JP2007268401A - In-situ cleaning method and in-situ cleaning system of contaminated soil and/or ground water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an in-situ cleaning method of a contaminated soil and/or a ground water which can prevent a decrease in activity of an oil decomposition microbe in bio-treatment and diminish the cleaning term. <P>SOLUTION: The in-situ cleaning method of the contaminated soil and/or the ground water adds in-situ a nutrient salt water to the contaminated soil and/or the ground water, wherein this method has a step for pumping water from the contaminated soil and/or the ground water by a pumping well and measuring pH of the ground water pumped by the pumping well and a step for injecting a pH adjusting agent into the contaminated soil and/or the ground water when pH of the ground water is the value determined beforehand or below. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention introduces bioremediation that purifies oil-contaminated soil and / or groundwater contaminated with oil in the field by biodegradation, and is preferably used to purify and repair oil-contaminated soil and / or groundwater. The present invention relates to an in-situ purification method and system for soil and / or groundwater.

In recent years, problems such as contamination of soil and groundwater due to oil leaks have occurred in factories and ruins of gasoline stations, and this problem has become serious.
The underground layer of oil-contaminated sites consists of a saturated layer, an unsaturated layer above it, and an aquifer below the unsaturated layer. The aquifer and unsaturated layer are contaminated with waste oil and other contaminants. include. Contaminants present in such a state are undiluted solution or adsorbed by organic matter in clay and soil, so the aquifer and unsaturated layer pollutants generate oily odor and oil film. Problems can occur and harmful substances in oil can contaminate groundwater. Therefore, it is necessary to purify soil contaminated with oil.

  As a conventional method for purifying contaminated soil / ground water, excavating soil containing oil as a pollutant, purifying it by washing, heat treatment, aeration, etc., and then refilling it Is mentioned. However, in order to perform such processing, there is a problem that it is necessary to secure a large-scale facility and a large site for that purpose, and cost is high. In addition, when there is a pollutant at a deep position, there is a problem that a great amount of labor and time are required for the excavation work.

In order to solve such problems, an in-situ purification method has been proposed as a method for purifying contaminated soil and / or groundwater that can be purified in situ without excavating contaminated soil / groundwater. . For example, Patent Document 1 discloses a method of performing biotreatment in situ after washing contaminated soil in situ. In Patent Document 1, when biotreatment is performed, the pH of the soil to be purified may change to acidic or alkaline. When the contaminated soil changes to acidic, the aqueous sodium hydroxide solution changes to phosphoric acid when the soil changes to alkaline. An in-situ purification method for contaminated soil that supplies an aqueous solution to the contaminated soil is disclosed.
However, there is no description about how acidic the pH adjuster is added when it becomes acidic, and there is a problem that the activity of the oil-degrading microorganisms during bioprocessing is reduced.

JP 2004-298830 A

  As described above, according to the in-situ purification method of contaminated soil described in Patent Document 1, it is not possible to prevent a decrease in the activity of oil-degrading microorganisms during bioprocessing, and purification takes a long time. End up. Accordingly, an object of the present invention is to provide an in-situ purification method and a purification system for contaminated soil and / or groundwater, which can prevent a decrease in the activity of oil-degrading microorganisms during bioprocessing and can shorten the purification period. It is to provide.

In order to achieve the above object, as a result of intensive studies, the present inventors measured the pH of the pumped water from the pumping well, and injected a pH adjusting agent when the pH was below a specific value. By doing so, the knowledge that the said objective can be achieved was acquired.
The present invention has been made based on the above knowledge, and is a method for purifying contaminated soil and / or groundwater by adding nutrient salt water to the contaminated soil and / or groundwater in situ. A step of measuring the pH of groundwater pumped from a soil and / or groundwater by a pumping well, and pumping the groundwater, and if the pH of the groundwater is equal to or lower than a preset value, the contaminated soil and / or groundwater The present invention provides an in-situ purification method for contaminated soil and / or groundwater, which includes a step of injecting a pH adjusting agent.

  The present invention also includes a gas and / or liquid injection well for injecting gas and / or liquid into the soil, and a pumping well installed in the ground for pumping up water in the groundwater or soil. An in-situ purification system for contaminated soil and / or groundwater, wherein the pumping well is provided with pH measuring means for measuring the pH of the pumped liquid, and the gas and / or liquid injection well has a pH Provided is an in-situ purification system for contaminated soil and / or groundwater to which a conditioning agent is supplied, to which a pH conditioning agent supply means is connected.

According to the in-situ purification method of contaminated soil and / or groundwater of the present invention, it is possible to prevent a decrease in the activity of oil-degrading microorganisms during bioprocessing, and to shorten the purification period.
Moreover, according to the in-situ purification system for contaminated soil and / or groundwater of the present invention, the in-situ purification method can prevent the decrease in the activity of oil-degrading microorganisms during bioprocessing and can shorten the purification period. Can be implemented.

Hereinafter, the in-situ purification method for contaminated soil and / or groundwater of the present invention will be described.
The in-situ purification method for contaminated soil and / or groundwater of the present invention is a method for purifying contaminated soil and / or groundwater by adding nutrient salt water to the contaminated soil and / or groundwater in situ. A step of measuring the pH of groundwater pumped from a soil and / or groundwater by a pumping well, and pumping the groundwater, and if the pH of the groundwater is equal to or lower than a preset value, the contaminated soil and / or groundwater a step of injecting a pH adjusting agent.

  The in-situ purification method for contaminated soil and / or groundwater of the present invention is to add nutrient salt water in situ to soil and / or groundwater contaminated with oil. The in-situ purification method for contaminated soil and / or groundwater of the present invention will be described as purifying soil and / or groundwater contaminated with oil. However, the present invention is not limited to soil and / or groundwater contaminated with oil. It is not limited to purification. The soil and / or groundwater contaminated with oil means soil and / or groundwater contaminated with hydrocarbon compounds such as crude oil, gasoline, light oil, heavy oil, and engine oil. It can be used as a method for carrying out bioremediation in / or groundwater. That is, this bioremediation activates indigenous microorganisms, i.e., provides nutrients to microorganisms that have the ability to decompose oil that inhabit contaminated soil and / or groundwater, and propagates and activates them. A method for promoting degradation (biostimulation) and introducing foreign microorganisms, that is, injecting microorganisms that have grown and activated in large quantities externally and have the ability to degrade oil into contaminated soil and / or groundwater. Includes both methods of purification (bioaugmentation).

  In order to carry out the bioremediation described above, there are a case where the treatment is performed in an aerobic atmosphere using an aerobic microorganism and a case where the treatment is performed in an anaerobic atmosphere using an anaerobic microorganism. Any of these may be used. Examples of the nutrient substance for growing and activating the microorganism include nutrient sources such as nitrogen and phosphorus. That is, the nutrient salt water added in the present invention includes the above-described nitrogen, phosphorus and the like.

  According to the present invention, the nutrient salt water is injected into the contaminated soil and / or groundwater, so that even when there are few oil-decomposing microorganisms in the soil and / or groundwater, the growth is promoted, and even when there are no microorganisms, Purification is promoted by injecting microorganisms that have grown and activated in large quantities. In addition, conventionally known microorganisms can be used as microorganisms injected from the outside and capable of decomposing oil, and examples include Rhodococcus bacteria, Pseudomonas bacteria, Acinetobacter bacteria, and the like.

  In addition, when the microorganisms which have the capability to decompose | disassemble oil are aerobic microorganisms, it is preferable to implement this invention, inject | pouring air (oxygen). The injection of air (oxygen) can be performed by, for example, an air compressor. The injection amount of air (oxygen) varies depending on conditions such as soil quality, treatment method, and contaminants, but is, for example, about 100 to 300 L / min.

  By injecting air (oxygen) and nutrient water into soil and / or groundwater, oxygen and nutrient water are supplied to the soil and / or groundwater, and the ability to decompose oil inhabiting the soil and / or groundwater. Microorganisms possessed are activated and oil is decomposed.

  The in-situ soil and / or groundwater purification method of the present invention includes a step of pumping up contaminated soil and / or groundwater by a pumping well and measuring the pH of the groundwater pumped up by the pumping well. The pH can be measured by sampling the groundwater pumped up by the pumping well and measuring it with a pH sensor. In the present invention, it is preferable to continuously and automatically measure the pH.

  Next, it is determined whether the pH measured as described above is equal to or lower than a preset value. If the pH is equal to or lower than a preset value, a pH adjuster is added to the contaminated soil and / or groundwater. inject. The preset value means a value within a range where microorganisms capable of decomposing oil do not grow and reduce oil resolution, and when this value falls below this value, it has the ability to decompose oil. It is a value that reduces the growth of microorganisms and the oil resolution. Specifically, it is 6.0 or less, preferably 6.5 or less.

  Next, when the pH of the groundwater pumped up by the pumping well is not more than a preset value, a pH adjusting agent is injected into the contaminated soil and / or the groundwater. Examples of the pH adjuster include an alkali agent, and examples of the alkali agent include a sodium hydroxide aqueous solution, a sodium hydrogen carbonate aqueous solution, and a sodium carbonate aqueous solution. The concentration of the aqueous solution of the alkali agent is not particularly limited, but can be, for example, about 0.1 to 10% by mass. Thus, when the pH of the groundwater pumped from the pumping well is lower than a preset value, the microorganism has the ability to decompose oil by making the pH near neutral with a pH adjuster. Is activated and oil degradation is activated, thereby shortening the purification period.

  In this way, when the pH of groundwater falls below a preset value, the pH adjuster can prevent the pH from becoming lower than the preset value, so the ability to decompose oil The growth of microorganisms and the activation of the oil decomposability continue, which makes it possible to shorten the purification period of soil and groundwater.

On the contrary, if the pH becomes larger than a certain value, the growth of microorganisms is reduced. Therefore, care must be taken not to be on the alkaline side when injecting the pH adjusting agent. Therefore, while measuring the pH, the injection of the pH adjusting agent is stopped when a certain value is reached.
In addition, the in-situ purification method of this invention can be implemented by the in-situ purification system of this invention mentioned later.

Next, the in-situ purification system for contaminated soil and / or groundwater of the present invention will be described with reference to the drawings.
FIG. 1 is a side view schematically showing an in-situ purification system 10 for contaminated soil and / or groundwater according to the present invention. The in-situ purification system 10 for contaminated soil and / or groundwater according to the present invention is mainly a gas. And / or liquid injection wells 12, 12 ′, pumping well 14, and pH measuring means 16.

In the in-situ purification system 10 of contaminated soil and / or groundwater of the present invention shown in FIG. 1, gas and / or the ground of the basin where the contaminated soil and / or groundwater exists (hereinafter also referred to as “target region”). Alternatively, two liquid injection wells 12 are provided. In the contaminated soil and / or groundwater in-situ purification system 10 shown in FIG. 1, the gas and / or liquid injection well includes injection wells 12 and 12 ′ for injecting gas and an injection well for injecting liquid. However, the present invention is not limited to such a form, and a gas and a liquid may be injected through one injection well.
Moreover, in the in-situ purification system 10 of the contaminated soil and / or groundwater shown in FIG. 1, one pumping well 14 is provided.

  The air supply pipe 22 of the air supply means means 20 is connected to the upper end of the injection well 12 for injecting the gas described above. The air supply unit 20 includes an air compressor 24 and an air supply pipe 22, and is a means for supplying air compressed by the air compressor 24 to the injection well 12 through the air supply pipe 22. Although not shown, a valve, a flow meter, and a pressure gauge for adjusting the amount of supplied air are disposed at predetermined positions of the air supply pipe 22.

  A water supply pipe 32 of the liquid supply means 30 is connected to the upper end of the injection well 12 ′ for injecting liquid. The liquid supply means 30 includes a liquid storage tank 34 and a water supply pipe 32, and a pump 36 for supplying liquid is provided at a predetermined position of the water supply pipe 32. Although not shown, the water supply pipe 32 is provided with a valve and a water meter for adjusting the amount of liquid to be supplied. The liquid storage tank 34 stores a pH adjusting agent or nutrient water. This liquid supply means 30 also functions as a pH adjusting agent supply means. That is, as will be described below, after the pH of the groundwater is measured by the pH sensor 16, the pH adjusting agent is supplied to the soil when the pH is not more than a preset value.

  The pumping well 14 is a well for pumping up contaminated groundwater or groundwater contained in contaminated soil (hereinafter also simply referred to as “polluted groundwater”). In the embodiment shown in FIG. Yes. The pumping well 14 is formed by piping a steel perforated pipe in the ground, and is a pump (not shown) arranged on the ground to pump up contaminated groundwater flowing into the pumping well 14. A water pipe 17 connected to the pump is connected to the upper end of the pumping well 14. In addition, a pH sensor 16 serving as a pH measuring unit is disposed at a predetermined position of the water supply pipe 17. When the pH of the groundwater is measured by the pH sensor 16 and the pH is equal to or lower than a preset value, the liquid supply means 30 injects a pH adjusting agent into the soil. In the system shown in FIG. 1, as a means for supplying the pH adjusting agent, the liquid supplying means 30 is used and the pH adjusting agent is supplied through the same route as the nutrient salt water, but the present invention is not limited to this. In addition to the liquid supply means 30, a means for supplying a pH adjusting agent may be provided.

  The lower end of the pumping well 14 reaches the vicinity of the unsaturated layer. In the above description, the pumping well 14 has been described as piped with a steel perforated pipe, but is not limited to this, and inflow of contaminated groundwater into the pumping well is possible. Any structure may be used as long as it is not deformed by earth pressure.

  Further, in the embodiment shown in FIG. 1, a sheet pile may be disposed as a water shielding wall so as to surround the entire periphery of the area where the contaminated groundwater is purified. In this way, by arranging the sheet pile, it is possible to prevent the inflow of groundwater to the area, and to prevent the outflow of contaminated groundwater from the area, outside the area of air or liquid injected into the soil. Can be prevented, and the impact on the surrounding area can be prevented. In addition, as a water-impervious wall, it is not limited to a sheet pile, The member excellent in water-stopping can be selected suitably and can be used.

Next, a method for purifying soil and / or groundwater using the soil and / or groundwater in-situ purification system of the present invention will be described with reference to FIG.
First, the air compressor 24 and a pump (not shown) are operated to inject air into the contaminated soil region from the gas and / or liquid injection well 12. On the other hand, the pump 36 is operated to supply the nutrient water stored in the liquid storage tank 34 filled with the nutrient water to the contaminated soil region from the gas and / or liquid injection well 12 '. inject.

At this time, the injection amount of air can be set to, for example, about 100 to 300 L / min. Further, the amount of nutrient water injected into the soil may be an amount that is about 1/200 to 1/10 of the amount of air that is injected from the gas and / or liquid injection well 12. It is preferable that the C, N, P ratio in the nutrient salt water is 100: 10: 1.
The air compressed by the air compressor 24 is supplied through the air supply pipe 22 while the amount thereof is adjusted by a valve (not shown) while being confirmed by a flow meter and a pressure gauge (not shown). The air supplied to the gas and / or liquid injection well 12 is injected into the soil from the lower end of the gas and / or liquid injection well 12.

  Further, the nutrient water stored in the liquid storage tank 34 is supplied through the water supply pipe 32 while being adjusted by a valve (not shown) while checking the amount of the nutrient water with a water meter (not shown). The nutrient water supplied to the gas and / or liquid injection well 12 'is injected into the soil from the lower end of the gas and / or liquid injection well 12'. The nutrient water may be injected only when necessary, and an alkaline agent that is a pH adjusting agent is stored in the liquid storage tank 34 except when necessary. Moreover, although not shown in FIG. 1, the water supply pipe | tube 32 may be branched on the way, the liquid storage tank 34 may be installed in both ends, you may make it store a nutrient salt water in one side and an alkali chemicals in the other.

  By supplying air and nutrient salt water to the soil, microorganisms living in the soil and capable of decomposing oil are activated, and the pollutant oil is decomposed. If only the microorganisms present in the soil do not decompose the oil sufficiently, the ability to decompose the oil may be injected separately. Examples of such microorganisms include those described above, and the injection method may be, for example, mixing microorganisms in nutrient salt water and injecting them together with nutrient salt water, or preparing another liquid storage tank. You may inject | pour by putting the microorganisms suspended in the culture medium into the liquid storage tank, and operating a pump.

  In addition, since the air supplied in the soil from the lower end part of the gas and / or liquid injection well 12 rises upward while being diffused in the soil, the air is supplied to the entire target region.

  Further, the groundwater contained in the contaminated groundwater or the contaminated soil is pumped from the pumping well 14 by operating a pump (not shown) and pumped up by the water pipe 17. For example, the pumped water may be sent to a water treatment device and purified by the water treatment device. Then, the purified water purified by this water treatment device may be sent to the liquid storage tank 34 and injected into the soil again. In addition, you may discard the water pumped up by the pumping well as it is appropriately processed. In this case, rivers or tap water may be used as water for injecting into the soil and / or groundwater.

  In the contaminated soil and / or groundwater purification system of the present invention, pH measuring means (pH sensor) 16 for measuring the pH of the groundwater pumped up from the pumping well 14 is arranged at a predetermined position of the water pipe 17. It is installed. The water pumped up from the pumping well 14 is measured by the pH sensor 16, and when the pH is equal to or lower than a preset value, the control device is activated and the pump 36 is activated, whereby the liquid storage tank 34 is injected into the gas and / or liquid injection well 12 ', and the pH adjuster is injected into the soil from the lower end of the gas and / or liquid injection well 12'. Change the pH of groundwater. Specifically, it is preferable that the control device operates when the pH of the groundwater pumped from the pumping well 14 becomes 6.0 or less. That is, the pH adjuster is preferably an alkali agent, and examples of such an alkali agent include those described above. On the other hand, if the amount of the alkaline agent is too large, the pH of the groundwater becomes too alkaline, which is not preferable. Therefore, it is preferable to use a diluted alkaline agent, and the injection amount may be small. When the pH of the groundwater pumped from the pumping well 14 reaches near neutral (preferably near pH 7.0), the control device is activated, the pump 36 is stopped, and the injection of the pH adjusting agent is stopped. The

  As described above, in the contaminated soil and / or groundwater purification system, since the pH of the groundwater is always near neutral, the activity of microorganisms does not decrease, the oil decomposition activity does not decrease, and the purification period is shortened. Is possible.

  Note that the number and interval of the gas and / or liquid injection wells 12 and 12 ′ are appropriately determined depending on the amount of air and nutrient water to be injected, the contaminated soil, and the contaminated groundwater. In addition, the amount of nutrient water that is injected into the soil relative to the amount of water that is pumped from the soil and / or groundwater can be adjusted as appropriate according to the local contamination status.

  In the contaminated soil and / or groundwater purification system shown in FIG. 1, it is exemplified as performing purification in an aquifer. However, the contaminated soil and / or groundwater purification system of the present invention is a saturated layer or unsaturated layer having a pollution source. In this case, it is possible to actively circulate water to the saturated layer or unsaturated layer, and to activate microorganisms and promote oil decomposition by supplying air. .

Hereinafter, the result of conducting a demonstration experiment related to the present invention will be described in Examples.
Example 1
The culture medium shown in Table 1 was prepared, and 100 mL of the obtained culture medium was put into a 500 mL baffled flask. Next, kerosene decomposition aggregates (derived from crude oil-contaminated soil) were planted in a flask with baffles to a concentration of 5% as a seeding source. Subsequently, 1 mL of kerosene was added to the flask, and the culture was performed at a temperature of 30 ° C. with shaking at 120 rpm. The pH of the culture solution was measured every 24 hours, and when the pH was 6 or less, 1N sodium hydroxide solution was added to adjust the pH to about 7.0, and the culture was performed.

The evaluation results performed in this example are as follows.
(1) Observation of oily odor and oil film Although there are no clear standards for oily odor and oil film, according to the Oil Pollution Countermeasure Guidelines (draft) prepared by the Ministry of the Environment and currently seeking public comments, Is recommended to be evaluated in five levels according to the intensity of odor. In addition, it is recommended to evaluate in two stages whether or not there is an oil film. In this example, both the oily odor and the oil film were evaluated with five levels by observing the smell of the culture solution or observing with the naked eye. The oily odor and the oil film were evaluated as 5 when the odor was strong and the oil film was large, and 1 when the odor was weak and there was no oil film.

(2) Bacterial measurement Transfer 1 mL of the culture solution to an Eppendorf tube, dilute to about 1 × 10 ⁴ to 1 × 10 ^{7 with} 0.86% physiological saline, and add 100 μL of the diluted solution to the R2A medium (composition: water). per 1L, peptone 0.5g, yeast extract 0.5g, casamino acid 0.5g, glucose 0.5g, soluble starch 0.5g, potassium monohydrogen phosphate 0.3 g, magnesium sulfate _(7H 2 O) 0.05g And sodium pyruvate (0.3 g, agar 15 g), followed by stationary culture at 30 ° C. for 1 week, and the number of colonies was measured after 1 week.

Comparative Example 1
Culturing was performed in the same manner as in Example 1 except that the pH was not adjusted.
Comparative Example 2
When the pH of the medium initially becomes 6 or less, 1N sodium hydroxide aqueous solution is added to bring the pH of the medium to about 7.0. Thereafter, even if the pH becomes 6 or less, 1N sodium hydroxide aqueous solution is not added. The culture was performed in the same manner as in Example 1 except that the culture was performed in the same manner as in Example 1.

Example 2
Incubation was carried out in the same manner as in Example 1 except that 500 mL of heavy oil A was added instead of 1 mL of kerosene.
Comparative Example 3
The culture was performed in the same manner as in Comparative Example 1 except that 1 mL of kerosene was added and 500 μL of A heavy oil was added.
Comparative Example 4
Culture was performed in the same manner as in Comparative Example 2 except that 500 mL of A heavy oil was added instead of 1 mL of kerosene.

  The graph which shows the change of the pH of the culture medium in the culture | cultivation of Example 1, the comparative example 1, and the comparative example 2 is shown in FIG. In FIG. 2, the horizontal axis represents the number of culture days, and the vertical axis represents pH. As shown in FIG. 2, the pH became 6 or less in all of Example 1, Comparative Example 1 and Comparative Example 2 after 1 day of culture. In Example 1 and Comparative Example 2, the pH was adjusted, and after 2 days of culture, the pH in all of Example 1, Comparative Example 1 and Comparative Example 2 was 5 or less, so only Example 1 was adjusted in pH. It was. After that, although there was a slight change in pH, in Example 1, the pH was always 6 or more, and in Comparative Example 1 and Comparative Example 2, the pH was always about 5.

A graph showing the bacterial count measurement results in the cultures of Example 1, Comparative Example 1 and Comparative Example 2 is shown in FIG. As apparent from FIG. 3, the number of bacteria increased significantly in all of Example 1, Comparative Example 1 and Comparative Example 2 after 2 days of culture. After 3 days of culture, it increased to 8.5 × 10 ⁸ CFU / mL in Example 1, whereas it was 2.9 × 10 ⁸ CFU / mL in Comparative Example 1, and 4.5 in Comparative Example 2. × 10 ⁸ CFU / mL. Thereafter, no increase in the number of bacteria was observed in all of Example 1, Comparative Example 1 and Comparative Example 2. Even after 7 days from the start of culture, the number of bacteria was the highest in Example 1, followed by Comparative Example 2 and Comparative Example 1.

  The results of observation of oily odor and oil film are shown in Table 2. The observation of oily odor and oil film was performed before the start of culture, 1 day after the start, 2 days, 3 days, 4 days, 6 days and 7 days.

As is clear from Table 2, in Example 1, the oily odor and oil film decreased significantly after 2 days from the start of the culture, and the oily odor and oil film decreased sufficiently after 7 days of culture. On the other hand, in Comparative Example 1 and Comparative Example 2, the oily odor and the oil film hardly decreased after the third day after the start of culture. This means that in Example 1, the decomposition of kerosene was promoted, but in Comparative Examples 1 and 2, the oil was not decomposed sufficiently.
In addition, as a result of oil concentration measurement by GC-FID 7 days after the start of the culture, it was 337 mg / L in Example 1, 899 mg / L in Comparative Example 1, and 833 mg / L in Comparative Example 2. It was. This result also means that in Example 1, the resolution of kerosene is superior to Comparative Example 1 and Comparative Example 2.

  The graph which shows the change of the pH of the culture medium in the culture | cultivation of Example 2, the comparative example 3, and the comparative example 4 is shown in FIG. In FIG. 4, the horizontal axis represents the number of culture days, and the vertical axis represents pH. As shown in FIG. 4, in all of Example 2, Comparative Example 3, and Comparative Example 4, the pH became 6 or less after one day of culture. In Example 2 and Comparative Example 4, the pH was adjusted, and after 2 days of culture, all of Example 2, Comparative Example 3 and Comparative Example 4 had a pH of 5 or less, so only Example 2 was adjusted for pH. It was. Thereafter, although there was a slight change in pH, in Example 2, the pH was always 6 or more, and in Comparative Examples 3 and 4, the pH was always about 4.

FIG. 5 shows a graph showing the results of bacterial count measurement in the cultures of Example 2, Comparative Example 3 and Comparative Example 4. As is apparent from FIG. 5, the number of bacteria increased to about 4 × 10 ⁸ CFU / mL in all of Example 2, Comparative Example 3 and Comparative Example 4 after 2 days of culture. After 7 days of culture, it increased to 1.2 × 10 ⁹ CFU / mL in Example 2, whereas it was 6.0 × 10 ⁷ CFU / mL in Comparative Example 3, and 1.2 in Comparative Example 4. × 10 ⁸ CFU / mL. Thereafter, no decrease in the number of bacteria was observed in Example 2 until 10 days after culturing, but the number of bacteria decreased in Comparative Examples 3 and 4. From this, it was found that when the pH was lowered to about 4, not only the ability of decomposing oil was decreased, but also the decomposing bacteria were killed.

  The results of observation of oily odor and oil film are shown in Table 3. The observation of the oily odor and oil film was performed before the start of culture, 1 day after start, 2 days later, 3 days later, 4 days later, 6 days later, 7 days later, 8 days later, 9 days later, 10 days later and 13 days later.

  As is apparent from Table 3, in Example 2, the oily odor and oil film decreased significantly after 3 days from the start of culture, and the oily odor and oil film decreased sufficiently after 13 days from the start of culture. In contrast, in Comparative Example 3, the decrease in oily odor and oil film was gradual after 3 days from the start of culture and in Comparative Example 4 after 6 days from the start of culture. From this result, it was found that when the pH was lowered to 4 or less, the degrading bacteria themselves were killed.

Example 3
After decomposing bacteria were killed due to a decrease in pH, it was examined whether or not the ability of oil decomposition activity was recovered by adjusting the pH again. The cultures of Example 1, Comparative Example 1 and Comparative Example 2 were cultured while adjusting the pH. For Example 1, the culture was continued from the start of the culture so that the pH of the medium was 6 or more. Comparative Example 1 started pH adjustment on the 13th day of culture start and Comparative Example 2 started on the 17th day of culture start Thereafter, in the same manner as in Example 1, when the pH became 6 or less, 1N aqueous sodium hydroxide solution was used and the medium was cultured at a pH of about 7.

The graph which shows the change of the pH of the culture medium in each culture | cultivation is shown in FIG. In FIG. 6, the horizontal axis represents the number of culture days, and the vertical axis represents pH.
Table 4 shows the observation results of oily odor and oil film in the cultures of Comparative Examples 1 and 2. The observation of the oily odor and the oil film was carried out 13 days, 14 days, 16 days, 17 days, 23 days, 27 days and 29 days after the start of the culture.

  As is clear from Table 4, it was found that oil odor and oil film were significantly reduced in Comparative Example 1 after 17 days from the start of culture and in Comparative Example 2 from the 23rd day of the start of culture. Therefore, it can be seen that the degradation activity of kerosene is restored by adjusting the pH to near neutral even after culturing at a low pH. However, it was found that Comparative Example 2 requires a longer period of time to reduce oily odor and oil film than Comparative Example 1.

  Oil is oxidized by the action of microorganisms and finally decomposed to carbon dioxide, but in the case of oils with high biodegradability such as fuel oil and lubricating oil, the decomposition of these fatty acids and organic acids becomes rate-limiting. Therefore, fatty acids and organic acids accumulate in the process, and the pH of oil-contaminated soil and / or groundwater decreases. When the pH is 5, the activity of microorganisms having oil-degrading ability is reduced, and when the pH is 4, microorganisms are killed. In the present invention, since the pH of oil-contaminated soil and / or groundwater can always be maintained at 6 or more, the activity of microorganisms having oil-decomposability can be maintained high, and the purification period can be shortened. .

It is a side view which shows the outline of the in-situ purification system 10 of the contaminated soil and / or groundwater of this invention. It is a graph which shows the change of the pH of the culture medium in the culture | cultivation of Example 1, the comparative example 1, and the comparative example 2. FIG. It is a graph which shows the bacterial count measurement result in the culture | cultivation of Example 1, the comparative example 1, and the comparative example 2. FIG. It is a graph which shows the change of the pH of the culture medium in the culture | cultivation of Example 2, the comparative example 3, and the comparative example 4. FIG. It is a graph which shows the bacterial count measurement result in the culture | cultivation of Example 2, the comparative example 3, and the comparative example 4. FIG. It is a graph which shows the change of pH of a culture medium.

Explanation of symbols

10 In-situ purification system for contaminated soil and / or groundwater 12, 12 ′ Gas and / or liquid injection well 14 Pumping well 16 pH measuring means 17 Water supply pipe 20 Air supply means 22 Air supply pipe 24 Air compressor 30 Liquid supply means 32 Water supply pipe 34 Liquid storage tank 36 Pump

Claims (6)

A method of purifying contaminated soil and / or groundwater by adding nutrient water in situ to contaminated soil and / or groundwater,
A step of measuring the pH of groundwater pumped from a contaminated soil and / or groundwater by a pumping well, and when the pH of the groundwater is equal to or lower than a preset value, the contaminated soil and / or groundwater A method for in-situ purification of contaminated soil and / or groundwater, comprising a step of injecting a pH adjusting agent into the soil. The in-situ purification method of contaminated soil and / or groundwater according to claim 1, wherein the pH adjuster is an alkaline agent. The in-situ purification method for contaminated soil and / or groundwater according to claim 1 or 2, wherein injection of the pH adjusting agent is stopped when the nutrient salt water is injected. A gas and / or liquid injection well for injecting gas and / or liquid into the soil;
A pumping well installed in the ground to pump up groundwater or soil moisture;
An in-situ purification system for contaminated soil and / or groundwater comprising:
The pumping well is provided with pH measuring means for measuring the pH of the pumped liquid,
An in-situ purification system for contaminated soil and / or groundwater, in which a pH adjusting agent supplying means is connected to the gas and / or liquid injection well. The in-situ purification of contaminated soil and / or groundwater according to claim 4, wherein the pH adjusting agent is supplied by the pH adjusting agent supply means when the pH of the pumped liquid becomes equal to or lower than a preset value. system. The in-situ purification system according to claim 4 or 5, wherein nutrients of microorganisms living in the soil and / or groundwater are contained in the liquid injected from the gas and / or liquid injection well.

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