JP2013202452A - Water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method capable of efficiently performing flotation, in a method of coagulating wastewater and then performing the flotation.SOLUTION: In a water treatment method including a coagulation reaction step of performing coagulation reaction by adding a coagulant to water to be treated, and a flotation step of solid-liquid separating coagulation treated water flowing out from the coagulation reaction step, the coagulant is a cationic polymer coagulant having a hydrophobic functional group. An inorganic coagulant or other polymer coagulants can be used together with the cationic polymer coagulant having the hydrophobic functional group.

Description

  The present invention relates to a water treatment method, and more particularly, to a water treatment method of subjecting water to be treated to a flocculation treatment and then a floating separation treatment.

  In order to remove pollutants such as suspended water and soluble substances in various effluents such as river water, industrial water, and biologically treated water, a method is widely used in which the effluent is coagulated and then floated and separated. ing. For example, JP-A-7-241597, JP-A-2002-113471, and JP-A-2007-209890 describe a method in which an organic waste water is subjected to a flocculation process and then a floating separation process. The floating separation device as the solid-liquid separation means has an advantage that a small installation space is sufficient as compared with the settling tank.

JP-A-7-241597 JP 2002-113471 A JP 2007-209890 A

  An object of the present invention is to provide a water treatment method capable of efficiently performing flotation separation in a method of flotation separation treatment after coagulating the effluent.

  The water treatment method of the present invention includes a flocculation reaction step in which a flocculating agent is added to the water to be treated to perform a flocculation reaction, and a floating separation step in which the flocculated water that flows out of the flocculation reaction step is subjected to solid-liquid separation. In the treatment method, the flocculant is a cationic polymer flocculant having a hydrophobic functional group.

  The cationic polymer flocculant is obtained by polymerizing (i) a cationic monomer having a hydrophobic functional group, or (ii) at least a monomer having a hydrophobic functional group and a monomer having a cationic functional group. Are preferred.

  In the aggregation reaction step, an inorganic flocculant may be further added.

  In the aggregation reaction step, an anionic or nonionic polymer flocculant may be further added.

  In the present invention, a cationic polymer flocculant having a hydrophobic functional group is used as the flocculant in the method of flocculating and separating the effluent after flocculation. Since the cationic polymer flocculant having a hydrophobic functional group is cationic, it generally agglomerates the suspended substances in the waste water for charging which are generally negatively charged. Further, since the cationic polymer flocculant having a hydrophobic functional group has a hydrophobic functional group, the micro-air for the floating separation process is easily attached, and the floating separation process is efficiently performed.

  When an inorganic flocculant, an anionic polymer flocculant, or a nonionic polymer flocculant is added in the aggregation reaction step, the aggregation efficiency is further improved. By using a cationic polymer flocculant having a hydrophobic functional group, it is sufficient that the amount of inorganic flocculant added is smaller than in the case of the conventional agglomeration treatment with an inorganic flocculant and a polymer flocculant. An effect can be obtained.

It is a flowchart of the water treatment method which concerns on embodiment. It is a flowchart of the water treatment method which concerns on embodiment. 3 is a flow sheet showing processing operations of Example 1 and Comparative Example 1.

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

[Treatment water]
In the present invention, the water to be treated includes waste water such as river water, industrial water, well water such as well water, electronic industrial waste water, chemical factory waste water, and food factory waste water. The wastewater may be organic wastewater biologically treated water.

[Cationic polymer flocculant having a hydrophobic functional group]
Examples of the cationic polymer flocculant having a hydrophobic functional group include (1) and (2) below, but are not limited thereto.

(1) Polymer flocculant essentially comprising a cationic monomer having a hydrophobic functional group Examples of cationic monomers having a hydrophobic functional group include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, and diethylamino. Examples thereof include methyl chloride salts such as ethyl (meth) acrylate, diethylaminopropyl (meth) acrylamide, N-methyl-N-ethylaminoethyl (meth) acrylate and N-methyl-N-ethylaminopropyl (meth) acrylamide. Cationic polymer flocculants having hydrophobic functional groups are homopolymers or copolymers with copolymerizable vinyl monomers.

(2) Polymer flocculant comprising hydrophobic monomer and cationic monomer as essential components Examples of the hydrophobic monomer include N-methyl (N, N-dimethyl) acrylamide, acrylonitrile, styrene, methyl or ethyl (meth) acrylate. Etc.

  Specific examples of the cationic monomer include cationic vinyl monomer, dimethylaminoethyl (meth) acrylate acid salt or quaternary ammonium salt thereof, dimethylaminopropyl (meth) acrylamide acid salt or quaternary ammonium salt thereof, diallyldimethyl Examples include ammonium chloride.

  Both (1) and (2) may be those obtained by copolymerizing nonionic monomers. Nonionic monomers include (meth) acrylamide, N-isopropylacrylamide, N-methyl (N, N-dimethyl) acrylamide and the like.

  The polymerization method is not particularly limited, and known radical polymerization methods such as aqueous solution polymerization, solution polymerization, reverse phase suspension polymerization, photopolymerization, precipitation polymerization, and reverse phase emulsion polymerization can be applied.

<Polymer physical properties of cationic polymer flocculant having hydrophobic functional group>
The weight average molecular weight of the cationic polymer flocculant having a hydrophobic functional group is preferably about 1,000 to 10,000,000, particularly about 3,000,000 to 10,000,000. Usually, an intrinsic viscosity using 1N-NaCl as a solvent is used as an index of molecular weight. However, since a polymer having a hydrophobic functional group precipitates in 1N-NaCl, an intrinsic viscosity using 0.1N-NaCl as a solvent can be used. In that case, it is preferable that it is 10 dl / g or more at 30 degreeC.

  The cationic degree is preferably 10 mol% or more, particularly 10 to 100 mol%, particularly 50 to 100 mol% of the cationic monomer unit. When the amount is less than 10 mol%, the cationic effect is insufficient and the aggregation effect is lowered. The monomer unit of the cationic monomer having a hydrophobic functional group is preferably 10 mol% or more, particularly 10 to 100 mol%, particularly 50 to 100 mol%. The monomer unit of the hydrophobic monomer is preferably 10 mol% or more, particularly 10 to 80 mol%, particularly 30 to 80 mol%.

<Product form of cationic polymer flocculant having hydrophobic functional group>
It may be a powder or a reverse emulsion or a suspension dispersion, and the form is not limited.

<Method for adding cationic polymer flocculant having hydrophobic functional group>
There is no particular limitation on the form of adding the polymer flocculant to the water to be treated, but it is reactive to add it in a solution dissolved in 0.05 to 1% by weight, particularly 0.1 to 0.5% by weight. Is preferable.

<Addition amount of cationic polymer flocculant having hydrophobic functional group>
The addition amount of the polymer flocculant is preferably about 0.1 to 100 mg / L, particularly about 0.1 to 10 mg / L with respect to the water to be treated.

[Other flocculants]
An inorganic flocculant may be used in combination with the agglomeration treatment. Examples of the inorganic flocculant include iron flocculants such as ferric chloride and polyiron sulfate, aluminum flocculants such as aluminum sulfate, aluminum chloride, and polyaluminum chloride, calcium hydroxide, and magnesium hydroxide. Among these, iron-based or aluminum-based flocculants are preferable. These inorganic flocculants may be used individually by 1 type, and may use 2 or more types together. The inorganic flocculant may be added either before, after, or simultaneously with the addition of the cationic polymer flocculant having a hydrophobic functional group.

  The amount of the inorganic flocculant added is preferably about 1 to 2000 mg / L, particularly about 50 to 300 mg / L, although it depends on the properties and water quality of the water to be treated.

  In addition, an anionic polymer flocculant and a nonionic polymer flocculant may be used in combination according to the properties of the water to be treated, which may further improve the water quality of the agglomerated treated water and improve the pressure floatability. . Examples of the anionic polymer flocculant include poly (meth) acrylic acid, a copolymer of (meth) acrylic acid and (meth) acrylamide, and anionic polymer flocculants such as alkali metal salts thereof. It is done. Nonionic polymer flocculants include nonionic organic polymer flocculants such as poly (meth) acrylamide.

  The anionic or nonionic polymer flocculant may be added either before, after, or simultaneously with the addition of the cationic polymer flocculant having a hydrophobic functional group. In general, the addition amount of the anionic or nonionic polymer flocculant is preferably about 0.01 to 10 mg / L, particularly about 1 to 10 mg / L as the solid content.

<PH adjustment>
The pH during the aggregation treatment is preferably pH 4 to 10 in the aggregation tank, and the pH is adjusted as necessary. For pH adjustment, an acid such as hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ) or an alkali such as sodium hydroxide (NaOH) is appropriately used.

[Floating separation]
The flocculated water is then subjected to floating separation to separate the produced flocculated floc into solid and liquid. In order to perform this floating separation, it is preferable that pressurized water in which air is dissolved under pressure is added to the agglomerated water and floated and separated in a floating tank. Various types of pressure levitation separation devices can be used for this pressure levitation separation.

[Other processing]
Furthermore, in this invention, you may use together other processes other than the above in the back | latter stage of a pressurization floating separator. For example, activated carbon treatment or membrane separation treatment may be performed in order to remove residual soluble organic substances.

[Processing equipment]
An example of the waste water treatment apparatus of the present invention will be described below with reference to the drawings.

  1 and 2 are system diagrams showing an example of the waste water treatment apparatus of the present invention, wherein 1, 2 are agglomeration tanks, and 3 is a pressurized flotation separation tank. Each aggregation tank is provided with a stirring means.

  In the wastewater treatment apparatus of FIG. 1, the water to be treated is added with a cationic polymer flocculant having a hydrophobic functional group in the first flocculation tank 1, and then in the second flocculation tank 2, an inorganic flocculant (for example, iron-based flocculant). Agent) is added and subjected to flocculation treatment, and then the flocculated water is added to the pressurized floating separation tank 3 to be floated and separated, the treated water is taken out from the lower part of the tank, and the levitated matter is taken out from the upper part of the tank. The pressurized water may be added before introduction into the floating separation tank 3.

  The apparatus shown in FIG. 2 is obtained by reversing the addition order of the cationic polymer flocculant having a hydrophobic functional group and the inorganic flocculant in FIG.

  The apparatus shown in FIGS. 1 and 2 is an example of the waste water treatment apparatus of the present invention, and the present invention is not limited to the illustrated method, and instead of the inorganic flocculant or together with the inorganic flocculant. An anionic or nonionic polymer flocculant may be added.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the following description of the embodiments, as the cationic polymer flocculating agent having a hydrophobic functional group, the polymer of the benzyl chloride quaternary product of dimethylaminoethyl methacrylate DAM (B Z _Cl) (Kurita Water Industries Ltd. Chestnut Farm PC797) was used. The polymer of dimethylaminoethyl methacrylate benzyl chloride quaternized product had an intrinsic viscosity of 12.5 dl / g at 0.1 N-NaCl, and the weight average molecular weight determined by GPC measurement was 9 million. .

[Example 1 and Comparative Example 1]
According to the test flow shown in FIG. 3, the following simulated organic wastewater was subjected to biological treatment, and the raw water was used for coagulation pressure floating treatment. The biological treatment was a continuous treatment. Aggregation and pressure levitation treatment were batch treatment using a beaker and a column.
[Simulated drainage]
BOD: 20 mg / L (mixed water of glucose and acetic acid)
[Biological treatment]
Sponge carrier type fluidized bed reaction tank: 10L
Residence time: 1 hour [Raw water (biologically treated water)]
BOD: <5mg / L
SS: 10 mg / L
Turbidity: 3.8 degrees [Aggregation 1 Aggregation Conditions]
Batch type agglomeration in 1 L beaker Inorganic flocculant (38% ferric chloride): 100 mg / L
Hydrophobic cationic polymer addition amount: 0.2 mg / L (added in Example 1. not added in Comparative Example 1)
Reaction time: 5 minutes pH: 5.5
[Aggregation 2 Aggregation Conditions]
Batch type agglomeration in 1L beaker Anionic polymer: Acrylamide polymer Kurifokku Co., Ltd. Cliff Rock PA331
Anionic polymer addition amount: 0.5 mg / L
Reaction time: 3 minutes pH: 5.5
[Pressure levitation]
Batch type pressure levitation on 1L column. Pure water was used as the pressurized water.
Pressurized pressure: 0.35 MPa
Pressurized water ratio: 20%
[Processing index]
The performance improvement evaluation of the pressure levitation treatment was evaluated by the ascent rate and strength of the generated scum and the turbidity of the treated water. The results are shown in Table 1.

  As shown in Table 1, according to the present invention, it is recognized that the flotation separation process is efficiently performed and the quality of the treated water is also improved.

DESCRIPTION OF SYMBOLS 1 1st flocculation tank 2 2nd flocculation tank 3 Pressurization floating separation tank

Claims (4)

An agglutination reaction step of adding an aggregating agent to the water to be treated and performing an agglutination reaction;
In a water treatment method comprising a flotation separation step for solid-liquid separation of the agglomerated treated water flowing out from the agglomeration reaction step,
The water treatment method, wherein the flocculant is a cationic polymer flocculant having a hydrophobic functional group.   2. The cationic polymer flocculant according to claim 1, wherein the cationic polymer flocculant is a cationic polymer having a hydrophobic functional group, or at least a monomer having a hydrophobic functional group and a monomer having a cationic functional group are polymerized. The water treatment method characterized by the above-mentioned.   3. The water treatment method according to claim 1, wherein an inorganic flocculant is further added in the aggregation reaction step.   The water treatment method according to any one of claims 1 to 3, wherein an anionic or nonionic polymer flocculant is further added in the aggregation reaction step.

Images