JP2001062480A - Treatment of sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating sewage by which the concn. of activated sludge is kept constant over the whole region in an aeration tank. SOLUTION: Plural immersion-type membrane separators 21 are set in a reaction tank 1, aeration air is diffused from a diffuser pipe 23 arranged in each of the separators 21, and the sewage flowing into the reaction tank 1 is biologically treated with activated sludge in this membrane-separation activated sludge process. In this case, the influent sewage is pretreated to remove the foreign matter by a screen and then supplied into the tank through the diffuser pipe 23 in the separators 21 along with the aeration air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating sewage, and more particularly to a membrane separation activated sludge treatment technique for treating organic sewage having a high concentration of organic substances and nitrogen using a membrane separation apparatus.

[0002]

2. Description of the Related Art Conventionally, there is an activated sludge treatment as a method for treating organic matter and organic wastewater having a high nitrogen concentration. A membrane separation activated sludge treatment for maintaining a high concentration of activated sludge in a tank by using a membrane separation device together is known. is there. As shown in FIGS. 5 and 6, the membrane separation device 21 includes a plurality of flat membrane cartridges 22 and an air diffuser 23 for ejecting a membrane cleaning gas from below the cartridges 22 in a case 24. is there. The case 24 is formed so as to be divided into a membrane case 25 and an air diffuser case 26 in order to facilitate transportation and maintenance, and formed so that the entire amount of the membrane surface cleaning gas ejected from the diffuser tube 23 enters the membrane case 25. are doing.

[0003] The membrane cartridge 22 has a filter membrane 22B disposed on both surfaces of a filter plate 22A made of ABS resin.
And a filtration membrane 22B, and inside the filter plate 22A, forming a permeate flow path, and a permeate outlet 2 communicating with the permeate flow path.
2C is formed on the upper edge of the filter plate 22A. Each membrane cartridge 22 communicates with a water collecting pipe 28 via a tube 27 connected to a permeated liquid outlet 22C, and the water collecting pipe 28 communicates with a permeated liquid outlet pipe 29 for extracting the membrane permeated liquid. At the upper part of the membrane case 25, a holding plate 30 for preventing the membrane cartridge 22 from floating is provided.

When the membrane separation device 21 is used in an activated sludge treatment facility, the membrane separation device 21 is immersed in an activated sludge mixture in an aeration tank, and aerated air is blown out from a diffuser tube 23. Organic matter and nitrogen in the raw water are treated by activated sludge, and the activated sludge mixture is gravity-filtered by the membrane cartridge 22 using the head in the tank as a driving pressure (a suction pump is inserted in the permeated liquid outlet pipe 29). Thus, the permeated liquid that has passed through the membrane surface of the membrane cartridge 22 is led out of the tank through the permeated liquid outlet pipe 29 as treated water. At this time, the membrane surface of the membrane cartridge 22 is washed by the bubbles of the aerated air ejected from the air diffuser 23 and the upward flow generated by the bubbles, thereby suppressing the decrease in the separation function and causing the membrane separation device 21 to malfunction. Has been prevented.

The general structure of a water treatment facility using the above-mentioned membrane is shown in FIGS. 3 and 4, inflow sewage 41 is stored in a flow control tank 43 after removing contaminants in a pretreatment facility 42 and supplied from a flow control tank 43 to an aeration tank (biological treatment tank) 44 at a constant flow rate. I do. In the aeration tank 44, activated sludge decomposes and removes organic substances in the sewage, and the membrane separation device 2 immersed and disposed in the aeration tank 44
The solid-liquid is separated in 1 and the filtrate is discharged through a sterilization tank 45.

[0006]

In the membrane separation activated sludge treatment using the immersion type membrane separation device as described above, as shown in FIG. 4, several membrane separation devices 21 are installed in an aeration tank 44. Although used, when the processing scale becomes large, several to more than ten membrane separation devices 21 are installed in one aeration tank 44. In such an aeration tank 44, a concentration distribution in which the activated sludge concentration on the inflow side of the wastewater is reduced by dilution with the inflowing wastewater and the concentration of the activated sludge on the opposite side becomes extremely high occurs.

[0007] It is an object of the present invention to provide a method for treating sewage which can maintain a uniform concentration of activated sludge in all regions in an aeration tank in a membrane separation activated sludge method using a submerged membrane separation apparatus. And

[0008]

According to a first aspect of the present invention, there is provided a method for treating sewage, comprising the steps of: installing a plurality of immersion type membrane separation devices in a reaction tank; In the membrane separation activated sludge method in which air for aeration is diffused from the air diffuser arranged in the apparatus and the wastewater flowing into the reaction tank is biologically treated with activated sludge, the inflowed wastewater is pretreated to remove impurities by a screen. Then, the sewage is supplied into the tank together with aeration air through the air diffuser of the immersion type membrane separation device.

According to a second aspect of the present invention, there is provided a method for treating sewage, wherein the supply of air for aeration is stopped when sewage is supplied to an air diffuser. According to a third aspect of the present invention, the method for treating wastewater is to sequentially inject water into each diffuser tube of each immersion type membrane separation device while changing the diffuser tube for supplying the wastewater every predetermined time.

[0010] With the above structure, the wastewater is dispersed and supplied into the tank through each diffuser pipe of each immersion type membrane separation device, so that the organic matter which is a load of biological treatment is dispersed in the tank, and the organic matter in the reaction tank is dispersed. The activated sludge concentration can be maintained uniform in all regions. The inflowing sewage usually contains a large amount of SS and contaminants, but by passing the sewage through a screen of about 1 mm, the air holes (about 10 mm) of the air diffuser do not become clogged. By pouring the sewage into the diffuser, oxygen is dissolved in the sewage at a high speed in the diffuser and the oxygen concentration in the sewage is almost saturated when the oxygen is released into the tank from the air hole of the diffuser. State. Due to the increase in the oxygen dissolving efficiency, the required amount of air to be supplied into the tank through the diffuser is reduced by 2
0 to 30% can be reduced, and the output of the blower can be suppressed to reduce energy consumption.

If the diffuser tube is used for a long period of time, when the activated sludge concentration is high (about 1 to 2%), the sludge that has entered the air holes of the diffuser tube is air-dried and becomes granular or clay-like. It becomes a solid and may block air holes. However, by injecting sewage into the diffuser tube as in the present invention, it is possible to prevent the air holes of the diffuser tube from being blocked. Injection of sewage into the air diffuser may be performed by stopping the blower that supplies air for aeration to the air diffuser, or may be performed while diffusing air. Further, even if the sewage is simultaneously injected into the air diffusers of all the immersion type membrane separation devices, the sewage may be sequentially removed at regular intervals, for example, 1 hour.
The air diffuser for injecting water every minute may be changed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 and FIG.
Has a long shape in which the plane shape is rectangular and the ratio of the short side to the long side is 1: 3 or more, and biological treatment for decomposing and removing organic substances in sewage by activated sludge in a tank is performed. Do.

Inside the reaction tank 1, a plurality (several to ten and several) of immersion type membrane separation devices 21 are arranged in a line at predetermined intervals. Since the immersion type membrane separation device 21 is the same as that described in FIGS. 5 and 6, the same reference numerals are given and the detailed description is omitted. Each diffuser tube 23 of each immersion type membrane separation device 21 has a plurality of air holes having a diameter of about 10 mm,
An air supply system 2 communicates with each of them. The air supply system 2 includes a blower 3 that supplies aeration air, an air supply main pipe 4 that communicates with the blower 3, an air diffuser pipe 5 that communicates the air supply main pipe 4 with each diffuser pipe 23, An air valve 6 interposed in the air diffuser pipe 5.

The sewage supply system 7 includes a sewage pump 8 for supplying sewage, a sewage supply main pipe 9 communicating with the sewage pump 8, and a sewage pipe 10 connecting the sewage supply main pipe 9 and each diffused air pipe 5.
And a sewage valve 11 interposed in each sewage pipe 10. As shown in FIG. 2, on the upstream side of the reaction tank 1, a pretreatment facility 42 for removing impurities of the flowing wastewater 41 with a screen having a mesh width of about 1 mm is arranged.
Downstream of 2, a flow control tank 43 for storing sewage from which impurities have been removed is provided. A sterilization tank 45 is provided downstream of the reaction tank 1.
Is provided.

The operation of the above configuration will be described below. Since the inflowing sewage 41 usually contains a large amount of SS and impurities, removing the impurities in the pretreatment facility 42 can prevent the air holes (about 10 mm) of the downstream air diffuser 23 from being clogged. To prevent. The sewage 41 from which the contaminants have been removed is stored in a flow control tank 43, and is supplied through the sewage supply system 7 to each diffuser 23 of each immersion type membrane separation device 21 in a constant amount. On the other hand, the air supply system 2 supplies the air for aeration supplied by the blower 3 to each of the diffuser pipes 23 through the main air supply pipe 4, the air valve 6, and the diffuser air pipe 5.

The sewage supply system 7 supplies sewage 41 supplied by a sewage pump 8 to a sewage supply main pipe 9, a sewage valve 11,
The air is injected into each diffused air pipe 5 through the sewage pipe 10. Oxygen dissolves in the sewage 41 injected into the diffuser air pipe 5 at a high speed while flowing through the diffuser air pipe 5 and the diffuser pipe 23.
The suction pipe of the sewage pump 8 may be provided with a strainer or the like.

Therefore, the air diffuser 23 and the air for aeration are used.
The oxygen concentration of the sewage 41 discharged into the liquid in the tank from the air hole is substantially saturated. Due to the increase in the oxygen dissolving efficiency, the required amount of air to be supplied into the tank through the air supply system 2 can be reduced by 20 to 30% as compared with the conventional case, and the output of the blower 3 can be suppressed to reduce energy consumption. In this way, by dispersing and supplying the sewage 41 into the tank through each diffuser 23 of each immersion type membrane separation device 21, the organic matter which is a load of biological treatment is dispersed in the tank, and the entirety of the reaction tank 1 is dispersed. Activated sludge concentration can be maintained uniform in the region.

Further, by injecting the sewage 41 into the air diffuser 23, the sludge that has entered the air holes of the air diffuser 23 does not dry out and block the air holes. (About 2%), the air diffuser 23 can be used for a long time. Sewage 41 spouting from the diffuser 23
Is filtered while flowing in a cross flow with respect to the membrane surface of the membrane cartridge 22 on the bubbles of the aeration air and the upward flow generated thereby. This cross flow suppresses the formation of a cake layer on the membrane surface, and the flow velocity is adjusted by adjusting the ejection pressure and the ejection flow rate of the sewage 41, or by adjusting the ejection pressure and the ejection flow rate of the aeration air. , Or by combining them.

The supply of the sewage 41 to the air diffuser 23 may be performed in a state where the air valves 6 are closed or the blower 3 is stopped to stop supplying the air for aeration. Further, by appropriately opening and closing the respective sewage valves 11, the air diffuser 23 for supplying the sewage 41 is changed at predetermined time intervals (for example, one minute), and the air diffuser 23 of each immersion type membrane separation device 21 is changed. Water may be injected sequentially. Further, when the amount of the sewage 41 flowing into the reaction tank 1 is small,
After the completion of the water injection, treated water or clean water can be injected into the air diffuser 23. In addition, the sewage 41 may contain oil, so that the air diffuser 23 is usually washed with treated water or fresh water about once a day.

[0020]

As described above, according to the present invention, organic matter is dispersed in the tank by dispersing and supplying sewage into the tank through each diffuser pipe of each immersion type membrane separation apparatus. Activated sludge concentration can be maintained uniform in all regions in the inside. By dissolving oxygen at high speed in the sewage in the air diffuser, the amount of air required to be supplied through the air diffuser can be reduced and the energy consumption can be suppressed. When activated sludge concentration is high (1
(About 2%), the sludge is not air-dried in the air holes of the air diffuser, and the air holes of the air diffuser can be prevented from being blocked.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a reaction tank according to an embodiment of the present invention.

FIG. 2 is a flow sheet showing a method for treating wastewater in the embodiment.

FIG. 3 is a flow sheet showing a conventional method for treating wastewater.

FIG. 4 is a schematic diagram showing a configuration of a conventional reaction vessel.

FIG. 5 is a cross-sectional view showing a membrane separation device.

FIG. 6 is a longitudinal sectional view showing a membrane separation device.

[Explanation of symbols]

 Reference Signs List 1 reaction tank 2 air supply system 3 blower 4 air supply main pipe 5 diffused air pipe 6 air valve 7 sewage supply system 8 sewage pump 9 sewage supply main pipe 10 sewage pipe 11 sewage valve 21 immersion type membrane separation device 23 diffuser pipe 41 sewage 42 pretreatment equipment 43 flow control tank 45 sterilization tank

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Taichi Uesaka 2-47, Shikitsu Higashi 1-chome, Namiwa-ku, Osaka-shi, Osaka Prefecture No. 2-47, Kubota Co., Ltd. (72) Susumu Kawakami, Inventor 1-47, Shishitsuhigashi, Naniwa-ku, Osaka-shi, Osaka F-term (reference) 4D006 GA02 HA41 HA93 KA12 KA44 KA47 KA64 KA66 KB22 MA03 PA01 PB08 PC62 4D028 BA00 BC17 BC22 BC24 BD17 CA09 CB08

Claims (3)

[Claims] 1. A plurality of immersion type membrane separation devices are installed in a reaction tank, air for aeration is diffused from a diffuser tube arranged in the immersion type membrane separation device, and waste water flowing into the reaction tank is activated sludge. In the membrane separation activated sludge method for biological treatment, inflow wastewater is pretreated to remove impurities by a screen, and then the wastewater is supplied into the tank together with aeration air through the diffuser pipe of the immersion type membrane separation device. Wastewater treatment method. 2. The method for treating sewage according to claim 1, wherein the supply of aeration air is stopped when the sewage is supplied to the air diffuser. 3. The sewage water according to claim 1, wherein water is sequentially injected into each of the air diffusion tubes of each immersion type membrane separation device while changing the air diffusion tube for supplying the waste water at predetermined time intervals. Processing method.