JP2010064039A - Apparatus and method for treating wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for treating wastewater capable of appropriately suppressing tangling and warping of hollow fiber membranes, clogging on a hollow fiber membrane surface, and clogging between the hollow fiber membranes, and capable of thereby treating the wastewater stably. <P>SOLUTION: The apparatus for treating the wastewater includes: an anaerobic treatment tank 2 and an aerobic treatment tank 3, both for purifying raw wastewater; a hollow fiber membrane module 4 for solid-liquid separation treatment; a conveying pump 5 for delivering a first treated water in the aerobic treatment tank 3 into the hollow fiber membrane module 4; and a minute bubble generator for mixing minute bubbles having a diameter of 100 μm or below into a water flow coming into contact with a hollow fiber membrane bundle. The hollow fiber membrane module 4 includes a hollow fiber membrane bundle comprising a plurality of hollow fiber membranes, one end of which is a fixed end and the other end a free end. At the fixed end of the membrane, the inside of the membranes 23 communicates with a water collecting portion which collects filtrate having filtered through the hollow fiber membrane. The length direction of the hollow fiber membrane is almost horizontal. The direction of the water flowing into the hollow fiber membrane module 4 is the one from the fixed end to the free end of the hollow fiber membrane. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wastewater treatment apparatus and a wastewater treatment method suitable for treating highly pollutant liquids such as sewage wastewater treatment and industrial wastewater treatment.

Conventionally, many membrane separation techniques have been used in the production of aseptic water, drinking water, highly pure water, air purification, etc. In addition to these applications, in recent years, secondary technologies in sewage treatment plants have been used. It is also used for the treatment of highly polluted water such as treatment, tertiary treatment, solid-liquid separation in septic tanks, and solid-liquid separation of suspended solids in industrial wastewater.
Above all, the method of immersing the separation membrane in activated sludge, bubbling from below, and simultaneously performing the aerobic treatment with microorganisms and washing the separation membrane can achieve good separation regardless of the sedimentation property of the sludge. In addition, since there is an advantage that the processing efficiency per volume can be increased by increasing the concentration of MLSS (Mixed liquor suspended solids), it has attracted attention in recent years and is being put into practical use.
As a problem when the hollow fiber membrane module is used for wastewater treatment such as actual human waste treatment, entanglement of very fine fibrous debris in the wastewater with the hollow fiber membrane can be mentioned. Large residue is removed by pretreatment or the like, but it becomes coarse by enveloping very small residue that cannot be removed by pretreatment in the hollow fiber membrane. Once the residue is entangled with the hollow fiber membrane, it is difficult to remove, and the entanglement of the residue gradually accumulates, and sludge adheres and accumulates using the residue as a core. The accumulated sludge becomes a lump and closes the space between the hollow fiber membranes, resulting in an increase in the differential pressure of filtration, which makes it difficult to use the hollow fiber membrane module in the waste water.

As countermeasures for preventing the stagnation of the residue on the hollow fiber membrane, in Patent Document 1 and Patent Document 2 below, the hollow fiber membrane module is placed in the activated sludge treatment tank or the membrane separation tank, and the length direction of the hollow fiber membrane is Is arranged in such a manner that the upper end of the hollow fiber membrane is a free end, and an aeration device or an aeration device is provided below the hollow fiber membrane to generate a swirling flow. ing. Since the residue entangled with the hollow fiber membrane can move along the length of the hollow fiber membrane, the upward flow from the lower part of the hollow fiber membrane toward the free end at the upper end is utilized using the upward flow portion of the swirl flow. By adding the above, it is intended to prevent tangling of the residue. Further, since the upper end of the hollow fiber membrane is a free end and freely swings by the water flow, sludge is unlikely to accumulate between the hollow fiber membranes, and entanglement of the residue hardly occurs.
Japanese Patent No. 3918304 JP 2006-142303 A

  However, in the configuration described in Patent Documents 1 and 2, since the length direction of the hollow fiber membrane is the longitudinal direction and the upper end of the hollow fiber membrane is a free end, the hollow fiber membrane is not sufficiently self-supporting. There is a problem that it tends to warp. In addition, in the state where the water flow from the lower end side to the upper end side of the hollow fiber membrane is applied, the entanglement between the hollow fiber membranes is difficult to occur. When the water level drops, the hollow fiber membrane sinks downward due to its own weight, and when the water level rises again, the hollow fiber membranes are disturbed and entangled with each other.

  Moreover, in the method of disposing the hollow fiber membrane module in the upward flow portion of the swirling flow including bubbles as described in Patent Documents 1 and 2, the contact between the bubbles and the hollow fiber membrane is uneven and insufficient. Cheap. For this reason, unevenness tends to occur in the effect of scraping off residue and sludge attached to the hollow fiber membrane by bubbles and upward flow, and the prevention of blockage of the hollow fiber membrane surface and between the hollow fiber membranes is not sufficient, There is a problem.

  The present invention has been made in view of the above circumstances, and in a wastewater treatment apparatus equipped with a hollow fiber membrane module and a wastewater treatment method using the same, the entanglement of the hollow fiber membranes, the warp of the hollow fiber membranes, the surface of the hollow fiber membranes It is an object of the present invention to satisfactorily prevent clogging and blocking between hollow fiber membranes so that stable wastewater treatment can be performed.

In order to solve the above problems, a wastewater treatment apparatus of the present invention includes a raw water treatment tank for purifying raw water, a hollow fiber membrane module for performing solid-liquid separation, and a liquid treated in the raw water treatment tank. A wastewater treatment apparatus having a liquid feed pump for flowing into a yarn membrane module, wherein the hollow fiber membrane module is a fixed end in which one end of a plurality of hollow fiber membranes is bonded and fixed to each other, and the other end is free A hollow fiber membrane bundle at the end, and at the fixed end of the hollow fiber membrane, the interior of the hollow fiber membrane communicates with a water collecting portion for collecting permeated water that has permeated through the hollow fiber membrane. The length direction of the hollow fiber membrane is a substantially horizontal direction, and the inflow direction of the liquid into the hollow fiber membrane module is a direction from the fixed end to the free end of the hollow fiber membrane, and the hollow fiber membrane bundle A fine gas containing bubbles of 100 μm or less in the liquid flow in contact with Wherein the generating device is provided.
It is preferable that the fine bubble generating device is provided in a flow path from the liquid feeding pump to the hollow fiber membrane module.
It is preferable that a suction means for lowering the pressure inside the hollow fiber membrane to be lower than the pressure outside the hollow fiber membrane is provided.

  The wastewater treatment method of the present invention is a wastewater treatment method comprising a step of causing a liquid obtained by purifying raw water to flow into a hollow fiber membrane module and performing solid-liquid separation with the hollow fiber membrane module, wherein the hollow fiber membrane module includes: And a hollow fiber membrane bundle in which one end of each of the plurality of hollow fiber membranes is bonded and fixed to each other, and the other end is a free end. The inside of the membrane communicates with a water collecting portion for collecting the permeated water that has passed through the hollow fiber membrane, and the length direction of the hollow fiber membrane is a substantially horizontal direction, and the liquid to the hollow fiber membrane module Is a direction from the fixed end of the hollow fiber membrane toward the free end, and bubbles having a diameter of 100 μm or less are contained in the liquid flow contacting the hollow fiber membrane bundle.

  According to the present invention, it is possible to satisfactorily perform wastewater treatment by satisfactorily preventing entanglement of hollow fiber membranes, warping of the hollow fiber membranes, blockage of the surface of the hollow fiber membranes, and blockage between the hollow fiber membranes. A treatment device and a wastewater treatment method are obtained.

The present invention will be specifically described below with reference to the drawings. In addition, this invention is not limited to the following embodiments.
FIG. 1 is a schematic configuration diagram showing an embodiment of a wastewater treatment apparatus of the present invention, and FIG. 2 is a cross-sectional view schematically showing an example of a hollow fiber membrane module 4.
In the wastewater treatment apparatus of this embodiment, raw water to be purified is fed to the raw water flow rate adjustment tank 1 by the first liquid feed pump 10a, and from here to the raw water treatment tank by the second liquid feed pump 10b. It is configured to be liquid.
The raw water treatment tank in this embodiment includes an anaerobic tank 2 and an aerobic tank 3. The raw water in the raw water flow rate adjusting tank 1 is first sent to the anaerobic tank 2 by the second liquid feed pump 10 b, and further the liquid in the anaerobic tank 2 is sent to the aerobic tank 3 by the first circulation pump 8. The A pipe communicating with the anaerobic tank 2 is provided at the bottom of the aerobic tank 3 so that the liquid in the aerobic tank 3 can be sent to the anaerobic tank 2 via the pipe by the second circulation pump 9. It has become. That is, the anaerobic tank 2 and the aerobic tank 3 are configured to be circulated.
The raw water is biochemically purified by the activated sludge retained in the anaerobic tank 2 and the aerobic tank 3 to become a first treatment liquid. The first treatment liquid is a suspension containing activated sludge and impurities such as residue in addition to biochemically purified treated water. In the lower part of the aerobic tank 3, an air diffuser 11 for supplying a gas containing oxygen to the activated sludge is disposed.

In the present embodiment, a part of the first processing liquid in the aerobic tank 3 is caused to flow into the hollow fiber membrane module 4 via the fine bubble generator 6 by the liquid feed pump 5 and permeate the hollow fiber membrane 23. A circulation channel for returning the liquid that has not been returned to the aerobic tank 3 is provided. The permeated liquid (second processing liquid) that has permeated through the hollow fiber membrane 23 is taken out from the water collection pipe 22 of the hollow fiber membrane module 4. Reference numeral 7 denotes a suction pump (suction means) connected to the water collecting pipe 22 of the hollow fiber membrane module 4.
The fine bubble generator 6 generates fine bubbles in the first processing liquid using the gas supplied from the gas supply means 12. Thereby, the gas-liquid mixed flow containing the fine bubbles flows into the hollow fiber membrane module 4.

  In the present embodiment, a gas containing oxygen is sent from the common gas supply means 12 to the air diffuser 11 and the fine bubble generator 6. The gas is, for example, air. Although it is preferable to use a blower as the gas supply means 12, other compressors, gas cylinders, compression tanks, and the like can also be used.

(Microbubble generator)
The fine bubble generating device 6 is not particularly limited as long as it is a device that can generate bubbles having a bubble diameter of 100 μm or less, and a known device can be used as appropriate.
As the fine bubble generating device 6, for example, a device that generates fine bubbles by the following method can be used.
(1) Method using pore filter (pore type, filter type): A method of generating fine bubbles by blowing pressurized gas into the liquid through a filter having the same diameter as the fine bubbles to be obtained. .
(2) Pressure dissolution method: First, bubbles having a diameter larger than 100 μm are contained in the liquid, the gas is over-dissolved by applying pressure to the liquid, and then the pressure is released to form fine bubbles in the liquid. Generate method.
(3) Shock wave method: In the middle of the liquid flow, a narrowed part whose flow path diameter suddenly narrows is provided, gas is supplied to the narrowed part, and a shock wave (cavitation) is given to the narrowed part to generate fine bubbles. Method to make.
(4) Sorting method: A method of generating fine bubbles by applying a mechanical sorting force such as a water jet.
(5) Swirl method: A method in which a cavity is generated by a high-speed swirling flow of liquid and gas, and fine bubbles are generated by a swirling flow difference before and after the cavity.
(6) Ultrasonic method: A method of generating fine bubbles by generating an ultrasonic field in a liquid and supplying gas from a thin needle tip.

For example, the microbubble generator 6 in the present embodiment includes an inflow portion having a rectifying plate in a tube, a tubular member having an ejector portion having a protrusion in the tube, and an intake means. When water is supplied, the apparatus may be a device that atomizes gas sucked by high-speed flow or turbulent flow and ejects a gas-liquid mixed flow. The rectifying plate at the inflow portion has a plate shape, a spiral shape, or the like, and the protrusions at the ejector portion have a cylindrical shape, a conical shape, a prism shape, a pyramid shape, a mushroom shape, or the like. For example, a microbubble generator manufactured by Nishida Iron Works can be used.
As a suction method for the fine bubble generating device 6, either natural suction or pressurized air may be used. In particular, in the case of a large module in which the length of the hollow fiber membrane module 4 exceeds 2 m, it is more preferable to use pressurized air because finer bubbles have a longer residence time.

As a method of measuring the bubble diameter (bubble diameter), a method of measuring by image processing using an optical microscope and a video camera, or a laser diffraction / scattering method is used. For example, a nanoparticle size distribution measuring device SALD-7100 (Shimadzu Corporation) can be used.
The bubble diameter generated by the fine bubble generator 6 is preferably 0.1 μm or more and 100 μm or less, more preferably 0.1 μm or more and 50 μm or less, and even more preferably 0.1 μm or more and 10 μm or less.

  It is preferable that the first treatment liquid flowing into the fine bubble generating device 6 removes a large solid in advance with a screen or the like. Further, even when a large solid is removed, there is still a concern about clogging, so that it is preferable that a fine liquid can be supplied to the fine bubble generator 6 for cleaning as necessary. . As the clear liquid, tap water, well water, filtrate and the like can be used. In addition, agents such as acids, alkalis, oxidizing agents and detergents can be used in combination. The cleaning may be automatically performed periodically using a timer or the like, or may be performed manually as necessary.

(Hollow fiber membrane module)
As the hollow fiber membrane module 4 in the present embodiment, for example, a container-integrated hollow fiber membrane module as shown in FIG. 2 can be used.
The hollow fiber membrane module 4 of the present embodiment includes a substantially tubular module case 26 having an inflow port 20 at one end in the length direction X and an outflow port 21 at the other end. Part of the circulation channel.
In this embodiment, the hollow fiber membrane module 4 is provided so that the length direction X becomes a substantially horizontal direction.

  As the module case 26, a container made of a resin such as ABS resin, polypropylene resin, polycarbonate resin, or the like; a container made of fiber reinforced resin reinforced with epoxy fiber, urethane resin, or the like with glass fiber, carbon fiber, or the like; stainless steel A metal container such as is exemplified.

A hollow fiber membrane bundle formed by bundling a plurality of hollow fiber membranes 23 is accommodated in the module case 26 so that the length direction of the hollow fiber membranes 23 and the length direction X of the module case 26 are parallel to each other. ing. That is, the length direction X of the hollow fiber membrane 23 is a substantially horizontal direction.
In the hollow fiber membrane 23, since the fine bubbles in the gas-liquid mixed flow flowing into the hollow fiber membrane module 4 have a strong oxidizing power, the membrane strength is strong and the oxidation resistance and durability are stable for stable operation. It is preferable to use an excellent material. For example, as an organic film, a polyvinylidene fluoride (PVDF) film, a polytetrafluoroethylene (PTFE) film, an ethylene-tetrafluoroethylene copolymer (ETFE) film, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer ( A fluorine-based resin film such as a (PFA) film is preferable. A polyvinylidene fluoride (PVDF) film is particularly preferable. An inorganic film such as ceramic is also preferable.

  The hollow fiber membrane 23 preferably has a pore size region from a nanofiltration (NF) membrane to a microfiltration (MF) membrane. In particular, an MF membrane having an average pore size of 10 μm or less is preferred from an NF membrane having a fractional molecular weight of about 100. Specifically, it is selected according to the particle size of the substance to be subjected to solid-liquid separation. When used for solid-liquid separation of activated sludge, the average pore size is preferably 0.5 μm or less.

In the hollow fiber membrane bundle, one ends of the plurality of hollow fiber membranes 23 are bonded and fixed to each other with an adhesive (potting material) by a known potting method to form a potting fixing portion 24. That is, one end of the hollow fiber membrane 23 is a fixed end.
The end surface of the potting fixing portion 24 is an opening surface 27 in which the fixing end of the hollow fiber membrane 23 is opened by cutting along a surface perpendicular to the length direction of the hollow fiber membrane 23 after the potting material is cured.

  When potting the hollow fiber membrane 23, as a method of allowing the adhesive to permeate between and inside the ends of the hollow fiber membrane 23, the “standing method” performed in a standing state or the penetration using centrifugal force A “centrifugation method” can be used. The adhesive (potting material) is preferably a thermosetting adhesive such as an epoxy resin, an unsaturated polyester resin, or a polyurethane resin. In order to adjust the solution viscosity of the adhesive and the exothermic reaction temperature, inorganic fine particles may be added.

  The potting fixing part 24 is attached to the water collector 28 in a liquid-tight manner, and the inside of the hollow fiber membrane 23 and the inside of the water collector 28 (the water collecting part 28a) via the opening surface 27 at the fixed end of the hollow fiber membrane 23. ). Reference numeral 22 denotes a water collection pipe 22 that communicates the water collection section 28 a with the outside of the hollow fiber membrane module 4. A suction pump 7 (suction means) is connected to the water collecting pipe 22.

  The other end (tip) of the hollow fiber membrane 23 is a free end 25 and is sealed. As a method of sealing the tip, a method of sealing the tip of the hollow fiber membrane 23 by heat fusion of the membrane itself; or a method of applying a hot melt resin made of a thermoplastic resin to the tip and sealing, or a tip The method of apply | coating and sealing a thermosetting resin is mentioned. The free end means a state in which the tip of the hollow fiber membrane can swing freely.

In the present embodiment, the cross section perpendicular to the length direction X of the hollow fiber membrane 23 of the potting fixing portion 24 and the water collector 28 is a donut shape having an outer diameter smaller than the inner diameter of the module case 26, and the through hole 29. The potting fixing part 24 and the water collector 28 are arranged so that the through hole 29 is coaxial with the inlet 20 and outlet 21 of the module case 26 and the fixing end (potting fixing part 24) of the hollow fiber membrane 23 is On the inlet 20 side, the tip (free end 25) is arranged so as to be on the outlet 21 side.
Therefore, the gas-liquid mixed flow flowing in from the inlet 20 of the module case 26 passes through the inside of the through hole 29 of the water collector 28 and the gap between the inner wall of the module case 26 and the outer peripheral surface of the water collector 28, While filling the inside of the module case 26, the hollow fiber membrane 23 flows from the fixed end side toward the tip end side and flows out from the outflow port 21.

Next, a method for performing wastewater treatment using the apparatus of the present embodiment will be described.
While purifying the raw water in the anaerobic tank 2 and the aerobic tank 3 by a known method, the first treated water in the aerobic tank 3 is fed to the fine bubble generating device 6 by the liquid feed pump 5, where Bubbles are generated to form a gas-liquid mixed flow and flow into the hollow fiber membrane module 4.
When the suction pump 7 connected to the water collecting pipe 22 of the hollow fiber membrane module 4 is operated, the pressure inside the water collecting portion 28a and the hollow fiber membrane 23 becomes lower than the pressure outside the hollow fiber membrane 23. A pressure difference is generated on the membrane surface of the hollow fiber membrane 23, and solid-liquid separation is performed by a suction filtration method.
Accordingly, a part of the first treated water that has flowed into the hollow fiber membrane module 4 as a gas-liquid mixed flow is filtered on the membrane surface of the hollow fiber membrane 23 and passes through the hollow fiber membrane 23 (second water). Treated water) and activated sludge are separated into solid and liquid. The permeated water flows inside the hollow fiber membrane 23 and is taken out to the outside through the opening surface 27 of the hollow fiber membrane, the water collecting portion 28a, and the water collecting pipe 22. The remaining liquid that has not permeated the hollow fiber membrane 23 flows out from the outlet 21 and returns to the aerobic tank 3.

The operation of the suction pump 7 may be performed intermittently. During operation, it is preferable to carry out reverse washing by supplying clean washing water from the water collecting pipe 22 into the hollow fiber membrane 23 as necessary. Permeated water that has passed through the hollow fiber membrane 23 (second treated water) may be used as the washing water.
In addition, if necessary, the liquid feeding pump 5 may stop feeding the liquid in the hollow fiber membrane module 4 and the hollow fiber membrane 23 may be maintained.

In the present embodiment, the diameter of the first treatment liquid treated in the raw water treatment tank (anaerobic tank 2 and aerobic tank 3) is in the middle of the flow path through which the liquid feed pump 5 flows into the hollow fiber membrane module 4. Fine bubbles of 100 μm or less are generated. As a result, a liquid flow (gas-liquid mixed flow) containing fine bubbles having a diameter of 100 μm or less flows into the hollow fiber membrane module 4, and the liquid flow contacts the hollow fiber membrane bundle.
Such fine bubbles can not only greatly increase the total contact surface area with the surrounding water compared to bubbles (macrobubbles) having a normal size diameter of 1 mm or more, but also the inside of the bubbles due to surface tension. The pressure rises extremely, and active oxygen is generated by the impact when it breaks down and exerts strong oxidizing power. In order to make the most of the effect, it is preferable that the residence time (contact time with the hollow fiber membrane bundle) is long.
In this embodiment, since the bubbles in the gas-liquid mixed flow flowing into the hollow fiber membrane module 4 are fine, the rising speed of the bubbles in the liquid is small. Further, since the hollow fiber membrane module 4 is arranged so that the length direction of the hollow fiber membrane 23 is substantially horizontal, the rise of the bubbles is hindered by the hollow fiber membrane 23, and the bubbles, the hollow fiber membranes 23, The contact time tends to increase. Therefore, the fine bubbles are not easily biased upward in the hollow fiber membrane module 4, and the contact between the bubbles and the hollow fiber membranes 23 tends to be uniform in the entire hollow fiber membrane bundle. Therefore, the effect of scraping off residue and sludge adhering to the hollow fiber membrane 23 due to the contact of bubbles and the effect of oxidizing and decomposing fine organic matter can be sufficiently obtained. Blockage between the membranes 23 can be prevented well.
Moreover, since the length direction of the hollow fiber membrane 23 is a substantially horizontal direction, the hollow fiber membrane 23 cannot be easily entangled or warped, and stable filtration can be performed.
In order to obtain such effects satisfactorily, the angle formed by the length direction of the hollow fiber membrane 23 and the horizontal direction is preferably 30 ° or less, more preferably 20 ° or less, and even more preferably 10 ° or less.

In the apparatus of this embodiment, one end of the hollow fiber membrane 23 is a fixed end, and the other end is an independent free end 25. Therefore, the hollow fiber membrane 23 can freely swing by a water flow. Therefore, the effect of scraping off residue and sludge adhering to the hollow fiber membrane 23 by the gas-liquid mixed flow containing fine bubbles can be obtained more favorably.
Furthermore, since the gas-liquid mixed flow that has flowed into the hollow fiber membrane module 4 is configured to flow in the direction from the fixed end side to the free end 25 side of the hollow fiber membrane 23, it is entangled with the hollow fiber membrane. The residue can be removed by moving along the length of the hollow fiber membrane.
Further, in the present embodiment, the potting fixing portion 24 is formed in a donut shape, and a flow path is also formed in the hollow fiber membrane bundle, so that the contact between the gas-liquid mixed flow and the hollow fiber membrane 23 is made more uniform. Prone.

In the present embodiment, the fine bubble generator 6 is provided in the middle of the flow path for allowing the first processing liquid to flow into the hollow fiber membrane module 4 by the liquid feed pump 5, but the present invention is not limited to this, and fine bubble generation is performed. The position where the device 6 is provided may be a position where fine bubbles can be contained in the liquid flow contacting the hollow fiber membrane bundle. Moreover, you may use it combining a some fine bubble generator as needed. FIG. 3 is a main part configuration diagram schematically showing a modification of the position where the fine bubble generating device 6 is provided. In FIG. 3, the same components as those in FIG.
For example, FIG. 3A is an example in which the fine bubble generating device 6 is provided in the module case of the hollow fiber membrane module 4 between the inlet of the module case and the hollow fiber membrane bundle.
FIG. 3 (b) shows a branch from the flow path between the liquid feed pump 5 and the hollow fiber membrane module 4 in the module case 26 of the hollow fiber membrane module 4 and upstream of the hollow fiber membrane bundle. This is an example in which a bypass channel 31 through which liquid flows is provided, and a microbubble generator 6 is provided in the middle of the bypass channel 31.
FIG. 3C shows a bypass channel 32 that branches off from the channel between the liquid feed pump 5 and the hollow fiber membrane module 4 and returns the liquid to the same channel again. This is an example in which a microbubble generator 6 is provided.
FIG. 3 (d) shows a branch from the flow path between the liquid feed pump 5 and the hollow fiber membrane module 4, and is inside the module case 26 of the hollow fiber membrane module 4 and upstream of the hollow fiber membrane bundle. This is an example in which a bypass channel 33 through which liquid flows is provided, and a microbubble generator 6 is provided between an inlet port that flows into the hollow fiber membrane module 4 from the bypass channel 33 and the hollow fiber membrane bundle.
FIG. 3 (e) shows the inside of the module case 26, upstream of the hollow fiber membrane bundle, without passing through the liquid feed pump 5, separately from the liquid flow flowing into the hollow fiber membrane module 4 from the liquid feed pump 5. This is an example in which another flow channel 34 through which liquid flows is provided on the side, and the fine bubble generating device 6 is provided in the middle of the other flow channel 34. The liquid flowing into the hollow fiber membrane module 4 from the other flow path 34 may not be the first treatment liquid, and for example, the remaining liquid that has not permeated the hollow fiber membrane 23 is preferable.

  In particular, in the point that the configuration of the hollow fiber membrane module 4 is not complicated, a fine bubble generator 6 is provided in the flow path from the liquid feed pump 5 to the hollow fiber membrane module 4 as shown in FIG. As shown in b) and (c), it is preferable to provide the fine bubble generator 6 in the bypass flow paths 31 and 32 branched from the flow path between the liquid feed pump 5 and the hollow fiber membrane module 4. Furthermore, it is more preferable to provide the fine bubble generating device 6 in the flow path from the liquid feed pump 5 to the hollow fiber membrane module 4 in terms of design ease of the device and space saving.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
Waste water treatment was performed using the waste water treatment apparatus having the configuration shown in FIG. As the hollow fiber membrane 23, a PVDF membrane (Mitsubishi Rayon Engineering Co., Ltd., pore diameter 0.4 μm, outer diameter 2.8 mm) using a polyester braid as a support was used. In the hollow fiber membrane bundle, the number of the hollow fiber membranes 23 is 330, the effective length of the hollow fiber membranes 23 is 1500 mm, and the cross-sectional shape perpendicular to the length direction of the hollow fiber membranes 23 is an outer diameter of 80 mm and an inner diameter of 40 mm. It is a donut shape. The module case 26 has an inner diameter of 100 mm at the largest cylindrical portion. The angle formed by the length direction of the hollow fiber membrane 23 and the horizontal direction is 0 °.
As the microbubble generator 6, a microbubble generator 15-A type manufactured by Nishida Tekko Co., Ltd. was used under the condition that the average bubble diameter was 50 μm. The diameter of the bubbles generated from the fine bubble generator 6 was in the range of 20 to 80 μm. A part of the air supplied to the air diffuser 11 of the aerobic tank 3 was used to supply the air to the fine bubble generator 6.

The liquid in the aerobic tank 3 is sent to the fine bubble generator 6 at a flow rate of 300 liters / hr by the liquid feed pump 5, where bubbles with an average bubble diameter of 50 μm are generated, and the obtained gas-liquid mixed flow is It was made to flow into the hollow fiber membrane module 4.
The suction pump 7 was operated at a flow rate of 46.2 liters / hr for 7 minutes to perform suction filtration, and then the operation of stopping for 2 minutes was repeated. An operation of supplying 100 liters of permeated water from the water collecting pipe 22 to the inside of the hollow fiber membrane 23 and performing back washing was performed once a day. These operations were repeated for operation to obtain permeated water.
During operation, it took about 100 days for the accumulation of suspended substances and the like in the vicinity of the hollow fiber membrane 23 and the potting fixing part 24 and the clogging of the membrane to be suppressed, and for the filtration differential pressure to rise to 20 kPa.
The filtration differential pressure is a value obtained from the difference between the suction pressure during filtration and the pressure when suction filtration is stopped.
During the 100 days, the hollow fiber membrane 23 did not warp. Moreover, even if the water level in the hollow fiber membrane module 4 was once lowered by performing the drainage operation and then the water level was raised again, the hollow fiber membranes 23 were not entangled. Since the tip of the hollow fiber membrane 23 is a free end, no tangling of residue on the hollow fiber membrane 23 was observed.

(Example 2)
The hollow fiber membrane module 4 having a membrane area 1/2 that of Example 1 is used in the same direction as described in Example 1 (the angle between the length direction of the hollow fiber membrane 23 and the horizontal direction is 0 °). As the microbubble generator 6, a microbubble generator D-2 manufactured by Dainichi Kogyo Co., Ltd. with a built-in liquid feed pump 5 was used under the condition that the average bubble diameter was 3 μm. The liquid was fed at a flow rate of 180 liters / hr, where bubbles were generated under the condition of an average bubble diameter of 3 μm, and the obtained gas-liquid mixed flow was allowed to flow into the hollow fiber membrane module 4. The diameter of the bubbles generated from the fine bubble generator 6 was in the range of 1.0 to 10 μm.
The suction pump 7 was operated at a flow rate of 23.1 liters / hr for 7 minutes to perform suction filtration, and then the operation of stopping for 2 minutes was repeated. An operation of supplying 100 liters of permeated water from the water collecting pipe 22 to the inside of the hollow fiber membrane 23 and performing back washing was performed once a day. These operations were repeated for operation to obtain permeated water.
During operation, it took about 120 days for accumulation of suspended substances and the like in the vicinity of the hollow fiber membrane 23 and the potting fixing portion 24 and clogging of the membrane to be suppressed, and for the filtration differential pressure to rise to 20 kPa.
The filtration differential pressure is a value obtained from the difference between the suction pressure during filtration and the pressure when suction filtration is stopped.
During the 100 days, the hollow fiber membrane 23 did not warp. Moreover, even if the water level in the hollow fiber membrane module 4 was once lowered by performing the drainage operation and then the water level was raised again, the hollow fiber membranes 23 were not entangled. Since the tip of the hollow fiber membrane 23 is a free end, no tangling of residue on the hollow fiber membrane 23 was observed.

(Comparative Example 1: Macro Bubble)
In Example 1, it was made the same as Example 1 except having changed the fine bubble generator 6 into the diffuser which generate | occur | produces a macro bubble. As the air diffuser, a perforated tube (hole diameter: 2 mm) that generates bubbles having a diameter of 2 mm was used.
During operation, in particular, air bubbles mainly flow to the upper part of the module case 26, and only the upper part is washed with air bubbles, resulting in a severe blockage on the lower side of the hollow fiber membrane bundle, and the filtration differential pressure becomes 20 kPa in about 10 days. Reached.

(Comparative example 2: the length direction of the hollow fiber membrane 23 is a substantially vertical direction + fine bubbles)
Example 1 was the same as Example 1, except that the hollow fiber membrane module 4 was arranged so that the length direction was substantially vertical and the inlet 20 was downward. The angle formed by the length direction of the hollow fiber membrane 23 and the horizontal direction is 90 °. Since the flow direction of the liquid in the hollow fiber membrane module 4 (from the lower side to the upper side) coincides with the rising direction of the bubbles in the hollow fiber membrane module 4, the stay of fine bubbles in the hollow fiber membrane module 4 Time has dropped. For this reason, the cleaning effect was reduced, and the filtration differential pressure reached 20 kPa in about 70 days.

(Comparative example 3: The length direction of the hollow fiber membrane 23 is a substantially vertical direction + macro bubble)
Comparative Example 2 was the same as Comparative Example 2 except that the fine bubble generator 6 was changed to the same air diffuser as in Comparative Example 1.
During operation, some accumulation of suspended solids and the like was observed in the vicinity of the hollow fiber membrane 23 and the potting fixing portion 24. Moreover, the hollow fiber membranes 23 were entangled with each other by the mixed phase flow of the liquid flowing into the hollow fiber membrane module 4 and the macro bubbles. The filtration pressure difference reached 20 kPa in about 40 days.

  The wastewater treatment apparatus of the present invention is suitable for water treatment in which raw water containing various pollutants such as sewage treatment and wastewater treatment is treated through a solid-liquid separation process.

It is a schematic block diagram which shows one Embodiment of the waste water treatment equipment of this invention. It is sectional drawing which shows typically the example of the hollow fiber membrane module used by this invention. It is a principal part block diagram which shows typically the modification of the position which provides a microbubble generator.

Explanation of symbols

1 Raw water inflow adjustment tank,
2 Anaerobic tank (raw water treatment tank),
3 Aerobic tank (raw water treatment tank),
4 hollow fiber membrane module,
5 Liquid feed pump,
6 Fine bubble generator,
7 Suction pump (suction means),
8 first circulation pump,
9 Second circulation pump,
10a 1st liquid feeding pump,
10b Second liquid feed pump,
11 Air diffuser,
12 gas supply means,
20 Inlet,
21 Outlet,
22 water collecting tube 23 hollow fiber membrane,
24 Potting fixing part,
25 Free end,
26 module case,
27 opening surface,
28 Water collector,
28a Water collection part,
29 Through-hole.

Claims (4)

A wastewater treatment apparatus equipped with a raw water treatment tank for purifying raw water, a hollow fiber membrane module for performing solid-liquid separation, and a liquid feed pump for allowing the liquid treated in the raw water treatment tank to flow into the hollow fiber membrane module There,
The hollow fiber membrane module includes a hollow fiber membrane bundle in which one end of a plurality of hollow fiber membranes is a fixed end bonded and fixed to each other, and the other end is a free end,
At the fixed end of the hollow fiber membrane, the interior of the hollow fiber membrane communicates with a water collecting portion that collects permeated water that has passed through the hollow fiber membrane,
The length direction of the hollow fiber membrane is a substantially horizontal direction, and the inflow direction of the liquid into the hollow fiber membrane module is a direction from the fixed end to the free end of the hollow fiber membrane,
A waste water treatment apparatus, wherein a fine bubble generating device is provided in which bubbles having a diameter of 100 μm or less are contained in a liquid flow contacting the hollow fiber membrane bundle.   The waste water treatment apparatus according to claim 1, wherein the fine bubble generating device is provided in a flow path from the liquid feeding pump to the hollow fiber membrane module.   The wastewater treatment apparatus according to claim 1 or 2, further comprising suction means for lowering the pressure inside the hollow fiber membrane than the pressure outside the hollow fiber membrane. A wastewater treatment method comprising a step of flowing raw liquid into a hollow fiber membrane module and performing solid-liquid separation with the hollow fiber membrane module,
The hollow fiber membrane module includes a hollow fiber membrane bundle in which one end of a plurality of hollow fiber membranes is bonded and fixed to each other, and the other end is a free end. At the fixed end, the inside of the hollow fiber membrane communicates with the water collecting portion that collects the permeated water that has permeated through the hollow fiber membrane,
The length direction of the hollow fiber membrane is a substantially horizontal direction, and the inflow direction of the liquid into the hollow fiber membrane module is a direction from the fixed end to the free end of the hollow fiber membrane,
A wastewater treatment method, wherein bubbles having a diameter of 100 μm or less are contained in a liquid flow in contact with the hollow fiber membrane bundle.

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