JP2001062481A - Treatment of concentrated sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating concd. sewage by which a necessary amt. of oxygen is sufficiently supplied to the activated sludge without increasing the amt. of aeration air. SOLUTION: An org. sewage 5 having high contents of org. matter and nitrogen is biologically treated in a reaction tank 1 in which an immersion-type membrane separator 21 is set in this membrane-separation activated sludge process. In this case, the concd. sewage 5 is pretreated by a pretreating equipment 6 to remove the foreign matter by a screen, and the concd. sewage 5 is injected into an air supply system 2 for supplying aeration air to a diffuser pipe 23 in the separator 21. Oxygen is dissolved in the concd. sewage 5 at high speed in the air supply system 2, and the concd. sewage 5 in which oxygen is sufficiently dissolved is supplied into the tank from the diffuser pipe 23 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 high-concentration sewage, and more particularly to a membrane separation activated sludge treatment technology for treating organic sewage having a high concentration of organic substances and nitrogen using a membrane separation apparatus. is there.

[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. 3 and 4, the membrane separation device 21 includes a plurality of flat membrane cartridges 22 and an air diffuser 23 that blows out 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 bubbles of the aerated air ejected from the air diffuser 23 and the upward flow generated thereby serve as a scavenging stream to wash the membrane surface of the membrane cartridge 22 and suppress a decrease in the filtration capacity, so that the membrane separation device 21 Prevents dysfunction.

A general structure of a water treatment facility using the above-mentioned membrane is shown in FIG. In FIG. 2, inflow sewage 41 is stored in a flow control tank 43 after removing impurities in a pretreatment facility 42, and is supplied from the flow control tank 43 to an aeration tank (biological treatment tank) 44 at a constant flow rate. In the aeration tank 44, organic substances in the wastewater are decomposed and removed by activated sludge, and solids and liquids are separated by the membrane separation device 21 immersed and arranged in the aeration tank 44. The filtrate is discharged through a sterilization tank 45.

[0006]

In the immersion type membrane separation activated sludge method using the immersion type membrane separation apparatus as described above, the air ejected from the diffuser pipe is mixed with aerated air for supplying oxygen to the activated sludge. , And also serves as a drive source for sweeping to perform film surface cleaning. By the way, when treating high-concentration sewage with a high concentration of organic matter and nitrogen, the amount of oxygen required by activated sludge increases, and it is necessary to increase the amount of aerated air spouted from a diffuser for this oxygen supply. . On the other hand, in order to clean the filtration membrane 22B of the membrane cartridge 22 by scavenging, the aeration intensity (determined by the ejection speed, the ejection pressure, and the ejection amount) has an appropriate value. 22B may be damaged.

[0007] For this purpose, a preaeration tank is provided upstream of the aeration tank, and sufficient oxygen is eliminated in the preaeration tank without a membrane separation device to eliminate the lack of oxygen. However, installation space is required to install the pre-aeration tank, and it has been difficult to install the pre-aeration tank in an existing facility having a limited area. The present invention is to solve the above-mentioned problem, and in the immersion type membrane separation activated sludge method using the immersion type membrane separation apparatus, a sufficient amount of oxygen is sufficiently supplied to the activated sludge without increasing the amount of aerated air. It is an object of the present invention to provide a method for treating high-concentration sewage that can be performed.

[0008]

In order to solve the above problems, a method for treating high-concentration sewage according to the present invention is directed to a method for treating organic sewage having a high concentration of organic substances and nitrogen in a reaction tank provided with a submerged membrane separation apparatus. In the membrane separation activated sludge method in which biological treatment is performed, wastewater is pretreated, impurities are removed by a screen, and this wastewater is injected into an air supply system that supplies aeration air to a diffuser pipe of a submerged membrane separation device, and is supplied with air. Oxygen is dissolved in sewage at a high speed in a supply system, and sewage in which oxygen is sufficiently dissolved is supplied from an air diffuser to the tank together with aerated air.

By injecting sewage into the air supply system according to the above configuration, oxygen is dissolved in the sewage at high speed in the system, and when oxygen is released into the liquid in the tank from the air holes of the air diffuser,
The oxygen concentration in the sewage becomes almost saturated. Due to the increase in the oxygen dissolving efficiency, the required amount of air to be supplied into the tank through the diffuser can be reduced by 20 to 30%, and the output of the blower can be suppressed to reduce energy consumption. Sewage usually contains a large amount of SS and contaminants.
By passing the air through a screen of a certain degree, the air holes (about 10 mm) of the air diffuser are not clogged.

[0010] When the diffuser 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 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.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the immersion type membrane separation device 21 disposed inside the reaction tank 1 is the same as that described in FIGS. 3 and 4, and thus the same reference numerals are given and the detailed description is omitted. Aeration tube 23 of immersion type membrane separation device 21
Has a plurality of air holes having a diameter of about 10 mm, and the air supply system 2 communicates with each of the air holes. The air supply system 2 includes a blower 3 for supplying aerated air, and a diffuser air tube 4 communicating with a diffuser tube 23.

On the upstream side of the reaction tank 1, there is disposed a pretreatment facility 6 for removing impurities of the high-concentration wastewater 5 flowing through a screen having a mesh width of about 1 mm. Flow control tank 7 for storing high-concentration sewage 5 from which waste has been removed
Is provided. The flow control tank 7 communicates with the air supply system 2 via a sewage supply system 8. The sewage supply system 8 includes a sewage pump 9 that supplies sewage and a sewage pipe 10 that communicates with the diffused air pipe 4. A sterilization tank 11 is provided downstream of the reaction tank 1.

The operation of the above configuration will be described below. The inflowing high-concentration sewage 5 usually contains a large amount of SS and contaminants. Therefore, by removing the contaminants in the pretreatment facility 6, the air holes (about 10 mm) of the downstream air diffuser 23 are clogged. To prevent that. The high-concentration sewage 5 from which the contaminants have been removed is stored in the flow rate adjusting tank 7, and supplied to the respective diffuser tubes 23 of the immersion type membrane separator 21 through the sewage supply system 8. On the other hand, the air supply system 2 supplies the aerated air supplied by the blower 3 to the air diffuser 23 through the air diffuser 4.

The sewage supply system 8 injects high-concentration sewage 5 supplied by a sewage pump 9 into a diffused air pipe 4 through a sewage pipe 10. Oxygen is dissolved at high speed in the sewage 5 injected into the diffuser air pipe 4 while flowing through the diffuser air pipe 4 and the diffuser pipe 23. A strainer or the like for removing contaminants may be provided in the suction pipe portion of the sewage pump 9.

Therefore, the oxygen concentration of the high-concentration sewage 5 discharged into the tank liquid through the air holes of the air diffuser 23 together with the aerated air 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. Also, by injecting the high concentration sewage 5 into the air diffuser 23,
Sludge that has entered the air holes of the air diffuser tube 23 does not dry out and closes the air holes, so that the air diffuser tube 23 can be used for a long time even when the activated sludge concentration is high.

The high-concentration sewage 5 spouting from the diffuser 23
The air is filtered while cross-flowing on the membrane surface of the membrane cartridge 22 on the bubbles of the aerated 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 high-concentration sewage 5 or adjusting the ejection pressure and the ejection flow rate of the aerated air. By
Alternatively, it can be controlled by combining them.

When a plurality of immersion type membrane separation devices 21 are arranged in the reaction tank 1, a diffuser pipe 23 for supplying high-concentration sewage 5 is used.
May be sequentially injected into each diffuser tube 23 of each immersion type membrane separation device 21 while changing the value at predetermined time intervals (for example, for one minute). Furthermore, when the amount of the high-concentration sewage 5 flowing into the reaction tank 1 is small, treated water or fresh water can be injected into the air diffuser 23 after the completion of the injection of the high-concentration sewage 5. Also,
Since the high-concentration sewage 5 may contain oil, the air diffuser 23 is usually washed with treated water or fresh water about once a day.

[0018]

As described above, according to the present invention, sewage is supplied into the tank through the air diffuser of the immersion type membrane separation apparatus, and oxygen is dissolved in the sewage at a high speed in the air supply system. ,
The required amount of oxygen can be sufficiently supplied to the activated sludge without increasing the amount of aerated air, and the required amount of air supplied through the air diffuser can be reduced to reduce energy consumption.
Even in the case of high-concentration sewage, it is possible to prevent the sludge from being air-dried in the air holes of the air diffuser and prevent the air holes of the air diffuser from being blocked.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a wastewater treatment method according to the embodiment.

FIG. 2 is a flow sheet showing a conventional method for treating wastewater.

FIG. 3 is a cross-sectional view showing a membrane separation device.

FIG. 4 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 diffuser air pipe 5 high concentration sewage 6 pretreatment equipment 7 flow rate control tank 8 sewage supply system 9 sewage pump 10 sewage pipe 11 sterilization tank 21 immersion type membrane separation device 23 diffuser pipe

Continuation of the front page (72) Inventor Taichi Uesaka 1-2-47, Shikitsu-Higashi 1-chome, Namiwa-ku, Osaka-shi, Osaka (72) Inventor Tatsuya Ueshima 1-2-2, Shikitsu-higashi, Namiwa-ku, Osaka-shi, Osaka No. 47 Kubota Co., Ltd. (72) Susumu Kawakami Inventor F-term (reference) 4D006 GA06 GA07 HA34 HA91 HA93 JA31Z JA34Z KA02 KA31 KA44 KB14 KB22 KC12 KC14 MA02 MB02 PA02 PA05 PB08 PB70 PC64 4D028 AA08 AB00 BA00 BD06 BD17

Claims (1)

[Claims] An organic matter, an organic wastewater having a high nitrogen concentration,
In a membrane separation activated sludge method in which biological treatment is performed in a reaction tank equipped with an immersion type membrane separation device, sewage is pretreated to remove impurities by a screen, and the sewage is aerated with an air diffuser pipe of the immersion type membrane separation device. Is injected into the air supply system that supplies oxygen, dissolves oxygen at high speed in the sewage in the air supply system, and supplies the sewage with sufficient oxygen dissolved into the tank together with aeration air from the air diffuser. High concentration wastewater treatment method.