JP7178808B2 - Organic wastewater treatment method and treatment system - Google Patents

Description

The present invention belongs to the technical field of treatment methods and treatment systems for organic wastewater such as food processing plant wastewater containing sap generated in the starch production process of starch factories, and more specifically, the BOD value (concentration) is 500 to 5000 mg. The present invention relates to a treatment method and a treatment system suitable for treating the so-called medium-concentration organic wastewater of / L .

Various techniques for treating organic wastewater having an aeration pond (aeration tank) for obtaining treated water from organic wastewater by an activated sludge method have been disclosed and put into practice (see, for example, Patent Documents 1 to 5).
Conventionally, an activated sludge method using an aeration pond has been suitably used as a treatment technology for medium-concentration organic wastewater, such as wastewater from chemical plants and livestock farming, in addition to wastewater from food processing plants. By the way, the activated sludge method using this aeration pond includes a continuous type and a batch type (batch type).

JP 2013-166128 A Japanese Unexamined Patent Application Publication No. 2007-90218 JP-A-2004-41981 Japanese Patent Application Laid-Open No. 2003-117580 JP-A-2002-346587

Although the continuous activated sludge process has the advantage of high treatment capacity, it requires the installation of a final sedimentation tank for sedimentation and separation of the activated sludge in addition to the aeration tank. In addition, it was also necessary to keep the concentration of activated sludge in the aeration basin constant by returning the settled sludge from the final sedimentation basin to the aeration basin. Therefore, there was a problem that the cost increased and the maintenance and management became complicated.
On the other hand, the batch-type activated sludge method is a system in which aeration is stopped in an aeration pond, and after the activated sludge is settled, the supernatant water is pumped up. has the advantage of being omitted. However, when the amount of water to be treated is large, the aeration stop time is inevitably long, during which time the activated sludge treatment must be stopped, resulting in a problem that the treatment capacity is inferior to that of the continuous system.

The present invention has been devised in view of the above-mentioned problems of the background art, and the object thereof is to achieve high processing capacity despite omitting the final sedimentation tank and the return operation of the settled sludge. To provide a treatment method and a treatment system for organic wastewater which are excellent in economic efficiency, rationality and treatment capacity, having advantages of both the continuous method and the batch method, such as being able to be carried out by a continuous activated sludge method. It is in. Among these, the object is to provide a treatment method and a treatment system which are particularly excellent in the ability to treat organic waste water of medium concentration.

As a means for solving the problems of the above background art, a method for treating organic wastewater according to the invention described in claim 1 includes wastewater from food processing factories containing sap generated in the starch manufacturing process of starch factories, chemical factories An aeration pond for obtaining treated water from wastewater or livestock wastewater with a BOD value of 500 to 5000mg/L medium-concentration organic wastewater by the continuous activated sludge method, is flat with a non-permeable partition wall. It is divided into two types of regions, an aeration region and an activated sludge sedimentation and separation region, when viewed in the vertical section, and the aeration region and the activated sludge sedimentation and separation region are communicated in the lower layer when viewed in a longitudinal section. ,
Furthermore, the activated sludge sedimentation separation area is formed so as to be surrounded by the wall of the aeration pond and the non-permeable partition wall when viewed in plan, and at least the pond wall on the side facing the partition wall is , the partition wall is formed on an inclined surface that is inclined in two steps from a gradient of about 60 degrees to a gradient of about 20 degrees in a direction of increasing the area from the lower end to the upper end; It is provided substantially vertically between the lower end and the upper end of the surface,
a step of aerating the organic wastewater in the aeration zone; a step of flowing the aerated activated sludge into the sedimentation zone through a communicating portion below the partition wall; and discharging the supernatant water of the activated sludge that has flowed into the aeration pond to the outside of the aeration pond as treated water.

The invention described in claim 2 is the method for treating organic wastewater described in claim 1, wherein the aeration treatment is performed at a position near the lower end of the pond wall formed on the inclined surface in the bottom of the aeration pond. It is characterized in that a damming wall for forming a storage area for storing the activated sludge is provided so as to rise from the bottom of the pond.

The invention described in claim 3 is the method for treating organic wastewater described in claim 1 or 2, wherein the aeration tank is provided at a position near the lower end of the pond wall formed on the inclined surface at the bottom of the aeration tank. A concave portion for forming a storage area for storing the treated activated sludge is provided by digging deeper than the bottom of the pond.

The invention recited in claim 4 is the method for treating organic wastewater recited in any one of claims 1 to 3, wherein the supernatant water of the activated sludge flowed into the sedimentation separation area is aerated as treated water. In addition to the step of discharging the sludge to the outside of the pond, the method includes a step of pumping up the activated sludge concentratedly stored at the lower end of the inclined surface of the pond wall and returning it to farmland.

The organic wastewater treatment system according to the invention described in claim 5 is for food processing plant wastewater, chemical plant wastewater, or livestock wastewater containing sap generated in the starch manufacturing process of a starch factory, and has a BOD value of 500 to 5000 mg. /L of medium-concentration organic wastewater treatment system comprising an aeration pond for obtaining treated water by a continuous activated sludge process, comprising:
The aeration pond is divided into two areas, an aeration area and an activated sludge sedimentation and separation area, by a non-permeable partition wall in a plan view, and the aeration area and the that the sedimentation separation region is configured to communicate with the lower layer;
Further, the activated sludge sedimentation separation area is formed so as to be surrounded by the wall of the aeration tank and the non-permeable partition wall when viewed in plan, and at least the wall facing the partition wall is , the partition wall is formed on a sloped surface that slopes in two stages from a slope of about 60 degrees to a slope of about 20 degrees in a direction that increases the area from the lower end to the upper end; It is characterized by being provided substantially vertically between the lower end and the upper end of the surface.

The invention described in claim 6 is the organic wastewater treatment system described in claim 5, wherein the aeration treatment is performed at a position near the lower end of the pond wall formed on the inclined surface in the bottom of the aeration pond. A damming wall forming a storage area for storing the activated sludge is provided so as to rise from the bottom of the pond.

The invention recited in claim 7 is the organic wastewater treatment system recited in claim 5 or 6, wherein the aeration treatment is performed at a position near the lower end of the pond wall formed on the inclined surface at the bottom of the aeration pond. It is characterized in that a recess forming a storage area for storing the activated sludge is provided with a structure that is dug deeper than the bottom of the pond.

The invention according to claim 8 is the organic wastewater treatment system according to any one of claims 5 to 7, wherein a lower end portion of the inclined surface of the pond wall is provided near the partition wall in the aeration area. It is characterized by having a pump for pumping up the activated sludge concentratedly stored in the sludge and returning it to farmland.

The invention according to claim 9 is the organic wastewater treatment system according to any one of claims 5 to 8, wherein the impermeable partition wall is a concrete plate, a plastic plate, a metal plate, or a silt fence. , or an oil fence.

The invention according to claim 10 is the organic wastewater treatment system according to any one of claims 5 to 9, wherein the inclination angle of the pond wall on the side facing the partition wall is set at the bottom of the aeration pond. is set within a range of about 30 to 70 degrees with respect to the reference plane.

The organic wastewater treatment method and treatment system according to the present invention have the following effects.
(1) By providing a partition wall in the aeration tank and dividing it into two areas, an aeration area and an activated sludge sedimentation separation area, etc., it is possible to realize a continuous activated sludge process and a final sedimentation tank. And the return operation of settled sludge can be omitted. Therefore, it is excellent in economy, rationality, maintainability, and processing capacity.
For example, in a starch factory in Hokkaido, when treating medium-concentration organic wastewater with activated sludge in a vast aeration pond, until now, in addition to the aeration pond, a sedimentation tank for obtaining treated water and a thickening/storage tank for excess sludge However, according to the present invention, good activated sludge treatment can be performed by the aeration pond having the above-described configuration without providing these facilities.
(2) By effectively utilizing one large aeration pond, it is possible to form two types of regions with different purposes, the so-called treatment region and the sedimentation region, and perform good activated sludge treatment. It is extremely rational because a simple method for completing the activated sludge treatment can be realized, the equipment scale can be made compact, and the centralized management of activated sludge and the like can be realized.
(3) Since the wall of the activated sludge sedimentation separation area is formed on the inclined surface, the activated sludge can be concentratedly stored (accumulated) at the lower end of the inclined surface. According to the inventions of Claims 2, 3, 6, and 7, the activated sludge can be stored intensively at the lower end of the inclined surface of the pond wall. Therefore, the stored activated sludge can be pumped up with a pump and effectively used for farmland return (inventions according to claims 4 and 8).
(4) In addition, the organic wastewater treatment system according to the present invention is highly rational and economical because it can be realized by modifying an existing aeration pond.

1 is a vertical cross-sectional view schematically showing a treatment method and treatment system for organic wastewater according to Example 1, and B is a plan view of the same. A is a vertical cross-sectional view schematically showing a treatment method and treatment system for organic wastewater according to Example 2, and B is a plan view of the same. A is a vertical cross-sectional view schematically showing a treatment method and treatment system for organic wastewater according to Example 3, and B is a plan view of the same. A is a vertical cross-sectional view schematically showing a treatment method and a treatment system for organic wastewater according to Example 4, and B is a plan view of the same. 4A and 4B are vertical cross-sectional views schematically showing variations of installation positions of water-impermeable partition walls, inclination angles of pond walls, and the like.

Next, an embodiment of the organic wastewater treatment method and treatment system according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the organic wastewater treatment method according to the first embodiment is a food processing factory wastewater , chemical factory wastewater, or livestock wastewater containing sap generated in the starch manufacturing process of a starch factory. An aeration pond 1 for obtaining treated water 9 by a continuous activated sludge method with medium concentration organic wastewater (stock solution) 8 with a value of 500 to 5000 mg / L , is planarly separated by a non-permeable partition wall 2 Looking at (see FIG. 1B), it is divided into two types of regions, an aeration region 3 and an activated sludge sedimentation and separation region 4, and when viewed in a longitudinal section (see FIG. 1A), the aeration region 3 and the activated sludge and the precipitation separation region 4 of the lower layer part 5 are connected,
Furthermore, the activated sludge sedimentation separation area 4 is formed so as to be surrounded in a rectangular shape by the pond wall 1a of the aeration pond 1 and the water-impermeable partition wall 2 when viewed in plan, and at least the partition wall 2 The pond wall 1a on the side facing the is formed on an inclined surface inclined in the direction of increasing the area from the lower end toward the upper end, and the partition wall 2 is formed between the lower end and the upper end of the inclined surface It is set almost vertically at
a step of aerating the organic wastewater 8 in the aeration region 3, and the aerated activated sludge passing through the communicating portion (lower layer portion) 5 below the partition wall 2 into the sedimentation separation region 4. The inflow step and the step of discharging the supernatant water of the activated sludge that has flowed into the sedimentation separation area 4 out of the aeration pond 1 as treated water 9 are continuously repeated.

Incidentally, reference numeral 6 in the figure indicates aerators (eight units in the illustrated example), reference numeral 7 indicates an overflow weir, and reference numeral 10 indicates the entire organic wastewater treatment system. Although the activated sludge that floats and sinks in the aeration zone 3 is omitted for convenience of illustration, the part where the activated sludge concentrates (storage) is hatched and denoted by reference numeral 11 .

Organic wastewater suitable for application of the present invention is so-called medium-concentration organic wastewater having a BOD value (concentration) of 500 to 5000 mg/ L . In particular, it is medium-concentration organic effluent containing sap generated in the starch manufacturing process of a starch factory in Hokkaido.
In the first place, from experience, etc., the applicant of the present application has decided to reduce the amount of excess sludge generated from the conditions of Hokkaido's potato starch drainage (separator drainage, hydrocyclone drainage, etc.) and the low water temperature of Hokkaido. As a result of taking into consideration the need to keep the BOD load per unit volume small, etc., the volume and plane size of the aeration pond 1 are formed larger than the general size, and the sedimentation tank (activated sludge sedimentation separation area Assuming that good aeration treatment can be performed by forming the plane size of 4) smaller than the general size, the applicant next conducted a full-scale test using the vast land of Hokkaido to confirm the present invention. I came up with the idea.

The form (size, shape) of the aeration pond 1 applied to the present invention is not particularly limited, but as a guideline for obtaining good treatment results, the planar area is about 900 m ² or more (for example, 30 m × 30 m, 60 m × 15 m, 80 m × 40 m) and a height of about 6 to 7 m (water depth of about 4 to 5 m).
By the way, the aeration pond 1 according to the first embodiment has a vertical dimension (X direction shown in FIG. 1B) of about 30 m and a horizontal dimension (Y direction of the same) of about 33 m (of which the aeration area 3 is 30 m). degree) of concrete. That is, the aeration pond 1 (the pond wall 1a and the pond bottom) is integrally formed by excavating a desired area of the ground and pouring concrete.

Said impermeable partition wall 2 is implemented in concrete in this example. That is, when constructing the aeration pond 1, concrete is cast and integrally formed in a configuration in which both ends are erected on the upper and lower pond walls 1a, 1a shown in FIG. 1B. Specifically, the partition wall 2 is positioned 30 m in the Y direction of the aeration pond 1, and has a width of about 10 cm and a height of about 4 m (immersed in water for about 2 m). is separated from the bottom of the pond by about 2 m, and is provided so as to traverse the aeration pond 1 in the X direction.
Thus, the aeration pond 1 is separated by the water-impermeable partition wall 2 into two areas, an aeration area 3 (approximately 30 m x 30 m) and an activated sludge sedimentation separation area 4 (approximately 3 m x 30 m). and the aeration zone 3 and the activated sludge sedimentation/separation zone 4 communicate with each other in the lower layer 5 (gap height is about 2 m or less).

In summary, in the organic wastewater treatment system 10 according to the present invention, the aeration pond 1 is divided into an aeration zone 3 and an activated sludge sedimentation separation zone 4 by a non-permeable partition wall 2 in a plan view. The aeration zone 3 and the sedimentation separation zone 4 are configured to communicate with each other in the lower layer part 5 when viewed in a longitudinal section, and the activated sludge sedimentation separation zone 4 is , the pond walls 1a of the aeration tank 1 (specifically, three pond walls 1a formed in a substantially U-shape in a plan view) and the water-impermeable partition wall 2 surround the aeration pond 1 in a rectangular shape. At least the pond wall 1a on the side facing the partition wall 2 is formed on an inclined surface that is inclined in the direction of increasing the area from the lower end toward the upper end, and the partition wall 2 is formed on the inclined surface It is provided substantially vertically between the lower end and the upper end of (the pond wall 1a).

The significance of forming the pond wall 1a on the side facing the non-permeable partition wall 2 as an inclined surface is that the activated sludge flowing into the sedimentation separation region 4 reaches the bottom of the pond without stagnation on the wall surface of the pond wall 1a. This is to promote natural settling as quickly as possible.
Further, the significance of providing the partition wall 2 between the lower end and the upper end of the pond wall 1a formed on the inclined surface is that the activated sludge to the sedimentation separation area 4 can be supplied as much as possible by providing it within the range of the inclined surface. This is to prevent the entry (intrusion) of
Although the inclination angle of the pond wall 1a is set to about 40 degrees, it is of course not limited to this. As shown in FIG. , θ=30 to 70 degrees. This is set based on the applicant's experience and the like.
For example, when the separator wastewater treatment in Hokkaido is performed in the aeration pond 1, when the soil that is leveled and not particularly civilly reinforced is used as the foundation of the aeration pond 1, the preferable inclination angle of the pond wall 1a as a civil engineering structure is about 30 to 45 degrees. It is known from the experience of the present applicant, full-scale experiments, etc. that this angle of inclination is just right considering the concentration of the separator wastewater, the water temperature in Hokkaido, and the processing efficiency of the aeration pond 1 .
In addition, when the inclination angle of the pond wall 1a is formed in two stages as shown in FIG. See paragraph [0021]), it is rational because the sedimentation efficiency of the activated sludge flowing into the sedimentation separation region 4 can be enhanced.

To explain the organic wastewater treatment method according to the present invention having the above-described structure, for example, first, the food processing factory wastewater 8 containing sap generated in the starch manufacturing process of the starch factory in Hokkaido is directly treated, or It is temporarily stored in a reservoir and quantitatively introduced into the aeration zone 3 of the aeration pond 1 .
Next, in the aeration zone 3, aerobic microorganisms are aerated by activating the movement of the aerobic microorganisms by means of oxygen supply stirring means such as aerators 6 arranged at appropriate intervals. This aeration treatment means is carried out in a continuous manner, and the activated sludge that floats and settles in the aeration region 3 while performing the aeration treatment repeats the floating and settling and passes through the communication part 5 below the partition wall 2 to the above-mentioned sedimentation. It flows into the separation area 4 .
The activated sludge that has flowed into the sedimentation separation area 4 promotes (promotes) natural settling along the inclined surface of the pond wall 1a, and finally accumulates at the lower end of the pond wall 1a. . Along with this, in the sedimentation separation area 4, the treated water 9 is quickly and efficiently separated from the activated sludge, overflows the overflow weir 7, and is discharged out of the aeration pond 1 as supernatant water 9 continuously. is repeated to

Next, an analysis simulation by the continuous activated sludge method, which is the organic wastewater treatment method according to the present invention, performed by the present applicant will be shown.
<Simulation 1 (Example 1 = see FIG. 1)>
Wastewater volume 1,000m ³ /day Wastewater BOD 1,000mg/L=1.0g/L=1.0kg/m ³
Amount of BOD 1.0×1,000 m ³ /day=1,000 kg/day Sedimentation separation area (4)
Required area 1,000 m ³ /day÷(10 to 15 m)/day ≒ 90 m ² (For example, set to 3 m (see symbol B in Fig. 5A) x 30 m)
Aeration pond (1)
Required volume 1,000 kg/day ÷ (0.15-0.40) kg/m ³ /day ≒ 3,600 m ³ (For example, set to 30 m × 30 m × 4 m (see same symbol H))
<Simulation 2>
Wastewater volume 500m ³ /day Wastewater BOD 2,000mg/L=2.0g/L=2.0kg/m ³
Amount of BOD 2.0×500 m ³ /day=1,000 kg/day Sedimentation separation zone (4)
Required area 500 m ³ /day ÷ (10 to 15 m) / day ≒ 45 m ² (for example, set to 1.5 m × 30 m)
Aeration pond (1)
Required volume 1,000 kg/day ÷ (0.15-0.40) kg/m ³ /day ≒ 3,600 m ³ (For example, set to 30 m × 30 m × 4 m)
<Simulation 3>
Wastewater volume 2,000m ³ /day Wastewater BOD 500mg/L=0.5g/L=0.5kg/m ³
Amount of BOD 0.5×2,000 m ³ /day=1,000 kg/day Sedimentation separation zone (4)
Required area 2,000 m ³ /day ÷ (10 to 15 m)/day ≒ 180 m ² (for example, set to 3 m × 60 m)
Aeration pond (1)
Required volume 1,000 kg/day ÷ (0.15-0.40) kg/m ³ /day ≒ 3,600 m ³ (For example, set to 60 m × 15 m × 4 m)

In the simulations 1 to 3, as shown in FIG. 5 in addition to FIG. ) is adjusted by appropriately changing the design.
By the way, during the full-scale test of the organic wastewater treatment method according to Example 1 <Simulation 1>, the records for arbitrary three days were as follows.
When the organic wastewater (undiluted solution) 8 has a BOD of 700 mg/L and a soluble BOD of 550 mg/L, the treated water 9 has a BOD of 11 mg/L and a soluble BOD of 7.1 mg/L. And when the SS of the organic waste water 8 is 180 mg/L, the SS of the treated water 9 is 37 mg/L.
When the organic waste water 8 has a BOD of 980 mg/L and a soluble BOD of 740 mg/L, the treated water 9 has a BOD of 65 mg/L and a soluble BOD of 10 mg/L. And when the SS of the organic waste water 8 is 330 mg/L, the SS of the treated water 9 is 120 mg/L.
When the organic waste water 8 has a BOD of 1100 mg/L and a soluble BOD of 840 mg/L, the treated water 9 has a BOD of 200 mg/L and a soluble BOD of 99 mg/L. And when the SS of the organic waste water 8 is 360 mg/L, the SS of the treated water 9 is 180 mg/L.
As described above, the applicant confirmed that the method for treating organic wastewater according to Example 1 can obtain generally good treatment results.

By the way, if a pump (not shown) is installed at the site 11 where the aerated activated sludge is concentrated, surplus activated sludge (excess sludge) can be effectively used as liquid fertilizer, which can contribute to agricultural land restoration. .

FIG. 2 shows a different embodiment of an organic wastewater treatment system 10 according to the invention.
Compared with the above-described Embodiment 1, this Embodiment 2 stores the aerated activated sludge at a position near the lower end of the pond wall 1a formed on the inclined surface at the bottom of the aeration pond 1. The difference is that the damming wall 12 forming the storage area of the pond has a new structure that rises from the bottom of the pond. Other constituent elements are the same as those of the first embodiment, so the same reference numerals are given and the description thereof is omitted.
According to the organic wastewater treatment method according to the second embodiment, the aerated activated sludge that has flowed into the sedimentation separation area 4 is prevented from returning to the aeration area 3 by the damming effect of the dam wall 12. Therefore, the activated sludge 11 can be further accumulated than in the first embodiment. Therefore, the excess sludge can further contribute to the return of agricultural land.
Further, by providing the damming wall 12, as shown in FIG. 5, the aerator 6, which inhibits the action of accumulating the activated sludge, is brought closer to the sedimentation separation area 4 as shown by the broken line. It is also possible to increase the degree of freedom in installation variations of the aerator 6, for example, the aerator 6 can be installed at any time.
As indicated by the broken line in FIG. 5A, the dam wall 12 should be installed within a range of about 2 m from the lower edge of the inclined surface of the pond wall 1a from the standpoint of activated sludge accumulation. preferable. By the way, the dam wall 12 is integrally constructed when the aeration pond 1 is constructed with cast concrete, and when constructing the aeration pond 1 with a water-impermeable sheet, which will be described later, is constructed using cast concrete, plastic plates, or the like. It is constructed by stretching metal plates.

FIG. 3 shows a different embodiment of an organic wastewater treatment system 10 according to the invention.
Compared with the above-described Embodiment 1, this Embodiment 3 stores the aerated activated sludge at a position near the lower end of the pond wall 1a formed on the inclined surface at the bottom of the aeration pond 1. The difference is that the concave portion 13 forming the storage area of the pond is dug deeper than the bottom portion of the pond. Other constituent elements are the same as those of the first embodiment, so the same reference numerals are given and the description thereof is omitted.
According to the method for treating organic wastewater according to the third embodiment, the aerated activated sludge that has flowed into the sedimentation separation region 4 is prevented from returning to the aeration region 3 by the confinement effect of the concave portion 13 after free fall. Since this can be prevented, the activated sludge 11 can be accumulated more than in the first embodiment, as in the second embodiment. Therefore, the excess sludge can further contribute to the return of agricultural land. Needless to say, the form (size, shape) of the concave portion 13 can be appropriately changed in design.

FIG. 4 shows a different embodiment of an organic wastewater treatment system 10 according to the invention.
In short, this Example 4 is a mixed type of the above Example 2 and the above Example 3, and needless to say, the activated sludge 11 is more than the above Example 1, as well as the above Examples 2 and 3. can be accumulated. Therefore, the excess sludge can further contribute to the return of agricultural land.

Although the embodiments have been described above with reference to the drawings, the present invention is not limited to the illustrated examples, and includes the range of design changes and application variations that are normally made by those skilled in the art without departing from the technical idea of the present invention. Just to be sure.
For example, although the aeration pond 1 is made of concrete, it is of course possible to stretch a water-blocking sheet over the site of excavating a desired area with an excavator. In this case, the water-impermeable partition wall 2 is preferably made of a plastic plate, a metal plate, a silt fence, or an oil fence.

REFERENCE SIGNS LIST 1 aeration pond 1a pond wall 2 water-impermeable partition wall 3 aeration region 4 sedimentation separation region of activated sludge 5 lower layer portion (communication portion)
6 aerator 7 overflow weir 8 medium-concentration organic wastewater (undiluted solution)
9 Treated water (supernatant water)
10 Organic wastewater treatment system 11 Accumulated activated sludge 12 Damping wall 13 Recess

Claims (10)

Medium-concentration organic wastewater with a BOD value of 500 to 5000mg/L, which contains sap generated in the starch manufacturing process of a starch factory, is processed by a continuous activated sludge method. An aeration pond for obtaining treated water is divided into two areas, an aeration area and an activated sludge sedimentation/separation area in a plan view, by a non-permeable partition wall. The aeration region and the activated sludge sedimentation separation region are configured to communicate in the lower layer,
Furthermore, the activated sludge sedimentation separation area is formed so as to be surrounded by the wall of the aeration pond and the non-permeable partition wall when viewed in plan, and at least the pond wall on the side facing the partition wall is , the partition wall is formed on an inclined surface that is inclined in two steps from a gradient of about 60 degrees to a gradient of about 20 degrees in a direction of increasing the area from the lower end to the upper end; It is provided substantially vertically between the lower end and the upper end of the surface,
a step of aerating the organic wastewater in the aeration zone; a step of flowing the aerated activated sludge into the sedimentation zone through a communicating portion below the partition wall; and discharging the supernatant water of the activated sludge that has flowed into the aeration pond as treated water to the outside of the aeration pond. A dam wall forming a storage area for storing the aerated activated sludge at a position near the lower end of the pond wall formed on the inclined surface in the bottom of the aeration pond rises from the bottom of the pond. The method for treating organic waste water according to claim 1, characterized in that it is provided with At a position near the lower end of the pond wall formed on the inclined surface in the bottom of the aeration pond, a recess for forming a storage area for storing the aerated activated sludge is dug deeper than the bottom of the pond. 3. The method for treating organic wastewater according to claim 1, wherein the organic wastewater treatment method is characterized by providing a structure. In addition to the step of discharging the supernatant water of the activated sludge that has flowed into the sedimentation separation area out of the aeration pond as treated water, the activated sludge concentratedly stored at the lower end of the inclined surface of the pond wall is pumped. 4. The method for treating organic wastewater according to any one of claims 1 to 3, characterized by including a step of pumping up and returning to farmland. The continuous activated sludge process is used to treat middle-concentration organic wastewater with a BOD value of 500 to 5000mg/ L, which is food processing plant wastewater, chemical plant wastewater, or livestock wastewater containing sap generated in the starch manufacturing process of a starch factory. An organic wastewater treatment system comprising an aeration pond for obtaining water, comprising:
The aeration pond is divided into two areas, an aeration area and an activated sludge sedimentation and separation area, by a non-permeable partition wall in a plan view, and the aeration area and the that the sedimentation separation region is configured to communicate with the lower layer;
Further, the activated sludge sedimentation separation area is formed so as to be surrounded by the wall of the aeration tank and the non-permeable partition wall when viewed in plan, and at least the wall facing the partition wall is , the partition wall is formed on a sloped surface that slopes in two stages from a slope of about 60 degrees to a slope of about 20 degrees in a direction that increases the area from the lower end to the upper end; provided substantially vertically between the lower end and the upper end of the surface;
A treatment system for organic wastewater, each characterized by:
A dam wall forming a storage area for storing the aerated activated sludge at a position near the lower end of the pond wall formed on the inclined surface in the bottom of the aeration pond rises from the bottom of the pond. The organic wastewater treatment system according to claim 5, characterized in that it is provided with: At a position near the lower end of the pond wall formed on the inclined surface in the bottom of the aeration pond, a recess forming a storage area for storing the aerated activated sludge is dug deeper than the bottom of the pond. 7. The organic wastewater treatment system according to claim 5 or 6, characterized in that it is provided in a configuration. A pump for pumping up activated sludge concentratedly stored at the lower end of the inclined surface of the pond wall and returning it to agricultural land is installed near the partition wall in the aeration area. The organic wastewater treatment system according to any one of 5 to 7. The treatment of organic wastewater according to any one of claims 5 to 8, wherein the impermeable partition wall is a concrete plate, a plastic plate, a metal plate, a silt fence, or an oil fence. system. The inclination angle of the pond wall on the side facing the partition wall is set within a range of about 30 to 70 degrees with the bottom of the aeration pond as a reference plane. A treatment system for organic waste water according to any one of the items.

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