JP2016002514A - Membrane separation activated sludge treatment apparatus and method of operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane separation activated sludge treatment apparatus that can improve the quality of treated water and suppress operation power, and to provide a method of operating the apparatus.SOLUTION: A membrane separation activated sludge treatment apparatus 1 comprises: a first biological reaction tank 20 that has aeration means (22, 24) and in which water to be treated is treated with activated sludge; a second biological reaction tank 30 in which the water to be treated is treated under an oxygen-free condition; a membrane separation tank 40 that has a membrane separator 41 and aeration means (42, 44) and in which the treated water is treated under an aerobic condition; a first treated water passage 110, 140 that makes the treated water of the first biological reaction tank 20 flow into the membrane separation tank 40; a connecting passage 120 that connects the second biological reaction tank 30 and the first biological reaction tank 20 to each other; a second treated water passage 130, 140 that makes the treated water of the second biological reaction tank 30 flow into the membrane separation tank 40; and a return passage that returns the treated water of the membrane separation tank 40 to the second biological reaction tank 30.

Description

  The present invention relates to a membrane separation activated sludge treatment apparatus for performing water treatment using a membrane separation activated sludge method and an operation method thereof.

  A membrane separation activated sludge method is used as a wastewater treatment method using activated sludge. Membrane separation activated sludge method is a treatment method that separates and recovers activated sludge by performing biological reaction treatment using activated sludge and then subjecting the treated water to filtration treatment using ultrafiltration membrane, microfiltration membrane, etc. It is. Membrane separation activated sludge treatment equipment that performs water treatment using the membrane separation activated sludge method includes an oxygen-free tank that performs denitrification treatment under anaerobic conditions, and nitrification treatment, organic matter treatment, dephosphorization under aerobic conditions. An aerobic tank for treatment, etc. in order, a membrane separator for solid-liquid separation of the treated water and activated sludge treated in the aerobic tank, and a portion of the treated water treated in the aerobic tank 2. Description of the Related Art A processing apparatus having a return flow path for returning to an oxygen tank is known.

In this type of membrane separation activated sludge treatment apparatus, biological reaction treatment based on an anaerobic aerobic method (AO method) which is a kind of wastewater treatment method is performed. In the anaerobic tank, the polyphosphate-accumulating bacteria contained in the activated sludge are treated in advance to release the phosphorus accumulated in the cells. In the aerobic tank, more phosphorus than the polyphosphate-accumulating bacteria is released. Incorporate and accumulate. Thereafter, such polyphosphoric acid accumulating bacteria are extracted as surplus sludge and dephosphorized. In the aerobic tank, the aerobic decomposition treatment of the organic matter by the activated sludge is performed, and ammonia nitrogen (NH ₄ -N) contained in the water to be treated is removed by the action of nitrifying bacteria contained in the activated sludge. nitrification process which oxidizes to a nitrate nitrogen _(NO 3 -N) is also performed. Then, treated water containing nitrate nitrogen is returned to the oxygen-free tank, and in the oxygen-free tank, denitrification that reduces nitrate nitrogen to molecular nitrogen (N ₂ ) by the action of denitrifying bacteria contained in the activated sludge. Treatment is performed to remove nitrogen.

  The membrane separator provided in the membrane separation activated sludge treatment device has the function of separating and recovering the activated sludge contained in the treated water, improving the activated sludge concentration, and simplification and miniaturization of the treatment device associated therewith. It is said that it is effective as means for realizing the above. In order to prevent clogging of the separation membrane, the membrane separator is often provided with an air diffuser for aeration cleaning of the separation membrane, and the treatment tank in which such a membrane separator is installed is an aerobic tank. Development of a membrane-separated activated sludge treatment device that can function as a device is underway.

  In such a form of membrane-separated activated sludge treatment apparatus, the dissolved oxygen consumption by microorganisms increases due to an increase in the activated sludge concentration accompanying the separation and recovery of activated sludge, or the viscosity of water to be treated increases to the water phase. The oxygen transfer rate of the gas decreases, and the oxygen dissolution efficiency with respect to the amount of air diffused deteriorates. Therefore, the amount of aeration for maintaining the required dissolved oxygen concentration tends to increase, and it is not easy to suppress the driving power.

  Therefore, a membrane separation activated sludge treatment apparatus that can reduce operating power has been proposed. For example, Patent Document 1 discloses that an aerobic tank for treating treated water with activated sludge is divided into a plurality of parts, and a first aerobic tank for treating the treated water aerobically and the first aerobic tank. A second aerobic tank having an activated sludge concentration set higher than the first aerobic tank. A membrane separation activated sludge treatment apparatus is disclosed in which the second aerobic tank is provided with a circulation line for circulating the nitrification liquid at least upstream of the first aerobic tank.

JP 2012-076081 A

  FIG. 5 is a diagram showing a schematic configuration of a membrane separation activated sludge treatment apparatus according to a comparative example. A conventional membrane separation activated sludge treatment apparatus (a membrane separation activated sludge treatment apparatus according to a comparative example) 100 as disclosed in Patent Document 1 diffuses fine bubbles with an oxygen-free tank 20C in which stirring means 32 is installed. The first aerobic tank 30C in which the first air diffuser means (22, 24) is installed, and the second air diffuser (42, 44) in which the membrane separator 41 and the second air diffuser means (42, 44) to diffuse coarse bubbles are installed. An aerobic tank 40C and a return flow path 150C for returning the treated water in the second aerobic tank 40C to the anoxic tank 20C are provided.

  In the membrane separation activated sludge treatment apparatus 100, the activated sludge concentrated in the membrane separator 41 is returned to the anoxic tank 20C together with the treated water by the return flow channel 150C, and the second bubble diffuses coarse bubbles. The aeration means (42, 44) can be used for aeration cleaning of the membrane separator 41 installed in the second aerobic tank 40C. On the other hand, the first aerobic tank 30C is compared with the second aerobic tank 40C by installing the first air diffuser (22, 24) for diffusing fine bubbles in the first aerobic tank 30C. Thus, the operation power of the entire apparatus is reduced by setting the state where oxygen is easily dissolved into the water to be treated and suppressing the amount of air diffused.

  In general, in order to improve the quality of treated water in wastewater treatment equipment, it is desirable to select the optimum operation format according to the quality of the treated water to be treated and the water quality standards to be adapted by the treatment. It is. For example, in the membrane separation activated sludge treatment apparatus 100, when the nitrogen load of the water to be treated is small, even the second aeration means (42, 44) that diffuses coarse bubbles is necessary for the aerobic treatment. Since it may be possible to maintain a high dissolved oxygen concentration, the first aerobic tank is provided while stopping the operation of the first aeration means (22, 24) for aeration of fine bubbles to reduce the operating power. An operation mode in which 30C is bypassed or the first aerobic tank 30C is used as an oxygen-free tank is efficient. In addition, when water quality standards related to phosphorus are strict, phosphorus is released in advance to polyphosphate-accumulating bacteria by performing biological reaction treatment under anaerobic conditions before the aerobic tanks 30C and 40C and the anoxic tank 20C. The type of operation to be allowed is appropriate.

  However, in the membrane separation activated sludge treatment apparatus 100 as shown in FIG. 5, when bypassing the first aerobic tank 30C, the activated sludge is transferred between the anaerobic tank 20C and the second aerobic tank 40C. Driving power is required separately. For example, as shown in FIG. 5, when a transfer flow path 140C for transferring the treated water in the anoxic tank 20C to the second aerobic tank 40C together with the activated sludge is provided, the transfer pump 54 installed on this flow path Driving power is required separately. In addition, when the first aerobic tank 30C is used as an anaerobic tank, the total volume of the processing tanks (20C, 30C) in which a biological reaction process under anoxic conditions is performed is increased, so that the residence occurs accordingly. Time may be affected or excess sludge may increase. Further, if the first aerobic tank 30C used as an anaerobic tank is provided with a stirring device that replaces the aeration stirring by the first aeration means (22, 24), the driving power is required separately. In addition, when performing a biological reaction treatment under anaerobic conditions before the aerobic tanks 30C and 40C and the anoxic tank 20C, treated water and activated sludge are exchanged with the treatment tank in which the biological reaction treatment is performed. Separate driving power is required for the pump to be transferred.

  Accordingly, an object of the present invention is to provide a membrane separation activated sludge treatment apparatus and an operation method thereof capable of improving the quality of treated water and suppressing operation power.

  In order to solve the above problems, a membrane separation activated sludge treatment apparatus according to the present invention has a first air diffuser for aeration of treated water, and performs biological reaction treatment of the treated water using activated sludge. A first biological reaction tank, a second biological reaction tank having a stirring means for stirring the water to be treated, and performing a biological reaction treatment of the water to be treated under oxygen-free conditions using activated sludge; A membrane separator that is provided adjacent to a reaction tank and separates the treated water and activated sludge that have been subjected to biological reaction treatment in at least one of the first biological reaction tank and the second biological reaction tank, and the membrane separator. A membrane separation tank for performing a biological reaction treatment of the treated water under an aerobic condition using activated sludge, and a first biological reaction. Treated water in the first biological reaction tank by connecting the tank and the membrane separation tank The first treated water flow path that flows into the membrane separation tank, the second biological reaction tank, and the first biological reaction tank are connected to each other in either the first biological reaction tank or the second biological reaction tank. A connection channel for allowing treated water to flow into the other biological reaction tank, a second biological reaction tank and the membrane separation tank are connected, and the treated water in the second biological reaction tank is allowed to flow into the membrane separation tank. Two treatment water flow paths, the membrane separation tank and the second biological reaction tank are connected, and a circulation path is formed with the second treatment water flow path between the second biological reaction tank and the membrane separation tank. And a return flow path for returning treated water in the membrane separation tank to the second biological reaction tank.

  Further, the operation method of the membrane separation activated sludge treatment apparatus according to the present invention is to open the connection flow path valve and the second treated water flow path valve, and close the first treated water flow path valve, Water to be treated is introduced into the first biological reaction tank from outside the system, and the biological reaction treatment of the treated water is performed in the order of the first biological reaction tank, the second biological reaction tank, and the membrane separation tank. And Alternatively, the first treated water flow path valve and the connection flow path valve are opened, the second treated water flow path valve is closed, and the treated water is allowed to flow into the first biological reaction tank from outside the system. Then, the biological reaction treatment of the water to be treated is performed in the order of the first biological reaction tank, the second biological reaction tank, and the membrane separation tank. Alternatively, the first aeration unit is operated to operate the first biological reaction tank as an aerobic tank, and the first aeration unit is stopped to function as the anaerobic tank. The biological reaction process is performed by switching the operation mode

  According to the present invention, it is possible to provide a membrane separation activated sludge treatment apparatus and an operation method thereof capable of improving the quality of treated water and suppressing operation power.

It is a figure which shows schematic structure of the membrane separation activated sludge processing apparatus which concerns on one Embodiment of this invention. It is the schematic which showed the flow path of the to-be-processed water for every operating method of the membrane separation activated sludge processing apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the selection process of the operation type in the membrane separation activated sludge processing apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the change process of the operation format in the membrane separation activated sludge processing apparatus which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the membrane separation activated sludge processing apparatus which concerns on a comparative example.

  Hereinafter, a membrane separation activated sludge treatment apparatus and an operation method thereof according to an embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the common part in each figure, and description about the overlapping part is abbreviate | omitted.

  FIG. 1 is a diagram showing a schematic configuration of a membrane separation activated sludge treatment apparatus according to an embodiment of the present invention.

  A membrane separation activated sludge treatment apparatus 1 according to the present embodiment is a wastewater treatment apparatus using a membrane separation activated sludge method, and performs wastewater treatment (wastewater treatment) by biological reaction treatment using activated sludge. It is an apparatus that separates and recovers activated sludge used for the treatment from the treated water by filtration using a filtration membrane, a microfiltration membrane, or the like.

  As shown in FIG. 1, the membrane separation activated sludge treatment apparatus 1 according to this embodiment includes a first biological reaction tank 20, a second biological reaction tank 30, and a membrane separation tank 40. Further, the first treated water flow path formed by the first treated water pipe 110 and the merged pipe 140, the connected flow path formed by the connected pipe 120, the second treated water pipe 130 and the merged pipe 140 formed by the second line. 2 The process water flow path and the return flow path formed by the overflow weir 150 are provided. In the membrane separation activated sludge treatment apparatus 1, the first biological reaction tank 20, the second biological reaction tank 30, and the membrane separation tank 40 in which biological reaction processing is performed are arranged in series, and are separated from each other by a partition plate. It is divided. The second biological reaction tank 30 and the membrane separation tank 40 are in communication with each other above the overflow weir 150.

  The treated water (raw water) to be treated by the membrane separation activated sludge treatment apparatus 1 is drawn from the first sedimentation basin of the sewage treatment facility by the intake pump 5 (outside the system of the membrane separation activated sludge treatment apparatus 1), and the screen tank 10 To be introduced. The screen tank 10 is provided with a screen 12 for performing solid-liquid separation, and when the raw water passes through the screen 12, coarse solid suspended matters, mixed foreign matters, and the like are separated and removed. . The raw water drawn into the membrane separation activated sludge treatment apparatus 1 is measured for the amount of load water by a flow rate measuring means (not shown).

  The raw water treated in the screen tank 10 is first introduced into either the first biological reaction tank 20 or the second biological reaction tank 30. The first raw water flow path connected to the first biological reaction tank 20 from outside the system is provided with a first raw water flow path valve V4. When the first raw water flow path valve V4 is open, the screen tank 10 When the raw water treated in step 1 is introduced into the first biological reaction tank 20 through the first raw water flow path and the first raw water flow path valve V4 is closed, the flow of the raw water is blocked. ing. Further, the second raw water flow path connected to the second biological reaction tank 30 from outside the system is provided with a second raw water flow path valve V5, and when the second raw water flow path valve V5 is in an open state, the screen The raw water treated in the tank 10 is introduced into the second biological reaction tank 30 through the second raw water flow path, and when the second raw water flow path valve V5 is closed, the flow of the raw water is blocked.

  The first biological reaction tank 20 is a treatment tank that performs biological reaction treatment of water to be treated using activated sludge. The biological reaction process in the first biological reaction tank 20 is performed under the anaerobic condition, the anaerobic condition, and the aerobic condition in accordance with the operation and stop of the first air diffuser (22, 24) and the opening and closing of each valve. One of the following processes. In addition, in this specification, the term of to-be-processed water means liquids, such as waste water processed by a biological reaction process, etc., and may be used in order to designate the process target for each process. The waste water treated in each treatment tank and the waste water treated in the entire membrane separation activated sludge treatment apparatus are treated water in the treatment.

The treatment under anoxic conditions is performed in an atmosphere in which oxygen is not aerated and substantially no molecular oxygen is present, while nitrate nitrogen is supplied and there is bound oxygen as nitrate. In the treatment under oxygen-free conditions, denitrification treatment is performed in which nitrate nitrogen (NO ₃ -N) contained in the water to be treated is reduced to nitrogen gas (N ₂ ) by the action of denitrifying bacteria contained in the activated sludge. Is done.

  The treatment under anaerobic conditions is carried out in an atmosphere substantially free of molecular oxygen and binding oxygen without aeration of oxygen and supply of nitrate nitrogen. In the treatment under anaerobic conditions, polyphosphate-accumulating bacteria contained in the activated sludge are allowed to release accumulated phosphorus and to take up organic substances. By performing such treatment, it becomes possible to accumulate more phosphorus than that released to the polyphosphate-accumulating bacteria in the subsequent treatment under aerobic conditions, and efficient dephosphorization treatment is performed. ing.

Treatment under aerobic conditions is performed under oxygen aeration. In the treatment under aerobic conditions, a dephosphorization treatment is performed in which polyphosphate-accumulating bacteria contained in activated sludge ingest and accumulate phosphorus contained in water to be treated. Further, by the action of nitrifying bacteria contained in activated sludge, ammonia nitrogen contained in the treated water (NH 4 _-N), nitrification treatment to oxidize up to nitrate nitrogen (NO 3 _-N) is performed . Moreover, aerobic decomposition treatment of various organic substances is performed by activated sludge.

  The 1st biological reaction tank 20 has the 1st aeration means which performs aeration of the to-be-processed water by which a biological reaction process is carried out. Examples of the first air diffuser include an air diffuser configured by an air diffuser 22 and a blower 24 that diffuse oxygen gas or fine air bubbles. The fine bubbles are characterized in that the bubble diameter is smaller and the specific surface area is larger than the coarse bubbles produced by the second air diffuser. For this reason, in the aeration by the first aeration means (22, 24), efficient aeration for increasing the dissolved oxygen concentration is performed. As the first air diffuser, an air diffuser agitator may be installed. This is because the water to be treated can be agitated even when oxygen is not diffused by functioning as an anaerobic tank or an anaerobic tank by aeration of oxygen-free gas with a diffused stirrer.

  Further, the first biological reaction tank 20 may be provided with various measuring means such as a dissolved oxygen concentration measuring means (not shown), a nitrogen (ammonia nitrogen etc.) concentration measuring means, and an oxidation-reduction potential measuring means. Appropriate by controlling the amount of air diffused by the first air diffuser (22, 24) under the measurement of the dissolved oxygen concentration by the dissolved oxygen concentration measuring means, and maintaining the dissolved oxygen concentration of the water to be treated in the predetermined concentration range. Nitrification treatment can be performed. Further, by grasping the ammonia nitrogen concentration by the nitrogen (ammonia nitrogen etc.) concentration measuring means, it is possible to control the amount of air diffused by the first air diffuser (22, 24) according to the nitrogen load. Become.

  The first biological reaction tank 20 and the membrane separation tank 40 are communicated with each other via a first treated water pipe 110 and a joining pipe 140 connected to the first treated water pipe 110, and the first treated water pipe 110 and the joining pipe are connected. 140 forms a first treated water flow path. The first treated water flow path connects the first biological reaction tank 20 and the membrane separation tank 40 to form a flow path for allowing treated water in the first biological reaction tank 20 to flow into the membrane separation tank 40.

  The first treated water flow path is provided with a first treated water flow path valve V1, and when the first treated water flow path valve V1 is in an open state, treated water in the first biological reaction tank 20 passes through the first treated water flow path. When the first treated water passage valve V1 is closed and introduced into the membrane separation tank 40, the treated water flow is blocked.

  The first biological reaction tank 20 and the second biological reaction tank 30 are communicated with each other via a connection pipe 120, and a connection flow path is formed by the connection pipe 120. The connection channel connects the first biological reaction tank 20 and the second biological reaction tank 30, and treats treated water in the first biological reaction tank 20 to the second biological reaction tank 30 according to the opening / closing of each valve, or A flow path for allowing the treated water in the second biological reaction tank 30 to flow into the first biological reaction tank 20 is formed.

  The connection flow path is provided with a connection flow path valve V2, and when the connection flow path valve V2 is open, the treated water in the first biological reaction tank 20 flows through the connection flow path and the second biological reaction tank. 30 or when the treated water in the second biological reaction tank 30 is introduced into the first biological reaction tank 20 through the connection flow path and the connection flow path valve V2 is closed, the flow of the treated water is blocked. It has come to be.

  The 2nd biological reaction tank 30 is a processing tank which performs the biological reaction process of to-be-processed water on oxygen-free conditions using activated sludge. The biological reaction process in the second biological reaction tank 30 is an anoxic condition process performed in the presence of nitrate nitrogen returned from the membrane separation tank 40, and nitrogen removal is performed by denitrification of nitrate nitrogen. Is made.

  The 2nd biological reaction tank 30 has the stirring means 32 which stirs the to-be-processed water by which a biological reaction process is carried out. Examples of the stirring means 32 include a mechanical stirring device that rotates and stirs a stirrer and the like, and a diffused stirring device that diffuses and stirs oxygen-free gas. The agitation means 32 makes the activated sludge in the water to be treated uniform and suppresses sedimentation due to sedimentation.

  The second biological reaction tank 30 and the membrane separation tank 40 are communicated with each other via a second treated water pipe 130 and a joining pipe 140 connected to the second treated water pipe 130, and the second treated water pipe 130 and the joining pipe are connected. 140 forms a second treated water flow path. The second treated water flow path connects the second biological reaction tank 30 and the membrane separation tank 40, and forms a flow path through which treated water in the second biological reaction tank 30 flows into the membrane separation tank 40.

  The second treated water flow path is provided with a second treated water flow path valve V3. When the second treated water flow path valve V3 is in an open state, treated water in the second biological reaction tank 30 passes through the second treated water flow path. When flowing and introduced into the membrane separation tank 40 and the second treated water flow path valve V3 is closed, the flow of treated water is blocked.

  The merge pipe 140 is provided with a transfer pump 54. By operating the transfer pump 54, when the first treated water flow path valve V1 is open, the treated water in the first biological reaction tank 20 is transferred to the membrane separation tank 40, and the second treated water flow path valve V3 is opened. At this time, the treated water in the second biological reaction tank 30 is transferred to the membrane separation tank 40.

  The membrane separation tank 40 is a treatment tank that performs biological reaction treatment of water to be treated under aerobic conditions using activated sludge while solid-liquid separating the treated water and activated sludge subjected to biological reaction treatment. The biological reaction process in the membrane separation tank 40 is a process under aerobic conditions performed under aeration of oxygen, and a dephosphorization process, a nitrification process, and the like are performed.

  The membrane separation tank 40 has a membrane separator 41 for solid-liquid separation of the biological reaction treated treated water and activated sludge. The primary side separated by the separation membrane of the membrane separator 41 is immersed in the water to be treated, and the secondary side communicates with the drainage pipe 160 drawn from the membrane separator 41. The drainage pipe 160 is provided with a suction pump 56, and when this suction pump 56 is operated, the secondary side is set to a negative pressure and the treated water containing activated sludge is sucked. And while the movement of activated sludge is blocked | prevented by a separation membrane, the treated water which permeate | transmitted the separation membrane is drained by the drain piping 160. FIG.

  The membrane separator 41 is a membrane separator (membrane separation device) provided with a separation membrane such as an ultrafiltration membrane or a microfiltration membrane. For example, a plurality of flat membrane-type separation membrane elements are arranged in parallel in the horizontal direction. A flat membrane type membrane separator having a configuration in which the membrane module is laminated in the vertical direction of the number of return stages can be given. In such a flat membrane type membrane separator, the membrane surface of the separation membrane is arranged in the vertical direction, and the flow velocity of the gas-liquid two-phase flow that exerts a shear force is increased. ) Can be performed more efficiently.

  Further, the membrane separation tank 40 has a second aeration means for aeration cleaning of the membrane separator 41 and aeration of treated water subjected to biological reaction treatment. Examples of the second air diffuser include an air diffuser configured by an air diffuser 42 and a blower 44 that diffuse oxygen gas having a bubble diameter (diameter) of 100 μm or larger and air coarse bubbles. Coarse bubbles form a cross-flow gas-liquid two-phase flow with respect to the membrane surface of the separation membrane when rising due to buoyancy. By the shearing force generated by the gas-liquid two-phase flow, the water component to be treated, the metabolite by the microorganisms, the contaminated foreign matter, and the like attached and deposited on the membrane surface of the separation membrane are aerated and washed. Coarse bubbles have a specific surface area smaller than that of fine bubbles and are less efficient in supplying oxygen, but they tend to form a circulation flow of water to be treated by the air lift effect when they rise by buoyancy. Therefore, in the aeration by the second aeration means (42, 44), the mixing and stirring of the supplied oxygen gas and the water to be treated is promoted, and an aerobic atmosphere is formed.

  Further, the membrane separation tank 40 may be provided with various measuring means such as a dissolved oxygen concentration measuring means (not shown), a nitrogen (ammonia nitrogen etc.) concentration measuring means, and an oxidation-reduction potential measuring means. By installing dissolved oxygen concentration measurement means and nitrogen (ammonia nitrogen etc.) concentration measurement means, the nitrification treatment and nitrogen component concentration in the membrane separation tank 40 can be monitored independently, and an appropriate operation mode is selected. Is possible.

  The activated sludge concentration in the membrane separation tank 40 is designed to be higher than that of the first biological reaction tank 20 and the second biological reaction tank 30. That is, the activated sludge concentration in the membrane separation tank 40 is set to a higher concentration range than the second biological reaction tank 30 that functions as an anoxic tank or the first biological reaction tank 20 that functions as an aerobic tank. When the activated sludge concentration in the membrane separation tank 40 is in such a concentration range, the liquid viscosity of the activated sludge is not too low, and the region where the gas-liquid two-phase flow velocity and shearing force are high is between the membranes of the membrane separator. The cleaning effect is less likely to concentrate in the central portion where the resistance in the flow path is low.

  The membrane separation tank 40 is provided adjacent to the second biological reaction tank 30. The membrane separation tank 40 and the second biological reaction tank 30 communicate with each other above the partition plate, and an overflow weir 150 is provided between the membrane separation tank 40 and the second biological reaction tank 30. A return flow channel is formed across the partition plate. The return flow path connects the membrane separation tank 40 and the second biological reaction tank 30, forms a circulation path together with the second treated water flow path between the second biological reaction tank 30 and the membrane separation tank 40, A flow path through which treated water in the membrane separation tank 40 flows into the second biological reaction tank 30 is formed. The highest water level in the membrane separation tank 40 is designed to be higher than the highest water level in the second biological reaction tank 30, and the water to be treated is transferred to the membrane separation tank 40 by the operation of the transfer pump 54 and subjected to biological reaction treatment. After that, the overflow weir 150 is overflowed by natural flow and returned to the second biological reaction tank 30. The treated water that has been subjected to the biological reaction treatment in the membrane separation tank 40 thus flows over the overflow weir 150 and is returned to the second biological reaction tank 30, so that the nitrification dehydration can be performed except for the transfer pump 54. A pump for circulating the nitrogen treatment is omitted.

  A sludge extraction pump 58 is connected to the membrane separation tank 40 via a sludge extraction pipe 170. Part of the activated sludge concentrated by the membrane separator 41 is extracted from the membrane separation tank 40 by the sludge extraction pump 58, and excess sludge containing phosphorus, nitrogen components, etc. accumulated in the polyphosphate accumulating bacteria is discharged out of the system. It has come to be.

  The membrane separation activated sludge treatment apparatus 1 is provided with a control device (controller) (not shown). Devices such as the first treated water passage valve V1, the connection passage valve V2, the second treated water passage valve V3, and the blowers 24 and 44 are electrically connected to the control device via signal lines. The control device controls the opening / closing of the first treated water flow path valve V1, the connection flow path valve V2, and the second treated water flow path valve V3 based on the measurement of the flow rate measuring means, or the second based on the dissolved oxygen concentration measuring means. Control the amount of air diffused by the air diffuser (42, 44), control the operation and stop of the first air diffuser (22, 24), and the amount of air diffused based on the measurement by the nitrogen concentration measuring means It has a function to do. Then, an operation type selection process and a change process are executed based on the quality of the treated water and the load water amount. In addition, the first raw water passage valve V4 and the second raw water passage valve V5 are further electrically connected to the control device, and the control device opens and closes the first raw water passage valve V4 and the second raw water passage valve V5. The flow rate measuring means installed in the first raw water flow path or the second raw water flow path, the oxidation-reduction potential measuring means installed in the first biological reaction tank 20 and the membrane separation tank 40, Various measurement means such as dissolved oxygen concentration measurement means and nitrogen (ammonia nitrogen) concentration measurement means installed in the first biological reaction tank 20 can be further connected, and control can be performed based on these measurements.

  Next, the operation method of the membrane separation activated sludge treatment apparatus will be described.

  FIG. 2 is a schematic diagram showing a flow path of water to be treated for each operation method of the membrane separation activated sludge treatment apparatus according to one embodiment of the present invention.

  In the membrane separation activated sludge treatment apparatus 1 according to the present embodiment, a plurality of operation modes having different flow paths of water to be treated can be selected, and the first biological reaction tank 20 is preferably subjected to treatment under favorable conditions. The operation which functioned as either an air tank, an anaerobic tank which performs processing under anaerobic conditions, and an anaerobic tank which performs processing under anaerobic conditions is possible. Moreover, the operation | movement which bypasses the 1st biological reaction tank 20 and does not perform a biological reaction process with the 1st biological reaction tank 20 is also possible. Such an operation method (operation format) includes the operation and stop of the first air diffuser (22, 24), the first treated water flow path valve V1, the connection flow path valve V2, the second treated water flow path valve V3, This is realized by switching between opening and closing of the first raw water passage valve V4 and the second raw water passage valve V5.

  As shown in FIG. 2 (a), in the membrane separation activated sludge treatment apparatus 1, the connection flow path valve V2, the second treated water flow path valve V3, and the first raw water flow path valve V4 are opened, and the first treated water flow path is formed. By closing the valve V1 and the second raw water flow path valve V5, the first raw water flow path F01 for introducing the raw water (treated water) into the first biological reaction tank 20 and the treated water in the first biological reaction tank 20 are supplied. The connection flow path F30 for flowing into the second biological reaction tank 30, the second treated water flow path F20 for flowing the treated water in the second biological reaction tank 30 into the membrane separation tank 40, and the treated water in the membrane separation tank 40 for the second biological reaction. A return flow path F40 to be returned to the tank 30 can be formed. Then, the second treated water flow path F20 and the return flow path F40 form a circulation path, and a part of the treated water is separated into solid and liquid, and then flows through the drainage flow path F50 to be drained outside the system.

  In this operation format, the biological reaction treatment of the water to be treated is performed in the order of the first biological reaction tank 20, the second biological reaction tank 30, and the membrane separation tank 40. At this time, the first biological reaction tank 20 functions as an anaerobic tank, the second biological reaction tank 30 functions as an anaerobic tank, and the membrane separation tank 40 functions as an aerobic tank, thereby accumulating in polyphosphate accumulating bacteria. The phosphorus that has been removed can be released prior to the biological reaction treatment under the favorable conditions, and the efficiency of the dephosphorization treatment can be improved.

  2B, in the membrane separation activated sludge treatment apparatus 1, the second treated water flow path valve V3 and the second raw water flow path valve V5 are opened to connect the first treated water flow path valve V1. Treatment in the second raw water flow path F02 and the second biological reaction tank 30 for introducing raw water (treated water) into the second biological reaction tank 30 by closing the flow path valve V2 and the first raw water flow path valve V4. A second treated water flow path F20 that allows water to flow into the membrane separation tank 40 and a return flow path F40 that returns treated water in the membrane separation tank 40 to the second biological reaction tank 30 can be formed. Then, the second treated water flow path F20 and the return flow path F40 form a circulation path, and a part of the treated water is separated into solid and liquid and then flows through the drainage flow path F50 to be drained outside the system.

  In this operation format, the biological reaction treatment of the water to be treated is performed in the order of the second biological reaction tank 30 and the membrane separation tank 40. At this time, the second biological reaction tank 30 functions as an oxygen-free tank, and the membrane separation tank 40 Functions as an aerobic tank, and the first biological reaction tank 20 is bypassed, so that the biological reaction treatment under favorable conditions can be performed only by the membrane separation tank 40. Therefore, it becomes a processing tank configuration corresponding to processing with a low load of water and nitrogen components, its operating power is reduced, adjustment of residence time and processing tank capacity, repair in the first biological reaction tank 20, sludge recovery, etc. Is possible.

  In addition, as shown in FIG. 2 (c), in the membrane separation activated sludge treatment apparatus 1, the first treated water flow path valve V1, the connection flow path valve V2, and the second raw water flow path valve V5 are opened to perform the second treatment. Treatment in the second raw water flow path F02 and the second biological reaction tank 30 for introducing the raw water (treated water) into the second biological reaction tank 30 by closing the water flow path valve V3 and the first raw water flow path valve V4. A connection flow path F30 for flowing water into the first biological reaction tank 20, a first treated water flow path F10 for flowing treated water in the first biological reaction tank 20 into the membrane separation tank 40, and a second treated water in the membrane separation tank 40. A return flow path F40 to be returned to the biological reaction tank 30 can be formed. The connection flow path F30, the first treated water flow path F10, and the return flow path F40 form a circulation path, and a portion of the treated water is separated into solid and liquid and then flows through the drainage flow path F50 to the outside of the system. Drained.

  In this operation format, the biological reaction treatment of the water to be treated is performed in the order of the second biological reaction tank 30, the first biological reaction tank 20, and the membrane separation tank 40. At this time, the second biological reaction tank 30 functions as an oxygen-free tank, the first biological reaction tank 20 functions as an oxygen-free tank, and the membrane separation tank 40 functions as an aerobic tank. A tank division type operation mode suitable for high-load processing is realized. Since nitrate nitrogen returned through the return flow path F40 is denitrified in the second biological reaction tank 30 and the first biological reaction tank 20, ensuring of the denitrification treatment residence time and improvement of treated water quality are achieved. Can be achieved.

  In addition, as shown in FIG. 2 (d), the first biological reaction tank 20 is caused to function as an aerobic tank by operating the first air diffuser (22, 24) and aeration of the water to be treated. Can do. In FIG. 2D, the first treated water passage valve V1, the connection passage valve V2 and the second raw water passage valve V5 are opened, and the second treated water passage valve V3 and the first raw water passage valve V4 are closed. By making the valve, the biological reaction treatment of the water to be treated is performed in the order of the second biological reaction tank 30, the first biological reaction tank 20, and the membrane separation tank 40, and the second biological reaction tank 30 functions as an oxygen-free tank, The first biological reaction tank 20 and the membrane separation tank 40 function as an aerobic tank. Since ammonia nitrogen contained in the water to be treated is nitrified in the first biological reaction tank 20 and the membrane separation tank 40, it is possible to secure a nitrification residence time and improve a nitrification rate.

  FIG. 3 is a flowchart showing an example of operation type selection processing in the membrane separation activated sludge treatment apparatus according to one embodiment of the present invention.

  The process of selecting the operation type in the membrane separation activated sludge treatment apparatus 1 is performed by the control device at the start of operation or when the operation is continued. In the following process flow, the control device that has started the operation type selection process in accordance with the operator's instruction controls the opening / closing of each valve and the switching of the operation and stop of the first air diffuser (22, 42). An example is shown. At the start of operation of the membrane separation activated sludge treatment apparatus 1, each valve is fully closed and the first air diffuser (22, 42) is stopped.

When the process of selecting the operation format is started, the control device acquires a measured value of the raw water phosphorus concentration (C _P ) (step S100). The phosphorus concentration (C _P ) is the concentration of organic phosphorus and inorganic phosphorus (total phosphorus (TP) concentration) contained in the raw water, and is measured in advance when drawing the raw water into the membrane separation activated sludge treatment apparatus 1. And stored in a storage device included in the control device.

In step S110, the control device determines whether or not the phosphorus concentration (C _P ) of the raw water is lower than the limit phosphorus concentration (C _PLV ) in the treated water. The critical phosphorus concentration (C _PLV ) means a target phosphorus concentration to be achieved by the dephosphorization treatment in the membrane separation activated sludge treatment apparatus 1. For example, a water quality reference value (for example, 1 mg) of the phosphorus concentration imposed on the treated water An arbitrary density equal to or less than a value such as / L) is set.

In Step S110, when it is determined that the phosphorus concentration (C _P ) of the raw water is lower than the limit phosphorus concentration (C _PLV ) in the treated water (Step S110: YES), the process proceeds to Step S120.

  In step S120, the control device outputs a control signal to each valve, opens the connection flow path valve V2 and the second treated water flow path valve V3, and closes the first treated water flow path valve V1. Further, the first raw water passage valve V4 is opened, and the second raw water passage valve V5 is closed. Then, when the switching control of opening and closing of each valve is performed, the operation type selection process ends.

  In such a process, as shown in FIG. 2A, a connection flow path F30 and a second treated water flow path F20 are formed, and water to be treated is caused to flow into the first biological reaction tank 20 from outside the system. The first raw water flow path F01 is formed, and a tank division type operation mode suitable for phosphorus removal is realized.

On the other hand, if it is determined in step S110 that the phosphorus concentration (C _P ) of the raw water is equal to or higher than the limit phosphorus concentration (C _PLV ) in the treated water (step S110: NO), the process proceeds to step S130. Transition.

  In step S130, the control device acquires a measured value of the load water amount (L). The load water amount (L) is an inflow amount of the raw water drawn into the membrane separation activated sludge treatment apparatus 1, and is measured by a flow rate measuring unit installed in a stage prior to the first biological reaction tank 20 and the second biological reaction tank. The measurement signal is transmitted to the control device.

  In step S140, the control device determines whether or not the measured load water amount (L) is less than the planned water amount (Q). The planned amount of water (Q) is the maximum amount of water per hour designed according to the usage of the membrane separation activated sludge treatment device 1, the type of raw water, etc., for example, a storage device that the control device has based on excessive nitrogen load, etc. A predetermined value is stored in advance.

  In step S140, when it is determined that the measured load water amount (L) is lower than the planned water amount (Q) (step S140: YES), the process proceeds to step S150.

  In step S150, the control device outputs a control signal to each valve, opens the second treated water passage valve V3, and closes the first treated water passage valve V1 and the connection passage valve V2. Further, the second raw water passage valve V5 is opened, and the first raw water passage valve V4 is closed. Then, when the switching control of opening and closing of each valve is performed, the operation type selection process ends.

  In such a process, as shown in FIG. 2 (b), a second treated water flow path F20 is formed, and a second raw water flow path F02 that allows treated water to flow into the second biological reaction tank 30 from outside the system. And a tank-integrated operation mode suitable for processing with a low load of water and nitrogen components is realized.

  On the other hand, if it is determined in step S140 that the measured load water amount (L) is equal to or greater than the planned water amount (Q) (step S140: NO), the process proceeds to step S160.

  In step S160, the control device outputs a control signal to each valve, opens the first treated water passage valve V1 and the connection passage valve V2, and closes the second treated water passage valve V3. Further, the second raw water passage valve V5 is opened, and the first raw water passage valve V4 is closed. Then, when the switching control of opening and closing of each valve is performed, the operation type selection process ends.

  In such a process, as shown in FIG. 2C, a connection flow path F30 and a first treated water flow path F10 are formed, and water to be treated is caused to flow into the second biological reaction tank 30 from outside the system. The second raw water flow path F02 is formed, and a tank division type operation mode suitable for processing with a high load of water and nitrogen components is realized.

  FIG. 4 is a flowchart showing an example of operation type change processing in the membrane separation activated sludge treatment apparatus according to the embodiment of the present invention.

  In the membrane separation activated sludge treatment apparatus 1 according to the present embodiment, when the operation mode for performing the biological reaction treatment in the first biological reaction tank 20 is selected, the first aeration means (22, 24) is further activated and stopped. The operation type is changed by switching the mode. That is, in the tank division type operation mode in which the biological reaction treatment is performed in both the first biological reaction tank 20 and the second biological reaction tank 30, an operation mode in which the first biological reaction tank 20 functions as an aerobic tank, It is possible to perform a biological reaction process by switching the operation mode in which one biological reaction tank 20 functions as an anaerobic tank or an anaerobic tank. In the membrane separation activated sludge treatment apparatus 1, the control apparatus repeatedly executes the operation type change process while performing the biological reaction process.

When the process of changing the operation format is started, the control device acquires a measured value of the nitrogen concentration (C _N ) of the water to be treated (Step S200). The nitrogen concentration (C _N ) is, for example, the ammonia nitrogen concentration of the water to be treated in the first biological reaction tank 20, and the nitrogen (ammonia nitrogen etc.) concentration of the water to be treated introduced into the first biological reaction tank 20. It is measured in advance by the measuring means.

In step S210, the control device determines whether the nitrogen concentration (C _N ) of the water to be treated is higher than the limit nitrogen concentration (C _NLV ) in the nitrification treatment. The critical nitrogen concentration (C _NLV ) in nitrification means the target nitrogen concentration (ammonia nitrogen concentration, etc.) after nitrification to be achieved in the membrane separation tank 40. For example, under a predetermined circulation ratio or water temperature. Ammonia nitrogen or the like contained in the raw water is nitrified in the membrane separation tank 40 and then returned to the second biological reaction tank 30 and denitrified in the second biological reaction tank 30 to remove nitrogen. It is set in advance based on the processing limit expected to be possible.

  It is appropriate to adjust the amount of air diffused by the second air diffuser (42, 44) of the membrane separation tank 40 in accordance with the detergency of the membrane separator 41 from the viewpoint of suppressing the driving power related to air diffusion. It is. For this reason, in the case of aeration only with the second aeration means (42, 44), the dissolved acid concentration may not be maintained, and the nitrification treatment may be incomplete. Therefore, in this step S210, whether or not the nitrogen component such as ammonia nitrogen contained in the water to be treated introduced into the first biological reaction tank 20 requires further nitrification treatment, a preliminary operation or the like in advance. Judgment is made by comparison with the treatment limit concentration of the nitrification treatment required in (1).

In step S210, when it is determined that the nitrogen concentration (C _N ) of the water to be treated is higher than the limit nitrogen concentration (C _NLV ) of nitrification treatment (step S210: YES), the process proceeds to step S220. To do.

  In step S220, the control device operates the first air diffuser (22, 24). That is, the control device starts the blower 24 of the first air diffuser in a stopped state, and starts aeration of the water to be treated with a predetermined amount of air diffused. Then, the process of changing the operation format ends.

  In such treatment, the operation format of the membrane separation activated sludge treatment apparatus 1 is changed so that the first biological reaction tank 20 functions as an aerobic tank. That is, in the tank division type operation format selected in step S120 (see FIG. 2A), the first biological reaction tank 20 that functions as an aerobic tank, the second biological reaction tank 30 that functions as an oxygen-free tank, An operation mode that sequentially passes through the membrane separation tank 40 functioning as an aerobic tank is realized. In this operation mode, prior to the biological reaction treatment under the oxygen-free condition in the second biological reaction tank 30, a high load organic matter can be aerobically decomposed or nitrified.

  Moreover, in the tank-divided operation type selected in step S160 (see FIG. 2C), the second biological reaction tank 30 that functions as an anoxic tank, the first biological reaction tank 20 that functions as an aerobic tank, An operation mode that sequentially passes through the membrane separation tank 40 functioning as an aerobic tank is realized (see FIG. 2D). In this operation mode, it is possible to change the residence time and treatment tank volume ratio between nitrification treatment and denitrification treatment, and it is easy to improve the quality of treated water according to the nitrogen load while keeping the equipment scale small. Can be aimed at.

On the other hand, when it is determined in step S210 that the nitrogen concentration (C _N ) of the water to be treated is equal to or lower than the limit nitrogen concentration (C _NLV ) of the nitrification treatment (step S210: NO), the processing ends. To do.

  In such treatment, the operation mode of the membrane separation activated sludge treatment apparatus 1 is maintained so that the first biological reaction tank 20 functions as an anoxic tank or an anaerobic tank. That is, in the operation mode in which raw water (treated water) is introduced into the second biological reaction tank 30 through the second raw water flow path F02, the first biological reaction tank 20 can function as an anoxic tank. In this operation mode, nitrate nitrogen is introduced into the first biological reaction tank 20 depending on the processing capacity of the denitrification process in the second biological reaction tank 30, so that the nitrogen load and the treatment in the second biological reaction tank 30 are performed. It is possible to perform an operation with an improved nitrogen removal rate depending on the conditions.

  In the operation mode in which raw water (treated water) is introduced into the first biological reaction tank 20 through the first raw water flow path F01, the first biological reaction tank 20 functions as an anaerobic tank. In this operation mode, the first biological reaction tank 20 performs a process of releasing phosphorus accumulated in the polyphosphate accumulating bacteria. Therefore, it becomes possible to perform the operation corresponding to the load fluctuation of phosphorus in the raw water.

  In the above operation type selection process, each process may be performed artificially. That is, by manually measuring the phosphorus concentration and the load water amount and determining using the measured value, the control device may control the opening and closing of each valve, and each valve may be manually opened and closed.

  Moreover, after performing the process of step S150 and step S160, by returning to the process of step S130, according to the load water amount (L) measured during the operation | movement of the membrane separation activated sludge processing apparatus 1, tank integrated type The operation mode (see FIG. 2B) and the tank division type operation format (see FIGS. 2C and 2D) may be repeatedly switched.

DESCRIPTION OF SYMBOLS 1 Membrane-separated activated sludge treatment apparatus 5 Water draw pump 10 Screen tank 12 Screen 20 1st biological reaction tank 22 Aeration pipe (1st aeration means)
24 Blower (first air diffuser)
30 Second biological reaction tank 32 Stirring means 40 Membrane separation tank 41 Membrane separator 42 Aeration tube (second aeration means)
44 Blower (second air diffuser)
54 Transfer Pump 56 Suction Pump 58 Sludge Extraction Pump 110 First Process Water Pipe 120 Connection Pipe 130 Second Process Water Pipe 140 Merge Pipe 150 Overflow Weir 160 Drain Pipe 170 Sludge Extraction Pipe V1 First Process Water Channel Valve V2 Connection Channel Valve V3 Second treated water passage valve V4 First raw water passage valve V5 Second raw water passage valve

Claims (9)

A first biological reaction tank having a first aeration means for performing aeration of the water to be treated, and performing a biological reaction treatment of the water to be treated using activated sludge;
A second biological reaction tank having a stirring means for stirring the water to be treated, and performing a biological reaction treatment of the water to be treated under oxygen-free conditions using activated sludge;
A membrane separator, which is provided adjacent to the second biological reaction tank and separates the treated water and activated sludge which have been subjected to biological reaction treatment in at least one of the first biological reaction tank and the second biological reaction tank; A membrane separation tank for performing a biological reaction treatment of the treated water under aerobic conditions using activated sludge, having a second air diffuser for aeration and washing of the membrane separator and aeration of the treated water;
A first treated water flow path for connecting the first biological reaction tank and the membrane separation tank, and allowing treated water in the first biological reaction tank to flow into the membrane separation tank;
A connection flow path for connecting the second biological reaction tank and the first biological reaction tank, and allowing treated water in one of the first biological reaction tank and the second biological reaction tank to flow into the other biological reaction tank. When,
A second treated water flow path for connecting the second biological reaction tank and the membrane separation tank, and allowing treated water in the second biological reaction tank to flow into the membrane separation tank;
In the membrane separation tank, the membrane separation tank and the second biological reaction tank are connected, and a circulation path is formed between the second biological reaction tank and the membrane separation tank together with the second treated water flow path. A return flow path for returning treated water to the second biological reaction tank;
A membrane separation activated sludge treatment apparatus characterized by comprising: The return flow path is formed by an overflow weir provided between the membrane separation tank and the second biological reaction tank,
2. The membrane separation activated sludge treatment apparatus according to claim 1, wherein the treated water subjected to the biological reaction treatment in the membrane separation tank is returned to the second biological reaction tank through the overflow weir. . The second air diffuser diffuses coarse bubbles having a bubble diameter of 100 μm or more into the water to be treated.
3. The membrane separation activated sludge treatment apparatus according to claim 1, wherein the first air diffuser diffuses fine bubbles having a smaller bubble diameter than the coarse bubbles into the water to be treated. further,
A first treated water channel valve for opening and closing the first treated water channel;
A connection flow path valve for opening and closing the connection flow path;
The membrane-separated activated sludge treatment apparatus according to any one of claims 1 to 3, further comprising a second treated water channel valve that opens and closes the second treated water channel. The operation method of the membrane separation activated sludge treatment apparatus according to claim 4,
Opening the second treated water flow path valve, closing the first treated water flow path valve and the connection flow path valve, and allowing treated water to flow into the second biological reaction tank from outside the system, A method for operating a membrane separation activated sludge treatment apparatus, wherein the biological reaction treatment of the treated water is performed in the order of the second biological reaction tank and the membrane separation tank. The operation method of the membrane separation activated sludge treatment apparatus according to claim 4,
Opening the connection flow path valve and the second treated water flow path valve, and closing the first treated water flow path valve, and allowing treated water to flow into the first biological reaction tank from outside the system, A method for operating a membrane separation activated sludge treatment apparatus, wherein the biological reaction treatment of the treated water is performed in the order of the first biological reaction tank, the second biological reaction tank, and the membrane separation tank. The operation method of the membrane separation activated sludge treatment apparatus according to claim 4,
Opening the first treated water flow path valve and the connection flow path valve, and closing the second treated water flow path valve, and flowing treated water from outside the system into the second biological reaction tank, A method for operating a membrane separation activated sludge treatment apparatus, wherein biological treatment treatment of the treated water is performed in the order of the second biological reaction tank, the first biological reaction tank, and the membrane separation tank. In the operation method of the membrane separation activated sludge treatment apparatus according to claim 6,
An operation mode in which the first aeration means is operated to cause the first biological reaction tank to function as an aerobic tank, and an operation in which the first aeration means is stopped to cause the first biological reaction tank to function as an anaerobic tank. A method for operating a membrane-separated activated sludge treatment apparatus, characterized in that a biological reaction treatment is performed by switching between formats. In the operation method of the membrane separation activated sludge treatment apparatus according to claim 7,
An operation mode in which the first aeration means is operated to cause the first biological reaction tank to function as an aerobic tank, and the first aeration means is stopped to cause the first biological reaction tank to function as an anaerobic tank. A method for operating a membrane-separated activated sludge treatment apparatus, wherein a biological reaction process is performed by switching between operation modes.

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