JP2009154152A - Method for clarifying contaminated soil or ground water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for clarifying contaminated soil or ground water by which soil or ground water contaminated with an organic compound such as oil is efficiently be clarified. <P>SOLUTION: In the method for clarifying contaminated soil or ground water, an inorganic nitrogen source or an inorganic phosphorous source is added to the soil or ground water contaminated with the organic compound to clarify the contaminated soil or ground water. The inorganic nitrogen source of 1/60 to 1/15 and the inorganic phosphorous source of 1/600 to 1/150 to the oxygen consumption or carbon dioxide generation amount upon the decomposition of the organic compound with microorganisms comprised in the soil or ground water are added to the soil or group water. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for purifying soil or groundwater contaminated with an organic compound, and more specifically, contamination with improved purification efficiency by adding a certain amount of an inorganic nitrogen source and an inorganic phosphorus source. The present invention relates to a method for purifying soil or groundwater.

  In recent years, contamination of soil with organic compounds such as petroleum hydrocarbon compounds has become a problem on the site of industrial facilities such as factories. Soil constitutes the foundation of people's lives and economic activities, and if contaminated soil is left unattended, it may affect human health by ingesting it directly or through crops, seafood, etc. is there. In addition, the organic compounds remaining in the soil are dissolved in groundwater by rainwater and spread around the periphery.

  As one of the technologies for purifying contaminated soil or groundwater, for example, Patent Document 1 discloses a method for purifying oil-contaminated soil by aerobic microorganisms, with a C / N / P ratio of approximately about the amount of carbon in the soil. A method of adding N / P type nutrients or the like to the soil to be treated so as to be 100/20/1 is disclosed. According to the method described in the patent document, for example, about 2,000 mg N / kg of nitrogen and about 100 mg P / kg of phosphorus need to be added to contaminated soil having an oil concentration of 10,000 mg / kg. If nitrogen or phosphorus is added excessively, nitrogen or phosphorus itself may cause groundwater contamination.

  Patent Document 2 discloses an oil-contaminated soil in which an inorganic N source and / or a P source are added to the soil so that the pH of the soil is in a specific range and the N / P and the amount of N in the soil are in a certain range. A biological purification method is disclosed. Even in the method described in the patent document, if the oil concentration is low, nitrogen and phosphorus may be excessive.

  In Patent Document 3, in a method of purifying soil by aeration to aerobic microorganisms in the soil, the rate of decrease in the residual oxygen concentration in the contaminated soil is measured, and aeration to the contaminated soil is performed based on the measured value of the decreased concentration. A method for controlling the amount is disclosed. In the method described in the patent document, it is described that the aeration can be controlled according to the decomposition activity of microorganisms by controlling the oxygen amount, but the nitrogen amount and the phosphorus amount are not mentioned.

  Patent Document 4 discloses a soil purification method in which a nutrient source having a weight ratio of carbon source / nitrogen content / phosphorus content of 100/1 to 10 / 0.1 to 1.0 is added to soil. Patent Document 5 discloses a soil purification method in which an aqueous solution of a nitrogen source and a phosphorus source is mixed with petroleum-contaminated soil. The nitrogen concentration is 100 to 2,000 mgN / kg with respect to 1 kg of the dry soil weight. It is disclosed that. In the methods disclosed in these patent documents, the amount of addition of nitrogen or the like is too wide, and it is not clear how much it should actually be added to the soil.

  Patent Document 6 discloses an environmental purification method using microorganisms that grow under low nutrient conditions where only nutrient salts such as phosphorus and nitrogen are low and can decompose environmental pollutants. In the method disclosed in the patent document, in order to purify the soil, it is necessary to add a microorganism satisfying the above condition to the soil to be purified.

Japanese National Patent Publication No. 9-501841 Japanese Patent No. 3346242 JP 2003-340431 A JP 2003-185986 A Japanese Patent Laid-Open No. 9-276831 Japanese Patent Laid-Open No. 10-276771

As described above, in order to purify soil and groundwater contaminated with organic compounds such as oil, methods for adding inorganic salts such as nitrogen and phosphorus to soil or groundwater have been known. It is not clear whether it should be added, and when it was added excessively, it was a cause of contaminating soil and groundwater. Thus, conventionally, there has been no actual method for adding an inorganic salt to purify soil or groundwater contaminated with an organic compound such as oil.
Accordingly, an object of the present invention is to provide a method for purifying contaminated soil or groundwater for efficiently purifying soil and groundwater contaminated with an organic compound such as oil. The method for purifying contaminated soil or groundwater of the present invention is particularly used as a method for purifying in situ organisms.

  In order to achieve the above object, the present inventors have conducted intensive studies, and as a result, the amount of oxygen consumed or carbon dioxide generated when microorganisms contained in the soil decompose organic compounds, and the inorganic nitrogen source and inorganic phosphorus to be added. An appropriate relationship with the source ratio was found and the present invention was completed.

  That is, the present invention is a method for purifying contaminated soil or groundwater by purifying the contaminated soil or groundwater by adding an inorganic nitrogen source and an inorganic phosphorus source to soil or groundwater contaminated with an organic compound, 1/60 to 1/15 times (nitrogen equivalent weight) of inorganic nitrogen source and 1/600 to 1/150 times the amount of oxygen consumed or carbon dioxide generated when microorganisms contained in soil or groundwater decompose organic compounds The present invention provides a method for purifying contaminated soil or groundwater, characterized by adding twice (phosphorus equivalent weight) inorganic phosphorus source to the soil or groundwater.

In the present invention, a part of the contaminated soil or groundwater is collected as a sample, and when the inorganic nitrogen source and inorganic phosphorus source are added to the sample, the amount of oxygen decrease or carbon dioxide increase, the inorganic nitrogen source and The amount of oxygen decrease or carbon dioxide increase when no inorganic phosphorus source is added is measured intermittently or continuously for a predetermined period, and the difference between the measured values is determined as oxygen consumption or carbon dioxide generation. Can do.
In the present invention, an inorganic nitrogen source and an inorganic phosphorus source are added to the contaminated soil or groundwater in a range that does not cause salt inhibition of microorganisms, that is, an inorganic salt of 1000 to 5000 mgN and 100 to 500 mgP per liter of water, respectively. The amount of oxygen decrease or carbon dioxide increase when added or not is measured intermittently or continuously for a predetermined period, and the difference between the measured values is defined as the oxygen consumption or carbon dioxide generation amount. be able to.
In the present invention, the organic compound that is a contamination source of soil or groundwater to be purified includes oil.

  According to the method for purifying contaminated soil or groundwater of the present invention, soil and groundwater contaminated with an organic compound such as oil can be efficiently purified. Moreover, the contaminated soil or groundwater purification method of the present invention can be used as an in situ biological purification method.

Hereinafter, the purification method of contaminated soil or groundwater of the present invention will be described. The method for purifying contaminated soil or groundwater of the present invention includes adding an inorganic nitrogen source and an inorganic phosphorus source.
The inorganic nitrogen source to be used is not particularly limited as long as it is used by microorganisms in the soil, and examples thereof include ammonium chloride, ammonium sulfate, nitrate nitrogen such as sodium nitrate and potassium nitrate, and the like. Ammonium is preferably used.

  The inorganic phosphorus source is not particularly limited as long as it is used by microorganisms in the soil, and examples thereof include phosphate, perphosphate, metaphosphate, polyphosphate, and the like. Include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium metaphosphate, potassium pyrophosphate, potassium tripolyphosphate, and the like. Among these, potassium dihydrogen phosphate and dipotassium hydrogen phosphate are preferable from an economical viewpoint. Moreover, in this invention, in order to produce the addition effect of inorganic salt, it is preferable that pH of soil is maintained at 6-8. Therefore, when the pH of the soil deviates from the above range, it is preferable to set the soil pH to the above range using a base or acid. When the pH of the soil is acidic, it is preferable to neutralize by adding an aqueous solution of sodium hydroxide, sodium hydrogen carbonate or sodium carbonate. Preference is given to sodium hydrogen carbonate. On the other hand, when the pH of the soil is basic, for example, it is preferable to neutralize by adding ferrous sulfate, potassium sulfate or the like.

  As the method for adding the inorganic nitrogen source, the inorganic phosphorus source, and the acid and base for adjusting the pH, in the case of in-situ treatment, water may be sprinkled from the ground surface or injected from a well. When processing excavated soil, the inorganic nitrogen source, inorganic phosphorus source, acid and base for adjusting pH can be added, and mixed by stirring.

In the method for purifying contaminated soil or groundwater of the present invention, 1/60 to 1/15 times the amount of oxygen consumption or carbon dioxide generation when microorganisms contained in soil or groundwater decompose organic compounds (weight in terms of nitrogen) ) And an inorganic phosphorus source 1/600 to 1/150 times (phosphorus equivalent weight) are added to the contaminated soil or groundwater. The preferred amount of the inorganic nitrogen source is 1/30 to 1/20 times (nitrogen equivalent weight) of the oxygen consumption or carbon dioxide generation amount, and 1/300 to 1/200 times (phosphorus equivalent weight) of the inorganic phosphorus source. It is. When the amount of the inorganic nitrogen source and the inorganic phosphorus source exceeds the above range, the decomposition activity of the organic compound is reduced. On the other hand, if the amount is less than the above range, the decomposition activity of the organic compound is reduced.
In addition, the amount of inorganic nitrogen source and inorganic phosphorus source in the present specification means the amount of nitrogen and phosphorus.

  Inorganic salts such as nitrogen and phosphorus are known to degrade the activity of microorganisms, which decompose organic compounds such as oil, when present at a certain concentration or more. For example, according to the knowledge obtained so far, when the content of ammonium salt exceeds 5,000 mgN per liter of water and that of phosphate exceeds 500 mgP per liter of water, the oil decomposition activity decreases. Yes. Therefore, in the present invention, the oxygen consumption amount or carbon dioxide generation amount when the microorganisms contained in the soil or groundwater decompose the organic compound refers to the inorganic nitrogen source and the inorganic phosphorus source in the contaminated soil or groundwater. When the salt is added to 1000 to 5000 mgN and 100 to 500 mgP per liter of water, and the oxygen decrease amount or carbon dioxide increase amount when not added is measured intermittently or continuously for a predetermined period, It means the difference between measured values.

In the present invention, when the amounts of the inorganic nitrogen source and the inorganic phosphorus source are within the above ranges, the purification efficiency is considered to be improved for the following reasons.
That is, when biodegradation tests have been carried out using various organic compounds such as oil as a substrate, the amount of COD incorporated into the cells by the decomposition of microorganisms is approximately equivalent to the amount of oxygen consumed or the amount of carbon dioxide generated. I know that there is. On the other hand, the amount of oil is known to be about 1/3 times the weight of COD. Therefore, it can be seen that one third of the oxygen consumption or the amount of carbon dioxide generation is the amount of oil decomposition. Moreover, it is known that the constituent ratio of the elements constituting the microbial cells is carbon (C): nitrogen (N): phosphorus (P) = 100: (5-20) :( 0.5-2). Therefore, the amount of nitrogen required for oil decomposition is about 1/60 to 1/15 times the amount of oxygen consumption or carbon dioxide generation (weight in terms of nitrogen), and the amount of phosphorus added is oxygen consumption or It is considered to be about 1/600 to 1/15 times the carbon generation amount (phosphorus equivalent weight).
Therefore, in the present invention, the amount of inorganic nitrogen source added is 1/60 to 1/15 times the amount of oxygen consumed or carbon dioxide generated when microorganisms contained in soil or groundwater oxidatively decompose organic compounds (nitrogen conversion) Weight), preferably 1/30 to 1/20 times (nitrogen equivalent weight), and the inorganic phosphorus source addition amount is 1/600 to 1/150 times the oxygen consumption or carbon dioxide generation amount (phosphorus equivalent weight), Preferably, 1/300 to 1/200 times (phosphorus equivalent weight), so that the amount of inorganic nitrogen source added in terms of nitrogen: inorganic phosphorus source added in terms of phosphorus = 1: 0.1 to 0.3 (weight ratio). It is preferable to control the addition amount.

  There is no particular limitation on the method of measuring oxygen consumption or carbon dioxide generation when microorganisms contained in soil or groundwater decompose organic compounds, and it can be carried out by a conventionally known method, for example, purification. The soil or groundwater to be sampled is sampled, and oxygen consumption or carbon dioxide generation can be measured in the laboratory using the soil or groundwater.

A method for measuring oxygen consumption or carbon dioxide generation will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an apparatus for measuring oxygen consumption.
As shown in FIG. 1, the column 12 is connected to a carbon dioxide absorption bottle 20 via a flow path 14, and the column 12 and the carbon dioxide absorption bottle 20 are connected via another flow path 15. The pump 16 is connected to the flow path 15. The column 12 is filled with contaminated soil or ground water, and the internal air is hermetically circulated by the pump 16. The column 12 is preferably made of a material that does not easily adhere to oil, and is preferably made of glass or stainless steel, for example. When the oil is decomposed, carbon dioxide is generated, and this carbon dioxide is absorbed by the carbon dioxide absorbent 22 filled in the carbon dioxide absorption bottle 20. Examples of the carbon dioxide absorbent 22 include calcium carbonate and sodium hydroxide, and a 5N sodium hydroxide aqueous solution is preferable.

In the apparatus shown in FIG. 1, a partial pressure change measuring device 26 is connected to the carbon dioxide absorption bottle 20 through a flow path 24. The partial pressure change measuring device 26 is a device that can measure the partial pressure of air in the carbon dioxide absorption bottle 20 and can continuously measure the oxygen concentration. As the oxygen is consumed, oxygen is continuously introduced into the system. What can be supplied to is preferable. An example of such an apparatus is an ANR manufactured by Challenge Systems. According to this apparatus, the oxygen supply amount supplied into the system can be continuously recorded and measured, and an integrated value of oxygen consumption can be calculated. The supply of oxygen can be performed by supplying from a partial pressure change measuring device 26 and an oxygen cylinder 30 connected via a flow path 28. The oxygen supply amount data is recorded in the partial pressure change measuring device 26 and the data recording device 34 connected via the flow path 32.
In addition, examples of the method for measuring oxygen consumption include a method using a lysimeter, and examples of a method for measuring the amount of carbon dioxide generated include a method of measuring IC concentration in an absorbent. Is mentioned.

  The period for measuring the oxygen consumption or carbon dioxide generation amount is preferably until the effect of adding the inorganic salt is no longer exhibited. That is, the inorganic nitrogen source and the inorganic phosphorus source are used as inorganic salts at 1000 to 5000 mgN per liter of water, respectively. And when adding so that it may become 100-500 mgP, the amount of oxygen decrease or the amount of carbon dioxide increase when not doing is measured intermittently or continuously for a predetermined period, and the difference of each measured value is meant. That is, the oxygen consumption rate when the inorganic nitrogen source and the inorganic phosphorus source were added as inorganic salts to 1000 to 5000 mgN and 100 to 500 mgP per liter of water, respectively, and the oxygen consumption rate (inclination of increase in oxygen consumption) It is preferable to carry out until the values are substantially the same.

  The method for purifying contaminated soil or groundwater of the present invention comprises an inorganic nitrogen source that is 1/60 to 1/15 times (nitrogen equivalent weight) of the oxygen consumption or carbon dioxide generation determined as described above, and 1/600. An inorganic phosphorus source of ~ 1/50 times (phosphorus equivalent weight) is added to soil or groundwater. The method for purifying contaminated soil or groundwater of the present invention purifies soil or groundwater contaminated with an organic compound such as oil, and is used particularly in the in situ purification method. Hereinafter, the present invention will be described as purifying soil or groundwater contaminated with oil, but the present invention is not limited to purifying soil or groundwater contaminated with oil, and other organic compounds. It can also be applied to the purification of soil or groundwater contaminated with water. The soil or groundwater contaminated with oil means, for example, soil 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 conducting bioremediation in 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. Method of promoting decomposition (biostimulation) and introduction of foreign microorganisms, that is, purifying by injecting microorganisms that have grown and activated in large quantities with the ability to decompose oil into contaminated soil or groundwater Includes both methods (bioaugmentation). For example, if the contaminated soil or groundwater does not contain microorganisms that decompose organic compounds, microorganisms that decompose organic compounds may be added. In addition, when adding a microorganism, when the organic compound to be decomposed is oil, a conventionally known microorganism can be used as such a microorganism. For example, Rhodococcus bacteria, Pseudomonas bacteria, Acinetobacter bacteria Etc.

  In order to perform 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.

According to the present invention, the amount of oxygen consumed or the amount of carbon dioxide generated when microorganisms contained in the soil decompose organic compounds is measured, and the inorganic nitrogen source and the inorganic phosphorus source are added based on the measured amount. Since the nitrogen source and the phosphorus source are not added excessively and the decomposition activity of the organic compound contained in the microorganism is not inhibited, a method for purifying soil or groundwater with improved purification efficiency is provided. Moreover, the danger of groundwater contamination by excess N / P can also be reduced.
For the biological purification treatment in the present invention, a sparging technique in which air is supplied to the soil and decomposed in-situ, or air is supplied to the excavated soil with a ventilation pipe, or the air is stirred and mixed to be on-site. Or the technique decomposed | disassembled off-site is mentioned.

  As the inorganic nitrogen source and inorganic phosphorus source used for addition in the present invention, those described above are used. That is, the inorganic nitrogen source is not particularly limited as long as it is used by microorganisms in the soil, and examples thereof include ammonium chloride, ammonium sulfate, nitrate nitrogen such as sodium nitrate, potassium nitrate, and the like. Ammonium is preferably used.

  The inorganic phosphorus source is not particularly limited as long as it is used by microorganisms in the soil, and examples thereof include phosphate, perphosphate, metaphosphate, polyphosphate, and the like. Include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium metaphosphate, potassium pyrophosphate, potassium tripolyphosphate, and the like. Among these, potassium dihydrogen phosphate and dipotassium hydrogen phosphate are preferable from an economical viewpoint. Moreover, in this invention, in order to produce the addition effect of inorganic salt, it is preferable that pH of soil is maintained at 6-8. Therefore, when the pH of the soil deviates from the above range, it is preferable to set the soil pH to the above range using a base or an acid.

  Although there is no restriction | limiting in particular in the method of adding an inorganic nitrogen source and an inorganic phosphorus source in this invention, When using for an in-situ purification method, you may water from the ground surface or you may inject from a well. When processing excavated soil, you may stir and mix an inorganic nitrogen source and an inorganic phosphorus source. In the present invention, the inorganic nitrogen source and the inorganic substance can be added as a solid inorganic substance, but are preferably added as an aqueous solution in order to disperse evenly in soil or groundwater. In this case, the concentration of the inorganic nitrogen source and the inorganic phosphorus source may be about 10 to 20 gN / L and about 1 to 2 gP / L, respectively.

  In addition, when implementing the purification method of the soil or groundwater of this invention, you may carry out, inject | pouring air (oxygen). The injection of air (oxygen) can be performed using, 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 10 to 100 L / min.

  The method for purifying soil or groundwater of the present invention is preferably used when the in-situ purification method is carried out, but a conventionally known method or the like can be used for the in-situ purification method system without particular limitation.

Hereinafter, the present invention will be described in more detail with reference to examples. Needless to say, the scope of the present invention is not limited to such examples.
[Example 1]
200 g of soil contaminated with heavy oil (oil concentration 10,000 mg / kg soil, moisture content 20% by mass) is packed in a 200 mL column, and ammonium chloride as a nitrogen source is 5000 mg per liter of soil moisture (about 1, 000 mg N / L), and potassium dihydrogen phosphate and dipotassium hydrogen phosphate as a phosphorus source were added to the column so as to be 100 mg P / L, and then ventilating (aeration rate: 100 L / min) The oxygen consumption was continuously measured using ANR manufactured by the company (see FIG. 1).
[Comparative Example 1]
The oxygen consumption was continuously measured in the same manner as in Example 1 without adding a nitrogen source and a phosphorus source.

The result of measuring the oxygen consumption is shown in FIG. FIG. 2 is a graph showing the results of continuous measurement of oxygen consumption in Example 1 and Comparative Example 1. In FIG. 2, the horizontal axis represents time (days), and the vertical axis represents oxygen consumption (mg / kg). As shown in FIG. 2, aeration was started, and after about 20 days, the oxygen consumption rate was almost the same in both Example 1 and Comparative Example 1, and the oxygen consumption at this time was 3000 mgO ₂ / kg in Example 1. In contrast, in Comparative Example 1, it was 1500 mgO ₂ / kg. Since the amount of oxygen consumed and the amount of COD taken into cells by the COD degradation of microorganisms (hereinafter referred to as “COD uptake”) are almost equal, the addition of an inorganic nitrogen source and an inorganic phosphorus source results in COD. About 1500 mg / kg has been decomposed. Further, since the amount of oil is about 1/3 times the weight of COD, the amount of oil that is largely decomposed by the addition of inorganic nitrogen source and inorganic phosphorus source is about 500 mg / kg (= 1500 mg / kg ÷ 3). It was calculated to be.
Therefore, as above-mentioned, the component ratio of the element which comprises a microbial cell is carbon (C): nitrogen (N): phosphorus (P) = 100: (5-20) :( 0.5-2) (weight) For example, the required nitrogen addition amount and phosphorus addition amount are about 25 to 100 mg N / kg (1/60 to 1/15 times the oxygen consumption (weight in terms of nitrogen), About 2.5 to 10 mg P / kg (considered to be 1/600 to 1/150 times the oxygen consumption (phosphorus equivalent weight). Here, the total amount of oil per soil is 10,000 mg / kg, so it is necessary. The amount of nitrogen and phosphorus to be added is at most C: N: P = 10,000: 100: 10 = 100: 1: 0.1 (weight ratio) with respect to the amount of carbon per total oil content in the soil. Become.

[Example 2, Comparative Example 2, Comparative Example 3]
Therefore, the above-mentioned soil to which potassium hydrogen phosphate was added to 10 mg P / kg so that ammonium chloride as a nitrogen source would be 100 mg N / kg (the water content is 20%, so 500 mg N / L per liter of soil water). (Example 2) and nitrogen (2,000 mgN / kg) and phosphorus (100 mgP / kg) in the amounts calculated by C: N: P = 100: 20: 1 (weight ratio), which is generally said. The residual amount of oil was measured after continuous aeration (aeration rate: 100 L / min) for 3 weeks with the added system (Comparative Example 2) and the system without any addition (Comparative Example 3).

The residual amount of oil was measured by the normal hexane weight method. This method is briefly described as follows.
After dehydrating the moisture in the soil, n-hexane is mixed and stirred, and then the hexane phase is recovered. Next, the hexane phase is heated to volatilize only the hexane, and the weight of the oil dissolved in the hexane phase is measured. The soil was collected 3 times and measured. Table 1 shows the measured values, average values, and decomposition rates.

  As shown in Table 1, in Example 2, it was found that about twice as much oil was decomposed as in Comparative Example 3 in which no inorganic salt was added. In Comparative Example 2, it is considered that salt addition was caused by adding an excessive amount of an inorganic substance, and decomposition of oil was inhibited.

[Example 3, Comparative Example 4, Comparative Example 5]
In Example 2, the oily odor and oil film of the soil after aeration for 3 weeks were tested. The respective evaluation results are shown in Table 2.
The oily odor was tested as follows.
Put 10 g of soil in a glass bottle with a capacity of 100 mL, cover it and leave it at a temperature of 25 ° C. for 30 minutes, then remove the lid, immediately sniff the odor generated from the soil, determine the presence or absence of odor and the odor intensity, Evaluation was performed according to the evaluation criteria.
0: Odorless.
1: The smell is barely perceivable.
2: The odor is weak although it can be understood what kind of smell it is.
3: The smell is easy to detect.
4: Strong odor.
5: Strong smell.

The oil film was evaluated as follows.
20 mL of pure water was placed in a petri dish having a diameter of 90 mm and a height of 14 mm, and left on a black desk. Next, about 2 g of soil was gently put into the pure water in the petri dish, and the liquid level immediately after that was visually observed and evaluated according to the following evaluation criteria.
0: No oil film is visible.
1: An oil film is faintly seen depending on how the light hits.
2: A slight oil film is visible.
3: An oil film appears thin on the petri dish surface.
4: An oil film is usually visible on the petri dish surface.
5: One side of the petri dish is glaring (including the case where oil droplets are observed).

As is clear from Table 2, it was found that both the oily odor and the oil film remained considerably in Comparative Example 5 in which the inorganic salt was not added. On the other hand, in Example 3 to which the inorganic salt was added, an oily odor and an effect of reducing the oil film were recognized. In Comparative Example 4 in which an excessive amount of inorganic salt was added, salt inhibition occurred, and it was considered that decomposition of the oil was inhibited.
As is clear from the above results, in purification of contaminated soil or contaminated groundwater, 1% of the amount of oxygen consumed or carbon dioxide generated when microorganisms contained in the contaminated soil or contaminated groundwater decompose organic compounds such as oil. It was found that the purification efficiency was improved by adding an inorganic nitrogen source of / 60 to 1/15 times (nitrogen equivalent weight) and an inorganic phosphorus source of 1/600 to 1/150 times (phosphorus equivalent weight).

It is the schematic which shows the apparatus for measuring oxygen consumption. It is a graph which shows the result of having measured oxygen consumption continuously in Example 1 and Comparative Example 1. FIG.

Explanation of symbols

12 column 14 flow path 15 flow path 16 pump 20 carbon dioxide absorption bottle 22 carbon dioxide absorbent 24 flow path 26 partial pressure change measuring device 28 flow path 30 oxygen cylinder

Claims (4)

A method for purifying contaminated soil or groundwater by purifying the contaminated soil or groundwater by adding an inorganic nitrogen source and an inorganic phosphorus source to soil or groundwater contaminated with an organic compound,
1/60 to 1/15 times (nitrogen equivalent weight) of inorganic nitrogen source and 1/600 to 1/150 times the amount of oxygen consumed or carbon dioxide generated when microorganisms contained in soil or groundwater decompose organic compounds A method for purifying contaminated soil or groundwater, comprising adding double (phosphorus equivalent weight) inorganic phosphorus source to the soil or groundwater.   A part of the contaminated soil or groundwater is collected as a sample, and when the inorganic nitrogen source and inorganic phosphorus source are added to the sample, the oxygen decrease amount or carbon dioxide increase amount, and the inorganic nitrogen source and inorganic phosphorus source are added. The oxygen decrease amount or the carbon dioxide increase amount when not performed is measured intermittently or continuously for a predetermined period, and a difference between the measured values is defined as an oxygen consumption amount or a carbon dioxide generation amount. For purification of contaminated soil or groundwater.   When the inorganic nitrogen source and the inorganic phosphorus source are added to the contaminated soil or groundwater as inorganic salts so as to be 1000 to 5000 mgN and 100 to 500 mgP per liter of water, respectively, the oxygen decrease amount or carbon dioxide increase when not added The method for purifying contaminated soil or groundwater according to claim 1, wherein the amount is measured intermittently or continuously for a predetermined period, and the difference between the measured values is defined as the oxygen consumption amount or the carbon dioxide generation amount.   The method for purifying contaminated soil or groundwater according to any one of claims 1 to 3, wherein the organic compound is oil.

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