JP3214489B2 - Sewage treatment method and sewage treatment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standard activated sludge treatment method and a wastewater treatment apparatus for biochemically treating wastewater such as sewage and industrial wastewater with microorganisms by a so-called activated sludge process. The present invention relates to control of a blower for supplying air required for aeration by blowing air to the biological treatment tank, and operation control of a return sludge pump and an excess sludge pump.

[0002]

2. Description of the Related Art Conventionally, a sewage treatment apparatus of a standard activated sludge method provided in a public sewage treatment plant or a wastewater treatment plant of a factory is configured as shown in FIG. 3, and sewage (raw water) such as sewage and wastewater.
Is firstly treated by a sedimentation basin, and then flows into a biological treatment tank (hereinafter referred to as a reaction tank) 2 through a flow meter 1.

[0003] The activated sludge in the reaction tank 2 biochemically treats organic matter in the raw water to be decomposed and removed, and the treated water subjected to the decomposition and removal is sent to a final sedimentation basin 3, where the sedimentation basin 3 is treated. From the river.

[0004] A diffuser 4 is provided in the reaction tank 2, and air required for aeration is supplied from a blower (blower) 5 to the diffuser 4 via a flow meter 6 to remove microorganisms in the reaction tank 2. Maintenance and proliferation are achieved.

The air volume of the blower 5 is controlled by feedforward (FF) or feedback (FB) using a PID controller 7.

As a typical example of the air volume control, conventionally, a control of an inflow water amount ratio of the reaction tank 2 or a reaction tank 2
There is a DO constant control for keeping the dissolved oxygen concentration (DO) constant. The inflow rate control measures the amount of sewage (raw water) flowing into the reaction tank 2 and reduces the flow rate to about 3 to 8 times the air flow.
The F control is performed, and the DO constant control measures the DO value near the outlet of the reaction tank 2 and performs the FB control of the air flow so that the DO value becomes constant.

FIG. 3 shows the former case where the inflow rate control is performed, in which a detection signal of the inflow rate of raw water from the flow meter 1 is sent to a multiplier 8, which sends a detection signal of the inflow rate of raw water. A signal of a target air volume (target value) SV ′ is formed by multiplying a constant of an air supply magnification (3 to 8 times) of the air magnification setter 9.

Further, the signal of the target air volume SV 'is
To the D controller 7, and by this controller 7,
Signal of target air volume SV 'and air volume measured by air volume meter 6 (measured value)
Based on the signal of PV ′, a signal of a ventilation control amount (operation amount) MV ′ of an error of the measured airflow PV ′ with respect to the target airflow SV ′ is formed, and the measured airflow PV ′ is changed to the target airflow S by this signal.
The operation of the blower 5 is FF-controlled so as to be maintained at V '.

On the other hand, the treated water of the reaction tank 2 flows into the final sedimentation tank 3 and a part of the activated sludge also flows.

A part of this sludge is returned to the reaction tank 2 through the flow meter 11 by the return sludge pump 10,
The remaining sludge is the BO of treated water discharged from the final sedimentation basin 3.
The excess sludge pump 12 pulls out the solution so that the D concentration is equal to or less than the reference amount of 20 milligrams (mg) / liter (L), and is sent to a sludge treatment system through a flow meter 13.

In FIG. 3, a solid line indicates a water pipe, a broken line indicates an air pipe, and a dotted line indicates an electric signal line.

[0012]

In the case of the sewage treatment apparatus shown in FIG. 3, the blowing of the blower 5 depends only on the amount of raw water flowing into the reaction tank 2 based on the detection signal of the amount of raw water flowing into the flow meter 1. Controlled.

On the other hand, the optimal amount of aeration air supplied to the reaction tank 2 depends on the degree of contamination of the raw water and the amount of inflow. For example, in the case of extremely dirty raw water, a large amount of air is required even if the amount of inflow is small. Become.

Therefore, in the conventional apparatus shown in FIG. 3 in which the flow rate of the blower 5 is controlled only depending on the flow rate of the raw water into the reaction tank 2, optimal blowing can be performed from the blower 5 to the reaction tank 2 according to the raw water. Absent.

In order to actually respect the water quality standard, the air supply ratio setting device 9 is conventionally sufficient so that the BOD value of the treated water discharged from the final sedimentation tank 3 does not exceed the standard value. A large magnification is set, and air is blown at an air volume larger than necessary.

In this case, there is a problem that excessive aeration by useless blowing is performed during a low load period in which the amount of raw water is small and energy cannot be saved.

By the way, instead of controlling the inflow water amount ratio, DO
When the constant control is performed, the air volume of the blower 2 is FB-controlled based on the DO value near the outlet of the reaction tank 2 as described above. In this case, the distance from the inlet to the outlet of the reaction tank 2 must be long. Therefore, the dead time of the control is long, and the control is likely to be delayed.

Once the DO value of the treated water drops, it takes time to recover the DO value. If the DO value standard is set low, the sewage may not be sufficiently treated and may be discharged to rivers and the like. Therefore, in practice, DO
It is necessary to set a high standard for the DO value of the treated water so that the value does not drop extremely.

Therefore, also in this case, excessive aeration due to useless blowing is performed as a result, and energy saving cannot be achieved.

Next, the operation of the pumps 10 and 12 is conventionally performed on the basis of the measured values of the flow meters 11 and 13 irrespective of the control of the blower volume of the blower 5.

Since the amount of sludge in the final sedimentation basin 3 changes depending on the state of contamination of the raw water flowing into the reaction tank 2 and also depends on the amount of air blown by the blower 5, conventionally, pumps 10 and 12 are used. There is also a problem that the sludge treatment is not optimally controlled.

The present invention relates to a sewage treatment method in which an air is blown from a blower to a reaction tank at an optimal flow rate according to the state of sewage flowing into a biological treatment tank (reaction tank) to save energy and perform optimal aeration. It is another object of the present invention to provide a sewage treatment apparatus, and further to make it possible to optimally control the amount of sludge by a return sludge pump and an excess sludge pump.

[0023]

According to a first aspect of the present invention, there is provided a sewage treatment method according to the first aspect, wherein raw effluent flows into a reaction tank for treating sewage (raw water) such as wastewater or sewage by a standard activated sludge method. The inflow amount and BOD amount of
The difference between the measured value and the target treated water BOD value of the amount D is calculated as the index value of the raw water stains, required raw water treatment flowing into the more reactive tank to the product of the measured value of the index value and the flow rate
The air flow rate is calculated, the denitrification and nitrification coefficients and the total
Nitrification and maintenance of dissolved oxygen in the reaction tank based on the product of the measured values
The required air flow and add the two products to the target air flow rate
It calculates a target air amount as a value, to control the air volume into the reaction tank from the blower in accordance with the target air volume.

Accordingly, an index value indicating the degree of contamination of the raw water is obtained from the measured value of the BOD amount of the raw water flowing into the reaction tank, and the product of the index value and the flow rate of the raw water is denitrification and denitrification.
By adding the product of the nitrification coefficient and the raw water inflow amount, a target air volume as a target value of the aeration air volume of the reaction tank in consideration of the degree of contamination of the raw water and the inflow amount is obtained.

Since the amount of air blown from the blower to the reaction tank is controlled in accordance with the target air flow, optimal aeration of the reaction tank is performed in consideration of not only the inflow of raw water but also the degree of contamination. .

[0026] Therefore, if the aeration air quantity is more than necessary to many as in the case of the conventional method that takes into account only the inflow of the raw water
In addition, it is possible to prevent excessive aeration due to useless blowing and thereby save energy.

The sewage treatment apparatus according to the second aspect of the present invention includes a reaction tank for treating wastewater (raw water) such as wastewater and sewage by a standard activated sludge method, a blower for blowing air to a diffuser of the tank, and a reaction tank for the reaction tank. A flow meter provided near the sewage inlet and measuring the amount of raw water flowing into the reaction tank; a BOD sensor provided near the sewage inlet and measuring the BOD amount of raw water flowing into the reaction tank; Total and BOD
A control device that takes in the measured values of the sensor and controls the air blowing from the blower to the air diffuser;
Processing of the raw water flowing into the more reactive tank to the product of the means for calculating the difference between the index value of the raw water stains, and the measured value of the index value and the flowmeter between the measured value and the target treated water BOD value of the sensor
Air flow required for the denitrification and nitrification and the flow meter
Necessary for maintaining the dissolved oxygen level in the reaction tank by multiplying the measured value
Calculate the appropriate air flow and add the two products to obtain the target value of the aeration air volume.
Means for calculating a target air volume of Te, provided with means for controlling the blowing amount of the blower in accordance with the target air volume.

Therefore, the BOD amount and the inflow amount of the raw water flowing into the reaction tank are measured by the BOD sensor and the flow meter, and these measured values are taken into the control device.

[0029] In this control system, a demand is calculated index value of the raw water in the soil from the difference between the measured value and the target treated water BOD value of BOD sensor further comprises a measurement value of the index value and the flowmeter , The coefficient of denitrification and nitrification and raw water
The product of the flow rate and the flow rate of the raw water is added to obtain a target airflow rate required for aeration of the reaction tank in consideration of the degree of contamination of the raw water and the flow rate.

Further, the amount of air blown from the blower to the air diffuser of the reaction tank is controlled in accordance with the target air amount.

Therefore, it is possible to provide a concrete sewage treatment apparatus for realizing the sewage treatment method of the first aspect.

Next, a sewage treatment apparatus according to a third aspect of the present invention is the sewage treatment apparatus according to the second aspect, wherein a return sludge pump for returning a part of the sludge settled from the reaction tank to the final sedimentation basin in the subsequent stage to the biological treatment tank; A surplus sludge pump for extracting the surplus amount of sludge from the final sedimentation basin and discharging the same, and a target value for control of both pumps in accordance with the state of contamination of raw water flowing into the reaction tank based on the measurement value of the BOD sensor, Means for controlling the operation of both pumps in connection with the amount of air blown from the blower to the reaction tank.

Therefore, the operation of the return sludge pump and the excess sludge pump is controlled in connection with the amount of air blown by the blower, and the control of the processing of the return sludge and the excess sludge controls the state (degree) of the contamination of the raw water flowing into the reaction tank. Optimum control according to the conditions, and more effective sewage treatment can be performed.

Since the state of contamination of the raw water flowing into the reaction tank changes every moment, the operation of the blower, the return sludge pump, and the excess sludge pump is simultaneously online in real time based on the measurement values of the BOD sensor every moment. It is preferable to control.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described with reference to FIGS. In FIG. 1, FIG.
The same reference numerals denote the same or corresponding components, and a flow meter 1 and a BOD sensor 14 are provided near the sewage inlet of the reaction tank 2 into which raw water of the sedimentation basin flows, and the flow meter 1 flows into the reaction tank 2. Measure the inflow of raw water and BOD
Sen 14 measures the BOD value of the raw water flowing into reaction tank 2.

The signals of the momentarily measured values of the inflow amount of the flow meter 1 and the BOD amount of the BOD sensor 14 are sent to an arithmetic unit 16 of a control unit 15 of a computer provided in, for example, an electric room of a sewage treatment plant. Taken in.

The operation unit 16 calculates the inflow amount of the flow meter 1,
In addition to the signal of the measured value of the BOD amount of the D sensor 14, the signal of the measured value of the activated sludge concentration of the reaction tank 2 measured by an optical MLSS (Mixed Liquor Suspended Solid) meter 17, the Kjeldahl nitrogen, and nitric acid inflow Signals of measured values of various process amounts of the reaction tank 2 such as nitrogen gas, excess sludge concentration, DO value, and water temperature are also taken in as needed.

The operation unit 16 includes the following means (i) and (iii) by software processing.

(I) Means for calculating an index value of the contamination of raw water flowing into the reaction tank 2 from the difference between the measured value of the BOD sensor 14 and the BOD value of the target treated water (ii) The calculated index value of the contamination and the flow meter the product of the first measured value, the product of the coefficient and the flow meter 1 of the measurement values of denitrification and nitrification pressure
Calculated to target air as the target value of the aeration amount of the reaction tank 2
Means for calculating amount (iii) Means for calculating target values for operation control of return sludge pump 10 and surplus sludge pump 12 by adding correction based on the measurement value of BOD sensor 14

That is, in this embodiment, the amount of air blown by the blower 5 is controlled on-line in consideration of the degree of contamination of the raw water flowing into the reaction tank 2 from time to time and the amount of flow. In order to control the operation of the blower 12 in connection with the control of the blowing amount of the blower 5, the blower 5 and the pump 1 are measured using the measurement results of the flow meter 1, the BOD sensor 14, and the like.
It is repeated to simultaneously calculate and determine the target values of the operation control of 0 and 12 in real time.

Next, the calculation of each target value by the calculation unit 16 will be described. First, the target value of the aeration air volume of the blower 5
The calculation of the target air volume as described above will be described. Since the optimal aeration air volume of the activated sludge in the reaction tank 2 depends on the degree of contamination of the sewage flowing into the reaction tank 2 and the inflow amount,
Assuming that a target air flow (set air flow) as a target value for operation control of the blower 5 is G _s ^* [Nm ³ / h], the target air flow G _s ^*
Is calculated by the following equation (1). Note that N is normal and h is time (the same applies hereinafter).

[0042]

[Number 1] ^{_{G s * = a · (S}} -S *) · Q i + b · Q i + c

In the equation (1), S is a measured value of the BOD sensor 14 (measured inflow BOD value) [mgBOD / L],
S ^* is a preset BOD amount reference value (target treated water B
OD value) [mgBOD / L], Q _i is the flow meter 1 of the measurement value (measurement inflow) [m ³ / h]. Note that mg is milligram and L is liter (the same applies hereinafter).

[0044] Also, a in the formula, b, c are each coefficient, specifically, coefficient a represents a coefficient of BOD removal of a = A · α _o, A that is required per remove BOD oxygen Amount [g
O ₂ / gBOD], α _o is a coefficient for converting to air volume (air volume conversion coefficient), and g is gram (the same applies hereinafter).

The coefficient b is a coefficient for denitrification and nitrification.
β _c · (KN _in -KN _out ^* )-γ _c · (DN _in -D
An N _out ^*) + δ _c, the coefficient of beta _c nitrification, KN _in the measurement value of the inlet Kjeldahl nitrogen [mgN / L], KN _out ^* set value of outflow Kjeldahl nitrogen [mgN / L], gamma _c is a denitrification coefficient, and DN _in is a measured value of inflowing nitrate nitrogen [mgN /
L], DN _out ^* is the set value of the outflow nitrate nitrogen [mgN /
L], δ _c is a coefficient of outflow DO of δ _c = DO ^* · α _o ,
DO ^* is the set value of the outflow DO of the reaction tank 2 [mgO ₂ / L]
It is.

The first term of the equation (1) is the reaction tank 2
Is the product of the degree of contamination of the raw water flowing into the tank and the amount of flow, and indicates the amount of air required for the treatment of the flowing wastewater. The second term is required for nitrification and for maintaining the dissolved oxygen amount of the treated water in the reaction tank 2. The third term indicates the amount of air required for endogenous respiration of the activated sludge in the reaction tank 2 based on the measurement value of the MLSS meter 17 and the like, and the third term indicates the contamination of the sewage flowing into the reaction tank 2 according to the equation (1). The optimum value of the airflow of the blower 5 is determined in consideration of the degree of the airflow and the inflow amount.

Next, the calculation of the target value for the control of the return sludge pump 10 will be described. Since the optimal amount of sludge returned from the final sedimentation tank 3 to the reaction tank 2 by the return sludge pump 10 changes depending on the state of the raw water flowing into the reaction tank 2 and is related to the air volume of the blower 5, the return sludge pump 10 Target sludge return amount (set return amount)
_{Assuming that r} ^* [m ³ / h], the target return amount Q _r ^* is calculated by the following equation (2).

[0048]

[Number 2] ^{_{Q r * = {1 / (}} X r / X A * -1)} · Q i = {1
/ (X _r / d · (S−S ^* ) − 1)｝ · Qi

In the equation (2), _Xr is the flow meter 11
A measurement value measured value of the return sludge concentration of the pump 10 based on the (measured return sludge amount) [MGSS / L], X _A ^* is the target value of the concentration of activated sludge in the reaction tank 2 [MGSS / L].

D is d = (1 + K_s/ S^*) / K ・ θ
Is the coefficient of K_sIs the half-saturation constant of substrate intake [mgBOD
/ L], k is the maximum substrate utilization rate [1 / h], θ is θ = V
/ Q _iHRT [h] of the reaction tank 2 indicated by
V is the capacity of the reaction tank 2 [m ^Three].

The target value X _A ^* changes according to the product of the degree of contamination of the raw water flowing into the reaction tank 2 and the amount of inflow, and is corrected in accordance with the degree of contamination of the raw water flowing into the reaction tank 2. Therefore, the target value of the optimal amount of returned sludge linked to the amount of air blown from the blower 5 to the reaction tank 2 is calculated in consideration of the degree of contamination of the raw water by the equation (2).

Next, the calculation of the target value for the control of the surplus sludge pump 12 will be described. The amount of surplus sludge withdrawn from the final sedimentation basin 3 is determined by the amount of returned sludge and the BOD value of the treated water discharged from the final sedimentation basin 3, so that the excess sludge as a target value for control of the surplus sludge pump 12 is used. Assuming that the drawing amount (target drawing amount) is M _w ^* [g / h],
This target withdrawal amount M _w ^* is calculated by the following equation (3).

[0053]

[ _Equation 3] M _w ^* = V · X _av / θ ^* −Q _iav · Xε = V · X _av
/ ^{[1 / {e · S * /} (f + S *) -g} ] - Q _iav · X
ε

[0054] In this equation (3), X _av is the average value of for example 5 days of the measurement values of MLSS meter 17 [MGSS / L]
θ ^* is the sludge residence time SRT [h] in the system, and Q _iav is the average value of raw water inflow into the reaction tank 2 for, for example, 5 days [m ³ /
h], Xε is the set amount of suspended solids (SS) [mgSS /
L].

Further, e, f, and g in the above equation are coefficients, and specifically, the coefficient e is a sludge yield Y [mgSS / mg
BOD] and the maximum substrate utilization rate k [1 / h] Y · k
And f is the half-saturation constant K _s [mgBOD /
L], and g is a self-decomposition coefficient k _d [1 / h].

The calculation of each target value is simultaneously executed in real time at a set control cycle of, for example, 1 to 30 minutes based on the latest measurement results of the flow meter 1 and the BOD sensor 14. 2 is updated in accordance with the moment-to-moment change of the raw water flowing into the tank.

Further, in the coefficients a to g in the equations (1) to (3), control parameters which do not change depending on the state of the raw water flowing into the reaction tank 2 and the like, that is, the oxygen amount A and the coefficient α
_With respect to _o , β _c , γ _c , δ _c , k _d , constant K _s , reaction rate k, sludge yield Y, etc., the past results are taken into account by, for example, a parameter determination calculation using a neutral network or the like. The optimum value is determined at any time by human operation.

Then, the target air volume G _s ^* , the target return volume Q _r ^* ,
The target withdrawal amount M _w ^* is the control target value SV1, SV2, SV3.
The PID controllers 18, 19 of the control device 15
20.

At this time, the PID controller 18 sets the measured value of the air flow meter 6 to PV1, and sets the measured value PV1 to the target value SV.
The operation amount M of the blower amount control of the blower 5 so as to be maintained at 1
V1 is set, the air flow supplied from the blower 5 to the diffuser 4 is controlled to the target air flow G _s ^* , and the air flow for aeration from the blower 5 to the reaction tank 2 is determined by the quality of the raw water flowing into the reaction tank 2. Based on the product of the inflow and the amount of inflow, control is made to an optimum amount of delivery in consideration of not only the inflow of raw water but also the degree of contamination.

Therefore, it is not necessary to set the target air flow rate G _s ^* to a value larger than necessary like the target value of the conventional control, and it is possible to prevent excessive aeration due to useless blowing and to save energy.

The PID controllers 19 and 20 use the measured values of the flow meters 11 and 13 as PV2 and PV3, and operate the pumps 10 and 12 so that the measured values PV2 and PV3 are maintained at the target values SV2 and SV3. The amounts MV2 and MV3 are set, and the amount of sludge returned by the pump 10 and the amount of sludge withdrawn by the pump 12 are controlled to the target return amount _Qr ^* and the target withdrawal amount _Mw ^* .

Then, the target return amount Q _r ^* and the target withdrawal amount M _w ^*
Is set in consideration of the quality of the dirt of the raw water flowing into the reaction tank 2. Depending on the quality of the dirt and the amount of the raw water flowing into the reaction tank 2, not only the amount of air blown by the blower 5 but also the amount of sludge returned by the pump 10 Since the amount of the extracted sludge of the pump 12 is determined, the pumps 10 and 12 are operated in connection with the amount of the air blown by the blower 5, and the amount of the returned sludge and the amount of the extracted sludge can be controlled to the optimum amounts.

Therefore, the quality of the treated water discharged from the final sedimentation basin 3 is maintained very stably at the target water quality regardless of the state of the raw water flowing into the reaction tank 2, and the water quality standard is set for energy saving. Efficient and excellent wastewater treatment that complies with the requirements can be realized.

The treated water discharged from the final sedimentation basin 3 based on the sewage treatment of the present invention shown in FIG. 1 and the treated water discharged from the final sedimentation basin 3 based on the conventional sewage treatment shown in FIG. And the change over time of the BOD amount are shown in FIG.
become that way.

In FIG. 2, the solid line indicates a change in the BOD amount of the treated water of the present invention (BOD change), and the solid line indicates a change in the BOD amount of the conventional treated water (BOD change).

The solid line A in the figure indicates the target water quality of the control of the present invention, and the solid line B indicates the target water quality of the conventional control.

As is apparent from FIG. 2, in the conventional sewage treatment, the degree of contamination of the raw water flowing into the reaction tank 2 is not taken into consideration, so that the degree of contamination of the raw water and the change in the amount of inflow are not considered. The water quality change of the treated water is large, and the target water quality of the control is set to a high value (low as the BOD amount) in advance as shown by a solid line B (consequently, the reaction tank 2 is over-aerated) so as to conform to the water quality standard. Although it is necessary, in the sewage treatment of the present invention, the control is performed in consideration of the degree of contamination of the raw water flowing into the reaction tank 2, and the control is performed in real time. Even if the change in the water quality of the treated water with respect to the change in the amount is small and the target water quality of the control is set lower than the conventional one (higher as the BOD value) as shown by the solid line A, the excess aeration of the reaction tank 2 is suppressed. Water is Enough to satisfy the quality criteria.

In this type of sewage treatment, since the operating energy of the blower 5 is extremely large, the most contributing to energy saving is a reduction in the operating energy of the blower 5.

Therefore, in the simplest case, only the target air volume G _s ^* is calculated by the calculation unit 16, and only the air volume of the blower 5 is determined based on the target air volume G _s ^*. The control may be performed in consideration of the amount.

[0070] Further, the target air volume by the operation unit 16 G _s ^*, the target return amount Q _r ^*, may be the target extraction amount M _w ^* of computation techniques different from the above embodiment, for example, several to several 3 The determination of the coefficients of the above equations may be performed not by a parameter determination operation using a neutral network or the like but by a numerical operation using an appropriate algebraic expression.

Further, the blower 5, the pumps 10, 12 are
Needless to say, one or more units may be used.
And it can be applied to various sewage treatments of the standard activated sludge method.

[0072]

The present invention has the following effects. First, in the case of claim 1, an index value indicating the degree of contamination of the raw water is calculated from the measured value of the BOD amount of the sewage (raw water) flowing into the biological treatment tank (reaction tank 2). Flow into the reaction tank 2 by multiplying the measured flow rate by the flow rate
The amount of air required for the treatment of raw water
Nitrification and reaction by product of coefficient and raw water inflow measurement
Find the amount of air required to maintain the dissolved oxygen level in tank 2 and calculate
The target value of the air volume required for aeration of the reaction tank 2 in consideration of the degree of contamination of the raw water and the inflow amount is calculated as the target air volume.
It is possible to determined.

[0073] Then, according to the target air volume, since the air volume from the blower 5 to the reaction tank 2 is controlled, not only the inflow of the raw water, anti <br/> response by considering the degree of soiling Optimal aeration of the tank 2 can be performed.

[0074] At this time, if the aeration amount is more than necessary in many such cases the conventional processing method considering only inflow of raw water
In addition , it is possible to prevent excessive aeration due to useless air blowing, save energy, and perform effective wastewater treatment using the standard activated sludge method .

Next, in the case of claim 2, the BOD amount and the inflow amount of the raw water flowing into the reaction tank are determined by the BOD sensor 14,
The flow rate is measured by the flow meter 1 and these measured values are
5 is taken.

Then, in this control device 15, BO
From the difference between the measurement value of the D sensor 14 and the target treated water BOD value, an index value of the contamination of the raw water is calculated and obtained. The product of this index value and the measurement value of the flow meter 1 is a coefficient of denitrification and nitrification. And flow
By adding the product of the measurement values of the meter 1, it is possible to obtain, as a target value, the amount of air required for aeration of the reaction tank 2 in consideration of the degree of contamination of raw water and the amount of inflow.

Further, according to the target value, the blower 5
Thus, the amount of air blown to the diffuser 4 of the reaction tank 2 can be controlled.

Therefore, it is possible to provide a concrete sewage treatment apparatus for performing sewage treatment based on the sewage treatment method of claim 1.

Next, in the case of the third aspect, the operation of the return sludge pump 10 and the excess sludge pump 12 can be controlled in connection with the amount of air blown by the blower 5, and the control of the processing of the return sludge and the excess sludge can be performed. The present invention provides a sewage treatment apparatus capable of performing optimal control according to the state (degree) of contamination of raw water flowing into the reaction tank 2 and performing more effective sewage treatment than the case of claim 2. be able to.

Next, in the case of claim 4, the operation of the blower 5, the return sludge pump 10, and the excess sludge pump 12 is simultaneously controlled in real time on-line based on the instantaneously measured values of the BOD sensor 14, thereby realizing a reaction. It becomes quality of treated water is extremely stable against changes in raw water flowing into the tank 2, to provide a practical sewage treatment apparatus capable of performing an effective and stable sewage work to energy saving Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an apparatus configuration according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of a change in the BOD amount of treated water.

FIG. 3 is a block diagram showing a device configuration of a conventional example.

[Explanation of symbols]

 1, 11, 13 Flow meter 2 Biological treatment tank (reaction tank) 3 Final sedimentation tank 5 Blower 10 Return sludge pump 12 Excess sludge pump 14 BOD sensor 15 Control device

Claims (4)

(57) [Claims] An inflow amount and a BOD amount of the wastewater flowing into a biological treatment tank for treating wastewater such as wastewater and sewage are measured by a standard activated sludge method, and the measured value of the BOD amount and a target treated water BOD value are measured. the calculated difference as an index value of contamination of the wastewater, and more the organism to the product of the measured value of the index value and the flow rate
The amount of air required for the treatment of sewage flowing into the treatment tank is determined, and the product of the coefficient of denitrification and nitrification and the measured value of the amount of inflow is obtained.
Nitrogenation and ventilation required to maintain dissolved oxygen in the biological treatment tank
Determine the amount, the by adding the two products and calculates a target air amount as a target value of the aeration air quantity, sewage treatment method characterized by controlling the air volume from the blower to the biological treatment tank according to the target air volume . 2. A biological treatment tank that treats wastewater such as wastewater and sewage by a standard activated sludge method, a blower that blows air to a diffuser of the biological treatment tank, and is provided near a sewage inlet of the biological treatment tank. A flow meter for measuring the amount of inflow of the sewage flowing into the biological treatment tank; a BOD sensor provided near the sewage inflow port for measuring a BOD amount of the sewage flowing into the biological treatment tank; And a control device for taking in the measurement values of the BOD sensor and the BOD sensor, and controlling the blowing of air from the blower to the air diffuser. The control device determines the difference between the measurement value of the BOD sensor and the target treated water BOD value. means for calculating as an index value of contamination of the wastewater, and more the organism to the product of the measured value of the index value and the flowmeter
Determine the amount of air required to treat the wastewater flowing into the treatment tank,
The product of the nitrogen and nitrification coefficients and the flow meter readings
The amount of air required to maintain the dissolved oxygen level in the biological treatment tank was determined,
Sewage, characterized in that said means for calculating a target air volume <br/> as the target value of the sum of both products aeration air quantity, and means of controlling the air volume of the blower according the target air volume provided Processing equipment. 3. A return sludge pump for returning a part of the sludge settled from a biological treatment tank to a final sedimentation basin in a subsequent stage to the biological treatment tank, and excess sludge drawn out of the final sedimentation basin for discharging the surplus amount of the sludge from the final sedimentation pond. A pump and a target value for control of the two pumps are calculated in accordance with the state of contamination of the sewage flowing into the biological treatment tank based on the measurement values of the BOD sensor, and the operation of the two pumps is performed from the blower to the biological treatment tank. 3. A sewage treatment apparatus according to claim 2, further comprising: means for controlling the amount of air to be linked to the amount of air blown. 4. The sewage treatment apparatus according to claim 3, wherein the operation of the blower, the return sludge pump, and the excess sludge pump is simultaneously controlled online in real time based on the measured value of the BOD sensor every moment. .