TWI757581B - water treatment device - Google Patents

Abstract

A water treatment device, comprising: an NF membrane module 23, which receives water from a water system 1 and performs permeation treatment, including a selective permeation membrane (NF membrane) that is impermeable to useful components; an RO device 9, which is used for the NF membrane. The permeated water of the module 23 is deionized; and the non-permeated water of the NF membrane module 23 and the permeated water of the RO device 9 are returned to the elements of the water system 1 .

Description

water treatment device

The present invention relates to a water treatment apparatus that treats water from a water system and returns the treated water to the water system.

In the open-circulation cooling system, a process of treating the cooling tower blow off water and returning the treated water to the cooling tower is performed (Patent Document 1, etc.).

Recently, the industry is seeking to reduce the amount of water used or recover water, and in systems that perform water treatment, for example, in cooling towers and boilers, recovery of drain water discharged to the outside of the system is also sought. However, existing water recycling technologies also remove components that are effective for water treatment. There is a waste of energy or pharmaceuticals due to excessive removal of components from the water.

In the process of recycling cooling tower discharge water, pre-treatment filtration (sand filtration, activated carbon, microfiltration (MF) membrane, etc.) and reverse osmosis (reverse osmosis, RO) membrane or reverse electrodialysis (electrodialysis reversal) , EDR) (polar switching electrodialysis device) combined treatment. In the existing effluent water recovery process, the total amount of effluent water is treated with a pretreatment membrane or MF membrane, and then supplied to the RO membrane. Using the RO membrane or the like, water treatment chemicals, dissolved salts, etc. are concentrated in the concentrated water and discharged to the outside of the system, and the permeated water of the RO membrane or the like is used as recovered water be recycled.

[Patent Document 1] Japanese Patent Laid-Open No. 2003-1255

In the previous recycling process, various useful components contained in the raw water, such as calcium, zinc, polymers, chemical components such as calcium, zinc, polymers, phosphoric acid, and phosphonic acid, which are effective for water treatment, are also contained in the concentrated water. discharged to the outside of the system. In the previous recycling process, zinc, phosphoric acid, organic matter (Total Organic Carbon (TOC), chemical oxygen demand (COD)) were also concentrated by RO membrane, etc. It is easy to cause fouling of the RO membrane and the like. Furthermore, when the concentrated water is discharged, zinc, phosphoric acid, COD, Biochemical Oxygen Demand (BOD) and the like must be removed.

An object of the present invention is to provide a water treatment apparatus that can recover useful components, facilitates treatment of water discharged to the outside of the system, and can prevent operating failures of the apparatus.

The water treatment device of the present invention includes: a selective permeation membrane device, which receives water from a water system and performs permeation treatment, and includes a selective permeation membrane that is impermeable to useful components; Deionization treatment is performed on the permeated water; and the non-permeated water of the selectively permeable membrane device and the deionized water of the deionization device are returned to the elements of the water system.

In one aspect of the present invention, the water in the water system contains at least one of a rust inhibitor, a scale inhibitor, and a slime inhibitor.

In one aspect of the present invention, the water system is a cooling water system, a water A make-up water system that supplies make-up water to a water treatment device or a water treatment device.

In one aspect of the present invention, the selective permeation membrane is a nanofiltration (NF) membrane, and the deionization device is an RO device or an electrodeionization device.

In the present invention, the water from the water system is treated with a selective permeation membrane (a membrane with a high rejection rate of ions with a valence of 2 or more, a membrane for removing organic substances, etc.), and the deionization device such as an RO membrane or EDR The permeated water of the selective permeation membrane is treated. Then, the non-permeated water that selectively permeates the membrane is returned to the water system to recover useful components. And the deionized water of a deionization apparatus is returned to a water system, and water is recovered. In the manner described above, the useful components and water are recovered.

In the present invention, since the useful components are removed from the water supplied to the deionization device by selective permeation through the membrane, the waste water from the deionization device does not contain useful components, and the treatment of the waste water from the deionization device becomes easy. The water supply to the deionization device is treated by the selective permeation membrane, so the impurity concentration is reduced, and the stable operation of the deionization device can be realized.

When a hollow fiber-type low-pressure NF membrane is used as the selective permeation membrane, the role of the conventional pretreatment membrane can be replaced, and the device can be miniaturized.

1: Water system

2, 8, 21, 30, 71: Pump

3: Pre-processing device

4:NF device

5, 6, 7, 10, 11, 12, 22, 24, 26, 29, 31, 41, 50, 72, 74, 77: Piping

9: RO device

20, 70: Storage tank

23, 73: NF membrane module

25: Constant flow valve

27: Through the sink

28, 45, 53, 76: Weight measuring device

32: RO unit

33: Container

34: RO membrane

35: Once Room

36: Secondary room

37: Water bath

38: Circulation pump

39: Heater

40: Magnetic Stirrer

42: Constant pressure valve

43, 51: Conductivity meter

44: Concentrate Sink

46, 54, 62: Logger

52: Through the sink

60, 61: Pressure sensor

75: Filter Sink

FIG. 1 is a block diagram of a water treatment apparatus according to an embodiment.

FIG. 2 is a block diagram of the test apparatus used in the examples.

FIG. 3 is a block diagram of the test apparatus used in the examples.

FIG. 4 is a block diagram of the test apparatus used in the comparative example.

FIG. 5 is a graph showing the test results.

FIG. 6 is a graph showing the test results.

FIG. 7 is a graph showing the test results.

Hereinafter, an embodiment will be described with reference to FIG. 1 . In FIG. 1 , the water system is a circulating cooling water system, but the present invention is not limited to this, and can be applied to the treatment of various water systems that hold water containing useful components.

In the water treatment device of FIG. 1 , a part of the water in the water system 1 is supplied by a pump 2 to a pre-treatment membrane (eg, MF membrane or sand filtration, multi-mbrane filtering (MMF), double membrane filtering) , DMF), cartridge (cartridge filter, etc.), filter (strainer) and other pre-treatment devices 3, remove solid matter with large particle size and become pre-treated water. The pretreated water is supplied to the NF device 4 which is a selective permeation membrane device. The non-permeated water (concentrated water) of the NF device 4 is returned to the water system 1 via the piping 5 . A part of the non-permeated water is discharged from the piping 6 to the outside of the system as needed.

The permeated water of the NF device is supplied to the RO device 9 as a deionization device via the piping 7 and the pump 8 . Instead of RO device, electrodialysis device such as EDR can also be used. The permeated water of the RO device 9 is returned to the water system 1 via the piping 10 . The non-permeated water (concentrated water) of the RO device 9 is discharged from the piping 11 to the outside of the system. In order to improve the water recovery rate, a part of it is returned to the water supply pipe 7 to the RO device through the pipe 12, and then The RO treatment is carried out.

In the above-described embodiment, water treatment chemicals such as rust inhibitors, scale inhibitors, and slime inhibitors are added to the cooling water system 1, and the water from the water system 1 contains various useful components (polymers, phosphates, etc.) , organic phosphoric acid compounds, zinc ions, calcium ions, etc.). These useful components are recovered to the impermeable water by the NF device 4 and returned to the water system 1 . The deionized water from the RO device 9 is also recovered to the water system 1 via the piping 10, so that the water can be effectively used and the amount of make-up water can be reduced.

The concentrated water of the RO device 9 contains components (chloride ions, silicon oxide, etc.) that are not required for water treatment or that determine the upper limit of water treatment depending on the components. These components are drained out of the system by draining the concentrated water. As described above, components that may cause problems in water treatment, such as chloride and silicon oxide, can be selectively removed, so that the concentration of such components in the water system can be reduced.

In the water system 1, the useful components must also be blowed from the water system 1 as required to prevent over-concentration. In the case of FIG. 1 , by discharging a part of the concentrated water of the NF device to the outside of the system from the piping 6 , the amount of discharged water from the water system can be reduced.

In addition to the cooling water system, the present invention can also be applied to various water systems to which chemicals such as rust inhibitor or scale inhibitor are added.

[Example]

[Example 1]

<Process 1>

Through the circulation processing device using the NF membrane module shown in Figure 2, the self-realization machine is The water samples selected from the circulating cooling water system are filtered by NF membrane and concentrated.

In FIG. 2 , the water sample in the tank 20 is supplied to the NF membrane module 23 via the pump 21 and the piping 22 . A part of the ejected water of the pump 21 is returned to the storage tank 20 through the piping 29 . The concentrated water of the NF membrane module 23 is returned to the storage tank 20 via the piping 24 including a constant flow valve 25 . The permeated water of the NF membrane module 23 is introduced into the permeated water tank 27 from the piping 26 , and the amount of water is measured by the weight measuring device 28 .

By continuing the operation of the apparatus, the water in the storage tank 20 is gradually concentrated.

As the NF membrane, an NF membrane (hollow fiber type NF membrane) manufactured by De.MEM Corporation (De.MEM Limited ASX: DEM) was used. Membrane filtration is carried out under the condition of 50% recovery at an inlet pressure of 0.25MPa~0.3MPa. A 5L water sample was placed in the storage tank 20, and when the amount of permeated water reached 2.5L, the water flow was terminated.

<Processing 2>

10 mg/L of an antifouling agent (Kuriverter N-500 manufactured by Kurita Kogyo Co., Ltd.) was added to the permeated water obtained in the above-mentioned treatment 1, and an RO-containing membrane shown in FIG. The RO system of amine (polyamide, PA) membrane ES-20) was operated with a permeated water recovery rate of 70% and a fixed permeated water amount. Monitor the differential pressure between membranes (Trans Membrane Pressure, TMP) and the conductivity of the solution, and calculate the normalized flux (m ³ /m ² /day).

In the RO system of FIG. 3, the concentrated water sample in the storage tank 20 is As water, it is supplied to the vessel 33 of the RO unit 32 via the pump 30 and the piping 31 . The inside of the container 33 is divided into a primary chamber 35 and a secondary chamber 36 by an RO membrane 34 including a flat membrane. The container 33 is arranged in a water bath 37 including a circulation pump 38 and a heater 39 . In the primary chamber 35 , it is stirred by a magnetic stirrer 40 . The impermeable water (concentrated water) that has passed through the primary chamber 35 flows into the concentrated water tank 44 via the piping 41 , the constant pressure valve 42 , and the conductivity meter 43 . The concentrated water tank 44 is installed on the weight measuring device 45 , measures the amount of concentrated water flowing into the concentrated water tank 44 , and records the data on a logger 46 .

The permeated water in the secondary chamber 36 that has permeated the RO membrane 34 flows into the permeated water tank 52 via the piping 50 and the conductivity meter 51 . The permeated water tank 52 is installed on the weight measuring device 53 , and the amount of permeated water flowing into the permeated water tank 52 is measured, and the data is recorded in the recorder 54 .

A pressure sensor 60 and a pressure sensor 61 are provided on the piping 31 and the piping 50 , and the water pressure data is recorded on the recorder 62 .

Table 1 shows the analysis results of the water quality of the water samples, the NF membrane concentrated water and the permeated water in FIG. 2 , and the RO membrane permeated water and the concentrated water in FIG. 3 . In Table 1, the rejection rates of the NF membrane and the RO membrane are also shown.

<Inspection>

In the water treatment of cooling water, calcium hardness, zinc, phosphoric acid ions or phosphonic acid, polymers, etc., which are important for anti-corrosion or anti-scaling, are treated by the NF membrane module 23 in FIG. High ratios are trapped. On the other hand, chloride ions or silicon oxides, which are factors of corrosion or scale, have a NF membrane rejection rate (rejection rate) as low as -1% to 11%, and pass through the NF membrane.

In the RO system of FIG. 3, most of the organic matter components causing the clogging of the RO membrane have been removed by the RO membrane treatment. Fig. 5 shows the transition of the normalized flux (Normalized Flux), the evaluation test of the RO membrane as the flat membrane test the result of. The permeation flux of the RO membrane was stable, and no clogging due to contamination by scale or organic matter was observed. From these results, it is considered that unnecessary ions can be concentrated and stably discharged to the outside of the system by the RO membrane.

The chemical components (Zn, T-PO4, polymer, etc.) and organic substances are shown in Table 1. They hardly pass through the NF membrane, but are recirculated in the system. Therefore, the amount of chemical used can be reduced, and the amount of Zn in the RO concentrated water , P and BOD concentrations decreased (Zn=0.7, P=1.3, BOD<20). Thereby, the environmental load can be reduced, and drainage can be performed without additional treatment.

[Comparative Example 1]

<Experimental Conditions>

In the same manner as in Example 1, the actual cooling water of the real machine was used as a water sample, and as shown in FIG. 4 , a MF membrane (Kuraray Co., Ltd., polyvinylidene fluoride (PVDF) with a pore size of 0.02 μm) was used. ), carry out total filtration under the condition of inlet pressure 0.25MPa~0.3MPa. In FIG. 4 , the water sample in the storage tank 70 flows in the order of the pump 71 , the piping 72 , the NF membrane module 73 , and the piping 74 , and is introduced into the filtered water tank 75 , and the water quantity is measured by the weight measuring device 76 . A part of the ejected water of the pump 71 is returned to the storage tank 70 through the piping 77 .

Test water A in which 10 mg/L of a scale inhibitor (Kuriverter N-500, manufactured by Kurita Kogyo Co., Ltd.) was added to the filtered water, and 3.4 mL/L of sulfuric acid (1N) was prepared to adjust the pH to 5.6 The detection water B.

Using the RO system shown in FIG. 3 (the RO membrane is the same as the one described above), each of the detection water A and the detection water B was operated under the conditions of a permeated water recovery rate of 70%, 30° C., and a fixed permeated water amount. , monitor the inter-membrane differential pressure (Trans Membrane Pressure, TMP) and the solution conductivity, and calculate the normalized flux (Normalized Flux) ( m ³ /m ² /day).

<Results and investigation>

Table 2 and FIG. 6 show the results of water quality analysis when the test water A was used and the observation results of changes in the normalized flux (Normalized Flux) of the flat membrane test apparatus, respectively. In addition, the results of the water quality analysis when the detection water B was used and the observation results of the transition of the normalized flux (Normalized Flux) of the flat membrane test apparatus are shown in Table 3 and FIG. 7 , respectively.

As shown in Table 2 and Fig. 6, in the test water A with only antifouling agent added in the MF membrane permeate water, the calcium concentration is also high and a large amount of organic matter remains, so even if antifouling agent is added for MF treatment and RO treatment, A clear tendency to block the normalized flux (Normalized Flux) was observed in the RO membrane. In the case of the detection water B whose pH was adjusted with sulfuric acid, there was no tendency to scale, so that a decrease in Flux was not observed, and stable operation was possible.

The pH adjustment by sulfuric acid is effective to stabilize the operation of the RO membrane, but in order to process a sample of ¹ m ³ , it is necessary to add 185 g of sulfuric acid as 90% sulfuric acid. The monthly consumption exceeds 1,300 kg, so the management of the storage tank or the storage place becomes a problem.

In addition, since chemical components (zinc, phosphoric acid, polymers, etc.) are contained in the concentrated water of RO, it is difficult to satisfy the standard of the discharge destination, and additional treatment, discharge of industrial waste, and reduction of recovery rate need to be considered.

The present invention has been described in detail using a specific form, but it is apparent to those skilled in the art that various modifications can be made without departing from the intent and scope of the present invention.

This application is based on Japanese Patent Application No. 2018-046832 filed on March 14, 2018, the entire contents of which are incorporated by reference.

1: Water system

2, 8: Pump

3: Pre-processing device

4:NF device

5, 6, 7, 10, 11, 12: Piping

9: RO device

Claims (5)

A water treatment device, comprising: a selective permeation membrane device, which receives water from a water system and performs permeation treatment, including a selective permeation membrane that is impermeable to useful components; a deionization device, which permeates the selective permeation membrane device water is deionized; and the non-permeated water of the selectively permeable membrane device and the deionized water of the deionization device are returned to the elements of the water system. The water treatment device according to claim 1, wherein the water in the water system contains at least one of a rust inhibitor, a scale inhibitor, and a slime inhibitor. The water treatment apparatus according to claim 1 or claim 2, wherein the water system is a cooling water system, a water treatment apparatus, or a make-up water system for supplying make-up water to the water treatment apparatus. The water treatment device according to claim 1 or claim 2, wherein the selective permeation membrane is a nanofiltration membrane, and the deionization device is a reverse osmosis device or an electrodeionization device. The water treatment device according to claim 3, wherein the selective permeation membrane is a nanofiltration membrane, and the deionization device is a reverse osmosis device or an electrodeionization device.

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