JPH0947780A - Method for controlling nitration reaction in circulation-type nitrating and denitrifying process and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance control precision by obtaining the real value for the oxygen consuming rate in the nitration reaction in a circulation-type nitrating and denitrifying process. SOLUTION: A measuring instrument having a value for the total oxygen consuming rate subtracted by the oxygen consuming rate accompanying the nitration reaction and a dissolved oxygen densitometer 16 are attached to an aerobic tank in a circulation-type nitrating and denitrifying process. The real value [Nit-Rr]real 19 for the oxygen consuming rate in the nitration reaction is obtained from the maximum oxygen consuming rate [Nit-Rr]max 17, half- saturation constant [Kdo] 18 and DO in the nitration reaction obtained from the measured values. The real value is inputted to a nitration reaction controller 20 to estimate the nitrating rate in an anaerobic tank, and DO control 21 and SRT control 22 as the sludge retention time are conducted to control the discharge of the blower 5 to the aerobic tank in accordance with the value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrification reaction control method and device for highly efficiently removing organic matter and nitrogen in wastewater by using a circulating nitrification denitrification method.

[0002]

2. Description of the Related Art Various methods have conventionally been proposed for efficiently removing organic matter in wastewater such as sewage and removing nitrogen and phosphorus which are considered to be the causative agents of eutrophication in closed water areas. . Furthermore, it is expected that the removal rate of nitrogen will be increased in recent years, and regulations on nitrogen will be tightened.Therefore, it is thought that the number of facilities adopting advanced treatment processes that can remove this will increase. To be

Although physicochemical methods and biological methods have been proposed as means for removing nitrogen and phosphorus in wastewater, physicochemical methods are not widely used because of the high cost. For example, a phosphorus removal method which has been put into practical use as a physicochemical method includes a coagulation precipitation method and a crystallization method, but this method has a drawback in terms of cost and maintenance.

On the other hand, as a method for biologically removing nitrogen and phosphorus simultaneously, a circulation type nitrification denitrification method has been attracting attention as a modification of the conventional activated sludge method. For example, as shown in FIG. 6, the biological reaction tank is divided into anaerobic tanks 1a and 1b in which dissolved oxygen (hereinafter abbreviated as DO) does not exist and a plurality of aerobic tanks 2a, 2b and 2c in which DO exists. , This anaerobic tank 1a,
1b, the inflowing raw water 3 is agitated by an agitation mechanism 10 under anoxic condition to denitrify by denitrifying bacteria in the activated sludge, and then scattered inside the aerobic tanks 2a, 2b, 2c. By supplying air from the blower 5 to the trachea 4, oxidative decomposition of organic matter by activated sludge and nitrification of ammonia by nitrifying bacteria are performed in the presence of oxygen by aeration.

Then, the nitrification solution in the last-stage aerobic tank 2c is fed into the anaerobic tank 1a by using the nitrification solution circulation pump 6, whereby the denitrification effect of the anaerobic tanks 1a and 1b is promoted.

The above-mentioned denitrifying bacterium refers to a bacterium that reduces N0 ₂ -N and N0 ₃ -N to N ₂ and NO ₂ by respiration of nitric acid under anaerobic conditions. Also, phosphorus in raw water is anaerobic tanks 1a and 1b.
It is released inside and is taken in and removed by the activated sludge in the aerobic tanks 2a, 2b and 2c. Reference numeral 7 denotes a final settling basin, and the supernatant of the final settling basin 7 is discharged as treated water 11 after passing through a disinfection tank or the like not shown in the figure, and a part of sludge settled in the final settling basin 7. Is returned to the anaerobic tank 1a by the sludge return pump 8, and other sludge is sent from the excess sludge drawing pump 9 to an excess sludge treatment device (not shown) for treatment.

[0007] By using such a circulating nitrification denitrification method, an effect comparable to the organic matter removal effect achieved by a normal standard activated sludge method can be obtained, and nitrogen and phosphorus removal rates higher than those of the activated sludge method. Is achieved.

In the nitrification reaction in the above circulation type nitrification denitrification method, ammonia is oxidized by nitrifying bacteria in the aerobic tank according to the following equation to produce nitric acid.

NH ₄ ⁺ + 2O ₂ → NO ₃ ⁻ + H ₂ O + 2H ⁺ ... (1) Nitrifying bacteria have a slower growth rate than BOD-assimilating bacteria, and fluctuations in inflow load and water temperature. , DO, pH, etc., and the nitrification reaction tends to be unstable. Therefore, in order to maintain a stable nitrification reaction, the dissolved oxygen (DO) in the nitrification tank is usually kept so that the nitrification reaction is not DO-controlled.
DO control that manages is performed.

[0010] Further, Japanese Patent Application No. 6-1 previously filed by the applicant.
07349 describes the amount of oxygen consumed by the nitrification reaction [Nit
-Rr] is measured and Nit is used to complete the nitrification reaction.
Nit-Rr control for controlling DO or SRT (sludge retention time) in the nitrification tank so as to keep -Rr is also proposed.

[0011]

The operation modes in the circulation type nitrification denitrification method can be roughly classified into a denitrification reaction in the anaerobic tanks 1a and 1b and a nitrification reaction in the aerobic tanks 2a, 2b and 2c. The rate-determining reaction is the latter, that is, the nitrification reaction. In particular, in order to remove nitrogen efficiently by the anaerobic-aerobic activated sludge treatment method, it is required to maintain denitrification in the anaerobic tank and nitrification in the aerobic tank under the optimum operating conditions, and the nitrogen removing step. Is highly affected by the nitrification process, so that the nitrification process must be performed well in order to perform good nitrogen removal.

However, since the above [Nit-Rr] control is a control method based on the nitrification reaction using the respiratory rate of nitrifying bacteria as an index, even when the nitrification rate is controlled compared to the simple DO control, Rr] will be calculated in a portion where the sampled liquid mixture is once raised and is not rate-determined by DO, and is a measuring instrument of the value obtained by subtracting the oxygen consumption rate accompanying the nitrification reaction from the total oxygen consumption rate [ The [Nit-Rr] value measured by the ATU-Rr] meter may not directly reflect the nitrification reaction state of the sampled reaction tank.

Therefore, the present invention solves the problem in the control of such a circulation type nitrification denitrification method, and obtains the true value [Nit-Rr] _real of the oxygen consumption rate involved in the nitrification reaction to improve the control accuracy. An object of the present invention is to provide a method and apparatus for controlling nitrification reaction in the nitrification denitrification method.

[0014]

In order to achieve the above-mentioned object, the present invention comprises a step of denitrifying raw water with denitrifying bacteria in an anaerobic tank, and a step of nitrifying with nitrifying bacteria in an aerobic tank,
In the treatment by the circulation type nitrification denitrification method including the step of solid-liquid separation in the settling tank and discharging the supernatant as treated water, the oxygen consumption rate accompanying the nitrification reaction is subtracted from the total oxygen consumption rate in the aerobic tank. And a dissolved oxygen concentration meter are attached, and the nitrification reaction is performed by the maximum oxygen consumption rate [Nit-Rr] _max value and the half-saturation constant [Kdo] and DO value, which are obtained from these measured values. The true value of the oxygen consumption rate [Nit-Rr] _real is calculated, input to the nitrification reaction controller to estimate the nitrification rate in the aerobic tank, and the blower air flow to the aerobic tank is calculated according to that value. Provided are a nitrification reaction control method and device in a circulating nitrification denitrification method for performing DO control for controlling the temperature and SRT control for sludge retention time.

Maximum oxygen consumption rate [Nit-Rr]
_{From the max} and the half-saturation constant [Kdo], the true value [Nit-Rr] _real of the oxygen consumption rate involved in the nitrification reaction is [Nit-Rr] _real = [Nit-Rr] _max · [DO / (DO + Kdo)] · ·・ Calculate based on equation (7).

According to the method and apparatus for controlling the nitrification reaction in the circulation type nitrification denitrification method, the raw water is denitrified in the anaerobic tank or the anaerobic condition, and the aeration and the action of the nitrifying bacteria in the aerobic tank or the aerobic condition are performed. On the other hand, the maximum oxygen consumption rate [N] for the nitrification reaction is measured by the ATU-Rr meter and the DO meter for the sample sampled from the aerobic tank.
It-Rr] _max and [DO] are measured, and the true value [Nit-Rr] _real of the oxygen consumption rate involved in the nitrification reaction is obtained from these values and the half-saturation constant [Kdo] and the DO value to determine the nitrification reaction controller. By inputting into, the nitrification rate in the aerobic tank is estimated and the DO control for controlling the blower air flow to the aerobic tank and the SRT control for sludge retention time are executed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method and apparatus for controlling a nitrification reaction in a circulating nitrification / denitrification method according to the present invention will be described below with reference to the drawings. It will be described in detail.

In the present embodiment, the main object is to provide a [Nit-Rr] control method using the oxygen consumption [Nit-Rr] accompanying the nitrification reaction under the same DO-controlled condition as the reaction tank. FIG. 1 is an example in which the present embodiment is applied to a circulation type nitrification denitrification method constituted by a continuous tank, and 1a, 1b, 1 in the figure
c is an anaerobic tank into which raw water 3 flows, 2a, 2b, 2c. Two
d and 2e are aerobic tanks of a plurality of stages for performing nitrification, and the anaerobic tanks 1a, 1b and 1c and the aerobic tanks 2a, 2b, 2c,
The same biological reaction tanks as 2d and 2e are divided by a partition plate 13 and divided.

The anaerobic tanks 1a, 1b have a stirring mechanism 10,
10 are provided and aerobic tanks 2a, 2b, 2c, 2d, 2e
Air diffusers 4, 4 and 4 as an air blowing mechanism are arranged inside, and a blower 5 for supplying air to the air diffusers 4, 4 and 4 is arranged outside. 6 is a nitrification solution circulation pump.

Reference numeral 7 is a final sedimentation pond, and this final sedimentation pond 7
A sludge return pump 8 for returning a part of the sludge to the anaerobic tank 1a, and a surplus sludge drawing pump 9 for sending another sludge to a surplus sludge treatment device (not shown) are provided in the. The excess sludge removal pump 9 is usually provided with a timer, and is set to perform the removal operation of the excess sludge at every predetermined time.

In this embodiment, the ATU is installed in the aerobic tank 2a.
-Rr meter 15 and DO meter (dissolved oxygen concentration meter) 16 are attached. The maximum oxygen consumption rate [Nit-R] required for the nitrification reaction obtained from the measurement value of the ATU-Rr meter 15.
r] _max value 17 and Kdo (half-saturation constant mg-O ₂ / l) 18 and DO value measured by DO meter 16 [Nit-R
r] The _real value 19 is obtained and input to the nitrification reaction control device 20 together with the inflow water quality analysis value.
DO control 21 and SR based on the set value output from 0
The T control 22 is performed. A DO meter 16a is attached to the aerobic tank 2e.

FIG. 2 shows an example in which the nitrification reaction control method according to the present invention is applied to a batch reaction tank 25. In this batch reaction tank 25, a stirring mechanism 26, an air diffuser pipe 4 and an excess sludge drawing pipe 27 are provided. It has been deployed. The other arrangements of the measuring device for control are the same as those in FIG.

The basic operation of such an apparatus will be described with reference to the embodiment shown in FIG. First, raw water 3 is anaerobic tank 1a, 1b, 1c
The NO ₃ —N and NO ₂ —N ions are reduced to N ₂ , that is, denitrification is performed based on the stirring action of the stirring mechanisms 10 and 10 in the water and the action of the denitrifying bacteria.

Next, raw water 3 is converted into aerobic tanks 2a, 2b, 2c, 2
The air is aerated by aeration from the air diffusers _{4, 4 and 4 as} the blower 5 is driven, and the ammonia nitrogen NH ₄ − is generated based on the action of nitrifying bacteria.
Oxidation of N to NO ₂ —N or NO ₃ —N, that is, nitrification is performed.

[0025] Thus nitrification reaction is oxidation of ammonium nitrogen by nitrifying bacteria, nitrification rate can be expressed as an increase rate of decreasing speed or NO _X -N ammoniacal nitrogen _{(NO 2 -N + NO 3 -N} ) .

The other denitrification reaction can be expressed as 2NO ₃ ⁻ +5 (H ₂ ) → N ₂ ↑ + 2OH ⁻ + 2H ₂ O.

During the above operation, the maximum oxygen consumption rate [Nit-Rr] _max value 17 for the nitrification reaction calculated on the basis of the value measured by the ATU-Rr meter 15 and the DO meter 16 were calculated.
DO value and Kdo (half-saturation constant mg-O ₂ /
l) and 18, the true value [Nit-Rr] _real 19 of the oxygen consumption rate involved in the nitrification reaction is obtained and input to the nitrification reaction control device 20, and based on the set value output from the nitrification reaction control device 20. The DO control 21 for controlling the air flow rate of the blower 5 and the SRT control 22 for controlling the operation of the excess sludge drawing pump 9 to reduce the outflow amount of nitrifying bacteria are carried out.

A part of the sludge settled in the final settling basin 7 is returned to the anaerobic tank 1a by the sludge return pump 8, and the other sludge is sent to the excess sludge treatment device by the excess sludge drawing pump 9 for treatment. The supernatant of the final sedimentation tank 7 is treated water 1
It is discharged after passing through a disinfection tank (not shown) as No. 1.

The above ATU-Rr meter 15 is usually used to monitor the progress of nitrification reaction in an aerobic tank. That is, oxygen utilization rat
e respiration, hereinafter abbreviated as Rr) includes the amount of oxygen consumed during oxidative decomposition of organic matter, the amount of oxygen consumed for endogenous respiration of activated sludge, and the amount of oxygen consumed for nitrification reaction. .

This value is expressed as a respiratory rate due to removal of organic substances and endogenous respiration, that is, a value obtained by subtracting the oxygen consumption rate associated with the nitrification reaction from the total oxygen consumption rate. Therefore, the progress of the nitrification reaction is based on the difference (ATU-Rr) between Rr and Rr measured by adding N-allylthiourea (chemical formula C ₄ H ₈ N ₂ S, hereinafter abbreviated as ATU), which is a nitrification inhibitor. You can ask.

When the difference is [Nit-Rr], [Nit-Rr] = [Rr]-[ATU-Rr] (2) In other words, [Nit-Rr] is the oxygen consumption rate associated with nitrification. If this value is small, it can be determined that the nitrification reaction has ended, and if it is large, the nitrification reaction has not ended. From this value, the nitrification rate in the aerobic tank 2a can be estimated.

[Nit-R in the above equation (2)
When the value of r] is large and the nitrification reaction must be enhanced, the amount of sludge returned from the final settling tank 7 to the anaerobic tank 1 by the sludge return pump 8 is increased to increase the MLSS which is the activated sludge suspended matter, and By controlling the excess sludge drawing pump 9, the SRT, which is the sludge retention time, is adjusted, and the aerobic tank 2
In the case where the nitrification by means of is carried out smoothly, the return amount of the nitrification solution from the aerobic tank 2 to the anaerobic tank 1 based on the action of the nitrification solution circulation pump 6 is increased (up to 200% in practical use),
By increasing the circulation ratio of the liquid, the nitrogen removal rate can be increased.

When the load is low at night, [Nit-R]
Since the value of r] is also extremely small, it is necessary to reduce the aeration amount in the aerobic tank and reduce the circulation amount of the nitrification solution.
Optimal operation control can be performed by performing control such as maintaining a high MLSS concentration and increasing the amount of dissolved oxygen consumed in the anaerobic tank 1.

Next, the nitrification reaction model will be described. The specific growth rate μ of the nitrifying bacteria is expressed by the following equation.

Μ = μ _max · [exp (θ (t−15))] · [1−0.833 (7.2−pH)] · [DO / (DO + Kdo)] (3) where μ: specific growth Velocity (l / day), μ _max = maximum specific growth rate (1 / day) θ: Temperature coefficient (−), Kdo: Half-saturation constant (mg-O ₂ / l), D
O: dissolved oxygen (mg / l), t: water temperature (° C) The nitrification rate G is expressed by the following equation (4). G = (μ ・ X _N・ Y ・ V _t ) / 24 ... (4) Here X _N : amount of nitrifying bacteria (mg), Y: yield (-), V _t : reaction tank volume (l) From equations (3) and (4), operating conditions such as pH, water temperature, and inflow ammonia concentration are constant. At this time, the nitrification rate G is represented by the equation (5) for DO. G = G _max · (DO / (DO + Kdo)) ········ (5) where G _max : maximum Nitrification rate (mg-N / L / h) According to Fig. 3, nitrification rate (mg-N / L / h) and [Nit-R]
It has been experimentally confirmed that r] (mg-O ₂ / L / h) is in a substantially proportional relationship, and thus [Nit-Rr] can be expressed by the following equation, like the nitrification rate. [Nit-Rr] = [Nit-Rr] _max · [DO / (DO + Kdo)] ··· (6) Rr is linearly approximated at a stable portion of the DO change curve, but when DO becomes low The rate of change of DO becomes slow, and the value of [Nit-Rr] changes depending on DO. That is, the slope of the DO change curve in various DOs is obtained, and the above equation (6) is optimized as a regression equation to obtain Kdo.
Can be requested.

Here, the rate-determining effect of the actual reaction tank is applied [Ni
When t-Rr] is [Nit-Rr] _real , the optimized [Nit-Rr] _max and [Kdo] are converted into [Nit-Rr] _max.
Rr] _real is expressed by the following expression (7).

[0037] [Nit-Rr] _real = [Nit-Rr] _max · [DO / (DO + Kdo)] (7) where DO is the DO measured value of the reaction vessel [Nit-Rr] _real and nitrification rate Is shown in FIG. The correlation coefficient was 0.83, which was higher than the correlation coefficient of 0.80 between [Nit-Rr] and the nitrification rate. This is [Nit-Rr] _real and the nitrification rate is the actual respiration rate of nitrifying bacteria that is DO-controlled.
r] is a value that is not subjected to DO rate control, that is, it is the maximum value of the respiration rate of nitrifying bacteria that is not considered even if it is actually rate controlled, so the correlation between [Nit-Rr] _real and nitrification rate is Is considered to be higher than the correlation between the nitrification rate that is rate-limited and the rate [Nit-Rr] that is not rate-controlled.

Therefore, [Nit-Rr] is more important than [Nit-Rr].
DO control using Rr] _real can improve accuracy.

Next, an actual example of the control will be described based on the flow chart of FIG. First, the control starts in step 100, and [Rr] and [ATU-Rr] are measured in step 101. Next, in step 102, [Kdo] and [Nit-Rr] _max are estimated from the [ATU-Rr] value, and in step 103, DO is measured.

In step 104, [Nit-
Rr] _real is estimated, and in step 105, [Nit-R
r] _real ≤ lower limit value is determined, and if YES, an optimal DO value is set in step 106, and if NO, that is, the measured value is equal to or greater than the lower limit value, control is performed in step 107 To finish.

[0041]

As described in detail above, according to the method and apparatus for controlling the nitrification reaction in the circulating nitrification denitrification method according to the present invention, the raw water is denitrified in the anaerobic tank, and aeration and nitrification in the aerobic tank are performed. While the nitrification based on the action of bacteria is performed, the maximum oxygen consumption rate [N] for the nitrification reaction [N] is measured by the ATU-Rr meter and the DO meter on the sample sampled from the aerobic tank.
It-Rr] _max and [DO] are measured, and the true value [Nit-Rr] _real of the oxygen consumption rate involved in the nitrification reaction is obtained from these values and the half-saturation constant [Kdo] and the DO value to determine the nitrification reaction controller. By inputting into, the nitrification rate in the aerobic tank, which is the rate-determining reaction, can be estimated without error, and the DO control of the aerobic tank and the SRT control accuracy which is the sludge retention time can be improved.

In particular, in order to remove nitrogen efficiently by the circulation type nitrification denitrification method, it is required to maintain denitrification in the anaerobic tank and nitrification in the aerobic tank under the optimum operating conditions, and the nitrogen removing step. Is highly affected by the nitrification process, it is necessary to maintain a good balance between the nitrification reaction and the denitrification reaction in order to maintain a high nitrogen removal rate. An accurate estimation of the nitrification rate has the effect of improving the nitrogen removal rate in the anaerobic tank.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a circulating nitrification denitrification method according to the present embodiment.

FIG. 2 is a schematic diagram showing an example in which the present embodiment is applied to a batch reaction tank.

FIG. 3 is a graph showing the correlation between nitrification rate and oxygen consumption rate involved in nitrification reaction.

FIG. 4 is a graph showing the correlation between the nitrification rate and the true value of the oxygen consumption rate involved in the nitrification reaction.

FIG. 5 is a chart showing the actual control of the present embodiment.

FIG. 6 is a schematic diagram showing an example of a conventional circulating nitrification denitrification method.

[Explanation of symbols]

 1a, 1b, 1c ... Anaerobic tank 2a, 2b, 2c, 2d, 2e ... Aerobic tank 4 ... Air diffuser 5 ... Blower 6 ... Nitrification solution circulation pump 7 ... Final sedimentation tank 8 ... Sludge return pump 9 ... Excess sludge extraction pump 13 ... Partition plate 15 ... ATU-Rr meter 16 ... DO meter 20 ... Nitrification reaction control device 21 ... DO control 22 ... SRT control 25 ... Batch reaction tank

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 6, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

On the other hand, as a method for biologically removing nitrogen and phosphorus simultaneously, a circulation type nitrification denitrification method has been attracting attention as a modification of the conventional activated sludge method. For example, as shown in FIG. 6, the biological reaction tank is divided into anaerobic tanks 1a and 1b in which dissolved oxygen (hereinafter abbreviated as DO) does not exist and a plurality of aerobic tanks 2a, 2b and 2c in which DO exists. , This anaerobic tank 1a,
1b, the inflowing raw water 3 and the circulating liquid are agitated by an agitation mechanism 10 under anoxic conditions to denitrify by denitrifying bacteria in the activated sludge, and then to the inside of the aerobic tanks 2a, 2b, 2c. By supplying air from the blower 5 to the arranged air diffuser 4, oxidative decomposition of organic matter by activated sludge and nitrification of ammonia by nitrifying bacteria are performed in the presence of oxygen by aeration.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

According to the method and apparatus for controlling the nitrification reaction in the circulation type nitrification denitrification method , NO ₂ ⁻ in the raw water and the circulating liquid is
Or NO ₃ ⁻ is denitrified in an anaerobic tank or under anaerobic conditions,
While the aeration in an aerobic tank or under aerobic conditions and nitrification based on the action of nitrifying bacteria are performed, the maximum oxygen consumption required for the nitrification reaction by the ATU-Rr meter and the DO meter on the sample sampled from the aerobic tank Speed [Nit-Rr] _max
And [DO] were measured, and this value and the half-saturation constant [Kdo]
And the DO value, the true value [Nit-Rr] _real of the oxygen consumption rate involved in the nitrification reaction is obtained and input to the nitrification reaction control device to estimate the nitrification rate in the aerobic tank, and to blower to the aerobic tank. DO control for controlling the amount of air blown and SRT control for sludge retention time are performed.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

[0026] On the other hand of the denitrification reaction is ^{_{2NO 3 - +5 (H 2)}} → N 2 ↑ + 2OH - + 4 H 2
It can be represented as O 2.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

When the load is low at night, [Nit-R]
Since the value of r] is also extremely small, the amount of aeration in the aerobic tank is reduced and the circulation amount of nitrification liquid is reduced. When the load is high, the concentration of MLSS is kept high and denitrification speed is increased.
It is possible to carry out operation management such as raising the degree .

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction contents]

Next, an actual example of the control will be described based on the flow chart of FIG. First, control starts at step 100, and [Rr] and [ATU-Rr] are measured at step 101. Next, at step 102, the above [Rr] , [AT
U-Rr] value to [Kdo] and [Nit-Rr] _max
Is estimated and DO is measured in step 103.

Claims (3)

[Claims] 1. A step of denitrifying raw water with denitrifying bacteria in an anaerobic tank, and a step of nitrifying with nitrifying bacteria in an aerobic tank.
In the treatment by the circulation type nitrification denitrification method including the step of solid-liquid separation in the settling tank and discharging the supernatant as treated water, the oxygen consumption rate accompanying the nitrification reaction is subtracted from the total oxygen consumption rate in the aerobic tank. And a dissolved oxygen concentration meter are attached, and the nitrification reaction is performed by the maximum oxygen consumption rate [Nit-Rr] _max value and the half-saturation constant [Kdo] and DO value, which are obtained from these measured values. The true value of the oxygen consumption rate [Nit-Rr] _real is calculated, input to the nitrification reaction controller to estimate the nitrification rate in the aerobic tank, and the blower air flow to the aerobic tank is calculated according to that value. A nitrification reaction control method in a circulation type nitrification denitrification method, characterized in that DO control for controlling the temperature and SRT control for sludge retention time are performed. 2. The maximum oxygen consumption rate [Nit-Rr]
_{From the max} and the half-saturation constant [Kdo], the true value [Nit-Rr] _real of the oxygen consumption rate involved in the nitrification reaction is [Nit-Rr] _real = [Nit-Rr] _max · [DO / (DO + Kdo)] · · (7) (DO is an actual measured value of DO in a reaction tank) The method for controlling nitrification reaction in the circulating nitrification denitrification method according to claim 1, which is obtained based on the equation. 3. A step of denitrifying raw water with denitrifying bacteria in an anaerobic tank, and a step of nitrifying with nitrifying bacteria in an aerobic tank.
In the treatment by the circulation type nitrification denitrification method including the step of solid-liquid separation in the settling tank and discharging the supernatant as treated water, the oxygen consumption rate accompanying the nitrification reaction from the total oxygen consumption rate attached to the aerobic tank From the measuring instrument and the dissolved oxygen concentration meter with the value obtained by subtracting, the maximum oxygen consumption rate [Nit-Rr] _max value and the half-saturation constant [Kdo] and the DO value required for the nitrification reaction from these measuring instrument and the dissolved oxygen concentration meter. In the circulation type nitrification denitrification method, which is equipped with a nitrification reaction controller for estimating the true value [Nit-Rr] _real of the oxygen consumption rate related to the nitrification reaction and estimating the nitrification rate in the aerobic tank. Nitrification reaction controller.