JP7621179B2 - Operation index calculation method and calculation device, biological treatment method and biological treatment device - Google Patents

Description

The present invention relates to biological treatment of organic wastewater, and in particular to a method and device for calculating an operational index used when performing biological treatment, and a method and device for performing biological treatment controlled based on the calculated operational index.

Biological treatment using microorganisms is widely used as a wastewater treatment method for wastewater containing organic matter, i.e., organic wastewater, before it is released into the environment. In biological treatment, in order to maintain a high level of activity in decomposing organic matter by the microorganisms, it is necessary to optimize environmental conditions such as water temperature and pH, as well as add nutrients such as nitrogen, phosphorus, and trace metals. Compared to wastewater from public sewerage systems into which domestic wastewater flows, wastewater from factories is more likely to be deficient in nutrients. In particular, wastewater from chemical plants and semiconductor manufacturing plants is noticeably deficient in the nutrients required for biological treatment.

It is recommended that the amount of nutrients added to organic wastewater be proportional to the organic matter concentration in the organic wastewater. Assuming that the organic matter concentration in organic wastewater is expressed as biochemical oxygen demand (BOD), the preferred amount of nitrogen (N) and phosphorus (P) added in wastewater treatment by aerobic microorganisms, i.e., aerobic treatment, is, for example, BOD:N:P = 100:5:1 by mass. In order to determine the amount of nutrients to be added, it is necessary to obtain the BOD value of the inflow water to the biological treatment tank or the water in the biological treatment tank. Although it is difficult to measure BOD online or in a short time, the total organic carbon (TOC) concentration in water can be measured online, so the correlation between the TOC concentration and BOD in the inflow water is obtained in advance, and the TOC concentration of the inflow water is monitored with an online TOC concentration meter and converted to a BOD value, and the amount of nitrogen and phosphorus added is controlled based on the obtained BOD value. However, the method of controlling the amount of nutrients added based on the TOC concentration measured online has the problem that the inside of the piping of the online TOC concentration meter can become clogged due to the accumulation of suspended solids (SS) and oil, and the formation of biofilms, making the measurement unstable.

Patent Document 1 discloses that when organic wastewater is subjected to biological treatment to obtain effluent, the concentration of carbon dioxide generated by the biological treatment is measured, the BOD value of the effluent is estimated based on the carbon dioxide concentration, and the estimated BOD value is used as an operating index to adjust the treatment, for example by increasing the amount of returned sludge.

Japanese Unexamined Patent Publication No. 54-60765

The method disclosed in Patent Document 1 is a method of estimating a BOD value based on the carbon dioxide generation rate generated in the biological treatment, based on the fact that the generation rate of inorganic carbon dioxide generated by the biological treatment is proportional to the organic matter concentration in the effluent, and adjusting the treatment using the estimated BOD value as an operation index. However, inorganic carbon dioxide in water changes its form into carbon dioxide (CO ₂ ), bicarbonate ion (HCO ₃ ^- ) and carbonate ion (CO ₃ ^2- ) depending on the pH of the water, and bicarbonate ion and carbonate ion remain in the water, so that measuring the carbon dioxide concentration alone is insufficient to estimate the amount of carbon dioxide generated in the biological treatment. Furthermore, the solubility of dissolved gas generally depends on temperature, and there are inorganic carbonic acid components remaining in the water in the form of carbon dioxide, and the amount of these components depends on temperature, so that it is difficult to accurately estimate the carbon dioxide generation rate generated in the biological treatment by simply measuring the carbon dioxide concentration in the gas phase. In the end, it is difficult to obtain an accurate BOD value using the method described in Patent Document 1, and it is inappropriate as a method for calculating an operation index.

In addition, in the method described in Patent Document 1, the activated sludge process is adjusted based on the BOD value of the effluent, for example by adopting a means for increasing the amount of returned sludge. However, since the BOD value of the effluent is estimated instead of the BOD value of the influent, a time lag occurs when adjusting the activated sludge process. In the end, the BOD value calculated by the method described in Patent Document 1 is inappropriate as an operation index. Furthermore, in the method described in Patent Document 1, for example, the aeration volume is adjusted based on the BOD value of the effluent. However, if the aeration volume is adjusted to increase, the carbon dioxide generated in the biological treatment is diluted, making it difficult to accurately estimate the increase or decrease in the carbon dioxide generated in the biological treatment. In this respect, it is difficult to obtain an accurate BOD value using the method described in Patent Document 1, and it is inappropriate as a method for calculating an operation index.

The object of the present invention is to provide a calculation method and calculation device that can quickly estimate accurate operating indices used to control the biological treatment when treating organic wastewater through biological treatment, and a biological treatment method and biological treatment device that executes biological treatment controlled based on the calculated operating indices.

The calculation method of the present invention is a method for calculating an operation index used when biologically treating organic wastewater in a biological treatment tank, and calculates an operation index from a measured value of the process amount of gas released from the water in the biological treatment tank and a measured value of the water quality in the biological treatment tank based on a predetermined relationship between the process amount of gas released from the water in the biological treatment tank, the water quality in the biological treatment tank, and the water quality of the inflow water to the biological treatment tank. The process amount of gas is at least one of gas concentration, flow rate, volume, pressure, and amount of substance, the water quality in the biological treatment tank includes at least one of water temperature, pH, and oxidation-reduction potential (ORP), and the operation index is the organic matter concentration in the inflow water.

The calculation device of the present invention is a calculation device for calculating an operation index used when biologically treating organic wastewater in a biological treatment tank, and includes a gas measurement unit for measuring a process amount of gas released from the water in the biological treatment tank, a water quality measurement unit for measuring the quality of the water in the biological treatment tank, and a calculation means for calculating an operation index from a measurement value in the gas measurement unit and a measurement value in the water quality measurement unit based on a predetermined relationship between the process amount of gas released from the water in the biological treatment tank, the quality of the water in the biological treatment tank, and the quality of the inflow water to the biological treatment tank. The process amount of gas is at least one of gas concentration, flow rate, volume, pressure, and substance amount, the water quality of the water in the biological treatment tank includes at least one of water temperature, pH, and ORP, and the operation index is the organic matter concentration in the inflow water.

The biological treatment method of the present invention is a biological treatment method for biologically treating organic wastewater, in which an operation index is calculated by the calculation method of the present invention, and at least one of the amount of nutrients added to the inflow water and the amount of aeration in the biological treatment tank is controlled in accordance with the calculated operation index, thereby performing biological treatment of the inflow water in the biological treatment tank.

The biological treatment device of the present invention is a biological treatment device that biologically treats organic wastewater, and is equipped with the calculation device of the present invention, an addition means that adds nutrients to the inflow water, and/or an aeration means that diffuses aeration into the biological treatment tank, and at least one of the addition means and the aeration means is controlled according to the calculated operation index.

According to the present invention, when treating organic wastewater using biological treatment, it is possible to quickly determine accurate operating indices used to control the biological treatment. This makes it possible, for example, to add nutrients to the influent water supplied to a biological treatment tank in an optimal amount based on the operating indices.

FIG. 1 is a diagram showing a biological treatment device including a calculation device according to an embodiment of the present invention. 10 is a flowchart showing a process of calculating a driving index. FIG. 2 is a diagram illustrating an example of a database configuration. FIG. 13 is a diagram showing another biological treatment device. FIG. 13 is a diagram showing yet another biological treatment device.

Next, an embodiment of the present invention will be described with reference to the drawings. The present invention relates to the calculation of an operating index used for controlling biological treatment when biological treatment using microorganisms is performed in a biological treatment tank on organic wastewater to decompose and remove organic matter. The organic wastewater targeted by the present invention is not particularly limited as long as biological treatment is applicable, and includes, for example, wastewater discharged in sewage treatment, wastewater discharged from various factories such as food factories, chemical factories, semiconductor manufacturing factories, liquid crystal manufacturing factories, and paper and pulp factories, and wastewater discharged from business establishments in other fields. Compared to wastewater from public sewerage systems, wastewater from private factories is more likely to lack nutrients necessary to maintain high decomposition activity of the microorganisms used in biological treatment, and the lack of nutrients is particularly noticeable in wastewater from chemical factories, semiconductor manufacturing factories, and liquid crystal manufacturing factories. When an external organic source such as methyl alcohol is added to inorganic nitrate wastewater (or inorganic nitrite wastewater) that does not contain organic matter and a denitrification treatment is performed, wastewater to which an external organic source has been added is also an organic wastewater targeted by the present invention.

The biological treatment in this invention includes aerobic treatment, anaerobic treatment, denitrification treatment, etc., and these biological treatments are carried out by the activated sludge process, the membrane bioreactor (MBR) process, the biofilm process using a fluidized bed or fixed bed, or the granular process, etc.

Figure 1 is a diagram for explaining a calculation device according to an embodiment of the present invention, and shows a biological treatment device equipped with the calculation device. The biological treatment device shown in Figure 1 is equipped with a fluidized bed type biological treatment tank 10 that stores organic wastewater supplied as inflow water and performs biological treatment of the organic wastewater under aerobic conditions. Treated water in which organic matter has been decomposed and removed by biological treatment is discharged from the biological treatment tank 10. The biological treatment tank 10 is filled with carriers 11, and an aeration device 12 is provided at the bottom of the biological treatment tank 10 to blow air into the biological treatment tank 10 to supply oxygen, i.e., to perform aeration. The biological treatment tank 10 is connected to an inlet pipe 13 that supplies inflow water to the biological treatment tank 10. The aeration device 12 is connected to a gas pipe 14 for supplying air to the aeration device 12, and the gas pipe 14 is provided with a blower 15 for supplying air. Examples of the carrier 11 that can be used here include plastic carriers, sponge-like carriers, and gel-like carriers, but among these, it is preferable to use a sponge-like carrier from the standpoint of cost and durability. The reaction tank 10 may be provided with a stirring device for stirring the carrier 11.

In the biological treatment apparatus shown in FIG. 1, an operation index used for controlling the biological treatment is calculated based on the process amount of a specific gas released from the water in the biological treatment tank 10 by biological treatment and one or more measured values related to the water quality of the water in the biological treatment tank 10. For this reason, the biological treatment tank 10 is provided with a gas measurement unit 31 that measures the process amount of a specific gas released from the water in the biological treatment tank 10, and a water quality measurement unit 32 that measures the water quality of the water in the biological treatment tank 10. Assuming that the biological treatment tank 10 is covered with a lid 16, the gas measurement unit 31 is installed in the gas phase part of the biological treatment tank 10 or in a pipe connected to this gas phase part. Since it is necessary to avoid condensation of the gas measurement unit 31, when it is installed in the pipe, the pipe may be kept warm, and a mist separator may be placed immediately before the gas measurement unit 31. In addition, a desulfurization device for removing corrosive gases may be placed. If the biological treatment tank 10 is an open system, in order to reduce the effect of outside air on the measurement results, the open area at the top of the biological treatment tank 10 can be made as small as possible, a cylindrical pipe or the like can be inserted below the water surface, and the gas measurement unit 31 can be placed in the pipe at a position above the water surface.

The process amount of the specific gas released in the biological treatment can be, for example, at least one of the following: the concentration of the specific gas (units are, for example, ppm or mL/m ³ ); the flow rate of the specific gas (units are, for example, mL/h) obtained by multiplying the concentration of the specific gas by the flow rate of the total gas released from the water in the biological treatment tank 10 by the biological treatment; the volume of the gas (units are, for example, mL) obtained by multiplying the flow rate by a predetermined time or an integrated time; and the partial pressure of the specific gas (units are, for example, Pa) calculated from the concentration of the specific gas and the pressure of the gas released from the water in the biological treatment tank 10 by the biological treatment. In addition to the volume and partial pressure, mass (units are, for example, kg) and substance amount (units are, for example, mol) can be used arbitrarily. Various gases can be generated in the biological treatment. When the biological treatment is an aerobic treatment, it is preferable to measure the process amount of carbon dioxide, which is the final product when organic matter is decomposed by the aerobic treatment, by the gas measurement unit 31. When measuring the concentration of carbon dioxide as a process quantity, for example, the gas measurement unit 31 may be, for example, an optical, electrochemical, or semiconductor carbon dioxide concentration sensor, but it is particularly preferable to use a sensor using a non-dispersive infrared absorption method (NDIR). The measurement of the gas process quantity may be performed manually or online. When measuring the flow rate as a process quantity of gas other than carbon dioxide, an ultrasonic, electromagnetic, Coriolis, Karman vortex, float, thermal, impeller, differential pressure, or other flow rate sensor may be used.

The water quality of the water in the biological treatment tank 10 is measured by the water quality measuring unit 32, and may include, for example, pH (hydrogen ion concentration index), water temperature, dissolved oxygen concentration (DO), oxidation-reduction potential (ORP), conductivity, turbidity, etc., and the water quality measuring unit 32 is configured to measure one or more of these items, including at least one of pH, water temperature, and ORP. As is well known, the form of inorganic carbonic acid in water changes to CO ₂ , HCO ₃ ^- , and CO ₃ ^2- depending on the pH, so it is considered that the pH is particularly closely related to the carbon dioxide concentration in the gas released from the water in the biological treatment tank 10 by the biological treatment, which is an aerobic treatment. In addition, the solubility of carbon dioxide changes depending on the water temperature, so the water temperature is also closely related to the carbon dioxide concentration in the gas released from the water in the biological treatment tank 10. The amount of oxygen and the oxidation-reduction tendency of the water in the biological treatment tank 10 can be grasped depending on the ORP and DO, and the ORP and DO are also closely related to the concentration of carbon dioxide released. The measurement in the water quality measuring unit 32 may be performed manually or online.

There are also online TOC concentration meters that measure the total organic carbon (TOC) concentration in water online, but these have thin pipes to draw in small amounts of sample water into the measuring device, which can easily become clogged and can lead to unstable measurements. On the other hand, carbon dioxide concentration sensors and gas flow sensors perform measurements without coming into contact with the water, so their measurements are very stable. In addition, the water quality measuring unit 33 that measures pH, water temperature, ORP, etc. is a sensor that is immersed in the reaction tank 10, so its measurements are also very stable.

In the biological treatment apparatus shown in FIG. 1, an operation index for the water supplied to the biological treatment tank 10, i.e., the inflow water, is calculated from the value of the gas process amount measured by the gas measurement unit 31 and the value of the water quality measured by the water quality measurement unit 32. The calculated operation index is used, for example, to determine the amount of nutrients to be added to the inflow water or the water in the biological treatment tank 10, or to determine the amount and flow rate of air or oxygen to be blown into the biological treatment tank 10. In order to calculate the operation index, the biological treatment apparatus is equipped with a calculation unit 40. The calculation unit 40 receives measured values from the gas measurement unit 31 and the water quality measurement unit 32, and the calculation unit 40 calculates the operation index from the measured values in the gas measurement unit 31 and the water quality measurement unit 32 based on a previously determined relationship between the process amount of gas released from the water in the biological treatment tank 10, the water quality of the water in the biological treatment tank 10, and the water quality of the inflow water. The previously determined relationship between the gas concentration, water quality, and the operation index is expressed by a model or a relational expression. The creation of the model and the relational expressions will be described later. The operation index calculated by the calculation device 40 is an operation index related to the inflow water. The operation index related to the inflow water is preferably at least one of the organic matter concentration, nitrogen concentration, phosphorus concentration, DO, and ORP in the inflow water, and more preferably at least one of the total organic carbon (TOC) concentration, biochemical oxygen demand (BOD), and chemical oxygen demand (COD) in the inflow water, which are organic matter concentrations.

Figure 2 is a flowchart showing the procedure for determining the organic matter concentration of the inflow water in the biological treatment device shown in Figure 1. First, in step 101, the gas measurement unit 31 measures the process amount (e.g., concentration) of gas (e.g., carbon dioxide) released from the water in the biological treatment tank 10, and in step 102, the water quality measurement unit 32 measures the water quality (e.g., pH, water temperature, or ORP) of the water in the biological treatment tank 10. Although Figure 2 shows step 102 being executed after step 101, step 102 may be executed prior to step 101, or steps 101 and 102 may be executed simultaneously. Then, in step 103, the calculation device 40 calculates an operation index (e.g., organic matter concentration) related to the inflow water by substituting the process amount of gas determined in step 101 and the water quality determined in step 102 into the model or relational expression already stored in the calculation device 40.

Next, the creation of a model or a relational expression used in the biological treatment apparatus shown in FIG. 1 will be described. The model or the relational expression is created by investigating in advance the relationship between the process amount of gas generated from the water in the biological treatment tank 10, the water quality in the biological treatment tank 10, and the water quality related to the operation index of the inflow water to the biological treatment tank 10. In order to create the model or the relational expression, the biological treatment apparatus shown in FIG. 1 is provided with an inflow water quality measuring unit 33 that measures the water quality of the inflow water as an operation index for the inlet pipe 13 that supplies the inflow water to the biological treatment tank 10. The water quality measured by the inflow water quality measuring unit 33 is preferably at least one of organic matter concentration, nitrogen concentration, phosphorus concentration, DO, and ORP, and more preferably any of the organic matter concentrations TOC, BOD, and COD. The calculation device 40 creates the model or the relational expression based on the water quality of the inflow water measured by the inflow water quality measuring unit 33, the measured value at the gas measuring unit 31 at the time of measuring the water quality of the inflow water, and the measured value at the water quality measuring unit 32. A certain number of combinations (e.g., several tens to a hundred sets) of measured values of the process amount of gas, the measured values of the water quality in the biological treatment tank 10 measured by the water quality measuring unit 32, and the measured values of the water quality of the inflow water measured by the inflow water quality measuring unit 33 are obtained, and multiple regression analysis (when deriving a relational expression) or neural network learning (when creating a model) is performed based on these sets of data. Note that the process amount of gas and the water quality vary depending on the configuration and size of the biological treatment tank 10, the size of the gas phase in the biological treatment tank 10, the type of biological treatment, etc., so models and relational expressions may be created for each biological treatment tank 10. Furthermore, the relationship between the water quality of the inflow water and the measured process amount of gas and the water quality of the water in the biological treatment tank 10 may vary depending on the type or source of the inflow water, so a model may be created for each type and source of the inflow water.

3 shows an example of a database that stores sets of measured values of the gas process quantity, measured values of the water quality in the biological treatment tank 10, and measured values of the influent water quality. Here, it is assumed that the carbon dioxide concentration is measured as the gas process quantity, the water temperature and pH are measured as the water quality in the biological treatment tank 10, and the TOC concentration is measured as the influent water quality. Then, by performing a multiple regression analysis on such a database, a relational equation for calculating the organic matter concentration as an operation index, as shown below, is obtained.
C=b ₁ X+b ₂ Y+b ₀
Here, C is the organic matter concentration as an operation index, X is the gas concentration as the gas process amount, Y is the water quality in the biological treatment tank 10, and b ₀ , b ₁ , and b ₂ are constants obtained by multiple regression analysis.

When generating a model using a neural network, the neural network can be trained using supervised learning based on a database such as that shown in Figure 3, with the gas process volume Xn and water quality Yn as input values (Xn, Yn) and the organic matter concentration Cn as an operation index as the output value (Cn). A model using a properly trained neural network provides a more accurate organic matter concentration as an operation index than a relational equation based on multiple regression analysis.

Figure 4 shows a biological treatment device in which a mechanism for adding nutrients to the inflow water has been added to the biological treatment device shown in Figure 1. For example, in biological treatment such as aerobic treatment, nutrients are necessary for microorganisms to grow while maintaining their high decomposition activity, and when nutrients are insufficient in the inflow water to the biological treatment tank 10, nutrients must be added to the inflow water in the biological treatment tank 10 or in the stage before the biological treatment tank 10. In the biological treatment device shown in Figure 4, a nutrient storage tank 21 is provided for storing a solution of nutrients (i.e., nutrient liquid), and the nutrient storage tank 21 and the inlet pipe 13 are connected via a nutrient liquid pipe 22. The nutrient liquid pipe 22 is provided with a pump 23 for feeding the nutrient liquid. Therefore, in this biological treatment device, it is possible to add nutrients to the inflow water that flows through the inlet pipe 13 and is supplied to the biological treatment tank 10, and the amount of nutrients added to the inflow water can be controlled by controlling the pump 23. Nutrients can be roughly divided into nutrients containing nitrogen and phosphorus, and trace elements that are required in smaller amounts than nitrogen and phosphorus. Trace elements include alkali metals such as sodium, potassium, calcium, and magnesium, and metals such as iron, manganese, and zinc. Urea and ammonium salts can be used as nitrogen sources. Phosphorus and phosphates can be used as phosphorus sources.

Next, the control of the amount of added nutrients in the biological treatment device shown in FIG. 4 will be described. It is recommended that the amount of added nutrients (nutrients and trace metals) when added to the inflow water to the biological treatment tank be proportional to the organic matter concentration in the inflow water. For example, it is recommended that the amount of added nitrogen (N) and phosphorus (P) in aerobic treatment be BOD:N:P=100:5:1 by mass, using BOD as the operating index. Therefore, in the biological treatment device shown in FIG. 4, the discharge amount and operating time of the pump 23 are controlled based on the operating index calculated by the calculation device 40, and the presence or absence and amount of added nutrients are controlled. This allows nutrients to be added to the inflow water in an optimal amount without measuring the organic matter concentration (e.g., BOD) in the inflow water.

In the biological treatment apparatus shown in FIG. 1, air is blown into the biological treatment tank 10, but the atmosphere usually contains about 400 ppm of carbon dioxide. When measuring the carbon dioxide concentration to estimate the amount of carbon dioxide generated by biological treatment, it is necessary to take into account the amount of carbon dioxide originally contained in the blown air. When the fluctuation in the amount of carbon dioxide in the blown air is small, the model created as described above already includes the contribution of the carbon dioxide contained in the blown air, so the amount of nutrients to be added can be determined using the model without measuring the carbon dioxide concentration in the blown air. However, when the carbon dioxide concentration in the blown air fluctuates, such as when air containing boiler exhaust gas is blown in at a factory, it is necessary to determine the amount of nutrients to be added by making a correction according to the carbon dioxide concentration in the gas blown into the biological treatment tank 10. FIG. 5 shows a biological treatment apparatus that performs such a correction according to the carbon dioxide concentration blown into the biological treatment tank 10.

The biological treatment device shown in FIG. 5 is similar to the biological treatment device shown in FIG. 1, but differs from that shown in FIG. 1 in that a carbon dioxide concentration sensor 35 is provided in the gas pipe 14 at the outlet side of the blower 15 to measure the carbon dioxide concentration in the air being blown in. The measurement value of the carbon dioxide concentration sensor 35 provided in the gas pipe 14 is also sent to the control device 40. The control device 40 applies the difference between the measurement value of the carbon dioxide concentration sensor 35 and the measurement value of the gas measurement unit 31 and the measurement value obtained by the water quality measurement unit 32 to a model to calculate the BOD of the inflow water, and controls the pump 23 based on the BOD.

Next, the present invention will be explained in more detail with reference to examples and comparative examples.

[Test conditions]
First, the common test conditions for each Example and Comparative Example will be described. A single-stage biological treatment tank with a volume of 19 L was used, and biological treatment was performed by aerobic treatment of influent water, which was organic wastewater. Aerobic microorganisms were supported on a sponge carrier made of hydrophobic polyurethane resin, and such sponge carriers were filled in the biological treatment tank at a bulk volume of 30% of the volume of the biological treatment tank. The residence time in the biological treatment tank was 8 hours. Wastewater containing isopropyl alcohol was used as the influent water. The nitrogen (N) concentration in the influent water was 2 mg/L or less, and the phosphorus (P) concentration was 0.1 mg or less. The pH of the water in the biological treatment tank was 5.6 to 7.8. The air flow rate in the aeration was set to 10 L/min, but actually fluctuated between 9.7 and 10.3 L/min.

Nutrients (nitrogen (N) and phosphorus (P) ) were added to the inflow water, and the carbon dioxide concentration discharged from the water in the biological treatment tank, as well as the pH, water temperature, and ORP of the water in the biological treatment tank were monitored. This monitoring was repeated while changing the TOC in the inflow water in the range of 50 mg/L to 350 mg/L.

[Comparative Example 1]
A simple regression analysis was performed using the measured values of carbon dioxide concentration and TOC concentration to derive a relational equation for calculating the TOC concentration from the carbon dioxide concentration. The TOC concentration was then estimated from the carbon dioxide concentration using this relational equation, and the coefficient of determination ^R2 with the measured TOC concentration was calculated to be 0.770.

[Example 1]
A multiple regression analysis was performed using the measured values of carbon dioxide concentration, water temperature, and TOC concentration, and a relational equation was derived to calculate the TOC concentration from the carbon dioxide concentration and water temperature.The TOC concentration was then estimated from the carbon dioxide concentration and water temperature using this relational equation, and the coefficient of determination ^R2 with the measured TOC concentration was calculated to be 0.801.

[Example 2]
A multiple regression analysis was performed using the measured values of the carbon dioxide concentration, ORP, and TOC concentration, and a relational equation was derived for calculating the TOC concentration from the carbon dioxide concentration and ORP. The TOC concentration was then estimated from the carbon dioxide concentration and ORP using this relational equation, and the coefficient of determination ^R2 with the actually measured TOC concentration was calculated to be 0.836.

[Example 3]
A multiple regression analysis was performed using the measured values of the carbon dioxide concentration, pH, and TOC concentration, and a relational equation was derived for calculating the TOC concentration from the carbon dioxide concentration and pH. The TOC concentration was then estimated from the carbon dioxide concentration and pH using this relational equation, and the coefficient of determination ^R2 with the actually measured TOC concentration was calculated to be 0.858.

[Example 4]
A multiple regression analysis was performed using the measured values of carbon dioxide concentration, water temperature, pH, and TOC concentration, and a relational equation was derived to calculate the TOC concentration from the carbon dioxide concentration, water temperature, and pH.The TOC concentration was then estimated from the carbon dioxide concentration, water temperature, and pH using this relational equation, and the coefficient of determination ^R2 with the actually measured TOC concentration was calculated to be 0.859.

[Example 5]
A model was constructed using a neural network by performing supervised learning using the measured values of carbon dioxide concentration and water temperature as inputs and the measured values of TOC concentration as output. The TOC concentration was estimated from the carbon dioxide concentration and water temperature using this trained model, and the coefficient of determination ^R2 with the measured TOC concentration was calculated to be 0.927.

[Example 6]
A model was constructed using a neural network by performing supervised learning using the measured values of carbon dioxide concentration and ORP as inputs and the measured value of TOC concentration as output. The TOC concentration was estimated from the carbon dioxide concentration and ORP using this trained model, and the coefficient of determination ^R2 with the actually measured TOC concentration was calculated to be 0.933.

[Example 7]
A model was constructed using a neural network by performing supervised learning using the measured values of carbon dioxide concentration and pH as input and the measured value of TOC concentration as output. The TOC concentration was estimated from the carbon dioxide concentration and pH using this trained model, and the coefficient of determination ^R2 with the measured TOC concentration was calculated to be 0.927.

[Example 8]
A model was constructed using a neural network by performing supervised learning using the measured values of carbon dioxide concentration, water temperature, and pH as inputs and the measured value of TOC concentration as output. The TOC concentration was estimated from the carbon dioxide concentration, water temperature, and pH using this trained model, and the coefficient of determination ^R2 with the actually measured TOC concentration was calculated to be 0.926.

[Example 9]
A model was constructed using a neural network by performing supervised learning using the measured values of carbon dioxide concentration, ORP, water temperature, and pH as inputs and the measured value of TOC concentration as output. The TOC concentration was estimated from the carbon dioxide concentration, ORP, and water temperature using this trained model, and the coefficient of determination ^R2 with the actually measured TOC concentration was calculated to be 0.949.

[Example 10]
The carbon dioxide flow rate was calculated by multiplying the carbon dioxide concentration by the aeration flow rate. The measured values of the carbon dioxide flow rate, ORP, water temperature, and pH were input, and the measured value of the TOC concentration was output, and supervised learning was performed to construct a model using a neural network. The TOC concentration was estimated from the carbon dioxide flow rate, ORP, and water temperature using this trained model, and the coefficient of determination ^R2 with the measured TOC concentration was calculated to be 0.971.

REFERENCE SIGNS LIST 10 Biological treatment tank 11 Carrier 12 Aeration device 13 Inlet pipe 14 Gas pipe 15 Blower 16 Lid 21 Nutrient storage tank 22 Nutrient liquid pipe 23 Pump 31 Gas measurement section 32 Water quality measurement section 33 Inflow water quality measurement section 35 Carbon dioxide concentration sensor 40 Calculation device

Claims (8)

A method for calculating an operation index used when biologically treating organic wastewater in a biological treatment tank, comprising:
calculating the operation index from the measured value of the process amount of gas released from the water in the biological treatment tank and the measured value of the water quality of the water in the biological treatment tank based on a predetermined relationship between the process amount of gas released from the water in the biological treatment tank, the water quality of the water in the biological treatment tank, and the water quality of the water inflowing into the biological treatment tank;
The process quantity of the gas is at least one of a concentration, a flow rate, a volume, a pressure, and an amount of substance of the gas;
The water quality of the water in the biological treatment tank includes at least one of water temperature, pH, and oxidation-reduction potential,
The operating indicator is an organic matter concentration in the influent;
Calculation method. The calculation method according to claim 1, wherein the gas is carbon dioxide. The calculation method according to claim 1 or 2, wherein the relationship is represented by a neural network model trained using a data set in which the measured value of the process amount of the gas and the measured value of the water quality in the biological treatment tank are input values, and the operation index is output values. A biological treatment method for biologically treating organic wastewater, comprising:
Calculating the driving index by the calculation method according to any one of claims 1 to 3,
A biological treatment method in which at least one of controlling the amount of nutrients added to the inflow water and controlling aeration in the biological treatment tank is performed in accordance with the calculated operating index, thereby performing biological treatment on the inflow water in the biological treatment tank. A calculation device for calculating an operation index used when biologically treating organic wastewater in a biological treatment tank,
A gas measurement unit that measures a process amount of gas released from the water in the biological treatment tank;
A water quality measuring unit for measuring the water quality in the biological treatment tank;
a calculation means for calculating the operation index from the measurement values of the gas measurement unit and the measurement values of the water quality measurement unit based on a predetermined relationship between the process amount of gas released from the water in the biological treatment tank, the water quality of the water in the biological treatment tank, and the water quality of the inflow water to the biological treatment tank;
Equipped with
The process quantity of the gas is at least one of a concentration, a flow rate, a volume, a pressure, and an amount of substance of the gas;
The water quality of the water in the biological treatment tank includes at least one of water temperature, pH, and oxidation-reduction potential,
The operating indicator is an organic matter concentration in the influent;
Calculation device. The calculation device according to claim 5, wherein the gas is carbon dioxide. Further, an inflow water quality measuring unit is provided for measuring the water quality of the inflow water,
The calculation device according to claim 5 or 6, wherein the calculation means trains a neural network using a data set in which the measurement values of the gas measurement unit and the measurement values of the water quality measurement unit are input values and the measurement values of the inflow water quality measurement unit are output values, and represents the relationship using a neural network model obtained by training. A biological treatment device for biologically treating organic wastewater,
A calculation device according to any one of claims 5 to 7,
An adding means for adding nutrients to the inflow water, and/or an aeration means for diffusing aeration into the biological treatment tank;
Equipped with
At least one of the adding means and the aeration means is controlled in accordance with the calculated operation index.

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