JP2006255505A - Biological treatment apparatus and biological treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological treatment apparatus and a biological treatment method which enable reduction in agitation costs. <P>SOLUTION: The biological treatment apparatus comprises a biological treatment tank for biologically treating organic waste water, a pressure device for pressurizing sludge-containing liquid pulled out from the biological treatment tank, a membrane separator which performs the membrane filtration of the sludge-containing liquid pressurized by the pressure device to separate the liquid into treated water which is permeate passing through a separation membrane and sludge concentrate which is nonpermeate, and a return passage for returning the nonpermeate separated by the membrane separator into the biological treatment tank. The return passage is formed so as to supply the nonpermeate to the biological treatment tank from the bottom while maintaining the nonpermeate under a pressurized condition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biological treatment apparatus and a biological treatment method. More specifically, the present invention relates to a biological treatment tank for biologically treating organic wastewater, and a pressurizing unit for applying a sludge-containing liquid drawn from the biological treatment tank. A membrane separator for separating a sludge-containing liquid pressurized by the pressure device into a treated water that is a permeate that has permeated the separation membrane and a sludge concentrate that is a non-permeate, and the membrane The present invention relates to a biological treatment apparatus and a biological treatment method comprising a return path for returning a non-permeated liquid separated by a separation device into the biological treatment tank.

A biological treatment apparatus using activated sludge is known as an apparatus for treating organic wastewater such as domestic wastewater and factory wastewater. The biological treatment apparatus generally has a biological treatment tank containing activated sludge and a precipitate that settles the activated sludge and separates the liquid extracted from the biological treatment tank into treated water (purified water) and sludge concentrate. A sludge concentrate separated from the sedimentation tank is poured from above the biological treatment tank and returned to the biological treatment tank.
Furthermore, in recent years, a biological treatment apparatus provided with a membrane separation device provided with a membrane element such as an ultrafiltration membrane or a microfiltration membrane has also been proposed. That is, as shown in FIG. 4, the biological treatment apparatus includes a biological treatment tank 51, a pressure device 52, and a membrane separation device 53, and the sludge-containing liquid drawn from the biological treatment tank 51 is added to the pressure device 52. And is introduced into the membrane separation device 53, where it is separated into treated water that is a permeate that permeates the membrane and sludge concentrate that is a non-permeate, and the treated water is discharged to the outside of the system. While being discharged, the non-permeating liquid is poured back from above the biological treatment tank 51 so as to be returned and supplied to the biological treatment tank 51.

  According to the biological treatment apparatus using such a membrane separation apparatus, there is an advantage that the installation area is greatly reduced as compared with a biological treatment apparatus using a conventional sedimentation tank.

By the way, in this kind of biological treatment equipment, the activated sludge in the biological treatment tank is sedimentary, and if it settles, the contact opportunity between the organic wastewater and the activated sludge decreases, which impedes treatment (purification). Therefore, the biological treatment tank is provided with a stirring blade, and the liquid in the tank is sufficiently stirred by the stirring blade.
JP 05-285490 A

  However, the biological treatment apparatus has a problem in that it requires a great amount of stirring cost since it is necessary to continue stirring without allowing the sedimentary activated sludge to settle.

  In view of the above problems, an object of the present invention is to provide a biological treatment apparatus and a biological treatment method that can reduce the stirring cost.

In order to solve the above problems, the present invention provides a biological treatment tank for biologically treating organic wastewater, a pressure device for pressurizing a sludge-containing liquid drawn from the biological treatment tank, and the pressure device. A membrane separator for separating the pressurized sludge-containing liquid into a treated water as a permeate that has permeated through a separation membrane and a sludge concentrate as a non-permeate, and a non-permeate separated by the membrane separator A biological treatment apparatus comprising a return path for returning the liquid to the biological treatment tank,
The return path is configured to supply the biological treatment apparatus from the lower part of the biological treatment tank into the biological treatment tank while maintaining the non-permeate in a pressurized state. provide.

In the biological treatment apparatus having such a configuration, since the non-permeate liquid is maintained in a pressurized state, the non-permeate liquid can be supplied into the tank from the lower part of the biological treatment tank and exists in the lower part of the biological treatment tank. The inside of the tank can be stirred while flowing activated sludge. Therefore, stirring by a stirring blade becomes unnecessary or the necessity thereof is reduced.
In the present invention, the lower part of the biological treatment tank means a part where the height from the bottom is at least half or less of the height from the bottom to the liquid level of the sludge-containing liquid.

Furthermore, in the biological treatment apparatus of the present invention, the return path is configured such that the supply direction of the non-permeate liquid into the biological treatment tank is inclined with respect to the horizontal direction. preferable.
According to such a configuration, the activated sludge existing in the lower part can be stirred while flowing in the vertical direction, and the difference in sludge concentration between the upper part and the lower part of the biological treatment tank can be sufficiently reduced.

Further, the present invention biologically treats organic wastewater in a biological treatment tank, extracts a sludge-containing liquid in the biological treatment tank treated with the organic wastewater from the biological treatment tank, and pressurizes the separation membrane. A biological treatment method that separates the treated water as a permeate and the sludge concentrate as a non-permeate, and returns the separated non-permeate into the biological treatment tank,
The biological treatment method is characterized in that the non-permeate is maintained in a pressurized state and is supplied into the biological treatment tank from a lower part of the biological treatment tank.

  As described above, the biological treatment apparatus according to the present invention does not require stirring by a stirring blade, or the necessity thereof is reduced, and thus the stirring cost can be reduced.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic flow diagram showing the biological treatment apparatus of the present embodiment.
As shown in FIG. 1, the biological treatment apparatus of this embodiment biologically treats organic wastewater A biologically (specifically, purifies with activated sludge), and the biological treatment tank. 1. Pressurizing device 3 for pressurizing sludge-containing liquid extracted from 1 and treated with organic waste water A, and permeate that has passed through the separation membrane by subjecting the sludge-containing liquid pressurized by the pressurizing device 3 to membrane filtration A membrane separation device 2 that separates C and non-permeate B and a return path 4 that returns the non-permeate B separated by the membrane separation device 2 into the biological treatment tank 1 are provided. Further, in order to supply the organic waste water A in the biological treatment tank 1 to the membrane separation device 2, the biological treatment tank 1 and the membrane separation device 2 are provided with a pipe 6 that communicates. It is interposed in the middle of the pipe 6.

The biological treatment tank 1 is usually an aeration tank, configured to be supplied with organic waste water A and filled with a sludge-containing liquid containing activated sludge, and from the bottom of the tank main body 1a. In order to supply air to the sludge-containing liquid, an air diffuser 16 such as an air diffuser disposed at the bottom of the tank body 1a and a blower 5 for supplying air to the air diffuser 16 are provided.
The said tank main body 1a is formed in a cylindrical shape, and the upper part is opened so that the organic waste water A can be supplied.

The pressurizing device 3 is configured to pressurize the sludge-containing liquid drawn from the lower part of the tank body 1a and supply the pressurized sludge-containing liquid to the membrane separation device 2.
As the pressurizing device 3, two pumps 3a and 3b are provided, and more specifically, in the upstream in the flow direction, which are interposed in series in pipes communicating the biological treatment tank 1 and the membrane separation device 2, respectively. A first pump 3a on the side and a second pump 3b on the downstream side are provided.
The first pump 3a primarily pressurizes the sludge-containing liquid drawn from the tank body 1a, and the second pump 3b primarily pressurizes the sludge according to the pressure loss when passing through the membrane separation device 2. The contained liquid is further subjected to secondary pressurization.
The pressure applied at the primary pressurization is usually 0.05 to 0.5 MPa, and the pressure applied at the secondary pressurization is usually 0.01 to 0.5 MPa.

The membrane separation device 2 includes a pressurized region 2a and a non-pressurized region 2b (atmospheric pressure region) defined by a separation membrane, and supplies a pressurized sludge-containing liquid to the pressurized region 2a. Is a device that separates the treated water as the permeate C permeated through the separation membrane 7 and the sludge concentrate as a non-permeate B in a pressurized state (that is, a pressure higher than atmospheric pressure). is there.
As the separation membrane 7, an ultrafiltration membrane or a microfiltration membrane is usually used.

The return path 4 is configured so that the pressurized non-permeate B discharged from the membrane separation apparatus 2 is supplied to the biological treatment tank 1 from the lower part of the biological treatment tank 1 while maintaining the pressurized state. A piping that communicates the pressurizing region 2 a of the separation device 2 and the lower part of the biological treatment tank 1 is provided.
Specifically, with respect to the height from the bottom to the liquid level of the sludge-containing liquid, the portion where the height from the bottom is at least half or less, preferably from the portion where the height is 1/5 or less, It is configured to be supplied.
By supplying the non-permeated liquid B from a portion that is at least 1/5 or less, only the upper layer portion in the tank is suppressed from being stirred, and the entire tank is sufficiently stirred.

  A valve 9 for controlling the pressure on the upstream side and the downstream side is interposed in the middle of the return path 4 (usually near the end of the return path 4).

FIG. 2 is a top view of a part of the biological treatment tank 1 and the return path 4 as viewed from above.
As shown in FIG. 2, the return path 4 is set such that the supply direction 12 of the non-permeate B into the biological treatment tank 1 is inclined with respect to the direction 11 toward the central axis 10 of the tank body 1a. Become.
That is, the supply direction 12 of the non-permeating liquid B is set to be a tangential direction of the virtual circle 13 that is coaxial with the tank body 1a and has a small diameter.
The diameter of the virtual circle 13 is preferably in the range of 40 to 80% of the inner diameter of the tank body 1a.

  By supplying the non-permeate B in the tangential direction of the virtual circle 13, from the vicinity of the center in the tank body 1 a to the vicinity of the inner peripheral surface of the tank body 1 a without forming a dead space (a staying part). The sludge-containing liquid can be stirred while rotating in the circumferential direction in all the regions.

Furthermore, it is preferable that the supply direction 12 of the non-permeate liquid B is inclined about 5 to 30 degrees upward or downward with respect to the horizontal direction.
According to such a configuration, not only the inside of the tank can be stirred in the circumferential direction but also in the vertical direction, the activated sludge settled in the lower part can be stirred while flowing upward, and contains sludge. The difference in sludge concentration between the upper and lower parts of the liquid can be sufficiently reduced.

  The supply amount of the non-permeate B to the biological treatment tank 1 is preferably 0.2 to 2 L / h per 1 L of the liquid in the tank, and the flow rate is preferably 0.5 to 2 m / sec.

  As shown in FIG. 1, a bypass 8 is provided in the middle of the return path 4 to supply the non-permeate B to the pipe between the first pump 3a and the second pump 3b. Part of B is configured to be supplied to the membrane separation device 2 again.

  In the biological treatment apparatus of this embodiment, the biological treatment tank 1 is formed in a cylindrical shape, and the return path is configured so that the supply direction of the non-permeate B into the biological treatment tank 1 is biological treatment. Since it is comprised so that it may become the direction 12 which inclines with respect to the direction 10 which goes to a tank center axis | shaft, it can stir, rotating the liquid in the biological treatment tank 1 to the circumferential direction, and more sufficient stirring is possible. It becomes possible.

The biological treatment apparatus of the present embodiment is configured as described above. However, in the present invention, the present invention is not limited to the above-described configuration, and the design can be changed as appropriate.
That is, in the present embodiment, the air diffuser 16 is provided at the bottom of the tank main body 1a and the blower 5 that supplies air to the air diffuser 16 is provided. Instead of the air diffuser 16 and the blower 5 for supplying air to the air diffuser 16, for example, as shown in FIG. The blower 5 for supplying air to the non-permeate liquid B may be provided, and the air diffuser 16 disposed at the bottom of the tank body 1a and the air to the air diffuser 16 are supplied. In addition to the blower 5, there may be provided a blower 5 that supplies air to the non-permeate B on the return path 4, particularly upstream of the valve 9.
According to the configuration in which the blower 5 for supplying air is provided in the middle of the path 4, the inside of the tank can be diffused while being agitated, the air can be diffused throughout the tank, and the pressure is increased. Since air is supplied to the non-permeated liquid B, the oxygen dissolution efficiency is increased, and the amount of air supply can be reduced compared with the air diffused in the biological treatment tank 1, thereby reducing the cost for air diffusion. it can.

Further, in the configuration in which air is supplied to the non-permeate B in the path 4, a network (not shown) that refines the bubbles in the non-permeate B on the downstream side in the flow direction from the portion to which air is supplied. May be provided.
In such a configuration, since the bubbles in the non-permeate liquid B collide with the net and are refined, the refined bubbles can be supplied into the biological treatment tank 1, That is, the ratio used for activated sludge with respect to the total supply air amount can be increased.

  Further, in the present embodiment, the two pumps 3a and 3b are provided as the pressurizing device 3, but when the bypass 8 is not provided, only one pump is provided as the pressurizing device 3. It may be obtained.

1 is a schematic flow diagram illustrating a biological treatment apparatus according to one embodiment. The schematic top view which shows a part of biological treatment tank and return path | route in the embodiment. The schematic flowchart which shows the biological treatment apparatus of other embodiment. The general | schematic flowchart which shows the conventional biological treatment apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Biological treatment tank, 2 ... Membrane separation device, 3 ... Pressurization device, 4 ... Return path, 5 ... Blower (air supply device), 12 ... Non-permeate liquid Supply direction A ... Organic waste water, B ... Non-permeate, C ... Permeate

Claims (4)

Biological treatment tank (1) for biologically treating organic wastewater (A), pressurizer (3) for pressurizing sludge-containing liquid drawn from the biological treatment tank (1), and the pressurizer Membrane separation device (2) for separating the sludge-containing liquid pressurized by (3) into treated water that is permeated liquid (C) and non-permeated liquid (B) that is permeated through the separation membrane And a return path (4) for returning the non-permeate (B) separated by the membrane separator (2) into the biological treatment tank (1),
The return path (4) is configured to supply the impermeable liquid (B) from the lower part of the biological treatment tank (1) into the biological treatment tank (1) while maintaining the impermeable liquid (B) in a pressurized state. A biological treatment device.   The return path (4) is configured such that the supply direction (12) of the non-permeate (B) into the biological treatment tank (1) is inclined with respect to the horizontal direction. Biological processing equipment.   The biological treatment device according to claim 1 or 2, wherein the return path (4) is provided with an air supply device (5) for supplying air to the non-permeate liquid (B). The organic wastewater (A) is biologically treated in the biological treatment tank (1), and the sludge-containing liquid in the biological treatment tank (1) treated with the organic wastewater (A) is removed from the biological treatment tank (1). ) And then pressurizing, and using the separation membrane (2a), it is separated into treated water as permeate (C) and sludge concentrate as non-permeate (B), and the separated non-permeate (B) is separated from the organism. A biological treatment method for returning to the treatment tank (1),
The biological treatment method characterized by maintaining the said impermeable liquid (B) in a pressurized state, and supplying in the said biological treatment tank (1) from the lower part of the said biological treatment tank (1).

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