Air supply volume control device, water treatment system, air supply volume control method, and program

Abstract

To provide an air sending amount control device which can reduce a cost for optimally controlling the amount of air sent to a biological reaction tank, a water treatment system, an air sending amount control method, and a program.SOLUTION: An air sending amount control device includes: a concentration backward calculation unit which, from a first ammonia nitrogen concentration of sewage water being treated in an aerobic tank of a biological reaction tank as measured by an ammonia meter, calculates backward a second ammonia nitrogen concentration of the sewage water when the sewage water flows into the biological reaction tank; an air sending amount calculation unit which, from the backward-calculated second ammonia nitrogen concentration, calculates a target sending amount of air sent from an air blower to the aerobic tank; and an air sending amount control unit which controls the sending amount of the air sent from the air blower to the aerobic tank so that the sending amount reaches the calculated target sending amount of the air.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an air supply volume control device, a water treatment system, an air supply volume control method, and a program. [Background technology]

[0002] Traditionally, sewage treatment plants have used activated sludge processes to treat wastewater, such as domestic wastewater. In these water treatment systems, for example, in a biological reaction tank, pollutants in the water are decomposed by microorganisms, resulting in clean treated water. Microorganisms require oxygen to function, and air is supplied to the biological reaction tank from the outside. If there is insufficient oxygen in the biological reaction tank, the quality of the treated water deteriorates. Therefore, it is necessary to supply air to the biological reaction tank to prevent oxygen deficiency, but since there is a cost associated with the amount of air supplied, it has been necessary to prevent excessive air supply.

[0003] Therefore, various techniques have been proposed to control the amount of air supplied to the biological reaction vessel. For example, Patent Document 1 below discloses a technique in which the ammonia nitrogen concentration of the raw water flowing into the biological reaction vessel is measured by an ammonia meter installed in the raw water tank, the ammonia nitrogen concentration of the aerobic tank is measured by an ammonia meter installed in the aerobic tank, and the amount of air supplied to the biological reaction vessel is controlled based on each ammonia nitrogen concentration. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5608027 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, in the technology described in Patent Document 1, when using a feedforward and feedback control system to regulate the amount of air supplied to the biological reactor, at least two ammonia meters are required. Since maintaining ammonia meters incurs considerable costs, it is desirable to reduce the number of ammonia meters in order to reduce the cost of supplying air to the biological reactor.

[0006] In view of the above-mentioned problems, the object of the present invention is to provide an air supply rate control device, a water treatment system, an air supply rate control method, and a program that can reduce the cost of optimally controlling the amount of air supplied to a biological reaction vessel. [Means for solving the problem]

[0007] To solve the above-mentioned problems, an air supply rate control device according to one aspect of the present invention comprises: a concentration inverse calculation unit that inversely calculates a second ammonia nitrogen concentration of sewage when it flows into the biological reaction tank based on a first ammonia nitrogen concentration of sewage being treated in the aerobic tank of the biological reaction tank, measured by an ammonia meter; an air supply rate calculation unit that calculates a target air supply rate of air supplied from a blower to the aerobic tank based on the inversely calculated second ammonia nitrogen concentration; and an air supply rate control unit that controls the air supply rate of air supplied from the blower to the aerobic tank so that it matches the calculated target air supply rate.

[0008] A water treatment system according to one aspect of the present invention includes an air supply volume control device.

[0009] An air supply volume control method according to one aspect of the present invention includes: a concentration inverse calculation process in which a concentration inverse calculation unit inversely calculates a second ammonia nitrogen concentration of sewage when it flows into the biological reaction tank, based on a first ammonia nitrogen concentration of sewage being treated in the aerobic tank of the biological reaction tank, measured by an ammonia meter; an air supply volume calculation process in which an air supply volume calculation unit calculates a target air supply volume of air supplied from a blower to the aerobic tank based on the inversely calculated second ammonia nitrogen concentration; and an air supply volume control process in which an air supply volume control unit controls the air supply volume supplied from the blower to the aerobic tank so that it becomes the calculated target air supply volume.

[0010] A program according to one aspect of the present invention causes a computer to function as: a concentration inverse calculation means that inversely calculates a second ammonia nitrogen concentration of sewage when it flows into the biological reaction tank, based on a first ammonia nitrogen concentration of sewage being treated in the aerobic tank of the biological reaction tank, measured by an ammonia meter; an air supply amount calculation means that calculates a target amount of air supplied from a blower to the aerobic tank based on the inversely calculated second ammonia nitrogen concentration; and an air supply amount control means that controls the amount of air supplied from the blower to the aerobic tank so that it matches the calculated target amount of air supplied. [Effects of the Invention]

[0011] According to the present invention, the cost of optimally controlling the amount of air supplied to the biological reaction vessel can be reduced. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a schematic configuration of the water treatment system according to this embodiment. [Figure 2] This is a diagram showing an example of the functional configuration of the air supply volume control device according to this embodiment. [Figure 3] This figure shows an example of the relationship between ammonia nitrogen and biochemical oxygen demand (BOD) according to this embodiment. [Figure 4] This figure shows an example of the relationship between ammonia nitrogen and suspended solids (SS) according to this embodiment. [Figure 5] This flowchart shows an example of the processing flow according to this embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0014] <1. Outline of the water treatment system> First, the schematic configuration of the water treatment system according to this embodiment will be described with reference to Figure 1. Figure 1 is a diagram showing the schematic configuration of the water treatment system according to this embodiment. The water treatment system 1 shown in Figure 1 is a system for treating sewage at a sewage treatment plant using the activated sludge method. Sewage (raw water) discharged from, for example, homes and factories is transported to the sewage treatment plant through sewer pipes. The sewage transported to the sewage treatment plant is first transported to a grit chamber (not shown). In the grit chamber, large debris and sediment are removed from the sewage. Next, the sewage is transported to the water treatment system 1. In the water treatment system 1, small debris and sand are removed from the sewage, and pollutants are decomposed. Next, the sewage (supernatant water) is transported to a disinfection facility (not shown). In the disinfection facility, the sewage is disinfected. The disinfected sewage is discharged into rivers, etc.

[0015] As shown in Figure 1, the water treatment system 1 according to this embodiment includes a primary sedimentation tank 10, a biological reaction tank 20, an aeration device 24, a blower 25, a control valve 26, a flow meter 27, an ammonia meter 28, a pump 29, a final sedimentation tank 30, a pump 32, and an air supply rate control device 100.

[0016] The primary sedimentation tank 10 is a facility that removes small debris and sand contained in the sewage flowing in from the grit tank by allowing them to settle. The primary sedimentation tank 10 discharges the sewage from which the primary sludge 11, consisting of settled small debris and sand, has been removed. The sewage discharged from the primary sedimentation tank 10 is transported to the biological reaction tank 20. The primary sludge 11 removed in the primary sedimentation tank 10 is transported to a sludge treatment facility for treatment. In addition, wastewater generated at the sludge treatment facility (for example, separated liquid discharged from a sludge thickening device) may be sent to the grit tank as return water and treated together with the sewage in the water treatment system 1.

[0017] The biological reaction tank 20 is a facility that removes pollutants contained in the sewage from which the primary sedimentation sludge 11 has been removed, using the activated sludge method. As shown in Figure 1, the biological reaction tank 20 includes an anaerobic tank 21, an oxygen-free tank 22, and an aerobic tank 23.

[0018] The anaerobic tank 21 receives sewage discharged from the primary sedimentation tank 10 and return sludge, mainly activated sludge, discharged from the final sedimentation tank 30 (described later). Since no air is supplied to the anaerobic tank 21 from the outside, the sewage is oxygen-free. As a result, phosphorus is released from the microorganisms in the return sludge due to their activity.

[0019] The anaerobic tank 22 receives sewage treated in the anaerobic tank 21 and circulating water supplied from the aerobic tank 23 by the pump 29. Similar to the anaerobic tank 21, no air is supplied to the anaerobic tank 22 from the outside, so the sewage is oxygen-free. In the anaerobic tank 22, microorganisms (denitrifying bacteria) obtain oxygen for respiration from the oxygen-free environment by absorbing nitrite ions (NO2) from the sewage. - ) and nitrate ions (NO3 - ) is broken down. Nitrogen is broken down into nitrogen gas, which is released into the atmosphere.

[0020] Sewage treated in the anaerobic tank 22 is transported to the aerobic tank 23. The aerobic tank 23 is also equipped with an aeration diffuser 24. The aeration device 24 is a device that releases air supplied from the blower 25 (an example of a fan) as bubbles into the sewage of the aerobic tank 23. An adjustment valve 26 is provided at any position between the aeration device 24 and the blower 25 to adjust the amount of air supplied from the blower 25 to the aeration device 24. The operation of the adjustment valve 26 is controlled by an air supply volume control device 100, which will be described later. Furthermore, a flow meter 27 is provided at any position between the aeration device 24 and the control valve 26 to measure the amount of air supplied to the aeration device 24, which is regulated by the control valve 26. Hereinafter, the amount of air supplied measured by the flow meter 27 will also be referred to as the "measured air supply amount." The measured air supply amount measured by the flow meter 27 is transmitted to the air supply amount control device 100. Furthermore, the aerobic tank 23 is equipped with an ammonia meter 28 for measuring the ammonia nitrogen concentration (first ammonia nitrogen concentration) of the sewage being treated in the aerobic tank 23. Hereinafter, the ammonia nitrogen concentration (first ammonia nitrogen concentration) measured by the ammonia meter 28 will also be referred to as the "measured ammonia nitrogen concentration." The measured ammonia nitrogen concentration measured by the ammonia meter 28 is transmitted to the air supply rate control device 100. The ammonia meter 28 may be installed at any location in the aerobic tank 23, or it may not be installed directly in the aerobic tank 23, as long as it is capable of measuring the ammonia nitrogen concentration of the sewage being treated in the aerobic tank 23.

[0021] As described above, the biological reaction tank 20 discharges sewage from which pollutants have been removed through the anaerobic tank 21, the oxygen-free tank 22, and the aerobic tank 23. The sewage discharged from the biological reaction tank 20 is transported to the final sedimentation tank 30. In addition, a portion of the sewage discharged from the biological reaction tank 20 is transported to the oxygen-free tank 22 by the pump 29 as circulating water.

[0022] The final sedimentation tank 30 is a facility that removes activated sludge contained in the sewage flowing in from the biological reaction tank 20 by allowing it to settle. The final sedimentation tank 30 discharges the supernatant water from which the settled activated sludge, i.e., final settled sludge 31, has been removed. The supernatant water discharged from the final sedimentation tank 30 is transported to the disinfection facility described above for treatment. A portion of the final settled sludge 31 removed in the final sedimentation tank 30 is transported to the anaerobic tank 21 by the pump 32. The remaining final settled sludge 31 is transported as excess sludge to a sludge treatment facility for treatment.

[0023] The air supply volume control device 100 is a device for controlling the amount of air supplied to the aerobic tank. The air supply volume control device 100 can be implemented, for example, by a PC (Personal Computer) or a server device. The air supply volume control device 100 controls the amount of air supplied to the aerobic tank 23 based on the measured ammonia nitrogen concentration received from the ammonia meter 28. Furthermore, the air supply volume control device 100 performs feedback control based on the measured ammonia nitrogen concentration received from the ammonia meter 28. Details of each control by the air supply volume control device 100 will be described later.

[0024] <2. Functional configuration of the air supply volume control device> The general configuration of the water treatment system 1 according to this embodiment has been described above. Next, the functional configuration of the air supply volume control device 100 according to this embodiment will be described with reference to Figures 2 to 4. Figure 2 is a block diagram showing an example of the functional configuration of the air supply volume control device 100 according to this embodiment. As shown in Figure 2, the air supply volume control device 100 includes a communication unit 110, a storage unit 120, and a control unit 130.

[0025] (1) Communications Department 110 The communication unit 110 has the function of communicating with external devices. External devices are devices located outside the air supply volume control device 100. External devices include, for example, sensor devices such as flow meters 27 and ammonia meters 28, and control devices such as control valves 26. The communication unit 110 outputs information received from external devices to the control unit 130. For example, the communication unit 110 outputs the measured air supply volume received from the flow meter 27 and the measured ammonia nitrogen concentration received from the ammonia meter 28 to the control unit 130. Furthermore, the communication unit 110 transmits signals input from the control unit 130 to an external device. For example, the communication unit 110 transmits the control signal for the control valve 26, input from the control unit 130, to the control valve 26.

[0026] (2) Storage section 120 The storage unit 120 has the function of storing various types of information. The storage unit 120 is composed of storage media provided as hardware by the air supply volume control device 100, such as an HDD (Hard Disk Drive), SSD (Solid State Drive), flash memory, EEPROM (Electrically Erasable Programmable Read Only Memory), RAM (Random Access read / write Memory), ROM (Read Only Memory), or any combination of these storage media. As shown in Figure 2, the memory unit 120 stores the prediction model 121. Further details about the prediction model 121 will be provided later.

[0027] (3) Control unit 130 The control unit 130 has the function of controlling the overall operation of the air supply volume control device 100. The control unit 130 is realized, for example, by causing the CPU (Central Processing Unit) provided as hardware in the air supply volume control device 100 to execute a program. As shown in Figure 2, the control unit 130 includes a reverse calculation information acquisition unit 131, a concentration reverse calculation unit 132, a prediction information acquisition unit 133, a concentration prediction unit 134, a calculation information acquisition unit 135, an air supply amount calculation unit 136, an ammonia control feedback information acquisition unit 137, an ammonia control feedback control unit 138, and an air supply amount control unit 139.

[0028] (3-1) Inverse calculation information acquisition unit 131 The reverse calculation information acquisition unit 131 has the function of acquiring reverse calculation information. The reverse calculation information is information necessary for the reverse calculation of the ammonia nitrogen concentration by the concentration reverse calculation unit 132. For example, the reverse calculation information includes the measured ammonia nitrogen concentration, information on the design of the biological reaction tank 20, information showing the water quality estimation formula in the aerobic tank 23, and information measured in the wastewater treatment process.

[0029] The measured ammonia nitrogen concentration is the ammonia nitrogen concentration measured by ammonia meter 28. The reverse calculation information acquisition unit 131 acquires the measured ammonia nitrogen concentration from the ammonia meter 28 via the communication unit 110.

[0030] Information regarding the design of the biological reactor 20 (hereinafter also referred to as "design information") includes, for example, the capacity of the biological reactor 20, the efficiency of the aeration device 24, the amount of oxygen per unit of BOD required for the oxidation of pollutants as measured as biochemical oxygen demand (BOD), the amount of oxygen per unit of sludge consumed by denitrification, the sludge conversion rate of soluble BOD, the sludge conversion rate of suspended solids (SS), the self-decomposition coefficient of sludge, and the nitrogen content of excess sludge. The design information is information that is pre-set by the user and is stored, for example, in the memory unit 120. The reverse calculation information acquisition unit 131 acquires the design information from the memory unit 120.

[0031] Information indicating the water quality estimation formula in the aerobic tank 23 (hereinafter also referred to as "estimation formula information") includes, for example, the correlation formula between BOD and ammonia nitrogen (NH4-N), the correlation formula between SS and ammonia nitrogen, and the correlation formula between BOD and soluble BOD (S-BOD: Soluble-Biochemical Oxygen Demand). BOD, SS, and S-BOD are difficult to measure continuously, and their acquisition can be costly. Therefore, in this embodiment, the correlation between each of BOD, SS, and S-BOD and the measured ammonia nitrogen concentration is acquired in advance, and correlation formulas for calculating BOD, SS, and S-BOD from this correlation are prepared in advance. This reduces the cost of acquiring BOD, SS, and S-BOD and improves the accuracy of calculating the ammonia nitrogen concentration inversely. The estimation formula information is information prepared in advance by the user and is stored, for example, in the memory unit 120. The reverse calculation information acquisition unit 131 acquires the estimation formula information from the memory unit 120.

[0032] Information measured during the sewage treatment process (hereinafter also referred to as "process measurement information") These include, for example, the amount of air supplied, the amount of sewage flowing in, the oxidation-reduction potential (ORP), the amount of activated sludge suspended solids (MLSS), the dissolved oxygen (DO), the hydrogen ion concentration (pH), the water temperature, the amount of circulating water, and the amount of sludge returned. The air supply volume is the amount of air supplied to the aerobic tank 23 and is measured by the flow meter 27. The sewage inflow is the amount of sewage flowing from the primary sedimentation tank 10 to the biological reaction tank 20, and this inflow is measured by a flow meter (not shown) installed at any position where measurement is possible. The oxidation-reduction potential is the oxidation-reduction potential of the sewage in the anaerobic tank 21, and is measured by an ORP meter (not shown) installed at any location where the oxidation-reduction potential can be measured. The activated sludge suspended solids are the activated sludge suspended solids in the sewage in the aerobic tank 23, and are measured by an MLSS meter (not shown) installed at any position where the activated sludge suspended solids can be measured. The dissolved oxygen is the dissolved oxygen in the sewage in the aerobic tank 23, and is measured by a DO meter (not shown) installed at any position where the dissolved oxygen can be measured. The hydrogen ion concentration is the hydrogen ion concentration of the sewage in the aerobic tank 23, and is measured by a pH meter (not shown) installed at any position where the hydrogen ion concentration can be measured. The water temperature is the water temperature of the sewage in the aerobic tank 23, and is measured by a thermometer (not shown) installed at any position where the water temperature can be measured. The circulating water volume is the amount of circulating water that is transported from the biological reaction tank 20 to the anoxic tank 22 by the pump 29, and this amount of circulating water is measured by a flow meter (not shown) installed at any position where measurement is possible. The amount of returned sludge is the amount of returned sludge (not shown) that is transported to the anaerobic tank 21 by the pump 32 from the final sedimentation sludge 31 removed in the final sedimentation tank 30, and this amount of returned sludge is measured by a flow meter (not shown) installed at any position where measurement is possible. The reverse calculation information acquisition unit 131 acquires process measurement information from the various measuring devices described above via the communication unit 110.

[0033] Now, with reference to Figure 3, the relationship between ammonia nitrogen and biochemical oxygen demand according to this embodiment will be explained. Figure 3 is a diagram showing an example of the relationship between ammonia nitrogen and biochemical oxygen demand (BOD) according to this embodiment.

[0034] Figure 3 plots the relationship between inlet ammonia nitrogen and biochemical oxygen demand (BOD) based on measured values, with the horizontal axis representing inlet ammonia nitrogen and the vertical axis representing BOD. From the approximate straight line ASL1 based on this plot, the correlation equation (y=ax+b) between BOD and ammonia nitrogen (NH4-N) can be obtained.

[0035] Now, with reference to Figure 4, the relationship between inlet-side ammonia nitrogen and suspended solids (SS) according to this embodiment will be explained. Figure 4 shows an example of the relationship between inlet-side ammonia nitrogen and suspended solids (SS) according to this embodiment.

[0036] In Fig. 4, with the horizontal axis representing the ammonia nitrogen on the inlet side and the vertical axis representing the suspended solids (SS), the relationship between the ammonia nitrogen on the inlet side and the suspended solids is plotted based on the measured values. Based on the approximate straight line ASL2 obtained from this plot, a correlation equation (y = ax + b) between SS and the ammonia nitrogen (NH4-N) on the inlet side can be obtained.

[0037] Note that S-BOD can be calculated by the following formula (1) commonly used in sewage. S-BOD,in = BOD,in × 2 / 3 …(1)

[0038] (3-2) Concentration inverse calculation unit 132 The concentration inverse calculation unit 132 has a function of inversely calculating the ammonia nitrogen concentration. For example, based on the measured ammonia nitrogen concentration of the sewage being treated in the aerobic tank 23, the concentration inverse calculation unit 132 inversely calculates the ammonia nitrogen concentration before the sewage is treated in the biological reaction tank 20 and when it flows into the biological reaction tank 20. Hereinafter, the ammonia nitrogen concentration (the second ammonia nitrogen concentration) inversely calculated by the concentration inverse calculation unit 132 is also referred to as the "inversely calculated ammonia nitrogen concentration".

[0039] Specifically, the concentration inverse calculation unit 132 calculates the inversely calculated ammonia nitrogen concentration based on the inverse calculation information including the measured ammonia nitrogen concentration obtained by the inverse calculation information acquisition unit 131. First, the concentration inverse calculation unit 132 calculates the oxygen concentration (SOR) supplied to the aerobic tank 23 by the following formula (2) based on the air supply volume actually sent from the blower 25 to the aerobic tank 23. SOR = f(G s , E a , ρ, O w ) = G s × E a / 100 × ρ × O w × 24 × {273 / (273 + 20)}…(2) In the above formula (2), G s is the actual air supply volume, E a is the oxygen transfer efficiency of the air diffuser, ρ is the air density, O wis the weight ratio of oxygen in the air. Note that formula (2) above is the formula used to calculate SOR at 20°C and 1 atmosphere.

[0040] Next, the concentration inverse calculation unit 132 calculates the amount of oxygen (AOR) required during actual operation (AOR) based on the calculated SOR using the following formula (3). AOR=f(SOR,C sw ,C s ,C oa ,r,H,T,α,β,P) =SOR×[{1.024^(T-20)×α(β×C s ×rC oa )} / (C sw ×r)]×(P / 101.3) …(3) In the above equation (3), C sw This is the saturated oxygen concentration of clean water at 20°C, C s This is the saturated oxygen concentration of fresh water at T℃, C oa is the average DO concentration of the activated sludge mixture, and r is the C due to the aeration water depth. s The correction coefficients are as follows: H is the aeration water depth, T is the water temperature of the activated sludge mixture, α is the correction coefficient for the difference in the overall oxygen transfer capacity coefficient compared to clean water, β is the correction coefficient for the difference in saturated dissolved oxygen concentration compared to clean water, and P is atmospheric pressure. Note that r is calculated by the following equation (4). r=1 / 2×[{(10.24+H) / 10.24}+1] …(4)

[0041] Next, the concentration inverse calculation unit 132 calculates the ammonia nitrogen concentration based on the calculated AOR using the following formula (5). AOR=D B +D N +D E +D O …(5) In the above equation (5), D B D is the amount of oxygen required for the oxidation of BOD. N D is the amount of oxygen required for the nitrification reaction. E This is the amount of oxygen needed for endogenous respiration, D O This represents the amount of oxygen released from the system by the reaction tank effluent.

[0042] D EThis is calculated by the following formula (6). D E =f(B,V a ,X a’ ) =B×V a ×X a’ / 1000 …(6) In the above equation (6), B is the amount of oxygen consumed by endogenous respiration per unit of microbial mass (MLVSS: Mixed liquor volatile suspended solid) in activated sludge, and V a is the aerobic tank capacity, X a’ It is MLVSS.

[0043] D O This is calculated and expressed by the following formula (7). D O =f(C OA Q in Q r Q c ) =C OA ×(Q in +Q r +Q c ) / 1000 …(7) In the above equation (7), C OA Q is the amount of dissolved oxygen at the end of the aerobic tank. in Q is the inflow volume. r This is the amount of sludge returned, Q c This represents the circulating water volume.

[0044] D B This is calculated by the following equation (8). D B =f(C BODin ,C BODeff Q in ,L NOXdn ,L NOXa ,K,A) ={(C BODin -C BODeff )×Q in / 1000-(L NOXdn -L NOXa ) × K} × A …(8) In the above equation (8), C BODin The influent water BOD, C BODeffis the effluent BOD, L NOXdn is the reaction tank NO T -N loading, L NOXa is the reaction tank NO T -N effluent volume, K is the BOD amount consumed by denitrification, A is the oxygen amount required per unit of removed BOD.

[0045] D N is calculated by the following formula (9). D N =f(C, C KNin , C KNeff , N x , a, C S-BODin , b, C SSin , c, θ, X a , Qin) =C × {(C KNin - C KNeff ) - N x (a × C S-BODin + b × C SSin + c × θ × X a )} × Q in / 1000 …(9) In the above formula (9), C is the oxygen amount consumed during nitrification, C KNin is the influent Kjeldahl nitrogen amount kj-N, C KNeff is the effluent Kjeldahl nitrogen amount kj-N, N x is the nitrogen content rate of excess sludge, a is the sludge conversion rate of dissolved BOD, C S-BODin is S-BOD (dissolved BOD), b is the sludge conversion rate of SS, C SSin is the suspended solids amount SS, c is the self-degradation coefficient of sludge, θ is the HRT, X a is the MLSS.

[0046] Generally, Kjeldahl nitrogen is defined as (organic nitrogen + ammonia nitrogen). Furthermore, since sewage generally has (organic nitrogen << ammonia nitrogen), the Kjeldahl nitrogen (kj-N) is represented by the measured value of influent ammonia nitrogen. That is, (influent Kjeldahl nitrogen amount C KNin = influent ammonia nitrogen). Furthermore, by substituting the following formulas (10) to (12) as conversion formulas, the inverse ammonia nitrogen concentration can be calculated in the above formulas (5) to (9). C SSin =Inflow ammonia nitrogen C KNin +31 …(10) C BODin =3.7317×[kj-N]+51.869 …(11) C S-BODin =BOD × 2 / 3 …(12)

[0047] (3-3) Predictive information acquisition unit 133 The prediction information acquisition unit 133 has the function of acquiring prediction information. The prediction information is the information necessary for predicting the third ammonia nitrogen concentration, taking into account the time lag by the concentration prediction unit 134.

[0048] Here, we will explain the time lag. First, let's assume that the ammonia nitrogen concentration of the sewage flowing into the biological reaction tank 20 at the first timing is the second ammonia nitrogen concentration (reverse-calculated ammonia nitrogen concentration) calculated by the concentration inverse calculation unit 132. Let's also assume that the timing at which the first ammonia nitrogen concentration (measured ammonia nitrogen concentration) is measured by the ammonia meter 28 after the first timing is the second timing. Furthermore, let's assume that the ammonia nitrogen concentration of the sewage flowing into the biological reaction tank 20 at the second timing is the third ammonia nitrogen concentration. In this case, the time lag indicates the time difference between the second ammonia nitrogen concentration at the first timing and the third ammonia nitrogen concentration at the second timing. The third ammonia nitrogen concentration is the ammonia nitrogen concentration predicted by the concentration prediction unit 134, which will be described later. For this reason, the third ammonia nitrogen concentration will also be referred to as the "predicted ammonia nitrogen concentration" below.

[0049] Predictive information includes, for example, the calculated ammonia nitrogen concentration, information indicating factors that change the ammonia nitrogen concentration of sewage when it flows into the biological reaction tank 20, and process measurement information.

[0050] The calculated ammonia nitrogen concentration is the ammonia nitrogen concentration calculated by the concentration calculation unit 132. The prediction information acquisition unit 133 acquires the calculated ammonia nitrogen concentration from the concentration inverse calculation unit 132.

[0051] Information indicating factors that cause changes in the ammonia nitrogen concentration of sewage when it flows into the biological reaction tank 20 (hereinafter also referred to as "factor information") includes, for example, precipitation information, date information, time information, day of the week information, and holiday information. Precipitation information indicates the amount of rainfall at sewage treatment plants. When rainwater flows into the sewage system due to precipitation, the ammonia nitrogen concentration in the sewage can change. The date information indicates the date on which the concentration prediction unit 134 performs the prediction. Depending on the date, the ammonia nitrogen concentration in the sewage may change due to seasonal factors, etc. The time information indicates the time when the concentration prediction unit 134 performs its prediction. Depending on the time, the ammonia nitrogen concentration in the sewage may change. The day-of-the-week information indicates the days of the week on which the concentration prediction unit 134 performs its predictions. The ammonia nitrogen concentration in the sewage may vary depending on the day of the week. The holiday information indicates whether the day on which the concentration prediction unit 134 makes its prediction is a holiday or not. Depending on whether it is a holiday or not, the ammonia nitrogen concentration in the sewage may change. The predictive information acquisition unit 133 may acquire factor information from the system date, the internet, etc., or it may acquire factor information from the storage unit 120 if it has been prepared in advance by the user and stored in the storage unit 120.

[0052] The process measurement information acquired by the prediction information acquisition unit 133 is the same as the process measurement information acquired by the reverse calculation information acquisition unit 131.

[0053] (3-4) Concentration prediction unit 134 The concentration prediction unit 134 has the function of predicting a third ammonia nitrogen concentration that takes time lag into account. For example, the concentration prediction unit 134 predicts a predicted ammonia nitrogen concentration that takes time lag into account from the back-calculated ammonia nitrogen concentration, based on the back-calculated ammonia nitrogen concentration, factor information, and process measurement information. The concentration prediction unit 134 predicts the ammonia nitrogen concentration using the prediction model 121. The prediction model 121 is a trained model that has learned the relationship between the inversely calculated ammonia nitrogen concentration, factor information, process measurement information, and the third ammonia nitrogen concentration (measured value) through machine learning. Therefore, the prediction model 121 takes the inversely calculated ammonia nitrogen concentration, factor information, and process measurement information as input and outputs the third ammonia nitrogen concentration (predicted value). Therefore, the concentration prediction unit 134 can input the prediction information acquired by the prediction information acquisition unit 133 into the prediction model 121 and obtain a third ammonia nitrogen concentration (predicted value) as the predicted ammonia nitrogen concentration. As a result, the air supply rate control device 100 can obtain, from the measured ammonia nitrogen concentration, the ammonia nitrogen concentration of the sewage that flowed into the biological reaction tank 20 at the present time when the measured ammonia nitrogen concentration was measured, rather than the ammonia nitrogen concentration at a past time when the sewage with the measured ammonia nitrogen concentration flowed into the biological reaction tank 20 in the aerobic tank 23. In other words, the air supply control device 100 can obtain the ammonia nitrogen concentration at the inlet and outlet of the biological reaction vessel 20 at the same time point using only one ammonia meter. As a result, the air supply rate control device 100 can obtain the current ammonia nitrogen concentration at the inlet side without any time lag from the measured ammonia nitrogen concentration measured by the ammonia meter installed only at the outlet side of the biological reaction vessel 20. Furthermore, the air supply rate control device 100 can obtain the appropriate air supply rate at the current time using the ammonia nitrogen concentration at the inlet side and control the air supply rate. Therefore, the air supply rate control device 100 can control the air supply rate with greater accuracy compared to when the air supply rate is controlled by calculating the ammonia nitrogen concentration at the inlet side in reverse without considering the time lag. Furthermore, in water treatment system 1, it is no longer necessary to install an ammonia meter on the inlet side of the biological reaction tank 20, and an ammonia meter only needs to be installed on the outlet side of the biological reaction tank 20, thus reducing the number of ammonia meters and thus reducing costs.

[0054] (3 - 5) Calculation Information Acquisition Unit 135 The calculation information acquisition unit 135 has a function of acquiring calculation information. The calculation information is information necessary for the calculation of the air supply volume by the air supply volume calculation unit 136. For example, the calculation information is the predicted ammonia nitrogen concentration, process measurement information, and the like.

[0055] The predicted ammonia nitrogen concentration is the predicted ammonia nitrogen concentration (the third ammonia nitrogen concentration) predicted by the concentration prediction unit 134. The calculation information acquisition unit 135 acquires the predicted ammonia nitrogen concentration from the concentration prediction unit 134.

[0056] The calculation information acquired by the calculation information acquisition unit 135 is the same as the process measurement information acquired by the inverse calculation information acquisition unit 131 and the concentration prediction unit 134.

[0057] (3 - 6) Air Supply Volume Calculation Unit 136 The air supply volume calculation unit 136 has a function of calculating the air supply volume. For example, the air supply volume calculation unit 136 calculates an appropriate air supply volume (hereinafter, also referred to as "target air supply volume") of the air sent from the blower 25 to the aerobic tank 23 based on the predicted ammonia nitrogen concentration predicted by the concentration prediction unit 134. Thereby, the air supply volume calculation unit 136 can calculate the air supply volume with higher accuracy.

[0058] More specifically, the air supply volume calculation unit 136 calculates the target air supply volume based on the predicted ammonia nitrogen concentration and the process measurement information acquired by the calculation information acquisition unit 135. First, the air supply volume calculation unit 136 calculates the AOR using Equations (5) to (12) described above.

[0059] Next, the air supply volume calculation unit 136 calculates the SOR by the following Equation (13) based on the calculated AOR. SOR = f(AOR, C sw , C s , C oa , r, H, T, α, β, P) =[(AOR × C sw×r) / {1.024^(T-20)×α×(β×C s ×rC oa )}] × 101.3 / P …(13) Note that r is calculated by equation (4).

[0060] Next, the air supply volume calculation unit 136 calculates the target air supply volume (= required air supply volume G) based on the calculated SOR. s ) is calculated using the following formula (14). G s =f(SOR,E a ,ρ,O w ) ={SOR / (E a / 100×ρ×O w (x24)} × {(273 + 20) / 273} …(14) Note that equation (14) above is the formula used to calculate the target air supply volume at 20°C and 1 atmosphere.

[0061] (3-7) Ammonia control feedback information acquisition unit 137 The ammonia control feedback information acquisition unit 137 has the function of acquiring feedback information for ammonia control. The feedback information is information necessary for feedback control by the ammonia control feedback control unit 138. For example, the feedback information is information that combines the measured ammonia nitrogen concentration measured by the ammonia meter 28 and the target ammonia nitrogen concentration in the aerobic tank 23, which is set in advance.

[0062] (3-8) Ammonia control feedback control unit 138 The ammonia control feedback control unit 138 has a function to perform feedback control. For example, the ammonia control feedback control unit 138 calculates the amount of air to be supplied (corrected air supply amount) to correct the measured ammonia nitrogen concentration measured by the ammonia meter 28 to the target ammonia nitrogen concentration in the aerobic tank 23. The target air supply amount calculated by the air supply amount calculation unit 136 is added to the corrected air supply amount to calculate the corrected target air supply amount. This reduces the impact of errors that occur in the calculation of the back-calculated ammonia nitrogen concentration, predicted ammonia nitrogen concentration, and target air supply rate.

[0063] (3-9) Air supply volume control unit 139 The air supply volume control unit 139 has the function of controlling the amount of air supplied. For example, the air supply volume control unit 139 controls the amount of air supplied from the blower 25 to the aerobic tank 23 so that it becomes the target amount of air supplied corrected by the ammonia control feedback control unit 138. Specifically, the air supply volume control unit 139 transmits a control signal to the control valve 26 via the communication unit 110 and controls the operation of the control valve 26. In this way, the air supply volume control unit 139 controls the amount of air supplied from the blower 25 to the diffuser 24 so that it becomes the corrected target amount of air supplied.

[0064] <3. Processing Flow> The functional configuration of the air supply volume control device 100 according to this embodiment has been described above. Next, the processing flow according to this embodiment will be described with reference to Figure 5. Figure 5 is a flowchart showing an example of the processing flow according to this embodiment.

[0065] As shown in Figure 5, first, the reverse calculation information acquisition unit 131 acquires reverse calculation information (step S101). Specifically, the reverse calculation information acquisition unit 131 acquires the measured ammonia nitrogen concentration from the ammonia meter 28, acquires design information and estimation formula information from the storage unit 120, and acquires process measurement information from various measuring devices (not shown). The reverse calculation information acquisition unit 131 outputs the reverse calculation information, including the acquired information, to the concentration reverse calculation unit 132. Next, the concentration inverse calculation unit 132 calculates the inverse ammonia nitrogen concentration (step S102). Specifically, the concentration inverse calculation unit 132 calculates the inverse ammonia nitrogen concentration based on the inverse calculation information acquired by the inverse calculation information acquisition unit 131.

[0066] Next, the prediction information acquisition unit 133 acquires prediction information (step S103). Specifically, the prediction information acquisition unit 133 acquires the inversely calculated ammonia nitrogen concentration from the concentration inverse calculation unit 132, acquires factor information from the system date, internet, storage unit 120, etc., and acquires process measurement information acquired by the inverse calculation information acquisition unit 131. The prediction information acquisition unit 133 outputs the prediction information, including each of the acquired pieces of information, to the concentration prediction unit 134. Next, the concentration prediction unit 134 predicts the predicted ammonia nitrogen concentration (step S104). Specifically, the concentration prediction unit 134 inputs the prediction information acquired by the prediction information acquisition unit 133 into the prediction model 121 and obtains the predicted ammonia nitrogen concentration output as the predicted ammonia nitrogen concentration.

[0067] Next, the calculation information acquisition unit 135 acquires the calculation information (step S105). Specifically, the calculation information acquisition unit 135 acquires the predicted ammonia nitrogen concentration from the concentration prediction unit 134 and the process measurement information acquired by the reverse calculation information acquisition unit 131. Next, the air supply volume calculation unit 136 calculates the target air supply volume (step S106). Specifically, the air supply volume calculation unit 136 calculates the target air supply volume based on the predicted ammonia nitrogen concentration and process measurement information obtained by the calculation information acquisition unit 135.

[0068] The ammonia control feedback information acquisition unit 137 acquires feedback information (step S107). Specifically, the ammonia control feedback information acquisition unit 137 acquires the measured ammonia nitrogen concentration from the ammonia meter 28 and the target ammonia nitrogen concentration from the storage unit 120. Next, the ammonia control feedback control unit 138 performs feedback control of the ammonia nitrogen concentration (step S108). Specifically, the ammonia control feedback control unit 138 calculates the amount of air to be supplied (corrected air supply amount) to correct the measured ammonia nitrogen concentration to match the target ammonia nitrogen concentration in the aerobic tank 23, based on the target ammonia nitrogen concentration and the measured ammonia nitrogen concentration obtained by the ammonia control feedback information acquisition unit 137. Next, the ammonia control feedback control unit 138 calculates a corrected target air supply amount by adding the target air supply amount calculated by the air supply amount calculation unit 136 to the corrected air supply amount (step S109). Next, the air supply volume control unit 139 controls the air supply volume (step S110). Specifically, the air supply volume control unit 139 transmits a control signal to the regulating valve 26 via the communication unit 110 to set the air supply volume to the corrected target air supply volume corrected by the ammonia control feedback control unit 138, and controls the operation of the regulating valve 26 to set the air supply volume to the corrected target air supply volume. After controlling the air supply volume, the air supply volume control device 100 repeats the process from step S101.

[0069] As described above, the air supply rate control device 100 according to this embodiment calculates the second ammonia nitrogen concentration of the sewage flowing into the biological reaction tank 20 based on the first ammonia nitrogen concentration of the sewage being treated in the aerobic tank 23 of the biological reaction tank 20, which is measured by the ammonia meter 28. The air supply rate control device 100 also calculates the target amount of air supplied from the blower 25 to the aerobic tank 23 based on the calculated second ammonia nitrogen concentration. The air supply rate control device 100 also controls the amount of air supplied from the blower 25 to the aerobic tank 23 so that it matches the calculated target amount of air.

[0070] With this configuration, the air supply rate control device 100 can measure the ammonia nitrogen concentration at the outlet side of the biological reaction vessel 20 using only one ammonia meter, calculate the ammonia nitrogen concentration at the inlet side, and control the amount of air supplied to the aerobic tank 23 so that the amount of air supplied corresponds to the calculated ammonia nitrogen concentration. Therefore, the air supply volume control device 100 according to this embodiment makes it possible to reduce the cost of optimally controlling the amount of air supplied to the biological reaction vessel.

[0071] <4. Variation> Embodiments of the present invention have been described above. Next, modifications of the embodiments of the present invention will be described. Each modification described below may be applied to the embodiments of the present invention individually or in combination. Furthermore, each modification may be applied in place of the configuration described in the embodiments of the present invention, or it may be applied in addition to the configuration described in the embodiments of the present invention.

[0072] In the embodiments described above, an example was described in which a pre-generated prediction model 121 is stored in the storage unit 120 of the air supply volume control device 100, but the invention is not limited to this example. For example, the air supply volume control device 100 may have a learning function, and the air supply volume control device 100 may be configured to generate a prediction model 121 by machine learning and store it in the storage unit 120. Furthermore, the water treatment system 1 may have a device equipped with a learning function, separate from the air supply volume control device 100. In this case, the air supply volume control device 100 stores the prediction model 121 generated by the separate device in the storage unit 120. Furthermore, in either case, the configuration may allow for retraining of the prediction model 121.

[0073] In the embodiments described above, an example was given in which an anaerobic, anoxic, aerobic method was used as the treatment method in the biological reactor 20, but the invention is not limited to this example. For example, other treatment methods in the biological reactor 20 may be an anaerobic, aerobic method or a standard activated sludge method. When using an anaerobic-aerobic method as an alternative treatment method in the biological reactor 20, the configuration of the biological reactor 20 will be such that there is no oxygen-free tank 22, and it will have an anaerobic tank 21 and an aerobic tank 23. In this case, the pump 29 will not be necessary. Furthermore, if the standard activated sludge method is used as another treatment method in the biological reactor 20, the configuration of the biological reactor 20 will consist only of an aerobic tank 23, without the anaerobic tank 21 and the oxygen-free tank 22. In this case as well, the pump 29 will not be required.

[0074] Embodiments of the present invention have been described above. It should be noted that some or all of the air supply volume control device 100 in the above-described embodiments may be implemented using a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. Here, "computer system" includes hardware such as an OS and peripheral devices. "Computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, "computer-readable recording medium" may also include those that dynamically hold programs for a short period, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period, such as volatile memory inside a computer system acting as a server or client. The program may also be for implementing some of the functions described above, or it may be a program that can implement the functions described above in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0075] Although embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to those described above, and various design changes can be made without departing from the spirit of this invention.

[0076] (Note 1) A concentration inverse calculation unit that calculates the second ammonia nitrogen concentration of sewage flowing into the biological reaction tank based on the first ammonia nitrogen concentration of sewage being treated in the aerobic tank of the biological reaction tank, as measured by an ammonia meter, An air supply amount calculation unit calculates a target amount of air supplied from the blower to the aerobic tank based on the second ammonia nitrogen concentration calculated in reverse, An air supply volume control unit controls the amount of air supplied from the blower to the aerobic tank so that the calculated target air supply volume of the air, An air supply volume control device equipped with the following features.

[0077] (Note 2) The concentration prediction unit predicts the third ammonia nitrogen concentration relative to the second ammonia nitrogen concentration, assuming that the ammonia nitrogen concentration of the sewage flowing into the biological reaction tank at a first timing is the second ammonia nitrogen concentration, and the ammonia nitrogen concentration of the sewage flowing into the biological reaction tank at a second timing, after the first timing, when the first ammonia nitrogen concentration is measured by the ammonia meter, relative to the second ammonia nitrogen concentration. Furthermore, The air supply volume calculation unit calculates the target air supply volume based on the predicted third ammonia nitrogen concentration. The air supply volume control device described in Appendix 1.

[0078] (Note 3) The concentration prediction unit predicts the third ammonia nitrogen concentration using a prediction model that has been machine-learned, which takes into account the relationship between the second ammonia nitrogen concentration, factor information indicating the factors that cause changes in the ammonia nitrogen concentration of sewage when it flows into the biological reaction tank, process measurement information measured in the process of treating the sewage, and the third ammonia nitrogen concentration. The air supply volume control device described in Appendix 2.

[0079] (Note 4) A feedback control unit corrects the calculated target air supply amount so that the first ammonia nitrogen concentration measured by the ammonia meter after the control of the air supply amount becomes the target ammonia nitrogen concentration in the aerobic tank. An air supply volume control device as described in any one of the appendices 1 to 3, further comprising the above.

[0080] (Note 5) A water treatment system equipped with an air supply volume control device as described in any one of the appendices 1 to 4. [Explanation of Symbols]

[0081] 1...Water treatment system, 10...Primary sedimentation tank, 11...Primary sludge, 20...Biological reaction tank, 21...Anaerobic tank, 22...Anoxic tank, 23...Aerobic tank, 24...Aeration device, 25...Blower, 26...Control valve, 27...Flow meter, 28...Ammonia meter, 29...Pump, 30...Final sedimentation tank, 31...Final sludge, 32...Pump, 100...Air supply volume control device, 110...Communication unit, 120...Storage unit, 121...Prediction model, 130...Control unit, 131...Inverse calculation information acquisition unit, 132...Concentration inverse calculation unit, 133...Prediction information acquisition unit, 134...Concentration prediction unit, 135...Calculation information acquisition unit, 136...Air supply volume calculation unit, 137...Ammonia control feedback information acquisition unit, 138...Ammonia control feedback control unit, 139...Air supply volume control unit

Claims

1. A concentration inverse calculation unit that calculates the second ammonia nitrogen concentration of sewage flowing into the biological reaction tank based on the first ammonia nitrogen concentration of sewage being treated in the aerobic tank of the biological reaction tank, as measured by an ammonia meter, An air supply amount calculation unit calculates a target amount of air supplied from the blower to the aerobic tank based on the second ammonia nitrogen concentration calculated in reverse, An air supply volume control unit controls the amount of air supplied from the blower to the aerobic tank so that the calculated target air supply volume of the air, An air supply volume control device equipped with the following features.

2. The concentration prediction unit predicts the third ammonia nitrogen concentration relative to the second ammonia nitrogen concentration, assuming that the ammonia nitrogen concentration of the sewage flowing into the biological reaction tank at a first timing is the second ammonia nitrogen concentration, and the ammonia nitrogen concentration of the sewage flowing into the biological reaction tank at a second timing, after the first timing, when the first ammonia nitrogen concentration is measured by the ammonia meter, relative to the second ammonia nitrogen concentration. Furthermore, The air supply volume calculation unit calculates the target air supply volume based on the predicted third ammonia nitrogen concentration. The air supply volume control device according to claim 1.

3. The concentration prediction unit predicts the third ammonia nitrogen concentration using a prediction model that has been machine-learned, which takes into account the relationship between the second ammonia nitrogen concentration, factor information indicating the factors that cause changes in the ammonia nitrogen concentration of sewage when it flows into the biological reaction tank, process measurement information measured in the process of treating the sewage, and the third ammonia nitrogen concentration. The air supply volume control device according to claim 2.

4. A feedback control unit corrects the calculated target air supply amount so that the first ammonia nitrogen concentration measured by the ammonia meter after the control of the air supply amount becomes the target ammonia nitrogen concentration in the aerobic tank. The air supply volume control device according to any one of claims 1 to 3, further comprising:

5. A water treatment system comprising an air supply volume control device according to any one of claims 1 to 3.

6. The concentration inverse calculation unit performs a concentration inverse calculation process that calculates the second ammonia nitrogen concentration of the sewage flowing into the biological reaction tank based on the first ammonia nitrogen concentration of the sewage being treated in the aerobic tank of the biological reaction tank, which is measured by an ammonia meter. The air supply amount calculation unit calculates a target air supply amount for the air supplied from the blower to the aerobic tank based on the second ammonia nitrogen concentration calculated in reverse, and The air supply volume control unit controls the amount of air supplied from the blower to the aerobic tank so that the amount of air supplied becomes the calculated target amount of air, and A method for controlling the amount of air supplied, including the air supply volume.

7. Computers, A concentration inverse calculation means for inversely calculating the second ammonia nitrogen concentration of sewage flowing into the biological reaction tank, based on the first ammonia nitrogen concentration of sewage being treated in the aerobic tank of the biological reaction tank, as measured by an ammonia meter, An air supply amount calculation means calculates a target amount of air supplied from the blower to the aerobic tank based on the second ammonia nitrogen concentration calculated in reverse, A supply volume control means controls the amount of air supplied from the blower to the aerobic tank so that the amount of air supplied becomes the calculated target amount of air, A program designed to function as such.

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