JP2000229282A - Treating method and treating device for waste water containing nonionic surfactant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method and a treating device of the waste water containing a nonionic surfactant low in waste water treating cost and low in sludge generation. SOLUTION: A first stage for obtaining the concentrated liq. 2a high in nonionic surfactant concn. in which the waste water 2 containing the nonionic surfactant is subjected to foam separation to frothed lid. and dilute liq. 2b and the frothed liq. is defoamed, a second stage for obtaining Fenton treating liq. 4 by executing Fenton treatment by adding hydrogen peroxide to the concentrated liq. 2a in the state in which iron ion coexists, and a third stage for controlling the addition of the hydrogen peroxide in accordance with the generation of the foam by introducing a gas to the Fenton treating liq. 4 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for treating wastewater containing a nonionic surfactant.

[0002]

2. Description of the Related Art Activated carbon treatment, foam separation treatment, Fenton treatment and the like have been conventionally known as a method of removing wastewater by removing detergents and other surfactants contained in domestic wastewater and the like. Activated carbon treatment is a process in which a surfactant is adsorbed on activated carbon to remove it, and foam separation is a process in which a surfactant is adsorbed on foam generated in the wastewater and separated from the wastewater, and the surfactant concentration in the raw wastewater This is a process for reducing.
Fenton treatment is performed by radicals (.OH) generated by the reaction of Fenton's reagent (H ₂ O ₂ and iron catalyst).
This treatment mainly reduces the COD in wastewater by chemically oxidatively decomposing nonionic surfactants.

[0003]

However, when the above-mentioned technique is used, there is a problem that the treatment of wastewater containing a nonionic surfactant is not sufficiently performed. For example, in the activated carbon treatment, since the nonionic surfactant is hardly adsorbed on the activated carbon, the drainage treatment becomes insufficient.

[0004] Fenton treatment is a treatment for decomposing nonionic surfactants, but the chemical cost of sulfuric acid and Fenton reagent used for pH adjustment is high. There is a problem that processing cost increases. In addition, there is a concern that the amount of sludge generated will increase as the amount of drug input increases. The present invention solves the above-mentioned problems in the conventional technology for treating wastewater containing a surfactant,
It is an object of the present invention to provide a method and an apparatus for treating wastewater containing a nonionic surfactant, which has a low wastewater treatment cost due to a small amount of a chemical used in the Fenton treatment and generates a small amount of sludge.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, waste water containing a nonionic surfactant is foam-separated into a foam liquid and a dilute liquid. A first step of obtaining a concentrated solution having a high surfactant concentration in which the solution is defoamed, and performing Fenton treatment by adding hydrogen peroxide to the concentrated solution in the presence of iron ions;
A non-ionic system comprising: a second step of obtaining a Fenton treatment liquid; and a third step of introducing a gas into the Fenton treatment liquid and controlling the amount of the hydrogen peroxide to be added according to the amount of foam generated. A method for treating wastewater containing a surfactant is provided.

According to the second aspect of the present invention, there is provided a first foam separation tank provided with a foam generator for separating foamed wastewater containing a nonionic surfactant, a concentrated liquid tank, and a Fenton treatment of the concentrated liquid. A second Fenton treatment tank, which includes a foam generator and introduces gas into the Fenton-treated liquid
And a means for controlling the amount of hydrogen peroxide added by detecting the amount of foam in the second foam separation tank, and a wastewater treatment apparatus containing a nonionic surfactant. Provided.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is to reduce the amount of liquid required for the Fenton treatment by preliminarily separating foamed raw wastewater to obtain a concentrated nonionic surfactant-containing liquid. Focusing on the fact that the state of foam in the liquid after the Fenton treatment serves as an indicator of the presence or absence of a surfactant, it is a technical idea to perform the Fenton treatment without excess or deficiency based on this.

[0008] From the above, it is essential that the wastewater to be treated in the present invention contains at least a nonionic surfactant. Further, in addition to the nonionic surfactant, an anionic surfactant may be contained in the wastewater. In this case, a predetermined pretreatment described later is performed to remove the anionic surfactant. There is a need.

First, an apparatus for treating wastewater containing a nonionic surfactant according to the present invention (hereinafter referred to as "wastewater") will be described with reference to FIG. In FIG. 1, a wastewater treatment device includes a first foaming device (aeration device) 11.
Foam separation tank 10, concentrated liquid tank 12, Fenton treatment tank 1
4 and a second foam separation tank 2 provided with a foam generator 21
0 and so on.

The first foam separation tank 10 is formed in a column shape, and an aeration device 11 composed of a diffuser plate is disposed at the bottom. The aeration device 11 is connected to a blower / compressor (not shown), and aeration is performed with air introduced from the blower, whereby the wastewater can be foam-separated into a foam liquid and a dilute liquid. Similarly, the second foam separation tank 20 is provided with an aeration device 21 so that gas can be introduced into the Fenton treatment liquid described later, but for monitoring purposes, the foam separation tank used in the first step is used. The device may be smaller than the device, and may be monitored continuously or intermittently.

The foam separation tank is not limited to the above-mentioned column-shaped one as long as it can float and separate generated foam. The foam generating device is not limited to the aeration device described above, and may be provided with a blade or the like for stirring drainage, or may generate foam using a pressurizing device or a depressurizing device. The foam separating means is not limited to the above-described embodiment, and the foam may overflow or may be separated by a scraping device. Further, a foam suction device may be provided.

The Fenton treatment tank 14 is provided with a predetermined stirrer 34.
, And it is possible to store the concentrated liquid and perform the Fenton treatment to be described later. Further, a hydrogen peroxide addition device 32 is provided in the Fenton treatment tank 14, and the amount of foam in the second foam separation tank 20 is detected (monitored).
(Electromagnetic valve) 35 for controlling the amount of hydrogen peroxide added
Are attached to the device 32.

If the wastewater contains an anionic surfactant, an activated carbon adsorption tower 30 is provided in front of the Fenton treatment tank 24, and an activated carbon treatment is performed in advance to remove the anionic surfactant. It is preferable to sufficiently remove them.
As the activated carbon adsorption tower 30, a column filled with various types of activated carbon such as charcoal, coconut shell, coal, and resin can be used.

Next, regarding the method (flow) of treating wastewater,
A description will be given based on FIG. First, the waste water 2 is foam-separated in the first foam separation tank 10, and the generated foam (foam liquid) rises in the foam separation tank 10 and is taken out to the outside. Next, the foam liquid is defoamed to become a concentrated liquid 2a having a high surfactant concentration, and is stored in the concentrated liquid tank 12 (first step). As a method of defoaming, for example, a foam can be mechanically defoamed by colliding a projection with foam, and a centrifugal dehydrator or an ultrasonic device can be used. Further, the foam may be left for a certain period of time. On the other hand, from the lower part of the foam separation tank 10, the dilute liquid 2b containing almost no surfactant is taken out. The diluted liquid 2b may be discharged out of the system as the final treated water 6 after the drainage treatment.

Next, the concentrated liquid 2a is supplied to the Fenton treatment tank 14
And the sulfuric acid and ferrous ions are added to adjust the pH of the solution. The pH of the solution is preferably adjusted to 4 or less, more preferably to pH 4 to 2. The addition of iron ions may be performed by, for example, adding ferrous chloride or ferrous sulfate. After adding sulfuric acid or iron ions to the concentrated liquid 2a, this liquid may be sent to the Fenton treatment tank 14.

Then, in a state in which iron ions coexist, a predetermined amount of hydrogen peroxide is added to the concentrated liquid 2a from the hydrogen peroxide addition device 32 via an electromagnetic valve 35 or the like, and a Fenton treatment is performed (second step). ). In this case, the nonionic surfactant is oxidatively decomposed and changes into an intermediate product different from the surfactant, and as a result, the Fenton treatment liquid 4 in which the surfactant is reduced and removed is obtained. Further, an alkali may be appropriately added to the Fenton treatment liquid 4 to neutralize the liquid, and the generated sludge may be settled and separated.

Next, the Fenton treatment liquid 4 is supplied to a second foam separation tank 20 for monitoring and aerated for monitoring.
The addition amount of hydrogen peroxide is controlled by adjusting the opening / closing degree of a valve or the like according to the obtained foam amount (third step). The control of the amount of addition is performed as follows.

(A) When foams are generated; the surfactant remains in the Fenton treatment liquid, and it is considered that the Fenton treatment is insufficient. Therefore, the amount of added hydrogen peroxide is increased to accelerate the Fenton treatment. I do. (B) No foam was generated; it is considered that the Fenton treatment was sufficient or excessive,
Fenton treatment is suppressed by reducing the amount of hydrogen peroxide added.

After performing the above operation (A) or (B), continuously or intermittently, the state of foam generation (foam generation amount) in the third step is monitored. If no bubbles are generated, the operation (B) is further performed. If bubbles are generated, the operation (A) is further performed. For example, when foam is generated, a slightly excessive amount of hydrogen peroxide is added at first to prevent the generation of foam, and thereafter, the amount of hydrogen peroxide is reduced by gradually reducing the addition amount within a range where no foam is generated. The addition amount can be reduced to a necessary minimum amount, and the Fenton treatment can be performed without excess or deficiency.

As a method of judging the amount of foam to be generated, it is sufficient to visually observe the foam, but it is also possible to detect the amount of foam using a predetermined foam detector. When monitoring is not performed, the Fenton treatment liquid 4 may be discharged as final treatment water 6 as it is. Further, when foam is generated by the above-described aeration operation, it is preferable that the foam (liquid) be defoamed to obtain the second concentrated liquid 4a and the Fenton treatment be performed again. On the other hand, the obtained second dilute liquid 4b can be discharged as the final treated water 6.

Since the foam separation in the first foam separation tank 10 may not be sufficient in some cases, the diluted liquid 2b is further sent to the third foam separation tank 36 to monitor the amount of foam. If the foam amount exceeds a certain level, the surfactant is not sufficiently separated in the first step,
The diluted liquid 2b is returned to the first step again. The monitoring in the third foam separation tank 36 may be performed continuously or intermittently.
May be discharged as final treated water 6 as it is.

Further, before the final treated water 6 is discharged, an advanced treatment may be performed if necessary. As advanced processing,
Examples include biological treatment (eg, activated sludge treatment), physical treatment (eg, activated carbon treatment), and chemical treatment (eg, oxidation treatment using chemicals or ozone). In particular, since the intermediate product generated by the Fenton treatment is a BOD component, for example, the final treated water 6 can be subjected to activated sludge treatment, and then the sludge can be subjected to coagulation and sedimentation, followed by activated carbon treatment.

[0023]

Embodiment 1 Embodiment 1 First Step and Second Step According to the flow shown in FIG. 1, wastewater containing a nonionic surfactant was treated. Wastewater 2 having the component composition shown in Table 1
To a first column 1 having a flow rate of 10 L / hr and a water depth of 0.5 m.
0 and aerated at an air flow rate of 2 L / min to generate foam. The obtained foam liquid was defoamed and stored in the concentrated liquid tank 12, and a concentrated liquid 2a having a flow rate of 20 mL / hr was obtained.

Next, the concentrated liquid 2a is introduced into an activated carbon adsorption tower 30 filled with granular activated carbon and treated with activated carbon. Then, sulfuric acid is added to adjust the pH to about 3.5,
Add iron to reduce the Fe ion concentration in the solution to 7430 mg / L
And Further, Fenton treatment was performed by adding a hydrogen peroxide solution having a concentration of 31% through a supply valve at a rate of 200 mL / hr. The components of the liquid after the activated carbon treatment and after the Fenton treatment have the values shown in Table 1.

2. Third Step Next, when the Fenton treatment liquid 4 was supplied to the second column 20 and aerated, foam was generated. Therefore, the opening of the supply valve was increased to adjust the addition amount of hydrogen peroxide to 225 mL / hr ( Increased). The wastewater was treated in accordance with the first and second steps with this added amount, and the Fenton treatment liquid 4 was subsequently aerated. However, no foam was generated. The addition amount was adjusted (reduced) to 220 mL / hr.

The wastewater treatment was continued for a while, but since no foam was generated thereafter, the wastewater treatment was continued while maintaining the addition amount of hydrogen peroxide at 220 mL / hr.
The Fenton treatment liquid 4 was mixed with the dilute liquid 2b obtained in the first column 10 to obtain the final treatment water 6.

Comparative Example 1 The same raw wastewater used in Example 1 was supplied to the Fenton treatment tank 14 at a flow rate of 10 L / hr without foam separation, and sulfuric acid was added to adjust the pH to about 3.5. At the same time, ferrous chloride was added to adjust the Fe ion concentration to 100 mg / L. Further, 6400 mL of 31% concentration hydrogen peroxide solution
/ Hr, and Fenton treatment was performed, and the treated liquid was used as final treated water as it was. The components of the liquid after the Fenton treatment and the final treated water have the values shown in Table 1.

[0028]

[Table 1]

Table 2 shows the amounts of sulfuric acid and hydrogen peroxide used in the above Examples and Comparative Examples, and the amounts of sludge generated by the Fenton treatment. In addition, sludge generation amount is neutralized by adding alkali to the solution after Fenton treatment,
The sludge generated was filtered, dried and weighed.

[0030]

[Table 2]

(1) As is clear from Table 2, before performing the Fenton treatment, the raw waste water is foam-separated, and the treatment liquid after the Fenton treatment is aerated to judge the treatment state, and hydrogen peroxide is accordingly determined. In the present invention in which the amount of addition of is controlled, the amounts of sulfuric acid and hydrogen peroxide used and the amount of generated sludge were extremely small. (2) In the case of Comparative Example 1 in which the wastewater was directly treated with Fenton without performing foam separation, the amount of sulfuric acid used increased because the amount of treatment liquid required for Fenton treatment was large. Further, since the addition amount of hydrogen peroxide was not controlled, the usage amount of hydrogen peroxide was increased as compared with the example, and the amount of generated sludge was also increased.

[0032]

As is apparent from the above description, according to the present invention, the raw wastewater is foam-separated before performing the Fenton treatment to reduce the amount of the liquid to be treated in the Fenton treatment. The amount of sulfuric acid used can be reduced as compared with the treatment of wastewater containing a nonionic surfactant.

Further, the liquid after the Fenton treatment is aerated to judge the state of foam generation, and the amount of hydrogen peroxide added is controlled accordingly. Can be reduced. And by these effects, the wastewater treatment cost can be reduced significantly. Furthermore, since the amount of hydrogen peroxide used is small, the amount of sludge inevitably generated in the Fenton treatment can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a treatment apparatus and a treatment flow for wastewater containing a nonionic surfactant according to the present invention.

[Explanation of symbols]

2 Wastewater containing nonionic surfactant 2a Concentrated liquid 2b Diluted liquid 4 Fenton treatment liquid 6 Final treatment water 10, 20 First and second foam separation tank 12 Concentrated liquid tank 14 Fenton treatment tank 32 Hydrogen peroxide addition device 34 stirrer 35 solenoid valve 36 third foam separation tank

Claims (2)

[Claims] 1. A first step of separating a wastewater containing a nonionic surfactant into a foam liquid and a dilute liquid to obtain a concentrated liquid having a high surfactant concentration by defoaming the foam liquid; A second step in which hydrogen peroxide is added to the concentrated liquid in a state where ions coexist to perform Fenton treatment to obtain a Fenton treatment liquid, and a gas is introduced into the Fenton treatment liquid; A third step of controlling the amount of hydrogen peroxide to be added. A method for treating wastewater containing a nonionic surfactant. 2. A first foam separation tank provided with a foam generator, for separating waste water containing a nonionic surfactant into a foam liquid and a dilute liquid, and a surfactant formed by defoaming the foam liquid. A concentrated solution tank containing a concentrated solution having a high concentration, a Fenton treatment tank for adding hydrogen peroxide to the concentrated solution in the presence of iron ions to perform Fenton treatment, and a foam generator, Nonionic comprising: a second foam separation tank for introducing a gas into the performed liquid; and means for detecting the amount of foam in the second foam separation tank and controlling the amount of the hydrogen peroxide added. Wastewater treatment equipment containing a system surfactant.