WO2016103707A1

WO2016103707A1 - Water treatment system and method for controlling aeration air quantity thereof

Info

Publication number: WO2016103707A1
Application number: PCT/JP2015/006444
Authority: WO
Inventors: 洋士山本; 崇嗣安部; 康二福本; 航介柁山; 直樹成島
Original assignee: 川崎重工業株式会社
Priority date: 2014-12-25
Filing date: 2015-12-24
Publication date: 2016-06-30
Also published as: CN205398370U; CN105731630A; JP6431363B2; CN105731630B; JP2016120465A

Abstract

A water treatment system is provided with: a first ammonia meter for measuring the ammoniacal nitrogen concentration in an activated sludge mixture in an aerobic tank provided with an aeration device; a second ammonia meter for measuring the ammoniacal nitrogen concentration in raw water flowing into a series of biological reaction tanks; an aeration air quantity control device for controlling the aeration air quantity in the aeration device on the basis of a target operation amount which is a target value for aeration air quantity in the aeration device; and an aeration air quantity calculation device for generating the target operation amount. The aeration air quantity calculation device has: a feedback control system including a first operation amount calculation element for generating a return target operation amount signal; a feed-forward control system including a second operation amount calculation element for generating a preceding target operation amount signal in accordance with the change amount per unit of time of the ammoniacal nitrogen concentration in the raw water; and an addition calculation element for adding the return target operation amount signal and the preceding target operation amount signal.

Description

Water treatment system and aeration air volume control method thereof

The present invention relates to a water treatment system provided with a biological reaction tank including an aerobic tank provided in a sewage treatment facility or the like. In particular, the present invention relates to the control of the amount of aeration air in the aerobic tank in the water treatment system.

Conventionally, a water treatment system that purifies wastewater using activated sludge in wastewater treatment such as domestic wastewater is known. Such a water treatment system, for example, converts a pollutant in a raw water tank for storing raw water (inflow sewage) and an activated sludge mixed liquid (hereinafter also simply referred to as “mixed liquid”) into which biological water and activated sludge are mixed. A series of biological reaction tanks to be treated and a sedimentation tank for precipitating and separating sludge from the mixed solution are provided. A series of biological reaction tanks include anaerobic tanks, anoxic tanks, and aerobic tanks, and in these reaction tanks, removal of pollutants contained in raw water such as carbon-based organic substances, nitrogen-containing compounds, and phosphorus-containing compounds. Is done.

In the above water treatment system, the aerobic tank is equipped with an aeration device for aerating the mixed solution. By aeration of the mixed solution, the dissolved oxygen concentration in the mixed solution necessary for the activity of the activated sludge microorganisms can be increased, or the mixed solution can be stirred. If the amount of air supplied to the mixed solution in the aerobic tank by the aeration apparatus (hereinafter referred to as “aeration air volume”) is insufficient, the quality of the treated water deteriorates.

In order to prevent this, a configuration has been proposed in which the aeration volume in the aerobic tank is feedback-controlled based on the ammonia nitrogen concentration in the aerobic tank (see Patent Document 1). In addition to the ammonia nitrogen concentration in the aerobic tank, the ammonia nitrogen concentration of raw water flowing into a series of biological reaction tanks is measured, and the aeration air volume is feedforward controlled based on the ammonia nitrogen concentration of the raw water. It has been proposed (see Patent Document 2).

JP 2005-199116 A JP 2012-66231 A

However, even in a configuration in which feedforward control is performed in addition to the feedback control as described above, it may be difficult to obtain an appropriate aeration air volume.

The present invention has been made in view of the above, and an object thereof is to provide a water treatment system capable of appropriately controlling the amount of air supplied to a mixed solution in an aerobic tank and a method for controlling the amount of aeration air.

A water treatment system according to an aspect of the present invention includes an aerobic tank provided with an aeration apparatus, and at least one anaerobic tank or an oxygen-free tank provided on the upstream side of the aerobic tank, and activated sludge. A series of biological reaction tanks for water treatment based on the law, a first ammonia meter for measuring the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank, and raw water flowing into the series of biological reaction tanks A second ammonia meter for measuring the ammonia nitrogen concentration, an aeration air volume control device for controlling the aeration air volume of the aeration device based on a target operation amount which is a target value of the aeration air volume of the previous aeration device, and the target operation An aeration air volume calculating device that generates a quantity of air, and the aeration air volume calculating device outputs a feedback target manipulated variable signal based on a deviation between the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank and its set value. First operation amount to be generated A feedback control system including a calculation element; a feedforward control system including a second operation amount calculation element that generates a preceding target operation amount signal according to a change amount per unit time of the ammonia nitrogen concentration of the raw water; and And an addition operation element for adding the feedback target operation amount signal and the preceding target operation amount signal to generate the target operation amount.

According to the above configuration, feedforward control is performed according to the amount of change in the ammonia nitrogen concentration of raw water per unit time while performing feedback control based on the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank. As a result, the aeration air volume can be changed in accordance with the rise of the ammonia nitrogen concentration in the raw water, so the aeration air volume can be adjusted appropriately even for abrupt changes in the ammonia nitrogen concentration that are difficult to follow with feedback control. Can be controlled. Further, if the amount of change per unit time is small even if the ammonia nitrogen concentration value itself of the raw water is high, the change in the amount of aeration air by feedforward control can be reduced. In such a case, since it is possible to sufficiently cope with only the feedback control, it is possible to save power while controlling to an appropriate aeration air volume by suppressing an excessive change in the aeration air volume due to the feedforward control.

The second manipulated variable calculation element calculates a preceding target manipulated variable according to a change amount per unit time of the ammonia nitrogen concentration of the raw water so that a decrease in the preceding target manipulated variable is suppressed for a predetermined period. The preceding target manipulated variable signal may be generated. According to this, when the change amount per unit time of the ammonia nitrogen concentration of the raw water indicates an increase in the ammonia nitrogen concentration of the raw water, the preceding target operation amount of the aeration air amount is set as the operation amount corresponding to the change amount. Thereafter, even if the amount of change in the ammonia nitrogen concentration of the raw water per unit time indicates a decrease in the ammonia nitrogen concentration of the raw water, the decrease in the preceding target manipulated variable is suppressed for a predetermined period. Therefore, when the ammonia nitrogen concentration rises, the aeration air volume increases rapidly following the increase of the ammonia nitrogen concentration in the activated sludge mixture in the aerobic tank, and when the ammonia nitrogen concentration decreases, feedforward control By suppressing an excessive change in the amount of aeration air due to the aeration, it is possible to reliably perform the aeration treatment in the aerobic tank and reliably reduce the ammonia nitrogen concentration after the treatment.

The predetermined period may be configured to be set according to the residence time of the activated sludge mixed liquid in the series of biological reaction tanks. Since the time required for aeration treatment changes according to the residence time of the activated sludge mixed liquid in a series of biological reaction tanks, by changing the period for suppressing the reduction of the aeration air volume according to the residence time of the activated sludge mixed liquid, It is possible to reliably reduce the concentration of ammonia nitrogen after the treatment by reliably performing the aeration treatment in the aerobic tank.

The second manipulated variable calculation element calculates a preceding target manipulated variable according to a change amount per unit time of the ammonia nitrogen concentration of the raw water, and calculates a time from a reference waveform indicating a temporal change of the preceding target manipulated variable. Generating at least one replicated waveform shifted in the axial direction by a predetermined first unit period, selecting at least two of the reference waveform and the replicated waveform according to the predetermined period, and Of these, the preceding target operation amount signal may be generated by selecting a value having the largest preceding target operation amount. According to this, it is possible to realize a process in which the decrease in the preceding target operation amount is suppressed during the decrease suppression period by duplicating and overlapping the reference waveform. Therefore, the process can be a relatively simple arithmetic process.

An aeration air volume control method for a water treatment system according to another aspect of the present invention includes an aerobic tank provided with an aeration apparatus, and at least one anaerobic tank or an oxygen-free tank provided upstream of the aerobic tank. A method for controlling the aeration air volume of a water treatment system comprising a series of biological reaction tanks having a tank and performing water treatment based on the activated sludge method, the target manipulated variable being a target value of the aeration air volume of the aeration apparatus An air volume control step for controlling the aeration air volume of the aeration device based on the above, and a target operation amount calculation step for generating the target operation amount, wherein the target operation amount calculation step comprises activated sludge in the aerobic tank A mixed liquid measuring step for measuring the ammonia nitrogen concentration of the mixed liquid, a raw water measuring step for measuring the ammonia nitrogen concentration of the raw water flowing into the series of biological reaction tanks, and the ammonia in the activated sludge mixed liquid in the aerobic tank Nitrogen concentration and its setting A feedback signal generating step for generating a feedback target manipulated variable signal based on the deviation from the above, and a preceding signal generating step for generating a preceding target manipulated variable signal according to the amount of change per unit time in the ammonia nitrogen concentration of the raw water And an operation amount generating step of generating the target operation amount by adding the feedback target operation amount signal and the preceding target operation amount signal.

According to the above method, while performing feedback control based on the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank, feed forward control is performed according to the amount of change in the ammonia nitrogen concentration of the raw water per unit time. As a result, the aeration air volume can be changed in accordance with the rise of the ammonia nitrogen concentration in the raw water, so the aeration air volume can be adjusted appropriately even for abrupt changes in the ammonia nitrogen concentration that are difficult to follow with feedback control. Can be controlled. Further, if the amount of change per unit time is small even if the ammonia nitrogen concentration value itself of the raw water is high, the change in the amount of aeration air by feedforward control can be reduced. In such a case, since it is possible to sufficiently cope with only the feedback control, it is possible to save power while controlling to an appropriate aeration air volume by suppressing an excessive change in the aeration air volume due to the feedforward control.

The preceding signal generation step calculates a preceding target operation amount according to a change amount per unit time of the ammonia nitrogen concentration of the raw water, and the preceding signal operation is performed such that a decrease in the preceding target operation amount is suppressed for a predetermined period. A target operation amount signal may be generated. According to this, when the change amount per unit time of the ammonia nitrogen concentration of the raw water indicates an increase in the ammonia nitrogen concentration of the raw water, the preceding target operation amount of the aeration air amount is set as the operation amount corresponding to the change amount. Thereafter, even if the amount of change in the ammonia nitrogen concentration of the raw water per unit time indicates a decrease in the ammonia nitrogen concentration of the raw water, the decrease in the preceding target manipulated variable is suppressed for a predetermined period. Therefore, when the ammonia nitrogen concentration rises, the aeration air volume increases rapidly following the increase of the ammonia nitrogen concentration in the activated sludge mixture in the aerobic tank, and when the ammonia nitrogen concentration decreases, feedforward control By suppressing an excessive change in the amount of aeration air due to the aeration, it is possible to reliably perform the aeration treatment in the aerobic tank and reliably reduce the ammonia nitrogen concentration after the treatment.

The above object, other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings.

According to the present invention, the amount of air supplied to the liquid mixture in the aerobic tank can be appropriately controlled.

FIG. 1 is a diagram showing a schematic configuration of a reclaimed water production system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a control configuration of the reclaimed water production system. FIG. 3 is a block diagram showing the signal flow of the aeration air volume calculation unit. FIG. 4 is a graph showing the characteristics of the FF manipulated variable function. FIG. 5 is a graph illustrating the temporal change in the ammonia nitrogen concentration of the raw water and the graph illustrating the temporal change in the FF manipulated variable included in the preceding target manipulated variable signal generated based on the graph. FIG. 6 is a graph showing temporal changes in the ammonia nitrogen concentration and aeration air volume in each tank in the reclaimed water production system to which the present embodiment is applied.

[Background to obtaining one embodiment of the present invention]
The inventors of the present invention can adjust the ammonia nitrogen concentration of raw water flowing into a series of biological reaction tanks in addition to feedback control for controlling the amount of aeration air based on the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank. Considering the cause of the fact that the amount of air supplied to the liquid mixture in the aerobic tank may not be appropriately controlled in the conventional configuration (the configuration of Patent Document 2) that performs feedforward control that controls the aeration air volume based on did. As a result, the inventors of the present invention have found that the conventional configuration has the following problems.

First, in the conventional configuration, the amount of aeration air is controlled according to the value of the ammonia nitrogen concentration of the raw water itself. When the concentration of ammonia nitrogen in the raw water rises rapidly, a reaction delay occurs in the biological reaction tank. Even in such a case, aeration is performed so that the ammonia nitrogen concentration in the treated water can be suppressed below the regulation value. The operation amount with respect to the air volume is set larger. However, when the increase in the concentration of ammonia nitrogen in the raw water is slow, there is no reaction delay in the biological reaction tank. However, it becomes an excessive aeration air volume.

Therefore, the inventors of the present invention, after earnest research, in the feedback control, while controlling the aeration air volume based on the ammonia nitrogen concentration value itself of the activated sludge mixed liquid in the aerobic tank, In the control, by controlling the amount of aeration air according to the amount of change in the ammonia nitrogen concentration of raw water flowing into a series of biological reactors per unit time, the rise of the change in ammonia nitrogen concentration that requires a quick response is required. It was conceived that an excessive change in the aeration air volume can be suppressed when the change in the ammonia nitrogen concentration is slow while following the aeration air volume.

Furthermore, the inventors of the present invention have sufficient feedforward control in the above-described conventional configuration when the residence time of the activated sludge mixed liquid in a series of biological reaction tanks is long, the time required for the aeration treatment becomes long. It has been found that there is a problem that the effect of may not be obtained.

Therefore, the inventors of the present invention can reliably perform the aeration treatment in the aerobic tank to change the ammonia state after the treatment by changing the period for suppressing the decrease in the amount of aeration air according to the residence time of the activated sludge mixed liquid. The inventors have conceived that the nitrogen concentration can be reliably reduced.

[Embodiment]
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout the drawings, and redundant description thereof is omitted.

FIG. 1 is a diagram showing a schematic configuration of a reclaimed water production system according to an embodiment of the present invention. A reclaimed water production system 1 shown in the figure is a water treatment system for purifying sewage using a standard activated sludge method. The reclaimed water production system 1 includes a raw water tank 2, a series of biological reaction tanks 10 including an anaerobic tank 3, an anaerobic tank 4, and an aerobic tank 5 and a sedimentation tank 6 in order from the upstream side.

The raw water tank 2 functions as a buffer tank that temporarily stores the inflowing sewage. The outflow side of the raw water tank 2 is connected to the inflow side of the anaerobic tank 3 located on the most upstream side of the series of biological reaction tanks 10 by a pipe 52. The pipe 52 is provided with a supply pump 51 that pumps the raw water stored in the raw water tank 2 to the anaerobic tank 3. On the outflow side of the raw water tank 2, the ammonia nitrogen concentration (hereinafter referred to as “raw water NH ₄ concentration”) flowing from the raw water tank 2 into a series of biological reaction tanks 10 (here, the most upstream anaerobic tank 3). ) For measuring raw water ammonia meter 31 (second ammonia meter).

The biological reaction tank 10 is provided in the order of the anaerobic tank 3, the oxygen-free tank 4 and the aerobic tank 5 from the upstream side. The raw water flowing into the biological reaction tank 10 is an activated sludge mixed liquid (hereinafter simply referred to as activated sludge). Also known as “mixed liquid”. In this Embodiment, the anaerobic tank 3 and the anoxic tank 4 are formed by dividing one reaction tank into two, and the anaerobic tank 3 and the anaerobic tank 4 are connected via the partition. . Therefore, the liquid mixture in the anaerobic tank 3 can move to the anoxic tank 4. The outflow side of the anaerobic tank 4 is connected to the inflow side of the aerobic tank 5 by a pipe 53. Furthermore, the outflow side of the aerobic tank 5 is connected to the inflow side of the settling tank 6 by a pipe 54.

The aerobic tank 5 is provided with an aeration device 9 for aeration of the mixed solution. The aeration apparatus 9 according to the present embodiment is of an aeration type, and compressed air sent from a blower (not shown) is made into fine bubbles to be blown into the mixed liquid from the bottom of the aerobic tank 5. It is configured. When the air blown into the mixed solution in the aerobic tank 5 rises to the water surface as bubbles, the mixed solution is stirred and mixed, and when activated sludge microorganisms remove nitrogen, phosphorus and organic matter. Necessary oxygen is supplied into the liquid mixture. The amount of air supplied to the mixed solution in the aerobic tank 5 by the aeration device 9 (hereinafter referred to as “aeration air amount”) is controlled by a control device 40 described later.

In the aerobic tank 5, an aerobic tank ammonia meter 32 (first ammonia meter) for measuring the ammonia nitrogen concentration (hereinafter referred to as “aerobic tank NH ₄ concentration”) of the mixed solution in the aerobic tank 5 is provided. Is provided. The aerobic tank ammonia meter 32 is preferably provided on the outflow side of the aerobic tank 5 from the viewpoint of measuring the components of the mixed solution to be discharged from the aerobic tank 5. Since these mixed solutions are considered to be completely mixed, their arrangement is not particularly limited.

In the sedimentation tank 6, sludge out of the treatment liquid flowing from the aerobic tank 5 is precipitated and separated into the treatment liquid and sludge. The sludge is returned to the anaerobic tank 3 through the sludge return pipe 63 provided with the sludge return pump 64.

Next, the control configuration of the reclaimed water production system 1 will be described. FIG. 2 is a block diagram showing a control configuration of the reclaimed water production system. In the figure, the control of the aeration apparatus 9 is shown in detail, and the remainder is omitted.

As shown in FIG. 2, the control device 40 mainly calculates the target operation amount of the operation control unit 42 and the aeration device 9 (that is, the target value of the aeration air amount in the aerobic tank 5) that controls the entire reclaimed water production system 1. It has functional units such as an aeration air amount calculation unit 41 to be generated and an aeration air amount control unit 91 that controls the aeration apparatus 9 based on the target operation amount. In the present embodiment, the aeration air volume control unit 91 is provided in the control device 40, but may be provided in the aeration device 9. The control device 40 is composed of one or a plurality of computers. Each computer is a CPU (Central Processing Unit), a main storage device that rewrites a program executed by the CPU and data used in the program, and a CPU executes the program. It is sometimes equipped with a secondary storage device that temporarily stores data, an interface for connecting the CPU and external devices, an internal path for connecting these, and the like (all not shown). Then, each function unit of the control device 40 shown in FIG. 2 is realized by the CPU executing a predetermined program.

The control device 40 and each pump provided in the reclaimed water production system 1, that is, the supply pump 51 and the drive unit of the sludge return pump 64 are connected by wire or wirelessly, and the operation of each

pump

51, 64 is performed by the control device 40. It is controlled by the operation control unit 42. The control device 40 and a blower (not shown) for changing the aeration air volume in the aeration device 9 are connected by wire or wirelessly, and the operation of the aeration device 9 is controlled by the aeration air volume control unit 91 of the control device 40. Yes. Further, the control device 40 and each of the

ammonia meters

31 and 32 are communicably connected, and the measurement signals of these

ammonia meters

31 and 32 are transmitted to the control device 40. And the control apparatus 40 operates each

pump

51 and 64 and the aeration apparatus 9 based on the measurement signal of the

ammonia meters

31 and 32. FIG. As a result, the control device 40 prevents the nitrogen, phosphorus and organic matter of the treated water in the filtered water tank 7 from exceeding the respective regulation values. The flow rate, excess sludge extraction amount and aeration air volume are managed and controlled to appropriate values.

In the reclaimed water production process by the reclaimed water production system 1 configured as described above, organic substances, nitrogen, phosphorus, and the like contained in the mixed liquid (raw water) are removed as shown below.

In the reclaimed water production process, the carbon-based organic matter contained in the mixed solution is decomposed by the action of aerobic and facultative anaerobic heterotrophic bacteria in the activated sludge, or discharged out of the system as activated sludge. Specifically, the organic matter in the mixed liquid comes into contact with the activated sludge and is adsorbed (condensed) on the surface of the activated sludge, and the organic matter adsorbed on the activated sludge is subjected to anaerobic conditions in the anaerobic tank 3 and the anaerobic tank 4. It is ingested and degraded by facultative anaerobic heterotrophic bacteria in activated sludge. In addition, the organic matter adsorbed on the activated sludge provides energy necessary for the maintenance of the living body and cell synthesis by the aerobic and facultative anaerobic heterotrophic bacteria in the activated sludge under the aerobic condition of the aerobic tank 5. Decomposed (oxidized) to obtain. Furthermore, this heterotrophic bacterium uses the energy obtained by oxidation to synthesize (anabolic) organic matter into new cellular material. In this way, most of the organic substances contained in the mixed solution are adsorbed on the activated sludge, and then used for the oxidation and assimilation of the activated sludge microorganisms and removed from the mixed solution. The organic matter that is not oxidized and assimilated is stored in the system, and is finally discharged out of the system as surplus sludge together with the cellular material that is not oxidized by the endogenous respiration of the activated sludge microorganisms.

In the reclaimed water production process, phosphorus contained in the mixed solution is discharged out of the system in a state where it is accumulated in the activated sludge by the action of the phosphorus accumulating bacteria in the activated sludge. Specifically, the phosphorus accumulating bacteria in the activated sludge take in and hold organic substances such as acetic acid contained in the raw water flowing into the anaerobic tank 3 from the raw water tank 2 under the anaerobic condition of the anaerobic tank 3. Releases phosphoric acid (PO ₄ ). Then, the phosphorus accumulating bacteria in the activated sludge excessively ingests phosphorus under the aerobic condition of the aerobic tank 5 and takes in more phosphoric phosphorus released in the anaerobic tank 3. Thus, phosphorus in the mixed liquid is accumulated in the activated sludge, and the activated sludge in which phosphorus is accumulated is discharged out of the system as surplus sludge.

Further, in the reclaimed water production process, nitrogen is released out of the system from the anoxic tank 4. Specifically, the raw water flowing from the raw water tank 2 into the anaerobic tank 3 contains ammonia nitrogen (NH ₄ ⁺ -N) and organic nitrogen. The organic nitrogen contained in the mixed solution changes to ammonia nitrogen in the anaerobic tank 3, the anoxic tank 4 and the aerobic tank 5. Ammonia nitrogen in the mixed solution is oxidized by the action of nitrifying bacteria in the aerobic tank 5 to become nitrite nitrogen (NO ₂ -N) or nitrate nitrogen (NO ₃ -N). Therefore, the circulated water sent from the settling tank 6 to the anoxic tank 4 by the circulation pump 62 contains nitrite nitrogen and / or nitrate nitrogen. Nitrite nitrogen and nitrate nitrogen in the mixed solution are nitrogen gas (N) by nitrate respiration or nitrite respiration by denitrifying bacteria using organic matter in the raw water as a nutrient source under anoxic conditions in the anaerobic tank 4. _It is reduced to ₂ ) and released from the anoxic tank 4 to the outside of the system.

Here, a method of generating a target operation amount of the aeration apparatus 9 by the aeration air amount calculation unit 41 of the control apparatus 40, that is, a target value of the aeration air volume of the aerobic tank 5, will be described with reference to FIG. Based on the target operation amount generated by the aeration air amount calculation unit 41, the aeration air amount control unit 91 operates the rotation amount of the blower (not shown) included in the aeration device 9 and the aerobic tank 5 from the aeration device 9. At least one of the operation amounts of an adjustment actuator (not shown) provided in the supply path of the air supplied into the inside is adjusted.

FIG. 3 is a block diagram showing the signal flow of the aeration air volume calculation unit. As shown in the figure, the aeration air volume calculation unit 41 generates a preceding target manipulated variable (hereinafter also simply referred to as FF manipulated variable) based on the amount of change per unit time of the raw water NH ₄ concentration, and the preceding target manipulated variable. A feedforward control system (hereinafter referred to as FF control system 48) that outputs as a signal and a feedback target manipulated variable (hereinafter also simply referred to as FB manipulated variable) are generated using the aerobic tank NH ₄ concentration as a controlled variable, and the feedback target manipulated variable is generated. A feedback control system (hereinafter referred to as FB control system 49) that outputs the signal as a quantity signal. The FF control system 48 and the FB control system 49 function in cooperation, and the addition operation element 70 adds the FF operation amount generated by the FF control system 48 and the FB operation amount generated by the FB control system 49. Thus, the target operation amount of the aeration apparatus 9 is generated.

First, the FB control system 49 will be described. The FB control system 49 is measured by a preset ammonia nitrogen concentration set value (hereinafter, also referred to as “aerobic tank NH ₄ concentration set value”) of the liquid mixture of the aerobic tank 5 and an aerobic tank ammonia meter 32. A deviation calculation element 71 for calculating a deviation from the aerobic tank NH ₄ concentration and an FB operation amount calculation element (first operation amount calculation element) 72 for generating an FB operation amount from the deviation are provided. The FB operation amount calculation element 72 is a calculation element that calculates an FB operation amount using, for example, a PID control method, a P control method, or a PI control method. An output signal (FB operation amount) of the FB control system 49 is input to the addition calculation element 70.

The aerobic tank NH ₄ concentration set value is a value that is appropriately determined based on the regulation value (target value) of the ammonia nitrogen concentration (treated water NH ₄ concentration) of the treated water. However, the aerobic tank NH ₄ concentration set value may be determined based on other factors such as the water temperature of the mixed liquid in addition to the regulation value of the treated water NH ₄ concentration.

Next, the FF control system 48 will be described. The FF control system 48 includes a differential operation element 73, an FF operation amount function element 74, a period setting element 75, and a feedforward gain element 76, and includes a second operation amount operation element that generates an FF operation amount. ing. An output signal (FF operation amount) of the FF control system 48 is input to the addition operation element 70. In the present embodiment, the FF control system 48 is configured to execute the period setting element 75 after executing the FF manipulated variable function element 74 as shown in FIG. The FF manipulated variable function element 74 may be executed later.

The differential calculation element 73 calculates the amount of change Δx per unit time of the raw water NH ₄ concentration by differentiating the raw water NH ₄ concentration x measured by the raw water ammonia meter 31. FF manipulated variable function F ₁ ([Delta] x), in order to control the ammonia nitrogen concentration in the treated water on the basis of the change amount [Delta] x per unit of raw NH ₄ concentration time (treated water NH ₄ concentration), the raw water NH ₄ concentration Is a function of the static characteristic relationship between the change amount Δx per unit time and the aeration air volume manipulated variable (in particular, the FF manipulated variable). The raw water NH ₄ concentration x is a measured value of the raw water ammonia meter 31 provided in the raw water tank 2 in the present embodiment, but may be any ammonia nitrogen concentration in the raw water flowing into the anaerobic tank 3. The measurement position is not limited.

FIG. 4 is a graph showing the characteristics of the FF manipulated variable function F ₁ (Δx). The vertical axis y represents the FF manipulated variable (L / min), and the horizontal axis Δx represents the change per unit time of the raw water NH ₄ concentration. Amount (mg / L) is shown. In FIG. 4, the case where the raw water NH ₄ concentration increases in the change amount Δx is positive. The FF manipulated variable (L / min) represents the amount of aeration air in the aerobic tank 5. The minimum air volume Y ₁ of the FF manipulated variable y is the minimum air volume required for maintaining the entire system. The minimum amount of air required to maintain the entire system is heterotrophic that agitates the mixture in the aerobic tank 5 and grows using carbon-based organic matter under aerobic conditions in the aerobic tank 5 It is the minimum amount of aeration air that provides oxygen necessary for maintaining living organisms by living sludge microorganisms such as nitrifying bacteria that nitrify living organisms and ammonia nitrogen. The minimum air volume Y ₁ is appropriately determined according to the number of activated sludge microorganisms in the aerobic tank 5 and the capacity of the aerobic tank 5.

The FF manipulated variable y is the minimum airflow Y in the range where the change amount Δx per unit time of the raw water NH ₄ concentration is from a negative value (concentration decreased state) to the predetermined first change ΔX _1. ₁ is constant. In the range of the first change amount ΔX ₁ or more, the FF manipulated variable y increases as the change amount Δx increases. The first change amount ΔX ₁ may be a positive value, may be 0, or may be a negative value. For example, as indicated by a broken line in FIG. 4, the minimum air volume Y ₂ may be set in a region below ΔX ₁ ′ which is a negative value.

When the concentration of the raw water NH ₄ decreases, it can be dealt with by feedback control alone. Therefore, the FF manipulated variable y is set to a fixed minimum air volume Y ₁ . By setting in this way, the FF manipulated variable function F ₁ (Δx) element 74 aerates when the change amount Δx per unit time of the ammonia nitrogen concentration of the raw water indicates an increase in the ammonia nitrogen concentration x of the raw water. A preceding target manipulated variable that does not change the aeration air volume y when the air volume y is increased and the amount of change Δx per unit time in the ammonia nitrogen concentration of the raw water indicates a decrease in the ammonia nitrogen concentration x of the raw water (a reference to be described later) Waveform).

According to this, when the ammonia nitrogen concentration rises, the aeration air volume following the increase in the ammonia nitrogen concentration in the activated sludge mixed liquid in the aerobic tank is quickly controlled, and when the ammonia nitrogen concentration is reduced, By suppressing an excessive change in the amount of aeration air by feedforward control, it is possible to reliably perform the aeration treatment in the aerobic tank and reliably reduce the ammonia nitrogen concentration after the treatment.

Further, when the first change amount ΔX ₁ is a positive value (when it is not 0), it is possible to prevent the FF manipulated variable y from frequently changing due to a minute change in the raw water NH ₄ concentration.

The period setting element 75 sets the period of effect of the FF manipulated variable y obtained by the FF manipulated variable function F ₁ (Δx) in order to add dynamic characteristics to the FF manipulated variable y. The effect display period includes a dead time (also referred to as shift time) and a decrease suppression period (also referred to as retention time).

As a general rule, the dead time is that the raw water whose ammonia nitrogen concentration is measured by the raw water ammonia meter 31 flows into the series of biological reaction tanks 10 and becomes a mixed liquid mixed with activated sludge, and enters the aerobic tank 5. This is the time required to flow in. However, since the growth rate of nitrifying bacteria that nitrify ammonia nitrogen in the aerobic tank 5 is slower than that of heterotrophic bacteria in normal activated sludge, the discontinuous surface of the ammonia nitrogen concentration of the mixed solution is the aerobic tank 5. The aeration air volume is increased before reaching the level, and when the discontinuous surface reaches the aerobic tank 5, the activated sludge microorganisms are activated so as to cope with the rapid increase in the ammonia nitrogen concentration. Is desirable. That is, the dead time is desirably set to a time shorter than the time required for the raw water whose ammonia nitrogen concentration is measured by the raw water ammonia meter 31 to flow into the aerobic tank 5.

Further, the decrease suppression period is the time until the ammonia nitrogen in the mixed liquid flowing into the aerobic tank 5 is oxidized by the aeration apparatus 9, that is, the residence time of the activated sludge mixed liquid in the series of biological reaction tanks 10. It is. In other words, a time during which the ammonia nitrogen in the mixed liquid in the series of biological reaction tanks 10 does not exceed the target value after the ammonia nitrogen concentration of the raw water starts to rise is set as the reduction suppression period. Since the time required for the aeration treatment changes according to the residence time of the activated sludge mixed liquid in the series of biological reaction tanks 10, by changing the period for suppressing the decrease in the amount of aeration air according to the residence time of the activated sludge mixture liquid And the aeration process in the aerobic tank 5 can be performed reliably, and the ammonia nitrogen concentration after a process can be reduced reliably.

For this reason, the period setting element 75 of the second manipulated variable calculation element calculates the FF manipulated variable according to the change amount Δx per unit time of the ammonia nitrogen concentration of the raw water, and the decrease in the FF manipulated variable is predetermined. A preceding target operation amount signal that is suppressed for a period (a decrease suppression period) is generated. More specifically, the second manipulated variable calculation element calculates the FF manipulated variable according to the amount of change Δx per unit time of the ammonia nitrogen concentration of the raw water, and is a reference indicating the temporal change of the FF manipulated variable. Generate a waveform. Further, the second manipulated variable calculation element generates at least one duplicate waveform that is shifted from the generated reference waveform by a predetermined first unit period in the time axis direction. The reference waveform and the at least one duplicate waveform overlap each other according to the first unit period. The second manipulated variable calculation element selects at least one of the reference waveform and the duplicate waveform according to the dead time and the decrease suppression period. When there are a plurality of selected waveforms, the second manipulated variable calculation element generates a preceding target manipulated variable signal by selecting a value having the largest FF manipulated variable from the plurality of waveforms selected per unit time. To do. That is, the value having the largest FF operation amount is selected at a location where the plurality of selected waveforms overlap each other. When there is one selected waveform, the second manipulated variable calculation element outputs a preceding target manipulated variable having the selected one waveform as a preceding target manipulated variable signal.

FIG. 5 is a graph illustrating the temporal change in the ammonia nitrogen concentration of the raw water and the graph illustrating the temporal change in the FF manipulated variable included in the preceding target manipulated variable signal generated based on the graph. The upper graph in FIG. 5 is a graph illustrating the temporal change in the ammonia nitrogen concentration of the raw water, and the lower graph in FIG. 5 is a preceding target manipulated variable signal generated with respect to the ammonia nitrogen concentration of the raw water. 3 is a graph illustrating a temporal change in the amount of FF operation included in the graph.

As shown in the upper graph of FIG. 5, when the ammonia nitrogen concentration of the raw water monotonously increases and then monotonously decreases, the change amount Δx of the raw water ammonia nitrogen concentration per unit time is the ammonia nitrogen concentration of the raw water. Increases monotonically until reaching a peak, and reaches a peak, and decreases monotonically from the peak until the ammonia nitrogen concentration of the raw water reaches the peak.

In the graph of FIG. 5, while the ammonia nitrogen concentration of the raw water is monotonously decreasing, the change amount Δx per unit time is zero. For example, the first change amount is set to ΔX ₁ = 0, and the minimum air amount Y ₁ (≧ 0) is set in an area where the change amount is ΔX ₁ or less.

The waveform indicating the temporal change of the change amount Δx per unit time is a waveform (reference waveform) indicated by 0h. In FIG. 5, the marks such as 0h, 1h,... Correspond to the waveform in which the peak is at the position of the mark.

The second manipulated variable calculation element calculates a waveform shifted from the 0h waveform by a predetermined first unit period in the time axis direction. In this example, the first unit period is set to 1 hour (1h). As shown in the lower graph of FIG. 5, the waveform of the FF manipulated variable calculated by the second manipulated variable calculation element is a waveform (1h, 2h, 3h) in which the waveform of 0h is translated in the time axis direction every hour. , 4h waveform: replicated waveform). Then, at least one of the calculated waveforms from 0h to 4h is selected according to the dead time A and the reduction suppression period B that are set. For example, when the dead time A is not provided, a waveform of at least 0h is selected. When the decrease suppression period B is only the first unit period (1 hour), only one waveform is selected according to the dead time A. For example, if the dead time A is 2 hours and the decrease suppression period B is only the first unit period, only the 2h waveform is selected. The dead time A and the decrease suppression period B may be set and input by an operator. Instead of this, the control device 40 may be configured to automatically set the dead time A and the decrease suppression period B according to the season and time zone.

For example, when a plurality of waveforms are selected, a value having the largest FF operation amount is selected for each unit time among the selected plurality of waveforms. For example, in the example of the lower graph in FIG. 5, the waveforms from 1h to 3h are selected in a state where they are overlapped with each other. This means that the dead time A is set to 1 hour and the decrease suppression period B is set to 3 hours. By selecting the value having the largest FF manipulated variable per unit time from the waveforms from 1h to 3h, the FF manipulated variable included in the preceding target manipulated variable signal is generated. That is, as shown by the solid line in the lower graph of FIG. 5, the generated FF operation amount has a waveform that follows the ridgeline of the waveform from 1h to 3h. The temporal change of the FF operation amount determined in this way is output as a preceding target operation amount signal. In the lower graph of FIG. 5, the dead time A and the decrease suppression period B are marked with respect to the peak point of each waveform. However, as long as the points corresponding to each other in each waveform are used as references, It may be a standard.

According to this, when the change amount Δx per unit time of the ammonia nitrogen concentration of the raw water indicates an increase in the ammonia nitrogen concentration of the raw water, the target operation amount of the aeration air amount is set to the FF operation amount corresponding to the change amount. After that, even if the amount of change in the ammonia nitrogen concentration of the raw water per unit time shows a decrease in the ammonia nitrogen concentration of the raw water, the decrease in the FF manipulated variable is suppressed for a predetermined period. Therefore, when the ammonia nitrogen concentration rises, the aeration air volume increases rapidly following the increase of the ammonia nitrogen concentration in the activated sludge mixture in the aerobic tank, and when the ammonia nitrogen concentration decreases, feedforward control By suppressing an excessive change in the amount of aeration air due to the aeration, it is possible to reliably perform the aeration treatment in the aerobic tank and reliably reduce the ammonia nitrogen concentration after the treatment. In addition, the process in which the decrease in the FF manipulated variable is suppressed in the decrease suppression period B can be realized by duplicating and overlapping the reference waveform. Therefore, the process can be a relatively simple arithmetic process.

In the description of the present specification and claims, the term “a decrease in the preceding target operation amount (FF operation amount) is suppressed” is a reference for the FF operation amount according to the change amount Δx per unit time. This means that the waveform (0h waveform) includes at least a part of the time zone in which the FF manipulated variable is larger than the value of the FF manipulated variable during the period in which the FF manipulated variable decreases.

The dead time A and the decrease suppression period B are experimental or calculated as the time including the residence time until the raw water flows into the anaerobic tank 3 and flows out of the anaerobic tank 4 and is aerated in the aerobic tank 5. Can be obtained.

The feedforward gain element 76 also functions as an element that gives the dynamic characteristic of the FF manipulated variable y. Feedforward gain K _f is the ratio of change in width of the FF manipulated variable y is an output value for the range of change in the change amount Δx per unit time of the raw water NH ₄ concentration is the input value is appropriately set.

In the present embodiment, the finally obtained FF manipulated variable y is set so as not to take a negative value, as in the graph shown by the solid line in FIG. For this purpose, as described above, the first change amount may be set to ΔX ₁ = 0, and the minimum air volume may be set to Y ₁ (> 0) in the region where the change amount is ΔX ₁ or less. . Instead, when generating a value of temporal change of the FF manipulated variable by duplicating and superimposing a reference waveform of the FF manipulated variable (when generating a graph indicated by the solid line in FIG. 5), the FF Calculation processing may be performed so that the manipulated variable does not take a negative value (below the minimum air volume). Thus, it is possible to first change amount [Delta] X ₁ is as FF operation amount does not take a negative value even in the case of negative.

As described above, the FF operation amount is calculated based on the change amount Δx per unit time of the raw water NH ₄ concentration in the FF control system 48, and the FB operation amount is calculated based on the aerobic tank NH ₄ concentration in the FB control system 49. Then, the target operation amount of the aeration apparatus 9 is generated by adding the FF operation amount and the FB operation amount.

FIG. 6 is a graph showing temporal changes in the ammonia nitrogen concentration and aeration air volume in each tank in the reclaimed water production system to which the present embodiment is applied. In FIG. 6, the horizontal axis is a common time axis, the raw water NH ₄ concentration, the aerobic tank NH ₄ concentration, and the ammonia nitrogen concentration of the treated water filtered in the settling tank 6 (in FIG. 6 and below, the treated water NH ₄ concentration). And a regulation value of the treated water NH ₄ concentration (referred to as a treated water regulation value in FIG. 6 and hereinafter), and a graph showing a temporal change in the aeration air volume. The treated water NH ₄ concentration is measured by, for example, an ammonia meter (not shown) that measures the ammonia nitrogen concentration of the treated water stored in the filtered water tank 7.

In the present embodiment, as described above, feedforward control is performed according to the amount of change Δx per unit time of the raw water NH ₄ concentration while performing feedback control based on the aerobic tank NH ₄ concentration. Thereby, the aeration air volume can be changed in accordance with the rising of the change in the raw water NH ₄ concentration. In the example of FIG. 6, the dead time A is set, and the aeration air volume is increased by the feedforward control at time t2 immediately after the dead time A has elapsed from the rise of the raw water NH ₄ concentration at time t1. For this reason, it is possible to control the amount of aeration air to an appropriate amount even for a sudden change in ammonia nitrogen concentration that is difficult to follow in feedback control.

Furthermore, in the example of FIG. 6, a reduction suppression period B is set, and even if a decrease in the raw water NH ₄ concentration occurs (even if the dead time A is subtracted), the increase period of the raw water NH ₄ concentration (until the peak is reached). The increase in aeration air volume by feedforward control is maintained for a longer period.

As a result, in the subsequent period C (period between time t3 and time t4), the increase in the aerobic tank NH ₄ concentration is suppressed, and the treated water NH ₄ concentration is also controlled to a value that does not exceed the treated water regulation value. ing.

Further, when the amount of change per unit time is small even if the ammonia nitrogen concentration value itself is high as in the period D (period between time t4 and time t5), aeration by feedforward control is performed. The change in air volume can be reduced. As shown in FIG. 6, in the period D, the raw water NH ₄ concentration gradually increases, so the aeration air volume does not increase rapidly. That is, feedback control is dominant in the change of the aeration air volume during the period D. In this way, during a period that can be adequately handled only by feedback control, it is possible to save power while controlling to an appropriate aeration air volume by suppressing an excessive change in the aeration air volume due to the feedforward control.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various improvements, changes, and modifications can be made without departing from the spirit of the present invention.

For example, the specific structure of the reclaimed water production system 1 is not limited to the above embodiment. The reclaimed water production system 1 according to the present embodiment exemplifies a configuration in which a settling tank 6 is provided after an aerobic tank 5, and sludge is produced from a mixed solution that flows from the aerobic tank 5 after the aerobic tank 5. The aspect of the above-described embodiment can also be applied to a water treatment system using a membrane separation activated sludge method (MBR: Membrane® Bio-Reactor) equipped with a membrane separation tank for separating the components. Moreover, although the reclaimed water manufacturing system 1 which concerns on this Embodiment is equipped with both the anaerobic tank 3 and the anaerobic tank 4, you may provide at least one among the anaerobic tank 3 and the anaerobic tank 4. FIG. Further, the aeration apparatus 9 according to the present embodiment is configured to adjust the aeration air volume by the operation amount of the rotation speed of the blower or the operation amount of the adjustment actuator, but the operation amount of the rotation speed of the blower and the adjustment actuator The aeration air volume may be adjusted by both of the manipulated variables.

Further, for example, in the present embodiment, the

ammonia meters

31 and 32 are concentration meters that continuously measure the ammonia nitrogen concentration of the raw water and the mixed solution, respectively. It can also be set as the method of measuring ammonia nitrogen concentration by a method.

In addition, in the generation of the preceding target manipulated variable based on the change amount Δx per unit time of the raw water ammonia nitrogen concentration, the configuration for ensuring the suppression of the preceding target manipulated variable in the decrease suppressing period B is 0h as described above. It is not limited to a mode in which the waveforms are superimposed while being shifted by the first unit period. For example, the second manipulated variable calculation element detects the peak of the waveform of 0h (or decreases the change amount Δx per unit time) and maintains the value of the peak according to the decrease suppression period or gradually decreases Such a preceding target operation amount may be generated. Further, for example, the second operation amount calculation element may be configured to generate the preceding target operation amount by expanding the waveform of 0h so as to expand in the time axis direction according to the decrease suppression period.

From the above description, many modifications and other embodiments of the present invention are apparent to persons skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

The present invention is useful for providing a water treatment system capable of appropriately controlling the amount of air supplied to a mixed solution in an aerobic tank and an aeration air volume control method thereof.

1 Reclaimed water production system (water treatment system)
5 Aerobic tank 9 Aeration device 10 Biological reaction tank 31 Raw water ammonia meter (second ammonia meter)
32 Aerobic tank ammonia meter (first ammonia meter)
40 Control Device 41 Aeration Air Volume Calculation Unit (Aeration Air Volume Calculation Device)
48 Feedforward control system 49 Feedback control system 72 FB manipulated variable computation element (first manipulated variable computation element)
73 Differential calculation element (second manipulated variable calculation element)
74 FF manipulated variable function element (second manipulated variable computation element)
75 Period setting element (second manipulated variable calculation element)
76 Feed forward gain element (second manipulated variable calculation element)
91 Aeration air volume control unit (Aeration air volume control device)

Claims

A series of biological reactions having an aerobic tank equipped with an aeration apparatus and at least one anaerobic tank or an oxygen-free tank provided upstream of the aerobic tank, and performing water treatment based on the activated sludge method A tank,
A first ammonia meter for measuring the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank;
A second ammonia meter for measuring the ammonia nitrogen concentration of the raw water flowing into the series of biological reaction tanks;
An aeration air volume control device that controls the aeration air volume of the aeration device based on a target operation amount that is a target value of the aeration air volume of the aeration device;
An aeration air volume calculating device for generating the target manipulated variable,
The aeration air amount calculation device includes a first operation amount calculation element that generates a feedback target operation amount signal based on a deviation between the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank and a set value thereof. A feedforward control system including a system and a second manipulated variable calculation element that generates a preceding target manipulated variable signal according to a change amount per unit time of the ammonia nitrogen concentration of the raw water, the feedback target manipulated variable signal, An addition operation element for adding the preceding target operation amount signal to generate the target operation amount,
Water treatment system.
The second manipulated variable calculation element calculates a preceding target manipulated variable according to a change amount per unit time of the ammonia nitrogen concentration of the raw water so that a decrease in the preceding target manipulated variable is suppressed for a predetermined period. Configured to generate the preceding target manipulated variable signal,
The water treatment system according to claim 1.
The predetermined period is configured to be set according to the residence time of the activated sludge mixed liquid in the series of biological reaction tanks.
The water treatment system according to claim 2.
The second manipulated variable calculation element calculates a preceding target manipulated variable according to a change amount per unit time of the ammonia nitrogen concentration of the raw water, and calculates a time from a reference waveform indicating a temporal change of the preceding target manipulated variable. Generating at least one replicated waveform shifted in the axial direction by a predetermined first unit period, selecting at least two of the reference waveform and the replicated waveform according to the predetermined period, and The preceding target operation amount signal is generated by selecting a value of which the preceding target operation amount is the largest,
The water treatment system according to claim 2 or 3.
A series of biological reactions having an aerobic tank equipped with an aeration apparatus and at least one anaerobic tank or an oxygen-free tank provided upstream of the aerobic tank, and performing water treatment based on the activated sludge method A method for controlling aeration air volume in a water treatment system equipped with a tank,
An air volume control step of controlling the aeration air volume of the aeration apparatus based on a target operation amount that is a target value of the aeration air volume of the aeration apparatus;
A target operation amount calculation step for generating the target operation amount,
The target manipulated variable calculation step includes:
A mixed solution measuring step for measuring the ammonia nitrogen concentration of the activated sludge mixed solution in the aerobic tank;
Raw water measurement step for measuring ammonia nitrogen concentration of raw water flowing into the series of biological reaction tanks,
A feedback signal generation step of generating a feedback target manipulated variable signal based on a deviation between the ammonia nitrogen concentration of the activated sludge mixed liquid in the aerobic tank and its set value;
A preceding signal generation step of generating a preceding target manipulated variable signal according to the amount of change per unit time of the ammonia nitrogen concentration of the raw water;
An aeration amount generation method for a water treatment system, comprising: an operation amount generation step of generating the target operation amount by adding the feedback target operation amount signal and the preceding target operation amount signal.
The preceding signal generation step calculates a preceding target operation amount according to a change amount per unit time of the ammonia nitrogen concentration of the raw water, and the preceding signal operation is performed such that a decrease in the preceding target operation amount is suppressed for a predetermined period. Generate a target manipulated variable signal,
The aeration air volume control method of the water treatment system according to claim 5.