JPS60175598A - Sewage treatment method - Google Patents

Abstract

PURPOSE:To perform certain sewage treatment corresponding to the inflow amount of sewage, by a method wherein a plurality of treatment tanks are provided and, when the inflow amount of sewage reaches a definite amount or more, one or more of tanks of the treatment tanks are used as continuous aeration tanks and one or more of tanks are used as continuous precipitation tanks. CONSTITUTION:Sewage is continuously flowed into a first treatment tank 1 and continuously aerated therein while the treated sewage is naturally flowed down to a second treatment tank 2 to receive precipitation treatment. In this case, if a series of treatments are continued for an extremely long time, the precipitated sludge in the second treatment tank 2 is portially stayed to form an anaerobic state and effective treatment is not performed. Because of this, the operation processes of both treatment tanks 1, 2 may be reversely changed over by a timer so that an aeration process is performed in the second treatment tank 2 while a precipitation and discharge process is performed in the first treatment tank 1. In this case, precipitation is performed in the treatment tank under an aeration process and said tank is held to a precipitation process until a supernatant water can be discharged and sewage is flowed into said tank.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to batch activated sludge treatment in which wastewater is treated by repeating the steps of exposure, precipitation, and discharge in a treatment tank during normal operation. The present invention relates to a wastewater treatment method that can effectively treat wastewater even when the wastewater exceeds the above limit.

In activated sludge treatment, which has become mainstream in domestic wastewater treatment in recent years, the process of aeration, precipitation, and discharge is treated as one cycle in a single treatment tank that receives wastewater continuously or at any time. The batch-type activated sludge treatment method is attracting attention.

This treatment method has various advantages such as not requiring a settling tank or sludge return equipment, and is an extremely effective treatment method. However, if the amount of inflowing sewage far exceeds the set value, If the water flows in as it is, an overflow situation will occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sewage treatment method that eliminates the above-mentioned drawbacks and allows reliable sewage treatment by changing the treatment and process accordingly even if the amount of sewage inflow exceeds a set value.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a processing apparatus to which the method of the present invention is applied.
, 2, a sewage supply path 3 for supplying sewage to the treatment tanks 1 and 2, a sludge extraction path 4 for pulling out the sludge settled in the treatment tanks 1 and 2, and a return path 5 for returning the sludge.

Each passage 3,4.5 is connected to a first and a second treatment tank 1.
Both tanks 1 and 2 are connected to each other so that the functions of the two tanks can be exchanged.

In addition, the treatment tanks 1 and 2 are communicated with each other through an overflow port 6 at the top of the tank.
Since it is a construction, only one side is shown. ), an aeration device 7 is provided at the bottom of the treatment tanks 1 and 2 for blowing air from an aeration blower (not shown) into the wastewater during the aeration process. At the top of the tank, an automatic decanter 8 for discharging the supernatant liquid during the discharge process following the precipitation process, and a fixed weir 9 as necessary are arranged.

The automatic decanter 8 includes a discharge pipe 11 connected to a rotatable shaft vibrator 10, an overflow pipe 12 attached to the free end of the discharge pipe 11, and having an overflow port 12a opened.
It is composed of a float 13 that also serves as a scum baffle. When the overflow pipe 12 is at the water surface, the supernatant water in the treatment tanks 1 and 2 flows into the overflow pipe 12 through the overflow port 12a, and is discharged to the outside through the shaft pipe 10. Further, when the overflow pipe 12 is rotated by a rotating means (not shown) so as to be at a position higher than the liquid level, the liquid in the processing tank 1.2 is not drained.

Similarly, the discharge from the fixed weir 9 is turned on and off as necessary.

Next, the operation and effect of this invention will be explained.

Under normal conditions, sewage is switched to the first treatment tank 1 and second treatment tank 2 sequentially and flows into the first treatment tank 1 and second treatment tank 2, and in each type 1 and 2, aeration by the aeration device 7, sedimentation by standing still, and discharge by the decanter 8 are performed. 4
As shown in the figure, normal batch activated sludge treatment is performed by switching sequentially. At this time, for example, if the first treatment tank 1 is performing the aeration process and the second treatment tank 2 is performing the sedimentation and discharge process, the valve MA1 in the wastewater supply path 3 is closed and the valve MB is opened. , so that wastewater flows into the treatment tank during the aeration process.

Next, in an emergency, for example, when the inflow of sewage exceeds a set value during rainy weather, an emergency flow signal is issued from the flow meter 14 in the sewage supply channel 3, but the sewage continues to flow through the open valve. It flows into the first processing tank l via MB1. Then, in response to this emergency flow rate signal, the decanter 8 in the second processing tank 2 is rotated and raised to a predetermined position of the continuous discharge reservoir.

In this case, the wastewater undergoes aeration treatment in the first treatment tank 1, and then overflows (=yo) as an aeration mixture and flows into the second treatment tank 2. Then, the water is subjected to sedimentation treatment in the second treatment tank 2, and when the water level reaches a predetermined position for continuous discharge,
The precipitated supernatant liquid flows through the overflow port 12a of the decanter 8 and the fixed weir 9.
It overflows and is discharged. Here, the activated sludge precipitated in the second treatment tank 2 is removed from the valve MB3 in the return path 5.
It is returned to the first processing tank 1 via the second pump P2 and valve MB□. (Valve MA3 in return path 5, first pump P
1. Valve MA2 is naturally stopped and closed. ) Also, excess sludge in the second treatment tank 2 is appropriately drawn out by the sludge drawing passage 4 via the pump P3.

In this way, sewage continuously flows into the treatment tank 1 of 1/1, and after continuous aeration, flows naturally to the second treatment tank 2 where it is subjected to sedimentation treatment.

Note that if this series of processing continues for a long time, the second
The precipitated sludge in the treatment tank 2 partially stagnates and becomes anaerobic, making it impossible to perform effective treatment. Therefore, both treatment tanks 1
．． 2 operation process is reversed using a timer etc., and the second process 41
It is preferable to switch the aeration process in step 12 so that the precipitation/discharge process is performed in the first treatment tank 1. In this case, sedimentation of the treatment tank that was in the aeration process is carried out until the supernatant can be discharged.
The treatment tank that was in the sedimentation process is kept in the sedimentation process, and wastewater is allowed to flow into it.

At this time, if a buckle 15 is provided as shown in FIG. 5, short-circuit discharge of waste water can be prevented. Further, the fixed weirs 9 provided in the treatment tanks 1 and 2 are submerged during the continuous aeration process. Therefore, the operating process of treatment tank 1.2 is reversed, and when it takes charge of the sedimentation process and discharges the sedimentation supernatant liquid, a certain amount of treated water after the start of discharge is transferred to the treatment tank into which the wastewater is flowing (
It is returned to Tsuma J7 (processing tank in charge of the air process). As mentioned above, in the fixed weir 9, the pulp of the discharge pipe is normally closed to prevent drainage.

Furthermore, continuous discharge may be performed only by an automatic decanter or fixed weir 9.

In addition, when replacing the treatment tank, the structure of the treatment tank 1.2 is the same, sludge supply path 3, return path 5, sludge withdrawal path 4.
are symmetrically connected to the image processing tanks 1 and 2, respectively, so that the pumps Pl, P2, P3, valves MA1-MA3, MB1-
MB, by performing the operation opposite to that described above.

FIG. 5 shows another embodiment of the treatment tank 1.2 (again, only one of the tanks is shown), in which the same processing as in the first embodiment described above is carried out, but in this embodiment, , baffle 14
Since the prereactor 16 is partitioned, the inflowing sewage is not short-circuited and discharged, and bulking of sludge can be prevented. Further, if the aerated liquid mixture during continuous treatment is allowed to flow into the prereactor 16 of the treatment tank in which the precipitation treatment is performed, the precipitation effect is improved. Furthermore, processing tank 1,
Similarly to the first embodiment described above, the fixed weir 9 provided at 2 is such that the pulp of the discharge pipe is normally closed and no discharge is performed.

FIG. 6 uses a jet aerator as the air diffuser 7, and is preferably applied to each of the above-mentioned embodiments. Jet Airle - In the evening, a mixture of pressurized water and air is injected. Although it is common to use the same liquid inside the treatment tank 1.2 as this pressure water, in this embodiment, it is particularly preferable to use this for returning sludge in the event of an abnormality.

It is preferable to draw out the settled sludge in the treatment tanks 1 and 2 which are in the settling process and to supply this to the jet aerators in the treatment tanks 1 and 2 which are in the aeration process.

In addition, in this invention, the aeration process and the continuous aeration process include a process in which aeration is performed intermittently in order to promote escaping the room.

As described above, according to the present invention, even if the amount of sewage inflow exceeds the design value, the treatment process can be changed accordingly to ensure reliable sewage treatment.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal sectional view of an apparatus to which this invention is applied;
Fig. 2 is a schematic plan view of the processing tank, Fig. 3 is a schematic longitudinal cross-sectional view of the same, Fig. 4 is a procedural diagram of each step, Fig. 5 is a longitudinal cross-sectional view of another embodiment of the processing tank, FIG. 6 shows a longitudinal sectional view of the air diffuser. 1.2... treatment tank, 7... aeration device, 8... decanter. Patent Applicant Nishihara Environmental Health Research Institute Co., Ltd. Representative Patent Attorney 1) Hiroshi Sawa (2 others) Drawing 171τ (1 (no change in content) Figure 1 Figure 2 Figure 4 - 374j phantom) 4 Arrow 1 Ship Figure 6 Procedural Amendment (Method) % Formula % 1. Indication of the case Japanese Patent Application No. 59-29641 2. Name of the invention Sewage treatment method 3. Person making the amendment 5. Date of amendment order 6. Subject of amendment (1) Application (2) Specification (3) Drawing 7, content of amendment (2) Engraving of specification (no change in content) (3) Engraving of drawing (no change in content)

Claims (1)

[Claims] A sewage treatment method that is applied to batch-type activated sludge treatment tanks that normally process sewage by repeating the steps of aeration, precipitation, and discharge, in which multiple treatment tanks are installed, and the inflow of sewage exceeds a certain amount. In this case, at least one of the treatment tanks is made into a continuous aeration tank and at least one tank is made into a continuous settling tank, and the wastewater is allowed to flow into the continuous aeration tank and after the aeration treatment, flow into the continuous settling tank. A sewage treatment method characterized in that the sludge is subjected to precipitation treatment, the supernatant liquid is discharged, and the settled sludge is returned to the continuous aeration tank.