JP2006341214A - Vacuum type aw method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and simultaneously recover both of groundwater and gas by continuously sucking gas with a vacuum pump capable of not only pumping groundwater but also keeping vacuum in super well point method (SWP method), with respect to an AW method for simultaneously pumping groundwater and sucking gas in soil using a single facility. <P>SOLUTION: The vacuum type AW method involves pumping polluted groundwater in soil and simultaneously sucking polluted air by employing a super well point method, newly hanging an electric water level sensor in a filter part in the well periphery with a signal capable, controlling the water level of the groundwater by a water level control board comprising a mesh cylinder with about 1 m/m mesh fitted in the lower half part and closing the bottom part of the cylinder with a bottom cover, and controlling the vacuum degree in the well in the optimum negative state satisfying Pv≈-0.04 to -0.065 MP or higher by using a safety valve type spring pressure installed in the tip face part of an upper cover. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a vacuum-type AW method in which groundwater pumping and soil gas suction are simultaneously performed with a single facility, using a deep vacuum drainage method (hereinafter referred to as “super well point method, abbreviated as SWP method”). In addition to pumping up groundwater, the purpose is to use a vacuum pump to keep the vacuum at a constant rate so that both groundwater and gas can be efficiently recovered at the same time by continuously sucking air.

Conventionally, as a method for removing volatile organic chlorine compounds (hereinafter referred to as “VOCs”), an underground pumping method (FIG. 6), a soil gas suction method (FIG. 7), an air sparging method (FIG. 8), and the like are known.
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  The above-described underground pumping method is a method of purifying soil by pumping up groundwater contaminated with VOCs, and is a method of preventing the diffusion of VOCs. Next, the soil gas suction method is a method of sucking and collecting gaseous VOCs that reach the unsaturated layer. The air sparging method is a method of injecting air into groundwater, volatilizing VOCs dissolved in the groundwater in the bubbles, and sucking and collecting gaseous VOCs reaching the unsaturated layer as the bubbles rise. Pumped groundwater and gaseous VOCs are processed in a plant installed on the ground.

  Moreover, the construction method which combined said construction method is also implemented. For example, there is a double suction method. This method is used when the ground gas is contaminated when applying the soil gas suction method, and is a method of pumping up groundwater together with gas. However, since this method has a small purification effect with one pumping well, many suction and pumping wells are often installed.

There are many examples of applying these methods, and a certain level of evaluation has been obtained. However, these methods often require a long period of time for purification, and it is difficult to reduce the concentration to the environmental standard level.
JP2001-181990 (Patent No. 3280935) Patented invention

  In the above case, although the pressure in the well is made negative, fresh air from the ground surface is sucked from the screen field, and the important VOC remains without being removed.

  Furthermore, in the groundwater pumping method shown in FIG. 6 and the soil gas suction method shown in FIG. 7, since a purification effect by one pumping well is small, many suction wells and pumping wells are often installed. There are many examples of applying these methods, and a certain level of evaluation has been obtained. However, these methods often require a long period of time for purification, and it is difficult to reduce the concentration to the environmental standard level.

  And patent document 1. When a large amount of groundwater is pumped by the invention of (1), (1) Raise the degree of vacuum, collect a large amount of groundwater and pump it. In this case, it is desirable not to infiltrate air as much as possible, but a certain amount of air infiltrates. (2) The submersible pump is loaded with negative pressure, so it is necessary to use a pump that can withstand this. (3) Prevent the submersible pump from running idly-it is necessary to ensure a constant water depth, set the water level, and stop the submersible pump when it reaches this level. A high water level is also set, and when this level is reached, the submersible pump is operated. (4) The water level in the well pipe measures the water level in the filter section, and this water level is regarded as the water level in the well pipe.

  Further, Patent Document 1. When the ground is improved by the invention of (1), it is necessary to control (1) groundwater pumping and air suction at the same time. That is, it is also necessary to maintain the operation of sucking air while pumping groundwater to lower the water level. (2) In this case, the water level in the well pipe is controlled between the two water levels (filter part). (3) The low water level is for reducing negative pressure and preventing the submersible pump from running idle. When this level is reached, the submersible pump is stopped. On the other hand, the high water level is for preventing air from entering the wells, and when this water level is reached, the submersible pump is operated (the water level is lowered).

Therefore, the present invention is provided in order to solve the conventional problems and achieve the object of the invention.

The first of the present invention is that in the vacuum type AW method, the groundwater in the ground is pumped up using the deep vacuum drainage method, and the contaminated air is sucked at the same time. A sensor is installed, and the water level control panel controls the groundwater level.

The second aspect of the present invention is that, in the vacuum type AW method, in the pumping by the deep vacuum drainage method, unlike the gravity drainage, the groundwater level lowering gradient becomes a linear gradient from the Log curve, thereby greatly reducing the groundwater surface. The contaminated soil is placed from the saturated zone to the unsaturated zone, and VOCs in the unsaturated zone are collected by air suction. At the same time, the contaminated groundwater is pumped and purified at the treatment plant and drained. is there.

In the third aspect of the present invention, in the vacuum type AW method, two electric water level sensors for measuring the water level are suspended by a signal cable in the upper half of the perforated pipe, and the lower half is approximately 1 m / m mesh. And the bottom of the perforated tube is closed with a bottom lid.

In the fourth aspect of the present invention, in the vacuum type AW method, an optimum negative pressure state of Pv≈−0.04 to −0.065 MP or more is obtained in the well by using a safety valve type spring pressure provided on the top surface portion of the SWP upper lid. The degree of vacuum is controlled.

  Since the present invention is configured as described above, contaminated groundwater and contaminated underground air can be collected simultaneously in one well. In addition, it pumps a larger amount than the conventional underground pumping method, and has a very high capacity to collect groundwater. In addition, a larger amount of air can be sucked than conventional gas suction. In addition, the groundwater level is greatly reduced, and the unsaturated zone is greatly expanded. The recovery efficiency of VOCs in soil by air suction is extremely high. Moreover, it is a system that collects groundwater and gas at the same time, and the economic effect is enhanced.

  In addition, when controlling the amount of pumped water and suction of underground air, the purpose is to collect groundwater and air at the same time as in the case of “Ground improvement” above, and the water level in the well pipe is set between two water levels. It is necessary to control.

  Furthermore, an automatic valve (a valve for taking outside air into the well pipe) is attached to the upper lid of the well pipe as a device to complement this so that the negative pressure in the well pipe does not become higher than the negative pressure determined. This action serves to prevent the rise of the groundwater surface. VOCs are mostly deposited on the groundwater surface of the aquifer, and high-concentration VOCs are efficiently removed. In addition, when the portion where VOC is accumulated becomes negative pressure, atmospheric pressure enters from behind, so that a blower effect by fresh air can be expected.

In the SWP method, a high degree of vacuum (about -0.04 MPa to -0.06 MPa) can be maintained up to a depth of 300 m regardless of the depth.
Furthermore, by pumping up and draining the groundwater, the groundwater surface is greatly lowered, so that the contaminated soil can be easily collected by air suction placed in the unsaturated zone.

Next, in claim 1, the water level in the well can be controlled by inserting two electric sensors in the SWP.
This makes it possible to control the water level outside the well. This purpose is characterized by the high concentration of VOC, which is also a feature of VOC, that accumulates near the groundwater surface. As a first stage, the decrease in water level is suppressed as much as possible, and high-concentration VOC is removed only with a vacuum pump. After confirming that the VOC is clean to some extent, it is possible to pump up the contaminated groundwater by pumping up a little and clean it up to the next stage.
By repeating this operation, purification can be performed without enlarging the contamination zone more than necessary.

  According to claim 2, in the case of vacuum pumping, it has been found that, unlike gravity drainage, the water level lowering gradient is a linear gradient from the Log curve due to atmospheric pressure. Therefore, it is possible to pump the amount of pumped water in a form that is almost horizontal. In addition, since groundwater can be pumped at the same time, contaminated groundwater can be pumped, purified at a treatment plant, and drained.

Furthermore, VOC can be removed in a wide range by changing the water level of the ground around the well from the hydrodynamic gradient of the Log curve to a linear gradient.
In addition, the well suction point is not at the top of the well, but at the bottom of the well separate screen, so it is possible to suck in from a high concentration VOC with a heavy specific gravity, and fresh air can be pushed into the well by pushing in the VOC from behind. it can.

  In the third aspect, when the water level is controlled and pumped up, there is water in the well, and when the air is sucked by the vacuum pump, the water in the well is in a boiling state. At this time, the water level sensor senses bubbles and sends a signal to the control panel assuming that the water level has dropped. The control panel is equipped with a protective timer to prevent damage to the magnets when the switch is turned on and off quickly. Therefore, the water level cannot be controlled.

Further, as the water level in the SWP well decreases, a large amount of air enters and the vacuum degree in the SWP well cannot be maintained. For this reason, the water level sensor is devised to prevent bubbles from entering, and the wire mesh has the advantage of preventing bubbles from entering as much as possible.
Furthermore, since bubbles have the property of floating vertically in the absence of water flow, good results were obtained by utilizing this fact and utilizing the protective cover.

  According to claim 4, in removing the VOC, the vacuum degree in the SWP well needs to be controlled by a certain vacuum pressure. Therefore, at a high vacuum negative pressure, even when the degree of vacuum is high in a state where the well is stuck with fine particles, VOC cannot flow in and cannot be purified (as a guide, Pv≈−0.065MP or more). From the experience, the optimum negative pressure is Pv≈−0.04 to −0.065MP. This also applies to the case of using as a soil improvement for cohesive soil in a state of “sucking air while applying a vacuum”. The place of setting is performed by using the spring pressure of the safety valve type at the SWP lid.

The construction method of the present invention uses the SWP construction method and continuously sucks air using a vacuum pump in order to keep not only the pumping of groundwater but also the vacuum inside the well at all times due to vacuum suction (Vair≈ 3.0m ³ / min).
This feature is conventionally known as a method of removing volatile organic chlorine compounds (hereinafter referred to as VOCs), such as a soil gas suction method and an air sparging method.

In any method, as a method of sucking gas, a vacuum pump is installed on the ground and a screen is processed in the unsaturated layer and sucked.
In this case, although the inside of the well is set to a negative pressure, the fresh air from the ground surface is sucked from the screen field, and the important VOC remains without being removed.

In contrast, in the SWP method, groundwater is pumped from the bottom end of the double pipe screen, and air is also sucked from the bottom end.
VOCs are mostly deposited on the groundwater surface of the aquifer, and high-concentration VOCs are efficiently removed.

In addition, when the portion where VOC is accumulated becomes negative pressure, atmospheric pressure enters from behind, so that a blower effect by fresh air can be expected.
In the SWP method, a high degree of vacuum (about -0.04 MPa to -0.06 MPa) can be maintained up to a depth of 300 m regardless of the depth.
In the normal gas suction method, it is about -0.02 MPa due to air blow from the ground surface.

Next, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, 1 is a well hole excavated in the vertical direction of the ground G, 2 is a well pipe inserted into the well hole, 3 is a top cover for SWP provided at the top of the well pipe 2, 4 is from the top of the top cover in the well pipe It is an electric water level sensor suspended by a signal cable 5 and plays a role of controlling the groundwater level between two water levels, a high water level and a low water level.
In FIG. 1, two electric water level sensors 4 are suspended. As a result, the water level inside and outside the well is also controlled.

  In FIG. 3, reference numeral 6 denotes a perforated cylinder that houses the water level sensor 4, and a plurality of holes 7 are provided on the peripheral surface thereof. 8 is a wire rod connecting the perforated cylinder 6 to the signal cable 5, 9 is a fine mesh wire mesh provided along the inner surface of the lower half of the cylinder, and 10 forms the bottom of the cylinder 6. The bottom lid is shown.

  11 is a pumping pipe which is inserted into the well pipe and the top is attached to the upper lid 3 of the well pipe, 12 is a submersible pump for pumping provided at the lower end of the pumping pipe, and 13 is a lower end position of the well pipe at the position of the submersible pump. 14 is a drain pipe provided on the top of the pumping pipe 11, 14n is an exhaust pipe provided on the top of the pumping pipe 11, 15 is an untreated plant connected to the drain pipe 14, and 15n is the exhaust pipe. An exhaust gas treatment plant provided in the pipe 14n, 16 is an air suction vacuum pump provided at the top of the upper cover of the well pipe 2, 17 is a pressure gauge, 18 is an automatic valve attached to the upper cover 3, and takes outside air into the well pipe. It is provided for this purpose. Reference numeral 19 denotes a control panel, 20 denotes a compressor installed on the ground G and communicates with the well pipe 2, and 21 denotes a flange joint provided on the peripheral surface of the upper lid 3.

"Specific work process examples"
(1) The ground water in the ground G is sucked toward the submersible pump 12 in the well pipe 2 and collected by driving the vacuum pump 16.
(2) The collected groundwater flows from the strainer 13 of the well pipe 2 into the pipe.
(3) Then, the groundwater in the well pipe 2 is pumped upward through the pumping pipe 11 through the submersible pump 12.
(4) In this case, a high concentration of VOS is deposited near the groundwater surface by two sensors in the well pipe. As a first step, high concentration VOC is removed only by the vacuum pump 16 described above.
(5) After confirming that the VOC is clean to a certain extent, pump up the contaminated groundwater a little and clean it up to the next stage. By repeating this operation, the purification is advanced without expanding the contamination zone more than necessary.
(6) In addition, VOC is removed in a wide range by changing the water level of the ground around the well from the hydrodynamic gradient of the Log curve to a linear gradient.
(7) When the water level sensor 4 controls the groundwater level and pumps up water, there is water in the well 2 and when the vacuum pump 16 sucks air, the water in the well becomes in a boiling state.
(8) At this time, a signal is sent to the control panel 19 assuming that the water level sensor 4 senses bubbles and the water level is lowered. The control panel 19 has a protective timer so that the magnets are not damaged when the switch is quickly turned on and off.
(9) In removing VOC, the degree of vacuum in the SWP well needs to be controlled to some extent by the vacuum pressure.
At high vacuum negative pressure, even if the degree of vacuum is high in a state where the well is stuck with fine particles, VOC cannot flow in and cannot be purified (as a guideline, Pv ≒-
(0.065MP or more) The optimum negative pressure state is Pv≈-0.04 to -0.065MP.
The same applies to the case of using as a soil improvement for cohesive soil in a state of sucking air while applying a vacuum.
The place of setting is performed by using the spring pressure of the safety valve type at the SWP lid.

  In Table 1, pattern A (FIG. 4) is considered to be a pattern without external conditions such as rainfall. When the operation starts in the natural state, the groundwater falls and the water level of the screen of the well pipe also falls, so the air in the unsaturated zone enters the well pipe. Since the air in the unsaturated zone is sucked, the air in this place becomes negative pressure. The well pipe has a reduced vacuum due to the ingress of air. This operating situation will continue if there is a small amount of permeated water that descends underground due to rainfall.

  However, if there is a lot of rainfall, it will be pattern B. The groundwater level rises due to rain, the groundwater level of the screen rises, and it becomes difficult for the air in the unsaturated zone to enter the well pipe. Therefore, the vacuum degree of the well pipe is increased. Unsaturated air is not sucked, so it approaches atmospheric pressure. However, if the rain stops, the groundwater level gradually decreases and approaches the state of pattern A.

  What should be controlled is the case of pattern B (FIG. 5). If this is a short time, there is no problem, but if the rise of the groundwater level is large as in this pattern, the amount of air sucked is reduced. To solve this problem, increase the amount of groundwater pumping and lower the groundwater level early.

  In addition, an automatic valve 18 is attached to the upper lid 3 of the well pipe 2, and when the degree of vacuum in the well pipe becomes high, outside air is sucked to lower the degree of vacuum in the well pipe 2, and the capacity of the submersible pump 12 is exhibited. A method is also conceivable.

  Although water treatment was experimented in the existing treatment plant of the applicant of the present application, only an amount corresponding to the design treatment amount could be pumped. Since the capacity of the submersible pump is sufficient, the groundwater level can be further lowered if the water can be pumped to the limit of the ground water collection capacity. As a result, there is a possibility that the unsaturated zone further expands and the purification further proceeds.

It is sectional drawing which shows the implementation state of the vacuum type AW method concerning this invention. It is sectional drawing of the water level sensor which concerns on this invention. It is a schematic sectional drawing of the air control valve which concerns on this invention. It is a schematic explanatory drawing of the pattern A of Table 1. It is a schematic explanatory drawing of the pattern B of Table 1. It is sectional drawing which shows the implementation state of the existing groundwater pumping method. It is sectional drawing which shows the implementation state of the existing soil gas suction method. It is sectional drawing which shows the implementation state of the existing air sparging method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Well hole 2 Well pipe 3 SWP top lid 4 Water level sensor 5 Signal cable 6 Bottomed cylindrical body 7 Plural holes opened in the peripheral surface of the cylindrical body 8 Wire rod 9 Wire net 10 Bottom lid 11 Pumping pipe 12 Submersible pump 13 Strainer 14 Drain pipe 14n Exhaust pipe 15 Untreated plant 15n Gas treatment plant 16 Air suction vacuum pump 17 Pressure gauge 18 Automatic valve 19 Control panel 20 Compressor 21 Flange joint

Claims (4)

Contaminated groundwater in the ground is pumped up using the deep vacuum drainage method, and contaminated air is sucked in at the same time. An electric water level sensor is newly installed in the filter around the well, and the groundwater level is adjusted with the water level control panel. A vacuum AW method characterized by controlling. In pumping by the deep vacuum drainage method, unlike the gravity drainage, the slope of the groundwater level changes from the Log curve to a linear slope, greatly reducing the groundwater surface and putting the contaminated soil from the saturated zone to the unsaturated zone. At the same time, the vacuum type AW method is characterized in that the VOC in the unsaturated zone is collected by air suction, and at the same time, the contaminated groundwater is pumped and purified and drained at the treatment plant. An electric water level sensor that measures the water level in the upper half of the perforated pipe is suspended by a signal cable, and a mesh tube of approximately 1 m / m mesh is fitted to the lower half, and the bottom of the perforated pipe is A vacuum AW method characterized by being closed with a bottom lid. A vacuum type AW characterized by controlling the vacuum degree in the well in an optimal negative pressure state of Pv≈−0.04 to −0.065MP or more by using a spring pressure of a safety valve type provided on the top surface of the top cover for SWP Construction method.