JP2011041907A - Water treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment system capable of effectively treating washing wastewater produced from a separation membrane, and, moreover, capable of treating the washing wastewater produced in washing the separation membrane even when liquid to be treated is water containing salt. <P>SOLUTION: The water treatment system includes a plurality of processes comprising a biological treatment process in which liquid to be treated A is treated by bringing it into contact with microorganisms and a membrane separation process having a membrane separation means for membrane separation of liquid to be treated B using the separation membrane installed in a liquid-to-be-treated container, a discharging means for discharging wastewater from the liquid-to-be-treated container and a membrane washing means for washing the separation membrane. The water treatment system further includes a wastewater supply means for supplying the biological treatment process with at least a part of the wastewater including the washing wastewater produced by the membrane washing means. The water treatment system is characterized in that the membrane washing means is for washing the separation membrane by replacing the liquid to be treated B in the liquid-to-be-treated container with washing liquid and then bringing the washing liquid into contact with the separation membrane. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water treatment system that includes a plurality of processes including a biological treatment process and a membrane separation process, and treats washing wastewater generated from the membrane separation process by the biological treatment process.

  In recent years, technological development related to separation membranes has progressed, and features such as space saving, labor saving, and improved filtered water quality have expanded the use in various applications including water treatment. For example, microfiltration membranes and ultrafiltration membranes can be applied to water purification processes that produce industrial water and tap water from river water, groundwater, and sewage treatment solutions, pretreatment in membrane desalination and reverse osmosis membrane treatment processes, membrane separation activity Application to the sludge method can be mentioned, and nanofiltration membranes and reverse osmosis membranes can be applied to removal of ions, seawater desalination, and wastewater reuse processes.

  However, if the liquid to be processed is separated by a separation membrane, the removal target such as turbidity and organic matter contained in the liquid to be processed accumulates on the surface of the separation membrane, and the separation membrane is clogged. As a result, the pressure difference in membrane filtration reaches the upper limit, and membrane separation cannot be performed. Therefore, in order to maintain membrane filtration performance, it is necessary to wash the separation membrane. For cleaning the separation membrane, back-pressure cleaning is performed in which the membrane permeate flows backward from the secondary side (membrane permeate side) of the separation membrane to the primary side (liquid side to be treated), and gas is supplied to the primary side of the separation membrane. Then, there are an air cleaning method for removing dirt from the separation membrane and a cleaning method in which a chemical solution is brought into contact with the separation membrane. It is very important to perform these washings effectively in order to stably operate the membrane separation.

  As a method for treating the washing wastewater discharged by washing the separation membrane, conventionally, when the pollutant concentration is low, it is discharged into a river or the ocean, and when it is high, it is treated as industrial waste. Since the washing wastewater is concentrated water obtained by concentrating water containing dirt accumulated in the separation membrane, the concentration of pollutants is often high. When the washing wastewater is treated as industrial waste, the cost increases, and there is a problem that the recovery rate of the treatment liquid is reduced by the amount of waste.

  Therefore, as a method other than treating the washing wastewater as industrial waste, Patent Document 1 describes a method of causing the backwash rinse washing wastewater to flow into the liquid tank to be treated. However, in this method, only rinse washing wastewater when backwashing and rinsing with water containing no chlorine can be used, and backwashing washing wastewater containing a large amount of chlorine cannot flow into the liquid tank to be treated. There are problems that the control by the concentration is complicated and that the recovery rate of the treatment liquid cannot be significantly improved. Further, in Patent Document 2, in a system in which a liquid to be treated is biologically treated and permeated water separated by membrane separation is separated by a reverse osmosis membrane, the concentrated water discharged from the reverse osmosis membrane is returned to the biological treatment tank. Are described. However, this method cannot be applied when the liquid to be treated is water having a high salt concentration such as seawater or brine, because it affects microorganisms.

  Some water purification plants are biologically treating concentrated wastewater from separation membranes and backwash wastewater. In this case, too, when the liquid to be treated is water having a high salt concentration such as seawater or brine, it could not be applied because it affects microorganisms.

JP 2008-183510 A JP 2008-279335 A

“1. Waterworks mechanics received an order, Sakai Water Purification Plant, Shimoshita Water Purification Plant, a facility with a daily capacity of 40,000 cubic meters × 2”, [online], March 6, 2006, Water Works Engineering Co., Ltd. column, [August 18, 2009 Search], Internet <http://www.suiki.co.jp/column/column29.htm>

  Accordingly, an object of the present invention is to provide a water treatment capable of treating cleaning wastewater efficiently and capable of treating the cleaning wastewater generated when washing the separation membrane even when the liquid to be treated contains water containing a high concentration of salt. Is to provide a system.

In order to achieve the above object, the water treatment system of the present invention has any of the following configurations.
(1) A biological treatment process in which the treatment liquid A is brought into contact with a living organism, a membrane separation means for separating the treatment liquid B by a separation membrane installed in the treatment liquid container, and the treatment liquid accommodation A plurality of processes including a drainage means for discharging wastewater from the body and a membrane separation process comprising a membrane washing means for washing the separation membrane, and at least of the wastewater including the washing wastewater generated by the membrane washing means In a water treatment system comprising a waste water supply means for supplying a part of the biological treatment process, the membrane washing means replaces the treatment liquid B contained in the treatment liquid container with a washing liquid, and the washing liquid And a membrane cleaning means for cleaning the separation membrane by bringing the separation membrane into contact with each other.
(2) The water treatment system according to (1), wherein the cleaning liquid is a biological treatment liquid A obtained from a biological treatment process.
(3) In the biological treatment process, the biological treatment liquid A is obtained by bringing the treatment liquid A into contact with a living organism and performing membrane separation, and the biological treatment liquid A is subjected to a semipermeable membrane treatment with the semipermeable membrane A. It is a process for obtaining treated water A and concentrated water A, and the membrane separation process is a process for membrane separation of mixed water obtained by mixing at least a part of liquid B to be treated and concentrated water A with the separation membrane. (1) or (2) water treatment system characterized by the above-mentioned.

  The effects of the present invention are as follows.

  (1) When the treatment liquid B in the membrane separation process is salt-containing water such as seawater or brine, when the separation liquid is washed by replacing the treatment liquid in the treatment liquid container with the washing liquid, the salt concentration of the washing wastewater is Because it is diluted, it can be biologically processed. Further, by supplying the cleaning wastewater to the biological treatment process, the recovery rate of the treatment liquid can be improved, and the cost can be reduced by reducing the industrial waste. When the adjustment of the hydrogen ion concentration of the liquid to be treated in the biological treatment process or the biological treatment tank can be performed with the washing waste water, the amount of the chemical solution used in the biological treatment process can be reduced. Moreover, when it can maintain with the hydrogen ion density | concentration which a living organism can act when cleaning wastewater is supplied to the biological treatment tank, the chemical | medical solution for neutralizing cleaning wastewater can be reduced.

  (2) When a treatment liquid generated from a treatment liquid of another process is used as the water for washing the separation membrane, the treatment liquid B and the treatment liquid have different ion concentrations, organic substance concentrations, and the like. However, for components with low concentrations, the dirt components adhering to the separation membrane are easily dissolved in the treatment liquid, and the cleaning effect is enhanced. In this case, since the washing wastewater is likely to become highly polluted, industrial waste can be reduced by biologically treating the washing wastewater.

  (3) When the liquid B to be treated is salt-containing water such as seawater or brine, the concentrated water A generated by the semipermeable membrane treatment of the biological treatment process is mixed with the liquid B to be treated, which is salt-containing water. The osmotic pressure of the treatment liquid B may be lowered to reduce the pressure of the booster pump for semipermeable membrane treatment in the separation membrane process. In this case, the biologically treated water often has a higher organic matter concentration than seawater, brine, etc., and the organic matter concentration also increases if the biological treatment is not performed properly. When the salt-containing water contained is subjected to a semipermeable membrane treatment, the organic matter concentration in the concentrated water B tends to increase. Therefore, when the concentrated water A generated in the biological treatment process is mixed with the liquid B, industrial waste can be reduced by biologically treating the washing wastewater.

It is a schematic flowchart which shows an example of the water treatment system to which the method of this invention is applied. It is a schematic flowchart which shows another example of the water treatment system with which the method of this invention is applied. It is a schematic flowchart which shows another example of the water treatment system to which the method of this invention is applied. It is a schematic flowchart which shows another example of the water treatment system to which the method of this invention is applied.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to these.

  FIG. 1 is a schematic view of a water treatment system to which the present invention is applied. The water treatment system according to the present invention includes, as biological treatment processes, a treatment liquid A tank 1 containing a treatment liquid A, a biological treatment tank 3 containing a biological liquid 5, and a treatment liquid A tank 1. The biological liquid 5 is solid-liquid separated by the treatment liquid A supply pump 2 for supplying the liquid A to the biological liquid 5, the separation membrane A4 installed so as to be immersed in the biological liquid 5, and the separation membrane A4. And a suction pump 6 for filtration for obtaining the biological treatment liquid A and a biological treatment liquid A tank 7 containing the biological treatment liquid A, and the liquid B to be treated is solid-liquid separated as a membrane separation process. The separation membrane B module 9 for supplying the treatment liquid B to the separation membrane B module 9, the treatment liquid B supply pump 8 for obtaining the treatment liquid B by the separation membrane B module 9, and the treatment liquid B Processing liquid B tank 15, processing liquid B tank 16, and separation membrane B module The gas supply means 14 for injecting gas into the liquid B to be treated of the fluid 9 and bringing bubbles into contact with the separation membrane B, and the treatment liquid B contained in the treatment liquid B tank 15 are separated from the secondary side of the separation membrane B. A reverse pressure cleaning pump 17 for backflow from the (processing liquid side) to the primary side (processing liquid side), a chemical tank 18 for storing a chemical liquid for cleaning the separation membrane B, and a chemical tank 18 A chemical solution supply pump 19 for supplying the stored chemical solution so as to come into contact with the separation membrane B, and a drainage means installed in the separation membrane B module 9 for discharging the liquid B to be processed stored in the separation membrane B module 9 10 and a cleaning wastewater transfer pipe 11 communicating with the drainage means 10 and a cleaning wastewater installed in the cleaning wastewater transfer pipe 11 in order to supply the wastewater discharged from the separation membrane B module 9 to the organism-containing liquid 5 of the biological treatment process. Supply pump 12 and separation membrane B module 9 And a cleaning water discharge outlet valve 13 for draining wastewater et discharged out of the system based.

  The structure and use method of this apparatus will be specifically described below.

  The liquid to be treated A stored in the liquid A tank 1 to be treated is supplied to the biological treatment tank 3 containing the biological liquid 5 by the liquid A supply pump 2 to contact the liquid A to be treated. I am letting.

  Here, the organism-containing liquid is a mixed liquid containing microorganisms, such as activated sludge and a microorganism culture liquid. The liquid A to be treated is a liquid containing a substance that becomes a substrate of microorganisms in the organism-containing liquid, and is, for example, an organic waste liquid such as household wastewater, urban sewage, and factory wastewater. Moreover, as means for supplying the liquid to be treated A to the biological liquid, for example, a suction means for supplying the biological liquid with a suction pump from a liquid tank to be treated, a river or a lake, or the liquid A to be treated and the biological liquid It may be a means for supplying the organism-containing liquid by utilizing the water head difference with the surface. In FIG. 1, the biological liquid containing liquid is supplied from the liquid A to be treated 1 by a suction pump.

  The biological treatment tank 3 is not particularly limited as long as the biological liquid 5 can be stored, and a concrete tank, a fiber reinforced plastic tank, or the like is preferably used. In the biological treatment tank 3, the liquid A is biologically treated with the biological liquid 5.

  Examples of a method for obtaining a treatment liquid by biologically treating the liquid to be treated A include an activated sludge method and a membrane separation activated sludge method. In the activated sludge method, organic matter such as activated sludge is used to decompose and remove organic substances in wastewater and pollutants such as nitrogen and phosphorus, and then the sludge mixture is separated into solid and liquid by gravity sedimentation, and the supernatant water is discharged. Wastewater treatment method. The membrane separation activated sludge method refers to a method that uses membrane separation to decompose organic substances in wastewater and pollutants such as nitrogen and phosphorus by microorganisms such as activated sludge to obtain a clear treatment liquid. . The membrane separation method is not particularly limited, such as an immersion membrane method, an external membrane separation method, and a rotating flat membrane method.

  The activated sludge introduced into the biological treatment tank 3 is generally used for wastewater treatment and the like, and as the seed sludge, drawn sludge from other wastewater treatment facilities is usually used. In the activated sludge method, the sludge concentration is about 2,000 mg / L to 5,000 mg / L and the residence time of the liquid to be treated A is usually operated in 1 hour to 24 hours. In the membrane separation activated sludge method, the sludge concentration is 2 The residence time of the treatment liquid A is usually 1 to 24 hours at about 2,000 mg / L to 20,000 mg / L, but it is preferable to select the optimum one according to the properties of the treatment liquid A. . In addition, by installing a device for adding a flocculant and adding flocculant to the liquid A to be treated containing activated sludge stored in the biological treatment tank 3, it is also possible to remove phosphorus and soluble organic matter from membrane-separated activated sludge. This is preferable in that it can be reduced from the processing solution.

  In addition, a separation membrane A4 is immersed in the organism-containing liquid 5, and a filtration suction pump 6 is provided as a treatment liquid acquisition means on the treatment liquid side of the separation membrane A4. The separation membrane A4 communicates with the treatment liquid side by piping. By operating the suction pump 6 for filtration, the biological liquid 5 is membrane-separated by the separation membrane A4, and the biological treatment / membrane-separated treatment is obtained. The obtained biological treatment liquid A can be stored in the biological treatment liquid A tank 7 and discharged to the outside of the system, or reused with industrial water, landscape water, or the like. The biological treatment liquid A tank 7 is not particularly limited as long as the biological treatment liquid A can be stored, and a concrete tank, a fiber reinforced plastic tank, or the like is preferably used. Here, as a means for obtaining the treatment liquid from the biologically-containing liquid, for example, a solid-liquid separation means using a separation membrane, or a solid liquid in which a solid content in the biologically-containing liquid is precipitated by gravity and a supernatant liquid is obtained as the treatment liquid. A separation means may be used, but a solid-liquid separation means using a separation membrane is preferable because the quality of the treatment liquid is good and the treatment liquid can be reused. In FIG. 1, a separation membrane is used. In solid-liquid separation by membrane separation, a treatment liquid which is permeated water of the separation membrane is generated by generating a pressure difference between the primary side (treated liquid side) and the secondary side (treatment liquid side) of the separation membrane. In this case, the processing liquid acquisition means for generating the pressure difference may be, for example, a pressurizing means for pressurizing the liquid to be processed, or a negative pressure is applied from the processing liquid side by a suction pump. For example, a suction means may be used, or a pressure difference may be generated by utilizing a water head difference between the organism-containing liquid and a pipe outlet. In FIG. 1, a suction pump is used.

  Examples of the membrane structure of the separation membrane A4 include a porous membrane and a composite membrane in which a functional layer is combined with the porous membrane, but are not particularly limited. Specific examples of these membranes include polyacrylonitrile porous membrane, polyimide porous membrane, polyethersulfone porous membrane, polyphenylene sulfide sulfone porous membrane, polytetrafluoroethylene porous membrane, polyvinylidene fluoride porous membrane, polypropylene Examples of the porous film include a porous film and a porous film such as a polyethylene porous film, and a polyvinylidene fluoride porous film and a polytetrafluoroethylene porous film are particularly preferable because of high chemical resistance. Furthermore, a composite film in which a rubbery polymer such as cross-linked silicone, polybutadiene, polyacrylonitrile butadiene, ethylene propylene rubber, or neoprene rubber is compounded as a functional layer can be given as a functional layer.

  Moreover, it is preferable that the membrane pore diameter of separation membrane A4 is a pore diameter which can carry out solid-liquid separation of activated sludge into a solid component and a dissolved component. If the membrane pore size is large, the membrane permeability is improved, but the possibility that a solid component is contained in the membrane filtrate tends to increase. On the other hand, if the membrane pore size is small, the possibility that a solid component is contained in the membrane filtrate is reduced, but the membrane permeability tends to be lowered. Specifically, it is preferably 0.01 to 0.5 μm, and more preferably 0.05 to 0.5 μm.

  The form of the separation membrane A4 includes a hollow fiber membrane, a tubular membrane, a flat membrane, and the like, but any form can be used in the present invention. Here, the hollow fiber membrane is a tubular separation membrane having an outer diameter of less than 2 mm, and the tubular membrane is a tubular separation membrane having an outer diameter of 2 mm or more. In the case of hollow fiber membranes, these separation membranes are hollow fiber membrane elements that are bundled in a U-shape or I-shape and accommodated in a case. In the case of tubular membranes, tubular-type elements are used. In this case, it is preferable that a spiral type element or a plate-and-frame type element is used, and a single element or a combination of a plurality of elements are modularized.

  In addition, the solid-liquid separation method using the separation membrane A4 includes total filtration for solid-liquid separation of the entire amount and cross-flow filtration for performing solid-liquid separation while generating a flow on the surface of the separation membrane. In the present invention, any solid-liquid separation method may be used, but in the case of performing membrane separation in a biological treatment process, the component in the biological liquid that adheres to the membrane surface due to the solid-liquid separation due to the shear stress due to the flow of the membrane surface. Since it is possible to operate while peeling, cross flow filtration is preferred.

  The separation membrane B is accommodated in the separation membrane B module 9, and the treatment liquid B is supplied to the separation membrane B module 9 by the treatment liquid B supply pump 8. By pressurizing the side (the liquid to be treated), the treatment liquid B is obtained through a pipe communicating with the secondary side (the treatment liquid side) of the separation membrane B. The obtained processing liquid B can be stored in the processing liquid B tank 15 and the processing liquid B tank 16 and discharged to the outside of the system, or reused with industrial water, landscape water, or the like. The treatment liquid B tank 15 and the treatment liquid B tank 16 are not particularly limited as long as the treatment liquid B can be stored, and a concrete tank, a fiber reinforced plastic tank, or the like is preferably used. Here, the liquid B to be treated contains a contaminant that can be captured by the separation membrane, and has a high osmotic pressure to the extent that it affects biological treatment. For example, seawater or brine and agglomerate seawater and brine It is a liquid such as a pretreatment liquid that has undergone pretreatment such as precipitation or sand filtration. The means for obtaining the treatment liquid with the separation membrane B module 9 may be, for example, a pressure means for pressurizing the liquid to be treated, or a suction means for applying a negative pressure from the treatment liquid side by a suction pump. Alternatively, a means for generating a pressure difference using a water head difference between the liquid to be treated and a pipe outlet may be used. In FIG. 1, a pressurizing pump is used.

  Here, the separation membrane B captures substances having a certain particle diameter or more contained in the liquid to be treated by applying pressure to the liquid to be treated or sucking with a pump from the treatment liquid side. It has a function of generating a treatment liquid from which substances are removed, and there are a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, and the like depending on the difference in the trapped particle diameter. The separation membrane used in the present invention may be any of a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane.

  Materials for microfiltration membranes and ultrafiltration membranes include organic materials such as polyacrylonitrile, polysulfone, polyphenylene sulfone, polyphenylene sulfide sulfone, polyvinylidene fluoride, cellulose acetate, polyethylene, polypropylene, and chlorinated polyethylene, and inorganic materials such as ceramics. Materials can be listed. In the present invention, the material is not particularly limited, but polyvinylidene fluoride, chlorinated polyethylene, polyacrylonitrile, cellulose acetate, polyphenylene sulfone, and polyphenylene sulfide sulfone are preferable because they have good stain resistance and washing recovery properties.

  Examples of the material for the nanofiltration membrane and reverse osmosis membrane include polyamide-based, polypiperazine amide-based, polyester amide-based, and water-soluble vinyl polymers that are crosslinked. In the present invention, the material is not particularly limited, but a polyamide-based or polypiperazine amide-based film is preferable from the viewpoint of the amount of permeated water and chemical resistance.

  The form of the separation membrane B module 9 includes a hollow fiber membrane, a tubular membrane, a flat membrane, and the like, but any form can be used in the present invention. Here, the hollow fiber membrane is a tubular separation membrane having an outer diameter of less than 2 mm, and the tubular membrane is a tubular separation membrane having an outer diameter of 2 mm or more. In the case of hollow fiber membranes, these separation membranes are hollow fiber membrane elements that are bundled in a U-shape or I-shape and accommodated in a case. In the case of tubular membranes, tubular-type elements are used. In this case, it is preferable that a spiral type element or a plate-and-frame type element is used, and a single element or a combination of a plurality of elements are modularized.

  The solid-liquid separation method using the separation membrane B module 9 includes total-volume filtration for solid-liquid separation of the entire amount and cross-flow filtration for performing solid-liquid separation while generating a flow on the surface of the separation membrane. In the present invention, any solid-liquid separation method may be used. However, in the membrane separation process, it is preferable to use the total amount filtration because the energy consumption is small. Furthermore, although it may be a pressurization type or an immersion type, the pressurization type is preferred from the viewpoint that membrane separation at a high flow rate is possible.

  The separation membrane B module 9 is subjected to membrane cleaning in order to remove dirt adhered to the surface of the separation membrane after membrane separation for a predetermined time. Examples of the membrane cleaning means include air cleaning for removing dirt by supplying gas to the primary side of the separation membrane and vibrating the separation membrane, and processing liquid from the secondary side (processing liquid side) of the separation membrane. There are methods such as back pressure cleaning that reversely flows to the next side (liquid side to be treated) to remove dirt on the separation membrane, and a method of cleaning by bringing a chemical solution into contact with the separation membrane.

  When air cleaning is performed, in order to bring bubbles into contact with the separation membrane B, a gas is supplied from the gas supply means 14 to the liquid B to be processed in the separation membrane B module 9. Here, the gas supply means is an air supply means such as a compressor or a blower.

  Further, when performing back pressure cleaning, the processing liquid B accommodated in the processing liquid B tank 15 is pressurized from the secondary side (processing liquid side) of the separation membrane B by the back pressure cleaning pump 17, Back flow to the primary side (liquid side to be treated) to remove dirt.

  Further, when performing chemical cleaning, a chemical tank 18 and a chemical supply pump 19 for supplying the chemical are provided, and as a chemical cleaning method, the chemical is added to the processing liquid to be flowed back during back pressure cleaning, and separated. There are a method of bringing a chemical solution into contact with a membrane, a method of supplying a chemical solution to the primary side or the secondary side of the separation membrane, and bringing the chemical solution into contact with the separation membrane.

  These film cleaning means may be performed alone or in combination.

  As chemicals, aqueous solutions containing drugs such as hydrochloric acid, sulfuric acid, nitric acid, citric acid, oxalic acid, ascorbic acid, sodium hydrogen sulfite, sodium hydroxide, sodium hypochlorite can be used only for drugs that do not damage the separation membrane. . The acid aqueous solution is more preferably an inorganic acid aqueous solution than an organic acid from the viewpoint of waste liquid treatment. The concentration of the counter-pressure cleaning chemical is preferably 10 mg / L to 10000 mg / L. This is because if it is lower than 10 mg / L, the cleaning effect is not sufficient, and if it is higher than 10000 mg / L, the cost of the drug becomes high and it becomes uneconomical. From such a point, it is more preferable that it is 100 mg / L to 1000 mg / L. It is preferable to use two or more kinds of drugs in order rather than one kind. For example, it is more preferable to use an acid and sodium hypochlorite alternately or to use an acid after alkali. In FIG. 1, a chemical solution is added to a processing solution to be backflowed at the time of back pressure cleaning.

  When these membrane cleaning means are performed, the cleaning wastewater discharged from the separation membrane B module 9 includes dirt removed from the separation membrane, and the drainage means 10 communicating with the separation membrane B module 9 It is discharged out of the separation membrane B module 9. Here, the drainage means is, for example, a valve, and the cleaning wastewater is discharged out of the separation membrane B module 9 by opening the valve after the membrane cleaning.

  Here, the to-be-processed liquid B is a liquid whose osmotic pressure is high to the extent that it affects biological treatment, such as seawater or brine. Therefore, if the membrane cleaning means is performed while the separation membrane B module 9 is in the state of the liquid B to be processed, the generated cleaning wastewater cannot be supplied to the organism-containing liquid 5. Therefore, before performing the membrane cleaning means, the liquid B to be treated in the separation membrane B module 9 is discharged to the outside of the separation membrane B module 9 by the drainage means 10 and opened to the outside of the system by opening the cleaning drainage discharge valve 13. The present invention can be used by discharging and closing the cleaning drainage discharge valve 13 and performing the membrane cleaning means using a liquid having a low osmotic pressure to such an extent that the biological treatment is not affected. In particular, in chemical solution cleaning, the concentration is often adjusted to a set concentration at which the chemical solution is brought into contact with the separation membrane in the chemical solution tank. If the liquid to be treated is a liquid with high osmotic pressure such as seawater or brine, tap water or Since liquids with low osmotic pressure such as industrial water and reverse osmosis membrane treatment liquid are often used, the present invention can be used effectively. The liquid B to be treated discharged from the separation membrane B module 9 before the membrane cleaning means has the same organic substance concentration as the liquid B to be treated at the time of water intake, so it can be returned to the water intake place. Don't be.

  Membrane cleaning means is performed using a liquid having a low osmotic pressure to the extent that it does not affect biological treatment, and the cleaning wastewater discharged by the drainage means 10 is biologically transferred by a cleaning drainage transfer pipe 11 communicating with the drainage means 10. Transferred to the processing process. Here, the transfer destination in the biological treatment process is the biological liquid 5 or the upstream side of the biological liquid 5, and is transferred to the liquid A tank 1 to be processed which is upstream of the biological liquid 5 in FIG. is doing. As a result, turbidity and organic components in the cleaning wastewater are biologically treated with the biological liquid 5 and are not discarded as industrial waste. In addition, when the concentration of the organic component of the liquid A to be treated is low, an organic chemical solution such as methanol may be added to maintain the microorganisms in the organism-containing liquid. As a result, the amount of the organic chemical used may be reduced.

  In addition, when the membrane cleaning means performs back-pressure cleaning or air cleaning using the processing liquid generated from the processing liquid of another process, the ionic concentration or organic substance concentration of the processing liquid B is different from that of the processing liquid. A component having a concentration lower than that of the treatment liquid B is preferable because the dirt component adhering to the separation membrane is easily dissolved in the treatment liquid and the cleaning effect is enhanced. In FIG. 2, a pipe communicating with the biological treatment liquid A tank 7 containing the biological treatment liquid A generated in the biological treatment process is communicated with the separation membrane B module 9, and a back pressure washing pump 17 installed in the pipe. The biological treatment liquid A is caused to flow backward from the secondary side (treatment liquid side) of the separation membrane B to the primary side (treatment liquid side) to remove the contamination of the separation membrane.

  Moreover, in FIG. 3, the biological treatment liquid A generated in the biological treatment process is subjected to a semipermeable membrane treatment with a semipermeable membrane A20. The semipermeable membrane is a nanofiltration membrane or a reverse osmosis membrane, and a treatment liquid and concentrated water are generated by the semipermeable membrane treatment. This concentrated water is sent to the liquid B tank 22 through the concentrated water A transfer pipe communicating with the semipermeable membrane A, mixed with the liquid B to be processed, and membrane-separated by the separation membrane B module 9. When the concentrated water generated in the biological treatment process is mixed with the liquid B to be treated, it is preferable to use the present invention because industrial waste can be reduced by biologically treating the washing waste water.

  Further, as shown in FIG. 4, a semipermeable membrane B24 for semipermeable membrane treatment of the treatment liquid B in the membrane separation process, a semipermeable membrane B supply pump 23 for pressurizing the treatment liquid B for semipermeable membrane treatment, A semipermeable membrane treatment liquid B tank containing a semipermeable membrane treatment liquid B generated by the semipermeable membrane treatment, and a concentrated water B tank containing the concentrated water B, and subjecting the treatment liquid B to a semipermeable membrane treatment Since treated water can be obtained and it can be used with industrial water etc., it is preferred.

  According to the water treatment system of the present invention, the washing waste water generated from the separation membrane can be efficiently treated and the amount of waste water can be reduced. For example, the present invention is effectively applied to a system that treats sewage wastewater and seawater in a plurality of processes. Can do.

1: treated liquid A tank 2: treated liquid A supply pump 3: biological treatment tank 4: separation membrane A
5: Bio-containing liquid 6: Filtration suction pump 7: Biological treatment liquid A tank 8: Liquid to be treated B supply pump 9: Separation membrane B module 10: Drainage means 11: Wash drainage transfer pipe 12: Wash drainage supply pump 13: Cleaning drainage discharge valve 14: Gas supply means 15: Treatment liquid B tank 16: Treatment liquid B tank 17: Back pressure washing pump 18: Chemical liquid tank 19: Chemical liquid supply pump 20: Semipermeable membrane A
21: Concentrated water A transfer pipe 22: Liquid B to be treated 23: Semipermeable membrane B supply pump 24: Semipermeable membrane B
25: Semipermeable membrane treatment liquid B tank 26: Concentrated water B tank

Claims (3)

A biological treatment process in which the treatment liquid A is brought into contact with a living thing, a membrane separation means for membrane-separating the treatment liquid B by a separation membrane installed in the treatment liquid container, and drainage from the treatment liquid container At least a part of the waste water including the cleaning waste water generated by the membrane cleaning means, and a membrane separation process including a membrane cleaning means for cleaning the separation membrane. In the water treatment system provided with the waste water supply means for supplying to the biological treatment process, the membrane washing means replaces the treatment liquid B contained in the treatment liquid container with a washing liquid, and separates the washing liquid from the separation liquid. A water treatment system, which is a membrane cleaning means for cleaning the separation membrane by contacting the membrane. The water treatment system according to claim 1, wherein the cleaning liquid is a biological treatment liquid A obtained from a biological treatment process. In the biological treatment process, the biological treatment liquid A is obtained by bringing the treatment liquid A into contact with a living organism and performing membrane separation, and the biological treatment liquid A is subjected to a semipermeable membrane treatment with the semipermeable membrane A, thereby treating water A. And the concentrated water A, and the membrane separation process is a process of separating the mixed water obtained by mixing the liquid B to be treated and at least a part of the concentrated water A with the separation membrane. The water treatment system according to claim 1 or 2.

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