JPH0985243A - Wastewater treatment device and operating method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the scraping effect by liquid to be treated on the surface of a separating membrane and provide the permeable flux stable at all times by dividing the inside of a treatment tank into a plurality of areas, providing a circulating flow generating device for circulating the liquid to be treated in the treatment tank and providing membrane separating devices in central sections of respective areas. SOLUTION: The inside of a treatment tank 20 for storing liquid to be treated is divided into a plurality of areas S1-S3 by interstructures 21, 21 in the up and down direction, and the upper and lower sections of the areas S1-S3 are communicated with adjoining areas. Air is fed into the treatment tank 20 by an aeration device 23 disposed on a bottom section of the central area S1, and an upward flow of the liquid to be treated is formed in the area S1, while a downward flow is formed in the areas S2 and S3, and a circulating flow is formed as a whole. Membrane separating devices 25 in which hollow yarn membranes are hung in the lateral direction are disposed between collection pipes 26 connected with a suction pump 29 almost on the central sections of respective areas S1-S3. Cake layers accumulated on the membrane surfaces can be released efficiently by the above arrangement, and a permeable flux can be retained stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment apparatus for treating domestic wastewater and industrial wastewater using a membrane separator and a method for operating the same.

[0002]

2. Description of the Related Art Domestic wastewater contains a large amount of nitrogen components and the like, and if it is directly discharged into a river or the sea, it will cause environmental pollution. Therefore, there is known a wastewater treatment device that gasifies and removes nitrogen components through a nitrification / denitrification process by microorganisms. Then, as this wastewater treatment device, one having a membrane separation device for separating activated sludge containing microorganisms (bacteria) from the liquid to be treated and quickly taking out only the liquid after the treatment is taken out of the treatment device. is there.

As a wastewater treatment apparatus equipped with a membrane separation device, for example, JP-A-4-190890 and JP-A-4190890
There are JP-A-247265, JP-A-4-290529 and JP-A-7-227525. Japanese Patent Laid-Open No. 4-
In JP-A-190890, the inside of the biological treatment tank is divided into a treatment chamber and a treatment chamber by a partition wall, and an agitator is provided in the treatment chamber.
An apparatus is disclosed in which a separation membrane is provided in a chamber and a process is performed while supplying a circulating flow from the treatment 1 chamber to the separation membrane in the treatment 2 chamber. In Japanese Patent Laid-Open No. 4-247265, a region surrounded by a baffle plate (partition plate) is formed in a biological treatment tank, an air diffuser (aeration device) is arranged at the bottom of this region, and a membrane separation device is arranged at the top. However, a device for forming an ascending flow in a region surrounded by a baffle plate by an air diffuser is disclosed. Japanese Patent Laid-Open No. 4-
In Japanese Patent No. 290529, a biological treatment tank is divided into a plurality of regions (chambers) by a partition wall, a plate-like separation membrane is vertically arranged in each region, and an air diffuser is arranged at the bottom of each region. , A device that allows a circulating flow to occur in each region is disclosed. Further, in Japanese Patent Laid-Open No. 7-227525,
An apparatus is disclosed in which a plurality of plate-shaped separation membranes are arranged vertically in a biological treatment tank, and an air diffuser is arranged below the plate-shaped separation membranes.

[0004]

First, Japanese Patent Laid-Open No. 7-22
In the device disclosed in Japanese Patent No. 7525, since the liquid to be treated does not form a circulating flow, the effect of scraping the liquid to be treated on the surface of the separation membrane is small, and recovery of the permeation flux cannot be expected.

Further, in the devices disclosed in JP-A-4-190890 and JP-A-4-247265, a circulation flow is formed to increase the flow velocity of the liquid to be treated on the surface of the separation membrane and scrape it. Although it is possible to enhance the effect, in the apparatus disclosed in Japanese Patent Laid-Open No. 4-190890, the processing 1 chamber is provided, and in the apparatus disclosed in Japanese Patent Laid-Open No. 4-247265, the outside of the baffle plate is provided. Each space becomes a space that does not participate in the membrane separation, the projected area of the membrane becomes small, and the efficiency of the entire apparatus is poor.

On the other hand, in the apparatus disclosed in Japanese Patent Laid-Open No. 4-290529, a separation membrane is provided in all the areas partitioned by the partition wall to further form a circulating flow. Since the separation membrane itself is a plate-shaped separation membrane, the separation membrane itself becomes a wall. As a result, the flow velocity on the surface of the separation membrane becomes small, and a stable permeation flux cannot be obtained.

Furthermore, in each of the above-mentioned prior arts, the flow of the liquid to be treated in the treatment tank is always in a constant direction, so that it is difficult to remove the fibers when they are entangled in the membrane.

[0008]

In order to solve the above-mentioned problems, a wastewater treatment apparatus according to the present invention divides the inside of a treatment tank for storing a liquid to be treated into a plurality of regions by vertical partition walls, Areas adjacent to each other are communicated with each other at the upper and lower parts, and a circulation flow generator for circulating the liquid to be treated by making one of the areas adjacent to each other into an upward flow and the other into a downward flow in the processing tank. Further, a membrane separation device having a hollow fiber membrane laterally installed between water collecting pipes was arranged at the central portion where the flow velocity in each region was high.

Here, an aeration device or a propeller device can be considered as the circulation flow generation device. When an aeration device is used, the ascending flow of the circulation flow becomes a gas-liquid two-phase flow and the propeller device is used. When used, both the upflow and downflow are liquid only.

Further, in the method for operating the wastewater treatment apparatus according to the present invention, the inside of the treatment tank for storing the liquid to be treated is partitioned into a plurality of regions by partition walls in the vertical direction. In a method of operating a wastewater treatment device in which upper and lower parts communicate with each other and a membrane separator is arranged in each region, after forming a circulating flow by making one of the regions adjacent to each other an upflow and the other downflow for a predetermined time. , The direction of the ascending flow and the direction of the descending flow were reversed to form the circulation flow in the opposite direction.

In order to obtain a stable permeation flux, it is preferable that the speed of the circulation flow is 0.1 m or more and 1.0 m or less and the concentration of the liquid to be treated is 8000 mg / l or more and 50,000 mg / l or less. .

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall view of an experimental device manufactured for confirming the effect of the wastewater treatment device according to the present invention. The experimental device has a first partition 2 in a vertical direction in a treatment tank 1 for storing a liquid to be treated. The region 3 and the second region 4 are divided, and the tubular membranes 5 and 5 are installed in the respective regions 3 and 4, and the aeration device 7 in which air is supplied to the bottom of the first region 3 from an external blower 6
Is installed.

Further, a water collecting pipe 8 is provided on each of the tubular membranes 5 and 5.
8 is connected, and these water collecting pipes 8 and 8 are connected to the containers 10 and 10 set on the electronic balance 9 and 9, and the containers 10 and 1 are further connected.
The inside of 0 is decompressed by the aspirator pump 11. still,
Reference numeral 12 is a personal computer for data collection connected to the electronic balances 9, 9.

In the above, when the aspirator pump 11 is driven and air is supplied from the aeration device 7 into the processing tank 1, the aeration device 7 is located immediately below the first region 3 and thus rises into the first region 3. A flow is formed, and by the formation of this upward flow, the liquid to be treated in the second region 4 enters the first region 3 from below, and a circulation flow is formed in the treatment tank 1.

By the way, FIG. 2 shows the relationship between the aeration amount and the circulation flow. From this figure, the upward streamline velocity is slightly higher than the downward streamline velocity, but the void fraction of the bubbles is high. When the minute is corrected, it is found that the two agree with each other, and the linear velocity is proportional to the aeration amount to the power of 0.3.

The permeation flux in the suction filtration experiment showed a substantially constant value from 2 hours to 8 hours after the start of filtration. Therefore, the permeation flux value at the time point when the rate of decrease of permeation flux per hour became 5% or less was taken as the steady value of the permeation flux. The relationship between this steady value and the linear velocity of the circulating flow is shown in FIG.

From FIG. 3, the linear velocity is 0.1 m or more and 1.0 m.
In the following range, the steady-state value of the permeation flux in the region 3 in which the upward flow with bubbles is formed and the steady-state value of the permeation flux in the region 4 in which the downward flow without bubbles are formed are substantially equal to each other. I understood. The concentration of the liquid to be treated is preferably 8,000 mg / liter or more and 50,000 mg / liter or less, and when it is more than 20,000 mg / liter, the viscosity becomes high and the power cost becomes high.
It should be g / liter or more and 20000 mg / liter or less.

From the above experiments, it can be said that if the permeation flux is within the predetermined range, the scraping effect on the membrane surface can be exhibited without immersing the separation membrane in the gas-liquid two-phase flow.

FIG. 4 is a sectional view of a wastewater treatment apparatus according to the present invention produced based on the above findings, and FIG. 5 is a sectional view taken along the line AA of FIG. 4, in which the wastewater treatment apparatus stores the liquid to be treated. The inside of the processing tank 20 is partitioned into a plurality of regions S1, S2, S3 by partition walls 21 and 21 in the vertical direction, and these regions communicate with the adjacent regions at the upper and lower portions.

A blower 2 is provided at the bottom of the central area S1.
An aeration device 23 that supplies the air from 2 into the processing tank 20 is arranged. Thus, due to the air supplied from the aeration device 23, an upflow of the liquid to be treated is formed in the central region S1, and a downflow is formed in the left and right regions S2 and S3.
A circulating flow is formed as a whole.

An apparatus for forming a circulating flow is shown in FIG.
You may arrange | position the propeller apparatus 24 as shown in FIG. In this case, a gas-liquid two-phase upward flow is not formed in the region S1, but a circulating flow is formed as a whole.

Further, a membrane separation device 25 is arranged at a substantially central portion of each of the areas S1, S2 and S3. The membrane separation device 25 includes a hollow fiber membrane 27 between water collecting pipes 26 in the vertical direction which are separated from each other in the left and right directions.
Is horizontally installed, and the water collection pipe 26 is connected to a suction pump 29 via a pipe 28.

Here, the central portion of each of the regions S1, S2, S3 is a portion where the linear velocity of the circulating flow is the highest, and in the present invention, since the hollow fiber membrane is used as the membrane separation device, The membrane can be installed at a location where the linear velocity is high, and the cake layer deposited on the membrane surface can be efficiently separated to maintain the permeation flux. Incidentally, when a plate-shaped separation membrane is installed, the membrane itself becomes a partition wall, and the linear velocity on the membrane surface becomes extremely small.

In the above, the suction pump 29 is driven and air is supplied from the aeration device 23 to form a circulating flow in the processing tank 20 while performing solid-liquid separation of the liquid to be processed. Here, in the illustrated example, the processing tank 20 is shown alone,
The treatment tank 20 may be integrally connected to another anaerobic treatment chamber or an aerobic treatment chamber.

FIG. 7 is a sectional view similar to FIG. 4 showing another embodiment, and FIG. 8 is a diagram showing an operating method of the apparatus shown in FIG. 7. In this embodiment, the bottom of the region S1 is aerated. Device 2
3a is arranged, and the aeration device 23b is provided at the bottom of the regions S2 and S3.
Has been arranged. Then, the aeration device 23a and the aeration device 2
The operation of 3b is alternately performed by switching the valve 30 so that the direction of the circulation flow formed in the processing tank 20 is reversed at regular intervals.

In this way, by inverting the direction of the circulating flow at regular intervals, the fibers and the like entangled in the hollow fiber membrane 27 can be effectively removed.

[0027]

As described above, in the wastewater treatment apparatus according to the present invention, the inside of the treatment tank for storing the liquid to be treated is partitioned into a plurality of regions by vertical partition walls, and these regions are adjacent to each other. The regions are made to communicate with each other at the upper part and the lower part, and one of the regions adjacent to each other is set as an upflow in the processing tank,
A circulation flow generator such as an aeration device or a propeller device that circulates the liquid to be treated by setting the other as a downward flow is installed, and a hollow fiber membrane is laterally placed between the water collection pipes in the central part where the flow velocity in each region becomes faster. Since the membrane separation device installed over the separation membrane is provided, the effect of scraping the surface of the separation membrane with the liquid to be treated is enhanced, and a stable permeation flux can be obtained. Moreover, since the membrane separation device is arranged in all the regions, the ratio of the projected area of the membrane installation can be increased, and as a result, the device can be downsized.

Further, as a method of operating the membrane separation device, the flow of the circulating flow is reversed at regular intervals, so that the fibers entangled in the membrane can be removed during operation. In particular, the circulation flow velocity is set to 0.1 m or more and 1.0 m or less, and the concentration of the liquid to be treated is 8000 mg / liter or more and 50,000 or more.
A stable permeation flux can be obtained by setting it to be mg / liter or less.

[Brief description of drawings]

FIG. 1 is an overall view of an experimental device manufactured to confirm the effects of a wastewater treatment device according to the present invention.

FIG. 2 is a graph showing the relationship between the amount of aeration and the linear velocity of the circulating flow.

FIG. 3 is a graph showing the relationship between the linear velocity of the circulating flow and the permeation flux (steady value).

FIG. 4 is a sectional view of a wastewater treatment device according to the present invention.

5 is a sectional view taken along line AA of FIG.

FIG. 6 is a sectional view similar to FIG. 4 showing another embodiment.

FIG. 7 is a sectional view similar to FIG. 4, showing another embodiment.

FIG. 8 is a diagram showing a method of operating the apparatus shown in FIG.

[Explanation of symbols]

1 ... Processing tank, 2 ... Partition wall, 3 ... 1st area | region, 4 ... 2nd area | region,
5 ... Tubular membrane, 6 ... Blower, 7 ... Aeration device, 8 ... Water collection pipe,
9 ... Electronic balance, 20 ... Processing tank, 21 ... Partition wall, 23, 23
a, 23b ... Aeration device, 24 ... Propeller device, 25 ... Membrane separation device, 26 ... Water collecting pipe, 27 ... Hollow fiber membrane, 29 ... Suction pump, 30 ... Switching valve, S1, S2, S3 ... Region.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsuo Watanabe 2-1, 1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture Totoki Equipment Co., Ltd. (72) Yuichi Okuno 2 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka 1st-1st Totoki Equipment Co., Ltd.

Claims (5)

[Claims] 1. A processing tank for storing a liquid to be processed is partitioned into a plurality of regions by vertical partition walls, and adjacent regions of the plurality of regions communicate with each other at an upper portion and a lower portion. Has one of the areas adjacent to each other as an upflow,
A circulation flow generator that circulates the liquid to be treated is provided by setting the other as a downward flow, and a membrane separation device in which a hollow fiber membrane is laterally installed between the water collection pipes is provided in the center where the flow velocity in each region becomes faster. A wastewater treatment device characterized by being provided. 2. The wastewater treatment apparatus according to claim 1, wherein the circulating flow generator is an aeration device or a propeller device provided at the bottom of the treatment tank. 3. A processing tank for storing a liquid to be processed is partitioned into a plurality of regions by vertical partition walls, and adjacent regions of the plurality of regions are connected to each other at an upper portion and a lower portion, and each region is connected to each other. In a method for operating a wastewater treatment device provided with a membrane separation device, one of the regions adjacent to each other for a predetermined time is formed as an upflow and the other is formed as a downflow to form a circulation flow, and then the directions of the upflow and the downflow are reversed. A method for operating a wastewater treatment device, characterized in that a reverse circulation flow is formed. 4. The method for operating the wastewater treatment apparatus according to claim 3, wherein the speed of the circulating flow is 0.1 m or more and 1.0 m or more.
A method for operating a wastewater treatment device characterized by the following. 5. The method for operating a wastewater treatment device according to claim 3, wherein the concentration of the liquid to be treated is 8000 mg / liter or more and 50000 mg / liter or less.