JP2001104953A - Method and apparatus for treating turbid water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively treat turbid water simply and inexpensively. SOLUTION: Turbid water with BOD of 50 mg/L or less and SS of 100 mg/L or more is subjected to cross flow filtering under an intermembranous pressure of 30 kPa or less by a separation membrane unit 5 using a nonwoven fabric membrane. A sedimentation tank for sedimenting and removing coarse particles of turbid water may be provided on the upstream side of the separation membrane unit for treating turbid water. Further, the separation membrane unit is constituted of nonwoven fabric membrane elements mutually separated to be opposed to each other and a treated water tank 6 for storing the filtered water from the separation membrane unit and a backwashing water tank 8 introducing a washing soln. or a chemical soln. to backwash the separation membrane unit may be equipped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for treating turbid water using a nonwoven fabric membrane.

[0002]

[Prior Art] Groundwater and muddy water generated at construction sites, etc.
Turbid water, such as sediment wash water, has a low BOD (biochemical oxygen demand) component, but contains a large amount of SS (suspended particle) components. . Therefore, in order to remove the SS component, the turbid water is roughly precipitated, then neutralized or agglomerated with a chemical, precipitated and separated, and the separated treatment liquid is post-treated and discharged if necessary.

In this method, for example, if the coagulation treatment is not performed sufficiently, it is difficult to remove the SS component, and in some cases, the treatment cannot be performed. Therefore, the coagulation treatment needs to be performed sufficiently. In order to effectively precipitate the SS component in the coagulation treatment, it is necessary to control the amount of chemicals to be injected according to the water quality, but the turbid water generated at the construction site fluctuates greatly, and it is necessary to control the coagulation treatment with high precision. difficult. Furthermore, in the conventional method, the cohesiveness varies depending on the conditions such as the flow rate and the number of stirring, in addition to the amount of the drug to be supplied depending on the water quality, and thus requires a skilled technique.

It is also conceivable to use a microfiltration membrane or the like without precipitating and separating the SS component. However, according to this method, clogging of the separation membrane is liable to occur, and the permeation rate is low. Therefore, it is difficult to efficiently filter the SS component, and the cost becomes high economically.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method and an apparatus for treating turbid water which can reliably treat turbid water by a simple and inexpensive method.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object. As a result, when turbid water is treated using a nonwoven fabric membrane, the turbid water can be treated with a simple and inexpensive method and reliably. We have found that we can do this and completed the present invention.

That is, the method for treating turbid water of the present invention
It is characterized in that turbid water having an OD of 50 mg / liter or less (particularly 0 to 10 mg / liter) and SS of 100 mg / liter or more is filtered by forming a cake layer of an object to be treated with a nonwoven fabric membrane. In the treatment of the turbid water, the turbid water may be filtered at a transmembrane pressure of 30 kPa or less, and the turbid water may be filtered by a cross-flow method using a separation membrane unit using a nonwoven fabric membrane. After the turbid water is subjected to a coagulation treatment, the turbid water may be filtered through a nonwoven fabric membrane. Also,
After the turbid water is preliminarily settled in a sedimentation tank that does not perform the coagulation treatment, the supernatant water may be filtered through a nonwoven fabric membrane (particularly by a cross-flow method using a separation membrane unit using a nonwoven fabric membrane),
Further, the non-filtrated water more than twice concentrated may be returned to the settling tank.

[0008] The present invention also includes an apparatus for treating turbid water having a BOD of 50 mg / liter or less and an SS of 100 mg / liter or more, wherein the apparatus comprises a separation membrane unit using a nonwoven fabric membrane. Turbid water treatment equipment includes
A settling tank for removing coarse particles of the turbid water by settling may be provided on the upstream side where the turbid water is treated by the separation membrane unit. Further, the separation membrane unit is composed of a plurality of nonwoven fabric elements having nonwoven fabric membranes facing each other at a distance from each other, and a treatment water tank for storing filtered water filtered by the separation membrane unit, and a cleaning liquid or a chemical solution. A backwash water tank for introducing and backwashing the separation membrane unit may be provided.

The present invention also provides a separation tank unit using a sedimentation tank without pre-coagulation treatment in which turbid water is settled in advance, a non-woven fabric membrane for filtering the supernatant water of the sedimentation tank, and a cross-flow unit using the separation membrane unit. It also includes a line for returning non-filtrated water concentrated by filtration to the sedimentation tank, and a turbid water treatment apparatus equipped with equipment for dewatering and solidifying sludge drawn from the sedimentation tank.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the turbid water treatment apparatus of the present invention will be described below using specific embodiments.

(Embodiment 1) An example of a turbid water treatment apparatus of the present invention will be described with reference to FIG. FIG. 1 shows Embodiment 1
FIG. 2 is a flowchart of a turbid water treatment device in FIG.
FIG. 3 is a schematic perspective view of a separation membrane unit using the nonwoven fabric membrane of FIG.

As shown in FIG. 1, first, a liquid to be treated (turbid water having a BOD of 5 mg / l and an SS component concentration of 1000 mg / l) is supplied from a stock solution supply line 1 at a flow rate of 100 m ³ / l.
It is supplied to the sedimentation tank 2 over time, and in the sedimentation tank 2, components having a high specific gravity, such as sand and stone, are naturally settled without using a coagulating agent. In addition, this sedimentation tank may have two stages.

The liquid to be treated has a relatively low BOD and a relatively high SS component concentration. That is, the BOD is 50 mg / liter or less, preferably 20 mg / liter or less (0 to
20 mg / liter), particularly preferably 10 mg / liter or less (0 to 10 mg / liter),
00 mg / liter or more (for example, 200 to 50,000
mg / L), preferably 500 mg / L or more (for example, 500 to 30000 mg / L), and particularly preferably about 500 to 10000 mg / L. The turbid water having such a component does not correspond to domestic wastewater having a relatively high BOD value, and includes, for example, groundwater, muddy water, and sediment washing water generated at a construction site.

Next, the supernatant water of the settling tank 2 is supplied to the raw water tank 3. The sediment in the sedimentation tank 2 is sent to the slurry tank 10 as drawn sludge, and is turned into a cake by the filter press 15 (equipment for dehydrating and solidifying). Here, a filter press is shown as an example of the equipment for dehydration and solidification,
Other known equipment may be used. On the other hand, the residual liquid is returned to the sedimentation tank 2 again from the residual liquid line 11.

Next, the liquid to be treated (supernatant water, SS component concentration: 1000 mg / liter) supplied to the raw water tank 3 is supplied from the membrane supply line 4 to the separation membrane unit (500 m ² ) 5 at a flow rate of 180 m ³ / hour. I do. In the separation membrane unit 5, the filtered water is sent to the treated water tank 6 at a flow rate of 120 m ³ / hour. The non-filtered water in the separation membrane unit 5 is concentrated three times and returned to the sedimentation tank 2 at a flow rate of 60 m ³ / hour.

An example of the separation membrane unit 5 is shown in FIG.
The unit is composed of a plurality of (seven in the figure) nonwoven fabric membrane elements 12, and is formed by juxtaposing and facing each other with a gap. Non-woven membrane element 12
Is a flat membrane element having a bag-like structure provided with nonwoven membranes facing each other at a distance from each other, and filtered water filtered by the nonwoven membrane flows out of the unit 5 through the nozzle 13.

Since the turbid water treatment apparatus of the present invention includes the separation membrane unit 5, no coagulation treatment is required, and there is no need to install a coagulation sedimentation tank as in a conventional apparatus. In this case, the non-filtrated water in which the turbid water is concentrated twice or more, preferably three times or more by the separation membrane unit 5 is returned to the return line 9.
Is preferably returned to the precipitation tank 2.

As shown in FIG. 1, the filtered water from the separation membrane unit 5 is supplied from a treated water tank 6 to a neutralization tank 7, where it is neutralized and discharged at a flow rate of 100 m ³ / hour. At this time, the SS component concentration of the discharge water is 10 mg / liter or less. The filtered water from the treatment water tank 6 may be sent to the backwash water tank 8 as a washing liquid, and may be used for backwashing the separation membrane unit 5 at a flow rate of 20 m ³ / hour (intermittent backwash average flow rate).
In addition, as the cleaning liquid, besides filtered water, separately supplied clean water may be used, and a chemical such as an aqueous solution of sodium hypochlorite can also be used for the reverse cleaning.

As the nonwoven fabric used in the separation membrane unit, for example, a nonwoven fabric having at least one of the following properties can be selected. (1) Weight per unit area: about 10 to 1,000 g / m ² , preferably about ²⁰ to 900 g / m ² (2) Air permeability: about 0.1 to 200 cm ³ / cm ² · s
Preferably 0.2~150cm ³ / cm ² · s about (3) average diameter of the fibers: about 0.5 to 30 m, preferably about 1 to 10 [mu] m (4) of fabric thickness: 30～5,00
About 0 μm, preferably about 100 to 2,000 μm The non-woven fabric is made of fibers (natural fibers, regenerated fibers, semi-synthetic fibers, etc.) using a conventional method (fibers are formed into a web and bonded by thermocompression bonding or an adhesive, etc.). , Needle punch method, etc.). Examples of the natural fiber include cotton, hemp, wool, and cellulose fiber. Regenerated fibers include rayon (such as viscose rayon). Examples of the semi-synthetic fibers include cellulose ester fibers (such as cellulose acetate fibers) and cellulose ether fibers (such as methyl cellulose fibers). Synthetic fibers include polyester (polyethylene terephthalate, polybutylene terephthalate, etc.), (meth) acrylic resin (poly (meth)
Acrylic acid ester, polyacrylonitrile, etc.), polycarbonate, polyether, polyetherester,
Thermoplastic resins such as polyamide (nylon 6, nylon 66, etc.), polyimide, polyamide imide, polyolefin (polyethylene, polypropylene, etc.), halogen-containing vinyl resins (polyvinyl chloride, polyvinylidene chloride, etc.), polystyrene, etc., and the composition of these resins Fibers obtained from copolymers and crosslinked products obtained by combining units, and mixtures thereof are exemplified. Preferred fibers include polyester fibers (polyethylene terephthalate fibers, polybutylene terephthalate fibers, etc.) and polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), especially polyester fibers.

The average pore size of the nonwoven fabric membrane can be selected within a range that does not impair the water permeability and the separation performance.
It may be about 0 μm (for example, about 1 to 200 μm), preferably about 10 to 300 μm (for example, about 10 to 200 μm), and more preferably about 15 to 300 μm (for example, about 15 to 200 μm). The average pore diameter can be calculated by taking electron microscope photographs of 100 times and 10,000 times the surface of the separation membrane and processing them with an image processing device.

The filtration rate of the nonwoven fabric membrane against pure water
At a transmembrane pressure of 1 kPa, for example, 10 to 10,
000m^Three/ M^Two-About a day, preferably 50 to 5, 0
00m ^Three/ M^Two・ About day, more preferably 100 to
1,000m^Three/ M^Two-It may be about day.

Since the nonwoven fabric membrane has a high filtration rate,
A small film area is sufficient. Furthermore, the nonwoven fabric membrane is also excellent in operability, for example, there is no need for pretreatment even if the membrane is dry,
It is ready for use at any time, and can be used again even after the membrane dries after use.

When the nonwoven fabric film is used as a unit, the unit may be in any of the commonly used types. For example, the unit is constituted by a plurality of nonwoven membrane elements, and can be formed by juxtaposing and facing each other with a gap. As the nonwoven membrane element, a flat membrane element having nonwoven membranes facing each other at a distance from each other is used. More specifically, for example, it is formed of a rectangular frame (or a support), and a nonwoven fabric film which is stretched on both sides of the frame by sticking or the like and which faces away from each other. A flat membrane element having a structure (internal cavity structure) is formed.

In the present invention, turbid water is filtered at a relatively low transmembrane pressure in the filtration by a nonwoven fabric membrane. The pressure between the membranes to be filtered is 30 kPa or less (for example, 0.1 to 30 kP
a), preferably about 0.1 to 20 kPa, more preferably about 0.2 to 10 kPa. With such a relatively low transmembrane pressure, dynamic filtration can be performed smoothly.

As a filtration method, it is preferable to perform cross-flow filtration using a separation membrane unit. By using the cross-flow method, clogging can be prevented and filtration can be performed at an appropriate filtration rate.

In the present invention, solid-liquid separation is performed by dynamic filtration using a nonwoven fabric membrane. The dynamic filtration is a filtration method in which a cake layer (flock layer) is formed on a membrane surface by an object to be processed (SS component), and the SS component in the muddy water is separated and removed by a filter action of the cake layer.

When the nonwoven fabric is used at a high pressure like a filter press, although the SS component can be removed to some extent, the membrane is immediately clogged. By the SS
The components are reliably removed, and the membrane is less likely to be clogged. Further, even if the concentration of the SS component contained in the turbid water changes, the SS component can be reliably filtered without any change, so that the liquid to be treated can be stably solid-liquid separated. Furthermore, even if the membrane is clogged,
It can be easily recovered by back washing.

In the case of dynamic filtration using a non-woven fabric membrane at a low pressure, filtration is performed using SS components accumulated on the membrane surface. In some cases, the SS component is not filtered and may pass through. Therefore, the initial 5
If the filtered water is returned to the raw water side for about a minute, the SS component in the filtered water is reliably removed. In addition, when the back washing is performed, the SS component attached to the film surface becomes solid (cake) and precipitates, and thus has an effect similar to that of coagulation and precipitation.

According to the turbid water treatment apparatus of the present embodiment,
Since a chemical solution for the coagulation process is not required, daily management of the coagulation process is also unnecessary. Further, since the separation membrane unit is operated automatically, the apparatus can be operated only by performing an inspection.

(Embodiment 2) Another example of the turbid water treatment apparatus of the present invention will be described with reference to FIG. FIG. 3 is a flowchart of the turbid water treatment device according to the second embodiment.

As shown in FIG. 3, first, a stock solution supply line
Turbid water (BOD 5 mg / liter, SS component concentration 1
000mg / l) at a flow rate of 100m^Three/ Hour
Supply to tank 2. In sedimentation tank 2, sand and stone
Heavy components precipitate. Use the supernatant water in settling tank 2
After being supplied to the water tank 3, it is further supplied to the neutralization tank 7. this
Is supplied to the coagulation sedimentation tank 14, where it is coagulated.
Sludge is settled using chemicals. In the coagulation sedimentation tank 14
Is a separation membrane unit using a nonwoven fabric membrane (500 m ^Two) 5
The supernatant water in the coagulation sedimentation tank 14 is installed
This is supplied to the unit 5. Meanwhile, the coagulation sedimentation tank
The sediment at 14 is drawn sludge as slurry tank 1
Sent to 0. In the slurry tank 10, the extracted sludge
Is with a filter press 15 (equipment for dehydration and solidification)
It becomes a cake, and the remaining liquid is again supplied from the remaining liquid line 11 to the raw water tank.
Returned to 3. Here, as an example of equipment for dehydration and solidification,
Filter press, but other known equipment
No.

In the separation membrane unit 5, the filtered water has a flow rate of 12
It is sent to the treated water tank 6 at 0 m ³ / hour. The filtered water from the separation membrane unit 5 is discharged from the treated water tank 6 at a flow rate of 100 m ³ / hour. At this time, the SS component concentration of the discharge water is 10 m.
g / liter or less. The filtered water in the treated water tank 6 is sent to the backwash water tank 8 as a cleaning liquid, and the flow rate is 20 m.
³ / hour (average flow rate of intermittent backwashing) may be used for backwashing the separation membrane unit 5. In addition, as the cleaning liquid, besides filtered water, separately supplied clean water may be used, and a chemical such as an aqueous solution of sodium hypochlorite can also be used for the reverse cleaning.

According to the turbid water treatment apparatus of the present embodiment,
Even if the coagulation treatment is insufficient, since the filtration is further performed by a separation membrane unit using a nonwoven fabric membrane, a skilled technique such as the conventional one is unnecessary for the coagulation treatment, and the SS component of the treatment liquid becomes stable. In particular, since the coagulation treatment and the membrane filtration are used in combination, the reliability of the treatment is high with respect to the fluctuation of the raw water quality.
On the other hand, as compared with the apparatus of the first embodiment, the number of facilities is increased, which is disadvantageous in cost.

[0034]

According to the present invention, when filtration is performed using the turbid water treatment apparatus, turbid water can be treated in a simple and inexpensive manner and reliably.

[0035]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

[0036] Example 1 nonwoven film (thickness 170 [mu] m, basis weight 75 g / m ^2, air permeability 60cm / sec) using a 0.002 m ^2, is discharged from the construction site, and allowed to stand for 10 minutes, SS about 1000mg
/ Liter, BOD 9mg / liter, chromaticity 25mg /
When 2 liters of turbid water of 1 liter was filtered and concentrated until the volume became 1/4 (pressure between membranes during filtration: 8 kPa),
The process was completed in about 3 hours, and the backwash was performed twice with filtered water. The quality of the filtered water was such that the SS component concentration was 1 mg / liter or less, the BOD was 5 mg / liter, and the chromaticity was 4 mg / liter. The filtered water flux averaged 6 m ³ / m ² · day.

[Brief description of the drawings]

FIG. 1 is a flowchart of a turbid water treatment device according to a first embodiment.

FIG. 2 is a schematic perspective view of a separation membrane unit according to the first embodiment.

FIG. 3 is a flowchart of a turbid water treatment device according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 1 stock solution supply line 2 sedimentation tank 3 raw water tank 5 separation membrane unit 6 treatment water tank 7 neutralization tank 8 backwash water tank 10 slurry tank 15 filter press

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4D006 GA02 HA41 KA02 KA63 KB13 KC03 KC13 KC16 KD24 KE02P KE03P KE04P KE05P KE06R KE12R KE13P KE15Q MA03 MA16 MA22 MA31 MA40 MB02 MC11 MC12 MC18 MC19 MC22 MC24 MC37 MC48 MC54 MC55 MC58 PA01 PB20 PB70

Claims (11)

[Claims] 1. SS1 at BOD 50 mg / L or less
A method for treating turbid water, comprising forming a cake layer of an object to be treated on a film surface of turbid water of 00 mg / liter or more using a nonwoven fabric membrane and filtering the turbid water. 2. The method for treating turbid water according to claim 1, wherein the BOD of the turbid water is 0 to 10 mg / liter. 3. The method for treating turbid water according to claim 1, wherein the filtration is performed at a transmembrane pressure of 30 kPa or less. 4. The method for treating turbid water according to claim 1, wherein the turbid water is filtered by a cross-flow method using a separation membrane unit using a nonwoven fabric membrane. 5. The method for treating turbid water according to claim 1, wherein the turbid water is subjected to coagulation treatment and then filtered through a nonwoven fabric membrane. 6. The method for treating turbid water according to claim 1, wherein the turbid water is preliminarily subjected to a sedimentation treatment in a sedimentation tank in which no coagulation treatment is performed, and then the supernatant water is filtered through a nonwoven fabric membrane. 7. Preliminarily settling treatment of turbid water in a sedimentation tank in which coagulation treatment is not performed, and then, supernatant liquid is filtered by a cross-flow method with a separation membrane unit using a non-woven fabric membrane, and non-filtrated water concentrated more than twice. The method for treating turbid water according to claim 1, wherein the water is returned to the sedimentation tank. 8. SS1 at a BOD of 50 mg / liter or less.
An apparatus for treating turbid water of not less than 00 mg / liter, comprising a separation membrane unit using a nonwoven fabric membrane. 9. The turbid water treatment apparatus according to claim 8, further comprising a sedimentation tank for removing coarse particles of the turbid water by settling on an upstream side of the separation membrane unit for treating the turbid water. 10. A treatment water tank for storing filtration water filtered by the separation membrane unit, wherein the separation membrane unit is constituted by a plurality of nonwoven fabric membrane elements having nonwoven fabric membranes facing each other at a distance from each other, and a cleaning liquid. 9. The turbid water treatment device according to claim 8, further comprising a backwash water tank for backwashing the separation membrane unit by introducing a chemical solution. 11. A sedimentation tank which does not involve a coagulation treatment for previously performing a sedimentation treatment of turbid water, a separation membrane unit using a nonwoven fabric membrane for filtering the supernatant water of the sedimentation tank, and a cross-flow filtration in the separation membrane unit. A turbid water treatment device equipped with a line for returning non-filtrated water to a sedimentation tank and a facility for dewatering and solidifying sludge drawn from the sedimentation tank.