JP2011136283A - Reverse osmosis membrane filter and reverse osmosis membrane filtration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve water treatment at a low cost and a high recovery rate. <P>SOLUTION: As a reverse osmosis membrane filter 10 has a structure of a single-stage concentrate system as a whole where concentrate is returned to the upstream side of a bank located on the most upstream side without being mixed into raw water, the treated water has good water quality equal to that of a conventional single-pass reverse osmosis membrane filter. In a pressurized circulating passage 22 including only a bank 18 whose inlet flow rate does not reach a minimum amount of concentrate, pressure of the concentrate is not released, which suppresses power consumption of a booster pump 24 for repressurizing the concentrate to a low level and does not cause increase of the power consumption of a pressurizing pump 12. As a result, the power consumption is suppressed to a level equal to that of a conventional pressurized circulating reverse osmosis membrane filter. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reverse osmosis membrane filtration apparatus and a reverse osmosis membrane filtration method.

Conventionally, a filtration device using a reverse osmosis membrane (RO membrane) has been put into practical use. For example, the configuration of this reverse osmosis membrane filtration device includes a transient type, a normal circulation type, and a pressurized circulation type. There is something called.
Here, the transient reverse osmosis membrane filtration device 100 has reverse osmosis membrane module units 104, 106, 108, 110 (in this description, “ A concentrated water channel 112 having a series of “banks” arranged in series is formed. In each bank, a necessary number of reverse osmosis membranes are loaded in a vessel (the same applies hereinafter).

  In general, reverse osmosis membranes are appropriately selected from those having channel diameters of 16 inches (16 "), 8 inches (8"), 4 inches (4 ") and 2 inches (2"). It is what is done. In these reverse osmosis membranes, an optimum concentrated water amount proportional to the size is specified, and the maximum supply water amount is 800 L / min for 16 inches and the minimum concentrated water amount is 160 L / min. 8 inches has a maximum supply water volume of 200 L / min and a minimum concentrated water volume of 40 L / min. 4 inches has a maximum supply water amount of 50 L / min, a minimum concentrated water amount of 10 L / min, 2 inches has a maximum supply water amount of 12.5 L / min, and a minimum concentrated water amount of 2.5 L / min.

  In the illustrated example, the banks 104 and 106 include four 8-inch reverse osmosis membranes in series. Banks 108 and 110 use six 4-inch reverse osmosis membranes in series. Moreover, with respect to the bank 108, two banks 108a and 108b are arranged in parallel. The configuration of these banks is selected in consideration of the inflow pressure and outflow pressure of each bank so that the inlet flow rate of all banks satisfies the minimum concentrated water amount as illustrated in the figure. Yes (the same applies below). In addition, the code | symbol 114 in a figure is the filtered water system flow path which collect | recovers the filtered water isolate | separated in each bank.

  Further, as shown in FIG. 3B, the normal circulation type reverse osmosis membrane filtration device 120 includes a concentrated water system flow path 128 in which banks 124 and 126 are arranged in series downstream of the pressurizing pump 122, and A circulation path 130 is provided for returning a part of the concentrated water from the concentrated water system flow path 128 to the upstream side of the pressurizing pump 122. In the illustrated example, each of the banks 124 and 126 includes four 8-inch reverse osmosis membranes in series, and two banks 124 a and 124 b are arranged in parallel with respect to the bank 124. In addition, the code | symbol 132 in a figure is the filtered water system flow path which collect | recovers the filtered water isolate | separated in each bank.

  Further, as shown in FIG. 3 (c), the pressurized circulation type reverse osmosis membrane filtration device 140 is a concentrated water system flow in which a booster pump 144 and banks 146 and 148 are arranged in series downstream of the pressure pump 142. A circulation path 152 is provided for supplying a part of the concentrated water from the concentrated water system flow path 150 to the downstream of the pressurizing pump 142 and the upstream of the booster pump 144. In the illustrated example, in each of the banks 146 and 148, four 8-inch reverse osmosis membranes are used in series, and two banks 146a and 146b are arranged in parallel with respect to the bank 146. In addition, the code | symbol 154 in a figure is the filtered water system flow path which collect | recovers the filtered water isolate | separated in each bank.

  In order to save energy and improve the recovery rate of the reverse osmosis membrane filtration device, a method of using the pressure of the concentrated water flowing through the concentrated water system flow path as the operating energy of the pressurizing pump under a certain condition has been proposed. (For example, Patent Document 1).

Japanese Patent No. 3963304

However, the following problems have been pointed out in the above prior art.
First, the transient reverse osmosis membrane filtration apparatus 100 has the advantages that the quality of treated water is good and the power consumption of the pressure pump 122 can be kept low, but on the other hand, the size of the usable reverse osmosis membrane is large. However, since it is practically limited to the above four types, it may be difficult to obtain an optimum apparatus configuration for improving the recovery rate or increasing / decreasing the amount of supplied water. In addition, considering the inflow pressure and outflow pressure of each bank, the size of the reverse osmosis membrane used in each bank is required to configure the bank so that the inlet flow rate of all banks satisfies the minimum concentrated water amount. Therefore, the equipment configuration becomes complicated by changing the number of banks and increasing the number of banks, resulting in an increase in equipment installation cost and maintenance cost.

  On the other hand, the normal circulatory reverse osmosis membrane filtration device 120 circulates a part of the concentrated water from the concentrated water system flow path 128 to the upstream of the pressurizing pump 122 by the circulation path 130, so that the inlet flow rate of the bank The minimum amount of concentrated water is satisfied, and the bank configuration is simplified as compared with the transient reverse osmosis membrane filtration device 100. However, the circulating water is returned to the upstream side of the pressurizing pump 122 to release the pressure and is pressurized again, so that the power consumption of the pressurizing pump 122 increases. Further, since the concentrated water is returned to the upstream side of the bank located at the most upstream and mixed with the raw water, water treatment with a concentration higher than that of the raw water is performed, and it is difficult to improve the water quality.

  In contrast, the pressurized circulation type reverse osmosis membrane filtration device 140 returns a part of the concentrated water from the concentrated water system flow path 150 to the downstream of the pressure pump 142 and the upstream of the booster pump 144 by the circulation path 152. Therefore, the pressure of the concentrated water is not released, and an increase in power consumption of the pressurizing pump 142 and the booster pump 144 is avoided. Therefore, the power consumption of the entire apparatus can be suppressed as compared with the normal circulation type reverse osmosis membrane filtration apparatus 120. However, as with the normal circulation type reverse osmosis membrane filtration device 120, the concentrated water is returned to the upstream side of the most upstream bank and mixed into the raw water. Therefore, it is difficult to improve the quality of the treated water.

In order to obtain a high recovery rate of 70 to 90% for water having a low osmotic pressure, the minimum concentrated water film can be used even by a technique of using the pressure of the concentrated water flowing through the concentrated water system flow path as the operating energy of the pressure pump. The surface flow velocity cannot be ensured, and highly efficient processing is impossible.
This invention is made | formed in view of the said subject, The place made into the objective is to implement | achieve water treatment with low cost and a high recovery rate.

(Aspect of the Invention)
The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each section does not limit the technical scope of the present invention, and some of the components of each section are replaced, deleted, or further while referring to the best mode for carrying out the invention. Those to which the above components are added can also be included in the technical scope of the present invention.

(1) A reverse osmosis membrane filtration device having a single-stage configuration of a concentrated water system, wherein a plurality of banks including a reverse osmosis membrane are arranged downstream of a pressurizing pump, and the pressurization includes only a bank whose inlet flow rate does not satisfy the minimum concentrated water amount. A reverse osmosis membrane filtration device provided with a circulation channel (Claim 1).
The reverse osmosis membrane filtration device described in this section has a one-stage configuration of the concentrated water system as a whole, so that the concentrated water is not returned to the upstream side of the most upstream bank and mixed into the raw water. ing. Further, in the pressurized circulation flow path including only the bank where the inlet flow rate does not satisfy the minimum concentrated water amount, the pressure of the concentrated pump is not released, so the power consumption of the pressure pump does not increase. In addition, the bank load not included in the pressure circulation flow path is set lightly to avoid clogging of the reverse osmosis membrane, while the load applied to the reverse osmosis membrane is concentrated on the bank located downstream and pressurized. The flow rate adjustment of the bank related to the circulation is arbitrarily performed by a booster pump, and the blockage of the reverse osmosis membrane of the bank related to the pressure circulation is positively controlled by the flow rate adjustment.

(2) In the above item (1), the booster pump of the pressurized circulation channel is a reverse osmosis membrane filtration device provided immediately before the reflux line or the corresponding bank (Claim 2).
The reverse osmosis membrane filtration device described in this section is a booster that performs pressure increase control of a pressure circulation channel including a bank in which the inlet flow rate does not satisfy the minimum concentrated water amount as long as the operation described in the above item (1) is exhibited. The pump may be arranged in the reflux line or may be arranged immediately before the corresponding bank, and the layout of the pressurized circulation channel is arbitrary.

(3) A reverse osmosis membrane filtration device according to the above items (1) and (2), wherein the recovery rate is 50% to 90% and the amount of supplied water is 500 L / min or less (claim 3).
The reverse osmosis membrane filtration device described in this section achieves the action described in the above item (1) under water treatment conditions with a recovery rate of 50% to 90% and a supply water amount of 500 L / min or less. .

(4) A reverse osmosis membrane filtration method in which a bank having a reverse osmosis membrane is arranged downstream of the pressurization pump in a concentrated water system, and pressure circulation is performed only in the bank where the inlet flow rate does not satisfy the minimum amount of concentrated water (claim) Item 4).
In the reverse osmosis membrane filtration method described in this section, the concentrated water is not returned to the upstream side of the bank located at the most upstream and mixed into the raw water. The processing is performed. Further, when the pressure circulation is performed only in the bank where the inlet flow rate does not satisfy the minimum amount of concentrated water, the pressure of the concentrated water during the pressure circulation is not released, so that the power consumption of the pressure pump is not increased. In addition, the load applied to the reverse osmosis membrane can be concentrated in the bank located downstream, and the flow rate of the bank related to the pressurization circulation can be adjusted arbitrarily by the booster pump. The load of the bank that is not set is lightly set to avoid the blockage of the reverse osmosis membrane, and the blockage concentrated on the reverse osmosis membrane of the bank related to the pressure circulation is positively controlled by adjusting the flow rate.

(5) The reverse osmosis membrane filtration method according to (4) above, wherein the pressure is increased immediately before the corresponding bank of the reflux line or the concentrated water system pipeline in the pressurized circulation channel (Claim 5).
The reverse osmosis membrane filtration method described in this section is a booster that performs pressure increase control of a pressurized circulation path including a bank whose inlet flow rate does not satisfy the minimum concentrated water amount as long as the operation described in the above item (4) is exhibited. The pump may be arranged in the reflux line or just before the corresponding bank, and the layout of the pressurized circulation flow path is arbitrary.

(6) A reverse osmosis membrane filtration method in which the treatment is performed at a recovery rate of 50% to 90% and a supply water amount of 500 L / min or less in the above items (4) and (5) (Claim 6).
The reverse osmosis membrane filtration method described in this section performs the function described in the above (4) under water treatment conditions with a recovery rate of 50% to 90% and a supply water amount of 500 L / min or less. .

  Since this invention was comprised in this way, it becomes possible to implement | achieve water treatment with a low cost and a high recovery rate.

BRIEF DESCRIPTION OF THE DRAWINGS The structure of the reverse osmosis membrane filtration apparatus based on embodiment of this invention is shown typically, (a) is a case where the booster pump of a pressurized circulation flow path is provided in the reflux line, (b) is the same. The case where the booster pump is provided immediately before the bank is shown. Components of purified water obtained by a reverse osmosis membrane filtration device having a one-stage configuration of a concentrated water system according to an embodiment of the present invention are converted into raw water, purified water obtained by a normal circulation type reverse osmosis membrane filtration device, and added water. It is the chart compared with each component of the purified water obtained by the pressure circulation type reverse osmosis membrane filtration apparatus. FIG. 1 schematically shows the configuration of a conventional reverse osmosis membrane filtration device, (a) is a transient reverse osmosis membrane filtration device, (b) is a normal circulation type reverse osmosis membrane filtration device, and (c) is This is a pressure circulation type reverse osmosis membrane filtration device.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. Note that the same or corresponding parts as those of the prior art are denoted by the same reference numerals, and detailed description thereof is omitted.

A reverse osmosis membrane filtration device 10 according to an embodiment of the present invention is a reverse osmosis membrane filtration device having a one-stage configuration of a concentrated water system, as shown in FIG. A plurality of banks 14, 16 and 18 are arranged in series. A pressurized circulation channel 22 is provided only for the bank 18 where the inlet flow rate does not satisfy the minimum concentrated water amount, and a part of the concentrated water is recirculated from the concentrated water system channel 20 to the bank 18. A booster pump 24 is disposed in the path 22. The booster pump 24 may be provided in the reflux line 26 as shown in FIG. 1 (a), and the bank 18 associated with the pressurized circulation channel 22 as shown in FIG. 1 (b). It may be provided immediately before. The code | symbol 28 in a figure is the filtered water system flow path which collect | recovers the filtered water isolate | separated in each bank.
In the illustrated example, each of the banks 14, 16, and 18 uses four 8-inch reverse osmosis membranes, and the pressurizing pump 12 uses a relatively low-cost multistage centrifugal pump. On the other hand, for the booster pump 24, a canned pump having a high cut-off allowable pressure is used.

  In the illustrated example, the amount of water supplied from the pressure pump 12 is 130 L / min, the amount of concentrated water flowing out from the bank 14 is 91.2 L / min, and the amount of concentrated water flowing out from the bank 16 is 52.4 L / min. As described above, the 8-inch reverse osmosis membrane has a minimum concentrated water amount of 40 L / min, and the concentrated water amount flowing into the bank 18 from the bank 16 exceeds the minimum concentrated water amount, but the filtered water is separated in the bank 18. Naturally, the amount of concentrated water discharged after this will be less than 40 L / min.

Therefore, in the embodiment of the present invention, the amount of concentrated water flowing out from the bank 16 is added with the amount of concentrated water 38 L / min returned by the circulation line 26, so that the amount of supplied water 90L / min to the bank 16 is secured. The amount of concentrated water discharged after the filtered water is separated at 18 is also secured to 51 L / min.
And the concentrated water finally discharged | emitted from a concentrated water system flow path is 13 L / min. As described above, the reverse osmosis membrane filtration device 10 according to the embodiment of the present invention is configured as a reverse osmosis membrane filtration device having a supply water amount of 500 L / min or less and a recovery rate of 90%. In addition, each said numerical value is an example to the last.

  The size of the reverse osmosis membrane used for each bank 14, 16, 18 is appropriately selected. In the example shown in the figure, only 8 inches, which has the highest distribution amount and low cost, are used at present. . Note that, regardless of the size of the reverse osmosis membrane selected, the membrane filtration flow rate of each bank 14, 16, 18 is used under the condition of 0.1 m / d to 1.0 m / d. It is desirable. As the reverse osmosis membrane, a hollow fiber membrane, a spiral membrane, a tubular membrane or the like is appropriately used, and cellulose acetate, aromatic polyamide, polyvinyl alcohol, polysulfone or the like is appropriately selected as the material. In addition, a so-called loose RO or NF film (nanofilter) can be used instead of the RO film as appropriate. Further, the number of the reverse osmosis membranes loaded in the vessels constituting the banks 14, 16, and 18 is appropriately selected from 1 to 6.

  Furthermore, the flow rate of the booster pump 24 is preferably measured by installing a flow meter in the pressurization circulation path 22 to measure the actual flow rate and feedback-controlling the flow rate. This feedback control is executed by a control device (not shown) (configured by a computing device such as a personal computer), and the flow rate control method is also proportionally increased, proportionally decreased, or a plurality of stages of flow rates as appropriate. Control shall be performed.

Now, according to the embodiment of the present invention configured as described above, the following operational effects can be obtained.
First, in the reverse osmosis membrane filtration device 10 according to the embodiment of the present invention, the concentrated water is not returned to the upstream side of the bank located at the most upstream and mixed into the raw water, but the concentrated water system as a whole. Since it has a one-stage configuration, the quality of treated water is as good as that of the conventional single-pass reverse osmosis membrane filtration device 100. Further, in the pressurized circulation flow path 22 including only the bank 18 whose inlet flow rate does not satisfy the minimum concentrated water amount, the pressure of the booster pump 24 for repressurizing the concentrated water is low because the pressure of the concentrated water is not released. Therefore, the power consumption of the pressurizing pump 12 is not increased. Therefore, it can be suppressed to the same power consumption level as that of the conventional pressurized circulation type reverse osmosis membrane filtration device 140.

  Further, the load of the banks 14 and 16 not included in the pressurized circulation flow path 22 is set lightly to prevent the reverse osmosis membrane from being blocked, while the load applied to the reverse osmosis membrane is applied to the bank 18 located downstream. The booster pump 24 can arbitrarily adjust the flow rate of the bank 18 related to the pressurized circulation, and the blockage of the reverse osmosis membrane of the bank 18 can be positively controlled by adjusting the flow rate. Therefore, the labor and cost required for maintenance of the reverse osmosis membrane filtration device 10 as a whole can be reduced.

  The chart of FIG. 2 shows the components of purified water obtained by the reverse osmosis membrane filtration device having a single-stage configuration of the concentrated water system according to the embodiment of the present invention, obtained by the raw water, the normal circulation type reverse osmosis membrane filtration device. The purified water and the purified water obtained by the pressurized circulation reverse osmosis membrane filtration device are compared with each of the components. Specific conditions are as follows.

(Raw water)
The ammonia nitrogen (MH4-N) concentration is 13 mg / L, the total organic carbon (TOC) concentration is 3.0 mg / L, the total soluble substance (TDS) concentration is 420 mg / L, and the silica (SiO ₂ ) concentration is 5 mg / L. L.

(Invention)
The pressure pump 12 was “CRN5-20 AJG-E-HQQE” manufactured by Grundfos Co., Ltd., and the booster pump 24 was “F-42-119F2AL-0204R1-AV” manufactured by Teikoku Seisakusho. In addition, “AK8040F (400)” manufactured by GE was used for the reverse osmosis membrane, and “80A304 4 element” manufactured by Cordline was used for the vessel.
And after passing water at 130 L / min for 1 hour with the pressurization pump 12, the filtered water of the filtration water system flow path 28 was sampled, and it used for the water quality analysis. At that time, voltage / current measurement was performed using “AC / DC Mini Clamp Meter M290RWS” manufactured by Multi Instrument Co., Ltd. as a clamp meter.
As a result, the ammonia nitrogen concentration of filtered water was 0.5 mg / L, the total organic carbon concentration was 0.1 mg / L, the total soluble substance concentration was 10.4 mg / L, and the silica concentration was 0.2 mg / L. .
In addition, the power consumption of the pressurization pump 12 and the booster pump 24 was a total of 2.26 kW.

(Normal circulation type)
“CRN10-10 AJG-E-HQQE” manufactured by Grundfos Co., Ltd. was used for the pressure pump 122 (FIG. 3B). In addition, “AK8040F (400)” manufactured by GE was used for the reverse osmosis membrane, and “80A304 4 element” manufactured by Cordline was used for the vessel.
And after passing water for 1 hour by 130 L / min with the pressurization pump 122, the filtrate of filtrate water system flow path 132 (FIG.3 (b)) was sampled, and it used for the water quality analysis. At that time, voltage / current measurement was performed using “AC / DC Mini Clamp Meter M290RWS” manufactured by Multi Instrument Co., Ltd. as a clamp meter.
As a result, the ammonia nitrogen concentration of filtered water was 1.05 mg / L, the total organic carbon concentration was 0.24 mg / L, the total soluble substance concentration was 33.75 mg / L, and the silica concentration was 0.4 mg / L. .
The power consumption of the pressurizing pump 122 was 2.97 kW in total.

(Pressurized circulation type)
“CRN5-20 AJG-E-HQQE” manufactured by Grundfos Co., Ltd. is used for the pressure pump 142 (FIG. 3C), and “F-42” manufactured by Teikoku Electric Co., Ltd. is used for the booster pump 144 (FIG. 3C). -119F2AL-0204R1-AV "was used. In addition, “AK8040F (400)” manufactured by GE was used for the reverse osmosis membrane, and “80A304 4 element” manufactured by Cordline was used for the vessel.
And after passing water at 130 L / min for 1 hour with the pressurization pump 142, the filtrate of filtrate water system flow path 154 (FIG.3 (c)) was sampled, and it used for water quality analysis. At that time, voltage / current measurement was performed using “AC / DC Mini Clamp Meter M290RWS” manufactured by Multi Instrument Co., Ltd. as a clamp meter.
As a result, the ammonia nitrogen concentration of filtered water was 1.05 mg / L, the total organic carbon concentration was 0.24 mg / L, the total soluble substance concentration was 33.75 mg / L, and the silica concentration was 0.4 mg / L. .
In addition, the power consumption of the pressurization pump 12 and the booster pump 24 was 2.35 kW in total.

  As described above, according to the reverse osmosis membrane filtration device 10 according to the embodiment of the present invention, the conventional reverse osmosis is performed under the conditions of a recovery rate of 50% to 90% and a supply water amount of 500 L / min or less. Compared with the filtration device, water treatment with the lowest cost and high recovery rate was realized.

  10: Reverse osmosis membrane filtration device, 12: Pressurization pump, 14, 16, 18: Bank, 20: Concentrated water system channel, 22: Pressurization circulation channel, 24: Booster pump, 26: Reflux line, 28: Filtration Water channel

Claims (6)

A concentrated osmosis system single-stage reverse osmosis membrane filtration device, wherein a plurality of banks including a reverse osmosis membrane are arranged downstream of a pressure pump, and a pressure circulation channel including only a bank whose inlet flow rate does not satisfy the minimum amount of concentrated water The reverse osmosis membrane filtration apparatus characterized by the above-mentioned. The reverse osmosis membrane filtration device according to claim 1, wherein the booster pump of the pressurized circulation flow path is provided immediately before the reflux line or the corresponding bank. The reverse osmosis membrane filtration device according to claim 1 or 2, wherein the recovery rate is 50% to 90%, and the amount of supplied water is 500 L / min or less. A reverse osmosis membrane filtration method characterized by disposing a bank having a reverse osmosis membrane downstream of a pressurization pump in a concentrated water system, and performing pressure circulation only in a bank whose inlet flow rate does not satisfy the minimum concentrated water amount. . 5. The reverse osmosis membrane filtration method according to claim 4, wherein the pressure is increased immediately before the corresponding bank of the reflux line or the concentrated water system conduit in the pressurized circulation channel. The reverse osmosis membrane filtration method according to claim 4 or 5, wherein the treatment is performed at a recovery rate of 50% to 90% and a supply water amount of 500 L / min or less.