JP2006094748A - Membrane type bioreactor and method for treating liquid by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a stable treating performance for a long period and realize a practical membrane type bioreactor. <P>SOLUTION: This membrane type bioreactor supplied with gas to the inside of the membrane and also supplied with liquid to the outside of the membrane is characterized by installing a gas filter and/or mass flow controller having a smaller pore diameter than that of the membrane at the rear stage of a gas-supplying means and also at the front stage of the membrane. The method for treating the liquid by using the same is also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a membrane bioreactor and a liquid treatment method using the same, and in particular, a wastewater treatment or a sewage treatment in which a biofilm composed of microorganisms is immobilized on the surface of the membrane and the biofilm is maintained in an appropriate state to perform the biotreatment. The present invention relates to a membrane bioreactor that can be suitably applied to the field of the above, and the field of production of useful substances using a biofilm, and a liquid treatment method using the same.

  A bioreactor, that is, a so-called membrane aeration bioreactor (hereinafter abbreviated as MABR) that immobilizes a biofilm composed of microorganisms on the surface of a membrane, particularly a hollow fiber membrane, and supplies gas from the inside of the hollow fiber membrane (hereinafter abbreviated as MABR) is a research level. Have been published (for example, Patent Document 1). It has been studied mainly as an effort to improve the efficiency of bioreactors that produce useful substances, but in recent years, it has also been applied to wastewater treatment and sewage treatment.

  Conventionally, biological treatments that have been carried out at sewage treatment plants, wastewater treatment plants, etc. are carried out using aeration devices to supply air to the aquarium. In order to go outside, the oxygen utilization efficiency is usually about 5 to 10%. In contrast, in MABR, gas can be directly supplied to a biofilm composed of a group of microorganisms attached to the outer surface of the hollow fiber membrane without generating bubbles, so that the oxygen utilization efficiency is 90 to 100%, and the energy associated with the aeration is increased. It can be significantly reduced.

However, since MABR uses a membrane, the cost is high, and for practical use, the point is that it can be processed with a much higher load (about 5 to 10 times) than a conventional aeration apparatus. For this reason, research on high-load processing using MABR has been conducted, and high-load processing has been achieved in a short period of time, but there has been a problem that processing performance is not stable in the long term. For these reasons, MABR is promising as a high-load, energy-saving device, but there are problems in terms of long-term performance stability, cost, etc., and it is actually not practical.
JP-A-11-162

  Therefore, in view of the above situation, an object of the present invention is to achieve a long-term stable processing performance and put MABR into practical use.

  In order to solve the above-mentioned problems, the present inventors have made various studies on the unstable processing performance using an aerobic MABR apparatus. As a result, it has been found that the supply gas amount decreases with a long-term operation of three months or more, and that when the gas supply amount decreases significantly, the necessary gas amount cannot be obtained, and thus the reactor processing performance decreases. As a result of studying this gas amount reduction, it was assumed that the pores of the membrane were clogged by solids and oil in the supplied gas. Conventionally, it has been necessary to stop the operation and clean or replace the membrane as the gas flow rate decreases. The present invention has been completed based on these examination results.

  That is, the membrane bioreactor according to the present invention is a membrane bioreactor in which a gas is supplied to the inside of the membrane and a liquid is supplied to the outside of the membrane. At least a gas filter having a pore diameter smaller than that of the membrane is provided. Since the solids and oil in the supply gas that cause clogging of the membrane pores are properly removed in advance by the gas filter, it is possible to prevent a decrease in the amount of gas supplied to the membrane, and long-term Stable processing performance can be obtained.

  A pressure gauge is preferably provided between the gas filter and the membrane, whereby it can be confirmed that gas is supplied to the inside of the membrane at an appropriate pressure. Further, if a pressure gauge is provided at the front stage of the gas filter, the differential pressure of the gas filter can be detected, and the clogging of the gas filter itself can be monitored.

  As another measure, the membrane bioreactor according to the present invention is a membrane bioreactor in which a gas is supplied to the inside of the membrane and a liquid is supplied to the outside of the membrane. And at least the mass flow controller was installed in the front | former stage of the said film | membrane. Here, the mass flow controller is a controller that can produce the same flow rate by its own control even if there is a pressure fluctuation within a certain range. Since the gas supply amount to the membrane is maintained at a substantially constant optimum flow rate, a long-term stable processing performance can be obtained.

  The structure in which the gas filter is provided and the structure in which the mass flow controller is provided can also be applied in combination. That is, the membrane bioreactor according to the present invention is a membrane bioreactor in which a gas is supplied to the inside of the membrane and a liquid is supplied to the outside of the membrane. In addition, a gas filter and a mass flow controller having a pore diameter smaller than that of the membrane are installed.

  As the membrane in the present invention, it is possible to use a membrane other than a hollow fiber membrane such as a flat membrane, but a hollow fiber membrane is used in order to efficiently form and treat a biological membrane on a membrane surface in a wide area. It is preferable.

  The liquid processing method according to the present invention comprises a method characterized in that a liquid is processed using such a membrane bioreactor.

  In the membrane type bioreactor and the liquid processing method using the membrane bioreactor according to the present invention, the gas filter is provided to remove foreign matters that cause clogging of the membrane in advance, or a mass flow controller is provided to the membrane. By maintaining a stable and optimal flow rate of gas, or by combining them, MABR achieves an overwhelming (5 to 10 times) high load and energy saving compared to conventional biological treatment equipment. Stable long-term operation is possible.

  The present invention can be used not only for a normal aerobic BOD treatment that requires oxygen, but also for nitrification treatment, denitrification treatment under anaerobic conditions, anaerobic treatment, etc., and is very useful. It is an invention. The gas to be supplied is air or oxygen if aerobic, inert gas such as nitrogen if anaerobic, and methane-utilizing bacteria, hydrogen-utilizing bacteria, etc. Methane gas or hydrogen gas can be used. The present invention is not limited to the fields of wastewater treatment and sewage treatment, but can also be applied to bioreactors for producing useful substances using microorganisms.

  As described above, according to the present invention, it is possible to solve the problems of the stability of the gas supply capability and the stability of the processing performance in the long-term operation, which has been a problem in the conventional MABR. By solving this problem, stable high-load operation becomes possible, and the practical application of MABR becomes possible. In particular, in a factory that treats wastewater with a relatively high concentration, or in a facility with a large aeration power cost such as a sewage treatment plant, it is possible to perform high load operation while suppressing the aeration power cost to about 1/10. It is possible, and there is a possibility that the biological treatment of the waste water treatment system can be fundamentally changed, and the practical value of the present invention is extremely high.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a membrane bioreactor 1 according to a first embodiment of the present invention. A large number of hollow fiber membranes 2 are provided in the membrane-type bioreactor 1, and the hollow fiber membrane 2 includes, for example, a dead-end type (having a tip of 0.1 μm pore size) of a hydrophilic polysulfone membrane (for example, a pore diameter of 0.1 μm). Are used). For example, air or oxygen is supplied into the hollow fiber membrane 2 by using a compressor 3 as a gas supply means. In this gas supply system, between the hollow fiber membrane 2 and the compressor 3, in order from the compressor 3 side, a first pressure gauge 4, a gas filter 5 having a pore diameter smaller than the hollow fiber membrane 2, a gas dryer 6, a pressure reducing valve 7, A second pressure gauge 8 and a gas flow meter 9 are provided. The liquid to be processed, which is supplied from the stock solution tank 10 to the processing tank 12 by the pump 11, is processed in the membrane bioreactor 1 and then discharged as the processing liquid 13. You may circulate the to-be-processed liquid in the processing tank 12 as needed.

  FIG. 2 shows a membrane bioreactor 21 according to the second embodiment of the present invention. In this embodiment, a pressure gauge 22, a gas dryer 23, a pressure reducing valve 24, and a mass flow controller 25 are provided between the hollow fiber membrane 2 and the compressor 3 in this order from the compressor 3 side. Other configurations are the same as those in the first embodiment.

  FIG. 3 shows a membrane bioreactor 31 according to a third embodiment of the present invention. In the present embodiment, a mass flow controller 25 is provided in place of the gas flow meter 9 in the structure shown in FIG. 1, and the first embodiment and the second embodiment are substantially combined.

  FIG. 4 shows a conventional membrane bioreactor 41 for comparison, but neither a gas filter nor a mass flow controller is provided as compared with the membrane bioreactor of FIGS.

  As the hollow fiber membrane of the bioreactor used in the present invention, various porous membranes having a pore diameter of 0.01 to 3 μm, preferably about 0.1 to 1 μm (porous membranes such as polypropylene, polyethylene, polysulfone, polyvinylidene fluoride, Teflon, and silicon) Can be used. Furthermore, it is preferable that the membrane surface is hydrophilized to increase the affinity with microorganisms. The gas supply into the hollow fiber membrane is preferably supplied by a compressor as shown in the figure that can increase the gas partial pressure in order to increase the dissolved gas concentration, or by a high-pressure cylinder. However, if the gas supply pressure is too high, bubbles are generated and the pressure resistance of the membrane is also present, so it is preferable to supply at about 0.01 to 1 MPa, preferably about 0.03 to 0.3 MPa.

  As the gas filter used in the present invention, an ordinary air filter, or what is called an air transformer or an air control set can be used as long as it can remove fine particles in the gas, and is usually commercially available. An air filter, a micro mist filter, an activated carbon filter, an air transformer in which an air cleaner and a pressure reducing valve are integrated, an air control set in which a pressure reducing valve and an air filter, an air cleaner are set, or the like can be used. Further, the compressor to be used is more preferably oil-free.

  Moreover, as a mass flow controller used for this invention, the commercially available thing for gas can be used. Such an air filter and a mass flow controller are installed after the gas supply means and before the hollow fiber.

Example 1
The device shown in FIG. 1 was used, and a hydrophilic polysulfone membrane (pore diameter 0.1 μm) dead-end type (tip bonded) was used for the hollow fiber membrane. Air was supplied to the inside of the membrane at 0.2 MPa using a compressor, and air was supplied to the outside of the membrane using an air pump. A pressure reducing valve, an air filter, and a flow meter were installed between the hollow fiber membrane and the compressor to remove the solid matter derived from the supply gas and to monitor the gas flow rate. For the air filter, a micro mist filter capable of removing oils and solids of 0.01 μm or more was installed, and an air dryer, a pressure reducing valve, and a flow meter were installed in the subsequent stage. As a result, although a decrease in gas flow rate is usually observed in operation for 3 months or more, in this example, a decrease in gas flow rate was not observed, and stable operation was possible.

  When the differential pressure between the first pressure gauge and the second pressure gauge rises from the initial setting, it is possible to maintain and manage the filter without changing the membrane of the reactor body by cleaning or replacing the filter.

Example 2
The device shown in FIG. 2 was used, and a dead-end type (tip bonded) of a hydrophilic polysulfone membrane (pore diameter: 0.1 μm) was used as the hollow fiber membrane. Air was supplied to the inside of the membrane at 0.2 MPa using a compressor, and air was supplied to the outside of the membrane using an air pump. A mass flow controller was installed between the hollow fiber membrane and the compressor. By this example, the gas flow set in advance can be maintained without any decrease in gas flow after 3 months without being affected by clogging of the membrane or fluctuations in gas pressure on the supply side, enabling stable operation. Met.

1 is a schematic configuration diagram of a membrane bioreactor according to a first embodiment of the present invention. It is a schematic block diagram of the membrane type bioreactor which concerns on 2nd embodiment of this invention. It is a schematic block diagram of the membrane type bioreactor which concerns on 3rd embodiment of this invention. It is a schematic block diagram of the conventional membrane type bioreactor.

Explanation of symbols

1, 21, 31 Membrane type bioreactor according to the present invention 2 Hollow fiber membrane 3 Compressor 4 First pressure gauge 5 Gas filter 6 Gas dryer 7 Pressure reducing valve 8 Second pressure gauge 9 Gas flow meter 10 Stock solution tank 11 Pump 12 Treatment tank 13 Treatment liquid 22 Pressure gauge 23 Gas dryer 24 Pressure reducing valve 25 Mass flow controller 41 Conventional membrane type bioreactor

Claims (6)

  In a membrane bioreactor in which a gas is supplied to the inside of the membrane and a liquid is supplied to the outside of the membrane, a gas filter having a pore diameter smaller than at least the membrane is provided at the rear stage of the gas supply means and at the front stage of the membrane. A membrane bioreactor that is installed.   The membrane bioreactor according to claim 1, wherein a pressure gauge is provided between the gas filter and the membrane.   In a membrane bioreactor in which a gas is supplied to the inside of the membrane and a liquid is supplied to the outside of the membrane, at least a mass flow controller is installed in the subsequent stage of the gas supply means and in the previous stage of the membrane. Membrane bioreactor.   In a membrane-type bioreactor in which a gas is supplied to the inside of the membrane and a liquid is supplied to the outside of the membrane, a gas having a pore diameter smaller than that of the membrane at least after the gas supply means and before the membrane A membrane bioreactor, which is equipped with a filter and a mass flow controller.   The membrane bioreactor according to any one of claims 1 to 4, wherein the membrane comprises a hollow fiber membrane.   A liquid treatment method, comprising treating a liquid using the membrane bioreactor according to claim 1.

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