Sludge treatment system, control device, sludge treatment method and program

Abstract

Even if the amount of sludge generated changes, a stable sludge processing volume and a consistent water content of the dewatered sludge after solid-liquid separation are maintained. [Solution] The system includes an interface measuring means 13 for measuring the height of the interface of the sludge to be treated in the water tank 12, a coagulation tank 20 into which the sludge to be treated flows from the water tank 12, a sludge supply device 200 for supplying the sludge to be treated from the water tank 12 to the coagulation tank 20, an additive device 300 for adding a coagulant to the sludge to be treated stored in the coagulation tank 20, a dewatering machine 30 for compressing the sludge to be treated to which the coagulant has been added, a pressure gauge 23 for measuring the inlet pressure of the sludge to be treated to which the coagulant has been added, and a control device 104 that controls the amount of coagulant added by the additive device 300 based on the property index of the sludge to be treated at the inlet of the dewatering machine 30, and controls at least one of the amount of sludge to be treated supplied by the sludge supply device 200 and the rotation speed of the rotating body based on the value measured by the interface measuring means 13 and the inlet pressure measured by the pressure gauge 23.

Description

[Technical Field]

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

[0002] One method for treating sludge involves adding a predetermined coagulant to sludge stored in a water tank, and then using a dewatering machine to remove water from the sludge containing the coagulant, thereby separating the solid-liquid into dewatered sludge and filtrate. When using such a method, the water content of the dewatered sludge that becomes waste is reduced, thereby reducing the amount of waste. For example, Patent Document 1 describes an operating method for a screw press type dewatering machine that controls at least two parameters: the slurry supply pressure, the screw rotation speed, and the amount of coagulant injected, and sets the screw drive torque within a set range. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-107628 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the technology described in Patent Document 1, the screw rotation speed and supply pressure are controlled to keep the screw drive torque within a set range in order to obtain a predetermined moisture content. However, when the amount of sludge generated is large, the water level in the tank where the sludge is stored rises, and the sludge processing of the dewatering machine cannot keep up with the control to keep the screw drive torque within a set range. This can cause the upstream equipment to stop, resulting in an unstable sludge supply and making it difficult to obtain a predetermined moisture content or a stable sludge processing rate.

[0005] The object of the present invention is to provide a sludge treatment system, control device, sludge treatment method, and program that can maintain a stable sludge treatment volume and a stable water content of solid-liquid separated dewatered sludge, even when the amount of sludge generated changes. [Means for solving the problem]

[0006] The sludge treatment system of the present invention is A tank into which the sludge to be treated flows, An interface measuring means for measuring the height of the interface of the sludge to be treated stored in the water tank, A flocculation tank into which the sludge to be treated flows from the water tank, A sludge supply unit that supplies the sludge to be treated from the water tank to the coagulation tank, An additive device for adding a coagulant to the sludge to be treated stored in the coagulation tank, A dewatering device that compresses the sludge to be treated, to which the coagulant has been added, by a rotating body, A pressure gauge for measuring the injection pressure of the sludge to be treated to which the coagulant has been added, The device includes a control device that controls the amount of the coagulant added by the additive device based on a property index indicating the properties of the sludge to be treated at the inlet of the dewatering device, and controls at least one of the amount of sludge to be treated supplied by the sludge supply unit and the rotation speed of the rotating body based on the value measured by the interface measuring means and the injection pressure measured by the pressure gauge.

[0007] Furthermore, the control device of the present invention is An index calculation unit that calculates a property index indicating the properties of the sludge to be treated at the inlet of the dewatering device, Based on the aforementioned property indicators, the addition amount control unit controls the amount of coagulant added by the addition device to the sludge to be treated, A sludge supply control unit controls the amount of sludge to be treated supplied from the water tank to a flocculation tank where the sludge to be treated to be stored is stored, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the flocculant has been added. The dewatering device includes a rotation speed control unit that controls the rotation speed of a rotating body, which compresses the sludge to be treated to a dewatering device, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the coagulant has been added.

[0008] Furthermore, the sludge treatment method of the present invention is A process for calculating a property index that indicates the properties of the sludge to be treated at the inlet of the dewatering device, A process in which the additive device controls the amount of coagulant added to the sludge to be treated based on the aforementioned property indicators, A process for controlling the amount of sludge to be treated supplied from the water tank to the flocculation tank where the sludge to be treated to be treated is stored, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the flocculant has been added, The process involves controlling the rotation speed of a rotating body in a dewatering device that compresses the sludge to be treated, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the coagulant has been added.

[0009] Furthermore, the program of the present invention, A program to be executed by a computer, On the computer, Procedure for calculating property indicators that show the properties of the sludge to be treated at the inlet of the dewatering device, A procedure for controlling the amount of coagulant added to the sludge to be treated by the additive device based on the aforementioned property indicators, A procedure for controlling the amount of sludge to be treated supplied from the water tank to the flocculation tank where the sludge to be treated to be treated is stored, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the flocculant has been added, The procedure involves controlling the rotation speed of a rotating body in a dewatering device that compresses the sludge to be treated, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the coagulant has been added. [Effects of the Invention]

[0010] In the present invention, even when the amount of sludge generated changes, it is possible to maintain a stable treatment amount of sludge and the water content of the dewatered sludge separated into solid and liquid components.

Brief Description of the Drawings

[0011] [Figure 1] It is a diagram showing a first embodiment of the sludge treatment system of the present invention. [Figure 2] It is a diagram showing an example of the components included in the control device shown in FIG. 1. [Figure 3A] It is a flowchart for explaining an example of a control method for the addition amount based on the aggregation index among the sludge treatment methods in the sludge treatment system shown in FIG. 1. [Figure 3B] It is a flowchart for explaining an example of a control method for the addition amount based on the aggregation index among the sludge treatment methods in the sludge treatment system shown in FIG. 1. [Figure 4] It is a flowchart for explaining an example of a control method for the sludge supply amount from the sludge supply device and the rotation speed of the squeezing part rotation device based on the water level of the sludge storage tank and the pressure of the sludge injection pressure among the sludge treatment methods in the sludge treatment system shown in FIG. 1. [Figure 5] It is a flowchart for explaining another example of a control method for the sludge supply amount from the sludge supply device and the rotation speed of the squeezing part rotation device based on the water level of the sludge storage tank and the pressure of the sludge injection pressure among the sludge treatment methods in the sludge treatment system shown in FIG. 1. [Figure 6] It is a diagram showing a second embodiment of the sludge treatment system of the present invention. [Figure 7] It is a diagram showing an example of the components included in the control device shown in FIG. 6. [Figure 8] It is a flowchart for explaining an example of a control method for the sludge supply amount from the sludge supply device and the rotation speed of the squeezing part rotation device based on the water level of the sludge storage tank, the pressure of the sludge injection pressure, and the supply amount of solids among the sludge treatment methods in the sludge treatment system shown in FIG. 6. [Figure 9]This figure shows a third embodiment of the sludge treatment system of the present invention. [Figure 10] This figure shows an example of the components of the control device shown in Figure 9. [Figure 11] Figure 9 is a flowchart illustrating an example of a method for controlling the amount of additives based on sludge concentration, which is part of the sludge treatment method in the sludge treatment system shown. [Figure 12] This figure shows a fourth embodiment of the sludge treatment system of the present invention. [Figure 13] This figure shows an example of the components of the control device shown in Figure 12. [Figure 14] Figure 12 is a flowchart illustrating an example of a method for controlling the amount of sludge supplied from the sludge supply device and the rotation speed of the compression unit's rotating mechanism, based on the height of the water tank interface and the sludge injection pressure, as part of the sludge treatment method in the sludge treatment system shown. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment)

[0013] Figure 1 shows a first embodiment of the sludge treatment system of the present invention. As shown in Figure 1, the sludge treatment system in this embodiment includes a sludge storage tank 10, a coagulation tank 20, a dewatering machine 30, a water level gauge 11, a sensor 22, a pressure gauge 23, a control device 100, a sludge supply device 200, an additive device 300, a coagulant storage tank 301, and a compression unit rotating device 400.

[0014] The sludge storage tank 10 is a storage tank into which the sludge to be treated flows and stores the incoming sludge. The sludge to be treated contains muddy substances formed by the aggregation of final organic and inorganic products generated during the treatment process of sewage treatment plants and the wastewater treatment process of factories. Examples of organic sludge include scum from coagulation sedimentation and pressurized flotation at food factories, semiconductor factories, paper mills, and wastewater treatment plant reuse plants, excess membrane separation sludge, and activated sludge from sewage treatment plants. Examples of inorganic sludge include sludge derived from metals, coagulants, lime, and calcium from wastewater, but are not limited to these. Furthermore, since the sludge to be treated is waste, it cannot be used as is. Therefore, the sludge to be treated is subjected to processes such as coagulation treatment by adding a coagulant, or dewatering treatment by pressing or centrifugal separation using a dewatering machine, to remove the dewatered sludge and obtain a reusable liquid. Dewatered sludge is preferable to have a lower moisture content and is either treated as waste or reused as fertilizer. The sludge storage tank 10 has a predetermined capacity.

[0015] The water level gauge 11 is installed in the sludge storage tank 10 and is a first water level gauge that measures the water level of the sludge to be treated stored in the sludge storage tank 10. The water level gauge 11 outputs the measured water level value to the control device 100. Alternatively, the water level gauge 11 may simply determine whether or not the water level exceeds a preset level and output the determination result to the control device 100.

[0016] The coagulation tank 20 is a tank into which the sludge to be treated, which has been stored in the sludge storage tank 10, is flowed in (supplied) using the sludge supply device 200 and stored. The coagulation tank 20 has a predetermined capacity. The coagulation tank 20 may also be equipped with a stirring member for agitating the treated sludge.

[0017] The sludge supply device 200 is a sludge supply unit that supplies sludge to be treated from the sludge storage tank 10 to the coagulation tank 20. The sludge supply device 200 supplies a quantity of sludge to be treated from the sludge storage tank 10 to the coagulation tank 20 based on instructions from the control device 100. The sludge supply device 200 is equipped with a sludge supply pump that sends the sludge stored in the sludge storage tank 10 to the coagulation tank 20. Preferably, the sludge supply pump is equipped with a mechanism that can control the pump rotation speed in accordance with the output signal from the control device 100, such as an inverter that controls the pump rotation speed. The method of controlling the amount of sludge supplied is not limited to inverter control of the sludge supply pump, but may also be controlled using a control valve that can adjust the opening between the sludge supply pump and the coagulation tank 20. Inverter control and control using a control valve may also be used in combination. In addition to frequency (Hz) control by an inverter, the pump rotation speed may also be controlled by sending analog or digital signals to the pump. There are no particular restrictions on the sludge supply pump, but examples of sludge supply pumps include screw pumps and rotary positive displacement single-screw eccentric pumps.

[0018] The additive device 300 adds the coagulant stored in the coagulant storage tank 301 to the sludge stored in the coagulation tank 20. The additive device 300 adds the amount of coagulant to the sludge stored in the coagulation tank 20 from the coagulant storage tank 301 based on instructions from the control device 100. The additive device 300 is equipped with a coagulant addition pump that delivers the coagulant from the coagulant storage tank 301. The coagulant addition pump is equipped with a mechanism that can control the pump rotation speed according to the output signal from the control device 100, such as an inverter that controls the pump rotation speed. In addition to frequency (Hz) control by an inverter, the pump rotation speed control may also be controlled by sending analog or digital signals to the pump. The coagulant stored in the coagulant storage tank 301 may be an inorganic coagulant or an organic coagulant. If the flocculant stored in the flocculant storage tank 301 is an inorganic flocculant, it may be aluminum-based (PAC, aluminum sulfate, etc.), iron-based (polyferrous iron, ferric chloride, etc.), etc., and is not particularly limited. If the flocculant stored in the flocculant storage tank 301 is an organic flocculant, it may be cationic, anionic, or amphoteric. The flocculant storage tank 301 may be divided according to the type of flocculant. In addition, the additive device 300 may not only add the flocculant to the flocculation tank 20, but also to the piping. When the additive device 300 adds multiple flocculants, multiple additives may be added to the same flocculation tank, or multiple flocculants may be added to each of the multiple flocculation tanks. When inorganic and organic flocculants are used in combination, it is preferable for the additive device 300 to add the inorganic flocculant before the organic flocculant.

[0019] Sensor 22 acquires the state of flocs in the sludge to which a coagulant has been added from the additive device 300, which is stored in the coagulation tank 20. Sensor 22 may be, for example, a non-wetted image sensor (camera) that captures images of the sludge. Sensor 22 is preferably an infrared sensor. Sensor 22 may also be a camera that captures images of the sludge in the coagulation tank 20 at time intervals less than or equal to a preset time interval (for example, a video camera that continuously captures images). Sensor 22 outputs image data showing the acquired (captured) image to the control device 100. There is no particular requirement for how to fix Sensor 22. If Sensor 22 is a camera, Sensor 22 does not necessarily need to capture images of the sludge stored in the coagulation tank 20 from above in the vertical direction; it may capture images from diagonally above at a predetermined angle, as long as it can capture images of the sludge through the liquid surface stored in the coagulation tank 20. In other words, the specific installation location of the sensor 22 should be a position where it can image the sludge stored in the coagulation tank 20 through the liquid surface. If the coagulation tank 20 is a sealed type, a transparent member may be provided on the top or side of the coagulation tank 20, and the liquid surface may be imaged through the transparent member. Alternatively, the sludge may be allowed to flow vertically, and the camera sensor 22 may image the flowing sludge from a horizontal direction. For example, a pipe made of a transparent member may be provided to allow the sludge stored in the coagulation tank 20 to flow vertically from top to bottom, and the camera may image the sludge flowing through the pipe from a horizontal direction outside the pipe.

[0020] The pressure gauge 23 measures the injection pressure of the sludge (coagulated flocs) to which the coagulant has been added. The pressure gauge 23 may be installed in the coagulation tank 20, or in the piping from the coagulation tank 20 to the dewatering machine 30, as long as it is a location where the injection pressure of the sludge (coagulated flocs) can be measured. The pressure gauge 23 outputs the measured value to the control device 100.

[0021] The dewatering machine 30 is a dewatering device that dewaters the sludge processed in the coagulation tank 20, separating it into filtrate and dewatered sludge (solid-liquid separation) before discharge. Specifically, the dewatering machine 30 compresses the sludge, to which a coagulant has been added from the additive device 300 that flows in from the coagulation tank 20, using a rotating body. The dewatering machine 30 has a compression section, such as a screw press type, a multi-disc type, or a belt press type. The dewatering machine 30 is equipped with a compression section rotating device 400. The compression section rotating device 400 is equipped with a rotating body such as a screw, multi-disc, or roller, and an inverter that outputs control of the rotation speed of the rotating body. The separated solid material, the dewatered sludge, is supplied as dewatered sludge from the rear of the rotating body to a hopper or the like, where it is further processed such as drying or transported as industrial waste. The separated filtrate is returned to a wastewater adjustment tank or the like. There are no restrictions on the method of supplying sludge from the coagulation tank 20 to the compression unit rotating device 400. For example, methods such as supplying sludge by the water level difference between the height of the sludge in the coagulation tank 20 and the height of the connection point connecting the coagulated sludge supply piping and the inlet of the compression unit rotating device 400, or using a pump, are also acceptable. However, using a pump may cause the coagulated sludge to collapse, so supplying sludge by the water level difference is preferred. When supplying sludge by the water level difference, it is preferable to shorten the sludge supply piping from the coagulation tank 20 to the compression unit rotating device 400 and to provide a downward slope from the coagulation tank 20 to the compression unit rotating device 400.

[0022] Figure 2 shows an example of the components of the control device 100 shown in Figure 1. As shown in Figure 2, the control device 100 shown in Figure 1 includes an index calculation unit 110, an additive amount control unit 120, a sludge supply amount control unit 130, and a rotation speed control unit 140. Note that Figure 2 shows only the main components of the control device 100 shown in Figure 1 that are relevant to this embodiment.

[0023] The index calculation unit 110 calculates an agglutination index that indicates the state of the aggregates acquired by the sensor 22. If the sensor 22 is an image sensor, the index calculation unit 110 calculates the characteristic quantities of the aggregates in the sludge in the agglutination tank 20 as an agglutination index from the image captured by the image sensor. Here, the index calculation unit 110 calculates the number of suspended solids, particle size, or displacement amount of suspended solids contained in the sludge in the agglutination tank 20 as characteristic quantities from the image captured by the image sensor. For example, the index calculation unit 110 may use image processing technology such as Motion History Image on the image (video) captured by the image sensor to color the parts that differ between frames in white, and calculate the count number (displacement amount) of these colored white dots as a characteristic quantity. Alternatively, the index calculation unit 110 may use image processing technology such as Optical flow to visualize the flow of flocs in the sludge in the agglutination tank 20, measure the width of the flow, and calculate the particle size as a characteristic quantity. Alternatively, if sensor 22 is an image sensor, the index calculation unit 110 calculates the number of edges of aggregates in the sludge within the coagulation tank 20 as a coagulation index from the image captured by the image sensor. Here, the index calculation unit 110 may detect pixels in the image captured by the image sensor where the color difference (for example, the difference in RGB values) of adjacent pixels is greater than or equal to a threshold as edges of aggregates, and then quantify the number of edge pixels, which is the sum of the number of detected pixels per unit area (imaging range), as a feature quantity of the aggregates and calculate the index. Alternatively, if sensor 22 is an image sensor, the index calculation unit 110 may calculate the area of ​​aggregates in the sludge within the coagulation tank 20 as a coagulation index from the image captured by the image sensor. Alternatively, if sensor 22 is an image sensor, the index calculation unit 110 may calculate the number of aggregates in the sludge within the coagulation tank 20 as a coagulation index from the image captured by the image sensor. Furthermore, if the sensor 22 is an image sensor, the index calculation unit 110 may calculate an arbitrary combination of the number of edges, area, and number of aggregates in the sludge within the coagulation tank 20 as a coagulation index from the image captured by the image sensor.

[0024] The addition amount control unit 120 controls the amount of flocculant added by the addition device 300 based on the property index, which is the change in the flocculation index calculated by the index calculation unit 110 when the amount of flocculant added by the addition device 300 is changed. Specifically, the addition amount control unit 120 controls the amount of flocculant added by the addition device 300 based on the change in the flocculation index when the amount of flocculant added by the addition device 300 is changed and the change in the amount of flocculant added by the addition device 300. More specifically, the addition amount control unit 120 compares the flocculation change amount, which is the ratio of the change in the flocculation index to the change in the amount of flocculant added by the addition device 300, with a preset threshold. Then, the addition amount control unit 120 controls the amount of flocculant added by the addition device 300 based on the result of this comparison. Flocculation change amount V n This is calculated using the following formula (Equation 1).

[0025]

number

[0026] In (Equation 1), C n This is an agglutination index. C n-1 This is the flocculation index before changing the amount of flocculant added. Also, P n This is the amount of flocculant added. n-1 This is the amount of flocculant added before the change in the amount of flocculant added.

[0027] Aggregation change amount V n If the amount of flocculant added by the additive device 300 is below a preset threshold, the additive amount control unit 120 controls the amount of flocculant added by the additive device 300 to be reduced. Meanwhile, the amount of flocculation change V n If the amount exceeds a preset threshold, the addition amount control unit 120 controls the amount of flocculant added by the addition device 300 to increase the amount added. By repeating this operation, the amount of flocculation change V n As it approaches a pre-set threshold, it becomes possible to maintain an optimal aggregation state.

[0028] Furthermore, a sludge concentration meter may be installed in the filtrate storage tank that stores the filtrate from the dewatering machine 30, and the control device 100 may control the amount of coagulant added from the additive device 300 based on the sludge concentration measured by the sludge concentration meter. In this case, it is preferable that the control device 100 increases the amount of coagulant added from the additive device 300 when the measured value of the sludge concentration meter exceeds a threshold, and decreases or maintains the amount of coagulant added from the additive device 300 when the measured value of the sludge concentration meter falls below a threshold.

[0029] The sludge supply control unit 130 controls the amount of sludge to be treated supplied by the sludge supply device 200 to the coagulation tank 20 based on the value measured by the water level gauge 11. If the value measured by the water level gauge 11 exceeds a preset threshold, there may not be enough room for sludge to be treated to be stored in the sludge storage tank 10, which could affect the upstream equipment. In that case, to lower the water level in the sludge storage tank 10, the sludge supply control unit 130 increases the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20. When the value measured by the water level gauge 11 falls below the preset threshold, the sludge supply control unit 130 maintains the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20. At this time, if the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 exceeds a preset threshold, the water level in the coagulation tank 20 may increase in order to reduce the water content by reducing the rotation speed of the rotating body of the compression unit rotating device 400. An increase in the water level in the coagulation tank 20 may cause the dewatering machine 30 to stop. Therefore, the sludge supply amount control unit 130 reduces the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20. Furthermore, if the value measured by the water level gauge 11 falls below a preset lower limit, the sludge supply amount control unit 130 may stop supplying sludge to be treated from the sludge storage tank 10 to the coagulation tank 20. The increase and decrease ranges of the amount of sludge to be treated are not specifically defined. For example, the increase and decrease ranges of the amount of sludge to be treated may be set in advance.

[0030] Furthermore, the sludge supply control unit 130 may substitute the value measured by the water level gauge 11 into a predetermined supply amount calculation formula to calculate the amount of sludge to be treated that the sludge supply device 200 will supply, and control the sludge supply device 200 to supply the calculated amount of sludge to be treated to the coagulation tank 20. The supply amount calculation formula used here is: Sludge supply amount = (value measured by water level gauge 11) × A + B This is a linear function equation. Here, A and B are pre-calculated constants. A and B are calculated as the slope (the ratio of the increase in sludge supply to the increase in water level) A and the intercept B (the intercept of the sludge supply axis) from a straight line (a linear line sloping upwards to the right) formed by plotting two sets of points representing the sludge supply amount and water level value measured in cases where the dewatering machine 30 operates suitably: a case where the value measured by the water level gauge 11 is large (a high sludge supply amount that increases the amount of sludge treated) and a case where the value measured by the water level gauge 11 is small (a low sludge supply amount corresponding to the decrease in the amount of treatment due to the decrease in the rotation speed of the rotating body in the compression rotating device 400) on a graph with the sludge supply amount on the vertical axis and the water level value on the horizontal axis.

[0031] Furthermore, the sludge supply control unit 130 also takes into consideration the value measured by the pressure gauge 23 when controlling the amount of sludge to be treated. If the value measured by the pressure gauge 23 is greater than the preset reference range, the amount of sludge supplied from the sludge storage tank 10 is excessive, the water level in the coagulation tank 20 may reach the upper limit, and the sludge supply may stop. If the sludge supply stops, the amount of sludge supplied from the coagulation tank 20 to the dewatering machine 30 will decrease, which may reduce the amount of solids supplied to the dewatering machine 30 and the compression pressure, potentially increasing the moisture content. Also, if the value measured by the pressure gauge 23 is greater than the reference range, there may be an excess of solids inside the dewatering machine 30, and the solids may not be properly discharged from the outlet of the dewatering machine 30, causing solids to leak to the filtrate side and potentially worsening the treatment process. Therefore, in order to prevent an oversupply of sludge from the sludge storage tank 10 to the coagulation tank 20 and an increase in pressure, the sludge supply control unit 130 reduces the amount of sludge supplied by the sludge supply device 200. On the other hand, if the value measured by the pressure gauge 23 is not greater than the reference range, the sludge supply control unit 130 determines whether the value measured by the pressure gauge 23 is less than the reference range. If the value measured by the pressure gauge 23 is less than the reference range, sufficient compressive pressure may not be applied, and the water content may increase. Therefore, the sludge supply control unit 130 increases the amount of sludge supplied by the sludge supply device 200. If the value measured by the pressure gauge 23 is not less than the reference range, the sludge supply is appropriate and there is sufficient compressive pressure, so the sludge supply control unit 130 maintains the amount of sludge supplied by the sludge supply device 200. Here, for example, if the reference range is 2 to 3, a value greater than the reference range means a value greater than 3. Furthermore, a value smaller than the reference range means a value less than 2. The reference range is a value with a certain margin around a predetermined threshold, and this margin can be changed as appropriate.

[0032] The rotation speed control unit 140 controls the rotation speed of the compression unit rotating device 400 based on the value measured by the water level gauge 11. If the value measured by the water level gauge 11 exceeds a preset threshold, there is insufficient capacity for storing the sludge to be treated in the sludge storage tank 10, and this may have an effect such as stopping the upstream equipment to prevent an excessive rise in the water level of the sludge storage tank 10. In that case, the rotation speed control unit 140 increases the rotation speed of the compression unit rotating device 400 to lower the water level of the sludge storage tank 10. However, an upper limit is set for the rotation speed of the compression unit rotating device 400, and the rotation speed control unit 140 controls the rotation speed of the compression unit rotating device 400 so that it is below the upper limit. On the other hand, if the value measured by the water level gauge 11 is below a preset threshold, there is sufficient capacity for storing the sludge to be treated in the sludge storage tank 10. In that case, the rotation speed control unit 140 decreases the rotation speed of the compression unit rotating device 400 to reduce the water content of the dewatered sludge after solid-liquid separation. However, a lower limit is set for the rotation speed of the pressing unit rotating device 400, and the rotation speed control unit 140 controls the rotation speed of the pressing unit rotating device 400 so that it is equal to or greater than this lower limit. This lower limit is a value that has been set in advance, taking into consideration the specifications of the dewatering machine 30, the load on the pressing unit such as the screw, and the avoidance of overcurrent generation.

[0033] Alternatively, the rotation speed control unit 140 may substitute the value measured by the water level gauge 11 into a predetermined rotation speed calculation formula to calculate the rotation speed of the compression unit rotating device 400, and then rotate the rotating body of the compression unit rotating device 400 at the calculated rotation speed. The rotation speed calculation formula used here is: Rotation speed = (value measured by water level gauge 11) × C + D It is a linear function formula. Here, C and D are constants calculated in advance. C and D are cases where the dehydrator 30 operates suitably, and cases where the value measured by the water level gauge 11 is a large value (a large squeezing part rotation speed that increases the sludge treatment amount), and cases where the value measured by the water level gauge 11 is a small value (a small squeezing part rotation speed that reduces the water content rate). The points of two sets of combinations of the rotation speed and the water level value measured in each case are plotted on a graph with the rotation speed on the vertical axis and the water level value on the horizontal axis and connected to form a straight line (an upward-sloping linear line). The slope (the ratio of the increase in the rotation speed to the increase in the water level value) C and the intercept D (the intercept on the rotation speed axis) are calculated from this.

[0034] Based on the value measured by the water level gauge 11, the control device 100 may perform either control of the supply amount of the sludge to be treated by the sludge supply amount control unit 130 or control of the rotation speed of the squeezing part rotating device 400 by the rotation speed control unit 140.

[0035] Hereinafter, the sludge treatment method in the sludge treatment system shown in FIG. 1 will be described. FIGS. 3A and 3B are flowcharts for explaining an example of a control method for the addition amount based on the aggregation index in the sludge treatment method in the sludge treatment system shown in FIG. 1.

[0036] First, the adding device 300 adds a flocculant from the flocculant storage tank 301 to the flocculation tank 20 in an addition amount P n-1 (step S1). After the elapse of a preset time (step S2), the index calculation unit 110 of the control device 100 calculates the aggregation index C n-1 from the state of the flocs in the sludge in the flocculation tank 20 acquired by the sensor 22 (step S3). Then, the adding device 300 adds a flocculant from the flocculant storage tank 301 to the flocculation tank 20 in an addition amount P n (step S4). After the elapse of a preset time (step S5), the index calculation unit 110 of the control device 100 calculates the aggregation index C n from the state of the flocs in the sludge in the flocculation tank 20 measured by the sensor 22 (step S6). Then, the index calculation unit 110 of the control device 100 uses (Equation 1) to calculate the aggregation change amount Vn Calculate (Step S7). Note that the amount of aggregation change V n The calculation may be performed by the additive amount control unit 120 instead of the index calculation unit 110.

[0037] The additive amount control unit 120 of the control device 100 calculates the aggregation change amount V n It is determined whether the amount of aggregation change V exceeds a predetermined threshold (step S8). n If the value exceeds a preset threshold, the addition amount control unit 120 increases the amount of flocculant added from the addition device 300 (step S9). The addition amount control unit 120 then increases the amount of addition P n+1 The addition device 300 is controlled to add the coagulant from the coagulant storage tank 301 (step S10). Meanwhile, in step S8, the amount of coagulation change V n If the amount is below a preset threshold, the addition amount control unit 120 reduces the amount of flocculant added from the addition device 300 (step S11). The addition amount control unit 120 then adjusts the reduced addition amount P n+1 The addition device 300 is controlled to add the coagulant from the coagulant storage tank 301 (step S12). Then, the process in step S5 is performed. The amount of coagulant to be increased or decreased may be a predetermined amount, or an amount calculated according to the change in coagulation.

[0038] Figure 4 is a flowchart illustrating an example of a method for controlling the amount of sludge supplied from the sludge supply device 200 and the rotation speed of the compression unit rotating device 400 based on the water level in the sludge storage tank 10 and the sludge injection pressure in the sludge treatment system shown in Figure 1.

[0039] First, the control device 100 determines whether the water level of the sludge to be treated stored in the sludge storage tank 10, as measured by the water level gauge 11, exceeds a threshold (step S21). If it is determined that the water level of the sludge to be treated stored in the sludge storage tank 10 exceeds the threshold, the rotation speed control unit 140 increases the rotation speed of the compression unit rotating device 400 (step S22). The rotation speed control unit 140 determines whether the increased rotation speed is below the upper limit (step S23). If it is determined that the increased rotation speed is below the upper limit, the sludge supply amount control unit 130 calculates the sludge supply amount by substituting the water level measured by the water level gauge 11 into the supply amount calculation formula described above, and controls the sludge supply device 200 to supply the calculated amount of sludge to the coagulation tank 20 (step S24). Furthermore, if it is determined in step S23 that the rotation speed has not fallen below the upper limit, the rotation speed control unit 140 maintains the rotation speed at the upper limit (step S25), and the sludge supply amount control unit 130 performs the processing in step S24. After that, the processing in step S21 is performed. If the water level of the sludge to be treated stored in the sludge storage tank 10 exceeds a threshold, this may cause an excessive rise in the water level of the sludge to be treated in the subsequent coagulation tank 20. For this reason, it is preferable for the control device 100 to first increase the rotation speed of the compression unit rotating device 400. This prevents the sludge supply from stopping (the dewatering treatment equipment from stopping) due to the rise in water levels in the sludge storage tank 10 and the coagulation tank 20.

[0040] On the other hand, if in step S21 it is determined that the water level of the sludge to be treated stored in the sludge storage tank 10 does not exceed a threshold, the rotation speed control unit 140 reduces the rotation speed of the compression unit rotating device 400 (step S26). The rotation speed control unit 140 determines whether the reduced rotation speed exceeds a lower limit (step S27). If the reduced rotation speed exceeds a lower limit, the sludge supply amount control unit 130 determines whether the value of the sludge injection pressure measured by the pressure gauge 23 is greater than a predetermined reference range (step S28). If in step S27 it is determined that the rotation speed does not exceed a lower limit, the rotation speed control unit 140 maintains the rotation speed at the lower limit (step S29), and the sludge supply amount control unit 130 performs the process in step S28.

[0041] In step S28, if the pressure gauge 23 determines that the sludge injection pressure is greater than a predetermined reference range, the sludge supply control unit 130 reduces the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S30). Subsequently, the process in step S21 is performed.

[0042] In step S28, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is not greater than a predetermined reference range, the sludge supply control unit 130 determines whether the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range (step S31). In step S31, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range, the sludge supply control unit 130 increases the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S32). On the other hand, in step S31, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is not less than a predetermined reference range, the sludge supply control unit 130 maintains the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S33). After that, the process in step S21 is performed.

[0043] Figure 5 is a flowchart illustrating another example of the sludge treatment method in the sludge treatment system shown in Figure 1, specifically the control method for the amount of sludge supplied from the sludge supply device 200 and the rotation speed of the compression unit rotating device 400, based on the water level in the sludge storage tank 10 and the sludge injection pressure.

[0044] First, the rotation speed control unit 140 calculates the rotation speed of the compression unit rotating device 400 by substituting the water level measured by the water level gauge 11 into the rotation speed calculation formula described above (step S41). The rotation speed control unit 140 determines whether the calculated rotation speed is greater than a preset lower limit and less than a preset upper limit (step S42). If the rotation speed calculated by the rotation speed control unit 140 is greater than the lower limit and less than the upper limit, the sludge supply amount control unit 130 determines whether the value of the sludge injection pressure measured by the pressure gauge 23 is greater than a predetermined reference range (step S43). Also, if in step S42 the rotation speed control unit 140 determines that the calculated rotation speed is less than or equal to the lower limit or greater than or equal to the upper limit, the rotation speed control unit 140 sets the rotation speed to the upper limit if the calculated rotation speed is greater than or equal to the upper limit, and sets the rotation speed to the lower limit if the calculated rotation speed is less than or equal to the lower limit (step S44). Then, the process in step S43 is performed.

[0045] In step S43, if the pressure gauge 23 determines that the sludge injection pressure is greater than a predetermined reference range, the sludge supply control unit 130 reduces the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S45). Subsequently, the process in step S41 is performed.

[0046] In step S43, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is not greater than a predetermined reference range, the sludge supply control unit 130 determines whether the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range (step S46). In step S46, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range, the sludge supply control unit 130 increases the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S47). On the other hand, in step S46, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is not less than a predetermined reference range, the sludge supply control unit 130 maintains the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S48). After that, the process in step S41 is performed.

[0047] It is possible to arbitrarily select whether to use the process described using the flowchart shown in Figure 4 or the process described using the flowchart shown in Figure 5 to control the amount of sludge supplied from the sludge supply device 200 and the rotation speed of the compression unit rotating device 400.

[0048] While a concentration-coagulation-mixing tank may be provided between the coagulation tank 20 and the dewatering machine 30, it is not necessary to concentrate the sludge in a concentration-coagulation-mixing tank to stabilize the sludge concentration (solid matter content) by maintaining an optimal coagulation state, and therefore a concentration-coagulation-mixing tank is not required. By not providing a concentration-coagulation-mixing tank, space savings and cost reductions can be achieved.

[0049] Furthermore, a second water level gauge may be provided in the coagulation tank 20 to measure the water level of the sludge to be treated stored in the coagulation tank 20. The second water level gauge outputs a value indicating the measured water level to the control device 100. The second water level gauge may simply determine whether the water level of the sludge to be treated stored in the coagulation tank 20 exceeds a preset water level and output the determination result to the control device 100. The control device 100 controls the amount of sludge supplied by the sludge supply device 200 and the rotation speed of the compression unit rotating device 400 according to the water level measured by the second water level gauge. This maintains an appropriate distance between the sensor 22 and the liquid surface of the sludge to be treated stored in the coagulation tank 20, enabling the sensor 22 to detect a stable coagulation state. The control device 100 may calculate the amount of sludge supplied by substituting the water level measured by the second water level gauge into a linear function equation similar to the supply amount calculation formula described above, rather than comparing the water level measured by the second water level gauge with a threshold value to increase or decrease the sludge supply amount. Furthermore, the control device 100 may not use a single threshold value for comparison with the water level measured by the second water level gauge, but may use multiple threshold values ​​or the reference range described above.

[0050] Furthermore, lighting may be provided to illuminate the imaging range of the sensor 22. The lighting illuminates the sludge to be treated stored in the coagulation tank 20. The light source for the lighting is not particularly limited, but infrared light is preferable. The installation position of the lighting and sensor 22 is not particularly limited, but if the coagulation tank 20 is a closed-type coagulation tank, the angle between the direction from the center of the horizontal plane of the window on the upper surface of the coagulation tank 20 toward the lighting and the direction from the center of the horizontal plane of the window toward the sensor 22 can be set to 30° to 180° (or -30° to -180°) to suppress reflection of the lighting from the water surface of the sludge to be treated and the window. Furthermore, setting this angle to 90° will show the most pronounced effect and maximize the field of view from the sensor 22. The lighting and sensor 22 may also be integrated. In order to detect a stable coagulation state by the sensor 22, the lighting may be equipped with a function to control the illuminance according to the water level.

[0051] As described above, the water level in the sludge storage tank 10 is kept below a threshold by controlling the rotation speed of the compression unit rotating device 400. As the water level in the sludge storage tank 10 is kept low, the water level in the coagulation tank 20 located in the next stage decreases. Fluctuations in the water level at low levels in the coagulation tank 20 cause fluctuations in the optimal amount of coagulant to be added. Meanwhile, the amount of coagulant to be added is controlled according to the state inside the coagulation tank 20 acquired by the sensor 22. In other words, by controlling the amount of coagulant to be added in accordance with the fluctuations in the water level of the coagulation tank 20, the optimal coagulation conditions can be maintained with greater precision, thereby maintaining an appropriate processing volume and water content.

[0052] Furthermore, in reality, the concentration, composition, viscosity, and color of the generated sludge—that is, its properties—can vary greatly depending on fluctuations in the influent raw water, the types of products manufactured at the factory, and the sludge-generating treatment processes such as coagulation and sedimentation, pressurized flotation, and membrane separation. For example, in food manufacturing plants, the properties of the sludge vary greatly due to frequent changes in the types of food and beverages produced. In such cases, the optimal amount of coagulant to be added differs depending on the properties of the supplied sludge, so it is necessary to control the amount of coagulant added to the optimal value according to the changes in properties. In this configuration, the coagulation state of the sludge is constantly monitored using the sensor 22, and the amount of coagulant added is controlled from the obtained coagulation index. Therefore, even when the sludge properties fluctuate greatly, the optimal coagulation state can be maintained, and the water content can also be reduced.

[0053] In this configuration, if the water level of the sludge to be treated stored in the sludge storage tank 10 exceeds a threshold, the sludge supply rate and the rotation speed of the compression section are increased to prevent an excessive rise in the water level of the sludge storage tank 10 and to prevent the equipment located upstream of the sludge storage tank 10 from stopping. Furthermore, if the water level of the sludge to be treated stored in the sludge storage tank 10 is below the threshold, the dewatering machine 30 performs dewatering over a longer period of time, thereby reducing the moisture content of the dewatered sludge. In addition, the sludge supply rate is controlled according to the sludge injection pressure. This allows for efficient operation of the equipment. Normally, sludge dewatering machines are designed with a sufficient margin over the planned sludge volume, so this margin can be used effectively. Furthermore, when the amount of sludge to be treated is rapidly changed by adjusting the water level of the sludge storage tank 10, conventional control methods for fixed or automatic addition of coagulants do not allow for appropriate adjustment of the amount added, making it impossible to optimize the coagulation state. Therefore, there was a problem in that it was difficult to reduce the moisture content of the dewatered sludge. However, in this configuration, the amount of coagulant added is rapidly controlled by constantly monitoring the sludge coagulation state using the sensor 22. This optimizes the coagulation state in the coagulation tank 20, making it possible to reduce the moisture content of the dewatered sludge even when the water level in the sludge storage tank 10 is adjusted. Thus, in this configuration, by monitoring the water level in the sludge storage tank 10 and controlling the amount of coagulant added, the sludge supply amount, and the dewatering machine rotation speed, a stable processing volume and moisture content of the dewatered sludge can be maintained even if the amount of sludge generated changes. (Second Embodiment)

[0054] Figure 6 shows a second embodiment of the sludge treatment system of the present invention. As shown in Figure 6, the sludge treatment system in this embodiment includes a sludge storage tank 10, a coagulation tank 20, a dewatering machine 30, a water level gauge 11, a sensor 22, a pressure gauge 23, a control device 102, a sludge supply device 200, an additive device 300, a coagulant storage tank 301, a compression unit rotating device 400, a solid matter supply amount measuring unit 40, a concentration meter 41, and a flow meter 42. The sludge storage tank 10, coagulation tank 20, dewatering machine 30, water level gauge 11, sensor 22, pressure gauge 23, sludge supply device 200, additive device 300, coagulant storage tank 301, and compression unit rotating device 400 are the same as those in the first embodiment.

[0055] The concentration meter 41 measures the sludge concentration of the sludge to be treated supplied by the sludge supply device 200 to the coagulation tank 20. The concentration meter 41 is not particularly limited as long as it can measure the sludge concentration of the sludge to be treated, but it is preferably an SS (Suspended Solids) meter. The concentration meter 41 outputs the measured value to the solids supply amount measuring unit 40.

[0056] The flow meter 42 measures the flow rate of sludge to be treated supplied by the sludge supply device 200 to the coagulation tank 20. The flow meter 42 outputs the measured value to the solids supply amount measuring unit 40.

[0057] The solid matter supply amount measuring unit 40 measures the amount of solid matter in the sludge to be treated that the sludge supply device 200 supplies to the coagulation tank 20. At this time, the solid matter supply amount measuring unit 40 acquires the value measured by the concentration meter 41 and the value measured by the flow meter 42, and uses the acquired values ​​to measure (calculate) the amount of solid matter in the sludge to be treated that the sludge supply device 200 supplies to the coagulation tank 20. The solid matter supply amount measuring unit 40 outputs the measured amount of solid matter to the control device 102. The solid matter supply amount measuring unit 40 also outputs the value measured by the concentration meter 41 to the control device 102.

[0058] Figure 7 shows an example of the components of the control device 102 shown in Figure 6. As shown in Figure 7, the control device 102 shown in Figure 6 includes an index calculation unit 110, an additive amount control unit 120, a sludge supply amount control unit 132, and a rotation speed control unit 142. The index calculation unit 110 and the additive amount control unit 120 are the same as the index calculation unit 110 and the additive amount control unit 120 in the first embodiment. Note that Figure 7 shows only the main components of the control device 102 shown in Figure 6 that are relevant to this embodiment.

[0059] In addition to the functions of the sludge supply control unit 130 in the first embodiment, the sludge supply control unit 132 also has the function of using the value measured by the solids supply amount measuring unit 40 to control the amount of sludge to be treated supplied by the sludge supply device 200 to the coagulation tank 20. For example, even if the value measured by the water level gauge 11 is below a preset threshold, if the value measured by the solids supply amount measuring unit 40 is below a preset threshold, the sludge supply control unit 132 may increase the amount of sludge to be treated supplied from the sludge storage tank 10 to the coagulation tank 20.

[0060] In addition to the functions of the rotation speed control unit 140 in the first embodiment, the rotation speed control unit 142 also has the function of using the value measured by the solid material supply amount measuring unit 40 to control the rotation speed of the pressing unit rotating device 400. For example, even if the value measured by the water level gauge 11 falls below a preset threshold, if the value measured by the solid material supply amount measuring unit 40 exceeds a preset threshold, the rotation speed control unit 142 reduces the rotation speed of the pressing unit rotating device 400. However, similar to the first embodiment, a lower limit is set for the rotation speed of the pressing unit rotating device 400, and the rotation speed control unit 142 controls the rotation speed of the pressing unit rotating device 400 so that it is greater than the lower limit. This lower limit is a value that is set in advance considering the specifications of the dewatering machine 30, the load on the pressing unit such as the screw, and the avoidance of overcurrent generation.

[0061] Figure 8 is a flowchart illustrating an example of a method for controlling the amount of sludge supplied from the sludge supply device and the rotation speed of the compression unit rotating device, based on the water level of the sludge storage tank 10, the sludge injection pressure, and the amount of solid material supplied, as part of the sludge treatment method in the sludge treatment system shown in Figure 6.

[0062] First, the control device 102 determines whether the water level of the sludge to be treated stored in the sludge storage tank 10, as measured by the water level gauge 11, exceeds a threshold (step S51). If it is determined that the water level of the sludge to be treated stored in the sludge storage tank 10 exceeds the threshold, the rotation speed control unit 142 increases the rotation speed of the compression unit rotating device 400 (step S52). The rotation speed control unit 142 determines whether the increased rotation speed is below the upper limit (step S53). If it is determined that the increased rotation speed is below the upper limit, the control device 102 determines whether the water level of the sludge to be treated stored in the sludge storage tank 10, as measured by the water level gauge 11, exceeds a threshold (step S54). Also, if it is determined in step S53 that the rotation speed is not below the upper limit, the rotation speed control unit 142 maintains the rotation speed at the upper limit (step S55), and the sludge supply amount control unit 132 performs the process in step S54. In step S54, if it is determined that the water level of the sludge to be treated stored in the sludge storage tank 10 exceeds a threshold, the sludge supply control unit 132 increases the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S56). Subsequently, the process in step S51 is performed.

[0063] On the other hand, if in step S51 it is determined that the water level of the sludge to be treated stored in the sludge storage tank 10 does not exceed a threshold, the rotation speed control unit 142 reduces the rotation speed of the compression unit rotating device 400 (step S57). If in step S54 it is determined that the water level of the sludge to be treated stored in the sludge storage tank 10 does not exceed a threshold, the process in step S57 is also performed. Next, the rotation speed control unit 142 determines whether the reduced rotation speed exceeds a lower limit (step S58). If it is determined that the reduced rotation speed exceeds a lower limit, the sludge supply amount control unit 132 determines whether the value of the sludge injection pressure measured by the pressure gauge 23 is greater than a predetermined reference range (step S59). If in step S58 it is determined that the rotation speed does not exceed a lower limit, the rotation speed control unit 142 maintains the rotation speed at the lower limit (step S60), and the sludge supply amount control unit 132 performs the process in step S59.

[0064] In step S59, if the pressure gauge 23 determines that the sludge injection pressure is greater than a predetermined reference range, the sludge supply control unit 132 reduces the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S61). Subsequently, the process in step S51 is performed.

[0065] In step S59, if it is determined that the value of the sludge injection pressure measured by the pressure gauge 23 is not greater than a predetermined reference range, the sludge supply control unit 132 determines whether the value of the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range (step S62). In step S62, if it is determined that the value of the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range, the sludge supply control unit 132 increases the amount of sludge to be treated that the sludge supply device 200 supplies from the sludge storage tank 10 to the coagulation tank 20 (step S63). On the other hand, in step S62, if it is determined that the value of the sludge injection pressure measured by the pressure gauge 23 is not less than a predetermined reference range, the sludge supply control unit 132 determines whether the amount of solids measured by the solids supply amount measuring unit 40 is greater than a predetermined threshold (or reference range; the same applies in the following description) (step S64). In step S64, if the solid amount measurement unit 40 determines that the amount of solids measured is greater than a predetermined threshold, the sludge supply control unit 132 maintains the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S65). Subsequently, the process in step S51 is performed. On the other hand, in step S64, if the solid amount measurement unit 40 determines that the amount of solids measured is not greater than a predetermined threshold, the sludge supply control unit 132 increases the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S66). Subsequently, the process in step S51 is performed.

[0066] Furthermore, the sludge supply control unit 132 may, instead of comparing the amount of solid matter measured by the solid matter supply measurement unit 40 with a reference range or threshold and controlling the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20, control the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 so that the amount of solid matter reaches a target value.

[0067] In this configuration, if the water level of the sludge to be treated stored in the sludge storage tank 10 exceeds a threshold, the sludge supply rate and the rotation speed of the compression unit are increased to prevent the equipment located upstream of the sludge storage tank 10 from stopping. Furthermore, even if the water level of the sludge to be treated stored in the sludge storage tank 10 does not exceed a threshold, if the water level of the coagulation tank 20 exceeds a threshold, the sludge supply rate is reduced or the rotation speed of the compression unit is increased to avoid stopping the sludge supply from the upstream equipment, reducing the amount of sludge supplied from the coagulation tank 20 to the dewatering machine 30, decreasing the amount of solids supplied to the dewatering machine 30 and the compression pressure, and increasing the water content of the dewatered sludge. In addition, if the water level of the coagulation tank 20 does not exceed a threshold, there is sufficient water level in the coagulation tank 20 and the sludge supply from the coagulation tank 20 to the compression unit rotating device 400 is stable, so it is further determined whether the amount of solids supplied exceeds a threshold. If the solid supply exceeds the threshold, the control device 102 reduces the rotation speed of the compression unit to lower the water content of the dewatered sludge, as it is considered that the solid supply is sufficient and there is no problem with the compression pressure. Considering the load on the compression unit such as the screw, the rotation speed of the compression unit is set higher than the lower limit. If the solid supply does not exceed the threshold, the pressure in the compression unit may decrease and the water content of the dewatered sludge may increase, so the control device 102 increases the sludge supply and thus the solid supply. In this embodiment, in addition to the effects of the first and second embodiments, by monitoring the sludge concentration, the water levels in the sludge storage tank 10 and the coagulation tank 20, and the solid supply, and controlling the amount of coagulant added, the sludge supply, and the dewatering machine rotation speed, it is possible to maintain an even more stable processing volume and water content even if the amount of sludge generated changes. (Third embodiment)

[0068] Figure 9 shows a third embodiment of the sludge treatment system of the present invention. As shown in Figure 11, the sludge treatment system in this embodiment includes a sludge storage tank 10, a coagulation tank 20, a dewatering machine 30, a water level gauge 11, a sensor 22, a pressure gauge 23, a control device 103, a sludge supply device 200, an additive device 300, a coagulant storage tank 301, a compression unit rotating device 400, and a concentration meter 41. The sludge treatment system in this embodiment is a form of the second embodiment shown in Figure 6, but without the solids supply amount measuring unit 40 and the flow meter 42. In coagulant control, optimizing the coagulation state of the sludge is of utmost importance. Therefore, control of the change in the coagulation index is essential. A system equipped with auxiliary control of the change in sludge concentration can improve the speed of adjustment of the additive amount when there is a rapid change in sludge concentration. In sludge concentration change control, the supply sludge concentration is measured, and if the change in sludge concentration per unit time is greater than or equal to a threshold, the coagulant addition concentration is controlled. If the change in sludge concentration increases, increase the amount of coagulant added; if the change in sludge concentration decreases, decrease the amount of coagulant added.

[0069] Figure 10 shows an example of the components of the control device 103 shown in Figure 9. As shown in Figure 10, the control device 103 shown in Figure 9 includes an index calculation unit 110, an additive amount control unit 123, a sludge supply amount control unit 130, and a rotation speed control unit 140. The index calculation unit 110, the sludge supply amount control unit 130, and the rotation speed control unit 140 are the same as those in the first embodiment. Note that Figure 10 shows only the main components of the control device 103 shown in Figure 9 that are relevant to this embodiment.

[0070] The addition amount control unit 123 has the following functions in addition to the addition amount control unit 120 in the first embodiment. The addition amount control unit 123 controls the amount of coagulant added by the additive device 300 based on the change in sludge concentration per unit time measured by the concentration meter 41 and the change in the calculated coagulation index. Specifically, the addition amount control unit 123 calculates the concentration change amount, which is the change in sludge concentration per unit time, a value output from the concentration meter 41. If the concentration change amount exceeds a preset threshold (first concentration change threshold), the addition amount control unit 123 controls the amount of coagulant added by the additive device 300 to increase if the concentration is changing towards an increased level. On the other hand, if the concentration change amount exceeds a preset threshold, the addition amount control unit 123 controls the amount of coagulant added by the additive device 300 to decrease if the concentration is changing towards a decreased level. Furthermore, if the concentration change amount is below a preset threshold, the addition amount control unit 123 controls the amount of addition based on the coagulation index described above.

[0071] The sludge treatment method in the sludge treatment system shown in Figure 9 will be described below. The method for controlling the amount of additive based on the coagulation index in the sludge treatment method in the sludge treatment system shown in Figure 9 is the same as in the first embodiment. Figure 11 is a flowchart illustrating an example of the method for controlling the amount of additive based on the sludge concentration in the sludge treatment method in the sludge treatment system shown in Figure 9.

[0072] The additive amount control unit 123 calculates the concentration change amount, which is the amount of change in sludge concentration per unit time, output from the concentration meter 41 (step S71). The additive amount control unit 123 determines whether the calculated concentration change amount exceeds a preset threshold (step S72). If the concentration change amount exceeds the preset threshold, the additive amount control unit 123 determines whether the sludge concentration is changing in the direction of increasing (higher) (step S73). If the sludge concentration is changing in the direction of increasing (higher), the additive amount control unit 123 increases the amount of coagulant added by the additive device 300 from the coagulant storage tank 301 (step S74). Then, the additive amount control unit 123 controls the additive device 300 to add the increased amount of coagulant from the coagulant storage tank 301 (step S75). The amount by which the additive amount is increased may be a preset amount, or it may be an amount calculated according to the change in sludge concentration.

[0073] On the other hand, if the sludge concentration decreases in step S73, the addition amount control unit 123 reduces the amount of coagulant added by the addition device 300 from the coagulant storage tank 301 (step S76). The addition amount control unit 123 then controls the addition device 300 to add the reduced amount of coagulant from the coagulant storage tank 301 (step S77). The amount by which the addition amount is reduced may be a preset amount or an amount calculated according to the change in sludge concentration.

[0074] Furthermore, in step S72, if the concentration change is below a preset threshold, the addition amount control unit 123 controls the addition amount based on the aggregation index explained using the flowcharts shown in Figures 3A and 3B (step S78).

[0075] Furthermore, even while the amount of additive is being controlled based on the flocculation index explained using the flowcharts shown in Figures 3A and 3B, the processes in steps S71 and S72 are still being carried out. If the concentration change exceeds a threshold, the processes in steps S73 to S77 are performed with priority over the control of the amount of additive based on the flocculation index explained using the flowcharts shown in Figures 3A and 3B.

[0076] As described above, in the first to third embodiments, the method of controlling the amount of coagulant added based on the coagulation index controls the amount of coagulant added to the sludge in the coagulation tank 20, respectively, based on the change in the coagulation index before and after the change in the amount of coagulant added to the sludge in the coagulation tank 20. Therefore, it does not require data collection work to set a standard value or standard range for the amount of coagulant added, and it is possible to respond quickly to changes in sludge properties. Furthermore, by imaging the coagulated matter in the existing mixing tank, it is possible to control the amount of coagulant added, without requiring additional costs or space. In other words, it is possible to easily control the amount of coagulant added to suit the change in the state of the coagulated matter when the coagulant is added. In addition, the control device 103 controls the amount of coagulant added based on the sludge concentration and the coagulation index in accordance with the change in sludge concentration. This allows for a quick response to changes in sludge concentration. As a control based on sludge concentration, a method may be applied in which the amount of coagulant added changes to a specified value according to the sludge concentration. When the change in sludge concentration exceeds a specified value, it is preferable to change the amount of coagulant added by the specified value. This allows for a more appropriate and rapid response to changes in sludge concentration, as the amount of coagulant added is changed based on the previous amount, rather than resetting the amount of coagulant added when the sludge concentration changes. (Fourth embodiment)

[0077] Figure 12 shows a fourth embodiment of the sludge treatment system of the present invention. As shown in Figure 12, the sludge treatment system in this embodiment includes a water tank 12, a coagulation tank 20, a dewatering machine 30, an interface measuring means 13, a pressure gauge 23, a control device 104, a sludge supply device 200, an additive device 300, a coagulant storage tank 301, and a compression unit rotating device 400. The pressure gauge 23, coagulation tank 20, dewatering machine 30, sludge supply device 200, additive device 300, coagulant storage tank 301, and compression unit rotating device 400 are the same as those in the first embodiment.

[0078] The tank 12 receives and stores the sludge to be treated. For example, excess sludge generated from wastewater treatment facilities flows into the tank 12 as sludge to be treated.

[0079] The interface measuring means 13 measures the height of the interface of the sludge to be treated stored in the water tank 12. The interface measuring means 13 may also be a water level gauge (water level gauge 11 in the first embodiment) that measures the water level of the sludge to be treated stored in the water tank 12. If the interface measuring means 13 is a water level gauge, instruments such as float type, electrode type, guide pulse type, optical type, pressure type, and ultrasonic type can be used as the interface measuring means 13. Alternatively, the interface measuring means 13 may also be an interface meter that measures the height of the interface of the concentrated sludge layer of the sludge to be treated stored in the water tank 12. The interface of the concentrated sludge layer is the boundary between the concentrated sludge layer and the separated liquid (dilute layer). If the interface measuring means 13 is an interface meter, instruments such as ultrasonic type and magnetic type can be used as the interface measuring means 13. When the sludge to be treated is subjected to a settling treatment in the tank 12 to concentrate it and form concentrated sludge, the height of the interface of the concentrated sludge layer represents the actual amount of sludge stored and supplied to the coagulation tank.

[0080] Figure 13 shows an example of the components of the control device 104 shown in Figure 12. As shown in Figure 13, the control device 104 shown in Figure 12 includes an index calculation unit 114, an additive amount control unit 124, a sludge supply amount control unit 134, and a rotation speed control unit 144. Note that Figure 13 shows only the main components of the control device 104 shown in Figure 12 that are relevant to this embodiment.

[0081] The index calculation unit 114 calculates a property index indicating the properties of the sludge to be treated at the inlet of the dewatering machine 30, based on the amount of sludge to be treated that the sludge supply control unit 134 is supplying from the water tank 12 to the coagulation tank 20. The value indicating the amount of sludge to be treated supplied from the water tank 12 to the coagulation tank 20 is maintained by the sludge supply control unit 134. At this time, the index calculation unit 114 may calculate the property index as the amount of sludge to be treated that the sludge supply device 200 is supplying to the coagulation tank 20, or it may calculate the property index as a value obtained by multiplying the amount of sludge to be treated that the sludge supply device 200 is supplying to the coagulation tank 20 by a predetermined coefficient. The inlet of the dewatering machine 30 is any position on the flow path from the sludge supply device 200 to the dewatering machine 30 via the coagulation tank 20. The index calculation unit 114 outputs the calculated property index to the additive amount control unit 124. Furthermore, if the configuration shown in Figure 14 is equipped with the sensor 22 shown in Figure 1, the index calculation unit 114 may calculate the change in the aggregation index, which indicates the state of aggregates acquired by the sensor 22, as a property index, similar to the process performed by the index calculation unit 110 shown in Figure 2.

[0082] The addition amount control unit 124 controls the amount of coagulant added by the additive device 300 based on the property index output from the index calculation unit 114. For example, the addition amount control unit 124 determines the amount of coagulant to add by multiplying the property index output from the index calculation unit 114 by a predetermined coefficient. The sludge supply amount used as the basis for calculating the property index used in this calculation may be the frequency (Hz), analog signal, or digital signal of the sludge supply pump used as the sludge supply device 200. For example, the addition amount control unit 124 determines the amount of coagulant to add by multiplying the frequency (Hz) of the sludge supply pump by a predetermined coefficient. The addition amount control unit 124 increases the amount of coagulant to add when the property index increases, and decreases the amount of coagulant to add when the property index decreases.

[0083] The sludge supply control unit 134, in order to control the amount of sludge to be treated, uses the height of the interface of the sludge to be treated, measured by the interface measuring means 13, instead of the water level of the sludge storage tank 10 measured by the water level gauge 11 used by the sludge supply control unit 130 in the first embodiment. When using the supply amount calculation formula, the sludge supply control unit 134, for example, substitutes the height of the interface of the sludge to be treated, measured by the interface measuring means 13, into a predetermined supply amount calculation formula (second supply amount calculation formula) to calculate the amount of sludge to be treated to be supplied by the sludge supply device 200, and controls the sludge supply device 200 to supply the calculated amount of sludge to be treated to the coagulation tank 20. The supply amount calculation formula used here is: Sludge supply amount = (Value measured by interface measuring means 13) × G + H This is a linear function equation. Here, G and H are pre-calculated constants. G and H are calculated as the slope (the ratio of the increase in sludge supply to the increase in interface height) G and the intercept H (the intercept of the sludge supply axis) from a straight line (a linear line sloping upwards to the right) formed by plotting two sets of points representing the sludge supply amount and interface height measured in cases where the dewatering machine 30 operates suitably, specifically in cases where the value measured by the interface measuring means 13 is large (a high sludge supply amount that increases the amount of sludge treated) and in cases where the value measured by the interface measuring means 13 is small (a low sludge supply amount corresponding to the decrease in the amount of treatment due to the decrease in the rotation speed of the rotating body in the compression rotating device 400) on a graph with the sludge supply amount on the vertical axis and the interface height on the horizontal axis. The intercept H is then calculated from these points. In addition, the sludge supply amount control unit 134 monitors and maintains a value indicating the amount of sludge to be treated that the sludge supply device 200 is supplying to the coagulation tank 20.

[0084] In order to control the rotation speed of the compression unit rotating device 400, the rotation speed control unit 144 uses the height of the interface of the sludge to be treated, measured by the interface measuring means 13, instead of the water level of the sludge storage tank 10 measured by the water level gauge 11 used by the rotation speed control unit 140 in the first embodiment.

[0085] The sludge treatment method in the sludge treatment system shown in Figure 12 will be described below. Figure 14 is a flowchart illustrating an example of a method for controlling the amount of sludge supplied from the sludge supply device 200 and the rotation speed of the compression unit rotating device 400 based on the height of the interface of the water tank 12 and the sludge injection pressure in the sludge treatment method in the sludge treatment system shown in Figure 12.

[0086] First, the control device 104 determines whether the height of the interface of the sludge to be treated, as measured by the interface measuring means 13, exceeds a threshold (step S81). If the interface measuring means 13 determines that the height of the interface of the sludge to be treated exceeds a threshold, the rotation speed control unit 144 increases the rotation speed of the compression unit rotating device 400 (step S82). The rotation speed control unit 144 determines whether the increased rotation speed is below the upper limit (step S83). If the increased rotation speed is determined to be below the upper limit, the sludge supply amount control unit 134 calculates the sludge supply amount by substituting the interface height measured by the interface measuring means 13 into the second supply amount calculation formula described above, and controls the sludge supply device 200 to supply the calculated amount of sludge to the coagulation tank 20 (step S84). Furthermore, if it is determined in step S83 that the rotation speed has not fallen below the upper limit, the rotation speed control unit 144 maintains the rotation speed at the upper limit (step S85), and the sludge supply amount control unit 134 performs the processing in step S84. After that, the processing in step S81 is performed. If the height of the interface of the sludge to be treated, as measured by the interface measuring means 13, exceeds a threshold, it may cause an excessive rise in the water level of the sludge to be treated in the subsequent coagulation tank 20. For this reason, it is preferable for the control device 104 to first increase the rotation speed of the compression unit rotating device 400. This prevents the sludge supply from being stopped (the dewatering equipment from stopping) due to the height of the interface of the sludge to be treated in the sludge storage tank 10 or the water level in the coagulation tank 20 rising.

[0087] On the other hand, if in step S81 the interface measuring means 13 determines that the height of the interface of the sludge to be treated does not exceed a threshold, the rotation speed control unit 144 reduces the rotation speed of the compression unit rotating device 400 (step S86). The rotation speed control unit 144 determines whether the reduced rotation speed exceeds a lower limit (step S87). If it is determined that the reduced rotation speed exceeds a lower limit, the sludge supply amount control unit 134 determines whether the value of the sludge injection pressure measured by the pressure gauge 23 is greater than a predetermined reference range (step S88). If in step S87 it is determined that the rotation speed does not exceed a lower limit, the rotation speed control unit 144 maintains the rotation speed at the lower limit (step S89), and the sludge supply amount control unit 134 performs the process in step S88.

[0088] In step S88, if the pressure gauge 23 determines that the sludge injection pressure is greater than a predetermined reference range, the sludge supply control unit 134 reduces the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S90). Subsequently, the process in step S81 is performed.

[0089] In step S88, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is not greater than a predetermined reference range, the sludge supply control unit 134 determines whether the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range (step S91). In step S91, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is less than a predetermined reference range, the sludge supply control unit 134 increases the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S92). On the other hand, in step S91, if it is determined that the sludge injection pressure measured by the pressure gauge 23 is not less than a predetermined reference range, the sludge supply control unit 134 maintains the amount of sludge to be treated supplied by the sludge supply device 200 from the sludge storage tank 10 to the coagulation tank 20 (step S93). After that, the process in step S81 is performed.

[0090] Thus, in this embodiment, if the interface height of the sludge to be treated, as measured by the interface measuring means 13, exceeds a threshold, the sludge supply rate and the rotation speed of the compression section are increased to prevent an excessive rise in the water level of the tank 12 and prevent the equipment located upstream of the tank 12 from stopping. Furthermore, if the interface height of the sludge to be treated, as measured by the interface measuring means 13, is below the threshold, the dewatering machine 30 performs dewatering over a longer period of time, thereby reducing the moisture content of the dewatered sludge. This allows for efficient operation of the equipment. Normally, sludge dewatering machines are designed with a sufficient margin over the planned sludge volume, so this margin can be used effectively. In addition, when the amount of sludge to be treated is rapidly changed by adjusting the water level of the tank 12, conventional fixed or automatic addition controls for coagulants do not allow for appropriate adjustment of the amount added, and the coagulation state cannot be optimized. Therefore, there was a problem in that it was difficult to reduce the moisture content of the dewatered sludge. However, in this embodiment, the amount of coagulant added is rapidly controlled by constantly monitoring the properties of the sludge to be treated. This optimizes the coagulation state in the coagulation tank 20, making it possible to reduce the water content of the dewatered sludge even when the water level in the tank 12 is adjusted. In this configuration, by monitoring the height of the interface of the sludge to be treated stored in the tank and the injection pressure of the sludge to be treated, and controlling the amount of coagulant added, the sludge supply amount, and the rotation speed of the dewatering machine, a stable processing volume and water content of the dewatered sludge can be maintained even if the amount of sludge generated changes.

[0091] The above explanation describes how each component is assigned a specific function (process), but this assignment is not limited to those described above. Furthermore, the configurations of the components described above are merely examples and are not limited to them. Also, the embodiments described above may be combined in any combination.

[0092] The processing performed by each of the control devices 100, 102-104 described above may be carried out by logic circuits created according to their respective purposes. Alternatively, a computer program (hereinafter referred to as "program") describing the processing content as a procedure may be recorded on a recording medium readable by each of the control devices 100, 102-104, and the program recorded on this recording medium may be read and executed by each of the control devices 100, 102-104. The recording medium readable by each of the control devices 100, 102-104 refers to portable recording media such as floppy disks, magneto-optical disks, DVDs (Digital Versatile Discs), CDs (Compact Discs), Blu-ray Discs, USB (Universal Serial Bus) memory, and SD cards, as well as memory such as ROM (Read Only Memory), RAM (Random Access Memory), and HDDs (Hard Disc Drives) built into each of the control devices 100, 102-104. The program recorded on this recording medium is read by the CPUs provided in each of the control devices 100, 102-104, and the same processing as described above is performed under the control of the CPU. Here, the CPU operates as a computer that executes the program read from the recording medium on which the program is recorded. [Explanation of symbols]

[0093] 10 Sludge storage tank 11 Water level gauge 12 aquariums 13 Interface measurement means 20 Coagulation tank 22 sensors 23 Pressure gauge 30 Dehydrator 40 Solids feed amount measuring section 41 Densitometer 42 Flow meter 100, 102~104 Control device 110,114 Indicator calculation section 120, 123, 124 Addition amount control unit 130, 132, 134 Sludge supply control unit 140, 142, 144 Speed ​​control unit 200 Sludge supply system 300 Addition equipment 301 Coagulant Storage Tank 400 Compression section rotating device

Claims

1. A tank into which the sludge to be treated flows, An interface measuring means for measuring the height of the interface of the sludge to be treated stored in the water tank, A flocculation tank into which the sludge to be treated flows in from the water tank, A sludge supply unit that supplies the sludge to be treated from the water tank to the coagulation tank, An additive device for adding a coagulant to the sludge to be treated stored in the coagulation tank, A dewatering device that compresses the sludge to be treated, to which the coagulant has been added, by a rotating body, A pressure gauge for measuring the injection pressure of the sludge to be treated to which the coagulant has been added, A sludge treatment system comprising: a control device that controls the amount of the coagulant added by the additive device based on a property index indicating the properties of the sludge to be treated at the inlet of the dewatering device; and a control device that controls at least one of the amount of the sludge to be treated supplied by the sludge supply unit and the rotation speed of the rotating body based on a value measured by the interface measuring means and the injection pressure measured by the pressure gauge.

2. In the sludge treatment system according to claim 1, A sludge treatment system characterized in that the interface measuring means is one of a first water level meter for measuring the water level of the sludge to be treated stored in the water tank, and an interface meter for measuring the height of the interface of the concentrated sludge layer of the sludge to be treated.

3. In the sludge treatment system according to claim 1, A sludge treatment system characterized in that the property index is a value indicating the amount of sludge supplied from the sludge supply unit.

4. In the sludge treatment system according to claim 1, The device has a sensor that acquires the state of the coagulated material in the treated sludge to which the coagulant has been added from the additive device. A sludge treatment system characterized in that the property index is the amount of change in the coagulation index when the control device calculates a coagulation index indicating the state of the aggregate acquired by the sensor and the amount of coagulant added by the additive device is changed.

5. In the sludge treatment system according to claim 1 or claim 2, The coagulation tank has a second water level gauge for measuring the water level of the sludge to be treated stored in the tank, A sludge treatment system in which the control device controls at least one of the amount of sludge to be treated supplied by the sludge supply unit and the rotation speed of the rotating body based on the value measured by the interface measuring means, the injection pressure measured by the pressure gauge and the value measured by the second water level gauge.

6. In the sludge treatment system according to claim 4, A sludge treatment system in which the control device compares the amount of change in the coagulation index, which is the ratio of the change in the amount of coagulation added to the change in the amount of coagulation added when the amount of coagulation added is changed, with a predetermined threshold, and increases the amount of coagulation added by the adding device when the amount of change in coagulation exceeds the threshold, and decreases the amount of coagulation added by the adding device when the amount of change in coagulation is less than or equal to the threshold.

7. In the sludge treatment system according to claim 4 or claim 6, The sensor is an image sensor that captures an image of the sludge to be treated in the coagulation tank, The control device is a sludge treatment system that calculates the characteristic quantities of aggregates in the sludge to be treated as the aggregation index from the image captured by the image sensor.

8. An index calculation unit that calculates a property index indicating the properties of the sludge to be treated at the inlet of the dewatering device, Based on the aforementioned property indicators, the addition amount control unit controls the amount of coagulant added by the addition device to the sludge to be treated, A sludge supply control unit controls the amount of sludge to be treated supplied from the water tank to a flocculation tank where the sludge to be treated to be stored is stored, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the flocculant has been added. A control device comprising a rotation speed control unit that controls the rotation speed of a rotating body provided in a dewatering device that compresses the sludge to be treated to which the coagulant has been added, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the coagulant has been added.

9. A process for calculating a property index that indicates the properties of the sludge to be treated at the inlet of the dewatering device, A process in which the additive device controls the amount of coagulant added to the sludge to be treated based on the aforementioned property indicators, A process for controlling the amount of sludge to be treated supplied from the water tank to the flocculation tank where the sludge to be treated to be treated is stored, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the flocculant has been added, A sludge treatment method comprising controlling the rotation speed of a rotating body provided in a dewatering device that compresses the sludge to be treated to a pressure, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the coagulant has been added.

10. On the computer, Procedure for calculating property indicators that show the properties of the sludge to be treated at the inlet of the dewatering device, A procedure for controlling the amount of coagulant added to the sludge to be treated by the additive device based on the aforementioned property indicators, A procedure for controlling the amount of sludge to be treated supplied from the water tank to the flocculation tank where the sludge to be treated to be treated is stored, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the flocculant has been added, A program for performing a procedure to control the rotation speed of a rotating body provided in a dewatering device that compresses the sludge to be treated to a pressure, based on the height of the interface of the sludge to be treated stored in the water tank and the injection pressure of the sludge to be treated to which the coagulant has been added.

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