JPH06285496A - Hollow fiber membrane separation biological treatment and device for organic drainage - Google Patents

Abstract

PURPOSE:To prevent the adhesion and solidification and press densification of sludge to membrane, keep the surface clean at all times and eliminate the necessity of maintenance work by coexisting biological granular solids in an aeration tank, keeping the solids in the suspension flowing state by aeration and discharing treated water through a hollow fiber membrane. CONSTITUTION:In the hollow fiber membrane separation biological treatment method, urethane foam square grains A, the gravity of which is almost equal to that of water, are fed into an aeration tank 1, and microbes such as BOD utilized bacteria are carried on microbe carriers composed of the grains A. Also water to be treated in the tank 1 is disturbed by diffused air exhausted from an air blower 7 through an air diffusion pipe 6, and the grains A are suspension flowed by the turbulence generated by the diffused air. A membrane module 2 fitted with hollow fiber membrane is immersed in the tank 1, and the water treated biologically in the tank 1 is sucked by a pump 4, passed through the membrane module 2, filtered by the hollow fiber membrane fitted thereon and flowed out of a treated water outflow pipe 3 in the form of cleaing treated water 5 completely free from SS.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for highly purifying various organic wastewater such as sewage by separating microorganisms and hollow fiber membranes.

[0002]

2. Description of the Related Art Conventionally, a hollow fiber membrane membrane separation module is immersed in an aeration tank for activated sludge to remove BOD by suspended microorganisms (activated sludge flocs), and microorganisms and other SS are completely filtered and separated by the membrane. However, a technique for obtaining clarified treated water is known. However, when the present inventor has treated organic sewage such as sewage according to this conventional technique, activated sludge strongly adheres to the surface of the hollow fiber membrane or between the bundles of membranes, and the attached sludge is dehydrated. It has been recognized that there is a serious drawback of sticking more and more. It was also found that this phenomenon becomes more remarkable as the MLSS concentration of the activated sludge increases. If this happens, the filtration resistance of the membrane will increase rapidly and operation will be impossible. However, it is impossible to clean the membrane while it is immersed in the aeration tank, and the membrane module must be taken out and the sludge attached to the membrane must be removed while jetting high-pressure spray water. This work is extremely troublesome, and takes a few days when there are many membrane modules.
In practice, this is not possible.

[0003]

DISCLOSURE OF THE INVENTION The inventor of the present invention removes BOD and the like contained in organic wastewater in an aeration tank by biological treatment according to the prior art, and filters and separates suspended activated sludge with a separation membrane, Perform processing to obtain clarified treated water,
The following findings were obtained from the results of detailed examination of the causes of problems. 1) The higher the concentration of suspended activated sludge in the aeration tank,
Sludge is likely to adhere to the membrane and become compacted. 2) If the concentration of suspended activated sludge in the aeration tank is several hundred milligrams / liter or less, the adhesion of sludge to the separation membrane will be significantly reduced. The present invention completely solves the serious drawbacks of the conventional device and provides an epoch-making technique which makes it unnecessary to take out and clean the membrane. Specifically, it aims to eliminate the need for maintenance work by preventing sludge from adhering to the membrane and fixing and consolidating the membrane to establish a new technology that keeps the membrane surface clean.

[0004]

The present invention has been completed by integrating the following new ideas into the above new knowledge. That is, (1) the organic waste water is introduced into a settling tank, sludge and the like are subjected to solid-liquid separation by settling, and then supplied into the aeration tank in which the hollow fiber membrane is immersed for biological treatment and membrane separation. The liquid in the aeration tank is refluxed to the sedimentation separation step, the bioadhesive particulate solid is allowed to coexist in the aeration tank, the particulate solid is placed in a suspended fluidized state by aeration, and treated water is taken out through the hollow fiber membrane. A method for biological treatment of hollow fiber membrane separation, which is characterized in that: And (2) a settling tank for organic wastewater and an aeration tank, which has a pipe for guiding the treated water in the precipitation tank to the aeration tank and a pipe for returning the water in the aeration tank to the precipitation tank, In the aeration tank, a hollow fiber membrane solid-liquid separator for filtering water in the aeration tank is provided in addition to the aeration means, and further, biologically attached particulate solids are allowed to float and coexist in the water in the aeration tank. This is a biotreatment device for separating a thread membrane.

[0005] In the aeration tank in which the membrane separation module loaded with the hollow fiber membrane is immersed, the easily-movable microbial-immobilized carrier particles are suspended and processed for treatment to maintain a high microbial concentration in the tank. By circulating the liquid in the aeration tank to the previous settling tank, floating microorganisms can be settled and separated, and the concentration of floating microorganisms (microorganisms not attached to the carrier) can be maintained at several hundred milligrams / liter or less, and microorganisms can be fixed. When the modified carrier particles come into contact with the surface of the hollow fiber membrane, the important effect of cleaning the surface of the membrane was obtained. As a result, it was found that the activated sludge did not adhere to and consolidate on the membrane, and the work of taking the membrane out of the tank and cleaning it became unnecessary.

As the microorganism-immobilized carrier particles, those which are light and easy to flow, have a large ability to immobilize microorganisms, and have a large cleaning effect on the membrane when contacting with the membrane are preferable.
Granules satisfying these conditions include plastic carriers, minerals such as lightweight zeolite, inorganic porous carriers such as lightweight aggregate, short bundles or agglomerates of strings (fibers), or gels. Although various well-known carriers can be used as the comprehensive microbial carrier, a granular filter medium having a three-dimensional network structure having a particularly large mesh is a preferable carrier granular material.

The three-dimensional mesh-like granular filter medium is formed so as to have continuous holes from the surface to the inside, and can be manufactured by a known foaming method or the like. The material of the granular material is not particularly limited as long as it has the above properties, and known materials such as organic polymers and inorganic compounds can be used, but among them, the material itself has appropriate elasticity and strength. A material is preferable, and a urethane resin is particularly preferable. For example,
An elastic porous granular material such as polyurethane foam is prepared by foaming plastics such as urethane resin by a foaming method for forming open cells, and is used as it is or cut into a desired shape and size for use.

The shape can be square, spherical, and various other shapes, but the square is preferable. In particular, the shape is angular, and the particle size is 10 × 10 × 10 mm or a dice shape or 10
A rectangular parallelepiped of × 20 × 20 mm, a rectangular parallelepiped of 10 × 30 × 30 mm, and the like are preferable. If the particle size of the granules is too small, the cleaning ability of the surface of the separation membrane will be small, and if the particle size is too large, the amount of microorganisms immobilized will be small, and the inside of the granules will easily decompose, which is not preferable. . The specific gravity of the material is
Usually, about 0.9 to 1.2 is preferable. The porosity is 9
0% or more is preferable. The pore size, that is, the pore size is 0.1 to
It is desirable to select from the range of 6 mm, preferably 2 to 4 mm. The number of holes per 1 cm length is 5 to
20 is preferable.

As the amount to be charged into the aeration tank, when using a rectangular parallelepiped granular material made of polyurethane foam and having a particle size of 10 × 20 × 20 mm, 20 to ³⁰ V per 1 m ^{3 of} the aeration tank is used.
/ V% is appropriate, and if it is charged too much, the carrier becomes difficult to flow and the object of the present invention cannot be achieved.
On the other hand, if the amount is too small, the microbial concentration cannot be kept high. When the treatment is continued according to the present invention, microorganisms propagate, some of which are retained by the microorganism-immobilized carrier, and some of them become suspended microorganisms and float in the aeration tank. These suspended microorganisms are supplied to the settling tank in the previous stage. It is separated by sedimentation. Therefore, even if the treatment is continued for a long time, the concentration of suspended microorganisms in the aeration tank does not increase,
No trouble of sticking sludge to the hollow fiber membrane.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a typical embodiment of the present invention will be described with reference to FIG.

(Example 1) The method for producing the dephosphorizing material of the present invention will be described in detail below. 1 is the aeration tank of the present invention,
In the aeration tank 1, the urethane foam horny granular material A shown in FIG. 2 having a specific gravity almost equal to that of water is charged, and the microbial carrier composed of these granular material A is a BOD that assimilates BOD.
Microbes such as assimilating bacteria are retained. The water to be treated in the tank 1 is disturbed by the diffused air discharged from the air blower 7, which is an air source, into the aeration tank 1 through the air diffuser 6. The urethane foam horny granular material A holding the microorganisms is suspended and flows by the turbulent flow caused by the diffused air. In addition, the membrane module 2 loaded with the hollow fiber membrane is immersed in the aeration tank 1, and the treated water biologically treated in the aeration tank 1 is sucked by the pump 4 and passes through the membrane module 2, It is filtered by the membrane loaded in the membrane module 2 and passes through the treated water outflow pipe 3 to become the clarified treated water 5 of SS zero and flows out of the system.

What is shown by B in FIG. 1 is a floating microorganism floating in the water to be treated in the aeration tank 1 which is not attached to the carrier made of the polyurethane foam horny granular material A.
These floating microorganisms B are refluxed by the reflux pump 10 to the settling tank 11 through the reflux pipe 9 together with the water to be treated. Raw water such as sewage flows into the settling tank 11 from the outside through the raw water inflow pipe 8. By the reflux pump 10, the water to be treated in the aeration tank 1 is refluxed to the sedimentation tank 11 together with the suspended microorganisms B, but at this time, the particulate matter A suspended and flowing in the biologically treated water is prevented from flowing out. A large net 14 is stretched over the inlet of the discharge pipe 9. This net may be any perforated plate or slit as long as it is water permeable. Further, in FIG. 1, 12 is a settled sludge settled at the bottom of the settling tank 11, and 13 is a sludge pipe for discharging the settled sludge 12.

As a result of treating raw water such as sewage by the method of the present invention, 15
It is recognized that microorganisms having a high concentration of 000 to 20000 mg / liter are retained, and even if the concentration of suspended microorganisms is estimated as low as several hundred milligrams / liter, the raw water is highly purified. Even if the biological treatment apparatus of the present invention is continuously operated for one year, there is no problem that sludge sticks to the surface of the membrane loaded in the hollow fiber module 2 or sludge bites into the bundle of hollow fibers to rapidly increase the filtration resistance. Did not occur. Further, in the biological treatment process in the aeration tank 1 of the present invention, if raw water contains impurities such as hair and vinyl pieces,
These become entangled troubles with the granular material A and the hollow fiber module 2, but in the present invention, since the contaminants can be removed in advance in the settling tank 11, such troubles can be prevented.

Comparative Example 1 As a comparative example, the biological treatment tank 1
The concentration of suspended microorganisms in the aeration tank was 18,000 m without introducing a microbial carrier consisting of the polyurethane foam horny granular material A and without causing the treated water in the aeration tank to recirculate.
When biological treatment of raw water was carried out while maintaining g / l, sludge adhered to the surface of the hollow fiber membrane, resulting in about 15 to 2
The filtration resistance of the hollow fiber membrane increases sharply once a day, and each time the hollow fiber module 2 is removed, the sludge adhered and fixed to the hollow fiber membrane while manually loosening the hollow fiber membranes one by one. Had to wash.

[0015]

By implementing the biological treatment apparatus of the present invention and the biological treatment method using the same, the following great effects can be obtained. Since the microbial sludge does not adhere to the surface of the hollow fiber membrane, the filtration resistance of the hollow fiber module can be kept low, and it is not necessary to remove and wash the hollow fiber membrane. Therefore, maintenance of the biological treatment device is extremely easy. Since the microbial sludge can be prevented from sticking to the hollow fiber membrane even if the microbial concentration is increased, the biological reaction rate can be increased,
The biological treatment device can be made compact.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a biological treatment apparatus of the present invention.

FIG. 2 is a perspective view showing an example of a granular microbial carrier used in the biological treatment of the present invention.

[Explanation of symbols]

 1 aeration tank 2 hollow fiber membrane module 3 treated water outflow pipe 4 pump 5 treated water 6 diffuser pipe 7 air source (blower) 8 raw water supply pipe 9 treated water reflux pipe 10 reflux pump 11 sedimentation tank 12 sedimentation sludge 13 drainage pipe 14 Net A Urethane foam Horny granular material B Suspended microorganisms

Claims (2)

[Claims] 1. An organic wastewater is subjected to solid-liquid separation by sedimentation, and then fed into an aeration tank in which a hollow fiber membrane is immersed for biological treatment and membrane separation, while the liquid in the aeration tank is subjected to the sedimentation separation step. A hollow fiber membrane-separating organism characterized in that the biological solid particles are allowed to coexist in the aeration tank while being aerated, and the granular solid material is placed in a suspended fluidized state by aeration, and treated water is taken out through the hollow fiber membrane. Processing method. 2. A settling tank for organic waste water and an aeration tank, and a pipe for guiding the treated water in the precipitation tank to the aeration tank, and a pipe for returning water in the aeration tank to the precipitation tank,
In the aeration tank, a hollow fiber membrane solid-liquid separator for filtering water in the aeration tank is provided in addition to the aeration means, and further, biologically attached particulate solids are allowed to float and coexist in the water in the aeration tank. Bioreactor for thread membrane separation.