Water treatment system and water treatment method

Abstract

To provide a water treatment system and a water treatment method allowing realization of power consumption reduction in the whole water treatment system by controlling heat exchange in a heat exchanger of a pure water manufacturing device that includes a pure water production equipment and a detoxicated wastewater treatment equipment and conducts heat exchange between detoxicated wastewater and raw water with a heat exchanger.SOLUTION: A water treatment system includes a pure water production equipment for manufacturing pure water by treating raw water from a raw water tank and a detoxicated wastewater treatment equipment for treating detoxicated wastewater from the exhaust gas treatment facility and recovery and reuse as an exhaust gas treatment facility water. A heat exchanger 22 lowering the temperature of detoxicated wastewater and a raw water tank 2 are connected by a circulation pipeline. The circulation pipeline is provided with a bypass piping 16 for bypassing the heat exchanger 22. A flow of raw water to the bypass piping 16 is controlled by a three-way valve 13 in a manner that a raw water temperature transferred from the raw water tank 2 to the pretreatment apparatus 4 becomes a specified value or under.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water treatment system and a water treatment method using a pure water production apparatus and a detoxification wastewater treatment facility. The detoxification wastewater treatment facility is a facility for treating wastewater from an exhaust gas treatment facility (abatement device) for treating gases containing PFCs and the like by abatement combustion or the like.

[0002] Note that PFCs (Perfluorocompounds) refers to perfluorocompounds such as CF4, C2F6, C4F8, SF6, and WF6. In this specification, however, in addition to these perfluorocompounds, it also refers to all harmful, flammable, and greenhouse gases used in the deposition, etching, and cleaning processes, including CH2F2, Cl2, BCl3, F2, HF, SiH4, NH3, PH3, TEOS (tetraethoxysilane), TRIS (triethoxysilane), and TiCl4. [Background technology]

[0003] Conventionally, ultrapure water used for semiconductor cleaning is produced by treating raw water (industrial water, city water, well water, etc.) in an ultrapure water production apparatus consisting of a pretreatment system, a primary pure water system, and a subsystem (see, for example, Patent Document 1).

[0004] Pretreatment systems, consisting of coagulation equipment, pressure flotation (sedimentation) equipment, filtration equipment, etc., remove suspended solids and colloidal substances from the raw water. Primary pure water systems equipped with reverse osmosis (RO) membrane separation equipment, degassing equipment, and ion exchange equipment (mixed bed type, 2-bed 3-tower type, or 4-bed 5-tower type) remove ions and organic components from the raw water. In addition to removing salts, the RO membrane separation equipment removes ionic and colloidal total organic carbon (TOC). In addition to removing salts, the ion exchange equipment removes TOC components that are adsorbed or ion-exchanged by the ion exchange resin. The degassing equipment (nitrogen degassing or vacuum degassing) removes dissolved oxygen.

[0005] The subsystem (secondary pure water system), which includes a heat exchanger, low-pressure ultraviolet (UV) oxidation device, mixed-bed ion exchange device, and ultrafiltration (UF) membrane separation device, further increases the purity of the water to make it ultrapure water. In the low-pressure UV oxidation device, ultraviolet rays with a wavelength of 185 nm emitted from a low-pressure UV lamp are used to break down TOC into organic acids and even CO2. The broken down organic acids and CO2 are removed by the downstream ion exchange resin. The UF membrane separation device removes fine particles and also removes particles that flow out of the ion exchange resin.

[0006] In the manufacturing process of semiconductors, etc., large amounts of the above-mentioned PFCs, such as perfluoro compounds, are used. Factories that use perfluoro compound gases are equipped with exhaust gas treatment equipment called detoxification equipment to render them harmless (Patent Document 2). In the detoxification equipment, the perfluoro compounds are combusted (oxidized) or decomposed by pyrolysis using combustion, electric heating, plasma, etc., to desorb fluorine (F2), and then the exhaust gas is cleaned with a water scrubber built into the equipment, and the F2 in the gas is absorbed and removed.

[0007] In addition to HF, scrubber wastewater contains organic hydrocarbon compounds (TOC components) derived from the organic skeletons of perfluorochemical molecules. Therefore, the scrubber wastewater is treated by being led to abatement wastewater treatment facilities equipped with organic matter decomposition means such as biological treatment equipment.

[0008] The temperature of the decontamination wastewater is generally relatively high, about 35 to 45° C. Patent Document 3 describes a method in which this high-temperature decontamination wastewater is heat-exchanged with low-temperature raw water from a pure water production system in a heat exchanger to raise the temperature of the raw water and lower the temperature of the decontamination wastewater, and the lowered temperature decontamination wastewater is sent to a decontamination wastewater treatment facility for treatment.

[0009] In the RO equipment (reverse osmosis membrane equipment) of the pure water production system and the UF equipment (ultrafiltration equipment) of the pretreatment system, when the water temperature drops, the treatment flow rate also drops, and if coagulation occurs in the pretreatment system, coagulation failure occurs. For this reason, it is effective from the viewpoint of the operational stability of the pure water production system to exchange heat with the decontaminated wastewater in the upstream stage of the pretreatment system. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2020-199436 A [Patent Document 2] Patent Publication No. 2022-72981 [Patent Document 3] Patent Publication No. 2022-70608 Summary of the Invention [Problem to be solved by the invention]

[0011] In order to treat the wastewater discharged from semiconductor factories and other plants at temperatures of about 35 to 45°C in abatement wastewater treatment facilities and reuse it as service water for abatement devices and other facilities, it is necessary to cool the wastewater beforehand in the treatment facilities to a temperature suitable for treatment.

[0012] In pure water production systems, the temperature of raw water (industrial water, city water, etc.) drops in winter, so the raw water needs to be heated.

[0013] Therefore, as described above, a method of exchanging heat between high-temperature detoxified wastewater and low-temperature raw water from a pure water production system in a heat exchanger is widely adopted.

[0014] However, in winter, since the temperature of the raw water is low, it is possible to sufficiently cool the decontamination wastewater with the raw water. However, in summer, the temperature of the raw water rises, and the heat exchanger is no longer able to sufficiently cool the decontamination wastewater. Therefore, a heat exchanger that uses cold water (cold water from a refrigerator) as the low-temperature fluid is installed downstream of the heat exchanger, and the decontamination wastewater is cooled with the cold water.

[0015] For this reason, when the temperature of the raw water becomes high, the amount of cold water used for cooling increases, and the power consumption of the chiller increases. Therefore, in order to reduce the power consumption of the chiller, a heat exchanger that uses cooling water from a cooling tower as a low-temperature fluid is installed before the heat exchanger that uses cold water, so that the raw water can be cooled with this cooling water.

[0016] The pretreatment device of the pure water production system is generally operated in an ON / OFF manner. Therefore, in a conventional pure water production system in which raw water is heated by the heat of the decontamination wastewater and supplied to the pretreatment device, when the operation of the pretreatment device is stopped, raw water is not passed through the heat exchanger, and the temperature of the decontamination wastewater is not lowered by the heat exchanger. In this case, the decontamination wastewater to be sent to the decontamination wastewater treatment facility is cooled by a cooler before being sent to the decontamination wastewater treatment facility.

[0017] As such, because pretreatment equipment generally operates in an ON / OFF mode, heat exchange between the decontamination wastewater and raw water becomes intermittent. To compensate for this, the decontamination wastewater is cooled using a cooler in the downstream stage, but the temperature adjustment of the decontamination wastewater cannot keep up, and there is a risk that the temperature of the decontamination wastewater sent to the decontamination wastewater treatment equipment will temporarily be higher than the specified upper limit temperature.

[0018] In addition, in the past, when heat exchange was performed between decontamination wastewater and raw water so that the temperature of the decontamination wastewater would reach a predetermined temperature, heat exchange was sometimes performed even when the raw water temperature was high, such as in summer, and the raw water would become warmer than the set temperature.

[0019] This resulted in an increase in the amount of chilled water required for cooling in downstream subsystems, resulting in increased power consumption by the chillers.

[0020] The present invention aims to provide a water treatment system and a water treatment method which use pure water production equipment and abatement wastewater treatment equipment, and exchange heat between abatement wastewater and raw water in a heat exchanger, and which can reduce power consumption throughout the entire water treatment system by controlling the amount of raw water passing through the heat exchanger. [Means for solving the problem]

[0021] The water treatment system of the present invention is a water treatment system having a pure water production equipment that treats raw water from a raw water tank to produce pure water, and a wastewater treatment equipment for treating wastewater from an exhaust gas treatment equipment (hereinafter referred to as abatement wastewater) and recovering and reusing it as exhaust gas treatment equipment water, the wastewater treatment equipment has a heat exchanger that lowers the temperature of the wastewater by heat exchange with raw water from the raw water tank, the heat exchanger and the raw water tank are connected by a circulation piping so that the raw water in the raw water tank is circulated and supplied to the heat exchanger as a low-temperature fluid, and the water treatment system is equipped with a temperature sensor (T1) that detects the raw water temperature of the raw water tank or the piping that supplies raw water from the raw water tank to the pure water production equipment, and a control means that controls the amount of raw water supplied to the heat exchanger so that the detected temperature of the temperature sensor (T1) is below a predetermined value.

[0022] In one aspect of the present invention, the control means for controlling the amount of raw water supplied to the heat exchanger includes a bypass pipe arranged to bypass the heat exchanger, and a means for controlling the flow of raw water through the bypass pipe.

[0023] In one aspect of the present invention, a pump for circulating and feeding raw water is provided in the circulation piping, and the control means for controlling the amount of raw water supplied to the heat exchanger controls the amount of water fed by the pump.

[0024] In one embodiment of the present invention, the decontamination wastewater treatment equipment has a heat exchanger (A) that uses cooling water from a cooling tower as a low-temperature fluid to lower the temperature of the decontamination wastewater that has been cooled in the heat exchanger, and a heat exchanger (B) that uses cold water from a refrigerator as a low-temperature fluid to lower the temperature of the decontamination wastewater from the heat exchanger (A).

[0025] In one aspect of the present invention, a temperature sensor (T2) is provided for detecting the temperature of the decontamination wastewater supplied to the heat exchanger (A) from the heat exchanger that exchanges heat between raw water and decontamination wastewater, and the control means controls the amount of raw water supplied to the heat exchanger (A) so that the temperature detected by the temperature sensor (T2) becomes a target temperature.

[0026] The water treatment method of the present invention includes a pure water production facility for treating raw water from a raw water tank to produce pure water; In a water treatment method for treating wastewater from an exhaust gas treatment facility (hereinafter referred to as abatement wastewater) and producing pure water using a water treatment system having abatement wastewater treatment equipment for treating the wastewater from an exhaust gas treatment facility and recovering and reusing it as water for the exhaust gas treatment facility, the abatement wastewater treatment equipment has a heat exchanger that lowers the temperature of the wastewater from the exhaust gas treatment facility by heat exchange with raw water from the raw water tank, and the heat exchanger and the raw water tank are connected by a circulation piping so that the raw water stored in the raw water tank is circulated and supplied as a low-temperature fluid for the heat exchanger, and the raw water temperature of the raw water tank or the piping that supplies raw water from the raw water tank to the pure water production facility is detected by a temperature sensor (T1), and the amount of raw water supplied to the heat exchanger is controlled so that the detected temperature of the temperature sensor (T1) is below a predetermined value.

[0027] In one aspect of the water treatment method of the present invention, a bypass pipe is provided to bypass the heat exchanger, and the detection temperature of the temperature sensor (T1) is set to a predetermined value or lower by controlling the flow of raw water through the bypass pipe.

[0028] In one aspect of the water treatment method of the present invention, a pump for circulating and feeding raw water is provided in the circulation piping, and the amount of water fed by the pump is controlled to make the temperature detected by the temperature sensor (T1) equal to or lower than a predetermined value.

[0029] In one aspect of the water treatment method of the present invention, the decontamination wastewater treatment equipment is equipped with a heat exchanger (A) that uses cooling water from a cooling tower as a low-temperature fluid to lower the temperature of the decontamination wastewater that has been lowered in the heat exchanger, a heat exchanger (B) that uses cold water from a chiller as a low-temperature fluid to lower the temperature of the decontamination wastewater from the heat exchanger (A), and a temperature sensor (T2) that detects the temperature of the decontamination wastewater supplied to the heat exchanger (A) from the heat exchanger that uses the raw water as a low-temperature heat source fluid, and the water treatment method controls the amount of raw water supplied to the heat exchanger (A) so that the detected temperature of the temperature sensor (T2) becomes a target temperature, and the amount of raw water supplied to the heat exchanger (A) is reduced by changing the target temperature to a higher temperature, and the amount of raw water supplied to the heat exchanger (A) is increased by changing the target temperature to a lower temperature. Effect of the Invention

[0030] According to the present invention, the temperature of the raw water supplied to the pure water production facility is prevented from rising excessively, and the power consumption of the entire water treatment system is reduced. [Brief description of the drawings]

[0031] [Figure 1] 1 is a configuration diagram of a water treatment system according to an embodiment. [Diagram 2] FIG. 11 is a configuration diagram of a water treatment system according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a configuration diagram of a water treatment system according to a first embodiment.

[0033] Raw water for producing ultrapure water, such as industrial water or city water, is introduced into raw water tank 2 through raw water piping 1. The raw water in raw water tank 2 is heated by heat exchanger 22, which will be described later. As described above, in the RO (reverse osmosis membrane device) of the pure water production system and the UF (ultrafiltration device) of the pretreatment system, the treatment flow rate decreases when the water temperature drops, and in the case of coagulation treatment in the pretreatment equipment, coagulation failure occurs. For this reason, it is effective from the viewpoint of operational stability of the pure water production system to heat the raw water in the stage preceding the pretreatment system 4 to raise the temperature.

[0034] The pretreatment device 4 is equipped with a flocculation device, a pressure flotation (sedimentation) device, a filtration device, etc., and removes suspended solids and colloidal substances from the raw water to produce pretreated water. This pretreated water is introduced into the primary pure water device 5.

[0035] In this embodiment, the primary pure water system 5 includes a decarbonation tower 5a, a storage tank (not shown) for storing decarbonated water, a steam type heat exchanger 5b for heating the decarbonated water from the storage tank, a safety filter (not shown) through which the decarbonated water heated by the heat exchanger 5b passes, an RO system 5c through which water that has passed through the safety filter is passed, and a desalted water tank (not shown) for storing permeated water (desalted water) from the RO system 5c. Steam from a boiler is supplied to the high-temperature fluid flow path of the steam type heat exchanger 5b.

[0036] The primary pure water from the primary pure water device 5 is introduced into a sub-tank 6. The primary pure water in the sub-tank 6 is passed through a heat exchanger 7 for cooling, where it is cooled to about 23°C, and is then supplied to a subsystem 8. Cold water from a refrigerator (not shown) is passed through the low-temperature fluid flow path of the heat exchanger 8. The water, which has been heated by passing through the low-temperature fluid flow path of the heat exchanger 8, is returned to the refrigerator.

[0037] Subsystem 8 is equipped with a heat exchanger, a low-pressure ultraviolet (UV) oxidation device, a mixed-bed ion exchange device, and an ultrafiltration (UF) membrane separation device. In the low-pressure UV oxidation device, ultraviolet light with a wavelength of 185 nm emitted from a low-pressure UV lamp is used to break down TOC into organic acids and even CO2. The broken down organic acids and CO2 are removed by the ion exchange resin in the subsequent stage. In the UF membrane separation device, fine particles are removed, as well as particles that flow out of the ion exchange resin. The ultrapure water produced in subsystem 8 is delivered to the point of use.

[0038] The pure water production system of this embodiment is equipped with a detoxifying wastewater treatment facility.

[0039] As mentioned above, large quantities of the above-mentioned PFCs, including perfluorocompounds, are used in the manufacturing processes of semiconductors, etc. In abatement equipment that treats exhaust gases containing PFCs, the perfluorocompounds are combusted (oxidized) or decomposed by pyrolysis using combustion, electrical heating, plasma, etc. to release fluorine (F2), and the exhaust gas is then cleaned with a water scrubber built into the equipment, which absorbs and removes the F2 in the gas.

[0040] The temperature of the scrubber wastewater and the wastewater from the combustion or pyrolysis reaction device is generally about 35 to 45°C.

[0041] The decontamination wastewater is sent to a heat exchanger 22 via a pipe 21, and is cooled by heat exchange with the raw water from the raw water tank 2. Next, the water is sent to a heat exchanger 24 as a heat exchanger (A) via a pipe 23, and is cooled by heat exchange with cooling water from a cooling tower (not shown). The temperature of the cooling water from the cooling tower is usually about 20 to 30°C.

[0042] The detoxified wastewater cooled in the heat exchanger 24 is sent to a heat exchanger 26 (heat exchanger (B)) via a pipe 25, where it exchanges heat with cold water from a refrigerator (not shown), and is further cooled to an appropriate temperature of about 17 to 33°C, and is introduced into a storage tank 27 where it is stored. The temperature of the cold water from the refrigerator is usually about 5 to 12°C.

[0043] The decontamination wastewater in the storage tank 27 is sent to the decontamination wastewater treatment facility 28 and treated to become treated water. This treated water is sent to the decontamination device and reused. The decontamination wastewater treatment facility 28 may be, for example, one described in Patent Document 3, but is not limited thereto.

[0044] In the decontamination wastewater treatment equipment of Patent Document 3, the decontamination wastewater passes through a pH adjustment tank, a biological treatment tank, and a filtration device, and is cooled by heat exchange with industrial water in the first heat exchanger. Thereafter, the water that has permeated the MF device and the RO device passes through the second and third heat exchangers for cooling to be cooled, and is sent to the water scrubber of the decontamination equipment. Make-up water from the cooling tower is passed through the low-temperature fluid flow path of the second heat exchanger, and cold water from the refrigerator is passed through the low-temperature fluid flow path of the third heat exchanger. In this decontamination wastewater treatment equipment, as long as the order of the heat exchangers and coolers is as in Patent Document 3, the arrangement of the other devices may be different.

[0045] The configuration of the raw water heating mechanism using the heat exchanger 22 will now be described.

[0046] The raw water in the raw water tank 2 is passed through a low-temperature fluid flow path of a heat exchanger 22 via a pump 11, a pipe 12, a three-way valve 13, and a pipe 14. Abatement wastewater at about 35 to 45°C from the pipe 21 is passed through a high-temperature fluid flow path of the heat exchanger 22. The raw water is heated by this abatement wastewater and returns to the raw water tank 2 via a pipe 15. A temperature sensor T2 is provided in the pipe 15.

[0047] A bypass pipe 16 is provided so as to bypass the heat exchanger 22. The upstream end of the bypass pipe 16 is connected to the three-way valve 13, and the downstream end is connected to the pipe 15.

[0048] In this embodiment, the pump 11 is constantly operating, regardless of whether the pretreatment device 4 is operating or not.

[0049] In this embodiment, detected temperature data from the temperature sensors T1, T2 is transmitted to a valve controller (not shown), and the three-way valve 13 is controlled by the valve controller.

[0050] This control is performed based on the temperature T1 detected by the temperature sensor T1 as follows. That is, when the temperature T1 of the raw water detected by the temperature sensor T1 is lower than a set value (for example, a value selected from the range of 20 to 25°C), the temperature detected by the temperature sensor T2 is lower than the preset target temperature t 2-1 The amount of raw water flowing to the heat exchanger 22 is controlled by controlling the three-way valve 13 so that the temperature is preferably approximately the same as the set value of the raw water temperature T1, and adjusting the amount of water flowing to the bypass pipe 16 and the amount of water flowing to the pipe 14.

[0051] When the raw water temperature T1 is equal to or higher than the set value, the target temperature of the temperature sensor T2 is lowered by a predetermined temperature (for example, 1°C) to t 2-2 The three-way valve 13 is controlled so that the target temperature is reached. 2-2However, if the raw water temperature T1 is equal to or higher than the set value, the target temperature of the temperature sensor T2 is further lowered, and the three-way valve 13 is controlled so as to reach the newly set target temperature. This operation is then repeated until the raw water temperature T1 falls below the set temperature, so that the raw water temperature T1 does not rise above the set value.

[0052] The second embodiment will be described with reference to FIG.

[0053] In this embodiment, the three-way valve 13 and the bypass drain 16 are omitted, and the entire amount of raw water delivered from the pump 11 is passed through the heat exchanger 22. In order to make the amount of raw water delivered to the heat exchanger 22 variable, a pump 11 capable of controlling the amount of delivered water, such as an inverter-controlled pump, is used. Also, a pump controller (not shown) is provided that controls the discharge amount (amount of delivered water) of the pump 11 according to the temperature detected by the temperature sensor T1.

[0054] Other configurations in FIG. 2 are the same as those in FIG. 1, and the same reference numerals denote the same parts.

[0055] In this embodiment as well, the pump 11 is always in operation, regardless of whether the pretreatment device 4 is in operation or not.

[0056] In this embodiment, when T1 is lower than a set value (e.g., selected from between 20 and 25°C), a high water supply mode is set in which the amount of water supplied by the pump 11 is increased, and when T1 is equal to or greater than the set value, a low water supply mode is set in which the amount of water supplied by the pump 11 is reduced.

[0057] In the case of the high water supply rate mode, the water supply rate of the pump 11 may be controlled to increase as the (set value - T1) increases.

[0058] [Another embodiment of FIG. 2] As another embodiment of FIG. 2, a temperature sensor T3 may be provided in the pipe 23 through which the detoxified wastewater from the heat exchanger 22 flows, and the discharge rate of the pump 11 may be controlled so that the temperature detected by the temperature sensor T3 becomes the target temperature.

[0059] In this case, under normal conditions, that is, when the raw water temperature T1 is within the set range (T L More than T H below. T L is selected, for example, between 18 and 22°C. H is selected from the range of 22 to 26°C. When the raw water temperature T1 is equal to the allowable lower limit T L If the raw water temperature T1 is lower than the allowable upper limit T, the target temperature T3 detected by the temperature sensor T3 is lowered, and the rotation speed of the pump 11 is increased so as to increase the amount of raw water sent to the heat exchanger 22. H If it is higher, the target temperature of the temperature T3 is increased, and the rotation speed of the pump 11 is reduced so that the amount of raw water sent to the heat exchanger 22 is reduced.

[0060] 1 and 2, excessive heating of raw water in summer, etc. is prevented. Therefore, the amount of cold water used in the subsystem heat exchanger 7 is reduced, and power consumption of the chiller is reduced.

[0061] 1, when the raw water temperature is relatively high, the amount of raw water passing through the abatement wastewater heat exchanger 22 decreases, and the temperature of the abatement wastewater flowing from the heat exchanger 22 to the pipe 23 increases. As a result, the amount of cooling water passing through the heat exchanger 24 increases, and the power consumption of the cooling tower increases. However, since the COP (coefficient of performance) of the cooling tower is higher than that of a chiller, the power consumption of the entire system can be reduced.

[0062] In the subsystem, the pure water is at room temperature and cannot be cooled by cooling water of a similar temperature (usually 20 to 30°C), so the pure water is cooled by cold water in the heat exchanger 7. On the other hand, the temperature of the abatement wastewater is high, at about 35 to 45°C, so in the heat exchanger 24, the temperature of the abatement wastewater can be sufficiently lowered by the cooling water from the cooling tower.

[0063] The above-mentioned embodiments are merely examples of the present invention, and the present invention is not limited to these. For example, in the above-mentioned embodiments, the three-way valve 13 and the pump 11 are controlled by a controller, but they may be controlled manually.

[0064] In the above embodiment, the temperature sensor T1 is installed in the pipe 3, but it may be installed in the raw water tank 2. In the above embodiment, the primary pure water system is equipped with a decarbonation tower, an RO device, etc. in addition to the steam type heat exchanger 5b, but it may also be equipped with an RO device, a degassing device, an ion exchange device, etc. [Explanation of symbols]

[0065] 2 Raw Water Tank 4 Pretreatment Equipment 5 Primary water purifier 6 Subtank 7 Heat exchanger 8 Subsystems 11 Pump 13 Three-way valve 16 Bypass piping 22 Heat exchanger 24 Heat exchanger (heat exchanger A) 26 Heat exchanger (heat exchanger B) T1, T2, T3 temperature sensors

Claims

1. a pure water production facility for producing pure water by treating raw water from a raw water tank; A wastewater treatment facility for treating wastewater from an exhaust gas treatment facility (hereinafter referred to as wastewater treatment) and recovering and reusing it as wastewater for the exhaust gas treatment facility. A water treatment system comprising: The wastewater treatment facility has a heat exchanger that exchanges heat between the wastewater and raw water from the raw water tank to lower the temperature of the wastewater, the heat exchanger and the raw water tank are connected by a circulation pipe so as to circulate and supply the raw water in the raw water tank to the heat exchanger as a low-temperature fluid; a temperature sensor (T1) for detecting a raw water temperature in the raw water tank or in a pipe for supplying raw water from the raw water tank to the pure water production facility; a control means for controlling the amount of raw water supplied to the heat exchanger so that the temperature detected by the temperature sensor (T1) is equal to or lower than a predetermined value; A water treatment system comprising:

2. 2. The water treatment system of claim 1, wherein the control means for controlling the amount of raw water supplied to the heat exchanger includes a bypass pipe provided to bypass the heat exchanger, and a means for controlling the flow of raw water through the bypass pipe.

3. A pump for circulating raw water is provided in the circulation piping, 2. The water treatment system according to claim 1, wherein said control means for controlling the amount of raw water supplied to said heat exchanger controls the amount of water fed by said pump.

4. The water treatment system of claim 1, wherein the decontamination wastewater treatment equipment comprises a heat exchanger (A) that uses cooling water from a cooling tower as a low-temperature fluid to lower the temperature of the decontamination wastewater that has been cooled in the heat exchanger, and a heat exchanger (B) that uses cold water from a refrigerator as a low-temperature fluid to lower the temperature of the decontamination wastewater from the heat exchanger (A).

5. A temperature sensor (T2) is provided to detect the temperature of the decontamination wastewater supplied to the heat exchanger (A) from the heat exchanger that exchanges heat between the raw water and the decontamination wastewater; 5. The pure water producing apparatus according to claim 4, wherein said control means controls the amount of raw water supplied to said heat exchanger (A) so that the temperature detected by said temperature sensor (T2) becomes a target temperature.

6. a pure water production facility for producing pure water by treating raw water from a raw water tank; A wastewater treatment facility for treating wastewater from an exhaust gas treatment facility (hereinafter referred to as wastewater treatment) and recovering and reusing it as wastewater for the exhaust gas treatment facility. A water treatment method for treating wastewater and producing pure water using a water treatment system having The wastewater treatment facility has a heat exchanger that exchanges heat between the wastewater and raw water from the raw water tank to lower the temperature of the wastewater, the heat exchanger and the raw water tank are connected by a circulation pipe so as to circulate and supply the raw water stored in the raw water tank as a low-temperature fluid for the heat exchanger; A temperature sensor (T1) detects the temperature of raw water in the raw water tank or in a pipe that supplies raw water from the raw water tank to the pure water production facility; The water treatment method controls the amount of raw water supplied to the heat exchanger so that the temperature detected by the temperature sensor (T1) is equal to or lower than a predetermined value.

7. 7. The water treatment method according to claim 6, further comprising: a bypass pipe provided to bypass the heat exchanger; and controlling the flow of raw water through the bypass pipe to keep the detected temperature of the temperature sensor (T1) below a predetermined value.

8. A pump for circulating raw water is provided in the circulation piping, 7. The water treatment method according to claim 6, wherein the amount of water delivered by said pump is controlled so that the temperature detected by said temperature sensor (T1) is kept below a predetermined value.

9. The decontamination wastewater treatment equipment includes a heat exchanger (A) that uses cooling water from a cooling tower as a low-temperature fluid to lower the temperature of the decontamination wastewater that has been lowered in the heat exchanger; A heat exchanger (B) that uses cold water from a refrigerator as a low-temperature fluid to lower the temperature of the wastewater from the heat exchanger (A); A temperature sensor (T2) is provided to detect the temperature of the wastewater supplied to the heat exchanger (A) from a heat exchanger using the raw water as a low-temperature heat source fluid. A water treatment method for controlling an amount of raw water supplied to the heat exchanger (A) so that a detected temperature of the temperature sensor (T2) becomes a target temperature, By changing the target temperature to a higher temperature, the amount of raw water supplied to the heat exchanger (A) is reduced; The amount of raw water supplied to the heat exchanger (A) is increased by changing the target temperature to a lower temperature. The water treatment method according to claim 7.

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