JP2008049321A - Gravity concentration tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gravity concentration tank capable of reducing the concentration of SS in flooding water by efficiently separating air bubbles attached to sludge from the sludge. <P>SOLUTION: The mutual rotary locus intervals L1 between the rotary loci adjacent diametrically in the rotation axis over all of air bubble separation means 12a1-12h20 are set to an almost equal interval while the mutual intervals L2 between the air bubble separation means 12a1-12h20 parallelly arranged to one arm are also set to an almost equal interval to be made larger than the rotation locus intervals L1. By this constitution, the air bubble separation means 12a1-12h20 are inclusively brought into contact with sludge while preventing the co-rotation of the sludge to more efficiently separate air bubbles bonded to the sludge as compared with a conventional gravitational concentration tank. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gravity concentration tank.

Conventionally, in a terminal treatment plant such as a sewer, a gravity concentration tank that settles and concentrates sludge by gravity is used as a treatment facility for sludge generated in a first sedimentation basin or the like. In such a gravity concentration tank, the following sludge concentration is generally performed. First, the sludge that has flowed into the tank settles below the tank (settlement zone) and settles and compresses by compaction due to its own weight (consolidation zone). Sludge having a high solid concentration accumulates at the bottom of the tank, and the separated supernatant liquid flows out from the overflow basin (clarification zone). As an example of a gravity concentration tank, Patent Document 1 describes a gravity concentration tank having a mechanism for discharging sludge that has settled and compressed to a sludge discharge section by a sludge scraping means provided in the tank. On the arm constituting the sludge scraping means, a round bar-like member called a picket fence is installed. This picket fence is used as a means for forming a water passage in the sludge to improve the separation between water and sludge. Non-Patent Document 1 discloses a method for improving a gravity concentration tank using a picket fence. Are listed.
JP2003-200192A Sewerage sludge treatment process management guidelines (draft) Ministry of Construction City Bureau Sewerage Department

  By the way, in the summertime when the water temperature rises, when the sludge residence time becomes longer, the sludge decays and gases such as methane gas, nitrogen gas, and air are generated from the sludge. These gases form bubbles and adhere to the sludge, and a reverse levitation phenomenon occurs where the sludge floats without sinking. As a result, there is a problem that the solid concentration of the sludge decreases and the SS (Suspended Solid) concentration of the overflowing supernatant increases. As measures for preventing the generation of gas, a method of performing vacuum degassing before charging the concentration tank, and a method of creating conditions under which anaerobic fermentation reaction or denitrification reaction does not occur by adjusting the pH are considered. However, in the former, it is necessary to deaerate the entire gravity concentration tank to a vacuum, and in the latter, there is a problem that chemicals are required and the sedimentation concentration property of sludge deteriorates. Moreover, in the said picket fence, although there existed the effect | action which isolate | separated the bubble adhering to the sludge in a sedimentation zone or a compaction zone from sludge by loose stirring, and it led to the upper part, it did not show sufficient effect.

  The present invention has been made in view of the above circumstances, and provides a gravity concentration tank capable of efficiently separating bubbles adhering to sludge from sludge and reducing the SS concentration of overflow water. Let it be an issue.

  A gravity concentration tank according to the present invention is a gravity concentration tank provided with a scraping rake that rotates at the bottom of the tank and scrapes sludge, and extends in a rotational axis radial direction from a substantially rotational axis of the scraping rake in a rotational direction. A plurality of arms that are spaced apart and rotate, and are arranged in parallel with each other in the radial direction of the rotation axis with respect to each of the arms, and extend in the vertical direction, thereby contacting the sludge to which bubbles are attached. A plurality of bubble separation means for separating the bubbles, and the rotation locus intervals of rotation traces adjacent to each other in the radial direction of the rotation axis of all the bubble separation means are substantially equal, and a plurality of bubble separation means arranged in parallel on the arm The bubble separation means interval is substantially equal, and the bubble separation means interval is larger than the rotation locus interval.

  In this way, the rotation trajectory intervals between the rotation trajectories adjacent to each other in the radial direction of the rotation axis of all the bubble separating means are substantially equal. Therefore, by appropriately setting the rotation trajectory interval between the rotation trajectories adjacent to each other in the radial direction of the rotation axis of all the bubble separation means, the bubble separation means is comprehensive as compared with the case where the rotation trajectory intervals are not substantially equal. Can contact sludge. In addition, since the intervals between the bubble separation means arranged in parallel on the arm are substantially equal, and the interval between the bubble separation means is larger than the rotation trajectory interval, sludge for the plurality of bubble separation means arranged in parallel on the arm. This reduces the resistance force caused by the sludge and prevents the sludge from rotating with the arm. Therefore, since the bubble separation means can comprehensively contact the sludge while preventing the sludge from circulating, the bubbles attached to the sludge can be separated more efficiently than the conventional gravity concentration tank.

  Here, it is preferable that the rotation trajectories of the bubble separation means do not overlap. In this case, the bubble separation means interval is set to be larger than the above-described bubble separation means interval, so that the effect of preventing the above-mentioned rotation is further enhanced.

  Further, as the bubble separation means that preferably exhibits the above-described action, specifically, a picket fence standing on an arm is exemplified.

  The picket fence preferably has a non-circular cross-sectional shape and corners. In this case, as compared with the case where a picket fence having a circular cross-sectional shape is used, the contact area of the picket fence with sludge is increased and the corners are in contact with the sludge. Therefore, bubbles can be separated more efficiently than when a picket fence having a circular cross-sectional shape is used.

  Further, the bubble separating means that preferably exhibits the above-described action may be a chain suspended on an arm. In this way, since the chain has a higher degree of freedom of movement than the picket fence, the contact area with the sludge is improved when the arm rotates. Therefore, bubbles attached to sludge can be separated more effectively than the picket fence.

  The chain is preferably suspended below a predetermined position below the water surface and in contact with the bottom surface of the tank. In this case, the chain, which is the bubble separation means, can contact the sludge present at the bottom of the gravity concentration tank. Since the sludge present at the bottom of the gravity concentration tank is in a state where it tends to rot and easily generate bubbles, the bubbles attached to the sludge can be more effectively separated.

  According to the gravity concentration tank of the present invention, it is possible to efficiently separate the bubbles attached to the sludge from the sludge and reduce the SS concentration of the overflow water.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. For the convenience of illustration, the dimensional ratios in the drawings do not necessarily match those described.

  This embodiment demonstrates the case where the gravity concentration tank which concerns on this invention is attached to the first sedimentation basin which isolate | separates waste water into sludge and a supernatant liquid. The gravity concentration tank plays a role of separating sludge generated in the first sedimentation basin into a supernatant and concentrated sludge, returning the separated supernatant to the first sedimentation basin, and collecting the concentrated sludge.

(First embodiment)
First, with reference to FIG. 1 thru | or FIG. 6, the structure of the gravity concentration tank 1 concerning 1st embodiment is demonstrated. FIG. 1 is a plan view showing a gravity concentration tank according to the first embodiment, FIG. 2 is a view taken along the line II-II of the gravity concentration tank shown in FIG. 1, and FIG. FIG. 4 is an explanatory diagram for explaining the shape shown by the arrangement of the bubble separating means, FIG. 5 is an explanatory diagram showing another example of the arrangement of the bubble separating means shown in FIG. 1, and FIG. It is a cross-sectional view which shows an example of the picket fence shown in FIG.

  As shown in FIGS. 1 and 2, the gravity concentration tank 1 according to the present embodiment includes a concentration tank 2, a sludge charging well 8, an overflow basin 4, an inflow trough 5, a driving device 7, a rotating shaft 10, and an arm 11a. To 11h, the scraping rake arm 3 and the picket fences 12a1 to 12h20.

  The concentration tank 2 has a circular cross section, and the internal space of the concentration tank 2 constitutes a storage space 2r for storing the introduced sludge. As a dimension example, for example, the diameter is 15700 mm and the effective water depth is 4 m. A sludge charging well 8 having a cylindrical shape is provided in the upper part of the storage space 2r. When the gravity concentration tank 1 is operated, the sludge A sent from the first sedimentation basin (not shown) through the sludge charging well 8 is provided. Is introduced into the storage space 2r.

  On the inner wall upper part of the concentration tank 2, an overflow basin 4 is provided on the inner side along the inner peripheral surface, and an inflow basin 5 is provided on the outer side of the overflow basin 4. At the water level close to the overflow basin 4 at the top of the storage space 2r, a supernatant is generated by the concentration action of the sludge. The produced supernatant flows over the overflow basin 4 and flows into the inflow basin 5, which becomes overflow water B and is first returned to the settling basin.

  As shown in FIG. 2, on the central axis X of the concentration tank 2, a rotation shaft 10 driven by a drive device 7 installed above the concentration tank 2 is provided. A scraping rake arm 3 extending in the axial direction of the rotary shaft 10 is attached to the bottom side. During the operation of the gravity concentration tank 1, the scraping rake arm 3 rotates with the rotation of the rotary shaft 10, and the concentrated sludge C that has settled in the lower part of the storage space 2 r by the sludge concentration action is provided at the center of the bottom of the concentration tank 2. Collected in the sludge pit 2d. A sludge scraping plate 6 is provided on the bottom surface side of the scraping rake arm 3 along the slope of the bottom of the concentration tank 2, and scrapes the sludge that has settled on the bottom of the concentration tank 2.

  1 and 2, a plurality of arms 11a to 11h are extended from the rotary shaft 10 in the radial direction of the rotary shaft and spaced apart in the rotational direction Y. The plurality of arms 11a to 11h are, for example, a plurality of arm members (eight in the present embodiment) made of steel or the like, and are spaced apart from each other at an equal angle. It is fixed. As a dimension example, the length of the arms 11a to 11h is 7850 mm, and the angle between the arms 11a to 11h is 45 degrees. During operation of the gravity concentration tank 1, the arms 11 a to 11 h are also rotated along with the rotation shaft 10.

  In each of the arms 11a to 11h, a plurality of bubble separation means are arranged apart from each other in the radial direction of the rotational axis and extend in the vertical direction. Here, the plurality of bubble separation means are picket fences 12a1 to 12h20 erected on the arms 11a to 11h. The picket fences 12a1 to 12a20 are juxtaposed to the arm 11a, the picket fences 12b1 to 12b20 are juxtaposed to the arm 11b, and the picket fences 12h1 to 12h20 are juxtaposed to the arm 11h. The picket fences 12a1 to 12h20 are rod-like members formed of steel or the like. For example, the picket fences arranged side by side on one arm are spaced apart from each other by a distance of 400 mm. It is fixed while standing on 11h. About the height of installation of the picket fences 12a1-12h20, it is preferable to make the front-end | tip part of picket fences 12a1-12h20 into the height lower than the lower end part of the sludge injection well 8 in 2 m below water surface. In this way, since the picket fences 12a1 to 12h20 are provided in the lower part of the storage space 2r where the SS concentration of sludge is relatively high, the bubbles attached to the sludge can be more effectively separated.

  As shown in FIG. 3, the picket fences 12 a 1 to 12 h 20 arranged on the arms 11 a to 11 h draw a concentric cylindrical rotation trajectory centered on the central axis X during operation of the gravity concentration tank 1. In FIG. 3, for convenience of space, the rotation trajectory when the picket fences 12a1 to 12h2 rotate 90 degrees is indicated by broken lines. In the entire picket fences 12a1 to 12h20, the rotation path intervals L1 between the rotation paths adjacent to each other in the rotational axis radial direction are equal, and a plurality of bubble separation means for picket fences arranged in parallel on one arm 11a to 11h. The intervals L2 are equally spaced, and the bubble separation means interval L2 is arranged to be larger than the rotation locus interval L1. Moreover, it is preferable that the rotation trajectories of the picket fences 12a1 to 12h20 do not overlap. And here, the arrangement form of the entire picket fences 12a1 to 12h20 (lines connecting the picket fences 12a1, 12b1, 12c1,..., 12h1, 12a2,..., 12h20) is, for example, as shown in FIG. Furthermore, it has a spiral arrangement. In this case, the bubble separation means interval L2 of one arm is the rotation locus interval L1 × 8 (number of arms). As specific dimension examples, the rotation locus interval L1 = 50 mm and the bubble separation means interval L2 = 400 mm. In addition, as shown in FIG. 5, it is good also as the gravity concentration tank 50 in which each rotation locus | trajectory of picket fence 12a1-12h20 has an overlap. In FIG. 5, the bubble separation means interval L2 is set as the rotation locus interval L1 × 2. Therefore, in the spiral arrangement form shown in FIG. 4, the bubble separation means interval L2 is set larger than the case shown in FIG.

  The cross-sectional shape of the picket fences 12a1 to 12h20 is preferably a non-circular cross-sectional shape having corners. For example, as shown in FIG. 6, the picket fences 12a1 to 12h20 have apexes on the rotation direction Y side. When the angle shape is adopted, the contact area where the picket fences 12a1 to 12h20 are in contact with the sludge during rotation can be increased and the corners are in contact with the sludge.

  Next, with reference to FIG. 2 and FIG. 3, operation | movement of the gravity concentration tank 1 which concerns on 1st embodiment is demonstrated.

  In the gravity concentration tank 1, first, the sludge A is stored in the storage space 2 r through the sludge charging well 8. The stored sludge settles below the storage space 2r, and the sludge settled below is settled and compressed by compaction due to its own weight. Therefore, sludge with a higher SS concentration is stored in the lower part of the storage space 2r. When the water temperature rises, the sludge located below the storage space 2r having a higher SS concentration is more rotted and generates gas. The generated gas causes air bubbles to adhere to the surrounding sludge, and the sludge to which the air bubbles have attached begins to rise above the storage space 2r by buoyancy.

  When the power source (not shown) of the drive device 7 is turned on and the operation is started, the rotational torque generated by the drive device 7 is transmitted to the rotary shaft 10 and the scraping rake arm 3 and the arms 11a to 11a fixed to the rotary shaft 10. 11h rotates. The scraping rake arm 3 rotates with the rotation of the rotary shaft 10 and collects the concentrated sludge C that has settled at the bottom of the storage space 2r due to the sludge concentration action in the sludge pit 2d provided at the center of the bottom of the concentration tank 2. . The arms 11a to 11h also rotate with the rotation of the rotating shaft 10, and the picket fences 12a1 to 12h20 disposed on the arms 11a to 11h draw a concentric cylindrical rotation locus centering on the central axis X. . At this time, the picket fences 12a1 to 12h20 come into contact with the sludge to which the gas on the rotation locus adheres, and separate the attached bubbles from the sludge. The sludge from which the bubbles have been separated settles again in the lower part of the storage space 2r. At this time, since sludge floating above the storage space 2r is reduced, the SS concentration of the supernatant liquid at a height near the overflow basin 4 is reduced. The supernatant liquid whose SS concentration is reduced exceeds the overflow basin 4 and becomes overflow water B and flows into the inflow basin 5 and is first returned to the settling basin.

  Here, in particular, according to the present embodiment, the rotation trajectory intervals L1 of the rotation trajectories adjacent to each other in the rotational axis diameter direction of all the picket fences 12a1 to 12h20 are equal intervals, and the picket fences 12a1 to 12h20 are the gravity concentration tank 1 During the operation, a rotation trajectory of a concentric cylinder having an interval of 50 mm centering on the central axis X is drawn and contacts the sludge on the rotation trajectory, so that the picket fence 12a1 is applied to the entire sludge stored in the lower portion of the storage space 2r. ~ 12h20 can be contacted exhaustively. Further, the bubble separation means intervals L2 between a plurality of picket fences arranged in parallel on one arm are substantially equal intervals, and the bubble separation means interval L2 is larger than the rotation locus interval L1. Therefore, the resistance force by the sludge with respect to the picket fence arranged in parallel by one arm is reduced, and the rotation which sludge rotates with the arms 11a-11h can be prevented. Therefore, since the picket fences 12a1 to 12h20 can comprehensively contact the sludge while preventing the sludge from circulating, the bubbles attached to the sludge can be separated more efficiently than the conventional gravity concentration tank.

  Further, the picket fences 12a1 to 12h20 of the gravity concentration tank 1 draw rotation trajectories that do not overlap each other. In this case, since the bubble separation means interval L2 is set larger than the bubble separation means interval L2 when the rotation trajectories overlap, the effect of preventing the circulation is further enhanced.

  Moreover, since the cross-sectional shape of picket fence 12a1-12h20 has an angle shape, compared with the case where the picket fence which has circular cross-sectional shape is used, the contact area with respect to the sludge of picket fence 12a1-12h20 is large. As the angle increases, the corners come into contact with the sludge and the bubble separation is improved. Therefore, bubbles can be separated more efficiently than when a picket fence having a circular cross-sectional shape is used.

(Second embodiment)
FIG. 7 is a view showing the gravity concentration tank 20 according to the second embodiment, and is a view taken in the direction of the arrow corresponding to FIG. The difference in configuration between the gravity concentration tank 20 of the second embodiment and the gravity concentration tank 1 shown in the first embodiment is that chains 13a1 to 13h20 are used instead of the picket fences 12a1 to 12h20 as the bubble separation means. It is a point. Except for this difference, the detailed description is omitted because it is the same as the first embodiment.

  Specifically, the chains 13a1 to 13h20 are suspended from the arms 11a to 11h. The chains 13a1 to 13h20 are, for example, chain members formed by connecting metal ring members, and the ring members at the ends are fixed to the lower ends of the arms 11a to 11h by welding or the like.

  During the operation of the gravity concentration tank 20, as the arms 11a to 11h rotate, the fixing points of the chains 13a1 to 13h20 draw a rotation locus similar to that of the first embodiment. At this time, the annular member connected below the fixing point can swing back and forth and right and left by receiving sludge resistance, and the contact area of the chains 13a1 to 13h20 with the sludge is improved as compared with the picket fence. Therefore, bubbles attached to sludge can be separated more effectively than the picket fence.

  The chains 13a1 to 13h20 are preferably suspended below a predetermined position below the water surface and are in contact with the bottom surface of the tank. For example, in the storage space 2r having an effective water depth of 4 m, the arms 11a to 11h are 2 m below the water surface. The upper end is fixed to 11h, and the lower end is installed in contact with the bottom of the concentration tank 2. The sludge located below the storage space 2r is more likely to generate gas due to the progress of decay, so that the chains 13a1 to 13h20 come into contact with the sludge to more effectively separate the bubbles attached to the sludge. Can do.

(Third embodiment)
FIG. 8 is a view showing the gravity concentration tank 30 according to the third embodiment, and is a view taken in the direction of the arrow corresponding to FIG. The difference in configuration between the gravity concentration tank 30 and the gravity concentration tank 1 shown in the first embodiment is that, in addition to the picket fences 12a1 to 12h20 as the bubble separation means, the bubble separation means as in the second embodiment. It is a point using chain 13a1-13h20. Except for this difference, the detailed description is omitted because it is the same as the first embodiment.

  In this way, the chains 13a1 to 13h20 are in contact with the sludge positioned below the fixing point of the picket fences 12a1 to 12h20, and the sludge positioned above the fixing points of the chains 13a1 to 13h20 is connected to the picket fences 12a1 to 12h1. 12h20 can contact. Therefore, the range of the vertical direction in which the bubble separating means contacts the sludge can be expanded, and both the advantage of the picket fence and the advantage of the chain can be obtained.

  In addition, embodiment mentioned above shows an example of the gravity concentration tank which concerns on this invention. The gravity concentration tank according to the present invention is not limited to such a tank, and the above embodiment may be modified so as not to change the gist of the present invention.

  For example, regarding the picket fence, the angle-shaped picket fence is shown in the above embodiment. However, as shown in FIG. 9, the cross-sectional shape is a rectangular shape (flat bar shape) with the rotation direction side being the long side of the rectangle. A picket fence may be used. Even with such a picket fence, compared with a picket fence having a circular cross-sectional shape, the contact area in contact with the sludge can be increased and the corners are in contact with the sludge. In addition, regarding the arm on which the picket fence or chain that is the bubble separation means is installed, the configuration in which the bubble separation means is installed on the eight arms has been shown in the above embodiment, but the number of arms other than eight may be used. . Moreover, in the said embodiment, although the bubble separation means is installed in the arm of a different member from the scratching rake arm, the structure installed in a scratching rake arm may be sufficient.

It is a top view which shows the gravity concentration tank which concerns on 1st embodiment. It is an II-II arrow line view of FIG. It is explanatory drawing explaining arrangement | positioning of a bubble separation means. It is explanatory drawing explaining the shape shown by arrangement | positioning of a bubble separation means. It is explanatory drawing which shows the other example of arrangement | positioning of the bubble separation means shown in FIG. It is a cross-sectional view which shows an example of the picket fence shown in FIG. It is a figure which shows the gravity concentration tank which concerns on 2nd embodiment, and is an arrow line view corresponding to FIG. It is a figure which shows the gravity concentration tank which concerns on 3rd embodiment, and is an arrow line view corresponding to FIG. It is a cross-sectional view which shows the other example of a picket fence.

Explanation of symbols

1, 20, 30, 50 ... gravity concentration tank, 2 ... concentration tank, 2d ... sludge pit, 2r ... storage space, 3 ... scraping rake arm (scratching rake), 4 ... overflow overflow, 5 ... inflow, 6 ... Sludge scraping plate, 7 ... Driving device, 8 ... Sludge injection well, 9 ... Scum scraping machine, 10 ... Rotating shaft, 11a-11h ... Arm, 12a1-12h20 ... Picket fence (bubble separation means), 13a1- 13h20 ... Chain (bubble separation means), A ... sludge, B ... overflow water, C ... concentrated sludge, L1 ... rotation locus interval, L2 ... bubble separation means interval, X ... central axis, Y ... rotation direction.

Claims (6)

In a gravity concentration tank equipped with a scraping rake that rotates at the bottom of the tank and scrapes sludge.
A plurality of arms that extend in the radial direction of the rotary shaft from the substantially rotating axis of the scraping rake and that are arranged spaced apart in the rotary direction and rotate;
A plurality of bubble separation means for separating the bubbles by contacting the sludge to which bubbles are attached, arranged in parallel with each other in the radial direction of the rotation axis with respect to each of the arms and extending in the vertical direction; ,
With
The rotation trajectory intervals between the rotation trajectories adjacent to each other in the radial direction of the rotation axis of all the bubble separation means are substantially equal intervals, and the bubble separation means intervals between the plurality of bubble separation means arranged in parallel on the arm are substantially equal intervals. The gravity concentration tank is characterized in that the bubble separation means interval is larger than the rotation trajectory interval.   2. The gravity concentration tank according to claim 1, wherein the rotation trajectories of the bubble separation means do not overlap.   The gravity concentration tank according to claim 1 or 2, wherein the bubble separation means is a picket fence erected on the arm.   The gravity concentration tank according to claim 3, wherein the picket fence has a non-circular cross-sectional shape and corners.   The gravity concentration tank according to claim 1 or 2, wherein the bubble separation means is a chain suspended from the arm. 6. The gravity concentration tank according to claim 5, wherein the chain is suspended below a predetermined position below the water surface and is in contact with the bottom surface of the tank.

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