Sludge removal device

Abstract

The invention proposes a device for removing scum that can reduce the burden on the natural environment by improving the quality of treated water and contributing to further energy savings, and can also be easily applied to existing settling tanks.The invention proposes a device for removing scum downstream of a settling tank located in a wastewater treatment plant by causing the scum to flow into a scum collector arranged to retain the flow of the water surface. This device comprises a pair of guide plates arranged such that the distance between the guide plates increases toward the direction in which the raw water flows toward the scum collector, and a fluid injection tube comprising gap sections arranged at intervals along the length, and injecting, through the gap sections, fluid rising from the lower ends of the pair of guide plates along the surfaces of the pair of guide plates on the side from which the raw water flows, wherein the pair of guide plates is arranged such that the upper part of each guide plate is positioned above the water surface and the lower part of each guide plate is positioned in the water.

Description

Scum removal equipment

[0001] The present invention relates to a scum removal device, and more particularly to a scum removal device suitable for use in a primary sedimentation tank installed in a sewage treatment plant. This application claims priority based on Japanese Patent Application No. 2023-151070, filed September 19, 2023, the contents of which are incorporated herein by reference.

[0002] Sewage treatment plants are equipped with primary sedimentation tanks, sometimes called first sedimentation tanks, which separate sedimentable substances from raw water received at the plant. While the primary sedimentation tank's primary purpose is to separate sedimentable substances, the raw water received by the primary sedimentation tank also contains floating substances due to its nature as sewage. Therefore, primary sedimentation tanks are equipped with scum removal devices that remove scum, which is formed by the aggregation of floating substances. Patent Document 1 shows an example of such a scum removal device.

[0003] Scum removal by the scum removal device is carried out by a scum intake section that is installed downstream of the primary sedimentation tank so that it is partially submerged. If this scum intake section is a pipe skimmer type, when the opportunity to remove scum arrives, the opening in the pipe that is horizontal to the water surface is rotated so that it is slightly below the water surface. This allows surface water containing scum to flow into the pipe, and the scum is removed.

[0004] If the scum intake is a trough type, when the opportunity to remove scum arrives, the inlet weir is lowered so that its top is below the water surface, allowing the surface water containing scum to flow into the trough and remove the scum.

[0005] Whether the scum intake section is a pipe skimmer type or a trough type, the scum is entrained in the water flowing into the pipe or trough, which has the drawback of requiring a huge amount of water to remove the scum and resulting in high processing costs. For this reason, the present applicant previously proposed a scum removal device as shown in Patent Document 2, and has a long track record with this proposed scum removal device. This proposed scum removal device is known as "Shuuichi-kun" (registered trademark).

[0006] The proposed scum removal device is a pipe skimmer type, and is configured with a jetting means for jetting a fluid (air) upward near the opening of the pipe into which the scum flows. When the air is jetted from the jetting means during scum discharge, the scum is induced to be taken in, and the scum flows into the pipe one after another. Once the scum starts to flow in, it continues to flow in even if the air jetting is stopped.

[0007] The proposed scum removal device has the excellent advantage of being able to improve the quality of treated water compared to conventional scum removal devices, and of being able to reduce the amount of water required to discharge scum to 1 / 20 to 1 / 30, thereby contributing to energy savings.

[0008] Japanese Patent Application Laid-Open No. 9-19682 Japanese Patent Application Laid-Open No. 2004-202493

[0009] Although the applicant has a proven track record with the scum removal device proposed above, there has been a long-awaited development of a scum removal device that can remove scum more efficiently, as well as a scum removal device that can be easily applied to the numerous existing settling tanks that currently exist.

[0010] The present invention has been made to meet the above-mentioned demands, and its object is to provide a scum removal device that can improve the quality of treated water, reduce the burden on the environment, contribute to greater energy savings, and can also be easily applied to existing settling tanks.

[0011] In order to achieve the above-mentioned object, the scum removal device of the present invention is a scum removal device that removes scum downstream of a settling tank installed in a sewage treatment plant, and comprises: a scum intake section that is installed to block the flow of raw water on the surface and allow scum to flow in; a pair of guide plates that are installed upstream of the scum intake section with their upper parts positioned above the water surface and their lower parts submerged, and are arranged so that the distance between them gradually increases toward the upstream side from which the raw water flows; and a first fluid ejection pipe that is installed near the lower end of the guide plate, has a plurality of openings spaced apart in the lengthwise direction, and ejects fluid that rises on the surface of the upstream side of the guide plate from the openings.

[0012] The scum flowing through the settling tank can be collected in the center by a pair of guide plates and guided to the scum intake section. In this case, the scum can be guided away from the guide plates by the fluid ejected from the first fluid ejection pipes provided near the lower ends of the guide plates, without adhering to the guide plates.

[0013] Furthermore, by ejecting the fluid from the first fluid ejection pipe, the scum to be taken into the scum intake section can be guided to the scum intake section while being lifted from below.

[0014] Therefore, the amount of scum left behind can be reduced, and it can be smoothly and reliably taken into the scum intake section, allowing scum intake to be achieved in a short time. As a result, the amount of water taken in with the scum is also reduced. The water taken in with the scum is returned upstream after scum treatment, but the amount of return water is reduced. This also reduces the amount of electricity required for scum removal and return. In addition, although the treated water after scum removal is released into the natural environment, the improved water quality reduces the burden on the environment.

[0015] The scum removal apparatus of the present invention may further include a front wall plate provided below the scum intake section along a direction perpendicular to the flow direction of the raw water; and a second fluid ejection pipe provided near the lower end of the front wall plate, having a plurality of openings spaced apart in the longitudinal direction, and ejecting from the openings the fluid rising on the upstream surface of the front wall plate.

[0016] The front wall plate can block the flow below the scum intake section, preventing the scum from flowing downstream of the scum intake port and ensuring reliable intake.

[0017] In the scum removing apparatus of the present invention, the second fluid ejection pipe and the first fluid ejection pipe may be connected to a fluid supply pipe via a flow rate adjusting valve, respectively.

[0018] The flow rate of the fluids ejected from the first and second fluid ejection pipes can be adjusted individually by using the flow control valves. Because the pair of guide plates are provided so as to protrude above the water surface, there is a risk that scum may be pressed against them by the current and adhere to them. However, by supplying a pressurized fluid such as compressed air from the first fluid ejection pipe provided at the lower end of the guide plates, it is possible to prevent scum from adhering to the surface of the guide plates and to separate the scum from the surface of the guide plates, thereby effectively guiding the scum to the scum intake section.

[0019] In the front wall plate located below the scum intake section, the pressure of the fluid ejected from the second fluid ejection pipe is made relatively small, so that the scum can be lifted from below and guided to the scum intake port without being destroyed or the like.

[0020] In the scum removal device of the present invention, the scum intake section comprises a pipe member that is placed horizontally on the water surface and has a scum intake port along the length of part of the peripheral wall; and a rotation mechanism that can rotate the pipe member to position the scum intake port between a scum intake position where it is partially submerged in water and a non-intake position where it is positioned above the water, and the upper end of the front wall plate is positioned at the same level as or lower than the lower end of the scum intake port at the scum intake position.

[0021] The scum intake port along the length of the horizontal pipe material allows for efficient intake of scum on the water surface, and in combination with the action of the aforementioned guide plate, front wall plate, and first and second fluid ejection pipes, scum can be effectively removed.

[0022] In the scum removal apparatus of the present invention, the fluid ejected from the openings of the first and second fluid ejection pipes may be compressed air. In this case, the scum can be kept away from the guide plate by the bubbling phenomenon. The front wall plate generates buoyancy in the scum, allowing it to be effectively guided to the scum intake port.

[0023] In the scum removing device of the present invention, the opening of the first fluid ejection pipe or the second fluid ejection pipe may be provided in a cup-shaped ejection outlet member and may be arranged facing downward.

[0024] In the scum removing device of the present invention, a plurality of water injection nozzles for injecting water onto scum generated on the water surface are provided upstream of the guide plate.

[0025] By spraying water from a water spray nozzle onto the scum that floats and collects on the water surface, the air bubbles adhering to the scum disappear, allowing the sedimentary substances that have risen to the surface to settle.

[0026] Furthermore, if scum has solidified on the water surface, it can be broken down to make it easier to flow, and the entire scum can be washed downstream, making it easier to discharge the scum.

[0027] In the scum removal device of the present invention, a plurality of underwater nozzles are provided upstream of the guide plate for spraying pressurized water from underwater to promote the flow of scum generated on the water surface downstream.

[0028] By flushing the scum floating on the water surface downstream from below in the water, the scum can be easily discharged.

[0029] The scum removal device of the present invention is configured to provide a front wall plate and a pair of guide plates in front of the scum intake section, each of which ejects pressurized fluid from a fluid ejection pipe. This allows for faster scum removal and reduces the amount of water entrained with the scum, thereby contributing to reduced power consumption, etc. Furthermore, the quality of the treated water from which the scum has been removed is improved, resulting in an extremely advantageous effect of reducing the environmental impact if the water is released into the natural environment. Furthermore, the pair of guide plates equipped with the fluid ejection pipes, which are the main components, can be prefabricated in a factory, making it easily applicable to existing sedimentation tanks.

[0030] 4A is a plan view showing a part of a sedimentation basin equipped with a scum removal device according to an embodiment of the present invention; FIG. 4B is a cross-sectional view taken along line A-A in FIG. 1; FIG. 4C is an enlarged view of the vicinity of the pipe gap in FIG. 2; FIG. 4D is a cross-sectional view (FIG. 4A) and a plan view (FIG. 4B) of a water injection nozzle;

[0031] A scum removing device 10 according to an embodiment of the present invention will be described below.

[0032] 1 is a plan view of the downstream portion of a sedimentation tank 1 equipped with a scum removal device 10 according to one embodiment of the present invention. Here, the sedimentation tank 1 is shown as a primary sedimentation tank installed in a sewage treatment plant.

[0033] This settling tank 1 is configured to receive sewage (hereinafter sometimes referred to as "raw water," meaning water before purification treatment) received at a sewage treatment plant via a conduit (not shown). The sewage received in the settling tank 1 moves from one side (the left side in the illustrated example) to the other side (the right side in the illustrated example). During this process, i.e., during the flow indicated by arrow a in the figure, sedimentary substances contained in the sewage settle and are separated.

[0034] Although not shown in the figure, the settleable material (sludge) that settles to the bottom of the sedimentation tank 1 is collected in a pit located at the bottom of one side of the sedimentation tank 1 by a sludge collector, and then sent to a sludge treatment facility for treatment.

[0035] The raw water contains floating substances in addition to sedimentary substances, and scum, which is a collection of floating substances, is formed on the water surface of the sedimentation tank 1. Therefore, in the sedimentation tank 1, the settling substances are separated as described above, and the scum (see "S" in Figure 3) is removed by the scum remover 10.

[0036] The treated water from which these precipitates and scum S have been removed is received in an overflow trough 2 provided on the other side (downstream side) of the sedimentation tank 1. The treated water received in the overflow trough 2 is taken out from the overflow trough 2 as shown by the arrow b in Figure 1 and sent to a reaction tank (aeration tank) (not shown) where it is subjected to biological treatment.

[0037] The scum removal device 10 is installed downstream of the flow of raw water from the sedimentation tank 1 and upstream of the overflow trough 2. This scum removal device 10 is provided with a pipe skimmer 11, which corresponds to the scum intake section of the present invention.

[0038] This pipe skimmer 11 comprises a pipe 12 that is installed to block the flow of water on the surface, and a rotation mechanism 5 that rotates the pipe 12. That is, this pipe 12 is installed horizontally so as to cross the sedimentation basin 1 in the width direction, and a slit-shaped opening (scum intake port) 13 is provided in the peripheral wall along the longitudinal direction.

[0039] One longitudinal end of the pipe material 12 passes through one side wall 3a of the settling tank 1 in a watertight manner and is supported so as to be freely rotatable, and the other end is supported so as to be freely rotatable on the other side wall 3b of the settling tank 1. The end of the pipe material 12 that passes through the side wall 3a is placed in the scum pit 4 provided on the outside of the side wall 3a.

[0040] A rotation mechanism 5 including a motor is provided on the upper surface of the other side wall 3b of the settling tank 1, where the other end of the pipe 12 is provided. This rotation mechanism 5 is configured to rotate the pipe 12 back and forth around its axis at a predetermined angle.

[0041] Normally, the pipe 12 is supported so that the scum intake port 13 provided in the longitudinal direction is positioned above the water surface as shown in Figures 1 and 2. When the time comes to remove scum, the rotating mechanism 5 rotates as shown by arrow d in Figure 3 (counterclockwise in Figure 3) so that the water surface is positioned approximately in the middle of the width of the scum intake port 13 (the width along the circumferential direction of the pipe 12).

[0042] As a result, the scum S in front of the pipe material 12 flows toward the scum intake port 13, drops into the pipe material 12 from the scum intake port 13, and is then sent to the scum pit 4 through the inside of the pipe material 12. The position of the scum intake port 13 at this time is referred to as the scum intake position, and the position where the scum intake port 13 is located above the water surface is referred to as the non-intake position.

[0043] The scum discharged into the scum pit 4 is removed from the scum pit 4 as indicated by the arrow c, and sent to a scum treatment facility (not shown) equipped with a dehydrator and the like for treatment.

[0044] When scum removal is complete, the pipe 12 is rotated in the direction opposite to the arrow d (clockwise in FIG. 3) so that the scum intake port 13 is positioned above the water surface as shown in FIG. 1 (see also the two-dot chain line in FIG. 3). The rotation of the rotation mechanism 5 is controlled by a programmable controller (not shown) that controls the entire settling tank 1, including the scum remover 10.

[0045] The rotation mechanism 5 may be configured to manually rotate the pipe 12 back and forth without providing a motor or the like.

[0046] 1, the pipe material 12 is formed to be longer than the width of the sedimentation tank 1 and is arranged to cross the sedimentation tank 1. The scum intake port 13 provided in the longitudinal direction of the pipe material 12 is formed to be shorter than the width of the sedimentation tank 1, and both ends in the longitudinal direction are arranged at a predetermined distance from the inner surfaces of both side walls 3a, 3b of the sedimentation tank 1.

[0047] The scum removal device 10 has the pipe skimmer 11, a front wall plate 20, and a pair of guide plates 30. The front wall plate 20 and the guide plates 30 are provided in front of (upstream of) the pipe material 12, i.e., on the side from which raw water approaches the pipe material 12 (on the left side of the pipe material 12 in the illustrated example).

[0048] The front wall panel 20 is made of a steel or synthetic resin plate, and when viewed from the direction of the raw water flow (upstream), it has a rectangular shape that is elongated in the width direction of the sedimentation tank 1. The length of the long side of the rectangle of the front wall panel 20 is set to be slightly longer than the length of the scum intake port 13 provided in the pipe material 12.

[0049] The short sides of the front wall plate 20 are aligned along the depth direction of the sedimentation tank 1. As shown in Figure 3, the upper end of the front wall plate 20 is positioned below the lower end of the scum intake port 13 when the pipe material 12 rotates and a portion of the scum intake port 13 is submerged in water (scum intake position). The lower end of the front wall plate 20 extends below the lower position of the pipe material 12.

[0050] One longitudinal end of the front wall panel 20 (widthwise of the sedimentation tank 1) is fixed to the inner surface of one side wall 3a of the sedimentation tank 1 using a support member 21, and the other end is fixed to the inner surface of the other side wall 3b of the sedimentation tank 1 using a support member 21. When fixing these two ends, the front wall panel 20 is carefully positioned so that the rear (downstream) surface of the front wall panel 20, i.e., the surface opposite the direction in which the raw water flows, is close to the pipe material 12 as far as not interfering with the rotation of the pipe material 12, and so that the upper edge of the front wall panel 20 is lower than the lower end of the scum intake port 13 of the pipe material 12 at the scum intake position.

[0051] However, the upper edge position of the front wall plate 20 may be set at approximately the same height as the lower end position of the scum intake port 13 of the pipe material 12 at the scum intake position.

[0052] A second fluid ejection pipe 22 extending in the width direction of the sedimentation basin is attached using a U-bolt or the like near the bottom edge of the front (upstream) surface of the front wall panel 20, i.e., near the surface near the bottom edge of the front wall panel 20 on the side from which the raw water flows. This second fluid ejection pipe 22 is made of a steel or synthetic resin pipe material, and has a number of discharge port members 23 arranged in a row at predetermined intervals along its length.

[0053] The discharge outlet members 23 are made of synthetic resin such as fluororesin, and have a cup-like (bowl-like, bell-like, etc.) outer shape with an opening 24 at the bottom. Each discharge outlet member 23 is fixed to the second fluid ejection pipe 22 with its internal space communicating with the inside of the second fluid ejection pipe 22, and the opening 24 is arranged facing vertically downward.

[0054] One longitudinal end of the second fluid ejection pipe 22 is closed, and the other end is connected to a flow control valve 25 via a fluid supply pipe 26. The fluid supply pipe 26 is provided with an on-off valve 27 such as a gate valve.

[0055] 1 to 3 show an example in which a front wall plate 20 is provided, this front wall plate 20 is not necessarily required, and there are cases in which the front wall plate 20 is not provided. However, providing the front wall plate 20 is preferable because it creates a wall below the pipe gap 11.

[0056] Even when the front wall plate 20 is not provided, the second fluid ejection pipe 22 having the discharge outlet member 23 is provided below the pipe gap 11 (gap intake portion).

[0057] The pair of guide plates 30 are identical in shape. Like the front wall plate 20, the guide plate 30 is made of steel or synthetic resin. The guide plate 30 is rectangular, with its short side aligned along the depth direction within the sedimentation tank 1. In this case, the width of the guide plate 30 (the dimension along the depth direction of the sedimentation tank 1) is approximately twice the length of the short side of the front wall plate 20 (the dimension along the depth direction of the sedimentation tank 1). When installed in the sedimentation tank 1, the upper edges of the guide plates 30 are positioned higher than the top surface of the scum S, and the lower edges are positioned approximately equal to the lower edge of the front wall plate 20 (see Figures 2 and 3). Note that the guide plate 30 may not be provided.

[0058] A first fluid ejection pipe 29 equipped with a plurality of ejection outlet members 28 is attached by a U-bolt or the like to the front (upstream) surface of this guide plate 30 near the lower edge thereof. The first fluid ejection pipe 29 provided on both guide plates 30 is connected to a flow control valve 25 via a fluid supply pipe 26, similar to the second fluid ejection pipe 22 of the front wall plate 20.

[0059] For convenience of drawing, the piping of the first fluid ejection pipe 29 on the side wall 3b is shown only partway, and is connected to the piping shown at the top of the drawing at the position indicated by the symbol "Q" in FIG.

[0060] The specific longitudinal dimensions of this guide plate 30 will be described later, but one longitudinal end (downstream side) of each guide plate 30 abuts against each end (upper and lower ends in Figure 1) of the front wall plate 20, and the other longitudinal end (upstream side) is fixed using a support member 32 so as to abut against the inner surfaces of each side wall 3a, 3b of the sedimentation tank 1.

[0061] When fixing the guide plates 30, they are carefully attached so that the upper edge of each guide plate 30 is higher than the upper surface of the scum S and the lower edge is approximately equal to the lower edge of the front wall plate 20.

[0062] The length of the pair of guide plates 30 is determined by the angle θ at which they are attached to the inner surfaces of both side walls 3a, 3b of the sedimentation tank 1. In the example of Figure 1, each guide plate 30 is attached at an angle θ of approximately 15° to the inner surfaces of the side walls 3a, 3b, and is arranged so that the distance between the pair of guide plates 30 gradually increases toward the upstream side.

[0063] The purpose of setting the mounting angle θ on the pair of guide plates 30 is to gradually collect the flowing scum S toward the center of the flow, thereby increasing the concentration of scum S and obtaining scum S with a low moisture content. In order to increase the concentration of scum S, it is possible to shorten the length (dimension along the width direction of the sedimentation tank 1) of the scum inlet 13 and front wall plate 20 provided on the pipe material 12, but if the mounting angle θ is increased, the guide plate 30 itself will increase the resistance to the flow of scum S. Therefore, the mounting angle θ is appropriately determined based on the properties of the raw water received in the sedimentation tank 1, the amount of scum S generated, etc.

[0064] In addition, a first fluid ejection pipe 29 is provided on each guide plate 30, and water ejection nozzles (above water nozzles) 40, 41 described later are provided between the guide plates 30, so the mounting angle θ of the guide plates 30 can be made relatively large.

[0065] If the mounting angle θ of the pair of guide plates 30 is brought closer to 0°, they will be closer to parallel to both side walls 3a, 3b of the settling basin 1, and therefore the effect of the guide plates 30 in accumulating the scum S will be reduced, but the resistance to the scum S will be reduced, thereby increasing the movement speed of the scum S. Furthermore, since the first fluid ejection pipe 29 and water injection nozzles (above water nozzles) 40, 41 described below are provided, the time required for discharging the scum S will be shorter, and therefore the amount of water required for discharge will also be reduced.

[0066] Water injection nozzles (above-water nozzles) 40 and 41 shown in Figures 4A and 4B are provided above the water surface near the water surface near the scum removal device 10, which is composed of the front wall plate 20 and a pair of guide plates 30, and a water injection nozzle (underwater nozzle) 42 is provided underwater near the water surface.

[0067] 1, a plurality of above-water nozzles 40 (five in the illustrated example) are provided at predetermined intervals in the direction across the sedimentation basin 1 in the region between the pair of guide plates 30. A plurality of above-water nozzles 41 and submerged nozzles 42 (six in total in the illustrated example) are provided in the same manner as the above-water nozzles 40, slightly upstream of the installation position of the above-water nozzles 40 (outside the gap between the pair of guide plates 30 in the illustrated example).

[0068] Each water injection nozzle 40, 41, 42 is configured to have a slit 43 that sprays water approximately parallel to the water surface, and a flow straightening piece 44 that protrudes from the top of the slit 43 and maintains the stratified water flow sprayed from the slit 43. The water injection nozzle 40 (above-water nozzle) arranged in the region between both guide plates 30 is provided at approximately the water surface position, and is installed so that the stratified water flow sprayed from the slit 43 is directed toward the scum removal device 10 (pipe skimmer 11).

[0069] The above-water nozzles 41 and the underwater nozzles 42 are located upstream of the area between the two guide plates 30, and three above-water nozzles 41 are arranged slightly above the water surface and three underwater nozzles 42 are arranged slightly below the water surface alternately.

[0070] The above-water nozzles 41 are installed at a slight downward incline, spraying water diagonally from above onto the water surface. The submerged nozzles 42 are installed at a slight upward incline, spraying water from underwater onto the water surface. In Figures 1 and 2, the above-water nozzles 41 are shown by solid lines, and the submerged nozzles 42 are shown by dashed lines. In the case of a primary sedimentation basin, the submerged nozzles 42 may not be installed.

[0071] These water injection nozzles 40 , 41 , 42 can adjust the injection amount appropriately by a flow rate adjusting valve 45 , and are connected to a water supply pipe 47 equipped with an opening / closing valve 46 .

[0072] Some of the solids that float up as scum would settle and separate if no air bubbles were attached. The water injection nozzles 41, 42 can destroy the air bubbles and allow the solids to settle and separate by spraying water from above the scum S and from underwater. For this reason, the number and arrangement of the above-water nozzles 41 and the underwater nozzles 42 are determined depending on the properties of the scum S on the water surface, etc.

[0073] The operation of removing scum S from the settling tank 1 equipped with the scum removing device 10 having the above-described configuration is carried out as follows.

[0074] As shown in Figure 3, when a certain amount of scum S accumulates on the water surface and it is time to discharge the scum, the pipe material 12 of the pipe skimmer 11 is rotated from the state shown in Figures 1 and 2 to the state (scum intake position) shown in Figure 3.

[0075] The on-off valves 27, 46 are opened simultaneously with or before the rotation of the pipe material 12. Water is sprayed onto the scum layer S from water spray nozzles 40, 41, 42 provided at upstream positions. This eliminates air bubbles adhering to the solid matter in the scum layer S, causing the solid matter floating due to the air bubbles to settle and separate, and also sweeps the scum downstream together with the water sprayed downstream.

[0076] The scum layer S then passes between the guide plates 30 and is swept away to the scum intake port 13 of the pipe skimmer 11 (pipe material 12). At this time, compressed air is being ejected as a pressurized fluid from the first fluid ejection pipe 29 onto the surface of the guide plate 30, and the bubbling flow reaches the water surface. As a result, the scum layer S flows away from the surface of the guide plate 30 and is guided to the scum intake port 13 without adhering to the guide plate 30.

[0077] On the front surface of the front wall panel 20, compressed air is ejected relatively slowly from the second fluid ejection pipes 22, and the buoyancy of the air causes the scum layer S to be lifted and flow into the scum intake port 13. In this way, the scum S is induced to be taken into the scum intake port 13, and thereafter the scum S is continuously flowed into the pipe skimmer 11. Once the inflow of scum S begins, the ejection of air from the second fluid ejection pipes 22 on the front wall panel 20 is stopped.

[0078] The ejection of compressed air from the first fluid ejection pipe 29 in the vicinity of the guide plate 30 prevents scum from adhering to the guide plate 30 and also moves the scum away from the surface of the guide plate 30, facilitating a smooth flow to the scum intake port 13, and therefore continues even after the start of scum intake.

[0079] The flow of scum S is promoted by the water jets ejected from the water injection nozzles 40 arranged in the area between the guide plates 30, and the scum S can be quickly discharged toward the pipe gap 11 (pipe material 12).

[0080] The scum S taken into the pipe skimmer 11 (pipe material 12) is discharged into the scum pit 4 and sent to a scum treatment facility for treatment.

[0081] When most of the scum S has been discharged into the pipe 12, the pipe 12 is rotated to the non-take-in position shown in Figure 1, and the on-off valves 27 and 46 are closed. This stops the compressed air from the second fluid ejection pipe 22 and the first fluid ejection pipe 29, and also stops the water ejection from the water ejection nozzles 40, 41, and 42. This completes the series of scum removal operations by the scum remover 10.

[0082] The scum removal device 10 configured as described above includes a front wall plate 20 equipped with a second fluid ejection pipe 22, a pair of guide plates 30 equipped with a first fluid ejection pipe 29, and water ejection nozzles 40, 41, and 42. This allows for quicker scum removal and reduces the amount of water that flows into the pipe gaps along with the scum, allowing for quicker scum removal. For example, scum can be removed by operating the device for approximately 7 to 10 minutes once a week. This reduces the amount of water returned upstream from the pipe gaps, reducing the amount of electricity required for scum removal and water return, thereby achieving energy savings.

[0083] Furthermore, although the treated water is released into the natural environment, the improved water quality has the extremely advantageous effect of reducing the burden on the natural environment. Therefore, the scum removal device 10 configured as described above has the excellent feature of being able to significantly contribute to further energy savings and reducing the burden on the natural environment.

[0084] Furthermore, the scum removal device 10 having the above-described configuration has the advantage that the main components, namely the front wall panel 20 equipped with the second fluid ejection pipe 22 and the first fluid ejection pipe 29, and the pair of guide plates 30, can be prefabricated in a factory, and therefore can be easily applied to existing sedimentation tanks.

[0085] In the above embodiment, the second fluid ejection pipe 22 and the first fluid ejection pipe 29 are provided with the ejection outlet members 23, but the fluid ejection pipes themselves may have small holes formed therein without the ejection outlet members 23. However, if the ejection outlet members 23 are provided, the upward flow of compressed air can be regulated. Furthermore, in the above embodiment, the fluid ejected from the second fluid ejection pipe 22 and the first fluid ejection pipe 29 is compressed air, but the same effect can be obtained by using a water flow or pressurized water containing air bubbles.

[0086] In the above embodiment, the scum intake section is a pipe skimmer type, but it may be a trough type that takes in scum by moving the inlet weir up and down. Also, while the example in which the scum removal device 10 is applied to a primary sedimentation basin has been shown, it can also be applied to a final sedimentation basin. In this case, the water injection nozzles 40, 41 can be omitted to prevent the scum from becoming pin flocs (fine particles).

[0087] The scum removal device according to the present invention has been described above with reference to the drawings. However, the specific configuration is not limited to the above-described embodiment, and design changes and the like are possible within the scope of the gist of the present invention.

[0088] This method can remove scum in a shorter time and also reduces the amount of water entrained with the scum, which contributes to reducing power consumption, etc. Furthermore, the quality of the treated water from which the scum has been removed is improved, which has the extremely excellent effect of reducing the environmental impact if the water is released into the natural environment. Moreover, it can be easily applied to existing sedimentation tanks.

[0089] DESCRIPTION OF SYMBOLS 1... Sedimentation tank (primary sedimentation tank) 2... Overflow trough 3a, 3b... Wall 4... Scum pit 5... Rotating mechanism 10... Scum removal device 11... Pipe gap (gap intake section) 12... Pipe material 13... Opening (scum intake port) 20... Front wall plate 21... Support member 22... Second fluid jet pipe 23... Discharge outlet member 24... Opening 25... Flow control valve 26... Fluid supply pipe 27... On-off valve 28... Discharge outlet member 29... First fluid jet pipe 30... Guide plate 32... Support member 40... Water injection nozzle (above water nozzle) 41... Water injection nozzle (above water nozzle) 42... Water injection nozzle (underwater nozzle) 43... Slit 44... Flow straightening piece 45... Flow adjustment valve 46... On-off valve 47... Water supply pipe S... Scum

Claims

1. A scum removal device for removing scum downstream of a sedimentation tank installed in a sewage treatment plant, comprising: a scum intake section that is arranged to block the surface flow of raw water and allow scum to flow in; a pair of guide plates that are installed upstream of the scum intake section with an upper part above the water surface and a lower part submerged in water, and are arranged so that the distance between them gradually increases toward the upstream side from which the raw water flows; and a first fluid ejection pipe that is installed near the lower end of the guide plate, has a plurality of openings spaced apart in the length direction, and ejects fluid that rises on the surface of the upstream side of the guide plate from the openings.

2. The scum removal device according to claim 1, further comprising: a front wall plate provided below the scum intake section in a direction perpendicular to the flow direction of the raw water; and a second fluid ejection pipe provided near the lower end of the front wall plate, having a plurality of openings spaced apart in the length direction, and ejecting from the openings the fluid rising on the upstream surface of the front wall plate.

3. A scum removal device as described in claim 2, characterized in that the second fluid ejection pipe and the first fluid ejection pipe are each connected to a fluid supply pipe via a flow rate regulating valve.

4. A scum removal device as described in claim 2, wherein the scum intake section comprises a pipe member arranged horizontally on the water surface and having a scum intake port along the length of part of the peripheral wall; and a rotation mechanism which can rotate the pipe member to position the scum intake port between a scum intake position where part of the scum intake port is submerged in water and a non-scum intake position where the scum intake port is above the water; and the upper end of the front wall plate is arranged at the same level as or lower than the lower end of the scum intake port in the scum intake position.

5. A scum removing apparatus according to claim 1, characterized in that the fluid ejected from said opening of said first fluid ejection pipe is compressed air.

6. A scum removing device according to claim 2, characterized in that the fluid ejected from said opening of said second fluid ejection pipe is compressed air.

7. A scum removal device as claimed in claim 1, characterized in that a plurality of water injection nozzles for injecting water onto scum generated on the water surface are provided upstream of the guide plate.

8. A scum removal device as described in claim 1, characterized in that a plurality of underwater nozzles are provided upstream of the guide plate for spraying pressurized water from underwater to promote the flow of scum generated on the water surface downstream.

9. A scum removing device as claimed in claim 1, characterized in that the opening of the first fluid ejection pipe is provided in a cup-shaped discharge outlet member and is arranged facing downward.

10. The scum removal device according to claim 2, characterized in that the opening of the second fluid ejection pipe is provided in a cup-shaped outlet member and is arranged facing downward. The scum removal device according to claim 1, characterized in that the opening of the second fluid ejection pipe is provided in a cup-shaped outlet member and is arranged facing downward.

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