JP3918657B2 - Method and apparatus for purifying contaminated soil - Google Patents

Description

【００２８】
【００２９】
【発明の効果】
本発明による処理方法は汚染土壌等と界面活性剤とを撹拌・混合することによって、汚染土壌等に含有される汚染物質を高効率に除去すると共に、洗浄水中の界面活性剤と汚染物質との結合体を効率的に水相から分離するといった効果を奏する。
【図面の簡単な説明】
【図１】本発明に係る汚染土壌等の浄化方法の実施形態を示す図。
【図２】本発明に係る汚染土壌等の浄化方法の別の実施形態を示す図。
【符号の説明】
１…第一混和槽、２…界面活性剤注入管、３…遠心脱水機、４…酸注入管、５…凝集剤注入管、６…第二混和槽、７…沈殿槽、８…ｐＨ調整槽、９…中和槽、１０…アルカリ注入管、１１…処理水循環管、１２…第三混和槽、１３…浮上分離槽、１４…加圧水注入管。[0001]
[Industrial application fields]
The present invention relates to a method and apparatus for treating soil containing pollutants, in addition to contaminated soil, landfill waste, rivers / lakes or bottom mud of sea areas, and sludge generated from water treatment processes. It can also be applied to purification treatment of dehydrated cake.
[0002]
[Prior art]
As a purification method for contaminated soil and the like, a thermal decomposition method, a purification method using microorganisms, a cleaning method using a chemical, and the like are conventionally known. The thermal decomposition method has a high energy cost for heating a large amount of contaminated soil to a temperature at which pollutants such as dioxins are decomposed, and the method of purifying with microorganisms is a yearly period before the purification treatment is completed. There was a drawback of requiring. Regarding a method of cleaning with a chemical, for example, Japanese Patent No. 3182546 shows a method of cleaning soil contaminated with trichlorethylene or the like with a surfactant. However, this method uses activated carbon adsorption treatment to remove contaminants contained in the washing water, and the replacement frequency is high because the washing solution containing surfactants and various organic substances in the soil at high concentrations is treated with activated carbon. There was a problem that it used a large amount of expensive activated carbon.
[0003]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and an object thereof is to provide a purification method and a purification device for contaminated soil and the like that efficiently remove contaminants contained in the contaminated soil and the like. To do.
[0004]
[Means for Solving the Problems]
The inventions of claims 1, 2, and 3 transfer the persistent organic substance from the solid matter of the soil to the liquid phase by mixing and washing the soil contaminated with the persistent organic substance and the surfactant. A step of separating the mixture into a solid-liquid separation after this step and taking out the solid phase as a purified product, and separating the combined surfactant and the hardly decomposable organic substance from the solid-liquid separated liquid phase In the purification method of contaminated soil comprising a process,
The surfactant is an amino acid type amphoteric surfactant, and the step of separating the conjugate of the surfactant and the hardly decomposable organic substance from the solid-liquid separated liquid phase is a step of mixing an acid with the liquid phase. A method for purifying contaminated soil, characterized by
The surfactant is a polyethylene glycol type nonionic surfactant, and the step of separating the binder of the surfactant and the hardly decomposable organic substance from the solid-liquid separated liquid phase is performed by heating the liquid phase. A method for purifying contaminated soil, characterized by being a step of raising the temperature above the cloud point , or
It said surfactant is an anionic surfactant, separating the conjugate of surfactants and flame decomposable organic matter from the solid-liquid separated liquid phase, composed mainly of calcium in the liquid phase It is a purification method for contaminated soil, which is a step of adding an inorganic compound.
In this method, since the contaminants and the surfactant in the liquid phase are separated from the liquid phase while being bonded, a clear liquid phase is obtained.
[0006]
The invention of claim 4 is the surfactant is added to the separated liquid phase conjugate of surfactant and hardly decomposable organic substances, used again for cleaning soil contaminated with persistent organic substances It is a processing method characterized by doing. In this method, by reusing the treated liquid phase, the amount of makeup water and the amount of discharged water outside the system can be greatly reduced.
[0007]
Further, the invention of claim 5 is characterized in that a contaminant and a hard-to-decompose organic substance combination separated from a liquid phase is put into an incinerator, a melting furnace or a thermal decomposition furnace to thermally decompose the pollutant. It is a processing method. In this method, contaminants separated from the liquid phase can be completely detoxified by thermally decomposing them.
[0008]
The inventions of claims 6, 7 and 8 include a mixing means for mixing and washing the soil contaminated with a hardly decomposable organic substance and a surfactant, a solid-liquid separation means for solid-liquid separation of the mixture, and a solid In the apparatus for purifying contaminated soil, comprising a separation means for separating the surfactant and the complex of the hardly decomposable organic substance from the liquid phase separated from the liquid,
The apparatus for purifying contaminated soil, wherein the surfactant is an amino acid type amphoteric surfactant, and the separation means includes means for mixing an acid with the liquid phase,
The contaminated soil purification apparatus, wherein the surfactant is a polyethylene glycol type nonionic surfactant, and the separation means has means for heating the liquid phase to a temperature higher than the cloud point . Or
Wherein a surfactant is an anionic surfactant, wherein the separating means is a purifying apparatus for contaminated soil, characterized in that it comprises means for adding an inorganic compound mainly containing calcium in the liquid phase.
This apparatus can embody the purification method of the present invention.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a purification method and a purification device for contaminated soil and the like according to the present invention will be described with reference to the drawings.
[0010]
(Embodiment 1)
FIG. 1 shows an embodiment of a purification method for contaminated soil and the like according to the present invention. In the figure, 1 is a first mixing tank, 2 is a surfactant injection pipe, 3 is a centrifugal dehydrator, 4 is an acid injection pipe, 5 is a flocculant injection pipe, 6 is a second mixing tank, and 7 is a precipitation tank. is there.
[0011]
The soil containing the pollutant is mixed with the surfactant supplied from the surfactant injection pipe 2 in the first mixing tank 1, and the pollutant contained in the contaminated soil or the like moves to the liquid phase. Next, it is supplied to the centrifugal dehydrator 3 and separated into a liquid phase containing a conjugate of a surfactant and a contaminant and a solid phase from which the contaminant has been removed. The solid phase is taken out as a purified product. The liquid phase was mixed with the acid supplied from the acid injection pipe 4 and the coagulant supplied from the coagulant injection pipe 5 in the second mixing tank 6, and the surfactant / contaminant conjugate was insolubilized and aggregated. Thereafter, it is precipitated and separated as sludge in the settling tank 7. The sludge is finally incinerated in an incinerator and the pollutants are pyrolyzed.
[0012]
Here, pollutants are dioxins, environmental hormones, agricultural chemicals, persistent organic substances such as PCBs, inorganic substances such as fluorine, boron, and heavy metals, and bonds that adsorb these substances and soil particles. It is a body and the like and is not limited to a specific substance. In addition, the soil and the like refer to soil, landfill waste, river / lake / marsh or sea bottom mud, and sludge generated from the water treatment process and dehydrated cake thereof.
[0013]
Since the contact efficiency between the surfactant and the pollutant increases when the content of the pollutant such as contaminated soil is as high as possible, the concentration treatment is performed as necessary within the range where the mixing operation can be easily performed. It is preferable to carry out the mixing of the surfactant and the contaminated soil after increasing the organic matter content in the contaminated soil. Of course, when the mixing operation is difficult in the form of soil or the like as it is, it is possible to add water until the mixing operation can be easily performed.
[0014]
As the surfactant used in the present invention, various surfactants such as an anionic type, a cationic type, an amphoteric type and a nonionic type can be used. For example, as anion type, carboxylate such as soap, sulfate ester salt, sulfonate, etc., as cation type, amine salt, quaternary ammonium salt, etc., as amphoteric type, amino acid type, betaine type, etc. As the nonionic type, a polyethylene glycol type or the like can be used.
[0015]
The mixing / cleaning means for contaminated soil or the like and the surfactant is not limited to this embodiment, but a mixing tank with a stirrer is usually used. In addition, the combined use of ultrasonic irradiation means is preferable because it can increase the contact efficiency between the contaminated soil and the surfactant. By doing in this way, a pollutant can be transferred from solid content, such as soil, to a liquid phase.
[0016]
As solid-liquid separation means for contaminated soil and the like, various devices such as a screen, a sedimentation tank, and a filter press can be used in addition to a centrifugal dehydrator.
[0017]
The means for separating the combined body of the surfactant and the contaminant from the liquid phase can be selected from several types according to the characteristics of the surfactant to be applied. When the surfactant to be applied is an amino acid type amphoteric surfactant, it can be insolubilized by adding an acid after the washing operation and adjusting the pH to the isoelectric point as in this embodiment. In the case of a polyethylene glycol type nonionic surfactant, it can be insolubilized by heating to a temperature higher than the cloud point. In the case of an anionic surfactant, an insoluble salt can be formed by adding an inorganic compound mainly composed of calcium or the like. The insolubilized surfactant / contaminant conjugate can be separated by means of levitation or sedimentation depending on its specific gravity. In some cases, centrifugation can be applied.
[0018]
In addition, when it is difficult to separate only by insolubilization, it is possible to promote separation by adding and mixing flocculants to form floc. As the flocculant used in this case, iron salts such as ferric chloride and polyferric sulfate, aluminum salts such as sulphates and PACs, etc. can be applied. Molecular compounds can also be used in combination.
[0019]
On the other hand, in the case of using a foaming surfactant, a large number of bubbles are formed by aeration of the liquid phase or injection of pressurized water in which the gas is supersaturated in the liquid phase, and the interface is formed on the surface of the bubbles. The active agent / contaminant conjugate can be concentrated and removed as scum.
[0020]
The liquid phase from which the combination of the surfactant and the contaminant is separated can be used again for the purification treatment. For example, it is possible to add a surfactant to bring it into contact with contaminated soil or the like, or to rinse the surfactant remaining in the soil after washing.
[0021]
Since the combination of the surfactant and the pollutant separated from the liquid phase is concentrated as compared with the contaminated soil before the treatment, the amount is significantly reduced. Therefore, it can be made harmless at low cost by using various means such as oxidative decomposition by ozone injection and dechlorination by ultraviolet irradiation, but it can be almost completely decomposed in a short time by a heating method. In particular, when an existing incinerator, melting furnace or pyrolysis furnace exists in the vicinity of the soil purification facility, the combined surfactant / pollutant separated from the liquid phase is treated with the heating system facility. This is preferable because the construction cost of the equipment can be reduced.
[0022]
(Embodiment 2)
FIG. 2 shows another embodiment of the purification method for contaminated soil and the like according to the present invention. In the figure, 1 is a first mixing tank, 2 is a surfactant injection pipe, 3 is a centrifugal dehydrator, 4 is an acid injection pipe, 5 is a flocculant injection pipe, 8 is a pH adjustment tank, 9 is a neutralization tank, 10 is an alkali injection pipe, 11 is a treated water circulation pipe, 12 is a third mixing tank, 13 is a floating separation tank, and 14 is a pressurized water injection pipe.
[0023]
The contaminated soil and the like are mixed with the acid supplied from the acid injection pipe 4 in the pH adjusting tank 8, the treated water supplied from the treated water circulation pipe 11 and the make-up water, and dissolve calcium compounds contained in the contaminated soil and the like. Next, the neutralization tank 9 is mixed with the alkali supplied from the alkali injection pipe 10 to adjust the pH to neutral. Subsequently, after being mixed with the surfactant supplied from the surfactant injection tube 2 in the first mixing tank 1, the liquid phase containing the combination of the surfactant and the contaminant and the contaminant are removed in the centrifugal dehydrator 3. The solid phase is separated. The liquid phase is mixed with the coagulant supplied from the coagulant injection pipe 5 and the pressurized water in which the air supplied from the pressurized water injection pipe 14 is supersaturated in the flotation separation tank 13, and the combined surfactant and contaminants are After being concentrated on the bubble surface, it is floated and separated as scum, and the remainder becomes treated water. On the other hand, the solid phase taken out by the centrifugal dehydrator is once mixed with the treated water in the third mixing tank 12, and then solid-liquid separated again by the centrifugal dehydrator 3, thereby binding the remaining surfactant and contaminants. After the body is washed out, it is taken out as a purified product.
[0024]
If the contaminated soil has a high content of metal components such as lime, iron, manganese, etc., and these impede contact between the contaminants and the surfactant and high cleaning efficiency cannot be obtained, the contamination will occur as in this embodiment. When the acid is mixed before or during the mixing of the soil and the surfactant with the surfactant to dissolve the lime component and the metal component, the contact efficiency is improved and a good cleaning effect is obtained. On the other hand, if the contaminated soil has a high content of organic substances such as humic acid and the contact between the target pollutant and the surfactant cannot be achieved and high cleaning efficiency cannot be obtained, before mixing the contaminated soil and the surfactant Alternatively, when an alkali is mixed during mixing to dissolve organic substances such as humic acid, the contact efficiency is improved and a good cleaning effect is obtained.
[0025]
In addition, by using the treated water obtained as in the present embodiment for rinsing the solid content after centrifugal dehydration, dissolving the surfactant, and adjusting the water content of the purification target, the total amount of water used can be reduced, and the purification cost The effect of reducing the amount of wastewater and the amount of drainage can be obtained.
[0026]
【Example】
Table 1 shows the results of treatment of soil contaminated with dioxins by the treatment method shown in FIG. However, the processing conditions are as follows.
[0027]
[Example processing method]
・ Surfactant type: Nonionic surfactant (alcohol)
・ Reaction time with surfactant: 30 minutes ・ Reaction temperature: room temperature ・ Surfactant injection rate: 0.5 wt%
[Table 1]

[0028]
[0029]
【The invention's effect】
The treatment method according to the present invention stirs and mixes the contaminated soil and the surfactant to efficiently remove the pollutants contained in the contaminated soil and the like. There exists an effect of isolate | separating a conjugate | bonded_body from an aqueous phase efficiently.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a purification method for contaminated soil and the like according to the present invention.
FIG. 2 is a view showing another embodiment of the purification method for contaminated soil and the like according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st mixing tank, 2 ... Surfactant injection pipe, 3 ... Centrifugal dehydrator, 4 ... Acid injection pipe, 5 ... Flocculant injection pipe, 6 ... Second mixing tank, 7 ... Precipitation tank, 8 ... pH adjustment A tank, 9 ... neutralization tank, 10 ... alkali injection pipe, 11 ... treated water circulation pipe, 12 ... third mixing tank, 13 ... flotation separation tank, 14 ... pressurized water injection pipe.

Claims (8)

Mixing and washing the soil contaminated with the persistent organic substance and the surfactant to transfer the persistent organic substance from the solid content of the soil to the liquid phase, and after this process, In a method for purifying contaminated soil, comprising a step of solid-liquid separation and taking out a solid phase as a purified product, and a step of separating a combined body of a surfactant and the hardly decomposable organic substance from the liquid phase subjected to solid-liquid separation. ,
The surfactant is an amino acid type amphoteric surfactant, and the step of separating the conjugate of the surfactant and the hardly decomposable organic substance from the solid-liquid separated liquid phase is a step of mixing an acid with the liquid phase. A method for purifying contaminated soil, characterized in that there is. Mixing and washing the soil contaminated with the persistent organic substance and the surfactant to transfer the persistent organic substance from the solid content of the soil to the liquid phase, and after this process, In a method for purifying contaminated soil, comprising a step of solid-liquid separation and taking out a solid phase as a purified product, and a step of separating a combined body of a surfactant and the hardly decomposable organic substance from the liquid phase subjected to solid-liquid separation. ,
The surfactant is a polyethylene glycol type nonionic surfactant, and the step of separating the binder of the surfactant and the hardly decomposable organic substance from the solid-liquid separated liquid phase is performed by heating the liquid phase. A method for purifying contaminated soil, characterized by being a step of raising the temperature above the cloud point . Mixing and washing the soil contaminated with the persistent organic substance and the surfactant to transfer the persistent organic substance from the solid content of the soil to the liquid phase, and after this process, In a method for purifying contaminated soil, comprising a step of solid-liquid separation and taking out a solid phase as a purified product, and a step of separating a combined body of a surfactant and the hardly decomposable organic substance from the liquid phase subjected to solid-liquid separation. ,
It said surfactant is an anionic surfactant, separating the conjugate of surfactants and flame decomposable organic matter from the solid-liquid separated liquid phase, composed mainly of calcium in the liquid phase A method for purifying contaminated soil, comprising adding an inorganic compound. 4. The liquid phase obtained by separating a conjugate of a surfactant and a hardly decomposable organic substance is reused for washing soil contaminated with the hardly decomposable organic substance. Processing method.   A combination of a surfactant and a hardly decomposable organic substance separated from a liquid phase is put into an incinerator, a melting furnace or a pyrolysis furnace to thermally decompose the hardly decomposable organic substance. 5. The processing method according to any one of 4. Mixing means for mixing and washing the soil contaminated with the hardly decomposable organic substance and the surfactant, solid-liquid separation means for separating the mixture into solid and liquid, and the surfactant and the difficulty from the solid-liquid separated liquid phase In a purification apparatus for contaminated soil, comprising a separating means for separating a combined body of degradable organic substances,
The apparatus for purifying contaminated soil, wherein the surfactant is an amino acid type amphoteric surfactant, and the separation means has means for mixing an acid with the liquid phase. Mixing means for mixing and washing the soil contaminated with the hardly decomposable organic substance and the surfactant, solid-liquid separation means for separating the mixture into solid and liquid, and the surfactant and the difficulty from the solid-liquid separated liquid phase In a purification apparatus for contaminated soil, comprising a separating means for separating a combined body of degradable organic substances,
The apparatus for purifying contaminated soil, wherein the surfactant is a polyethylene glycol type nonionic surfactant, and the separation means has means for heating the liquid phase to a temperature higher than the cloud point . Mixing means for mixing and washing the soil contaminated with the hardly decomposable organic substance and the surfactant, solid-liquid separation means for separating the mixture into solid and liquid, and the surfactant and the difficulty from the solid-liquid separated liquid phase In a purification apparatus for contaminated soil, comprising a separating means for separating a combined body of degradable organic substances,
Wherein a surfactant is an anionic surfactant, wherein the separating means, purifier of contaminated soil, characterized in that it comprises means for adding an inorganic compound mainly containing calcium in the liquid phase.

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