JP6554781B2 - Operation method of reverse osmosis membrane device and reverse osmosis membrane device - Google Patents

Description

The present invention relates to a reverse osmosis membrane treatment applied to seawater desalination, ultrapure water production, industrial water treatment, wastewater recovery treatment, etc., and adsorbs on a membrane such as MBR treated water, lake water, river water, groundwater, etc. When treating water containing a large amount of organic metabolites that promote contamination, it suppresses membrane fouling and permeation flux (hereinafter referred to as “flux”) reduction, reduces the frequency of chemical cleaning, and is stable for a long time. The present invention relates to a method for operating a reverse osmosis membrane device and a reverse osmosis membrane device therefor.
The present invention also relates to a water treatment method using the reverse osmosis membrane device.

  Reverse osmosis membranes are conventionally used for removing ions, organic substances, and the like in raw water in seawater desalination, ultrapure water production, industrial water treatment, wastewater recovery treatment, and the like. With reverse osmosis membranes, the flux may decrease due to the growth of microorganisms on the membrane surface or adsorption of organic matter, or the module differential pressure may increase due to blockage by turbidity. It is necessary to recover the pressure difference between the raw water side and the concentrated water side (hereinafter referred to as element differential pressure).

  Among membrane contamination components contained in raw water, in particular, high molecular organic substances such as polysaccharides and proteins are known to significantly contaminate reverse osmosis membranes. Conventionally, as pretreatment of reverse osmosis membrane treatment, Generally, removal of high molecular organic substances in raw water by membrane treatment with an ultrafiltration membrane or the like is performed.

  On the other hand, with regard to the timing and frequency of chemical cleaning when the reverse osmosis membrane is contaminated, chemical cleaning is performed when the flux is reduced by about 10% compared to the initial level, and the cleaning frequency is about twice a year or less. Is considered appropriate (Non-Patent Document 1). The Dow website also states that the time when the flux of the reverse osmosis membrane is reduced by 10% is the timing of the chemical cleaning, and if it is later than that, the recovery effect of the flux by cleaning cannot be sufficiently obtained ( Non-patent document 2).

  By the way, the mass transfer of the membrane module is analyzed, the concentration of the solute is calculated using the concentration polarization equation, and the membrane transport parameter is predicted (Non-patent Document 3, Patent Document 1). ). However, since the target solute is an ionic component such as NaCl that requires the solute permeation coefficient, stable operation is difficult even when applied to the treatment of raw water containing a large amount of organic matter.

  The present inventors focused on the behavior of organic matter in this concentration polarization phenomenon, and as a result of investigating the influence of the membrane surface concentration of the organic matter, which is a membrane contaminant, on membrane contamination, In particular, there was a correlation between the film surface concentration of the polymer organic substance and the rate of flux reduction, and it was clarified that the flux decrease was caused by the adsorption of the polymer organic substance concentrated on the film surface. In addition, the present inventors have separately confirmed that the membrane contamination does not occur when the feed water of the reverse osmosis membrane is treated with an ultrafiltration membrane, and the molecular weight cut off at that time is around 10,000. It was found that 10,000 or more macromolecular organic substances are involved in film contamination (Patent Documents 2 and 3).

The concentration polarization on the film surface depends on the diffusion coefficient of the solute, and the diffusion coefficient decreases as the molecular weight increases. In the ultrafiltration method, the relationship between the molecular weight and the diffusion coefficient represented by the following formula (3) is required for dextran and polyethylene glycol (Non-patent Document 3). It has also been found that high-molecular organic substances such as sugars and proteins are similarly concentrated on the reverse osmosis membrane surface according to this relationship.
D = 8.76 × 10 ⁻⁹ (Mw) ^−0.48 formula (3)
D [m ² / s]: diffusion coefficient
Mw [g / mole]: molecular weight of high molecular organic substance

Membrane separation activated sludge method (MBR: membrane bioreactor) that treats activated sludge such as sewage in a biological treatment tank and separates the activated sludge mixed solution into solid and liquid using an immersion membrane separator installed in the biological treatment tank ) Is capable of obtaining treated water with stable water quality, and increasing the activated sludge concentration to enable high-load treatment, which is becoming widespread. In addition, a method for treating organic wastewater in which this MBR-treated water (membrane filtered water of a submerged membrane separator) is directly fed to a reverse osmosis membrane device and treated with a reverse osmosis membrane has also been proposed (for example, Non-Patent Document 4). ).
However, MBR-treated water contains a large amount of high-molecular organic matter having a molecular weight of 10,000 or more, which is a membrane contaminant, and in reverse osmosis membrane devices that treat MBR-treated water, there is a decrease in flux or increase in transmembrane pressure over time. There is a problem of being big.

  Most of the organic matter on the earth is synthesized by photosynthesis by plants on land and by phytoplankton in oceans and lakes. Humic substances are organic substances whose chemical structure is unspecified after the death of organisms due to the microbial and chemical action of organic substances, and exist in surface water such as seawater, lake water, river water, and groundwater .

The amount of humic substances in the water is 0.3 to 15 mg / L in seawater as the amount of dissolved organic carbon (TOC), but 1 to 50 mg / L in lake water and 1 to 60 mg / L in river water. In groundwater, it becomes 0.3 to 500 mg / L, and depending on the location, a very high concentration of humic substances may be contained. The concentration of humic substances present in seawater is low (Non-patent Document 5).
Even when lake water, river water, or groundwater containing such humic substances is treated with a reverse osmosis membrane device, there is a problem that a decrease in flux with time or an increase in transmembrane pressure difference is large.

Japanese Patent No. 3520906 JP 2014-159015 A Japanese Patent Application No. 2013-92657

"Measures against membrane degradation and fouling: From membrane contamination prevention and cleaning methods to troubleshooting" (NTS issue) p323 (2008) “Cleaning Procedures for DOW FILMTEC FT30 Elements” (Dow) p1 Form No. 609-23010-0211 (on the Web) "Design Method of Membrane Separation Process" (Membrane Society of Japan) p37-49 (1985) “Water Treatment Membrane Formation Technology and Material Evaluation” (published January 30, 2012, first edition, first print, Science & Technology Co., Ltd.) p. 11 "Humic substances in the environment-its characteristics and research methods" (supervised by the Japanese Society of Humic Substances) Roshi Ishiwatari, Koyo Yonebayashi, edited by Toru Miyajima, p2-9, 30-32 (2008)

  The present invention is a reverse osmosis membrane capable of stably treating raw water containing a large amount of high molecular weight organic substances having a molecular weight of 10,000 or more and organic metabolite organic substances such as humic substances as membrane contaminants while preventing a decrease in flux. It is an object of the present invention to provide a device, a method for operating the device, and a method for treating biologically treated water using the reverse osmosis membrane device.

As a result of intensive studies to solve the above problems, the present inventors calculated the membrane surface concentration (Cm) of the biometabolite organic substance for each reverse osmosis membrane element loaded in the reverse osmosis membrane device, It has been found that the above-mentioned problems can be solved by controlling the operating conditions, pretreatment of raw water, adding a dispersing agent, or designing the device configuration so that the average value is not more than a predetermined value.
That is, the gist of the present invention is as follows.

[1] Reverse Osmosis Membrane Device Operation Method for Treating Water Containing Biological Metabolite-Based Organic Substances as Raw Water] The reverse osmosis membrane device comprises a vessel incorporating a reverse osmosis membrane element or a plurality of such vessels arranged in parallel 1 or two or more stages connected in series, and based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, according to the following formula (1) The membrane surface concentration (Cm) of the biological metabolite-based organic substance for each reverse osmosis membrane element is calculated, and the operation of the following (I) is performed so that the average value of the calculated values in the reverse osmosis membrane device is a predetermined value X or less. And / or when the average value of the calculated values in the reverse osmosis membrane device exceeds a predetermined value X, the operation of the following (II) is performed.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite-based organic substance concentration of the treated water of the reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of the biological metabolite-based organic substance (I): Reverse in the reverse osmosis membrane device Any one or more of the number of reverse osmosis membrane elements used for osmosis membrane treatment, the configuration of the bank, the amount of permeated water, the amount of concentrated water, and the concentration of biological metabolites in the reverse osmosis membrane device supply water by the pretreatment of the raw water Adjust.
(II): A dispersant is added to the raw water or the water supplied to the reverse osmosis membrane device.

[2] In [1], the biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water has a concentration of 0.01 mg / L or higher. The method of operating a reverse osmosis membrane device, wherein the predetermined value X is 0.7 kg / m ³ .

[3] In [1], the biological metabolite-based organic substance is humic substance, and the raw water contains humic substance as TOC at a concentration of 0.05 mg / L or more, and the predetermined value X is The operating method of a reverse osmosis membrane device, characterized in that it is 0.4 × 10 ⁻³ kg / m ³ .

[4] The method of operating a reverse osmosis membrane device according to any one of [1] to [3], wherein the pretreatment is an aggregation treatment and / or an ultrafiltration membrane treatment.

[5] In any one of [1] to [3], the reverse osmosis membrane device is formed by connecting the banks in a plurality of stages of two or more stages in series, and the biometabolite-based organic matter membranes in all the banks. The operation (I) is performed so that the calculated value of the surface concentration (Cm) is equal to or less than the predetermined value Y, and / or the film surface concentration (Cm) of the biological metabolite-based organic substance is calculated in one or more banks. A method of operating a reverse osmosis membrane device, characterized in that the operation (II) is performed when the value exceeds a predetermined value Y.

[6] The method of operating a reverse osmosis membrane device according to [5], wherein the biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the predetermined value Y is 1 kg / m ^3. .

[7] The method of operating a reverse osmosis membrane device according to [5], wherein the biological metabolite organic substance is humic substance and the predetermined value Y is 0.6 × 10 ⁻³ kg / m ^3. .

[8] The method of operating a reverse osmosis membrane device according to any one of [1] to [7], wherein the reverse osmosis membrane device is cleaned with a chemical solution at a frequency of 2 times / year or less.

[9] The method for operating a reverse osmosis membrane device according to any one of [1] to [8], wherein the reverse osmosis membrane is an aromatic polyamide reverse osmosis membrane.

[10] The method of operating a reverse osmosis membrane device according to any one of [1] to [9], wherein the dispersant is a biological metabolite-based organic dispersant and / or a scale dispersant.

[11] A reverse osmosis membrane apparatus that treats water containing biological metabolite-based organic matter as raw water, and includes a vessel containing a reverse osmosis membrane element or a bank formed by arranging a plurality of the vessels in parallel. Two or more stages connected in series, flow rate adjusting means for adjusting the amount of permeated water and / or concentrated water in the reverse osmosis membrane device, and the mass transfer coefficient of the reverse osmosis membrane element in the reverse osmosis membrane device ( k) based on the following formula (1), calculating means for calculating the membrane surface concentration (Cm) of the biological metabolite organic substance for each reverse osmosis membrane element, and based on the calculated value of the calculating means, A reverse osmosis membrane device comprising: a flow rate control means for controlling the flow rate adjustment means so that an average value of the calculated values in the osmosis membrane device is a predetermined value X or less.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance

[12] A reverse osmosis membrane apparatus that treats water containing biological metabolite-based organic matter as raw water, and includes a vessel having a reverse osmosis membrane element or a bank formed by arranging a plurality of the vessels in parallel. Two or more stages are connected in series, and the raw water is pretreated by coagulation treatment and / or ultrafiltration membrane treatment to remove part of the biological metabolite organic matter in the raw water. Pretreatment means for reducing the concentration of biological metabolites in the supply water to the osmosis membrane device, a flow path for supplying the raw water as the direct supply water to the reverse osmosis membrane device, and the reverse through the pretreatment means. Each reverse osmosis membrane according to the following formula (1) based on the raw water channel switching means for switching the channel supplied to the osmosis membrane device and the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device Biological metabolite organic membrane for each element The calculation means for calculating the surface concentration (Cm), and the raw water flow path switching means so that the average value of the calculated values in the reverse osmosis membrane device is not more than a predetermined value X based on the calculated value of the calculating means. A reverse osmosis membrane device comprising a flow path switching by means of or a raw water adjusting means for adjusting processing conditions in the pretreatment means.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance

[13] A reverse osmosis membrane apparatus that treats water containing a biological metabolite-based organic substance as raw water, wherein a vessel having a reverse osmosis membrane element or a bank formed by arranging a plurality of the vessels in parallel is provided in two or more stages. By switching the flow path for connecting the supply water of the reverse osmosis membrane device to the first-stage bank and / or the flow path for supplying the concentrated water of the preceding-stage bank to the subsequent-stage bank. Based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device and the feed water flow path switching means for adjusting the number of vessels used for the reverse osmosis membrane treatment, Calculation means for calculating the membrane surface concentration (Cm) of the biological metabolite-based organic substance for each osmosis membrane element, and based on the calculated value of the calculation means, the average value of the calculated values in the reverse osmosis membrane device is a predetermined value X So that A reverse osmosis membrane device comprising a flow path control means for controlling the supply water flow path switching means.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance

[14] A reverse osmosis membrane apparatus that treats water containing biological metabolite-based organic matter as raw water, and includes a vessel having a reverse osmosis membrane element or a bank formed by arranging a plurality of the vessels in parallel. Two or more stages connected in series, a dispersant addition means for adding a dispersant to the raw water or the water supplied to the reverse osmosis membrane device, and a mass transfer coefficient of the reverse osmosis membrane element in the reverse osmosis membrane device Based on (k), the calculation means for calculating the membrane surface concentration (Cm) of the biological metabolite organic substance for each reverse osmosis membrane element according to the following formula (1), and based on the calculated value of the calculation means, A reverse osmosis membrane device comprising a dispersant addition amount control means for controlling the dispersant addition means.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance

[15] The reverse osmosis membrane device according to [14], wherein the dispersant is a biological metabolite organic dispersant and / or a scale dispersant.

[16] In [14] or [15], when the average value of the calculated values in the reverse osmosis membrane device calculated by the calculating means exceeds the predetermined value X, the dispersant addition amount control means A reverse osmosis membrane device characterized by increasing the amount of dispersant added by the dispersant addition means or starting the addition of the dispersant.

[17] In [16], the bank is connected in a plurality of stages of two or more stages, and the dispersant addition amount control means is a film surface concentration of the biometabolite organic substance calculated by the arithmetic means. When the calculated value of (Cm) exceeds a predetermined value Y in one or more banks, the dispersant addition amount of the dispersant addition means is increased or the addition of the dispersant is started. Reverse osmosis membrane device.

[18] In any one of [11] to [13] and [16], the biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water has a high molecular weight of 10,000 or more. A reverse osmosis membrane device comprising a molecular organic substance at a concentration of 0.01 mg / L or more, wherein the predetermined value X is 0.7 kg / m ³ .

[19] In any one of [11] to [13] and [16], the biological metabolite-based organic substance is humic substance, and the raw water has a concentration of 0.05 mg / L or more with the humic substance as TOC. A reverse osmosis membrane device comprising: the predetermined value X is 0.4 × 10 ⁻³ kg / m ³ .

[20] In any one of [11] to [13], the bank is connected in two or more stages in series, and in all banks, the membrane surface concentration (Cm) of the biometabolite-based organic substance is A reverse osmosis membrane device, wherein the calculated value is controlled to be equal to or less than a predetermined value Y.

[21] The reverse osmosis membrane according to [17] or [20], wherein the biological metabolite organic substance is a high molecular weight organic substance having a molecular weight of 10,000 or more, and the predetermined value Y is 1 kg / m ^3. apparatus.

[22] The reverse osmosis membrane according to [17] or [20], wherein the biological metabolite organic substance is humic substance and the predetermined value Y is 0.6 × 10 ⁻³ kg / m ^3. apparatus.

[23] The reverse osmosis membrane device according to any one of [11] to [22], further comprising a chemical cleaning means for cleaning the reverse osmosis membrane at a frequency of 2 times / year or less.

[24] The reverse osmosis membrane device according to any one of [11] to [23], wherein the reverse osmosis membrane is an aromatic polyamide reverse osmosis membrane.

[25] A water treatment method characterized by subjecting biologically treated water, surface layer water or groundwater to reverse osmosis membrane treatment with the reverse osmosis membrane device according to any one of [11] to [24].

  According to the present invention, in reverse osmosis membrane treatment applied to seawater desalination, ultrapure water production, industrial water treatment, wastewater recovery treatment, etc., MBR treated water, surface water such as lake water, river water, ground water, etc. When treating water containing a large amount of biological metabolite organic substances that adsorb to the membrane and promote membrane contamination, the fouling of the membrane and the decrease in flux are suppressed, the frequency of chemical cleaning is reduced, and the treatment is continued for a long time. A stable reverse osmosis membrane device can be operated.

It is a systematic diagram which shows an example of the bank structure of the reverse osmosis membrane apparatus of this invention. It is a systematic diagram which shows the other example of a bank structure of the reverse osmosis membrane apparatus of this invention. It is a systematic diagram which shows embodiment of the processing method of the biologically treated water of this invention.

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

  In the present invention, the “raw water” refers to water that is pretreated as necessary to be subjected to a reverse osmosis membrane treatment by a reverse osmosis membrane device, and the raw water is pretreated as necessary and then reversed. The water supplied to the osmosis membrane device is referred to as “supply water”, and the water subjected to the reverse osmosis membrane treatment with each reverse osmosis membrane element is referred to as “treated water”.

[Reverse osmosis membrane element]
As a reverse osmosis membrane element to be loaded into the reverse osmosis membrane device in the present invention, a raw water spacer for passing water to be treated is disposed on the primary side of the flat membrane of the reverse osmosis membrane, and the treated water is passed on the secondary side. A spiral-type reverse osmosis membrane element in which permeated water spacers for watering are arranged, stacked, and wound into a spiral shape can be suitably used, but is not limited thereto.
The membrane diameter of the spiral type reverse osmosis membrane element is not particularly limited, and those of 4 inches, 8 inches, and 16 inches are usually used. The length of the spiral type reverse osmosis membrane element is usually about 1 m.

  As the material of the reverse osmosis membrane in the present invention, aromatic organic compounds synthesized using phenylenediamine and acid chloride from the viewpoint of adsorptivity of high molecular organic substances such as polysaccharides and proteins, which are biological metabolite organic substances, and humic substances. A group polyamide-based reverse osmosis membrane is preferred.

[Bank configuration]
Usually, a reverse osmosis membrane apparatus takes the arrangement | positioning called a Christmas tree as shown, for example in FIG. 1, 2 in order to raise the water recovery rate with respect to supplied water.

In FIG. 1, a first vessel group (hereinafter referred to as “bank”) 1 in which 10 vessels (RO body) 1A to 1J having a reverse osmosis membrane element are arranged in parallel and 5 vessels 2A to 2E are provided. A Christmas tree type multi-stage reverse osmosis membrane device is constituted by the second bank 2 arranged in parallel.
The water supplied to the reverse osmosis membrane device first flows into the first bank 1 and is separated into permeated water and concentrated water. Subsequently, the concentrated water in the first bank 1 flows into the second bank 2 and is again separated into permeated water and concentrated water. The permeated water of the first bank 1 and the permeated water of the second bank 2 merge and are transferred to the post-treatment process, and the concentrated water of the second bank is discharged out of the system or transferred to a discharge treatment facility or the like.

The multi-stage reverse osmosis membrane device of FIG. 2 includes a first bank 1 in which eight vessels 1A to 1H including reverse osmosis membrane elements are arranged in parallel and a second bank in which four vessels 2A to 2D are arranged in parallel. 2 and a third bank 3 in which two vessels 3A and 3B are arranged in parallel.
The water supplied to the reverse osmosis membrane device first flows into the first bank 1 and is separated into permeated water and concentrated water. Subsequently, the concentrated water in the first bank 1 flows into the second bank 2 and is again separated into permeated water and concentrated water. The concentrated water in the second bank 2 flows into the third bank 3 and is further separated into permeated water and concentrated water. The permeated water of the first bank 1, the permeated water of the second bank 2, and the permeated water of the third bank 3 are merged and transferred to the subsequent processing step. On the other hand, the concentrated water in the third bank is discharged out of the system or transferred to a discharge treatment facility or the like.

  As described above, the Christmas tree structure in the reverse osmosis membrane apparatus is usually composed of 2 or 3 banks, depending on the required water recovery rate, but the latter bank is the concentrated water of the former bank. Therefore, the concentration of the solute in the water used for the reverse osmosis membrane treatment increases in the latter bank.

However, the reverse osmosis membrane device of the present invention is not limited to a Christmas tree structure in which such banks are arranged in multiple stages, and may be composed of only one bank. It may be composed of only one vessel. Further, one vessel may be connected in series in multiple stages. Further, it may be composed of four or more multi-stage banks.
Usually, about 1 to 6 reverse osmosis membrane elements are built in one vessel.

[Raw water]
In the present invention, the raw water subjected to the reverse osmosis membrane treatment by the reverse osmosis membrane device contains a biological metabolite organic substance, and specifically includes the following raw water (i) or raw water (ii). In addition, it is good also considering the water by which raw | natural water (i) and raw | natural water (ii) were mixed as raw | natural water.
Raw water (i): High molecular organic substance having a molecular weight of 10,000 or more is 0.01 mg / L or more
Concentrated water Raw water (ii): Water containing humic substance as TOC at a concentration of 0.05 mg / L or more

<Raw water (i)>
The raw water (i) is water containing a high molecular weight organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 mg / L or more. High-molecular organic substances having a molecular weight of 10,000 or more, particularly biological metabolites such as polysaccharides and proteins, easily contaminate the membrane and easily cause a decrease in flux. In the present invention, such high molecular organic substances are contained in an amount of 0.01 mg / L or more, for example, 0.05 to 0.5 mg / L, and water that greatly reduces the flux of the reverse osmosis membrane by passing water is effectively used as raw water. Reverse osmosis membrane treatment can be performed.

  Examples of such high molecular organic substance-containing water include recovered water from various wastewaters and biologically treated water, and the present invention is particularly suitably applied to the treatment of biologically treated water such as MBR treated water.

  In addition, the molecular weight of the polymer organic substance in the present invention can be determined from the position of the peak top using dextran as a standard substance by high performance liquid chromatography. In particular, high-performance liquid chromatography using a TOC as a detector is effective for determining the concentration of a high molecular weight organic substance having a molecular weight of 10,000 or more. A component having an elution time faster than that of an organic substance having a molecular weight of 10,000 is selected to have a molecular weight of 10, 000 or more high molecular organic substances. According to the measurements so far, it has been recognized that the polysaccharide has a molecular weight of 1 million or more, and possibly more than 10 million. As an alternative to high performance liquid chromatography, a method of measuring the concentration of the permeation component and the non-permeation component using an ultrafiltration membrane with a molecular weight cut off of 10,000 can also be used.

<Raw water (ii)>
The raw water (ii) is water containing humic substance as TOC at a concentration of 0.05 mg / L or more. When humic substances coexist with polyvalent cations such as calcium and magnesium, the membrane tends to contaminate the membrane and cause a decrease in flux. In the present invention, such humic substances are contained in TOC as 0.05 mg / L or more, preferably 0.1 mg / L or more, for example, 0.5 to 5 mg / L, and the flow of the reverse osmosis membrane is greatly reduced by water flow. Thus, the reverse osmosis membrane treatment can be effectively performed as raw water.

  In particular, humic substances such as fulvic acid and humic acid cause a significant decrease in flux when polyvalent metal ions such as Ca, Mg, Fe, Al, Ba, and Sr coexist. Along with humic substances, these polyvalent metal ions contain 10 mg / L or more, for example, about 10 to 50 mg / L if Ca ions, and the total polyvalent metal ion concentration is 0.1 mg / L or more, for example 1 to 100 mg / L. Effective for raw water of about L level.

  Examples of such humic substance-containing water include surface water, groundwater, biologically treated water, and the present invention is particularly suitably applied to the treatment of surface water or groundwater such as lake water and river water.

  In addition, the molecular weight of the humic substance in the present invention can be determined from the peak top position by high performance liquid chromatography using dextran as a standard substance. It is appropriate to use a TOC or differential refractive index detector for text runs and a UV detector for humic substances. High-performance liquid chromatography using UV and TOC as detectors is effective for determining the concentration of humic substances. As an alternative to high performance liquid chromatography, a method of simply measuring the concentration of humic substances from UV absorption measurement values such as E260 of raw water can also be used.

[Preprocessing]
If the concentration of the biological metabolite-based organic matter in the raw water treated in the present invention is excessively high, the reverse osmosis membrane causes fouling, and in other conditions control, the average of the membrane surface concentration (Cm) of the biological metabolite-based organic matter. In some cases, the value cannot be made equal to or less than the predetermined value X.
For this reason, when the concentration of the biological metabolite organic substance in the raw water is excessively high, or the membrane surface concentration of the biological metabolite organic substance (without changing other conditions such as the amount of permeated water and concentrated water of the reverse osmosis membrane device) In order to make the average value of Cm) equal to or less than the predetermined value X, the raw water is pretreated by coagulation treatment, ultrafiltration membrane treatment, etc., and a part of the biological metabolite organic substances in the raw water is removed, and the reverse osmosis membrane It is also a preferable method to reduce the concentration of biological metabolite-based organic matter in the apparatus supply water.

In the present invention, when the raw water (i) is treated, the raw water is treated as necessary so that the concentration of the high molecular organic substance having a molecular weight of 10,000 or more in the reverse osmosis membrane apparatus is 0.2 mg / L or less. It is preferable to process.
Moreover, when processing raw | natural water (ii), it is preferable to pre-process raw | natural water as needed so that the humic substance density | concentration of the supply water of a reverse osmosis membrane apparatus may be 0.1 mg / L or less as TOC.

[Regarding Formula (1)]
In the present invention, based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, the membrane surface of the biometabolite-based organic substance for each reverse osmosis membrane element calculated according to the following formula (1) Biological metabolism by controlling so that the average value of the concentration (Cm) in the reverse osmosis membrane device is less than or equal to the predetermined value X, or adding a dispersant to the raw water or the supply water of the reverse osmosis membrane device according to this average value By preventing the adhesion of physical organic matter film, the flux is prevented from lowering.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance

In the reverse osmosis membrane, a phenomenon called concentration polarization occurs on the membrane surface due to water flow, and when the concentration polarization increases, the solute concentration on the membrane surface increases.
Conventionally, as in Patent Document 1, there has been a report of obtaining the membrane surface concentration of a low-molecular solute such as NaCl and examining the effect of osmotic pressure on the flux. The relationship between the rate of flux reduction has not been elucidated based on membrane contamination.
In this invention, the fall of the flux in a reverse osmosis membrane apparatus is estimated in the following procedures.

1) Understand the influence of the structure of the reverse osmosis membrane element, the quality of the treated water and the operating conditions on the mass transfer coefficient (k) of the reverse osmosis membrane element, and calculate the mass transfer coefficient (k).
2) Investigate and formulate the relationship between the membrane surface concentration of biological metabolites and organic matter and the rate of flux reduction.
3) Measure the concentration of organic metabolites in the treated water.
4) Using the biological metabolite organic substance concentration obtained in 3) and the mass transfer coefficient (k) of 1), obtain the membrane surface concentration of the biological metabolite organic substance, and obtain the flux reduction rate from 2).

In calculating the mass transfer coefficient (k), the mass transfer correlation equation of Sherwood number, Reynolds number, and Schmidt number in the [0023] to [0029] paragraphs of Non-Patent Document 3 and Patent Document 1 can be used. In the present invention, in calculating the mass transfer coefficient (k) from the mass transfer correlation equation, the biological metabolite-based organic matter in the raw water is expressed as the solute diffusion coefficient (D) by the formula (3) of Non-Patent Document 3 described above. The value calculated from the molecular weight (Mw) is used.
In Non-Patent Document 3 and Patent Document 1, the mass transfer coefficient (k) can be determined by obtaining the Sherwood number, and the Sherwood number is represented by the Reynolds number and the Schmidt number. At this time, the flow parallel to the film surface is considered as the Reynolds number, but the flow in the permeation direction of the film is not considered.

In the present invention, the mass transfer coefficient (k) for the biological metabolite-based organic matter in the water to be treated can be obtained by using the calculated value of Equation (3) of Non-Patent Document 3 described above as the solute diffusion coefficient (D). it can.
Using the solute diffusion coefficient (D) calculated from the equation (3), the mass transfer coefficient (k) is calculated as follows, but various methods for calculating the Sherwood number of the diffusion coefficient (D) are known, Whatever expression is used, it is sufficient that the film surface concentration can be controlled.
Sh = k · d / D
Re = u · d / ν
Sc = ν / D
Sh [-]: Sherwood number Re [-]: Reynolds number Sc [-]: Schmidt number d [m]: Representative diameter (in the case of a spiral element, channel spacer thickness x 2)
u [m / s]: Flow velocity parallel to the film surface ν [m ² / s]: Kinematic viscosity of water to be treated The mass transfer coefficient (k) is expressed by the following equation.
k = (D / d) · Sh
When the amount of concentrated water (Fc) per reverse osmosis membrane element is used, the flow velocity (u) parallel to the membrane surface can be expressed by the following equation.
u = (Fc + Fp / 2) / ((d / 2) · S / (2L))
Fc [m ³ / s]: Concentrated water amount per reverse osmosis membrane element L [m]: Effective membrane length

In Non-Patent Document 3 and Patent Document 1, Sh is represented by the following equation using Re and Sc.
Sh = A · Re ^b · Sc ^c
A, b, c [-]: constant

In general, the constant A is expressed by the following equation in consideration of the shape of the film.
A = a · (d / L) ^e
a, e [-]: Constant L [m]: Effective film length

In Non-Patent Document 6 (An analytical model for spiral wound reverse osmosis membrance modules: Part II-Experimental validation, S. Sundaramoorthy et al., Desalination, 277, p. 257-264 (2011)), Sh is Re, Sc, Cb is expressed by the following formula.
Sh = A · Re ^b · Sc ^c · (Cb / ρ) ^f
ρ [kg / m ³ ]: treated water density A, b, c, f [−]: constant

In Non-Patent Document 7 (“Effect of membrane permeation flux on mass transfer coefficient” (Takao Anazawa et al., Abstracts of Papers Presented at the 25th Autumn Meeting of the Chemical Engineering Society of Japan) F313 (1992)), Sh is the permeation direction of the membrane A formula that takes into account the flow (Jv) is used.
Sh = a · (Re ^b + gRey ^h ) · Sc ^c · (d / L) ^e
Rey = Jv · d / ν
Rey [−]: Reynolds number in the flow in the permeation direction of the membrane Jv [m / s]: Flow in the permeation direction of the membrane (Fp / S)
a, b, c, e, g, h [-]: constant In the narrow range of Rey, the following equations are also considered to hold.
Sh = a · Re ^b · Rey ^h · Sc ^c · (d / L) ^e
a, b, c, e, h [-]: constant

  As described above, various formulas representing the Sherwood number (Sh) have been proposed. It is necessary to select an appropriate one and obtain the mass transfer coefficient (k) from the obtained Sherwood number. If more factors are taken into account, it is expected that a more accurate Sherwood number can be obtained, but there is a problem that the examination for obtaining the constant and the handling of the formula become complicated. The essence of the present invention is not in the expression format of the Sherwood number for obtaining the mass transfer coefficient (k), but using the mass transfer coefficient (k), the membrane surface concentration (Cm) of the biological metabolite-based organic substance is determined. The purpose is to control the film surface concentration or to control the addition of the dispersing agent in accordance with the film surface concentration (Cm).

  From the above, as factors affecting the mass transfer coefficient (k), the diffusion coefficient of biological metabolites, the amount of concentrated water per reverse osmosis membrane element, the amount of permeated water, the membrane area, the flow of spiral reverse osmosis membrane elements Examples include the road spacer thickness, the effective film length, and the kinematic viscosity of the water to be treated.

Then, as shown in Experimental Examples 1 and 2, which will be described later, when the relationship between the film surface concentration of the polymer organic matter or humic substance and the flux reduction rate is examined, the results shown in Tables 1 and 2 below are obtained. Here, the flux reduction rate represents the rate at which the flux decreases when the initial flux is 100%.
As described in Non-Patent Documents 1 and 2 described above, it is preferable to perform chemical cleaning up to twice a year as the allowable value for continuous operation until the flux decreases by 10%. In order to suppress the flux decrease to 10% or less with a chemical cleaning frequency of twice a year or less, the flux decrease rate needs to be 20% / year or less.

<When raw water (i) is treated with a reverse osmosis membrane>
From the relationship of Table 1 described later, paying attention to the polymer organic matter, the flux reduction rate can be made 20% / year or less by setting the film surface concentration of the polymer organic matter to 0.7 kg / m ³ or less. It can be seen that the flux can be recovered with a chemical cleaning frequency of less than twice a year and can be stably operated. That is, in the reverse osmosis membrane treatment of raw water (i), the predetermined value X is 0.7 kg / m ³ .

Therefore, when the raw water (i) is subjected to a reverse osmosis membrane treatment, the average value of the membrane surface concentration (Cm) of the polymer organic matter for each reverse osmosis membrane element calculated by the equation (1) is 0.7 kg / m ³ or less. The operation (I) which will be described later is performed so as to become or the operation (II) which will be described later is performed when the average value exceeds 0.7 kg / m ³ . Note that the operation (I) and the operation (II) may be performed together.
When the average value of the membrane surface concentration (Cm) of the polymer organic substance for each reverse osmosis membrane element calculated by the formula (1) exceeds 0.7 kg / m ³ , the rate of flux decrease exceeds 20% / year, The chemical solution cleaning twice a year cannot maintain a stable operation, and requires chemical cleaning three times or more a year, which is not preferable. The average value of the membrane surface concentration (Cm) of the polymer organic matter for each reverse osmosis membrane element may be 0.7 kg / m ³ or less, preferably 0.5 kg / m ³ or less, more preferably 0. 2 kg / m ³ or less.

In addition, when the reverse osmosis membrane device is configured by providing banks in multiple stages as described above, as a condition that the rate of flux decrease in the entire reverse osmosis membrane device is 20% / year or less, in any bank In addition, it is desirable that the membrane surface concentration (Cm) of the polymer organic substance for each reverse osmosis membrane element is 1 kg / m ³ or less as the predetermined value Y. This is because the concentration of solutes in the latter bank tends to increase and the membrane surface concentration (Cm) of the polymer organic matter tends to be higher. Usually, the number of reverse osmosis membrane elements in the latter bank is the number of reverse osmosis membrane elements in the former bank. Therefore, even in the latter bank, by controlling the membrane surface concentration (Cm) of the polymer organic material for each reverse osmosis membrane element to 1 kg / m ³ or less, the flux in the entire reverse osmosis membrane device It is considered that the rate of decrease in the temperature can be suppressed to 20% / year or less.

<When reverse osmosis membrane treatment of raw water (ii)>
Focusing on humic substances from the relationship of Table 2 described later, the flux reduction rate is set to 20% / year or less by setting the film surface concentration of the humic substances to 0.4 × 10 ⁻³ kg / m ³ or less. It can be seen that the flux can be recovered with a chemical cleaning frequency of not more than twice a year and the operation can be stably performed. That is, in the reverse osmosis membrane treatment of raw water (ii), the predetermined value X is 0.4 kg / m ³ .

Therefore, when the raw water (ii) is treated with the reverse osmosis membrane, the average value of the membrane surface concentration (Cm) as the TOC of the humic substance for each reverse osmosis membrane element calculated by the equation (1) is 0.4 × 10. The operation (I) described later is performed so as to be ⁻³ kg / m ³ or less, or the operation (II) described later is performed when the average value exceeds 0.4 × 10 ⁻³ kg / m ³ . Note that the operation (I) and the operation (II) may be performed together.
When the average value of the membrane surface concentration (Cm) of the humic substance for each reverse osmosis membrane element calculated by the formula (1) exceeds 0.4 × 10 ⁻³ kg / m ³ , the rate of flux decrease is 20% / It is not preferable that the chemical cleaning performed twice a year cannot maintain a stable operation and requires chemical cleaning three or more times a year. The average value of the membrane surface concentration (Cm) of the humic substance for each reverse osmosis membrane element may be 0.4 × 10 ⁻³ kg / m ³ or less, preferably 0.2 × 10 ⁻³ kg / m ³ or less.

In addition, when the reverse osmosis membrane device is configured by providing banks in multiple stages as described above, as a condition that the rate of flux decrease in the entire reverse osmosis membrane device is 20% / year or less, in any bank In addition, it is desirable that the membrane surface concentration (Cm) of the humic substance as the TOC of each reverse osmosis membrane element is not more than 0.6 × 10 ⁻³ kg / m ³ as the predetermined value Y. This is because the concentration of solutes in the latter bank tends to increase, and the membrane surface concentration (Cm) of the humic substance tends to increase. Usually, the number of reverse osmosis membrane elements in the latter bank is equal to the number of reverse osmosis membrane elements in the former bank. Since it is about 1/2, the reverse osmosis membrane can be reduced by suppressing the humic substance membrane surface concentration (Cm) for each reverse osmosis membrane element to 0.6 × 10 ⁻³ kg / m ³ or less even in the latter bank. It is considered that the rate of flux decrease in the entire apparatus can be suppressed to 20% / year or less.

[Control of membrane concentration (Cm) of biological metabolites and organic substances / Dispersant addition control]
In the present invention, the calculation means calculates the membrane surface concentration (Cm) of the biometabolite-based organic substance for each reverse osmosis membrane element according to the formula (1), and for each reverse osmosis membrane element in the reverse osmosis membrane device. The following operation (I) is carried out so that the average value (hereinafter referred to as “average Cm value”) of the membrane surface concentration (Cm) of the biological metabolite-based organic substance is equal to or less than the predetermined value X, and / or When the average Cm value exceeds the predetermined value X, the following operation (II) is performed.
(I): the number of reverse osmosis membrane elements used for the reverse osmosis membrane treatment in the reverse osmosis membrane device, the configuration of the bank, the amount of permeated water, the amount of concentrated water, and the biological metabolism of the water supplied to the reverse osmosis membrane device by the pretreatment of the raw water Adjust any one or more of the physical organic matter concentrations.
(II): A dispersant is added to the raw water or the water supplied to the reverse osmosis membrane device.
The adjustment and control of the film surface concentration (Cm) of this biometabolite organic substance and the addition control of the dispersant will be described below.

(1) Adjustment of the amount of permeated water and the amount of concentrated water of the reverse osmosis membrane device When the average Cm value exceeds the predetermined value X, the reverse osmosis membrane element of the formula (1) is reduced by reducing the amount of permeated water of the entire reverse osmosis membrane device. The permeated water amount (Fp) per bottle can be reduced to lower the membrane surface concentration (Cm) of the biological metabolite organic substance, thereby lowering the average Cm value.
Conversely, by increasing the amount of concentrated water (Fc) of the entire reverse osmosis membrane device, the membrane surface concentration (Cm) of the biometabolite organic substance can be lowered and the average Cm value can be lowered.

The adjustment of the amount of permeated water and the amount of concentrated water may be a change in operating conditions that reduces the amount of permeated water without increasing the amount of water supplied to the reverse osmosis membrane device and increases the amount of concentrated water, without changing the amount of concentrated water. By reducing the amount of water supplied to the reverse osmosis membrane device, the operating condition may be changed to reduce only the amount of permeated water.
The adjustment of the permeated water amount and / or the concentrated water amount is provided with a flow rate adjusting means such as a flow rate adjusting valve for adjusting the permeated water amount and / or the concentrated water amount of the reverse osmosis membrane device, and the calculation result is input from the calculating means This can be done by controlling the flow rate adjusting means.

(2) Adjustment of the concentration of biological metabolites in the reverse osmosis membrane device supply water When the average Cm value exceeds the predetermined value X, the raw water is treated by pretreatment means such as coagulation treatment and / or ultrafiltration membrane treatment. Then, a part of the biological metabolite organic substances in the raw water is removed, and the biological metabolite organic substance concentration of the water to be treated (Cb) is reduced by reducing the biological metabolite organic substance concentration of the water supplied to the reverse osmosis membrane device. ) Can be reduced, and the membrane surface concentration (Cm) of the biological metabolite-based organic substance can be lowered to lower the average Cm value.

  In this case, a raw water flow path switching means for switching between a flow path for supplying raw water as direct supply water to the reverse osmosis membrane apparatus and a flow path for supplying the raw water to the reverse osmosis membrane apparatus through the pretreatment means is provided. The switching means is operated by the control means to which the calculation result from the calculation means is input, and when the average Cm value exceeds the predetermined value X, the raw water is treated by the pretreatment means and then supplied to the reverse osmosis membrane device, When the average Cm value is less than or equal to the predetermined value X, the pretreatment means is bypassed and supplied to the reverse osmosis membrane device, or the processing conditions of the pretreatment means are controlled according to the average Cm value. In addition, it is possible to control to adjust the removal rate of the biological metabolite-based organic matter.

(3) Adjustment of bank configuration When the reverse osmosis membrane device is configured by connecting two or more banks in series, the flow path for supplying the supply water of the reverse osmosis membrane device to the first stage bank and / or Or, by switching the flow path for supplying the concentrated water from the preceding bank to the subsequent bank, a water flow path switching means for adjusting the number of vessels used for the reverse osmosis membrane treatment is provided, and the calculation result from the calculation means is input. The average Cm value can be made equal to or less than the predetermined value X by switching the flow path of the water to be treated by the control means.

For example, in a reverse osmosis membrane device constituted by three-stage banks, in the reverse osmosis membrane treatment using only the previous two-stage banks, if the average Cm value exceeds the predetermined value X, the concentrated water in the second-stage bank The number of banks used for the reverse osmosis membrane treatment, that is, the number of reverse osmosis membrane elements, is selected by selecting the flow channel for the reverse osmosis membrane treatment by feeding to the third-stage bank from the channel for discharging It can be increased to reduce the average Cm value. This flow path switching can be performed by an open / close valve or the like provided in a pipe between the preceding bank and the succeeding bank.
Similarly, even within the same bank, the average Cm value can be controlled by increasing or decreasing the number of vessels used for the reverse osmosis membrane treatment by switching the flow path.

(4) Addition of dispersant When the average Cm value exceeds the predetermined value X, the dispersant is added to the raw water or the feed water pretreated with the raw water by the dispersant addition means, and the biological metabolism in the reverse osmosis membrane device feed water It is possible to disperse physical organic substances to prevent adhesion to the film and to perform stable operation.

In this case, the dispersant addition means for adding the dispersant to the raw water or the supply water and the calculation result from the calculation means are input, and based on the input value, the presence or absence of the dispersant addition by the dispersant addition means or the dispersant addition Dispersant addition amount control means for controlling the amount is provided, and when the average Cm value exceeds the predetermined value X, the dispersant is added, or the dispersant addition amount is increased so that the average Cm value is the predetermined value. If it becomes less than X, the method of performing chemical injection control, such as reducing the addition amount of a dispersing agent or stopping the addition of a dispersing agent, can be employ | adopted.
Furthermore, when the reverse osmosis membrane device is configured by providing banks in multiple stages as described above, the membrane surface concentration (Cm) of the polymer organic substance for each reverse osmosis membrane element in at least one bank is the predetermined value Y. Is exceeded, or the dispersant addition amount is increased, and in all banks, the membrane surface concentration (Cm) of the polymer organic matter for each reverse osmosis membrane element is equal to the predetermined value Y. When it becomes lower, it is possible to adopt a method of performing chemical injection control such as reducing the amount of the dispersant added or stopping the addition of the dispersant.

As the dispersant, a biometabolite-based organic dispersant and / or a scale dispersant can be used. For example, as the bio-metabolite-based organic dispersant, the agents listed in Japanese Patent Application No. 2014-055253 can be used. Specifically, polyvinylpyrrolidone, polyacrylamide, poly (2-alkyl-2-oxazoline) and the like can be mentioned. As scale dispersants, chelating scale inhibitors such as ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), (meth) acrylic acid polymers and salts thereof, maleic acid polymers and salts thereof, etc. Low molecular weight polymers, ethylenediaminetetramethylenephosphonic acid and its salts, hydroxyethylidene diphosphonic acid and its salts, nitrilotrimethylenephosphonic acid and its salts, phosphonobutanetricarboxylic acid and its salts, phosphonic acids and phosphonates, hexametaphosphoric acid And inorganic polymerized phosphoric acid and inorganic polymerized phosphate such as salts thereof, tripolyphosphoric acid and salts thereof, and the like can be used.
These dispersing agents may use only 1 type and may use 2 or more types together.

[Water treatment]
The present invention can be applied to various reverse osmosis membrane devices used for seawater desalination, ultrapure water production, industrial water treatment, wastewater recovery treatment, etc., but in particular, lake water, river water, or ground water is used as raw water. The present invention is preferably applied to a reverse osmosis membrane device that is processed as follows.
Moreover, the reverse osmosis membrane device of the present invention is particularly preferably used for reverse osmosis membrane treatment of biologically treated water.

FIG. 3 is a system diagram showing an embodiment of the water treatment method of the present invention for treating biologically treated water with a reverse osmosis membrane using the reverse osmosis membrane device of the present invention.
As a treatment procedure of the treatment method of biologically treated water according to the present invention, for example, as shown in FIG. 3 (a), a solid solution such as aerobic and / or anaerobic biological treatment means 11, flocculation treatment means 12, and pressure levitation The biological treatment water treated by the liquid separation means 13 and the filtration means 14 is introduced into the reverse osmosis membrane device 16 through the safety filter 15 and subjected to the reverse osmosis membrane treatment, as shown in FIG. A method in which water obtained by solid-liquid separation of the treated water directly by the filtration means 14 such as a membrane filtration device is introduced into the reverse osmosis membrane device 16 to perform a reverse osmosis membrane treatment, or, as shown in FIG. Examples include a method of directly introducing the treated water of the mold membrane separation device 17 into the reverse osmosis membrane device 16 and processing, but the method is not limited to these methods.

  Hereinafter, the present invention will be described in more detail with reference to experimental examples and examples.

[Experimental Example 1]
A reverse osmosis membrane treatment was performed using biologically treated water having a polymer organic substance concentration of 0.2 mg / L as raw water.
About the high molecular weight organic substance in this raw water, the molecular weight Mw measured by the high performance liquid chromatography is 1,300,000, and the diffusion coefficient D calculated from the formula (3) is 1.0 × 10 ⁻¹¹ m ² / s. It is.

The reverse osmosis membrane apparatus used was 15 vessels (60 reverse osmosis membrane elements) loaded with 4 Nitto Denko 8-inch aromatic polyamide reverse osmosis membrane “ES20” elements (membrane area 37 m ² per one). As shown in FIG. 1, the first bank has 10 vessels arranged in parallel, and the second bank has 5 vessels arranged in parallel.
When the reverse osmosis membrane device thus configured was operated for one year under the conditions of the permeated water amount of the entire reverse osmosis membrane device being 60 m ³ / h and the concentrated water amount being 20 m ³ / h, in the second bank, 79 % / Year flux reduction occurred, and chemical cleaning was required 5 times a year.

From the value of the diffusion coefficient D of the polymer organic matter in the raw water, the mass transfer coefficient (k) of the membrane element was calculated as follows according to the method described in Patent Document 1.
The following formula was used as a formula for obtaining the mass transfer coefficient.
Sh = 0.080 · Re ^0.875 · Sc ^0.25
k = (D / d) · 0.080 · Re ^0.875 · Sc ^0.25
As a result, the mass transfer coefficient (k) was as follows in both the first bank and the second bank.
k = 9.6 × 10 ⁻⁷ [m / s]

The amount of permeated water (Fp) per reverse osmosis membrane element is 2.8 × 10 ⁻⁴ m ³ / s, the membrane area (S) per membrane element is 37 m ² , and the polymer organic matter of the water to be treated Concentration (Cb) is 0.2 × 10 ⁻³ kg / m ³ (0.2 mg / L) in the first bank, and 0.4 × 10 ⁻³ kg / m ³ (0.4 mg / L) in the second bank. Therefore, when the membrane surface concentration (Cm) of the polymer organic substance of each reverse osmosis membrane element is calculated from the above formula (1), the reverse osmosis membrane element of the first bank is 1.5 kg / m ³ , the second bank of a reverse osmosis membrane element is 3.0 kg / ^{m 3,} the average value of the entire reverse osmosis unit is (1.5 × 40 + 3.0 × 20 ) /60=2.0kg/m 3, 0.7kg / M ³ was exceeded.

  In the above reverse osmosis membrane treatment, experiments were conducted under various operating conditions with different amounts of permeate and concentrated water, and the relationship between the membrane surface concentration (Cm) of the polymer organic matter and the flux reduction rate was examined. The results shown are obtained.

The results in Table 1 were expressed by the following approximate expression (2A).
Z = 0.016 · {log (Cm) +3} ^6.8 formula (2A)
Z [% / year]: Flux reduction rate

  The value of this equation depends on the material of the membrane, and it was confirmed by conducting a similar experiment using different reverse osmosis membranes. However, in the case of a general aromatic polyamide reverse osmosis membrane such as “ES20”. In other words, the above approximate expression (2A) was satisfied.

[Example 1]
In Experimental Example 1, when the operating conditions of the permeated water amount 56 m ³ / h and the concentrated water amount 24 m ³ / h of the entire reverse osmosis membrane device were set, the membrane surface concentration (Cm) of the polymer organic substance calculated by the above formula (1) the first bank 0.68 kg / ^{m 3,} the second bank 0.68 kg / ^{m 3} (hence, mean Cm value is ^{0.68kg / m 3 (= 0.68 ×} 40 + 0.68 × 20) / 60 )).
The flux reduction rate (Z) calculated from the film surface concentration (Cm) of the polymer organic substance by the approximate expression (2A) is 19.2% / year for the first bank and 19.5% / year for the second bank. It is 19.3% for the reverse osmosis membrane device as a whole.
Therefore, when the operation conditions were actually set to the permeated water amount 56 m ³ / h and the concentrated water amount 24 m ³ / h of the entire reverse osmosis membrane device, the stable operation was maintained by chemical cleaning twice a year. I was able to.
From this Example 1, reverse osmosis is performed so that the average value of the membrane surface concentration (Cm) of the polymer organic matter for each reverse osmosis membrane element calculated by the formula (1) is 0.7 kg / m ³ or less. It can be seen that stable operation can be achieved by controlling the amount of permeated water and the amount of concentrated water in the membrane device.

[Example 2]
In Experimental Example 1, water having a macromolecular organic substance concentration of 0.065 mg / L by agglomeration treatment of raw water is used as supply water, the amount of permeated water of the entire reverse osmosis membrane device is 60 m ³ / h, and the amount of concentrated water is 20 m ³ / h. The reverse osmosis membrane treatment was performed.
From this operating condition, the film surface concentration of the high molecular organic material to be calculated by the formula (1) (Cm) is, 0.49 kg / ^{m 3} in the first bank, a 0.99 kg / ^{m 3} in the second bank ( Therefore, the average Cm value is 0.66 kg / m ³ (= (0.49 × 40 + 0.99 × 20) / 60)), and the flux decrease rate calculated by the approximate expression (2A) is 13 for the first bank. 7% / year, the second bank was 28.3% / year, and the total reverse osmosis membrane device was 18.6% / year.
When membrane treatment was performed under these operating conditions, stable operation could be maintained by chemical cleaning twice a year.
From this Example 2, the raw water was adjusted so that the average value of the membrane surface concentration (Cm) of the polymer organic matter for each reverse osmosis membrane element calculated by the formula (1) was 0.7 kg / m ³ or less. It can be understood that stable operation can be performed even if the amount of the permeated water and the amount of concentrated water are kept as they are by using pre-treated water with reduced concentration of polymer organic matter in the raw water as the feed water.

[Example 3]
In Example 2, the concentration of the polymer organic substance was further reduced by the pretreatment of the raw water, and when the reverse osmosis membrane treatment was performed using water with the polymer organic substance concentration of 0.035 mg / L as the feed water, the flux reduction of the entire reverse osmosis membrane device Although the calculation result that the speed is reduced to 9.4% / year is obtained, when membrane treatment was actually performed under this pretreatment condition, stable operation could be maintained by chemical cleaning once a year. .

[Example 4]
Using 14 vessels loaded with four reverse osmosis membrane device elements identical to those used in Experimental Example 1, the bank configuration of the reverse osmosis membrane device is as shown in FIG. Parallel arrangement, the second bank is arranged in parallel with four vessels, the third bank is arranged in parallel with two vessels, and the same raw water (polymer organic substance concentration 0.2 mg / L) is used under the same operating conditions (the whole reverse osmosis membrane device) The reverse osmosis membrane treatment was performed with a permeated water amount of 60 m ³ / h and a concentrated water amount of 20 m ³ / h).
Under these operating conditions, the linear flow velocity becomes higher in the later stage, and the membrane surface concentration (Cm) of the polymer organic substance for each reverse osmosis membrane element calculated by the above formula (1) is 0.34 kg / kg in the first bank. m ^3, 0.20 kg / ^{m 3} in the second bank, the third bank at 0.08 kg / ^{m 3} next (hence, mean Cm value is ^{0.26kg / m 3 (= (0.34} × 32 + 0.20 × 16 + 0 0.08 × 8) / 56)), the flux decrease rate calculated by the approximate expression (2A) from the film surface concentration (Cm) of the high molecular organic substance is 9.1% / year for the first bank and the second bank Is 4.8% / year, the third bank is 1.3% / year, and the total reverse osmosis membrane device is 6.8% / year.
Therefore, when reverse osmosis membrane treatment was actually performed with the reverse osmosis membrane device having the first to third bank configurations, the operation could be maintained with chemical cleaning less than twice a year.
From this Example 4, by changing the bank configuration, each reverse osmosis membrane element can be supplied without changing the permeated water amount and the concentrated water amount of the entire reverse osmosis membrane device even if the supply water has the same polymer organic matter concentration. It can be seen that the film surface concentration (Cm) of the polymer organic substance can be adjusted, and the average Cm value can be lowered to perform stable operation.

[Experiment 2]
A reverse osmosis membrane treatment was performed using groundwater having a humic substance concentration of 0.08 mg / L as TOC (containing 20 mg / L of Ca ions as polyvalent ions) as raw water. The concentration of humic substances was measured by high performance liquid chromatography using UV as a detector. Canadian fulvo (manufactured by PIIC Bio) was used as a standard substance. The molecular weight Mw of the humic substance is 7,000, and the diffusion coefficient D calculated from the formula (3) is 1.25 × 10 ⁻¹⁰ m ² / s.

The reverse osmosis membrane apparatus used was 15 vessels (60 reverse osmosis membrane elements) loaded with 4 Nitto Denko 8-inch aromatic polyamide reverse osmosis membrane “ES20” elements (membrane area 37 m ² per one). As shown in FIG. 1, the first bank has 10 vessels arranged in parallel, and the second bank has 5 vessels arranged in parallel.
When the reverse osmosis membrane device thus configured was operated for one year under the conditions of the permeated water amount of the entire reverse osmosis membrane device being 60 m ³ / h and the concentrated water amount being 20 m ³ / h, % / Year flux reduction occurred, and chemical cleaning was required four times a year.

From the value of the diffusion coefficient D of the humic substance in the raw water, the mass transfer coefficient (k) of the membrane element was calculated as follows according to the method described in Patent Document 1.
The following formula was used as a formula for obtaining the mass transfer coefficient.
Sh = 0.080 · Re ^0.875 · Sc ^0.25
k = (D / d) · 0.080 · Re ^0.875 · Sc ^0.25
As a result, the mass transfer coefficient (k) was as follows in both the first bank and the second bank.
k = 5.7 × 10 ⁻⁶ [m / s]

The amount of permeated water (Fp) per reverse osmosis membrane element is 2.8 × 10 −4 m ³ / s, the membrane area (S) per membrane element is 37 m ² , and the humic substance concentration of treated water ( Cb) is 0.11 × 10 ⁻³ kg / m ³ (0.11 mg / L) in the first bank and 0.22 × 10 ⁻³ kg / m ³ (0.22 mg / L) in the second bank. Accordingly, when the membrane surface concentration (Cm) of the humic substance of each reverse osmosis membrane element is calculated from the formula (1), the reverse osmosis membrane element of the first bank is 0.41 × 10 ⁻³ kg / m ³ (0 .41 mg / L), the reverse osmosis membrane element of the second bank is 0.82 × 10 ⁻³ kg / m ³ (0.82 mg / L), and the average value of the entire reverse osmosis membrane device is (0.41 × 10 ⁻³ × 40 + 0.82 × 10 ⁻³ × 20) /60=0.54×10 ⁻³ kg / m ³ (0.54 mg / L), which exceeded 0.4 × 10 ⁻³ kg / m ³ .

  In the above reverse osmosis membrane treatment, experiments were conducted under various operating conditions with different amounts of permeated water and concentrated water, and the relationship between the humic substance membrane surface concentration (Cm) and the flux reduction rate was examined. Results were obtained.

The results in Table 2 were expressed by the following approximate expression (2B).
Z = 43.8 × Cm ^0.859 formula (2B)
Z [% / year]: Flux reduction rate

  The value of this equation depends on the material of the membrane, and it was confirmed by conducting a similar experiment using different reverse osmosis membranes. However, in the case of a general aromatic polyamide reverse osmosis membrane such as “ES20”. In other words, the above approximate expression (2B) was satisfied.

[Example 5]
In Experimental Example 2, when operating conditions of the permeated water amount 54 m ³ / h and the concentrated water amount 26 m ³ / h of the entire reverse osmosis membrane device are set, the membrane surface concentration (Cm) of the humic substance calculated by the above formula (1) is The first bank is 0.33 × 10 ⁻³ kg / m ³ and the second bank is 0.52 × 10 ⁻³ kg / m ³ (therefore, the average Cm value is 0.39 × 10 ⁻³ kg / m ^3). (= 0.33 × 10 ⁻³ × 40 + 0.52 × 10 ⁻³ × 20) / 60)).
The flux reduction rate (Z) calculated from the humic substance membrane surface concentration (Cm) by the approximate expression (2B) is 17.0% / year for the first bank and 24.8% / year for the second bank. The overall reverse osmosis membrane device is 19.6% / year.
Therefore, when the operation conditions were actually set to the permeated water amount of 50 m ³ / h and the concentrated water amount of 31 m ³ / h for the entire reverse osmosis membrane device, the stable operation was maintained by the chemical cleaning twice a year. I was able to.
From Example 5, the average value of the membrane surface concentration (Cm) of the humic substance for each reverse osmosis membrane element calculated by the formula (1) is 0.4 × 10 ⁻³ kg / m ³ or less. In addition, it can be seen that stable operation can be achieved by controlling the amount of permeated water and the amount of concentrated water in the reverse osmosis membrane device.

[Example 6]
In Experimental Example 2, water having a humic substance concentration of 0.055 mg / L (Ca ion concentration 20 mg / L) by agglomeration treatment of raw water is used as supply water, and the amount of permeated water of the entire reverse osmosis membrane device is 60 m ³ / h. The reverse osmosis membrane treatment was performed with a concentrated water amount of 20 m ³ / h.
From these operating conditions, the film surface concentration (Cm) of the humic substance calculated by the formula (1) is 0.28 × 10 ⁻³ kg / m ³ in the first bank and 0.57 × 10 2 in the second bank. ⁻³ kg / m ³ (thus, the average Cm value is 0.38 × 10 ⁻³ kg / m ³ (= (0.28 × 10 ⁻³ × 40 + 0.57 × 10 ⁻³ × 20) / 60) , Cm ≦ 0.6 × 10 ⁻³ kg / m ³ ) of the second bank, and the flux decrease rate calculated by the approximate expression (2B) is 14.8% / year for the first bank and It was 26.9% / year, and the total reverse osmosis membrane device was 18.9% / year.
When membrane treatment was performed under these operating conditions, stable operation could be maintained by chemical cleaning twice a year.
From Example 6, the average value of the membrane surface concentration (Cm) of the humic substance for each reverse osmosis membrane element calculated by the formula (1) is 0.4 × 10 ⁻³ kg / m ³ or less. In addition, it can be seen that stable operation can be performed even if the amount of permeated water and the amount of concentrated water are kept as they are by pre-treating the raw water and using the water with reduced humic substance concentration of the raw water as the feed water.

[Example 7]
In Example 6, the pre-treatment of the raw water further reduced the humic substance concentration, and the reverse osmosis membrane treatment was performed using water with a humic substance concentration of 0.025 mg / L (Ca ion concentration of 20 mg / L) as supply water. Although the calculation result that the flux reduction rate of the whole membrane device is reduced to 9.6% / year is obtained, when membrane treatment was actually performed under this pretreatment condition, stable operation was achieved with chemical cleaning once a year. Could be maintained.

[Example 8]
Using 14 vessels loaded with four reverse osmosis membrane device elements identical to those used in Experimental Example 2, the bank configuration of the reverse osmosis membrane device is shown in FIG. Parallel arrangement, the second bank is arranged in parallel with four vessels, the third bank is arranged in parallel with two vessels, and the same raw water (humic substance concentration 0.08 mg / L) is used under the same operating conditions (for the entire reverse osmosis membrane device) The reverse osmosis membrane treatment was performed with a permeated water amount of 60 m ³ / h and a concentrated water amount of 20 m ³ / h).
Under these operating conditions, the membrane surface concentration (Cm) of the humic substance for each reverse osmosis membrane element calculated by the formula (1) is 0.31 × 10 ⁻³ kg / m ³ in the first bank, 2 banks ^{0.45 × 10 -3 kg / m 3} , the third bank at 0.55 × ¹⁰ -3 kg / ^{m 3} next (hence, mean Cm value is ^{0.38 × 10 -3 kg / m 3} ( = (0.31 × 10 ⁻³ × 32 + 0.45 × 10 ⁻³ × 16 + 0.55 × 10 ⁻³ × 8) / 56)), the approximate expression (2B) from the film surface concentration (Cm) of this humic substance The rate of flux decrease calculated in step 1 is 16.1% / year for the first bank, 22.0% / year for the second bank, and 26.4% / year for the third bank. 3% / year.
Therefore, when reverse osmosis membrane treatment was actually performed with the reverse osmosis membrane device having the first to third bank configurations, the operation could be maintained with chemical cleaning less than twice a year.
From this Example 8, by changing the bank configuration, even if the supply water has the same humic substance concentration, the reverse osmosis membrane element for each reverse osmosis membrane element without changing the permeated water amount and the concentrated water amount of the entire reverse osmosis membrane device. It can be seen that the film surface concentration (Cm) of the humic substance can be adjusted, and the average Cm value can be lowered to perform stable operation.

[Example 9]
In Experimental Example 2, 10 mg / L of “Kriverter-N500” (manufactured by Kurita Kogyo Co., Ltd.) as a polyvalent cation dispersant in the same raw water (humic substance concentration 0.08 mg / L), and polyvinyl as a humic substance dispersant Reverse osmosis membrane treatment was performed with water added with 3 mg / L of pyrrolidone as the feed water, with the total amount of permeated water of the reverse osmosis membrane device being 60 m ³ / h and the amount of concentrated water being 20 m ³ / h. The flux of the entire reverse osmosis membrane device was stabilized, and stable operation could be maintained by chemical cleaning once a year.
From Example 9, by adding a dispersing agent, even when the membrane surface concentration (Cm) of humic substances for each reverse osmosis membrane element increases, adhesion to the membrane is suppressed and stable operation can be performed. I understand.

  The present invention can be applied to various reverse osmosis membrane devices used for seawater desalination, ultrapure water production, industrial water treatment, wastewater recovery treatment, etc., and in particular, treats biologically treated water, especially MBR treated water. It is preferably applied to a reverse osmosis membrane device or a reverse osmosis membrane device for treating lake water, river water, or groundwater.

DESCRIPTION OF SYMBOLS 1 1st bank 2 2nd bank 3 3rd bank 11 Biological treatment means 12 Aggregation treatment means 13 Solid-liquid separation means 14 Filtration means 15 Security filter 16 Reverse osmosis membrane device 17 MBR (immersion type membrane separation device)

Claims (17)

In a method for operating a reverse osmosis membrane device for treating biologically treated water, surface layer water or groundwater containing biological metabolite-based organic matter as raw water,
The biological metabolite organic substance is a corrosive substance or a high molecular organic substance having a molecular weight of 10,000 or more,
The reverse osmosis membrane device is formed by connecting a vessel containing a reverse osmosis membrane element or a bank formed by arranging a plurality of the vessels in parallel in one or more stages.
Based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, the membrane concentration (Cm) of the biometabolite organic substance for each reverse osmosis membrane element is calculated according to the following formula (1). ,
The following operation (I) is performed so that the average value of the calculated values in the reverse osmosis membrane device is equal to or less than the predetermined value X, and / or the average value of the calculated values in the reverse osmosis membrane device is the predetermined value X A method of operating a reverse osmosis membrane device that performs the following operation (II) when exceeding the above value, wherein the predetermined value X satisfies the following (i) or (ii) : .
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite-based organic substance concentration of the treated water of the reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of the biological metabolite-based organic substance (I): Reverse in the reverse osmosis membrane device Any one or more of the number of reverse osmosis membrane elements used for osmosis membrane treatment, the configuration of the bank, the amount of permeated water, the amount of concentrated water, and the concentration of biological metabolites in the reverse osmosis membrane device supply water by the pretreatment of the raw water Adjust.
(II): A dispersant is added to the raw water or the water supplied to the reverse osmosis membrane device.
(I) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water contains the high molecular organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 mg / L or more. Yes, the predetermined value X is 0.7 kg / m ³ .
(Ii) The biological metabolite-based organic substance is humic substance, and the raw water contains the humic substance as TOC at a concentration of 0.05 mg / L or more, and the predetermined value X is 0.4 × 10. ⁻³ kg / m ³ . Oite to claim 1, wherein the pretreatment process operation of the reverse osmosis membrane device, characterized in that the aggregation treatment and / or ultrafiltration membrane treatment. 3. The reverse osmosis membrane device according to claim 1 or 2 , wherein the bank is formed by connecting the banks in a plurality of stages of two or more stages, and the calculated value of the membrane surface concentration (Cm) of the biometabolite-based organic substance in all the banks. When the operation of (I) is performed so that is less than or equal to the predetermined value Y, and / or the calculated value of the membrane surface concentration (Cm) of the biological metabolite-based organic substance exceeds the predetermined value Y in one or more banks A method for operating a reverse osmosis membrane device that performs the operation of (II) above, wherein the predetermined value Y satisfies the following (iii) or (iv) :
(Iii) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the predetermined value Y is 1 kg / m ³ .
(Iv) The biological metabolite organic substance is humic substance, and the predetermined value Y is 0.6 × 10 ⁻³ kg / m ³ . The method of operating a reverse osmosis membrane device according to any one of claims 1 to 3 , wherein the reverse osmosis membrane device is cleaned with a chemical solution at a frequency of 2 times / year or less. 5. The method of operating a reverse osmosis membrane device according to any one of claims 1 to 4 , wherein the reverse osmosis membrane is an aromatic polyamide reverse osmosis membrane. In any one of claims 1 to 5, the method operation of reverse osmosis membrane apparatus, wherein the dispersing agent is a biological metabolite-based organic dispersants and / or scale dispersant. A reverse osmosis membrane device for treating biologically treated water, surface layer water or groundwater containing biological metabolite organic matter as raw water,
The biological metabolite organic substance is a corrosive substance or a high molecular organic substance having a molecular weight of 10,000 or more,
A bank in which a reverse osmosis membrane element is embedded or a bank formed by arranging a plurality of the vessels in parallel is connected in series in one or more stages.
Flow rate adjusting means for adjusting the amount of permeated water and / or the amount of concentrated water of the reverse osmosis membrane device;
Based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, the membrane surface concentration (Cm) of the biometabolite organic substance for each reverse osmosis membrane element is calculated according to the following formula (1). Computing means;
Based on the calculated value of said calculating means, so that the average value of the calculated value in the reverse osmosis unit is equal to or less than a predetermined value X, and a flow control means for controlling said flow rate adjusting means, the predetermined value X Satisfies the following (i) or (ii): a reverse osmosis membrane device.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance
(I) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water contains the high molecular organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 mg / L or more. Yes, the predetermined value X is 0.7 kg / m ³ .
(Ii) The biological metabolite-based organic substance is humic substance, and the raw water contains the humic substance as TOC at a concentration of 0.05 mg / L or more, and the predetermined value X is 0.4 × 10. ⁻³ kg / m ³ . A reverse osmosis membrane device for treating biologically treated water, surface layer water or groundwater containing biological metabolite organic matter as raw water,
The biological metabolite organic substance is a corrosive substance or a high molecular organic substance having a molecular weight of 10,000 or more,
A bank in which a reverse osmosis membrane element is embedded or a bank formed by arranging a plurality of the vessels in parallel is connected in series in one or more stages.
The raw water is pretreated by coagulation treatment and / or ultrafiltration membrane treatment to remove a part of the biological metabolite-based organic matter in the raw water, thereby supplying the biological metabolite-based organic matter of the water supplied to the reverse osmosis membrane device Pretreatment means for reducing the concentration;
Raw water flow path switching means for switching the flow path for supplying the raw water directly to the reverse osmosis membrane apparatus as a supply water and the flow path for supplying the reverse osmosis membrane apparatus through the pretreatment means;
Based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, the membrane surface concentration (Cm) of the biometabolite organic substance for each reverse osmosis membrane element is calculated according to the following formula (1). Computing means;
Based on the calculated value of the arithmetic means, the raw water flow path switching means is switched so that the average value of the calculated values in the reverse osmosis membrane device is not more than a predetermined value X, or the pretreatment A reverse osmosis membrane device, characterized in that the predetermined value X satisfies the following (i) or (ii) .
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance
(I) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water contains the high molecular organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 mg / L or more. Yes, the predetermined value X is 0.7 kg / m ³ .
(Ii) The biological metabolite-based organic substance is humic substance, and the raw water contains the humic substance as TOC at a concentration of 0.05 mg / L or more, and the predetermined value X is 0.4 × 10. ⁻³ kg / m ³ . A reverse osmosis membrane device for treating biologically treated water, surface layer water or groundwater containing biological metabolite organic matter as raw water,
The biological metabolite organic substance is a corrosive substance or a high molecular organic substance having a molecular weight of 10,000 or more,
A bank formed by arranging a plurality of vessels containing reverse osmosis membrane elements in parallel is connected in series of two or more stages,
A flow path switching means for adjusting the number of banks used for reverse osmosis membrane processing by switching between a flow path for discharging the concentrated water of the preceding bank to the outside of the system and a flow path for feeding to the subsequent bank;
Based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, the membrane surface concentration (Cm) of the biometabolite organic substance for each reverse osmosis membrane element is calculated according to the following formula (1). Computing means;
Based on the calculated value of said calculating means, so that the average value of the calculated value in the reverse osmosis unit is equal to or less than a predetermined value X, and a flow path control means for controlling the flow path switching means, the predetermined A reverse osmosis membrane device, wherein the value X satisfies the following (i) or (ii):
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance
(I) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water contains the high molecular organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 mg / L or more. Yes, the predetermined value X is 0.7 kg / m ³ .
(Ii) The biological metabolite-based organic substance is humic substance, and the raw water contains the humic substance as TOC at a concentration of 0.05 mg / L or more, and the predetermined value X is 0.4 × 10. ⁻³ kg / m ³ . A reverse osmosis membrane device for treating biologically treated water, surface layer water or groundwater containing biological metabolite organic matter as raw water,
The biological metabolite organic substance is a corrosive substance or a high molecular organic substance having a molecular weight of 10,000 or more,
A bank formed by arranging a plurality of vessels containing reverse osmosis membrane elements in parallel is connected in series of two or more stages,
A channel switching means for adjusting the number of vessels used for reverse osmosis membrane treatment in the same bank;
Based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, the membrane surface concentration (Cm) of the biometabolite organic substance for each reverse osmosis membrane element is calculated according to the following formula (1). Computing means;
Based on the calculated value of said calculating means, so that the average value of the calculated value in the reverse osmosis unit is equal to or less than a predetermined value X, and a flow path control means for controlling the flow path switching means, the predetermined A reverse osmosis membrane device, wherein the value X satisfies the following (i) or (ii):
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance
(I) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water contains the high molecular organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 mg / L or more. Yes, the predetermined value X is 0.7 kg / m ³ .
(Ii) The biological metabolite-based organic substance is humic substance, and the raw water contains the humic substance as TOC at a concentration of 0.05 mg / L or more, and the predetermined value X is 0.4 × 10. ⁻³ kg / m ³ . A reverse osmosis membrane device for treating biologically treated water, surface layer water or groundwater containing biological metabolite organic matter as raw water,
The biological metabolite organic substance is a corrosive substance or a high molecular organic substance having a molecular weight of 10,000 or more,
A bank in which a reverse osmosis membrane element is embedded or a bank formed by arranging a plurality of the vessels in parallel is connected in series in one or more stages.
A dispersant addition means for adding a dispersant to the raw water or the reverse osmosis membrane device supply water;
Based on the mass transfer coefficient (k) of the reverse osmosis membrane element in the reverse osmosis membrane device, the membrane surface concentration (Cm) of the biometabolite organic substance for each reverse osmosis membrane element is calculated according to the following formula (1). Computing means;
A reverse osmosis membrane device comprising: a dispersant addition amount control means for controlling the dispersant addition means based on a calculated value of the calculation means.
Cm = Cb exp {Fp / (S · k)} Formula (1)
k [m / s]: Mass transfer coefficient of reverse osmosis membrane element Fp [m ³ / s]: Permeated water amount per reverse osmosis membrane element S [m ² ]: Membrane area per reverse osmosis membrane element Cb [Kg / m ³ ]: Biological metabolite organic substance concentration of water to be treated of reverse osmosis membrane element Cm [kg / m ³ ]: Membrane surface concentration of biological metabolite organic substance 12. The reverse osmosis membrane device according to claim 11 , wherein the dispersant is a biometabolite-based organic dispersant and / or a scale dispersant. 13. The dispersant addition means according to claim 11 or 12 , wherein an average value of the calculated values in the reverse osmosis membrane device calculated by the calculation means exceeds a predetermined value X. or increasing the dispersing agent amount, or all SANYO to start addition of dispersant, the reverse osmosis membrane apparatus the predetermined value X is characterized by satisfying the following (i) or (ii).
(I) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the raw water contains the high molecular organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 mg / L or more. Yes, the predetermined value X is 0.7 kg / m ³ .
(Ii) The biological metabolite-based organic substance is humic substance, and the raw water contains the humic substance as TOC at a concentration of 0.05 mg / L or more, and the predetermined value X is 0.4 × 10. ⁻³ kg / m ³ . According to claim 13, made by connecting the bank in a plurality of stages in series of two or more stages, the dispersant amount control means, the film surface concentration of the biological metabolite based organic matter calculated by the calculating means (Cm) values calculated, if it exceeds a predetermined value Y in one or more banks, or to increase the dispersant additive amount of the dispersing agent addition means, or all SANYO to start addition of dispersing agent, the predetermined value Y Satisfies the following (iii) or (iv): a reverse osmosis membrane device.
(Iii) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the predetermined value Y is 1 kg / m ³ .
(Iv) The biological metabolite organic substance is humic substance, and the predetermined value Y is 0.6 × 10 ⁻³ kg / m ³ . In any one of Claims 7 thru | or 10 , the said bank is connected in two or more steps | paragraphs in multiple stages in series, and the calculation value of the film surface density | concentration (Cm) of the said biological metabolite system organic substance is in all the banks. A reverse osmosis membrane device controlled so as to be equal to or less than a predetermined value Y, wherein the predetermined value Y satisfies the following (iii) or (iv) .
(Iii) The biological metabolite organic substance is a high molecular organic substance having a molecular weight of 10,000 or more, and the predetermined value Y is 1 kg / m ³ .
(Iv) The biological metabolite organic substance is humic substance, and the predetermined value Y is 0.6 × 10 ⁻³ kg / m ³ . 16. The reverse osmosis membrane device according to any one of claims 7 to 15 , further comprising a chemical cleaning means for cleaning the reverse osmosis membrane at a frequency of 2 times / year or less. The reverse osmosis membrane device according to any one of claims 7 to 16 , wherein the reverse osmosis membrane is an aromatic polyamide-based reverse osmosis membrane.

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