JP2003053388A - Control system and control method for biologically nitrogen removing facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control system for biologically nitrogen removing facilities that automatically performs contrast control of the concentration of sludge by regulating the flow rate of returned sludge calculated from the concentration of inflowing sludge converted from a measured flow rate of inflowing waste water and a measured concentration of returned sludge. SOLUTION: The control system for biologically nitrogen removing facilities having a nitrification tank 11, a denitrification tank 12, a re-aeration tank 13 and a sedimentation tank 14 has a device for calculating and controlling the flow rate A4 of returned sludge from the concentration of inflowing sludge converted from a measured flow rate A1 of inflowing waste water and a measured concentration A3 of returned sludge in such a way that the previously set desired value of the concentration of sludge is attained, a device for calculating the loading dose of nitrogen removable at a measured concentration of activated sludge in the denitrification tank 12, a device for measuring and calculating the loading dose of nitrogen from the measured flow rate A1 of inflowing waste water and the concentration A0 of total nitrogen and controlling the flow rate A1 of inflowing waste water in such a way that the calculated loading dose of nitrogen is obtained and a device for calculating and controlling the injection rate of chemicals according to the loading dose of nitrogen in inflowing waste water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has been particularly measured with respect to a control apparatus and control method for a biological nitrogen removing apparatus including a single-input type nitrification tank (aerobic) -denitrification tank (anaerobic) -re-aeration tank. By adjusting the inflow sludge concentration converted from the wastewater inflow rate and the return sludge flow rate calculated from the measured return sludge concentration, control is performed to maintain the sludge concentration target value in the biological nitrogen removal device set in advance, At the same time, the activated sludge concentration in the denitrification tank was measured, the removable nitrogen load calculated from the measured activated sludge concentration was used as the target value, and the wastewater inflow rate was adjusted, and the chemical injection amount was adjusted according to the nitrogen load. By doing so, the present invention relates to a control device and a control method for a biological nitrogen removal device that performs biological nitrogen removal.

[0002]

2. Description of the Related Art Conventionally, the control method of this type of biological nitrogen removing apparatus has been to measure the concentration of activated sludge in a nitrification tank and return the sludge flow rate so as to reach a preset target value of the activated sludge concentration in the nitrification tank. Was being adjusted. Further, the inflow rate of waste water is adjusted based on the preset nitrogen load amount, and the chemical injection amount proportional to the preset nitrogen load amount is adjusted.

However, the conventional methods for controlling the biological nitrogen removing apparatus have the following problems (1) to (3) and, as a result, cannot achieve nitrogen removal.

Due to the influence of aerated air in the nitrification tank, an error occurs in the measured value of the activated sludge concentration, and the returned sludge flow rate becomes unstable.

Wastewater exceeding the nitrogen load that can be removed by the concentration of activated sludge in the denitrification tank flows in, and nitrogen removal is not completed in the denitrification tank.

By performing denitrification treatment in the settling tank with nitrate nitrogen and the excess methanol flowing out from the denitrification tank to the latter stage, sludge containing nitrogen gas floats and sludge in the apparatus flows out.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and in order to eliminate the above-mentioned drawbacks of the prior art, the concentration of inflow sludge converted from the measured inflow flow rate of wastewater and the measured return sludge. An object of the present invention is to provide a control device and a control method for a biological nitrogen removal device that automatically executes a sludge concentration constant control by adjusting the flow rate of returned sludge calculated from the concentration.

Further, the concentration of activated sludge in the denitrification tank is measured, the removable nitrogen load calculated from the measured activated sludge concentration is set as a target value, the inflow rate of wastewater is adjusted, and the chemical injection amount corresponding to the nitrogen load amount is adjusted. It is an object of the present invention to provide a control device and a control method for a biological nitrogen removal device that can automatically perform biological nitrogen removal control by adjusting the.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a nitrification tank, a denitrification tank, a re-aeration tank and a precipitation tank, and the ammonia in the waste water introduced into the nitrification tank. The body nitrogen decomposes into nitric acid and nitrous acid by the action of nitrifying bacteria, the nitrate nitrogen is decomposed into nitrogen gas by the action of denitrifying bacteria in the denitrification tank, and re-aeration is performed in the re-aeration tank, and solid-liquid in the precipitation tank. A control device for a biological nitrogen removal device configured to return a part of sludge that has been separated and solid-liquid separated to the nitrification tank as return sludge. From the returned sludge concentration, means for calculating and controlling the returned sludge flow rate so as to be a preset sludge concentration target value, and means for calculating the nitrogen load that can be removed by the measured activated sludge concentration of the denitrification tank, Measured wastewater inflow and nitrogen concentration Measure and calculate the nitrogen load, and control the drainage inflow flow rate so that the calculated nitrogen load is achieved, and the means for calculating and controlling the chemical injection amount that matches the nitrogen load of the inflowing wastewater. It is characterized by having.

As described above, the control device calculates and controls the return sludge flow rate from the measured inflow sludge concentration converted from the inflow sludge concentration and the measured return sludge concentration so as to reach the preset sludge concentration target value. And means for calculating the nitrogen load that can be removed by the measured activated sludge concentration of the denitrification tank, and measuring and calculating the nitrogen load from the measured wastewater inflow flow rate and nitrogen concentration, and the calculated nitrogen load As described above, since the means for controlling the inflow rate of the waste water and the means for calculating and controlling the chemical injection amount commensurate with the nitrogen load amount of the inflowing waste water are provided, stable nitrogen removal can be achieved.

The invention according to claim 2 is provided with a nitrification tank, a denitrification tank, a re-aeration tank, and a precipitation tank, and the ammonia nitrogen of the waste water introduced into the nitrification tank is nitric acid or nitrous acid by the action of nitrifying bacteria. Decomposed into nitrogen gas, decomposed nitrate nitrogen into nitrogen gas by the action of denitrifying bacteria in the denitrification tank, re-aerated in the re-aeration tank, solid-liquid separated in the precipitation tank, and part of the solid-liquid separated sludge Is a control method of a biological nitrogen removal device configured to return the sludge to the nitrification tank as returned sludge, and the sludge concentration set in advance from the inflow sludge concentration converted from the measured wastewater inflow flow rate and the measured returned sludge concentration Calculate the returned sludge flow rate to reach the target value, calculate the nitrogen load that can be removed by the measured activated sludge concentration of the denitrification tank, and measure and calculate the nitrogen load from the measured wastewater inflow rate and nitrogen concentration. And calculated nitrogen load Comprising wastewater input flow rate control as to calculate the dosing amount commensurate with the nitrogen load of the waste water which flows characterized by on.

As described above, in the control method, the returned sludge flow rate is calculated and measured so as to reach the preset sludge concentration target value from the inflow sludge concentration converted from the measured wastewater inflow flow rate and the measured returned sludge concentration. The nitrogen load that can be removed by the activated sludge concentration of the denitrification tank was calculated, and the nitrogen load was measured and calculated from the measured wastewater inflow rate and nitrogen concentration, and the wastewater inflow rate was adjusted so that the calculated nitrogen load was obtained. Is controlled, and the chemical injection amount that matches the nitrogen load amount of the inflowing waste water is calculated and input, so that stable nitrogen removal can be achieved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a configuration example of a biological nitrogen removing apparatus that executes a control method according to the present invention, FIG. 2 is a diagram showing a configuration example of a sludge concentration constant control circuit, and FIG. 3 is a processable inflow load constant control circuit. A diagram showing a configuration example of
FIG. 4 is a diagram showing the configuration of the chemical liquid injection amount control arithmetic circuit.

As shown in FIG. 1, the biological nitrogen removing apparatus 10 comprises a nitrification tank 11, a denitrification tank 12, a re-aeration tank 13 and a precipitation tank 14. 20 is a nitrogen concentration meter for measuring the total nitrogen concentration A ₀ of the inflowing wastewater, 21 is an inflowing drainage flowmeter for measuring the inflowing drainage flow rate A ₁ , 22 is an activated sludge concentration for measuring the activated sludge concentration A ₂ in the denitrification tank 12. Total, 23 is returned sludge concentration A ₃
Return sludge concentration meter, 24 is a return sludge flow meter that measures the return sludge flow rate A ₄ , 25 is an inflow drainage flow control valve that controls the inflow drainage flow rate, and 26 is a return sludge flow control valve that controls the return sludge flow rate Is. In addition, in FIG. 1, P is a pump.

In FIG. 1, the wastewater flowing in the direction of the arrow 101 is decomposed into nitric acid and nitrous acid by the action of nitrifying bacteria adhering to the surface of the carrier charged in the nitrification tank 11, and further deaerated. Nitrogen nitrogen is decomposed into nitrogen gas by the action of denitrifying bacteria in the nitrification tank 12, and the re-aeration tank 13 is used.
Solid-liquid separation in the settling tank 14 via, and flows out in the direction of arrow 102 as treated water.

The sludge solid-liquid separated in the settling tank 14 is indicated by an arrow 1.
It is returned to the nitrification tank 11 as return sludge in the 03 direction. In addition, some sludge is discharged in the direction of arrow 104 as excess sludge. In addition, phosphoric acid 1 is used as a chemical required for nitrogen removal.
05 and ammonium sulfate 106 are poured into the nitrification tank 11, and methanol 107 is poured into the denitrification tank 12. In addition,
In FIG. 1, B ₁ is an inflow drainage flow rate setting value, B ₂ is a returning sludge flow rate setting value, B ₃ is a phosphoric acid injection amount setting value, B ₄ is an ammonium sulfate injection amount setting value, and B ₅ is a methanol injection amount setting value. is there. In order for the biological nitrogen removing apparatus 10 having the above-described configuration to perform nitrogen removal, it is necessary to keep the biological amount (nitrifying bacteria) in the nitrification tank 11 at a necessary and sufficient amount.

The constant sludge concentration control circuit 30 of FIG. 2 uses the inflow sludge concentration converted from the inflow drainage flow rate A ₁ measured by the inflow drainage flowmeter 21 and the return sludge concentration A ₃ measured by the return sludge concentration meter 23 This is a circuit for calculating and controlling the returned sludge flow rate setting value B ₂ so that the sludge concentration target value C ₁ is set in advance. Here, it is assumed that the biomass is regarded as the sludge concentration, and that the sludge concentration set as the sludge concentration target value C ₁ always exists in the nitrification tank 11, and the concentration at which the inflowing wastewater becomes sludge is the inflowing wastewater sludge conversion coefficient C ₂ And the inflowing wastewater flow rate A ₁ , and the concentration at which the returned sludge becomes sludge is determined from the returned sludge concentration A ₃ measured by the returned sludge concentration meter 23, which is an operation value for operating the returned sludge flow control valve 26. Set the sludge flow rate setting value B ₂ {B ₂ = (C _{1
-C 2) × A 1 / (} A 3 -C 1)}, executes control.

Further, in order for the biological nitrogen removing apparatus 10 to perform nitrogen removal, it is necessary to maintain the nitrogen load in the denitrification tank 12 so that the biological amount (denitrifying bacteria) can remove nitrogen. In the processable inflow load constant control circuit 31 of FIG. 3, the nitrogen load obtained from the inflow effluent flow rate A ₁ measured by the inflow effluent flow meter 21 and the total nitrogen concentration A ₀ of the inflow effluent measured by the nitrogen concentration meter 20 is activated. This is a circuit for controlling the inflow drainage flow rate A ₁ by controlling the inflow drainage flow rate control valve 25 so that the activated sludge concentration A ₂ in the denitrification tank 12 measured by the sludge concentration meter 22 provides a removable nitrogen load.

As shown in FIG. 3, when the activated sludge concentration A ₂ in the denitrification tank 12 measured by the activated sludge concentration meter 22 is detected to be below the sludge concentration low level threshold D ₁ (A ₂ <D ₁ ), The nitrogen load amount that can be processed by the activated sludge concentration meter 22 is a nitrogen load coefficient (a nitrogen load coefficient that can process a unit activated sludge concentration per 1 m ^{3 of the} denitrification tank 12) D ₂ and a volume D _{3 of the} denitrification tank 12. The nitrogen load amount target value D ₀ is calculated from (D ₀ = D ₂ × D ₃ ×
A ₂ ), and further, an inflow drainage flow rate set value B which is an operation value of the inflow drainage flow rate control valve 25 together with the total nitrogen concentration A ₀ of the inflow drainage.
₁ is set (B ₁ = D ₀ / A ₀ ) and the control is executed.

The chemical injection amount control arithmetic circuit of FIG. 4 is a circuit for calculating and controlling the chemical injection amount corresponding to the nitrogen load amount of the inflowing waste water. The chemical, that is, methanol 107, is added to the nitrogen load amount of the inflowing wastewater determined from the total nitrogen concentration A ₀ of the inflowing wastewater measured by the nitrogen concentration meter 20 and the inflowing wastewater flow rate A ₁ measured by the inflowing wastewater flow meter 21 (injection ratio (nitrogen Load amount: Methanol injection ratio) E ₁ is multiplied, and the specific gravity (methanol specific gravity) E ₂ of the chemical and the concentration (methanol concentration) E ₃ of the chemical are converted to determine the methanol injection amount set value B ₅ {B ₅ = (E ₁ ×
A ₀ × A ₁ ) / (E ₂ × E ₃ )}, control is executed.

The chemical, namely phosphoric acid 105, is multiplied by the injection ratio (methanol: phosphoric acid injection ratio) F ₂ of the methanol injection amount set value B ₅ determined above, and the molecular weight F _{1 of} phosphoric acid 105 is further multiplied.
And atomic weight F ₃ of phosphoric acid 105 are converted into phosphoric acid 1
The concentration F _{4 of} 0.05 and the specific gravity F ₅ are converted to determine the phosphoric acid injection amount setting value B ₃ {B ₃ = (F ₁ × F ₂ × B ₅ ) / (F ₃ × F ₄ ×
F ₅ )}, control is executed.

The chemical, that is, ammonium nitrate 106, is further measured by the nitrogen concentration meter 20 from the target value D _{0 of} the treatable nitrogen load amount in the nitrification tank 11 obtained by the controllable processable inflow load control circuit 31 of FIG. The total nitrogen concentration A ₀ of the wastewater and the inflowing wastewater flow rate A ₁ measured by the inflowing wastewater flow meter 21 are subtracted from the inflowing nitrogen load amount (D ₀ −A ₀ × A ₁ ) to obtain the inflowing wastewater nitrogen load amount. On the other hand, it is determined as a shortage of the treatable nitrogen load, and further, the molecular weight G _{1 of} ammonium nitrate 106 and the atomic weight G _{2 of} nitrogen are converted, and the concentration G _{3 of} ammonium nitrate 106 and the specific gravity G ₄ are also converted to inject the amount of ammonium sulfate. Set value B ₄ is determined {B ₄ = G ₁ × (D ₀ −A ₀ ×
A ₁ ) / (G ₂ × G ₃ × G ₄ )}, and control is executed.

[0023]

As described above, according to the invention described in each claim, the following excellent effects can be obtained.

According to the first and second aspects of the invention, the sludge concentration constant control is performed by adjusting the inflow sludge concentration converted from the measured inflow drainage flow rate and the return sludge flow rate calculated from the measured return sludge concentration. It is possible to provide a control device and a control method for a biological nitrogen removal device, which can automatically perform the above process and achieve stable nitrogen removal.

Further, the concentration of activated sludge in the denitrification tank is measured, the removable nitrogen load calculated from the measured activated sludge concentration is used as a target value, and the inflow and outflow flow rate is adjusted, and further chemical injection is performed in accordance with the nitrogen load. By adjusting the amount, biological nitrogen removal control can be automatically executed, and a control device and a control method for a biological nitrogen removal device that can achieve stable nitrogen removal can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a biological nitrogen removing apparatus that executes a control method according to the present invention.

FIG. 2 is a diagram showing a configuration example of a sludge concentration constant control circuit of a biological nitrogen removing apparatus that executes a control method according to the present invention.

FIG. 3 is a diagram showing a configuration example of a controllable constant inflow load control circuit of a biological nitrogen removing apparatus that executes a control method according to the present invention.

FIG. 4 is a diagram showing a configuration of a chemical liquid injection amount control arithmetic circuit of a biological nitrogen removing apparatus that executes a control method according to the present invention.

[Explanation of symbols]

10 Biological nitrogen removal equipment 11 Nitrification tank 12 denitrification tank 13 Re-aeration tank 14 settling tank 20 Nitrogen concentration meter 21 Inflow drainage flow meter 22 Activated sludge concentration meter 23 Return sludge densitometer 24 Return sludge flow meter 25 Inflow / outflow flow control valve 26 Return sludge flow control valve 30 Sludge concentration constant control circuit 31 Processable inflow load constant control circuit 32 Chemical injection amount control arithmetic circuit

Continued front page    (72) Inventor Yoshihiro Yamaguchi             11-1 Haneda Asahi-cho, Ota-ku, Tokyo Co., Ltd.             Inside the EBARA CORPORATION F-term (reference) 4D040 BB02 BB23 BB25 BB52 BB91                       BB93

Claims (2)

[Claims] 1. A denitrification tank comprising a nitrification tank, a denitrification tank, a re-aeration tank and a precipitation tank, wherein ammonia nitrogen in wastewater introduced into the nitrification tank is decomposed into nitric acid and nitrous acid by the action of nitrifying bacteria. At the decomposition of nitrate nitrogen into nitrogen gas by the action of denitrifying bacteria, re-aeration is performed in the re-aeration tank, solid-liquid separation is performed in the settling tank, and a part of the solid-liquid separated sludge is returned as sludge. A control device for a biological nitrogen removal device configured to return to the nitrification tank, and a preset sludge concentration target value is obtained from the inflow sludge concentration converted from the measured wastewater inflow flow rate and the measured returned sludge concentration. Means for calculating and controlling the flow rate of the returned sludge,
A means for calculating the nitrogen load amount that can be removed by the measured activated sludge concentration of the denitrification tank, and measuring and calculating the nitrogen load amount from the measured wastewater inflow flow rate and nitrogen concentration, and become the calculated nitrogen load amount. A control device for a biological nitrogen removing apparatus, comprising: a means for controlling the inflow rate of waste water, and a means for calculating and controlling the amount of chemical injection corresponding to the nitrogen load quantity of the inflowing waste water. 2. A denitrification tank comprising a nitrification tank, a denitrification tank, a re-aeration tank and a precipitation tank, wherein ammonia nitrogen in wastewater introduced into the nitrification tank is decomposed into nitric acid and nitrous acid by the action of nitrifying bacteria. At the decomposition of nitrate nitrogen into nitrogen gas by the action of denitrifying bacteria, re-aeration is performed in the re-aeration tank, solid-liquid separation is performed in the settling tank, and a part of the solid-liquid separated sludge is returned as sludge. A control method for a biological nitrogen removal device configured to return to a nitrification tank, where a preset sludge concentration target value is obtained from the measured inflow sludge concentration converted from the measured inflow of wastewater and the measured returned sludge concentration. Calculate the return sludge flow rate, calculate the nitrogen load that can be removed by the measured activated sludge concentration of the denitrification tank, and measure and calculate the nitrogen load from the measured wastewater inflow rate and nitrogen concentration, Calculated nitrogen load and Controls wastewater inflow rate in so that the control method for biological nitrogen removal device, characterized in that calculating the dosing amount commensurate with the nitrogen load of the waste water flowing to introduce.