JPS61129094A - Apparatus for treating membrane - Google Patents

Abstract

PURPOSE:To efficiently perform activated sludge treatment, by providing a membrane apparatus in an aeration tank and contacting the flow of a gas-liquid mixture with the surface of a membrane. CONSTITUTION:An air diffusion pipe is provided in the vicinity of the bottom surface of an aeration tank 1 and air is fed to the air diffusion pipe 2 by an air feed pipe 21. A membrane apparatus 3 is arranged directly above the air diffusion pipe 2. The membrane apparatus 3 has vertically directed passages 31, 31... for passing the flow of a gas-liquid mixture from the air diffusion pipe 2 and the flow of the gas-liquid mixture is contacted with the surfaces of the membranes in these passages and the concn. polarization of activated sludge on the membrane surfaces and the contamination of the membrane surfaces by activated sludge can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a membrane treatment device that can efficiently perform sewage purification treatment using aerobic microorganisms, such as activated sludge treatment of wastewater and sewage.

Prior Art and Problems In the normal activated sludge method, which treats sewage containing organic substances by the biological action of aerobic microorganisms, sewage treated in an aeration tank is advected to a settling tank, and supernatant liquid and sludge are This separated sludge must be returned to the aeration tank for quenching. However, it is necessary to provide a long residence time for the treated water in each of the aeration tank and the settling tank, which inevitably leads to an increase in the size of the apparatus. Furthermore, in order to reuse the treated water, it is necessary to add activated carbon filtration or a membrane device, which inevitably increases equipment costs and operating costs, making it extremely difficult to reuse it.

As a method to eliminate this disadvantage, a reverse osmosis device or an ultrapolar filtration device is installed in place of the above-mentioned settling tank to reduce the installation area of the ancillary equipment required for sludge separation, and the aeration tank is used under high sludge concentration. It has been proposed to significantly reduce the volume of the aeration tank if possible.

However, in this method, since a liquid containing highly concentrated sludge is treated with a membrane device, a decrease in the amount of permeated water due to concentration polarization and membrane surface fouling is unavoidable. To overcome this disadvantage, a large-capacity pump, piping, valves, and control panel are required for the membrane device, which requires a high flow rate at the membrane surface and a high liquid pressure. In order to increase the membrane surface flow velocity, the power cost of the bonder increases dramatically, the processing cost increases, and it is not necessarily possible to reduce the equipment cost. Therefore, its use is limited to fields where economic efficiency is not important, such as small-capacity medium water conveyance equipment.

Purpose of the Invention The purpose of the present invention is to prevent concentration polarization and membrane fouling by using a diffused air flow in an aeration tank, and to simplify the equipment attached to the membrane device, even though a membrane device is used. Our objective is to provide a membrane treatment device that can reduce equipment costs and operating costs.

Structure of the Invention The membrane treatment device according to the present invention is provided with a membrane device in an aeration tank that purifies wastewater with aerobic bacteria while aerating with oxygen-containing gas from an aeration device, and the above-mentioned aeration device is attached to the membrane surface of the aeration tank. By bringing the mixed flow of gas and liquid into contact with each other, the concentration polarization effect between the membranes and dirt can be removed. This is a characteristic configuration.

Description of examples The present invention will be explained below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a diffuser type aeration tank, in which a diffuser pipe 2 (porous pipe) is provided near the bottom. This air diffuser 2
Air or oxygen-containing gas is pumped through the air pipe 21 to
Air bubbles are released from the air diffuser pipe, and the treated liquid is circulated by the air diffuser flow (air/liquid mixture), and the activated sludge in the liquid decomposes the liquid in the presence of oxygen by the action of aerobic bacteria. .

Reference numeral 3 denotes a membrane device, which is disposed directly above the aeration pipe 2. This membrane device has vertical passages 31, 31... through which the gas/liquid mixed flow from the aeration pipe 2 passes, and in these passages, the gas/liquid mixed flow comes into contact between the membranes, and the membrane surface Concentration polarization of activated sludge above the membrane and fouling caused by activated sludge between the membranes can be prevented.

Reference numeral 4 denotes a vacuum pump for reducing the pressure on the permeated water side of the membrane device 3 and transferring it, so that the permeated water can be taken out from the membrane device 3. Instead of reducing the pressure on the permeated water side of the membrane device 3, the transmembrane pressure difference can be obtained by making the aeration tank a closed type and pressurizing it above atmospheric pressure. These depressurization and pressurization can also be used together.

The membrane device 3 may be a so-called parallel flow path membrane module in which a plurality of tubular membranes each having an inner diameter of about 10 mrx or more are lined up, or a flat membrane type of arbitrary width (for example, a spiral type,
A membrane module can be used in which membrane elements of pleated type or flat plate type are assembled to ensure the above-mentioned vertical passage. The vertical length of such a membrane module varies depending on the depth of the aeration tank, but is usually the length of the aeration tank minus 0.3 m, and is generally 0.5 m or more. These can also be used in several divided formats.

In a flat membrane type membrane element such as the spiral type described above, it is desirable that no flow path spacer is provided in the above-mentioned vertical passage. In any membrane element, it is desirable that the thickness of the vertical passage be 10 mm or more. However, if the thickness is too large, the area of the membrane that can be installed will be reduced, which is not preferable.

FIG. 2A shows an example of a membrane device used in the present invention, in which several tubular membranes 30, each having a membrane 33 provided on a porous support tube 32 made of non-woven fabric, are housed in an outer cylinder 34 (see FIG. 2B). ), both ends are sealed with end plates 35, 35 or casting resin, the above-mentioned gas/liquid mixed flow flows within the tubular membrane, and permeated water is taken out from the outer cylinder through the permeable wood outlet. .

As the membrane, a precision filtration membrane, a semipermeable membrane, especially an ultrafiltration membrane, or a so-called loose reverse osmosis membrane with a low salt removal rate is used.

FIG. 3A shows another example of the membrane device used in the present invention, in which a pair of permeate water flux pipes 35, 35 are connected to a flat plate type membrane (a permeate channel between the flat membranes 33 and 33) as shown in FIG. 3B. (with a spacer 36 interposed) are communicated, and the units are arranged side by side at regular intervals by a holder. In the case of this membrane element, diffuser pipes can be arranged between the units.

In the present invention, as shown in FIG. 4, the system of the membrane device 3 and the system of the air diffuser 2 are set up, and a cleaning tank 5 (for example, a chemical tank for sodium hypochlorite or surfactant) is used. These can also be cleaned periodically at the same time. In FIG. 4, 6 is pulp and 4 is a vacuum pump.

In the membrane treatment device according to the present invention, since concentration polarization on the membrane surface and membrane fouling can be prevented, the sludge concentration in the aeration tank can be made high (6000 to 10.00ppm).
Since the biological reaction residence time of the organic substances to be treated can be shortened (1 to 2 hours), the capacity of the aeration tank can be greatly reduced (1/2 to 1/6 of the conventional amount). ). Since the organic substances (BOD) in the treated water are highly removed by activated sludge, virtually no SS, E. coli, or viruses are detected in the permeated water. Therefore, the permeated water can be used as industrial water without so-called tertiary treatment. , can be reused as water for miscellaneous purposes, etc.

In the conventional example where the membrane device is installed outside the aeration tank system, high energy is required to operate the membrane device in order to obtain a membrane surface flow velocity that does not cause in situ polarization on the membrane surface (the membrane surface flow velocity is In the membrane treatment apparatus according to the present invention, the amount of aerated air is increased by 2 to 6 times per aeration volume, which particularly increases the amount of air. With this amount of air, the flow velocity at the membrane surface can be set to 1 to 1.5 m/sec, without requiring high energy as described above.

leprosy case In an aeration tank with an effective volume of 4 m3, an inner diameter of 12 mm and a length of 1
．． 648 25m tubular ultrap membranes (total membrane area 29m1)
) is installed, and the factory wastewater containing a large amount of organic substances such as Solserp and acetone is processed at 2 times an hour while maintaining the activated sludge concentration in the aeration tank at approximately aooooppm.
．． When treated with 5rrLI, the quality of the treated water relative to the raw water was as follows.

Raw water Treated water PH6,87,4 S S (ppm) 30 <I B OD (ppm) 315 4.3
COD (PPm) 117 15.0 E. coli count (MpN/ml) 5XIO5 not detected In addition, the permeation characteristics of the membrane were stable, and the amount of permeated water one month after operation was 12o1/rn'・h-atm .

Effects of the Invention As mentioned above, the membrane treatment device according to the present invention uses permeation treatment instead of sludge sedimentation treatment, and the membrane treatment device is installed in the aeration tank and utilizes the aeration flow of the aeration tank. This prevents concentration polarization on the membrane surface and membrane fouling. Therefore, compared to conventional examples in which a membrane device is installed outside the aeration tank, it is possible to downsize the entire device, reduce the installation area, reduce operating power costs, and simplify the equipment.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a membrane treatment device according to the present invention, Fig. 2 A is an explanatory diagram showing a single-layer device used in the present invention, and Fig. 2 B is an explanatory diagram of the b-b cross section in Fig. 2 A. , Figure 3A
is an explanatory diagram showing another example of the membrane device used in the present invention,
FIG. 3B is an explanatory cross-sectional view taken along line bb in FIG. 3A, and FIG. 4 is an explanatory view showing another embodiment of the present invention. In the figure, l is an aeration tank, 2 is an aeration device, 3 is a membrane device,
4 is a vacuum pump. :5/ Ji,/71m. 3...?

Claims (1)

[Claims] A membrane device is installed in an aeration tank that purifies wastewater with aerobic bacteria while aerating with gas containing oxygen from an aeration device, and the air/liquid mixed flow from the aeration device is brought into contact with the membrane surface. 1. A membrane treatment device capable of removing concentration polarization and dirt on the membrane surface, and provided with means for applying negative pressure to the membrane permeation side or pressurizing the liquid in the tank.