JP5743096B2 - Membrane separation activated sludge equipment - Google Patents

Description

  The present invention relates to a membrane separation activated sludge apparatus used for treatment of sewage and factory waste water.

  Various activated sludge apparatuses are known, and among them, an apparatus comprising a membrane immersion tank equipped with an aeration tank and a permeation type membrane separation apparatus is known (Patent Document 1). As shown in FIG. 8, this apparatus includes an aeration tank 20 and a membrane separation tank 30. The aeration tank 20 has an air diffuser composed of an air diffuser 21 and a blower 22. A membrane separation device 40 is installed in the membrane separation tank 30, and an air diffuser 41 for ejecting a membrane surface cleaning gas is disposed below the membrane separation device 40. The raw water to be treated is introduced into the aeration tank 20 from the raw water supply system 50, treated with activated sludge bacteria, and enters the membrane separation tank 30 together with the activated sludge. Therefore, the membrane is separated and the treated water is taken out through the membrane. Part of the sludge remaining without passing through the membrane is returned to the aeration tank through the circulation system 60, and part is taken out of the system as excess sludge from the excess sludge discharge system 70.

JP 2002-192182 A (page 3, FIG. 1)

  The cleaning of the membrane is usually performed by aeration from directly below the membrane, so that the power consumption is high.

  An object of the present invention is to provide a membrane separation activated sludge apparatus capable of efficiently cleaning a membrane and reducing power consumption.

  The present invention has been made to solve the above-mentioned problems, and by forming a water flow using mechanical force and applying it to the membrane surface, the membrane surface can be efficiently cleaned, and such an object is achieved. Is achieved.

  That is, the present invention includes an aerobic tank provided with an air diffuser for supplying oxygen to activated sludge, an osmotic membrane separator, and a water flow forming device for forming a water flow toward the membrane surface of the membrane separator. And a membrane separation activated sludge apparatus having a membrane separation tank.

  In the above apparatus, the present inventors preferably have a water flow rate in the membrane module of 0.5 to 1.0 m / s, and in order to generate this flow rate with low power, a turning mechanism is attached as mechanical force. It has also been found that the use of a propeller-type underwater stirrer or water pump is effective. Further, it has been found that a sufficient membrane cleaning effect can be obtained by simply using a membrane separator as a plurality of membrane units and supplying a water flow for a short time to each of them.

  Therefore, the present invention provides a device in which the water flow forming device is a propeller type underwater agitator with a swivel mechanism, the water flow forming device is a water flow pump, and the water flow rate formed by these water flow forming devices is within the membrane module. The apparatus which is 0.5-1.0 m / s is also provided.

  The present invention also provides the above apparatus using a water flow pump, wherein the osmotic membrane separation device comprises a plurality of membrane units, and the membrane units are directed to the membrane surface of the membrane unit at the lower part or the upper part thereof. An automatic on-off valve for each membrane unit is provided in the water supply pipe from the water flow pump to the water flow discharge port, and the water supply is made possible by sequentially switching one or more water flow discharge ports. A device is also provided.

  According to the present invention, the power consumption can be greatly reduced and the activated sludge treatment cost can be reduced.

It is side surface sectional drawing which shows schematic structure of an example of the apparatus of this invention. It is side surface sectional drawing which shows schematic structure of another example of the apparatus of this invention. It is side surface sectional drawing which shows schematic structure of another example of the apparatus of this invention. It is side surface sectional drawing which shows schematic structure of another example of the apparatus of this invention. It is the figure which showed the apparatus of FIG. 4 in the plane. It is a figure which shows the structure of the apparatus which measured the flow rate which can wash | clean a membrane surface. It is a graph which shows a time-dependent change of the transmembrane differential pressure measured with the apparatus of FIG. It is side surface sectional drawing which shows schematic structure of the conventional apparatus.

  The aerobic tank in the apparatus of the present invention is a tank that accommodates and works activated sludge, and is also called an aeration tank. The shape may take various forms such as a cylindrical shape, but is usually a box shape.

  The air diffuser jets bubbles to supply oxygen to activated sludge. The structure may be basically the same as that of a normal air diffuser, and a large number of air jets are provided in a manifold having a shape such as a box or a tube. The air outlet may be a fine hole, and a nozzle may be attached. The diameter of the air outlet is determined so as to form fine bubbles in order to increase the oxygen dissolution efficiency, and the diameter of the bubbles should be about 0.5 to 4 mm, particularly about 0.5 to 1.0 mm. . If the bubble diameter is too large, sufficient oxygen dissolution efficiency cannot be obtained, and if it is too small, the pressure loss of the air diffuser is high and it is difficult to perform stable operation. A bubble diameter of 0.5 to 1.0 mm is preferable because an oxygen dissolution efficiency of 30 to 40% can be obtained.

  The membrane separation tank is a place where an osmotic membrane separation device is provided to separate water treated with activated sludge. Regarding the pore diameter of the membrane, a microfiltration membrane or an ultrafiltration membrane can be applied. As the shape of the membrane, a flat membrane type, a hollow fiber type, a tubular type or the like can be used, and a membrane having an appropriate area is installed based on the permeation flux of the membrane and the amount of treated water. The arrangement of the membranes is usually parallel to each other so as not to disturb the water flow.

  The membrane separation tank is further provided with a water flow forming device that forms a water flow toward the membrane surface of the membrane separation device. This water flow forming device forms a water flow by mechanical force, and there is a method of installing a stirrer and a submersible pump. It is preferable because the water flow can be applied evenly. Although the cleaning effect can be obtained by setting the flow rate of the film surface portion to 0.5 m / s or more, it is preferably 0.5 to 1.0 m / s.

  FIG. 6 shows the configuration of an apparatus for examining the flow rate at which the membrane surface can be cleaned. This device consists of a membrane separation device in which one hollow fiber is installed in a transparent PVC cylinder in the cylinder length direction and an activated sludge tank, and a tube for sending liquid from the bottom of the activated sludge tank to the lower part of the transparent PVC cylinder A tube for returning the liquid to the upper surface of the activated sludge layer is connected from the upper part of the transparent PVC cylinder, and a circulation line for the liquid in the activated sludge tank is formed. A circulation pump, a pressure gauge, a flow meter, and a flow rate adjusting valve are provided in the middle of the circulation line. The lower part of the hollow system penetrates the lower end of the transparent PVC cylinder, and a suction pump and a pressure gauge are attached to the lower part. A beaker for receiving the liquid filtered with the hollow fiber is disposed under the lower end of the hollow system. FIG. 7 shows the results of examining the time-dependent change in transmembrane pressure difference by changing the flow rate to 0.25 m / s, 0.4 m / s, and 0.55 m / s using this apparatus. As shown in the figure, when the flow rate is 0.25 m / s and 0.4 m / s, the transmembrane pressure difference increases with time, resulting in clogging. However, when the flow rate is 0.55 m / s, the transmembrane difference It shows that the pressure is almost constant and washing is performed sufficiently. As a result, it was found that if the flow velocity flowing on the membrane surface was 0.5 m / s or more, there was a sufficient cleaning effect.

The angle at which the water flow is applied to the membrane surface is preferably as shallow as possible, and about 0 to 45 degrees is appropriate. When a swirl flow is generated in the entire tank in the membrane arranged perpendicular to the membrane separation tank, a water flow parallel to the membrane surface can be efficiently generated.

  As a water flow forming device, a water flow pump is also effective for the device of the present invention. The water flow pump efficiently cleans the membrane surface by applying the water flow to the membrane surface, and the water flow outlet may be directed vertically upward from the bottom of the membrane to form a water flow parallel to the membrane surface. Alternatively, a water flow parallel to the membrane surface may be formed vertically downward from the top of the membrane. If the water flow is discharged from below or above all the membranes, there is no part where the water flow is weak, and the entire membrane can be washed with water efficiently. The position of the water pump does not matter inside or outside the tank.

  In addition, a timer can be connected to the pump so that the operation of the water pump can be controlled. For example, the suction of treated water from the membrane can be stopped at regular intervals, and the water flow can be efficiently washed by operating the water flow pump during the stop period. The time schedule can be determined as appropriate. For example, the suction of the treated water is performed for 5 to 60 minutes, the suction is stopped for 30 seconds to 5 minutes, and the water flow pump is operated during that time to perform water flow cleaning.

  In the apparatus of the present invention, a plurality of membrane units can be provided with one membrane separator as one unit. An air diffuser and an upward water flow outlet are provided at the lower part of each membrane unit, and an automatic on-off valve for each membrane unit is provided in the water supply pipe from the water flow pump to the water flow outlet. It is possible to supply water by sequentially switching every time. This is because the present inventor found that it is not necessary to flow the water flow for the entire cleaning time, and sufficient film surface cleaning can be achieved even if intermittent supply of water flow is performed for a short time. Is. Since appropriate operating conditions differ for each membrane separation device, it is preferable to obtain this through experiments. Appropriate operating conditions can be set by investigating changes over time in the differential pressure on the membrane surface, and are determined in consideration of operating costs such as power costs. In general, it is not preferable to stop the water flow for a long time. The stop time of the water flow is about 30 seconds to 5 minutes, and an appropriate water flow supply time for each membrane unit should be determined.

  The water flow is sequentially supplied to each membrane unit in the single water flow supply time determined in this way, and the time for completing the water flow supply for all the membrane units is defined as one cycle, and the water flow cleaning is performed for about 1 to 5 cycles during the suction pump stop time. To implement.

  By this method, it is possible to perform cleaning of a plurality of membrane units with one pump, and it is possible to further reduce power.

  In addition, the aerobic tank is appropriately provided with a dissolved oxygen concentration meter, a pH meter, a thermometer, and the like.

  A schematic configuration of a membrane separation activated sludge apparatus according to an embodiment of the present invention is shown in FIG.

  Both the aerobic tank 1 and the membrane separation tank 5 of this apparatus are box-shaped.

  A diffuser 2 is installed at the bottom of the aerobic tank 1. The air diffuser 2 has a flat plate or straight pipe shape, and its surface is made of rubber, a metal plate, a ceramic sintered body, or the like, and has a large number of pores for releasing bubbles. The bubbles released from the pores have a diameter of about 1.5 mm immediately above the diffuser surface. Each straight pipe is connected by a connecting pipe and connected to the blower 3 outside the tank. Raw water treated with activated sludge in the aerobic tank 1 is introduced into the aerobic tank 1 from the raw water pump 4 installed outside the tank. A pipe for sending treated water is connected to the upper part of the membrane separation tank 5.

  In the membrane separation tank 5, an osmotic membrane separation device 6 and a water flow forming device 7 are installed.

  The membrane separation device 6 is a device in which a large number of hollow fiber type membranes are arranged vertically. The upper and lower ends are connected to a water collecting part, and a filtrate can be obtained by a suction pump 9. In many cases, the pore diameter of the membrane is in the range of about 0.01 to 1 μm, and particularly in the range of 0.02 to 0.5 μm, a clear treated water quality is obtained and an economical permeate flux is obtained. Often used in

As the water flow forming device 7, a propeller type underwater stirrer with a turning mechanism is used. This stirrer is a stirrer provided with a mechanism in which the propeller turns left and right in accordance with the rotation of the shaft that transmits the power of the drive device installed above the membrane separation tank to the propeller installed at the bottom of the tank. The water flow formed by the agitator forms a swirl flow in the membrane separation tank 5 and is attached to the lower part of the side surface of the membrane separation tank 5 opposite to the membrane separation device 6 so as to be an upward flow in the membrane installation section. ing. Reference numeral 8 denotes a current plate. Further, the membrane separation tank 5 is provided with a line for returning sludge therein to the aerobic tank 1 and a drawing line for surplus sludge. With this equipment configuration, the upward flow velocity on the membrane surface could be 0.5 m / s at the maximum.

  FIG. 2 shows a schematic configuration of a membrane separation activated sludge apparatus which is another embodiment of the present invention.

  This apparatus is the same as that of Example 1 except that a water flow pump is used for the water flow forming device 7. However, there is a case where the current plate 8 is not provided. The purpose of installing the rectifying plate 8 is the same, and is to create a swirling flow to create an upward flow with respect to the membrane surface or to increase the flow velocity of the upward flow.

  The water flow pump 10 is attached outside the membrane separation tank 5, and a drawing pipe is connected to the upper part of the membrane separation tank 5. On the other hand, a pipe for blowing a water flow is provided directly below the membrane separation device 6. This pipe is branched into multiple pipes in the middle, and a large number of nozzles 71 are arranged uniformly so that the entire membrane can be washed with water vertically upwardly.

  The schematic structure of the membrane separation activated sludge apparatus which is another embodiment of this invention is shown in FIG.

  This apparatus is the same as Example 2 except that the water flow sent to the membrane surface is a downward flow.

  A schematic configuration of a membrane separation activated sludge apparatus according to another embodiment of the present invention is shown in a side sectional view in FIG. 4 and in a plan view in FIG.

  In this apparatus, eight membrane units 61 are arranged, and a water flow forming device 7 having an upward water discharge outlet 71 is provided at the lower part of each. Each of the water flow forming devices 7 is connected to the water flow cleaning pump 10 via the automatic opening / closing valve 12. Each automatic open / close valve 12 is automatically controlled to open and close by a computer (not shown). The raw water to be treated is fed into the aerobic tank 1 by the raw water pump 4 and treated with activated sludge, and the treated water is transferred to the membrane separation tank 5 and sucked by the suction pump 9, each of which is a membrane unit 6. 61 is passed out of the system. Each membrane unit 61 opens and closes the automatic opening / closing valve 12 according to a command from the computer to supply and stop the cleaning water flow. As for the opening / closing of the automatic opening / closing valve 12, only one of the automatic opening / closing valves 12 is open during membrane cleaning, and the water flow is supplied by a single pump. A timer 11 is connected to the suction pump 9, whereby the suction of the treated water is stopped at regular intervals, and the water flow pump can be operated during the stop period to efficiently perform the water flow cleaning.

  Tables 1 and 2 show the results of measuring the change in transmembrane pressure difference for the MF membrane and the UF membrane using the apparatus shown in FIG. 6 while changing the cleaning water flow rate, the cleaning water flow supply time, and the stop time.

表１の結果から、１分運転−７分停止では膜間差圧が上昇し、２分運転−６分停止の条件から徐々に膜表面にケーキが堆積して洗浄が不十分になっていたことが分かる。０．８ｍ^３／分で１０秒運転−５０秒停止が最も好ましかった。

From the results in Table 1, the transmembrane pressure difference increased at 1 minute operation-7 minutes stop, and the cake gradually deposited on the film surface from the condition of 2 minute operation-6 minutes stop, resulting in insufficient cleaning. I understand that. A 10 second run at 0.8 m ³ / min-50 second stop was most preferred.

From this experience, Table 2 shows the results of examining the change in transmembrane pressure with the water flow rate set to 0.8 m ³ / min, the operation time set to 10 to 30 seconds, and the stop time set to 105 to 160 seconds.

この結果、１５秒運転−１０５秒停止で膜面を洗浄でき、これにより、１台のポンプで８基の膜ユニットの洗浄を担当させることができることが分かった。

As a result, it was found that the membrane surface could be cleaned by running for 15 seconds-stopping for 105 seconds, thereby allowing the single membrane pump to be responsible for cleaning the eight membrane units.

  According to the present invention, since the electric power used for the activated sludge treatment can be greatly reduced, it can be widely used in membrane separation activated sludge treatment equipment.

DESCRIPTION OF SYMBOLS 1 Aerobic tank 2 Aeration apparatus 3 Blower 4 Raw water pump 5 Membrane separation tank 6 Membrane separation apparatus 61 Membrane unit 7 Water flow formation apparatus 71 Water flow outlet 8 Current plate 9 Suction pump 10 Flow water pump 11 Timer 12 Automatic opening / closing valve 20 Aeration tank 21 Aeration pipe 22 Blower 30 Membrane separation tank 40 Membrane separation device 41 Aeration pipe 42 Blower 50 Raw water supply system 60 Circulation system 70 Excess sludge discharge system

Claims (3)

An aerobic tank equipped with an air diffuser for supplying oxygen to activated sludge, and a membrane separation tank equipped with a osmotic membrane separator and a water flow forming device for forming a water flow toward the membrane surface of the membrane separator. A membrane separation activated sludge apparatus , wherein the water flow forming device is attached to a lower part of the side surface of the tank opposite to the osmotic membrane separation apparatus with a rectifying plate dividing the membrane separation tank into two regions. A membrane-separated activated sludge apparatus characterized by being a propeller-type underwater agitator with a mechanism . An aerobic tank equipped with an air diffuser for supplying oxygen to activated sludge, and a membrane separation tank equipped with a osmotic membrane separator and a water flow forming device for forming a water flow toward the membrane surface of the membrane separator. A membrane separation activated sludge device, wherein the osmotic membrane separation device comprises a plurality of membrane units, and the water flow forming device is disposed on a membrane surface of the membrane unit disposed at the lower or upper portion of each of the membrane units. a water discharge port toward, it is a water pump sends the water, and automatic opening and closing valves for each membrane unit is formed from the water pump to the water supply pipe to the water discharge port, one or more water-discharge membrane bioreactor device you characterized by sequentially switched every outlet and is capable of water supply. The membrane separation activated sludge device according to claim 1 or 2 , wherein a flow rate of water formed by the water flow forming device is 0.5 to 1.0 m / s in the membrane module.

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