Sludge separation device

Abstract

The present invention provides a sludge separation device that can reduce electricity costs compared to conventional devices and also adjust the concentration of sludge. [Solution] A sludge separation device 10 for separating sludge from raw water comprises: a separation tank 11 for separating the raw water into treated water, floating sludge, and settled sludge; a sludge adjustment tank 13 for receiving and storing the separated floating sludge and settled sludge, and for discharging sludge in a mixed state of floating sludge and settled sludge; a floating sludge scraper 14 for moving the separated floating sludge from the separation tank 11 to the sludge adjustment tank 13; a pipe 10c extending from the separation tank 11 to the sludge adjustment tank 13 for sending the separated settled sludge to the sludge adjustment tank 13; and a sludge extraction valve 16 installed in the pipe 10c that can be opened and closed. When the sludge extraction valve 16 is open, the settled sludge is sent to the sludge adjustment tank 13 due to the difference in water levels between the separation tank 11 and the sludge adjustment tank 13.

Description

Technical Field

[0001] The present invention relates to a sludge separation device.

Background Art

[0002] In water treatment, a process of separating sludge from raw water may be carried out. For example, the wastewater treatment device described in Patent Document 1 sends settled sludge to a sludge storage tank by a pump and mixes it with floating sludge in the sludge storage tank (see FIG. 1 of Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In sewage treatment, reduction of power cost is an important issue. In recent years, energy recovery from sludge has been demanded. For example, there is a technology for generating compost by dehydrating sludge. Also, there is a technology for gasifying combustible components in sludge by digestion. In these technologies, concentration of sludge becomes a problem, and a concentration process may be required.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a sludge separation device that can reduce power cost more than before and can adjust the concentration of sludge.

Means for Solving the Problems

[0006] To achieve the above objective, the present invention provides a sludge separation apparatus for separating sludge from raw water, comprising: a separation tank for separating the raw water into treated water, floating sludge, and settled sludge; a sludge adjustment tank for receiving and storing the separated floating sludge and settled sludge, and for discharging sludge in a mixed state of the floating sludge and settled sludge; a moving means for moving the separated floating sludge from the separation tank to the sludge adjustment tank; piping extending from the separation tank to the sludge adjustment tank for sending the separated settled sludge to the sludge adjustment tank; and a sludge extraction valve installed in the piping that can be opened and closed, wherein when the sludge extraction valve is open, the settled sludge is sent to the sludge adjustment tank due to the difference in water levels between the separation tank and the sludge adjustment tank.

[0007] The sludge extraction valve may be equipped with a sensor for detecting the water level in the sludge adjustment tank, and the sludge extraction valve may be configured to open when the water level in the sludge adjustment tank drops due to the discharge of sludge and reaches a first set position, thereby sending the settled sludge to the sludge adjustment tank, and to close when the water level in the sludge adjustment tank reaches a second set position higher than the first set position, thereby stopping the sending of the settled sludge to the sludge adjustment tank. [Effects of the Invention]

[0008] The sludge separation apparatus of the present invention can reduce electricity costs compared to conventional methods and can also adjust the concentration of sludge. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram of a sludge separation apparatus according to an embodiment of the present invention. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail with reference to the drawings as appropriate. The sludge separation apparatus 10 according to an embodiment of the present invention is a device that separates raw water into treated water and sludge by causing the sludge contained in the raw water to float and settle. The separated sludge is in a liquid state by containing a predetermined amount of water.

[0011] As shown in Figure 1, the sludge separation apparatus 10 comprises a separation tank 11, a treated water tank 12, a sludge adjustment tank 13, a floating sludge scraper 14, and a control device 19. The treated water tank 12 is located adjacent to the separation tank 11. The sludge adjustment tank 13 is connected to the separation tank 11 via a connecting section 15. The floating sludge scraper 14 is installed over the separation tank 11, the connecting section 15, and the sludge adjustment tank 13. The control device 19 controls the operation of the entire sludge separation apparatus 10.

[0012] The separation tank 11 is the part that separates raw water into three components: treated water, settled sludge, and floating sludge. Raw water is, for example, wastewater or sewage. Raw water and microbubble water flow into the separation tank 11. Microbubble water is water containing microbubbles (ultrafine bubbles with a diameter of 1 to 100 μm). Raw water stored in the raw water tank flows into the separation tank 11 via piping 10a. In addition, a portion of the treated water treated in the separation tank 11 is converted into microbubble water and flows into the separation tank 11 via piping 10b. Note that the supply of microbubble water does not necessarily have to be the treated water treated in the separation tank 11; for example, treated sewage water or water specifically for microbubbles may be used. Although the microbubble water piping 10b is connected to the separation tank 11, this piping 10b may be connected to the raw water piping 10a, which is connected to the separation tank 11, a little before the separation tank 11, and the microbubble water may be mixed with the raw water in piping 10a.

[0013] The raw water contains sludge (suspended components), and the microbubbles attach to the suspended components in the raw water, reducing its apparent specific gravity. The components that float to the surface due to the microbubbles become floating sludge, while the rest sink to become settled sludge. The floating sludge accumulates on the surface of the liquid in the separation tank 11, while the settled sludge accumulates at the bottom 11c of the separation tank 11.

[0014] The separation tank 11 mainly comprises a first side wall portion 11a, a second side wall portion 11b, a bottom portion 11c, and a partition portion 11d.

[0015] The partition section 11d divides the inside of the separation tank 11 into two spaces (first space 11t and second space 11u). The first space 11t is where the raw water is separated and where the separated settled sludge and floating sludge collect before discharge. The second space 11u is where the separated treated water collects before discharge. The lower end of the partition section 11d does not reach the bottom 11c, and the treated water separated in the first space 11t moves to the second space 11u through the space below the partition section 11d. The upper end of the partition section 11d is located above the water surface in the separation tank 11. The partition section 11d plays a role in preventing floating sludge from moving into the second space.

[0016] The first side wall portion 11a is the side wall portion on the sludge adjustment tank 13 side. The second side wall portion 11b is the side wall portion on the treated water tank 12 side. The first side wall portion 11a and the second side wall portion 11b are, for example, perpendicular to the horizontal plane.

[0017] A pipe 10a connecting the raw water tank and the separation tank 11, and a pipe 10b connecting the treated water tank 12 and the separation tank 11 are installed on the first side wall 11a. Pipe 10a is a route for sending raw water to the separation tank 11, and raw water flows into the separation tank 11 via pipe 10a. Pipe 10b is a route for sending microbubble water to the separation tank 11, and microbubble water flows into the separation tank 11 via pipe 10b.

[0018] Furthermore, a pipe 10c connecting the separation tank 11 and the sludge adjustment tank 13 is installed near the bottom 11c of the first side wall 11a. The pipe 10c is a path for sending settled sludge to the sludge adjustment tank 13, and the settled sludge moves to the sludge adjustment tank 13 via the pipe 10c. A sludge extraction valve 16 is provided in the pipe 10c. The sludge extraction valve 16 is controlled to change its open / closed state according to changes in the water level of the sludge stored in the sludge adjustment tank 13.

[0019] The bottom 11c is shaped to easily collect settled sludge near the pipe 10c. In this embodiment, the bottom 11c has a horizontal portion 11ca and an inclined portion 11cb that is inclined with respect to the horizontal portion 11ca. The horizontal portion 11ca is continuously formed from the lower end of the first side wall portion 11a. The inclined portion 11cb is continuously formed from the lower end of the second side wall portion 11b and rises toward the second side wall portion 11b. The inclined portion 11cb plays a role in suppressing the movement of the settled sludge into the second space. The position and inclination angle of the inclined portion 11cb are designed so that the settled sludge does not move into the second space 11u. As a result, the settled sludge mainly accumulates on the horizontal portion 11ca.

[0020] An overflow weir 11g is provided at the upper end of the second side wall portion 11b. The overflow weir 11g is a weir for evenly discharging the separated treated water into the treatment water tank 12. The treated water collected in the second space 11u flows into the treatment water tank 12 through the overflow weir 11g.

[0021] The treatment water tank 12 temporarily stores the treated water. The treatment water tank 12 has pipes 10b and 10d. The pipe 10d is connected to a treated water storage tank, and a part of the treated water stored in the treatment water tank 12 is discharged to the treated water storage tank through the pipe 10d. The pipe 10b is connected to the first space 11t of the separation tank 11, and a part of the treated water stored in the treatment water tank 12 flows back into the first space 11t through the pipe 10b. When the supply of microbubble water is, for example, the treated water of sewage, the pipe 10b is not connected to the treatment water tank 12 but is connected to a treatment water tank of a final sedimentation tank not shown.

[0022] A microbubble generation pump 17 is installed in the pipe 10b. The microbubble generation pump 17 is a pump that generates microbubbles and produces microbubble water. That is, a part of the treated water treated in the separation tank 11 is extracted into the pipe 10b in the treatment water tank 12, microbubbles are imparted by the microbubble generation pump 17, and it is supplied to the separation tank 11 as microbubble water.

[0023] The floating sludge scraping device 14 is a device that scrapes the floating sludge accumulated on the liquid surface of the liquid in the separation tank 11 and moves it to the sludge adjustment tank 13. The floating sludge scraping device 14 is an example of the moving means for moving the floating sludge to the sludge adjustment tank 13. The moving means for the floating sludge may be means other than the floating sludge scraping device 14 (an example is a pump or the like).

[0024] The floating sludge scraping device 14 shown in FIG. 1 has a conveyor belt 14a and a driving means 14b. The conveyor belt 14a is arranged across the separation tank 11, the connecting portion 15, and the sludge adjustment tank 13. The conveyor belt 14a has a belt portion 14aa formed by forming a belt-shaped member in an annular ( endless) shape, and a protruding portion 14ab formed to protrude outward from the belt portion 14aa. The driving means 14b generates a driving force for rotating the conveyor belt 14a. The driving means 14b is, for example, a motor, and rotates the conveyor belt 14a in the α direction (counterclockwise). Note that the conveyor belt 14a may be a chain.

[0025] The protruding portions 14ab are provided at arbitrary intervals in the moving direction of the conveyor belt 14a, are continuously formed in the width direction of the conveyor belt 14a, and move while pushing the floating sludge. By rotating the conveyor belt 14a in the α direction, the floating sludge in the separation tank 11 is moved to the sludge adjustment tank 13 through the connecting portion 15. The moved floating sludge flows into the sludge adjustment tank 13 from above. The position where the belt portion 14aa is arranged and the shape of the protruding portion 14ab are designed so that the floating sludge can be appropriately conveyed into the sludge adjustment tank 13. Note that when the conveyor belt 14a is a chain, the protruding portion 14ab may be spanned on the chains on both sides.

[0026] The sludge adjustment tank 13 temporarily stores the sludge (including sedimented sludge and floating sludge) separated in the separation tank 11. The sedimented sludge and floating sludge stored in the sludge adjustment tank 13 are mixed to a certain concentration and then discharged. The water content of the sludge stored in the sludge adjustment tank 13 is, for example, "90%" or more (an example is about "95 - 98%") and is in a liquid state. The sludge adjustment tank 13 preferably has a stirring device.

[0027] The piping 10e is connected to the sludge storage tank, and the sludge stored in the sludge adjustment tank 13 is discharged to the sludge storage tank via the piping 10e. Specifically, a sludge discharge pump 18 is installed in the piping 10e, and the sludge is sent to the sludge storage tank by the sludge discharge pump 18.

[0028] The sludge adjustment tank 13 is box-shaped with an open top and has pipes 10c and 10e. Pipe 10c is connected to the separation tank 11, and settled sludge flows into the sludge adjustment tank 13 via pipe 10c. A sludge extraction valve 16 is provided in pipe 10c, and when the sludge extraction valve 16 is open, settled sludge is sent to the sludge adjustment tank 13 due to the difference in water levels between the separation tank 11 and the sludge adjustment tank 13 (settled sludge is extracted from the separation tank 11). Note that the liquid in the separation tank 11 and the liquid in the sludge adjustment tank 13 both have high water content and are therefore assumed to have the same mass (the difference in mass due to the difference in concentration will not be considered).

[0029] The sludge adjustment tank 13 has a sensor 13a that detects the water level of the stored liquid. There are no particular restrictions on the type or number of sensors 13a that the sludge adjustment tank 13 has. The control device 19 controls the opening and closing state of the sludge extraction valve 16 based on the detection result of the sensor 13a (i.e., the water level in the sludge adjustment tank 13). In this embodiment, the case in which the opening and closing state of the sludge extraction valve 16 is controlled using two preset water levels (first setting position L1, second setting position L2) will be described.

[0030] The second setting position L2 is higher than the first setting position L1. The second setting position L2 is, for example, a position where there is no difference between the water level in the separation tank 11 and the water level in the sludge adjustment tank 13, or a position lower than the water level in the separation tank 11.

[0031] The control device 19 opens the sludge extraction valve 16 when the water level in the sludge adjustment tank 13 drops due to the sludge being sent to the sludge storage tank by the sludge discharge pump 18 and reaches the first set position L1. When the sludge extraction valve 16 is open, settled sludge is sent to the sludge adjustment tank 13 due to the water level difference between the separation tank 11 and the sludge adjustment tank 13 (settled sludge is extracted from the separation tank 11).

[0032] Next, the control device 19 closes the sludge extraction valve 16 when the water level in the sludge adjustment tank 13 rises and reaches the second set position L2. When the sludge extraction valve 16 is closed, the supply of settled sludge to the sludge adjustment tank 13 is stopped. Subsequently, the water level in the sludge adjustment tank 13 begins to fall again due to the operation of the sludge discharge pump 18. Then, the control device 19 opens the sludge extraction valve 16 again when the water level reaches the first set position L1.

[0033] According to the sludge separation device 10 described above, the settled sludge is sent to the sludge adjustment tank 13 due to the difference in water levels between the separation tank 11 and the sludge adjustment tank 13. Therefore, no electrical energy is required to send the settled sludge to the sludge adjustment tank 13 (no pumps or other devices are needed to transfer the settled sludge), and electricity costs can be reduced compared to conventional methods.

[0034] Furthermore, the sludge separation device 10 controls the opening and closing state of the sludge extraction valve 16 based on the water level in the sludge adjustment tank 13. This allows for an appropriate mixing of settled sludge and floating sludge, and enables adjustment of the sludge concentration. In other words, the sludge concentration can be changed by appropriately setting the first setting position L1 and the second setting position L2. For example, if the settled sludge extracted has a lower concentration than the floating sludge, reducing the difference between the first setting position L1 and the second setting position L2 reduces the amount of settled sludge extracted, maintaining the sludge concentration in the separation tank at a certain high concentration (slightly lower than the concentration of floating sludge but considerably higher than the concentration of settled sludge). Also, if the settled sludge extracted has a higher concentration than the floating sludge, increasing the difference between the first setting position L1 and the second setting position L2 increases the amount of settled sludge extracted, raising the sludge concentration in the separation tank to a high concentration. In this way, the mixed sludge reaches the required and high concentration, eliminating the need for a concentration process. This is expected to reduce the amount of coagulant and lower the moisture content in the subsequent dewatering process, resulting in better sludge composting. Furthermore, if the next process is a digester, the energy recovery rate will improve.

[0035] Although embodiments of the present invention have been described above, the design can be modified as appropriate without violating the spirit of the invention. For example, the floating sludge scraper 14, which is a means of moving floating sludge, may be a pump or the like. [Explanation of symbols]

[0036] 10. Sludge Separation Unit 10a, 10b, 10c, 10d, 10e Piping 11 Separation tank 11a First side wall part 11b Second side wall part 11c bottom 11d Partition 11g overflow weir 11t 1st space 11u 2nd space 12 Treatment tanks 13. Sludge adjustment tank 13a Sensor 14. Floating sludge scraper (means of transport) 14a Conveyor belt 14b Driving means 15 Connecting part 16. Sludge extraction valve 17 Microbubble Generating Pump 18. Sludge discharge pump 19 Control device

Claims

1. In a sludge separation device that separates sludge from raw water, A separation tank for separating the raw water into treated water, floating sludge, and settled sludge, A sludge adjustment tank receives and stores the separated floating sludge and settled sludge, and discharges sludge in a mixed state of the floating sludge and settled sludge, A means for moving the separated floating sludge from the separation tank to the sludge adjustment tank, A pipe extends from the separation tank to the sludge adjustment tank, and is used to send the separated settled sludge to the sludge adjustment tank. The aforementioned piping is equipped with a sludge extraction valve that can be opened and closed, When the sludge extraction valve is open, the settled sludge is sent to the sludge adjustment tank due to the difference in water levels between the separation tank and the sludge adjustment tank. A sludge separation apparatus characterized by the following features.

2. It is equipped with a sensor that detects the water level in the sludge adjustment tank. The sludge extraction valve is, As the sludge is discharged, the water level in the sludge adjustment tank drops, and when the water level reaches the first set position, the valve opens and the settled sludge is sent to the sludge adjustment tank. When the water level in the sludge adjustment tank reaches a second set position that is higher than the first set position, the tank closes, and the supply of settled sludge to the sludge adjustment tank is stopped. The sludge separation apparatus according to feature 1.

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