JPH0148835B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for treating domestic sewage, industrial wastewater, or similar wastewater containing organic pollutants. [Prior art and its problems] The prior art will be explained based on FIG. 5. FIG. 5 is an example of a conventional sewage treatment apparatus that integrates an aeration section and a settling section, in which the settling section is configured to form a sludge blanket zone. In this example, sewage flows into the aeration section 2 from the inflow pipe 1, and the aeration device 3
The agitation effect of the air introduced from the tank mixes with the sludge, and the polluted organic matter in the inflow water is aerobically decomposed. The mixed liquid of sewage and sludge passes through the communication section 5 between the aeration section 2 and the settling section 4, is led to the settling section 4, and is separated into treated supernatant liquid and sludge.
is returned by a return means 6 such as a pump or an air lift. The settling section 4 is narrow at the part where the mixed liquid flows from the aeration section 2 and widens upward, so that the sludge forms a sludge blanket zone. As the wastewater passes through this blanket zone, even the finest flocs are completely captured, making it possible to obtain extremely clear treated water with this method. Additionally, since the aeration section and precipitation section are integrated, the device is compact. However, this method has the following problems. (1) Since the aeration section is a complete mixing tank, bulking is likely to occur in wastewater containing a large amount of low-molecular carbohydrates or in separated sewage.
Moreover, since the sedimentation part forms a sludge blanket zone, the sludge interface suddenly rises as the sedimentation property of the sludge decreases, causing the sludge to flow out together with the treated water. (2) Furthermore, with conventional equipment and operating methods, it has been almost impossible to remove N and P, which cause eutrophication. [Object of the Invention] The object of the present invention is to provide a method and apparatus for treating organic wastewater that can suppress conventional problems, particularly bulking, and also remove N and P. be. [Structure of the Invention] The present invention provides: 1. Organic sewage in which the aeration part and the settling part are integrated, and the aeration part and the settling part are configured to communicate at the lower part, and the settling part forms a sludge blanket zone. 1. A method for treating organic sewage, comprising: performing aeration intermittently while continuously causing the sewage to flow into the bottom of the aeration section. 2. In an organic wastewater treatment device in which the aeration section and the settling section are integrated, the aeration section and the settling section are configured such that the aeration section and the settling section communicate at the bottom and the settling section forms a sludge blanket zone. It has a means for returning sludge to the aeration part, and also has a control means for causing sewage to uniformly flow upward from the bottom of the aeration part regardless of whether aeration is started or stopped, and for performing aeration intermittently. An organic sewage treatment device featuring: It is. Next, the present invention will be explained in detail based on the drawings. Figure 1 shows the basic configuration of the present invention, Figure 2 shows a partition plate in the center of the aeration section, and the aeration device is installed above the sewage inlet, and Figure 3 shows the sewage inlet. An aeration device is installed on the opposite side. Sewage is led from the wastewater flow pipe 1 to the bottom of the aeration section 2, and uniformly flows upward into the aeration section 2 in a diffused state so as not to flow for a short period of time. As a means for this purpose, the inlet may be formed into an inverted conical shape, or it may be branched into a perforated pipe. When there is no partition plate 7 in the aeration part 2, the sewage inlet is installed at a position as far away from the settling part 4 as possible, but when there is a partition plate 7, it is always installed on the opposite side from the settling part 4. The aeration device 3 may be located above the wastewater inlet or on the opposite side as in the example shown in FIG. 3, but when it is in the position shown in FIG.
Since a horizontal flow is generated from the bottom toward the sedimentation section 4,
It is necessary to provide a baffle plate 8 to obstruct this flow. When the partition plate 7 is provided in the center of the aeration section 2, the lower part and the upper part are communicated with each other, but the height of the lower end of the partition plate 7 is set to be lower than the position of the aeration device 3.
The height of the upper end of the partition plate 7 is at least the height of the aeration device 3
Although it is necessary to install it at a higher position,
As shown in Fig. 2, it is sufficient to reach about half the height of the aeration section. Further, in the present invention, it is also possible to have a bilaterally symmetrical structure as shown in FIG.
If the structure is symmetrical, the partition plate 7
Alternatively, the aeration device 3 may be surrounded by a cylinder or a rectangular tube. During aeration, the sewage flowing in from the sewage inlet pipe 1 is mixed with sludge and aerated in a circulating flow as shown by arrows in FIGS. 1 to 4, and organic matter in the sewage is decomposed. The mixed liquid of treated sewage and sludge passes through the communication section 5 between the settling section 4 and the aeration section 2, flows into the settling section 4, passes through the sludge blanket zone, is separated into treated water supernatant liquid and sludge, and is separated into the treated water supernatant liquid and sludge. The clear liquid flows out from the outlet 9, and the sludge is returned to the aeration section 2 by a return means 6 using a pump or an air lift. Sewage flows into the aeration section 2 even when the aeration is stopped, but in this case,
As shown in FIG. 6, the sewage flows through the settled sludge zone to the upper side of the sludge interface formed in the aeration section, and then flows through the sludge zone again to the sludge blanket zone from the settling section communication section 5. street,
It flows out to the upper part of the settling section 4. This flow will flow more smoothly if there is a partition plate 7 in the center of the aeration section. When the aeration is stopped, the sludge in the mixed liquid settles toward the bottom of the aeration section, forming a sludge zone. At this time, the sewage flows into the bottom part where the sludge concentration is highest, so the oxygen in the mixed liquid is rapidly consumed in this part, resulting in an anoxic state. Under such conditions, the growth of filamentous bacteria that causes bulking is suppressed, so that bulking is prevented from occurring. Anoxic conditions can also be achieved by stirring without aeration, but in this case, the sludge concentration becomes uniform and thinner.
Since rapid consumption of dissolved oxygen is unlikely to occur, the bulking prevention effect is small. It is effective to allow sludge to stand still and concentrate, as in the present invention, and to bring it into contact with wastewater at the bottom, where the sludge concentration is highest. At this time, if the aeration stop time is lengthened, the anaerobic degree of the sludge will progress, and turbidity will be generated on the supernatant side. However, as shown in FIG. 6, this turbidity is sufficiently clarified by passing through the sludge zone again and passing through the sludge blanket zone from the lower part of the settling section. In this case, the partition plate 7 can be moved up and down, and when the aeration is stopped, it is lowered to close the lower part. Alternatively, as shown in FIG. 6, it is more effective to close the lower part of the partition plate with a flap type movable plate provided at the lower part of the partition plate. The present invention aims to prevent bulking by continuously inflowing sewage and forming an anaerobic state even when aeration is stopped, and also allows turbidity generated due to a long stop time to pass through the sludge zone twice. It was designed to improve the clarity of the water. The latter function becomes more effective when the partition plate 7 is installed in the center of the aeration section. Furthermore, in the present invention, when the load condition of the aeration tank is low and nitrification progresses, de-N occurs in an anoxic state while aeration is stopped, making it possible to remove N. When nitric acid disappears and the anaerobic degree further increases, bacteria that have the ability to remove phosphorus will proliferate, and will also have the ability to remove phosphorus. Even if sewage continuously flows in with aeration stopped, the organic matter in the sewage will be decomposed by the action of de-N bacteria or de-phosphorizing bacteria, or will be incorporated into activated sludge from the liquid side. Water quality will be good. The time ratio of aeration and stop is bulking stop and de-N
Although it differs slightly depending on the purpose of dephosphorization, an aeration:stopping time ratio of 1:0.5 to 5 is effective in any case, and a range of 1:1 to 3 is optimal. In addition, one stoppage time should not exceed 1/3 of the residence time in the aeration section. Stopping for longer than this will reduce the effectiveness of trapping suspended solids. The time for this aeration and stopping can be controlled by the controller 10. This time does not need to be constant, and can be adjusted through the control system 10 according to load fluctuations and flow rate fluctuations. Aeration and standing (stopping) are carried out intermittently, but the moment aeration is started again after standing, a significant upward flow occurs in the aeration section, and the sludge at the bottom of the settling section is swept into the aeration section. For this reason, the precipitation part 4
The sludge in the sludge is constantly replaced, the sludge does not stay in the sedimentation section for a long time, and the rate of rise of the sludge interface in the aeration section becomes slower. This function becomes more prominent when the aeration device is installed in the position shown in FIG. Therefore, it is not necessary to continuously return the sludge from the settling section to the aeration section, and the return means 6 is operated only when the sludge interface rises. For example, in FIG. 3, the sludge interface can be detected by a sludge interface detector 11, and the sludge can be returned as appropriate by a controller 12 that controls the return means. Targeting food processing wastewater ( ^Q630m3 /day),
The conventional apparatus shown in the figure (aeration section volume: 220 m ³ , sedimentation section volume: 110 m ³ ) was modified using the apparatus of the present invention shown in FIG. 2 (aeration time: 40 minutes, stop time: 80 minutes). The effect of improving the settling property of sludge at this time is shown in Fig. 7. Table 1 shows an example of the quality of treated water before and after modification. Before modification, the SVI value (sludge capacity index) of activated sludge was as high as 400 to 800 ml/g, and in severe cases, sludge sometimes flowed out from the settling section. However, after modification, SVI settled down to 100-200ml/g,
Operation management has become easier. Also, in terms of water quality, Table 1
As shown in the figure, after the modification, N and P were also removed, improving the processing function. 【table】

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 3, FIG. 4, and FIG. 6 are schematic diagrams for explaining specific examples of the present invention, and FIG. 7 is a graph for showing the effects of the present invention, FIG. 5 is a drawing for explaining a conventional example. 1... Sewage inflow pipe, 2... Aeration section, 3... Aeration device, 4... Sedimentation section, 5... Communication section, 6... Sludge return section, 7... Partition plate, 8... Baffle plate, 13,1
4...Movable plate.

Claims (1)

[Claims] 1. An organic sewage treatment device in which the aeration section and the settling section are integrated, and the aeration section and the settling section are configured such that the aeration section and the settling section communicate at the bottom and the settling section forms a sludge blanket zone. A method for treating organic wastewater, characterized in that aeration is performed intermittently while the wastewater is continuously allowed to flow into the bottom of the aeration section. 2. In an organic wastewater treatment device in which the aeration section and the settling section are integrated, the aeration section and the settling section are configured such that the aeration section and the settling section communicate at the bottom and the settling section forms a sludge blanket zone. It has a means for returning sludge to the aeration section, and has a control means for causing sewage to uniformly flow upward from the bottom of the aeration section regardless of whether aeration is started or stopped, and for performing aeration intermittently. An organic sewage treatment device characterized by: 3. A partition plate is provided in the center of the aeration section that communicates between the lower part and the upper part, and a sewage inlet that allows sewage to flow upward is provided at the bottom of the aeration section opposite to the sedimentation part separated by the partition plate, and the sewage flow is 3. The organic sewage treatment device according to claim 2, further comprising an aeration device provided above the inlet. 4. A partition plate is provided in the central part of the aeration section that communicates with the lower and upper parts, and a sewage inlet that allows sewage to flow upward is provided at the bottom of the aeration section opposite to the sedimentation section separated by the partition plate. Claim 2, comprising: an aeration device provided on the side closer to the sedimentation portion; and a baffle plate in contact with the bottom plate provided at the bottom of the aeration device.
The organic sewage treatment equipment described in Section 1. 5 A sludge interface meter is provided in the settling section, and means for returning the sludge in the settling section to the aeration section when the sludge interface in the settling section rises to a preset position is provided in claims 2 and 3. Or the organic sewage treatment device according to item 4. 6. According to any one of claims 2 to 5, the lower part of a partition plate provided in the central part of the aeration part so that the lower part and the upper part communicate with each other can be closed when the aeration is stopped. organic sewage treatment equipment. 7. Organic sewage according to claim 6, which is constructed so that the lower part can be closed when the aeration is stopped by raising and lowering a partition plate provided in the central part of the aeration part so that the lower part and the upper part communicate with each other. Processing equipment. 8. The organic material according to claim 6, wherein a movable plate or a flap-type movable plate that can be moved up and down is provided at the lower part of the partition plate, and the lower part of the partition plate can be closed by the movable plate when aeration is stopped. Wastewater treatment equipment.