JP2009202101A - Monitoring method of aeration tank - Google Patents

Abstract

[PROBLEMS] To display the oxygen consumption rate of endogenous respiration, which is a criterion for judgment, as an oxygen consumption rate in an unloaded state reflecting the change in the sludge active state, so that the manager of the wastewater treatment facility can treat the aeration tank. It aims at realizing the monitoring method of an aeration tank which can grasp visually a change of a state, a load state, and an activated state of sludge.
SOLUTION: The Rr of a mixed liquid of sludge and waste water at a plurality of locations is measured along the flow direction in the aeration tank 2, the sludge capacity of the sludge in the aeration tank 2 is measured, and the measured Rr distribution and sludge A method for monitoring an aeration tank that compares Rr of endogenous respiration and compares the measured sludge capacity with a predetermined value to determine whether the wastewater treatment status by sludge is appropriate and displays the determined result to the outside.
[Selection] Figure 1

Description

  The present invention relates to a method for monitoring an aeration tank, which is a main treatment step in which wastewater, which is treated water containing organic matter discharged from a sewer or a factory, is oxidized and decomposed by microorganisms in a wastewater treatment facility.

  Conventionally, organic wastewater treatment at sewage treatment plants, factories and business establishments has been performed by an activated sludge method using microorganisms.

  In the activated sludge method, aerobic microorganisms (bacteria, protozoa, etc.) in activated sludge decompose organic matter in wastewater into carbon dioxide and water by metabolic action, and the treatment efficiency is high and economical wastewater treatment. Widely used as a method. However, since microorganisms in the sludge change the decomposition characteristics of organic matter due to various factors, it is necessary to carry out proper operation management in order to perform wastewater treatment continuously and stably.

  The items to be managed in wastewater treatment are typically dissolved oxygen concentration (hereinafter abbreviated as DO), pH, redox potential (hereinafter abbreviated as ORP), and sludge concentration (hereinafter abbreviated as MLSS). In addition, water temperature, influent water volume, sludge capacity, etc. are also measured. The administrator manages the operation of the aeration tank by adjusting the aeration air volume, MLSS, inflow load amount, drug injection amount, etc. so that the wastewater treatment is appropriate while monitoring changes in these measurement items.

By the way, in recent years, social responsibilities of companies, national and local governments, etc. have been highlighted, and in wastewater treatment, not only cost reduction but further pursuit of environmental load reduction is required. For example, in the field of public sewage treatment, based on multiple management items measured at the same time, the optimal operating conditions are estimated by numerical calculation of a mathematical model, and advanced measurement control technology that automatically manages the aeration tank, ADSL, optical fiber, etc. With the spread of high-speed broadband services, remote monitoring technology that centrally manages remote processing plants in one place is being introduced. However, there are few examples in which such measurement control / monitoring technology is applied to business wastewater treatment fields such as food factories. The reason is the following three points.
・ In business wastewater treatment facilities, the cost for introducing advanced technology cannot be generated.
• Compared to public sewage treatment, the inflow load varies greatly depending on the operation status of the factory, making it difficult to apply measurement and control technology.
-Managers of business wastewater treatment facilities have experience and intuition cultivated over many years, such as the operational status of factories and the effects of seasonal fluctuations, and have psychological resistance to automatic operation by equipment.

  Therefore, in medium- and large-scale wastewater treatment facilities for business, managers are always assigned at most treatment plants, and operation management is performed by manned personnel. However, due to the recent declining birthrate and aging population, know-how in wastewater treatment facility management has not been handed down from skilled managers to younger managers, so in order to support managers unfamiliar with wastewater treatment facility management, There is a need for an aeration tank monitoring technique that can solve the problems (1) to (3).

Therefore, depending on the type of wastewater treatment, the purpose of control, the scale of the treatment plant, the nature of the wastewater, etc., (1) monitoring by dissolved oxygen concentration, (2) monitoring by oxygen consumption rate (hereinafter abbreviated as Rr), (3 ) Various monitoring methods, such as monitoring based on the state of the aeration tank, have been proposed and implemented. Hereinafter, these will be described.
(1) Monitoring by dissolved oxygen concentration This is a method of displaying the state of the aeration tank by continuously measuring the dissolved oxygen concentration in the aeration tank. The dissolved oxygen concentration in the aeration tank represents the ratio of the oxygen supply rate to the aeration tank and the Rr of sludge in the aeration tank. If the oxygen supply rate is constant, it increases or decreases depending on the Rr of sludge. In addition, since Rr changes depending on whether there is a load or not, and the dissolved oxygen concentration also changes accordingly, the load state of the aeration tank should be visually grasped by continuously measuring the time change of the dissolved oxygen concentration. Can do. However, such a monitoring technique for the aeration tank based on the dissolved oxygen concentration is based on the assumption that the oxygen supply rate to the aeration tank is always constant. If this assumption does not hold, the state of the aeration tank cannot be grasped correctly. The oxygen supply capacity of the aeration tank is represented by a general oxygen transfer capacity coefficient (hereinafter abbreviated as KLa), but this value changes due to the influence of sludge concentration, clogging of the air diffuser, etc. and is not constant. In addition, since measurement requires considerable labor and labor, it is difficult to measure and correct KLa while the aeration tank is in operation.
(2) A method for directly measuring Rr of monitoring sludge by Rr. This method utilizes the fact that there is a correlation between the Rr of sludge and the load, and the load is estimated from the measured value of Rr and displayed. According to this method, a change in the load flowing into the aeration tank can be obtained by excluding the influence of the variation of KLa.
However, in this method, since the criterion for judging the quality of Rr is not clear, it is impossible to judge the state of the aeration tank, only to know the relative load.
(3) Monitoring according to the state of the aeration tank A method of monitoring the aeration tank has been proposed in which the processing state of the aeration tank is judged from a plurality of Rr along the flow direction of the aeration tank (for example, Patent Documents 1 and 2). reference).
In this method, in the extruded flow type activated sludge process in which the load continuously flows in and out, the distribution of Rr in the downstream direction in the aeration tank is obtained by utilizing the distribution that Rr decreases from upstream to downstream. The quality of the aeration tank is determined by measuring and displaying the standard Rr distribution set in advance and the measured Rr distribution for comparison.
JP-A 61-8862 JP-A 63-156596

  However, the methods described in the above-mentioned conventional patent documents 1 and 2 display and judge the state of the aeration tank by a method of comparison with a standard Rr distribution set in advance, but the Rr of sludge is In addition to the load, it changes depending on the water temperature change and the nature of the inflow load, so the standard Rr distribution cannot be uniquely defined, and it is difficult to correctly determine and display the state of the aeration tank. .

  Therefore, the present invention displays the oxygen consumption rate of endogenous respiration, which is a criterion for judgment, as an oxygen consumption rate in an unloaded state reflecting the change in the sludge active state, so that the manager of the wastewater treatment facility can operate the aeration tank. It aims at realizing the monitoring method of the aeration tank which can grasp visually the change of the treatment state, the load state, and the activated state of sludge.

  It is another object of the present invention to provide an aeration tank monitoring method that enables an unskilled administrator to appropriately grasp the aeration tank state by judging and displaying the state of the aeration tank.

  In order to solve the above-mentioned conventional problems, the monitoring method of the aeration tank of the present invention measures Rr of a mixed liquid of sludge and waste water at a plurality of locations along the flow direction in the aeration tank, and sludge in the aeration tank. The sludge capacity of the sludge is measured, the measured Rr distribution is compared with the Rr of the sludge's endogenous respiration, and the measured sludge capacity is compared with a predetermined value to determine whether the wastewater treatment status by sludge is appropriate and judged. The result is displayed externally.

  According to the present invention, the oxygen consumption rate of endogenous respiration, which is a criterion for judgment, is displayed as an unloaded oxygen consumption rate reflecting the change in sludge active state, so that the manager of the wastewater treatment facility can An aeration tank monitoring method that can visually grasp changes in the treatment state, load state, sludge active state, and the like is obtained.

  Furthermore, it is possible to determine and display the state of the aeration tank based on the criteria reflecting the change in the activated state of the sludge, and it is possible to obtain an aeration tank monitoring method that enables an unskilled administrator to appropriately grasp the state of the aeration tank.

  The monitoring method of the aeration tank according to the first embodiment of the present invention measures the oxygen consumption rate distribution of the mixed liquid of sludge and waste water at a plurality of locations along the flow direction in the aeration tank, and the sludge in the aeration tank. The sludge capacity of the sludge is measured, and the distribution of the measured oxygen consumption rate is compared with the oxygen consumption rate of the sludge's endogenous breathing. Judgment is made, and the judgment result is displayed outside.

  According to this embodiment, by comparing not only the oxygen consumption rate distribution and the oxygen consumption rate of endogenous respiration, but also by comparing the sludge capacity with a predetermined value, However, more accurate monitoring of wastewater treatment status can be realized.

  The aeration tank monitoring method according to the second embodiment of the present invention is the aeration tank monitoring method according to the first embodiment, wherein the oxygen consumption rate of endogenous respiration is the oxygen consumption rate of the mixed liquid in an unloaded state. This is the measured value.

  According to the present embodiment, by measuring the oxygen consumption rate of endogenous respiration directly from the liquid mixture in the aeration tank, a more accurate oxygen consumption rate of endogenous respiration can be obtained.

  The aeration tank monitoring method according to the third embodiment of the present invention is the aeration tank monitoring method according to the second embodiment, in which the no-load state is a state in which there is no load flowing into the aeration tank. .

  According to the present embodiment, when the day and time when there is no load on the aeration tank can be specified in advance, it can be easily determined as the no-load state, and the oxygen consumption rate of endogenous respiration can be obtained.

  The aeration tank monitoring method according to the fourth embodiment of the present invention is the aeration tank monitoring method according to the second embodiment, wherein the no-load state is oxygen measured at a plurality of locations along the flow direction of the aeration tank. The slope of the consumption speed distribution is in a horizontal state.

  According to the present embodiment, it is possible to determine from the inclination of the distribution of the oxygen consumption rate that there is no load on the aeration tank, and it is unnecessary to specify in advance the date and time when the load on the aeration tank does not flow It becomes.

  The aeration tank monitoring method according to the fifth embodiment of the present invention is the aeration tank monitoring method according to the second embodiment. In the no-load state, the mixed liquid is sampled from the most downstream portion in the flow direction of the aeration tank. Then, the collected mixed solution is aerated so that all the residual load is consumed.

  According to the present embodiment, in the case where the aeration tank does not necessarily become an unloaded state at an appropriate frequency by forcing the mixed solution in the most downstream portion having the lowest residual load into an unloaded state. In addition, the oxygen consumption rate of endogenous respiration can be obtained with certainty.

  The aeration tank monitoring method according to the sixth embodiment of the present invention is the aeration tank monitoring method according to the fifth embodiment, wherein the collected mixed solution is separated into a supernatant and a suspension before aeration, The supernatant is replaced with unloaded fresh water.

  According to the present embodiment, by forcibly removing the load remaining in the mixed liquid, it is possible to significantly reduce the aeration time for setting the unloaded state.

  The aeration tank monitoring method according to the seventh embodiment of the present invention is measured when the measured oxygen consumption rate is lower than the oxygen consumption rate of endogenous breathing in the aeration tank monitoring method according to the first embodiment. The oxygen consumption rate is the oxygen consumption rate of endogenous breathing.

  According to the present embodiment, even when the activity of microorganisms decreases and the measured oxygen consumption rate becomes equal to or lower than the oxygen consumption rate of endogenous respiration, the measured oxygen consumption rate is set as the oxygen consumption rate of endogenous respiration. Thus, even when the aeration tank does not become unloaded, it is possible to follow the change in the activity and obtain the oxygen consumption rate of endogenous respiration.

  The aeration tank monitoring method according to the eighth embodiment of the present invention is the aeration tank monitoring method according to the first embodiment, wherein the sludge capacity is the sludge capacity measured at the most downstream portion in the flow direction of the aeration tank. To do.

  According to this embodiment, since it is possible to determine whether the wastewater treatment is appropriate based on the sludge capacity of the sludge immediately before flowing out from the aeration tank to the settling tank, the settling separation of the sludge and treated water in the settling tank It becomes possible to grasp the sex accurately.

  The aeration tank monitoring method according to the ninth embodiment of the present invention is the aeration tank monitoring method according to the first embodiment, wherein the oxygen consumption rate measured at the most downstream portion in the flow direction of the aeration tank is endogenous respiration. If the sludge capacity is larger than the predetermined value, it is determined that the waste water treatment by the sludge is insufficient.

  According to the present embodiment, there is no endogenous breathing transition point inside the aeration tank, and the state where sedimentation and separation of sludge and treated water are becoming impossible in the settling tank, that is, a state that is becoming a problem as wastewater treatment Can be grasped.

  The aeration tank monitoring method according to the tenth embodiment of the present invention is the aeration tank monitoring method according to the first embodiment, wherein the oxygen consumption rate measured at the most downstream portion in the flow direction of the aeration tank is endogenous respiration. When the sludge capacity is larger than the predetermined value, it is determined that the wastewater treatment with sludge is appropriate.

  According to the present embodiment, the endogenous breathing transition point is not in the aeration tank, but it is possible to grasp the state in which the sludge and treated water can be separated and settled in the settling tank, that is, the state appropriate for wastewater treatment. Become.

  The aeration tank monitoring method according to the eleventh embodiment of the present invention is the aeration tank monitoring method according to the first embodiment, wherein the oxygen consumption rate measured at the most downstream portion in the flow direction of the aeration tank is endogenous respiration. When the sludge capacity is lower than the predetermined value and the sludge capacity is smaller than the predetermined value, the measured oxygen consumption rate is regarded as the oxygen consumption rate of endogenous respiration, and it is judged that the waste water treatment by sludge is excessive. .

  According to the present embodiment, it is possible to accurately detect the excess or deficiency of the waste water treatment in the aeration tank even when the endogenous respiration fluctuates due to a change in the temperature of the activated sludge, a change in the quality of the waste water, or the like.

  The aeration tank monitoring method according to the twelfth embodiment of the present invention is the aeration tank monitoring method according to the first embodiment, wherein the oxygen consumption rate measured at the most downstream portion in the flow direction of the aeration tank is endogenous respiration. When the sludge capacity is equal to the oxygen consumption rate and the sludge capacity is smaller than a predetermined value, it is determined that the waste water treatment by the sludge is excessive.

  According to the present embodiment, the endogenous breathing transition point is at the most downstream part in the aeration tank, but the state in which the sludge and the treated water can be separated and settled in the sedimentation tank, that is, the proper state as the wastewater treatment is grasped. It becomes possible.

  The aeration tank monitoring method according to the thirteenth embodiment of the present invention is the aeration tank monitoring method according to the first embodiment, in which whether or not the waste water treatment by sludge is appropriate is determined using MLSS simultaneously with the oxygen consumption rate. The oxygen utilization rate coefficient is calculated by measurement, and the oxygen utilization rate coefficient is used instead of the oxygen utilization rate.

  According to the present embodiment, the influence of the oxygen consumption rate due to the change in sludge concentration can be removed, and the oxygen consumption rate due to the activity of microorganisms can be determined more accurately than simply measuring only the oxygen consumption rate.

  The method for monitoring an aeration tank according to the fourteenth embodiment of the present invention is the same as the method for monitoring an aeration tank according to the first embodiment. Thus, the sludge capacity index is calculated, and the sludge capacity index is used instead of the sludge capacity.

  According to the present embodiment, it is possible to remove the influence of the sludge capacity due to the change in the sludge concentration, and it is possible to grasp the sedimentation and separability of sludge and treated water more accurately than merely measuring the sludge capacity.

  The aeration tank monitoring method according to the fifteenth embodiment of the present invention displays the wastewater treatment status in characters in the aeration tank monitoring method according to the first embodiment.

  According to this embodiment, the manager of the facility can easily check whether the state of the aeration tank is appropriate.

  The aeration tank monitoring method according to the sixteenth embodiment of the present invention displays the wastewater treatment status as a figure in the aeration tank monitoring method according to the first embodiment.

  According to this embodiment, the manager of the facility can easily check whether the state of the aeration tank is appropriate.

  Hereinafter, an aeration tank monitoring method according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a system diagram showing an example of a method for controlling an aeration tank in the present embodiment, and shows a wastewater treatment system 10 and a measurement control system 20 including a control target.

■ Configuration and operation of the wastewater treatment system 10 The wastewater treatment system 10 is an aeration tank that oxidizes and decomposes organic matter in wastewater by aeration of an adjustment tank 1 that temporarily stores wastewater and a mixture of wastewater and activated sludge. It consists of a tank 2 and a sedimentation tank 3 that settles and separates the mixed liquid treated in the aeration tank 2 into activated sludge and treated water by gravity. Here, the arrow represents the flow direction of the waste water and the mixed liquid.

  The wastewater containing the organic matter to be treated flows into the adjustment tank 1 and is stored therein. Here, a certain amount of load fluctuation is averaged and sent to the aeration tank 2 at a substantially constant flow rate / load.

  In the aeration tank 2, the waste water and sludge are mixed to form a mixed solution, and air is sent from the aeration blower 6 through the diffuser tube 4, and oxygen bubbles generated from the diffuser tube 4 supply oxygen into the mixed solution and mix it. Stir the liquid.

  Inside the aeration tank 2, microorganisms take in organic substances while consuming oxygen, and then oxidatively decompose the organic substances into water and carbon dioxide. Oxidative decomposition of organic matter by microorganisms proceeds as it flows from the most upstream portion of the aeration tank 2 to the most downstream portion, and the mixed solution flows into the precipitation tank 3.

  The mixed solution fed into the settling tank 3 is separated by gravity into sludge and a supernatant, and the supernatant is discharged out of the system as treated water. A portion of the sludge separated and separated is returned to the upstream portion of the aeration tank 2 as return sludge and reused for biological treatment.

(1) Configuration and Operation of Measurement Control System 20 The measurement control system 20 includes an Rr measurement tank 11, a sludge volume (SV) measurement tank 30, a control unit 12, and a display unit 90 in the control unit 12.

  The Rr measurement tank 11 includes a DO sensor 13, a temperature sensor 14, a measurement tank aeration pipe 15, and a stirrer 17. The measurement tank aeration pipe 15 is connected to an air pump 16 by an air pipe.

  In the aeration tank 2, Rr sampling pumps 7 are arranged at a plurality of locations including the most upstream part and the most downstream part along the flow direction. The Rr sampling pump 7 is connected to the Rr measurement tank 11 via the mixed liquid sampling valve 8. Connected to the inlet 18. An Rr measurement tank outlet 27 is provided at the bottom of the Rr measurement tank 11, and the Rr measurement tank outlet 27 is connected to the vicinity of the most upstream part of the aeration tank 2 via the Rr measurement tank discharge valve 21. Further, an SV sampling pump 9 is disposed at the most downstream portion of the aeration tank 2, and the mixed liquid is supplied to the SV measurement tank 30. An SV measurement tank outlet 31 is provided at the bottom of the SV measurement tank 30, and the SV measurement tank outlet 31 is connected to the most downstream portion of the aeration tank via the SV measurement tank discharge valve 22.

  The control unit 12 is electrically connected to the air pump 16, the stirrer 17, the inverter 5, the Rr sampling pump 7, the SV sampling pump 9, the Rr measuring tank discharge valve 21, and the SV measuring tank discharge valve 22 (in the figure, The operation of each device can be controlled. Further, the measurement signal lines (indicated by broken lines in the figure) of the DO sensor 13 and the temperature sensor 14 are connected to the control unit 12, respectively, and the measurement signal can be taken into the control unit 12. The measurement data and the determination result can be displayed on the display unit 90 with characters and diagrams. In FIG. 1, the signal lines of the Rr sampling pump 7, the mixed liquid collection valve 8, the Rr measurement tank discharge valve 21, and the SV measurement tank discharge valve 22 are shown by a single broken line for convenience. It can be controlled.

  An Rr cleaning pipe 25 and an SV cleaning pipe 26 are connected to the Rr measuring tank 11 and the SV measuring tank 30 for cleaning the sensors so that clear water such as tap water and groundwater is supplied. It has become.

  First, the oxygen consumption rate is measured as follows. One of the Rr sampling pumps 7 is operated, and the mixed solution collection valve 8 corresponding to the activated Rr sampling pump 7 is opened (normally, the mixed solution collection valve 8 is closed), and the mixed solution is introduced into the inlet. The mixture liquid is caused to flow from 18 into the Rr measurement tank 11, and a certain amount of the liquid mixture is stored in the Rr measurement tank 11. Next, the air pump 16 and the stirrer 17 are operated to aerate the mixed solution in the Rr measurement tank 11 through the measurement tank diffuser tube 15 and at the same time, measurement by the DO sensor 13 and the temperature sensor 14 is also started. After the measurement is started, the measured values of the DO sensor 13 and the temperature sensor 14 are sequentially recorded in the control unit 12 at regular intervals, and the DO of the mixed liquid in the Rr measurement tank 11 rises by aeration and becomes a stirrer when it becomes constant. 17 is operated, and the operation of the air pump 16 is stopped to calculate the oxygen consumption rate of the mixed liquid in the Rr measuring tank 11 from the decrease curve of DO. In addition, since the oxygen consumption rate largely changes depending on the water temperature, the influence of the temperature can be eliminated by compensating the temperature change by the control unit 12.

  When DO becomes almost zero, the measurement by the DO sensor 13 and the temperature sensor 14 is stopped, the Rr measurement tank discharge valve 21 is opened, and the mixed liquid in the Rr measurement tank 11 is transferred from the Rr measurement tank outlet 27 to the aeration tank 2. Return it. Here, the position to be returned to the aeration tank 2 is preferably the most upstream part of the aeration tank 2 in consideration of the influence on the treated water. After returning the mixed liquid to the aeration tank 2, wash water such as tap water or groundwater is flowed into the Rr measurement tank 11 from the Rr cleaning pipe 25, and the measurement tank aeration pipe 15 and the stirrer 17 are operated. It is desirable to clean the sensor 13, the temperature sensor 14, and the Rr measurement tank 11.

  The oxygen consumption rate is measured as described above. By sequentially measuring this measurement from the most upstream part to the most downstream part of the aeration tank 2, an oxygen utilization rate distribution in the aeration tank 2 can be obtained. It becomes possible.

  Next, the sludge capacity is measured as follows. The SV sampling pump 9 is operated, the mixed liquid at the most downstream part of the aeration tank 2 is caused to flow into the SV measurement tank 30, the sludge capacity is measured, and the measured value is sent to the control unit 12. After completion of the measurement, the SV measurement tank discharge valve 22 is opened, and the liquid mixture inside the SV measurement tank 30 is returned to the aeration tank 2 from the SV measurement tank outlet 31. After returning the mixed liquid to the aeration tank 2, it is desirable to wash the SV measurement tank 30 by flowing wash water such as tap water or groundwater from the SV washing pipe 26 into the SV measurement tank 30.

  The above is the configuration and operation of the waste water treatment system 10 and the measurement control system 20. Here, the waste water treatment state in the aeration tank 2 will be described in more detail with reference to FIG.

  The wastewater that has flowed into the aeration tank 2 is mixed with sludge at the uppermost stream part of the aeration tank 2, and microorganisms in the sludge rapidly take up organic matter in the wastewater as a load. At this time, since the microorganisms consume a large amount of oxygen, the oxygen consumption rate rapidly decreases after showing the highest value in the most upstream part (A part in the figure).

  As the mixed solution flows down the aeration tank 2, the microorganisms gradually oxidize and decompose the organic matter taken into the body, so that the oxygen consumption rate gradually decreases as it goes downstream. Then, when all the organic matter taken in by the microorganism is decomposed, breathing without consumption of organic matter, so-called endogenous breathing state is obtained, and the oxygen consumption rate becomes constant.

Here, the situation of the aeration tank 2 can be broadly classified into four categories: (1) processing excess A, (2) processing excess B, (3) optimal processing, and (4) processing shortage. The points in judging each situation of 4) are “where in the aeration tank 2” the position where the respiration that decomposes organic matter transitions to endogenous respiration (endogenous respiration transition point) and “precipitation” “Whether or not the tank 3 can satisfactorily separate the treated water and the activated sludge”. Next, a method for determining each situation (1) to (4) will be described.
(1) Overtreatment A
As shown in b in FIG. 2, when the endogenous breathing transition point is upstream from the most downstream portion of the aeration tank 2 and the sedimentation separation of the treated water and activated sludge can be satisfactorily performed in the sedimentation tank 3, The sludge downstream from the breathing transition point is not subjected to oxidative decomposition treatment, and it can be determined that the treatment such as aeration is excessive with respect to the inflow load.
(2) Overtreatment B
As shown in f in FIG. 2, when the endogenous breathing transition point is in the most downstream portion of the aeration tank 2 and the sedimentation separation of the treated water and activated sludge can be satisfactorily performed in the sedimentation tank 3, the inside of the aeration tank 2 However, the oxidative decomposition treatment with sludge is not finished, but there is a margin as the waste water treatment, and it can be determined that the treatment such as aeration is excessive with respect to the inflow load.
(3) Optimal processing As shown by a in FIG. 2, when the endogenous breathing transition point is behind the most downstream portion of the aeration tank 2, that is, when the endogenous breathing transition point is not reached in the aeration tank 2, the aeration tank Even in the most downstream part of 2, the organic matter remains in the microbial body. However, if the sedimentation of the treated water and activated sludge can be satisfactorily performed in the sedimentation tank 3, it can be determined that the treatment such as aeration with respect to the inflow load is not excessive or insufficient, and is the most efficient situation for wastewater treatment. .
(4) Insufficient treatment As shown in c in FIG. 2, the endogenous breathing transition point is behind the most downstream portion of the aeration tank 2, that is, does not reach the endogenous breathing transition point in the aeration tank 2, and the sedimentation tank If it is in the situation where sedimentation of treated water and activated sludge cannot be performed in No. 3, it can be judged that it is the situation where processing is insufficient as wastewater treatment.

  Activated sludge is excessively aerated, and excessive processing may cause deterioration of sludge sedimentation due to insufficient production of extracellular materials. Remains and accumulates, the ability of microorganisms to absorb organic matter decreases, and the sedimentation and separation of sludge deteriorates. In other words, in order to optimally control the operation status of the aeration tank 2, even when there is no endogenous breathing transition point inside the aeration tank, it is judged and displayed whether sludge and treated water can be separated and separated in the settling tank. The biggest point is to do.

  Next, the monitoring method of the aeration tank in this Embodiment is demonstrated using the flowchart of FIG.

In FIG. 3, R _{1 to} R ₄ represent oxygen consumption rates in the flow direction in the aeration tank 2 measured in the Rr measuring tank 11, R ₁ represents a value in the most upstream area, and R ₄ represents a value in the most downstream area. . N represents the oxygen consumption rate of endogenous respiration at the time of measurement.

First, R _{1 to} R ₄ are measured.

Next, R ₁ and R ₂ are compared, and if R ₁ > R ₂ , it is determined that there is a load flowing into the aeration tank. On the other hand, if R ₁ > R _{2 is} not satisfied, it can be regarded that R ₁ = R ₂ = R ₃ = R ₄ , there is no inclination of the oxygen consumption rate distribution in the aeration tank 2, and the aeration tank 2 is unloaded, that is, internal Since it can be determined that the situation is a live breathing state, N is updated with R ₄ as the value of the endogenous breathing.

If it is determined that the next there is a load, compares the oxygen consumption rate N and R ₄ of the current endogenous respiration, R _4> If N, oxygen consumption rate of oxygen consumption most downstream portion of the endogenous respiration If it is higher than the speed and SV> C, it is possible to determine that the treatment is insufficient because the sedimentation property of the sludge is getting worse, and control is performed to increase the amount of aeration air. On the other hand, if R ₄ > N and SV <C, it can be determined that the processing such as aeration is not excessive or insufficient with respect to the inflow load, and the processing is appropriate. Incidentally, C is is a value to be input in advance as the predetermined value, it is desirable to 50% or less in SV _30. If C is set too large, deterioration of the sludge sedimentation and separation properties cannot be stopped, and environmental pollution due to sludge carryover may be caused.

Next, when R ₄ <N and SV <C, it can be determined that the sludge activity has decreased due to changes in water temperature or water quality, etc., and the value of R ₄ is forcibly endogenous. N is updated as the oxygen consumption rate of respiration, and it can be determined that the processing is excessive. On the other hand, in the case of R ₄ <N and SV> C, it is determined that the treatment is insufficient for safety because the activity of the sludge is reduced for some reason and the sedimentation and separability of the sludge is getting worse.

Next, when R ₄ > N and R ₄ <N, that is, when R ₄ = N and SV <C, the sludge activity is endogenous respiration at the most downstream portion of the aeration tank 2. In addition, since the sedimentation property of sludge is good, it is determined that the treatment is excessive. On the other hand, in the case of R ₄ = N and SV> C, the activity of sludge is endogenous respiration at the most downstream portion of the aeration tank 2, but the state where the sludge sedimentation and separation properties are deteriorating for some reason. Therefore, it is judged that the processing is insufficient for safety.

  Here, four oxygen consumption rates in the flow direction and oxygen consumption rates of endogenous respiration are obtained, and this result is displayed on the display unit 90. As an example of the display method on the display unit 90, if the elapsed time and date are displayed on the horizontal axis and the measured value of each oxygen consumption rate and the oxygen consumption rate of endogenous respiration are displayed on the vertical axis as shown in FIG. Can visually grasp the presence or absence of the load on the aeration tank 2 and the change in the oxygen consumption rate of the endogenous breath with reference to the standard of oxygen consumption rate of the endogenous breath. As another display method, as shown in FIG. 4B, the horizontal axis indicates the position of the aeration tank 2, and the current oxygen consumption rate of endogenous breathing and the distribution of the oxygen consumption rate for each measurement time are displayed. Thus, the processing state of the aeration tank 2 can be grasped in more detail.

  Thus, the state of the aeration tank 2 can be appropriately displayed by setting the criterion for determination to the oxygen consumption rate in an unloaded state reflecting the change in the activated state of sludge.

  Next, the determination result is displayed on the display unit 90 so that the administrator can grasp the state of the aeration tank 2. As a display method of the determination result of the processing state, the graph showing the change over time of the oxygen consumption rate shown in FIG. 5 and the graph showing the position of the aeration tank 2 on the horizontal axis are displayed. It is easy to understand if it is displayed in characters such as “Appropriate”, “Excessive processing”, “Insufficient processing”. Further, as shown in FIG. 5, a picture of the aeration tank 2 is displayed. For example, when the treatment is appropriate as shown in (a), the color of sludge in the aeration tank 2 indicates a standard sludge color. If the color or picture is changed depending on the situation, for example, when the processing is insufficient, the color is changed to a color close to black as shown in (b), the administrator can more easily understand the state of the aeration tank 2.

  In this way, not only the state of the aeration tank 2 is visually displayed by a graph, but also the judgment of the processing state is performed and the result is displayed, thereby not only assisting a skilled administrator but also an inexperienced administrator. The state of the aeration tank 2 can be properly grasped.

  Here, in the conventional aeration tank monitoring method, it is judged whether the position of the endogenous breathing transition point is appropriate at the inflection point where the slope of the distribution of oxygen consumption rate changes, but the optimal oxygen consumption rate investigated and measured in advance. Since the optimum oxygen consumption rate distribution changes when the sludge activity changes, for example, a in FIG. 2 changes, so that the endogenous breathing transition point Make a mistake in determining whether is in the correct position.

  However, as described above, in the present embodiment, the determination of whether the endogenous breathing transition point is at an appropriate position is compared with the oxygen consumption rate value of endogenous breathing, and the oxygen consumption rate of endogenous breathing is Since it can always be updated using the liquid mixture in the aeration tank 2, it is possible to correctly determine whether or not the endogenous breathing transition point is at an appropriate position even when the activity changes. And even if there is no endogenous breathing transition point inside the aeration tank 2, it is judged whether the sedimentation tank 3 is capable of settling and separating sludge and treated water, and the quality of the accurate aeration tank is maintained while maintaining good treated water quality. A monitoring method can be realized.

  In this embodiment, the four measurement positions are described. However, the number of measurement positions may be determined according to the installation status of the treatment plant, the required accuracy of the treatment, the cost, etc. Yes, but the cost will increase.

  Next, the oxygen consumption rate distribution in the wastewater treatment facility of a certain office will be described.

  FIG. 6 shows the flow direction distribution of the oxygen consumption rate in the wastewater treatment facility of a certain office.

  Here, the measurement was performed on the day when the office is operating and on the non-operating day, and the inflow load was 0 on the non-operating day.

As shown in FIG. 6, the oxygen consumption rate on the working day showed a very high value in the uppermost stream part of the aeration tank 2, rapidly decreased as it went downstream, and became almost constant before the most downstream part. . Here, since R ₁ > R ₂ , it can be determined from the figure that there is a load on the operating day.

Further, the oxygen consumption rate on the non-working day when the inflow load is 0 is constant regardless of the position of the aeration tank, and R ₁ ≈R ₂ ≈R ₃ ≈R ₄ , so it can be determined that there is no load. This value is the oxygen consumption rate N of endogenous respiration.

  By comparing this N with the distribution of oxygen consumption rate on the working day, it can be seen that the endogenous breathing transition point is at the position 5 in FIG. 4, and on the working day, the aeration is excessive and the amount of aeration is reduced. It was found that energy saving can be realized. Thus, the monitoring method of the aeration tank of the present invention can be applied to an actual processing facility.

  As described above, according to the present embodiment, it becomes possible to monitor and control the aeration tank so that the activated sludge is in an optimal state, such as busy periods, holidays, nighttime, etc. Even when the load fluctuates rapidly, there is no need to operate with excessive aeration in view of safety as in the past, and energy savings can be achieved, and at the same time, a manager to respond to sudden load fluctuations is always assigned. This is no longer necessary and can contribute to a reduction in management costs.

  In the present embodiment, the method of specifying the endogenous breathing transition point based on the oxygen consumption rate has been described. However, since the aeration tank is normally operated to keep the sludge concentration constant, there is no problem with this method.

  However, for more accurate detection, it is better to install a sludge concentration meter in the measuring tank and use the oxygen consumption rate so-called oxygen utilization rate coefficient (Kr) per unit sludge weight obtained by dividing the oxygen consumption rate by the sludge concentration. It is possible to accurately identify the endogenous respiratory transition point. Moreover, regarding the sludge capacity, it is possible to more accurately determine the sludge sedimentation / separation property by using a sludge capacity index (volume occupied by sludge) obtained by dividing the sludge capacity by the sludge concentration. In general, the sludge capacity index is preferably 300 mg / l or less.

  In the present embodiment, the control object is described as the aeration air volume, but the control object of the aeration tank 2 is not limited to the aeration air volume, the amount of return sludge in the aeration tank 2, the inflow amount of the load, etc. May be controlled.

  Moreover, although the method of measuring the oxygen consumption rate using the Rr measuring tank 11 as a separate tank has been described, the method of measuring the oxygen consumption rate directly in the aeration tank 2 may be used.

  Further, in the present embodiment, it has been described that the determination of the no-load state is based on the fact that the gradient of the oxygen consumption rate distribution in the aeration tank 2 is horizontal, but for example, the day and time when the load does not flow into the aeration tank 2 When it is known in advance and can be specified, it is not necessary to examine the slope of the oxygen consumption rate distribution, and the oxygen consumption rate during the time of no load may be used as the oxygen consumption rate of endogenous breathing.

  As described above, according to this embodiment, the fluctuation range of the load is large, and it can be applied to an aeration tank of a wastewater treatment facility such as a business office that changes rapidly, and can cope with a change in the activity of sludge. An aeration tank monitoring method can be obtained.

(Embodiment 2)
FIG. 7 shows another embodiment of the aeration tank control method of the present invention. In addition, the same code | symbol is attached | subjected about what has the structure and effect | action similar to Embodiment 1, and the description is abbreviate | omitted.

  In this embodiment, as a method for measuring the oxygen consumption rate of endogenous respiration in the no-load state in the first embodiment, the measurement is not performed on the day when there is no inflow load of the aeration tank 2, but the no-load state is forced. It is a method of creating it.

  In Embodiment 1, it is assumed that a no-load state such as a non-working day or a nighttime appears at an appropriate frequency. However, depending on the establishment, the no-load state cannot be obtained for a long period of time, or it can be obtained at all. There may be no case.

  In such a case, the oxygen consumption rate of the endogenous respiration cannot be updated, the influence of the change in the sludge activity cannot be followed, and the endogenous respiration transition point cannot be specified accurately. In order to cope with such a case, the present embodiment compulsorily creates a no-load state and measures the oxygen consumption rate of endogenous respiration.

  In FIG. 7, a sludge interface meter 43 is installed in the Rr measurement tank 11, and a signal line of the sludge interface meter 43 is connected to the control unit 12. A sludge receiving tank 41 is installed below the measuring tank and is connected to the bottom of the Rr measuring tank 11 by a pipe. A sludge receiving tank inflow valve 44 is installed in the middle of the pipe. Moreover, the bottom part of the sludge receiving tank 41 and the upper part of the Rr measuring tank are connected by piping, and the circulation pump 42 is arrange | positioned in the middle of piping.

  Next, the processing operation of this embodiment will be described.

  When measuring the oxygen consumption rate of endogenous respiration, the Rr sampling pump 7 at the most downstream position where the residual load is considered to be the lowest is operated, and the mixed liquid sampling valve 8 of the pump is opened to flow the mixed liquid into the inlet. 18 is introduced into the Rr measuring tank 11.

  After a certain amount of the liquid mixture is stored in the Rr measuring tank 11, it is separated into sludge and supernatant liquid by gravity sedimentation by being left stationary for a certain time.

  Here, the sludge is discharged to the sludge receiving tank 41 until the value of the sludge interface gauge 43 coincides with the bottom surface of the Rr measuring tank 11 when it is determined from the signal of the sludge interface gauge 43 that the measured value is stable.

  The remaining supernatant is returned from the Rr measurement tank outlet 27 to the aeration tank 2.

  Here, the sludge in the sludge receiving tank 41 is returned to the Rr measuring tank 11 by the circulation pump 42, and then tap water, groundwater, etc. so as to be equal to the amount of the original mixed liquid from the Rr cleaning pipe 25 to the Rr measuring tank 11. Supply. Next, the air pump 16 and the stirrer 17 are operated to aerate the mixed solution in the Rr measurement tank 11 through the measurement tank diffuser tube 15 and at the same time, measurement by the DO sensor 13 and the temperature sensor 14 is also started. After the measurement is started, the measured values of the DO sensor 13 and the temperature sensor 14 are sequentially recorded in the control unit 12 at regular intervals, and the DO of the mixed liquid in the Rr measurement tank 11 rises by aeration and becomes a stirrer when it becomes constant. 17 is operated, and the operation of the air pump 16 is stopped to calculate the oxygen consumption rate of the mixed liquid in the Rr measuring tank 11 from the decrease curve of DO.

  Here, the supernatant is not replaced with tap water or groundwater, etc., and it can be made into a no-load state just by continuously aeration of the collected mixed solution, but it may take a long time to consume the load due to microorganisms, Replacing the supernatant with tap water, ground water, or the like can greatly reduce the residual load of the liquid mixture, so that the aeration time to the stable stage can be shortened.

  For tap water and groundwater, treated water from the wastewater treatment system can be used, but considering the stability of measurement and the effects of deterioration of treated water, tap water and groundwater other than the wastewater treatment system should be used. desirable.

  In this way, the oxygen consumption rate of endogenous breathing is periodically updated, and in the same manner as in Embodiment 1, this value is compared with the distribution of oxygen consumption rate to determine whether the endogenous breathing transition point is at an appropriate position. Judge whether.

  As described above, according to this embodiment, even when the load is always high and an unloaded state cannot be obtained at an appropriate frequency, the oxygen consumption of endogenous respiration is forcibly created by creating the unloaded state. Speed can be obtained, and a widely applicable aeration tank control method can be obtained.

(Embodiment 3)
The SV measuring tank 30 for measuring the sludge capacity is composed of a cylindrical container having a volume of 1 liter and an inner diameter of about 65 mm in accordance with the sewage test method. A light emitting unit 54 is disposed on one side of the SV measuring tank 30, and an optical sensor 59 is disposed on the other side facing the light emitting unit 54.

  The light source 52 is disposed in the first light collecting unit 51, the first light collecting unit 51 is connected to the light guide unit 53, and the light guide unit 53 is connected to the light emitting unit 54. The light emitting unit 54 includes an irregular reflection layer 56, and the light guide unit 53 is filled with a light guide material such as acrylic, and the light emitting surface of the light emitting unit 54 is in close contact with the SV measuring tank 30. .

  The optical sensor 59 is disposed so as to be in close contact with the second light collecting means 58 disposed so as to be in close contact with the SV measurement tank 30. A plurality of optical sensors 59 are arranged in series in the depth direction of the SV measuring tank 30 and are connected to the control unit 12 by a signal line 60 of the optical sensor. Here, the optical sensor 59 is a phototransistor, a photodiode, a photo IC, or the like.

  The first light collecting means 51 is made of a material that reflects light, such as stainless steel, a plated iron plate, or a mirror. Above the SV measuring tank 30, a sludge mixed liquid introducing pipe 28 for introducing a sludge mixed liquid from an aeration tank or the like and an SV cleaning pipe 26 for cleaning the inside of the SV measuring tank 30 are provided. In the lower part of the pipe, an SV measurement tank outlet 31 for discharging the sludge mixed liquid after the measurement, a sludge mixed liquid discharge pipe 28 and an SV measurement tank discharge valve 22 connected to the SV measurement tank outlet 31 are provided.

  In the above configuration, when measuring the sludge capacity, the sludge mixed solution in the aeration tank is introduced into the SV measurement tank 30 from an aeration tank (not shown) by an underwater pump, a land pump, an air lift pump, or the like. The amount of the sludge mixed liquid introduced into the SV measuring tank 30 is measured by a timer, an electromagnetic flow meter (not shown), or a liquid level sensor (not shown). After introducing the sludge mixed liquid into the SV measuring tank 30, it is allowed to stand for 30 minutes, and the height of the interface between the concentrated sludge 57 and the sludge supernatant 61 is measured.

  For this reason, the light source 52 is turned on, the light is condensed by the first light collecting means 51, the collected light is guided to the light emitting part 54 by the light guiding means 53, and the light is irregularly reflected by the irregular reflection layer 56 of the light emitting part 54. Then, the light is made uniform in the light guide means 53, and then the SV measuring tank 30 is irradiated with surface light emitted from the light emitting portion 54.

  Since the light irradiated into the SV measuring tank 30 is blocked by the concentrated sludge 57, the optical sensor 59 does not detect the light. On the other hand, since the light is not blocked by the sludge supernatant 61, the optical sensor 59 detects the light. In this manner, the sludge interface can be easily and reliably grasped and the sludge capacity can be measured by the number of light sensors 59 that detect light and the number of light sensors 59 that do not detect light and preset positions. The standing time (30 minutes) is an example, and can be set from several minutes to several hours as necessary.

  Because of the measuring device having such a configuration, the accuracy of measurement depends on the number of optical sensors 59. For example, in FIG. 8, since the number of the optical sensors 59 is 10 and they are arranged at equal intervals, it is possible to measure the sludge capacity in increments of 10%. Here, when the number of the optical sensors 59 is 20, it becomes possible to measure the sludge capacity in 5% increments. Judging from the actual situation of activated sludge treatment and maintenance, it can be said that the accuracy is enough to withstand practical use in 5% increments.

  The signal from the optical sensor 59 is transmitted to the control unit 12 through the signal line 60.

  After measuring the sludge capacity, the SV measuring tank discharge valve 22 is opened to discharge the sludge mixed liquid in the SV measuring tank 30, and then the SV measuring tank discharge valve 22 is closed and the cleaning water is introduced from the SV cleaning pipe 26. By doing so, the inside of the SV measurement tank 30 is cleaned. Here, the washing water may be tap water, industrial water such as groundwater, treated water of a wastewater treatment facility, or the like.

  With the above configuration, the light from the light source 52 can be radiated to the SV measurement tank 30 without waste, and the light transmitted through the SV measurement tank 30 can be reliably detected by the optical sensor 59. Further, since the light of the light source 52 can be emitted from the light emitting unit 54 to the SV measuring tank 30, the unevenness of the light transmitted through the SV measuring tank 30 can be suppressed, and the unevenness of the light reaching the optical sensor 59 can be suppressed. And stable light detection is possible.

  Here, as the light source 52, a fluorescent lamp or an incandescent lamp is generally used, but it is best to use an LED. Since the LED directly converts electrical energy into light, there is no generation of radiant heat, preventing convection of the sludge mixture in the SV measuring tank 30 due to the influence of radiant heat generated from the light source 52, and measuring a stable sludge capacity. Is possible.

  Further, the light emitted from the light source 52 may be visible light, but it is desirable that the light is red among visible light. Since red light has a long wavelength of about 700 nm, it has the property that it is difficult for light to be attenuated by suspended matter in water. Can be measured.

  Further, since the optical sensor 59 collects light from the SV measuring tank 30 by the second condensing means 58, even if the sludge mixed solution is colored or the like and hardly transmits light, it is ensured. It becomes possible to measure the sludge capacity. Here, the second light condensing means 58 is a lens made of plastic (acrylic or the like) or glass, and is used to collect as much light transmitted through the SV measuring tank 30 as possible.

  In addition, since the wavelength at which the sensitivity of the optical sensor 59 is maximum differs depending on the type, it is important to select the optical sensor 59 that matches the wavelength of the light from the light source 52.

  FIG. 9 is a structural view of the horizontal cross section of the optical sensor 59 portion of the sludge capacity measuring device in FIG.

  The SV measuring tank 30 is composed of an inner surface and an outer surface with an air layer 71d interposed therebetween (for the sake of simplicity, it is omitted from the description with reference to FIG. 6). The surface is made of a transparent material so as to transmit light like the light receiving / transmitting portion 71b. A light shielding layer 71c (shown by a thick line in FIG. 2) is provided on the outer surface except for the light transmission / transmission part 71a and the light reception / transmission part 71b, and reflects light from the outside.

  Here, the material of the SV measuring tank 30 is preferably plastic or glass. In addition, the light shielding layer 71c may be simply aluminum foil, but it is also possible to use a paint that easily reflects light, such as silver or white, after being undercoated such as black.

  Thus, by providing the air layer 71d in the SV measurement tank 30, the SV measurement tank 30 has a heat insulating effect, and the outer surface of the SV measurement tank 30 reflects light. For this reason, the sludge mixed liquid in the SV measuring tank 30 is not easily affected by the outside air temperature and radiant heat. As a result, the temperature distribution in the SV measuring tank 30 is uniform, and the sludge mixed liquid in the SV measuring tank 30 is convected. This makes it possible to measure sludge capacity stably without being affected by changes in the external environment such as high and low temperatures, night and daytime.

  The aeration tank control method according to the present invention can be applied to monitoring of an aeration tank in an organic wastewater treatment facility at a sewage treatment plant, a business office or the like.

The block diagram which shows the aeration tank control system of Embodiment 1 of this invention The graph which shows distribution of the oxygen consumption rate in the aeration tank of Embodiment 1 of this invention The flowchart which shows operation | movement of Embodiment 1 of this invention. (A) is the graph which showed the state of the aeration tank of Embodiment 1 of this invention by the relationship between elapsed date and time and oxygen consumption rate, (b) the graph which showed the state of the aeration tank by distribution of oxygen consumption rate (A) is the graph which showed the case where the process state of the aeration tank of Embodiment 1 of this invention is appropriate, (b) is the graph which showed the case where the process of the aeration tank is insufficient Graph showing the distribution of oxygen consumption rate in a general wastewater treatment facility The block diagram which shows the measurement control apparatus of Embodiment 2 of this invention The block diagram which shows SV measurement tank 30 in this Embodiment The block diagram which shows the cross section of SV measurement tank 30 in FIG. 6 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Adjustment tank 2 Aeration tank 3 Precipitation tank 4 Aeration pipe 5 Inverter 6 Aeration blower 7 Rr sampling pump 8 Mixed liquid collection valve 9 SV sampling pump 10 Waste water treatment system 11 Rr measurement tank 12 Control part 13 DO sensor 14 Temperature sensor 15 Measurement tank Aeration pipe 16 Air pump 17 Stirrer 18 Inlet 20 Measurement control system 21 Rr measurement tank discharge valve 22 SV measurement tank discharge valve 25 Rr cleaning pipe 26 SV cleaning pipe 27 Rr measurement tank outlet 28 Sludge mixture introduction pipe 30 SV measurement Tank 31 SV measurement tank outlet 41 Sludge receiving tank 42 Circulation pump 43 Sludge interface meter 44 Sludge receiving tank inlet valve 51 First light collecting means 52 Light source 53 Light guiding means 54 Light emitting part 56 Diffuse reflection layer 57 Concentrated sludge 58 Second light collecting Means 59 Optical sensor 60 Signal line 61 Sludge supernatant 71a Light transmission part 71b Light transmitting portion 71c Light shielding layer 71d Air layer 75 Light emitting portion 80 Optical sensor 90 Display portion

Claims (16)

Along the flow direction in the aeration tank, measure the oxygen consumption rate distribution of the mixed liquid of sludge and waste water at multiple locations, measure the sludge capacity of the sludge in the aeration tank, measure the oxygen consumption rate distribution and the sludge A method of monitoring an aeration tank that compares the oxygen consumption rate of endogenous respiration and compares the measured sludge capacity with a predetermined value to determine whether the wastewater treatment by sludge is appropriate and displays the result of the determination to the outside . The aeration tank monitoring method according to claim 1, wherein the oxygen consumption rate of the endogenous breath is a measured value of the oxygen consumption rate of the mixed liquid in an unloaded state. The aeration tank monitoring method according to claim 2, wherein the no-load state is a state in which there is no load flowing into the aeration tank. The aeration tank monitoring method according to claim 2, wherein the no-load state is a state in which the slope of the oxygen consumption rate distribution measured at a plurality of locations along the flow direction of the aeration tank is horizontal. The aeration tank monitoring according to claim 2, wherein the no-load state is a state in which a mixed liquid is collected from the most downstream portion in the flow direction of the aeration tank, and the residual load is consumed by aeration of the collected mixed liquid. Method. 6. The method for monitoring an aeration tank according to claim 5, wherein the collected mixed liquid is separated into a supernatant and a suspension before aeration, and the supernatant is replaced with unloaded fresh water. The method for monitoring an aeration tank according to claim 1, wherein when the measured oxygen consumption rate is lower than the oxygen consumption rate of endogenous respiration, the measured oxygen consumption rate is used as the oxygen consumption rate of endogenous respiration. The aeration tank monitoring method according to claim 1, wherein the sludge capacity is a sludge capacity measured at a most downstream portion in a flow direction of the aeration tank. When the oxygen consumption rate measured at the most downstream part in the flow direction of the aeration tank is larger than the endogenous breath and the sludge capacity is larger than a predetermined value, it is determined that the waste water treatment by the sludge is insufficient. The aeration tank monitoring method according to claim 1. When the oxygen consumption rate measured at the most downstream portion in the flow direction of the aeration tank is larger than the endogenous breathing and the sludge capacity is smaller than a predetermined value, it is determined that the wastewater treatment with sludge is appropriate. The aeration tank monitoring method according to claim 1. When the oxygen consumption rate measured at the most downstream part in the flow direction of the aeration tank is lower than the oxygen consumption rate of endogenous respiration and the sludge capacity is smaller than a predetermined value, the measured oxygen consumption rate is The method for monitoring an aeration tank according to claim 1, wherein the oxygen consumption rate is set and it is determined that the waste water treatment with sludge is excessive. When the oxygen consumption rate measured at the most downstream part in the flow direction of the aeration tank is equal to the oxygen consumption rate of endogenous respiration and the sludge capacity is smaller than a predetermined value, the wastewater treatment with sludge is excessive. The method for monitoring an aeration tank according to claim 1 for determination. The determination as to whether the state of wastewater treatment by sludge is appropriate is performed by measuring the MLSS simultaneously with the oxygen consumption rate to calculate an oxygen utilization rate coefficient, and using the oxygen utilization rate coefficient instead of the oxygen utilization rate. Aeration tank monitoring method. The aeration tank monitoring according to claim 1, wherein the determination of whether the wastewater treatment by sludge is appropriate is performed by measuring the MLSS simultaneously with the sludge volume, calculating a sludge volume index, and using the sludge volume index instead of the sludge volume. Method. The aeration tank monitoring method according to claim 1, wherein the wastewater treatment status is displayed in characters. The aeration tank monitoring method according to claim 1, wherein the wastewater treatment status is displayed in a diagram.

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