JP6866918B2 - Aerobic biological treatment equipment - Google Patents

Description

The present invention relates to an aerobic biological treatment apparatus for organic wastewater.

Since aerobic organism treatment methods are inexpensive, they are often used as treatment methods for organic wastewater. In this method, it is necessary to dissolve oxygen in the water to be treated, and aeration is usually performed by an air diffuser.

Aeration with an air diffuser has a low dissolution efficiency of about 5 to 20%. In addition, it is necessary to aerate at a pressure higher than the water pressure applied to the water depth where the air diffuser is installed, and a large amount of air is blown at a high pressure, so that the power cost of the blower is high. Usually, more than two-thirds of the electricity costs in aerobic biotreatment are used for oxygen dissolution.

A membrane aeration bioreactor (MABR) that performs aerobic biological treatment by attaching a biofilm to the outside of the hollow fiber membrane and supplying oxygen from the inside can dissolve oxygen without generating bubbles. In MABR, since it is sufficient to ventilate air having a pressure lower than the water pressure applied to the water depth, the required pressure of the blower is low and the oxygen dissolution efficiency is high.

Japanese Unexamined Patent Publication No. 2006-87310

In MABR, condensed water is generated inside the oxygen dissolution membrane due to the permeation of water vapor from the reaction tank and the condensation of water vapor in the ventilation gas, and the gas flow path and a part of the hollow fiber membrane are blocked, resulting in a decrease in ventilation efficiency. There was a problem of doing.

That is, the amount of air ventilated through the hollow fiber membrane of MABR is small, and the air flow velocity in the hollow fiber is extremely slow at 1 mm / sec or less in the normally used hollow fiber oxygen-dissolved membrane. Therefore, even if a small amount of condensed water enters some of the hollow fibers, a large pressure difference is generated with the other hollow fibers, and the gas flow is stopped. When a large amount of condensed water accumulates in the header pipe, a large amount of condensed water enters the hollow fiber membrane, and many hollow fiber membranes cannot be ventilated, resulting in a large decrease in oxygen dissolution efficiency.

In Patent Document 1, a large number of hollow fiber membranes are arranged in the vertical direction, and air is supplied to each hollow fiber membrane from below by a compressor. If the MABR of Patent Document 1 attempts to discharge condensed water to the outside of the hollow fiber membrane by air pressure, a compressor having a pressure higher than the water pressure of the reaction tank is required and the power consumption is extremely large. Become.

An object of the present invention is to provide an aerobic biological treatment apparatus capable of easily discharging condensed water from the oxygen dissolution membrane and maintaining a high oxygen dissolution efficiency for a long period of time.

The aerobic biological treatment apparatus of the present invention comprises a reaction vessel, an oxygen dissolution membrane module installed in the reaction vessel so that the ventilation direction is in the vertical direction, and oxygen for supplying oxygen-containing gas to the oxygen dissolution membrane module. It is provided with a gas-containing gas supply means, an exhaust gas pipe for discharging exhaust gas from the oxygen dissolution film module to the outside of the tank, and a drainage pipe for discharging condensed water from the oxygen dissolution film module to the outside of the reaction tank.

In one aspect of the present invention, the condensed water is discharged to a position lower than the lower end of the oxygen dissolution membrane module (when a plurality of modules are used, it is lower than the lowest one among the lower ends of each module) and discharged from the oxygen dissolution membrane module. It is provided so that the condensed water is discharged to the outside of the tank.

In one aspect of the present invention, the drainage pipe is provided so as to have a vertical downward direction or a downward slope.

In one aspect of the present invention, the inner diameter of the drainage pipe is 50 mm or less, and the end thereof is arranged at a position higher than the upper end of the oxygen dissolution membrane module.

In one aspect of the present invention, a tank that receives the condensed water flowing out of the drainage pipe and a pump that sends the water in the tank to the reaction tank are provided.

In one aspect of the present invention, the drainage pipe is provided with a valve.

In one aspect of the invention, the oxygen dissolution membrane module comprises a non-porous oxygen dissolution membrane.

In one aspect of the invention, the oxygen-dissolved membrane is hydrophobic.

In one aspect of the present invention, the reaction vessel is filled with a fluidized bed carrier.

In the aerobic biological treatment apparatus of the present invention, the oxygen-dissolved membrane module is ventilated in the vertical direction, and the condensed water of the oxygen-dissolved membrane module is discharged to the outside of the reaction vessel via the drain pipe, so that the condensed water is discharged from the oxygen-dissolved membrane. It is quickly discharged to the outside of the reaction vessel. Therefore, the oxygen dissolution efficiency of the oxygen dissolution membrane can always be maintained high.

It is a vertical sectional view of the biological processing apparatus which concerns on embodiment. (A) is a side view of the oxygen dissolution membrane unit, and (b) is a perspective view of the oxygen dissolution membrane unit. It is a graph which shows the experimental result. It is a vertical sectional view of the biological processing apparatus which concerns on another embodiment. It is a block diagram of the oxygen dissolution membrane unit of FIG. It is a vertical sectional view of the biological treatment apparatus which concerns on still another Embodiment. It is a block diagram of the oxygen dissolution membrane unit of FIG.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of the aerobic organism treatment apparatus 1 according to the embodiment. The aerobic biological treatment apparatus 1 is provided on a water permeable plate 3 made of a reaction tank (tank body) 2, a perforated plate such as a punching plate horizontally installed under the reaction tank 2, and an upper side of the water permeable plate 3. A flow formed by filling the formed large-diameter particle layer 4, the small-diameter particle layer 5 formed on the upper side of the large-diameter particle layer 4, and the biological attachment carrier such as powdered and granular activated charcoal on the upper side of the small-diameter particle layer 5. The floor F, the oxygen dissolving membrane module 6 in which at least a part is arranged in the fluidized floor F when unfolded, the receiving chamber 7 formed under the water permeable plate 3, and the raw water in the receiving chamber 7. It has a raw water spray pipe 8 for supplying the raw water, and a cleaning pipe 9 and the like for supplying gas or the like for backwashing when cleaning the packed bed. A trough 10 and an outlet 11 for allowing the treated water to flow out are provided in the upper part of the reaction tank 2. The trough 10 forms an annular flow path along the inner wall of the tank.

In FIG. 1, the reaction vessel is filled with a fluidized bed carrier so that the adhesion of the biofilm to the surface of the oxygen dissolution film is suppressed by the shearing force due to the flow of the carrier so that most of the biofilm adheres to the fluidized bed carrier. At this time, the oxygen-dissolving membrane is used only for the purpose of supplying oxygen. On the other hand, although not shown, when the reaction vessel is not filled with the fluidized bed carrier, the oxygen-dissolved membrane acts as a MABR, that is, the biological membrane adheres to the surface of the oxygen-dissolved membrane and dissolves and supplies from the primary side of the oxygen-dissolved membrane. The oxygen produced is consumed by the biological membrane on the secondary side, and aerobic biological treatment is performed.

In FIG. 1, a non-porous (non-porous) oxygen-dissolving membrane is used as the oxygen-dissolving membrane, oxygen-containing gas is ventilated from the outside of the tank to the primary side of the oxygen-dissolving membrane through a pipe, and exhaust is discharged to the outside of the tank through the pipe. It is configured to do. Therefore, the oxygen-containing gas is aerated through the oxygen-dissolving membrane at a low pressure, passes between the constituent atoms of the oxygen-dissolving membrane as oxygen molecules (dissolves in the membrane), and is brought into contact with the water to be treated as oxygen molecules (water). (Since it dissolves directly in the gas, no bubbles are generated), so to speak, the treatment using the mechanism of molecular diffusion by the concentration gradient is performed, so that the air diffusion by the air diffuser or the like becomes unnecessary as in the conventional case.

Further, it is preferable to use a hydrophobic material as the oxygen dissolving membrane because it is difficult for water to infiltrate into the membrane, but even if it is hydrophobic, a small amount of water infiltration is unavoidable, so the use of the present invention is preferable.

FIG. 2 shows an example of the oxygen dissolution membrane module 6 according to the embodiment of FIG. The oxygen-dissolving membrane module 6 uses a hollow fiber membrane 22 as the oxygen-dissolving membrane. In this embodiment, the hollow fiber membranes 22 are arranged in the vertical direction, the upper end of each hollow fiber membrane 22 is connected to the upper header 20, and the lower end is connected to the lower header 21. The inside of the hollow fiber membrane 22 communicates with the upper header 20 and the lower header 21, respectively. Each header 20 and 21 has a hollow tubular shape. Even when a flat membrane or a spiral membrane is used, they are arranged so that the ventilation direction is in the vertical direction.

As shown in FIG. 2B, a plurality of units composed of a pair of headers 20 and 21 and a hollow fiber membrane 22 are arranged in parallel. As shown in FIG. 2A, it is preferable that the upper manifold 23 is connected to the upper part of each upper header 20 via a pipe, and the lower manifold 24 is connected to the lower part of each lower header 21 via a pipe. In the case of the embodiment of FIG. 1, the oxygen-containing gas is supplied to the upper part of the oxygen-dissolving membrane module 6 and discharged from the lower part of the oxygen-dissolving membrane module 6. Oxygen-containing gas such as air flows from the upper header 20 through the hollow fiber membrane 22 to the lower header 21, and during this time, oxygen permeates the hollow fiber membrane 22 and dissolves in water in the reaction tank 2.

The headers 20, 21 and the manifolds 23, 24 may be provided to have a running water gradient. The oxygen dissolution membrane module 6 may be installed in multiple stages in the upper and lower stages.

In the embodiment of FIG. 1, in order to supply air to the oxygen dissolution membrane module 6, a blower 26 and an air supply pipe 27 for air supply are provided (which constitutes an oxygen-containing gas supply means). The air supply pipe 27 is connected to the upper manifold 23. A relay pipe 28 for exhaust gas is connected to the lower manifold 24. The relay pipe 28 is connected to the discharge pipe 29. The discharge pipe 29 is provided so as to have a downward slope (including vertically downward), and extends to the outside of the reaction tank 2. Although the discharge pipe 29 is pulled out to the side of the reaction tank 2 in FIG. 1, it may be pulled out downward from the bottom of the reaction tank 2.

As shown in FIG. 1, the rest of the oxygen-containing gas that was not dissolved in the oxygen dissolution film is exhausted to the outside of the tank through the discharge pipe 29, and the end thereof is the lower end of the oxygen dissolution film module (in the lower end of each module when there are a plurality of modules). Since it is arranged so as to be lower than the lowermost one), if the exhaust contains condensed water, the condensed water flows out to the tank 32 installed below the discharge pipe 29. The water in the tank 32 can also be sent to the reaction tank 2 by the pump 33 and the pipe 34.

In the case of the above configuration, the discharge pipe 29 serves both as an exhaust gas pipe for discharging the exhaust gas to the outside of the tank and a drainage pipe for discharging the condensed water to the outside of the tank. An exhaust gas pipe 30 that branches and discharges the exhaust gas to the outside of the tank may be separately provided. In this case, since the condensed water is discharged through the discharge pipe 29, the exhaust gas pipe 30 separately provided by branching can be arranged at a position where the exhaust portion at the end thereof is higher than the lower end of the oxygen dissolution film module. It is preferable that the piping does not have a downward slope and is configured only with an upward slope or a vertical upward direction so as to prevent the accumulation of water. Further, at this time, a valve A may be provided on the downstream side of the branch point of the discharge pipe 29 with the exhaust gas pipe 30, and the condensed water may flow out to the tank 32 by opening the valve A. Further, a valve B may be provided in the exhaust gas pipe 30, and the valve A may be closed and the valve B may be opened during normal ventilation, and the valve A may be opened and the valve B may be closed when the condensed water is discharged.

The valve may be either an automatic valve or a manual valve. The valve for discharging the condensed water may be opened continuously or intermittently. In the case of the intermittent type, it changes due to temperature change and humidity change, but in normal operation, once a day to once every 30 days (at most once a day, at least once a month, ten times a month) Seconds), preferably once a day to once every 15 days, drain by opening the valve.

In the aerobic biological treatment apparatus 1 configured in this way, the raw water is introduced into the receiving chamber 7 through the spray pipe 8 and is flowed upward through the water permeation plate 3 and the large-diameter and small-diameter particle layers 4 and 5, and the SS is generated. After being filtered, it is transiently upwardly distributed in the fluidized bed F of the powdered activated carbon adhering to the biofilm, undergoes a biological reaction, and is taken out as treated water from the upper clarification region through the trough 10 and the outlet 11.

The oxygen-containing gas such as air supplied from the air supply pipe 27 flows downward through the oxygen dissolution film module 6 and then flows out from the lower end position of the oxygen dissolution module 6 via the lower header 21 and the lower manifold 24. , Exhaust air is discharged into the atmosphere from the exhaust pipe 29 (or from the exhaust gas pipe 30 when the exhaust gas pipe 30 is provided). The condensed water flows out to the tank 32 through the discharge pipe 29.

FIGS. 4 and 5 show another embodiment. The condensed water may stay in the lower header 21 and the lower manifold 24, but since the condensed water is periodically discharged through the discharge pipe 29, it is possible to prevent the membrane from being hindered by the condensed water.

A valve A is provided in the discharge pipe 29, a valve B is provided in the exhaust gas pipe 30, the valve A is closed during normal ventilation, the valve B is opened for exhaust, and the valve A is opened when the condensed water is discharged. B is closed and the condensed water is discharged together with the exhaust gas.

6 and 7 show still another embodiment. An exhaust pipe 29 is installed which also serves as an exhaust gas pipe 30. Arrange so that the end is higher than the upper end of the oxygen dissolution membrane, particularly on or near the water surface in the tank (about ± 1 m on the water surface).

The condensed water existing from the lower header of the oxygen dissolution membrane to the lower manifold is discharged to the outside of the tank or near the water surface together with the exhaust gas through the discharge pipe 29 (in this case, the inner diameter is 50 mm or less) by the ventilation LV (about 10 to 20 m / s). If the end of the discharge pipe 29 is near the water surface, the influence on the supply pressure of the blower is small because the water pressure is low.

When a hollow fiber membrane is used as the oxygen dissolution membrane, the cross-sectional area of the ventilation part is small, so that the invasion of condensed water tends to hinder ventilation and has a large effect. Therefore, an aerobic biological treatment apparatus in which the oxygen dissolution membrane is a hollow fiber membrane. The present invention can be used more preferably.

In the present invention, by installing a non-porous oxygen dissolution film on the fluidized bed of a biological carrier such as activated carbon, the amount of oxygen supplied increases, so that there is no upper limit to the concentration of organic wastewater in the target raw water.

In addition, since the biological carrier is operated in a fluidized bed, it is not exposed to severe disturbance. Therefore, since a large amount of organisms can be stably maintained, the load can be increased.

Further, since the oxygen dissolving membrane is used in the present invention, the oxygen dissolving power is smaller than that of pre-aeration and direct aeration.

From these facts, according to the present invention, it is possible to treat organic wastewater from low concentration to high concentration with a high load and at low cost.

<Biological carrier>
Activated carbon is suitable as the biological carrier.

The filling amount of the fluidized bed carrier is preferably about 40 to 60%, particularly about 50% of the volume of the reaction vessel. The larger the filling amount, the larger the biological amount and the higher the activity, but if the filling amount is too large, there is a risk of outflow. Therefore, it is preferable to pass water at an LV (for example, about 7 to 15 m / hr) in which the fluidized bed expands by about 20 to 50%. As the material of the carrier, a gel-like substance other than activated carbon, a porous material, a non-porous material and the like can be used under the same conditions. For example, polyvinyl alcohol gel, polyacrylamide gel, polyurethane foam, calcium alginate gel, zeolite, plastic and the like can also be used. However, when activated carbon is used as the carrier, it is possible to remove a wide range of pollutants by the interaction between the adsorption action and the biodegradation action of the activated carbon.

The average particle size of the carrier is preferably about 0.2 to 3 mm. If the average particle size is large, it is possible to obtain a high LV, and when a part of the treated water is circulated to the reaction tank, the circulation amount can be increased, so that a high load is possible. However, since the specific surface area is small, the amount of organisms is small. If the average particle size is small, the pump power can be reduced because the flow can be performed at a low LV. Moreover, since the specific surface area is large, the amount of attached organisms increases.

The optimum particle size is determined by the concentration of wastewater, and is preferably about 0.2 to 0.4 mm for TOC: 50 mg / L and about 0.6 to 1.2 mm for TOC: 10 mg / L.

The expansion rate of the fluidized bed is preferably about 20 to 50%. If the expansion rate is lower than 20%, there is a risk of clogging and short circuit. If the unfolding rate is higher than 50%, there is a risk of carrier outflow and the pump power cost becomes high.

In ordinary biological activated carbon, the expansion coefficient of the fluidized bed of activated carbon is about 10 to 20%, but in this case, the fluidized state of the activated carbon is non-uniform and flows up, down, left and right. As a result, the membranes installed at the same time are rubbed by the activated carbon, and are worn away and consumed. In order to prevent this, in the present invention, it is necessary to sufficiently flow the fluidized bed carrier such as activated carbon, and it is desirable that the expansion coefficient is 20% or more. Therefore, the particle size of the carrier is preferably smaller than that of ordinary bioactivated carbon. In the case of activated carbon, there is no particular limitation on palm charcoal, coal, charcoal and the like. The shape is preferably spherical charcoal, but ordinary granular charcoal or crushed charcoal may also be used.

<Oxygen-containing gas>
The oxygen-containing gas may be a gas containing oxygen such as air, oxygen-enriched air, and pure oxygen. It is desirable that the aerated gas is passed through a filter to remove fine particles in advance.

The amount of aeration is preferably about twice as much as the amount of oxygen required for the biological reaction. If it is less than this, BOD and ammonia remain in the treated water due to lack of oxygen, and if it is more than this, the air volume becomes unnecessarily large and the pressure loss becomes high, which impairs economic efficiency.

It is desirable that the aeration pressure is slightly higher than the pressure loss of the hollow fiber generated at a predetermined aeration amount.

<Flow velocity of water to be treated>
The flow velocity in the reaction vessel of the water to be treated is LV10 m / hr or more, and the treated water can be treated in one pass without circulating.

Increasing the LV increases the oxygen dissolution rate proportionally. At LV50 m / hr, oxygen dissolves twice as much as 10 m / hr. When the LV is high, it is preferable to use activated carbon having a large particle size and not to increase the development rate too much. From the biological quantity and oxygen dissolution rate, the optimum LV range is about 7 to 20 m / hr.

<Stay time>
It is preferable to set the residence time so that the tank load is 1 to 2 kg-TOC / m ^{3 / day.}

<Blower>
It is sufficient for the blower to have a discharge air pressure equal to or less than the water pressure coming from the water depth. However, it is necessary that the pressure loss is greater than or equal to the pressure loss of piping or the like. Usually, the piping resistance is about 1 to 2 kPa.

In the case of a water depth of 5 m, a general-purpose blower having an output of up to about 0.55 MPa is usually used, and in a water depth of more than that, a high-pressure blower has been used.

In the present invention, a general-purpose blower having a pressure of 0.5 MPa or less can be used even at a water depth of 5 m or more, and it is preferable to use a low pressure blower of 0.1 MPa or less.

The supply pressure of the oxygen-containing gas is higher than the pressure loss of the hollow fiber membrane and lower than the water depth pressure, and the membrane is not crushed by the water pressure. Since the pressure loss of the flat film and the spiral film is negligible as compared with the water pressure, the pressure is extremely low, about 5 kPa or more, water pressure or less, and preferably 20 kPa or less.

In the case of a hollow fiber membrane, the pressure loss changes depending on the inner diameter and length. Since the amount of air to be aerated is ²⁰ mL to 100 mL / day per 1 m 2 of the membrane, the amount of air doubles when the membrane length doubles, and even if the membrane diameter doubles, the amount of air only doubles. It doesn't become. Therefore, the pressure loss of the membrane is directly proportional to the membrane length and inversely proportional to the diameter.

The value of the pressure loss is about 3 to 20 kPa for a hollow fiber having an inner diameter of 50 μm and a length of 2 m.

The following experiments were conducted on the discharge of condensed water from the hollow fiber membrane.

[Example 1]
30 non-porous silicon hollow fiber membranes with an inner diameter of 300 μm and an outer diameter of 500 μm are bundled together and installed in a column (transparent PVC pipe) with a diameter of 25 mm and a length of 1 m to blow air from the top to the bottom. It was aerated at 10 mL / min. The lower part of the bundle of silicon hollow fibers projects to the lower part of the outside of the column.

In addition, synthetic wastewater prepared by adding 100 mg / L of isopropyl alcohol to pure water was circulated upward on the column so as to have a residence time of 20 minutes. By operating the device, about 2 mL of condensed water was discharged from the lower end of the hollow fiber membrane protruding to the lower part of the column in 2 weeks.

The oxygen dissolution rate of this oxygen dissolution membrane is shown in FIG. The oxygen dissolution rate of the oxygen dissolution membrane was stable at about 8 g-O / m ² / day or more ^{per 1 m 2 for 140 days.} The oxygen dissolution rate was below 8 g-O / m ² / day around 70 and 120 days, because the TOC concentration of the raw water temporarily decreased, the load became low, and the supply load itself became low. It is presumed that the driving force of dissolution and diffusion of oxygen to the membrane decreased and the oxygen dissolution rate decreased.

[Comparative Example 1]
Using the same test equipment as in Example 1, the operation was performed under the same conditions except that the air ventilation direction was changed from the lower part to the upper part.

The oxygen dissolution rate of the oxygen dissolution membrane is shown in FIG. As shown in FIG. 2, the oxygen dissolution rate began to decrease about 2 weeks after the start of operation, and decreased to about ^{2 g-O / m 2 / day after 100 days.}

[Comparative Example 2]
In Example 1, the same test equipment as in Example 1 was used and the operation was performed under the same conditions except that one end of a thin tube was connected to the air outlet pipe at the bottom of the column and the other end of the tube was arranged in the upper part of the reaction tank. did. As a result, the oxygen dissolution rate was in the range of ^{3 to 4 g-O / m 2 / day.}

[Example 2]
In Comparative Example 2, a T-shaped tube was attached to the other end of the tube, a pinch cock was attached immediately below the air outlet pipe, the pinch cock was opened once every two weeks, and condensed water was discharged. As a result, the oxygen dissolution rate ^{recovered to 9 g-O / m 2} / day.

1 Aerobic biological treatment equipment 2 Reaction tank 6 Oxygen dissolution membrane module 20, 21 Header 22 Hollow fiber membrane 27 Air supply pipe 29 Discharge pipe (drainage pipe)
30 Exhaust gas piping 32 Tank

Claims (8)

A reaction tank through which organic wastewater is passed, and
An oxygen-dissolved membrane module having an oxygen-dissolved membrane installed in the reaction vessel so that the ventilation direction is in the vertical direction, and
An oxygen-containing gas supply means for supplying the oxygen-containing gas to the oxygen-containing membrane module, and
An exhaust gas pipe that discharges the exhaust gas consisting of the remainder of the oxygen-containing gas supplied to the oxygen-dissolving membrane module to the outside of the reaction vessel, and
It is equipped with a drainage pipe that discharges condensed water from the oxygen dissolution membrane module to the outside of the reaction tank.
Discharge the condensed water to a position lower than the lower end of the oxygen dissolution film module (when using multiple modules, it is lower than the lowest one among the lower ends of each module), and discharge the condensed water discharged from the oxygen dissolution film module to the reaction tank. Aerobic biological treatment equipment for organic wastewater that is provided to discharge to the outside
And
The oxygen-dissolving membrane is a hollow fiber membrane, and the oxygen-dissolving membrane is a hollow fiber membrane.
An aerobic biological treatment characterized in that an exhaust gas pipe 29 that also serves as the exhaust gas pipe and a drainage pipe is provided, and the exhaust gas pipe 30 is provided by branching the discharge pipe 29 inside or outside the reaction tank. Equipment . The aerobic biological treatment apparatus according to claim 1, wherein the exhaust gas pipe 30 at the end thereof is arranged at a position higher than the lower end of the oxygen dissolution film module and does not have a downward gradient . The aerobic biological treatment apparatus for organic wastewater according to claim 1 or 2 , wherein the drainage pipe is provided so as to have a vertically downward direction or a downward slope. The aerobic nature of the organic wastewater according to any one of claims 1 to 3, further comprising a tank for receiving the condensed water flowing out from the drainage pipe and a pump for sending the water in the tank to the reaction tank. Biological processing equipment. The aerobic biological treatment apparatus for organic wastewater according to any one of claims 1 to 4 , wherein a valve is provided in the drainage pipe. The aerobic biological treatment apparatus for organic wastewater according to any one of claims 1 to 5 , wherein the oxygen-dissolving membrane module includes a non-porous oxygen-dissolving membrane. The aerobic biological treatment apparatus for organic wastewater according to claim 6 , wherein the oxygen dissolution membrane is hydrophobic. The aerobic biological treatment apparatus for organic wastewater according to any one of claims 1 to 7 , wherein the reaction vessel is filled with a fluidized bed carrier.

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