JP2018187539A - Membrane separation active sludge treatment device, and membrane separation active sludge treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane separation active sludge treatment device and method, enhancing nitrogen removal efficiency further, exhibiting high applicability even to load change of inflow sewage amount, and further capable of largely shortening processing time (HRT) in a reaction tank, and capable of being adopted even in middle or large scale sewage disposal plant or the like.SOLUTION: There are provided a partition plate insertion type membrane separation active sludge treatment device having a single reaction tank 1 for conducting an aerobic treatment and an oxygen-free treatment, an impregnation membrane separation unit 2a arranged inside of the reaction tank 1, and aeration means 4a, in which the reaction tank 1 is divided into a plurality of sections by a partition plate 7, at least one section of the plurality of sections is set as an aerobic section in which the impregnation membrane separation unit and the aeration means, and the oxygen-free treatment is conducted in other sections, a circulation water amount adjustment device is arranged, and a first dissolved oxygen meter 10a is arranged in the aerobic section and a second dissolved oxygen meter 10b is arranged in other sections, and a membrane separation active sludge treatment method using the device.SELECTED DRAWING: Figure 3

Description

  TECHNICAL FIELD The present invention relates to a membrane separation activated sludge treatment apparatus and method that can efficiently perform nitrogen removal together with membrane separation and have high applicability to load fluctuations in inflow sewage.

  Conventionally, when treating sewage wastewater containing nutrient salts such as nitrogen and phosphorus, an activated sludge method is used in which sewage is introduced into a reaction tank and aerated and agitated together with activated sludge for biological treatment. Especially in recent years, in order to obtain clear treated water that does not contain solid matter from the treated water treated by this activated sludge method, membrane separation is performed by immersing the membrane separation device in the reaction tank and separating the treated water into a membrane. The activated sludge method (Membrane Bioreactor (MBR) method) is frequently used.

  In such a submerged membrane separator, it is necessary to blow air from the lower air diffuser in order to prevent fouling (membrane clogging) from occurring on the membrane surface. Has a continuous aeration. In the activated sludge method, nitrification proceeds by the action of nitrifying bacteria under such an aerobic condition. On the other hand, in order to perform denitrification treatment with denitrifying bacteria, it is necessary to make the inside of the tank oxygen-free. . Therefore, in the membrane separation activated sludge method, it is necessary to ensure both membrane surface cleaning during membrane filtration and aeration for nitrification and oxygen-free conditions for denitrification treatment. As a technology to be realized, a membrane separation activated sludge apparatus and method for aerobic treatment (nitrification treatment) and oxygen-free treatment (denitrification treatment) in a single reaction tank have been proposed (Patent Document 1).

  As shown in FIG. 1 of the present application, the apparatus proposed in Patent Document 1 includes a single reaction tank 1 that performs aerobic treatment and oxygen-free treatment, and a submerged membrane separation unit disposed inside the reaction tank. 2 and the aeration means 4, the reaction tank 1 is divided into a plurality of compartments by a partition plate 7 provided with a bottom portion spaced apart from the bottom surface of the reaction tank. At least one of the compartments is an aerobic compartment in which the submerged membrane separation unit 2 and the aeration means 4 are arranged, and the remaining compartment is changed from an aerobic state to an anaerobic state, and from an anaerobic state to an aerobic state. Partition plate insertion that is provided with a liquid level control means or a partition plate height control means for switching between a state in which the liquid level in the reaction tank is higher and lower than the upper end of the partition plate. Type membrane separation activated sludge treatment equipment (Baffled Membrane Bioreactor (B-MBR method)).

  In the method of Patent Document 1, the raw water pump 8 is turned on when the liquid level in the reaction tank 1 becomes a low water level (LWL: Low Water Level), and the raw water pump 8 when the liquid level becomes a high water level (HWL: High Water Level). By changing the liquid level so as to be OFF, a state where the liquid level is higher than that of the partition plate and a state where the liquid level is lower than that of the partition plate are alternately created (FIG. 1). Here, in a state where the liquid level is higher than that of the partition plate, the circulation flow that extends over the entire tank by the air from the diffuser pipe 4 (from the membrane unit storage section, enters the other section over the partition plate 7, and enters the other section. A circulating flow that descends in the compartment and returns to the membrane unit accommodation compartment through a region below the partition plate 7 is formed (FIG. 2). By forming such a circulating flow, sludge containing a large amount of nitrate nitrogen obtained by nitrification in the membrane separation unit accommodating section is transferred to other sections, and aerobic treatment (nitrification treatment) is performed inside and outside the partition plate 7. Proceeds (this time zone is called “nitrification promotion operation time zone”). On the other hand, when the liquid level is lower than that of the partition plate, the flow of the liquid is divided between the membrane separation unit accommodating section and the other sections, and as a result, the other sections become oxygen-free and oxygen-free treatment (denitrification). Treatment) (this time zone is referred to as “denitrification promotion operation time zone”) Thus, the method of patent document 1 is a method of repeating a nitrification promotion operation time zone and a denitrification promotion operation time zone by alternately creating a state where the liquid level is higher and lower than that of the partition plate.

  Patent Document 2 discloses an oxidation ditch method (hereinafter referred to as an aerobic water area and an anoxic water area) in which a circulating water flow generating means and an oxygen supply means (aeration device) are installed in a ditch (endless water channel). In the “OD method”), dissolved oxygen meters (DO meters) are installed on the upstream and downstream sides of the aerobic water area, and the oxygen supply by the oxygen supply means is adjusted based on the measured values of the upstream dissolved oxygen meter. And the apparatus and method of adjusting the flow rate of the circulating water by a circulating water flow generation means based on the measured value of a downstream dissolved oxygen meter are disclosed.

JP 2004-261711 A JP 2005-52804 A

  However, in the method described in Patent Document 1, it has been desired to further improve the nitrogen removal efficiency. Further, in the method of Patent Document 1, the nitrification promotion operation time zone and the denitrification promotion operation time zone are switched by alternately creating a state in which the liquid level is higher and lower than that of the partition plate. It took a long time to switch.

  In sewage treatment, daily fluctuations in inflow sewage volume (inflow wastewater volume and pollutant concentration fluctuations) are large. Generally, large-scale treatment equipment has fluctuations of about 0.5 to 1.5 times the daily average value. In small-scale processing apparatuses, there is a fluctuation of about 0.2 to 3 times. With respect to such daily load fluctuations, it has been difficult to perform efficient nitrification and denitrification by the method of Patent Document 1. Moreover, in order to reduce the daily fluctuation of the inflow sewage amount, it was necessary to provide a large capacity flow rate adjustment tank.

  Furthermore, the OD method disclosed in Patent Document 2 is a gravity-type sedimentation separation method in which solid-liquid separation is performed in a final sedimentation basin. In order to facilitate solid-liquid separation, the MLSS (Mixed Liquor Suspended Solid) concentration is 2000 to 2000. It is managed in a low range of about 4000 mg / L. Therefore, in the OD method, the processing time (HRT) in the ditch is as long as about 12 hours, and about 6 hours are required even in the final sedimentation basin. The OD method has been adopted for small-scale sewage treatment plants because it requires a large facility capacity and requires a large installation space. There was a problem that it was difficult to adopt in factory wastewater treatment.

  In view of the above-described conventional problems, the present invention further improves the nitrogen removal efficiency, shows high applicability to daily load fluctuations of the inflow sewage amount, and further reduces the processing time (HRT) in the reaction tank. An object of the present invention is to provide a membrane separation activated sludge apparatus and method which can be greatly shortened and can be used in medium- and large-scale sewage treatment plants and industrial wastewater treatment.

  The inventors of the present application have intensively studied the cause of the insufficient nitrogen removal efficiency in the conventional partition plate insertion type membrane separation activated sludge treatment method. As a result, in a state where the liquid level is lower than the partition plate (denitrification promotion operation time zone), the circulation of the liquid is divided inside and outside the partition plate, and no circulation flow is generated in the section where the membrane separation unit is not arranged. The raw water, nitrification liquid (liquid containing nitrate nitrogen after nitrification) and denitrifying bacteria that are involved in the denitrification reaction are not sufficiently mixed, and as a result, the efficient denitrification reaction is difficult to proceed. I found.

  Then, a circulating water amount adjusting device is provided in the reaction tank, and a membrane separation activated sludge treatment device in which a first dissolved oxygen meter is provided in the membrane separation unit accommodation section and a second dissolved oxygen meter is provided in the other compartment is used. Thus, in the other compartments, the above-mentioned sufficient mixing necessary for the denitrification reaction can be achieved, and the dissolved oxygen (DO) that interferes with the denitrification can be maintained at a low level. It was thought that the removal efficiency was improved. In addition, by using such a membrane separation activated sludge treatment device, it can be adapted to fluctuations in the load of the inflow sewage, and the treatment time (HRT) in the reaction tank is greatly reduced compared to the OD method. The present invention was completed by conceiving that it would be a compact activated sludge treatment apparatus.

That is, the present invention relates to the following (1) to (6).
(1) A membrane separation activated sludge treatment apparatus having a single reaction tank for performing an aerobic treatment and an oxygen-free treatment, a submerged membrane separation unit disposed in the reaction tank, and an aeration means. The tank is divided into a plurality of compartments by a partition plate provided with a bottom portion separated from the bottom surface of the reaction tank, and at least one of the plurality of compartments is arranged with a submerged membrane separation unit and an aeration means. In the membrane separation activated sludge treatment apparatus that performs oxygen-free treatment in the other aerobic compartments, a circulating water amount adjusting device is provided, a first dissolved oxygen meter is provided in the aerobic compartment, and the other A membrane separation activated sludge treatment apparatus, characterized in that a second dissolved oxygen meter is provided in the compartment.

(2) The membrane according to (1), wherein an auxiliary aeration means is further provided in the aerobic compartment, and the circulating water amount adjusting device is a circulating water amount adjusting device capable of adjusting an opening degree in an upper part of the partition plate. Separation activated sludge treatment equipment.
(3) Means for controlling the amount of aeration by the auxiliary aeration means so that the dissolved oxygen concentration measured by the first dissolved oxygen meter becomes a preset target value, and the dissolved oxygen concentration measured by the second dissolved oxygen meter are The membrane separation activated sludge treatment apparatus according to (2), provided with means for controlling the opening degree of the circulating water amount adjusting device so as to have a preset target value.
(4) The membrane separation activated sludge treatment apparatus according to any one of (1) to (3), further comprising an ammonia meter and / or a nitric acid meter for controlling.

(5) (1) to (4) provided with means for controlling by the target values of the first dissolved oxygen meter and the second dissolved oxygen meter set in advance according to the load state of the raw water supplied to the reaction tank The membrane separation activated sludge treatment apparatus according to any one of the above.
(6) A membrane separation activated sludge treatment method for performing an aerobic treatment and an oxygen-free treatment in a single reaction tank in which an immersion membrane separation unit is arranged, wherein the bottom of the periphery of the immersion membrane separation unit is from the bottom of the reaction vessel By partitioning with a partition plate provided at a distance and performing aeration from below the immersion membrane separation unit, the inside of the partition where the immersion membrane separation unit is placed is maintained in an aerobic state, while there is no air in other compartments. In the membrane separation activated sludge treatment method for performing oxygen treatment, the dissolved oxygen concentration in the aerobic compartment and the dissolved oxygen concentration in the other compartments are measured, and the measured values of the dissolved oxygen concentrations become preset target values. A membrane separation activated sludge treatment method characterized by controlling the amount of aeration and the flow rate of circulating water.

  In the present specification, the “anoxic state” does not mean only a complete anoxic state but also a state where the oxygen concentration is low enough to reduce nitrate nitrogen to nitrogen molecules by the action of denitrifying bacteria. Used in the meaning of inclusion.

  According to the present invention, since the denitrification reaction can be efficiently advanced in the section where the membrane separation unit is not arranged, the efficiency of removing nitrogen from the organic wastewater can be improved. Further, it can be applied to load fluctuations of the inflow sewage amount, and efficient nitrification and denitrification reactions can be performed. Furthermore, the processing time (HRT) in the reaction vessel can be greatly shortened, and a compact and efficient membrane separation activated sludge treatment can be performed.

It is a figure which shows typically the membrane separation activated sludge processing apparatus of the conventional method (patent document 1). It is a figure which shows typically the flow of the circulating water in a partition plate insertion type membrane separation activated sludge processing apparatus. It is a figure which shows typically one embodiment of the membrane separation activated sludge processing apparatus of this invention. It is the side view and top view which show typically the one aspect | mode of the circulating water amount adjusting device of this invention. It is a figure which shows typically another aspect of the circulating water amount adjusting device of this invention. It is a figure which shows typically another aspect of the circulating water amount adjusting device of this invention. It is a figure which shows typically another one embodiment of the membrane separation activated sludge processing apparatus of this invention.

Hereinafter, embodiments of a membrane separation activated sludge treatment apparatus and method according to the present invention will be described based on the drawings. 1 to 7, members having the same function are denoted by the same reference numerals.
The feature of the present invention is that, as will be described later, in the membrane separation activated sludge treatment apparatus of the partition plate insertion type, the circulating water amount adjusting device and the first and second dissolved oxygen meters are provided. The overall configuration of one embodiment of the apparatus and method will be described with reference to FIG.

In the membrane separation activated sludge apparatus of FIG. 3, an immersion type membrane separation unit 2 a is provided in a single tank type reaction tank 1, and a suction pump 3 is provided outside the reaction tank 1 in this membrane separation unit 2 a. It is connected.
As the membrane separation unit 2a, it is preferable to use a material using a material that does not easily become dirty as the membrane itself, or a device having an appropriate gap between the membranes so that the surface of the membrane is less likely to get dirty. As the membrane separation unit 2a, a module formed using a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane or the like can be used. From the economical point of view, a module using a microfiltration membrane or an ultrafiltration membrane that has a high filtration rate and can be made compact and is easy to maintain is preferable. The membrane may be a flat membrane, a hollow fiber membrane or the like. The submerged membrane separation unit itself used here is widely used in this field and is also commercially available.

  A membrane cleaning aeration means 4a (aeration device) is provided below the membrane separation unit 2a, and an auxiliary aeration means 4b (aeration device) is provided below the membrane separation unit 2a. Yes. The aeration means 4a and 4b are connected to the blowers 5a and 5b, respectively, and air (air) is supplied from the blowers 5a and 5b.

The aeration means 4a for membrane cleaning generates coarse bubbles to enhance the scrubbing effect on the membrane surface of the membrane separation unit 2a. In order to reduce power consumption, a device that generates coarse bubbles intermittently can be incorporated. The bubbles generated by the membrane cleaning aeration means 4a are coarse bubbles, so that the rising speed is large and the effect of increasing the circulation flow rate is large, but the oxygen transfer efficiency is small.
The auxiliary aeration means 4b is installed for the purpose of supplementing the amount of oxygen that is insufficient with the oxygen supply by the film cleaning aeration means 4a. As the auxiliary aeration means 4b, a membrane-type air diffuser that normally generates fine bubbles is used, and the oxygen transfer efficiency is generally 2 to 5 times higher than that of the membrane cleaning aeration means.

  The reaction tank 1 contains sludge containing microorganisms, and these microorganisms act as organic matter-degrading bacteria and further as microorganisms-degrading bacteria for biological treatment. Therefore, it is preferable that the reaction tank 1 has no corners or irregularities on the inner surface so that sludge is not partially unevenly distributed and oxygen is supplied uniformly. As a result, the temperature and pH of the treatment liquid become uniform in the reaction tank 1, and the decomposition treatment can proceed stably. Microorganisms contained in sludge contribute to the degradation of soluble organic matter such as bacteria, yeasts and fungi including fungi, and are obtained from nature, such as soil, compost, and sludge, by accumulating culture and acclimatization. The It is also possible to isolate and use the main microbial group involved in the degradation from this conditioned solution. In addition, the sludge itself containing these microorganisms is well known in this field.

  The activated sludge treatment conditions in the reaction tank 1 may be known conditions that are usually used in the membrane separation activated sludge method, but the MLSS concentration is usually 3000 to 20000 mg / L, preferably 5000 to 15000 mg / L. A higher MLSS concentration can be maintained compared to the OD method. Moreover, HRT (hydraulic residence time) in the reaction tank 1 is usually 2 to 24 hours, preferably 4 to 8 hours, and it is possible to achieve a shortened HRT compared to the OD method.

  In the reaction tank 1 of FIG. 3, a partition plate 7 is further provided. The partition plate 7 is provided with a bottom portion spaced apart from the bottom surface of the reaction tank, and surrounds the lateral periphery of the membrane separation unit 2a (upper and lower sides), but substantially surrounds the periphery of the membrane separation unit 2a. As long as it surrounds. The partition plate 7 may be combined with the tank wall and surround the periphery of the membrane separation unit 2a, and preferably has two flat plates that cooperate with the tank wall of the reaction tank 1 to define a rectangular region. As shown in FIG. 3, among the four surfaces around the membrane separation unit 2a, one surface is surrounded by the partition plate 7 and the other three surfaces are surrounded by the tank wall, or the partition plate 7 is the membrane separation unit. It may be one that surrounds the entire circumference of 2. The capacity ratio between the storage compartment of the membrane separation unit 2a and other compartments is usually 1: 0.5 to 5, and can be preferably set within the range of 1: 1 to 3.

  In the specific example of FIG. 3, there is only one submerged membrane separation unit accommodation section (hereinafter also referred to as “membrane separation unit accommodation section”). In order to increase the processing amount, a plurality of membrane separation unit accommodating sections (aerobic sections) may be provided if desired, and the membrane separation units may be immersed in each of these sections. In this case, it is possible to provide a plurality of compartments other than the membrane separation unit accommodation compartment (hereinafter also referred to as “other compartments”). However, since one is simpler and the reaction liquid is more uniform. preferable.

  The sewage that has flowed into the sewage treatment facility such as a sewage treatment plant is introduced into the reaction tank 1 from the raw water tank by the raw water pump 8 as raw water after separating and removing sand and garbage in the pretreatment equipment. In this invention, it is preferable to supply raw | natural water to divisions other than a membrane separation unit accommodation division. As a result, a hydrogen donor necessary for the denitrification reaction is supplied, and the denitrification reaction proceeds efficiently during the denitrification promotion time zone.

  The membrane separation activated sludge treatment apparatus of the present invention may have a liquid level control means for adjusting the liquid level in the reaction tank 1. As the liquid level control means, for example, a level sensor for checking the liquid level in the reaction tank, that is, the position of the liquid surface is provided, and the raw water supplied to the reaction tank by the raw water pump according to the liquid level detected by the level sensor. Means for controlling the flow rate of the gas.

  With such a configuration shown in FIG. 3, sewage is biologically treated in the reaction tank 1, and the air from the aeration means 4 a prevents sludge substances and the like from adhering to the membrane surface of the membrane separation unit 2 a. However, the treatment liquid in the reaction tank 1 can be filtered by the membrane separation unit 2a, and the filtered water can be sucked by the suction pump 3 and taken out of the tank. In the specific example of FIG. 3, the filtration pressure is obtained by the suction pump 3, but the filtration pressure may be obtained only by the difference between the water level in the reaction tank and the water level of the filtrate water outlet, that is, only by the natural water head, Further, the filtration pressure may be obtained by pressurization from the stock solution side.

  The feature of the present invention resides in that in such a partition plate insertion type membrane separation activated sludge treatment apparatus, a circulating water amount adjusting device and first and second dissolved oxygen meters are provided.

  The circulating water amount adjusting device in the present invention is not particularly limited as long as it is a device or a device that generates a water flow in the reaction vessel, but the circulating flow amount formed in the reaction vessel by the air from the aeration means (aeration device). An apparatus capable of controlling the flow rate is preferred. Here, as shown in FIG. 3, when the inside and outside of the partition plate is in an overflow state, the “circulation flow” is entered from the membrane separation unit housing section to the other section over the partition plate 7, This is a liquid flow that descends within the compartment and returns to the membrane unit accommodation compartment via a region below the partition plate 7. The circulating water amount adjusting device is preferably provided on the upper or upper end of the partition plate, and is preferably a means for adjusting the flow rate of the circulating flow moving from the membrane separation unit accommodating section to the other section.

Below, the circulating water amount adjusting device in this invention is demonstrated, referring FIGS. In FIG. 4, the dissolved oxygen meter and the auxiliary aeration means are omitted in order to facilitate understanding of the circulating water amount adjusting device.
A first aspect of the circulating water amount adjusting device according to the present invention is a swing type circulating water amount adjusting device including a circulating water amount adjusting plate and an adjusting plate moving means for swinging (swinging) the circulating water amount adjusting plate. Specifically, as shown in FIG. 4, a circulating water amount adjusting plate (hereinafter also referred to as “swing plate”) 20a, a fixing member 21a for fixing one side in the longitudinal direction of the swing plate, and the swing plate 20a are provided. This is a swing type circulating water amount adjusting device provided with adjusting plate moving means 22 for swinging. 4 is a top view of the membrane separation activated sludge treatment apparatus of the present invention when the swing plates 20a and 20b completely cover the upper part of the partition plate and block the circulation flow (the side surface of FIG. 4). In the figure, the right circulating water amount adjusting device is omitted, and the adjusting plate moving means 22 is omitted in the top view).

  The swing plate 20a shown in FIG. 4 has one side of the two sides in the longitudinal direction fixed to a rod-like fixing member 21a. The swing plate 20a is detachably connected to the adjustment plate moving means 22, and the adjustment plate moving means 22 moves the swing plate 20a up and down to swing, thereby opening the opening above the partition plate. Can be adjusted.

  Here, the opening degree of the swing plate is set to 0% when the swing plate completely covers the upper part of the partition plate and almost completely interrupts the circulation flow in the side view of FIG. When the swing plate is moved upward and the lower end of the swing plate is higher than the liquid level in the reaction tank (when fully open), the opening is 100%, and the swing plate is moved around the fixed member. It is set between 0 and 100% depending on the angle.

  The swing plate can have any shape such as a rectangular shape, a trapezoidal shape, a flat plate shape, etc., as long as it can adjust the amount of water in the circulating flow from the membrane separation unit accommodating compartment to the other compartment beyond the partition plate 7. It may be a thing. The swing plate 20a shown in FIG. 4 is a rectangular adjustment plate that is curved in the short direction, and when installed so as to be curved (convex) in the direction of the adjustment plate moving means 22 (upward), Is preferable because adjustment along the flow of the circulating flow is possible.

  The length of the swing plate in the longitudinal direction can be approximately the same as the upper end of the partition plate so as to cover the entire upper portion of the partition plate, but a part of the upper end of the partition plate, for example, 1/5 of the length of the upper end of the partition plate It may be a length covering ½. Moreover, even when a plurality of partition plates are installed in the reaction vessel, the swing plate does not need to be installed so as to cover the upper part of all the partition plates, and a part of the upper end length of all the partition plates. For example, you may install in 1/5-1/2 of the upper end length of the whole partition plate. The length of the swing plate in the short direction is such that when the swing plate is moved in the direction of the partition plate (downward) by the adjusting plate moving means 22, the swing plate completely covers the upper part of the partition plate and the circulation flow is almost completely completed. The length is preferably such that it can be blocked. The thickness of the swing plate may be any thickness that can withstand the control of the circulation flow.

  The fixing member 21a is not particularly limited as long as it fixes the swing plate so that it can swing. As the fixing member 21a, for example, one side in the longitudinal direction of the swing plate 20a is fixed to the side surface of the rod-shaped fixing member, and both ends of the rod-shaped member are connected to the tank wall of the reaction tank so as to be rotatable using bearings. It can be configured. Alternatively, a member in which a hollow tube and a rod-like member penetrating through the hollow tube are used, and one side in the longitudinal direction of the swing plate 20a is fixed to the side surface of the hollow tube, and the hollow tube It can be set as the structure by which the both ends of the rod-shaped member which penetrates the inside of a pipe | tube are fixed to the tank wall of a reaction tank. With this configuration, the swing plate 20a can be swung up and down by the adjustment plate moving means 22 while the one side in the longitudinal direction of the swing plate 20a is fixed to the fixing member, and the upper portion of the partition plate can be opened and closed. it can.

  The position where both ends of the fixing member 21a are fixed to the tank wall of the reaction tank is more efficient than the maximum liquid level in the reaction tank from the viewpoint of efficiently adjusting the amount of circulating water and reducing the corrosion of the fixing member 21 by the processing liquid. Is also preferred to be higher. Moreover, it is preferable to fix the both ends of the fixing member 21 in the position shifted in the said other division direction rather than just above the partition plate 7 from a viewpoint of adjusting the amount of circulating water efficiently.

  The adjusting plate moving means 22 is not particularly limited as long as it can move the swing plate up and down, but a known driving device such as an electric cylinder, a pneumatic or a hydraulic cylinder can be used.

  In addition to the circulating water amount adjusting means shown in FIG. 4, various mechanisms and shapes can be used. For example, as shown in FIG. 5, a rectangular swing plate 20c bent in the short direction can also be used. It is preferable to install such a swing plate so as to be bent (convex) in the direction of the adjustment plate moving means 22 (upward) because adjustment along the flow of the circulation flow is possible at the upper part of the partition plate. . The circulating water amount adjusting means shown in FIG. 5 has the same configuration as the circulating water amount adjusting means shown in FIG. 4 except that the swing plate is bent in the short direction, and can achieve the same function. it can.

  In addition to the swing type configuration shown in FIGS. 4 and 5, the swing plate (circulating water amount adjusting plate) is fixed to the upper end of the partition plate via a hinge member or the like, and the swing plate can be attached to and detached from the adjusting plate moving means. In this way, the circulating water amount adjusting means having an overturning dam structure that opens and closes the upper part of the partition plate by turning over the swing plate by the adjusting plate moving means can also be used.

  Also, instead of the swing plate, a member that can be expanded or expanded by introducing air into the interior, such as a balloon or a hollow sheet, is installed at the upper end or upper part of the partition plate, and the circulation flow is blocked A damping-type circulating water amount adjusting means for adjusting the circulating water amount can also be used.

  A second aspect of the circulating water amount adjusting device according to the present invention is a circulating water amount adjusting device including a slide plate 30 having an opening 31 as shown in FIG. The slide plate 30 is installed in the vicinity of the upper end of the partition plate 7 that also has the opening portion 32. When the slide plate 30 is slid in the horizontal direction, the opening portion 31 of the slide plate 30 and the opening portion 32 of the partition plate overlap. By adjusting the condition, the opening degree (opening ratio) of the partition plate can be adjusted.

  Here, the opening degree of the slide plate (opening ratio) is the opening degree 0% when the opening of the partition plate and the opening of the slide plate do not overlap in FIG. 6 and the circulation flow is almost completely blocked, The opening is 100% when the openings are completely overlapped with each other, and is defined as the ratio of the total area of the openings to the total opening area when the openings are fully opened.

  The shapes of the opening portions of the slide plate and the partition plate can be appropriately selected from a rectangular shape, a circular shape, an elliptical shape, and the like. Further, the total area of all the openings in the area of the entire slide plate is preferably about 1/3 to 2/3. The shape of the entire slide plate is not particularly limited, but normally, a rectangular plate that can easily slide in the horizontal direction can be used. By using the plurality of slide plate fixing members 33, the slide plate 30 can be fixed near the upper end of the partition plate so as to be slidable in the horizontal direction. The slide plate can be moved in the horizontal direction by using a slide plate moving means 34. As the slide plate moving means 34, for example, a known drive device such as an electric cylinder, a pneumatic or a hydraulic cylinder is used. be able to.

  In the case of using a circulating water amount adjusting device equipped with such a slide plate, the liquid level operation water level in the reaction tank is lower than the upper ends of the openings of the slide plate and the partition plate, as shown in FIG. The operating water level is preferably higher than about one third from the bottom of the opening of the partition plate. If the liquid level is maintained in such an operating water level range, an efficient denitrification reaction can be advanced by adjusting the opening degree (opening ratio) of the partition plate using the slide plate 30.

The membrane-separated activated sludge treatment apparatus of the present invention is provided with first and second dissolved oxygen meters (DO meters) for measuring the dissolved oxygen concentration in the circulating water together with the circulating water amount adjusting device described above. .
The first dissolved oxygen meter (DO1) is provided in the membrane separation unit accommodation section. However, in order to perform efficient control, the first dissolved oxygen meter (DO1) is near the center of the membrane separation unit accommodation section and higher than the upper end of the membrane separation unit. Even if the liquid level in the reaction tank is the lowest water level, it is preferable that the DO1 be installed at a position where the DO1 is immersed in the liquid. In addition, the second dissolved oxygen meter (DO2) is provided in a section (other section) other than the membrane separation unit accommodation section, but in order to perform efficient control, it is half of the liquid level depth in the reaction tank. It is better to install at a certain position.

  In the present invention, by controlling by combining the above circulating water amount adjusting device and the first and second dissolved oxygen meters (DO meters), the nitrogen removal efficiency is high and can be applied to load fluctuations of the inflow sewage amount. Processing can be performed. Specifically, the amount of air blown by the auxiliary aeration means (blower) is controlled so that the dissolved oxygen concentration measured by the first dissolved oxygen meter (DO1) becomes a preset target value of DO1, and the second dissolved oxygen The opening degree of the circulating water amount adjusting device is controlled so that the dissolved oxygen concentration measured by the meter (DO2) becomes a preset target value of DO2.

  The preset target value of DO1 is about 0.5 to 2.0 mg / L, and the preset target value of DO2 is about 0.1 to 0.5 mg / L. Although the target values of DO1 and DO2 can be fixed for 24 hours, as shown in Table 1 below, finer control is possible by changing according to the time zone in accordance with the load situation as shown in Table 1 below. In Table 1 below, the load status is classified as high load, medium load, and low load in descending order of the amount of influent wastewater and the concentration of pollutants.

Below, based on FIG. 3, the specific control method in this invention is demonstrated.
The raw water pump 8 for supplying the raw water to the reaction tank 1 can be controlled within a frequency range of 20 to 50 Hz for the inverter. In principle, the flow rate is the same as or slightly higher than the suction flow rate of the filtration pump, and is constant at 50 Hz or the like. Operate at flow rate. When the water level in the reaction tank reaches the highest water level (H), the raw water pump is stopped, and when the water level drops to the lowest water level (L), the level control is performed so that the operation of the raw water pump is started. Further, when the water level in the raw water tank becomes lower than the minimum water level (L) level, an interlock operation is performed to prevent idling.

  The filtration pump 3 can be controlled within a frequency range of the inverter of 20 to 50 Hz. In principle, operation is performed at a constant flow rate of 50 Hz or the like. In order to prevent fouling of the membrane surface of the submerged membrane separation unit, a cycle of stopping for 1 minute after repeating suction for 9 minutes is repeated. Or you may make it change the amount of filtrate water according to the fluctuation | variation of the inflow raw | natural water amount. When the liquid level in the reaction tank drops to the upper end of the submerged membrane separation unit (LL level), the filtration pump 3 is interlocked to prevent idling.

The membrane cleaning blower (B1) can be controlled within a frequency range of 20 to 50 Hz for the inverter, and the aeration amount SADm per membrane area is in the range of 0.1 to 0.15. Operation (SADm (Specific-Air-Demand per membrane surface area) means a necessary amount of aeration and is usually expressed in units of Nm ³ / m ² / h).

In addition, when changing the amount of filtrate water according to the fluctuation | variation of inflow raw | natural water amount, according to a membrane flux, the ventilation volume of the film | membrane washing blower (B1) is adjusted in the range of 0.05-0.2 as SADm. It is also effective. Here, the membrane flux represents the amount of membrane filtrate (m ³ / m ² / d) per unit membrane area / unit time.
Table 2 below shows an example of the target value of the membrane flux set in accordance with the daily load time zone, and the SADm of the membrane cleaning blower (B1) that can be adjusted according to the value of this membrane flux.

  The auxiliary aeration blower (B2) can be controlled within a frequency range of 20 to 50 Hz of the inverter, and automatically controls the blast volume (PID control) so that the dissolved oxygen concentration value measured by DO1 becomes a target value. Thus, the aeration amount of the auxiliary aeration means is adjusted. Specifically, when the measured value of DO1 is smaller than the target value, control is performed so as to increase the amount of air blown from the auxiliary aeration blower (B2), and when the measured value of DO1 is larger than the target value, auxiliary Control is performed to reduce the amount of air blown from the aeration blower (B2). Even when the frequency of the inverter is the lower limit value of the controllable range, if DO1 is equal to or higher than the target value, the auxiliary aeration blower (B2) is stopped for a certain time (for example, 30 minutes).

  The auxiliary aeration blower (B2) is used to supply an oxygen amount (auxiliary oxygen amount) obtained by subtracting the oxygen amount supplied by the membrane cleaning blower (B1) from the required oxygen amount. As described above, the auxiliary aeration means has an oxygen transfer efficiency 2 to 5 times higher than that of the membrane cleaning aeration means. Therefore, after reducing the air volume of the membrane cleaning blower as much as possible (for example, as described above SADm is set in accordance with the load time zone), and efficient control of the auxiliary aeration blower can contribute to power consumption reduction. It is also effective to use a blower (for example, a screw type blower) having a wide range that can be efficiently controlled.

  The circulating water amount adjusting device automatically controls the opening degree (PID control) within a range of 10 to 100% so that the dissolved oxygen concentration measured by DO2 becomes a target value. That is, when DO2 is larger than the target value, it means that the amount of oxygen consumed in the time from DO1 to DO2 is small, so the opening degree of the circulating water amount adjusting device is set to slow down the circulation flow rate. Control to make it smaller. On the contrary, since oxygen consumption is large when DO2 is smaller than the target value, control is performed to increase the degree of opening of the circulating water amount adjusting device in order to increase the circulation flow rate. Even when the opening degree of the circulating water amount adjusting device is 10%, which is the control lower limit value, when the measured value of DO2 is larger than the target value, the circulating water amount adjusting device is fully closed for a certain period of time (such as 30 minutes).

  FIG. 7 shows another embodiment of the membrane separation activated sludge treatment apparatus of the present invention. In the present embodiment, a plurality of membrane separation units 2b are provided near the partition plate 7 so that the circulation flow rate can be kept high, and an aeration means (aeration device) 4c for membrane cleaning is installed below the membrane separation unit 2b. did. The auxiliary aeration means (aeration device) 4d was arranged at the center below the membrane separation unit accommodation section, and DO1 was arranged above it. Moreover, DO2 was installed in divisions other than a membrane separation unit accommodation division.

  In the embodiment shown in FIG. 7, a stirrer 15 is installed to complement the circulating water amount adjusting device. If sufficient control is possible with a swing-type circulating water amount adjusting device, the energy saving effect is great. However, if a sufficient water flow cannot be obtained, it is effective to install a stirrer. As the stirring blade of the stirrer, various types such as a propeller type, a screw type, and a paddle type can be used.

  Even with such an apparatus shown in FIG. 7, the above-described control, that is, the amount of aeration by the auxiliary aeration means and the circulating water amount adjustment apparatus so that the dissolved oxygen concentration measured by DO1 and DO2 becomes a preset target value. By controlling the opening degree, it is possible to perform efficient nitrogen removal adapted to the load fluctuation of the inflow sewage amount.

  3 and 7, the aerobic zone is a zone above the aeration means in the membrane separation unit accommodating section and the other section, and the anoxic zone is DO2 in the other section. The lower zone and the lower zone than the aeration means in the membrane separation unit accommodating section. The capacity ratio of the aerobic zone and the anaerobic zone can be designed to be 1: 1 to 1: 2. In general, the nitrification rate becomes a bottleneck when the load of BOD or nitrogen is large, and the denitrification rate becomes a bottleneck when the load is small. Accordingly, the ratio of the aerobic zone to the anaerobic zone is preferably about 1: 1 when the load is large, and about 1: 2 when the load is low. It is preferable to adjust the installation position of DO2 up and down so that the zone ratio is appropriate according to the load situation, or to change the target value of DO2 according to the load as shown in Table 1 above.

  As described above, by controlling the circulating water amount adjusting device and the first and second dissolved oxygen meters (DO meters) in combination, the liquid is passed over and outside the partition plate as in the conventional method (Patent Document 1). Since it is not necessary to greatly change the liquid level in order to create a flow state and a divided state, raw water can be continuously supplied to the reaction tank at a constant flow rate. For this reason, it is not necessary to install a special raw water supply device or raw water flow rate control device. In the present invention, the “constant flow rate” is not limited as long as the flow rate is constant at a predetermined time, and may be changed to obtain an optimum flow rate.

  In the present invention, an ammonia meter and / or a nitric acid meter can be provided and controlled instead of the DO meter or for the purpose of complementing the DO meter. That is, the control is performed so that the nitrification zone is enlarged when ammonia is large, and the denitrification zone is enlarged when nitric acid is large.

  Since the membrane separation activated sludge treatment method using the apparatus of the present invention can maintain a higher MLSS concentration than the OD method, A-SRT (Aerobic Solid Retention Time) required for nitrification is ensured. Even under a low BOD-MLSS load condition, the oxygen consumption rate due to the endogenous respiration of microorganisms is increased, so that it is easy to control the aerobic zone and the anaerobic zone.

  The present invention is limited to the above embodiment as long as it is a membrane separation activated sludge treatment apparatus provided with a circulating water amount control device and first and second dissolved oxygen meters, and a membrane separation activated sludge treatment method using this device. However, the treatment conditions other than the above and the pretreatment of the raw water can be performed under the same conditions as conventionally known methods.

  The present invention further improves the nitrogen removal efficiency, shows high applicability to daily load fluctuations of the inflow sewage amount, and further significantly shortens the processing time (HRT) in the reaction tank. It is possible to provide a membrane separation activated sludge apparatus and method that can be employed in a sewage treatment plant and a factory wastewater treatment.

DESCRIPTION OF SYMBOLS 1 Reaction tank 2, 2a, 2b Membrane separation unit 3 Suction pump 4, 4a, 4c Aeration means for membrane cleaning 4b, 4d Auxiliary aeration means 5, 5a, 5b, 5c Blower 6 Level sensor 7 Partition plate 8 Raw water pump 9 Raw water tank 10a First dissolved oxygen meter 10b Second dissolved oxygen meter 15 Stirrer 20a, 20b, 20c Circulating water amount adjusting plate (swing plate)
21a, 21b, 21c Fixing member 22 Adjustment plate moving means 30 Slide plate 31 Slide plate opening 32 Partition plate opening 33 Slide plate fixing member 34 Slide plate moving means

Claims (6)

  A membrane separation activated sludge treatment apparatus having a single reaction tank for performing an aerobic treatment and an anaerobic treatment, an immersion membrane separation unit disposed inside the reaction tank, and an aeration means, The bottom is divided into a plurality of compartments by a partition plate provided apart from the bottom surface of the reaction vessel, and at least one of the compartments is preferably provided with an immersion membrane separation unit and aeration means. In the membrane-separated activated sludge treatment apparatus that performs oxygen-free treatment in the other compartments, a circulating water amount adjusting device is provided, a first dissolved oxygen meter is provided in the aerobic compartment, and a first in the other compartments. 2. A membrane separation activated sludge treatment apparatus provided with two dissolved oxygen meters.   The membrane separation activated sludge treatment according to claim 1, wherein auxiliary aeration means is further provided in the aerobic section, and the circulating water amount adjusting device is a circulating water amount adjusting device capable of adjusting an opening degree in an upper part of the partition plate. apparatus.   The means for controlling the amount of aeration by the auxiliary aeration means and the dissolved oxygen concentration measured by the second dissolved oxygen meter are preset so that the dissolved oxygen concentration measured by the first dissolved oxygen meter becomes a preset target value. The membrane separation activated sludge treatment apparatus according to claim 2, wherein means for controlling the opening degree of the circulating water amount adjusting device is provided so as to achieve a target value.   The membrane separation activated sludge treatment apparatus according to any one of claims 1 to 3, further comprising an ammonia meter and / or a nitric acid meter for control.   The means to control by the target value of the 1st dissolved oxygen meter and the 2nd dissolved oxygen meter which were preset according to the load condition of the raw | natural water supplied to a reaction tank was provided. The membrane separation activated sludge treatment apparatus as described in 1.   A membrane separation activated sludge treatment method that performs aerobic treatment and oxygen-free treatment in a single reaction vessel in which an immersion membrane separation unit is arranged, and the bottom of the immersion membrane separation unit is separated from the bottom surface of the reaction vessel. By partitioning with the partition plate provided and performing aeration from below the immersion membrane separation unit, anaerobic treatment is performed in the other compartments while maintaining the compartment in which the immersion membrane separation unit is placed in an aerobic state. In the membrane separation activated sludge treatment method to be performed, the dissolved oxygen concentration in the section in which the submerged membrane separation unit is disposed and the dissolved oxygen concentration in the other section are respectively measured, and the measured value of each dissolved oxygen concentration is set in advance. A membrane separation activated sludge treatment method characterized by controlling the amount of aeration and the flow rate of circulating water so as to obtain a value.

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