JP2003340431A - Biological cleaning method and apparatus for polluted soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological cleaning method and an apparatus for contaminated soil capable of controlling ventilation according as degradation activity of microorganisms. <P>SOLUTION: An oxygen analyzer 5 is disposed in the contaminated soil S and a decrease rate (δ[O<SB>2</SB>]/δt) of residual oxygen concentration [O<SB>2</SB>] is measured by using the oxygen analyzer 5. The contaminated soil S is cleaned while the ventilation volume into the contaminated soil S is controlled in accordance with the decrease rate (δ[O<SB>2</SB>]/δt). The oxygen consumption C<SB>02</SB>in the contaminated soil S is calculated from the decrease rate (δ[O<SB>2</SB>]/δt) of residual oxygen concentration [O<SB>2</SB>] and the soil air volume VSPACE of the contaminated soil S and the ventilation volume into the contaminated soil S is controlled in accordance with the oxygen consumption C<SB>02</SB>. Further preferably, a thermometer 6 is disposed in the contaminated soil S and a soil temperature TSOIL is measured by using the thermometer 6. The ventilation into the contaminated soil is then controlled in accordance with the oxygen consumption C<SB>02</SB>and the soil temperature TSOIL. The ventilation volume is preferably controlled by each of respective areas by disposing the oxygen analyzers 5 and/or the thermometers 6 into a plurality of the areas of the contaminated soil S. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological purification method and apparatus for contaminated soil, and more particularly to a biological purification method and apparatus for purifying contaminated soil by supplying oxygen necessary for activation of aerobic microorganisms in the soil.

[0002]

2. Description of the Related Art In recent years, there has been an increasing number of cases where soil pollution by petroleum hydrocarbon compounds, halogenated hydrocarbon compounds, etc. has become a problem at sites such as industrial sites such as factories. Soil constitutes the land that is the basis of human life and economic activities, and if contaminated soil is left untreated, there is a concern that it may affect human health through direct intake, groundwater, agricultural products, seafood, etc. If it is difficult to block or contain the contaminated soil or if it interferes with the redevelopment project, it is necessary to clean the contaminated soil.

As one of the techniques for purifying contaminated soil, an aerobic pollutant naturally existing in the soil or artificially added to the soil is a substance causing contamination in the soil (hereinafter referred to as pollutant). A biological treatment method has been developed in which a degrading microorganism (hereinafter, simply referred to as an aerobic microorganism) is decomposed and removed. The biological treatment method is a method of directly decomposing pollutants, and is expected to have effects such as no secondary waste generation, less energy required for treatment, and purification to low concentrations that are difficult to achieve by physical and chemical treatment alone. There is.

In the biological treatment method, since aerobic microorganisms in the soil are artificially activated, nutrients such as nitrogen and phosphorus and moisture are supplied to the soil, and aeration of the soil is appropriately controlled. There is a need to. Oxygen in soil (including oxygen in soil voids) is consumed by aerobic microorganisms along with the decomposition of pollutants, so if the amount of aeration is low, the oxygen concentration in soil will gradually decrease and the decomposition reaction will not proceed. . On the other hand, too much ventilation not only makes economic soil remediation difficult,
It is not preferable from the environmental point of view because it wastes energy.

[0005] For example, as an example of aeration method of biological treatment method, excavated contaminated soil is piled up in a pile shape and forcedly aired through a ventilation pipe laid or inserted at the lower end of the pile or an intermediate portion between the lower end and the top end. A forced ventilation method is used in which (or oxygen) is injected or sucked. Conventionally, in the forced ventilation method of a method of sucking air (air suction method), the oxygen concentration in the sucked exhaust gas is measured, and the oxygen concentration is 5 to 8% or more and 20% or less (desirably 15 to 20%). The air flow rate is controlled so that

[0006]

However, the above-mentioned control of the ventilation amount based on the oxygen concentration in the exhaust gas has the following problems.

(A) Aeration of contaminated soil is performed by oxygen consumption of aerobic microorganisms in the soil, that is, pollutant decomposition activity (hereinafter,
It may be simply called decomposition activity. ) Is suitable and economical. However, it is difficult to accurately grasp the oxygen consumption amount or rate of aerobic microorganisms from the oxygen concentration in the exhaust gas. For example, when consolidation or humidity change occurs in the soil, the ventilation state in the soil changes and the oxygen concentration in the exhaust gas changes. The oxygen consumption rate of microorganisms also changes depending on the soil temperature. That is, it is difficult to perform aeration according to the decomposition activity of aerobic microorganisms by the control based only on the oxygen concentration in the exhaust gas.

(B) It is appropriate and economical to control the ventilation of the contaminated soil according to the progress of soil purification. As the purification progresses and the concentration of pollutants in the soil decreases, the oxygen consumption of microorganisms decreases, and the oxygen concentration in the exhaust gas increases accordingly. However, as described above, the oxygen concentration in the exhaust gas changes due to factors other than oxygen consumption by microorganisms,
For example, an increase in oxygen concentration in exhaust gas due to excessive ventilation may be mistaken for a decrease in oxygen consumption of microorganisms or a decrease in pollutant concentration in soil. That is, it is also difficult to perform ventilation according to the progress of soil purification by the control based only on the oxygen concentration in the exhaust gas.

(C) Aeration of contaminated soil may be performed by a method of injecting air into the soil (air intrusion method). However, although the control of the ventilation amount based on the oxygen concentration in the exhaust gas described above is applicable in the ventilation of the air suction method,
It cannot be used for air-pressurized ventilation. This is because, in the air injection method, exhaust gas is ejected from the entire soil surface, so there is no suitable method for measuring the oxygen concentration in the exhaust gas. It is desired to develop a ventilation control technology that can be applied to the air injection method.

Therefore, an object of the present invention is to provide a method and apparatus for biological purification of contaminated soil, which can control aeration according to the decomposition activity of microorganisms.

[0011]

The present inventor has paid attention to measuring the residual oxygen concentration in the contaminated soil in order to judge the degrading activity of aerobic microorganisms in the contaminated soil. For example, since residual oxygen in soil without air is exclusively consumed and reduced in the process of decomposing pollutants by aerobic microorganisms in soil, the rate of decrease in residual oxygen concentration can be regarded as the rate of oxygen consumption by aerobic microorganisms. . That is, the activity of decomposing aerobic microorganisms in the soil can be determined by measuring the rate of decrease in the residual oxygen concentration in the soil without aeration. Also, for example, if the air flow rate is constant,
Degradation activity of aerobic microorganisms in soil can be estimated to some extent from the rate of decrease of residual oxygen concentration in soil during aeration.
The present invention has been completed as a result of research and development based on this knowledge.

See the block diagram of FIG. 1 and the flow chart of FIG.
In addition, the method for biological purification of contaminated soil according to the present invention is
Purify soil S by aeration of aerobic microorganisms in the soil
In the method, an oxygen meter 5 is provided in the contaminated soil S to remove residual acid.
Elementary concentration [O₂] Decrease rate (δ [O ₂] / Δt) is measured with an oxygen meter 5.
(See steps 205 to 207 in Fig. 2) and the rate of decrease
(Δ [O₂] / Δt) Aeration to the contaminated soil S based on the measured value
The amount is controlled.

Preferably, the oxygen consumption amount C _O2 in the contaminated soil S is calculated from the decrease rate (δ [O ₂ ] / δt) of the residual oxygen concentration [O ₂ ] and the soil air volume V _SPACE of the contaminated soil S. (Refer to step 208 of FIG. 2), the aeration amount to the contaminated soil S is controlled based on the calculated value of the oxygen consumption amount C _O2 . More preferably, a thermometer 6 is provided in the contaminated soil S, and the soil temperature T _S is measured by the thermometer 6.
_{The OIL} is measured, and the air flow rate to the contaminated soil S is calculated based on the oxygen consumption C _O2 and the soil temperature T _SOIL (step 20 in FIG. 2).
See 9). Desirably, the rate of decrease of the residual oxygen concentration [O ₂ ] (δ [O ₂ ] / δt) is measured without aeration. It is desirable to provide the oxygen meter 5 and / or the thermometer 6 at a plurality of sites in the contaminated soil S and control the amount of ventilation to the contaminated soil S for each site.

Further, referring to the block diagram of FIG. 1, the biological purification apparatus for polluted soil according to the present invention has a ventilation device 1 for ventilating the polluted soil S, an oxygen meter 5 provided in the polluted soil S, and a residual oxygen concentration [ Control for measuring the rate of decrease of O ₂ ] (δ [O ₂ ] / δt) with an oximeter 5 and controlling the ventilation rate of the ventilation device 1 based on the measured value of the rate of decrease (δ [O ₂ ] / δt). The device 10 is provided.

Preferably, the controller 10 determines the amount of oxygen consumption in the contaminated soil S from the decreasing rate (δ [O ₂ ] / δt) of the residual oxygen concentration [O ₂ ] and the soil air volume V _SPACE of the contaminated soil S. C _O2
Is calculated and the ventilation amount of the ventilation device 1 is controlled based on the calculated value of the oxygen consumption amount C _O2 . More preferably, a thermometer 6 for measuring the soil temperature T _SOIL is provided in the contaminated soil S, and the controller 10 calculates the ventilation amount of the ventilation device 1 based on the oxygen consumption amount C _O2 and the soil temperature T _SOIL . Desirably, the rate of decrease of the residual oxygen concentration [O ₂ ] (δ [O ₂ ] / δt) is measured without aeration.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the present invention is applied to the purification of contaminated soil S excavated from the ground and piled up. In the illustrated example, the contaminated soil S mixed with a nutrient substance such as a suitable nutrient salt after excavation is piled up as a pile in the purification yard Y, and the ventilation device 1 keeps the humidity of the contaminated soil S appropriate while the contaminated soil pile is piled up. Is vented to. Hereinafter, the apparatus of the present invention will be described with reference to FIG. 1, but the scope of application of the present invention is not limited to the purification of the excavated contaminated soil S, but the purification of the contaminated soil E as shown in FIG. Sometimes, it is also applicable.

The ventilation device 1 in the illustrated example is a blower.
4 and a porous ventilation pipe 3 with a flow rate control valve 2. Air is supplied from the pile surface into the soil S by inserting the ventilation pipes 3 side by side on the horizontal section of the contaminated soil S and sucking air through the blower 4 and the ventilation pipe 3. However, the number and arrangement of the ventilation pipes 3, the presence or absence of control valves, the number of holes, etc. are not limited to the illustrated examples, and for example, the ventilation pipes 3 are laid in the purification yard Y and air is sucked from the lower end surface of the contaminated soil S. May be. Further, the ventilation pipes 3 can be provided in two or three or more stages between the lower end and the middle of the contaminated soil S depending on the size of the ventilation resistance of the contaminated soil S and the height of the pile. Although the illustrated example shows the air suction type ventilation device 1, the present invention is also applicable to the case where the ventilation device 1 is of the air pressure type. In the case of the air pressure injection method, air or oxygen gas can be supplied.

Further, the biological purification device of the present invention comprises a ventilation device 1.
In addition, it has an oxygen meter 5 installed in the contaminated soil S. For example, the oxygen meter 5 is buried in an appropriate portion on the way of stacking the contaminated soil S. When the contaminated soil S has a plurality of parts with different ventilation states, it is desirable to provide the oxygen meter 5 in each part. In the illustrated example, a plurality of oximeters 5 are arranged along the length direction of the ventilation pipe 3 at an intermediate portion between the adjacent ventilation pipes 3 so as to have an intermediate height between the insertion cross-section of the ventilation pipe 3 and the pile top surface. (See FIGS. 1A and 1B). If necessary, an oxygen meter 5 may be provided between the ventilation pipe 3 and the side surface of the pile. However, the number and arrangement of the oximeters 5 are not limited to the example shown in the figure, and the oximeters 5 may be arranged at appropriate positions according to the ventilation characteristics of the contaminated soil S, the arrangement position of the ventilation pipe 3, the height of the pile, and the like.
Can be placed.

The oximeter 5 has, for example, a thin sampling pipe inserted into the contaminated soil S, and a general oxygen sensor (for example, a polarographic type or a galvanic cell type) for measuring the oxygen concentration in the gas sucked from the contaminated soil S. ) Can be. However, the gas suction type oxygen sensor requires a long measurement time because the batch measurement is repeated, and gas suction may affect the oxygen concentration in the soil, and measurement error may occur due to oxygen consumption of the sensor itself. There is a problem. A preferable example of the oximeter 5 used in the present invention is a fluorescence oximeter which consumes less oxygen. The fluorescence oximeter utilizes a phenomenon in which the intensity of fluorescence generated when a special organic substance is irradiated with near-ultraviolet light is attenuated according to the oxygen concentration, and the contaminated soil S is consumed in real time without consuming oxygen.
The oxygen concentration in the inside can be measured.

Further, the biological purifying device of the present invention comprises a ventilation device 1.
And a control device 10 connected to the oximeter 5. The control device 10 inputs the measurement value of the oximeter 5 and controls the flow control valve 2 and / or the blower 4 of the ventilation device 1. The control device 10 of the illustrated example includes a storage unit 20, a ventilation control unit 30, an input unit 32, and a display unit 33. The storage means 20 stores the ventilation amount 24, the ventilation time 25, the no ventilation time 26, etc., and the ventilation control means 30 controls the ventilation of the ventilation device 1 based on the ventilation amount 24, the ventilation time 25, the no ventilation time 26, etc. . The input means 32 includes a keyboard, a mouse, etc. for inputting a decomposition reaction formula 22 of pollutants, a change 23 in the concentration of remaining pollutants over time, and the like, which will be described later. Display means
One example of 33 is the measured value of the oxygen meter 5 and the ventilation volume of the ventilation device 1 of 24.
It is a display that displays, etc.

The control device 10 of the illustrated example inputs the measured value of the oxygen meter 5 and decreases the residual oxygen concentration [O ₂ ] in the soil S (δ).
[O _2] / δt) decrease rate measuring means 12 for measuring the reduction rate _{(δ [O 2] / δt} ) and contaminated soil oxygen consumption C _O2 contaminated soil S from the soil air volume V _SPACE of S It has an oxygen consumption calculating means 13 for calculating, and an updating means 14 for updating the ventilation amount 24 of the storage means 20 based on the rate of decrease (Δ [O ₂ ] / Δt) or the oxygen consumption C _O2 . For example, the control device 10 may be a computer, and the decrease rate measuring means 12, the oxygen consumption calculating means 13, the updating means 14, and the ventilation control means 30 may be a computer built-in program.

The biological purification apparatus in the illustrated example is designed to control the temperature of the soil S.
Degree T_SOILSupply thermometer 6 to measure soil and contaminated soil S
Air temperature T_AIRAnd a thermometer 7 for measuring. thermometer
6 and 7 are connected to the control unit 10, and the above-mentioned decreasing speed (δ
[O₂] / Δt) or oxygen consumption C _O2In addition to soil temperature T_SOIL
And air temperature T_AIRIf you update the ventilation rate 24 based on
Temperature T_SOILAnd air temperature T_AIRIf there is a temperature difference between
In addition, avoiding excess or shortage of ventilation volume 24 due to the temperature difference.
You can kick. However, the thermometers 6 and 7 are essential to the present invention.
Not the one.

Next, referring to the flow chart of FIG.
A method of controlling the ventilation device 1 by 10 will be described. First, in step 203, the ventilation control means 30 of the control device 10 adjusts the flow rate control valve 2 and / or the blower 4 of the ventilation device 1 to the initial ventilation amount, and the purification of the contaminated soil S is started. The oxygen concentration is measured by the oximeter 5, and ventilation is continued until the oxygen concentration in the contaminated soil S reaches a predetermined concentration or higher (for example, 20% or higher). The initial ventilation amount of the ventilation device 1 can be appropriately set so that a predetermined oxygen concentration can be obtained, or the ventilation amount can be appropriately adjusted after the start of ventilation. Note that steps 201, 202 and 204 in FIG.
Will be described later.

After the predetermined oxygen concentration is obtained, step 205
At step 206, the aeration device 1 is stopped, and at step 206, the oxygen meter 5 measures the change in the residual oxygen concentration [O ₂ ] when there is no ventilation. An example of the measured value of the oximeter 5 is shown in the graph of FIG.
As can be seen from the graph, the residual oxygen concentration [O ₂ ] decreases with the passage of the non-aeration time. The rate of decrease can be expressed as in equation (1). In the equation (1), [O ₂ ] ₀ is the initial residual oxygen concentration immediately after the ventilation is stopped (≈the above predetermined concentration), t
Represents the elapsed time of no ventilation, and k represents the oxygen consumption rate coefficient.
Equation (2) is derived by integrating equation (1). In the equation (2), [O ₂ ] _M represents the residual oxygen concentration after the lapse of time M (for example, after M days), and D _O2 represents the difference between the initial residual oxygen concentration and the residual oxygen concentration after the lapse of time M.

[0025]

[Equation 1]

In step 207, for example, by determining the constants [O ₂ ] ₀ and k in the equation (1) based on the measured values shown in FIG. 4, the rate of decrease of the residual oxygen concentration [O ₂ ] (δ [O ₂ ] / δt) is measured. An example of the decrease rate measuring means 12 of FIG.
It is a program that determines the constants [O ₂ ] ₀ and k of the equation (1) from the measured values of. Decrease rate of residual oxygen concentration [O ₂ ] (δ
From [O ₂ ] / δt), the decomposition activity of aerobic microorganisms around the oxygen meter can be judged. That is, by controlling the aeration to the contaminated soil S based on the rate of decrease (δ [O ₂ ] / δt), the aeration according to the decomposition activity of aerobic microorganisms becomes possible. Note that, for example, if the aeration amount is constant, it is also possible to determine the degrading activity of aerobic microorganisms in the soil to some extent from the rate of decrease in the residual oxygen concentration in the soil during aeration, and in this case, step 205
It is not necessary to stop the ventilation device 1 at.

Steps 208 to 209 in FIG. 2 are the residual oxygen concentration.
Shows an example of a method of calculating the airflow amount Q of [O _2] to decrease the speed ([delta] [O _2] / .DELTA.t) based on the contaminated soil S in. Step 207
If the rate of decrease (δ [O ₂ ] / δt) measured in step 3 is integrated over M days, the oxygen concentration consumed by aerobic microorganisms during M days
D _O2 (% unit) can be calculated (Equation (2)). Furthermore, from the oxygen concentration D _O2 to be consumed, the soil air volume V _SPACE of the contaminated soil S, and the equation of state of gas, the oxygen consumption C _O2 of the contaminated soil S for M days can be calculated by the equation (3). In the equation (3), the output of the thermometer 6 is the soil temperature T _SOIL (° C), and the volume S _{P of the} soil S is
The product of (volume in piles in this case, in liters) and the volume ratio of the gas phase to the entire soil S (= φ−φ _WT ) is the soil air volume V _SPACE, and the oxygen consumption of the entire soil S is equal. I assumed. In the equation (3), φ is the porosity of the soil S (including the gas phase and the liquid phase), and φ _WT is the product of the porosity φ and the saturation degree Sr (the volume ratio of the liquid phase to the entire pore) (= φ. × Sr).

Step 208 in FIG. 2 shows a process for calculating the oxygen consumption amount C _O2 of the contaminated soil S by the equations (2) and (3).
When oxygen gas is supplied by the aeration device 1 by the press-fitting method, for example, the oxygen consumption amount C _O2 (per M days) or C _O2 / M (per day) calculated in step 208 is passed to the contaminated soil S (flow rate (flow rate)). ) Q and update means 1 in step 209
The ventilation amount 24 of the storage means 20 is updated by 4.

Step 209 of FIG. 2 shows a process of calculating the required air amount V _AIR by the equation (4) when the oxygen consumption amount C _O2 calculated in step 208 is _covered by air. In the same equation,
The oxygen volume ratio in the air was 20.9%, and the output of the thermometer 7 was the air temperature T _AIR (° C). When the air volume V _AIR is supplied in M days, the daily air flow rate Q can be calculated by the equation (5). When air is supplied by the ventilator 1 by a press-fitting method, for example, the air volume V _AIR of (4) formula (per M days)
Alternatively, V _AIR / M (per day) in the equation (5) is set as the air flow rate (flow rate) Q to the contaminated soil S, and the updating means 14 is set in step 209.
Thus, the ventilation amount 24 of the storage means 20 can be updated.

In step 214, the ventilation control means 30 adjusts the flow rate control valve 2 and / or the blower 4 of the ventilation device 1 to the ventilation amount 24 of the storage means 20 to restart the ventilation. Oxygen consumption C _O2 or air amount V _AIR calculated in step 208 or 209
Is, so to speak, the minimum required ventilation amount Q for purifying the contaminated soil S at the time when ventilation is stopped. If the ventilation is restarted with the ventilation amount Q, it is possible to avoid unnecessary ventilation and economically proceed with the purification of the contaminated soil S. Furthermore, steps 205 to 209 and 214 can be repeated according to the progress of soil purification, and the minimum required ventilation amount Q can be updated according to the progress of soil purification.

For example, when purifying the soil S contaminated with oil, it is known that if the oxygen concentration in the contaminated soil S is about 5%, no problem occurs in the decomposition activity of aerobic microorganisms. Therefore, the oxygen concentration in the soil S is reduced to about 5% as shown in FIG. 4 when no ventilation is performed in steps 205 to 209, and thereafter the oxygen concentration in the soil S is reduced to 5% by the minimum aeration amount Q.
If maintained at about%, it is possible to expect extremely economical purification of contaminated soil.

After restarting ventilation with the minimum ventilation amount Q, the oxygen concentration in the soil S remains constant (for example, 5%) for a while.
However, the oxygen consumption of aerobic microorganisms gradually decreases with the progress of soil remediation. For this reason, the oxygen concentration after resumption of ventilation is measured by the oximeter 5, and when the oxygen concentration increases to a predetermined concentration (for example, 20%), the process returns to step 205, the ventilation is stopped, and the storage means is executed by steps 205 to 209. Update airflow rate 24 of 20 according to soil remediation and step 21
Repeat the cycle to restart ventilation with the air volume updated in 4.

However, the ventilation amount at the time of renewing and restarting the ventilation of steps 209 and 214 is not limited to the above-mentioned minimum ventilation amount Q, but may be any other appropriate ventilation amount. For example, as will be described later, according to the present invention, the amount of ventilation to the contaminated soil S can be adjusted based on the increasing tendency of the oxygen concentration after resumption of ventilation, so that, for example, the rate of decrease of the residual oxygen concentration [O ₂ ] (δ [ O
₂ ] / δt), the ventilation is restarted at an appropriate ventilation Q, and after the ventilation is restarted, the ventilation Q is adjusted based on the increasing tendency of the oxygen concentration, thereby controlling the ventilation according to the decomposing activity of aerobic microorganisms. It is also possible.

Further, the repeating method of steps 205 to 209 and 214 is not limited to this example, and the cycle may be controlled based on the ventilation time 25 and the non-venting time 26 of the storage means 20, for example, as described later. Good. It is also conceivable to combine the method for controlling the ventilation device 1 according to the present invention with conventional PID control or the like. That is, after restarting the ventilation with the minimum ventilation amount Q in step 214, the ventilation can be controlled by the conventional PID control so that the oxygen concentration in the contaminated soil S reaches the target value.

According to the present invention, the aeration to the contaminated soil can be controlled according to the decomposing activity of aerobic microorganisms in the contaminated soil, and the soil purification can be economically promoted by the necessary minimum aeration. . Further, by updating the minimum required ventilation amount according to the progress of soil purification, it is possible to perform appropriate and economical ventilation according to the progress of soil purification. Moreover, the present invention is applicable not only to the air suction method but also to the air (or oxygen) injection method. In addition, automatic control of ventilation to contaminated soil can be expected by combining with the control of ventilation time and non-venting time, which will be described later.

Thus, the object of the present invention is to provide the "method and apparatus for biological purification of contaminated soil in which aeration can be controlled according to the activity of microorganisms to decompose pollutants".

In the above equation (3), the oxygen consumption amount C _O2 was calculated assuming that the oxygen consumption amount of the entire contaminated soil S was equal. Oxygen consumption C _O2 of aerobic microorganisms differs at different sites.
Therefore, it is desirable to provide the oxygen meter 5 (preferably together with the thermometer 6) at a plurality of sites in the contaminated soil S and control the ventilation amount Q for each site according to the flowchart of FIG.

For example, in FIG. 1, a plurality of ventilation pipes 3 with flow rate control valves 2 are provided in the vicinity of the installation positions of a plurality of oximeters 5, respectively, and the aeration amount 24 is measured according to the flow chart of FIG. Is updated and the flow rate control valve 2 corresponding to each part is adjusted. Blower 4 for a plurality of ventilation pipes 3
Or a separate blower 4 is provided for each part. By controlling the aeration independently for each part of the contaminated soil S having different pollutant concentrations, more appropriate and economical soil purification can be expected.

In the example of FIG. 1, the porous ventilation pipes 3a, 3b, 3c
, A plurality of oximeters 5 are arranged along each of the lengths. In this case, the amount of ventilation to the ventilation pipes 3a and 3b is controlled based on the minimum measurement value of each oxygen meter 5 between the ventilation pipes 3a and 3b, and the minimum measurement of each oxygen meter 5 between the ventilation pipes 3b and 3c is controlled. The amount of ventilation to the ventilation pipes 3b and 3c can be controlled based on the value.

[0040]

[Examples] Steps 210 to 213 in FIG. 2 grasp the progress of soil purification based on the rate of decrease (δ [O ₂ ] / δt) of the residual oxygen concentration [O ₂ ] when there is no aeration, and the progress The process of controlling the ventilation time (and / or non-venting time) of the ventilation device 1 and detecting the completion of purification according to the above. In this case step 20
In 1, a formula for decomposing a pollutant in a contaminated soil S by an aerobic microorganism is determined as shown in formula (12) and stored in the storage means 20 of the control device 10.

[0041]

[Chemical formula 1] C _a H _b + (a + b / 4) O ₂ → a CO ₂ + (b / 2) H ₂ O …………………………………… (11) C ₆ H _7.5 ＋7 .875O ₂ → 6CO ₂ + 3.75H ₂ O ………………………………………… (12)

For example, when the pollutant is oil, theoretically, as shown in the formula (11), 1 mol of the pollutant is calculated from the analysis result of the composition of the oil (chemical formula of the hydrocarbon compound CaHb in the formula (11)). The amount of oxygen (a + b / 4) required to decompose can be estimated. However, the oxygen content of the pollutant decomposition reaction in actual soil remediation does not match the theoretical oxygen content (a + b / 4) because the pollutant is not completely decomposed and changes into various intermediate metabolites. Many. Therefore, by performing indoor experiments, etc., the time-dependent concentration changes of residual pollutants and residual oxygen in the contaminated soil S due to the decomposition of aerobic microorganisms are measured, and the decomposition reaction formula of the pollutants in the contaminated soil S by the aerobic microorganisms is determined. There is a need.
Equation (12) shows an example of an experimentally determined pollutant decomposition reaction equation.

If the pollutant decomposition reaction equation is defined as in the equation (12), the rate of decrease of the residual oxygen concentration [O ₂ ] (δ [O ₂ ] / δt) can be calculated from the pollutant decomposition rate ( _{δD CaHb} / δt). ) Can be calculated (step 210). The graph of FIG. 5 shows experimentally measured values of changes over time in the concentration of residual pollutants in contaminated soil S due to the decomposition of aerobic microorganisms, and the decomposition rate of pollutants ( _{δD CaHb} / δt) is shown in the graph. It corresponds to the slope (soil cleaning rate). As can be seen from the graph, the decomposition rate of pollutants decreases as the concentration of residual pollutants in the polluted soil S decreases. That is, the degree of progress of soil purification can be grasped from the decomposition rate of pollutants, and the aeration time required for soil purification thereafter and the completion of soil purification can be determined based on the decomposition rate of pollutants.

For example, when the decomposition rate is high, it can be estimated that the concentration of residual pollutants in the contaminated soil S is high, and the decomposition activity of aerobic microorganisms changes greatly in a short time of aeration. Repeat the cycle of the flow chart of 2 in a short time. On the other hand, when the decomposition rate is low, it can be estimated that the concentration of residual pollutants in the contaminated soil S is low, and the decomposition activity of aerobic microorganisms is also small, so that the aeration time can be lengthened. When the decomposition rate is low, it is desirable to secure a sufficient non-venting time or to ventilate the soil S intermittently so that the oxygen concentration in the soil S does not unnecessarily increase. The ventilation time / non-venting time depending on the decomposition rate can be experimentally determined in advance and stored in the storage means 20.

Preferably, in step 202, the measured value of the time-dependent concentration change of the remaining pollutant as shown in FIG. 5 is stored in the storage means 20 of the control device 10, and the pollutant decomposition rate and the storage means calculated in step 210 are stored. 20 Concentration change over time (Fig. 5
(Gradient of the graph) and the soil S in step 211
Detect the concentration of residual pollutants in. If the residual pollutant concentration is known, it is possible to easily determine the ventilation time required for soil purification after that and the completion of soil purification, and further energy saving of soil purification can be expected. The aeration time / non-aeration time according to the residual pollutant concentration and the residual pollutant concentration after completion of purification can be stored in the storage means 20 in advance.

The control device 10 of FIG. 1 stores in the storage means 20 the decomposition reaction formula 22 (for example, formula (12)) of pollutants and the measured value of the concentration change 23 of residual pollutants with time (for example, the graph of FIG. 5). I remember. Further, the decomposition rate detection for detecting the decomposition rate of pollutants in the soil S from the decrease rate (δ [O ₂ ] / δt) of the residual oxygen concentration [O ₂ ] when there is no aeration and the decomposition reaction formula 22 of the storage means 20. It has means 15 and residual pollutant concentration detection means 16 for detecting the residual pollutant concentration in the soil S from the decomposition rate of pollutants and the time-dependent concentration change 23 of the storage means 20. In step 210 of FIG. 2, the decomposition rate detecting means 15 calculates the decomposition rate of the pollutant in the soil S, and in step 211 the residual pollutant concentration detecting means 16 detects the residual pollutant concentration in the soil S. In step 212, it is determined based on the residual pollutant concentration whether or not the soil purification should be ended, and if the soil purification should be continued, the process proceeds to step 213. Step 213
In the ventilation device 1, the ventilation time 25 and the non-ventilation time 26 of the storage device 20 are updated by the updating device 14, and the ventilation amount 24, the ventilation time 25, and the non-ventilation time 26 are updated by the ventilation control device 30 in step 214. To resume ventilation.

Steps 215 to 217 of FIG. 2 show a process for detecting the apparent air permeability of the contaminated soil S based on the tendency of the oxygen concentration in the contaminated soil S to increase during aeration. In the purification of the contaminated soil S, the soil voids decrease due to compaction, excess water, etc. with the passage of time, and the ventilation state of the soil S may change at the beginning of purification and during the purification even when the same pressure is used. When the voids in the soil decrease, oxygen supply to the entire contaminated soil becomes non-uniform due to a short path of air flow, etc., which causes a reduction in purification efficiency. In steps 215 to 217, the apparent air permeability of the soil S (porosity in the soil = soil air volume V _{SPACE in the} soil S / volume S _{P of the} soil S) from the increasing tendency of the oxygen concentration during aeration.
Is being detected.

In the flow chart of FIG. 2, first, in step 204, the change in oxygen concentration in the soil S during the initial ventilation is measured by the oximeter 5, and then in step 215, the oxygen concentration in the soil S when the ventilation is restarted. Is measured with an oxygen meter 5.
FIG. 6 shows an example of the measured values of the oxygen concentration change at the time of initial ventilation and when the ventilation is restarted. The solid line graph in the figure is an example of the oxygen concentration change at the time of initial ventilation, and the dotted line graph is an example of the oxygen concentration change after the restart of ventilation. Represents The dotted line graph has a larger oxygen concentration increase rate (slope of the graph in FIG. 6) than the solid line graph,
The reason for this is that, although consolidation and the like have not yet occurred at the beginning of purification, apparent breathability has decreased due to consolidation and excess water when ventilation was resumed.

The control device 10 shown in FIG.
Increasing rate measuring means 17 for measuring the increasing rate of oxygen concentration in the inside
And the air permeability detecting means 18 for detecting the apparent air permeability of the soil S based on the increasing speed. Also, the storage means 20
The relationship between the air flow rate during the initial aeration and the oxygen concentration increase rate is stored in. In step 216 of FIG. 2, the increasing rate measuring means 17 measures the oxygen concentration increasing rate at the time of restarting ventilation, for example, from the slope of the dotted line graph of FIG. The apparent air permeability of the soil S is detected by comparison with the rate of increase in oxygen concentration.

In order to detect the apparent air permeability, it is desirable to compare the oxygen concentration increasing rates with the same air flow rate. However, even if the air flow rate Q at the time of restarting air flow differs from the initial air flow rate, From the relationship with the oxygen concentration increase rate, it is possible to calculate the oxygen concentration increase rate with respect to the ventilation amount Q at the time of restarting, assuming that the initial apparent air permeability is maintained. The breathability detecting means 18 compares the calculated value of the oxygen concentration increase rate under the above assumption with the measured value of the oxygen concentration increase rate at the time when the actual ventilation is restarted to determine the apparent change in the air permeability of the soil S. Can be detected.
For example, the decrease of soil voids, that is, the occurrence of consolidation or excess water in the contaminated soil S is detected based on the apparent decrease in air permeability.

The rate of increase in oxygen concentration in the soil S during aeration varies depending on not only compaction and excess water content but also the decomposition activity of aerobic microorganisms. However, when oxygen consumption by microorganisms is small, changes in oxygen concentration due to the activity of microorganisms can be virtually ignored. Further, as described above, in the present invention, the rate of decrease of the residual oxygen concentration [O ₂ ] when no gas is passed (δ [O ₂ ] / δ
The decomposition rate of pollutants ( _{δD CaHb} / δt), that is, the decomposition activity of microorganisms can be calculated from t). Therefore, while considering the oxygen concentration change due to the activity of microorganisms, the apparent rate of soil S It is possible to detect changes in the air permeability of the.

When the apparent reduction in air permeability cannot be regarded as normal (at the time of abnormality), it is necessary to take measures such as turning back the contaminated soil S. If the reduction in apparent air permeability is within a range that can be regarded as normal, it is possible to restore the apparent air permeability to the initial state by adjusting the air flow rate. For example, in the flow chart of FIG. 2, in step 218, the air permeability detecting means 18 obtains an appropriate air pressure (suction pressure in the case of FIG. 1) based on the change in the apparent air permeability of the soil S, and the air permeability control means 30 causes the air permeability device 30 to operate. The ventilation amount (suction amount) of 1 is adjusted. Such an appropriate ventilation amount according to the change in the apparent permeability of the soil S can be experimentally determined in advance and stored in the storage unit 20.

Detection of Apparent Breathability in Steps 215-218
By repeating the procedure at appropriate time intervals,
Occurrence of consolidation, etc. is detected early and residual oxygen concentration is detected.
Degree [O ₂] Decrease rate (δ [O₂] / Δt) cannot be measured
It is possible to avoid the occurrence of a situation. Also, due to consolidation, etc.
Economical soil according to the present invention while avoiding reduction of purification efficiency
It becomes possible to continue the purification. The storage means 20
The ventilation pressure 27 is updated by the ventilation detection means 18, and the storage means 20 is updated.
Of the ventilation device 1 by the ventilation control means 30 based on the ventilation pressure 27 of
The ventilation rate may be controlled.

Although the case where the present invention is applied to the purification of the excavated contaminated soil S has been described above, the present invention can also be applied to the in-situ purification as shown in FIG. In the figure, a measurement well 8 and an aeration well 9 are provided in the contaminated soil S of the contaminated ground E.
And adjacent to each other, insert the oxygen meter 5 and / or the thermometer 6 into the measuring well 8 (see FIG. 2B), and connect the ventilation device 1 to the ventilation well 9 by inserting the ventilation pipe 3. There is. Based on the measured values of the oxygen meter 5 and / or the thermometer 6 of the measurement well 8, that is, the residual oxygen concentration decrease rate (δ [O ₂ ] / δt), the oxygen concentration increase rate, and / or the soil temperature shown in FIG. The ventilation to each ventilation well 9 can be controlled according to the flow chart.

[0055]

As described above, the biological purification method and apparatus for polluted soil according to the present invention is a method for purifying polluted soil by aeration of aerobic microorganisms in the soil, and an oxygen meter is provided in the polluted soil. The rate of decrease of the residual oxygen concentration is measured by the oximeter, and the ventilation of the contaminated soil is controlled based on the rate of decrease, so that the following remarkable effects are obtained.

(A) Since the aeration is controlled according to the decomposing activity of aerobic microorganisms in the contaminated soil, soil purification can be economically promoted by the minimum necessary aeration. (B) By updating the minimum necessary ventilation amount according to the progress of soil purification, it is possible to perform appropriate and economical ventilation according to the progress of soil purification. (C) Not only the ventilation method of sucking air from the soil,
It is also applicable to an aeration method in which air or oxygen is pressed into the soil. (D) It is possible to control the length of the ventilation time and the interval between the start and stop of ventilation, based on the rate of decrease of the residual oxygen concentration. (E) Combining control of air flow rate, ventilation time, and non-ventilation time can be expected to contribute to automatic control of purification of contaminated soil. (F) From the rate of increase of oxygen concentration in contaminated soil during aeration,
It is possible to detect the apparent air permeability in the contaminated soil and to detect the occurrence of a short path of the air flow due to compaction or excessive water content. (G) Not only the purification of excavated contaminated soil, but also the in-situ purification of contaminated soil existing in the ground.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment according to the present invention.

FIG. 2 is an explanatory view of an example of a flow chart of the method of the present invention.

FIG. 3 is an explanatory diagram of another embodiment according to the present invention.

FIG. 4 is an example of a graph showing a change in oxygen concentration in a contaminated soil when there is no aeration.

FIG. 5 is an example of a graph showing changes over time in concentration of residual pollutants in contaminated soil measured experimentally.

FIG. 6 is an example of a graph showing changes in oxygen concentration in contaminated soil with and without aeration.

[Explanation of symbols]

1 ... Ventilation device 2 ... Flow control valve 3 ... (perforated) ventilation pipe 4 ... Blower 5 ... Oxygen meter 6, 7 ... Thermometer 8 ... Measuring well 9 ... Ventilation well 10 ... Control device 12 ... Decrease speed measuring means 13 ... Oxygen consumption calculation means 14 ... Update means 15 Decomposition rate detection means 16 ... Residual contaminant concentration detection means 17 ... Increase speed measuring means 18 ... Breathability detecting means 20 ... Memory means 21 ... Contaminated soil volume 22 ... Decomposition reaction formula 23 ... Concentration change over time 24 ... aeration amount 25 ... aeration time 26… No ventilation time 27… Ventilation pressure 30 ... Ventilation control means 32 ... Input means 33 ... Display means E: Contaminated ground S: Contaminated soil Y ... Purification yard

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akitoshi Iwamoto             Kashima-ken, 1-2-7 Moto-Akasaka, Minato-ku, Tokyo             Inside the corporation (72) Inventor Akiko Sato             Kashima-ken, 1-2-7 Moto-Akasaka, Minato-ku, Tokyo             Inside the corporation F-term (reference) 4B029 AA03 AA27 BB02 BB06 CC07                       EA18 EA20                 4B065 AA01X AA57X BC34 BC39                       CA56                 4D004 AA41 AB02 AB05 AC07 CA19                       CC02 DA01 DA02 DA06 DA10                       DA12 DA16 DA17

Claims (21)

[Claims] 1. A method for purifying a contaminated soil by aerating aerobic microorganisms in the soil, wherein an oxygen meter is provided in the contaminated soil, and a decrease rate of residual oxygen concentration is measured by the oxygen meter to measure the decrease rate. A biological purification method for contaminated soil, which comprises controlling the amount of ventilation to the contaminated soil based on measured values. 2. The purification method according to claim 1, wherein the oxygen consumption in the soil is calculated from the rate of decrease of the residual oxygen concentration and the soil air volume of the contaminated soil, and the contaminated soil is calculated based on the calculated value of the oxygen consumption. A biological purification method for contaminated soil by controlling the amount of ventilation to the soil. 3. The purification method according to claim 2, wherein a thermometer is provided in the contaminated soil, the soil temperature is measured by the thermometer, and the aeration amount to the contaminated soil is calculated based on the oxygen consumption amount and the soil temperature. A biological purification method for contaminated soil. 4. The purification method according to any one of claims 1 to 3, wherein the concentration of residual pollutants and residual oxygen in the polluted soil due to the decomposition of aerobic microorganisms is measured to measure the pollutants in the polluted soil. A biological purification method for contaminated soil, wherein a decomposition reaction formula by an aerobic microorganism is determined, and the residual pollutant concentration in the soil is detected from the reduction rate of the residual oxygen concentration and the decomposition reaction formula. 5. The biological purification method for polluted soil according to claim 4, wherein the aeration time or stoppage to the polluted soil is controlled based on the residual pollutant concentration. 6. The biological purification method for polluted soil according to any one of claims 1 to 5, wherein the rate of decrease of the residual oxygen concentration is measured without aeration. 7. The purification method according to claim 1, wherein the rate of increase in oxygen concentration in the soil is measured by the oximeter, and the apparent air permeability of the contaminated soil is determined based on the measured value of the rate of increase. Method for biological purification of contaminated soil detected. 8. The method for purifying contaminated soil according to claim 7, wherein a decrease in soil voids is detected by the apparent air permeability. 9. The method for purifying contaminated soil according to claim 7 or 8, wherein the amount of ventilation to the contaminated soil is controlled based on the apparent air permeability. 10. The purification method according to any one of claims 7 to 9, wherein the rate of increase in oxygen concentration is measured at the time of initial ventilation and when ventilation is restarted, and the rate of increase in oxygen concentration at the time of restarting ventilation is compared by comparing the rate of increase in oxygen concentration during both ventilation. A biological purification method for contaminated soil by detecting apparent air permeability. 11. The purification method according to any one of claims 1 to 10, wherein the oximeter and / or thermometer are provided at a plurality of sites in the contaminated soil, and aeration of the contaminated soil is controlled for each site. Biological purification method for contaminated soil. 12. The purification method according to any one of claims 1 to 11, wherein the contaminated soil is contaminated ground, a ventilation well and a measurement well are bored in the ground, and an oxygen meter and / or
Alternatively, a method for biological purification of contaminated soil, in which a thermometer is inserted and a ventilation device is connected to the ventilation well. 13. An aeration device for aerating a contaminated soil, an oxygen meter provided in the contaminated soil, and a rate of decrease of residual oxygen concentration measured by the oxygen meter, and an aeration amount of the aeration device based on the measured value of the decrease rate. A bioremediation device for polluted soil, comprising a control device for controlling. 14. The purifying apparatus according to claim 13, wherein the controller calculates the oxygen consumption in the soil from the decreasing rate of the residual oxygen concentration and the soil air volume of the contaminated soil, and calculates the oxygen consumption. A biological purification device for contaminated soil, wherein the ventilation amount of the ventilation device is controlled based on the value. 15. The purification device according to claim 14, wherein a thermometer for measuring soil temperature is provided in the contaminated soil, and the controller calculates the ventilation amount of the ventilation device based on the oxygen consumption amount and the soil temperature. A biological purification device for contaminated soil. 16. The purifying apparatus according to claim 13, wherein the controller stores a decomposition reaction formula of a pollutant in contaminated soil by aerobic microorganisms, and the controller reduces the residual oxygen concentration. A biological purification apparatus for polluted soil, which calculates a decomposition rate of residual pollutants in soil from a speed and a decomposition reaction formula, and controls aeration time or stop of the aeration device based on the calculated value of the decomposition rate. 17. The purification apparatus according to claim 16, wherein the controller stores a measured value of a change in concentration of residual pollutants with time due to decomposition of aerobic microorganisms in polluted soil, and the controller controls the residual pollutants. Biodegradation of contaminated soil by detecting residual pollutant concentration from the calculated decomposition rate and measured concentration change over time, and controlling the ventilation time or stoppage of the aeration device based on the detected residual pollutant concentration apparatus. 18. The biological purification apparatus for polluted soil according to any one of claims 13 to 17, wherein the control device measures the rate of decrease of the residual oxygen concentration during no ventilation. 19. The purifying apparatus according to any one of claims 13 to 18, wherein the control device measures an increasing rate of oxygen concentration during aeration with the oximeter and based on the measured value of the increasing rate. A bioremediation device for contaminated soil by controlling the air flow rate. 20. The purifying apparatus according to claim 19, wherein the control device measures the rate of increase of the oxygen concentration at the time of initial ventilation and at the time of restarting ventilation, and by comparing the oxygen concentration increasing rates at the time of both ventilation, the apparent appearance at restarting ventilation. Bioremediation device for polluted soil by detecting air permeability of the soil. 21. The biological purification apparatus for polluted soil according to claim 13, wherein the oximeter is a fluorescence oximeter.