JP2014166619A - Method of suppressing rise of transmembrane pressure difference in membrane separation active sludge apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of suppressing the rise of the transmembrane pressure difference by improving the method of adding a water-soluble polymer to treated water after an active sludge treatment in a membrane separation active sludge apparatus.SOLUTION: A method of suppressing the rise of the transmembrane pressure difference in a membrane separation active sludge apparatus uses an unused separation membrane and a separation membrane having an initial transmembrane pressure difference in non-use of +10 kPa or smaller and comprises adding at least one water-soluble polymer selected from cationic and amphoteric polymers to the membrane separation active sludge apparatus so that the deformation ratio, measured by the following method, of concentrated sludge separated by the separation membranes is 30% or lower.

Description

  The present invention relates to a method for suppressing an increase in transmembrane pressure difference in a membrane separation activated sludge apparatus.

In recent years, from the viewpoint of water quality improvement, ease of water reuse, reduction of excess sludge generation, necessity of water recycling, etc., treatment of wastewater generated in factories such as municipal sewage, food, chemistry, electric and electronic As a method, the membrane separation activated sludge method is spreading. Here, the membrane separation activated sludge method is a method of performing solid-liquid separation using a separation membrane such as a precision membrane or an ultrafiltration membrane without providing a final sedimentation tank in the activated sludge method.
However, in the membrane separation activated sludge method, if the activated sludge treated water contains a substance that causes membrane clogging, the pores of the separation membrane are clogged and the separation membrane is clogged. The pressure was sometimes increased.
The demand for water is increasing globally, the need for reclaimed water is further increased, and there is a need to develop an efficient water treatment method that is low in cost, easy to maintain and manage.

Thus, various methods have been disclosed as measures for suppressing the increase in transmembrane pressure difference.
For example, there is a method in which the flocculant is unreacted and present in a high concentration in the flow on the separation membrane surface of the membrane separation activated sludge apparatus (Patent Document 1).
In addition, a method of adding activated carbon to a polymer flocculant made of a water-soluble polymer, an inorganic flocculant made of ferric chloride, a sulfuric acid band, etc. and adding it to a membrane separation activated sludge device (Patent Document 2), a control device There is also a method (Patent Document 3) in which an aluminum-based inorganic flocculant is added to a membrane separation activated sludge device to suppress an increase in transmembrane pressure difference.

JP 2005-279448 A JP 2006-223922 A JP 2008-168199 A

However, Patent Document 1 describes the injection method, but does not specifically describe the amount of water-soluble polymer added. In addition, the method described in Patent Document 2 discloses a method of determining the amount of water-soluble polymer added based on the phosphorus concentration, but is not applicable to membrane-separated activated sludge that does not contain phosphorus. . Further, the methods described in Patent Documents 2 and 3 have a problem of increasing sludge by adding an inorganic flocculant. Therefore, as a result of repeated studies, the inventors have suppressed the increase in the transmembrane pressure difference, which is affected by the state of the membrane when adding the water-soluble polymer and the reactivity of the activated sludge and the water-soluble polymer. As a result, the present inventors have invented this method.
An object of the present invention is to improve a method for adding a water-soluble polymer to treated water subjected to activated sludge treatment in a membrane separation activated sludge apparatus, and provide a method for stably suppressing an increase in transmembrane pressure difference. There is.

That is, the present invention is as follows.
[1] Membrane-separated activated sludge apparatus having a function of introducing treated water, aeration treatment of the organic matter of the treated water together with activated sludge, and solid-liquid separation of the activated sludge mixed liquid to which the flocculant is added with a separation membrane In this method, the increase in the transmembrane pressure difference applied to the separation membrane by the suction pump is controlled by using an unused separation membrane and a separation membrane having an initial transmembrane pressure difference of 10 kPa or less when unused by washing. A water-soluble polymer of at least one of a cationic polymer and an amphoteric polymer is added to the membrane separation activated sludge apparatus so that the deformation rate of the concentrated sludge obtained by the following measurement method separated by a membrane is 30% or less. A method for suppressing an increase in transmembrane pressure difference in a membrane separation activated sludge apparatus.
<Method for measuring deformation rate of concentrated sludge>
300 mL of sludge mixed with a water-soluble polymer is mixed with a transparent filter cylinder having an inner diameter of 36 mm placed on a 48 mesh nylon filter cloth. The sludge height when the filtrate runs out is Acm, the sludge height after removing the filter cylinder is Bcm, and the deformation rate is obtained by the following equation.
Concentrated sludge deformation rate (%) = (1−B / A) × 100

［一般式（１）、（２）中、Ｒ^１〜Ｒ^４は各々独立して水素原子またはメチル基である。Ｘ⁻、Ｙ⁻は各々陰イオンである。］ [2] The method according to 1 above, wherein the cationic polymer is a cationic polymer having an amidine structural unit represented by the following general formula (1) and / or the following general formula (2): .

[In General Formulas (1) and (2), R ^{1 to} R ⁴ each independently represents a hydrogen atom or a methyl group. X ⁻ and Y ⁻ are each an anion. ]

  According to the method for adding a water-soluble polymer of the present invention, the amount of the water-soluble polymer added can be easily determined, and an increase in transmembrane pressure difference can be stably suppressed.

  Hereinafter, the present invention will be described in more detail, but the scope of the present invention is not limited thereto.

  In the present invention, the membrane separation activated sludge apparatus refers to an apparatus that performs solid-liquid separation using a separation membrane such as a precision membrane without providing a final sedimentation tank in the activated sludge method. That is, it is an apparatus for supplying raw water to an aeration tank containing activated sludge, biologically treating the raw water by aeration, and drawing out the obtained treated water while passing through a separation membrane for solid-liquid separation.

  The present invention is a membrane-separated activated sludge having a function of introducing treated water, aeration treatment of organic matter of the treated water together with activated sludge, and solid-liquid separation of the activated sludge mixed liquid to which the flocculant is added by a separation membrane. In the apparatus, the increase in the transmembrane pressure applied to the separation membrane by the suction pump is suppressed. The membrane separation activated sludge device is not particularly limited as long as it has the above function, and the membrane separation activated sludge device described in the above-mentioned prior literature can be used. In addition to the aeration tank, other biological treatment tanks such as another aeration tank, anaerobic tank, anoxic tank, and aerobic treatment tank may be provided independently.

Examples of the separation membrane used in the membrane separation activated sludge apparatus include a microfiltration membrane and an ultrafiltration membrane. A microfiltration membrane is preferable in that a high permeation flow rate can be obtained.
The shape of the separation membrane may be any shape such as a flat membrane, a tubular membrane or a hollow fiber membrane. Materials made of various materials such as cellulose, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polysulfone, and polyvinylidene fluoride can be used.
Extraction of treated water is performed by sucking the secondary side (downstream side) of the separation membrane with a pump. At the time of drawing, the treated water passes through the separation membrane, but particulate matter such as floc is difficult to pass through. Therefore, solid-liquid separation can be performed by drawing the treated water.

  In the membrane separation activated sludge method, the treated water is drawn through the separation membrane while the raw water is being treated with activated sludge in an aeration tank. The withdrawal speed of the treated water varies depending on the treated water, but is generally 0.1 to 1.5 m / day.

The raw water or activated sludge contains substances that cause membrane clogging (hereinafter referred to as “membrane clogging substances”). Specific examples of membrane clogging substances include inorganic salts such as calcium carbonate and calcium sulfate, inorganic colloids such as silica and iron hydroxide, organic colloids such as sugars and proteins, soluble organic substances, and adherent microorganisms. And suspended substances.
In the case where the drawing speed cannot be increased due to the membrane occlusion due to the membrane occlusion cause substance and becomes 0.1 to 1.0 m / day, the effect of suppressing the membrane occlusion according to the present invention becomes remarkable.

Examples of the “water-soluble polymer” added to the aeration tank include one or more selected from the group consisting of a cationic polymer and an amphoteric polymer.
The “cationic polymer” is a polymer having a cationic monomer unit, and may be a cationic monomer unit alone or a nonionic monomer unit. . Further, the “cationic polymer” may be a cationic polymer having an amidine structural unit represented by the general formula (1) and / or the general formula (2).
The “amphoteric polymer” is a polymer having a cationic monomer unit and an anionic monomer unit, and may be only a cationic monomer unit and an anionic monomer unit. And may have a nonionic monomer unit.

  The cationic monomer unit is derived from a cationic monomer. Examples of the cationic monomer include quaternary or tertiary ammonium group-containing cationic methacrylate monomers, quaternary ammonium group-containing cationic acrylate monomers, diallyl quaternary ammonium monomers, and the like. . Specific examples include methyl chloride quaternary salts such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate, benzyl chloride quaternary salts, chloride salts of diallyldimethylammonium, and sulfuric acid or hydrochloride such as dimethylaminoethyl methacrylate. These may be used alone or in combination of two or more.

In the cationic polymer having an amidine structural unit, in the general formulas (1) and (2), R ^{1 to} R ⁴ are each independently a hydrogen atom or a methyl group, but they may all be the same. , May be different.
X ⁻ and Y ⁻ are each independently an anion, but all may be the same or different. In the general formulas (1) and (2), the anions represented by X ⁻ and Y ⁻ are specifically Cl ⁻ , Br ⁻ , 1 / 2SO ₄ ²⁻ , CH ₃ (CO) O ^−. , H (CO) O 2 ^{— and the} like.

  The nonionic monomer unit is derived from a nonionic monomer. Examples of nonionic monomers include acrylamide and methacrylamide. These may be used alone or in combination of two or more.

  The anionic monomer unit is derived from an anionic monomer. Examples of the anionic monomer include acrylic acid, methacrylic acid, 2-acrylamido-2methylpropanesulfonic acid, and sodium salts and potassium salts thereof. These may be used alone or in combination of two or more.

  Either the cationic polymer or the amphoteric polymer may have a vinyl monomer unit other than the cationic monomer unit, the nonionic monomer unit, and the anionic monomer unit.

As a manufacturing method of a cationic polymer and an amphoteric polymer, it can manufacture with a well-known general polymerization method.
Specifically, each monomer unit can be produced by polymerizing by a known method in the presence of a polymerization initiator. Examples of the polymerization initiator include radical initiators such as potassium persulfate and persulfate 2,2′-azobiz-2-amidinopropane hydrochloride. The polymerization method is not particularly limited, and methods such as aqueous solution polymerization, photopolymerization, suspension polymerization, and emulsion polymerization can be applied.
When the cationic polymer is a cationic polymer having an amidine structural unit, N-vinylcarboxylic acid amides such as N-vinylformamide and N-vinylacetamide and nitriles of acrylonitrile or methacrylonitrile are bulky. After copolymerization by a known method such as polymerization, aqueous precipitation polymerization, suspension polymerization, emulsion polymerization, etc., acid hydrolysis is carried out, and a cyano group and a primary amino group in the copolymer obtained by copolymerization are reacted. It can be produced by a method for amidine formation.

As the water-soluble polymer added to the aeration tank, at least one of a cationic polymer and an amphoteric polymer is preferable from the viewpoint that the increase in transmembrane pressure difference can be further suppressed. The reason why at least one of the cationic polymer and the amphoteric polymer can suppress the increase in the transmembrane pressure difference is that the substance causing the membrane occlusion is generally anionic, and the cationic polymer and the amphoteric polymer are occluded. This is probably due to the strong interaction with the causative substance. For this reason, the cation equivalent of the water-soluble polymer is preferably as high as possible, and if it is at least 2 meq / g, the effect is easily exhibited. The effect can be obtained even if a cationic polymer and an amphoteric polymer are used in combination, and the addition is a method of adding a cationic polymer and an amphoteric polymer separately, or a method of adding a mixture of both in advance. Either of these is acceptable.
Furthermore, among the cationic polymers, a cationic polymer having an amidine structural unit as a main component is preferable because of its stronger interaction with a substance that causes membrane blockage. The amidine structure has a high charge density and is hydrophobic, so it forms a strong flock with the substances that clog the membrane and activated sludge, and the interaction with the separation membrane is also low, which can further prevent clogging of the membrane, The increase in differential pressure can be further suppressed.

  The feature of the present invention is that the deformation rate of the concentrated sludge obtained by the following measurement method separated by the separation membrane using an unused separation membrane and a separation membrane having an initial transmembrane pressure difference of 10 kPa or less when not used due to washing is as follows. The water-soluble polymer of at least one of a cationic polymer and an amphoteric polymer is added to the membrane separation activated sludge apparatus so that it becomes 30% or less.

<Method for measuring deformation rate of concentrated sludge>
300 mL of sludge mixed with a water-soluble polymer is mixed with a transparent filter cylinder having an inner diameter of 36 mm placed on a 48 mesh nylon filter cloth. The sludge height when the filtrate runs out is Acm, the sludge height after removing the filter cylinder is Bcm, and the deformation rate is obtained by the following equation.
Concentrated sludge deformation rate (%) = (1−B / A) × 100

  The lower the value of the deformation rate of the concentrated sludge, the stronger the flocs are formed by the water-soluble polymer and the membrane clogging substances and activated sludge. If it is 30% or less, it forms a strong flock with the membrane clogging substances and activated sludge, and a necessary and sufficient amount of water-soluble polymer is adsorbed on the surface of the sludge, so that the membrane clogged from the activated sludge thereafter It is thought that causative substances are less likely to be released from the floc into the liquid phase. The deformation rate of the concentrated sludge can be adjusted by the amount of water-soluble polymer added. The addition amount of the water-soluble polymer at which the deformation rate of the concentrated sludge becomes 30% or less can be obtained by measuring the concentration sludge deformation rate while changing the addition amount of the water-soluble polymer.

The form when adding the water-soluble polymer is preferably an aqueous solution in that it can be mixed with the membrane separation activated sludge in a short time. The water-soluble polymer concentration in the aqueous solution is preferably 0.05 to 1% by mass. When the water-soluble polymer concentration is at least the lower limit value, the supply time can be shortened, and when the water-soluble polymer concentration is at most the upper limit value, it can be mixed uniformly and the adhesion to the film can be further prevented.
In the form of an aqueous solution, a solid acid may be added in order to improve the solubility of the water-soluble polymer and to improve the storage stability of the aqueous solution. Examples of the solid acid include sulfamic acid.

  As a water-soluble polymer to be added to the aeration tank, 0.5% salt viscosity is 3 to 40 mPa from the time required for mixing with the membrane separation activated sludge and the ease of floc formation with the membrane clogging substance. -S is preferable. If the amount of the water-soluble polymer added is equal to or greater than the lower limit value, it can form a strong flock with the membrane clogging cause substance. An increase in the differential pressure can be further suppressed.

The increase in the transmembrane pressure difference due to membrane clogging is due to the fact that organic colloids such as sugars and proteins, and membrane clogging substances such as soluble organic substances start to adhere to the membrane surface or pores. This is thought to be due to the fact that substances adhere to the membrane one after another and membrane clogging proceeds. By adding a water-soluble polymer, such a membrane clogging substance is flocked with activated sludge and removed from the liquid phase in contact with the membrane, and a necessary and sufficient amount of the water-soluble polymer is adsorbed on the surface of the sludge. It is considered that the membrane blockage causative substance secreted from activated sludge is not easily released from the floc into the liquid phase.
When the concentration of sugar, which is one of the membrane clogging substances, is 10 mg / L or more in the sludge, membrane clogging is likely to occur, and the suppression effect due to the addition of the water-soluble polymer is likely to be exhibited. On the other hand, if the sugar concentration in the sludge is less than or equal to the lower limit, membrane clogging is unlikely to occur.
Moreover, the amount of filter paper filtration is known as an indicator of the presence of a substance that causes membrane blockage. The amount of filter paper filtration is the amount of filtration that passes through the filter paper for 5 minutes when 50 mL of sludge is filtered. If this value is 20 mL or less, membrane clogging due to membrane clogging substances tends to occur, and this method is effective. is there.
On the other hand, if the filtration amount is equal to or more than the upper limit, membrane clogging hardly occurs.
Moreover, even if a water-soluble polymer is added in a state where membrane occlusion has progressed, an increase in transmembrane pressure difference cannot be effectively suppressed. This is because the water-soluble polymer removes organic colloids such as sugar and protein, soluble organic substances, etc. This is probably because the adhesion of these substances cannot be suppressed.

  Therefore, in the present invention, an unused film and a film having an initial inter-membrane differential pressure of +10 kPa or less when not used due to cleaning are used.

  When the membrane is washed with a hypo-cleaning solution, as is generally done, the membrane-causing substance can be removed by immersing the membrane in the hypo-cleaning solution and rinsing with water.

  Moreover, the aeration amount in the activated sludge treatment is not particularly limited, and is appropriately selected according to the inflow amount of the raw water, the organic substance content in the raw water, the activity of the activated sludge, and the like. The aeration amount may be the same or different when the water-soluble polymer is added and when it is not added. Conventionally, the amount of aeration in the membrane separation activated sludge apparatus was larger than the standard activated sludge method for membrane cake layer formation and membrane clogging suppression, but the water treatment method of the present invention was applied to standardize the membrane cleaning frequency. If it is equivalent to the activated sludge method, the amount of aeration can be reduced.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

<Measurement of cation equivalent>
The cationic polymer and the amphoteric polymer were dissolved in demineralized water, and titrated with a 1/400 normal PVSK (polyvinyl potassium sulfate) aqueous solution at pH = 3.0 using toluidine blue as an indicator.

<Measurement of 0.5% salt viscosity>
2.5 g of the cationic polymer and the amphoteric polymer were dissolved in 4% NaCl aqueous solution to prepare 500 g of 0.5% polymer aqueous solution. Using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.), at a temperature of 25 ° C. and a rotational speed of 60 rpm, 0.5% salt viscosity after 5 minutes from the start of stirring of the 0.5% polymer aqueous solution It was measured.

<Cationic polymer and amphoteric polymer>
In Examples and Comparative Examples, a cationic polymer or an amphoteric polymer was used as the water-soluble polymer added to the membrane separation activated sludge.
In addition, as the cationic polymer, KP201G which is a homopolymer of methyl chloride quaternary salt of dimethylaminoethyl methacrylate (Daanitrix Co., Ltd., cation equivalent 3.9 meq / g 0.5% salt viscosity 16 mPa · s), or KP7000 (Daninitx Co., Ltd., cation equivalent 5.4 meq / g 0.5% salt viscosity 7 mPa · s) containing an amidine polymer as the main component was used.
In addition, as an amphoteric polymer, KA405D (Daanitrix Co., Ltd., cation equivalent 2 meq / m) is a copolymer of methyl chloride quaternary salt of dimethylaminoethyl methacrylate, methyl chloride quaternary salt of dimethylaminoethyl acrylate, acrylamide and acrylic acid. g 0.5% salt viscosity 25 mPa · s) was used.

<Measurement method of deformation rate of concentrated sludge by addition of water-soluble polymer>
In the following test examples (Examples and Comparative Examples), the concentrated sludge deformation rate was measured by the following method in order to determine the amount of addition to the membrane-separated activated sludge of the water-soluble polymer.
300 mL of sludge mixed with a water-soluble polymer is mixed with a transparent filter cylinder having an inner diameter of 36 mm placed on a 48 mesh nylon filter cloth. The sludge height when the filtrate runs out is Acm, the sludge height after removing the filter cylinder is Bcm, and the deformation rate is obtained by the following equation.
Concentrated sludge deformation rate (%) = (1−B / A) × 100

<Evaluation of increase effect of transmembrane pressure difference by addition of water-soluble polymer>
In the following test examples (Examples and Comparative Examples), the effect of suppressing the increase in transmembrane pressure difference due to the addition of a water-soluble polymer is evaluated as the transmembrane difference when membrane filtration is performed with a constant water flow rate in a membrane separation activated sludge apparatus This was done by measuring the rate of pressure rise. The results are shown in Tables 1, 2, 3 and 4, respectively.

<Measurement of sugar concentration>
The sugar concentration indicates the concentration of polysaccharide dissolved in water or colloidally, and the absorbance near 490 nm is measured with an ultraviolet-visible spectrophotometer (UV-3100, manufactured by Shimadzu Science Co., Ltd.). It calculated from the calibration curve by a liquid.
The sugar concentration in the sludge was measured as follows. That is, for the treatment liquid obtained by filtering the collected sludge with a syringe filter having a pore diameter of 0.45 μm (25 mm GD / X Sterile Syringe Filters manufactured by Whatman Co., Ltd.), the total sugar concentration is measured by a conventional method; the phenol-sulfuric acid method [Hodge, J. et al. E. and Hofreiter, B .; T.A. , Method in Carbohydrate Chemistry, 1, 338 (1962)].

<Measurement of filter paper filtration rate>
The amount of filter paper filtration is 16 folds of 5C filter paper (ADVANTEC) with a diameter of 185 mm, put in a funnel and attached to a 50 ml graduated cylinder. The amount of filtration of was measured.

<Membrane hypochlorous acid cleaning and cleaning completion confirmation>
The membrane taken out after use was immersed in 1 L of hypochlorous acid water adjusted to a concentration of 0.3% for 20 hours, and then the membrane was taken out and rinsed with tap water. When the treated water is drawn out from the unused membrane at the same flow rate, the membrane after rinsing is confirmed to be within the range of the initial membrane differential pressure when not used +10 kPa or less. The completion of washing was judged and an unoccluded membrane was obtained. In addition, the transmembrane differential pressure of the unused product was 2.0 kPa.

<Example 1>
19 hollow fiber microfiltration membranes (Mitsubishi Rayon Co., Ltd., "SADF membrane" made of polyvinylidene fluoride) were equally arranged in a width of 0.088 m, and both ends of the hollow fiber microfiltration membrane were connected to an annular support. An unoccluded membrane module (effective membrane length 0.077 m, membrane area 0.0012 m ² ) was prepared. The membrane module is installed above the air diffuser in the aeration tank (width 0.2 m, depth 0.1 m, height 0.35 m) so that the membrane length direction is along the vertical direction. A separation activated sludge apparatus was used.
Activated sludge (pH 6.7) of wastewater treatment equipment of company A with MLSS of 5000 mg / L, sugar concentration of 10 mg / L, and filter paper filtration rate of 10 mL / 5 was collected, and a 0.3 mass% aqueous solution of KP7000. When 100 mg / L of activated sludge was added per total amount of sludge, the deformation rate of the concentrated sludge of activated sludge was 10%. This activated sludge is filled with 4000 mL of membrane-separated chemical sludge apparatus, and the aeration rate is 9 L / min. A 0.3 mass% aqueous solution of KP7000 is added at 100 mg / L per activated sludge, and chemical industrial wastewater is supplied at a flow rate of 0.42 m. The supply was started to be / day. The transmembrane pressure difference at this time was 2.2 kPa. The transmembrane pressure difference was measured on day 1 and day 14 after the addition. The measurement at each time point was measured using a pressure sensor (manufactured by Keyence Co., Ltd., AP-10S (achieved pressure type)), and the value obtained by dividing the differential pressure increase in each day by 24 hours was measured between the membranes. It was determined as the differential pressure increase rate.

<Example 2>
The same procedure as in Example 1 was carried out except that a 0.3 mass% aqueous solution of KP7000 was added at 70 mg / L of activated sludge in total (deformation rate of concentrated sludge of activated sludge was 25%). The transmembrane pressure difference when the supply of chemical industrial wastewater was started was 2.1 kPa.

<Comparative Example 1>
The same procedure as in Example 1 was performed except that 40 mg / L of an aqueous solution of 0.3% by mass of KP7000 was added per 40% of activated sludge (deformation rate of concentrated sludge of activated sludge was 40%). The transmembrane pressure difference when the supply of chemical industrial wastewater was started was 2.1 kPa.
However, since the transmembrane pressure difference became 50 kPa or more before the 14th day and it became impossible to draw a certain amount of treated water, the experiment was stopped.

<Comparative example 2>
The same operation as in Example 1 was carried out except that a 0.3 mass% aqueous solution of KP7000 was added at 20 mg / L (total activated sludge deformation rate of 60%) per activated sludge. The transmembrane pressure difference when starting the supply of chemical industrial wastewater was 2.0 kPa.
However, since the transmembrane pressure difference became 50 kPa or more before the 14th day and it became impossible to draw a certain amount of treated water, the experiment was stopped.

<Comparative Example 3>
The same procedure as in Example 1 was performed except that the water-soluble polymer was not added. The transmembrane pressure difference when the supply of chemical industrial wastewater was started was 2.1 kPa.
However, since the transmembrane pressure difference became 50 kPa or more before the 14th day and it became impossible to draw a certain amount of treated water, the experiment was stopped.

To the aeration tank, the concentration of sugar in the supernatant liquid is 10 mg / L, the amount of filter paper filtration is 10 mL, and KP7000 as a water-soluble polymer is 100 mg / L (total sludge deformation rate: 15%) per activated sludge. In Examples 1 and 2 added so as to be 100 mg / L per minute (concentration sludge deformation rate: 25%), the rate of increase in transmembrane pressure difference is lower than that in Comparative Example 3 where no water-soluble polymer was added. It was suppressed.
Comparative Examples 2 and 3 using KP7000 as the water-soluble polymer so that the deformation rate of the concentrated sludge was 40% (20 mg / L per activated sludge total amount) and 60% (40 mg / L) Similar to Comparative Example 3 in which KP7000 was not used as the coalescence, the transmembrane pressure increase rate was high.

<Example 3>
The activated sludge (pH 6.7) of the same chemical factory wastewater treatment facility of Company A as in Example 1 was collected, and a 0.3 mass% aqueous solution of KP7000 was added at 100 mg / L per activated sludge to concentrate the activated sludge. The deformation rate of sludge was 10%. This activated sludge is filled in 4000 mL of the same membrane-separation conversion sludge apparatus as in Example 1, and an aeration rate of 9 L / min is added, and an aqueous solution of 0.3% by mass of KP7000 is added at 100 mg / L per activated sludge. The supply was started so that the flow rate became 0.42 m / day. The transmembrane pressure difference at this time was 2.3 kPa. The transmembrane pressure difference was measured on day 1 and day 14 after the addition. The measurement at each time point was measured using a pressure sensor (manufactured by Keyence Co., Ltd., AP-10S (achieved pressure type)), and the value obtained by dividing the differential pressure increase in each day by 24 hours was measured between the membranes. It was determined as the differential pressure increase rate.

<Example 4>
The same procedure as in Example 1 was performed except that an aqueous solution of 0.3% by mass of KP201G was added at 100 mg / L (total sludge deformation rate of activated sludge of 20%) per activated sludge. The transmembrane pressure difference when the supply of chemical industrial wastewater was started was 2.1 kPa.

<Example 5>
The same procedure as in Example 1 was performed, except that 100 mg / L of an aqueous solution of 0.3% by mass of KA405D was added per activated sludge in total (deformation rate of concentrated sludge of activated sludge was 30%). The transmembrane pressure difference when starting the supply of chemical industrial wastewater was 2.2 kPa.

<Example 6>
Example: Except that the aqueous solution of 0.3% by mass of KP201G and KA405D was added in an amount of 50 mg / L per activated sludge in total (deformation rate of concentrated sludge of activated sludge was 25%) and then withdrawing of treated water was resumed. 1 was performed. The transmembrane pressure difference when the supply of chemical industrial wastewater was started was 2.1 kPa.

<Comparative example 4>
The same procedure as in Example 1 was performed except that the water-soluble polymer was not added. The transmembrane pressure difference when starting the supply of chemical industrial wastewater was 2.3 kPa. However, since the transmembrane pressure difference became 50 kPa or more before the 14th day and it became impossible to draw a certain amount of treated water, the experiment was stopped.

<Example 7>
The same operation as in Example 3 was performed except that the transmembrane pressure difference when the water-soluble polymer was added was 12.3 kPa.

<Example 8>
The same operation as in Example 4 was performed except that the transmembrane pressure difference when the water-soluble polymer was added was 12.1 kPa.

<Example 9>
The same operation as in Example 5 was conducted except that the transmembrane pressure difference when the water-soluble polymer was added was 12.2 kPa.

<Example 10>
The same operation as in Example 6 was performed except that the transmembrane pressure difference when the water-soluble polymer was added was 12.1 kPa.

<Comparative Example 5>
The same procedure as in Example 7 was performed except that the water-soluble polymer was not added. Since the transmembrane pressure difference became 50 kPa or more before the 14th day from the time when the transmembrane pressure difference was 12.3 kPa, and a certain amount of treated water could not be drawn, the experiment was stopped.

In Examples 3 to 10 in which the water-soluble polymer was added to the activated sludge having a sugar concentration of 10 mg / L in the supernatant liquid in the aeration tank and a filter paper filtration amount of 10 mL, the rate of increase in transmembrane pressure difference was kept low.
In addition, Example 3 and Example 7 using KP7000 as the water-soluble polymer were more transmembrane pressure differential than Examples 4, 5, 6, 8, 9 and 10 where KP7000 was not used as the water-soluble polymer. The rate of rise was low, and the differential pressure was small even on the 14th day.
In Comparative Examples 4 and 5 in which no water-soluble polymer was added, the rate of increase in transmembrane pressure difference was fast.

<Example 11>
The activated sludge (pH 6.7) of the same chemical factory wastewater treatment facility of Company A as in Example 1 was collected, and a 0.3 mass% aqueous solution of KP7000 was added at 100 mg / L per activated sludge to concentrate the activated sludge. The deformation rate of sludge was 10%. The activated sludge was charged in 4000 mL of the same membrane separation chemical sludge apparatus as in Example 1, and the supply of chemical industrial wastewater was started at a flow rate of 0.42 m / day with an aeration rate of 9 L / min. When the transmembrane pressure difference reached 20 kPa, a 0.3 mass% aqueous solution of KP7000 was added at 100 mg / L per activated sludge. On the first day after the addition, the transmembrane pressure difference was 43.8 kPa, and the transmembrane pressure increase rate was 1.2 kPa / hour. Next, when the drawing is stopped, the drawing is resumed after replacement with an unoccluded membrane (transmembrane pressure difference 2.1 kPa), and the rate of increase in transmembrane pressure difference is measured on the second day after addition and on the 17th day after membrane exchange. , Respectively, were kept low at 0.015 kPa / hour and 0.025 kPa / hour.

<Comparative Example 6>
The same procedure as in Example 11 was performed except that the membrane was not changed on the first day after the addition of the water-soluble polymer. However, the experiment was stopped because the transmembrane pressure difference became 50 kPa or more after the first day after the addition, and it became impossible to draw a certain amount of treated water.

In Example 7 in which the water-soluble polymer was added to the activated sludge having a sugar concentration of 10 mg / L in the aeration tank and the filter paper filtration amount to 10 mL with an unwashed membrane, the transmembrane pressure difference until the first day after the addition. Although the rate of increase was fast, when the membrane was replaced with an unoccluded membrane, the rate of increase in transmembrane pressure difference was kept low even on the 17th day after the replacement.
On the other hand, although the water-soluble polymer was added to the aeration tank, the rate of increase in the transmembrane pressure difference was high in Comparative Example 3 which was continued without replacing the membrane.

<Example 12>
Activated sludge (pH 6.7) of wastewater treatment equipment of company B with MLSS of 4000 mg / L, sugar concentration of 15 mg / L, and filter paper filtration amount of 5 mL / 5 min. Was added at 100 mg / L per activated sludge, and the deformation rate of the concentrated sludge of activated sludge was 15%. This activated sludge is filled in 4000 mL of the same membrane-separation conversion sludge apparatus as in Example 1, and an aeration rate of 9 L / min is added, and an aqueous solution of 0.3% by mass of KP7000 is added at 100 mg / L per activated sludge. The supply was started so that the flow rate became 0.42 m / day. The transmembrane pressure difference at this time was 2.3 kPa. The transmembrane pressure difference was measured on day 1 and day 14 after the addition.

<Example 13>
The same procedure as in Example 1 was performed except that an aqueous solution of 0.3% by mass of KP201G was added at 100 mg / L (total sludge deformation rate of activated sludge of 20%) per activated sludge. The transmembrane pressure difference when starting the supply of chemical industrial wastewater was 2.2 kPa.

<Example 14>
The same procedure as in Example 1 was performed, except that 100 mg / L of an aqueous solution of 0.3% by mass of KA405D was added per activated sludge in total (deformation rate of concentrated sludge of activated sludge was 30%). The transmembrane pressure difference when the supply of chemical industrial wastewater was started was 2.1 kPa.

<Example 15>
Example: Except that the aqueous solution of 0.3% by mass of KP201G and KA405D was added in an amount of 50 mg / L per activated sludge in total (deformation rate of concentrated sludge of activated sludge was 25%) and then withdrawing of treated water was resumed. 1 was performed. The transmembrane pressure difference when the supply of chemical industrial wastewater was started was 2.1 kPa.

<Comparative Example 7>
The same procedure as in Example 1 was performed except that the water-soluble polymer was not added. The transmembrane pressure difference when starting the supply of chemical industrial wastewater was 2.4 kPa. However, since the transmembrane pressure difference became 50 kPa or more before the 14th day and it became impossible to draw a certain amount of treated water, the experiment was stopped.

<Example 16>
The same operation as in Example 3 was performed except that the transmembrane pressure difference when the water-soluble polymer was added was 12.3 kPa.

<Example 17>
The same operation as in Example 3 was performed except that the transmembrane pressure difference when the water-soluble polymer was added was 12.2 kPa.

<Example 18>
The same operation as in Example 3 was performed except that the transmembrane pressure difference when the water-soluble polymer was added was 12.1 kPa.

<Example 19>
The transmembrane differential pressure when the water-soluble polymer was added was the same as in Example 3 except that the transmembrane differential pressure was 12.1 kPa.

<Comparative Example 8>
The same procedure as in Example 1 was performed except that the water-soluble polymer was not added. Since the transmembrane pressure difference became 50 kPa or more before the 14th day from the time when the transmembrane pressure difference was 12.4 kPa, and a certain amount of treated water could not be drawn, the experiment was stopped.

In Examples 12 to 19, the water-soluble polymer was added to the activated sludge having a sugar concentration of 15 mg / L in the supernatant and the filtration amount of the filter paper to 5 mL, and then replaced with an unoccluded membrane. The differential pressure increase rate was kept low.
In addition, Example 12 and Example 16 using KP7000 as the water-soluble polymer were more transmembrane differential pressures than Examples 13, 14, 15, 17, 18, and 19 where KP7000 was not used as the water-soluble polymer. The rate of rise was low, and the differential pressure was small even on the 14th day.
In Comparative Examples 7 and 8 in which no water-soluble polymer was added, the rate of increase in transmembrane pressure difference was fast.

Claims (2)

In a membrane separation activated sludge apparatus equipped with a function of introducing treated water, aeration treatment of the organic matter of the treated water together with activated sludge, and solid-liquid separation of the activated sludge mixed liquid added with the flocculant with a separation membrane, suction This is a method to suppress the increase in transmembrane pressure applied to the separation membrane by the pump, using an unused separation membrane and a separation membrane with an initial membrane differential pressure of 10 kPa or less when not used by washing, and separating with the separation membrane A water-soluble polymer of at least one of a cationic polymer and an amphoteric polymer is added to the membrane separation activated sludge apparatus so that the deformation rate of the concentrated sludge required by the following measurement method is 30% or less. The method of suppressing the raise of the transmembrane differential pressure in a membrane separation activated sludge apparatus.
<Method for measuring deformation rate of concentrated sludge>
300 mL of sludge mixed with a water-soluble polymer is mixed with a transparent filter cylinder having an inner diameter of 36 mm placed on a 48 mesh nylon filter cloth. The sludge height when the filtrate runs out is Acm, the sludge height after removing the filter cylinder is Bcm, and the deformation rate is obtained by the following equation.
Concentrated sludge deformation rate (%) = (1−B / A) × 100 The water-soluble heavy polymer according to claim 1, wherein the cationic polymer is a cationic polymer having an amidine structural unit represented by the following general formula (1) and / or the following general formula (2). How to add coalescence.

[In General Formulas (1) and (2), R ^{1 to} R ⁴ each independently represents a hydrogen atom or a methyl group. X ⁻ and Y ⁻ are each an anion. ]