KR100236921B1 - Immersion type hollow fiber membrane module and method for treating waste water by using the same - Google Patents

Abstract

The present invention relates to an immersion type hollow fiber membrane module (hollow fiber membrane module) used for filtration of high concentration wastewater and a wastewater treatment method using the same, and comprising: a filtration unit including a hollow fiber membrane bundle, a hollow fiber membrane fixing unit and a suction line; Hollow fiber is contaminated by contaminating the hollow fiber membrane module including a bubbling portion consisting of an air pipe and an air nozzle in the wastewater and intermittently sucking and filtering the wastewater from the membrane surface to the inside of the membrane while washing the surface of the hollow fiber membrane by abandoning the air. Because of this, the hollow fiber membranes can be effectively washed without lumping, thereby preventing the blockage of the membranes, minimizing the loss of filtration function, and treating wastewater economically and efficiently.

Description

Immersion hollow fiber membrane module and wastewater treatment method using the same

The present invention relates to an immersion type hollow fiber membrane module for use in filtration of high concentration wastewater, and a wastewater treatment method using the same. By intermittently sucking and filtering wastewater from the membrane surface to the inside of the membrane while giving up air to wash the surface of the hollow fiber membrane, the hollow fiber does not agglomerate due to contaminants and effectively washes the hollow fiber membrane during filtration to prevent clogging of the membrane.

Traditionally, hollow fiber membrane modules have been widely used in the field of precision filtration, such as sterile water, drinking water, ultrapure water production, and recently, secondary and tertiary treatment in sewage treatment, solid-liquid separation in septic tanks, suspended solids in industrial wastewater ( Its application has been attempted for the removal of SS, Suspended Solids, filtration of river water, filtration of industrial water and filtration of swimming pool water (see Environmental Tech., 8, 121-132 (1987)).

However, most hollow fiber membrane modules used in these applications are casing-type cylindrical modules that include a bundle of hollow fiber membranes arranged circularly in a cylindrical tube (Capital Association Magazine, 62 (2), 28 (1993)). Up to now, only improvements to the packing density and the filling type of the hollow fiber membranes have often been made. However, when a conventional cross flow type casing type cylindrical hollow fiber membrane module is applied to high concentration wastewater (SS 50 ppm or more and TOC (TOC) of 100 ppm or more), turbidity or casing remains inside the casing. It reduces the filtration flow rate such as turbidity deposited between the hollow fiber membranes that are tightly packed inside, or the filter section is clogged due to the turbidity (euro blockage), which requires frequent backwashing and complicated backwashing device, making it difficult to operate. In addition to high energy costs (see Water and Wastewater, 29 (10), 954-965 (1987)), there is a disadvantage that the filtration function of the module is not readily restored after backwashing and periodic membrane surface cleaning. Such flow path blockage occurs particularly well in the hollow fiber membrane of the central portion of the cylindrical module. For this reason, the existing casing type cylindrical module requires a large membrane area when applied to wastewater treatment.

Accordingly, the present inventors have continued their research, and by using the hollow fiber membrane module including the filtration unit and the aeration unit to abandon the air to wash the surface of the hollow fiber membrane while intermittently suction filtration of the waste water from the membrane surface to the inside of the membrane It has been found that this can be solved and the present invention has been completed.

An object of the present invention is to provide a submerged hollow fiber membrane module and a method of using the hollow fiber membrane module of the hollow fiber membrane module to prevent the blockage of the membrane by effectively washing the hollow fiber membrane during filtration during high concentration wastewater treatment.

1 is a longitudinal cross-sectional view of the submerged hollow fiber membrane module according to the present invention (FIG. 1A) and a cross-sectional view of the middle portion of the module with a nozzle (FIG. 1B),

2 is a cross-sectional view showing an air pipe including an air nozzle of the immersion hollow fiber membrane module according to the present invention,

3 is a longitudinal sectional view showing a hollow fiber membrane fixing portion for fixing the hollow fiber membrane and the air pipe according to the present invention,

4 is a schematic diagram of a wastewater treatment process using the submerged hollow fiber membrane module according to the present invention,

Figure 5 is a graph showing the suction pressure of the hollow fiber membrane module according to the operating time during the wastewater treatment by the wastewater treatment process of Figure 4 according to the present invention,

Figure 6 is a graph showing the filtration flow rate of the hollow fiber membrane module according to the operating time during the wastewater treatment by the wastewater treatment process of Figure 4 according to the present invention,

Figure 7 is a graph comparing the change in the suction pressure difference with the operation time of the immersion hollow fiber membrane module and the conventional casing type cylindrical module of the present invention.

<Brief Description of Drawings>

1: air pipe 2: hollow fiber membrane fixing part

3: hollow fiber membrane bundle 4: suction line

5: air nozzle 6: resin

7: enemies 8: aeration tank

9: air supply line 10: suction pump

11: blower 12: treated water reservoir

13: Submerged Hollow Fiber Membrane Module

In order to achieve the above object, in the present invention, the hollow fiber membrane bundle 3 of the vertical shape, the hollow fiber membrane fixing portion 2 located at the upper and lower ends of the hollow fiber membrane bundle 3, and the hollow through the fixing portion 2 Aeration made up of a filter section consisting of a suction line 4 connected to the desert bundle 3, an air pipe 1 located inside the hollow fiber membrane bundle, and an air nozzle 5 mounted on the side of the air pipe 1. It provides an immersion hollow fiber membrane module comprising a portion.

In addition, the present invention provides a method for intermittently suction filtration of wastewater from the membrane surface to the inside of the membrane while immersing the hollow fiber membrane module in the wastewater and giving up air to wash the surface of the hollow fiber membrane.

Hereinafter, the present invention will be described in more detail.

As shown in FIG. 1, the hollow fiber membrane module of the present invention includes a filtration unit consisting of a hollow fiber membrane bundle 3, a hollow fiber membrane fixing part 2, and a suction line 4, an air pipe 1, and an air nozzle 5. Consists of abandons made up of.

Hollow fiber membrane used in the immersed hollow fiber membrane module of the present invention is used in a vertical form as a bundle, it can be prepared by a conventional method by selecting from polysulfone, polyvinyl alcohol, polymethyl methacrylate, cellulose acetate and polyolefin, Among them, a hollow fiber membrane made of a material such as polyethylene or polypropylene having excellent mechanical strength and tensile strength is most preferred.

In addition, the pore size, porosity, membrane thickness, and outer diameter of the hollow fiber membranes are not particularly limited when performing the filtration function, but the pore size is generally considered in consideration of the material to be removed from the wastewater, the membrane area per unit volume, and the strength of the hollow fiber. Is 0.01 to 1 탆, porosity is 20 to 90%, film thickness is 5 to 300 탆, and outer diameter of the film is 20 to 2,000 탆. At this time, the pore size for removing bacteria and suspended solids in wastewater is appropriately 0.2㎛ or less, and ultrafiltration is appropriate to separate viruses and organic materials. The pore size of the hollow fiber membrane of the present invention is preferably 0.1 to 0.5㎛.

In general, a membrane having a hydrophobic surface has a hydrophobic interaction between the organic substance and the membrane in the water to be treated and a membrane occlusion due to the adsorption of the membrane surface to shorten the membrane's filtration life. The recovery of filtration performance by surface cleaning is difficult. However, hydrophilic hollow fiber membranes are more suitable for wastewater treatment than hydrophobic hollow fiber membranes because hydrophilic hollow fiber membranes minimize the adsorption of organic substances by inhibiting hydrophobic interactions between organic and membrane surfaces.

According to the present invention, the hollow fiber membrane fixing part 2 has a cylindrical shape according to the hollow fiber membrane arrangement, and serves to fix the entire hollow fiber membrane module. The hollow fiber membrane fixing portion 2 is a portion in which both ends are woven and the hollow fiber membrane 3, which is rolled in a cylindrical shape, is filled and fixed. The aggregation phenomenon due to the organic material of the can be suppressed, and it is easy to insert the hollow fiber membrane in the fixing portion.

When the thickness of the dried hollow fiber membrane is thin, the number of hollow yarns is small, so that the surface area of the hollow fiber membrane is small, and when the thickness is thick, it is difficult to fix the hollow fiber to the fixing part. For this reason, the thickness of the hollow fiber membrane dried is preferably about 10 to 200mm. The material of the fixing part for fixing the hollow fiber membrane is made of polycarbonate, polysulfone, polypropylene, acrylic resin, acrylonitrile-butadiene-styrene (ABS) resin and modified polyphenylene ether (PPE) having appropriate mechanical strength and durability. ) It can select from resin and can use.

In order to fix a hollow fiber membrane to a fixed part, it hardens using a liquid resin, such as an epoxy resin, an unsaturated polyester resin, or a polyurethane resin. In order to prevent the liquid resin from penetrating through the end of the hollow fiber membrane when the hollow fiber membrane is fixed using the liquid resin, it is preferable to use a liquid having a viscosity of about 1,000 to 2,500 centipoise.

According to the present invention, the hollow fiber membrane module of the present invention can be operated by pressure filtration method (method of placing the module in a sealed container and pressurizing the water to be treated and passing it through the membrane), but by suction filtration. It is more preferable to apply a suction filtration method (method of dipping the module in an activated sludge tank or a settling tank and sucking it from the outside of the membrane to the inside of the membrane).

In general, the degree of blockage of the membrane surface during operation by the pressure filtration method is measured by the increase in the interlayer differential pressure. An increase in the interlayer differential pressure means that a large amount of interfering substances accumulate on the membrane surface. However, in the suction filtration method, the suction pressure is measured by a vacuum gauge attached to the suction line 4 to monitor the degree of blockage of the membrane surface.

The suction line 4 of the present invention is a passage connecting the suction pump 10 and the hollow fiber membrane bundle 3, and the treated water passing through the hollow fiber membrane by the suction pressure of the suction pump is treated through the suction line. Are transferred to 12. There is no particular restriction on the suction pressure, but it is recommended to operate the suction pressure below 40 cmHg in order to suppress the generation of gas bubbles in the suction line, and in particular, to prevent the adsorption of organic substances into the pores of the membrane, it is recommended to operate below 10 cmHg. good. The hollow fiber membrane module of the present invention can smoothly perform filtration by suppressing contaminant deposition on the membrane surface even at a low pressure of 5 to 15 cmHg during suction filtration.

The hollow fiber membrane bundle 3 according to the present invention, the hollow fiber membrane fixing portion 2 for fixing them, and the suction line 4 connected to the fixing portion are shown in detail in FIG. 3, and the resin 6 for fixing the hollow fiber membrane is shown. ) Is used for curing.

According to the present invention, it is preferable to use an intermittent suction method to prevent accumulation of deposits on the film surface. In the case of intermittent suctioning, the optimal conditions of the suction time intervals are difficult to determine because the optimum conditions of the suction time intervals depend on the degree of contamination of the water to be treated, but in the case of wastewater having a mixed liquor suspended solid (MLSS) concentration of about 5,000 ppm, suction cycles 1 to 30 Minutes and stop cycles of 10 seconds to 15 minutes are preferred.

On the other hand, when high concentration wastewater is filtered using the hollow fiber membrane module, a large amount of SS and organic matter are usually deposited on the membrane surface. In order to clean organic substances deposited on the surface of the membrane, sediment on the surface of the membrane is separated using methods such as water current, air vibration, and ultrasonic waves. Accumulated organic matter causes membrane obstruction and consequently shortens membrane life. In addition, the cross-flow filtration method used for this purpose is a method of equilibrating the water flow to the membrane surface and washing it, using a pump or a motor to create a turbulent flow of water in the housing containing the module, the upflow of air Aeration method to be used, a method of shaking the module itself, and a method of vibrating the water to be treated using ultrasonic waves.

The hollow fiber membrane module of the present invention can be applied to all of the membrane surface cleaning method as described above, in particular, the aeration method using the upward flow of air, and can be carried out continuously or intermittently depending on the degree of membrane surface occlusion.

According to the present invention, the air pipe 1 including the air nozzle 5 is inserted into the bundle of hollow fiber membranes, thereby maximizing the efficiency of cleaning the membrane surface by air (see FIG. 3). As shown in detail in FIG. 2, the air pipe 1 having the air nozzle 5 is inserted into the hollow fiber membrane bundle to blow air from the inside of the hollow fiber membrane bundle to the outside, and the air nozzle 5 is connected to the nozzle end. By installing it upward, the air flow is discharged in a direction parallel to the surface of the membrane to remove the contaminants attached to the membrane surface and to prevent the contaminants from adhering to the membrane surface. Therefore, according to the method of the present invention, it is possible to clean the membrane surface while continuously filtering without applying the periodic backwashing method used in the existing hollow fiber membrane module, it is possible to operate for a long time without periodic membrane exchange.

The installation position and number of air nozzles 5 depend on the length of the membrane and the quality of the wastewater to be treated.In the case of applying a 80 cm-long hollow fiber membrane module to wastewater with an MLSS concentration of 5,000 ppm, eight nozzles are used for the hollow fiber membrane. It is most preferable to install 4 pieces each at 3 cm and 50 cm from the bottom of the module.

According to the suction filtration method and the aeration of air according to the present invention, not only can perform filtration and washing of the membrane surface by air aeration at the same time, but also the circulation of wastewater in the activated sludge tank and oxygen supply at the same time, so that the microorganisms in the activated sludge tank can be A side effect of increasing the activity of can also be obtained. In particular, it is more effective to combine the air aeration and the intermittent suction method that can effectively prevent the accumulation of organic substances on the film surface.

The hollow fiber membrane module 13 having the structure and operating principle as described above can be used by immersing in one or more wastewater, and the applicable wastewater includes organic sewage and wastewater (food, animal husbandry) having an MLSS concentration of 5,000 to 15,000 ppm. And manure) such as industrial wastewater such as SS or turbidity-inducing substances such as river water containing contaminants having a particle size of 0.1 μm or more, industrial water and swimming pool water, and high concentration wastewater such as low concentration wastewater. After immersing one or more hollow fiber membrane modules in a wastewater treatment tank, such as aeration tank 8, suction is maintained while maintaining a constant suction pressure by the suction pump 10 while giving up air through the air pipe 1 by the blower 11. Waste water is intermittently suction filtered from the membrane surface through the line 4 into the membrane to be transferred to the treated water reservoir 12. In the case of wastewater having a concentration of 5,000 ppm of MLSS used in the following example, the suction pump (suction pressure 15 cmHg) was operated at an interval of 10 minutes while giving up 50 L of air per minute using the submerged hollow fiber membrane module of the present invention. And 0.3 L of wastewater per 1 m ^{2 of} hollow fiber membranes.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the invention only.

Example

Experimental Results of Wastewater Treatment Pilot Plant Using Submerged Hollow Fiber Membrane Module

Both ends of the hollow fiber membrane made of hydrophilized polypropylene hollow fiber with a pore size of 0.2 μm are inserted into a cylindrical fixture having a height of 15 cm and a diameter of 20 cm, and an air pipe containing an air nozzle is placed in the center of the cylindrical module. A hollow fiber membrane module having a length of 80 cm and an effective membrane area of 4 m ² was prepared by inserting and fixing with a polyurethane resin at the fixing portion. Using the manufactured hollow fiber membrane module was applied to the wastewater treatment process as shown in FIG. Experimental method was supplied to the aeration tank (8) in which the hollow fiber membrane module (13) was soaked in the raw water (7) with an MLSS concentration of 5,000 ppm in an amount of 72 L per hour, using a suction pump (10) to draw a suction pressure of 15 cmHg (0.2 kg / Filtration was performed intermittently at intervals of 10 minutes while maintaining cm ² ). At this time, the raw water in the aeration tank 8 was maintained at a temperature of 17 ° C. and pH 6-8. At the same time, the blower 11 was used to supply 50 L / min of air through the air supply line 9 to the air pipe including the air nozzle, thereby continuously giving up. The filtered raw water was transferred to the treated water reservoir 14 through the suction line 4. The changes in suction pressure and filtration flow rate were measured while treating wastewater for 30 days under the conditions shown in Table 1, and the results are shown in FIGS. 5 and 6, respectively.

As can be seen from Figure 5 and Figure 6, using the immersion hollow fiber membrane module of the present invention smoothly performs the wastewater treatment process while maintaining a constant filtration flow rate (0.3L / min m ² ) without clogging the membrane in a low pressure (15cmHg) can do.

division Condition Air aeration 50L / min Intermittent aspiration Driving time 10 minutes Stop time 10 minutes Suction pressure 15 cmHg Filtration rate 0.3 L / min m ² Raw water temperature 17 ℃ Raw water pH 6 to 8

Comparative example

By using the existing casing-type cylindrical module to operate the same raw water as the embodiment for 15 days under the same conditions as in the embodiment (however, the casing-type cylindrical module does not give up air) while measuring the difference in suction pressure. Is shown in FIG. 7.

7 is a graph comparing the change in suction pressure difference (suction pressure difference = suction pressure-initial suction pressure) between the immersed hollow fiber membrane module and the conventional casing type cylindrical module of the present invention. It can be expected that the suction pressure is continuously increased compared to the initial suction pressure, and consequently, the filtration flow rate is reduced, but the immersion type hollow fiber membrane module of the present invention can maintain stable suction pressure.

In addition, as shown in Table 2, it can be seen that the water quality of the treated water of the Example is better than the treated water of the comparative example.

division Comparative example Example Before treatment After treatment Average efficiency (%) Before treatment After treatment Average efficiency (%) COD _cr (mg / L) 1,500 48 86.5 1,500 27 98.2 BOD (mg / L) 700 10 98.5 700 5 99.2 SS (mg / L) 150 18 88 150 One 99.99

Immersion type hollow fiber membrane module according to the present invention, when immersed in high concentration wastewater, the hollow fiber does not agglomerate due to contaminants, and effectively washes the hollow fiber membrane during filtration to prevent blockage of the membrane, as well as to minimize the loss of filtration function In addition, wastewater can be treated economically and efficiently.

Claims (4)

Hollow fiber membrane bundle (3) of the vertical form, the hollow fiber membrane bundle (2) and the hollow fiber membrane bundle (3) located at the top and bottom of the hollow fiber membrane bundle (3) (3) Aeration consisting of an air pipe (1) located on the inside of the bundle of hollow fiber membranes and an air nozzle (5) mounted on the side of the air pipe (1) consisting of a suction line (4) connected to the Immersion hollow fiber membrane module comprising a bubbling). The method of claim 1, Immersion type hollow fiber membrane module, characterized in that the pore size of the hollow fiber membrane is 0.1 to 0.5㎛, made of hydrophilized polypropylene hollow fiber. The method of claim 1, Immersion hollow fiber membrane module, characterized in that the end of the air nozzle facing up. The wastewater treatment method of claim 1, wherein the hollow fiber membrane module according to claim 1 is immersed in the wastewater, and the wastewater is intermittently suction filtered from the surface of the membrane to the inside of the membrane through a suction line while giving up air through the air pipe.