JP4046445B2 - Wastewater treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating sewage, and relates to a membrane separation activated sludge treatment technique in which organic matter and organic sewage having a high nitrogen concentration are treated using a membrane separator.
[0002]
[Prior art]
Conventionally, there is an activated sludge treatment as a method for treating organic matter and organic sewage having a high nitrogen concentration, and there is a membrane separation activated sludge treatment in which the activated sludge concentration in the tank is kept high by using a membrane separation device in combination.
As shown in FIGS. 5 to 6, the membrane separation device 21 includes a plurality of flat plate membrane cartridges 22 and an air diffuser tube 23 that ejects a membrane surface cleaning gas from below the case 24. is there. The case 24 is divided into a membrane case 25 and an air diffuser case 26 to facilitate transport and maintenance, and is formed so that the entire amount of the film surface cleaning gas ejected from the air diffuser 23 enters the film case 25. is doing.
[0003]
The membrane cartridge 22 has filtration membranes 22B disposed on both surfaces of a filter plate 22A made of ABS resin, and a permeate flow path is formed between the filtration plate 22A and the filtration membrane 22B and inside the filtration plate 22A. A permeate outlet 22C communicating with the liquid flow path is formed at the upper edge of the filter plate 22A. Each membrane cartridge 22 communicates with a water collection pipe 28 via a tube 27 connected to the permeate outlet 22C, and the water collection pipe 28 communicates with a permeate discharge pipe 29 that extracts the membrane permeate. A pressing plate 30 for preventing the membrane cartridge 22 from floating is provided on the upper portion of the membrane case 25.
[0004]
When this membrane separation device 21 is used in an activated sludge treatment facility, the membrane separation device 21 is immersed in the activated sludge mixed solution inside the aeration tank, and aeration air is ejected from the aeration tube 23 in the raw water. Organic matter and nitrogen are treated with activated sludge, and the activated sludge mixed solution is gravity filtered through the membrane cartridge 22 with the water head in the tank as the driving pressure (by sucking the permeate outlet tube 29 through a suction pump) Filtration is also possible), and the permeate permeated through the membrane surface of the membrane cartridge 22 is led out of the tank through the permeate outlet tube 29 as treated water. At this time, the membrane surface of the membrane cartridge 22 is washed with the bubbles of aerated air ejected from the air diffuser 23 and the upward flow generated thereby, and the membrane separation device 21 becomes malfunctioning by suppressing the lowering of the separation function. Is preventing.
[0005]
The general structure of the water treatment facility using the membrane described above is shown in FIGS. 3 to 4, the inflow wastewater 41 is stored in the flow rate adjustment tank 43 after removing impurities in the pretreatment facility 42, and supplied from the flow rate adjustment tank 43 to the aeration tank (biological treatment tank) 44 at a constant flow rate. To do. In the aeration tank 44, organic substances in the sewage are decomposed and removed by activated sludge, the solid liquid is separated by the membrane separation device 21 arranged soaked in the aeration tank 44, and the filtrate is discharged through the sterilization tank 45.
[0006]
[Problems to be solved by the invention]
In the membrane separation activated sludge treatment using the submerged membrane separation device as described above, as shown in FIG. 4, several membrane separation devices 21 are installed and used in the aeration tank 44. However, when the treatment scale increases. Several to a dozen membrane separation devices 21 are installed in one aeration tank 44. In such an aeration tank 44, a concentration distribution is generated in which the activated sludge concentration on the sewage inflow side is diluted and diluted on the inflow sewage, and the activated sludge concentration on the opposite side becomes extremely high.
[0007]
An object of the present invention is to provide a method for treating sewage that can maintain the activated sludge concentration uniformly in the entire region in the aeration tank in the membrane separation activated sludge method using the submerged membrane separation apparatus.
[0008]
In order to solve the above-described problem, the wastewater treatment method of the present invention according to claim 1 is provided with a plurality of submerged membrane separators in a reaction tank and is used for aeration from an air diffuser arranged in the submerged membrane separator. and aeration air, the membrane bioreactor for biological treatment of sewage flowing into the reaction vessel in the activated sludge, impurities were removed in the screen the inflow wastewater preprocess is removed contaminants pretreatment The sewage is supplied into the tank through the diffuser of the submerged membrane separator.
[0009]
The sewage treatment method of the present invention according to claim 2 stops the supply of aeration air when supplying sewage into the tank through the air diffuser.
[0010]
With the configuration described above, by supplying the sewage dispersed in the tank through each diffusion tube of each submerged membrane separation device, the organic matter that is a biological treatment load is dispersed in the tank, and in all regions in the reaction tank The activated sludge concentration can be maintained uniformly.
The inflowing sewage usually contains a large amount of SS and impurities, but by passing the sewage through a screen of about 1 mm, the air holes (about 10 mm) of the air diffuser are not clogged. By pouring sewage into the diffuser, oxygen dissolves in the sewage at a high speed in the diffuser, and the oxygen concentration in the sewage is almost saturated when released from the air holes of the diffuser into the tank. It becomes the state of. This increase in oxygen dissolution efficiency can reduce the amount of air required to be supplied into the tank through the air diffuser by 20 to 30%, thereby reducing the blower output and reducing energy consumption.
[0011]
If the air diffuser is used over a long period of time, if the activated sludge concentration is high (about 1 to 2%), the sludge that has entered the air holes of the air diffuser is air dried to form a granular or clay-like solid. The air hole may be blocked. However, blocking of air holes in the air diffuser can be prevented by pouring sewage into the air diffuser as in the present invention.
The injection of sewage into the air diffuser may be performed by stopping the blower that supplies the aeration air to the air diffuser, or the water may be injected while being diffused. Further, the sewage may be simultaneously poured into the diffuser pipes of all the submerged membrane separators, or the diffuser pipes that are sequentially poured every certain time, for example, every minute, may be replaced.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 2, the reaction tank 1 has a rectangular shape in plan view and a long shape with a ratio of a short side to a long side of 1: 3 or more. Biological treatment to decompose and remove with activated sludge.
[0013]
Inside the reaction tank 1, a plurality (several to tens of units) of submerged membrane separation devices 21 are arranged in a line at predetermined intervals. The submerged membrane separator 21 is the same as that described with reference to FIGS.
Each diffuser tube 23 of each submerged membrane separation device 21 has a plurality of air holes with a diameter of about 10 mm, and the 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, a diffused air pipe 5 that communicates the air supply main pipe 4 and each of the diffuser pipes 23, It consists of an air valve 6 interposed in the air diffuser pipe 5.
[0014]
The sewage supply system 7 includes a sewage pump 8 that supplies sewage, a sewage supply main pipe 9 that communicates with the sewage pump 8, a sewage pipe 10 that communicates the sewage supply main pipe 9 and each aeration air pipe 5, and each sewage It consists of a sewage valve 11 interposed in the pipe 10.
As shown in FIG. 2, a pretreatment facility 42 is disposed upstream of the reaction tank 1 to remove impurities in the sewage 41 flowing with a screen having a mesh width of about 1 mm, and downstream of the pretreatment facility 42. Is provided with a flow rate adjusting tank 43 for storing sewage from which impurities have been removed. A sterilization tank 45 is provided on the downstream side of the reaction tank 1.
[0015]
Hereinafter, the operation of the above-described configuration will be described. Since the inflowing sewage 41 usually contains a large amount of SS and contaminants, removing the contaminants in the pretreatment facility 42 may clog the air holes (about 10 mm) in the downstream diffuser 23. To prevent. The sewage 41 from which the impurities have been removed is stored in the flow rate adjustment tank 43 and is quantitatively supplied to each air diffuser 23 of each submerged membrane separator 21 through the sewage supply system 7. On the other hand, the air supply system 2 supplies the aeration air supplied by the blower 3 to each of the diffusion tubes 23 through the air supply main tube 4, the air valve 6, and the diffusion air tube 5.
[0016]
The sewage supply system 7 injects sewage 41 supplied by the sewage pump 8 into each diffused air pipe 5 through the sewage supply main pipe 9, the sewage valve 11, and the sewage pipe 10. Oxygen dissolves at high speed in the sewage 41 poured into the diffuser air pipe 5 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.
[0017]
For this reason, the oxygen concentration of the sewage 41 released into the liquid in the tank from the air hole of the diffusing tube 23 together with the aeration air is almost saturated. This increase in oxygen dissolution efficiency can reduce the amount of air required to be supplied into the tank through the air supply system 2 by 20 to 30% compared to the conventional case, and can suppress the output of the blower 3 and reduce energy consumption.
In this way, by supplying the sewage 41 dispersed in the tank through the air diffusers 23 of the submerged membrane separation devices 21, the organic matter that is a biological treatment load is dispersed in the tank, and the entire reaction tank 1 The activated sludge concentration can be kept uniform in the region.
[0018]
In addition, by pouring the sewage 41 into the air diffuser 23, the sludge that has entered the air holes of the air diffuser 23 does not air dry and block the air holes, and the activated sludge concentration is high (about 1-2%). However, the diffuser 23 can be used for a long time.
The sewage 41 ejected from the air diffuser 23 is filtered while flowing in a cross flow with respect to the membrane surface of the membrane cartridge 22 on the aeration air bubbles and the upward flow generated thereby. This cross flow suppresses the formation of a cake layer on the membrane surface, and its flow rate is adjusted by adjusting the jet pressure and jet flow rate of the sewage 41 or by adjusting the jet pressure and jet flow rate of aeration air. Or by combining them.
[0019]
The supply of the sewage 41 to the air diffuser 23 may be performed in a state where each air valve 6 is closed or the blower 3 is stopped to stop the supply of aeration air. In addition, by appropriately opening and closing each sewage valve 11, the diffusing pipes 23 that supply the sewage 41 are changed every predetermined time (for example, 1 minute), and to each diffusing pipe 23 of each submerged membrane separator 21. You may inject water sequentially. Furthermore, when the amount of sewage 41 flowing into the reaction tank 1 is small, treated water or fresh water can be poured into the diffuser pipe 23 after the sewage 41 has been poured. Further, the sewage 41 may contain oil, and therefore, the diffuser 23 is usually washed with treated water or clean water once a day.
[0020]
【The invention's effect】
As described above, according to the present invention, the organic matter is dispersed in the tank by supplying the sewage dispersed in the tank through each aeration tube of each submerged membrane separator, and in all regions in the reaction tank. The activated sludge concentration can be maintained uniformly. By dissolving oxygen at high speed in the sewage in the air diffuser, the amount of necessary air supplied through the air diffuser can be reduced to reduce energy consumption. Even when the activated sludge concentration is high (about 1 to 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 showing a configuration of a reaction tank in an embodiment of the present invention.
FIG. 2 is a flow sheet showing a wastewater treatment method according to the embodiment.
FIG. 3 is a flow sheet showing a conventional method for treating sewage.
FIG. 4 is a schematic diagram showing the configuration of a conventional reaction tank.
FIG. 5 is a cross-sectional view showing a membrane separation apparatus.
FIG. 6 is a longitudinal sectional view showing a membrane separation apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Air supply system 3 Blower 4 Air supply main pipe 5 Aeration 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 separator 23 Aeration pipe 41 Wastewater 42 Pretreatment equipment 43 Flow rate adjustment tank 45 Sterilization tank

Claims (3)

Membrane separation in which a plurality of submerged membrane separation devices are installed in the reaction tank, aeration air is diffused from the air diffuser installed in the submerged membrane separation device, and the sewage flowing into the reaction tank is biologically treated with activated sludge In the activated sludge method, the influent sewage is pretreated to remove contaminants with a screen, and the sewage from which the contaminants have been removed by the pretreatment is supplied into the tank through the diffuser pipe of the submerged membrane separator. Wastewater treatment method. 2. The method for treating sewage according to claim 1, wherein the supply of aeration air is stopped when sewage is supplied into the tank through the air diffuser.   The method for treating sewage according to claim 1 or 2, wherein water is sequentially poured into each diffusing pipe of each submerged membrane separation device while changing the diffusing pipe for supplying sewage every predetermined time.

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