JP2011020108A - Method and apparatus for treating chemical substance contamination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating chemical substance contamination, with which the chemical substances can be more safely and more efficiently treated as compared with the conventional treatment with persulfate, in cleaning the soil and ground water contaminated with chemical substances, particularly, a chlorinated organic compound or an aromatic hydrocarbon. <P>SOLUTION: The method for treating chemical substance contamination includes a step of adding persulfate and chelated iron to the soil and ground water contaminated with chemical substances and a step of cleaning the contaminated soil and ground water. Persulfate and chelated iron are added so that the concentration of the added persulfate becomes ≥5,000 mg/L and the molar ratio (the persulfate/the iron) of the added persulfate to the added iron becomes ≥5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a treatment method and a treatment apparatus for purifying soil and groundwater contaminated with chemical substances, particularly organic chlorine compounds or aromatic hydrocarbons.

  Organochlorine compounds such as trichlorethylene (TCE) and tetrachlorethylene (PCE) are widely used as cleaning agents in various factories and cleaning shops, and aromatic hydrocarbons such as benzene are widely used as chemical raw materials in various factories. ing. On the other hand, chemical substances such as organic chlorine compounds and aromatic hydrocarbons are highly suspected of causing health problems such as carcinogenesis. In recent years, contamination of soil, groundwater, etc. due to the above-mentioned organic chlorine compounds and aromatic hydrocarbons and other chemical substances is high. It has become a major social problem.

Conventionally, as a method for treating soil contaminated with organochlorine compounds, etc. , containment of contaminated soil, excavation / containment of contaminated soil, and the like have been mainly performed. As the treatment method of contaminated ground water with organic chlorine compounds such as, by pumping groundwater, contaminated chemicals in groundwater by transition in a gas phase, and purify groundwater (pumping aeration), by the subsequent active carbon The pump-and-treat method, etc., which adsorbs the gas phase (activated carbon treatment) is mainly performed. In addition, the water after purification flows to the surface. In addition, a biostimulation method or the like is performed in which chemicals are injected into microorganisms that inhabit contaminated soil, temperature control is performed, and the microorganisms are activated to decompose chemical substances.

  However, the above containment process, excavation / containment process, and pump and treat method are not technologies for actively decomposing and detoxifying polluted chemical substances, and enormous costs, energy, and labor are required. There are problems such as a long purification period of 10 to 20 years. Furthermore, the biostimulation method is a treatment method that has a low environmental impact and is low in cost. On the other hand, in the treatment of chemical contamination, there is an applicable concentration range of the pollutant chemical, and the purification period is long. There are problems such as.

  On the other hand, in recent years, in-situ chemical oxidation in which an oxidizing agent is directly injected into a well has been developed. Oxidizing agents include potassium permanganate, hydrogen peroxide, persulfate, hypochlorous acid, perchloric acid, chlorine, ozone, etc., but from the standpoints of solubility in water, operability, etc. Therefore, methods using potassium permanganate or hydrogen peroxide are mainly put into practical use.

  However, the method using potassium permanganate has a problem that the potassium permanganate itself has a purple color and it is not preferable to inject it directly into groundwater or the like. Further, the method using hydrogen peroxide has a problem that the purification range is small due to rapid hydrogen peroxide decomposition in the ground.

  In addition, there are an increasing number of cases of in-situ chemical substance degradation research using oxidants and other reagents in combination.

  For example, Patent Document 1 discloses a method for purifying contaminated soil by adding hydroxycarboxylic acid such as hydrogen peroxide and citric acid to soil contaminated with organic matter. In this purification method, in order to suppress rapid decomposition and consumption of the oxidizing agent, it is disclosed that citric acid is added, and that a pH adjuster and a metal catalyst are added to the soil before adding these agents to the soil. Has been.

  For example, Patent Document 2 discloses a method for purifying contaminated soil by adding percarbonate (oxidant) and iron or an iron compound to soil contaminated with organic matter.

  Further, for example, Patent Document 3 discloses a method for purifying contaminated soil and groundwater by adding hydrogen peroxide, potassium permanganate (oxidant) and a chelating agent to soil and groundwater contaminated with organic matter. Is disclosed. The addition of the chelating agent in this purification method is to suppress the production of insoluble substances such as iron oxyhydroxide produced by oxidation of divalent iron ions.

  Non-Patent Documents 1 and 2 disclose methods for treating TCE and benzene by adding persulfate, citric acid and divalent iron.

JP 2008-246414 A JP 2006-167713 A JP 2000-301172 A

Chenju Liang etc. , Chemosphere, vol55 (2004), p1225-1233. Chenju Liang etc. , Water Research, vol42 (2008), p4091-4100

  However, when hydrogen peroxide is used as an oxidizing agent as in the method of Patent Document 1, the hydrogen peroxide is decomposed by the reducing substances in the soil and groundwater, and the reaction area is narrowed, so that organic substances cannot be efficiently purified. There is a fear.

  In addition, in the method of Patent Document 2, iron or iron compound-derived insoluble substances derived from iron or iron compounds are used in combination with the percarbonate, and the insoluble substances block the injection well and the underground water channel and cannot efficiently purify organic matter. There is a fear.

  In addition, when hydrogen peroxide and potassium permanganate are used as the oxidizing agent as in the method of Patent Document 3, as described above, in the case of hydrogen peroxide, the reaction area becomes narrow and the organic matter is efficiently purified. In the case of potassium permanganate, potassium permanganate itself has a purple color and it is not preferable to inject it directly into groundwater or the like. The purpose of adding a chelating agent in the method of Patent Document 3 is to suppress the production of insoluble substances such as iron oxyhydroxide generated by oxidation of divalent iron ions, and to promote the purification of organic substances. is not.

  In Non-Patent Documents 1 and 2, the molar ratio of persulfate, citric acid, and divalent iron, etc., which are suitable for decomposing chemical substances mainly in pure water system, are examined. Unlike the properties of soil and groundwater, it does not contain reducing substances, decomposition inhibiting substances, persulfate consuming substances, or total organic carbon. Therefore, the verification in the pure water system may show a particularly good decomposition reaction, and there is an unrealistic aspect. In other words, it is possible to understand the effects of unconfirmed reducing substances, decomposition inhibitors, etc. on the treatment of chemical contamination only after verification using actual soil and groundwater, and then persulfate and citric acid. And the optimum molar ratio of divalent iron can be studied.

  In addition, in the methods of Non-Patent Documents 1 and 2, the actual purification construction is not assumed, so the persulfate concentration disclosed in Non-Patent Documents 1 and 2 depends on the type of target soil and groundwater. Persulfate is decomposed by reducing substances, decomposition inhibitors, persulfate consuming substances, or all organic carbon in groundwater, and persulfate is consumed, so there is a high possibility that organic substances cannot be purified efficiently. .

  Therefore, an object of the present invention is to treat chemical substances safely and more efficiently than conventional treatment with persulfate in the purification of soil and groundwater contaminated with chemical substances, especially organic chlorine compounds and aromatic hydrocarbons. It is an object of the present invention to provide a chemical contamination treatment method and treatment apparatus that can perform the above-described process.

  The present invention is a chemical contamination treatment method for purifying soil and groundwater by adding persulfate and chelated iron to soil and groundwater contaminated with a chemical substance, and the persulfate concentration is 5000 mg / L or more. In addition, persulfate and chelated iron are added so that the molar ratio of persulfate to iron (persulfate / iron) is 5 or more.

  Further, in the chemical contamination treatment method, the chelated iron is an organic acid iron, and the organic acid and divalent iron of citric acid or sodium gluconate have a molar ratio of organic acid to iron (organic acid / iron). It is preferable to prepare the organic acid iron by mixing so as to be 1 or less.

  In the chemical substance contamination treatment method, the chelated iron is preferably an organic acid iron containing iron (III) citrate or iron (II) gluconate.

  Moreover, in the chemical substance treatment method, when adding the persulfate and the chelate iron, it is preferable to add the chelate iron and then add the persulfate.

  Further, in the chemical substance contamination treatment method, the chemical substance is preferably an organic chlorine compound and an aromatic hydrocarbon.

  In the chemical contamination treatment method, it is preferable to purify the soil and groundwater by adding the persulfate and the chelate iron at the original position of the soil and the groundwater.

  In the chemical contamination treatment method, it is preferable to purify the soil and groundwater by adding the persulfate and the chelated iron to the soil and groundwater excavated from the original position of the soil and the groundwater.

  The chemical substance contamination treatment apparatus of the present invention comprises persulfate addition means for adding persulfate in situ to soil and groundwater contaminated with chemical substances, and chelate iron to the soil and groundwater in situ. A chelate iron addition means to be added, and the persulfate addition means and the chelate iron addition means provide a persulfate concentration of 5000 mg / L or more and a molar ratio of persulfate to iron (persulfate / iron ) Is added to the persulfate and the chelated iron so that it is 5 or more.

  In the chemical contamination processing apparatus, the chelated iron is an organic acid iron, and the organic acid and divalent iron of citric acid or sodium gluconate have a molar ratio of organic acid to iron (organic acid / iron). It is preferable to provide the production | generation reaction tank which mixes so that it may become 1 or less and prepares the said organic acid iron.

  In the chemical substance contamination treatment apparatus, the chelate iron is preferably an organic acid iron containing iron (III) citrate or gluconic acid (II).

  In the chemical contamination processing apparatus, when the persulfate and the chelate iron are added by the persulfate addition means and the chelate iron addition means, the chelate iron is added, and then the chelate iron is added. It is preferred to add persulfate.

  In the chemical substance contamination treatment apparatus, the chemical substance is preferably an organic chlorine compound and an aromatic hydrocarbon.

  In the chemical contamination processing apparatus, it is preferable that the persulfate addition means and the chelate iron addition means add the persulfate and the chelate iron to the soil and the groundwater in situ.

  Further, in the chemical contamination processing apparatus, the persulfate addition means and the chelate iron addition means may add the persulfate and the chelate iron to the soil and groundwater excavated from the original position of the soil and the groundwater. It is preferable to add.

  According to the present invention, it is preferable to treat chemical substances, particularly organic chlorine compounds and aromatic hydrocarbons, more safely and efficiently than conventional treatment with persulfate.

It is a schematic diagram which shows an example of a structure of the processing apparatus of the chemical substance contamination which concerns on embodiment of this invention. It is a schematic diagram which shows an example of a structure of the processing apparatus of the chemical substance contamination which concerns on other embodiment of this invention. It is a schematic diagram which shows an example of a structure of the processing apparatus of the chemical substance contamination which concerns on other embodiment of this invention. It is a schematic diagram which shows an example of a structure of the processing apparatus of the chemical substance contamination which concerns on other embodiment of this invention. It is a schematic diagram which shows an example of a structure of the processing apparatus of the chemical substance contamination which concerns on other embodiment of this invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic diagram showing an example of the configuration of a chemical contamination processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the chemical contamination treatment apparatus 1 includes a persulfate addition means including a first pump 10 and a persulfate supply line 12, a persulfate tank 14, a second pump 16, and chelate iron. Chelating iron addition means including a supply line 18, chelating iron tank 20, injection means including a switching valve 22, an injection line 24 and an injection well 26, a third pump 28, a pumping line 30, a pumping well 32 and a pumping tank 34 And a fourth pump 36, a fifth pump 38, pipes 40 and 42, and an activated carbon device 44. The switching valve 22 has a switching function of allowing only persulfate to pass through, allowing only chelated iron to pass through, and allowing both persulfate and chelated iron to pass through.

  The persulfate supply line 12 is provided with a first pump 10, and the chelate iron supply line 18 is provided with a second pump 16. The persulfate supply line 12 from the persulfate tank 14 is connected to one end of the injection line 24 via the switching valve 22, and the chelate iron supply line 18 from the chelate iron tank 20 is connected to the switching valve 22. 22 is connected to one end of the injection line 24. The other end of the injection line 24 is disposed in the injection well 26.

  The persulfate and the chelated iron are supplied from the persulfate addition means and the chelate iron addition means through the switching valve 22 and the injection line 24 to soil and groundwater contaminated with organic chlorine compounds, aromatic hydrocarbons and other chemical substances. Supplied in situ. However, the switching valve 22 and the injection line 24 are not necessarily required. For example, the persulfate supply line 12 and the chelate iron supply line 18 are installed in the injection well 26, and the persulfate supply line 12 and the chelate iron supply line 18 are installed. Persulfate and chelated iron may be supplied directly to the soil and groundwater.

  The pumping means pumps ground water after purification treatment to the surface. Here, the pumping well 32 constituting the pumping means needs to be disposed at least downstream of the groundwater from the injection well 26 in order to pump up the groundwater after the purification treatment. A third pump 28 is provided in the pumping line 30 disposed in the pumping well 32. The pumping line 30 is connected to a pumping tank 34.

  The pumping tank 34 and the activated carbon device 44 are connected by a pipe 40, and the pipe 40 is provided with a fourth pump 36. The activated carbon device 44 and the injection line 24 are connected by a pipe 42 via the switching valve 22, and a fifth pump 38 is provided in the pipe 42.

  The activated carbon device 44 mainly treats unreacted persulfate remaining in the treated water and remaining chemical substances. Examples of the activated carbon treatment by the activated carbon device 44 include activated carbon treatment using a complete mixing tank using powdered activated carbon, treatment using a fixed bed of granular activated carbon using an activated carbon tower, treatment using a fluidized bed using granular activated carbon, and the like. . However, it is not necessarily limited to these.

  Hereinafter, a method for treating chemical contamination using the treatment apparatus according to the present embodiment will be described.

  The persulfate in the persulfate tank 14 is transferred from the persulfate supply line 12 to the injection line 24 through the switching valve 22 by the first pump 10, and the chelate in the chelate iron tank 20 by the second pump 16. Iron is supplied from the chelate iron supply line 18 to the injection line 24 via the switching valve 22. Then, persulfate and chelated iron are supplied from the injection line 24 through the injection well 26 to the soil and groundwater contaminated with chemical substances. Then, while the groundwater to which persulfate and chelated iron are added flows through the reaction region X, chemical substances such as organic chlorine compounds and aromatic hydrocarbons existing in the reaction region X are decomposed.

  Next, the groundwater purified by the addition of persulfate and chelated iron is sent from the pumping line 30 to the pumping tank 34 by the third pump 28. When the water in the pumping tank 34 is supplied again to the original position of the groundwater contaminated with the chemical substance, the fourth pump 36 and the fifth pump 38 are operated, and the groundwater in the pumping tank 34 is treated with the activated carbon by the activated carbon device 44. It is preferable to remove the remaining chemical substances such as organic chlorine compounds and aromatic hydrocarbons. Then, the treated water treated with activated carbon by the activated carbon device 44 is supplied from the pipe 42 to the injection line 24 through the switching valve 22 and is supplied again to the original position of the soil and groundwater. Moreover, when discharging the water in the pumping tank 34 to the ground surface, it is preferable to perform activated carbon treatment with the activated carbon device 44 to remove the remaining chemical substances.

  As described above, the setting of the treatment chemical concentration using real soil and groundwater, the configuration of the treatment apparatus, and the like are findings obtained for the first time by the present inventors' intensive study. And the treatment method of decomposing chemical substances by adding persulfate and chelated iron is more efficient than decomposing chemical substances such as organic chlorine compounds and aromatic hydrocarbons with persulfate alone. Can be raised.

  Although the mechanism related to this phenomenon has not been clarified, the addition of chelating iron such as iron citrate makes sulfuric acid effective in decomposing chemical substances such as organochlorine compounds and aromatic hydrocarbons resulting from the decomposition of persulfuric acid. Not only promotes the generation of radicals, but also releases sulfuric acid radicals in a sustained manner, and by generating organic radicals by adding organic substances such as citric acid, it is efficient at normal pressure regardless of temperature. It is thought that chemical substances such as organochlorine compounds and aromatic hydrocarbons are often decomposed.

  In the present embodiment, in the purification of groundwater and soil contaminated with chemical substances, the persulfate concentration is 5000 mg / L (21 mmol / L) or more, and the molar ratio of persulfate to iron (persulfate / iron). Persulfate and chelated iron are added so that is 5 or more. In addition, the persulfate and the chelate are adjusted so that the persulfate concentration is 5000 mg / L to 50,000 mg / L and the molar ratio of persulfate to iron (persulfate / iron) is 5 to 59. It is preferable to add iron. If the persulfate concentration is less than 5000 mg / L and the molar ratio of persulfate to iron is less than 5, persulfate is decomposed by reducing substances present in soil or groundwater when actual purification is assumed. As a result, it is difficult to sufficiently decompose chemical substances such as organic chlorine compounds and aromatic hydrocarbons. On the other hand, if the persulfate concentration exceeds 50000 mg / L, the amount of chemicals used increases and the cost increases.

  In the present embodiment, when the treated water is passed through the activated carbon device 44, a pH adjuster such as caustic soda is injected into the pipe 40 or the like to neutralize the treated water or adjust the pH of the treated water to 5.5 to 7. It is preferable to adjust to the range of 5 from the point which can extend the lifetime of activated carbon. Moreover, it is preferable that the superficial velocity at the time of water flow to the activated carbon device 44 is in a range of 1 to 20 (1 / hr).

  Furthermore, it is more preferable to reduce the remaining persulfate by injecting a reducing agent such as sodium sulfite, sodium thiosulfate, or hydrogen peroxide into the pipe 40 or the like in terms of extending the life of the activated carbon.

  As the persulfate used in the present embodiment, potassium persulfate or sodium persulfate can be preferably used, but is not limited thereto.

  Examples of the chelated iron used in this embodiment include organic acid irons such as EDTA-iron, iron citrate, and iron gluconate, among which citric acid and divalent iron, or sodium gluconate and divalent iron. The chelated iron to be adjusted is more preferable from the viewpoint of cost, decomposition effect, and handling.

  FIG. 2 is a schematic diagram showing an example of the configuration of a chemical contamination processing apparatus according to another embodiment of the present invention. In the chemical contamination processing apparatus 2 shown in FIG. 2, the same components as those in the chemical contamination processing apparatus 1 shown in FIG. The chemical substance contamination treatment apparatus 2 shown in FIG. 2 includes a production reaction tank 46 for producing organic acid iron, which is chelated iron, an organic acid supply line 48 as organic acid addition means, and iron salt addition means. The iron salt supply line 50 is provided.

  An organic acid supply line 48 is connected to the organic acid supply port (not shown) of the production reaction tank 46, and an iron salt supply line 50 is connected to the iron salt supply port (not shown) of the production reaction tank 46. Has been. Further, the chelate iron supply line 18 from the production reaction tank 46 is connected to the injection line 24 via the switching valve 22. Other configurations are the same as those of the chemical contamination processing apparatus 1 shown in FIG.

  The production reaction tank 46 of the present embodiment is a tank for producing chelated iron, and is a stirrer (stirrer, air diffuser, submersible pump, etc.) in the production reaction tank 46 in terms of increasing the production efficiency of chelated iron. Is preferably provided.

  Hereinafter, a method for treating chemical contamination using the treatment apparatus according to the present embodiment will be described.

  An organic acid is supplied from the organic acid supply line 48 and an iron salt is supplied from the iron salt supply line 50 to the production reaction tank 46 and mixed to produce organic acid iron. Then, the persulfate in the persulfate tank 14 is transferred from the persulfate supply line 12 to the injection line 24 through the switching valve 22 by the first pump 10, and in the production reaction tank 46 by the second pump 16. The organic acid iron is supplied from the chelate iron supply line 18 to the injection line 24 via the switching valve 22. Then, the persulfate and the organic acid iron are supplied from the injection line 24 to the soil and groundwater contaminated with the chemical substance through the injection well 26. Also by such a method, it is possible to decompose chemical substances such as organochlorine compounds and aromatic hydrocarbons as described above.

  Here, the chelated iron produced by the production reaction tank 46 of this embodiment is an organic acid iron, the organic acid supplied from the organic acid supply line 48 is citric acid or sodium gluconate, and the iron salt supply line 50. The iron salt supplied from is divalent iron. And in the production | generation reaction tank 46, it mixes so that the molar ratio (organic acid / iron) of the said organic acid and iron may become 1 or less, Preferably it is 0.1-1 or less, and organic acid iron is prepared. When the above molar ratio of organic acid to iron (organic acid / iron) exceeds 1, the organic acid itself that does not participate in chelation behaves as an organic substance that consumes an oxidizing agent, and the decomposition efficiency of organic chlorine compounds, aromatic hydrocarbons, etc. May decrease.

  In addition, it is easier to produce organic acid iron from an organic acid such as citric acid or sodium gluconate and an iron salt such as divalent iron, and to use the produced organic acid iron for the decomposition of the aromatic chlorine compound. The processing cost can be greatly reduced as compared with the case of purchasing organic acid iron such as. However, when the organic acid and divalent iron are mixed as in the present embodiment, it is preferable that the organic acid iron is sufficiently generated and then supplied to the reaction region X. Note that the organic acid supply line 48 and the iron salt supply line 50 are not necessarily required if the organic acid and divalent iron can be mixed in the generation reaction tank 46 to generate the organic acid iron.

  The organic acid used in the present embodiment is preferably a soluble carboxylic acid, and particularly preferably citric acid, sodium gluconate, succinic acid, oxalic acid, fumaric acid, EDTA, nitrilotriacetic acid, and the like are preferably used. Can do. As the citric acid used in the present embodiment, citric acid, sodium citrate or the like is preferably used. The divalent iron used in the present embodiment is not particularly limited, and examples thereof include iron salts such as iron sulfate.

  FIG. 3 is a schematic diagram showing an example of the configuration of a chemical contamination processing apparatus according to another embodiment of the present invention. In the chemical substance contamination treatment apparatus 3 shown in FIG. 3, the same components as those in the chemical substance contamination treatment apparatus 2 shown in FIG. The chemical contamination processing apparatus 3 shown in FIG. 3 does not include a pumping means, an activated carbon apparatus 44, or the like. In addition, in the chemical substance contamination purification apparatus 3 shown in FIG. 3, an observation well 52 for observing the groundwater quality such as the degree of purification of the reaction region Y and pH is provided in the reaction region Y (in addition, the reaction region Y). Y may be provided outside Y).

  When the pumping of the groundwater after such purification is not performed, the reaction region Y to which persulfate and chelate iron are added spreads in a substantially circular shape around the injection well 26. Such a method can also be used to purify soil and groundwater contaminated with chemical substances. However, as with the chemical substance contamination treatment apparatus 1 or 2 shown in FIG. 1 or FIG. It is possible to treat chemical substances more efficiently by providing 44 and the like.

  The above-described embodiment is an example, and for example, pollutants such as water, drainage, soil, sediment, sludge, and groundwater contaminated with organic pollutants proposed by the present inventors are oxidized in situ. A method of kneading with an agent (see Japanese Patent Application Laid-Open No. 2007-105556), excavating contaminants such as water, drainage, soil, sediment, sludge, and groundwater contaminated with organic contaminants, and kneading with an oxidant on the ground It is also possible to decompose chemical substances such as organic chlorine compounds and aromatic hydrocarbons using the method (see Japanese Patent No. 3784654, Japanese Patent Laid-Open No. 2003-71425, and Japanese Patent Laid-Open No. 2002-326080). is there. An example is described below.

  FIG. 4 is a schematic diagram showing an example of the configuration of a chemical contamination processing apparatus according to another embodiment of the present invention. The chemical contamination processing apparatus shown in FIG. 4 rotates a base machine 60 (a machine in which a driven member can be replaced), a rotary shaft 64 having a rotary stirring blade 62 below, and a rotary shaft 64. A persulfate supply means comprising a rotational drive source 66, a persulfate supply line 68 and a first pump 70, a chelate iron supply means comprising a persulfate tank 72, a chelate iron supply line 74 and a second pump 76, and a chelate iron tank 78 is provided.

  The persulfate and the chelate iron are supplied to the upper portion of the rotating shaft 64 from the persulfate supply line 68 and the chelate iron supply line 74 by the first pump 70 and the second pump 76. The rotating shaft 64 has a hollow structure or a double pipe structure. The rotating shaft 64 transfers persulfate and chelated iron supplied to the upper part of the rotating shaft 64 and injects it into contaminated soil and groundwater through an opening provided in the lower part. The chemical substances such as organic chlorine compounds and aromatic hydrocarbons can be directly kneaded with persulfate and chelated iron.

  FIG. 5 is a schematic diagram showing an example of the configuration of a chemical contamination processing apparatus according to another embodiment of the present invention. The chemical substance contamination treatment apparatus 5 shown in FIG. 5 is a self-propelled type in which a soil supply device 82, a chemical supply device 84, a mixing device 86, and a soil discharge device 88 are installed on a base machine 80 provided with traveling means. It is a soil conditioner. Then, chemical substances such as organic chlorine compounds and aromatic hydrocarbons, and persulfate and chelated iron are continuously supplied to the mixing device 86 by the soil supply device 82 and the chemical supply device 84, respectively. A chemical substance such as an aromatic hydrocarbon, persulfate and chelated iron are continuously mixed by the mixing device 86 and discharged continuously by the soil discharging device 88.

  Also by such a method, it is possible to purify groundwater, soil, etc. contaminated with chemical substances. If the contamination position by chemical substances such as organochlorine compounds and aromatic hydrocarbons is shallow, excavate the contaminated soil etc. by the method of purifying contaminated soil etc. In addition, it is preferable to purify by adding and kneading contaminated soil, persulfate, and chelated iron.

  In these embodiments, the order of addition of persulfate and chelate iron is preferably such that after addition of chelate iron to the soil and groundwater in situ (for example, by switching the switching valve 22), the persulfate is added. . This is because chelate iron is also decomposed by persulfate, so if persulfate and chelate iron are added simultaneously or after chelate iron, insoluble substances such as iron oxyhydroxide are generated, and the injection well In some cases, underground waterways are blocked. However, after adding chelated iron and diffusing it widely in groundwater, adding persulfate suppresses the generation of insoluble substances such as iron oxyhydroxide and maintains the effectiveness of chelated iron. it can. About the effect of such a chemical | medical agent mixing addition order to real soil and groundwater, it is the knowledge acquired for the first time by earnest examination of this inventor.

  In these embodiments, the adjustment of the addition amount of persulfate and the addition amount of chelated iron is not particularly limited as long as it is added so as to satisfy the above numerical range. For example, the concentration of persulfate in the treated water passing through the pumping line 30 and the pumping well 32 (or the observation well 52) is measured, and the addition amount of persulfate and chelated iron is adjusted based on the measured value. (For example, if the concentration of the contaminating chemical substance in the reaction region is clear in advance, a predetermined amount of persulfate and chelated iron may be added).

  The treatment method of the present embodiment is preferably used for treatment of contaminants such as water, drainage, soil, sediment, sludge, and groundwater contaminated with organochlorine compounds and aromatic hydrocarbons, but is not limited thereto. It is not something. That is, this embodiment is not only for purification of contamination by organic chlorine compounds such as TCE, PCE, dioxins, PCBs, and aromatic hydrocarbons such as benzene, but also for purification of contamination by other pollutant chemicals such as oil. Is also applicable.

  In order to promote the decomposition of the chemical substance, a heating means using a steam injection method or the like may be provided. However, in this embodiment, the decomposition of the chemical substance hardly depends on the temperature. Not necessary. As a result, the energy required for heating becomes unnecessary, so that the processing cost can be reduced. A heating means is provided with the compressor which produces | generates compressed air, the boiler which produces | generates water vapor | steam, and the injection equipment which mixes compressed air and water vapor | steam and supplies mixed gas to an injection well, for example.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

Example 1
TCE and benzene decomposition tests were performed. In Example 1, persulfuric acid having a concentration of 10,000 mg / L (42 mmol / L) was added to soil groundwater containing TCE having a concentration of 37 mg / L (0.28 mmol / L) and benzene having a concentration of 30 mg / L (0.38 mmol / L). Iron citrate prepared by mixing sodium citrate at a concentration of 688 mg / L (3.58 mmol / L) and iron sulfate heptahydrate at a concentration of 200 mg / L (3.58 mmol / L) as divalent iron Added. Then, 7 hours after the start of the reaction, the TCE and benzene concentrations in the waste water were measured by a gas chromatograph (GC). In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC. Table 1 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 7 hours of decomposition reaction being 100%.

(Example 2)
Example 2 was the same as Example 1 except that sodium gluconate having a concentration of 781 mg / L (3.58 mmol / L) was used instead of citric acid having a concentration of 688 mg / L (3.58 mmol / L). It went on condition of. Table 1 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 7 hours of decomposition reaction being 100%.

(Comparative Example 1)
In Comparative Example 1, persulfuric acid having a concentration of 10,000 mg / L (42 mmol / L) was added to soil groundwater containing TCE having a concentration of 37 mg / L (0.28 mmol / L) and benzene having a concentration of 30 mg / L (0.38 mmol / L). Sodium was added. Then, 7 hours after the start of the reaction, the TCE and benzene concentrations in the waste water were measured by a gas chromatograph (GC). In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC. Table 1 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 7 hours of decomposition reaction being 100%.

  As can be seen from Table 1, Examples 1 and 2 in which persulfate and organic acid iron composed of an organic acid and an iron salt were added to TCE and benzene-containing groundwater were comparative examples 1 in which only sodium persulfate was added. As a result, the decomposition efficiency of TCE and benzene was remarkably improved, and it was possible to process rapidly.

(Example 3)
TCE and benzene decomposition tests were performed. In Example 1, persulfuric acid having a concentration of 10,000 mg / L (42 mmol / L) was added to soil groundwater containing TCE having a concentration of 37 mg / L (0.28 mmol / L) and benzene having a concentration of 30 mg / L (0.38 mmol / L). Sodium citrate n-hydrate (iron content about 18%) with a concentration of 1111 mg / L (4.54 mmol / L) was added to adjust to 200 mg / L as an iron salt. Then, 7 hours after the start of the reaction, the TCE and benzene concentrations in the waste water were measured by a gas chromatograph (GC). In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC. Table 2 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 7 hours of decomposition reaction being 100%.

Example 4
In Example 4, instead of iron citrate n-hydrate having a concentration of 1111 mg / L (4.54 mmol / L), iron gluconate dihydrate having a concentration of 1727 mg / L (3.58 mmol / L) was used. The procedure was the same as in Example 3 except that the iron salt was 200 mg / L. Table 2 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 7 hours of decomposition reaction being 100%.

  In Table 2, the data of Comparative Example 1 are also shown for comparison with Examples 3 and 4.

  As can be seen from Table 2, the decomposition efficiency of TCE and benzene was higher in Examples 3 and 4 in which persulfate and organic acid iron were added to TCE and benzene-containing groundwater than in Comparative Example 1 in which only sodium persulfate was added. Can be improved rapidly and processed quickly.

(Example 5)
TCE and benzene decomposition tests were performed. In Example 5, citric acid and divalent iron having a concentration of 961 mg / L (5 mmol / L) were added to soil groundwater containing TCE having a concentration of 131 mg / L (1 mmol / L) and benzene having a concentration of 78 mg / L (1 mmol / L). Sodium persulfate was added so that the molar ratio of iron citrate prepared by mixing iron sulfate heptahydrate at a concentration of 279 mg / L (5 mmol / L) and persulfate to iron was 10 . Then, 9 hours and 48 hours after the start of the reaction, TCE and benzene concentrations in the waste water were measured by a gas chromatograph (GC). In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC. Table 3 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 9 hours of decomposition reaction being 100%. Table 4 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 48 hours of decomposition reaction being 100%.

(Example 6)
In Example 6, the test was performed under the same conditions as in Example 5 except that sodium persulfate was added so that the molar ratio of persulfate to iron was 5. Table 3 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 9 hours of decomposition reaction being 100%. Table 4 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 48 hours of decomposition reaction being 100%.

(Comparative Examples 2 and 3)
In Comparative Example 2, sodium persulfate was added so that the molar ratio of persulfate to iron was 4, and in Comparative Example 3, sodium persulfate was added so that the molar ratio of persulfate to iron was 1. The test was performed under the same conditions as in Example 5 except that was added. Table 3 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 9 hours of decomposition reaction being 100%. Table 4 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 48 hours of decomposition reaction being 100%.

  As can be seen from Table 3, persulfate and organic acid iron were added to TCE and benzene-containing groundwater so that the persulfate concentration was 5000 mg / L or more and the molar ratio of persulfate to iron was 5 or more. In Nos. 5 and 6, the decomposition rate of TCE and benzene reached about 40 to 70% even at an early stage after 9 hours of reaction time, whereas the persulfate concentration was less than 5000 mg / L, In Comparative Examples 2 and 3 having a molar ratio of less than 5, TCE and benzene were hardly decomposed. As can be seen from Table 4, after 48 hours of reaction time, the decomposition rates of TCE and benzene of Examples 5 and 6 were 95% or more. Therefore, in terms of decomposition rate, decomposition rate, etc., soil and groundwater contaminated with chemical substances should have a persulfate concentration of 5000 mg / L or more and a persulfate to iron molar ratio of 5 or more. It was found that salt and organic acid iron need to be added.

(Example 7)
A PCE degradation test was performed. In Example 7, in soil groundwater containing PCE having a concentration of 50 mg / L (0.3 mmol / L) or more, sodium persulfate having a concentration of 10000 mg / L (42 mmol / L), concentration of 344 mg / L (1.79 mmol / L) Of citric acid and iron citrate prepared by mixing iron sulfate heptahydrate at a concentration of 100 mg / L (1.79 mmol / L) as divalent iron was added. Then, 30 hours and 48 hours after the start of the reaction, PCE in the waste water was measured by a gas chromatograph (GC). In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC. Table 5 summarizes the PCE decomposition rates, with the blank concentration after 30 hours of decomposition reaction being 100%. Table 6 summarizes the PCE decomposition rates, with the blank concentration after 48 hours of decomposition reaction being 100%.

(Example 8)
Example 8 was carried out except that the concentration of citric acid was 688 mg / L (3.58 mmol / L), and iron sulfate heptahydrate was used as divalent iron at a concentration of 200 mg / L (3.58 mmol / L). The test was conducted under the same conditions as in Example 7. Table 5 summarizes the PCE decomposition rates, with the blank concentration after 30 hours of decomposition reaction being 100%. Table 6 summarizes the PCE decomposition rates, with the blank concentration after 48 hours of decomposition reaction being 100%.

(Comparative Example 4)
Comparative Example 4 was carried out except that the concentration of citric acid was 3440 mg / L (17.91 mmol / L), and iron sulfate heptahydrate was used as divalent iron at a concentration of 1000 mg / L (17.91 mmol / L). The test was conducted under the same conditions as in Example 7. Table 5 summarizes the PCE decomposition rates, with the blank concentration after 30 hours of decomposition reaction being 100%. Table 6 summarizes the PCE decomposition rates, with the blank concentration after 48 hours of decomposition reaction being 100%.

  As can be seen from Table 5, even when the persulfate concentration was 5000 mg / L or more, the molar ratio of persulfate to iron was higher in Examples 7 and 8 where the molar ratio of persulfate to iron was 5 or more. From Comparative Example 4 with a value of less than 5, the PCE decomposition rate was improved, and the PCE decomposition rate after 30 hours was 95% or more. Moreover, when Example 7 and Example 8 were compared, it turned out that the direction of Example 8 with a higher molar ratio of persulfate and iron improves the PCE decomposition rate.

Example 9
A PCE degradation test was performed. In Example 9, in soil groundwater containing PCE having a concentration of 50 mg / L (0.3 mmol / L) or more, sodium persulfate having a concentration of 10000 mg / L (42 mmol / L), concentration of 688 mg / L (3.58 mmol / L) Of citric acid and iron citrate prepared by mixing iron sulfate heptahydrate at a concentration of 400 mg / L (7.16 mmol / L) as divalent iron was added. And 24 hours after the reaction start, PCE in waste water was measured by the gas chromatograph (GC). In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC. Table 7 summarizes the PCE decomposition rates, with the blank concentration after 24 hours of decomposition reaction being 100%.

(Examples 10 and 11)
In Example 10, iron sulfate heptahydrate having a concentration of 200 mg / L (3.58 mmol / L) was used as divalent iron, and in Example 11, a concentration of 100 mg / L (1.79 mmol / L) was used as divalent iron. The test was performed under the same conditions as in Example 9 except that iron sulfate heptahydrate was used. Table 7 summarizes the PCE decomposition rates with the blank concentration after 24 hours of decomposition reaction being 100%.

  As can be seen from Table 7, in Examples 9 and 10 in which the molar ratio of citric acid to iron was 1 or less, the decomposition ratio of PCE was higher than that in Example 11 in which the molar ratio of citric acid to iron exceeded 1. Had improved. Therefore, in order to improve the decomposition rate, the molar ratio of citric acid and iron is preferably 1 or less.

(Example 12)
In Example 12, after iron sulfate heptahydrate having a concentration of 200 mg / L and citric acid having a concentration of 688 mg / L were previously mixed as divalent iron to produce iron citrate, the concentration was 5000 mg / L (42 mmol / L). L) Sodium persulfate was added, and the stability of the organic acid was examined using total organic carbon as an index. In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC. Table 7 summarizes the residual ratio of citric acid 315 hours after the addition of sodium persulfate.

(Comparative Example 5)
In Comparative Example 5, iron sulfate heptahydrate with a concentration of 200 mg / L as divalent iron and citric acid with a concentration of 688 mg / L were first mixed to produce iron citrate, and the organic acid was measured using total organic carbon as an index. Stability was examined. In addition, the water temperature in a decomposition test was implemented in the range of 15-20 degreeC.

  As can be seen from Table 8, in the presence of sodium persulfate, citric acid is decomposed. In general, an insoluble substance such as iron oxyhydroxide is generated with the decomposition of citric acid by sodium persulfate. Similarly, other organic acids are also decomposed by persulfate, and as a result, insoluble substances such as iron oxyhydroxide are generated. Therefore, in actual purification construction, when persulfate is injected first and then organic acid iron is injected (or injected simultaneously), high concentration of organic acid iron reacts with persulfate around the injection well. Therefore, insoluble substances such as iron oxyhydroxide are likely to be generated, and as a result, wells and groundwater channels are likely to be blocked. On the other hand, by injecting the organic acid iron first and diffusing it in the groundwater over a wide area, the persulfate is injected, so that the decomposition of the organic acid by the persulfate is suppressed, and the well or groundwater channel due to the insoluble material is suppressed. It becomes possible to prevent occlusion.

(Examples 13 to 17)
A decomposition test of TCE and benzene by different curing temperatures was performed. In Example 13, in soil groundwater containing TCE at a concentration of 22.3 mg / L (0.17 mmol / L) and benzene at a concentration of 23.1 mg / L (0.3 mmol / L), the concentration was 10,000 mg / L (42 mmol / L). ) Sodium persulfate, citric acid at a concentration of 688 mg / L (3.58 mmol / L) and iron sulfate heptahydrate at a concentration of 200 mg / L (3.58 mmol / L) as divalent iron. Iron citrate was added and stored at 5 ° C. in Example 13, 15 ° C. in Example 14, 20 ° C. in Example 15, 30 ° C. in Example 16, and 40 ° C. in Example 17. And 9 hours after the reaction start, TCE and benzene were measured by gas chromatograph (GC). Table 9 summarizes the decomposition rates of TCE and benzene, with the blank concentration after 9 hours of decomposition reaction being 100%.

  Usually, when a chemical substance such as an organic chlorine compound or an aromatic hydrocarbon is decomposed only by adding a persulfate, the decomposition rate is improved if the curing temperature is high. On the other hand, when persulfate and chelated iron were added so that the persulfate concentration was 5000 mg / L or more and the molar ratio of persulfate to iron was 5 or more, as shown in Table 9, the curing temperature Regardless, the decomposition rate of TCE and benzene was high, and it was found that rapid treatment was possible. Therefore, in the actual purification construction, for example, it is not necessary to install heating equipment such as steam for promoting the decomposition of chemical substances and to take a heating means.

  1-5 Chemical contamination treatment apparatus 10, 70 First pump 12, 68 Persulfate supply line 14, 72 Persulfate tank 16, 76 76 Second pump 18, 74 Chelate iron supply line 20 , 78 Chelated iron tank, 22 selector valve, 24 injection line, 26 injection well, 28 3rd pump, 30 pumping line, 32 pumping well, 34 pumping tank, 36 4th pump, 38 5th pump, 40, 42 piping, 44 activated carbon device, 46 production reaction tank, 48 organic acid supply line, 50 iron salt supply line, 52 observation well, 60, 80 base machine, 62 rotary stirring blade, 64 rotary shaft, 66 rotary drive source, 82 soil supply device, 84 Drug supply device, 86 mixing device, 88 soil discharge device.

Claims (14)

A method for treating chemical contamination by purifying soil and groundwater by adding persulfate and chelated iron to soil and groundwater contaminated with chemicals,
Chemical contamination characterized by adding persulfate and chelated iron so that the persulfate concentration is 5000 mg / L or more and the molar ratio of persulfate to iron (persulfate / iron) is 5 or more Processing method.   The chelated iron is organic acid iron, citric acid or sodium gluconate organic acid and divalent iron are mixed so that the molar ratio of organic acid to iron (organic acid / iron) is 1 or less, and the organic 2. The method for treating chemical contamination according to claim 1, wherein iron oxide is prepared.   3. The method for treating chemical contamination according to claim 1, wherein the chelated iron is an organic acid iron containing iron (III) citrate or iron (II) gluconate.   The chemistry according to any one of claims 1 to 3, wherein when the persulfate and the chelate iron are added, the chelate iron is added, and then the persulfate is added. How to deal with substance contamination.   The chemical substance treatment method according to any one of claims 1 to 4, wherein the chemical substance is an organic chlorine compound and an aromatic hydrocarbon.   The chemical substance according to any one of claims 1 to 5, wherein the persulfate and the chelated iron are added at the in-situ position of the soil and the groundwater to purify the soil and the groundwater. Contamination treatment method.   The soil and the groundwater excavated from the original position of the soil and the groundwater are added with the persulfate and the chelated iron to purify the soil and the groundwater. The method for treating chemical contamination according to Item 1. Persulfate addition means for adding persulfate to soil and groundwater contaminated with chemical substances,
A chelated iron addition means for adding chelated iron to the soil and groundwater,
By the persulfate addition means and the chelate iron addition means, the persulfate concentration is 5000 mg / L or more and the persulfate to iron molar ratio (persulfate / iron) is 5 or more. And a chemical contamination treatment apparatus, wherein chelating iron is added.   The chelated iron is organic acid iron, citric acid or sodium gluconate organic acid and divalent iron are mixed so that the molar ratio of organic acid to iron (organic acid / iron) is 1 or less, and the organic The apparatus for treating chemical contamination according to claim 8, further comprising a production reaction tank for preparing iron oxide.   10. The chemical contamination treatment apparatus according to claim 8, wherein the chelated iron is an organic acid iron containing iron (III) citrate or iron (II) gluconate.   When the persulfate and the chelate iron are added by the persulfate addition means and the chelate iron addition means, the chelate iron is added, and then the persulfate is added. The chemical substance contamination treatment apparatus according to any one of claims 8 to 10.   The said chemical substance is an organic chlorine compound and an aromatic hydrocarbon, The processing apparatus of the chemical substance contamination of any one of Claims 8-11 characterized by the above-mentioned.   The said persulfate addition means and the said chelate iron addition means add the said persulfate and the said chelate iron to the original position of the said soil and the said groundwater, The any one of Claims 8-12 characterized by the above-mentioned. Chemical contamination treatment equipment described in 1.   The said persulfate addition means and the said chelate iron addition means add the said persulfate and the said chelate iron to the soil and groundwater excavated from the original position of the said soil and the said groundwater. 14. The apparatus for treating chemical contamination according to any one of items 13 to 13.

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