JP2002200485A - Water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method which is capable of reducing the load to be exerted on cleaning treatment equipment by removing iron (III) hydroxide in the groundwater without influencing to the original quality of water. SOLUTION: This method includes a process step of removing the iron (III) hydroxide from the groundwater containing the iron (III) hydroxide by passing the groundwater through a container and filtration equipment 2 having filter media to be packed into the container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a water treatment method for purifying groundwater.

[0002]

2. Description of the Related Art In so-called water treatment represented by sewage treatment and wastewater treatment in factories, solid products or corrosive organisms formed by the action of the environment such as iron rust or scale adhere to the surface of metal pipes and the like. However, the flow of water in the pipes may be affected, or the pipes themselves may be corroded and damaged, thereby affecting the water treatment flow. For this reason, in recent water treatment, the generation of scale is prevented in advance by mixing chemicals such as a scale deposition inhibitor into water to be treated at a corresponding portion of the water treatment flow, Alternatively, measures such as not using metal products for piping and the like are taken as much as possible to deal with scale-related problems.

[0003] In the purification of contaminated groundwater, whose demand has been increasing for several years, basically, the technology of wastewater treatment performed on the ground is diverted. Groundwater has a low concentration of dissolved components compared to sewage and industrial wastewater and has been clarified, and the purification treatment was not intended to generate scale or the like. Therefore, in the purification process of contaminated groundwater, there is no complicated chemical treatment process, etc., and the water treatment flow has a simple design. In many cases, the contaminated groundwater is directly brought into contact with an adsorbent such as activated carbon.

However, as the experience of purification of contaminated groundwater accumulates, iron (II) dissolved in groundwater
It has been found that iron (III) hydroxide produced due to I) adheres to the inside of piping and equipment for purification treatment and also to activated carbon. This iron hydroxide (II
I) is a kind of so-called scale and has adhesiveness.

[0005] For this reason, there arises a problem that iron (III) hydroxide also adheres to the activated carbon and clogs the activated carbon, thereby deteriorating the performance of the activated carbon, as well as imposing a load on the devices. I have. This problem was not anticipated in the early days of purification technology for contaminated groundwater. As a countermeasure, a treatment using a scale deposition inhibitor or the like in an appropriate place in the treatment flow, which is performed in sewage or wastewater treatment, can be considered. However, in the groundwater purification treatment, the purified groundwater may be returned to the ground again. In the purification treatment of contaminated groundwater, mixing of chemicals and the like in the middle of the treatment is not desired at present.

[0006]

Therefore, there is a need for a technique for removing iron (III) hydroxide without affecting the quality of groundwater in the treatment of contaminated groundwater.

[0007] The present invention has been made to solve the above problems, and removes iron (III) hydroxide from groundwater without affecting the original water quality to reduce the load on the purification treatment apparatus. It is an object of the present invention to provide a water treatment method that can be reduced.

Further, the present invention is intended to remove iron (III) hydroxide in groundwater and to extend the life of an adsorbent for removing volatile organic compounds without affecting the original water quality. It is an object to provide a possible water treatment method.

[0009]

In the water treatment method according to the present invention, groundwater containing a volatile organic compound and iron (III) hydroxide is passed through a filter medium to remove the iron (III) hydroxide from the groundwater. A step of removing the volatile organic compound from the groundwater by passing the groundwater through an adsorbent.

Another water treatment method according to the present invention is characterized in that ground water containing a volatile organic compound and iron (III) hydroxide is passed through a filtration device provided with a container and a filter medium filled in the container. The iron (III) hydroxide from groundwater
Removing the volatile organic compounds from the groundwater by passing the groundwater through an adsorbent, wherein the filter medium is filled in the container in multiple layers, the uppermost layer The filter medium has a granular shape, and the following relational expression is established between the particle size of the filter medium in the uppermost layer and the concentration of iron (III) in the groundwater.

(Fe (III)_Two/ Fe (III)₁) = ALn + b where Fe (III)₁The concentration of iron (III) before passing through the filter material
The Fe (III) _TwoIron (III) concentration after passing through the filter material
Ln is the particle size of the uppermost filter medium, and a is
Where b is a constant.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first water treatment method according to the present invention will be described.

In the first water treatment method, the groundwater containing iron (III) hydroxide is passed through a filtration device provided with a vessel and a filter medium filled in the vessel, so that the iron hydroxide ( III).

Iron (III) hydroxide contained in groundwater is
Iron (III) dissolved in groundwater is produced by air oxidation.

The filter medium in the filtration device will be described.

Examples of the filter medium include sand, glass beads, anthracite, garnet (garnet) and the like. Among them, sand is preferable because of its high ability to adsorb iron (III) hydroxide. The type of the filter medium may be one type, but may be two or more types.

Preferably, the shape of the filter medium is granular.

It is preferable to fill the container with the filter medium in multiple layers (two or more layers). As the number of layers of the filter medium increases, the removal rate of iron (III) hydroxide can be increased, but if the amount is too large, the frequency of mixing of the lower layer filter medium into the upper layer during the backwashing operation increases, Further, the cost of water treatment increases, which is not preferable.

When the filter medium is filled into the container in multiple layers, the particle size of the uppermost layer of the filter medium is preferably in the range of 0.5 to 0.7 mm. This is due to the following reasons. If the particle size is larger than 0.7 mm, the specific surface area of the filter medium may be insufficient, and the removal rate of iron (III) hydroxide may be reduced. On the other hand, when the particle size is less than 0.5 mm, the filter medium in the uppermost layer is likely to be clogged with iron (III) hydroxide, the number of backwash operations is increased, and the treatment efficiency may be reduced. Also, the optimum particle size of the uppermost filter medium tends to vary depending on the concentration of iron (III) in the groundwater and the amount of iron (III) hydroxide in the groundwater. That is, the smaller the particle size, the more iron (III) in groundwater can be adsorbed, and the more iron (III) hydroxide can be removed from groundwater. On the other hand, if the particle size is large, iron (II
Because of its weak ability to adsorb I), iron hydroxide (I
The removal efficiency of II) decreases. The optimum concentration of iron (III) in groundwater for using a filtration device in which the particle size of the uppermost filter medium is within the above range is 10 mg / L or less.

The particle size of the uppermost filter medium and the iron (II
It is preferable that the following relational expression holds between the concentration of I).

(Fe (III)_Two/ Fe (III)₁) = ALn + b where Fe (III)₁The concentration of iron (III) before passing through the filter material
The Fe (III) _TwoIron (III) concentration after passing through the filter material
Ln is the particle size of the uppermost filter medium, and a is
Where b is a constant.

The particle size and specific gravity of the filter medium layers other than the uppermost layer are set in consideration of the removal efficiency of iron (III) hydroxide and the prevention of the reversal of the upper and lower filter media during the backwashing operation. It is desirable to do.

In the filtering device, it is desirable to fill a support gravel layer at the bottom of the container and fill the filter material on the support gravel layer in order to prevent the filter medium from leaking out of the container.

According to the first water treatment method of the present invention described above, groundwater containing iron (III) hydroxide is passed through a filter provided with a container and a filter medium filled in the container. The iron hydroxide from the groundwater
By removing iron, it is possible to prevent iron (III) hydroxide from adhering to the piping and the inside of the device for the purification treatment, so that corrosion of the piping and the purification device can be suppressed. In addition, since it is not necessary to add chemicals such as scale deposition inhibitors to the groundwater, the quality of the groundwater does not change and the environment is adversely affected without any special operation after the removal of iron (III) hydroxide. Groundwater can be returned to the ground without impact.

Next, a second water treatment method according to the present invention will be described.

(First Step) The groundwater containing a volatile organic compound and iron (III) hydroxide is passed through a filtration device provided with a container and a filter medium filled in the container, whereby the iron hydroxide is removed from the groundwater. (III) is removed.

Iron (III) hydroxide contained in groundwater is
Iron (III) dissolved in groundwater is produced by air oxidation. Examples of the volatile organic compound include cis-1,2-dichloroethylene, trichloroethylene, and the like.

As the filtration device, the same one as described in the first water treatment method can be used.

(Second Step) The volatile organic compounds are removed from the groundwater by passing the groundwater through an adsorbent.

Activated carbon is preferred as the adsorbent.

According to the second water treatment method according to the present invention described above, the volatile organic compound and the iron hydroxide (II) are added to the filter provided with the container and the filter medium filled in the container.
The iron (III) hydroxide is removed from the groundwater by passing the groundwater containing I), and then the volatile organic compound is removed from the groundwater by passing the groundwater through an adsorbent. Since it is possible to prevent iron (III) hydroxide from adhering to the adsorbent, it is possible to maximize the treatment capacity of the adsorbent.
In addition, since the quality of groundwater is not deteriorated by the removal treatment of iron (III) hydroxide, the groundwater can be returned to the ground after the removal of volatile organic compounds, which is advantageous in terms of environmental conservation.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

First, a water treatment apparatus used in an embodiment of the present invention will be described with reference to FIGS.

The treated water in the sampling well 1 is filtered by a filtration device 2
After the filtration process, the activated carbon device 3 removes contaminants. The water that has undergone such purification treatment is collected in the collection well 4. Pumping from the collecting well 1 and water supply to each device and the collecting well 4 are performed by a pump 5 provided in a path between the collecting well 1 and the filtering device 2. In addition, in FIG. 1, 6 is a ground surface and 7 is a groundwater table.

As shown in FIG. 2, the filtration device 2
And a support gravel layer 9 filled in the lower part of the container 8;
A filter medium layer 10 laminated on the supporting gravel layer 9. In the present embodiment, the number of filter medium layers 10 is set to three.
A treated water supply path 11 is connected to a side surface of the container 8. In addition, the bottom of the container 8 has an outlet 1 for treated water.
2 are provided.

Example 1 In Example 1, sand having a particle size of 0.5 mm was used for the uppermost filter medium layer of the filtration device 2 and a filter medium having a particle size of 5 mm was used for the second (middle) filter medium layer. Sand was used, and sand having a particle size of 10 mm was used for the third (lower) filter medium layer.

The particle size of the sand constituting the filter medium was determined by the editor of the editing committee of the soil test practice book (second revised edition) and published in 1991 by the Japan Society of Geotechnical Engineers. Practicing Book (2nd revised edition) ”on page 25-36
It is measured by a method according to the Chapter Particle Size Test.

From the sampling well 1, groundwater having a concentration of 1.7 mg / L of iron (III) dissolved and a concentration of cis-1,2-dichloroethylene of 0.3 mg / L was pumped.
The water was supplied to the sand filtration device 2 through the treated water supply path 11. This groundwater was passed through the uppermost filter layer, the second filter layer, and the third filter layer in this order, and filtered. The concentration of iron (III) in groundwater after filtration is shown in Table 1 below.

Next, this groundwater was charged with an activated carbon filling amount of 1
After passing through a 000 kg activated carbon apparatus to remove volatile organic compounds, the groundwater thus purified was returned to the recovery well 4. Table 1 below shows the amount of groundwater treated until the activated carbon broke through a series of operations of collecting groundwater from the collection well, filtering sand, treating with activated carbon, and collecting the collected water into the recovery well.

As a result of this example, 33 kg of cis-1,2-dichloroethylene in groundwater recovered by activated carbon was obtained. On the other hand, when groundwater is passed through activated carbon as a comparison and then passed through the sand filtration device 2, cis-1,2-dichloroethylene in the groundwater recovered by activated carbon is 21 kg, and the groundwater is passed through the activated carbon before passing through the activated carbon. A larger amount could be recovered when passed through the filtration device 2.
This is because the sand filtration device 2 is used after passing groundwater through activated carbon.
, Iron (III) in groundwater causes iron (III) hydroxide to be generated, which causes clogging of activated carbon and reduces the ability of activated carbon to recover cis-1,2-dichloroethylene. It is considered that this was done.

Example 2 In Example 2, sand having a particle size of 0.6 mm was used for the uppermost filter medium layer of the filtration device 2 and a filter medium having a particle size of 5 mm was used for the second (middle) filter medium layer. Sand was used, and sand having a particle size of 10 mm was used for the third (lower) filter medium layer.

From the sampling well 1, ground water having a concentration of 1.4 mg / L of iron (III) dissolved and a concentration of cis-1,2-dichloroethylene of 0.1 mg / L was pumped up.
The water was supplied to the sand filtration device 2 through the treated water supply path 11. This groundwater was passed through the uppermost filter layer, the second filter layer, and the third filter layer in this order, and filtered. The concentration of iron (III) in groundwater after filtration is shown in Table 1 below.

Next, this groundwater was passed through an activated carbon device in which the amount of activated carbon was set to the same value as in Example 1 to remove volatile organic compounds.
The groundwater thus purified was returned to the recovery well 4. Table 1 below shows the amount of groundwater treated until the activated carbon broke through a series of operations of collecting groundwater from the collection well, filtering sand, treating with activated carbon, and collecting the collected water into the recovery well.

Example 3 In Example 3, sand having a particle size of 0.5 mm was used for the uppermost filter medium layer of the filtration device 2 and a filter medium having a particle size of 5 mm was used for the second (middle) filter medium layer. Sand was used, and sand having a particle size of 10 mm was used for the third (lower) filter medium layer.

From the sampling well 1, ground water with iron (III) dissolved at a concentration of 2.9 mg / L and a cis-1,2-dichloroethylene concentration of 0.1 mg / L was pumped.
The water was supplied to the sand filtration device 2 through the treated water supply path 11. This groundwater was passed through the uppermost filter layer, the second filter layer, and the third filter layer in this order, and filtered. The concentration of iron (III) in groundwater after filtration is shown in Table 1 below.

Next, this groundwater was passed through an activated carbon device in which the amount of activated carbon was set to the same value as in Example 1 to remove volatile organic compounds.
The groundwater thus purified was returned to the recovery well 4. Table 1 below shows the amount of groundwater treated until the activated carbon broke through a series of operations of collecting groundwater from the collection well, filtering sand, treating with activated carbon, and collecting the collected water into the recovery well.

Example 4 In Example 4, sand having a particle diameter of 0.7 mm was used for the uppermost filter medium layer of the filtration device 2 and a filter medium having a particle diameter of 5 mm was used for the second (middle) filter medium layer. Sand was used, and sand having a particle size of 10 mm was used for the third (lower) filter medium layer.

From the sampling well 1, iron (III) is dissolved at a concentration of 12 mg / L, and groundwater having a cis-1,2-dichloroethylene concentration of 0.5 mg / L is pumped up. It was supplied to the sand filtration device 2. This groundwater was passed through the uppermost filter layer, the second filter layer, and the third filter layer in this order, and filtered. The concentration of iron (III) in groundwater after filtration is shown in Table 1 below.

Example 5 In Example 5, sand having a particle size of 0.5 mm was used for the uppermost filter medium layer of the filtration device 2 and a filter medium having a particle size of 5 mm was used for the second (middle) filter medium layer. Sand was used, and sand having a particle size of 10 mm was used for the third (lower) filter medium layer.

From the sampling well 1, ground water with iron (III) dissolved at a concentration of 9.9 mg / L and a cis-1,2-dichloroethylene concentration of 0.4 mg / L was pumped.
The water was supplied to the sand filtration device 2 through the treated water supply path 11. This groundwater was passed through the uppermost filter layer, the second filter layer, and the third filter layer in this order, and filtered. The concentration of iron (III) in groundwater after filtration is shown in Table 1 below.

(Comparative Example) Dissolved iron (II
I) The groundwater whose concentration and cis-1,2-dichloroethylene concentration are the same as described in Example 1 described above is pumped up and passed through an activated carbon device in which the activated carbon filling amount is set to the same value as in Example 1. By doing so, volatile organic compounds were removed. Table 1 below shows the amount of groundwater treated by repeating such treatment with activated carbon until the activated carbon breaks through.

[0052]

[Table 1]

As is evident from Table 1, according to the methods of Examples 1 to 5 in which iron (III) hydroxide in groundwater is removed by filtration and then pollutants are removed by activated carbon, the life of activated carbon is compared. It turns out that it is longer than the example.

In Examples 1 to 3, the relational expression ｛(Fe (III) ₂ / Fe (III)) between the particle size of the filter medium in the uppermost layer and the concentration of iron (III) in the groundwater was used. ₁ ) = aLn
+ B｝ holds.

[0055]

According to the water treatment method of the present invention described in detail above, iron (III) hydroxide can be removed from groundwater without affecting the quality of the groundwater, and the purification apparatus and the adsorption apparatus can be used. It has a remarkable effect that the load of the agent can be reduced and groundwater can be returned to the ground without adversely affecting the environment. Therefore, it is a technology effective for environmental measures and has great industrial value.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a water treatment apparatus used in a water treatment method according to a first embodiment.

FIG. 2 is a schematic configuration diagram showing a filtration device incorporated in the water treatment device of FIG.

[Explanation of symbols]

 Reference Signs List 1 ... sampling well, 2 ... filtration device, 3 ... activated carbon device, 4 ... recovery well, 5 ... pumping and water supply pump 6 ... ground surface, 7 ... groundwater surface.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Kinoshita 8 Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa Prefecture Inside the Toshiba Yokohama Office (72) Inventor Ken Suzuki 8 Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa F-term in the Toshiba Yokohama office of formula company (reference) 4D017 AA01 BA04 CA03 CB01 DA01 EA01 4D024 AA01 AB04 BA02 BB01 CA01 DB03

Claims (2)

[Claims] 1. A volatile organic compound and iron (III) hydroxide
A step of removing the iron (III) hydroxide from the groundwater by passing groundwater containing the same through a filter medium; and a step of removing the volatile organic compound from the groundwater by passing the groundwater through an adsorbent. A water treatment method comprising: 2. A container and a filter medium filled in the container.
A volatile organic compound and iron hydroxide (II
By passing through the groundwater containing I)
Removing the iron (III) hydroxide from the groundwater by passing the groundwater through an adsorbent.
Removing the volatile organic compound from the above, wherein the container is filled with the filter medium in a multilayer, and the uppermost layer
The filter medium is granular, and the particle size of the filter
The following relational expression holds between the concentration of iron (III) in sewage
A water treatment method, comprising: (Fe (III)_Two/ Fe (III)₁) = ALn + b where Fe (III)₁The concentration of iron (III) before passing through the filter material
The Fe (III) _TwoIron (III) concentration after passing through the filter material
Ln is the particle size of the uppermost filter medium, and a is
Where b is a constant.