JP2000140842A - Waste water treating method using ceramic filter for waste water from silicon polishing and waste water treating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treating method capable of concentrating polishing water to a high concn. and capable of facilitating the maintenance administration of a system without increasing ionic silica. SOLUTION: In the waste water treating system 1, a storage tank 2, a filtering instrument 4, a circulating pump 3, a circulation piping are provided. In such a case, the filter in which a ceramic filter membrane is formed at the inner periphery surface of many parallel circulating passages formed at the longitudinal direction of the cylindrical porous body consisting of a ceramic is incorporated in the filtering instrument 4, and the polishing waste water is introduced to the circulating passage of the filter. In this way, the filtrate made to flow out to the filter outer periphery side by permeating the filter membrane and the fine pore of the porous body and the concentrated liq. passing the circulating passage as it is are recovered separately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a concentrated solution containing silicon particles from a silicon polishing wastewater containing silicon particles discharged when polishing and cutting a silicon ingot or a silicon wafer in a semiconductor manufacturing facility, and a filtration method. The present invention relates to a wastewater treatment method or a wastewater treatment system for individually collecting collected water.

[0002]

2. Description of the Related Art Semiconductors are obtained by slicing a cylindrical single ingot of silicon single crystal, polishing and polishing the silicon ingot to form a silicon wafer, subjecting the silicon wafer to a device, and further performing polishing such as back grinding and dicing. Manufactured.

Usually, silicon ingots and silicon wafers are cut and polished by a wet process using pure water to prevent heat generation or to prevent chipping of silicon. , "Polishing wastewater"). Since such a polishing wastewater has a simple composition in which pure water contains only silicon particles, it is conventionally filtered through a filtration membrane (hereinafter, referred to as a “polymer membrane”) made of an organic polymer such as a hollow fiber membrane. By doing so, a wastewater treatment method of individually collecting a concentrated liquid containing filtered silicon particles and pure water as recovered water has been adopted.

[0004]

However, the wastewater treatment method using a polymer membrane has caused the following problems. First, there is a problem that the SS concentration of the polishing wastewater (a value obtained by subtracting the ionic silica concentration from the total silicon concentration) cannot be concentrated to a high concentration exceeding 5000 ppm (0.5%).

That is, when high-concentration polishing wastewater having an SS concentration exceeding 5000 ppm is introduced into the flow path of the polymer film,
This is because there is a high possibility that breakage occurs due to a low membrane strength, or a problem that the flow path is closed due to a small flow path diameter of the hollow fiber of 1.1 to 1.3 mmφ occurs. . Therefore, in the treatment with the polymer membrane, the concentrated liquid to be separated becomes thin, the amount of the concentrated liquid that becomes industrial waste increases, and the water recovery rate is low.

Second, there is a problem in that maintenance of the system is complicated, for example, it is necessary to frequently change the membrane in a short cycle of about one year. That is, because the physical strength of the polymer film is low, the film may be broken or the film may be worn by silicon particles contained in the polishing wastewater.

In addition to these problems, in the conventional drainage treatment, the silicon in the drainage is dissolved in pure water due to the long residence time of the drainage in the system, and the removal by filtration is difficult. There was also a problem that unusable ionic silica increased.

[0008] Ionic silica may be a problem when pure water is recovered and reused. In such a case, an ion exchanger must be provided after the filter, and
If the concentration of ionic silica is too high, the load on the ion exchanger becomes large. Therefore, a processing method and a processing system capable of rapidly filtering silicon particles have been desired.

The present invention has been made in view of the problems of the prior art as described above, and an object of the present invention is to enable polishing wastewater to be concentrated to a high concentration and to remove ionic silica. Easy to maintain and manage the system without increasing
An object of the present invention is to provide a wastewater treatment method and a wastewater treatment system for silicon polishing wastewater.

[0010]

Means for Solving the Problems As a result of intensive studies by the present inventors, it has been found that the above-mentioned problems of the prior art can be solved by using a ceramic filter instead of a polymer membrane for filtering polishing wastewater. Thus, the present invention has been completed.

That is, according to the present invention, the inner peripheral surface of the flow passage in the cylindrical porous body made of ceramic, in which a single flow passage or a number of parallel flow passages are formed in the longitudinal direction, is provided. Prepare a filter on which a ceramic filtration membrane having a smaller pore diameter than the pores of the porous body is formed, introduce silicon polishing wastewater into the flow passage of the filter, and pass through the filtration membrane and the pores of the porous body. And recovering separately the filtrate that has flowed out to the outer periphery of the filter and the concentrated liquid that has passed through the flow passage as it is.

[0012] In the wastewater treatment method of the present invention, it is preferable to repeat the operation of introducing the collected concentrated liquid again into the flow passage and filtering it at least once or more, and to discharge the silicon polishing wastewater or the concentrated liquid into the flow passage of the filter. When introducing, the flow velocity in the flow passage is set to 0.1 to 5 m
/ Sec is preferable, and it is preferable to control the outflow of the filtrate from the start of filtration to the end of filtration so as to be constant.

Further, according to the present invention, a storage tank for storing silicon polishing wastewater containing silicon particles, a filter for removing silicon particles from the silicon polishing wastewater, and a liquid sending device for sending the silicon polishing wastewater A wastewater treatment system for silicon polishing wastewater, comprising: a pump, wherein a single flow passage or a plurality of parallel flow passages are formed in a longitudinal direction, wherein the flow passage is a cylindrical porous body made of ceramic. By incorporating a filter in which a ceramic filtration membrane having a smaller pore diameter than the pores of the porous body is formed on the inner peripheral surface of the porous body in the filter, and introducing silicon polishing wastewater into the flow passage of the filter, It is configured such that the filtrate that has passed through the filtration membrane and the pores of the porous body and has flowed out to the outer periphery of the filter and the concentrated solution that has passed through the flow passage as they are can be separately collected. A wastewater treatment system for silicon polishing wastewater is provided.

[0014] The wastewater treatment system of the present invention is preferably provided with a filter having a pore size of the filtration membrane of 10 nm to 0.2 µm, and the filtrate is caused to flow backward from the outer peripheral side of the filter toward the flow passage side. It is preferable to have a backwash mechanism for removing silicon particles fixed on the surface of the filtration membrane.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is not a polymer membrane,
A ceramic filter is used for filtering polishing wastewater. This makes it possible to concentrate the polishing wastewater to a high concentration, thereby facilitating the maintenance and management of the system. Hereinafter, the present invention will be described in detail.

The ceramic filter used in the present invention is obtained by forming a ceramic thin film on the surface of a porous support made of ceramic. Such a ceramic filter is superior in physical strength and durability as compared with a polymer film, and has extremely little film breakage and abrasion of the film due to silicon particles contained in polishing wastewater.

[0017] Accordingly, the silicon polishing wastewater has an SS concentration of 5
It is possible to construct a wastewater treatment system that can be concentrated to a high concentration of 0000 ppm and is easy to maintain. Specifically, the replacement frequency of the polymer membrane is about one year, while the replacement frequency of the ceramic filter is about two to five years.

[0018] Further, since the fineness of the fine pores which determines the filtering ability can be controlled in the ceramic filter as compared with the polymer membrane, the optimum fine pore diameter is set for the submicron order silicon particles to be filtered. It has the feature that it can be.

That is, since the polymer membrane has a broad pore diameter distribution, the silicon particles cannot be reliably filtered out unless a membrane having a pore diameter of 0.05 μm or less is used, while a ceramic having a sharp pore diameter distribution is used. If the filter is a filter having a pore diameter of 0.1 to 0.2 μm, the filtration can be sufficiently performed. Since the outflow speed of the filtrate decreases in proportion to the pore diameter of the filtration membrane, the system using a ceramic filter can perform wastewater treatment more quickly than the system using a polymer membrane. Becomes

In the present invention, in a cylindrical porous support made of ceramic and having a flow passage formed in the longitudinal direction (hereinafter, referred to as “support”), the support is provided on the inner peripheral surface of the flow passage. A ceramic filter (hereinafter, referred to as "filter") having a ceramic filtration membrane (hereinafter, referred to as "filtration membrane") having a smaller pore diameter than the pores is used.

[0021] The filter having such a shape can improve the filtration performance while securing the water permeation amount, as compared with the flat filter, and can perform the cross-flow filtration and the continuous filtration described later. This is because it becomes possible.

The porous body constituting the support has a pore diameter of 1
Although it is preferable to make the filtration liquid permeate easily by making it relatively large to 50 μm, the pore size of the filtration membrane which determines the filtration function of the filter is 10 nm to 0.2 μm. If it is less than 10 nm, the filtration resistance increases and the outflow speed of the filtrate decreases, and the drainage treatment speed decreases. On the other hand, if it exceeds 0.2 μm, the silicon particles are clogged in the pores of the filtration membrane, and the stable This is because it becomes difficult to maintain the outflow speed.

However, from the viewpoint of preventing clogging of the filtration membrane and reducing the frequency of performing backwashing, the pore diameter of the filtration membrane is preferably 10 nm to 0.1 μm. In general, a filter having pores of 0.1 μm or less is often defined by the molecular weight (fraction molecular weight) of a spherical protein that can be filtered, but the pore diameter of 10 nm of the present invention is equivalent to the fraction molecular weight of 50,000. I do.

Usually, both the support and the filtration membrane are made of ceramics such as alumina, titania, mullite, zirconia, silica, spinel, or a mixture thereof, but are made of a material having high corrosion resistance (eg, alumina). Is preferred.

The support is a cylindrical body (for example, a cylindrical body)
If it is a tubular shape having a single flow passage formed in the longitudinal direction, it does not matter whether it is a honeycomb shape having a number of parallel flow passages formed, but the filtration area per unit volume of the support is large. It is preferable that the filter has a honeycomb shape having a high filtration treatment capacity.

The hole shape of each flow passage of the honeycomb-shaped support is not particularly limited, and may be a circle, a square, a hexagon, or the like. However, the cake layer of silicon particles deposited on the surface of the filtration membrane is peeled off. A circular shape is preferred in terms of ease, and a square or hexagon is preferred in terms of a large filtration area per unit volume. The number and diameter of the holes are not particularly limited, but those having a hole diameter of about 2 to 5 mm are commonly used.

The filter having the above-mentioned shape can be used in any of a direct filtration system and a cross-flow filtration system, and the present invention employs a cross-flow filtration system.

In the direct filtration method, as shown in FIG. 2B, one end of a flow passage 32 is sealed with a sealing member 31 or the like, and the entire amount of polishing wastewater 35 introduced into the flow passage 32 is transmitted through the filtration membrane 33. This is because there is a problem that the flow rate of the filtrate 36 is remarkably reduced as the filtration proceeds.

That is, in the direct filtration method, as the filtration proceeds, the cake layer of the silicon particles filtered on the surface of the filtration membrane 33 increases, and the cake layer is filtered by the water pressure of the polishing wastewater introduced into the flow passage 32. This is because the pressure is applied to the surface of the membrane 33 so that the filtration membrane 33 is clogged.

On the other hand, the cross-flow filtration method is
As shown in FIG. 2 (a), polishing drainage 35 is introduced into the flow passage 32 of the filter, and the filtrate 36 which has passed through the pores of the filtration membrane 33 and the support 34 and has flowed out to the outer periphery of the filter. This is a filtration method in which the concentrated liquid 37 that has passed through the filter 32 as is is collected separately.

According to this method, the polishing wastewater is supplied to the filtration membrane 3.
Since the silicon particles are separated by filtration while flowing continuously in parallel with the three surfaces, the cake layer of the silicon particles deposited on the surface of the filtration membrane 33 by the shearing force when the polishing wastewater flows moves toward the concentrated solution 37 side. Is discharged. That is, the cake layer
Since the thickness is kept to a minimum and pressure is not applied to the surface of the filtration membrane 33, stable filtration can be performed for a long time.

The filtration method includes a batch processing method and a continuous processing method. In the present invention, it is preferable to employ a continuous processing method. This is because the continuous processing method can shorten the residence time of the waste liquid in the system as compared with the batch processing method, and thus can prevent an increase in ionic silica.

In the batch processing method, wastewater to be processed is sequentially processed in predetermined units (ie, batches), and when a certain batch of wastewater is being processed, another batch of wastewater is added to the system. Since it is a method that does not accept, batch switching operation is required. That is, unless the processing amount for each batch is increased, the operation becomes complicated and efficient processing cannot be performed, so that the retention time of the drainage in the system is prolonged.

On the other hand, in the continuous treatment method, the waste liquid to be treated is continuously received into the system at a fixed ratio, and the filtrate and the concentrated liquid corresponding to the waste liquid received in the system are continuously collected. It is a method of doing. In the continuous processing method, there is no batch switching operation, and the installation area of the system is smaller than that in the batch processing. Further, it is possible to shorten the residence time of the drainage in the system. Therefore,
The time during which silicon stays in the drainage water is also shortened, and it is possible to prevent silicon from dissolving in water and increasing ionic silica.

In the wastewater treatment method of the present invention, when the silicon polishing wastewater or its concentrated liquid is introduced into the flow passage of the filter, the flow velocity in the flow passage is set to 0.1 to 5 m /.
It is preferable to control within the range of seconds. If the flow rate is less than 0.1 m / sec, the effect of the cross-flow filtration is reduced and the thickness of the cake layer on the surface of the filtration membrane is increased. This is because the effect of the cross-flow filtration does not increase any more, and only the power consumption of the pump increases, which is not economical.

When the polishing wastewater is introduced at a high flow rate from the beginning of the filtration, the cake layer of silicon particles adheres to the surface of the filtration membrane to cause clogging even in the case of the cross-flow method, and the outflow velocity of the filtrate is remarkably high. May decrease. In order to avoid such a situation, in the wastewater treatment method of the present invention, when the silicon polishing wastewater or its concentrated liquid is introduced into the flow passage of the filter, the amount of the filtrate discharged from the start to the end of the filtration is constant. It is preferable to control so that

That is, by suppressing the amount of outflow at the beginning of the filtration, it is possible to prevent the cake layer from sticking to the surface of the filtration membrane at a stretch, and it is possible to suppress an increase in the filtration differential pressure. Specifically, there is a method in which a constant flow valve is provided on the filtrate outflow side of the filter to keep the outflow amount of the filtrate constant.

[0038] The wastewater treatment method of the present invention includes a filter having the above-described ceramic filter, a storage tank for storing silicon polishing wastewater, a circulation pump for circulating the silicon polishing wastewater or its filtrate, and a circulation pipe. This is achieved by a wastewater treatment system having: That is, once the polishing wastewater is received in the storage tank, the polishing wastewater is fed into the filter at a constant speed from the storage tank using a circulation pump, and the circulation system formed by the filter and the circulation pipe is continuously circulated. The polishing wastewater can be treated.

In the wastewater treatment system of the present invention,
The circulation pipe may be connected via a storage tank, but is preferably directly connected to the inlet side of the circulation pump without using the storage tank.
Such a structure has an advantage that the capacity of the storage tank can be reduced, and can be suitably used in a system arranged in a narrow place.

In the filter in the wastewater treatment system of the present invention, the above-described ceramic filter is installed in the housing, and the concentrated liquid collected from the flow passage side and the collected water collected from the outer peripheral side of the filter are individually mixed without being mixed. Any structure that can be collected at the site is sufficient. It is sufficient that at least one ceramic filter is provided in the filter, but a plurality of ceramic filters may be provided depending on required processing capacity.

Further, the wastewater treatment system of the present invention may be provided with a backwashing mechanism for backflowing the filtrate from the outer peripheral side of the filter toward the flow passage side to remove silicon particles fixed on the surface of the filtration membrane. preferable. This is because, even when the cross-flow method is employed, it is preferable to perform regular back washing in order to prevent the cake layer on the surface of the filtration membrane from sticking.

As a backwashing mechanism, a liquid pool for backwashing (hereinafter, referred to as “backwashing pot”) is provided on the filtrate recovery side.
A mechanism for causing the filtrate to flow back into the flow passage by an air compressor or a pump may be used.

[0043]

Hereinafter, the wastewater treatment method or wastewater treatment system of the present invention will be described in more detail with reference to examples.
However, the present invention is not limited to these examples.

First, according to Example 1 and Comparative Example 1, polishing wastewater was treated in a system incorporating a hollow fiber filter made of an organic polymer and in a system incorporating a ceramic filter, and the performance was compared.

As the waste water treatment system, a system provided with a storage tank 42, a circulation pump 43, and a filter 44 as shown in FIG. 3 was used. In this system, a constant flow valve 50 was attached to a filtrate collection pipe, and pressure gauges 51, 52, and 53 were attached to three places of a filter inlet, a concentrate collection pipe, and a filtrate collection pipe.

The filtration method is a constant-speed cross-flow filtration, and the flow rate of the filtrate is 100 l / (m ² · hour).
Was controlled by the constant flow valve 50 so that The flow rate of the drainage or concentrate in the flow passage of the filter was 2 m / sec. In addition, SS discharged from Dicer as polishing wastewater
Dicer wastewater having a concentration of 50 mg / l was used.

(Example 1) In Example 1, a ceramic filter was arranged in the filter 44 to filter the polishing wastewater. The filter 44 has a total length of 1000 mm x an outer diameter of 30 m.
The inner diameter of a honeycomb structure having a cylindrical shape of mφ and having 61 circular through holes with an inner diameter of 2.5 mmφ is formed on the inner peripheral surface of the honeycomb structure.
A filter in which 11 ceramic filters each having a 1 μm filtration membrane formed therein were arranged in a housing was used.

(Comparative Example 1) In Comparative Example 1, a hollow fiber filter made of an organic polymer was disposed in the filter 44 to filter the polishing wastewater. As a hollow fiber filter, the total length is about 1
In a cylindrical housing of 000 mm × outer diameter of about 100 mmφ, an inner diameter of 1.1 to 1.3 mmφ and a molecular weight cutoff of 13,000
A capillary type hollow fiber filter in which hollow fibers of 20000 (pore diameter of about 4 to 5 nm) were arranged was used.

As a result, as shown in Table 1, in the system of Example 1, the SS concentration of the polishing wastewater was 50,000 mg /
l, ie, concentration up to 1000 times higher concentration,
99.9% of water could be recovered. On the other hand, in the system of Comparative Example 1, the SS concentration of the polishing wastewater was 5000 mg / l, that is, 1%.
It could be concentrated only up to 00 times and only 99% of the water could be recovered.

The pressure P _{1 of} the pressure gauge 51 and the pressure gauge 5
The pressure of 2 P _2, the pressure of the pressure gauge 53 and P _3, to calculate the filtered differential pressure P by the following equation (1), the plotted correlation SS concentration and filtration differential pressure of the concentrate in FIG It is a graph. As shown in FIG. 4, the filtering differential pressure of Example 1 is smaller than that of Comparative Example 1, and when the filtering differential pressure is the same, the ceramic filter of Example 1 can be designed to have a higher filtering speed. Become. _{P = ((P 1 + P} 2) / 2) -P 3 ... (1)

[0051]

[Table 1]

Next, according to Example 2 and Comparative Example 2, the treatment of the polishing wastewater in the continuous treatment and the batch treatment was compared. The wastewater treatment system according to the second embodiment for performing the continuous treatment includes a storage tank 42, a circulation pump 43, and the like as shown in FIG.
A system with a filter 44 was used. In this system, a constant flow valve 50 was attached to the filtrate collection pipe. The hold amount in the circulation system including the storage tank 42 of this system was 300 l.

On the other hand, a system as shown in FIG. 6 was used as a waste water treatment system of Comparative Example 2 for performing batch processing. The system of the second embodiment is different from the system of the second embodiment only in that two storage tanks 42a and 42b are provided for performing batch switching, and a pipe is additionally provided. The hold amount in the circulation system including the storage tank 42 of this system was 3000 l. Since this system has two storage tanks 42, the hold amount as a circulating system including one storage tank 42 was calculated.

The other conditions were the same as in Example 2 and Comparative Example 2. The filter 44 has a cylindrical shape with a total length of 1000 mm x an outer diameter of 30 mmφ and a filtration membrane with a hole diameter of 0.1 µm formed on the inner peripheral surface of a honeycomb structure having 61 circular through holes with an inner diameter of 2.5 mmφ. A filter in which 11 ceramic filters were arranged in a housing was used.

As a filtration method, constant-speed cross-flow filtration was performed, and the outflow speed of the filtrate was 100 l / (m ² · hr).
Was controlled by the constant flow valve 50 so that The flow rate of the drainage or concentrate in the flow passage of the filter was 2 m / sec. In addition, SS discharged from Dicer as polishing wastewater
Dicer wastewater having a concentration of 50 mg / l was used.

Example 2 In Example 2, the polishing wastewater was filtered by a continuous treatment method. Polishing wastewater was continuously supplied at a rate of 30 l / min, a filtrate was continuously collected at a rate of 28.5 l / min, and a concentrated liquid was continuously collected at a rate of 1.5 l / min. In the first 200 minutes of the supply of the polishing wastewater, only the filtration was performed without extracting the concentrated liquid, and after the concentration of the concentrated liquid was sufficiently increased, the extraction of the concentrated liquid was started.

Comparative Example 2 In Comparative Example 2, the polishing wastewater was filtered by a batch processing method. After a predetermined amount of the polishing wastewater is stored in the storage tank 42a, the filtration process is started, and the storage tank 42a
Only the processing of the batch was performed until the entire amount of the polishing wastewater in the inside was concentrated. The operation of storing the polishing wastewater discharged during that time in the storage tank 42b, and starting the concentration of the storage tank 42b when the concentration of the polishing wastewater in the storage tank 42a is completed was repeated.

The polishing wastewater was continuously supplied at a rate of 30 l / min as in Example 2, and the filtrate was continuously collected at a rate of 30 l / min. The concentrated liquid was withdrawn after the concentration was completed.

As a result, as shown in Table 2, in the processing method of Example 2, since the hold amount of the system was small, the residence time of the drainage liquid was as short as 10 minutes, and no increase in ionic silica was observed. On the other hand, in the treatment method of Comparative Example 2, since the hold amount of the system was large, the residence time of the drainage liquid was long at 100 minutes, and the ionic silica concentration was increased to 0.2 mg / l.

[0060]

[Table 2]

(Embodiment 3) Hereinafter, the wastewater treatment system of the present invention will be described in more detail with reference to the drawings.
However, the present invention is not limited by this embodiment.

FIG. 1 shows one embodiment of the wastewater treatment system of the present invention. The wastewater treatment system 1 mainly includes a storage tank 2, a circulation pump 3, and a filter 4 provided with a honeycomb-shaped ceramic filter.

The polishing wastewater is injected into the storage tank 2 via the pipe 5, and is introduced into each flow passage of the ceramic filter in the filter 4 by the circulation pump 3. Since the portion of the polishing wastewater that has not passed through the filtration membrane passes through the flow passage as it is, it is continuously circulated through the circulation system including the circulation pipe 9, the circulation pump 3, and the filter 4, and finally, It can be recovered from the pipe 8 as a concentrated liquid.

A part of the polishing wastewater is recovered from the pipe 7 as a filtrate that has passed through the filtration membrane formed on the inner peripheral surface of the flow passage and the support. The recovered filtrate is once treated water tank 1
After being collected to zero, it is circulated by the water supply pump 11 in order to prevent the quality of the filtrate from being deteriorated due to absorption of carbon dioxide gas.
The circulation line is provided with an ultraviolet sterilizer 12 for preventing generation of viable bacteria.

The ionic silica is removed from the ultraviolet-sterilized filtrate by the ion exchanger 13 and the fine particles are removed by the filter 14 equipped with a microfiltration membrane, and then reused as recovered water. The pipe 7 is connected to the air compressor 15 by a pipe 16, and has a structure in which the filtrate in the backwash pot 17 can flow backward from the filter outer peripheral side to the flow passage side.

[0066]

EFFECTS OF THE INVENTION According to the method and system for treating wastewater of silicon polishing wastewater of the present invention, it is possible to cope with high-concentration polishing wastewater, achieve a high water recovery rate, achieve high concentration of wastewater and The ionic silica concentration can be reduced, and the maintenance and management of the system becomes easy.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of a wastewater treatment system of the present invention.

FIGS. 2A and 2B are schematic diagrams showing a filtration method of a ceramic filter, wherein FIG. 2A shows a cross-flow method and FIG. 2B shows a direct filtration method.

FIG. 3 is a schematic diagram showing a wastewater treatment system used in Example 1 and Comparative Example 1.

FIG. 4 is a graph showing the relationship between SS concentration and filtration pressure difference.

FIG. 5 is a schematic diagram showing a wastewater treatment system used for continuous treatment in Example 2.

FIG. 6 is a schematic diagram illustrating a wastewater treatment system used for batch processing in Comparative Example 2.

[Explanation of symbols]

1 ... wastewater treatment system, 2 ... storage tank, 3 ... liquid pump, 4
... filter, 5 ... pipe, 7 ... pipe, 8 ... pipe, 9 ... circulation pipe, 10 ... treatment water tank, 11 ... water supply pump, 12 ... ultraviolet sterilizer, 13 ... ion exchanger, 14 ... filter, 15
... air compressor, 16 ... piping, 31 ... sealing member, 3
2 ... flow passage, 33 ... filtration membrane, 34 ... support, 35 ... polishing drainage, 36 ... filtrate, 37 ... concentrated solution, 42 ... storage tank, 43
… Sending pump, 44… Filter, 49… Circulation piping, 50…
Constant flow valves, 51, 52, 53 ... pressure gauges.

Continuation of the front page (72) Inventor Hideo Amaike 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi F-term in Japan Insulator Co., Ltd. (Reference) 4D006 GA02 HA21 JA53A JA56A KA63 KC03 KE02Q KE02R KE03Q KE12Q MA02 MA22 MC03 PB08 PB20 PC01

Claims (7)

[Claims] 1. A cylindrical porous body made of ceramic, in which a single flow passage or a number of parallel flow passages are formed in a longitudinal direction, the inner peripheral surface of the flow passage is provided with pores of the porous body. A filter having a ceramic filtration membrane having a smaller pore diameter is prepared, and silicon polishing wastewater is introduced into the flow passage of the filter, and passes through the filtration membrane and the pores of the porous body to the outer periphery of the filter. A wastewater treatment method for silicon polishing wastewater, comprising separately collecting a filtrate that has flowed out and a concentrate that has passed through the flow passage as it is. 2. The wastewater treatment method according to claim 1, wherein the wastewater is treated by a continuous treatment method. 3. The method according to claim 1, wherein the flow rate in the flow passage is controlled within a range of 0.1 to 5 m / sec when introducing the silicon polishing waste water or the concentrate thereof into the flow passage of the filter. Wastewater treatment method. 4. The method according to claim 1, wherein when the silicon polishing waste water or its concentrated liquid is introduced into the flow passage of the filter, the flow rate of the filtrate from the start to the end of the filtration is controlled to be constant. Wastewater treatment method according to any one of the preceding claims. 5. A storage tank for storing silicon polishing wastewater containing silicon particles, a filter for removing silicon particles from the silicon polishing wastewater, a circulation pump for feeding the silicon polishing wastewater, and the filter A circulating pipe for forming a circulating system between the circulating pump and the circulating pump, wherein a single flow passage or a number of parallel flow passages are formed in the longitudinal direction. In addition, in the cylindrical porous body made of ceramic, a filter in which a ceramic filtration membrane having a smaller pore diameter than the pores of the porous body is formed on the inner peripheral surface of the flow passage is built in the filter, By introducing the silicon polishing wastewater into the flow passage of the filter, the filtrate flowing through the filtration membrane and the pores of the porous body and flowing out to the outer periphery of the filter, and the flow passage are left as they are. Wastewater treatment system of the silicon polishing waste water, characterized in that the concentrate spent configured to be separately recovered. 6. The filtration membrane having a pore diameter of 10 nm to 0.2 μm.
The wastewater treatment system according to claim 5, further comprising a filter. 7. The wastewater treatment according to claim 5, further comprising a backwashing mechanism for backflowing the filtrate from the outer peripheral side of the filter toward the flow path side and removing silicon particles fixed on the surface of the filtration membrane. system.