JP6015811B1 - Water treatment method and water treatment apparatus - Google Patents

Abstract

Polymers in water to be treated that cause contamination of separation membranes and ion exchange resins in water treatment in which water to be treated containing organic substances is agglomerated, solid-liquid separated, and then subjected to membrane separation treatment or ion exchange resin treatment By efficiently coagulating organic matter and humic substances and separating them to a high degree by solid-liquid separation, stable and efficient water treatment can be achieved over a long period of time by suppressing deterioration in the performance of membrane separation treatment or ion exchange resin treatment. Do. A flocculant containing a melamine aldehyde condensate is added as a flocculant. The flocculant is an acid solution of melamine / aldehyde condensate, and the molecular weight of the melamine / aldehyde condensate is preferably in the range of 400 to 10,000,000, and the colloidal particle size is preferably in the range of 5 to 500 nm. [Selection] Figure 3

Description

  The present invention relates to a flocculant and a water treatment method for efficiently agglomerating organic substances contained in various industrial wastewater, domestic wastewater, biologically treated water of the wastewater, surface water, groundwater, or the like. Specifically, the present invention relates to a flocculant to be added to the water to be treated when performing agglomeration and solid-liquid separation as a pretreatment when subjecting the water to be treated containing organic matter to membrane separation treatment or ion exchange resin treatment. And a water treatment method using the flocculant.

i) Membrane separation treatment and ion exchange resin treatment are used as advanced treatment for removing impurities and ions in order to obtain pure water from wastewater, surface water, and groundwater. Prior to these water treatment steps, pretreatment by agglomeration and solid-liquid separation treatment for reducing water-soluble organic substances, which are contaminants that degrade the treatment performance of membranes and resins, is widely performed.

ii) Examples of pollutants include biological metabolites (polysaccharides, proteins), humic substances (humic acid, fulvic acid), etc. These high molecular organic substances are not suitable for microfiltration membranes, Adhering to the membrane surface of the outer filtration membrane or reverse osmosis membrane, or blocking the flow path of the membrane module, causes a decrease in the amount of permeated water. Further, in the ion exchange resin treatment, it is adsorbed on the ion exchange resin to cause regeneration failure.

iii) Conventionally, inorganic flocculants such as ferric chloride and polyaluminum chloride have been used for pretreatment to remove contaminants. However, in the flocculation process using only the inorganic flocculant, a large amount of inorganic flocculant is required, which leads to an increase in the amount of sludge generated. Attempts have been made to reduce the amount of sludge generated by using an inorganic flocculant and a cationic polymer flocculant in combination (for example, Patent Document 1), but the aggregation removal effect on biological metabolites is sufficient. It wasn't.

iv) Water treatment that includes organic matter, especially treated water that contains macromolecular organic matter derived from biological metabolites, followed by agglomeration and solid-liquid separation treatment followed by membrane separation treatment, particularly reverse osmosis membrane separation treatment In this case, the removal of the polysaccharide by the coagulation treatment is insufficient (Non-patent Document 1), and the remaining polysaccharide decreases the water permeability of the reverse osmosis membrane and becomes a causative substance that causes irreversible fouling. ing.

  Moreover, also in ion exchange resin, as a result of investigation by the present inventors, it has been found that the performance of the ion exchange resin is deteriorated due to adsorption of humic substances to the anion exchange resin. Specifically, the organic matter detection type size exclusion chromatography (LC-OCD) and the three-dimensional fluorescence spectroscopy reduce the concentration of the humic substance before and after the ion exchange resin flow, so that the humic substance is reduced. It has been confirmed that it is adsorbed by the resin. As a result of the tests conducted by the present inventors, when water containing humic substance is passed through an ion exchange resin, the humic substance is adsorbed, and as shown in FIG. 1, the total exchange capacity and neutral salt resolution are reduced. This knowledge has been obtained (Fig. 1).

JP 2013-202452 A

Tambo et al. Water Research, Vol. 12 (1978), 931-950

  The present invention provides a flocculating agent to be added to the water to be treated when the water to be treated containing organic matter is subjected to a membrane separation treatment or an ion exchange resin treatment as a pretreatment or a solid-liquid separation treatment. To provide a flocculant capable of efficiently aggregating high-molecular organic substances and humic substances in water to be treated, which is a cause of contamination of separation membranes and ion exchange resins, and a water treatment method using this aggregating agent. Let it be an issue.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have effectively agglomerated the polymer organic matter and humic substances in the water to be treated by using a melamine / aldehyde condensate as a flocculant. The present inventors have found that this can be highly solid-liquid separated and completed the present invention.
That is, the gist of the present invention is as follows.

[ 1 ] In a water treatment method in which a coagulant is added to water to be treated containing an organic substance to perform coagulation and solid-liquid separation treatment, and the resulting separated water is subjected to reverse osmosis membrane separation treatment or ion exchange resin treatment, Water containing a flocculant containing a melamine aldehyde condensate and adding bisulfite and / or a salt thereof to the agglomerated water before the solid-liquid separation or the separated water after the solid-liquid separation. Processing method.

[ 2 ] The water treatment method according to [ 1 ], wherein the water to be treated contains a high molecular weight organic substance having a molecular weight of 10,000 or more and / or a humic substance.

[ 3 ] The water treatment method according to [ 1 ] or [ 2 ], wherein the solid-liquid separation treatment is any one of a precipitation treatment, a pressure levitation treatment, a filtration treatment, and a membrane separation treatment.

[ 4 ] In any one of [ 1 ] to [ 3 ], before or after the addition of the flocculant, or simultaneously with the addition, an inorganic flocculant is added to the water to be treated for aggregation and solid-liquid separation. A water treatment method characterized by the above.

[ 5 ] In any one of [1] to [4], an aldehyde concentration of treated water obtained by the reverse osmosis membrane separation treatment or the ion exchange resin treatment with the addition of the bisulfurous acid and / or a salt thereof is 0.01 mg. / L or less, The water treatment method characterized by the above-mentioned.

  According to the present invention, water to be treated containing organic matter is agglomerated, solid-liquid separated, and then subjected to membrane separation treatment or ion exchange resin treatment. High-molecular organic substances and humic substances can be efficiently agglomerated and separated into a highly solid-liquid separation. This suppresses the performance degradation of membrane separation or ion-exchange resin treatment and is stable and efficient for a long time. Water treatment.

It is a graph which shows the fall rate of the total exchange capacity | capacitance with respect to the amount of water flow, and neutral salt resolution | decomposability when water containing humic substance is passed through an ion exchange resin. It is a schematic diagram which shows the RO flat membrane evaluation apparatus used in the Example. It is a graph which shows the result of Example 4-1 and Comparative Example 4-1. It is a graph which shows the result of comparative example 5-1 and comparative example 5-1.

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

[Action mechanism]
The operation mechanism according to 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 melamine / aldehyde condensate is insolubilized as the pH increases, and in a state of being bound to organic substances in the water to be treated, particularly polysaccharides. To meet. As a result, it is possible to efficiently aggregate and remove polysaccharides, proteins, humic substances, and the like, which are contaminants of separation membranes and ion exchange resins.

[Melamine aldehyde condensate]
The melamine / aldehyde condensate used in the present invention is used as an acid solution of melamine / aldehyde condensate, specifically, an acid colloid solution of melamine / aldehyde condensate or an acid solution of low molecular weight melamine / aldehyde condensate. Is done.
In particular, the melamine / aldehyde condensate is preferably used as an acid colloid solution of the melamine / aldehyde condensate. This is because the melamine aldehyde condensate dissolved in a colloidal state in the acid solution is immediately insolubilized as the pH rises and becomes a nucleus of the aggregate, so that a high aggregation effect can be expected.

  The acid solution of the melamine / aldehyde condensate is produced by further adding acid to methylolmelamine obtained by reacting melamine and aldehyde. May be added.

  Examples of the aldehyde used in the reaction include formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, etc. Among them, formaldehyde and paraformaldehyde are preferable in terms of reaction efficiency and handleability.

  As an example of the production of an acid solution of a melamine / aldehyde condensate, the following method may be mentioned particularly for the production of an acid colloid solution of a melamine / aldehyde condensate.

  The production ratio of melamine and aldehyde when producing methylolmelamine is preferably 1 to 6 mol of aldehyde with respect to 1 mol of melamine. However, if the amount of aldehyde exceeds 2.5 moles relative to 1 mole of melamine, the amount of free aldehyde increases when the acid colloid solution is prepared. Therefore, the aldehyde should be 2.5 moles or less per mole of melamine. preferable.

  The obtained methylol melamine does not dissolve in water but dissolves in a colloidal form in the acid solution. The alkylated methylol melamine obtained by further alkylating methylol melamine is water-soluble and becomes colloidal when an acid is added.

  A monobasic acid is suitable as the acid used here. Specific examples include organic acids such as formic acid, acetic acid, lactic acid, and propionic acid in addition to mineral acids such as hydrochloric acid and nitric acid. Hydrochloric acid is particularly preferable because a stable colloidal solution can be obtained.

  The amount of the monobasic acid, particularly hydrochloric acid, is about 0.5 to 1.5 mol, preferably 0.7 to 1.3 mol, per 1 mol of melamine.

In the initial stage of preparation of the colloidal solution, there are many free aldehydes. However, after the preparation, the free aldehydes are reduced when left standing at room temperature for aging. The aging time is suitably 5 days to 3 months at room temperature and about 2 to 3 hours at 50 ° C. when heating.
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 preferably has a molecular weight in the range of 400 to 10,000,000, particularly 1,000 to 100,000. When the molecular weight of the melamine / aldehyde condensate is large, the aggregation effect tends to be excellent, but when it is excessively large, the solubility of the melamine / aldehyde condensate decreases when an acid solution is formed. The molecular weight of the melamine / aldehyde condensate can be determined, for example, by the method described in the Examples section below.

  The melamine / aldehyde condensate used in the present invention preferably has a colloid particle size of 5 to 50 nm, particularly 10 to 30 nm, when an acid colloid solution is used. The larger the colloid particle size, the better the agglomeration effect. However, when the colloid particle size is too large, the total surface area of the added colloid becomes small, and the efficiency becomes worse. The colloidal particle size of the acid colloid solution of the melamine / aldehyde condensate can be measured, for example, by a dynamic light scattering method and obtained as an average value.

  In the melamine / aldehyde condensate produced by the above-mentioned method, the aldehyde which is the production raw material remains or is contained, or aldehyde is liberated from the melamine / aldehyde condensate during storage, and the aldehyde is contained. There is a case. Aldehyde contained in the melamine aldehyde condensate will be contained in the coagulated water and solid-liquid separation water, but aldehyde, especially formaldehyde, has low molecular weight and no charge, so reverse osmosis in the latter stage (RO) It cannot be sufficiently removed by membrane treatment or ion exchange resin treatment. For example, when the treated water obtained by the water treatment according to the present invention is used as ultrapure raw water, it is preferable to keep the TOC of the treated water at 0.01 mg / L or less. However, when formaldehyde is mixed, the TOC is sufficiently reduced. Can not do it. For this reason, when using the flocculant of this invention, it is preferable to refine | purify a melamine aldehyde condensate and to reduce aldehyde content. In this case, the purification method of the melamine / aldehyde condensate includes 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 will be described later, formaldehyde may be converted to hydroxymethanesulfonate by bisulfite treatment. Since hydroxymethanesulfonate has a negative charge, it 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, it is preferable that the aldehyde content in 1 g of the melamine / aldehyde condensate is 7 mg or less, particularly 4 mg or less.
The aldehyde content in the melamine / aldehyde condensate can be quantified by the method described in the Examples section below.

[Treatment water]
The treated water to be agglomerated in the present invention is water containing organic matter, particularly high molecular weight organic matter having a molecular weight of 10,000 or more, and humic substance. For example, various industrial wastewater, domestic wastewater, biologically treated water or surface water of the wastewater. And groundwater. Although there is no restriction | limiting in particular about the organic substance density | concentration in to-be-processed water, When the above water is made into to-be-processed water, content of the high molecular organic substance and humic substance of molecular weight 10,000 or more in to-be-processed water is 0.1 mg. / L or more, for example, about 0.1 to 1 mg / L.

  This water to be treated is agglomerated by the aggregating agent of the present invention and then solid-liquid separated, and the separated water is subjected to membrane separation treatment or ion exchange resin treatment.

[Aggregation treatment]
The amount of melamine aldehyde condensate acid solution, which is the flocculant of the present invention, is added to the water to be treated containing the organic matter for flocculation treatment, and the amount added depends on the content of organic matter in the water to be treated. The addition amount of the melamine / aldehyde condensate is preferably 0.1 to 5 mg / L, particularly preferably 0.2 to 2 mg / L. If the amount added is too small, a sufficient coagulation effect cannot be obtained. If the amount added is too large, unreacted melamine / aldehyde condensate remains, and the organic matter concentration in the treated water increases.

  Further, the pH of the water to be treated when adding the acid solution of the melamine / aldehyde condensate is preferably near neutral, and is preferably pH 4 or more, and more preferably pH 5-10. This is because if the pH is too low, the melamine / aldehyde condensate is hardly insolubilized and the aggregating ability is lowered. If the pH exceeds 10, the cost due to the pH adjusting agent increases, and the salt concentration increases during neutralization, which is inappropriate.

  Therefore, after adding an acid solution of a melamine / aldehyde condensate to the water to be treated, an alkali such as sodium hydroxide is added as necessary to adjust the pH to perform the aggregation treatment.

  In the present invention, an aggregating treatment may be performed using an inorganic flocculant or an organic polymer flocculant together with a melamine / aldehyde condensate. In this case, the inorganic flocculant and the organic polymer flocculant may be added before the acid solution of the melamine / aldehyde condensate is added, or may be added after the addition of the acid solution of the melamine / aldehyde condensate, You may add simultaneously with the addition of the acid solution of a melamine aldehyde condensate.

  Examples of the inorganic flocculant used in combination include aluminum chloride, sulfuric acid band, ferric chloride, and ferrous sulfate. The organic polymer flocculant is preferably an acrylamide-based or anionic organic polymer flocculant, and examples thereof include polyacrylamide, polymethacrylamide, polyacrylic acid, and polyvinyl sulfonic acid. These may be used alone or in combination of two or more.

  When an inorganic flocculant is used in combination, the amount of inorganic flocculant added depends on the quality of the water to be treated and the type of inorganic flocculant used, but the amount of inorganic flocculant added should be about 5 to 100 mg / L. Is preferred. Moreover, although the addition amount in the case of using an organic polymer flocculent also changes with the quality of to-be-processed water and the kind of organic polymer flocculant to be used, the addition amount of an organic polymer flocculant is about 1-20 mg / L. It is preferable to do.

  In the case where an inorganic flocculant is used in combination, the pH during the flocculant treatment is preferably set to a pH suitable for the flocculant treatment with the inorganic flocculant in the above-described pH range depending on the type of the inorganic flocculant used. For example, the pH is preferably about 4 to 10 for an iron-based inorganic flocculant and about 4 to 8 for an aluminum-based inorganic flocculant.

  The aggregation treatment according to the present invention is usually performed for about 2 to 30 minutes with stirring.

[Solid-liquid separation]
In the present invention, the solid-liquid separation method of the agglomerated treated water is not particularly limited, and the solid-liquid separation can be performed by precipitation, pressure flotation, filtration, membrane separation, or the like according to a conventional method. Two or more of these may be combined for solid-liquid separation.

[Bisulfite treatment]
Bisulfite treatment may be performed in order to remove the aldehyde that coexists with or is liberated from the melamine / aldehyde condensate.
That is, bisulfite or bisulfite (hereinafter referred to as “bisulfite (salt)”) is added to the agglomerated water or separated water obtained by solid-liquid separation, and melamine aldehyde condensation is performed. Aldehydes, especially formaldehyde, contained in the product and brought into the flocculated water may be converted into hydroxymethanesulfonate. As described above, hydroxymethanesulfonate can be easily removed by RO membrane treatment or ion exchange resin treatment, and does not affect the TOC of treated water.

  In this case, the amount of bisulfite (salt) added is appropriately adjusted depending on the aldehyde content in the coagulation treated water, and the aldehyde concentration in the aqueous solution obtained by subjecting the solid-liquid separated water to membrane separation treatment or ion exchange resin treatment is 0.01 mg. It is preferable to add so that it may become / L or less.

[Post-processing]
In the present invention, the separated water obtained by agglomerating and solid-liquid separating the water to be treated as described above is subjected to membrane separation treatment or ion exchange resin treatment.
As this membrane separation treatment, it is particularly preferable to perform RO membrane separation treatment.

  According to the present invention, the organic matter and humic substances in the water to be treated, which are contamination-causing substances of the separation membrane and ion exchange resin, can be highly removed by the aggregation and solid-liquid separation treatment in the previous stage. In separation treatment or ion exchange resin treatment, it is possible to perform stable and efficient water treatment over a long period of time by suppressing performance degradation of the separation membrane or ion exchange resin.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

  In the following examples and comparative examples, the following were used as flocculants. Moreover, the addition amount of the inorganic flocculant shown below is the addition amount as an aqueous solution.

<Inorganic flocculant>
Ferric chloride (FeCl ₃ , 38% by weight aqueous solution)
Polyaluminum chloride (PAC, 10 wt% aqueous solution)

<Melamine aldehyde condensate>
MF-1: Acid colloid solution of melamine aldehyde condensate 1 mol of melamine 0.05 mol of methylolated melamine obtained by reacting 2 mol of formaldehyde with 100 ml of 1.35 wt% hydrochloric acid aqueous solution (1 mol of melamine) Aged and prepared in addition to hydrochloric acid (0.75 mol) (melamine / formaldehyde condensate content 10% by weight, pH 2)
MF-2: Acid solution of low molecular weight melamine / aldehyde condensate: Methylated melamine / formaldehyde condensate (weight average molecular weight 432, Sigma / Aldrich) dissolved in 0.1M hydrochloric acid aqueous solution (melamine / formaldehyde condensate 10 weight) % Aqueous solution, pH 1)

About the molecular weight of the acid colloid of the melamine aldehyde condensate contained in the above MF-1, the following conversion formula is based on the diffusion coefficient resulting from the particle size peak obtained by using the dynamic light scattering method. The calculated molecular weight was calculated by using (Membrane Society of Japan (ed.), Design method of membrane separation process). As a result, the molecular weight was 6.6 million.
D = 8.76 × 10 ⁻⁹ (Mw) ^−0.48
(D: diffusion coefficient (m ² / s), Mw: molecular weight)

<Example 1-1>
Concentrated water (containing 0.1 mg / L of a high molecular organic substance having a molecular weight of 10,000 or more) obtained by subjecting biologically treated water to RO membrane treatment was used as water to be treated.
While 500 mL of water to be treated at 25 ° C. was put into a beaker and stirred at 150 rpm for 5 minutes, MF-1 was added to an active ingredient concentration of 1 mg / L, and then 20 mg / L of FeCl ₃ aqueous solution was added. The pH was adjusted to 5.5 using an aqueous sodium hydroxide solution. Furthermore, the aggregation process was performed by stirring for 10 minutes at 50 rpm. The water after the aggregation treatment was filtered through a hydrophilic PTFE (polytetrafluoroethylene) syringe filter having a pore diameter of 0.45 μm to perform solid-liquid separation. This filtered water was analyzed by LC-OCD, and the peak area of an organic carbon component having a molecular weight of 10,000 or more was calculated. Dextran was used as a molecular weight marker. The organic substance removal rate was calculated by the following formula.
Removal rate (%) = (1-Organic carbon component peak area of coagulated treated water / Organic carbon component peak area of non-aggregated treated water) × 100

<Example 1-2>
Aggregation treatment was performed in the same manner as in Example 1-1 except that MF-2 was added instead of MF-1, and the organic matter removal rate was determined.

<Comparative Example 1-1>
Aggregation treatment was performed 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 organic matter removal rate was determined.

<Comparative Example 1-2>
In the same manner as in Example 1-1 except that 1 mg / L of poly (2-methacryloyloxyethyltrimethylammonium) (PMETMA, molecular weight 9 million), which is a cationic organic polymer flocculant, was added instead of MF-1. Aggregation treatment was performed to determine the organic matter removal rate.

<Comparative Example 1-3>
Other than the addition of 1 mg / L of poly (2-methacryloyloxyethyl) -N-benzyl-N, N-dimethylammonium (PMEBDA, molecular weight 10 million) which is a cationic organic polymer flocculant instead of MF-1. Was agglomerated in the same manner as in Example 1-1 to determine the organic matter removal rate.

<Example 2-1>
In Example 1-1, aggregation treatment was performed in the same manner as in Example 1-1 except that 20 mg / L of a PAC aqueous solution was added instead of the FeCl ₃ aqueous solution and the pH was adjusted to 6.5 using a sodium hydroxide aqueous solution. And the removal rate of organic matter was determined.

<Comparative Example 2-1>
Aggregation treatment was performed 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 organic matter removal rate was determined.

<Example 3-1>
In Example 1-1, after addition of MF-1, agglomeration treatment was performed in the same manner as in Example 1-1 except that the pH was adjusted to 7.0 using a sodium hydroxide aqueous solution without adding an FeCl ₃ aqueous solution. And the removal rate of organic matter was determined.

<Comparative Example 3-1>
Aggregation treatment was performed in the same manner as in Example 3-1 except that 20 mg / L of an FeCl ₃ aqueous solution was added in place of MF-1, and the organic matter removal rate was determined.
The results are shown in Table 1.

Table 1 shows the following.
From Example 1-1, Example 1-2, and Comparative Example 1-1, an increase in the removal rate could be confirmed by adding the melamine-aldehyde condensate before adding the inorganic flocculant (FeCl ₃ ). Further, Comparative Examples 1-2 and 1-3 show that the removal rate is hardly improved even when the inorganic flocculant (FeCl ₃ ) and the cationic polymer flocculant are used in combination.
From Example 2-1 and Comparative Example 2-1, it can be seen that even when PAC is used as the inorganic flocculant, the removal rate is higher when melamine / aldehyde condensate is added.
From Example 3-1 and Comparative Example 3-1, it can be seen that, under neutral conditions, the removal rate is higher when a melamine / aldehyde condensate is used than when an inorganic flocculant is used.

<Example 4-1>
Gua gum (Guarcoal F50, manufactured by Sanei Pharmaceutical Co., Ltd.) was dissolved in pure water as a polysaccharide model substance, and 2 L of an aqueous solution having a guar gum concentration of 1 mg / L and pH 6.5 was prepared and placed in a beaker. While the aqueous solution in the beaker was being stirred at 150 rpm for 5 minutes, MF-1 was added to an active ingredient concentration of 1 mg / L, and then the pH was adjusted to 6.5 using an aqueous sodium hydroxide solution. Furthermore, the aggregation process was performed by stirring for 10 minutes at 50 rpm. The water after the aggregation treatment was subjected to solid-liquid separation by suction filtration through a cellulose acetate membrane having a pore diameter of 0.45 μm.

This filtered water was passed through the RO flat membrane evaluation apparatus shown in FIG. 2 under the following water passage conditions, and the change with time of the flux was measured.
<Measurement conditions>
Supply water flow rate: 0.7 mL / min
Water temperature: 25 ° C
Recovery rate: 80%

This flat membrane test apparatus is provided with a flat membrane cell 2 at an intermediate position in the height direction of a cylindrical container 1 having a bottom and a lid, and the inside of the container is divided into a raw water chamber 1A and a permeated water chamber 1B, and the container 1 is divided into a stirrer. 3, feed water (filtered water) is supplied to the raw water chamber 1 </ b> A via the pipe 11 by the pump 4, and the stirrer 5 in the container 1 is rotated to stir the raw water chamber 1 </ b> A. Is taken out from the permeate water chamber 1B through the pipe 12, and the concentrated water is taken out from the raw water chamber 1A through the pipe 13. The feed water supply pipe 11 is provided with a pressure gauge 6, and the concentrated water outlet pipe 13 is provided with an opening / closing valve 7.
In the flat membrane cell 2, a polyamide RO membrane (“ES-20” manufactured by Nitto Denko Corporation) having a membrane area of 8 cm ² was installed.

The recovery rate and flux were calculated by the following formulas. The same applies to Example 6-1 described later.
Recovery [%] = (permeate flow rate [mL / min] / feed water flow rate [mL / min]) × 100
Flux [m ³ / (m ² · d)]] = permeate flow rate [m ³ / d] / membrane area [m ² ] × temperature conversion coefficient [−]

<Comparative Example 4-1>
Aggregation treatment was performed 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 change over time in the flux of the obtained filtrate was measured.

<Example 5-1>
Canadian fulvo (manufactured by PII Bio) as a humic substance was dissolved in pure water to 1 mg / L, and 2 L of a pH 6.5 aqueous solution containing 10 mg / L of calcium was prepared and placed in a beaker. While the aqueous solution in the beaker was being stirred at 150 rpm for 5 minutes, MF-1 was added to an active ingredient concentration of 1 mg / L, and then the pH was adjusted to 6.5 using an aqueous sodium hydroxide solution. Furthermore, the aggregation process was performed by stirring for 10 minutes at 50 rpm. The water after the aggregation treatment was subjected to solid-liquid separation by suction filtration through a cellulose acetate membrane having a pore diameter of 0.22 μm. About this filtered water, the change of the flux was measured using the RO flat membrane test apparatus similarly to Example 4-1.

<Comparative Example 5-1>
Aggregation treatment was performed 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 change over time in the flux of the obtained filtrate was measured.

  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.

  3 and 4, it was possible to suppress a decrease in flux by adding a melamine-aldehyde condensate to a guar gum solution or a Canadian flvo solution. It was confirmed that polysaccharides and humic substances, which are membrane contaminants, can be aggregated and removed by adding melamine-aldehyde condensate and filtering.

<Example 6-1>
MF-1 was purified using an ultrafiltration membrane. Specifically, 6 mL of MF-1 was put into a centrifugal ultrafiltration unit (Amicon Ultra, Millipore) having a molecular weight cut-off of 3,000, and further adjusted to pH 2 by adding hydrochloric acid to pure water. 9 mL) was added. Thereafter, centrifugation was performed at a gravitational acceleration of 2,500 G for 1 hour to separate the permeate and the concentrate. The acidic solution was added to the concentrate to dilute to 15 mL, and the centrifugation was performed again. This procedure was repeated two more times, and the concentrated liquid was collected to obtain purified MF-1.

  The formaldehyde content contained in this purified MF-1 was determined by colorimetric determination by the following acetylacetone method.

<Acetylacetone method>
Sample: supply water and permeated water Acetylacetone reagent: ammonium acetate 15 g, acetic acid 0.3 mL, acetylacetone 0.2 mL dissolved in pure water to make 100 mL Determination method: sample 5 mL and acetylacetone reagent were mixed and heated at 40 ° C. for 30 min. It was allowed to stand for 30 minutes. Thereafter, the absorbance at a wavelength of 413 nm was measured, and the formaldehyde content was calculated based on a calibration curve prepared from an aqueous formaldehyde solution having a known concentration.

Moreover, after adding refined MF-1 to pure water so that an active ingredient density | concentration might be 1 mg / L, pH was adjusted to 6.5 using sodium hydroxide aqueous solution. The pure water to which MF-1 was added was subjected to the following procedure using the RO flat membrane evaluation apparatus shown in FIG. 2 (polyamide RO membrane having a membrane area of 8 cm ² : “ES-20” manufactured by Nitto Denko Corporation). Water was passed under water conditions, and the formaldehyde content of feed water and permeated water was measured by the GC / MS method. The permeated water was collected after passing through for 2 hours.
<Water flow conditions>
Supply water flow rate: 1.6 mL / min
Water temperature: 25 ° C
Recovery rate: 75%

<Example 6-2>
MF-1 was purified using a dialysis membrane. Specifically, 6 mL of MF-1 was put into a dialysis membrane unit (manufactured by regenerated cellulose, manufactured by Thermo Fisher Scientific Co., Ltd.) having a molecular weight cut off of 7,000, and 5 L of acidic solution (hydrochloric acid was added to pure water, pH 2 Dialyzed for 1 week. The formaldehyde content of the purified MF-1 was determined by the acetylacetone method as in Example 6-1.

<Example 6-3>
After adding 10 mg / L of 35% by weight aqueous sodium bisulfite solution to pure water to which unrefined MF-1 was added to an active ingredient concentration of 1 mg / L, the pH was adjusted using an aqueous sodium hydroxide solution. Adjusted to 6.5. About this liquid mixture, it passed through the RO flat membrane evaluation apparatus similarly to Example 6-1, and measured the formaldehyde content of supply water and permeated water.

<Comparative Example 6-1>
The formaldehyde content of unpurified MF-1 was determined by the acetylacetone method as in Example 6-1.
Except that unpurified MF-1 was used instead of purified MF-1, water was passed through the RO flat membrane evaluation device in the same manner as in Example 6-1, and the formaldehyde content of the feed water and permeate was determined. It was measured.
The results of Examples 6-1 to 6-3 and Comparative Example 6-1 are shown in Table 2.

Since unpurified MF-1 was used in Comparative Example 6-1, formaldehyde was contained in an amount of 2000 mg / L or more, and the formaldehyde contained in the feed water was not sufficiently removed even when RO membrane treatment was used. It remained in the water.
Example 6-1 used MF-1 purified with an ultrafiltration membrane, and the amount of formaldehyde could be reduced to 1/3 or less. Therefore, the amount of formaldehyde contained in the feed water and the permeated water is less than the detection lower limit value of the analysis, and it has become clear that the TOC in the permeated water can be reduced.
Example 6-2 was MF-1 purified with a dialysis membrane, and the amount of formaldehyde could be reduced to 1/40 or less. It can be expected that the TOC in the permeated water can be similarly reduced by this purification method.
In Example 6-3, as a result of the reaction between formaldehyde and sodium bisulfite, hydroxymethanesulfonate was produced, and formaldehyde was below the lower limit of detection in the feed water and permeated water.

1 container 1A raw water chamber 1B permeate water chamber 2 flat membrane cell 3 stirrer

Claims (18)

In a water treatment method in which an aggregating agent is added to water to be treated containing organic matter and agglomerated and solid-liquid separated, and the resulting separated water is subjected to reverse osmosis membrane separation treatment or ion exchange resin treatment , A water treatment method characterized by using a flocculant containing an aldehyde condensate and adding bisulfurous acid and / or a salt thereof to the flocculated water before the solid-liquid separation or the separated water after the solid-liquid separation . The water treatment method according to claim 1 , wherein the water to be treated contains a high molecular weight organic substance having a molecular weight of 10,000 or more and / or a humic substance. 3. The water treatment method according to claim 1 , wherein the solid-liquid separation treatment is any one of a precipitation treatment, a pressure flotation treatment, a filtration treatment, and a membrane separation treatment. The inorganic flocculant is added to the water to be treated before, after, or simultaneously with the addition of the flocculant according to any one of claims 1 to 3 , wherein the flocculant is subjected to agglomeration and solid-liquid separation treatment. Water treatment method. 5. The aldehyde concentration in treated water obtained by the reverse osmosis membrane separation treatment or the ion exchange resin treatment by adding the bisulfuric acid and / or a salt thereof according to claim 1, is 0.01 mg / L or less. And a water treatment method. In any one of claims 1 to 5, water treatment method, wherein the coagulant is an acid solution of a melamine-aldehyde condensation product. The water treatment method according to any one of claims 1 to 6 , wherein the melamine aldehyde condensate has a molecular weight in the range of 400 to 10,000,000 or a colloidal particle size in the range of 5 to 500 nm. . The water treatment method according to any one of claims 1 to 7 , wherein the content of free aldehyde in 1 g of the melamine / aldehyde condensate is 7 mg or less. According to claim 8, wherein the coagulant is water treatment wherein the ultrafiltration membrane treatment or dialysis membrane process in which removal process of the aldehyde has been made. In a water treatment apparatus comprising means for adding a flocculant to water to be treated containing organic matter and aggregating and solid-liquid separation treatment, and means for subjecting the obtained separated water to reverse osmosis membrane separation treatment or ion exchange resin treatment, A water treatment apparatus using a flocculant containing a melamine aldehyde condensate as a flocculant, wherein bisulfurous acid and / or a salt thereof is added to the flocculant treated water before the solid-liquid separation or the separated water after the solid-liquid separation. A water treatment apparatus comprising means for adding. The water treatment apparatus according to claim 10, wherein the water to be treated contains a high molecular weight organic substance having a molecular weight of 10,000 or more and / or a humic substance. 12. The water treatment apparatus according to claim 10 or 11, wherein the solid-liquid separation treatment means is a solid-liquid separation means by any of precipitation treatment, pressurized flotation treatment, filtration treatment, or membrane separation treatment. 13. The method according to claim 10, further comprising means for adding an inorganic flocculant to the water to be treated before, after, or simultaneously with the addition of the flocculant. The water treatment apparatus is characterized in that the water to be treated is agglomerated and solid-liquid separated. 14. The aldehyde concentration in treated water obtained by means of the reverse osmosis membrane separation treatment or the ion exchange resin treatment by adding the bisulfite and / or a salt thereof according to any one of claims 10 to 13 is 0.01 mg / A water treatment apparatus characterized by being L or less. 15. The water treatment apparatus according to claim 10, wherein the flocculant is an acid solution of melamine / aldehyde condensate. The water treatment apparatus according to any one of claims 10 to 15, wherein the melamine aldehyde condensate has a molecular weight in the range of 400 to 10,000,000 or a colloidal particle size in the range of 5 to 500 nm. . The water treatment device according to any one of claims 10 to 16, wherein the content of free aldehyde in 1 g of the melamine-aldehyde condensate is 7 mg or less. 18. The water treatment apparatus according to claim 17, wherein the flocculant has been subjected to the aldehyde removal treatment by ultrafiltration membrane treatment or dialysis membrane treatment.

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