KR20120085713A - Method for removing substance causative of flow velocity decrease in membrane-separation activated-sludge process - Google Patents

Abstract

The present invention provides a method for efficiently removing the causative agent for lowering the filtration flow rate present in the membrane separation activated sludge mixture using a small amount of organic polymer flocculant. Specifically, the removal agent for lowering the filtration flow rate, which comprises a water-soluble and / or water-absorbing cationic polymer containing a structural unit represented by a predetermined chemical formula as an active ingredient, is an ex vivo polymer compound of humus-like substances, polysaccharides, and proteins. Provided is a method for removing a filtration flow rate lowering cause substance of the membrane separation active sludge method, which is added to a membrane separation activated sludge mixed liquid containing at least one filtration flow rate lowering cause substance.

Description

METHODS FOR REMOVING SUBSTANCE CAUSATIVE OF FLOW VELOCITY DECREASE IN MEMBRANE-SEPARATION ACTIVATED-SLUDGE PROCESS}

The present invention relates to a method for removing the causative agent for lowering the filtration flow rate of a separator in a membrane separation activated sludge method.

This application claims priority based on Japanese Patent Application No. 2009-182867 for which it applied to Japan on August 5, 2009, and uses the content here.

In the present invention, the substance causing the decrease in the filtration flow rate refers to a substance capable of causing clogging by blocking the pores of the membrane in the membrane separation active sludge method. The material refers to polysaccharides, proteins, humic-like substances, or other water-soluble high molecular substances that cause a decrease in the flow rate of membranes contained in the influent or produced by the microorganism.

The membrane separation activated sludge method is a method of performing solid-liquid separation by a separation membrane such as a precision membrane or an ultrafiltration membrane without providing a final settling tank in the active sludge method, and is widely used in view of high treatment water quality and operational stability. In addition, the demand for the membrane separation activated sludge method is increasing recently from the necessity of recycling water.

However, the membrane separation activity sludge method has a maintenance problem related to membrane cleaning, replacement, etc. due to the presence of a substance that causes a decrease in the filtration flow rate, resulting in a clogging of the membrane or a decrease in the amount of filtered water. It is true.

In addition, although the polysaccharides and proteins known as the causative agent of lowering the filtration flow rate may be contained in the incoming raw water, they may be produced by microorganisms as disclosed in Non Patent Literature 1. The biodegradable components, such as humus, are polymeric substances contained in wastewater, groundwater, etc., as disclosed in the nonpatent literature 2 and the nonpatent literature 3, for example, and combine hydrophilicity and hydrophobicity. Since these filtration flux-lowering substances are water-soluble, they are dissolved in water and cannot be separated and removed by coagulation precipitation. In addition, since humus and the like are difficult to be decomposed by microorganisms, it is difficult to remove them by the activated sludge process and the like, and the adsorption treatment with activated carbon and the like is possible, but it is very expensive.

Therefore, it is economically difficult to carry out the removal of these filtration flow rate-causing substances by a known method, so urgent measures are required.

In recent years, as the demand for water has increased worldwide, the necessity of regeneration water is increasing, and development of an efficient water treatment method which is low in cost and easy to maintain is desired.

Therefore, various methods are proposed as a countermeasure of a membrane filtration flow rate fall, For example, the method of adding hypochlorous acid to to-be-processed water (for example, patent document 1), and the method of washing | cleaning a membrane by a coarse bubble generation | occurrence | production apparatus. (For example, patent document 2), the method of adding an inorganic flocculant to a membrane separation active sludge (for example, patent document 3), the method of adding an organic polymer flocculant (for example, patent document 4), etc. are mentioned. Can be. However, these methods cannot be said to be still satisfactory from the viewpoint of maintenance complexity, removal efficiency and economical efficiency.

Moreover, it is described in patent document 5 that polyvinylamine which is one of a cationic polymer can be used for bulking elimination use.

Japanese Patent Laid-Open No. 2000-237555 Japanese Patent Laid-Open No. 2005-95798 Japanese Patent Laid-Open No. 2006-15236 Japanese Patent Laid-Open No. 2006-334587 Japanese Patent Publication No. 2009-000676

 Nagaoka H, Ueda S and Miya A: Effect of Bacterial Extracellular Polymer in Membrane Separation Active Sludge System, Water Science and Technology, 34 (9) 165-172 (1996)  Masato Ueda, Yoshiaki Sakamoto: Collection and Characterization of Groundwater Corrosives Using Rigid Adsorbent Resin, Vol.12 No.1-2 (2006)  Nogami-Sawaku, Tomomi Minami-Arita, Masamitsu Miyanaga: Effect of Fulvic Acid on COD of Active Sludge Treatment Water in Domestic Drainage, 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 substance causing the filtration flow rate drop in the membrane separation activated sludge. For example, the method of adding hypochlorous acid to the to-be-processed water described in patent document 1 has a high chemical liquid cost and labor cost, and there exists a possibility of reducing the activity of a microorganism. Moreover, in the method of washing | cleaning a film | membrane with the coarse bubble generation | occurrence | production apparatus described in patent document 2, there existed waste in the operation rate fall of the apparatus by frequent washing | cleaning, and oxygen dissolution efficiency.

In addition, as described in Patent Literature 3, the method of adding the inorganic coagulant not only requires a large amount of the coagulant, but also has a problem of fear of pH drop and increase of sludge. In addition, the method of adding the organic polymer flocculent described in Patent Document 4 has room for improvement in the durability of the effect because the organic polymer flocculant has hydrolysis resistance or low fracture resistance. In patent document 5, the use is limited to bulking elimination and it is not known that water-soluble polysaccharide, humus, etc. can be removed.

The present invention is not only inexpensive and simple, but also reduces the concentration to a small amount of sludge in the process of removing the causative agent for lowering the filtration flow rate present in the membrane separation active sludge, thereby reducing the cleaning time of the separation membrane to reduce the cleaning interval. It is an object of the present invention to provide a method for extending the service.

The present invention relates to a method for efficiently removing the causative agent for lowering the filtration flow rate present in the membrane separation activated sludge. The gist of the present invention is that a filtration flow rate lowering cause substance removal agent comprising a water-soluble and / or water-absorbing cationic polymer as an active ingredient is added to the membrane separation active sludge mixed liquid, followed by membrane separation. How to remove the cause substance.

A preferred method of the method of the present invention, wherein the caustic flow-lowering agent in the membrane separation is at least one of a caustic-like substance and a polysaccharide or protein produced or contained in the influent; Addition of 10-2000 mg / L of membrane filtration flow rate lowering substance removal agent with respect to active sludge mixture is mentioned.

As another preferable aspect, the following aspects are mentioned.

A cationic polymer containing an amidine structural unit represented by the following formulas (1) and / or (2) containing a cationic water-soluble polymer as an active ingredient, wherein A method for removing a causative flow rate lowering cause of the membrane separation activated sludge method, which is added to a membrane separation activated sludge mixed liquid to perform membrane separation.

R ¹ to R ⁴ in Formulas 1 and 2 are each a hydrogen atom or a methyl group, and may be the same or different, and X ⁻ and Y ⁻ are each an anion and may be the same or different.

A method for removing a filtration-flow-rate-causing substance according to the above, wherein the filtration-flow-rate-causing substance is at least one of an in vitro high molecular compound of humus-like substance, polysaccharide and protein.

A method for removing a filtration flow rate-causing substance according to the above, wherein a filtration flow rate-causing substance removing agent of 10 to 2000 mg / L is added to the activated sludge mixture.

The water-soluble and / or water-absorbing cationic polymer contains 5 to 90 mol% of monomer units represented by the above formulas (1) and / or (2).

According to the method of the present invention, using a water-soluble and / or water-absorbing cationic polymer that is an organic polymer flocculant in a small amount compared to the conventional method, the concentration of the substance causing the lowering of the filtration flow rate in the membrane separation activated sludge with low sludge generation amount is inexpensive. Can be reduced. In addition, according to the method of the present invention, it is sufficient to simply add the organic polymer flocculant to the activated sludge mixed liquid, so that the substance causing the filtration flow rate drop can be easily removed without complicating the removal step.

The method of the present invention relates to a method for removing a membrane filtration flow rate lowering cause substance in a membrane separation active sludge by a flow rate lowering substance removing agent. The agent for removing the flow rate lowering substance is a so-called polymer flocculant and is mainly composed of a water-soluble and / or an absorbent cationic polymer. The polymer may also be a crosslinkable gel.

The water-soluble and / or water-absorbing cationic polymer used as the main component of the material for removing the flow rate lowering agent of the present invention is a cationic polymer containing an amidine structural unit represented by the following general formulas (1) and / or (2).

<Formula 1>

<Formula 2>

R ¹ to R ⁴ in Formulas 1 and 2 are each a hydrogen atom or a methyl group, and may be the same or different, and X ⁻ and Y ⁻ are each an anion and may be the same or different.

The water-soluble and / or absorbent cationic polymer used in the present invention is one having an amidine structural unit represented by the formulas (1) and / or (2). In addition, as the anion represented by X ⁻ , Y ⁻ in Chemical Formulas 1 and 2, specifically Cl ⁻ , Br ⁻ , 1 / 2SO ₄ ^{2 −} , CH ₃ (CO) O ⁻ , H (CO) O ⁻ , and the like. Can be mentioned. Among these, Cl ^- is preferable.

Although it does not restrict | limit especially as a manufacturing method of such a cationic polymer, For example, ethylenically unsaturated monomer which has a primary amino group or the substituted amino group which a primary amino group can produce | generate by a conversion reaction, and acrylonitrile or methacrylonitrile. The method of manufacturing the copolymer with the nitriles, hydrolyzing the acid, and then reacting with the cyano group and the primary amino group in the copolymer to amidine.

Examples of the ethylenically unsaturated monomer is a compound represented by the formula CH ₂ = CR ^a -NHCOR ^b (wherein, R ^a represents a hydrogen atom or a methyl group, R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms) desirable. 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 dialcohol decomposition. Moreover, this primary amino group reacts with an adjacent cyano group and amidines. 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.

Although the polymerization molar ratio of these ethylenically unsaturated monomers and nitriles is 20: 80-80: 20 normally, depending on the objective, the polymerization molar ratio outside this range, for example, the polymerization molar ratio with a large ratio of an ethylenically unsaturated monomer, can also be used further. In general, when the ratio of the amidine structural unit in the water-soluble and / or the water-absorbing cationic polymer is large, the performance is excellent when the material for removing the filtration flow rate is used as a substance removal agent. In addition, it is thought that the vinylamine structural unit also contributes favorably to the performance as a substance removal agent which reduces a filtration flow rate. Accordingly, the polymerization molar ratio of the above-mentioned ethylenically unsaturated monomer and nitriles, which provides a copolymer which is preferable as the material for removing the filtration flow rate lowering material, is generally 20:80 to 80:20, particularly preferably 40:60 to 60:40. .

As a copolymerization method of an ethylenically unsaturated monomer and nitriles, the normal radical polymerization method is used, and all the bulk polymerization, aqueous solution precipitation polymerization, suspension polymerization, emulsion polymerization, etc. can be used. When superposing | polymerizing in a solvent, a raw material monomer concentration is 5 to 80 mass% normally, Preferably it is implemented at 20 to 60 mass%. Although a general radical polymerization initiator can be used as a polymerization initiator, an azo compound is preferable and the hydrochloride of 2,2'- azobis (2-amidinopropane) etc. are more preferable. In addition, the polymerization reaction is generally carried out at a temperature of 30 to 100 ° C. under an inert gas stream. The obtained copolymer can be used as it is or in dilution for the amidation reaction. The solvent may be desolvated or dried by a known method to separate the copolymer as a solid, and then dissolved again to use the amidation reaction.

In an amidation reaction, when using the N-vinylamide compound represented by the said chemical formula as an ethylenically unsaturated monomer, the substituted amino group of a copolymer is converted into the primary amino group, and then the cyano group adjacent to the produced | generated primary amino group is carried out. The cationic polymer used in the present invention can be prepared by carrying out a two-step reaction in which the amidine structure is reacted.

The copolymer may also be warmed in water in the presence of a strong acid to produce an amidine structure in one step. Also in this case, it is considered that a primary amino group is produced as an intermediate structure.

As specific conditions for the amidation reaction, for example, 0.1 to 5.0 times equivalent of strong acid, preferably 0.5 to 3.0 times equivalent of strong acid, more preferably 0.7 to 1.5 times equivalent of hydrochloric acid, relative to the substituted amino group in the copolymer. It is possible to obtain a cationic polymer having an amidine structural unit by adding and heating at a temperature of usually 80 to 150 ° C, preferably 90 to 120 ° C for 0.5 to 20 hours. In general, the higher the reaction temperature and the higher the equivalent ratio of the strong acid to the substituted amino group, the more amidated. In addition, in the case of amidation, it is preferable to make water 10 mass% or more normally, preferably 20 mass% or more exist in a reaction system with respect to the copolymer used for reaction.

The water-soluble and / or absorbent cationic polymer used in the present invention is most typically copolymerized with N-vinylformamide and acrylonitrile as described above, and the resulting copolymer is usually used as an aqueous suspension to present hydrochloric acid. It is preferably prepared by heating to form an amidine structural unit from a cyano group adjacent to the substituted amino group. Moreover, the cationic polymer of various compositions is obtained by selecting the molar ratio of N-vinylformamide and acrylonitrile used for copolymerization, and the amidation conditions of a copolymer.

It is preferable that the water-soluble and / or water absorbing cationic polymer obtained in this way contains 5 to 90 mol% of amidine structural units represented by the said Formula (1) and / or 2 as a repeating unit in 100 mol% of said cationic polymers. . When the content rate of the amidine structural unit is less than 5 mol%, the content of the amidine structural unit is too small, so that the amount of the amidine structural unit used increases when the substance removing agent for causing the filtration flow rate decreases. On the other hand, it is difficult to manufacture by the method mentioned above that content of an amidine structural unit exceeds 90 mol%. 10 mol% or more is more preferable, as for the lower limit of the content rate of an amidine structural unit, 15 mol% or more is more preferable, 20 mol% or more is especially preferable. Moreover, 85 mol% or less is more preferable, and, as for the upper limit of the content rate of an amidine structural unit, 80 mol% or less is more preferable.

In addition, the water-soluble and / or water-absorbing cationic polymer may be prepared by the above-described method, and may contain units represented by the following formulas (3) to (5) in addition to the amidine structural units.

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

When the water-soluble and / or absorptive cationic polymer contains a unit represented by the above formulas (3) to (5), 0 to 40 mol% of the repeating unit represented by the above formula (3) is usually contained in 100 mol% of the cationic polymer. 0 to 70 mol% of the repeating unit represented by the above, and 0 to 70 mol% of the repeating unit represented by the said Formula (5).

The composition of the amidine structural unit represented by the formula (1) and / or 2 and the unit represented by the formulas (3) to (5) is determined by the polymerization molar ratio of the ethylenically unsaturated monomer and the nitriles or the conditions (temperature or time) of the amidation reaction. Can be adjusted accordingly.

In addition, these compositions can be calculated | required by measuring ¹³ C-NMR ( ¹³ C-nuclear magnetic resonance) of a cationic polymer, Specifically, the integral value of the peak (signal) of the ¹³ C-NMR spectrum corresponding to each repeating unit It can be calculated from

Moreover, as a method of manufacturing an absorptive cationic polymer, the method of superposing | polymerizing by adding polyfunctional crosslinking agents, such as a glyoxal and a diepoxy compound, to a raw material monomer mixture of a polymer, etc., and the polytube which reacts with a polymer to a water-soluble polymer, for example Examples thereof include a method of reacting and post-crosslinking a material having a tackiness, a method of heating and crosslinking a water-soluble polymer, and the like.

The substance removal agent for lowering the filtration flow rate in the present invention contains an active ingredient amount of a water-soluble and / or absorbent cationic polymer which is a main component, but may also contain other components. As other components, formic acid, ammonium chloride, etc. are mentioned, for example.

In addition, in this invention, "amount of active ingredient" means content of the water-soluble and / or water absorbing cationic polymer in 100 mass% of filtration flow rate fall cause substance removal agents, It is preferable to contain 10-100 mass% normally.

In the case where the substance removing agent causing the filtration flow rate decreases contains other components, other components may be added to the desired blending amount after the cationic polymer is prepared, or the other components may be mixed with the raw materials for preparing these (co) polymers in advance. have.

The water-soluble cationic polymer, which is the main component of the filtration flux-lowering substance removing agent of the present invention, when the solution is 0.1 g / dL with 1 N saline, preferably has a reduced viscosity of 0.01 to 10 dL / g at 25 ° C. More preferably, it is 0.1-8 dL / g. When the reduced viscosity is less than 0.01 dL / g, it becomes difficult to produce a filtration flow rate lowering substance removing agent or the function of the filtration flow rate lowering substance removing agent tends to be lowered. On the other hand, when the reduced viscosity exceeds 10 dL / g, since the viscosity of the aqueous solution of the filtration flow rate lowering cause substance removal agent becomes too high, there may be a problem in addition.

In addition, the reduction viscosity mentioned above can be controlled by adjustment of the molecular weight, ionic ratio, molecular weight distribution, manufacturing method, composition distribution, etc. of a water-soluble cationic polymer. For example, when the molecular weight of the water-soluble cationic polymer is increased, the reducing viscosity tends to increase.

In the method of the present invention, the above-described filtration flow rate lowering substance removing agent is added to the membrane separation activated sludge mixture liquid containing the filtration flow rate lowering substance, followed by membrane separation to prevent the decrease of the membrane filtration flow rate.

In addition, as long as the effect of removing the filtration flow rate lowering substance of the present invention is not impaired, it can also be used in combination with other membrane blocking agents, inorganic coagulants, and polymer coagulants.

In the present invention, "added to the membrane separation activated sludge mixed liquid" means that the membrane is separated by a precision membrane, an ultrafiltration membrane, or the like, and added to any place in the active sludge treatment system prior to the membrane separation tank. It means contact with microorganisms, for example, it is added to raw water tank with activated sludge, led to aeration tank, and added directly to membrane-activated sludge, directly added to anoxic tank in an anoxic tank for denitrification. In addition, any addition method may be used as long as there is an effect of removing the substance causing the lowered filtration flow rate. Furthermore, it is also possible to add to flow paths, such as a side port and piping which connect each tank, and the flow volume adjustment tank provided in front of each tank.

(Addition of activated sludge)

In the method of the present invention, in the case where the filtration flux lowering causative agent is added to the activated sludge in advance, the amount of the filtration flux lowering caustic agent is preferably 10 to 2000 mg / L with respect to the activated sludge mixture, and 10 to 1000 mg / L Is more preferable. If the addition amount is less than 10 mg / L, the effect of the substance removing agent for lowering the filtration flow rate becomes difficult to be obtained sufficiently. On the other hand, when the added amount exceeds 2000 mg / L, not only the effect of the substance removing agent for lowering the filtration flow rate becomes difficult to be sufficiently obtained, but also adversely affect the microbial activity in the activated sludge.

(Addition to raw water storage tank)

In the case of adding the substance removing agent for lowering the filtration flow rate to the raw water storage tank, it is usually dissolved directly in water or the like, or directly added to the raw water storage tank, or injected into the line flowing into the membrane separation activated sludge to be introduced into the membrane separation activated sludge.

The amount of the removal agent for lowering the filtration flow rate is not particularly limited because it is different depending on the concentration for lowering the filtration flow rate and the concentration of the activated sludge. For example, the filtration flow rate lowering cause of 10 to 2000 mg / L with respect to the activated sludge mixture. Preference is given to using a remover.

In addition, the usage-amount of the substance removal agent of the filtration flow rate fall cause material can also be determined by extracting the activated sludge in a processing apparatus, etc., and adding the said removal agent, and evaluating the total sugar concentration (phenol sulfate) method and filter paper filterability of a supernatant liquid.

[Example]

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to this.

In the following test examples (Examples and Comparative Examples), evaluation of the removal agent of the cause of lowering the filtration flow rate was performed by measuring the total sugar concentration of the treated water after sludge treatment and the filter paper filtration amount.

<Measurement of total sugar concentration>

The total sugar concentration indicates the concentration of polysaccharides present in dissolved or colloidal form in water. The absorbance at around 490 nm is measured by an ultraviolet visible spectrophotometer (UV-3100 manufactured by Shimadzu Science Co., Ltd.), and the calibration curve by the standard solution Calculated from

In addition, the measurement of total sugar concentration is a conventional method; It carried out according to the phenol sulfate method (Hodge, J. E. and Hofreiter, B. T., Method in Carbohydrate Chemistry, 1, 338 (1962)).

The determination of the removal effect of the filtration flow rate lowering cause substance was performed by calculating the removal rate of the filtration flow rate lowering cause substance by the following equation.

&Quot; (1) &quot;

Removal rate (%) = (1-A ₂ / A ₁ ) × 100

(A ₁ : total sugar concentration of the treated wastewater, A ₂ : total sugar concentration after removal of the substance causing the filtration flow rate drop)

<Measurement of filter paper filtration amount>

Filter paper Filtration amount is 5 times of 5C filter paper (ADVANTEC Co., Ltd. product) of diameter 185mm, put in funnel, put in 50 ml measuring cylinder, and 50 ml of sludge after removal of the substance which reduced the filtration flow rate is introduced, and it is 5 minutes After filtration amount is measured.

It means that the more the filtration amount after 5 minutes, the more excellent filterability and the removal effect of the substance which causes the filtration flow rate fall is high.

The cationic polymer used in the test example is collectively shown 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 cooling tube, 6 g of a mixture of acrylonitrile and N-vinylformamide (molar ratio 55:45) and 34 g of demineralized product were placed. The mixture was heated to 60 ° C. while stirring in nitrogen gas, 0.12 g of 10 mass% aqueous 2,2′-azobis (2-amidinopropane) dihydrochloride solution was added and held for 3 hours to maintain the polymer in water. The precipitate which precipitated 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, followed by maintaining at 100 DEG C for 4 hours to obtain a yellow high viscosity liquid. After adding the high viscosity liquid to a large amount of acetone, the polymer was precipitated. Thereafter, the obtained polymer was sintered and dried at 60 ° C. for 1 day, and then the polymer was pulverized to obtain a powder cationic polymer.

(Composition of Cationic Polymer A1)

The cationic polymer A1 was dissolved in heavy water, and the ¹³ C-NMR spectrum was measured by an NMR spectrometer (270 MHz, manufactured by Nippon Denshi Co., Ltd.). The composition of each unit was computed from the integrated value of the peak corresponding to each repeating unit of a ¹³ C-NMR spectrum. In addition, the structural unit of the said General formula (1) and (2) was calculated | required as the total amount, without distinguishing. The results are shown in Table 1.

In addition, each unit contained in the cationic polymer A1 obtained in this way is R <^1> -R <^4> and R <^5> -R <^{8> in a} said Formula (1, 2, 3-5) are hydrogen atoms, and X <^-> , Y <^-> , Z ^- was a chloride ion.

(Measurement of Reduced Viscosity of Cationic Polymer A1)

0.1 g of cationic polymer A1 was dissolved in 100 mL of 1 N 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 by an Ostwald viscometer (manufactured by Harios Corporation). The results are shown in Table 1.

<Production of Cationic Polymer A2>

In a 500 ml four-necked flask equipped with a stirrer, a nitrogen inlet tube, and a cooling tube, 40 g of demineralized water, 1.2 g of polyethylene glycol 20000, and 0.2 g of sodium hypophosphite were added thereto, and the temperature was raised to 70 ° C., followed by acrylonitrile and 120 g of 70 mass% aqueous solution of the mixture of N-vinylformamide (molar ratio 50:50) was dripped over 2 hours. Meanwhile, 12.6 g of a 10 mass% 2,2'-azobis (2-amidinopropane) aqueous dihydrochloride solution was added in 5 portions. After the mixture was aged for 2 hours, concentrated hydrochloric acid (equivalent to 100 mol% based on formyl group) was added to increase the temperature to 90 ° C and to stand for 3 hours. The mixture was added to a large amount of acetone to precipitate a polymer, the obtained polymer was crushed, the polymer was dried at 60 ° C. for 1 day, and then ground to obtain a powder cationic polymer.

(Composition of Cationic Polymer A2)

¹³ C-NMR spectrum of the cationic polymer A2 was measured in the same manner as the cationic polymer A1, and the composition of each unit was calculated. In addition, the structural unit of the said Formula (1) and (2) was calculated | required as the total amount, without distinguishing. The results are shown in Table 1.

In addition, in each unit contained in the cationic polymer A2 obtained in this way, R <^1> -R <^4> and R <^5> -R <^8> are hydrogen atoms in the said General formula (1, 2, 3-5), and X <^-> , Y <^-> , Z ^- was a chloride ion.

(Reduced Viscosity of Cationic Polymer A2)

The reduction 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>

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

In addition, as a comparative example, commercially available polymer coagulant B1: diyaprok K-405 (containing 55% by weight of dicyandiamide, ammonium chloride, formaldehyde polycondensate), B2: diyaprok K-403B (containing 50% by weight of quaternary polyamine) Was used.

Amidine: Amidine Hydrochloride Unit

NVF: N-vinylformamide unit

AN: Acrylonitrile Unit

VAM: Vinylamine Hydrochloride Unit

AA: acrylic acid unit

[Test Example]

&Lt; Example 1 >

200 ml of active sludge (pH 6.7, MLSS 9,000 mg / L) of the membrane-separated activated sludge apparatus for processing domestic drainage was placed in a beaker, and a predetermined amount of the filtration flow rate lowering substance removing agent shown in Table 2 was placed in an aqueous solution of 0.1 mass%. Added. Thereafter, the mixture was stirred and mixed for 2 minutes, and allowed to stand overnight. Thereafter, the supernatant was colored by the phenol sulfate method, the absorbance at a wavelength of 490 nm was measured, and the total sugar concentration of the supernatant was calculated from the measured value, thereby determining the effect of removing the caustic flow rate lowering cause. On the other hand, 50 ml of sludge after the removal of the causative agent for lowering the filtration flow rate was introduced into the filter paper attached to the measuring cylinder, and the amount of filtered water after 5 minutes was measured. The results are shown in Table 2.

&Lt; Comparative Example 1 &

The removal effect of the filtration flow rate reduction cause substance was determined similarly to Example 1 except not having added the filtration flow rate reduction cause substance removal agent. The results are shown in Table 2.

Comparative Example 2

Except for using polymer coagulants (B1, B2) manufactured by Dyanitrix Co., Ltd., the same effects as those in Example 1 were carried out, and the effect of removing the filtration flow rate deterioration causing substance was determined. The results are shown in Table 2.

According to the method of the present invention, using a water-soluble and / or water-absorbing cationic polymer that is an organic polymer flocculant in a small amount compared to the conventional method, the concentration of the substance causing the lowering of the filtration flow rate in the membrane separation activated sludge with low sludge generation amount is inexpensive. Can be reduced. In addition, according to the method of the present invention, it is sufficient to simply add the organic polymer flocculant to the activated sludge mixed liquid, so that the substance causing the filtration flow rate drop can be easily removed without complicating the removal step.

Claims (4)

A cationic water-soluble polymer comprising an amidine structural unit represented by the following formulas (1) and / or (2) as the active ingredient: A method for removing a causative flow rate lowering cause material of the membrane separation activated sludge method, which is added to a membrane separation activated sludge mixed liquid containing a substance, and membrane separation is performed.
<Formula 1>

(2)

R ¹ to R ⁴ in Formulas 1 and 2 are each a hydrogen atom or a methyl group, and may be the same or different, and X ⁻ and Y ⁻ are each an anion and may be the same or different. The method for removing a filtration-flow-rate-causing substance according to claim 1, wherein the filtration-flow-rate-causing substance is at least one of a humic-like substance, a polysaccharide, and a protein in vitro. The method for removing a filtration-flow-rate-causing substance according to claim 1, wherein a filtration flow-rate-causing substance removing agent of 10 to 2000 mg / L is added to the activated sludge mixture. The method of claim 1, wherein the water-soluble and / or water-absorbing cationic polymer contains 5 to 90 mol% of monomer units represented by Formulas (1) and / or (2). Way.