JPH04290594A - Method and device for biological treatment - Google Patents

Abstract

PURPOSE:To supply oxygen to the org. sewage in a treating tank without any power or with a small amt. of power if needed in the biological treatment of org. sewage. CONSTITUTION:At least a part of the wall of a treating tank 1 to be charged with org. sewage is formed with a hydrophobic porous membrane 2, and oxygen is permeated through the membrane 2 and introduced into a liq. mixture 4 to aerobically treat the liq. mixture.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a biological treatment method and apparatus for organic wastewater, and in particular to a biological treatment method and apparatus that can supply oxygen to organic wastewater in a treatment tank without or with a small amount of power. The present invention relates to a chemical treatment method and apparatus.

0002

[Prior Art] As a method of biologically treating organic wastewater such as sewage, human waste, and industrial wastewater, there is a method of aerobic treatment by supplying oxygen-containing gas in the presence of activated sludge or bacterial cells. A well-known and frequently used method is to use a blower to supply air to the porous body of an aeration device installed underwater to generate bubbles, and then dissolve the oxygen in the bubbles into the liquid. There is a way to do it. This method requires only a blower and a diffuser, so a simple device is sufficient.
It is widely used because it has a considerable ability to dissolve oxygen, its processing capacity can be changed freely, and it also has a stirring effect on the liquid as bubbles rise from the aeration device.

0003

[Problems to be Solved by the Invention] However, in this method, it is necessary to supply air at a pressure equivalent to at least the water pressure equivalent to the water depth in which the porous body is installed, and the power required for this is extremely large. When diffusing air into a liquid, the power required per amount of oxygen supplied is at the same level even when using an oxygen supply means other than the above-mentioned aeration device constructed from a porous material. be.

[0004] In order to carry out biological treatment of organic wastewater economically, it is necessary to reduce the energy required for treatment as much as possible. For this reason, it is preferable to reduce the power required to supply oxygen in biological treatment. An object of the present invention is to provide a means for supplying oxygen to activated sludge or bacterial cells without power or with minimal power in biological treatment.

[0005]

[Means for Solving the Problems] The present invention can achieve the above object by the following means. 1. A treatment method for aerobic biological treatment of organic wastewater, characterized in that the organic wastewater is subjected to aerobic treatment using oxygen that is taken in through a hydrophobic porous membrane that constitutes at least a part of the tank wall of a treatment tank. biological treatment method. 2. A treatment device for aerobic biological treatment of organic wastewater, characterized in that at least a part of the tank wall is made of a hydrophobic porous membrane, and the hydrophobic porous membrane is permeable to oxygen-containing gas. Biological treatment equipment.

[0006] At least a part of the tank wall of the treatment tank is formed of a hydrophobic porous membrane made of polytetrafluoroethylene, polypropylene, polyethylene, etc., and oxygen from outside the tank is passed through the minute pores of this porous membrane. Oxygen is supplied to the liquid in the processing tank by permeating oxygen from the contained gas. The porous membrane preferably has a porosity (ratio of space to the apparent volume of the membrane) of about 50 to 70% in order to not allow liquid to pass through it, but to allow oxygen to pass therethrough. Further, the pore size of the membrane is preferably from 0.01 micron to several microns, and since increasing the pore size makes it easier for water to leak, it is usually preferably about 1 micron. The thinner the porous membrane is, the better in terms of permeating oxygen, but it is necessary to have a certain degree of thickness in order to withstand the water pressure of the liquid. Of course, if the porous membrane was made thick enough to withstand the water pressure of the liquid, it would be quite thick and the permeation of oxygen would be reduced, so a thin hydrophobic porous membrane that is thick enough to permeate oxygen is used. It is preferable to support a sheet-like support with greater porosity, and then to support it with a support having stronger strength and larger pores, such as a punched metal or a perforated metal plate. In addition, the hydrophobic porous membrane has an inner side that sufficiently blocks the passage of liquid and a porous layer that has a porosity that allows oxygen to pass through, and an outer side that has a porosity that allows oxygen to pass through more easily than the above-mentioned layer. A double layer membrane with a porous layer can be used. The number of layers can be two or more.

Furthermore, since at least a portion of the tank wall is formed of a hydrophobic porous membrane, it is undesirable for liquid to flow out from the porous membrane. In order to prevent liquid from flowing out, it is necessary that the immersion pressure be greater than the water pressure. In order to be able to construct a container using the porous membrane, it is preferable that the membrane itself has a suitable tensile strength. Specifically, the tensile strength of the membrane is preferably 4 to 6 kgf/mm2. This tensile strength is comparable to the tensile strength of 5 to 6 kgf/mm2 of polyvinyl chloride pipes. On the other hand, the water immersion pressure of the porous membrane is usually 2 kgf/cm.
It is 2.

[0008] In the hydrophobic porous membrane, it is preferable that the substance constituting the membrane is hydrophobic in order to prevent the liquid from flowing out as described above. It is preferable that the layer has the effect of promoting the dissolution of oxygen that has passed through the layer, and for this purpose, it may contain a catalyst or the like. The shape of the treatment tank can be various shapes such as cylindrical and rectangular, but it is preferable to make it as thin as possible so that the liquid is not placed far from the hydrophobic porous membrane. Oxygen is supplied to the liquid by permeation and dissolution of oxygen through the porous membrane, as well as by diffusion of dissolved oxygen, so stirring of the liquid can be performed to promote this.

[0009] Almost all of the portion of the tank wall of the processing tank that is in contact with the liquid may be composed of the porous membrane, or only a portion thereof may be composed of the porous membrane. Since the amount of dissolved oxygen is proportional to the area of the porous membrane, in order to increase the area of the tank wall made of the porous membrane, a hollow tank wall is provided in the processing tank, the inside of which communicates with the outside air. Can be done.

[0010] Furthermore, in the present invention, oxygen is supplied from outside air through a hydrophobic porous membrane by permeation and dissolution by diffusion of oxygen. By sending a gas with a high oxygen concentration instead of air, the amount of oxygen supplied to the processing tank can be increased.

[0011]

[Function] In the aerobic biological treatment of organic wastewater, at least a part of the tank wall of the treatment tank is composed of a hydrophobic porous membrane, and oxygen is supplied by passing through the porous membrane from the outside air. Regardless of the depth of the water in the treatment tank, oxygen can be directly supplied only through diffusion permeation, so the power required to supply oxygen to the liquid in the treatment tank is almost zero, and as a result, oxygen can be supplied with extremely little power. Furthermore, in the present invention, it is possible to stir the liquid in the processing tank in order to promote the supply of oxygen or to make the processing uniform, but the conventional method does not involve chaotic stirring due to air suction. Since it is sufficient to perform the necessary and sufficient stirring that is optimal for the treatment of the liquid, there is no wasted energy consumption during stirring, and there is no adverse effect on the properties of the activated sludge.

0012

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. Example 1 FIG. 1 shows a schematic diagram of a biological treatment apparatus that is an example of the present invention. The treatment tank 1 has a cylindrical shape and is made of a hydrophobic porous membrane (pore diameter 1 micron) made of polytetrafluoroethylene with a porosity of 70%.
2 constitutes a tank wall, and organic sewage 3 flows into this treatment tank 1, mixes with activated sludge to form a mixed liquid 4, passes through the porous membrane 2, and is treated by dissolved oxygen in the atmosphere. Activated sludge slurry 5 subjected to aerobic treatment
The activated sludge enters the sedimentation tank 6 from the treatment tank 1, the activated sludge is precipitated, and the clarified treatment liquid 7 is taken out.The activated sludge accumulated in the sedimentation tank 6 is sent to the treatment tank 1 as return sludge 8.

Example 2 FIG. 2 shows a schematic diagram of a biological treatment device as another example of the present invention, and FIG. 3 shows a schematic plan view of a treatment tank in the device. The treatment tank 1 of this biological treatment equipment includes an upper liquid storage section 11
A cylindrical body 10 consisting of six hydrophobic porous membranes 2 is disposed between the upper and lower liquid reservoirs 12 and communicates vertically through them, and the cylindrical body 10 increases the membrane area of the porous membranes 2. is being measured. Air is passed between the cylindrical bodies 10 by a blower 9 to improve oxygen permeation. The other configurations are the same as shown in FIG. This biological treatment equipment is
Since the area of the porous membrane is large, the processing capacity can be increased, and it can be further increased by ventilation.

Example 3 FIG. 4 shows a schematic diagram of a biological treatment apparatus which is another example of the present invention. The processing tank 1 of this device is divided by surrounding the outside of the hydrophobic porous membrane 2 that constitutes the tank wall to form an oxygen gas chamber 13, and by supplying an oxygen-enriched gas 14 to this,
The amount of oxygen that passes through the porous membrane 2 and enters the liquid is increased. By driving the stirrer 15, the necessary minimum amount of stirring can be performed. This stirring may not be performed when mixing within the processing tank is not required.

Example 4 This example is a test example for explaining the effectiveness of the present invention. This test example does not directly treat organic wastewater, but since biological treatment is closely related to the oxygen supply capacity, the oxygen supply capacity of the treatment tank in the present invention was tested and the treatment It's about looking at ability. In this test example, a test apparatus shown in FIG. 5 was used. This testing device has a cylindrical treatment tank 1 with a height of 5 m and a diameter of 5 cm, the cylindrical surface of which is made of a hydrophobic porous membrane made of polytetrafluoroethylene resin (porosity 70%, pore diameter 1 micron) 2. , the upper end of the processing tank 1 is sealed. In order to mix the inside of the tank, a liquid path 16 is provided that communicates from the upper end to the lower end of the processing tank, and a pump 17 is provided in the middle of the tank and is driven to drive the liquid path 1.
6, the liquid is sent from the upper end of the processing tank 1 to the lower end of the processing tank 1.
Mixing and agitation is performed by flowing the inside as an upward flow. A DO sensor 18 is installed in the treatment tank 1 and connected to a dissolved oxygen meter 19.

[0016] In the test, deoxygenated ion-exchanged water was placed in the treatment tank 1, and after the dissolved oxygen concentration in this water was brought to zero, the change in dissolved oxygen in the water in the tank was measured by driving the pump. The oxygen supply capacity was measured. The results are shown in Table 1.
Table 1
Average flow velocity in the tank
Oxygen supply capacity [c
m/sec]
[mg/Lh]
5
43
10
64
15
84
20
92
30
107
40
122 Oxygen supply capacity is expressed as the amount of oxygen [mg] that can be supplied to 1 L (liter) per hour, and as shown in Table 1, the oxygen supply capacity of the present invention is sufficient for general activated sludge treatment. . No power was used to supply oxygen in this test.

[0017]

Industrial Applicability According to the present invention, oxygen can be supplied to activated sludge or bacterial cells without or with very little power during aerobic treatment of organic wastewater. In addition, stirring the liquid in the processing tank can increase its oxygen supply capacity, but in the present invention, stirring and mixing for processing only needs to be carried out within the minimum necessary range, so energy consumption can be reduced. . This method is preferable for biological treatment because it does not cause severe disturbance of the liquid or activated sludge, unlike when air is blown into the liquid using an aeration device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a biological treatment device that is an example of the present invention.

FIG. 2 is a schematic diagram of a biological treatment measure that is another example of the present invention.

3 is a schematic plan view of a treatment tank in the biological treatment apparatus shown in FIG. 2. FIG.

FIG. 4 is a schematic diagram of a biological treatment device that is another example of the present invention.

FIG. 5 is a schematic diagram of a test device used to measure oxygen supply capacity in the present invention.

[Explanation of symbols]

1 Processing tank 2 Hydrophobic porous membrane 3. Organic wastewater 4 Mixed liquid 5 Activated sludge slurry 6 Sedimentation tank 7. Treated water

Claims (2)

[Claims] Claim 1. A treatment method for aerobic biological treatment of organic wastewater, in which organic wastewater is subjected to aerobic treatment using oxygen introduced through a hydrophobic porous membrane that constitutes at least a part of the tank wall of a treatment tank. A biological treatment method characterized by: [Claim 2] A treatment device for aerobic biological treatment of organic wastewater, wherein at least a portion of a tank wall is composed of a hydrophobic porous membrane, and the hydrophobic porous membrane is permeable to an oxygen-containing gas. A biological treatment device characterized by: