JPH08267094A - Waste water treatment in production of alpha-sulfofatty acid alkyl ester - Google Patents

Abstract

PURPOSE: To effectively reduce COD and to make overall waste water treatment possible in the succeeding stage at the time of treating the bottom waste water of a fractionating tower obtained by fractionating the spent solvent recovered from the production process by adding an oxidizing substance such as hydrogen peroxide to the waste water, mixing, flocculating and then biologically oxidizing the water. CONSTITUTION: The bottom waste water of a fractionating tower generated by fractionating the spent solvent recovered from the production process of α-sulfofatty acid alkyl ester is treated as follows. Namely, an oxidizing substance such as hydrogen peroxide is added to the waste water and mixed, then the mixture is flocculated, and the flocculated material is biologically oxidized. In this case, the waste water is appropriately flocculated with an inorg. flocculant and further flocculated with a high molecular flocculant. Besides, a biological oxidation device wherein the the microorganism, vorticella and/or philodina, are immobilzed is used in the biological oxidation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating bottom effluent of a rectification column produced by rectifying and separating a used solvent recovered from a process for producing an α-sulfofatty acid alkyl ester salt in a rectification column. Regarding

[0002]

2. Description of the Related Art In order to produce a good quality .alpha.-sulfofatty acid alkyl ester salt, it is necessary to use a solvent in the production process. The α-sulfofatty acid alkyl ester salt is generally produced as an aqueous solution or slurry through sulfonation and neutralization of a fatty acid alkyl ester. However, since the reaction rate is slow, sulfonation is required under severe reaction conditions. Therefore, the obtained sulfonated product is colored brown or blackish brown and needs to be bleached, but in order to suppress the generation of by-products and efficiently perform this bleaching, the number of carbon atoms is 1 to 1
Techniques for adding 12 lower alcohols have been developed and established (Japanese Patent Publication No. 53-46825 and Japanese Patent Publication No. 6-25).
0-36421, Japanese Patent Publication No. 1-441138, Japanese Patent Publication No. 2-10144, Japanese Patent Publication No. 2-1014.
No. 5, Japanese Patent Publication No. 5-1022).

Alcohol (usually methanol) used in the bleaching step is recovered as a mixed solution with water from the alcohol topping after neutralization, the concentration step by a thin film type condenser, the flash evaporator, etc., but from an economical point of view. It is important to recover alcohol from the water and purify it for recycling. Generally, the used solvent (mostly water) recovered is
Purified by rectification. Regarding the rectification operation, the present inventors have previously filed a patent application as Japanese Patent Application No. 6-334349.

[0004]

However, in such a rectification operation, COD (chemical oxygen demand) is usually 3 in the rectification tower bottom wastewater discharged from the bottom of the rectification tower.
It is as high as 00 to 800 ppm, and there is a problem that it cannot be treated at the integrated wastewater treatment plant as it is.

When the present inventors have investigated the cause of this, organic substances such as surfactants, oils such as fatty acid alkyl esters, and side reaction products of the above bleaching process mainly increase the COD of the bottom waste water of the rectification column. It became clear that this was the cause. As a treatment method for such high COD wastewater, there are an activated carbon adsorption method, an ion exchange resin treatment method, an evaporation treatment method and the like.

[0006] However, the method of removing the above organic substances by the activated carbon adsorption method is low in equipment cost, but the reduction rate of COD is as low as 20 to 70% and the running cost is also great. The ion exchange resin treatment method is a method of removing ionic organic substances by ion exchange, and although the COD reduction rate is relatively good, the equipment cost and running cost are enormous.

The evaporation treatment method is topping, thin film type concentrator,
This is a method of evaporating and separating a low boiling point solvent using a flash evaporator or the like, and although the COD lowering rate is relatively good, equipment costs are required and running costs are enormous. An object of the present invention is to provide a method for suppressing an increase in equipment cost and running cost, and moreover, for efficiently reducing the COD of the bottom water of the rectification column.

[0008]

The method for treating wastewater in the production of α-sulfofatty acid alkyl ester salt of the present invention comprises α
The effluent bottom wastewater produced by rectifying and separating the used solvent recovered from the sulfo fatty acid alkyl ester salt production step in the rectification tower is sequentially subjected to the following treatments. (A) Oxidation treatment: A hydrogen peroxide-based acidic substance is added and mixed. (B) Aggregation treatment: Aggregation treatment is performed on the mixed product obtained by the oxidation treatment of (a). (C) Biooxidation treatment: Bioaggregation treatment of (b) is performed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The α-sulfofatty acid alkyl ester salt is a salt of a sulfonated product of a fatty acid alkyl ester, and the number of carbon atoms of the fatty acid residue is preferably 10 to 20. The carbon number of the group is preferably 1 to 5. As the salt, a salt that imparts water solubility to the α-sulfofatty acid alkyl ester salt, such as an alkali metal salt such as a sodium salt, is used.

In the production of the α-sulfo fatty acid alkyl ester salt, the raw material fatty acid alkyl ester is sulfonated, and the obtained sulfonated product is bleached with hydrogen peroxide or the like in the presence of a lower alcohol having 1 to 12 carbon atoms. It is bleached with water and then neutralized to obtain an aqueous solution or an aqueous slurry of an α-sulfofatty acid alkyl ester salt containing a lower alcohol. Removal of alcohol from this aqueous solution by topping or thin film evaporator, flash evaporator, etc. The used solvent is recovered in the concentration step. The used solvent has a solvent (usually methanol) such as alcohol and water as main components, and includes entrained substances such as oil.

Therefore, rectification is separated by a rectification tower, and a solvent such as methanol is recovered from the top of the tower and reused, while effluent from the bottom of the rectification tower is recovered from the bottom of the tower. Bottom effluent of the rectification tower is an aqueous solution containing 10 to 1000 ppm of alcohol (usually methanol) used in the bleaching step, and in addition to this, surfactants (mainly soap), oils such as lower fatty acid alkyl esters, It contains decomposition or side reaction products of formic acid, acetic acid, oxalic acid, etc., reducing inorganic substances (sulfites), etc.

Therefore, in the present invention, as the first stage, the rectification tower bottom wastewater is subjected to (a) oxidation treatment. (A) The oxidation treatment is
It is carried out by adding a hydrogen peroxide-based oxidizing substance to the bottom effluent of the rectification column and performing a mixing process. At this time, hydrogen peroxide, sodium hydrogen peroxide, hydrogen peroxide (which is obtained by treating alkali metal metasilicate or borax with hydrogen peroxide) is used as the hydrogen peroxide-based oxidizing substance. it can. Particularly, hydrogen peroxide is preferable, and usually, the concentration is 30 to
Handled as a 60% aqueous solution.

The amount of the hydrogen peroxide-based oxidizing substance added is preferably 500 ppm or less of the reducing substance (as sodium sulfite) after the mixing treatment, more preferably 300 pp.
It is added so that it becomes m or less. Usually, the amount of the reducing substance added in such a range is 0.03 to 1% with respect to the bottom waste water of the rectification tower in the case of 35% hydrogen peroxide water. If the reducing substance (a) after the oxidation treatment exceeds 500 ppm, the load on the biological oxidation treatment (c) becomes large and the treatment becomes difficult. The pH during the mixing treatment is preferably 7-1.
1, more preferably 8 to 10. If the pH is out of this range, the reducing rate of the reducing substance is remarkably inferior. The reducing substance means the amount of the reducing substance in the sample, which was obtained by back titration with sodium sulfite after the sample was oxidized with excess hydrogen peroxide, and expressed as ppm of sodium sulfite.
It is expressed in units.

In the coagulation treatment (b) following the above treatment, a commercially available coagulant for water treatment can be used.
This agglomeration treatment is preferably carried out in two stages:
After performing the aggregating treatment with an inorganic salt-based aggregating agent,
It is preferable to perform a coagulation treatment with a polymer coagulant. This treatment allowed efficient removal of oil and surfactants (mainly soaps).

As the inorganic salt-based coagulant used in the first treatment, polyaluminum chloride, aluminum sulfate (sulfate band), alum, etc. can be used. Preference is given to polyaluminum chloride, which is also known as basic aluminum chloride or pack (PAC). The amount of the flocculant added is preferably 300 to 1000 ppm, more preferably 400 to 600 ppm. The pH is preferably 6-8, more preferably 6.5-7.5.

The polymer flocculant used in the second treatment is preferably an anionic polymer, for example, a copolymer of acrylamide and acrylic acid, a partial hydrolyzate of polyacrylamide, or a polyacrylate salt. . The addition amount of the polymer flocculant is preferably 1 to 10 ppm, more preferably 3 to 7 ppm. The pH is preferably 6-8, more preferably 6.5-7.5. After the above-mentioned two-stage aggregation treatment, the treatment liquid is introduced into the separation tank to perform the separation treatment. By these treatments, oil and surfactant (mainly soap) can be efficiently removed.

(B) After the coagulation treatment, a biological oxidation treatment is then performed. Examples of organisms used for the biological oxidation treatment include Vorticella (Coleoptera) of the ciliate of the protozoa and Philodina of the phylum of the metazoan rotifer.
Etc. are particularly preferable. As a device for biological oxidation treatment, any device can be used as long as it can utilize these microorganisms, but preferably, the filter medium (crushed stone, which is immobilized on the surface of the microorganisms with a gelatinous membrane, etc. (Mineral particles, etc.) is a sprinkling filter bed for sprinkling waste water in a tank filled with mineral particles, or a dipping filter bed for immersion and passage. In particular, it is preferably an immersion filter bed in which the above-mentioned microorganisms are immobilized on the surface of actilite particles, and a specific example of this device is Acticontact (manufactured by Organo Corporation).

The conditions of use of these devices depend on the usual method,
It is preferable to use a microorganism that has been acclimated in advance to the treated wastewater. By this biological oxidation treatment, organic substances such as formic acid, acetic acid, oxalic acid and methanol are mainly decomposed.

[0019]

INDUSTRIAL APPLICABILITY According to the present invention, the COD of the bottom effluent of the rectification column produced by rectifying and separating the used solvent recovered from the production process of the α-sulfofatty acid alkyl ester salt in the rectification column is efficiently The water quality can be maintained in a stable state for a long period of time by enabling the wastewater treatment at the integrated wastewater treatment plant in the next process.

[0020]

【Example】

Example 1 1000 kg of rectification tower bottom drainage generated by rectifying and separating a used solvent recovered from the production process of α-sulfofatty acid alkyl ester salt in a rectification tower was put in an aeration tank, and 35% thereof was added thereto. Add 1.2 kg of hydrogen peroxide water,
After adjusting the pH to about 9, the mixture was aerated and stirred at a flow rate of 9 Nm ³ / min for 15 hours.

By this treatment, the reducing substance in the wastewater is 50
It dropped from 0 ppm to 100 ppm. This treatment liquid was transferred to a coagulation tank, polyaluminum chloride (PAC) was added to this liquid in an amount of 500 ppm, and the mixture was stirred. In addition, p of the liquid
H was adjusted to 6.8 with a 10% sulfuric acid aqueous solution. Next, AP-1 manufactured by Organo Co., Ltd. as a polymer flocculant was added to this solution at 5 ppm and stirred.

The treated liquid was transferred to a flotation tank through pressurized air (internal pressure 4 kg / cm ² · G), and the agglomerates formed were floated and separated. The liquid treated in this way is further subjected to biological oxidation treatment as Acticontact (manufactured by Organo Corporation).
And treated for about 20 hours. In addition, for Acti contact, Vorticella, P
A filter medium on which hilodina was fixed was used. By such wastewater treatment, the COD of the treated liquid is about 50 ppm (C
The OD reduction rate was about 90%), and the quality of the water was such that it could be treated at the integrated wastewater treatment plant.

Example 2 When the same operation as in Example 1 was continued for 6 months, the COD reduction rate of the treatment liquid was maintained at about 90%, and the quality of the waste water was stable.

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Claims (3)

[Claims] 1. A rectification tower bottom wastewater produced by rectifying and separating a used solvent recovered from a production process of an α-sulfofatty acid alkyl ester salt in a rectification tower, wherein (a) a hydrogen peroxide system [Alpha] -sulfofatty acid alkyl, characterized in that (b) the coagulation treatment is carried out on the treated product obtained in (a) above, and (c) the biological oxidation treatment is carried out. Wastewater treatment method in ester salt production. 2. The production of α-sulfofatty acid ester salt according to claim 1, wherein in (b) the aggregating treatment, the aggregating treatment with an inorganic salt-based aggregating agent is carried out, and then the aggregating treatment with a polymer aggregating agent is carried out. Wastewater treatment method. 3. (c) In the biological oxidation treatment, the microorganism vo
The wastewater treatment method for producing an α-sulfofatty acid alkyl ester salt according to claim 1 or 2, wherein a biooxidation treatment device in which rticella and / or philodina is immobilized is used.