High-speed coagulation and sedimentation apparatus

Abstract

To provide a high-speed coagulation and sedimentation apparatus that can accurately determine the interface value of sludge. [Solution] The high-speed coagulation and sedimentation apparatus comprises stirring chambers 18, 19 that agitate impurities in raw water while stirring to form flocs, a separation chamber 21 that separates the flocs from water by sedimentation, a sludge discharge line for discharging the sludge separated in the separation chamber 21, a turbidity sensor 51 provided in the separation chamber 21, a sensor moving device 52 that moves the turbidity sensor 51 in the water depth direction of the separation chamber 21 and measures the position of the turbidity sensor 51 in the water depth direction within the separation chamber 21, and a control device 50 connected to the turbidity sensor 51 and the sensor moving device 52. The control device 50 uses the turbidity sensor 51 and the sensor moving device 52 to acquire the turbidity distribution in the water depth direction within the separation chamber 21 at predetermined time intervals, and when the measured value of the turbidity sensor 51 exceeds a preset threshold for the turbidity in the separation chamber 21, it determines the water depth corresponding to the measured value of the turbidity sensor that exceeds the threshold as the interface value.

Description

Technical Field

[0001] The present invention relates to a high-speed coagulation sedimentation apparatus that forms and sedimentates flocs in a sedimentation basin, and particularly to a slurry circulation type high-speed coagulation sedimentation apparatus that promotes the formation and sedimentation of flocs by a circulating flow.

Background Art

[0002] A high-speed coagulation sedimentation apparatus is a device that aggregates impurities composed of suspended matter, microorganisms, etc. by an aggregation operation in a sedimentation basin to form flocs and separates the flocs from water (see, for example, Patent Documents 1 and 2). In the sedimentation basin, raw water (water to be treated) and a raw water coagulant are mixed to form minute flocs, and the minute flocs grow into larger flocs by colliding with each other. The high-speed coagulation sedimentation apparatus can form larger flocs than ordinary coagulation sedimentation apparatuses by causing the raw water to collide with the formed flocs. The flocs are carried by a circulating flow to a concentrator called a concentrator in the sedimentation basin and sediment as sludge in the concentrator. This type of high-speed coagulation sedimentation apparatus is sometimes referred to as a "slurry circulation type high-speed coagulation sedimentation apparatus". Further, a high-speed coagulation sedimentation apparatus that forms a blanket without circulating the flocs and passes the raw water through the blanket is sometimes referred to as a "slurry blanket type high-speed coagulation sedimentation apparatus".

[0003] In a high-speed coagulation sedimentation apparatus that utilizes the formed flocs, such as a slurry blanket type high-speed coagulation sedimentation apparatus, in order to form large flocs by causing the raw water to collide with the flocs, it is necessary to have a certain amount of flocs in the sedimentation basin. Therefore, in a slurry blanket type high-speed coagulation sedimentation apparatus, in order to manage and maintain an appropriate amount of flocs in the sedimentation basin, a turbidity sensor capable of continuously detecting the turbidity distribution in the depth direction of the sedimentation basin may be provided (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In this type of high-speed coagulation and sedimentation system, the location of the sludge interface, which is the boundary between areas containing a large amount of flocs and areas containing a small amount of flocs within the sedimentation tank, is an important control item in order to prevent impurities such as flocs from flowing out of the sedimentation tank. In this specification, the sludge interface is simply referred to as the "interface," and the position of the sludge interface in the direction of water depth is referred to as the "interface value."

[0006] However, in conventional high-speed coagulation and sedimentation systems, the interface value was estimated based on the experience and intuition of the workers managing the sedimentation tank, and the management and maintenance of the tank, such as controlling the amount of sludge discharged from the tank, was carried out accordingly. On the other hand, in the high-speed coagulation and sedimentation systems described above, the slurry is constantly circulated or held, so the interface value may not be stable. In particular, when the slurry is circulated, the interface value tends to be unstable due to the influence of the circulating flow. For example, in the depth direction of the sedimentation tank, there may be areas with turbidity concentrations corresponding to multiple interface values. In this case, it is difficult to determine how to identify the interface value.

[0007] The interface value is an important control item because it can be used to determine the amount of sludge to be discharged from the sedimentation tank and to determine whether or not there are any abnormalities in the sedimentation tank. Furthermore, if multiple interface values ​​exist, there is a risk that the sludge may not be discharged properly.

[0008] Therefore, the present invention aims to provide a high-speed coagulation and sedimentation apparatus that can accurately determine the interface value of sludge. [Means for solving the problem]

[0009] In one embodiment, a high-speed coagulation and sedimentation apparatus is provided, comprising: a stirring chamber that forms flocs by agitating and coagulating impurities in raw water; a separation chamber communicating with the stirring chamber for settling and separating the flocs from water; a sludge discharge line communicating with the separation chamber for discharging the sludge separated in the separation chamber; a turbidity sensor provided in the separation chamber; a sensor moving device that moves the turbidity sensor in the water depth direction of the separation chamber and measures the position of the turbidity sensor in the water depth direction within the separation chamber; and a control device connected to the turbidity sensor and the sensor moving device, wherein the control device uses the turbidity sensor and the sensor moving device to acquire the turbidity distribution in the water depth direction within the separation chamber at predetermined time intervals, and when the turbidity distribution exceeds a preset threshold for turbidity in the separation chamber, the control device determines the water depth corresponding to the measurement value of the turbidity sensor that exceeds the threshold as the interface value.

[0010] In one embodiment, if multiple locations in the turbidity distribution exceed the threshold, the control device determines the water depth corresponding to the measurement value of the turbidity sensor located at the lowest of the multiple locations as the interface value. In one embodiment, the threshold is a first threshold, the control device has a second threshold having a smaller value than the first threshold stored in advance, and if multiple locations in the turbidity distribution exceed the second threshold, the control device determines the water depth corresponding to the measurement value of the turbidity sensor located at the lowest of the multiple locations as the interface value. In one embodiment, the control device stores in advance an alarm level set for the water depth in the separation chamber, and the control device issues an alarm when the turbidity distribution exceeds the second threshold while being above the alarm level.

[0011] In one embodiment, the control device obtains the rate of increase of the interface value by comparing a plurality of turbidity distributions acquired at predetermined time intervals. In one embodiment, the control device stores in advance a sludge discharge start level set in the direction of the water depth in the separation chamber and a sludge discharge stop level set below the sludge discharge start level. The control device operates the sludge discharge line to start discharging the sludge when the interface value reaches the sludge discharge start level, and operates the sludge discharge line to stop discharging the sludge when the interface value reaches the sludge discharge stop level. In one embodiment, the control device acquires the turbidity distribution at intervals shorter than the predetermined time interval during the sludge removal operation. In one embodiment, the control device creates a graph representing the turbidity distribution and displays the graph on a display device. [Effects of the Invention]

[0012] The control device uses a turbidity sensor and a sensor movement device to acquire the turbidity distribution in the depth direction within the separation chamber. It determines the water depth corresponding to the turbidity sensor reading where the turbidity distribution exceeds a threshold as the interface value. This operation allows the control device to determine an accurate interface value based on the turbidity sensor reading. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram showing the overall configuration of a high-speed coagulation and sedimentation apparatus according to one embodiment. [Figure 2] Figure 2 is a top view of a low-speed agitator. [Figure 3] Figure 3 is an example of a graph showing the turbidity distribution. [Figure 4] Figure 4 shows another example of a graph illustrating turbidity distribution. [Figure 5] Figure 5 shows yet another example of a graph illustrating turbidity distribution. [Figure 6] Figure 6 shows yet another example of a graph illustrating turbidity distribution. [Figure 7] Figure 7 shows yet another example of a graph illustrating turbidity distribution. [Figure 8] Figure 8 shows yet another example of a graph illustrating turbidity distribution. [Figure 9] FIG. 9 is yet another example of a graph showing the turbidity distribution. [Figure 10] FIG. 10 is yet another example of a graph showing the turbidity distribution.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of a high-speed coagulation sedimentation apparatus according to an embodiment. The high-speed coagulation sedimentation apparatus shown in FIG. 1 is a slurry circulation type high-speed coagulation sedimentation apparatus. Hereinafter, the slurry circulation type high-speed coagulation sedimentation apparatus will be described as an example of the high-speed coagulation sedimentation apparatus. However, as long as it is a high-speed coagulation sedimentation apparatus that forms a circulation flow in the sedimentation tank or forms a slurry blanket, the embodiments described below are applicable.

[0015] As shown in FIG. 1, the high-speed coagulation sedimentation apparatus includes a frustum-shaped skirt plate 15 that partitions the inside of a circular sedimentation tank 1 into a stirring chamber 18, 19 and a separation chamber 21, a high-speed stirrer 2 that stirs the flocs and forms a circulation flow in the sedimentation tank 1, a first driving device 3 that rotates the high-speed stirrer 2, a concentrator 5 where the flocs settle, a low-speed stirrer 30 that stirs the flocs deposited on the bottom of the sedimentation tank 1, and a second driving device 34 that rotates the low-speed stirrer 30.

[0016] Inside the skirt plate 15, a primary stirring chamber 18 located below the high-speed stirrer 2 and a secondary stirring chamber 19 located above the high-speed stirrer 2 are formed. Outside the skirt plate 15, a separation chamber 21 where sludge and water are separated is formed. The low-speed stirrer 30 is disposed in the primary stirring chamber 18, and the concentrator 5 is disposed in the separation chamber 21.

[0017] The high-speed agitator 2 is equipped with a stirring blade 2a that agitates the flocs in the primary stirring chamber 18 and a circulation blade 2b that creates an upward flow from the primary stirring chamber 18 to the secondary stirring chamber 19. As the high-speed agitator 2 rotates, the raw water (water to be treated) circulates in the primary stirring chamber 18, the secondary stirring chamber 19, and the separation chamber 21 in that order. In the primary stirring chamber 18, the raw water, coagulant, and flocs circulating in the sedimentation tank 1 (circulating flocs) are mixed to form floc cores. In the secondary stirring chamber 19, the floc cores collide with each other and grow into larger flocs, and in the separation chamber 21, the flocs and purified water are separated.

[0018] A rotating shaft 7 is connected to the high-speed agitator 2. The rotating shaft 7 extends above the water surface of the sedimentation tank 1 and is connected to a drive unit 3. By driving the drive unit 3, the high-speed agitator 2 is rotated via the rotating shaft 7. The rotating shaft 7 is hollow, and a rotating shaft 38 extends through its interior. The upper end of the rotating shaft 38 is connected to a drive unit 34, and the lower end is connected to a low-speed agitator 30. By driving the drive unit 34, the low-speed agitator 30 is rotated via the rotating shaft 38. The drive unit 34 is configured to allow variable speed operation, and the rotational speed of the low-speed agitator 30 can be changed. For example, the drive unit 3 and the drive unit 34 consist of an electric motor and a gearbox, respectively.

[0019] The low-speed agitator 30 is positioned below the high-speed agitator 2 and near the bottom of the sedimentation tank 1. The low-speed agitator 30 includes an arm 32 for agitating the flocs accumulated at the bottom of the sedimentation tank 1, and a plurality of scraping plates 33 fixed to the arm 32. The arm 32 extends parallel to the bottom of the sedimentation tank 1. A tapered member 35 with a frustoconical shape is provided in the center of the low-speed agitator 30.

[0020] The low-speed agitator 30 has the function of agitating the flocs accumulated at the bottom of the sedimentation tank 1 by rotating at a certain high speed, while also functioning as a sludge scraper that scrapes the sludge accumulated at the bottom of the sedimentation tank 1 toward the center of the sedimentation tank 1 by rotating at a low speed. Figure 2 is a top view of the low-speed agitator. As shown in Figure 2, the multiple scraping plates 33 are inclined at a predetermined angle with respect to the center line of the arm 32. Therefore, when the low-speed agitator 30 is rotated at a low speed in the direction indicated by the arrow, the scraping plates 33 can scrape the sludge on the bottom of the tank toward the center of the sedimentation tank 1.

[0021] As shown in Figure 1, a cylindrical inner draft tube 8 is provided around the high-speed agitator 2, and an outer draft tube 9 is provided around the inner draft tube 8. A ring plate 10 is attached to the lower end of the inner draft tube 8. The skirt plate 15, the inner draft tube 8, and the ring plate 10 form an annular raw water supply chamber 14. The supply pipe 6 is connected to the raw water supply chamber 14, and raw water (water to be treated) is supplied into the raw water supply chamber 14 through the supply pipe 6. An annular gap is formed between the skirt plate 15 and the ring plate 10, and the raw water is uniformly introduced into the primary agitation chamber 18 through this annular gap. Sludge discharge pipes 16 and 17 for discharging concentrated sludge are provided at the bottom of the concentrator 5 and the bottom of the sedimentation tank 1, respectively.

[0022] In this embodiment, a first sludge discharge valve 43 is provided in the sludge discharge pipe 17, and a second sludge discharge valve 44 is provided in the sludge discharge pipe 16. The sludge discharge pipes 16 and 17, and the sludge discharge valves 43 and 44 constitute a sludge discharge line for discharging sludge accumulated in the sedimentation tank.

[0023] Furthermore, the high-speed coagulation and sedimentation apparatus shown in Figure 1 is equipped with a control device 50 that controls the operation of the components of the high-speed coagulation and sedimentation apparatus. In Figure 1, the wires and / or signal lines extending from the control device 50 to each component are omitted from the illustration to avoid complexity in the diagram. For example, a first drive unit 3, a second drive unit 34, a first sludge discharge valve 43, and a second sludge discharge valve 44 are connected to the control device 50, and the control device 50 is configured to control the operation of these components 3, 4, 43, and 44.

[0024] When the drive unit 3 drives the stirring blades 2a of the high-speed agitator 2, the raw water, coagulant, and circulating flocs are mixed in the primary stirring chamber 18, causing impurities in the raw water to aggregate and form tiny floc cores. These floc cores rise due to the rotation of the circulating blades 2b and are carried to the secondary stirring chamber 19. In the secondary stirring chamber 19, the floc cores collide with each other to form larger flocs. The flocs descend between the inner draft tube 8 and the outer draft tube 9, are guided to the skirt plate 15, and flow into the separation chamber 21.

[0025] In the separation chamber 21, some of the flocs contained in the treated water settle in the concentrator 5 and become sludge, which is then discharged through the sludge discharge pipe 16. The remaining flocs descend to the lower end of the skirt plate 15 and return to the primary stirring chamber 18 through the gap 23 between the side wall 1a of the sedimentation tank 1 and the lower end of the skirt plate 15. The flocs then flow into the secondary stirring chamber 19 on the upward current. In this way, the flocs grow while circulating through the primary stirring chamber 18, the secondary stirring chamber 19, and the separation chamber 21.

[0026] In the separation chamber 21, flocs and clear water are separated. Multiple inclined pipes 36 are arranged in the upper part of the separation chamber 21. The inclined pipes 36 are located above the concentrator 5 and near the water surface. The inclined pipes 36 are inclined outward with respect to the vertical direction. Each inclined pipe 36 has a polygonal horizontal cross-section, and the purified water rises inside it. Tiny flocs contained in the purified water are designed to settle on the inclined inner surface of the inclined pipes 36. By arranging the inclined pipes 36 in the separation chamber 21, the settling area for the flocs is increased, so tiny flocs in the purified water moving from the bottom to the top of the inclined pipes 36 settle inside the inclined pipes 36. The purified water that has passed through the inclined pipes 36 is discharged from the sedimentation tank 1 as supernatant water (treated water). The inclined pipes 36 can promote the separation of purified water and flocs, thus preventing tiny flocs from flowing out of the sedimentation tank 1 together with the purified water.

[0027] Flocs that have settled in the separation chamber 21 return to the primary stirring chamber 18 through the gap 23 between the lower end of the skirt plate 15 and the side wall 1a of the sedimentation tank 1. At this time, some flocs may accumulate in the gap 23, blocking the gap 23. Therefore, in this embodiment, the accumulation of flocs is prevented by destroying the clumps of flocs accumulated in the gap 23 with the arm 32 of the low-speed stirrer 30. As shown in Figure 1, the arm 32 extends to the gap 23 between the lower end of the skirt plate 15 and the side wall 1a of the sedimentation tank 1. When the low-speed stirrer 30 rotates, both ends of the arm 32 destroy the clumps of flocs accumulated in the gap 23, preventing the gap 23 from becoming blocked.

[0028] As shown in Figure 1, the high-speed coagulation and sedimentation apparatus further includes a turbidity sensor (turbidimeter) 51 that moves in the direction of the water depth in the sedimentation tank 1 to continuously detect turbidity in the direction of the water depth in the separation chamber 21, and a sensor moving device 52 that moves the turbidity sensor 51 in the direction of the water depth. The turbidity sensor 51 is, for example, a photoelectric type or an ultrasonic type. The turbidity sensor 51 is connected to a control device 50, and the measured value of the turbidity sensor 51 is input to the control device 50.

[0029] The sensor moving device 52 is a device that supports the turbidity sensor 51 so that it can move in the direction of the water depth in the separation chamber 21, and is configured to measure the water depth of the turbidity sensor 51 in the separation chamber 21. The sensor moving device 52 shown in Figure 1 consists of a cable 54, which is an example of a string-like member connected to the turbidity sensor 51, and a winch 55 that can wind up and feed out the cable 54. The turbidity sensor 51 is suspended from the end of the cable 54. In one embodiment, a wire may be used as the string-like member that suspends the turbidity sensor 51.

[0030] The winch 55 is equipped with a depth gauge 56 capable of measuring the amount of cable 54 being fed out and / or retracted. The depth gauge 56 is connected to a control device 50 and can send its measurements to the control device 50. The measurement from the depth gauge 56 corresponds to the amount of cable 54 being fed out (or retracted), i.e., the position of the turbidity sensor 51 in the depth direction in the separation chamber 21.

[0031] In this embodiment, the cable 54 extends vertically due to the weight of the turbidity sensor 51 suspended from the cable 54. In one embodiment, a weight (not shown) may be attached to the turbidity sensor 51 so that the cable 54 extends vertically in the circulating flow of the water to be treated in the separation chamber 21.

[0032] The control device 50 is configured to acquire the turbidity distribution in the separation chamber 21 based on the measurements from the turbidity sensor 51 and the depth measuring device 56. Furthermore, the control device 50 may be configured to create a graph representing the acquired turbidity distribution. In this specification, the turbidity distribution represents the relationship between turbidity and the depth of the turbidity sensor 51 in the separation chamber 21, where turbidity is measured by the turbidity sensor 51 and the depth of the turbidity sensor 51 in the separation chamber 21 is measured by the depth measuring device 56. The following description describes an embodiment in which a graph representing the turbidity distribution is created to facilitate understanding of the invention, but the control device 50 is not necessarily required to create a graph representing the turbidity distribution.

[0033] Figure 3 is an example of a graph showing turbidity distribution, and Figure 4 is another example of a graph showing turbidity distribution. The graphs shown in Figures 3 and 4 are created by the control device 50 based on the measurements from the turbidity sensor and the depth measuring instrument. In Figures 3 and 4, the vertical axis represents the water depth of the turbidity sensor 51, and the horizontal axis represents the turbidity acquired by the turbidity sensor 51. Similarly, in the graph showing turbidity distribution described later, the vertical axis represents the water depth of the turbidity sensor 51, and the horizontal axis represents the turbidity acquired by the turbidity sensor 51.

[0034] As shown by the double arrows in Figure 1, the turbidity sensor 51 is moved in the water depth direction by the sensor moving device 52. To move the turbidity sensor 51, the control device 50 issues a command to the winch 55 of the sensor moving device 52, causing the turbidity sensor 51, which is suspended by the cable 54, to move in the water depth direction in the separation chamber 21. In this embodiment, the water depth direction is parallel to the vertical direction.

[0035] The control device 50 moves the turbidity sensor 51 in the direction of water depth, continuously acquiring measurements from the turbidity sensor 51, and stores the acquired measurements from the turbidity sensor 51 in association with the measurements from the water depth measuring device 56. Using the measurements from the turbidity sensor 51 obtained in this way, and the water depth of the turbidity sensor 51 associated with these measurements, the control device 50 can create a graph showing the turbidity distribution as shown in Figures 3 and 4.

[0036] As shown in the graph of Figure 3, the control device 50 pre-stores a threshold value L set for the sludge present in the separation chamber 21. This threshold value L is determined in accordance with the turbidity corresponding to the interface within the sedimentation tank 1, and is determined, for example, using experiments and / or simulations. Alternatively, the threshold value L may be determined from past operating data of the high-speed coagulation and sedimentation apparatus.

[0037] As shown in Figure 3, if the control device 50 detects any point in the turbidity sensor 51's measurements where the threshold L is exceeded, it determines the water depth H at which the turbidity crosses the threshold as an interface and sets the corresponding water depth H as the interface value. The interface value (=water depth H) thus obtained is a very important control item that represents the state of the sedimentation tank 1. Based on the interface value, operators can determine various states of the sedimentation tank 1, and this interface value can be used for sludge removal control. Embodiments related to sludge removal control will be described later.

[0038] On the other hand, as shown in Figure 4, if there are no values ​​in the turbidity sensor 51 measurements that exceed the threshold L, the control device 50 determines that there is no interface in the separation chamber 21. This information that there is no interface in the sedimentation tank 1 is also treated as important information for operating and managing the sedimentation tank 1.

[0039] The control device 50 periodically acquires such turbidity distributions and graphs at predetermined time intervals (e.g., every 30 minutes). The operator can use the multiple turbidity distributions and / or graphs acquired periodically at predetermined time intervals for the operation and management of the sedimentation tank 1. The predetermined time intervals are stored in advance in the control device 50, and the control device 50 activates the sensor moving device 52 at predetermined time intervals to obtain measurement values ​​from the turbidity sensor 51, and further creates a turbidity distribution in the depth direction of the separation chamber 21 from the measurement values ​​from the turbidity sensor 51 and the measurement values ​​from the depth measuring device 56.

[0040] In one embodiment, the control device 50 may display a graph (see, for example, Figures 3 and 4) created based on the acquired turbidity distribution on a display so that the operator can visually recognize the turbidity distribution. In the example shown in Figure 1, the control device 50 is equipped with a display 60, which displays a graph representing the turbidity distribution in the separation chamber 21.

[0041] In one embodiment, the control device 50 may be connected to other devices (not shown) via wired or wireless means to send and receive data. In this case, when the control device 50 transmits graph data representing the turbidity distribution to the other devices, the other devices display the graph representing the turbidity distribution on their own displays (corresponding to displays provided on the other devices) based on the transmitted graph data. Examples of other devices connected to the control device 50 via wired or wireless means include mobile devices such as smartphones, and a central monitoring panel installed in the central monitoring room of a facility where a high-speed coagulation and sedimentation apparatus is deployed.

[0042] Figure 5 shows yet another example of a graph showing the turbidity distribution. As described above, the control device 50 acquires the turbidity distribution in the separation chamber 21 at predetermined time intervals, creates a graph based on the turbidity distribution, and stores the turbidity distribution and the graph. Therefore, the control device 50 stores multiple graphs containing information on the interface values ​​that change moment by moment. Thus, as shown in Figure 5, the control device 50 may calculate the interface rise rate based on the change in interface values.

[0043] Specifically, the control device 50 determines a turbidity distribution X1 having an interface value H1 as the reference turbidity distribution, and determines a turbidity distribution X2 having an interface value H2, which is created after the reference turbidity distribution X1, as the comparison turbidity distribution. Next, the control device 50 calculates the increase in interface value by subtracting the interface value H1 of the reference turbidity distribution X1 from the interface value H2 of the comparison turbidity distribution X2. Then, the control device 50 calculates the rate of increase of the interface per unit time by dividing the calculated rate of increase of the interface by a predetermined time interval. The rate of increase of the interface obtained in this way is stored in the control device 50. In one embodiment, the control device 50 may display the rate of increase of the interface on the display 60 of the control device 50. The operator can use the rate of increase of the interface for the operation and management of the high-speed coagulation and sedimentation apparatus.

[0044] Figure 6 shows yet another example of a graph showing the turbidity distribution. As described above, in the high-speed coagulation and sedimentation apparatus according to this embodiment, a circulating flow is formed that circulates through the primary stirring chamber 18, the secondary stirring chamber 19, and the separation chamber 21. When such a circulating flow is formed, the state of floc formation changes moment by moment depending on various conditions in the sedimentation tank 1, such as the state of the raw water and the state of the circulating flow, and areas with temporarily and locally high turbidity may occur.

[0045] For example, as shown in Figure 6, there may be cases where multiple points in the turbidity distribution exceed the threshold L. Figure 6 shows an example where the turbidity distribution exceeds the threshold L in two places. More specifically, Figure 6 shows an example where turbidity exceeding the threshold L is detected at three water depths A, B, and C. In this case, the actual interface occurs at water depth A, where the threshold L is exceeded at the lowest point, while a temporary and localized area of ​​high turbidity occurs between water depths B and C, which are above water depth A. Therefore, the control device 50 determines that the interface occurs at water depth A, the lowest point, rather than at water depth C, and determines water depth A as the interface value. With this configuration, even if a temporary and localized area of ​​high turbidity occurs in the sedimentation tank 1, the control device 50 can accurately detect the interface value.

[0046] Since the control device 50 can determine the precise interface value based on the acquired turbidity distribution, the control device 50 may perform the sludge discharge operation using the determined interface value. Figure 7 is yet another example of a graph showing the turbidity distribution. As shown in Figure 7, the control device 50 pre-stores the sludge discharge start level Hb and the sludge discharge stop level Hs to be used for the sludge discharge operation. The sludge discharge start level Hb corresponds to the sludge discharge start water depth set relative to the interface value and is set to the water depth corresponding to the interface value at which the sludge accumulated in the sedimentation tank 1 should be discharged. The sludge discharge stop level Hs corresponds to the sludge discharge stop water depth set relative to the interface value and is set to the water depth corresponding to the interface value necessary for appropriate floc formation. The sludge discharge start level Hb is set higher than the sludge discharge stop level Hs. These sludge discharge start level Hb and sludge discharge stop level Hs may be determined, for example, using experiments and / or simulations, or they may be determined from past operating data of the high-speed coagulation and sedimentation apparatus.

[0047] The control device 50 starts the sludge discharge operation when the interface value determined as described above reaches the sludge discharge start level Hb. Specifically, the control device 50 opens the sludge discharge valve 43 and / or the sludge discharge valve 44 and discharges the sludge from the separation chamber 21 via the sludge discharge piping 16 and / or the sludge discharge piping 17. As the sludge is discharged from the separation chamber 21, the interface value decreases. When the interface value reaches the sludge discharge stop level Hs, the control device 50 closes the sludge discharge valve 43 and / or the sludge discharge valve 44 and stops the discharge of sludge from the separation chamber 21.

[0048] With this configuration, the control device 50 can perform the sludge discharge operation based on accurate interface values. In particular, even if a temporary and locally high turbidity area occurs during the sludge discharge operation, as described with reference to Figure 6, the control device 50 can detect accurate interface values ​​(i.e., the water depth A at which the turbidity crosses the threshold L, which is at the very bottom in Figure 6), so that the sludge discharge operation can be started at the appropriate timing, and the amount of sludge necessary for floc formation can be left in the sedimentation tank 1. Note that during the sludge discharge operation, the control device 50 may acquire the turbidity distribution at shorter time intervals (e.g., 5 minutes) than the predetermined time interval (e.g., 30 minutes) described above. With this configuration, the amount of sludge necessary for floc formation can be reliably left in the sedimentation tank 1.

[0049] Depending on the condition of the raw water and / or the condition of the flocs formed in the sedimentation tank 1, flocs that are difficult to settle may form. In this case, even though there is an amount of sludge in the separation chamber 21 that should initiate the sludge discharge operation, the measurement value of the turbidity sensor 51 may not exceed the threshold L. If this condition continues for a long time, there is a risk that water containing flocs will flow out of the sedimentation tank 1. Therefore, the control device 50 may store in advance a threshold value set to a value smaller than the threshold L described above. In the embodiments described below, the threshold L described above will be referred to as the "first threshold L1," and the threshold value set to a value smaller than the first threshold L1 will be referred to as the "second threshold L2."

[0050] Figures 8 and 9 are yet another example of graphs showing the turbidity distribution. As shown in Figure 8, the control device 50 pre-stores a first threshold L1 and a second threshold L2. As described above, the second threshold L2 is set to a value smaller than the first threshold L1.

[0051] In the example shown in Figure 8, the turbidity distribution obtained from the turbidity sensor 51 and the depth measuring instrument 56 does not exceed the first threshold L1, but exceeds the second threshold L2 in multiple places. In this case, the control device 50 determines that flocs that are difficult to settle have formed in the sedimentation tank 1. The control device 50 then determines that an interface exists at the lowest water depth AA, where the second threshold L2 intersects, and determines water depth AA to be the interface value.

[0052] Based on the interface value AA thus determined, the control device 50 performs the sludge discharge operation described with reference to Figure 7. Specifically, the control device 50 starts the sludge discharge operation when the interface value AA reaches the sludge discharge start level Hb (see Figure 7), while stopping the discharge of sludge from the separation chamber 21 when the interface value AA reaches the sludge discharge stop level Hs (see Figure 7). With this configuration, even if a condition in which flocs that are difficult to settle are formed in the separation chamber 21 continues for a long time, it is possible to prevent the flocs from flowing out of the sedimentation tank 1.

[0053] In contrast, as shown in Figure 9, if the turbidity distribution does not exceed the first threshold L1 but exceeds the second threshold L2 at only one location, the control device 50 determines that there is no condition in which flocs that are difficult to settle are formed in the separation chamber 21, and that there are only areas where the turbidity is temporarily and locally somewhat high. In this case, the control device 50 determines that there is no interface in the separation chamber 21, as explained with reference to Figure 4.

[0054] As shown in Figure 10, the control device 50 may store the alarm level AL in advance. The alarm level AL is an alarm value provided to prevent flocs from flowing out of the sedimentation tank 1. As shown in Figure 10, when the turbidity distribution exceeds the second threshold L2 above the alarm level AL in the turbidity distribution, the control device 50 issues an alarm to notify the operator that there may be some abnormality in the sedimentation tank 1. In one embodiment, the control device 50 may issue an alarm and reduce the amount of raw water inflow or stop the inflow of raw water. Furthermore, in one embodiment, the control device 50 may issue an alarm and reduce or stop the operating speed of the high-speed agitator 2 and / or the low-speed agitator 30 to reduce the flow velocity of the circulating flow.

[0055] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of Symbols]

[0056] 1. Sedimentation tank 2. High-speed agitator 3,34 Drive unit 5 Concentrator 14 Raw water supply room 15 Skirt Plate 16,17 Piping 18 Primary stirring chamber 19 Secondary stirring chamber 21 Separation room 23 gaps 30 Low-speed agitator 43. First sludge discharge valve 44. Second sludge discharge valve 50 Control device 51 Turbidity Sensor 52 Sensor moving device 54 Cable (string-like component) 55 Winch 56. Depth gauge 60 displays

Claims

1. A stirring chamber that forms flocs by agitating and coagulating impurities in the raw water, A separation chamber, which is connected to the aforementioned stirring chamber, separates the floc and water by sedimentation, A sludge discharge line is provided, which is connected to the separation chamber and is used to discharge the sludge separated in the separation chamber. A turbidity sensor is provided in the separation chamber, A sensor moving device capable of moving the turbidity sensor in the direction of the water depth in the separation chamber and measuring the position of the turbidity sensor in the direction of the water depth in the separation chamber, The system comprises the turbidity sensor and a control device connected to the sensor moving device, The control device is Using the turbidity sensor and the sensor moving device, the turbidity distribution in the water depth direction within the separation chamber is acquired at predetermined time intervals. A high-speed coagulation and sedimentation apparatus that, when the turbidity distribution exceeds a preset threshold for the turbidity in the separation chamber, determines the water depth corresponding to the measurement value of the turbidity sensor that exceeds the threshold as the interface value.

2. The high-speed coagulation and sedimentation apparatus according to claim 1, wherein, if multiple locations in the turbidity distribution exceed the threshold, the control device determines the water depth corresponding to the measurement value of the turbidity sensor located at the lowest of the multiple locations as the interface value.

3. The aforementioned threshold is the first threshold, The control device has a second threshold value that is smaller than the first threshold value stored in advance. The high-speed coagulation and sedimentation apparatus according to claim 1, wherein the control device determines the water depth corresponding to the measurement value of the turbidity sensor located at the lowest of the multiple locations as the interface value when multiple locations in the turbidity distribution exceed the second threshold.

4. The control device has pre-stored alarm levels set for the water depth in the separation chamber. The high-speed coagulation and sedimentation apparatus according to claim 3, wherein the control device issues an alarm when the turbidity distribution exceeds the second threshold while being above the alarm level.

5. The high-speed coagulation and sedimentation apparatus according to claim 1, wherein the control device obtains the rate of increase of the interface value by comparing a plurality of turbidity distributions acquired at predetermined time intervals.

6. The control device pre-stores a sludge discharge start level set in the direction of the water depth in the separation chamber, and a sludge discharge stop level set below the sludge discharge start level. The high-speed coagulation and sedimentation apparatus according to claim 1, wherein the control device operates the sludge discharge line to start discharging the sludge when the interface value reaches the sludge discharge start level, and operates the sludge discharge line to stop discharging the sludge when the interface value reaches the sludge discharge stop level.

7. The high-speed coagulation and sedimentation apparatus according to claim 6, wherein the control device acquires the turbidity distribution at intervals shorter than the predetermined time interval during the sludge discharge operation.

8. The high-speed coagulation and sedimentation apparatus according to any one of claims 1 to 7, wherein the control device creates a graph representing the turbidity distribution and displays the graph on a display.

Images