Water treatment device

Abstract

A water treatment device 10 comprises: a first crossflow filter 1 for separating first treatment water W1 into first permeated water P1 and first concentrated water C1; and a second crossflow filter 2 for separating at least a portion of the first concentrated water C1 into second permeated water P2 and second concentrated water C2. The second permeated water P2 is mixed with at least one of the first treatment water W1 and the first permeated water P1, and the molecular weight of the molecules that can be permeated through the first crossflow filter 1 is smaller than the molecular weight of the molecules that can be permeated through the second crossflow filter 2.

Description

Water treatment equipment

[0001] The present invention relates to a water treatment device that utilizes a crossflow filter.

[0002] In water treatment systems that use cross-flow filtration filters (hereinafter referred to as cross-flow filters), improving the recovery rate of treated water is a very important factor in reducing the labor required for the system, making it more compact, and reducing the cost.

[0003] FIG. 4 is a schematic diagram showing the configuration of a conventional water treatment device 100 disclosed in Patent Documents 1 to 3. The water treatment device 100 includes a crossflow filter 101, a pressure pump 102, and flow control valves B101 and B102. The crossflow filter 101 separates water to be treated W101, which has been pressurized by the pressure pump 102, into permeate P101 and concentrated water C101. A portion of the concentrated water C101 is discharged through the flow control valve B101. The remainder of the concentrated water C101 passes through the flow control valve B102 and is mixed with the water to be treated W101 and recovered as treated water. This improves the recovery rate of treated water compared to when all of the concentrated water C101 is discharged.

[0004] Japanese Patent No. 6161384 Japanese Patent Application Laid-Open No. 2016-203084 Japanese Patent No. 7045870

[0005] However, in the conventional water treatment device 100, the osmotic pressure in the cross-flow filter 101 increases compared to when all of the concentrated water C101 is discharged, which increases the load on the cross-flow filter 101. This increases the power consumption of the pressure pump 102, resulting in a problem of reduced energy efficiency.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a water treatment device that is highly energy efficient.

[0007] The above-mentioned problem of the present invention is solved by a water treatment device comprising a first cross-flow filter that separates a first treated water into a first permeate and a first concentrate, and a second cross-flow filter that separates at least a portion of the first concentrate into a second permeate and a second concentrate, wherein the second permeate is mixed with at least one of the first treated water and the first permeate, and the molecular weight of molecules that can pass through the first cross-flow filter is smaller than the molecular weight of molecules that can pass through the second cross-flow filter.

[0008] In a preferred aspect of the present invention, the second permeate is mixed with the first treated water.

[0009] In a preferred embodiment of the present invention, the second permeate is mixed with the first permeate.

[0010] In a preferred aspect of the present invention, the second permeated water is mixed with both the first treated water and the first permeated water.

[0011] In the above embodiment, the first crossflow filter may be an RO filter, and the second crossflow filter may be an NF filter.

[0012] In a preferred embodiment of the present invention, the water treatment device further includes a third cross-flow filter that separates the second treated water into a third permeate and a third concentrated water, or a dead-end filter that permeates the second treated water to produce the third permeate, and the third permeate is supplied to the first cross-flow filter, and the molecular weight of molecules that can permeate the second cross-flow filter is smaller than the molecular weight of molecules that can permeate the third cross-flow filter or the dead-end filter.

[0013] In the above embodiment, the third cross-flow filter or the dead-end filter may be a UF filter or an MF filter.

[0014] According to the present invention, a water treatment device with high energy efficiency can be provided.

[0015] It is a schematic diagram showing the configuration of a water treatment device according to one embodiment of the present invention. It is a schematic diagram showing the configuration of a water treatment device according to a modified example. It is a schematic diagram showing the configuration of a water treatment device according to another modified example. It is a schematic diagram showing the configuration of a conventional water treatment device.

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0017] 1 is a schematic diagram showing the configuration of a water treatment device 10 according to one embodiment of the present invention. The water treatment device 10 is a device for removing impurities contained in raw water such as seawater, and includes a first crossflow filter 1, a second crossflow filter 2, a third crossflow filter 3, a pressure pump 4, flow control valves B1 to B4, a check valve B5, a flow meter M1, and electrical conductance meters M2 and M3.

[0018] The first crossflow filter 1, the second crossflow filter 2, and the third crossflow filter 3 are arranged in this order from upstream to downstream: third crossflow filter 3, first crossflow filter 1, second crossflow filter 2. The pressure pump 4 is provided between the third crossflow filter 3 and the first crossflow filter 1.

[0019] The first crossflow filter 1, the second crossflow filter 2, and the third crossflow filter 3 allow molecules to pass through different molecular weights, with the molecular weight of molecules that pass through the first crossflow filter 1 being smaller than the molecular weight of molecules that pass through the second crossflow filter 2, and the molecular weight of molecules that pass through the second crossflow filter 2 being smaller than the molecular weight of molecules that pass through the third crossflow filter 3. As long as this condition is met, the types of the first crossflow filter 1, the second crossflow filter 2, and the third crossflow filter 3 are not particularly limited, but in this embodiment, the first crossflow filter 1 is an RO filter (reverse osmosis membrane), the second crossflow filter 2 is an NF filter, and the third crossflow filter 3 is a UF filter or MF filter.

[0020] The raw water is subjected to known pretreatments such as filtration, coagulation, and sedimentation, and then supplied as second treated water W2 to the third cross-flow filter 3. The third cross-flow filter 3 separates the second treated water W2 into third permeate P3 and third concentrate C3. The third permeate P3 is the second treated water W2 from which fine particles such as bacteria have been removed, is pressurized by the pressure pump 4, and is supplied to the first cross-flow filter 1 as the first treated water W1. The third concentrate C3 is discharged as drain water.

[0021] The first cross-flow filter 1 separates the first treated water W1 into a first permeate P1 and a first concentrate C1. The first permeate P1 is the first treated water W1 from which ions, proteins, etc. have been removed, and is recovered as treated water (freshwater). At least a portion of the first concentrate C1 passes through a flow control valve B1 and is supplied to the second cross-flow filter 2. The remainder of the first concentrate C1 passes through a flow control valve B2 and is discharged as drain water.

[0022] The second cross-flow filter 2 separates at least a portion of the first concentrate C1 into a second permeate P2 and a second concentrate C2. The second permeate P2 is the first concentrate C1 from which proteins and other substances have been removed. The second permeate P2 undergoes the process (1) when the operation mode of the water treatment device 10 is in the high-quality mode, and the process (2) when the operation mode is in the mass-production mode. (1) Mixed with the first treated water W1 (2) Mixed with the first permeate P1

[0023] In the high-quality mode, the flow rate adjustment valve B3 is opened and the flow rate adjustment valve B4 is closed, so that the second permeated water P2 is supplied to the line through which the first treated water W1 flows. This reduces the impurity concentration of the first treated water, increasing the purity of the first permeated water P1 treated by the first cross-flow filter 1 and lowering the osmotic pressure in the first cross-flow filter 1. This reduces the power consumption of the pressure pump 4 and improves energy efficiency. It also extends the life of the first cross-flow filter 1.

[0024] The second permeated water P2 may be supplied either downstream or upstream of the pressure pump 4.

[0025] In the mass production mode, the flow rate regulating valve B3 is closed and the flow rate regulating valve B4 is opened, so that the second permeate P2 is supplied to the line through which the first permeate P1 flows. Because the impurity concentration of the second permeate P2 is higher than that of the first permeate P1, the quality (purity) of the treated water is lower than in the high-quality mode, but the amount of treated water is greater than in the high-quality mode. Furthermore, the power consumption of the pressure pump 4 is the same as when the second permeate P2 is not mixed with the first permeate P1, so the power consumption of the pressure pump 4 per unit amount of treated water is reduced, improving energy efficiency. Furthermore, the quality of the treated water can be set as desired by adjusting the flow rate of the flow rate regulating valve B4.

[0026] As described above, it is possible to provide a water treatment device that is highly energy efficient in both the high-quality mode and the mass-production mode.

[0027] The flow rate regulating valves B1 to B4 are controlled by a control device (not shown) based on the measurement results of the flow meter M1 and the electrical conductivity meters M2 and M3. The flow meter M1 and the electrical conductivity meters M2 and M3 are provided on the line through which the first permeated water P1 flows. More specifically, the flow meter M1 and the electrical conductivity meter M2 are provided upstream of the confluence of the first permeated water P1 and the second permeated water P2, and the electrical conductivity meter M3 is provided downstream of the confluence of the first permeated water P1 and the second permeated water P2.

[0028] The water treatment device 10 may also be configured with an intermediate mode between the high-quality mode and the mass-production mode. In the intermediate mode, by opening both flow control valves B3 and B4, the second permeate P2 is mixed with both the first treated water W1 and the first permeate P1. This allows for simultaneous improvements in both the quantity and quality of the recovered treated water compared to the conventional water treatment device 100 shown in FIG. 4. Although there is a trade-off between the quantity and quality of the treated water, controlling the flow rate ratio of the flow control valves B3 and B4 allows for maximizing the production volume of treated water of the minimum acceptable quality depending on the intended use of the treated water.

[0029] Furthermore, in this embodiment, the third cross-flow filter 3 is provided upstream of the first cross-flow filter 1, which improves the quality of treated water in all operation modes of the water treatment device 10. However, the provision of the third cross-flow filter 3 is not essential.

[0030] Furthermore, a dead-end filter that allows the second treated water W2 to permeate and produce third permeate P3 may be provided instead of the third cross-flow filter 3. The molecular weight of molecules that can permeate the dead-end filter is greater than the molecular weight of molecules that can permeate the second cross-flow filter 2, and the dead-end filter may be a UF filter or an MF filter.

[0031] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Forms obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present invention.

[0032] For example, in the above embodiment, the water treatment device 10 has a plurality of operation modes, but the present invention is not limited to this.

[0033] Specifically, the second permeated water P2 may be mixed only with the first treated water W1, as in the water treatment device 11 shown in Fig. 2. This allows the water treatment device 11 to function in the same manner as the water treatment device 10 in the high-quality mode.

[0034] 3, the second permeated water P2 may be mixed only with the first permeated water P1, so that the water treatment device 12 functions in the same manner as the water treatment device 10 in the mass production mode.

[0035] REFERENCE SIGNS LIST 1 First cross flow filter 2 Second cross flow filter 3 Third cross flow filter 4 Pressure pump 10 Water treatment device B1 Flow rate adjustment valve B2 Flow rate adjustment valve B3 Flow rate adjustment valve B4 Flow rate adjustment valve B5 Check valve C1 First concentrated water C2 Second concentrated water C3 Third concentrated water M1 Flow meter M2 Electrical conductivity meter M3 Electrical conductivity meter P1 First permeated water P2 Second permeated water P3 Third permeated water W1 First treated water W2 Second treated water

Claims

1. A water treatment device comprising: a first cross-flow filter that separates a first treated water into a first permeate and a first concentrated water; and a second cross-flow filter that separates at least a portion of the first concentrated water into a second permeate and a second concentrated water, wherein the second permeate is mixed with at least one of the first treated water and the first permeate, and the molecular weight of molecules that can pass through the first cross-flow filter is smaller than the molecular weight of molecules that can pass through the second cross-flow filter.

2. The water treatment device according to claim 1, wherein the second permeate is mixed with the first treated water.

3. The water treatment device of claim 1, wherein the second permeate is mixed with the first permeate.

4. The water treatment device according to claim 1, wherein the second permeate is mixed with both the first treated water and the first permeate.

5. The water treatment device according to claim 1, wherein the first cross-flow filter is an RO filter, and the second cross-flow filter is an NF filter.

6. A water treatment device as described in any one of claims 1 to 5, further comprising a third cross-flow filter that separates the second treated water into a third permeate and a third concentrate, or a dead-end filter that passes the second treated water to produce the third permeate, wherein the third permeate is supplied to the first cross-flow filter, and the molecular weight of molecules that can pass through the second cross-flow filter is smaller than the molecular weight of molecules that can pass through the third cross-flow filter or the dead-end filter.

7. The water treatment device according to claim 6, wherein the third cross-flow filter or the dead-end filter is a UF filter or an MF filter.

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