JPH04131182A - Biological treating device for organic polluted water - Google Patents

Abstract

PURPOSE:To permit a chemical washing to be effected with a membrane module set in a treating chamber by forming the structure of a treating tank of a treating tank, a membrane module immersed in the treating device, a filter means for passing a liq. from the outer surface of the membrane into the interior thereof and a washing means for force feeding a cleaning solution into the membrane. CONSTITUTION:To effect a chemical washing, a liq. is force fed by a pump 11 from a membrane cleaning solution tank 10 into a hollow fiber modulus 4 with a hollow fiber membrane immersed in a treating tank 2. The membrane cleaning solution runs through a filter liq. collecting part 5 into the individual hollow fibers and passes from the interior of the hollow membrane to the outer surface thereof. At this time, the contaminants adsorbed on the outer surface of the hollow fiber membrane come in contact with the cleaning solution, reacts chemically therewith and is separated and removed therefrom. This method permits the contaminants on the outer surface of the membrane to be washed off effectively with the hollow fiber membrane immersed in the treating tank.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for biologically treating organic wastewater using microorganisms such as activated sludge.

[Conventional technology]

Conventionally, ceramic membranes or hollow fiber membranes are directly immersed in the aeration tank of the activated sludge treatment process, and the turbulence generated by the aeration air applies shear flow to the outer surface of the membrane, while the membrane permeate is sucked in by a pump. There are well-known methods for obtaining treated water.

However, when the present inventor tested this conventional device, it was found that the turbulent flow caused by aeration was sufficient to prevent contamination of the outer membrane surface, and gradually FluX (membrane permeation flux)
It turns out that there is a major drawback in that the temperature decreases.

Therefore, in order to sufficiently prevent membrane contamination (fouling), it is necessary to periodically remove contaminants from the membrane surface using a cleaning agent such as NaCl0, or conventional equipment requires the membrane module to be placed in an aeration tank during chemical cleaning. They had to take it out, wash it with chemicals, and then immerse it in the aeration tank again, a complicated and troublesome process.

It is safe to say that such work can be easily carried out using experimental equipment, but it is extremely troublesome and almost impossible to carry out on an actual scale.

[Invention or problem to be solved]

The present invention aims to solve the drawbacks of such conventional devices, and provides a device configured to perform effective chemical cleaning while the membrane module is installed in the aeration tank. .

[Means to solve the problem]

The present invention provides a biological treatment tank for biologically purifying organic sewage, a membrane module consisting of a hollow fiber membrane or a ceramic membrane immersed in the treatment tank, and a liquid flowing from the outer surface of the membrane into the inside of the membrane. There is a biological treatment device characterized by comprising a filtration means for permeating the membrane, and a cleaning means for pressurizing a cleaning solution into the membrane for cleaning membrane contamination, thereby solving the above problem. Solvable.

The present invention provides a device that more effectively cleans membrane contamination in a biological treatment device that performs biological treatment and filtration treatment in parallel, while the membrane module used for the filtration treatment remains installed inside the device without taking it out of the system. It is characterized by the following:

That is, the present invention aims to improve the membrane outer surface, that is, the side of the membrane that comes into contact with the treatment tank liquid (therefore, the inside of the membrane does not come into contact with the treatment tank liquid) as biological treatment and activated sludge filtration treatment progresses. The membrane permeation flux decreases due to contaminants attached to the membrane (pointing to the side). At this time, is it necessary to clean the membrane? In the present invention, with the membrane moneur as it is, the filtration pump is stopped and the cleaning solution is pumped into the membrane using the cleaning pump, and the cleaning solution is injected from the inside of the membrane to the outside. By moving the membrane and providing turbulent flow to the liquid in the processing tank by aeration from an air diffuser if necessary, contaminants such as SS and slime attached to the membrane are peeled off and removed.

In this case, since the membrane module is an external pressure type, the filtration means is provided so that a pressure difference is generated between the membrane and the liquid in the processing tank so that the liquid moves from the outside of the membrane to the inside of the membrane, and its arrangement is arbitrary. be. For example, the treated water may be discharged by using a pump inside the membrane and/or by using a water level difference.

Further, the cleaning means for cleaning the membrane may be configured to pump and pressurize the cleaning solution so that the liquid moves in the opposite direction to the filtration process.

Further, in the present invention, when cleaning solution remains in the membrane module after membrane cleaning is completed, it can be sucked out by a pump and collected into a cleaning agent solution storage tank.

In the present invention, the injection of the detergent solution is carried out in an amount of -1 to 5
kgf/cm2, preferably 1-2 kgf/cm2
The pressure is selected from the range of 10 to 30 minutes.

In this case, the above value is adjusted as appropriate depending on the type of contaminant (ie, the type of raw water), the membrane pore diameter, etc.

As the detergent solution used in the present invention, an aqueous solution adjusted to a predetermined concentration of a known drug may be used, or membrane cleaning may be used in combination with cleaning with a detergent solution and simple water.

For example, when NaC10 is used as a cleaning agent, the solution concentration is 0.03 to 1% by weight, preferably 0.03 to 1% by weight.
It is 0.05% by weight. In addition, the processing tank capacity is
When cleaning a membrane module surface area of 200rd, the cleaning solution can be used for 100 to 200 hours, and the membrane can be thoroughly cleaned. This is because the amount of the cleaning agent that adversely affects microorganisms is 200 g/rn' or more, so the present invention is a very effective cleaning method that can sufficiently clean the membrane and does not adversely affect microorganisms. Recognize.

If the treatment tank of the present invention uses air during cleaning, it may be convenient to use a type of aerobic biological treatment tank, but there are no particular limitations on whether the treatment tank is aerobic or anaerobic in its microbial treatment.

In the present invention, in order to ensure anaerobic properties through membrane cleaning, a gas such as nitrogen may be used in the aeration device. Further, the specific arrangement of the air diffuser in the tank is not particularly limited, and it may be configured so that the above function can be achieved, or at least,
It is preferable that the membrane module be arranged so that aeration comes from the bottom.

Therefore, in the present invention, there are no particular limitations on the type and level of the organic wastewater that can be introduced into the treatment tank and subjected to biological treatment. In this case, the organic wastewater may be one that has not been subjected to biological treatment or may contain activated sludge that has been subjected to biological treatment. Therefore, the present invention can include any other biological treatment tank or a known treatment tank other than the biological treatment tank before and/or after the biological treatment tank. The treated water and/or activated sludge slurry that has been filtered by the membrane module can be introduced into these other treatment tanks.

In the case of these other treatment tanks or biological treatment tanks, the biological treatment conditions may be aerobic or anaerobic.

In addition, the biological treatment tank of the present invention partitions the space where the membrane module is present and other spaces with a partition wall, and the space where the membrane module is present and the space where it is not present are separated from each other by the same or different microbial growth. It can also function as a biological treatment tank.

For those who still have membrane modules even if they are separated under the same growth conditions,
The filtration function is prioritized over biological treatment, and the one that does not exist is exclusively for biological treatment. In addition, in the case of different growth conditions, for example, the space where the membrane module is present can be used as an aerobic nitrification part that nitrifies ammonia nitrogen components, and the space where it is not present can be used as an anaerobic denitrification part. Denitrification can be carried out by flowing the NO and -N solutions nitrified in the nitrification section.

By partitioning the biological treatment tank with partition walls as described above, the functions of each space are separated, allowing for more efficient and space-saving biological treatment. In this case, the activated sludge slurry and/or membrane permeate water may be circulated between the spaces through the partition walls and/or the pipes.

The present invention can include a discharge device for discharging membrane contaminants exfoliated by membrane module cleaning to the outside of the system, and a discharge device for discharging unnecessary activated sludge used in a biological treatment tank.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to FIG. 1, and the structure and operation of the present invention will be explained using an example using a hollow fiber membrane.

1 is an inlet for organic wastewater such as sewage, 2 is an activated sludge treatment tank, and 3 is an air diffuser.

The hollow fiber membrane module 4 is suspended or immersed in the upper part of the air diffusion member, and is arranged so that the turbulent flow caused by the diffused air reaches the surface of the hollow fiber membrane. The hollow fiber membrane module 4 has an extremely large number of hollow fibers bundled together, and the activated sludge SS is membrane-separated on the outer surface of the hollow fibers.
The liquid that has permeated into the interior of the single hollow fiber collects in the filtrate collecting section 5, and is sucked by the suction pump 6 to obtain clarified treated water 7 from which SS has been completely removed.

Since the surface of the hollow fiber membrane is subjected to intense turbulence due to aeration air, the degree of activated sludge adhesion is reduced and a stable membrane permeation flux can be obtained for a long period of time.

However, after a long period of time, some membrane contaminants (
It is assumed that the main substance is biopolymers such as proteins secreted from activated sludge. ) or mainly adsorbed on the surface of the hollow fiber membrane,
The membrane permeation flux decreases significantly.

Therefore, in the past, the entire hollow fiber membrane module was taken out of the activated sludge treatment tank 2, immersed in a solution of membrane cleaning agents such as NaOH, HCI, NaC10, etc. to chemically remove membrane contaminants, and then put back into the treatment tank. It was necessary to immerse it in water and restart operation. However, even if such work can be carried out on an experimental scale, it is extremely troublesome and difficult to carry out on an actual machine.

The present invention can completely solve these drawbacks with the following new configuration.

That is, when chemical cleaning is to be performed, the valve 8 is closed while the hollow fiber membrane is immersed in the treatment tank, the pump 6 is stopped, the valve 9 is opened, and the liquid in the membrane cleaning side solution storage tank 10 is transferred to the hollow fiber by the pump 11. Press fit into the membrane module. The membrane cleaning agent solution flows into each hollow fiber through the filtrate collection section 5,
It permeates from the inside of the hollow fiber membrane toward the outside surface. At this time, it was confirmed that the contaminants adsorbed on the outer surface of the hollow fiber membrane come into contact with the cleaning agent, causing a chemical change and making it easier to peel off and be removed.

The time required to press in the membrane cleaning solution (usually 10 to 30 ml)
It is enough. ) while performing aeration using the air diffuser 3, the membrane contamination-causing substances (substances that cause a decrease in membrane permeation flux) that were firmly adsorbed on the outer surface of the hollow fiber membrane are removed, and the membrane permeation flux is reduced. or recover.

It was also confirmed that the membrane cleaning agent that seeped into the activated sludge treatment tank from the outer surface of the hollow fiber membrane had no adverse effect on the activity of the activated sludge.

After closing the valve 9 and stopping the pressure bomb 11,
After opening the valve 8, driving the suction pump 6, closing the valve 12, and opening the valve 13 to return the cleaning agent remaining in the hollow fiber membrane to the membrane cleaning agent solution storage tank 10, open the valve 3. Close the valve 12 and open the valve 12 to obtain the treated water 7.

Due to the above-described action, contaminants on the outer surface of the hollow fiber membrane can be very effectively cleaned while the hollow fiber membrane remains immersed in the treatment tank 2. Incidentally, it is also possible to perform the same process with a ceramic film.

In addition, a partition wall 14 is provided in the activated sludge treatment tank 2, and a valve 15 is closed, so that the space on the left side of the partition wall where no hollow fiber membrane exists becomes a denitrification section, and the space on the right side becomes a digestion section. I can do something. In this case, the partition wall may be provided so that the denitrification section and the nitrification section are partially in communication, or may be completely separated.
Even if the activated sludge is allowed to move naturally between the denitrification section and the nitrification section, the activated sludge and/or nitrification section can be moved by installing appropriate pipes, valves, pumps, etc. between the denitrification section and the nitrification section. The movement of the nitrification solution treated with the hollow fiber membrane may be controlled.

〔Effect of the invention〕

■ Without taking out the membrane module from the biological treatment tank,
Chemical cleaning is possible, greatly improving workability.

(2) By combining the chemical cleaning of the present invention with the method of applying turbulent flow to the membrane surface by aeration, the membrane permeation flux can be maintained at a stable and high value semi-permanently.

■ By partitioning the biological treatment tank, nitrification and denitrification can be performed in a space-saving manner.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining one specific embodiment of the apparatus of the present invention. Explanation of symbols 1・Inflow part 2: Activated sludge treatment tank 3: Air diffuser 4: Hollow fiber membrane module 5, filtrate collection part 6 Suction pump 7: Clarified treated water 8: Valve 9: Valve lO: Membrane cleaning agent Solution storage tank 11 Pump 12/Valve 13/Valve 14: Bulkhead 15 Valve Attorney (8107) Kiyotaka Sasaki (and 3 others)

Claims (1)

[Claims] (1) A biological treatment tank that biologically purifies organic wastewater;
A membrane module consisting of a hollow fiber membrane or a ceramic membrane immersed in the treatment tank, a filtration means for permeating a liquid from the outer surface of the membrane into the inside of the membrane, and cleaning membrane contamination from the inside of the membrane. and cleaning means for pressurizing a cleaning solution for cleaning.