JP4791775B2 - Contaminated soil purification test method and contaminated soil purification test apparatus - Google Patents

Description

  The present invention relates to a test method and test apparatus for evaluating the purification ability of soil microorganisms by passing simulated contaminated groundwater through a purification test tank containing test soil, and a method and apparatus for preparing simulated contaminated groundwater. Here, the simulated contaminated groundwater is a simulation in which organic chemical substances such as benzene, toluene and xylene contained in liquid petroleum products are dissolved at a very dilute concentration of about 1 to 100 mg / L in total. Contaminated groundwater (hereinafter referred to as “raw water”).

In recent years, as a measure for the purification of soil and groundwater contamination of organic chemical substances, a technology that utilizes the purification ability of soil microorganisms is expected.
As a soil evaluation apparatus, a column test apparatus is generally used (see Non-Patent Document 1). This is a column tube having an inner diameter of several centimeters to several tens of centimeters filled with test soil, and raw water is allowed to pass through it to evaluate how much contaminants in the raw water have been removed.
However, since this device is different from the actual underground environment (groundwater flow, diffusion, etc.), the test results may differ from the actual site.
Therefore, a test for evaluating the purification capacity of soil microorganisms in the field is required.
Examples of such a test include a method in which raw water is passed through a lysimeter filled with test soil and the obtained water is analyzed (see Non-Patent Document 2).
However, since the concentration of the organic chemical substance in the raw water is very dilute (up to 100 mg / L), it is difficult to control the concentration of the organic chemical substance. Further, when the organic chemical substance is volatile, the concentration of the organic chemical substance is lowered, and it is difficult to maintain a constant concentration. If the concentration of organic chemicals in the raw water is not kept constant, the test results will vary and the test reliability will be reduced.
Shimomura et al., Research on modeling of permeable groundwater purification walls using iron powder, Journal of Groundwater Society Vol. 40, No. 4, pp. 445-454, 1998 Iwasaki et al. Bioaugmentation test of trichlorethylene contamination by large soil and groundwater lysimeter, 36th Annual Meeting of Japan Society on Water Environment, Japan Society on Water Environment, page 504, 2002

  Accordingly, an object of the present invention is to provide a method capable of easily supplying raw water having a constant concentration of organic chemicals, and a soil purification ability test method and apparatus using this method.

  As a result of diligent research to solve the above-mentioned problems, the present inventor obtained raw water containing a small amount of organic chemical substance at a constant concentration by extruding a certain amount of organic chemical substance in a calibration tube with gas and feeding it to a dissolution tank. The present invention has been completed.

  That is, according to the present invention, an organic chemical substance is circulated through a six-way valve between a calibration tube and an organic chemical substance tank, and a certain amount of the organic chemical substance in the calibration tube is pushed out by gas by switching the six-way valve. The present invention provides a raw water preparation method characterized by feeding the solution into a dissolution tank, stirring and mixing the organic chemical substance and water in the dissolution tank, and storing the obtained mixed liquid in a raw water tank.

  In addition, the present invention circulates an organic chemical substance between a calibration tube and an organic chemical tank through a 6-way valve, and by switching the 6-way valve, a certain amount of the organic chemical substance in the calibration tube is pushed out by gas. A purification test in which the organic chemical and water are stirred and mixed in the dissolution tank, the obtained raw water is stored in the raw water tank, and the raw water in the raw water tank is put in the test soil. The present invention provides a soil remediation test method characterized by being supplied to a tank and evaluating the soil passage liquid.

  Furthermore, the present invention has an organic chemical substance tank, a pump for circulating the organic chemical substance, a calibration pipe, and a six-way valve, and the organic chemical substance is passed between the calibration pipe and the organic chemical substance tank via the six-way valve. By circulating and switching the 6-way valve, an organic chemical substance addition device that pushes a certain amount of organic chemical substance in the calibration tube with gas and sends it to the dissolution tank, and dissolution that stirs and mixes the organic chemical substance and water A raw water preparation device characterized by having a raw water tank for storing a tank and a mixed liquid obtained in a dissolution tank is provided.

  Furthermore, the present invention has an organic chemical substance tank, a pump for circulating the organic chemical substance, a calibration pipe, and a six-way valve, and the organic chemical substance is placed between the calibration pipe and the organic chemical substance tank. The organic chemical substance adding device for extruding a certain amount of organic chemical substance in the calibration tube with gas and feeding it to the dissolution tank by stirring and mixing the organic chemical substance and water A soil remediation test apparatus characterized by having a dissolution tank, a raw water tank for storing a mixed solution obtained in the dissolution tank, and a purification test tank for storing test soil through which the raw water in the raw water tank passes. To do.

  According to the soil purification test method and the soil purification test apparatus of the present invention, since a constant concentration of raw water is supplied to the soil, a highly reliable test result can be obtained.

As an outline of the soil purification test apparatus of the present invention, the one shown in FIG.
That is, the soil purification test apparatus of the present invention includes an organic chemical substance addition apparatus, a dissolution tank that stirs and mixes an organic chemical substance and water, a raw water tank that stores a mixed liquid obtained in the dissolution tank, and the raw water tank. It has a purification test tank that puts the soil to be tested through which the raw water passes. Moreover, you may provide the dissolved oxygen (DO) density | concentration adjustment tank for adjusting the dissolved oxygen of the water supplied to a dissolution tank in the upstream of a dissolution tank as needed.

Organic Chemical Substance Adder The organic chemical substance used in the present invention may be appropriately selected according to the purpose of the test, and benzene, toluene, xylene or a mixture of two or more of these may be mentioned as a preferable one.
The organic chemical substance adding device is composed of an organic chemical substance tank containing the organic chemical substance, a circulation pump, a six-way valve, a calibration pipe, and piping. One embodiment of the organic chemical substance adding apparatus is shown in FIG.
First, as shown in the left diagram of FIG. 2, an organic chemical substance is circulated in the order of an organic chemical substance tank, a six-way valve, a calibration tube, a six-way valve, and an organic chemical substance tank by a circulation pump. Thereby, the bubble in an organic chemical substance can be extracted. In the figure, the organic chemical substance is BTX (benzene, toluene, xylene), but is not limited thereto.
Then, the 6-way valve is switched (the right diagram in FIG. 2), and the gas (which does not react with the organic chemical substance is preferable. For example, air, nitrogen, and rare gases are included). Send to. After the organic chemical substance in the calibration tube is completely replaced with gas, the 6-way valve returns to its original state and enters a circulation state.
Such switching of the six-way valve is preferably performed automatically by a signal from a liquid height sensor or the like of the dissolution tank or raw water tank.

  Here, the organic chemical substance tank is preferably a thermostatic tank in order to prevent density change and volatilization. Moreover, what is used for the sample injection | pouring by a high performance liquid chromatography can be used for a 6-way valve and a calibration tube. Moreover, the amount of the organic chemical substance added can be controlled by exchanging the calibration tube, and thus the concentration of the organic chemical substance in the raw water can be arbitrarily controlled. The capacity of the calibration tube is preferably about 0.01 to 0.3 mL.

Dissolving tank A tank in which a certain amount of organic chemical substance is added and stirred and mixed after filling with water.
Although the capacity | capacitance of a tank is not specifically limited and should just be determined from the usage-amount per unit time of raw | natural water, about 2L is preferable.
The amount of water, the amount of organic chemicals, and the timing of addition are preferably controlled by a liquid height sensor.
In order to dissolve organic chemical substances such as BTX (benzene, toluene, xylene), which are poorly water-soluble, in a short time, it is necessary to optimize the stirring speed and the addition amount of the organic chemical substance stock solution. If the stirring speed is slow, it takes a long time to dissolve the organic chemical. On the other hand, when the stirring speed is too high, loss due to volatilization of the organic chemical substance is large, and as a result, it is difficult to dissolve the organic chemical substance at a predetermined concentration in a short time. Therefore, it is necessary to set an appropriate stirring speed and time. As an example, when 100 mg / L of BTX (benzene, toluene, xylene) is dissolved in total, it is preferable to stir at 600 rpm for 10 minutes using a stirring blade having a diameter of 60 mm.
Moreover, since the dissolution tank is not a closed tank, volatilization cannot be made zero. Therefore, when preparing raw water, it is preferable to add a large amount of organic chemicals in advance in consideration of loss due to volatilization during stirring. As a rule of thumb, it is preferable to add about 10 to 300 μL of organic chemicals to 2 L of water.
In addition, in the case of a method of constantly preparing raw water by line mixing, in which organic chemicals are mixed in the middle of a pipe for passing raw water to a purification test tank, the amount of organic chemicals relative to water is very small. It is difficult to obtain raw water of concentration.
It is convenient to automatically transfer the solution after dissolution of organic chemicals to the raw water tank using a solenoid valve.

Raw water tank The raw water obtained in the dissolution tank is sent to the raw water tank. Although the internal volume of a raw | natural water tank is not specifically limited, About 5-20L is preferable from the surface of cost. Since the raw water is preferably controlled to the purification test temperature (preferably around 20 ° C.), the raw water tank is preferably a thermostatic bath. Note that when the temperature of the raw water is lower than the purification test temperature, the volatilization of the organic chemical substance can be reduced. In this case, it is necessary to adjust the raw water to the purification test temperature before entering the purification test tank.
As the amount of raw water in the tank decreases and the head space at the top of the tank increases, the organic chemicals in the raw water are likely to volatilize. Therefore, it is desirable to keep the tank nearly full. For this reason, when the volume of the raw water in the tank is detected by a liquid height sensor and reduced by a certain amount, the raw water is preferably prepared in a dissolution tank and immediately replenished.

Dissolved oxygen concentration adjustment tank This is a tank for adjusting the dissolved oxygen of water supplied to the dissolution tank as desired, and is an optional tank.
For example, if the amount of dissolved oxygen in water is large and the organic chemical is a relatively highly biodegradable substance, the aerobic microbial decomposition of the organic chemical occurs in the raw water tank, and the concentration of the organic chemical changes. Sometimes, you want to reduce the amount of dissolved oxygen in water. In this case, nitrogen gas or the like is bubbled.
On the other hand, when there is no risk of decomposition of the organic chemicals in the raw water tank, and in the purification test, raw water with a high dissolved oxygen concentration may be required. In this case, dissolved oxygen is bubbled with dissolved oxygen. The concentration can be increased.
In cases other than the above, the dissolved oxygen concentration adjusting tank is not particularly required.
The capacity | capacitance of a dissolved oxygen concentration adjustment tank is not specifically limited, What is necessary is just to determine from the usage-amount per unit time of raw | natural water, but a water tank of about 3L is preferable.
Moreover, it is preferable to make the water temperature in a tank into the fixed temperature of about 20 degreeC. When the water temperature is high, the volatilization of the organic chemical substance increases in the next dissolution tank, which is not preferable.

Purification test tank The purification test tank is a tank for investigating the ability of microorganisms in the test soil to decompose the organic chemical substances, the environment of the microorganisms, and the like.
The purification test tank and the pipe are made of a material that does not adsorb the organic chemical substance to be tested (preferably stainless steel, fluororesin, etc.).
Although the magnitude | size of a tank is not specifically limited, About 200L-12000L is preferable and the intensity | strength which can be endured even if it fills with soil is required. In addition, it is desirable to keep the temperature in the tank constant, and therefore, it is preferable to provide a water jacket or the like. Moreover, in order to prevent volatilization of organic chemical substances, it is preferable to put a lid and make it semi-sealed.
The raw water inlet section has a structure that can adjust the flow rate by branching a number of pipes from the feed pump and installing a flow meter in each line (Fig. 3). It is desirable that water flowing through the test tank (hereinafter referred to as “flowing water”) does not drift (FIG. 5). The rectifying unit is preferably composed of silica sand, gravel, glass beads, and a filter (such as glass and stainless steel). In the case where the purification test tank is about 500 L, it is preferable that the liquid feed pump is capable of feeding a stable flow rate with a pump having a flow rate range of about 5 to 60 mL / min.
Moreover, it is desirable to provide a rectification | straightening part also in an exit part and to provide many exit piping, and to prevent flowing water from drifting in a tank (FIG. 5).
If all the outlet pipes are once raised to the same height and then discharged, the water level in the tank can be adjusted to that height (FIG. 4).
Furthermore, the purification test tank may be provided with a monitoring (sampling) well to collect running water. The inner diameter of the well tube is preferably 20 to 30 mm, and a large number of holes are formed on the side surface, and a structure in which running water flows in the tube is preferable. Further, in addition to making a large number of holes on the side surface of the well pipe, a necessary part of the pipe may be meshed or may have a slit structure.

  It is environmentally preferable to discharge the effluent from the purification test tank after treating it in an aeration tank or the like.

Example 1
A soil purification test apparatus shown in FIG. 6 was prepared and used for the test.
The soil purification test apparatus includes an organic chemical substance addition apparatus, a dissolution tank that stirs and mixes the organic chemical substance and water, a raw water tank that stores a mixed liquid obtained in the dissolution tank, and raw water in the raw water tank. And a purification test tank for containing soil to pass through, and a dissolved oxygen concentration adjusting tank for adjusting the dissolved oxygen concentration of water supplied to the dissolving tank is provided upstream of the dissolving tank.

Organic Chemical Substance Adder The organic chemical substance used here is a mixture (BTX) mixed at a ratio of 10% by weight of benzene, 80% by weight of toluene and 10% by weight of xylene.
The organic chemical substance adding device is composed of an organic chemical substance tank containing the BTX, a circulation pump, a six-way valve, a calibration pipe (capacity 0.3 mL) and a pipe.
First, BTX is circulated in the order of an organic chemical tank, a 6-way valve, a calibration tube, a 6-way valve, and an organic chemical tank by a circulation pump.
Then, the 6-way valve is switched by a signal from the sensor, and the organic chemical substance in the calibration tube is pushed out by air and sent to the dissolution tank. After the organic chemicals in the calibration tube are completely replaced with gas, the 6-way valve returns to its original state and enters the circulation state again.
Such switching of the 6-way valve was automatically performed by a signal from a liquid height sensor of a dissolution tank or a raw water tank. That is, the capacity of the raw water tank is 20L, but when it is reduced by 10%, raw water is prepared and supplied to the raw water tank.

  Here, the organic chemical substance tank was a constant temperature bath of 4 ° C. The 6-way valve and the calibration tube used were those used for sample injection in high performance liquid chromatography (UV 6162S manufactured by Denso Sangyo Co., Ltd.).

Dissolution tank The dissolution tank is a 2 L tank as shown in FIG. 6 and has stirring blades having a diameter of 60 mm.
First, 300 μL of an organic chemical substance was automatically added to 2 L of water using the organic chemical substance addition apparatus.
Next, the mixture was stirred with a stirring blade at 600 rpm for 10 minutes to obtain raw water. The concentration of BTX in the raw water was automatically adjusted to 100 mg / L.

Raw water tank The raw water obtained in the dissolution tank was sent to the raw water tank by opening the solenoid valve at the bottom of the dissolution tank. The internal capacity of the raw water tank is 20L. The raw water tank is a thermostatic tank controlled to a purification test temperature (20 ° C.).
When the amount of raw water in the tank decreases by 10% (2 L), raw water is prepared as described above and immediately supplied to the tank.
The raw water produced as described above was 80 L per day.

Dissolved oxygen concentration adjusting tank A 3 L water tank was used. Nitrogen gas was bubbled to reduce the amount of dissolved oxygen in the water.

Purification test tank As a purification test tank, a stainless steel water tank having an internal volume of 540 L and an internal size (mm) of 1500 W × 600 D × 600 H was used. The inside of the tank was kept at a constant temperature (20 ° C.) with a water jacket. About 700 kg of soil was put in this.
The raw water inlet section is divided into four pipes from the pump, and a flow meter is installed in each line so that the flow rate can be adjusted (Fig. 3). Provided (FIG. 5), so that running water does not drift in the tank. The rectifying unit was provided by filling No. 1 silica sand with a thickness of 15 cm over the entire raw water inflow side of the purification test tank.
Also, the outlet portion is provided with a rectifying portion, and nine outlet pipes are provided so that running water does not drift in the tank. All the outlet pipes were once raised to the same height and then discharged (FIG. 4), and the water level in the tank was adjusted to that height.
The flow rate of running water in the purification test tank was 80 L / day.
Furthermore, a sampling well was provided in the purification test tank. The inner diameter of the well tube was 27.6 mm, and a large number of holes were made on the side surface, so that running water flowed through the tube.

  The effluent from the purification test tank was treated with an aeration tank and then drained.

Raw water preparation results Raw water was prepared using the apparatus of the above example. The raw water was automatically prepared about 40 times a day and supplied to the raw water tank. Table 1 shows the results of measuring the concentration of BTX by sampling from the raw water tank once a day.

Example 2
Oxygen was vented from the center of the purification test tank, and the test was performed in the same manner as in Example 1 except that the BTX concentration in the raw water was 75 mg / L. As a comparison, a test using a test apparatus in which soil was packed in a conventional column was also conducted. These results are shown in FIG. Oxygen ventilation conditions are as follows: Six stainless steel tubes with an outer diameter of 1.6 mm and an inner diameter of 0.8 mm are inserted into the soil in which the flowing water flows in the purification test tank, and oxygen gas is supplied to the flowing water at a flow rate of 5 mL / min. And bubbling.
From this result, it can be seen that the conventional column test apparatus cannot supply oxygen and BTX is hardly purified. Moreover, it turns out that the microorganisms in this soil require oxygen in order to exhibit BTX resolution.

  According to the present invention, since raw water having a stable concentration is supplied, highly reliable data can be obtained.

It is a figure which shows the outline | summary of the purification test apparatus of this invention. It is a figure which shows an organic chemical substance addition apparatus. It is a figure which shows the entrance part of a purification test tank. It is a figure which shows the exit part of a purification test tank. It is a top view of a purification test tank. It is a figure which shows the purification test apparatus of an Example. It is a figure which shows a purification test result.

Claims (4)

The organic chemical substance is circulated through the 6-way valve between the calibration tube and the organic chemical substance tank, and by switching the 6-way valve, a certain amount of the organic chemical substance in the calibration tube is extruded with gas and sent to the dissolution tank . Process ,
A step of stirring and mixing the organic chemical substance and water in the dissolution tank to adjust the concentration of the organic chemical substance in the mixed solution to a predetermined concentration ;
A step of storing the simulated contaminated groundwater resulting in simulated groundwater contaminated tank,
Adjusting the liquid level of the simulated contaminated groundwater in the simulated contaminated groundwater tank ;
A step of supplying the simulated groundwater contamination of the simulated polluted ground water tank during cleaning test bath containing test soil,
A step of evaluating the fluid passing through the soil
With
In the process of adjusting the liquid height, when it is detected that the amount of simulated contaminated groundwater in the simulated contaminated groundwater tank has decreased, a simulated contaminated groundwater is prepared in the dissolution tank, and the simulated contaminated groundwater is placed from the dissolution tank to the simulated contaminated groundwater tank. A soil remediation test method characterized by adjusting the liquid level by quantitative replenishment . Water supplied to the dissolving tank is clean test methods soil according to claim 1, wherein in which the dissolved oxygen concentration has been adjusted. An organic chemical substance tank, a pump for circulating the organic chemical substance, a calibration pipe, and a six-way valve are provided, and the organic chemical substance is circulated between the calibration pipe and the organic chemical substance tank via the six-way valve. An organic chemical substance addition device that pushes out a certain amount of organic chemical substance in the calibration tube with gas and sends it to the dissolution tank by switching the direction valve,
A dissolution tank for stirring and mixing the organic chemical substance and water to adjust the concentration of the organic chemical substance in the mixed solution to a predetermined concentration ;
A simulated contaminated groundwater tank for storing the mixed liquid obtained in the dissolution tank;
Liquid level adjusting means for adjusting the liquid level of the simulated contaminated groundwater in the simulated contaminated groundwater tank;
Purification test tank for storing the test soil through which the simulated contaminated groundwater in the simulated contaminated groundwater tank passes.
With
When the liquid level adjustment means detects that the simulated contaminated groundwater in the simulated contaminated groundwater tank has decreased by a predetermined amount, it prepares the simulated contaminated groundwater in the dissolution tank and replenishes the simulated contaminated groundwater from the dissolution tank to the simulated contaminated groundwater tank. Then , a soil purification test apparatus characterized in that the liquid height is adjusted . Furthermore, the soil purification test apparatus of Claim 3 which has a dissolved oxygen concentration adjustment tank which adjusts the dissolved oxygen concentration of the water supplied to a dissolution tank by bubbling.