JP6825179B2 - How to purify contaminated soil and groundwater - Google Patents
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- JP6825179B2 JP6825179B2 JP2016167539A JP2016167539A JP6825179B2 JP 6825179 B2 JP6825179 B2 JP 6825179B2 JP 2016167539 A JP2016167539 A JP 2016167539A JP 2016167539 A JP2016167539 A JP 2016167539A JP 6825179 B2 JP6825179 B2 JP 6825179B2
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- 239000002689 soil Substances 0.000 title claims description 74
- 239000003673 groundwater Substances 0.000 title claims description 58
- 238000000034 method Methods 0.000 claims description 33
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 claims description 26
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 14
- 238000002347 injection Methods 0.000 claims description 13
- 239000007924 injection Substances 0.000 claims description 13
- 238000000746 purification Methods 0.000 claims description 13
- 239000003054 catalyst Substances 0.000 claims description 9
- 150000003839 salts Chemical class 0.000 claims 1
- 239000000126 substance Substances 0.000 description 15
- 239000003814 drug Substances 0.000 description 12
- 229940079593 drug Drugs 0.000 description 12
- 238000005086 pumping Methods 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 239000012855 volatile organic compound Substances 0.000 description 6
- 239000007800 oxidant agent Substances 0.000 description 5
- 239000000383 hazardous chemical Substances 0.000 description 4
- 230000020169 heat generation Effects 0.000 description 4
- 229910001385 heavy metal Inorganic materials 0.000 description 4
- 238000011109 contamination Methods 0.000 description 3
- 150000002505 iron Chemical class 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 239000000575 pesticide Substances 0.000 description 3
- 238000007348 radical reaction Methods 0.000 description 3
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 244000005700 microbiome Species 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 230000002085 persistent effect Effects 0.000 description 2
- 125000005575 polycyclic aromatic hydrocarbon group Chemical group 0.000 description 2
- 229920000139 polyethylene terephthalate Polymers 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 1
- -1 Polyethylene terephthalat Polymers 0.000 description 1
- DWAQJAXMDSEUJJ-UHFFFAOYSA-M Sodium bisulfite Chemical compound [Na+].OS([O-])=O DWAQJAXMDSEUJJ-UHFFFAOYSA-M 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000000711 cancerogenic effect Effects 0.000 description 1
- 231100000315 carcinogenic Toxicity 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 150000002013 dioxins Chemical class 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000003895 groundwater pollution Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 description 1
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 1
- 238000003900 soil pollution Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 239000013076 target substance Substances 0.000 description 1
- 239000000341 volatile oil Substances 0.000 description 1
- 238000003911 water pollution Methods 0.000 description 1
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Description
本願発明は、汚染土壌と地下水を浄化する技術に関するものであり、より具体的には、１，４−ジオキサンによって汚染された土壌と地下水を、硫酸ラジカルを活用して浄化する方法に関するものである。 The present invention relates to a technique for purifying contaminated soil and groundwater, and more specifically, to a method for purifying soil and groundwater contaminated with 1,4-dioxane by utilizing sulfate radicals. ..
土壌汚染とは、人の健康にとって有害な物質で土壌が汚染された状態をいい、操業活動での不用意な取り扱いによって有害物質が地表から浸透することで、あるいは排煙に含まれる有害物質が地表面に降下して堆積または浸透することで発生し、盛土や埋土が行われる際に汚染土壌が持ち込まれることで発生するケースもある。この有害物質は土壌汚染対策法によって指定されており、現在、揮発性有機化合物、重金属、農薬等の計２５物質が特定有害物質とされている。 Soil contamination refers to the state in which the soil is contaminated with substances that are harmful to human health, and the harmful substances permeate from the ground surface due to careless handling in operational activities, or the harmful substances contained in smoke exhaust It occurs when it descends to the ground surface and accumulates or infiltrates, and in some cases it occurs when contaminated soil is brought in when filling or burying soil. This hazardous substance is designated by the Soil Contamination Countermeasures Law, and currently, a total of 25 substances such as volatile organic compounds, heavy metals, and pesticides are designated as specified hazardous substances.
また、土壌汚染対策法で指定された特定有害物質以外にも、ダイオキシン類、ＰＡＨ（ｐｏｌｙｃｙｃｌｉｃ ａｒｏｍａｔｉｃ ｈｙｄｒｏｃａｒｂｏｎ）など、人の健康に被害を与える物質があることが知られており、その他、発がん性が疑われている１，４−ジオキサンも近年では注目されている。１，４−ジオキサンは有機溶剤に反応剤や安定剤として添加されるものであり、界面活性剤やＰＥＴ（Ｐｏｌｙｅｔｈｙｌｅｎｅｔｅｒｅｐｈｔｈａｌａｔ）樹脂の製造工程で副生成されることもある。また１，４−ジオキサンは、原料や製品に不純物として混入することがあり、あるいは製造工程からの排水に非意図的に含まれていることもあることから、直接使用していないにもかかわらず１，４−ジオキサンが排出されることも珍しくない。我が国では河川や地下水における１，４−ジオキサンの検出事例の増加に伴い、平成２１年１１月に水質環境基準及び地下水環境基準の対象物質に追加され、平成２４年５月には水質汚濁防止法の有害物質に指定されるなど、排水基準や地下浸透規制等により環境中への排出規制がなされることとなった。 In addition to the specified hazardous substances specified by the Soil Contamination Countermeasures Law, it is known that there are substances that are harmful to human health, such as dioxins and PAHs (polycyclic aromatic hydrocarbons), and are also carcinogenic. The suspected 1,4-dioxane has also attracted attention in recent years. 1,4-dioxane is added to an organic solvent as a reactant or a stabilizer, and may be by-produced in the manufacturing process of a surfactant or PET (Polyethylene terephthalat) resin. In addition, 1,4-dioxane may be mixed as an impurity in raw materials and products, or it may be unintentionally contained in wastewater from the manufacturing process, so even though it is not used directly. It is not uncommon for 1,4-dioxane to be excreted. In Japan, as the number of cases of 1,4-dioxane detected in rivers and groundwater increased, it was added to the target substances of the water quality environmental standard and the groundwater environmental standard in November 2009, and the Water Pollution Control Law was added in May 2012. It has been decided that emissions into the environment will be regulated by wastewater standards and underground infiltration regulations, such as being designated as a hazardous substance in Japan.
１，４−ジオキサンは、水に溶け易く揮発しにくい難分解性の合成化学物質であり、揮発性有機化合物（ＶＯＣ：ＶｏｌａｔｉｌｅＯｒｇａｎｉｃＣｏｍｐｏｕｎｄｓ）とはその性質が異なる。また１，４−ジオキサンには、土壌粒子への吸着性が低いという特徴もあり、浅層部に残留しやすい重金属類や農薬類とも性質が異なる。そのため地下環境中における１，４−ジオキサンの挙動（浸透性や地下水汚染の広がり方等）は、ＶＯＣや重金属類、農薬類とは異なり、したがってＶＯＣや重金属類等に対して採用される浄化方法では１，４−ジオキサンを適切に浄化できないこともある。 1,4-Dioxane is a persistent synthetic chemical substance that is easily dissolved in water and difficult to volatilize, and its properties are different from those of volatile organic compounds (VOCs). In addition, 1,4-dioxane is also characterized by its low adsorptivity to soil particles, and is different in properties from heavy metals and pesticides that tend to remain in shallow layers. Therefore, the behavior of 1,4-dioxane in the underground environment (permeability, how the groundwater pollution spreads, etc.) is different from VOCs, heavy metals, pesticides, etc. Therefore, the purification method adopted for VOCs, heavy metals, etc. In some cases, 1,4-dioxane cannot be properly purified.
１，４−ジオキサンは水に溶け易いことから帯水層（地下水のある層）に高濃度で存在することもあり、したがって浄化方法としては地下水揚水処理が効果的である。ＶＯＣや油類を対象に用いられるバイオレメディエーション（微生物を活用した土壌汚染浄化）も浄化方法として考えられるが、１，４−ジオキサンに対する分解能をもつ微生物の存在は既に確認されているものの、未だ原位置での浄化は実用化されていないのが現状である。 Since 1,4-dioxane is easily dissolved in water, it may be present in aquifer (a layer with groundwater) at a high concentration. Therefore, groundwater pumping treatment is effective as a purification method. Bioremediation (soil pollution purification using microorganisms) used for VOCs and oils can also be considered as a purification method, but although the existence of microorganisms with resolution for 1,4-dioxane has already been confirmed, it is still raw. At present, purification at the position has not been put into practical use.
地下水揚水処理の他、酸化剤の地中注入による原位置浄化が行われることもある。１，４−ジオキサンは難分解性ではあるが、ラジカル反応によって分解することが確認されており、薬剤からのラジカル生成を促すことで１，４−ジオキサンを分解することができる。特許文献１でも、重亜硫酸塩などの触媒とともに過硫酸塩を添加することによって、土壌と地下水を浄化する技術を提案している。添加する触媒と過硫酸塩を適切なモル比とすることで過硫酸塩のラジカル反応を促し、このラジカル反応により１，４−ジオキサンを分解するわけである。 In addition to groundwater pumping treatment, in-situ purification may be performed by injecting an oxidizing agent into the ground. Although 1,4-dioxane is persistent, it has been confirmed that it is decomposed by a radical reaction, and 1,4-dioxane can be decomposed by promoting the generation of radicals from a drug. Patent Document 1 also proposes a technique for purifying soil and groundwater by adding persulfate together with a catalyst such as sodium bisulfite. By setting the catalyst to be added and the persulfate in an appropriate molar ratio, the radical reaction of the persulfate is promoted, and 1,4-dioxane is decomposed by this radical reaction.
１，４−ジオキサンの浄化方法としての地下水揚水処理は、直接的な浄化対策としてだけでなく拡散防止の意味でも効果的であるが、適切な井戸設計（数・配置・揚水量等）を行わなければ期待した浄化効果が得られないという難しさがある。また、地下水濃度が排水基準を大きく上回る場合は高度な水処理設備が必要であり、さらに、流動性の小さい地下水（宙水や難透水層中の間隙水）等、十分量の揚水が困難な場合には採用することができない。 Groundwater pumping treatment as a purification method for 1,4-dioxane is effective not only as a direct purification measure but also in terms of preventing diffusion, but appropriate well design (number, arrangement, pumping amount, etc.) is performed. Without it, it is difficult to obtain the expected purification effect. In addition, if the groundwater concentration greatly exceeds the drainage standard, advanced water treatment equipment is required, and it is difficult to pump a sufficient amount of groundwater with low fluidity (airwater or pore water in the impervious layer). In some cases it cannot be adopted.
一方の酸化剤の地中注入による原位置浄化は、流動性の小さい地下水に対しても適用できるが、従来の手法では鉄塩などの触媒の添加が必要であり、しかも浄化効果を得るためには酸化剤に対して適切な比率で鉄触媒を添加しなければならず、相当の手間とコストがかかっていた。更に、添加した鉄塩の析出により、井戸閉塞等の弊害もでていた。 On the other hand, in-situ purification by injecting an oxidizing agent into the ground can be applied to groundwater with low fluidity, but the conventional method requires the addition of a catalyst such as iron salt, and in order to obtain a purification effect. The iron catalyst had to be added in an appropriate ratio to the oxidant, which required considerable labor and cost. Furthermore, the precipitation of the added iron salt also caused adverse effects such as well blockage.
本願発明の課題は、従来が抱える問題を解決することであり、すなわち揚水が難しい場所でも採用でき、そのうえ触媒の添加を必要としない、汚染土壌と地下水の浄化方法を提供することである。 An object of the present invention is to solve a conventional problem, that is, to provide a method for purifying contaminated soil and groundwater, which can be adopted even in a place where pumping is difficult and which does not require the addition of a catalyst.
本願発明は、加温した土壌と地下水に過硫酸塩をすることで、熱活性状態で硫酸ラジカルを発生させ、これにより１，４−ジオキサンを分解する、という点に着目したものであり、従来にはなかった発想に基づいてなされた発明である。 The present invention has focused on the fact that by adding persulfate to heated soil and groundwater, sulfuric acid radicals are generated in a thermally active state, thereby decomposing 1,4-dioxane. It is an invention made based on an idea that was not found in.
本願発明の「汚染土壌と地下水の浄化方法」は、１，４−ジオキサンで汚染された土壌と地下水を浄化する浄化方法であり、土壌加温工程と注入工程を備えた方法である。土壌加温工程では、土壌内に構築された３以上の電極井戸に印加し（電圧をかけ）、土壌に電流を流すことでジュール熱によって土壌と地下水を加温する。また注入工程では、常温水に溶解した過硫酸塩を、加温された状態の土壌又は地下水に注入し、この過硫酸塩が加温されることで硫酸ラジカルを発生させる。そして、この硫酸ラジカルによって１，４−ジオキサンが分解される。 The "method for purifying contaminated soil and groundwater" of the present invention is a method for purifying soil and groundwater contaminated with 1,4-dioxane, and is a method including a soil heating step and an injection step. In the soil heating step, the soil and groundwater are heated by Joule heat by applying (applying a voltage) to three or more electrode wells constructed in the soil and passing an electric current through the soil. In the injection step, persulfate dissolved in room temperature water is injected into heated soil or groundwater, and the persulfate is heated to generate sulfuric acid radicals. Then, 1,4-dioxane is decomposed by this sulfuric acid radical.
本願発明の「汚染土壌と地下水の浄化方法」は、土壌加温工程において土壌又は地下水を４０〜５０℃に加温する方法とすることもできる。 The "method for purifying contaminated soil and groundwater" of the present invention can also be a method for heating soil or groundwater to 40 to 50 ° C. in the soil heating step.
本願発明の「汚染土壌と地下水の浄化方法」は、注入工程において薬剤（常温水に溶解した過硫酸塩）を帯水層に向けて注入する方法とすることもできる。 The "method for purifying contaminated soil and groundwater" of the present invention can also be a method of injecting a chemical (persulfate dissolved in room temperature water) toward the aquifer in the injection step.
本願発明の「汚染土壌と地下水の浄化方法」には、次のような効果がある。
（１）揚水を伴わないことから揚水処理が難しい場所でも幅広く採用でき、鉄触媒の添加を必要としないことから従来の酸化剤注入方法よりも手間とコストを軽減することができる。
（２）電気発熱法（ジュール熱により土壌自体を発熱させる方法）を用いることから、継続して土壌等を加温することができ、常温の薬剤を注入しても土壌等の中高温（例えば４０〜５０℃）状態を維持することができる。
（３）常温で溶解できる、すなわち薬剤自体を暖める必要がないことから、過硫酸塩のロスを低減することができる。
（４）目標とする土壌等の温度は中高温（例えば４０〜５０℃）程度でよいため、他の加温方法（例えば、スチームやヒーター）と比べエネルギーの消費量を抑えることができる。
（５）過硫酸塩注入後も加温が可能である（特に過硫酸塩がイオン化するため電気も流れやすくなる）ことから、他の酸化剤よりも効果の持続期間が長い過硫酸の特徴を生かすことができる。
（６）加温することによって反応性も高まることから、常温で実施するより薬剤量を削減することができる。
The "method for purifying contaminated soil and groundwater" of the present invention has the following effects.
(1) Since it does not involve pumping, it can be widely used even in places where pumping treatment is difficult, and since it does not require the addition of an iron catalyst, labor and cost can be reduced as compared with the conventional oxidizing agent injection method.
(2) Since the electric heat generation method (a method of heating the soil itself by Joule heat) is used, the soil can be continuously heated, and even if a chemical at room temperature is injected, the soil or the like is medium-high temperature (for example). The state of 40 to 50 ° C.) can be maintained.
(3) Since it can be dissolved at room temperature, that is, it is not necessary to warm the drug itself, the loss of persulfate can be reduced.
(4) Since the target temperature of the soil or the like may be about medium to high temperature (for example, 40 to 50 ° C.), energy consumption can be suppressed as compared with other heating methods (for example, steam or heater).
(5) Since it is possible to heat even after injecting persulfate (especially because persulfate is ionized, electricity easily flows), the characteristic of persulfate is that the duration of effect is longer than that of other oxidizing agents. You can make use of it.
(6) Since the reactivity is also increased by heating, the amount of the drug can be reduced as compared with the case of carrying out at room temperature.
本願発明の「汚染土壌と地下水の浄化方法」の実施形態の一例を、図１に示すフロー図を参照しながら説明する。本願発明は、あらかじめ土壌と地下水を加温し、加温状態の土壌や地下水に過硫酸塩を注入することを一つの特徴としている。そこで大きく２段階に分けて、すなわち土壌と地下水を加温する段階と、過硫酸塩を注入する段階とに分けて説明する。 An example of the embodiment of the "method for purifying contaminated soil and groundwater" of the present invention will be described with reference to the flow chart shown in FIG. One of the features of the present invention is that the soil and groundwater are preheated and persulfate is injected into the heated soil and groundwater. Therefore, the description will be roughly divided into two stages, that is, a stage of heating the soil and groundwater and a stage of injecting persulfate.
１．電気発熱法による加温
本願発明の場合、土壌と地下水を加温する手法としては、加温にかかる設備規模を軽減できる、容易に温度調整できる、土壌自体を発熱するため熱容量が高く温度が低下しにくい、といった理由から電気発熱法が適している。以下、電気発熱法による加温について説明する。
1. 1. Heating by electric heat generation method In the case of the present invention, as a method of heating soil and groundwater, the scale of equipment required for heating can be reduced, the temperature can be easily adjusted, and the heat capacity is high and the temperature drops because the soil itself generates heat. The electric heat generation method is suitable because it is difficult to do. Hereinafter, heating by the electric heat generation method will be described.
浄化対象となる土壌内に３以上の電極井戸を設置する（Ｓｔｅｐ１０）。図２は、複数（この図では３つ）の電極井戸１０を示す断面図である。この電極井戸１０は鋼製のケーシングで形成されており、したがって図２に示すように各電極井戸１０のケーシングを電源装置２０に接続することで、電極井戸１０間に電流が流れ、途中の土壌にジュール熱を発生させることができる。そのため各電極井戸１０は、対象となる土壌を取り囲むように配置するとよく、例えば図３に示すように三角形を形成するように配置することができる。なお図３に示す４つの三角形はそれぞれ一辺が約３．５ｍの正三角形となっているが、もちろんこれに限らず種々の形状となるよう電極井戸１０を配置することができる。
Three or more electrode wells are installed in the soil to be purified (Step 10). FIG. 2 is a cross-sectional view showing a plurality of (three in this figure)
電極井戸１０が設置できると、上記したとおり電源装置２０を利用して電極井戸１０に印加する（Ｓｔｅｐ２０）。印加された電極井戸１０間には電流が流れ、電極井戸１０間にある土壌にジュール熱が発生し、これに伴って土壌や地下水の温度が上昇していく。このとき、土壌や地下水があらかじめ設定した温度となるよう、印加する電圧の大きさを調整するとよい。
When the electrode well 10 can be installed, it is applied to the electrode well 10 by using the
ところで本願発明の発明者は、鉄塩等の触媒がなくても過硫酸塩から硫酸ラジカルを発生させる手法を模索した結果、加熱することで硫酸ラジカルが発生することを見出した。具体的には、土壌や地下水を適当な温度に加温した条件で、溶解した過硫酸塩を注入すると、過硫酸塩が熱活性して硫酸ラジカルが発生することを確認している。つまり、鉄触媒に代えて加熱することで、硫酸ラジカルの発生を促進するわけである。さらに本願発明の発明者は、土壌や地下水の温度が中高温となった状況で硫酸ラジカルの発生が促進され、特に４０〜５０℃となった土壌や地下水に過硫酸塩を注入すると硫酸ラジカルが発生しやすいことを確認している。 By the way, as a result of searching for a method for generating sulfuric acid radicals from persulfate without a catalyst such as an iron salt, the inventor of the present invention has found that sulfuric acid radicals are generated by heating. Specifically, it has been confirmed that when dissolved persulfate is injected under the condition that soil or groundwater is heated to an appropriate temperature, the persulfate is thermally activated to generate sulfuric acid radicals. That is, by heating instead of the iron catalyst, the generation of sulfuric acid radicals is promoted. Furthermore, the inventor of the present invention promotes the generation of sulfuric acid radicals when the temperature of soil or groundwater is medium or high, and in particular, when persulfate is injected into soil or groundwater at 40 to 50 ° C., sulfuric acid radicals are generated. We have confirmed that it is likely to occur.
つまり土壌や地下水の温度を上げる目的は、硫酸ラジカルが発生し得る環境をつくることである。そのため、土壌や地下水の温度が中高温（特に、４０〜５０℃）になるまで上昇するように、電圧を調整したうえで各電極井戸１０に印加するとよい。なお、加温された土壌や地下水の現実の温度は、予測された（あるいは解析された）温度とは異なることも十分考えられるため、実際の温度を観測しながら（Ｓｔｅｐ３０）電極井戸１０に印加していくこともできる。この場合、図３に示すように各電極井戸１０の間に温度観測井戸３０を構築しておき、この温度観測井戸３０を利用して土壌や地下水の温度を観測するとよい。
In other words, the purpose of raising the temperature of soil and groundwater is to create an environment in which sulfuric acid radicals can be generated. Therefore, it is advisable to apply the voltage to each electrode well 10 after adjusting the voltage so that the temperature of the soil or groundwater rises to a medium high temperature (particularly 40 to 50 ° C.). Since it is quite possible that the actual temperature of the heated soil or groundwater is different from the predicted (or analyzed) temperature, it is applied to the electrode well 10 while observing the actual temperature (Step 30). You can also do it. In this case, as shown in FIG. 3, a temperature observation well 30 may be constructed between the
２．薬剤の注入
電極井戸１０に印加する一方で、土壌や地下水に注入する薬剤を調整する（Ｓｔｅｐ４０）。薬剤とは、常温（１５〜２５℃）の水に過硫酸塩を溶解したものであり、ここで用いる過硫酸塩としては過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウムなどが例示できる。なお、過硫酸塩を溶解させる水を常温とする理由は、過硫酸塩は常温では熱活性しないことから常温水に溶解することで土壌や地下水に到達する前に硫酸ラジカルが発生することを防止できるからであり、換言すると常温水に溶解することで過硫酸塩の状態のまま土壌や地下水に送ることができるからである。
2. 2. Injection of chemicals While applying to the electrode well 10, the chemicals to be injected into soil and groundwater are adjusted (Step 40). The drug is prepared by dissolving persulfate in water at room temperature (15 to 25 ° C.), and examples of the persulfate used here include sodium persulfate, potassium persulfate, and ammonium persulfate. The reason why the water in which persulfate is dissolved is set to room temperature is that persulfate is not thermally active at room temperature, so dissolving it in room temperature water prevents the generation of sulfate radicals before it reaches soil or groundwater. This is because it can be done, in other words, by dissolving it in room temperature water, it can be sent to soil or groundwater in the state of persulfate.
土壌や地下水が目的の温度（中高温）になったことを確認したうえで（Ｓｔｅｐ３０）薬剤の調整を行い（Ｓｔｅｐ４０）、土壌や地下水に薬剤を注入していく（Ｓｔｅｐ５０）。このとき、図３に示すように、対象となる土壌内に構築した注入井戸４０を利用することができる。具体的には、ポンプ等の圧送手段を用いて貯留槽から薬剤を圧送し、注入井戸４０から土壌や地下水に対して薬剤を注入していく。あるいは注入井戸４０に代えて、電極井戸１０を利用して薬剤を注入してもよい。 After confirming that the soil and groundwater have reached the target temperature (medium and high temperature) (Step 30), the chemicals are adjusted (Step 40), and the chemicals are injected into the soil and groundwater (Step 50). At this time, as shown in FIG. 3, the injection well 40 constructed in the target soil can be used. Specifically, the chemicals are pumped from the storage tank using a pumping means such as a pump, and the chemicals are injected from the injection well 40 into the soil or groundwater. Alternatively, the drug may be injected using the electrode well 10 instead of the injection well 40.
１，４−ジオキサンは水に溶け易い性質があることから、地下水に多く存在することが考えられる。したがって薬剤の注入は、地下水を含む土層を選んで行うとよい。図４は、帯水層に向けて薬剤が注入される状況を示す断面図である。帯水層は透水性が高いことから地下水を多く含んでおり、すなわち多くの１，４−ジオキサンが存在していることから、この帯水層を選んで薬剤を注入すると効果的となる。もちろん、土層を選ぶことなく全体的に薬剤を注入してもよい。 Since 1,4-dioxane has the property of being easily dissolved in water, it is considered that it is abundant in groundwater. Therefore, it is advisable to select a soil layer containing groundwater for injecting the drug. FIG. 4 is a cross-sectional view showing a situation in which the drug is injected toward the aquifer. Since the aquifer has high permeability, it contains a large amount of groundwater, that is, a large amount of 1,4-dioxane is present. Therefore, it is effective to select this aquifer and inject a drug. Of course, the drug may be injected as a whole without selecting the soil layer.
土壌や地下水は中高温が保たれていることから、土壌や地下水に到達した薬剤は徐々に温度を上げて中高温となり、その結果、過硫酸塩が熱活性して硫酸ラジカルが発生する（Ｓｔｅｐ６０）。そして、この硫酸ラジカルによって１，４−ジオキサンが分解していく（Ｓｔｅｐ７０）。あらかじめ設定した時間だけ薬剤の注入を続けた後、薬剤注入を停止し、電極井戸１０への引加も停止する（Ｓｔｅｐ８０）。 Since the soil and groundwater are maintained at medium and high temperatures, the chemicals that reach the soil and groundwater gradually increase in temperature to medium and high temperatures, and as a result, persulfate is thermally activated to generate sulfuric acid radicals (Step 60). ). Then, 1,4-dioxane is decomposed by this sulfuric acid radical (Step 70). After continuing the injection of the drug for a preset time, the injection of the drug is stopped, and the attraction to the electrode well 10 is also stopped (Step 80).
本願発明の「汚染土壌と地下水の浄化方法」は、１，４−ジオキサンが使用され、排出され、あるいは副生成される操業地（又は操業跡地）で利用することができる。本願発明が、我が国の環境改善にとって極めて有益であることを考えれば、産業上利用できるばかりでなく社会的にも大きな貢献が期待できる発明といえる。 The "method for purifying contaminated soil and groundwater" of the present invention can be used in an operation site (or an operation site) where 1,4-dioxane is used, discharged, or by-produced. Considering that the invention of the present application is extremely beneficial for improving the environment in Japan, it can be said that the invention can be used not only industrially but also can be expected to make a great contribution to society.
１０ 電極井戸
２０ 電源装置
３０ 温度観測井戸
４０ 注入井戸
10 Electrode well 20
Claims (3)
土壌内に構築された３以上の電極井戸に印加し、土壌に電流を流すことによって、土壌と地下水を加温する土壌加温工程と、
土壌又は地下水が目的の中高温になったことを確認したうえで、触媒を用いることなく常温水に溶解した過硫酸塩のみを、加温された状態の土壌又は地下水に注入し、該過硫酸塩が加温されることで硫酸ラジカルを発生させる注入工程と、を備え、
前記硫酸ラジカルによって１，４−ジオキサンを分解する、ことを特徴とする汚染土壌と地下水の浄化方法。 In a purification method that purifies soil and groundwater contaminated with 1,4-dioxane,
A soil heating process that heats the soil and groundwater by applying an electric current to three or more electrode wells constructed in the soil and passing an electric current through the soil.
After confirming that the soil or groundwater has reached the target medium and high temperature, only persulfate dissolved in room temperature water without using a catalyst is injected into the warmed soil or groundwater, and the persulfate is injected. It is equipped with an injection step that generates sulfuric acid radicals by heating the salt.
A method for purifying contaminated soil and groundwater, which comprises decomposing 1,4-dioxane by the sulfuric acid radical.
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