JPH11319852A - Treatment of waste water containing surfactant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly operate a reverse osmosis membrane treating device for a long time by biologically treating a collected raw water, bringing the treated water into contact with a cation exchange resin and then subjecting the water to reverse osmosis membrane treatment. SOLUTION: First, the collected raw water as a waste water containing surfactants is biologically treated. The biologically treated water is then brought into contact with a strong acid cation exchange resin. In this process, it is preferable to pass the water through a bacteria separator to remove a solid content such as microbes and bacteria in the treated water. The biologically treated water after the bacteria separation is passed as a downward flow or upward flow through an ion exchange tower packed with a strong acid cation exchange resin and brought into contact with the strong acid cation exchange resin. In this contact treatment with the ion exchange resin, the TOC(total org. compd.) component which is the main factor substance for pollution of the reverse osmosis membrane in the reverse osmosis membrane treatment in the succeeding process is removed by exchanging ions. As the strong acid cation exchange resin, a porous resin is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater containing a surfactant discharged from the manufacturing process of precision optical equipment and semiconductors, and more particularly, to a method for treating optical elements such as lenses and optical fibers. To process, collect and reuse wastewater containing surfactants discharged from the manufacturing process of various glass substrates used for glass, liquid crystals, hard disks, solar cells, etc., silicon wafers for semiconductors, compound semiconductor wafers, etc. In the processing method.

[0002]

2. Description of the Related Art In recent years, despite increasing demand for water, it has become more difficult to secure a new water source. In addition, since wastewater regulations such as total volume regulations are being strengthened from the viewpoint of environmental conservation, collection and reuse of factory wastewater is becoming an important issue in order to cope with such a situation. Since factory wastewater contains various components according to its manufacturing process, there are various wastewater treatment and recovery methods for reuse.

[0003] For example, in the manufacturing process of lenses, optical glass such as optical fibers, liquid crystal, hard disks, various glass substrates used for solar cells, silicon wafers for semiconductors, compound semiconductor wafers, etc., manufacturing is performed with ultrapure water manufacturing equipment. A large amount of the purified ultrapure water is used as cleaning water, and the ultrapure water used for the cleaning is discharged as cleaning wastewater containing a surfactant. Although the concentration of the surfactant in the wastewater varies depending on the product of the factory and the manufacturing process, the surfactant generally contains about 0.5 to 10 mg / L (liter) as TOC (total organic matter). As the surfactant contained,
Various surfactants such as a cationic surfactant, a nonionic surfactant, and an anionic surfactant.

When treating and recovering and reusing these washing wastewaters, it is necessary to remove impurities to such an extent that no trouble occurs when the recovered and treated water is reused. The water is desired to reach the primary pure water level. In particular, in the treatment of wastewater containing a surfactant, if the surfactant remains in the recovered water after the treatment even if the concentration is low, the recovered water foams at the time of reuse, and the recovered water is further removed. When the salt is reused after the treatment, the ion exchange resin of the ion exchange device may be contaminated by the surfactant, and the treatment performance may be reduced. Therefore, when treating and collecting and reusing the surfactant-containing wastewater, it is necessary to lower the concentration of the TOC containing the surfactant at a low value to a certain concentration or less.

Conventionally, in the method for treating wastewater containing a surfactant as described above, a method of treating and recovering wastewater by passing it through a biological treatment, a bacterial cell separator, and a reverse osmosis membrane device in this order is used. Have been. In this method, first, wastewater treated for recovery (hereinafter sometimes referred to as recovered raw water) is biologically treated. In this case, if necessary, the wastewater is passed through an activated carbon tower in advance to remove harmful substances such as hydrogen peroxide. After removing the matter, most of the TOC component is decomposed and reduced by, for example, a method in which the microorganisms are suspended in raw water and treated while aerating, or a method in which the recovered raw water is brought into contact with the microorganisms carried on the activated carbon surface. Next, the treated water is removed with a microbial cell separator comprising a microfiltration membrane or an ultrafiltration membrane to remove viable bacteria in the biologically treated water. Next, the treated water of the microbial cell separator is passed through a reverse osmosis membrane device to remove the remaining TO.
The C component is almost completely removed, and the permeated water is recovered and reused.

However, these conventional methods for treating surfactant-containing wastewater have the following disadvantages. That is, when the concentration of the surfactant contained in the recovered raw water increases, or when the properties of the components such as the surfactant in the raw water are switched, rapid clogging occurs in the reverse osmosis membrane. However, there has been a problem that the reverse osmosis membrane device cannot be smoothly operated because of the difficulty in recovering even by various chemical cleaning.

[0007]

SUMMARY OF THE INVENTION The present inventors have repeatedly studied a method for treating and recovering a surfactant-containing wastewater in order to solve this problem. It was found that the membrane contaminants were well adsorbed on the cation exchange resin. In order to remove membrane contaminants, it is very effective to subject the recovered raw water to biological treatment and then contact it with a cation exchange resin, especially a porous strong acid cation exchange resin. The inventors have found that the permeable membrane device can be operated smoothly for a long time, and have completed the present invention.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for treating a surfactant-containing wastewater, wherein the wastewater containing the surfactant is subjected to biological treatment and reverse osmosis membrane treatment to recover the treated water. The gist of the present invention is a method for treating a surfactant-containing wastewater, which comprises subjecting the wastewater to biological treatment, bringing the wastewater into contact with a strongly acidic cation exchange resin, and then treating the wastewater with a reverse osmosis membrane.

In a preferred embodiment of the present invention, a porous strongly acidic cation exchange resin is used as the strongly acidic cation exchange resin; a porous strongly acidic cation exchange resin having a degree of crosslinking of 8% or less is used. A treatment method comprising using a Na type strongly acidic cation exchange resin, wherein the surfactant contained in the waste water is a surfactant mainly composed of a cationic surfactant. Processing method.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to FIG. FIG. 1 shows an example of a schematic system diagram of a method for treating surfactant-containing wastewater according to the method of the present invention. Wastewater discharged from precision optical equipment and semiconductor manufacturing processes contains various components according to the process, and is roughly classified into acid-based wastewater such as hydrofluoric acid, sulfuric acid, and nitric acid and organic wastewater such as acetic acid. The method of the present invention is mainly intended for wastewater containing a surfactant. Recovered raw water, which is surfactant-containing wastewater, is first subjected to biological treatment. At that time, if the raw water contains substances harmful to biological treatment such as hydrogen peroxide,
It is preferable to remove them with activated carbon or the like before performing biological treatment in advance.

As the biological treatment, an activated sludge method or a biological activated carbon method, which has been conventionally performed, is appropriately employed. In this biological treatment, the recovered raw water has a TOC of 1 to 10 mg / L.
When a relatively high concentration of surfactant is contained, it can be treated by a usual operation method such as the activated sludge method or the biological activated carbon method. In addition, TOC O.D. 5 to 1 mg /
In the case of a wastewater containing a surfactant having a relatively low concentration of L, a biological activated carbon method in which microorganisms are supported on the surface of activated carbon is preferably used. The type of surfactant contained in the recovered raw water is not particularly limited, such as a cationic surfactant, an anionic surfactant, and a nonionic surfactant, but the surfactant is mainly a cationic surfactant. In this case, it is desirable to adopt a method such as lengthening the aeration time or employing a specially acclimated microorganism, since the processing ability of the microorganism may decrease.

The treated water subjected to the biological treatment is then subjected to a contact treatment with a strongly acidic cation exchange resin. At this time, the treated water is passed through a microbial cell separator comprising a microfiltration membrane or an ultrafiltration membrane to be included in the treated water. It is preferable to remove solids such as microorganisms and cells. This cell separation is performed to prevent pressure loss due to the accumulation of microorganisms during the contact treatment with a strongly acidic cation exchange resin, and if such a purpose is achieved, a filter medium such as sand is used. Filtration may be used.

Next, the biologically treated water from which the cells have been separated is passed down or upward through an ion exchange tower loaded with a strongly acidic cation exchange resin, and brought into contact with the strongly acidic cation exchange resin. By the contact treatment with the ion exchange resin, the TOC component serving as a pollutant substance on the reverse osmosis membrane surface in the next step of the reverse osmosis membrane treatment is ion exchanged and removed. In the method of the present invention, it is essential that the treated water subjected to the biological treatment is brought into contact with the strongly acidic cation exchange resin. However, depending on the type of the components contained in the treated water, the contact with the strongly acidic cation exchange resin is required. Can be carried out in the coexistence of an anion exchange resin. For example, the treated water may be passed through an ion exchange tower composed of a mixed bed of a strongly acidic cation exchange resin and an anion exchange resin to perform contact treatment.

In the method of the present invention, the strongly acidic cation exchange resin for ion-exchange removal of membrane contaminants contained in the treated water after the biological treatment includes gel type and porous type strongly acidic cation exchange resins. Any of them can be employed, but it is preferable to employ a porous strong acid cation exchange resin. Because TOC contained in biologically treated water
Although the film contaminants in the components are not fully understood, the film contaminants have an average molecular weight of 200 to 400.
It is presumed that this is larger than that of inorganic ions such as sodium ion. Therefore, in the case of a gel-type strongly acidic cation exchange resin, ion exchange of membrane contaminants can be performed only near the resin surface. Since a porous cation exchange resin is used for ion exchange to the inside of the resin particles and increases the exchange capacity, it is advantageous to use a porous resin.

As porous strong acid cation exchange resins, Diaion (Mitsubishi Chemical Corp .: trade name) PK series, Amberlite 200 series (Rohm & Haas Co., Ltd .: trade name) and the like are generally commercially available. Although it can be used as appropriate from commercial products, those having a degree of crosslinking of 8% or less are particularly preferable. For example, Diaion PK manufactured by Mitsubishi Chemical Corporation
208, PK216 and PK212. Further, the strongly acidic cation exchange resin may be either H type or Na type, but it is preferable to use Na type strongly acidic cation exchange resin. The reason for this is that when an H-type strongly acidic cation exchange resin is used, the pH of the treated water after contact with the cation exchange resin decreases, so that the treated water must be treated in advance in the reverse osmosis membrane treatment in the next step. This requires a summation treatment, which is disadvantageous because the operation becomes complicated in addition to the use of the neutralizing agent. When an anion exchange resin is used together, a porous strong basic anion exchange resin is preferable, and examples thereof include Diaion PA306, PA308, PA312, and PA316.

The flow rate of the biologically treated water to the ion exchange tower filled with the strongly acidic cation exchange resin is usually SV10.
To 60, preferably 20 to 40. Water can be passed until the strongly acidic cation exchange resin is saturated with TOC.
When the amount of TOC in the treated biological water reaches a predetermined amount, or when the amount of TOC in the treated water of the strongly acidic cation exchange resin increases.
It is preferable to stop when the concentration of C starts to leak beyond a predetermined value.

The ion exchange performance of the ion exchange column is reduced,
When treated water having a predetermined TOC concentration cannot be obtained, the flow of water is stopped and the ion exchange resin is replaced. At this time, the strongly acidic cation exchange resin used for the ion exchange treatment of the biologically treated water is preferably regenerated and not used, but replaced with a new resin.
The reason is that the TOC component mainly composed of the membrane fouling substance trapped in the strongly acidic cation exchange resin by the ion exchange treatment has a strong affinity with the ion exchange resin. This is because even if the reproduction can be performed, the reproduction operation is complicated, the reproduction efficiency is low, and it is not economical.

The treated water treated with the strongly acidic cation exchange resin is then subjected to a reverse osmosis membrane treatment. The TOC component remaining in the treated water is almost completely removed by the reverse osmosis membrane treatment, and the water quality level of the permeated water from which the TOC component has been removed is 1
Since it is about next pure water, it is reused as recovered water. In the method of the present invention, since the recovered raw water is treated with a strongly acidic cation exchange resin after the biological treatment to remove the membrane contaminant, the pressure loss of the reverse osmosis membrane during the reverse osmosis membrane treatment is greatly reduced. In addition, the reverse osmosis membrane treatment can be stably performed over a long period of time. The reverse osmosis membrane is not particularly limited and can be appropriately selected from those usually used such as cellulose acetate-based and polyamide-based membranes, and is subjected to a treatment operation by a conventional method.

According to the present invention, the biological treatment water of the recovered raw water is subjected to contact treatment with a strongly acidic cation exchange resin, whereby membrane contamination is reduced and reverse osmosis membrane treatment can be carried out smoothly.
Moreover, the effect of preventing membrane contamination does not appear for a specific reverse osmosis membrane. The reason why the treatment with the strong acidic cation exchange resin reduces contamination of the reverse osmosis membrane is not necessarily clear, but when a wastewater containing a surfactant, particularly a cationic surfactant is subjected to biological treatment, Due to incomplete or non-uniform biodegradation, medium-molecular-weight organic components remain, and some of them are acting as reverse osmosis membrane contaminants. It is presumed that it has strong affinity with the resin and is easily removed by the treatment with the cation exchange resin.

[0020]

The present invention will be described below in more detail with reference to Examples and Comparative Examples for comparison, but the present invention is not limited by the following Examples unless it exceeds the gist thereof.

Example A test was conducted using a surfactant-containing wastewater treatment apparatus having a flow as shown in FIG. After biological treatment of surfactant-containing cleaning wastewater (recovered raw water) discharged from the semiconductor manufacturing process, microorganisms were separated by a cell separator equipped with a UF membrane microza (manufactured by Asahi Kasei Corporation). Table 1 shows the quality of the biologically treated water obtained from the cell separator. This biologically treated water was subjected to a treatment with a strongly acidic cation exchange resin, followed by a treatment with a reverse osmosis membrane to conduct a test.

[0022]

[Table 1]

The strong acid cation exchange resin column has an inner diameter of 125
A raw water introduction pipe was provided at the top of the tower at a height of 750 mm and a height of 750 mm, and a treated water discharge pipe was provided at the bottom of the tower. In this column, as a porous strong acid cation exchange resin, Diaion PK208 (N
a type) [manufactured by Mitsubishi Chemical Corporation] was packed at 7.0 L with a packed bed height of about 570 mm. The biologically treated water was passed through this ion exchange resin tower at a flow rate of 210 L / h. The reverse osmosis membrane device is equipped with a wholly aromatic polyamide-based composite membrane ES-10D (manufactured by Nitto Denko Corporation), with a supply water flow rate of 210 L / h,
Concentrated water discharge flow rate 30 L / h, permeate flow rate 180 L / h
Then, the treated water obtained from the ion exchange resin tower was treated. FIG. 2 shows the change over time in the operating pressure loss (kgf / cm ² ) of the reverse osmosis membrane device when the recovery treatment was performed under the above treatment conditions, and Table 2 shows the average quality of the treated water.

Comparative Example Biologically treated water having the same water quality as that used in the examples shown in Table 1 was directly passed through a reverse osmosis membrane device without being treated in an ion exchange resin tower to perform a recovery treatment. The reverse osmosis membrane device used for the treatment and the treatment conditions were the same as in the example. FIG. 2 shows the change over time in the operating pressure loss of the reverse osmosis membrane device when the recovery treatment was performed under the above treatment conditions, and Table 2 shows the average quality of the recovered water.

[0025]

[Table 2]

[0026]

According to the treatment method of the present invention, if the wastewater containing surfactant is treated in the order of biological treatment, strongly acidic cation exchange resin treatment, and reverse osmosis membrane treatment, wastewater by conventional biological treatment and reverse osmosis membrane treatment can be obtained. As compared with the treatment method of the above, the operating pressure loss of the reverse osmosis membrane device can be stably maintained at a lower level, so that not only a smooth operation can be performed for a long time but also the TOC of the reverse osmosis membrane treated water can be improved. Can be stably maintained at a lower concentration, so that the recovered water can be effectively reused.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram illustrating an example of a method for treating a surfactant-containing wastewater according to the present invention.

FIG. 2 shows the change over time of the operating pressure loss of the reverse osmosis membrane devices of Examples and Comparative Examples. In the figure, the vertical axis represents RO operating pressure loss (kgf / cm ² ), and the horizontal axis represents days of water passage.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C02F 9/00 502 C02F 9/00 502J 503 503C 504 504A

Claims (5)

[Claims] Claims: 1. A method for treating a surfactant-containing wastewater, wherein the surfactant-containing wastewater is subjected to biological treatment and reverse osmosis membrane treatment to recover treated water. A method for treating a surfactant-containing wastewater, comprising contacting with a cation exchange resin, and then treating with a reverse osmosis membrane. 2. The method for treating wastewater containing a surfactant according to claim 1, wherein a porous strong acid cation exchange resin is used as the strong acid cation exchange resin. 3. The surfactant-containing wastewater according to claim 1, wherein a porous strong acid cation exchange resin having a degree of crosslinking of 8% or less is used as the strong acid cation exchange resin. Processing method. 4. The treatment of a surfactant-containing wastewater according to claim 1, wherein a strongly acidic cation exchange resin of Na type is used as the strongly acidic cation exchange resin. Method. 5. The method for treating a surfactant-containing wastewater according to claim 1, wherein the surfactant contained in the wastewater is a surfactant mainly composed of a cationic surfactant.