JP2002346562A - Method and apparatus for water treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the precipitation, and the like of, iron by supplying iron in a state of an iron ion to a membrane separator and treating it together with a material-to-be-treated in the case that a raw water containing iron is treated with the membrane separator. SOLUTION: The raw water containing iron is pumped up with a pump 4, then pressurized by a booster pump 20 installed in a closed pipe line to be supplied to reverse osmosis membrane filtration modules 23, 24 constituting the membrane separator 40. Desalting, deironing, or the like, are carried out in the membrane separator 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating raw water such as groundwater, and more particularly, to a membrane separation apparatus in which iron contained in raw water is dissolved in raw water as iron ions without being oxidized. And a water treatment method and a water treatment apparatus characterized in that iron ions and raw materials such as salts in raw water are simultaneously treated there.

[0002]

2. Description of the Related Art In the case of using salty groundwater as, for example, tap water, it is necessary to remove the contained salt to an acceptable level. As a desalination apparatus for removing salt, a membrane separation apparatus using a separation membrane is widely used. RO membranes (reverse osmosis membranes) and NF membranes (nanofilters) are used as separation membranes used in membrane separation devices, and various types of spiral-type composite membranes having a large effective membrane area are generally used as these separation membranes. . For example, in an RO membrane composed of a spiral-type polyamide-based composite membrane, raw water introduced into the interior of the membrane module causes the salt to permeate through the membrane by reverse osmosis and is separated. The membrane separation device is usually configured as a module in which a large number of separation membranes are accommodated in a container, and the container is provided with a supply part and a discharge part of raw water and an outlet part of desalted treated water.

[0003] In general, iron in raw water is dissolved as ferrous ions (divalent iron), but when it comes into contact with oxygen in the air, it is oxidized and precipitates as iron hydroxide. Iron hydroxide is not preferred because it accumulates as slime or sludge in the pipes and blocks the pipes, and corrodes (rusts) gunmetal valves and the like. Further, a biofilm may be formed on the inner wall of the tank or the inner wall of the pipe by iron bacteria or the like, or in the worst case, the separation membrane may be closed.

Therefore, conventionally, an iron removing device for removing iron in raw water has been provided. FIG. 2 is a process flow diagram of a conventional water treatment apparatus using such an iron removing device. In the figure, 100 is a pump for pumping groundwater as raw water, 200 is an iron removing device, 201 and 201a are automatic three-way switching valves, 202 is a water receiving tank, 203 is a flow meter, 204
Is a chemical liquid flow control device, 205 is a chemical liquid pump, 206 is a chemical liquid tank, 207 and 209 are liquid supply pumps, 208 is a sand filter device, 210 is a backwash water tank having an overflow part, 211 is a storage tank installed underground, 30
0 is a membrane separation device.

Next, the operation of the above apparatus will be described. First, raw water pumped by the pump 100 is supplied to the water receiving tank 202, from which it is transferred to the sand filter device 208 and the backwash water tank 210 by the liquid sending pump 207. Finally, it flows into the storage tank 211. The flow rate of raw water transferred from the water receiving tank 202 by the liquid sending pump 207 is measured by the flow meter 203, and the measurement signal is input to the chemical liquid flow rate control device 204. The chemical liquid flow control device 204 controls the rotation speed of the chemical liquid pump 205 so as to inject the chemical liquid in proportion to the flow value measured by the flow meter 203. An oxidizing agent such as sodium hypochlorite that oxidizes iron ions and converts it into water-insoluble iron hydroxide is used as the chemical solution.

When an oxidizing agent, which is a chemical, is injected into raw water,
The iron ions contained therein are gradually oxidized and become precipitated iron hydroxide while reaching the inside of the sand filter device 208. The iron hydroxide is filtered and separated by the sand filter device 208, and the raw water containing no iron flows into the backwash water tank 210. When the raw water in the backwash water tank 210 is full, the raw water overflows from the overflow section and is stored in the storage tank 211. Storage tank 2 from which iron has been removed
The raw water No. 11 is supplied to the membrane separation device 300 by a pump (not shown), and is supplied to a treatment water tank (not shown) as treated water from which salt, which is an object to be treated, has been removed.

[0007] If the operation of the iron removal process of raw water is continued,
Since the captured iron hydroxide gradually accumulates in the sand filter device 208 and causes clogging, the accumulated iron hydroxide is washed (backwashed) once a day, for example, to remove the accumulated iron hydroxide. In the cleaning, the liquid feed pump 207 is stopped by a signal from a timer device provided in a control device (not shown) and the automatic three-way switching valve 20 is stopped.
1, 201a is switched, and the feed pump 209 is operated to feed the raw water in the backwash water tank 210 to the sand filter device 20.
Backwashing is performed by flowing back to 8. The washing wastewater from the backwash water tank 210 is discharged out of the system.

[0008]

However, such a large-scale iron removing apparatus as described above has a problem that equipment cost and operation cost are large. In addition, the periodic cleaning operation of the clogged sand filter device 208 includes:
It requires a considerable amount of downtime, large consumption of raw water and regular replacement of filter media. In addition, a large amount of wastewater generated during backwashing is also a problem. Then, this invention makes it a subject to solve such a problem, and aims at providing the new water treatment method and the water treatment apparatus for that.

[0009]

According to a first aspect of the present invention, there is provided a method for treating raw water containing iron, wherein the iron is dissolved as iron ions in the raw water while the other raw material is dissolved. The raw water is treated by a membrane separation device together with the treated material. (Claim 1)

According to the above-mentioned method, water treatment can be performed while removing iron contained in raw water without using a large-scale iron removing device as in the prior art, so that equipment costs and operation costs are greatly reduced. Can be reduced. Also,
Since the membrane is separated in a state in which iron is dissolved in raw water as iron ions, it is possible to effectively prevent pipe clogging or the like caused by precipitation of iron in a main processing system and generation of sludge. Furthermore, since the iron ions are simultaneously separated and removed together with the components to be treated in the membrane separation device, the treatment efficiency is high, and since there is substantially no iron in the treated water, the treated water comes into contact with oxygen in the piping system after the membrane separation device. However, there is no danger of forming sludge or the like.

In the above-mentioned water treatment method, the raw water can be supplied from the raw water supply source to the membrane separation device via the closed supply path without passing through the water receiving tank. (Claim 2) Further, in any of the above water treatment methods, the raw water supplied to the membrane separation device can be stirred at a high speed to reduce the activity of the microorganisms contained therein. (Claim 3)

Further, in any of the above-described water treatment methods, the raw water in which iron is dissolved in the raw water as iron ions can be supplied to the membrane surface of the membrane separation device at high speed for flushing cleaning. (Claim 4) In the above-mentioned water treatment method, a filter device is provided in a supply path of raw water to be supplied to the membrane separation device, and the drained water after flushing can be used as a cleaning liquid for the filter device. (Claim 5)

According to a second aspect of the present invention for solving the above-mentioned problems, in a device for treating raw water containing iron, a pump for pumping raw water from a raw water supply source, a membrane separation device,
A treatment water tank, and at least a portion from the raw water suction part of the pump to the membrane separation device is a closed treatment system. (Claim 6)

In the above-mentioned water treatment apparatus, the number of revolutions of a pump for pumping raw water can be controlled. (Claim 7) Further, in any of the above water treatment apparatuses, a pressure pump for supplying raw water in a state where iron is dissolved in raw water as iron ions to the membrane separation device can be provided. (Claim 8)

[0015]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a process flow diagram of a water treatment apparatus for performing a water treatment method according to the present invention. In the figure, 1 is a raw water supply source such as groundwater, 2, 8, 9 and 10 are disk filters, 3 is a two-way electromagnetic ball valve as an automatic opening / closing valve, 4 is a pump for raw water pumping whose rotation speed is controlled, 5
Is an inverter control device for controlling the rotation speed of the pump 4,
Reference numerals 6, 7, 11, and 29 denote three-way electromagnetic ball valves as automatic switching valves, and 12 denotes a wind filter.

Further, 13, 14, 22, 25 are pressure gauges,
15 is a pressure sensor, 16, 28, 30 are flow meters, 17,
31 is a three-way manual ball valve, 18 is a check valve, 19 and 3
6 is a two-way manual ball valve, 20 is a pressurizing pump for the membrane separator 40, 21 is a controller, 23 and 24 are membrane filtration modules constituting the membrane separator 40, 26 is a sensor for an electric conductivity meter , 27 is an electric conductivity meter, 32 is a treated water tank, 33
Is a water level sensor for detecting the upper limit water level of the treatment water tank, 34 is a water level sensor for detecting the lower limit water level of the treatment water tank, 35 is a drain, 40 is a membrane separation device, and a to v are pipes.

The pump 4 for pumping raw water is driven by, for example, an AC motor, and the rotation speed of the motor is controlled by an inverter control device 5. By using a pump that performs such rotation speed control, the pumping amount of raw water, that is, the raw water flow rate can be set and changed arbitrarily. Furthermore, since the engine can be started by gradually increasing the rotation speed and conversely, by gradually decreasing the rotation speed and stopped, it is possible to avoid a sudden change in hydraulic pressure during the start-stop. As a result, the disc filter and wind filter installed on the downstream side are damaged by sudden changes in water pressure, and unexpected accidents such as leakage from the seam of the pipe and suction of air are prevented. Damage can be avoided.

The disk filters 2, 8, 9, and 10 constituting the solid content removing device separate and remove fine solid content contained in raw water. For example, "Disk Filter AR-315" manufactured by Sun Hope Co., Ltd. What is marketed as can be used. This disk filter is formed by coaxially stacking a large number of ring-shaped disks, and separating solids by filtration holes formed of a large number of grooves formed radially on each disk. For example, the disk filters 2, 8, 9, and 10 are 200 μm, 115 μm,
Those having a pore diameter of 75 μm and 115 μm are used. During the water treatment operation, the disk filters 8 and 9 perform the main function of removing solids.

The wind filter 12 is for removing finer solids that could not be removed by the disk filters 8, 9 or 10, and is, for example, an Advantech (Adv).
A "wind cartridge filter" having a pore size of about 10 [mu] m and commercially available from Antec) can be used.

The three-way electromagnetic ball valves 6, 7, 11, and 29 communicate between the ports A and B when power is not supplied, and when the power is supplied to the ports A and B.
C communicates. The two-way electromagnetic ball valve 3 is closed when not energized and is opened when energized. The driving of these electromagnetic ball valves is controlled by a signal from a control device (not shown).
Membrane filtration modules 23 and 24 constituting the membrane separation device 40
Can have a RO membrane (reverse osmosis membrane) or an NF membrane (nano filter membrane) inside. In this embodiment, Toray's “model SUL-G10” reverse osmosis module was used as the membrane filtration modules 23 and 24.

The pressurizing pump 20 is a turbine type pump (for example, model SQ commercially available from Grundfos) which rotates at a high speed of 12000 rpm or more. And supplied to the membrane separation device 40. The start-stop control and the rotation speed control of the pressurizing pump 20 are performed by the controller 21, and the discharge pressure can be adjusted by changing the setting of the rotation speed. In the present embodiment, a closed treatment system is configured from the raw water supply source 1 to the treatment water tank 32. However, the closed treatment system only includes at least the raw water supply source 1 where iron ions are present to the membrane separation device 40. May be.

Next, a method of treating raw water using the apparatus shown in FIG. 1 will be described. (Raw water treatment) In the raw water treatment step, the three-way manual ball valve 31 is switched in advance so that the pipe k-l communicates.
At this time, the opening of the two-way manual ball valve 36 is set so as to generate a constant flow resistance. This is to set the raw water speed to a design value lower than that at the time of cleaning described later. Also, 2
The manual ball valve 19 is used to save the raw water, and when the raw water pressure increases due to some abnormality, the pressure pump 2
0 and an appropriate opening degree are set in order to protect the membrane filtration modules 23 and 24. Further, an operation start button is provided in a control device (not shown), and when the operation start button is pressed to issue an operation command, the three-way electromagnetic ball valves 6, 7, 11, and 29 are in a non-energized state, that is, the connection between their ports A and B Communication is established.

Further, the two-way electromagnetic ball valve 3 is opened by the operation command, and the pump 4 and the pressurizing pump 20 are started.
Then, raw water is supplied from raw water supply source 1 to pipes a, b, c, d,
It flows in the order of e, f, g, i, j, k, l. During that time, the solid content contained in the disk filters 2, 8, 9 and the wind filter 12 is removed, and the pressure is increased by the pressure pump 20 at a water pressure of 0.5 to 0.7 MPa.
0, constituting the membrane filtration module 23,
The processing is sequentially performed at 24.

In the membrane separator 40, the salt and iron, which are the substances to be treated, which are present in the raw water in the form of ions, are separated by reverse osmosis, and the ions remaining on the primary side of the membrane are removed from the raw water together with the piping m, n, o , P, q, and r, and is discharged out of the system as a drain 35. On the other hand, the treated water flows into the treated water tank 32 through the pipes k and l. The pipe h is a bypass pipe of the high-pressure pump. In some cases, the membrane separation device 40 is connected to the membrane filtration module 23 (or 24).
It can also be composed only.

Generally, the discharge pressure of the pressurizing pump 20 changes in proportion to the raw water pressure on the inlet side. Then, the pressure on the inlet side is measured by the pressure sensor 15, and the controller 21
Controls the number of rotations of the pressure pump 20 to make the discharge pressure constant. The pressure gauges 13, 14, 22, 25 and the flow meters 16, 28, 30 are used for operation management. For example, the clogging of the wind filter 12 is monitored from the difference between the pressure gauges 13 and 14, and the pressure gauges are similarly monitored. From the difference between 22 and 25, clogging of the membrane separation device 40 is monitored. Water level sensors 33, 34
Is for monitoring the water level of the treated water tank, and when these are operated, an alarm display can be displayed on an operation panel (not shown) or the like.

(Cleaning of Membrane Separation Device) When the membrane separation device 40 is operated, the separation membrane gradually becomes clogged. Cleaning is automatically performed by a command from a timer device provided in a control device (not shown). The timer device issues a cleaning instruction for four minutes, for example, every three hours.
At the time of cleaning, the three-way electromagnetic ball valves 6, 7, 11, and 29 are energized, and the ports AC are in communication.

At the time of washing, the raw water is supplied to pipes a, b, p, s,
The flows flow in the order of e, f, g, i, j, m, t, u, c, v, and r. That is, the raw water pumped up from the raw water supply source 1 is first removed of solid components in the order of the disc filters 2, 10 and the wind filter 12, and then the pressurized pump 2
The pressure is increased to 0 to flush and wash the membrane filtration modules 23 and 24. The cleaning liquid further cleans the disc filters 8 and 9 and is discharged as drain 35 out of the system.
Since the flow resistance is not affected by the two-way manual ball valve 36 at the time of cleaning, the raw water for cleaning is supplied to the membrane filtration modules 23 and 24 at a higher speed than during the raw water treatment operation, and adheres to the surfaces of the separation membranes. The substance is efficiently washed away by the high-speed flow.

[0028]

EXAMPLE Raw water was treated using the apparatus of FIG. Raw water pumped from raw water supply source 1 has an iron ion concentration of 3 to 8 m
g / L and electric conductivity was 400 μS / cm. The raw water is used for disk filters 2, 8,
9, and a wind filter 12 to sufficiently remove solids, and then a membrane filtration module 23 comprising a membrane separation device 40 by a pressurizing pump 20 (a Grundfos SQ multi-stage turbine type pump) that rotates at a high speed of 12000 rpm or more. 24 (a reverse osmosis membrane module SUL available from Toray)
-G10).

In the membrane separator 40, iron as well as the salt to be treated were separated by reverse osmosis. The electric conductivity of the treated water passing through the membrane is 4 μS / cm, and the iron ion concentration is 0.01
mg / L, and a satisfactory processing result was obtained. Although the operation was continued for half a year while repeating the washing operation of the apparatus as described above, the membrane filtration modules 23, 24, the disc filters 2, 8, 9, 10, the wind filter 12, and the like remained in a normal state.

[0030]

As described above, the water treatment method according to the present invention is a method for treating raw water containing iron, wherein the iron is dissolved in the raw water as iron ions, and the raw water is dissolved together with other objects to be treated. The treatment is performed by a membrane separation device. Therefore, water treatment can be performed while stably removing iron contained in raw water without using a large-scale iron removing device as in the related art, so that equipment costs and operation costs can be significantly reduced. Further, since the membrane is separated in a state where the iron is dissolved in the raw water as iron ions, it is possible to effectively prevent the pipe from being clogged due to the precipitation of the iron in the main processing system and the generation of sludge. further,
Both the component to be treated and the iron ions are separated and removed by the membrane separation device, so that the treatment efficiency is high, and even if the treated water comes into contact with oxygen in the piping system after the membrane separation device because the iron content does not substantially exist in the treated water. There is no risk of sludge generation.

In the above-mentioned water treatment method, raw water can be supplied from the raw water supply source to the membrane separation device through the closed supply path without passing through the water receiving tank, and thereby the water receiving tank requiring a large installation area can be provided. By omitting, iron ions can be efficiently removed without contacting with oxygen. Furthermore, in any of the above-mentioned water treatment methods, raw water can be agitated at high speed to pulverize contained microorganisms and reduce the activity thereof, whereby a biofilm is formed on a separation membrane in a membrane separation apparatus. The occurrence of clogging can be effectively prevented.

Further, in any of the above-mentioned water treatment methods, the raw water can be sprayed at high speed onto the surface of the separation membrane in the membrane separation apparatus to perform flushing cleaning, whereby the operation of the separation membrane apparatus can be stably continued for a long period of time. Further, the flushed wastewater can be used as a washing liquid for the filter device, thereby reducing the consumption of raw water used for washing and shortening the washing time.

Further, the water treatment apparatus according to the present invention includes a pump for pumping raw water, a membrane separation device, and a treatment water tank, and at least a raw water supply passage from the pump to the membrane separation device is a closed treatment system. It is characterized by. Therefore, by using the present apparatus, the water treatment method can be suitably performed.

In the water treatment apparatus, a pump whose rotation speed is controlled can be used as a pump for pumping raw water, and the amount of raw water to be pumped, that is, the flow rate of raw water, can be arbitrarily set. Furthermore, since the engine can be started by gradually increasing the rotation speed and conversely, by gradually decreasing the rotation speed and stopped, it is possible to avoid a sudden change in hydraulic pressure during the start-stop. As a result, it is possible to prevent a filter device such as a disk filter or a wind filter installed on the downstream side from being damaged by a sudden change in water pressure, or to prevent an unexpected accident such as leakage from a pipe joint portion or suction of air.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of a water treatment apparatus for performing a water treatment method according to the present invention.

FIG. 2 is a process flow diagram of a conventional water treatment apparatus using an iron removing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw water supply source 2 Disk filter 3 2-way electromagnetic ball valve 4 Pump 5 Inverter control device 6 3-way electromagnetic ball valve 7 3-way electromagnetic ball valve 8 Disk filter 9 Disk filter 10 Disk filter 11 3-way electromagnetic ball valve 12 Wind filter 13 Pressure gauge 14 Pressure gauge 15 Pressure sensor 16 Flow meter 17 Three-way manual ball valve 18 Check valve 19 Two-way manual ball valve 20 Pressure pump 21 Controller 22 Pressure gauge 23 Membrane filtration module 24 Membrane filtration module 25 Pressure gauge 26 Electric conduction Sensor for rate meter 27 Electric conductivity meter 28 Flow meter 29 Three-way solenoid ball valve 30 Flow meter 31 Three-way manual ball valve 32 Treated water tank 33 Water level sensor 34 Water level sensor 35 Drain 36 Two-way manual ball valve 40 Membrane separation Apparatus av piping 100 pump 200 iron removal Reference Signs List 201 Automatic three-way switching valve 201a Automatic three-way switching valve 202 Water receiving tank 203 Flow meter 204 Chemical liquid flow rate control device 205 Chemical liquid pump 206 Chemical liquid tank 207 Liquid sending pump 208 Sand filter device 209 Liquid sending pump 210 Backwash water tank 211 Storage tank 300 Membrane Separation device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazumasa Sanin 2-1-6 Kitamagome, Ota-ku, Tokyo F-term in Yamakage Filtech Co., Ltd. (Reference) 4D006 GA03 KA12 KC01 KC12 KE02P KE03P KE07P KE08P KE19P KE21P KE23Q PA01 PB05 PB27

Claims (8)

[Claims] 1. A method for treating raw water containing iron, wherein iron is dissolved in raw water as iron ions.
A water treatment method, wherein raw water is treated with a membrane separation device together with another object to be treated. 2. The water treatment method according to claim 1, wherein the raw water is supplied from the raw water supply source 1 to the membrane separation device through a closed supply path without passing through a water receiving tank. 3. The water treatment method according to claim 1, wherein the raw water supplied to the membrane separation device is stirred at a high speed to reduce the activity of microorganisms contained therein. 4. The method according to claim 1, wherein raw water in which iron is dissolved in raw water as iron ions is supplied to the membrane surface of the membrane separation device at a high speed for flushing cleaning. The water treatment method according to 1. 5. The water treatment method according to claim 4, wherein a filter device is provided in a supply path of raw water to be supplied to the membrane separation device, and the flushed wastewater is used as a cleaning liquid for the filter device. 6. An apparatus for treating raw water containing iron, comprising: a pump 4 for pumping raw water from a raw water supply source 1, a membrane separation device 40, and a treated water tank 32, wherein at least a raw water suction portion of the pump 4 A water treatment apparatus characterized in that a closed treatment system is used up to the separation device 40. 7. The water treatment apparatus according to claim 6, wherein the rotation speed of the pump 4 for pumping the raw water is controlled. 8. A pressurizing pump 2 for supplying raw water in a state where iron is dissolved in raw water as iron ions to a membrane separation device 40.
The water treatment apparatus according to claim 6, wherein 0 is provided.