JPS6365398B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating urban sewage, industrial wastewater, or similar organic wastewater containing organic pollutants.

[Conventional technology]

Conventionally, in order to treat organic wastewater, a compact high-speed aeration-sedimentation device in which an aeration section and a precipitation separation section are integrated has been frequently used.

For example, as shown in Fig. 3, in a high-speed aeration and precipitation apparatus, an aeration section 3 is formed in the center of a tank 1 by a partition wall 2 whose lower end is bulged and whose lower end is separated from the bottom of the tank, and the outside of the partition wall 2 is used for precipitation. The lower part of the sedimentation separation part 4 is connected to the aeration part 3 by a separation part from the bottom of the tank at the lower end of the partition wall 2. Further, a communication passage 5 is opened in the upper part of the partition wall 2, and a draft tube 6 whose upper end protrudes above the water surface is vertically installed on the outside of the communication passage 5.
A draft portion 7 is formed between the draft tube 6 and the partition wall 2, and the aeration portion 3 and the precipitation separation portion 4 are communicated via the draft portion 7.

Further, in the aeration section 3, an air supply pipe 8 and an agitator 10 driven by a drive device 9 are disposed above the air supply pipe 8, and a control mechanism 11 controls opening and closing of an on-off valve 12 in the air supply pipe 8. Starting and stopping of the drive device 9 is controlled.

In the figure, 13 is a sewage inflow pipe that opens at the bottom of the aeration section 3, 14 is an overflow gutter provided at the top of the sedimentation separation section 4, 15 is a treated water outflow pipe, and 16 is a sludge drain pipe that discharges excess sludge. show.

Such a high-speed aeration-sedimentation device performs aerobic treatment by aerating organic wastewater while continuously flowing into the aeration section 3 from the wastewater inflow pipe 13, and then performs solid-liquid separation in the precipitation separation section 4 for clarification. While obtaining treated water,
The settled sludge is recycled to the aeration section 3 again, but in order to enable even more advanced treatment,
A treatment technique for intermittently performing aeration in the aeration section 3 has been developed and filed as Japanese Patent Application No. 132904/1983.

That is, in the treatment technology using the intermittent aeration method, during aeration, organic sewage is led into the aeration part 3 from the sewage inflow pipe 13, and is passed through the agitator together with the activated sludge in the tank 1 and the air sent from the air supply pipe 8. 10 and subjected to aerobic decomposition, the mixed liquid of sewage and activated sludge passes through the communication passage 5 in the upper part of the partition wall 2, descends in the draft part 7, and flows into the sedimentation separation part 4. do. Solid-liquid separation is performed in the sedimentation separation section 4, and the separated supernatant water becomes treated water and overflows into the overflow gutter 14 and flows out from the treated water outflow pipe 15, and the sludge settles and flows between the partition wall 2 and the tank bottom. The air is circulated again to the aeration section 3 through the separated section.

Furthermore, when the aeration is stopped, organic wastewater continuously flows into the aeration section 3 from the wastewater inflow pipe 13, but when the control mechanism 11 closes the on-off valve 12 and stops the drive device 9, the organic wastewater flows from the air supply pipe 8 into the aeration section 3. Since the air supply and the agitator 10 are stopped, the activated sludge in the aeration section 3 settles to form a sludge zone, and a sludge interface 17 is formed as shown by the broken line. Therefore, the wastewater inflow pipe 1
The organic sewage that has flowed into the aeration section 3 from the sludge interface 17 rises through the sludge zone below the sludge interface 17, passes through the communication section 5 at the top of the partition wall 2, passes through the draft section 7, and reaches the sedimentation separation section 4. Overflow gutter 1 as treated water
4, the treated water flows out of the tank from the outflow pipe 15, but as the sewage passes through the sludge zone, it undergoes decomposition due to denitrification, and sludge is taken in during aeration by bacteria that have the ability to accumulate phosphorus. At the same time as the phosphorus inside is discharged, organic matter is taken into the sludge.
After passing through the sludge zone, the wastewater becomes relatively clear treated water.

In this way, the method of using a high-speed aeration-sedimentation device with an integrated aeration section and sedimentation separation section to perform aeration intermittently while continuously inflowing wastewater has been difficult to achieve with high-speed aeration-sedimentation devices. This was an excellent technology that prevented bulking, which had previously been known, and also made it possible to remove nitrogen and phosphorus.

[Problem that the invention seeks to solve]

However, in the above-mentioned intermittent aeration method, it is necessary to take a long aeration stop time (anaerobic time) in order to give priority to bacterial groups that have the ability to dephosphorize. As a result, there is a tendency for a large amount of suspended solids to be generated in the supernatant water that becomes the treated water, and these suspended solids flow into the sedimentation separation section 4 through the communication section 5 and the draft section 7 and are not separated. The quality of the treated water tended to deteriorate as it flowed out as it was. In particular, when the depth in tank 1 was shallow or under conditions where the MLSS concentration was low, the ability to remove suspended solids and organic matter was significantly reduced.

The present invention takes advantage of the bulking prevention effect and nitrogen and phosphorus removal effect of intermittent aeration of the high-speed aeration-sedimentation device, and also prevents suspended solids and other substances from being mixed into the treated water as the aeration is stopped for a long time. It is an object of the present invention to provide a method for treating organic wastewater that can obtain good treated water quality.

[Means for solving problems]

The present inventor investigated the relationship between the aeration stop time and suspended solids in the supernatant water using a laboratory-scale device regarding the intermittent aeration method of the high-speed aeration-sedimentation device.
That is, as shown in FIGS. 4a and 4b, as an experimental apparatus, the inside of the tank 21 is separated into an aeration section 23 and a sedimentation separation section 24 by a partition wall 22 whose upper end is above the water surface and whose lower end is separated from the tank bottom. The interior of the aeration section 23 is partitioned by a partition wall 25 whose upper end is below the water surface and whose lower end is separated from the bottom of the tank. The sewage inflow pipe 3 is opened, and the other 23' is communicated with the lower part of the sedimentation separation section 24 via the lower end of the partition wall 22,
A system in which a treated water outflow section 34 was provided above the precipitation separation section 24 was used.

Then, the sewage is transferred from the sewage inflow pipe 33 to the aeration section 23.
Intermittent aeration was performed while continuously flowing into the tank.

During aeration, as shown in FIG. 4a, air is diffused from the aeration pipe 28, and the wastewater undergoes aerobic decomposition in the aeration section 23 and then passes over the upper end of the partition wall 25 to the aeration section 23'. A part of the water flows into the aeration part 23 from the lower end of the partition wall 25, and the other part flows into the lower part of the precipitation separation part 24 from the lower end of the partition wall 22, and after solid separation, the supernatant water is transferred to the treated water outflow part. It leaked from 34.

On the other hand, when the aeration is stopped, as shown in FIG. 4b, by stopping the aeration from the aeration pipe 8, the sludge interface is formed at the lower part of each of the aeration sections 23, 23' and the sediment separation section 24. Sludge zones A, B, and C with 37 are formed, and the sewage flowing in from the sewage inflow pipe 33 passes upward through the sludge zone A formed in the aeration section 23, passes over the upper end of the partition wall 25, and is aerated. It flows into the section 23', becomes a downward flow, passes through the sludge zone B of this section, and then passes upward through the sludge zone C from the lower end of the partition wall 22 to the sedimentation separation section 24, where nitrogen and phosphorus are removed. The treated water was discharged from the treated water outlet 34.

In this way, after the sludge is acclimatized by intermittent aeration treatment while flowing sewage continuously, the supernatant water b and c of the aeration section 23' and the sedimentation separation section 24 after only aeration is stopped (Fig. 4b). The results of examining the turbidity over time were as shown in Figure 5. This fifth
As can be seen from the figure, in the aeration section 23', the turbidity of the supernatant water b gradually increased from about 15 minutes after the aeration stopped. On the other hand, in the precipitation separation section 24, the turbidity of the supernatant water c increased about 80 minutes after the aeration stopped, and the increase in turbidity was shown to be delayed by about 65 minutes compared to the aeration section 23'. These results revealed that suspended solids can be significantly reduced by passing through the sludge zone twice.

The present invention was made based on the observation results of the above-mentioned experiments, and includes forming in the tank a sedimentation separation section having an aeration section with a sewage inflow section at the bottom and a treated water outflow section; In a method of intermittently aerating while continuously inflowing sewage using a high-speed aeration-sedimentation device in which the upper and lower parts of the aeration part are connected to the sedimentation separation part to circulate the water in the tank, when the aeration is stopped, The present invention provides a method for treating organic wastewater, characterized in that the outflow from the upper part of the aeration part to the precipitation separation part is stopped, and the flow is allowed to flow only from the lower part of the aeration part to the precipitation separation part.

〔Example〕

Next, an embodiment of the present invention will be described with reference to FIG. 1. Most of the high-speed aeration precipitation apparatus shown in FIG. An opening/closing mechanism 18 is provided in the upper communication portion 5. The opening/closing mechanism 18 is preferably an automatic opening/closing mechanism, and is closed in conjunction with the control mechanism 11 when the opening/closing valve 12 of the air supply pipe 8 is closed and when the drive device 9 of the stirrer 10 is stopped.

Therefore, when the aeration is stopped, the opening/closing mechanism 1
8 is closed and the sewage flows from the lower end of the partition wall 2 to the lower part of the sedimentation separation section 4, the sewage passes through the aeration section 3 below the sludge interface 17 and the sludge zone of the sedimentation separation section 4 and becomes suspended. While quality is effectively captured,
The water rises through the sediment separation unit 4, passes through the overflow gutter 14, and flows out from the treated water outflow pipe 15 as good treated water.
In addition, during aeration, the opening/closing mechanism 18 is opened, and the mixed liquid is transferred from the aeration part 3 to the communication part 5 as in the past.
and flows through the draft section 7 to the precipitation separation section 4,
The sludge is circulated to the aeration section 3.

The opening/closing of the opening/closing mechanism 18 is preferably controlled by the control mechanism 11 along with the starting and stopping of the agitator 10 and the opening/closing of the opening/closing valve 12 of the air pipe 8.
The opening/closing mechanism 18 does not necessarily have to be opened and closed at the same time as the start and stop of aeration; it is preferable that the opening/closing mechanism 18 is opened at the same time as the aeration starts, but it is closed 5 to 10 minutes after the aeration stops. You can do it later.

In addition, as shown in FIG.
By surrounding it with a double-sided cylinder 19 with open upper and lower ends, the sewage that flows in when the aeration is stopped passes through the sludge zone and exits to the upper part of the sludge interface 17, as shown by the arrow, and then returns to the sludge zone of the aeration section 3. It can penetrate into the sludge zone of the sedimentation separation section 4 and further improve the effect of removing suspended solids entrained in the treated water.

FIG. 2 shows another embodiment of the present invention, in which the inlet of organic sewage is connected to one side of the tank 1 by a partition wall 38 whose upper end is above the water surface and whose lower end is near the bottom of the tank. An aeration section 3 is formed by the partition wall 38 and the partition wall 2, and the top and bottom of the aeration section 3 are communicated with the settling section 4 through a draft section 7 formed by a draft tube 6. The operation is almost the same as that of the above embodiment.

〔Effect of the invention〕

As described above, according to the present invention, intermittent aeration is performed using a high-speed aeration precipitation device, and while taking advantage of the bulking prevention effect and the nitrogen and phosphorus removal effect,
It is possible to effectively remove suspended solids that occur as the aeration stop time is increased, and to always obtain good quality treated water.

[Brief explanation of drawings]

FIG. 1 is an overall explanatory diagram showing one embodiment of the present invention;
FIG. 2 is an explanatory diagram showing another embodiment of the present invention, and FIG.
The figure is an overall explanatory diagram showing a conventional example, and Fig. 4 a and b
is an explanatory diagram showing an experimental example, and FIG. 5 is a diagram showing the relationship between the inflow time of wastewater and the turbidity of supernatant water in the experimental example. 1... Tank, 2... Partition wall, 3... Aeration section, 4... Precipitation separation section, 5... Communication section, 6... Draft tube, 7... Draft section, 8... Air supply pipe, 9... Drive device, 10... Stirrer, 11 ...control mechanism, 12...on/off valve, 13...sewage inflow pipe, 14...overflow gutter, 15...treated water outflow pipe,
16... Sludge drainage pipe, 17... Sludge interface, 18... Opening/closing mechanism, 19... Buttful tube, 21... Tank, 22... Partition wall,
23, 23'... Aeration section, 24... Precipitation separation section, 25
…Partition wall, 28…Diffuser pipe, 33…Sewage inflow pipe, 34
... Treated water outflow section, 37 ... Sludge interface, 38 ... Partition wall.

Claims (1)

[Claims] 1. In a tank, an aeration part with a sewage inflow part at the bottom and a sedimentation separation part with a treated water outflow part are formed, and the upper and lower parts of the aeration part communicate with the sedimentation separation part to drain water in the tank. In a method in which wastewater is intermittently aerated while continuously flowing in using a high-speed aeration-settling device configured to circulate, when the aeration is stopped, the outflow from the upper part of the aeration section to the sedimentation separation section is stopped, and the aeration is stopped. A method for treating organic wastewater, characterized in that the organic wastewater is allowed to flow out only from the lower part of the section to the precipitation separation section.