Water treatment system, control device, water treatment method, and program

Abstract

To provide a water treatment system capable of appropriately controlling an amount of flocculant added according to the biological treatment conditions.SOLUTION: A water treatment system 1 has a biological reaction tank 20 for biologically treating treated water containing organic matter, a flocculation reaction tank 21 for storing biologically treated water, a gas concentration measuring means 11 for measuring the concentration of gas released from the treated water stored in the biological reaction tank 20, and a control means 12 for controlling an amount of a flocculant added to the biologically treated water stored in the flocculation reaction tank 21 based on the measured concentration of gas measured by the gas concentration measuring means 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water treatment system, a control device, a water treatment method, and a program.

Background Art

[0002] In sewage treatment plants, water purification plants, wastewater treatment facilities, etc., water treatment is performed according to the physical properties of pollutants. Among them, there is one that uses biological treatment to decompose organic substances into microorganisms. In this type of water treatment, after subjecting raw water containing organic substances (hereinafter, water to be treated) to biological treatment, a coagulation solid-liquid separation treatment is performed to remove suspended substances contained in the biologically treated water. Since most of the organic substances (especially low-molecular organic substances) contained in the water to be treated cannot be coagulated in their original state, they are subjected to biological treatment to make them in a coagulable state. In the coagulation solid-liquid separation treatment, a coagulation operation of adding a coagulant to coarsen suspended substances and a solid-liquid separation operation of separating the aggregates (flocs) generated by the coagulation operation are performed. When the load of organic substances contained in the water to be treated changes over time, the amount of biologically derived suspended substances (substances generated by biological growth, biological dead bodies, etc.) contained in the biologically treated water also changes accordingly. Therefore, it is preferable to appropriately control the addition amount of the coagulant in the coagulation operation according to the biological treatment situation. Patent Document 1 describes a treatment method in which the BOD (Biochemical Oxygen Demand) concentration of the biologically treated water flowing into the coagulation reaction tank is measured with an absorbance sensor, and the addition amount of the coagulant is controlled based on the measured value of the BOD concentration.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the treatment method described in Patent Document 1, the absorbance sensor measures the absorption or dispersion by the turbidity components in the biologically treated water by passing a light beam through the biologically treated water. However, the biologically treated water also contains suspended substances other than the substances generated by biological treatment. For this reason, it is difficult for the absorbance sensor to accurately measure the BOD concentration. In addition, since the absorbance sensor is inserted into the flow path of the biologically treated water, there is a risk that the sensor part will be contaminated and the BOD concentration cannot be accurately measured. As described above, in the treatment method described in Patent Document 1, since the BOD concentration cannot be accurately measured, it is difficult to appropriately control the addition amount of the flocculant according to the biological treatment situation.

[0005] An object of the present invention is to provide a water treatment system, a control device, a water treatment method, and a program capable of appropriately controlling the addition amount of a flocculant according to the biological treatment situation.

Means for Solving the Problems

[0006] According to one aspect of the present invention, a biological reaction tank for biologically treating water to be treated containing organic matter, a coagulation reaction tank for storing the biologically treated water, gas concentration measuring means for measuring the concentration of the gas released from the water to be treated stored in the biological reaction tank, control means for controlling the addition amount of the flocculant added to the biologically treated water stored in the coagulation reaction tank based on the measured value of the concentration of the gas measured by the gas concentration measuring means, is provided.

[0007] The gas concentration measuring means preferably includes a carbon dioxide concentration measuring device.

[0008] imaging means for imaging the aggregates contained in the biologically treated water to which the flocculant has been added, image processing means for calculating a feature amount indicating the aggregation state of the aggregates from the image captured by the imaging means, is further provided. The control means preferably controls the addition amount of the flocculant based on the measured value of the concentration of the gas measured by the gas concentration measuring means and the feature amount of the aggregate calculated by the image processing means.

[0009] The image processing means preferably detects edge pixels, which are pixels in the image captured by the imaging means and have a color difference from adjacent pixels exceeding a specified value, and calculates the feature amount of the aggregate based on the edge pixels.

[0010] The control means is capable of executing a first control for controlling the addition amount of the flocculant based on the measured value of the concentration of the gas measured by the gas concentration measuring means and a second control for controlling the addition amount of the flocculant based on the feature amount of the aggregate calculated by the image processing means. It is preferable to execute one of the first and second controls every predetermined time and execute the other of the first and second controls within the period of the predetermined time.

[0011] The control means preferably executes the second control within the period of the predetermined time and switches to the first control when the change amount of the concentration of the gas per unit time exceeds a threshold value.

[0012] The control means preferably executes the first control within the period of the predetermined time and switches to the second control when the change amount of the feature amount of the aggregate per unit time exceeds a threshold value.

[0013] It is preferable to further include a flotation separation tank for floating and separating the aggregate from the biologically treated water to which the flocculant is added.

[0014] Also, according to another aspect of the present invention, a step of biologically treating the water to be treated containing organic substances; a step of measuring the concentration of the gas generated in the biological treatment; A step of adding a flocculant to the biologically treated water that has undergone the biological treatment and controlling the addition amount of the flocculant based on the measured value of the concentration of the gas is included in the water treatment method provided.

[0015] Furthermore, according to still another aspect of the present invention, Gas concentration measuring means for measuring the concentration of the gas generated when biologically treating the water to be treated containing organic matter, A control device is provided that has control means for controlling the addition amount of the flocculant added to the biologically treated water obtained by biologically treating the water to be treated based on the measured value of the concentration of the gas measured by the gas concentration measuring means.

[0016] Furthermore, according to still another aspect of the present invention, To a computer, A procedure for obtaining the measured value of the concentration of the gas from the gas concentration measuring means for measuring the concentration of the gas generated when biologically treating the water to be treated containing organic matter, A program is provided for executing a procedure for controlling the addition amount of the flocculant added to the biologically treated water obtained by biologically treating the water to be treated based on the measured value of the concentration of the gas.

Advantages of the Invention

[0017] According to the present invention, the addition amount of the flocculant can be appropriately controlled according to the biological treatment situation.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

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Figure 5

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Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the components described in the embodiments are merely examples and are not intended to limit the scope of the present invention thereto.

[0020] (First Embodiment) FIG. 1 is a block diagram showing the configuration of the water treatment system according to the first embodiment of the present invention. Referring to FIG. 1, the water treatment system 1 includes a control device 10, a biological reaction tank 20, a coagulation reaction tank 21, a floc formation tank 22, a flotation separation tank 23, and a flocculant storage tank 24.

[0021] The biological reaction tank 20 is a tank that stores the water to be treated (raw water) containing organic substances and performs biological treatment to decompose the organic substances by microorganisms. The water to be treated may be, for example, wastewater provided by customers, and may contain suspended substances called SS (Suspended Solid) and substances to be insolubilized. As the biological treatment, either an aerobic treatment method or an anaerobic treatment method can be applied. In this embodiment, a biofilm method, which is an example of the aerobic treatment method, is applied. The biofilm method is a method of treating organic substances in the water to be treated by a biological reaction using microorganisms attached to a carrier. Since oxygen is required for microorganisms to consume organic substances, the biological reaction tank 20 is provided with a mechanism for aerating the water to be treated (an air bubbling mechanism for supplying oxygen required for microorganisms). Aeration causes microorganisms to grow and generate floating suspended substances. The floating suspended substances include organic and inorganic floating substances in addition to a large number of microorganisms.

[0022] The coagulation reaction tank 21 is connected to the biological reaction tank 20 via a pipe, and the biologically treated water flows from the biological reaction tank 20 into the coagulation reaction tank 21. The biologically treated water is the result of biologically treating the water to be treated and contains biological-derived suspended substances (substances generated by the growth of microorganisms, biological dead bodies, etc.). The coagulation reaction tank 21 is a tank that stores the biologically treated water and performs a first coagulation operation by adding a coagulant to the biologically treated water. In the first coagulation operation, aggregates (flocs), which are minute lumps obtained by aggregating suspended substances by a coagulation reaction, are precipitated. The coagulant used in the first coagulation operation is, for example, an inorganic coagulant such as an aluminum-based (polyaluminum chloride (PAC), ferric sulfate, etc.) or an iron-based (polyiron, ferric chloride) coagulant, or an organic coagulant, but is not limited thereto.

[0023] In addition, a pH adjuster for adjusting the hydrogen ion exponent (pH) of the biologically treated water is also added to the flocculation reaction tank 21. Here, the hydrogen ion exponent (pH) represents the degree of acidity and alkalinity of the solution. The flocculation reaction tank 21 is provided with a stirring mechanism, and it is possible to stir the flocculant and the pH adjuster. Further, a buffer tank and a pump may be provided in the middle of the pipe between the flocculation reaction tank 21 and the biological reaction tank 20 as needed to appropriately adjust the inflow rate of the biologically treated water into the flocculation reaction tank 21.

[0024] The floc formation tank 22 is connected to the flocculation reaction tank 21 via a pipe, and the biologically treated water subjected to the first flocculation operation flows from the flocculation reaction tank 21 into the floc formation tank 22. The floc formation tank 22 is a flocculation reaction tank that performs a second flocculation operation of adding a flocculant to the biologically treated water subjected to the first flocculation operation to coarsen the flocs. In the second flocculation operation, larger flocs are formed by entrapping suspended substances in the biologically treated water and the minute flocs formed in the first flocculation operation. The flocculant used in the second flocculation operation is an organic flocculant (polymer flocculant) such as a polymer. The polymer may be cationic or anionic.

[0025] The floatation separation tank 23 is connected to the floc formation tank 22 via a pipe, and the biologically treated water subjected to the second flocculation operation flows from the floc formation tank 22 into the floatation separation tank 23. The floatation separation tank 23 is a solid-liquid separation tank. In the floatation separation tank 23, pressurized water in which gas is dissolved under pressure is injected from the lower part of the tank, and bubbles are attached to the flocs to give buoyancy for floatation separation. The clean water in the lower layer of the stored water in the floatation separation tank 23 is discharged as the floatation separation treated water. The floatation separation treated water is discharged into, for example, a river or the ocean, or reused as recovered water.

[0026] The flocculant storage tank 24 stores the flocculant used in the first flocculation operation. The flocculant storage tank 24 is connected to the flocculation reaction tank 21 via a pipe, and it is possible to add the flocculant to the flocculation reaction tank 21. A pump 25 for sending out the flocculant stored in the flocculant storage tank 24 to the flocculation reaction tank 21 is provided in the pipe between the flocculant storage tank 24 and the flocculation reaction tank 21. The pump 25 can adjust the amount of the flocculant sent out according to a flocculant control signal S11 for controlling the addition amount of the flocculant. The flocculant storage tank 24 and the pump 25 are an example of the flocculant addition means.

[0027] The control device 10 controls the addition amount of the flocculant according to the biological treatment situation. The control device 10 includes a gas concentration measuring means 11 for measuring the concentration of the gas released from the biological reaction tank 20, and a control means 12 for controlling the addition amount of the flocculant based on the measured value of the gas concentration measured by the gas concentration measuring means 11.

[0028] The gas concentration measuring means 11 includes a sensor part 11a inside the biological reaction tank 20, and measures the concentration of the gas generated in the biological treatment through this sensor part 11a. The gas concentration measuring means 11 supplies a measurement signal S10 indicating the gas concentration measurement value to the control means 12. The gas to be measured is oxygen, nitrogen, hydrogen sulfide, carbon dioxide, etc. From the viewpoint of the control accuracy when controlling the addition amount of the flocculant according to the biological treatment situation, it is preferable to use a carbon dioxide concentration measuring device (CO2 sensor) for the sensor part 11a.

[0029] The control means 12 receives the measurement signal S10 from the gas concentration measuring means 11, and controls the addition amount of the flocculant to the flocculation reaction tank 21 based on the gas concentration measurement value indicated by the measurement signal S10. The control means 12 supplies a flocculant control signal S11 for controlling the addition amount of the flocculant to the pump 25. The control means 12 can control the addition amount of the flocculant continuously or stepwise by controlling the delivery amount of the pump 25.

[0030] Figure 2 is a block diagram showing a configuration example of the control means 12. As shown in Figure 2, the control means 12 includes a control unit 121 and a storage unit 122. The control unit 121 is a computer including a microprocessor or the like. The control unit 121 may be configured by, for example, a PLC (Programmable Logic Controller). The storage unit 122 is composed of a semiconductor memory or the like and stores information (for example, programs and data) necessary for operating the control device 10. For example, a program for controlling the addition amount of the flocculant based on the gas concentration measurement value, data and calculation results necessary for the control, etc. are stored in the storage unit 122. Note that Figure 2 shows only the main components related to the present embodiment among the components of the control device 10.

[0031] Figure 3 shows an example of control characteristic data for controlling the addition amount of the flocculant based on the gas concentration. In Figure 3, the vertical axis represents the addition amount of the flocculant, and the horizontal axis represents the gas concentration in the biological reaction tank. The control characteristic data defines the addition amount of the flocculant for a stepwise change in the gas concentration. This control characteristic data is stored in the storage unit 122. The control unit 121 can calculate the addition amount of the flocculant based on the measurement value of the gas concentration measured by the gas concentration measuring means 11 with reference to the control characteristic data stored in the storage unit 122.

[0032] Figure 4 shows another example of control characteristic data for controlling the addition amount of the flocculant based on the gas concentration. Similar to Figure 3, in Figure 4, the vertical axis represents the addition amount of the flocculant, and the horizontal axis represents the gas concentration in the biological reaction tank. The control characteristic data defines the addition amount of the flocculant for a continuous change in the gas concentration. This control characteristic data is also stored in the storage unit 122. The control unit 121 can calculate the addition amount of the flocculant based on the measurement value of the gas concentration measured by the gas concentration measuring means 11 with reference to the control characteristic data stored in the storage unit 122.

[0033] Next, the water treatment method performed in the above-described water treatment system 1 will be described. Here, for convenience, only the steps related to the process of controlling the addition amount of the flocculant will be described. FIG. 5 is a flowchart showing an example of a water treatment method. First, in the biological reaction tank 20, the water to be treated containing organic matter is biologically treated (step S21). Next, the gas concentration measuring means 11 measures the concentration of the gas generated by the biological treatment (step S22). Then, in the coagulation reaction tank (coagulation reaction tank 21 / floc formation tank 22), a coagulant is added to the biologically treated water that has undergone biological treatment, and the control means 12 controls the addition amount of the coagulant based on the measured value of the gas concentration (step S23).

[0034] In the coagulation treatment / addition amount control process of step S23, specifically, in the coagulation reaction tank 21, a coagulant for the first coagulation operation is added to the biologically treated water that has undergone biological treatment, and further, in the floc formation tank 22, a coagulant for the second coagulation operation is added. Then, the control unit 121 refers to the control characteristic data stored in the storage unit 122, calculates the addition amount of the coagulant used in the first coagulation operation based on the measured value of the gas concentration measured by the gas concentration measuring means 11, and controls the addition amount of the coagulant to the coagulation reaction tank 21 based on the calculation result.

[0035] According to the water treatment system 1 of the present embodiment described above, the following operational effects are achieved. For example, bacteria, which are microorganisms, generate carbon dioxide when they eat organic matter. When the load of organic matter (pollution load) in the water to be treated increases, the amount of carbon dioxide increases, and accordingly, the amount of biological-derived suspended matter also increases. Thus, there is a correlation between the concentration of the gas generated by biological treatment and the amount of biological-derived suspended matter, and when the gas concentration changes, the amount of biological-derived suspended matter also changes accordingly. In the water treatment system 1, the above correlation is utilized to control the addition amount of the coagulant according to the concentration of the gas generated by biological treatment. Therefore, the addition amount of the coagulant can be appropriately controlled according to the biological treatment situation.

[0036] Also, by appropriately controlling the addition amount of the coagulant, it is possible to reduce the cost of the coagulant and the amount of sludge generated. Furthermore, a stable coagulation solid-liquid separation treatment can be performed on the water to be treated (raw water) in which the concentrations of organic matter and suspended substances change. In addition, the water recovery facility employs a system including processes such as biological treatment, coagulation solid-liquid separation treatment, and membrane filtration (turbidity removal membrane, reverse osmosis membrane (RO membrane)). If the present invention is used in this system, it is possible to reduce the load on membrane filtration. Therefore, it is possible to achieve stable operation of the entire system.

[0037] In the water treatment system 1 of the present embodiment, the addition amount of the coagulant to the coagulation reaction tank 21 is controlled. Instead of this, the addition amount of the coagulant to the floc formation tank 22 may be controlled. In this case, a coagulant storage tank and a pump corresponding to the coagulant storage tank 24 and the pump 25 are provided for the floc formation tank 22. Further, the addition amount of the coagulant may be controlled for both the coagulation reaction tank 21 and the floc formation tank 22. However, since adjustment of the first coagulation operation is important in the coagulation operation, it is preferable to adjust the addition amount of the coagulant used in the first coagulation operation.

[0038] In the present embodiment, pressure flotation separation is used for solid-liquid separation, but sedimentation separation may be used instead. However, since the density of the suspended substances (SS) generated in the biological treatment is low, it is preferable to use pressure flotation separation. Furthermore, a tank for performing coagulation solid-liquid separation treatment may be arranged in front of the biological reaction tank 20 for the purpose of roughly removing suspended substances (SS) and BOD components.

[0039] (Second Embodiment) FIG. 6 is a block diagram showing the configuration of a water treatment system according to the second embodiment of the present invention. The water treatment system 2 of the present embodiment is different from the first embodiment in that the control device 10 includes the image processing means 13 and the imaging means 14. Since the configuration excluding the image processing means 13 and the imaging means 14 is the same as that described in the first embodiment, detailed description of those configurations is omitted here.

[0040] The imaging means 14 is attached to the flocculation reaction tank 21. The imaging means 14 images the aggregates (hereinafter referred to as flocs) contained in the biologically treated water to which the flocculant has been added. The imaging means 14 may be any device that can image the flocs, such as a camera or an image sensor. Considering maintainability and cost-effectiveness, it is preferable to use a non-contact type image sensor as the imaging means 14, and it is more preferable to use an infrared sensor.

[0041] The image processing means 13 calculates a feature amount indicating the aggregation state of the flocs from the image captured by the imaging means 14. The image processing means 13 detects edge pixels, which are pixels whose color difference from adjacent pixels in the image captured by the imaging means 14 exceeds a specified value, and calculates the feature amount of the flocs based on the edge pixels. For example, the image processing means 13 calculates the sum of the number of edge pixels per unit area as the feature amount of the flocs. Here, the unit area is the imaging range.

[0042] Specifically, the image processing means 13 performs shading processing on the image captured by the imaging means 14, performs differential processing on the image subjected to the shading processing, and acquires edge pixels from the result of the differential processing. In the shading processing, the shading (brightness and darkness) of the image is digitized into three or more gradations, for example, 256 gradations (0 to 255 gradations). In the differential processing, the numerical data obtained as a result of the shading processing is subjected to differential processing to detect the change points (edges) of the numerical data of the shading (brightness). The larger the shading change that can form an edge, the larger the differential value. The number of pixels of the edge obtained from the result of the differential processing may be used as the above-mentioned number of edge pixels.

[0043] The control means 12 controls the addition amount of the flocculant based on the measured value of the gas concentration measured by the gas concentration measuring means 11 and the feature amount of the flock calculated by the image processing means 13. The control means 12 can execute a first control for controlling the addition amount of the flocculant based on the measured value of the gas concentration measured by the gas concentration measuring means 11 and a second control for controlling the addition amount of the flocculant based on the feature amount of the aggregate calculated by the image processing means 13. The control means 12 executes one of the first and second controls every predetermined time, and may execute the other of the first and second controls within a period of the predetermined time.

[0044] FIG. 7 shows an example of the control of the addition amount of the flocculant. The first control (control based on the gas concentration) is executed every specified time T1, and within the period of the specified time T1, the second control (control based on the edge pixels) is executed every time T2.

[0045] Specifically, at time t1, the first control is executed. The gas concentration at time t1 is A, and the addition amount of the flocculant corresponding to this gas concentration A is set. During the period from time t1 to time t2 when the specified time T1 has elapsed, the second control is executed every time T2. In the second control, for example, the feature amount of the flock is compared with a preset threshold value, and based on the result of the comparison, it is determined whether to increase, decrease, or maintain the addition amount of the flocculant. Therefore, within the period from time t1 to time t2, the addition amount of the flocculant increases or decreases according to the feature amount of the flock. After that, at time t2, the first control is executed again. The gas concentration at time t2 is B (>A), and the addition amount of the flocculant corresponding to this gas concentration B is set.

[0046] According to the water treatment system 2 of the present embodiment described above, the following operational effects are achieved. The dosage of the flocculant for the bio-derived suspended substances (such as bacterial cells and metabolites) can be calculated from the concentration of the gas generated in the biological treatment. However, the biologically treated water flowing out from the biological reaction tank 20 contains suspended substances that can be flocculated, but are difficult to calculate only based on the gas concentration. For example, bio-derived EPS (Extracellular polymeric substances), substances that cannot be decomposed by microorganisms (such as inorganic suspended substances contained in the water to be treated before biological treatment), etc.

[0047] In the water treatment system 2 of the present embodiment, by the first control, the dosage of the flocculant for the bio-derived suspended substances (such as bacterial cells and metabolites) can be appropriately adjusted. Also, by the second control, the dosage of the flocculant can be appropriately adjusted for the suspended substances including bio-derived EPS and substances that cannot be decomposed by microorganisms.

[0048] Also, when a membrane filtration device such as a microfiltration (MF) membrane, an ultrafiltration (UF) membrane, or a reverse osmosis (RO) membrane is provided at the subsequent stage of the flotation separation tank 23, bio-derived EPS becomes a substance that causes membrane fouling. Therefore, it is necessary to reduce the amount of EPS in the flocculation operation. FIG. 8 shows an example of a measurement of LC-OCD (Liquid Chromatography-Organic Carbon Detection) before and after the flocculation sub-liquid separation treatment. LC-OCD is a method of separating organic substances by molecular weight and measuring the organic substance concentration of each component. In FIG. 8, the upper side shows the chromatogram of the biologically treated water, and the lower side shows the chromatogram of the flocculation solid-liquid separation treated water. From these chromatograms, it can be seen that by using the first control and the second control in combination, the amount of the suspended substances including bio-derived EPS has decreased. By reducing the amount of EPS in this way, the filtration performance of the membrane filtration device can be maintained.

[0049] In addition, when the turbidity of the water to be treated (e.g., organic matter load) increases and the gas concentration rises rapidly, it is preferable to execute the first control even within the period of the specified time T1. This will be specifically described below. In the second control (control based on edge pixels), since the increase or decrease in the dosage of the flocculant changes slowly, when the gas concentration changes rapidly, it may become impossible to appropriately perform the flocculation operation. To solve this problem, the gas concentration is measured at predetermined time intervals, and when the change amount of the gas concentration exceeds the threshold value, the first control is executed. Specifically, within the period of the specified time T1, when the change amount of the gas concentration per unit time exceeds the threshold value, the control is switched from the second control to the first control. Thereby, the flocculation operation can be appropriately performed. Here, the unit time is, for example, the time interval for executing the second control.

[0050] Also, the second control may be executed every predetermined time (T1), and the first control may be executed within the period of the predetermined time (T1). According to this control flow, for example, when a large amount of organic matter that cannot be biologically treated is present in the water to be treated, it is possible to appropriately control the dosage of the flocculant.

[0051] Furthermore, in the above control flow, when the change amount of the feature amount of the flocs per unit time exceeds the threshold value during the period of the specified time (T1) in which the control means 12 is executing the first control, the control may be switched from the first control to the second control. Thereby, when the concentration of suspended substances containing EPS derived from organisms and substances that cannot be decomposed by microorganisms in the water to be treated increases rapidly, the flocculation operation can be appropriately performed.

[0052] In this embodiment, the imaging means 14 is attached to the agglutination reaction tank 21, but is not limited thereto. The imaging means 14 may be attached to the floc formation tank 22. In this case, the imaging means 14 images the flocs in the biologically treated water (the biologically treated water in which the first agglutination operation has been performed) stored in the floc formation tank 22. However, since a certain amount of time elapses from the first agglutination operation to the second agglutination operation, the addition amount of the flocculant is calculated from an image after a certain amount of time has elapsed from the time point (injection time point) of the first agglutination operation. Considering the problem of error due to this time lag, from the viewpoint of accurately controlling the addition amount of the flocculant, it is preferable to attach the imaging means 14 to the agglutination reaction tank 21.

[0053] Also, the imaging means 14 may be attached to both the agglutination reaction tank 21 and the floc formation tank 22. In this case, the addition amount of the flocculant is controlled as follows.

[0054] If the addition amount of the flocculant is appropriate, usually, the feature amount of the flocs in the floc formation tank 22 is smaller than the feature amount of the flocs in the agglutination reaction tank 21. In other words, when the difference between the feature amount of the flocs in the floc formation tank 22 and the feature amount of the flocs in the agglutination reaction tank 21 is small, it can be said that the addition amount of the flocculant is not appropriate. Therefore, it is preferable to control the addition amount of the flocculant so that the difference between the feature amount of the flocs in the floc formation tank 22 and the feature amount of the flocs in the agglutination reaction tank 21 becomes large. Specifically, the image processing means 13 calculates the feature amount of the first flocs from the captured image of the imaging means 14 attached to the floc formation tank 22, and calculates the feature amount of the second flocs from the captured image of the imaging means 14 attached to the agglutination reaction tank 21. The feature amounts of the first and second flocs are supplied from the image processing means 13 to the control means 12. The control means 12 controls the addition amount of the flocculant so that the difference between the feature amount of the first flocs and the feature amount of the second flocs becomes small in the second control.

[0055] (Third Embodiment) FIG. 9 is a block diagram showing the configuration of a water treatment system according to a third embodiment of the present invention. The water treatment system 3 of the present embodiment includes a nutrient storage tank 26 and a pump 27, and is different from the second embodiment in that the control means 12 controls the addition amount of the nutrient. Since the configuration excluding the nutrient storage tank 26 and the pump 27 is the same as that described in the first and second embodiments, detailed description of these configurations is omitted here.

[0056] The nutrient storage tank 26 stores nutrients necessary for microorganisms. The nutrient storage tank 26 is connected to the coagulation reaction tank 21 via a pipe, and it is possible to add the nutrient to the coagulation reaction tank 21. A pump 27 for sending out the nutrient stored in the nutrient storage tank 26 to the coagulation reaction tank 21 is provided in the pipe between the nutrient storage tank 26 and the coagulation reaction tank 21. The pump 27 can adjust the sending amount of the nutrient according to a nutrient control signal S13 for controlling the addition amount of the nutrient.

[0057] The control means 12 controls the addition amount of the nutrient to the coagulation reaction tank 21 based on the measured value of the gas concentration acquired by the gas concentration measuring means 11. The control means 12 supplies a nutrient control signal S13 for controlling the addition amount of the nutrient to the pump 27. The control means 12 can control the addition amount of the nutrient continuously or stepwise by controlling the sending amount of the pump 27.

[0058] According to the water treatment system 3 of the present embodiment, in addition to the operational effects described in the first and second embodiments, the addition amount of the nutrient can be appropriately controlled according to the amount of microorganisms. For example, when the microorganisms grow, the required amount of the nutrient also increases. Thus, there is a correlation between the amount of microorganisms and the amount of the nutrient. By utilizing this correlation relationship, the addition amount of the nutrient is appropriately controlled. Thereby, the cost of the nutrient required for biological treatment can be reduced.

[0059] In the above-described first to third embodiments, the components described in each embodiment may be combined. For example, the configuration for controlling the addition amount of the nutrient described in the third embodiment may be applied to the first embodiment.

[0060] Also, in the first to third embodiments, the following modifications 1 to 4 can be applied. (Modification Example 1) The addition amount of the pH adjuster to the coagulation reaction tank 21 may be controlled according to the hydrogen ion exponent (pH) of the water to be treated stored in the biological reaction tank 20. Specifically, a pH meter is attached to the biological reaction tank 20, and a pH adjuster storage tank and a pump corresponding to the coagulant storage tank 24 and the pump 25 are provided. The pH meter measures the pH of the water to be treated and supplies the measurement result to the control means 12. The control means 12 controls the delivery amount of the pump based on the measurement result of the pH meter. Thereby, the addition amount of the pH adjuster to the coagulation reaction tank 21 can be appropriately controlled, and the cost of the pH adjuster can be reduced.

[0061] Note that even if the organic matter load of the water to be treated flowing into the biological reaction tank 20 is constant, when the pH of the water to be treated changes, the amount (gas concentration) of the gas generated in the biological reaction tank 20 may change. In this case, the control characteristic data shown in FIG. 3 or FIG. 4 may be provided for each pH value, and the control means 12 may switch the control characteristic data used for the control of the coagulant based on the measurement result of the pH meter.

[0062] (Modification Example 2) Since the flow rate of the biologically treated water flowing from the biological reaction tank 20 to the coagulation reaction tank 21 is constant, when the flow rate of the water to be treated flowing into the biological reaction tank 20 changes, the BOD concentration of the biologically treated water changes. Therefore, it is preferable to control the addition amount of the coagulant to the coagulation reaction tank 21 according to the flow rate of the water to be treated.

[0063] Specifically, a flow meter is provided in the pipe for supplying the water to be treated to the biological reaction tank 20. The flow meter measures the flow rate of the water to be treated and supplies the measurement result to the control means 12. The control means 12 controls the addition amount of the flocculant based on the measured value of the gas concentration acquired by the gas concentration measurement means 11 and the flow rate of the water to be treated acquired by the flow meter. For example, for a plurality of preset flow rates, control characteristic data as shown in FIG. 3 or FIG. 4 is provided for each flow rate, and between each flow rate, it is obtained by interpolating the corresponding control characteristic data. The control means 12 switches the control characteristic data used for controlling the flocculant based on the measured value of the flow meter.

[0064] (Modification Example 3) In the biological reaction tank 20, microorganisms grow by aeration. Since there is a correlation between the aeration amount and the amount of microorganisms, it is preferable to control the aeration amount according to the gas concentration. Specifically, the control means 12 controls the aeration amount of the air bubbling mechanism based on the measured value of the gas concentration acquired by the gas concentration measurement means 11. Thereby, more stable biological treatment becomes possible.

[0065] (Modification Example 4) At least one of the flow rate of the water to be treated, the gas concentration in the biological reaction tank 20, the pH of the water to be treated, and the characteristic quantity of the floc may be used as the input layer, and the addition amount of the flocculant may be used as the output layer, and the relationship between them may be analyzed by a neural network. In this case, the control means 12 determines the addition amount of the flocculant based on the analysis result of the neural network.

[0066] In the first to third embodiments described above, a computer program (hereinafter referred to as a program) that describes the content of the processing performed by the control means 12 (for example, control related to the flocculant) as a procedure may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read by the control means 12 and executed. Here, the computer-readable recording medium refers to a removable recording medium such as a floppy (registered trademark) disk, a magneto-optical disk, a DVD (Digital Versatile Disc), a CD (Compact Disc), a Blu-ray (registered trademark) Disc, a USB (Universal Serial Bus) memory, etc., and also refers to a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory) built in the control device 10, an HDD (Hard Disc Drive), etc.

[0067] As an example of the program recorded on the recording medium, the computer is caused to acquire a measurement value of the concentration of a gas from a gas concentration measurement means that measures the concentration of the gas generated when biologically treating the water to be treated containing organic substances, and control the addition amount of the flocculant added to the biologically treated water obtained by biologically treating the water to be treated based on the measurement value of the gas concentration. Examples of the program for executing these procedures are given.

Explanation of Signs

[0068] 10 Control device 11 Gas concentration measurement means 11a Sensor unit 12 Control means 20 Bioreactor 21 Flocculation reaction tank 22 Floc formation tank 23 Floatation separation tank 24 Flocculant storage tank 25 Pump

Claims

1. A biological reaction tank for biologically treating treated water containing organic matter, A coagulation reaction tank for storing the biologically treated water, Gas concentration measuring means for measuring the concentration of gas released from the treated water stored in the biological reaction tank, A water treatment system having control means for controlling the addition amount of a coagulant added to the biologically treated water stored in the coagulation reaction tank based on the measured value of the concentration of the gas measured by the gas concentration measuring means.

2. In the water treatment system according to Claim 1, The gas concentration measuring means includes a carbon dioxide concentration measuring device. A water treatment system.

3. In the water treatment system according to Claim 1 or 2, Imaging means for imaging the aggregates contained in the biologically treated water to which the coagulant has been added, Image processing means for calculating a feature amount indicating the aggregation state of the aggregates from the image captured by the imaging means, and further having, The control means controls the addition amount of the coagulant based on the measured value of the concentration of the gas measured by the gas concentration measuring means and the feature amount of the aggregates calculated by the image processing means. A water treatment system.

4. In the water treatment system according to Claim 3, The image processing means detects edge pixels that are pixels whose color difference from adjacent pixels in the image captured by the imaging means exceeds a specified value, and calculates the feature amount of the aggregates based on the edge pixels. A water treatment system.

5. In the water treatment system according to Claim 3 or 4, The control means can execute a first control for controlling the addition amount of the coagulant based on the measured value of the concentration of the gas measured by the gas concentration measuring means and a second control for controlling the addition amount of the coagulant based on the feature amount of the aggregates calculated by the image processing means, and executes one of the first and second controls every predetermined time, and within the period of the predetermined time, executes the other of the first and second controls. A water treatment system.

6. In the water treatment system according to Claim 5, The control means executes the second control within the period of the predetermined time, and when the change amount of the concentration of the gas per unit time exceeds a threshold value, executes the first control instead of the second control. A water treatment system.

7. In the water treatment system according to Claim 5 or Claim 6, The control means executes the first control within the period of the predetermined time, and when the change amount of the characteristic amount of the aggregate per unit time exceeds a threshold value, the second control is executed instead of the first control. A water treatment system.

8. A step of biologically treating the water to be treated containing organic matter, A step of measuring the concentration of the gas generated by the biological treatment, A step of adding a flocculant to the biologically treated water obtained by the biological treatment and controlling the addition amount of the flocculant based on the measured value of the concentration of the gas. A water treatment method including:

9. Gas concentration measuring means for measuring the concentration of the gas generated when biologically treating the water to be treated containing organic matter, A control device having control means for controlling the addition amount of a flocculant added to the biologically treated water obtained by biologically treating the water to be treated based on the measured value of the concentration of the gas measured by the gas concentration measuring means.

10. On a computer, A procedure for obtaining a measured value of the concentration of the gas from gas concentration measuring means for measuring the concentration of the gas generated when biologically treating the water to be treated containing organic matter, A program for causing the computer to execute a procedure for controlling the addition amount of a flocculant added to the biologically treated water obtained by biologically treating the water to be treated based on the measured value of the concentration of the gas.

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