JP2017186771A - Groundwater recharge system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a groundwater recharge system, in which water flow efficiency in the recharge system is maintained and clogging of ground near a water injection well may be prevented.SOLUTION: It comprises a drawn water well 1 for drawing groundwater W, an oxidation agent supplementation part 12 in which groundwater W drawn from the drawn water well 1 is supplied with oxidation agent Ox, a removal part 20 into which groundwater W supplied with the oxidation agent Ox is introduced and in which groundwater W is processed, a reducing agent supplementation part 14 in which the groundwater W processed in the removal part 20 is supplied with reducing agent Re at a level where remaining volume of the oxidation agent Ox in the groundwater W is reduced to a predetermined value or less, and a water injection well 2 for injection of the groundwater W supplied with the reducing agent Re to the ground.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a groundwater recharge system.

  In general, in underground excavation work, in order to moderate moisture in the excavation work part, excavation is performed in a state in which the groundwater in the excavation part is pumped up near the ground surface in advance and the groundwater level is lowered before excavation. At this time, in order to reduce the sewage discharge flow and the effects of lowering the water level around the site, a recharge method may be employed in which the pumped groundwater is returned to the ground again.

  However, in the conventional recharge method and groundwater treatment method, the ground in the vicinity of the screen of the recharge well (water injection well) is likely to be clogged, and it has been difficult to maintain the water injection performance of the recharge well for a long time.

In view of this, various techniques have been proposed for removing clogging substances contained in groundwater pumped from the excavated portion near the surface before excavation on the surface.
For example, Patent Document 1 discloses a clogging prevention device (recharge system) including a cylindrical hollow tube and a cylindrical filter provided at the center of the hollow tube. . In this clogging prevention device, an annular space is formed between the inner periphery of the hollow tube body and the outer periphery of the filter portion, and the discharged water (groundwater) containing construction-generated water, rainwater, groundwater, etc. is contained in the annular space. ) Is introduced into the annular space so that a swirling flow that faces downward from the tangential direction with respect to the horizontal line occurs. Large foreign matter in the discharged water falls downward due to the centrifugal force and gravity difference, and the small foreign matter floats upward, and the solid content in the discharged water is filtered by passing through the filter section. . Then, the treated water after filtration is taken out from the inner peripheral side of the filter unit.

Japanese Patent No. 4379086

  However, since the clogging prevention device disclosed in the above-mentioned Patent Document 1 is mainly intended to remove suspended solids (hereinafter referred to as SS) components such as clay particles, clogging occurs. There was a problem that the occurrence of the phenomenon could not be fundamentally suppressed. In addition, even if the recharge is stopped and the recharge well is backwashed over time in order to restore the water charge performance of the recharge well, the ground near the recharge well will be clogged. It was difficult to recover.

  As a result of intensive studies, the present inventor has found that iron contributes significantly in addition to SS components such as clay particles as the cause of clogging of the ground near the recharge well. Normally, iron in groundwater exists in a divalent form (bivalent iron), but even if it is pumped to the ground surface through a sealed pipe, as in a conventional recharge system, deep well If a slight amount of air is touched inside the (pumped well) or the recharge well, it changes to a trivalent form (trivalent iron, ie, insoluble iron). In particular, trivalent iron causes significant clogging in the ground and recharge well screen and filter material on the water injection side even at low concentrations. The present inventor studied the configuration of a groundwater recharge system for preventing trivalent iron from reaching the vicinity of the water injection portion of the recharge well, and completed the present invention.

  The present invention has been made in view of the above circumstances, and provides a groundwater recharge system capable of maintaining the water flow performance of the recharge system and preventing clogging of the ground near the water injection well.

  The groundwater recharge system according to claim 1 is a groundwater recharge system for performing a recharge method for injecting groundwater that has been pumped into the ground, a pumping well for pumping the groundwater, and pumping from the pumped well An oxidant addition unit for adding an oxidant to the groundwater, and a removal unit for introducing the groundwater to which the oxidant has been added and removing suspended solid components and metal oxides existing in the groundwater after the addition of the oxidant; A reducing agent adding unit that adds a reducing agent to the groundwater treated by the removing unit until a redox potential of the groundwater is equal to or lower than a predetermined value; and the groundwater to which the reducing agent is added is poured into the ground. And a water injection well.

According to the above-described configuration, the oxidant is added to the groundwater pumped from the pumping well by the oxidizer addition unit, whereby the divalent iron in the groundwater is oxidized and the trivalent iron is deposited. At this time, manganese that can affect the clogging of the ground in the same manner as iron can be deposited as hydrated manganese dioxide. The deposited metal oxide such as trivalent iron is removed from the groundwater by passing through the removal portion together with the SS component such as clay particles. That is, the clogging cause component in the groundwater is removed by the removing unit. Then, the oxidant remaining in the groundwater treated by the removing unit is reduced by the reducing agent adding unit until the amount becomes a predetermined value or less. Therefore, the groundwater pumped from the pumping well is in a state where the components that cause clogging of the ground near the water injection well have been removed. And clogging of the ground near the recharge well almost disappears. Further, since the added oxidizing agent loses its oxidizing power due to the reducing agent, there is no fear of clogging due to oxidation / precipitation of iron or other metals contained in the existing groundwater by injection of recharged water.
The above-mentioned predetermined value is a redox potential that indicates the allowable amount of oxidant remaining in the groundwater that can satisfactorily prevent clogging of the ground when water is poured into the ground by a water injection well. Is the amount that completely loses oxidizing power.

  In the groundwater recharge system according to claim 2, the predetermined value is 200 mV or less.

  According to the above-described configuration, the groundwater to which the reducing agent is added by the reducing agent addition unit is sufficiently and well clogged in the ground in the vicinity of the water injection well even when water is injected into the ground from the water injection well having the existing configuration. It will be in a state that can be prevented.

  The groundwater recharge system according to claim 3 is characterized in that the removing unit includes a device constituted by a spring-type filter.

  According to the above-described configuration, the groundwater to which the oxidant is added by the oxidant addition unit is filtered by the spring filter, so that it is positively oxidized by the SS component contained in the groundwater and the oxidant, The deposited metal oxide such as trivalent iron is captured by the spring filter of the spring filter. Even if the spring filter is clogged, backwashing air or water is added to the spring filter and the pressure is controlled, so that it is easy and almost automatic. Components are also removed and discharged. Therefore, a groundwater recharging system having an excellent self-cleaning effect and a low maintenance burden can be obtained.

  5. The groundwater recharge system according to claim 4, wherein the reducing agent adding unit adds the reducing agent to the ground water treated by the removing unit, and the reducing agent is added by the reducing agent adding device. A first oxidant detector that detects the amount of the oxidant in the groundwater before being fed back, and feeds back the detected amount of the oxidant to the reducing agent addition device; and the reduction by the reducing agent addition device. And detecting at least one of the redox potential detecting unit for detecting the redox potential of the groundwater after the agent is added, and feeding back the detected redox potential to the reducing agent adding device, The reducing agent addition amount is configured to be adjustable based on information fed back from at least one of the first oxidant detector and the second dioxide detector detector. And features.

  According to the above-described configuration, the ground water oxidation-reduction potential is detected by at least one of the first oxidant detecting unit and the second dioxide agent detecting unit, and fed back to the reducing agent addition device, whereby excessive addition or addition of the reducing agent is performed. The shortage is suppressed, the groundwater is efficient, and clogging can be prevented well when water is poured into the ground.

  In the groundwater recharge system according to claim 5, the oxidizing agent contains sodium hypochlorite.

  According to the above configuration, since sodium hypochlorite contained in the oxidizing agent is added to the groundwater pumped from the pumping well, the divalent iron in the groundwater instantaneously reacts with sodium hypochlorite. And more rapidly and reliably deposited as trivalent iron. Moreover, if a stirring apparatus is added, reaction of an oxidizing agent, divalent iron, and another metal with sodium hypochlorite will occur more reliably and uniformly.

  According to the groundwater recharge system of the present invention, the divalent iron that is included in the groundwater pumped from the pumping well and is the root cause of clogging of the ground in the vicinity of the filter and the pouring well is dared as trivalent iron. The trivalent iron is deposited and removed by the removing unit, and the groundwater is reduced by the reducing agent adding unit. Therefore, when the groundwater pumped from the pumping well is poured into the ground, the ground can be satisfactorily prevented from being clogged. Thereby, the water flow performance of a recharge system can be kept favorable and the clogging of the ground can be prevented.

It is the schematic which shows one Embodiment of the groundwater recharge system which concerns on this invention. It is a schematic diagram which shows the structure of the test apparatus at the time of performing the column test which passed the water which adjusted the density | concentration of trivalent iron, and the water processed with the spring type filter with the fixed head difference. It is a graph which shows the measurement result at the time of performing the column test which passed the water which adjusted the density | concentration of trivalent iron, and the water processed with the spring type filter with the fixed head difference. It is the schematic which shows the mode of operation in the spring type filter used for the spring type filter of the removal part of the groundwater recharge system shown in Drawing 1, and (a) is a figure showing the mode at the time of normal operation (recharge operation). Yes, (b) is a diagram showing a state during the backwash operation. It is a graph which shows an example of the filtration performance by the spring type filter used for the spring type filter of the removal part of the groundwater recharge system shown in FIG. It is the schematic which shows the modification of the groundwater recharge system which concerns on this invention.

  Hereinafter, an embodiment of a groundwater recharge system according to the present invention will be described with reference to the drawings. Note that the drawings used in the following description are schematic, and the ratios of length, width, and thickness are not necessarily the same as actual ones, and can be changed as appropriate.

FIG. 1 is a schematic diagram illustrating a configuration of a groundwater recharge system 10 according to the present embodiment.
As shown in FIG. 1, the groundwater recharge system 10 is installed at a site where excavation work or the like is performed, and the groundwater W pumped from the aquifer (ground) S2 by the pumping well 1 to the water injection well 2. It is a system for conducting a recharge method for guiding water from the water injection well 2 into the aquifer (ground) S3.

  The ground illustrated in FIG. 1 has a structure in which aquifers S1, S2, S3,... And clay layers C1, C2,. In addition, if a recharge construction method is applicable, the structure of a ground, a pumping position, and a water pouring position will not be specifically limited.

FIG. 1 is a schematic diagram showing a groundwater recharge system 10 of the present embodiment.
As shown in FIG. 1, a groundwater recharge system 10 includes a pumping well 1 for pumping up groundwater W, an oxidizing agent adding unit 12 for adding an oxidizing agent Ox to the groundwater W pumped from the pumping well 1, and an oxidizing agent. The removal unit 20 that introduces groundwater W to which Ox is added and removes SS components present in the groundwater, and the remaining amount of the oxidizer Ox in the groundwater W (the amount of the groundwater W in the groundwater W treated by the removal unit 20). A reducing agent addition unit 14 for adding the reducing agent Re until the oxidation-reduction potential becomes equal to or lower than a predetermined value, and a water injection well 2 for injecting the groundwater W to which the reducing agent Re has been added into the aquifer (ground) S3. And.

  The pumping well 1 is a well-known drainage facility for pumping up groundwater W in the aquifer S2, and specifically, a deep well (so-called so-called deep well) installed in an excavation region X partitioned by earth retainings D and D. , Deep well). Near the lower end of the pumping well 1, a screen 1a embedded in the ground deeper than the groundwater level (the aquifer S2 in FIG. 1) is formed, and groundwater W in the ground flows from the screen 1a. Groundwater W is stored in the pumping well 1.

  In the groundwater W pumped from the pumping well 1, iron exists in a divalent state, that is, as divalent iron having solubility. The divalent iron in the groundwater W changes to trivalent iron when it is exposed to air or the like even during the process of pumping, or during the subsequent treatment.

  FIG. 2 is a schematic diagram showing a configuration of a test apparatus when a column test is performed in which water adjusted in the concentration of trivalent iron is passed with a constant water head difference H (that is, H shown in FIG. 2). In the test apparatus shown in FIG. 2, the inner diameter D of the column 50 is 30 mm. The Toyoura sand S which assumed the soil in the ground was put in the bottom part, and water WF 'which adjusted the density | concentration of trivalent iron, stirring in the water tank 52 was flowed through the column 50. FIG. The water flow rate of the water WF at the initial stage of water flow was set to 15 mL / min to 16 mL / min. The water WF that passed through the column S was introduced into the water tank 54. In order to maintain a constant water head difference H, the water tank 54 is provided with a mechanism for discharging the groundwater WF higher than a predetermined position in the water tank 54 and a water tank 56 for storing the discharged groundwater WF.

FIG. 3 is a graph showing the measurement results when the above-described column test is performed by changing the concentration of trivalent iron from 0.05 mg / L to 10 mg / L as indicated by the numerical values shown in the graph. The measurement results when the above-described column test is performed using tap water (the concentration of iron and its compound is 0.01 mg / L to 0.02 mg / L) used in the experiment are also shown. The horizontal axis of the graph indicates the elapsed time of water flow to the column 50, and the vertical axis of the graph indicates the amount of passing water WF from the column 50 to the water tank 54. If the Toyoura sand S is not clogged, in the graph, the relationship between the elapsed time of water flow to the column 50 and the amount of water WF passed to the column 50 is linear (the (linear) straight line shown in FIG. 3) and Become. As shown in FIG. 3, when the concentration of trivalent iron in water is 0.1 mg / L or more, clogging occurs in Toyoura sand S in a short time, and the amount of water flow (that is, the amount of water injection) cannot be maintained. I understand that.
Therefore, in the groundwater recharge system 10, in order for the groundwater W to be in a state that can sufficiently and satisfactorily prevent clogging of the ground near the water injection well, the concentration of trivalent iron in the groundwater W is at least 0.1 mg / L. It is important that it is smaller, preferably smaller than 0.05 mg / L, more preferably smaller than 0.01 mg / L.

  As shown in FIG. 1, the pumping well 1 and the removal unit 20 are communicated with each other by a pumping pipe 9 </ b> A. One end of the pumping pipe 9 </ b> A is inserted into the pumping well 1 from the upper end of the pumping well 1, and the other end of the pumping pipe 9 </ b> A is connected to the inlet of the removal unit 20. One end of a pumping pipe 9A inserted in the pumping well 1 is connected to a discharge port of a pumping pump P1 arranged in the pumping well 1, and the groundwater W in the pumping well 1 is pumped by the pumping pump P1. It is pumped into the removing section 20 through 9A.

  One end of an oxidant supply pipe 9a is connected to the middle of the pumping pipe 9A. The other end of the oxidant supply pipe 9a is connected to the oxidant discharge port of the oxidant addition section 12, and the oxidant supply pipe 9a is supplied to the groundwater W pumped from the pumping well 1 and flowing in the pumping pipe 9A. The oxidizing agent Ox can be supplied from the oxidizing agent adding section 12 through

The oxidant addition unit 12 includes an oxidant supply device (not shown). In addition, the structure of the oxidizing agent addition part 12 will not be specifically limited if the oxidizing agent Ox can be discharged | emitted by the other end of the oxidizing agent supply pipe | tube 9a.
The oxidizing agent Ox supplied from the oxidizing agent adding unit 12 is not particularly limited as long as it contains a substance that can oxidize divalent iron generally contained in the groundwater W and precipitate trivalent iron. Examples of substances capable of oxidizing divalent iron in groundwater W and precipitating trivalent iron include oxidizing agents such as sodium hypochlorite, hydrogen peroxide, sodium chlorate, ozone and chlorine. As long as the oxidizing agent Ox is a reactive oxidizing agent, the type and the material thereof are not limited. However, similar to iron, manganese can be clogged even at a relatively low concentration. The oxidizing agent Ox preferably contains a substance capable of oxidizing soluble manganese and precipitating trivalent iron and hydrated manganese dioxide in addition to divalent iron generally contained in groundwater W.

  As described above, the oxidizer Ox preferably contains sodium hypochlorite. The reaction with at least divalent iron in the groundwater W is instantaneously and reliably performed by sodium hypochlorite, and is precipitated as trivalent iron. Hypochlorous acid is advantageous not only because of its fast reactivity, but also because it is safe for use in disinfection of tap water. Moreover, the quick oxidation rate means that the reaction for eliminating the oxidizing power can be performed quickly. Further, the deactivation method such as passing through activated carbon can be easily performed.

  A stirring device 22 for mixing the ground water W and the oxidant Ox added to the ground water W is located in the middle of the pumping pipe 9A and downstream of the position where one end of the oxidant supply pipe 9a is connected. Is provided. As the agitation device 22, for example, a static mixer or the like provided with a blade plate arranged in the pipe and automatically agitated by the flow of water can be used. However, the ground water W and the oxidizer Ox can be mixed. If there is, it will not be specifically limited.

  The removal unit 20 introduces groundwater W that has been pumped into the removal unit 20 through the pumping pipe 9A, and metal oxides such as SS components in the groundwater W and iron and manganese oxidized by the oxidizer Ox. It is equipment for removing (ie, trivalent iron, etc.), and is equipped with a device composed of a spring filter. Specific examples of the spring filter include a liquid filter element disclosed in Japanese Patent Laid-Open No. Hei 8-196211, a spring filter apparatus disclosed in Japanese Patent No. 1822317, and the like. Is mentioned. The spring type filter is made of stainless steel (SUS) made of a very rust-resistant material into a special wire shape, and after applying this pre-coating material to a spring type filter with this hard spring wire wound in a coil shape, This is based on the concept of removing the residue adhering to the precoat material together with the precoat material. Such a spring type filter has a particularly excellent self-cleaning effect and a backwashing regeneration function, and has features and conditions suitable for filtering the groundwater W in the present invention, such as making maintenance substantially unnecessary. .

  Conventionally, the spring type filter used in the spring type filter of the removing unit 20 has been used mainly for drainage (turbid water) treatment. However, in the filtration process, the spring type filter is coated at the first stage. By appropriately selecting the precoat material (i.e., filter aid), the particle size (i.e., filtration accuracy) filtered by the spring filter can be determined. In addition, precise filtration can be realized at high speed and low pressure.

Further, the spring filter of the removing unit 20 does not require an additive such as a flocculant.
FIG. 4A is a schematic diagram showing a normal operation (recharge operation) in the spring filter of the spring filter of the removing unit 20, and FIG. 4B is a clogging component of the spring filter. It is the schematic which shows the mode at the time of the backwash operation for removing. During normal operation, as shown in FIG. 4 (a), groundwater W containing an SS component and metal oxide is introduced into the spring filter, and the filtered groundwater W flows out from the outlet of the spring filter. . As a self-cleaning effect of the spring type filter, as shown in FIG. 4B, the spring type filter is clogged with SS components and metal oxides such as iron and manganese (that is, trivalent iron, etc.). When the efficiency falls below a predetermined efficiency, backwashing air and water are press-fitted through the water injection pipe 9b (see FIG. 1) connected to the outlet side of the spring-type filter of the removing unit 20. Thus, the pressure from the inside to the outside of the spring type filter is automatically applied and controlled. As a result, so-called backwashing is performed, and the clogging component captured by the spring filter can be collected and discarded as a concentrated liquid via a drain pipe (not shown in FIG. 1).

  FIG. 5 is a graph showing an example of filtration performance by a spring filter when a spring filter device (manufacturer: Monobe Engineering Co., Ltd.) is used as a spring filter used in the spring filter of the removing unit 20. is there. In this filtration performance measurement, the flow rate per spring of the spring type filter was made constant at 1 L / min, and the concentration of trivalent iron in the water flow was set to 2 mg / L. Under such conditions, the pressure change in the spring type filter was measured. As the precoat material, silica # 600H (average particle diameter: 38 μm, pass rate: 2.2 darcy, manufacturer: Chuo Silica Co., Ltd.) was used.

  As shown in FIG. 5, assuming that the cleaning is performed when the internal pressure of the spring filter reaches 200 kPa, when silica # 600H is used as the precoat material, the cleaning is performed once every 60 minutes (ie, Equivalent to washing 24 times a day). The frequency of such washing depends on the concentration of SS components and trivalent iron in the water to be treated. However, as can be seen from the frequency of washing, cleaning and replacement of removal materials or filtration materials that rely on human power are subject to treatment. It is difficult to keep the concentration of SS water and the concentration of trivalent iron so that the ground is not clogged to the same extent as when using a spring-type filter. In addition, when the above-mentioned precoat material was used, the density | concentration of the trivalent iron contained in the water after filtration became 0.05 mg / L or less. As a result of passing the filtered water through the column test apparatus shown in FIG. 2, it was found that clogging was almost the same as tap water as shown by “treated water” in FIG. This also shows that the water filtered with the spring filter has a water quality that allows the long-term water injection to be successfully removed from the substances causing clogging.

  The removal unit 20 is not limited to the above-described spring-type filter or a similar structure, and the metal oxide generated by the SS component and the oxidant Ox contained in the groundwater W introduced into the removal unit 20. If it has the capability which can remove, it will not specifically limit. For example, the removing unit 20 may be any one of a filter press, a belt press, a back filter, a centrifuge, a sand filter, and the like.

  As shown in FIG. 1, the removal part 20 and the filtrate water tank 32 are connected by the water flow pipe 9B. One end of the water conduit 9 </ b> B is connected to the lead-out portion of the removing unit 20, and the other end of the water conduit 9 </ b> B is opened inside the filtrate water tank 32. The groundwater W filtered by the removing unit 20 is supplied into the filtrate water tank 32 through the water pipe 9B.

  The filtrate water tank 32 is configured to accommodate the groundwater W in which the oxidant Ox remains and be derived from a predetermined position, and is not particularly limited, and a known tank or the like can be applied. A drainage pump P <b> 4 for discharging the groundwater W is provided at the outlet portion of the filtrate water tank 32.

  In the filtrate water tank 32, one end of a reducing agent supply pipe 9c is arranged in addition to the other end of the water pipe 9B. The other end of the reducing agent supply pipe 9 c is connected to the reducing agent discharge port of the reducing agent addition device 15 of the reducing agent addition unit 14, and the ground water W processed in the removal unit 20 and accommodated in the filtrate water tank 32. On the other hand, the reducing agent Re can be supplied from the reducing agent addition unit 14 via the reducing agent supply pipe 9c.

  The reducing agent adding unit 14 is configured to remove the oxidizing agent Ox remaining in the groundwater W filtered (processed) by the removing unit 20 and to reduce the groundwater W to a reduced state. In the present embodiment, the reducing agent adding unit 14 is reduced by the reducing agent adding device 15 that adds the reducing agent Re to the ground water W that is processed by the removing unit 20 and accommodated in the filtrate water tank 32, and the reducing agent adding device 15 performs the reduction. A first oxidant detector 16 that detects the amount of the oxidant Ox in the groundwater W before the agent Re is added based on the oxidation-reduction potential of the groundwater W and feeds back the detected oxidation-reduction potential to the reducing agent addition device 15; And at least any one of the second dioxide agent detection units 17 that detects the redox potential of the groundwater W after the reducing agent Re is added by the reducing agent addition device 15 and feeds back the detected oxidation-reduction potential to the reducing agent addition device 15. Or one of them. And the reducing agent addition part 14 is comprised so that adjustment of the addition amount of reducing agent Re is possible based on the information fed back from at least any one of the 1st oxidizing agent detection part 16 and the 2nd dioxide detection part 17. .

The reducing agent addition device 15 is not particularly limited as long as the reducing agent Re can be discharged to the other end of the reducing agent supply pipe 9c.
The reducing agent Re supplied from the reducing agent addition device 15 of the reducing agent addition unit 14 is not particularly limited as long as it is a substance that can remove the oxidizing agent Ox remaining in the groundwater W. Examples of such substances include sodium thiosulfate, sodium sulfite, and sodium hydrosulfide. Sodium thiosulfate is suitable because it is a highly safe substance such as being used as a material for dechlorination of ornamental fish.

  The 1st oxidizing agent detection part 16 will not be specifically limited if a part of groundwater W which flows through the inside of the water flow pipe 9B after processing by the removal part 20 is introduce | transduced, and the oxidation-reduction potential of the introduced groundwater W can be detected. . The water pipe 9B is provided with a pumping pump P2 for introducing a part of the groundwater W into the first oxidant detector 16 as necessary. The detected oxidation-reduction potential is directly fed back to the reducing agent adding device 15, and the supply amount (adding amount) of the reducing agent Re in the reducing agent adding device 15 (reducing agent adding unit 14) is adjusted based on the fed back information. May be. In the present embodiment, the oxidation-reduction potential of the groundwater W detected by the first oxidant detection unit 16 is sent to the control unit 30 as a signal S16.

  The second dioxide agent detection unit 17 is supplied with the reducing agent Re from the reducing agent addition device 15 and introduces part of the groundwater W led out from the filtrate water tank 32 to the water pipe 9C, and the redox potential of the introduced groundwater W. If it is detectable, it will not specifically limit. The water pipe 9 </ b> C is provided with a pumping pump P <b> 3 for introducing a part of the groundwater W into the second dioxide agent detection unit 17 as necessary. The detected oxidation-reduction potential of the groundwater W is directly fed back to the reducing agent adding device 15, and the supply amount (adding amount) of the reducing agent Re in the reducing agent adding device 15 (reducing agent adding unit 14) based on the fed back information. May be adjusted. In the present embodiment, the amount of redox potential of the groundwater W detected by the second dioxide agent detection unit 17 is also sent to the control unit 30 as a signal S17.

  Although the reducing agent addition part 14 is provided with at least one of the 1st oxidizing agent detection part 16 and the 2nd dioxide detection part 17, the oxidation-reduction potential of the groundwater W supplied to the water injection well 2 is more reliably below predetermined value. In order to prevent excessive addition and insufficient addition of the reducing agent Re to the groundwater W, it is preferable that both the first oxidant detector 16 and the second dioxide detector 17 are provided. Note that the first oxidant detector 16 and the second dioxide detector 17 may be integrated because the measurement object is the oxidizer Ox in common, and may be integrated as one detector. It may be configured.

  Examples of the first oxidant detector 16 and the second dioxide detector 17 include an ORP (Oxidation-Reduction Potential) sensor and a dissolved oxygen sensor. From the viewpoint of simple configuration and easy installation, the first oxidant detector 16 and the second dioxide detector 17 are preferably ORP sensors. When using the ORP sensor, an ORP that is a potential determined by an equilibrium state between an oxidant and a reductant coexisting in the groundwater W is appropriately set. As a state in which the groundwater W can sufficiently and satisfactorily prevent clogging of the aquifer (ground) S3 in the vicinity of the injection well, it is preferable that no oxidant remains in the groundwater W after the addition of the reducing agent. The oxidation-reduction potential measured by the ORP sensor of the oxidant detector 16 and the second dioxide detector 17 is at least 200 mV or less, preferably 100 mV or less, more preferably 0 mV or less.

  In addition, the residual amount of SS component in the groundwater W processed by the removal part 20 can be measured using the turbidimeter etc. which are not shown in figure. From the point that the clogging of the ground can be satisfactorily prevented when the groundwater W is poured into the ground, for example, the concentration of the SS component in the groundwater W treated by the removing unit 20 is less than 1 mg / L. It is preferable that this is confirmed.

The groundwater recharge system 10 according to this embodiment includes a control unit 30. The control unit 30 sets the supply amount (addition amount) of the reducing agent Re in the reducing agent addition device 15 based on the information fed back from the first oxidant detection unit 16 and the second dioxide agent detection unit 17 to reduce the reduction. It has the function to send to the agent addition apparatus 15 as signal S15.
An example of what constitutes the control unit 30 is a computer, but is not particularly limited as long as it has the above-described function.

When the control unit 30 detects from the feedback of the second dioxide agent detection unit 17 that the oxidation-reduction potential of the groundwater W derived from the filtrate water tank 32 after the addition of the reducing agent Re is greater than the predetermined value described above. Preferably has a function of stopping the derivation of groundwater W from the filtrate water tank 32.
That is, it is preferable that the control unit 30 is configured by a computer in which a control program or the like is built. The control program described above is a procedure in which the computer captures the oxidation-reduction potential of the groundwater W detected by the second dioxide agent detection unit 17 and the oxidation-reduction potential of the groundwater W is equal to or less than a preset threshold value (predetermined value). If the outlet of the filtrate water tank 32 and the water pipe 9C are in communication with each other, and if the oxidation-reduction potential of the groundwater W exceeds the threshold, the outlet of the filtrate water tank 32 and the water pipe 9C are not in communication. It is preferable that it is comprised so that it may perform.

  Further, the control unit 30 appropriately sets the supply amount (addition amount) of the oxidant Ox in the oxidant addition unit 12 based on the information fed back from the first oxidant detection unit 16 and the second dioxide detection unit 17 or It is preferable to have a function of correcting and sending the signal to the oxidizer addition section 12 as a signal S12. Accordingly, if the supply amount (addition amount) of the oxidant Ox in the oxidant addition unit 12 is adjusted according to the amount of the oxidant Ox remaining in the groundwater W led out from the filtrate water tank 32, the oxidant Ox. Excessive or insufficient addition of is also prevented.

  The filtrate water tank 32 and the water injection well 2 are communicated by a water pipe 9C and a water pipe 9D branched from the middle of the water pipe 9C. One end of the water pipe 9C is connected to the outlet of the filtrate water tank 32, and the other end of the water pipe 9C is opened deeper than a predetermined water level of the water injection well 2B in the water injection well 2. A stirring device 24 for mixing the ground water W and the reducing agent Re added to the ground water W is provided on one end side of the water conduit 9C. As the stirring device 24, for example, a static mixer having a small and simple configuration can be used, but is not particularly limited as long as the ground water W and the reducing agent Re can be mixed.

  One end of the water pipe 9D is connected to the middle of the water pipe 9C, and the other end of the water pipe 9D is opened in a deep portion from the predetermined water level of the water injection well 2A in the water injection well 2. Groundwater W derived from the filtrate water tank 32 and having an oxidation-reduction potential of a predetermined value or less is supplied to the water injection wells 2A and 2B through the water pipes 9C and 9D.

The water injection well 2 includes the two water injection wells 2A and 2B as described above. However, the number of wells provided in the water injection well 2 is not particularly limited.
The water injection wells 2A and 2B are well-known water injection facilities (so-called recharge wells) for injecting the groundwater W in a reduced amount with the oxidizer Ox contained therein to a predetermined value or less. Consists of a well installed outside the excavation area X. In the water injection wells 2A and 2B, a screen 2a embedded in the ground deeper than the groundwater level (the aquifer S3 in FIG. 1) is formed, and the groundwater W in the water injection wells 2A and 2B flows out from the screen 2a. Then, groundwater W is injected into the aquifer S3. Moreover, the lid | cover is attached to the upper end of the water injection well 2, the upper end of the water injection well 2 is sealed with the lid | cover, and the water injection well 2 has a sealed structure.

  As described above, in the groundwater recharge system 10 of the present embodiment, the oxidizer Ox is added to the groundwater W pumped from the pumping well 1 by the oxidizer adding unit 12 to oxidize the divalent iron in the groundwater W. And deposited as trivalent iron. The precipitated metal oxides such as trivalent iron and manganese are removed from the ground water W by being filtered by the removing unit 20 together with SS components such as clay particles. That is, the clogging cause component contained in the groundwater W can be removed by the removing unit 20. Then, the groundwater W is reduced until the oxidizing agent Ox remaining in the groundwater W filtered by the removing unit 20 becomes an amount equal to or less than a predetermined value by the reducing agent adding unit 14. Therefore, the groundwater W pumped from the pumping well 1 can be in a good state in which components that cause clogging of the ground near the water injection well are removed.

  As described above, according to the groundwater recharge system 10 of the present embodiment, it is included in the groundwater W pumped from the pumping well 1, and the root cause of clogging of the screen 2a of the pouring well 2 and the ground near the pouring well 2 Then, the divalent iron to be precipitated is dared as trivalent iron, and the trivalent iron is removed by the removing unit 20 and the groundwater W can be reduced by the reducing agent adding unit 14. Therefore, when the groundwater W pumped from the pumping well 1 is poured into the ground, the ground can be satisfactorily prevented from being clogged. Thereby, the water flow performance of the groundwater recharge system 10 can be maintained satisfactorily, and clogging of the screen 2a of the water injection well 2 and the ground can be prevented.

  In addition, according to the groundwater recharge system 10 of the present embodiment, the groundwater W to which the reducing agent Re is added by the reducing agent addition unit 14 has a predetermined amount in which the amount of the oxidizing agent Ox, that is, the oxidation-reduction potential of the groundwater W is appropriate. Since the value is set, even if water is poured into the ground from the water injection well 2 having the existing configuration, clogging of the ground near the water injection well 2 can be sufficiently and well prevented.

  Further, according to the groundwater recharge system 10 of the present embodiment, the removal unit 20 is configured by a spring filter, so that the oxidant Ox is added by the oxidant addition unit 12 and is actively added by the oxidant Ox. Oxidized and precipitated metal oxides such as trivalent iron and manganese are captured by the spring filter of the spring filter, and even if clogging occurs, backwash air is added to the spring filter to control the pressure. Then, it is possible to easily and substantially automatically remove and discharge the metal oxide such as trivalent iron and manganese and the SS component captured by the spring type filter. Therefore, it is possible to construct the groundwater recharge system 10 that has an excellent self-cleaning effect and has a small maintenance burden.

  Further, according to the groundwater recharge system 10 of the present embodiment, the amount of the oxidant Ox in the groundwater W is detected by at least one of the first oxidant detector 16 and the second dioxide detector 17, and the reducing agent addition device 15. Thus, it is possible to suppress excessive addition or insufficient addition of the reducing agent Re, and make it possible to effectively prevent clogging when the groundwater W is poured into the ground efficiently. By using both the first oxidant detection unit 16 and the second dioxide detection unit 17, the groundwater W can be made more efficiently and in a state where clogging can be satisfactorily prevented when water is poured into the ground. Further, by feeding back the amount of the oxidant Ox in the groundwater W detected by the first oxidant detection unit 16 and the second dioxide agent detection unit 17 to the oxidant addition unit 12, excessive addition or insufficient addition of the oxidant Ox is detected. It can also be suppressed.

  In addition, according to the groundwater recharge system 10, since sodium hypochlorite is added as an oxidizer Ox to the groundwater W pumped from the pumping well, divalent iron in the groundwater W is instantaneously converted to hypochlorous acid. It can be reacted with sodium and deposited as trivalent iron more quickly and reliably. Thereby, the removal precision of the trivalent iron in the ground water W in the removal part 20 can also be improved.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications are possible within the scope of the gist of the present invention described in the claims. It can be changed.

  For example, in the above-described embodiment, the device for adding the reducing agent Re has been described as the reducing agent adding device 15 of the reducing agent adding unit 14, but as the reducing agent adding device 15, as shown in FIG. You may use the activated carbon tank which has the function to reduce | restore. In such a configuration, the groundwater W treated by the removing unit 20 can be passed through the activated carbon tank, and the groundwater W after the water flow can be guided to the water injection well 2.

  For example, in order to observe the state of the groundwater W pumped from the pumping well 1, the pumped groundwater W may be temporarily stored in a known notch tank or the like.

DESCRIPTION OF SYMBOLS 1 Pumping well 2,2A, 2B Injection well 10 Groundwater recharge system 12 Oxidant addition part 14 Reductant addition part 20 Removal part Ox Oxidant Re Reductant W Groundwater

Claims (5)

A groundwater recharge system for performing a recharge method for pouring pumped groundwater into the ground,
A pumping well for pumping the groundwater;
An oxidant addition unit for adding an oxidant to the groundwater pumped from the pumping well;
A removal unit for introducing the groundwater to which the oxidant is added and removing suspended solids components and metal oxides present in the groundwater after the addition of the oxidant;
A reducing agent addition unit for adding a reducing agent to the groundwater treated in the removal unit until a redox potential of the groundwater becomes a predetermined value or less;
A water injection well for pouring the groundwater to which the reducing agent is added into the ground;
A groundwater recharge system characterized by comprising:   The groundwater recharge system according to claim 1, wherein the predetermined value is 200 mV or less.   The groundwater recharging system according to claim 1, wherein the removing unit includes a device including a spring filter. The reducing agent addition part is
A reducing agent addition device for adding the reducing agent to the groundwater treated in the removal unit;
A first oxidant detector that detects the amount of the oxidant in the groundwater before the reducing agent is added by the reducing agent addition device and feeds back the detected amount of the oxidant to the reducing agent addition device. And the amount of the oxidizing agent in the groundwater after the reducing agent is added by the reducing agent addition device, and the detected amount of the oxidizing agent is fed back to the reducing agent addition device. At least one of the detectors;
With
The reductant addition amount is configured to be adjustable based on information fed back from at least one of the first oxidant detection unit and the second dioxide detection unit. Item 4. The groundwater recharge system according to any one of Items 3 to 3.   The groundwater recharging system according to any one of claims 1 to 4, wherein the oxidizing agent contains sodium hypochlorite.

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