JP2003305313A - Solid-liquid separation method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-liquid separation method for activated sludge treated water capable of ensuring and keeping high and uniform filter flux and low and uniform filtered water turbidity, and an apparatus therefor. <P>SOLUTION: Water to be treated is introduced into a biological reaction tank for activated sludge treatment and a sludge mixed liquid after activated sludge treatment is introduced into a filtering separation tank in which filter moduli each comprising a plurality of filter elements are immersed and arranged while filtered water is obtained from the filter moduli by head pressure and the sludge mixed liquid after filtering is returned to the biological reaction tank. In this treatment method, a partition wall is arranged between the filter moduli in the filtering separation tank and air diffusion pipes are respectively provided to the lower parts of the filter moduli and, when filtering and washing, air is alternately passed through two air diffusion pipes adjacent to each other through the partition wall. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to solid-liquid separation in activated sludge treatment, and more particularly to a solid-liquid separation method and device in activated sludge treatment of sewage, organic industrial wastewater, domestic wastewater and the like.

[0002]

2. Description of the Related Art Conventionally, in water treatment using activated sludge, solid-liquid separation of activated sludge must be carried out in order to obtain treated water. Usually, a method is used in which the activated sludge mixed liquid is introduced into a sedimentation tank, the sludge is sedimented by gravity sedimentation, and the supernatant liquid is discharged as treated water from the sedimentation tank. In this case, in order to settle the activated sludge, a settling tank having a sufficient settling area and residence time is required, which is a factor of increasing the size of the processing apparatus and increasing the installation volume. In addition, when the activated sludge deteriorates in sedimentation due to bulking or the like, the sludge flows out of the settling basin, resulting in deterioration of the treated water.

On the other hand, a method of performing solid-liquid separation of activated sludge by membrane separation instead of a sedimentation tank has been used for a long time.
In this case, a microfiltration membrane or an ultrafiltration membrane is generally used as the solid-liquid separation membrane. Suction or pressurization with a pump is required as a filtration / separation means, and usually several tens kPa to several hundreds k
Since the pressure is Pa, the power of the pump is large and the running cost is increased. In addition, S for membrane separation
While clear treated water containing no S can be obtained, the permeation flux is low and it is necessary to regularly wash with chemicals in order to prevent membrane contamination.

Recently, as a solid-liquid separation method for activated sludge instead of a sedimentation basin, a plurality of filter bodies made of filter cloth such as non-woven fabric are soaked in a biological reaction tank, and in the filtration by a dynamic filter layer, the filter body is intermittently placed below A treatment method of supplying gas and cleaning is disclosed. Furthermore, apart from the aeration tank, the aeration tank sludge is introduced into the solid-liquid separation tank in which a plurality of filters with partition walls are placed between the filters, and the filter bodies on both sides with the partition walls are periodically removed. Disclosed is a treatment method in which filtration and aeration are alternately performed.

[0005]

In the treatment method in which gas is intermittently supplied to the lower part of the filter body for cleaning, the flow on the surface of the filter body immersed in the biological reaction tank is from the diffusion tube of the biological reaction tank sandwiching the partition wall. It is formed by aeration of, and the surface flow of each filter is non-uniform. The flow is downflow in all the filters. On the other hand, the ventilation pipe for cleaning the filter is located at the bottom of the filter, and when cleaning by gas supply, the flow on the surface of the filter becomes an upward flow, and due to the sludge flow in the downward flow, a high rising speed or a uniform rising speed. May not be obtained. In this case, the peeling effect of the sludge adhering layer is reduced, and it becomes difficult to maintain a high filtration flux.

Separately from the aeration tank, the aeration tank sludge is introduced into the solid-liquid separation tank in which a plurality of filter bodies having partition walls are immersed between the filter bodies, and the filter bodies on both sides sandwiching the partition wall, In the treatment method in which filtration and aeration are alternately performed on a regular basis, since half of the filter bodies in the solid-liquid separation tank are constantly stopping the filtration operation, an effective amount of filtered water cannot be obtained, and the filter body cannot be obtained. There is a problem that it cannot be effectively used. Further, the sludge flow on the surface of the filter body is a circulation flow due to air diffusion on the opposite side across the partition wall-that is, it is an upward flow for the filter body during aeration of the ventilation pipe and a downward flow for the filter body during filtration. Therefore, if the filter body during filtration cannot obtain a uniform flow rate and the continuous filtration time before cleaning is long, the sludge adhesion layer grows excessively on the surface of the filter body with a slow flow rate, increasing the resistance of the sludge flow path. May cause stagnation of flow. This causes a decrease in filtration flux. It is an object of the present invention to provide a solid-liquid separation method and apparatus which eliminates the conventional drawbacks, can be effectively used for a filter in a solid-liquid separation tank, and can obtain a high filtration flux.

[0007]

The present invention has the following constitution in order to solve the above problems. (1) Introduce the water to be treated into the biological reaction tank for activated sludge treatment,
The sludge mixture after the activated sludge treatment is introduced into a filtration separation tank in which a plurality of filtration modules consisting of a filter are immersed, and filtered water is obtained from the filtration module by head pressure, and the sludge mixture after the filtration is used as a biological reaction tank. In the processing method of returning to the above, a partition wall is installed between each filtration module in the filtration separation tank, and each diffusion module has an air diffuser at the bottom of each filtration module, and adjacent to each other via the partition wall during filtration and washing. A solid-liquid separation method characterized in that only one side of the air diffuser is aerated alternately.

(2) The solid-liquid separation according to the above (1), characterized in that the aeration pipe under the filtration module is continuously aerated when the filtration is stopped and intermittently or continuously when the filtration is continued. Method. (3) When the filtration water turbidity is above a specified value during ventilation, the flow rate is reduced or stopped, and when the filtration water turbidity is below a specified value, the flow rate is increased or restarted. The solid-liquid separation method according to (1) or (2) above. (4) The air flow rate to the air diffuser under the filtration module is 2.5 m ³ / m ² flow path / min or more during washing, and 1.
The solid-liquid separation method according to any one of (1) to (3), which has a flow rate of 0 m ³ / m ² or less.

(5) A filtration module having a partition wall in the tank, and a dynamic filtration layer is formed on the surface of a plurality of filter bodies arranged on both sides of the partition wall; and a filtration module attached to the filtration module. A filtered water discharge pipe, an air diffusing pipe disposed below the filtration module, a ventilation valve that alternately switches ventilation to the diffusing pipe at the time of filtration and washing, and a pipe for supplying biological treated water from a biological reaction tank. A solid-liquid separation apparatus for biologically treated water, comprising a filtration separation tank provided with a return sludge return pipe.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. According to the present invention, the sludge mixed liquid is supplied from the biological reaction tank to the filtration separation tank, and in the dynamic filtration by the filtration module, between the plurality of filtration modules immersed in the filtration separation tank, between the adjacent filtration modules. A partition wall is provided on the partition wall so that 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 with the upper and lower sides of the partition wall. By installing air diffusers at the bottom of the filtration module, if air is vented to any air diffuser of the filtration modules that sandwich the partition wall during air washing, the gas-liquid mixed sludge flow in the air passage side filtration module flow path Results in a relatively uniform upward flow and the opposite filtration module flow path can form a downward sludge flow. By alternately performing this, it is possible to reliably form a flow having a high flow velocity in the same direction with respect to the flow path of the filtration module. Therefore, the sludge cake layer overgrown on the surface of the filtration module can be reliably peeled off, and a high cleaning effect can be obtained.

Similarly, at the time of filtration, the sludge mixed solution in the flow path of the filtration module is removed by ventilating from one of the two filtration modules sandwiching the partition wall with an air diffusion amount smaller than that at the time of air washing, from the air diffusion pipe. It is possible to reliably flow, suppress the growth of the filter surface sludge layer, and maintain a high filtration flux. Further, in the filtration module flow path on the opposite side of the partition wall, a sludge flow that surely becomes a downward flow can be formed, and the sludge bridge caused by the overgrowth of the sludge cake layer due to the flow stagnation can be eliminated. Aeration during filtration is alternately performed on the filtration modules, so that any module can perform filtration at the same time and a high filtration flux can be obtained at all times.

The air diffusing tube for air washing may also be used as the air diffusing tube when the filtration is in progress. However, depending on the sludge properties and concentration, the sludge flow should be surely in the same direction to form a uniform flow in each flow path. To do so, a ventilation pipe may be provided separately. As a ventilation pipe during the progress of filtration, a perforated pipe having a small pore size, preferably a pore size of 1 m
Any of a perforated tube of about m to 3 mm and a diffuser may be used. In addition, in the filtration module that receives ventilation,
Increase in turbidity of filtered water is expected due to sludge concentration and properties. In addition, there is also a decrease in the filtrate flux due to changes in head pressure. Therefore, the size of the ventilation amount and the frequency of switching the ventilation to the air diffuser can be adjusted intermittently by appropriately adjusting the amount of filtered water and the turbidity of filtered water.

The filtration module is composed of a plurality of filtration bodies. The shape of the filter body is mainly a plane type, but a cylindrical type or a hollow type can also be used. The number of filters per filter module is usually about 2 to 100,
In order to make the sludge flow in the filtration module flow path relatively uniform and to obtain a uniform cleaning effect for each filter,
It is preferable that one filter module is used.

[0014]

The present invention will be described in detail below with reference to the drawings showing an example of an embodiment. However, the present invention is not limited to this embodiment.

Example 1 FIG. 1 is a flow sheet showing an example of treatment of beverage wastewater according to the present invention. As shown in FIG. 1, inflow raw water 1 flows into a biological reaction tank 2 to perform activated sludge treatment. The sludge mixture after the activated sludge treatment is sent from the sludge supply pump 3 to the bottom of the filtration separation tank 4. The filtration separation tank 4 has a filtration module A.
7 and 8 of the filtration module B are installed with the partition wall 18 interposed therebetween. In the lower part of the filtration module A and the filtration module B, 9 of the air diffuser A and 10 of the air diffuser B are respectively provided.
Are arranged. Aeration of air diffusers A and B is performed by blower 11 through aeration valves A 5 and B 6, respectively. During aeration, only one of the ventilation valves A and B is opened. The ventilation switching between the air diffusers A and B is performed by switching the ventilation valves A and B, while the ventilation blower 1
1 is a continuous operation.

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 backwashing with water, the water backwashing pump 13 uses the filtered water 14 in the treated water tank 12 to carry out backwashing with water by supplying it to the inside of the filtration module. At the time of backwashing with water, the sludge invading the inside of the module is returned to the biological reaction tank 2 as the discharged sludge 16 from the bottom of the filtration module. Further, the sludge mixed solution 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.

[0017]

[Table 1]

In this embodiment, the filtration and separation tank 4 has three and seven flat water-permeable filters having an effective filtration area of 0.7 m ² / sheet.
Was used as the filter body module, and two filtration modules A and B were dipped and installed. Thickness 20 between A and B filtration modules
A mm partition wall 18 was provided. The partition wall 18 communicates with the upper and lower parts as shown in the figure. As a water-permeable filter of the filtration module, a thickness of about 0.1 mm,
A polyester woven fabric having a pore size of 114 μm was used. The head pressure during filtration was set to about 10 cm, the flow rate of the sludge mixed solution supplied to the filtration separation tank 4 was set to 30 m ³ / d, and the sludge flow velocity on the surface of the filter was set to 0.01 m / s on average.

The filtration process was carried out for 120 minutes per cycle. In this cycle of 120 minutes filtration, ventilation valve A
Aeration cycle is ON for 5 minutes through (5) or B (6), 1
Perform intermittent ventilation for 0 minutes OFF. Venting is vent pipe A or B
Since it is performed for either of the above, the ventilation from the ventilation pipes A and B is a ventilation for 5 minutes and a stop for 25 minutes, respectively. The air flow rate during filtration was 0.2 m ³ / m ² / min. Vent valve A
At the time of air diffusion from (5), for the filtration module A,
The liquid is an upward flow, and the liquid is a downward flow for the filtration module B, and the flow of the liquid to the filtration modules A and B is reversed when air is diffused from the ventilation valve B (6). Then, 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 in the sludge passage, and the flow velocity of the liquid to each filtration surface is Can be maintained.

Since the filtration resistance increases after a certain time has passed in the filtration step, external air washing is carried out. As an external air washing method for the filtration module, the aeration blower 11 is activated every 120 minutes of filtration, and continuous ventilation for 6 minutes is performed. Wash with air. During that time, the air-washing time from the ventilation valve A to the filtration module A and the air-washing time from the ventilation valve B to the filtration module B were each set to 3 minutes. When 5 of the aeration valve A is opened and aeration pipe 9 at the bottom of the filtration module A is aerated, ventilation is performed by closing 6 of the aeration valve B. At this time, the sludge mixed liquid is directed upward on the surface of the filtration module A. Flow and then the sludge mixture is separated by the partition wall 18
Enters the side of the filtration module B through the upper end of and passes through the surface of the filtration module B in a descending flow. Similarly, when ventilating to the vent pipe B 10 at the bottom of the B module, the sludge flow on the surfaces of the A and B modules becomes a downward flow and an upward flow.

The backwashing with water is performed by using the filtered water 14 in the treated water tank 12 and supplying it to the inside of the filtration module. The amount of water backwash is
The filtration area was set to 40 m / d, and in this example, it was set to 117 liter / min, and the operation was performed for 30 seconds. Simultaneously with the backwashing with water, the sludge is discharged from the inside of the filtration module, and the sludge is continued for another minute after backwashing with water.

FIG. 2 shows the course of filtration flux of all the filtration modules in the example. MLSS at the time of implementation is about 60
It is 00 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 the stable treatment was obtained. FIG. 3 shows the course of filtered water turbidity. In continuous operation for about 2 months, the turbidity of the filtered water was about 10 degrees or less, showing good filtering performance, and clear filtered water was stably obtained.

[0023]

According to the present invention, the sludge mixture is supplied from the biological reaction tank to the filtration separation tank, and in the dynamic filtration by the filtration module, adjacent to the plurality of filtration modules immersed in the filtration separation tank. If a partition wall is provided between the filtration modules of the two filters, air diffusers are installed at the bottoms of the filtration modules, and air is vented to any air diffuser of the filtration modules that sandwich the partition wall during washing, the ventilation side module The gas-liquid mixed sludge flow in the channel becomes a relatively uniform upward flow, and the module channel on the opposite side can form a downward sludge flow. By alternately performing this, it is possible to reliably form a flow having a high flow velocity in the same direction with respect to the module flow path. Therefore, the sludge cake layer overgrown on the surface of the filtration module can be reliably peeled off, and a high cleaning effect can be obtained.

Similarly, at the time of filtration, one of both modules sandwiching the partition wall with a smaller amount of air diffused than during air washing,
Ventilation from the air diffuser can reliably fluidize the sludge mixed solution in the filtration module flow path, suppress the growth of the sludge layer on the surface of the filter body, and maintain a high filtration flux. Further, 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 pledge caused by the overgrowth of the sludge cake layer due to the stagnant flow can be eliminated. Aeration at the time of filtration is alternately performed to the filtration modules, so that a high filtration flux is always obtained in any of the filtration modules.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an apparatus for performing solid-liquid separation in activated sludge treatment of the present invention.

FIG. 2 is a graph showing changes over time in the filtered water flux of the examples of the present invention.

FIG. 3 is a graph showing changes with time in turbidity of filtered water according to an example of the present invention.

[Explanation of symbols]

1 Inflow raw water 2 Biological reaction tank 3 Sludge supply pump 4 Filtration separation tank 5 Vent valve A 6 Vent valve B 7 Filtration module A 8 Filtration module B 9 Air diffuser A 10 Air diffuser B 11 ventilation blower 12 treated water tank 13 Water backwash pump 14 filtered water 15 Return sludge 16 Discharged sludge 17 Treated water 18 partition walls

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiro Tanaka             11-1 Haneda Asahi-cho, Ota-ku, Tokyo Co., Ltd.             Inside the EBARA CORPORATION F-term (reference) 4D006 GA02 HA93 KA01 KA43 KB22                       KC03 KC14 KE24Q PB20                       PC62                 4D028 AB00 BC01 BC17 BD17                 4D066 BA01 BB01 DA03 FA02

Claims (5)

[Claims] 1. The water to be treated is introduced into a biological reaction tank for treatment of activated sludge, and the sludge mixed solution after the treatment of activated sludge is introduced into a filtration separation tank in which a filtration module consisting of a plurality of filter bodies is submerged and installed. In the treatment method of obtaining filtered water from the filtration module by pressure and returning the sludge mixed solution after filtration to the biological reaction tank, a partition wall is installed between the filtration modules in the filtration separation tank, and each filtration module has a lower part at the bottom. With an air diffuser
A solid-liquid separation method, characterized in that during filtration and washing, aeration of only one of the adjacent air diffusers through the partition wall is performed alternately. 2. The solid-liquid separation method according to claim 1, wherein aeration of the air diffusing pipe below the filtration module is continuously performed when filtration is stopped and intermittently or continuously when filtration is continued. 3. When ventilation of filtration is continued, when the turbidity of filtered water exceeds a predetermined value, the flow rate is reduced or stopped, and when turbidity of filtered water is below a predetermined value, the flow rate is increased. Alternatively, the solid-liquid separation method according to claim 1 or 2, which is restarted. 4. The air flow rate to the air diffuser under the filtration module is 2.5 m ³ / m ² flow passages / min or more during washing and 1.0 m ³ / m ² passages / min or less during filtration. The solid-liquid separation method according to any one of claims 1 to 3, characterized in that. 5. A filtration module having a partition wall in a tank, wherein a dynamic filtration layer is formed on the surface of a plurality of filter bodies arranged on both sides of the partition wall, and a filtration module attached to the filtration module. A filtered water discharge pipe, an air diffusing pipe arranged below the filtration module, a ventilation valve that alternately switches ventilation to the diffusing pipe during filtration and washing, and a feed pipe for biologically treated water from a biological reaction tank. A solid-liquid separation apparatus for biologically treated water, comprising a filtration separation tank provided with a return sludge return pipe.