JP6914863B2 - Sewage treatment system and agitator - Google Patents

Description

The present invention relates to a sewage treatment system for treating sewage by a biological treatment method and a stirring device used therein.

In the conventional standard sewage treatment, sludge is first separated in a settling basin, and then in a reaction tank, BOD, nitrogen, phosphorus, etc. are removed by biological treatment to generate flocs, and then the final settling basin is used. Further separate the sludge and discharge the treated water. That is, the system for treating this sewage consists of three tanks: a first settling basin, a reaction tank, and a final settling basin.

High-speed filtration methods, inclined plate methods, and the like are provided as functional enhancement techniques for the first settling basin and the final settling basin (hereinafter, both are simply referred to as "settling basins"). Further, in the case of the gravity sedimentation method, the sedimentation basin requires a large site due to the restriction of the water area load required for the separation of solid matter. Further, since scum is generated and floats in the settling basin, it is usually provided with a removing mechanism (for example, a pipe type scum gap, a watering device, etc.).

Further, as a technique for enhancing the function of the reaction vessel, an advanced treatment method having enhanced functions is used as compared with the usual standard activated sludge method. Advanced treatment methods include an anaerobic anoxic aerobic method (A2O method), a carrier method, a membrane separation activated sludge method (MBR method), and the like.

Japanese Unexamined Patent Publication No. 9-47783

However, sewage treatment by the conventional advanced treatment method requires an anaerobic tank for removing phosphorus, an oxygen-free tank for removing nitrogen, and / or an aerobic tank mainly for removing BOD for biological treatment, and is anaerobic. A stirrer is required for the tank and the oxygen-free tank, and an aeration device is required for the aerobic tank. Therefore, a plurality of aquarium skeletons and a site area are required.

Further, as described above, the capacity of the gravity sedimentation type sedimentation basin depends on the water area load, and therefore, a large site area and a water tank skeleton are required to secure a sufficient capacity. If the high-speed filtration method or the inclined plate method is adopted to reduce the site area of the settling basin, maintenance and power costs will be incurred.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the site area of a water treatment system.

The sewage treatment system of one aspect of the present invention is a sewage treatment system that treats water to be treated by a biological treatment method, and is a biology that first performs biological treatment on a settling basin and water to be treated. It has a configuration including a pretreatment tank including a front stage of a target treatment unit, a rear stage of the biological treatment unit, and a post-treatment tank including a final settling basin.

With this configuration, the first stage of the biological treatment unit is provided in the pretreatment tank together with the first settling basin, and the second stage of the biological treatment unit is provided in the post-treatment tank together with the final sedimentation basin. Can be miniaturized, and the required site area can be reduced.

The front stage of the biological treatment unit may include an anaerobic compartment and a first anoxic compartment, and the rear stage of the biological treatment unit may include an aerobic compartment.

With this configuration, the biological treatment can be performed by the A2O method, which is an advanced treatment method.

The subsequent stage of the biological treatment section may further include a second anoxic compartment.

With this configuration, even when the residence time in the first oxygen-free section of the pretreatment tank is insufficient, sufficient oxygen-free treatment can be performed in the post-treatment tank.

The aeration section may consist of an aeration section for aeration and a settling section for settling sludge.

With this configuration, since the settling section is provided, the settling of sludge in the final settling basin can be assisted.

The anaerobic compartment may have an opening at the bottom, and below the opening of the anaerobic compartment may be provided with a first scraper that scrapes sludge into the first settling basin.

With this configuration, the sludge can be settled and recovered even in the anaerobic section, so that the initial settling basin can be designed to be smaller than the case where the sludge is settled only in the first settling basin.

The first oxygen-free compartment may have an opening at the bottom, and below the opening of the first oxygen-free compartment, a first scraper for attracting sludge to the first sedimentation basin is provided. It's okay.

With this configuration, the sludge can be settled and recovered even in the first anoxic section, so that the initial settling basin can be designed to be smaller than the case where the sludge is settled only in the first settling basin.

The aerobic compartment may have an opening at the bottom, and below the opening of the aerobic compartment, a second scraper for attracting sludge to the final settling basin may be provided.

With this configuration, sludge can be settled and recovered even in the aerobic section, so that the final settling basin can be designed to be smaller than the case where sludge is settled only in the final settling basin.

Below the front stage of the biological treatment unit, a first scraper may be provided to scrape the sludge settling from the front stage of the biological treatment unit into the first settling basin.

With this configuration, the sludge can be settled and recovered even in the pre-stage of the biological treatment section, so that the initial settling basin can be designed to be smaller than the case where the sludge is settled only in the first settling basin.

A second scraper may be provided below the rear stage of the biological treatment unit to scrape the sludge settling from the rear stage of the biological treatment unit into the final settling basin.

With this configuration, the sludge can be settled and recovered even in the subsequent stage of the biological treatment section, so that the final settling basin can be designed to be smaller than the case where the sludge is settled only in the final settling basin.

An overflow mechanism for removing scum and discharging the water to be treated may be provided above the final settling pond.

With this configuration, the scum can be removed and the treated water can be discharged.

The sewage treatment system may further include a return mechanism that crushes the scum removed from the post-treatment tank and returns it to the pre-treatment tank together with the sludge settled in the final settling basin.

With this configuration, scum treatment such as inactivation of actinomycetes can be performed in the pretreatment tank.

The skeleton of the pretreatment tank and the skeleton of the post-treatment tank may have the same shape in which the first settling basin and the final settling basin correspond to each other.

With this configuration, the skeleton of the pretreatment tank and the skeleton of the post-treatment tank can have the same shape, and the manufacturing cost can be suppressed.

The pretreatment tank may have the first settling pond on the upstream side and may have a pre-stage of the biological treatment unit on the downstream side, below the pre-stage of the biological treatment unit. The post-treatment tank may have a first scraping section for scraping sludge settled from the front stage of the biological treatment section to the first settling pond, and the post-treatment tank may have a rear stage of the biological treatment section on the upstream side. It may have the final settling pond on the downstream side, and sludge settled from the rear stage of the biological treatment section is placed in the final settling pond below the rear stage of the biological treatment section. It may have a second scraping portion to scrape, and sewage discharged from the downstream of the pretreatment tank may be supplied to the upstream of the posttreatment tank.

With this configuration, as a whole, a sewage treatment system is configured in which the first settling basin, the biological treatment unit, and the final settling basin are transferred in this order in two tanks, a pretreatment tank and a posttreatment tank.

The stirring device according to one aspect of the present invention is a stirring device used in the front stage of the biological treatment unit of the sewage treatment system or the rear stage of the biological treatment unit of the sewage treatment system, and is rotationally driven. The apparatus includes a vertical rotation shaft that is rotationally driven by the rotation drive device, and a stirring blade supported by the vertical rotation shaft, and the stirring blade is in a direction perpendicular to the vertical rotation axis or parallel to the vertical rotation axis. It has a configuration including a stirring action part that forms an upward flow and a settling action part that forms a downward flow parallel to the vertical rotation axis.

With this configuration, the biological treatment unit can realize a stirring function and a sludge sedimentation function.

The stirring blade may have an inclined surface that is inclined with respect to the vertical rotation axis.

With this configuration, both sides can be effectively utilized on the inclined surface.

According to the present invention, the first stage of the biological treatment unit is provided in the pretreatment tank together with the first settling basin, and the second stage of the biological treatment unit is provided in the post-treatment tank together with the final settling basin. The skeleton of the water tank can be miniaturized, and the required site area can be reduced.

FIG. 1 is a diagram schematically showing an overall configuration of a sewage treatment system according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a configuration of a pretreatment tank according to an embodiment of the present invention. FIG. 3 is a diagram schematically showing the configuration of the stirring device according to the embodiment of the present invention. FIG. 4A is a perspective view showing an example of the schematic shape of the stirring device according to the embodiment of the present invention, and FIG. 4B is an example of the schematic shape of the stirring device according to the embodiment of the present invention. 4 (c) and 4 (d) are views showing an example of the inclination of the stirring blade of the stirring device according to the embodiment of the present invention. FIG. 5 is a diagram schematically showing the configuration of a post-treatment tank according to an embodiment of the present invention. FIG. 6 is a cross-sectional view taken along the line AA of the post-treatment tank according to the embodiment of the present invention. FIG. 7 is a diagram schematically showing an overflow mechanism according to an embodiment of the present invention. FIG. 8 is a diagram schematically showing an overflow mechanism according to an embodiment of the present invention. FIG. 9 is a plan view schematically showing the overflow mechanism according to the embodiment of the present invention. FIG. 10 is a plan view schematically showing the overflow mechanism according to the embodiment of the present invention. FIG. 11 is a diagram schematically showing the connection between the sludge return mechanism and the overflow mechanism according to the embodiment of the present invention. FIG. 12 is a diagram schematically showing details of a sludge return mechanism according to an embodiment of the present invention. FIG. 13 is a diagram schematically showing an example of a stirring blade group according to an embodiment of the present invention. FIG. 14 is a diagram schematically showing an example of a stirring blade group according to an embodiment of the present invention. 15 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 15 (b) is a plan view of the example of FIG. 15 (a). 16 (a) is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 16 (b) is a plan view of the example of FIG. 16 (a). FIG. 17 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. FIG. 18A is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 18B is a plan view of the example of FIG. 18A. 19 (a) is a plan view schematically showing an example of a stirring blade group according to the embodiment of the present invention, and FIG. 19 (b) is a plan view of the example of FIG. 19 (a). FIG. 20 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. 21 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 21 (b) is a plan view of the example of FIG. 21 (a). 22 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 22 (b) is a plan view of the example of FIG. 22 (a). FIG. 23 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. FIG. 24 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 24 (b) is a plan view of the example of FIG. 24 (a). 25 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 25 (b) is a plan view of the example of FIG. 25 (a). FIG. 26 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. 27 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 27 (b) is a plan view of the example of FIG. 27 (a). FIG. 28 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 28 (b) is a plan view of the example of FIG. 28 (a). FIG. 29 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. FIG. 30 is a diagram illustrating the operation of a stirring blade having a surface perpendicular to the rotation direction. FIG. 31 is a diagram illustrating the operation of the stirring blade having a surface inclined with respect to the rotation direction.

Hereinafter, the sewage treatment system according to the embodiment of the present invention will be described with reference to the drawings. It should be noted that the embodiments described below show an example of the case where the present invention is carried out, and the present invention is not limited to the specific configuration described below. In carrying out the present invention, a specific configuration according to the embodiment may be appropriately adopted.

FIG. 1 is a diagram schematically showing an overall configuration of a sewage treatment system according to an embodiment of the present invention. As shown in FIG. 1, the sewage treatment system 1 includes a pretreatment tank 2, a posttreatment tank 3, and a sludge return mechanism 4. The sewage to be treated is introduced into the inflow side (upstream side) of the pretreatment tank 2, and is treated in the pretreatment tank 2 from the discharge side (downstream side) of the pretreatment tank 2 to the posttreatment tank 3. It is introduced to the inflow side (upstream side), discharged from the discharge side (downstream side) of the aftertreatment tank 3, and discharged. Hereinafter, the sewage treated in the pretreatment tank 2 and the posttreatment tank 3 is also referred to as “water to be treated”. The sludge return mechanism 4 returns the sludge obtained in the post-treatment tank 3 to the pre-treatment tank 2.

The sewage treatment system 1 of the present embodiment performs the A2O method, which is an advanced treatment, as a biological treatment. A part of the configuration for performing this biological treatment is provided in the rear stage of the pretreatment tank 2, and the remaining part is provided in the front stage of the post-treatment tank. In other words, the post-stage 22 of the pretreatment tank 2 has a configuration in which a part of the pre-stage of the biological treatment is performed, and the pre-stage 31 of the post-treatment tank 3 has a configuration in which a part of the post-stage of the biological treatment is performed. Then, the biological treatment unit 5 is composed of the rear stage of the pretreatment tank 2 and the front stage of the post-treatment tank 3. In other words, the first settling basin 21 is formed on the upstream side of the pretreatment tank 2, the final settling basin 32 is formed on the downstream side of the post-treatment tank 3, and the biological treatment unit 5 is formed between them. Provided.

Further, below the front stage of the biological treatment unit 5 in the pretreatment tank 2, sludge, sand, sediment, impurities and the like that have settled from the front stage of the biological treatment unit 5 are first collected in the settling basin 21. A sediment recovery unit 23 is provided, and below the rear stage of the biological treatment unit 5 in the post-treatment tank 3, a sediment recovery unit that collects the sludge that has settled from the rear stage of the biological treatment unit 5 into the final settling basin 32. 33 is provided.

The sludge return mechanism 4 includes a pipe and a pump 42 for returning sludge, and a scum pit 41 that mixes sludge settled in the final settling basin 32 and scum floating in the final settling basin 32. The pipe 48 is arranged so as to connect the final settling basin 32 and the scum pit 41, and the scum pit 41 and the anaerobic section 51 and the first settling basin 21.

FIG. 2 is a diagram schematically showing a configuration of a pretreatment tank according to an embodiment of the present invention. In the pretreatment tank 2, the first settling basin 2 is formed on the upstream side, and the anaerobic section 51 and the first anoxic section 53 are formed on the downstream side of the first settling basin 2 as a configuration for performing the pre-stage of advanced treatment. ing. Specifically, an anaerobic compartment 51 is formed on the downstream side of the first settling basin 21, and a first anoxic compartment 53 is formed on the downstream side of the anaerobic compartment 51.

The height of the pretreatment tank 2 is preferably 5 to 10 m, and in the present embodiment, it is 7 m. In the pretreatment tank 2, the portion corresponding to the first settling basin 21 is formed deeper than the other portions so that the sludge settled in the upstream first settling basin 21 does not flow to the downstream side. The pretreatment tank 2 may be made of RC or a steel plate.

Since watertightness is not required for the division between the first settling basin 2 and the anaerobic compartment 51 and the division between the anaerobic compartment 51 and the first anoxic compartment 53, a structure with a simple partition plate may be adopted for each. These partition plates are initially formed with an opening 501 that communicates the sedimentation basin 21 and the anaerobic compartment 51, and an opening 503 that communicates the anaerobic compartment 51 and the first anoxic compartment 52. The openings 501 and 503 are formed so as to be located below the surface of the water to be treated in the pretreatment tank 2. A plurality of openings may be formed in the partition plate.

Further, an opening 502 is formed on the bottom surface of the anaerobic compartment 51, and an opening 504 is formed on the bottom surface of the first anoxic compartment 53. In the example of FIG. 2, one opening is formed in the center of the bottom members of the anaerobic compartment 51 and the first anoxic compartment 53, but the bottoms of the anaerobic compartment 51 and the first anoxic compartment 53 are entirely covered. The openings 502 and 504 may be formed by being released to the bottom member, or a plurality of openings may be formed in the bottom surface member.

A first scraper 230 is provided in the lower sediment recovery section 23 in the front stage of the biological treatment section 5 including the anaerobic section 51 and the first anoxic section 53. The first scraper 230 includes a drive device 231, an endless chain 232, a first driven wheel 233, and a second driven wheel 234. The drive device 231 includes drive wheels (not shown) for rotating the endless chain 232. The endless chain 232 is bridged over the drive wheels, the first driven wheel 233, and the second driven wheel 234 of the drive device 231 and rotationally driven.

Flight (not shown) is fixed to the endless chain 232 at predetermined intervals, and sludge settled from the front stage of the biological treatment unit 5 in this flight is first scraped to the settling basin 21. As the first scraper 230, a two-axis chain flight type or monorail type sludge scraper can be adopted so as not to interfere with the anaerobic section 51 and the first oxygen-free section 53 above the first scraper 230.

The anaerobic compartment 51 includes a mechanical agitator 52 for agitating and mixing the returned sludge and the water to be treated that flows in from the first settling basin 21. The stirring device 52 rotates at a low speed of, for example, about 10 rpm.

FIG. 3 is a diagram schematically showing the configuration of the stirring device according to the embodiment of the present invention. The stirring device 52 includes a vertical rotating shaft 522, a driving device 521 that rotationally drives the vertical rotating shaft 522, and a stirring blade group 523 supported by the vertical rotating shaft 522. The stirring blade group 523 has a stirring action unit 5231 that forms a flow in the direction perpendicular to the vertical rotation shaft 522 in the outer portion, and a settling action portion that forms a downward flow parallel to the vertical rotation shaft 522 in the inner portion. It has 5232. The stirring blade group 523 has a swirling stirring function in the outer portion and a settling function in the inner portion.

FIG. 4A is a perspective view showing an example of the schematic shape of the stirring device according to the embodiment of the present invention, and FIG. 4B is an example of the schematic shape of the stirring device according to the embodiment of the present invention. 4 (c) and 4 (d) are views showing an example of the inclination of the stirring blade of the stirring device according to the embodiment of the present invention. In this example, as shown in FIG. 4A, the stirring blade group 523 is supported by the vertical rotation axis 522 to form a rectangular parallelepiped shape with a side of 3 m as a whole, and the area of the projection surface thereof is 9 square meters. It becomes (3m × 3m). A stirring blade group 523 of this size is used, for example, in an anaerobic compartment 51 having a width of 6 m. As shown in FIG. 4B, the rotation of the vertical rotation shaft 522 causes the stirring blade group 523 to rotate in a circle having a diameter of about 4.3 m.

Further, as shown in FIGS. 4 (c) and 4 (d), the surface area of the inclined plate used for the stirring blade group 523 is 0.6 square m (0.2 m × 3 m), and the inclined angle is 60 degrees. The spacing between the inclined plates is 0.1 m in the horizontal direction and 0.18 m in the vertical direction, the number of inclined plates is 16 (3 m ÷ 0.18 m), and the number of inclined plates is 30 (3 m ÷ 0.18 m). 0.1 m), the total number of inclined plates is 480 (16 steps × 30 rows), and the effective sedimentation area is 140 square meters (≈ surface area × total number × cos 60 °).

Returning to FIG. 2, the first anoxic compartment 52 includes a mechanical agitator 54 for agitating the water to be treated flowing from the anaerobic compartment 51. The stirring device 54 has the same configuration as the stirring device 52, and includes a vertical rotation shaft 542, a drive device 541 that rotationally drives the vertical rotation shaft 542, and a stirring blade group 543 supported by the vertical rotation shaft 542. ing.

FIG. 5 is a diagram schematically showing the configuration of a post-treatment tank according to an embodiment of the present invention. In the post-treatment tank 3, a second anoxic section 55 and an aerobic section 57 are formed on the upstream side as a configuration for performing the post-stage of advanced treatment, and a final settling basin 32 is formed on the downstream side of the aerobic section 57. ing. Specifically, an aerobic section 57 is formed on the downstream side of the second anoxic section 55, and a final settling basin 32 is formed on the downstream side of the aerobic section 57. Further, the aerobic compartment 57 includes an aeration compartment 571 formed on the downstream side of the second anoxic compartment 55 and a subsidence compartment 572 formed on the downstream side thereof.

The height of the post-treatment tank 3 is preferably 5 to 10 m, and is 7 m in the present embodiment. Further, in the present embodiment, the skeleton of the pretreatment tank 2 and the skeleton of the post-treatment tank 3 have the same shape corresponding to the first settling basin 21 and the final settling basin 32. The post-treatment tank 3 may be made of RC or a steel plate.

Since watertightness is not required for the division between the second anoxic compartment 55 and the aeration compartment 571, the division between the aeration compartment 571 and the sedimentation compartment 572, and the division between the sedimentation compartment 572 and the final sedimentation basin 32, each is a simple partition. A board structure may be adopted. The partition plate between the second oxygen-free compartment 55 and the aeration compartment 571 crosses the surface of the water to be treated, and the water to be treated flows into the aeration compartment 572 from the lower part of the second oxygen-free compartment 55. Further, the upper end of the partition plate between the aeration section 571 and the settling section 572 is located below the water surface of the water to be treated, and the water to be treated passes over this partition plate and flows into the settling section 572 from the aeration section 571.

An opening 505 is formed on the bottom surface of the second anoxic compartment 55, an opening 506 is formed on the bottom surface of the aeration compartment 571, and an opening 507 is formed on the bottom surface of the settling compartment 572. In the example of FIG. 5, the second oxygen-free section 55, the aeration section 571, and the settling section 572 are not provided with a bottom surface member, and the bottom surface is completely opened to form openings 504, 506, and 507. However, instead of this, a bottom surface member may be provided and one opening may be formed in the center thereof, or a plurality of openings may be formed in the bottom surface member.

At the lower part of the aeration section 571, two air diffusers 59 are provided so as to cover the opening 506. The aeration plate 59 is connected to an aeration source (not shown) that supplies air, and fine holes are formed on the surface thereof. The air supplied from the aeration source is discharged from the micropores of the aeration plate 59 and comes into gas-liquid contact with the water to be treated in the aeration section 571.

FIG. 6 is a cross-sectional view taken along the line AA of the post-treatment tank according to the embodiment of the present invention. In the aeration section 571, the opening ratio, that is, the ratio of the portion of the area of the aeration section 571 that does not have the aeration member including the aeration plate 59, the pipe, and the gantry is 20 to 40%, preferably 30%. The method is adopted. As a result, the amount of sludge that circulates back to the aeration section 571 after settling below the aeration plate 59 from the periphery of the aeration plate 59 in the aeration section 571 can be reduced.

Returning to FIG. 5, a second scraper 330 is provided in the sediment collection section 33 below the aerobic section 57. The second scraper 330 includes a drive device 331, an endless chain 332, a first driven wheel 333, and a second driven wheel 334. The drive device 331 includes drive wheels (not shown) for rotating the endless chain 332. The endless chain 332 is bridged over the drive wheels, the first driven wheel 333, and the second driven wheel 334 of the drive device 331 and rotationally driven.

A flight (not shown) is fixed to the endless chain 332 at predetermined intervals, and sludge settled from the aerobic section 57 in this flight is scraped to the final settling basin 21. As the second scraper 330, a two-axis chain flight system or a monorail sludge scraper can be adopted so as not to interfere with the aerobic section 57 above the second scraper 330.

The second oxygen-free compartment 55 includes a mechanical stirring device 56 for stirring the water to be treated flowing from the pretreatment tank 2. The stirring device 56 has the same configuration as the stirring device 52, and includes a vertical rotation shaft 562, a drive device 561 for rotationally driving the vertical rotation shaft 562, and a stirring blade group 563 supported by the vertical rotation shaft 562. ing.

The settling section 572 includes a mechanical stirring device 58 for stirring the water to be treated flowing from the aeration section 571. The stirring device 58 has the same configuration as the stirring device 52, and includes a vertical rotation shaft 582, a drive device 581 that rotationally drives the vertical rotation shaft 582, and a stirring blade group 583 supported by the vertical rotation shaft 582. ing. An overflow mechanism 34 is provided in the upper part on the downstream side of the aftertreatment tank 3.

FIG. 7 is a diagram schematically showing an overflow mechanism according to an embodiment of the present invention. The overflow mechanism 34 includes a cylindrical screen 341 and a driving device 342 that rotationally drives the cylindrical screen 341. The cylindrical screen 341 removes scum by the screen by passing the water to be treated from the outside to the inside. The clear water to be treated from which the scum has been removed flows axially inside the cylindrical screen 341. The mesh width of the cylindrical screen 341 is 0.1 to 3 mm, more preferably about 0.5 to 3 mm. The drive 432 intermittently or constantly rotates the cylindrical screen 341.

FIG. 8 is a diagram schematically showing an overflow mechanism according to an embodiment of the present invention. The overflow mechanism 34 includes a cleaning spray 343 that removes scum trapped on the screen by injecting water on the outside of the cylindrical screen 341. Further, in the cylindrical screen 341, the shaft 3411 is supported by the bearing 344 provided in the aftertreatment tank 3. A scum discharge path 345 for discharging scum that could not pass through the screen of the cylindrical screen 34 is formed on the downstream side of the cylindrical screen 341. The cleaning spray 343 may be configured and arranged to spray water from the inside to the outside of the screen. In this case, the cleaning spray 343 is arranged to inject water in the direction toward the scum discharge path 345.

9 and 10 are plan views schematically showing an overflow mechanism according to an embodiment of the present invention. The cylindrical screen 341 is installed in the post-treatment tank 3 with gaps at both ends. A movable weir 346 that can move up and down is provided between both ends of the cylindrical screen 341 and the post-treatment tank 3. The scum discharge path 345 has a length similar to that of the cylindrical screen 341, and is installed in the post-treatment tank 3 with gaps at both ends. Further, a connecting path 348 for connecting the scum discharge path 345 and the scum pit 41 provided outside the post-treatment tank 3 is provided.

Normally, as shown in FIG. 9, the movable weir 346 is raised, and all the water to be treated passes through the cylindrical screen 341 from the outside to the inside, flows axially inside, and the scum discharge path 345 and the post-treatment tank. It is discharged from the discharge port 349 through the space with 3. When the amount of water to be treated is large, such as when the water is blocked or in rainy weather, the water to be treated overflows the movable weir 346 and is discharged, or as shown in FIG. 10, the movable weir 346 is lowered. Some of the water to be treated is discharged through the cylindrical screen 341, and some of the water to be treated is discharged over the movable weir 346 without passing through the cylindrical screen 341.

FIG. 11 is a diagram schematically showing the connection between the sludge return mechanism and the overflow mechanism according to the embodiment of the present invention. The sludge return mechanism 4 includes a scum pit 41, a pump 42, and a suction ejector 43. The suction ejector 43 is arranged in the scum pit 41. By injecting sludge sucked from the bottom of the final settling basin 32 by the pump 42 into the suction ejector 43 at a high flow velocity, the inside of the scum pit 41 becomes a negative pressure state, and the sludge is put into a negative pressure state through the connecting pipe 348 connected to the scum pit 41. The scum of the scum discharge path 345 is sucked into the flow path. By such suction, the scum is crushed.

FIG. 12 is a diagram schematically showing details of a sludge return mechanism according to an embodiment of the present invention. The sludge sucked up from the final settling basin 32 by the pump 42 is supplied to the scum pit 41 through the pipe 44 and the scum suction source valve 45. The scum suction source valve 45 is opened and closed by a drive device 46 in order to prevent excess air from being sucked due to idle pulling. The scum pit 41 is provided with a water level gauge 47 that measures the water level in the scum pit 41.

The operation of the sewage treatment system 1 configured as described above will be described. First, the sludge is introduced into the first settling basin 21 on the upstream side of the pretreatment tank 2. In the first settling basin 21, sludge, sand, sediment, impurities, etc. in the water to be treated are settled. The water to be treated that first passed through the settling basin 21 flows into the anaerobic compartment 51 formed in the pretreatment tank 2 through the opening 501.

In the anaerobic compartment 51, the return sludge is added to the water to be treated and stirred in an anaerobic state to dephosphorify the water to be treated as activated sludge. Here, in the stirring device 52 of the anaerobic compartment 51, as described above, the stirring blade group 523 rotates, so that a downward flow is generated by the settling function on the inside and an outward flow is generated by the swirling stirring function on the outside. Here, the sludge adhering to the inclined plate can be regarded as a simple fixed bed, and contributes to the maintenance of the suspended solids concentration as the amount of sludge corresponding to the surface area.

In the anaerobic compartment 51, mud, sand, sediment, and contaminants that could not be completely precipitated in the sedimentation basin 21 are settled in the sediment collection section 23 through the opening 502 by the downward flow by the stirring device 52. As described above, in the anaerobic compartment 51, the stirring device 52 provided with the stirring blade having the inclined surface is operated at a low rotation speed to achieve both gentle stirring and sedimentation due to the action of the inclined surface. Return sludge is added to the anaerobic compartment 51. As a result, the suspended solids concentration (MLSS) in the anaerobic compartment 51 and thereafter is maintained. The anaerobic compartment 51 plays a role of ensuring the residence time required for the release of soluble phosphorus.

The water to be treated that has undergone the dephosphorization treatment in the anaerobic compartment 51 flows into the first anoxic compartment 53 through the opening 503. In the first anoxic section 53, the water to be treated is denitrified by stirring the water to be treated. The stirring device 54 provided in the first oxygen-free compartment 53 also creates a downward flow on the inside and an outward flow on the outside to agitate the water to be treated and sludge, sand, and dirt from the water to be treated. Promotes sedimentation of residues and contaminants.

In the first anoxic section 53, sludge, sand, sediment, and contaminants that could not be settled in the settling basin 21 and the anaerobic section 51 were settled in the settling collection section 23 through the opening 504 due to the downward flow by the stirring device 54. do. In this way, by operating the stirring device 54 provided with the stirring blade having the inclined surface at a low rotation speed, both gentle stirring and sedimentation due to the action of the inclined surface can be achieved at the same time. The first anoxic compartment 53 plays a role of securing a residence time required for denitrification treatment. The flow from the first settling basin 21 to the anaerobic section 51 and from the anaerobic section 51 to the first anoxic section 53 in the pretreatment tank 2 is a natural flow.

In the settling basin 23, sludge, sand, sediment, and contaminants that have settled from the anaerobic section 51 and the first anoxic section 53 are first scraped in the direction of the settling basin 21 by flight to the bottom of the first settling basin 21. Guide.

The water to be treated is discharged from the downstream of the pretreatment tank 2, that is, the upper part of the downstream of the first oxygen-free compartment 53, and introduced into the upstream of the post-treatment tank 3. In the second anoxic section 55 upstream of the post-treatment tank 3, the water to be treated is denitrified following the first anoxic section 53. Further, similarly to the first oxygen-free section 53, the stirring device 56 stirs the water to be treated to create a downward flow. If the first oxygen-free compartment 53 can sufficiently perform the denitrification treatment, the post-treatment tank 3 may not be provided with the oxygen-free compartment. For example, when phosphorus is removed by a chemical treatment such as addition of PAC, the anaerobic compartment 51 of the pretreatment tank 2 becomes unnecessary, and the first anoxic compartment 53 of the pretreatment tank 2 can be enlarged. The anoxic compartment 55 can be omitted.

The water to be treated that has flowed to the lower part of the second anoxic compartment 55 flows into the aeration compartment 571. In the aeration section 571, by discharging air from the micropores of the aeration plate 59, this air comes into contact with the water to be treated in the aeration section 571, and is aerobic such as decomposition of organic substances, removal of phosphorus, and nitrification of ammonia. Processing is done. As described above, as the air diffuser 59, a plate having a relatively large area is adopted, and a full aeration type air supply is performed.

The sludge in the aeration section 571 settles in the sediment collection section 33 provided below the aerobic section 57 through a portion of the bottom surface where there is no aeration member including the aeration plate 59. As described above, since the area of the aeration member is relatively large and the opening ratio is small, it is possible to prevent the sludge settled in the sediment collection section 33 from being agitated and returning to the aeration section 571.

The water to be treated, which has undergone aerobic treatment, flows into the sedimentation section 572 near the water surface. In the settling section 572, further aerobic treatment is performed using the oxygen in the aeration section 571, and the agitator 58 creates a downward flow to promote the settling of sludge. The sediment collection unit 33 scoops the sludge that has settled from the aerobic compartment 57 toward the final sedimentation basin 32 by flight and guides it to the bottom of the final sedimentation basin.

As described above, in the post-treatment tank 3, from the upstream side, the second oxygen-free compartment 55 and the aeration compartment 571 communicate with each other at the bottom, and the aeration compartment 571 and the sedimentation compartment 57 2 communicate with each other at the top, and the sedimentation compartment 572 and the aeration compartment 572. Since it communicates with the final settling basin 32 at the bottom, the water to be treated flows from upstream to downstream after being sufficiently treated in each section.

In the final settling basin 32, sludge in the water to be treated is settled and scum is suspended on the water surface. The scum is removed by the cylindrical screen 341 of the overflow mechanism 34 provided in the upper part of the final settling basin 32, and the clear water to be treated is discharged from the discharge port 349. The scum removed by the cylindrical screen 341 is stored in the scum discharge path 345 and supplied to the scum pit 41 as scum drainage through the connecting path 348.

On the other hand, a part of the sludge settled at the bottom of the final settling basin 32 is pulled out by the action of the pump 42 and conveyed to the scum pit 41 through the pipe 48. In the scum pit 41, the scum is crushed by merging the scum drainage and the sludge (return sludge) drawn from the final settling basin 32 by the suction ejector 43. The returned sludge mixed with scum is returned to the pretreatment tank 2 by the pipe 48. The scum is crushed by turbulent crushing even while flowing through the pipe 48 together with the sludge. The returned sludge is first supplied to the settling basin 21 and the anaerobic compartment 51.

By returning the returned sludge mixed with the aerated scum wastewater to the upstream side of the first settling basin 21, the upstream side of the first settling basin 21 can be kept in a slightly aerobic state, the generation of hydrogen sulfide can be suppressed, and the sludge can be suppressed. BOD adsorption to the water can be promoted.

In the following, various examples that can be adopted by the stirring devices 52, 54, 56, and 58 will be described by taking the stirring blade 52 as an example. As described above, the stirring blade group 523 of the stirring device 52 has a stirring action portion 5231 forming a flow in a direction perpendicular to the vertical rotation shaft 522 in the outer portion, and a lower portion parallel to the vertical rotation shaft 522 in the inner portion. It has a settling action section 5232 that forms a directional flow. The stirring blade group 523 having both the stirring action section 5231 and the settling action section 5232 can be realized by the following various specific shapes.

FIG. 13 is a diagram schematically showing an example of a stirring blade group according to an embodiment of the present invention. As shown in FIG. 13, the stirring blade group 523 may have a rectangular parallelepiped shape as a whole. In this case, an inclined plate inclined with respect to the vertical rotation shaft 522 may be used as the stirring action unit 5231 on the outside of the stirring blade group 523.

FIG. 14 is a diagram schematically showing an example of a stirring blade group according to an embodiment of the present invention. As shown in FIG. 14, the stirring blade group 523 may have a cylindrical shape as a whole. In this case, an inclined plate inclined with respect to the vertical rotation shaft 522 may be used as the stirring action unit 5231 on the outside of the stirring blade group 523.

15 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 15 (b) is a plan view of the example of FIG. 15 (a). Note that, in FIG. 15B, only a part of the stirring blades is shown, and the other stirring blades are not shown. Will be installed. The same applies to the following example. Further, in this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole.

As shown in FIG. 15A, the stirring blade group 523 is divided in the vertical direction, and the stirring blades are aligned in the upper and lower stages. The stirring blade group 523 is divided into upper and lower two stages, but the stirring blade group 523 and the stirring blade group described below may be divided into a plurality of stages of three or more bullets. Further, as shown in FIG. 15B, the stirring device 523 has a frame 524 fixed to the vertical rotation shaft 522, and each stirring blade is fixed to this frame. The frame 524 includes a quadrangular outer frame frame 5241 and a diagonal frame 5242 that is a diagonal line of the outer frame. Each stirring blade of the stirring blade group 523 is supported from the diagonal frame to the side of the nearest outer frame frame 5241 so as to be perpendicular to the side.

16 (a) is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 16 (b) is a plan view of the example of FIG. 16 (a). In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole.

As shown in FIG. 16A, the stirring blade group 523 is divided in the vertical direction, and the positions of the stirring blades are displaced from each other in the upper and lower stages. Further, as shown in FIG. 16B, the stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522, and each stirring blade is fixed to the frame 524. The frame 524 is fixed to the quadrangular outer frame frame 5241 and the diagonal frame 5242 which is the diagonal line of the outer frame. Each stirring blade of the stirring blade group 523 is supported from the diagonal frame 5242 to the side of the nearest outer frame frame 5241 so as to be perpendicular to the side.

FIG. 17 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole. The stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522. The frame 524 is composed of a quadrangular outer frame frame 5241 and a diagonal frame 5242 that is a diagonal line of the outer frame. Further, in this example, each stirring blade is divided inside and outside, the inner stirring blade is fixed to the diagonal frame 5242, and the outer stirring blade is fixed to the outer frame frame 5241.

FIG. 18A is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 18B is a plan view of the example of FIG. 18A. In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole.

As shown in FIG. 18A, the stirring blade group 523 is divided in the vertical direction, and each stirring blade is inclined with respect to the vertical rotation axis 522, and the positions are aligned in the upper and lower stages. Further, as shown in FIG. 16B, the stirring device 52 has a frame fixed to the vertical rotation shaft 522, and each stirring blade is fixed to the frame 524. The frame 524 includes a quadrangular outer frame frame 5241 and a middle frame 5243 that divides the quadrangle into upper and lower and left and right sides, respectively. Each stirring blade of the stirring blade group 523 is supported by the other middle frame 5243 so as to be parallel to one middle frame 5243.

19 (a) is a plan view schematically showing an example of a stirring blade group according to the embodiment of the present invention, and FIG. 19 (b) is a plan view of the example of FIG. 19 (a). In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole.

As shown in FIG. 19A, the stirring blade group 523 is divided in the vertical direction, and each stirring blade is inclined with respect to the vertical rotation axis 522, and the positions of the stirring blades are displaced from each other in the upper and lower stages. .. Further, as shown in FIG. 19B, the stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522, and each stirring blade is fixed to the frame 524. The frame 524 includes a quadrangular outer frame frame 5241 and a middle frame 5243 that divides the quadrangle into upper and lower halves and left and right, respectively. Each stirring blade of the stirring blade group 523 is supported by the other middle frame 5243 so as to be parallel to one middle frame 5243.

FIG. 20 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole. The stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522. The frame 524 includes a quadrangular outer frame frame 5241 and a middle frame 5243 that divides the quadrangle into upper and lower and left and right sides, respectively.

In this example, each stirring blade of the stirring blade group 523 is divided inside and outside, and the inner stirring blade is fixed to the other middle frame 5243 so as to be parallel to one middle frame 5243, and the outer stirring blade is fixed to the other middle frame 5243. Is fixed to the side of the outer frame frame 5241 parallel to the other middle frame 5243.

21 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 21 (b) is a plan view of the example of FIG. 21 (a). In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole.

As shown in FIG. 21A, the stirring blade group 523 is divided in the vertical direction, and the stirring blades are aligned in the upper and lower stages. Further, as shown in FIG. 21B, the stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522, and each stirring blade is fixed to the frame 524. The frame 524 includes a quadrangular outer frame frame 5241 and a diagonal frame 5242 that is a diagonal line of the outer frame. Each stirring blade of the stirring blade group 523 is supported by the other diagonal frame 5242 so as to be parallel to one diagonal frame 5242.

22 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 22 (b) is a plan view of the example of FIG. 22 (a). In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole.

As shown in FIG. 22A, the stirring blade group 523 is divided in the vertical direction, and the positions of the stirring blades are displaced from each other in the upper and lower stages. Further, as shown in FIG. 22B, the stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522, and each stirring blade is fixed to the frame 524. The frame 524 includes a quadrangular outer frame frame 5241 and a diagonal frame 5242 that is a diagonal line of the outer frame. Each stirring blade of the stirring blade group 523 is supported by the other diagonal frame 5242 so as to be parallel to one diagonal frame 5242.

FIG. 23 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. In this example, the stirring blade group 523 has a rectangular parallelepiped shape as a whole. The stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522. The frame 524 includes a quadrangular outer frame frame 5241 and a diagonal frame 5242 that is a diagonal line of the outer frame.

In this example, each stirring blade of the stirring blade group 523 is divided inside and outside, and the inner stirring blade is supported by the other diagonal frame 5242 so as to be parallel to one diagonal frame 5242 and outside. The stirring blade is supported by the outer frame frame 5241.

FIG. 24 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 24 (b) is a plan view of the example of FIG. 24 (a). In this example, the stirring blade group 523 has a cylindrical shape as a whole.

As shown in FIG. 24A, the stirring blade group 523 is divided in the vertical direction, and the stirring blades are aligned in the upper and lower stages. Further, as shown in FIG. 24B, the stirring device 52 has a frame 524 fixed to the vertical rotation shaft 522. The frame 524 includes a circular inner frame 5244 centered on the vertical rotation axis 522 and a circular outer frame 5245 (concentric with the inner frame) centered on the vertical rotation axis 522. Each stirring blade of the stirring blade group 523 is arranged radially in the radial direction of a circle centered on the vertical rotation shaft 522, and is supported by the inner frame 5244 and the outer frame 5245.

25 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 25 (b) is a plan view of the example of FIG. 25 (a). In this example, the stirring blade group 523 has a cylindrical shape as a whole.

As shown in FIG. 25 (a), the stirring blade group 523 is divided in the vertical direction, and the positions of the stirring blades are displaced from each other in the upper and lower stages. Further, as shown in FIG. 25B, the stirring blade 52 has a frame fixed to the vertical rotation shaft 522. The frame 524 includes a circular inner frame 5244 centered on the vertical rotation axis 522 and a circular outer frame 5245 (concentric with the inner frame 5244) centered on the vertical rotation axis 522. Each stirring blade of the stirring blade group 523 is arranged radially in the radial direction of a circle centered on the vertical rotation shaft 522, and is supported by the inner frame 5244 and the outer frame 5245.

FIG. 26 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. In this example, the stirring blade group 523 has a cylindrical shape as a whole. The stirring device 52 has a frame fixed to the vertical rotation shaft 522. The frame 524 includes a circular inner frame 5244 centered on the vertical rotation axis 522 and a circular outer frame 5245 (concentric with the inner frame 5244) centered on the vertical rotation axis 522.

In this example, each stirring blade of the stirring blade group 523 is divided inside and outside. The inner stirring blades are arranged radially in the radial direction of a circle centered on the vertical rotation shaft 522, and are supported by the inner frame 5244. The outer stirring blades are arranged radially in the radial direction of a circle centered on the vertical rotation shaft 522, and are supported by the outer frame 5245. The positions of the inner stirring blade and the outer stirring blade in the circumferential direction are aligned.

27 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 27 (b) is a plan view of the example of FIG. 27 (a). In this example, the stirring blade group 523 has a cylindrical shape as a whole.

As shown in FIG. 27 (a), the stirring blade group 523 is divided in the vertical direction, and the stirring blades are aligned in the upper and lower stages. Further, as shown in FIG. 27A, the stirring device 52 has a frame fixed to the vertical rotation shaft 522. The frame 524 includes a circular inner frame 5244 centered on the vertical rotation axis 522 and an outer frame 5245 (concentric with the inner frame 5244) centered on the vertical rotation axis 522. Each stirring blade of the stirring blade group 523 extends while curving outward around the vertical rotation shaft 522, and is supported by the inner frame 5244 and the outer frame 5245. The shape and bending direction of each stirring blade are the same.

FIG. 28 (a) is a front view schematically showing an example of a stirring blade group according to an embodiment of the present invention, and FIG. 28 (b) is a plan view of the example of FIG. 28 (a). In this example, the stirring blade group 523 has a cylindrical shape as a whole.

As shown in FIG. 28A, the stirring blade group 523 is divided in the vertical direction, and the positions of the stirring blades are displaced from each other in the upper and lower stages. Further, as shown in FIG. 28A, the stirring device 52 has a frame fixed to the vertical rotation shaft 522. The frame 524 includes a circular inner frame 5244 centered on the vertical rotation axis 522 and an outer frame 5245 (concentric with the inner frame 5244) centered on the vertical rotation axis 522. Each stirring blade of the stirring blade group 523 extends while curving outward around the vertical rotation shaft 522, and is supported by the inner frame 5244 and the outer frame 5245. The shape and bending direction of each stirring blade are the same.

FIG. 29 is a plan view schematically showing an example of a stirring blade group according to an embodiment of the present invention. In this example, the stirring blade group 523 has a cylindrical shape as a whole. The stirring device 52 has a frame fixed to the vertical rotation shaft 522. The frame 524 includes a circular inner frame 5244 centered on the vertical rotation axis 522 and a circular outer frame 5245 centered on the vertical rotation axis 522 (concentric with the inner shake).

In this example, each stirring blade of the stirring blade group 523 is divided inside and outside. The inner stirring blade is supported by the inner frame 5244 and extends while curving outward. The outer stirring blade is supported by the outer frame 5245 and extends from the outer frame 5245 while curving inward. The positions of the inner stirring blade and the outer stirring blade in the circumferential direction are aligned.

FIG. 30 is a diagram for explaining the action of the stirring blade having a surface perpendicular to the rotation direction, and FIG. 31 is a diagram for explaining the action of the stirring blade having a surface inclined with respect to the rotation direction. First, the larger the number of stirring blades, the larger the flat area and the higher the stirring effect, but the smaller the number, the smaller the weight and the cost of steel materials. Further, the larger the rotation speed, the larger the movement effect, and the smaller the rotation speed, the longer the contact time.

As shown in FIG. 30, when the stirring blade is perpendicular to the rotation direction, the sludge comes into contact with only one side of the stirring blade, but as shown in FIG. 31, the stirring blade is inclined with respect to the rotation direction. If so, both sides of the stirring blade can be effectively used.

As described above, according to the sewage treatment system 1 of the embodiment of the present invention, the function of the conventional sewage treatment system including at least three tanks of the first settling basin, the advanced treatment tank, and the final settling basin is added to the pretreatment tank 2 Since it was realized by two tanks, the post-treatment tank 3 and the post-treatment tank 3, the site area can be reduced as compared with the conventional sewage treatment system.

Further, in the pretreatment tank 2, also in the anaerobic section 51 and the first anoxic section 52 where the advanced treatment is performed, the settling mud, sand, residue and contaminants are collected by the lower sedimentation recovery section 23 and first settled. It can be transferred to the pond 21, and it is not necessary to secure a flow velocity of 0.1 m / s or more at the bottom of the anaerobic section 51 and the first anoxic section 52. Similarly, in the post-treatment tank 3, the sludge that settles in the aerobic section 57 that undergoes advanced treatment can be collected by the lower sedimentation recovery unit 33 and transferred to the final settling basin 32.

Further, in each section where the advanced treatment is performed, by using a stirring device equipped with a stirring blade having an inclined surface, the amount of sludge adhering to the stirring blade can be used as a pseudo-fixed bed instead of a biological treatment carrier.

Further, the stirring device used for each section for advanced treatment has both a swirling stirring function and a settling function because the inner stirring blades generate a downward flow and the outer stirring blades generate an outward flow. Can be done.

Further, since the overflow mechanism 34 is provided on the downstream side of the post-treatment tank 3, the scum can be continuously discharged, and the finishing treatment can be performed at the same time.

Further, in the aeration section 571, a planar partition is provided between the aeration plate 59 and the pipe for transporting air to the aeration section 59, and the upper aeration section 571 and the lower settling recovery section 33 are separated. The backflow of sludge from 33 to the aeration section 571 can be suppressed.

Further, since the settling section 572 is provided in the aerobic section 57, the water to be treated that has become aerobic due to the aeration in the aeration section 571 can be further aerobically treated and the sludge can be assisted in settling.

Further, a movable weir 346 is provided on the downstream side of the post-treatment tank 3, and the movable weir 346 is set at an appropriate position during normal operation to discharge only the water to be treated that has passed through the cylindrical screen 341. When the inflow load temporarily increases and exceeds the screen processing capacity of the cylindrical screen 341, the movable weir 346 is overflowed or the movable weir 346 is lowered to discharge the water to be treated that does not pass through the cylindrical screen 341. Therefore, sewage treatment can be appropriately performed according to the inflow load.

In the above embodiment, the biological treatment unit 5 is treated by the A2O method, which is an advanced treatment, but the biological treatment performed by the biological treatment unit 5 is a carrier method or a membrane. It may be another advanced treatment such as a separation activated sludge method (MBR method), or it may be a standard activated sludge method. In these cases as well, by integrally configuring the tank for executing it with the first settling basin 21 or the final settling basin 32, the entire sewage treatment system 1 includes the pretreatment tank 2 including the first settling basin 21. It can be composed of two tanks, the post-treatment tank 3 including the final settling basin 32, and the site area can be reduced.

Further, in the above embodiment, the rear stage of the pretreatment tank 2 (anaerobic compartment 51 and the first oxygen-free compartment 53) and the front stage of the post-treatment tank 3 (second oxygen-free compartment 55, aeration compartment 571, and sedimentation compartment 572). ) Are collectively referred to as the biological processing unit 5, but as is clear from the above explanation, it is not necessary for all the processing to be performed biologically in the biological processing unit 5. For example, the dephosphorization treatment may be a scientific treatment, and the sedimentation of sludge, sand, residue, impurities, etc. by the stirring blade in the above embodiment is a physical treatment.

In the present invention, the first stage of the biological treatment unit is provided in the pretreatment tank together with the first settling basin, and the second stage of the biological treatment unit is provided in the post-treatment tank together with the final settling basin. It has the effect of being able to reduce the size of the site and the required site area, and is useful as a sewage treatment system that treats sewage by a biological treatment method.

1 Sewage treatment system 2 Pre-treatment tank 21 First settling basin 22 Post-treatment tank rear stage 23 Sediment recovery unit 230 First scraper 3 Post-treatment tank 31 Post-treatment tank front stage 32 Final settling basin 33 Sediment recovery unit 330 Second scratch Stopper 34 Overflow mechanism 341 Cylindrical screen 342 Drive device 343 Cleaning spray 344 Bearing 345 Scum discharge path 346 Movable dam 348 Connection path 349 Discharge port 4 Sewage return mechanism 41 Scum pit 42 Pump 43 Suction ejector 438 Connection path 44 Valve 46 Driver 47 Water level gauge 48 Piping 5 Biological treatment section 51 Anaerobic compartment 52, 54, 56, 58 Stirrer 521 Driver 522 Vertical rotation shaft 523 Stirrer blade group 524 Frame 53 1st anoxic compartment 55 2nd None Oxygen compartment 57 Aerobic compartment 571 Exposed compartment 572 Sewage compartment

Claims (9)

A sewage treatment system that treats water to be treated by a biological treatment method.
A pretreatment tank equipped with a first settling basin and a pre-treatment stage of a biological treatment section that performs biological treatment on the water to be treated.
It is provided with a post-treatment tank provided with a rear stage of the biological treatment section and a final settling basin.
The pretreatment tank and the posttreatment tank are separate tanks.
The pre-stage of the biological treatment section includes an anaerobic compartment and a first anoxic compartment.
The latter part of the biological treatment section includes an aerobic compartment.
A sewage treatment system characterized by that. The sewage treatment system according to claim 1 , further comprising a second anoxic compartment after the biological treatment unit. The sewage treatment system according to claim 1 or 2 , wherein the aerobic section comprises an aerated section for aeration and a settling section for settling sludge. The anaerobic compartment has an opening at the bottom and
The sewage treatment system according to any one of claims 1 to 3 , wherein a first scraping machine for attracting sludge to the first settling basin is provided below the opening of the anaerobic compartment. The first anoxic compartment has an opening at the bottom and
The sewage treatment system according to any one of claims 1 to 3 , wherein a first scraper for attracting sludge to the first settling basin is provided below the opening of the first oxygen-free compartment. The aerobic compartment has an opening at the bottom and
The sewage treatment system according to any one of claims 1 to 3 , wherein a second scraper for attracting sludge to the final settling basin is provided below the opening of the aerobic compartment. According to claim 1 or 2 , a first scraper for scraping sludge settling from the front stage of the biological treatment unit to the first settling basin is provided below the front stage of the biological treatment unit. The described sewage treatment system. According to claim 1 or 2 , a second scraper is provided below the rear stage of the biological treatment unit to scrape the sludge settling from the rear stage of the biological treatment unit into the final settling basin. The described sewage treatment system. The pretreatment tank has the first settling basin on the upstream side, the front stage of the biological treatment unit on the downstream side, and the biological treatment unit below the front stage of the biological treatment unit. It has a first scraping part that scrapes the sludge settled from the previous stage to the first settling basin.
The post-treatment tank has the post-stage of the biological treatment unit on the upstream side, the final settling basin on the downstream side, and the biological treatment unit below the rear stage of the biological treatment unit. It has a second scraping portion that scrapes the sludge settled from the latter stage to the final settling basin.
The sewage treatment system according to claim 1, wherein the sewage discharged from the downstream of the pretreatment tank is supplied to the upstream of the post-treatment tank.

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