JP2006289188A - Sewage treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sewage treatment apparatus which can circulate carriers well throughout a water tank without precipitating them even in a deep water tank. <P>SOLUTION: The sewage treatment apparatus comprises an anaerobic tank 1 accommodating sewage mixed with the carriers 26, an oxygen-free tank 2, and an aerobic tank 3. An agitation shaft 21 having agitation vanes 23, 24, and a driving means 22 for performing low-speed rotation drive of the agitation shaft 21 are installed in the anaerobic tank 1 and the oxygen-free tank 2, and a draft tube 25 is disposed around the agitation vanes 23, 24. A partition plate 27 and an aeration means 28 are disposed in the aerobic tank 3. The water depth of the anaerobic tank 1, oxygen-free tank 2, and aerobic tank 3 is 5-15 m, and the distance between the upper end of the draft tube 25 and a water surface is ≤1/5 times the water depth. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sewage treatment apparatus such as a biological reaction tank or a storage tank in which a large number of carriers carrying bacteria are suspended in sewage containing organic matter and sewage in a sewage treatment plant is treated by an activated sludge method. .

  A conventional sewage treatment apparatus such as a sewage treatment plant is provided with water tanks (anaerobic tank, anoxic tank, and aerobic tank) of a water treatment series for storing sewage containing activated sludge. The sewage in the water tank of this water treatment series contains a large number of carriers for efficiently performing biological aerobic treatment and denitrification / dephosphorization treatment. Each carrier is porous or sponge-like, and bacterial cells are attached or included, and its specific gravity is greater than 1, so the carrier may settle at the bottom of an anaerobic tank, anoxic tank, or aerobic tank. is there. In this case, the opportunity for the carrier to come into contact with the activated sludge is reduced, and the progress of the biological reaction is reduced. In order to cope with such a problem, that is, to keep the carrier floating in the sewage without precipitating, a stirrer may be installed in the anaerobic tank and the oxygen-free tank. The stirrer includes an anaerobic tank, an agitation shaft disposed on the axis of the anaerobic tank, a one-stage or two-stage agitation blade attached to the agitation axis, and a drive motor that rotationally drives the agitation shaft. . A draft tube may be installed outside the stirring blade.

  In such a conventional sewage treatment apparatus, the stirring shaft is provided in the center of the anaerobic tank and the oxygen-free tank in the vertical direction, the drive motor is connected to the upper end of the stirring blade, and the lower end of the stirring shaft is a free end. Or is supported by bearings. The stirring blade is usually provided in one stage on the stirring shaft so as to be located in the sewage, and in two stages when the water depth is deep. The length of the agitation shaft is likely to fluctuate at its free end, so the limit is 5 m. When the water depth is deep, the agitation blade is configured to rotate at a high speed. Since the carrier is sponge-like and soft, the carrier is worn or damaged when the flow of sewage is fast. Therefore, when the anaerobic tank and anaerobic tank are deep, it is necessary to rotate the stirring blade at a high speed so that the carrier reaches the bottom. On the other hand, the flow rate of sewage is 10 cm to prevent the carrier from being worn or damaged. Per second.

  The above prior art is a technique generally known to those skilled in the art, and does not relate to a known literature invention. However, as a stirrer that can be installed in the conventional sewage treatment apparatus, for example, a low-speed carrier floating machine disclosed in JP 2000-135497 A is known. This low-speed carrier floating gas has a rotating shaft suspended from the drive unit installed in the center of the ceiling of the reaction tank into the reaction tank, and provided with a stirring blade on the rotating shaft. Is equipped with an auxiliary stirring blade. The agitation auxiliary blade has a front surface that is offset from the center line of the rotating shaft and a mounting side end that protrudes downward at a position that is deviated from the center line in a direction perpendicular to the offset direction.

JP 2000-135497 A (paragraph 0012 and FIGS. 1 to 4)

  The draft tube of the conventional sewage treatment apparatus needs to be maintained once a year, but the draft tube and the drive means are installed below the middle part below the water surface, so the maintenance is easy. Not expensive. Moreover, although the depth of an anaerobic tank, an anaerobic tank, and an aerobic tank is about 5 m normally, it may become as deep as 10 m in the place where land is narrow. In this way, when the anaerobic tank and anoxic tank become deep, it is necessary to install the stirring blade at a deep position, but the length of the stirring shaft is normally up to 5 m, so the water depth is doubled. Therefore, it is difficult to install the rotary blade at a position twice as deep due to the strength of the agitation shaft and the relationship of vibration. In addition, when the water depth has doubled, it is conceivable to increase the diameter of the stirring blade instead of installing it at a deep position, but this is also limited by the strength and runout of the stirring shaft. .

  In addition, the low-speed carrier floating machine disclosed in Japanese Patent Laid-Open No. 2000-135497 has the advantage that the carrier to be precipitated is not allowed to settle by giving a flow velocity to the carrier to be precipitated by the auxiliary stirring blade. Since the length and the rotation speed of the stirring blade are limited, it is expected that it is not easy to adapt to a deep reaction tank.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to provide an anaerobic tank, an anaerobic tank, and an anaerobic tank having a deep water depth without causing the carrier to settle. A sewage treatment apparatus that can be circulated satisfactorily throughout the oxygen tank and aerobic tank is obtained.

  The sewage treatment apparatus according to the present invention is a sewage treatment apparatus provided with a draft tube, a driving means, a stirring shaft, and a multistage stirring blade in an anaerobic tank and an oxygen-free tank in which a carrier exists in a biological reaction series. The water depth of the anaerobic tank and the oxygen-free tank is 5 to 15 m, and the distance between the upper end of the draft tube and the water surface is 1/5 or less of the water depth.

  The sewage treatment apparatus according to the present invention is a sewage treatment apparatus in which a partition plate and a diffuser are provided in an aeration tank in which a carrier is present in a biological reaction series, and the water depth of the aeration tank is 5 to 15 m. And it is divided | segmented by the said partition plate, and the ratio of the flat cross-sectional area by the side of the said aeration means is larger than 1/2 with respect to the flat cross-sectional area of the said aeration tank.

  This invention limits the water depth of the anaerobic tank, anaerobic tank, and aerobic tank to 5 to 15 m, provides a plurality of stirring blades in the draft tube, and sets the distance between the upper end of the draft tube and the water surface to the depth of water. Since it is set to 1/5 or less, it is possible to cause a favorable swirling flow, and it is not necessary to rapidly rotate the stirring blade, so that the shake of the stirring shaft can be suppressed within the limit. Therefore, even if the anaerobic tank, anaerobic tank, and aerobic tank are deep, the sewage can be swirled and aerated well in the anaerobic tank, anaerobic tank, and aerobic tank to prevent carrier precipitation. can do. Thereby, a support | carrier contacts a sewage well and the processing efficiency of a sewage improves. Further, since the stirring blades can be provided in a plurality of stages, the sewage can be swirled satisfactorily even if the number of rotations is reduced, and the precipitation of the carrier can be prevented. Furthermore, since the number of rotations of the stirring blade can be reduced, not only the carrier is not worn or damaged, but also the power for driving the stirring blade can be reduced. Since the stirring blades are provided in the draft tube and the stirring blades are provided in multiple stages, it is not necessary to lengthen the stirring shaft if the water depth of the anaerobic tank and the anaerobic tank is 15 m or less. There is no. In addition, since the driving means for driving the stirring blades is provided outside the anaerobic tank and the oxygen-free tank, maintenance management becomes easy.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a water treatment (biological reaction) series including a sewage treatment apparatus according to Embodiment 1 for carrying out the present invention. This sewage treatment apparatus is a biological reaction tank that performs aerobic treatment, denitrification and dephosphorization treatment of sewage containing activated sludge by the activated sludge method, and comprises an anaerobic tank 1, anoxic tank 2, and aerobic tank (aeration tank) The water depth is relatively deep. The water treatment system includes a first sedimentation basin (primary sedimentation) 4 and a final sedimentation basin (final sedimentation) 5 together with a sewage treatment apparatus. The supernatant of the first settling basin 4 flows into the anaerobic tank 1 through the sewage inflow pipe 6, and the outflow water from the aerobic tank 3 flows out to the final settling basin 5 through the treated water outflow pipe 7. . The sedimentation sludge in the settling tanks 4 and 5 is transferred out of the series via the transfer pipes 8 and 9, and the sludge in the final sedimentation tank 5 is returned to the anaerobic tank 1 through the return pipe 10. is there.

  2 is a schematic longitudinal sectional view of the anaerobic tank 1, FIG. 3 is a schematic plan view of the anaerobic tank 1, FIG. 4 is a schematic longitudinal sectional view of the aerobic tank 3, and FIG. Although the shape of the anaerobic tank 1, the anaerobic tank 2, and the aerobic tank 3 is not limited, in this Embodiment 1, since the normal deep beam exists every 5 m, it is adapted to it. Therefore, the cross-sectional shapes of the anaerobic tank 1, the anaerobic tank 2, and the aerobic tank 3 are generally rectangular (long square) by, for example, the short side walls 11, 11 facing in parallel and the long side walls 12, 12 facing in parallel. ). An upper inclined wall 12a and a lower inclined wall 12b that are inclined inward are provided on the upper and lower portions of each short side wall 11, respectively. The lower end of the anaerobic tank 1, the anaerobic tank 2, and the aerobic tank 3 is a horizontal bottom wall 13, and the upper openings of the anaerobic tank 1 and the anaerobic tank 3 are detachably closed by a top plate (not shown). In addition, means, such as a weir, a pipe, and an opening, are provided between the anaerobic tank 1 and the anaerobic tank 2 and between the anoxic tank 2 and the aerobic tank 3.

  The configurations of the anaerobic tank 1 and the anoxic tank 2 are the same. That is, at the center of the top plate of the anaerobic tank 1 and the anaerobic tank 2, the stirring shaft 21 is rotatably supported in the vertical direction. The upper part of the stirring shaft 21 penetrates the top plate, and driving means 22 such as a driving motor or a speed reducer is connected to the upper end of the stirring shaft 21. In the anaerobic tank 1 and the anaerobic tank 2, the stirring shaft 21 is vertically moved so that the upper first stirring blade 23 and the lower second stirring blade 24 do not cancel out the mutual discharge force. It is attached separately. A draft tube 25 is installed inside the anaerobic tank 1 and the anoxic tank 2 so as to surround the first and second stirring blades 23 and 24. The draft tube 25 can be installed on the bottom wall 13 of the anaerobic tank 1 and the anaerobic tank 2 via legs, suspended from the top plate, or fixed by a fastener from the side wall. A number of carriers 26 are suspended in the sewage in the anaerobic tank 1 and the anoxic tank 2. For the carrier 26, a material having low biodegradability and excellent corrosion resistance and durability, for example, polyurethane, polyester, polypropylene, or the like can be used.

  The aerobic tank 3 is provided with a partition plate 27 and an air diffuser 28. The air diffuser 28 includes a plurality of air diffusers 28a aligned on the same horizontal plane on the downstream side of the partition plate 27, a blower (not shown) for supplying air to the air diffusers 28a, An air supply pipe (not shown) connected to the air diffusion pipe 28a is used. The air diffuser 28 generates a swirling flow in the sewage by an air lift effect, thereby improving the oxygen dissolution efficiency. The air diffuser 28 can be suspended from the top plate or fixed to the side walls 11 and 12, but the installation method is not limited as long as it exhibits a good air lift effect. The shape of the air diffusing tube 28a can be cylindrical or plate-like, but is not limited as long as it does not cause clogging. A number of carriers 26 similar to those described above are also suspended in the sewage in the aerobic tank 3.

  Here, the anaerobic tank 1, the anaerobic tank 2, and the aerobic tank 3 are 5 to 15 m deep in water depth, and 10 m in the first embodiment. The first stirring blade 23 provided in the anaerobic tank 1 and the anaerobic tank 2 is positioned near the water surface, but needs to be positioned inside the draft tube 25. The second stirring blade 24 is preferably located within ½ of the water depth from the water surface, that is, within 2.5 to 7.5 m. In the first embodiment, the second stirring blade 24 is located 3.5 m from the water surface. . The distance between the upper end of the draft tube 25 and the water surface is preferably 1/5 of the water depth, i.e., 1 to 3 m or less, and is 0.5 m in the first embodiment. The distance between the lower end of the draft tube 25 and the bottom wall 13 is preferably 1 to 2.5 m, and is 1 m in the first embodiment.

  The horizontal position of the partition plate 27 is such that the plane cross-sectional area on the side where the air diffuser 28 is disposed is at least 1/2 of the plane cross-sectional area of the aerobic tank 3. The distance between the upper end of the partition plate 27 and the water surface is 0.5 m or more, and the distance between the lower end of the partition plate 27 and the bottom wall 13 is 3 m or less. The vertical position of the air diffuser 28 is 2 to 8 m below the water depth of the aerobic tank 3.

  As other dimensions, the length of the stirring shaft 21 is about 4 m, the rotation diameter of the first stirring blade 23 and the rotation diameter of the second stirring blade 24 are the same 3.3 m, The distance from the water surface is 1 m, and the distance between the first stirring blade 23 and the second stirring blade 24 is 2.5 m. The inner diameter of the draft tube 25 is 3.5 m. Therefore, a gap of 0.1 m exists between the end portions of the stirring blades 23 and 24 and the inner surface of the draft tube 25. The ratio of the cross-sectional area (flat cross-sectional area) of the anaerobic tank 1 and the anaerobic tank 2 and the cross-sectional area of the draft tube 25 is preferably determined as appropriate depending on the shape of the anaerobic tank 1 and the anaerobic tank 2. The first and second stirring blades 23 and 24 are rotated at a low speed of about 2 to 30 rotations / minute, and the sewage at the bottom of the anaerobic tank 1 and the anaerobic tank 2 has a flow rate greater than about 0.1 m / second. Is preferred. Moreover, it is preferable to give the flow rate larger than about 0.1 m / sec also to the sewage at the bottom of the aerobic tank 3.

  The stirring blades 23 and 24 are preferably an axial flow type that generates a vertical flow in the sewage, but may have any blade shape as long as the flow can be generated in the axial flow direction. For example, it can be a propeller type or a paddle type. However, one of the stirring blades 23 and 24 can be a propeller type and the other can be a paddle type. The stirring blades 23 and 24 can be configured by arranging 2 to 4 blade elements at equal intervals on a horizontal plane. Although the rotation diameters of the stirring blades 23 and 24 are the same, the rotation diameter of the first stirring blade 23 can be made smaller than the rotation diameter of the second stirring blade 24. Further, instead of the upper and lower two-stage stirring blades 23 and 24, only one stage of the stirring blades can be used. In this case, the number of blades needs to be 4-8. In any case, the diameter or the number of stages of the stirring blades 23 and 24 may be appropriately configured depending on the concentration of activated sludge and the amount of the carrier 26 introduced. Further, the partition plate 27 and the air diffuser 28 of the aerobic tank 3 may be appropriately configured and positioned depending on the concentration of activated sludge and the amount of the carrier 26 introduced.

  In the sewage treatment apparatus configured as described above, sewage flows into the anaerobic tank 1 from the sewage inflow pipe 6, and the same amount of treated water overflows from the aerobic tank 3 to the treated water outflow pipe 7. During this time, the first and second stirring blades 23 and 24 rotate in the draft tube 25 by the operation of the driving means 22 of the anaerobic tank 1 and the anaerobic tank 2. Thereby, for example, when the stirring blades 23 and 24 rotate forward, the sewage in the draft tube 25 flows downward and reaches the bottom wall 13 of the anaerobic tank 1 and the anaerobic tank 2. This sewage flows in a horizontal radial direction between the lower end of the draft tube 25 and the bottom wall 13 of the anaerobic tank 1 and the anaerobic tank 2, along the lower inclined wall 12 b of the anaerobic tank 1 and the anaerobic tank 2. Then, the outer side of the draft tube 25 is directed vertically upward. The sewage flows toward the inside along the upper inclined wall 12a of the anaerobic tank 1 and the anaerobic tank 2, toward the horizontal center along the water surface, and finally toward the lower side in the draft tube 25.

  On the other hand, in the aerobic tank 3, the sewage flowing from the anaerobic tank 2 is aerated by the air diffuser 28, so that an upward flow is generated in the sewage on the side where the air diffuser 28 is disposed due to the air lift effect. Therefore, a downward flow is generated in the sewage on the side where the air diffuser 28 is not disposed, and therefore a swirling flow is generated in the aerobic tank 3 with the partition plate 27 interposed therebetween.

  In this way, the sewage above the stirring blades 23 and 24 passes through the gaps between the respective blades of the stirring blades 23 and 24 and between the ends of the stirring blades 23 and 24 and the inner surface of the draft tube 25. Circulate. During this time, the carrier 26 circulates between the bottom wall 13 of the anaerobic tank 1 and the anaerobic tank 2 and the water surface together with the sewage without precipitation. In the aerobic tank 3, the carrier 26 circulates between the partition plate 27 and the bottom wall 13 and between the partition plate 27 and the water surface together with sewage without being precipitated. Thereby, the carrier 26 is uniformly distributed in the sewage and makes good contact with the activated sludge in the sewage, and the biological aerobic treatment / denitrogenation / dephosphorization treatment proceeds well, and the treatment efficiency is improved. To do. In addition, the anaerobic tank 1 consists of 3 tanks, the anoxic tank 2 consists of 3 tanks, and the aerobic tank 3 consists of 6 tanks. Moreover, the adjacent wall may be present or absent as long as it has a structure with good stirring and aeration efficiency.

  In the anaerobic tank 1 or the anaerobic tank 2 of the sewage treatment apparatus of the first embodiment, one draft tube 25, one drive means 22, one drive shaft 21, and two stages in one tank among a plurality of tanks. The stirring blade 23 is provided. The shape of one tank is that the width of the long side wall 12 is 5 m, the width of the short side wall 11 is 9 m, the water depth is 10 m, the rotating diameter of the stirring blades 23 and 24 is 3.3 m, and the first stirring blade 23 and the water surface The distance is 1 m, the spacing between the stirring blades 23 and 24 is 2.5 m, the inner diameter of the draft tube 25 is 3.5 m, the distance between the upper end of the draft tube 25 and the water surface is 0.5 m, the lower end and the bottom wall of the draft tube 25 The distance from 13 was 1 m. Therefore, the clearance between the end portions of the stirring blades 23 and 24 and the inner surface of the draft tube 25 was 0.1 m. Then, when the stirring blades 23 and 24 were rotated at 10 revolutions / minute (peripheral speed was 1.7 m / second), the carrier 26 flowed well together with sewage without being precipitated. Further, the horizontal position of the partition plate 27 of the aerobic tank 3 is such that the distance from the long side wall 12 on the side where the air diffuser 28 is disposed to the partition plate 27 is 6 m, and the length of the short side wall 11 is The length of the longitudinal side wall 12 is 5 m as 9 m. The distance between the upper end of the partition plate 27 and the water surface is 2.0 m, and the distance between the lower end of the partition plate 27 and the bottom wall 13 is 2.0 m. The vertical position of the air diffuser 28 is 4 m from the water surface of the aerobic tank 3. As a result, even in the aerobic tank 3, the carrier 26 flowed well together with the sewage without being precipitated.

  The rotational speed of the stirring blades 23 and 24 and the position of the draft tube 25 were changed from those in Example 1. That is, the width of the long side wall 12 is 5 m, the width of the short side wall 11 is 9 m, the water depth is 10 m, the rotating diameter of the stirring blades 23 and 24 is 3.3 m, the distance between the first stirring blade 23 and the water surface is 1 m, The distance between the stirring blades 23 and 24 is 2.5 m, the inner diameter of the draft tube 25 is 3.5 m, the distance between the upper end of the draft tube 25 and the water surface is 0.55 m, and the distance between the lower end of the draft tube 25 and the bottom wall 13. Was 1.11 m. Then, when the stirring blades 23 and 24 were rotated at 7 revolutions / minute using a propeller type, the average cross-sectional flow velocity of sewage became 0.23 m / second, and the carrier 26 did not settle in the anaerobic tank 1 and the anaerobic tank 2. It flowed well with sewage. Moreover, when the aerobic tank 3 was carried out with the same structure as in Example 1, the carrier 26 flowed well together with sewage in the aerobic tank 3 without precipitation.

  When the distance between the upper end of the draft tube 25 and the water surface was changed as shown in Table 1 below with respect to the water depth, the flow rate of sewage at the bottom of the anaerobic tank 1 was as shown in Table 1. Other conditions were the same as in Example 1. As can be seen from Table 1, when the distance between the upper end of the draft tube 25 and the water surface is 1/5 or less of the water depth, the flow rate of sewage at the bottom of the anaerobic tank 1 is increased, which is preferable. .

The horizontal position of the partition plate 27 is determined from the longitudinal side wall 12 on the side where the air diffuser means 28 is disposed so that the plane cross-sectional area on the air diffuser means 28 side becomes 2/3 of the plane cross-sectional area of the aerobic tank 3. 6 m and 3 m from the longitudinal side wall 12 on the side where the air diffuser 28 is not disposed. Further, the vertical position of the partition plate 27 was set such that the distance between the upper end of the partition plate 27 and the water surface was 2.3 m, and the distance between the lower end of the partition plate 27 and the bottom wall 13 was 2.3 m. Then, when aeration is performed from the air diffuser 28 with an air volume of 1 m ³ -air / m ³ / hour, that is, 1 m ³ of air is supplied to the volume 1 m ^{3 of the} aerobic tank 3 per hour. The flow rate of sewage at the bottom of the aerobic tank 3 was 41 cm / second, and the carrier 26 smoothly flowed without staying at the bottom of the aerobic tank 3, and the swirling flow of sewage was efficiently generated.

The aeration unit 28 aerated with an air volume of 0.9 m ³ -air / m ³ / hour, and the plane cross-sectional area on the side where the aeration unit 28 is arranged is shown in the following table with respect to the plane cross-sectional area of the aerobic tank 3. As shown in Table 2, the results shown in Table 2 were obtained. As can be seen from this result, it is preferable that the plane cross-sectional area on the side where the air diffuser 28 is disposed is not less than ½ of the plane cross-sectional area of the aerobic tank 3.

  As described above, in the sewage treatment apparatus according to the first embodiment, the draft tube 25 is disposed in the anaerobic tank 1 and the anaerobic tank 2, and the stirring blades 23 and 24 are vertically arranged in the draft tube 25. The sewage is provided even if the stirring blades 23 and 24 are rotated at a low speed by setting the distance between the upper end of the draft tube 25 and the water surface to 5 to 15 m in depth in the anaerobic tank 1 and the anaerobic tank 2 to 1/5 or less. It is possible to sufficiently flow until the bottom wall 13 of the anaerobic tank 1 and the anaerobic tank 2 is reached, and it is possible to prevent the carrier 26 from being deposited on the bottoms of the anaerobic tank 1 and the anaerobic tank 2. Further, since the stirring blades 23 and 24 are rotated at a low speed, the carrier 26 is not worn or damaged, and the power of the driving means 22 can be reduced. And since the support | carrier 26 can be made to contact favorably with sewage, the processing efficiency of sewage can be improved. Further, since it is not necessary to lengthen the stirring shaft 21, the stirring shaft 21 does not shake even if it is cantilevered. Therefore, it is not necessary to increase the diameter of the stirring shaft 21 or to support it with a bearing. Moreover, since the drive means 22 is provided outside the anaerobic tank 1 and the anaerobic tank 2, maintenance management becomes easy.

  Furthermore, the inside of the aerobic tank 3 is partitioned by a partition plate 27, and a diffuser means 28 is disposed at a water depth of 2 to 8 m on one side of the partition plate 27 so that the ratio of the plane cross-sectional area on the diffuser means 28 side is favorable. Since the plane cross-sectional area of the air tank 3 is larger than 1/2, it is possible to prevent the carrier 26 from being deposited on the bottom of the aerobic tank 3. Moreover, since the support | carrier 26 can be made to contact favorably with sewage because it can raise | generate a swirl flow favorably, the process efficiency of sewage can be improved.

Embodiment 2. FIG.
6 is a schematic longitudinal sectional view showing a sewage treatment apparatus according to Embodiment 2 for carrying out the present invention. The same parts as those in FIG. The sewage treatment apparatus in the second embodiment is that a third stirring blade 31 is provided between the first and second stirring blades 23 and 24 of the anaerobic tank 1 and the anaerobic tank 2 of the first embodiment. It differs from the sewage treatment apparatus in the first embodiment. In this case, the rotation diameter of the third stirring blade 31 is the same as that of the first and second stirring blades 23 and 24, and is positioned between them.

  In the sewage treatment apparatus of the second embodiment, the width of the long side wall 12 of the anaerobic tank 1 and the anaerobic tank 2 is 9 m, the width of the short side wall 11 is 5 m, the water depth is 10 m, and the stirring blades 23, 24, 31 are rotated. The diameter is 3.3 m, the distance between the first stirring blade 23 and the water surface is 1 m, the inner diameter of the draft tube 25 is 3.5 m, the distance between the upper end of the draft tube 25 and the water surface is 0.55 m, and the lower end of the draft tube 25 And the distance between the bottom wall 13 and 1.11 m. And when the stirring blades 23, 24, 31 were rotated at 6 rotations / minute as a propeller type, the longitudinal cross-sectional average flow velocity of sewage was 0.23 m / second as in Example 1, and the stirring blades 23, 24, Even if the rotational speed of 31 was made lower than that of Example 1, the same speed as that of Example 1 could be given to the sewage. Therefore, not only the effect similar to Example 1 was acquired, but the effect of power reduction and maintenance management by rotating the stirring blades 23, 24, and 31 at a lower speed was obtained.

Embodiment 3 FIG.
FIG. 7 is a schematic longitudinal sectional view for explaining the sewage treatment apparatus according to Embodiment 3 for carrying out the present invention, and FIG. 8 is a schematic plan view thereof. The same parts as those in FIG. Duplicate explanation is omitted. The sewage treatment apparatus according to the third embodiment is provided with an air diffusion means 32 outside the draft tube 25 of the anaerobic tank 2 according to the first embodiment, and the aerobic tank 3 is not installed. Different from the device. The air diffuser 32 includes a plurality of air diffusers 32a arranged radially in the middle of the upper and lower sides of the draft tube 25, a blower (not shown) for supplying air to the air diffusers 32a, and all of the diffusers An air supply pipe (not shown) connected to the trachea 32a is used.

  Thereby, in the anaerobic tank 2 in this Embodiment 3, both the anaerobic process and the aerobic process of wastewater can be repeatedly performed by a swirl flow. That is, air (oxygen) is mixed into the sewage from the air diffuser 32a to make the sewage aerobic, and the flow of sewage is accelerated by the air lift effect. Therefore, the rotation speed of the stirring blades 23 and 24 can be reduced by the amount of the air lift effect, and the power consumption of the driving means 22 can be saved. Moreover, since an anaerobic process and an aerobic process can be performed in one tank, an aerobic process and denitrification and dephosphorization process can be performed efficiently.

Embodiment 4 FIG.
FIG. 9 is a schematic longitudinal sectional view showing a sewage treatment apparatus according to Embodiment 4 for carrying out the present invention. The same parts as those in FIG. The sewage treatment apparatus in the fourth embodiment is different from the sewage treatment apparatus in the first embodiment in that a mount 33 is provided at the bottoms in the anaerobic tank 1 and the anoxic tank 2 in the first embodiment. The mount 33 acts like a current plate for regulating the flow of sewage, and is provided in the center on the bottom wall 13 of the anaerobic tank 1 and the anaerobic tank 2 as a conical shape. In the sewage treatment apparatus according to the fourth embodiment, since the mount 33 is provided, the direction of the sewage descending in the draft tube 25, that is, the flow of the carrier 26 is smoothly changed by the mount 33, and the treatment efficiency is the first embodiment. In other respects, the same effects as those of the first embodiment can be obtained.

Embodiment 5. FIG.
FIG. 10 is a schematic longitudinal sectional view showing a sewage treatment apparatus according to Embodiment 5 for carrying out the present invention. The same parts as those in FIG. The sewage treatment apparatus according to the fifth embodiment is different from the first embodiment in that guide portions 27a and 27b exhibiting a rectifying effect are provided above and below the partition plate 27 arranged in the aerobic tank 3 of the first embodiment. It is different from the sewage treatment equipment. In the sewage treatment apparatus according to the fifth embodiment, the direction of the sewage that descends on the upstream side of the partition plate 27 is smoothly changed by the guide portion 27b, and the direction of the sewage flow that rises on the downstream side of the partition plate 27. Is smoothly changed by the guide portion 27a, the processing efficiency is improved as compared with the case of the first embodiment, and the other effects similar to those of the first embodiment are obtained.

Embodiment 6 FIG.
FIG. 11 is a block diagram showing a sewage treatment apparatus according to Embodiment 6 for carrying out the present invention. The same parts as those in FIG. In the sewage treatment apparatus according to the sixth embodiment, an oxygen-free tank 41 similar to the oxygen-free tank 2 of the first embodiment is arranged instead of the anaerobic tank 1 of the first embodiment, and the oxygen-free tank of the first embodiment is arranged. In place of 2, a first aerobic tank 42 and a second aerobic tank 43 similar to the aerobic tank 3 of the first embodiment are arranged, and the aerobic tank 3 of the first embodiment is replaced with the third aerobic tank 3. The treated water is returned to the anaerobic tank 41 through the treated water return pipe 45 from the treated water outflow pipe 7.

In the sewage treatment apparatus according to the sixth embodiment, the width of each longitudinal side wall 12 of the anaerobic tank 41, the first aerobic tank 42, the second aerobic tank 43, and the third aerobic tank 44 is 5 m. The width of the short side wall 11 was 9 m, and the water depth was 10 m. The anaerobic tank 41 is provided with a draft tube 25, and two stages of stirring blades 23 and 24 are installed in the draft tube 25. The horizontal position of the partition plate 27 of the aerobic tanks 42 to 44 was 6 m from the long side wall 12 on the side where the air diffuser 28 was disposed, and 3 m from the long side wall 12 on the side where the air diffuser 28 was not disposed. The vertical position of the partition plate 27 was set such that the distance between the upper end of the partition plate 27 and the water surface was 0.5 m, and the distance between the lower end of the partition plate 27 and the bottom wall 13 was 1 m. The air diffuser 28 was installed at a water depth of 5 m. Then, the carrier 26 was not charged into the first aerobic tank 42, and the carrier 26 was charged at 10 V / V% into the second and third aerobic tanks 43 and 44. Under such conditions, the nitrification-promoted circulation modification method was operated with an inflow water amount of 12000 m ³ / day, a circulating water amount of 10,000 m ³ / day, and an aeration volume per unit volume of 1.2 m ³ -air / m ³ / hour. However, the flow rate of sewage at the bottom of the water tank becomes 35 cm / second, and the sewage efficiently turns in the lower part of the second aerobic tank 43 and the third aerobic tank 44, and the carrier 26 flows without stagnation. Was successfully processed.

It is a block diagram of the biological reaction series containing the sewage treatment apparatus by Embodiment 1 of this invention. It is a schematic longitudinal cross-sectional view of the anaerobic tank or an oxygen-free tank of the sewage treatment apparatus by Embodiment 1 of this invention. It is a schematic plan view of the anaerobic tank or an oxygen-free tank of the sewage treatment apparatus according to Embodiment 1 of the present invention. It is a schematic longitudinal cross-sectional view of the aerobic tank of the sewage treatment apparatus by Embodiment 1 of this invention. It is a schematic plan view of the aerobic tank of the sewage treatment apparatus by Embodiment 1 of this invention. It is a schematic longitudinal cross-sectional view of the anaerobic tank or an oxygen-free tank of the sewage treatment apparatus by Embodiment 2 of this invention. It is a schematic longitudinal cross-sectional view of the anoxic tank of the sewage treatment apparatus by Embodiment 3 of this invention. It is a schematic plan view of the anoxic tank of the sewage treatment apparatus according to Embodiment 3 of the present invention. It is a schematic longitudinal cross-sectional view of the anaerobic tank or an oxygen-free tank of the sewage treatment apparatus by Embodiment 4 of this invention. It is a schematic longitudinal cross-sectional view of the aerobic tank of the sewage treatment apparatus by Embodiment 5 of this invention. It is a block diagram of the sewage treatment apparatus by Embodiment 6 of this invention.

Explanation of symbols

1 Anaerobic tank 2, 41 Anoxic tank 3, 42, 43, 44 Aerobic tank (aeration tank)
21 Stirring shaft 22 Drive means 23, 24, 31 Stirring blade 25 Draft tube 26 Carrier 27 Partition plate 28, 32 Air diffuser means 33 Mount

Claims (5)

  In the sewage treatment apparatus provided with a draft tube, a driving means, a stirring shaft, and a multistage stirring blade in an anaerobic tank or an anaerobic tank in which a carrier exists in a biological reaction series, the anoxic tank and the anaerobic tank The sewage treatment apparatus is characterized in that the water depth is 5 to 15 m and the distance between the upper end of the draft tube and the water surface is 1/5 or less of the water depth.   The sewage treatment according to claim 1, wherein the number of revolutions of the stirring blade is 2 to 30 revolutions / minute.   2. The sewage treatment apparatus according to claim 1, wherein the agitation blade is provided above a position half the water depth in the draft tube.   In a sewage treatment apparatus in which a partition plate and a diffuser are provided in an aeration tank in which a carrier exists in a biological reaction series, the aeration tank has a water depth of 5 to 15 m and is divided by the partition plate. The ratio of the flat area on the air means side is larger than ½ with respect to the flat area of the aeration tank.   The sewage treatment apparatus according to claim 4, wherein the aeration means is disposed at a position of 2 to 8 m of the water depth of the aeration tank.

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