JPH05292A - Method and apparatus for treating wastewater containing organic chlorine compounds - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a method for treating wastewater containing an organic chlorine compound, for example, wastewater containing trichlorethylene, tetrachloroethylene, and the like, and a treatment apparatus therefor. [Structure] When oxidative decomposition treatment of organochlorine compound-containing wastewater is performed in the presence of an iron-based metal porous body and hydrogen peroxide, the organochlorine compound-containing wastewater contained in a sealable container is forcibly circulated and the wastewater is forcibly circulated. Using the circulation force, a method of oxidizing and decomposing while circulating the gas phase mainly containing the organochlorine compound-containing gas in the closed vessel in the wastewater and using an ejector, two circulations with one pump A device that activates a road.

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 organic chlorine compounds, for example, wastewater containing trichlorethylene, tetrachloroethylene and the like, and a treatment apparatus therefor.

[0002]

2. Description of the Related Art Wastewater containing organic chlorine compounds such as trichlorethylene and tetrachloroethylene is subject to various laws and regulations from the viewpoint of environmental hygiene, so it is desirable to establish advanced treatment technology for the treatment of these wastewaters. It is rare.

As a general treatment method for these organic chlorine compound-containing wastewater, for example, an aeration treatment method using an aeration tank, a diffusion treatment method using a filling (aeration) tower, an adsorption treatment method using activated carbon, or a combination thereof is appropriately used. The method is known.

Further, a treatment method in which Fenton's reagent is allowed to act on wastewater containing an oxidizable substance, for example, Japanese Patent Laid-Open No. 50-136947.
No. 6/158188.

[0005]

However, the above-mentioned aeration method, desorption method, adsorption method, etc. are all physical treatment methods, and a secondary treatment of a substance containing an organic chlorine compound, such as activated carbon, removed from wastewater is carried out. Therefore, it is necessary to detoxify it, and it is necessary to replace the activated carbon when the adsorption capacity of the activated carbon is lost.

On the other hand, when the Fenton reaction is used, for example, when a divalent ionic compound such as FeSO ₄ is used, Fe is used.
⁺⁺ Reaction of H ₂ O ₂ with ions occurs extremely rapidly, while the content of organic chlorine compounds in wastewater is usually several tens ppm
Since it is at a very low level of ~ several hundred ppm, most of it is released as oxygen gas rather than being consumed for the oxidation of organochlorine compounds.

Therefore, in order to oxidize and remove the organic chlorine compounds, it is necessary to add a large amount of H ₂ O ₂ and FeSO ₄ , and as a result, the organic chlorine compounds in the wastewater are removed, while COD and Fe in the wastewater are removed. There is a drawback that the treatment of ions and pH becomes large.

[0008] In the Fenton reaction utilizing the Fe3 divalent ions such as Fe ₂ (SO _{4) 3,} but does not occur abrupt reactions like Fe2 valent ions, for Fe3 valent compound is hardly soluble in water, use In that case, it is necessary to dissolve the acid before use, and to treat COD, Fe ions, and pH after treatment, use Fe.
The same large-scale processing as in the case of divalent ions is required.

The present invention focuses on a method for treating wastewater containing an organic chlorine compound with an iron-based metal porous body and hydrogen peroxide, and provides a method and an apparatus for more efficiently performing oxidative decomposition removal of this organic chlorine compound. To do.

[0010]

Means for Solving the Problems The present invention provides (1) an organic chlorine compound-containing wastewater, which is housed in a hermetically sealed container when oxidatively decomposed in the presence of an iron-based metal porous body and hydrogen peroxide. By forcibly circulating the chlorine compound-containing wastewater and utilizing the forced circulation force of the wastewater, it is possible to oxidize and decompose while circulating a gas phase mainly composed of an organochlorine compound-containing gas in the closed container in the wastewater. A method for treating wastewater containing a characteristic organic chlorine compound.

(2) A ferrous metal porous body is placed in a hermetically sealed container, and the treated wastewater and the organic chlorine compound-containing gas are mainly contained above and below the treated wastewater contained in the container. And one end of the gas-phase circulation path is connected, a pump is provided in the circulation path for the wastewater to be treated, an ejector is provided in the circulation path on the downstream side of the pump, and the other end of the gas-phase circulation path is provided in the ejector. Is connected to the ejector and an aeration pipe installed below the iron-based metal porous body in the container to connect the organic chlorine compound-containing wastewater.

(3) In the treatment apparatus for wastewater containing an organic chlorine compound according to (2), an aeration gas supply pipe equipped with a check valve and an opening / closing valve is connected in the middle of the vapor phase circulation path. is there.

[0013]

[Function] When the water containing an organic chlorine compound such as tetrachloroethylene is brought into contact with the iron-based metal porous body, the following reaction occurs due to the reduction reaction of Fe, and it can be decomposed and removed.
It was disclosed in No. 1-249008. CCl ₂ : CCl ₂ ＋ 4Fe ＋ 4H ₂ O → CH ₂ : CH ₂ ＋ 4Fe ⁺⁺ ＋ 4OH ⁻ ＋ 4Cl ⁻

Further, it was disclosed in Japanese Patent Application No. 2-214289 that the organic chlorine compound-containing wastewater can be decomposed and removed in a relatively short time by reacting it in the presence of a ferrous metal porous material and hydrogen peroxide.

(1) Reductive decomposition reaction of an iron-based metal porous body mainly composed of iron, which is a reducing metal, and tetrachloroethylene; CCl ₂ : CCl ₂ + 4Fe + 4H ₂ O → CH ₂ : CH ₂ + 4Fe ⁺⁺ + 4OH ⁻ + 4Cl ⁻

(2) H₂O₂And generate Fe⁺⁺Ionic fenton
Oxidative decomposition reaction by reaction; Fe⁺⁺+ H₂O₂→ Fe⁺⁺⁺+ OH^-+ ・ OH (Radical) CCl₂: CCl₂＋4 ・ OH → 2CO₂+ 4H Cl

[0017] (3) oxidative degradation by Fenton reaction by Fe ⁺⁺ with the oxidation of the iron-based porous metal body of the _{H 2 O 2; Fe + H} 2 O 2 → Fe ++ + 2OH - Fe ++ + H 2 O 2 → Fe ⁺⁺⁺ ＋ OH ⁻ ＋ ・ OH (radical) CCl ₂ ： CCl ₂ ＋4 ・ OH → 2CO ₂ ＋ 4HCl

The reduction reaction and oxidation reaction of (1) to (3)
Occur at the same time, and Fe generated by the reaction of (1)
⁺⁺Ions, or generated by the reaction of (2) and (3)
Fe⁺⁺Ion generation rate is, for example, FeSO_FourDuring direct drainage
Fe produced by adding to⁺⁺Compared to the ion production rate, the pole
FeSO is so slow_Four+ H₂O It is not a sudden reaction like
Fenton's oxidative decomposition reaction of organic chlorine compounds progresses efficiently
As a result, COD and Fe ions after treatment are extremely low
It is assumed to indicate a value.

The inventors of the present invention have made various investigations on the progress of the reaction based on the above-mentioned Japanese Patent Application No. 2-214289 in a shorter time, and as a result, as a result, evaporation in the course of the above-described Fenton oxidative decomposition reaction of organic chlorine Then, a gas phase of the organochlorine compound-containing gas is formed in the treatment vessel, and the organochlorine compound-containing gas is redissolved in the wastewater from the gas phase following the progress of the Fenton oxidation treatment of the organochlorine in the wastewater with some delay. I found out that it is doing.

That is, it can be said that the behaviors of evaporation of the organochlorine compound-containing material from the liquid phase and dissolution of the organochlorine compound-containing gas from the gas phase to the liquid phase delay the Fenton reaction of the entire system.

Based on the above findings, the present invention uses the forced circulation force of this treated wastewater to positively circulate the organic chlorine compound-containing gas in the gas phase while forcibly circulating the treated wastewater. It was found that organochlorine compounds can be rapidly oxidatively removed by circulating the supply into the Fenton reaction system.

Specifically, when the organic chlorine compound-containing wastewater is oxidatively decomposed in the presence of the iron-based metal porous body and hydrogen peroxide, the organic chlorine compound-containing wastewater stored in a sealable container is forcedly circulated. At the same time, by utilizing the forced circulation force of the waste water, the oxidative decomposition treatment is performed while circulating the gas phase mainly containing the organic chlorine compound-containing gas in the closed container in the waste water.

The forced circulation of the waste water to be treated according to the present invention accelerates the Fenton reaction, and the gas phase circulation of the organochlorine compound-containing gas causes the gas to come into direct contact with the Fenton reaction system and the wastewater containing the organochlorine compound. Stirring also brings about an action of accelerating the Fenton reaction.

The iron-based metal porous body used in the present invention may contain iron as a main component and also a metal such as Cu, Cr, Ni, Sn, or Zn which improves the corrosion resistance of iron.

As the shape of the porous body, a spherical or columnar laminated body formed by molding a metal, a porous plate or a laminated body thereof, a fiber-shaped or honeycomb-shaped one, or an iron-based metal powder into a three-dimensional molded body such as a urethane home. Examples of the carrier include a coated carrier and a sintered product thereof.

The amount of hydrogen peroxide added varies depending on the amount of organic chlorine compounds or other coexisting ions contained in the water, but is generally 0.05 to 2.
00wt% is enough.

In the above treatment, the organic chlorine compound-containing wastewater is first contacted with the iron-based metal porous body in a closed container,
It is also possible to firstly treat the organic chlorine compound by reductive decomposition, then add hydrogen peroxide, and secondarily treat the organic chlorine compound by oxidative decomposition.

[0028] That is, when contacting the metallic iron and an organic chlorine compounds containing waste water, since the Fe ⁺⁺ ion concentration at the same time the organic chlorine compounds is reductive decomposition is several tens of ppm, then H ₂ O ₂
When added, it can be utilized for the oxidative decomposition of organochlorine compounds by the Fenton reaction of Fe ions and H ₂ O ₂ preferentially over the reaction of H ₂ O ₂ and metallic iron.

As described above, the oxidative decomposition treatment of wastewater containing an organochlorine compound by the combined use of vapor phase circulation utilizing the forced circulation force of the wastewater to be treated can not only reduce the organochlorine compound to the environmental regulation value, but also reduce the operating power. The cost can be reduced.

Another embodiment of the present invention is, for example, 10% after the concentration of the organic chlorine compound in the waste water is reduced to a predetermined concentration.
Under the condition that the upper part of the closed container is opened from the stage when the concentration becomes mg / l or less, the organic chlorine compound-containing wastewater is treated while being aerated, so that the oxidative decomposition by the Fenton reaction is promoted rapidly.

The oxidative decomposition efficiency decreases as the concentration of the organic chlorine compound contained in the exhaust gas decreases. For example, it takes a long time to oxidize and decompose the organic chlorine compound in the waste water to 0.1 mg / l or less.

However, the Fenton reaction is promoted by forcibly stirring the treated wastewater by aeration.

The aeration gas supplied to the system by the aeration, that is, the air, is exhausted from the open end provided at the upper end of the closed container.

The exhaust gas from the open end of the processing container contains a very small amount of organic chlorine compound gas within the environmental regulation value range.

In order to make this almost zero, it is possible to adsorb and remove it from the exhaust gas by installing an adsorbent, for example, activated carbon, iron-based metal porous material or silica gel in the middle of the exhaust pipe. The amount of organic chlorine compounds in the exhaust gas is very small so that it functions for a long time.

Next, the processing apparatus of the present invention will be described with reference to FIG.

Reference numeral 1 is a container that can be closed. An iron-based metal porous body 2 is placed in the container 1. This iron-based metal porous body 2
An aeration pipe 3 is installed in the lower part of the container 1 and at the bottom of the container 1.
Waste water 4 containing a predetermined amount of organic chlorine compounds is contained in the container 1.
To house.

One end of a circulation path 6 for circulating the gas phase 5 is connected to a position above the water surface of the housed wastewater 4 to be treated.

Further, one end of a circulation path 7 for circulating the treated wastewater 4 is connected to a position below the water surface of the treated wastewater 4.

A pump 8 is provided in the middle of the circulation path 7.
An ejector 9 is provided at the downstream end of the pump 8 in the circulation path 7, and the ejector 9 is connected to the aeration pipe 3.

The other end of the vapor phase circulation path 6 is connected to the side portion of the ejector 9.

At the upper part of the container 1, a hydrogen peroxide addition device for storing the amount of hydrogen peroxide required for the oxidative decomposition treatment.
Provide 10.

This apparatus 10 is provided with an opening / closing valve 11 which is opened / closed at a predetermined time to add a predetermined amount of hydrogen peroxide or is maintained at a predetermined opening so that the predetermined amount of hydrogen peroxide is substantially continuous. Can be added in a positive manner. 12 is a safety valve.

In the processing apparatus configured as described above,
In the treatment of wastewater containing an organic chlorine compound, first, a predetermined amount of the wastewater 4 to be treated is stored in the container 1, and then the pump 8 is started to forcibly circulate the wastewater 4 to be treated. The circulation of phase 5 is carried out, and the oxidative decomposition treatment in the container 1 effectively proceeds.

An aeration gas suction pipe 15 equipped with a check valve 13 and an on-off valve 14 is connected in the middle of the gas-phase circulation path 6 of the processing apparatus, and an exhaust valve provided with an on-off valve 16 at the upper part of the container 1 Tube 17
By adding a configuration in which the above are connected, the oxidative decomposition treatment can be performed while aerating.

In the middle of the exhaust pipe 17, there is prepared a space 18 in which an adsorbent such as activated carbon can be attached and detached. 19 is a drain pipe,
20 is an on-off valve, 21 is a drain pipe, and 22 is a filter.

This device is like dry cleaning wastewater, and has a discharge of 1 l to 10 l / day and a tetrachloroethylene concentration.
It is suitable for cases of around 50 mg / l, and the amount of hydrogen peroxide added should be 0.05 to 2 wt% with respect to the wastewater to be treated.

[0048]

Example 1 Using the apparatus shown in FIG. 1, an initial concentration of 62 mg / l
Charge 6 liters of waste water containing tetrachloroethylene, and put 360g of iron-based metal porous body with mesh No. 13 in a sealed state for 20
The treated wastewater was circulated for 7 hours at ℃. Hydrogen peroxide is 1.5w
When the first step was performed with t% added, 0.75 wt% of H ₂ O ₂ was additionally added at 3 hours after the treatment. The components of the wastewater to be treated are shown in Table 1.

[0049]

Example 2 After treating for 3 hours under the same conditions as in Example 1, the container 1 was opened and the aeration means 4 was operated to add 0.75 wt% of hydrogen peroxide for treatment. The components of the wastewater to be treated are shown in Table 1.

[0050]

[Table 1]

[0051]

EFFECTS OF THE INVENTION According to the present invention, the treatment with the iron-based metal porous body and hydrogen peroxide makes it possible to use hydrogen peroxide efficiently and to circulate the gas phase in the Fenton reaction system. Therefore, the concentration of the organic chlorine compound can be decomposed and removed to an extremely small amount.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a processing apparatus according to the present invention.

[Explanation of symbols]

1 processing container 2 Iron-based porous metal 3 aeration pipe 4 treated wastewater 5 gas phase 6 Gas phase circuit 7 Wastewater circulation path to be treated 8 pumps 9 ejector 10 Hydrogen peroxide addition device 11, 14, 16, 20 Open / close valve 12 Safety valve 13 Check valve 15 Gas suction pipe for aeration 17 Exhaust pipe 18 vacant place 19 drainage pipe 21 Drainage line 22 filters

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Watanabe             5-3 Tokai-cho, Tokai City Nippon Steel Corporation             Inside Nagoya Steel Works

Claims (3)

[Claims] 1. When oxidative decomposition treatment of organic chlorine compound-containing wastewater in the presence of an iron-based metal porous body and hydrogen peroxide,
By forcibly circulating the organic chlorine compound-containing wastewater stored in a sealable container and utilizing the forced circulation force of the wastewater, a gas phase mainly composed of the organic chlorine compound-containing gas in the closed container is introduced into the wastewater. A method for treating wastewater containing an organic chlorine compound, which comprises oxidative decomposition treatment while circulating. 2. An iron-based metal porous body is placed in a container that can be sealed, and the treated wastewater and the organic chlorine compound-containing gas are mainly contained above and below the treated wastewater contained in the container. Connecting one end of the gas-phase circulation path, a pump is provided in the circulation path of the wastewater to be treated, an ejector is provided in the circulation path on the downstream side of the pump, and the other end of the gas-phase circulation path is provided in the ejector. An apparatus for treating wastewater containing an organic chlorine compound, characterized in that the ejector and the aeration pipe installed below the iron-based metal porous body in the container are connected to each other. 3. The apparatus for treating wastewater containing an organochlorine compound according to claim 2, wherein an aeration gas supply pipe equipped with a check valve and an opening / closing valve is connected in the middle of the vapor phase circulation path.