Water treatment device and water treatment method

Abstract

A water treatment device (100) is provided with: an inflow part water quality meter (14) for measuring the water quality of water to be treated flowing into a biological reaction tank (10); an outflow part water quality meter (15) for measuring the water quality that serves as an index for the aeration amount control of the biological reaction tank (10) at the outflow part (17)-side end of the biological reaction tank (10); and a control device (20) which is provided with an inflow pollutant concentration estimation part (21) for estimating the inflow pollutant concentration on the basis of the measurement value of the inflow part water quality meter (14), a water quality target value calculation part (22) for calculating a water quality target value that serves as an index of the aeration amount control on the basis of the inflow pollutant concentration estimation value estimated by the inflow pollutant concentration estimation part (21), and an aeration amount calculation part (23) for calculating an aeration amount to the biological reaction tank (10) on the basis of the water quality target value.

Description

Water treatment device and water treatment method

[0001] The present disclosure relates to a water treatment device and a water treatment method.

[0002] The activated sludge process is a method for treating wastewater containing organic matter and ammonia nitrogen. In this process, activated sludge, a group of microorganisms with purification capabilities, is stored in a biological reactor, and the activated sludge is mixed with wastewater and aerated while air is supplied to oxidize and decompose the pollutants in the wastewater. In order to stably treat wastewater, it is necessary to aerate the biological reactor with an appropriate amount of air in response to fluctuations in the load of pollutants entering the reactor.

[0003] Therefore, a technology has been developed in which the electrical conductivity of the water to be treated is measured and the aeration rate is controlled using the measured electrical conductivity as an index. Because there is a correlation between the ammoniacal nitrogen concentration in the water to be treated and the electrical conductivity, the ammoniacal nitrogen concentration can be estimated from the electrical conductivity, and the aeration rate can be calculated according to the ammoniacal nitrogen concentration (see, for example, Patent Document 1).

[0004] Japanese Patent Application Publication No. 5-293490

[0005] The dissolved oxygen (DO) concentration in the reaction tank is an index that represents the amount of oxygen dissolved in the water, and it can be used to estimate the activity of microorganisms, which indicates whether microorganisms are oxidizing organic matter using oxygen, and the stability of the effluent water quality. Therefore, in order to stably treat wastewater, it is necessary to keep the DO (Dissolved Oxygen) concentration (residual oxygen concentration) stable.

[0006] However, in conventional technology, the aeration volume is directly estimated using fluctuations in the influent water quality as an index, which makes it impossible to control the aeration efficiency or to follow the activity of microorganisms, leading to unstable water quality in the biological reactor.When the water quality in the biological reactor is unstable, the activity of microorganisms decreases, and wastewater cannot be treated even when aeration is supplied, or organic matter is not decomposed, resulting in a loss of stability in the quality of the discharged water.

[0007] The present disclosure discloses technology for solving the above-mentioned problems, and aims to provide a water treatment device and a water treatment method that can supply an appropriate amount of air to a biological reactor in response to load fluctuations in the concentration of inflowing pollutants, while stabilizing the water quality in the biological reactor, which is an indicator for aeration volume control.

[0008] A water treatment device according to the present disclosure controls the aeration rate, which is the amount of oxygen-containing gas supplied to a biological reactor that performs biological treatment on water to be treated, and includes an inlet water quality meter that measures the water quality of the water to be treated flowing into the biological reactor, an outlet water quality meter that measures the water quality at the end of the outlet side of the biological reactor as an indicator for controlling the aeration rate of the biological reactor, and a control device including an inlet water quality meter that estimates the inlet pollutant concentration based on the measurement value of the inlet water quality meter, a water quality target value calculation unit that calculates a water quality target value that serves as an indicator for controlling the aeration rate based on the inlet pollutant concentration estimated by the inlet pollutant concentration estimator, and an aeration rate calculation unit that calculates the aeration rate to the biological reactor based on the water quality target value.A water treatment method according to the present disclosure uses a water treatment device, and supplies the gas to the biological reactor in response to load fluctuations in the inlet pollutant concentration while stabilizing the water quality at the end of the biological reactor that serves as an indicator for controlling the aeration rate.

[0009] According to the water treatment device and water treatment method disclosed herein, it is possible to supply an appropriate amount of air to the biological reactor in response to load fluctuations in the concentration of inflowing pollutants, while stabilizing the water quality at the end of the biological reactor, which serves as an indicator for aeration volume control.

[0010] FIG. 8A is a diagram schematically showing an example of a basic configuration of a water treatment device according to the present disclosure. FIG. 8B is a graph showing the time variation of the inflow pollutant concentration estimated value obtained by the water quality target value calculation unit according to embodiment 1. FIG. 8B is a graph showing the time variation of the DO concentration target value obtained by the water quality target value calculation unit according to embodiment 2. FIG. 9A is a graph showing the time variation of the inflow pollutant concentration estimated value obtained by the water quality target value calculation unit according to embodiment 2. FIG. 9B is a graph showing the time variation of the DO concentration target value obtained by the water treatment device according to embodiment 2. FIG. 10A is a graph showing the time variation of the normalized inflow pollutant concentration estimated value obtained by the water quality target value calculation unit according to embodiment 2. FIG. 11B is a graph showing the time variation of the DO concentration target value obtained by the water treatment device according to embodiment 2. Fig. 1 is a diagram schematically showing an example of the configuration of a water treatment device according to embodiment 3. Fig. 2 is a flowchart showing the flow of treatment of water to be treated by the water treatment device according to embodiment 3. Fig. 3 is a diagram schematically showing an example of the configuration of a water treatment device according to embodiment 4. Fig. 4 is a flowchart showing the flow of treatment of water to be treated by the water treatment device according to embodiment 4. Fig. 5 is a block diagram showing the configuration of a control device according to each embodiment.

[0011] The basic configuration of a water treatment device according to the present disclosure will be described below before describing water treatment devices and water treatment methods according to each embodiment. Fig. 1 is a diagram schematically illustrating an example of the basic configuration of a water treatment device according to the present disclosure. The water treatment device 100 includes a biological reaction tank 10, an air diffuser plate 11, a blower 12, an air volume regulator 13, an inlet water quality meter 14, an outlet water quality meter 15, and a control device 20. The control device 20 also includes an inflow pollutant concentration estimator 21, a water quality target value calculator 22, and an aeration volume calculator 23.

[0012] The biological reactor 10 is a water tank that performs biological treatment on water to be treated A. The biological reactor 10 is installed in a water purification plant, a sewage treatment plant, a wastewater treatment facility in a factory, or the like. An inlet 16 and an outlet 17 are connected to the biological reactor 10. The inlet 16 is a pipe or waterway into which the water to be treated A flows in. The outlet 17 is a pipe or waterway through which the water treated in the biological reactor 10 flows out of the biological reactor 10.

[0013] The air diffuser plate 11 is installed in the biological reaction tank 10 and is a device that supplies air (gas containing oxygen) to the water A to be treated in the biological reaction tank 10. The air blower 12 is connected to the air diffuser plate 11 via piping and blows air to the air diffuser plate 11. The air volume regulator 13 adjusts the volume of air flowing from the air blower 12 to the air diffuser plate 11. As an example, the air volume regulator 13 is an air volume adjustment valve installed in the piping that connects the air blower 12 and the air diffuser plate 11.

[0014] In this case, the amount of aeration supplied to the air diffuser plate 11 is adjusted by adjusting the opening of the air volume adjustment valve. The air volume adjuster 13 adjusts the air volume in accordance with the aeration volume target value calculated by the aeration volume calculation unit 23 of the control device 20.

[0015] The inlet water quality meter 14 is a measuring instrument capable of measuring a water quality index correlated with the concentration of pollutants in the water A to be treated, and measures, for example, one of the following water quality items: ammonia concentration, conductivity, organic matter concentration, UV, turbidity, water temperature, pH, etc. Here, UV refers to 254 nm ultraviolet light, and organic matter tends to absorb ultraviolet light of this wavelength. The absorbance of 254 nm UV measured by the UV meter correlates with the concentration of organic matter in the water, and can therefore be used to estimate water quality indices such as COD (Chemical Oxygen Demand).

[0016] As an example, the inflow water quality meter 14 is installed in the inflow section 16. Alternatively, the inflow water quality meter 14 may be installed upstream of the biological reaction tank 10 near the inflow section 16. The inflow water quality meter 14 is connected to the inflow pollutant concentration estimation unit 21 of the control device 20 via a signal line W, and transmits the measured inflow water quality measurement value of the water to be treated A to the inflow pollutant concentration estimation unit 21.

[0017] The outflow water quality meter 15 includes one or more meters that measure water quality, such as the DO concentration and ammonia concentration of the water to be treated A, which serve as indicators for controlling the aeration amount. As an example, the outflow water quality meter 15 is installed at the end of the biological reaction tank 10. The outflow water quality meter 15 is connected to the aeration amount calculation unit 23 of the control device 20 via a signal line W, and transmits the measured outflow water quality value of the water to be treated A to the aeration amount calculation unit 23.

[0018] The aeration volume calculation unit 23 of the control device 20 performs aeration volume control, which adjusts the aeration volume so that the outflow water quality measurement value approaches the water quality target value, based on the water quality target value determined by the water quality target value calculation unit 22 and the outflow water quality measurement value transmitted from the outflow water quality meter 15. By the aeration volume control, the aeration volume target value to be supplied to the biological reaction tank 10 is repeatedly calculated, and the aeration volume target value is transmitted to the air volume regulator 13 via the signal line W.

[0019] Embodiment 1. A water treatment device and a water treatment method according to Embodiment 1 will now be described with reference to the drawings. Fig. 2 is a diagram schematically illustrating an example of the configuration of a water treatment device 100 in which the inflow water quality meter 14 described above with reference to Fig. 1 is a conductivity meter 114, and the outflow water quality meter 15 is a DO meter 115. That is, in Embodiment 1, an example of a water treatment device 100 is shown in which the inflow water quality meter 14 is a conductivity meter 114 that measures the conductivity of the water to be treated A, and the outflow water quality meter 15 is a DO meter 115 that measures the DO concentration of the water to be treated A. Fig. 3 is a flowchart illustrating the flow of treatment of the water to be treated A by the water treatment device.

[0020] The conductivity meter 114 measures the conductivity of the water to be treated A (step S001). As an example, the conductivity meter 114 is installed in the inflow section 16. The conductivity meter 114 may also be installed upstream of the biological reactor 10 near the inflow section 16. The conductivity meter 114 is connected to the inflow pollutant concentration estimation unit 21 of the control device 20 via a signal line W, and transmits the measured conductivity value of the water to be treated A to the inflow pollutant concentration estimation unit 21.

[0021] The DO meter 115 measures the DO concentration of the water to be treated A. As an example, the DO meter 115 is installed at the end of the biological reaction tank 10. The DO meter 115 is connected to the aeration amount calculation unit 23 of the control device 20 via a signal line W, and transmits the measured DO concentration value of the water to be treated A to the aeration amount calculation unit 23.

[0022] The aeration volume calculation unit 23 performs DO control, which is an aeration volume control method that adjusts the aeration volume so that the DO concentration measurement value approaches the DO concentration target value, based on the DO concentration target value determined by the water quality target value calculation unit 22 and the DO concentration measurement value transmitted from the DO meter 115. As an example of DO control, the aeration volume is calculated based on a PI control (proportional-integral control) algorithm so that the DO concentration measurement value becomes the DO concentration target value. The DO control repeatedly calculates the aeration volume target value to be supplied to the biological reactor 10, and transmits the aeration volume target value to the air volume regulator 13 via the signal line W.

[0023] Fig. 4 is a diagram schematically showing an example of the configuration of the inflow pollutant concentration estimation unit 21. Fig. 5 is a diagram showing the configuration of the database 21D. The inflow pollutant concentration estimation unit 21 includes the database 21D and an inflow pollutant concentration estimation equation derivation unit 21M. In the first embodiment, a conductivity meter 114 is provided as the inflow water quality meter 14, and an inflow pollutant concentration estimation value is estimated from the inflow conductivity measurement value. The estimated inflow pollutant concentration estimation value is transmitted to the water quality target value calculation unit 22 via a signal line W.

[0024] As shown in FIG. 5 , database 21D stores time-series data showing the correlation between the conductivity of water A to be treated and the ammonia concentration, total nitrogen concentration, organic pollutant concentration, total phosphorus concentration, phosphate phosphorus concentration, and other pollutant concentrations to be treated in water A. Note that FIG. 5 only shows ammonia concentration. Because the properties of water A to be treated change over time, the database needs to be updated if the accuracy of the influent pollutant concentration estimation formula (described later) falls below a preset standard. For example, for the pollutant concentration to be treated (ammonia concentration in FIG. 5 ), the database is updated if the mean absolute error rate between the daily inspection data and the estimated influent pollutant concentration deviates from the preset standard for a continuous period. Here, daily inspection data refers to data manually analyzed once a day for inspection at the treatment plant.

[0025] The influent pollutant concentration estimation formula derivation unit 21M derives an influent pollutant concentration estimation formula using the conductivity of the water to be treated A as the explanatory variable and the influent pollutant concentration of the water to be treated A as the objective variable, from information in the database 21D indicating the correlation between the conductivity of the water to be treated A and the influent pollutant concentration of the water to be treated A. An example of the influent pollutant concentration estimation formula is expressed as formula (1). Here, a, b, and c are parameters derived from a correlation analysis between the conductivity and the pollutant concentration. Since the properties of the water to be treated A change over time, if the accuracy of the influent pollutant concentration estimation formula falls below a preset standard, the parameters need to be updated. Influent pollutant concentration estimated value = a x (conductivity)^2 + b x (conductivity) + c ... formula (1)

[0026] The influent pollutant concentration (here, ammonia concentration as an example) of the water to be treated A is estimated by providing the measured conductivity value of the water to be treated A sent from the conductivity meter 114 as the explanatory variable of the influent pollutant concentration estimation formula (step S002).In addition to the polynomial regression method shown in formula (1), the influent pollutant concentration estimation formula may be derived using a physical model based on physical laws, a statistical model, or a statistical method such as probability distribution, or a machine learning algorithm such as random forest or neural network.

[0027] 6 is a diagram schematically illustrating an example of the configuration of the water quality target value calculation unit 22. The water quality target value calculation unit 22 includes an inflow pollutant concentration estimated value database 22D and a water quality target value threshold determination unit 22H, and determines the water quality target value (DO concentration) from the inflow pollutant concentration estimated value transmitted from the inflow pollutant concentration estimation unit 21. The determined water quality target value is transmitted to the aeration volume calculation unit 23 via signal line W. In the first embodiment, a DO meter 115 is provided as the outflow water quality meter 15, and the DO concentration target value that becomes the water quality target value is determined.

[0028] 7 is a diagram showing the configuration of the inflow pollutant concentration estimated value database 22D. The inflow pollutant concentration estimated value database 22D stores the inflow pollutant concentration estimated values ​​(e.g., ammonia concentration) transmitted from the inflow pollutant concentration estimation unit 21 along with the date and time as time-series data. The inflow pollutant concentration estimated value database 22D also has a function for calculating statistical indices, and calculates statistical indices such as the mean, quartiles, median, mode, and standard error of the stored inflow pollutant concentration estimated values ​​and stores them in the database. Furthermore, the inflow pollutant concentration estimated value database 22D determines the inflow pollutant concentration threshold value (step S003) using these statistical indices. The determined inflow pollutant concentration threshold value is transmitted to the water quality target value threshold determination unit 22H via signal line W.

[0029] The water quality target value threshold determination unit 22H determines the DO concentration target value from the inflow pollutant concentration estimated value based on the inflow pollutant concentration estimated value and the inflow pollutant concentration threshold value (step S004). An example of the water quality target value (DO concentration target value) determination is expressed as shown in Equation (2). Here, d1 and d2 are inflow pollutant concentration threshold values ​​(selected from the first quartile, average, third quartile, etc.) determined from the inflow pollutant concentration estimated value database 22D, and e1, e2, and e3 are determination values ​​for the DO concentration target value, satisfying d1 < d2 and e1 < e2 < e3. The number of inflow pollutant concentration threshold values ​​d and DO concentration target value determination values ​​e is set so that the DO concentration target value sufficiently fluctuates in accordance with the inflow pollutant concentration estimated value.

[0030] DO concentration target value = e1 if inflow pollutant concentration estimated value < d1 DO concentration target value = e2 if d1 <= inflow pollutant concentration estimated value < d2 DO concentration target value = e3 if d2 <= inflow pollutant concentration estimated value Formula (2)

[0031] 8A is a graph showing the time variation of the inflow pollutant concentration estimated by the water quality target value calculation unit 22. FIG. 8B is a graph showing the time variation of the DO concentration target value. The inflow pollutant concentration estimated value tends to vary over time, and when the inflow pollutant concentration estimated value is smaller than the inflow pollutant concentration threshold d1, the DO concentration target value is e1. When the inflow pollutant concentration estimated value is equal to or greater than the inflow pollutant concentration threshold d1 and smaller than the inflow pollutant concentration threshold d2, the DO concentration target value is e2. When the inflow pollutant concentration estimated value is equal to or greater than the inflow pollutant concentration threshold d2, the DO concentration target value is e3. By the above-described water quality target value determination, the determination value of the DO concentration target value is switched when the inflow pollutant concentration exceeds the inflow pollutant concentration threshold or when the inflow pollutant concentration falls below the inflow pollutant concentration threshold.

[0032] The aeration volume calculation unit 23 of the control device 20 performs aeration volume control to adjust the aeration volume so that the DO concentration measurement value approaches the DO concentration target value (step S006) based on the DO concentration target value determined by the water quality target value calculation unit 22 and the DO concentration measurement value transmitted from the DO meter 115 (step S005). By the aeration volume control, the target aeration volume to be supplied to the biological reaction tank 10 is repeatedly calculated (step S007), and the target aeration volume value is transmitted to the air volume regulator 13 via the signal line W (step S008).

[0033] As a result, during times when the influent pollutant concentration (here, ammonia concentration) is high, the DO concentration target value increases, so an appropriate amount of aeration is supplied to the biological reactor tank, and the water quality becomes stable. Also, during times when the influent pollutant concentration is low, the DO concentration target value decreases, so an excessive amount of aeration is not supplied to the biological reactor tank 10.

[0034] As described above, in the first embodiment, the concentration of a specific influent pollutant (ammonia was used as an example in the above description) is estimated from the conductivity of the water to be treated A, and the estimated influent pollutant concentration is used to determine the DO concentration target value, which serves as an index for DO control, in the water quality target value calculation unit. Based on the determined DO concentration target value, the aeration volume calculation unit 23 calculates the target aeration volume to be supplied to the biological reaction tank 10, and DO control is performed by repeating these processes (step S000).

[0035] When the inflow pollutant concentration is higher than past data, the target DO concentration can be set higher to promote pollutant purification, and when the inflow pollutant concentration is lower than past data, the target DO concentration can be set lower to prevent excessive aeration. This allows an appropriate amount of air to be supplied to the biological reactor.

[0036] According to the water treatment device of embodiment 1, the water treatment device controls the aeration rate, which is the amount of oxygen-containing gas supplied to a biological reaction tank that performs biological treatment on water to be treated, and is equipped with an inlet water quality meter that measures the water quality of the water to be treated flowing into the biological reaction tank, an outlet water quality meter that measures the water quality at the end of the outlet side of the biological reaction tank, which serves as an indicator for controlling the aeration rate of the biological reaction tank, and a control device that is equipped with an inlet pollutant concentration estimation unit that estimates the inlet pollutant concentration based on the measurement value of the inlet water quality meter, a water quality target value calculation unit that calculates a water quality target value that serves as an indicator for controlling the aeration rate based on the inlet pollutant concentration estimated value estimated by the inlet pollutant concentration estimation unit, and an aeration rate calculation unit that calculates the aeration rate to the biological reaction tank based on the water quality target value.Therefore, it is possible to supply an appropriate amount of air to the biological reaction tank in response to load fluctuations in the inflow pollutant concentration, while stabilizing the water quality at the end of the biological reaction tank, which serves as an indicator for controlling the aeration rate. Furthermore, since the inflow water quality meter is a conductivity meter that measures the conductivity of the biological reactor, the inflow pollutant concentration can be easily estimated from the correlation between the conductivity and a specific type of inflow pollutant measured in the past. Furthermore, since the outflow water quality meter is a dissolved oxygen concentration meter and the water quality target value calculation unit calculates the dissolved oxygen concentration target value, an appropriate amount of air can be supplied to the biological reactor in response to load fluctuations in the inflow pollutant concentration while maintaining a stable DO concentration in the reaction tank.

[0037] Embodiment 2. A water treatment device and water treatment method according to embodiment 2 will be described below, focusing on the differences from embodiment 1. Figure 9 is a diagram schematically showing an example of the configuration of the water quality target value calculation unit 222 of a water treatment device 200 according to embodiment 2. Figure 10 is a flowchart showing the flow of treatment of water to be treated A by the water treatment device 200. The water treatment device 200 according to embodiment 2 has roughly the same configuration as that shown in Figure 2 of embodiment 1, but the configuration of the water quality target value calculation unit 222 is different. Note that the same components as those in embodiment 1 are assigned the same reference numerals, and their description will be omitted, and only the differences will be described.

[0038] The water quality target value calculation unit 222 includes an inflow pollutant concentration estimated value database 22D, an inflow pollutant concentration estimated value normalization unit 22S, and a water quality target value calculation formula setting unit 22T, and determines the water quality target value (DO concentration target value) from the inflow pollutant concentration estimated value transmitted from the inflow pollutant concentration estimation unit 21. The determined water quality target value is transmitted to the aeration amount calculation unit 223 via a signal line W.

[0039] The influent pollutant concentration estimated value database 22D stores the influent pollutant concentration estimated values ​​transmitted from the influent pollutant concentration estimating unit 21. The influent pollutant concentration estimated value database 22D extracts the most recent influent pollutant concentration estimated value from the stored influent pollutant concentration estimated values, and transmits the maximum and minimum values ​​within a predetermined data period to the influent pollutant concentration estimated value normalizing unit 22S. Here, the most recent period for calculating the maximum and minimum values ​​is set arbitrarily depending on the fluctuation pattern of the influent pollutant concentration of the target water treatment process. For example, in the case of a treatment plant where the fluctuation pattern of the influent pollutant concentration is roughly the same throughout a week, the maximum and minimum values ​​can be calculated for a one-week period (step S203A).

[0040] The inflow pollutant concentration estimated value normalization unit 22S normalizes the inflow pollutant concentration estimated value transmitted from the inflow pollutant concentration estimation unit 21 to a scale of 0 to 1 using the maximum and minimum values ​​transmitted from the inflow pollutant concentration estimated value database 22D (step S203B). Normalizing the inflow pollutant concentration estimated value makes it easier to set the range of possible DO concentration target values ​​in the process of calculating the DO concentration target value, which will be described later.

[0041] The water quality target value calculation formula setting unit 22T calculates the DO concentration target value using the water quality target value calculation formula based on the normalized estimated inflow pollutant concentration (step S204). An example of the water quality target value calculation formula is expressed as formula (3). Here, f is the fluctuation range of the DO concentration target value with respect to load fluctuations in the water to be treated A, and g is the lower limit of the DO concentration target value. DO concentration target value = f × normalized estimated inflow pollutant concentration + g ... formula (3)

[0042] 11A is a graph showing the time variation of the normalized inflow pollutant concentration estimate by the water quality target value calculation unit 222. FIG. 11B is a graph showing the time variation of the DO concentration target value. Because the inflow pollutant concentration estimate is normalized, when the inflow pollutant concentration estimate indicates a minimum value within the data period extracted from the inflow pollutant concentration estimate value database 22D, the normalized inflow pollutant concentration estimate is 0, and the DO concentration target value is the lower limit set by the above-mentioned water quality target value calculation formula. On the other hand, when the inflow pollutant concentration estimate indicates a maximum value within the data period, the normalized inflow pollutant concentration estimate is 1, and the DO concentration target value increases in accordance with the fluctuation range of the DO concentration target value in response to load fluctuations in the treated water A.

[0043] According to the above water quality target value calculation formula, the DO concentration target value increases as the influent pollutant concentration increases during the day, and decreases as the influent pollutant concentration decreases during the day. As a result, the DO concentration target value increases during the time periods when the influent pollutant concentration increases, so an appropriate amount of aeration is supplied to the biological reactor, and the water quality remains stable. Furthermore, the DO concentration target value decreases during the time periods when the influent pollutant concentration decreases, so an excessive amount of aeration is not supplied to the biological reactor.

[0044] As described above, according to the water treatment device and water treatment method of the second embodiment, the normalized influent pollutant concentration is estimated from the conductivity of the water to be treated A, and the normalized estimated influent pollutant concentration is used to calculate the DO concentration target value, which serves as an index for DO control, in the water quality target value calculation unit 222. DO control is performed in the aeration volume calculation unit 223 based on the calculated DO concentration target value, and the target aeration volume to be supplied to the biological reaction tank 10 is calculated.

[0045] The water quality target value calculation unit includes an inflow pollutant concentration estimated value database that stores the inflow pollutant concentration estimated values ​​transmitted together with date and time as time-series data, an inflow pollutant concentration estimated value normalization unit that normalizes the multiple inflow pollutant concentration estimated values ​​for a predetermined period, and a water quality target value calculation formula setting unit that calculates the water quality target value based on the normalized inflow pollutant concentration estimated values. Therefore, since the DO concentration target value fluctuates according to the inflow pollutant concentration estimated value, an appropriate DO concentration target value for the inflow pollutant concentration can be calculated. When the inflow pollutant concentration increases, the DO concentration target value can be set higher to promote pollutant purification, and when the inflow pollutant concentration decreases, the DO concentration target value can be set lower to suppress excessive aeration. This allows an appropriate amount of air to be supplied to the biological reactor.

[0046] Furthermore, whereas in embodiment 1 the DO concentration target value changes discretely, in embodiment 2 the DO concentration target value calculated using the normalized inflow pollutant estimate value changes continuously in accordance with fluctuations in the inflow pollutant concentration, thereby significantly improving response to load fluctuations and further stabilizing the treated water quality.

[0047] Embodiment 3. A water treatment device and a water treatment method according to Embodiment 3 will be described below, focusing on differences from Embodiments 1 and 2. FIG. 12 is a diagram schematically illustrating an example of the configuration of a water treatment device according to Embodiment 3. FIG. 13 is a flowchart illustrating the treatment flow of water to be treated A by a water treatment device 300. Note that components identical to those in Embodiment 1 are assigned the same reference numerals and their description will be omitted, and only differences will be described. The water treatment device 300 includes a biological reaction tank 10, an aeration plate 11, a blower 12, an air volume regulator 13, an inlet water quality meter 14, an outlet water quality meter 15, a flow meter 18, and a control device 320. The control device 320 also includes an inflow pollutant concentration estimation unit 21, a water quality target value calculation unit 322, an aeration volume calculation unit 23, and an inflow load calculation unit 24.

[0048] The inflow pollutant concentration estimation unit 21 estimates the inflow pollutant concentration from the inflow water quality measurement value measured by the inflow water quality meter 14, and transmits the inflow pollutant concentration estimation value to the inflow load calculation unit 24 via the signal line W.

[0049] The flow meter 18 measures the flow rate of the water A to be treated flowing into the biological reaction tank 10 (step S303A). As an example, the flow meter 18 is installed at the inlet 16, but it may also be installed upstream of the biological reaction tank 10 near the inlet 16. The measured flow rate value is transmitted to the inflow load calculation unit 24 via the signal line W.

[0050] The inflow load calculation unit 24 calculates an inflow load estimate using the inflow pollutant concentration estimate sent from the inflow pollutant concentration estimation unit 21 and the flow rate measurement value sent from the flow meter 18 (step S303B). Here, the inflow load estimate is the result of multiplying the inflow pollutant concentration estimate by the flow rate measurement value. The calculated inflow load estimate is sent to the water quality target value calculation unit 322 via signal line W.

[0051] The water quality target value calculation unit 322 calculates the water quality target value based on the inflow load estimated value transmitted from the inflow load calculation unit 24. As an example, in the configuration of the water quality target value calculation unit 22 shown in Embodiment 1, the inflow pollutant concentration estimated value is replaced with the inflow load estimated value calculated by the inflow load calculation unit 24 to calculate the inflow load threshold (step S303C) and calculate the water quality target value (DO concentration target value). By using the inflow load estimated value, it is possible to set the water quality target value for the total amount of pollutants flowing into the biological reaction tank 10.

[0052] In the method of calculating the target water quality value from the estimated influent pollutant concentration, as in the first or second embodiment, if the influent pollutant concentration is diluted by rainwater during rainy weather, for example, it is determined that the amount of pollutants flowing into the biological reactor 10 will decrease, and the target water quality value is calculated to be low. However, in reality, the amount of water flowing into the biological reactor 10 may increase due to the inclusion of rainwater, which may prevent the calculation of an appropriate target water quality value for the load fluctuations at the influent. Therefore, by using an influent load estimate based on the flow rate measurement value in addition to the estimated influent pollutant concentration, it is possible to calculate an appropriate target water quality value for the load fluctuations at the influent. The calculated target water quality value is transmitted to the aeration volume calculation unit 23 via signal line W.

[0053] As described above, in the third embodiment, the influent pollutant concentration is estimated from the conductivity of the water A to be treated, and the water quality target value calculation unit 322 calculates the water quality target value, which serves as an index for aeration volume control, using the influent load estimated value obtained by multiplying the estimated influent pollutant concentration by the measured flow rate. This allows for an accurate estimation of the total amount of pollutants flowing into the biological reactor 10, thereby calculating a more appropriate water quality target value. Furthermore, if the estimated influent load value increases, the water quality target value can be set higher to promote pollutant purification, and if the estimated influent load value decreases, the DO concentration target value can be set lower to suppress excessive aeration. This allows for an appropriate amount of aeration to be supplied to the biological reactor 10.

[0054] In this way, the water treatment device is equipped with a flow meter that measures the amount of the water to be treated flowing into the biological reaction tank, an inflow load calculation unit that calculates the inflow load based on the estimated inflow pollutant concentration value and the water amount, and a water quality target value calculation unit that calculates the water quality target value that serves as an indicator for aeration volume control based on the inflow load.Therefore, while stabilizing the water quality at the end of the biological reaction tank, which serves as an indicator for aeration volume control, an appropriate amount of air can be supplied to the biological reaction tank in response to load fluctuations in the pollutant concentration and flow rate of the inflowing water to be treated.

[0055] Fourth Embodiment A water treatment device and a water treatment method according to a fourth embodiment will be described below, focusing on the differences from the first to third embodiments. FIG. 14 is a diagram schematically illustrating an example of the configuration of a water treatment device 400 according to the fourth embodiment. FIG. 15 is a flowchart illustrating the flow of treatment of water A to be treated by the water treatment device 400. The water treatment device 400 according to the fourth embodiment has a configuration that is generally the same as that shown in FIG. 2 of the first embodiment, but differs in the configuration of the outflow water quality meter 15. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0056] As shown in Figure 14, embodiment 4 takes as an example a water treatment device 400 equipped with a conductivity meter 114 as the inlet water quality meter 14 shown in Figure 1 and an ammonia concentration meter 415 as the outlet water quality meter 15.

[0057] The ammonia concentration meter 415 measures the ammonia concentration of the water to be treated A. As an example, the ammonia concentration meter 415 is installed at the end of the biological reaction tank 10. The ammonia concentration meter 415 is connected to the aeration amount calculation unit 23 via a signal line W, and transmits the measured ammonia concentration value of the water to be treated A to the aeration amount calculation unit 23.

[0058] The water quality target value calculation unit 422 of the control device 420 determines the water quality target value (ammonia concentration) from the inflow pollutant concentration estimated value (step S402) transmitted from the inflow pollutant concentration estimation unit 21 (step S404). The determined water quality target value is transmitted to the aeration volume calculation unit 23 via signal line W. In the fourth embodiment, an ammonia concentration meter 415 is provided as the outflow water quality meter 15, and calculates the ammonia concentration target value, which serves as the water quality target value. As an example, the ammonia concentration target value is calculated in the configurations of the water quality target value calculation units 22, 222 shown in the first and second embodiments. The ammonia concentration target value increases when the inflow pollutant concentration estimated value increases, and decreases when the inflow pollutant concentration estimated value decreases.

[0059] As a result, when the estimated influent pollutant concentration increases, the amount of air required to treat the pollutants also increases, but by setting the ammonia concentration target value high, the minimum amount of air necessary to maintain treated water quality is supplied, and excessive aeration is suppressed.Also, when the estimated influent pollutant concentration decreases, the pollutants are treated with a small amount of air, so by setting the ammonia concentration target value low, good treated water quality can be obtained with a small amount of air.

[0060] The aeration volume calculation unit 423 performs ammonia control, which is an aeration volume control method that adjusts the aeration volume so that the measured ammonia concentration approaches the target ammonia concentration value (step S406) based on the target ammonia concentration value calculated by the target water quality value calculation unit 422 and the measured ammonia concentration value transmitted from the ammonia concentration meter 415 (step S405). As an example of ammonia control, the aeration volume is calculated based on a PI control algorithm so that the measured ammonia concentration value becomes the target ammonia concentration value. The target aeration volume to be supplied to the biological reactor 10 is calculated by ammonia control, and the target aeration volume value is transmitted to the air volume regulator 13.

[0061] As described above, in the fourth embodiment, the inflow pollutant concentration (ammonia concentration) is estimated from the conductivity of the water to be treated A, and the estimated inflow pollutant concentration is used to calculate the target ammonia concentration value, which serves as an index for ammonia control, in the water quality target value calculation unit. The aeration volume calculation unit performs ammonia control based on the calculated target ammonia concentration value, and calculates the target aeration volume to be supplied to the biological reaction tank 10.

[0062] The target ammonia concentration is calculated based on the estimated influent pollutant concentration, and is therefore calculated in accordance with fluctuations in the influent pollutant concentration. The target ammonia concentration increases when the estimated influent pollutant concentration increases, and decreases when the estimated influent pollutant concentration decreases. This reduces the amount of aeration that was previously excessive in response to fluctuations in the influent pollutant concentration, and allows an appropriate amount of air to be supplied to the biological reactor, thereby achieving good treated water quality.

[0063] Furthermore, the water treatment device is equipped with an ammonia meter as the outflow water quality meter, and the water quality target value calculation unit calculates the ammonia concentration target value, so that an appropriate amount of air can be supplied to the biological reaction tank in response to fluctuations in ammonia concentration while maintaining the water quality in the reaction tank stable.

[0064] FIG. 16 is a block diagram showing an example of the hardware configuration of the control devices 20, 320, and 420. The control devices 20, 320, and 420 each include a processor 90 and a storage device 91. The storage device 91 includes a volatile storage device such as a random access memory (not shown) and a non-volatile auxiliary storage device such as a flash memory. Alternatively, a hard disk auxiliary storage device may be provided instead of the flash memory. The processor 90 executes a program input from the storage device 91. In this case, the program is input to the processor 90 from the auxiliary storage device via the volatile storage device. The processor 90 may output data such as calculation results to the volatile storage device of the storage device 91, or may store the data in the auxiliary storage device via the volatile storage device.

[0065] Although various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0066] 100, 200, 300, 400 Water treatment device, 10 Biological reaction tank, 11 Aeration plate, 12 Blower, 13 Air flow regulator, 14 Inflow water quality meter, 114 Conductivity meter, 15 Outflow water quality meter, 115 DO meter, 415 Ammonia concentration meter, 16 Inflow section, 17 Outflow section, 18 Flow meter, 20, 320, 420 Control device, 21 Inflow pollutant concentration estimation unit, 21D Database, 21M Inflow pollutant concentration estimation formula derivation unit, 22D Inflow pollutant concentration estimated value database, 22, 222, 322, 422 Water quality target value calculation unit, 22H Water quality target value threshold determination unit, 22S Inflow pollutant concentration estimated value normalization unit, 22T Water quality target value calculation formula setting unit, 23, 223, 423 Aeration amount calculation unit, 24 Inflow load calculation section, d1, d2 inflow pollutant concentration threshold, W signal line.

Claims

1. A water treatment device that controls the aeration rate, which is the amount of oxygen-containing gas supplied to a biological reaction tank that performs biological treatment on water to be treated, comprising: an inlet water quality meter that measures the water quality of the water to be treated flowing into the biological reaction tank; an outlet water quality meter that measures water quality at the end of the outlet side of the biological reaction tank, which serves as an indicator for controlling the aeration rate of the biological reaction tank; an inlet pollutant concentration estimation unit that estimates the inlet pollutant concentration based on the measurement value of the inlet water quality meter; a water quality target value calculation unit that calculates a water quality target value that serves as an indicator for controlling the aeration rate based on the inlet pollutant concentration estimated value estimated by the inlet pollutant concentration estimation unit; and an aeration rate calculation unit that calculates the aeration rate to the biological reaction tank based on the water quality target value.

2. The water treatment device according to claim 1, wherein the inlet water quality meter is a conductivity meter that measures the conductivity of the biological reactor.

3. A water treatment device as described in claim 1 or claim 2, wherein the outflow water quality meter is either a dissolved oxygen concentration meter or an ammonia meter, and the water quality target value calculation unit calculates either a dissolved oxygen concentration target value or an ammonia concentration target value.

4. A water treatment device described in any one of claims 1 to 3, wherein the water quality target value calculated by the aeration volume calculation unit increases when the estimated value of the inflow pollutant concentration increases, and decreases when the estimated value of the inflow pollutant concentration decreases.

5. A water treatment device as described in any one of claims 1 to 4, wherein the water quality target value calculation unit comprises: an inflow pollutant concentration estimated value database that stores inflow pollutant concentration estimated values ​​transmitted together with date and time as time series data; an inflow pollutant concentration estimated value normalization unit that normalizes the inflow pollutant concentration estimated values ​​for a predetermined period; and a water quality target value calculation formula setting unit that calculates the water quality target value based on the normalized inflow pollutant concentration estimated values.

6. A water treatment device as described in any one of claims 1 to 5, comprising a flow meter that measures the amount of water to be treated flowing into the biological reaction tank, an inflow load calculation unit that calculates an inflow load based on the estimated inflow pollutant concentration value and the water amount, and a water quality target value calculation unit that calculates the water quality target value that serves as an indicator for aeration volume control based on the inflow load.

7. A water treatment method using a water treatment device according to any one of claims 1 to 6, in which the gas is supplied to the biological reaction tank in response to load fluctuations in the inflow pollutant concentration while stabilizing the water quality at the end of the biological reaction tank, which serves as an indicator for aeration volume control.

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