KR102065304B1 - Treatment Method of The Wastewater Containing Silica With Improved Treatment Efficiency - Google Patents

Abstract

The present invention relates to a method for treating silica-containing wastewater with improved treatment efficiency, which comprises the steps of: firstly precipitating and removing silica by introducing silica-containing wastewater into a first gravity precipitation bath; precipitating and removing residual silica contained in treated water by transferring the treated water to a second gravity precipitation bath installed at a rear end of the first gravity precipitation bath; performing solid liquid separation and nitrification of the treated water by introducing the treated water to a membrane separation aerobic bath installed at a rear end of the second gravity precipitation bath for aeration treatment; reducing dissolved oxygen contained in the treated water by introducing the treated water into a degassing bath installed at a rear end of the membrane separation aerobic bath; performing nitrification and denitrification by conveying the treated water to a reactor from the degassing bath; performing nitrification and removal of phosphorus while oxidizing and removing organic matters which may remain in the treated water by introducing the treated water passing through the reactor into the membrane separation aerobic bath; and introducing the treated water passing through the membrane separation aerobic bath into the degassing bath to reduce the dissolved oxygen, conveying a part of the treated water to the reactor again via a conveying line, and discharging the remainder thereof. According to the present invention, silica generated in a semiconductor, especially wafer process, can be effectively treated, and organic matters contained in wastewater and nitrogen and phosphorus, which are nutritive salts, can be simultaneously treated.

Description

Treatment Method of The Wastewater Containing Silica With Improved Treatment Efficiency

The present invention relates to a method for treating silica-containing wastewater, and more particularly, to effectively treat wastewater containing silica generated in semiconductor processes, particularly wafer processes, as well as organic substances and nutrients contained in various sewage. The present invention relates to a method for treating silica-containing wastewater capable of treating phosphorus nitrogen and phosphorus simultaneously.

Various methods and facilities are being researched and operated in the field for the treatment of wastewater from industrial facilities. Patent No. 0385706 may be referred to the prior art for the treatment of wastewater and sewage generated in the semiconductor manufacturing process.

Patent No. 0385706 discloses a method and system for removing silica from a large amount of wastewater. According to this method, the wastewater stream containing silica is treated with a flocculant such as epichlorohydrin / dimethylamine polymer to produce clustered agglomerated spherical particles having a diameter of 5 microns or more. The treated wastewater then passes through a microfiltration membrane that physically separates the silica contaminant particles from the wastewater. A commercially available microfiltration membrane having a pore size of 0.5 microns to 5 microns can be used for this. The flow rate of the treated wastewater passing through the microfiltration membrane is from 150 gallons per square foot of membrane per day (GFD) to 600 GFD. To maintain this, the microfiltration membrane is periodically backwashed and the membrane is placed intermittently draining. By removing the solids from the surface of the membrane.

However, it is generally pointed out that the wastewater generated in the semiconductor manufacturing process has a high concentration of suspended solids (SS), and the differential pressure increases due to membrane contamination during the treatment. This phenomenon is due to the silica (SiO ₂ ) discharged from the semiconductor wafer (Wafer) process.

However, the existing silica-containing wastewater is difficult to take a lot of cost and time in actual operation, such as the need to clean or replace by using a method such as back washing from time to time due to problems such as membrane fouling. In addition, wastewater generated at various industrial sites in the industrial complex includes not only wastewater containing silica, but also substances polluting the water environment by causing eutrophication, such as nitrogen and phosphorus, from organic wastes from various wastewaters. The facility alone cannot solve this problem and requires a separate treatment facility. This also requires additional cost and time.

Therefore, it is possible to effectively treat wastewater containing silica generated in semiconductor process, especially wafer process, as well as to develop technology that can simultaneously process nitrogen and phosphorus which are organic substances and nutrients contained in various sewage mixed with the wastewater. This is urgently needed.

[Prior art document]

[Patent Documents]

Korean Patent Publication No. 10-0385706 (2003.05.16)

Therefore, the present invention has been devised to solve the above problems, and effectively treats wastewater containing silica generated in semiconductor processes, especially wafer processes, as well as organic substances and nutrients contained in various sewage. It is an object to provide a method for treating silica-containing wastewater capable of treating phosphorus nitrogen and phosphorus simultaneously.

The technical problem of the present invention as described above is achieved by the following means.

(1) first precipitation of silica by introducing silica-containing wastewater into the first gravity settling tank;

Sending treated water to a second gravity sedimentation tank installed at a rear end of the first gravity sedimentation tank to precipitate out residual silica contained in the treated water;

Injecting treated water into a membrane separation aerobic tank installed at a rear end of the second gravity settling tank to give up aeration to perform solid solution separation and nitrification of the treated water;

Reducing the dissolved oxygen contained in the treated water by introducing the treated water into the degassing tank installed at the rear end of the aerobic tank;

Carrying out nitrification and denitrification by returning the treated water to the reaction tank in the degassing tank;

Flowing the treated water through the reaction tank back into the membrane separation aerobic tank to perform nitrification and phosphorus removal while oxidizing and removing organic substances remaining in the treated water; And

Treating the treated water passed through the membrane separation aeration tank to the degassing tank to reduce the dissolved oxygen, a part of the treated water is returned to the reaction vessel via a return line, the rest of the discharge treatment; comprising a method for treating wastewater containing silica .

(2) In the above (1),

A method for treating wastewater containing silica, characterized by receiving the returned treated water that has undergone a degassing tank in a reaction tank, and then treating it in the order of anaerobic, aerobic, and anaerobic using an intermittent aeration method.

(3) In the above (1),

The first gravity sedimentation tank, the second gravity sedimentation tank, the membrane separation aeration tank, the degassing tank, and the reaction tank are arranged in pairs left and right so as to be symmetrical, and a distribution tank is installed at the foremost end where the wastewater flows in, and a pair of left and right sides of the raw water introduced from the outside And further distributing to the first gravity settling tank.

(4) As described in (3),

One of the pair of reactors sets the time to receive the treated water in the anaerobic state from the degassing tank, and the other is to alternate the process cycle of the reactor by performing the alternate reaction of anaerobic, aerobic, and anaerobic. A method for treating silica-containing wastewater, characterized in that.

(5) As described in (3),

Placing a scum reservoir tank at the rear end of the degassing tank, the step of removing the scum before discharge of the final treatment water, characterized in that the method of treating the silica-containing waste water.

(6) In the above (1),

The reactor consists of a first reaction chamber and a second reaction chamber, the anaerobic and aerobic processes are sequentially performed in the first reaction chamber, and subsequently the anaerobic process in the second reaction chamber, characterized in that the treatment method for wastewater containing silica .

(7) As for (6),

A method for treating wastewater containing silica, further comprising: providing a connection pipe between the first reaction chamber and the second reaction chamber, and supplying heat to the treated water through a heat supply means to the connection pipe.

(8) As described in (6),

And a vacuum pump connected to the outside along with a closed structure for vacuum decompression on the second reaction chamber to remove dissolved oxygen using reduced pressure.

(9) As for (8),

The heat supply means is installed in the connection pipe of the degassing tank and the membrane separation exhalation tank to supply heat to the treated water, and a vacuum pump is connected to the outside of the degassing tank together with a hermetic structure for vacuum decompression. Method of treating the waste water containing silica, characterized in that it further comprises the step of removing.

(10) As for (9),

A method of treating wastewater containing silica, characterized in that a baffle with hemispherical protrusions is mounted on the surface of the first gravity settling tank and the second gravity settling tank to prevent flocculation of the suspended solids in the treated water.

As described above, the apparatus according to the present invention is a very useful and effective invention that can effectively process silica generated in semiconductor, especially wafer processing, and simultaneously process nitrogen and phosphorus, which are organic substances and nutrients contained in sewage. .

1 is a view showing the treatment process of the waste water containing the embodiment according to the present invention.
2 is a view showing an apparatus for treating waste car containing wastewater according to the present invention,
Figure 3 is a view showing the configuration of the gravity sedimentation tank according to the present invention.
4 is a view showing a preferred embodiment of the reactor according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention.

Throughout the specification, when a part is said to "comprising" (or including) a component, this means that it may further include other components, except to exclude other components unless specifically stated otherwise. do. In addition, the term "... part" described in the specification means a unit for processing at least one function or operation. Also, "a or an", "one", "the", and the like are used differently in the context of describing the present invention (particularly in the context of the following claims). Unless otherwise indicated or clearly contradicted by context, it may be used in the sense including both the singular and the plural.

In describing the embodiments of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the embodiments of the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a view showing a treatment process of silica-containing wastewater according to the present invention, Figure 2 is a view showing a treatment apparatus of silica-containing wastewater according to the present invention, Figure 3 is a configuration of the gravity sedimentation tank according to the present invention 4 is a view showing a preferred embodiment of the reactor according to the present invention.

As shown in the figure, the method for treating silica-containing wastewater according to the present invention comprises the steps of introducing the silica-containing wastewater into the first gravity settling tank to remove the first precipitate of silica (S101); Sending the treated water to a second gravity settling tank installed at the rear end of the first gravity settling tank to precipitate out residual silica contained in the treated water (S102); Performing a solid-liquid separation and nitrification of the treated water by introducing the treated water into a membrane separation aerobic tank installed at the rear end of the second gravity settling tank (S103); Injecting the treated water into the degassing tank installed in the rear end of the aerobic tank, to reduce the dissolved oxygen contained in the treated water (S104); Performing nitrification and denitrification by returning the treated water from the degassing tank to a reaction tank (S105); Flowing the treated water through the reaction tank back into the membrane separation aeration tank to perform nitrification and phosphorus removal while oxidizing and removing organic substances remaining in the treated water (S106); And reducing the dissolved oxygen by introducing the treated water that has undergone the membrane separation aeration tank into the degassing tank, and a part of the treated water is returned to the reaction tank via a conveying line, and the rest is discharged (S107).

Hereinafter, the content of the present invention will be described in detail using the apparatus configuration of FIG.

In order to implement the method of the present invention, the treatment apparatus 100 according to the embodiment shown in FIG. 2 may be used, and the treatment apparatus of the silica-containing wastewater according to this may be introduced into the silica-containing wastewater to remove the first precipitate of silica. A first gravity settling tank 10; A second gravity sedimentation tank 20 installed at a rear end of the first gravity sedimentation tank for sedimenting and removing residual silica contained in the treated water; A membrane separation aerobic tank (30) installed at the rear end of the second gravity settling tank and carrying out the treated water introduced to perform solid-liquid separation and nitrification of the treated water; A degassing tank 40 installed at the rear end of the aeration tank to reduce dissolved oxygen contained in the introduced treated water; And a reaction tank 50 which receives the treated water returned from the degassing tank and performs nitrification and denitrification contained in the treated water.

Preferably, the apparatus 100 for treating silica-containing wastewater according to the present invention is installed in parallel in pairs. To this end, a distribution tank 60 is installed at the foremost end where the wastewater flows in. The distribution tank 60 receives raw water (or treated water that has been pretreated) introduced from the outside and distributes the same to the left and right pairs of first gravity settling tanks 10. In the front end of the distribution tank 60, a pressure floatation tank (not shown) may be installed for pretreatment to remove various floating matters, including fats and oils contained in raw water.

At this time, the distribution can be made in consideration of the processing capacity of each device and the operating state of the equipment, which is preferably to be controlled automatically through a controller (not shown). For example, the distribution tank 60 controls so as to introduce the raw water to the other side when one of the facilities, such as replacement or repair occurs.

A baffle 11 is formed inside the first gravity settling tank 10 to induce particles including silica to settle by gravity by the baffle. At this time, the silica removed is about 30 to 60%.

Preferably, the surface of the baffle is formed with a hemispherical protrusion (not shown) at a predetermined interval. The hemispherical protrusion prevents flocculation in the wastewater from agglomeration on the surface and prevents the cake from being formed, thereby preventing the silica from adsorbing to the cake and consequently increasing the recovery or removal efficiency of the silica.

The treated water having passed through the first gravity settling tank 10 is introduced into the second gravity settling tank 20. The second gravity sedimentation tank 20 has a baffle 21 mounted thereon at right angles to the traveling direction of the treated water. Therefore, most of the remaining silica particles contained in the moving treatment water may be blocked by the baffle 21 to be precipitated and removed by gravity.

The treated water having passed through the second gravity settling tank 20 is in a state in which silica particles are almost removed. Therefore, according to the present invention, it is possible to prevent the contamination of the separation membrane provided in the membrane separation aeration tank 30 provided at the rear end.

The membrane separation aeration tank 30 performs solid-liquid separation and nitrification of the treated water, and together with the intake of phosphorus. Separation membrane 31 immersed therein is preferably a hollow fiber precision filtration membrane, and can be cleaned using only aeration air without the need for backwashing of water, air, chemicals, it is possible to operate the membrane for more than six months .

In addition, in the present invention, since the hollow fiber microfiltration membrane of the suction filtration method is used in place of the conventional sedimentation tank, filtration tank and disinfection tank as described above, the operation of the process is performed at an MLSS concentration of about 7,000 to 13,000 mg / L. It is possible to eliminate the need for additional chemicals to remove phosphorus, and stable nitrification is possible even in winter.

The degassing tank 40 reduces the dissolved oxygen contained in the treated water passing through the membrane separation aeration tank 30 at the front end. The degassing tank 40 may be simply carried out through stirring without additional compressed air. Since the treated water from the membrane separation aeration tank 30 includes a large amount of dissolved oxygen, the degassing tank 40 consumes such dissolved oxygen to oxidize and remove organic substances present in the treated water, thereby dissolving dissolved oxygen in the treated water. Is reduced.

As described above, an anaerobic atmosphere is performed in the reaction tank 50 at the rear stage through the reduction of the dissolved oxygen by the degassing tank 40. Preferably, the dissolved oxygen in the treated water that has passed through the degassing tank 40 is 0.2 mg / L or less.

The treated water from the degassing tank 40 is returned to the reaction tank 50.

The reaction tank 50 receives the treated water returned through the degassing tank 40, and is preferably operated in the order of anaerobic, aerobic, and anaerobic processes using an intermittent aeration method. Therefore, the treated water that has passed through the degassing tank 40 is first operated in an anaerobic process, during which denitrification of the treated water and release of phosphorus are induced. Subsequently, the treated water leads to an aerobic process through which nitrification of residual nitrogen is carried out. Then, the nitric acid nitrate produced through the nitrification process is subjected to the denitrification and phosphorus removal process in the anaerobic atmosphere again by a subsequent anaerobic process. The series of processes can be performed by a simple method of intermittently aeration in one reaction chamber.

In a preferred embodiment of the present invention, the reactor 50 is preferably the first reaction chamber 51 for the anaerobic, aerobic process and the second for the last anaerobic process in order to efficiently form the anaerobic atmosphere of the last stage The reaction chamber 52 can be separated and installed. In this case, preferably, a connecting pipe 53 is provided between the first reaction chamber 51 and the second reaction chamber 52, and a heat supply unit 54 may be additionally installed in the connecting pipe. The heat supply means may be a heat exchanger that receives heat through a heat exchange method from a high temperature fluid supplied from a thermal jacket or a boiler covering a part of the connection pipe. In addition, a vacuum pump (not shown) may be connected to the outside of the second reaction chamber 52 along with a hermetic structure for reducing the vacuum.

According to this configuration, since the anaerobic and aerobic reactions must occur continuously in the first reaction chamber 51, an aerobic means is required in the lower portion of the first reaction chamber, and after the anaerobic reaction, the aerobic reaction proceeds through aeration treatment. You can. The treated water undergoing the aerobic reaction contains dissolved oxygen, which is heated by heat supply means prior to entering the second reaction chamber 52 (preferably, the temperature of the treated water is raised to reach 30 to 40 ° C). ), The heated treated water flows into the second reaction chamber 52 to reduce the oxygen solubility according to the temperature rise, and the oxygen solubility is further reduced when the vacuum pump is operated to maintain a reduced pressure at the top. Most dissolved oxygen can be removed in a short time. By this process, the second reaction chamber 52 may be formed in an anaerobic atmosphere in a short time.

As described above, the operation of the configuration such as the heat supply means 54 or the vacuum pump may be controlled by a controller (not shown).

Through this series of reactions, most of the nitrogen and phosphorus compounds present in the treated water can be removed. The treatment process through the reactor 50 may be normally operated for 60 minutes.

In the present invention, the reactor 50 is preferably maintained in the anaerobic atmosphere for a time (approximately set to 60 minutes) flow of the treated water from the degassing tank 40 before starting a series of reactions of anaerobic, aerobic, anaerobic process .

As a preferred embodiment of the present invention, one of the pair of reaction tank 50 is set to the time to receive the treated water in the anaerobic state from the degassing tank 40, the other is the anaerobic, aerobic, anaerobic process A series of reactions is carried out so that the process cycle of the reactor can be carried out alternately.

In the present invention, because it uses the intermittent aeration method as described above, there is a self-sludge conveying effect it is possible to reduce the maintenance cost.

As described above, the treated water having passed through the reaction tank 50 is introduced into the membrane separation aeration tank 30 again, while oxidizing and removing organic substances remaining in the treated water, complete nitrification and phosphorus removal is performed. The treated water passing through the membrane separation aeration tank (30) is introduced into the degassing tank (40) to reduce dissolved oxygen, and a part of the treated water is returned to the reaction tank (50) via a return line, and the rest is scum reservoir tank (70). After the scum is removed, it is discharged.

Preferably, the connection pipe (not shown) of the degassing tank 40 and the membrane separation exhalation tank 30 is provided with heat supply means such as a heat jacket or a heat exchanger, and the vacuum decompression is provided on the upper part of the degassing tank 40. The vacuum pump 55 is connected to the outside with a sealed structure for. This can reduce the dissolved oxygen almost completely during the short residence time in the degassing tank, thereby improving the treatment efficiency.

Hereinafter, the content of the present invention will be described in more detail with reference to Examples. However, the following illustrated examples are only presented to aid the understanding of the present invention and should not be construed as limiting the scope of the present invention.

Example 1

As a result of experiments on wastewater generated in Asan Digital Industrial Complex, which is known to contain a large amount of silica using the apparatus of the present invention, the daily average TMS measurement values are shown in Table 1 below. However, the day of 2018.04.10. And the day of 2018.04.11. Were performed by the existing treatment method (MBR method), and the test was performed using the treatment apparatus according to the present invention shown in FIG. Was performed.

Measurement date COD T-N T-P pH SS Comparative example 2018.04.02 7.2 1.57 0.049 7.75 41.2 2018.04.11 8.3 1.42 0.049 7.82 27.7 Example 2018.04.12 9.7 1.27 0.049 7.93 5.4 2018.04.21 6.8 1.26 0.031 7.84 0.5

As described above, it can be seen that the conventional MBR method alone does not effectively remove the suspended solids (SS) including silica, while the improved method according to the present invention can confirm that the silica is completely removed.

10: first gravity settling tank
20: second gravity settling tank
30: membrane separation aerobic tank
40: degassing tank
50: reactor
60: distribution tank
70: scum reservoir

Claims (3)

Introducing a silica-containing wastewater into the first gravity settling tank to first remove and remove silica;
Sending treated water to a second gravity sedimentation tank installed at a rear end of the first gravity sedimentation tank to precipitate out residual silica contained in the treated water;
Injecting treated water into a membrane separation aerobic tank installed at the rear end of the second gravity settling tank to give up aeration to perform solid-liquid separation and nitrification of the treated water;
Reducing the dissolved oxygen contained in the treated water by introducing the treated water into the degassing tank installed at the rear end of the aerobic tank;
Carrying out nitrification and denitrification by returning the treated water to the reaction tank in the degassing tank;
Flowing the treated water through the reaction tank back into the membrane separation aerobic tank to perform nitrification and phosphorus removal while oxidizing and removing organic substances remaining in the treated water; And
Including the treated water passed through the membrane separation aeration tank to the degassing tank to reduce the dissolved oxygen, a portion of the treated water is returned to the reaction vessel through a return line, the rest of the discharge treatment;
The first gravity sedimentation tank, the second gravity sedimentation tank, the membrane separation aeration tank, the degassing tank, and the reaction tank are arranged in pairs left and right so as to be symmetrical, and a dispensing tank is installed at the foremost end where the wastewater flows in, and a pair of left and right sides of the raw water introduced from the outside To the first gravity settler,
One of the reactors is set to the time to receive the treated water in the anaerobic state from the degassing tank, the other is to perform the process cycle of the reactor by alternately performing the reaction of anaerobic, aerobic, anaerobic ,
The reactor consists of a first reaction chamber and a second reaction chamber, the anaerobic and aerobic processes are sequentially performed in the first reaction chamber, and subsequently the anaerobic process in the second reaction chamber, characterized in that the wastewater treatment method. . The method of claim 1,
And a connection pipe line between the first reaction chamber and the second reaction chamber, and supplying heat to the treated water through a heat supply means to the connection pipe line. The method of claim 2,
And a vacuum pump connected to the outside along with a closed structure for vacuum decompression on the second reaction chamber to remove dissolved oxygen by using a reduced pressure.

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