JP2020195974A - Sewage treatment apparatus - Google Patents

Abstract

To provide a sewage treatment apparatus capable of efficiently treating sewage by eliminating adverse effects of OH radicals on aerobic microorganisms while maintaining space efficiency.SOLUTION: A sewage treatment apparatus includes an inlet 6 for water to be treated containing sludge, a pump P1 which sucks and discharges water to be treated flowing in from the inlet 6, bubble generating means 3 which is directly connected to the downstream side of the discharge direction of the pump P1 and generates fine bubbles to activate aerobic microorganisms, an outlet 7 for water to be treated provided downstream of the bubble generating means, and a distribution time consumption passage 8 provided between the bubble generating means 3 and the outlet 7. The distribution time consumption passage 8 has a length which maintains the distribution time necessary to dissipate OH radicals in the process of the water to be treated distributing through the distribution time consumption passage 8.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sewage treatment apparatus for treating sewage containing sludge by aerobic microorganisms.

As an apparatus of this type, for example, there was an apparatus shown in FIG.
In the device shown in FIG. 4, the bubble generation tank 1 and the processing tank 2 are provided close to each other. The reason why both tanks 1 and 2 are provided close to each other in this way is to improve the space efficiency when installing these tanks 1 and 2.
Each of the tanks 1 and 2 as described above contains the water to be treated containing sludge. A circulation pump P1 for circulating the water to be treated in the tank 1 via the bubble generation means 3 is provided on the bubble generation tank 1 side, and the bubble generation tank 1 is provided on the downstream side in the discharge direction of the pump P1. A bubble generation means 3 provided inside is connected, and a fine bubble (hereinafter referred to as "FB") or an ultrafine bubble (hereinafter referred to as "UFB") is included in the bubble generation tank 1 from the bubble generation means 3. However, the water to be treated is discharged directly.

Further, the bubble generation tank 1 and the treatment tank 2 are directly connected by a supply pipe 4, and the supply pipe 4 is provided with a supply pump P2 for pumping the water to be treated from the bubble generation tank 1 to the treatment tank 2. ing.
Further, both tanks 1 and 2 are directly connected via a return pipe 5 different from the supply pipe 4. The return pipe 5 is provided with a return pump P3 for returning the water to be treated in the treatment tank 2 to the bubble generation tank 1.

The water to be treated in the bubble generation tank 1 circulates between the tank 1, the circulation pump P1 and the bubble generation means 3, and FB or UFB is supplied into the bubble generation tank 1 by this circulation. Therefore, oxygen is dissolved in the water to be treated in the bubble generation tank 1.
The water to be treated in which oxygen is dissolved in this way is sent to the treatment tank 2 by the action of the supply pump P2. When the sent water to be treated is allowed to stay in the treatment tank 2 for a certain period of time, aerobic microorganisms are activated in the treatment tank 2 and sludge is decomposed.
When the sludge is not sufficiently decomposed in the treatment tank 2, the water to be treated in the treatment tank 2 is returned to the bubble generation tank 1 via the return pipe 5.

The water to be treated returned to the bubble generation tank 1 as described above circulates through the circulation pump P1 and the bubble generation means 3, and FB or UFB is supplied into the bubble generation tank 1. Therefore, oxygen is dissolved again in the bubble generation tank 1.
The water to be treated in which oxygen is dissolved in this way is supplied to the treatment tank, activates aerobic microorganisms in the treatment tank 2, and contributes to the decomposition of sludge.

The bubble generation tank 1 and the processing tank 2 are separated as described above for the following reasons.
In the bubble generating means 3, FB or UFB is generated, but in the process of generating FB or UFB, many OH radicals are also generated at the same time. This OH radical damages aerobic microorganisms and significantly inhibits their activity. However, since OH radical is highly reactive, it is considered that it disappears immediately after its formation.
Therefore, by providing the bubble generation tank 1 and the processing tank 2 separately, it was expected that the OH radicals would disappear in the process of supplying the bubble generation tank 1 to the processing tank 2.
No particular literature search has been conducted.

In the above-mentioned conventional device, in consideration of space efficiency, the bubble generation tank 1 and the processing tank 2 are brought close to each other and directly connected to each other, but in such a device, the bubbles are discharged to the bubble generation tank 1. The OH radical remains and is supplied to the processing tank 2. Therefore, there has been a problem that aerobic microorganisms are damaged in the treatment tank 2 and the sludge decomposition efficiency is deteriorated.

On the other hand, if the distance between the bubble generation tank 1 and the treatment tank 2 is increased, the process of supplying the water to be treated from the bubble generation tank 1 to the treatment tank 2 can be lengthened, so that the amount of OH radicals can be reduced during that period. Can be considered. However, as the distance between the bubble generation tank 1 and the processing tank 2 increases, there arises a problem that the space efficiency when installing both the tanks 1 and 2 deteriorates.
That is, in the conventional apparatus, the elimination of OH radicals and the improvement of space efficiency have been in a trade-off relationship.
An object of the present invention is to provide a sewage treatment apparatus capable of efficient treatment by eliminating the adverse effects of OH radicals on aerobic microorganisms while maintaining space efficiency.

In order to solve the above-mentioned problems, the present inventor has made the following hypothesis.
It is said that the generated OH radicals disappear rapidly under normal circumstances, but it is hypothesized that they do not disappear immediately after formation and remain for some time.
If this hypothesis is correct, when the bubble generation tank 1 and the processing tank 2 are brought close to each other in the conventional apparatus, the OH radicals generated in the bubble generation tank 1 are supplied to the processing tank 2 while remaining. It will interfere with the activity of microorganisms.

In other words, if the OH radical generated at the same time as FB or UFB is eliminated by the time it reaches the treatment tank 2, the activity of the aerobic microorganism is not hindered. That is, if the water to be treated after a predetermined time has passed since the generation of OH radicals is supplied to the treatment tank 2, the treatment efficiency can be improved.

In order to substantiate the above hypothesis, an experiment was conducted using the apparatus of the present invention.
In this experiment, a circulation time consumption passage was provided in the path for sending the treatment target water discharged from the bubble generation means to the treatment tank, and the sludge decomposition degree in the treatment target water was measured using the length as a parameter. The result is as shown in the graph of FIG.
In the graph of FIG. 2, the horizontal axis shows the treatment time, and the vertical axis shows the normalized value obtained by dividing the total amount of nitrogen in the water to be treated by the initial value (measured value at the time of untreatment). The total amount of nitrogen is an index showing the degree of decomposition of organic matter in sludge, and becomes smaller as the decomposition progresses.

Further, the graphs (1), (2), (3), (4), and (5) in FIG. 2 are the measurement results when the circulation time consumption passage is lengthened in order in the apparatus of the present invention. Further, graph (6) is a measurement result by the conventional apparatus shown in FIG. 4 in which the bubble generation tank 1 and the processing tank 2 are brought close to each other.
From these results, in the case of the graphs (1) and (2) in which the circulation time consumption passage is relatively short, there is no great difference from the conventional device shown in the graph (6). However, in the cases of the graphs (3), (4), and (5) when the distribution time consumption passage is lengthened to some extent or more, it was found that the processing efficiency is higher than before.

For this reason, in a device having a long circulation time consumption passage, OH radicals disappear in the circulation time consumption passage. As a result, it can be inferred that the OH radical does not inhibit the activity of aerobic microorganisms in the treatment tank and the treatment efficiency is improved. That is, the above hypothesis that a certain amount of time is required for the OH radicals generated together with the fine bubbles to disappear has been demonstrated.
Based on this hypothesis, the following invention was completed.

According to the first invention, an inlet of water to be treated containing sludge, a pump for sucking and discharging the water to be treated flowing from this inlet, and an aerobic one are directly connected to the downstream side in the discharge direction of the pump. It is provided between a bubble generating means for generating fine bubbles for activating microorganisms, an outlet of water to be treated provided on the downstream side of the bubble generating means, and the bubble generating means and the outlet. , A circulation time consumption passage that is directly connected to the bubble generating means and consumes the circulation time of the water to be treated is provided.
The circulation time consumption passage is characterized in that the water to be treated has a length that maintains the circulation time required to eliminate OH radicals in the process of flowing through the circulation time consumption passage.
The circulation time consumption passage is the entire process from the bubble generation means to the outlet.
The annihilation of the OH radical includes not only complete annihilation but also annihilation to a range that does not adversely affect the activity of aerobic microorganisms.

Further, the fine bubbles in the present invention are bubbles having a size capable of remaining in the water to be treated for a long time and dissolving oxygen. For example, when the diameter of the bubble is large, the buoyancy in the water to be treated becomes large and the oxygen in the bubble is released from the water surface to the atmosphere in a short time. Therefore, even if a bubble having a large diameter is generated, the amount of dissolved oxygen in the water to be treated cannot be maintained. Therefore, bubbles having a size in which oxygen cannot be dissolved in the water to be treated are excluded from the fine bubbles.

The second invention is characterized in that the distribution time is 2.1 seconds or more. That is, the OH radical disappears in a circulation time of 2.1 seconds or more.

In the third invention, the outlet is connected to a tank, and the water to be treated in which oxygen is dissolved is supplied from the outlet to the tank, and the total amount of nitrogen in the tank is equal to or less than the reference value. The reference length X of the passage is experimentally specified, and the time required to eliminate OH radicals using this specified reference length X T = S · X / Q (where S is the passage cross-sectional area and Q is the unit. (Distribution amount per hour) was calculated, and the required length x = TQ / S of the distribution time consumption passage was obtained by setting the calculated required time T as a constant.

The fourth invention is characterized in that a cooling means for cooling the water to be treated is added.
The cooling means may be provided in the circulation passage of the water to be treated, or may be connected to a tank or the like separately from the circulation passage.

According to the present invention, OH radicals generated together with fine bubbles by the bubble generation means can be extinguished in the process of passing through the flow time consumption passage.
Therefore, OH radicals are hardly contained in the water to be treated that flows out from the outlet after passing through the circulation time consumption passage. Therefore, if the outlet is connected to the treatment tank, the activity of the aerobic microorganism can be maintained by eliminating the damage caused by the OH radical to the aerobic microorganism in the treatment tank. As a result, the purification function is fully exhibited.

Further, since fine bubbles are generated between the inlet and outlet of the water to be treated and OH radicals can be reduced or eliminated in the bubbles, unlike the conventional generation of fine bubbles in the tank. Bubble generation tank can be eliminated. Since the bubble generation tank is not required in this way, space efficiency is improved.
Furthermore, the pump that connects the bubble generation tank and the processing tank is no longer required, and the device configuration can be simplified.

In the second invention, since the circulation time of the water to be treated passing through the circulation time consumption passage is maintained for 2 seconds or more, the OH radicals generated by the bubble generation means can be extinguished during that time. Therefore, OH radicals do not flow out from the outlet.

According to the third invention, the required time T can be specified by experimentally obtaining the reference length X of the circulation time consumption passage. Based on this required time T, it is possible to obtain the required length of the distribution time consumption passage when the device conditions change.

According to the fourth invention, even if the water to be treated becomes hot in the process of passing through the bubble generating means, it can be cooled, so that the water to be treated can be kept at an appropriate temperature for aerobic microorganisms. For example, it is said that the optimum temperature at which aerobic microorganisms are most activated is about 30 ° C to 40 ° C.

It is a conceptual diagram of the processing apparatus of 1st Embodiment. This is an experimental result for confirming the effect of the present invention, and is a graph showing a change in the total amount of nitrogen in the water to be treated with the length of the circulation time consumption passage as a parameter. It is a conceptual diagram of the processing apparatus of 2nd Embodiment. It is a conceptual diagram of a conventional processing apparatus.

The first embodiment shown in FIG. 1 is characterized in that the conventional bubble generation tank is not required and the purification function can be fulfilled only by the processing tank T.
Then, the sewage treatment device A according to the present invention is provided outside the treatment tank T so that the water to be treated is circulated through the sewage treatment device A.
The sewage treatment device A constitutes a distribution path for the water to be treated between the inflow port 6 and the outflow port 7. A circulation pump P1, a bubble generating means 3, and a distribution time consumption passage 8 are provided between the inflow port 6 and the outflow port 7 in this order from the inflow port 6 side. The distribution time consumption passage 8 refers to the total length from the bubble generation means 3 to the outlet 7.

The circulation pump P1 sucks the water to be treated in the treatment tank T and supplies it to the bubble generation means 3. The bubble generation means 3 passes the water to be treated pumped from the circulation pump P1 and generates fine bubbles in the water to be treated during the passing process.
The bubble generating means 3 includes, for example, a pore blowing stirring method, a pressure melting method, a swirling liquid flow method, a shearing method, and the like, but any method may be used in this embodiment.
Further, in the first embodiment, the bubble generation means 3 as described above is used to generate FB which is a fine bubble or UFB which is an ultrafine bubble as fine bubbles. Usually, FB means a bubble having a diameter of 100 [μm] or less, and UFB means a bubble having a diameter of 1 [μm] or less. Since such fine bubbles have a small buoyancy, they can stay in the water to be treated and dissolve oxygen. It should be noted that which bubble should be selected may be determined according to the quality and quantity of the water to be treated.

The circulation time consumption passage 8 connected to the downstream side of the bubble generation means 3 as described above is provided with a spiral portion 8a to secure the passage length. Therefore, a longer distribution time can be secured by passing through the time-consuming passage 8 provided with such a spiral portion 8a than by passing through a pipe on a straight line.
Then, the water to be treated that has passed through the circulation time consumption passage 8 flows out from the outflow port 7. Therefore, if the inflow port 6 and the outflow port 7 are provided in the treatment tank T, the water to be treated in the treatment tank T circulates through the device A.

Now, if the inflow port 6 and the outflow port 7 are provided in the processing tank T as shown in the figure and the circulation pump P1 is driven, the bubble generation means 3 passes through the water to be processed in the processing tank T as described above. UFB is generated in the process of pumping.
When UFB is generated in the water to be treated in this way, OH radicals are also generated at the same time. However, in this first embodiment, since the water to be treated consumes a sufficient amount of time in the process of passing through the circulation time consumption passage 8, the OH radicals disappear and the OH radicals are not supplied to the treatment tank T. That is, the treatment target water containing only dissolved oxygen is supplied to the treatment tank T.

Further, FIG. 2 shows the result of an experiment on the length of the distribution time consumption passage 8.
The experimental conditions are as follows.
[Processing device]
As shown in FIG. 1, the inflow port 6 and the outflow port 7 are provided in the water to be treated in the treatment tank T, and the lengths of the circulation time consumption passage 8 are set to 3 [m], 4 [m], 5 [. Five sewage treatment devices A with m], 6 [m], and 10 [m] and a conventional device with the supply pipe 4 set to 1 [m] were used as experimental devices. The inner diameters of the circulation time consumption passage 8 and the supply pipe 4 were all the same, 20 [mm].

[Water to be treated and microorganisms]
The water to be treated used in this experiment was seawater 30 [L] collected from the quay of Funabashi fishing port in Chiba prefecture. About 1 [kg] of sedimentary sludge was contained in the seawater 30 [L]. Aerobic microorganisms in the sludge were used for the decomposition treatment of the sludge, and no microorganisms were added during the experiment.

[Bubble generation means]
In this experiment, the same bubble generating means 3 was used in all the experimental devices. In this bubble generation device 3, UFB is generated.
Further, the discharge amount of the circulation pump P1 connected to the bubble generation means 3 was also set to 40 [L / min], which is the same.

[Water temperature to be treated]
The temperature of the water to be treated in the treatment tank T was controlled so as to be around 30 ° C. at which aerobic microorganisms were most activated. However, frictional heat is generated when the water to be treated passes through the bubble generating means 3, and the temperature of the water to be treated rises. Therefore, the water to be treated was cooled by a cooler (not shown) in this embodiment. The cooler takes out a part of the water to be treated in the treatment tank T, cools it, and then returns it to the treatment tank T.

The water to be treated in the treatment tank T was sampled every 12 hours or 24 hours from the start of driving the circulation pump P1 of the sewage treatment device A as described above, and the sampling was completed after 120 hours had elapsed. The total amount of nitrogen [mg / L] in the water to be treated sampled in this way was measured, and the measurement results are shown in graphs (1) to (5) of FIG.
Note that graph (6) is a measurement result of a conventional device in which conditions other than the device structure are the same as those of the device of this embodiment.
In these graphs, the horizontal axis shows the treatment time, and the vertical axis shows the total nitrogen [-] in the water to be treated. This total nitrogen [−] is normalized by dividing the measured total nitrogen amount [mg / L] by the initial value (measured value at the time of untreatment). The total amount of nitrogen is an index showing the degree of decomposition of organic matter in sludge, and is a value that becomes smaller as the decomposition progresses. A zero total nitrogen [-] indicates that the water to be treated does not contain nitrogen.

The graphs (1) to (5) show the measurement results when the lengths of the circulation time consumption passages 8 are 3 [m], 4 [m], 5 [m], 6 [m], and 10 [m], respectively. Is shown.
From these results, when the circulation time consumption passage 8 is as short as 3 [m] and 4 [m] as shown in the graphs (1) and (2), the processing time is compared with the case of the conventional apparatus. However, it was found that the value of total nitrogen [-] at 120 hours was almost unchanged.
From this, when the lengths of the circulation time consumption passage 8 are 3 [m] and 4 [m], the OH radicals are not completely extinguished at the circulation length, and the residual OH radicals flow into the processing tank T. It can be inferred that it has been done.
From these facts, it is clear that the OH radical does not disappear immediately after the generation, and the above-mentioned inventor's hypothesis has been proved.

On the other hand, when the circulation time consumption passage 8 is lengthened to 5 [m], 6 [m], 10 [m], as shown in graphs (3), (4), and (5), the conventional device The value of total nitrogen [-] is not smaller than in the case of. In particular, the value of total nitrogen [-] is zero at 5 [m] and 10 [m], which means that the water to be treated flowing out from the outlet 7 has almost no OH radicals or is completely eliminated. it seems to do.
This is because if OH radicals continue to flow out from the outlet 7 into the treatment tank T, the activity of aerobic microorganisms in the treatment tank T is lost, and it is considered that the total nitrogen [−] does not become zero.

However, if the amount of OH radicals flowing out from the outlet 7 is very small, it can be easily imagined that it does not affect the activity of aerobic microorganisms. Therefore, the annihilation of OH radicals in the present invention includes not only complete annihilation but also a range that does not adversely affect the activity of aerobic microorganisms.
The present invention is characterized in that the disappearance of OH radicals flowing out from the outlet 7 is estimated based on the total nitrogen [−]. Therefore, in the present invention, not only when the total nitrogen [-] becomes completely zero, but also in the range where the effectiveness of the sludge decomposition degree is recognized, for example, the circulation time consumption passage 8 in the graph of FIG. 2 is 6 [m. ], It is estimated that the OH radicals are almost completely or completely eliminated.

Further, although not shown in FIG. 2, the same experiment as above was carried out for an apparatus in which the length of the distribution time consumption passage 8 was 4.5 [m]. In this experiment, the OH radical disappears in the circulation time consumption passage 8 having a length between 4 [m], which has no difference in processing effect from the conventional device, and 5 [m], which has a sufficient effect. It is for confirming whether or not.
As a result, it was confirmed that the total nitrogen [−] in the treatment tank T became zero 120 hours after the start of continuous operation of the sewage treatment device having the passage 8 of 4.5 [m].

As described above, in this embodiment, the experiment in which the length of the circulation time consumption passage 8 is changed is repeated, and the length of the circulation time consumption passage 8 in which the total amount of nitrogen becomes zero is used as the reference length X. The required time T for extinguishing the OH radical was calculated by the following equation 1.
T = S ・ X / Q ・ ・ ・ (1)
In the above formula (1), S is the passage cross-sectional area, and Q is the amount of water to be treated per unit time.

In the above experiment, the inner diameter of the circulation time consumption passage 8 was set to 20 [mm] and Q was set to 40 [L / min]. Therefore, this condition and the reference length X = 4.5 of the circulation time consumption passage 8 [M] was applied to the above formula (1) to determine the required time T for extinguishing OH radicals. As a result, T = 2.1 [seconds].
From this result, it became clear that the OH radical does not disappear immediately after its formation, but requires a certain period of time.

Further, if the required time T can be specified in the above equation (1), the following equation (2) can be obtained with the required time T as a constant.
x = TQ / S ... (2)
From such an equation (2), even if the passage cross-sectional area S and the circulation amount Q per unit time of the water to be treated change significantly, the required length x of the circulation time consumption passage 8 for extinguishing OH radicals. Can be sought.

It is considered that the longer the length of the circulation time consumption passage 8, the more surely the OH radicals can be extinguished.
On the other hand, if the circulation time consumption passage 8 is too long, the pressure loss in the circulation path becomes large, a large amount of energy is required for water supply, and the circulation pump also has to be enlarged. Therefore, it is not realistic to lengthen the distribution time consumption passage 8 excessively.
Further, even when the appropriate length of the circulation time consumption passage 8 is experimentally determined, if the total nitrogen [-] does not become zero as a result of performing the treatment with the required length x obtained by the calculation, The experiment can be repeated with a length longer than the required length x (x + α) to determine an appropriate required length suitable for the actual situation. In this case, since the required length x is obtained in advance by calculation, an efficient experiment can be performed as compared with the case where the length of the distribution time consumption passage 8 is changed unnecessarily.

In the above, the length 4.5 [m] of the circulation time consumption passage 8 in which the total nitrogen [−] becomes zero after the treatment time of the sewage treatment experiment is 120 hours is defined as the reference length X of the present invention. .. However, the total nitrogen [-] corresponding to the reference length X of the present invention specified experimentally is not limited to zero. If the value of total nitrogen [-] after the elapse of a predetermined time is sufficiently smaller than the value of total nitrogen [-] when the conventional apparatus is used, the OH radical disappears in the passage time of the circulation time consumption passage 8. You may guess. A value sufficiently smaller than the total nitrogen [−] when the above-mentioned conventional device is used is the reference value of the total nitrogen amount of the present invention.

As described above, in the processing apparatus of the first embodiment, the OH radicals generated by the bubble generating means 3 can be extinguished before flowing out from the outlet 7. Therefore, if the outlet 7 is made to face the inside of the treatment tank, the damage of OH radicals to aerobic microorganisms can be suppressed and the treatment efficiency can be maintained.
Further, the sewage treatment device A provided outside the treatment tank T functions as a conventional bubble generation tank. Therefore, the bubble generation tank becomes unnecessary and space efficiency is improved.

Further, if the inflow port 6 and the outflow port 7 are located not in the treatment tank T but in a pond containing sludge, the pond functions as the treatment tank T, and thus aerobic microorganisms as in the above embodiment. Can be activated to treat sludge-containing water to be treated.
Further, the inflow port 6 may be connected to a water channel such as a river, and the outflow port 7 may be connected to a processing tank or the like. In this case, if the water to be treated in the treatment tank is returned to the river, it is useful for purifying the river.

In the second embodiment shown in FIG. 3, two sewage treatment devices A1 and A2 are provided, and these devices A1 and A2 are connected in series.
However, each of the sewage treatment devices A1 and A2 is the same as the sewage treatment device A of the first embodiment by itself. The components having the same reference numerals as those in FIG. 1 in FIG. 3 are the same as those in the first embodiment.

By connecting the sewage treatment devices A1 and A2 in series in this way, the amount of dissolved oxygen in the water to be treated can be increased each time the sewage treatment devices A1 and A2 are passed. The larger the amount of dissolved oxygen, the more aerobic microorganisms can be activated.
Reference numeral T1 in FIG. 3 is a primary tank containing water to be treated, T2 is a secondary tank connected to the primary tank T1 via the sewage treatment device A1, and T3 is a secondary tank via the sewage treatment device A2. It is a tertiary tank connected to T2.

Also in this second embodiment, UFB can be generated in the sewage treatment devices A1 and A2 provided outside the 1st to 3rd tanks T1, T2 and T3, and the generated OH radicals can be reduced or eliminated. .. Therefore, efficient treatment of the water to be treated can be realized without damaging the microorganisms by OH radicals, and the conventional bubble generation tank becomes unnecessary, and space efficiency can be improved.
Further, if the inflow port 6 of the most upstream sewage treatment device A1 is provided in a pond or river where sludge is accumulated without providing the primary tank T1, the water of the pond or river can be used as a secondary tank. It can be guided to T2 and the tertiary tank T3 for processing.

In FIG. 3, the sewage treatment devices A1 and A2 are connected in series via the secondary tank T2, but the secondary tanks T2 may be omitted and the devices A1 and A2 may be directly connected in series.
Further, the number of sewage treatment devices connected in series is not limited to two, and the larger the number, the larger the amount of dissolved oxygen in the water to be treated that flows out from the most downstream outlet 7. Then, the degree of purification of the water to be treated in the tank provided with the most downstream outlet 7 is increased, and a high degree of purification can be realized.
However, there is a saturation value in the amount of dissolved oxygen in the water to be treated. Therefore, once the saturated dissolved oxygen amount is reached, there is no point in connecting a sewage treatment device any more.

In the first and second embodiments, the cooling means for maintaining the temperature of the water to be treated at an appropriate temperature for aerobic microorganisms may be provided not only in the tank but also anywhere in the distribution process of the water to be treated. .. For example, if a cooling means for cooling the circulation time consumption passage 8 is provided, even if heat is generated by the bubble generation means 3, the water to be treated flowing out from the outlet 7 can be kept at an appropriate temperature.

Further, the distribution time consumption passage 8 of the first and second embodiments is configured as long as the required distribution time can be secured, such as a pipe provided with a spiral portion 8a, a meandering pipe, and a flexible hose. May be good. For example, if the circulation time consumption passage 8 is configured with a flexible hose, the degree of freedom in the installation position of the sewage treatment device is increased, and the space efficiency can be further improved.

The present invention is most suitable for a sewage treatment apparatus using aerobic microorganisms.

P1 Circulation pump 3 Bubble generation means 6 Inflow port 7 Outlet 8 Circulation time consumption passage A, A1, A2 Sewage treatment equipment

Claims (4)

The inlet of the water to be treated containing sludge and
A pump that sucks and discharges the water to be treated that flows in from this inflow port,
A bubble generating means that is directly connected to the downstream side of the discharge direction of this pump and generates fine bubbles for activating aerobic microorganisms.
The outlet of the water to be treated provided on the downstream side of this bubble generation means,
It is provided between the bubble generating means and the outlet, and is provided with a circulation time consumption passage which is directly connected to the bubble generating means and consumes the circulation time of the water to be treated.
The above distribution time consumption passage is
A sewage treatment apparatus having a length that maintains the circulation time required for extinguishing OH radicals in the process in which the water to be treated flows through the circulation time consumption passage. The sewage treatment apparatus according to claim 1, wherein the distribution time is 2.1 seconds or more. The reference length X of the distribution time consumption passage where the outlet is connected to the tank, the water to be treated in which oxygen is dissolved is supplied from the outlet to the tank, and the total amount of nitrogen in the tank becomes equal to or less than the reference value. Is experimentally specified, and the required time T = S · X / Q for extinguishing OH radicals using this specified reference length X (where S is the cross-sectional area of the passage and Q is the amount of circulation per unit time). The sewage treatment apparatus according to claim 1, wherein the required length x = TQ / S of the distribution time consumption passage is obtained by calculating the required time T and using the calculated required time T as a constant. The sewage treatment apparatus according to any one of claims 1 to 3, to which a cooling means for cooling the water to be treated is added.

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