JPH0683831B2 - Sewage treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sewage treatment method for purifying urban sewage or industrial wastewater by aerobic organisms.

(Prior art) Generally, in aerobic sewage treatment methods such as the activated sludge method and contact aeration method, a precipitation tank is installed after the reaction tank to separate solid and liquid to obtain clear treated water. ing.

In recent years, there has been known a treatment method that can reliably obtain treated water with extremely high clarity by using a membrane filtration device using a polymer membrane such as microfiltration or ultrafiltration instead of a settling tank.

Further, as described in JP-B-48-40971 or JP-A-62-68599, a circulation path for circulating water to be treated to a membrane filtration device is formed, and a treatment object circulating in the circulation path is formed. Methods of filtering water are known.

(Problems to be Solved by the Invention) One of the main problems of the treatment method using the membrane filtration device as described above is that the energy required for separation is large,
In order to prevent particles such as suspended solids and colloids from accumulating on the surface of the separation membrane and significantly reducing the filtration rate, the separation liquid must always be filtered while continuously flowing the separation liquid at a very high flow rate. However, there is a problem that a large amount of energy is consumed as a result.

In addition, in order to treat the water to be treated, a circulation path for filtration must be formed separately from the circulation flow for contacting,
There is a problem in that the cost is low, the operating cost is high, and the device is large and expensive.

The present invention has been made in view of the above-mentioned problems, and the water to be treated is filtered by using a circulating flow for contacting, and the energy required for membrane filtration is reduced to achieve high clarity by membrane filtration. It is intended to provide a sewage treatment method for obtaining treated water.

(Means for Solving the Problem) The sewage treatment method of the invention of claim 1 is a method for treating treated water introduced into a contact aeration tank provided with a dipping hearth to which microorganisms adhere, Of the draft tube provided below the water surface of the draft tube is circulated by the upward flow in the draft tube and the downward flow of the immersion hearth by the air lift action generated by the diffuser. A method for treating sewage by contact oxidation, in which the water to be treated that has been contact-oxidized by passing through the submerged filter bed flows into the draft tube at a high speed as an upward flow due to the air lift action, The treated water is filtered by a filtration membrane of a membrane filtration device provided, and the filtered treated water is led out of the contact aeration tank by a treated water pipe provided in the draft tube.

The sewage treatment method according to claim 2, wherein the water to be treated introduced into the contact aeration tank provided with an immersion hearth to which microorganisms adhere is
From the circulation pipe connected to the upper part of the contact aeration tank by a liquid pump, flow through the draft tube provided with the upper end protruding to the water surface to the contact aeration tank to the bottom of the dipping hearth, and to the draft tube. A sewage treatment method in which water to be treated is circulated in a dipping hearth while being contact-oxidized by air sucked from a connected air suction pipe, and is filtered by a filtration membrane of a membrane filtration device provided in the middle of the circulation pipe. The treated water is led out of the contact aeration tank by a treated water pipe connected to a membrane filtration device.

(Operation) In the sewage treatment method of the invention according to claim 1, in the treated water, the sludge substance is filtered by the submerged hearth filled with the contact filter medium to which microorganisms adhere due to the air lift action generated in the draft tube, and the water is oxidized by the microorganisms. Circulates while being decomposed. The treated water is filtered by the filtration membrane of the membrane filtration device provided in the draft tube in the middle of this circulation, and a filtration circulation path for the treated water is not required to filter the treated water.
Most of the contaminants are removed by the immersion hearth, and the water to be treated flowing through the draft tube is a high-speed flow, so the treated water that has passed through the membrane surface of the membrane filtration device and washed the membrane surface and has permeated the membrane. Is discharged from the treated water pipe to the outside of the tank.

In the sewage treatment method of the invention of claim 2, when the water to be treated passes through a draft tube connected to an air suction pipe by a liquid pump, air is sucked in to be circulated in the submerged filter bed and passed through the submerged filter bed. While the water to be circulated while being oxidatively decomposed is filtered by the filtration membrane of the membrane filtration device in the course of this circulation, a circulation path for the filtration treatment is not required, and most of the pollutants by the immersion hearth In addition, the high-speed flow of the water to be treated flowing through the circulation pipe connected to the draft tube flows through the membrane surface of the filtration membrane of the membrane filtration device to wash the membrane surface, and the treated water that has passed through the filtration membrane is It is discharged from the contact tank.

(Example) An example of the sewage treatment method of the present invention will be described with respect to the sewage treatment apparatus shown in FIG.

Reference numeral 1 is a contact aeration tank, in which a draft tube 2 having upper and lower open surfaces opened in the water to be treated is erected upright, and an immersion hearth 3 filled with a contact filter medium on which microorganisms adhere is provided around the draft tube 2. Has been formed.

An air diffuser 4 for feeding air into the draft tube 2
An air diffusing portion communicating with each other, that is, an air diffusing head 5 is provided. Further, a membrane filtration device 6 having a filtration membrane is inserted into the draft tube 2 located below the air diffuser.

Further, the membrane filtration device 6 is composed of a hollow closed body formed of a filtration membrane made of a permeation membrane, and the treated water pipe 7 is communicated with the membrane filtration device 6, and the treated water pipe 7 is drawn out from the draft tube 2 and brought into contact therewith. It is led to the outside of the air tank 1.

Next, an example of a sewage treatment method implemented by this sewage treatment apparatus will be described.

When the water to be treated is introduced into the contact aeration tank 1 and the air is introduced into the draft tube 2 from the air diffusing head 5 of the air diffuser 4, the water to be treated rises in the draft tube 2 due to the air lift action. A countercurrent is generated, flows out from the upper end of the draft tube 2 and is flowed to the upper side of the immersion hearth 3 filled with the contact filter medium on which the microorganisms are adhered, and the water to be treated becomes a downward flow while filtering the immersion hearth 3. It flows, is contact-oxidized, rises again from the lower end of the draft tube 2, and circulates in the contact aeration tank 1 while contact-oxidizing.

Further, the membrane filtration device 6 in the draft tube 2 is constantly washed with the water to be treated flowing at a high speed on the surface, so that the floating residue of the filtration residue in the immersion hearth 3 and the pollutants such as colloids do not adhere to the surface. The filtration action of the filtration membrane effectively proceeds. The clear treated water that has penetrated into the membrane filtration device 6 is discharged to the outside by the treated water pipe 7.

Next, the second embodiment of the sewage treatment apparatus for carrying out another embodiment of the present invention
It will be described with reference to the drawings.

The upper end of the draft tube 2 arranged in the contact aeration tank 1 is projected above the water surface of the contact aeration tank 1, and the contact tube 1 is located above the immersion hearth 3 above the water surface. A circulation pipe 9 having a liquid pump 8 in the middle is communicated downward.

Further, the circulation pipe 9 is communicated with the draft tube 2 protruding above the contact aeration tank 1.
A large diameter portion 10 is formed in the middle of the circulation pipe 9 located between the liquid pump 8 and the draft tube 2,
A membrane filtration device 6 is inserted into the large-diameter portion 10, and the membrane filtration device 6 is composed of a hollow closed body formed of a permeation membrane filtration membrane, and the treated water pipe 7 is connected to the membrane filtration device 6. ing.

Further, an air suction pipe 11 is axially inserted from the upper end opening of the draft tube 2, and the tip of the air suction pipe 11 is opened in a nozzle shape slightly below the opening 12 of the circulation pipe 9. .

Next, another embodiment of the present invention will be described using this sewage treatment apparatus.

The water to be treated introduced into the contact aeration tank 1 is the immersion hearth 3
Is fed from the upper part of the liquid pump 8 by the liquid pump 8 to the upper part of the draft tube 2 by the circulation pipe 9, and the draft tube 2 is flowed down and discharged to the lower part of the dipping hearth 3 to be filled with a contact filter medium to which microorganisms adhere. Floating pollutants in the water to be treated are filtered from the floor 3, rise as they are oxidatively decomposed by microorganisms, and are sucked up again from above the immersion furnace floor 3 by the liquid pump 8 and introduced into the draft tube 2 for circulation.

The tip nozzle-shaped opening of the air inflow pipe 11 inserted into the upper portion of the draft tube 2 is
A negative pressure is generated by the descending water flow and the air is sucked, and the air is forcibly supplied to the water to be treated in the draft tube 2 for oxidative decomposition by the microorganisms.

Further, the clarified treated water that has penetrated into the membrane filtration device 6 by the osmotic pressure is drawn out of the contact aeration tank 1 by the treated water pipe 7.

Further, since the membrane filtration device 6 is located in the large diameter portion 10 of the circulation pipe 9 through which the water to be treated is fed at a high speed by the liquid pump 8, the outer surface of the permeation membrane is washed away, and the filtration residue on the immersion hearth 3 floats. The attachment of pollutants such as objects and colloids is prevented.

Next, as shown in FIG. 3, the membrane filtration device 6 shown in FIG. 2 is inserted by inserting both ends of the membrane filtration device 6 in the middle of the circulation pipe 9 through which the water to be treated is forced to flow. Then, the treated water pipe 7 can be led out from the outer casing 13 that hermetically surrounds the membrane filtration device 6.

In the membrane filtration device 6 shown in FIG. 3, the treated water that has been permeated and filtered permeates the outer surface of the membrane filtration device 6, and the treated water that has accumulated in the outer casing 13 is led out by the treated water pipe 7.

(Effect of the invention) According to the invention of claim 1, the water to be treated is circulated by the draft tube which is forced to flow by the air lift, and the pollutants floating in the water to be treated are filtered through the immersion hearth and contacted. It circulates while being oxidatively decomposed by the microorganisms adhering to the filter medium, and a membrane filtration device is installed at a position where the water to be treated circulates at a high speed in the middle of the circulation, so that the membrane filtration device is always in the water to be treated which has a speed. Since it is exposed, the contact surface with the water to be treated is washed away to prevent floating substances and colloids from adhering to the surface of the filtration membrane, and the filtration effect can be enhanced. In addition, there is no need to form a separate circulation path for membrane filtration, and no additional energy is required to flow the high-speed separated water for cleaning the membrane filtration device, so there is no operating cost and it is economical. This is advantageous, and the entire device can be downsized.

According to the second aspect of the present invention, the water to be treated is circulated by the circulation pipe forcibly fed by the liquid pump, the pollutants floating in the water to be treated are filtered through the immersion hearth, and adhered to the contact filter medium. Circulates while being oxidatively decomposed by
During the circulation, the water to be treated is filtered by the membrane filtration device at a high-speed position, so the membrane filtration device is constantly exposed to the water to be treated, and the contact surface with the water to be treated is washed away. It is possible to prevent floating substances and colloids from adhering to the surface of the filtration membrane and enhance the filtration effect. Also,
There is no need to form a separate circulation path for membrane filtration, and there is no need for additional energy for flowing the high-speed separated water for cleaning the membrane filtration device, so operating costs are low.
It is economically advantageous, and the entire device can be downsized.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a sewage treatment apparatus for carrying out the sewage treatment method of the present invention, FIG. 2 is a vertical sectional view of another sewage treatment apparatus for carrying out the sewage treatment method of the present invention, and FIG. It is a longitudinal cross-sectional view of a part of a circulation pipe showing another embodiment of the membrane filtration device shown in the figure. 1 ... contact air tank, 2 ... draft tube, 6 ...
... Membrane filter, 7 ... Treatment water pipe, 8 ... Liquid pump, 9 ...
… Circulation pipe.

Claims (2)

[Claims] 1. The water to be treated introduced into a contact aeration tank provided with a submerged bed to which microorganisms adhere is disposed inside a draft tube provided below the water surface of the contact aeration tank. A sewage treatment method of contact oxidation by circulating by the upward flow in the draft tube and the downward flow of the submerged bed by the air lift action generated by the air diffused from the air diffuser which passes through the submerged filter bed. When the water to be treated that has been contact-oxidized by the draft tube flows upward at a high speed due to the air lift action, it is filtered by the filtration membrane of the membrane filtration device arranged in the draft tube, and this filtered water is filtered. The treated water is discharged to the outside of the contact aeration tank by means of a treated water pipe arranged in the draft tube. 2. The contact aeration through a circulation pipe in which water to be treated introduced into a contact aeration tank provided with an immersion bed to which microorganisms adhere is communicated to the upper part of the contact aeration tank by a liquid pump. Sewage that circulates the water to be treated while flowing through the draft tube provided with the upper end protruding to the water surface below the immersion bed, and causing the treated water to circulate through the immersion bed while being contact-oxidized by the air sucked from the air suction pipe connected to the draft tube. A treatment method, wherein treated water filtered by a filtration membrane of a membrane filtration device provided in the middle of the circulation pipe is led out of the contact aeration tank by a treatment water pipe connected to the membrane filtration device. Sewage treatment method.