JP2009050780A - Waste water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment method which is satisfactory in a filtration operation performance in a water treatment using a biological treatment tank. <P>SOLUTION: In the waste water treatment method, one or two or more hollow fiber membrane elements 10 are dipped in the biological treatment tank 100, air is diffused from an air diffusion means 133 inside the hollow fiber membrane elements 10, when filtering by the hollow fiber membrane elements 10 and when diffusing air into the biological treatment tank 100 during filtration, and air is diffused from air diffusion means 122, 125 outside the hollow fiber membrane elements 10 for filtering operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method in which a hollow fiber membrane element is immersed in a biological treatment tank and filtered.

  When the hollow fiber membrane module is used in the field of water treatment having a relatively high turbidity, it is often used in a state of being immersed in a biological treatment tank. In the case of such an immersion filtration type hollow fiber membrane module, there is a problem that, when filtration is continued, dirt due to suspended matter (SS) or the like adheres to the membrane surface and the filtration performance deteriorates. .

  Conventionally, dirt attached to the film surface is removed by air bubbling from below the film. However, dirt on the surface of the hollow fiber membrane positioned outside the hollow fiber membrane bundle is easy to remove, but dirt on the surface of the hollow fiber membrane inside the hollow fiber membrane bundle is difficult to remove, so air bubbling alone is sufficient. Recovery of filtration performance was difficult.

Moreover, in the biological treatment tank, it is necessary to diffuse into the tank, and normally, a method is used in which the air is diffused from an air diffuser arranged at the bottom of the tank.
JP 2005-342690 A JP 2006-239642 A JP 2003-326140 A

  In the hollow fiber membrane modules of Patent Documents 1 and 2, the air supply unit and the hollow fiber membrane are mixed in the lower fixing part, but it is difficult to generate fine bubbles and the cleaning effect is not sufficient.

  Furthermore, in the module of Patent Document 2, an air supply pipe and an ejection hole are provided in the lower fixing part. In such a module, an air supply pipe and an ejection hole are processed in the adhesive layer of the fixing part. More man-hours and higher processing costs.

  It is an object of the present invention to stably exhibit a high wastewater treatment capacity by performing cleaning of a hollow fiber membrane bundle and aeration in a biological treatment tank by aeration means installed inside and outside the hollow fiber membrane element. And

The invention of claim 1 is a wastewater treatment method in which one or two or more hollow fiber membrane elements are immersed in a biological treatment tank as a means for solving the problem, and filtration is performed by the hollow fiber membrane elements.
A wastewater treatment method in which when air is diffused into the biological treatment tank during filtration treatment, air is diffused from the air diffuser in the hollow fiber membrane element and air is diffused from the air diffuser outside the hollow fiber membrane element. provide.

  Invention of Claim 2 provides the waste water treatment method of Claim 1 which performs the aeration from the said hollow fiber membrane element from the aeration means arrange | positioned at the bottom part of the biological treatment tank as a solution means of a subject. .

  The invention according to claim 3 uses, as the means for solving the problem, as the hollow fiber membrane element, a plurality of hollow fiber membranes are arranged around a support tube, and the support tube also serves as an air diffuser. Claim | item 1 or the waste water treatment method of 2 is provided.

  According to a fourth aspect of the present invention, as a means for solving the problem, as the hollow fiber membrane element, a large number of hollow fiber membranes are arranged around a support tube, and the support tube is disposed outside and inside the diffuser tube. The wastewater treatment method according to claim 1 or 2, wherein a double pipe structure having a water collecting pipe arranged is used.

  As a means for solving the problem, the invention of claim 5 is characterized in that the diameter (dm) of the air diffusion holes of the air diffuser that diffuses from inside the hollow fiber membrane element and the air diffuser that diffuses from outside the hollow fiber membrane element. The waste water treatment method according to any one of claims 1 to 4, wherein a diameter (d) of the air diffusion holes of the material is d ≦ dm.

  According to the wastewater treatment method of the present invention, high filtration performance can be stably exhibited when biological treatment and membrane separation are used in combination.

  The waste water treatment method of the present invention will be described with reference to FIG. FIG. 1 is a conceptual diagram of a wastewater treatment apparatus used in the wastewater treatment method of the present invention, and illustrates a biological treatment tank in the apparatus. The wastewater treatment method of the present invention is characterized by a treatment flow using a wastewater treatment apparatus including a biological treatment tank, and the treatment flow by treatment means other than the biological treatment tank is the same as a known treatment flow. Can be.

<Wastewater treatment equipment>
A biological treatment tank used in the wastewater treatment apparatus will be described with reference to FIG. The inside of the biological treatment tank 100 is divided into three by partition walls 111 and 112, and is separated into a first tank 114, a second tank 115, and a third tank 116. The processing liquid can move to the adjacent tank beyond the upper ends of the partition plates 111 and 112. The biological treatment tank 100 may have one partition plate, three or more partition plates, or may have no partition plate.

  A raw water supply line 121 is connected to the first tank 114, and raw water is supplied. The raw water here may be water that has not been treated at all (drainage from various facilities, river water, etc.), or treated by known treatment means such as oil / water separation treatment, coagulation treatment, filtration treatment using a microfilter, etc. Treated water may be used.

  A first air diffuser 122 is arranged on the bottom surface of the first tank 114 and is connected to the first air diffuser line 123. Further, in the first tank 114, a water level meter 124 used for adjusting the raw water supply amount is placed. As the first air diffuser 122, a cylindrical member having a large number of pores (however, the end surface not connected to the first air diffuser line 123 is closed), US Publication No. 2005/151128 A1. 2. What was shown by FIG. 1 of Unexamined-Japanese-Patent No. 2007-777 etc. can be used.

  A second air diffuser 125 is disposed on the bottom surface of the third tank 116 and is connected to the second air diffuser line 126. The second air diffuser 125 can be the same as the first air diffuser 122.

  Furthermore, a plurality of hollow fiber membrane elements 10 are immersed in the third tank 116, which is located immediately above the second air diffuser 125 and spaced from the bottom surface. The plurality of hollow fiber membrane elements 10 are connected to the permeate line 131 and the air supply line 132. The hollow fiber membrane element 10 can be connected to a well-known counter pressure cleaning means (such as a cleaning water tank, a chemical solution tank, a counter pressure cleaning line, a pump, etc.) to enable counter pressure cleaning.

  The first aeration means 122 is for supplying oxygen for biological treatment in the biological treatment tank 100, and the second aeration means 125 is for mainly washing the hollow fiber membrane element 10 from the outside. It is. Both the first air diffuser 122 and the second air diffuser 125 may be installed, or only one of them may be installed. When the first air diffuser 122 is not installed, the second air diffuser 125 both cleans the hollow fiber membrane element 10 and supplies oxygen into the biological treatment. In this case, the partition plate Is not installed.

  The hollow fiber membrane element 10 has an internal air diffusion means 133 inside the membrane bundle, and has a structure in which the membrane surface can be cleaned by aeration from the inside of the membrane bundle.

  The diameter (dm) of the air diffuser hole of the internal air diffuser 133 included in the hollow fiber membrane element 10 and the diameter (d) of the air diffuser hole included in the first air diffuser 122 and the second air diffuser 125 are d ≦ dm. Preferably there is. By making such a magnitude relationship, it is possible to appropriately supply oxygen to the biological treatment tank and clean the membrane surface.

  In addition, the diameter of the diffuser hole which the 1st diffuser means 122 and the 2nd diffuser means 125 may differ may be different, and in that case, the diameter (d) of the said diffuser hole is a hole diameter with a larger diameter. is there. Further, when the diameters of the air diffusion holes of the first air diffusion means 122 and the second air diffusion means 125 are different, it is desirable that the diameter of the air diffusion holes of the first air diffusion means 122 is smaller.

  Next, a plurality of embodiments of the hollow fiber membrane element 10 applicable to the wastewater treatment apparatus used in the present invention will be described.

(1) Hollow fiber membrane element of FIG. 2 FIG. 2 is a longitudinal sectional view of a hollow fiber membrane element 10A according to an embodiment of the present invention.

  The hollow fiber membrane element 10 </ b> A has a large number of hollow fiber membranes (hollow fiber membrane bundles) 20 arranged around the support tube 11.

  The support tube 11 has a double tube structure having an outer diffuser tube 12 and a water collecting tube 13 disposed inside the diffuser tube 12. The air diffuser 12 and the water collecting tube 13 are made of metal, plastic, or a combination thereof.

  The air diffuser 12 has a diffuser cylinder 15 having a large number of pores (air diffuser holes) 16 connected to one end side of an air diffuser main pipe 14 having no holes, and these are internal diffuser means shown in FIG. It corresponds to 133. As the dust cylinder 15, a known porous cylinder can be used, and for example, one made of a synthetic resin such as ABS resin described in JP-A-8-155484, or one made of ceramics can be used.

  The diffuser main pipe 14 and the diffuser cylinder 15 are detachably connected by a screwing method or a fitting method. The opening direction of the air diffusion holes 16 is not particularly limited, and may be any of a direction facing the hollow fiber membrane bundle 20, a diagonally upward direction, a diagonally downward direction, and a direction in which these directions are mixed. An air introduction pipe 18 for introducing air into the diffusion pipe 12 from the outside is connected to the upper end side of the diffusion main pipe 14. The air introduction pipe 18 is connected to the air supply line 132 of FIG.

The diameter and density (the number of holes per unit area) of the fine holes (aeration holes) 16 of the diffusion cylinder 15 can be appropriately set in consideration of the number of hollow fiber membranes constituting the hollow fiber membrane bundle 20 and the like. For example, the diameter can be in the range of 0.01 to 1 mm, and the density can be in the range of 100 to 10,000 pieces / cm ² .

The water collecting pipe 13 is disposed such that the central axis in the length direction thereof coincides with the central axis of the diffuser main pipe 14. The ratio of the outer diameter (d ₁ ) of the water collecting pipe 13 and the inner diameter (d ₂ ) of the diffuser main pipe 14 is not particularly limited, and d ₁ / d ₂ is in the range of 0.2 to 0.8. Can be. The outer diameter of the diffuser main pipe 14 can be about 10 to 30 mm.

  The hollow fiber membranes constituting the hollow fiber membrane bundle 20 are publicly known, one having an outer diameter of about 1 to 3 mm, an inner diameter of about 0.5 to 2 mm, and a length of 30 to 300 cm per one hollow fiber membrane element. Several hundreds can be used.

  The upper ends of the hollow fiber membrane bundle 20, the diffuser main pipe 14 and the water collecting pipe 13 are fixed and integrated in the upper ring 32 with a resin 33 such as urethane resin or epoxy resin. An upper water collecting cap 31 is screwed around the upper ring 32 so as to be integrated. The ends of the hollow fiber membrane bundle 20 facing the inside of the upper water collecting cap 31 and the water collecting pipe 13 are opened, and the diffuser main pipe 14 is sealed with the resin 33 and is not opened.

  The lower ends of the hollow fiber membrane bundle 20, the diffuser main pipe 14, and the water collecting pipe 13 are fixed and integrated in a lower ring 42 with a resin 43 such as urethane resin or epoxy resin. A lower water collecting cap 41 is screwed around the lower ring 42 so as to be integrated. The ends of the hollow fiber membrane bundle 20 and the water collecting pipe 13 facing the lower water collecting cap 41 are opened, and the diffuser main pipe 14 is sealed with the resin 43 and is not opened.

  Such a fixing method using the resins 33 and 43 applies a known hollow fiber membrane bundle resin sealing method, and seals both ends of the hollow fiber membrane bundle 20, the diffuser main pipe 14 and the water collecting pipe 13 with resin. After stopping, a method of cutting and opening both ends of the hollow fiber membrane bundle 20 and the water collecting pipe 13 can be applied.

  The inside of the upper cap 31 is an upper water collecting chamber 35 and is connected to the water collecting main through a communication pipe 36 when used. The lower cap 41 is a lower water collecting chamber 45.

(2) Hollow fiber membrane element of Fig. 3 Fig. 3 is a longitudinal sectional view of a hollow fiber membrane element 10B which is another embodiment of the present invention. The hollow fiber membrane element 10A in FIG. 2 has the same structure except for a part. Only different parts will be described below.

  The support tube 11 has a double tube structure having an outer diffuser tube 12 and a water collecting tube 13 disposed inside the diffuser tube 12. The air diffuser 12 and the water collecting tube 13 are made of metal, plastic, or a combination thereof.

  The air diffuser 12 has a large number of air diffusers 16 only on the lower end side, and the air diffuser 15 in FIG. 2 is not used. The air diffuser 16 may also be formed in other parts (the center part and the upper end part) of the air diffuser 12. The air diffuser 12 corresponds to the internal air diffuser 133 shown in FIG.

  One end side of the air introduction pipe 18 penetrates the resin 33 and communicates with the diffuser pipe 12, and the other end side penetrates the curved surface portion of the upper water collecting cap 31. In the case of this embodiment, the width of the hollow fiber membrane element 10B including the air introduction tube 18 is made narrower than the configuration in which the air introduction tube 18 is extended in the lateral direction as in the hollow fiber membrane element 10A of FIG. be able to.

  The upper end side of the air diffusing tube 12 is connected to the upper adapter 17a, and the lower end side of the air diffusing tube 12 is connected to the lower adapter 17b. Each connecting portion is detachably connected by a screwing method or a fitting method. An air introduction pipe 18 that introduces air into the diffusion pipe 12 from the outside is connected to the upper end side of the diffusion pipe 12. The air introduction pipe 18 is connected to the air supply line 132 of FIG.

  The upper end side of the upper adapter 17 a is fixed and integrated with the resin 33 together with the upper end side of the hollow fiber membrane bundle 20 and the water collecting pipe 13. The lower end side of the lower adapter 17 b is fixed and integrated with the resin 43 together with the hollow fiber membrane bundle 20 and the lower end side of the water collecting pipe 13.

(3) Hollow fiber membrane element of Fig. 4 Fig. 4 is a longitudinal sectional view of a hollow fiber membrane element 10C which is still another embodiment of the present invention. The hollow fiber membrane element 10A in FIG. 2 has the same structure except for a part. Only different parts will be described below.

  The support tube 11 has a double tube structure having an outer diffuser tube 12 and a water collecting tube 13 disposed inside the diffuser tube 12. The air diffuser 12 and the water collecting tube 13 are made of metal, plastic, or a combination thereof.

  The air diffuser 12 includes a rubber membrane 19 and a support tube 12a ′ for supporting the rubber membrane 19, and the cylindrical rubber membrane 19 is in close contact with the surface of the support tube 12a ′ having a large number of ventilation holes 16 over the entire surface. It is covered. These correspond to the internal air diffusion means 133 shown in FIG. Both ends of the rubber membrane 19 are fixed to the upper adapter 17a and the lower adapter 17b.

  The rubber membrane does not have a visible hole in a normal state (a state in which no pressure is applied), but when subjected to pressure, the rubber membrane itself expands to form a fine hole. As such a rubber membrane, there are fine holes in a stretchable rubber sheet as disclosed in JP-A-2006-75771, JP-A-2007-14898, JP-A-2004-33889, and the like. Can be used.

(4) Hollow fiber membrane element of FIG. 5 FIG. 5 is a longitudinal sectional view of a hollow fiber membrane element 10D which is still another embodiment of the present invention. The structure is similar to the hollow fiber membrane element 10C of FIG.

  The support tube 11 has a double tube structure having an outer rubber membrane 19 (corresponding to the diffuser tube 12 in FIG. 4) and a water collecting tube 13 disposed therein. The water collection pipe 13 is made of metal, plastic, or a combination thereof. The rubber membrane 19 is placed in close contact with the surface of the water collection tube 13. Both ends of the rubber membrane 19 are fixed to the upper adapter 17a and the lower adapter 17b.

  In the present embodiment, the water collection pipe 13 also serves as a support pipe 12 'in the hollow fiber membrane element 10C. Since the rubber membrane 19 (corresponding to the internal air diffuser 133 shown in FIG. 1) that becomes the air diffuser is inflated and opened by pressurization, the rubber membrane 19 is in close contact with the water collecting tube 13. Therefore, an outer diameter can be made smaller than the diffuser tube 12 in the hollow fiber membrane element 10C. For this reason, when the membrane elements have the same outer diameter, the filling rate of the hollow fiber membrane is higher than that of the hollow fiber membrane element 10C.

<Wastewater treatment method>
Next, the waste water treatment method of the present invention will be described with reference to FIG. Raw water is supplied from the raw water supply line 121 into the first tank 114 of the biological treatment tank 100. The supply amount is adjusted using the water level gauge 124.

  In the 1st tank 114, aeration is performed by the 1st aeration means 122, and biological treatment is performed. The water treated in the first tank 114 flows into the second tank 115 beyond the partition plate 111, and further flows into the third tank 116 beyond the partition plate 112.

  In the third tank 116, membrane separation by the plurality of hollow fiber membrane elements 10 is performed. At this time, the hollow fiber membrane element 10 can maintain high filtration performance because the membrane surface is washed from the outside by the second aeration means 125 and the membrane surface from the inside is washed by the internal aeration means 133. . The second air diffuser 125 and the internal air diffuser 133 may be operated continuously, intermittently, simultaneously, or alternately.

  In addition, by setting the relationship between the diameter (dm) of the air diffuser of the internal air diffuser 133 and the diameter (d) of the air diffuser included in the first air diffuser 122 and the second air diffuser 125, d ≦ dm. Balancing supply of oxygen into the biological treatment tank 100 by the first air diffuser 122, cleaning of the membrane surface from the inside by the internal air diffuser 133, and cleaning of the membrane surface from the outside by the second air diffuser 125 Since it can perform well, the filtration performance combining biological treatment and membrane separation can be improved.

Example 1
Waste water treatment was performed using a waste water treatment apparatus having a biological treatment tank (the tank internal volume 0.1 m ³ ; however, the tank 115 is not included) whose interior is not separated by a partition plate. A total of four air diffusers were installed at positions corresponding to the first air diffuser 122 and the second air diffuser 125 shown in FIG. The air diffuser used was a Pearlcon Membrane Diffuser Ultra Fine Bubble Tube Type (PMD-T03) (manufactured by Daisen Membrane Systems). The aeration pore diameter is as shown in Table 1.

The hollow fiber membrane element 10A shown in FIG. 2 was used as the hollow fiber membrane element. The hollow fiber membrane element 10A has an effective membrane area of 0.9 m ² , an effective membrane length of 400 mm, an inner diameter / outer diameter of one hollow fiber membrane = 0.9 mm / 2.0 mm, and a diameter of an air diffuser dm = 0.3 mm. Yes, two of them were used.

  As raw water, simulated waste water of 1,000 mg / L BOD mainly composed of glucose, urea and inorganic salts was supplied to a biological treatment tank filled with activated sludge. In the filtration operation, filtration was performed at a constant flow rate of 20 L / h, and this was repeated with a filtration time of 7 minutes and a filtration stop time of 1 minute as one cycle.

  During the filtration operation, air was diffused at 60 L / min from the air diffuser corresponding to the first and second air diffusers 122 and 125 and the internal air diffuser in the hollow fiber membrane element.

While the filtration was stopped, back pressure washing using a permeate was performed at 20 L / h for 1 minute. The difference in the differential pressure of the hollow fiber membrane at the start of operation and after one week from the start of operation (the degree of increase in the differential pressure)
The dissolved oxygen concentration was measured. The results are shown in Table 1.

Example 2
A filtration operation was carried out in the same manner as in Example 1 except that a pearl-con porous material small diameter (manufactured by Daisen Membrane Systems Co., Ltd.) was used as the air diffuser corresponding to the second air diffuser 125. The results are shown in Table 1.

Comparative Example 1
As the hollow fiber membrane element, the same element as in Examples 1 and 2 was used except that it did not have an internal air diffuser, and the same air diffuser as that in Example 2 was used as the air diffuser corresponding to the second air diffuser 125. The filtration operation was performed in the same manner as in Example 1 except for the above. The results are shown in Table 1.

The conceptual diagram of the processing flow of the waste water treatment method of this invention. The longitudinal cross-sectional view of the hollow fiber membrane element used by this invention. The longitudinal cross-sectional view of other embodiment of the hollow fiber membrane element used by this invention. The longitudinal cross-sectional view of other embodiment of the hollow fiber membrane element used by this invention. The longitudinal cross-sectional view of other embodiment of the hollow fiber membrane element used by this invention.

Explanation of symbols

10 (10A to 10D) Hollow fiber membrane element 100 Biological treatment tank 111, 112 Partition wall 114 First tank 115 Second tank 116 Third tank 122 First air diffuser 125 Second air diffuser

Claims (5)

A wastewater treatment method in which one or two or more hollow fiber membrane elements are immersed in a biological treatment tank and filtration is performed by the hollow fiber membrane element.
A wastewater treatment method in which when air is diffused into the biological treatment tank during filtration treatment, air is diffused from the air diffuser in the hollow fiber membrane element and from the air diffuser outside the hollow fiber membrane element.   The wastewater treatment method according to claim 1, wherein aeration from the outside of the hollow fiber membrane element is performed from aeration means arranged at the bottom of the biological treatment tank.   The wastewater treatment method according to claim 1 or 2, wherein a plurality of hollow fiber membranes are arranged around a support tube as the hollow fiber membrane element, and the support tube also serves as an air diffusion tube.   As the hollow fiber membrane element, a plurality of hollow fiber membranes are arranged around a support tube, and the support tube has a double tube structure having an outer air diffuser tube and a water collecting tube disposed inside the air diffuser tube. The waste water treatment method of Claim 1 or 2 which uses a thing.   The diameter (dm) of the air diffuser that the air diffuser that diffuses from inside the hollow fiber membrane element and the diameter (d) of the air diffuser that the air diffuser diffuses from outside the hollow fiber membrane element are d ≦ The wastewater treatment method according to any one of claims 1 to 4, which is dm.

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