JP2009214011A - Water treating method and water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple water treating method and a water treatment apparatus suppressing clogging of a membrane by manganese, when performing membrane-filtering of raw water containing dissolvable manganese. <P>SOLUTION: The water treatment apparatus is provided with a membrane filtration means 12 performing membrane-filtering of the raw water 1 containing the dissolvable manganese, an oxidizing agent adding means 14 adding the oxidizing agent 24 to membrane filtrate 22 by the membrane filtration means 12, and a manganese removing means 16 removing manganese contained in treating water by passing the treating water by the oxidizing agent adding means 14 through a manganese removal device with a manganese removing agent packed therein. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a water treatment method and a water treatment apparatus used in water and sewerage and wastewater treatment facilities, and in particular, a water treatment method and a water treatment apparatus for removing soluble manganese contained in raw water such as river water and groundwater. It is about.

  2. Description of the Related Art Conventionally, in water purification facilities such as water and sewage systems and industrial wastewater treatment plants, a water treatment method or apparatus using membrane filtration that removes contaminants in raw water using a membrane is known (for example, patent literature). 1).

  In such a water treatment apparatus or method using membrane filtration, when raw water is continuously filtered, contaminants in the raw water adhere to and accumulate on the surface of the membrane and inside the micropores, causing clogging. Resistance increases and filtration efficiency decreases. Therefore, conventionally, as a measure to eliminate clogging of the membrane in order to perform membrane filtration stably, physical washing methods such as backwashing by passing water in the direction opposite to the membrane filtration direction, strong acidity, etc. A chemical cleaning method such as chemical cleaning by adding a chemical is used (see, for example, Patent Document 2).

  Moreover, since it is difficult to remove soluble components in raw water only by membrane filtration, various pretreatments and posttreatments for improving water quality have been studied. In particular, manganese is abundantly contained in raw water such as groundwater, river water, or wastewater, so it is difficult to remove by membrane filtration, but oxidized and insolubilized manganese causes clogging. It is also a cause.

  As solutions to the problems related to membrane filtration of raw water containing soluble manganese, for example, proposals shown in Patent Documents 2, 3, and 4 have been made.

  In Patent Document 2, manganese is insolubilized by adding an oxidizing agent to raw water and then removed by membrane filtration. On the other hand, the membrane filtration surface (primary side) is washed with a reducing agent to remove manganese on the membrane filtration surface. A method or apparatus for removing oxide is shown.

  Patent Document 3 discloses a method or apparatus in which raw water is brought into contact with manganese sand to oxidize and precipitate soluble manganese and then remove manganese by membrane filtration. FIG. 6 is a diagram schematically showing the configuration of the method or apparatus disclosed in Patent Document 3. As shown in FIG. 6, raw water 1 containing soluble manganese is fed into manganese gravel contact device 4 by pump 3 after oxidant 2 such as sodium hypochlorite is injected. Manganese gravel contact device 4 is filled with manganese gravel, and after soluble manganese in raw water 1 is oxidized and precipitated, it is sent to membrane filtration device 6 by pump 5, and membrane filtrate 7 is treated water tank. 8 is introduced. A part of the membrane filtrate 7 is sent to the membrane filtration device 6 by a backwash pump 9 and used as backwash water for washing the membrane from the secondary side.

  Patent Document 4 discloses a method or apparatus for performing membrane filtration without adding a reducing agent to raw water to insolubilize manganese.

JP 2007-152163 A JP 2005-74386 A JP 2003-220394 A JP 2001-79367 A

  By the way, the method or apparatus disclosed in Patent Document 2 and Patent Document 3 have the following problems. In other words, since oxidized and insolubilized manganese is removed by membrane filtration, membrane cleaning with a reducing agent for removing manganese adhering to the membrane surface is necessary. In addition, the reducing agent used for removing manganese oxide is not effective for removing other metal components and organic components contained in raw water and for sterilizing the membrane. There is a need to do. In addition, when organic substances are mixed in the raw water, harmful by-products may be generated by adding an oxidizing agent.

  In addition, in the method or apparatus disclosed in Patent Document 2, manganese insolubilization may be insufficient unless an oxidizing agent having strong oxidizing power such as ozone, which has a high processing cost, is added. Moreover, in the control of the ozone oxidation treatment, it is extremely difficult to maintain the contact time and the ozone injection amount without excess or deficiency.

  Further, in the method or apparatus disclosed in Patent Document 3 described above, manganese can be oxidized with a relatively small amount of an oxidizing agent, but manganese gravel is used to pass water without removing impurities in the raw water 1. The filtration resistance in the contact device 4 rises early and a blockage occurs. For this reason, the maintenance frequency for eliminating the blockage increases.

  Further, in the method or apparatus disclosed in Patent Document 4 mentioned above, it is possible to suppress clogging of manganese on the membrane surface by adding a reducing agent to the raw water. However, since other metal components contained in the raw water leak into the treated water, there is a possibility that good treated water quality cannot be obtained. In addition, when an oxidizing agent is added to raw water from which metal components have not been removed and sterilization is performed to prevent biofouling, manganese is precipitated, and in the subsequent filtration step, high-concentration manganese is removed from the membrane filtration water. There is a risk of leakage. Moreover, in order to use as drinking water, chlorine sterilization is required. For this reason, chlorine will be added to the membrane filtration water containing a reducing agent, and the usage-amount of a chemical | medical agent will increase. Furthermore, the addition of chlorine may cause manganese to precipitate and contaminate the piping.

  This invention is made | formed in view of the said situation, and it aims at providing the simple water treatment method and water treatment apparatus which suppress the film | membrane clogging by manganese.

  In order to achieve the above object, a water treatment method according to claim 1 of the present invention includes a membrane filtration step for membrane filtration of raw water containing soluble manganese, and an oxidant added to the membrane filtration water by the membrane filtration step An oxidizing agent adding step, and a manganese removing step of removing manganese contained in the treated water by passing the treated water from the oxidizing agent adding step through a manganese removing device filled with a manganese removing agent. Features.

  The water treatment method according to claim 2 of the present invention is the above-described membrane filtration step according to claim 1, wherein the membrane filtration step uses membrane filtration of treated water that has undergone a step of adding and mixing a flocculant to raw water containing soluble manganese. It is characterized by doing.

  Further, the water treatment method according to claim 3 of the present invention is the membrane cleaning step of cleaning the membrane used in the membrane filtration step using the treated water from the manganese removing device in the above-described claim 1 or claim 2. Is further included.

  The water treatment method according to claim 4 of the present invention is characterized in that, in any one of claims 1 to 3 described above, the manganese removing agent is manganese sand.

  Moreover, the water treatment apparatus according to claim 5 of the present invention is a membrane filtration means for membrane filtering raw water containing soluble manganese, an oxidant addition means for adding an oxidant to the membrane filtered water by the membrane filtration means, It has a manganese removing means for removing manganese contained in the treated water by passing the treated water by the oxidizing agent adding means through a manganese removing device filled with a manganese removing agent.

  In the water treatment apparatus according to claim 6 of the present invention, in the above-described claim 5, the membrane filtration means performs membrane filtration on treated water obtained by adding and mixing a flocculant to raw water containing soluble manganese. Features.

  Moreover, the water treatment apparatus according to claim 7 of the present invention is the membrane cleaning means for cleaning the membrane used in the membrane filtration means using the treated water from the manganese removal apparatus according to claim 5 or claim 6 described above. Is further provided.

  Moreover, the water treatment apparatus according to claim 8 of the present invention is characterized in that in any one of claims 5 to 7 described above, the manganese removing agent is manganese sand.

  According to the present invention, since membrane filtration is performed without oxidizing and precipitating soluble manganese in raw water, membrane clogging due to manganese can be suppressed.

  Hereinafter, preferred embodiments (Examples 1 to 3) of a water treatment method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a system diagram showing a schematic configuration according to a first embodiment of a water treatment apparatus 100 of the present invention.

Example 1
As shown in FIG. 1, a water treatment apparatus 100 according to the present invention includes a membrane module 12 as membrane filtration means, an oxidant injection facility 14 as oxidizer addition means, and a manganese removal facility 16 as manganese removal means. , A treated water tank 18 and a backwash pump 20 as a membrane cleaning means. The manganese removal equipment 16 has a manganese sand layer (not shown) filled with manganese sand as a manganese removal agent. In the present invention, membrane filtration is performed as the first stage, and filtration with manganese sand is performed at the second stage.

  First, raw water 1 taken from a water source such as river water or groundwater is pumped up by a supply pump 3 and passed to a membrane module 12. Here, the raw water 1 contains soluble manganese. Thus, in this invention, since membrane filtration is performed without adding an oxidizing agent to the raw water 1, the soluble manganese in the raw water 1 passes through the membrane module 12 without being oxidized. Then, SS and fine particles in the raw water 1 are removed from the membrane. For this reason, the clogging of the filtration membrane due to adhesion of SS and fine particles can be easily eliminated by washing with a normal chemical solution such as acid or sulfuric acid.

  And the sodium hypochlorite 24 as an oxidizing agent is added from the oxidizing agent injection equipment 14 to the membrane filtrate 22 obtained by passing through the membrane module 12. The membrane filtered water 22 to which the oxidizing agent has been added is passed through the manganese sand layer of the manganese removal facility 16 by the supply pump 5, and the precipitated manganese oxide is removed from the raw water by contacting the manganese sand. By doing so, clogging due to SS and turbidity substances does not occur in the manganese sand layer of the manganese removal equipment 16. Therefore, the water passing performance in the manganese sand layer is improved. The filtered water 26 that has passed through the manganese sand layer is stored in the treated water tank 18 and supplied to the customer as treated water 28, while the filtered water 26 is guided to the membrane module 12 by the backwash pump 20. The membrane can be backwashed. In this case, since this filtered water 26 contains almost no manganese, there is no fear that manganese is deposited on the secondary side of the membrane module 12.

(Example 2)
Next, Example 2 will be described. FIG. 2 is a system diagram showing a schematic configuration according to the second embodiment of the water treatment apparatus 200 of the present invention.

  As shown in FIG. 2, the water treatment apparatus 200 according to the present invention includes a membrane module 12 as membrane filtration means, a membrane treatment water tank 30, an oxidant injection facility 14 as oxidant addition means, and manganese removal means. The manganese removal equipment 16, the treated water tank 18, and a backwash pump 20 as a membrane cleaning means are configured. In this configuration, raw water 1 taken from a water source such as river water or ground water is passed to the membrane module 12 by the supply pump 3. The obtained membrane filtered water 22 is stored in the membrane treated water tank 30. The membrane filtrate 22 in the membrane treatment water tank 30 is pumped up by the supply pump 32 and is introduced into the manganese removal facility 16 after the oxidant is injected from the oxidant injection facility 14. Here, as the oxidizing agent, sodium hypochlorite, chlorine dioxide, ozone, or the like can be used. In this case, when the treated water 28 is used as drinking water, it is convenient if sodium hypochlorite is used.

  The treated water 26 treated by the manganese removal facility 16 is stored in the treated water tank 18 and supplied to the customer as treated water 28. Further, a part of the treated water 26 stored in the treated water tank 18 is passed through the membrane module 12 by the backwash pump 20 and used for backwashing of the membrane.

  In this case, instead of periodic physical cleaning by backflow cleaning, chemical cleaning may be performed by injecting and adding chemicals from the membrane cleaning chemical injection facility 34 to the treated water 26 as film cleaning water. These cleaning methods may be used in combination. As this chemical, sulfuric acid or sodium hypochlorite can be used. Here, in the embodiment of the present invention, since the treated water 26 from which manganese has been removed is used for cleaning, chemical cleaning with an oxidizing agent that also serves as a disinfectant is possible. In this case, for example, the oxidant may be injected and added from the cleaning oxidant injection facility 14 a connected to the treated water 26 with the oxidant injection facility 14.

  Next, the effect by the water treatment apparatus 200 of this invention is demonstrated using FIG. FIG. 3 is a schematic diagram showing the change over time in the transmembrane pressure difference in membrane filtration, and compares the method using the water treatment apparatus 200 of the present invention with the conventional method. The horizontal axis represents the membrane operation time, and the vertical axis represents the transmembrane pressure difference. As shown in FIG. 3, in the water treatment apparatus 200 of the present invention, the value of the transmembrane pressure difference is maintained at a substantially constant value even when the membrane filtration operation time has elapsed, and is stable without using a reducing agent. It can be seen that the membrane filtration operation is possible. In contrast, in the conventional method in which an oxidant is added before membrane filtration, the transmembrane pressure difference increases with the passage of operating time, and the filtration resistance tends to increase with time. Recognize.

(Example 3)
Next, Example 3 will be described. FIG. 4 is a system diagram showing a schematic configuration according to the third embodiment of the water treatment apparatus 300 of the present invention. As shown in FIG. 4, the water treatment apparatus 300 is configured to inject a flocculant as a pretreatment for membrane filtration. In addition, since the structure of the downstream from the membrane module 12 is the same as that of the water treatment apparatus 200 of Example 2, it shall represent with the same code | symbol given to the same component, and detailed description is abbreviate | omitted.

  The water treatment apparatus 300 includes a flocculant injection facility 36 that adds a flocculant to raw water 1 taken from a water source such as river water, and a stirring mechanism 38 that stirs the raw water 1 and the flocculant. The raw water 1 added with the flocculant from the flocculant injection facility 36 and stirred by the stirring mechanism 38 is passed through the membrane module 12 by the supply pump 3. In the case of raw water containing organic matter such as river water, it is desirable to perform membrane filtration after such a coagulation operation.

  Next, the effect by the water treatment apparatus 300 of this invention is demonstrated using FIG. FIG. 5: has shown the schematic diagram which compared the process 1 by the water treatment apparatus 300 of this invention, and the conventional process 2. As shown in FIG. As shown in FIG. 5, in each of the steps 1 and 2, a flocculant is added to the raw water 1, and the water subjected to the agglomeration treatment is subjected to membrane treatment. In step 1, the raw water 1 to which the flocculant has been added is subjected to membrane filtration, chlorine is then added, and then the manganese removal facility 16 performs manganese removal. On the other hand, in step 2, chlorine is added before membrane filtration of the raw water 1 to which the flocculant is added, and manganese is removed only by membrane filtration. In addition, the chlorine concentration added in each process 1 and 2 is added so that it may become 0.5 mg / L as residual chlorine.

  In step 1 performed by the water treatment apparatus 300 of the present invention, manganese was sufficiently oxidized by manganese sand, so the manganese concentration in the treated water that passed through the manganese removal equipment 16 was below the limit of quantification. Thus, in Step 1, the water quality that was a problem when removing manganese by membrane filtration was satisfied.

  Table 1 shows the water quality data of chemical wastewater when the membrane in step 2 is chemically cleaned. Here, as cleaning chemicals, sodium bisulfite 0.1%, sulfuric acid (pH 2.5), and sodium hypochlorite 10 mg / L were used, and the contact times were all 20 minutes.

  According to Table 1, sodium bisulfite used as a reducing agent is effective for removing manganese, but is not effective for removing other metal components (aluminum, iron). . On the other hand, sulfuric acid is effective for removing metal components other than manganese and TOC (organic component), and sodium hypochlorite generally used for suppressing biofilm formation of the membrane was effective for removing aluminum and TOC. . From these facts, it is understood that sodium bisulfite is effective for removing manganese, but is not effective for other clogging components, and other chemicals are necessary for stable operation of the membrane.

  As mentioned above, although embodiment (Examples 1-3) of this invention has been demonstrated, according to the water treatment method and water treatment apparatus of this invention, when filtering the raw | natural water containing soluble manganese, it depends on manganese. While the membrane can be filtered without clogging the membrane, the operation related to the membrane cleaning can be simplified. Further, as a post-treatment of membrane filtration, contact with manganese sand can be performed to remove manganese in raw water. In this case, the quality of the treated water can be improved by performing sufficient manganese oxidation treatment. Furthermore, it is not necessary to use a reducing agent in the cleaning and sterilization of the membrane, and water from which the metal component has been removed can be used as cleaning water.

  When a large amount of soluble organic matter is contained in the raw water, impurities in the raw water can be removed by performing membrane filtration after adding and mixing the flocculant as in Example 3 above. . And the production | generation of the by-product by an oxidizing agent can be suppressed by adding an oxidizing agent after the process. Moreover, according to the water treatment method and the water treatment apparatus of the present invention, filtration clogging due to the accumulation of organic substances in the manganese sand layer can be suppressed, and therefore, it can be applied to raw water of various water quality.

It is a systematic diagram which shows schematic structure by Example 1 to this invention. It is a systematic diagram which shows schematic structure by Example 2 of this invention. It is the schematic which showed the time-dependent change of transmembrane pressure difference, and is the figure which compared the method of this invention, and the conventional method. It is a systematic diagram which shows schematic structure by Example 3 of this invention. It is the schematic diagram which compared the process 1 of this invention, and the conventional process 2. FIG. It is a systematic diagram of the schematic structure of the conventional water treatment apparatus or method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water 3, 5, 32 Supply pump 12 Membrane module 14 Oxidant injection equipment 16 Manganese removal equipment 18 Treatment water tank 20 Backwash pump 30 Membrane treatment water tank 34 Membrane cleaning chemical injection equipment 36 Coagulant injection equipment 38 Stirring mechanism 100,200 , 300 Water treatment equipment

Claims (8)

A membrane filtration step for membrane filtration of raw water containing soluble manganese;
An oxidant addition step of adding an oxidant to the membrane filtrate by the membrane filtration step;
And a manganese removal step of removing manganese contained in the treated water by passing the treated water from the oxidizing agent adding step through a manganese removing device filled with a manganese removing agent.   The water treatment method according to claim 1, wherein the membrane filtration step performs membrane filtration of treated water that has undergone the step of adding and mixing a flocculant to raw water containing soluble manganese.   The water treatment method according to claim 1 or 2, further comprising a membrane cleaning step of cleaning a membrane used in the membrane filtration step using treated water from the manganese removing apparatus.   The water treatment method according to any one of claims 1 to 3, wherein the manganese removing agent is manganese sand. Membrane filtration means for membrane filtration of raw water containing soluble manganese;
An oxidizing agent adding means for adding an oxidizing agent to the membrane filtered water by the membrane filtering means;
A water treatment apparatus comprising: manganese removal means for removing manganese contained in the treated water by passing the treated water from the oxidant addition means through a manganese removal apparatus filled with a manganese removal agent.   The said membrane filtration means membrane-filters the treated water which added and mixed the flocculant with the raw | natural water containing soluble manganese, The water treatment apparatus of Claim 5 characterized by the above-mentioned.   The water treatment apparatus according to claim 5 or 6, further comprising a membrane cleaning means for cleaning a membrane used for the membrane filtration means using treated water from the manganese removing apparatus.   The water treatment apparatus according to any one of claims 5 to 7, wherein the manganese removing agent is manganese sand.

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