JP2000070940A - Solid-liquid separation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a high water permeating rate and low turbidity of permeated water over a long period by equipping a turbidimeter for measuring the turbidity after permeation in a permeated liquid line further arranging a switching valve and a return line for returning the permeated liquid to a biologically treating vessel when the turbidity of the permeated liquid becomes equal to or above a specific value. SOLUTION: At the time of normal filtration, a biologically treated liquid in a biologically treating vessel 2 is filtered and treated by a filtration body 1 by operating a suction pump 8 and the permeated liquid is sent through a permeated liquid line 5. At this time, a valve 7a in the permeated liquid line 5 is opened and a valve 7b in a washing line 3 and a valve 7c in a return line 6 are closed. Then, when the measured value of a turbidimeter 4 disposed in the permeated line 5 is >=50, each of the valve 7a and 7b is closed and the valve 7c is opened to return the permeated liquid to the biological reaction vessel 2 through the return line 6. As a result, the permeated liquid increased in the turbidity is filtered again in the biologically treating vessel 2 to keep the turbidity of the permeated liquid constantly low and to prevent the lowering of a water permeation rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-liquid separation system which is particularly suitable for solid-liquid separation of a biological treatment tank containing suspended matter such as sludge and can maintain high filtration performance.

[0002]

2. Description of the Related Art
Water treatment using a nonwoven fabric has been attempted for the separation treatment of liquids including suspended matter and sludge, and various measures have been taken to improve and stabilize filtration performance. JP-A-10-1283
No. 75 discloses that a supporting material having an opening having a separation particle size of 30 μm or more and a thickness of 2 mm or less is immersed, a filtration membrane made of activated sludge and turbidity is formed on the supporting material, and a head difference is generated. A sewage treatment apparatus for performing filtration is disclosed. Japanese Patent Application Laid-Open No. H10-128397 discloses a hollow filtration apparatus having a support having a mesh size of 50 μm or more and a thickness of 2 mm or less. An anaerobic sludge digester is disclosed in which a body is immersed below a scum layer, a filtration membrane composed of digested sludge and turbid matter is formed on the support material, and filtration is performed by head difference. These filtration methods incorporate so-called dynamic filtration, and the dynamic filtration using this nonwoven fabric is described in Daito et al., “Proceedings of the 34th Sewerage Research Conference”, pp. 647-649. "Dynamic membrane filtration of 7-89 activated sludge mixture"
Has also been reported. However, in the case of performing dynamic filtration, a phenomenon in which the turbidity of the permeate (the concentration of the suspended matter) increases until a dynamic layer is formed on the membrane surface is observed, so that the permeate is stable for a long time. There is room for improvement in that it is difficult to maintain low permeate turbidity.

Accordingly, an object of the present invention is to provide a solid-liquid separation system capable of maintaining a high water permeation rate and a low permeate turbidity over a long period of time.

[0004]

Means for Solving the Problems The present inventors have studied the operating conditions and the filtration performance in the activated sludge separation, and as a result, have found that a method of returning a permeate having high turbidity to a filtration device and performing re-filtration is adopted. By paying attention, the present inventors have found out the optimum conditions and means for the return without lowering the filtration performance of the apparatus itself, and have completed the present invention.

That is, the present invention provides a solid-liquid separation system comprising at least a biological treatment tank, a filter for filtering the biological treatment liquid, and a permeate line for sending a permeate from the filter. The liquid line is provided with a turbidity meter for measuring the turbidity of the permeate, and further provided with a switching valve and a return line for returning the permeate to the biological treatment tank when the turbidity of the permeate becomes 50 or more. A solid-liquid separation system.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The solid-liquid separation system of the present invention comprises a system in which a filter is immersed in a biological treatment tank such as an activated sludge tank and a system in which a liquid to be treated from the biological treatment tank is circulated to an externally mounted filter. Can be applied to any of the above. Hereinafter, a solid-liquid separation system of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a solid-liquid separation system of an immersion type, and FIG.
FIG. 3 is a schematic perspective view of a membrane element constituting a filter (membrane module) used in the present invention, FIG. 3 is a conceptual diagram of an external solid-liquid separation system, and FIG. 4 is a filter (membrane module) used in FIG. It is a schematic perspective view of.

As shown in FIG. 1, the biological treatment tank 2 contains
A filter 1 for filtering the biological treatment liquid is immersed, and a permeate line 5 for sending a permeate is connected to the filter 1. Reference numeral 10 denotes an air diffuser.

As shown in FIG. 2, a filter element 1 in which a plurality of membrane elements 20 are collectively connected in parallel can be used. The membrane element 20 has a net as a flow path material inserted therein, and both ends of the membrane element 20 are support members 22.
Sealed and supported by Reference numeral 24 denotes a water intake for the permeated liquid from the membrane element, which is connected to the permeated liquid line 5.

The filter material constituting the filter body 1 is not particularly limited, but the average pore diameter is desirably 1 to 200 μm, particularly desirably 3 to 100 μm, in order to maintain a suitable water permeation rate. A nonwoven fabric is preferred as such a filtering material.
Examples of the material of the fibers constituting the nonwoven fabric include natural fibers such as cotton, hemp, and wool, polyester, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly (meth) acrylate, viscose rayon, cellulose acetate, and methyl cellulose. Examples include cellulose derivatives, polyolefins such as polyethylene and polypropylene, polycarbonates, polyamides, polyesteramides, polyethers, polyimides, polyamideimides, polyetherimides, and synthetic fibers composed of a mixture or copolymer of two or more thereof. Among them, those made of polyester, polyethylene, polypropylene or polycarbonate fibers are preferable, and those made of polyester or polypropylene are particularly preferable. For the average pore size of the nonwoven fabric, a method of mechanically bonding, pressure processing or heat processing, laminating a porous polymer film, an adhesive or a chemical treatment method on one surface of the fiber layer of the nonwoven fabric is applied. And can be controlled.

At a desired position of the permeate line 5, a turbidity meter 4 for measuring the turbidity of the permeate is provided. A return line 6 for returning the permeate to the biological treatment tank 2 is branched and connected to the permeate line 5 on the downstream side of the permeate from the mounting position of the turbidimeter 4, and is connected downstream from the branch position. The permeate line 5 on the side is provided with a valve 7a. 8 in the permeate line 5 is a suction pump, 9a is a pressure gauge, 9b
Indicates a flow meter, and 7c in the return line 6 indicates a valve.

Further, the solid-liquid separation system may be provided with a backwashing mechanism for pressurizing a fluid from the permeate side of the filter 1, for example, a washing line 3 connected to the permeate line 5.
And the valve 7b can be a backflow cleaning mechanism.

Next, a solid-liquid separation method using the solid-liquid separation system shown in FIG. 1 will be described. During normal filtration, the biological treatment liquid in the biological treatment tank 2 is filtered by the filter 1 by operating the suction pump 8, and the permeate is sent through the permeate line 5. At this time, the valve 7a of the permeate line 5 is opened, and the valve 7b of the washing line 3 and the valve 7c of the return line 6 are closed.

In the solid-liquid separation system shown in FIG. 1, when the value of the turbidity meter 4 installed in the permeate line 5 becomes 50 or more, the valves 7a and 7b are closed manually or automatically, and the valve 7c is opened. The permeate is returned to the biological reaction tank 2 through the return line 6. By this operation, the permeate having increased turbidity is returned to the biological treatment tank 2 and re-filtered, whereby the turbidity of the permeate can be constantly maintained at a low value, and the permeation rate decreases. Can be prevented.

In the solid-liquid separation system shown in FIG. 1, it is desirable to carry out backwashing of the filter 1 with a washing fluid in order to prevent a reduction in water permeation rate. When performing backwashing, the valve 7a and the valve 7c are closed, the valve 7b is opened, and the cleaning fluid is supplied to the cleaning line 3.
And permeate liquid line 5, and is pressure-fed from the permeate side of filter 1 to the supply water side. Examples of the fluid used for backflow cleaning include air, gas such as nitrogen, water, and a chemical cleaning agent.
Air and water are preferred for simplicity of operation, and reuse of the permeate is particularly preferred from the viewpoint of effective utilization of resources.

In the case of backwashing in the solid-liquid separation system shown in FIG. 1, the permeated liquid for a maximum of 5 minutes from the start of backflow washing is used together with the control by the turbidimeter 4 or separately from the control of the turbidimeter. It is desirable to return the biological treatment tank 2 from the return line 6 by operating in the same manner as described above. When backwashing is performed,
Since dirt adhering to the filter body 1 is released in a short time, and the turbidity of the permeated liquid at the time of restarting the operation rapidly increases, it is desirable to return the permeated liquid for a predetermined time after the restart of the operation. The predetermined time is appropriately set within a maximum of 5 minutes in accordance with the backwash time, the degree of contamination of the filter 1 and the like.
By such an operation, the turbidity of the permeate can be constantly maintained at a low value by returning the permeate having increased turbidity to the biological treatment tank 2 and re-filtrating, and reducing the permeate rate. Can also be prevented.

Next, another embodiment of the solid-liquid separation system will be described with reference to FIG. FIG. 3 shows an external solid-liquid separation system, in which a filter 11 is installed outside a biological treatment tank 12, and there is a slight difference with the filter 11. They have the same configuration and perform the same operation.

Next, a solid-liquid separation method using the solid-liquid separation system shown in FIG. 3 will be described, and differences from the system shown in FIG. 1 will also be described.

At the time of ordinary filtration, the liquid feed pump 18 is operated, and the liquid to be treated is sent from the biological treatment tank 12 to the filter 11.
Filter. 17d is a valve, 20b is a pressure gauge, 21
Is an air diffuser, 22 is a stock solution (biological treatment solution) supply line, 2
3 indicates a bypass line.

As the filter 11, a membrane module 30 as shown in FIG. 4 can be used. Membrane module 3
Numeral 0 indicates that the two membrane elements 20 described in FIG. 2 are housed in the casing 32, the concentrated liquid outlet 34, the permeated liquid intake 3
6. A stock solution supply port 38 is provided. The concentrate outlet port 34 is connected to the concentrate line 19, the permeate inlet port 36 is connected to the permeate line 15, and the stock solution supply port 38 is connected to the stock solution supply line 22.

The permeate from the filter 11 is sent through a permeate line 15. At this time, the valve 17a of the permeated liquid line 5 is opened, and the valve 17b of the washing line 13 is opened.
And the valve 17c of the return line 16 is closed. 20a of the permeate line 15 is a pressure gauge, and 20e is a flow meter. The concentrated liquid is returned to the biological treatment tank 12 from the concentrated liquid line 19 in parallel with the supply of the permeated liquid.

In the solid-liquid separation system of FIG. 3, when the value of the turbidity meter 14 installed in the permeate line 15 becomes 50 or more, the valves 17a and 17b are closed manually or automatically, and the valve 17c is opened. The permeate is returned to the biological reaction tank 12 through the return line 16.

In the solid-liquid separation system shown in FIG. 3, it is desirable to carry out backwashing of the filter 11 with a washing fluid in order to prevent a decrease in the amount of permeate. When performing backwashing, the valve 17a and the valve 17c are closed and the valve 17b is opened, and the cleaning fluid is pumped from the permeate side of the filter 11 to the supply water side through the cleaning line 13 and the permeate line 15. Is done.

In the case of backwashing in the solid-liquid separation system of FIG. 3, the permeate for a maximum of 5 minutes from the start of backwashing may be used together with the control by the turbidimeter 14 or separately from the control of the turbidimeter. It is desirable to return the biological treatment tank 12 from the return line 16 by operating in the same manner as described above.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, the method of the performance test performed in the following Examples is as follows.

(1) Average Pore Diameter A nonwoven fabric was photographed at a magnification of 100 and / or 10,000 times at an electron microscope surface, and three places having an area of 2 × 2 cm were processed by an image processor to calculate an average pore diameter.

(2) Thickness The thickness of the nonwoven fabric was measured with a micrometer.

(3) Water Permeation Rate The amount of filtration in Examples and Comparative Examples was measured, and
The amount of permeate per unit membrane area was defined as the permeation rate, and was used as an index of the permeation performance of the filtrate of the separation membrane. The unit is m ³ / (m ² · d
ay).

(4) Permeate turbidity Permeate turbidity was measured by a turbidity meter (Model 2100P, manufactured by HACH).

Example 1 The solid-liquid separation system shown in FIG. 1 was used to perform the solid-liquid separation using the filter shown in FIG. As this filter, two non-woven fabrics (FC3105, manufactured by Japan Vilene Co., Ltd., average pore diameter 15 μm, length 40 cm, width 5 cm, thickness 1.4 mm) as a filtering material, an opening 16 with a fiber diameter of 0.8 mm
Laminated on both sides of a two-layer mesh net made of polyethylene, a permeate water inlet 24 is attached to the upper end, and both upper and lower ends are bonded and sealed with a sealing material 22 and both ends of the nonwoven fabric are sealed by heat sealing. ^Two bag-shaped membrane elements (effective membrane area: 0.04 m ² ) were arranged in parallel to form a membrane module, which was used without being loaded in a casing. For the solid-liquid separation, a permeated liquid return operation was performed for 2 minutes from the start of the operation, and then a normal filtration operation was performed for 28 minutes, followed by air backwashing for 1 minute, and this was repeated. The operating conditions were as follows: activated sludge treatment wastewater (MLSS 3,0) collected at the Himeji Works of Daicel Chemical Industries, Ltd. as a stock solution.
00 mg / liter, average particle diameter 50 μm), the permeate volume was 2.0 m ³ / (m ² · day), and the temperature was 20 ° C. FIG. 5 shows the change over time in the turbidity of the permeate. Table 1 shows the average values of the turbidity of the permeate and the water permeation rate when operated for 2 hours.

Example 2 Solid-liquid separation was performed using the solid-liquid separation system shown in FIG. 3 and the filter shown in FIG. As the filter, two of the membrane elements 20 of Example 1 were connected to the undiluted solution supply port 3
8. A membrane module loaded in a casing 32 having a concentrate outlet 34 and a permeate inlet 36 was used. Solid-liquid separation was performed under the same conditions as in Example 1, and this was repeated.
The operating conditions were the same stock solution as in Example 1, the supply liquid linear velocity was 0.1 m / s, the transmembrane pressure was 4 kPa, and the temperature was 20 ° C.
The change over time in the turbidity of the permeate was the same as in FIG.
Table 1 shows the average values of the permeate turbidity and the water permeation rate when the operation was performed for 2 hours.

Example 3 Solid-liquid separation was carried out in the same manner as in Example 1, except that H8007 (manufactured by Nippon Vilene Co., Ltd., average pore diameter 100 μm, thickness 0.2 mm) was used as the nonwoven fabric of the filtering material. The change over time in the turbidity of the permeate was the same as in FIG. Also, 2
Table 1 shows the average values of the turbidity of the permeate and the permeation rate when the operation was performed for an hour.

Example 4 Solid-liquid separation was carried out in the same manner as in Example 2 using MF180 (manufactured by Japan Vilene Co., Ltd., average pore diameter: 10 μm, thickness: 1.4 mm) as a non-woven fabric of a filtering material. The change over time in the turbidity of the permeate was the same as in FIG. Table 1 shows the average values of the turbidity of the permeate and the water permeation rate when operated for 2 hours.

Comparative Example 1 Solid-liquid separation was carried out in the same manner as in Example 1 except that FC3105 was used as the nonwoven fabric of the filtering material. However, after performing the filtration operation for 30 minutes, the air backwash was performed for 1 minute.
Minutes, and this was repeated. FIG. 6 shows the change over time in the turbidity of the permeate. Table 1 shows the average values of the turbidity of the permeate and the water permeation rate when operated for 2 hours.

Comparative Example 2 Solid-liquid separation was performed in the same manner as in Example 2 except that FC3105 was used as the nonwoven fabric of the filtering material. However, after performing the filtration operation for 30 minutes, the air backwash was performed for 1 minute.
Minutes, and this was repeated. The change over time in the turbidity of the permeate was the same as in FIG. Table 1 shows the average values of the turbidity of the permeate and the water permeation rate when operated for 2 hours.

Comparative Example 3 Solid-liquid separation was carried out in the same manner as in Example 2 except that FC3105 was used as the nonwoven fabric of the filtering material. However, the operation was performed for 10 minutes, the permeated liquid return operation, the normal filtration operation was performed for 20 minutes, and then the air backwash was performed for 1 minute.
This was repeated. The change over time in the turbidity of the permeate was the same as in FIG. Table 1 shows the average values of the turbidity of the permeate and the water permeation rate when operated for 2 hours.

[0036]

[Table 1]

In Examples 1 to 4, the water permeation rate could be kept high while the permeate turbidity was kept low. This is because, as is clear from FIG. 5, the permeate having a high turbidity was returned at the start of the operation and after the backwashing with air, and was filtered again. In Comparative Examples 1 and 2, the water permeation rate could be maintained high, but the permeate turbidity was high. This is clear from FIG.
This is because the permeated liquid having a high turbidity at the start of the operation and after the backflow cleaning was not returned. In Comparative Example 3, the turbidity of the permeate was low because the permeate return time from the start of operation was too long, but the water permeation rate was significantly reduced.

[0038]

The solid-liquid separation system of the present invention can maintain a low turbidity of a permeate while maintaining a high water permeation rate.

[Brief description of the drawings]

FIG. 1 is a schematic view of a membrane-immersion type solid-liquid separation system.

FIG. 2 is a perspective view of a membrane element constituting a filter used in the membrane immersion type solid-liquid separation system of FIG.

FIG. 3 is a schematic diagram of an extra-membrane solid-liquid separation system.

4 is a perspective view of a filter used in the extra-membrane solid-liquid separation system of FIG.

FIG. 5 is a graph showing the change over time in the turbidity of a permeate in Example 1.

FIG. 6 is a graph showing the change over time in the turbidity of a permeate in Comparative Example 1.

[Explanation of symbols]

 1, 11: filter body 2, 12: biological treatment tank 3, 13: washing line 4, 14: turbidity meter 5, 15: permeate line 6, 16: return line 7a to 7c, 17a to 17c: valve 8: Suction pump 9a, 20a to 20c: pressure gauge 9b, 20d, 20e: flow meter 10, 21: air diffuser 18: liquid sending pump 19: concentrated liquid line

 ──────────────────────────────────────────────────続 き Continued on front page F-term (reference) 4D006 GA02 HA77 HA93 JA06A JA31A JA53A JA58A JA63A JA70A JB04 KA12 KA67 KB22 KC03 KC14 KE03P KE09P KE13P KE22P KE24P KE28P MA09 MA22 MA40 MB02 MC11 MC23 MC24 MC27 MC48 MC23 MC23 MC48 MC54 MC57 MC58 MC59 MC69 NA46 NA47 NA50 NA54 PB08 PC62 4D028 BC03 BC17 BD16 CD05

Claims (4)

[Claims] 1. A solid-liquid separation system comprising at least a biological treatment tank, a filter for filtering a biological treatment liquid, and a permeate line for sending a permeate from the filter, wherein the permeate line is It is provided with a turbidity meter for measuring the turbidity of the permeate, and further provided with a switching valve and a return line for returning the permeate to the biological treatment tank when the turbidity of the permeate becomes 50 or more. Liquid separation system. 2. A backflow washing mechanism for pressurizing a fluid from the permeate side of the filter body, and for returning the permeate from the filter body to the biological treatment tank up to 5 minutes after the start of the backflow washing. The solid-liquid separation system according to claim 1, further comprising a switching valve and a return line. 3. A solid-liquid separation system comprising at least a biological treatment tank, a filter for filtering the biological treatment liquid, and a permeate line for sending a permeate from the filter, the permeate side of the filter. And a switching valve and a return line for returning the backwash water from the filter body to the biological treatment tank up to 5 minutes from the start of the backflow washing. Characterized solid-liquid separation system. 4. The filter according to claim 1, wherein the filter is a non-woven fabric having an average pore diameter of 1 to 200 μm.
A solid-liquid separation system as described.