JP2021003665A - Aerobic biological treatment apparatus and operational method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aerobic biological treatment apparatus capable of stable biological treatment for a long period of time by preventing sticking and agglomeration of carriers to each other and removing slime adhering to an oxygen dissolution membrane, and an operation method thereof. I will provide a. SOLUTION: An aerobic biological treatment apparatus 1 has a reaction tank (tank body) 2, a fluidized bed F formed on the upper side of a strainer 3 horizontally installed below the reaction tank 2, and a fluidized bed F. The oxygen dissolution membrane module 6 arranged in the above, the receiving chamber 7 formed under the strainer 3, the sprinkler pipe 19 for supplying a part of the treated water into the receiving chamber 7, and the valves 11v to 13v. It has raw water pipes 11 to 13 having. At a predetermined time, the outflow flow rate from the outlets of some of the raw water pipes 11 to 13 is reduced to increase the flow rate from the other outlets. [Selection diagram] Fig. 1

Description

The present invention relates to an aerobic biological treatment apparatus for organic wastewater and an operating method thereof. More specifically, the present invention relates to an aerobic biological treatment apparatus in which an oxygen dissolution film is arranged in a fluidized bed, and an operation method thereof.

Patent Document 1 describes an aerobic organism treatment method using an aerobic organism treatment apparatus having a fluidized bed and an oxygen dissolution membrane.

In the aerobic biological treatment apparatus of Patent Document 1, a fluidized bed of a carrier such as activated carbon is formed in the reaction vessel, and an oxygen dissolution film module having a hollow fiber membrane is arranged in the fluidized bed. The raw water is supplied to the lower part of the reaction tank via the raw water pipe to form a fluidized bed. Oxygen-containing gas such as air is supplied into the hollow fiber membrane of the oxygen dissolution film module, oxygen permeates the oxygen dissolution film molecularly, and molecular oxygen is based on the diffusion phenomenon due to the difference in oxygen concentration inside and outside the hollow fiber membrane. It diffuses and moves toward the outer peripheral surface of the hollow fiber membrane, and dissolves directly from the outer peripheral surface of the hollow fiber membrane into the raw water around the outside in the form of molecules.

JP-A-2018-89564

If the aerobic biological treatment apparatus of Patent Document 1 is continuously operated, there is a risk that carriers may adhere to each other or agglomerate, or microbial slime may excessively adhere to the surface of the oxygen dissolution membrane, resulting in a decrease in biological treatment efficiency. is there.

The present invention is an aerobic biological treatment apparatus capable of stably biologically treating for a long period of time by preventing sticking and agglomeration of carriers to each other and removing slime adhering to an oxygen dissolution membrane, and its operation. The purpose is to provide a method.

The aerobic biological treatment apparatus of the present invention includes a reaction vessel, a fluidized bed carrier filled in the reaction vessel, a raw water supply means for supplying raw water into the reaction vessel, and oxygen installed in the reaction vessel. In an aerobic biological treatment apparatus comprising a dissolution film module and an oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen dissolution film module, the raw water supply means has a plurality of raw water outlets, and each of them has a plurality of raw water outlets. The raw water outlets are arranged at different positions in the plan view of the reaction tank, and are characterized by being provided with a control means for controlling the raw water flow velocity flowing out from each raw water outlet.

In one aspect of the invention, the raw water outlet is located below the oxygen dissolved membrane module.

In one aspect of the present invention, as the raw water outlet, one arranged below the oxygen dissolution membrane module and one arranged in the middle of the oxygen dissolution membrane module in the vertical direction are provided.

In one aspect of the present invention, a circulation means for circulating a part of the treated water flowing out of the reaction tank to the lower part of the reaction tank or the raw water supply means is provided.

In one aspect of the present invention, a receiving chamber partitioned by a strainer having an opening is provided in the lower part of the reaction vessel, and a fluidized bed of the fluidized bed carrier is formed above the receiving chamber. A circulation means is provided for circulating a part of the treated water flowing out of the reaction vessel to the receiving chamber.

In one aspect of the invention, the raw water outlet below the oxygen dissolution membrane module is located above the strainer and opens downward and towards the opening of the strainer.

In one aspect of the present invention, the control means can control the flow rate so that the outflow rate from some of the raw water outlets is larger than the outflow rate from other raw water outlets.

In one aspect of the present invention, the oxygen dissolution membrane constituting the oxygen dissolution membrane module is a hollow fiber membrane provided in the vertical direction.

The method of operating the aerobic biological treatment apparatus of the present invention is a method of operating the aerobic biological treatment apparatus of the present invention, which includes a steady operation mode in which the outflow rate of raw water from each raw water outlet is substantially the same. It is characterized by performing an antifouling operation mode in which the outflow rate of raw water from the raw water outlet of the unit is made larger than the outflow rate of raw water from other raw water outlets.

In one aspect of the present invention, the total amount of raw water supplied in the antifouling operation mode is substantially the same as that in the steady operation mode.

In one aspect of the present invention, the distance from the raw water outlet to the lower end of the oxygen dissolution membrane module is 50 to 500 mm, and the outflow rate of raw water from the raw water outlet in the antifouling operation mode is 0.05 to 2 m / sec. And.

In the aerobic biological treatment apparatus of the present invention and its operation method, the flow rates from the raw water pipes are made substantially equal to each other in the steady operation mode. Antifouling operation to reduce or reduce the flow rate of other raw water pipes in order to increase the raw water flow rate of a part (for example, one or two) of the raw water pipes at a predetermined time, for example, at predetermined time intervals. Perform the mode. As a result, the raw water flows out from the partial raw water pipe at a high flow velocity, and the adhesion of slime to the oxygen dissolution membrane module and the agglomeration of the carrier are prevented or eliminated.

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 vertical sectional view of the biological processing apparatus which concerns on another embodiment.

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 filled with a reaction tank (tank body) 2, a strainer 3 horizontally installed under the reaction tank 2, and a biofouling carrier such as powdered activated coal on the upper side of the strainer 3. The fluidized bed F formed by the above, the oxygen dissolution membrane module 6 in which at least a part (in this embodiment, the whole) is arranged in the fluidized bed F, and the receiving chamber 7 formed under the strainer 3. It also has raw water pipes 11 to 13 for supplying raw water into the reaction tank 2, a blower 26 for supplying oxygen-containing gas such as air to the oxygen dissolution membrane module 6, and the like. A trough 8 and an outlet 9 for flowing out the treated water are provided in the upper part of the reaction tank 2. The trough 8 forms an annular flow path along the inner wall of the tank.

The plan view shape of the reaction tank 2 may be rectangular, circular, polygonal, or the like, but in this embodiment, it is rectangular.

The raw water is drawn from a raw water tank (not shown), sent through the raw water source pipe 10, and is supplied through the raw water pipes 11, 12, and 13 of a plurality of (three in this embodiment) branched from the raw water source pipe 10. It is supplied to the lower part of 2. The raw water tank, the raw water source pipe, and the raw water pipe form the raw water supply means.

In this embodiment, the raw water outlets 11N, 12N, 13N at the ends of the raw water pipes 11, 12, 13 are opened vertically upward on the lower side of the oxygen dissolution membrane module 6.

The raw water outlets 11N, 12N, and 13N have different arrangement positions. In this embodiment, the raw water outlet 12N is located at the center of the reaction tank 2, and the raw water outlets 11N and 13N are located on opposite sides of the raw water outlet 12N in a plan view of the reaction tank 2. ..

The raw water outlets 11N to 13N are all located below the oxygen dissolution membrane module 6, and the raw water flowing upward from each of the raw water outlets 11N to 13N directly hits the oxygen dissolution membrane module 6. ing.

The distance from each raw water outlet 11N to 13N to the lower end of the oxygen dissolution membrane module 6 is preferably about 50 to 500 mm. This is because, as will be described later, the jet flow from the outlets 11N to 13N is directly applied to the oxygen dissolution membrane.

Valves 11v, 12v, 13v for opening / closing or increasing / decreasing the flow rate are provided in the raw water pipes 11, 12, and 13. The number of raw water pipes is not limited to three, and two or more so that the horizontal cross-sectional area assigned to one raw water pipe is 0.5 to 25 m ² / line, especially 1 to 5 m ² / line. It suffices to provide the raw water pipe of. However, in a small reaction tank having a horizontal cross-sectional area of less than 1.0 m ² , the number may be about 2 to 3 regardless of the allocated area of the raw water pipe. In either case, it is preferable that the raw water outlets at the ends are located below the oxygen dissolution membrane module 6 and are arranged as evenly as possible in the plan view of the reaction vessel 2.

The treated water from the outlet 9 is introduced into the treated water tank 16 via the pipe 15. A part of the treated water in the treated water tank 16 is taken out of the system as treated water. The remaining portion is supplied to the sprinkler pipe 19 in the receiving chamber 7 via the circulation pump 17 and the circulation pipe 18, and flows into the fluidized bed F through the opening 3a of the strainer 3.

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.

In FIG. 1, a non-porous (non-porous) oxygen-dissolving film is used as the oxygen-dissolving film, oxygen-containing gas is ventilated from the outside of the tank into the oxygen-dissolving film through the pipe 27, and exhaust is discharged to the outside of the tank through the pipe 28. It is configured to do. Therefore, the oxygen-containing gas is aerated through the oxygen dissolving membrane at low pressure, oxygen is passed between the constituent atoms of the oxygen dissolving membrane as oxygen molecules (penetrates into the membrane), and is brought into contact with the water to be treated as oxygen molecules (water). Since it dissolves directly in oxygen, no bubbles are generated), so to speak, a process using the mechanism of molecular diffusion by a concentration gradient is performed.

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 vapor infiltrates unavoidably.

FIG. 2 shows an example of the oxygen dissolution membrane module 6. The oxygen-dissolving membrane module 6 uses a non-porous 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. The headers 20 and 21 are hollow tubular. Even when a flat membrane or a spiral membrane is used, it is desirable that the membranes 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 one end or both ends of each upper header 20 is connected to the upper manifold 23, and one end or both ends of each lower header 21 is connected to the lower manifold 24.

In this embodiment, air is supplied from the blower 26 to the upper part of the oxygen dissolution film module 6 via the air supply pipe 27 as an oxygen-containing gas, and the non-permeated gas is discharged from the lower part of the oxygen dissolution film module 6 by the exhaust gas pipe 28. To do. Air flows from the upper header 20 through the hollow fiber membrane 22 to the lower header 21, during which oxygen permeates the hollow fiber membrane 22 and dissolves in the water in the reaction vessel 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 vertically.

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), and the air supply pipe 27 is the upper manifold 23. It is connected to the. An exhaust gas pipe 28 is connected to the lower manifold 24.

In the aerobic biological treatment apparatus 1 configured in this way, the raw water drawn from the raw water tank is supplied from the raw water source pipe 10 to the fluidized bed F of the powdered and granular activated carbon adhering to the biofilm via the raw water pipes 11 to 13. .. In the steady operation mode, raw water is supplied in an equal amount from each raw water pipe 11 to 13. Further, as described later, a part of the treated water is supplied from the sprinkler pipe 19 to the receiving chamber 7, passes through the opening 3a of the strainer 3 and is supplied to the fluidized bed F, and is mixed with the raw water of the raw water pipes 11 to 13. , An upward flow is secured to form a fluidized bed. The organic components in the raw water introduced into the reaction tank 2 in this way are treated by performing a biological reaction in the fluidized bed F, and the treated water flows out from the upper clarification region to the treated water tank 16 through the trough 8 and the outlet 9. , A part of it is taken out of the system. The remaining portion is supplied to the sprinkler pipe 19 in the receiving chamber 7 via the circulation pump 17 and the circulation pipe 18.

Oxygen-containing gas such as air supplied from the air supply pipe 27 flows downward from the oxygen dissolution film module 6 and then flows out from the lower end position of the oxygen dissolution module 6, and the exhaust air flows from the exhaust gas pipe 28 to the atmosphere. It is discharged.

While air flows through each of the hollow fiber membranes 22 of the oxygen dissolving membrane module 6, oxygen permeates through the hollow fiber membranes 22 and dissolves in water to perform aerobic biological treatment.

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 high load and at low cost.

If the operation is continued as described above, the microbial slime may be excessively attached to the oxygen-dissolved membrane, and the fluidized carriers may be stuck to each other or agglomerated.

Therefore, in this embodiment, the antifouling operation mode is performed in which the flow rates of the branched raw water pipes 11 to 13 are switched and changed at regular intervals without changing the inflow flow rate from the raw water source pipe 10. That is, the valve (1 or 2 of 11v to 13v) of the raw water pipe of a part (1 or 2) is temporarily closed to concentrate the raw water inflow in the remaining raw water pipe, and the high flow velocity is ejected. The carrier is loosened by the flow to make the blockage less likely to occur (or to eliminate the blockage that has occurred), or the hollow fiber membrane is shaken to prevent excessive adhesion of slime.

By moving the outlets 11N to 13N of the raw water pipes 11 to 13 close to the oxygen dissolution membrane and increasing the ejection speed (preferably 0.05 to 2 m / sec), slime can be attached to the surface of the oxygen dissolution membrane. The sticking of the carrier is sufficiently eliminated.

<Biological carrier>
Activated carbon is suitable as the biological carrier. As the fluidized bed carrier, a gel-like substance other than activated carbon, a porous material, a non-porous material, or 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 filling amount of the fluidized bed carrier is preferably about 30 to 70%, particularly about 40 to 60% of the volume of the reaction vessel. The larger the filling amount, the larger the biomass and the higher the activity, but if it is too large, the carrier may flow out. Therefore, it is preferable to pass water at an LV where the fluidized bed develops by about 20 to 50%, for example, 7 to 30 m / hr, particularly 8 to 15 m / hr.

The average particle size of the fluidized bed carrier such as activated carbon is preferably about 0.2 to 1.2 mm, particularly about 0.3 to 0.6 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 biomass is small. When 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 depends on the concentration of wastewater, but if the TOC is 50 mg / L, it is preferably about 0.2 to 0.4 mm.

The development rate of activated carbon 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 expansion 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 rate of the activated carbon fluidized bed 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 film installed at the same time is rubbed by the activated carbon and is worn out 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 development rate 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 such that the DO in the treated water flowing out from the upper part of the reaction tank 2 or the reaction tank 2 is 1 mg / L or less. By setting the treated water DO to 1 mg / L or less in this way, the power consumption of the blower 26 can be suppressed. Further, when DO is approximately 0 mg / L, nitrification and denitrification proceed at the same time, so that the biological treatment efficiency is improved. If the DO is excessively large, the biofilm adhering to the activated carbon is enlarged, oxygen does not reach the deep part of the biofilm, and the deep part of the biofilm is anaerobic, which may reduce the bioreaction efficiency. In addition, the enlarged biofilm-attached activated carbon may be washed away to the outside of the reaction vessel.

The lower limit of DO may be 0 (zero), but is preferably 0.01 mg / L or more in order to confirm that the oxygen required for aerobic treatment is supplied.

In one aspect of the present invention, the DO is set to 0.2 to 1 mg / L. By setting the DO to 0.2 mg / L or more, the amount of rotifer growth in the reaction tank 2 is increased, sludge is preyed on by the rotifer, sludge is reduced in volume, and excess sludge is reduced.

When an oxygen-containing gas such as air is allowed to flow downward through the hollow fiber membrane 22, condensed water from the oxygen-containing gas is prevented from staying in the hollow fiber membrane 22.

<Flow velocity of water to be treated>
It is preferable to circulate the treated water so that the upward flow velocity of the water to be treated in the reaction tank 2 is LV 7 m / hr or more.

Increasing the LV increases the oxygen dissolution rate proportionally. 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 viewpoint of biomass and oxygen dissolution rate, the optimum LV range is about 7 to 30 m / hr, particularly about 8 to 15 m / hr.

<Stay time>
It is preferable to set the residence time so that the tank load is 0.5 to 4 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 that of the piping. 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 the condition is that the membrane is not crushed by 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, the water depth 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 ventilated is 50 to 200 mL / day per 1 m ² of the membrane, the amount of air doubles when the membrane length doubles, and the amount of air only doubles when the membrane diameter 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 yarn having an inner diameter of 50 μm and a length of 2 m. In the present invention, even if the TOC in the raw water is treated at a high concentration (for example, 100 mg / L or more, particularly 500 mg / L or more), the treatment can be performed efficiently and stably.

Another embodiment will be described with reference to FIG.

In this embodiment, the second raw water source pipe 30 is branched from the raw water source pipe 10, and the second raw water source pipe 30 is branched into three raw water pipes 31, 32, 33. Each raw water pipe 31 to 33 is provided with valves 31v, 32v, 33v that can be opened and closed or for increasing or decreasing the flow rate.

The outlets 31N, 32N, and 33N at the ends of the raw water pipes 31 to 33 are 20 to 70% from the lower end in the vicinity of the middle of the oxygen dissolution membrane module 6 in the vertical direction (for example, when the total height of the oxygen dissolution membrane module 6 is 100%). It is arranged at a height of 40 to 60%). When the oxygen dissolution membrane modules are installed in multiple stages above and below, it is preferable to arrange the raw water pipes so as to correspond to the respective membrane modules. The outlets 31v to 33N are open downward. In the plan view of the reaction tank 2, the outlet 32N is located in the center of the oxygen dissolved membrane module 6, and the outlets 31N and 33N are located on opposite sides of the outlet 32N. The outlets 31N to 33N are all located in the oxygen dissolution membrane module 6.

In this embodiment, three raw water pipes 31 to 33 are provided, but the horizontal cross-sectional area assigned to one raw water pipe is 0.5 to 25 m ² / line, particularly 1 to 5 m ² / line. As described above, two or more raw water pipes may be provided. In either case, it is preferable that the outlets 31N to 33N of the raw water pipes 31 to 33 are evenly located in the plan view of the reaction tank 2.

In FIG. 3, the outlets 11N to 13N of the raw water pipes 11 to 13 are located above the opening 3a of the strainer 3 and are open downward. This is because the deposits near the opening 3a are removed by the discharge water flow of the outlets 11N to 13N.

The other configurations of FIG. 3 are the same as those of FIG. 1, and the same reference numerals indicate the same parts.

Also in this embodiment, the raw water is supplied into the reaction tank 2 via the outlets 11N to 13N and 31N to 33N, respectively. A part of the treated water is circulated in the receiving chamber 7, and the rest of the treated water is taken out of the system from the treated water tank 16.

In the embodiment of FIG. 3, the flow rates of the raw water pipes 31 to 33 are made equal to each other in the steady state. The flow rates of the raw water pipes 11 to 13 are also equal to each other.

At predetermined time intervals, in order to increase the raw water flow rate of a part (for example, one or two) of the raw water pipes 31 to 33, the flow rate of the other raw water pipes is reduced or set to zero. As a result, the raw water flows out from the partial raw water pipe at a high flow velocity, and the adhesion of slime to the oxygen dissolution membrane module and the agglomeration of the carrier are prevented or eliminated.

Further, in order to increase the raw water flow rate of a part (for example, one or two) of the raw water pipes 11 to 13 at predetermined time intervals, the flow rates of the other raw water pipes are reduced or set to zero. As a result, the raw water flows out from the part of the raw water pipes at a high flow velocity, and the adhesion of slime to the vicinity of the opening 3a of the strainer 3 and the agglomeration of the carrier in the vicinity thereof are prevented or eliminated.

The timing of the flow rate fluctuations of the raw water pipes 31 to 33 and the timing of the flow rate fluctuations of the raw water pipes 11 to 13 may be simultaneous or different.

<Outflow velocity from raw water pipe>
In the present invention, when a part of the raw water pipe is stopped or restricted, and the raw water is passed through the remaining raw water pipe at a high flow velocity, the ejection speed of the remaining raw water pipe from the raw water pipe into the tank is set to 0. It is preferable that the speed is 05 m / sec or more, for example, 0.05 to 2 m / sec.

Since the purpose of increasing the flow velocity in this way is to remove the adhered slime on the hollow fiber membrane and the surface of the carrier, and to loosen the adhesion and agglomeration of the carriers, the high flow velocity of each raw water pipe can be changed. It may be a short time, for example, 0.5 to 20 minutes, particularly 1 to 10 minutes.

In the long term, it is desirable that the raw water is evenly sprayed over the entire area of the reaction tank. It is preferable to carry out the process of passing water through the raw water branch pipes of the book at a high flow velocity in order according to the number of raw water branch pipes.

In the embodiment shown in FIGS. 1 and 3, the entire amount of circulating water is supplied to the receiving chamber of the reaction tank, but by returning a part of the circulating water to the raw water source pipe, the raw water flows out from the raw water pipe outlet. The flow rate may be increased. Further, it is possible in principle to return the entire amount of circulating water to the raw water source pipe, but in this case, the fluidized bed F is formed from the lower part of the reaction tank without providing the strainer 3 and the receiving chamber 7 in the lower part of the reaction tank. To do so.
On the other hand, in FIGS. 1 and 3, a particle layer (for example, a large-diameter particle layer at the bottom and a small-diameter particle layer at the top) may be provided on the upper part of the strainer 3. As a result, clogging of the strainer 3 by the fluidized bed carrier can be prevented. In this case, the raw water pipe and the raw water pipe outlet are preferably arranged above the particle layer.

[Example 1, Comparative Example 1]
<Experimental conditions>
Granular activated carbon up to a carrier layer height of about 2.7 m in a reaction vessel having a bottom area (0.3 m × 1.2 m =) 0.36 m ² and a water depth of 4 m and a volume of 1.44 m ³ having the configuration shown in FIG. (Average particle size 0.5 mm) is deposited, and an oxygen dissolution film module having a film area of 25 m ² and a height of 2 m and having a polyethylene hollow fiber is immersed and arranged to supply raw water and a part of treated water. Was circulated.

Other conditions are as follows.

Circulating water volume: 2.5m ³ / h
Raw water volume: 3m ³ / h
Raw water and its BOD concentration: Synthetic wastewater obtained by adding micronutrients to isopropanol. BOD 100mg / L

Automatic valves were installed as valves 11v to 13v in the raw water pipes 11 to 13 to operate individual opening and closing in sequence.

The inner diameter of the raw water pipe is 20 mm, and the set value of the ejection speed when three raw water pipes are evenly flowed in at the same time is 0.037 m / sec.

In both Example 1 and Comparative Example 1, the outlet (spout hole) of the branched raw water pipe is located 100 mm away from the lower side of the oxygen dissolution membrane module in the lower part of the reaction tank, and the spouted raw water is the oxygen dissolution membrane. It was installed facing upward so that it would hit directly.

<Example 1>
As shown in Table 1, the inflow pattern in the embodiment is as shown in Table 1, steps 1, 3 and 5 for opening three valves, step 2 for opening only the valve 11v, step 4 for opening only the valve 12v, and a valve. Step 6 in which only 13v is opened is performed in sequence.

Table 2 shows the measured values of the flow velocity in each raw water pipe 5 minutes after each step was switched.

<Comparative example 1>
In Comparative Example 1, the valves of the three raw water pipes were always "open". The set flow velocity was 0.037 m / sec. Table 3 below shows the measured values of the flow velocities in each of the raw water pipes 11 to 13 when a predetermined time has passed since the start of operation.

<Results / Discussion>
In the first embodiment, in the steady operation mode (Steps 1, 3, 5), the set flow velocities of the raw water pipes 11 to 13 were adjusted to be uniform as shown in Table 1, but water flow was performed as shown in Table 2. It was observed that the flow velocity became uneven 5 minutes after the start. This is because the length from the pump to the outlet of the raw water pipe differs depending on the outlets 11N to 13N, the height of the outlets 11N to 13N also differs slightly, and the granules around the outlets 11N to 13N. It is presumed that the main causes are subtle differences in water flow resistance and the likelihood of short-circuit flow depending on the deposition status of activated carbon.
However, by periodically switching to the antifouling operation mode (Steps 2, 4, 6) and temporarily increasing the ejection speed from each outlet 11N to 13N to loosen the granular activated carbon deposited around the outlet, in the steady operation mode. The non-uniformity of the flow velocity was settled within a predetermined range, and a good state of treated water BOD concentration of 5 mg / L or less and BOD removal rate of 95% or more was stably maintained for 2 months or more.

The flow condition of the biological carrier observed from the peephole of the reaction tank was good, and no outflow of the carrier into the treated water was observed. After two months of operation, the oxygen-dissolved membrane was pulled up and observed, and although some obstruction due to the adhesion of the biofilm was observed, no significant adhesion of the biofilm was observed near the raw water inflow pipe. It was.

In Comparative Example 1, as in Example 1, it was observed that the flow velocity became non-uniform 5 minutes after the start of water flow, but the flow velocity became more non-uniform 1 week after the start of operation. It was observed. This is because the degree of clogging in the raw water pipe and the outlet of the raw water pipe (degree of water flow resistance), changes in valve opening due to vibration, and changes in water flow resistance due to short-circuit flow of granular activated carbon around the outlet over time. It is presumed that the non-uniformity gradually increased as the size increased.
Then, two weeks after the start of operation, the day when the BOD concentration of the treated water exceeded 5 mg / L began to appear, and in the third week, an agglomerated carrier having a diameter of about 5 to 30 mm flowed out as scum into the treated water. It became so.

The flow status of the biological carrier observed from the peephole of the reaction tank did not show a large difference as compared with the examples, but the flow may appear to be slightly deteriorated from the middle to the bottom of the reaction tank. It was.

One month after the start of operation, the BOD concentration of the treated water constantly exceeded 5 mg / L, and deterioration to about 20 mg / L was observed. Therefore, the raw water was temporarily stopped and the treated water at the top of the reaction tank was used. After removing and lowering the water level, air was blown from the inflow pipe of circulating water to attempt air backwashing of the reaction tank.

The water flow operation was restarted after the air backwash, but the treated water BOD did not fall below 5 mg / L. Therefore, when the test was stopped and the oxygen-dissolved membrane was pulled up and observed, slime consisting of a mixture of the biological membrane and the carrier adhered to the oxygen-dissolved membrane near the raw water inflow pipe, and the closed range was the lower part of the oxygen-dissolved membrane. The film area ranged from 20% to 30%.

1 Aerobic biological treatment equipment 2 Reaction tank 3 Strainer 3a Opening 6 Oxygen dissolution membrane module 7 Receiving chamber 10, 30 Raw water pipes 11 to 13, 31 to 33 Raw water pipes 11v to 13v, 31v to 33v Valves 11N to 13N, 31N to 33N Raw water pipe outlet 16 Treatment water tank 19 Sprinkler pipe 20, 21 Header 22 Hollow fiber membrane 26 Blower 27 Air supply pipe 28 Exhaust pipe

Claims (11)

Reaction tank and
The fluidized bed carrier filled in the reaction vessel and
A raw water supply means for supplying raw water into the reaction vessel,
The oxygen dissolution membrane module installed in the reaction vessel and
In an aerobic biological treatment apparatus provided with an oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen-containing membrane module.
The raw water supply means has a plurality of raw water outlets, and each raw water outlet is arranged at a different position in a plan view of the reaction vessel.
An aerobic biological treatment apparatus comprising a control means for controlling the flow velocity of raw water flowing out from each raw water outlet. The aerobic biological treatment apparatus according to claim 1, wherein the raw water outlet is arranged below the oxygen dissolution membrane module. Claim 1 or claim 1, wherein as the raw water outlet, one arranged below the oxygen dissolution membrane module and one arranged in the middle of the oxygen dissolution membrane module in the vertical direction are provided. 2 aerobic biological treatment apparatus. The aerobic biological treatment apparatus according to any one of claims 1 to 3, wherein a circulation means for circulating a part of the treated water flowing out of the reaction tank to the lower part of the reaction tank or the raw water supply means is provided. .. A receiving chamber partitioned by a strainer having an opening is provided in the lower part of the reaction vessel, and the fluidized bed of the fluidized bed carrier is formed on the upper side of the receiving chamber.
The aerobic biological treatment apparatus according to claim 4, wherein a circulation means for circulating a part of the treated water flowing out of the reaction tank to the receiving chamber is provided. The aerobic biological treatment apparatus according to claim 5, wherein the raw water outlet on the lower side of the oxygen dissolution membrane module is arranged on the upper side of the strainer and opens downward and toward the opening of the strainer. .. The aerobic organism according to any one of claims 1 to 6, wherein the control means can control the flow rate so that the outflow rate from some of the raw water outlets is larger than the outflow rate from other raw water outlets. Processing equipment. The aerobic biological treatment apparatus according to any one of claims 1 to 7, wherein the oxygen-dissolving membrane constituting the oxygen-dissolving membrane module is a hollow fiber membrane provided in the vertical direction. A method for operating the aerobic biological treatment apparatus according to any one of claims 1 to 8.
A steady operation mode in which the outflow rate of raw water from each raw water outlet is approximately the same, and an antifouling operation mode in which the outflow rate of raw water from some raw water outlets is larger than the outflow rate of raw water from other raw water outlets. A method of operating an aerobic biological treatment apparatus, which comprises performing. The operation method of the aerobic biological treatment apparatus according to claim 9, wherein the total amount of raw water supplied in the antifouling operation mode is substantially the same as that in the steady operation mode. The distance from the raw water outlet to the lower end of the oxygen dissolution membrane module is 50 to 500 mm, and the outflow rate of raw water from the raw water outlet in the antifouling operation mode is 0.05 to 2 m / sec. The method of operating the aerobic biological treatment apparatus according to claim 9 or 10.

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