Drainage filter, drainage treatment device, and drainage treatment method

Abstract

A kind of filter for drainage that can simply and stably remove trace of abrasive particles such as abrasive particles contained in abrasive drainage, and the processing device and processing method of abrasive drainage using the filter for drainage. The filter for drainage (1) has a cylindrical filter body (11) with two ends open and a plurality of filter holes on the side, and a cover member (12) liquid-tightly bonded to one end of the filter body (11), the filter body (11) is provided with a filter body main body composed of metal and a fluororesin film provided on the entire surface of the filter body main body, the cover member (12) is convex towards the outside of the filter body main body (11), and the entire liquid receiving surface is composed of fluororesin.

Description

Technical Field

[0001] This invention relates to a drainage filter, as well as a drainage treatment apparatus and a drainage treatment method using the drainage filter. Background Technology

[0002] In the semiconductor device manufacturing process, surface polishing based on CMP (chemical mechanical polishing) is performed to planarize the surface of semiconductor wafers. In CMP, a CMP polishing slurry is supplied to the surface of the semiconductor wafer while the surface is polished using a polishing pad or similar material. The CMP polishing slurry typically consists of a dispersion of fine abrasive particles such as silicon dioxide (SiO2), cerium oxide (CeO2), and aluminum oxide (Al2O3), with the addition of alkalis such as ammonia or potassium hydroxide as processing promoters. Furthermore, after CMP polishing, the abrasive particles adhering to the semiconductor wafer surface are removed using a cleaning solution. Ammonia or an aqueous solution of ammonia and hydrogen peroxide is used as the cleaning solution.

[0003] The polishing wastewater generated during CMP contains, in addition to polishing slurry, polishing debris from semiconductor wafers and polishing pads used in the polishing process. It may also contain used cleaning fluid discharged during the cleaning process.

[0004] Most of this grinding wastewater is typically discharged into the environment after undergoing treatments such as neutralization, decomposition, and dilution. However, thicker or less readily decomposed wastewater is collected and treated by wastewater treatment companies. Grinding wastewater with relatively low impurity (grinding slurry) concentrations is reused as recycled water after prescribed treatment, such as as raw water for pure water production, air conditioning water, and miscellaneous water use in factories. Furthermore, grinding wastewater is sometimes mixed with other acidic or alkaline wastewater to obtain recycled water.

[0005] As a method for treating grinding wastewater to obtain recycled water, one known method involves adding a coagulant to the concentrated water after passing the grinding wastewater through a separation membrane such as an ultrafiltration membrane or a microfiltration membrane, and then performing solid-liquid separation on the coagulants to obtain recycled water as a liquid phase (for example, see Patent Document 1). Furthermore, another known method involves adding a coagulant after oxidizing the grinding wastewater, and then performing solid-liquid separation on the coagulants to obtain recycled water as a liquid phase (for example, see Patent Document 2).

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 11-347569 Patent Document 2: Japanese Patent Application Publication No. 2001-170652 Summary of the Invention

[0007] The problem that the invention aims to solve However, in methods of adding coagulants to grinding wastewater, pH adjustment is usually performed to achieve effective coagulation, which leads to an increase in the amount of acid and alkali used. Furthermore, coagulants, especially polymeric coagulants, tend to remain in the treated water, easily causing malfunctions and other problems in water treatment equipment.

[0008] Furthermore, grinding wastewater with low slurry concentration (diluted slurry wastewater), despite its low concentration, still contains acids, alkalis, hydrogen peroxide, and abrasive particles, making reuse difficult. For example, trace amounts of residual abrasive particles in the wastewater can cause malfunctions in ion exchange and membrane treatment devices. Therefore, it is preferable to perform ion exchange or membrane treatment on the grinding wastewater after removing the abrasive particles. While using filter cartridges to filter grinding wastewater is considered, attempting to filter wastewater containing acids and hydrogen peroxide using metal cartridges such as stainless steel would result in the filter cartridge components dissolving within days, making it impossible to remove abrasive particles from the wastewater using such metal cartridges. Additionally, although fluoropolymer filter cartridges have high resistance to chemicals such as acids and alkalis, their low mechanical strength can cause problems when filtering large volumes of wastewater generated in semiconductor manufacturing processes, such as reduced filtration performance due to deformation during water flow.

[0009] The present invention was made to solve the above-mentioned problems, and its object is to provide a drainage filter that can easily and stably remove trace amounts of abrasive particles and other microparticles contained in grinding drainage, as well as a treatment apparatus and treatment method for grinding drainage using the drainage filter.

[0010] Solution for solving the problem The drainage filter, drainage treatment device, or drainage treatment method according to embodiments of the present invention are as follows.

[0011] [1] A drainage filter having a cylindrical filter body with openings at both ends and multiple filter holes on the sides, and a cover member liquid-tightly bonded to one end of the filter body. The filter body comprises a filter body body made of metal and a fluoropolymer membrane disposed on the entire surface of the filter body body. The cover member faces outward from the filter body and is convex, with the entire liquid-contacting surface made of fluororesin.

[0012] [2] The drainage filter according to [1], wherein, The size of the filter pores is greater than 0.01 mm and less than 0.2 mm.

[0013] [3] The drainage filter according to [1] or [2], wherein, It also has a cylindrical outer shell. The outer casing has a water outlet at one end and a water inlet at the other end. The housing accommodates the filter body and the cover member with the cover member facing the water inlet of the housing. The opening of the filter body is connected to the water outlet of the outer shell.

[0014] [4] The drainage filter according to [3], wherein, The outer shell and the filter body are cylindrical. The cover component is a solid cone or a solid hemisphere.

[0015] [5] The drainage filter according to [3], wherein, The open end of the filter body is connected to the water outlet of the outer shell.

[0016] [6] A drainage filter according to [1] or [2], wherein, The drainage filter has a connecting portion that connects the filter body and the cover member.

[0017] [7] The drainage filter according to [6], wherein, The connecting part has a threaded member that passes through the end face of the cover member and the filter body.

[0018] [8] A drainage filter according to any one of [1], [2], [6] and [7], wherein, The fluoropolymer membrane and the fluoropolymer contain polytetrafluoroethylene.

[0019] [9] A drainage filter according to any one of [1], [2], [6] to [8], wherein, To prepare a comparison sample, after immersing the drainage filter and the comparison sample in hydrogen peroxide for one day, the iron (Fe) concentration in the hydrogen peroxide was compared. The iron concentration in the hydrogen peroxide sample immersed in the drainage filter was significantly reduced.

[0020]

[10] A drainage treatment device, comprising: A first and a second drainage filter connected in parallel; The wastewater treatment unit supplies abrasive wastewater to the first wastewater filter to produce treated water; and The backwashing mechanism uses a portion of the treated water to backwash the second drain filter. The first drainage filter and the second drainage filter are both drainage filters as described in any one of [1], [2], [6] to [9].

[0021]

[11] According to the drainage treatment device described in

[10] , wherein, The drainage treatment mechanism includes: A drainage supply device is used to supply the grinding wastewater. The first liquid delivery pipe delivers the grinding wastewater to the first drainage filter; The first liquid delivery valve is located in the first liquid delivery pipe; The second liquid delivery pipe transports the grinding wastewater to the second drainage filter; The second liquid delivery valve is located in the second liquid delivery pipe; The first discharge pipe discharges the treated water from the first drainage filter; The second discharge pipe discharges the treated water from the second drainage filter; and A collection and discharge pipe is connected to the first and second discharge pipes, and the treated water is transported to the outside. The backwashing mechanism includes: A variable-opening valve is installed in the collection and discharge pipe; The first backwash tube has a branch located on the first liquid delivery tube; The second backwash tube is branched off from the second liquid delivery tube; A first backwash valve is located in the first backwash pipe; and The second backwash valve is located in the second backwash pipe. The drainage treatment mechanism selectively opens the first liquid delivery valve to allow the grinding drainage supplied from the drainage supply device to pass through the first drainage filter, and selectively closes the second liquid delivery valve. The backwash mechanism is controlled to selectively close the first backwash valve and selectively open the second backwash valve so that a portion of the treated water from the first drain filter passes through the second drain filter in the backwash direction via the second discharge pipe, and to narrow the opening of the variable valve.

[0022]

[12] A wastewater treatment method comprising filtering and grinding wastewater using a filter, the wastewater treatment method comprising: The wastewater treatment process involves filtering and grinding wastewater through multiple wastewater filters connected in parallel to obtain treated water; and In the backwashing process, grinding wastewater is supplied to one or more of the plurality of drainage filters to generate treated water, and the treated water is then backwashed by passing it through drainage filters other than the one to which the grinding wastewater was supplied. The plurality of drainage filters are drainage filters as described in any one of [1], [2], [6] to [9].

[0023] It should be noted that the symbol “~” indicates the range of values ​​including the values ​​before and after it.

[0024] Invention Effects The drainage filter according to the embodiment can easily and reliably remove trace amounts of abrasive particles and other fine particles contained in the grinding drainage.

[0025] The grinding drainage treatment apparatus or method according to the embodiments can easily and stably remove trace amounts of abrasive particles and other microparticles contained in the grinding drainage. Attached Figure Description

[0026] Figure 1 This is a schematic cross-sectional view of a drainage filter according to an embodiment.

[0027] Figure 2 This is a schematic cross-sectional view of the first connection 13 in other ways.

[0028] Figure 3 This is a flowchart that schematically illustrates a method for manufacturing a drainage filter according to an embodiment.

[0029] Figure 4 This is a block diagram that schematically illustrates a drainage treatment apparatus according to an embodiment.

[0030] Figure 5 This is a flowchart illustrating the drainage treatment method of the implementation method. Detailed Implementation

[0031] [Drainage filter] Hereinafter, a drainage filter according to an embodiment of the present invention will be described. Figure 1 This is a schematic cross-sectional view of a drainage filter 1 according to an embodiment. The drainage filter 1 of this embodiment includes a cylindrical filter body 11 with openings at both ends and a cover member 12. The side surface of the filter body 11 has multiple filter holes, forming a filter surface 11a. In the drainage filter 1, as the water to be treated flows from the filter surface 11a on the side surface of the filter body 11 into the interior of the filter body 11, impurities such as abrasive particles and abrasive debris in the drainage are removed, and the treated water flows out from the opening at the downstream end of the filter body 11. Hereinafter, the two ends of the filter body 11 will be referred to as the upstream end and the downstream end, depending on the flow of water through the filter body 11.

[0032] The filter element 11 comprises a filter element body made of metal and a fluoropolymer membrane disposed on its entire surface. The fluoropolymer membrane spans the entire surface of the filter element body; specifically, the liquid-contacting surfaces of the filter element 11, such as the filter surface, the surface of the filter pores, and the inner wall surface of the filter element, are all covered by the fluoropolymer membrane. Regarding the metal constituting the filter element body, examples include stainless steel (SUS) such as SUS304, SUS316, SUS316L, and SUS304. From the perspective of strength and corrosion resistance, SUS316 or SUS316L is preferred. The filter element body is composed, for example, of a filter element and multiple rod-shaped support members. The filter element is composed of a spirally wound wire, and the multiple rod-shaped support members are arranged along the spiral length direction of the filter element and are separated in the circumferential direction of the spiral. The cross-sectional shape of the wire is, for example, triangular, and the wire is arranged with the apex of the triangle facing inwards towards the filter element, forming a gap between the spiral wire and the support members that functions as filter pores. The gap in the support member (the size of the filter hole) only needs to be small enough to prevent grinding debris and particles in the grinding slurry from passing through, for example, 0.01 mm to 0.2 mm, preferably 0.02 mm to 0.1 mm. Furthermore, the filter body 11 is, for example, a cylinder with an outer diameter of 15 mmφ to 220 mmφ or 15 mmφ to 165 mmφ. When the filter body 11 is composed of a filter element and a support member as described above, the shape of the filter hole is usually quadrilateral, and the size of the filter hole in this case represents the length of one side of the quadrilateral. When the shape of the filter hole is rectangular, the size of the filter hole represents the length of the shorter side of the rectangle. Furthermore, when the filter hole has other shapes, the size of the filter hole only needs to be a minimum length of 0.01 mm to 0.2 mm, preferably 0.02 mm to 0.1 mm, to prevent grinding debris, grinding particles, and other fine particles from passing through. It should be noted that, during the initial water flow, concentrated slurry can also be supplied to the drainage filter 1 for drainage. In this case, by supplying the concentrated slurry to the drainage filter 1, a filter cake (filtered slurry layer) (referred to as a pre-coating layer) is formed on the filter surface 11a of the drainage filter 1. This filter cake functions as a filter layer, thus improving the filtration accuracy. In this case, the size of the gaps in the support members is not limited, allowing the filtration of even smaller grinding debris and particles. It should be noted that this operation is performed immediately after each backwash.

[0033] The drainage filter 1 of this embodiment, for example, is manufactured as described later in the drainage filter manufacturing method, by forming a fluoropolymer membrane on the surface of a filter body 11 with openings at both ends, and then connecting a cover member 12, thereby allowing easy lining or coating of the surface of the filter body 11. Therefore, even for complex shapes with many filter holes, the fluoropolymer membrane can be formed easily and uniformly. If the lining or coating is insufficient, the fluoropolymer membrane may have defects such as pinholes, and even small defects can lead to the generation of resin fragments and the leaching of iron from the SUS surface covered by the resin. However, for example, by forming a fluoropolymer membrane on the surface of the filter body 11 with openings at both ends, a fluoropolymer membrane without the above-mentioned defects can be formed by lining or coating, and the entire liquid-contacting surface of the filter body 11 can be covered with the fluoropolymer membrane.

[0034] It should be noted that, for example, the fact that the fluoropolymer membrane is disposed on the entire surface of the filter body 11 can be confirmed by the following methods. First, for example, the drain filter is immersed in ultrapure water for 7 days, and the iron concentration in the ultrapure water after immersion is measured. At the same time, under the same conditions, the iron concentration in the ultrapure water after immersion is measured by immersion in a fluoropolymer sheet having the same or equal (error ±5%) surface area as the drain filter, or an SUS sheet that has been lined or coated with fluoropolymer (hereinafter, both are referred to as "comparative samples"). It can also be confirmed by comparing the measured values ​​obtained from the drain filter and the comparative samples to determine whether there is a significant difference between the iron concentration in the ultrapure water impregnated with the drain filter and the iron concentration in the ultrapure water impregnated with the comparative samples. In this case, for example, based on the iron concentration obtained by measuring the iron concentration in the ultrapure water impregnated with multiple comparative samples, and using a significance level of 2.5%, if the iron concentration in the ultrapure water impregnated with the drain filter is set as F samp The average value calculated based on the iron concentration in the ultrapure water impregnated with the comparative sample is denoted as F. ave If the standard deviation is set as σ, then in F samp ≤F aveIn the case of +1.96×σ, it can be determined that a fluoropolymer membrane is present on the entire surface of the filter body 11. Similarly, this can also be determined by repeatedly measuring the iron concentration in the ultrapure water in which a comparative sample is immersed. It should be noted that the test method is preferably based on, for example, the leaching test method for piping materials for ultrapure water according to UC standard specifications (UCS12 Semiconductor Industry Development and UCS12 Results, edited by the Semiconductor Base Technology Research Association, published September 28, 2002, ISBN 4898080278, pp. 1181-1188). When using this method, since it is a non-flowing system, the leaching material can dissolve in a small amount of ultrapure water, thus becoming an accelerated test and easily measurable. Thirdly, as a further accelerated test, it can be confirmed by using an aqueous solution of hydrogen peroxide or sulfuric acid or a mixture thereof instead of ultrapure water in the second method, otherwise using the same method as the second method. In this case, the immersion time can be measured, for example, in about one day.

[0035] In the drainage filter 1, the cover member 12 is liquid-tightly bonded to the upstream end of the filter body 11. The cover member 12 has a convex shape extending outward from the upstream end of the filter body 11, and at least the liquid-contact surface is made of fluororesin. The cover member 12 may also be composed of a cover member body made of metal such as SUS and a fluororesin membrane provided on the surface of the cover member body, and the entire cover member may also be made of fluororesin. Due to its light weight and ease of operation, it is preferable that the entire cover member 12 is made of fluororesin. The cover member may be hollow or solid, but from the perspective of ease of manufacture, a solid cover member is preferred, and more preferably, the entire cover member 12 is made of solid fluororesin.

[0036] Preferably, the cover member 12 has at least a bottom surface and a side surface rising from the bottom surface. The bottom surface of the cover member 12, i.e., the opposite side of the convexity, is connected to the opening at the upstream end of the filter body 11 via the first connecting portion 13. As for the convex shape of the cover member 12, examples include a convex cross-section, i.e., a cover member with a cross-section perpendicular to the bottom surface and passing through the point farthest from the bottom surface that is a polygon, quadrilateral, triangle, semicircle, etc.

[0037] Preferably, the convex shape of the cover member 12 is such that it does not generate flow deviation or eddy current in the water flow on the surface of the cover member 12. If flow deviation or eddy current occurs in the water flow on the surface of the convex cover member 12, the filter will vibrate due to the water flow. Since the drainage treatment device operates continuously for at least one year, and sometimes for several years, the long-term vibration of the filter will promote the deterioration of the fluoropolymer membrane on the filter surface, potentially causing the generation of resin fragments and the leaching of iron from the resin-covered SUS surface. Specifically, a triangular, semi-circular, or semi-elliptical convex cross-section is preferred as a way to prevent such flow deviation or eddy current. In the case of a triangular convex cross-section, for example, one side of the triangle is located on the upstream end side of the filter body 11. In the case of a semi-circular convex cross-section, for example, the diameter of the semicircle is located on the upstream end side of the filter body 11. In the case of a semi-elliptical convex cross-section, for example, the major or minor axis of the semi-ellipse is located on the upstream end side of the filter body 11. As for the convex shape of the cover member 12, for example, when the opening of the filter body 11 is circular, a hemisphere, a semi-ellipsoid, or a cone is preferred from the viewpoint that it is not easy to cause flow deviation on the surface of the cover member 12. In particular, when the shape of the cover member 12 is conical, the inclination of the side from the apex to the bottom surface is fixed, so the flow rectification effect of drainage can also be obtained, which is more preferred.

[0038] The outer diameter of the cover member 12 is preferably the same as, or approximately the same as, the outer diameter of the opening of the filter body 11 and is larger than the outer diameter of the opening of the filter body 11. As a result, the water flow around the first connection 13 between the filter body 11 and the cover member 12 can be adjusted, thereby suppressing the deterioration of the lining or coating as described above.

[0039] The fluororesin used for the cover member 12 and the fluororesin membrane on the surface of the filter body 11 is not particularly limited; examples include tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane), polytetrafluoroethylene (PTFE), and ethylene / tetrafluoroethylene copolymer (ETFE). The fluororesin used for the cover member 12 and the fluororesin membrane on the surface of the filter body 11 can be the same or different, but are preferably the same. The cover member can be made of stainless steel, polypropylene, or polyethylene. In these cases, it is preferable to use fluorinated raw materials for surface coating or lining.

[0040] When using ETFE as a fluoropolymer, to control crystallinity, ETFE is preferably a substance obtained by copolymerizing ethylene and tetrafluoroethylene with other fluorinated monomers. As for the other fluorinated monomers mentioned above, there are no particular limitations as long as they can be added to both ethylene and tetrafluoroethylene, but fluorinated vinyl monomers with 3 to 8 carbon atoms are readily used; examples include hexafluoroisobutylene and CH2=CFC3F6H. From the viewpoint of not impairing heat resistance, flame retardancy, and chemical resistance, the other fluorinated monomers mentioned above are preferably 5 mol% or less of the total monomer content of the ETFE.

[0041] When ETFE is a substance obtained by copolymerizing other fluorinated monomers, the fluorine content in the ETFE is preferably 50% by mass or more. A fluorine content of 50% by mass or more provides excellent heat resistance, flame retardancy, and chemical resistance. For example, the fluorine content of ETFE is 70% by mass or less. The fluorine content can be adjusted by appropriately regulating the ratio of ethylene, tetrafluoroethylene, and the other monomers mentioned above used as needed. The aforementioned fluorine content is obtained by burning the fluoropolymer, causing the fluorine contained therein to be absorbed into alkaline water, etc., and then measuring it using an ion chromatograph or the like.

[0042] Among the aforementioned fluororesins, tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane) and polytetrafluoroethylene (PTFE) resin are widely and commonly used raw materials in ultrapure water production equipment due to their excellent heat resistance and chemical resistance, and can be appropriately used for fluororesin membranes on cover component 12 and filter body 11.

[0043] The first connecting portion 13 is not particularly limited as long as it can liquid-tightly connect the filter body 11 and the cover member 12. Examples of the first connecting portion 13 include those formed by soldering, fusion, welding, etc., where the material state of the connecting portion changes during connection. Alternatively, it can be a mechanically structurally connected portion, such as one or more threaded components, without a change in the material state of the connecting portion during connection. The first connecting portion 13 is preferably a mechanically structurally connected portion so as not to cause defects in the fluoropolymer film on the surface of the filter body 11 when connecting the filter body 11 and the cover member 12.

[0044] like Figure 1 As shown, for example, a first connector 131 with a mountain-shaped portion 131a on its outer surface is connected to the bottom surface of the cover member 12, and a cylindrical second connector 132 with a spiral groove 132a on its inner wall that engages with the mountain-shaped portion is connected to the upstream end of the filter body 11. The filter body 11 and the cover member 12 can be connected by the engagement of the mountain-shaped portion 131a of the first connector 131 and the groove 132a of the second connector 132. In this case, the first connector 13 includes a first connector 131, a mountain-shaped portion 131a provided in the first connector 131, a second connector 132, and a groove 132a provided in the second connector 132. Alternatively, instead of the first connector 131 having a mountain-shaped portion and the second connector 132 having a groove, the first connector 131 may have a groove, and the inner wall of the second connector 132 may have a mountain-shaped portion. To improve the liquid tightness between the filter body 11 and the cover member 12, a sealing member such as an O-ring made of resin can be sandwiched between the end face of the second connector 132 of the filter body 11 and the outer periphery of the bottom surface of the cover member 12.

[0045] Figure 2This is a schematic cross-sectional view of the first connection portion 13 in other configurations. For example... Figure 2 As shown, a third connector 133 is provided on the end face of the upstream end of the filter body 11. The third connector 133, for example, is arranged along the periphery of the upstream end of the filter body 11 and is a solid annular shape with thickness in both the axial and circumferential directions. A plurality of threaded holes 134 are provided near the outer periphery of the cover member 12, through which threaded members 142, etc., pass through the cover member 12 and the third connector 133, thereby connecting the filter body 11 and the cover member 12. In this case, the first connecting portion 13 includes the cover member 12 and the threaded members 142 that pass through the cover member 12 and are inserted into the third connector 133. It should be noted that, in order to improve the liquid tightness between the filter body 11 and the cover member 12, a sealing member such as an O-ring formed of resin may also be sandwiched between the end face of the upstream end of the third connector 133 and the bottom surface of the cover member 12. In this case, the first connecting portion 13 also includes a sealing member.

[0046] like Figure 2 As shown, when using threaded member 142 to connect filter body 11 and cover member 12, water may accumulate on or near the surface (thread head) of threaded member 142, and iron may leach out if threaded member 142 is metal. Therefore, if there is a depression on or near the surface of threaded member 142, it is preferable to fill the depression with fluororesin to form a protective portion. The material of the protective portion in this case can be a different fluororesin than that of cover member 12, or it can be the same fluororesin, but it is preferable to use the same fluororesin.

[0047] Figure 1 The drainage filter 1 shown also includes a cylindrical outer shell 15 that houses the filter body 11. The outer shell 15 internally houses the entire filter body 11. At both ends of the outer shell 15, there is a discharge port 15a at the downstream end and a water inlet 15b at the upstream end. The outer shell 15 can be a continuous cylindrical shape with a fixed inner diameter, or it can be a shape in which multiple cylindrical sections with different inner diameters are continuously connected. In addition, a portion of the cylinder, particularly at both ends or one end, may have a tapered shape with the diameter decreasing towards the end. It should be noted that a fluoropolymer membrane is preferably provided on the inner surface of the outer shell 15, and, if necessary, on the liquid-contacting surface outside the inner surface. The fluoropolymer membrane on the inner surface of the outer shell 15, like that of the filter body 11, can be formed by lining or coating.

[0048] In the drainage filter 1, the filter body 11 and the cover member 12 are arranged and housed within the housing 15 with the cover member 12 facing the water inlet 15b of the housing 15. Furthermore, the opening at the downstream end of the filter body 11 communicates with the water outlet 15a of the housing 15, and the treated water that has passed through the filter surface 11a of the filter body 11 is discharged from the water outlet 15a of the housing.

[0049] The filter element 11 and the outer casing 15 are connected via a second connecting portion 18. The second connecting portion 18 is not particularly limited as long as it allows for a liquid-tight connection between the filter element 11 and the outer casing 15. Figure 1 In the drainage filter 1 shown, the outlet pipe 20 is connected to the housing 15 via a second connecting portion 18. The outlet pipe 20 has an outlet pipe body 24 and a flange portion 22 that is continuously disposed along the outer circumferential direction from the upstream end of the outlet pipe body 24. A threaded hole is provided in the flange portion 22. The housing 15 has a flange portion 151 that is continuously disposed along the outer circumferential direction from the downstream end of the housing 15, and a threaded hole is provided in the flange portion 151. Furthermore, a fourth connecting body 148 is connected to the downstream end of the filter body 11. The fourth connecting body 148 is disposed along the periphery of the downstream end of the filter body 11 and is a solid annular shape with thickness in both the axial and circumferential directions. A portion of the outer diameter of the downstream end side of the outer periphery of the fourth connecting body 148 (the side opposite to the side connected to the downstream end of the filter body 11) is larger than that of the upstream end, and a cutout is provided for the flange portion 151 to fit into.

[0050] In the drainage filter 1, a cutout of a fourth connector 148 is provided between the flange portion 151 and the flange portion 22, allowing a threaded member 144a to pass through the threaded holes of the flange portion 151 and the flange portion 22. The threaded member 144a is fixed by a threaded fixing member 144b, thus forming a second connection portion 18. That is, the second connection portion 18 includes the flange portion 151 and the fourth connector 148, the flange portion 22, the threaded member 144a passing through the flange portion 151 and the flange portion 22, and the threaded fixing member 144b. It should be noted that sealing members such as O-rings formed of resin can also be sandwiched between the cutout of the flange portion 151 and the fourth connector 148, and between the downstream end face of the fourth connector 148 and the flange portion 22, respectively, to improve the liquid tightness of the second connection portion 18. In this case, the second connection portion 18 also includes sealing members 146a and 146b.

[0051] Next, other connection methods between the filter body 11 and the housing 15 will be described. In this method, a connection with... Figure 1The filter body 11 and the cover member 12 shown have the same connection structure. That is, a cylindrical sixth connector with a spiral groove on its inner wall is connected to the upstream end of the outlet pipe 20, and a cylindrical fifth connector with a bevel on its outer surface that screws into the groove is connected to the downstream end of the filter body 11, and the connection is achieved by the screwing of the groove and the bevel. In this case, the second connection part 18 includes a fifth connector, a bevel provided on the fifth connector, a sixth connector, and a groove provided on the inner wall of the sixth connector. Alternatively, instead of having a bevel on the inner wall of the fifth connector and a groove on the sixth connector, the inner wall of the fifth connector may have a groove, and the sixth connector may have a bevel. To improve the liquid tightness between the filter body 11 and the outer casing 15, a sealing member such as an O-ring formed of resin may be sandwiched between the end face of the downstream end of the fifth connector and the end face of the upstream end of the sixth connector. In this case, the second connection part 18 also includes a sealing member.

[0052] [Manufacturing method of drainage filter] The manufacturing method of the drainage filter according to this embodiment will be described. Figure 3 This is a flowchart that schematically illustrates a method for manufacturing a drainage filter according to an embodiment. Figure 3 The method for manufacturing a drainage filter shown includes: an assembly step S80, assembling a filter body 11; a fluoropolymer membrane forming step S82, forming a fluoropolymer membrane on the surface of the filter body; and a connection step S84, connecting a cover member 12 and each connector (a first connector, a second connector, or a third connector) to the filter body 11 on which the fluoropolymer membrane is formed.

[0053] First, in assembly step S80, the filter body 11 is assembled. In assembly step S80, a commercially available bag-shaped filter with a sealed upstream end and an open downstream end can also be used as raw material, and the filter body 11 of the embodiment is obtained by opening the upstream end of the filter.

[0054] Next, in the fluoropolymer membrane forming step S82, the aforementioned fluoropolymer membrane is formed on the surface of the filter body. The method for forming the fluoropolymer membrane can be a coating method such as dip coating, spray coating, electrostatic coating, brush coating, or roller coating, or a lining method such as electrostatic powder coating or sheet lining. Spray coating is preferred for uniformly forming the fluoropolymer membrane on the inner surface of the filter pores. The thickness of the fluoropolymer membrane on the surface of the filter body 11 formed in this way is typically about 200 μm to 300 μm.

[0055] Next, the cover member 12 and each connector are connected to the filter body 11 as described above. Furthermore, the filter body 11 with the cover member 12 attached is housed in the outer casing 15 as needed. When using a hollow or solid cover member 12 made of fluororesin, the cover member 12 can be obtained by machining the fluororesin block using a machine tool or the like after the fluororesin has been formed into a block. More specifically, a cylindrical fluororesin rod can be cut from the fluororesin block, or the desired shape can be manufactured by machining the fluororesin rod after it has been formed into a cylindrical shape. It should be noted that since the cover member 12 is solid, drainage can be prevented from stagnating inside the cover. Therefore, since the cover member 12 is solid, it does not contribute to the main factors of water quality deterioration, and is therefore preferred.

[0056] It should be noted that, in the above description, the scheme of connecting each connector after forming a fluoropolymer membrane on the filter body 11 has been explained. However, it is also possible to form a fluoropolymer membrane after connecting each connector to the filter body 11. In the manufacturing method of the drainage filter of this embodiment, by forming a fluoropolymer membrane on the surface of the filter body 11 which is open at both ends, lining or coating can be easily performed. Therefore, although it has a complex shape with many filter holes, the fluoropolymer membrane can be formed easily and uniformly. If the lining or coating is insufficient, the fluoropolymer membrane will have defects such as pinholes. Even small defects can lead to corrosion of the filter due to drainage treatment. As a result, the filtration accuracy decreases, and the filter surface is prone to disappearance. However, by forming a fluoropolymer membrane on the surface of the filter body 11 which is open at both ends, a fluoropolymer membrane without the above-mentioned defects can be formed by lining or coating, and a drainage filter suitable for grinding drainage treatment can be obtained.

[0057] [Drainage treatment apparatus and methods] Next, the drainage treatment apparatus and drainage treatment method of this embodiment will be described. The drainage treatment apparatus of this embodiment includes a first drainage filter and a second drainage filter connected in parallel. The drainage treatment apparatus of this embodiment includes a drainage treatment mechanism that supplies abrasive drainage to the first drainage filter to generate treated water, and a backwashing mechanism that uses a portion of the treated water to backwash the second drainage filter. In the drainage treatment apparatus of this embodiment, both the first drainage filter and the second drainage filter are the same drainage filters as the drainage filter 1 of the above embodiment. Furthermore, both the first drainage filter and the second drainage filter may be filter groups consisting of two or more drainage filters connected in parallel.

[0058] The wastewater treatment mechanism includes: a wastewater supply device; a first supply pipe for conveying grinding wastewater to a first wastewater filter and a second supply pipe for conveying grinding wastewater to a second wastewater filter; a first discharge pipe connected to the first wastewater filter and discharging treated water from the first wastewater filter; and a second discharge pipe connected to the second wastewater filter and discharging treated water from the second wastewater filter. Furthermore, the wastewater treatment mechanism includes a first supply valve provided on the first supply pipe and a second supply valve provided on the second supply pipe. The wastewater treatment mechanism also includes a collection and discharge pipe connected to the first and second discharge pipes, which collects the treated water and discharges it to the outside.

[0059] The backwashing mechanism includes: a variable opening valve located in the path of the collection and discharge pipe, a first backwashing pipe branching off to the first liquid delivery pipe, a second backwashing pipe branching off to the second liquid delivery pipe, a first backwashing valve located in the path of the first backwashing pipe, and a second backwashing valve located in the path of the second backwashing pipe.

[0060] Then, the drainage treatment mechanism selectively opens the first liquid delivery valve to allow the grinding drainage supplied from the drainage supply device to pass through the first drainage filter. At the same time, the backwashing mechanism selectively closes the first backwash valve provided in the first backwash pipe and the second liquid delivery valve provided in the second liquid delivery pipe, and selectively opens the second backwash valve provided in the second backwash pipe to allow a portion of the treated water obtained from the first drainage filter to pass through the second drainage filter in the backwashing direction. The opening of the variable valve, which is controlled to narrow the path of the collection discharge pipe, is also controlled.

[0061] It should be noted that when the first drainage filter or the second drainage filter is a filter group consisting of two or more drainage filters connected in parallel, the first liquid delivery valve and the first backwash valve, as well as the second liquid delivery valve and the second backwash valve, can also be liquid delivery valve groups or backwash valve groups, each having multiple valves. Similarly, the first liquid delivery pipe and the first discharge pipe and the first backwash pipe, as well as the second liquid delivery pipe, the second discharge pipe, and the second backwash pipe, can also be liquid delivery pipe groups, discharge pipe groups, or backwash pipe groups, each having multiple piping.

[0062] Wastewater treated by wastewater treatment devices is typically grinding wastewater. Grinding wastewater is generated by grinding a workpiece using a grinding fluid (grinding slurry) containing abrasive particles (grinding grains). Grinding wastewater contains abrasive particles and grinding debris as the main components of the grinding fluid, and sometimes also contains dispersants, grinding accelerators, etc., as any component of the grinding fluid. Abrasive particles are, for example, fine particles such as silicon dioxide (SiO2), alumina (Al2O3), cerium oxide (cerium dioxide, CeO2), zirconium oxide (ZrO2), and silicon carbide (silicon carbide, SiC). Processing accelerators are, for example, alkalis such as ammonia and potassium hydroxide. In addition, grinding wastewater may also contain cleaning fluid generated from cleaning the surface of the workpiece after grinding. As a cleaning fluid, it may be ammonia water, or an aqueous solution of ammonia and hydrogen peroxide, etc.

[0063] Examples of wastewater treatment processes include wastewater from the polishing of glass substrates and lenses using polishing slurries containing abrasive particles such as colloidal silica and cerium oxide; wastewater from the polishing (rough polishing) process in silicon wafer manufacturing using polishing slurries containing abrasive particles such as colloidal silica; wastewater from the grinding (mirror polishing) process using polishing slurries containing abrasive particles such as colloidal silica, alumina, and silicon carbide; and wastewater from the CMP process in semiconductor device manufacturing using polishing slurries containing abrasive particles such as colloidal silica, alumina, zirconium oxide, and cerium oxide. In addition to wastewater, the wastewater treated by the wastewater treatment device 50 can also be acidic or alkaline wastewater.

[0064] Next, the drainage treatment apparatus of the embodiment will be described in more detail with the help of the accompanying drawings. Figure 4 This is a block diagram schematically representing the drainage treatment apparatus 50 of this embodiment. The drainage treatment apparatus 50 includes: a drainage supply device 51 for storing and supplying grinding drainage to the drainage treatment apparatus 50, and three filters 1A, 1B, and 1C connected in parallel. Furthermore, the drainage treatment apparatus 50 includes: a delivery pipe 51a for conveying drainage to filter 1A, a delivery pipe 51b for conveying drainage to filter 1B, and a delivery pipe 51c for conveying drainage to filter 1C. Delivery pipes 51a, 51b, and 51c are respectively connected to openings at the upstream ends of filters 1A, 1B, and 1C. Valves V1a, V1b, and V1c are respectively fitted into delivery pipes 51a, 51b, and 51c.

[0065] The wastewater treatment device 50 includes: a discharge pipe 52a for discharging treated water filtered by filter 1A, a discharge pipe 52b for discharging treated water filtered by filter 1B, and a discharge pipe 52c for discharging treated water filtered by filter 1C. Discharge pipes 52a, 52b, and 52c are respectively connected to openings at the downstream ends of filters 1A, 1B, and 1C. The wastewater treatment device 50 also includes a discharge pipe (collecting discharge pipe) 53, which is connected to discharge pipes 52a, 52b, and 52c and collects the treated water discharged from these pipes. A valve V3 is fitted into the discharge pipe 53.

[0066] The wastewater treatment device 50 also includes a backwash pipe 54a, which branches off and connects to the upstream opening of the filter 1A in the path of the delivery pipe 51a between the filter 1A and valve V1a. The wastewater treatment device 50 also includes a backwash pipe 54b, which branches off and connects to the upstream opening of the filter 1B in the path of the delivery pipe 51b between the filter 1B and valve V1b. The wastewater treatment device 50 also includes a backwash pipe 54c, which branches off and connects to the upstream opening of the filter 1C in the path of the delivery pipe 51c between the filter 1C and valve V1c. Valve V4a, valve V4b, and valve V4c are respectively fitted into the backwash pipes 54a, 54b, and 54c.

[0067] Filters 1A, 1B, and 1C have the same configuration as the drainage filter 1 in the above embodiment, and the preferred embodiment is also the same. Valves V1a, V1b, V1c, V4a, V4b, and V4c are, for example, on-off valves or variable-opening valves with adjustable opening. Valve V3 is a variable-opening valve. Furthermore, the drainage treatment device 50 may also include a control device that adjusts the drainage supply amount, the opening and closing of each valve, and the opening degree of the drainage supply device 51 according to a preset program.

[0068] Next, the drainage treatment method using the drainage treatment device 50 will be explained. Figure 5 This is a flowchart illustrating the drainage treatment method of this embodiment. The drainage treatment method of this embodiment includes a drainage treatment step S51 and a backwashing step S52.

[0069] Before the drainage treatment step S51, at the front end of the drainage treatment apparatus 50, it is preferable to divide the grinding drainage into concentrated slurry drainage with a relatively high grinding slurry concentration and diluted slurry drainage with a relatively low grinding slurry concentration. This classification method is not particularly limited, but it allows for the systematic classification of the drainage being processed during the semiconductor manufacturing process based on the amount and properties of the mixed chemicals and impurities. For example, in the case of batch cleaning, most of the impurities (grinding slurry, grinding debris) and chemicals are washed away from the surface of the wafer or other object being cleaned at the initial stage of cleaning. As the cleaning process progresses, the concentration of impurities mixed into the cleaning drainage decreases. Therefore, by classifying the drainage from the front and rear ends of the cleaning process, it is possible to separate it into concentrated slurry drainage with a relatively high grinding slurry concentration and diluted slurry drainage with a relatively low grinding slurry concentration. Furthermore, the classification and recovery method using a slurry recovery device with a slurry capture bag, as described in Japanese Patent No. 5479781, can also be applied.

[0070] In the wastewater treatment step S51, the grinding wastewater is passed through the wastewater filter of the above embodiment to remove abrasive particles, grinding debris, and other fine particles. When the grinding wastewater is divided into thin slurry wastewater and thick slurry wastewater, each is passed separately through the aforementioned wastewater filter. Preferably, the thin slurry wastewater is treated in the wastewater treatment step S51, while the thick slurry wastewater is collected and treated by a wastewater treatment company or the like.

[0071] In the drainage treatment process S51, when using Figure 4 In the case of the drainage treatment device 50 shown, the grinding drainage is treated using filters 1A, 1B, and 1C. Specifically, valves V1a, V1b, V1c, and V3 are opened, and valves V4a, V4b, and V4c are closed. The grinding drainage is supplied from the drainage supply device 51 to filters 1A, 1B, and 1C via liquid delivery pipes 51a, 51b, and 51c, respectively. The grinding drainage is filtered as it flows through filters 1A, 1B, and 1C, removing grinding particles, grinding debris, and other particulate matter, producing treated water. The treated water is discharged from filters 1A, 1B, and 1C via discharge pipes 52a, 52b, and 52c, respectively, and collected by discharge pipe 53.

[0072] As the wastewater treatment process S51 continues for the specified period, blockages gradually form in each filter. Therefore, a backwashing process S52 is performed before each filter becomes completely blocked.

[0073] In the backwashing process S52, at least one of the multiple filters continues to be drained, and its permeate water (treated water) is used to backwash the other filters. As a result... Figure 4The method for performing the backwashing process S52 of the drainage treatment device 50 shown will first be described as follows: the method of performing backwashing of filter 1C while continuing drainage treatment with filter 1A and filter 1B.

[0074] In the backwashing process S52, valves V1a, V1b, and V4c are opened, and valves V1c, V4a, and V4b are closed, while 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 less than the flow rate of drainage supplied by the drainage supply device 51. In this state, the drainage supply device 51 supplies abrasive drainage to filters 1A and 1B. At least a portion of the treated water from filters 1A and 1B flows from the downstream end of filter 1C into filter 1C, i.e., in the backwashing direction, and is discharged through the backwash pipe 54c. During this process, abrasive particles and other particles that are trapped by filter 1C and cause clogging are removed from filter 1C. The remaining portion of the treated water from filters 1A and 1B is collected in the discharge pipe 53 via discharge pipe 52a or discharge pipe 52b.

[0075] For example, a drainage supply device 51 can be constructed from a drainage tank for storing drainage and a pump located at the outlet side of the drainage tank, which supplies drainage from the drainage tank to the filters. Alternatively, the drainage supply device 51 can be constructed from a drainage tank for storing drainage, with a height difference between the drainage tank and the drainage treatment device 50 such that the drainage tank is positioned higher than each filter, and drainage is supplied to each filter by its own weight. Since the filters in this embodiment have low water flow resistance, water can easily flow through them by gravity, thus utilizing the height difference described above. Furthermore, in the method of supplying drainage by its own weight, there are no problems such as pump material corrosion caused by drainage, and drainage treatment can be performed easily. In addition, to improve the efficiency of backwashing, gas-assisted backwashing can also be used. In this case, for example, backwash water (using the treated water obtained from the drainage treatment device 1) is stored in a tank, and the tank is pressurized with an inert gas such as air or nitrogen, thereby supplying the backwash water to the filters by the gas pressure. Since no pump is used in this method, there is no problem of pump material corrosion due to drainage.

[0076] In this example, filters 1A and 1B function as a first drainage filter (group), and filter 1C functions as a second filter. Furthermore, supply pipes 51a and 51b function as a first supply pipe (group), and supply pipe 51c functions as a second supply pipe. Discharge pipes 52a and 52b function as a first discharge pipe (group), and discharge pipe 52c functions as a second discharge pipe. Backwash pipes 54a and 54b function as a first backwash pipe (group), and backwash pipe 54c functions as a second backwash pipe. Additionally, valves V1a and V1b function as a first supply valve (group), and valve V1c functions as a second supply valve. Valve V4a and V4b function as a first backwash valve (group), and valve V4c functions as a second backwash valve.

[0077] Furthermore, while backwashing filter 1B while continuing to drain water from filters 1A and 1C, in 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 discharge pipe 53 is less than the flow rate supplied by drainage supply device 51. In this state, drainage supply device 51 supplies abrasive drainage to filters 1A and 1C. A portion of the treated water from filters 1A and 1C flows from the downstream end of filter 1B into filter 1B, i.e., in the backwashing direction, and is discharged via backwash pipe 54b. During this process, abrasive particles and other particles captured by filter 1B that cause clogging are removed from filter 1B. Another portion of the treated water from filters 1A and 1C is collected in discharge pipe 53 via discharge pipe 52a or discharge pipe 52c.

[0078] In this example, filters 1A and 1C function as a first drainage filter (group), and filter 1B functions as a second filter. Furthermore, supply pipes 51a and 51c function as a first supply pipe (group), and supply pipe 51b functions as a second supply pipe. Discharge pipes 52a and 52c function as a first discharge pipe (group), and discharge pipe 52b functions as a second discharge pipe. Backwash pipes 54a and 54c function as a first backwash pipe (group), and backwash pipe 54b functions as a second backwash pipe. Additionally, valves V1a and V1c function as a first supply valve (group), and valve V1b functions as a second supply valve. Valve V4a and V4c function as a first backwash valve (group), and valve V4b functions as a second backwash valve.

[0079] Furthermore, while backwashing filter 1A continues to process water using filters 1B and 1C, in backwashing step S52, valves V4a, V1b, and V1c are opened, and valves V1a, V4b, and V4c are closed, reducing or closing the opening of valve V3. The opening of valve V3 is adjusted so that the flow rate of the processed water in the discharge pipe 53 is less than the flow rate supplied by the drainage supply device 51. In this state, the drainage supply device 51 supplies abrasive drainage to filters 1B and 1C. Thus, a portion of the processed water from filters 1B and 1C flows from the downstream end of filter 1A into filter 1A, i.e., in the backwashing direction, and is discharged via backwash pipe 54a. During this process, abrasive particles and other particles captured by filter 1A that cause clogging are removed from filter 1A. The remaining portion of the processed water from filters 1B and 1C is collected in discharge pipe 53 via discharge pipe 52b or discharge pipe 52c.

[0080] In this example, filters 1B and 1C function as a first drainage filter (group), and filter 1A functions as a second filter. Furthermore, supply pipes 51b and 51c function as a first supply pipe (group), and supply pipe 51a functions as a second supply pipe. Discharge pipes 52a and 52c function as a first discharge pipe (group), and discharge pipe 52 functions as a second discharge pipe. Backwash pipes 54b and 54c function as a first backwash pipe (group), and backwash pipe 54a functions as a second backwash pipe. Additionally, valves V1b and V1c function as a first supply valve (group), and valve V1a functions as a second supply valve. Valve V4b and V4c function as a first backwash valve (group), and valve V4a functions as a second backwash valve.

[0081] Next, the case where backwashing of filters 1B and 1C is performed while continuing to drain water from filter 1A will be described. In this case, during 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 the discharge pipe 53 is less than the drainage flow rate supplied by the drainage supply device 51. In this state, the drainage supply device 51 supplies abrasive drainage to filter 1A. As a result, a portion of the treated water from filter 1A flows from the downstream end of filters 1B and 1C into filters 1B and 1C, i.e., in the backwashing direction, and is discharged through backwash pipes 54b and 54c, respectively. During this process, abrasive particles and other particles that are the cause of blockage and are captured by filters 1B and 1C are removed from each filter. The remaining portion of the treated water from filter 1A is collected in discharge pipe 53 through discharge pipe 52a.

[0082] In this example, filter 1A functions as a first drainage filter, and filters 1B and 1C function as a second filter (group). Furthermore, supply pipe 51a functions as a first supply pipe, and supply pipes 51b and 51c function as second supply pipes. 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). Additionally, valve V1a functions as a first supply valve, and valves V1b and V1c function as a second supply valve (group). Valve V4a functions as a first backwash valve, and valves V4b and V4c function as a second backwash valve (group).

[0083] The same procedure is also used when backwashing other filters while continuing to drain water using filter 1B or filter 1C.

[0084] It should be noted that, in this embodiment, a drainage treatment device 50 with three filters connected in parallel is described as an example, but the number of filters is not particularly limited. When there is only one filter, backwashing is performed only, without drainage treatment, during the backwashing process. In this case, backwashing may involve setting up a tank to store treated water, and using a pump to supply the treated water from the tank to the filter in the backwashing direction. When there are two or more filters, drainage treatment and backwashing can be performed in parallel during the backwashing process, similarly to the above. Furthermore, the combination of the filter performing drainage treatment and the filter performing backwashing during the backwashing process is not limited. In addition, in the above embodiment, a method of backwashing one or two filters among multiple filters and draining the water using the other filters during the backwashing process has been described, but the number of each filter performing drainage treatment and the number of filters performing backwashing are not limited.

[0085] In the wastewater treatment process S51 and the backwashing process S52, the treated water obtained from the discharge pipe 53 is supplied to the pure water production system or the ultrapure water production system for use as raw water. The treated water preferably undergoes one or more of the following treatments: ion exchange treatment, reverse osmosis membrane treatment, and hydrogen peroxide decomposition treatment, and is then supplied to the pure water production system or the ultrapure water production system.

[0086] In ion exchange treatment, the treated water (hereinafter referred to as "recycled treated water") from the wastewater treatment device 50 is passed through an ion exchange resin to remove ionic components from the recycled treated water. The ion exchange resin can be selected appropriately based on the quality of the recycled treated water, including strong acid cation exchange resin, weak acid cation exchange resin, strong base anion exchange resin, and weak base anion exchange resin. Furthermore, the ion exchange resin can be regenerable or non-regenerable, but for large-scale treatment of recycled treated water with high levels of impurities, a regenerable type is preferred.

[0087] In reverse osmosis (RO) membrane treatment, recycled water is passed through a reverse osmosis membrane to remove salts. RO membrane treatment can use any type of RO membrane, including ultra-low pressure, low pressure, medium pressure, and high pressure types, but ultra-low pressure or low pressure types are preferred. It should be noted that the operating pressure (design operating pressure, the same below) of ultra-low pressure RO membranes is, for example, 0.4 MPa to 0.8 MPa. The operating pressure of low pressure RO membranes is, for example, more than 0.8 MPa and less than 2.0 MPa. The operating pressure of medium pressure RO membranes is, for example, 2 MPa to 5 MPa. The operating pressure of high pressure RO membranes is, for example, more than 5 MPa and less than 8 MPa.

[0088] Hydrogen peroxide decomposition treatment involves passing the recycled water through activated carbon and catalyst resin to decompose and remove hydrogen peroxide from the recycled water. The catalyst resin used here is anion exchange resin supported on palladium (Pd).

[0089] The recycled water obtained by the wastewater treatment apparatus 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. In the wastewater treatment method of this embodiment, since the above-mentioned wastewater filter 1 and wastewater treatment apparatus 50 are used, filter corrosion and malfunctions due to insufficient filter strength are avoided, and abrasive particles and other particulate matter can be stably and effectively removed from the wastewater. Therefore, the occurrence of adverse conditions in the downstream apparatus of the wastewater treatment apparatus 50, such as ion exchange treatment, reverse osmosis membrane treatment, and hydrogen peroxide decomposition treatment, can be significantly suppressed.

[0090] Explanation of reference numerals in the attached figures 1: Drainage filter; 11: Filter body; 11a: Filter surface; 12: Cover component; 13: First connecting part; 131: First connecting body; 131a: Mountain part; 132: Second connecting body; 132a: Groove part; 133: Third connecting body; 134: Threaded hole; 146a, 146b: Sealing component; 142: Threaded component; 15: Outer shell; 15a: Water outlet; 15b: Water inlet; 18: Second connecting part; 20: Water outlet pipe; 24: Water outlet pipe body; 22, 151: Flange part; 144a: Threaded component; 144b: Threaded fixing component; 148: Fourth connector; 50: Drainage treatment device; 51: Drainage supply device; 1A, 1B, 1C: Filters; 51a, 51b, 51c: Liquid delivery pipes; 52a, 52b, 52c, 53: Discharge pipes; 54a, 54b, 54c: Backwash pipes; V1a, V1b, V1c, V3, V4a, V4b, V4c: Valves; S51: Drainage treatment process; S52: Backwash process; S80: Assembly process; S82: Fluoropolymer membrane formation process; S84: Connection process.

Claims

1. A drainage filter comprising a cylindrical filter body open at both ends and having a plurality of filter holes on its sides, and a cover member liquid-tightly bonded to one end of the filter body. The filter body comprises a filter body body made of metal and a fluoropolymer membrane disposed on the entire surface of the filter body body. The cover component is convex towards the outside of the filter body, and the entire liquid contact surface is made of fluororesin.

2. The drain filter according to claim 1, wherein, The size of the filter pores is greater than 0.01 mm and less than 0.2 mm.

3. The drain filter according to claim 1 or 2, wherein, It also has a cylindrical outer shell. The outer casing has a water outlet at one end and a water inlet at the other end. The housing accommodates the filter body and the cover member with the cover member facing the water inlet of the housing. The opening of the filter body is connected to the water outlet of the outer shell.

4. The drain filter according to claim 3, wherein, The outer shell and the filter body are cylindrical. The cover component is a solid cone or a solid hemisphere.

5. The drain filter according to claim 3, wherein, The open end of the filter body is connected to the water outlet of the outer shell.

6. The drain filter according to claim 1 or 2, wherein, The drainage filter has a connecting portion that connects the filter body and the cover member.

7. The filter for drainage according to claim 6, wherein, The connecting part has a threaded member that passes through the end face of the cover member and the filter body.

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

9. The drain filter according to claim 1 or 2, wherein, To prepare a comparison sample, after immersing the drainage filter and the comparison sample in hydrogen peroxide for one day, the iron (Fe) concentration in the hydrogen peroxide was compared. The iron concentration in the hydrogen peroxide sample with the drainage filter immersed in it was significantly reduced.

10. A drainage treatment device, comprising: A first and a second drainage filter connected in parallel; The wastewater treatment unit supplies abrasive wastewater to the first wastewater filter to produce treated water; and The backwashing mechanism uses a portion of the treated water to backwash the second drain filter. Both the first drainage filter and the second drainage filter are drainage filters as described in claim 1 or 2.

11. The wastewater treatment apparatus according to claim 10, wherein, The drainage treatment mechanism includes: A drainage supply device is used to supply the grinding wastewater. The first liquid delivery pipe delivers the grinding wastewater to the first drainage filter; The first liquid delivery valve is located in the first liquid delivery pipe; The second liquid delivery pipe transports the grinding wastewater to the second drainage filter; The second liquid delivery valve is located in the second liquid delivery pipe; The first discharge pipe discharges the treated water from the first drainage filter; The second discharge pipe discharges the treated water from the second drainage filter; as well as A collection and discharge pipe is connected to the first and second discharge pipes, and the treated water is transported to the outside. The backwashing mechanism includes: A variable-opening valve is installed in the collection and discharge pipe; The first backwash tube has a branch located on the first liquid delivery tube; The second backwash tube is branched off from the second liquid delivery tube; The first backwash valve is located in the first backwash pipe; as well as The second backwash valve is located in the second backwash pipe. The drainage treatment mechanism selectively opens the first liquid delivery valve to allow the grinding drainage supplied from the drainage supply device to pass through the first drainage filter, and selectively closes the second liquid delivery valve. The backwash mechanism is controlled to selectively close the first backwash valve and selectively open the second backwash valve so that a portion of the treated water from the first drain filter passes through the second drain filter in the backwash direction via the second discharge pipe, and to narrow the opening of the variable valve.

12. A wastewater treatment method comprising filtering and grinding wastewater using a filter, the wastewater treatment method comprising: The wastewater treatment process involves filtering and grinding wastewater through multiple wastewater filters connected in parallel to obtain treated water; and In the backwashing process, grinding wastewater is supplied to one or more of the plurality of drainage filters to generate treated water, and the treated water is backwashed in the backwashing direction through drainage filters other than the drainage filter to which the grinding wastewater is supplied. The plurality of drainage filters are all drainage filters as described in claim 1 or 2.

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