JP6530931B2 - Method of desalting, method of cleaning demineralizer and demineralizer - Google Patents

Description

  The present invention relates to a method of desalting, a method of cleaning demineralizer, and a method of demineralizer, and in particular, to a method of demineralizer using a membrane module containing a reverse osmosis membrane element provided with a spacer It relates to the cleaning method.

  Conventionally, a reverse osmosis membrane (RO: reverse osmosis membrane) method, an electrodialysis method, an electric desalting method, an evaporation method, etc. are used as a desalting method when desalination of seawater or brackish water to obtain industrial water or drinking water. Is widely known. When these techniques are employed, it is necessary to pre-treat suspended solids contained in seawater or brackish water in advance. Therefore, the coagulation method, sand filtration method, pressurized floating method, microfiltration membrane (MF: Micro Filtration membrane) / ultrafiltration membrane (UF: Ultra Filtration membrane) membrane method, etc. are used alone or in combination.

  Recently, not only suspended solids but also organic substances dissolved in liquid under the influence of urban sewage flowing into seawater or brackish water are used in RO membrane method, electrodialysis method, electric deionization method, and evaporation method operation. It has become apparent that the maintenance and costs are greatly affected. In particular, in the above-described desalting method using a membrane such as an MF membrane, a UF membrane, or an RO membrane, organic substances and suspended solids dissolved on the membrane surface are accumulated to cause fouling (clogging, clogging, etc.). There are problems such as a decrease in flow velocity, an increase in backwash frequency, and a decrease in membrane life.

  Therefore, in recent years, a desalination apparatus is widely known in which a pretreatment device having a pretreatment membrane for filtering suspended solids in raw water is provided at the front stage of a reverse osmosis membrane (RO) device. For example, using separation membranes, such as an ultrafiltration membrane (UF) or a microfiltration membrane (MF), as a pretreatment membrane is described (patent document 1).

  Alternatively, as a method of cleaning the RO membrane with reduced desalting efficiency, when the membrane performance of the membrane module is reduced by the gel layer, the number of rotations of the pump drive motor is reduced and the opening degree of the outlet valve is increased. It is known to increase the internal flow rate and remove the gel layer with raw water (Patent Document 2).

  Furthermore, in recent years, a membrane module equipped with a spiral reverse osmosis membrane element provided with a mesh-like spacer has also been used. It is necessary to remove the slime accumulated in the spacer in order to wash the RO membrane with reduced desalting efficiency, and it is known to use a chemical solution containing hydrazine monohydrate and an alkali (Patent Document 3) ).

  In Japanese Patent No. 5100678 (Patent Document 4), in order to efficiently remove deposits attached to an RO membrane, a method of washing a reverse osmosis membrane by supplying a cleaning chemical solution from a concentrate discharge port to a raw water supply port Has been proposed.

  In Japanese Patent No. 4251879 (Patent Document 5), in the operation of the separation membrane module to which the spiral membrane element is attached, raw water is alternately flowed in the flow direction and the direction opposite to the flow direction of the separation membrane module to perform flushing several times A way to do that has been proposed.

  In Japanese Patent No. 4765874 (patent document 6), there is a method of circulating raw water and gas from the washing fluid inlet to the washing fluid outlet and washing in a cylindrical housing that accommodates the reverse osmosis membrane element. Proposed.

  Japanese Patent No. 3615918 (Patent Document 7) proposes a method in which washing water is caused to flow through a pipe through which concentrated water of a membrane module flows, in the direction opposite to the flow direction of concentrated water.

JP, 2011-031121, A Japanese Patent Application Laid-Open No. 63-93304 JP 2004-113973 A Patent No. 5100678 gazette Patent No. 4251879 Patent No. 4765874 gazette Patent No. 3615918 gazette

  However, even when the pretreatment device is provided at the front stage of the reverse osmosis membrane as described in Patent Document 1, the amount of water permeating water or The operating pressure may increase and the desalting efficiency may decrease.

  In the washing method for controlling the rotational speed of the pump drive motor and the opening degree of the outlet valve using the raw water as described in Patent Document 2 to remove the gel layer on the reverse osmosis membrane surface, the control is complicated. Does not provide the expected cleaning effect. In patent document 3, since a special chemical | medical solution is used, there exists a problem that the chemical | medical solution cost for washing | cleaning will cost.

  In the methods described in Patent Document 4 and Patent Document 6, since the cleaning chemical solution or the cleaning water is supplied only from one direction on the concentrated water outlet side, the membrane module upstream side may not be sufficiently cleaned. Similarly, in the method described in Patent Document 7, since the cleaning is performed only from the raw water inflow space side, a sufficient cleaning effect can not be obtained in the entire membrane module. Although the method described in Patent Document 5 discloses an example in which flushing is alternately performed from both the upstream side and the downstream side of the membrane module, the cleaning effect is still sufficient depending on the component deposited on the reverse osmosis membrane. May not be obtained.

  In view of the above problems, the present invention provides a desalting method, a desalting apparatus cleaning method, and a desalting apparatus capable of uniformly washing the inside of a membrane module by an inexpensive and simple method.

  As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, by alternately supplying the cleaning chemical solution from the raw water supply port and the concentrated water discharge port of the membrane module containing the reverse osmosis membrane element provided with the spacer, It has been found that it is possible to uniformly clean the entire membrane module by removing the contaminants contained in the membrane module, in particular the local contaminants accumulated near the spacers.

The present invention completed based on the above findings, in one aspect, supplies raw water to a membrane module containing a reverse osmosis membrane element provided with a mesh-like spacer that can cause accumulation of contaminants to obtain concentrated water and permeated water Demineralization process , forward direction cleaning process for supplying cleaning solution from raw water supply port of membrane module and discharging cleaning solution containing contaminants remaining in membrane module from concentrated water outlet of membrane module, Concentrated water discharge The reverse direction cleaning step of supplying the cleaning solution from the outlet and discharging the cleaning solution containing the contaminants staying in the membrane module from the raw water supply port , and alternately repeating the forward direction cleaning step and the reverse direction cleaning step Controlling the flow rate of the cleaning chemical solution in the directional cleaning process to be slower than the flow rate of the cleaning chemical solution in the reverse directional cleaning process; Desalting method of reducing the flow rate control of the wash liquor in the process and the reverse cleaning process is provided.

The desalting method according to the present invention, in one embodiment, is a method of supplying raw water to a membrane module containing a reverse osmosis membrane element provided with a mesh-like spacer capable of causing accumulation of contaminants to obtain concentrated water and permeate water. A salting step, a forward direction cleaning step of supplying a cleaning solution from a raw water supply port of a membrane module and discharging a cleaning solution containing contaminants remaining in the membrane module from a concentrated water outlet of the membrane module, a concentrated water outlet Supplying a cleaning chemical solution from the feed water and discharging the cleaning chemical solution containing the contaminants remaining in the membrane module from the raw water supply port; and the flow rate of the cleaning chemical solution in the forward direction cleaning process and the reverse direction cleaning process , from the fluid analysis result of the membrane module of the membrane surface concentration of contaminants reverse osmosis membrane element is calculated based on mass transfer rates obtained by using the analogy type Chirutonko Le burn Desalting method of controlling on the basis of the output result is provided.

  The desalting method according to the present invention, in another embodiment, comprises alternately repeating the forward washing step and the reverse washing step.

  The desalting method according to the present invention includes, in yet another embodiment, that the flow rate of the cleaning solution in the forward cleaning step is slower than the flow rate of the cleaning solution in the reverse cleaning step.

  The desalting method according to the present invention includes, in yet another embodiment, supplying a cleaning solution mixed with air bubbles in at least one of the forward washing step and the reverse washing step.

  The desalting method according to the present invention further includes a flushing step after the desalting step and before the washing step, wherein the flushing step supplies raw water from the concentrated water outlet to carry out the inside of the membrane module. Discharge of contaminants from the raw water supply port.

  In yet another embodiment of the desalting method according to the present invention, the cleaning solution contains at least one or more of an acid, sodium hydroxide, a chelating agent, a surfactant, and an enzyme.

In another aspect of the present invention, a cleaning solution is supplied from a raw water supply port for supplying raw water provided to a membrane module containing a reverse osmosis membrane element provided with a mesh spacer capable of causing accumulation of contaminants. A forward cleaning step of discharging the cleaning solution containing the contaminants staying in the membrane module from the concentrated water outlet for discharging the concentrated water provided in the membrane module , and supplying the cleaning solution from the concentrated water outlet Alternately repeating a reverse direction cleaning step of discharging a cleaning solution containing a contaminant staying in the membrane module from the raw water supply port, and a forward direction cleaning step and a reverse direction cleaning step; Control step to control the flow rate to be lower than the flow rate of the cleaning solution in the reverse direction cleaning step, and the accumulation of contaminants on the mesh spacer is performed in the forward direction cleaning step and the reverse direction cleaning step Method for cleaning a desalter to reduce the flow rate control of the kick wash liquor is provided.

In still another aspect of the present invention, a reverse osmosis membrane element provided with a mesh spacer capable of causing accumulation of contaminants, and a raw water inlet for supplying raw water, and a permeation obtained by membrane treatment of raw water comprising a membrane module having a permeate outlet and the concentrated water outlet for out discharge of water and concentrated water, supplying wash liquor from the raw water supply port, the contaminants accumulated from the concentrated water discharge port into the membrane module A forward direction switching valve for forward cleaning process for discharging the cleaning solution and a reverse direction for supplying the cleaning solution from the concentrated water discharge port and discharging the cleaning solution containing contaminants remaining in the membrane module from the raw water supply port By opening and closing the reverse direction switching valve for the cleaning process and the forward direction switching valve and the reverse direction switching valve, the supply direction of the cleaning chemical solution is from the raw water supply port side to the concentrated water discharge port side or concentrated water discharge. Raw water from the exit side A control unit for the flow rate of the wash liquor of the forward cleaning step is controlled to be slower than the flow rate of the wash liquor of the reverse washing step with switched alternately to the supply port side, the raw water inlet and concentrate outlet And a storage tank for solid-liquid separation of the cleaning solution containing the contaminants discharged from the concentrated water discharge port and the raw water supply port while storing the cleaning solution to be supplied to the storage tank. There is provided a demineralizer that reduces the flow rate control of the cleaning solution in the cleaning step and the reverse direction cleaning step .

The present invention in yet another aspect, housing a reverse osmosis membrane element with a mesh-shaped spacer, the raw water supply port for supplying raw water, leaving discharging the permeate and retentate obtained by membrane treatment raw water Pipe connected between the raw water supply port and the concentrated water discharge port and connected to the supply pipe and drain pipe for supplying the cleaning solution , and a membrane module having a permeated water outlet and a concentrated water outlet for And a cleaning pump capable of forward and reverse operation that is connected to the piping and supplies the cleaning chemical solution into the membrane module through the raw water supply port and the concentrated water outlet port for cleaning, and the supply direction of the cleaning chemical solution from the raw water supply port side Control is performed to switch alternately to the concentrated water outlet or from the concentrated water outlet to the raw water inlet, and the flow rate of the cleaning solution in the forward direction cleaning process is slower than the flow rate of the cleaning solution in the reverse direction cleaning process control so And a control device, desalination apparatus is provided for reducing the accumulation of contaminants in the mesh spacer by a flow rate control of the wash liquor in the forward cleaning step and reverse cleaning step.

  According to the present invention, there is provided a desalting method, a desalting apparatus cleaning method and a desalting apparatus capable of uniformly washing the inside of a membrane module in an inexpensive and simple manner.

It is a schematic diagram showing an example of the demineralizer concerning an embodiment of the invention. It is sectional drawing of the membrane module which accommodated the reverse osmosis membrane element inside. It is a partial disassembled perspective view of a reverse osmosis membrane element provided with a spacer It is a block diagram showing an example of a control device concerning an embodiment of the invention. Fig.5 (a) and FIG.5 (b) are image figures showing the adhesion state of the contamination vicinity of the spacer of the reverse osmosis membrane element based on the fluid analysis at the time of supplying a washing | cleaning chemical | medical solution from a raw water supply port or a concentrated water discharge port. is there. It is a flowchart showing an example of the desalting method which concerns on embodiment of this invention. It is a flowchart showing an example of the processing flow which the control apparatus shown in FIG. 4 performs. It is the schematic showing the example of the desalination apparatus (1st modification) which concerns on other embodiment. It is a schematic diagram showing an example of the desalting device (the 2nd modification) concerning other embodiments. It is the schematic showing the comparative example of a demineralizer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment shown below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention specifies the structure, arrangement and the like of the component parts as follows. It is not something to do.

(Demineralizer)
FIG. 1 shows an example of a demineralizer according to an embodiment of the present invention. The demineralizer according to the embodiment of the present invention comprises a pretreatment device 1 for pretreatment of raw water, a membrane module 3 for membrane treatment of the pretreated raw water treated by the pretreatment device 1, and a membrane module 3. It comprises a storage tank 6 for storing a cleaning chemical solution to be cleaned, a pump 4 for pumping the raw water and cleaning chemical solution processed by the pretreatment device 1, and a control device 5 for controlling various operations of the demineralizer.

  The demineralization apparatus shown in FIG. 1 has a first introduction pipe between the pretreatment device 1, the pump 4, the membrane module 3 and the storage tank 6 in order to supply and discharge the raw water and the cleaning chemical solution into the membrane module 3. 11, a second introduction pipe 12, a first return pipe 13, a second return pipe 14, a discharge pipe 15, and a cleaning liquid supply pipe 16 are provided. A switching valve V1 is disposed in the first introduction pipe 11. A switching valve V3 is disposed in the second introduction pipe 12. A switching valve V4 is disposed in the first return pipe 13. A switching valve V2 is disposed in the second return pipe. A switching valve V5 is disposed in the discharge pipe 15. A switching valve V6 is disposed in the cleaning chemical solution supply pipe 16.

  The type of raw water to be supplied is not particularly limited, but a fluid containing at least a contaminant such as a soluble organic substance or a turbid substance is used. For example, secondary treated water of sewage, various production drainage, underground water, irrigation water, seawater, brackish water, leachate generated from the final disposal site of waste, etc. can be used as raw water according to the present embodiment.

  It is preferable that the pretreatment device 1 be disposed on the upstream side of the membrane module 3 in order to suppress fouling (clogging, clogging, etc.) of the membrane module 3, reduction in membrane flow velocity, reduction in membrane life, etc. . The pretreatment performed by the pretreatment device 1 includes, for example, pretreatment with a screen device, sand filtration device, flocculation sand filtration, air flotation device (DAF), turbidity removal film using MF film or UF film, etc. .

  The water quality of the feed water supplied to the membrane module 3 is preferably pretreated by the pretreatment device 1 such that SDI (silt concentration index: FI value) is 4 or less. In addition, when SDI of the raw water before pre-processing is four or less, of course, it is not necessary to process by the pre-processing apparatus 1. FIG.

  The membrane module 3 receives the treated water or the permeated water obtained by the pretreatment device 1 and removes salts to make the permeated water. The membrane module 3 preferably has a spiral reverse osmosis membrane element with a spacer inside. The reverse osmosis membrane embedded in the reverse osmosis membrane element is a semipermeable membrane which can obtain a very high desalting rate, and as a material, cellulose acetate polymer, polyamide, polyester, polyimide, vinyl polymer etc. are used Be done. A polyamide is generally used as a material of the spacer.

  Not all feed water supplied from the pretreatment device 1 to the membrane module 3 is demineralized, and in addition to the permeated water, concentrated water in which the feed water is concentrated is discharged. The distribution of the permeated water and the concentrated water is designed in consideration of the concentration factor at which no scale is generated, the flow velocity in the membrane module 3 and the like.

  The membrane module 3 is not limited to the following configuration. For example, as shown in FIG. 2, the cylindrical case 31 and the end plates 32 a and 32 b disposed at both ends of the cylindrical case 31 are disposed. The membrane module 3 which accommodated the reverse osmosis membrane element 20 provided with the spacers 24 and 25 (refer FIG. 3) in the inside of the pressure container which was made is usable.

  As shown in FIG. 2, the raw water supply port 33 is formed in the end plate 32a. A permeated water outlet 34 and a concentrated water outlet 35 are formed in the end plate 32 b. A packing 37 is attached near one end of the outer peripheral surface of the reverse osmosis membrane element 20, whereby the reverse osmosis membrane element 20 is mounted at a predetermined position inside the cylindrical case 31. The reverse osmosis membrane element 20 has a cylindrical water collection pipe 22 at its center. One end of the water collection pipe 22 is connected to the permeated water outlet 34. An end cap 36 is attached to the other end of the water collection pipe 22.

  For example, as shown in FIG. 3, the reverse osmosis membrane element 20 mounted in the membrane module 3 is a bag by superposing the reverse osmosis membrane 26 on both sides of the spacer 25 (permeate water spacer) and bonding three sides. Membrane 23 is formed, and the opening of the bag-like membrane 23 is attached to a water collecting pipe 22 consisting of a perforated hollow pipe, and wound around the outer peripheral surface of the water collecting pipe 22 together with a mesh spacer 24 (raw water spacer). Rolled membrane elements are available.

  In addition, although the reverse osmosis membrane element 20 shown in FIG. 3 is illustrated for reference in this embodiment, the specific structure of the reverse osmosis membrane element 20 which concerns on this embodiment is restrict | limited only to the aspect shown in FIG. It is not something to be done. That is, in this embodiment, the reverse osmosis membrane element 20 provided with at least one spacer can solve a certain purpose, and a spiral membrane element other than the configuration shown in FIG. Of course, the present embodiment is applicable.

  When the desalting treatment is continued in the membrane module 3, although the turbidity and the organic matter are removed by the pretreatment device 1, the amount of permeated water decreases with the passage of time to secure a predetermined amount of permeated water The operating pressure of the membrane module 3 has to be increased. This is because water permeability is reduced by the generation of contaminants including organic matter, bacteria, oil, inorganic scale and the like on the surface of the reverse osmosis membrane accommodated in the membrane module 3.

  Therefore, in the deionization apparatus according to the present embodiment, a constant reference is provided regularly or under a predetermined operating condition, for example, a predetermined operation pressure, and a reduction in the amount of permeated water, and based on the reference The reverse osmosis membrane in module 3 is cleaned. The cleaning solution is stored in the storage tank (cleaning tank) 6 of FIG. 1 and supplied into the membrane module 3 via the pump 4.

  As the cleaning solution, a general-purpose membrane cleaning agent can be used. For example, a solution obtained by adding a cleaning agent to a solution not containing salts such as demineralized water or municipal water can be used as a cleaning solution. As the cleaning solution, for example, a cleaning solution containing at least one or more of an acid, sodium hydroxide, a chelating agent, a surfactant, and an enzyme is used. More preferably, a cleaning solution containing at least one or more of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, citric acid, ascorbic acid, sodium hydroxide, a chelating agent, a surfactant and an enzyme is used. According to the present embodiment, the entire membrane module can be uniformly cleaned without using a special cleaning chemical solution, so that cheaper and highly productive membrane processing can be performed.

  As a still more preferable form, the inside of the storage tank 6 doubles as the solid-liquid separator 7. The solid-liquid separation device 7 is a device for removing the contaminants discharged from the membrane module 3 mixed in the cleaning solution by solid-liquid separation. The solid-liquid separation device 7 may be any device provided with a mechanism capable of removing contaminants in the cleaning solution. For example, it is preferable to use a solid-liquid separation device 7 that performs precipitation separation, floatation separation, membrane separation, aggregation separation, bubble separation and the like.

  According to the present embodiment, since the cleaning chemical solution from which the contaminants have been removed can be used again as the cleaning chemical solution to be supplied to the membrane module 3 as the regeneration cleaning chemical solution, the contamination to the reverse osmosis membrane element housed in the membrane module 3 It is possible to suppress the reattachment of objects and to enhance the cleaning effect. In addition, the cost of cleaning chemicals can be reduced.

  As shown in FIG. 1, it is preferable that the solid-liquid separator 7 be disposed in the storage tank 6 and that both be used. Thereby, the whole demineralization apparatus can be miniaturized. When there is a sufficient space for arranging the solid-liquid separator 7 separately from the storage tank 6, it goes without saying that the solid-liquid separator 7 and the storage tank 6 do not have to be combined.

  The control device 5 can be configured by a general purpose or special purpose computer (computer) that sends out a predetermined operation based on the control algorithm according to the present embodiment. For example, the control device 5 performs the cleaning process of the membrane module 3, the first introduction pipe 11, the second introduction pipe 12, the first return pipe 13, the second return pipe 14, the discharge pipe 15, and the like. It is possible to control switching control of the switching valves V1 to V6 respectively connected to the cleaning chemical solution supply pipe 16, adjustment of the supply flow rate of the raw water supplied into the membrane module 3 and the cleaning chemical solution, and the like.

  For example, the control device 5 performs forward direction cleaning in which the supply direction of the cleaning chemical solution is from the raw water supply port 33 side to the concentrated water discharge port 35 side, or reverse direction cleaning in which the concentrated water discharge port 35 is from the concentrated water discharge port 35 side Can be switched alternately.

  In the forward direction cleaning, the control device 5 performs switching control to open the switching valves V1, V4, and V6 and close the switching valves V2, V3, and V5. In this case, the switching valves V1 and V4 supply the cleaning chemical solution from the raw water supply port 33, and as the forward direction switching valve for discharging the cleaning chemical solution containing the contaminants remaining in the membrane module 3 from the concentrated water outlet 35. Function.

  In the reverse direction cleaning, the control device 5 performs switching control of opening the switching valves V2, V3 and V6 and closing the switching valves V1, V4 and V5. In this case, the switching valves V2 and V3 supply cleaning fluid from the concentrated water discharge port 35, and serve as reverse direction switching valves for discharging cleaning fluid containing contaminants remaining in the membrane module 3 from the raw water supply port 33. Function.

In a preferred embodiment, the control unit 5, based on the flow rate of the wash liquor in the forward cleaning and reverse washing, the mass transfer rates obtained by using the analogy type Chirutonko Le Bahn fluid analysis results within the membrane module 3 It can control using the calculation result of the film surface concentration of the reverse osmosis membrane element 20 calculated.

  Therefore, for example, as shown in FIG. 4, the control device 5 stores the input / output control module 51, the fluid analysis module 52, the substance movement speed calculation module 53, the film surface concentration calculation module 54, the cleaning liquid chemical module 55 and various information. Storage device 50 can be provided.

The input / output control module 51 receives input of various conditions such as water quantity, water temperature, operating pressure, viscosity, liquid density, spacer thickness, spacer shape, etc., which are the premise of various calculations, and Output control signal to the device. The fluid analysis module 52 performs fluid analysis in the membrane module 3 based on each of the input conditions. Mass transfer rate calculation module 53 uses the result of fluid analysis, determine the mass transfer rate using the analogy type Chirutonko Le burn. The membrane surface concentration calculation module 54 calculates the membrane surface concentration of the contaminants of the reverse osmosis membrane contained in the membrane module 3 from the mass transfer rate. The cleaning solution module 55 calculates the flow rate of the cleaning solution in the forward direction cleaning and the reverse direction cleaning based on the membrane surface concentration of the reverse osmosis membrane. Details will be described using a flowchart shown in FIG. 7 described later.

  The mesh-like spacers 24 and 25 disposed in the reverse osmosis membrane element 20 as shown in FIGS. 2 and 3 form a flow path through which the feed water (raw water) passes on the reverse osmosis membrane 26, and reverse osmosis It is arranged for the purpose of disturbing the flow of fluid supplied on the membrane. The spacers 24, 25 can suppress a decrease in the amount of water permeated by accumulation of contaminants on the surface of the reverse osmosis membrane 26, an increase in the operating pressure, or a decrease in the desalting efficiency.

  However, when the inventors of the present invention calculated the concentration of contaminants (salt concentration) on the membrane surface using the results of fluid analysis by computational fluid dynamics (CFD) and the calculation results, the results are shown in FIGS. As shown in (b), there is still locally a stagnant portion of the liquid (a stagnation portion) in a portion (around the linear portion and the intersection portion) of the mesh spacer, and the accumulation of contamination occurs. Was confirmed.

  In such a state, even if the cleaning chemical solution is passed only in the same introduction direction as desalting or in the opposite direction to that in desalting, the cleaning chemical solution sufficiently reaches the stagnation portion of the solution during cleaning. It was found that no effective cleaning effect was obtained.

  According to the desalination apparatus in accordance with the embodiment of the present invention, the cleaning solution is supplied from the raw water supply port 33 of the membrane module 3 and the cleaning solution containing the contaminants staying in the membrane module 3 is concentrated water of the membrane module 3 At least two of the forward direction cleaning for discharging from the discharge port 35 and the reverse direction cleaning for supplying the cleaning chemical solution from the concentrated water discharge port 35 and discharging the cleaning chemical solution containing the contaminants staying in the membrane module 3 from the raw water supply port 33 Directional washing takes place.

  As a result, the stain generated on the stagnant part of the liquid generated in the forward direction washing can be washed by the reverse direction washing, and the stain generated on the stagnant part of the liquid generated in the reverse direction wash can be cleaned by the forward direction wash Therefore, the entire membrane module can be cleaned more uniformly. In addition, it is preferable that the forward direction cleaning and the reverse direction cleaning alternately repeat at least one set or more of combinations of the forward direction cleaning and the reverse direction cleaning.

  The flow rate control of the cleaning solution in the forward direction cleaning and the reverse direction cleaning may be performed strictly by performing flow analysis by performing control based on fluid analysis performed by the control device 5 shown in FIG. The control based on fluid analysis may not be performed. That is, the control device 5 can also control the flow rate of the cleaning solution in the forward direction cleaning and the reverse direction cleaning based on the predetermined flow rate control information input from the input person.

  In a preferable mode of the present embodiment, it is preferable to control so that the flow rate of the cleaning solution in the forward direction cleaning is slower than the flow rate of the cleaning solution in the reverse direction cleaning. Although FIG. 2 shows the case where one reverse osmosis membrane element 20 is disposed in the membrane module 3, about 2 to 8 reverse osmosis membrane elements 20 are inserted in series in the membrane module 3. It may be done. In such a case, contaminants such as organic matter, solid particles, and bacteria are most likely to be attached to the element to which the raw water (feed water) is first introduced. Therefore, in the present embodiment, by slowing the flow rate of the cleaning chemical solution in the forward direction cleaning in which the cleaning chemical solution is supplied from the raw water supply port 33, it is difficult for the contaminants to reach the second and third elements.

  On the other hand, in the reverse direction cleaning in which the cleaning solution is supplied from the concentrated water discharge port 35, the flow rate of the cleaning solution is made faster than at least the previous forward direction cleaning in order to facilitate pushing out the contaminants out of the membrane module 3. . By doing so, contaminants are more likely to flow out of the membrane module 3. The flow rate of the cleaning solution can be any speed. The higher the flow rate, the higher the cleaning effect. However, since it is usually used in combination with the pump 4 used for desalting, the capacity of the pump 4 is within the range.

  The preferred flow rate of the cleaning solution is 1/3 to 2 times the flow rate of the feed water during desalting in the forward direction washing, and 1/2 to the flow rate during the desalting flow in the reverse direction cleaning. About three times is preferable. In any of the flow rates, the flow rate of the cleaning solution in the reverse direction is made faster than the flow rate of the cleaning solution in the forward direction.

  In a further preferable mode of the present embodiment, an immersion process of immersing the inside of the membrane module 3 with the cleaning solution can be further included between the forward cleaning and the reverse cleaning. The immersing step is a step of stopping the flow of the fluid in a state in which the contaminated reverse osmosis membrane element 20 is immersed in the cleaning solution. Thereby, the contaminants can be made to float from the reverse osmosis membrane element 20, so that the cleaning by the flow rate control can be performed more effectively.

  In a further preferable mode of the present embodiment, the cleaning solution containing bubbles is supplied in at least one of the forward cleaning and the reverse cleaning. The bubble diameter is not particularly limited, and may be 1 μm or less of ultra fine bubbles (nano bubbles), 1 to 50 μm of fine bubbles (micro bubbles) or coarse bubbles of more than that, but the surface charge is negative charge Preferred are charged microbubbles. The negative charge of the microbubbles adheres to the contaminants attached to the film, which has the effect of making it easier for the contaminants to peel off the film.

  At the time of washing using air bubbles, it is preferable to use a chemical such as a chelating agent in combination. When raw water is seawater or leachate, calcium is contained in the raw water and calcium is likely to be accumulated on the surface of the membrane. The calcium accumulated at the surface of the membrane becomes a binder and can attract contaminants, resulting in the deposition of contaminants on the membrane. By using a chelating agent in combination, the calcium and the chelating agent are combined to reduce the role of the binder, so that the contaminants are easily peeled off.

  The water flow rate of the cleaning solution may be any amount, but it is preferable to flow 1 to 10 times, preferably 1 to 5 times, the reverse osmosis membrane module in one washing. Once one wash is completed, water is passed one to ten times, preferably one to five times, the reverse osmosis membrane module in the direction opposite to the washing direction.

  In a further preferred embodiment of the present embodiment, after the desalting treatment of the feed water, the raw water is supplied from the concentrated water discharge port 35 before the forward washing and the reverse washing, and the raw water and the contaminants in the membrane module 3 are To flush the raw water from the raw water supply port 33. At the time of flushing, the control device 5 opens the switching valves V2 and V3 and performs switching control to close the switching valves V1, V4, V5 and V6. As described above, the feed water (raw water) supplied from the pretreatment device 1 is made to flow from the concentrated water discharge port 35 and is discharged from the raw water supply port 33, so that the convective portion of the liquid is in the vicinity of the spacers 24 and 25. Contamination accumulated can be discharged in advance. At this time, pressure may be applied, but water may be passed as it is without applying pressure.

  By performing the above-described flushing before the cleaning of the membrane module 3, it is possible to suppress the contamination of the cleaning chemical solution with the contaminants in the membrane module 3, and the cleaning effect according to the present embodiment can be maintained for a long time. The flushing time can be any time, but if the water flow rate is large, the amount of discharged raw water will increase, so it is usually 10 to 180 minutes, preferably 20 to 120 minutes. The water flow rate can be any speed, but since it uses the same pump as the feed water pump 4, it is set according to the same flow rate of the feed water, or 1/2 to 3 times the pump volume You can

(Desalting method)
The desalting method according to the embodiment of the present invention comprises a desalting step S101 of supplying raw water to the membrane module 3 accommodating the reverse osmosis membrane element 20 provided with the spacers 24, 25 to obtain concentrated water and permeate water; And washing steps S104 to S105 for washing the membrane module 3.

  In the cleaning steps S104 to S105, the cleaning chemical solution is supplied from the raw water supply port 33 of the membrane module 3, and the cleaning chemical solution containing the contaminants retained in the membrane module 3 is discharged from the concentrated water outlet 35 of the membrane module 3. The cleaning step S104, and the reverse direction cleaning step S105 of supplying the cleaning chemical solution from the concentrated water discharge port 35 and discharging the cleaning chemical solution containing the contaminants remaining in the membrane module 3 from the raw water supply port 33.

  Hereinafter, specific examples of the desalting method according to the embodiment of the present invention will be described with reference to FIGS. 1 and 6.

  In step S101 of FIG. 6, the control device 5 included in the demineralizer of FIG. 1 performs switching control to open the switching valves V1, V5, and V6 and to close the switching valves V2, V3, and V4. As a result, raw water is fed from the raw water supply port 33 of the membrane module 3 into the membrane module 3 through the pretreatment device 1, the pump 4, the first introduction pipe 11 and the switching valve V 1. In the membrane module 3, the feed water supplied into the membrane module 3 is RO-treated by the reverse osmosis membrane element 20 mounted in the membrane module 3, and separated into permeate water and concentrated water. Permeate is discharged from the permeate outlet 34. The concentrated water is discharged from the concentrated water discharge port 35 through the discharge pipe 15 and the switching valve V5.

  In step S102, the control device 5 determines whether water has flowed for a set time based on the condition input value input from the input person. If the water has not been supplied for the set time, the process returns to step S101 to continue the water supply. If the water has been set for the set time, the process proceeds to step S103.

  In step S103, the control device 5 performs switching control of opening the switching valves V2 and V3 and closing the switching valves V1, V4, V5, and V6. As a result, raw water is supplied to the concentrated water outlet 35 of the membrane module 3 through the pretreatment device 1, the pump 4, the first inlet pipe 11, the second inlet pipe 12, the switching valve V 3 and the outlet pipe 15. The contaminants in the membrane module 3 are discharged from the raw water supply port 33 (flushing step). In addition, implementation of process S103 is arbitrary. That is, step S104 may be performed immediately after step S102.

  In step S104, the control device 5 performs switching control of opening the switching valves V1, V4, V6 and closing the switching valves V2, V3, V5. Thus, the cleaning solution in the storage tank 6 is supplied from the raw water supply port 33 of the membrane module 3 through the cleaning solution supply pipe 16, the switching valve V6, the pump 4, the first introduction pipe 11, and the switching valve V1. Water flows in. The feed water supplied into the membrane module 3 takes in the contaminants in the membrane module 3, and the concentrated water outlet 35 through the discharge pipe 15, the first return pipe 13 and the second return pipe 14. It is sent to the storage tank 6 (forward cleaning). In the storage tank 6, the contaminants are removed by the solid-liquid separation device 7 and discharged to the outside.

  In step S105, the control device 5 performs switching control to open the switching valves V2, V3 and V6 and to close the switching valves V1, V4 and V5. Thereby, the cleaning solution in the storage tank 6 is a film through the cleaning solution supply pipe 16, the switching valve V6, the pump 4, the first introduction pipe 11, the second introduction pipe 12, the switching valve V3, and the discharge pipe 15. Water is passed from the concentrated water outlet 35 of the module 3 into the membrane module 3. The feed water supplied into the membrane module 3 is sent from the raw water supply port 33 to the storage tank 6 through the first inlet pipe 11 and the second return pipe 14 in a state where the contaminants in the membrane module 3 are taken in. Be washed (reverse direction washing). In the storage tank 6, the contaminants are removed by the solid-liquid separation device 7 and discharged to the outside.

  In step S106, the control device 5 determines whether or not step S104 and step S105 have been performed the set number of times based on the condition input value input from the input person. If the set number of times has not been performed, the process returns to step S104 to continue water flow. If the set number of times has been performed, the work is ended.

  As described above, according to the desalting method according to the embodiment of the present invention, the forward cleaning (step S104) and the reverse cleaning (step S105) of the membrane module 3 are alternately repeated. It is possible to remove contaminants more uniformly.

  The cleaning time in step S104 and step S105 can be any time. In the present embodiment, it is preferable to set each for at least 30 minutes or more. The washing temperature may also be any temperature, but preferably 20 to 40 ° C. When the temperature is 20 ° C. or less, the cleaning effect is low, and when the temperature is 40 ° C. or more, the membrane may be damaged or the members constituting the membrane element may be damaged. The order of step S104 and step S105 may be reversed. Although the upper limit in particular of repetition of process S104 and process S105 is not restrict | limited, In view of processing efficiency, it is about 3 times.

  In a further preferred embodiment, the flow rate of the cleaning solution in step S104 and step S105 is more strictly controlled by the control device 5 shown in FIG. The flow rate control method of the cleaning chemical solution by the control device 5 will be described using the flowchart shown in FIG.

  In step S51 of FIG. 7, information to be a premise of calculation is input via an input device (not shown), and the input / output control module 51 stores the input information in the storage device 50 of FIG. Examples of the information to be the basis of the calculation include the configuration of the reverse osmosis membrane element 20 (for example, the spacer thickness, spacer shape, membrane area, membrane density, etc.), physical properties of the feed water flowing into the reverse osmosis membrane element 20 (water amount, Water temperature, viscosity, liquid density, etc.), operation conditions (operation pressure, etc.) of the membrane module 3, etc. are input.

  In step S52, the fluid analysis module 52 of FIG. 4 performs fluid analysis (CFD) in the membrane module 3. The fluid analysis module 52 calculates the water volume and vector of a certain space based on the information input in step S51. If the flow in the spacers 24 and 25 is understood from a macroscopic viewpoint, even if it looks as if it is flowing uniformly, if it is grasped from a microscopic viewpoint by the fluid analysis module 52, the space with a slow flow and the flow velocity are extremely fast. You can calculate the space that is The fluid analysis result is stored in the storage device 50.

In step S53, the mass transfer rate calculation module 53 of Figure 4, using the fluid analysis results obtained in step S52, it calculates the mass transfer rate using the analogy type Chirutonko Le burn. The analogy type Chirutonko Le Bahn (Chilton-Colburn), momentum, heat transfer, a analogy equation showing the similarity of mass transfer, is represented by the following equation (1).
f / 2 = j _H = j _D (1)
Here, f is the coefficient of friction, j _H is the j factor of heat transfer, and j _D is the j factor of mass transfer.

Furthermore, j _D has the following relationship (2).
j _D = Sh / (Re · Sc ^1/3 ) (2)
Here, Sh is the Sherwood number, Re is the Reynolds number, and Sc is the Schmid number. By analogy formula of the Chirutonko Le burn, fluid flow and the vector of the minute space obtained by fluid analysis (Um; m / s) from the mass transfer rate of the salts of the minute space (K; m / s) can be calculated. The calculation result of the mass transfer rate is stored in the storage device 50.

  In step S54, based on the mass balance of the reverse osmosis membrane surface based on the calculation result of the mass transfer rate of salts obtained in step S53, the membrane surface concentration calculating module 54 of FIG. Calculate the polarization. The film surface concentration of the contaminant (salt concentration of the film surface: C [mg / L]) determined by this calculation result is that the concentration polarization of the film surface is higher in the space where the fluid flow velocity in the space is slower, and water permeates Hardness is calculated and indicates that dirt is likely to accumulate. The film surface concentration calculation result is stored in the storage device 50.

  In step S55, the cleaning solution module 55 in FIG. 4 determines the flow rate of the cleaning solution in the cleaning process in steps S104 and S105 in FIG. 6 from the film surface concentration calculation result obtained in step S54. In step S56, the input / output control module 51 outputs the determination result of the flow rate to a flow meter (not shown) that controls the flow rate of the cleaning solution into the membrane module 3. The flow meter controls the flow rate of the cleaning solution based on the flow rate information output from the input / output control module 51.

According to desalting method according to the embodiment of the present invention, the flow rate of the wash liquor in the forward cleaning step S104 and reverse cleaning step S105, using the analogy type Chirutonko Le Bahn fluid analysis results within the membrane module 3 It can control using the calculation result of the film surface concentration of the contaminant of the reverse osmosis membrane element 20 calculated based on the mass transfer rate obtained. As a result, it is possible to grasp the space in the membrane module 3 where the flow is slow and the space where the flow velocity is extremely high, and it is possible to supply the cleaning chemical solution at the flow velocity suitable for the situation. It becomes possible to wash | clean the reverse osmosis membrane element 20 whole mounted in the membrane module 3 more uniformly compared with a salt apparatus.

(Other embodiments)
Although the present invention has been described by the above embodiment, it should not be understood that the description and the drawings, which form a part of this disclosure, limit the present invention. Various alternative embodiments and operation techniques will be apparent to those skilled in the art from this disclosure.

(First modification)
As the deionization apparatus according to the first modification, as shown in FIG. 8, a plurality of membrane modules 3 are arranged in parallel and in series, and concentrated water obtained by the upstream membrane module 3 is connected in series thereto. There is also an apparatus for further desalting treatment with the downstream membrane module 3. This style is called a Christmas tree type, and the number of reverse osmosis membrane modules installed in the later stages decreases.

  As described above, the membrane module 3 desalts all the inflowing raw water and does not obtain permeated water, and partially discharges it as concentrated water. Since the permeated water is discharged in the treatment process, the linear flow velocity on the separation membrane primary side on the concentrate discharge side becomes slow. Therefore, in order to prevent concentration polarization and inorganic scale formation, the water is discharged as concentrated water while leaving a certain amount of water (linear velocity).

  Therefore, there is a case where the method of further desalting the concentrated water to improve the water recovery rate may be taken. Even in such a case, it is also possible to carry out forward washing and reverse washing as a washing method of the second stage reverse osmosis membrane. In this case, the washing tank and the solid-liquid separation tank can also be used in combination.

(2nd modification)
The example shown in FIG. 9 is connected between a membrane module 3 containing a reverse osmosis membrane element provided with a spacer, a raw water supply port 33 and a concentrated water discharge port 35, and a supply pipe for cleaning chemical solution (cleaning chemical solution supply pipe 17) The pipe 19 connected to the drain pipe 18 and the pipe 19 are connected, and supply and wash the cleaning chemical solution into the membrane module 3 through the raw water supply port 33 and the concentrated water discharge port 35 so that forward and reverse operation is possible The cleaning pump 40 and the control device 5 alternately switching the supply direction of the cleaning chemical solution from the raw water supply port 33 side to the concentrated water discharge port 35 side or from the concentrated water discharge port 35 side to the raw water supply port 33 side Desalination equipment.

  Although various pumps can be used as the washing pump 40 capable of forward and reverse operation, a rotary pump is preferable. The rotary pump is positive displacement type, and can transfer liquid in the forward direction and the reverse direction depending on the rotation direction of the screw type rotor. In the example of FIG. 9, when the cleaning process is started, the switching valves V1 and V5 are closed, the switching valves V7 and V8 are opened, and the liquid in the membrane module 3 is passed from the concentrated water outlet 35 through the discharge pipe 15 and the pipe 19 And drain from the drain pipe 18. Next, the cleaning solution is introduced into the pipe 19 through the cleaning solution supply pipe 17 and supplied from the first introduction pipe 11 to the raw water supply port 33 of the membrane module 3 to fill the inside of the membrane module 3 with the cleaning solution. Thereafter, the washing pump 40 capable of forward and reverse operation is operated, and the pump 40 is washed in the forward direction or operated in the reverse direction based on the predetermined control method as described above. The inside of the module 3 is cleaned with a cleaning solution. When the predetermined cleaning is completed, the cleaning solution can be drained from the drain pipe 18.

  Examples of the present invention are given below together with comparative examples, but these examples are provided to better understand the present invention and its advantages, and are not intended to limit the invention.

Example 1
The desalting treatment was performed using the demineralizer (treatment apparatus for seawater desalination) according to the present embodiment shown in FIG. In the treatment flow, raw water was subjected to coagulation filtration in the pretreatment device 1, and then the treated water obtained in the pretreatment device 1 was passed through the reverse osmosis membrane element in the membrane module 3 for desalting treatment. The reverse osmosis membrane element was a spiral reverse osmosis membrane (manufactured by Nitto Denko) having a mesh spacer.

  About 3 months after the start of water flow, the reverse osmosis membrane was cleaned because the water permeability of the reverse osmosis membrane decreased to 70% compared to the initial value. In the washing method, a step (forward washing) of passing the washing chemical solution from the raw water supply port to the concentrated water outlet in the same direction as the feed direction of feed water during desalting (forward washing) is carried out for 2 hours, The step (reverse direction washing) of passing the cleaning chemical solution from the concentrated water discharge port to the raw water supply port (reverse direction washing) was carried out for 2 hours in the direction opposite to the supply direction of the feed water. The detergent was a pH 11 alkaline solution. The permeability after washing recovered to 90% of the start of operation. The water permeation performance was recovered well by alternately performing the washing.

(Comparative example)
The desalination treatment was performed using the seawater desalination treatment apparatus of the comparative example shown in FIG. In the treatment flow, raw water was subjected to coagulation filtration in the pretreatment device 1 and then water was passed through the reverse osmosis membrane element in the membrane module 3 for desalting treatment. The reverse osmosis membrane element was a spiral RO membrane (manufactured by Nitto Denko Corporation) having a mesh spacer.

  About 3 months after the start of water flow, the reverse osmosis membrane was cleaned because the water permeability of the reverse osmosis membrane decreased to 70% compared to the initial value. In the cleaning method, the cleaning solution is supplied from the storage tank 6 through the cleaning solution supply pipe 16 and the first introduction pipe 11 from the raw water supply port 33 to the concentrated water discharge port 35, and the discharge pipe 15 and the first return pipe It returned to the storage tank 6 through 13, and this was implemented for 4 hours. The detergent was a pH 11 alkaline solution. The permeability after washing recovered only up to 80% of the operation start.

DESCRIPTION OF SYMBOLS 1 ... Pre-processing apparatus 3 ... Membrane module 4 ... Pump 5 ... Control apparatus 6 ... Reservoir 7 ... Solid-liquid separation device 11 ... 1st introductory pipe 12 ... 2nd introductory pipe 13 ... 1st return pipe 14 ... 2nd 2 return pipe 15 ... drain pipe 16, 17 ... cleaning chemical solution supply pipe 18 ... drain pipe 19 ... piping 20 ... reverse osmosis membrane element 22 ... water collecting pipe 23 ... bag-like membrane 24 ... spacer 25 ... spacer 26 ... reverse osmosis membrane 31 ... Cylindrical case 32a ... End plate 32b ... End plate 33 ... Raw water supply port 34 ... Permeate water discharge port 35 ... Concentrated water discharge port 36 ... End cap 37 ... Packing 40 ... Cleaning pump 50 ... Storage device 51 ... I / O control module 52: Fluid analysis module 53: Mass transfer rate calculation module 54: Film surface concentration calculation module 55: Cleaning chemical solution module

Claims (7)

A desalting step of supplying raw water to a membrane module containing a reverse osmosis membrane element provided with a reticulated spacer capable of causing accumulation of contaminants to obtain concentrated water and permeate water;
A forward cleaning step of supplying a cleaning chemical solution from a raw water supply port of the membrane module and discharging the cleaning chemical solution containing contaminants remaining in the membrane module from a concentrated water discharge port of the membrane module;
A reverse direction cleaning step of supplying a cleaning chemical solution from the concentrated water discharge port and discharging the cleaning chemical solution containing a contaminant remaining in the membrane module from the raw water supply port;
A control step of alternately repeating the forward cleaning step and the reverse cleaning step, and controlling the flow rate of the cleaning solution in the forward cleaning step to be slower than the flow rate of the cleaning solution in the reverse cleaning step; hints, the accumulation of the reticulated space polluted dyeing, desalination method characterized by reducing the flow rate control of the wash liquor in the forward cleaning step and the reverse cleaning step. A desalting step of the raw water to the membrane module containing a reverse osmosis membrane element with a mesh Josu pacer accumulation of contaminants may occur supplies obtain retentate and permeate,
A forward cleaning step of supplying a cleaning chemical solution from a raw water supply port of the membrane module and discharging the cleaning chemical solution containing contaminants remaining in the membrane module from a concentrated water discharge port of the membrane module;
Reverse direction cleaning step of supplying a cleaning chemical solution from the concentrated water discharge port and discharging the cleaning chemical solution containing a contaminant remaining in the membrane module from the raw water supply port ;
The flow rate of the wash liquor in the forward cleaning step and the reverse cleaning step, is calculated based on the mass transfer rate obtained using the analogy type Chirutonko Le Bahn fluid analysis results within the membrane module the A desalting method characterized in that it is controlled based on the calculation result of the membrane surface concentration of the contaminant of the reverse osmosis membrane element. After the desalting step, before the washing step, further including a flushing step,
The desalination method according to claim 1 or 2, wherein the flushing step includes supplying raw water from the concentrated water discharge port and discharging contaminants in the membrane module from the raw water supply port. . Contamination to be accumulated in the membrane module by supplying the cleaning chemical solution from the raw water supply port for supplying the raw water provided in the membrane module containing the reverse osmosis membrane element provided with the mesh spacer which may cause the accumulation of contaminants Forward cleaning step of discharging the cleaning solution containing impurities from the concentrated water outlet for discharging the concentrated water provided in the membrane module;
A reverse direction cleaning process for supplying a cleaning solution from the concentrated water discharge port and discharging the cleaning solution containing contaminants remaining in the membrane module from the raw water supply port; a forward direction cleaning process; and a reverse direction cleaning process And alternately controlling the flow rate of the cleaning solution in the forward direction cleaning process to be slower than the flow rate of the cleaning solution in the reverse direction cleaning process,
What is claimed is: 1. A method of cleaning a demineralizer comprising: reducing accumulation of contaminants on the mesh spacer by controlling a flow rate of a cleaning solution in the forward direction cleaning step and the reverse direction cleaning step. A reverse osmosis membrane element provided with a mesh spacer capable of causing accumulation of contaminants is accommodated, a raw water supply port for supplying raw water, a permeated water and a concentrated water obtained by membrane processing the raw water A membrane module having a permeated water outlet and a concentrated water outlet;
A forward direction switching valve for a forward direction cleaning step of supplying a cleaning chemical solution from the raw water supply port and discharging the cleaning chemical solution containing contaminants remaining in the membrane module from the concentrated water outlet;
A reverse direction switching valve for a reverse direction cleaning step of supplying a cleaning chemical solution from the concentrated water discharge port and discharging the cleaning chemical solution containing contaminants remaining in the membrane module from the raw water supply port;
By opening and closing the forward direction switching valve and the reverse direction switching valve, the supply direction of the cleaning chemical solution is from the raw water supply port side to the concentrated water discharge port side, or the raw water from the concentrated water discharge port side a control unit for the flow rate of the wash liquor of the forward cleaning step is controlled to be slower than the flow rate of the wash liquor of the reverse washing step with switched alternately to the supply port side,
A storage tank for storing a cleaning solution supplied to the raw water supply port and the concentrated water discharge port, and for performing solid-liquid separation of a cleaning solution containing the contaminants discharged from the concentrated water discharge port and the raw water supply port; A demineralizer characterized in that the accumulation of contaminants on the mesh spacer is reduced by controlling the flow rate of a cleaning solution in the forward direction cleaning step and the reverse direction cleaning step. The controller performs fluid analysis by inputting various conditions, calculates the mass transfer rate from the fluid analysis result, calculates the film surface concentration of the contaminant in the film module from the calculation result, and based on the film surface concentration The demineralization apparatus according to claim 5, comprising controlling the flow rate of the cleaning solution in the forward washing step and the reverse washing step. Raw water supply port for accommodating a reverse osmosis membrane element provided with a reticulated spacer and supplying raw water, permeated water obtained by membrane treatment of the raw water and permeated water outlet for discharging concentrated water, concentrated water A membrane module having an outlet,
A pipe connected between the raw water supply port and the concentrated water discharge port and connected to a supply pipe and a drain pipe for supplying a cleaning chemical solution;
A forward / backward operable washing pump connected to the pipe and supplying and washing the washing chemical solution into the membrane module via the raw water supply port and the concentrated water outlet;
Control for alternately switching the supply direction of the cleaning chemical solution from the raw water supply port side to the concentrated water discharge port side or from the concentrated water discharge port side to the raw water supply port side and cleaning the forward direction cleaning process A controller for controlling the flow rate of the chemical solution to be slower than the flow rate of the cleaning chemical solution in the reverse direction cleaning process;
What is claimed is: 1. A demineralizer characterized in that the accumulation of contaminants on the mesh spacer is reduced by controlling the flow rate of a cleaning solution in the forward direction cleaning step and the reverse direction cleaning step.