JP2018197472A - Recharge method - Google Patents

Abstract

To provide a recharge method that makes it possible to appropriately perform optimum setting of a specification and the like of a filter device.SOLUTION: A recharge method including removing an insoluble substance in object water W1 by filtering the object water W1 using a spring-type filter 11 having a surface on which precoat material is deposited and a precoat layer is formed and pouring object water W2 after processing of removing the insoluble substance has been performed, from a water pouring well 4 into the underground includes: performing recharging by repeating a cycle of filtering processing and back washing of the water pouring well 4 and previously generating relation among total surface area of spring-type filters, filtering time of one cycle, number/length of the spring-type filters, and iron concentration in object water; and on the basis of the relation among total surface area of spring-type filters, filtering time of one cycle, number/length of the spring-type filters, and iron concentration in object water, setting a cycle time and a processing flow rate for the object water W1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a recharge method used in excavation work or the like.

  In general, in underground excavation work, in order to moderate moisture in the excavation part, excavation is often performed in a state where 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 discharge amount of groundwater and to reduce the influence due to the lowering of the water level around the site, a recharge method for returning the groundwater pumped back to the ground is often used.

  On the other hand, in the conventional recharge method, clogging of the ground near the screen of the water injection well (recharge well) is likely to occur, and it is difficult to maintain the water flow performance / water injection performance of the water injection well for a long period of time. For this reason, various techniques for removing clogging substances contained in the groundwater pumped to the ground surface have been proposed and put into practical use.

  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 unit, and effluent water containing construction-generated water, rainwater, groundwater, etc. is tangentially connected to the annular space. It introduce | transduces so that the swirl | flow may arise so that it may face downward with respect to a horizontal line from a direction. At this time, the foreign matter having a large weight falls in the discharged water due to the centrifugal force and the difference in gravity, and the foreign matter having a small weight floats upward. The foreign matter can be filtered and removed by the filter unit.

  However, since the clogging prevention device is mainly intended to remove suspended solids (SS) components such as clay particles, even if this clogging prevention device is used, clogging of the recharge method is not possible. It is difficult to sufficiently suppress the occurrence of the phenomenon.

  In addition, in order to restore the water flow performance of the water injection well, even if the recharge is stopped and the water injection well is backwashed over time, the water flow performance will be reduced if the ground near the water injection well is clogged. It is difficult to restore to the initial state.

  On the other hand, the inventors / applicants of the present application have made extensive studies, and the clogging of the ground near the water injection well is caused by a large amount of iron components contained in groundwater (discharged water) in addition to SS components such as soil particles. For example, a method for treating groundwater to prevent trivalent iron from reaching the vicinity of the water injection part (screen) of the water injection well has been invented, and a patent application has already been filed (Japanese Patent Application No. 2006). 075417).

  In addition, the inventors / applicants of the present application attach a precoat material manufactured using, for example, diatomaceous earth as a raw material to the surface of the spring-type filter, and filter groundwater using a spring-type filter device made of this spring-type filter and precoat material. By doing so, it has been found that precise filtration can be realized at high speed and low pressure, and trivalent iron and the like can be suitably removed.

  Further, when the precoat material 12 is attached to the surface of the spring type filter 11, for example, as shown in FIG. 6, the powder precoat material 12 is placed in the precoat tank 13 in the lower precoat tank 13 in which predetermined water is stored. (Hopper) A fixed amount is dropped from the charging port of 14 and mixed and stirred. Then, the precoat liquid S in which the precoat material 12 is uniformly dispersed / mixed is filtered from the precoat tank 13 by the spring type filter 11 of the filtration device 16 to form the precoat layer 17 on the surface of the spring type filter 11.

Japanese Patent No. 4379086

  However, for example, when the iron content in groundwater is oxidized as described above, and is recharged after being filtered by a spring-type filter of the filtration device, the optimum condition setting (setting of the filtration device specification) method is not clear.

  That is, in a spring-type filtration device, if a precoat material having a small particle size is used, the filtration accuracy is improved. However, since the permeability of the precoat material is small and the internal pressure of the container containing the spring-type filter is easily increased, backwashing is performed. It is necessary to increase the frequency of cleaning due to. On the other hand, if a precoat material having a large particle size is used, iron oxide or the like to be filtered passes through the filter.

  For this reason, it has been confirmed that the desired filtration performance can be ensured by conducting preliminary experiments, etc., and the optimum settings of the filtration equipment for the purpose of groundwater recharge are more accurately set. There was a strong demand for a method that could be used in the future.

  In view of the above circumstances, an object of the present invention is to provide a recharge method capable of accurately setting the specifications and the like of an optimum filtration device.

  In order to achieve the above object, the present invention provides the following means.

  In the recharge method of the present invention, the target water is filtered using a spring-type filter in which a precoat material is attached to the surface to form a precoat layer to remove insoluble substances in the target water, and the insoluble substances are removed. It is a recharge method for injecting target water into the ground from a water injection well. The recharge cycle is repeated by repeating the filtration process and the backwashing of the water injection well. The relationship between the filtration time of the spring-filter number / length-iron concentration of the target water is prepared, and the total surface area of the spring-type filter-1 cycle filtration time-number of spring-type filters / length-target The cycle time and the treatment flow rate of the target water are set based on the relationship between the iron concentration of water.

  Further, in the recharge method of the present invention, the planned processing flow rate and the total surface area of the spring filter are temporarily set and the iron concentration of the target water is measured, and the total surface area of the spring filter—one cycle filtration time—spring type The specification of the filtration device comprising the spring filter and the precoat material is determined from the relationship between the number / length of the filter and the iron concentration of the target water, and the backwash time and the backwash time are determined using the filtration device with the specification. It is desirable to obtain a processing flow rate when the cycle time is increased or decreased step by step, and adopt the cycle time and the processing flow rate when the processing flow rate converges.

  In the recharge method of the present invention, a design chart of the relationship between the total surface area of the spring type filter, the filtration time of one cycle, the number / length of the spring type filter, and the iron concentration of the target water is prepared in advance. By using, it is possible to install / determine the specifications of the filtration device and the specifications of the spring filter according to the water quality (iron concentration) of the target water and the treatment flow rate.

  Therefore, according to the recharge method of the present invention, it is possible to more accurately set the specifications and the like of the optimum filtration device.

It is a figure which shows the recharge system which concerns on one Embodiment of this invention. It is a figure which shows the cycle of the recharge construction method which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the water flow amount per spring type filter by the difference in a precoat material, and the time of 1 cycle. It is a figure which shows the relationship of the total surface area of a spring type filter-the filtration time of 1 cycle-the number / length of a spring type filter-iron concentration of object water. It is a flowchart which shows the method of setting cycle time and process flow volume in the recharge construction method which concerns on one Embodiment of this invention. It is a figure which shows an example of the method of forming a precoat layer on the surface of a spring type filter.

  Hereinafter, with reference to FIG. 1 to FIG. 6, a recharge method (a filtration performance setting method of a spring-type filtration device) according to an embodiment of the present invention will be described.

  First, in the present embodiment, the spring-type filtration device according to the present invention is installed at a site where excavation work or the like is performed, for example, and groundwater is pumped from the groundwater aquifer by a pumping well to control the groundwater level, Explanation will be made assuming that the groundwater pumped up is introduced into a water injection well (recharge well) installed at a desired position, and then injected into the ground from the water injection well and returned to the ground.

  In the recharge system of this embodiment, for example, an oxidant is added to the pumped ground water, and the divalent iron dissolved in the ground water of the target water in the present invention is oxidized to form insoluble / slightly soluble trivalent iron. It is configured to return groundwater to the ground after filtering off valence iron (insoluble material) from the groundwater.

  Specifically, as shown in FIG. 1, the recharge system A of the present embodiment includes a pumping well (not shown) for pumping up the groundwater that is the target water of the present embodiment, and the groundwater W1 pumped from the pumped well. The oxidant addition means 1 for adding the oxidant P, the raw water tank 2 for temporarily storing the groundwater W1 after the addition of the oxidant P, and the groundwater W1 from the raw water tank 2 are introduced into the groundwater W1. It comprises a removal processing means 3 for removing SS components and the like, and a water injection well 4 for injecting and returning the groundwater W2 treated by the removal processing means 3 to the underground aquifer.

  The pumping well is a facility for pumping groundwater from the underground aquifer to the ground, and includes, for example, a deep well provided in an excavation area partitioned by earth retaining. In addition, the pumping well is provided with a screen (collecting part) disposed in an aquifer deeper than the groundwater level, and is configured to allow groundwater to flow into the inside through this screen.

  Here, in the groundwater W1 pumped from the pumping well, iron is generally dissolved as divalent iron. When the divalent iron dissolved in the groundwater W1 comes into contact with air (oxygen), insoluble / slightly soluble trivalent iron. To change. For this reason, in the recharge system A of this embodiment, it connects between a pumping well and the oxidizing agent addition means 1 with a pumping pipe, prevents that the groundwater W1 pumped up from the pumping well to the ground is exposed to air, and groundwater W1 It is configured so that the divalent iron inside does not change to trivalent iron.

  The oxidant addition means 1 is for adding the oxidant P to the groundwater W1 sent through the pumping pipe, mainly for oxidizing the divalent iron dissolved in the groundwater W1 to the trivalent iron, and the groundwater W1. And an agitation device (mixing device) 5 for agitating the ground water W1 to which the oxidant P is added. The configuration of the oxidant adding means 1 is not particularly limited as long as the oxidant P can be supplied to the groundwater W1.

  The oxidant P supplied by the oxidant addition means 1 is not particularly limited as long as it can oxidize divalent iron generally contained in the groundwater W1 and precipitate trivalent iron. Examples of the oxidizing agent P include sodium hypochlorite, hydrogen peroxide, sodium chlorate, ozone, chlorine and the like.

  Further, since it has been confirmed by the inventors of the present application that manganese, like iron, is clogged, the oxidizing agent P oxidizes not only divalent iron but also manganese dissolved in the groundwater W1 and hydrates it. It is preferable to include a substance that can be deposited as manganese dioxide or the like.

  The stirring device (mixing device) 5 is a static mixer or the like, and is configured so that the groundwater W1 to which the oxidizing agent P is added flows and the groundwater W1 and the oxidizing agent P can be mixed. In addition, if the groundwater W1 and the oxidizing agent P can be mixed in a desired state, the configuration (mixing method) is not particularly limited.

  The removal treatment means 3 is composed of SS components (insoluble substances) in the groundwater W1 sent from the raw water tank 2, and insoluble / slightly soluble metal oxides (insoluble substances) including iron and manganese oxidized by the oxidizing agent P. This is a facility for removing water and is provided with a filtration device 16.

  The filtration device 16 of this embodiment is a spring-type filtration device. For example, stainless steel (SUS) made of a very rust-resistant material is processed into a special wire shape, and a hard spring wire material is formed into a coiled substantially cylindrical shape. And a precoat material 12 attached so as to cover the entire surface / outer peripheral surface of the spring filter 11 (see FIG. 6).

  In addition, the spring filtration device 16 has a spring filter 11 with a precoat material 12 attached in a sealed container, and supplies groundwater W1 to be filtered according to the present embodiment into the container and the spring filter 11. And by applying pressure from the outside of the precoat material 12, the groundwater W1 is filtered using the deposited layer (precoat layer 17) of the precoat material 12 as a filter, and the groundwater W2 after the filtration is formed into a substantially cylindrical and tubular spring-type filter 11 It is comprised so that it may collect | recover out of a container through the inside. In addition, the spring type filter 16 of this embodiment is comprised by accommodating the several spring type filter 11 in one container.

  Furthermore, the precoat material 12 adhering to the surface of the spring type filter 11 can be peeled off and removed simply by expanding / contracting / elastically deforming the spring type filter 11. That is, the removal residue is separated together with the precoat material 12 by peeling off the precoat material 12 at the stage where the removal residue such as the SS component in the groundwater W1 and the metal oxide such as trivalent iron is filtered and captured. It is configured so that it can be collected.

  Examples of such a spring type filtration device 16 include a liquid filtration filter element disclosed in Japanese Patent Laid-Open No. 8-196211, a spring type filter filtration device disclosed in Japanese Patent No. 1822317, and the like. Especially, it has excellent self-cleaning effect and backwashing regeneration function.

  The water injection well 4 is a recharge well, that is, a known water injection facility for injecting groundwater into the aquifer. The water injection well 4 includes a screen (water injection part) 4a embedded in the ground (aquifer) deeper than the groundwater level, and is configured so that the ground water W2 in the water injection well 4 can be injected into the aquifer from the screen 4a. Has been. Moreover, a lid is attached to the upper end of the water injection well 4, and the water injection well 4 is sealed.

  In the recharge method using the recharge system A of the present embodiment configured as described above, the oxidant P is added by the oxidant addition means 1 to the groundwater W1 pumped from the pumping well, and the divalent iron in the groundwater W1 Oxidize (and manganese) to precipitate as trivalent iron.

  Precipitated metal oxides such as trivalent iron and manganese, and insoluble substances such as SS components such as clay particles are filtered by the removal treatment means 3 and removed from the groundwater W1. Thereby, the clogging cause component contained in the groundwater W1 can be removed by the removal processing means 3.

  According to the recharge system A and the recharge method of the present embodiment, the groundwater W1 pumped from the pumping well is removed to remove the components that cause clogging of the ground G in the vicinity of the water injection well 4 to be in a good state. The groundwater W1 pumped up can be returned to the ground G while preventing clogging of the ground G and the screen 4a of the water injection well 4 and maintaining good water flow performance.

  Here, as described above, the SS component, iron, and the like in the groundwater W1 are effectively removed by the filtration device 16 of the removal processing means 3. For this reason, it is necessary to maintain the filtration device 16 by backwashing.

  Further, when the filtration time is t and the backwash time is Δt, the cycle of performing recharge with the recharge system A and the recharge method of the present embodiment can be expressed as shown in FIG. 2, and the backwash time Δt is taken into account. Assuming that the processing flow rate for flowing at the average processing flow rate Q as the whole system is Q ′, Q ′ is expressed by the following equation (1).

  Further, the inventors of the present application installed one spring filter 11 inside the container, supplied the precoat liquid S into the container and filtered it with the spring filter 11, and placed it on the surface of the spring filter 11. An experiment was conducted in which a fixed amount of the precoat material 12 was attached and the groundwater W1 was filtered at a constant flow rate. According to this experiment, as shown in FIG. 3, in contrast to the case of using two types of precoat materials (precoat material (600H) manufactured by Central Silica Co., Ltd./precoat material (645) manufactured by Central Silica Co., Ltd.) The relationship between the amount of water per filter and the time of one cycle (for example, the time until the internal pressure of the container in which the spring filter 11 is stored reaches 200 kPa) was determined.

  As shown in FIG. 3, in any of the two types of precoat materials, it was confirmed that there was a correlation between the amount of water per spring type filter and the time of one cycle. In addition, as shown in FIG. 3, it was confirmed that the same results as in the laboratory experiment were obtained even when groundwater was passed through the realization site by automatically controlling the inverter to have a constant flow rate.

Through these indoor and outdoor experiments, the permeation resistance of the spring filter 11 is determined by the absolute amount of iron adhering to the unit surface area, and in the case of a precoat material (600H), 1.3 to When 1.5 mg / cm ² of iron adheres, in the case of the precoat material (645), when 2.7 to 2.9 mg / cm ² of iron per unit area of the spring-type filter 11 adheres, the spring-type filter 11 respectively. It was possible to obtain the knowledge that the internal pressure of the container for storing the pressure reaches 200 kPa.

The specifications of the spring type filter 11 used here are a diameter φ = 15 mm, a length L = 400 mm, and a slit width 60 μm. When back pressure is applied from the inside through the upper part at the time of backwashing, it is 2 to 3 μm depending on the internal pressure. It grows. The precoat material (600H) has a transmittance of 2.2 darcy, an average particle size of 38 μm, a bulk density of 0.37 g / cm ³ , and a soil particle density of 2.3 g / cm ^{3. The} precoat material (645) has a transmittance of The density is 5.0 darcy, the average particle size is 70 μm, the bulk density is 0.37 g / cm ³ , and the soil particle density is 2.3 g / cm ³ .

  Next, Table 1 shows the result of examining the iron concentration in the treated water (W2) that has passed through the spring filter 11.

  As shown in Table 1, there is a difference in iron concentration depending on the treatment flow rate. Precoat material (Chuo Silica Co., Ltd .: 600H), water flow rate of 1 L / min, one spring type filter with iron concentration of 0.05 mg / L or less. It was confirmed that From the above results, it can be said that it is effective to increase the total surface area of the spring type filter 11 by increasing the number and length of the spring type filter 11 in order to extend the filtration time of one cycle.

Based on this, in the recharge method of the present embodiment, the total surface area (cm ² ) of the spring-type filter 11 corresponding to the iron concentration of the groundwater W1 as shown in FIG. 4 for each of a plurality of average processing flows (planned processing flows). And the filtration time (min) of one cycle, that is, the total surface area of the spring filter—the filtration time of the cycle—the number / length of the spring filter—the iron concentration of the target water.

  And in the recharge construction method of this embodiment, as shown in FIG. 5, the average processing flow rate (plan processing flow rate) Q is determined, the water quality such as the iron concentration of the groundwater (target water) W1 to be pumped is confirmed, and prepared in advance. The total surface area of the spring type filter as shown in FIG. 4—the filtration time of one cycle—the number / length of the spring type filter—the specification of the filtration device 16 such as the number of the spring type filter 11 is determined from the relationship of the iron concentration of the target water. .

  Furthermore, using the filtration device 16 that defines the specifications, the processing flow rate Q ′ when the backwashing time and the backwashing cycle time are increased or decreased in stages is obtained, and the convergence state of the processing flow rate Q ′ is confirmed. The cycle time t + Δt and the treatment flow rate Q ′ are determined so that the convergence of the treatment flow rate Q ′ is minimized.

  In the recharge method of the present embodiment, if the convergence of the processing flow rate Q ′ is minimized as described above, the optimum cycle time t + Δt and processing flow rate Q ′ that can realize efficient and effective processing are achieved. Can be set / determined.

  Therefore, in the recharge method of the present embodiment, a design chart of the relationship between the total surface area of the spring-type filter as shown in FIG. 4-the filtration time of the cycle-the number / length of the spring-type filters-the iron concentration of the target water is shown. By creating this in advance and using this design chart, it is possible to install / determine the specifications of the filtration device 16 and the specifications of the spring filter 11 according to the water quality (iron concentration) of the groundwater W1 and the treatment flow rate.

  Therefore, according to the recharge method of the present embodiment, it is possible to more accurately set the optimum filter specifications and the like.

  As mentioned above, although one embodiment of the recharge method according to the present invention has been described, the present invention is not limited to the above embodiment, and can be appropriately changed without departing from the scope of the present invention.

  In the present embodiment, a pumping well is installed at a site where excavation work or the like is performed, and the groundwater W1 pumped from the pumping well is treated and returned to the ground aquifer from the water injection well 4. The invention may be applied, for example, when pumping contaminated groundwater to the ground and purifying it, returning it to the ground, or treating water such as drainage on the ground and pouring water into the ground. There is no need to limit.

1 Oxidizer addition means 2 Raw water tank 3 Removal treatment means 4 Water injection well 4a Screen 5 Stirring device (mixing device)
11 Spring type filter 12 Precoat material 13 Precoat tank 14 Auxiliary agent supply tank (hopper)
16 Filtration device 17 Precoat layer A Recharge system G Ground P Oxidant S Precoat liquid W1 Groundwater (target water)
Groundwater after W2 treatment

Claims (2)

The target water is filtered using a spring-type filter in which a precoat material is attached to the surface to form a precoat layer to remove insoluble substances in the target water, and the target water after removing the insoluble substances is removed from the water injection well. A recharge method that pours water into
Recharging is performed by repeating the filtration process and the backwashing cycle of the water injection well, and the total surface area of the spring type filter—the cycle time of the cycle—the number / length of the spring type filter—the iron of the target water Create a density relationship,
Based on the relationship between the total surface area of the spring filter, the filtration time of one cycle, the number / length of spring filters, and the iron concentration of the target water, the cycle time and the treatment flow rate of the target water are set. Characteristic recharge method. In the recharge method according to claim 1,
Temporarily set the planned processing flow rate and the total surface area of the spring-type filter and measure the iron concentration of the target water.
From the relationship between the total surface area of the spring-type filter, the filtration time of one cycle, the number / length of the spring-type filters, and the iron concentration of the target water, the specifications of the filtration device comprising the spring-type filter and the precoat material are determined,
Use a filtration device with specified specifications, obtain the treatment flow rate when the backwash time and backwash cycle time are increased or decreased in stages, and adopt the cycle time and treatment flow rate when the treatment flow rate converges. Recharge method characterized by

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