JP3724287B2 - Purification method of contaminated groundwater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for purifying contaminated groundwater, and more particularly to a method for purifying groundwater (hereinafter referred to as contaminated groundwater) contaminated with organic matter by installing a wall in the ground.
[0002]
[Prior art]
In recent years, environmental pollution by organic compounds such as aromatic hydrocarbons or organic chlorine compounds such as trichlorethylene (hereinafter referred to as TCE) has become a problem. Many of these penetrate into the soil, dissolve in the groundwater, and are carried to the groundwater and diffuse.
[0003]
That is, as shown in FIG. 3, the groundwater accumulates on the upper side of the impermeable layer 7 (or the hardly water-resistant layer 7) formed in the ground 1 to form an aquifer 5 having a predetermined depth. However, since the groundwater 5a in the aquifer 5 flows in a certain direction as shown by the arrow, the contaminated area is expanded.
[0004]
For this reason, conventionally, as a measure for preventing the expansion of the contaminated area, the water permeability deeper than that so as to surround the periphery of the pollution source or to cross the aquifer 5 downstream of the aquifer 5 below the pollution source. A wall body 10 (hereinafter also referred to as a purification wall) 10 is installed to purify the contaminated groundwater 5a when it passes through the purification wall 10.
[0005]
For example, the purification wall 10 is provided with a groove 10a deeper than the aquifer 5 so as to cross the aquifer 5 through which the contaminated groundwater 5a flows, and iron powder 10b and excess It is formed by filling sand, crushed stone, gravel 10c or the like to which magnesium oxide 10b or the like is added. Here, the iron powder 10b reduces and purifies the organochlorine compound in the contaminated groundwater 5a that permeates the purification wall 10, and the magnesium peroxide 10b supplies oxygen to the contaminated groundwater 5a and surrounds it. In an aerobic atmosphere, organic matter-decomposing microorganisms that live in the groundwater 5a are activated to promote the purification of organic matter and purify it. In other words, the latter applies bioremediation (introducing oxygen or the like into the environment and enhancing the activity of decomposing microorganisms present therein to promote the decomposition of organic substances and the like to purify the contamination).
[0006]
[Problems to be solved by the invention]
However, when the former iron powder is added, if all the iron powder 10b is oxidized, the purification ability is lost. In the latter case, when the magnesium peroxide 10b releases oxygen and changes to magnesium oxide, the purification ability is lost. That is, the purification action of the purification wall 10 has a lifetime, and it is difficult to exert the purification action permanently.
In addition, magnesium oxide or the like remains as a foreign substance in the purification wall 10 that has lost its purification ability, which may cause secondary environmental pollution.
Furthermore, once the purification wall 10 is buried, it is difficult to re-add the iron powder 10b and the magnesium peroxide 10b, and the purification capacity according to the purification status of the contaminated groundwater 5a and the change in the contamination status Cannot be controlled.
[0007]
The present invention has been made in view of such conventional problems, and can provide a permanent purifying capability, and can further control the purifying capability without leaving foreign matter in the ground. It aims at providing the purification method of the polluted groundwater using.
[0008]
[Means for Solving the Problems]
In order to achieve such an object, the invention shown in claim 1 is a method for purifying contaminated groundwater contaminated with organic matter, which comprises excavating a slot that vertically traverses the veins of the contaminated groundwater, into the slot. A plurality of fluid supply pipes each having a fluid ejection port formed of a slit facing the width direction of the slot are inserted at appropriate intervals and filled with crushed stone or gravel to form a water-permeable wall body, which is embedded in the wall body A fluid containing a substance that grows and activates organic matter-decomposing microorganisms in water is supplied from the fluid supply pipe.
[0009]
According to the above method, since the fluid supply pipes are arranged at appropriate intervals in the slot so that the slits face the width direction of the slot, the substance for growing and activating the organic matter-degrading microorganisms has a width in the wall. It can be uniformly supplied in the form of curtains in the direction, so that organic matter-decomposing microorganisms in the contaminated groundwater passing through the wall can be propagated and activated as much as possible, and the organic matter is decomposed to purify the contaminated groundwater. It becomes possible to do. And since the said substance can be supplied permanently from a fluid jet nozzle via a fluid supply pipe | tube, the purification | cleaning capability through a wall body can be made to function permanently and can be maintained.
Furthermore, by adjusting the amount, type, etc. of the substance, the purification capacity can be adjusted according to the contamination status, purification status and changes in the contaminated groundwater.
[0010]
The invention described in claim 2 is characterized in that the substances for growing and activating the organic matter-decomposing microorganisms in the water are oxygen and methane.
[0011]
According to the above method, by supplying methane as the substance, it is possible to grow a methane-assimilating bacterium that is one of the organic matter-decomposing microorganisms that inhabit the water. Therefore, since the growth amount of the fungus can be adjusted by adjusting the supply amount of the methane, the purification capacity can be adjusted according to the contamination status of contaminated groundwater, particularly the contamination status due to TCE.
[0012]
In addition, by supplying oxygen as the substance, the surroundings of the organic matter-decomposing microorganism can be brought into an aerobic atmosphere, and in particular, the decomposition of the aromatic hydrocarbon can be promoted. Therefore, since the degree of acceleration of decomposition can be adjusted by adjusting the supply amount of oxygen, the purification capacity can be adjusted according to the contaminated groundwater contamination status, particularly the contamination status with aromatic hydrocarbons.
Furthermore, since only methane is supplied or, for example, air containing oxygen is supplied, no foreign matter remains in the ground.
[0013]
According to a third aspect of the present invention, the water-permeable wall body is previously stored in a rebar rod on the ground and formed into a unit, and the unitized water-permeable wall body is inserted into the slot. It is characterized by that.
[0014]
According to the above method, since it is unitized in advance, since construction on site is completed by inserting the unitized wall into the slot, the construction period on site can be significantly shortened. it can.
Moreover, since it is unitized, standardization can be easily performed, and mass production can greatly reduce the cost.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the method for purifying contaminated groundwater of the present invention, and FIG. 1 is a perspective partial sectional view showing a purification wall as a wall used in the purification method.
[0016]
As shown in FIG. 1, the purification method according to the present invention first has a broader and deeper width than the aquifer 5 so as to cross the aquifer 5 in which the contaminated groundwater 5a in the ground 1 flows vertically. A rectangular parallelepiped slot 11a is excavated. A plurality of slit pipes 13 as fluid supply pipes are arranged substantially vertically at the approximate center of the slot thickness of the slot 11a. As will be described later, the slit tube 13 has a slit 13a that ejects air in the width direction of the slot 11a. Next, the slit tube 13 is filled with crushed stone or gravel 15 up to a position higher than the upper end 5c of the aquifer to form a base of the purification wall 17, and the slit tube 13 fixing and groove 11a are formed on the remaining slot 11a. The bentonite 19 for filling is filled. Then, air is blown from the slit tube 13 of the purification wall 17 configured as described above, and oxygen in the air is supplied to organic matter-decomposing microorganisms in the groundwater 5a to grow and activate the microorganisms. . That is, in this case, oxygen is used as a material to be activated, and air is used as a fluid containing the oxygen.
[0017]
The slit tube 13 is a bottomed cylindrical pipe 13 made of a corrosion-resistant material such as slenless and having a slit 13a formed in the longitudinal direction thereof. The slits 13 a are formed at two locations on the outer periphery of the pipe, and are provided at positions that are line-symmetric with respect to the central axis of the pipe 13. A hose 21 is connected to the upper end of the pipe 13 via a coupling (not shown), and an air compressor 23 for supplying air is connected to the other end of the hose 21 so that a constant pressure is supplied from the slit 13a. It is designed to spout out the air. The slit tube 13 is arranged at appropriate intervals in the slot 11a so that the slit 13a faces the width direction of the slot 11a, and a curtain-like air laminar flow 25 flowing in the width direction in the slot 11a. It comes to form. Then, oxygen is evenly and uniformly supplied to the groundwater 5a traversing the air laminar flow 25.
[0018]
The length of the slit 13a is set to be longer than the thickness of the aquifer 5 in the depth direction, so that oxygen can be reliably supplied to the entire region of the aquifer 5.
[0019]
Since the air compressor 23 has a well-known device configuration, the description thereof is omitted. However, the air compressor 23 detects a contamination level by a sensor embedded in the aquifer 5 and controls the air amount according to the level. You may make it do.
[0020]
Here, the operation of the purification method will be described.
Air is supplied from the slit pipe 13 to the contaminated groundwater 5a that passes through the purification wall 17 to increase the amount of oxygen in the groundwater 5a. Then, decomposing microorganisms inhabiting the groundwater 5a are activated to promote the organic substance decomposing action, and in particular, the decomposition of aromatic hydrocarbons is promoted. Since the oxygen can be supplied permanently by the slit tube 13, the purification ability through the purification wall 17 can be maintained and functioned permanently, and since only air is supplied, it can be underground. No foreign matter remains. Further, by adjusting the amount of the air, the purification capacity can be appropriately changed according to the purification status of the contaminated groundwater.
[0021]
In addition, methane can also be used as a substance for growing a decomposed microorganism and a fluid containing the substance. In this case, a methane supply device (not shown) is provided instead of the air compressor 23, and methane is supplied from the slit pipe 13 while the contaminated groundwater 5a permeates the purification wall 17, and the groundwater 5a Increase the amount of methane. As a result, methane-utilizing bacteria that inhabit the groundwater 5a grow and the decomposition ability of the organic chlorine compounds, particularly TCE, is improved. Thus, since the growth amount of the methane-assimilating bacterium can be adjusted by adjusting the supply amount of the methane, the purification ability thereof can be adjusted according to the state of contamination by TCE.
[0022]
If the desired decomposing microorganism is not present in the groundwater 5a or if its absolute amount is small, the hose 21 between the air compressor 23 and the slit tube 13 is bifurcated and decomposed to the branch end. A microorganism supply device (not shown) is connected. And what is necessary is just to supply decomposing microorganisms in the groundwater 5a through the slit pipe | tube 13 with this apparatus.
[0023]
As 2nd embodiment of this invention, the said purification | cleaning wall 17 can also be previously accommodated in a reinforcement rod on the ground, and can also be unitized. FIG. 2 is a perspective view in which a part of the purification wall unit 31 is cut away.
[0024]
As shown in the figure, the purification wall unit 31 is revolved inward so that only a reinforcing bar rod 33 assembled in a hook shape with vertical reinforcing bars 33a and horizontal reinforcing bars 33b and an upper portion of the reinforcing bar rod 33 is opened. The arranged net member 35, the slit pipe 13 arranged in the net member 35, the crushed stone and gravel 15 filled between the slit pipe 13 and the net member 35, and the crushed stone and gravel 15 and bentonite 19 filled in the upper part.
[0025]
The reinforcing bar rod 33 is a well-known one configured by arranging a plurality of vertical reinforcing bars 33a in a rectangular shape in a flat cross section, and wrapping and fixing a plurality of horizontal reinforcing bars 33b around the outside of the plurality of vertical reinforcing bars 33a. . Inside the reinforcing bar rod 33, a metal net 35 made of an iron-based material is provided as a net member 35 so as to be formed in a bag shape with the upper part opened, and is fixed to the reinforcing bar rod 33 by welding or the like.
[0026]
The mesh of the wire mesh 35 is set according to the particle size of the crushed stone or gravel 15 to be filled, but basically the water permeability is not impaired and there is no problem if the crushed stone and gravel 15 does not leak.
[0027]
Inside the bag-shaped wire mesh 35, the plurality of slit tubes 13 are arranged with the direction of the slits 13 a directed in the width direction of the reinforcing bar rod 33 (the left-right direction in the figure). The arrangement pitch in the width direction of the slit tube 13 is set so that the fluid ejected from the slit 13 a reaches the width direction of the reinforcing bar 33 evenly. Then, the crushed stone and gravel 15 are filled higher than the upper end of the slit 13 a around the slit tube 13, and the crushed stone and gravel 15 are used for fixing the slit tube 13 and of the purification wall unit 31. The bendnite 19 which is also used for closing the upper end is filled.
[0028]
In addition, since the structure of the slit pipe | tube 13 other than the above is the same as the structure mentioned above, the description is omitted.
[0029]
The purification wall unit 31 having such a configuration can be easily disposed on site as described below.
[0030]
First, a substantially rectangular parallelepiped-shaped groove that is wider and deeper than the aquifer is excavated in the ground so as to cross the aquifer in which contaminated groundwater flows vertically. And when the said purification wall unit is inserted in this slot and the width | variety of a slot is large, according to the width | variety, several purification wall units are arrange | positioned adjacently. Next, a gap between the crushed stone / sand gravel of the purification wall unit and the groove hole is filled with a water-permeable sealing material, and bentonite is filled between the bentonite and the groove hole of the purification unit to close the groove hole.
[0031]
In order to completely close the upper end portion of the slot, that is, to completely prevent the fluid from leaking upward, the following may be performed. When the purification wall unit 31 is installed, the depth of the slot or the height of the purification wall unit 31 is set so that the upper end is lower than the ground surface, that is, is buried at a predetermined depth from the ground surface. Then, bentonite is filled into the slot portion at the upper end that remains when the purification wall unit 31 is installed in the slot, and is closed.
[0032]
Also, the purification wall unit 31 is basically installed and used as it is once installed, and the reinforcing bar 33 and the wire mesh 35 are corroded and decayed, so there is no problem. The material is used. However, it is desirable to use a corrosion-resistant material such as stainless steel when periodically removing the purification wall unit 31 from the ground and performing maintenance such as clogging of crushed stones and gravel 15.
[0033]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, In the range which does not deviate from the summary, various deformation | transformation as shown to the following (a)-(d). Is possible.
[0034]
(A) In the present embodiment, the slit 13a is formed in the fluid supply pipe 13 in order to supply the fluid uniformly in the depth direction. However, the present invention is not limited to this as long as the fluid can be supplied uniformly into the purification wall 17. A large number of holes and nozzles may be arranged at an appropriate pitch in the longitudinal direction of the fluid supply pipe 13. Further, when the concentration of the contaminant changes in the depth direction, the hole diameter and the nozzle model number may be changed so that the concentration distribution matches the fluid supply amount distribution.
[0035]
(B) In this embodiment, since methane-utilizing bacteria were used as decomposing microorganisms that decompose TCE, methane was supplied. Toluene-utilizing bacteria, phenol-utilizing bacteria, nitrifying bacteria, propane were used for TCE decomposition. When oxidizing bacteria, isopropylene oxidizing bacteria, etc. are used, it is desirable to use a fluid containing a growth / activation substance suitable for each.
[0036]
(C) In this embodiment, air, that is, gas is used as the fluid for supplying oxygen, but liquid may be used. For example, oxygen can be supplied using hydrogen peroxide (H ₂ O ₂ ) or an aqueous solution thereof. In this case, it is desirable to use a microorganism having resistance to hydrogen peroxide as the decomposing microorganism.
[0037]
(D) In this embodiment, air is supplied to the fluid supply pipe 13 at a constant pressure by the air compressor 23. However, the air is not limited to this as long as the air can be reliably supplied to the contaminated groundwater. By supplying the fluid supply pipe 13 intermittently (for example, at a cycle of 1/30 to 1/5 Hz) with 2 to 10 atm), it may be instantaneously blown into the contaminated groundwater with the intermittent timing. As an apparatus configuration in this case, a configuration including a high-pressure intermittent injection device connected to the upper end of the fluid supply pipe 13 and an air compressor that supplies ultrahigh-pressure air to the high-pressure intermittent injection device via a hose or the like can be given. It is done.
[0038]
This high-pressure intermittent injection device includes a tank for storing high-pressure air supplied from an air compressor and an intermittent valve for intermittently discharging high-pressure air in the tank, and intermittently when the pressure in the tank exceeds a predetermined pressure. The valve is opened instantly to supply high-pressure air to the fluid supply pipe 13, and the intermittent valve is closed instantly when the pressure in the tank is reduced by this discharge. The supply can be continued intermittently in the form of pulses at time intervals.
[0039]
In this configuration, since the pulses are supplied in the form of pulses at short intervals, the pressure at the time of blowing the air can be increased to an ultrahigh pressure and reach farther, and purification per fluid supply pipe can be performed. The range can be expanded. Therefore, the arrangement pitch of the fluid supply pipes can be increased to reduce the number of the fluid supply pipes arranged.
[0040]
【The invention's effect】
As described above, according to the first aspect of the present invention, a substance that grows and activates organic matter-decomposing microorganisms is supplied into the wall, and the organic matter-decomposing microorganisms in the contaminated groundwater are propagated and activated. By supplying the substance permanently, the purification ability can be maintained permanently.
Furthermore, the purification capacity can be adjusted according to the purification status of the contaminated groundwater by adjusting the amount and type of the substance.
[0041]
According to the second aspect of the present invention, since the growth amount of the methane-utilizing bacterium can be adjusted by adjusting the supply amount of methane, the purification capacity is adjusted according to the state of contamination by TCE. Is possible.
In addition, since the degree of promotion of decomposition can be adjusted by adjusting the amount of oxygen supplied, it is possible to adjust the purification capacity particularly in accordance with the state of contamination by aromatic hydrocarbons.
Furthermore, since it can be purified by supplying only methane or oxygen, no foreign matter remains in the ground.
[0042]
According to the invention shown in claim 3, since the water-permeable wall body is previously unitized, the construction period at the site can be significantly shortened. In addition, standardization is possible, and mass production can greatly reduce costs.
[Brief description of the drawings]
FIG. 1 is a perspective sectional view showing a first embodiment of a method for purifying contaminated groundwater according to the present invention.
FIG. 2 is a partially cutaway perspective view showing a purification wall unit as a second embodiment of the present invention.
FIG. 3 is a perspective cross-sectional view showing a conventional purification method using a purification wall.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ground 3 Aquifer 5 Aquifer 5a Groundwater, contaminated groundwater, water vein 5b Purified groundwater 5c Aquifer upper end 7 Impervious layer, Difficult water layer 10 Purification wall, wall 10a Groove 10b Iron powder, excess Magnesium oxide 10c Sand, crushed stone, gravel 13 Slit pipe (fluid supply pipe) 13a Slit (fluid outlet)
15 Crushed stones and gravel 17 Purified wall 19 Bendite 21 Hose 23 Air compressor 25 Laminar air flow 31 Purified wall unit (unitized water-permeable wall)
33 Reinforcing bar rod 33a Vertical reinforcing bar 33b Horizontal reinforcing bar 35 Net member, wire mesh

Claims (3)

A method for purifying contaminated groundwater contaminated with organic matter, comprising excavating a slot that vertically traverses the veins of the contaminated groundwater, and providing a fluid jet comprising a slit facing the width direction of the slot in the slot A plurality of fluid supply pipes are inserted at appropriate intervals and filled with crushed stones or gravel to form a water-permeable wall, and organic matter-degrading microorganisms in the water are propagated and activated from the fluid supply pipe embedded in the wall. A method for purifying contaminated groundwater, characterized by supplying a fluid containing a substance to be discharged.   2. The method for purifying contaminated groundwater according to claim 1, wherein the substances that grow and activate organic matter-decomposing microorganisms in the water are oxygen and methane.   2. The water-permeable wall body is previously stored in a reinforcing bar cage on the ground and formed into a unit, and the unitized water-permeable wall body is inserted into the slot. Or the purification method of the contaminated groundwater in any one of 2.

Images