JPH0975970A - Dipping type membrane separation device using hollow fiber membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a dipping type membrane separation device that the total concn. of the sludge held in the treating tank is increased, permeation of the hollow fiber membrane does not decrease even when the device is operated with a high load, high-quality treated water can be stably obtd, and maintenance of the device is easy because the frequency for washing of the hollow fiber membrane is low. SOLUTION: This dipping type membrane separation device has such a structure that a membrane element 12 having lots of hollow fiber membranes 13 is made to stand in a water containing activated sludge in a treating tank 10, an air-lifted upward flow which rises and touches the hollow fiber membranes is generated by bubbles diffused from a diffusion pipe 7 in the bottom of the tank, and that the permeated water through the membranes of the hollow fiber membrane is recovered. In this device, a cleaning member 20 on which activated sludge can deposit is arranged in the water in the tank in such a manner that the member 20 is vibrated by the air-lifted flow in the tank and is brought into contact with the hollow fiber membrane 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion type membrane separation device as an activated sludge treatment device using a membrane element having a large number of hollow fiber membranes.

[0002]

2. Description of the Related Art A membrane having a large number of hollow fiber membranes in water containing activated sludge in a treatment tank of an activated sludge treatment device in order to make wastewater treatment equipment compact and stably obtain advanced treated water. A hollow fiber membrane that raises an element, causes an air lift upward flow that rises by contacting the hollow fiber membrane with air bubbles diffused by the air diffuser at the bottom of the tank, and collecting permeated water that has permeated the hollow fiber membrane. An immersion type membrane separation device has been developed. The main purpose of immersing the membrane element having a hollow fiber membrane in the activated sludge treatment is to facilitate solid-liquid separation and, as a result, increase the concentration of the activated sludge suspended in water in the tank.
That is, as compared with the conventional solid-liquid separation of natural sedimentation in a sedimentation tank using activated sludge, the membrane element having a hollow fiber membrane is immersed, and the permeated water obtained by permeating the membrane of the hollow fiber membrane to the hollow part is obtained. When water is sampled, the concentration of activated sludge in the tank can be increased to more than double that of the conventional method, to 10,000 mg / cubic or more, and as a result, operation with an increased load can be performed.

[0003]

However, if the activated sludge is kept at a high concentration in the tank, the amount of sludge adhering to the surface of the hollow fiber of the immersed membrane element increases, and the amount of permeated water that permeates the hollow fiber membrane. Is reduced. Normally, the concentration of activated sludge is 1000, which does not significantly reduce the amount of permeated water that permeates the hollow fiber membrane.
It is said to be around 0 mg / stand. Even if the activated sludge concentration in the tank is set to the above-mentioned 10,000 mg / stand, even if the operation is carried out in the high load range of 10 kg-BOD / m ³ · day or more, Since the load amount increases, undecomposed organic matter is likely to remain in the tank. Then, when the concentration of undegraded organic matter or intermediate metabolites generated in the decomposition process increases, they adhere to the surface of the hollow fiber membrane,
The amount of permeated water that permeates the hollow fiber membranes is also reduced by forming adjacent hollow fiber membranes into a lump. For this reason,
An apparatus in which a membrane element having a hollow fiber membrane is immersed is currently operating at a maximum activated sludge concentration of 10000 mg / stand and a maximum load of 5 kg-BOD / m ³ · day. .

[0004]

SUMMARY OF THE INVENTION The present invention increases the concentration of retained sludge in the entire treatment tank to achieve a load of 10 kg-BOD / m ³
・ Permeability of the hollow fiber membrane does not decrease even if it is operated for more than a day, highly treated water can be stably obtained, and the frequency of cleaning the hollow fiber membrane is low, and the immersion type membrane separation is easy to maintain. It was developed to obtain a device, and a membrane element with a large number of hollow fiber membranes is set up in water containing activated sludge in a treatment tank, and the air diffusers at the bottom of the tank form hollow fiber membranes. In the submerged membrane separation device with a hollow fiber membrane, which causes upward airflow to rise by contact with the air and collects permeated water that has permeated through the membrane of the hollow fiber membrane, activated sludge can adhere to the water in the tank. The cleaning member is arranged so as to be capable of contacting the hollow fiber membrane while being swung by an upward flow of an air lift in the tank.

[0005]

DETAILED DESCRIPTION OF THE INVENTION In the illustrated embodiment, 10
Is an organic wastewater as a raw water pump P1, supply pipe 11
In the treatment tank of the activated sludge treatment apparatus, a plurality of membrane elements 12 having a plurality of hollow fiber membranes 13 arranged in the vertical direction are flowed in the longitudinal direction in the water in the tank in which the activated sludge floats. They are arranged in a line with a space 16 kept therebetween.
The membrane element is composed of an upper support member 14a having the upper ends of a plurality of hollow fiber membranes 13 fixed and a lower support member 1 having the lower ends fixed.
4b and the upper support member 14a is a water sampling pipe communicating with the hollow part of the hollow fiber membrane 13 addressed to one, and the header pipe 15 for water sampling is connected to the water sampling pipe of each membrane element to form a header pipe. The permeated water in the raw water in the tank is permeated into the hollow portion of the hollow fiber membrane by the suction action of the suction pump P2 connected to 15, and is collected as treated water. At the bottom of the treatment tank, there are multiple spargers for aerobically biotreating organic matter in the raw water with activated sludge and for generating upward airlift flow in contact with the hollow fiber membrane in the raw water in the tank. A blower B having a trachea 17 laid and provided in a header pipe 18 for air diffusion connected to the air diffuser
The air blown from is diffused as air bubbles from the air diffuser 17.

Reference numeral 20 is a cleaning member in the up-down direction that is swayed by the upward flow of the air lift generated by the air diffusion of the air diffusion pipe 17 and comes into contact with the hollow fiber membrane. In order to clean the opposite surfaces of the hollow fiber membrane, a plurality of them are provided along the flow path interval 16 and along the front surface of the hollow fiber membrane of the front end membrane element and the rear surface of the hollow fiber membrane of the rear end membrane element, They are arranged between the upper and lower support members 23a and 23b.

As shown in FIG. 3, each cleaning member 20 has a cylindrical brush in which innumerable branch yarns 22 to which the activated sludge can be similarly radially projected from around the core yarn 21 to which the activated sludge can be attached. Take on a shape. As the cleaning member, a diabio fringe (trade name of NT Co., Ltd.) made of polyester (core yarn) and acrylic fiber (branch yarn) can be used. If a length of 1 m is used for a volume of 1 m ^{3 of a} treatment tank with a diameter of 100 mm, it is possible to retain activated sludge at the surface of 20,000 mg / stand or more, and in the treatment tank 10,000 mg /
When the standing activated sludge is set to be in a floating state, the amount of activated sludge held in the treatment tank reaches 30000 mg / stand including the amount held by the diabio fringe.
It is possible to operate in a high load area of 5 kg-BOD / m ³ · day.

The cleaning member 20 is provided with upper and lower support members 23.
It is loosely attached between a and 23b, and is constantly shaken by the upward flow of the air lift generated in the water in the tank so as to come into contact with the hollow fiber membrane of the membrane element, and the surface of the membrane is rubbed with the branch yarn 22.

When the pumps P1 and P2 and the blower B are driven for operation, the raw water containing organic substances supplied through the supply pipe 11 into the treatment tank is activated sludge floating in the water in the tank and the cleaning member. The organic matter is decomposed by being biologically treated by the activated sludge that is attached to and retained by 20. Then, the permeated water that permeates the hollow fiber membrane in the raw water contacts the hollow fiber membranes 13 of each membrane element 12 by the bubbles ejected from the air diffuser 17 and flows upward, and the negative pressure of the suction pump P2 is increased. It permeates the membrane into the hollow portion of the hollow fiber membrane that acts, and flows into the hollow portion, and the water is sampled through the water sampling pipe 14a and the water sampling header pipe 15.

Since activated sludge floats in the water in the tank and also adheres to and is retained on the cleaning member 20, when the concentration of floating sludge is set to 10000 mg / stand, the concentration in the cleaning member 20 should be 10,000 mg / stand or more. Hold and easily 200
Loaded by activated sludge with a concentration of 00 mg / stand or more, 10
Operate in the high load range of kg-BOD / m ³ · day or more,
Highly treated water can be obtained. Even if the cleaning member 20 has a large amount of sludge retained and is operated in a high load range, the cleaning member 20 constantly contacts the hollow fiber membrane 13 and shakes during operation, and sludge and contaminants attached to the surface of the hollow fiber membrane. Since the water is removed and washed, the amount of permeated water that permeates the membrane does not decrease, and it is possible to prevent the adjoining members of the hollow fiber membrane from solidifying in sludge or contaminants. Therefore, the frequency of cleaning is greatly reduced and maintenance is easy.

In the illustrated embodiment, the upper and lower support members 14a and 14b of the membrane element 12 and the upper and lower support members 23a and 23b of the cleaning member 20 are fixed to the upper inner surface of the side walls of the processing tank 10 which face each other. Instead, the membrane element and the cleaning member are housed inside the tubular frame by fixing them to the upper portions of the inner surfaces of the opposite side walls of the open and closed tubular frame, and the tubular frame is immersed in the treatment tank so that it can be pulled up. May be. Further, the upper support member 14a to which the upper end of the hollow fiber membrane is fixed is used as a water sampling tube, and the upper end of the hollow fiber membrane is fixed and the permeated water that permeates the hollow fiber membrane is also collected. Depending on the structure, a support member for fixing the upper end of the hollow fiber membrane and a pipe for collecting permeated water that has permeated the hollow fiber membrane may be installed separately. Further, the lower support member 14b for fixing the lower end of the hollow fiber membrane may also be used as a water sampling pipe so that the lower end of the hollow fiber membrane is fixed and the permeated water that has permeated through the hollow fiber membrane is also used. Furthermore, the hollow fiber membranes are not limited to being arranged vertically, but may be arranged horizontally.

[0012]

[Example] Width 600 mm, depth 900 mm, depth 120
0mm, in the water in a test tank with an effective capacity of 540
Fractionation characteristic 0.1μm, material is polyethylene, width 486m
m, height 798 mm, effective surface area 4 m ² hollow fiber UF membranes arranged vertically, one membrane element (Mitsubishi Rayon Co., Ltd., product name Stellapore L) is set up, and the above-mentioned diameter is used as a cleaning member on each one side. 100 mm, height 100
5 0mm diamond bio fringes (10 on both sides)
Book) installed. The distance between the centers of the diamond biofringes for 5 fibers on one side was 100 mm, and the distance between the centers of the diamond biofringes and the hollow fiber membrane was 50 mm. An air diffuser was laid on the bottom of the tank so that air could be blown out uniformly from the entire bottom surface.

Activated sludge was introduced into the above treatment tank at a sludge concentration of 5000 mg / vertical, and synthetic raw water having a BOD concentration of 10000 mg / vertical using peptone and glucose was passed for 48 hours. Loadings 5kg-BOD / m ³
・ It is a day. Treated water is -0.2 from the hollow part of the hollow fiber membrane.
It was sucked at a reduced pressure of kg / cm ² . As a result of continuous operation for 12 days, the concentration of suspended sludge in the tank was 10500 mg / stand and the amount of sludge attached to the diamond biofringe was 3 in total.
Reached 500g, the total sludge concentration in the treatment tank was 1700
It became 0 mg / stand. Then, the stagnant time of raw water was increased to 24 hours, the load was increased to 10 kg-BOD / m ³ · day, and continuous operation was performed for 7 days. During this period, sludge was drawn out so that the concentration of floating sludge in the tank was maintained at 9000 to 11000 mg / stand. During the operation period with a load of 10 kg-BOD / m ³ · day, the advanced treatment with BOD of treated water of 10 mg / cubic or less was stably performed. Also, from the hollow fiber membrane-0.3 kg
The maximum amount of permeated water that can be sucked in under a reduced pressure of / cm ² is 0.
There was no tendency for the amount of water to decrease from 8 to 1.1 m ³ / m ² · day. When the hollow fiber membrane was observed by pulling up the membrane element above the water surface, it was confirmed that sludge did not adhere to the surface of the membrane and the hollow fiber membrane was well washed by the washing member.

[0014]

As is clear from the above, the present invention uses a cleaning member to which activated sludge can be adhered, and the cleaning member constantly cleans the surface of the hollow fiber membrane during operation, so that it floats in the water in the tank. By increasing the activated sludge and the activated sludge adhering to the cleaning member, the concentration of the retained sludge in the entire treatment tank is increased to 10 kg-B.
It is possible to stably collect highly treated water by operating in a high load area of OD / m ³ · day or more. Therefore, it is possible to meet the demands for downsizing of the equipment and reduction of the installation area, and since the cleaning member constantly cleans the surface of the hollow fiber membrane during operation, the frequency of cleaning is greatly reduced and the maintenance of the equipment is reduced. Is significantly easier.

[Brief description of drawings]

FIG. 1A is a plan view of an embodiment of the present invention, and FIG.
FIG. 4B is a sectional view taken along the line AB of FIG.

FIG. 2 is a vertical side view of the embodiment of FIG.

3A is an elevation view of the cleaning member, and FIG. 3B is a plan view thereof.

[Explanation of symbols]

 10 Treatment Tank 11 Raw Water Supply Pipe 12 Membrane Element 13 Hollow Fiber Membrane 14 Upper and Lower Support Members of Hollow Fiber Membrane 15 Water Collection Header Pipe 16 Flow Path Interval Between Membrane Elements 17 Diffuser Pipe 18 Diffuser Header Pipe 20 Cleaning Member 21 core thread of cleaning member 22 branch thread of cleaning member 23 upper and lower support members of cleaning member

Claims (1)

[Claims] 1. A membrane element having a large number of hollow fiber membranes is erected in water containing activated sludge in a treatment tank, and an air diffuser at the bottom of the tank contacts the hollow fiber membranes by air bubbles to rise. In a submerged membrane separation device using a hollow fiber membrane that produces an upward flow of an air lift and collects permeated water that has permeated the membrane of the hollow fiber membrane, a cleaning member that can attach activated sludge to the water in the tank An immersion type membrane separation device using a hollow fiber membrane, wherein the hollow fiber membranes are arranged so that they can be shaken by the upward flow of the air lift and contact the hollow fiber membranes.