Water treatment system

Abstract

A water treatment system that treats first and second raw water with a water treatment device, wherein the supply of second raw water to the water treatment device is switched according to the water quality of second raw water, and the system appropriately switches the destination of the second raw water. [Solution] The system comprises a first raw water supply route, a second raw water supply route, a water treatment device, a water quality detection means for detecting the water quality of the second raw water, and a water destination switching means for switching the destination of the second raw water. It includes a first TOC meter that detects only easily degradable TOC components, and a second TOC meter that detects both easily degradable TOC components and difficult-to-degradable TOC components. The water destination is switched based on the difference between the second TOC value detected by the second TOC meter and the first TOC value detected by the first TOC meter.

Description

Technical Field

[0001] The present invention relates to a water treatment system, and particularly to a water treatment system having a water treatment apparatus for treating a first raw water and a second raw water. Specifically, the present invention relates to a water treatment system configured to switch the water supply destination of the second raw water based on the amount of refractory TOC components and the amount of biodegradable TOC components in the second raw water. One aspect of the present invention relates to a water treatment system using recovered water from a use point using ultrapure water as the second raw water.

Background Art

[0002] The water treatment facilities in semiconductor manufacturing plants are designed to have the ability to treat specific components and their amounts determined in advance. However, depending on the operating conditions of semiconductor manufacturing plants, the target water quality and water volume of raw water and treated water may vary significantly. In addition, due to fluctuations in the water quality of wastewater in wastewater recovery treatment facilities, the treated water quality may deteriorate, and it is very difficult to appropriately judge the switching of the destination of the wastewater and the recovered treated water.

[0003] Patent Document 1 describes providing an evaluation pure water production unit in a water treatment system, analyzing the treated water of the evaluation pure water production unit, and controlling the raw water supply destination flow path according to the result.

[0004] Patent Document 2 describes analyzing the TOC of the treated water from a sub-ultrapure water production apparatus and switching the water supply destination of the treated water of the recovery treatment apparatus.

[0005] [[ID=2q]]However, the above evaluation pure water production unit and sub-ultrapure water production apparatus are composed of a plurality of units, resulting in a long residence time. It takes a lot of time to measure the treated water with water quality analysis means and obtain the analysis result.

[0006] In addition, there are periods, labor, and impacts on analysis accuracy due to unit contamination during which switching cannot be judged due to maintenance of the evaluation pure water production unit and sub-ultrapure water production apparatus.

[0007] If a significant amount of time is spent measuring the water quality of wastewater or recovered treated water and determining whether to switch to a different water supply system, the time lag until the water supply is switched may adversely affect the receiving facility or cause deterioration of water quality. Therefore, it is desirable to use a method that allows for a quick decision to switch the wastewater supply destination using simple and minimal components.

[0008] Furthermore, the fact that it consists of multiple units increases maintenance effort, and periods when a unit is unavailable could negatively impact the receiving facilities, lead to water quality deterioration, or reduce the recovery rate. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2023-150984 [Patent Document 2] Japanese Patent Publication No. 2016-107249 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention relates to a water treatment system that treats first raw water from a first raw water supply route and second raw water from a second raw water supply route with a water treatment device, and aims to provide a water treatment system that can appropriately switch the supply of second raw water to the water treatment device according to the water quality of the second raw water. [Means for solving the problem]

[0011] The water treatment system of the present invention is as follows:

[0012] [1] The first raw water supply route, The second raw water supply route, A water treatment apparatus that receives and treats first raw water from the first raw water supply route and second raw water from the second raw water supply route to produce treated water, A water quality detection means for detecting the water quality of the second raw water, A water supply destination switching means that switches the destination of the second raw water from the second raw water supply route between the water treatment device and another water system based on the detection results of the water quality detection means. In a water treatment system having, The water quality detection means includes a first TOC meter that detects only easily degradable TOC components, and a second TOC meter that detects both easily degradable TOC components and difficult-to-degradable TOC components. The water supply destination switching means is characterized by switching the water supply destination based on the difference between the second TOC value detected by the second TOC meter and the first TOC value detected by the first TOC meter.

[0013] [2] The water treatment apparatus is a primary pure water system and subsystem of an ultrapure water production apparatus, and the first raw water supply route includes a pretreatment system of the ultrapure water production apparatus. The aforementioned second raw water supply route is equipped with a water treatment facility for recovered water from the ultrapure water use point. [1] Water treatment system.

[0014] [3] The water supply destination switching means supplies the second raw water to the water treatment device when the difference between the second TOC value and the first TOC value is lower than the first reference value, and supplies the second raw water to the other water system when it is higher than the first reference value. [2]

[0015] [4] The first reference value is a value selected from 0 to 20 μg / L [3] in the water treatment system. [Effects of the Invention]

[0016] In the water treatment system of the present invention, the destination of the second raw water is switched based on the difference between the TOC concentration of the second raw water (second TOC value) and the TOC concentration of the first raw water (first TOC value), either by supplying the second raw water to the water treatment device or to another water treatment system.

[0017] Since the difference between the second TOC value and the first TOC value is the concentration of the refractory TOC component in the second raw water, according to the present invention, the second raw water with a low concentration of the refractory TOC component is supplied to the water treatment apparatus and treated as treated water, so that the water quality of the treated water in the water treatment system becomes good. In addition, the operation of the water treatment system becomes stable.

[0018] In one aspect of the present invention, the second raw water is recovered water from the ultrapure water use point, and this recovered water is treated by the primary pure water system and the subsystem of the ultrapure water production apparatus. According to this aspect, it is possible to accurately recover the recovered water with good water quality and reuse it for ultrapure water production.

[0019] Also, in this aspect, it is possible to make the following determinations 1) and 2) with only a simple configuration of an online instrument (TOC meter) with a very short residence time without requiring a plurality of unit configurations such as an evaluation pure water production unit or a sub-ultrapure water production apparatus. 1) It becomes possible to determine whether the TOC component in the drainage has an adverse effect such as poor flocculation or membrane fouling in the drainage recovery apparatus. 2) It becomes possible to determine whether the TOC component in the drainage recovery treated water affects the deterioration of the water quality of the pure water production apparatus or the like.

[0020] Thereby, it is possible to prevent adverse effects on the water treatment equipment and deterioration of the water quality in the pure water production apparatus, and to meet the requirement of improving water recovery in the entire semiconductor manufacturing factory.

Brief Description of the Drawings

[0021] [Figure 1] It is a flowchart of the water treatment system according to the embodiment.

Mode for Carrying Out the Invention

[0022] The water treatment system according to the embodiment will be described below with reference to Figure 1. In the water treatment system of Figure 1, the water treatment device is an ultrapure water production device. This water treatment system includes a pretreatment system 1, a primary pure water system, a subsystem 4, a treatment facility 9 for water recovered at the use point, and a means for switching the destination of wastewater from the use point.

[0023] In this embodiment, raw water such as industrial water is first subjected to coagulation filtration in the pretreatment system 1 to remove suspended solids and colloidal substances from the raw water. Furthermore, this process can also remove high-molecular-weight organic substances and hydrophobic organic substances.

[0024] The water that has undergone coagulation filtration is decarboxylated in a decarbonation tower and then introduced into tank 3 via piping 2. In this embodiment, the pretreatment system 1 and piping 2 constitute the first raw water supply route, and the water from piping 2 is the first raw water.

[0025] This tank 3 can receive recovered water via the piping 13 described later. The water in tank 3 is sent to the primary pure water system 4, where it is treated by an RO system, UV system, ion exchange system (mixed bed type or 4-bed 5-column type, etc.) to remove ions and organic components from the raw water. The RO system removes salts as well as ionic and colloidal TOC. The ion exchange system removes salts as well as ionic TOC components. In addition, a degasser may be installed downstream of the ion exchange system to remove inorganic carbon (IC) and dissolved oxygen.

[0026] The primary pure water produced by the primary pure water system is introduced into subsystem 6 via sub-tank 5, where it is treated by a low-pressure ultraviolet oxidation unit, a degasser, an ion exchange unit, and an ultrafiltration (UF) unit. In the low-pressure ultraviolet oxidation unit, 185nm ultraviolet light emitted from a low-pressure ultraviolet lamp decomposes TOC into organic acids and then into CO2. The organic matter and CO2 generated by the decomposition are removed by the degasser and ion exchange unit. In the ultrafiltration unit, fine particles are removed, as well as particles leached from the ion exchange resin.

[0027] The ultrapure water produced in subsystem 6 is sent to use point 7, and any unused ultrapure water is returned to sub-tank 5 via return piping (not shown).

[0028] Wastewater generated from semiconductor cleaning and other applications at Use Point 7 is introduced to the recovery and treatment facility 9 via piping 8 for treatment. For example, TOC (organic matter) components are biodegraded in a biological treatment tank, suspended solids and colloidal substances are removed in a coagulation, pressurized flotation, and filtration system, then residual organic matter is adsorbed and removed in an activated carbon tower, and finally desalination and removal of ionic and colloidal TOC components in an RO (reverse osmosis) system. The treated water from this recovery water treatment facility 9 is then sent to piping 10.

[0029] A first TOC meter 11 and a second TOC meter 12 are installed in the piping 10. The first TOC meter 11 is for detecting only easily degradable TOC components, while the second TOC meter is for detecting both easily degradable and difficult-to-degradable TOC components.

[0030] Examples of easily degradable TOC components include substances such as isopropyl alcohol, which are largely (e.g., 90% or more) degraded by normal treatment in an ultraviolet oxidation device. Examples of persistently degradable TOC components include substances that are difficult to degrad by UV oxidation treatment, such as urea, tetramethylammonium (TMA), tetramethylammonium hydroxide (TMAH), urea, urea derivatives, acetic acid, and formic acid. The first TOC analyzer 11 and the second TOC analyzer 12 differ in the UV intensity irradiated onto the water sample. In the first TOC analyzer 11, the UV intensity is low, so that virtually only easily degradable TOC components are degraded and detected.

[0031] The second TOC meter 12, capable of measuring the concentrations of persistent and easily degradable TOC, is a TOC meter that can detect 90% or more, preferably 99% or more, of persistent TOC components (such as urea and TMA) that are not easily oxidized by UV, and can also detect 90% or more, preferably 99% or more, of easily degradable TOC components (such as IPA).

[0032] The first TOC meter 11, which can measure only the concentration of easily degradable TOC, is a TOC meter that can detect 10% or less, preferably 1% or less, of the persistent TOC components, and 90% or more, preferably 99% or more, of the easily degradable TOC components.

[0033] For the first TOC meter, you can use the Anatel A1000XP (discontinued) manufactured by Beckman Coulter, Inc. or the ACCURA SX manufactured by T&C Technical Co., Ltd. For the second TOC meter, you can use the Sievers 500RLe or Sievers M9e manufactured by Central Scientific Co., Ltd., but you are not limited to these.

[0034] The downstream end of pipe 10 branches into three pipes 13, 14, and 15, and each of these pipes 13, 14, and 15 is equipped with an on / off valve 13a, 14a, and 15a, respectively.

[0035] Pipe 13 leads to the tank 3. Pipe 14 leads to the water supply system 16. Pipe 15 leads to the drainage system 17.

[0036] In this embodiment, a second raw water supply route is formed by the recovered water treatment equipment 9 and the piping 10, and the water from the piping 10 is the second raw water.

[0037] The means for switching the destination of the second raw water supply consists of pipes 13, 14, and 15, valves 13a, 14a, and 15a, and a valve controller.

[0038] The detection signals from the first TOC meter 11 and the second TOC meter 12 are input to a valve controller (not shown). The valve controller calculates the difference ΔTOC between the TOC concentration detected by the second TOC meter 12 (second TOC value) and the TOC concentration detected by the first TOC meter 11 (first TOC value). When this ΔTOC is lower than the first reference value, valve 13a is opened and valves 14a and 15a are closed, supplying water from the piping 10 to the tank 3.

[0039] In this way, by distributing the destination of the treated water recovered from the recovered water treatment facility 9 using ΔTOC, the amount of recovered water can be increased while maintaining ultrapure water quality.

[0040] For reference, an example of the first reference value is as follows:

[0041] First reference value: A value selected from TOC concentrations of 0-20 μg / L. [Examples]

[0042] An example of operation (simulation) of the present invention apparatus, assuming the following operating conditions, is described below.

[0043] <Assumed Operating Conditions> (1) The reduction rates of persistent and readily degradable TOC components in the primary pure water system and subsystems, and the detection rates in the first and second TOC meters are assumed to be as follows: • Reduction rate of persistent TOC components in primary pure water systems: 90% (This 90% represents the sum of removal by the functional components and the dilution effect from mixing with other influent water.) • Reduction rate of easily degradable TOC components in primary pure water systems: 99% or more • Detection rate of difficult-to-decompose and easily decompose TOC components by the second TOC analyzer: over 99% • Detection rate of recalcitrant TOC components in the first TOC analyzer: less than 1%, detection rate of easily decomposable TOC: 99% or more

[0044] (2) The guaranteed TOC value at the outlet of the primary pure water system shall be 1 μg / L or less.

[0045] The reduction rate of recalcitrant components in the recovered water is set at 90%, combining the removal effect of functional materials such as RO in the primary pure water system and the dilution effect of other influent water. In this case, the permissible concentration of recalcitrant TOC components in the treated water of the wastewater recovery facility, which is allowed in order to comply with the guaranteed value at the outlet of the primary pure water system, is set at 10 μg / L according to the following formula.

[0046] 1 μg / L / (1 - 0.9) = 10 μg / L

[0047] (3) The TOC concentration of the treated wastewater (water discharged into pipe 10) is set to 1000 μg / L (of which the persistent TOC component fluctuates between 0.5 and 2%).

[0048] At this time, the following values ​​are detected by each TOC meter. · 2nd TOC meter: 1000μg / L • First TOC meter: fluctuates between 980 and 995 μg / L

[0049] [Example of actual operation 1] (Example of operation (simulation) based on ΔTOC) The first reference value for ΔTOC is set at 10 μg / L.

[0050] <In the case where the amount of persistent TOC components in the total TOC components of treated wastewater is 0.5%> Measurement value from the second TOC analyzer: 1000 μg / L. Measurement from the first TOC analyzer: 995 μg / L ΔTOC = 5 μg / L Therefore, since ΔTOC < 10 μg / L, valve 13a is opened and valves 14a and 15a are closed (water is supplied to tank 3).

[0051] <In the case of 2% of the total TOC components in wastewater recovery treatment water containing persistent TOC components> Measurement value from the second TOC analyzer: 1000 μg / L. Measurement from the first TOC analyzer: 980 μg / L ΔTOC = 20 μg / L Therefore, since ΔTOC > 10 μg / L, valve 13a is closed and valve 14a or 15a is opened.

[0052] [Comparative Operation Example 1] (Operation (simulation) example based only on the detected values ​​of the second TOC totaler 12) In Figure 1, the first TOC analyzer 11 is omitted, and based solely on the detected TOC value (second TOC value) of the second TOC analyzer 12, if the second TOC value is less than or equal to the threshold value of 100 μg / L, only valve 13a is opened; otherwise, valve 13a is closed and valve 14a or 15a is opened.

[0053] In this case, when the proportion of persistent TOC components in the second TOC value of 1000 μg / L is 0.5 to 1%, the amount of persistent TOC components in the recovered treated water is 5 to 10 μg / L, which satisfies the guaranteed TOC value for the effluent of the primary pure water system. However, when the proportion of persistent TOC components in the TOC of 1000 μg / L is 1 to 2%, the amount of persistent TOC components in the recovered treated water becomes 10 to 20 μg / L, which deviates from the guaranteed TOC value for the effluent of the primary pure water system.

[0054] Therefore, when managing with only the second TOC meter, in order to prevent deviation from the guaranteed TOC value of the primary pure water system effluent, it is necessary to set the separation criterion value higher than that in the actual operation example 1, based on the wastewater trend, as shown in comparative operation example 2 below. However, in that case, as explained below, waste will occur as water that could have been recovered will also be discarded.

[0055] [Comparative Operation Example 2] (If the second TOC value is 500 μg / L or less, only valve 13a is opened; if it is higher, valve 13a is closed and valve 14a or 15a is opened.) To prevent deviations from guaranteed water quality, as seen in Comparative Operation Example 1, it is necessary to determine the set value for recovery by working backward from the maximum concentration of persistent TOC components present, based on the relationship between the minimum proportion of persistent TOC components and the TOC concentration.

[0056] Assuming the proportion of persistent TOC components fluctuates between 0.5% and 2%, When TOC = 1000 μg / L, the minimum percentage of persistent TOC components is 0.5%. If we calculate the TOC concentration when the maximum percentage is 2% at the same rate, it will be 500 μg / L.

[0057] Therefore, in this comparative operation example 2, if the TOC meter reading is 500 μg / L or less, only valve 13a is opened; otherwise, valve 13a is closed and valve 14a or 15a is opened.

[0058] In this case, depending on the proportion of persistent TOC components, the recovered treated water with TOC concentrations of 500-2000 μg / L, which might otherwise be recoverable, will not be fully recovered. Thus, operation based solely on the detection values ​​of the second TOC meter results in a considerably low utilization rate of the recovered water.

[0059] To avoid this, operating as in Comparative Operation Example 1 above would carry the risk of deviating from the guaranteed water quality values. [Explanation of symbols]

[0060] 1. Pre-processing system 3 tanks 4. Primary pure water system 5 Sub-tank 6 subsystems 7 Youth Points 9. Reclaimed Water Treatment Facility 11 1st TOC meter 12 2nd TOC meter

Claims

1. The first raw water supply route, The second raw water supply route, A water treatment apparatus that receives and treats first raw water from the first raw water supply route and second raw water from the second raw water supply route to produce treated water, A water quality detection means for detecting the water quality of the second raw water, A water supply destination switching means that switches the destination of the second raw water from the second raw water supply route between the water treatment device and another water system based on the detection results of the water quality detection means. In a water treatment system having, The water quality detection means includes a first TOC meter that detects only easily degradable TOC components, and a second TOC meter that detects both easily degradable TOC components and persistent TOC components. The water supply destination switching means is characterized by switching the water supply destination based on the difference between the second TOC value detected by the second TOC meter and the first TOC value detected by the first TOC meter.

2. The water treatment apparatus is a primary pure water system and subsystem of an ultrapure water production apparatus, and the first raw water supply path includes a pretreatment system for the ultrapure water production apparatus. The aforementioned second raw water supply route is equipped with a water treatment facility for recovered water from the ultrapure water use point. The water treatment system according to claim 1.

3. The water treatment system according to claim 2, wherein the water supply destination switching means supplies the second raw water to the water treatment device when the difference between the second TOC value and the first TOC value is lower than the first reference value, and supplies the second raw water to the other water system when it is higher than the first reference value.

4. The first reference value is a value selected from 0 to 20 μg / L in the water treatment system [3].

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