WO2011122175A1

WO2011122175A1 - Water treatment device and water treatment method

Info

Publication number: WO2011122175A1
Application number: PCT/JP2011/053813
Authority: WO
Inventors: 克義谷田; 草介小野田; 一貴高田; 野下　昌伸; 昇宮岡
Original assignee: 株式会社神鋼環境ソリューション
Priority date: 2010-03-30
Filing date: 2011-02-22
Publication date: 2011-10-06

Abstract

Disclosed are a water treatment device and a water treatment method, both of which can prevent the clogging of a membrane using a chemical substance containing a chlorine component and can also prevent the increase in the amount of the chlorine-component-containing chemical component to be used. Specifically disclosed is a water treatment device which is equipped with a membrane unit comprising a membrane and is so adapted that water to be treated can be separated through the membrane in the membrane unit. The device is characterized by being so adapted as to conduct a first filtration step and a washing step or a second filtration step alternatively, wherein the first filtration step comprises separating residual-free-chlorine-containing water (i.e., water containing a residual free chlorine) to be treated that has the same or lower residual free chlorine concentration as or than a predetermined value through the membrane in the membrane unit, the washing step comprises immersing the membrane in the membrane unit in a wash solution having a higher residual free chlorine concentration than the predetermined value, and the second filtration step comprises separating residual-free-chlorine-containing water that has a higher residual free chlorine concentration than the predetermined value through the membrane in the membrane unit.

Description

Water treatment apparatus and water treatment method

The present invention relates to a water treatment apparatus and a water treatment method, and more particularly, to a water treatment apparatus and a water treatment method in which water to be treated is membrane-separated by a membrane unit having a membrane.

Conventionally, as this kind of water treatment method, for example, water containing suspended substances such as river water is turbidized by membrane separation with a hollow fiber membrane unit having a microfiltration membrane (MF membrane). There is known a method of obtaining permeate as purified water by obtaining permeate and separating the permeate with a membrane unit having a reverse osmosis membrane (RO membrane) (for example, Patent Document 1).

In such a water treatment method, in order to prevent clogging of the membrane, the membrane unit separates the water to be treated containing free residual chlorine containing treated water obtained by mixing the water to be treated and a chemical containing a chlorine component by the membrane unit. (For example, Patent Document 2).

Japanese Unexamined Patent Publication No. 7-60248 Japanese Unexamined Patent Publication No. 2005-152688

However, when the free residual chlorine concentration of the free residual chlorine-containing treated water is low, clogging of the film cannot be sufficiently suppressed.
On the other hand, if the residual chlorine concentration in the residual chlorine-containing treated water is simply set to a high concentration, there are problems such as costs, deterioration of the film, and an increase in environmental load.

In view of the above problems, the present invention provides a water treatment apparatus and a water treatment method capable of suppressing an increase in the amount of chemicals containing a chlorine component while suppressing clogging of a film using the chemicals containing a chlorine component. The task is to do.

The present invention is a water treatment apparatus comprising a membrane unit having a membrane and configured such that water to be treated is separated by the membrane unit.
A first filtration step in which the membrane unit separates free residual chlorine-containing treated water having a free residual chlorine concentration of a predetermined value or less as treated water, and the washing water has a free residual chlorine concentration higher than the predetermined value; A washing step of immersing the membrane in the membrane unit or a second filtration step of membrane separation by the membrane unit using free residual chlorine-containing treated water having a free residual chlorine concentration higher than the predetermined value as the treated water The water treatment apparatus is configured to be implemented.

Further, the present invention is a water treatment method for membrane separation of water to be treated by a membrane unit having a membrane,
A first filtration step in which the membrane unit separates free residual chlorine-containing treated water having a free residual chlorine concentration of a predetermined value or less as treated water, and the washing water has a free residual chlorine concentration higher than the predetermined value; A washing step of immersing the membrane in the membrane unit or a second filtration step of membrane separation by the membrane unit using free residual chlorine-containing treated water having a free residual chlorine concentration higher than the predetermined value as the treated water It is in the water treatment method characterized by implementing.

Furthermore, the present invention is a water treatment apparatus configured so that water to be treated is membrane-separated,
A spiral type turbidity-eliminating membrane unit having at least one of an ultrafiltration membrane and a microfiltration membrane is provided,
At the time of filtration, free residual chlorine-containing treated water obtained by mixing treated water and a chemical containing a chlorine component and having a free residual chlorine concentration in the range of 0.05 to 2.5 mg / L. Membrane separation is carried out by the turbidity membrane unit as water to be treated, and at the time of washing, washing water having a free residual chlorine concentration in the range of more than 2.5 mg / L and not more than 250 mg / L is supplied to the turbidity membrane unit The water treatment apparatus is configured such that the membrane in the turbidity-eliminating membrane unit is immersed in the washing water.

Further, the present invention is a water treatment method for membrane separation of water to be treated,
At the time of filtration, the concentration of free residual chlorine is obtained by mixing water to be treated and chemicals containing chlorine components by a spiral-type turbidity-eliminating membrane unit having at least one of an ultrafiltration membrane and a microfiltration membrane. Is subjected to membrane separation as water to be treated, and the free residual chlorine concentration is higher than 2.5 mg / L and 250 mg / L. A water treatment method is characterized in that cleaning water in a range of L or less is supplied to the turbidity-eliminating unit and the membrane in the turbidity-eliminating unit is immersed in the rinsing water.

According to such a water treatment device and a water treatment method, during the filtration, the above-mentioned removal is performed by subjecting the treated water containing free residual chlorine having a free residual chlorine concentration within the range of 0.05 to 2.5 mg / L to a membrane. While suppressing clogging of the membrane of the turbid membrane unit and the flow path of the water to be treated, the membrane in the turbidity membrane unit is washed by immersing with washing water having a higher free residual chlorine concentration than during filtration at the time of washing. Clogging of the membrane and the flow path of the water to be treated can be further suppressed. In addition, the amount of chemicals containing chlorine components is suppressed while reducing the clogging of the membrane and the flow path of treated water by lowering the free residual chlorine concentration of treated water containing free residual chlorine at the time of filtration rather than at the time of washing. Can be suppressed.
Therefore, according to such a water treatment device and a water treatment method, even when treated water containing a suspended substance to some extent is treated using a spiral membrane unit, the flow path of the membrane or treated water is clogged. Is less likely to occur, and the amount of chemicals containing a chlorine component can be suppressed.

Further, the present invention is a water treatment apparatus comprising a reverse osmosis membrane unit having a reverse osmosis membrane, and configured such that water to be treated is separated by the reverse osmosis membrane unit,
A differential pressure measuring device for measuring the differential pressure on the non-permeating side of the reverse osmosis membrane unit is provided,
When the measured value measured by the differential pressure measuring device is less than the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L Is separated by the reverse osmosis membrane unit as water to be treated, and when the measured value measured by the differential pressure measuring device is equal to or higher than a reference value, the free residual chlorine concentration is 1. The water treatment apparatus is characterized in that free residual chlorine-containing treated water in the range of 2 to 2 mg / L is separated by the reverse osmosis membrane unit as treated water.

According to such a water treatment apparatus, when the measured value is less than the reference value, the free residual chlorine-containing treated water having a low free residual chlorine concentration (0.20 mg / L or more and less than 1.2 mg / L). ) Can be obtained, and purified water which is permeated water can be obtained by suppressing deterioration of the reverse osmosis membrane (RO membrane) while suppressing clogging of the membrane. Further, when the measured value is equal to or higher than the reference value, the membrane water is separated by membrane separation of the free residual chlorine-containing treated water (1.2 to 2 mg / L) having a higher free residual chlorine concentration. Clogging can be further suppressed. In addition, when the water to be treated is membrane-separated with a constant flux, if the differential pressure starts to rise, the difference may be detected even if the reverse osmosis membrane (RO membrane) is washed with a chemical such as alkali other than free residual chlorine. Although the pressure continues to rise, according to such a water treatment device, the differential pressure can be lowered even if the differential pressure rises somewhat.
Therefore, according to such a water treatment device, the reverse osmosis membrane (RO membrane) is hardly deteriorated while clogging of the reverse osmosis membrane (RO membrane) is suppressed using a chemical containing a chlorine component.

Furthermore, the present invention is a water treatment apparatus comprising a reverse osmosis membrane unit having a reverse osmosis membrane, and configured such that water to be treated is separated by the reverse osmosis membrane unit.
A differential pressure measuring device for measuring the differential pressure on the non-permeating side of the reverse osmosis membrane unit is provided,
When the measured value measured by the differential pressure measuring device is below the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L Is separated by the reverse osmosis membrane unit as water to be treated, and when the measured value measured by the differential pressure measuring device exceeds the reference value, the free residual chlorine concentration is 1.2. The water treatment apparatus is characterized in that free residual chlorine-containing treated water in a range of ˜2 mg / L is separated by the reverse osmosis membrane unit as treated water.

Further, the present invention is a water treatment method for membrane separation of water to be treated by a reverse osmosis membrane unit having a reverse osmosis membrane,
Measure the differential pressure on the non-permeate side of the reverse osmosis membrane unit with a differential pressure measuring device,
When the measured value measured by the differential pressure measuring device is less than the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L Is treated as water to be treated by the reverse osmosis membrane unit, and when the measured value measured by the differential pressure measuring device is equal to or higher than the reference value, the free residual chlorine concentration is in the range of 1.2 to 2 mg / L. The water treatment method is characterized in that membrane treatment is carried out by the reverse osmosis membrane unit using the treated water containing free residual chlorine as the treated water.

Furthermore, the present invention is a water treatment method for membrane separation of water to be treated by a reverse osmosis membrane unit having a reverse osmosis membrane,
Measure the differential pressure on the non-permeate side of the reverse osmosis membrane unit with a differential pressure measuring device,
When the measured value measured by the differential pressure measuring device is below the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L When the measured value measured by the differential pressure measuring device exceeds the reference value, the free residual chlorine concentration is within the range of 1.2 to 2 mg / L. The water treatment method is characterized in that membrane treatment is performed by the reverse osmosis membrane unit using the water to be treated containing free residual chlorine as the water to be treated.

As described above, according to the present invention, it is possible to suppress an increase in the amount of a chemical containing a chlorine component while suppressing clogging of the film using the chemical containing a chlorine component.

1 is a schematic view of a water treatment device according to an embodiment of the present invention. The figure which shows the time-dependent change of the transmembrane differential pressure | voltage of the turbidity-elimination membrane unit in Test Example 1, and the free residual chlorine concentration of the 1st free residual chlorine containing treated water. The figure which shows the time-dependent change of the free residual chlorine density | concentration of the 2nd free residual chlorine containing to-be-processed water in Test Example 2, and the differential pressure | voltage of the non-permeation | transmission side of a reverse osmosis membrane unit. The figure which shows the time-dependent change of the salt rejection of the reverse osmosis membrane of the reverse osmosis membrane unit in Test Example 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1st Embodiment First, the water treatment apparatus and water treatment method of 1st Embodiment are demonstrated.

By the way, conventionally, as a water treatment method, for example, water containing suspended substances such as river water is turbidized and separated by membrane separation with a hollow fiber membrane unit having a microfiltration membrane (MF membrane). A method for obtaining permeated water as purified water by obtaining water and separating the permeated water with a reverse osmosis membrane (RO membrane) is known (for example, Patent Document 1).

However, the hollow fiber membrane unit is relatively expensive, and a method using a cheaper membrane is desired.
From such a viewpoint, it is conceivable to use a spiral membrane unit having an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane), which is relatively inexpensive.
By the way, the spiral membrane unit is a membrane unit having a structure in which a flat membrane-like filtration membrane is overlapped with a net-like spacer for maintaining strength, which becomes a flow path of water to be treated.

However, when such a spiral-type membrane unit is used to treat water (water to be treated) containing a suspended substance to some extent, there is a possibility that the mesh spacer is clogged with turbidity. .
From this point of view, residual chlorine-containing treated water obtained by mixing treated water and chemicals containing chlorine components is membrane-separated to prevent clogging of the membrane and the flow path of treated water by residual chlorine. However, it is conceivable to treat the treated water with a membrane, but simply increasing the residual chlorine concentration in the treated water containing residual chlorine increases the cost, degrades the membrane, and increases the burden on the environment. There are problems such as.

In the first embodiment, in view of the above problems, clogging of the membrane and the flow path of the water to be treated and the chlorine component even if the water to be treated containing a suspended substance to some extent is treated using a spiral membrane unit. It is an object of the present invention to provide a water treatment apparatus and a water treatment method that can suppress an increase in the amount of chemicals used.

First, the water treatment apparatus of 1st Embodiment is demonstrated.
As shown in FIG. 1, the water treatment apparatus 1 of the first embodiment includes a turbidity membrane unit 21 that obtains first permeate and first concentrated water C by subjecting water to be treated A containing suspended solids to membrane separation. A turbidity treatment unit 2 for membrane separation of water to be treated A by the turbidity-eliminating membrane unit 21, and a reverse osmosis membrane for obtaining a second permeated water and a second concentrated water D by membrane separation of the first permeated water. A unit 31 is provided, and a reverse osmosis membrane treatment unit 3 for membrane separation of the water to be treated A by the reverse osmosis membrane unit 31. In the water treatment apparatus 1 of the first embodiment, the water to be treated A is transferred to the turbidity treatment unit 2, the first permeate is transferred to the reverse osmosis membrane treatment unit 3, and the first concentrated water C is the first. The concentrated water storage tank (not shown) is transferred, the second permeated water is transferred to the purified water storage tank (not shown) as the purified water B, and the second concentrated water D is transferred to the second concentrated water storage tank (not shown). It is configured to be transported.

Further, the water treatment apparatus 1 of the first embodiment includes a chlorinated aqueous solution storage unit 4 for storing an aqueous solution of a chemical containing a chlorine component such as sodium hypochlorite. Further, in the water treatment apparatus 1 of the first embodiment, the chlorinated aqueous solution in the chlorinated aqueous solution storage unit 4 is transferred to the turbidity treatment unit 2, and the chlorinated aqueous solution in the chlorinated aqueous solution storage unit 4 is subjected to reverse osmosis membrane treatment. It is configured to be transferred to the unit 3.

The turbidity treatment unit 2 includes a mixing unit 22 that mixes the water to be treated A and a chlorine-based aqueous solution to obtain first free residual chlorine-containing water to be treated. The treated water A is transferred to the turbidity membrane unit 21 and separated from the membrane.

Moreover, the said turbidity treatment part 2 adjusts the mixing ratio of the to-be-processed water A and chlorine system aqueous solution, and adjusts the free residual chlorine concentration of the 1st free residual chlorine containing to-be-processed water obtained. An adjustment mechanism (not shown) is provided.

The treated water A mixed with the chlorinated aqueous solution in the mixing unit 22 is not particularly limited. Examples of the treated A include human waste water, sewage, and factory waste water (food factories, chemical factories, Examples include supernatant water obtained by biological treatment and precipitation separation of organic wastewater such as wastewater from factories such as electronics industry and pulp mills, river water, and lake water.
The to-be-treated water A is water having turbidity, and the turbidity in the to-be-treated water A is, for example, 0.1 degrees or more, more specifically 0.1 to 50 degrees. In this specification, turbidity means a value measured by a laser scattering method.

The turbidity treatment unit 2 is obtained by mixing the water to be treated A and a chlorine-based aqueous solution at the time of filtration (first filtration step) and has a free residual chlorine concentration of 0.05 to 2.5 mg. The first free residual chlorine-containing treated water within the range of / L is continuously separated by the turbidation membrane unit 21 as the treated water A, and the free residual chlorine concentration is 2.5 mg / L during washing. The cleaning water which is larger than the range of 250 mg / L or less is supplied to the turbidity membrane unit 21 so that the membrane in the turbidity membrane unit 21 is immersed in the cleaning water.

Further, the water treatment apparatus 1 of the first embodiment is configured such that at the time of cleaning, the chlorine-based aqueous solution is transferred from the chlorine-based aqueous solution storage unit 4 to the turbidity processing unit 2 as cleaning water. Further, the water treatment apparatus 1 according to the first embodiment is configured so that the chlorinated aqueous solution transferred from the chlorinated aqueous solution storage unit 4 to the turbidity treatment unit 2 is diluted with water to a necessary concentration as necessary. The chlorinated aqueous solution thus formed is configured to be used in the turbidity treatment unit 2 as washing water.

In addition, the turbidity treatment unit 2 is configured such that the frequency of cleaning is preferably once every 10 to 80 hours, more preferably once every 20 to 60 hours.

Furthermore, the turbidity-treating unit 2 is configured such that the film immersion time with the washing water at the time of washing is 0.2 to 5 hours.

Further, the turbidity-treating unit 2 has a permeation flux of the first permeate obtained from the turbidity-eliminating membrane unit 21 of preferably 0.6 m / d or less, more preferably 0.1 to 0.5 m / d. It is comprised so that it may become. The turbidity treatment unit 2 is configured such that the permeation flux of the first permeate obtained from the turbidity membrane unit 21 is 0.6 m / d or less. There is an advantage that clogging of the flow path can be further suppressed.

The turbidity unit 21 has at least one of an ultrafiltration membrane and a microfiltration membrane, and is a spiral membrane unit. The spiral membrane unit is a membrane unit having a structure in which a flat membrane filter membrane is overlapped with a net-like spacer for maintaining strength.

The reverse osmosis membrane treatment unit 3 includes a first permeate storage unit 32 that stores a first permeate containing free residual chlorine, and the first permeate as the second free residual chlorine-containing treated water is treated water. It is configured to be transferred to the reverse osmosis membrane unit 31 as A and to be membrane-separated. The reverse osmosis membrane treatment unit 3 is configured such that a chlorine-based aqueous solution can be added to the first permeated water storage unit 32 in order to adjust the free residual chlorine concentration of the first permeated water.

Further, the reverse osmosis membrane treatment unit 3 regulates the free residual chlorine concentration of the first permeated water as the second free residual chlorine-containing treated water by adjusting the mixing ratio of the first permeated water and the chlorine-based aqueous solution. A second mixing ratio adjusting mechanism (not shown) is provided.

The reverse osmosis membrane treatment unit 3 includes a differential pressure measurement device (not shown) that measures the differential pressure (flow path pressure loss) on the non-permeation side of the reverse osmosis membrane unit 31.
The differential pressure on the non-permeate side (flow path pressure loss) is obtained without passing through the reverse osmosis membrane from the pressure value of the supply water supplied to the reverse osmosis membrane of the reverse osmosis membrane unit 31. It means a value obtained by subtracting the value of the concentrated water pressure, and more specifically, from the value of the feed water pressure at the feed water inlet of the membrane module of the reverse osmosis membrane unit 31, the concentrated water of the membrane module. It means a value obtained by subtracting the pressure of concentrated water at the outlet.

Further, the reverse osmosis membrane treatment unit 3 has a free residual chlorine concentration of 0.20 mg / L or more when the measured value measured by the differential pressure measuring device (not shown) is less than a reference value. A second free residual chlorine-containing treated water that is less than 2 mg / L, preferably greater than 0.25 mg / L and less than 1.2 mg / L, more preferably in the range of 0.3 to 1.0 mg / L. In the case where water A is continuously separated by the reverse osmosis membrane unit 31 and the measured value measured by the differential pressure measuring device (not shown) is equal to or higher than a reference value, The second free residual chlorine-containing treated water having a free residual chlorine concentration of 1.2 to 2 mg / L, preferably 1.4 to 1.8 mg / L is continuously treated as the treated water A by the reverse osmosis. It is configured to be separated by the membrane unit 31. It made.

In addition, the reverse osmosis membrane device 3 contains the second free residual chlorine content by the second mixing ratio adjusting mechanism (not shown) based on the measured value obtained by the differential pressure measuring device (not shown). It is comprised so that the free residual chlorine density | concentration of the 1st permeated water which is to-be-treated water may be adjusted.

The reference value per reverse osmosis membrane unit is preferably 0.01 to 0.1 MPa, more preferably 0.02 to 0.09 MPa.

The reverse osmosis membrane unit 31 has a reverse osmosis membrane (RO membrane) and is a hollow fiber type membrane unit.
The reverse osmosis membrane (RO membrane) is a reverse osmosis membrane (RO membrane) made of cellulose acetate.

The water treatment apparatus of the first embodiment is configured as described above. Next, the water treatment method of the first embodiment will be described.

The water treatment method of the first embodiment is obtained by mixing the water to be treated A and a chlorine-based aqueous solution at the time of filtration by the turbidity-eliminating membrane unit 21, and the free residual chlorine concentration is 0.05-2. The first free residual chlorine-containing treated water within the range of 5 mg / L is membrane-separated as treated water A, and the free residual chlorine concentration is larger than 2.5 mg / L and lower than 250 mg / L at the time of washing. In this method, the cleaning water within the range is supplied to the turbidity membrane unit 21 and the membrane in the turbidity membrane unit is immersed in the cleaning water.

Since the water treatment device and the water treatment method of the first embodiment are configured as described above, they have the following advantages.

For example, the water treatment device 1 of the first embodiment has a free residual chlorine concentration of 0.20 mg / L or more when the measurement value measured by the differential pressure measurement device (not shown) is less than a reference value. A second free residual chlorine-containing treated water that is less than 1.2 mg / L, preferably greater than 0.25 mg / L and less than 1.2 mg / L, more preferably in the range of 0.3 to 1.0 mg / L. When the water to be treated A is continuously separated by the reverse osmosis membrane unit 31, and the measured value measured by the differential pressure measuring device (not shown) is a reference value or more. The second free residual chlorine-containing treated water having a free residual chlorine concentration in the range of 1.2 to 2 mg / L, preferably 1.4 to 1.8 mg / L is continuously treated as the treated water A. Configured to be separated by reverse osmosis membrane unit 31 It has the following advantages by being composed.
That is, according to the water treatment apparatus 1, when the measured value is less than the reference value, the second free residual chlorine-containing treated water (0.20 mg / L or more 1) having a low free residual chlorine concentration. (Less than 2 mg / L) can be purified to obtain purified water which is the second permeated water while suppressing clogging of the membrane and suppressing deterioration of the reverse osmosis membrane (RO membrane). Further, when the measured value is equal to or higher than the reference value, the membrane is separated from the second free residual chlorine-containing treated water (1.2 to 2 mg / L) having a higher free residual chlorine concentration. Can be further suppressed. In addition, when the water to be treated A is subjected to membrane separation with a constant flux, if the differential pressure starts to rise, the reverse osmosis membrane (RO membrane) may be washed with a chemical such as alkali other than free residual chlorine. Although the differential pressure continues to rise, the water treatment apparatus 1 can reduce the differential pressure even if the differential pressure rises somewhat.

In addition, although the water treatment apparatus and the water treatment method of 1st Embodiment had the said advantage by the said structure, the water treatment apparatus and the water treatment method of this invention are not limited to the said structure, suitably The design can be changed.
For example, in the water treatment apparatus according to the first embodiment, when the reverse osmosis membrane treatment unit 3 has a measurement value measured by the differential pressure measurement device (not shown) less than a reference value, free residual chlorine The second free residual chlorine-containing treated water having a concentration in the range of 0.20 mg / L or more and less than 1.2 mg / L is continuously separated by the reverse osmosis membrane unit 31 as the treated water A. When the measured value measured by the differential pressure measuring device (not shown) is equal to or higher than a reference value, the second residual chlorine concentration is in the range of 1.2 to 2 mg / L. The free residual chlorine-containing treated water is continuously separated by the reverse osmosis membrane unit 31 as the treated water A, but the water treatment device of the present invention includes the reverse osmosis membrane treatment unit 3. Measured by the differential pressure measuring device (not shown). When the value is below the reference value, the second free residual chlorine-containing treated water having a free residual chlorine concentration within the range of 0.20 mg / L or more and less than 1.2 mg / L is continuously treated water A. When the measured value measured by the differential pressure measuring device (not shown) exceeds a reference value, the free residual chlorine concentration is 1 The second free residual chlorine-containing treated water in the range of 2 to 2 mg / L may be continuously separated by the reverse osmosis membrane unit 31 as the treated water A.

Second Embodiment Next, a water treatment device and a water treatment method according to a second embodiment will be described.

By the way, conventionally, as a water treatment method, in order to prevent clogging of the membrane, water to be treated and a chemical containing a chlorine component are mixed, and the free residual chlorine concentration obtained by the mixing is 0.1 to 1 mg / mg. A method of performing membrane separation with a reverse osmosis membrane unit using treated water containing free residual chlorine in the range of L as treated water is known (for example, Patent Document 2).

However, such a method cannot sufficiently suppress clogging of the reverse osmosis membrane (RO membrane).

On the other hand, simply trying to sufficiently suppress clogging of the reverse osmosis membrane (RO membrane) by increasing the free residual chlorine concentration of the treated water containing free residual chlorine, the free residual chlorine containing water There is a possibility that the reverse osmosis membrane (RO membrane) may deteriorate due to the free residual chlorine of the treated water.

In view of the above problems, the second embodiment uses a chemical containing a chlorine component to suppress clogging of the reverse osmosis membrane (RO membrane), and the water treatment device in which the reverse osmosis membrane (RO membrane) is hardly deteriorated and It is an object to provide a water treatment method.

First, the water treatment apparatus of 2nd Embodiment is demonstrated.
As shown in FIG. 1, the water treatment apparatus 1 of the second embodiment includes a turbidity-eliminating membrane unit 21 that obtains first permeated water and first concentrated water C by subjecting water to be treated A to membrane separation. A turbidity treatment unit 2 for membrane-separating the water to be treated A by the turbid membrane unit 21 and a reverse osmosis membrane unit 31 for separating the first permeate to obtain a second permeate and a second concentrated water D are provided. The reverse osmosis membrane unit 31 includes a reverse osmosis membrane treatment unit 3 for membrane separation of the first permeate. In the water treatment apparatus 1 of the second embodiment, the water to be treated A is transferred to the turbidity treatment unit 2, the first permeate is transferred to the reverse osmosis membrane treatment unit 3, and the first concentrated water C is the first. The concentrated water storage tank (not shown) is transferred, the second permeated water is transferred to the purified water storage tank (not shown) as the purified water B, and the second concentrated water D is transferred to the second concentrated water storage tank (not shown). It is configured to be transported.
In the present specification, turbidity is filtration that is rougher than reverse osmosis membrane filtration, that is, before filtration through a reverse osmosis membrane (RO membrane) and separated by a reverse osmosis membrane (RO membrane). It means removing coarser impurities (for example, solid substances).

Further, the water treatment apparatus 1 of the second embodiment includes a chlorinated aqueous solution storage unit 4 for storing a chlorinated aqueous solution of a chemical containing a chlorine component such as sodium hypochlorite. In the water treatment apparatus 1 of the second embodiment, the chlorinated aqueous solution in the chlorinated aqueous solution storage unit 4 is transferred to the turbidity treatment unit 2, and the chlorinated aqueous solution in the chlorinated aqueous solution storage unit 4 is subjected to reverse osmosis membrane treatment. It is configured to be transferred to the unit 3.

The treated water A mixed with the chlorinated aqueous solution in the mixing unit 22 is not particularly limited, for example. Examples of the treated A include human waste water, sewage, and factory waste water (food factories, chemicals). Examples include supernatant water obtained by biological treatment and precipitation separation of organic wastewater such as wastewater from factories such as factories, electronic industry factories, and pulp factories, river water, and lake water.
The to-be-treated water A is water having turbidity, and the turbidity in the to-be-treated water A is, for example, 0.1 degrees or more, more specifically 0.1 to 50 degrees. In this specification, turbidity means a value measured by a laser scattering method.

The turbidity unit 21 has at least one of an ultrafiltration membrane and a microfiltration membrane.
Further, the turbidity unit 21 is a spiral membrane unit. The spiral membrane unit is a membrane unit having a structure in which a flat membrane filter membrane is overlapped with a net-like spacer for maintaining strength.

Furthermore, the reverse osmosis membrane treatment unit 3 has a free residual chlorine concentration of 0 when the measured value measured by the differential pressure measuring device (not shown) is less than a reference value (in the first filtration step). Second free residual chlorine that is greater than or equal to 20 mg / L and less than 1.2 mg / L, preferably greater than 0.25 mg / L and less than 1.2 mg / L, more preferably in the range of 0.3 to 1.0 mg / L. The water to be treated is configured to be continuously separated by the reverse osmosis membrane unit 31 as the water to be treated A, and the measured value measured by the differential pressure measuring device (not shown) is a reference value. If this is the case (in the second filtration step), the second free residual chlorine-containing coating having a free residual chlorine concentration in the range of 1.2 to 2 mg / L, preferably 1.4 to 1.8 mg / L. The reverse osmosis membrane unit is treated as treated water A continuously. The preparative 31 becomes configured to be membrane separation.

The water treatment apparatus according to the second embodiment is configured as described above. Next, a water treatment method according to the second embodiment will be described.

The water treatment method of the second embodiment is measured by the differential pressure measuring device (not shown), and when the measured value measured by the differential pressure measuring device (not shown) is less than a reference value, The reverse osmosis membrane unit 31 separates the second free residual chlorine-containing treated water having a free residual chlorine concentration within the range of 0.20 mg / L or more and less than 1.2 mg / L as the treated water A, and the difference When the measured value measured by the pressure measuring device (not shown) is equal to or higher than the reference value, the second free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 1.2 to 2 mg / L Is treated with the reverse osmosis membrane unit 31 as water to be treated A.

In addition, although the water treatment apparatus and the water treatment method of 2nd Embodiment had the said structure, the water treatment apparatus and the water treatment method of this invention are not limited to the said structure, A design change is possible suitably. is there.

For example, in the water treatment apparatus according to the second embodiment, when the reverse osmosis membrane treatment unit 3 has a measurement value measured by the differential pressure measurement device (not shown) less than a reference value, free residual chlorine The second free residual chlorine-containing treated water having a concentration in the range of 0.20 mg / L or more and less than 1.2 mg / L is continuously separated by the reverse osmosis membrane unit 31 as the treated water A. When the measured value measured by the differential pressure measuring device (not shown) is equal to or higher than a reference value, the second residual chlorine concentration is in the range of 1.2 to 2 mg / L. The free residual chlorine-containing treated water is continuously separated by the reverse osmosis membrane unit 31 as the treated water A, but the water treatment device of the present invention includes the reverse osmosis membrane treatment unit 3. Was measured by the differential pressure measuring device (not shown). When the fixed value is below the reference value, the second free residual chlorine-containing treated water having a free residual chlorine concentration within the range of 0.20 mg / L or more and less than 1.2 mg / L is continuously treated water A. When the measured value measured by the differential pressure measuring device (not shown) exceeds a reference value, the free residual chlorine concentration is 1 The second free residual chlorine-containing treated water in the range of 2 to 2 mg / L may be continuously separated by the reverse osmosis membrane unit 31 as the treated water A.

Next, the present invention will be described more specifically with reference to test examples.

(Test Example 1)
The supernatant water obtained by biological treatment of sewage and subsequent precipitation separation (turbidity: fluctuates between 0.1 and 50 degrees) and chlorinated aqueous solution (sodium hypochlorite aqueous solution) are mixed to form the first Free treated chlorine-containing water was obtained. Then, the first free residual chlorine-containing treated water was subjected to membrane separation using a spiral type turbidity membrane unit (trade name: RS50-S8, manufactured by Nitto Denko Corporation) having an ultrafiltration membrane (UF membrane). The transmembrane pressure difference of the turbidity separation membrane unit during membrane separation was measured with a pressure data logger (trade name: DAQSTATIONION DX120, manufactured by Yokogawa Electric Corporation).
Moreover, the free residual chlorine concentration of the 1st free residual chlorine containing treated water at the time of filtration was made into the density | concentration shown in FIG. 2, and the free residual chlorine concentration of the wash water at the time of washing | cleaning was 125 mg / L.
Furthermore, the film immersion time with the washing water at the time of washing was set to 1 hour, and the test was carried out with the washing frequency shown in Table 1 in each section (period) in FIG.
Moreover, the test was implemented so that the permeation | transmission flux of the 1st permeated water obtained from a turbidity membrane unit might become the value shown in Table 1 in each area (period) in FIG.

As shown in FIG. 2, by subjecting the water to be treated to membrane separation with a water treatment device and a water treatment method within the scope of the present invention, the water to be treated containing suspended substances is removed using a spiral-type turbidity removal membrane unit. It has been clarified that even when the treatment is performed, clogging of the flow path of the membrane and the water to be treated and an increase in the amount of the chemical containing the chlorine component can be suppressed.

(Test Example 2)
The first free residual chlorine-containing treated water of Test Example 1 is a spiral type turbidity membrane unit (trade name: RS50-S8, manufactured by Nitto Denko Corporation) having the ultrafiltration membrane (UF membrane) of Test Example 1. The membrane was separated to obtain the first permeated water as the second treated water containing free residual chlorine. The second free residual chlorine-containing treated water is subjected to membrane separation with a hollow fiber type reverse osmosis membrane unit (trade name: HB10255FI, manufactured by Toyobo Co., Ltd.) having a cellulose triacetate reverse osmosis membrane (RO membrane). Thus, second permeated water was obtained. The differential pressure on the non-permeation side of the reverse osmosis membrane unit during membrane separation was measured with a pressure data logger (trade name: DAQSTATION DX120, manufactured by Yokogawa Electric Corporation) as a differential pressure measuring device. The results are shown in FIG.
In addition, as shown in FIG. 3, when the measured value measured by this differential pressure measuring device is less than a reference value (0.06 MPa), the second free residual chlorine-containing treated water is used as the free residual chlorine concentration. Was within the range of 0.20 mg / L or more and less than 1.2 mg / L, and membrane separation was performed by the reverse osmosis membrane unit as water to be treated. Further, when the measured value measured by the differential pressure measuring device is equal to or higher than the reference value, the second free residual chlorine-containing water to be treated has a free residual chlorine concentration within the range of 1.2 to 2 mg / L. Then, membrane separation was performed by the reverse osmosis membrane unit as water to be treated.
Moreover, in order to calculate the salt rejection of the reverse osmosis membrane (RO membrane) of the reverse osmosis membrane unit, the electrical conductivities of the second free residual chlorine-containing treated water and the second permeated water were measured. The electrical conductivity was measured according to the electrode method. The results are shown in FIG.
The salt rejection of the reverse osmosis membrane (RO membrane) of the reverse osmosis membrane unit is a value calculated by the following equation.
Salt rejection (%) = (1−Cp / Cf) × 100
Cf: electric conductivity of the second free residual chlorine-containing treated water, Cp: electric conductivity of the second permeated water

As shown in FIG. 3, the differential pressure was 0.1 MPa or less, and it was shown that the flow path blockage of the reverse osmosis membrane (RO membrane) hardly occurred. Further, when the differential pressure becomes 0.06 MPa or more, the differential pressure increases by making the free residual chlorine concentration within the range of more than 0.25 mg / L and less than 1.2 mg / L. It was suggested that it can be lowered even at the beginning.
Moreover, as shown in FIG. 4, the salt rejection was 97% or more, suggesting that the reverse osmosis membrane (RO membrane) was not deteriorated by free residual chlorine.

1: water treatment device, 2: turbidity treatment unit, 3: reverse osmosis membrane treatment unit, 4: chlorinated aqueous solution storage unit, 21: turbidity membrane unit, 22: mixing unit, 31: reverse osmosis membrane unit, 32: First permeated water storage unit, A: treated water, B: purified water, C: first concentrated water, D: second concentrated water

Claims

A water treatment apparatus comprising a membrane unit having a membrane and configured such that water to be treated is separated by the membrane unit,
A first filtration step in which the membrane unit separates free residual chlorine-containing treated water having a free residual chlorine concentration of a predetermined value or less as treated water, and the washing water has a free residual chlorine concentration higher than the predetermined value; A washing step of immersing the membrane in the membrane unit or a second filtration step of membrane separation by the membrane unit using free residual chlorine-containing treated water having a free residual chlorine concentration higher than the predetermined value as the treated water It is comprised so that it may implement, The water treatment apparatus characterized by the above-mentioned.
A water treatment method for separating water to be treated by a membrane unit having a membrane,
A first filtration step in which the membrane unit separates free residual chlorine-containing treated water having a free residual chlorine concentration of a predetermined value or less as treated water, and the washing water has a free residual chlorine concentration higher than the predetermined value; A washing step of immersing the membrane in the membrane unit or a second filtration step of membrane separation by the membrane unit using free residual chlorine-containing treated water having a free residual chlorine concentration higher than the predetermined value as the treated water The water treatment method characterized by implementing.
A water treatment apparatus configured to perform membrane separation of water to be treated,
A spiral type turbidity-eliminating membrane unit having at least one of an ultrafiltration membrane and a microfiltration membrane is provided,
At the time of filtration, free residual chlorine-containing treated water obtained by mixing treated water and a chemical containing a chlorine component and having a free residual chlorine concentration in the range of 0.05 to 2.5 mg / L. Membrane separation is carried out by the turbidity membrane unit as water to be treated, and at the time of washing, washing water having a free residual chlorine concentration in the range of more than 2.5 mg / L and not more than 250 mg / L is supplied to the turbidity membrane unit. And a water treatment apparatus configured such that the membrane in the turbidity-eliminating membrane unit is immersed in the washing water.
A reverse osmosis membrane unit having a reverse osmosis membrane composed of cellulose acetate is provided, and the reverse osmosis membrane unit is configured so that the permeated water containing free residual chlorine obtained by the turbidity removal membrane unit is membrane-separated. The water treatment apparatus according to claim 3.
The water treatment device according to claim 3 or 4, wherein the permeate flux obtained from the turbidity-eliminating membrane unit is 0.6 m / d or less.
The water treatment apparatus according to claim 3 or 4, wherein the frequency of washing is once every 10 to 80 hours.
The water treatment apparatus according to claim 5, wherein the frequency of washing is once every 10 to 80 hours.
The water treatment apparatus according to claim 3 or 4, wherein the film immersion time in the cleaning water at the time of cleaning is 0.2 to 5 hours.
6. The water treatment apparatus according to claim 5, wherein the film immersion time in the cleaning water at the time of cleaning is 0.2 to 5 hours.
The water treatment apparatus according to claim 6, wherein the film immersion time with the washing water at the time of washing is 0.2 to 5 hours.
The water treatment apparatus according to claim 7, wherein the film immersion time in the cleaning water at the time of cleaning is 0.2 to 5 hours.
A water treatment method for membrane separation of water to be treated,
At the time of filtration, the concentration of free residual chlorine is obtained by mixing water to be treated and chemicals containing chlorine components by a spiral-type turbidity-eliminating membrane unit having at least one of an ultrafiltration membrane and a microfiltration membrane. Is subjected to membrane separation as water to be treated, and the free residual chlorine concentration is higher than 2.5 mg / L and 250 mg / L. A water treatment method, comprising supplying cleaning water in a range of L or less to the turbidity membrane unit and immersing the membrane in the turbidity membrane unit in the cleaning water.
A water treatment apparatus comprising a reverse osmosis membrane unit having a reverse osmosis membrane, and configured such that water to be treated is separated by the reverse osmosis membrane unit,
A differential pressure measuring device for measuring the differential pressure on the non-permeating side of the reverse osmosis membrane unit is provided,
When the measured value measured by the differential pressure measuring device is less than the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L Is separated by the reverse osmosis membrane unit as water to be treated, and when the measured value measured by the differential pressure measuring device is equal to or higher than a reference value, the free residual chlorine concentration is 1. A water treatment apparatus, wherein water to be treated containing free residual chlorine in the range of 2 to 2 mg / L is separated by the reverse osmosis membrane unit as water to be treated.
When the measured value is less than the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of more than 0.25 mg / L and less than 1.2 mg / L is treated as the reverse water. The water treatment apparatus according to claim 13, wherein the water treatment apparatus is configured to be separated by a osmosis membrane unit.
A water treatment apparatus comprising a reverse osmosis membrane unit having a reverse osmosis membrane, and configured such that water to be treated is separated by the reverse osmosis membrane unit,
A differential pressure measuring device for measuring the differential pressure on the non-permeating side of the reverse osmosis membrane unit is provided,
When the measured value measured by the differential pressure measuring device is below the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L Is separated by the reverse osmosis membrane unit as water to be treated, and when the measured value measured by the differential pressure measuring device exceeds the reference value, the free residual chlorine concentration is 1.2. A water treatment apparatus, wherein water to be treated containing free residual chlorine within a range of ˜2 mg / L is separated by the reverse osmosis membrane unit as water to be treated.
When the measured value is not more than the reference value, the free residual chlorine-containing treated water having a free residual chlorine concentration in the range of more than 0.25 mg / L and less than 1.2 mg / L is treated as the reverse water. The water treatment apparatus according to claim 15, wherein the water treatment apparatus is configured to be membrane-separated by an osmosis membrane unit.
The water treatment apparatus according to any one of claims 13 to 16, wherein the reverse osmosis membrane is composed of cellulose acetate.
A water treatment method for membrane separation of water to be treated by a reverse osmosis membrane unit having a reverse osmosis membrane,
Measure the differential pressure on the non-permeate side of the reverse osmosis membrane unit with a differential pressure measuring device,
When the measured value measured by the differential pressure measuring device is less than the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L Is treated as water to be treated by the reverse osmosis membrane unit, and when the measured value measured by the differential pressure measuring device is equal to or higher than the reference value, the free residual chlorine concentration is in the range of 1.2 to 2 mg / L. A water treatment method characterized in that membrane treatment is carried out by the reverse osmosis membrane unit using free residual chlorine-containing treated water as treated water.
A water treatment method for membrane separation of water to be treated by a reverse osmosis membrane unit having a reverse osmosis membrane,
Measure the differential pressure on the non-permeate side of the reverse osmosis membrane unit with a differential pressure measuring device,
When the measured value measured by the differential pressure measuring device is below the reference value, the free residual chlorine-containing treated water whose free residual chlorine concentration is in the range of 0.20 mg / L or more and less than 1.2 mg / L When the measured value measured by the differential pressure measuring device exceeds the reference value, the free residual chlorine concentration is within the range of 1.2 to 2 mg / L. A water treatment method characterized in that membrane treatment is carried out by the reverse osmosis membrane unit using the treated water containing free residual chlorine as the treated water.