JP2012213675A - Method of determining addition amount of coagulant and water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of determining addition amount of coagulant, which can determine that an aggregation condition is appropriate and determine an appropriate addition amount of a coagulant for performing stable water treatment before treatment performance of a separation membrane deteriorates in a membrane separation apparatus.SOLUTION: There is provided the method of determining addition amount of coagulant in the water treatment for performing aggregation treatment in which a coagulant is added to water to be treated supplied to the membrane separation apparatus with the separation membrane. The method includes: a concentration treatment step (S3) of performing concentration treatment of the treated water subjected to the aggregation treatment using an ultrafiltration membrane; a concentration measuring step (S4) of measuring the concentration of an organic substance contained in concentrated water obtained by the concentration treatment step; and an addition amount determining step (S5) of determining the addition amount of the coagulant to be added to the treated water based on a measured concentration of the organic substance.

Description

  The present invention relates to a method for determining the addition amount of a flocculant and a water treatment apparatus, and more specifically, a method for determining the addition amount of a flocculant added to water to be treated such as industrial wastewater, river water, lake water, etc. containing water-soluble organic matter. The present invention also relates to a water treatment apparatus for aggregating water-soluble organic substances using such a method.

  Conventionally, pure water or ultrapure water has been produced by a membrane separation method using reverse osmosis membrane (hereinafter referred to as RO membrane) using natural water such as river water, lake water, seawater, or industrial water as raw water. ing. These raw waters contain a large amount of water-soluble organic substances as well as various suspended substances and inorganic ion components. As water-soluble organic substances, for example, humic acid, fulvic acid present in natural water, natural organic substances such as monosaccharides, polysaccharides and glycoproteins produced by algae, and produced by activated sludge treatment in industrial wastewater treatment And microbial metabolites such as polysaccharides and proteins, and synthetic chemicals such as surfactants. When industrial wastewater or natural water in which such organic matter exists is filtered using RO membrane as raw water, the RO membrane is contaminated with organic matter, resulting in a problem that the membrane separation performance of the RO membrane is lowered.

  Examination of substances affecting the filtration performance of RO membranes has revealed that they are polymers having molecular weights of several thousand or more, particularly polysaccharides and glycoproteins. Such a polymer contaminates the RO membrane even if the abundance in the raw water is very small, and lowers the membrane separation performance. Therefore, before the raw water containing such a polymer is passed through the RO membrane. In addition, it is necessary to agglomerate with an aggregating agent. By the way, if the addition amount of the flocculant is small, organic substances that contaminate the film cannot be sufficiently removed. If the addition amount is too large, it is economically disadvantageous, and the flocculant itself may contaminate the film. Therefore, various methods for determining an appropriate amount of the flocculant have been proposed.

  As such a method, for example, a method of measuring the organic substance concentration present in the water to be treated by ultraviolet absorption (see Patent Document 1), a method of measuring the sugar concentration of raw water and controlling the amount of flocculant added (patent) Reference 2), a method of fractionating organic matter in raw water into a plurality of groups according to molecular weight, measuring the concentration of organic matter, and controlling the amount of flocculant added according to the concentration of organic matter (Patent Literature 3), etc. Are known.

JP 2007-245078 A JP 2008-68199 A JP 2008-68200 A

  However, in Patent Documents 1 and 2 described above, when the amount of the organic substance present in the raw water is very small, it is not preferable because the concentration of the organic substance cannot be accurately measured. In addition, in the method disclosed in Patent Document 3, flux, desalination rate, transmembrane pressure difference, recovery rate, etc. are measured in a membrane treatment apparatus in order to determine whether the obtained treatment conditions are appropriate. Therefore, it is not possible to determine whether or not proper processing is performed before the filtration performance of the RO membrane deteriorates.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to determine that the agglomeration treatment conditions are appropriate before the treatment performance of the separation membrane of the membrane separation device is lowered. Another object of the present invention is to provide a method for determining the addition amount of a flocculant capable of performing stable water treatment by making the addition amount of the flocculant appropriate, and a water treatment apparatus using this method.

  In order to achieve the above object, the method for determining the addition amount of a flocculant according to claim 1 is a flocculation in a water treatment in which a flocculant is added to water to be treated supplied to a membrane separation apparatus equipped with a separation membrane to perform the agglomeration treatment. A method for determining the addition amount of an agent, the concentration treatment step of concentrating the treated water subjected to the aggregation treatment with an ultrafiltration membrane, and the concentration of the organic matter contained in the concentrated water obtained in the concentration treatment step It is characterized by having a concentration measuring step for measuring and an addition amount determining step for determining the addition amount of the flocculant added to the water to be treated based on the measured organic substance concentration.

  The method for determining the addition amount of the flocculant according to claim 2 is characterized in that, in claim 1, the organic substance concentration is a sugar concentration.

  The water treatment apparatus according to claim 3 is a water treatment apparatus for performing a coagulation treatment by adding a flocculant to water to be treated supplied to a membrane separation apparatus including a separation membrane, and the water to be treated subjected to the coagulation treatment Concentration treatment means for concentration treatment with an ultrafiltration membrane, concentration measurement means for measuring the concentration of organic substances present in the concentrated concentrated water, and a flocculant added to the water to be treated based on the measured organic substance concentration And an addition amount control means for controlling the addition amount.

  The water treatment apparatus according to claim 4 is characterized in that, in claim 3, the organic substance concentration is a sugar concentration.

  A water treatment device according to a fifth aspect is characterized in that, in the third or fourth aspect, the molecular weight cut-off of the ultrafiltration membrane is 5000 or more.

  According to the method for determining the addition amount of the flocculant according to claim 1, the water to be treated which has been subjected to the coagulation treatment is filtered through an ultrafiltration membrane, and based on the organic substance concentration measured from the obtained concentrated water, the membrane separation device Before supplying the water to be treated, it can be determined whether or not the water to be treated is appropriately agglomerated as water to be supplied to the membrane separation device. In addition, the amount of flocculant added to the water to be treated is required, it is possible to perform an appropriate flocculation treatment, it is possible to suppress the contamination of the separation membrane provided in the membrane separation device, and membrane cleaning The frequency of performing can be reduced, and the membrane separation apparatus can be operated stably.

  According to the method for determining the addition amount of the flocculant according to claim 2, since the organic substance concentration is the sugar concentration, the concentration of the high molecular organic substance can be measured, and the sugar component contained in the concentrated water can be determined from the measured sugar concentration. The amount of the flocculant added for aggregation can be determined, and contamination of the separation membrane provided in the membrane separation apparatus can be suppressed.

  According to the water treatment device of claim 3, the water to be treated that has been subjected to the coagulation treatment is filtered through an ultrafiltration membrane, and the water to be treated is supplied to the membrane separation device based on the organic substance concentration measured from the obtained concentrated water. Before the supply, it can be determined whether the water to be treated has been appropriately agglomerated as the water supplied to the membrane separation device. Further, since the amount of flocculant added to the water to be treated is determined and the amount of flocculant added is controlled, contamination of the separation membrane provided in the membrane separator is suppressed, and the membrane separator is stably provided. Can drive.

  According to the water treatment device of claim 4, since the organic substance concentration is a sugar concentration, the concentration of the high molecular organic substance among the organic substances can be measured, and is necessary for aggregating the sugar component contained in the concentrated water. The amount of the flocculant added can be determined, and contamination of the separation membrane provided in the membrane separation apparatus can be suppressed.

  According to the water treatment apparatus of claim 5, since an ultrafiltration membrane having a molecular weight cut-off of 5000 or more is used, a high molecular weight organic substance is concentrated among organic substances, and the concentration of the organic substance in the concentrated water is measured. Thus, it is possible to obtain an appropriate addition amount of a flocculant for aggregating the polymer organic material.

It is the schematic of the water treatment apparatus which concerns on embodiment of this invention. It is the schematic of a residual concentration measuring apparatus. It is a longitudinal cross-sectional view of the ultrafilter shown in FIG. It is a flowchart which shows the water treatment method which concerns on embodiment of this invention. It is a flowchart which shows the modification of the water treatment method shown in FIG. 3 is a table showing the results of organic substance concentration measured in Example 1. 6 is a table showing the results of organic substance concentrations measured in Example 2. It is a graph showing the relationship between the flux of the TOC and RO membrane obtained in Examples 1 and 2. 4 is a table showing the results of sugar concentration measured in Example 3. 6 is a table showing the results of sugar concentration measured in Example 4. It is a graph showing the relationship between the sugar concentration obtained in Examples 3 and 4 and the flux of the RO membrane.

  Hereinafter, embodiments of a method for determining the addition amount of a flocculant and a water treatment apparatus of the present invention will be described in detail with reference to the drawings.

(Water treatment equipment)
In FIG. 1, the schematic of the water treatment apparatus 1 which concerns on this invention is shown. As shown in FIG. 1, the water treatment device 1 includes a coagulation solid-liquid separation device 10 and a membrane separation device 40. The flocculated solid-liquid separation device 10 has a treated water storage tank 12 for introducing treated water. A predetermined amount of the flocculant is supplied from the flocculant storage tank 16 through the pump 18 to the stirring tank 14 to which the water to be processed is supplied from the water to be processed storage tank 12. Water to be treated is supplied from the agitation tank 14 to the solid-liquid separator 34 via the pump 32. Pretreated water to be treated is supplied from the solid-liquid separator 34 to the membrane separator 40. A part of the water to be treated is supplied from the solid-liquid separator 34 to the residual concentration measuring device 36 that measures the residual concentration of the organic matter. The pumps 18, 24, 26, 32, the pH sensor 30, and the residual concentration measuring device 36 are electrically connected to a control unit (addition amount control means) 38 including a CPU, a memory, and the like.

  Examples of treated water introduced into the treated water storage tank 12 include industrial water, river water, lake water, seawater, well water, city water, industrial wastewater, agricultural wastewater, and the like, but are not limited thereto. Absent.

  To-be-treated water is supplied to the agitation tank 14 from the to-be-treated water storage tank 12, and based on a control signal from the control unit 38, a predetermined amount of aggregating agent from the aggregating agent storage tank 16 passes through the pump 18 in the agitation tank 14. Added to the water to be treated. The amount of the flocculant supplied is controlled by the control unit 38 in accordance with the organic substance concentration detected by the residual concentration measuring device 36, as will be described later.

  Examples of the flocculant added to the water to be treated from the flocculant storage tank 16 include inorganic flocculants and polymer flocculants. Examples of the inorganic flocculant include aluminum salts such as aluminum sulfate and polyaluminum chloride, and iron salts such as ferric chloride and ferrous sulfide, but are not limited thereto.

  The polymer flocculant is selected from a cationic polymer, an anionic polymer, or a nonionic polymer. Examples of the cationic polymer include primary amines, secondary amines, tertiary amines and their homopolymers of cationic monomers or allyl monomers having functional groups such as acid salts and quaternary ammonium groups, or copolymers thereof. Examples thereof include a copolymer with a polymerizable vinyl monomer or an anionic allyl monomer. Examples of the cationic monomer include dimethylaminoethyl (meth) acrylate acid salt or quaternary ammonium salt thereof, dimethylaminopropyl (meth) acrylamide acid salt or quaternary ammonium salt, diallyldimethylammonium chloride, vinylaniline, and the like. Can be mentioned. It is good also as a copolymer with such an anionic monomer or nonionic monomer copolymerizable with a cationic monomer.

  Examples of nonionic monomers include (meth) acrylamide, N-isopropylacrylamide, N-methylacrylamide, N, N-dimethylacrylamide, acrylonitrile, styrene, methyl (meth) acrylate, and ethyl (meth) acrylate. Such monomers may be used alone or in combination. In addition, as cationic polymers, copolymers of dialkylamine and epichlorohydrin, polyethylenimine, N-vinylformamide, hydrolyzate of polymer using N-vinylacetamide as a monomer, polyacrylamide Hoffman degradation product, polyacrylamide And Mannich modified products.

  Examples of the anionic polymer include a homopolymer of (meth) acrylic acid, itaconic acid, or an alkali metal salt thereof, or a copolymer with a copolymerizable monomer.

  Nonionic polymers include, for example, homopolymers such as (meth) acrylamide, N-isopropylacrylamide, N-methylacrylamide, N, N-dimethylacrylamide and copolymers with copolymerizable monomers, such as phenol, catechol, Examples thereof include a novolak resin having cresol as a monomer unit, polyvinyl alcohol obtained by saponifying polyvinyl acetate, polyvinyl phenol, polyvinyl pyrrolidone and the like.

  Such inorganic flocculants and polymer flocculants may be added alone or in combination of two or more at any ratio. When an inorganic flocculant and a polymer flocculant are used in combination, there is no restriction on the order of addition. Such an inorganic flocculant and a polymer flocculant may be added before the membrane separation process of the membrane separator 40. However, when the solid-liquid separator 34 is provided as in the present embodiment, the solid flocculant is added. It is added before the liquid separator 34. The flocculant added to the agitation tank 14 is agglomerated by being agitated by the agitator 28 together with the water to be treated in the agitation tank 14.

  An acid storage tank 20 and an alkali storage tank 22 are provided as pH adjusting agents for adjusting the pH of the water to be treated in the stirring tank 14. From the acid storage tank 20 and the alkali storage tank 22, a predetermined amount of acid and alkali is supplied so that the water to be treated in the stirring tank 14 has a predetermined pH based on a control signal from the control unit 38 via the pumps 24 and 26. Either one is added to the stirring tank 14. The added pH adjuster and flocculant are stirred together with the water to be treated by a stirrer 28 provided in the stirring tank 14 to become water to be treated which has been subjected to agglomeration treatment. The pH sensor 30 provided in the stirring tank 14 measures the pH of the water to be treated in the stirring tank 14 and notifies the control unit 38 of the measured pH. The control part 38 controls the addition amount of the pH adjuster added from either the acid storage tank 20 or the alkaline storage tank 22 so that the pH in the stirring tank 14 becomes 5.0 to 7.0.

  The water to be treated that has been agglomerated in the stirring tank 14 is introduced into the solid-liquid separator 34. Although not shown, the solid-liquid separation device 34 is provided with a separation membrane, and flocs and the like contained in the water to be treated which have been subjected to the aggregation treatment via the separation membrane are removed. Examples of the separation membrane used in the solid-liquid separation device 34 include a microfiltration membrane, an ultrafiltration membrane, and a nanofiltration membrane. In the present embodiment, a membrane separation device using a microfiltration membrane or the like is exemplified as the solid-liquid separation device 34, but the present invention is not limited to this, and any solid-liquid separation material used for solid-liquid separation can be used. For example, a sedimentation separator, a pressure levitation device, a filtration device, or the like may be used alone or in combination.

  The water to be treated separated by the solid-liquid separation device 34 (that is, the clarified water from which the aggregated floc has been separated) is supplied to the membrane separation device 40 and a part thereof is supplied to the residual concentration measuring device 36. The water to be treated to the residual concentration measuring device 36 may be supplied from a sampling port of a pipe, or may be supplied using a pump (not shown).

  Specifically, FIG. 2 shows a schematic diagram of the residual concentration measuring device 36. As shown in FIG. 2, water to be treated is supplied to an ultrafilter (concentration treatment means) 44 through a pump 42. The ultrafilter 44 includes a container 46 and a lid body 48, and the flange portions of the container 46 and the lid body 48 are sandwiched between sandwiching bodies 50 and 50. The ultrafilter 44 is provided on the stirrer 52, and stirs to-be-processed water using the stirring bar mentioned later. The concentrated water obtained by the ultrafilter 44 is introduced into a measurement sensor (concentration measuring means) 53 for measuring the concentration of organic matter. This measurement sensor 53 is electrically connected to the control unit 38, measures the organic substance concentration or sugar concentration contained in the concentrated water with the measurement sensor 53, and notifies the control unit 38 of the measurement. The residual concentration measuring device 36 is a cross flow method.

  As shown in the longitudinal sectional view of FIG. 2 in FIG. 3, a stirrer 54 is placed in the container 46, and the rotational speed of the stirrer 54 is adjusted by a stirrer 52 and supplied to the ultrafilter 44. Stir the treated water. The treated water supplied to the ultrafilter 44 is filtered by an ultrafiltration membrane (hereinafter referred to as UF membrane) 56, and the permeated water is purified through a sintered porous plate 58 having water permeability. As the UF membrane 56, a filtration membrane having a fractional molecular weight of 5000 or more, preferably a fractional molecular weight of 10,000 or more and a fractional molecular weight of 50,000 or less, preferably a fractional molecular weight of 30,000 or less is used. If the molecular weight cut off is too small, it will be measured including the concentration of low molecular weight organic substances that do not significantly affect membrane separation. Conversely, if the molecular weight cut off is too large, the organic substances to be measured will be removed. Because.

  On the other hand, the concentrated water in which the substance that cannot pass through the UF membrane 56 is concentrated is stored in the container 46. The concentrated water obtained by the ultrafilter 44 is preferably concentrated water obtained by concentrating the water to be treated supplied to the ultrafilter 44 10 times or more in order to be used in organic substance concentration measurement described later. On the other hand, in order to measure the sugar concentration contained in the concentrated water, the concentrated water is preferably concentrated 100 times or more.

  The measurement sensor 53 for measuring the concentration of organic substances contained in the concentrated water is selected from total organic carbon concentration measurement, sugar concentration measurement, COD measurement, and the like, but is not limited thereto. A TOC meter is mainly used as the total organic carbon concentration.

  As a measurement of the sugar concentration contained in the concentrated water, the phenol-sulfuric acid method used for sugar analysis is generally used. Other examples include an anthrone sulfate method for analyzing neutral polysaccharides and a carbazole sulfate method for analyzing acidic polysaccharides. In addition, the sugar contained in the concentrated water can be hydrolyzed with acid to form a glucose unit monosaccharide, which can be analyzed using high performance liquid chromatography or using a urine sugar test kit. .

  Moreover, it is also possible to measure the sugar concentration of the hydrolyzed monosaccharide by using a test paper and using a simple chemical analyzer with a reflection photometer. For example, a test paper for Merck RQ flex can be mentioned. In this method, the pH of the acid-treated water is returned to neutral, the test paper is immersed in the acid-treated water that has been returned to neutral, and the sugar concentration is measured according to the measurement operation of RQ flex. Specifically, the test paper is immersed in acid-treated water that has been neutralized at pH, and the sugar concentration is measured according to the RQ flex measurement procedure. The amount of concentrated water necessary for measuring the sugar concentration is about 2 to 3 ml. The sugar concentration is measured in this way because the organic component in the polymer region is mainly composed of polysaccharides or glycoproteins, so that the organic component concentration in the polymer region can be known by analyzing the sugar. It is. The measurement of the sugar concentration is not limited to the method described above.

  As the COD measurement, the organic substance concentration can be measured by measuring COD chromium or COD manganese. In addition to the total organic carbon concentration measurement, sugar concentration measurement, and COD measurement described above, an ultraviolet absorption spectrum capable of quantitatively measuring the organic substance concentration, high performance liquid chromatography, or the like can also be used, but it is not limited to these. Is not to be done.

  The membrane separation device 40 into which the water to be treated is introduced from the solid-liquid separation device 34 is provided with an RO membrane, and the water to be treated is filtered through the RO membrane to purify the permeated water.

(Method for determining the amount of flocculant added)
A method for determining the addition amount of the flocculant using the water treatment apparatus 1 according to the present invention including the thus-aggregated solid-liquid separation apparatus 10 will be described below based on the flowchart shown in FIG. This flowchart is performed by the control unit 38.

  In step S1, a predetermined amount of a flocculant is added to the water to be treated in the stirring tank 14, and the water to be treated is agglomerated. In step S2, the water to be treated after the aggregation treatment is introduced into the solid-liquid separator 34 and filtered. In step S3, the water to be treated that has been filtered by the solid-liquid separator 34 is introduced into the ultrafilter 44, and filtered through a UF membrane to concentrate the water to be treated (concentration treatment step).

  In the subsequent step S4, when the concentration of the concentrated water obtained by the concentration treatment in the above step S3 is not less than a specified value, that is, 10 times or more compared with the water to be treated filtered by the solid-liquid separation device 34, the concentrated water. The organic substance density | concentration contained in is measured using a TOC meter (concentration measurement process). In step S5, the addition amount of the flocculant added to the stirring tank 14 is determined from the organic substance concentration measured in step S4 (addition amount determination step). The addition amount of the flocculant to be added to the stirring tank 14 may be obtained from, for example, a map indicating the organic substance concentration registered in advance in the control unit 38, that is, the relationship between the TOC and the addition amount of the flocculant. Not limited. In step S6, the addition amount of the flocculant determined in step S5 is added to the water to be treated in the stirring tank 14.

  As described above, in the present embodiment, before the membrane separation process is performed by the membrane separation apparatus 40, a coagulant such as an inorganic coagulant or a polymer coagulant is added to the water to be treated, and the water to be treated which has been coagulated. By measuring the concentration of organic matter contained in the concentrated water obtained by passing a part through the ultrafilter 44, the amount of the present flocculant added is the amount of organic matter contained in the water to be treated in the stirring tank 14. An appropriate addition amount can be determined by determining whether the amount is appropriate for the aggregation treatment, and the addition amount of the flocculant can be increased or decreased based on the determination. Accordingly, it is not necessary to determine whether or not the addition amount of the flocculant is an appropriate amount from the purification result of the water to be treated filtered by the membrane separator 40, and the target to be supplied to the membrane separator 40 can be obtained. Treated water can be supplied. Moreover, since the contamination by the organic substance of the RO membrane provided in the membrane separation apparatus 40 is suppressed, the membrane separation apparatus 40 can be operated stably.

(Modification of the method for determining the amount of flocculant added)
A modification of the method for determining the amount of flocculant added to the water treatment apparatus 1 will be described below based on the flowchart shown in FIG. In this flowchart, since the water treatment method shown in FIG. 4 and steps S1 to S3 and S6 are common, description of common portions is omitted and only differences are described.

  In step S41, the sugar concentration of the concentrated water obtained by the concentration process in step S3 is measured (concentration measuring step). The sugar concentration may be measured by the phenol sulfuric acid method as described above. However, when the test paper is used, it is necessary to perform acid hydrolysis of concentrated water as a pretreatment. This is because the test paper for measuring the sugar concentration measures monosaccharides such as glucose and fructose, and therefore it is necessary to hydrolyze the polysaccharide contained in the concentrated water with acid to form a monosaccharide. . As a method for acid hydrolysis of the concentrated water, for example, 1 ml of the concentrated water obtained in the above step S3 is mixed with 2N hydrochloric acid or 2N sulfuric acid in a 0.5 ml test tube and mixed at 80 ° C. or above in a water bath or heater. And neutralizing by adding 0.5 ml of 2N sodium hydroxide. The sugar concentration of the concentrated water thus treated is measured.

  In the subsequent step S51, the addition amount of the flocculant added to the stirring tank 14 is determined from the sugar concentration measured in step S41 (addition amount determination step). The addition amount of the flocculant to be added to the stirring tank 14 may be obtained from, for example, a map showing the relationship between the sugar concentration registered in advance in the control unit 38 and the addition amount of the flocculant, but is not limited thereto. .

  Thus, by measuring the sugar concentration contained in the concentrated water treated by the ultrafilter 44, and determining the addition amount of the flocculant added to the water to be treated in the stirring tank 14 from the measured sugar concentration. The same effects as described above can be obtained.

  In the above-described embodiment, the water treatment apparatus 1 includes the aggregation solid-liquid separation apparatus 10 and the membrane separation apparatus 40. However, the apparatus may further include other apparatuses and processes, for example, membrane separation. Even if the pretreatment performed before the apparatus 40 and the posttreatment performed after the membrane separation apparatus 40 are further subjected to purification treatment of water to be treated such as deionization treatment such as ion exchange treatment, decarbonization treatment, and activated carbon treatment. Good. Further, if necessary, a bactericidal agent, a deodorant, an antifoaming agent, an anticorrosive, or the like may be added, or ultraviolet irradiation, ozone treatment, biological treatment, etc. may be used in combination.

  In the embodiment described above, the flocculant is added to the agitation tank 14 via the pump 18, but the flocculant may be added by injecting the line into a pipe through which the water to be treated flows.

  In the embodiment described above, the solid-liquid separation device 34 is included in the coagulation solid-liquid separation device 10. However, the solid-liquid separation device 34 may not be provided, and the water to be treated that has been coagulated in the stirring tank 14. A part of the sample may be collected with a pump, and the water to be treated may be filtered with a No5A filter paper and then introduced into the residual concentration measuring device 36.

  In the embodiment described above, the addition amount of the flocculant is automatically determined by the control of the control unit 38, but the separated water from the solid-liquid separation device 34 is collected from a sampling port provided in the pipe. The steps S3 to S5 of the flowchart shown in FIG. 4 may be manually performed to manually set the addition amount of the flocculant. Furthermore, as shown in the examples described later, the addition amount of the flocculant is determined by a desktop test, and the addition amount of the flocculant obtained by the desktop test is used as an addition amount in an actual water treatment system, for example, a water treatment device. You may make it employ | adopt.

  The present invention will be described in more detail according to the following examples. Note that the present invention is not limited to this.

<Example 1>
Four beakers containing 1000 ml of industrial water from lake water as the water to be treated were installed in the jar tester, and polyaluminum chloride (hereinafter referred to as PAC) (10% by weight) was added to each beaker as a flocculant. After adding 10, 30, and 50 ml and adjusting the pH to 6.5 with a 5% aqueous sodium hydroxide solution, the mixture was stirred at 170 rpm for 3 minutes and then stirred at 50 rpm for 5 minutes. Thereafter, the floc particle diameter was confirmed. In addition, the water quality of the industrial water used was 35 mS / m in electrical conductivity, pH 6.8, and 1.2 mg / l in TOC.

The total amount of each treated water was filtered using No5A filter paper, and the obtained filtrate was passed through a UF membrane with a molecular weight cut off of 30000 provided in an ultrafiltration device (UF filter holder made by Advantech), and the concentration factor was the filtrate. The concentrated water was obtained by adjusting to about 10 times. Here, the amount of treated water (Aml) and the amount of concentrated water (Bml) used for UF filtration were measured accurately. Moreover, the TOC measurement (Cmg / l) of concentrated water was performed. Based on these results, TOC ₃₀₀₀₀ of an organic substance having a molecular weight of 30,000 or more in the water to be treated was obtained from the formula (1).

TOC ₃₀₀₀₀ = B / A × C (1)

  Next, in the same manner as above, 2 L of industrial water as treatment water is put in a plastic container, 5 mg / L of PAC is added as a flocculant, and 5% sodium hydroxide aqueous solution is added to pH 6.5 while stirring with a stirrer. After adjusting and stirring at 170 rpm for 3 minutes, it stirred at 50 rpm for 5 minutes. The same operation was carried out by changing the addition amount of PAC to 10, 30, and 50 mg / L to perform aggregation treatment. Then, the water to be treated which has been subjected to the coagulation treatment is respectively filtered using No5A filter paper, and the flow rate is 1 ml / min through the RO membrane (RO membrane ES20 manufactured by Nitto Denko) installed in the RO flat membrane test apparatus. Flux measurement was performed by passing water under conditions of a pressure of 0.78 MPa and 400 rpm. The RO membrane was washed by adjusting it to pH 12 using sodium hydroxide and immersing it overnight. In the flux measurement, pure water adjusted with sodium chloride so that the electric conductivity is approximately equal to the industrial water used is passed through the RO flat membrane test device, and when the permeate flow rate is stabilized, the water to be treated is passed. The flux was measured at regular intervals (starting on day 0). The flux was measured by the equation (2) after measuring the amount of permeated water for 10 minutes with a graduated cylinder.

Flux [m ³ / m ² · d] = Fr × 1.7905 × Pc × Tc (2)

  Here, Fr represents a flow rate [ml / min], Pc represents a pressure correction coefficient, and Tc represents a temperature correction coefficient. The obtained result is shown in FIG.

<Example 2>
A jar test was performed using the same water to be treated as in Example 1. As a flocculant, dimethylamine / epichlorohydrin polymer was used. The dimethylamine / epichlorohydrin polymer used was a 50% aqueous solution, and the amount added was 1, 2, 5, 10 mg / l, respectively. The obtained results are shown in FIG.

  Based on the results shown in FIG. 6 and FIG. 7, the organic component TOC with a molecular weight cut off of 30000 or more converted from the water to be treated and the RO membrane flux from 0 to 7 days obtained in the RO flat membrane test. The relationship of the reduction rate is summarized in a graph. FIG. 8 shows the graph. FIG. 8 clearly shows a correlation between the TOC of the organic component having a molecular weight cut off of 30000 or more in the water to be treated and the flux of the RO membrane, and it is possible to grasp the current treatment state by measuring the TOC. Moreover, it is possible to read the sign of the membrane processing performance fall in a membrane separator from this graph, and it can suppress the filtration performance fall of RO membrane by increasing / decreasing the addition amount of a coagulant | flocculant.

<Example 3>
A jar test was performed using water to be treated and a flocculant similar to those in Example 1. The amount of treated water (Aml) and the amount of concentrated water (Bml) used for UF filtration were measured accurately. Further, a glucose measuring test paper of Merck RQ flex was immersed in concentrated water, and the test paper was inserted into the RQ flex main body to determine the sugar concentration (Dmg / l). Based on these results, the sugar concentration L ₃₀₀₀₀ (mg / l) having a molecular weight of 30000 or more contained in the water to be treated was determined from the following formula (3).

L ₃₀₀₀₀ = B / A × D (3)

  Further, flux measurement was performed under the same conditions as in Example 1. The results are shown in FIG.

<Example 4>
A jar test was performed using the same treated water as in Example 3. As a flocculant, dimethylamine / epichlorohydrin polymer was used. The dimethylamine / epichlorohydrin polymer used was a 50% aqueous solution, and the amount added was 1, 2, 5, 10 mg / l, respectively. The obtained result is shown in FIG.

  9 and 10, the relationship between the sugar concentration of the component having a molecular weight cut off of 30000 or more converted from the water to be treated and the rate of decrease in the flux of the RO membrane from 0 to 7 days obtained in the RO flat membrane test. FIG. 11 shows a graph summarizing the above. FIG. 11 clearly shows a correlation between the sugar concentration in the component with a molecular weight cut off of 30,000 or more and the flux of the RO membrane, and the current treatment state can be grasped by measuring the sugar concentration. I understand. Moreover, since the sign of the RO membrane filtration performance deterioration can be read, the decrease in the RO membrane filtration performance can be suppressed by increasing or decreasing the amount of the flocculant added.

DESCRIPTION OF SYMBOLS 1 Water treatment apparatus 10 Aggregation solid-liquid separation apparatus 14 Stirrer tank 36 Residual concentration measuring apparatus 44 Ultrafiltration machine 56 Ultrafiltration membrane

Claims (5)

A method for determining the addition amount of a flocculant in water treatment in which a flocculant is added to water to be treated supplied to a membrane separation apparatus including a separation membrane,
A concentration treatment step of concentrating the treated water subjected to the aggregation treatment with an ultrafiltration membrane;
A concentration measuring step for measuring the concentration of organic matter contained in the concentrated water obtained in the concentration treatment step;
An addition amount determining step for determining the amount of the flocculant added to the water to be treated based on the measured organic matter concentration;
A method for determining the amount of an aggregating agent to be added.   The method of claim 1, wherein the organic substance concentration is a sugar concentration. A water treatment apparatus for performing a coagulation treatment by adding a coagulant to water to be treated supplied to a membrane separation apparatus including a separation membrane,
A concentration treatment means for concentrating the treated water subjected to the aggregation treatment with an ultrafiltration membrane;
A concentration measuring means for measuring the concentration of organic substances present in the concentrated water subjected to the concentration treatment;
An addition amount control means for controlling the addition amount of the flocculant added to the water to be treated based on the measured organic substance concentration;
A water treatment apparatus comprising:   The water treatment apparatus according to claim 3, wherein the organic substance concentration is a sugar concentration.   The water treatment device according to claim 3 or 4, wherein the ultrafiltration membrane has a molecular weight cut-off of 5000 or more.

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