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

Abstract

To reduce a moisture content of dewatered sludge.SOLUTION: A sludge treatment system includes: a coagulation tank 500; a sludge supply device 200 that supplies sludge to be treated to the coagulation tank 500; a sludge concentration meter 300 that measures a sludge concentration of the sludge to be treated that is supplied from the sludge supply device 200; an addition device 600 that adds a coagulant to the sludge to be treated stored in the coagulation tank 500; a sensor 400 that acquires a state of the coagulant in the sludge to be treated to which the coagulant has been added from the addition device 600; and a control device 100 that controls the amount of the sludge to be treated that is supplied by the sludge supply device 200 based on a sludge concentration measured by the sludge concentration meter 300, calculates an aggregation index that indicates a state of an aggregate acquired by the sensor 400, and controls the amount of the coagulant to be added by the addition device 600 based on the amount of change in the aggregation index when the amount of the coagulant to be added by the addition device 600 is changed.SELECTED DRAWING: Figure 1

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 specific coagulant to sludge stored in a water tank, and then using a dehydrator to separate the sludge into dehydrated sludge and filtrate to remove water from the coagulant-added sludge. This method reduces the water content of the dehydrated sludge, which becomes waste, thereby reducing the amount of waste. In some cases, this dehydration process automatically adjusts the amount of coagulant added and the amount of sludge supplied depending on the treatment status. For example, Patent Document 1 discloses a technology that controls the rotation speed of a sludge supply pump based on the sludge concentration measured by a concentration sensor, the sludge supply rate measured by a flow meter, and the liquid level fluctuation in the tank measured by a water level sensor, thereby controlling the amount of sludge solids supplied to the dehydrator per hour to a constant value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-263488 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the amount of flocculant added to the sludge to be treated is not controlled according to the properties of the sludge being fed in. As a result, the sludge does not flocculate well, which causes a problem of an increase in the moisture content of the dewatered sludge.

[0005] An object of the present invention is to provide a sludge treatment system, a control device, a sludge treatment method, and a program that can reduce the moisture content of dewatered sludge. [Means for solving the problem]

[0006] The sludge treatment system of the present invention comprises: a flocculation tank; a sludge supply device for supplying sludge to be treated to the coagulation tank; a sludge concentration meter for measuring the sludge concentration of the sludge to be treated supplied from the sludge supply device; an adding device that adds a flocculant to the sludge to be treated stored in the flocculation tank; a sensor for acquiring the state of flocculants in the sludge to be treated to which the flocculant has been added from the adding device; The device has a control device that controls the amount of sludge to be treated supplied by the sludge supply device based on the sludge concentration measured by the sludge concentration meter, calculates an aggregation index indicating the state of the aggregate obtained by the sensor, and controls the amount of flocculant added by the addition device based on the amount of change in the aggregation index when the amount of flocculant added by the addition device is changed.

[0007] The control device of the present invention also includes: a solids amount calculation unit that calculates the amount of solids contained in the sludge to be treated based on the amount of sludge to be treated that is supplied to the coagulation tank and the sludge concentration of the sludge to be treated measured by a sludge concentration meter; a sludge supply amount control unit that controls the supply amount of the sludge to be treated that is supplied to the coagulation tank based on the amount of solid matter calculated by the solid matter amount calculation unit; a coagulation index calculation unit that calculates a coagulation index that indicates the state of coagulation in the sludge to be treated that has been supplied to the coagulation tank and to which a coagulant has been added from an addition device; The device has an addition amount control unit that controls the amount of the flocculant added by the addition device based on the amount of change in the flocculation index when the amount of the flocculant added by the addition device is changed.

[0008] Further, the sludge treatment method of the present invention comprises: a process of calculating the amount of solids contained in the sludge to be treated based on the amount of sludge to be treated supplied to the coagulation tank and the sludge concentration of the sludge to be treated measured by a sludge concentration meter; a process of controlling the amount of the sludge to be treated supplied to the coagulation tank based on the calculated amount of solids; a process of calculating a coagulation index that indicates the state of coagulation in the sludge to be treated that has been supplied to the coagulation tank and to which a coagulant has been added from an addition device; The amount of the flocculant added by the addition device is controlled based on the amount of change in the flocculation index when the amount of the flocculant added by the addition device is changed.

[0009] The program of the present invention also includes: A program to be executed by a computer, On the computer, calculating the amount of solids contained in the sludge to be treated based on the amount of sludge to be treated supplied to the coagulation tank and the sludge concentration of the sludge to be treated measured by a sludge concentration meter; a step of controlling the amount of the sludge to be treated supplied to the coagulation tank based on the calculated amount of solids; a step of calculating a coagulation index that indicates the state of coagulation in the sludge to be treated that has been supplied to the coagulation tank and to which a coagulant has been added from an addition device; and a procedure for controlling the amount of the flocculant added by the addition device based on the amount of change in the flocculation index when the amount of the flocculant added by the addition device is changed. [Effects of the Invention]

[0010] In the present invention, the water content of the dewatered sludge can be reduced. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a first embodiment of a sludge treatment system according to the present invention. [Figure 2] 2 is a diagram illustrating an example of components included in the control device illustrated in FIG. 1. FIG. [Figure 3] 2 is a flowchart illustrating an example of a method for controlling the supply amount of sludge to be treated, among methods for treating sludge in the sludge treatment system shown in FIG. [Figure 4A] 2 is a flowchart for explaining an example of a method for controlling an amount of addition based on a coagulation index, among methods for treating sludge in the sludge treatment system shown in FIG. 1. [Figure 4B] 2 is a flowchart for explaining an example of a method for controlling an amount of addition based on a coagulation index, among methods for treating sludge in the sludge treatment system shown in FIG. 1. [Figure 5] 2 is a flowchart for explaining an example of a control method for keeping constant the amount of sludge supplied and the amount of flocculant added, among the sludge treatment methods in the sludge treatment system shown in FIG. 1. [Figure 6] FIG. 2 is a diagram showing a second embodiment of a sludge treatment system according to the present invention. [Figure 7] 7 is a diagram illustrating an example of components included in the control device illustrated in FIG. 6. FIG. [Figure 8] 7 is a flowchart for explaining an example of an illumination control method among the sludge treatment methods in the sludge treatment system shown in FIG. 6. [Figure 9] 1 is a diagram showing an application example of a sludge treatment system according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First embodiment)

[0013] Fig. 1 is a diagram showing a first embodiment of a sludge treatment system of the present invention. As shown in Fig. 1, the sludge treatment system in this embodiment includes a control device 100, a sludge supply device 200, a sludge concentration meter 300, a sensor 400, a coagulation tank 500, an addition device 600, and a coagulant storage tank 700.

[0014] The sludge supply device 200 is a sludge supply unit that supplies the supplied sludge to be treated to the coagulation tank 500. Examples of the sludge to be treated include organic sludge and inorganic sludge. Examples of organic sludge include scum from coagulation sedimentation or pressurized flotation in food factories, semiconductor factories, paper factories, and sewage treatment water reuse plants, excess sludge from membrane separation, and activated sludge from sewage treatment plants. Examples of inorganic sludge include sludge derived from metals, coagulants, lime, and calcium in wastewater. However, the sludge to be treated is not limited to these. The sludge supply device 200 supplies the amount of sludge to be treated to the coagulation tank 500 based on instructions from the control device 100. The sludge supply device 200 is equipped with a sludge supply pump that transfers sludge stored in a sludge storage tank located upstream of the sludge supply device 200 to the coagulation tank 500. The sludge supply pump preferably includes a mechanism capable of controlling the pump rotation speed in response to an output signal from the control device 100, such as an inverter that controls the pump rotation speed. The method for controlling the sludge supply amount is not limited to inverter control of the sludge supply pump; it may also be a control method using a control valve between the sludge supply pump and the coagulation tank 500 that can adjust the opening. In addition, inverter control and control using a control valve may be used in combination. Regarding the control of the sludge supply amount, the pump rotation speed may be controlled by frequency (Hz) control using an inverter, or by sending an analog or digital signal to the pump. The sludge supply pump is not particularly limited, but examples of the sludge supply pump include a screw pump and a rotary positive displacement uniaxial eccentric screw pump. This allows the amount of sludge supplied to the coagulation tank 500 to be increased or decreased.

[0015] The sludge concentration meter 300 measures the sludge concentration of the sludge to be treated supplied from the sludge supply device 200. The sludge concentration meter 300 is not particularly limited, but is preferably an SS (Suspended Solids) meter. The installation location of the sludge concentration meter 300 is not particularly limited. The sludge concentration meter 300 may be installed, for example, in a sludge storage tank or in the piping from the sludge storage tank to the coagulation tank (also called the sludge supply piping). The sludge concentration meter 300 measures the sludge concentration using transmitted light, scattered light, a laser, or the like. The sludge concentration meter 300 notifies the control device 100 of the measured sludge concentration value.

[0016] The sensor 400 acquires the state of flocs in the sludge stored in the coagulation tank 500 to which a coagulant has been added from the addition device 600. The sensor 400 may be, for example, a non-wetted image sensor (camera) that captures images of the sludge. The sensor 400 is preferably an infrared sensor. The sensor 400 may also be a camera that captures images of the sludge in the coagulation tank 500 at intervals equal to or shorter than a predetermined time interval (for example, a video camera that continuously captures images). The sensor 400 outputs image data representing the acquired (captured) images to the control device 100. There are no particular restrictions on how the sensor 400 is fixed. If the sensor 400 is a camera, the sensor 400 does not necessarily need to capture images of the sludge stored in the coagulation tank 500 from above in the vertical direction. The sensor 400 may capture images from diagonally above at a predetermined angle relative to the vertical direction, as long as it can capture an image of the sludge through the liquid surface stored in the coagulation tank 500. In other words, the specific installation position of the sensor 400 may be any position that allows the sludge stored in the coagulation tank 500 to be imaged through the liquid surface. If the coagulation tank 500 is a sealed type, a transparent member may be provided on the top or side of the coagulation tank 500, and the liquid surface may be imaged through the transparent member. Alternatively, the sludge may be made to flow vertically downward, and the camera serving as the sensor 400 may image the flowing sludge from a horizontal direction. For example, a pipe made of a transparent member may be provided through which the sludge stored in the coagulation tank 500 flows vertically downward, and the camera may image the sludge flowing down the pipe from a horizontal direction outside the pipe.

[0017] The coagulation tank 500 is a water tank in which the sludge to be treated supplied from the sludge supply device 200 is stored. The coagulation tank 500 has a predetermined capacity. The coagulation tank 500 may be provided with an agitator for agitating the treated sludge.

[0018] The dosing device 600 adds the flocculant stored in the flocculant storage tank 700 to the sludge stored in the coagulation tank 500. The dosing device 600 adds the amount of flocculant from the flocculant storage tank 700 to the sludge stored in the coagulation tank 500 based on instructions from the control device 100. The dosing device 600 is equipped with a flocculant dosing pump that sends the flocculant from the flocculant storage tank 700. The flocculant dosing pump is equipped with a mechanism that can control the pump rotation speed in response to an output signal from the control device 100, such as an inverter that controls the pump rotation speed. Note that the pump rotation speed can be controlled by sending an analog signal or a digital signal to the pump, in addition to frequency (Hz) control using an inverter. The flocculant stored in the flocculant storage tank 700 may be either an inorganic or organic flocculant. If the flocculant stored in the flocculant storage tank 700 is inorganic, the flocculant may be aluminum-based (PAC, aluminum sulfate, etc.), iron-based (polyferric chloride, ferric chloride), or the like, and is not particularly limited. Furthermore, if the flocculant stored in the flocculant storage tank 700 is organic, the flocculant may be cationic, anionic, or amphoteric. The flocculant storage tanks 700 may be divided according to the type of flocculant. Furthermore, the dosing device 600 may not only add the flocculant to the coagulation tank 500, but also add it to the piping. When the dosing device 600 adds multiple flocculants, it may add multiple additives to the same coagulation tank, or it may add multiple flocculants to multiple coagulation tanks, respectively. Furthermore, the dosing device 600 may add multiple flocculants to the piping and the coagulation tank 500, respectively. For example, the dosing device 600 may add some of the multiple flocculants (e.g., inorganic flocculants) to the piping, and add the remaining flocculants (e.g., organic flocculants) to the flocculation tank 500. When the dosing device 600 adds multiple flocculants, it may control the amount of a first flocculant added based on instructions from the control device 100, and control the amount of a second flocculant added by maintaining a constant ratio between the amount of a second flocculant added and the amount of the first flocculant added. This simplifies the control logic for the amounts added. When an inorganic flocculant and an organic flocculant are used in combination, it is preferable that the dosing device 600 add the inorganic flocculant at an earlier stage than the organic flocculant.

[0019] Fig. 2 is a diagram showing an example of components included in the control device 100 shown in Fig. 1. As shown in Fig. 2, the control device 100 shown in Fig. 1 has a solids amount calculation unit 110, a sludge supply amount control unit 120, a flocculation index calculation unit 130, and an addition amount control unit 140. Note that Fig. 2 shows only the main components related to this embodiment among the components included in the control device 100 shown in Fig. 1.

[0020] The solid amount calculation unit 110 calculates the amount of solids contained in the sludge to be treated per unit time (kg / h) based on the amount of sludge to be treated supplied to the coagulation tank 500 per unit time and the sludge concentration of the sludge to be treated notified from the sludge concentration meter 300. Specifically, the solid amount calculation unit 110 calculates the amount of solids using (Equation 1). Solids volume DS = Sludge supply volume P × Sludge concentration S (Equation 1) Here, the supply amount of the sludge to be treated supplied to the coagulation tank 500 may be a value calculated by converting a signal (e.g., a pump output value) used by the sludge supply amount control unit 120 to control the supply amount, or may be a value measured by a flow meter (not shown) installed in the sludge supply pipe. The solid amount calculation unit 110 notifies the sludge supply amount control unit 120 of the calculated solid amount. The solid amount calculation unit 110 also compares the sludge concentration of the sludge to be treated notified by the sludge concentration meter 300 with preset upper and lower limit values. If the comparison results in the sludge concentration of the sludge to be treated notified by the sludge concentration meter 300 being equal to or greater than the upper limit value, or if the sludge concentration of the sludge to be treated notified by the sludge concentration meter 300 being equal to or less than the lower limit value, the solid amount calculation unit 110 notifies the sludge supply amount control unit 120 and the addition amount control unit 140 of this fact.

[0021] The sludge supply amount control unit 120 controls the supply amount of the sludge to be treated that is supplied from the sludge supply device 200 to the coagulation tank 500 based on the amount of solids notified by the solid amount calculation unit 110. Specifically, the sludge supply amount control unit 120 controls the supply amount of the sludge to be treated that is supplied from the sludge supply device 200 to the coagulation tank 500 using (Equation 2) so that the amount of solids notified by the solid amount calculation unit 110 becomes a predetermined amount (target solid amount DS') that has been set in advance. Sludge supply amount to be treated P = target solids amount DS' / sludge concentration S ... (Equation 2) It is preferable to give the target solids content DS' a certain margin (for example, ±5%). This is because there is a possibility that the moisture content will increase if the target solids content cannot be maintained. Furthermore, when the sludge supply volume control unit 120 receives a notification from the solids content calculation unit 110 that the sludge concentration of the sludge to be treated notified from the sludge concentration meter 300 is equal to or higher than the upper limit, or that the sludge concentration of the sludge to be treated notified from the sludge concentration meter 300 is equal to or lower than the lower limit, the sludge supply volume control unit 120 controls the supply volume of the sludge to be treated supplied from the sludge supply device 200 to the coagulation tank 500 to a fixed supply volume.

[0022] The flocculation index calculation unit 130 calculates a flocculation index indicating the state of the flocs acquired by the sensor 400. When the sensor 400 is an image sensor, the flocculation index calculation unit 130 calculates a feature quantity of the flocs in the sludge in the flocculation tank 500 as the flocculation index from the image captured by the image sensor. Here, the flocculation index calculation unit 130 calculates the number of suspended solids contained in the sludge in the flocculation tank 500, the particle diameter, or the displacement amount as the feature quantity from the image captured by the image sensor. For example, the flocculation index calculation unit 130 may use an image processing technique such as Motion History Image to color parts that differ between frames in white for the images (videos) captured by the image sensor, and calculate the count number (displacement amount) of the colored white dots as the feature quantity. Alternatively, the flocculation index calculation unit 130 may use an image processing technique such as Optical Flow to visualize the flow of flocs in the sludge in the flocculation tank 500, measure the width of the flow, and calculate the particle diameter as the feature quantity. Alternatively, if the sensor 400 is an image sensor, the flocculation index calculation unit 130 calculates the number of edges of flocculants in the sludge in the coagulation tank 500 from the image captured by the image sensor as the flocculation index. Here, the flocculation index calculation unit 130 may detect pixels in the image captured by the image sensor where the color difference (e.g., the difference between RGB values) between adjacent pixels is equal to or greater than a threshold as the edge of the flocculant, and calculate the number of detected edges (number of pixels) as the flocculation index. Alternatively, if the sensor 400 is an image sensor, the flocculation index calculation unit 130 may calculate the area of ​​flocculants in the sludge in the coagulation tank 500 from the image captured by the image sensor as the flocculation index. Alternatively, if the sensor 400 is an image sensor, the flocculation index calculation unit 130 may calculate the number of flocculants in the sludge in the coagulation tank 500 from the image captured by the image sensor as the flocculation index. Furthermore, if the sensor 400 is an image sensor, the coagulation index calculation unit 130 may calculate an arbitrary combination of the number of edges, area, and number of coagulation particles in the sludge in the coagulation tank 500 from the image captured by the image sensor as the coagulation index.

[0023] The addition amount control unit 140 controls the amount of flocculant added by the addition device 600 based on the flocculation index calculated by the flocculation index calculation unit 130. The addition amount control unit 140 calculates the flocculation change amount, which is the ratio of the change in the flocculation index to the change in the addition amount of flocculant added by the addition device 600, and the flocculation change amount V at a preset optimal addition amount. n Compare with the change in aggregation V n is calculated using the following formula (3):

[0024]

number

[0025] In (Equation 3), C n is the aggregation index. C n-1 is the coagulation index before changing the amount of coagulant added. n is the amount of flocculant added. n-1 is the amount of flocculant added before the amount of flocculant added is changed. Furthermore, when the addition amount control unit 140 receives a notification from the solid amount calculation unit 110 that the sludge concentration of the sludge to be treated notified from the sludge concentration meter 300 is equal to or higher than the upper limit value, or when the addition amount control unit 140 receives a notification from the solid amount calculation unit 110 that the sludge concentration of the sludge to be treated notified from the sludge concentration meter 300 is equal to or lower than the lower limit value, the addition amount control unit 140 controls the amount of flocculant added by the addition device 600 to a fixed addition amount.

[0026] Amount of change in aggregation V n is the amount of change in aggregation at the optimum addition amount, V n If the amount of change in aggregation V exceeds 1, the amount of flocculant added is insufficient, so the addition amount control unit 140 controls the amount of flocculant added by the addition device 600 to increase. n is the amount of change in aggregation at the optimum addition amount, V n If the amount of flocculant added does not exceed the value V', the amount of flocculant added is excessive, so the addition amount control unit 140 controls the addition amount of flocculant added by the addition device 600 to decrease. By repeating this operation, the amount of flocculation change V n is the amount of change in aggregation at the optimum addition amount, V n ', making it possible to maintain an optimal aggregation state.

[0027] The following describes a sludge treatment method in the sludge treatment system shown in Fig. 1. Fig. 3 is a flowchart for explaining an example of a method for controlling the supply amount of sludge to be treated, which is part of the sludge treatment method in the sludge treatment system shown in Fig. 1.

[0028] First, the sludge supply device 200 supplies the supplied sludge to be treated at a supply amount P2 n-1 After a preset time has elapsed (step S2), the solid amount calculation unit 110 calculates the supply amount P2 of the sludge to be treated supplied to the coagulation tank 500 per unit time. n-1 and the sludge concentration S of the sludge to be treated notified by the sludge concentration meter 300 n Based on this, the amount of solids contained in the treated sludge per unit time, DS, is calculated using (Equation 1). n (Step S3). The solid amount calculation unit 110 notifies the calculated solid amount to the sludge supply amount control unit 120. The sludge supply amount control unit 120 calculates the solid amount DS n It is determined whether the target solids amount DS' is equal to the target solids amount DS' (step S4). At this time, as described above, the target solids amount DS' may have a predetermined range, or the solids amount DS notified from the solids amount calculation unit 110 may be set to a value within the range. n and the target solids amount DS' is smaller than a preset value, the sludge supply amount control unit 120 n It may be determined that the target solids content DS' is equal to the target solids content DS'.

[0029] Solids content DS n and the target solid content DS' are not equal, the sludge supply amount control unit 120 controls the supplied treated sludge to be supplied at a supply amount P2 n The sludge supply device 200 is controlled so that the sludge is supplied to the coagulation tank 500 at a supply amount P2 n teeth, Supply amount P2 n = Target solids amount DS' / Sludge concentration S n On the other hand, the solid content DS nis equal to the target solids amount DS', the sludge supply amount control unit 120 controls the supplied treated sludge to be supplied at a supply amount P2 n The sludge supply device 200 is controlled so that the sludge is supplied to the coagulation tank 500 at a supply amount P2 n teeth, Supply amount P2 n =Supply amount P2 n-1 is.

[0030] If the sludge concentration of the sludge to be treated decreases, the solids content will decrease below the target solids content at the current sludge supply rate and become unstable. Therefore, the sludge supply rate control unit 120 increases the sludge supply rate from the sludge supply device 200. If the solids content decreases below the target solids content, the moisture content may increase due to a decrease in the dehydration pressure of the dehydration unit, etc. Furthermore, if the sludge concentration of the sludge to be treated increases, the solids content will increase above the target solids content at the current sludge supply rate and become unstable. Therefore, the sludge supply rate control unit 120 decreases the sludge supply rate from the sludge supply device 200. If the solids content increases above the target solids content, the water level in the coagulation tank will rise due to the increase in the sludge supply rate, causing the sludge supply to stop. This unstable sludge supply may cause the dehydration pressure of the dehydration unit to become unstable, resulting in an increase in the moisture content. To prevent this from occurring, steps S1 to S6 are performed.

[0031] 4A and 4B are flowcharts for explaining an example of a method for controlling the amount of addition based on the coagulation index among the methods for treating sludge in the sludge treatment system shown in FIG.

[0032] First, the adding device 600 adds the flocculant from the flocculant storage tank 700 to the flocculation tank 500 in an amount P n-1 After a preset time has elapsed (step S12), the coagulation index calculation unit 130 of the control device 100 calculates the coagulation index C from the state of the coagulation in the sludge in the coagulation tank 500 acquired by the sensor 400. n-1 (Step S13). After that, the adding device 600 adds the flocculant from the flocculant storage tank 700 to the flocculation tank 500 in an amount P nAfter a preset time has elapsed (step S15), the coagulation index calculation unit 130 of the control device 100 calculates the coagulation index C from the state of the coagulation in the sludge in the coagulation tank 500 measured by the sensor 400. n (Step S16). Then, the aggregation index calculation unit 130 of the control device 100 calculates the amount of change in aggregation V n (Step S17). n The calculation of may be performed by the addition amount control unit 140 instead of the aggregation index calculation unit 130.

[0033] The addition amount control unit 140 of the control device 100 calculates the calculated change in aggregation V n is a preset threshold (V n It is determined whether the change in aggregation V n If the value exceeds the preset threshold, the addition amount control unit 140 increases the amount of flocculant added from the addition device 600 (step S19). n+1 The adding device 600 is controlled so that the flocculant is added from the flocculant storage tank 700 (step S20). n is equal to or less than a preset threshold, the addition amount control unit 140 reduces the amount of flocculant added from the addition device 600 (step S21). n+1 The adding device 600 is controlled so as to add the flocculant from the flocculant storage tank 700 (step S22). Then, the process of step S15 is performed. The amount of flocculant to be increased or decreased may be a preset amount, or may be an amount calculated according to the amount of change in flocculation.

[0034] The concentration, composition, viscosity, and color of the sludge generated, i.e., its properties, can vary significantly depending on the raw water input, the types of products produced in the plant, and the sludge-generating treatment processes such as coagulation sedimentation, flotation, and membrane separation. For example, in food manufacturing plants, the types of food and beverages produced frequently change, causing the sludge properties to vary significantly. In such cases, the optimal amount of coagulant to be added to the sludge varies depending on the properties of the sludge supplied. Therefore, it is necessary to control the amount of coagulant added in response to changes in sludge properties. Therefore, a sensor is used to constantly monitor the sludge coagulation state, and the amount of coagulant added is adjusted based on the obtained coagulation index. Therefore, even when sludge properties fluctuate significantly, the optimal coagulation state can be maintained and the moisture content can be reduced.

[0035] When the sludge concentration is very high, the constant solids amount control described using the flowchart shown in Figure 3 significantly reduces the sludge supply rate. If the sludge supply rate reaches the lower output limit of the sludge supply device 200, the sludge supply rate may be too low, resulting in a risk of insufficient sludge supply. Furthermore, if the sludge supply rate significantly decreases, the water level in the coagulation tank 500 drops, the distance between the sensor 400 and the water surface becomes too long, and the sensor 400 may not be able to properly detect the coagulation state, resulting in inappropriate control of the coagulant addition rate. On the other hand, when the sludge concentration is very low, the constant solids amount control described using the flowchart shown in Figure 3 significantly increases the sludge supply rate. If the sludge supply rate reaches the upper output limit of the sludge supply device 200, the sludge supply rate may become excessive, resulting in a cessation of sludge supply. Furthermore, if the sludge supply rate significantly increases, the water level in the coagulation tank 500 rises, the distance between the sensor 400 and the water surface becomes too short, resulting in the sensor 400 not being able to properly detect the coagulation state, resulting in inappropriate control of the coagulant addition rate. Therefore, when the sludge concentration is equal to or higher than a preset upper limit value or equal to or lower than a preset lower limit value, the amount of sludge supplied and the amount of flocculant added are made constant at preset amounts.

[0036] FIG. 5 is a flowchart for explaining an example of a control method for keeping constant the amount of sludge supplied and the amount of flocculant added, among the sludge treatment methods in the sludge treatment system shown in FIG.

[0037] First, the sludge supply device 200 supplies the supplied sludge to be treated at a supply amount P2 n-1 The adding device 600 adds the flocculant from the flocculant storage tank 700 to the flocculation tank 500 at an amount P n-1 After a preset time has elapsed (step S32), the solid amount calculation unit 110 calculates the sludge concentration S of the sludge to be treated notified from the sludge concentration meter 300. n is compared with a threshold value TC1, which is a preset upper limit (step S33).

[0038] Sludge concentration S n is equal to or greater than the threshold value TC1, the sludge supply amount control unit 120 controls the supply amount of the sludge to be treated that is supplied from the sludge supply device 200 to the coagulation tank 500 to a fixed supply amount B1. n is equal to or greater than the threshold value TC1, the addition amount control unit 140 controls the amount of flocculant added by the addition device 600 to the fixed addition amount A1 (step S34).

[0039] In step S33, the sludge concentration S n is not equal to or greater than the threshold value TC1, the solids amount calculation unit 110 calculates the sludge concentration S n The sludge concentration S is compared with a threshold value TC2, which is a preset lower limit (step S35). n is equal to or less than the threshold value TC2, the sludge supply amount control unit 120 controls the supply amount of the sludge to be treated supplied from the sludge supply device 200 to the coagulation tank 500 to a fixed supply amount B2. n is equal to or less than the threshold value TC2, the addition amount control unit 140 controls the amount of flocculant added by the addition device 600 to a fixed addition amount A2 (step S36), where A1 is a value greater than A2, and B1 is a value smaller than B2.

[0040] In step S35, the sludge concentration Sn If is not less than or equal to the threshold value TC2, the sludge supply amount control unit 120 controls the supply amount of sludge to be sludge using the process described using the flowchart shown in Figure 3, and the addition amount control unit 140 controls the addition amount of coagulant using the process described using the flowchart shown in Figures 4A and 4B (step S37).

[0041] In this embodiment, the control device 100 controls the amount of sludge supplied from the sludge supply device 200 to the coagulation tank 500 based on the concentration of the sludge so that the amount of solids contained in the sludge is constant. The control device 100 also controls the amount of flocculant added by the addition device 600 based on the sludge coagulation state acquired by the sensor 400. Maintaining a constant amount of solids contributes to maintaining a stable moisture content, but it also results in large fluctuations in the sludge supply rate. Therefore, to maintain a stable moisture content or achieve a reduced moisture content, the amount of flocculant added must also be automatically controlled. However, simply controlling the amount of flocculant added by proportional control of the sludge supply rate makes it difficult to maintain an optimal flocculation state when the flocculation state deteriorates due to fluctuations in sludge properties, etc. This can lead to poor dewatering and an increase in moisture content. Therefore, by combining this with control of the amount of flocculant added based on the flocculation state, the flocculation state can be optimized, avoiding poor dewatering and reducing the moisture content. In this way, even if the sludge concentration or sludge properties change suddenly, by combining the control of the amount of flocculant added based on the flocculation state while keeping the solids amount constant, it is possible to avoid poor dewatering, maintain a stable moisture content of the dewatered sludge, and reduce the moisture content. Furthermore, when the concentration of the sludge to be sludge is very low or very high, the amount of flocculant added can be appropriately controlled by setting the sludge supply rate and the amount of flocculant added to fixed values. (Second embodiment)

[0042] Fig. 6 is a diagram showing a second embodiment of the sludge treatment system of the present invention. As shown in Fig. 6, the sludge treatment system in this embodiment includes a control device 101, a sludge supply device 200, a sludge concentration meter 300, a sensor 400, a coagulation tank 500, an addition device 600, a coagulant storage tank 700, a water level meter 800, and a light 900. In this embodiment, the control device 100 in the first embodiment is replaced with the control device 101, and the water level meter 800 and the light 900 are added to the first embodiment.

[0043] The water level meter 800 measures the water level of the sludge to be treated stored in the coagulation tank 500. Examples of the water level meter 800 include guide pulse type, float type, ultrasonic type, electrode type, optical type, and pressure type water level meter. The installation position of the water level meter 800 is not particularly limited, but it is desirable that it be located above the coagulation tank 500. The water level meter 800 notifies the control device 101 of a water level value indicating the measured water level.

[0044] The lighting 900 shines light onto the sludge to be treated stored in the coagulation tank 500. The illuminance of the lighting 900 can be changed by the control device 101. The light source of the lighting 900 is not particularly limited, but infrared light is preferable. The lighting 900 and the sensor 400 may be integrated together.

[0045] Fig. 7 is a diagram showing an example of components included in the control device 101 shown in Fig. 6. As shown in Fig. 7, the control device 101 shown in Fig. 6 has an illuminance control unit 151 in addition to the solid matter amount calculation unit 110, sludge supply amount control unit 120, coagulation index calculation unit 130, and addition amount control unit 140 included in the control device 100 in the first embodiment. Note that Fig. 7 shows only the main components related to this embodiment among the components included in the control device 101 shown in Fig. 6.

[0046] The illuminance control unit 151 controls the illuminance of the lighting 900 based on the water level value notified from the water level meter 800. The illuminance control unit 151 may compare the water level value notified from the water level meter 800 with a preset threshold value, and control the illuminance of the lighting 900 based on the comparison result. For example, if the water level value notified from the water level meter exceeds the threshold value, the illuminance of the lighting 900 may be controlled. Multiple threshold values ​​may be set.

[0047] The following describes an illuminance control method among the sludge treatment methods in the sludge treatment system shown in Fig. 6. Fig. 8 is a flowchart for explaining an example of the illuminance control method among the sludge treatment methods in the sludge treatment system shown in Fig. 6. The following describes an example of processing when two threshold values ​​are set.

[0048] First, lighting 900 is illuminance B n-1 After a preset time has elapsed (step S42), the illuminance control unit 151 controls the illuminance of the lighting 900 so that the lighting is turned on at a water level value L n The water level value L is compared with a threshold value TL1 (step S43). n does not exceed the threshold value TL1, the illuminance control unit 151 adjusts the illuminance B n is controlled to an illuminance C1 (step S44).

[0049] In step S43, the water level value L n exceeds the threshold value TL1, the illuminance control unit 151 n The water level value L is compared with a threshold value TL2 (step S45). The threshold value TL2 is a value greater than the threshold value TL1. n does not exceed the threshold value TL2, the illuminance control unit 151 adjusts the illuminance B n The illuminance C2 is controlled to be lower than the illuminance C1 (step S46).

[0050] In step S45, the water level value L n exceeds the threshold value TL2, the illuminance control unit 151 adjusts the illuminance Bn The illuminance C3 is controlled to be illuminance C3 (step S47). The illuminance C3 is a value lower than the illuminance C2.

[0051] The threshold value to be compared with the illuminance, the number of threshold values, and the illuminance to be controlled are not particularly limited, but it is preferable that the sensor 400 can more accurately obtain the coagulation state of the sludge to be treated in the coagulation tank 500.

[0052] In this manner, in addition to the features of the first embodiment, in this embodiment, even if the water level of the sludge to be treated stored in the coagulation tank 500 fluctuates due to fluctuations in the amount of sludge supplied from the sludge supply device 200, the illuminance of the light 900 is appropriately controlled in accordance with the water level. This allows the sensor 400 to stably detect the coagulation state of the sludge to be treated, enabling appropriate control of the amount of coagulant to be added. Note that the water level meter 800 may determine whether the water level of the sludge to be treated stored in the coagulation tank 500 exceeds a preset water level (for example, the above-mentioned threshold value TL1 or TL2) and output the determination result to the control device 101. This eliminates the need for the illuminance control unit 151 to compare the water level with the threshold value. Furthermore, a mechanism may be provided to change the installation height of the sensor 400 in accordance with the water level measured by the water level meter 800. In this case, the installation height of the sensor 400 may be lowered as the water level measured by the water level meter 800 decreases, so as to maintain a constant distance between the sensor 400 and the liquid level of the sludge to be treated stored in the coagulation tank 500. This mechanism may be configured, for example, to include a floating member that moves in conjunction with the liquid level of the sludge to be treated stored in the coagulation tank 500, and to attach the sensor 400 to the floating member. In this case, the distance between the sensor and the water level (liquid surface) does not change, so the illuminance of the lighting 900 may be constant.

[0053] Fig. 9 is a diagram showing an example of application of the sludge treatment system of the present invention. The application example shown in Fig. 9 is an example in which the form of the sludge treatment system shown in Fig. 1 is applied to a system having a sludge storage tank 10 and a dehydrator 20.

[0054] The sludge storage tank 10 is a storage tank into which the sludge to be treated flows and stores the sludge. The sludge to be treated includes muddy materials formed by the aggregation of organic and inorganic end products generated during the treatment process at sewage treatment plants and industrial wastewater treatment processes. Examples of organic sludge include scum from coagulation sedimentation and pressurized flotation in food factories, semiconductor factories, paper mills, and sewage treatment water reuse plants, excess sludge from membrane separation, and activated sludge from sewage treatment plants. Examples of inorganic sludge include, but are not limited to, sludge derived from metals, coagulants, lime, and calcium in wastewater. Furthermore, the sludge to be treated cannot be disposed of as is. Therefore, the sludge to be treated is subjected to a coagulation process, for example, by adding a coagulant, or a dehydration process, such as squeezing using a dehydrator or centrifuging, to remove dewatered sludge from the sludge to obtain reusable liquid. A lower moisture content of the dewatered sludge is desirable. The dewatered sludge is either disposed of as waste or reused as fertilizer, etc. The sludge storage tank 10 has a predetermined capacity. The sludge supply device 200 supplies the sludge to be treated stored in the sludge storage tank 10 to the coagulation tank 500.

[0055] The dehydrator 20 is a dehydration device that dehydrates the sludge treated in the coagulation tank 500, separates it into filtrate and dehydrated sludge (solid-liquid separation), and discharges the filtrate. Specifically, the dehydrator 20 uses a rotor to compress the sludge that has been fed from the coagulation tank 500 and to which a coagulant has been added from the addition device 600. The dehydrator 20 has a chemical feed section, and may be a screw press, multi-disk type, belt press type, or centrifugal separator type. The dehydrator 20 separates the coagulated sludge generated in the coagulation tank 500 into solids and liquid. The separated solids, i.e., dehydrated sludge, are supplied from the rear end of the rotor to a hopper or the like for further processing such as drying, or transported as industrial waste. The separated liquid, i.e., filtrate, is returned to a wastewater adjustment tank or the like.

[0056] Although the above description has been given by allocating each function (process) to each component, this allocation is not limited to the above. Furthermore, the configuration of the components is also not limited to the above-described embodiments, which are merely examples. Furthermore, the above-described embodiments may be combined in any combination.

[0057] The processes performed by the control devices 100 and 101 described above may be performed by logic circuits individually designed for each purpose. Alternatively, a computer program (hereinafter referred to as a program) describing the process procedures may be recorded on a recording medium readable by each of the control devices 100 and 101, and the program recorded on the recording medium may be read and executed by each of the control devices 100 and 101. Examples of recording media readable by the control devices 100 and 101 include removable recording media such as floppy disks, magneto-optical disks, digital versatile discs (DVDs), compact discs (CDs), Blu-ray discs, universal serial bus (USB) memories, and SD cards, as well as memories such as read-only memories (ROMs) and random access memories (RAMs) and hard disc drives (HDDs) built into each of the control devices 100 and 101. The programs recorded on the recording media are read by a CPU provided in each of the control devices 100 and 101, and the same processes as those described above are performed under the control of the CPU. Here, the CPU operates as a computer that executes a program read from a recording medium on which the program is recorded. [Explanation of symbols]

[0058] 10 Sludge storage tank 20 Dehydrator 100,101 Control device 110 Solids amount calculation unit 120 Sludge supply amount control unit 130 Agglomeration index calculation section 140 Addition amount control unit 151 Illuminance control unit 200 Sludge supply device 300 Sludge concentration meter 400 sensors 500 flocculation tank 600 Addition equipment 700 Flocculant storage tank 800 Water Level Gauge 900 lighting

Claims

1. a flocculation tank; a sludge supply device for supplying sludge to be treated to the coagulation tank; a sludge concentration meter for measuring the sludge concentration of the sludge to be treated supplied from the sludge supply device; an adding device that adds a flocculant to the sludge to be treated stored in the flocculation tank; a sensor for acquiring the state of flocculants in the sludge to be treated to which the flocculant has been added from the adding device; A sludge treatment system having a control device that controls the amount of sludge to be treated supplied by the sludge supply device based on the sludge concentration measured by the sludge concentration meter, calculates a coagulation index indicating the state of the coagulation obtained by the sensor, and controls the amount of coagulant added by the addition device based on the amount of change in the coagulation index when the amount of coagulant added by the addition device is changed.

2. 2. The sludge treatment system according to claim 1, The control device controls the amount of treated sludge supplied by the sludge supply device based on the sludge concentration measured by the sludge concentration meter so that the amount of solids contained in the treated sludge supplied by the sludge supply device becomes a predetermined amount.

3. 3. The sludge treatment system according to claim 1, The control device compares the amount of coagulation change, which is the ratio of the change in the coagulation index to the change in the amount of coagulant added when the amount of coagulant added is changed, with a predetermined threshold value, and if the amount of coagulation change exceeds the threshold value, increases the amount of coagulant added by the addition device, and if the amount of coagulation change is equal to or less than the threshold value, decreases the amount of coagulant added by the addition device.

4. 3. The sludge treatment system according to claim 1, the sensor is an image sensor that captures an image of the sludge in the coagulation tank, The control device is a sludge treatment system that calculates, as the coagulation index, a characteristic amount of the coagulation in the sludge from the image captured by the image sensor.

5. 3. The sludge treatment system according to claim 1, The control device controls the amount of the treated sludge supplied by the sludge supply device to a fixed supply amount when the sludge concentration measured by the sludge concentration meter is above a predetermined upper limit value or below a predetermined lower limit value, and controls the amount of the coagulant added by the addition device to a fixed addition amount.

6. 3. The sludge treatment system according to claim 1, the adding device adds a plurality of flocculants to the sludge to be treated, The control device controls the amounts of the flocculants to be added so that the ratio of the amounts of the flocculants to each other is constant in the sludge treatment system.

7. 3. The sludge treatment system according to claim 1, a water level meter for measuring the water level of the sludge to be treated stored in the coagulation tank; a light that irradiates the sludge to be treated stored in the coagulation tank, The control device controls the illuminance of the lighting based on the water level measured by the water level meter.

8. 8. The sludge treatment system according to claim 7, The control device controls the illuminance of the lighting when the water level measured by the water level meter exceeds a threshold value.

9. a solids amount calculation unit that calculates the amount of solids contained in the sludge to be treated based on the amount of sludge to be treated that is supplied to the coagulation tank and the sludge concentration of the sludge to be treated measured by a sludge concentration meter; a sludge supply amount control unit that controls the supply amount of the sludge to be treated that is supplied to the coagulation tank based on the amount of solid matter calculated by the solid matter amount calculation unit; a coagulation index calculation unit that calculates a coagulation index that indicates the state of coagulation in the sludge to be treated that has been supplied to the coagulation tank and to which a coagulant has been added from an addition device; A control device having an addition amount control unit that controls the amount of flocculant added by the addition device based on the amount of change in the flocculation index when the amount of flocculant added by the addition device is changed.

10. a process of calculating the amount of solids contained in the sludge to be treated based on the amount of sludge to be treated supplied to the coagulation tank and the sludge concentration of the sludge to be treated measured by a sludge concentration meter; a process of controlling the amount of the sludge to be treated supplied to the coagulation tank based on the calculated amount of solids; a process of calculating a coagulation index that indicates the state of coagulation in the sludge to be treated that has been supplied to the coagulation tank and to which a coagulant has been added from an addition device; A sludge treatment method that controls the amount of flocculant added by the addition device based on the amount of change in the flocculation index when the amount of flocculant added by the addition device is changed.

11. On the computer, calculating the amount of solids contained in the sludge to be treated based on the amount of sludge to be treated supplied to the coagulation tank and the sludge concentration of the sludge to be treated measured by a sludge concentration meter; a step of controlling the amount of the sludge to be treated supplied to the coagulation tank based on the calculated amount of solids; a step of calculating a coagulation index that indicates the state of coagulation in the sludge to be treated that has been supplied to the coagulation tank and to which a coagulant has been added from an addition device; and a procedure for controlling the amount of flocculant added by the addition device based on the amount of change in the flocculation index when the amount of flocculant added by the addition device is changed.

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