JPS6268599A - Apparatus for treating sewage - Google Patents

Abstract

PURPOSE:To enhance operating efficiency, by providing a submerged aeration tank and a membrane separation means and mounting a liquid supply system and a take-out system for taking out treated water. CONSTITUTION:A gas-liquid separation tank 8, in which the liquid in a submerged aeration tank 1 is flooded, is mounted to the outside upper part of said aeration tank 1 and a liquid falling pipe 9 is mounted together in said aeration tank 1. Raw water is supplied to the liquid falling pipe 9 from a supply pipe 11 to fall therethrough. At this time, raw water is mixed with air to dissolve oxygen and issued to the bottom part in the tank 1 from the lower end of the pipe 9 and upwardly rises while being violently stirred by rising air bubbles to be biologically treated. Then, treated water is flooded in the gas- liquid separation tank 8 and pumped up to an injector 10 from the bottom of said tank 8 by a recirculation pump 13 to flow down through the injector 10 and, during this time, mixed with air fed by a blower 15 and sucked in the injector 10 and falls through the liquid lowering pipe 9 to perform recirculation. By this method, the power reduction of the recirculation pump is achieved.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention circulates and processes sewage and human waste in a deep aeration tank, and transfers a portion of the circulating treatment liquid to a permeable membrane such as an ultrafiltration membrane or precision filtration 119. This invention relates to a sewage treatment device that performs turbidity removal, organic matter removal, and other treatments using a membrane separation L stage with a built-in membrane separation.

In recent years, due to the difficulty in securing land for treatment facilities and the demand for improved quality of effluent water, research and development has been carried out to perform membrane treatment as described above instead of treating aerated treated water in a sedimentation separation tank. has been done.

(Prior Art) Conventionally, as shown in Japanese Patent Publication No. 4B-41584, biological treatment in an aeration tank and treatment by membrane separation means have been combined as completely separate systems.

(Problems to be Solved by the Invention) For this reason, the contamination of the membrane of the membrane separation means that progresses with the passage of operating time is removed by periodic cleaning with chemicals n1, which reduces the operating efficiency of the entire apparatus.

Furthermore, since pressurization of the liquid supplied to the membrane separation means depends on the circulation pump attached to the membrane separation means, the circulation pump needs to have a large capacity, which increases both equipment costs and running costs.

(Means for Solving the Problems) Accordingly, the present invention provides a sewage treatment apparatus including a deep aeration tank having a circulation system for circulating liquid in the tank.

- Membrane separation means that incorporates a permeable membrane such as an ultrafiltration membrane or a precision filtration membrane provided near the bottom of the aeration tank, and for supplying a portion of the liquid flowing through the circulation system to the membrane separation means. a return system for returning the concentrate on the cla side of the desorption a+ stage to the deep aeration tank, and a take-out system for taking out the permeate on the permeate side of the membrane separation-L stage as treated water. It is characterized by having

(Function) The aeration tank is a deep aeration tank in which the seed crystals are about 5 to several tens of meters long, and the membrane separation stage is provided near the bottom of the tank. Since the supply system to the removal stage supplies part of the liquid from the circulation system that circulates the liquid in the deep aeration tank to the removal stage sL, the water head of the deep aeration tank is added to the removal stage 1F1 stage. It can be effectively used for pressure. The treated water that passes through the permeable membrane and is obtained on the permeate side of the membrane separation p stage is supplied to the after-treatment or advanced treatment equipment by the take-out system, and the concentrated liquid on the e-line side of the membrane separation means is sent to the deep layer in the return system. It is returned to the aeration tank and circulated in the deep aeration tank.

(Example) In each of the illustrated examples, 1 is the deep aeration tank described above, 2 is
3 is the circulation system, 3 is the membrane separation means, 3' is the permeation membrane such as the ultrafiltration membrane or microfiltration IF2, 3a is the C line side, 3b is the permeation side, and 4 is the liquid flowing through the circulation system 2. 6 is a return system that returns the e-culture solution on the e-line side of the membrane separation means to the deep aeration tank 1, and 7 is the permeation system of the membrane separation means. Transmits through the membrane 3', and the permeate side 3
b shows a take-off system for taking out the obtained permeate and supplying it to post-treatment or advanced treatment equipment.

The deep aeration tank l has a gas-liquid separation tank 8 into which the liquid inside the tank overflows into the upper part of the outside of the tank, and a downcomer pipe 9 that is installed vertically in the center of the tank and opens at the bottom.
The downcomer pipe 9 has an injector 10 for air suction and mixing at its upper end, and penetrates the tank wall of the aeration tank to a level slightly below the overflow weir 8' of the gas-liquid separation tank 8. A supply pipe 11 for raw water is connected. The bottom of the gas-liquid separation tank 8 is a pipe 12.
It is connected to the suction side of the circulation pump 13, and its discharge side is connected to the injector 10 through a pipe 14. In addition, 15 is a blower that sends air to the injector 10, and 1' is an aeration tank l.
This is a gas vent pipe provided on the upper wall that commonly closes the end of the gas/liquid #i tank 8.

As a result, the raw water is supplied from the supply pipe 11 to the downcomer pipe 9 and descends inside the pipe 9. At this time, as will be described later, the raw water is mixed with air and dissolves the # element, which flows from the end of the pipe 9 to the bottom of the tank. While vigorously agitated by the rising air bubbles, the liquid flows countercurrently over the entire cross section of the tank for biological treatment, then overflows into the gas-liquid S tank 8, flows from the bottom to the circulation pump 13, and is pumped into the injector 10. When the liquid is pumped and flows through the injector 10, air blown by the blower 15 is sucked and mixed, and the liquid descends through the downcomer pipe 9 to perform circulation. The circulatory system 2 therefore includes a downcomer pipe 9 in each of the illustrated embodiments.
, deep aeration tank 1, gas-liquid separation S tank 8, piping 12) circulation pump 13, piping 14, and injector 10.

In the first embodiment shown in FIG. 1.2, a plurality of membrane separation means 3 are arranged near the outer bottom of the deep aeration tank 1, whereas in the second embodiment shown in FIG. The only difference is that 3 is incorporated into the bottom of the deep aeration tank 1, and the relationship between the deep aeration tank and the membrane separation means is exactly the same.

That is, a part of the liquid discharged from the circulation pump 13 is guided to the cyclone 16 by the supply system 4, where floating sludge and foreign matter are separated and discharged out of the system as return sludge.
The liquid exiting the cyclone 18 is then supplied to the injector 17, where it sucks and mixes air from the blower 18 and the air supply system 5, and then is supplied to the concentration side 3a of each membrane separation means 3 through a pipe 19. be done. Then, the permeate v3' that has come out on the permeate side 3b is supplied to a post-processing or advanced treatment device by the take-out system 7, and the e-culture liquid that does not pass through the permeable membrane 3' is on the e-line side 3.
A is returned to the bottom of the aeration tank 1 through a return system 6.

In the first embodiment, since the degassing element aL stage 3 is placed outside the aeration tank, the return system 6 is a pipe that enters the bottom of the tank, and this pipe is used to collect the concentrated liquid as shown in Fig. 2. It is preferable to add the liquid in the tangential direction to ensure good mixing and agitation in the tank.

Further, in the second embodiment, since each membrane separation/first stage 3 is built into the bottom of the aeration tank 1, no particular piping is required for the return system 6, and a hole may be used instead.

In this way, the water head pressure of the deep aeration tank 1 can be used to pressurize the liquid to the e-contraction side 3a necessary for permeating the permeable membrane 3' of the membrane separation means 3, so the discharge pressure of the yfI ring bond 13 is small. Good too. The permeable membrane 3' for supplying the liquid mixed with air to the C line side by the air supply system 5 is oscillated by the bubbling agitation of air bubbles, and the width is several times larger than when only the liquid is supplied. It has an agitating effect and removes contaminants that have adhered to the membrane, and also prevents contaminants from adhering to the membrane.This reduces the number of times membrane cleaning is performed and increases the operating rate of the facility. The cost of chemicals and labor can be reduced, making the facility more economical.

Although not shown in the second embodiment, the plurality of membrane separation means 3... are connected to the supply system 4 and the aeration tank 1 by valves v1 and Vl' so that they can be inspected and cleaned individually and regularly. Cut) 3 Chemical washing? ' / I tank 19 wash water is separated into individual membranes P using a circulation pump.
It is fed into the e-line side of the stage and circulated to the chemical cleaning tank.

In addition, the flow rate for supplying the liquid flowing through the circulation system 2 to the membrane separation stage 3 shall be appropriately adjusted by the residence time in the aeration tank 1. On the way, supply system 4 person ``1 to flow rate adjustment brake r2
Place 0.21 one submersion.

The embodiment shown in FIG. 4 is the same as the embodiment shown in FIGS. The point is gas-liquid #tank 8
A supply system 4 is connected to the middle of the pipe 12 that leads the circulating liquid from the bottom of the cyclone to the circulation pump 13, and a liquid feeding pump 22 to the membrane separation means 3 is connected to the middle of this supply system 4. 6
, the liquid is sent to the separation means 3 119 through the injector 17.

In this embodiment, when the inspection quality of the deep aeration tank 1 is relatively low and the effective pressure applied to the permeable membrane of the membrane separation means 3 cannot be sufficiently obtained from the water head, this is compensated for by the discharge pressure of the liquid feed pump 22.

Of course, this embodiment also operates in the same manner as the first and second embodiments described above.

(Effects of the Invention) According to the present invention, operation can be continued while constantly preventing the progress of membrane contamination of the membrane separation means, and the operating rate of the apparatus is high. Furthermore, in combination with a deep aeration tank, the water head is used as effective pressure for the membrane separation means, so the power of the circulation pump can be reduced. Furthermore, under pressure within the membrane separation means, the liquid and air agitate and mix with the permeable membrane, promoting dissolution of the air into the liquid.

[Brief explanation of drawings]

Fig. 1 is a system diagram of the first embodiment of the present invention, Fig. 2 is a cross-sectional layout diagram of the main parts of L, Fig. 3 is a system diagram of the second embodiment of the invention, and Fig. 4 is the system diagram of the present invention. In the diagram, 1 is a deep aeration tank, 2 is its circulation system, 3 is a membrane separation means,
3' is its transmission membrane, 3a is its C line side, and 3b is its transmission side. 4 is a supply system to the membrane separation means, 6 is a return system, and 7 is a take-out system. 2nd fI!

Claims (2)

[Claims] (1) A deep aeration tank having a circulation system for circulating the liquid in the tank, and a membrane separation means having a built-in permeable membrane such as an ultrafiltration membrane or a microfiltration membrane provided near the bottom of the aeration tank; a supply system for supplying a part of the liquid flowing through the circulation system to the membrane separation means; a return system for returning the concentrated liquid on the concentration side of the membrane separation means to the deep aeration tank; A sewage treatment device comprising: a take-out system for taking out permeate on the permeate side as treated water. (2) In the sewage treatment device according to claim (1),
A wastewater treatment apparatus, wherein a supply system to the membrane separation means is provided with a solid-liquid separation means.