JP7220740B2 - MEMBRANE ACTIVATED SLUDGE TREATMENT APPARATUS AND MEMBRANE ACTIVATED SLUDGE TREATMENT METHOD - Google Patents

Description

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

Conventionally, in treating sewage and wastewater containing nutrients such as nitrogen and phosphorus, an activated sludge method has been used in which sewage is introduced into a reaction tank and aerated and agitated together with activated sludge for biological treatment. Especially in recent years, in order to obtain clear treated water that does not contain solids from the treated water treated by this activated sludge method, a membrane separation device is immersed in the reaction tank, and the treated water is separated and discharged. The activated sludge method (Membrane Bioreactor (MBR) method) is often used.

In such a submerged membrane separator, it is necessary to blow air from the air diffuser at the bottom in order to prevent sludge from adhering to the membrane surface and causing fouling (clogging of the membrane). is almost continuously aerated. In the activated sludge process, nitrification proceeds by the action of nitrifying bacteria under such aerobic conditions, but on the other hand, in order to perform denitrification treatment by denitrifying bacteria, it is necessary to make the inside of the tank anoxic. . Therefore, in the membrane separation activated sludge process, it is necessary to ensure both membrane surface cleaning during membrane filtration and diffusion for nitrification treatment, and to ensure an oxygen-free state for denitrification treatment. As a technique to realize this, a membrane separation activated sludge apparatus and method for advancing aerobic treatment (nitrification treatment) and anoxic 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 for performing aerobic treatment and anoxic treatment, and an immersion membrane separation unit disposed inside the reaction tank. 2 and an aeration means 4, wherein the reaction vessel 1 is divided into a plurality of compartments by a partition plate 7 having a bottom spaced apart from the bottom surface of the reaction vessel. 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 compartments are changed from the aerobic condition to the anoxic condition and from the anoxic condition to the aerobic condition. A partition plate inserted as a compartment for switching and provided with liquid level control means or partition plate height control means for switching between a state where the liquid level in the reaction vessel is higher and lower than the upper end of the partition plate type membrane separation activated sludge treatment equipment (Baffled Membrane Bioreactor (B-MBR method)).

In the method of Patent Document 1, when the liquid level in the reaction tank 1 reaches a low water level (LWL), the raw water pump 8 is turned on, and when the liquid level reaches a high water level (HWL), the raw water pump 8 is turned on. is set to OFF to change the liquid level, alternately creating a state in which the liquid level is higher than the partition plate and a state in which the liquid level is lower than the partition plate (FIG. 1). Here, when the liquid level is higher than the partition plate, the air from the diffuser pipe 4 circulates throughout the tank (from the membrane unit storage compartment, over the partition plate 7, into other compartments, and A circulation flow descending in the compartment and returning to the membrane unit housing compartment via the area below the partition plate 7 is formed (FIG. 2). Due to the formation of such a circulating flow, the sludge containing a large amount of nitrate nitrogen obtained by the nitrification treatment in the membrane separation unit storage compartment migrates to other compartments, and aerobic treatment (nitrification treatment) takes place inside and outside the partition plate 7. progress (this time period is referred to as the "nitrification promotion operation time period"). On the other hand, when the liquid level is lower than the partition plate, the liquid flow is interrupted between the membrane separation unit housing compartment and the other compartments, resulting in anoxic conditions in the other compartments and anoxic treatment (denitrification). treatment) progresses (this period of time is referred to as the "denitrification promotion operation period"). As described above, 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 in which the liquid level is higher and lower than the partition plate. be.

Japanese Patent Application Laid-Open No. 2004-261711

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

Furthermore, in sewage treatment, daily fluctuations in the amount of sewage inflow (fluctuations in the amount of inflowing wastewater and the concentration of pollutants) are large. , there is a variation of about 0.2 to 3 times in small-scale processing equipment. With such daily load fluctuations, it was difficult for the method of Patent Document 1 to perform efficient nitrification and denitrification reactions. In addition, in order to reduce daily fluctuations in the amount of sewage inflow, it was necessary to install a large-capacity flow control 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. was not mentioned at all.

In view of the above-mentioned conventional problems, the present invention further improves the nitrogen removal efficiency, makes it possible to easily switch between the nitrification promotion operation time zone and the denitrification promotion operation time zone in a short time, and further reduces the amount of inflowing sewage. It is an object of the present invention to provide a partition plate insertion type membrane separation activated sludge apparatus and method that exhibits high applicability even to daily load fluctuations.

The inventors of the present application have extensively studied the cause of the insufficient nitrogen removal efficiency in the conventional membrane separation activated sludge treatment method of inserting a partition plate. As a result, when the liquid level is lower than the partition plate (during the denitrification promotion operation period), the liquid flow is interrupted inside and outside the partition plate, and circulation flow does not occur in the compartment where the membrane separation unit is not installed. Insufficient mixing of raw water, nitrifying liquid (liquid containing nitrate nitrogen after nitrification) and denitrifying bacteria involved in the denitrification reaction, resulting in difficulty in efficient denitrification reaction. I found

Then, by using a membrane separation activated sludge treatment apparatus having a means for adjusting the amount of circulating water in the reaction tank, it is possible to secure a small amount of circulating flow for achieving the above-mentioned sufficient mixing during the denitrification promotion operation period, In addition, the inventors have conceived that dissolved oxygen (DO), which hinders denitrification, can be maintained at a low level, and as a result, nitrogen removal efficiency is improved. In addition, by using such a membrane separation activated sludge treatment apparatus, it is possible to easily switch between the nitrification-promoting operation period and the denitrification-promoting operation period in a short time. can also be applied, and an efficient progress of the denitrification reaction can be achieved, and the present invention has been completed.

That is, the present invention relates to the following (1) to (5).
(1) A membrane separation activated sludge treatment apparatus having a single reaction tank for performing aerobic treatment and anoxic treatment, an immersion membrane separation unit arranged inside the reaction tank, and an aeration means, wherein the reaction The tank is divided into a plurality of compartments by a partition plate whose bottom is spaced apart from the bottom of the reaction tank, and at least one of the plurality of compartments is provided with an immersion membrane separation unit and an aeration means. In a membrane separation activated sludge treatment apparatus having an aerobic compartment and other compartments for performing anoxic treatment in anoxic conditions, as a means for mixing anoxic sewage in the other compartments A membrane separation activated sludge treatment apparatus characterized by providing a notch in the upper end of the partition plate .

(2) The membrane separation activated sludge treatment apparatus according to (1), wherein a plurality of notches are formed in the upper end of the partition plate .
(3) The membrane separation activated sludge treatment apparatus according to (1) or (2), wherein the notch provided at the upper end of the partition plate is a combination of notches with different depths.
(4) The membrane separation activated sludge treatment apparatus according to any one of (1) to (3), wherein the notch has a semi-elliptical shape.

(5) A membrane separation activated sludge treatment method in which aerobic treatment and anoxic treatment are performed in a single reaction tank in which a submerged membrane separation unit is arranged, wherein the bottom of the submerged membrane separation unit extends from the bottom of the reaction tank. By partitioning with a partition plate provided at a distance and aerating from below the submerged membrane separation unit, the inside of the compartment in which the submerged membrane separation unit is arranged is maintained in an aerobic state, while the other compartments are empty . In the membrane separation activated sludge treatment method in which anoxic treatment is performed in an oxygen state , a notch is provided at the upper end of the partition plate to mix the anoxic wastewater in the other compartment. Separation activated sludge treatment method.

In this specification, the term "anoxic state" does not mean only a complete anoxic state, but also a state in which the oxygen concentration is low enough to reduce nitrate nitrogen to nitrogen molecules by the action of denitrifying bacteria. Used in the sense of inclusion.

According to the present invention, in compartments other than the membrane separation unit accommodation compartment, even during the denitrification promotion operation period, a small amount of circulation flow rate that brings about sufficient mixing of raw water, nitrifying liquid, and denitrifying bacteria necessary for denitrification reaction can be accurately controlled. Because it can be well controlled and ensured, the efficiency of nitrogen removal from organic sewage can be improved. In addition, the nitrification promotion operation time zone and the denitrification promotion operation time zone can be easily switched in a short time, and furthermore, it can be applied to daily fluctuations in the amount of inflow sewage, resulting in efficient membrane separation activated sludge treatment. becomes possible.

It is a figure which shows typically the membrane-separation activated sludge treatment apparatus of the conventional method (patent document 1). FIG. 2 is a diagram schematically showing the flow of circulating water in a partition plate insertion type membrane separation activated sludge treatment apparatus. It is a side view and a top view which show typically the membrane-separation activated sludge treatment apparatus of the conventional method (patent document 1). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view and a top view schematically showing a membrane separation activated sludge treatment apparatus of the present invention; FIG. 4 is a diagram schematically showing another embodiment of the circulating water amount adjusting means of the present invention; FIG. 5 is a diagram schematically showing still another embodiment of the circulating water amount adjusting means of the present invention; FIG. 5 is a diagram schematically showing still another embodiment of the circulating water amount adjusting means of the present invention; FIG. 5 is a diagram schematically showing still another embodiment of the circulating water amount adjusting means of the present invention;

Embodiments of the membrane separation activated sludge treatment apparatus and method according to the present invention will be described below based on the drawings. In addition, in FIGS. 1 to 8, members having the same functions are denoted by the same reference numerals.
As will be described later, the feature of the present invention resides in that a partition plate insertion type membrane separation activated sludge treatment apparatus is provided with a circulating water amount adjusting means. The overall configuration of the mode will be described based on FIG.

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

It is preferable that the membrane separation unit 2 uses a material that is resistant to contamination as the membrane itself, or that has an appropriate gap between the membranes so that the surface of the membrane is resistant to contamination. For the membrane separation unit 2, a module formed using a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, or the like can be used. From the viewpoint of economy, a module using a microfiltration membrane or an ultrafiltration membrane, which has a high filtration rate, can be made compact, and is easy to maintain, is preferable. As for the shape of the membrane, a flat membrane, a hollow fiber membrane, or the like is used. The submerged membrane separation unit itself used here is widely used in this field and is commercially available.

The reaction tank 1 contains sludge containing microorganisms, and the microorganisms act as bacteria that decompose organic matter and further as bacteria that decompose these microorganisms to perform biological treatment. Therefore, it is preferable that the inner surface of the reaction tank 1 has no corners or irregularities so that the sludge is not unevenly distributed and the oxygen is uniformly supplied. As a result, the temperature and pH of the treatment liquid in the reaction tank 1 become uniform, and the decomposition treatment can proceed stably. In addition, microorganisms contained in sludge, such as bacteria, yeast and fungi including mold, contribute to the decomposition of soluble organic matter, etc., and are obtained from nature such as soil, compost, and sludge by enrichment culture and acclimatization. be. It is also possible to isolate and use the main microbial groups involved in decomposition from this acclimation fluid. 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 normally 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 15000 mg/L and HRT (Hydraulic Retention Time) is usually 2 to 24 hours, preferably 4 to 8 hours.

A partition plate 7 is further provided in the reaction vessel 1 of FIG. The partition plate 7 has a bottom portion spaced apart from the bottom surface of the reaction vessel, and surrounds the membrane separation unit 2 in the horizontal direction (opens vertically), but substantially surrounds the membrane separation unit 2. Anything that surrounds you physically is fine. The partition plate 7 may surround the membrane separation unit 2 in combination with the tank wall, and is preferably two flat plates that cooperate with the tank wall of the reaction tank 1 to define a rectangular area. Alternatively, one of the four sides of the membrane separation unit 2 is surrounded by the partition plate 7 and the other three sides are surrounded by the tank wall, or the partition plate 7 surrounds the entire circumference of the membrane separation unit 2. It's okay. The capacity ratio of the storage compartment of the membrane separation unit 2 and the other compartments is usually 1:0.5-5, preferably 1:1-3.

In the specific example of FIG. 4, there is only one storage compartment for the immersion membrane separation unit (hereinafter also referred to as "membrane separation unit storage compartment"), but in the case of large-scale sewage treatment, etc., If desired, a plurality of membrane separation unit storage compartments (aerobic compartments) may be provided and a membrane separation unit may be immersed in each of these compartments in order to increase the throughput of . In this case, it is possible to provide a plurality of compartments other than the membrane separation unit storage compartment (hereinafter also referred to as "other compartments"), but one has a simpler structure and is easier to ensure uniformity of the reaction solution. preferable.

Sewage that has flowed into a sewage treatment facility such as a sewage treatment plant is subjected to separation and removal of sand, dust, etc. in a pretreatment facility, and then introduced as raw water from a raw water tank into a reaction tank 1 by a raw water pump. In the present invention, raw water is preferably supplied to compartments other than the membrane separation unit housing compartment. As a result, the 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 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 is provided for checking the liquid level in the reaction tank, that is, the position of the liquid surface. means for controlling the flow rate of

With such a configuration shown in FIG. 4, wastewater is biologically treated in the reaction tank 1, and the air from the air diffuser 4 prevents sludge substances and the like from adhering to the membrane surface of the membrane separation unit 2. Meanwhile, the treated 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 from the difference between the water level in the reaction tank and the water level at the filtered water outlet, that is, the natural head. Furthermore, filtration pressure may be obtained by pressurizing from the undiluted solution side.

A feature of the present invention is that the membrane separation activated sludge treatment apparatus is provided with circulating water amount adjusting means. The circulating water amount adjusting means adjusts the water amount of the circulating flow formed in the tank by the air from the air diffuser 4 . Here, the term "circulating flow" means that, as shown in FIG. , and returns to the membrane unit accommodation compartment via the area below the partition plate 7. The circulating water amount adjusting means is preferably provided in the upper part or the upper end of the partition plate, and is preferably a means for adjusting the amount of circulating water flowing from the membrane separation unit housing compartment to other compartments.

Hereinafter, the circulating water amount adjusting means in the present invention will be described with reference to FIGS. 4 to 8, but in order to understand the circulating water amount adjusting means of the present invention, The processing equipment is shown in comparison with FIG.
A first embodiment of the circulating water amount adjusting means of the present invention is a swing type circulating water amount adjusting device comprising a circulating water amount adjusting plate and 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 a “swing plate”) 20a, a fixing member 21 for fixing one side of the swing plate in the longitudinal direction, and the swing plate 20a. It is a swing-type circulating water amount adjusting device provided with adjusting plate moving means 22 for swinging. The upper view of FIG. 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 (side view of FIG. 4). In the figure, the circulating water amount adjusting means on the right side is omitted, and in the top view, the adjusting plate moving means 22 is omitted).

A swing plate 20a shown in FIG. 4 is fixed to a rod-shaped fixing member 21 at one of its two longitudinal sides. In addition, the swing plate 20a is detachably connected to the adjusting plate moving means 22. By moving the swing plate 20a up and down by the adjusting plate moving means 22 and swinging it, the opening degree is adjusted at the upper part of the partition plate. can be adjusted.

Here, in the side view of FIG. 4, 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 blocks the circulation flow almost completely. When the swing plate is moved upward and the lower end of the swing plate is higher than the liquid level in the reaction vessel (in the case of full opening), the opening is set to 100%, and the swing plate moves around the fixing member. It is set between 0 and 100% depending on the angle. The degree of opening of the swing plate can be adjusted according to the detected dissolved oxygen concentration (DO value), for example, by installing a dissolved oxygen meter (DO meter) in the reaction tank.

The swing plate may be of any shape such as a rectangular shape, a trapezoidal shape, a flat plate shape, etc., as long as it can adjust the amount of circulating water flowing from the membrane separation unit housing compartment over the partition plate 7 and into the other compartments. Anything is fine. The swing plate 20a shown in FIG. 4 is a rectangular adjusting plate curved in the lateral direction. is preferable because it enables adjustment along the flow of the circulating flow.

The longitudinal length of the swing plate can be about the same length as the upper edge of the partition plate so as to cover the entire upper portion of the partition plate, but a portion of the upper edge of the partition plate, e.g. The length may cover ~1/2. In addition, even when a plurality of partition plates are installed in the reaction vessel, the swing plate need not be installed so as to cover the upper part of all the partition plates, and the length of the upper end of all the partition plates For example, it may be installed at 1/5 to 1/2 of the length of the upper end of the entire partition plate. The length of the swing plate in the lateral direction is such that when the swing plate is moved in the direction of the partition plate (downward) by the adjustment plate moving means 22, the swing plate completely covers the upper part of the partition plate and the circulating flow is almost completely formed. It is preferable to set the length so that it can be blocked. Moreover, the thickness of the swing plate may be any thickness as long as it is strong enough to withstand the control of the circulating flow.

The fixing member 21 is not particularly limited as long as it fixes the swing plate so that it can swing. As the fixing member 21, for example, one side of the swing plate 20a in the longitudinal direction is fixed to the side surface of a bar-shaped fixing member, and both ends of the bar-shaped member are rotatably connected to the tank walls of the reaction tank using bearings. can be configured. Alternatively, a member that is a combination of a hollow tube and a rod-shaped member passing through the hollow tube is used, and one side of the swing plate 20a in the longitudinal direction is fixed to the side surface of the hollow tube, and the hollow Both ends of a rod-like member passing through the tube may be fixed to the tank wall of the reaction tank. With such a configuration, the swing plate 20a can be swung up and down by the adjusting plate moving means 22 while one side of the swing plate 20a in the longitudinal direction is fixed to the fixed member, thereby opening and closing the upper part of the partition plate. can.

The position where both ends of the fixing member 21 are fixed to the tank wall of the reaction tank is set at a position lower than the maximum 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, from the viewpoint of efficiently adjusting the amount of circulating water, both ends of the fixing member 21 are preferably fixed at positions shifted from directly above the partition plate 7 toward the partition other than the membrane separation unit accommodation partition.

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, pneumatic or 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 lateral direction can also be used. If such a swing plate is installed so as to be in a bent state (convex state) in the direction of the adjustment plate moving means 22 (upward), adjustment along the flow of the circulating flow is possible at the upper part of the partition plate, which is preferable. . The circulating water amount adjusting means shown in FIG. 5 has the same configuration as the circulating water amount adjusting means shown in FIG. 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 compartments other than the membrane separation unit storage compartment, even during denitrification promotion operation, a small amount of circulating water that provides sufficient mixing necessary for denitrification reaction is secured, and dissolved oxygen ( DO) can be maintained at a low level, and the nitrogen removal efficiency from organic sewage can be improved.

In the time period during which nitrification is promoted (nitrification promotion operation time period), the opening of the swing plate is increased to ensure a large amount of circulating water, so that the entire reaction tank can be maintained in an aerobic state. As a result, the nitrification reaction can be promoted.

In addition to the swing type configuration shown in FIGS. 4 and 5, a swing plate (circulating water amount adjustment 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 adjustment plate moving means. A circulating water amount adjusting means having a tipping type dam structure that opens and closes the upper part of the partition plate by tipping the swing plate by the adjusting plate moving means can also be used.

Also, in place of the swing plate, a member such as a balloon or a hollow sheet that can be inflated or expanded by introducing air inside is installed at the upper end or upper part of the partition plate to dam the circulating flow. A dam-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 of 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 also installed near the upper end of the partition plate 7 having an opening 32. When the slide plate 30 is slid in the horizontal direction, the opening 31 of the slide plate 30 and the opening 32 of the partition plate overlap each other. By adjusting the condition, the degree of opening (opening ratio) of the partition plate can be adjusted.

Here, the opening degree (opening ratio) of the slide plate is set to 0% when the openings of the partition plate and the openings of the slide plate do not overlap and the circulating flow is almost completely blocked in FIG. The degree of opening is defined as 100% when the openings are completely overlapped with each other and fully opened, and is defined as the ratio of the total area of the openings to the total area of the openings when fully opened. The opening degree (opening ratio) of the slide plate can be adjusted according to the dissolved oxygen concentration (DO value) detected by installing a dissolved oxygen meter (DO meter) in the reaction tank, for example.

The shape of the openings of the slide plate and the partition plate can be appropriately selected from rectangular, circular, elliptical, and the like. Also, the total area of all openings in the area of the entire slide plate is preferably about 1/3 to 2/3. The shape of the slide plate as a whole is not particularly limited, but a rectangular plate that can be easily slid in the horizontal direction can usually be used. By using a 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 driving device such as an electric cylinder or a pneumatic or hydraulic cylinder is used. be able to.

In the case of using a circulating water amount adjusting device equipped with such a slide plate, as shown in FIG. The operating water level is preferably in the range of greater than about one-third above the bottom of the partition opening.

By using the circulating water amount adjusting device having 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 compartments other than the membrane separation unit storage compartment, even during denitrification promotion operation, a small amount of circulating water that provides sufficient mixing necessary for denitrification reaction is secured, and dissolved oxygen ( DO) can be maintained at a low level, and the nitrogen removal efficiency from organic sewage can be improved.

In the time period during which nitrification is promoted (nitrification promotion operation time period), the entire reaction tank can be maintained in an aerobic state and the nitrification reaction can be promoted by adjusting the opening ratio of the slide plate so as to increase. .

A third embodiment of the circulating water amount adjusting means of the present invention is a partition plate having a notch 40 provided at the upper end of the partition plate as shown in FIG. The shape of the notch can be appropriately selected from rectangular, inverted trapezoidal, inverted triangular, semicircular, semielliptical, and the like. Moreover, 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 a means for adjusting the amount of circulating water, the amount of circulating water can be finely and accurately adjusted by adjusting the liquid level in the reaction tank within the range of A to C (FIG. 7). Adjustment is possible. 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 operating hours). When the liquid level is adjusted to a position between B and C, it is possible to fine-tune the amount of circulating water, and during the enhanced denitrification operation period, a small amount of circulation is provided to provide sufficient mixing necessary for the denitrification reaction. It is possible to maintain a low level of dissolved oxygen (DO), which is an obstacle to denitrification, while securing the amount of water, and to proceed with efficient denitrification reaction. Further, when the liquid level is adjusted to a position lower than C, the inside and outside of the partition plate are separated, and a state in which there is no circulation can be achieved.

As for the shape of the notch, in addition to the plurality of notches 40 having approximately the same width and depth as shown in FIG. 7, as shown in FIG. It may be a shape in which the notches 41a to 41c are combined in a certain repeating order. The shape of the notch is not limited to a semi-elliptical shape, and may be any shape such as a rectangular shape, as long as it is possible to finely adjust the amount of circulating water efficiently. In the case of a partition plate with notches of different depths, as shown in FIG. 8, the width of one notch is usually 3-30 cm, preferably 5-25 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 promotion operation period. It can be appropriately set according to the amount of circulating water.

When using a partition plate having a plurality of notches of different depths as shown in FIG. , it is possible to finely adjust the amount of circulating water with high accuracy. Specifically, when the liquid level is adjusted between AB operating hours). When the liquid level is adjusted to a position between B and C, the circulating water volume becomes large, and when the liquid level is adjusted to a position between C and D, the circulating water volume becomes medium, and the liquid level is adjusted to D ~ If the position is adjusted to a position between E, the amount of circulating water will be small, and if the liquid level is adjusted to a position lower than E, the inside and outside of the partition plate will be separated, and there will be no circulating water. can.

Therefore, during the denitrification promotion operation time zone, by adjusting the liquid level to a position between B and E in FIG. 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 denitrification during denitrification promotion operation hours. 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 vessel is not particularly described, and the upper end is assumed to be a flat horizontal surface. In such a partition plate, in order to secure a small amount of circulation flow rate required during the denitrification promotion operation period, it is necessary to control the liquid level at a position about 5 mm to 20 mm from the upper end of the partition plate. It was difficult to precisely control the circulation flow rate due to fluctuations in the amount of sewage, the influence of contaminants, the adhesion of biofilms, and the like. On the other hand, by using a partition plate having notches as shown in FIGS. 7 and 8, it is possible to form a water level difference according to the required circulating flow rate, and it is possible to control the circulating water rate with high accuracy. . Therefore, a flow rate adjusting tank for raw water becomes unnecessary, and even when a flow rate adjusting tank is installed, the capacity can be reduced.

In the membrane separation activated sludge treatment apparatus of the present invention, as the above-described circulating water amount adjusting means, the swing type circulating water amount adjusting apparatus of the first embodiment and the notch at the upper end of the third embodiment are provided. When used in combination with partition plates, the amount of circulating water can be finely adjusted more accurately and efficiently. In this case, the swing plate (circulating water amount adjusting plate) used in the first embodiment completely covers the upper part of the partition plate when moved most in the direction of the partition plate (downward), thereby preventing the circulation flow. It is desirable to have a size or shape that blocks almost completely and completely closes the notched portion at the upper end of the partition plate of the third embodiment.

Since the apparatus and method of the present invention have a wide range of adjustment of the circulating water volume by the circulating water volume control means, the liquid level is adjusted by adjusting the difference between the raw water supply flow rate and the membrane filtration flow rate according to the daily fluctuation of the inflow sewage volume. can be easily controlled. Specifically, when the liquid level in the reaction tank rises, the flow rate of membrane filtration is made higher than the raw water supply flow rate, and when the liquid level becomes low, the raw water supply flow rate is made higher than the membrane filtration flow rate. . When the liquid level in the reaction tank is intermediate between them, the operation is performed so that the raw water supply flow rate and the membrane filtration flow rate are approximately the same. For example, it is necessary to increase the flow rate of raw water during times when the amount of sewage inflow is high. If so, it becomes easy to operate within the circulating water amount adjustable range.

In the present invention, unlike the method of Patent Document 1, it is not necessary to greatly fluctuate the liquid level in order to create an overflow state and a separation state of the liquid inside and outside the partition plate. Raw water can be continuously supplied to the reactor at a constant flow rate so that the optimum amount of circulating water is obtained in each operating time period. Therefore, there is an advantage that it is not necessary to install a special raw water supply device or a raw water flow control device. In the present invention, the term "constant flow rate" means that the flow rate is constant for a predetermined period of time, and may be changed in order to obtain an optimum flow rate.

The present invention is not limited to the above embodiments as long as it is a membrane separation activated sludge treatment apparatus and method provided with a means for adjusting the amount of circulating water. It can be performed under the same conditions as the method.

The present invention can further improve 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 furthermore, can cope with the daily load fluctuation of the amount of sewage inflow. Therefore, it is possible to provide a partition plate insertion type membrane separation activated sludge apparatus and method that exhibit high applicability.

1 Reaction Tank 2 Membrane Separation Unit 3 Suction Pump 4 Aeration Means 5 Blower 6 Level Sensor 7 Partition Plate 8 Raw Water Pump 9 Raw Water Tank 20a, 20b, 20c Circulating Water Volume Control Plate (Swing Plate)
21 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 (5)

A membrane separation activated sludge treatment apparatus having a single reaction tank for performing aerobic treatment and anoxic treatment, an immersion membrane separation unit arranged inside the reaction tank, and an aeration means, the reaction tank comprising: The bottom is divided into a plurality of compartments by a partition plate spaced apart from the bottom of the reaction vessel, and at least one of the plurality of compartments is preferably provided with an immersion membrane separation unit and an aeration means. In a membrane separation activated sludge treatment apparatus having an air compartment and other compartments for performing anoxic treatment under anoxic conditions ,
A membrane separation activated sludge treatment apparatus characterized by providing a notch in the upper end of the partition plate as a means for mixing the oxygen-free sewage in the other compartments. 2. The membrane separation activated sludge treatment apparatus according to claim 1, wherein a plurality of said notches are formed in the upper end of said partition plate . 3. The membrane separation activated sludge treatment apparatus according to claim 1 or 2, wherein the notch provided in the upper end of the partition plate is a combination of notches having different depths. The membrane separation activated sludge treatment apparatus according to any one of claims 1 to 3, wherein said notch has a semi-elliptical shape. A membrane separation activated sludge treatment method in which aerobic treatment and anoxic treatment are performed in a single reaction tank in which a submerged membrane separation unit is arranged, wherein the bottom of the submerged membrane separation unit is separated from the bottom of the reaction tank. By partitioning with the provided partition plate and aerating from below the submerged membrane separation unit, the inside of the compartment where the submerged membrane separation unit is arranged is maintained in an aerobic state, while the other compartments are kept in anoxic conditions. In the membrane separation activated sludge treatment method for performing anoxic treatment , the membrane separation activated sludge is characterized by mixing the oxygen-free wastewater in the other compartment by providing a notch in the upper end of the partition plate. Processing method.

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