Sewage treatment device, control method for sewage treatment device, and program

Abstract

The purpose of the present invention is to provide a sewage treatment device capable of executing sewage treatment efficiently.　A sewage treatment device 10 is provided with a reaction tank 11, an overflow determination unit 13, an operation control unit 14, and a partition plate 15. The reaction tank 11 has a lowest water level LWL at which the supply of sewage is started and a highest water level HWL at which the supply of sewage is stopped, and executes nitrification reaction and denitrification reaction. The partition plate 15 divides the reaction tank 11 into an area 15a in which the nitrification reaction is executed and an area 15b in which the denitrification reaction is executed, and has a partition plate upper end 15d between the lowest water level LWL and the highest water level HWL. The overflow determination unit 13 determines whether the sewage in the area 15a is overflowing the partition plate upper end 15d. The operation control unit 14 has an overflow amount control unit 21 that controls the amount of sewage that overflows the partition plate upper end 15d and a DO control unit 22 that controls the level of dissolved oxygen dissolved in the sewage in the area 15a when the sewage in the area 15a does not overflow the partition plate upper end 15d.

Description

[Technical Field]

[0001] The present invention relates to a sewage treatment device, a control method for a sewage treatment device, and a program.

[0002] Conventionally, the activated sludge process has been known, which biologically treats wastewater containing nitrogen, phosphorus, organic matter, etc. using organic sludge containing microorganisms (hereinafter referred to as "activated sludge"). Biological treatment of wastewater based on the activated sludge process is carried out based on a nitrification reaction that converts ammonia to nitrite and nitrate in the presence of oxygen (aerobic conditions), and a denitrification reaction that converts nitrite and nitrate to nitrogen in anoxic conditions. The nitrification reaction and the denitrification reaction may be carried out in separate reaction tanks, but in light of recent demands for space-saving wastewater treatment facilities, there is known a wastewater treatment device in which the nitrification reaction and the denitrification reaction are carried out in a single reaction tank (see, for example, Patent Document 1).

[0003] FIG. 5 is a schematic diagram of a conventional wastewater treatment system 50, which includes a single reaction tank for carrying out nitrification and denitrification reactions.

[0004] The sewage treatment device 50 in Figure 5 includes a raw water tank 51 for storing sewage, a reaction tank 52 for biologically treating the sewage supplied from the raw water tank 51 by performing nitrification and denitrification reactions on the sewage, partition plates 53 for dividing the reaction tank 52 into multiple compartments and arranged at a distance from the bottom of the reaction tank 52, and a level sensor LS for detecting the level of the sewage in the reaction tank 52.The area 54 surrounded by the partition plate 53 has a membrane separation device 55 for removing solids from the biologically treated sewage, an aeration device 56a located closer to the bottom of the reaction tank 52 than the membrane separation device 55 and supplying air or the like as bubbles to the membrane separation device 55, and an aeration device 56b for supplying air or the like as bubbles to the area 54 to supplement the amount of oxygen required for the nitrification reaction.

[0005] The partition plate 53 has a partition plate lower end 53a located near the bottom of the reaction tank 52 and the aeration devices 56a and 56b, and a partition plate upper end 53b located far from the aeration devices 56a and 56b. The reaction tank 52 is set with a minimum water level (LWL) at which the supply of wastewater from the raw water tank 51 to the reaction tank 52 begins, and a maximum water level (HWL) at which the supply of wastewater from the raw water tank 51 to the reaction tank 52 is stopped. The minimum water level LWL is located between the partition plate upper end 53b and the membrane separation device 55, and the maximum water level HWL is located between the opening 52a of the reaction tank 52 and the partition plate upper end 53b.

[0006] Region 54 is in an aerobic state because air is supplied as bubbles from, for example, air diffusers 56a and 56b, while region 57 surrounded by reaction tank 52 and partition plate 53 is in an anaerobic state because no air is supplied. Therefore, in region 54, a nitrification reaction that converts ammonia into nitrite and nitrate proceeds, while in region 57, a denitrification reaction that converts nitrite and nitrate into nitrogen proceeds.

[0007] When the wastewater level is between the highest water level HWL and the upper end 53b of the partition plate, the wastewater in region 54 overflows the upper end 53b of the partition plate due to the air supplied from the air diffusers 56a and 56b, forming a circulation flow 60 ( FIG. 6 ) that circulates around the partition plate 53. At this time, nitrite and nitrate are produced in region 54 through a nitrification reaction, and the produced nitrite and nitrate move from region 54 to region 57 through the circulation flow 60. The nitrite and nitrate that move to region 57 are converted to nitrogen through a denitrification reaction. On the other hand, when the wastewater level is between the upper end 53b of the partition plate and the lowest water level LWL, the wastewater in region 54 does not overflow the upper end 53b of the partition plate. In other words, the circulation flow 60 is not formed. Therefore, the nitrite and nitrate produced through the nitrification reaction do not move from region 54 to region 57.

[0008] Therefore, in order for the denitrification reaction to proceed efficiently in region 57 when circulating flow 60 is not formed, it is necessary that a considerable amount of nitrous acid and nitric acid be generated in advance when circulating flow 60 is formed, and that the generated nitrous acid and nitric acid move from region 54 to region 57. In response to this, the air diffuser 56b supplies the maximum amount of air or the like that can be supplied to region 54 as air bubbles. As a result, when the wastewater level is between the highest water level HWL and the upper end portion 53b of the partition plate, the maximum-scale circulating flow 60 is formed, and the nitrous acid and nitric acid are reliably moved from region 54 to region 57. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-261711 Summary of the Invention [Problem to be solved by the invention]

[0010] However, if the air diffuser 56b supplies the maximum amount of air or the like that it can supply to the region 54 as air bubbles, when the wastewater level is between the highest water level HWL and the upper end 53b of the partition plate, there is a risk that not only nitrite and nitrate but also oxygen will move from the region 54 to the region 57 due to the maximum-scale circulating flow 60. In this case, the region 57 is not in an anoxic state and the denitrification reaction does not proceed for a certain period of time after the wastewater level changes from the upper end 53b of the partition plate to the lowest water level LWL and the circulating flow 60 disappears.

[0011] Furthermore, the air diffuser 56b supplies the maximum amount of air and the like that can be supplied as air bubbles to the region 54 even when the wastewater level is between the upper end 53b of the partition plate and the lowest water level LWL. Therefore, there is a risk that the air diffuser 56b may be supplying excessive oxygen relative to the progress of the nitrification reaction, and in this case, unnecessary power consumption occurs in the operation of the air diffuser 56b.

[0012] In other words, when the wastewater does not overflow the upper end 53b of the partition plate, the nitrification reaction in region 54 and the denitrification reaction in region 57 are not carried out under optimal conditions, which causes a problem that wastewater treatment cannot be carried out efficiently.

[0013] An object of the present invention is to provide a sewage treatment device, a control method for a sewage treatment device, and a program that can efficiently perform sewage treatment. [Means for solving the problem]

[0014] In order to achieve the above object, the wastewater treatment device of the present invention comprises a reaction tank having a first water level at which the supply of wastewater is started and a second water level at which the supply of said wastewater is stopped, and performing a first treatment for treating said wastewater under conditions in the presence of oxygen and a second treatment for treating said wastewater under conditions in the absence of oxygen; a dividing means for dividing said reaction tank into an area for performing said first treatment and an area for performing said second treatment, said dividing means having an end between said first water level and said second water level; an oxygen supply means for supplying a gas containing oxygen to the region where the first process is performed; The apparatus is provided with a determination means for determining whether or not the wastewater in the area where the first treatment is performed is overflowing the end portion, and a control means for controlling the amount of wastewater overflowing the end portion when the wastewater in the area where the first treatment is performed is overflowing the end portion, and for controlling the concentration of oxygen dissolved in the wastewater in the area where the first treatment is performed when the wastewater in the area where the first treatment is performed is not overflowing the end portion. The control means controls the amount of wastewater overflowing the end portion by adjusting the amount of gas supplied to the region where the first treatment is performed by the oxygen supply means, or by adjusting the first water level or the second water level. It is characterized by the following.

[0015] In order to achieve the above object, the control method of the present invention for treating sewage includes a reaction tank having a first water level at which the supply of sewage is started and a second water level at which the supply of said sewage is stopped, and performing a first treatment for treating said sewage under conditions in the presence of oxygen and a second treatment for treating said sewage under conditions in the absence of oxygen; a dividing means for dividing said reaction tank into an area for performing said first treatment and an area for performing said second treatment, said dividing means having an end between said first water level and said second water level; an oxygen supply means for supplying a gas containing oxygen to the region where the first process is performed;a control step of controlling the amount of sewage overflowing the end portion when the sewage in the area where the first treatment is performed is overflowing the end portion, and a control step of controlling the dissolved oxygen concentration in the sewage in the area where the first treatment is performed when the sewage in the area where the first treatment is performed is not overflowing the end portion. The control step controls the amount of wastewater overflowing the end portion by adjusting the amount of gas supplied by the oxygen supply means to the region where the first treatment is performed, or by adjusting the first water level or the second water level. It is characterized by:

[0016] In order to achieve the above object, the program of the present invention includes a reaction tank having a first water level at which the supply of wastewater is started and a second water level at which the supply of said wastewater is stopped, and performing a first treatment for treating said wastewater under conditions in the presence of oxygen and a second treatment for treating said wastewater under conditions in the absence of oxygen; a dividing means for dividing said reaction tank into an area for performing said first treatment and an area for performing said second treatment, said dividing means having an end between said first water level and said second water level; an oxygen supply means for supplying a gas containing oxygen to the region where the first process is performed; a control step of controlling the amount of sewage overflowing the end portion when the sewage in the area where the first treatment is performed is overflowing the end portion, and a control step of controlling the dissolved oxygen concentration in the sewage in the area where the first treatment is performed when the sewage in the area where the first treatment is performed is not overflowing the end portion. The control step controls the amount of wastewater overflowing the end portion by adjusting the amount of gas supplied by the oxygen supply means to the region where the first treatment is performed, or by adjusting the first water level or the second water level. It is characterized by:

[0017] In order to achieve the above object, the storage medium of the present invention comprises a reaction tank having a first water level at which the supply of wastewater is started and a second water level at which the supply of said wastewater is stopped, and performing a first process for treating said wastewater under conditions in the presence of oxygen and a second process for treating said wastewater under conditions in the absence of oxygen; a dividing means for dividing said reaction tank into an area for performing said first process and an area for performing said second process, said dividing means having an end between said first water level and said second water level; an oxygen supply means for supplying a gas containing oxygen to the region where the first process is performed;a computer-readable storage medium storing a program for causing a computer to execute a control method for a sewage treatment device, the control method for the sewage treatment device including: a determining step of determining whether or not sewage in an area where the first treatment is performed is overflowing the end portion; and a control step of controlling the amount of sewage overflowing the end portion when the sewage in the area where the first treatment is performed is overflowing the end portion, and controlling the dissolved oxygen concentration in the sewage in the area where the first treatment is performed when the sewage in the area where the first treatment is performed is not overflowing the end portion. The control step controls the amount of wastewater overflowing the end portion by adjusting the amount of gas supplied by the oxygen supply means to the region where the first treatment is performed, or by adjusting the first water level or the second water level. It is characterized by: [Effects of the Invention]

[0018] According to the present invention, wastewater treatment can be carried out efficiently. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram of a wastewater treatment device according to an embodiment of the present invention. [Figure 2] 2 is a schematic diagram for explaining a circulation flow circulating around the partition plate in FIG. 1. FIG. [Figure 3] 2 is a block diagram showing an outline of the internal configuration of an operation control unit shown in FIG. 1. FIG. [Figure 4] 2 is a flowchart showing a procedure for sewage treatment carried out by the sewage treatment device of FIG. 1. [Figure 5] FIG. 1 is a schematic diagram of a conventional sewage treatment device. [Figure 6] 6 is a diagram for explaining a circulating flow formed in the sewage treatment device of FIG. 5. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0021] FIG. 1 is a schematic diagram of a wastewater treatment device 10 according to an embodiment of the present invention.

[0022] 1 includes a reaction tank 11, a photographing device 12 (image forming means), an overflow determination unit 13 (determination means), and an operation control unit 14 (control means). The reaction tank 11 includes a partition plate 15 (separation means), a membrane separation device 16, aeration devices 17a and 17b, pumps 18a and 18b, blowers 19a and 19b, a level sensor LS, and a dissolved oxygen meter DO. The reaction tank 11 is connected to a raw water tank (not shown) that stores the wastewater to be treated via pump 18a. The pump 18a and the level sensor LS, the photographing device 12 and the overflow determination unit 13, the overflow determination unit 13 and the operation control unit 14, the operation control unit 14 and the blower 19b, the operation control unit 14 and the dissolved oxygen meter DO, the blower 19b and the aeration device 17b (oxygen supply means), the aeration device 17a and the blower 19a, and the membrane separation device 16 and the pump 18b are also connected.

[0023] Wastewater is supplied to the reaction tank 11 from a raw water tank (not shown) by a pump 18a, and the supplied wastewater is biologically treated by activated sludge. In this embodiment, the pump 18a performs intermittent operation by repeatedly starting and stopping. The biological treatment of the wastewater is carried out based on a nitrification reaction (first treatment carried out under oxygen-free conditions) that converts ammonia to nitrite and nitrate in the presence of oxygen, and a denitrification reaction (second treatment carried out under oxygen-free conditions) that converts nitrite and nitrate into nitrogen in the absence of oxygen. Partition plates 15 divide the reaction tank 11 into multiple compartments and are arranged at a distance from the bottom of the reaction tank 11.

[0024] The membrane separation device 16 is disposed in an area 15a (area where the first treatment is performed) surrounded by the partition plate 15, and when the pump 18b is operating, it performs continuous operation, and the biologically treated wastewater is filtered by the membrane separation device 16. As a result, solids are removed from the biologically treated wastewater, and the treated water, which is the filtrate, is discharged outside the reaction tank 11. Therefore, the level of the wastewater in the reaction tank 11 changes depending on the supply of wastewater to the reaction tank 11 and the discharge of treated water outside the reaction tank 11. Note that the membrane separation device 16 may be any device as long as it is capable of removing solids from the biologically treated wastewater, and for example, a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, or the like formed as a flat membrane or a hollow fiber membrane can be used.

[0025] The dissolved oxygen meter DO is disposed in region 15a. Furthermore, air diffusers 17a and 17b are disposed closer to the bottom of reaction tank 11 than membrane separation device 16, and supply air (oxygen-containing gas) from blowers 19a and 19b as air bubbles toward region 15a. This creates oxygen in region 15a, and the dissolved oxygen meter DO measures the dissolved oxygen concentration of the wastewater in region 15a. Meanwhile, region 15b (the region where the second treatment is performed), surrounded by reaction tank 11 and partition plate 15, is anoxic because no air is supplied. Therefore, during the biological treatment of the wastewater, a nitrification reaction that converts ammonia to nitrite and nitrate proceeds in region 15a, while a denitrification reaction that converts nitrite and nitrate to nitrogen proceeds in region 15b. The nitrification reaction is carried out by nitrifying bacteria in activated sludge, and the denitrification reaction is carried out by denitrifying bacteria in activated sludge.

[0026] Both air diffusers 17a and 17b supply air bubbles toward region 15a. However, since membrane separation device 16 filters wastewater, sludge and other substances in the wastewater adhere to the membrane surface of membrane separation device 16. If this is left unchecked, membrane separation device 16 will become clogged and will be unable to filter the wastewater. In response to this, air diffuser 17a supplies air bubbles to the membrane surface of membrane separation device 16 to clean the membrane surface of membrane separation device 16, thereby preventing sludge and other substances from adhering to the membrane surface of membrane separation device 16.

[0027] The air diffuser 17a supplies air bubbles to the membrane surface of the membrane separation device 16, which in turn supplies the air bubbles toward the region 15a. Although oxygen exists in the region 15a, the oxygen supplied to the region 15a from the air diffuser 17a is insufficient to provide the oxygen required by the nitrifying bacteria that carry out the nitrification reaction in the region 15a. In response to this, the air diffuser 17b supplies the oxygen that is insufficient to the region 15a.

[0028] The reaction tank 11 is set with a minimum water level LWL (first water level) at which the supply of wastewater to the reaction tank 11 begins, and a maximum water level HWL (second water level) at which the supply of wastewater to the reaction tank 11 is stopped. The wastewater level is detected by a level sensor LS. When the level sensor LS detects the minimum water level LWL, the supply of wastewater begins. When the level sensor LS detects the maximum water level HWL, the supply of wastewater to the reaction tank 11 is stopped. The partition plate 15 has a partition plate lower end 15c located near the bottom of the reaction tank 11 and the aeration devices 17a and 17b, and a partition plate upper end 15d (end) located far from the aeration devices 17a and 17b. The minimum water level LWL is located between the partition plate upper end 15d and the membrane separation device 16, and the maximum water level HWL is located between the opening 11a of the reaction tank 11 and the partition plate upper end 15d.

[0029] When the wastewater level in the reaction tank 11 is between the highest water level HWL and the upper end 15d of the partition plate, air is supplied from the air diffusers 17a and 17b, which causes an upward flow from the bottom of the reaction tank 11 to the opening 11a around the membrane separation device 16, and the wastewater in the region 15a flows over the upper end 15d of the partition plate to move to the region 15b, thereby forming a circulation flow 20 that circulates around the partition plate 15 (FIG. 2). In the region 15a, a nitrification reaction proceeds to produce nitrite and nitrate, which then move to the region 15b together with the circulation flow 20, where a denitrification reaction proceeds based on the nitrite and nitrate that have moved from the region 15a.

[0030] When the wastewater level in the reaction tank 11 is between the upper end 15d of the partition plate and the lowest water level LWL, air is supplied from the air diffusers 17a and 17b, forming an upward flow from the bottom of the reaction tank 11 to the opening 11a around the membrane separation device 16, but the flow of wastewater is interrupted between the regions 15a and 15b, and the wastewater in the region 15a does not overflow the upper end 15d of the partition plate, so that the circulation flow 20 circulating around the partition plate 15 is not formed. In the region 15a, a nitrification reaction proceeds to produce nitrite and nitrate, and in the region 15b, a denitrification reaction proceeds based on the nitrite and nitrate that moved from the region 15a before the flow of wastewater was interrupted.

[0031] The photographing device 12 is disposed, for example, at the opening 11a of the reaction tank 11. Specifically, the photographing device 12 is fixed to the opening 11a of the reaction tank 11 with bolts, nuts, etc. This fixes the photographing range of the photographing device 12, and when the photographing device 12 takes a photograph, an image corresponding to that photographing range is formed. The image formed by the photographing device 12 may be either a still image or a video. In this embodiment, the photographing device 12 is fixed at a position where it photographs, as a subject, at least a portion of the upper end 15d of the partition plate that is exposed from the wastewater when the water level of the wastewater is between the upper end 15d of the partition plate and the lowest water level LWL (hereinafter referred to as the "discrimination image photographing range").

[0032] Therefore, when the wastewater level is between the highest water level HWL and the upper end 15d of the partition plate, a circulating flow 20 is formed, so that the upper end 15d of the partition plate is submerged in the wastewater and is not recognized in the image formed by the photographing device 12, but when the wastewater level is between the upper end 15d of the partition plate and the lowest water level LWL, a circulating flow 20 is not formed, so that at least a part of the upper end 15d of the partition plate is exposed from the wastewater and is recognized in the image formed by the photographing device 12. The photographing device 12 transmits the formed image to the overflow determination unit 13.

[0033] The overflow determination unit 13 determines whether the image received from the photographing device 12 is an overflow image in which the wastewater in the area 15a is overflowing the partition plate 15, or a non-overflow image in which the wastewater in the area 15a is not overflowing the partition plate 15. Specifically, when at least a part of the upper end 15d of the partition plate is recognized in the image formed by the photographing device 12, the overflow determination unit 13 determines the image as a non-overflow image indicating that the circulating flow 20 is not formed and the wastewater in the area 15a is not overflowing the partition plate 15, and when the upper end 15d of the partition plate is not recognized in the image formed by the photographing device 12, the overflow determination unit 13 determines the image as an overflow image indicating that the circulating flow 20 is formed and the wastewater in the area 15a is overflowing the partition plate 15.

[0034] Incidentally, in order to determine whether an image formed by the photographing device 12 is an overflow image or a non-overflow image, the overflow determination unit 13 performs deep learning on a large number of overflow images and non-overflow images formed in advance by the photographing device 12. In this embodiment, the overflow determination unit 13 performs deep learning based on a CNN (Convolutional Neural Network) model in which the system automatically extracts and learns the features of each of a large number of images that are the subject of learning through multi-stage arithmetic processing.

[0035] Specifically, the overflow determination unit 13 performs convolution operations to extract local features of the overflow image, pooling operations to compress the data while retaining important features of the overflow image, and fully connected operations to combine multiple features obtained by performing convolution operations, pooling operations, etc. on the overflow image, calculates the unique features of the overflow image as specific values, and performs deep learning by associating the specific values ​​with the fact that it is an overflow image.

[0036] In addition, the overflow determination unit 13 performs deep learning by performing convolution operations to extract local features of the non-overflow image, pooling operations to compress the data while retaining important features of the non-overflow image, and fully connected operations to combine multiple features obtained by performing convolution operations, pooling operations, etc. on the non-overflow image, calculating the unique features of the non-overflow image as specific values, and associating the specific values ​​with the fact that the image is a non-overflow image.

[0037] When the overflow determination unit 13, which has performed deep learning on overflow images and non-overflow images, receives a new image to be determined as either an overflow image or a non-overflow image, it performs processes on the new image, such as convolution processing to extract local features of the new image, pooling processing to compress the data while retaining important features of the new image, and fully connected processing to combine multiple features obtained by performing convolution processing, pooling processing, etc. on the new image, calculates the unique feature of the new image as a specific value, and determines whether the new image is an overflow image or a non-overflow image based on the calculated specific value.The overflow determination unit 13 then transmits whether the new image is an overflow image or a non-overflow image to the operation control unit 14.

[0038] FIG. 3 is a block diagram that schematically shows the internal configuration of the operation control unit 14 in FIG.

[0039] The operation control unit 14 in Fig. 3 includes an overflow rate control unit 21 and a DO control unit 22. When the overflow determination unit 13 determines that a new image, which should be determined as either an overflow image or a non-overflow image, is an overflow image, the overflow rate control unit 21 controls the overflow rate of wastewater overflowing the partition plate upper end 15d. When the overflow determination unit 13 determines that a new image, which should be determined as either an overflow image or a non-overflow image, is a non-overflow image, the DO control unit 22 controls the dissolved oxygen concentration in the region 15a.

[0040] When the overflow determination unit 13 determines that the new image is an overflow image, the circulating flow 20 is formed, so that the nitrification reaction proceeds in the region 15a to produce nitrate and nitrite, and the nitrate and nitrite produced in the region 15a move to the region 15b together with the circulating flow 20, and in the region 15b, a denitrification reaction proceeds based on the nitrite and nitrate that have moved from the region 15a. At this time, most of the bubbles supplied from the aeration devices 17a and 17b toward the region 15a pass through the region 15a and are released from the surface of the wastewater without moving to the region 15b.

[0041] That is, in order for the denitrification reaction to proceed efficiently in region 15b when circulating flow 20 is formed, the amounts of nitrate and nitrite moving from region 15a to region 15b are important, and the amounts of nitrate and nitrite moving from region 15a to region 15b are determined by the overflow rate of wastewater overflowing the upper end portion 15d of the partition plate. Therefore, an optimal overflow rate for efficiently proceeding with the denitrification reaction in region 15b when circulating flow 20 is formed is set in overflow rate control portion 21.

[0042] The overflow rate set in the overflow rate control unit 21 (hereinafter referred to as the "set overflow rate") is a value obtained by multiplying the normal average treatment rate, which is the amount of wastewater treated per day by the sewage treatment device 10, by a predetermined magnification factor. The predetermined magnification factor may be 1 to 30 times, and is preferably 3 to 10 times. When the set overflow rate is less than 1 time, only a small amount of the nitrate and nitrite generated in region 15a moves to region 15b, and this small amount is quickly consumed by the denitrification reaction. Therefore, even though the denitrifying bacteria have room to carry out the denitrification reaction, the nitrate and nitrite necessary for the denitrification reaction are not present in region 15b, and the denitrification reaction is not carried out efficiently.

[0043] Furthermore, when the set overflow rate exceeds 30 times, the amount of wastewater overflowing the upper end 15d of the partition plate is so large that oxygen dissolved in the wastewater moves from region 15a to region 15b, creating a period of time in region 15b where the state is not anoxic. The denitrification reaction does not proceed during this period, and therefore is not carried out efficiently. For these reasons, the set overflow rate should be set to 1 to 30 times the normal average treatment volume of the wastewater treatment device 10. Furthermore, although the quality of the wastewater treated in the reaction tank 11 changes over time, if the set overflow rate is set to 3 to 10 times the normal average treatment volume of the wastewater treatment device 10, even if the quality of the wastewater changes, the effect on the quality of the treated water discharged from the reaction tank 11 is minimal, allowing for stable wastewater treatment.

[0044] The overflow rate control unit 21 controls the overflow rate of wastewater overflowing the upper end 15d of the partition plate by adjusting at least one parameter, for example, the position of the upper end 15d of the partition plate, the position of the highest water level (HWL), the position of the lowest water level (LWL), the amount of wastewater supplied from the raw water tank (not shown) to the reaction tank 11, the amount of treated water filtered by the membrane separation device 16 and discharged outside the reaction tank 11, or the amount of air bubbles supplied from the air diffuser 17b to the region 15a. Adjusting each of these parameters controls the time it takes for wastewater to overflow from the region 15a to the region 15b and the amount of overflow of wastewater overflowing from the region 15a to the region 15b per unit time. In this embodiment, the overflow rate control unit 21 controls the overflow rate of wastewater to a set overflow rate by adjusting the position of the highest water level (HWL), the position of the lowest water level (LWL), or the amount of air bubbles supplied from the air diffuser 17b to the region 15a.

[0045] When the overflow determination unit 13 determines that the new image is a non-overflow image, the circulating flow 20 is not formed. Therefore, the nitrification reaction proceeds in the region 15a to produce nitrate and nitrite, but the nitrate and nitrite produced in the region 15a do not move to the region 15b. In the region 15b, a denitrification reaction is carried out based on the nitrite and nitrate that have already moved from the region 15a to the region 15b.

[0046] When the overflow determination unit 13 determines that the new image is a non-overflow image, the DO control unit 22 controls the dissolved oxygen concentration in the region 15a to, for example, 1 to 3 mg-O2 / L in order to remove organic matter from the wastewater or oxidize ammonia. The dissolved oxygen concentration in the region 15a is controlled, for example, by adjusting the amount of air bubbles supplied from the air diffuser 17b to the region 15a.

[0047] FIG. 4 is a flowchart showing the procedure of wastewater treatment carried out by the wastewater treatment device 10 of FIG.

[0048] 4, first, wastewater is supplied from a raw water tank (not shown) to the reaction tank 11 by a pump 18a operating intermittently (S1). When the wastewater level rises and exceeds the upper end 15d of the partition plate on the maximum water level HWL side, an upward flow is formed around the membrane separation device 16, and the wastewater overflows the region 15a and moves to the region 15b, forming a circulating flow 20 (S2). After that, the level sensor LS detects the maximum water level HWL, and the supply of wastewater to the reaction tank 11 is stopped (S3).

[0049] Although the supply of wastewater to the reaction tank 11 is stopped, the pump 18b is still operating, so the biologically treated wastewater is filtered by the membrane separation device 16, and the filtrate, or treated water, is discharged outside the reaction tank 11. Therefore, the level of the wastewater gradually drops and reaches the upper end 15d of the partition plate.

[0050] When the wastewater level is between the highest water level HWL and the upper end 15d of the partition plate and a circulating flow 20 is formed, the photographing device 12 photographs the discrimination image photographing range at regular time intervals, for example, at intervals of one second, to form images, and transmits the images to the overflow determination unit 13 (S4). The overflow determination unit 13 receives the images from the photographing device 12 (S5), performs predetermined processing on the images, and determines whether or not the images are overflow images (determination step).

[0051] Here, since the photographing device 12 photographs the discrimination image photographing range and forms an image when the circulating flow 20 is formed in S4, the following processing will be explained on the assumption that the overflow determination unit 13 determines that the image received from the photographing device 12 is an overflow image.

[0052] The overflow determination unit 13 determines that the image received from the photographing device 12 is an overflow image, and transmits to the operation control unit 14 that the image received from the photographing device 12 is an overflow image (S6). The operation control unit 14 receives the overflow image determination result from the overflow determination unit 13, and in response, the overflow amount control unit 21 controls the overflow amount of the wastewater overflowing the upper end portion 15d of the partition plate (S7, control step). Specifically, the overflow amount control unit 21 controls the overflow amount of the wastewater to a set overflow amount (1 to 30 times the normal average treatment amount).

[0053] The overflow rate of wastewater is controlled by adjusting at least one parameter, for example, the position of the upper end 15d of the partition plate, the position of the highest water level HWL, the position of the lowest water level LWL, the amount of wastewater supplied from the raw water tank (not shown) to the reaction tank 11, the amount of treated water filtered by the membrane separation device 16 and discharged outside the reaction tank 11, or the amount of air bubbles supplied from the air diffuser 17b to the region 15a. In this embodiment, the overflow rate control unit 21 controls the overflow rate of wastewater to a set overflow rate by adjusting the position of the highest water level HWL, the position of the lowest water level LWL, or the amount of air bubbles supplied from the air diffuser 17b to the region 15a.

[0054] When the wastewater level in the reaction tank 11 continues to drop and exceeds the upper end 15d of the partition plate toward the lowest water level (LWL), an upward flow is formed from the bottom of the reaction tank 11 to the opening 11a around the membrane separation device 16, but the flow of wastewater is divided between areas 15a and 15b by the partition plate 15, and the wastewater in area 15a does not overflow the upper end 15d of the partition plate, and therefore the circulation flow 20 circulating around the partition plate 15 disappears (S8).

[0055] When the wastewater level is between the upper end 15d of the partition plate and the lowest water level LWL and no circulating flow 20 is formed, the photographing device 12 photographs the discrimination image photographing range at regular time intervals, for example, at one-second intervals, to form images, and transmits the images to the overflow determination unit 13 (S9). The overflow determination unit 13 receives the images from the photographing device 12 (S10), performs predetermined processing on the images, and determines whether or not the images are non-overflow images (determination step).

[0056] Here, since the photographing device 12 photographs the discrimination image photographing range and forms an image when the circulating flow 20 is not formed in S9, the following processing will be explained on the assumption that the overflow determination unit 13 determines that the image received from the photographing device 12 is a non-overflow image.

[0057] The overflow determination unit 13 determines that the image received from the photographing device 12 is a non-overflow image, and transmits to the operation control unit 14 that the image received from the photographing device 12 is a non-overflow image (S11). The operation control unit 14 receives the non-overflow image determination result from the overflow determination unit 13, and in response, the DO control unit 22 controls the dissolved oxygen concentration in the region 15a to, for example, 1 to 3 mg-O2 / L (S12, control step). Because the dissolved oxygen concentration in the region 15a varies based on the amount of bubbles supplied from the air diffuser 17b to the region 15a, the DO control unit 22 controls the dissolved oxygen concentration in the region 15a to 1 to 3 mg-O2 / L by adjusting the amount of bubbles supplied from the air diffuser 17b to the region 15a.

[0058] After that, the wastewater level drops further and reaches the lowest water level LWL (S13), and this process ends. When the wastewater level reaches the low water level LWL, the level sensor LS detects the lowest water level LWL, and the wastewater process shown in Figure 4 starts again.

[0059] 4, when the sewage level is between the highest water level HWL and the partition upper end 15d and a circulating flow 20 is formed, the photographing device 12 photographs the discrimination image photographing range to form an image, and the overflow determination unit 13 transmits a discrimination result that the image is an overflow image to the operation control unit 14 (S2 to S6). The overflow amount control unit 21 controls the overflow amount of the sewage overflowing the partition upper end 15d based on the discrimination result received by the operation control unit 14, i.e., the discrimination result indicating an overflow image (S7).

[0060] As a result, the nitrification reaction proceeds in region 15a to produce nitrate and nitrite, and the produced nitrate and nitrite move from region 15a to region 15b in accordance with the controlled overflow rate. Therefore, the denitrification reaction in region 15b proceeds not only when the circulating flow 20 is formed, but also when the circulating flow 20 is not formed based on a sufficient amount of nitrate and nitrite that has already moved from region 15a to region 15b in accordance with the controlled overflow rate, thereby eliminating time periods in which the denitrification reaction does not proceed in wastewater treatment.

[0061] Furthermore, when the wastewater level is between the upper end 15d of the partition plate and the lowest water level LWL and no circulating flow 20 is formed, the photographing device 12 photographs the discrimination image photographing range to form an image, and the overflow determination unit 13 transmits a discrimination result that the image is a non-overflow image to the operation control unit 14 (S9-S11). The DO control unit 22 controls the dissolved oxygen concentration in the region 15a based on the discrimination result received by the operation control unit 14, i.e., the discrimination result indicating a non-overflow image (S12).

[0062] This ensures that sufficient oxygen is supplied to the nitrification reaction that occurs in the region 15a when the circulating flow 20 is not formed, thereby reducing the power consumption of the diffuser 17b, which would otherwise be required to supply excess oxygen if oxygen unnecessary for the nitrification reaction were excessively supplied from the diffuser 17b. That is, by accurately determining whether the circulating flow 20 is formed or not, and controlling the amount of wastewater overflowing the upper end 15d of the partition plate when the circulating flow 20 is formed (S7), and controlling the dissolved oxygen concentration in the region 15a when the circulating flow 20 is not formed (S12), the nitrification reaction and denitrification reaction in the regions 15a and 15b when the circulating flow 20 is formed and the nitrification reaction and denitrification reaction in the regions 15a and 15b when the circulating flow 20 is not formed proceed under optimal conditions, thereby enabling efficient wastewater treatment.

[0063] Furthermore, when the sewage treatment device 10 performed the sewage treatment shown in Figure 4, the power consumption of the aeration device 17b in the sewage treatment device 10 was approximately 20% of the power consumption of the aeration device 56b in the conventional sewage treatment device 50, thereby reducing the unnecessary power consumption caused by the operation of the aeration device 56b.

[0064] The present invention provides software (programs) that realize the functions of the above-described embodiments to a system or device via a network or various storage media, and the computer (CPU, MPU, etc.) of the system or device reads and executes the programs. The programs and the computer-readable storage media that store the programs constitute the present invention, and may be applied to a system consisting of multiple devices, or to a device consisting of a single device.

[0065] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. [Explanation of symbols]

[0066] HWL Highest water level LWL Lowest water level 10 Sewage treatment equipment 11 Reaction tank 12 Imaging equipment 13 Overflow judgment section 14 Operation control unit 15 Divider 15a area 15b area 15d Partition plate upper end 17b Air diffuser 21 Overflow control section 22 DO control unit

Claims

1. a reaction tank having a first water level at which the supply of wastewater is started and a second water level at which the supply of said wastewater is stopped, and which performs a first treatment for treating said wastewater under conditions in the presence of oxygen and a second treatment for treating said wastewater under conditions in the absence of oxygen; a dividing means for dividing the reaction tank into an area for performing the first treatment and an area for performing the second treatment, the dividing means having an end between the first water level and the second water level; an oxygen supply means for supplying a gas containing oxygen to the region where the first process is performed; a determination means for determining whether or not the wastewater in the area where the first treatment is performed is overflowing the end portion; a control means for controlling the amount of wastewater overflowing the end portion when the wastewater in the area where the first treatment is performed overflows the end portion, and for controlling the dissolved oxygen concentration in the wastewater in the area where the first treatment is performed when the wastewater in the area where the first treatment is performed does not overflow the end portion, The control means controls the amount of wastewater overflowing the end by adjusting the amount of gas supplied by the oxygen supply means to the area where the first treatment is performed, or by adjusting the first water level or the second water level.

2. further comprising an image forming means for photographing the surface of the wastewater in the reaction tank and forming an image; the image forming means is disposed at a position where it photographs a part of the end portion as a subject when the water level of the wastewater in the reaction tank is between the first water level and the end portion, 2. The wastewater treatment device according to claim 1, wherein the determining means makes the determination based on the image.

3. 3. The wastewater treatment apparatus according to claim 1, wherein the control means controls the amount of wastewater overflowing the end portion to 1 to 30 times the amount of wastewater to be treated per day.

4. 4. The wastewater treatment device according to claim 1, wherein when the control means controls the oxygen concentration dissolved in the wastewater in the area where the first treatment is performed, the oxygen supply means adjusts the amount of gas supplied to the area where the first treatment is performed.

5. The control means controls the concentration of oxygen dissolved in the wastewater in the area where the first treatment is performed to 1 to 3 mg-O 2 5. The sewage treatment device according to claim 1, wherein the sewage treatment device is controlled to a temperature of 1 / L.

6. A method for controlling a wastewater treatment device, comprising: a reaction tank having a first water level at which a supply of wastewater is started and a second water level at which the supply of said wastewater is stopped, and performing a first treatment for treating said wastewater under conditions in the presence of oxygen and a second treatment for treating said wastewater under conditions in the absence of oxygen; a dividing means for dividing said reaction tank into an area for performing said first treatment and an area for performing said second treatment, said dividing means having an end between said first water level and said second water level; and an oxygen supplying means for supplying an oxygen-containing gas to the area for performing said first treatment, a determining step of determining whether or not the wastewater in the area where the first treatment is performed is overflowing the end portion; a control step of controlling the amount of wastewater overflowing the end portion when the wastewater in the area where the first treatment is performed overflows the end portion, and controlling the dissolved oxygen concentration in the wastewater in the area where the first treatment is performed when the wastewater in the area where the first treatment is performed does not overflow the end portion, A control method for a sewage treatment device, characterized in that the control step controls the amount of sewage overflowing the end by adjusting the amount of gas supplied by the oxygen supply means to the area where the first treatment is performed, or by adjusting the first water level or the second water level.

7. A program that causes a computer to execute a control method for a wastewater treatment device, the program comprising: a reaction tank having a first water level at which a supply of wastewater is started and a second water level at which the supply of said wastewater is stopped, and performing a first treatment for treating said wastewater under conditions in the presence of oxygen and a second treatment for treating said wastewater under conditions in the absence of oxygen; a partitioning means that divides the reaction tank into an area where the first treatment is performed and an area where the second treatment is performed, and has an end between the first water level and the second water level; and an oxygen supplying means that supplies an oxygen-containing gas to the area where the first treatment is performed, The control method for the sewage treatment device includes: a determining step of determining whether or not the wastewater in the area where the first treatment is performed is overflowing the end portion; a control step of controlling the amount of wastewater overflowing the end portion when the wastewater in the area where the first treatment is performed overflows the end portion, and controlling the dissolved oxygen concentration in the wastewater in the area where the first treatment is performed when the wastewater in the area where the first treatment is performed does not overflow the end portion, The control step is characterized by controlling the amount of wastewater overflowing the end by adjusting the amount of gas supplied by the oxygen supply means to the area where the first treatment is performed, or by adjusting the first water level or the second water level.

8. A computer-readable storage medium storing a program for causing a computer to execute a control method for a sewage treatment device, the control method comprising: a reaction tank having a first water level at which a supply of sewage is started and a second water level at which the supply of the sewage is stopped, and performing a first treatment for treating the sewage under an oxygen-presence condition and a second treatment for treating the sewage under an oxygen-free condition; a partitioning means for dividing the reaction tank into an area for performing the first treatment and an area for performing the second treatment, the partitioning means having an end between the first water level and the second water level; and an oxygen supplying means for supplying an oxygen-containing gas to the area for performing the first treatment, The control method for the sewage treatment device includes: a determining step of determining whether or not the wastewater in the area where the first treatment is performed is overflowing the end portion; a control step of controlling the amount of wastewater overflowing the end portion when the wastewater in the area where the first treatment is performed overflows the end portion, and controlling the dissolved oxygen concentration in the wastewater in the area where the first treatment is performed when the wastewater in the area where the first treatment is performed does not overflow the end portion, A storage medium characterized in that the control step controls the amount of wastewater overflowing the end by adjusting the amount of gas supplied by the oxygen supply means to the area where the first process is performed, or by adjusting the first water level or the second water level.