TW201708122A - Coagulant and water treatment method - Google Patents

Abstract

Provided is a water treatment wherein water containing organic matter is coagulated and solids and liquids are separated before the water is subjected a membrane separation treatment or an ion-exchange resin treatment. In this water treatment, substances in the water that could contaminate the separation membrane or the ion-exchange resin, such as high polymer organic substances and humic substances, are subjected to an efficient coagulation treatment, and then the solids and liquids are thoroughly separated, thereby minimizing decreases in the performance of the membrane separation treatment or the ion-exchange resin treatment and consequently allowing stable and efficient water treatment over a long period of time. A coagulant containing a melamine-aldehyde condensation product is added. It is preferable for the coagulant to be an acidic solution of the melamine-aldehyde condensation product, wherein the molecular weight of the melamine-aldehyde condensation product is within the range of 400-10,000,000 and the colloidal particle diameter is within the rage of 5-500nm.

Description

Coagulant and water treatment method

The present invention relates to a coagulant and a water treatment method for efficiently performing coagulation treatment on various industrial drainage or domestic drainage or organic matter contained in treated water such as biologically treated water or surface water or groundwater. Specifically, the present invention relates to a coagulating agent which is added to the water to be treated, and a coagulating agent which is subjected to a coagulation and solid-liquid separation treatment as a process for performing a membrane separation treatment or an ion exchange resin treatment on an organic water-containing treated water. The water treatment method of the coagulant.

i) In order to obtain pure water from drainage or surface water or groundwater, membrane separation treatment or ion exchange resin treatment is used as a treatment for removing impurities or ions. Prior to such a water treatment step, a pretreatment for coagulation and solid-liquid separation treatment of a water-soluble organic substance for reducing a pollutant causing a decrease in the treatment property of a film or a resin is widely performed.

Ii) Examples of the pollutants include biological metabolites (polysaccharides, proteins), humic plants (humic acid, fulvic acid), etc., and these polymer organic substances adhere to the fine filtration membrane during membrane separation treatment. Ultrafiltration membrane, membrane surface of reverse osmosis membrane or flow path of closed membrane module, And cause a decrease in the amount of penetrating water. Further, in the ion exchange resin treatment, it is adsorbed to the ion exchange resin to cause regeneration failure.

Iii) In the past, inorganic coagulants such as ferric chloride or polyaluminum chloride were gradually used in the treatment to remove contaminants. However, in the coagulation treatment with only the inorganic coagulant, a large amount of coagulant is required, resulting in an increase in the amount of sludge generated. Although an inorganic coagulant and a cationic polymer coagulant have been tried and used to reduce the amount of sludge generated (for example, Patent Document 1), the effect of coagulation removal with respect to biological metabolites is still insufficient.

Iv) After coagulation and solid-liquid separation treatment of treated water containing organic matter, especially high molecular organic matter derived from biological metabolites, membrane separation treatment is carried out in the latter stage, especially reverse osmosis membrane separation treatment. In the water treatment, the removal of the polysaccharide by the coagulation treatment is insufficient (Non-Patent Document 1), and the remaining polysaccharide not only lowers the water permeability of the reverse osmosis membrane but also causes the irreversible scale.

According to the results of investigations conducted by the inventors of the present invention, it has been found that the performance of the ion exchange resin is lowered by the adsorption of the humus plant material to the anion exchange resin. Specifically, by organic carbon detection type size exclusion chromatography (LC-OCD) and three-dimensional fluorescence spectrometry, it is known that the concentration of humic plant matter is reduced before and after the water passing through the ion exchange resin, so that the adsorption of humic substances can be confirmed. For the resin. As a result of experiments conducted by the present inventors, it has been found that when water containing humic plant matter is passed through the ion exchange resin, the humic plant material is adsorbed, and as shown in Fig. 1, the total exchange capacity and the neutral salt decomposition energy are reduced.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2013-202452

Non-Patent Document 1: Tambo et al. Water Research, Vol. 12 (1978), 931-950

An object of the present invention is to provide a coagulating agent and a water treatment method using the coagulating agent, which is subjected to coagulation and solid-liquid separation treatment as a membrane separation treatment or an ion exchange resin treatment of treated water containing organic substances. At the time of the previous treatment, the coagulant added to the water to be treated can efficiently coagulate the polymer organic matter or the humus plant material in the water to be treated which is the contamination factor of the subsequent stage or the ion exchange resin.

The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, it has been found that by using a melamine-aldehyde condensate as a coagulant, it is possible to efficiently coagulate high molecular organic substances or humus plants in the water to be treated. Highly solid-liquid separation, thus completing the present invention.

The present invention is mainly directed to the following.

[1] a coagulating agent which is subjected to coagulation and solid-liquid separation treatment as a coagulant added to the water to be treated when subjected to a membrane separation treatment or an ion exchange resin treatment for the water containing the organic substance, It is characterized by containing a melamine-aldehyde condensate.

[2] The coagulant according to [1], which is an acid solution of a melamine-aldehyde condensate.

[3] The coagulant according to [1] or [2], wherein the aforementioned melamine-aldehyde The molecular weight of the condensate is in the range of 400 to 10,000,000 or the colloidal particle diameter is in the range of 5 to 500 nm.

[4] The coagulant according to any one of [1] to [3] wherein the water to be treated contains a polymer organic substance having a molecular weight of 10,000 or more and/or a humus plant material.

[5] The coagulant according to any one of [1] to [4] wherein the content of the free aldehyde in 1 g of the aforementioned melamine-aldehyde condensate is 7 mg or less.

[6] The coagulant according to [5], wherein the aldehyde removal treatment is carried out by an ultrafiltration membrane treatment or a dialysis membrane treatment.

[7] A water treatment method in which a coagulant is added to a water to be treated containing an organic substance to carry out coagulation, solid-liquid separation treatment, and the obtained separated water is subjected to a membrane separation treatment or an ion exchange resin treatment. It is characterized in that the coagulating agent according to any one of [1] to [6] is used as the coagulating agent.

[8] The water treatment method according to [7], wherein the water to be treated contains a polymer organic substance having a molecular weight of 10,000 or more and/or a humus plant material.

[9] The water treatment method according to [7] or [8] wherein the solid-liquid separation treatment is any one of a precipitation treatment, a pressure floating treatment, a filtration treatment, and a membrane separation treatment.

[10] The water treatment method according to any one of [7] to [9] wherein an inorganic coagulant is added to the treated water for coagulation before, after, or simultaneously with the addition of the coagulant. , solid-liquid separation treatment.

[11] The water treatment method according to any one of [7] to [10] wherein the membrane separation treatment after the coagulation and solid-liquid separation treatment is a reverse osmosis membrane Off processing.

[12] The water treatment method according to any one of [7] to [11] wherein hydrogen sulphite and/or the salt is added to the condensed treated water after the addition of the coagulating agent.

[13] The water treatment method according to [12], wherein the hydrogen sulfite and/or the salt is added to the condensed water before the solid-liquid separation or the separated water after the solid-liquid separation, and the separation is performed by the separation The aldehyde concentration of the treated water obtained by the membrane separation treatment or the ion exchange resin treatment of water is set to 0.01 mg/L or less.

According to the present invention, in the water treatment for performing the membrane separation treatment or the ion exchange resin treatment after coagulation and solid-liquid separation of the water containing the organic substance, the substance which is a cause of contamination of the separation membrane or the ion exchange resin can be The high-molecular organic matter or the humus plant material in the water is treated efficiently, and the coagulation treatment is efficiently performed, and this highly solid-liquid separation is performed, so that the performance of the membrane separation treatment or the ion exchange resin treatment can be suppressed from being lowered, and the stability and the efficiency are covered for a long period of time. Water treatment.

1‧‧‧ container

1A‧‧‧ Raw Water Room

1B‧‧‧ penetrating water room

2‧‧ ‧ flat membrane unit

3‧‧‧Agitator

Fig. 1 is a graph showing the reduction rate of the total exchange capacity and the neutral salt decomposition energy with respect to the amount of water passing through the ion exchange resin when the water containing the humic plant material is passed.

Fig. 2 is a schematic view showing the RO flat film evaluation device used in the examples.

Fig. 3 is a graph showing the results of Example 4-1 and Comparative Example 4-1.

Fig. 4 is a graph showing the results of Example 5-1 and Comparative Example 5-1.

Hereinafter, embodiments of the present invention will be described in detail.

[Mechanism]

The mechanism of action of the present invention is as follows.

When the melamine-aldehyde condensate contained in the acid solution of the melamine-aldehyde condensate is added to the water to be treated, the pH of the melamine-aldehyde condensate rises and forms insolubilization, and the organic substance, especially the polysaccharide bond, with the water to be treated The state of the knot is gathered. As a result, the polysaccharide, protein, humus, and the like which are the cause of contamination of the separation membrane or the ion exchange resin can be efficiently coagulated and removed.

[melamine-aldehyde condensate]

The melamine-aldehyde condensate used in the present invention is used as an acid solution of a melamine-aldehyde condensate, specifically, an acid colloidal solution of a melamine-aldehyde condensate or an acid solution of a low molecular melamine-aldehyde condensate. .

In particular, the melamine-aldehyde condensate is preferably used as an acid colloidal solution of a melamine-aldehyde condensate. In this case, the melamine-aldehyde condensate which is dissolved in the colloidal state in the acid solution forms a core which is insolubilized and becomes a condensate immediately with an increase in pH, so that a high coagulation effect can be expected.

The acid solution of the melamine-aldehyde condensate may be further prepared by adding an acid to methylol melamine obtained by reacting melamine with an aldehyde. However, if necessary, the methylol melamine may be further alkylated and then an acid may be added.

The aldehyde to be used in the reaction may, for example, be formaldehyde, paraformaldehyde, acetaldehyde or propionaldehyde. Among them, formaldehyde or formaldehyde is preferred in terms of reaction efficiency or handleability.

Examples of the production of an acid solution of a melamine-aldehyde condensate, in particular, the production of an acid colloid solution of a melamine-aldehyde condensate include the following methods.

The ratio of the melamine to the aldehyde in the production of methylol melamine is preferably 1 to 6 moles per aldehyde based on 1 mole of melamine. However, when the aldehyde is more than 2.5 mol with respect to melamine 1 mol, the amount of free aldehyde increases when the acid colloid solution is formed, so the aldehyde is preferably set to 2.5 mol or less with respect to melamine 1 mol.

The obtained methylol melamine is insoluble in water but dissolves in a colloidal state in an acid solution. The alkylated methylol melamine obtained by further alkylating the methylol melamine is water-soluble, and when it is added with an acid, it is colloidal.

The acid used herein, a single protonic acid is suitable. Specifically, in addition to the mineral acid such as hydrochloric acid or nitric acid, an organic acid such as formic acid, acetic acid, lactic acid or propionic acid may be mentioned. In particular, hydrochloric acid is preferred because it provides a stable colloidal solution.

The amount of monoprotic acid, especially hydrochloric acid, is about 0.5 to 1.5 moles, preferably 0.7 to 1.3 moles, relative to melamine 1 mole.

At the initial stage of the preparation of the colloidal solution, the free aldehyde is present in a large amount, and after preparation, it is placed at room temperature to be aged, and the free aldehyde is reduced. The aging time is preferably about 5 days to 3 months at room temperature, and about 2 to 3 hours at 50 ° C when heating is performed.

The content of the melamine-aldehyde condensate in the acid solution of the melamine-aldehyde condensate is usually 5 to 20% by weight and the pH is about 1.5 to 2.5.

The melamine-aldehyde condensate used in the present invention has a molecular weight of 400 to 10,000,000, particularly preferably in the range of 1,000 to 100,000. When the molecular weight of the melamine-aldehyde condensate is large, the coagulation effect tends to be excellent. However, when the acid solution is too large, the solubility of the melamine-aldehyde condensate is lowered. The molecular weight of the melamine-aldehyde condensate can be determined, for example, by the method described in the item of the examples described later.

The melamine-aldehyde condensate used in the present invention preferably has a colloidal particle diameter of 5 to 50 nm, particularly preferably 10 to 30 nm, in the formation of an acid colloid solution. When the colloidal particle size is larger, the coagulation effect becomes excellent, but if it is too large, the total surface area of the added colloid becomes small, and the efficiency is deteriorated. The colloidal particle size of the acid colloidal solution of the melamine-aldehyde condensate can be determined, for example, by dynamic light scattering, and can be obtained as the average value.

The melamine-aldehyde condensate produced by the above method may be contained in the aldehyde of the raw material to be produced, or may be freed from the melamine-aldehyde condensate to contain the aldehyde during storage. The aldehyde contained in the melamine-aldehyde condensate is contained in the coagulated water and is further contained in the solid-liquid separation water. However, the aldehyde, especially formaldehyde, is low-molecular weight and has no charge, so the reverse osmosis in the latter stage ( RO) cannot be sufficiently removed in the film treatment or ion exchange resin treatment. For example, when the treated water obtained by the water treatment of the present invention is used as raw water of ultrapure water, the TOC of the treated water is preferably kept at 0.01 mg/L or less, but when formaldehyde is mixed, the TOC cannot be sufficiently lowered. Therefore, when the coagulant of the present invention is used, it is preferred to purify the melamine-aldehyde condensate to lower the aldehyde content. In this case, the method for purifying the melamine-aldehyde condensate may be a membrane treatment using an ultrafiltration membrane or a dialysis membrane having a molecular weight cut off of about 500 to 1,000,000. Further, as described later, formaldehyde can also be converted to hydroxymethanesulfonate by treatment with hydrogen sulfite. Hydroxymethane sulfonate, because of its negative charge, can be easily removed by RO membrane treatment or ion exchange resin treatment.

When the aldehyde in the melamine-aldehyde condensate is removed by purification, the content of the aldehyde in 1 g of the melamine-aldehyde condensate is preferably 7 mg or less, and particularly preferably 4 mg or less.

The content of the aldehyde in the melamine-aldehyde condensate can be quantified by the method described in the item of the examples below.

[treated water]

The treated water subjected to the coagulation treatment in the present invention contains an organic substance, In particular, water containing a high molecular weight organic substance or a humus plant having a molecular weight of 10,000 or more may, for example, be various industrial drainage or domestic drainage or biological treatment water, surface water or ground water of the drainage. The concentration of the organic substance in the water to be treated is not particularly limited, and when the water is used as the water to be treated, the content of the polymer organic substance or the humus plant having a molecular weight of 10,000 or more in the water to be treated is 0.1 mg/L or more. For example, it is about 0.1~1mg/L.

The water to be treated is subjected to coagulation treatment by the coagulating agent of the present invention, followed by solid-liquid separation, and then the separated water is subjected to a membrane separation treatment or an ion exchange resin treatment.

[condensation treatment]

When the acid solution of the melamine-aldehyde condensate of the coagulant of the present invention is added to the water to be treated containing the organic substance to be coagulated, the amount of addition is different depending on the organic content of the water to be treated, but it is an active ingredient ( The amount of the melamine-aldehyde condensate added is preferably 0.1 to 5 mg/L, particularly preferably 0.2 to 2 mg/L. When the amount of addition is too small, a sufficient coagulation effect cannot be obtained. When the amount is too large, the unreacted melamine-aldehyde condensate remains, and the concentration of the organic substance in the treated water is increased.

When the acid solution of the melamine-aldehyde condensate is added, the pH of the water to be treated is preferably near neutral, and particularly preferably pH 4 or higher, and pH 5 to 10. This is because when the pH is too low, the melamine-aldehyde condensate is not easily insolubilized, and the coagulation ability is lowered. When the pH exceeds 10, not only the cost of the pH adjuster increases, but also the salt concentration increases during neutralization, which is not appropriate.

Therefore, after the acid solution of the melamine-aldehyde condensate is added to the water to be treated, a base such as sodium hydroxide may be added as needed, and the pH may be adjusted to carry out a coagulation treatment.

In the present invention, the coagulation treatment may be carried out together with the melamine-aldehyde condensate using an inorganic coagulant or an organic polymer coagulant. In this case, the inorganic coagulant and the organic polymer coagulant may be added before the addition of the melamine-aldehyde condensate acid solution, or after the addition of the melamine-aldehyde condensate acid solution, or may be condensed with the addition of melamine-aldehyde. The acid solution of the substance is added at the same time.

Examples of the inorganic coagulant to be used together include aluminum chloride, aluminum sulfate, iron chloride, and ferrous sulfate. Further, the organic polymer coagulant is preferably a acrylamide-based or an anionic organic polymer coagulant, and examples thereof include polyacrylamide, polymethacrylamide, polyacrylic acid, and polyvinylsulfonic acid. These may be used alone or in combination of two or more.

When the inorganic coagulant is used in combination, the amount of the inorganic coagulant added varies depending on the quality of the water to be treated and the type of the inorganic coagulant to be used, but the amount of the inorganic coagulant added is preferably about 5 to 100 mg/L. Further, although the amount of the organic polymer coagulant used in combination is different depending on the quality of the water to be treated or the type of the organic polymer coagulant to be used, the amount of the organic polymer coagulant added is preferably about 1~ 20mg/L.

When the inorganic coagulant is used in combination, the pH during the coagulation treatment is set to a pH suitable for the coagulation treatment of the inorganic coagulant in the pH range depending on the type of the inorganic coagulant to be used. For example, when it is an iron-based inorganic coagulant, the pH is preferably about 4 to 10, and when it is an aluminum-based inorganic coagulant, the pH is higher. Good about 4~8.

The coagulation treatment of the present invention is usually carried out for about 2 to 30 minutes under stirring.

[solid-liquid separation]

In the present invention, the solid-liquid separation method of the coagulation-treated water is not particularly limited, and solid-liquid separation can be carried out by a precipitation treatment, a pressure-floating treatment, a filtration treatment, a membrane separation treatment, or the like according to a usual method. Two or more of these may be combined to perform solid-liquid separation.

[Hydroxysulfite treatment]

In order to remove the aldehyde which is present in the melamine-aldehyde condensate or freed from the melamine-aldehyde condensate, hydrogen sulfite treatment can be carried out.

That is, hydrogen sulfite or hydrogen sulfite (hereinafter referred to as "hydrogen sulfite (salt)") may be added to the condensed water or the separated water obtained by separating the solid liquid to condense the melamine-aldehyde. The aldehyde, especially formaldehyde, which is carried in the coagulated water, is converted to hydroxymethanesulfonate. The hydroxymethanesulfonate can be easily removed by RO membrane treatment or ion exchange resin treatment as described above without affecting the TOC of the treated water.

In this case, the amount of hydrogen sulfite (salt) added may be appropriately adjusted depending on the aldehyde content in the coagulation treatment water, and is preferably an aldehyde of an aqueous solution obtained by subjecting the solid-liquid separation water to membrane separation treatment or ion exchange resin treatment. The concentration is added in an amount of 0.01 mg/L or less.

[post-processing]

In the present invention, the separated water obtained by coagulating the treated water and solid-liquid separation as described above is subjected to a membrane separation treatment or an ion exchange resin treatment.

This membrane separation treatment is particularly excellent for RO membrane separation treatment.

According to the present invention, since the polymer organic matter or the humus plant material in the water to be treated which is a contamination cause of the separation membrane or the ion exchange resin can be highly removed by the condensation and solid-liquid separation treatment in the preceding stage, the membrane separation treatment or In the ion exchange resin treatment, the performance of the separation membrane or the ion exchange resin can be suppressed from being lowered, and the stable and efficient water treatment for a long period of time can be covered.

Example

The invention will be more specifically described by the following examples and comparative examples.

In the following examples and comparative examples, the coagulant was used as follows. The amount of the inorganic coagulant to be added shown below is the amount of the aqueous solution added.

<Inorganic Coagulant>

Ferric chloride (FeCl ₃ , 38% by weight aqueous solution)

Polyaluminium chloride (PAC, 10% by weight aqueous solution)

<melamine-aldehyde condensate>

MF-1: acid colloidal solution of melamine-aldehyde condensate

2 mol of formaldehyde was reacted with methylolated melamine 0.05 mol obtained from melamine 1 mol, and added to 100 ml of a 1.35 wt% hydrochloric acid aqueous solution (relative to melamine 1 mol, 0.75 mol hydrochloric acid) and matured. (melamine-formaldehyde condensate content 10% by weight, pH 2)

MF-2: acid solution of low molecular melamine-aldehyde condensate: a methylated melamine-formaldehyde condensate (weight average molecular weight 432, Sigma Aldrich) dissolved in 0.1 M hydrochloric acid aqueous solution (melamine-formaldehyde condensate 10% by weight, pH1)

The molecular weight of the acid colloid of the melamine-aldehyde condensate contained in the MF-1 is calculated from the diffusion coefficient caused by the peak of the particle diameter obtained by the dynamic light scattering method, and the converted molecular weight is calculated by the following conversion formula (Japanese film). Learn (edit), design method of membrane separation program). The result was a molecular weight of 6.6 million.

D=8.76×10 ^-9 (Mw) ^-0.48

(D: diffusion coefficient (m ² /s), Mw: molecular weight)

<Example 1-1>

As the water to be treated, concentrated water (containing 0.1 mg/L of a polymer organic substance having a molecular weight of 10,000 or more) obtained by subjecting the biologically treated water to RO membrane treatment was used.

500 mL of water to be treated at 25 ° C was placed in a beaker, and stirred at 150 rpm for 5 minutes, and MF-1 was added so that the concentration of the active ingredient became 1 mg/L, and then 20 mg/L of an aqueous solution of FeCl _{3 was} added thereto, and sodium hydroxide was used. The aqueous solution was adjusted to pH 5.5. It was then stirred at 50 rpm for 10 minutes to carry out a coagulation treatment. The water after the coagulation treatment was filtered with a hydrophilic PTFE (polytetrafluoroethylene) syringe filter having a pore size of 0.45 μm to carry out solid-liquid separation. The filtered water was analyzed by LC-OCD to calculate the peak area of the organic carbon component having a molecular weight of 10,000 or more. Glucan was used as a molecular weight marker. The removal rate of the organic matter was calculated by the following formula.

Removal rate (%) = (1 - the peak area of the organic carbon component of the coagulated water / the peak area of the organic carbon component of the uncondensed treated water) × 100

<Example 1-2>

The coagulation treatment was carried out in the same manner as in Example 1-1 except that MF-2 was added instead of MF-1, and the removal rate of the organic matter was determined.

<Comparative Example 1-1>

The coagulation treatment was carried out in the same manner as in Example 1-1 except that the same amount of pure water was added instead of MF-1, and the removal rate of the organic matter was determined.

<Comparative Example 1-2>

Aside from the addition of 1 mg/L of a cationic organic polymer coagulant poly(2-methylpropenyloxyethyltrimethylammonium) (PMETMA, molecular weight 9 million) instead of MF-1, In the same manner, the coagulation treatment was carried out, and the removal rate of the organic matter was determined.

<Comparative Example 1-3>

In addition to the addition of 1 mg / L of cationic organic polymer coagulant poly(2-methylpropenyloxyethyl)-N-benzyl-N,N-dimethylammonium) (PMEBMA, molecular weight 10 million) to replace Other than MF-1, the coagulation treatment was carried out in the same manner as in Example 1-1, and the removal rate of the organic matter was determined.

<Example 2-1>

In Example 1-1, a 20 mg/L aqueous solution of PAC was added to replace the FeCl ₃ aqueous solution, and the pH was adjusted to 6.5 using an aqueous sodium hydroxide solution, and the coagulation treatment was carried out in the same manner as in Example 1-1. And the removal rate of organic matter is obtained.

<Comparative Example 2-1>

The coagulation treatment was carried out in the same manner as in Example 2-1 except that the same amount of pure water was added instead of MF-1, and the removal rate of the organic matter was determined.

<Example 3-1>

In the same manner as in Example 1-1, the coagulation treatment was carried out in the same manner as in Example 1-1 except that the aqueous solution of FeCl _{3 was} not added and the pH was adjusted to 7.0 using a sodium hydroxide aqueous solution. The removal rate of organic matter is obtained.

<Comparative Example 3-1>

The coagulation treatment was carried out in the same manner as in Example 3-1 except that 20 mg/L of an aqueous FeCl ₃ solution was added instead of MF-1, and the removal rate of the organic matter was determined.

The above results are shown in the first table.

From the first table, the following can be known.

From Example 1-1, Example 1-2, and Comparative Example 1-1, it was confirmed that the removal rate can be improved by adding a melamine-aldehyde condensate before the addition of the inorganic coagulant (FeCl ₃ ). Further, from Comparative Examples 1-2 and 1-3, it was found that even when the inorganic coagulant (FeCl ₃ ) and the cationic polymer coagulant were used in combination, almost no improvement in the removal rate was observed.

From Example 2-1 and Comparative Example 2-1, it was found that even if PAC was used as the inorganic coagulant, the addition of the melamine-aldehyde condensate showed a high removal rate.

From Example 3-1 and Comparative Example 3-1, it can be known that the neutral condition is The use of a melamine-aldehyde condensate showed a high removal rate compared to those using an inorganic coagulant.

<Example 4-1>

The guar gum (Guarcol F50, manufactured by Sanyo Pharmaceutical Trading Co., Ltd.), which is a model substance of the polysaccharide, was dissolved in pure water to prepare a 2 L aqueous solution of guar gum concentration of 1 mg/L and pH 6.5, and was charged in Beaker. The aqueous solution in the beaker was stirred at 150 rpm for 5 minutes, and MF-1 was added so that the concentration of the active ingredient became 1 mg/L, and then the pH was adjusted to 6.5 using an aqueous sodium hydroxide solution. It was then stirred at 50 rpm for 10 minutes to carry out a coagulation treatment. The water after the coagulation treatment was suction-filtered with a cellulose acetate membrane having a pore diameter of 0.45 μm to carry out solid-liquid separation.

Using the RO flat membrane evaluation apparatus shown in Fig. 2, the filtered water was passed through under the following water-passing conditions, and the change in flux with time was measured.

<Measurement conditions>

Supply water flow: 0.7mL/min

Water temperature: 25 ° C

Recovery rate: 80%

In the flat film testing device, the flat film unit 2 is disposed at an intermediate position in the height direction of the bottomed lid-shaped cylindrical container 1, and the inner portion of the container is partitioned into the raw water chamber 1A and the penetrating water chamber 1B. The container 1 is placed on the agitator 3, and the supply water (filtered water) is supplied to the raw water chamber 1A via the pipe 11 by the pump 4, and the agitating member 5 in the container 1 is rotated to stir In the raw water chamber 1A, from the penetrating water chamber 1B, the penetrating water is taken up between the pipes 12, and the concentrated water is taken up from the raw water chamber 1A through the pipe 13. A pressure gauge 6 is provided in the supply water supply pipe 11, and an on-off valve 7 is provided in the concentrated water extraction pipe 13.

In the flat membrane unit 2, a polyamine-based RO membrane having a membrane area of 8 cm ² was provided ("ES-20" manufactured by Nitto Denko Corporation).

The recovery rate and the flux were calculated by the following formula. The same applies to Example 6-1 which will be described later.

Recovery rate [%] = (penetrating water flow [mL / min] / supply water flow [mL / min]) × 100

Flux [m ³ /(m ² ‧d)] = penetrating water flow [m ³ /d] / membrane area [m ² ] × temperature conversion factor [-]

<Comparative Example 4-1>

The coagulation treatment was carried out in the same manner as in Example 4-1 except that the same amount of pure water was added instead of MF-1, and the flux of the filtered water obtained was measured as a function of time.

<Example 5-1>

Canadian Fulvic (manufactured by PIC Bio Inc.), a model substance of humic plant material, was dissolved in pure water to obtain 1 mg/L, and 2 L of an aqueous solution of pH 6.5 containing 10 mg/L of calcium was prepared and placed in a beaker. After stirring the aqueous solution in the beaker at 150 rpm for 5 minutes, MF-1 was added so that the concentration of the active ingredient became 1 mg/L, and then the pH was adjusted using an aqueous sodium hydroxide solution. Adjust to 6.5. It was then stirred at 50 rpm for 10 minutes to carry out a coagulation treatment. The water after the coagulation treatment was suction-filtered with a cellulose acetate membrane having a pore diameter of 0.22 μm to carry out solid-liquid separation. For this filtered water, the same change in flux was measured using the same RO flat film evaluation device as in Example 4-1.

<Comparative Example 5-1>

The coagulation treatment was carried out in the same manner as in Example 5-1 except that the same amount of pure water was added instead of MF-1, and the flux of the obtained filtered water was measured with time.

The results of Example 4-1 and Comparative Example 4-1 are shown in Fig. 3, and the results of Example 5-1 and Comparative Example 5-1 are shown in Fig. 4.

From Fig. 3 and Fig. 4, it was found that the reduction of the flux can be suppressed by adding the melamine-aldehyde condensate to the guar gum solution or the Canadian Fulvic solution. By adding a melamine-aldehyde condensate and filtering it, it was confirmed that the polysaccharide of the membrane fouling substance and the humus plant substance can be coagulated and removed.

<Example 6-1>

The ultrafiltration membrane was used to purify MF-1. Specifically, 6 mL of MF-1 was placed in a centrifugal ultrafiltration unit (Amicon Ultra, manufactured by Millipore Corporation) having a molecular weight cut off of 3,000, followed by the addition of 9 mL of an acidic solution (hydrochloric acid was added to pure water and adjusted to pH 2). . Then, the centrifugal operation was performed at a gravity acceleration of 2,500 G for 1 hour, and separated into a penetrating liquid and a concentrated liquid. Add the acidic solution to the concentrate to dilute to 15 mL, and then Centrifugal operation is performed. This step was repeated twice and the concentrate was recovered, whereby purified MF-1 was obtained.

The formaldehyde content of the purified MF-1 was determined by the following colorimetric quantification according to the acetonitrile method.

<Ethylacetone method>

Sample: water supply and penetrating water

Acetylacetone reagent: 15 g of ammonium acetate, 0.3 mL of acetic acid, and 0.2 mL of acetamidine acetone were dissolved in pure water and became 100 mL.

Quantitative method: Mix 5 mL of sample with acetamidine acetone, heat at 40 ° C for 30 min, and let stand for 30 min. Then, the absorbance at a wavelength of 413 nm was measured, and the formaldehyde content was calculated from a calibration curve prepared from a known aqueous formaldehyde solution.

After the purified MF-1 was added so that the concentration of the active ingredient became 1 mg/L, the pH was adjusted to 6.5 using an aqueous sodium hydroxide solution. The RO flat film evaluation device (polyamide-based RO film having a membrane area of 8 cm ² : "ES-20" manufactured by Nitto Denko Corporation) shown in Fig. ² was used, and MF-1 was added under the following water-passing conditions. The pure water passes through the water, and the formaldehyde content of the supplied water and the penetrating water is determined by the GC/MS method. Penetration of water, collected after 2 hours of water.

<Water conditions>

Supply water flow: 1.6mL/min

Water temperature: 25 ° C

Recovery rate: 75%

<Example 6-2>

A dialysis membrane was used to purify MF-1. Specifically, 6 mL of MF-1 was placed in a dialysis membrane unit (manufactured by Regenerated Cellulose, Thermo Fisher Scientific Co., Ltd.) having a molecular weight cut off of 7,000, and 5 L of an acidic liquid (hydrochloric acid was added to pure water and adjusted to pH 2). ) Perform 1 week of dialysis. The formaldehyde content of the purified MF-1 was determined by the acetonitrile method in the same manner as in Example 6-1.

<Example 6-3>

After adding unrefined MF-1 so that the concentration of the active ingredient became 1 mg/L, 10 mg/L of a 35 wt% aqueous sodium hydrogensulfite solution was added and mixed, and the pH was adjusted to 6.5 using an aqueous sodium hydroxide solution. This mixture was passed through a RO flat film evaluation apparatus in the same manner as in Example 6-1, and the formaldehyde content of the supplied water and the penetrating water was measured.

<Comparative Example 6-1>

The formaldehyde content of the unrefined MF-1 was determined by the acetonitrile method in the same manner as in Example 6-1.

In the same manner as in Example 6-1 except that unrefined MF-1 was used instead of the purified MF-1, water was supplied to the RO flat film evaluation apparatus, and the formaldehyde content of the supplied water and the penetrating water was measured.

The results of Examples 6-1 to 6-3 and Comparative Example 6-1 are shown in Table 2.

In Comparative Example 6-1, since unrefined MF-1 was used, the formaldehyde contained 2000 mg/L or more, and the formaldehyde contained in the supplied water was not sufficiently removed by the treatment with the RO membrane, and remained in the penetrating water.

In Example 6-1, MF-1 purified by an ultrafiltration membrane was used, so that the amount of formaldehyde can be reduced to 1/3 or less. Therefore, the amount of formaldehyde contained in the feed water and the penetrating water does not reach the detection lower limit value of the analysis, and it can be known that the TOC in the penetrating water can be reduced.

In Example 6-2, MF-1 was purified by a dialysis membrane, so that the amount of formaldehyde can be reduced to 1/40 or less. In this purification method, it is also expected to reduce the TOC in the water.

In Example 6-3, formaldehyde was reacted with sodium hydrogen sulfite, and as a result, hydroxymethanesulfonate was formed, and in the supply water and the penetrating water, the formaldehyde did not reach the detection lower limit.

The present application is based on a Japanese patent application filed on May 19, 2015 (Japanese Patent Application No. 2015-101956), which is incorporated herein by reference.

Claims (13)

A coagulating agent which is a coagulating agent which is added to the water to be treated when subjected to a coagulation and solid-liquid separation treatment as a process for performing a membrane separation treatment or an ion exchange resin treatment on the water containing the organic substance, and is characterized in that : Contains a melamine-aldehyde condensate. The coagulant of claim 1 which is an acid solution of a melamine-aldehyde condensate. The coagulant according to claim 1 or 2, wherein the melamine-aldehyde condensate has a molecular weight of 400 to 10,000,000 or a colloidal particle diameter of 5 to 500 nm. The coagulant according to any one of claims 1 to 3, wherein the water to be treated contains a polymer organic substance having a molecular weight of 10,000 or more and/or a humus plant material. The coagulant according to any one of claims 1 to 4, wherein the content of the free aldehyde in 1 g of the aforementioned melamine-aldehyde condensate is 7 mg or less. The coagulant of claim 5, wherein the aldehyde removal treatment is carried out by ultrafiltration membrane treatment or dialysis membrane treatment. A water treatment method is a water treatment method in which a coagulant is added to a treated water containing an organic substance to perform coagulation, solid-liquid separation treatment, and the obtained separated water is subjected to a membrane separation treatment or an ion exchange resin treatment, and is characterized in that The coagulant according to any one of claims 1 to 6 is used as the coagulant. The water treatment method according to claim 7, wherein the water to be treated contains a polymer organic substance having a molecular weight of 10,000 or more and/or a humus plant material. The water treatment method according to claim 7 or 8, wherein the solid-liquid separation treatment is any one of a precipitation treatment, a pressure floating treatment, a filtration treatment, and a membrane separation treatment. The water treatment method according to any one of claims 7 to 9, wherein an inorganic coagulant is added to the treated water for coagulation and solid-liquid separation before, after, or simultaneously with the addition of the coagulant. . The water treatment method according to any one of claims 7 to 10, wherein the membrane separation treatment after the coagulation and solid-liquid separation treatment is a reverse osmosis membrane separation treatment. The water treatment method according to any one of claims 7 to 11, wherein hydrogen sulphite and/or the salt is added to the condensed treated water after the addition of the coagulating agent. The water treatment method according to claim 12, wherein the hydrogen sulfite and/or the salt is added to the condensed water before the solid-liquid separation or the separated water after the solid-liquid separation, and the membrane is separated by the water. The aldehyde concentration of the treated water obtained by the separation treatment or the ion exchange resin treatment is set to 0.01 mg/L or less.