JP4023959B2 - High-concentration wastewater treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating high-concentration sewage, and relates to a membrane separation activated sludge treatment technique for treating organic matter and organic sewage with a high nitrogen concentration using a membrane separation apparatus.
[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. 3 to 4, the membrane separation device 21 includes a plurality of flat plate membrane cartridges 22 and a diffuser tube 23 for ejecting a membrane 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 that has passed 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 bubbles of the aeration air ejected from the diffuser tube 23 and the upward flow generated thereby clean up the membrane surface of the membrane cartridge 22 and suppress the reduction of the separation function. Preventing malfunctions.
[0005]
A general configuration of a water treatment facility using the above-described membrane is shown in FIG. In FIG. 2, inflowing sewage 41 is stored in a flow rate adjustment tank 43 after removing impurities in the pretreatment facility 42, and is supplied from the flow rate adjustment tank 43 to an aeration tank (biological treatment tank) 44 at a constant flow rate. 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 submerged membrane separation activated sludge method using the submerged membrane separation apparatus as described above, the air ejected from the aeration tube is aerated air for supplying oxygen to the activated sludge and a sweeping flow for performing membrane cleaning. Also serves as a drive source.
By the way, when treating organic matter and high-concentration sewage with a high nitrogen concentration, the amount of oxygen required by activated sludge increases, and it is necessary to increase the amount of aerated air ejected from the air diffuser to supply this oxygen. . On the other hand, in order to wash the filtration membrane 22B of the membrane cartridge 22 by sweeping, the aeration intensity (determined by the ejection speed, ejection pressure, and ejection amount) has an appropriate value, and if the aeration air amount increases excessively, the filtration membrane 22B may be damaged.
[0007]
For this reason, a pre-aeration tank is provided on the upstream side of the aeration tank, and sufficient aeration is performed in the pre-aeration tank without a membrane separation device to solve the shortage of oxygen. However, in order to install the preaeration tank, an installation space is required, and it is difficult to install the preaeration tank in an existing facility with a limited area.
The present invention solves the above-described problems, and in the submerged membrane separation activated sludge method using a submerged membrane separator, the required amount of oxygen is sufficiently supplied to the activated sludge without increasing the amount of aerated air. It aims at providing the processing method of the high concentration wastewater which can be done.
[0008]
In order to solve the above-mentioned problems, the high-concentration sewage treatment method of the present invention is a membrane separation activated sludge method in which organic matter and organic sewage with a high nitrogen concentration are biologically treated in a reaction tank in which a submerged membrane separator is installed. Then, a part of the treated water filtered by the submerged membrane separator is injected into an air supply system that supplies aeration air to the diffuser pipe of the submerged membrane separator, and oxygen is introduced into the treated water at a high speed in the air supply system. Dissolved and sufficiently treated dissolved oxygen is supplied into the tank along with aeration air from the diffuser. The injection of the treated water is monitored by measuring the dissolved oxygen concentration in the reaction tank with an oximeter. Water is injected when the dissolved oxygen concentration is less than a predetermined value .
[0009]
With the above configuration, when the treated water is poured into the air supply system, oxygen is dissolved in the treated water at a high speed in the system, and when the oxygen is released from the air holes of the air diffuser into the liquid in the tank, The oxygen concentration of 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 diffuser by 20 to 30%, thereby reducing the blower output and reducing energy consumption.
[0010]
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, it is possible to prevent the air holes of the air diffuser from being blocked by pouring the treated water into the air diffuser as in the present invention.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the submerged membrane separation device 21 disposed inside the reaction vessel 1 is the same as that described in FIGS.
The diffuser tube 23 of the 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 and an air diffuser tube 4 that communicates with the air diffuser 23.
[0012]
On the upstream side of the reaction tank 1, a pretreatment facility 6 for removing contaminants of the high-concentration sewage 5 flowing with a screen having a mesh width of about 1 mm is disposed, and the contaminants are removed downstream of the pretreatment facility 6. A flow rate adjusting tank 7 for storing the high-concentration sewage 5 is provided. A treated water tank (sterilization tank) 8 is provided on the downstream side of the reaction tank 1, and the treated water tank 8 communicates with the diffused air pipe 4 via the treated water return system 9. The treated water return system 9 includes a water injection pump 10 that supplies treated water and a treated water pipe 11 that communicates with the diffused air pipe 4. The reaction vessel 1 is provided with an oxygen concentration meter 12.
[0013]
Hereinafter, the operation of the above-described configuration will be described. The inflowing high concentration sewage 5 usually contains a large amount of SS and contaminants. Therefore, the pretreatment facility 6 removes the contaminants and stores the high concentration sewage 5 in the flow rate adjustment tank 7 so that the flow rate is constant. Feed to reaction vessel 1. On the other hand, aeration air supplied from the blower 3 in the air supply system 2 is supplied to the diffusion pipe 23 through the diffusion air pipe 4, and the liquid in the reaction tank 1 is aerated by the aeration air ejected from the diffusion pipe 23.
[0014]
In the reaction tank 1, oxygen is supplied by aeration air ejected from the diffuser pipe 23 and treated water described later, organic substances contained in the high-concentration sewage 5 are decomposed and removed by activated sludge, and solidified by the submerged membrane separator 21. Separate the liquid. The filtrate separated by the submerged membrane separator 21 is discharged through the treated water tank 8, and a part of the treated water is diffused through the treated water pipe 11 by the water injection pump 10 of the treated water return system 9 and the diffused air pipe 4 of the air supply system 2. Water.
[0015]
While the treated water flows through the diffuser air pipe 4 and the diffuser pipe 23, oxygen is dissolved at a high speed. For this reason, the oxygen concentration of the treated water released into the liquid in the tank from the air hole of the diffusing pipe 23 together with the aerated air is almost saturated. This increase in oxygen dissolution efficiency enables the required amount of oxygen to be sufficiently supplied to the activated sludge without increasing the amount of aerated air, and the required amount of air to be supplied into the tank through the air supply system 2 is conventionally increased. Compared to 20 to 30%, the output of the blower 3 can be suppressed and energy consumption can be reduced.
[0016]
The treatment water is injected by measuring the dissolved oxygen concentration in the reaction tank 1 with an oxygen concentration meter 12 and injecting water when the dissolved oxygen concentration is less than 0.5 mg / L, and the dissolved oxygen concentration is 1.0 mg / L or more. It stops when it becomes.
In this way, by pouring the treated water into the diffuser pipe 23, the air holes of the diffuser pipe 23 can always be washed, and the sludge that has entered the air holes of the diffuser pipe 23 is air-dried to block the air holes. Even if the activated sludge concentration is high, the air diffuser 23 can be used over a long period of time.
[0017]
The high-concentration sewage 5 is filtered while flowing in a cross flow with respect to the membrane surface of the membrane cartridge 22 by the upward flow generated by the treated water and aeration air ejected from the air diffuser 23. 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 treated water, or by adjusting the jet pressure and jet flow rate of the aerated air, Or it can control by combining them.
[0018]
Further, when a plurality of submerged membrane separators 21 are arranged in the reaction tank 1, each submerged membrane separator 21 is changed while changing the diffuser pipe 23 for supplying treated water every predetermined time (for example, one minute). Water may be sequentially poured into each of the diffuser tubes 23.
[0019]
【The invention's effect】
As described above, according to the present invention, treated water is injected into the air supply system, and oxygen is dissolved in the treated water at a high speed in the air supply system, so that the necessary amount is increased without increasing the amount of aerated air. Can sufficiently supply oxygen to activated sludge, reduce the amount of air required through the air diffuser, reduce energy consumption, and even in high-concentration sewage, the sludge is air-dried in the air holes of the air diffuser Without blocking, the air hole of the air diffuser can be prevented 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 sewage.
FIG. 3 is a cross-sectional view showing a membrane separation apparatus.
FIG. 4 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 Aeration air pipe 5 High concentration sewage 6 Pretreatment equipment 7 Flow control tank 8 Treated water tank 9 Treated water return system 10 Injection water pump 11 Treated water pipe 12 Oxygen meter 21 Immersion type membrane separator 23 Diffuser

Claims (1)

In the membrane separation activated sludge method for biological treatment of organic matter and organic sewage with high nitrogen concentration in a reaction tank equipped with a submerged membrane separator, a part of the treated water filtered by the submerged membrane separator is submerged. It is injected into the air supply system that supplies aeration air to the diffuser pipe of the separator, oxygen is dissolved in the treated water at a high speed in the air supply system, and the treated water in which oxygen is sufficiently dissolved is tanked together with the aerated air from the diffuser pipe The high- concentration, which is supplied to the inside of the processing water, is measured by monitoring the dissolved oxygen concentration in the reaction vessel with an oxygen concentration meter and injecting water when the dissolved oxygen concentration is less than a predetermined value. Wastewater treatment method.

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