JPH09215979A - Clean water processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the vol. of a precipitation part by providing the precipitation part wherein muddy substance is accumulated below a membrane module and arranging a baffle with an opening part in the horizontal direction between the membrane module and the precipitation part. SOLUTION: An introduction part 2 for introducing raw water such as river water being offered for clean water processing into a filter tank 1 is provided and a membrane module 3 being arranged in the filter tank 1 is provided below the introduction part 2. A precipitation part 6 wherein muddy substance is accumulated is provided below the membrane module 3 and a baffle 5 with an opening part is arranged in the horizontal direction between the precipitation part 6 and the membrane module 3. As it is possible thereby to decrease the vol. of the precipitation part 6 provided below the baffle 5, it is possible to accumulate the muddy substance with high concn. in the precipitation part 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water purification treatment for producing purified water from raw water such as river water, and particularly to a water purification apparatus for purifying raw water using a separation membrane such as a microfiltration membrane or an ultrafiltration membrane. It is about.

[0002]

2. Description of the Related Art Conventionally, in a water purification process for producing tap water from river water, raw water such as river water is introduced from a settling tank into a filter tank as shown in FIG. Purification is performed by sterilizing the filtered water obtained by removing the chlorine. In addition, the wastewater produced in the settling tank and the filtration tank, in which the suspended matter in the raw water is concentrated, is appropriately drained from the settling tank and the filtration tank, and the solid-liquid separation is further performed in the concentration tank by the gravity sedimentation method or the like. Be seen.

However, in the water purification treatment of the raw water in the settling tank and the filtration tank, since the coagulant is added to the raw water, it is necessary to control the amount of the coagulant to be added according to the turbid mass of the raw water. It is complicated.

As a method for solving such a problem, a method for purifying raw water by a membrane separation method in which suspended matter is filtered by a membrane module provided with a separation membrane such as a microfiltration membrane or an ultrafiltration membrane. Are being studied. When the membrane separation method is used for water purification, it is basically not necessary to add a coagulant to the raw water, so a system for controlling the amount of coagulant added is not required, and the water purification device has a simple structure. be able to. Further, the settling tank and the filtration tank can be integrated into one tank, and the water purification treatment can be performed with high filtration efficiency.

[0005]

When the raw water is filtered using the membrane module, as the filtration treatment is continued, turbidity adheres to the surface of the separation membrane and the filtration flow rate decreases. In order to recover such a decrease in filtration flow rate of the separation membrane,
An air diffuser is installed below the membrane module, bubbling is performed from the air diffuser, and the separation membrane is shaken to wash the separation membrane, or the filtered water is fed from the secondary side of the separation membrane to the primary side. By the method of washing the separation membrane by passing water,
The membrane module is cleaned.

However, when the separation membrane is washed by these methods, the suspended matter accumulated on the bottom surface of the filtration tank is rolled up toward the membrane module due to the water flow caused by backwashing or the water flow generated by bubbling from the diffuser pipe. Therefore, if filtration is started again in this state, suspended matter tends to adhere to the membrane surface again.

As means for preventing floating of suspended matter, a partition plate having an inclination as shown in Japanese Patent Laid-Open No. 6-100338 is provided below the membrane module to prevent floating of suspended suspended matter. Attempts have also been made, but even if the raw water is purified by such a device, the suspended turbidity tends to accumulate on the partition plate, and the suspended turbidity is rolled up by the water flow. There was an inconvenience.

Further, when a slanted partition plate is provided in the filtration tank, the volume of the sedimentation portion, which is provided below the partition plate and accumulates suspended matter, becomes large. Therefore, when drainage of drainage is performed, there is no choice but to drain a large amount of drainage containing a large amount of water, which reduces the recovery rate of purified water from raw water.

[0009]

Means for Solving the Problems As a result of investigations in view of such inconveniences, the present inventors have found that the separation membrane can be efficiently washed and the raw water is purified with high filtration efficiency. We have found a water purification device that can do this.

That is, the gist of the present invention is to introduce raw water to be treated for purification into a filtration tank from an introduction section and to filter raw water using the membrane module. The water purification apparatus is characterized in that a settling section for accumulating is provided, and a baffle plate having an opening is horizontally arranged between the membrane module and the settling section.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below, but it goes without saying that the present invention is not limited to these. FIG. 1 is a schematic diagram showing an example of the form of a water purification apparatus of the present invention.

The introduction unit 2 introduces raw water such as river water used for water purification into the filtration tank 1. The position at which the introduction part 2 is provided is not particularly limited, but if it is provided at the upper part of the filtration tank 1 and the raw water corresponding to the amount filtered by the membrane module 3 is gently allowed to flow into the tank, the turbidity of the raw water Raw water can be introduced into the filtration tank 1 without disturbing the sedimentation of the quality, which is preferable.

The filtration tank 1 is for filtering raw water by the membrane module 3 inside the tank, and its size, material, etc. are not particularly limited.

Membrane module 3 disposed in filtration tank 1
Is a device in which a porous separation membrane for substantially separating and filtering suspended matter in raw water is disposed. As the separation membrane used in the membrane module 3, a flat membrane, a hollow fiber membrane, a tubular membrane, a multi-lumen type separation membrane of any shape can be used.

As the material of the separation membrane, any of an inorganic membrane (ceramic membrane) and an organic membrane (PAN type, cellulose type, polyolefin type, polysulfone type, Teflon type, vinylidene fluoride type, acrylic type, polyamide type, etc.) can be used. Can be used. This separation membrane has an average pore size of 0.01 to 5
Even with a microfiltration membrane of about μm, the molecular weight cutoff is 1000
Although an ultrafiltration membrane of about 3,000,000 daltons may be used, it is preferable to use a microfiltration membrane because treatment can be performed at a high filtration flow rate.

Of these, when a hollow fiber membrane module having a plurality of hollow fiber membranes as a separation membrane is used, the membrane area per unit volume is larger than that of a membrane module using a flat membrane or a tubular membrane. Since it can be taken, the membrane module 3 having high volume efficiency can be obtained, and the water purification apparatus can be downsized.

More preferably, as shown in FIG. 2, a flat hollow fiber membrane module in which hollow fiber membranes are arranged in a flat plate shape is used,
Filtration tank 1 such that the arrangement direction of each hollow fiber membrane is horizontal and the flat plate surface on which the hollow fibers are laminated faces the vertical direction.
When it is arranged inside, when the air diffuser 4 is provided below the membrane module 3 and the cleaning by bubbling is performed, it is possible to provide a water purification treatment device with good cleaning efficiency of the membrane module 3.

In the water purifying apparatus of the present invention, as a method for washing the separation membrane, a method of backwashing the filtered water from the secondary side of the membrane module 3 by pressurizing it or backwashing the membrane module 3 is used. The separation membrane can be washed by a method in which an air diffuser 4 for diverging air is provided and bubbling is performed. In this case, alkaline solution, acidic solution,
It is also possible to use cleaning with a chemical solution such as a surfactant solution or an organic solvent in combination.

Preferably, when the separation membrane is washed by providing an air diffusing tube 4 below the membrane module 3 and bubbling from the air diffusing tube 4, the separation membrane is shaken and turbidity adhering to the membrane surface is removed. Since it can be removed from the membrane surface,
The increased filtration resistance can be efficiently restored. In this case, the air diffuser 4 may be arranged at the upper end of the baffle plate 5.

As the filtration method, the pressure tank is used as the filtration tank 1 and the primary side of the membrane module 3 is pressurized to filter the raw water, and the secondary side of the membrane module 3 is the suction pump 7. It is possible to use both of the suction filtration methods in which the raw water is filtered by suctioning with, etc., but it is said that the can body is not required, and the control of air bleeding when performing bubbling cleaning from the air diffusing pipe 4 is not required. From the viewpoint, it is preferable to use the suction filtration method.

Further, in the cleaning treatment of the separation membrane by bubbling from the air diffusing tube 4, the turbidity adheres to the membrane surface of the separation membrane so that the filtration resistance rises beyond a certain pressure (or the filtration flow rate is a certain flow rate). It will be done at the time when it has decreased).
Note that it is preferable to stop the filtration process when performing the cleaning process.

In the water purification treatment of the present invention, a precipitation section 6 for depositing suspended matter is provided below the membrane module 3 in the filtration tank. By providing the settling section 6, it is possible to accumulate and hold the suspended matter that increases as the filtration of the raw water continues, so that the suspended matter is contained after the introduced raw water is sufficiently filtered. The waste water can be discharged to the outside of the filtration tank 1.

In the water purification apparatus of the present invention, the baffle plate 5 having an opening is provided between the membrane module 3 and the settling section 6. By arranging the baffle plate 5 having the openings in the horizontal direction, the volume of the sedimentation portion 6 provided below the baffle plate 5 can be made smaller, so that the suspended matter can be deposited on the sedimentation portion 6 at a high concentration. Can be made. Therefore, filtration tank 1
The amount of drained water can be further reduced, and the recovery rate of filtered water can be improved.

As the baffle plate 5 having an opening, a flat plate,
Lattice assembly plates, honeycomb structure plates, pipe structure plates and the like can be used. When the baffle plate 5 is composed of a plurality of flat plates and arranged horizontally in the filtration tank 1, as shown in FIG. 3 (a), a plurality of flat plates with the surface direction of each plate oriented in the vertical direction is used. , Are arranged so that the arrangement direction as a whole is horizontal. In this case, the gap formed between the flat plates becomes the opening.

As another embodiment of the disposing method of the baffle plate 5 having an opening, as shown in FIG. 3B, a plate having a lattice assembly structure is disposed horizontally in the filtration tank 1. Alternatively, as shown in FIG. 3C, the honeycomb structure plate may be arranged in the horizontal direction. Alternatively, as shown in FIG. 3D, a plurality of pipe plates having pipe-shaped openings may be arranged in the horizontal direction.

The baffle plate 5 having these openings is
If arranged as a whole in the horizontal direction, as shown in FIG.
The opening may have a tapered shape as shown in FIG. 4B, or the opening may have an inclined shape as shown in FIGS. 5A and 5B.

Baffle plate 5 provided in the water purification apparatus of the present invention
Since it has a structure having an opening, the suspended matter settling from above is settled in the settling section 6 from the opening, so that suspended matter does not deposit on the baffle plate 5. Further, the water flow generated when the raw water is introduced into the filtration tank 1 from the introduction part 2 or when the membrane module 3 is washed is blocked by the baffle plate 5 and circulates above the baffle plate 5, It is possible to prevent the suspended matter accumulated in the precipitation unit 6 from floating toward the membrane module 3 due to the water flow.

In the water purification apparatus of the present invention, it is possible to perform water purification filtration without adding a coagulant, but for the purpose of removing soluble substances such as viruses and ionic substances in raw water, Alternatively, an appropriate amount of a coagulant may be added for the purpose of reducing the increase in the differential pressure of the porous membrane.

In the water purification apparatus of the present invention, since the raw water is filtered by the membrane separation method, the settling tank and the filtration tank can be combined as shown in FIG. Further, the raw water can be sufficiently filtered with high efficiency, and the recovery rate of the filtered water from the raw water can be improved.

An operation example when the water purification treatment of the present invention is performed will be described below. Raw water is introduced into the filtration tank 1 from the introduction part 2 provided at the upper part of the filtration tank 1, and the membrane module 3
By being filtered by, it moves downward while being gradually concentrated. The concentrated suspended matter passes through the baffle plate 5 arranged below the membrane module 3 and is deposited on the precipitation part 6 provided below the baffle plate 5. Since the accumulated turbidity has the baffle plate 5 above it, it does not float toward the membrane module 3 due to the water flow caused by the introduction of raw water.

When filtration is continued for a certain period of time, suspended matter in the raw water adheres to the membrane surface of the separation membrane to form a cake layer and the filtration resistance increases, so the filtration process is stopped and air is blown from the air diffusing tube 4. By bubbling, the suspended matter attached to the surface of the separation membrane is peeled off. The water flow caused by the bubbling is obstructed by the baffle plate 5 arranged above the settling unit 6 and circulates above the baffle plate 5, so that the suspended matter deposited on the settling unit 6 may float toward the membrane module 3. Therefore, a good cleaning process can be performed. In addition, the suspended matter that has fallen off from the separation membrane due to the washing process is deposited in the precipitation unit 6 provided below the membrane module 3.

After the washing treatment is completed, the water purification treatment can be continued by repeating the filtration treatment and the washing treatment again. After performing a predetermined amount of water purification treatment, the turbidity concentrated and accumulated in the settling section 6 is drained to the outside of the filtration tank 1 through a sludge discharge port provided at the bottom of the filtration tank 1 for drainage treatment. Be seen. Even when this drainage is performed, the drainage can be discharged to the outside of the filtration tank 1 without floating the suspended matter toward the membrane module 3.

[0033]

EXAMPLES The present invention will be illustrated concretely by examples. [Example 1] A filtration test was performed using the water purification apparatus shown in FIG.

The membrane module 3 includes Mitsubishi Rayon Co., Ltd.
Manufactured hydrophilic polyethylene hollow fiber membrane EX410TS (average pore diameter 0.1 μm, outer diameter 410 μm, inner diameter 270 μm)
, Which were accumulated in a flat plate shape and provided with water collecting pipes at both ends of the hollow fiber membrane,
The flat hollow fiber membrane module shown in FIG. 2 was used.

In the flat plate type hollow fiber membrane module, the hollow fiber membranes are arranged in the horizontal direction and the plate surface of the integrated hollow fiber membranes is arranged in the vertical direction, and the three modules are arranged in the vertical direction. The membrane module 3 was connected and used. The effective membrane area of these hollow fiber membrane modules was 1.2 m ² .
In addition, in the filtration tank 1, below the air diffuser 4, one side is 30 mm.
A honeycomb structure plate having a hexagonal opening and having a vertical thickness of 30 cm was arranged in the horizontal direction.

Kaolin was added to tap water in the filtration tank 1.
From the introduction section 2, a suspension of 0 mg / L was added,
It was introduced at a rate of m ³ / hr. The filtration by the membrane module 3 is performed by sucking the inside of the hollow fiber membrane module with the suction pump 7, and the filtration speed is 0.04 m ³ / m ² ·.
I went under the condition of hr.

First, after performing a filtration treatment by the membrane module 3 for 60 minutes, the suction pump 7 is stopped, air is bubbled through the air diffusing tube 4 for 1 minute, and the hollow fiber membrane is shaken to wash the membrane surface. I went. After the washing, it is left to stand for 5 minutes, and a part of the drainage (0.0
0015 m ³ ) was discharged. This was set as one cycle, and a plurality of cycles of filtration treatment and washing treatment were repeated (note that after the washing treatment, the next filtration treatment was started immediately).

Table 1 shows changes in the suction pressure in the suction pump 7 after the end of the predetermined cycle. In addition, the recovery rate of the filtered water from the raw water after 1500 cycles was 9
9.7%. When the water purification apparatus of this example is used, even if the above filtration processing and bubbling are repeated, the suction pressure does not increase so much that the suspended matter can be sufficiently concentrated, so that the collected water of the filtered water is highly recoverable. It is possible to perform water purification treatment with excellent filtration efficiency.

[0039]

[Table 1]

[Comparative Example 1] As shown in FIG. 7, the same as Example 1 except that a filtration tank 1'in which two flat plates 5'are arranged with an inclination in the direction of the precipitation portion 6'is used. Water purification treatment and washing treatment were performed under the same conditions. Table 1 shows the obtained results. In addition, in this comparative example, the recovery rate of the filtered water from the raw water was 90% when the treatment was performed for 500 cycles.

[0041]

According to the water purification apparatus of the present invention, since the baffle plate having the opening is horizontally arranged below the membrane module in the filtration tank, the volume of the precipitation part can be reduced. This is possible and the recovery rate of filtered water can be improved. Moreover, since the baffle has a structure having an opening,
Since the suspended matter does not accumulate on the baffle plate and the suspended matter does not float toward the membrane module during the cleaning process, the separation membrane can be efficiently cleaned, and thus the filtration efficiency can be improved. It is possible to perform water purification treatment with excellent recoverability of water purification.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a water purification apparatus of the present invention.

FIG. 2 is a schematic view of a flat-plate type hollow fiber membrane module used in Examples.

FIG. 3 is a schematic view showing an example of the form of a baffle plate having an opening used in the water purification apparatus of the present invention.

FIG. 4 is a schematic view showing another embodiment of the baffle plate having an opening used in the water purification apparatus of the present invention.

FIG. 5 is a schematic view showing another example of a baffle plate having an opening used in the water purification apparatus of the present invention.

FIG. 6 is a flow chart showing a conventional water purification process.

FIG. 7 is a schematic diagram showing a filtration tank used in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Filtration tank 2 ... Introductory part 3 ... Membrane module 4 ... Air diffuser 5 ... Baffle plate having an opening 6 ... Sedimentation part 7 ... Suction pump

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Honjo 4-60 Sunadabashi, Higashi-ku, Nagoya, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory

Claims (5)

[Claims] 1. In a water purification apparatus that introduces raw water to be subjected to water purification treatment into a filtration tank from an introduction unit and filters the raw water using a membrane module, a sedimentation unit for accumulating suspended matters below the membrane module is provided. A water purification apparatus characterized in that a baffle plate having an opening is horizontally arranged between the membrane module and the settling unit. 2. The water purification apparatus according to claim 1, wherein an air diffuser is provided between the membrane module and the baffle plate. 3. The water purification apparatus according to claim 1 or 2, wherein the membrane module uses a hollow fiber membrane. 4. The water purification apparatus according to claim 3, wherein a flat hollow fiber membrane module in which hollow fiber membranes are laminated in a flat plate shape is used. 5. The purified water treatment apparatus according to claim 1, wherein the filtration by the membrane module is performed by a suction filtration method.