WO2018198422A1 - Membrane-separation activated sludge treatment device and membrane-separation activated sludge treatment method - Google Patents

Abstract

[Problem] The purpose of the present invention is to provide a membrane-separation activated sludge treatment device and method in which nitrogen removal efficiency is further improved and which is highly applicable even with respect to load fluctuations in the amount of influent wastewater, the device and method furthermore making it possible to greatly reduce the treatment time in a reaction tank (HRT) and being usable in medium- and large-scale wastewater treatment facilities, etc. [Solution] Provided are: a membrane-separation activated sludge treatment device having a single reaction tank for performing an aerobic treatment and an anaerobic treatment, an immersion membrane separation unit disposed within the reaction tank, and an aeration means, wherein the reaction tank is divided into a plurality of compartments by a partition plate, at least one compartment from among the plurality of compartments is an aerobic compartment, the remaining compartments are compartments for performing at least an anaerobic treatment, and there is provided a circulation water amount regulation means or a water flow generation means; and a membrane-separation activated sludge treatment method in which the aforementioned device is used.

Description

Membrane separation activated sludge treatment apparatus and membrane separation activated sludge treatment method

The present invention relates to a membrane separation activated sludge treatment apparatus and method capable of efficiently performing nitrogen removal together with membrane separation.

Conventionally, when treating sewage wastewater containing nutrient salts such as nitrogen and phosphorus, an activated sludge method in which sewage is introduced into a reaction tank and aerated and stirred together with activated sludge for biological treatment is used. 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 Memb rane 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: Low８WaterＯＮLevel), and the raw water pump 8 when the liquid level becomes a high water level (HWL: High Water 原 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 in which the nitrification promotion operation time zone and the denitrification promotion operation time zone are alternately repeated by alternately creating a state where the liquid level is higher and lower than the partition plate. is there.

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 devices, 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.
Under such circumstances, in Patent Document 1, no attention is paid to accurately adjusting the flow rate of the circulating flow in the reaction vessel, and the upper end shape of the partition plate installed in the reaction vessel. Was not described at all.

In recent years, energy conservation in water treatment equipment has been highlighted, and as a result of extensive research and development, the air volume of the aeration means (aeration equipment) that accounts for the majority of the power consumed by the MBR method has been greatly reduced. ing. As a result, there is a concern that the air lift effect due to the air volume of the aeration means, that is, the propulsive force of the circulating water is significantly lower than before, and the possibility of sufficient activated sludge treatment becomes difficult with the method of Patent Document 1. It was.

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 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 tank. 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 can further improve nitrogen removal efficiency, and can easily switch between a nitrification promotion operation time zone and a denitrification promotion operation time zone in a short time. An object of the present invention is to provide a partition-insertion-type membrane separation activated sludge apparatus and method showing high applicability to daily load fluctuations.

In addition, in view of the above-mentioned conventional problems, the present invention further improves the nitrogen removal efficiency, brings about the driving force of circulating water efficiently at a low cost, and further significantly increases the processing time (HRT) in the reaction vessel. An object of the present invention is to provide an energy-saving membrane separation activated sludge apparatus and method that can be shortened and 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 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 that of the partition plate (denitrification promotion operation time zone), the flow of the liquid is divided inside and outside the partition plate (FIG. 1), and a circulation flow is generated in the section where the membrane separation unit is not arranged. Therefore, the raw water, nitrification liquid (liquid containing nitrate nitrogen after nitrification) and denitrification bacteria that are involved in the denitrification reaction are not sufficiently mixed, resulting in efficient denitrification reaction. I found it difficult to do.

Then, by using a membrane separation activated sludge treatment device provided with circulating water amount adjusting means or water flow generating means in the reaction tank, the above-mentioned sufficient mixing necessary for the denitrification reaction is achieved in the denitrification promotion operation time zone. Therefore, it was conceived that a small amount of circulating flow for the purpose could be ensured, and dissolved oxygen (DO) that would be an obstacle to denitrification could be maintained at a low level. As a result, nitrogen removal efficiency was improved. By using such a membrane separation activated sludge treatment device, it is possible to easily switch between a nitrification promotion operation time zone and a denitrification promotion operation time zone in a short time, and it can be applied to daily fluctuations in the inflow sewage amount, It was conceived that an efficient denitrification reaction could be achieved.

Furthermore, by using such a membrane separation activated sludge treatment device, it is possible to bring about the driving force of circulating water at a low cost, and the treatment time (HRT) in the reaction vessel is significantly shortened 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 apparatuses (1) to (4) and methods (5) to (8).
(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 in which the aerobic compartment is used and the other compartment is at least an oxygen-free treatment compartment, a circulating water amount adjusting means or a water flow generating means is provided. .

(2) The other compartment is a compartment for switching from an aerobic state to an anaerobic state and from an anaerobic state to an aerobic state, and a circulating water amount adjusting means is provided in the membrane separation activated sludge treatment apparatus. (1) The membrane separation activated sludge processing apparatus of description.
(3) The other compartment is a compartment for performing anoxic treatment, a circulating water amount adjusting device is provided in the membrane separation activated sludge treatment apparatus, a first dissolved oxygen meter is provided in the aerobic compartment, and the other compartment is provided. The membrane-separated activated sludge treatment apparatus according to (1), wherein a second dissolved oxygen meter is provided.
(4) The membrane-separated activated sludge treatment apparatus according to (1), wherein the other compartment is a compartment that performs anoxic treatment, and a water flow generator is provided in the other compartment.

(5) 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, while maintaining the inside of the compartment where the immersion membrane separation unit is placed in an aerobic state, at least in other compartments A membrane separation activated sludge treatment method for performing an oxygen-free treatment, wherein the amount of circulating water or the flow rate of circulating water is adjusted.
(6) The membrane separation activity according to (5), wherein the inside of the other compartment is switched from an aerobic state to an anaerobic state, or from an anaerobic state to an aerobic state, and the circulating water amount is adjusted by the circulating water amount adjusting means. Sludge treatment method.
(7) Perform oxygen-free treatment in the other compartments, measure the dissolved oxygen concentration in the compartment where the submerged membrane separation unit is disposed, and the dissolved oxygen concentration in the other compartment, and measure each dissolved oxygen concentration. The membrane separation activated sludge treatment method according to (5), wherein the aeration amount and the flow rate of the circulating water are controlled so that the value becomes a preset target value.
(8) The membrane separation activated sludge treatment method according to (5), wherein an oxygen-free treatment is performed in the other compartment, and a flow rate of circulating water is controlled in the other compartment.

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, in a section other than the membrane separation unit accommodation section, a small amount of circulating flow that brings about sufficient mixing of raw water, nitrification liquid, and denitrifying bacteria necessary for the denitrification reaction can be accurately performed even in the denitrification promotion operation time zone. Since it can be well controlled and secured, the denitrification reaction can be efficiently advanced, and the nitrogen removal efficiency from organic wastewater can be improved.
In addition, the nitrification promotion operation time zone and the denitrification promotion operation time zone can be switched easily in a short time, and can be applied to daily load fluctuations of the inflow sewage amount, enabling efficient membrane separation activated sludge treatment. It becomes.
Furthermore, it is possible to efficiently provide the driving force for circulating water at a low cost, and the processing time (HRT) in the reaction tank can be greatly shortened, enabling compact and efficient membrane separation activated sludge treatment. It becomes.

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 the side view and top view which show typically the membrane separation activated sludge processing apparatus of the conventional method (patent document 1). It is the side view and top view which show typically one embodiment of the membrane separation activated sludge processing apparatus of this invention. It is a figure which shows typically another embodiment of the circulating water amount adjustment means of this invention. It is a figure which shows typically another embodiment of the circulating water amount adjustment means of this invention. It is a figure which shows typically another embodiment of the circulating water amount adjustment means of this invention. It is a figure which shows typically another embodiment of the circulating water amount adjustment means of this invention. It is a figure which shows typically another embodiment of the membrane separation activated sludge processing apparatus of this invention. It is a figure which shows typically another embodiment of the membrane separation activated sludge processing apparatus of this invention. It is the side view and top view which show typically another embodiment of the membrane separation activated sludge processing apparatus of this invention. It is the side view and top view which show typically another 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. In FIGS. 1 to 12, 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, a circulating water amount adjusting means or a water flow generating means is provided in a partition plate insertion type membrane separation activated sludge treatment apparatus. First, a membrane separation activated sludge treatment apparatus according to the present invention and The overall configuration of one embodiment of the method will be described with reference to FIG.

In the membrane separation activated sludge apparatus of FIG. 4, an immersion type membrane separation unit 2 is provided in a single tank type reaction vessel 1. A suction pump 3 is connected to the membrane separation unit 2 outside the reaction tank 1, and an aeration means 4 (aeration device) for membrane cleaning and aerobic biological treatment is provided below the membrane separation unit 2. ing. The aeration means 4 is connected to a blower 5, and air (air) is supplied from the blower 5.

The membrane separation unit 2 preferably uses a material that does not easily get dirty as the membrane itself, or a device that has an appropriate gap between the membranes so that the membrane surface is less likely to get dirty. The membrane separation unit 2 may be a module formed using a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, or the like. 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.

In the reaction tank 1, sludge containing microorganisms is accommodated, and these microorganisms act as organic matter decomposing bacteria, and further as decomposing bacteria of these microorganisms, and perform 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 well-known conditions that are usually used in the membrane separation activated sludge method, but the MLSS (Mixed Liquor Suspended Solid) concentration is usually 3000 to 20000 mg / L, preferably 5000 to The HRT (hydraulic residence time) is usually 2 to 24 hours, preferably 4 to 8 hours, and an HRT shortened compared to the OD method can be achieved.

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

In the specific example of FIG. 4, 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. For example, you may provide a membrane separation unit accommodation section in the four corners of a rectangular reaction tank, respectively. 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.

Sewage that has flowed into a sewage treatment facility such as a sewage treatment plant is separated and removed from sand and garbage in a pretreatment facility, and is then introduced as raw water from a raw water tank to a reaction tank 1 by a raw water pump. 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. 4, sewage is biologically treated in the reaction tank 1, and the sludge substance or the like is prevented from adhering to the membrane surface of the membrane separation unit 2 due to the air from the diffusion tube 4. However, the treatment liquid in the reaction tank 1 can be filtered by the membrane separation unit 2, and the filtered water can be sucked by the suction pump 3 and taken out of the tank. In the specific example of FIG. 4, 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 natural water head, Further, the filtration pressure may be obtained by pressurization from the stock solution side.

(First feature of the present invention: installation of circulating water amount adjusting means)
The first feature of the present invention is that in such a membrane separation activated sludge treatment apparatus, a circulating water amount adjusting means is provided. By this circulating water amount adjusting means, the amount of water in the circulating flow formed in the tank by the air from the air diffuser 4 is adjusted. Here, “circulation flow” means that when the inside and outside of the partition plate are in an overflow state, as shown in FIG. 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 means is preferably provided at the upper or upper end of the partition plate, and is preferably means for adjusting the amount of water in the circulating flow moving from the membrane separation unit accommodating section to other sections.

Hereinafter, the circulating water amount adjusting means in the present invention will be described with reference to FIGS. 4 to 8. In order to understand the circulating water amount adjusting means of the present invention, the membrane separation activated sludge of the conventional method (the method of Patent Document 1) is used. The processing apparatus is shown in comparison with FIG.
The first embodiment of the circulating water amount adjusting means in the present invention is a swing type circulating water amount adjusting device provided with 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 21 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 circulating water amount adjusting means on the right side is omitted, and the adjusting plate moving means 22 is omitted in the top view).

The swing plate 20a shown in FIG. 4 is fixed to a rod-shaped fixing member 21 on one side of the two sides in the longitudinal direction. 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 opening degree of the swing plate can be adjusted, for example, by installing a dissolved oxygen meter (DO meter) in the reaction vessel and detecting the dissolved oxygen concentration (DO value).

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 21 is not particularly limited as long as the swing plate is fixed so as to be swingable. As the fixing member 21, 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 positions where both ends of the fixing member 21 are fixed to the tank wall of the reaction tank are adjusted from the highest liquid level in the reaction tank from the viewpoint of efficiently adjusting the amount of circulating water and reducing 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 to the position shifted in the division direction other than the membrane separation unit accommodation division rather than just above the partition plate 7 from a viewpoint of adjusting the amount of circulating water efficiently.

Further, 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.

By using such a swing-type circulating water amount adjusting device, it is possible to easily switch between the nitrification promotion operation time zone and the denitrification promotion operation time zone in a short time. In addition, in the sections other than the membrane separation unit storage section, even during the denitrification promotion operation period, after ensuring a small amount of circulating water that provides sufficient mixing necessary for the denitrification reaction, dissolved oxygen ( DO) can be maintained at a low level, and nitrogen removal efficiency from organic wastewater can be improved.

In addition, in the time zone for promoting nitrification (nitrification promotion operation time zone), the entire reaction tank can be maintained in an aerobic state by increasing the opening of the swing plate and securing a large amount of circulating water. As a result, the nitrification reaction can be promoted.

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 embodiment of the circulating water amount adjusting means in the present invention is a circulating water amount adjusting device provided with 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. The degree of opening (opening ratio) of the partition plate can be adjusted by adjusting the condition.

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 opening degree (opening ratio) of the slide plate can be adjusted, for example, by installing a dissolved oxygen meter (DO meter) in the reaction tank and detecting the dissolved oxygen concentration (DO value).

The shape of the opening 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.

</ RTI> By using the circulating water amount adjusting device provided with such a slide plate, it is possible to easily switch between the nitrification promotion operation time zone and the denitrification promotion operation time zone in a short time. In addition, in the sections other than the membrane separation unit storage section, even during the denitrification promotion operation period, after ensuring a small amount of circulating water that provides sufficient mixing necessary for the denitrification reaction, dissolved oxygen ( DO) can be maintained at a low level, and nitrogen removal efficiency from organic wastewater can be improved.

In addition, in the time zone for promoting nitrification (nitrification promotion operation time zone), the nitrification reaction can be promoted by maintaining the entire reaction tank in an aerobic state by adjusting the opening ratio of the slide plate to be large. .

A third embodiment of the circulating water amount adjusting means in the present invention is a partition plate provided with a notch 40 at the upper end of the partition plate as shown in FIG. The shape of the notch can be appropriately selected from a rectangle, an inverted trapezoid, an inverted triangle, a semicircle, a semi-ellipse, and the like. The width and depth of one notch are usually 3 to 30 cm, preferably 5 to 25 cm, respectively.

When a partition plate having a notch as shown in FIG. 7 is used as the circulating water volume adjusting means, the circulating water volume can be accurately adjusted by adjusting the liquid level in the reaction tank in the range of A to C (FIG. 7). It becomes possible to adjust. Specifically, when the liquid level is adjusted to a position between A and B, the amount of circulating water increases, and the entire reaction tank can be maintained in an aerobic state to promote the nitrification reaction (nitrification promotion). Driving hours). When the liquid level is adjusted to a position between B and C, the amount of circulating water can be finely adjusted, and a small amount of circulation that provides sufficient mixing necessary for the denitrification reaction during the denitrification promotion operation time period. It is possible to maintain a low level of dissolved oxygen (DO), which is an obstacle to denitrification, while ensuring the amount of water, and an efficient denitrification reaction can proceed. Further, when the liquid level is adjusted to be lower than C, the inside and outside of the partition plate are divided, and the circulation amount can be reduced.

In addition to the case where the plurality of notches 40 have substantially the same width and depth as shown in FIG. 7, a plurality of semi-elliptical shapes having different depths as shown in FIG. The cutouts 41a to 41c may be combined in a certain repeating order. As long as the amount of circulating water can be finely adjusted efficiently, the shape of the notch is not limited to a semi-elliptical shape, and may be any shape such as a rectangular shape. In the case of a partition plate having notches with different depths as shown in FIG. 8, the width of one notch is usually 3 to 30 cm, preferably 5 to 25 cm. In addition, the depth of the notch is usually 20 to 60 cm, preferably 30 to 50 cm in the deepest case, and the depth of the notch shallower than this is supplied during the denitrification promoting operation time zone. It can set suitably according to the amount of circulating water which should be.

When a partition plate having a plurality of notches having different depths as shown in FIG. 8 is used as the circulating water amount adjusting means, the liquid level in the reaction tank is adjusted within the range of A to E (FIG. 8). It becomes possible to finely adjust the amount of circulating water with high accuracy. Specifically, when the liquid level is adjusted to a position between A and B, the amount of circulating water is maximized, and the entire reaction tank can be maintained in an aerobic state to promote the nitrification reaction (nitrification promotion). Driving hours). When the liquid level is adjusted to a position between B and C, the circulating water volume increases. When the liquid level is adjusted to a position between C and D, the circulating water volume becomes moderate, and the liquid level changes from D to D. When adjusted to a position between E, the amount of circulating water decreases, and when the liquid level is adjusted to a position lower than E, the inside and outside of the partition plate are divided, and there may be no circulation amount. it can.

Therefore, in the denitrification promotion operation time zone, the circulating water volume can be finely adjusted to the required circulating water volume by adjusting the liquid level to a position between B and E in FIG. During the denitrification promotion operation period, it is possible to maintain a low level of dissolved oxygen (DO), which hinders denitrification, while securing a small amount of circulating water that provides sufficient mixing necessary for the denitrification reaction. Thus, an efficient denitrification reaction can proceed.

In the method of Patent Document 1, the upper end shape of the partition plate installed in the reaction tank is not particularly described, and it is assumed that the upper end is a flat horizontal surface. In such a partition plate, it is necessary to control the liquid level at a position of about 5 mm to 20 mm from the upper end of the partition plate in order to secure a small amount of circulating flow required during the denitrification promotion operation time zone. It was difficult to accurately control the circulation flow rate due to fluctuations in the amount of sewage, the influence of contaminants, biofilm adhesion, and the like. On the other hand, by using a partition plate having a notch as shown in FIGS. 7 and 8, a water level difference corresponding to the required circulating flow rate can be formed, and the circulating water amount can be controlled with high accuracy. . Therefore, the flow rate adjustment tank of raw water becomes unnecessary, and the capacity can be reduced even when the flow rate adjustment tank is installed.

In the membrane-separated activated sludge treatment apparatus relating to the first feature of the present invention, as the above-mentioned circulating water amount adjusting means, the swing-type circulating water amount adjusting device which is the first embodiment and the upper end which is the third embodiment. If a partition plate provided with a notch is used in combination, the amount of circulating water can be finely adjusted more efficiently and efficiently. In this case, the swing plate (circulation water amount adjustment plate) used in the first embodiment completely covers the upper part of the partition plate when it is moved most in the direction of the partition plate (downward), and the circulation flow is It is desirable that the size or shape be such that the notch portion at the upper end of the partition plate according to the third embodiment is completely blocked while being almost completely blocked.

Since the apparatus and method relating to the first feature of the present invention have a wide adjustable range of the circulating water volume by the circulating water volume adjusting means, the difference between the supply flow rate of the raw water and the membrane filtration flow rate is adjusted according to the daily fluctuation of the inflowing sewage amount. Thus, the liquid level can be easily controlled. Specifically, when the liquid level in the reaction tank becomes higher, the membrane filtration flow rate may be controlled to be higher than the raw water supply flow rate, and when the liquid level becomes lower, the raw water supply flow rate may be controlled to be higher than the membrane filtration flow rate. . When the liquid level in the reaction tank is an intermediate liquid level, operation is performed so that the raw water supply flow rate and the membrane filtration flow rate are substantially the same. For example, it is necessary to increase the raw water flow rate during a period of high inflow sewage volume, and if the membrane filtration flow rate is constant, the liquid level in the reaction tank will rise, but the membrane filtration flow rate can be increased as the liquid level rises. In this case, it becomes easy to operate within the adjustable range of circulating water.

In the present invention, unlike the method of Patent Document 1, it is not necessary to greatly change the liquid level in order to create a liquid overflow state and a divided state inside and outside the partition plate. The raw water can be continuously supplied to the reaction tank at a constant flow rate so as to obtain an optimum amount of circulating water in each of the operation time zones. For this reason, there is an advantage that 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.

(Second feature of the present invention: installation of circulating water amount adjusting device and first and second dissolved oxygen meters)
The second feature of the present invention resides in the provision of the circulating water amount adjusting device and the first and second dissolved oxygen meters in the partition plate insertion type membrane separation activated sludge treatment apparatus. An apparatus and method showing the second feature of the present invention will be described with reference to FIG.

The circulating water amount adjusting device in the second feature of the present invention is not particularly limited as long as it is a device or equipment that generates a water flow in the reaction vessel, but is formed in the reaction vessel by air from aeration means (aeration device). It is preferable that the apparatus can control the flow rate of the circulating flow. Here, “circulation flow” means that when the inside and outside of the partition plate is in an overflow state, as shown in FIG. 9, the membrane separation unit accommodating section enters the other section beyond 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.

As the circulating water amount adjusting device in the second feature of the present invention, the same means as the circulating water amount adjusting device which is the first feature of the present invention described above can be used. The description of can be applied to the circulating water amount adjusting device in the second feature of the present invention.
Specifically, as the circulating water amount adjusting device according to the second feature of the present invention, the swing type circulating water amount adjusting device (first embodiment) shown in FIGS. A device similar to the circulating water amount adjusting device (second embodiment) provided with the slide plate shown in FIG. 6 can be used, and all of the above description regarding FIGS. It can be applied to the circulating water amount adjusting device in the feature.

The description of the membrane separation activated sludge treatment apparatus shown in FIG. 4 described above can be applied to the overall configuration and each member of the membrane separation activated sludge treatment apparatus shown in FIG.

In FIG. 9, an aeration means 4a (aeration device) for membrane cleaning is provided below the membrane separation unit 2a, and an auxiliary aeration means 4b (aeration device) is provided at the lower side of the membrane separation unit 2a. Is provided. 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 usually 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.

In the 2nd characteristic of this invention, the 1st and 2nd dissolved oxygen meter (DO meter) for measuring the dissolved oxygen concentration in circulating water is provided with the circulating water amount control apparatus mentioned 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. 9, the specific control method in this invention is demonstrated.
The raw water pump 8 for supplying 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 20 to 50 Hz for the inverter. 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 the frequency range of 20 to 50 Hz, 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 an inflow raw | natural water amount, according to a membrane flux, it adjusts in the range of 0.05-0.2 by making the ventilation volume of the film | membrane washing blower (B1) into 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 the 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 that is 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 within a range of 10 to 100% (PID control) 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. 10 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. 10, 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 the apparatus shown in FIG. 10, 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.

9 and FIG. 10, 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 volume 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.

(Third feature of the present invention: installation of a water flow generator)
The third feature of the present invention resides in that a water flow generating device is provided in a partition other than the membrane separation unit accommodation section in the partition plate insertion type membrane separation activated sludge treatment apparatus. An apparatus and method showing the third feature of the present invention will be described with reference to FIG.

The description of the membrane separation activated sludge treatment apparatus shown in FIG. 4 described above can be applied to the entire configuration and each member of the membrane separation activated sludge treatment apparatus shown in FIG.

In FIG. 11, an aeration means 4a (aeration device) for membrane cleaning is provided below the two membrane separation units 2a, and an auxiliary aeration means 4b (aeration device) is provided below the aeration means 4a. Is provided. 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 usually 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.
Moreover, as shown in FIG. 11, in order to supply raw water uniformly, you may supply the reaction tank 1 from several places.

The water flow generation device according to the third feature of the present invention is not particularly limited as long as it is a device or equipment that can generate a necessary water flow in the reaction tank, but air from the aeration means (aeration device) is not limited. It is preferable that the apparatus can control the flow rate of the circulating flow formed in the reaction tank. Here, “circulation flow” means that, as shown in FIG. 11, when the inside and outside of the partition plate are in an overflow state, the membrane separation unit accommodating section enters the other section beyond the partition plate 7, and the others. 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.

Below, the water flow generator in this invention is demonstrated, referring FIG.11 and FIG.12.
The 1st aspect of the water flow generator in this invention is the stirring apparatus 15a installed in the division in which the submerged membrane separation unit and the aeration means are not arrange | positioned in the membrane separation activated sludge processing apparatus shown in FIG. This stirring device generates a downward driving force of the circulating water. As the stirring device 15a, a general stirring device in which a driving unit 16a installed on water and a stirring blade installed in water are connected via a shaft can be used.

The shape of the stirring blade includes a propeller type, a screw type, a paddle type, and the like. The size of the stirring blade is not particularly limited as long as a necessary driving force can be obtained, but generally the rotation speed is small with a large stirring blade and the rotation speed is large with a small stirring blade. It is also possible to use a stirring device that can obtain a large driving force with a small amount of power by slowly rotating a large blade. From the viewpoint of efficiently controlling the circulation flow rate, the installation position of the stirring device is preferably near the center of the section where the submerged membrane separation unit and the aeration means are not arranged in the top view of FIG. The arrangement position of the stirring blade may be any of the upper layer part, middle part and lower layer part of the reaction tank in the side view of FIG. 11, but it is installed in the upper layer part of the reaction tank from the viewpoint of efficiently controlling the circulation flow rate. Is preferred.

A second aspect of the water flow generator in the present invention is a float type water flow generator installed near the water surface in the reaction tank in the membrane separation activated sludge treatment apparatus shown in FIG. The float type water flow generator is composed of a float 17 floating on the water surface, an impeller (stirring blade) 18, a discharge unit 19 for storing the stirring blade, and a drive unit 16b, and water is supplied from an opening at the top of the discharge unit. It is sucked in and generates a downward jet water flow by rotating the impeller at high speed. The float is a cylindrical member for floating the water flow generator on the water surface, has a diameter of 1 m to 3 m, and a height of 200 mm to 500 mm. Examples of the shape of the impeller (stirring blade) include a propeller type.

The float type water flow generator is further connected to the partition plate extending means 12 as shown in FIG. The partition plate extending means 12 is installed so that it can be extended at the upper end of the partition plate by a fixing member 13 fixed to the tank wall of the reaction tank. Is connected to the float-type water flow generator 15b. By adopting a structure in which the float-type water flow generator and the partition plate extension means are integrated in this way, the partition plate extender also moves up and down as the water flow generator moves up and down in conjunction with fluctuations in the water level in the reaction tank. To do. As a result, the distance from the upper end of the partition plate to the water surface can be kept constant (about 100 to 500 mm), and the circulation flow rate can be easily controlled. As a result, the water level range of the reaction tank that can be operated is widened, the control is easy even with respect to fluctuations in the amount of inflow water during the day, and the capacity of the flow rate adjustment tank of the raw water can be reduced or omitted. Such a float-type water flow generator has advantages in that power consumption can be reduced and maintenance is easy because there are no operating parts or replacement parts, compared to other general underwater agitators.

For the water flow generator (FIGS. 11 and 12) as described above, the flow rate of the circulating flow is controlled by changing the frequency of the inverter in the drive unit 16a or 16b and controlling the rotational speed of the stirring blade (impeller). be able to. Thereby, in the section containing the water flow generator (hereinafter also referred to as "water flow generator storage section"), sufficient mixing of raw water, nitrification liquid and denitrifying bacteria involved in the denitrification reaction is achieved, and Dissolved oxygen (DO) that interferes with denitrification can be maintained at a low level. As a result, an efficient denitrification reaction can proceed.

When arranging a plurality of membrane separation units in a reaction vessel, from the viewpoint of efficiently performing activated sludge treatment, a membrane separation unit accommodation section is provided near the wall of the reaction tank, and a water flow generator accommodation section is provided in the reaction tank. It is preferable to provide it at the center.

In the present invention, as shown in the side views (below) of FIGS. 11 and 12, water flow guides (baffles) 11a, 11b, and 11c are provided on the water surface and the bottom of the reaction tank so that the activated sludge in the reaction tank settles. And a water flow that does not cause stagnation can be formed. The water flow guide 11a is a rectangular shape installed near the water surface in the upper part of the membrane separation unit accommodation section so that the circulating flow rising in the membrane separation unit accommodation section moves efficiently in the direction of the water flow generator over the partition plate. It is made up of plates. One side of the water flow guide 11a is fixed in water to one wall surface of the reaction vessel that surrounds the membrane separation unit, and the opposite side is installed to be higher than the water surface. The water flow guides 11b and 11c are rectangular plates arranged at the bottom of the reaction tank so that the circulating flow descending the water flow generator housing section moves efficiently in the direction of the membrane separation unit through the lower part of the partition plate. It is configured. One side of the water flow guide 11b is fixed to one wall surface of the reaction tank, and the opposite side is fixed to the bottom surface of the reaction tank. The water flow guide 11c is bent into a convex shape arranged at the bottom of the water flow generating device accommodating section so that the circulating flow descending the water flow generating device accommodating section is efficiently divided and moved to the two membrane separation unit accommodating sections. It is composed of a rectangular plate. These water flow guides may be provided on the entire length of one wall surface or the bottom surface of the reaction tank, or may be provided on a part thereof. The shape and size of the water flow guide are not particularly limited as long as the activated sludge in the reaction tank forms a water flow that does not settle or stay. As shown in FIGS. 11 and 12, a linear shape may be used, but it is more preferable to form a curve along the flow of water because the loss head (resistance) is reduced.

The membrane separation activated sludge treatment apparatus according to the third feature of the present invention can further be provided with first and second dissolved oxygen meters (DO meters) for measuring the dissolved oxygen concentration in the circulating water. The first dissolved oxygen meter (DO1) is preferably provided in the membrane separation unit accommodating section, and in order to perform efficient control, the dissolved oxygen concentration in the circulating flow between the upper end of the membrane separation unit and the upper end of the partition plate It is good to install in a position where DO1 can be immersed in the liquid even if the liquid level in the reaction tank reaches the lowest water level. In addition, the second dissolved oxygen meter (DO2) is preferably provided in the water flow generator housing section, and in order to perform efficient control, it is below the water flow generator and the liquid level in the reaction tank. It is better to install at a position about half the depth.

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 a scale processing apparatus, there is a fluctuation of about 0.2 to 3 times. In the conventional method (Patent Document 1), it has been difficult to perform efficient nitrification and denitrification reaction against such daily load fluctuations. 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.

In the present invention, by controlling the activated sludge treatment by combining the above-described water flow generator and the first and second dissolved oxygen meters (DO meters), the degree of freedom of DO control is increased, It is possible to perform a process applicable to fluctuations in water load. 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 the preset target value of DO1, and the second dissolved oxygen The number of revolutions of the water flow generator 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 3 below, the load status is classified into high load, medium load, and low load in descending order of the inflow wastewater amount and the concentration of pollutants.

Below, based on FIG. 11, the specific control method in this invention is demonstrated.
The raw water pump 8 for supplying 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. Note that proportional control (control in which the flow rate of the raw water pump is increased when the water level is high and the flow rate of the raw water pump is decreased when the water level is low in the control range) may be performed in accordance with the raw water tank water level.

The filtration pump 3 can be controlled within a frequency range of 20 to 50 Hz for the inverter. In principle, operation is performed at a constant flow rate of 50 Hz or the like, and 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. For example, the amount of filtered water can be controlled by the water level in the reaction vessel. Specifically, when the water level in the reaction tank reaches the highest water level (H), the filtration pump 3 is set to the maximum flow rate, and when the water level drops to the lowest water level (L), the operation of the filtration pump 3 is stopped, and the highest water level (H) and the lowest water level are reached. Between the water levels (L), proportional control based on the water level can be performed. Further, according to the load time zone, a membrane flux (a membrane membrane water amount / a membrane filtered water amount per unit time (m ³ / m ² / d)) can be set in advance, and a filtered water amount corresponding to this can be set. 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 the frequency range of 20 to 50 Hz, and the aeration amount SADm per membrane area is in the range of 0.1 to 0.20. 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 an inflow raw | natural water amount, according to a membrane flux, it adjusts in the range of 0.05-0.2 by making the ventilation volume of the film | membrane washing blower (B1) into 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 4 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 the membrane flux.

The auxiliary aeration blower (B2) can be controlled within a frequency range of 20 to 50 Hz for the inverter, and automatically controls the air flow rate so that the dissolved oxygen concentration value measured by DO1 becomes a preset target value (PID). Control), the aeration amount of the auxiliary aeration means can be 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 that is 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 water flow generator automatically controls (PID control) the inverter frequency within a range of 20 to 50 Hz so that the dissolved oxygen concentration measured by DO2 becomes a preset 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 rotation speed of the water flow generator is reduced to slow down the circulation flow rate. Control to do. On the other hand, when the measured value of DO2 is smaller than the target value, the oxygen consumption is large, so that the rotational speed of the water flow generator is increased in order to increase the circulation flow rate. The number of rotations of the water flow generator varies depending on the size and shape of the stirring blade, but can be controlled in the range of 5 r.p.m. to 50 r.p.m. when having a relatively large blade. Even when the frequency of the water flow generator is 10%, which is the lower limit of control, if the measured value of DO2 is larger than the target value, the water flow generator is fully closed for a certain time (such as 30 minutes). In addition, as a water flow generator, even when the float type water flow generator of FIG. 12 is used instead of the stirrer of FIG. 11, the rotation speed can be controlled similarly.

11 and 12, the aerobic zone is a zone above the aeration means in the membrane separation unit accommodation section and the upper part of the water flow generation apparatus accommodation section, and the anoxic zone is the water flow generation apparatus accommodation. The zone below the DO2 in the compartment and below the aeration means in the membrane separation unit accommodating compartment. The volume 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 by combining the water flow generator and the first and second dissolved oxygen meters (DO meters), the liquid overflows inside 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 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.

The direction of the circulating flow in the reaction tank is opposite to the direction shown in FIGS. 11 and 12, that is, the water flow generator housing section is an upward flow, and the membrane separation unit housing section is a downward flow. Also good. In this case, it is necessary to set the installation positions of DO1 and DO2 to the positions opposite to those described above.

In the apparatus and method according to the second and third features of 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 the amount of ammonia is large, and the denitrification zone is enlarged when the amount of nitric acid is large.

Since the membrane separation activated sludge treatment method using the apparatus according to the second and third features of the present invention can maintain a higher MLSS concentration compared to the OD method, the A-SRT (Aerobic Solid Retention Time) required for nitrification is favorable. It is easy to control the aerobic zone and anaerobic zone because the oxygen consumption rate due to the endogenous respiration of microorganisms is increased even under conditions of low BOD-MLSS load. Has the advantage.

The present invention is not limited to the above embodiment as long as it is a membrane separation activated sludge treatment apparatus and method provided with a circulating water amount adjusting means or a water flow generating means, and other treatment conditions and raw water pretreatment are as follows: It can be performed under the same conditions as conventionally known methods.

The present invention further improves the nitrogen removal efficiency, can easily switch between the nitrification promotion operation time zone and the denitrification promotion operation time zone in a short time, and further, against the daily load fluctuation of the inflow sewage amount. It is possible to provide a partition plate insertion type membrane separation activated sludge apparatus and method exhibiting high applicability.
In addition, the present invention provides a driving force for circulating water efficiently at a low cost, and further significantly reduces the processing time (HRT) in the reaction tank, so that it can be used in medium- and large-scale sewage treatment plants and factory wastewater treatment. An energy-saving membrane-separated activated sludge apparatus and method that can be employed can be provided.

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 1st dissolved oxygen meter 10b 2nd dissolved oxygen meter 11a, 11b, 11c Water flow guide (baffle)
12 partition plate extending means 13 partition plate extending means fixing member 15 stirrer 15a stirrer (water flow generator)
16a, 16b Drive unit 17 Float 18 Impeller (stirring blade)
19 Discharge part 20a, 20b, 20c Circulating water amount adjustment board (swing board)
21, 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 40 Notch 41a, 41b, 41c Notch

Claims (19)

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. A membrane-separated activated sludge treatment apparatus comprising a circulation water amount adjusting means or a water flow generating means in a membrane-separated activated sludge treatment apparatus having an air compartment and the other compartments at least performing oxygen-free treatment. The other compartment is a compartment for switching from an aerobic state to an anaerobic state, or from an anaerobic state to an aerobic state, and a circulating water amount adjusting means is provided in the membrane separation activated sludge treatment apparatus. The membrane separation activated sludge treatment apparatus according to 1. The membrane separation activated sludge treatment device according to claim 2, wherein the circulating water amount adjusting means is a swing type circulating water amount adjusting device including a circulating water amount adjusting plate and an adjusting plate moving means for swinging the circulating water amount adjusting plate. . The membrane separation according to claim 2, wherein the circulating water amount adjusting means is a circulating water amount adjusting device provided with a slide plate having an opening, the slide plate being capable of adjusting an opening ratio of the opening provided in the partition plate. Activated sludge treatment equipment. The membrane separation activated sludge treatment apparatus according to claim 2, wherein the circulating water amount adjusting means is a partition plate provided with a notch at an upper end. The other compartment is an oxygen-free treatment compartment, a circulating water amount adjusting device is provided in the membrane separation activated sludge treatment device, a first dissolved oxygen meter is provided in the aerobic compartment, and a second is provided in the other compartment. The membrane separation activated sludge treatment apparatus according to claim 1, further comprising a dissolved oxygen meter. The membrane separation activated sludge treatment according to claim 6, further comprising an auxiliary aeration means in the aerobic section, wherein 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 7, further comprising means for controlling the opening degree of the circulating water amount adjusting device so as to be a target value. 9. A means for controlling according to a target value of a first dissolved oxygen meter and a second dissolved oxygen meter set in advance according to the load condition of raw water supplied to the reaction tank. The membrane separation activated sludge treatment apparatus as described in 1. The membrane separation activated sludge treatment apparatus according to claim 1, wherein the other section is a section for performing oxygen-free treatment, and a water flow generator is provided in the other section. The membrane-separated activated sludge treatment apparatus according to claim 10, wherein a first dissolved oxygen meter is provided in the aerobic compartment, and a second dissolved oxygen meter is provided in the other compartment. An auxiliary aeration means is further provided in the aerobic compartment, and a 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; The membrane separation activated sludge treatment apparatus according to claim 11, further comprising means for controlling the rotational speed of the water flow generator so that the dissolved oxygen concentration measured by a dissolved oxygen meter becomes a preset target value. When the water flow generator is installed on the water surface in the reaction tank, and the water flow generator moves up and down in conjunction with the fluctuation of the water level in the reaction tank, the partition plate extending means connected to the water flow generator moves up and down. The membrane separation activated sludge treatment apparatus according to any one of claims 10 to 12, wherein the distance from the upper end of the partition plate to the water surface is kept constant. The means for controlling according to the target values of the first dissolved oxygen meter and the second dissolved oxygen meter preset according to the load condition of the raw water supplied to the reaction tank is 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 provided partition plate and performing aeration from below the submerged membrane separation unit, while maintaining the inside of the compartment where the submerged membrane separation unit is placed in an aerobic state, at least oxygen-free treatment in other compartments In the membrane separation activated sludge treatment method to perform, the membrane separation activated sludge treatment method characterized by adjusting the amount of circulating water or the flow rate of circulating water. The membrane separation activated sludge treatment method according to claim 15, wherein the other compartment is switched from an aerobic state to an anaerobic state or from an anaerobic state to an aerobic state, and the circulating water amount is adjusted by the circulating water amount adjusting means. . Perform oxygen-free treatment in the other compartments, measure the dissolved oxygen concentration in the compartment where the submerged membrane separation unit is disposed, and the dissolved oxygen concentration in the other compartment, respectively. The membrane separation activated sludge treatment method according to claim 15, wherein the aeration amount and the flow rate of the circulating water are controlled so that the set target value is obtained. The membrane separation activated sludge treatment method according to claim 15, wherein an oxygen-free treatment is performed in the other compartment, and a flow rate of circulating water is controlled in the other compartment. Measure the dissolved oxygen concentration in the compartment where the submerged membrane separation unit is disposed and the dissolved oxygen concentration in the other compartment, and the aeration amount and circulation so that the measured value of each dissolved oxygen concentration becomes a preset target value. The membrane separation activated sludge treatment method according to claim 18, wherein the flow rate of water is controlled.

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