JPWO2013105421A1 - Reverse osmosis processing method - Google Patents

Abstract

Provided is a reverse osmosis treatment method capable of preventing deterioration of an RO membrane due to heavy metals in an iron-based inorganic flocculant. In a reverse osmosis treatment method in which an iron-based inorganic flocculant is added to the water to be treated and solid-liquid separation is performed by flotation separation, two-layer filtration, etc., and then treated with a reverse osmosis device, Add inhibitor and scale dispersant. The chelate scale inhibitor is preferably ethylenediaminetetraacetic acid or nitrilotriacetic acid.

Description

  The present invention relates to a reverse osmosis treatment method, and more particularly to a method of reverse osmosis treatment after adding an iron-based inorganic flocculant to water to be treated and solid-liquid separation.

  Patent Document 1 discloses a method of performing membrane separation treatment with a reverse osmosis membrane device (hereinafter sometimes referred to as RO device) after adding ferric chloride to water to be treated, separating by pressure floating and sand filtering. It is well-known as described in 2 etc. In the RO treatment, a scale dispersant is also added to the RO water supply (Patent Documents 3 and 4).

  Patent Document 5, paragraph 0003 describes that the flocculant made of iron chloride contains Mn (manganese), and that 38% concentration of ferric chloride solution contains 400 to 1000 mg / L of manganese. Has been.

JP2009-240974 JP2008-246386 JP-A-5-269463 JP 10-202066 A JP 2006-342007 A

  In a method of adding an iron-based inorganic flocculant to the water to be treated and separating it into solid and liquid, followed by RO treatment, heavy metals such as Mn in the iron-based inorganic flocculant adhere to the RO membrane surface, and this acts as an oxidation catalyst. , RO membrane may be deteriorated.

  An object of this invention is to provide the reverse osmosis processing method which can prevent degradation of RO membrane by the heavy metal in an iron-type inorganic flocculant.

  The reverse osmosis treatment method of the present invention is a reverse osmosis treatment method in which an iron-based inorganic flocculant is added to water to be treated, solid-liquid separated, and then treated with a reverse osmosis device. A scale inhibitor and a scale dispersant are added.

  The present invention is suitable for application when the total content of Mn, Zn and Ni in the iron-based inorganic flocculant is 0.05% by weight or more.

  In the present invention, an iron-based inorganic flocculant is added to the water to be treated, and the separated water that has been subjected to solid-liquid separation is used as RO water supply. In addition to the scale dispersant, a chelate scale inhibitor is added to the RO water supply. Thereby, the deterioration of the RO membrane due to the heavy metal oxidation catalyst action is prevented.

It is explanatory drawing of the reverse osmosis processing method which concerns on embodiment. 6 is a graph showing the results of Example 1 and Comparative Example 1.

  Hereinafter, the present invention will be described in more detail.

[Treatment water]
Examples of water to be treated include industrial water, river water, lake water, well water, biologically treated water of organic waste water, waste water from various manufacturing processes and cleaning processes, and the like.

[Iron-based inorganic flocculant]
Examples of the iron-based inorganic flocculant include ferric chloride and polyiron sulfate, and particularly ferric chloride having a high heavy metal content. When the present invention is applied when the total content of Mn, Ni and Zn in the iron-based inorganic flocculant is 0.05 wt% or more and 5 wt% or less, for example 0.1 wt% or more and 2 wt% or less It is effective. The amount of iron-based inorganic flocculant added to the water to be treated is preferably determined experimentally by jar test or the like. The amount of the iron-based inorganic flocculant added to the water to be treated is usually about 10 to 400 mg / L, although it varies depending on the quality of the water to be treated.

  When an iron-based inorganic flocculant is added to the water to be treated, it is preferable to add a pH adjuster as necessary to adjust the pH to about 4 to 8, particularly about 5 to 8 for the flocculant treatment. Examples of the pH adjuster include acids such as hydrochloric acid and sulfuric acid, and alkalis such as sodium hydroxide, but are not limited thereto. After adding the iron-based inorganic flocculant, a polymer flocculant such as an anionic polymer flocculant may be added.

[Solid-liquid separation]
As solid-liquid separation after the flocculation treatment, it is desirable to use both floating separation or sedimentation separation and filtration for passing water through the filter medium layer. Sand, anthracite, or the like can be used as the filter medium.

[Chelate scale inhibitor]
As the chelate scale inhibitor, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), or the like is preferably used. These chelate-based scale inhibitors may be used alone or in combination of two or more.

  The addition amount of chelate-based scale inhibitors such as EDTA and NTA is preferably 20 times or more, particularly 30 to 40 times the total equivalent amount of heavy metals of Mn, Zn and Ni in the RO water supply. By adding this chelate scale inhibitor, the chelate scale inhibitor forms a chelate compound with the heavy metal in the RO water supply, solubilizes the heavy metal, so that the heavy metal flows out together with the concentrated water from the RO device, and the heavy metal is RO Adhering to the membrane surface is prevented, and deterioration of the RO membrane due to the catalytic action of heavy metals is prevented.

[Scale dispersant]
Scale dispersants include (meth) acrylic acid polymers and salts thereof, low molecular weight polymers such as maleic acid polymers and salts thereof, ethylenediaminetetramethylenephosphonic acid and salts thereof, hydroxyethylidene diphosphonic acid and salts thereof, nitrilotrimethylene Use phosphonic acid and phosphonate such as phosphonic acid and its salt, phosphonobutanetricarboxylic acid and its salt, hexametaphosphoric acid and its salt, inorganic polyphosphoric acid such as tripolyphosphoric acid and its salt, inorganic polymeric phosphate, etc. be able to. These scale dispersants may be used alone or in combination of two or more.
The addition amount of the scale dispersant is preferably about 1 to 100 mg / L with respect to the solid-liquid separated water which is the water supply of the RO device.

[Example 1]
Simulated waste water (Ca: 100 mg / L, F: 13 mg / L, pH 3) is prepared and introduced into the reaction tank 1 as shown in FIG. 1, and sodium hydroxide is added to adjust the pH to 6-7. While adjusting, ferric chloride was added so that the density | concentration in the reaction tank 1 might be set to 150 mg / L. In this ferric chloride, the Mn content was 1% by weight, the Ni content was 0.05% by weight, and the Zn content was 0.05% by weight. The effluent water from the reaction tank 1 is introduced into the coagulation tank 2 and reacted, and then subjected to pressure levitation treatment in the pressure levitation tank 3, and the treated water is treated with the two-layer filter 4 (filter medium: sand, anthracite). And filtered. 10 mg / L of Wellclin A801 (manufactured by Kurita Kogyo) as a chelate scale inhibitor is added to the filtered water of the filter 4, and 10 mg / L of Clifloat N900 (manufactured by Kurita Kogyo) is added as a scale dispersant, and then the RO device. RO membrane treatment was performed at 5. The RO membrane was Nitto Denko ES-20, and the recovery rate was 85%. FIG. 2 shows changes over time in the desalting rate and the differential pressure of the RO device 5.

[Comparative Example 1]
The treatment was performed under the same conditions as in Example 1 except that the chelate scale inhibitor was not added. FIG. 2 shows changes over time in the desalting rate and the differential pressure of the RO device 5.

  As shown in FIG. 2, according to the present invention, the deterioration of the RO membrane is prevented, and the desalination rate is maintained high over a long period of time.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
In addition, this application is based on the Japanese patent application (Japanese Patent Application No. 2012-003287) for which it applied on January 11, 2012, The whole is used by reference.

Claims (8)

In the reverse osmosis treatment method in which the iron-based inorganic flocculant is added to the water to be treated and separated into solid and liquid, and then treated with a reverse osmosis apparatus,
A reverse osmosis treatment method comprising adding a chelate-based scale inhibitor and a scale dispersant to the water supplied to the reverse osmosis device.   The reverse osmosis treatment method according to claim 1, wherein the chelate scale inhibitor is ethylenediaminetetraacetic acid and / or nitrilotriacetic acid.   3. The reverse osmosis treatment method according to claim 1, wherein the scale dispersant is at least one selected from the group consisting of a (meth) acrylic acid polymer and a salt thereof, and a maleic acid polymer and a salt thereof. .   The reverse osmosis treatment method according to any one of claims 1 to 3, wherein the iron-based inorganic flocculant has a total content of Mn, Zn, and Ni of 0.05% by weight or more.   5. The reverse osmosis treatment method according to claim 1, wherein 10 to 400 mg / L of the iron-based inorganic flocculant is added to the water to be treated.   The reverse osmosis according to any one of claims 1 to 5, wherein the addition amount of the chelate scale inhibitor is 20 times or more the total equivalent weight of heavy metals of Mn, Zn and Ni in the feed water. Processing method.   The reverse osmosis treatment method according to any one of claims 1 to 6, wherein 1 to 200 mg / L of a scale dispersant is added to the water supply.   8. The reverse osmosis treatment method according to any one of claims 1 to 7, wherein an iron-based inorganic flocculant is added to the water to be treated and the mixture is subjected to agglomeration treatment at pH 4 to 8, followed by solid-liquid separation.

Images