0001]TECHNICAL FIELD The present invention relates to a water treatment system and a water treatment method, for example, for desalination treatment of seawater.BACKGROUND ART [0002]
　A water treatment system for desalination treatment of sea water is equipped with a desalination treatment apparatus using a reverse osmosis membrane or the like. In the water treatment system, in order to suppress the processing performance deterioration due to contamination of the reverse osmosis membrane of the desalination treatment apparatus, a filtration device for filtering particulate matter, bacteria and the like in the seawater is used as a pretreatment part at the front stage of the desalination treatment apparatus .
[0003]
　While using the water treatment system, water quality variation of the water to be treated after filtration may occur. Then, since the reverse osmosis membrane of the desalination treatment apparatus is contaminated, it is necessary to stabilize the filtration performance in the pretreatment section.
[0004]
　Patent Document 1 discloses a configuration in which a plurality of filtration devices are provided as preprocessing portions and the flow paths among a plurality of filtration devices are switched when the filtration performance of the filtration device is deteriorated. According to such a configuration, when the filtration performance is lowered, it is possible to stabilize the quality of the water after filtration by switching the flow path and cleaning or replacing the filter of the filtration device with reduced filtration performance.
Prior Art Document
Patent literature
[0005]
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-221459
Summary of the invention
Problem to be Solved by Invention
[0006]
　By the way, in the water treatment system, due to fluctuation of seawater which is water to be treated, fluctuation of water quality of the water to be treated after filtration may occur. Such fluctuations in the sea water include, for example, fluctuations in the temperature of the seawater.
　However, if sea water fluctuations are overcome, the water quality of the water to be treated also returns. For this reason, in the configuration disclosed in Patent Document 1, it is not possible to deal with the case where the water quality fluctuation after filtration occurs due to such seawater fluctuation.
　The present invention provides a water treatment system and a water treatment method capable of suppressing fluctuation of filtered water quality even when water quality fluctuation of water to be treated occurs.
Means for solving the problem
[0007]
　According to a first aspect of the present invention, there is provided a water treatment system comprising: a first flow passage through which water to be treated flows; and a second flow passage provided downstream of the first flow passage, A second flow passage connected to the filtration device and through which the for-treatment water subjected to the filtration flows, a second flow passage connected to the downstream side of the second flow passage to concentrate the for-treatment water A reverse osmosis membrane device for separating water into fresh water and water, a third flow passage connecting the first flow passage and the second flow passage, and a third flow passage provided in the third flow passage, A pump for pumping a part of the treated water from the second flow passage to the first flow passage through the third flow passage, and an on-off valve for opening and closing the third flow passage.
　According to such a configuration, the water to be treated is filtered through a first flow passage through a filtration device and then separated into concentrated water and fresh water in a reverse osmosis membrane device via a second flow passage , The water to be treated can be desalinated. Here, a part of the for-treatment water passed through the filtration device is pressure-fed from the second flow passage to the first flow passage through the third flow passage, and is again passed through the filtration device. In this way, since a part of the for-treatment water passes through the filtration device twice to be filtered, the quality of the water after filtration is improved. This makes it possible to suppress fluctuations in the quality of the water after filtration.
[0008]
　According to a second aspect of the present invention, in the first aspect, the water treatment system further comprises: a detection unit that detects a water quality evaluation value of the for-treatment water; a value of the water quality evaluation value is equal to or higher than a predetermined threshold value And a control device that operates the pump and switches the on-off valve from the closed state to the open state.
　According to such a water treatment system, the water quality evaluation value of the for-treatment water after the filtration treatment can be detected by the detection unit. If the detected water quality evaluation value is equal to or larger than the predetermined threshold value, the flow rate adjustment unit can operate the pump and switch the on-off valve from the closed state to the open state. As a result, a part of the for-treatment water that has passed through the filtration device is pressure-fed from the second flow passage to the first flow passage through the third flow passage, and can be passed through the filtration device again.
　In this manner, when the water quality of the for-treatment water drops, water quality to be filtered in the filtration device can be improved by re-flowing the water to be treated to the filtration device. Therefore, when the water quality of the for-treatment water fluctuates, it is possible to suppress the deterioration of the water quality after filtration.
[0009]
　According to a third aspect of the present invention, in the first aspect, the water treatment system further includes: a detection unit that detects a water quality evaluation value of the for-treatment water; a display unit that displays information based on the water quality evaluation value; , An operation unit which can be operated by an operator and an operation signal sent by operation of the operation unit which is made in accordance with the information displayed on the display unit, And a control device for switching from a closed state to an open state.
　According to such a water treatment system, the water quality evaluation value of the for-treatment water can be detected by the detection unit. Information based on the detected water quality evaluation value can be displayed on the display unit, for example, as a water quality evaluation value itself, a determination result on whether the water quality evaluation value is acceptable or not, and the like. The operator can judge whether it is necessary to adjust the flow rate of re-flowing by looking at the information displayed on the display unit. As a result of the judgment, if it is necessary to adjust the flow rate of re-flowing water, the operator inputs a predetermined operation to the operation section. Then, the operation unit transmits an operation signal corresponding to the operation by the operator. On the basis of the operation signal sent from the operation section, the flow rate adjustment section operates the pump and switches the on-off valve from the closed state to the open state. As a result, a part of the for-treatment water that has passed through the filtration device is pressure-fed from the second flow passage to the first flow passage through the third flow passage, and is again passed through the filtration device.
　In this way, when the water quality of the water to be treated decreases, by filtering a part of the water to be treated after filtration to the filtration device, the quality of the water after filtration in the filtration device is improved. Therefore, when the water quality of the water to be treated fluctuates, it is possible to suppress the deterioration of the water quality after filtration.
[0010]
　According to a fourth aspect of the present invention, the water treatment system according to any one of the first to third aspects is characterized in that the water to be treated, which is supplied from the upstream side, is filtered at the upstream side of the first flow passage And a preliminary filtration device for performing treatment and discharge to the first flow passage may be provided.
　As a result, the for-treatment water is sequentially filtered in two stages by the pre-stage filtration device provided on the upstream side of the filtration device and the filtration device provided at the downstream side thereof. Here, when the water quality of the water to be treated drops in the downstream filtering device, the quality of the water after filtration in the filtration device is improved by re-flowing the water to be treated to the filtration device.
[0011]
　According to a fifth aspect of the present invention, the water treatment method is a water treatment method of subjecting water to be treated to a filtration treatment with a filtration device before desalination treatment, and obtains a water quality evaluation value of the water to be treated , A part of the for-treatment water subjected to the filtration treatment is returned to the inlet side of the filtration device when the acquired water quality evaluation value is equal to or larger than a predetermined threshold value, and is returned to the filtration device again And flowing water.
　As a result, if the water quality evaluation value of the water to be treated after the filtration processing is equal to or higher than a predetermined threshold value, a part of the water to be treated that has passed through the filtration device is returned to the inlet side and is again passed through the filtration device.
　In this manner, when the water quality of the water to be treated is lowered, the quality of the water after filtration in the filtration device is improved by re-flowing the water to be treated to the filtration device. Therefore, when the water quality of the for-treatment water fluctuates, it is possible to suppress the deterioration of the water quality after filtration.
Effect of the invention
[0012]
　According to the water treatment system and the water treatment method described above, it is possible to suppress the fluctuation of the filtered water quality even when the water quality of the for-treatment water occurs.
Brief Description of the Drawings
[0013]
FIG. 1 is a diagram showing the overall configuration of a water treatment system according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a preprocessing section of the water treatment system.
FIG. 3 is a view showing a flow of a water treatment method in a pretreatment section.
FIG. 4 is a view showing a water passing state of a pretreatment section in a state where a part of water to be treated is re-passed through a re-water pipe to a filtration device.
5 is a graph showing the correlation between the ratio L / D of the height L of the filter portion to the diameter D of the filter portion of the filtration device and the removal rate of suspended matter and the like in the water to be treated by the filtration process in the filter portion, is there.
FIG. 6 is a diagram showing a correlation between the inlet water quality of the filtration device and the turbidity removal rate in the filter portion of the filtration device.
FIG. 7 is a graph showing the correlation between the inlet water quality of the filtration device and the water quality evaluation value of the water to be treated after filtration at the filter portion of the filtration device.
FIG. 8 is a diagram showing a configuration of a preprocessing unit in a modification of the first embodiment.
FIG. 9 is a diagram showing a configuration of a preprocessing unit in the second embodiment of the water treatment system and the water treatment method.
FIG. 10 is a view showing a change in the water quality evaluation value after filtration when the filtration speed is varied in the first-stage sand filtration device.
[Fig. 11] Change in the water quality evaluation value after filtration in the second-stage sand filtration device when the filtration speed is kept constant in the first-stage sand filtration device and the filtration speed of the second-stage sand filtration device is changed FIG.
MODE FOR CARRYING OUT THE INVENTION
[0014]
　Hereinafter, a water treatment system and a water treatment method according to embodiments of the present invention will be described with reference to the drawings.
(First Embodiment)
　FIG. 1 is a diagram showing the overall configuration of a water treatment system of this embodiment.
　As shown in FIG. 1, the water treatment system 10 of this embodiment includes a pretreatment section 20, a cartridge filter 30, a high-pressure pump 40, a desalination treatment section 50, and an energy recovery apparatus 60 .
[0015]
　In the pretreatment section 20, sea water (water to be treated) W taken in by a water intake pump (not shown) is fed through a water intake pipe (first flow passage) P 1. The pretreatment section 20 filters the seawater W that has been fed into the seawater W before filtration to the desalination treatment section 50, in other words, before the desalination treatment is performed by the desalination treatment section 50, Remove turbid material and so on. In this embodiment, a sand filtration device (filtration device) 21 is used as the pretreatment portion 20, and so-called drug-free pretreatment is performed without introducing flocculants, pH adjusters or the like.
　The sand filtration device 21 includes one or more filter portions 21 f. In this embodiment, the sand filtration device 21 includes two stages of filter portions 21 f. The filter portion 21f has a predetermined amount of sand (not shown) as a filter material and a biofilm (not shown) which is grown and maintained on the surface of sand. The filter unit 21 f removes the SDI (Silt Dencity Index) component that contaminates the desalination processing unit 50, the BOD (Biological Oxygen Demand) component that causes biofouling, and the like by the biofilm. The filter unit 21 f removes fine particle components contained in the seawater W with sand.
[0016]
　The cartridge filter 30 is connected to the downstream side of the preprocessing section 20 via a connecting pipe (second flow path) P 3. The cartridge filter 30 removes foreign matters having a diameter equal to or larger than a predetermined diameter so that fine foreign matters of, for example, about 1 to 5 μm, which could not be removed by the pretreatment section 20, enter the high-pressure pump 40.
[0017]
　The high-pressure pump 40 is connected to the downstream side of the cartridge filter 30 via a connecting pipe P 4. The high pressure pump 40 boosts the seawater W that has passed through the cartridge filter 30 to a predetermined pressure and sends it to the desalination processing section 50 through the connecting pipe P 5.
[0018]
　The desalination processing unit 50 performs desalination processing. Here, the desalination treatment is, for example, a process of removing or concentrating salinity in sea water. In the desalination processing unit 50 in this embodiment, for example, the reverse osmosis membrane F is used to remove ion components from the sea water W. In this embodiment, a sea water reverse osmosis membrane (Sea Water Reverse Osmosis Membrane) treatment apparatus (reverse osmotic membrane apparatus) 51 and a brackish water reverse osmosis membrane (brackish water reverse osmosis membrane) treatment apparatus Reverse osmosis membrane device) 52.
[0019]
　The reverse osmosis membrane treatment apparatus 51 for seawater is connected to the downstream side of the high pressure pump 40 via a connection pipe P 5. The reverse osmosis membrane treatment apparatus 51 for seawater passes the sea water W pressurized by the high pressure pump 40 through the reverse osmosis membrane F via the connection pipe P 5 to obtain the permeated water W 2 from which the salt content (ion component) has been removed . The obtained permeated water W 2 is sent to the brackish water reverse osmosis membrane treating apparatus 52 via the connecting pipe P 6. The concentrated water W 3 containing the ion component removed by the seawater reverse osmosis membrane treatment device 51 is sent to the energy recovery device 60 via the connection pipe P 7. The concentrated water W 3 passed through the energy recovery device 60 is drained to the outside (sea) via a drain pipe P 8.
[0020]
　The brackish water reverse osmosis membrane treatment device 52 is connected to the downstream side of the seawater reverse osmosis membrane treatment device 51 via a connection pipe P 6. The brackish water reverse osmosis membrane treating apparatus 52 passes the permeated water W 2 passed through the reverse osmosis membrane treating apparatus 51 for seawater through the reverse osmosis membrane F to further remove ion components to obtain pure water W 2 '. The obtained deionized water W 2 'is supplied to a water tank (not shown) or the like via a supply pipe P 9. Here, when the obtained pure water W 2 'is to be used for a beverage or the like, minerals are added at the charging part P 10 provided in the supply pipe P 9. The concentrated water W 3 'containing the ion component removed by the brackish water reverse osmosis membrane treatment device 52 is discharged to the drain pipe P 8 via the drain pipe P 11 and discharged to the outside (sea).
[0021]
　The energy recovery device 60 recovers energy from the concentrated water W 3 discharged from the seawater reverse osmosis membrane treatment device 51. The concentrated water W 3 discharged from the seawater reverse osmosis membrane treatment apparatus 51 is pressurized by the high pressure pump 40. The energy recovery device 60 includes a rotor (water wheel) 61 that is rotated by the water flow of the concentrated water W 3 sent from the connection pipe P 7. The rotor 61 obtains rotational energy by the pressurized concentrated water W 3 and rotates the rotor 62 integrally connected to the rotor 61. On the downstream side of the cartridge filter 30, a branch pipe P 12 branching off from the connecting pipe P 4 is provided. A part of the sea water W that has passed through the cartridge filter 30 passes through the branch pipe P 12, passes through the energy recovery device 60, and is sent to the reverse osmosis membrane processing apparatus 51 for seawater by the rotor 62. In this way, the energy of the concentrated water W 3 recovered by the energy recovery device 60 can be used as a part of the energy for sending the seawater W to the reverse osmosis membrane treatment device 51 for seawater.
[0022]
　FIG. 2 is a diagram showing a configuration of a preprocessing unit of the water treatment system.
　As shown in FIG. 2, the pretreatment unit 20 includes a sand filtration device 21, a re-flow pipe (third flow passage) P 20, a pump 22, an open / close valve 23, a detection unit 25, a display unit 26, An operation unit 27, and a flow rate adjustment unit (control device) 28.
[0023]
　In this embodiment, in the sand filtration device 21, the seawater W is passed through the intake pipe P 1, and this seawater W is filtered. The sand filtration device 21 delivers the filtered seawater W from the connecting pipe P 3.
[0024]
　The re-water pipe P 20 is provided to connect the intake pipe P 1 and the connecting pipe P 3. A part of the seawater W filtered by the sand filtration device 21 and delivered to the connection pipe P 3 can be returned to the water intake pipe P 1, that is, upstream of the sand filtration device 21 through the re-water pipe P 20.
[0025]
　The pump 22 pumps a part of the filtered seawater W to the water intake pipe P 1 from the connecting pipe P 3 through the re-water pipe P 20, provided in the re-water pipe P 20.
　The on-off valve 23 opens and closes the re-water pipe P 20.
[0026]
　The detection unit 25 detects the water quality evaluation value of the sea water between the pretreatment unit 20 and the reverse osmosis membrane treatment device 51 for seawater. Examples of the water quality evaluation value to be detected include SDI (Silic Dencity Index: water quality index relating to occlusion of the water treatment membrane), Biofilm Formation Rate (BFR): risk of biofilm (biofilm) The number of bacteria (the number of bacteria present in the sample water), ATP (Adenosine Tri-Phoshate: an energy substance existing in all organisms), TOC (Total Organic Carbon): the total of organic matter Carbon content), AOC (Assimilable organic carbon: the carbon content of organisms that can be assimilated), COD (Chemical Oxygen Demand: oxidizing agent (potassium manganese peroxide, dichromedic acid ), BOD (Biological Oxygen Demand: the amount of oxygen consumed when organisms decompose organic matter etc.), FT-IR (Fourier Transform - Infrared spectrometer (Fourier transform infrared spectrophotometer)), the amount of UV absorption (absorption amount of Ultra Violet (ultraviolet light) by organic matter), and the like.
[0027]
　The detection unit 25 detects at least one of the water quality evaluation values ​​as described above. The water quality evaluation value may be detected by providing a sensor or the like in the connection pipe P 3 between the pretreatment section 20 and the reverse osmosis membrane treatment apparatus 51 for seawater, for example. The water quality evaluation value may be detected by providing a sensor or the like in the water intake pipe P1 on the upstream side of the preprocessing section 20, for example. Detection of the water quality evaluation value may be performed separately by a sample sampled from the connecting pipe P 3 or the intake pipe P 1.
[0028]
　The display unit 26 displays information based on the water quality evaluation value. The display unit 26 can display the information based on the water quality evaluation value as a result of judgment of good or bad such as, for example, the water quality evaluation value itself or whether the water quality evaluation value is not less than a predetermined threshold or not.
[0029]
　The operation unit 27 includes various switches and the like that can be operated by the operator. The operator operates the operation unit 27 according to the information based on the water quality evaluation value displayed on the display unit 26. The operation unit 27 transmits a predetermined operation signal in response to an operation by an operator.
[0030]
　The flow rate adjusting unit 28 adjusts the flow rate to the re-water pipe P 20 in the sand filtration device 21, that is, the re-flow rate of the seawater W, based on the operation signal sent from the operation unit 27.
[0031]
　Next, a water treatment method in the above-described preprocessing section 20 will be described.
　FIG. 3 is a diagram showing the flow of the water treatment method in the preprocessing unit. FIG. 4 is a diagram showing a water passing state of the pretreatment section in a state where a part of the seawater is being re-passed through the re-flow pipe to the sand filtration apparatus.
(Water Quality Obtaining Step) As
　shown in FIG. 3, in the pretreatment section 20, the water quality evaluation value of the seawater W filtered by the sand filtration apparatus 21 is first acquired by the detection section 25 (step S 1).
[0032]
　The operator confirms the information based on the water quality evaluation value displayed on the display unit 26 and judges the quality of the seawater W subjected to the filtration process (step S2).
[0033]