JPH0899094A - Waste water treatment apparatus - Google Patents

Abstract

PURPOSE: To provide a waste water treatment apparatus capable of withstanding the temporary introduction of waste water high in BOD concn., capable of easily performing maintenance and capable of always keeping treatment capacity high. CONSTITUTION: In waste water treatment due to an activated sludge method, at least three batchwise treatment tanks 10, 20, 30 capable of independently performing respective processes of preparatory aeration, main aeration and sedimentation and at least one sludge tank 40 storing activated sludge used in the batchwise treatment tanks are installed and the treatment processes in the respective batchwise treatment tanks are shifted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wastewater treatment equipment,
Specifically, it relates to a wastewater treatment device for purifying wastewater discharged from factories and the like by the activated sludge method.

[0002]

2. Description of the Related Art The activated sludge method has been widely adopted as a method for purifying various wastewater. FIG. 4 shows an example of a conventional wastewater treatment apparatus using the activated sludge method. Wastewater continuously discharged from the factory at a substantially constant flow rate is supplied to a preliminary aeration tank 1, a main aeration tank 2, and a precipitation tank 3. The continuous processing is carried out by.

Wastewater discharged from the factory in various BOD concentrations is first introduced into the preliminary aeration tank 1 through the pipe 1a so that the BOD concentrations are averaged and the preliminary aeration tank 1 is also introduced.
The air discharged from the aeration pipe 1b provided inside is aerated by oxygen or oxygen-enriched air, and the dissolved oxygen concentration is increased, and at the same time, BOD is treated to some extent.

Next, the waste water in the preliminary aeration tank 1 is introduced into the main aeration tank 2 via the pump 2a and the pipe 2b, and is purified by the activated sludge filled in the main aeration tank 2. Oxygen is supplied to the activated sludge by air or the like ejected from the aeration pipe 2c provided in the main aeration tank 2.

The waste water from the factory is directly fed to the main aeration tank 2
If the BOD concentration in the wastewater is temporarily high, the sludge in the part in contact with the high-concentration wastewater temporarily lacks oxygen, causing bulking, and such partial bulking is mainly aerated. The processing capacity is reduced by spreading to the whole tank 2. Therefore, as described above, the waste water is introduced into the preliminary aeration tank 1 to average the BOD concentration and then introduced into the main aeration tank 2.

Next, the wastewater in the main aeration tank 2 is introduced into the settling tank 3 together with the activated sludge by the pipe 3a for solid-liquid separation, and the activated sludge is settled and collected at the hopper-shaped bottom and the supernatant is collected at the upper part. Liquid (purified water) collects. The purified water in the upper part of the settling tank 3 overflows by the waste water continuously introduced from the main aeration tank 2 and is discharged to a river or reused.

On the other hand, the activated sludge collected at the bottom of the settling tank 3 is returned to the main aeration tank 2 via the pump 3b and the pipe 3c for reuse, but the amount of sludge increases with the wastewater treatment. The excess sludge is discarded via the valve 3d as needed.

[0008]

As described above, in the conventional wastewater treatment equipment, wastewater continuously discharged from a factory or the like at a substantially constant flow rate is treated as the preliminary aeration tank 1, the main aeration tank 2, and the precipitation tank. Three
However, the following inconveniences were encountered because they were successively introduced into each treatment tank and treated continuously.

First, since each processing tank is always operated with treated water, even if an abnormality such as a leak occurs in the processing tank, maintenance cannot be performed while continuing the operation. In addition, in the settling tank 3, in order to prevent the wastewater flowing from the main aeration tank 2 from mixing with the purified water that overflows the settling tank 3, a partition for introducing the wastewater from the main aeration tank 2 to the center of the settling tank 3 It is necessary to take measures such as providing a pipe 3e, and since such a special structure is required, the settling tank 3 itself becomes expensive.

Furthermore, while the overall processing status can be monitored during operation, the progress of processing in the main aeration tank 2 cannot be monitored. For this reason, since the activity of sludge cannot be monitored, sludge with high activity remains and sludge with low activity cannot be discarded, and sludge is deteriorated as a whole and the treatment capacity gradually decreases.

What is particularly problematic is that the time required for the wastewater to pass through each treatment tank, that is, the treatment time in each treatment tank is determined, so that the high-concentration wastewater flows into the preliminary aeration tank 1 and the preliminary aeration tank 1 If the average BOD concentration in the main aeration tank 2 becomes high, oxygen will be insufficient in the main aeration tank 2, and the main aeration tank 2 will be damaged by bulking or the like. In this case, the amount of oxygen supplied to the sludge is increased by increasing the amount of gas to be aerated and increasing the oxygen concentration, but this is not enough. The best treatment is to extend the treatment time in the main aeration tank 2. However, as mentioned above, the treatment time in the main aeration tank 2 is fixed, so that the wastewater treatment is not possible to recover the damage. Will continue. Therefore, even if the BOD concentration in the wastewater returns to a normal value thereafter, it takes a long time for the treatment capacity of the main aeration tank 2 to return to the normal value, and the treatment capacity of the wastewater treatment apparatus as a whole is reduced. Since it decreases over a long period of time, it is inevitable that the purified water will be discharged while the BOD concentration remains higher than the specified value, or that the drainage from the factory will be stopped.

[0012] Therefore, it is an object of the present invention to provide a wastewater treatment apparatus which can withstand the temporary introduction of wastewater having a high BOD concentration and which can solve the above-mentioned disadvantages.

[0013]

In order to achieve the above-mentioned object, the wastewater treatment equipment of the present invention independently performs wastewater treatment by the activated sludge method, that is, preaeration, main aeration, and precipitation. Is provided with at least three batch type treatment tanks and at least one sludge tank for storing the activated sludge used in the batch type treatment tank. It is characterized in that it is arranged in a stack in the upper and lower stages.

[0014]

[Operation] With the above configuration, wastewater treatment can be performed independently in each batch type treatment tank. Therefore, by appropriately shifting the treatment process in each batch type treatment tank, preliminary aeration, main aeration, Each step of precipitation can be performed continuously. In addition, since each batch type treatment tank performs treatment independently, it is possible to extend the main aeration time even when high-concentration wastewater needs to be treated. Since it can be monitored individually, the activity of sludge can be known.

Further, since the sludge tank for exchanging sludge with each batch type treatment tank is provided, the sludge in the batch type treatment tank can be extracted into the sludge tank to pre-aerate the waste water. The concentration can be lowered to some extent and averaged to prevent sludge bulking during the main aeration process. Also, during the series of steps, not only the drainage but also the sludge can be extracted to completely empty the batch type processing tank,
Maintenance can be performed easily.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail based on an embodiment shown in the drawings. FIG. 1 shows an embodiment of the wastewater treatment equipment of the present invention, which is constituted by three batch treatment tanks 10, 20, 30 of first to third and one sludge tank 40. Is.

In each of the processing tanks 10, 20, and 30, a drainage introduction valve 11, 21, 31 connected to a drainage supply system 51 from a drainage tank 50 and an aeration gas supply system 5 are provided.
Aeration gas introduction valves 12, 22, 32 connected to 2, sludge introduction valves 13, 23, 33 connected to a sludge supply system 41 from the sludge tank 40, and a sludge extraction system 42 returning sludge to the sludge tank 40. Sludge extraction valves 14, 24, 34 to be connected
And drainage valves 15, 25 connected to the purified water discharge system 53
And 35 are provided. Further, the sludge tank 40 is provided with an aeration gas supply means 43 for supplying oxygen for maintaining the activity of the sludge.

If the pressure of the waste water from the factory is high and the waste water can be directly supplied to each processing tank 10, 20, 30, the waste water tank 50 can be omitted. Further, exhaust valves 16, 26, 36 for exhausting the aerated gas are provided in each of the processing tanks 10, 20, 30.
If the airtightness of each of the processing tanks 10, 20, 30 is not high and the supplied gas naturally escapes, this can also be omitted. Further, air, oxygen-enriched air, or oxygen can be used as the aeration gas. Moreover, not only one sludge tank but also a plurality of sludge tanks may be provided, and the sludge tanks may be provided corresponding to each treatment tank.

The respective treatment tanks 10, 20, 30 perform wastewater treatment by sequentially performing the water injection step, the preliminary aeration step, the main aeration step, and the precipitation step. For example, in the first treatment tank 10, first, the drainage introduction valve 11 is opened to perform a water injection process of injecting a predetermined amount of wastewater from the drainage tank 50 into the tank, and then the aeration gas introduction valve 12 is opened to perform a preliminary operation. Perform the aeration process. Next, while the aeration gas introduction valve 12 is open, the pump 44 attached to the sludge tank 40 is activated, and the sludge introduction valve 13 is opened to introduce a predetermined amount of sludge into the tank to perform the main aeration process. After completing the predetermined aeration process, the aeration gas introduction valve 12 is closed to stop the introduction of the aeration gas, and the aeration gas is allowed to stand to perform the precipitation step. Then, when the purified water and the sludge are sufficiently separated, the sludge extraction valve 14 is opened, the pump 45 is activated, and the sludge deposited on the bottom of the tank is extracted and collected in the sludge tank 40. At this time, the excess sludge can be discarded by opening the valve 46 as needed. When the sludge removal is completed, the purified water discharge valve 15 is opened to discharge the purified water. This completes one cycle of wastewater treatment, returns to the water injection step again, and repeats the same step.

In this way, each processing tank 10, 20, 30
Performs a wastewater treatment by performing a water injection step, a preliminary aeration step, a main aeration step (including sludge introduction), and a precipitation step (including sludge extraction and purified water discharge), but each treatment tank 10, 20 , 30, the waste water treatment is continuously performed by sequentially shifting the steps.

That is, as shown in FIG. 2, when the first treatment tank 10 is in the stage of the water injection step, the second treatment tank 20
Is the standby stage, and the third treatment tank 30 performs the treatment steps from the preliminary aeration step to the main aeration step to the precipitation step, and the steps of water injection, treatment and precipitation are sequentially performed so as not to overlap in each treatment tank. Set to.

Next, an operation example of the apparatus of this embodiment is shown in FIG.
The description will be made in comparison with the conventional device shown in FIG. The apparatus of the present invention is basically different in processing method from the conventional apparatus and cannot be simply compared, but the apparatus of the same scale will be described.

First, the amount of drainage is set to 10 m ^{3 /} h, and the volume of each dedicated treatment tank in the conventional apparatus is set to 30 in the preliminary aeration tank 1.
m ^3, primary aeration tank 2 is 120 m ^3, when the settling tank 3 and 60 m ^3, from a 210 m ³ in a total volume of processing tanks 10, 20, 30 of the embodiment apparatus with each 70m ³ .

The treatment time of the waste water in the conventional apparatus is 3 hours for the preliminary aeration process from the relation between the waste water amount and the volume of each tank.
The main aeration step is 12 hours and the precipitation step is 6 hours, for a total of 21 hours. On the other hand, in the apparatus of the present embodiment, since the tank volume is 70 m ^3, it takes 7 hours for water injection, so this 7 hours is set as the basic time of one cycle, and the preliminary aeration process in each treatment tank is performed for 1 hour. The main aeration step is 4 hours and the precipitation step is 2 hours, and the total treatment time is 7 hours. That is, each step is set to one-third the time of the conventional apparatus, and the remaining seven hours of the twenty-one hours is set as the standby time.

In the present embodiment, the processing time for main aeration and the like is set to one third of that of the conventional apparatus. However, in the case of the apparatus of the present embodiment, not only is the tank volume smaller than that of the conventional apparatus, Since each treatment is performed in a batch system, each treatment can be sufficiently performed even if the treatment time is shorter than in the conventional case. For example, the solid-liquid separation effect is enhanced by performing the precipitation step in a stationary state,
Even if the time of the precipitation step is one-third that of the conventional method, the precipitation process can be sufficiently performed. Further, in the conventional main aeration tank, a large-sized main aeration tank having a large area is provided so that the wastewater having a predetermined BOD concentration continuously introduced from the preliminary aeration tank and the wastewater having the BOD concentration lowered by the aeration process are not mixed. Need
As a result, the main aeration process takes a long time, but in the device of the present invention, main aeration is performed in a treatment tank having a volume of about one-third that of the conventional apparatus, and there is no new inflow of waste water and there is no problem of mixing. Since the main aeration is carried out in BOD, it is possible to perform the BOD process without any problem even if the time of the main aeration process is reduced to one-third of that of the conventional case.

Each processing tank 10, 2 in the apparatus of this embodiment
As shown in FIG. 2, in each stage of 0 and 30, the first treatment tank 10 is the water injection stage, and the second treatment tank 20 is the first 7 hours.
Is a standby stage, and the third treatment tank 30 is a treatment stage consisting of preliminary aeration, main aeration, and precipitation. Hereinafter, every seven hours, the first treatment tank 10 changes from the treatment stage to the standby stage to the first stage. 2 The treatment tank 20 has a third stage from the water injection stage to the treatment stage.
The treatment tank 30 is switched from the standby stage to the water injection stage, and after 21 hours, one cycle ends and returns to the initial state.

In this way, the three processing tanks 10, 20, 3
For 0, the switching timing of each treatment stage is set so that one of them is the water injection stage, one is the treatment stage, and one is the standby stage. It is poured into the processing tank and continuously processed as in the conventional case. That is, in each batch type processing tank, each process of preliminary aeration, main aeration, and precipitation is performed independently, but since the timing of execution is different from other batch type processing tanks, the operation of each processing tank is batch Although it is a formula, when viewed as a whole device, continuous wastewater treatment is performed.

Further, as described above, since the sludge is extracted from the treatment tank after the precipitation step and collected in the sludge tank 40 and the purified water is discharged, the inside of the treatment tank can be completely emptied and the standby stage It is possible to easily perform maintenance such as cleaning and leak check by using the time. Further, since the wastewater does not flow in during the precipitation step, the treatment tank can be manufactured inexpensively without the need for a complicated structure such as the conventional precipitation tank.

Moreover, since wastewater treatment is performed independently in each treatment tank, the progress of each treatment can be monitored and the activity of sludge can be known. For example, FIG. 3 shows an example of changes in the BOD concentration in the main aeration process. When the sludge activity is high, the BOD in the wastewater is rapidly removed by the sludge as shown by the line A. As the activity decreases, the decrease in BOD as shown by line B decreases. Therefore, sludge in the tank after the precipitation process
When returning to 0, a certain ratio is not always returned, but sludge with high activity like line A returns the whole amount to sludge tank 40, and sludge with low activity like line B shows sludge tank 40. If the sludge with high activity is reused while maintaining the required amount of sludge as a whole by decreasing the amount of recovery to the valve 46 and increasing the amount of waste from the valve 46, the state of sludge will always be high. Can be maintained at. This cannot be done because the conventional apparatus cannot monitor the progress of processing.

In particular, when the wastewater having a high BOD concentration returns to the normal value after flowing for a certain period of time, in the apparatus of this embodiment,
Since the wastewater having a high BOD concentration only flows into one treatment tank and the other treatment tanks do not change, the other treatment tanks can perform the usual treatment. On the other hand, in the case of a treatment tank containing wastewater having a high BOD concentration, not only can the oxygen supply amount be increased, but the treatment time can be extended by utilizing the waiting time. Therefore, even if bulking occurs during the main aeration process due to the inflow of the wastewater having a high BOD concentration, the wastewater can be sufficiently recovered and a large effect that the wastewater treatment capacity is not deteriorated as a whole is exhibited.

In the above embodiment, three processing tanks are provided, but the processing tanks may be provided with four or more processing tanks for further processing. Moreover, in the case of the configuration of four or more units, if the wastewater with a high BOD concentration flows into one of the treatment tanks and the recovery cannot be achieved by the extension of the processing time using the waiting time, the non-recoverable processing tank is used. Detach,
If the amount of wastewater from factories is limited to some extent, the treatment can be continued in the remaining three or more treatment tanks.

Further, in the above embodiment, the processing tanks are arranged in a plane, but since the processing tanks of the present invention can be manufactured in the same shape, the processing tanks can be stacked and arranged in multiple stages. By arranging the treatment tanks in multiple layers, the installation area of the wastewater treatment equipment can be reduced.

[0033]

As described above, since the wastewater treatment equipment of the present invention comprises three or more batch type treatment tanks and at least one sludge tank, it is possible to shift the wastewater treatment steps. It is possible to continuously perform wastewater treatment as a whole while individually operating each batch type treatment tank. Moreover, since the precipitation step is performed in a stationary state,
It does not require a complicated structure like a conventional settling tank, it can be manufactured at low cost, and since the progress of processing in each processing tank can be monitored, the age of the sludge can be known and the activity of the sludge can be checked. It can be kept high and the throughput can always be kept high.

Moreover, even if the wastewater having a high BOD concentration flows for a certain period of time, it is possible to recover by extending the treatment time by using the waiting time without partially damaging the bulking and spreading it to the whole. Yes, there is no reduction in wastewater treatment capacity as a whole. Furthermore, by appropriately setting the operating time of each batch type processing tank, the inside of the processing tank can be completely emptied, so that the processing tank can be easily maintained.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a wastewater treatment device of the present invention.

FIG. 2 is a time chart showing an operation example of the wastewater treatment device of the present invention.

FIG. 3 is a diagram showing an example of changes in BOD concentration in the main aeration process.

FIG. 4 is a system diagram showing an example of a conventional wastewater treatment device.

[Explanation of symbols]

10, 20, 30 ... Batch type treatment tank, 40 ... Sludge tank, 4
1 ... Sludge supply system, 42 ... Sludge extraction system, 50 ... Drain tank, 51 ... Drainage supply system, 52 ... Aeration gas supply system

Claims (2)

[Claims] 1. At least three batch-type treatment tanks for independently performing wastewater treatment by the activated sludge method, and at least one sludge tank for exchanging activated sludge with the batch-type treatment tanks. Wastewater treatment equipment characterized by 2. The wastewater treatment equipment according to claim 1, wherein the batch type treatment tanks are arranged in a stack in upper and lower stages.