WO2019163427A1

WO2019163427A1 - Aerobic biological treatment device

Info

Publication number: WO2019163427A1
Application number: PCT/JP2019/002701
Authority: WO
Inventors: 小林　秀樹; 哲朗深瀬
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: JP2019141784A; TW201936519A; JP6558455B1

Abstract

Provided is an aerobic biological treatment device 1 comprising: a reaction tank (a tank body) 2; a water-permeable plate 3 installed horizontally in the lower part of the reaction tank 2; a large-diameter particle layer 4 formed on the upper side of the water-permeable plate 3; a small-diameter particle layer 5 formed on the upper side of the large-diameter particle layer 4; an oxygen-dissolving membrane module 6 arranged on the upper side of the small-diameter particle layer 5; a reception chamber 7 formed on the lower side of the water-permeable plate 3; a raw water spray tube 8 for supplying raw water within the reception chamber 7; and an air diffuser tube 9 installed for the purpose of diffusing air within the reception chamber 7. The upper part of the reaction tank 2 is a widened section 2W having a large horizontal cross-sectional area.

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

In order to increase the raw water to be treated, if the amount of the carrier is increased or the LV in the fluidized bed reaction vessel is increased, the carrier easily flows out of the reaction vessel.

An object of the present invention is to provide an aerobic biological treatment apparatus that can increase the filling amount of a carrier or have a high LV.

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 An aerobic biological treatment apparatus comprising a fluidized bed of a carrier formed in the upper part of the reaction tank, wherein the upper part of the reaction tank is a widened part having a larger horizontal sectional area than the lower part thereof.

In one aspect of the present invention, the upper surface of the carrier fluidized bed is positioned in the widened portion when water is passed through a normal LV during steady operation.

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 upper part of the reaction tank is a widened part having a large horizontal cross-sectional area, the upper part of the reaction tank can be used even when the filling amount of the carrier is increased or the raw water is passed through high LV. The LV at this point becomes smaller than the lower part, and the outflow of the carrier is suppressed.

It is a longitudinal cross-sectional view of the biological treatment apparatus which concerns on embodiment. (A) is a side view of an oxygen-dissolved membrane unit, and (b) is a perspective view of the oxygen-dissolved membrane unit. It is a perspective view which shows another example of a reaction tank.

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) 2 having a circular horizontal section, a perforated plate such as a punching plate installed horizontally below the reaction tank 2, and a plurality of dispersion nozzles on a flat plate. A water permeable plate 3 such as one provided uniformly, a large particle layer 4 formed on the upper side of the water permeable plate 3, a small particle layer 5 formed on the large particle layer 4, and a small particle layer A fluidized bed F formed by filling a bioadhesive carrier such as granular activated carbon on the upper side of 5, an oxygen-dissolving membrane module 6 at least partially disposed in the fluidized bed F, and a lower side of the water permeable plate 3. It has a receiving chamber 7 formed, a raw water spray tube 8 for supplying raw water into the receiving chamber 7, an aeration tube 9 installed in the receiving chamber 7, and the like. Air is supplied to the air diffuser 9 from a compressor (or blower) 13.

The raw water spray pipe 8 is supplied with raw water by a pump. In addition, when passing high LV water, it is preferable to use a high capacity pump as a pump.

The upper part of the reaction tank 2 is a widened part 2W having a larger horizontal cross-sectional area than the lower side. Below the widened portion 2W, there is provided a tapered portion 2T whose horizontal cross-sectional area decreases as it goes downward. Below the tapered portion 2T is a small horizontal cross-sectional area 2S having a uniform horizontal cross-sectional area up to the bottom of the reaction vessel 2. The horizontal cross-sectional area of the widened portion 2W is preferably larger by 150 to 300%, particularly 175 to 225% than the horizontal cross-sectional area of the small horizontal cross-sectional area 2S.

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.

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. In addition, it is preferable to use a hydrophobic material as the material of 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.

FIG. 2 shows an example of the oxygen-dissolving membrane module 6. This oxygen dissolution membrane module 6 uses a non-porous hollow fiber membrane 22 as an oxygen dissolution membrane. In this embodiment, the hollow fiber membranes 22 are arranged in the vertical direction, and 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 interior of the hollow fiber membrane 22 communicates with the upper header 20 and the lower header 21, respectively. Each

header

20, 21 is a hollow tube. Even when a flat membrane or a spiral membrane is used, it is desirable to arrange the ventilation direction to be the vertical direction.

FIG. 1 illustrates an example of a reaction tank having a circular horizontal cross-sectional area, but a reaction tank having a square horizontal cross-section can also be used, and an example of this case is shown in FIG. The reaction tank having a square cross section is not an inversely tapered shape when the portion where the width is widened toward the widened portion above the reaction region is circular, but has a shape in which only the horizontal and vertical widths are expanded as shown in FIG. A reaction tank of this shape is easily multistaged in series.

2B, a plurality of units each including a pair of

headers

20 and 21 and a hollow fiber membrane 22 are arranged in parallel. As shown in FIG. 2A, one end or both ends of each upper header 20 are preferably connected to the upper manifold 23, and one end or both ends of each lower header 21 are preferably connected to the lower manifold 24. An oxygen-containing gas is supplied to the upper part of the oxygen-dissolving membrane module 6 through the air supply pipe 27 and discharged from the lower part of the oxygen-dissolving membrane module 6 to the outside of the tank through the discharge pipe 29. Oxygen-containing gas such as air flows from the upper header 20 through the hollow fiber membrane 22 to the lower header 21, during which oxygen passes through the hollow fiber membrane 22 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 multiple stages up and down.

In order to supply air to the oxygen-dissolving membrane module 6, a blower 26 and an air supply pipe 27 for supplying air are provided, and 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 a discharge pipe 29. The discharge pipe 29 is provided to have a downward slope and extends to the outside of the reaction tank 2. In FIG. 1, the discharge pipe 29 is drawn to the side of the reaction tank 2, but may be drawn downward from the bottom of the reaction tank 2.

As shown in FIG. 1, the remainder of the oxygen-containing gas that did not dissolve in the oxygen-dissolving film is exhausted outside the tank through the discharge pipe 29. The end of the pipe 29 is disposed so as to be lower than the lower end of the oxygen-dissolving membrane module 6 (the lowest one among the lower ends of the modules when there are a plurality of modules 6). Therefore, when the condensed water is contained in the exhaust gas, the condensed water flows out to the tank 32 installed below the discharge pipe 29. The water in the tank 32 may be sent to the reaction tank 2 by the pump 33 and the pipe 34.

An exhaust gas pipe 30 for exhausting the exhaust gas to the outside of the tank may be connected to the discharge pipe 29 inside or outside the tank. In this case, the condensed water is discharged through the discharge pipe 29. The exhaust part at the end of the exhaust gas pipe 30 may be disposed at a position higher than the lower end of the oxygen-dissolving membrane module. In order to prevent the condensate from accumulating, it is preferable that the exhaust gas pipe 30 has only an upward gradient or a vertically upward direction without a downward gradient. Further, at this time, a valve (not shown) may be provided on the downstream side of the branch point of the discharge pipe 29 with the exhaust gas pipe 30 so that the condensed water flows out into the tank 32 by opening the valve.

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 intermittent operation, in normal operation, once a day to once every 30 days (at most once a day, at least once a month for 10 seconds), preferably once a day Drain by opening the valve once every 15 days.

In the aerobic biological treatment apparatus 1 configured as described above, raw water is introduced into the receiving chamber 7 through the spray pipe 8, and is circulated upward through the water permeable plate 3 and the large and small

diameter particle layers

4 and 5, and SS is generated. Then, in the fluidized bed F of the granular activated carbon adhered to the biofilm, the water is flowed upward in a transient manner, undergoes a biological reaction, and is taken out as treated water from the upper clarified region through the trough 10 and the outlet 11. In LV during steady operation, the upper surface of the fluidized bed F is located in the widened portion 2W.

In a normal biological treatment operation, the oxygen-containing gas such as air supplied from the air supply pipe 27 flows downward through the oxygen-dissolving membrane module 6 and then the lower header 21 and the lower part from the lower end position of the oxygen-dissolving module 6. It flows out through the manifold 24, and the exhaust air is exhausted from the exhaust pipe 29 (or from the exhaust gas pipe 30 when the exhaust gas pipe 30 is provided) to the atmosphere. The condensed water flows out to the tank 32 through the discharge pipe 29.

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. (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 it.) Also, the carriers adhere to each other through the grown biofilm, and the carrier flows out. Biological treatment efficiency is reduced.

Therefore, the compressor 13 is operated periodically or based on the observation result of the flow state in the reaction tank 2, the air is caused to flow out from the air diffuser 9, and the reaction tank 2 is aerated. 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, it is preferable to feed the raw water into the reaction tank 2 at a higher LV than the LV during normal treatment. 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 discharged as treated water and processed in a subsequent process (such as coagulation sedimentation), separately processed 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.

When the above-described high LV water flow, the expansion rate of the fluidized bed F increases and the interface of the fluidized bed F rises, but the horizontal cross-sectional area of the widened portion 2W is large, so the rising flow velocity in the widened portion 2W is small. Since it becomes smaller than the horizontal cross-sectional area 2S, the loss of the carrier is suppressed. After performing the high LV operation for a predetermined time, the LV is returned to the normal LV, and the normal biological treatment operation is resumed.

In addition, by this aeration, the inside of the reaction tank 2 is decarboxylated, and the effect that the lowered pH rises or the carbonic acid accumulated between the carriers (activated carbon) is decarboxylated is also exhibited.

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.

Also, since the biological carrier is operated in a fluidized bed, it is not exposed to intense disturbance. Therefore, since a large amount of organisms can be stably maintained, 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, the aeration maintains the pH in the reaction tank 2 in the vicinity of neutrality with little or no use of a neutralizing agent, and organic wastewater from low concentration to high concentration can be loaded with high load. In addition, it is possible to stably process at a low cost.

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

The packed amount of the fluidized bed carrier such as activated carbon is preferably about 30 to 70%, particularly about 40 to 60% of the volume of the reaction vessel. The larger the filling amount, the more the biomass and the higher the activity. However, if the amount is too large, the carrier may flow out. Therefore, it is preferable to pass water through an LV in which the fluidized bed develops about 20 to 50%. The water flow LV is about 7 to 30 m / h, particularly about 8 to 15 m / hr. As the fluidized bed carrier, a gel material other than activated carbon, a porous material, a non-porous material, etc. 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 specific surface area is large and the amount of attached organisms increases, but the carrier tends to flow out when the LV is high.

The deployment rate of activated carbon during normal operation is preferably about 20 to 50%. If the expansion rate is lower than 20%, there is a possibility of clogging and short circuit. If the development rate is higher than 50%, there is a risk of carrier outflow, and the pump power cost increases.

In normal biological activated carbon, the development rate of the activated carbon fluidized bed is about 10 to 20%, but in this case, the activated carbon flow is uneven and flows vertically and horizontally. As a result, the membrane installed at the same time is rubbed by activated carbon and worn out. In order to prevent this, in the present invention, the fluidized bed carrier such as activated carbon needs to be sufficiently fluidized, and the development rate is desirably 20% or more, for example, 20 to 50%. For this reason, the particle size of the carrier is preferably smaller than that of normal biological activated carbon. In addition, in the case of activated carbon, it is not specifically limited, such as coconut charcoal, coal, charcoal. The shape is preferably spherical charcoal, but may be ordinary granular charcoal or crushed charcoal.

<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.

<Flow rate of treated water>
The flow rate in the reaction tank of the water to be treated during normal operation is LV 7 m / hr or more, and the low-concentration waste water having a TOC concentration of 20 mg / L or less can be treated in one pass without circulating the treated water. Pumping power can be reduced by a one-time process. However, in order to obtain a high LV, a part of the treated water from the outlet 11 may be returned to the raw water spray pipe 8.

When the LV is increased, the oxygen dissolution rate is increased proportionally. When LV is high, it is preferable to use activated carbon having a large particle size so that the expansion rate is not so large. From the biomass and oxygen dissolution rate, the optimum LV range is about 7 to 30 m / hr, particularly about 8 to 15 m / hr.

<Residence time>
The residence time is preferably set so that the tank load is 0.5 to 4 kg-TOC / m ³ / day.

<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. 2018-028198 filed on Feb. 20, 2018, which is incorporated by reference in its entirety.

DESCRIPTION OF SYMBOLS 1 Aerobic biological treatment apparatus 2 Reaction tank 2W Widening part 6 Oxygen dissolution membrane module 9

Air diffuser pipe

20,21 Header 22 Hollow fiber membrane 27 Air supply piping 29 Exhaust piping 30 Exhaust gas piping 32 Tank

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;
An aerobic biological treatment apparatus comprising a fluidized bed of a carrier formed in a reaction vessel,
An aerobic biological treatment apparatus in which the upper part of the reaction tank is a widened part having a larger horizontal cross-sectional area than the lower side.
The aerobic biological treatment apparatus according to claim 1, wherein an upper surface of the fluidized bed is located in the widened portion during steady operation.
The aerobic biological treatment apparatus according to claim 1 or 2, wherein the oxygen-dissolving membrane module includes a non-porous oxygen-dissolving membrane.
The aerobic biological treatment apparatus according to claim 3, wherein the oxygen-dissolving membrane is hydrophobic.