JP2019188338A - Water treatment method and water treatment apparatus - Google Patents

Abstract

To perform stable and efficient water treatment by preventing coagulation treatment means and a membrane separation apparatus from being tainted and further preventing a subsequent-stage apparatus that receives water subjected to membrane separation from being tainted, in water treatment in which water to be treated such as industrial water, city water, river water, lake water, well water, industrial exhaust water and biologically treated water is subjected to coagulation treatment and the water subjected to coagulation treatment is directly subjected to membrane separation.SOLUTION: Water to be treated is subjected to coagulation treatment by adding a cationic polymer with water solubility of mass average molecular weight of 100 thousand-8 million which has, at a polymer side chain, functional groups selected from a primary amino group, a secondary amino group and a tertiary amino group as well as acid-bases of the amino groups and a quaternary ammonium base and does not have a hydrophobic group, and then water subjected to coagulation treatment is directly subjected to membrane separation, with a separation membrane with a hole diameter of 0.2 μm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment method in which water to be treated such as industrial water, city water, river water, lake water, well water, industrial waste water, biological treatment water is subjected to agglomeration treatment to directly subject the agglomerated treated water to membrane separation. More particularly, the present invention relates to a water treatment method and a water treatment apparatus for preventing contamination of a downstream apparatus that receives membrane separation water and performing stable and efficient treatment.

  Methods for treating treated water such as industrial water, city water, river water, lake water, well water, industrial wastewater, biologically treated water include ferric chloride, polyferric sulfate, ferrous sulfate, poly A general method is to obtain clarified water using a solid-liquid separation device such as a precipitation device or a flotation device after performing a flocculation treatment with an inorganic flocculant such as aluminum chloride or aluminum sulfate. In addition to coagulation with an inorganic coagulant, humic acids such as humic acid and fulvic acid in raw water, biological metabolites, surfactants, turbidity, etc. are coagulated with a polymer, and adsorbed to fine particles. Processing may be used in combination. The treatment with these high molecular polymers and particles may be carried out independently, but is generally used in combination with the agglomeration treatment with an inorganic flocculant for the purpose of reducing the amount of the inorganic flocculant used.

  However, when a polymer is used, there is a problem that the polymer itself contaminates the solid-liquid separator.

  Patent Document 1 discloses a technique in which an inorganic flocculant and a polymer flocculant are added and subjected to agglomeration treatment, and then added again before solid-liquid separation. There is a problem that the number of additions is large, the apparatus is complicated, and the operation becomes complicated.

  Patent Document 2 discloses a technique of performing membrane separation after an adsorption treatment using particles made of a cationic polymer that does not dissolve in water as an adsorbent that adsorbs organic substances in the water to be treated. However, in this method, there is a problem that the apparatus (aggregation tank) is contaminated by particles that have not been adsorbed with organic matter or turbidity in the water to be treated, and the aggregated floc containing particles becomes coarse, so it accumulates in the membrane separation apparatus. There is a problem of causing turbid contamination in the membrane separation device.

  As a means for avoiding contamination in the flocculation tank, Patent Document 3 discloses a method of adding an inorganic flocculant prior to the addition of particles made of a cationic polymer that does not dissolve in water. The problem of turbid contamination in the equipment remains.

  In Patent Literature 4, a water-soluble polymer having a melamine ammonium group is used in a treatment for adding salt iron and a water-soluble polymer in a biological treatment tank to cause aggregation and aggregating the agglomerated treated water into a membrane. Although described, the SS concentration in the biological treatment tank to which it is added greatly deviates from the SS concentration range of the water to be treated which is the subject of the present invention, and is different from the present invention in the technical field. .

  Patent Document 5 describes a treatment in which a cationic polymer having a hydrophobic group is added to water to be treated for membrane separation. However, since a cationic polymer having a hydrophobic group is strongly bonded to a reverse osmosis (RO) membrane material by a hydrophobic bond, it is difficult to remove it by washing under alkaline conditions, which is a general RO membrane washing method. Cationic polymers containing hydrophobic groups tend to be adsorbed on materials commonly used for separation membranes such as polyvinylidene fluoride and polyacrylonitrile, and when unreacted polymers leak through the aggregation process and leak into the separation membrane. May significantly contaminate the separation membrane.

  Conventionally, among the compounds exemplified as many of the cationic polymers used for the aggregation treatment, a cationic polymer having a primary amino group, a secondary amino group, a tertiary amino group and their acid base, quaternary ammonium base, in particular There is a copolymer having a dimethylaminoethyl acrylate quaternized product, and it has been conventionally known that agglomeration treatment with such a cationic polymer is carried out. Membrane separation is not performed. In addition, the cationic polymer is not selected from the viewpoint of the stability of a membrane separation device for direct membrane separation and a subsequent RO membrane separation device.

Japanese Patent Laid-Open No. 11-77062 JP 2009-56454 A JP 2009-240974 A JP 2009-226373 A JP 2009-101260 A

  The present invention has been made in view of the above-described prior art, and agglomeration treatment is performed by subjecting water to be treated such as industrial water, city water, river water, lake water, well water, industrial wastewater, biological treatment water, and the like. A water treatment method and a water treatment apparatus for performing stable and efficient treatment by preventing the contamination of a coagulation treatment means, a membrane separation apparatus, and a subsequent apparatus for receiving the membrane separation water in water treatment for direct membrane separation of water. The purpose is to provide.

As a result of repeated studies to solve the above-mentioned problems, the present inventor has a specific cationic functional group in the polymer side chain as a flocculant and a water-soluble cationic polymer having a specific molecular weight and no hydrophobic group. It has been found that the above-mentioned problems can be solved by using.
That is, the gist of the present invention is as follows.

[1] A primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, and no hydrophobic group. A water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million is added to the water to be treated and agglomerated, and then the agglomerated water is directly subjected to membrane separation with a separation membrane having a pore size of 0.2 μm or less. Water treatment method.

[2] A primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, and no hydrophobic group. A water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million is added to the water to be treated and subjected to agglomeration, and then the agglomerated water is directly subjected to membrane separation, and the separated water is subjected to a reverse osmosis membrane treatment. Water treatment method.

[3] A primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, and no hydrophobic group. After adding a water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million to the water to be treated and aggregating it, the agglomerated water is directly separated by a separation membrane having a pore size of 0.2 μm or less, and the separated water is reversed. A water treatment method characterized by performing osmosis membrane treatment.

[4] The water to be treated has industrial water, city water, river water, lake water, well water, turbidity concentration of less than 200 mg / L, and dissolved organic matter concentration of 0.01 mg / L or more and less than 200 mg / L, The water treatment method according to any one of [1] to [3], which is wastewater or biologically treated water.

[5] The water treatment method according to any one of [1] to [4], wherein the cationic polymer is a copolymer having a structural unit derived from dimethylaminoethyl acrylate quaternized product.

[6] The cationic polymer contains 20 to 50 mol% of a structural unit derived from dimethylaminoethyl acrylate quaternized product, and has an intrinsic viscosity of 0.5 to 5.5 dL / g. The water treatment method according to [5].

[7] The water treatment method according to any one of [1] to [6], in which the cationic polymer and an inorganic flocculant are added to the water to be treated to perform an agglomeration treatment.

[8] The required amount of the cationic polymer necessary for neutralizing the charge of the water to be treated is determined as the cation consumption A by titrating the water to be treated with the cationic polymer by the streaming potential method. In the flocculation treatment, when the cationic polymer is added to the water to be treated and no inorganic flocculant is added, the cation consumption A and the addition concentration of the cationic polymer satisfy the following relational formula (Ia): In addition, when the addition amount of the cationic polymer is controlled and the cationic polymer and the inorganic flocculant are added to the water to be treated in the flocculation treatment, the cation consumption A, the inorganic flocculant and the cationic flocculant [1] to [7], wherein the addition amount of the cationic polymer and the addition amount of the inorganic flocculant are controlled such that the addition concentration of the polymer satisfies the following relational expression (Ib): Water treatment method.
Cation consumption A × α = cationic polymer addition concentration (mg / L) (Ia)
Cation consumption A × α =
Cationic polymer addition concentration (mg / L) + Inorganic flocculant addition concentration (mg / L) × β
... (Ib)
α: Safety factor taking into account fluctuations in water quality β: Factor for converting the cation amount of the inorganic flocculant into the cation amount of the cationic polymer

[9] A primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, and no hydrophobic group. Aggregation treatment means for adding a water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million to the water to be treated for aggregation treatment, and the aggregation treatment water of the aggregation treatment means is directly applied to a separation membrane having a pore size of 0.2 μm or less. A water treatment device comprising a membrane separation device for membrane separation.

[10] A primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, and no hydrophobic group. A coagulation treatment means for adding a water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million to the water to be treated for coagulation treatment, a membrane separation apparatus for directly performing membrane separation of the coagulation treatment water of the coagulation treatment means, A water treatment device comprising a reverse osmosis membrane separation device for treating the separated water of a membrane separation device with a reverse osmosis membrane.

[11] A functional group selected from a primary amino group, a secondary amino group, a tertiary amino group, and an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, and no hydrophobic group. Aggregation treatment means for adding a water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million to the water to be treated for aggregation treatment, and the aggregation treatment water of the aggregation treatment means is directly applied to a separation membrane having a pore size of 0.2 μm or less. A water treatment device comprising: a membrane separation device for membrane separation; and a reverse osmosis membrane separation device for treating a separation water of the membrane separation device with a reverse osmosis membrane.

[12] The water to be treated is industrial water, city water, river water, lake water, well water, having a turbidity concentration of less than 200 mg / L and a dissolved organic matter concentration of 0.01 mg / L or more and less than 200 mg / L, The water treatment apparatus according to any one of [9] to [11], which is wastewater or biologically treated water.

[13] The water treatment apparatus according to any one of [9] to [12], wherein the cationic polymer is a copolymer having a structural unit derived from dimethylaminoethyl acrylate quaternized product.

[14] The cationic polymer contains 20 to 50 mol% of a structural unit derived from dimethylaminoethyl acrylate quaternized product, and has an intrinsic viscosity of 0.5 to 5.5 dL / g. The water treatment device according to [13].

[15] The water treatment apparatus according to any one of [9] to [14], wherein the aggregation treatment unit performs the aggregation treatment by adding the cationic polymer and the inorganic flocculant to the water to be treated.

[16] When the cationic polymer is added to the water to be treated by the aggregating treatment means and the inorganic flocculant is not added, the water to be treated is titrated with the cationic polymer by a streaming potential method. The necessary amount of the cationic polymer necessary for neutralizing the charge of the water to be treated is defined as cation consumption A, and the cationic polymer is added so that the concentration of the cationic polymer satisfies the following relational formula (Ia): In the case where the cationic polymer and the inorganic flocculant are added to the water to be treated by the aggregating treatment means, the cation consumption A, the inorganic flocculant and the concentration of the cationic polymer added The water according to any one of [9] to [15], further comprising control means for controlling the addition amount of the cationic polymer and the addition amount of the inorganic flocculant so that the above satisfies the following relational formula (Ib): Processing equipment.
Cation consumption A × α = cationic polymer addition concentration (mg / L) (Ia)
Cation consumption A × α =
Cationic polymer addition concentration (mg / L) + Inorganic flocculant addition concentration (mg / L) × β
... (Ib)
α: Safety factor taking into account fluctuations in water quality β: Factor for converting the cation amount of the inorganic flocculant into the cation amount of the cationic polymer

  According to the present invention, in water treatment in which water to be treated such as industrial water, city water, river water, lake water, well water, industrial wastewater, biologically treated water is subjected to agglomeration treatment, and the agglomerated treated water is directly subjected to membrane separation, By using a specific cationic polymer as the agent, it is possible to prevent the contamination of the coagulation treatment means, the membrane separation device, and the subsequent device that receives the membrane separation water, and perform a stable and efficient treatment.

It is a block diagram which shows the external pressure type | mold mini-module test apparatus used in the Example. 10 is a graph showing the results of Experimental Example IV. It is a block diagram which shows the RO membrane module test apparatus used in Experimental example V.

  Hereinafter, embodiments of a water treatment method and a water treatment apparatus of the present invention will be described in detail.

  The water treatment method of the present invention has a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid group and a quaternary ammonium group of these amino groups in the polymer side chain, and a hydrophobic group. The water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million is added to the water to be treated and subjected to agglomeration treatment, and then the agglomerated water is directly subjected to membrane separation.

  The water treatment apparatus of the present invention has a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, and a hydrophobic group. A coagulation treatment means for adding a water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million to the water to be treated and a membrane for directly separating the coagulation treated water of the coagulation treatment means And a separation device.

In the following, as used in the present invention, “a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain, The water-soluble cationic polymer having a weight average molecular weight of 100,000 to 8 million and having no hydrophobic group is sometimes referred to as “cationic polymer of the present invention”.
In addition, “a primary amino group, secondary amino group, tertiary amino group, and a functional group selected from acid bases and quaternary ammonium bases of these amino groups” may be referred to as “specific cation groups”.
In addition, “structural units derived from dimethylaminoethyl acrylate / methyl chloride quaternary salt”, “structural units derived from dimethylaminoethyl methacrylate / methyl chloride quaternary salt” and “dimethylaminoethyl methacrylate / benzyl chloride quaternary salt” The “derived structural unit” is referred to as “DAA monomer unit or DAA”, “DAM monomer unit or DAM” and “DAM (Bzl) monomer unit or DAM (Bzl)”, respectively, and occupies all the structural units in the cationic polymer. The “ratio of DAA monomer units” and “ratio of DAM monomer units in all constituent units in the cationic polymer” may be referred to as “DAA monomer unit amount” and “DAM monomer unit amount”, respectively.

[mechanism]
According to the present invention, water to be treated such as industrial water, city water, river water, lake water, well water, industrial wastewater, biologically treated water is agglomerated by the following effects of the cationic polymer of the present invention. In the water treatment in which the flocculated water is directly subjected to membrane separation, it is possible to prevent the contamination of the flocculation means, the membrane separation apparatus, and the subsequent apparatus that receives the membrane separation water, and perform stable and efficient treatment.

In a membrane separation device (turbidity membrane device) such as an ultrafiltration (UF) membrane separation device or a microfiltration (MF) membrane separation device for the purpose of turbidity, dirt is attached to the separation membrane, usually 30 seconds. Physical cleaning of the membrane is performed by supplying cleaning fluid (water and / or gas) intermittently every 60 minutes.
As a pretreatment of such a membrane separator, when the water-soluble cationic polymer of the present invention having a specific cationic group in the polymer side chain is added to the water to be treated, the cationic polymer of the present invention is in the water to be treated. Since it binds to membrane contaminants having anion charge such as humic acid, fulvic acid, SS, etc., and coagulates to a size that can be sufficiently removed by the separation membrane, this is directly applied to the membrane after the aggregation treatment with the cationic polymer of the present invention. Membrane separation can be performed with a separation device. Further, when the inorganic flocculant and the cationic polymer of the present invention are used in combination, it is possible to suppress the clogging of the separation membrane as compared with the case of the inorganic flocculant alone aggregation. In addition, since the cationic polymer can be combined with a fine inorganic flocculant colloid to form a floc, when used in combination with the inorganic flocculant, the amount of the inorganic flocculant used and thus the amount of sludge generated can be reduced. It is possible to prevent subsequent contamination of the advanced processing apparatus due to leakage of the coagulant colloid to the subsequent stage of the membrane separation apparatus.

A small cationic polymer is likely to pass through the separation membrane, and thus becomes a source of contamination of the subsequent apparatus, and has a low coagulation force to humic acid, fulvic acid, SS, etc. in the water to be treated. Furthermore, since fine flocs are formed, internal contamination of the separation membrane may occur. On the other hand, an excessively large cationic polymer causes turbid contamination of the separation membrane due to coarse flocs, and deteriorates handling properties due to increased viscosity of the chemical solution. Further, if the pore size of the separation membrane is large, the cationic polymer tends to pass through the separation membrane and cause contamination in the subsequent apparatus, and flocs enter the inside of the membrane, resulting in in-membrane contamination that is difficult to remove by physical cleaning.
Since the cationic polymer of the present invention has an appropriate size such as a mass average molecular weight of 100,000 to 8 million, it does not cause the above-mentioned problems. By performing membrane separation with a separation membrane having a pore size of 0.2 μm or less and a small pore size, it is possible to prevent leakage of the cationic polymer to the subsequent apparatus.

  In the cationic polymer having a specific cationic group, if the colloidal equivalent and the mass average molecular weight are the same, the cationic polymer having the specific cationic group in the polymer side chain is more cationic than the cationic polymer having the specific cationic group in the polymer main chain. The coagulation ability is higher than that of the conductive polymer. This action is thought to be due to the way in which the specific cationic group spreads within the cationic polymer. If the side chain has a length of at least 1 to 3 carbon atoms, the structure having the specific cationic group in the polymer side chain However, a higher agglomeration effect can be obtained than a cationic polymer having a specific cationic group in the polymer main chain.

  In addition, if the cationic polymer has a hydrophobic site such as a benzene ring or a hydrophobic functional group of a long-chain alkyl group or a surfactant, it will cause general organic contamination when the RO membrane in the latter stage is blocked. Although it is difficult to remove by alkaline washing which is a washing method, the cationic polymer of the present invention does not have such a hydrophobic group. Can be easily removed from the film surface. Furthermore, when the unreacted cationic polymer passes through the agglomeration step and reaches the separation membrane, the cationic polymer of the present invention having no hydrophobic group can be peeled off from the membrane surface relatively easily. Risk is low.

  Furthermore, as a result of evaluation of the structure and aggregation of the cationic polymer by the present inventor based on how the specific cationic group spreads, it was found that the cationic polymer having a DAA monomer unit amount of 20 to 50 mol% exhibits the highest aggregation ability. did. In addition, the cationic polymer of the present invention having DAA monomer units at this ratio also has the advantage that it is less likely to be adsorbed on the separation membrane and less likely to contaminate the separation membrane than the other cationic polymers of the present invention.

[Treatment water]
Although there is no restriction | limiting in particular as to-be-processed water processed by this invention, In this invention, suspended matter (SS) density | concentration is less than 200 mg / L, for example, 10-100 mg / L, and dissolved organic matter density | concentration is 0.01 mg / L or more. Effectively applied to industrial water, city water, river water, lake water, well water, waste water, or biologically treated water of less than 200 mg / L, preferably 1 to 30 mg / L.

  In addition, the biologically treated water as the water to be treated is the primary treated water separated from the supernatant of the biological treatment tank or the carrier-containing sludge containing living organisms by a screen or precipitation treatment.

[Cationic Polymer of the Present Invention]
The cationic polymer of the present invention has a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid group and a quaternary ammonium group of these amino groups in the polymer side chain, and a hydrophobic group. It is a water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million.

  That is, as explained in the above-mentioned mechanism section, those having a specific cation group in the polymer side chain are used from the viewpoint of aggregation, and mass average molecular weight is 100,000 to 800 from the viewpoint of contamination and handling properties of the separation membrane. Use a water-soluble cationic polymer that does not have a hydrophobic group. The mass average molecular weight of the cationic polymer of the present invention is preferably 200,000 to 5,000,000, and more preferably 200,000 to 1,000,000.

The weight average molecular weight of the cationic polymer refers to the value of the weight average molecular weight measured by a chromatography method (GPC method).
In addition, the “cationic polymer” indicates a positive colloidal equivalent, and the colloidal equivalent of the cationic polymer of the present invention is preferably 1.0 to 6.0 meq / g.
Here, the colloidal equivalent is a value obtained by titration with 1 / 400N PVSK (potassium polyvinyl sulfate) and measured by the streaming potential method.
The term “water-soluble” means that the solubility in water is 1 g or more / 100 g of water (20 ° C.).

In addition, the cationic polymer of the present invention preferably has an intrinsic viscosity of 0.5 to 5.5 dL / g. If the intrinsic viscosity is less than 0.5 dL / g, the molecular weight is too small, so that the unreacted polymer may pass through the separation membrane and contaminate the subsequent apparatus, and the coagulation ability may be further reduced. When the intrinsic viscosity exceeds 5.5 dL / g, the viscosity increases and handling becomes difficult.
Here, the intrinsic viscosity of the cationic polymer is a value measured at 30 ° C. with an Ubbelohde viscometer or the like using a 1N sodium nitrate aqueous solution as a solvent.

The cationic polymer is not particularly limited as long as it satisfies the above-mentioned preferred physical properties, but a copolymer of a cationic monomer and a nonionic monomer such as acrylamide can be preferably used. As specific examples of the cationic monomer, dimethylaminoethyl acrylate or dimethylaminoethyl methacrylate acid salt or quaternary ammonium salt thereof, dimethylaminopropyl acryamide or dimethylaminopropyl methacrylate acid acid salt or quaternary ammonium salt are suitable. However, the present invention is not limited to this. As the quaternary ammonium salt, a quaternary ammonium salt such as methyl chloride or ethyl chloride can be used.
These cationic polymers may be used individually by 1 type, and 2 or more types may be mixed and used for them.
As described above, the cationic polymer of the present invention preferably has a DAA monomer unit from the viewpoint of cohesion, and particularly preferably has a DAA monomer unit amount of 20 to 50 mol%.

  The amount of the cationic polymer added to the water to be treated varies depending on the quality of the water to be treated, the kind of the cationic polymer to be used, whether or not the inorganic flocculant is used in combination, and the amount of the active ingredient is 0.1 to 5 mg / L. It is preferable to make the range.

[Inorganic flocculant]
In the present invention, an aggregating treatment may be performed by adding an inorganic flocculant together with the cationic polymer of the present invention. In this case, as the inorganic flocculant added to the water to be treated, it is preferable to use an iron-based or aluminum-based inorganic flocculant capable of forming flocs in a wide pH range. Examples of the iron-based inorganic flocculant include ferric chloride, ferric sulfate, polyferric chloride, and polyferric sulfate. Examples of the aluminum-based inorganic flocculant include polyaluminum chloride and aluminum sulfate. It is done. In particular, ferric chloride, which is an iron-based inorganic flocculant, is preferable from the viewpoints of the aggregation effect and cost. These inorganic flocculants may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The amount of the inorganic flocculant added to the water to be treated varies depending on the quality of the water to be treated, the type of the inorganic flocculant to be used, the quality of the water to be treated, etc., but the amount of the active ingredient is in the range of 2 to 100 mg / L. It is preferable that

[Aggregation treatment]
After adding the cationic polymer of this invention to to-be-processed water, in order to ensure reaction time, it is preferable to agitate about 2 to 10 minutes.

[Membrane separator]
In the present invention, after the cationic polymer of the present invention or the cationic polymer of the present invention and an inorganic flocculant are added and subjected to an agglomeration treatment, the agglomerated water is directly subjected to membrane separation with a membrane separator.
Here, “directly membrane-separated” refers to supplying water directly to the membrane separation apparatus without adding a flocculant to the flocculated water or performing solid-liquid separation using a precipitation tank or the like.

The membrane separator used in the present invention is not particularly limited in terms of membrane type or structure, but it is preferable to use an MF membrane separator or a UF membrane separator as the membrane separator.
As described above, the pore size of the UF membrane and the MF membrane is preferably 0.2 μm or less, for example, about 0.1 to 0.01 μm.

The material of the separation membrane is not particularly limited, but for example, a separation membrane produced by a stretching method such as polyethylene, polypropylene, polytetrafluoroethylene, etc., has a pore diameter larger than 0.2 μm. Inappropriate.
Moreover, there is no restriction | limiting in particular also in the membrane separation system by a membrane separator, In the below-mentioned Example, although it carries out by the dead end water flow system, a cross flow water flow system may be sufficient.

[Advanced processing]
In the present invention, the treated water obtained by membrane separation by the membrane separation apparatus is of high water quality from which organic substances, SS, etc. are sufficiently removed, and can be used or discharged as industrial water as it is. If necessary, the RO membrane may be treated with a reverse osmosis (RO) membrane separator. In this case, the cationic polymer of the present invention has low RO membrane contamination, and even when RO membrane contamination occurs. The film properties can be easily recovered by ordinary alkali cleaning.

[Control of amount of flocculant added]
When the cationic polymer is excessively added to the water to be treated, the charge in the cationic flocculation water becomes a positive atmosphere, so removal of the cationic polymer adsorption target material (raw water SS, organic matter, inorganic flocculant colloid) As a result, the rate decreases. Therefore, it is preferable to measure the cation consumption A necessary for neutralizing the charge of the water to be treated and adjust the total cation amount of the flocculant to be added to the cation consumption A or less of the water to be treated. The cation consumption A of the water to be treated can be determined by titrating with a cationic polymer that uses the water to be treated by the streaming potential method.

In the present invention, the cation consumption A of the water to be treated is obtained in this way. When the cationic polymer of the present invention is added to the water to be treated in the flocculation treatment and the inorganic flocculant is not added, the cation consumption A and It is preferable to control the addition amount of the cationic polymer of the present invention so that the addition concentration of the cationic polymer of the present invention satisfies the following relational formula (Ia). In addition, when the cationic polymer and the inorganic flocculant of the present invention are added to the water to be treated in the flocculation treatment, the cation consumption A, the concentration of the inorganic flocculant and the cationic polymer of the present invention are represented by the following relational formula (Ib): It is preferable to control the addition amount of the cationic polymer of the present invention and the addition amount of the inorganic flocculant so as to satisfy the above.
Cation consumption A × α = cationic polymer addition concentration (mg / L) (Ia)
Cation consumption A × α =
Cationic polymer addition concentration (mg / L) + Inorganic flocculant addition concentration (mg / L) × β
... (Ib)
Here, α is a safety factor taking into account water quality fluctuations, and is generally about 0.6 to 0.9.
Β is a coefficient for converting the cation amount of the inorganic flocculant used to the cation amount of the cationic polymer, and is determined by a rheometer.

  Hereinafter, the present invention will be described in more detail with reference to experimental examples, examples and comparative examples.

[Experimental Example I]
Using domestic industrial water (SS concentration: 10 mg / L, dissolved organic matter concentration: 1-2 mg / L) as test water, an experiment was conducted to examine the aggregation effect of various cationic polymers by the following method.

75 mg / L of inorganic flocculant (ferric chloride) as a 38% aqueous solution and 0.6 mg / L of various cationic polymers shown in Table 1 (as pure components) were added while rapidly stirring the test water at 150 rpm (however, No. I-1 was adjusted to pH 5.5 using only an inorganic flocculant and then a pH adjuster (hydrochloric acid). After further stirring rapidly for 5 minutes, flocs were grown by stirring gently at 50 rpm for 5 minutes.
The obtained agglomerated treated water was No. After filtration with 5A filter paper, the filtrate was filtered under reduced pressure at −500 mmHg using a cellulose acetate membrane filter having a diameter of 25 mm and a pore diameter of 0.45 μm. At this time, the time required to filter the first 150 mL is T1 (seconds), the time required to filter the next 150 mL is T2 (seconds), and the treated water is evaluated at MFF = T2 / T1. It was.
A smaller value of MFF means better water quality. The results are shown in Table 1.

Table 1 shows the following.
Compared with the inorganic flocculant single treatment (No. I-1), a decrease in the treated water MFF was observed with the addition of the water-soluble cationic polymer. In particular, No. 1 using the cationic polymer of the present invention having a specific cationic group in the side chain. Nos. I-5 to 7 are Nos. 1 to 5 using a cationic polymer having a specific cationic group in the main chain. The treated water MFF which is low compared with I-3-4 is shown.
In addition, No. The cationic polymer used in I-2 has almost no cationic property (electron-withdrawing property) because it has no electron-donating functional group (such as a carbonyl group) in the vicinity of the cationic group and the cationic group is difficult to induce. Therefore, no. The cationic polymer used in I-2 is a polymer generally classified as a nonionic polymer, and is different from the cationic polymer of the present invention, so that the treated water MFF is high and the aggregating ability is inferior. ing.

[Experimental example II]
The test was conducted in the same manner as in Experimental Example I except that the cationic polymer shown in Table 2 was used. However, the addition amount of the cationic polymer was 0.3 mg / L, 0.9 mg / L, and 1.2 mg / L as pure components, and the treated water MFF was evaluated at each addition amount. The results are shown in Table 2.

Table 2 shows the following.
Among those using a water-soluble cationic polymer having a specific cationic group in the polymer side chain, dimethylaminoethyl acrylate / methyl chloride quaternary salt / acrylamide copolymer (DAA / AN copolymer, DAA monomer unit amount 50 mol%) No.). II-5 had the lowest treated water MFF relative to the amount added, and showed high coagulation ability. In the above-mentioned patent document 5, the removability with respect to the humic acid reagent was evaluated, and in that case, the cationic polymer having a hydrophobic group showed higher removal performance than the cationic polymer having no hydrophobic group. However, when the aggregating ability is evaluated by MFF using practical water containing organic substances other than humic acid, the aggregating ability of the cationic polymer having a hydrophobic group (No. II-1) is a cation having no hydrophobic group. Results were inferior to those of the conductive polymer (No. II-2 to 5).

[Experimental Example III]
Biologically treated water (SS concentration: 40 mg / L, dissolved organic matter concentration: 2.5 mg / L) as test water, as a cationic polymer, dimethylaminoethyl acrylate / methyl chloride quaternary salt / acrylamide with different DAA monomer unit amounts Other than using a polymer (DAA / AN copolymer) (mass average molecular weight 2 million to 3 million) (however, polyacrylamide was used in No. III-1, and polydimethylaminoethyl was used in No. III-2). Acrylate / methyl chloride quaternary salt was used) and was tested in the same manner as in Experimental Example I.
Table 3 shows the DAA unit amount of the cationic polymer and the treated water MFF.

Table 3 shows the following.
When a cationic polymer having a DAA unit amount of 20 to 50 mol% is used (No. III-5, 6), treated water MFF having a lower DAA unit amount than when a cationic polymer having a DAA unit amount outside this range is used. Indicated.
A cationic polymer having a mass average molecular weight of 100,000 to 8 million and a DAA unit amount of 20 to 50 mol% showed an intrinsic viscosity of 0.5 to 5.5 dL / g.

[Experimental example IV]
As the cationic polymer, those shown in Table 4 below are used for each example, and the test apparatus is an external pressure type mini-module test apparatus (external pressure type hollow fiber UF membrane, pore size: 0 shown in FIGS. 1 (a) and 1 (b). 0.02 μm, membrane length: 7.5 cm, membrane area: 10.6 cm ² , membrane material polyvinylidene fluoride), and the contamination property of the cationic polymer was examined. Evaluation of the structure and operation of this test apparatus will be described in the sections of Examples 1 to 5 and Comparative Examples 1 and 2.

Each cationic polymer is diluted with pure water to a concentration of 0.5 mg / L, and 50 mL of the diluted solution is introduced into the external pressure mini-module 10 from the pipe 11 by a dead-end water flow system, from the primary side of the hollow fiber membrane 1. After passing through the membrane to the secondary side and contaminating the membrane 1 with the cationic polymer, the time T1 (second) required to pass 30 mL of pure water was measured.
Next, after performing reverse cleaning in which air of 0.15 MPa is supplied from the pipe 13A to the pipe 13 and water in the pipe 13 is passed from the secondary side to the primary side of the hollow fiber membrane 1, the same as described above. The time T2 (second) required to pass 30 mL of pure water was measured.
The degree of contamination of the membrane by the cationic polymer was determined by T2 / T1. The greater T2 / T1, the higher the degree of membrane contamination.
FIG. 2 shows the relationship between the degree of membrane contamination, the kind of the cationic polymer, and the mass average molecular weight.

The following can be seen from FIG.
High molecular polymers are likely to clog the separation membrane pores and are easily contaminated. The cationic polymers used in IV-7 to No. 9 contain no hydrophobic groups having the same mass average molecular weight. It turns out that it is easy to contaminate a film | membrane compared with the cationic polymer used by IV-1-6. Furthermore, no. It can be seen that the cationic polymers of IV-4 to 6 are more easily peeled off from the membrane than other cationic polymers having the same mass average molecular weight and are less likely to contaminate the separation membrane.

[Experiment V]
Using the test apparatus shown in FIG. 3, an experiment was conducted to examine the RO membrane contamination by allowing the diluted solution of the cationic polymer to permeate the RO membrane module.
In this test apparatus, the water supply in the water supply tank 6 is introduced into the RO membrane module 8 from the pipe 21 by the pump P, the permeated water is supplied from the pipe 22 to the treated water tank 7, and the concentrated water is discharged from the pipe 23. It is comprised as follows. A general ultra-low pressure RO membrane (flat membrane) was used as the RO membrane.
PI is a pressure gauge, _{V 4} is a back pressure valve.

As the cationic polymer, those shown in Table 5 below were used, and a diluted solution obtained by diluting each cationic polymer to a concentration of 0.5 mg / L with pure water was supplied to the RO membrane module 8 with a flux of 0.7 m ³ / m ² / d, The RO membrane was blocked by passing water for 20 hours at a water recovery rate of 80%. Next, pH 12 NaOH aqueous solution was circulated through the RO membrane module for 30 minutes to the water supply side for cleaning.
The new membrane before this test, the contaminated membrane after passing through the cationic polymer diluent for 20 hours, and the flux of the membrane after washing with NaOH were examined by permeating pure water at 0.75 MPa. The results are shown in Table 5.

Table 5 shows the following.
Any cationic polymer contaminates the RO membrane, but when a cationic polymer having a hydrophobic group in the molecule is used (No. V-2), the circulation cleaning for 30 minutes almost gives a flux recovery effect. I can't.
In contrast, when the cationic polymer of the present invention having no hydrophobic group was used (No. V-1), the flux recovery effect by washing was high, and the flux recovered to 96% of the new film.

[Examples 1-5, Comparative Examples 1-2]
Using the following inorganic flocculant and cationic polymer, the effect of the weight average molecular weight of the cationic polymer was examined.
Inorganic flocculant: ferric chloride Cationic polymer: DAA / AN copolymer shown in Table 6 (having specific cationic group in polymer side chain)

In addition, as a test apparatus, an external pressure type mini-module test apparatus (external pressure type hollow fiber UF membrane, pore diameter: 0.02 μm, membrane length: 7.5 cm, membrane area: 10 shown in FIGS. .6 cm ² , a membrane material polyvinylidene fluoride).
In FIG. 1A, 1 is a hollow fiber membrane, 2 is a potting agent, 3 is a raw water introduction port, 4 is a drainage port, 5 is a module housing, and the hollow fiber membrane 1 is loaded therein. The raw water is introduced into the housing 5 from the introduction port 3, and the permeated water that has permeated through the hollow fiber membrane 1 is taken out from the inside of the hollow fiber membrane 1 to the outside of the housing 5.

A pipe was connected to the external pressure type hollow fiber mini-module 10 as shown in FIG. In this test apparatus, when the raw water is treated, the valves V ₁ , V ₂ and V ₃ are closed, the pump P is operated, and the raw water is introduced from the water supply tank 6 through the pipe 11 into the external pressure mini-module 10. Membrane filtration is performed by a dead-end water passing method in which the permeate is supplied to the treated water tank 7 through the pipe 13. When performing backwashing of the membrane, the pump P is stopped, the valve V ₁ is closed, the V _2, V ₃ is opened and air was supplied to the pipe 13 from the pipe 13A, the hollow fiber water in the pipe 13 Permeation from the inner side (secondary side) of the membrane 1 to the outer side (primary side). During wastewater, while stopping the pump P, and valve _V 1, _{V 2} opens, the valve _{V 3} is closed, the air air into the pipe 11 from the pipe 11A, the discharge of water of the pipe 12 from the module 10 Let Air from the pipes 11A and 13A was supplied at 0.15 MPa. At the time of water filling, the valve V ₂ is opened, the valves V ₁ and V ₃ are closed, the pump P is operated, and the water in the water supply tank 6 is introduced into the module 10. PI is a pressure gauge.

Biologically treated water (SS concentration 40 mg / L, dissolved organic matter concentration 2 to 2.5 mg / L) of liquid crystal factory effluent is rapidly stirred at 150 rpm while inorganic flocculant (ferric chloride) is used as a 38% aqueous solution and 100 mg / L Then, the pH was adjusted to 5.5 using a pH adjuster (hydrochloric acid). After further rapidly stirring for 5 minutes and then continuously stirring at 150 rpm, as shown in Table 6, 0.6 mg / L of a cationic polymer having a different mass average molecular weight was added and reacted for 5 minutes. Aggregation was carried out with gentle stirring for 5 minutes.
The obtained agglomerated water was passed through an external pressure mini-module test apparatus shown in FIGS. 1 (a) and 1 (b) for 48 hours. Measured with a pressure gauge Pl provided on the pipe 11 after passing through water and backwashing every 30 minutes with a flux of 4 m ³ / m ² / d (30 seconds), then draining (30 seconds), and then watering (30 seconds). The rate of increase in transmembrane pressure was investigated.
Further, the SS concentration of the feed water (flocculated treated water subjected to membrane separation) and the amount of SS in the wastewater obtained by passing water for 48 hours were measured, and the SS residual ratio in the module was calculated by the following formula.

  The feed water SS concentration and the amount of SS in the wastewater were measured as the dry weight of the filtered product obtained when these waters were filtered through a glass filter paper having a diameter of 47 mm and a pore diameter of 1 μm. The results are shown in Table 6.

Table 6 shows the following.
When the mass average molecular weight having a low molecular weight was used, the flocs became fine, so that the membrane was likely to be clogged and the rate of increase in the differential pressure tended to increase (Comparative Example 1). When the molecular weight of the cationic polymer is increased, flocs are coarsened, so that they are easily deposited in the module, and the SS residual ratio is increased (Comparative Example 2). From these results, it is understood that the proper weight average molecular weight of the cationic polymer is 100,000 to 8 million, and desirably 200,000 to 1 million from the viewpoint of membrane contamination.

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane 2 Potting agent 3 Raw water introduction port 4 Drainage port 5 Module housing 6 Water supply tank 7 Treated water tank 8 RO membrane module 10 External pressure type hollow fiber mini module

Claims (16)

  Mass average molecular weight having a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain and no hydrophobic group A water treatment method characterized in that 100,000 to 8 million water-soluble cationic polymer is added to the water to be treated and agglomerated, and then the agglomerated water is directly subjected to membrane separation with a separation membrane having a pore diameter of 0.2 μm or less .   Mass average molecular weight having a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain and no hydrophobic group A water treatment method characterized in that 100,000 to 8 million water-soluble cationic polymer is added to the water to be treated for coagulation treatment, the coagulation treatment water is directly subjected to membrane separation, and the separated water is subjected to reverse osmosis membrane treatment. .   Mass average molecular weight having a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain and no hydrophobic group After adding 100,000 to 8 million water-soluble cationic polymer to the water to be treated and aggregating, the agglomerated water is directly separated by a separation membrane having a pore size of 0.2 μm or less, and the separated water is treated with a reverse osmosis membrane. A water treatment method characterized by:   The water to be treated is industrial water, city water, river water, lake water, well water, drainage water, having a turbidity concentration of less than 200 mg / L and a dissolved organic matter concentration of 0.01 mg / L or more and less than 200 mg / L, or The water treatment method according to claim 1, which is biologically treated water.   The water treatment method according to any one of claims 1 to 4, wherein the cationic polymer is a copolymer having a structural unit derived from dimethylaminoethyl acrylate quaternized product.   The cationic polymer is a cationic polymer having a structural unit derived from dimethylaminoethyl acrylate quaternized compound in an amount of 20 to 50 mol% in all structural units and having an intrinsic viscosity of 0.5 to 5.5 dL / g. Item 6. The water treatment method according to Item 5.   The water treatment method according to claim 1, wherein the cationic polymer and an inorganic flocculant are added to the water to be treated for agglomeration treatment. The amount of the cationic polymer necessary to neutralize the charge of the water to be treated is determined as a cation consumption amount A by titrating the water to be treated with the cationic polymer by the streaming potential method, and the aggregation When the cationic polymer is added to the water to be treated and no inorganic flocculant is added in the treatment, the cation consumption A and the addition concentration of the cationic polymer satisfy the following relational formula (Ia): When the addition amount of the cationic polymer is controlled and the cationic polymer and the inorganic flocculant are added to the water to be treated in the flocculation treatment, the cation consumption A, the addition of the inorganic flocculant and the cationic polymer are added. The water treatment according to any one of claims 1 to 7, wherein the addition amount of the cationic polymer and the addition amount of the inorganic flocculant are controlled so that the concentration satisfies the following relational expression (Ib). Law.
Cation consumption A × α = cationic polymer addition concentration (mg / L) (Ia)
Cation consumption A × α =
Cationic polymer addition concentration (mg / L) + Inorganic flocculant addition concentration (mg / L) × β
... (Ib)
α: Safety factor taking into account fluctuations in water quality β: Factor for converting the cation amount of the inorganic flocculant into the cation amount of the cationic polymer   Mass average molecular weight having a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain and no hydrophobic group Aggregation treatment means for adding 100,000 to 8 million water-soluble cationic polymer to the water to be treated for aggregation treatment, and the aggregation treatment water of the aggregation treatment means are directly subjected to membrane separation with a separation membrane having a pore size of 0.2 μm or less. A water treatment device comprising a membrane separation device.   Mass average molecular weight having a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain and no hydrophobic group Aggregation treatment means for adding 100,000 to 8 million water-soluble cationic polymer to the water to be treated for aggregation treatment, membrane separation apparatus for directly performing membrane separation of the aggregation treatment water of the aggregation treatment means, and the membrane separation apparatus And a reverse osmosis membrane separation device for treating the separated water with a reverse osmosis membrane.   Mass average molecular weight having a primary amino group, a secondary amino group, a tertiary amino group, and a functional group selected from an acid base and a quaternary ammonium base of these amino groups in the polymer side chain and no hydrophobic group Aggregation treatment means for adding 100,000 to 8 million water-soluble cationic polymer to the water to be treated for aggregation treatment, and the aggregation treatment water of the aggregation treatment means are directly subjected to membrane separation with a separation membrane having a pore size of 0.2 μm or less. A water treatment device comprising: a membrane separation device; and a reverse osmosis membrane separation device for treating the separated water of the membrane separation device with a reverse osmosis membrane.   The water to be treated is industrial water, city water, river water, lake water, well water, drainage water, having a turbidity concentration of less than 200 mg / L and a dissolved organic matter concentration of 0.01 mg / L or more and less than 200 mg / L, or The water treatment device according to any one of claims 9 to 11, which is biologically treated water.   The water treatment apparatus according to any one of claims 9 to 12, wherein the cationic polymer is a copolymer having a structural unit derived from dimethylaminoethyl acrylate quaternized product.   The cationic polymer is a cationic polymer having a structural unit derived from dimethylaminoethyl acrylate quaternized compound in an amount of 20 to 50 mol% in all structural units and having an intrinsic viscosity of 0.5 to 5.5 dL / g. Item 14. A water treatment device according to item 13.   The water treatment apparatus according to any one of claims 9 to 14, wherein in the coagulation treatment means, the cationic polymer and an inorganic coagulant are added to the water to be treated for coagulation treatment. When the cationic polymer is added to the water to be treated by the aggregating treatment means and no inorganic flocculant is added, the water to be treated is obtained by titrating the water to be treated with the cationic polymer by a streaming potential method. The required amount of the cationic polymer necessary to neutralize the charge of the product is defined as cation consumption A, and the amount of the cationic polymer added so that the concentration of the cationic polymer satisfies the following relational formula (Ia): When the cationic polymer and the inorganic flocculant are added to the water to be treated by the flocculation treatment means, the cation consumption A and the additive concentration of the inorganic flocculant and the cationic polymer have the following relationship: The water treatment apparatus according to any one of claims 9 to 15, further comprising control means for controlling the addition amount of the cationic polymer and the addition amount of the inorganic flocculant so as to satisfy the formula (Ib).
Cation consumption A × α = cationic polymer addition concentration (mg / L) (Ia)
Cation consumption A × α =
Cationic polymer addition concentration (mg / L) + Inorganic flocculant addition concentration (mg / L) × β
... (Ib)
α: Safety factor taking into account fluctuations in water quality β: Factor for converting the cation amount of the inorganic flocculant into the cation amount of the cationic polymer

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