Operating method of a water treatment system

Abstract

This invention provides a method for operating a water treatment system that measures specific information in concentrated water from a water treatment unit and controls the operating conditions of the water treatment system according to these measurements. [Solution] The pure water production apparatus 1 includes an RO raw water tank 2 for storing pre-treated water W and recovered water W0, a water supply pump 3, a first reverse osmosis membrane 4, a concentrated water tank 5 for storing concentrated water from the reverse osmosis membrane 4, a water supply pump 6 for the concentrated water from the first reverse osmosis membrane 4, and a second reverse osmosis membrane 7. Furthermore, an SiO2 concentration measuring means is provided to measure the SiO2 concentration of the concentrated water W3 from the second reverse osmosis membrane 7 as information on a specific substance. By measuring the SiO2 concentration of the concentrated water W3 from the second reverse osmosis membrane 7 and controlling the recovery rate as an operating condition of the second reverse osmosis membrane 7 according to this measurement, the water utilization efficiency in the pure water production apparatus 1 can be improved.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for operating a water treatment system having a water treatment unit that produces treated water and concentrated water, and particularly relates to a method for operating a water treatment system that measures specific information in the concentrated water of the water treatment unit and controls the operating conditions of the water treatment system in accordance with the measured value.

BACKGROUND ART

[0002] In semiconductor factories, a large amount of water is used for cleaning and the like in product manufacturing processes, and a wide variety of wastewaters are discharged from multiple manufacturing processes. In recent years, for the purpose of reducing environmental load in water treatment facilities, needs for water saving and needs for recycling and recovering valuable substances contained in wastewater have been increasing.

[0003] For example, in an ultrapure water production apparatus as a water treatment system, raw water such as industrial water and well water is treated under fixed operating conditions to produce ultrapure water, and the operation under such fixed conditions largely contributes to stabilizing the quality of treated water.

[0004] However, in order to meet the needs for water saving in addition to water quality stabilization, it is necessary to make these operating conditions variable. In practice, the feed water concentration of the ultrapure water production apparatus may fluctuate greatly due to multiple factors such as raw water quality fluctuation, inflow of recovered water, and recovered water quality fluctuation, and under the fixed condition operation of the pure water production apparatus, the current situation is that it cannot be said that the water recovery rate is maximized and water saving is achieved.

[0005] Further, in a wastewater recovery treatment apparatus or a resource recovery apparatus as a water treatment system, wastewater containing specific valuable substances is concentrated, but for efficient treatment, it is preferable to recover the concentrated effluent at a constant concentration. Even when valuable substances are concentrated as a pretreatment for resource recovery of valuable substances, keeping the concentration of valuable substances in the concentrated effluent constant leads to stable operation of the resource recovery apparatus.

[0006] However, wastewater discharged from various manufacturing processes experiences variations in the concentration and volume of valuable substances due to the manufacturing recipe. If wastewater recovery and treatment equipment or resource recovery equipment is operated under constant conditions to concentrate the wastewater in this state, the concentration of valuable substances in the concentrated wastewater will vary greatly, posing a risk of unstable operation of the resource recovery equipment. While these issues can be mitigated by increasing the size of the raw water tank, this is difficult in limited space, and a simpler solution through operational control methods is preferable. [Overview of the project] [Problems that the invention aims to solve]

[0007] As mentioned above, there is a need for technology that can stably conserve water and recover resources in water treatment systems without increasing the size of the raw water tank, in response to the fluctuating quality of the raw water used in water treatment systems.

[0008] The present invention has been made in view of the above problems, and aims to provide a method for operating a water treatment system that measures specific information in concentrated water of a water treatment unit and controls the operating conditions of the water treatment system according to the measured values. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a method for operating a water treatment system having a water treatment unit that produces treated water and concentrated water, wherein specific information in the concentrated water of the water treatment unit is measured, and the operating conditions of the water treatment system are controlled according to the measured value (Invention 1). In the above invention (Invention 1), it is preferable that the water treatment unit that produces the treated water and concentrated water is one or more selected from a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane, an ion exchange membrane, and a gas separation membrane (Invention 2).

[0010] According to these inventions (Inventions 1 and 2), the concentrated water from water treatment units such as reverse osmosis membranes, nanofiltration membranes, ultrafiltration membranes, ion exchange membranes, and gas separation membranes contains information that affects operating conditions, such as the concentration of specific substances like scale components and components to be recovered. By controlling the water treatment system based on the measured values ​​of this information about specific substances, it is possible to improve the water recovery rate, the recovery rate of valuable materials, and furthermore, to ensure stable operation of the water treatment system.

[0011] In the above invention (Invention 2), it is preferable that the water treatment system is a pure water production apparatus, and the water treatment unit that produces the treated water and concentrated water is a reverse osmosis membrane (Invention 3).

[0012] According to this invention (Invention 3), a pure water production system can be operated with a high recovery rate without depending on fluctuations in the water quality of the raw water to be treated or the recovered water, or the inflow ratio of the recovered water. For example, by measuring the concentration of scale components in the concentrated water of the reverse osmosis membrane, the system can be operated at a concentration near the limit of the concentration at which scale occurs, thereby maximizing the water recovery rate for the supply water such as raw water to be treated or recovered water, and enabling effective water-saving operation.

[0013] In the above invention (Invention 2), it is preferable that the water treatment system is a wastewater recovery device, and the water treatment unit that produces the treated water and concentrated water is a reverse osmosis membrane (Invention 4).

[0014] According to this invention (Invention 4), the wastewater recovery device can be operated at a high concentration rate of the target substance without depending on fluctuations in the water quality of the treated water. For example, when concentrating and discharging valuable substances from concentrated water using a reverse osmosis membrane, the concentration of valuable substances in the concentrated water can be measured and the recovery rate of the reverse osmosis membrane can be controlled so that this concentration remains approximately constant, thereby effectively recovering the valuable substances. Furthermore, when discharging the water as a pre-concentration for a resource recovery device, concentrated water with a predetermined concentration of valuable substances can be supplied to the resource recovery device, enabling stable operation of the resource recovery device.

[0015] In the above inventions (Inventions 1 to 4), it is preferable that the water treatment system comprises one or more types of raw water tanks, water pumps, reverse osmosis membrane flow control valves, and chemical solution addition devices, and that the control of the operating conditions of the water treatment system is one of the following: the water level in the raw water tank, the frequency of the water pump, the opening degree of the reverse osmosis membrane flow control valve, or the amount of chemical solution added (Invention 5).

[0016] According to this invention (Invention 5), by controlling one or more of the water level in the raw water tank, the frequency of the water supply pump, the opening degree of the flow control valve of the reverse osmosis membrane, or the amount of chemical solution added, it is possible to improve the water recovery rate, improve the recovery rate of valuable materials, and furthermore, ensure stable operation of the water treatment system. [Effects of the Invention]

[0017] According to the water treatment system operation method of the present invention, specific information in the concentrated water of the water treatment unit is measured, and the operating conditions of the water treatment system are controlled according to these measured values. This makes it possible to improve the water recovery rate, the valuable material recovery rate, and furthermore, to ensure stable operation of the water treatment system. [Brief explanation of the drawing]

[0018] [Figure 1] A flowchart illustrating a water treatment system to which the operation method of the first embodiment of the present invention can be applied. [Figure 2] A flowchart illustrating a water treatment system to which the operation method of the water treatment system according to the second embodiment of the present invention can be applied. [Modes for carrying out the invention]

[0019] The water treatment system of the present invention will now be described in detail. The water treatment system of the present invention has a water treatment unit that produces treated water and concentrated water, and has means for measuring information on specific substances in the concentrated water of this water treatment unit. Here, the water treatment system is one or more of a pretreatment device, a primary pure water production device (pure water production device), a secondary pure water production device, and a wastewater recovery device (including a resource recovery device).

[0020] Examples of the configuration flow of the pretreatment device include a tank, a heat exchanger, a flocculation tank, a filter, an activated carbon tower, and the like.

[0021] Examples of the configuration flow of the primary pure water device include a tank, a reverse osmosis membrane, a decarbonation membrane, a degassing membrane, an ultraviolet oxidizer, an ion exchange resin tower (or an electrodeionization device), and the like.

[0022] Examples of the configuration flow of the secondary pure water production device include a primary pure water tank, a heat exchanger, an ultraviolet oxidizer, a degassing membrane, an ion exchange resin tower, an ultrafiltration membrane, and the like.

[0023] Examples of the configuration flow of the wastewater recovery device (including a resource recovery device) include a neutralization tank, a flocculation tank, a turbidity removal membrane (filter), a tank, a reverse osmosis membrane, and the like.

[0024] Examples of the configuration flow of the resource recovery device include a flocculation tank, a filter, an activated carbon tower, a reverse osmosis membrane, and the like.

[0025] In each of these devices, examples of the water treatment unit that produces treated water and concentrated water include membrane-type units such as a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane, an ion exchange membrane, and a gas separation membrane.

[0026] Specific information in the concentrated water includes the concentration of metal ions, the concentration of components that cause scale such as silica, the concentration of organic components such as TOC, the concentration of components that cause slime such as nitrogen and phosphorus, the concentration of fluorine ions, the concentration of phosphate ions, the concentration of components that have recovery applications as resources such as ammonium ions, the concentration of chemical solutions used for specific applications, and further water quality information in the target such as pH and electrical conductivity, and the like.

[0027] For measuring (monitoring) specific information in the concentrated water of a water treatment unit, online measuring instruments for various concentrations, pH meters, conductivity systems, etc., are preferred. When measuring specific substances online, in addition to directly measuring the concentration in the wastewater, it is also acceptable to continuously dilute the solution with pure water or the like according to the measurement range before measurement.

[0028] Operating conditions for a water treatment system controlled according to measurements of specific information in concentrated water include the frequency of the water supply pump, the opening degree of the flow control valve of the reverse osmosis membrane, and the amount of chemical solution added.

[0029] [First Embodiment] <Pure water production equipment> First, we will describe the operating method of a pure water production apparatus (primary pure water production apparatus) as a water treatment system, which is the first embodiment of the present invention.

[0030] Figure 1 shows a pure water production apparatus to which the operating method of the water treatment system of the present invention can be applied. In Figure 1, the pure water production apparatus 1 as a water treatment system includes an RO raw water tank 2 for storing pre-treated water W and recovered water W0, a water supply pump 3, a first reverse osmosis membrane 4, a concentrated water tank 5 for storing concentrated water from the reverse osmosis membrane 4, a water supply pump 6 for the concentrated water from the first reverse osmosis membrane 4, and a second reverse osmosis membrane 7. Furthermore, an SiO2 concentration measuring means (not shown) is provided for measuring the SiO2 concentration of the concentrated water W3 from the second reverse osmosis membrane 7 as information on a specific substance.

[0031] The pure water production apparatus 1 described above uses pre-treated water W and recovered water W0 as raw water to be treated with a first reverse osmosis membrane 4 to obtain treated water W1, and also treats the concentrated water from the first reverse osmosis membrane 4 with a second reverse osmosis membrane 7 to obtain treated water W2 and concentrated water W3.

[0032] (First operational control) In the pure water production apparatus 1 described above, the flow rate of the pre-treated water W (SiO2 concentration 40 mg / L) is 100 m 3 At a rate of / h, the flow rate of recovered water W0 (SiO2 concentration 1 mg / L) is 30 m³. 3The RO raw water is introduced into the RO raw water tank 2 at a rate of / h, and the first reverse osmosis membrane 4 and the second reverse osmosis membrane 7 are operated to achieve a recovery rate of 75%. As a result, the flow rates and SiO2 concentrations are as shown in Table 1, and the SiO2 concentration of the discharged water (concentrated water from the second reverse osmosis membrane 7) W3 is 496 mg / L.

[0033] [Table 1]

[0034] (Second driving control) Next, keeping the concentrations of pre-treated water W and recovered water W0 the same, the flow rate of pre-treated water W is increased to 80 m³. 3 / h, 50m³ of recovered water 3 When the flow rate fluctuates to / h and the first reverse osmosis membrane 4 and the second reverse osmosis membrane 7 are operated to achieve a recovery rate of 75%, the flow rates and SiO2 concentrations are as shown in Table 2, and the SiO2 concentration of the concentrated water W3 in the second reverse osmosis membrane 7 decreases to 400 mg / L. In other words, there is room to increase the water recovery rate compared to the first operating control.

[0035] [Table 2]

[0036] (Third operational control) Furthermore, the concentrations of the pre-treated water W and recovered water W0 are the same as in the second operation control, and the flow rate of the pre-treated water W is 80 m³. 3 / h, 50m³ of recovered water 3 The first reverse osmosis membrane 4 was operated at a rate of 75% per hour, while the SiO2 concentration of the concentrated water W3 in the second reverse osmosis membrane 7 was continuously measured. The flow rate of the concentrated water W3 in the second reverse osmosis membrane 7 was controlled by a valve acting as a flow control valve so that the measured value was 500 mg / L, resulting in the flow rates and SiO2 concentrations shown in Table 3. As a result, the recovery rate of the second reverse osmosis membrane 7 improved from 75% to 80%, and the amount of treated water W2 in the second reverse osmosis membrane 7 increased to 1.6 m³. 3 An improvement in / h is expected.

[0037] [Table 3]

[0038] Thus, by measuring the SiO2 concentration of the concentrated water W3 in the second reverse osmosis membrane 7 and controlling the recovery rate as an operating condition of the second reverse osmosis membrane 7 according to this measurement, it is possible to improve the water utilization efficiency in the pure water production apparatus 1.

[0039] [Second Embodiment] <Wastewater recovery device> Next, a method for operating a wastewater recovery device as a water treatment system, which is a second embodiment of the present invention, will be described.

[0040] Figure 2 shows a wastewater recovery device to which the operating method of the water treatment system of the present invention can be applied. In Figure 2, the wastewater recovery device 11 as a water treatment system includes a raw water tank 12 for storing wastewater (pre-treated water) W, a water supply pump 13, and a reverse osmosis membrane 14. Furthermore, an F concentration measuring means (not shown) is provided to measure the F (fluorine) concentration of the concentrated water W5 in the reverse osmosis membrane 14 as information on a specific substance. This wastewater recovery device 11 is an example of treating wastewater (pre-treated water) W with the reverse osmosis membrane 14 to concentrate F (fluorine) in the concentrated water W5 and recover it as a resource.

[0041] This wastewater recovery device 11 treats wastewater (pre-treated water) W with a reverse osmosis membrane 14 to obtain treated water W4, and also recovers the concentrated water W5 from the reverse osmosis membrane 14.

[0042] (First operational control) In the wastewater recovery device 11 described above, the flow rate of the pre-treated water W (F concentration 850 mg / L) is 100 m 3 The reverse osmosis membrane 14 is operated at a rate of 66% recovery rate (approximately 3-fold concentration) at a rate of / h. As a result, the flow rate and the concentration of F in the concentrated water W5 are concentrated to 2500 mg / L, as shown in Table 4.

[0043] [Table 4]

[0044] (Second driving control) Next, when the F concentration of the pre-treated water W fluctuated up to 500 mg / L and the reverse osmosis membrane 14 continued to operate with a recovery rate of 66%, the flow rate and F concentration became as shown in Table 5, and the F concentration of the concentrated water W5 in the reverse osmosis membrane 14 decreased to 1471 mg / L. If this concentrated water W5 were sent to the F resource recovery device, it is expected that stable operation of the resource recovery device would be difficult due to the decreased F concentration.

[0045] [Table 5]

[0046] (Third operational control) Then, with the F concentration of the pre-treated water W set to 500 mg / L, similar to the second operational control, the F concentration of the concentrated water W3 in the reverse osmosis membrane 14 was continuously measured. The flow rate of the concentrated water W5 in the reverse osmosis membrane 14 was controlled by a valve acting as a flow control valve so that the measured value was 2500 mg / L, resulting in the flow rate and F concentration shown in Table 6. As a result, the recovery rate of the reverse osmosis membrane 14 improved from 66% to 80%, and the F concentration of the concentrated water W5 in the reverse osmosis membrane 14 stabilized, allowing for stable operation of the resource recovery device.

[0047] [Table 6]

[0048] Thus, by measuring the F concentration of the concentrated water W5 in the reverse osmosis membrane 14 and controlling the recovery rate of the reverse osmosis membrane 14 so that this measured value remains nearly constant, it is possible to stabilize the operation of the resource recovery device.

[0049] Although the present invention has been described above based on the embodiments described above, the present invention is not limited thereto and can be applied to various pretreatment devices, primary pure water production devices, secondary pure water production devices, and wastewater recovery devices and resource recovery devices with various device configurations. In this specification, concentrated water of a water treatment unit and operating conditions to be controlled do not include sample water used for measurement by online instruments. [Explanation of Symbols]

[0050] 1. Pure water production equipment (water treatment system) 2 RO raw water tanks 3. Water supply pump 4. First reverse osmosis membrane 5. Concentrated water tank 6. Water supply pump 7. Second reverse osmosis membrane 11. Wastewater recovery equipment (water treatment system) 12 Raw water tank 13 Water supply pump 14 Reverse osmosis membrane W Pre-treated water W W0 Recovered Water W1 treated water W2 treated water W3 Concentrated water W4 treated water W5 Concentrated water

Claims

1. A method for operating a water treatment system having a water treatment unit that produces treated water and concentrated water, wherein specific information in the concentrated water of the water treatment unit is measured, and the operating conditions of the water treatment system are controlled according to the measured value.

2. The method for operating a water treatment system according to claim 1, wherein the water treatment unit that generates the treated water and concentrated water is one or more selected from a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane, an ion exchange membrane, and a gas separation membrane.

3. The method for operating a water treatment system according to claim 2, wherein the water treatment system is a pure water production apparatus, and the water treatment unit that produces the treated water and concentrated water is a reverse osmosis membrane.

4. The method for operating a water treatment system according to claim 2, wherein the water treatment system is a wastewater recovery device, and the water treatment unit that generates the treated water and concentrated water is a reverse osmosis membrane.

5. The method for operating a water treatment system according to any one of claims 1 to 4, wherein the water treatment system comprises one or more types of raw water tanks, water pumps, reverse osmosis membrane flow control valves, and chemical additive devices, and the control of the operating conditions of the water treatment system is one of the following: the water level in the raw water tank, the frequency of the water pumps, the opening degree of the reverse osmosis membrane flow control valve, or the amount of chemical additive.

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