JP2011189242A - Water treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment system which can be simplified and can inhibit fouling of a membrane separation device. <P>SOLUTION: The water treatment system 1 includes a reduction treatment device 2 for adjusting groundwater W1 to a reduced state by a chemical means or a physical means, and the membrane separation device 8 for treating the groundwater W1, having been adjusted to the reduced state, with a separation membrane 8a (a nanofiltration membrane or a reverse osmosis membrane) to obtain a permeate W2. The reduction treatment device 2 adjusts an oxidation reduction potential of the groundwater W1 in a range of from E1 to E2 obtained by the following equations: E1 [V]=-0.059×pH value and E2 [V]=0.7-0.059×pH value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water treatment system for pretreating groundwater supplied to a boiler or the like.

Conventionally, a water treatment system that removes dissolved iron and dissolved manganese contained in raw water such as groundwater by a so-called catalytic oxidation method is known (see, for example, Patent Document 1).
Such a conventional water treatment system includes an iron removal manganese removal device that removes dissolved iron and dissolved manganese with a filter medium while adding a chlorine agent, and a membrane separation device that produces permeate by subjecting the treated water to membrane separation treatment. And comprising.

JP 2003-220394 A

However, a conventional water treatment system needs to use a large amount of a chlorinating agent (for example, sodium hypochlorite) to remove dissolved iron and dissolved manganese contained in raw water. This complicates the system and increases the running cost.
Further, when the raw water contains a large amount of ammonia nitrogen, chloramine was generated by the reaction of ammonia nitrogen and the chlorine agent, and the required amount of the chlorine agent was further increased. In addition, the use of chlorinating agents has sometimes been problematic in generating by-products (for example, carcinogenic trihalomethanes).

  In addition, when a chlorine agent such as sodium hypochlorite is injected into groundwater containing dissolved iron and dissolved manganese, or when this groundwater is stored in a tank, the dissolved iron is oxidized by the contact of the groundwater with air and becomes insoluble. Of iron hydroxide is produced. Therefore, this insoluble iron hydroxide causes clogging (fouling) of the membrane separator and the like.

  An object of this invention is to provide the water treatment system which can simplify a system and can suppress the fouling of a membrane separator.

The present invention relates to a reduction treatment apparatus that adjusts groundwater to a reduced state by chemical means or physical means, and membrane separation that produces groundwater by treating the groundwater adjusted to the reduced state with a nanofiltration membrane or a reverse osmosis membrane. The reduction treatment device relates to a water treatment system that adjusts the oxidation-reduction potential of groundwater to a range of E1 to E2 obtained by the following equation.
E1 [V] = − 0.059 × pH value E2 [V] = 0.7−0.059 × pH value

  Moreover, it is preferable to provide the acid addition apparatus which adjusts pH value to 6 or less by adding an acid to groundwater.

  Moreover, it is preferable to provide the water softening apparatus which processes a ground water with a cation exchanger in the back | latter stage of the said reduction | restoration processing apparatus and the said acid addition apparatus.

  Moreover, it is preferable to provide the dispersing agent addition apparatus which adds a scale dispersing agent to groundwater in the back | latter stage of the said reduction processing apparatus and the said acid addition means.

  Moreover, it is preferable that the said reduction processing apparatus is a reducing agent addition apparatus which adds a reducing agent to groundwater.

  In addition, the reduction treatment apparatus is a membrane-type deoxygenation device that removes dissolved oxygen by passing groundwater through a gas separation membrane, a decompression-type deoxygenation device that depressurizes groundwater and removes dissolved oxygen, or nitrogen gas in groundwater. It is preferably any one of nitrogen substitution type deoxygenation devices which blows in and removes dissolved oxygen.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to simplify a system, the water treatment system which can suppress the fouling of a membrane separator can be provided.

It is a lineblock diagram showing water treatment system 1 of a 1st embodiment of the present invention. It is a block diagram which shows 1A of water treatment systems of 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG. Drawing 1 is a lineblock diagram showing water treatment system 1 of a 1st embodiment of the present invention.
As shown in FIG. 1, the water treatment system 1 manufactures the permeated water W2 that pretreats groundwater W1 and supplies it to a boiler (not shown) or the like.

As shown in FIG. 1, the water treatment system 1 includes a first distribution line L1 through which groundwater W1 is circulated, a reduction treatment device 2 that adjusts the groundwater W1 to a reduced state, and a groundwater W1 that has been adjusted to a reduced state downstream. The second distribution line L2 to be circulated, the acid addition device 3 for adding acid to the groundwater W1 provided in the second distribution line L2, the sand separator 4 provided in the second distribution line L2, and the second distribution line L2. A water softening device 5 that softens groundwater W1 provided at the downstream end, a third distribution line L3 that distributes the softened groundwater W1 downstream, and an ultraviolet irradiation that is provided in the third distribution line L3. An apparatus 6 and a filter 7; a membrane separation apparatus 8 that is provided at the downstream end of the third distribution line L3 and that produces permeated water W2 by subjecting the softened groundwater W1 to membrane separation; A fourth flow line L4 for circulating W2 on the downstream side, and forms the transmission water storage tank 9 is connected to the fourth flow line L4 storing permeate W2, the mainly.
In addition, the “line” in this specification is a general term for a line capable of flowing a fluid such as a flow path, a path, and a pipeline.

  The first distribution line L1 distributes groundwater W1 such as well water pumped from the underground by a pump or the like (not shown) to the reduction treatment device 2.

The reduction treatment device 2 adjusts the groundwater W1 to a reduced state by chemical means. Specifically, the reduction treatment device 2 adjusts the oxidation-reduction potential (ORP value) of the groundwater W1 from E1 obtained by the following equation (1) to a range of E2 obtained by the following equation (2). The oxidation-reduction potential E1 is an upper limit value that includes an actual measurement value of the oxidation-reduction potential of the groundwater W1 at the time of pumping. The oxidation-reduction potential E2 is a theoretical value of the reduction potential of water.
E1 [V] = − 0.059 × pH value (1)
E2 [V] = 0.7-0.059 × pH value (2)

  In the present embodiment, the reduction treatment device 2 is configured as a reducing agent addition device that adds a reducing agent to the groundwater W1. The reduction treatment device 2 adds a reducing agent equivalent to 1 to 2 times the amount of dissolved oxygen in the groundwater W1. Examples of the reducing agent include sodium bisulfite and sodium thiosulfate.

  The acid addition device 3 is connected to the second distribution line L2 at the addition point J1. The acid addition device 3 adjusts the pH value of the groundwater W1 to 6 or less by adding an acid to the groundwater W1. Examples of the acid include hydrochloric acid, sulfuric acid and the like.

  The sand separator 4 removes solid particles such as sand mixed in the groundwater W1. Specifically, the sand separator 4 is configured to remove solid particles mixed in the groundwater W1 during pumping by centrifugal action.

  The water softening device 5 is connected to the downstream end of the second distribution line L2. The water softening device 5 includes a cation exchanger 5a, and a control valve and a regenerant supply device (not shown). The cation exchanger 5a is a sodium-type cation exchanger, and is made of, for example, a strongly acidic cation exchange resin.

  The water softening device 5 introduces the ground water W1 flowing through the second distribution line L2 into the cation exchanger 5a and performs ion exchange treatment, so that dissolved iron, dissolved manganese, hardness components (calcium ions and magnesium ions) and Softened water from which cations such as ammonia nitrogen have been removed is produced.

  The control valve is provided inside the water softening device 5 and flows through the water softening device 5 (regenerant solution for regenerating the groundwater W1 before softening, the groundwater W1 softened, and the cation exchanger 5a). Etc.) is controlled. The regenerant supply device is configured to be able to supply a regenerant solution for regenerating the cation exchanger 5a to the cation exchanger 5a. An example of the regenerant solution is a sodium chloride (NaCl) solution.

  The third distribution line L3 distributes the groundwater W1 softened by the water softening device 5 to the downstream side. The third distribution line L3 is provided with a hardness monitoring device (not shown). The hardness monitoring device monitors (measures) the hardness of the softened groundwater W1.

  The ultraviolet irradiation device 6 is provided in the third distribution line L3, and irradiates the groundwater W1 softened by the water softening device 5 with ultraviolet rays. When irradiating ultraviolet rays with the ultraviolet irradiation device 6, the concentration of dissolved iron and dissolved manganese on the upstream side of the membrane separation device 8 (described later) is preferably 0.05 ppm or less.

  The filter 7 is provided in the third distribution line L3, and removes suspended substances from the groundwater W1 that has been subjected to ultraviolet irradiation treatment by the ultraviolet irradiation device 6. As the filter 7, for example, a wind filter can be used.

  The membrane separation device 8 has a predetermined separation membrane 8a. The membrane separation device 8 performs the membrane separation treatment on the groundwater W1 adjusted to the reduced state by the reduction treatment device 2 with the separation membrane 8a, and produces the permeated water W2 and concentrated water (not shown). Examples of the separation membrane 8a include a nanofiltration membrane or a reverse osmosis membrane.

  In the nanofiltration membrane, the removal rate of dissolved silica is 1 to 10%, and the removal rate of chloride ions and the removal rate of sulfate ions is 40 to 60%. In the reverse osmosis membrane, the removal rate of dissolved silica is 90% or more, and the chloride ion removal rate and the sulfate ion removal rate are 90% or more.

  In addition, the concentrated water (not shown) manufactured with the permeated water W2 in the membrane separator 8 is discharged out of the system. The concentrated water may be refluxed upstream of the membrane separation device 8.

  The upstream end of the fourth distribution line L4 is connected to the membrane separation device 8. The downstream end of the fourth distribution line L4 is connected to a permeate storage tank 9 (described later). The 4th distribution line L4 distributes permeate W2 manufactured in membrane separation device 8 to permeate storage tank 9 of the downstream.

The permeated water storage tank 9 is connected to the downstream end of the fourth distribution line L4 and stores the permeated water W2. A fifth distribution line L5 is connected to the permeate storage tank 9.
The fifth distribution line L5 distributes the permeated water W2 stored in the permeated water storage tank 9 to a boiler (not shown).

  Pump means and valve means (not shown) are provided at appropriate locations on the distribution line of the water treatment system 1 configured as described above. The operation of the water treatment system 1 is controlled by a control device (not shown).

  Next, the operation of the water treatment system 1 will be described with reference to FIG. As shown in FIG. 1, the groundwater W1 is circulated to the reduction treatment apparatus 2 through the first distribution line L1. In the reduction treatment device 2, a reducing agent equivalent to 1 to 2 times the amount of dissolved oxygen in the groundwater W1 is added. Thereby, the oxidation-reduction potential (ORP value) of the groundwater W1 is adjusted from the range E1 obtained by the equation (1) to the range E2 (reduction state) obtained by the equation (2).

Therefore, it is not necessary to use a chlorinating agent that causes generation of carcinogenic trihalomethanes. Moreover, the iron content contained in groundwater W1 will be in the state (dissolved state) of a ferrous ion (Fe2 ⁺ ). Furthermore, the growth of aerobic microorganisms is suppressed in the groundwater W1.

  Next, the acid is added to the groundwater W1 adjusted to the reduced state by the reduction treatment device 2 at the addition point J1 by the acid addition device 3, and the pH value of the groundwater W1 is adjusted to 6 or less. Thereby, in the separation membrane 8a of the downstream membrane separation device 8, the generation of calcium-based scale is suppressed. Further, the colloidal iron in the groundwater W1 is changed to dissolved iron.

  In the groundwater W <b> 1 to which acid is added by the acid addition device 3, solid particles such as sand are removed in the sand separator 4. Therefore, clogging of the cation exchanger 5a and the like is suppressed by removing solid particles from the groundwater W1 prior to the softening of the groundwater W1 by the water softening device 5.

  From the groundwater W1 from which the solid particles have been removed, the hardness component is removed by the water softening device 5 prior to membrane separation by the membrane separation device 8. Therefore, the generation of calcium scale in the separation membrane 8a is suppressed. Prior to this membrane separation, dissolved iron and dissolved manganese are removed from the groundwater W1. Therefore, the iron removal manganese removal apparatus etc. which were conventionally required become unnecessary, and the iron fouling in the separation membrane 8a is suppressed. Furthermore, the dissolved salts of the groundwater W1 supplied to the membrane separation device 8 are replaced with sodium ions that are easily removed by the separation membrane 8a. Therefore, the purity of the permeated water W2 produced by the membrane separation device 8 is improved.

  Note that the hardness of the groundwater W1 that has passed through the water softening device 5 is monitored (measured) by a hardness monitoring device (not shown) provided in the third distribution line L3. When the hardness of the groundwater W1 reaches a predetermined threshold value, the regenerant solution is supplied to the cation exchanger 5a by the regenerant supply device (not shown) of the water softening device 5. Thereby, the cation exchanger 5a is regenerated.

  Next, the groundwater W <b> 1 that has passed through the water softening device 5 is irradiated with ultraviolet rays by the ultraviolet irradiation device 6. Therefore, aerobic microorganisms and the like in the groundwater W1 are sterilized, and propagation of the aerobic microorganisms and the like is suppressed in the separation membrane 8a of the membrane separation device 8 at the subsequent stage.

  Next, suspended substances such as fine particles are removed from the groundwater W1 that has passed through the ultraviolet irradiation device 6 by the filter 7. Therefore, the clogging of the separation membrane 8a is suppressed by removing suspended substances from the groundwater W1 prior to the membrane separation processing of the groundwater W1 by the membrane separation device 8.

The groundwater W1 that has passed through the filter 7 is introduced into the membrane separation device 8 and subjected to membrane separation treatment by the separation membrane 8a. Thereby, the permeated water W2 is manufactured from the groundwater W1. At that time, ammoniacal nitrogen and organic substances are also removed.
The permeated water W2 produced by the membrane separation device 8 flows through the fourth distribution line L4 and is stored in the permeated water storage tank 9. The permeated water W2 stored in the permeated water storage tank 9 flows through the fifth distribution line L5 and is supplied to a boiler (not shown) or the like.

According to the water treatment system 1 of 1st Embodiment demonstrated above, each effect shown below is show | played.
A water treatment system 1 according to the first embodiment includes a reduction treatment device 2 that adjusts groundwater W1 to a reduced state, and a membrane separation device that processes groundwater W1 adjusted to a reduced state with a separation membrane 8a to produce permeated water W2. 8, the reduction treatment apparatus 2 adjusts the oxidation-reduction potential of the groundwater W <b> 1 to the range (reduction state) of E <b> 2 obtained from Equation (2) from E <b> 1 obtained from Equation (1).

  Therefore, a water treatment system for removing ammonia nitrogen and organic substances from the ground water W1 can be simplified and configured without using a chlorinating agent that causes carcinogenic trihalomethanes. Further, while suppressing iron fouling of the separation membrane 8a due to the generation of insoluble iron hydroxide, the iron content can be removed from the groundwater W1 in the state of dissolved iron. Further, biofouling of the separation membrane 8a due to the growth of aerobic microorganisms can be suppressed, and a stable amount of product water can be ensured.

  Therefore, according to the water treatment system 1 of the first embodiment, it is not necessary to add sodium hypochlorite or the like, which is conventionally required for iron removal / manganese removal treatment, or deoxygenation treatment for corrosion prevention. Can be. Thereby, while being able to simplify the water treatment system 1, the fouling of the membrane separator 8 can be suppressed.

Moreover, in the water treatment system 1 of 1st Embodiment, the acid addition apparatus 3 which adds an acid to groundwater W1 and adjusts pH value to 6 or less is provided.
Therefore, in the membrane separator 8, the production | generation of the calcium-type scale in the separation membrane 8a can be suppressed, and the stable amount of produced water can be ensured. Moreover, the colloidal iron in the groundwater W1 can be changed to dissolved iron, and iron can be removed from the groundwater W1 in the state of dissolved iron.

Moreover, in the water treatment system 1 of 1st Embodiment, the water softening apparatus 5 which processes the ground water W1 with the cation exchanger 5a is provided in the back | latter stage of the reduction processing apparatus 2 and the acid addition apparatus 3. FIG.
Therefore, by removing the hardness component from the groundwater W1 prior to the membrane separation by the membrane separation device 8, the generation of calcium-based scale in the separation membrane 8a can be suppressed. Further, by removing dissolved iron and dissolved manganese from the groundwater W1 prior to membrane separation by the membrane separation device 8, iron fouling in the separation membrane 8a can be suppressed. Furthermore, the purity of the permeated water W2 can be improved by replacing the dissolved salts of the groundwater W1 supplied to the membrane separation device 8 with sodium ions that are easily removed by the separation membrane 8a.

Moreover, in the water treatment system 1 of 1st Embodiment, the reduction process apparatus 2 is a reducing agent addition apparatus which adds a reducing agent to the groundwater W1.
Therefore, the oxidation-reduction potential (ORP value) can be easily adjusted to the range of E1 to E2 only by adding a reducing agent equivalent to 1 to 2 times the amount of dissolved oxygen in the groundwater W1.

  Next, another embodiment of the present invention will be described. The other embodiments will be described mainly with respect to differences from the first embodiment, and the same configurations as those of the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted. For the points not specifically described in other embodiments, the description of the first embodiment is appropriately applied or incorporated.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a configuration diagram illustrating a water treatment system 1A according to the second embodiment of the present invention.
As shown in FIG. 2, the water treatment system 1 </ b> A of the second embodiment includes a dispersant addition device 10 instead of the water softening device 5 (see FIG. 1) of the water treatment system 1 in the first embodiment. Other configurations are the same as those of the water treatment system 1 of the first embodiment.

Specifically, as shown in FIG. 2, the dispersant addition device 10 is disposed in the subsequent stage of the sand separator 4 disposed in the subsequent stage of the reduction treatment apparatus 2 and the acid addition apparatus 3, and the groundwater W <b> 1 passed through the sand separator 4. Add scale dispersant to
A scale dispersing agent disperses the hardness component, silica component, etc. of groundwater W1, and suppresses precipitation of a scale. Examples of the scale dispersant include polyacrylic acid, polymaleic acid, and alkali metal salts thereof.

  Next, the operation of the water treatment system 1A will be described with reference to FIG. Since the operation from the reduction treatment apparatus 2 to the sand separator 4 is the same as the operation of the water treatment system 1 of the first embodiment, a duplicate description is omitted.

The dispersant addition device 10 adds a scale dispersant to the groundwater W1 that has passed through the sand separator 4. Thereby, the hardness component, silica component, etc. of groundwater W1 disperse | distribute. Therefore, the deposition of scale is suppressed in the separation membrane 8a of the membrane separation device 8.
The groundwater W1 to which the scale dispersant has been added by the dispersant addition device 10 is irradiated with ultraviolet rays by the ultraviolet irradiation device 6, and after suspended substances are removed by the filter 7, it is introduced into the membrane separation device 8. In the membrane separation device 8, the permeated water W2 is produced by membrane separation by the separation membrane 8a.

According to 1 A of water treatment systems of 2nd Embodiment demonstrated above, while having the same effect as the water treatment system 1 of the said 1st Embodiment, each effect shown below is show | played.
A water treatment system 1A of the second embodiment includes a dispersant addition device 10 instead of the water softening device 5 of the water treatment system 1 of the first embodiment.

Therefore, even if scale nuclei are generated in concentrated water (not shown) in the membrane separation device 8 due to an abnormality in the acid addition device 3, the scale dispersant added by the dispersant addition device 10 Scale nuclei can be dispersed. Therefore, the production | generation of the calcium-type scale in the separation membrane 8a can be suppressed.
Further, even when insoluble iron hydroxide is generated in the groundwater W1 due to an abnormality in the reduction treatment device 2, the insoluble iron hydroxide is dispersed by the scale dispersant added by the dispersant adding device 10. Can be made. Therefore, iron fouling at the separation membrane can be suppressed.

As mentioned above, although one Embodiment of this invention was described, this invention is not restrict | limited to embodiment mentioned above, It can change suitably.
In the said 1st Embodiment and the said 2nd Embodiment, although the acid addition apparatus 3 demonstrated as what adds an acid to the groundwater W1 in the addition point J1 of the downstream of the reduction processing apparatus 2, it is not restrict | limited to this. . For example, the acid addition device 3 may be configured to add an acid to the groundwater W1 on the upstream side (first distribution line L1) of the reduction treatment device 2.

  Moreover, in the said 1st Embodiment and the said 2nd Embodiment, although the reduction processing apparatus 2 demonstrated as what is comprised as a reducing agent addition apparatus (chemical means) which adds a reducing agent to groundwater W1, this is demonstrated. Not limited to. For example, the reduction treatment apparatus 2 may be configured to adjust the groundwater W1 to a reduced state by physical means.

Specifically, the reduction treatment device 2 may be a membrane deoxygenation device (not shown) that removes dissolved oxygen by allowing the groundwater W1 to pass through a gas separation membrane. Further, the reduction treatment device 2 may be a reduced pressure deoxygenation device (not shown) that removes dissolved oxygen by reducing the pressure of the groundwater W1. Further, a nitrogen substitution type deoxygenation device (not shown) that blows nitrogen gas into the groundwater W1 to remove dissolved oxygen may be used.
By configuring the reduction treatment device 2 as the deoxygenation device, the oxidation-reduction potential (ORP value) can be easily adjusted to the range of E1 to E2 simply by passing the groundwater W1 through the deoxygenation device. it can.

  Further, in the subsequent stage of the acid addition device 3, when the ground water W1 is treated by the deoxygenation device, the ground water W1 is decarboxylated. Therefore, in the membrane separation device 8, the purity of the permeated water W2 can be improved.

1,1A Water treatment system 2 Reduction treatment device (reducing agent addition device)
DESCRIPTION OF SYMBOLS 3 Acid addition apparatus 5 Water softening apparatus 5a Cation exchanger 8 Membrane separation apparatus 8a Separation membrane 10 Dispersant addition apparatus W1 Ground water W2 Permeated water

Claims (6)

A reduction treatment apparatus for adjusting groundwater to a reduced state by chemical means or physical means;
A groundwater adjusted to a reduced state is treated with a nanofiltration membrane or a reverse osmosis membrane, and equipped with a membrane separation device for producing permeated water,
The said reduction processing apparatus is a water treatment system which adjusts the oxidation-reduction potential of groundwater to the range of E1 to E2 calculated | required by following Formula.
E1 [V] = − 0.059 × pH value E2 [V] = 0.7−0.059 × pH value   The water treatment system of Claim 1 provided with the acid addition apparatus which adjusts pH value to 6 or less by adding an acid to groundwater.   The water treatment system of Claim 2 provided with the water softening apparatus which processes groundwater with a cation exchanger in the back | latter stage of the said reduction | restoration processing apparatus and the said acid addition apparatus.   The water treatment system of Claim 2 provided with the dispersing agent addition apparatus which adds a scale dispersing agent to groundwater in the back | latter stage of the said reduction processing apparatus and the said acid addition apparatus.   The water treatment system according to any one of claims 1 to 4, wherein the reduction treatment device is a reducing agent addition device that adds a reducing agent to groundwater.   The reduction treatment apparatus is a membrane-type deoxygenation device that removes dissolved oxygen by passing groundwater through a gas separation membrane, a decompression-type deoxygenation device that depressurizes groundwater and removes dissolved oxygen, or nitrogen gas is blown into groundwater. The water treatment system according to any one of claims 1 to 4, wherein the water treatment system is any one of a nitrogen substitution type deoxygenation device for removing dissolved oxygen.

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