TW201945294A - Water treatment method and water treatment apparatus - Google Patents

Abstract

A water treatment method in which an inorganic flocculant is added to water of interest to perform a flocculation treatment of the water and then the water is subjected to membrane separation using a membrane separation apparatus, wherein the inorganic flocculant is added to the water, then the flocculation treatment is performed by adding a water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8,000,000 to the water, and then the water that has undergone the flocculation treatment is directly subjected to membrane separation using a membrane separation apparatus.

Description

Water treatment method and water treatment device

The invention relates to a water treatment method and a water treatment device, which prevent the membrane separation device from being contaminated in the water treatment for membrane separation of the agglomerated treatment water by a membrane separation device after adding an inorganic coagulant to the treated water to perform agglomeration treatment, and prevent the membrane separation device from being polluted and Reduce the amount of coagulant used.

As a method for treating treated water such as industrial water, urban water, well water, industrial drainage, etc., there are the following methods: using inorganic coagulants for the purpose of removing organic matters and turbid substances (SS) in raw water After the treatment, the aggregation treatment is performed by a precipitation separation device or a floating separation device, or a membrane separation device using a precision filtration membrane (MF (Millipore Filtration) membrane) module or an ultrafiltration membrane (UF (Urtra Filtration) membrane) module. Water is subjected to solid-liquid separation to obtain clear water. However, in the method, for example, when the water to be treated has a high pH or a high alkalinity, or when it contains a high concentration of phosphorus or a biological metabolite, these substances disperse the inorganic aggregating agent, so only A large amount of inorganic coagulant is required in the coagulation treatment of the inorganic coagulant, which results in an increase in the amount of sludge generated. Furthermore, by increasing the concentration of the inorganic coagulant, the cleaning frequency of the membrane separation device used in the solid-liquid separation is increased.

There is a method of using a cationic polymer together with the inorganic coagulant for the water to be treated in which the coagulation treatment is difficult using only the inorganic coagulant. For example, Patent Document 1 describes a technique for performing a coacervation treatment on water to be treated with high pH or alkalinity by adding a cationic polymer before adding an inorganic flocculant. In this method, the organic matter or SS in the raw water reacts with the cationic polymer initially, so the necessary addition amount of the cationic polymer is large, resulting in an increase in cost.

Patent Document 2 discloses a technique of adding an inorganic flocculant after adding an inorganic flocculant and a polymer flocculant to perform agglomeration treatment, and then before solid-liquid separation. In the method, the coagulant is added many times, the device is complicated, and the operation is complicated.

Patent Document 3 discloses a method using particles containing a cationic polymer that is substantially insoluble in water, and adding an inorganic coagulant before adding the particles. In this method, since the aggregated flocculent containing water-insoluble particles becomes coarse, turbidity contamination can be caused in the membrane separation device used in the solid-liquid separation. In addition, since the polymer insoluble in water is settled in a standing state, it must be constantly stirred in the medicine tank, which not only complicates the dosing equipment, but also increases the equipment maintenance cost.

Patent Literature 1: Japanese Patent Laid-Open No. 2017-140577 Patent Literature 2: Japanese Patent Laid-Open No. 11-77062 Patent Literature 3: Japanese Patent Laid-Open No. 2009-240974

An object of the present invention is to provide a water treatment method and a water treatment device. After an inorganic coagulant is added to the water to be treated for aggregation treatment, the membrane separation device is used to prevent the membrane separation device from being used in the water treatment for membrane separation of the aggregation treatment water by the membrane separation device. Pollution and reduce the use of coagulant.

The inventors discovered that by initially reacting an organic substance or SS in raw water with an inorganic flocculant and adding a water-soluble cationic polymer of a specific molecular weight, it is possible to efficiently disperse the colloidal or fine floc of the inorganic flocculant with cationic For polymer reaction, even if a membrane separation device is used for membrane separation directly after adding a cationic polymer, the membrane separation device will not be polluted, and the amount of coagulant used can also be reduced.
The present invention has the following main points.

[1] A water treatment method comprising adding an inorganic flocculant to a treated water and performing an agglomeration treatment to perform membrane separation using a membrane separation device. The water treatment method is characterized by adding an inorganic flocculant to the water to be treated, A water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million is added to perform agglomeration treatment, and a membrane separation device is used to directly perform membrane separation on the agglomerated treatment water.

[2] The water treatment method according to [1], wherein the water to be treated is industrial water, urban water, any one of phosphorus, a biological metabolite, an organic acid having a chelating effect, and inorganic carbon, Well water, industrial drainage or biologically treated water for drainage.

[3] The water treatment method according to [1] or [2], wherein the membrane separation device is a precision filtration membrane separation device or an ultrafiltration membrane separation device.

[4] The water treatment method according to any one of [1] to [3], wherein the treated water obtained by the membrane separation device is further subjected to reverse osmosis membrane treatment.

[5] The water treatment method according to any one of [1] to [4], wherein the treated water is titrated with the cationic polymer by a flow potential method, thereby neutralizing the water The necessary amount of the cationic polymer required for the charge of the water to be treated is taken as the cation consumption amount A, and the added concentration of the cation consumption amount A and the inorganic flocculant and the cationic polymer satisfies the following relationship The manner of formula (I) controls the addition amount of the cationic polymer and the addition amount of the inorganic coagulant;

Cation consumption A × α =
Cationic polymer added concentration (mg / L) + inorganic flocculant added concentration (mg / L) × β ··· (I)

α: Safety factor in consideration of water quality fluctuations β: Coefficient for converting the cation amount of the inorganic flocculant into the cation amount of the cationic polymer.

[6] A water treatment device, comprising: a first coagulation treatment mechanism for adding an inorganic coagulant to the water to be treated for coagulation treatment; and a second coagulation treatment mechanism for adding the coagulation treatment water to the first coagulation treatment water The water-soluble cationic polymer having a mass average molecular weight of 100,000 to 8 million is subjected to agglomeration treatment; and a membrane separation device directly performs membrane separation on the agglomerated treatment water of the second agglomeration treatment mechanism.

[7] The water treatment device according to [6], wherein the water to be treated is industrial water, urban water, or any one of phosphorus, a biological metabolite, an organic acid having chelation, and inorganic carbon, Well water, industrial drainage or biologically treated water for drainage.

[8] The water treatment device according to [6] or [7], wherein the membrane separation device is a precision filtration membrane separation device or an ultrafiltration membrane separation device.

[9] The water treatment device according to any one of [6] to [8], further comprising a reverse osmosis membrane separation device that treats the treated water obtained by the membrane separation device.

[10] The water treatment device according to any one of [6] to [9], further including a mechanism for titrating the water to be treated with the cationic polymer by a flow potential method, thereby obtaining A necessary amount of the cationic polymer required to neutralize the charge of the water to be treated is taken as the cation consumption A, and the added concentration of the inorganic agglomerating agent and the cationic polymer satisfies the following relational expression ( The method of I) controls the addition amount of the cationic polymer and the addition amount of the inorganic coagulant;

Cation consumption A × α =
Cationic polymer added concentration (mg / L) + inorganic flocculant added concentration (mg / L) × β ··· (I)

α: Safety factor in consideration of water quality fluctuations β: Coefficient for converting the cation amount of the inorganic flocculant into the cation amount of the cationic polymer.

[Effect of the invention]
According to the present invention, in the water treatment that performs agglomeration treatment on the water to be treated and performs membrane separation by a membrane separation device, the amount of coagulant used can be reduced while preventing the membrane separation device from being contaminated.

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

The water treatment method of the present invention is characterized in that, in a water treatment method in which a membrane separation device is used to perform membrane separation after an inorganic coagulant is added to the water to be treated for coagulation treatment, the inorganic coagulant is added to the water to be treated, and the mass is averaged The water-soluble cationic polymer with a molecular weight of 100,000 to 8 million is subjected to a coacervation treatment, and a membrane separation device is used to directly perform membrane separation on the cohesion-treated water.

The water treatment device of the present invention is characterized by having a first aggregation treatment mechanism for adding an inorganic coagulant to the water to be treated for aggregation treatment, and a second aggregation treatment mechanism for adding an average mass to the aggregation treatment water of the first aggregation treatment mechanism. A water-soluble cationic polymer having a molecular weight of 100,000 to 8 million is subjected to agglomeration treatment; and a membrane separation device directly performs membrane separation on the agglomerated treatment water of the second agglomeration treatment mechanism.

[mechanism]
According to the present invention, since an inorganic coagulant is initially added to the water to be treated and an organic substance or SS in the water to be treated is reacted with the inorganic coagulant, a cationic polymer is added, so that the dispersed inorganic coagulant colloid or fine flocculent can be efficiently made. Reaction with cationic polymer, even if the membrane separation device is used for membrane separation directly after adding the cationic polymer, the membrane separation device will not be polluted, and the amount of coagulant used can also be reduced.

It is assumed that when a cationic polymer is added before the inorganic flocculant, the cationic polymer reacts with anionic components such as SS and organic matter in raw water and is consumed. Therefore, compared with the case where a cationic polymer is added after the inorganic flocculant, the amount of the cationic polymer required to react with the dispersed inorganic flocculant colloid is increased. When the ratio of the amount of the cationic polymer added / the amount of the inorganic flocculant added is constant or more, the aggregated floc is easily adsorbed on the separation membrane, and the membrane is easily polluted. Therefore, in the present invention, a cationic polymer is added after the inorganic coagulant is added.

The mass average molecular weight of the cationic polymer used in the present invention is 100,000 or more and is relatively large. Therefore, as shown in the examples described later, it is difficult for the aggregated floc to cause clogging of the membrane. Since the mass average molecular weight of the cationic polymer used in the present invention is 8 million or less and is water-soluble, it is difficult for the aggregated floc to accumulate in the membrane module. Therefore, it is possible to prevent contamination in the membrane separation device and continue processing stably for a long time.

In the present invention, by using an inorganic flocculant and a cationic polymer together, the amount of the inorganic flocculant can be reduced. At this time, since the cationic polymer is added after the inorganic flocculant, the necessary amount of the cationic polymer can be reduced As a result, the overall amount of coagulant used can be reduced.

[Treated water]
The treated water to be treated in the present invention is not particularly limited, but the present invention is not suitable for industries including phosphorus, biological metabolites, organic acids having chelation, or inorganic carbon, which is difficult to obtain a sufficient agglomeration treatment effect using only an inorganic aggregating agent. The treatment of water, city water, well water, industrial drainage or biologically treated water is effective.

Examples of the chelating organic acid include citric acid, formic acid, succinic acid, acetic acid, and butyric acid. These organic acids are used in, for example, a plating step in a semiconductor manufacturing step and the like, and act as a complex ion-forming agent or dispersant for an inorganic agglomerating agent when treating the wastewater. Regarding the aggregation of the drainage containing the organic acid, the higher the aggregation pH is, the higher the complex ion-forming ability of the organic acid is, and therefore the aggregation state is deteriorated. The case where the agglomeration pH becomes high refers to, for example, a case where agglomeration is performed for the purpose of treating heavy metals such as Cu or Mn, or a case where the optimal agglomeration pH during removal of total organic carbon (TOC) in raw water is 6 or more In the case of using polyaluminum chloride in an inorganic coagulant.

[Coagulation treatment using inorganic coagulant]
As the inorganic flocculant added to the water to be treated, an iron-based or aluminum-based inorganic flocculant capable of forming flocs in a wide pH range can be preferably used. Examples of the iron-based inorganic coagulant include iron chloride, iron sulfate, polyferric chloride, and polyferric sulfate. Examples of the aluminum-based inorganic coagulant include polyaluminum chloride or aluminum sulfate. Particularly, in terms of agglomeration effect and cost, ferric chloride is preferable as an iron-based inorganic agglomerating agent. These inorganic coagulants may be used singly or in combination of two or more kinds.

The addition amount of the inorganic coagulant in the treated water varies depending on the water quality of the treated water, the type of the inorganic coagulant used, and the required treated water quality, but it is preferably set to 2 mg / L to 100 mg / L.

The inorganic flocculant has a suitable pH range for flocculation treatment according to its type. The pH in iron-based inorganic flocculants such as ferric chloride is preferably about 5 to 6, and the pH in aluminum-based inorganic flocculants is preferably about 6 to 7. Therefore, it is preferable to adjust the pH to an appropriate pH range by adding an acid or an alkali as necessary.

After the inorganic coagulant is added to the water to be treated, in order to fully react the organic matter or SS in the water to be treated with the inorganic coagulant, it is preferable to stir rapidly for about 2 to 10 minutes.

In the present invention, the rapid stirring means that the rotation speed is about 100 rpm to 200 rpm, and the slow stirring means that the rotation speed is about 20 rpm to 100 rpm.

[Aggregation treatment using cationic polymer]
The cationic polymer used in the present invention is a water-soluble polymer having a mass average molecular weight of 100,000 to 8 million.

The "water-soluble" means that the solubility in water is 1 g or more / 100 g of water (20 ° C).
The "cationic polymer" means a polymer having a positive colloidal equivalent, and for example, the colloidal equivalent is preferably 1.0 meq / g to 6.0 meq / g. The colloidal equivalent was titrated with PVSK (polypotassium potassium sulfate) at 1/400 N, and was measured by a flow potential method.

The mass average molecular weight of the cationic polymer is a value of the mass average molecular weight measured by a chromatography method (Gel Permeation Chromatography (GPC) method).

When the mass-average molecular weight of the cationic polymer is less than 100,000, the formed flocculated matter becomes fine, and therefore the membrane is liable to cause clogging. If the mass average molecular weight of the cationic polymer exceeds 8 million, the aggregated floc will become too coarse and easily accumulate in the membrane module. Therefore, the mass average molecular weight of the cationic polymer used in the present invention is in the range of 100,000 to 8 million, and preferably in the range of 200,000 to 1 million.

The cationic polymer is not particularly limited as long as it is a water-soluble polymer having the above-mentioned mass average molecular weight, and a copolymer of a cationic monomer and a nonionic monomer such as acrylamide may be preferably used. .

As the cationic monomer, for example, a dimethylaminoethyl acrylate or a dimethylaminoethyl methacrylate acid salt or a quaternary ammonium salt thereof, or dimethylaminopropylacrylic acid can be preferably used. The amine or dimethylaminopropylmethacrylamide acid salt or its quaternary ammonium salt is not particularly limited. As the quaternary ammonium salt, a quaternary ammonium salt such as methyl chloride or ethyl chloride can be used.

A cationic polymer may be used individually by 1 type, and may use 2 or more types together.

The amount of the cationic polymer added to the coagulation-treated water (hereinafter, sometimes referred to as "inorganic coagulation-treated water") using an inorganic coagulant depends on the water quality of the water to be treated or the inorganic coagulation-treated water or the cationic polymerization used. The type of the substance varies, and the amount of the active ingredient is preferably within a range of 0.1 mg / L to 5 mg / L.

After the cationic polymer is added to the inorganic agglomerated treatment water, in order to ensure the reaction time with the cationic polymer, it is preferable to perform rapid stirring for about 2 minutes to 10 minutes, and then slow down for about 2 minutes to 10 minutes. Stir quickly.

[Membrane separation by membrane separation device]
Coagulation-treated water (hereinafter, sometimes referred to as "cationic aggregation treatment water") obtained by adding a cationic polymer to the inorganic aggregation treatment water and performing the aggregation treatment is directly subjected to membrane separation by a membrane separation device.

The "direct membrane separation" refers to supplying water directly to the membrane separation device without further adding a coagulant to the cation agglomeration treatment water, and without performing solid-liquid separation using a precipitation tank or the like.

The membrane separation device used in the present invention is not particularly limited in its membrane material, membrane form, or structure. As the membrane separation device, an MF membrane separation device or a UF membrane separation device is preferably used.

The pore diameter of the UF film and the MF film is preferably 0.2 μm or less, for example, about 0.1 μm to 0.01 μm.

The membrane separation method using the membrane separation device is also not particularly limited. In the embodiment described later, the closed-end water flow method is used, and the horizontal water flow method may also be used.

[Highly processed]
The treated water obtained by the membrane separation using the membrane separation device is a highly water-removed substance such as organic matter and SS, which can be directly used or discharged as industrial water, but reverse osmosis can also be used if necessary. (Reverse Osmosis, RO) Membrane separation device performs RO membrane treatment. In this case, since the water supplied to the RO membrane treatment is of sufficiently high water quality, it does not cause problems such as an increase in the differential pressure of the RO membrane separation device, and stable and efficient treatment can be performed to obtain high-quality pure water.

[Control of the amount of coagulant added]
When the cationic polymer is excessively added to the inorganic agglomerated treated water, the charge in the cationic agglomerated treated water is a positive environment, and as a result, the target substance for adsorption of the cationic polymer (SS in the raw water, organic matter, and inorganic agglomerant colloid) The removal rate is reduced. Therefore, to measure the amount of cation consumption A required to neutralize the charge of the water to be treated, it is preferable to adjust the total amount of cations of the coagulant added to be less than or equal to the amount of cations A of the water to be treated. The cation consumption A of the treated water can be determined by titration with a cationic polymer using the treated water using a flow potential method.

In the present invention, the cation consumption A of the treated water is preferably determined in the manner described above, and the inorganic coagulant and the cation are controlled so that the concentration of the inorganic coagulant and the cationic polymer satisfies the following relationship (I). The amount of polymer added.

Cation consumption A × α =
Cationic polymer added concentration (mg / L) + inorganic flocculant added concentration (mg / L) × β ··· (I)

α is a safety factor that takes into account changes in water quality, and is usually about 0.6 to 0.9.
β is a coefficient that converts the amount of cations of the inorganic coagulant used to the amount of cations of the cationic polymer, and is determined by titration using a flow galvanometer.

The control of the addition amounts of the cationic polymer and the inorganic coagulant can be performed by inputting the conversion coefficient β of the cation consumption amount A of the treated water obtained in advance and the inorganic coagulant used and the preset safety factor α. The control mechanism is performed using automatic control.
[Example]

The following examples illustrate the present invention in more detail.

The inorganic flocculants and cationic polymers used in the following examples and comparative examples are shown below.
Inorganic flocculant: Ferric chloride cationic polymer: Mass average molecular weight 50,000, 100,000, 200,000, 700,000, 1 million, 8 million or 10 million dimethylaminoethyl acrylate · methyl chloride Grade salt / acrylamide copolymer (colloidal equivalent of 2.5 meq / g ～ 3.0 meq / g)

As a test device, an external pressure type micro-module test device (external pressure type hollow fiber UF membrane, pore diameter: 0.02 μm, membrane length: 7.5 cm, membrane area: 10.6 cm) shown in FIGS. 1 (a) and (b) was used. ^2. Film material: polyvinylidene fluoride).

In Fig. 1 (a), 1 is a hollow fiber membrane, 2 is a potting agent, 3 is a raw water inlet, and 4 is a drain. 5 is a module case, and the inside is filled with a hollow fiber membrane 1. The raw water is introduced into the casing 5 through the introduction port 3, and the permeated water that has passed through the hollow fiber membrane 1 is taken out of the membrane of the hollow fiber membrane 1 to the outside of the casing 5.

As shown in Fig. 1 (b), the piping is connected to the external pressure type hollow fiber micromodule 10 as an external pressure type micromodule test device. In the test device, membrane separation is performed by using a closed-end water supply method. When processing raw water, the valves V ₁ , V ₂ , and V _{3 are} closed to make the pump P work, and the raw water is supplied from the water supply tank 6 through the pipe 11. The external pressure micro module 10 is introduced, and permeated water is supplied to the treated water tank 7 through a pipe 13. When in inverse membrane cleaning, stops the pump P, closes the valve V _1, open V _2, V _3, by a pipe 13A air into pipe 13, a piping of water inside 13 of the hollow fiber membrane inside 1 (2 (Secondary side) penetrates to the outside (primary side). At the time of drainage, the pump P is stopped at the state of opening the valve V _1, valve V _2, close the valve V _3, from the air supply pipe 11 to the pipe 11A, the pipe 12 by the module 10 and discharge the water. The air from the pipes 11A and 13A is supplied at 0.15 MPa. When filling with water, 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.

[Examples 1 to 5 and Comparative Examples 1 to 2]
While rapidly stirring the biologically treated water (SS concentration: 40 mg / L, TOC: 2 mg / L to 2.5 mg / L) of the liquid crystal factory drainage at 150 rpm, add 100 mg / L of inorganic as a 38% aqueous solution. Coagulant (ferric chloride),
Then, it adjusted to pH 5.5 using the pH adjuster (sodium hydroxide). After further rapid stirring for 5 minutes, the stirring was continued at 150 rpm, and as shown in Table 1, 0.6 mg / L of cationic polymers having different mass average molecular weights were added and allowed to react for 5 minutes, and then further slowed at 50 rpm. Stir for 5 minutes and perform agglomeration.

The obtained agglomerated treated water was allowed to pass through water for 48 hours in the external pressure type micro-module test device shown in Figs. 1 (a) and 1 (b). In the flowing water, the filtration with a flux of 4 m ³ / m ² / d was performed with backwashing every 30 minutes (30 seconds), followed by drainage (30 seconds), and then filling with water (30 seconds). The rising speed of the differential pressure between the membranes was measured by a pressure gauge P1 provided in.

In addition, the SS concentration of the water supply (agglomerated treatment water supplied to the membrane separation treatment) and the SS amount in the drainage obtained in the through-flow water for 48 hours were measured, and the SS residual rate in the module was calculated by the following formula.

[Number 1]

The concentration of SS in the water supply and the amount of SS in the water were measured as the dry weight of the filtrate obtained when the water was filtered with glass filter paper having a diameter of 47 mm and a pore diameter of 1 μm. The results are shown in Table 1.

[Table 1]

Table 1 shows the following.
The use of a low-molecular weight average molecular weight tends to cause the membrane to become clogged due to the fineness of the floc, and the differential pressure rise rate is increased (Comparative Example 1). When the molecular weight of the cationic polymer is increased, the floc becomes coarse, and therefore it is easy to accumulate in the module, and the SS residual rate increases (Comparative Example 2). From these results, it is understood that the appropriate mass average molecular weight of the cationic polymer is from 100,000 to 8 million, and preferably from 200,000 to 1 million, from the viewpoint of membrane contamination.

[Experimental example I]
An experiment was conducted to investigate the effects of the order of addition of the inorganic agglomerating agent and the cationic polymer using the following inorganic agglomerating agent and cationic polymer.
Inorganic coagulant: Ferric chloride cationic polymer: Polydiallyldimethylammonium chloride with a mass average molecular weight of 200,000 (colloidal equivalent of 5.9 meq / g, intrinsic viscosity of 0.75 dg / L)
Test water: Model water with phosphoric acid (phosphoric acid added for the purpose of dispersing inorganic flocculants) to 6 mg / L asP in domestic industrial water was used.

The test method is described below.

75 mg / L of inorganic coagulant (ferric chloride) as a 38% aqueous solution was added to the test water, and 0.6 mg / L (based on purity) of a cationic polymer was added. The pH was adjusted using a pH adjuster (sodium hydroxide). The coagulation treatment was performed at pH 5.5. The obtained coagulation-treated water was filtered with No. 5A filter paper, and then the filtrate was filtered under a reduced pressure of -500 mmHg using a cellulose acetate membrane filter with f25 mm and a pore diameter of 0.45 μm. At this time, the time required to filter the first 150 mL was set to T1 (seconds), the time required to filter the next 150 mL was set to T2 (seconds), and the treated water was evaluated using MFF = T2 / T1.
A smaller MFF value means better water quality.

The order of the aggregation treatment using the inorganic aggregation agent and the cationic polymer is as follows for each example.
Experimental example I-1 (adding cationic polymer after adding inorganic flocculant): While rapidly stirring the test water at 150 rpm, add inorganic flocculant, and then adjust the pH to 5.5 with a pH adjuster, and then stir rapidly While stirring for 5 minutes, the cationic polymer was added and allowed to react for 5 minutes while being stirred, and then the mixture was stirred at 50 rpm for 5 minutes and agglomerated.
Experimental Example I-2 (Inorganic coagulant is added after adding a cationic polymer): While the test water is rapidly stirred at 150 rpm, a cationic polymer is added, and then an inorganic coagulant is added to adjust the pH to an pH 5.5, and further stirred for 5 minutes. Thereafter, the mixture was agitated at 50 rpm for 5 minutes, and then subjected to agglomeration treatment.
Experimental Example I-3 (simultaneous addition of cationic polymer and inorganic flocculant): While rapidly stirring the test water at 150 rpm, the inorganic flocculant and cationic polymer were added simultaneously, and then adjusted to pH 5 using a pH adjuster .5, and agitate at 50 rpm for 5 minutes with slow speed.

The results are shown in Figure 2.
The following situation can be seen from FIG. 2.
Compared with Experimental Example I-1 in which the cationic polymer was added after adding the inorganic aggregating agent, Experimental Example I-2 and Experimental Example I-3 had large MFF and poor aggregation. The reason is that the anionic component in the raw water reacts with the cationic polymer and does not fully react with the dispersed inorganic coagulant colloid. From this result, it is understood that when a cationic polymer is used for the purpose of capturing a dispersed inorganic aggregating agent, when a cationic polymer is added after the inorganic aggregating agent, the cationic polymer can be used efficiently, so a small amount Adding amount to obtain a sufficient cohesion effect.

[Experimental Example II]
Using the same inorganic agglomerating agent and cationic polymer as the inorganic agglomerating agent and cationic polymer used in Experimental Example 1, an experiment was conducted to investigate the effect of the cationic polymer on the drainage containing an organic acid having a chelating effect.
As the test water, the drainage of the plating process in a domestic semiconductor factory was used (the dissolved organic matter concentration containing organic acids was 10 mg / L to 20 mg / L, and the copper concentration was 6 mg / L).

The test method is described below.

Aggregation treatment was performed for the purpose of removing copper in the test water. While rapidly stirring the test water at 150 rpm, 50 mg / L of an inorganic coagulant (ferric chloride) as a 38% aqueous solution was added, and then the pH was adjusted to pH 9 using a pH adjuster (sodium hydroxide). After further rapid stirring for 5 minutes, cationic polymer 0 mg / L to 5 mg / L (purity is the added amount shown in Table 2) was added and reacted for 5 minutes while rapidly stirring. After that, the mixture was slowly stirred at 50 rpm for 5 minutes to grow the floc. After filtering the obtained coagulation-treated water with No. 5A filter paper, the copper ion concentration in the filtrate was measured.
The lower the copper ion concentration, the more effectively the aggregation treatment is performed, and the better the aggregation state.
The results are shown in Table 2.

[Table 2]

As can be seen from Table 2, as the addition amount of the cationic polymer increases, the copper ion concentration of the filtrate decreases, and the aggregation state is improved.

Although this invention is demonstrated in detail using a specific aspect, it is clear to those skilled in the art that various changes can be made without deviating from the meaning and scope of this invention.
This application is based on Japanese Patent Application No. 2018-084264 filed on April 25, 2018, which is incorporated by reference in its entirety.

1‧‧‧ hollow fiber membrane

2‧‧‧ potting agent

3‧‧‧ raw water inlet

4‧‧‧ Drain

5‧‧‧Module housing

6‧‧‧ water tank

7‧‧‧ treatment tank

10‧‧‧External Pressure Hollow Wire Miniature Module

11, 11A, 12, 13, 13A‧‧‧ Piping

V ₁ , V ₂ , V ₃ ‧‧‧ Valve

P‧‧‧Pump

PI‧‧‧Pressure gauge

1 (a) and 1 (b) are configuration diagrams showing an external pressure type micro-module test device used in the examples.

FIG. 2 is a graph showing the influence of the order of addition of the cationic polymer and the inorganic flocculant on the water quality (MFF) of the coalescing treatment in Experimental Example 1. FIG.

Claims (10)

A water treatment method comprising adding an inorganic flocculant to a treated water and performing an agglomeration treatment to perform membrane separation using a membrane separation device. The water treatment method is characterized by adding an average mass after adding an inorganic flocculant to the treated water. The water-soluble cationic polymer with a molecular weight of 100,000 to 8 million is subjected to a coacervation treatment, and a membrane separation device is used to directly perform membrane separation on the cohesion-treated water. The water treatment method according to item 1 of the scope of patent application, wherein the water to be treated is industrial water, urban water, any one of phosphorus, biological metabolites, organic acids with chelation, and inorganic carbon, Well water, industrial drainage or biologically treated water for drainage. The water treatment method according to item 1 or item 2 of the patent application scope, wherein the membrane separation device is a precision filtration membrane separation device or an ultrafiltration membrane separation device. The water treatment method according to any one of claims 1 to 3, wherein the treated water obtained by using the membrane separation device is further subjected to reverse osmosis membrane treatment. The water treatment method according to any one of claims 1 to 4, wherein the treated water is titrated with the cationic polymer by a flow potential method, thereby neutralizing the water. The necessary amount of the cationic polymer required for the charge of the water to be treated is taken as the cation consumption amount A, and the added concentration of the cation consumption amount A and the inorganic flocculant and the cationic polymer satisfies the following relationship The manner of formula (I) controls the addition amount of the cationic polymer and the addition amount of the inorganic coagulant; Cation consumption A × α = Cationic polymer added concentration (mg / L) + inorganic flocculant added concentration (mg / L) × β ··· (I) α: Factor of safety taking into account changes in water quality β: Coefficient for converting the cation amount of the inorganic agglomerating agent into the cation amount of the cationic polymer. A water treatment device, comprising: a first agglomeration treatment mechanism for adding an inorganic coagulant to the water to be treated for agglomeration treatment; and a second agglomeration treatment mechanism for adding a mass average molecular weight to the agglomeration treatment water of the first agglomeration treatment mechanism. 100,000 to 8 million water-soluble cationic polymers are subjected to aggregation treatment; and a membrane separation device directly performs membrane separation on the aggregation treatment water of the second aggregation treatment mechanism. The water treatment device according to item 6 of the scope of patent application, wherein the water to be treated is industrial water, urban water, any one of phosphorus, biological metabolites, organic acids with chelation, and inorganic carbon, Well water, industrial drainage or drainage organisms, and industrial water, municipal water, well water, industrial drainage or drainage biological treatment water containing any of inorganic carbon. The water treatment device according to item 6 or item 7 of the patent application scope, wherein the membrane separation device is a precision filtration membrane separation device or an ultrafiltration membrane separation device. The water treatment device according to any one of claims 6 to 8 of the patent application scope, further comprising a reverse osmosis membrane separation device that treats the treated water obtained by the membrane separation device. The water treatment device according to any one of claims 6 to 9 of the patent application scope, further comprising a mechanism for titrating the water to be treated by the cationic polymer by a flow potential method, thereby obtaining A necessary amount of the cationic polymer required to neutralize the charge of the water to be treated is taken as the cation consumption A, and the added concentration of the inorganic agglomerating agent and the cationic polymer satisfies the following relational expression ( The method of I) controls the addition amount of the cationic polymer and the addition amount of the inorganic coagulant; Cation consumption A × α = Cationic polymer added concentration (mg / L) + inorganic flocculant added concentration (mg / L) × β ··· (I) α: Factor of safety taking into account changes in water quality β: Coefficient for converting the cation amount of the inorganic agglomerating agent into the cation amount of the cationic polymer.