KR101284966B1 - Method of purifying polluted soil - Google Patents

Abstract

An object of the present invention is to provide a purification method capable of controlling the temperature of contaminated soil even at low temperatures, promoting activation of aerobic microorganisms having a decomposition performance of organic pollutants, and sufficiently improving the purification efficiency of contaminated soil. do. The present invention relates to a method for purifying contaminated soil by aeration of contaminated soil contaminated with organic contaminants, activating aerobic microorganisms capable of decomposing organic contaminants, and purifying contaminated soil by fermentative decomposition of organic contaminants. A fermentation aid containing crude oil is added to the soil to control the amount of aeration so that the temperature of the contaminated soil is 10 to 50 ° C.

Description

Method of purification of contaminated soil {METHOD OF PURIFYING POLLUTED SOIL}

The present invention relates to a method for purifying contaminated soil by aeration of contaminated soil contaminated with organic contaminants, activating aerobic microorganisms having a decomposition performance of organic contaminants, and purifying contaminated soil by fermenting and decomposing organic contaminants. .

In recent years, as a method for purifying contaminated soil contaminated with organic pollutants, the air is contaminated by contaminating soil contaminated with organic pollutants, activated aerobic microorganisms capable of decomposing organic pollutants, and fermented and decomposed organic pollutants to contaminate the soil. There is a ventilation bioremediation method (for example, see Japanese Patent Application Laid-Open No. 7-100459) for purifying soil.

In such a contaminated soil purification method, since cold air is vented to the contaminated soil at low temperatures such as in winter and cold regions, the temperature of the contaminated soil is lowered and the aerobic microorganism cannot be sufficiently activated. As a result, the purification efficiency of contaminated soil is significantly reduced.

Therefore, in order to activate aerobic microorganisms even at low temperatures such as in winter and cold regions, a method of purifying contaminated soil using artificial humus and sugars (see, for example, Japanese Unexamined Patent Application Publication No. 2002-1303) There is a method of purifying contaminated soil (see, for example, Japanese Patent Laid-Open No. 2004-254508).

DISCLOSURE OF INVENTION

Problems to be solved by the invention

However, in order to sufficiently improve the purification efficiency of the contaminated soil, it is necessary to control the contaminated soil at a temperature that promotes the activity of aerobic microorganisms having the decomposition performance of organic contaminants. However, in the conventional method, there is a problem that the temperature of the contaminated soil at low temperature cannot be sufficiently increased and the activation of aerobic microorganisms is insufficient. Moreover, when the temperature of the contaminated soil rises more than necessary, there existed a problem that the bacterium active in the soil differs and it cannot fully improve a purification efficiency.

Therefore, the present invention provides a purification method that can control the temperature of contaminated soil even at low temperatures, promote the activation of aerobic microorganisms with decomposition performance of organic pollutants, and sufficiently improve the purification efficiency of contaminated soil. The purpose.

Means for solving the problem

In order to solve the above problems, the present invention aerated contaminated soil contaminated with organic pollutants, activate aerobic microorganisms having a decomposition performance of the organic pollutants, purify the contaminated soil by fermentation and decomposition of the organic pollutants A method for purifying contaminated soil, characterized by adding a fermentation aid containing crude oil to the contaminated soil, and controlling the amount of aeration so that the temperature of the contaminated soil is 10 to 50 ° C.

In addition, the present invention is characterized in that the fermentation aid is added 0.2 to 5% by mass relative to the mass of the contaminated soil.

In addition, the present invention is characterized in that the ventilation amount is controlled by combining the intake air and the air supply.

In addition, the present invention is characterized in that the ventilation is temporarily stopped in the control of the ventilation amount.

Further, the present invention is characterized in that, after the easy decomposition component of the organic pollutant is decomposed, the aeration amount is reduced.

<Cross Reference with Related Documents>

This application claims the priority based on Japanese Patent Application No. 2005-54140 for which it applied on February 28, 2005, and uses the content.

BRIEF DESCRIPTION OF THE DRAWINGS The graph which shows the change of the soil temperature in the purification method by adding HC2 mass% to the said soil, and a biopile type ventilation.

Figure 2 is a graph showing the results of examining the purification efficiency of contaminated soil in the intake type aeration method for the contaminated soil contaminated with oil (n-hexane extract) as a contaminant.

3 is a graph showing the relationship between air temperature and soil temperature according to the amount of HC added.

4 is a graph showing the relationship between the amount of HC added to the contaminated soil and the amount of aeration;

5 is a graph showing test results when a combination of air intake and air delivery is performed.

Fig. 6 is a graph showing the test results when aeration is temporarily stopped;

Fig. 7 is a graph showing the test results when the air flow rate is reduced after the decomposition component of the organic pollutant is decomposed, (a) shows the change over time in soil temperature, and (b) shows the oil content. Showing changes over time.

Carrying out the invention  Best form for

EMBODIMENT OF THE INVENTION Hereinafter, the best form for implementing this invention is demonstrated, referring an accompanying drawing.

First, the method for purifying contaminated soil in the embodiment of the present invention allows aeration to contaminated soil contaminated with organic contaminants (hereinafter referred to simply as "soil"), and aerobic microorganisms capable of decomposing organic contaminants. A method of purifying contaminated soil by selectively activating and fermenting and decomposing contaminants, the method for purifying contaminated soil, by adding a fermentation aid containing crude oil to the contaminated soil, and allowing the contaminated soil to have a temperature of 10 to 50 ° C. It is in charge of configuration to control this.

Moreover, as an organic pollutant which this invention purifies, For example, gasoline, kerosene, light oil, heavy oil, machine oil, lubricating oil, crude oil, such as oil derived from petroleum, oil derived from coal, such as tar and benzene, and trichloro Organic chlorine compounds, such as ethylene and tetrachloroethylene, Benzene, toluene, ethylbenzene, xylene, etc. which are contained in the said oil are mentioned.

In addition, although aerobic microorganisms in the above-described configuration include general live bacteria, filamentous fungi, actinomycetes, petroleum magnetizable bacteria, and the like, the present invention is not necessarily limited to these microorganisms, provided that they have the ability to ferment and decompose organic contaminants. Other aerobic microorganisms may be used. Further, in consideration of reuse of the purified soil, a method of activating aerobic microorganisms contained in the contaminated soil is good, but is not limited thereto.

Next, the effects of the present invention, that is, the effect of improving the purification efficiency by appropriate temperature control of the contaminated soil and the effect of improving soil, will be described.

The fermentation aid according to the present invention is composed mainly of crude algae, which is at least one selected from the group consisting of wheat bran, wheat flour, rice bran, corn bran and gluten field. In addition, the fermentation aids may be made entirely of crude steel, for example, appropriately distribute pH buffers, humic acids, minerals such as calcium and magnesium, minerals such as pearlite, zeolite and diatomaceous earth, and other soil improving materials as necessary. Also good. Examples of the fermentation aid of the present invention include commercially available heat comps (trade name) mainly comprising bran. In addition, in the Example of this invention, this heat compo was used as a fermentation auxiliary material. The soil temperature can be sufficiently raised by adding and blending such a fermentation aid, for example, a heat compo (hereinafter abbreviated as "HC") to contaminated soil.

For this reason, even if cold air is ventilated and / or aspirated into contaminated soil at low temperatures such as winter and cold regions, aerobic microorganisms are activated and contaminant decomposition performance is improved. In some cases, control by ventilation is performed.

Moreover, when the soil temperature is less than 10 ° C, the degradation activity of the contaminants of aerobic microorganisms in the soil is so low that it can hardly be confirmed. On the other hand, in the range where the soil temperature exceeds 50 ° C, the total flora is completely different, and the decomposition activity of the pollutant cannot be expected. Moreover, since 25-40 degreeC has an optimal decomposition activity preferably as soil temperature, the purification efficiency of an organic pollutant improves fully.

In the example, purification was performed by the ventilation of the biopile type. In addition, HC addition amount was 2 mass%. In addition, in order to adjust to the soil temperature at which the decomposition activity of an aerobic microorganism becomes high, the air volume ventilated to contaminated soil was 0.02 m <^3> / min (= 0.02 VVM) per 1 m <^3> of soil. In addition, nitrogen and phosphorus were added at a ratio of C (oil): N (nitrogen): P (phosphorus) = 100: 5: 0.5 as nutrient sources.

Thus, HC2 mass% is added to the said soil, and the change of the soil temperature in the purification method by the ventilation of a biopile type is shown in FIG. 1 (a) is a graph which shows the change of the soil temperature in a ventilation type ventilation system, and FIG. 1 (b) is a graph which shows the change of the soil temperature in an intake type ventilation system. In addition, GL in the figure means a ground level, for example, GL + 30 means the division of +30 cm from a ground level.

As shown in Fig. 1 (a) by adding HC, the soil temperature in the air flow type ventilation system was confirmed to be a maximum temperature rise of about 30 ° C. On the other hand, as shown in Fig. 1 (b), the soil temperature in the intake type aeration system was a temperature rise of about 5 ° C. As a cause, it can be considered that the file of the intake-type ventilation system is small (the file of the intake-type ventilation system is 32 m ³ , whereas the intake-type ventilation system is 5 m ³ ), and heat dissipation is easy. In addition, the standard ball was added with manure compost and nutrient source, and the stirring tool was stirred every week after adding the manure compost and nutrient source, similarly to the standard ball.

Also, the polluted soil contaminated with oil (n-hexane extract), which is a pollutant, was investigated. The results are shown in Fig.

FIG. 2 (a) is a graph showing measurement results of oil concentration using GC / FID (gas chromatograph with hydrogen flame ionization detector) method for purification of contaminated soil, and FIG. 2 (b) shows carbon tetrachloride / IR method. It is a graph showing the measurement result of the oil concentration using. In addition, FID (hydrogen flame ionization detector) detects the electric current which flows through the ion and electron which generate | occur | produce when a flammable organic compound burns in a hydrogen flame. In addition, carbon tetrachloride / IR method analyzes the organic compound extracted with carbon tetrachloride according to the absorption state by infrared irradiation.

As shown in FIG. 2, in the intake type pile, the oil concentrations based on the GC / FID method (see FIG. 2 (a)) and the carbon tetrachloride / IR method (see FIG. 2 (b)) were all 1 month in the standard sphere. On the contrary, the decrease was continued until the second week, but the concentration was not observed until the first month thereafter. In addition, the HC addition group decreased rapidly until 2 weeks, but no change in concentration was observed until 1 month thereafter. In addition, in the HC addition port, as a result of the increase in the rate of decrease in the oil concentration, the main easy-to-decompose components of the oil (for example, gasoline components and diesel oil components, aliphatic hydrocarbons having a relatively low carbon number, aromatic hydrocarbons up to 3 rings, etc.) until the second week. ) Is decomposed and suggests that the equilibrium is rapidly reaching. Further, as a cause of the decrease in the oil concentration, it is conceivable that the evaporation and scattering of the volatile components in the oil is promoted by increasing the soil temperature in accordance with the improvement of the oil decomposition activity of the aerobic microorganisms.

<Soil Improvement Effect>

In addition, since the fermentation aid in the present invention contains a lot of vegetable fibers, by adding the fermentation aid, the air permeability of the soil is improved, and the loss of ignition is also increased. As a result, the soil improvement effect was seen. The wet density (g / cm 2) and the gap ratio (%) between the soil particles indicating the air permeability of the soil are shown in Table 1 below. On the other hand, the loss on ignition (%) as a standard of the amount of organic matter contained in the soil is shown in Table 2 below.

Wet Density (g / cm ³ ) Clearance rate (%) Remarks Standard Average (Send) 1.641 47.2 HC addition average (air supply) 1.572 49.4 HC addition (2 mass%) Standard Average (Intake) 1.682 48.0 HC addition average (intake) 1.579 51.3 HC addition (2 mass%)

As shown in Table 1, by adding 2% by mass of HC, the wet density was reduced and the gap ratio between the soil particles was increased. This shows that the air permeability of soil improves by adding 2 mass% of HC.

Name of sample Loss on ignition (%) Immediately after start Standard sphere 5.8 HC addition port 6.4 After 1 month Standard sphere 5.3 HC addition port 6.1 3 months later Standard sphere 4.7 HC addition port 5.7

As shown in Table 2, by adding 2% by mass of HC, the loss on ignition increased by about 0.6%. In addition, although not shown in the said table | surface, HC addition amount in summer may be a small quantity compared with low temperature because soil temperature is high enough. By improving the air permeability of the soil to become a soil containing a lot of organic matter, there is no obstruction to the activation of aerobic microorganisms, thereby promoting the decomposition of organic pollutants by aerobic microorganisms.

3 is a graph showing the relationship between air temperature and soil temperature according to the amount of HC added. According to these relationships, when the soil temperature is 10 to 50 ° C, the amount of HC added may be 0.2 to 5% by mass. In addition, when making soil temperature into 25-40 degreeC which is more preferable temperature, the addition amount of HC may be made into 0.5-5 mass%. The specific addition amount shall be determined suitably according to conditions, such as temperature.

4 is a graph showing the relationship between the amount of HC added to the contaminated soil and the amount of aeration. If sufficient aeration is not performed even if HC is added, the activity of aerobic microorganisms becomes insufficient. On the other hand, if the aeration is performed more than necessary, for example, if the amount of aeration is excessively high at low temperatures, it may result in lowering the soil temperature. . Therefore, it is preferable that the ventilation amount satisfies the required ventilation amount and is further controlled in the range of the required ventilation amount +0.03 VVM.

Ventilation in the above-mentioned purification | cleaning construction is by control of either intake | air-intake or airflow. These control methods may be determined depending on the size of the file or the ventilation performance. However, depending on the soil quality, when airflow control is performed by either intake or airflow, an air line is formed in the pile, or oxygen in the air is consumed by activation of aerobic microorganisms in the pile, and the air does not spread sufficiently. It is also conceivable that the aerobic microorganisms throughout the pile are not sufficiently activated. Therefore, in order to make aerobic microorganisms perform sufficient decomposition activity all over the inside of a pile, it is preferable to perform in combination with intake and air sending. This can change the air line or allow ventilation from inside and outside the pile to allow air to be sufficiently widespread in the soil. Such ventilation control facilitates control of the temperature in the pile so that the activation of aerobic microorganisms is sufficiently performed. In addition, the combination of the intake air and the air supply is appropriately set. For example, the intake air and the air supply are periodically changed while switching alternately. In addition, the timing of switching from intake to intake and switching from intake to intake is appropriately set while measuring the soil temperature and carbon dioxide concentration at the time of aeration, and considering the measurement result.

The results of this example are shown in FIG. 5. In the present Example, 0.3 mass% of HC was added to the soil, and the air was aspirated from the first day (day 0) to the 20th day.

As shown in FIG. 5, by adding HC to the soil, the soil temperature started to rise and reached a maximum temperature of 30 ° C. in 7 to 11 days, and then gradually decreased. As the soil temperature increased, the oxygen concentration decreased and the carbon dioxide concentration increased. This suggests that the microbial activity is increased. On the other hand, even in a period in which the soil temperature is gradually decreasing (from the 11th to the 20th day), the values of the oxygen concentration and the carbon dioxide concentration hardly change, so that starvation of oxygen requiring microbial activity is concerned. Thus, by switching from intake to air on day 20, the oxygen concentration was raised and the carbon dioxide concentration was decreased. This switching of the ventilation system improved the diffusion effect of air (oxygen) into the soil, and the oil decomposition effect was also improved. That is, the oil concentration, which was 413 mg / kg on the first day, was only slightly reduced to 378 mg / kg on the 16th day. However, by switching the aeration system to air on day 20, the oil concentration significantly decreased to 250 mg / kg or less on day 26.

As a method of spreading the air sufficiently widely, there is also a method (e.g., intermittent aeration) in which a time for not circulating air is provided by temporarily stopping the aeration. In such a control method, it is easy to make the temperature in a pile constant at low temperature. In addition, by temporarily stopping the supply of oxygen consumed by the aerobic microorganisms, the load can be applied to the microorganisms, and when the aeration is performed next, the microbial activity can be improved. For example, after 12 hours of ventilation, it is possible to repeat the 12 hours of stopping the ventilation. The timing for performing such ventilation control is appropriately set according to the condition of the pile such as soil, pollution, temperature, and the like.

The results of this example are shown in FIG. 6. In the present Example, 2 mass% of HC was added to the soil, and intermittent aeration was performed at 20 mL / min / L air flow rate and 5 degreeC of atmospheric temperature. This intermittent aeration was repeated with an 8 hour aeration / day. In addition, continuous aeration (24 hours aeration / day) was also performed as a comparative example.

As shown in FIG. 6, when intermittent aeration was performed, the maximum temperature of the soil temperature was low, but the temperature was high as compared with the case where continuous aeration was performed. From this, in the purification test for two to three weeks, the intermittent ventilation can be expected to promote the purification effect rather than the continuous ventilation.

The contaminant degrading activity of such aerobic microorganisms also depends on the mass of the organic contaminant to be degraded. Therefore, after the easily decomposable component is almost decomposed to reduce the oxygen consumption due to the microbial activity, for example, at low temperature, low temperature outdoor air is sent to the inside of the pile by aeration, so a decrease in soil temperature may occur. Since the remaining organic pollutants are not easy decomposition components, by reducing the aeration amount, it is possible to further promote the pollution purification by maintaining the soil temperature at which the aerobic microorganisms are activated.

The results of this example are shown in FIG. 7. 2 mass% of HC was added to the soil and stirred at 1 month (28 days), after which the soil was partitioned to control the air flow rate (this embodiment) and the air flow volume not controlled (comparative example) Divided by). In addition, in the sphere for controlling the air flow rate, the air flow amount was reduced from 25 mL / minute / L to 5 mL / minute / L after the 28th day. On day 28, the soil temperature was drastically reduced, suggesting that the easily decomposable components of the organic pollutants contained in the soil were decomposed. On the other hand, in the sphere which controls the ventilation amount, the ventilation amount was continued in 25 ml / min / L state. As a result, in the sphere that controls the airflow amount as in the present embodiment, the reduction in the soil temperature can be reduced compared to the sphere that does not control the airflow amount (see Fig. 7 (a)). It was possible to increase the reduction range of (see Fig. 7 (b)).

According to the present invention, even at a low temperature, the temperature of the contaminated soil can be controlled to a temperature at which the activity of the aerobic microorganism is sufficient, so that the purification efficiency of the contaminated soil can be sufficiently improved. In addition, the air permeability of the soil is also improved, it is also possible to improve the properties of the soil.

Claims (5)

A method of purifying contaminated soil which purifies the contaminated soil by aeration of contaminated soil contaminated with organic contaminants, activating aerobic microorganisms having a decomposition performance of the organic contaminants, and fermenting and decomposing the organic contaminants. Based on the relationship between the temperature obtained for each addition ratio of the fermentation aid containing crude steel and the soil temperature when the fermentation aid is added at the addition ratio, the soil temperature corresponding to the air temperature in the above relationship. Is determined as an addition ratio of the fermentation aid to the contaminated soil, And adding the fermentation aid to the contaminated soil at the determined addition ratio, and controlling the aeration amount so that the desired temperature can be maintained. The method for purifying contaminated soil according to claim 1, wherein the fermentation aid is added in an amount of 0.2 to 5% by mass based on the mass of the contaminated soil. The method of purifying polluted soil according to claim 1 or 2, wherein the amount of aeration is controlled by combining intake and air. The method for purifying polluted soil according to claim 1 or 2, wherein in the control of the ventilation amount, the ventilation is temporarily stopped. The method for purifying polluted soil according to claim 1 or 2, wherein after the decomposable component of the organic pollutant is decomposed, the aeration amount is reduced.

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