JPWO2011016482A1 - Removal method of flux-causing substances in membrane separation activated sludge process - Google Patents

Abstract

The present invention provides a method for efficiently removing a filtration flux lowering cause substance present in a membrane separation activated sludge mixed liquid by using a small amount of an organic polymer flocculant. A filtration flux lowering agent removing agent comprising a water-soluble and / or water-absorbing cationic polymer containing a structural unit represented by a predetermined formula as an active ingredient is used for in vitro humin-like substances, polysaccharides, and proteins. Addition to a membrane separation activated sludge mixed liquid containing a filtration flux lowering substance that is at least one of molecular compounds, and performing membrane separation to remove the filtration flux lowering cause substance of the membrane separation activated sludge method Method.

Description

The present invention relates to a method for removing a filtration flux lowering cause substance of a separation membrane in a membrane separation activated sludge method.
This application claims priority based on Japanese Patent Application No. 2009-182867 filed in Japan on August 5, 2009, the contents of which are incorporated herein by reference.

In the present invention, the filtration flux lowering substance is a substance that can be clogged by blocking the pores of the membrane in the membrane separation activated sludge method. The substance refers to a polysaccharide, protein, humin-like substance, or other water-soluble polymer substance that causes a decrease in membrane flux, contained in inflow water or produced by microorganisms.
Membrane separation activated sludge method is a method in which solid-liquid separation is performed using a separation membrane such as a precision membrane or ultrafiltration membrane without providing a final sedimentation tank in the activated sludge method, and is popular from the viewpoint of high treated water quality and stable operation. It's getting on. In recent years, the demand for the membrane separation activated sludge method has increased due to the necessity of water recycling.
However, in the membrane separation activated sludge method, the presence of substances that cause a decrease in the filtration flux causes clogging of the membrane or a decrease in the amount of filtered water. Therefore, the fact is that it is not widely spread.

Furthermore, polysaccharides and proteins that are said to be a causative substance for lowering the filtration flux may be contained in the inflow raw water, but as shown in Non-Patent Document 1, they may be produced by microorganisms. is there. The non-biodegradable component such as humic substances is a polymer substance contained in waste water, groundwater, etc. as shown in Non-Patent Document 2 and Non-Patent Document 3, for example, and has both hydrophilicity and hydrophobicity. These substances that cause a decrease in the filtration flux are soluble in water due to water solubility, and cannot be separated and removed by coagulation sedimentation. In addition, since humic substances and the like are hardly decomposed by microorganisms, it is difficult to remove them by the activated sludge method and the like, and adsorption treatment with activated carbon or the like is possible, but the cost is extremely high.
Therefore, it is economically difficult to remove these filtration flux lowering cause substances by a known method, so that an immediate countermeasure is required.

In recent years, when the demand for water is increasing worldwide, the need for reclaimed water has further increased, and the development of an efficient water treatment method that is easy to maintain at low cost is desired.
Therefore, various methods have been proposed as countermeasures for reducing the membrane filtration flux. For example, a method of adding hypochlorous acid to the water to be treated (for example, Patent Document 1), a membrane by using a coarse bubble generation diffuser. Methods for cleaning (for example, Patent Document 2), methods for adding an inorganic flocculant to a membrane separation activated sludge tank (for example, Patent Document 3), methods for adding an organic polymer flocculant (for example, Patent Document 4), etc. Are listed. However, these methods are not yet satisfactory from the viewpoints of the complexity of maintenance and management, removal efficiency, and economic efficiency.
Patent Document 5 describes that polyvinylamine, which is one of the cationic polymers, can be used for bulking elimination.

JP 2000-237555 A JP 2005-95798 A JP 2006-15236 A JP 2006-334487 A JP 2009-000676 A

Nagaoka H, Ueda S, and Miya A: Effects of bacterial extracellular polymers in membrane activated sludge systems, Water Science and Technology, 34 (9) 165-172 (1996) Masato Ueda, Yoshiaki Sakamoto: Collection and characterization of groundwater humic substances using rigid adsorbent resin, nuclear backend research, vol. 12 No. 1-2 (2006) Yusaku Nogami, Tomoko Minami Arita, Masamitsu Miyanaga: Effect of fulvic acid on the COD of activated sludge treated water from domestic wastewater, water and wastewater vol. 43 No. 12 (2001)

As described above, the known method cannot be said to be a satisfactory method for removing the filtration flux lowering cause substance in the membrane separation activated sludge. For example, the method described in Patent Document 1 for adding hypochlorous acid to water to be treated has a risk of reducing the activity of microorganisms as well as high chemical costs and labor costs. Further, in the method of cleaning a film with a coarse bubble generating air diffuser described in Patent Document 2, there is a waste in reduction in operating rate of the apparatus due to frequent cleaning and oxygen dissolution efficiency.
Furthermore, as described in Patent Document 3, the method of adding an inorganic flocculant not only requires a large amount of flocculant, but also has a problem of pH reduction and sludge increase. Moreover, the method of adding the organic polymer flocculant described in Patent Document 4 has room for improvement in the sustainability of the effect due to the fact that the organic polymer flocculant has hydrolyzability and low fracture resistance. . For Patent Document 5, the use is limited to eliminating bulking, and it has not been known that water-soluble polysaccharides, humic substances, and the like can be removed.
In the process of removing the filtration flux lowering cause substance present in the membrane separation activated sludge tank, the present invention reduces the concentration by reducing the concentration with less sludge generation compared to the conventional method at a lower cost. An object of the present invention is to provide a method capable of shortening the cleaning time of the film and extending the cleaning interval.

  The present invention relates to a method for efficiently removing a filtration flux lowering cause substance present in a membrane separation activated sludge tank. The gist of the present invention is that a filtration flux lowering agent removing agent containing a water-soluble and / or water-absorbing cationic polymer as an active ingredient is added to a membrane separation activated sludge mixed solution, followed by membrane separation. It is the filtration flux fall cause substance removal method.

  As a preferred method of the method of the present invention, the filtration flux lowering substance in the membrane separation is at least one of a humin-like substance and a polysaccharide or protein produced by microorganisms or contained in the influent water; On the other hand, it is mentioned that 10 to 2000 mg / L of a membrane filtration flux lowering agent removing agent is added.

［式（１）、（２）中、Ｒ^１〜Ｒ^４は各々水素原子またはメチル基であり、同一であっても異なっていてもよい。Ｘ⁻、Ｙ⁻は各々陰イオンであり、同一であっても異なっていてもよい。］
ろ過流束低下原因物質がフミン様物質、多糖類、及びたんぱく質の生体外高分子化合物の少なくとも１種であることを特徴とする前記に記載のろ過流束低下原因物質の除去方法。
活性汚泥混合液に対し、１０〜２０００ｍｇ／Ｌのろ過流束低下原因物質除去剤を添加することを特徴とする前記に記載のろ過流束低下原因物質の除去方法。
水溶性及び／又は吸水性カチオン性重合体は、上記一般式（１）及び／又は（２）で示される単量体単位を５〜９０モル％含有することを特徴とする前記に記載のろ過流束低下原因物質の除去方法。Still other preferred embodiments include the following embodiments.
Removal of substances that cause a decrease in filtration flux comprising a cationic water-soluble polymer as an active ingredient, which is a cationic polymer containing an amidine structural unit represented by the following general formula (1) and / or (2) A method for removing a filtration flux lowering cause substance of the membrane separation activated sludge method, wherein the agent is added to a membrane separation activated sludge mixed liquid containing a filtration flux lowering cause substance to perform membrane separation.

[In the formulas (1) and (2), R ^{1 to} R ⁴ are each a hydrogen atom or a methyl group, and may be the same or different. X ⁻ and Y ⁻ are each an anion and may be the same or different. ]
The method for removing a filtration flux lowering cause substance as described above, wherein the filtration flux lowering cause substance is at least one of a humin-like substance, a polysaccharide, and a protein in vitro polymer compound.
10 to 2000 mg / L of a filtration flux lowering substance removing agent is added to the activated sludge mixed liquid, as described in the above, wherein the filtration flux lowering substance is removed.
The water-soluble and / or water-absorbing cationic polymer contains 5 to 90 mol% of the monomer unit represented by the general formula (1) and / or (2), as described above How to remove flux-causing substances.

  According to the method of the present invention, membrane separation activity can be achieved at low cost and with a small amount of sludge generation, using a water-soluble and / or water-absorbing cationic polymer that is a small amount of organic polymer flocculant compared with the conventional method. The density | concentration of the filtration flux fall cause substance which exists in sludge can be reduced. Moreover, according to the method of the present invention, it is only necessary to add the organic polymer flocculant to the activated sludge mixed liquid, and therefore, the filtration flux lowering substance can be easily removed without complicating the removal process.

The method of the present invention relates to a method for removing a membrane filtration flux lowering cause substance in a membrane separation activated sludge tank by a flux lowering cause substance removing agent. The flux lowering agent removing agent is a so-called polymer flocculant, and contains a water-soluble and / or water-absorbing cationic polymer as a main component. The polymer may be a crosslinkable gel.
The water-soluble and / or water-absorbing cationic polymer used as a main component of the flux reducing agent removing agent of the present invention contains an amidine structural unit represented by the following general formula (1) and / or (2). A cationic polymer.

［式（１）、（２）中、Ｒ^１〜Ｒ^４は各々水素原子またはメチル基であり、同一であっても異なっていてもよい。Ｘ⁻、Ｙ⁻は各々陰イオンであり、同一であっても異なっていてもよい。］

[In the formulas (1) and (2), R ^{1 to} R ⁴ are each a hydrogen atom or a methyl group, and may be the same or different. X ⁻ and Y ⁻ are each an anion and may be the same or different. ]

The water-soluble and / or water-absorbing cationic polymer used in the present invention has an amidine structural unit represented by the above general formula (1) and / or (2). Specific examples of the anions represented by X ⁻ and Y ⁻ in the general formulas (1) and (2) include Cl ⁻ , Br ⁻ , 1 / 2SO ₄ ²⁻ , and CH ₃ (CO). O ⁻ , H (CO) O ^{− and the} like can be mentioned. Of these, Cl ^- is preferable.
The method for producing such a cationic polymer is not particularly limited. For example, an ethylenically unsaturated monomer having a primary amino group or a substituted amino group capable of generating a primary amino group by a conversion reaction, and acrylonitrile or methacrylonitrile. A method of producing a copolymer with a nitrile of the above, reacting a cyano group in the copolymer with a primary amino group after acid hydrolysis, and amidinating is mentioned.

Examples of the ethylenically unsaturated monomer include the general formula CH ₂ ═CR ^a —NHCOR ^b (wherein R ^a represents a hydrogen atom or a methyl group, and R ^b represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom). .) Are preferred. In the copolymer with nitriles, the substituted amino group derived from such a compound is easily converted to a primary amino group by hydrolysis or alcoholysis. Furthermore, this primary amino group reacts with an adjacent cyano group to be amidined. Examples of the compound include N-vinylformamide (R ^a = H, R ^b = H), N-vinylacetamide (R ^a = H, R ^b = CH ₃ ) and the like.

  The polymerization molar ratio of these ethylenically unsaturated monomers and nitriles is usually 20:80 to 80:20, but if desired, the polymerization molar ratio outside this range, for example, the ratio of ethylenically unsaturated monomers. It is also possible to employ a large polymerization molar ratio. In general, when the ratio of the amidine structural unit in the water-soluble and / or water-absorbing cationic polymer is larger, the performance when the filtration flux lowering agent is removed is superior. Further, it is considered that the vinylamine structural unit also advantageously contributes to the performance as a filtration flux lowering substance removing agent. Accordingly, the polymerization molar ratio of the ethylenically unsaturated monomer and the nitrile that gives a copolymer suitable as a filter flux lowering agent removing agent is generally 20:80 to 80:20, particularly preferably 40: 60-60: 40.

As a method for copolymerizing the ethylenically unsaturated monomer and the nitrile, an ordinary radical polymerization method is used, and any of bulk polymerization, aqueous solution precipitation polymerization, suspension polymerization, emulsion polymerization, and the like can be used. When polymerizing in a solvent, the raw material monomer concentration is usually 5 to 80% by mass, preferably 20 to 60% by mass. Although a general radical polymerization initiator can be used as the polymerization initiator, an azo compound is preferable, and a hydrochloride of 2,2′-azobis (2-amidinopropane) is more preferable. The polymerization reaction is generally performed at a temperature of 30 to 100 ° C. under an inert gas stream. The obtained copolymer can be used as it is or diluted to be subjected to an amidation reaction. Alternatively, the solvent can be removed by a known method and dried to separate the copolymer as a solid, and then dissolved again to be subjected to an amidation reaction.
In the amidation reaction, when the N-vinylamide compound represented by the above general formula is used as the ethylenically unsaturated monomer, the substituted amino group of the copolymer is converted into a primary amino group, and then the generated primary amino group The cationic polymer used in the present invention can be produced by carrying out a two-step reaction in which an amidine structure is formed by reacting with a cyano group adjacent to the.
Note that the copolymer may be heated in water in the presence of a strong acid to produce an amidine structure in one step. Even in this case, it is considered that a primary amino group is first generated as an intermediate structure.

  Specific conditions for the amidation reaction include, for example, usually 0.1 to 5.0 times equivalent of strong acid, preferably 0.5 to 3.0 times equivalent of strong acid, relative to the substituted amino group in the copolymer, More preferably 0.7 to 1.5 times equivalent of hydrochloric acid is added, and the cation having an amidine structural unit is usually heated at a temperature of 80 to 150 ° C., preferably 90 to 120 ° C., usually for 0.5 to 20 hours. It can be made a functional polymer. In general, the larger the equivalent ratio of strong acid to substituted amino group and the higher the reaction temperature, the more the amidation proceeds. In addition, it is preferable that 10% by mass or more, preferably 20% by mass or more of water is usually present in the reaction system with respect to the copolymer to be subjected to the reaction in the amidine formation.

Most typically, the water-soluble and / or water-absorbing cationic polymer used in the present invention is obtained by copolymerizing N-vinylformamide and acrylonitrile in accordance with the above description. Usually, it is preferably produced as an aqueous suspension by heating in the presence of hydrochloric acid to form an amidine structural unit from a cyano group adjacent to the substituted amino group. And the cationic polymer of various compositions is obtained by selecting the molar ratio of N-vinylformamide and acrylonitrile to be subjected to copolymerization, and the amidation conditions of the copolymer.
The water-soluble and / or water-absorbing cationic polymer thus obtained is a repeating unit of the amidine structural unit represented by the above formula (1) and / or (2) in 100 mol% of the cationic polymer. It is preferable to contain 5-90 mol% as. When the content of the amidine structural unit is less than 5 mol%, the content of the amidine structural unit is too small, so that the amount used is increased when using the agent for removing a filtration flux lowering substance. On the other hand, it is difficult to produce those in which the content of the amidine structural unit exceeds 90 mol% by the method described above. The lower limit of the content of the amidine structural unit is more preferably 10 mol% or more, further preferably 15 mol% or more, and particularly preferably 20 mol% or more. Further, the upper limit of the content of the amidine structural unit is more preferably 85 mol% or less, and further preferably 80 mol% or less.

  The water-soluble and / or water-absorptive cationic polymer may contain units represented by the following formulas (3) to (5) in addition to the amidine structural unit when produced by the above-described method. .

In formulas (3) to (5), R ⁵ , R ⁷ and R ⁸ are each a hydrogen atom or a methyl group, and may be the same or different.
R ⁶ is an alkyl group having 1 to 4 carbon atoms or a hydrogen atom.
Z ⁻ is an anion. The anion is the same as the anion exemplified above in the description of the above formulas (1) and (2).

When the water-soluble and / or water-absorbing cationic polymer contains units represented by the above formulas (3) to (5), it is usually represented by the above formula (3) in 100 mol% of the cationic polymer. The repeating unit is 0 to 40 mol%, the repeating unit represented by the formula (4) is 0 to 70 mol%, and the repeating unit represented by the formula (5) is contained in an amount of 0 to 70 mol%.
The composition of the amidine structural unit represented by the above formula (1) and / or (2) and the unit represented by the above formulas (3) to (5) is a polymerization mole of the ethylenically unsaturated monomer and the nitrile. It can be adjusted by the ratio and the conditions (temperature and time) of the amidine reaction.
Further, these compositions can be obtained by measuring ¹³ C-NMR ( ¹³ C-nuclear magnetic resonance) of the cationic polymer. Specifically, the ¹³ C-NMR spectrum corresponding to each repeating unit is obtained. It can be calculated from the integrated value of the peak (signal).
As a method for producing a water-absorbing cationic polymer, for example, a method in which a polyfunctional crosslinking agent such as glyoxal or diepoxy compound is added to a raw material monomer mixture of the polymer to polymerize, a water-soluble Examples thereof include a method in which a polyfunctional substance that reacts with the polymer is reacted with the polymer, followed by cross-linking, and a method in which a water-soluble polymer is heated to cross-link.

The filtration flux lowering agent removing agent in the present invention contains an effective amount of a water-soluble and / or water-absorbing cationic polymer as a main component, but may contain other components. Examples of other components include formic acid and ammonium chloride.
In the present invention, the “active ingredient amount” means the content of the water-soluble and / or water-absorbing cationic polymer in 100% by mass of the filtration flux lowering substance removing agent, It is preferable to contain 100 mass%.
When the filtration flux lowering substance removing agent contains other components, the other components may be added so that the desired blending amount is obtained after the cationic polymer is produced. Other components may be mixed with the combined production raw material.

The water-soluble cationic polymer, which is the main component of the agent for removing the flux reduction factor of the present invention, has a reduced viscosity at 25 ° C. of 0.1 g / dL in 1N saline. It is preferably 01 to 10 dL / g, more preferably 0.1 to 8 dL / g. When the reduced viscosity is less than 0.01 dL / g, it tends to be difficult to produce a filtration flux lowering substance removing agent, or the function of the filtration flux lowering substance removing agent tends to be reduced. On the other hand, when the reduced viscosity exceeds 10 dL / g, the viscosity of the aqueous solution of the filtration flux lowering substance removing agent becomes too high, which may cause inconvenience in addition.
The reduced viscosity described above can be controlled by adjusting the molecular weight, ionic ratio, molecular weight distribution, production method, composition distribution, and the like of the water-soluble cationic polymer. For example, when the molecular weight of the water-soluble cationic polymer is increased, the reduced viscosity tends to increase.

In the method of the present invention, the filtration flux lowering agent removing agent as described above is added to the membrane separation activated sludge mixed solution containing the filtration flux lowering agent, and then membrane separation is performed to perform the membrane separation of the membrane filtration flux. This prevents the decrease.
In addition, you may use the filtration flux fall cause substance removal agent of this invention in combination with another film | membrane obstruction | occlusion countermeasure agent, an inorganic flocculant, and a polymer flocculant, as long as the effect is not impaired.

  In the present invention, “added to the membrane separation activated sludge mixed solution” is added to a membrane separation tank using a precision membrane, an ultrafiltration membrane or the like, and an arbitrary place in the activated sludge treatment system in the process preceding the membrane separation tank. This means that it is brought into contact with microorganisms in the activated sludge. For example, it is added to the raw water tank together with the activated sludge and led to the aeration tank. It is added directly to the membrane activated sludge tank. In addition to adding directly to an oxygen-free tank at a certain facility, any addition method may be used as long as it has an effect of removing substances that cause a decrease in filtration flux. Further, it can be added to a flow path such as a side groove or a pipe connecting the tanks or a flow rate adjusting tank provided in front of each tank.

(Addition to activated sludge)
In the method of the present invention, when the filtration flux lowering agent removing agent is added to the activated sludge in advance, the addition amount of the filtration flux lowering agent removing agent is preferably 10 to 2000 mg / L with respect to the activated sludge mixed solution. -1000 mg / L is more preferable. When the addition amount is less than 10 mg / L, it is difficult to sufficiently obtain the effect of the filtration flux lowering substance removing agent. On the other hand, when the addition amount exceeds 2000 mg / L, not only the effect of the filtration flux lowering substance removing agent is not sufficiently obtained, but also the microbial activity in the activated sludge may be adversely affected.

(Addition to raw water storage tank)
When adding a removal agent for reducing the filtration flux to the raw water storage tank, it is usually added directly to the membrane separation activated sludge tank by dissolving it in water, etc. or injecting it into the membrane separation activated sludge tank. That's fine.
The amount of the filtration flux lowering cause substance removing agent used is not particularly limited because it varies depending on the concentration of the filtration flux lowering cause substance and activated sludge. For example, a filtration flow of 10 to 2000 mg / L with respect to the activated sludge mixed solution. It is preferable to use a bundle lowering agent removing agent.
Moreover, the amount of the filtration flux lowering agent removing agent used is that the activated sludge in the processing apparatus is collected in a beaker or the like, the removing agent is added, the total sugar concentration of the supernatant (phenol sulfuric acid method), and the filter paper It can also be determined by evaluating filterability.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
In the following test examples (Examples and Comparative Examples), the filtration flux lowering agent removing agent was evaluated by measuring the total sugar concentration of the treated water after the sludge treatment and the filter paper filtration amount.

<Measurement of total sugar concentration>
The total sugar concentration indicates the concentration of polysaccharide dissolved in water or in a colloidal form, and the absorbance near 490 nm is measured with an ultraviolet-visible spectrophotometer (Shimadzu Science Co., Ltd. UV-3100), It calculated from the calibration curve by a standard solution.
The total sugar concentration is measured by a conventional method; the phenol sulfate method [Hodge, J. et al. E. and Hofreiter, B .; T.A. , Method in Carbohydrate Chemistry, 1, 338 (1962)].
The effect of removing the filtration flux lowering cause substance was determined by calculating the removal rate of the filtration flux lowering cause substance by the following equation.
Removal rate (%) = (1−A ₂ / A ₁ ) × 100
(A ₁ : Total sugar concentration of treated wastewater, A ₂ : Total sugar concentration after removal of substances that cause filtration flux reduction)

<Measurement of filter paper filtration rate>
The amount of filter paper filtration is 16 folds of 5C filter paper with a diameter of 185 mm (ADVANTEC), put into a funnel and attached to a 50 ml graduated cylinder, and then poured 50 ml of sludge after removing the filter flux lowering cause substance, 5 minutes later The amount of filtration of was measured.
The greater the filtration amount after 5 minutes, the better the filterability, and the higher the effect of removing the filtration flux lowering cause substance.

  The cationic polymers used in the test examples are summarized in Table 1 below.

[Cationic polymer]
As the cationic polymer of the present invention, cationic polymers (A1, A2, A3) produced by the following method were used.
<Production of cationic polymer A1>
In a 50 ml four-necked flask equipped with a stirrer, a nitrogen inlet tube, and a condenser tube, 6 g of a mixture of acrylonitrile and N-vinylformamide (molar ratio 55:45) and 34 g of a mixture of demineralized water were placed. In nitrogen gas, the temperature of the mixture was increased to 60 ° C. while stirring, 0.12 g of 10% by mass of 2,2′-azobis (2-amidinopropane) dihydrochloride solution was added, and the mixture was further maintained for 3 hours. Thus, a suspension in which the polymer was precipitated in water was obtained. 20 g of water was added to the suspension, and 2 equivalents of concentrated hydrochloric acid was added to the formyl group of the polymer, and then kept at 100 ° C. for 4 hours to obtain a yellow high-viscosity liquid. After the high viscosity liquid was added to a large amount of acetone, a polymer was precipitated. Thereafter, the obtained polymer was shredded and dried overnight at 60 ° C., and then the polymer was pulverized to obtain a powdered cationic polymer.

(Composition of cationic polymer A1)
Cationic polymer A1 was dissolved in heavy water, and a ¹³ C-NMR spectrum was measured with an NMR spectrometer (manufactured by JEOL Ltd., 270 MHz). The composition of each unit was calculated from the integrated value of the peak corresponding to each repeating unit of the ¹³ C-NMR spectrum. The structural units of the general formulas (1) and (2) were determined as the total amount without distinction. The results are shown in Table 1.
Moreover, each unit contained in the cationic polymer A1 obtained in this way is represented by R ^{1 to} R ⁴ and R in the above formula [(1), (2), (3) to (5)]. ^{5 to} R ⁸ were hydrogen atoms, and X ⁻ , Y ⁻ and Z ⁻ were chloride ions.
(Measurement of reduced viscosity of cationic polymer A1)
0.1 g of the cationic polymer A1 was dissolved in 100 mL of 1N saline to prepare a 0.1 g / dL solution. The reduced viscosity of the cationic polymer A1 at 25 ° C. of the solution was measured with an Ostwald viscometer (manufactured by Hario Laboratories). The results are shown in Table 1.

<Production of cationic polymer A2>
A 500 ml four-necked flask equipped with a stirrer, a nitrogen inlet tube, and a cooling tube was charged with 40 g of demineralized water, 1.2 g of polyethylene glycol 20000, and 0.2 g of sodium hypophosphite, and then heated to 70 ° C. Then, under a nitrogen stream, 120 g of a 70% by mass aqueous solution of a mixture of acrylonitrile and N-vinylformamide (molar ratio 50:50) was added dropwise over 2 hours. Meanwhile, 12.6 g of a 2% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride in 10% by mass was added in five portions. The mixture was aged for 2 hours, concentrated hydrochloric acid (corresponding to 100 mol% of formyl group) was added, the temperature was raised to 90 ° C., and the mixture was allowed to stand for 3 hours. The mixture is added to a large amount of acetone, the polymer is precipitated, the obtained polymer is shredded, the polymer is dried overnight at 60 ° C., and then pulverized into a powdered cationic polymer. Got.

(Composition of cationic polymer A2)
Similarly to the cationic polymer A1, the ¹³ C-NMR spectrum of the cationic polymer A2 was measured, and the composition of each unit was calculated. Further, the structural units of the above general formulas (1) and (2) were determined as the total amount without distinction. The results are shown in Table 1.
In addition, each unit contained in the cationic polymer A2 thus obtained is represented by R ^{1 to} R ⁴ and R in the above formula [(1), (2), (3) to (5)]. ^{5 to} R ⁸ were hydrogen atoms, and X ⁻ , Y ⁻ and Z ⁻ were chloride ions.
(Reduced viscosity of the cationic polymer A2)
The reduced viscosity of the cationic polymer A2 was measured in the same manner as the cationic polymer A1. The results are shown in Table 1.

<Production of cationic polymer A3>
The cationic polymer A3 is obtained by crosslinking the cationic polymer A1 by heat treatment (120 ° C., 5 hours), and the reduced viscosity of the cationic polymer A3 was measured in the same manner as the cationic polymer A1. . The results are shown in Table 1.

  As comparative examples, commercially available polymer flocculants B1: Diafloc K-405 (containing 55 wt% dicyandiamide / ammonium chloride / formaldehyde polycondensate), B2: Diafloc K-403B (containing quaternary polyamine 50 wt%) used.

Amidine: Amidine hydrochloride unit NVF: N-vinylformamide unit AN: Acrylonitrile unit VAM: Vinylamine hydrochloride unit AA: Acrylic acid unit

[Test example]
<Example 1>
200 ml of activated sludge (pH 6.7, MLSS 9,000 mg / L) of a membrane separation activated sludge apparatus for treating domestic wastewater is placed in a beaker, and a 0.1% by mass aqueous solution of the filter flux lowering agent removing agent shown in Table 2 A predetermined amount was added. Thereafter, the mixture was stirred for 2 minutes and allowed to stand overnight. Thereafter, the supernatant liquid was colored by the phenol-sulfuric acid method, the absorbance at a wavelength of 490 nm was measured, and the total sugar concentration of the supernatant liquid was calculated from the measured value to determine the effect of removing the filtration flux lowering cause substance. On the other hand, 50 ml of sludge after removal of the substance causing the filtration flux reduction was poured into a filter paper attached to a graduated cylinder, and the amount of filtrate after 5 minutes was measured. The results are shown in Table 2.

<Comparative Example 1>
The filtration flux lowering cause substance removal effect was determined in the same manner as in Example 1 except that the filtration flux lowering cause substance removing agent was not added. The results are shown in Table 2.
<Comparative example 2>
The filtration flux lowering substance removal effect was determined in the same manner as in Example 1 except that the polymer flocculants (B1, B2) manufactured by Dianitricks Co., Ltd. were used. The results are shown in Table 2.

According to the method of the present invention, membrane separation activity can be achieved at low cost and with a small amount of sludge generation, using a water-soluble and / or water-absorbing cationic polymer that is a small amount of organic polymer flocculant compared with the conventional method. The density | concentration of the filtration flux fall cause substance which exists in sludge can be reduced. Moreover, according to the method of the present invention, it is only necessary to add the organic polymer flocculant to the activated sludge mixed liquid, and therefore, the filtration flux lowering substance can be easily removed without complicating the removal process.

Claims (4)

Removal of substances that cause a decrease in filtration flux comprising a cationic water-soluble polymer as an active ingredient, which is a cationic polymer containing an amidine structural unit represented by the following general formula (1) and / or (2) A method for removing a filtration flux lowering cause substance of the membrane separation activated sludge method, wherein the agent is added to a membrane separation activated sludge mixed liquid containing a filtration flux lowering cause substance to perform membrane separation.

[In the formulas (1) and (2), R ^{1 to} R ⁴ are each a hydrogen atom or a methyl group, and may be the same or different. X ⁻ and Y ⁻ are each an anion and may be the same or different. ]   The method for removing a filtration flux lowering cause substance according to claim 1, wherein the filtration flux lowering cause substance is at least one of a humin-like substance, a polysaccharide, and a protein in vitro polymer compound.   The method for removing a filtration flux lowering cause substance according to claim 1, wherein 10 to 2000 mg / L of a filtration flux lowering cause substance removing agent is added to the activated sludge mixed liquid.   The water-soluble and / or water-absorbing cationic polymer contains 5 to 90 mol% of the monomer unit represented by the general formula (1) and / or (2). To remove substances that cause filtration flux reduction.