JP2005342697A - Oxidation ditch tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxidation ditch tank which needs no complicated maintenance and which can prevent accumulation of sludge. <P>SOLUTION: The oxidation ditch tank 1 is provided with an non-termination water channel 3 which circulates waste water together with sludge as mixed liquid and a communicating pipe 31 by which an inner peripheral water channel 5 and an outer peripheral water channel 7 adjacently arranged in the non-termination water channel 3 communicate with each other. The communicating pipe 31 has a water intake port 35 for taking in the mixed liquid from the inner peripheral water channel 5 and a water exhaust port 37 for discharging the mixed liquid taken-in from the water intake port 35 to a bottom part 7g of a corner exit inside 7f of the outer peripheral water channel 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an oxidation ditch tank.

In an oxidation ditch tank equipped with an endless water channel that circulates a mixed liquid of drainage and sludge, there is a portion where the flow rate of the mixed liquid is slow in the water channel, and sludge tends to accumulate in that portion. Conventionally, an oxidation ditch tank is known in which a pit is provided at a location where the flow rate is low and sludge accumulated in the pit is removed by a sand pump. (For example, refer to Patent Document 1).
JP-A-6-226283

  However, in this oxidation ditch tank, since the sludge is removed through the sand pump, the maintenance of the sand pump is complicated and the maintainability is poor.

  Then, an object of this invention is to provide the oxidation ditch tank which can prevent the accumulation of sludge without requiring complicated maintenance.

  In order to solve the above problems, the oxidation ditch tank of the present invention is an oxidation ditch tank that biologically treats wastewater with microorganisms in sludge, and has an endless water channel for circulating the wastewater as a mixed liquid together with sludge, A communication pipe that connects adjacent water paths in the water channel, and the communication pipe is a water inlet that takes in the mixed liquid from one of the water channels that is in communication, and the other that is in communication with the liquid mixture that is taken in from the water inlet. And a drain outlet for discharging to the bottom of a predetermined position of the water channel.

  In this oxidation ditch tank, the liquid mixture is taken from the water inlet of the communication pipe and discharged from the drain outlet to the bottom of a predetermined position. The sludge accumulated at the bottom of the predetermined position is swept away by the mixed liquid discharged from the drain port. When the sludge is washed away, the accumulation of sludge at a predetermined position is suppressed, the sludge decay phenomenon is prevented, and good biological treatment is possible. Moreover, in this oxidation ditch tank, since sludge is not removed outside the water channel but is washed away again into the water channel by the mixed liquid, no device for removing sludge is required, and maintenance is facilitated.

  Further, in the oxidation ditch tank of the present invention, the communication pipe communicates between one water channel and the other water channel having a height difference between the water levels of the mixed liquid, and the water surface in one water channel is higher than the water surface in the other water channel. It may be characterized by being at a higher position.

  In this oxidation ditch tank, the liquid mixture is directed from the water inlet to the water outlet due to the difference in level of the water surface between one water channel and the other water channel, so that the liquid mixture can be circulated through the communication pipe without using power. Sludge accumulation is prevented without using power.

  Moreover, the oxidation ditch tank of the present invention may be characterized in that the water inlet of the communication pipe opens toward the upstream side of one water channel.

  In this oxidation ditch tank, the water inlet is open toward the upstream side of one water channel, so when the liquid mixture flowing through one water channel enters the water inlet, the kinetic energy causes the water from the water inlet to the water outlet. Head. Therefore, the liquid mixture can be circulated through the communication pipe without using power, and sludge accumulation can be prevented without using power.

  The oxidation ditch tank according to the present invention includes an opening / closing means for opening and closing the communication pipe, a sludge accumulation detecting means for detecting a sludge accumulation state at a bottom portion at a predetermined position, and a deposition state detected by the sludge accumulation detecting means. Opening / closing control means for controlling the opening / closing means to open the communication pipe when it is higher than the predetermined accumulation state and close the communication pipe in other cases may be further provided.

  In this oxidation ditch tank, when sludge is accumulated at a predetermined position, a deposition state higher than a predetermined value is detected by the sludge accumulation detection means, and the opening / closing means is controlled so as to open the communication pipe. As a result, the mixed liquid taken in from the water inlet of the communication pipe is discharged from the bottom at a predetermined position, and the sludge accumulated on the bottom is swept away by the mixed liquid. In addition, when the sludge is not accumulated at a predetermined position, the opening / closing means is controlled so as to close the communication pipe. According to this oxidation ditch tank, the operation of the opening / closing means as described above is automatically performed by the opening / closing control means. For this reason, since a communicating pipe is closed except when it is required, the mixed liquid of waterways does not mix, and the stable biological treatment advances.

  The oxidation ditch tank of the present invention is an oxidation ditch tank that biologically treats the wastewater with microorganisms in the sludge, and has a first water channel and a second water channel that are adjacent to each other with a partition wall interposed therebetween. A terminalless water channel that circulates as a mixed liquid together with sludge, a through hole that penetrates the partition wall and introduces the mixed liquid of the first water channel to a predetermined position of the second water channel, and a door portion that can open and close the through hole And.

  In this oxidation ditch tank, when the door is open, the mixed liquid in the first water channel passes through the through hole and is introduced into the second water channel. The sludge accumulated near the through hole in the second water channel is swept away by the mixed liquid introduced through the through hole. For this reason, the accumulation of sludge at this position is suppressed, the sludge decay phenomenon is prevented, and good biological treatment is possible.

  Further, the oxidation ditch tank of the present invention has a door portion driving means for driving the door portion to open and close the through hole, and sludge accumulation detection for detecting a sludge accumulation state at the bottom on the second water channel side near the through hole. And a door part that controls the door drive means to open the through hole when the accumulation state detected by the sludge accumulation detection means is higher than the predetermined accumulation state, and to close the through hole otherwise. And a control means.

  In this oxidation ditch tank, when sludge accumulates near the through hole of the second water channel, the accumulation state higher than the predetermined value is detected by the sludge accumulation detecting means, and the door portion is driven so that the through hole is opened. . As a result, the liquid mixture in the first water channel passes through the through hole and is introduced into the second water channel, and the accumulated sludge is washed away by the liquid mixture. Further, when the sludge is not accumulated at this position, the door is driven so that the through hole is closed. According to this oxidation ditch tank, the operation of opening and closing the through hole as described above is automatically performed by the door control means. For this reason, since a through-hole is closed except when needed, the liquid mixture between waterways does not mix, and the stable biological treatment advances.

  ADVANTAGE OF THE INVENTION According to this invention, the oxidation ditch tank which can prevent accumulation of sludge without requiring complicated maintenance can be provided.

  Hereinafter, embodiments of the present invention will be described. In addition, the same code | symbol is used for the same element and the overlapping description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a plan view of an oxidation ditch tank 1 according to the first embodiment of the present invention. The oxidation ditch tank 1 has a horseshoe-shaped endless waterway 3. The oxidation ditch tank 1 mixes wastewater with sludge, and circulates a mixed liquid of the wastewater and sludge (hereinafter simply referred to as “mixed liquid”) in the endless water channel 3 in the direction of arrow A in the figure. It is a wastewater treatment tank that biologically treats wastewater with these microorganisms.

  The endless water channel 3 is formed in a horseshoe shape so as to be surrounded by the horseshoe-shaped inner peripheral water channel 5 defined by the partition wall 21 and the inner wall 22, and to be surrounded by the outer wall 23 and the partition wall 21. A peripheral water channel 7 is provided. End portions of the inner peripheral water channel 5 and the outer peripheral water channel 7 are connected to each other at a corner 9 and a corner 11. The outer peripheral water channel 7 includes a straight portion 7a, a straight portion 7b, and a corner portion 7c that is formed in a semicircular arc shape and connects the straight portion 7a and the straight portion 7b. Hereinafter, a portion where the straight portion 7a and the corner portion 7c are connected is referred to as a corner inlet 7e, and a portion where the corner portion 7c and the straight portion 7b are connected is referred to as a corner outlet 7f.

  The oxidation ditch tank 1 has a drainage inflow line L1 and a return sludge inflow line L2 connected to the vicinity of the corner 11 of the endless water channel 3, and a treated water outflow line L3 connected to the vicinity of the corner 9. The drainage inflow line L <b> 1 is a line that takes the wastewater to be treated into the endless water channel 3. The treated water outflow line L3 is a line through which treated water after treatment flows out from the endless water channel 3. The return sludge inflow line L3 is a line that takes in the sludge that flows out together with the treated water into the endless water channel 3 again.

  The oxidation ditch tank 1 has an aeration stirrer 13 provided at the corner 9 and a stirrer 15 provided at the corner 11. The aeration stirrer 13 and the stirrer 15 are so-called vertical axis stirrers, and are used as power for circulating the mixed liquid. The aeration stirrer 13 rotates around the vertical axis to push the mixed liquid from the corner 9 toward the straight portion 7 a of the outer peripheral water channel 7. The aeration and stirring device 13 also has an aeration function, and blows air into the liquid mixture that passes through the corner 9. The stirring device 15 rotates around the vertical axis to push the mixed liquid from the corner 11 toward the inner peripheral water channel 5. Since the mixed solution is aerated by the aeration stirrer 13 when passing through the corner 9 and the oxygen is dissolved, the mixed solution is subjected to aerobic treatment by aerobic microorganisms in the sludge while passing through the outer peripheral water channel 7. Moreover, since the dissolved oxygen is used up when the mixed solution passes through the corner 11, it is subjected to anaerobic treatment by anaerobic microorganisms in the sludge while passing through the inner peripheral water channel 5. Thus, the aerobic treatment and the anaerobic treatment are alternately performed while the wastewater is circulated through the endless water channel 3 as a mixed liquid together with the sludge.

  In the oxidation ditch tank 1, as described above, in order to circulate the mixed solution in the arrow A direction, the mixed solution is pushed along the arrow A direction by the stirring device 15 in the corner 11. For this reason, the mixed liquid receives a horizontal force in the direction of arrow A by the stirring device 15 when passing through the corner 11. As a result, the water level of the mixed liquid in the inner peripheral water channel 5 after passing through the corner 11 is higher than the water level of the mixed liquid in the outer peripheral water channel straight part 7 b before passing through the corner 11.

  FIG. 2 is a side view showing the vicinity of the corner outlet 7f of the oxidation ditch tank 1 in the flow direction of the mixed liquid. As described above, the water surface 7 h of the corner outlet 7 f of the outer peripheral water channel 7 is at a position lower than the water surface 5 h of the inner peripheral water channel 5. The oxidation ditch tank 1 includes a communication pipe 31 provided on the inner side 7g (predetermined position) of the corner outlet 7f. The communication pipe 31 communicates the inner peripheral water channel 5 and the adjacent outer peripheral water channel 7 through the partition wall 21. The communication pipe 31 is formed in a cylindrical shape with one end 35 and the other end 37 opened. The one end 35 is provided slightly below the water surface 5h of the inner peripheral water channel 5 and opens upward. The one end 35 functions as a water inlet for taking in the mixed liquid in the inner peripheral water passage 5 (hereinafter, the one end 35 is referred to as a “water inlet 35”). The other end 37 is provided at the bottom of the inner side 7g of the corner outlet 7f of the outer peripheral water channel 7 and opens downward. The other end 37 functions as a discharge port for discharging the mixed liquid taken in from the water inlet 35 (hereinafter, the other end 37 is referred to as a “drain port 37”).

  The communication pipe 31 has an opening / closing device 39 that switches between opening and closing of the communication pipe 31. The opening / closing device 39 includes, for example, an electromagnetic valve 39 a and a valve driving unit 39 b that supplies driving power to the electromagnetic valve 39. The electromagnetic valve 39 a is provided between the water inlet 35 and the water outlet 37 in the communication pipe 31. When the electromagnetic valve 39a is opened, the inner peripheral water passage 5 and the outer peripheral water passage 7 are communicated with each other through the internal space of the communication pipe 31. When the inner circumferential water channel 5 and the outer circumferential water channel 7 communicate with each other, the mixed solution is taken in from the water inlet 35 and discharged from the drain port 37 due to the difference in height between the water surfaces 5 h and 7 h.

  The oxidation ditch tank 1 is provided with a sludge accumulation detection device 29 provided on the inside 7 g of the corner outlet. The sludge accumulation detection device 29 detects the accumulation state of the sludge accumulated on the bottom of the corner outlet inner side 7g. For example, as the sludge accumulation detecting device 29, a sludge concentration measuring device for detecting the sludge concentration of the mixed liquid at the bottom of the corner outlet inner 7g is used. This sludge concentration measuring device is provided, for example, at the bottom of the corner outlet inner 7g, a sampling tube 29a for sampling the mixed solution at the bottom, and a measuring device 29b for measuring the sludge concentration of the mixed solution collected by this sampling tube 29a. The sludge density | concentration measuring apparatus which has is provided. Further, for example, as the sludge accumulation detection device 29, an oxidation-reduction potential measurement device that has an ORP meter (oxidation-reduction potential difference meter) and measures the oxidation-reduction potential of the mixed liquid at the bottom by the ORC meter may be used.

  The sludge accumulation state at the bottom has a correlation with the sludge concentration of the mixed solution and the oxidation-reduction potential of the mixed solution, and the more sludge accumulated at the bottom, the higher the sludge concentration of the mixed solution at the bottom, In addition, the redox potential is lowered. Therefore, the accumulation state of sludge can be detected by the measuring device as described above, and it is determined that more sludge is accumulated as the sludge concentration of the mixed solution is higher and as the oxidation-reduction potential is lower. . The opening / closing device 39 and the sludge accumulation detection device 29 are connected to a control unit 43 that controls the opening / closing of the communication pipe 31.

  The control for opening and closing the communication pipe 31 in the oxidation ditch tank 1 will be described with reference to the block diagram of FIG. The sludge accumulation detection device 29 is connected to a control unit 43 such as a computer, for example, and transmits the detected sludge accumulation state to the control unit 43 as an electrical signal, for example. The control unit 43 transmits a drive signal to the connected opening / closing device 39 to drive the electromagnetic valve 39a to open / close the communication pipe 31.

  FIG. 4 is a flowchart showing a process for controlling the opening / closing device 39. Here, a case where a sludge concentration measuring device is used as the sludge accumulation detecting device 29 will be described. First, the sludge accumulation detection device 29 transmits an electrical signal corresponding to the sludge concentration of the mixed liquid at the bottom of the corner outlet inner side 7g to the control unit 43 (S102). The control unit 43 compares the measured sludge concentration with a predetermined concentration based on the received electrical signal (S104). When the control unit 43 determines that the sludge concentration measured in S104 is higher than the predetermined sludge concentration, the control unit 43 transmits a drive signal to the opening / closing device 39 and opens the communication pipe 31 by opening the electromagnetic valve 39a. (S106). However, when the communication pipe 31 is already opened, the control unit 43 does not drive the opening / closing device 39. When the control unit 43 determines that the sludge concentration measured in S104 is not higher than the predetermined sludge concentration, the control unit 43 transmits a drive signal to the opening / closing device 39 and closes the communication valve 31 by closing the electromagnetic valve 39a. (S108). However, when the communication pipe 31 is already closed, the control unit 43 does not drive the opening / closing device 39. In the oxidation ditch tank 1, the above process may be continuously repeated for a certain time or may be performed once.

  As described above, the oxidation ditch tank 1 includes the communication pipe 31 that communicates the inner peripheral water channel 5 and the outer peripheral water channel 7. When the communication pipe 31 is opened, the mixed liquid is taken in from the water inlet 35 of the communication pipe 31 and discharged from the drain outlet 37 to the bottom of the corner outlet inside 7g due to the difference in height between the water surfaces 5h and 7h. The sludge accumulated at the bottom of the corner outlet inner side 7 g is swept away by the mixed liquid discharged from the drainage port 37. When the sludge is swept away, sludge accumulation at the inner corner exit 7 g is suppressed, and the sludge rot phenomenon is prevented, thereby enabling a good biological treatment. Further, in this oxidation ditch tank, since sludge is not removed outside the water channel but is washed away again into the water channel by the mixed liquid, a device for removing sludge such as a pump is not required, and maintenance is easy.

  Moreover, in the oxidation ditch tank 1, since the liquid mixture is directed from the water inlet 35 to the water outlet 37 due to the height difference between the water surface 5h and the water surface 7h, the liquid mixture can be circulated through the communication pipe 31 without using power. Sludge accumulation is prevented without using power.

  In addition, in the oxidation ditch tank 1, when sludge is accumulated on the bottom of the corner outlet inner 7 g, the sludge accumulation detection device 29 detects a deposition state higher than a predetermined value, and the opening / closing device 39 opens the communication pipe 31. Be controlled. As a result, the mixed liquid taken in from the water inlet 35 of the communication pipe 31 is discharged from the bottom of the corner outlet inner 7 g, and the accumulated sludge is washed away by the mixed liquid. In addition, when no sludge is accumulated at this position, the opening / closing device 39 is controlled so as to close the communication pipe 31. According to the oxidation ditch tank 1, the opening / closing device 39 is automatically operated. For this reason, except when necessary, the communication pipe 31 is closed, so that the mixed liquid of the inner peripheral water passage 5 and the outer peripheral water passage 7 does not coexist, and good biological treatment is performed. Moreover, since an anaerobic liquid mixture is not mixed in an aerobic liquid mixture except when needed, control of dissolved oxygen (OD) becomes easy and nitrification denitrification progresses favorably.

  The present invention is not limited to the first embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the communication pipe 31 having the water inlet 35 opened upward is used. However, as shown in FIG. 5A, the water inlet opened toward the upstream side in the inner peripheral water channel 5 is used. A communication pipe 131 having 135 may be used. If the communication pipe 131 is used, since the water inlet 135 is opened toward the water flow in the direction of arrow A in the inner peripheral water channel 5, the mixed liquid is smoothly circulated through the communication pipe 131 by the kinetic energy of the water flow. .

  Alternatively, a communication pipe 231 having a water inlet 235 that opens toward the upstream side so as to cross the water surface 5h may be used. If the communication pipe 231 is used, the mixed liquid is smoothly circulated through the communication pipe 231 by the kinetic energy of the water flow, air is taken into the communication pipe 231, and the mixed liquid and air are discharged from the drain outlet 237. Therefore, the effect of flushing sludge is further enhanced.

  Moreover, although the oxidation ditch tank 1 of the above-described embodiment uses the electromagnetic valve 39 or the like as the opening / closing device of the communication pipe 31, a manual opening / closing valve that can be manually opened / closed may be used. In the present invention, it is not essential to detect the state of sludge accumulation, and the communication pipe 31 may be opened periodically regardless of the state of sludge accumulation. Further, in the present invention, means for opening and closing the communication pipe 31 is not essential, and the communication pipe 31 may be always opened.

  Moreover, in the oxidation ditch tank 1 of the above-described embodiment, the drainage port 37 is opened downward, but the drainage port 37 may be opened toward the downstream side of the outer peripheral water channel 7. By doing so, the discharge direction of the mixed liquid from the drain port 37 and the direction of the water flow in the outer peripheral water channel 7 coincide with each other, so that smooth discharge can be performed and the effect of flushing sludge is further enhanced.

(Second Embodiment)
FIG. 6 is an enlarged plan view showing the vicinity of the corner outlet 7f of the outer peripheral water channel 7 in the oxidation ditch tank 301 according to the second embodiment of the present invention. The oxidation ditch tank 301 includes a through hole 311 provided through the partition wall 21 on the inner side 7g of the corner outlet 7f, and a door portion 313 that closes the through hole 311. The door portion 313 is formed in a plate shape extending in the vertical direction, for example, and is fixed to a shaft 313z extending in the vertical direction. The shaft 313z is fixed so as to be rotatable about a vertical axis on the partition wall 21. The door portion 313 has a shape that closes the through hole 311 when it is at a position along the partition wall 21 (a position indicated by a broken line in the drawing). Hereinafter, a state in which the door portion 313 is in this position and the through hole 311 is closed is referred to as a “closed state”.

  The door part 313 has the guide surface 313a which guides the water flow of a liquid mixture. When the door 313 rotates and is on the inner peripheral water channel 5 side (the position indicated by the solid line in the figure), the guide surface 313a intersects the flow path of the mixed liquid flowing in the inner peripheral water channel 5 in the direction of arrow A and mixes. The liquid is guided toward the through hole 311 side. Hereinafter, a state in which the door portion 313 is in this position and the through hole 311 is opened is referred to as an “open state”.

  The oxidation ditch tank 301 has a drive device (door drive means) 315 that rotates the shaft 313z. For example, a motor or the like is used as the driving device 315. The door 313 is rotated by the driving force of the driving device 315, and is set to the above-described open state or closed state. The drive device 315 is connected to the control unit 43 and is driven according to a drive signal from the control unit 43. The sludge accumulation detection device 29 is connected to the control unit 43. The sludge accumulation detection device 29 detects the accumulation state of sludge at the corner outlet inner side 7 g near the through hole 311.

  Control for opening and closing the through hole 311 in the oxidation ditch tank 1 will be described with reference to the block diagram of FIG. The sludge accumulation detection device 29 is connected to a control unit 43 such as a computer, for example, and transmits the detected sludge accumulation state to the control unit 43 as an electrical signal, for example. The control unit 43 transmits a drive signal to the connected drive device 315 to drive the door unit 313.

  FIG. 8 is a flowchart showing a process for controlling the driving device 315. Here, a case where a sludge concentration measuring device is used as the sludge accumulation detecting device 29 will be described. First, the sludge accumulation detection device 29 transmits an electrical signal corresponding to the sludge concentration of the mixed liquid at the bottom of the corner outlet inner side 7g to the control unit 43 (S302). The control unit 43 compares the measured sludge concentration with a predetermined concentration based on the received electrical signal (S304). When the control unit 43 determines that the sludge concentration measured in S304 is higher than the predetermined sludge concentration, the control unit 43 transmits a drive signal to the drive device 315 to open the door 313, thereby opening the through hole 311. Is opened (S306). However, if the door 313 is already open, the controller 43 does not drive the driving device 315. If the control unit 43 determines that the sludge concentration measured in S304 is not higher than the predetermined sludge concentration, the control unit 43 transmits a drive signal to the drive device 315 and closes the door 313 to thereby close the through-hole. 311 is closed (S308). However, when the door 313 is already closed, the controller 43 does not drive the driving device 315. In the oxidation ditch tank 301, the above process may be continuously repeated for a certain period of time or may be performed once.

  In this oxidation ditch tank 301, when the door portion 313 is open and the through hole 311 is open, the liquid mixture in the inner peripheral water passage 5 is guided by the guide surface 313a of the door portion 313 and passes through the through hole 311. In this way, it is introduced into the peripheral water channel 7 along the arrow B in the figure. The sludge accumulated near the through hole 311 at the corner outlet inner side 7 g is washed away by the mixed liquid introduced through the through hole 311. For this reason, the accumulation of sludge at this position is suppressed, the sludge decay phenomenon is prevented, and good biological treatment is possible.

  In this oxidation ditch tank 301, when sludge is accumulated near the through hole 311 on the inside 7 g of the corner outlet of the outer peripheral water channel 7, a deposition state higher than a predetermined value is detected by the sludge accumulation detecting device 29, and the through hole 311 is opened. Thus, the door 313 is driven. As a result, the mixed liquid in the inner peripheral water channel 5 passes through the through hole 311 and is introduced into the corner outlet inner side 7 g of the outer peripheral water channel 7, and the sludge accumulated near the through hole 311 is washed away by this mixed liquid. Further, when the sludge is not accumulated at this position, the door portion 313 is driven so that the through hole 311 is closed. According to the oxidation ditch tank 301, the above-described operation for opening and closing the through hole 311 is automatically performed. For this reason, except when necessary, the mixed solution of the inner peripheral water channel 5 and the outer peripheral water channel is not mixed by closing the through hole 311, and a favorable biological treatment is performed. Moreover, since an anaerobic liquid mixture is not mixed in an aerobic liquid mixture except when needed, control of dissolved oxygen (OD) becomes easy and nitrification denitrification progresses favorably.

  The present invention is not limited to the second embodiment described above, and various modifications can be made. For example, although the oxidation ditch tank 301 drives the door 313 with an electric drive device 315 such as a motor, it may be driven manually. In the present invention, it is not essential to detect the sludge accumulation state, and the door 313 may be periodically opened regardless of the sludge accumulation state.

  In addition, in the oxidation ditch tank 301, the door portion 313 is opened so that the guide surface 313a of the door portion 313 guides the mixed solution, but the mixed solution is guided by the guide surface 313a and introduced into the outer peripheral water channel 7. However, it is not essential that the mixed liquid may be introduced into the outer peripheral water channel 7 by utilizing the difference in level between the inner peripheral water channel 5 and the outer peripheral water channel 7.

  In addition, in the oxidation ditch tanks 1 and 301 of the first and second embodiments described above, a vertical axis type stirring device is used to generate the water flow in the endless water channel 3, but the horizontal axis type, screw Any stirring device of a type, an axial pump type, or a propeller type may be used.

  Further, in the horseshoe-shaped endless water channel 3, the inventors found that the inner flow 7g of the corner outlet 7f of the outer peripheral water channel 7 has the slowest flow rate of the mixed liquid, and sludge easily accumulates in this portion. In 1 and 2nd embodiment, the position (predetermined position) which provides the drain outlet 37 or the door part 313 is made into the corner exit inner side 7g of the outer periphery water channel 7. FIG. The present invention is not limited to this, and can also be applied to the case where the drainage port 37 or the door portion 313 is provided at another position of the endless water channel 3 to prevent the accumulation of sludge at the other position.

  Moreover, although the oxidation ditch tank 1,301 of the above-described first and second embodiments includes a horseshoe-shaped endless water channel 3, the present invention provides an oxidation ditch tank including an oval endless water channel. It can also be applied to tanks.

It is a top view of an oxidation ditch tank. It is a side view near the corner exit of an oxidation ditch tank. It is a block diagram which shows the control means of opening and closing of a communicating pipe. It is a flowchart which shows the process which controls opening and closing of a communicating pipe. (A), (b) is a figure which shows the modification of the water inlet of a communicating pipe. It is a top view near the corner exit of an oxidation ditch tank. It is a block diagram which shows the control means of opening and closing of a through-hole. It is a flowchart which shows the process which controls opening and closing of a through-hole.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,301 ... Oxidation ditch tank, 3 ... Endless water channel, 5 ... Inner peripheral water channel, 7f ... Corner outlet, 7g ... Corner outlet inner side, 7c ... Corner part, 7 ... Outer peripheral water channel, 5h, 7h ... Water surface, 9, DESCRIPTION OF SYMBOLS 11 ... Corner, 13 ... Aeration stirrer, 15 ... Stirrer, 21 ... Bulkhead, 22 ... Inner wall, 23 ... Outer wall, 29 ... Sludge accumulation detector, 31 ... Communication pipe, 35 ... Water inlet, 37 ... Drain port, 39b DESCRIPTION OF SYMBOLS ... Valve drive part, 39 ... Opening / closing device, 39a ... Solenoid valve, 43 ... Control part, 311 ... Through-hole, 313a ... Guide surface, 313z ... Shaft, 313 ... Door part, 315 ... Drive device.

Claims (6)

An oxidation ditch tank that biologically treats wastewater with microorganisms in sludge,
An endless water channel for circulating the waste water together with the sludge as a mixed liquid;
A communication pipe communicating the water channels adjacent to each other in the endless water channel,
The communication pipe includes a water inlet for taking in the mixed liquid from one communicated water channel, and a water discharge port for discharging the mixed liquid taken from the water inlet to a bottom of a predetermined position of the other water channel communicated. An oxidation ditch tank characterized by comprising: The communication pipe communicates the one water channel and the other water channel, which have a difference in height between the water levels of the mixed liquid,
The oxidation ditch tank according to claim 1, wherein the water surface in the one water channel is at a position higher than the water surface in the other water channel. The inlet of the communication pipe is
The oxidation ditch tank according to claim 1, wherein the oxidation ditch tank is opened toward the upstream side of the one water channel. Opening and closing means for opening and closing the communication pipe;
Sludge accumulation detecting means for detecting the accumulation state of sludge at the bottom of the predetermined position;
Opening / closing for controlling the opening / closing means to open the communication pipe when the accumulation state detected by the sludge accumulation detection means is higher than a predetermined accumulation state, and to close the communication pipe otherwise. Control means;
The oxidation ditch tank according to any one of claims 1 to 3, further comprising: An oxidation ditch tank that biologically treats wastewater with microorganisms in sludge,
An endless water channel that has a first water channel and a second water channel adjacent to each other with a partition wall interposed therebetween, and circulates the waste water together with the sludge as a mixed liquid;
A through hole penetrating the partition wall and introducing the liquid mixture of the first water channel into a predetermined position of the second water channel;
A door part capable of opening and closing the through hole;
An oxidation ditch tank equipped with Door portion driving means for driving the door portion to open and close the through hole;
Sludge accumulation detecting means for detecting the accumulation state of sludge at the bottom of the second water channel near the through hole;
A door that controls the door drive means to open the through hole when the accumulation state detected by the sludge accumulation detection means is higher than a predetermined accumulation state, and to close the through hole otherwise. Part control means;
The oxidation ditch tank according to claim 5, further comprising:

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