WO2019163425A1

WO2019163425A1 - Aerobic biological treatment device

Info

Publication number: WO2019163425A1
Application number: PCT/JP2019/002699
Authority: WO
Inventors: 哲朗深瀬; 小林　秀樹
Original assignee: 栗田工業株式会社
Priority date: 2018-02-20
Filing date: 2019-01-28
Publication date: 2019-08-29
Also published as: JP6652147B2; JP2019141782A; TW201936520A

Abstract

Provided is an aerobic biological treatment device 1 comprising: a reaction tank (tank body) 2; an untreated-water inlet 3 which is disposed at the lowest part of the reaction tank 2 and opens upward so that the untreated water flows upward; first partition walls 4 and second partition walls 5 provided in the reaction tank 2; a fluidized bed F formed by filling an organism-adhering carrier such as a granular activated charcoal; an oxygen-dissolving membrane module 6 arranged between the first partition walls 4,4; the untreated-water inlet 3 disposed beneath the portion between the first partition walls 4,4; an aeration pipe 9, and the like.

Description

Aerobic biological treatment equipment

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

The aerobic biological treatment method is widely used as a treatment method for organic wastewater because it is inexpensive. In this method, it is necessary to dissolve oxygen in the water to be treated, and aeration with a diffuser is usually performed.

Aeration with a diffuser has a low dissolution efficiency of about 5-20%. In addition, it is necessary to aerate at a pressure higher than the water pressure applied to the water depth where the diffuser pipe is installed, and a large amount of air is blown at a high pressure, so the power cost of the blower is high. Usually, more than 2/3 of the power cost in aerobic biological treatment is used for oxygen dissolution.

Membrane aeration bioreactor (MABR) using hollow fiber membrane can dissolve oxygen without generating bubbles. In MABR, it is only necessary to ventilate air having a pressure lower than the water pressure applied to the water depth, so that the required pressure of the blower is low and the oxygen dissolution efficiency is high.

JP 2006-87310 A

An object of the present invention is to provide an aerobic biological treatment apparatus capable of performing sufficient treatment even when the organic matter concentration of raw water is high.

The aerobic biological treatment apparatus of the present invention includes a reaction vessel, an oxygen-dissolving membrane module installed in the reaction vessel, an oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen-dissolving membrane module, and a reaction vessel And a circulating means for circulating the carrier up and down in the reaction tank.

In one aspect of the present invention, the circulation means has a first partition that divides the reaction tank into an ascending zone and a descending zone, and the oxygen-dissolving membrane module is located in the ascending zone and / or the descending zone. The raw water supply means which is arrange | positioned and supplies raw water so that it may become a circulation flow direction is provided.

In one aspect of the present invention, the raw water supply means has a raw water inlet provided at the bottom of the reaction tank to allow the raw water to flow upward.

In one aspect of the present invention, the bottom of the reaction tank is an inclined structure having a lower horizontal cross-sectional area as it goes downward, and the raw water inlet is provided at the lowermost part of the inclined structure.

In one aspect of the present invention, the upper portion of the reaction tank is a widened portion having a larger horizontal cross-sectional area than the lower side, and a second zone that divides the widened portion into a first zone and a second zone. A partition wall is provided, an upper end portion of the first partition wall enters the first zone, and a treated water take-out portion is provided in the second zone.

In one embodiment of the present invention, the oxygen-dissolving membrane module includes a non-porous oxygen-dissolving membrane.

In one embodiment of the present invention, the oxygen-dissolving film is hydrophobic.

In the aerobic biological treatment apparatus of the present invention, since the carrier circulates up and down, raw water can be flowed at a high LV, and raw water can be treated in a completely mixed state. For this reason, dissolved oxygen (DO) is present in almost the entire region of the reaction vessel, and adhesion of the biofilm to the oxygen-dissolved film surface can be prevented without locally increasing the undecomposed TOC. Therefore, even raw water having a high organic matter concentration (for example, 100 mg / L or more, particularly 500 mg / L or more) can be efficiently and stably treated.

It is a longitudinal cross-sectional view of the biological treatment apparatus which concerns on embodiment. It is a perspective view which shows the arrangement | sequence of the hollow fiber membrane unit of an oxygen melt | dissolution membrane module. (A) is the perspective view from the lower part which shows the upper header of an oxygen melt | dissolution membrane module, (b) is the BB sectional drawing of (a). It is a perspective view of an oxygen dissolution membrane module. It is a perspective view of the coupling body of an oxygen dissolution membrane module.

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

FIG. 1 is a longitudinal sectional view of an aerobic biological treatment apparatus 1 according to an embodiment. The aerobic biological treatment apparatus 1 includes a reaction tank (tank body) 2, a raw water inlet 3 that opens upward at the lowermost end of the reaction tank 2 so that raw water flows upward, and a reaction tank 2. The first partition 4 and the second partition 5 installed in the vertical direction, the fluidized bed F formed by filling a bioadhesive carrier such as granular activated carbon, and the oxygen disposed between the first partitions 4 and 4. It has a dissolved membrane module 6 and an air diffuser 9 installed below between the first partition walls 4 and 4. Air is supplied to the air diffuser 9 from a compressor (or blower), and the inside of the tank is backwashed. The bottom of the reaction tank 2 is an inclined structure portion 2C whose horizontal cross-sectional area becomes smaller as it goes downward, and the inflow port 3 is provided at the lowermost portion of the inclined structure portion 2C.

In this embodiment, the horizontal cross section of the reaction vessel 2 is rectangular, and the partition walls 4 and 5 are flat plates extending in the long side direction (perpendicular to the paper surface in FIG. 1) of the rectangle.

Note that the horizontal cross section of the reaction tank 2 may be either substantially square or substantially circular. When the horizontal cross section is substantially square, each of the partition walls 4 and 5 may be a pair of flat plates or a rectangular tube shape. In the case of a substantially circular shape, the partition walls 4 and 5 may be substantially cylindrical.

The upper part of the reaction tank 2 is a widened part 2W having a larger horizontal cross-sectional area than the lower narrow part 2S. Between the widened portion 2W and the small width portion 2S, there is an inclined portion 2T in which the horizontal cross-sectional area increases toward the top.

The trough 10 and the outflow port 11 for making treated water flow out are provided in the upper part of the widening part 2W. The trough 10 forms an annular flow path along the inner wall of the tank.

The first partition 4 is installed from the narrow part 2S to the lower part of the wide part 2W. The lower end of the first partition 4 is located higher than the inclined structure portion 2C. The space between the first partition 4 and the inner wall surface of the narrow portion 2S is a descending zone of the carrier. The space between the first partition walls 4 and 4 is a rising zone of the carrier, and the oxygen-dissolving membrane module 6 is installed in the rising zone between the first partition walls 4 and 4.

2nd partition 5 is installed in wide part 2W. A space between the

second partition walls

5 and 5 is a first zone, and a space between the second partition wall 5 and the inner wall surface of the widened portion 2W is a second zone. The lower end of the second partition 5 is located near the boundary between the inclined portion 2T and the widened portion 2W. The distance between the

second partition walls

5 and 5 is larger than the distance between the first partition walls 4 and 4, and the upper end of the first partition wall 4 enters the lower part in the first zone between the

second partition walls

5 and 5.

FIG. 1 shows that the reaction vessel is filled with a fluidized bed carrier, and the biofilm adheres to the surface of the oxygen-dissolved membrane by the shearing force caused by the flow of the carrier so that most of the biofilm adheres to the fluidized bed carrier. The oxygen-dissolved film is used only for the purpose of supplying oxygen.

In FIG. 1, a non-porous oxygen-dissolving film is used as the oxygen-dissolving film, and an oxygen-containing gas is vented from the outside of the tank to the primary side of the oxygen-dissolving film through the pipe, and the exhaust is discharged outside the tank through the pipe. It is configured to do. Therefore, an oxygen-containing gas is passed through the oxygen-dissolved film at a low pressure, passes oxygen as oxygen molecules between constituent atoms of the oxygen-dissolved film (dissolves in the film), and is brought into contact with the water to be treated as oxygen molecules. Since oxygen is dissolved directly in water, no bubbles are generated. This method uses a molecular diffusion mechanism based on a concentration gradient, and does not require aeration using a diffuser tube as in the prior art.

It is preferable to use a hydrophobic material as the material for the oxygen-dissolving film because it is difficult to be immersed in the film. A trace amount of water vapor enters even a hydrophobic film.

In FIG. 1, the raw water is supplied from the bottom, but the raw water can be supplied from the inner wall of the tank or the upper part of the tank with the bottom as a plane. In either case, it is necessary to supply raw water in the direction of the circulating flow in order to generate the circulating flow in the tank. In order to prevent the carrier and SS from depositing at the corner of the tank bottom with the tank inner wall, it is preferable to provide an inclined plate so as to incline downward in the axial direction at the intersection corner between the tank inner wall and the bottom. . A rectifying member having a cone shape may be provided at the center of the bottom of the tank so that no carrier or SS is deposited at the center of the bottom of the tank.

In FIG. 1, the tank center side is the rising zone and the tank side wall side is the falling zone, but the first partition is a single flat plate and is fixed so that the tank center is partitioned left and right, and one of the partitioned walls is lifted It is also possible to use a zone and the other as a descending zone. In this case, the widened portion and the trough are provided only in the upper part of the rising zone in the upper part of the tank. On the other hand, it is also possible in principle to set the tank center side as a descending zone and the tank side wall as an ascending zone.

In FIG. 1, in order to prevent the carrier outflow by providing the widened portion 2W in the upper part of the tank, the second partition 5 partitions the first zone of the reaction region and the second zone of the clarification region. Not. By raising the tank body height and providing the first partition wall 4 at a position where the distance between the upper end of the first partition wall 4 and the water surface becomes longer, the clarified region ( It can also function as a carrier precipitation region). It can also be divided into a reaction region and a clarification region by GSS (gas-solid-liquid separation member).

In any of the above embodiments, in order to reduce the water flow resistance of the circulating flow, the horizontal sectional area of the cylinder of the first partition, the horizontal sectional area of the portion sandwiched between the inner wall of the tank and the first partition, the first The area of the boundary surface between the lower end of the partition wall and the bottom surface of the tank (for example, a circular peripheral wall if a circular reaction tank, a rectangular reaction tank and a rectangle if the first partition wall is a single flat plate) is similar (for example, It is desirable that one is about 80 to 120% of the other).

2 shows the arrangement of the hollow fiber membrane units, FIG. 3 is a cross-sectional perspective view of the upper header of each hollow fiber membrane unit, and FIG. 4 shows an example of the oxygen-dissolving membrane module 6. The oxygen-dissolving membrane module 6 uses a non-porous hollow fiber membrane strand 22 (a plurality of hollow fiber membranes arranged together) as an oxygen-dissolving membrane. In this embodiment, the hollow fiber membrane strands 22 are arranged in the vertical direction, and the upper end of each hollow fiber membrane strand 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 strand 22 communicates with the upper header 20 and the lower header 21, respectively. Each

header

20, 21 is a hollow tube made of a potting material.

As shown in FIG. 2, a plurality of hollow fiber membrane units each composed of a pair of

headers

20 and 21 and hollow fiber membrane strands 22 are arranged in parallel. Each unit is connected and integrated by a frame (not shown). As shown in FIG. 4, each upper header 20 is connected to the upper manifold 23, and each lower header 21 is connected to the lower manifold 24.

As shown in FIG. 3, in this embodiment, each of the

headers

20 and 21 has a rectangular outer shape in a cross section perpendicular to the longitudinal direction. The upper header 20 is provided with an air circulation hole 20a on the upper side, and the lower surface portion is thick. The upper end portion of the hollow fiber membrane strand 22 is embedded in this thick portion, and the upper end surface is open toward the air circulation hole 20a. The lower header 21 has a vertically symmetrical structure with the upper header 20, an air circulation hole is provided on the lower side, and the upper surface portion is thick. The lower end portion of the hollow fiber membrane strand 22 is embedded in this thick portion, and the lower end surface is open toward the air circulation hole of the lower header 21.

As shown in FIG. 3, hollow fiber membrane strands 22 are arranged in parallel in two rows on one upper header 20 and lower header 21 in the header longitudinal direction. The interval a (FIG. 3 (b)) between the rows of the hollow fiber membrane strands 22 is at least several times the average particle diameter of the activated carbon that is the fluidized bed carrier. Moreover, the space | interval b of the header longitudinal direction of hollow fiber membrane strands 22 may closely_contact | adhere, or may leave a space | interval.

The interval c between the

adjacent headers

20 and 20 and between the

headers

21 and 21 is not particularly limited.

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. An oxygen-containing gas such as air flows from the upper header 20 through the hollow fiber membrane strand 22 to the lower header 21, during which oxygen passes through the hollow fiber membrane strand 22 and dissolves in the water in the reaction vessel 2.

As shown in FIG. 5, a plurality of oxygen-dissolving membrane modules 6 may be arranged in a line, and the

manifolds

23 and 24 of each module may be connected to a common upper communication pipe 41 and lower communication pipe 42, respectively.

In this embodiment, the oxygen-dissolving membrane module 6 is installed in two upper and lower stages, and air is supplied to the upper portion of the upper oxygen-dissolving membrane module 6 via the blower 26 and the air supply pipe 27, and the upper oxygen-dissolving membrane module 6 is supplied. The air that flows out from the lower part of the dissolved membrane module 6 is supplied to the lower oxygen-dissolved membrane module 6 through the connecting pipe 28, and the exhaust air is discharged from the lower part of the lower oxygen-dissolved membrane module 6 through the exhaust gas pipe 29. An oxygen-containing gas such as air flows from the upper header 20 through the hollow fiber membrane strand 22 to the lower header 21, during which oxygen passes through the hollow fiber membrane and dissolves in the water in the reaction vessel 2.

Each

header

20, 21 and each manifold 23, 24 may be provided so as to have a running water gradient. The oxygen-dissolving membrane module 6 may be installed in one stage or in three or more stages.

In the aerobic biological treatment apparatus 1 configured in this manner, the raw water inlet 3 flows upward into the reaction tank 2, rises in the ascending zone in the cylinder of the first partition wall 4, and the granular activated carbon adhered to the biofilm In the fluidized bed F, water is flowed upward in a transient manner to perform a biological reaction. The activated carbon and the water in the tank go around the upper end of the first partition 4. This activated carbon descends the descending zone between the first partition 4 and the inner wall surface of the reaction tank 2 to reach the bottom of the reaction tank 2, wraps around the lower end of the first partition 4, and the cylinder of the first partition 4 again. Ascend the rising zone.

A part of the biologically treated water that has circulated around the upper end of the first partition 4 wraps around the lower end of the second partition 5 and ascends the second zone between the second partition 5 and the widened portion 2W, and performs this increase. Activated charcoal is settled and separated between them, and then taken out as treated water through the trough 10 and the outlet 11.

In this embodiment, by increasing the amount of raw water supplied from the inlet 3, the rising flow velocity LV between the first partition walls 4 and 4 is increased and the fluidized bed F is brought into a completely mixed state. Thereby, DO exists in almost the entire reaction tank 2, and even raw water having a high organic matter concentration is sufficiently treated.

It should be noted that the flow rate of the fluidized bed F increases due to high LV water flow, and the interface of the fluidized bed F rises to the first zone between the

second partition walls

5 and 5. Since the interval between the

second partition walls

5 and 5 is larger than the interval between the first partition walls 4 and 4, the rising flow velocity between the

second partition walls

5 and 5 becomes small, and the distance between the

second partition walls

5 and 5 is reduced. A clear zone is formed at the top of the first zone.

When the biological treatment operation is continued, the biological film on the surface of the carrier becomes gradually thicker. When this biofilm becomes excessively thick, the carrier flows out and the biological treatment efficiency decreases. (The aerobic biological treatment is not performed in the deep part of the biofilm, that is, on the side close to the carrier, because oxygen does not reach.) Processing efficiency may decrease.

Therefore, air is discharged from the diffuser tube 9 periodically or based on the observation result of the flow state in the reaction tank 2 to aerate the reaction tank 2. By this aeration, the excess sludge on the surface of the carrier is peeled off by the shearing force of the water flow.

After performing this air aeration, the raw water may be circulated in the reaction tank 2 at a higher LV than the LV during normal processing. Thereby, the sludge which peeled and existed in the reaction tank 2 flows out from the outflow port 11. The discharged water at this time is not treated but treated separately as washing wastewater or sent to the raw water tank. In this way, sticking of the carriers can be suppressed, and drift and blockage in the reaction tank 2 can be prevented. This aeration also has the effect that the inside of the reaction tank 2 is decarboxylated, the pH is increased, and the carbonic acid accumulated between the carriers (activated carbon) is decarboxylated.

In the present invention, since a non-porous oxygen-dissolving membrane is installed in a fluidized bed of a biological carrier such as activated carbon to increase the amount of oxygen supplied, there is no upper limit to the organic wastewater concentration of the target raw water.

In addition, since the biological carrier is operated in a fluidized bed, a large amount of microorganisms can be stably maintained and the load can be increased.

In addition, since an oxygen-dissolving film is used in the present invention, the dissolution power of oxygen is small compared to preaeration and direct aeration.

From these facts, according to the present invention, the pH in the reaction tank 2 is maintained in the vicinity of neutrality with little or no use of a neutralizing agent, and organic wastewater from a low concentration to a high concentration is heavily loaded. In addition, it is possible to stably process at a low cost.

<Biological carrier>
As the biological carrier, activated carbon is suitable, but gel-like substances other than activated carbon, porous materials, non-porous materials, 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 activated carbon adsorption and biodegradation.

The average particle diameter of the activated carbon is preferably 0.2 to 1.2 mm, particularly preferably about 0.3 to 0.6 mm. When the average particle size is large, it is possible to increase the LV, and when a part of the treated water is circulated to the reaction tank, the amount of circulation can be increased, so that a high load is possible. However, since the specific surface area is small, the biomass is reduced. If the average particle size is small, the pump power can be reduced because it can flow at a low LV. And since the specific surface area is large, the amount of attached organisms increases.

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

The aeration rate is preferably about twice the amount of oxygen required for biological reactions. If it is less than this, BOD and ammonia will remain in the treated water due to insufficient oxygen, and if it is greater, the air flow will be unnecessarily increased and the pressure loss will be increased, so the economy will be impaired.

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

<Blower>
The blower 26 is sufficient if the discharge wind pressure is equal to or lower than the water pressure coming from the water depth. However, it is necessary to be more than the pressure loss of piping. Usually, the pipe resistance is about 1 to 2 kPa.

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

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 a low-pressure blower of 0.1 MPa or less is preferably used.

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

In the case of a hollow fiber membrane, the pressure loss varies depending on the inner diameter and length. Since the amount of air vent is a membrane 1 m ² per 50 ~ 200 mL / day, film air quantity when the doubled length is doubled, the air quantity even Maku径becomes doubled only doubles Don't be. Therefore, the pressure loss of the membrane is directly proportional to the membrane length and inversely proportional to the diameter.

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

In the above embodiment, air is allowed to flow downward through the oxygen-dissolving membrane module 6, but it may be allowed to flow upward.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2018-028196 filed on Feb. 20, 2018, which is incorporated by reference in its entirety.

DESCRIPTION OF SYMBOLS 1 Aerobic biological treatment apparatus 2 Reaction tank 6 Oxygen melt | dissolution membrane module 9

Air diffuser pipe

20,21 Header 22 Hollow fiber membrane 27 Air supply piping 29 Exhaust gas piping

Claims

A reaction vessel;
An oxygen-dissolving membrane module installed in the reaction vessel;
Oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen-dissolving membrane module;
A fluidized bed of support formed in the reaction vessel;
An aerobic biological treatment apparatus comprising circulation means for circulating the carrier up and down in the reaction tank.
The circulating means has a first partition that partitions the inside of the reaction tank into an ascending zone and a descending zone,
The oxygen-dissolving membrane module is disposed in the ascending zone and / or descending zone;
The aerobic biological treatment apparatus according to claim 1, further comprising raw water supply means for supplying the raw water in a circulating flow direction.
The aerobic biological treatment apparatus according to claim 2, wherein the raw water supply means has a raw water inlet provided at the bottom of the reaction tank to allow the raw water to flow upward.
The bottom of the reaction tank is an inclined structure part with a lower horizontal cross-section as it goes down,
The aerobic biological treatment apparatus according to claim 3, wherein the raw water inlet is provided at a lowermost portion of the inclined structure portion.
The upper part of the reaction tank is a widened part having a larger horizontal cross-sectional area than the lower side,
A second partition that divides the widened portion into a first zone and a second zone is provided;
An upper end portion of the first partition wall enters the first zone;
The aerobic biological treatment apparatus according to any one of claims 1 to 4, wherein a treatment water take-out part is provided in the second zone.
6. The aerobic biological treatment apparatus according to claim 1, wherein the oxygen-dissolving membrane module includes a non-porous oxygen-dissolving membrane.
The aerobic biological treatment apparatus according to claim 6, wherein the oxygen-dissolving membrane is hydrophobic.