JP2019039301A - Method for preventing increase in dissolved oxygen amount of groundwater - Google Patents

Abstract

To provide a method for preventing an increase in a dissolved oxygen amount in groundwater capable of preventing oxidation of metal ions and propagation of iron bacteria in the groundwater in a well.SOLUTION: Provided is a method for preventing an increase in a dissolved oxygen amount of groundwater W springing in a well 11, wherein a contact preventive 18 for preventing the groundwater W from being brought into contact with an atmosphere A is fed on a water surface S of the groundwater W in a state in which the well 11 is not hermetically sealed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for preventing an increase in dissolved oxygen content of groundwater.

Conventionally, groundwater is pumped up using wells and used for various purposes such as domestic water, industrial water, and agricultural water.
Since metals such as iron and manganese exist in the soil, these metals exist in an ionic state in the groundwater. When groundwater containing metal ions comes into contact with the atmosphere, oxygen in the atmosphere dissolves in the groundwater and the metal ions are oxidized.

  As a method for preventing oxidation of dissolved elements in groundwater, for example, Patent Document 1 discloses a method for preventing oxidation of dissolved elements in groundwater by supplying an inert gas to a storage tank that stores groundwater pumped by self-injection or pumping. Is disclosed.

JP2012-122189A

However, the method described in Patent Document 1 is a method of preventing the oxidation of dissolved elements of groundwater pumped from a well and stored in a water storage tank, and prevents the oxidation of metal ions in the groundwater flowing out of the well. Has not reached.
The amount of dissolved oxygen in groundwater is low immediately after springing in the well, but gradually increases because oxygen in the atmosphere in contact with the water surface dissolves in groundwater. When oxygen dissolves in groundwater, the oxygen concentration in the atmosphere near the water surface decreases, but the water level in the groundwater fluctuates, so new air flows into the wells, returning the oxygen concentration in the atmosphere near the water surface to its original value and saturation. Dissolution of oxygen into groundwater proceeds until it reaches a state. When oxygen dissolves in groundwater in the well, metal ions in the groundwater are oxidized, aggregated and suspended in the groundwater, and adhere to various pipes and pumps used to pump up the groundwater, causing them to become clogged. .
In addition, when oxygen dissolves in groundwater, iron bacteria are likely to propagate. Iron bacteria take up and accumulate iron ions in the body. When these iron bacteria aggregate or adhere, various pipes and pumps used for pumping up groundwater are blocked.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the increase prevention method of the dissolved oxygen amount of groundwater which can prevent the oxidation of the metal ion in groundwater and the reproduction of iron bacteria in a well.

The present invention has the following aspects.
[1] A method for preventing an increase in the amount of dissolved oxygen in groundwater flowing out from a well, wherein a contact inhibitor that prevents contact between the groundwater and the atmosphere is supplied to the surface of the groundwater when the well is not sealed. To prevent the increase of dissolved oxygen in groundwater.
[2] Increasing the dissolved oxygen content of groundwater according to [1], wherein the well is covered with a lid with air holes and a contact inhibitor that prevents contact between the groundwater and the atmosphere is supplied to the surface of the groundwater. Prevention method.
[3] The method for preventing an increase in dissolved oxygen content of groundwater according to [1] or [2], wherein the contact inhibitor is an inert gas or oil.
[4] The method for preventing an increase in the amount of dissolved oxygen in groundwater according to any one of [1] to [3], wherein a gas-impermeable protective tube is inserted into the well.
[5] The method for preventing an increase in dissolved oxygen content of groundwater according to [4], wherein the contact inhibitor is supplied to the surface of the groundwater by supplying an inert gas to the groundwater.

  According to the method for preventing an increase in the dissolved oxygen content of groundwater of the present invention, oxidation of metal ions and propagation of iron bacteria in groundwater can be prevented in a well.

It is the schematic which shows one Embodiment of the increase prevention system for implementing the increase prevention method of the dissolved oxygen amount of groundwater of this invention. It is the schematic which shows other embodiment of the increase prevention system for enforcing the increase prevention method of the dissolved oxygen amount of groundwater of this invention. It is the schematic which shows other embodiment of the increase prevention system for enforcing the increase prevention method of the dissolved oxygen amount of groundwater of this invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.
In the following drawings, the scale of each member is appropriately changed to make each member a recognizable size.
2 and 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

<Increase prevention system>
FIG. 1 is a schematic view showing an embodiment of an increase prevention system for carrying out the method for preventing an increase in dissolved oxygen content of groundwater according to the present invention.
In this example, the increase prevention system (prevention system for increasing the dissolved oxygen amount of groundwater) 10 prevents contact with the well 11, the pump 12 and the pumping pipe 13 for pumping up the groundwater W springing into the well 11, and the surface S of the groundwater W. The supply means 14 which supplies the agent 18, and the addition means 15 which adds a pH adjuster to the groundwater W are provided.

The well 11 has a gas-impermeable protective tube 16 inserted into a drill hole H drilled downward from the ground G to the aquifer X.
The protective tube 16 is a bottomed tubular tube for protecting the excavation hole H from landslides.
In the vicinity of the bottom of the protective tube 16, a water intake 16 a is formed at the position of the aquifer X when the protective tube 16 is inserted into the excavation hole H to take the groundwater of the aquifer X into the protective tube 16. A wire mesh 17 for preventing sand and the like from entering the protective tube 16 is attached to the intake port 16a.
In the present invention, “gas impermeable” means that gas is not allowed to permeate from the protective tube 16 to the soil such as the aquifer X.

  It does not restrict | limit especially as the pump 12 and the pumping-up piping 13, The well-known pump and pumping-up piping used for a well can be used.

The supply means 14 supplies the contact inhibitor 18 that prevents the contact between the groundwater W and the atmosphere A to the water surface S of the groundwater W.
The supply means 14 has a supply pipe 14 a that is connected at its end to a tank (not shown) that stores the contact inhibitor 18.
The supply pipe 14a is installed such that its tip 14b is located above and in the vicinity of the water surface S of the groundwater W.

Examples of the contact inhibitor 18 include inert gases such as nitrogen and argon; oils such as edible oils, and the like. An inert gas is preferable in that it is excellent in the effect of preventing the contact between the groundwater W and the atmosphere A. Further, when oil is used as the contact preventing agent 18, the oil is also pumped up when the groundwater W is pumped up. Therefore, before the pumped-up groundwater W is used for various types of water, a process for removing oil is required. Therefore, an inert gas is preferable also in the point that the process after pumping up the ground water W is unnecessary.
In addition, although inert gas other than nitrogen and argon can be used, carbon dioxide dissolves in the ground water W and causes oxidation of metal ions. Therefore, when using an inert gas as a contact inhibitor, an inert gas other than carbon dioxide is used. Among these, nitrogen and argon are suitable as the contact inhibitor 18 because they are inexpensive and easy to handle. Moreover, these inert gases may be used individually by 1 type, and may use 2 or more types together.

The adding means 15 adds a pH adjuster to the groundwater W.
The addition means 15 has an addition pipe 15a whose end is connected to a tank (not shown) for storing a pH adjusting agent.
The addition pipe 15a is installed such that its tip 15b is immersed in the groundwater W.

  The pH adjuster is not particularly limited as long as it adjusts the pH of the groundwater W to be acidic, and examples thereof include sulfuric acid and hydrochloric acid.

<Method for preventing increase in dissolved oxygen in groundwater>
In the method for preventing an increase in the dissolved oxygen amount of groundwater according to the first aspect of the present invention using such an increase prevention system 10, the groundwater springs out of the aquifer X and enters the protection pipe 16 from the intake 16 a of the protection pipe 16. The contact preventing agent 18 is supplied from the supply means 14 to the water surface S of the groundwater W taken in. By supplying the contact preventing agent 18, the atmosphere A in the vicinity of the water surface S of the ground water W is driven away, and a layer made of the contact preventing agent 18 is formed on the water surface S, and contact between the ground water W and the air A is prevented.
When oil is used as the contact inhibitor 18, the amount of oil supplied is preferably such that the layer made of the contact inhibitor 18 has a thickness of 5 to 300 mm.

On the other hand, when an inert gas is used as the contact inhibitor 18, it is preferable to supply the inert gas until at least the atmosphere in the vicinity of the water surface S of the groundwater W is replaced with the inert gas.
Further, for example, as shown in FIG. 2, an inert gas may be supplied by providing a lid 19 in which air holes (not shown) are formed in the well 11. If the well 19 is covered with a lid 19, it is possible to suppress the entry of dust such as dead leaves into the well 11.
Although nitrogen is lighter than air, if nitrogen is continuously supplied to the water surface S of the groundwater W, nitrogen tends to stay in the vicinity of the water surface S of the groundwater W, and contact between the groundwater W and the atmosphere A is prevented.

In the method for preventing an increase in the dissolved oxygen content of the groundwater, it is preferable to add a pH adjuster to the groundwater W from the adding means 15. By adding a pH adjuster to the groundwater W, oxidation of metal ions such as iron and manganese in the groundwater W is less likely to occur. Further, it is possible to sterilize iron bacteria in the groundwater W or prevent propagation.
From the viewpoint of preventing oxidation of metal ions and preventing sterilization / reproduction of iron bacteria, the lower the pH of the groundwater W, the better. However, if the pH of the groundwater W is too low, for example, in order to use the groundwater as drinking water, a process for returning the pH of the groundwater is necessary, which takes time. Therefore, the addition amount of the pH adjuster is preferably such that the pH of the groundwater W is about 5-6. If the pH of groundwater W is 5-6, the process which returns the pH of the groundwater W pumped up becomes unnecessary, or even if it is a case where it is a process, it will not take much time and effort.
The timing of adding the pH adjusting agent into the groundwater W may be simultaneous with the supply of the contact preventive agent 18 or before or after the supply of the contact preventive agent 18, but simultaneously with the supply of the contact preventive agent 18 or the contact prevention. Prior to the supply of agent 18 is preferred.

<Effect>
According to the above-described method for preventing an increase in the dissolved oxygen amount of groundwater according to the first aspect of the present invention, since the contact inhibitor that prevents the contact between the groundwater and the atmosphere is supplied to the surface of the groundwater, It is possible to suppress the dissolution of oxygen and to prevent an increase in the dissolved oxygen amount of groundwater. Therefore, according to the present invention, it is possible to prevent oxidation of metal ions and propagation of iron bacteria in groundwater, and as a result, it is possible to suppress clogging of pumping pipes and pumps used for pumping up groundwater.
The groundwater pumping may be performed while the method for preventing the increase in dissolved oxygen content of the groundwater of the present invention is performed, or may be performed after the method for preventing the increase of dissolved oxygen content of the groundwater of the present invention is performed.

By the way, a biosparging method is known as a method for purifying contaminated soil and groundwater. In the bio sparging method, the gas sent from the sparging well permeates through the screen provided near the lower end of the sparging well and diffuses into the contaminated soil and groundwater. Is removed from the liquid phase to the gas phase, and the VOC gas transferred to the gas phase is sucked and removed by a blower or the like. In addition, the screen of a sparging well is a thing which permeate | transmits gas, and is different from the water intake for taking in groundwater.
The gas used in the biosparging method is selected according to the type of microorganisms that inhabit the soil. For example, if the microorganism is aerobic, a gas containing oxygen such as air is used, and if the microorganism is anaerobic, an inert gas such as carbon dioxide is used.
In the biosparging method, a nutrient for activating microorganisms may be supplied to contaminated soil or groundwater.

However, when air or carbon dioxide is supplied to groundwater, they dissolve into groundwater and oxidize metal ions in groundwater. When nutrients are supplied to groundwater, iron bacteria propagate and metal ion oxidation proceeds.
Therefore, in this invention, a contact inhibitor is supplied to the water surface of groundwater, without supplying a nutrient to groundwater. In addition, when an inert gas is used as the contact inhibitor, an inert gas other than carbon dioxide is used.
In addition, the groundwater used as the object of this invention is used for various uses, such as domestic water, industrial water, and agricultural water, after being pumped up. Therefore, the place where the well is installed is preferably a place where soil and groundwater are not contaminated. Here, “soil and groundwater are not polluted” means a degree that does not require purification by the biosparging method.

<Other embodiments>
The method for preventing an increase in the dissolved oxygen amount of groundwater of the present invention is not limited to the method described above. For example, in the increase prevention system 10 shown in FIG. 1, the supply pipe 14a is installed so that the tip 14b of the supply pipe 14a is located above and in the vicinity of the water surface S of the groundwater W, but the contact inhibitor 18 is inactive. In the case of gas, the tip 14b of the supply pipe 14a may be immersed in the groundwater W as shown in FIG.

  In the method for preventing an increase in the dissolved oxygen amount of groundwater according to the second aspect of the present invention using the increase prevention system 10 shown in FIG. 3, the protection pipe 16 is discharged from the aquifer X and is taken from the intake 16 a of the protection pipe 16. The contact preventing agent 18 is supplied from the supply means 14 into the groundwater W taken in (stripping). The contact inhibitor 18 used at this time is an inert gas. By supplying the inert gas into the groundwater W, oxygen dissolved in the groundwater W is degassed, and a layer made of inert gas is formed on the water surface S of the groundwater W. Contact with is prevented.

According to the method for preventing an increase in the dissolved oxygen content of groundwater according to the second aspect of the present invention, it is possible to suppress the dissolution of oxygen in the groundwater in the well and to prevent an increase in the dissolved oxygen content of the groundwater. In addition, since the oxygen already dissolved in the groundwater can be degassed, the amount of dissolved oxygen in the groundwater can be further reduced. In addition, when the groundwater in the well dissolves a gas other than oxygen (for example, ammonia gas or VOC), if an inert gas is supplied to the groundwater, a gas other than oxygen is degassed in addition to oxygen. So it can be removed from groundwater.
In the method for preventing an increase in the dissolved oxygen content of groundwater according to the second aspect of the present invention, since a gas-impermeable protective tube is inserted into the well, the inert gas permeates the protective tube and becomes an aquifer. Difficult to diffuse into.

  Moreover, in the increase prevention system 10 shown in FIGS. 1-3, although the front-end | tip 15b of the addition piping 15a is immersed in the groundwater W, when the contact inhibitor 18 is an inert gas, the front-end | tip 15b of the addition piping 15a is groundwater. You may install the addition piping 15a so that it may be located above the water surface S of W.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

"Example 1"
Drilling downward from the ground to a diameter of about 150 mm and a depth of 30 m, a bottomed cylindrical shape is inserted into the obtained drilling hole, a gas-impermeable protective tube is inserted, and a well 11 as shown in FIG. installed. For the installation of the well, we chose a place where the soil and groundwater were not contaminated. As the protective pipe 16, a water intake 16a is formed at the position of the aquifer X when inserted into the excavation hole H, and a metal mesh 17 is attached to the water intake 16a.
As shown in FIG. 1, the pump 12 and the pumping pipe 13 are arranged in the protective pipe 16, and the groundwater W can be pumped up. Moreover, the supply means 14 was installed so that the front-end | tip 14b of the supply piping 14a might be located above the water surface S of the groundwater W, and its vicinity.
3 L of edible oil is supplied as a contact inhibitor 18 from the supply means 14 to the surface S of the groundwater W that is springed out from the aquifer X and taken into the protection tube 16 from the intake port 16a of the protection tube 16. Groundwater W was pumped up in a state where a layer (thickness: 170 mm) made of edible oil was formed. The dissolved oxygen amount of the groundwater W pumped up using the dissolved oxygen meter was measured. The results are shown in Table 1.

"Example 2"
In the same manner as in Example 1, the well 11 was installed, the pump 12 and the pumping pipe 13 were arranged in the protective pipe 16, and the groundwater W could be pumped up. Moreover, the supply means 14 was installed so that the front-end | tip 14b of the supply piping 14a might be located above the water surface S of the groundwater W, and its vicinity.
The groundwater W is pumped up while supplying nitrogen as the contact inhibitor 18 from the supply means 14 to the water surface S of the groundwater W that has come out of the aquifer X and is taken into the protection tube 16 from the intake port 16a of the protection tube 16. It was. The supply amount of nitrogen was 5 L / min. The dissolved oxygen amount of the groundwater W pumped up using the dissolved oxygen meter was measured. The results are shown in Table 1.

"Example 3"
The well 11 was installed in the same manner as in Example 1.
As shown in FIG. 3, the pump 12 and the pumping pipe 13 are arranged in the protective pipe 16, and the groundwater W can be pumped up. Further, the supply means 14 was installed so that the tip 14 b of the supply pipe 14 a reached the vicinity of the bottom of the protective pipe 16.
The groundwater W was pumped up while supplying nitrogen as the contact inhibitor 18 from the supply means 14 into the groundwater W that came out of the aquifer X and was taken into the protection tube 16 from the intake port 16a of the protection tube 16. The supply amount of nitrogen was 5 L / min. The dissolved oxygen amount of the groundwater W pumped up using the dissolved oxygen meter was measured. The results are shown in Table 1.

"Comparative Example 1"
Groundwater was pumped in the same manner as in Example 1 except that edible oil was not supplied to the surface of the groundwater. The dissolved oxygen amount of the groundwater W pumped up using the dissolved oxygen meter was measured. The results are shown in Table 1.

  As is clear from the results in Table 1, the dissolved oxygen content of the groundwater pumped in each example was much lower than the dissolved oxygen content of the groundwater pumped in Comparative Example 1. Therefore, in each Example, compared with Comparative Example 1, it can be said that oxidation of metal ions in groundwater and reproduction of iron bacteria can be prevented.

DESCRIPTION OF SYMBOLS 10 Increase prevention system 11 Well 12 Pump 13 Pumping pipe 14 Supply means 14a Supply pipe 14b Tip 15 Addition means 15a Addition pipe 15b Tip 16 Protective pipe 16a Water intake 17 Wire mesh 18 Contact preventive agent 19 Lid A Atmosphere G Ground H Drilling hole X belt Water layer S Water surface W Groundwater

Claims (5)

A method for preventing an increase in the amount of dissolved oxygen in groundwater flowing out from a well,
A method for preventing an increase in the amount of dissolved oxygen in groundwater, wherein a contact inhibitor that prevents contact between the groundwater and the atmosphere is supplied to the surface of the groundwater in a state where the well is not sealed.   The method for preventing an increase in the amount of dissolved oxygen in groundwater according to claim 1, wherein the well is covered with an air hole and a contact inhibitor that prevents contact between the groundwater and the atmosphere is supplied to the surface of the groundwater.   The method for preventing an increase in dissolved oxygen content of groundwater according to claim 1 or 2, wherein the contact inhibitor is an inert gas or oil.   The method for preventing an increase in dissolved oxygen content of groundwater according to any one of claims 1 to 3, wherein a gas-impermeable protective tube is inserted into the well.   The method for preventing an increase in the amount of dissolved oxygen in groundwater according to claim 4, wherein the contact inhibitor is supplied to the surface of the groundwater by supplying an inert gas to the groundwater.

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