Processing wastewater treatment equipment

Abstract

The goal is to reduce costs and labor by decreasing the frequency of filter replacement. [Solution] A processing wastewater treatment apparatus 1 comprising a wastewater tank T1, a filter 13, a water tank 18, a wastewater filtration means 10 equipped with fine particle powder 17 introduced into the filter 13, a wastewater pump P1, a filtered water tank T2, a pure water generation means 20 that converts the filtered water into pure water, and a filtered water pump P2, comprises at least one of a differential pressure gauge 31 that measures the differential pressure inside and outside the filter 13 and a flow meter 30 that measures the flow rate of processing wastewater supplied to the filter 13, a suction mechanism (cake layer breaking means) 40 that breaks the cake layer of fine particle powder 17 formed on the inner wall surface of the filter 13 when the differential pressure measured by the differential pressure gauge 31 exceeds a set value or the flow rate measured by the flow meter falls to a set value, and a concentrated water tank T3 that contains concentrated water containing processing scraps that pass through the filter 13 by sending processing wastewater into the filter 13 after the cake layer has been broken.

Description

[Technical Field]

[0001] The present invention relates to a processing wastewater treatment device for treating processing wastewater discharged from a processing device. [Background technology]

[0002] For example, in the manufacturing process of semiconductor devices such as ICs and LSIs used in various electronic devices, the back surface of a wafer is ground with a grinding wheel to reduce its thickness to a predetermined level in order to miniaturize and lighten the semiconductor device. In this wafer grinding process, pure water or the like is supplied as processing water to the contact point (processing point) between the grinding wheel and the wafer. This removes the frictional heat generated at the contact point (processing point) and cools the contact point, while also washing away the grinding debris generated by the grinding process.

[0003] Therefore, grinding equipment discharges processing wastewater containing grinding debris, etc. However, if this processing wastewater is disposed of as is, it not only pollutes the environment but also increases the consumption of processing water such as pure water, leading to soaring processing costs. For this reason, a processing wastewater treatment device for regenerating processing wastewater discharged from processing equipment such as grinding equipment into pure water for reuse has been proposed, for example, in Patent Document 1.

[0004] In other words, Patent Document 1 proposes a configuration that aims to make the entire device more compact by compactly housing various components such as a waste liquid tank, waste liquid filtration means, fresh water storage tank, pure water generation means, pure water temperature adjustment means, and control means in a device housing.

[0005] Incidentally, processing wastewater treatment equipment is equipped with a filter to separate and remove grinding debris and other materials from the processing wastewater. However, in order to reliably separate (filter) the grinding debris and other processing materials from water using this filter, it is necessary to use a filter with a fine mesh. However, there is a problem in that filters with a fine mesh are expensive, making them economically disadvantageous.

[0006] Therefore, Patent Documents 2 and 3 propose a processing wastewater treatment device that can reliably separate processing debris even with a filter that has a relatively coarse mesh, and can also extend the lifespan of the filter. In such a processing wastewater treatment device, fine particles such as silica are introduced into the inside of the filter, and these fine particles adhere to the inner surface of the filter to form a cake layer. This cake layer achieves high filtration efficiency, and processing debris can be reliably separated and removed from the processing wastewater even when using an inexpensive filter with a relatively coarse mesh. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2009-190128 [Patent Document 2] Japanese Patent Publication No. 2010-082791 [Patent Document 3] Japanese Patent Publication No. 2014-124753 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in recent years, the abrasive particle size of the grinding wheel used for finish grinding in grinding equipment equipped with both rough grinding and finish grinding has decreased, and consequently, the grinding chips have also become finer. Therefore, in the processing wastewater treatment equipment proposed in Patent Documents 2 and 3, which achieve high filtration efficiency by forming a cake layer on the inner surface of the filter with fine powder particles, the filtration efficiency decreases due to clogging of the cake layer over time. As a result, the differential pressure inside and outside the filter due to clogging is detected, and the filter is replaced with a new one when this differential pressure exceeds a predetermined set value. This leads to a problem in that the frequency of filter replacement increases, and the cost and labor required for replacement increase.

[0009] This invention has been made in view of the above problems, and its purpose is to provide a processing wastewater treatment device that can reduce the frequency of filter replacement, thereby achieving cost reduction and labor savings. [Means for solving the problem]

[0010] The invention described in claim 1 is a processing wastewater treatment apparatus comprising at least: a wastewater tank for containing processing wastewater containing processing scraps generated in a processing apparatus for processing a workpiece; a wastewater filtration means comprising a cylindrical filter, a water tank for containing the filter, and fine powder particles for being introduced into the filter to form a cake layer on the inner wall surface of the filter; a wastewater pump for sending the processing wastewater contained in the wastewater tank to the filter; and a filtered water tank for containing the filtered water filtered by the wastewater filtration means, wherein the apparatus comprises at least one of a differential pressure gauge for measuring the differential pressure inside and outside the filter and a flow meter for measuring the flow rate of processing wastewater sent to the filter; and a cake layer breaking means for breaking the cake layer formed on the inner wall surface of the filter when the differential pressure measured by the differential pressure gauge exceeds a preset value or when the flow rate measured by the flow meter falls to a preset value.

[0011] The invention described in claim 2 is characterized in that, in the invention described in claim 1, the cake layer is destroyed and the filter contains a concentrated water tank which contains concentrated water containing processing wastewater contained in the wastewater tank or filtered water contained in the filtered water tank, thereby containing concentrated water that has a particle size smaller than the fine powder that passes through the filter.

[0012] The invention described in claim 3 is characterized in that, in the invention described in claim 1, the cake layer breaking means comprises a control unit for stopping the operation of the wastewater pump and a suction mechanism for drawing air into the filter so that the pressure inside the filter becomes negative.

[0013] The invention according to claim 4 is characterized in that, in the invention according to claim 1, the cake layer breaking means comprises a control unit for stopping the drive of the waste water pump and a vibration transmitting means for transmitting vibration to the cake layer.

[0014] The invention according to claim 5 is characterized in that, in the invention according to claim 1, it comprises a counter for counting the number of times that the differential pressure measured by the differential pressure gauge exceeds a preset set value or the flow rate measured by the flow meter drops to a preset set value, and a display unit for displaying that it is the time to replace the filter when the number of times counted by the counter reaches a preset set number of times.

[0015] The invention according to claim 6 is characterized in that, in the invention according to claim 5, it comprises a concentrated water pump for sending the concentrated water stored in the concentrated water tank to the filter, and after the concentrated water is sent to the filter by the concentrated water pump, the filter can be replaced.

[0016] The invention according to claim 7 is characterized in that, in the invention according to claim 1 or 5, a plurality of the filters are provided, and when the differential pressure inside and outside the filter in use measured by the differential pressure gauge exceeds the set value, switching means for switching the water supply path of the process waste water to the filter to the water supply path of the process waste water to another filter is provided.

[0017] The invention according to claim 8 is characterized in that, in the invention according to claim 1 or 5, a plurality of the filters are provided, and when the flow rate of the process waste water to the filter in use measured by the flow meter drops to the set value, switching means for switching the water supply path of the process waste water to the filter to the water supply path of the process waste water to another filter is provided.

Advantages of the Invention

[0018] According to the invention described in claim 1, due to clogging of the filter and the cake layer formed on its inner wall surface, when the differential pressure inside and outside the filter measured by the differential pressure gauge exceeds a preset value, or when the flow rate measured by the flow meter drops below a preset value, the cake layer is destroyed by the cake layer destruction means, so the filter performance of the filter is restored. For this reason, the replacement time of the filter can be extended and the replacement frequency can be reduced. As a result, cost reduction and labor reduction can be achieved.

[0019] According to the invention described in claim 2, after the cake layer of the filter is destroyed, process wastewater or the like is fed into the filter, and the concentrated water containing processing scraps with a particle size smaller than the fine particle powder passing through the filter remaining in the filter is discharged from the filter, so the filter performance of the filter is effectively restored.

[0020] According to the invention described in claim 3, when the differential pressure inside and outside the filter measured by the differential pressure gauge exceeds a preset value, or when the flow rate measured by the flow meter drops below a preset value, with the drive of the wastewater pump stopped by the control unit, the inside of the filter is sucked by the suction mechanism and the pressure inside the filter becomes negative pressure. Therefore, the cake layer is surely destroyed by this negative pressure.

[0021] According to the invention described in claim 4, when the differential pressure inside and outside the filter measured by the differential pressure gauge exceeds a preset value, or when the flow rate measured by the flow meter drops below a preset value, with the drive of the wastewater pump stopped by the control unit, vibration is transmitted to the cake layer by the vibration transmission means, so the cake layer is surely destroyed by the vibration.

[0022] According to the invention described in claim 5, the number of times the differential pressure inside and outside the filter exceeds the set value, or the number of times the flow rate of the process wastewater passing through the filter drops below the set value, is counted by the counter. When the counted number exceeds the set number of times, the replacement time of the filter is properly displayed on the display unit.

[0023] According to the invention described in claim 6, the concentrated water contained in the concentrated water tank can be sent to the filter by a concentrated water pump, thereby separating and removing the processing waste contained in the concentrated water by containing it in the filter, and the filter can then be replaced with a new one.

[0024] According to the invention described in claim 7, a plurality of filters are provided, and when the differential pressure inside and outside a filter in use, as measured by a differential pressure gauge, exceeds a set value, the water supply path for the processing wastewater to that filter is switched to the water supply path for the processing wastewater to another filter. As a result, the filtration of the processing wastewater by the filters can be continued without interruption, and the filter that was previously in use can be replaced with a new one during this time.

[0025] According to the invention described in claim 8, a plurality of filters are provided, and when the flow rate of processing wastewater supplied to the filter in use, as measured by a flow meter, drops to a set value, the supply path of processing wastewater to that filter is switched to the supply path of processing wastewater to another filter. As a result, the filtration of processing wastewater by the filters can be continued without interruption, and the filter that was previously in use can be replaced with a new one during this time. [Brief explanation of the drawing]

[0026] [Figure 1] This is a perspective view showing the configuration of the processing wastewater treatment apparatus according to the present invention. [Figure 2] This is a broken perspective view showing the configuration of the filter unit of the processing wastewater treatment device according to the present invention. [Figure 3] This is a cross-sectional side view of the filter unit and water tank of the processing wastewater treatment device according to the present invention. [Figure 4] (a) is a partial cross-sectional view showing the state of cake layer formation on the inner wall surface of the filter, and (b) is a partial cross-sectional view of the filter in a state where the cake layer has been destroyed. [Figure 5] This is a time chart showing the time change between the differential pressure inside and outside the filter and the water flow rate supplied to the filter in the processing wastewater treatment apparatus according to the present invention. [Figure 6A]This flowchart shows a first example of the wastewater treatment procedure for the processing wastewater treatment apparatus according to the present invention. [Figure 6B] This flowchart shows a second example of the wastewater treatment procedure for the processing wastewater treatment apparatus according to the present invention. [Figure 6C] This flowchart shows a third example of the wastewater treatment procedure for the processing wastewater treatment apparatus according to the present invention. [Figure 6D] This flowchart shows a fourth example of the wastewater treatment procedure for the processing wastewater treatment apparatus according to the present invention. [Figure 6E] This flowchart shows a fifth example of the wastewater treatment procedure for the processing wastewater treatment apparatus according to the present invention. [Figure 6F] This flowchart shows a sixth example of the wastewater treatment procedure for the processing wastewater treatment apparatus according to the present invention. [Figure 7] A perspective view showing the configuration of a processing wastewater treatment apparatus according to another embodiment 1 of the present invention. [Figure 8] A perspective view showing the configuration of a processing wastewater treatment apparatus according to another embodiment 2 of the present invention. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0028] First, the overall configuration of the processing wastewater treatment device 1 according to the present invention will be described below with reference to Figure 1.

[0029] [Configuration of the processing wastewater treatment system] The processing wastewater treatment apparatus 1 according to the present invention is a device for regenerating processing wastewater discharged from a grinding apparatus 100 that grinds a disc-shaped wafer (not shown) which is a workpiece, into pure water and reusing the pure water for grinding the wafer in the grinding apparatus 100, and comprises the following components.

[0030] In other words, the processing wastewater treatment device 1 includes a wastewater tank T1 for containing processing wastewater discharged from the grinding device 100, a wastewater filtration means 10 for removing grinding debris (processing debris) from the processing wastewater sent from the wastewater tank T1 and purifying the filtered water, a wastewater pump P1 for sending the processing wastewater contained in the wastewater tank T1 to the wastewater filtration means 10, a filtered water tank T2 for containing the filtered water purified by the wastewater filtration means 10, a pure water generation means 20 for generating pure water from the filtered water contained in the filtered water tank T2, and a pure water generation means 20 for generating pure water from the filtered water contained in the filtered water tank T2. The system comprises a filtered water pump P2 for supplying water to the water generation means 20, a differential pressure gauge 31 for measuring the differential pressure inside and outside the filter 13 (see Figure 2) provided in the wastewater filtration means 10, a flow meter 30 for measuring the flow rate of processing wastewater supplied to the wastewater filtration means 10, a suction mechanism 40 as a means for breaking the cake layer, a concentrated water tank T3 for storing concentrated water that has passed through the filter 13 after the cake layer K (see Figure 4(a)) has been broken, a concentrated water pump P3 for supplying the concentrated water stored in the concentrated water tank T3 to the wastewater filtration means 10, and a control unit 50 as its components.

[0031] Although the details of the configuration of the grinding apparatus 100 are not shown here, the grinding apparatus 100 is a device that grinds a wafer, which is a workpiece, using a plurality of grinding wheels attached in a ring shape to a grinding wheel that rotates at high speed, and during the grinding process, pure water, which is the processing water, is supplied to the contact point (processing point) between the grinding wheel and the wafer.

[0032] Next, the main components of the processing wastewater treatment apparatus 1 according to the present invention, namely the wastewater tank T1, wastewater filtration means 10, filtered water tank T2, pure water generation means 20, suction mechanism 40, concentrated water tank T3, and control unit 50, will be described.

[0033] (Wastewater tank) The wastewater tank T1 is, for example, a rectangular container that contains the processing wastewater discharged from the grinding machine 100, and a pipe a extending from the lower side of the grinding machine 100 is connected to its upper part. A wastewater pump P1 is also installed on the upper part of the wastewater tank T1, and a pipe b extends from the discharge side of the wastewater pump P1.

[0034] (Wastewater filtration method) The wastewater filtration means 10 removes processing debris from processing wastewater supplied from the wastewater tank T1 by the wastewater pump P1 to obtain filtered water. In this embodiment, it comprises two first filter units 11 and a second filter unit 12. Since the configurations of the two first filter units 11 and the second filter unit 12 are the same, the configuration of one of the first filter units 11 will be described below with reference to Figures 2 and 3.

[0035] The first filter unit 11 consists of a cylindrical filter 13 that is folded radially in multiple ways to enlarge the filtration area, a cylindrical body 14 that covers the outer circumference of the filter 13, and disc-shaped top plate 15 and bottom plate 16 that cover the top and bottom surfaces of the body 14, respectively. A wastewater inlet 15a is formed in the center of the top plate 15. In addition, multiple circular openings 14a are formed on the side surface of the body 14.

[0036] Here, for example, a CC filter (product name) manufactured by Disco Corporation is used for filter 13, and fine particle powder 17 such as silica with a particle size of 0.5 to 2.0 μm is placed inside this filter 13. In the second filter unit 12, the same reference numerals are used for elements that are the same as those in the first filter unit 11.

[0037] The first filter unit 11 and the second filter unit 12, configured as described above, are detachably housed inside a bottomed cylindrical water tank 18 with an open top, and the two water tanks 18 are detachably arranged on a rectangular tray-shaped filter rack 19. The filter rack 19 has a filtered water outlet 19a and a concentrated water outlet 19b, respectively.

[0038] Incidentally, as shown in Figure 1, the pipe b extending from the wastewater pump P1 branches into two pipes c and d above the first filter unit 11 and the second filter unit 12. One pipe c is connected to a wastewater inlet 15a that opens into the top plate 15 of the first filter unit 11 (see Figures 2 and 3), and the other pipe d is connected to a wastewater inlet 15a that opens into the top plate 15 of the second filter unit 12.

[0039] One pipe c is equipped with an on-off valve V1, and the other pipe d is equipped with an on-off valve V2. The on-off valves V1 and V2 constitute a switching means for switching the water supply route of the processing wastewater to the first filter unit 11 and the second filter unit 12.

[0040] Furthermore, piping b is equipped with an on-off valve V3, a flow meter 30 for measuring the flow rate of wastewater supplied to the first filter unit 11 or the second filter unit 12, and a differential pressure meter 31 for measuring the differential pressure inside and outside the first filter unit 11 or the second filter unit 12. Electromagnetic normally closed valves are used for the on-off valves V1 to V3, and these are electrically connected to the control unit 50, which controls their opening and closing operations. The flow meter 30 and the differential pressure meter 31 are also electrically connected to the control unit 50, and the flow rate of the processing wastewater supplied to the first filter unit 11 or the second filter unit 12, measured by the flow meter 30, and the differential pressure inside and outside the filters 13 of the first filter unit 11 and the second filter unit 12, measured by the differential pressure meter 31, are transmitted to the control unit 50, respectively.

[0041] (Water filtration tank) As shown in Figure 1, the filtered water tank T2 is, for example, a rectangular container located below the wastewater filtration means 10. A pipe e extending downward from a filtered water outlet 19a that opens into a filter rack 19 provided on the wastewater filtration means 10 is connected to its upper part, and an electromagnetic on-off valve V4 is provided on this pipe e. A filtered water pump P2 is attached to the side of the filtered water tank T2. The on-off valve V4 is an electromagnetic normally closed valve that is electrically connected to the control unit 50, and its opening and closing operation is controlled by the control unit 50.

[0042] (Pure water generation means) The pure water generation means 20 is used to purify the filtered water contained in the filtered water tank T2. As shown in Figure 1, it comprises an ultraviolet irradiation unit 23, a precision filter 24, and two first ion exchange units 25 and a second ion exchange unit 26, which are arranged on both sides of a partition plate 22 that is erected vertically on a rectangular tray-shaped support base 21. The precision filter 24, the first ion exchange unit 25, and the second ion exchange unit 26 are detachably installed on the support base 21.

[0043] Here, a pipe f extending from the filtered water pump P2 is connected to the top of the ultraviolet irradiation unit 23, and a pipe g extending from the top of the ultraviolet irradiation unit 23 branches into two pipes h and i. One pipe h is connected to the top of the first ion exchange unit 25, and the other pipe i is connected to the top of the second ion exchange unit 26. These pipes h and i are each provided with electromagnetic on-off valves V5 and V6, respectively, and each on-off valve V5 and V6 is electrically connected to the control unit 50, and their opening and closing operations are controlled by the control unit 50.

[0044] Furthermore, pipes j and k extending from the tops of the first ion exchange unit 25 and the second ion exchange unit 26, respectively, merge into a single pipe m, which is connected to the bottom of the precision filter 24. A pressure gauge 33 and a resistivity meter 34 are installed in pipe m, and these pressure gauges 33 and resistivity meter 34 are electrically connected to the control unit 50. The pressure and resistivity measured by these pressure gauges 33 and resistivity meter 34 are transmitted to the control unit 50. In addition, pipe n extending from the top of the precision filter 24 is connected to the side of the grinding device 100.

[0045] (Suction mechanism) As described later, the suction mechanism 40 constitutes a cake-breaking means that, under predetermined conditions, breaks the cake layer K (see Figure 4(a)) formed on the inner wall surface of the filter 13 by the fine powder 17 (see Figure 2) introduced into the filter 13 of the first filter unit 11 or the second filter unit 12 of the wastewater filtration means 10. In this embodiment, as shown in Figure 1, it is equipped with a suction pump 41.

[0046] As shown in Figure 1, a pipe p branches off from a pipe b extending from a wastewater pump P1 installed at the top of the wastewater tank T1, and this pipe p is connected to the suction side (lower part) of an electric suction pump 41. An electromagnetic on-off valve V7 is also provided on pipe p and is electrically connected to the control unit 50. The suction pump 41 is also electrically connected to the control unit 50. Therefore, the control unit 50 controls the drive of the suction pump 41, and the opening and closing operation of the on-off valve V7 is also controlled by the control unit 50. A pipe q extending from the discharge side (upper part) of the suction pump 41 is connected to the top of the wastewater tank T1.

[0047] (Concentrated water tank) As shown in Figure 1, the concentrated water tank T3 is, for example, a rectangular container located below the wastewater filtration means 10. A pipe r extending downward from a concentrated water outlet 19b that opens into a filter rack 19 provided on the wastewater filtration means 10 is connected to the top of the tank. An electromagnetic on-off valve V8 is provided on this pipe r. A concentrated water pump P3 is attached to the side of the concentrated water tank T3. The on-off valve V8 is an electromagnetic normally closed valve, electrically connected to the control unit 50, and its opening and closing operation is controlled by the control unit 50.

[0048] Furthermore, a pipe s extends from the discharge side (top) of the concentrated water pump P3, and this pipe s is connected to pipe b midway. A check valve V is provided in pipe s to allow the concentrated water discharged from the concentrated water pump P3 to flow toward pipe b (upwards in Figure 1) and to prevent flow in the reverse direction.

[0049] Furthermore, a pipe u extends from the bottom of the filtered water tank T2, and this pipe u is connected to pipe q. An electromagnetic on-off valve V9 is installed in pipe u. The on-off valve V9 is also electrically connected to the control unit 50, and its opening and closing operation is controlled by the control unit 50.

[0050] (Control Unit) The control unit 50 shown in Figure 1 includes a CPU (Central Processing Unit) that performs calculations according to a control program, and a storage unit such as ROM (Read Only Memory) and RAM (Random Access Memory). In particular, in this embodiment, the control unit 50 has the function of destroying the cake layer K (see Figure 4(a)) of fine particles formed on the inner wall surface of the filter 13 of the first filter unit 11 or the second filter unit 12 of the wastewater filtration means 10 by the suction mechanism 40 when necessary (when predetermined conditions are met), based on the differential pressure ΔP inside and outside the filter 13 measured by the differential pressure gauge 31 during the processing of the processing wastewater and the flow rate of the processing wastewater sent to the first filter unit 11 or the second filter unit 12 of the wastewater filtration means 10 measured by the flow meter 30, and also displaying information on an unshown display unit prompting the replacement of the first filter unit 11 or the second filter unit 12.

[0051] Here, the control unit 50 includes a counter 51 that counts the number of times the differential pressure ΔP inside and outside the filter 13, measured by the differential pressure gauge 31, exceeds a preset value, or the number of times the flow rate Q of the processing wastewater, measured by the flow meter 30, falls to a preset value, and a display unit 52 that indicates that it is time to replace the filter 13 when the number of times counted by the counter 51 reaches a preset number.

[0052] [Function of the processing wastewater treatment system] Next, the operation of the processing wastewater treatment apparatus 1 configured as described above, that is, a first example of the wastewater treatment procedure of the processing wastewater treatment apparatus 1, will be explained below with reference to the flowchart shown in Figure 6A.

[0053] In this embodiment, the grinding apparatus 100, which is a processing device, performs grinding on the wafer while receiving pure water as processing water. Specifically, in the grinding apparatus 100, the back surface of the wafer (the surface opposite to the surface on which the device is formed) is ground by a grinding wheel that rotates at high speed, and the wafer is thinned until it reaches a predetermined thickness. During this wafer grinding process, pure water is supplied from a nozzle (not shown) to the contact point (processing point) between the grinding wheel and the wafer.

[0054] As described above, the pure water used as processing water in the grinding device 100 becomes processing wastewater containing processing debris, etc., which is discharged from the grinding device 100 into piping a and sent into the wastewater tank T1 where it is stored.

[0055] The processing wastewater contained in the wastewater tank T1 is treated by the processing wastewater treatment device 1 according to the present invention and recycled into pure water. In this processing of processing wastewater, first, an initial setting is performed (step S1). That is, in this initial setting, the number of times the set flow rate Qs is exceeded is set to i=0, and the set value N is set as the upper limit of the number of times i. In this embodiment, N is set to 3 (3 times).

[0056] Next, a water supply path is formed for the processing wastewater discharged from the grinding device 100 to the selected filter 13, which is either the first filter unit 11 or the second filter unit 12 (step S2), and the wastewater pump P1 is started (step S3). That is, when the wastewater pump P1 is started with one of the on-off valves V2 shown in Figure 1 closed and the other on-off valve V1 open, the processing wastewater contained in the wastewater tank T1 is supplied to the first filter unit 11 of the wastewater filtration means 10, and the flow rate Q of the processing wastewater supplied to the first filter unit 11 is measured by the flow meter 30 (step S4).

[0057] Then, the control unit 50 determines that the flow rate Q measured by the flow meter 30 is the preset set flow rate Q S Whether or not it exceeds (Q>Q) S ?) is determined (step S5). Here, the set flow rate Q SThis refers to the minimum flow rate required by the grinding device 100, and in this embodiment, the set flow rate Q. S It is set to 8 L / min.

[0058] The flow rate Q measured by the flow meter 30 is equal to the set flow rate Q S If the value exceeds (Step S5: Yes), the processing wastewater is filtered by the filter 13 of the first filter unit 11 to purify the filtered water (Step S6), and this filtered water overflows from the water tank 18 and falls onto the filter rack 19. The filtered water that falls onto the filter rack 19 is then stored in the tank T2. The filtered water is then sent to the pure water generation means 20 by the filtered water pump P2, and pure water is produced by the pure water generation means 20 through the following process (Step S7).

[0059] In other words, the filtered water that has been filtered by the first filter unit 11 of the wastewater filtration means 10 and overflows from the water tank 18 and falls onto the filter rack 19 is sent from the filtered water outlet 19a opening in the filter rack 19 through piping e to the filtered water tank T2 where it is stored. At this time, the on-off valve V4 is open and the on-off valve V8 is closed.

[0060] Subsequently, when the filtered water pump P2 is driven, the filtered water contained in the filtered water tank T2 is sent through piping f to the ultraviolet irradiation unit 23 of the pure water generation means 20. The filtered water is sterilized by ultraviolet (UV) irradiation in the ultraviolet irradiation unit 23 and then discharged to piping g. However, when one on-off valve V6 is closed and the other on-off valve V5 is open, the sterilized filtered water is sent through piping h to the first ion exchange unit 25, where it is ion-exchanged and produced as pure water.

[0061] As described above, when pure water is generated by ion exchange in the first ion exchange unit 25, this pure water passes through pipes j and m, and after fine debris is removed by the precision filter 24, it is returned to the grinding device 100 for reuse (step S8). Subsequently, the control unit 50 determines whether the grinding of a predetermined number of wafers by the grinding device 100 has been completed (step S9). If the grinding of the predetermined number of wafers has been completed (step S9: Yes), the wastewater pump P1 is stopped (step S10), the cake layer K is destroyed by the suction mechanism 40 (step S11), and the series of processes for processing wastewater is completed (step S12). If the grinding process has not been completed (step S9: No), the processes in steps S2 to S9 are repeated.

[0062] Incidentally, in the pure water generation means 20, the pressure of the pure water flowing through pipe m is measured by a pressure gauge 33, and the measurement signal is transmitted to the control unit 50. When the pressure of the pure water flowing through pipe m exceeds a predetermined set value, the control unit 50 determines that the filtering function of the precision filter 24 has deteriorated and displays information prompting the replacement of the precision filter 24 on a display unit (not shown).

[0063] Furthermore, the resistivity of the pure water flowing through pipe m is measured by the resistivity meter 34, and the measurement signal is transmitted to the control unit 50. If the resistivity of the pure water flowing through pipe m falls below a predetermined value (for example, 10 MΩ·cm), the control unit 50 determines that the pure water production capacity of the first ion exchange unit 25 has decreased and displays information prompting the replacement of the first ion exchange unit 25 on an unillustrated display unit (touch panel or warning lamp).

[0064] Then, as described above, when the control unit 50 displays information on an indicator (not shown) indicating that the first ion exchange unit 25 should be replaced, the first ion exchange unit 25 is replaced with a new one according to the following procedure, but the water supply path for filtered water is switched from the first ion exchange unit 25 to the second ion exchange unit 26 by the on-off valves V5 and V6.

[0065] In other words, one on-off valve V5, which is in the open state, is closed, and the other on-off valve V6, which is in the closed state, is opened. As a result, the water supply path for the filtered water sterilized by the ultraviolet irradiation unit 23 is switched from the first ion exchange unit 25 to the second ion exchange unit 26, and the filtered water sterilized by the ultraviolet irradiation unit 23 is sent from pipe g through pipe i to the second ion exchange unit 26, and the production of pure water by the second ion exchange unit 26 is carried out continuously and efficiently without interruption. Furthermore, while the production of pure water by the second ion exchange unit 26 is continuing, the first ion exchange unit 25 can be replaced with a new one.

[0066] Here, the processing wastewater sent to the first filter unit 11 or the second filter unit 12 has its flow rate Q measured by a flow meter 30, and the differential pressure ΔP inside and outside each filter 13 is measured by a differential pressure meter 31. The changes in these values ​​over time are shown in Figure 5. As shown in the figure, the flow rate Q of the processing wastewater sent to each filter 13, that is, the flow rate Q of the processing wastewater passing through each filter 13, gradually decreases due to clogging of the cake layer K (see Figure 4(a)) formed on the inner wall surface of the filter 13.

[0067] Then, the flow rate Q of the processing wastewater measured by the flow meter 30 is set to a preset flow rate Q. S (For example, it decreased to 8 L / min) (Q=Q S If (Step S5: No), the counter 51 of the control unit 50 counts i to 1 (Step S13), and it is determined whether the counted value i is equal to the set value N (=3) (i=N?) (Step S14).

[0068] Next, the drive of the wastewater pump P1 is stopped (step S15), and for example, the suction mechanism 40 is driven to destroy the cake layer K (first destruction). When the cake layer K is destroyed, the on-off valve V3 is closed and the on-off valve V7 is open, and when the suction pump 41 is driven, the inside of the filter 13 of the first filter unit 11 is sucked in by the suction pump 41, and water (filtered water) between the filter 13 and the water tank 18 flows in from the outside to the inside of the filter 13. As a result of the inflow of filtered water, the cake layer K is destroyed (step S16), the cake layer K is removed from the inner wall surface of the filter 13, and the inner wall surface of the filter 13 is exposed. The processing wastewater sucked from the inside of the filter 13 by the suction pump 41 is returned to the wastewater tank T1 through the pipe q.

[0069] As described above, when the cake layer K is destroyed (step S16), the shut-off valve V3 is opened and the shut-off valve V7 is closed to form a water supply path for processing wastewater from the wastewater tank T1 to the concentrated water tank T3 (step S17), and the wastewater pump P1 is started (step S18).

[0070] Then, the processing wastewater contained in the wastewater tank T1 is sent through pipes b and c to the inside of the filter 13 of the first filter unit 11, and together with the small processing debris remaining inside the filter 13, it passes through the filter 13 as shown in Figure 4(b), becoming concentrated water containing processing debris. This concentrated water overflows from the water tank 18 of the first filter unit 11 and falls onto the filter rack 19, and is sent from the concentrated water outlet 19b opening in the filter rack 19 through pipe r and the open on / off valve V8 to the concentrated water tank T3, where it is stored (step S19). The processing of the concentrated water stored in the concentrated water tank T3 will be described later.

[0071] Thereafter, the wastewater pump P1 is stopped (step S20), and the process returns to step S2, and thereafter, the same process is repeated. Note that the concentrated water stored in the concentrated water tank T3 is sent by the concentrated water pump P3 through the check valve V and the pipe s to the pipe b, and together with the processed wastewater flowing through the pipe b, it is sent to the first filter unit 11, and is filtered by the first filter unit 11 and purified as filtered water.

[0072] By the way, a new cake layer K is formed on the inner wall surface of the filter 13 where the cake layer K has been broken by the fine particle powder 17 into which the new cake layer K is introduced into the filter 13. When a new cake layer K is formed on the inner wall surface of the filter 13 where the cake layer K was broken at the time t1 shown in FIG. 5, the flow rate Q of the processed wastewater measured by the flow meter 30 suddenly increases, and then gradually decreases with the passage of time t. Also, the differential pressure ΔP of the filter 13 measured by the differential pressure gauge 31 suddenly decreases at the time t1, and then gradually increases with the passage of time t.

[0073] And after the time t1 shown in FIG. 5, while the flow rate Q measured by the flow meter 30 exceeds the set flow rate Q S (step S5: Yes), steps S6 to S9 in FIG. 6A are executed to generate pure water. However, when the flow rate Q decreases to the set flow rate Q S at the time t2 shown in FIG. 5 (step S5: No), the count i is incremented to i = 2 (step S13). Then, steps S13 to S20 shown in FIG. 6A are executed, and the cake layer K is broken (second break) (step S16).

[0074] Subsequently, after forming a path to the concentrated water tank T2, for example, the wastewater pump P1 is started to send the processing wastewater to the filter 13, where the cake layer K has been destroyed, and processing debris with a particle size smaller than the fine powder remaining in the filter 13 is discharged from the filter 13. At this time, concentrated water, which is a liquid containing processing debris with a particle size smaller than the fine powder, is discharged from the filter 13. This concentrated water is sent to the concentrated water tank T3. This supply of concentrated water to the concentrated water tank T3 is carried out for a predetermined set time. This allows the processing debris with a particle size smaller than the fine powder to be discharged from the filter 13, and then the cake layer K can be formed in the filter 13. Then, the wastewater pump P1 is temporarily stopped to block the path of the water discharged from the filter 13 to the concentrated water tank T3, and then the wastewater pump P1 is started again to perform filtration of the processing wastewater by the filter 13 once more. In the above procedure, the wastewater pump P1 is activated to discharge concentrated water and reform the cake layer K using processing wastewater; however, filtered water may be used instead of processing wastewater.

[0075] The flow rate Q measured by the flow meter 30 is equal to the set flow rate Q S While the flow rate Q exceeds the set flow rate Q (Step S5: Yes), steps S6-S9 in Figure 6A are executed to produce pure water, but the flow rate Q is not equal to the set flow rate Q. S When it decreases to (Step S5: No), the value of count i is incremented to i=3 (Step S13).

[0076] In this embodiment, the flow rate Q measured by the flow meter 30 is set to the flow rate Q S While the value exceeds (Step S5: Yes), pure water is produced (Step S7). In this embodiment, the setting value N for the number of times i is set to N=3 (breaking the cake layer K up to 2 times), but the setting value N can be set to any number other than 3.

[0077] In this embodiment, as shown in Figure 5, at time t3 when the cake layer K is broken, the flow rate Q increases sharply and the differential pressure ΔP decreases sharply. Thereafter, the flow rate Q of the processing wastewater gradually decreases with the passage of time t, and the differential pressure ΔP of the filter 13 gradually increases with the passage of time t, but at time t4, the flow rate Q becomes the set flow rate Q S When it decreases to this level (Step S5 in Figure 6A: No), the count i is set to i=3 in Step S13, so the result of the determination in Step S14 is Yes.

[0078] Then, the display unit 52 of the control unit 50 displays information indicating that the filter 13 of the first filter unit 11 should be replaced (step S21), and switches the water supply route for the processing wastewater from the first filter unit 11 to the second filter unit 12 (step S22). In other words, when one on-off valve V1 is closed and the other on-off valve V2 is opened, the water supply route for the processing wastewater from the wastewater tank T1 is switched from the first filter unit 11 to the second filter unit 12.

[0079] Furthermore, by opening the on-off valve V8, a path is formed by the piping r that connects the first filter unit 11 to be replaced with the concentrated water tank T3 (step S23). Then, the concentrated water pump P3 is driven and the concentrated water in the concentrated water tank T3 is sent to the first filter unit 11 via pipes s, b, and c (step S24), and then the first filter unit 11 is replaced with a new one (step S25). Here, the replacement of the first filter unit 11 is carried out efficiently without interrupting the purification of the processing wastewater into filtered water by the second filter unit 12. Then, the same process as the first filter unit 11 is repeated for the second filter unit 12 (step S26).

[0080] As described above, in this embodiment, due to clogging of the filter 13 and the cake layer K formed on its inner wall surface, the flow rate Q measured by the flow meter 30 becomes a preset set flow rate Q SWhen the temperature drops, the suction mechanism 40, which is a means for destroying the cake layer, destroys the cake layer K, and processing wastewater from the wastewater tank T1 or filtered water from the filtered water tank T2 is sent to the filter 13 from which the cake layer K has been destroyed for a predetermined period of time. This water supply causes the filter 13 to discharge concentrated water containing processing debris (processing debris remaining in the filter 13) with a particle size smaller than the particle size of the fine powder particles introduced into the filter 13 to form the cake layer K remaining in the filter 13, thereby restoring the filtration performance of the filter 13. Subsequently, the cake layer K is formed again on the inner wall surface of the filter 13, enabling the filtration of processing wastewater. This extends the replacement period of the filter 13 and reduces the replacement frequency, resulting in cost reduction and labor savings.

[0081] Furthermore, the reformation of the cake layer K is performed automatically after the concentrated water is discharged by sending the processing wastewater from wastewater tank T1 or the filtered water from filtered water tank T2 to the filter 13 from which the cake layer K has been destroyed.

[0082] In other words, in this embodiment, the set value N is set to 3 times (N=3), and the flow rate Q of the processing wastewater measured by the flow meter 30 is set to the set flow rate Q S When the temperature drops to a certain level, a count is taken to destroy the cake layer K. When the counted number i reaches a set value N, it is determined that the filter 13 has reached the end of its service life and the filter 13 is replaced with a new one. By destroying the cake layer K, the timing of filter 13 replacement can be set to the time t3 shown in Figure 5, thereby extending the replacement period of the filter 13.

[0083] By the way, the timing at which the cake layer K is broken is determined by the flow rate measured by the flow meter 30, which is the set flow rate Q. S The point at which the pressure drops is defined as the time when the cake layer K is broken, for example, when the differential pressure ΔP inside and outside the filter 13, measured by the differential pressure gauge 31, reaches the set value P. SWhen the set value Ps is exceeded (times t1, t2, t3 shown in Figure 5), the filter 13 may be replaced based on the number of times the set value Ps is exceeded. A flowchart for this case is shown in Figure 6B as a second example. In Figure 6B, the processing in steps S4' and S5' differs from the processing in steps S4 and S5 shown in Figure 6A, while the other processing is the same as in Figure 6A. That is, in step S4' in Figure 6B, the differential pressure ΔP is measured, and in step S5', the measured differential pressure ΔP is set to the set value P S Whether or not it is less than (ΔP <P S The result is determined to be (?). Therefore, the same effect as described above is obtained in this case as well.

[0084] Here, the third and fourth examples of the wastewater treatment procedure in the processing wastewater treatment apparatus 1 according to the present invention are shown in Figures 6C and 6D, respectively. In Figures 6C and 6D, the same steps as those shown in Figures 6A and 6B are assigned the same step numbers as those in Figures 6A and 6B. Note that in the first and second examples, the flow rate Q and differential pressure ΔP are monitored and the count i is incremented, whereas in the third and fourth examples, the part that counts the number of times the cake layer K is broken is different.

[0085] In the third example shown in Figure 6C and the fourth example shown in Figure 6D, when the cake layer K is destroyed because a predetermined condition is met (step S15), the number of times the cake layer K has been destroyed i is counted by the counter 51 of the control unit 50 (step S16). Then, in step S13, it is determined whether the number of times the cake layer K has been destroyed i has reached the set number N. If the number of times the cake layer K has been destroyed i has not reached the set number N (step S13: No), the wastewater pump P1 stops (step S14) and the cake layer K is destroyed (step S15).

[0086] Then, when the number of times i the cake layer K is destroyed reaches the set number N (step S13: Yes), steps S21 to S25 are executed and the filter 13 is replaced with a new one.

[0087] Furthermore, the fifth and sixth examples of the wastewater treatment procedure in the processing wastewater treatment apparatus 1 according to the present invention are shown in Figures 6E and 6F, respectively. In Figures 6E and 6F, the same steps as those shown in Figures 6A and 6B are assigned the same step numbers as those assigned in Figures 6A and 6B. Note that, similar to the third and fourth examples, the fifth and sixth examples differ from the first and second examples in that they count up the number of times the cake layer K is broken i.

[0088] In the fifth example shown in Figure 6E and the sixth example shown in Figure 6F, the wastewater pump P1 stops because predetermined conditions are met (step S13), and the cake layer K is destroyed (step S14). The number of times the cake layer K is destroyed i is counted by the counter 51 of the control unit 50 (step S15), and it is determined whether the counted number of destructions i has reached the set number N (step S13). If the number of times the cake layer K is destroyed i has not reached the set number N (step S13: No), the processes in steps S17 to S20 are executed, as in the first to fourth examples, and concentrated water is stored in the concentrated water tank T3.

[0089] Then, when the number of times i the cake layer K is destroyed reaches the set number N (step S16: Yes), steps S21 to S25 are executed and the filter 13 is replaced with a new one.

[0090] In the above embodiment, the first filter unit 11 and the second filter unit 12 are arranged on the filter rack 19. However, by providing a filter rack for the first filter unit 11 and a filter rack for the second filter unit 12, and arranging a filtered water outlet 19a and a concentrated water outlet 19b on the first filter unit 11 and the second filter unit 12, respectively, it is also possible to configure the system so that when one filter unit (for example, the first filter unit 11) is breaking down the cake layer K and discharging concentrated water, the other filter unit (for example, the second filter unit 12) is simultaneously purifying the filtered water.

[0091] [Another form of processing wastewater treatment equipment] Next, another embodiment of the processing wastewater treatment apparatus according to the present invention will be described with reference to Figures 7 and 8.

[0092] <Alternative form 1> In the alternative configuration 1 processing wastewater treatment apparatus 1' shown in Figure 7, concentrated water is sent to the wastewater tank T1 through pipes r and q. The concentrated water contained in the wastewater tank T1 is then sent together with the processing wastewater by the wastewater pump P1 through pipes b and x to the concentrated water tank T3, where it is contained. The concentrated water contained in the concentrated water tank T3 is then sent to the first filter unit 11 through pipes y and c by the concentrated water pump P3. An electromagnetic on-off valve V10 is provided in pipe x, and a check valve V is provided in pipe y.

[0093] Furthermore, in the processing wastewater treatment apparatus 1', the on-off valve V8 is opened, and the concentrated water that has fallen onto the filter rack 19 is collected in the wastewater tank T1 via pipes r and q. Then, the on-off valves V1 and V2 are closed, and the wastewater pump P1 is driven to send the concentrated water collected in the wastewater tank T1 to the concentrated water tank T3, where it is collected. If the amount of water in the wastewater tank T1 is low, the on-off valve V9 may be opened to send the filtered water in the filtered water tank T2 to the wastewater tank T1. In this case, since the filtered water tank T2 is located above the wastewater tank T1, the filtered water in the filtered water tank T2 can be sent to the wastewater tank T1 by free fall.

[0094] The other components of the processing wastewater treatment apparatus 1' according to alternative form 1 are the same as those of the processing wastewater treatment apparatus 1 shown in Figure 1. Therefore, the same reference numerals are used for the same elements as those shown in Figure 1, and further explanation of them is omitted. However, the processing wastewater treatment apparatus 1' can obtain the same effects as those obtained with the processing wastewater treatment apparatus 1 shown in Figure 1.

[0095] <Alternative form 2> In the processing wastewater treatment apparatus 1" according to alternative form 1 shown in Figure 8, a disc-shaped ultrasonic vibrating plate 60 is provided on the bottom plate 16 of the first filter unit 11 and the second filter unit 12 to transmit ultrasonic vibrations to the cake layer K, as a means for breaking the cake layer. The other configurations are the same as those of the processing wastewater treatment apparatus 1 shown in Figure 1. Therefore, in Figure 8, the same elements as those shown in Figure 1 are denoted by the same reference numerals, and further explanation of them is omitted below.

[0096] Furthermore, the other components of the processing wastewater treatment apparatus 1' according to alternative form 2 are the same as those of the processing wastewater treatment apparatus 1 shown in Figure 1. Therefore, the same reference numerals are used for the same elements as those shown in Figure 1, and further explanation of them is omitted. In this processing wastewater treatment apparatus 1'', by energizing the ultrasonic vibrating plate 60 and causing it to vibrate ultrasonically, the ultrasonic vibrations are transmitted to the filter 13, thereby causing the cake layer K formed on the inner wall surface of the filter 13 to vibrate ultrasonically and reliably destroy the cake layer K. Therefore, the processing wastewater treatment apparatus 1'' according to alternative form 2 can obtain the same effects as those obtained with the processing wastewater treatment apparatus 1 shown in Figure 1. Here, the location of the ultrasonic vibrating plate 60 is not limited to the bottom plate 16. It may be on the top plate 15, or it may be placed on the bottom plate or side plate of the water tank 18. Alternatively, it may be placed inside the filter 13.

[0097] In the embodiments described above, a grinding device 100 was given as an example of a processing device. However, other processing devices that can be used include a cutting device that cuts a wafer with a high-speed rotating disc-shaped cutting blade, a polishing device that polishes a wafer with a high-speed rotating polishing pad, a cleaning device that cleans a wafer using pure water, and a cutting device that turns a wafer or sheet with a cutting tool. Furthermore, the workpiece processed by the processing device is not limited to a wafer, but may be any other material.

[0098] Furthermore, in this embodiment, the purified water obtained by treating the processing wastewater is returned to the grinding device 100 for reuse, but the filtered water filtered by the filter 13 may also be returned to the grinding device 100 for reuse.

[0099] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the technical idea described in the claims, specification, and drawings. [Explanation of Symbols]

[0100] 1,1',1”: Processing wastewater treatment device, 10: Wastewater filtration means, 11: First filter unit, 12: Second filter unit, 13: Filter, 14: Tube, 14a: Opening, 15: Top plate, 15a: Wastewater inlet, 16: Bottom plate, 17: Fine powder, 18: Water tank, 19: Filter rack, 19a: Filtered water outlet, 19b concentrated water outlet, 20: means for producing pure water, 21: support stand, 22: partition plate, 23: ultraviolet irradiation unit, 24: Precision filter, 25: First ion exchange unit, 26: Second ion exchange unit, 30: Flow meter, 31: Differential pressure gauge, 33: Pressure gauge, 34: Resistivity meter, 40: Suction mechanism (cake layer breaking means), 41: Suction pump, 50: Control unit, 51: Counter, 52: Display unit, 60: Ultrasonic vibrating plate (cake layer breaking means), 100: Grinding equipment (processing equipment), K: Cake layer, P1: Wastewater pump, P2: Filtered water pump, P3: Concentrated water pump, ΔP: Differential pressure, P S : Differential pressure setting value, Q: Flow rate, Q S : Flow rate setting value, T1: Wastewater tank, T2: Filtered water tank, T3: Concentrated water tank, V: Check valve V1~V10: Shut-off valves

Claims

1. A wastewater tank for containing processing wastewater containing processing scraps generated in a processing machine for processing a workpiece, A wastewater filtration means comprising a cylindrical filter, a water tank housing the filter, and fine powder particles introduced into the filter to form a cake layer on the inner wall surface of the filter, A wastewater pump that sends the processing wastewater contained in the wastewater tank to the filter, A filtered water tank for containing filtered water filtered by the wastewater filtration means, A processing wastewater treatment apparatus comprising at least the following: At least one of the following: a differential pressure gauge for measuring the differential pressure inside and outside the filter, and a flow meter for measuring the flow rate of processing wastewater supplied to the filter. When the differential pressure measured by the differential pressure gauge exceeds a preset value, or when the flow rate measured by the flow meter falls to a preset value, the cake layer breaking means breaks the cake layer formed on the inner wall surface of the filter. A processing wastewater treatment device equipped with the following features.

2. The processing wastewater treatment apparatus according to claim 1, further comprising a concentrated water tank that contains concentrated water containing processing wastewater with a particle size smaller than the fine powder particles passing through the filter, by sending processing wastewater contained in the wastewater tank or filtered water contained in the filtered water tank into the filter from which the cake layer has been destroyed.

3. The aforementioned cake layer breaking means is A control unit that stops the operation of the wastewater pump, A suction mechanism that draws air into the filter so that the pressure inside the filter becomes negative, A processing wastewater treatment apparatus according to claim 1, comprising:

4. The aforementioned cake layer breaking means is A control unit that stops the operation of the wastewater pump, A vibration transmission means for transmitting vibrations to the cake layer, A processing wastewater treatment apparatus according to claim 1, comprising:

5. The processing wastewater treatment apparatus according to claim 1, comprising: a counter that counts the number of times the differential pressure measured by the differential pressure gauge exceeds a preset value, or the flow rate measured by the flow meter falls to a preset value; and a display unit that indicates that it is time to replace the filter when the number of times counted by the counter reaches a preset number.

6. The system includes a concentrated water pump that sends the concentrated water contained in the concentrated water tank to the filter, The processing wastewater treatment apparatus according to claim 5, wherein the concentrated water is sent to the filter by the concentrated water pump, and the filter is made replaceable.

7. The system includes multiple of the aforementioned filters, The processing wastewater treatment apparatus according to claim 1 or 5, further comprising a switching means that switches the water supply route for processing wastewater to one filter to another filter when the differential pressure inside and outside the filter during use, as measured by the differential pressure gauge, exceeds a set value.

8. The system includes multiple of the aforementioned filters, The processing wastewater treatment apparatus according to claim 1 or 5, further comprising a switching means that switches the water supply path for processing wastewater to the filter in use, when the flow rate of processing wastewater to the filter in use, as measured by the flow meter, falls to a set value, to a water supply path for processing wastewater to another filter.

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