JP2006289370A - Solid-liquid separation method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-liquid separation method for activated sludge treatment water, which can ensure and maintain a high and uniform filtration flux and a low and uniform filtrate water turbidity, and to provide its apparatus. <P>SOLUTION: In the solid-liquid separation method and apparatus, water to be treated is introduced into an activated sludge treatment bioreaction tank. A sludge mixed liquid in the bioreaction tank is introduced into a filtration separation tank, in which a plurality of filtration modules are provided in an immersed state, to obtain filtrate water from the filtration modules by water head. The sludge mixed liquid after the filtration is returned to the bioreaction tank. A partition wall is provided between the filtration modules within the filtration separation tank. An aeration tube is provided on the lower part of each of the filtration modules. In the filtration, while obtaining filtrate water from filtration modules on both sides with the partition wall interposed in between, after air flow into the lower aeration tube in one of the filtration modules with the partition wall interposed in between, the air flow is carried out for the other aeration tube. The air flow for the aeration tubes in the filtration modules is changed and alternately carried out. In the washing of the filtration module, the filtration is stopped. The air washing of the filtration modules are alternately carried out for both the filtration modules with the partition wall interposed in between every predetermined time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to solid-liquid separation in activated sludge treatment, and relates to a solid-liquid separation method and apparatus in activated sludge treatment such as sewage, organic industrial wastewater, and domestic wastewater.

  Conventionally, in water treatment with activated sludge, solid sludge separation of activated sludge has to be performed in order to obtain treated water. Usually, a method is used in which an activated sludge mixed liquid is introduced into a sedimentation basin, the sludge is sedimented by gravity sedimentation, and the supernatant liquid is discharged from the sedimentation basin as treated water. In this case, a sedimentation basin having a sufficient sedimentation area and residence time is necessary to settle the activated sludge, which is a factor for increasing the size of the processing apparatus and increasing the installation volume. Moreover, when activated sludge deteriorates sedimentation property, such as bulking, sludge flows out from a sedimentation basin and causes deterioration of treated water.

On the other hand, instead of a sedimentation basin, a method of performing solid-liquid separation of activated sludge by membrane separation has been used for some time. In this case, a microfiltration membrane or an ultrafiltration membrane is generally used as the solid-liquid separation membrane.
As the filtration / separation means, suction or pressurization by a pump is necessary, and since it is usually performed at a pressure of several tens of kPa to several hundred kPa, the power of the pump is large and the running cost is increased. In addition, clear treated water having no SS can be obtained by membrane separation, while the permeation flux is low, and it is necessary to periodically wash the medicine in order to prevent membrane contamination.

  Recently, as a solid-liquid separation method for activated sludge as an alternative to a sedimentation basin, a plurality of filter media made of filter cloth such as non-woven fabric are immersed in a biological reaction tank, and gas is intermittently supplied to the bottom of the filter media during filtration using a dynamic filtration layer. And a cleaning method is disclosed. In addition to the aeration tank, the filtration bodies on both sides sandwiching the partition wall by introducing the aeration tank sludge into the solid-liquid separation tank in which multiple filter bodies with partition walls provided between the filter bodies are immersed are periodically In particular, a treatment method in which filtration and aeration are alternately performed is disclosed.

  In the treatment method in which gas is intermittently supplied to the lower part of the filter body and washed, the flow on the surface of the filter body immersed in the bioreaction tank is formed by aeration from the bioreactor aeration tube sandwiching the partition wall. The surface flow of the filter body is uneven. In any filter body, it is a downward flow. On the other hand, the ventilation pipe for cleaning the filter body is located at the lower part of the filter body, and when cleaning by gas supply, the flow of the filter body is an upward flow, and a high rising speed or a uniform rising speed due to the sludge flow of the downstream flow. May not be obtained. In this case, the peeling effect of a sludge adhesion layer falls and it becomes difficult to maintain a high filtration flux.

Separately from the aeration tank, the filter bodies on both sides sandwiching the partition wall by introducing the aeration tank sludge into the solid-liquid separation tank in which multiple filter bodies with partition walls provided between the filter bodies are immersed In the treatment method that alternately performs filtration and aeration, since the filtration operation of half of the filter in the solid-liquid separation tank is constantly stopped, an effective amount of filtered water cannot be obtained, and the filter is effectively used. There is a problem that can not be. In addition, the sludge flow on the surface of the filter body is a circulating flow by the opposite side air pipe diffused across the partition wall-that is, an upward flow in the filter medium in the air pipe diffused, and a downward flow in the filter medium being filtered. Therefore, if the filter during filtration does not provide a uniform flow rate and the continuous filtration time until washing is long, a sludge adhesion layer grows excessively on the surface of the filter with a slow flow rate, increasing the sludge flow path resistance. Cause flow stagnation. This is a factor that causes a reduction in filtration flux.
The object of the present invention is to provide a solid-liquid separation method and apparatus that eliminates the disadvantages of the prior art, can be used effectively as a filter in a solid-liquid separation tank, and provides a high filtration flux.

In order to solve the above-described problems, the present invention has the following configuration.
(1) Treated water is introduced into a biological reaction tank to perform activated sludge treatment, and the sludge mixed liquid discharged from the biological reaction tank is introduced into a filtration separation tank in which a filtration module composed of a plurality of filter bodies is immersed. In the solid separation method of obtaining filtered water from the filtration module by water head pressure and returning the sludge mixed solution in the filtration separation layer to the biological reaction tank,
A partition wall is installed between adjacent filtration modules A and B in the filtration separation tank so that liquid can communicate with the upper and lower sides of the partition wall. An air diffuser B is provided at the lower part of B, and at the time of filtration, ventilation is performed by alternately conducting air to the air diffuser A and air to the air diffuser B while filtering both the filter module A and the filter module B. The sludge mixed liquid forms an upward flow with respect to the filtration module on the side, and the sludge mixed liquid forms a downward flow with respect to the filtration module on the non-ventilated side. By stopping and alternately ventilating the diffuser tube A and ventilating tube B, the sludge mixed liquid flows up to the filtration module on the ventilation side and flows into the filtration module on the non-ventilation side. for The mud mixture forms a downward flow, and the amount of air diffused during filtration should be smaller than the amount of air diffused during air washing. After filtering for a predetermined time, perform air washing for a short time and repeat filtration and air washing. A solid-liquid separation method characterized by that.

(2) The solid-liquid separation method according to (1), wherein the ventilation to the air diffuser A or the air diffuser B is performed intermittently or continuously during filtration and continuously during air washing. .
(3) When the filtered water turbidity becomes equal to or higher than a predetermined value in the ventilation to the air diffuser A or the diffuser B during filtration, the air flow is reduced or the air flow is stopped, and the filtered water turbidity is equal to or lower than the predetermined value. The solid-liquid separation method as described in (1) or (2) above, wherein the aeration amount is increased or the aeration is resumed when it becomes.
(4) The air flow rate to the air diffuser A or the air diffuser B is 1.0 m ³ / m ² flow path / min or less at the time of filtration and 2.5 m ³ / m ² flow path / min or more at the time of air washing A solid-liquid separation method according to any one of (1) to (3), wherein

(5) A partition wall that allows liquid to communicate with the upper and lower sides in the tank is disposed, and filtration modules in which a dynamic filtration layer is formed on the surface composed of a plurality of filter bodies are disposed on both sides of the partition wall, A diffusing pipe is provided below the filtration module, and a filtered water discharge pipe attached to the filtration module to stop the entire filtration at the time of air washing, and an air supply pipe for ventilation attached to each of the diffusing pipes. The air supply pipe is alternately ventilated to one air diffuser and the other air diffuser at the time of filtration, and to the one air diffuser and the other air diffuser at the time of air washing with a larger air flow rate than at the time of filtration. The aeration valve for switching the ventilation destination, the sludge mixed liquid supply pipe for introducing the sludge mixed liquid from the biological reaction tank, and the sludge mixed liquid in the tank are returned to the biological reaction tank. Filtration with sludge mixed liquid return pipe Solid-liquid separation device characterized by having a Hanareso.

  According to the present invention, the sludge mixed solution is supplied from the biological reaction tank to the filtration separation tank, and in the dynamic filtration by the filtration module, between the filtration modules adjacent to each other with respect to the plurality of filtration modules immersed in the filtration separation tank. If a partition wall is provided in the filter module, a diffuser pipe is installed at the bottom of the filtration module, and air is passed through one of the filtration modules that sandwich the partition wall during air washing, the gas-liquid in the vent-side module flow path The mixed sludge flow becomes a relatively uniform upward flow, and the module flow path on the opposite side can form a downflow sludge flow. By alternately performing this, a flow in the same direction with a high flow rate can be reliably formed in the module flow path. For this reason, the sludge cake layer overgrown on the filtration module surface can be reliably peeled, and a high cleaning effect is obtained.

  Similarly, during filtration, the sludge mixed liquid in the filtration module flow path is surely fluidized by aeration from the air diffusion pipe against one of both modules sandwiching the partition wall with a smaller amount of air diffusion than during air washing, The growth of the filter surface sludge layer can be suppressed, and a high filtration flux can be maintained. Moreover, in the filtration module flow path on the opposite side of the partition wall, a sludge flow that is surely a downward flow can be formed, and the sludge bridge caused by sludge cake layer overgrowth accompanying flow stagnation can be eliminated. Aeration at the time of filtration is alternately performed on the filtration module, so that a high filtration flux is always obtained in any filtration module.

Hereinafter, embodiments of the present invention will be described.
According to the present invention, the sludge mixed solution is supplied from the biological reaction tank to the filtration separation tank, and in the dynamic filtration by the filtration module, between the filtration modules adjacent to each other with respect to the plurality of filtration modules immersed in the filtration separation tank. A partition wall is provided, the upper end of the partition wall is below the liquid level, and the lower end is above the tank bottom so that the liquid can communicate above and below the partition wall; By installing a diffuser pipe at the bottom of the filtration module, if air is passed through any of the diffuser pipes that sandwich the partition wall during air washing, the gas-liquid mixed sludge flow in the ventilation side filtration module flow path Becomes a relatively even upward flow, and the opposite filtration module flow path can form a downward sludge flow. By alternately performing this, a flow in the same direction with a high flow rate can be reliably formed with respect to the filtration module flow path. For this reason, the sludge cake layer overgrown on the filtration module surface can be reliably peeled, and a high cleaning effect is obtained.

  Similarly, during filtration, the sludge mixed liquid in the flow path of the filtration module flows reliably by ventilating from one of the two filtration modules that sandwich the partition wall with a smaller amount of air diffusion than when washing with air. In addition, the growth of the filter surface sludge layer can be suppressed, and a high filtration flux can be maintained. Moreover, in the filtration module flow path on the opposite side of the partition wall, a sludge flow that is surely a downward flow can be formed, and a sludge bridge caused by sludge cake layer overgrowth accompanying flow stagnation can be eliminated. Aeration at the time of filtration is alternately performed on the filtration module, so that any module can perform filtration at the same time, and a high filtration flux is always obtained.

As the air diffuser during filtration, an air diffuser for air washing may be used as well, but in order to ensure the sludge flow in the same direction and to form a uniform flow in each flow path, corresponding to the sludge properties and concentration A separate vent pipe may be provided. As the ventilation tube during the progress of filtration, any of a porous tube having a small pore diameter, a porous tube having a pore diameter of preferably about 1 mm to 3 mm, a diffuser, or the like may be used.
In addition, in the filtration module which receives ventilation | gas_flowing, the raise of filtered water turbidity is anticipated with sludge density | concentration and a property. There is also a reduction in the filtrate flux due to changes in the water head pressure. For this reason, the magnitude | size of ventilation | gas_flowing amount and the frequency of switching of ventilation | gas_flowing to a diffuser can be adjusted suitably according to the amount of filtrate water and filtration water turbidity, and can also be performed intermittently.

  The filtration module is composed of a plurality of filter bodies. Although the flat shape is the center as the filter body shape, a cylindrical shape or a hollow shape can also be used. The number of filter bodies per filtration module is usually about 2 to 100, but in order to make the sludge flow in the filtration module flow path relatively uniform and obtain a uniform cleaning effect for each filter body, 5 to 20 is required. The sheet is preferably a single filtration module.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment. However, the present invention is not limited to this example.

Example 1
FIG. 1 shows an example of processing according to the present invention for beverage wastewater in a flow sheet.
As shown in FIG. 1, the inflow raw water 1 flows into the biological reaction tank 2 and performs activated sludge treatment. The sludge mixed liquid after the activated sludge treatment is sent to the bottom of the filtration separation tank 4 from the sludge supply pump 3. In the filtration separation tank 4, filtration module A 7 and filtration module B 8 are installed with a partition wall 18 interposed therebetween. In the lower part of the filtration module A and the filtration module B, 9 of the diffuser tube A and 10 of the diffuser tube B are arranged, respectively. Ventilation to the air diffusers A and B is performed from the blower 11 through the vent valves A 5 and B 6, respectively. It should be noted that only one of the vent valves A and B is opened when air is diffused. The ventilation switching between the air diffusers A and B is performed by switching the ventilation valves A and B. During that period, the ventilation blower 11 is continuously operated.

Filtration is performed simultaneously using both filtration modules. The filtered water 14 from the filtration module flows into the treated water tank 12 and is discharged as treated water 17. In the case of water backwashing, the water backwashing pump 13 uses the filtered water 14 of the treated water tank 12 and performs water backwashing by supplying it into the filtration module. At the time of backwashing with water, the sludge entering the module is returned from the bottom of the filtration module to the biological reaction tank 2 as discharged sludge 16. Moreover, the sludge mixed liquid in the filtration separation tank 4 after obtaining the filtered water 14 is returned to the biological reaction tank 2 as return sludge 15.
Table 1 shows the processing conditions of the filtration separation tank in this example.

In this example, two filtration modules A and B were immersed and installed in the filtration separation tank 4 with 7 and 8 of three flat water-permeable filtration bodies having an effective filtration area of 0.7 m ² / sheet as filter bodies modules. . A partition wall 18 having a thickness of 20 mm was provided between the A and B filtration modules. The partition wall 18 is in fluid communication with the top and bottom as shown in the figure. A polyester woven fabric having a thickness of about 0.1 mm and a pore diameter of 114 μm was used as a water-permeable filter for the filtration module. The head pressure at the time of filtration was about 10 cm, the flow rate of the sludge mixed solution supplied to the filtration separation tank 4 was 30 m ³ / d, and the sludge flow rate on the surface of the filter body was 0.01 m / s on average.

The filtration process was performed as 120 minutes per cycle. In this one-cycle 120-minute filtration, the ventilation cycle is intermittently aerated for 5 minutes ON and 10 minutes OFF through the ventilation valve A (5) or B (6). Since ventilation is performed with respect to either the ventilation pipe A or B, ventilation from the ventilation pipes A and B is stopped for 5 minutes and stopped for 25 minutes, respectively. The air flow during filtration was 0.2 m ³ / m ² / min.
When the air is vented from the vent valve A (5), the liquid flows upward to the filtration module A, and the liquid is descended to the filtration module B. When the air diffuses from the vent valve B (6), the liquid is filtered. The liquid flow to modules A and B is reversed. And even when the ventilation from the ventilation pipes A and B is stopped, the driving force for the liquid given at the time of ventilation remains, there is almost no flow resistance of the sludge flow path, and the flow velocity of each liquid to the filtration surface is increased. Can be maintained.

  Since filtration resistance increases when a certain time passes, external air washing is performed, but as an external air washing method for the filtration module, the ventilation blower 11 is activated every 120 minutes of filtration, and continuous air washing for 6 minutes is performed. Do. Meanwhile, the washing time from the ventilation valve A to the filtration module A and the washing time from the ventilation valve B to the filtration module B were each 3 minutes. When the vent valve A 5 is opened and vented to the diffuser tube A 9 at the bottom of the filtration module A, the vent valve B 6 is closed and ventilated, but the sludge mixture is directed upward on the filtration module A surface. Then, the sludge mixture enters the filtration module B side through the upper end of the partition wall 18 and passes through the surface of the filtration module B in a downward flow. Similarly, when the air is vented to the air pipe B 10 at the lower part of the B module, the sludge flow on the surface of the A and B modules becomes a downward flow and an upward flow.

  Water backwashing is performed using the filtered water 14 of the treated water tank 12 and supplying it to the inside of the filtration module. The amount of water backwashing was 40 m / d per filtration area, and in this example, 117 liters / min. Simultaneously with the water backwashing, a mud draining operation is performed to discharge the infiltrated sludge from the inside of the filtration module.

FIG. 2 shows the flow of the filtration flux of the entire filtration module in the example. The MLSS at the time of execution is about 6000 mg / liter.
In the operation for 2 months from the start of the treatment, the filtration flux was about 2 to 2.5 m / d, and a stable treatment was obtained.
FIG. 3 shows the course of filtered water turbidity.
In continuous operation for about 2 months, the turbidity of the filtrate was approximately 10 degrees or less, showing good filtration performance, and clear filtrate was stably obtained.

It is a schematic explanatory drawing of the apparatus which implements the solid-liquid separation of the activated sludge process of this invention. It is a graph which shows the time-dependent change of the filtrate water flux of the Example of this invention. It is a graph which shows the time-dependent change of the filtration water turbidity of the Example of this invention.

Explanation of symbols

1 Inflow raw water 2 Biological reaction tank 3 Sludge supply pump 4 Filtration separation tank 5 Ventilation valve A
6 Ventilation valve B
7 Filtration module A
8 Filtration module B
9 Diffuser A
10 Diffuser B
DESCRIPTION OF SYMBOLS 11 Aeration blower 12 Treated water tank 13 Water backwash pump 14 Filtration water 15 Return sludge 16 Discharged sludge 17 Treated water 18 Partition wall

Claims (5)

Water to be treated is introduced into a biological reaction tank to perform activated sludge treatment, and the sludge mixed liquid discharged from the biological reaction tank is introduced into a filtration separation tank in which a filtration module composed of a plurality of filter bodies is immersed and installed. In the solid separation method of obtaining filtered water from the filtration module by pressure and returning the sludge mixed solution in the filtration separation layer to the biological reaction tank,
A partition wall is installed between adjacent filtration modules A and B in the filtration separation tank so that liquid can communicate with the upper and lower sides of the partition wall. An air diffuser B is provided at the lower part of B, and at the time of filtration, ventilation is performed by alternately conducting air to the air diffuser A and air to the air diffuser B while filtering both the filter module A and the filter module B. The sludge mixed liquid forms an upward flow with respect to the filtration module on the side, and the sludge mixed liquid forms a downward flow with respect to the filtration module on the non-ventilated side. By stopping and alternately ventilating the diffuser tube A and ventilating tube B, the sludge mixed liquid flows up to the filtration module on the ventilation side and flows into the filtration module on the non-ventilation side. for The mud mixture forms a downward flow, and the amount of air diffused during filtration should be smaller than the amount of air diffused during air washing. After filtering for a predetermined time, perform air washing for a short time and repeat filtration and air washing. A solid-liquid separation method characterized by that.   2. The solid-liquid separation method according to claim 1, wherein the ventilation to the air diffuser A or the air diffuser B is performed intermittently or continuously during filtration and continuously during air washing.   When the filtered water turbidity is greater than or equal to a predetermined value in the ventilation to the diffuser pipe A or the diffuser pipe B during filtration, when the filtered water turbidity is reduced or stopped, the filtered water turbidity is less than or equal to a predetermined value. The solid-liquid separation method according to claim 1 or 2, wherein the aeration amount is increased or aeration is resumed. The air flow rate to the air diffuser A or the air diffuser B was set to 1.0 m ³ / m ² flow path / min or less at the time of filtration and 2.5 m ³ / m ² flow path / min or more at the time of air washing. The solid-liquid separation method according to any one of claims 1 to 3.   A partition wall that allows the liquid to communicate with the upper and lower sides in the tank is disposed, and a filtration module in which a dynamic filtration layer is formed on the surface composed of a plurality of filter bodies is disposed on both sides of the partition wall. A diffusing pipe is provided below each, and a filtered water discharge pipe attached to the filtration module for stopping the entire filtration at the time of air washing, an air supply pipe for ventilation attached to each of the diffusing pipes, It is provided in the air supply pipe, and it alternately ventilates one air diffuser and the other air diffuser during filtration, and when air-washed, it ventilates one air diffuser and the other air diffuser with a larger air flow than during filtration. Alternately, a vent valve for switching the aeration destination, a sludge mixture supply pipe for introducing a sludge mixture from the biological reaction tank, and a sludge mixture in the tank for returning to the biological reaction tank Filtration separation tank with sludge mixed liquid return pipe Solid-liquid separation device characterized in that it has.

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