JP2008279335A - Apparatus and method for water reclamation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for water reclamation allowing a suppression of energy consumption for cleaning aeration pipes, capable of utilizing a reverse osmosis membrane concentrate having a high pressure effectively as it is, and yet effectively carrying out cleaning the internal of the aeration pipes. <P>SOLUTION: The method for water reclamation includes the step of: flowing raw water into a tank having a liquid containing microorganisms stored therein; biologically treating the liquid containing microorganisms while supplying a gas containing oxygen through the aeration pipes; obtaining biologically treated water by separating the liquid containing microorganisms into solid and liquid with a separation membrane immersed in the liquid containing microorganisms; and separating the obtained biologically treated water into a concentrate and a membrane permeated water with a reverse osmosis membrane, wherein a part or all of the concentrate is refluxed to the liquid containing microorganisms through the aeration pipes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fresh water generation method and a fresh water generating apparatus that include a membrane separation type biological treatment step and a reverse osmosis membrane treatment step, and perform biological separation of biologically treated water from the biological treatment step with a reverse osmosis membrane.

  In recent years, water shortages are becoming a serious problem on a global scale, and in such a situation, there is a growing demand for technologies for recycling organic wastewater, including industrial wastewater and domestic wastewater. Therefore, a method for producing reclaimed water having extremely good water quality that can be used as industrial, agricultural, or household water is attracting attention.

  The reverse osmosis membrane is a membrane that can eliminate even monovalent ions in the filtrate by applying a pressure higher than the osmotic pressure of the filtrate to be filtered from the side of the filtrate. The reclaimed water obtained by this is high quality water that can be reused as industrial water, agricultural water, and even drinking water. However, the liquid to be filtered supplied to the reverse osmosis membrane has a low concentration of BOD (Biochemical Oxygen Demand) which is a pollutant in water and SS (Suspended Solid). Since good and stable water quality is required, the organic waste water cannot be directly applied to the reverse osmosis membrane. Therefore, by treating organic wastewater with activated sludge, the concentration of BOD components is reduced, and activated sludge is solid-liquid using separation membranes such as microfiltration membranes and ultrafiltration membranes that can remove SS components almost completely. A method (membrane separation activated sludge method) in which pretreatment for separation is performed and the pretreated water obtained is used as a filtrate for a reverse osmosis membrane has attracted attention.

  However, when filtration is performed using a reverse osmosis membrane, an extremely high quality reclaimed water can be obtained, but a BOD component remaining without permeating the reverse osmosis membrane, a COD (Chemical Oxygen Demand) component, salt content, etc. Concentrated water (hereinafter referred to as concentrated water) is generated, and it is difficult to use or discard the concentrated water as it is, so that it is necessary to further process the concentrated water. Concentrated water is treated by electrolyzing the concentrated water to remove BOD and COD in the concentrated water (Patent Document 1), or by a loose low-pressure reverse osmosis membrane that passes about 50% of the salt content (Patent Document) 2) A method of treatment by oxidation treatment such as ozone treatment, ultraviolet treatment, hydrogen peroxide treatment, catalyst treatment (Patent Document 3) has been proposed so far.

  Further, when treating organic wastewater with activated sludge, it is necessary to supply oxygen necessary for microorganisms in the activated sludge to ingest and decompose organic components. For that purpose, air (gas containing oxygen, air) is supplied into the activated sludge through a diffuser tube immersed in the activated sludge by a blower or the like. At this time, if the air diffuser is continued using the diffuser pipe immersed in the activated sludge, the solid component in the activated sludge enters the diffuser pipe and is dried by the diffused air. To do. When the air diffuser is blocked, not only the pressure required for air diffusion increases, but also the air diffuses unevenly, making efficient air diffusion difficult. In the membrane-separated activated sludge method, an air diffuser is placed below the microfiltration membrane or ultrafiltration membrane, and the air bubbles supplied from the air diffuser or the upward flow generated by the supply of air bubbles are attached to the membrane surface. Since the activated sludge is subjected to membrane filtration while removing the substances to be removed, if the air diffuses unevenly, the membrane surface is not sufficiently cleaned, and it is difficult to continue membrane filtration. Therefore, it is important for the stable operation of the membrane separation activated sludge method to suppress the blockage of the diffuser tube. As a method for suppressing the blockage of the diffuser tube, for example, pressure is applied to the cleaning liquid at the same time or intermittent aeration. A method of supplying cleaning liquid to the air diffuser (Patent Document 4) and a method of supplying a cleaning water tank into the air diffuser using the water head difference by providing a cleaning water tank above the water level of the activated sludge (Patent Document 4) Reference 5).

JP-A-7-155759 JP-A-9-141059 JP 2002-306930 A JP 2003-154236 A JP 2004-66025 A

  However, when the concentrated water treatment method in Patent Documents 1 to 3 is adopted, a separate treatment device is required for the treatment of the concentrated water, so that considerable cost and energy are required for its construction, operation, and maintenance. As a result, there arises a problem that the production cost of reclaimed water is increased. In addition, the method for cleaning an air diffuser according to Patent Document 4 requires a cost and energy for operation and maintenance because a pressure applying device such as a liquid feed pump is separately used when supplying the cleaning liquid under pressure. Become. Further, in the method for cleaning the air diffuser according to Patent Document 5, it is necessary to separately prepare a tank for cleaning water, and in order to give sufficient pressure to the cleaning water, the tank for cleaning water is much more than the water level of activated sludge. It is necessary to install at a high position, which is not realistic.

  Therefore, the present invention solves the above-mentioned problems of the prior art, can efficiently use the concentrated water of the reverse osmosis membrane having a high pressure as it is, and moreover, the cleaning of the air diffuser can be efficiently performed. An object of the present invention is to provide a fresh water generating apparatus and a fresh water generating method that can be performed and can suppress energy consumption for cleaning a diffuser.

In order to achieve the above-mentioned object, a reclaimed water freshwater generator and a fresh water generation method according to the present invention have any of the following configurations.
(1) A microorganism-containing liquid storage tank for storing a microorganism-containing liquid, an air diffuser pipe for injecting bubbles into the microorganism-containing liquid in the microorganism-containing liquid storage tank, and an oxygen-containing gas continuously or Gas supply means for intermittently supplying, gas supply piping connecting the diffuser pipe and the gas supply means, a separation membrane installed so as to be immersed in the microorganism-containing liquid, and the separation membrane Solid-liquid separation of the microorganism-containing liquid to obtain biological treated water, a reverse osmosis membrane for treating the obtained biological treated water, and the biological treatment supplied to the reverse osmosis membrane And a pressurizing means for pressurizing water, and a concentrated water feed pipe for feeding the concentrated water concentrated by the reverse osmosis membrane communicates with the gas supply pipe. A fresh water generator.

(2) The fresh water generation apparatus according to (1), characterized in that a backflow prevention means is provided between a connecting portion between the concentrated water feeding pipe and the gas supply pipe and the gas supply means. apparatus.
(3) The (1) or (2) is characterized in that the concentrated water feeding pipe is arranged so as to communicate with the gas supply pipe and the discharge portion of the concentrated water in the reverse osmosis. The fresh water generator described.
(4) The fresh water generator according to any one of (1) to (3), wherein the air diffuser has a discharge hole of 2 to 6 mmφ.
(5) The fresh water generator according to (4), wherein the air diffuser is installed in a lower part of the separation membrane, and a discharge hole is in the upper part of the air diffuser.
(6) The raw water is introduced into a tank in which the microorganism-containing liquid is stored, the biological treatment is performed while supplying the oxygen-containing gas to the microorganism-containing liquid through an air diffuser, and the microorganism-containing liquid is separated by the separation membrane immersed in the microorganism-containing liquid. The biological treatment water is obtained by solid-liquid separation, and the obtained biological treatment water is membrane-separated into concentrated water and membrane permeated water using a reverse osmosis membrane, and part or all of the concentrated water Is recirculated to the microorganism-containing liquid through the aeration tube.
(7) The fresh water generation method according to (6), wherein the gas supply through the air diffuser and the concentrated water supply through the air diffuser are simultaneously performed.

The effects of the present invention are as follows.
(1) By using the concentrated water of the reverse osmosis membrane as the diffuser cleaning water, the concentrated water is refluxed into the microorganism-containing liquid at the same time as the diffuser is cleaned, so that the concentrated water is biologically treated. Can do.
(2) By using the pressure applied to the concentrated water of the reverse osmosis membrane, highly efficient air diffuser cleaning can be performed without newly adding energy.
(3) The surface of the separation membrane is efficiently washed by the influence of concentrated water and air discharged at a high flow rate by disposing a diffusion tube below the separation membrane and making the discharge hole of the diffusion tube upward. .

  Hereinafter, the fresh water generator according to the present invention will be described with reference to FIG.

  The fresh water generating apparatus according to the present invention includes a microorganism-containing liquid storage tank 3 that stores a microorganism-containing liquid 4, an air diffuser pipe 5 for ejecting bubbles into the microorganism-containing liquid 4 in the microorganism-containing liquid storage tank 3, and Gas supply means 6 for continuously or intermittently supplying oxygen-containing gas to the air diffuser 5, gas supply pipe 14 connecting the air diffuser 5 and the gas supply 6, and the microorganism-containing liquid 4 A separation membrane 2 installed so as to be immersed in water, a treated water acquisition means 7 for obtaining a biologically treated water 8 by solid-liquid separation of the microorganism-containing liquid 4 by the separation membrane 2, and the acquired organism A reverse osmosis membrane 9 for treating the treated water; and a pressurizing pressure means 17 for pressurizing the biologically treated water supplied to the reverse osmosis membrane 9, and is concentrated in the reverse osmosis membrane 9. Concentrated water supply pipe 13 for supplying concentrated water And it communicates with the serial gas supply pipe 14.

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

  Raw water is continuously or intermittently introduced into the microorganism-containing liquid storage tank 3 containing the microorganism-containing liquid 4 through the raw water inflow pipe 1. Here, the microorganism-containing liquid is a mixed liquid containing microorganisms, such as activated sludge and a microorganism culture liquid. Moreover, raw | natural water is a liquid containing the substance used as the substrate of the microorganism in the microorganism-containing liquid, for example, organic waste liquids, such as domestic waste water, city sewage, and factory waste water.

  Further, a diffuser pipe 5 is installed so as to be immersed in the microorganism-containing liquid 4, and the diffuser pipe 5 and the gas supply means 6 are connected by a gas supply pipe 14. As a result, when supplying oxygen necessary for microbial reaction and providing the diffuser tube at the lower part of the separation membrane, which will be described later, air bubbles generated from the diffuser tube and the upward flow caused by the bubbles adhere to the membrane surface. Suppress. Here, the air diffuser must have a structure in which an oxygen-containing gas such as air can be dispersed and diffused as bubbles into the microorganism-containing liquid, and the concentrated water is scattered as described later. Since it flows out from the discharge hole of the trachea, in order to efficiently perform this, it is preferable to provide a plurality of discharge holes 5a having a diameter of 2 to 6 mm in a hollow pipe as shown in FIG. Moreover, it is preferable that a separation membrane is installed on the upper part of the air diffusing pipe, and the discharge hole is provided on the upper part of the air diffusing pipe. Thereby, the concentrated water discharged from the discharge holes comes into contact with the surface of the separation membrane, and there is an effect of further suppressing the substance adhesion to the surface of the separation membrane. Examples of the gas supply means include a blower.

  Further, the separation membrane 2 is immersed in the microorganism-containing liquid 4, and a suction means 7 is provided as a treated water acquisition means on the permeate side of the separation membrane 2, and the suction means 7 is used for biological treatment. It communicates with the permeate side of the separation membrane in the water storage tank 18 by piping. By operating the suction means 7, the microorganism-containing liquid is filtered by the separation membrane, and the biologically treated and filtered biologically treated water 8 is stored in the biologically treated water storage tank 18 through the pipe.

  Here, the separation membrane captures substances having a certain particle diameter or more contained in the microorganism-containing liquid by applying pressure to the microorganism-containing liquid 4 or sucking with a pump from the permeation side, and these substances. There is a function of generating biologically treated water from which water is removed, and there are microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc., depending on the difference in trapped particle size. The separation membrane used in the present invention is preferably a microfiltration membrane, an ultrafiltration membrane, or a nanofiltration 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 as a material for a microfiltration membrane for filtering a microorganism-containing liquid and an ultrafiltration membrane, polyvinylidene fluoride, chlorinated polyethylene, polyacrylonitrile, cellulose acetate, polyphenylenesulfone, Polyphenylene sulfide sulfone is preferable because it has good stain resistance and good cleaning recovery.

  Examples of the material for the nanofiltration membrane include polyamide-based, polypiperazine amide-based, polyester amide-based, and water-soluble vinyl polymer 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 includes a hollow fiber membrane, a tubular membrane, a flat membrane, and the like, and 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.

  Solid-liquid separation methods using separation membranes include total-volume filtration that separates the entire amount while concentrating the microorganism-containing liquid, and cross-flow filtration that performs solid-liquid separation while generating a flow of the microorganism-containing liquid on the surface of the separation membrane. . In the present invention, any solid-liquid separation method may be used, but the cross-flow filtration circulates a microorganism-containing liquid on the membrane surface, so that the microorganisms adhere to the membrane surface due to the solid-liquid separation due to the shear stress caused by the flow of the membrane surface. Since it is possible to operate while peeling off the components in the contained liquid, it is more preferable. In particular, by arranging an air diffuser at the bottom of the separation membrane and bringing bubbles discharged from the discharge holes of the air diffuser into contact with the surface of the separation membrane, the effect of separating the microorganism-containing liquid components from the surface of the membrane increases. Further preferred.

  Further, by generating a pressure difference between the raw water side and the permeated water side of the separation membrane, biological treated water that is the permeated water of the separation membrane is obtained. Here, the treated water for generating the pressure difference is obtained. The means may be, for example, a pressurizing means for pressurizing the raw water side, a suction means for applying a negative pressure from the permeate water side by a suction pump, or a microorganism-containing liquid and a pipe outlet. A means for generating a pressure difference using a water head difference may be used. In FIG. 1, the suction means 7 is used.

  The biologically treated water 8 stored in the biologically treated water storage tank 18 is pressurized by the pressurizing means 17 and supplied to the reverse osmosis membrane 9, and is supplied to the membrane permeated water 10 and the concentrated water 11. To be separated. An example of the pressurizing means is a high-pressure pump. A part of the biologically treated water may be discharged as it is without being supplied to the reverse osmosis membrane.

  The reverse osmosis membrane is a membrane that excludes even monovalent ions in the filtrate by applying a pressure higher than the osmotic pressure of the filtrate. The structure of the reverse osmosis membrane includes, for example, an asymmetric membrane having a dense layer on at least one side of the membrane and the pore diameter gradually increasing as the distance from the dense layer is increased, or a thickness made of another material on the dense layer of the asymmetric membrane. There are composite membranes with a thin active layer. As the film material, polymer materials such as cellulose acetate, cellulose polymer, polyamide, and vinyl polymer can be used. Typical reverse osmosis membranes include cellulose acetate or polyamide asymmetric membranes and composite membranes having polyamide or polyurea active layers. Among them, a cellulose acetate asymmetric membrane, a composite membrane having a polyamide active layer, or a composite membrane having an aromatic polyamide active layer, which has a high salt rejection performance, is preferable. Is more preferable.

  The reverse osmosis membrane includes hollow fiber membranes, tubular membranes, flat membranes and the like, and any of them can be used in the present invention. The reverse osmosis membrane is a hollow fiber membrane element in the case of a hollow fiber membrane, a tubular element in the case of a tubular membrane, a spiral type element or a plate-and-frame type element in the case of a flat membrane, alone or It is preferable to make a module by combining a plurality.

  Membrane permeated water 10 obtained by filtering with a reverse osmosis membrane can be used for purposes such as industrial water, agricultural water, and drinking water because water quality higher than tap water is obtained. On the other hand, the concentrated water 11 is water in which BOD, COD, salinity, etc. remaining without passing through the reverse osmosis membrane are concentrated, and is sent through the concentrated water feed pipe 13 at a high pressure. It is preferable that the concentrated water flow rate adjusting means 12 is incorporated in the middle of the concentrated water feeding pipe so that the flow rate of the concentrated water and the flow rate ratio of the concentrated water and the membrane filtrate water can be adjusted. Examples of the concentrated water flow rate adjusting means include a valve.

  In the present invention, the concentrated water supply pipe 13 is communicated with the gas supply pipe 14 to supply the concentrated water into the diffuser pipe 5 via the gas supply pipe 14 and discharge of the diffuser pipe. It can be discharged into the microorganism-containing liquid 4 from the hole 5a. Thus, the inside of the air diffuser can be cleaned and the organic component in the concentrated water can be biodegraded in the microorganism-containing liquid storage tank 3. Moreover, it is preferable that the said concentrated water supply piping 13 is piped so that between the said gas supply piping 14 and the said discharge part 16 of the concentrated water in the said reverse osmosis membrane 9 may be connected. As a result, the pressure applied to the concentrated water of the reverse osmosis membrane can be used effectively, and highly efficient diffuser cleaning can be performed without newly adding energy. Further, since a high pressure is applied to the concentrated water, a backflow prevention means 15 for preventing the concentrated water from flowing into the gas supply means 6 is provided between the concentrated water feed pipe and the gas supply pipe. It is preferable to be provided at a position closer to the gas supply means 6 than the connecting portion 19. Examples of the backflow prevention means include a check valve.

  When this apparatus is used, the flow rate of the concentrated water for performing the diffuser tube cleaning is adjusted using the concentrated water flow rate adjusting means 20 for cleaning the diffuser tube, and the remaining concentrated water is produced according to the present invention. It is preferable that the water can be discharged out of the water device. Thereby, it is possible to efficiently perform the air diffuser cleaning. Examples of the flow rate adjusting means for cleaning the diffuser tube include a valve. The concentrated water discharged out of the fresh water generator may be discharged after being treated separately. Moreover, it is preferable that the supply of gas through the air diffuser 5 and the supply of concentrated water through the air diffuser are performed simultaneously. As a result, the inside of the air diffuser can be effectively washed with a high-pressure air-water mixed fluid, and the air-water mixed fluid is discharged at a high flow rate and rises. It is cleaned efficiently.

  According to the reclaimed water desalination apparatus and the desalination method in the present invention, the organic waste liquid can be efficiently reused, and the amount of waste water can be reduced.For example, factories that want to reduce the amount of purified water used, agricultural areas where irrigation water is insufficient, It can be applied in urban areas where there is a shortage of drinking water.

It is the process schematic of an example of the fresh water generation apparatus based on this invention. It is a schematic perspective view of an example of the diffuser tube 5 in the apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water inflow pipe 2 Separation membrane 3 Microorganism containing liquid storage tank 4 Microorganism containing liquid 5 Aeration pipe 6 Gas supply means 7 Treated water acquisition means (suction means)
8 Biologically treated water 9 Reverse osmosis membrane 10 Membrane permeate water extraction pipe 12 Concentrated water flow rate adjusting means 13 Concentrated water feeding pipe 14 Gas supply pipe 15 Backflow preventing means 16 Concentrated water discharge part 17 Pressurizing means 18 Biologically treated water storage tank 19 Connecting portion of concentrated water feed pipe and gas supply pipe 20 Concentrated water flow adjusting means for cleaning diffuser pipe

Claims (7)

A microorganism-containing liquid storage tank for storing a microorganism-containing liquid, a diffuser tube for ejecting bubbles into the microorganism-containing liquid in the microorganism-containing liquid storage tank, and an oxygen-containing gas in the diffuser pipe continuously or intermittently A gas supply means for supplying; a gas supply pipe connecting the diffuser pipe and the gas supply means; a separation membrane installed to be immersed in the microorganism-containing liquid; and the microorganism-containing liquid by the separation membrane The treated water acquisition means for obtaining the biological treated water, the reverse osmosis membrane for treating the obtained biological treated water, and the biological treated water supplied to the reverse osmosis membrane are added. A pressure supply means for pressurizing, and a concentrated water feed pipe for feeding concentrated water concentrated by the reverse osmosis membrane communicates with the gas supply pipe. Water equipment. The fresh water generator according to claim 1, wherein a backflow prevention means is provided between a connecting portion between the concentrated water feed pipe and the gas supply pipe and the gas supply means. 3. The fresh water producing apparatus according to claim 1, wherein the concentrated water supply pipe is arranged so as to communicate the gas supply pipe with a discharge portion of the concentrated water in the reverse osmosis membrane. apparatus. The fresh water generator according to any one of claims 1 to 3, wherein the air diffuser has a discharge hole of 2 to 6 mmφ. The fresh water generator according to claim 4, wherein the air diffuser is installed in a lower part of the separation membrane, and a discharge hole is in the upper part of the air diffuser. The raw water is allowed to flow into the tank in which the microorganism-containing liquid is stored, and biological treatment is performed while supplying oxygen-containing gas to the microorganism-containing liquid through an air diffuser, and the microorganism-containing liquid is solid-liquid separated by a separation membrane immersed in the microorganism-containing liquid. To obtain a biologically treated water and membrane-separate the obtained biologically treated water into a concentrated water and a membrane permeated water using a reverse osmosis membrane, wherein a part or all of the concentrated water is A method for producing fresh water comprising refluxing the microorganism-containing liquid through a trachea. The fresh water generation method according to claim 6, wherein the gas supply through the air diffuser and the concentrated water supply through the air diffuser are simultaneously performed.

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