JP2000126558A - Immersion-type film separation device and method for cleaning fouled water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the filtering characteristics over time by providing a draining aperture for an accumulated deposit with a valve on the side face of an air diffusion pipe, in a film separation device which has the air diffusion pipe with an aperture for blowing air upward arranged in a stock solution tank and treats a stock solution by filtration while cleaning the film face of a film element with the help of air spewed from the air diffusion pipe. SOLUTION: When a fouled water is treated, it is supplied into a tank 61 for a solution to be treated with the help of a feeder pump 67 and air is spewed out of an air diffusion pipe 3 by driving a blower 33. Further the fouled water is made to ascend to a gap (a) between film elements by the air lift action of the jet air current, and is made to gyrate in the tank 61 following the ascending flow of the fouled water. At the same time, the pressure, on the filtering chamber side, of the film element is reduced intermittently to perform the filtering operation by the intermittent driving of a suction pump 64, and thereby a filtrate is cumulatively stored in a filtrate storage tank 65. In this case, a draining aperture for an accumulated deposit with a valve is installed in the air diffusion pipe 3, and when the infiltration and accumulation of sludge in the air diffusion pipe 3 occur, it is possible to discharge the accumulated sludge by an air pressure generated by the blower 33 through opening/closing the valve of the draining aperture 303.

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 apparatus for purifying human waste, sewage, domestic wastewater, and industrial wastewater (hereinafter referred to as sewage) or solid-liquid separation, and an immersion type membrane separation apparatus. The present invention relates to a method for purifying sewage.

[0002]

2. Description of the Related Art Recently, a gravity separation activated sludge treatment method, which is a traditional treatment method for wastewater (microbial decomposition treatment is performed in an aeration tank, the treated wastewater is led to a sedimentation separation chamber, and the activated sludge is separated by gravity separation. The membrane separation activated sludge treatment method has attracted attention as an alternative to the method of returning a part of the separated sludge to the aeration tank). In this treatment method, solid-liquid separation is performed by membrane filtration, the filtrate is taken out, and excess sludge is directly drawn out of the aeration tank. The MLSS (mixed liquid suspended solids) in the aeration tank is compared with the gravity separation method. Can be significantly higher,
The aeration tank can be considerably reduced as compared with the gravity separation method, and the sedimentation separation chamber is not required, so that the entire device can be downsized and the MLSS concentration in the aeration tank can be kept high. On the other hand, there are advantages such as reduction of dehydration during the treatment of excess sludge and saving of operation energy.

In the present applicant, as a sewage treatment apparatus by a membrane separation method, "a membrane element group having an air diffuser and having a vertical passage along a membrane surface is disposed immediately above the air diffuser, A diffusing aeration tank provided with a means (suction pump) for making the membrane filtration side of the membrane element group a negative pressure ”has already been proposed (Japanese Patent Publication No. 4-70958). According to this aeration type aeration tank, the undiluted solution in the tank is swirled by raising the undiluted solution toward the vertical passage between the membrane elements by the air-lifting action of the air ejected from the aeration device, thereby removing organic matter in the wastewater. In contact with air, aerobic microorganisms adsorb and metabolize and decompose to reduce organic matter and aerobic microorganisms. Sludge force acting on the membrane surface by the shear force acting on the membrane surface due to the upward flow in the vertical passage Water can be separated from the activated sludge by filtration with a transmembrane pressure difference by reducing the pressure on the filtrate side of the membrane element while suppressing the formation of a filtration layer.

[0004]

In the membrane separation activated sludge treatment method in which the membrane surface is washed by the air-lift action of the air ejected from the air diffuser, the purification efficiency is greatly affected by the membrane surface washing effect. According to the results of the study by the present inventors, since the concentration of MLSS in the tank is as high as 10,000 mg / liter, MLSS invades into the air diffuser through the air diffuser, and this invasion occurs with time. The MLSS is deposited and the air distribution to each diffuser port is uneven, causing the diffuser tube to have an irregular diffused state. Is reduced.

[0005] It is an object of the present invention to dispose an air diffuser having an upward air inlet in a stock solution tank, and dispose a membrane element having a filter chamber on the inner side above the air diffuser. An object of the present invention is to stabilize the filtration characteristics with time in a membrane separation apparatus that filters a stock solution while washing the membrane surface with air ejected from the membrane.

[0006]

According to the immersion type membrane separation device of the present invention, an air diffuser having an upward air inlet is disposed in a stock solution tank, and a filter chamber is provided above the air diffuser and inside. In a membrane separation apparatus for arranging a membrane element to be filtered and filtering the undiluted solution while washing the membrane surface with the air jetted from the air diffuser, a valve-equipped accumulation outlet is provided on the side surface of the air diffuser. This is a characteristic configuration.

[0007] A method for purifying sewage according to the present invention is a method of filtering sewage by the immersion type membrane separation device, wherein the accumulated waste outlet with a valve is opened and closed at predetermined time intervals to accumulate sewage in a diffuser pipe. It is a configuration characterized by discharging solid matter.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view of an example of a membrane element used in the present invention, FIG. 1B is a cross-sectional view of FIG. 1A along a roll, and FIG. 1 (a) is a cross-sectional view of a hammer, and a space for a filtrate passage is provided in a plastic frame 11.
A frame 12 (for example, a plastic net, a plastic nonwoven fabric, a tricot, etc.) is accommodated, and the periphery of the flat membranes 13 is sealed and fixed to the upper and lower surfaces of the frame 11 with an adhesive 14 or fusion. 11 is provided with a filtrate extraction pipe 15.

The flat membrane 13 is obtained by bonding an ultrafiltration membrane or a microfiltration membrane on a supporting material such as a nonwoven fabric or a woven fabric.
A material obtained by embedding a support material such as a woven fabric or a nonwoven fabric in an ultrafiltration membrane or a microfiltration membrane can be used. An epoxy resin, a urethane resin, a hot melt resin, or the like can be used for the adhesive 14, and a thermal fusion method, an ultrasonic fusion method, or the like can be used for fusion.
Reference numeral 10 denotes a filtrate collecting pipe section. The dimensions of the flat membrane element are usually 50 to 150 cm in length and 20 to 100 c in width.
m, and the thickness (the thickness of the frame) is 10 mm to 20 mm.

FIG. 2A shows the appearance of the membrane module used in the present invention, and FIG. 2B shows the internal structure of the membrane module. FIG. .. Indicate the above-mentioned flat membrane elements, respectively, and a plurality of flat membrane elements 1,...
And the thickness of the gap a is 2 to 5 m.
m.

Reference numeral 3 denotes an air diffuser having a valve-equipped accumulation outlet 303 disposed below the membrane element group, and is, for example, shown in FIG. 3 (A) and FIG. 3 (B) [FIG. Flat box 3 having a rectangular top surface as shown in FIG.
, A plurality of upper ventilation ports 302,.
It is possible to use one having attached discharge outlets 303 with valves at the four corners of the side, and is supported by the skirt portion 21 in the air supply pipe 31.

FIG. 4 shows an example of an immersion type membrane separation apparatus according to the present invention. In FIG. 4, reference numeral 61 denotes an open type liquid tank to be treated. A is the above-mentioned membrane module. Reference numeral 62 denotes a filtrate collecting header which communicates with a filtrate discharge pipe (reference numeral 100 in FIG. 1) of each membrane element 1 of the membrane module A; 63, a filtrate discharge pipe connected to an outlet of the header 62; A suction pump 65 provided in the pipe 63 is a filtrate storage tank. 66 is a sewage supply pipe, and 67 is a liquid feed pump provided in this pipe 66. Reference numeral 3 denotes an air diffuser having the above-described valved accumulation outlet disposed immediately below the membrane element group, and 33 denotes a blower connected to the air diffuser 3 by an air supply pipe.

In order to treat sewage by the above-mentioned membrane separation device, the sewage is supplied to the liquid tank 61 to be treated by a liquid feed pump 67, and air is blown out of the air diffuser 3 by driving the blower 33. The sewage is raised to the gap a between the membrane elements by the air lift action, and the sewage is swirled into the tank 61 by flowing the sewage into the skirt 21 from the lower end opening 210 of the skirt 21 with the rising flow. . At the same time, the filtration chamber side of the flat membrane element 1 is intermittently reduced in pressure by intermittent operation of the suction pump 64 to perform filtration, and the filtrate is stored in the filtrate storage tank 65.

[0014] By turning the sewage, organic substances in the sewage are adsorbed and metabolically decomposed by the aerobic microorganisms in contact with the air, whereby the organic substances are reduced and the aerobic microorganisms (activated sludge) are proliferated. . Further, a shear force acts on the membrane surface due to the upward flow of the sewage in the gap a between the membrane elements based on the air lift action by the air ejected from the air blowing port of the diffuser pipe 3. At the time of non-pressure reduction, suction of the membrane surface is released and sludge is less likely to adhere to the membrane surface. As a result, the formation of a cake layer on the membrane surface is suppressed.

In the immersion type membrane separation device according to the present invention, since the accumulating material discharge port 303 with a valve is attached to the diffuser tube 3, even if infiltration and accumulation of sludge into the diffuser tube 3 occurs, the accumulation with the valve is performed. By opening and closing the valve of the material discharge port, the accumulated sludge can be discharged at the supply pressure of the blower. Therefore, during the above-mentioned sewage treatment, by opening and closing the accumulated discharge port with a valve of the diffuser at a predetermined time interval, the inside of the diffuser pipe is always kept in the initial state, and the air is accumulated from the accumulated discharge port with the valve of the diffuser. -Can be ejected in an initial uniform state, and the membrane surface cleaning by the air-lifting action of the air diffuser can be performed uniformly as in the initial stage regardless of the elapse of time. It is possible to stabilize the filtration characteristics while suppressing deterioration over time.

The opening / closing of the accumulation outlet 303 with a valve is performed by a remote control, and it is preferable to use an electromagnetic valve as the valve. The outlet of the accumulation outlet 303 with a valve can be located outside the tank so that the valve can be operated outside the tank. In the present invention, a hollow fiber membrane bundle or a tubular membrane (a tubular membrane inserted into a porous hollow tube) may be used as the membrane element.

It is preferable to set the flow rate of the diffuser 3 so that the swirling velocity of the wastewater in the tank due to the diffuser is 0.01 to 2 m / s. And it becomes difficult to satisfactorily adsorb and metabolize and decompose by the aerobic microorganisms, and the adhesion of activated sludge particles to the membrane surface becomes remarkable.If it exceeds 2 m / s, a problem occurs in the strength of the membrane element).

To reduce the pressure on the permeation chamber side of the membrane element,
If a transmembrane pressure required for filtration can be obtained, a method other than a vacuum pump can be used. For example, in FIG. 4, a stock solution tank 61 is installed at a high place, and a filtrate solution tank 65 and a pipe 63 are provided.
And airtightly connected to each other to install the filtrate storage tank 65 in a low place,
A method of omitting the decompression pump and depressurizing the permeation chamber side of the membrane element with a high and low water head pressure difference, or a method of obtaining a transmembrane pressure difference for filtration by a natural head depending on the immersion depth of the membrane element can be used.

[0019]

EXAMPLE [Example] The membrane element shown in FIG. 1 was used, and the dimensions were 1060 mm in length × 610 mm in width (width).
× Thickness (thickness of the frame) is 14 mm, a polyolefin-based microfiltration membrane having a nominal pore size of 0.4 μm and an area of 1 m ² is used for the membrane, and a plastic net is used for the sheet for the filtrate flow path. A urethane resin was used for the bonding between the film and the film and the bonding seal between the frames. The membrane module was configured as shown in FIG. 2, and 11 membrane elements were stacked on the rack at an interval of 3 mm. The air diffuser is provided with six ventilation openings of 5 mm in diameter on the upper surface of an outer rectangular box almost equal to the outer shell of the membrane element group, and has a diameter of 10 m at the four corners of the side surface.
The one equipped with a m-valve accumulation outlet was used. Activated sludge solution with an MLSS concentration of 10,000 mg / liter was used for the treatment solution, and the aeration was intermittent aeration.
The aeration was stopped for 30 minutes, and the amount of aeration was 176 liters / minute. The suction pump was operated intermittently with one cycle consisting of 8 minutes driving and 2 minutes stopping. Immediately before shifting from the stop of the aeration to the aeration, the accumulated discharge outlet with a valve was opened to discharge the accumulated sludge in the diffuser into the diffuser. When the constant flow rate operation was performed so as to maintain the filtration flux at a constant value (aeration-time flux 0.5 m ³ / m ² · day), as shown in FIG. Filtration could be performed with a constant and stable filtration flux.

Comparative Example A constant flow rate was maintained in such a manner as to maintain the filtration flux at a constant value in the same manner as in the example except that the accumulated discharge port with a valve of the air diffuser was kept closed for the entire period without being operated. As a result of the treatment, a rapid increase in the degree of decompression was observed after 50 days, as shown in FIG.

From the comparison between the comparative example and the example, according to the present invention, it is possible to clean the membrane surface as well as at the initial stage even after a lapse of time, and to stably maintain the filtration flux. You can check.

[0022]

According to the present invention, an air diffusion tube having an upward air blowing port is provided in a stock solution tank, and a membrane element having a filtration chamber inside is provided above the air diffusion tube. In a membrane separation device for filtering a stock solution while washing a membrane surface with air blown out from a trachea, stabilization of a filtration flux can be achieved only by providing an accumulation outlet with a valve in the diffuser tube, and high wastewater can be obtained. It is extremely useful in purifying with efficiency.

[Brief description of the drawings]

1 (a) is a plan view showing an example of a membrane element used in the present invention, FIG. 1 (b) is a cross-sectional view of FIG. 1 (a), and FIG. 2) is a sectional view taken along the line c-c of FIG.

FIG. 2 is a drawing showing an example of a membrane module used in the present invention.

FIG. 3 is a drawing showing an example of an air diffuser used in the present invention.

FIG. 4 is a drawing showing an example of an immersion type membrane separation device according to the present invention.

FIG. 5 is a table showing the filtration characteristics of a submerged membrane separation device according to the present invention and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Membrane element 3 Air diffuser 302 Upward blower port 303 Accumulated matter discharge port with valve

Claims (3)

[Claims] An air diffusion tube having an upward air blowing port is disposed in a stock solution tank, and a membrane element having an inside as a filtration chamber is disposed above the air diffusion tube, and air blown from the air diffusion tube is provided. A immersion type membrane separation device for filtering a stock solution while washing a membrane surface by using a gas discharge port with a valve in the air diffuser. 2. The immersion type membrane separation apparatus according to claim 1, wherein the accumulation outlet with a valve is provided on a side surface of the air diffuser. 3. A method for filtering waste water by the immersion type membrane separation device according to claim 1, wherein a stored discharge outlet with a valve is opened and closed every predetermined time to discharge accumulated waste water solids in the air diffuser. A method of purifying sewage, comprising: