KR20120112108A - Method of treating organic waste water by membrane separator activated sludge device - Google Patents

Abstract

PURPOSE: A treatment method of organic drainage is provided to stably implement a solid-liquid separating process using a membrane by maintaining the proper concentration of sludge. CONSTITUTION: A treatment method of organic drainage includes a membrane separation-activated sludge apparatus. The membrane separation-activated sludge apparatus includes an aerating bath(1) and a membrane separation bath(3). Organic drainage is introduced into the aerating bath. The membrane separation bath circulates sludge in the aerating bath and solid-liquid separates the sludge. [Reference numerals] (AA) Feed water; (BB) Treated water; (CC) Air; (DD) Aerating bath; (EE) Membrane separating bath; (FF) Air

Description

METHODS OF TREATING ORGANIC WASTE WATER BY MEMBRANE SEPARATOR ACTIVATED SLUDGE DEVICE}

The present invention relates to a treatment method in which organic wastewater is biologically treated in an aeration tank and solid-liquid separated into a membrane.

Treatment method of organic wastewater using the membrane separation active sludge apparatus (MBR) provided with the aeration tank into which organic wastewater flows in, and the membrane separation tank which solid-separates into a membrane, circulating the sludge of an aeration tank (for example, patent document 1, 2 By using the membrane, the water quality of the treated water can be maintained satisfactorily, and the MLSS concentration of the aeration tank can be maintained high, and the high load treatment is possible, and the settling tank is unnecessary, so that the apparatus can be made small. have.

In the membrane separation activated sludge treatment method, when the sludge concentration (MLSS) is less than 2,000 mg / L, the decomposition ability of the BOD component is insufficient, and the BOD component is adsorbed in a large amount on the membrane surface of the membrane module, so that the filtration treatment can be stably performed. It becomes impossible. Therefore, Patent Literature 3 discloses a method of adding seed sludge so that the sludge concentration in the aeration tank is 2,000 mg / L or more before the first start of operation.

Japanese Unexamined Patent Publication No. 2009-50764 Japanese Unexamined Patent Publication No. 2004-8176 Japanese Unexamined Patent Publication No. 2000-189993

In the membrane separation activated sludge treatment method, it is known that when the sludge is removed to increase the concentration of the sludge in the aeration tank and excessively long SRT (slow residence time) increases the self-extinguishing product of the sludge, it becomes easy to contaminate the membrane. have.

Therefore, when sufficient amount of sludge is not obtained at the start-up, or when the load condition which is low compared with the planned load is continued for a long time, sludge concentration was not kept high and stable membrane filtration was not able to be performed. In particular, since the low molecular weight organic compound having low sludge conversion rate is a main component, the liquid crystals and semiconductor manufacturing plants in which the demand for water recovery is high and MBR is being applied in recent years, do not excessively lengthen the SRT. It was difficult to maintain high and perform stable operation.

An object of the present invention is to provide a method for treating organic wastewater, which can maintain stable sludge concentration and perform stable operation even in wastewater containing a low molecular organic compound as a main component such as semiconductor manufacturing plant drainage.

The organic wastewater treatment method of the present invention (claim 1) is an organic wastewater using an aeration tank into which an organic wastewater flows in and a membrane separation active sludge apparatus having a membrane separation tank for solid-liquid separation into a membrane while circulating sludge of the aeration tank. In the treatment method, the amount of circulation of the sludge to the membrane separation tank is 1.5? Of the amount of raw water according to the organic matter load of the raw water. It is characterized by switching between 10 times.

The treatment method of the organic wastewater of Claim 2, The sludge concentration of the said membrane separation tank of Claim 1 is 3,000? The sludge is circulated in the membrane separation tank so as to be 20,000 mg / L.

The treatment method of the organic wastewater of Claim 3 is a sludge according to Claim 1 or 2 which is 1/10? Of the total amount of sludge retained in the aeration tank and the membrane separation tank per day. It is characterized by subtracting 1/50.

The processing method of the organic wastewater of Claim 4 is organic wastewater discharged from liquid crystal or a semiconductor manufacturing plant in any one of Claims 1-3, It is characterized by the above-mentioned.

In the organic wastewater treatment method of the present invention, in the organic wastewater treatment method using an aeration tank into which the organic wastewater flows and a membrane separation tank for solid-liquid separation into membranes while circulating sludge in the aeration tank The amount of sludge circulated to the membrane separation tank can be changed to 1.5? 10 times, preferably the sludge concentration of the membrane separation tank is 3000? Sludge is circulated in the membrane separation tank to 20000 mg / l.

As a result, solid-liquid separation by membranes can be stably performed by maintaining the appropriate sludge properties and concentrations without excessively lengthening the SRT even at the time of starting or low load where a sufficient amount of sludge is not obtained.

1 is a flowchart of a method for treating organic wastewater according to an embodiment.
2 is a graph showing experimental results.
3 is a graph showing experimental results.

In the present invention, the organic wastewater to be treated may be any organic-containing wastewater that is usually biologically treated, and is not particularly limited. Examples thereof include electronic industrial wastewater, chemical plant wastewater and food plant wastewater. For example, in the electronic component manufacturing process, various organic wastewaters are generated in a large amount from a developing process, a peeling process, an etching process, a cleaning process, and the like, and it is desired to recover the wastewater, purify it to a pure water level, and reuse it. These wastewaters are suitable as the wastewater to be treated in the present invention. Such organic drainage may include, for example, organic wastewater containing isopropyl alcohol, ethyl alcohol, organic wastewater containing monoethanolamine (MEA), tetramethylammonium hydroxide (TMAH), and organic wastewater containing ammonia nitrogen. And organic wastewater containing organic sulfur compounds such as dimethyl sulfoxide (DMSO). The organic matter concentration of the organic wastewater is not particularly limited, but the present invention particularly has a BOD of 300? It is suitable for the treatment of organic matter-containing wastewater of 5,000 mg / l.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described by drawing. 1 is a system diagram of an activated sludge treatment apparatus using an immersion membrane, and the apparatus includes an aeration tank 1, an air dispersing apparatus 2, and a membrane separation tank 3. In the membrane separation tank 3, an immersion type membrane separation membrane 4 is formed so as to be immersed in the crude liquid, and the membrane 4 is permeated to concentrate the crude liquid. Raw water is introduced into the aeration tank 1 from the raw water passage 11, air is diffused from the air dispersing apparatus 2, mixed with the activated sludge in the tank, and aerobic biological treatment. The crude liquid is sent from the system 12 to the membrane separation tank 3 to separate the membrane.

In the membrane separation tank 3, the pump P is driven to allow the inner liquid to pass through the separation membrane 4 of the immersion type membrane and to be discharged as treated water. In the membrane separation tank 3, air is released from the air diffuser 5 in order to keep the inside of the tank aerobic and to prevent microbial adhesion to the surface of the membrane 4. The permeate is discharged from the treatment channel 13 as treated water, and the concentrated liquid is conveyed from the conveying sludge system 14 to the aeration tank 1 as the conveying sludge. In addition, in this system, although the sludge (tank liquid) which overflowed from the membrane separation tank 3 is conveyed to the aeration tank 1, you may be comprised so that it may convey from the lower part of the tank 3.

In the present invention, the amount of circulation of the sludge (inner tank liquid of the aeration tank 1) from the aeration tank 1 by the system 12 to the membrane separation tank 3 is 1.5? Switch between 10 times. When the BOD load of raw water is low (for example, less than 0.5 kg / m 3 · d), the circulation amount is reduced, and the sludge concentration of the membrane separation tank is preferably 3,000? 20,000 mg / l (3-20 g / l), particularly preferably 3,000? 12,000 mg / l. In addition, the sludge concentration of the membrane separation tank is preferably 3,000? It is preferable to control the circulation amount so as to have a sludge concentration within ± 20%, particularly ± 10%, of the target value selected between 20,000 mg / L.

The BOD load of the aeration tank 1 is 0.2? 2 kg / m 3? D, especially 0.5? 1.2 kg / m <3> -d is preferable. In addition, a plurality of aeration tanks 1 may be provided in series. The MLSS concentration in the aeration tank (1) is 1,000? 20,000 mg / l, especially 3,000? It is preferable from the viewpoint of membrane filterability that it is about 12,000 mg / L.

As for the membrane 4 of the membrane separation tank 3, MF and UF are preferable, and any of a flat membrane, a tubular membrane, and a hollow fiber membrane may be sufficient. Filterability is improved by scattering and cleaning gas such as air on the membrane surface.

As surplus sludge, 1/10 of the total amount of sludge retained in the aeration tank and membrane separation tank per day. 1/50 (SRT 10 – 50 days), especially 1/20 – It is desirable to extract an amount corresponding to 1/30. Extraction may be performed from any of the tanks 1 and 3, and may be performed from 12 or 14 in the furnace.

Example

Hereinafter, an Example and a comparative example are demonstrated. The raw water used by the following example and the comparative example was as follows, and the process was performed using the apparatus shown in FIG. 1 which has the following aeration tank and membrane separation tank.

[enemy]

Simulated drainage of the liquid crystal manufacturing plant (the raw water fed on the first 30 days contains 80 mg / l of MEA, 40 mg / l of DMSO, and nutrient inorganic salts. BOD concentration of 100 mg / l.)

Raw water supply 4 ㎥ / d

[Aeration tank and membrane separation tank]

Aeration tank 2 ㎥. The sludge is supplied to the membrane separation tank at a predetermined flow rate, and the sludge overflowed from the membrane separation tank is returned to the aeration tank.

Membrane separation vessel 0.4 ㎥. A MF membrane (membrane area 6 m 2) manufactured by Mitsubishi Rayon was immersed, and the membrane filtered water was sucked in a cycle of 7 min filtration / 1 min rest (effective flux 0.5 m / d). When the interlayer differential pressure exceeded 30 kPa, the membrane was picked up and immersed in a NaOH + NaClO solution (pH 12, 0.3% effective chlorine) overnight and washed.

[How to drive]

The activated sludge of the wastewater treatment facility of a liquid crystal manufacturing plant is made into the seed sludge, the amount of sludge of an aeration tank and a membrane separation tank is 1,500 mg / L, and the said density | concentration is input, and the said density | concentration is carried out in the 1st stage from the beginning of water supply to the 30th day. Supply a simulated drain of 31, The second stage of 60 days is supplied with simulated drainage of twice the concentration of the first stage (0-30 days), and the 61? The third phase of 90 days was fed a simulated drainage three times the concentration of the first phase. The BOD load is as follows.

1st stage (0-30 days): 0.2 kg / ㎥? D

Second period (31 to 60 days): 0.4 kg / ㎥? D

Third period (61 to 90 days): 0.6 kg / ㎥? D

&Lt; Comparative Example 1 &

The circulation rate from the aeration tank 1 to the membrane separation tank 3 is constant (20 m 3 / d (5 times the amount of raw water)), and the sludge is removed from the aeration tank 1 on the 20th day of SRT. Was carried out.

<Comparative Example 2>

The circulation rate from the aeration tank 1 to the membrane separation tank 3 is constant (20 m 3 / d (5 times the amount of raw water)), and the sludge extraction amount is adjusted so that the sludge concentration of the membrane separation tank is 3,000 mg / l or more. The operation was adjusted.

<Example>

Sludge is removed from the aeration tank 1 on the 20th day of SRT, and the circulation rate is adjusted to 7 to 3,000 mg / l of the sludge concentration of the membrane separation tank 3. It operated by adjusting between 20 m <3> / d (1.8-5 times with respect to raw water quantity).

[result]

In Comparative Examples 1, 2 and Example 1, the BOD concentration of the treated water was less than 5 mg / L throughout the entire period.

The transition of sludge concentration is shown in FIG. 2, and the transition of interlude differential pressure is shown in FIG. In the third phase (61 to 90 days), the cleaning intervals of the membranes did not show any difference around 15 days, but the periods of the first and second phases with low load and sludge concentration were in Comparative Examples 1 and 2 In contrast to the sharp increase in the differential pressure and the markedly shortened washing frequency, in the examples, 20? A 30 day wash interval could be maintained.

The concentration of the biological metabolite (TOC) in the tank which caused the clogging was high until 20 days when the sludge was removed in Comparative Example 2, but no difference was observed in any system other than that. The reduction in the differential pressure rising rate in the present embodiment is considered to be caused by the suppression of adsorption of the biometabolites to the membrane surface by maintaining the sludge concentration in the membrane separation tank.

As is clear from the above examples and comparative examples, the present invention can maintain a sludge concentration suitable for membrane filtration in a membrane separation tank even at startup or at low load, when a sufficient amount of sludge is not obtained. Solid-liquid separation can be performed stably.

1: aeration tank
3: membrane separation tank
4: separator

Claims (4)

In the treatment method of organic wastewater using the membrane separation active sludge apparatus provided with the aeration tank into which organic wastewater flows in, and the membrane-separation tank which solid-separates into a membrane while circulating the sludge of an aeration tank,
The amount of sludge circulated to the membrane separation tank is 1.5? According to the organic load of the raw water. A method of treating organic drainage, characterized by switching between 10 times. The method of claim 1,
The sludge concentration of the membrane separation tank is 3,000? A method for treating organic wastewater, wherein the sludge is circulated in the membrane separation tank so as to be 20,000 mg / l. The method according to claim 1 or 2,
As surplus sludge, 1/10 of the total amount of sludge retained in the aeration tank and membrane separation tank per day. A method for treating organic wastewater, comprising extracting 1/50. The method according to any one of claims 1 to 3,
Organic wastewater is discharged | emitted from a liquid crystal thru | or a semiconductor manufacturing plant, The processing method of organic wastewater characterized by the above-mentioned.

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