

An object of the present invention is to provide a method and an apparatus capable of highly decomposing and removing terephthalic acid by effectively anaerobically treating degradation-resistant terephthalic acid-containing wastewater at a low cost without requiring complicated apparatus equipment or troublesome operation.

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when a predetermined amount of sulfuric acid radicals (SO ₄ ^{2 -} ) is added in the anaerobic treatment of terephthalic acid-containing wastewater, the decomposition efficiency of terephthalic acid in the anaerobic treatment is remarkable . ≪ / RTI >

The present invention has been achieved on the basis of the above-described findings, and the following will be devised.

[1] A method for anaerobic treatment of wastewater containing terephthalic acid, characterized by adding sulfuric acid radicals to the wastewater so that the concentration of the sulfate ion in the anaerobic treatment water is 5 to 200 mg / Processing method.

[2] The anaerobic treatment method of terephthalic acid-containing wastewater according to [1], wherein a sulfuric acid radical is added to the drainage water so that the content of the sulfate radical in the drainage water is 60 to 400 mg / l.

[3] The anaerobic treatment method of terephthalic acid-containing wastewater according to [1] or [2], wherein a sulfuric acid radical is added to the drainage so that the content of sulfuric acid radical is 10% by mass or more with respect to terephthalic acid in the drain water.

[4] The anaerobic treatment method of terephthalic acid-containing wastewater according to any one of [1] to [3], wherein the drainage contains terephthalic acid in an amount of 50 to 2000 mg / l.

[5] The anaerobic treatment method of terephthalic acid-containing wastewater according to any one of [1] to [4], wherein the drainage further contains para-toluene acid.

[6] In order to add sulfuric acid to drain water, at least one selected from the group consisting of sulfuric acid, iron (I) sulfate, iron (II) sulfate, iron polysulfate, ammonium sulfate, aluminum sulfate, sodium sulfate, Is added to the wastewater. The method for anaerobic treatment of wastewater containing terephthalic acid according to any one of [1] to [5].

[7] A device for anaerobic treatment of wastewater containing terephthalic acid, which comprises means for adding sulfuric acid radicals to the multiples thereof so that the concentration of the sulfate ion in the anaerobic treatment water is 5 to 200 mg / An apparatus for anaerobic treatment of drainage.

[8] The anaerobic treatment device for terephthalic acid-containing wastewater according to [7], further comprising a means for adding a sulfuric acid radical to the drainage water such that the content of the sulfate radical in the drainage water is 60 to 400 mg / l.

[9] The apparatus for anaerobic treatment of terephthalic acid-containing wastewater according to [7] or [8], wherein sulfuric acid is added to the wastewater so that the content of sulfuric acid radicals relative to terephthalic acid in the wastewater is 10% by mass or more.

[10] The anaerobic treatment device for terephthalic acid-containing wastewater according to any one of [7] to [9], wherein the drainage contains terephthalic acid in an amount of 50 to 2000 mg / l.

[11] The anaerobic treatment device for terephthalic acid-containing wastewater according to any one of [7] to [10], wherein the drainage further contains paratoluenic acid.

According to the present invention, sulfuric acid radicals (SO ₄ ^{2 -} ) are added to the terephthalic acid-containing wastewater so that the concentration of the sulfate ion in the anaerobic treatment water becomes 5 to 200 mg / L, whereby the degradable terephthalic acid is efficiently decomposed and removed by the anaerobic treatment , Whereby a high-quality processed water can be obtained (claims 1 and 7).

The present invention can be carried out easily and inexpensively with a simple apparatus without requiring complicated apparatus equipment or troublesome operation.

In the present invention, sulfuric acid is preferably added in an amount of 10% by mass or more with respect to terephthalic acid in the wastewater, and the content of the sulfuric acid in the wastewater is 60 to 400 mg / l (claims 2, 3, 8 and 9).

The present invention is preferable for the treatment of terephthalic acid-containing wastewater containing 50 to 2000 mg / L of terephthalic acid and further containing para-toluene acid (claims 4, 5, 10 and 11).

Hereinafter, embodiments of the present invention will be described in detail.

In the present invention, in the anaerobic treatment of the terephthalic acid-containing wastewater, a predetermined amount of sulfuric acid is added to the wastewater. It is possible to accelerate the sulfuric acid reduction reaction by adding an excessive amount of sulfuric acid radicals to the waste water in an amount larger than that required for bacterial cell synthesis. As a result, the hydrogen partial pressure is lowered. As a result, the anaerobic treatment system is in a reduced state, promoting the methane production reaction, and decomposing terephthalic acid is considered to be decomposed and removed.

[Terephthalic acid-containing drainage water]

The raw water to be treated in the present invention may be terephthalic acid-containing wastewater, terephthalic acid-containing wastewater discharged from various industrial fields such as the chemical industry field and the electronic industry field, for example, a manufacturing process drainage of polyethylene terephthalate.

The concentration of terephthalic acid in the wastewater containing terephthalic acid is usually about 50 to 2000 mg / l, preferably about 100 to 1000 mg / l, but is not limited thereto. When the concentration of terephthalic acid in the wastewater is less than this lower limit, there is a significant difference from the normal treatment. If the concentration is higher than the upper limit, terephthalic acid tends to be crystallized, which may lower the treatment efficiency.

The wastewater containing terephthalic acid may further contain decomposable organic substances such as paratoluenic acid, benzoic acid, sugar, and organic acids.

The addition of sulfuric acid in the anaerobic treatment is effective for improving the anaerobic treatment efficiency of paratoluenic acid and shows a good treatment effect even for wastewater containing paratoluenic acid together with terephthalic acid.

The content of paratoluenic acid in the wastewater is preferably 5000 mg or less, particularly preferably 50 to 5000 mg / l, and more preferably 100 to 2000 mg / l, but is not limited thereto.

[Sulfuric acid]

Sulfate (SO ₄ ^{2 -)} in the drainage agent for addition of the sulfuric acid, iron sulfate (I), iron sulfate (II), poly ferric sulfate, such as SO ₄ ^{2 -} containing an acid solution, ammonium sulfate, aluminum sulfate, sodium sulfate , And a soluble sulfate such as potassium sulfate, and the like, but is not limited thereto.

Calcium sulphate and magnesium sulphate are water-insoluble, but at low concentrations they are soluble in water.

The agent for adding the sulfuric acid radical is preferably added as an aqueous solution having a SO ₄ ^{2 -} concentration of 5 to 30 mass%.

If the addition amount of the sulfuric acid radical to the drainage is excessively small, the effect of the present invention by adding the sulfuric acid radical can not be sufficiently obtained, and if it is too much, a large amount of hydrogen sulfide gas is generated.

The sulfuric acid radical has a SO ₄ ^{2 -} concentration of preferably 30 to 400 mg / l, more preferably 60 to 400 mg / l, more preferably 50 to 200 mg / l, particularly preferably 70 to 200 mg / Mg / l. ≪ / RTI >

The sulfuric acid radical is preferably added to the wastewater at a ratio of 10 mass% or more, particularly 15 to 30 mass%, based on the terephthalic acid in the wastewater. When the sulfuric acid radical content with respect to terephthalic acid in the drainage water is excessively small, the decomposition efficiency of terephthalic acid may not be sufficiently increased.

When the wastewater to be treated contains terephthalic acid and para-toluene acid, the sulfuric acid radical is preferably added to the wastewater at a ratio of 10 mass% or more, particularly 15 to 30 mass%, based on the total amount of terephthalic acid and para-toluene acid in the wastewater.

Sulfuric acid is added to the drain water so that the concentration of the sulfate ion in the treated water obtained by the anaerobic treatment is 5 to 200 mg / l, preferably 10 to 20 mg / l. The addition effect of the sulfuric acid radical according to the present invention can not be sufficiently obtained when the sulfuric acid anhydrous amount of the anaerobic treatment water is lower than 5 mg / l. If the concentration of the sulfate ion in the anaerobic treatment water is excessively high, the amount of hydrogen sulfide gas generated is increased, and the water quality of the anaerobic treatment water itself deteriorates, thereby increasing the load of the downstream treatment process.

[Anaerobic Treatment]

The anaerobic treatment method may be a one-phase system in which the acid production process by acid-producing bacteria and the methane fermentation process by methanogenic bacteria are carried out in the same tank, or the two-phase system may be carried out in another tank.

The anaerobic treatment tank is composed of a UAST (Upflow Anaerobic Sludge Blanket) system, an EGSB (Expanded Granule Sludge Bed) system, a UASB (Upflow Anaerobic Sludge Bottom) system capable of high load treatment by granulation of a fixed bed, Sludge phase) system, but it is preferably a UASB system or an EGSB system capable of high load processing.

In the single-phase anaerobic treatment apparatus, the sulfuric acid muscle may be added to any of the raw water introduced into the anaerobic treatment tank and the anaerobic treatment tank. When sulfuric acid is added as the sulfuric acid radical, the pH is lowered by the addition of sulfuric acid. Therefore, if a pH adjustment tank is formed, it is preferably added at the front stage.

In the two-phase anaerobic treatment apparatus, the point of addition of the sulfuric acid radical is selected according to the amount of the substance to be treated in the wastewater. When the decomposable substance in the waste water is large, it is preferable to add the sulfuric acid radical at a position close to the methane fermentation tank. When the decomposable substance in the wastewater is small, it is preferable to add sulfuric acid radicals at the upstream side, for example, in the acid production tank. This is because, if sulfuric acid radicals are consumed at the time of decomposing the decomposable substance, the decomposition promoting effect of terephthalic acid or para-toluic acid is lowered.

Even in the two-phase processing apparatus, when sulfuric acid is added as the sulfuric acid radical, the pH is lowered. Therefore, in the case where the pH adjustment tank is formed, sulfuric acid is preferably added at the front end thereof.

The anaerobic sludge concentration is 10,000 to 40,000 mg-VSS / ℓ, the loading is 1 to 15 kg-1, the pH is 6 to 8, the temperature is 25 to 39 ° C, the residence time is 4 hours to 3 days, BOD / m 3 · day, CODcr load of 2 to 30 kg-CODcr / m 3 · day.

The anaerobic treatment water can be further provided for aerobic treatment such as activated sludge treatment and other post treatment for decomposing the remaining organic matter. According to the present invention, in the anaerobic treatment, the degradable terephthalic acid can be efficiently decomposed and removed by the anaerobic treatment. Even when aerobic treatment is performed after anaerobic treatment of wastewater, the load of the anaerobic treatment is reduced and the treatment cost is reduced.

[Treatment of hydrogen sulfide gas]

In the present invention, since sulfuric acid radicals are added to the terephthalic acid-containing wastewater at the above-described addition amount, the methane fermentation is not inhibited, the generation of hydrogen sulfide gas is suppressed, and the decomposition efficiency of terephthalic acid is enhanced. When a small amount of hydrogen sulfide gas is generated, the hydrogen sulfide gas may be subjected to biological desulfurization treatment. Generally, in the biological desulfurization treatment, when the concentration of hydrogen sulfide in the gas to be treated fluctuates, sulfur oxidizing bacteria do not grow stably and the treatment becomes unstable. In the present invention, since the concentration of hydrogen sulfide in the exhaust gas is stabilized by adding a predetermined amount of sulfuric acid to the waste water, the biological desulfurization treatment is stably performed.

The biological desulfurization treatment of the hydrogen sulfide-containing exhaust gas is preferably carried out by the method described in Japanese Patent No. 3235131. [ In this method, hydrogen sulfide-containing exhaust gas is brought into contact with a cleaning liquid, for example, a treatment liquid in the oxidation of aerobic microbes of an organic substance to absorb hydrogen sulfide in the gas, oxidizing the obtained absorption liquid to aerobic microorganisms, The hydrogen sulfide is oxidized by sulfuric acid ions or a single sulfur to render it harmless.

According to this method, desulfurization can be performed at a high desulfurization efficiency without causing a decrease in the content of methane gas, at a low cost, efficiently, and without causing new wastewater accompanied by desulfurization. However, the method of treating the hydrogen sulfide gas is not limited to this method.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

The water quality of the anaerobic treated raw water in Examples and Comparative Examples is as follows.

<Raw water quality>

COD _Cr : 4050 mg / l

Terephthalic acid concentration: 400 mg / l

Concentration of paratoluenic acid: 620 mg / l

SO ₄ ^{2 -} Concentration: 30 to 40 mg / l

pH: 10

[Examples 1 to 3, Comparative Examples 1 and 2]

Raw water was treated by a two-phase anaerobic treatment apparatus equipped with an acid generation tank and an EGSB methane fermentation tank. The raw water was introduced into an acid producing tank, treated with a methane fermenter, part of treated water from a methane fermenter was circulated in an acid producing tank, and the remainder was taken out as treated water.

The specifications and treatment conditions of each tank are as follows, and the raw water flow rate is 5 L / day.

Acid production: 0.5 liter

Acid production bath pH: 6.5 to 7.5

Methane fermentation tank Capacity: 2 ℓ

Methane fermenter pH: 7 ~ 8

Methane fermenter sludge concentration: 67 g / ℓ as VSS

Methane fermenter temperature: 35 ℃

The circulation quantity from the methane fermentation tank to the acid production tank was circulated 1 Q (= 5 l / day) for the raw water flow Q (= 5 l / day).

In Comparative Example 1, sulfuric acid was not added to the raw water. Examples 1 to 3 and Comparative Example 2, SO ₄ ² shown in Table 1 in a set of acid generated ^{shear-sulfate} was added to the raw water to the added amount. Sulfuric acid was added as an aqueous solution of 20 mass%. Since the pH was lowered by the addition of sulfuric acid, the pH was adjusted by adding sodium hydroxide after the addition of sulfuric acid. With the addition of sulfuric acid, the SO ₄ ^{2 -} content in the wastewater provided for the anaerobic treatment, including SO ₄ ^{2 -} contained in the raw water, was as shown in Table 1.

Table 1 shows the water quality of the treated water obtained by the anaerobic treatment, the activity of the sludge obtained from the treatment result, and the occurrence of the hydrogen sulfide gas.

From Table 1, it can be seen that according to the present invention, highly refined water can be obtained by effectively anaerobically treating waste water containing refractory terephthalic acid.

While the invention has been described in detail with reference to certain embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

The present application is based on Japanese Patent Application (Patent Application No. 2010-224001) filed on October 1, 2010, which is incorporated by reference in its entirety.

Claims (11)

A method for anaerobic treatment of wastewater containing terephthalic acid, characterized in that a sulfuric acid radical is added to the water so that the concentration of the sulfate ion in the treated water obtained by the anaerobic treatment is 5 to 200 mg / Processing method. The method according to claim 1,
Wherein a sulfuric acid radical is added to the drainage so that the content of the sulfate radical in the drainage is 60 to 400 mg / l. 3. The method according to claim 1 or 2,
Wherein a sulfuric acid radical is added to the wastewater so that the content of sulfuric acid radicals relative to terephthalic acid in the wastewater is 10 mass% or more. 3. The method according to claim 1 or 2,
Wherein the wastewater contains 50 to 2000 mg / l of terephthalic acid. 3. The method according to claim 1 or 2,
Wherein said wastewater further comprises paratoluenic acid. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; 3. The method according to claim 1 or 2,
At least one member selected from the group consisting of sulfuric acid, iron (I) sulfate, iron (II) sulfate, iron polysulfate, ammonium sulfate, aluminum sulfate, sodium sulfate, and potassium sulfate is added to the water Wherein the terephthalic acid-containing waste water is added to the anaerobic treatment tank. An apparatus for anaerobic treatment of wastewater containing terephthalic acid, characterized by comprising a means for adding a sulfuric acid radical to the drain water so that the concentration of the sulfate ion in the treated water obtained by the anaerobic treatment is 5 to 200 mg / An apparatus for anaerobic treatment of drainage. 8. The method of claim 7,
And a means for adding a sulfuric acid radical to the drain water so that the content of the sulfuric acid radical in the drainage water is 60 to 400 mg / l. 9. The method according to claim 7 or 8,
Wherein the sulfuric acid is added so that the content of the sulfuric acid radical in the drain water is 10% by mass or more with respect to terephthalic acid in the drain water. 9. The method according to claim 7 or 8,
Wherein the wastewater contains terephthalic acid in an amount of 50 to 2000 mg / l. 9. The method according to claim 7 or 8,
Wherein the drainage further comprises paratoluenic acid. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;