Strainer for drainage, drainage water treatment device, and drainage water treatment method

Abstract

Provided are: a strainer for drainage capable of easily and stably removing minute amounts of fine particles such as abrasive grains contained in polishing drainage water; and a device and method that use the strainer to treat polishing drainage water. A strainer 1 for drainage comprises a cylindrical filter 11 open at both ends, and a cap 12 that is liquid-tightly adhered to one end of the filter 11, wherein the filter 11 has multiple filtration pores on a side surface thereof, the filter 11 includes a filter main body formed from metal and a fluororesin film provided over the entire surface of the filter main body, the cap 12 projects toward the outside of the filter 11, and the entire liquid contact surface is formed from fluororesin.

Description

Drainage strainer, drainage treatment device, and drainage treatment method

[0001] The present invention relates to a drainage strainer, a drainage treatment device using the same, and a drainage treatment method.

[0002] In the manufacturing process of semiconductor devices, surface polishing by CMP (chemical mechanical polishing) is performed to flatten the surface of a semiconductor wafer. In CMP, the surface of a semiconductor wafer is polished with a polishing pad or the like while a polishing slurry for CMP is supplied to the surface. The polishing slurry for CMP is a material containing silica (SiO ２ ), ceria (CeO ２ ), alumina (Al ２ O ３ CMP is typically performed by adding ammonia or alkalis such as potassium hydroxide as processing accelerators to a dispersion of fine abrasive grains such as ammonium hydroxide. After CMP polishing, abrasive grains adhering to the semiconductor wafer surface are removed with a cleaning solution. Examples of cleaning solutions include aqueous ammonia or an aqueous solution of ammonia and hydrogen peroxide.

[0003] The wastewater generated during CMP contains not only polishing slurry but also polishing debris from semiconductor wafers and polishing debris from the polishing pads used in polishing. The wastewater may also contain used cleaning fluid discharged during cleaning.

[0004] Most of this polishing wastewater is usually discharged into the environment after undergoing wastewater treatment such as neutralization, decomposition, and dilution. Among the polishing wastewater, concentrated wastewater (wastewater) and persistent wastewater (wastewater) are taken over by wastewater treatment companies for disposal. Polishing wastewater with a relatively low concentration of impurities (polishing slurry) undergoes a prescribed treatment and is then reused as recovered water for pure water production, air conditioning water, general plant water, etc. Furthermore, polishing wastewater is sometimes mixed with other acidic or alkaline wastewater and treated to obtain recovered water.

[0005] Known methods for treating polishing wastewater to obtain recovered water include passing the polishing wastewater through a separation membrane such as an ultrafiltration membrane or a microfiltration membrane, adding a coagulant to the resulting concentrated water, subjecting the flocculants to solid-liquid separation, and obtaining recovered water as a liquid phase (see, for example, Patent Document 1).Also known is a method for subjecting polishing wastewater to an oxidation treatment, adding a coagulant, and then subjecting the flocculants to solid-liquid separation, thereby obtaining recovered water as a liquid phase (see, for example, Patent Document 2).

[0006] Japanese Patent Laid-Open No. 11-347569 Japanese Patent Laid-Open No. 2001-170652

[0007] However, in the method of adding a flocculant to the polishing wastewater, the pH is often adjusted to achieve effective flocculation, which results in the problem of using a large amount of acid or alkali.Furthermore, the flocculant, especially the polymer flocculant, tends to remain in the treated water, which can easily cause problems such as breakdowns in the water treatment equipment used for wastewater treatment.

[0008] Furthermore, polishing wastewater with a low polishing slurry concentration (dilute slurry wastewater) still contains acids, alkalis, hydrogen peroxide, abrasives, etc., despite its low slurry concentration, making it difficult to process for reuse. For example, traces of abrasives remaining in the polishing wastewater can cause malfunctions in ion exchange treatment devices and membrane treatment devices. Therefore, it is preferable to remove the abrasives from the polishing wastewater and then subject the polishing wastewater to ion exchange treatment or membrane treatment. Therefore, filtering the polishing wastewater through a filter is considered. However, if polishing wastewater containing acid and hydrogen peroxide is filtered through a metal filter such as stainless steel, the filter components will dissolve within a few days, making it impossible to filter and remove the abrasives from the polishing wastewater using a metal filter such as stainless steel. Furthermore, although fluororesin filters have high resistance to chemicals such as acids and alkalis, their low mechanical strength poses a problem when filtering large volumes of wastewater generated in semiconductor manufacturing processes, such as deterioration of filtration performance due to deformation during water flow.

[0009] The present invention has been made to solve the above-mentioned problems, and aims to provide a drainage strainer that can easily and stably remove minute amounts of fine particles such as abrasive grains contained in polishing wastewater, as well as a polishing wastewater treatment device and treatment method using the same.

[0010] The drain strainer, drainage treatment device, and drainage treatment method according to the present invention are as follows: [1] A drain strainer comprising: a cylindrical filter body having openings at both ends and a plurality of filter holes on a side surface; and a cap member liquid-tightly adhered to one end of the filter body, wherein the filter body comprises a metal filter body body and a fluororesin membrane provided on the entire surface of the filter body body, and the cap member has a convex shape facing the outside of the filter body body, and the entire liquid-contacting surface is made of fluororesin. [2] The drain strainer according to [1], wherein the size of the filter holes is 0.01 mm or more and 0.2 mm or less. [3] The drain strainer according to [1] or [2], further comprising a cylindrical housing having a water outlet at one end and a water inlet at the other end, wherein the housing accommodates the filter body and the cap member so that the cap member faces the water inlet of the housing, and wherein the opening of the filter body and the water outlet of the housing are in communication. [4] The drain strainer according to [3], wherein the housing and the filter body are cylindrical, and the cap member is a solid cone or a solid hemisphere. [5] The drain strainer according to [3], wherein the open end of the filter body is connected to the discharge port of the housing. [6] The drain strainer according to [1] or [2], which has a connecting part connecting the filter body and the cap member. [7] The drain strainer according to [6], wherein the connecting part comprises a screw member that penetrates the cap member and the end face of the filter body. [8] The drain strainer according to any of [1], [2], [6] and [7], wherein the fluororesin membrane and the fluororesin contain polytetrafluoroethylene. [9] A drainage strainer according to any one of [1], [2], [6] to [8], wherein when a comparative sample is prepared and the iron (Fe) concentration in the hydrogen peroxide solution is compared after the drainage strainer and the comparative sample are immersed in hydrogen peroxide solution for one day, the iron concentration in the hydrogen peroxide solution in which the drainage strainer is immersed is significantly lower.

[0011] [Correction based on Rule 91 25.02.2025]

[10] A wastewater treatment device comprising: a first drainage strainer and a second drainage strainer connected in parallel; a wastewater treatment mechanism that supplies polishing wastewater to the first drainage strainer to produce treated water; and a backwash mechanism that backwashes the second drainage strainer using a portion of the treated water, wherein both the first drainage strainer and the second drainage strainer are the drainage strainers described in any one of [1], [2], and [6] to [9].

[11] The wastewater treatment mechanism comprises: a wastewater supply device for supplying the polishing wastewater; a first liquid feed pipe for feeding the polishing wastewater to a first wastewater strainer; a first liquid feed valve provided in the first liquid feed pipe; a second liquid feed pipe for feeding the polishing wastewater to a second wastewater strainer; a second liquid feed valve provided in the second liquid feed pipe; a first discharge pipe for discharging treated water from the first wastewater strainer; a second discharge pipe for discharging treated water from the second wastewater strainer; and a collection discharge pipe connected to the first discharge pipe and the second discharge pipe for feeding the treated water to the outside; and the backwash mechanism comprises: a variable opening valve provided in the collection discharge pipe; a first backwash pipe provided branching off from the first liquid feed pipe; a second backwash pipe provided branching off from the second liquid feed pipe; and a first backwash valve provided in the first backwash pipe. and a second backwash valve provided in a second backwash pipe, wherein the wastewater treatment mechanism selects and opens a first liquid supply valve and selects and closes a second liquid supply valve so that the polishing wastewater supplied from the wastewater supply device passes through a first drainage strainer, and the backwash mechanism selects and closes the first backwash valve and selects and opens a second backwash valve, and is controlled to narrow the aperture of the variable aperture valve so that a portion of the treated water in the first drainage strainer passes through a second discharge pipe to the second drainage strainer in the backwash direction.

[12] A wastewater treatment method for filtering polishing wastewater through a strainer, comprising: a wastewater treatment step of filtering the polishing wastewater through a plurality of drainage strainers connected in parallel to obtain treated water; and a backwashing step of supplying the polishing wastewater to one or more of the plurality of drainage strainers to produce treated water, and passing the treated water in a backwash direction through drainage strainers other than the drainage strainer to which the polishing wastewater is supplied, thereby performing backwashing, wherein all of the plurality of drainage strainers are the drainage strainers described in any one of [1], [2], and [6] to [9]. Note that the symbol "to" indicates a numerical range including the numerical values ​​before and after it.

[0012] According to the drainage strainer of the embodiment, minute amounts of fine particles such as abrasive grains contained in the polishing wastewater can be easily and stably removed. According to the polishing wastewater treatment device or treatment method of the embodiment, minute amounts of fine particles such as abrasive grains contained in the polishing wastewater can be easily and stably removed.

[0013] [Correction based on Rule 91 25.02.2025] A cross-sectional view schematically showing a drainage strainer of an embodiment. A cross-sectional view schematically showing a first connection portion 13 of another embodiment. A flow chart schematically showing a method for manufacturing a drainage strainer of an embodiment. A block diagram schematically showing a wastewater treatment device of an embodiment. A flow chart showing a wastewater treatment method of an embodiment.

[0014] [Drainage Strainer] A drainage strainer according to an embodiment of the present invention will now be described. FIG. 1 is a cross-sectional view schematically illustrating a drainage strainer 1 according to the embodiment. The drainage strainer 1 according to the embodiment includes a cylindrical filter body 11 having open ends and a cap member 12. The side surface of the filter body 11 has a plurality of filter holes to form a filter surface 11a. In the drainage strainer 1, as the water to be treated flows from the filter surface 11a on the side surface of the filter body 11 into the filter body 11, impurities such as abrasive grains and polishing debris in the wastewater are removed, and the treated water flows out from the opening at the downstream end of the filter body 11. Hereinafter, the opposite ends of the filter body 11 will be referred to as the upstream end and the downstream end, depending on the flow of water passing through the filter body 11.

[0015] The filter body 11 includes a metal filter body body and a fluororesin membrane disposed over the entire surface of the filter body body. The fluororesin membrane is disposed over the entire surface of the filter body body. Specifically, all liquid-contacting surfaces of the filter body 11, such as the filtration surface, the surfaces of the filter pores, and the inner wall surface of the filter body, are covered with the fluororesin membrane. Examples of metals constituting the filter body body include stainless steel (SUS) such as SUS304, SUS316, SUS316L, and SUS304. From the viewpoints of strength and corrosion resistance, SUS316 or SUS316L is preferred. The filter body body includes, for example, a filter body element formed of a spirally wound wire and multiple rod-shaped support members disposed in the longitudinal direction of the spiral of the filter body element and spaced apart in the circumferential direction of the spiral. The cross-sectional shape of the wire is, for example, triangular, and the wire is arranged so that the apex of the triangle faces the interior of the filter body. The gaps between the spiral wire and the support members function as filter pores. The voids (size of the filter holes) in the support material may be large enough to prevent the passage of polishing debris and abrasive grains in the polishing slurry, for example, 0.01 mm to 0.2 mm, preferably 0.02 mm to 0.1 mm. The filter body 11 is cylindrical, for example, with an outer diameter of 15 mm to 220 mm or 15 mm to 165 mm. When the filter body 11 is composed of filter body elements and a support material as described above, the shape of the filter holes is usually quadrangular, and the size of the filter holes in this case refers to the length of one side of the quadrangle. When the shape of the filter holes is rectangular, the size of the filter holes refers to the length of the short side of the rectangle. When the filter holes have other shapes, the size of the filter holes may be large enough to prevent the passage of fine particles such as polishing debris and abrasive grains, with a minimum length of 0.01 mm to 0.2 mm, preferably 0.02 mm to 0.1 mm. It is also possible to supply concentrated slurry drainage to the drainage strainer 1 at the beginning of water flow. In this case, by supplying the thick slurry wastewater to the drainage strainer 1, a cake (filtered slurry layer) can be formed on the filtering surface 11a of the drainage strainer 1 (called a precoat), and the cake functions as a filtering layer, thereby improving filtration accuracy. In this case, it is possible to filter smaller polishing debris and polishing abrasive grains without being limited by the size of the voids in the support material. This operation is performed every time immediately after backwashing.

[0016] The drain strainer 1 of this embodiment can be easily lined or coated on the surface of the filter body 11 by forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, and then connecting the cap member 12, as described below. This allows for a simple and uniform formation of a fluororesin membrane even on a complex shape with numerous filter holes. If the lining or coating is insufficient and the fluororesin membrane has defects such as pinholes, even if the defects are minor, they can lead to the generation of resin fragments and the elution of iron from the SUS surface covered by the resin. However, by forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, a fluororesin membrane without such defects can be formed by lining or coating, and the entire liquid-contacting surface of the filter body 11 can be covered with the fluororesin membrane.

[0017] The presence of a fluororesin film on the entire surface of the filter body 11 can be confirmed, for example, by the following method. First, for example, a drain strainer is immersed in ultrapure water for seven days, and the iron concentration in the ultrapure water after immersion is measured. Simultaneously, under the same conditions, a fluororesin piece or a SUS piece lined or coated with a fluororesin (hereinafter, both are referred to as "comparison samples") having the same or equivalent surface area as the drain strainer (with an error of ±5%) is immersed, and the iron concentration in the ultrapure water after immersion is measured. It is also possible to compare the measured values ​​obtained for the drain strainer and the comparison sample and test whether the iron concentration in the ultrapure water in which the drain strainer is immersed is significant compared to the iron concentration in the ultrapure water in which the comparison sample is immersed. In this case, for example, when the iron concentrations in the ultrapure water in which multiple comparison samples are immersed are tested at a significance level of 2.5% based on the iron concentrations measured for each, the iron concentration in the ultrapure water in which the drain strainer is immersed is measured by F ｓａｍｐ The average value calculated from the iron concentration in the ultrapure water in which the comparative sample was immersed was F. ａｖｅ , and the standard deviation is σ, F ｓａｍｐ ≦F ａｖｅIf the value is +1.96 × σ, it can be determined that a fluororesin film is formed over the entire surface of the filter body 11. Alternatively, the iron concentration in ultrapure water in which a single comparative sample has been immersed can be measured multiple times to make a similar determination. The test method is preferably based on, for example, the UC Standard: Leaching Test Method for Piping Materials for Ultrapure Water (UCS12 Semiconductor Industry Development and UCS12 Achievements, edited by the Semiconductor Fundamental Technology Research Group, pp. 1181-1188). This method is a non-flow system, and since eluates are eluted in a small amount of ultrapure water, it constitutes an accelerated test and allows for easy measurement. Third, as a further accelerated test, confirmation can be achieved by using the same method as in the second method, except that an aqueous solution of hydrogen peroxide, sulfuric acid, or a mixture thereof is used instead of ultrapure water. In this case, measurement can be performed within a immersion time of, for example, about one day.

[0018] In the drain strainer 1, the cap member 12 is liquid-tightly adhered to the upstream end of the filter body 11. The cap member 12 has a convex shape extending outward from the upstream end of the filter body 11, and at least the liquid-contacting surface is made of fluororesin. The cap member 12 may be made of a metal cap member body such as SUS and a fluororesin film provided on the surface of the cap member body, or the entire cap member may be made of fluororesin. It is preferable that the entire cap member 12 be made of fluororesin because it is lightweight and easy to handle. The cap member may be hollow or solid, but a solid cap member is preferable because it is easy to manufacture, and it is particularly preferable that the entire cap member 12 be made of a solid fluororesin.

[0019] The cap member 12 preferably has at least a bottom surface and a side surface rising from the bottom surface. The bottom surface, i.e., the side opposite the convex surface, of the cap member 12 is connected to the opening at the upstream end of the filter body 11 via a first connecting portion 13. Examples of the convex shape of the cap member 12 include those in which the convex cross section, i.e., the cross section perpendicular to the bottom surface and passing through the point farthest from the bottom surface, is polygonal, rectangular, triangular, semicircular, etc.

[0020] The convex shape of the cap member 12 is preferably such that the water flow on the surface of the cap member 12 does not produce a unidirectional flow or a vortex. If a unidirectional flow or a vortex occurs on the surface of the convex cap member 12, the strainer will vibrate due to the water flow. Because wastewater treatment devices are continuously operated for at least one year, and in some cases for several years, long-term vibration of the strainer can accelerate deterioration of the fluororesin film on the strainer's filtering surface, potentially causing resin fragments and iron leaching from the SUS surface that was previously covered by the resin. Convex cross sections that do not produce such unidirectional flow or a vortex are preferably triangular, semicircular, or semi-elliptical. When the convex cross section is triangular, for example, one side of the triangle is located on the upstream end of the filter body 11. When the convex cross section is semicircular, for example, the diameter of the semicircle is located on the upstream end of the filter body 11. When the convex cross section is semi-elliptical, for example, the major axis or minor axis of the semi-ellipse is located on the upstream end of the filter body 11. For example, when the opening of the filter body 11 is circular, the convex shape of the cap member 12 is preferably a hemisphere, a semi-elliptical sphere, or a cone, since one-sided flow is less likely to occur on the surface of the cap member 12. In particular, if the shape of the cap member 12 is a cone, the inclination of the side surface from the apex to the bottom is constant, which is more preferable because it also provides a rectifying effect on the drainage.

[0021] The outer diameter of the cap member 12 is preferably the same as or approximately the same as the outer diameter of the opening of the filter body 11 but larger than the outer diameter of the opening of the filter body 11. This makes it possible to adjust the water flow around the first connecting portion 13 between the filter body 11 and the cap member 12, thereby suppressing the deterioration of the lining or coating as described above.

[0022] The fluororesin used for the cap member 12 and the fluororesin film on the surface of the filter body 11 is not particularly limited, but examples include tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane), polytetrafluoroethylene (PTFE), ethylene / tetrafluoroethylene copolymer (ETFE), etc. The fluororesin of the cap member 12 and the fluororesin film on the surface of the filter body 11 may be the same or different, but are preferably the same type. The cap member may be made of stainless steel, polypropylene, or polyethylene. In these cases, it is preferable to coat or line the surface with a fluorine-based material.

[0023] When ETFE is used as the fluororesin, for the purpose of controlling crystallinity, it is preferable that the ETFE is obtained by copolymerizing ethylene and tetrafluoroethylene with other fluorine-containing monomers. The other fluorine-containing monomers are not particularly limited as long as they can be added to both ethylene and tetrafluoroethylene, but fluorine-containing vinyl monomers having 3 to 8 carbon atoms are easily used, for example, hexafluoroisobutylene, CH ２ = CFC ３ F ６ The amount of the other fluorine-containing monomer is preferably 5 mol % or less of the total monomers of the ETFE, in order not to impair the heat resistance, flame retardancy and chemical resistance.

[0024] When ETFE is obtained by copolymerizing other fluorine-containing monomers, the fluorine content in ETFE is preferably 50% by mass or more. A fluorine content of 50% by mass or more exhibits excellent heat resistance, flame retardancy, and chemical resistance. The fluorine content of ETFE is, for example, 70% by mass or less. The fluorine content can be adjusted by appropriately adjusting the ratio of ethylene, tetrafluoroethylene, and other monomers used as desired. The fluorine content is a value obtained by burning a fluororesin, absorbing the fluorine contained therein into alkaline water, etc., and measuring it by ion chromatography, etc.

[0025] Among the above-mentioned fluororesins, tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane) and polytetrafluoroethylene (PTFE) resin are materials that are widely and generally used in ultrapure water production systems due to their excellent heat resistance and chemical resistance, and can also be suitably used for the cap member 12 and the fluororesin membrane on the filter body 11.

[0026] The first connecting portion 13 is not particularly limited as long as it can connect the filter body 11 and the cap member 12 liquid-tightly. Examples of the first connecting portion 13 include a connecting portion formed by soldering, welding, or the like, which undergoes a change in the state of the material of the connecting portion when connected. Alternatively, the first connecting portion 13 may be a connecting portion formed by a mechanical structure without undergoing a change in the state of the material of the connecting portion when connected, for example, a connecting portion using threaded engagement or one or more screw members. It is preferable that the first connecting portion 13 be a connecting portion formed by a mechanical structure, in that no defects are generated in the fluororesin film on the surface of the filter body 11 when the filter body 11 and the cap member 12 are connected.

[0027] 1 , for example, a first connector 131 having ridges 131a on its outer surface can be connected to the bottom surface of the cap member 12, and a cylindrical second connector 132 having a spiral groove 132a on its inner wall that threadably engages with the ridges can be connected to the upstream end of the filter body 11, connecting the filter body 11 and the cap member 12 by threading the ridges 131a of the first connector 131 with the groove 132a of the second connector 132. In this case, the first connector 13 includes the first connector 131, the ridges 131a provided on the first connector 131, the second connector 132, and the groove 132a provided on the second connector 132. Furthermore, instead of the embodiment in which the first connector 131 has ridges and the second connector 132 has grooves, the first connector 131 may have grooves and the inner wall of the second connector 132 may have ridges. In order to improve the liquid-tightness between the filter body 11 and the cap member 12, a sealing member such as an O-ring made of resin or the like may be interposed between the end face of the second connector 132 of the filter body 11 and the vicinity of the outer periphery of the bottom surface of the cap member 12.

[0028] [Correction pursuant to Rule 91, February 25, 2025] Figure 2 is a cross-sectional view schematically illustrating another embodiment of the first connecting portion 13. As shown in Figure 2, a third connecting body 133 is provided on the end face of the upstream end of the filter body 11. The third connecting body 133 is, for example, arranged along the periphery of the upstream end of the filter body 11 and has a solid ring shape with thickness in the axial and circumferential directions. The filter body 11 and the cap member 12 can be connected by providing multiple threaded holes 134 near the outer periphery of the cap member 12 and inserting a screw member 142 or the like through the threaded holes 134 into the cap member 12 and the third connecting body 133. In this case, the first connecting portion 13 includes the cap member 12 and the screw member 142 that penetrates the cap member 12 and is inserted into the third connecting body 133. In order to improve the liquid-tightness between the filter body 11 and the cap member 12, a sealing member such as an O-ring made of resin or the like may be interposed between the end face of the upstream end of the third connector 133 and the bottom surface of the cap member 12. In this case, the first connector 13 further includes a sealing member.

[0029] 2, when the filter body 11 and the cap member 12 are connected using the screw member 142, there is a possibility that water may accumulate on the surface (screw head) of the screw member 142 or in the vicinity thereof, or that iron may leach out from the screw member if the screw member 142 is made of metal. Therefore, if the screw member 142 has a depression on the surface or in the vicinity thereof, it is preferable to form a protective part by filling the depression with a fluororesin. In this case, the material of the protective part may be a different fluororesin from or the same fluororesin as the cap member 12, but it is preferable that it be the same fluororesin.

[0030] The drain strainer 1 shown in FIG. 1 further includes a cylindrical housing 15 that houses the filter body 11. The housing 15 houses the entire filter body 11. The housing 15 has a water outlet 15a at the downstream end and a water inlet 15b at the upstream end. The housing 15 may have a continuous cylindrical shape with a constant inner diameter, or may have a shape in which multiple cylindrical sections with different inner diameters are connected in series. Furthermore, a portion of the cylindrical shape, particularly both ends or one end, may have a tapered shape with a diameter that decreases toward the end. It is preferable that a fluororesin film be provided on the inner surface of the housing 15 and, if necessary, on liquid-contacting surfaces other than the inner surface. The fluororesin film on the inner surface of the housing 15, etc., can be formed by lining or coating, similar to the filter body 11.

[0031] In the drainage strainer 1, the filter body 11 and the cap member 12 are arranged and housed in the housing 15 so that the cap member 12 faces the water inlet 15b of the housing 15. The opening at the downstream end of the filter body 11 communicates with the water outlet 15a of the housing 15, so that treated water that has passed through the filtering surface 11a of the filter body 11 is discharged from the water outlet 15a of the housing.

[0032] [Correction based on Rule 91, February 25, 2025] The filter body 11 and the housing 15 are connected via a second connecting portion 18. The second connecting portion 18 is not particularly limited as long as it can connect the filter body 11 and the housing 15 liquid-tightly. In the drain strainer 1 shown in FIG. 1 , a discharge pipe 20 is connected to the housing 15 via the second connecting portion 18. The discharge pipe 20 has a discharge pipe main body 24 and a flange portion 22 extending circumferentially from the upstream end of the discharge pipe main body 24. A threaded hole is provided in the flange portion 22. The housing 15 has a flange portion 151 extending circumferentially from the downstream end of the housing 15, and the flange portion 151 has a threaded hole. Furthermore, a fourth connecting portion 148 is connected to the downstream end of the filter body 11. The fourth connecting portion 148 is arranged along the periphery of the downstream end of the filter body 11 and has a solid ring shape with thickness in both the axial and circumferential directions. A portion of the downstream end of the outer periphery of the fourth connector 148 (opposite the side that contacts the downstream end of the filter body 11) has a larger outer diameter than the upstream end, and is provided with a notch into which the flange portion 151 fits.

[0033] [Correction based on Rule 91, February 25, 2025] In the drain strainer 1, the second connecting portion 18 can be formed by arranging the notch of the fourth connecting body 148 between the flange portion 151 and the flange portion 22, passing a screw member 144a through the threaded holes in the flange portion 151 and the flange portion 22, and securing the passing screw member 144a with a screw fastener 144b. That is, the second connecting portion 18 includes the flange portion 151, the fourth connecting body 148, the flange portion 22, and the screw member 144a and screw fastener 144b that pass through the flange portion 151 and the flange portion 22. Note that, to improve the liquid-tightness of the second connecting portion 18, sealing members 146a, 146b, such as O-rings made of resin, may be interposed between the flange portion 151 and the notch of the fourth connecting body 148 and between the downstream end face of the fourth connecting body 148 and the flange portion 22. In this case, the second connection portion 18 further includes sealing members 146a and 146b.

[0034] Next, another method for connecting the filter body 11 and the housing 15 will be described. This method uses a structure similar to that of the filter body 11 and the cap member 12 shown in FIG. 1 . That is, a cylindrical sixth connector having a spiral groove on its inner wall is connected to the upstream end of the discharge pipe 20, and a cylindrical fifth connector having ridges on its outer surface that threadably engage with the groove is connected to the downstream end of the filter body 11, thereby achieving a connection by threading the groove and the ridge. In this case, the second connector 18 includes a fifth connector, ridges provided on the fifth connector, a sixth connector, and a groove provided on the inner wall of the sixth connector. Furthermore, instead of the fifth connector having ridges on its inner wall and the sixth connector having grooves, the fifth connector may have grooves on its inner wall and the sixth connector may have ridges. To improve the liquid-tightness between the filter body 11 and the housing 15, a sealing member such as an O-ring made of resin or the like may be interposed between the downstream end face of the fifth connector and the upstream end face of the sixth connector. In this case, the second connection portion 18 further includes a sealing member.

[0035] [Method of Manufacturing Drain Strainer] A method of manufacturing the drain strainer of this embodiment will be described. Fig. 3 is a flow chart that schematically shows the method of manufacturing the drain strainer of this embodiment. The method of manufacturing the drain strainer shown in Fig. 3 includes an assembly step S80 of assembling the filter body 11, a fluororesin film forming step S82 of forming a fluororesin film on the surface of the filter body, and a connection step S84 of connecting the cap member 12 and each connector (first connector and second connector, or third connector) to the filter body 11 with the fluororesin film formed on its surface.

[0036] First, in an assembly step S80, the filter body 11 is assembled and manufactured. In the assembly step S80, a commercially available bag-shaped strainer having a sealed upstream end and an open downstream end may be used as a raw material, and the upstream end of the strainer may be opened to obtain the filter body 11 of the embodiment.

[0037] Subsequently, in the fluororesin film forming step S82, the above-described fluororesin film is formed on the surface of the filter body. The fluororesin film may be formed by a coating method such as dip coating, spray coating, electrostatic painting, brush painting, or roll coating, or by a lining method such as electrostatic powder painting or sheet lining. Spray coating is preferred because it allows a fluororesin film to be formed uniformly on the inner surfaces of the filter pores. The thickness of the fluororesin film formed on the surface of the filter body 11 in this manner is usually about 200 μm to 300 μm.

[0038] Thereafter, the cap member 12 and each connector are connected to the filter body 11 as described above. Furthermore, if necessary, the filter body 11 connected to the cap member 12 is housed in the housing 15. When a hollow or solid cap member 12 made of fluororesin is used, the cap member 12 can be obtained by forming the fluororesin into a block shape and then cutting the fluororesin block using a machine tool or the like. More specifically, the cap member 12 can be manufactured into the desired shape by cutting a cylindrical fluororesin rod from a block of fluororesin, or by forming the fluororesin into a cylindrical fluororesin rod and then cutting it. Note that the cap member 12 being solid can prevent wastewater from stagnating inside the cap. Therefore, a solid cap member 12 is more preferable because it does not cause deterioration of water quality.

[0039] Although the above description deals with a mode in which the fluororesin membrane is formed on the filter body 11 and then the connectors are attached, the fluororesin membrane may also be formed after the connectors are attached to the filter body 11. In the drain strainer manufacturing method of this embodiment, forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, allows for easy lining or coating. Therefore, it is possible to easily and uniformly form a fluororesin membrane even on a complex shape with numerous filter holes. If the lining or coating is insufficient and the fluororesin membrane has defects such as pinholes, even minor defects can lead to corrosion of the strainer during wastewater treatment. This results in a decrease in filtration accuracy and the elimination of the filtering surface. However, by forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, a fluororesin membrane without such defects can be formed by lining or coating, resulting in a drain strainer suitable for treating polishing wastewater.

[0040] [Wastewater Treatment Device and Method] Next, a wastewater treatment device and a wastewater treatment method according to this embodiment will be described. The wastewater treatment device according to this embodiment has a first drainage strainer and a second drainage strainer connected in parallel. The wastewater treatment device according to this embodiment has a wastewater treatment mechanism that supplies polishing wastewater to the first drainage strainer to produce treated water, and a backwash mechanism that backwashes the second drainage strainer using a portion of the treated water. In this embodiment, both the first drainage strainer and the second drainage strainer are drainage strainers similar to the drainage strainer 1 of the above-described embodiment. Furthermore, both the first drainage strainer and the second drainage strainer may be a strainer group in which two or more drainage strainers are connected in parallel.

[0041] The wastewater treatment mechanism includes a wastewater supply device, a first feed pipe for feeding polishing wastewater to a first drainage strainer, a second feed pipe for feeding polishing wastewater to a second drainage strainer, a first discharge pipe connected to the first drainage strainer and for discharging treated water from the first drainage strainer, and a second discharge pipe connected to the second drainage strainer and for discharging treated water from the second drainage strainer. The wastewater treatment mechanism further includes a first feed valve provided on the first feed pipe and a second feed valve provided on the second feed pipe. The wastewater treatment mechanism also includes a collection discharge pipe connected to the first discharge pipe and the second discharge pipe for collecting and discharging the treated water to the outside.

[0042] The backwash mechanism includes a variable opening valve provided in the path of the collection and discharge pipe, a first backwash pipe branched off from the first liquid supply pipe, a second backwash pipe branched off from the second liquid supply pipe, a first backwash valve provided in the path of the first backwash pipe, and a second backwash valve provided in the path of the second backwash pipe.

[0043] The wastewater treatment mechanism selects and opens the first liquid supply valve so that the polishing wastewater supplied from the wastewater supply device passes through the first wastewater strainer, and at the same time, the backwash mechanism selects and closes the first backwash valve provided in the first backwash pipe and the second liquid supply valve provided in the second backwash pipe, and selects and opens the second backwash valve provided in the second backwash pipe, and is controlled to narrow the aperture of the variable aperture valve provided in the path of the collection and discharge pipe so that a portion of the treated water obtained from the first wastewater strainer passes through the second wastewater strainer in the backwash direction.

[0044] If the first drain strainer or the second drain strainer is a strainer group in which two or more drain strainers are connected in parallel, the first liquid supply valve and the first backwash valve, and the second liquid supply valve and the second backwash valve, may each be a liquid supply valve group or a backwash valve group having a plurality of valves. Similarly, the first liquid supply pipe, the first discharge pipe, and the first backwash pipe, and the second liquid supply pipe, the second discharge pipe, and the second backwash pipe may each be a liquid supply pipe group, a discharge pipe group, or a backwash pipe group having a plurality of pipes.

[0045] The wastewater treated in the wastewater treatment equipment is typically polishing wastewater. Polishing wastewater is generated by polishing an object to be polished with a polishing liquid (polishing slurry) containing abrasive particles (abrasive grains) and the like. Polishing wastewater contains polishing abrasive grains, which are the main components of the polishing liquid, and polishing waste, and may also contain optional components of the polishing liquid, such as a dispersant and a polishing accelerator. The polishing abrasive grains are, for example, silica (SiO ２ ), alumina (Al ２ O ３ ), ceria (selenium oxide, CeO ２ ), zirconia (ZrO ２ The processing accelerator is, for example, an alkali such as ammonia or potassium hydroxide. The polishing wastewater may also contain used cleaning fluid generated by cleaning the surface of the workpiece after polishing. Examples of the cleaning fluid include aqueous ammonia and an aqueous solution of ammonia and hydrogen peroxide.

[0046] Examples of polishing wastewater include wastewater from a polishing process for glass substrates or lenses using a polishing liquid containing abrasive grains such as colloidal silica or ceria, wastewater from a polishing (rough polishing) process in silicon wafer manufacturing using a polishing liquid containing abrasive grains such as colloidal silica, wastewater from a lapping (mirror finish polishing) process in semiconductor device manufacturing using a polishing liquid containing abrasive grains such as colloidal silica, alumina, silicon carbide, etc., and wastewater from a CMP process in semiconductor device manufacturing using a polishing liquid containing abrasive grains such as colloidal silica, alumina, zirconia, ceria, etc. In addition to polishing wastewater, the wastewater treated by the wastewater treatment device 50 may also be acid wastewater or alkaline wastewater.

[0047] Next, the wastewater treatment device of this embodiment will be described in more detail with reference to the drawings. Fig. 4 is a block diagram schematically illustrating a wastewater treatment device 50 according to this embodiment. The wastewater treatment device 50 includes a wastewater supply device 51 that stores polishing wastewater and supplies it to the wastewater treatment device 50, and three strainers 1A, 1B, and 1C connected in parallel. The wastewater treatment device 50 also includes a liquid feed pipe 51a for feeding wastewater to the strainer 1A, a liquid feed pipe 51b for feeding wastewater to the strainer 1B, and a liquid feed pipe 51c for feeding wastewater to the strainer 1C. The liquid feed pipes 51a, 51b, and 51c are connected to openings at the upstream ends of the strainers 1A, 1B, and 1C, respectively. Valves V1a, V1b, and V1c are installed in the liquid feed pipes 51a, 51b, and 51c, respectively.

[0048] The wastewater treatment device 50 includes a discharge pipe 52a for discharging treated water filtered by strainer 1A, a discharge pipe 52b for discharging treated water filtered by strainer 1B, and a discharge pipe 52c for discharging treated water filtered by strainer 1C. Discharge pipes 52a, 52b, and 52c are connected to openings at the downstream ends of strainers 1A, 1B, and 1C, respectively. The wastewater treatment device 50 further includes a discharge pipe (collection discharge pipe) 53 connected to discharge pipes 52a, 52b, and 52c, and for collecting treated water discharged from discharge pipes 52a, 52b, and 52c. A valve V3 is installed in discharge pipe 53.

[0049] The wastewater treatment device 50 also includes a backwash pipe 54a that branches off from the liquid feed pipe 51a between the opening at the upstream end of the strainer 1A and the valve V1a. Similarly, the wastewater treatment device 50 also includes a backwash pipe 54b that branches off from the liquid feed pipe 51b between the opening at the upstream end of the strainer 1B and the valve V1b. Similarly, the wastewater treatment device 50 also includes a backwash pipe 54c that branches off from the liquid feed pipe 51c between the opening at the upstream end of the strainer 1C and the valve V1c. Valves V4a, V4b, and V4c are installed in the backwash pipes 54a, 54b, and 54c, respectively.

[0050] Strainers 1A, 1B, and 1C have the same configuration as the drainage strainer 1 of the above-described embodiment, and preferred aspects are also the same. Valves V1a, V1b, V1c, V4a, V4b, and V4c are, for example, open / close valves or variable opening valves whose opening degree can be adjusted. Valve V3 is a variable opening valve. Furthermore, the drainage treatment device 50 may be equipped with a control device that adjusts the amount of drainage water supplied by the drainage water supply device 51 and the opening / closing and opening degree of each valve according to a preset program.

[0051] Next, a description will be given of a wastewater treatment method using the wastewater treatment device 50. Fig. 5 is a flow diagram showing the wastewater treatment method of this embodiment. The wastewater treatment method of this embodiment includes a wastewater treatment step S51 and a backwashing step S52.

[0052] [Correction based on Rule 91, February 25, 2025] Prior to the wastewater treatment step S51, the polishing wastewater is preferably separated into a thick slurry wastewater with a relatively high polishing liquid concentration and a dilute slurry wastewater with a relatively low polishing liquid concentration in the upstream stage of the wastewater treatment device 50. This separation method is not particularly limited, but it can be used to systematically separate the wastewater to be treated during the semiconductor manufacturing process based on the amount and properties of the chemicals and impurities contained therein. For example, in batch cleaning, most impurities (polishing slurry and polishing debris) and chemicals are washed away from the surface of the object being cleaned, such as a wafer, at the beginning of the cleaning process. As the cleaning process progresses, the concentration of impurities in the cleaning wastewater decreases. Therefore, by separating the wastewater from the upstream and downstream stages of the cleaning process, it is possible to separate the wastewater into a thick slurry wastewater with a relatively high polishing liquid concentration and a dilute slurry wastewater with a relatively low polishing liquid concentration. The method of separation and recovery using a slurry recovery device with a slurry capture pocket, as described in Japanese Patent No. 5,479,781, is also applicable.

[0053] In the wastewater treatment step S51, the polishing wastewater is passed through the drainage strainer of the above-described embodiment to remove fine particles such as abrasive grains and polishing debris from the polishing wastewater. If the polishing wastewater is separated into dilute slurry wastewater and concentrated slurry wastewater, each is passed through the drainage strainer separately. Preferably, the dilute slurry wastewater is treated in the wastewater treatment step S51, and the concentrated slurry wastewater is collected and treated by a wastewater treatment company or the like.

[0054] In the wastewater treatment step S51, when using the wastewater treatment device 50 shown in FIG. 4 , the polishing wastewater is treated using strainers 1A, 1B, and 1C. Specifically, valves V1a, V1b, V1c, and V3 are opened, and valves V4a, V4b, and V4c are closed. The polishing wastewater is supplied from the wastewater supply device 51 to strainers 1A, 1B, and 1C via liquid feed pipes 51a, 51b, and 51c, respectively. The polishing wastewater is filtered as it flows through strainers 1A, 1B, and 1C, removing fine particles such as polishing grains and polishing debris, to produce treated water. The treated water is discharged from strainers 1A, 1B, and 1C via discharge pipes 52a, 52b, and 52c, respectively, and collected in discharge pipe 53.

[0055] If the wastewater treatment step S51 is continued for a predetermined period of time, the strainers will gradually become clogged. Therefore, the backwashing step S52 is performed before the strainers become completely clogged.

[0056] In the backwashing step S52, wastewater treatment is continued using at least one of the multiple strainers, and the permeated water (treated water) is used to backwash the other strainers. As a method of performing the backwashing step S52 using the wastewater treatment device 50 shown in Figure 4, first, a method of backwashing strainer 1C while continuing wastewater treatment using strainers 1A and 1B will be described.

[0057] In the backwashing process S52, valves V1a, V1b, and V4c are opened, valves V1c, V4a, and V4b are closed, and the opening of valve V3 is reduced or closed. The opening of valve V3 is adjusted so that the treated water flow rate in the discharge pipe 53 is smaller than the wastewater flow rate supplied by the wastewater supply device 51. In this state, the wastewater supply device 51 supplies polishing wastewater to strainers 1A and 1B. Then, at least a portion of the treated water from strainers 1A and 1B flows from the downstream end of strainer 1C into strainer 1C, i.e., in the backwash direction, and is discharged via backwash pipe 54c. During this process, abrasive grains and other particles trapped in strainer 1C that cause clogging are removed from strainer 1C. The other portion of the treated water from strainers 1A and 1B is collected in discharge pipe 53 via discharge pipe 52a or 52b.

[0058] For example, the wastewater supply device 51 can be configured with a wastewater tank for storing wastewater and a pump installed on the outlet side of the wastewater tank, and the wastewater in the wastewater tank can be supplied to the strainer by the pump. Alternatively, the wastewater supply device 51 can be configured with a wastewater tank for storing wastewater, and a height difference can be provided between the wastewater tank and the wastewater treatment device 50 so that the wastewater tank is higher than each strainer, and wastewater can be supplied to each strainer by gravity. The strainer of this embodiment has low water resistance, allowing water to easily pass through by gravity, making it possible to utilize the above-mentioned height difference. Furthermore, a method of supplying wastewater by gravity does not involve problems such as corrosion of the pump material due to wastewater, and allows for easy wastewater treatment. Furthermore, gas-assisted backwashing can be used to improve backwash efficiency. In this case, for example, backwash water (treated water obtained by the wastewater treatment device 1) can be stored in a tank, and the tank can be pressurized with an inert gas such as air or nitrogen, and the backwash water can be supplied to the strainer by gas pressure. Since this method does not use a pump, the problem of corrosion of the pump material due to wastewater does not occur.

[0059] In this example, strainers 1A and 1B function as first drain strainers (group), and strainer 1C functions as a second strainer. Furthermore, liquid feed pipes 51a and 51b function as first liquid feed pipes (group), and liquid feed pipe 51c functions as a second liquid feed pipe. Discharge pipes 52a and 52b function as first discharge pipes (group), and discharge pipe 52c functions as a second discharge pipe. Backwash pipes 54a and 54b function as first backwash pipes (group), and backwash pipe 54c functions as a second backwash pipe. Furthermore, valves V1a and V1b function as first liquid feed valves (group), and valve V1c functions as a second liquid feed valve. Valves V4a and V4b function as first backwash valves (group), and valve V4c functions as a second backwash valve.

[0060] Furthermore, when backwashing the strainer 1B while continuing wastewater treatment using the strainers 1A and 1C, in the backwashing step S52, valves V1a, V4b, and V1c are opened, valves V1b, V4a, and V4c are closed, and the opening of valve V3 is reduced or closed. The opening of valve V3 is adjusted so that the flow rate of treated water in the discharge pipe 53 is smaller than the flow rate of wastewater supplied by the wastewater supply device 51. In this state, the wastewater supply device 51 supplies polishing wastewater to the strainers 1A and 1C. Then, a portion of the treated water from the strainers 1A and 1C flows from the downstream end of the strainer 1B into the strainer 1B, i.e., in the backwash direction, and is discharged via the backwash pipe 54b. During this process, abrasive grains and other particles trapped in the strainer 1B that cause clogging are removed from the strainer 1B. Another portion of the treated water from the strainers 1A and 1C is collected in the discharge pipe 53 via the discharge pipe 52a or the discharge pipe 52c.

[0061] In this example, strainers 1A and 1C function as first drain strainers (group), and strainer 1B functions as a second strainer. Furthermore, liquid feed pipes 51a and 51c function as first liquid feed pipes (group), and liquid feed pipe 51b functions as a second liquid feed pipe. Discharge pipes 52a and 52c function as first discharge pipes (group), and discharge pipe 52b functions as a second discharge pipe. Backwash pipes 54a and 54c function as first backwash pipes (group), and backwash pipe 54b functions as a second backwash pipe. Furthermore, valves V1a and V1c function as first liquid feed valves (group), and valve V1b functions as a second liquid feed valve. Valves V4a and V4c function as first backwash valves (group), and valve V4b functions as a second backwash valve.

[0062] Furthermore, when backwashing the strainer 1A while continuing wastewater treatment using the strainers 1B and 1C, in the backwashing step S52, valves V4a, V1b, and V1c are opened, valves V1a, V4b, and V4c are closed, and the opening of valve V3 is reduced or closed. The opening of valve V3 is adjusted so that the flow rate of treated water in the discharge pipe 53 is smaller than the flow rate of wastewater supplied by the wastewater supply device 51. In this state, the wastewater supply device 51 supplies polishing wastewater to the strainers 1B and 1C. Then, a portion of the treated water from the strainers 1B and 1C flows from the downstream end of the strainer 1A into the strainer 1A, i.e., in the backwash direction, and is discharged via the backwash pipe 54a. During this process, abrasive grains and other particles trapped in the strainer 1A that cause clogging are removed from the strainer 1A. Another portion of the treated water from the strainers 1B and 1C is collected in the discharge pipe 53 via the discharge pipe 52b or the discharge pipe 52c.

[0063] [Correction based on Rule 91 25.02.2025] In this example, strainers 1B and 1C function as the first drain strainer(s), and strainer 1A functions as the second strainer. Furthermore, liquid supply pipes 51b and 51c function as the first liquid supply pipe(s), and liquid supply pipe 51a functions as the second liquid supply pipe. Discharge pipes 52a and 52c function as the first discharge pipe(s), and discharge pipe 52 functions as the second discharge pipe. Backwash pipes 54b and 54c function as the first backwash pipe(s), and backwash pipe 54a functions as the second backwash pipe. Furthermore, valves V1b and V1c function as the first liquid supply valve(s), and valve V1a functions as the second liquid supply valve. Valves V4b and V4c function as a first backwash valve(s), and valve V4a functions as a second backwash valve.

[0064] Next, we will explain the case where strainers 1B and 1C are backwashed while drainage treatment continues through strainer 1A. In this case, in the backwashing step S52, valves V1a, V4b, and V4c are opened, valves V1b, V4a, and V1c are closed, and the opening of valve V3 is reduced or closed. The opening of valve V3 is adjusted so that the flow rate of treated water in discharge pipe 53 is smaller than the flow rate of wastewater supplied by wastewater supply device 51. In this state, wastewater supply device 51 supplies polishing wastewater to strainer 1A. Then, a portion of the treated water from strainer 1A flows from the downstream ends of strainers 1B and 1C into strainers 1B and 1C, i.e., in the backwash direction, and is discharged via backwash pipes 54b and 54c, respectively. During this process, abrasive grains and other substances trapped in strainers 1B and 1C, which cause clogging, are removed from each strainer. Another portion of the treated water from strainer 1A is collected in discharge pipe 53 via discharge pipe 52a.

[0065] In this example, strainer 1A functions as a first drain strainer, and strainers 1B and 1C function as a second strainer (group). Furthermore, liquid supply pipe 51a functions as a first liquid supply pipe, and liquid supply pipes 51b and 51c function as a second liquid supply pipe. Discharge pipe 52a functions as a first discharge pipe, and discharge pipes 52b and 52c function as a second discharge pipe (group). Backwash pipe 54a functions as a first backwash pipe, and backwash pipes 54b and 54c function as a second backwash pipe (group). Furthermore, valve V1a functions as a first liquid supply valve, and valves V1b and V1c function as a second liquid supply valve (group). Valve V4a functions as a first backwash valve, and valves V4b and V4c function as a second backwash valve (group). The same operation is carried out when backwashing other strainers while continuing wastewater treatment with strainer 1B or strainer 1C.

[0066] In this embodiment, the wastewater treatment device 50 has been described with an example of three strainers connected in parallel, but the number of strainers is not particularly limited. When there is only one strainer, backwashing alone is performed without wastewater treatment during the backwashing process. In this case, backwashing is performed, for example, by providing a tank for storing treated water and supplying the treated water from the tank to the strainer from the backwashing direction using a pump. When there are two or more strainers, wastewater treatment and backwashing can be performed in parallel during the backwashing process, as described above. Furthermore, the combination of strainers performing wastewater treatment and strainers being backwashed during the backwashing process is not limited. Furthermore, in the above embodiment, a method was described in which one or two of the multiple strainers are backwashed during the backwashing process, and wastewater treatment is performed using the remaining strainers. However, the number of strainers performing wastewater treatment and strainers being backwashed is not limited.

[0067] In the wastewater treatment step S51 and the backwashing step S52, the treated water obtained from the discharge pipe 53 is supplied to a pure water production system or an ultrapure water production system and used as raw water. The treated water is preferably supplied to the pure water production system or the ultrapure water production system after undergoing one or more of ion exchange treatment, reverse osmosis membrane treatment, and hydrogen peroxide decomposition treatment.

[0068] In the ion exchange treatment, treated water from the wastewater treatment device 50 (hereinafter referred to as "recovered treated water") is passed through an ion exchange resin to remove ionic components from the recovered treated water. The ion exchange resin can be selected appropriately from strong acid cation exchange resins, weak acid cation exchange resins, strong basic anion exchange resins, weak basic anion exchange resins, etc. depending on the quality of the recovered treated water. In addition, the ion exchange resin may be either regenerated or non-regenerated, but regenerated resins are preferred in order to treat large amounts of recovered treated water that contains relatively high levels of impurities.

[0069] In reverse osmosis membrane treatment, recovered treated water is passed through a reverse osmosis membrane to remove salts from the recovered treated water. For reverse osmosis membrane treatment, any of ultra-low pressure, low pressure, medium pressure, and high pressure reverse osmosis membranes may be used, but ultra-low pressure or low pressure reverse osmosis membranes are preferred. The operating pressure (design operating pressure, the same applies hereinafter) of an ultra-low pressure reverse osmosis membrane is, for example, 0.4 MPa to 0.8 MPa. The operating pressure of a low pressure reverse osmosis membrane is, for example, greater than 0.8 MPa and less than 2.0 MPa. The operating pressure of a medium pressure reverse osmosis membrane is, for example, 2 MPa to 5 MPa. The operating pressure of a high pressure reverse osmosis membrane is, for example, greater than 5 MPa and equal to or less than 8 MPa.

[0070] In the hydrogen peroxide decomposition treatment, the recovered treated water is passed through activated carbon or a catalytic resin to decompose and remove the hydrogen peroxide in the recovered treated water. The catalytic resin used here is an anion exchange resin carrying palladium (Pd), or the like.

[0071] The recovered treated water obtained by the wastewater treatment device 50 or wastewater treatment method of this embodiment can be supplied to a pure water production system or an ultrapure water production system for reuse. The wastewater treatment method of this embodiment uses the wastewater strainer 1 and wastewater treatment device 50 described above, so that fine particles such as abrasive grains can be stably and thoroughly removed from wastewater without causing strainer corrosion or failure due to insufficient strainer strength. This significantly reduces the occurrence of problems in the devices downstream of the wastewater treatment device 50 that perform ion exchange treatment, reverse osmosis membrane treatment, and hydrogen peroxide decomposition treatment.

[0072] [Correction based on Rule 91 25.02.2025] 1...Strainer for producing pure water, 11...Filter body, 11a...Filter surface, 12...Cap member, 13...First connecting part, 131...First connecting body, 131a...Groove portion, 132...Second connecting body, 132a...Crooked portion, 133...Third connecting body, 134...Threaded hole, 146a, 146b...Sealing member, 142...Screw member, 15...Housing, 15a...Water outlet, 15b...Water inlet, 18...Second connecting part, 20...Discharge pipe, 24...Discharge pipe main body, 22, 151...Flange portion, 144a...Thread screw member, 144b...screw fastening member, 148...fourth connector, 50...wastewater treatment device, 51...wastewater supply device, 1A, 1B, 1C...strainer, 51a, 51b, 51c...liquid supply pipe, 52a, 52b, 52c, 53...discharge pipe, 54a, 54b, 54c...backwash pipe, V1a, V1b, V1c, V3, V4a, V4b, V4c...valve, S51...wastewater treatment process, S52...backwash process, S80...assembly process, S82...fluororesin film forming process, S84...connection process

Claims

1. A drainage strainer comprising a cylindrical filter body that is open at both ends and has a plurality of filtering holes on the side, and a cap member that is liquid-tightly adhered to one end of the filter body, wherein the filter body comprises a filter body body made of metal and a fluororesin membrane provided on the entire surface of the filter body body, and the cap member is convex toward the outside of the filter body, and the entire liquid-contacting surface is made of fluororesin.

2. The drain strainer according to claim 1, wherein the size of the filter holes is 0.01 mm or more and 0.2 mm or less.

3. A drain strainer as claimed in claim 1 or 2, further comprising a cylindrical housing having a water outlet at one end and a water inlet at the other end, the housing containing the filter body and the cap member so that the cap member faces the water inlet of the housing, and the opening of the filter body and the water outlet of the housing are in communication.

4. The drain strainer according to claim 3, wherein the housing and the filter body are cylindrical, and the cap member is shaped like a solid cone or a solid hemisphere.

5. The drain strainer according to claim 3, wherein the open end of the filter body is connected to the discharge port of the housing.

6. The drain strainer according to claim 1 or 2, further comprising a connecting portion that connects the filter body and the cap member.

7. A drainage strainer according to claim 6, wherein the connecting portion comprises a screw member that penetrates the cap member and the end face of the filter body.

8. The drain strainer according to claim 1 or 2, wherein the fluororesin membrane and the fluororesin contain polytetrafluoroethylene.

9. A drain strainer as described in claim 1 or 2, wherein when a comparative sample is prepared and the drain strainer and the comparative sample are immersed in hydrogen peroxide for one day, and the iron (Fe) concentration in the hydrogen peroxide solution is compared, the iron concentration in the hydrogen peroxide solution in which the drain strainer is immersed is significantly lower.

10. A wastewater treatment device comprising: a first drainage strainer and a second drainage strainer connected in parallel; a wastewater treatment mechanism that supplies polishing wastewater to the first drainage strainer to produce treated water; and a backwash mechanism that uses a portion of the treated water to backwash the second drainage strainer, wherein both the first drainage strainer and the second drainage strainer are the drainage strainers defined in claim 1 or 2.

11. The wastewater treatment mechanism comprises: a wastewater supply device for supplying the polishing wastewater; a first liquid feed pipe for feeding the polishing wastewater to a first wastewater strainer; a first liquid feed valve provided in the first liquid feed pipe; a second liquid feed pipe for feeding the polishing wastewater to a second wastewater strainer; a second liquid feed valve provided in the second liquid feed pipe; a first discharge pipe for discharging treated water from the first wastewater strainer; a second discharge pipe for discharging treated water from the second wastewater strainer; and a collection discharge pipe connected to the first discharge pipe and the second discharge pipe for sending the treated water to the outside; and the backwash mechanism comprises: a variable opening valve provided in the collection discharge pipe; a first backwash pipe provided branching off from the first liquid feed pipe; a second backwash pipe provided branching off from the second liquid feed pipe; and a first backwash valve provided in the first backwash pipe. and a second backwash valve provided in a second backwash pipe, wherein the wastewater treatment mechanism selects and opens a first liquid supply valve and selects and closes a second liquid supply valve so that the polishing wastewater supplied from the wastewater supply device passes through a first drainage strainer, and the backwash mechanism selects and closes the first backwash valve and selects and opens a second backwash valve, and is controlled to narrow the opening of the variable opening valve so that a portion of the treated water in the first drainage strainer passes through a second discharge pipe to the second drainage strainer in the backwash direction.

12. A wastewater treatment method for filtering polished wastewater with a strainer, comprising: a wastewater treatment step of filtering the polished wastewater with a plurality of drainage strainers connected in parallel to obtain treated water; and a backwash step of supplying the polished wastewater to one or more of the plurality of drainage strainers to produce treated water, and passing the treated water in a backwash direction through drainage strainers other than the drainage strainer to which the polished wastewater is supplied to perform backwashing, wherein all of the plurality of drainage strainers are drainage strainers as defined in claim 1 or 2.

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