TW201934498A - Operating method for aerobic organism treatment device - Google Patents

Abstract

An aerobic organism treatment device 1 has: a reaction tank (tank body) 2; a fluidic bed carrier packed into the reaction tank; a water-permeable plate 3 arranged horizontally at the bottom 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 dissolution film module 6 disposed on the upper side of the small-diameter particle layer 4; a receiving chamber 7 formed on the lower side of the water-permeable plate 3; a raw water dispersion tube 8 that supplies raw water into the receiving chamber 7; an air-diffusing tube 9 arranged so as to diffuse air inside the receiving chamber 7; etc. A blower 26 is controlled so that the DO of treated water is 1 mg/L or less.

Description

Operation method of aerobic biological treatment device

The invention relates to a method for operating an aerobic biological treatment device for organic drainage.

Because aerobic biological treatment methods are cheap, they are often used as treatment methods for organic wastewater. In this method, it is necessary to dissolve oxygen in the water to be treated, and usually aeration is performed by using a diffuser pipe.

The dissolving efficiency is low when using aeration tube for aeration, about 5-20%. In addition, it is necessary to perform aeration at a pressure higher than the water pressure received at the depth of the installation water of the air diffuser. Since a large amount of air is blown at a high pressure, the power cost of the blower is high. Generally, more than two thirds of the electricity cost in aerobic biological treatment is used for oxygen dissolution.

A membrane aerated biofilm reactor (MABR) using a hollow fiber membrane can dissolve oxygen without generating bubbles. In MABR, it is sufficient to ventilate the air at a pressure lower than the water pressure due to the water depth, so the required pressure of the blower is low, and the oxygen dissolution efficiency is high.

[Patent Document 1] Japanese Patent Laid-Open No. 2006-87310

An object of the present invention is to provide a method for operating an aerobic biological treatment device, which can minimize the amount of oxygen supplied to the water from the oxygen-dissolving membrane and reduce the power cost for supplying oxygen-containing gas. Furthermore, an object of one embodiment of the present invention is to provide a method for operating an aerobic biological treatment device capable of reducing the amount of excess sludge produced.
[Means for solving problems]

In the method for operating an aerobic biological treatment device of the present invention, the aerobic biological treatment device includes: a reaction tank; a fluidized bed carrier filled in the reaction tank; an oxygen-dissolved membrane module disposed in the reaction tank; and The oxygen-containing gas supply unit supplies the oxygen-containing gas to the oxygen-dissolved membrane module; and the operation method measures the dissolved oxygen concentration of the treated water in the upper clarified area of the reaction tank or the treated water flowing out of the reaction tank to The oxygen-containing gas supply unit is controlled so that the dissolved oxygen concentration is 1 mg / L or less.

In one embodiment of the present invention, the dissolved oxygen concentration (DO) is controlled to be 0.01 to 1 mg / L, particularly 0.2 to 1 mg / L.

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-soluble film is hydrophobic.

In one embodiment of the present invention, a fluidized bed carrier is filled in the reaction tank.
[Inventive effect]

In the method for operating an aerobic biological treatment device of the present invention, by controlling the DO of the treated water to be 1 mg / L or less, the supply amount of the oxygen-containing gas is not excessive, and the amount of oxygen-containing gas to be supplied can be reduced. Power costs (such as the cost of electricity for the blower).

If the DO of the treated water is 0.01 mg / L to 1 mg / L, the insufficient supply of oxygen-containing gas can be prevented. If the DO of the treated water is 0.2 to 1 mg / L, the number of rotifers in the reaction tank increases and the sludge in the reaction tank is preyed by tiny organisms such as rotifers, so the excess sludge is reduced.

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 device 1 according to the embodiment. The aerobic biological treatment device 1 includes a reaction tank (tank body) 2 and a water-permeable plate 3 which is a perforated plate such as a punching plate horizontally provided at the lower portion of the reaction tank 2 or a plurality of dispersion nozzles are evenly provided on the plate. 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; a fluidized bed F The upper side is formed by filling biologically-attached carriers such as powdered activated carbon; at least a part of the oxygen-dissolving membrane module 6 is arranged in the fluidized bed F; the receiving chamber 7 is formed on the lower side of the water-permeable plate 3; the raw water distribution pipe 8, Raw water is supplied into the receiving chamber 7; a washing pipe 9 is used to supply a gas for backwashing when the filling layer is washed; and a blower 26 is used to supply an oxygen-containing gas such as air to the oxygen-dissolving membrane module 6. . A trough 10 and an outflow port 11 for allowing the treated water to flow out are provided on the upper part of the reaction tank 2. The groove 10 forms an annular flow path along the inner wall of the groove.

A DO meter 13 is installed in the upper part of the reaction tank 2 or the treated water extraction pipe 12 connected to the outflow port 11, and a detection signal of the DO meter 13 is input to the blower controller 14.

In Fig. 1, the reaction tank is filled with a fluidized bed carrier, and the shear force generated by the carrier flow is used to suppress the adhesion of the biofilm to the surface of the oxygen-dissolved membrane, so that most of the biofilm is attached to the fluidized-bed carrier, and the oxygen is dissolved at this time. The membrane is used only for the purpose of oxygen supply. On the other hand, although not shown, when the reaction tank is not filled with a fluidized bed carrier, the oxygen-dissolved membrane functions as MABR, that is, the biofilm is adhered to the surface of the oxygen-dissolved membrane and dissolved from the primary side of the oxygen-dissolved membrane. Oxygen is consumed by the biofilm on the secondary side for aerobic biological treatment.

In FIG. 1, a non-porous (non-porous) oxygen-dissolving membrane is used as the oxygen-dissolving membrane, and an oxygen-containing gas is vented to the primary side of the oxygen-dissolving membrane through a pipe from the outside of the tank, and the exhaust gas is discharged to the outside of the tank through a pipe. discharge. Therefore, the oxygen-containing gas is vented to the oxygen-dissolving membrane at a low pressure, and oxygen is passed between constituent atoms of the oxygen-dissolving membrane (dissolved in the membrane) as oxygen molecules, and is contacted with the water to be treated as oxygen molecules. Since oxygen is directly dissolved in water, air bubbles are not generated. The above-mentioned method uses a mechanism for achieving molecular diffusion by using a concentration gradient, and does not need to use an air diffuser or the like to diffuse air as is conventionally known.

If a hydrophobic material is used as the material of the oxygen-dissolving film, it is difficult to immerse water in the film, which is preferable. However, even a hydrophobic membrane may have a slight amount of water vapor infiltration.

An example of the oxygen-dissolved membrane module 6 is shown in FIG. 2 (a) and FIG. 2 (b). The oxygen-soluble membrane module 6 uses a non-porous hollow fiber membrane 22 as an oxygen-soluble membrane. In this embodiment, the hollow fiber membranes 22 are arranged in the up-down 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 inside of the hollow fiber membrane 22 communicates with the inside of the upper header 20 and the lower header 21, respectively. Each of the upper header 20 and the lower header 21 is a hollow tube. In the case where a flat film or a spiral film is used, it is desirable to also arrange so that the ventilation direction is the vertical direction.

As shown in FIG. 2 (b), a plurality of units including a pair of the upper header 20, the lower header 21, and the hollow fiber membrane 22 are arranged in parallel. As shown in FIG. 2 (a), one or both ends of each upper header 20 are preferably connected to the upper manifold 23, and one or both ends of each lower header 21 are connected to the lower manifold 24.

In the present embodiment, air is supplied from the blower 26 to the lower portion of the oxygen-dissolving membrane module 6 as an oxygen-containing gas through a gas supply pipe 27, and non-permeable gas is discharged from the upper portion of the oxygen-dissolving membrane module 6 from the exhaust pipe 28. An oxygen-containing gas, such as air, flows from the lower header 21 through the hollow fiber membrane 22 to the upper header 20. During this period, oxygen passes through the hollow fiber membrane 22 and is dissolved in water in the reaction tank 2.

The amount of air supplied from the blower 26 is controlled by the blower controller 14.

Each of the upper header 20, the lower header 21, and each of the upper manifold 23 and the lower manifold 24 may have a flowing water gradient. The oxygen dissolving membrane module 6 may be arranged in multiple stages.

In order to supply air to the oxygen-dissolved membrane module 6, a blower 26 and an air supply pipe 27 are provided, thereby constituting an oxygen-containing gas supply unit. The air supply pipe 27 is connected to the lower manifold 24. An exhaust pipe 28 is connected to the upper manifold 23.

In the aerobic biological treatment device 1 configured in this manner, raw water is introduced into the receiving chamber 7 through the raw water distribution pipe 8, and the suspended solids are filtered by circulating water on the water-permeable plate 3 and the large-diameter particle layer 4 and the small-diameter particle layer 5 ( SS), followed by a fluidized bed of powdered granular activated carbon with a biofilm attached to it, a one-through type is used to circulate water to carry out a biological reaction, and pass through the groove 10 and the flow from the upper clarified area The outlet 11 is taken out as treated water.

After oxygen-containing gas such as air supplied from the gas supply pipe 27 flows upward in the oxygen dissolving membrane module 6, it flows out from the upper end position of the oxygen dissolving module 6, and the exhaust air is discharged from the exhaust pipe 28 to the atmosphere.

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

In addition, since the biological carrier operates in a fluidized bed, it is not severely disturbed. Therefore, since a large amount of living things can be stably maintained, the load can be increased.

In addition, since the oxygen dissolving membrane is used in the present invention, compared with pre-aeration and direct aeration, the dissolving power of oxygen is small.

According to the above description, according to the present invention, organic wastewater having a low concentration to a high concentration can be processed at a high load and inexpensively.

＜ Biocarriers ＞
The biological carrier is preferably 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 tank. The more the above-mentioned filling amount, the more the biomass and the higher the activity, but if it is too much, there is a concern that the carrier will flow out. Therefore, it is preferable to carry out water flow at a linear velocity (LV) (for example, about 7 to 30 m / hr, especially about 8 to 15 m / hr) at a fluidized bed development of about 20 to 50%.

In addition, as a fluidized bed carrier, a gel-like substance other than activated carbon, a porous material, a non-porous material, and the like can also be used under the same conditions. For example, a polyvinyl alcohol gel, a polypropylene gel, a polyurethane foam, a calcium alginate gel, a zeolite, a plastic, and the like can also be used. However, if activated carbon is used as a carrier, a wide range of pollutants can be removed by the interaction between the adsorption action of activated carbon and the biodegradation action.

The average particle diameter of the activated carbon is preferably about 0.2 to 1.2 mm, particularly about 0.3 to 0.6 mm. If the average particle diameter is large, a high LV can be obtained, and when a part of the treated water is circulated in the reaction tank, a high load can be achieved due to an increase in the amount of circulation. However, as the specific surface area becomes smaller, the biomass becomes smaller. If the average particle diameter is small, it can flow at a low LV, so the pump power is cheap. And because the specific surface area is large, the attached biomass is increased.

The optimal particle size also depends on the concentration of wastewater. If the total organic carbon content (TOC): 50 mg / L, the optimal particle size is preferably about 0.2 to 0.4 mm.

The expansion rate of the fluidized bed is preferably about 20 to 50%. If the expansion rate is less than 20%, there is a fear of clogging and short circuit. If the expansion rate is higher than 50%, there is a concern that the carrier flows out, and the pump power cost becomes high.

Among ordinary biological activated carbons, the activated carbon fluidized bed has a spreading rate of about 10 to 20%. However, in this case, the flow state of the activated carbon is uneven and flows up, down, left, and right. As a result, the simultaneously installed films are consumed due to friction and reduction due to activated carbon. In order to prevent this, in the present invention, since the fluidized bed support such as activated carbon needs to flow sufficiently, the expansion ratio is preferably 20% or more. Therefore, the particle diameter of the carrier is preferably smaller than the particle diameter of ordinary bioactive carbon. In the case of activated carbon, it is not particularly limited, and may be coconut shell carbon, coal, charcoal, and the like. The shape is preferably spherical carbon, but it may also be ordinary granular carbon or crushed carbon.

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

The ventilation was set so that the DO detected by the DO meter 13 became 1 mg / L or less. As described above, by setting the treated water DO to 1 mg / L or less, the power consumption of the blower 26 can be suppressed. In addition, if the DO is approximately 0 mg / L, nitrification and denitrification are performed simultaneously, so the biological treatment efficiency is improved. On the other hand, if the amount of DO is too large, the biofilm attached to the activated carbon becomes enlarged, oxygen cannot reach the deep part of the biofilm, and there is a concern that the deep biofilm is anaerobic and the biological reaction efficiency is reduced. In addition, there is also a concern that activated carbon adhering to an enlarged biofilm may leak out of the reaction tank.

The lower limit of DO may be 0 (zero), but in order to confirm the supply of oxygen required for aerobic treatment, it is preferably 0.01 mg / L or more, especially 0.2 mg / L or more.

In one embodiment of the present invention, the detection DO of the DO meter 13 is set to 0.2 to 1 mg / L. By setting DO to be 0.2 mg / L or more, the rotifer fertility in reaction tank 2 is increased, and sludge is eaten by rotifers, and the sludge is reduced, and excess sludge is reduced.

In the present invention, since the supply amount of the oxygen-containing gas is reduced so that the DO is 1 mg / L or less, it is preferred that the oxygen-containing gas flow upward through the hollow fiber membrane 22. This is because raw water is supplied to the lower part of the reaction tank 2, and it is preferable that the lower the lower part, the larger the amount of oxygen permeated through the membrane. When an oxygen-containing gas is supplied to the lower end of the hollow fiber membrane 22, the lower the inner portion of the hollow fiber membrane 22, the higher the oxygen partial pressure, and the upper the lower the oxygen partial pressure (dissolved in water due to oxygen permeation). Since the TOC component concentration in the water is lower as the upper part of the reaction tank 2 is lower, the oxygen partial pressure in the hollow fiber membrane 22 becomes lower in the upper part of the hollow fiber membrane 22, so even if the oxygen transmission rate through the hollow fiber membrane 22 is reduced, It is also ensured that the amount of oxygen required for the biological treatment is supplied to the water through the hollow fiber membrane 22.

In addition, if an oxygen-containing gas such as air is caused to flow upward in the hollow fiber membrane 22, there is a concern that the condensed water of the oxygen-containing gas may remain in the hollow fiber membrane 22.

Therefore, in the present invention, a drain pipe for allowing condensed water to flow out from the lower part of the oxygen permeation membrane module may be connected to the lower manifold 24, and an oxygen-containing gas may be supplied upward during normal operation, and the oxygen-containing gas may be intermittently supplied. The gas flows downward, and a condensate drainage operation to discharge the condensed water is performed.

＜ Flow rate of treated water ＞
The flow rate of the treated water in the reaction tank is LV7 m / hr or more, and the low-concentration drainage with a TOC concentration of 20 mg / L or less can also be processed in one pass without circulating the treated water. One-pass processing reduces pump power.

Increasing LV increases the rate of oxygen dissolution proportionally. When the LV is high, it is preferable to use activated carbon having a large particle diameter so that the expansion ratio is not so large. According to the biomass and the rate of oxygen dissolution, the optimal LV range is about 7-30 m / hr, especially about 8-15 m / hr.

＜ Residence 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 that the blower's discharge wind pressure is less than the water pressure generated by the water depth. However, it must be at least the pressure loss of the piping. Generally, the piping resistance is about 1 to 2 kPa.

When the water depth is 5 m, a general blower with a maximum output of about 0.55 MPa is usually used. When the water depth is more than 5 m, a high-pressure blower is used.

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

The conditions for the supply pressure of the oxygen-containing gas are that the pressure loss is higher than that of the hollow fiber membrane, and that the membrane is not crushed by water pressure. Compared with water pressure, the membrane pressure loss of flat and spiral membranes is negligible, so it is extremely low pressure (about 5 kPa or more) and below the water depth pressure, preferably 20 kPa or less.

In the case of a hollow fiber membrane, the pressure loss varies depending on the inner diameter and length. The amount of aerated air is 50-200 mL / day per square meter of membrane, so if the membrane length is doubled, the air volume is doubled, but even if the membrane diameter is doubled, the air volume is only doubled. Therefore, the pressure loss of the membrane is proportional to the length of the membrane and inversely proportional to the diameter.

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

Although the present invention has been described in detail using specific embodiments, those skilled in the art should understand that various changes can be made without departing from the spirit and scope of the present invention.
This case is based on Japanese Patent Application No. 2018-028200 filed on February 20, 2018, and the entirety of the above application is incorporated herein by reference.

1‧‧‧ aerobic biological treatment device

2‧‧‧ reaction tank

3‧‧‧ permeable board

4‧‧‧ large diameter particle layer

5‧‧‧ Trail particle layer

6‧‧‧ oxygen dissolving membrane module

7‧‧‧ Reception Room

8‧‧‧ raw water distribution pipe

9‧‧‧washing piping

10‧‧‧ Trench

11‧‧‧ Outflow

12‧‧‧ Piping for taking out treated water

13‧‧‧DO meter

14‧‧‧ Blower Controller

20‧‧‧ Upper header

21‧‧‧ Lower header

22‧‧‧ hollow fiber membrane

23‧‧‧ Upper Manifold

24‧‧‧ Lower Manifold

26‧‧‧ Blower

27‧‧‧Gas supply piping

28‧‧‧ exhaust pipe

F‧‧‧ fluidized bed

FIG. 1 is a vertical cross-sectional view of a biological treatment apparatus according to an embodiment.

FIG. 2 (a) is a side view of the oxygen-dissolving membrane unit, and FIG. 2 (b) is a perspective view of the oxygen-dissolving membrane unit.

Claims (5)

A method for operating an aerobic biological treatment device. The aerobic biological treatment device includes: Reaction tank A fluidized bed carrier filled in the reaction tank; An oxygen-dissolving membrane module is disposed in the reaction tank; and An oxygen-containing gas supply unit for supplying an oxygen-containing gas to the oxygen-dissolved membrane module; and The operation method measures the treated water in the upper clarified area of the reaction tank or the dissolved oxygen concentration of the treated water flowing out of the reaction tank, and controls the oxygen-containing gas supply unit so that the dissolved oxygen concentration is 1 mg / L or less. The operating method of the aerobic biological treatment device according to item 1 of the scope of the patent application, wherein the dissolved oxygen concentration is controlled in a manner of 0.01 to 1 mg / L. The method for operating an aerobic biological treatment device according to item 1 of the scope of the patent application, wherein the control is performed in such a manner that the dissolved oxygen concentration is 0.2 to 1 mg / L. The method for operating an aerobic biological treatment device according to any one of claims 1 to 3, wherein the oxygen-dissolving membrane module includes a non-porous oxygen-dissolving membrane. The method for operating an aerobic biological treatment device according to claim 4 in the patent application range, wherein the oxygen-dissolved membrane is hydrophobic.