JP6468384B1 - Water treatment equipment - Google Patents

Abstract

Provided is a water treatment apparatus in which useful components are recovered, water discharged outside the system can be easily treated, and operation troubles of the apparatus can be prevented.
An NF membrane module 4 having a selective permeable membrane (NF membrane) that is impermeable to useful components and accepts water from an aqueous system 1 and deionizes the permeated water of the NF membrane module 4 A water treatment device comprising: an RO device 9 to be treated; a non-permeate water of the NF membrane module 4; and a means for returning the permeate water of the RO device 9 to the water system 1.
[Selection] Figure 1

Description

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

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

  Recently, there has been a demand for reduction and recovery of water usage, and in systems where water treatment is performed, such as cooling water and boilers, it is required to recover the blown water discharged outside the system. Yes. However, conventional water recovery techniques also remove components that are effective in water treatment. Energy and chemicals were wasted in order to remove excessive water components.

  In the process of collecting the cooling tower blow water, a combination of pretreatment filtration (sand filtration, activated carbon, MF membrane, etc.) and RO membrane or EDR (polarity conversion electrodialyzer) is performed. In the conventional blow water recovery process, the entire amount of blow water is treated with a pretreatment membrane, MF membrane or the like and then supplied to the RO membrane. With this RO membrane or the like, water treatment chemicals or dissolved salts are concentrated in the concentrated water and discharged out of the system, and the permeated water such as the RO membrane is recovered as recovered water.

JP 2003-1255 A

  In the above conventional recovery process, all the useful components contained in the raw water such as calcium, zinc, polymer, phosphoric acid and phosphonic acid, which are effective components for water treatment, are also contained in the concentrated water. Will be discharged outside the system. Further, in the conventional recovery process, zinc, phosphoric acid, organic substances (TOC, COD), etc. are concentrated in the RO membrane or the like, so that fouling of the RO membrane or the like is likely to occur. Further, when discharging concentrated water, it is necessary to remove zinc, phosphoric acid, COD, BOD, and the like.

  An object of the present invention is to provide a water treatment apparatus in which useful components are recovered, water discharged from the system is easily treated, and operation troubles of the apparatus are prevented.

  The water treatment device of the present invention is a permselective membrane device having a selective permeation membrane that is impermeable to useful components and accepts permeate water from an aqueous system, and removes the permeated water of the selective permeation membrane device. A deionizing apparatus for performing ion treatment; and means for returning non-permeated water of the selective permeable membrane apparatus and deionized water of the deionizing apparatus to the water system.

  In one embodiment of the present invention, the aqueous water contains at least one of a rust inhibitor, a scale inhibitor, and a slime inhibitor.

  In one embodiment of the present invention, the water system is a cooling water system, a water treatment apparatus, or a makeup water system (containing a chemical such as a rust inhibitor or a scale inhibitor) supplied to the water treatment apparatus.

  In one aspect of the present invention, the selective permeable membrane is an NF membrane, and the deionization device is an RO device or an electrodeionization device.

  In the present invention, water from an aqueous system is treated with a selective permeable membrane (a membrane with a high exclusion rate of divalent or higher ions, a membrane that excludes organic matter, etc.), and the permeable water of this selective permeable membrane is treated with an RO membrane or a membrane. Process with deionization equipment such as EDR. And the non-permeated water of a selective permeable membrane is returned to an aqueous system, and useful components are collect | recovered. Also, deionized water from the deionizer is returned to the water system to recover the water. In this way, useful components and water are recovered.

  In the present invention, since the useful components are removed from the water supply to the deionizer by the selective permeable membrane, the drainage from the deionizer contains no useful components, and the deionizer drainage Processing becomes easy. Moreover, since the water supply to the deionization apparatus is processed by the selective permeable membrane, the impurity concentration is reduced, and the deionization apparatus can be stably operated.

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

It is a block diagram of the water treatment equipment concerning an embodiment. It is a block diagram of the test apparatus used in the Example. It is a block diagram of the test apparatus used in the Example. It is a block diagram of the testing apparatus used in the comparative example. It is a graph which shows a test result. It is a graph which shows a test result. It is a graph which shows a test result.

  Hereinafter, an embodiment will be described with reference to FIG. 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 treatment of various water systems holding water containing useful components.

  In the water treatment apparatus of FIG. 1, a part of water in the water system 1 is pretreated by a pump 2 (for example, MF membrane, sand filtration, multilayer filtration (MMF), two-layer filtration (DMF), cartridge filter, etc.) or strainer. After the solid substance having a large particle size is removed, it is supplied to an NF device 4 as a selective permeable membrane device. The non-permeate water (concentrated water) of the NF device 4 is returned to the water system 1 via the pipe 5. In addition, a part of non-permeate water is discharged | emitted out of the system from the piping 6 as needed.

  The permeated water of the NF device is supplied to the RO device 9 as a deionization device via the pipe 7 and the pump 8. An electrodialyzer such as EDR may be used instead of the RO device. The permeated water of the RO device 9 is returned to the water system 1 through the pipe 10. The non-permeated water (concentrated water) of the RO device 9 is discharged out of the system from the pipe 11, but part of the non-permeated water (concentrated water) is supplied to the RO water supply pipe 7 through the pipe 12 to improve the water recovery rate. Returned and RO processed again.

  In this embodiment, the cooling water system 1 is added with water treatment agents such as a rust inhibitor, a scale inhibitor, and a slime inhibitor, and various useful components (polymer, phosphoric acid) are contained in the water from the aqueous system 1. Salt, organophosphate compound, zinc ion, calcium ion, etc.), but these useful components are recovered into non-permeate water by the NF device 4 and returned to the water system 1. In addition, since deionized water from the RO device 9 is also collected in the water system 1 via the pipe 10, the water is effectively used and the amount of makeup water is reduced.

  The concentrated water of the RO device 9 includes components (such as chloride ions and silica) that are not necessary for water treatment or that determine the upper limit of water treatment depending on the components. These components are discharged out of the system. In this way, components that may cause problems in water treatment, such as chloride and silica, can be selectively removed, so that the concentration of such components in the aqueous system can be reduced.

  In addition, in order to prevent the useful components from being excessively concentrated in the aqueous system 1, it is also blown from the aqueous system 1 as necessary. In the case of FIG. 1, in the case of FIG. By doing so, the amount of blow from the water system can be reduced.

  The present invention is applicable not only to cooling water systems but also to various water systems to which chemicals such as rust inhibitors and scale inhibitors are added.

[Example 1]
<Process 1>
The sample water collected from the actual circulating cooling water system was subjected to NF membrane filtration and concentration treatment by a circulation processing apparatus using the NF membrane module shown in FIG.

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

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

  As the NF film, De. A product manufactured by MEM (hollow fiber type NF membrane) was used. Membrane filtration was performed under conditions of 50% recovery at an inlet pressure of 0.25 to 0.3 MPa. When 5 L of sample water was taken into the tank 20 and the amount of permeated water reached 2.5 L, water flow was terminated.

<Process 2>
10 mg / L of a scale inhibitor (Kuriverter N-500, manufactured by Kurita Kogyo Co., Ltd.) was added to the permeated water obtained in the above-mentioned treatment 1, and the RO membrane (Hydranautics, PA membrane ES-20) shown in FIG. ) Using a RO system with a permeate recovery rate of 70% and a constant permeate flow rate, monitoring transmembrane pressure (TMP) and solution electrical conductivity, and solution osmotic pressure. The normalized permeation flux Normalized Flux (m ³ / m ² / day) under the conditions of the transmembrane differential pressure of 0.75 MPa and 25 ° C. was calculated.

  In the RO system of FIG. 3, the concentrated sample water in the tank 20 is supplied as feed water to the vessel 33 of the RO unit 32 via the pump 30 and the piping 31. The inside of the vessel 33 is partitioned into a primary chamber 35 and a secondary chamber 36 by an RO membrane 34 made of a flat membrane. The vessel 33 is disposed in a water bath 37 provided with a circulation pump 38 and a heater 39. The inside of the primary chamber 35 is agitated by a magnetic stirrer 40. Non-permeated water (concentrated water) that has passed through the primary chamber 35 flows into the concentrated water tank 44 through the pipe 41, the constant pressure valve 42, and the electric conductivity meter 43. The concentrated water tank 44 is installed on the weight measuring device 45, the amount of concentrated water flowing into the concentrated water tank 44 is measured, and the data is recorded in the logger 46.

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

  The pipes 31 and 50 are provided with pressure sensors 60 and 61, and water pressure data is recorded in the logger 62.

  Table 1 shows the analysis results of the sample water, the NF membrane concentrated water and the permeated water in FIG. 2, and the RO membrane permeated water and the concentrated water in FIG. Table 1 also shows the rejection rates of the NF membrane and the RO membrane.

<Discussion>
Calcium hardness, zinc, phosphate ion, phosphonic acid, polymer, etc., which are important for corrosion prevention and scale prevention in cooling water treatment, are rejected at a high rate of 65 to 100% by the treatment of the NF membrane module 23 in FIG. It was done. On the other hand, chloride ions and silica, which are factors of corrosion and scale, have a low NF film rejection rate (rejection rate) of −1 to 11% and pass through the NF film.

  In the RO system of FIG. 3, most of organic components that cause the blockage of the RO membrane are removed by the RO membrane treatment. FIG. 5 shows the transition of normalized flux as a result of the RO membrane evaluation test by the flat membrane test. The permeation flux of the RO membrane was stable, and no clogging due to fouling of scales or organic substances was confirmed. From this result, it was confirmed that unnecessary ions were concentrated by the RO membrane and stably discharged out of the system.

Pharmaceutical ingredients _{(Zn, T-PO 4,} Polymer , etc.) and organic matter, as shown in Table 1, hardly transmitted through the NF membrane, to be recycled in the system can reduce the use of chemicals, RO concentrate water Zn, P, and BOD of Zn were reduced (Zn = 0.7, P = 1.3, BOD <20). As a result, the environmental load can be reduced and drainage can be performed without requiring additional treatment.

[Comparative Example 1]
<Experimental conditions>
The same actual machine cooling water as in Example 1 was used as sample water, and this was used as shown in FIG. 4 using an MF membrane (Kuraray Co., Ltd., PVDF pore size 0.02 μm), conditions of inlet pressure 0.25 to 0.3 MPa. The whole amount was filtered at. In FIG. 4, the sample water in the tank 70 flows in the order of the pump 71, the pipe 72, the NF membrane module 73, and the pipe 74, is introduced into the filtered water tank 75, and the amount of water is measured by the weight measuring device 76. A part of the water discharged from the pump 71 is returned to the tank 70 through a pipe 77.

  Sample water A to which 10 mg / L of a scale inhibitor (Kuriverter N-500 manufactured by Kurita Kogyo Co., Ltd.) was added to this filtered water, and sample water whose pH was adjusted to 5.6 by adding 3.4 mL / L of sulfuric acid (1N). B was prepared.

Using the RO system shown in FIG. 3 (RO membrane is the same as that described above), each sample A and B was operated at a permeate recovery rate of 70%, 30 ° C., and a constant permeate amount. Monitors the differential pressure (TMP, Trans Membrane Pressure) and solution conductivity, and calculates Normalized Flux (m ³ / m ² / day) under the conditions of 0.75 MPa, transmembrane differential pressure corrected for solution osmotic pressure, and 25 ° C. did.

<Results and discussion>
The results of water quality analysis using Sample A and the observation results of Normalized Flux transition using a flat membrane test apparatus are shown in Table 2 and FIG. 6, respectively. Further, Table 3 and FIG. 7 show the results of water quality analysis using Sample B and the observation results of Normalized Flux transition using a flat membrane test apparatus, respectively.

  As shown in Table 2 and FIG. 5, in the sample water A in which only the scale inhibitor is added to the MF membrane permeated water, the calcium concentration is high and a large amount of organic matter remains. Even when the RO treatment was performed, a clear normalized flux blocking tendency was confirmed in the RO membrane. In the case of Sample B whose pH was adjusted with sulfuric acid, there was no tendency to scale, so that a decrease in flux was not confirmed and stable operation was possible.

Although the pH adjustment with sulfuric acid there is effective in stabilizing the operation of the RO membrane, to process samples of 1 m ^3, the addition of 185g is needed as 90% sulfuric acid, if for example the device time 10 m ³ Since more than 1,300 kg is consumed per month, management of tanks and storage locations becomes an issue.

  In addition, RO concentrated water contains chemical components (zinc, phosphoric acid, polymer, etc.), making it difficult to meet the standards of the destination, additional treatment or discharge to industrial waste, recovery rate It is necessary to consider reducing the amount of noise.

1 Water system 4 NF device 9 RO device

Claims (4)

A selective permeable membrane device having a selective permeable membrane that is impermeable to useful components and receives and permeates water from an aqueous system;
A deionization device for deionizing the permeated water of the selective permeable membrane device;
A water treatment device comprising means for returning non-permeate water of the selective permeable membrane device and deionized water of the deionization device to the water system.   The water treatment apparatus according to claim 1, wherein the water-based water contains at least one of a rust inhibitor, a scale inhibitor, and a slime inhibitor.   The water treatment apparatus according to claim 1 or 2, wherein the water system is a cooling water system, a water treatment apparatus, or a makeup water system supplied to the water treatment apparatus.   The water treatment device according to any one of claims 1 to 3, wherein the selective permeable membrane is an NF membrane, and the deionization device is an RO device or an electrodeionization device.

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