JP2002233738A - Submerged flat membrane separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a submerged flat membrane separator which can perform stable treatment as the result of prevent against the clogging of a membrane surface, the putrefaction of sludge, and a decrease in the capacity of treating biological materials when the viscosity of the water to be treated increases. SOLUTION: A nitrification/denitrification apparatus 10 in an embodiment has membrane modules 18, 18, and the like, in the inside of an aerating guide wall 38, and an aeration pipe 36 is disposed under the membrane modules 18, 18, and the like. Nozzles 40 that spray the water 16 to be treated are disposed perpendicularly and downwardly in the outside of the wall 38. Inclined plates 52 that direct the flow of the water 16 toward the pipe 36 are provided under the nozzles 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a submerged flat membrane separator, and more particularly to a submerged flat membrane separator used in the fields of industrial wastewater treatment and activated sludge treatment such as sewage.

[0002]

2. Description of the Related Art An immersion flat membrane separator is a type of membrane separator in which a flat membrane is immersed in a suspension, and is used for treating coagulated sludge of industrial wastewater and activated sludge such as sewage and human waste. ing. As shown in FIG. 4, this apparatus immerses the membrane modules 2, 2,... In the treated water 1 in which the activated sludge is highly concentrated, and sucks the treated water 1 into the membrane module 2. Obtain treated water (filtrate). The membrane module 2
The membrane module 2 is installed so that the membrane surface 2A is vertical.
A diffuser 3 is provided below the lower part. Here, the purpose of performing the air diffusion by the air diffusing means 3 is to obtain a cleaning effect of removing the sludge cake deposited on the membrane surface 2A to suppress the blockage of the membrane surface 2A, and to generate a swirling flow in the tank 4. This is to provide a cross flow to the membrane surface 2A and to agitate the inside of the tank 4, and to supply oxygen for aerobic treatment when the water to be treated 1 is activated sludge or the like.

[0003] Around the membrane module 2, a box-shaped air diffusion guide wall 5 which is opened up and down is provided. The air diffusion guide wall 5 allows air bubbles 6 diffused from the air diffusion means 3 to be formed. It is guided to the membrane module 2. Thereby, the flow path of the swirling flow is secured, and the film surface cleaning by the air diffusion is effectively performed.

[0004]

In the conventional immersion flat membrane separation apparatus, the concentration of the activated sludge in the water 1 to be treated rises to a predetermined value or more (for example, MLSS = 10000 mg / L or more), or in winter. When the temperature of the to-be-treated water 1 falls, there is a problem that the viscosity of the to-be-treated water 1 increases and the fluidity of the to-be-treated water 1 decreases. When the fluidity of the water to be treated 1 decreases, the stirring effect decreases, and the activated sludge precipitates on the bottom A of the tank 4 and rots. Further, when the fluidity is reduced, the cleaning effect of the film surface 2A is also reduced, so that clogging of the film surface 2A proceeds early, and a maintenance cycle such as cleaning with a chemical solution is shortened.

[0005] In addition, since the viscosity of the water to be treated 1 is increased, the bubbles 6 are coarsened in the internal region B of the diffusion induction wall 5, so that the efficiency of diffusion and dissolution is reduced, and the biological treatment ability by aerobic microorganisms is reduced. There was a risk of lowering.

Further, the conventional immersion flat membrane separation apparatus has a problem that the concentration of dissolved oxygen in the water 1 to be treated is reduced in the outer region C of the diffusion induction wall 5, and the biological treatment ability by aerobic microorganisms is reduced. there were.

[0007] The present invention has been made in view of such circumstances, and when the viscosity of the water to be treated increases, blockage of the membrane surface,
It is an object of the present invention to provide a submerged flat membrane separation device capable of preventing decay of sludge and a decrease in biological treatment capacity and performing stable treatment.

[0008]

According to a first aspect of the present invention, there is provided a membrane module which is immersed in treated water containing activated sludge in a tank and filters the treated water. An immersion flat membrane separation device, which is provided below the membrane module and is provided with an aeration unit for performing aeration, comprising an injection unit that pressurizes the water to be treated and injects the water toward the bottom in the tank. It is characterized by that.

According to the first aspect of the present invention, since the pressurized water to be treated is jetted toward the bottom in the tank, the activated sludge deposited on the bottom in the tank can be scraped out and circulated. Thereby, it is possible to prevent sludge decay and decrease in biological treatment capacity. In addition, since the velocity of the swirling flow in the tank is increased by injecting the water to be treated, the cleaning effect of the membrane surface is increased, and the clogging of the membrane surface can be prevented.

According to the second aspect of the present invention, since air is supplied to the water to be injected, the concentration of dissolved oxygen in the water to be processed in the tank can be increased.

According to the third aspect of the present invention, since the flow of the injected water to be treated is directed to the air diffuser, the formation of the swirling flow can be promoted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an immersion flat membrane separation device according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a nitrification / denitrification apparatus 10 to which an immersion flat membrane separation apparatus according to the present invention is applied. Is shown.

The water 16 to be treated is stored in the nitrification tank 12 and the denitrification tank 14, and a plurality of membrane modules 18 are immersed in the water 16 to be treated in the nitrification tank 12.

FIG. 2 is a perspective view showing the structure of the membrane module 18.

As shown in FIG. 1, the membrane module 18 comprises:
A plurality of (for example, ten) membrane plates 20 (only one is shown) are provided. The membrane plate 20 includes a hollow support plate (plastic step) 22.
And an organic flat film 26 attached to both sides of the support plate 22 via spacers 24 such as nonwoven fabric. Membrane plate 2
Are arranged side by side in parallel, and the left and right ends of each membrane plate 20 are embedded and fixed in the membrane end fixing members 28, 28. Further, a film end fixing material 3 is provided on both upper and lower ends of each film plate 20.
0 and 30 are attached. Each membrane end fixing material 30
Are held at regular intervals by urethane rubber interval holding members 32, 32,..., And the interval holding members 32 are supported by the membrane end fixing members 28, 28 by support bars 33, 33,.

The membrane end fixing member 28 is made of a resin such as PVC, and has a water collecting channel (not shown) connected to the support plate 22 formed therein. This water collecting passage is communicated with the water collecting pipe 34 of FIG. 1, and the water collecting pipe 34 is provided with a suction means such as a pump (not shown). By driving the suction means, a suction force acts on the inside of the membrane plate 20 of FIG.
Sucked inside. Thereby, the water 16 to be treated is filtered by the organic flat membrane 26, and the treated water is obtained. In addition,
The suction pressure (filtration pressure) at that time is measured by a measuring device (not shown).

The membrane module 18 configured as described above
Are arranged upright so that the organic flat film 26 is vertical, and as shown in FIGS. 1 and 3, they are arranged side by side in two upper and lower stages.

A diffuser 36 is provided below the membrane module 18.
Is provided. The air diffuser 36 is connected to a blower (not shown), and air is supplied to the air diffuser 36 from the blower.
A large number of diffuser holes (not shown) are formed on the outer peripheral surface of the diffuser tube 36, and the air supplied to the diffuser tube 36 becomes fine bubbles from the diffuser holes and diffuses into the water 16 to be treated. Is done.

A box-shaped diffusion guide wall 38 which is opened up and down is installed around the membrane module 18, and air bubbles from the diffusion tube 36 are removed by the diffusion guide wall 38.
8 As shown in FIG. 3, the air bubbles guided to the membrane module 18 rise inside the air diffusion guide wall 38. Therefore, due to the air lift effect, an upward flow of the water 16 to be treated is formed in the internal region of the air diffusion guide wall 38. The raised water 16 goes around beyond the upper end of the diffusion guide wall 38, descends the outer region of the diffusion guide wall 38, and enters the inner region again from the lower end of the diffusion guide wall 38. As a result, a swirling flow that swirls between the inner region and the outer region of the air diffusion guide wall 38 is formed.

The upper end portion of the air diffusion guide wall 38 is folded outward twice to form a folded portion 38A. Thereby, the flow path of the swirling flow swirling beyond the air diffusion guide wall 38 is gradually increased, so that a smooth swirling flow can be obtained. In addition, as shown in FIG.
A plurality of holes 38B, 38B,... Are formed so that bubbles do not accumulate inside the folded portion 38A.

A large number of nozzles 40, 40,... The nozzle 40 is
They are arranged at equal intervals in the width direction of the membrane module 18 and are installed vertically downward. Each nozzle 40 is connected to the denitrification tank 14 via a supply pipe 42. The supply pipe 42 has a pump 4
4 is provided, and the water to be treated 16 in the denitrification tank 14 is supplied to the nozzle 40 by the pump 44. The water 16 to be treated supplied to the nozzle 40 is rapidly accelerated by passing through a constricted portion (not shown) of the nozzle 40 and is jetted vertically downward.

Below the nozzle 40, as shown in FIG.
The inclined plate 52 is provided obliquely. The water 16 to be treated injected from the nozzle 40 collides with the inclined plate 52, so that the flow direction is directed to the air diffuser 36.

The pump 44 shown in FIG. 1 has a function of varying the supply pressure of the water 16 to be supplied to the nozzle 40, and the supply pressure is variably controlled by a control device (not shown). For example, when the filtration pressure of the membrane module 18 is equal to or lower than a predetermined value, the pump 44 is controlled to a low supply pressure, and the required minimum amount of the water 16 to be treated is supplied to the nitrification tank 12. When the filtration pressure exceeds a predetermined value, the pump 44 is switched to a high supply pressure, and the water 16 to be treated is injected from the nozzle 40.

The supply port side of the pump 44 (that is, the denitrification tank 14
Side), an air supply pipe 46 communicates with the air supply pipe 46, and an on-off valve 48 is provided in the air supply pipe 46. The on-off valve 48 is controlled to open and close by the control device. For example, when the dissolved oxygen concentration of the water 16 to be treated measured by a measuring device (not shown) falls below a predetermined value, the on-off valve 48 is opened to supply air to the pump 44. Thereby, the water 16 into which the air is blown is supplied to the nozzle 40 and is jetted.

The nitrification tank 12 and the denitrification tank 14 are connected via a return pipe 50. Therefore, when the water 16 to be treated is injected from the nozzle 40 into the nitrification tank 12, a part of the water 16 to be treated in the nitrification tank 12 is returned to the denitrification tank 14 via the return pipe 50. An overflow weir (not shown) may be provided in place of the return pipe 50, and the water 16 to be treated may be returned to the denitrification tank 14 when the water level in the nitrification tank 12 exceeds the overflow weir.

Next, the operation of the nitrification / denitrification device 10 configured as described above will be described.

When the filtration pressure is lower than a predetermined value, a normal operation is performed, and the pump 44 is driven at a low supply pressure to supply the nitrification tank 12 with a required minimum amount of the water 16 to be treated. In this case, since the viscosity of the water 16 to be treated is low,
Has high fluidity. Accordingly, a swirling flow having a sufficient flow velocity can be obtained only by diffusing air from the diffuser 36 without injecting the water 16 to be treated from the nozzle 40 at high speed.

However, when the filtration pressure increases, the viscosity of the water 16 to be treated increases with the increase of the filtration pressure, and the fluidity of the water 16 decreases. For this reason, sufficient swirling flow cannot be obtained only by air diffusion, and the cleaning effect of the organic flat film 26 and the stirring effect in the nitrification tank 12 are reduced.

Therefore, when the filtration pressure rises and exceeds a predetermined value, the pump 44 is switched to a higher supply pressure. Thereby, the to-be-processed water 16 is blown out vertically from the nozzle 40 at a high speed, and the flow velocity of the swirling flow is increased. In particular, in the present embodiment, since the flow of the water 16 to be treated injected from the nozzle 40 is directed toward the air diffuser 36 by the inclined plate 52, a smooth swirl flow is formed, and the flow velocity of the swirl flow is greatly increased. be able to. Therefore, even if the viscosity of the water 16 to be treated increases, a swirling flow having a sufficient flow velocity can be obtained, and the effect of cleaning the organic flat membrane 26 and the effect of stirring the nitrification tank 12 can be improved.

Further, the rising speed of the swirling flow increases the rising speed of the bubbles from the air diffuser 36, so that the bubbles are prevented from becoming coarse. Thereby, the oxygen dissolving efficiency of the water 16 to be treated is increased, so that the biological treatment capacity such as oxidation and nitrification is improved.

Further, since the water 16 to be treated is jetted from the nozzle 40 toward the bottom in the nitrification tank 12, the sludge deposited on the bottom is scraped out and swirls together with the swirling flow. Therefore, sludge does not accumulate at the bottom of the nitrification tank 12, so that it is possible to prevent sludge from decay or to reduce the biological treatment capacity.

On the other hand, when the concentration of dissolved oxygen in the water 16 to be treated decreases, the on-off valve 48 is opened to supply air to the pump 44, and the water 16 to which the air has been blown is injected from the nozzle 40. As a result, the concentration of dissolved oxygen in the water to be treated 16 can be increased, so that the biological treatment capacity such as oxidation and nitrification can be restored. In addition, since oxygen is supplied to a region having a low dissolved oxygen concentration, the dissolved oxygen concentration distribution in the nitrification tank 12 can be made uniform.

As described above, according to the nitrification / denitrification apparatus 10 of the present embodiment, when the viscosity of the water 16 to be treated increases,
Since the to-be-processed water 16 is jetted from the nozzle 40 to the bottom of the nitrification tank 12, it is possible to prevent the organic flat membrane 26 from being clogged, decay sludge, and decrease the biological treatment capacity, and perform stable treatment. it can.

The nitrification / denitrification device 10 is provided with
When the dissolved oxygen concentration of No. 6 was lowered, air was blown into the water 16 to be treated and jetted from the nozzle 40,
It is possible to recover the dissolved oxygen concentration of the water 16 to be treated,
Biological processing capacity can be improved.

Further, since the nitrification / denitrification device 10 drives the pump 44 at a low supply pressure during the normal operation, the power cost can be reduced.

In the above-described embodiment, the nozzle 40 and the pump 44 may be configured so that the water 16 to be treated injected from the nozzle 40 is accompanied by a cavitation phenomenon. That is, the supply pressure of the pump 44 is increased,
By narrowing the constricted portion of the nozzle 40, the pressurized water 16 to be treated is jetted from the nozzle 40 at a high speed to a low-pressure region, thereby causing a cavitation phenomenon. When the cavitation phenomenon occurs, the activated sludge is sufficiently dispersed and the reaction of microorganisms is enhanced, so that the biological treatment capacity is improved, and the effect of reducing the volume of excess sludge periodically removed is also improved. In this case, by opening the on-off valve 48 and supplying air, the dispersion of the activated sludge can be enhanced.

In the above-described embodiment, the supply pressure of the pump 44 is switched to a high pressure when the filtration pressure of the membrane module 18 increases, but the invention is not limited to this. For example, the switching may be performed when a decrease in processing performance such as nitrification or oxidation is observed. Moreover, you may make it switch periodically.

[0039]

As described above, according to the immersion flat membrane separation apparatus of the present invention, the pressurized water to be treated is jetted toward the bottom in the tank, so that the flow velocity of the swirling flow is increased and the membrane surface is increased. As a result, the sludge is prevented from being deposited and the biological treatment capacity is prevented from deteriorating.

[Brief description of the drawings]

FIG. 1 shows nitrification and immersion using the immersion flat membrane separation device according to the present invention.
Perspective view showing the structure of the denitrification device

FIG. 2 is a perspective view showing the structure of a membrane module.

FIG. 3 is a schematic view of a nitrification tank in an operation state.

FIG. 4 is a schematic view of a conventional immersion flat membrane separation device.

[Explanation of symbols]

10: nitrification / denitrification equipment, 12: nitrification tank, 14: denitrification tank
16 ... water to be treated, 18 ... membrane module, 36 ... air diffuser,
40 nozzle, 42 supply pipe, 44 pump, 46 air supply pipe, 48 on-off valve, 52 inclined plate

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C02F 3/12 C02F 3/12 SF term (reference) 4D006 GA02 HA42 HA93 JA08C JA30A JA31A JA53A JA55A JA63A KA42 KA44 KA47 KB22 KE01Q KE11P KE22Q KE30P MA03 PB08 PB24 PC62 4D028 AA01 AB00 BC03 BC17 BC26 BD10 BD17 CA09 CB08 CC07

Claims (3)

[Claims] 1. A membrane module that is immersed in treated water containing activated sludge in a tank and filters the treated water; a diffuser installed below the membrane module to diffuse air;
An immersion flat membrane separation device comprising: an immersion flat membrane separation device, comprising: an injection unit that pressurizes the water to be treated and injects the water toward the bottom in the tank. 2. The method according to claim 1, wherein the injection unit includes an air supply unit that supplies air to the pressurized water to be treated, and the air supply unit supplies air based on a dissolved oxygen amount of the water to be treated. The immersion flat membrane separation device according to claim 1, wherein: 3. An immersion flat according to claim 1, wherein an inclined plate for directing the flow of the water to be treated injected by said injection means to said air diffusing means is provided at the bottom of said tank. Membrane separation device.