JP2001104982A - Apparatus and method for treating organic sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject apparatus and method enabling more continuous high flux operation and the maintenance control by chemical washing at a lower frequency. SOLUTION: In a biological treatment apparatus of organic sewage, a membrane separation mechanism obtaining treated water by membrane separation and a microorganism immobilized carrier are housed in a biological reaction apparatus and the concentration of MLSS in org. sewage excepting the microorganism immobilized carrier is lowered in the biological reaction apparatus. The housing amount of the microorganism immobilized carrier is preferably set to less than 30% of the volume of the biological reaction apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic wastewater treatment apparatus and method for biologically treating sewage, wastewater, human waste, and other organic wastewater, and more particularly to an organic wastewater treatment method for obtaining improved treated water by membrane separation. The present invention relates to a wastewater treatment apparatus and method.

[0002]

2. Description of the Related Art A membrane separation activated sludge treatment of organic wastewater obtained by immersing a separation membrane such as an MF membrane or a UF membrane in an activated sludge tank to obtain biologically treated water by membrane separation has been known. In this case, a major problem is performance degradation due to blockage of the separation membrane. This is because the surface of the separation membrane must always be washed. For example, as shown in FIG.
In a biological reaction tank (hereinafter sometimes referred to as “aeration tank”) 1, a membrane separation device 5 is immersed together with an aeration device 2. It is customary that the air diffuser 2 is arranged below the membrane separation device 5. The organic wastewater 3 is absorbed and decomposed and purified by the activity of activated sludge microorganisms under the supply of oxygen from the air diffuser 2. The obtained treated water is separated into solid and liquid by the separation membrane of the membrane separation device 5 and is guided to the outside of the system. At the same time, bubbles from the air diffuser 2 shake the separation membrane surface together with the carrier flow and cause friction. To clean the surface of the separation membrane. In general, such a membrane separation activated sludge method has a feature that a volume load can be increased because MLSS (activated sludge mixed liquid suspension) can be maintained at a high concentration of about 10,000 mg / liter. According to the conventional idea, if a large amount of organic wastewater 3 is to be rapidly treated, a higher concentration of activated sludge may be used. However, the separation membrane structurally has many small holes on its surface. High concentration of activated sludge (and therefore high concentration of MLS
The separation membrane immersed in S) is liable to cause clogging, so that it is impossible to increase the amount of passing water per unit area (hereinafter sometimes referred to as “flux”).
In addition, the separation membrane must be frequently washed with chemicals, which requires labor and cost for maintenance and maintenance, and the inconvenience that the actual operation time is shortened by washing and replacing the membrane is likely to occur.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned disadvantages of the prior art, and enables sewage treatment which enables more continuous operation at a high flux and maintenance and management at a less frequent chemical washing. It is an object to provide a method and a bag holder.

[0004]

The present invention has solved the above problems by the following means. (1) In a biological treatment apparatus for organic wastewater, a bioreactor is provided with a built-in membrane separation mechanism for obtaining treated water by membrane separation and a microorganism-immobilized carrier. An organic sewage treatment apparatus characterized by lowering the concentration of MLSS in sewage. (2) The organic wastewater treatment apparatus according to claim 1, wherein the built-in amount of the microorganism-immobilized carrier is 30% or less of the volume of the bioreactor. (3) The organic wastewater treatment device according to claim 1 or 2, wherein the concentration of MLSS in the biological reaction device excluding the microorganism-immobilized carrier is 2000 mg / liter or less. (4) In the biological treatment method for organic wastewater, treated water is obtained by a membrane separation step incorporated in a biological reaction step, and a microorganism-immobilized carrier is incorporated in the biological reaction step;
A method for treating organic sewage, comprising operating the MLSS at a low concentration in a biological reaction step excluding the microorganism-immobilized carrier, at a low concentration.

[0005]

Embodiments of the present invention will be described below. The essence of the embodiment of the present invention is to use a microorganism-immobilized carrier instead of using a high concentration of activated sludge.
An object of the present invention is to provide a function of absorbing and decomposing organic substances in wastewater by microorganisms, and to enable membrane separation under a lower concentration of activated sludge and MLSS. As the microorganism-carrying carrier, for example, a polyethylene glycol hydrophilic gel or a hydrophilic carrier having a three-dimensional network structure made of polyurethane is preferable. These can hold many microorganisms in the carrier and are soft and hard to damage the membrane. other,
Any material that flows in the aeration tank, such as a plastic carrier, activated carbon, a ceramic carrier, or a carrier of a biodegradable material such as cellulose, can be used in accordance with the properties of the separation membrane. Above all, a hydrophilic carrier having a three-dimensional network structure made of polyurethane has an excellent ability to retain microorganisms. The carrier carrying the highly accumulated microorganisms has a high biological treatment capacity and a diameter much larger than the pores on the surface of the separation membrane. as a result,
Since there is little problem of clogging, the degree of freedom in selecting a separation membrane is high, and a high flux can be obtained. Further, in the cleaning of the film, an effect due to collision or friction of large suspended matter can be expected.

[0006] The shape of the carrier is not particularly limited, but it is preferable that the particle size is small because the ratio of the supported surface area is large and the amount of microorganisms that can be retained is large, but it is determined in consideration of fluidity and ease of handling. Good. 5m for granular carrier
m or less, preferably 3 mm or less. In the case of a three-dimensional net structure, a dice having a size of about 10 mm square is preferably used because microorganisms can be retained on the surface of the internal structure. The amount of the carrier in the aeration tank is not more than 30%, preferably 2%, of the capacity of the reaction vessel such as the aeration tank.
It is better to be 0% or less. If it exceeds about 30%, the flow state in the container may be deteriorated. In addition to the above-mentioned carrier, the present invention does not obviate the use of the entrapping immobilization carrier. On the other hand, activated sludge can be reduced in concentration, and the possibility of filter clogging is further reduced. In the present invention, MLS including SS content in incoming sewage
S is less than 2000 mg / liter, preferably 1000 m
Operation at g / liter or less is desirable. This is about 1/10 of the conventional method. Even at this level, the processing ability of the entire biological treatment step is maintained at a high level by the microorganisms on the carrier, and there is almost no decrease in the ability to decompose organic substances.

FIG. 1 shows an embodiment of the present invention. This is an example of an aerobic treatment having an air diffuser 2 in a reaction tank 1. The introduction of the microorganism-immobilized carrier 6 allows the membrane separation device 5 to work well. The present invention is effective not only in aerobic treatment but also in anoxic treatment and anaerobic treatment. In this case, the flow of the carrier may be agitated by a gas containing no oxygen such as nitrogen aeration or a mechanical agitation means such as a pump, a paddle, and a screw. Of course, any other known stirring means such as magnets may be used without distinction between anaerobic and aerobic. In the present invention as well, surplus sludge is generated due to biological treatment. These sludges are separated and processed by a separately provided solid-liquid separating means, for example, a sedimentation tank. 3 to 5 show such cases. FIG. 3 uses a sedimentation tank 8 separately from the biological reaction tank 1. A carrier separation screen 9 is provided in the biological reaction tank 1 so that the microorganism-immobilized carrier 6 does not flow into the sedimentation tank 8. Biological reaction tank 1 from sedimentation tank 8
The supernatant water 10 of the sedimentation tank 8 returns.
Excess sludge 11 is separated from the bottom of the settling tank 8. FIG. 4 shows the sedimentation tank 8 integrated with the biological reaction tank 1. Depending on the configuration, the outflow of the carrier mixed in the biological reaction tank 1 may be prevented by a bar screen, a porous wall, or the like. Settling tank 8
Instead, a concentration separation layer or the like due to membrane separation can be provided. FIG. 5 shows an example in which an initial settling basin 12 is provided if a sufficient residence time is obtained. A part of the supernatant liquid may be returned to the initial settling basin 12 as the return liquid 13 and used for separating excess sludge. From the initial sedimentation basin 12, SS in the wastewater and excess sludge 11 are separated and eliminated. Since the biologically treated water has already been filtered in the membrane separation step, a load such as a water area load on the settling tank for treating excess sludge can be reduced.

[0008]

【Example】

Example 1 <Run1 Flux = 0.6 m / day> Run1 was performed. Using the apparatus shown in FIG. 1, a purification experiment of organic wastewater was performed using a polyurethane hydrophilic carrier having a three-dimensional network structure as a microorganism-immobilizing carrier. Table 1 shows the specifications of the device.

[0009]

[Table 1]

Table 2 shows the processing conditions. As shown in Table 2, the MLSS was 1000 mg / L,
The value was 0.6 m / day.

[0011]

[Table 2]

[0012] Of the filtered water filtered by the separation membrane, the same amount of water as the inflow of raw water was discharged out of the system, and the rest was returned to the biological reaction tank 1. The organic wastewater purification treatment was continuously performed for about 7 months, but the differential pressure of the membrane was almost constant at 0.5 m. No increase in differential pressure was observed. Further, when the separation membrane was taken out and observed, almost no sludge was attached. [Comparative Example 1] <Run 1> An organic wastewater purification experiment was performed under the treatment conditions shown in Table 2, except that the carrier was not used. In addition,
The MLSS was 10,000 mg / L, and the membrane flux value was 0.6 m / day as in Example 1. In about 7 months, the pressure difference of the membrane increased to 3 m in terms of the head pressure. The separation membrane was taken out and washed with a chemical.

Embodiment 2 <Run2 Flux =
0.9 m / day> Run 1 was followed by Run 2. As in Example 1, a polyurethane hydrophilic carrier having a three-dimensional network structure was used as a microorganism-immobilized carrier. The processing conditions were as shown in Table 2. The MLSS was 1000 mg / L, and the membrane Flu
The x value was 0.9 m / day. The operation was continued for about 5 months, but there was almost no increase in the differential pressure. [Comparative Example 2] <Run 2> An organic wastewater purification experiment was performed under the treatment conditions shown in Table 2, except that the carrier was not used. In addition,
The MLSS was 10,000 mg / L, and the membrane flux value was 0.9 m / day according to Example 2. The differential pressure increased in about two months. As a result, chemical cleaning was performed again.

[0014]

According to the present invention having the above-described structure, it is possible to provide a method for treating organic wastewater which can treat a large amount of organic wastewater more quickly than before. Because a microorganism-immobilized carrier is used, a large amount of sludge is supported by the microorganism-immobilized carrier, and the purification membrane has very little clogging without lowering the purification processing ability.
Efficient processing becomes possible. This is because the treated water is filtered by the membrane separation device and sucked, so that the water area load of the sedimentation tank is only the amount of sludge drawn out of the sedimentation tank, and the sedimentation tank is small and sufficient. That is, since the treated water is filtered by the membrane separation device and sucked, in the present invention, in order to utilize the microorganism-immobilized carrier having a small particle diameter, the specific surface area of the microorganism-immobilized carrier may have a substantially high value. it can. As a result, the amount of microorganisms stored in the microorganism-immobilized carrier can be increased, and a volume load substantially equal to that of the conventional membrane separation activated sludge method can be achieved. Since the MLSS concentration in the biological reaction tank is kept low, there is little contamination of the separation membrane. In addition, due to the effect of washing the membrane surface by the microorganism-immobilized carrier, clogging and contamination with organic substances can be prevented, and a high Flux value can be obtained. Normally, cleaning with a chemical should be performed, but the frequency is reduced. The microorganism-immobilized carrier comes into appropriate contact with the separation membrane of the membrane separation device while flowing. Thereby, the biofilm adhered to the surface of the microorganism-immobilized carrier is maintained at an appropriate thickness, and a stable organic substance decomposition treatment proceeds.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an embodiment of the present invention.

FIG. 2 is a conceptual diagram illustrating an example of a conventional processing method.

FIG. 3 is an example in which a sedimentation tank is used separately from a biological reaction tank.

FIG. 4 is an example in which a sedimentation tank is integrated with a biological reaction tank.

FIG. 5 is an example in which an initial settling tank is provided.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Biological reaction tank 2 Aerator 3 Organic sewage 5 Membrane separation apparatus 6 Microorganism immobilization support 7 Carrier separation apparatus 8 Sedimentation tank 9 Carrier separation screen 10 Supernatant water 11 Excess sludge 12 Initial settling basin 13 Return liquid

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kyoko Maki 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside the Ebara Corporation (72) Inventor Kosuke Mori 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Inside Ebara Works (72) Inventor Yasunari Kojima 11-1, Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Works (72) Inventor Yuichi Fuchu 11-1, Haneda Asahi-cho, Ota-ku, Tokyo Inside Ebara Works F Terms (Reference) 4D003 AA14 AB02 BA02 CA02 CA03 DA08 EA14 EA16 EA21 EA24 EA25 EA30 FA02 4D006 GA06 GA07 HA41 KA44 KB22 KB25 KC16 MA03 MC22 PA02 PB08 PC64 4D028 BB02 BC03 BC17 BC18 BD16 BD17 BE04 CA00 CA05

Claims (4)

[Claims] 1. A biological treatment apparatus for an organic wastewater, comprising: a membrane separation mechanism for obtaining treated water by membrane separation in a biological reactor;
An apparatus for treating organic sewage, comprising a microorganism-immobilized carrier therein, wherein the concentration of MLSS in the organic sewage excluding the microorganism-immobilized carrier is reduced in the biological reaction apparatus. 2. The organic wastewater treatment apparatus according to claim 1, wherein the amount of the microorganism-immobilized carrier contained therein is 30% or less of the volume of the biological reaction apparatus. 3. The organic wastewater treatment apparatus according to claim 1, wherein the concentration of the MLSS excluding the microorganism-immobilized carrier in the biological reaction device is 2000 mg / liter or less. 4. A biological treatment method for an organic wastewater, wherein treated water is obtained by a membrane separation step incorporated in a biological reaction step, and a microorganism-immobilized carrier is incorporated in the biological reaction step. A method for treating organic sewage, comprising operating the MLSS at a low concentration in a biological reaction process excluding MLSS.