KR100235588B1 - A control method of activated sludge process by means of intermittent areation - Google Patents

Abstract

In spite of fluctuations in the magnitude of the load, it is possible to sufficiently cope with the load fluctuation without manually adjusting the ratio between blower operation time and aerobic time and anaerobic time.

In other words, in an active sludge treatment method in which an anaerobic state and an aerobic state are alternately aerated by intermittently discharging sewage in a single reactor, a drop in DO (dissolved oxygen concentration) is time-series immediately after the aeration device is stopped. The Rr (oxygen utilization rate of activated sludge) representing the slope of DO drop is measured at each aeration cycle, and the aeration interval is automatically set according to the measured Rr, and the nitriding reaction proceeds in the aeration interval. The aerobic anaerobic time ratio RA0 with DO in the anaerobic time Tan in which the denitrification proceeds in the reaction tank between which the denitrification reaction progresses between the time that the DO value exceeds the DO value and the time that the oxygen supply is stopped is set automatically according to the measured Rr. The aeration apparatus stop time is controlled by predicting from the Rr measured in the previous cycle so that RA0 is equal to the set value in the aeration interval time.

Description

Control method of intermittent aeration activated sludge method

The present invention relates to an aeration-type activated sludge method for performing nitrification-denitrification treatment of small-scale sewage, such as sewage and industrial wastewater, such as an oxidation quench method and a forged anaerobic aerobic method. The control method in the intermittent aeration type sludge method by a batch method or the like.

As a conventional technique related to the control method of this kind of intermittent aeration type sludge method, Japanese Patent Application Laid-Open No. 5-50092 (hereinafter referred to as "Prior Example 1") and Japanese Patent Application Laid-Open No. 7-136682 (Patent) Example 2 ').

Hereinafter, the outline | summary of the point is demonstrated according to FIGS. 10-13.

The method of the prior art example 1 is aerobic time B and anaerobic time A in the control curve of time (horizontal axis) with respect to DO (dissolved oxygen concentration) value shown in FIG. 10 in the apparatus structure shown in FIG. Is a method of controlling the time of A so that the ratio of A / B is 0.6 to 1.0. In FIG. 10, 21 is an intermittent aeration tank, 22 is a sedimentation basin, 23 is an underwater aerator, 24 is a compressor, and 25 is a DO system. In FIG. 11, T is the aeration cycle time, A is the anaerobic time, B is the exhalation time, C is the air supply time, D is the air supply stop time.

The method of the conventional example 2 measures the expiration time τ in the control curve of time with respect to the DO value shown in FIG. 13 in the device configuration shown in FIG. 12, and resumes aeration after elapsed by this time from τ-αt. It is a control method to operate the cycle. In Fig. 12, 11 is an oxidization dig, 12 is a sedimentation basin, 13 is an aerator, 14 is a DO system, 15 is a control panel, and 16 is an arithmetic unit.

The conventional control method of the intermittent aeration type sludge method has the following problems.

First, in the conventional example 1, the compressor operation timer is fixed at 40 minutes, the expiration time B is measured from this result, and the anaerobic time A is secured. In the conventional example 2, the peak of DO is the upper limit value C2 level. The aeration is stopped at the time of (= 2-3 mg / l), the aerobic time τ is measured, and the anaerobic time T is secured.

Therefore, these conventional examples and the interval time of each cycle are indefinite and are not intended to start processing at the right time, which is undesirable for maintenance.

Subsequently, small-scale facilities are mainly applied to the intermittent aeration activated sludge method by the oxidation dichroic method, forging anaerobic aerobic method, and batch method. In many cases, a long time passes from the excessively low load, where only sewage water enters, and the active sludge concentration in the reaction tank is reduced to the rated load. Therefore, it is preferable that the automatic control of the intermittent aeration activated sludge method can be controlled without manual adjustment from excessively low load to rated load.

However, in the conventional example 1, the DO value is 8.0 mg / 40 after 40 minutes because the operating time of the blower is fixed at 40 minutes even though the Rr (oxygen utilization rate of activated sludge) is very small under excessive load. Reaching the saturation value of l is easily estimated from the following equation (1), which not only wastes the power consumption of the blower, but also the time until DO falls to 0 when the DO value immediately after the aeration stop is 8 mg / l. Is extremely large, and if the same anaerobic time is set, the interval time is excessive, and during this time, the water quality deteriorates due to the low BOD removal reaction.

dC / dt = k _La (Cs-C) -Rr ------ (1)

Where dC / dt is the time change of dissolved oxygen concentration in the reactor (mg / l / Hr)

Rr: Oxygen utilization rate of activated sludge (mg / l / Hr)

Cs: Saturated dissolved oxygen concentration (mg / l) --- 8.84 in water at 20 ℃, 1 atmosphere

C: dissolved oxygen concentration in the reaction tank (mg / l)

k _La : Overall material oxygen transfer capacity factor (l / Hr) --- Oxygen of aeration device

Coefficient proportional to supply capacity

Therefore, in the conventional example 1, it is possible to cope with time fluctuations and weekly fluctuations of the inflow load, but it is not possible to cope with the wide load fluctuations from the excessive low load with little active sludge concentration and the inflow load to the rated load immediately after the commencement of public use. Accordingly, it is necessary to manually adjust the operating time of the blower and the ratio between the aerobic and anaerobic times.

In the conventional method 2, the aeration device is stopped when the DO value reaches the upper limit value C2 (= 2 to 3 mg / l), so that the problem of excessive DO value immediately after the aeration stop can be prevented. However, in order to achieve good nitrogen removal, almost all the nitrification of Kjeldahl nitrogen by aerobic treatment and almost all the denitrification by anaerobic treatment of nitric acid produced by this are required. The denitrification rate is almost the same, and the aerobic and anaerobic times are good at 1: 1, but at low loads, unless the aerobic time is less than that of the anaerobic time, the deoxidation does not occur sufficiently since it oxidizes to the hydrogen donor (organic substance in the sewage) necessary for denitrification. Do not. Therefore, it is necessary to adjust the ratio of aerobic time and anaerobic time according to the magnitude of load.

The present invention has been made in order to solve the above problems, despite the change in the magnitude of the load intermittent aeration type sludge that can adequately cope with the load fluctuation without manually adjusting the ratio of blower operation time or aerobic time and anaerobic time It aims to provide a method of controlling the law.

1 is a flowchart illustrating a basic configuration of a control method according to the first embodiment of the present invention.

Figure 2 is a schematic configuration diagram showing an example of the intermittent aeration activated sludge apparatus used in the present invention.

3 is a DO diagram showing a control method of the present invention.

4 is a flowchart of the set value input process shown in FIG. 1;

5 is a flow chart of the initial operation mode of FIG.

FIG. 6 is a flow chart of the predictive driving mode of FIG. 1. FIG.

7 is a flow chart of the aeration amount adjusting process in FIG. 1.

Fig. 8 is a flowchart of the set value input process in the second embodiment of the method of the present invention.

Fig. 9 is a flow chart of a predictive driving mode in a second embodiment of the method of the present invention.

10 is a device configuration diagram of a conventional example 1. FIG.

11 is an explanatory diagram of a control method of a conventional example 1. FIG.

12 is a device configuration diagram of a conventional example 2. FIG.

13 is an explanatory diagram of a control method of a conventional example 2. FIG.

* Explanation of symbols for main parts of the drawings

1: Reactor 2, 12, 22: Settling basin

3: aeration device 4, 14, 25: DO system

5: oxygen supply device control panel 6: underwater stirring device

11: Oxidation Ditch 13: Aeration

15: control panel 16: computing device

21: intermittent aeration tank 23: underwater aerator

24: compressor

In the control method of the intermittent aeration activated sludge method according to the present invention, by continuously stirring the sewage in a single reactor to supply aeration (oxygen supply), the activated sludge of the sewage is alternately anaerobic and aerobic in the reaction tank. In the treatment method, it has two steps of (1) and (2) below or three steps of (1) to (3).

(1) The drop in DO is taken in time series immediately after the aeration device is stopped in the reactor, the respiratory rate Rr of the sludge is measured for each intermittent aeration cycle, and the intermittent aeration interval time is measured according to the measured Rr. Automatic setting process,

(2) In the intermittent aeration interval time, DO in the reactor where the denitrification reaction proceeds between the expiration time Tox when DO in the reactor exceeds the DO value in which the nitriding reaction proceeds and the time when the supply of oxygen is stopped is near 0. Analyze the aeration device stop time from Rr measured in the previous cycle so that the anaerobic anaerobic time ratio RA0 (= Tox / [Tox + Tan]) with the anaerobic time Tan is equal to the set value,

(3) If the aeration device is capable of shifting, the peak value of the DO for each cycle so that the peak value of DO immediately after the aeration stop falls within a value before and after the target peak DO value at which nitriding is sufficiently performed (peak DO tolerance). The process of automatically adjusting the oxygen supply proportional to the deviation from the target peak DO value when the peak DO is outside the allowable range.

In addition, the control method of the intermittent aeration activated sludge method according to the present invention is to continuously agitate the sewage in a single reaction tank to aeration (oxygen supply) to activate the sewage in the reaction tank alternately between anaerobic and aerobic conditions. The sludge treatment method includes three steps (1) to (3) below or four steps (1) to (4).

(1) collecting DO drop in time series immediately after the aeration device stops in the reactor, measuring the respiratory rate Rr of the sludge for each intermittent aeration cycle, and automatically setting the intermittent aeration interval according to the measured Rr;

(2) In the intermittent aeration interval time, DO in the reactor where the denitrification reaction proceeds between the expiration time Tox when DO in the reactor exceeds the DO value in which the nitriding reaction proceeds and the time when the supply of oxygen is stopped is near 0. Process of automatically setting the anaerobic anaerobic time ratio RA0 (= Tox / [Tox + Tan]) with the anaerobic time according to Rr measured in the previous cycle,

(3) three steps of a step of estimating the aeration device stop time from the Rr measured in the last cycle so that the aerobic anaerobic time ratio RA0 in the intermittent aeration interval time is equal to the set value,

(4) If the aeration system is capable of shifting, DO's peak value should be set for each cycle so that the peak value of DO immediately after the aeration stops falls within the value before and after the target peak DO value that is sufficiently nitrided (peak DO tolerance). The process of automatically adjusting the oxygen supply proportional to the deviation from the target peak DO value when the peak DO is outside the allowable range.

The DO value (DOox) in which the nitriding reaction proceeds is 0.5 to 1.0 mg / l or more, and the DO value (DOo) in the reaction tank in which the denitrification reaction proceeds is 0.1 to 0.2 mg / l near 0, and the anaerobic anaerobic time ratio RA0. The set value of is preferably in the range of 0.2 or more and less than 0.5 in proportion to Rr measured in the previous cycle. The target peak DO value is preferably 1.5 to 3 mg / l.

In this invention, the outstanding characteristic as shown to the following (a)-(bar) is acquired.

(A) In the system by the intermittent aeration activated sludge method of continuously agitating sewage and intermittently aeration, Rr measurement takes a time series of the drop in DO value immediately after the aeration device stops, and this is determined by the least-squares method. Obtained by the calculation process, it is possible to achieve the purpose by configuring only the DO system and the calculator so that no new device is needed.

(B) By measuring Rr, it is possible to quantify the load situation and set the corresponding aeration interval. In other words, a large Rr indicates that the activated sludge concentration MLSS in the reaction tank is large and the load of influent sewage (inflow amount x BOD concentration) is large. In this case, since the BOD removal rate is large, it is necessary to shorten the aeration interval time. The reason for this is that if the interval time is excessive, the BOD component is introduced even though the BOD removal reaction is small at the time of stopping the aeration, the concentration of untreated BOD in the reaction tank increases, resulting in deterioration of the treated water quality.

Therefore, it is necessary to automatically adjust the appropriate aeration interval according to the measured Rr as follows so that manual adjustment is not required.

Here, the relationship between Rr and the aeration interval may be replaced by the following equation in FIG. 3.

TI = (Tox + Tan) × (1 + α)

Where TI: Aeration Interval Time (Hr)

Tox: Exhalation Time (Hr)

Tan: Anaerobic Time (Hr)

α: margin ratio (0.1 to 0.4)

If RA0 = 0.5, Tan = Tox

If t1 = t2, Tox = 2 × t2

If DOpeak = 2.0mg / l and DOmin = 0.5mg / l, t2 = 1.5 / Rr

∴ TI = 2 × Tox × (1 + α)

= 2 x 2 x t2 x (1 + α)

= 2 × 2 × 1.5 / Rr × (1 + α)

TI = 6.6 / Rr∼8.4 / Rr → 8.0 / Rr ------ (2)

From the above results, the aeration interval time TI is proportional to the inverse of Rr. Therefore, if the minimum unit of the aeration interval time TI is 1 hour, and increases by every multiple, the relationship between Rr and aeration interval is as shown in Table 1 below.

Rr (mg / l / Hr) Aeration Interval Time (Hr) Rr≥8 1.0 4≤Rr <8 2.0 2≤Rr <4 4.0 Rr <2 8.0

(C) Since the aeration stop time is controlled so that the set RA0 is set at the interval time automatically set by Rr measured for each aeration cycle, every cycle always starts the processing at the right time. This makes it possible to know the start time of the next operation of the aeration device, which is advantageous in terms of maintenance.

In the case where the reaction tank is a plurality of series, the power consumption can be smoothed by not overlapping the operation timing of the aeration device so that the first system starts at 0:00 minutes and the second system starts at 0:30. Save money

(D) At the rated load, the nitrification rate and denitrification rate are almost the same, and the aerobic and anaerobic times are good at 1: 1, but when it is applied at low load, the aerobic time becomes excessive and the hydrogen donors (organic substances in sewage, etc.) required for denitrification are increased. As it is oxidized, the denitrification rate is lowered and not enough denitrification. Therefore, the ratio between aerobic and anaerobic times needs to be adjusted according to the size of the load. In the present invention, the load is quantified in Rr, and the anaerobic anaerobic time ratio RA0 and Rr are given by the following relationship.

RA0 = a + b × Rr

(E) Since the measured value hardly fluctuates in the previous cycle and the next cycle, Rr can accurately calculate the timing of stopping the aeration device that secures the target anaerobic time Tan from the previous Rr value.

(F) There are two operational factors for aeration: operating time and oxygen supply rate. Since the former can be set as theoretical in the above-mentioned (e), the latter can be controlled by deriving the addition or subtraction so that the peak value of DO is before and after the target value. Therefore, it is possible to more precisely manage the peak value of DO.

In this way, almost all of the nitriding and denitrification is possible, and at the same time, the energy saving operation of the aerator is possible.

(Embodiment 1)

A control method of the intermittent aeration activated sludge according to the first embodiment of the present invention will be described based on the drawings in FIGS. 1 to 7.

As described above, the intermittent aeration treatment sludge treatment method is generally the oxidation drift method, forged anaerobic aerobic method, batch method, etc. In the present embodiment, the apparatus of the oxidation drift method, forged anaerobic aerobic method shown in FIG. The configuration will be described.

In Fig. 2, the apparatus of the forged anaerobic aerobic method is divided into a reaction tank 1 for activating a mixed liquid mixed with sewage and activated sludge, and a sedimentation basin 2 for storing and treating a mixed liquid. It is part. The reactor 1 is provided with an aeration device 3 (combination of a blower and an acid generator in the drawing) and an underwater stirrer 6. The DO system 4 is arranged, and the DO system 4 and the aeration device 3 are connected to the oxygen supply control panel 5.

The general treatment of sewage is well known, so it is only briefly described here.

The influent sewage is treated by aeration from the blower while being agitated by the agitator 6 in the reaction tank 1 to be transferred to the settling basin 2 after almost the entire amount of nitriding and denitrification is completed.

Here, it stands still for a while, and sediment accumulates at the bottom of the sedimentation basin, and the clean supernatant liquid is collected from the upper side and discharged as treated water.

On the other hand, most of the sediment deposited on the bottom of the sedimentation basin is refluxed in the reaction tank 1 as a return sludge, and the rest is disposed of as a surplus sludge.

1 is a flowchart illustrating a basic configuration of a control method of the present invention, and FIG. 3 is a DO diagram according to the control method of the present invention. 4 to 7 are flow charts showing the details of each process of FIG. 1, FIG. 4 is a flow chart of the set value input process, FIG. 5 is a flow chart of the initial operation mode, and FIG. 6 is a prediction drive mode. Flow chart of the process, Fig. 7 is a flow chart of the aeration amount adjustment process.

Hereinafter, the detailed structure of this invention is demonstrated using FIGS. 1-7 in the order of the steps [1]-[5] below.

As a processing procedure, as shown in Fig. 1, step 1 is input of a set value, step 2 is an initial operation mode, step 3 is a prediction operation mode, and step 4 is an adjustment of the aeration amount in the prediction operation mode.

[1] Initially, 12 items of setting values, such as the initial aeration interval time shown in Figs. 1 and 4, are input (step 1).

[2] The control start command is then issued.

[3] The initial operation mode is started (step 3).

The initial operation is an operation for easily collecting Rr, and stops the aeration device 3 at the minimum peak DO value (DOpmin), and waits for a predetermined time (the timing at which the distance between the aeration device 3 and the DO system 4 is generated). Record DO value for Rr measurement. The reason why the minimum peak DO value is used as the aeration device stop condition is that if the DO value for determining the aeration device stop is the minimum that Rr can be obtained, Rr can be taken in the shortest time and the prediction operation can be started quickly. to be.

When Rr is calculated, the next aeration interval time TI is waited until the initial aeration time interval elapses from Equation 1 below, and the next time goes to the predictive operation (②).

On the other hand, when Rr is larger than the oxygen supply amount of the aerator 3, the DO value is the minimum peak even after passing the aerator operation timeout condition (time multiplied by the initial operation time ratio R ₀ by the initial aeration interval time T _I0 ). It is assumed that the DO value does not reach.

In this case, since the peak DO value is low, Rr calculation is difficult and Rr calculation is disabled. Therefore, in the next initial operation, the aeration amount is maximized, the air is awaited until the initial aeration interval time elapses, and the operation returns to the initial operation (①).

C = 2 × 2 × 1.5 × (1 + α) α = 0.1 to 0.4

= 6.6 to 8.4 to 8.

∴ Rr≥8 T _I = 1Hr

4≤Rr <8 T _I = 2Hr

2≤Rr <4 T _I = 4Hr

Rr <2 T _I = 8Hr

In addition, as a reason for setting the aeration device operation timeout condition, the aeration device operation time cannot be obtained without stopping the aeration time, and the anaerobic time must be secured in each cycle. In addition, by taking the initial operation time ratio R ₀ larger than 0.5, the amount of aeration can be made significant, thereby reducing the Rr in the next cycle.

[4] The prediction operation mode is started (step 3).

Predictive driving is the anaerobic anaerobic time ratio set by Tox and Anaerobic Time (Tan)

RA0 (= Tox / [Tox + Tan])

The aeration device stop time t is estimated by the equation (2) from Rr measured in the previous cycle so that is equal to the range of the set value (0.2 or more and less than 0.5).

The calculation method of Rr after the aeration device stops and the method of determining the aeration interval time are the same as in the case of Step 2.

Tox≥ (Tox + Tan) × RA0 ------ ①

Tox = t ₁ + t ₂ ------ ②

------ ③

------ ③

------ ④

------ ④

①From meal

------ ①'

------ ① '

Assign ②, ③ to ① '

------ ⑤

------ ⑤

Substituting ④ into ⑤

However, the peak value of DO is taken and the next aeration is adjusted in the next step 4. He waits until the aeration time elapses this time and returns to the next prediction prediction (②).

On the other hand, if the DO value does not reach the predicted stop value even if Rr is larger than the oxygen supply and the aerator operation timeout condition (aeration interval time T _I multiplied by the initial operation time ratio R ₀ ) passes, the peak DO Since the value is low, Rr calculation is difficult and Rr calculation is disabled. Therefore, the next time, the aeration amount is maximized and waits until the aeration interval elapses and returns to the initial operation (①).

[5] The aeration amount is adjusted in the predictive operation (step 4).

In step 3 (predictive operation), the peak value of the DO value that appears after the aeration device stops is the peak DO allowable range [(1-K) x DO _SV ≤ DO peak value ≤ (1 + K) x DO _SV (Fig. 3). 7), the aeration amount is kept as a developing condition, and when it is outside the peak DO allowable range, the aeration amount is adjusted by [Equation 3]. However, the upper limit and the lower limit of the aeration amount are maintained.

Qn + 1: Next aeration amount (kgO ₂ / Hr)

Qn: Current Aeration Volume (kgO ₂ / Hr)

α: proportional constant (-)

(Embodiment 2)

Next, a second embodiment of the control method of the present invention will be described with reference to Figs. 1, 5, 7 and 8 and 9 below.

The basic processing procedure of the control method by this embodiment is as showing in FIG. However, in the input of the set value of step 1, as shown in FIG. 8, all items other than the anaerobic anaerobic time ratio RA0 of FIG. 4 are set. The reason for not setting RA0 is that RA0 is determined and automatically set by Equation 4 as described below.

The processing and operation in the initial operation mode (step 2) are the same as in the above [3].

The processing and operation in the predictive driving mode (step 3) are basically the same as in [4] above, but the aerobic anaerobic time ratio RA0 (= Tox / [Tox + Tan]) enters the predictive driving mode as shown in FIG. It is determined by Equation 4 from Rr measured before in the previous cycle. Furthermore, the aeration device stop time t is determined by predicting [Equation 2] from Rr measured in the previous cycle so that the aerobic anaerobic time ratio RA0 becomes the set value.

RA0 = a + b × Rr

0.2≤RA0 <0.5

In the oxidization drift method, in which the BOD-SS load is designed to 0.05 kg BOD / kg SS-day, as a result of the study, a = 0.2 and b = 0.02 were obtained empirically as the optimum values of the above equation.

In addition, the processing and operation in the adjustment of the aeration amount (step 4) are also the same as in the above-mentioned [5].

As described above, according to the present invention, in the intermittent aeration type activated sludge method in which aerobic anaerobic treatment is performed in a single reactor, the load in the reactor is quantitatively determined by measuring Rr using an oxygen supply stop time. It is possible to set the appropriate interval time and to control the aeration timing of the aeration device so that the aerobic anaerobic time ratio is set to ensure almost 100% of denitrification at the set interval time. Not only can it cope, but it can obtain a good active sludge treatment effect without any manual adjustment from excessive low load with little active sludge concentration and inflow load to the rated load immediately after the start of public use.

Claims (6)

As a control method of the intermittent aeration type activated sludge method of filthy water which alternately anaerobic state and aerobic state in time in the reaction tank by continuously stirring and filthy water in a single reaction tank, (1) Collecting the drop of DO in time series immediately after the aeration device stops in the reactor, measuring the respiratory rate Rr of the sludge for each intermittent aeration cycle, and automatically setting the intermittent aeration interval according to the measured Rr. Fair, (2) In the intermittent aeration interval time, the DO in the reactor where the denitrification reaction proceeds between the expiration time Tox at which the DO in the reaction vessel exceeds the DO value at which the nitriding reaction proceeds and the time at which the oxygen supply is stopped is near 0. It has two processes of predicting aeration device stop time from Rr measured in the previous cycle so that the anaerobic anaerobic time ratio RA0 (= Tox / [Tox + Tan]) with the phosphorus anaerobic time Tan is equal to the set value. A control method of an intermittent aeration type activated sludge method. After the two processes of claim 1, (3) When the aeration device is capable of shifting, the peak of the DO for each cycle so that the peak value of DO immediately after the aeration stop falls within a value before and after the target peak DO value at which nitriding is sufficiently performed (peak DO tolerance). And a step of automatically adjusting an oxygen supply amount proportional to a deviation from the target peak DO value when a value is outside the peak DO allowable range. As a control method of the intermittent aeration type activated sludge method of filthy water which alternately anaerobic state and aerobic state in time in the reaction tank by continuously stirring and filthy water in a single reaction tank, (1) Collecting the drop of DO in time series immediately after the aeration device stops in the reactor, measuring the respiratory rate Rr of the sludge for each intermittent aeration cycle, and automatically setting the intermittent aeration interval according to the measured Rr. Fair, (2) In the intermittent aeration interval time, the DO in the reactor where the denitrification reaction proceeds between the expiration time Tox at which the DO in the reaction vessel exceeds the DO value at which the nitriding reaction proceeds and the time at which the oxygen supply is stopped is near 0. Process of automatically setting the anaerobic anaerobic time ratio RA0 (= Tox / [Tox + Tan]) with phosphorus anaerobic time Tan according to the above Rr measured in the previous cycle, (3) an intermittent aeration type comprising: a step of predicting an aeration device stop time from the Rr measured in the previous cycle so that the aerobic anaerobic time ratio RA0 becomes the set value in the intermittent aeration interval time; Control method of active sludge method. After the three processes of claim 3, (4) When the aeration device is capable of shifting, the peak of the DO for each cycle so that the peak value of DO immediately after the aeration stop falls within a value before or after the target peak DO value where the nitriding is sufficiently performed (peak DO allowable range). And a step of automatically adjusting an oxygen supply amount proportional to a deviation from the target peak DO value when a value is outside the peak DO allowable range. The DO value (DO0X) in which the nitriding reaction proceeds is 0.5 to 1.0 mg / l or more, and the DO value (DO0) in the reaction tank in which the denitrification reaction proceeds is 0.1 to 0.2 according to claim 1, 2, 3 or 4. It is mg / l, The control method of the intermittent aeration-type activated sludge method characterized by setting the setting value of aerobic anaerobic time ratio RA0 to the range of 0.2 or more and less than 0.5 in proportion to Rr measured in the last cycle. The method according to claim 2 or 4, wherein the target peak value is 1.5 to 3 mg / l.

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