JP5961916B2 - Water treatment equipment - Google Patents

Description

  The present invention relates to a water treatment apparatus, and more particularly to a water treatment apparatus for purifying raw water having a specific property.

  In the manufacturing process of semiconductors and pharmaceuticals, from the viewpoint of improving product quality and ensuring safety, a large amount of purified water from which contaminated components such as dissolved natural components and suspended substances are removed is used. Such purified water is produced, for example, by subjecting raw water such as industrial water, tap water, or groundwater to filtration using a reverse osmosis membrane device.

  In the production of such purified water, efficient mass production is required. Therefore, by increasing the recovery rate in the reverse osmosis membrane device, that is, the ratio of the permeate obtained with respect to the raw water, ) Must be increased. However, in the reverse osmosis membrane device, if the recovery rate is increased, the concentration of contaminated components in concentrated water increases, so the ability to remove contaminated components decreases, and the quality of permeated water tends to decrease.

  As one countermeasure against such a problem, Patent Document 1 describes a water treatment device that supplies raw water treated by a water softening device to a reverse osmosis membrane device. The water softening device used here removes the hardness component of the contaminated components contained in the raw water from the raw water by ion exchange with a cation exchange resin. This water treatment device using a water softening device removes some of the contaminating components contained in the raw water in advance before the filtration treatment in the reverse osmosis membrane device, so when supplying the raw water as it is to the reverse osmosis membrane device In comparison, it is considered that the increase in the concentration of contaminating components in the concentrated water can be suppressed, and the recovery rate can be increased while maintaining the ability to remove the contaminating components, thereby improving the treatment efficiency of the raw water.

  However, since this water treatment device needs to regenerate the cation exchange resin used in the water softening device, the operation management becomes complicated, and the water treatment cost is not increased due to the water softening device. Absent.

JP 2010-82610 A

  An object of the present invention is to increase the recovery rate by suppressing deterioration of the quality of permeated water in water treatment for purifying raw water using a reverse osmosis membrane device, without complicated operation management.

  The present inventors have determined that the hardness components derived from the geology of the water source, such as industrial water, tap water, ground water (such as shallow well water, deep well water, spring water or underground water) and surface water (such as river water or lake water) General raw water that contains calcium ions and magnesium ions), sodium ions, and silica as impurities, except for special ones that have a very high sodium ion concentration due to seawater infiltration, etc. It was noted that the molar ratio was generally 1.5 or more. And when researching the purification of raw water with such a molar ratio by a reverse osmosis membrane device from various viewpoints, when a reverse osmosis membrane with specific properties is used, the recovery rate of the permeated water is reduced and the recovery rate is increased. I found that I can do it.

The present invention according to a first aspect relates to a water treatment apparatus for purifying raw water containing silica and a hardness component and having a molar ratio of calcium ions to sodium ions of 1.5 or more. This water treatment apparatus has a raw water supply path, a negatively charged skin layer using a crosslinked wholly aromatic polyamide, and a concentration of 500 mg / L, pH 7 under conditions of an operating pressure of 0.7 MPa and a recovery rate of 15%. The water permeation coefficient when a sodium chloride aqueous solution of 0.0 and a temperature of 25 ° C. is supplied is 1.3 × 10 ^{−11 to} 1.7 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ . In addition, a reverse osmosis membrane device including a reverse osmosis membrane having a salt removal rate of 99% or more for filtering raw water from a supply path to separate it into permeated water and concentrated water is provided.

This water treatment device includes an addition device for adding a scale dispersant to raw water, a first adjusting means for adjusting the pH of the raw water, and reverse osmosis, provided in the supply route. A second adjustment means for adjusting the permeated water recovery rate in the membrane device, a water quality inspection device for inspecting the quality of the concentrated water, and a Languelia concentrated water based on the water quality inspected by the water quality inspection device An arithmetic means for calculating an index, and a first adjustment means and a second adjustment so that the Langeria index of concentrated water is maintained at 0.3 or less and the silica concentration is maintained at 150 mgSiO ₂ / L or less. Water quality control means for controlling the means may be further provided.

The present invention according to another aspect purifies raw water containing silica and a hardness component and having a molar ratio of calcium ions to sodium ions of 1.5 or more to produce purified water having a salt removal rate of 99% or more. The present invention relates to a water treatment method. In this water treatment method, raw water is supplied to the reverse osmosis membrane device, and the recovery rate is set to 70 to 90% to separate the permeated water and the concentrated water, and a part of the concentrated water flowing out from the reverse osmosis membrane device. In the reverse osmosis membrane device, and the remaining concentrated water flowing out from the reverse osmosis membrane device is discarded. Water permeability coefficient when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and a temperature of 25 ° C. is supplied under the conditions of an operation pressure of 0.7 MPa and a recovery rate of 15%. A reverse osmosis membrane having a salt removal rate of 99% or more and a flow rate of permeated water (B) is × 10 ^{−11 to} 1.7 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ^−1. ) Concentrated outflow from reverse osmosis membrane device Adjusting the ratio of the flow rate of (D) a (D / B) to 3 or more.

This water treatment method may further include a step of adding a scale dispersant to the raw water. In this case, the Langeveria index of the concentrated water is 0.3 or less, and the silica concentration is 150 mgSiO ₂ / L. Maintain below.

  In purifying raw water containing silica and a hardness component and having a molar ratio of calcium ions to sodium ions of 1.5 or more using a reverse osmosis membrane device, a negative charge using a crosslinked wholly aromatic polyamide is used. Since a reverse osmosis membrane having a specific property having a skin layer on the surface is used, it is possible to suppress the deterioration of the quality of the permeated water and increase the recovery rate.

1 is a schematic diagram of a water treatment device according to Embodiment 1 of the present invention. Schematic of the water treatment apparatus which concerns on Embodiment 2 of this invention. The flowchart which shows operation | movement of the water treatment apparatus which concerns on Embodiment 2. FIG.

Embodiment 1
With reference to FIG. 1, the water treatment apparatus which concerns on Embodiment 1 of this invention is demonstrated. In the figure, a water treatment apparatus 1 is for producing purified water by subjecting raw water to filtration treatment, and mainly includes a raw water supply path 10, a reverse osmosis membrane apparatus 20, a treatment water path 30, and a drainage path 40. ing.

  The supply path 10 is for supplying raw water from a raw water supply source (not shown) to the reverse osmosis membrane device 20, and includes a water supply control valve 11 for controlling the supply and stop of the raw water. Have.

  The reverse osmosis membrane device 20 is for filtering raw water from the supply path 10 and mainly includes a reverse osmosis membrane module 21 and a pressure pump 22.

The reverse osmosis membrane module 21 includes a single or a plurality of reverse osmosis membrane elements (not shown). The reverse osmosis membrane forming the reverse osmosis membrane element has a negatively charged skin layer using a cross-linked wholly aromatic polyamide, that is, a skin layer that is easily negatively charged, and has an operating pressure of 0.7 MPa and The water permeability coefficient when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and temperature of 25 ° C. was supplied under conditions of a recovery rate of 15% was 1.3 × 10 ^{−11 to} 1.7 × 10 ⁻¹¹ m ^3. m ⁻² · s ⁻¹ · Pa ⁻¹ and a salt removal rate of 99% or more.

Here, the operating pressure refers to the average operating pressure defined in Japanese Industrial Standard JIS K3802: 1995 “Membrane Terminology”. Here, the primary side inlet pressure and the primary side outlet pressure of the reverse osmosis membrane module 21 The average value of The recovery rate is the ratio (%) of the flow rate (B) of the permeated water to the flow rate (A) of water (here, sodium chloride aqueous solution) supplied to the reverse osmosis membrane module 21 (ie, B / A × 100). Say. The water permeation coefficient is a value obtained by dividing the amount of permeated water (m ³ / s) by the membrane area (m ² ) and the effective pressure (Pa), and is an index indicating the permeation performance of water through the reverse osmosis membrane. That is, the water permeation coefficient means the amount of water that permeates the unit area of the membrane per unit time when a unit effective pressure is applied. The effective pressure is defined in Japanese Industrial Standard JIS K3802: 1995 “Membrane Term”, and is a pressure obtained by subtracting the osmotic pressure difference and the secondary pressure from the operating pressure (average operating pressure). The salt removal rate is a value calculated from the concentration of specific salts before and after permeating the membrane (here, the sodium chloride concentration), and is an index indicating the solute blocking performance in the reverse osmosis membrane. The salt removal rate is calculated as (1-C ₂ / C ₁ ) × from the concentration (C ₁ ) of the specific salt in the raw water at the inlet of the reverse osmosis membrane module 21 and the concentration (C ₂ ) of the specific salt in the permeated water. 100.

A reverse osmosis membrane having the above-described skin layer and properties is commercially available as a reverse osmosis membrane element. As such a reverse osmosis membrane element, for example, model name “TMG20-400” manufactured by Toray Industries, Ltd. (water permeability coefficient under the above conditions is 1.7 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ ), model name “RE8040-BLN” manufactured by Unjin Chemical Co., Ltd. (water permeability coefficient under the above conditions is 1.6 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ ) and “ESPA1” manufactured by Nitto Denko Corporation (water permeability coefficient under the above conditions is 1.6 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ ) and the like.

  The pressurization pump 22 can pressurize the raw water from the supply path 10 and supply it to the reverse osmosis membrane module 21. The raw water from the supply path 10 is supplied to the reverse osmosis membrane module 21 in a state of being pressurized to a pressure higher than the osmotic pressure of the reverse osmosis membrane by the pressure pump 22, thereby reverse osmosis in the reverse osmosis membrane element. Part permeates the reverse osmosis membrane element. Thereby, in the reverse osmosis membrane element, the raw water is separated into permeated water from which the contaminating components have been removed (that is, purified water) and concentrated water having an increased concentration of the contaminating components.

  The treatment water channel 30 is a path for sending out the permeated water generated in the reverse osmosis membrane device 20, and a tank for temporarily storing the permeated water, and various devices (for example, semiconductor manufacturing apparatus) using the permeated water. , Pharmaceutical manufacturing equipment and steam boiler equipment).

  The drainage channel 40 is a path for discharging the concentrated water generated in the reverse osmosis membrane device 20 from the device, and includes a circulation path 41 and a drainage control valve 42 in this order from the reverse osmosis membrane device 20 side.

  The circulation path 41 is for circulating a part of the concentrated water from the reverse osmosis membrane device 20 to the supply path 10. The circulation path 41 branches from the drainage path 40 and is between the water supply control valve 11 and the pressure pump 22. The supply channel 10 is communicated. The drainage control valve 42 is for controlling the amount of concentrated water discarded from the reverse osmosis membrane device 20.

  Next, operation | movement of the above-mentioned water treatment apparatus 1 is demonstrated. In the water treatment apparatus 1, when the water supply control valve 11 is opened and raw water is supplied from the raw water supply source to the supply path 10, the raw water is pressurized by the pressurization pump 22 to a pressure higher than the osmotic pressure in the reverse osmosis membrane module 21. And supplied to the reverse osmosis membrane module 21. The raw water supplied under pressure to the reverse osmosis membrane module 21 partially passes through the reverse osmosis membrane (that is, is filtered), and is discharged from the treatment water channel 30 as permeated water from which impurities are removed. On the other hand, the remaining raw water is washed away into the drainage channel 40 as concentrated water in which the concentration of the contaminated components whose permeation is blocked by the reverse osmosis membrane is increased. Part of the concentrated water that has flowed to the drainage channel 40 flows to the circulation path 41 and joins the raw water flowing through the supply path 10. Further, the remaining concentrated water that does not circulate to the circulation path 41 is discarded from the drainage control valve 42.

  Here, the flow rate of the concentrated water flowing from the drainage channel 40 to the circulation path 41 is controlled by controlling at least one of the flow rate of raw water supplied through the water supply control valve 11 and the flow rate of concentrated water discarded from the drainage control valve 42. Adjusted. The flow rate of the raw water can be adjusted by increasing or decreasing the number of rotations of the pressure pump 22. The flow rate of the concentrated water flowing to the circulation path 41 is a ratio D of the flow rate (D) of the concentrated water flowing out from the reverse osmosis membrane module 21 to the flow rate (B) of the permeated water (that is, the flow rate before branching to the circulation path 41). It is preferable to adjust so that / B becomes 3 or more, and it is more preferable to adjust so that it becomes 5 or more. When the flow rate ratio D / B is less than 3, since the membrane surface flow velocity on the primary side of the reverse osmosis membrane is low, suspended substances contained in the raw water are easily deposited and scales are easily deposited. May block the desired water permeation performance.

The raw water to be purified by using the water treatment apparatus 1, that is, the raw water supplied to the supply path 10 is silica (here, “44. Silica (SiO ₂ )” of Japanese Industrial Standards JIS K0101: 1998 “Industrial Water Test Method”). In which all of the silicas defined in 1) are included as impurities and sodium ions and hardness components (calcium ions and magnesium ions) are included, and the molar ratio of calcium ions to sodium ions is 1.5 or more. It is. In general, water used as raw water, such as industrial water, tap water, groundwater (shallow well water, deep well water, spring water, underground water, etc.) and surface water (river water or lake water, etc.) is derived from the water source. It contains natural components such as silica, sodium ions, and hardness components, and the molar ratio of contained calcium ions to contained sodium ions is 1.5 or more. Moreover, if it satisfies the above-mentioned conditions also about factory wastewater, it can become the raw water of the process target in the water treatment apparatus 1. FIG. In contrast, seawater, brackish water, and groundwater that uses the strata in which they have permeated as a water source have a high sodium ion concentration, so the above molar ratio is less than 1.5 (in many cases, less than 1). It is difficult to be processed by the apparatus 1.

  The molar ratio of the calcium ion contained to the sodium ion contained in the raw water can be confirmed by measuring the sodium ion concentration and the calcium ion concentration in the raw water. The sodium ion concentration can be measured, for example, by using a commercially available ion electrode. The calcium ion concentration can be measured by, for example, a chemical analysis method using a commercially available measurement reagent kit or the like, but can also be measured using a commercially available ion electrode.

  Since the water treatment apparatus 1 uses the reverse osmosis membrane element provided with the above-mentioned specific reverse osmosis membrane in the reverse osmosis membrane module 21, the molar ratio of the contained calcium ion to the contained sodium ion is generally 1.5 or more. Raw water is supplied as it is from the supply path 10 to the reverse osmosis membrane device 20, so that the recovery rate in the reverse osmosis membrane device 20 is set to a relatively high rate of about 70 to 90%, in particular high-purity permeate, Further, permeated water having a salt removal rate of 99% or more can be efficiently produced.

  In addition, about raw | natural water which does not satisfy the conditions whose molar ratio of the calcium ion containing with respect to a sodium ion which contains a silica and a hardness component is 1.5 or more, it adjusts so that the said conditions may be satisfied, and this embodiment Purification by the water treatment apparatus 1 is possible. The quality of raw water to satisfy the above conditions can be adjusted by adding chemicals to the raw water.In this case, however, the concentration of impurities in the raw water is increased, increasing the electrical conductivity and reducing the quality of the permeated water. There is a possibility of damage. Therefore, it is preferable to adjust the quality of raw water by appropriately mixing water of different water quality. In this case, the type of water mixed with the raw water is not particularly limited. For example, modified water obtained by ion exchange of sodium ions with an H-type cation exchange resin, or monovalent ion selection Modified water from which sodium ions have been removed by an electrodialyzer using a neutral ion exchange membrane can be used.

  Further, the water treatment device 1 employs a cross flow method in which a circulation path 41 is provided in the drainage channel 40 of the reverse osmosis membrane device 20 for the purpose of increasing the membrane surface flow velocity on the primary side of the reverse osmosis membrane. Even when the crossflow method is not adopted, the present invention can be similarly implemented.

Embodiment 2
With reference to FIG. 2, the water treatment apparatus which concerns on Embodiment 2 of this invention is demonstrated. In the figure, a water treatment device 2 is for producing purified water by subjecting raw water to filtration treatment. The raw water supply channel 10, reverse osmosis membrane device 20, treatment water channel 30, drainage channel 40, and control device 50. It is mainly equipped with.

  The supply path 10 is for supplying raw water from a raw water supply source (not shown) to the reverse osmosis membrane device 20, and includes a water supply control valve 11 for controlling supply and stop of the raw water, and A first addition device 12 and a second addition device 13 for adding a chemical to raw water are provided in this order. The raw water from the supply source supplied through the supply path 10 is the same as that described in the first embodiment, that is, contains silica, sodium ions, and hardness components, which are natural components derived from the water source, and contains sodium. The molar ratio of calcium ions to ions is 1.5 or more.

  The 1st addition apparatus 12 (an example of a 1st adjustment means) is for inject | pouring a pH adjuster with respect to the raw | natural water supplied to the reverse osmosis membrane apparatus 20, The 1st site | part 12a and the 2nd site | part 12b are used. I have. The 1st site | part 12a is a site | part for inject | pouring the acidic chemical | medical agent which reduces the pH of raw | natural water with respect to raw | natural water. The acidic drug used here is not particularly limited and is, for example, an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, and is usually used as an aqueous solution. On the other hand, the 2nd site | part 12b is a site | part for inject | pouring the alkaline chemical | medical agent which raises the pH of raw | natural water with respect to raw | natural water. The alkaline agent used here is, for example, a hydroxide or carbonate of an alkali metal such as sodium or potassium, and is usually used as an aqueous solution.

  Each of the first part 12a and the second part 12b has a pH adjusting agent storage part and an injection part for injecting the pH adjusting agent from the storage part into the raw water. It has a control valve for adjusting the injection amount.

  The second addition device 13 is for adding the scale dispersant to the raw water supplied to the reverse osmosis membrane device 20, and adds the storage portion of the scale dispersant and the scale dispersant from the storage portion to the raw water. And an addition part for. The addition unit has a control valve for adjusting the amount of the scale dispersant added.

  The scale dispersant used here is not particularly limited as long as it is water-soluble, and examples thereof include polycarboxylic acids such as acrylic acid polymers, methacrylic acid polymers, and maleic acid polymers, polysulfonic acids, and the like. Examples thereof include phosphonic acid. Two or more kinds of these scale dispersants may be used in combination. The scale dispersant is usually used as an aqueous solution.

  As a scale dispersant, since it is possible to effectively suppress calcium carbonate scale from adhering to the membrane surface of the reverse osmosis membrane in the reverse osmosis membrane module 21 to be described later on the reverse osmosis membrane device 20, polycarboxylic acid and Those containing phosphonic acid are preferred. As an example of such a scale dispersant, BWA WATER ADDITIVES trade name “Flocon 260” which is an aqueous solution containing polycarboxylic acid and phosphonic acid and having a concentration of 33 to 37% by weight can be mentioned.

  The reverse osmosis membrane device 20 is for filtering raw water from the supply path 10 and includes a reverse osmosis membrane module 21 and a pressure pump 22 similar to those used in the water treatment device 1 of the first embodiment. Mainly prepared.

  The treatment water channel 30 is a path for sending out the permeated water generated in the reverse osmosis membrane device 20, and a tank for temporarily storing the permeated water, and various devices (for example, semiconductor manufacturing apparatus) using the permeated water. , Pharmaceutical manufacturing equipment and steam boiler equipment).

  The drainage channel 40 is a path for discharging the concentrated water generated in the reverse osmosis membrane device 20 from the device, and the circulation path 41, the water quality inspection device 42, and the drainage control valve 43 are arranged in this order from the reverse osmosis membrane device 20 side. I have.

  The circulation path 41 is for circulating a part of the concentrated water from the reverse osmosis membrane apparatus 20 to the supply path 10, branches from the drainage path 40, and is between the second addition apparatus 13 and the pressure pump 22. To the supply path 10.

  The water quality inspection device 42 is for measuring the quality of the concentrated water flowing through the drainage channel 40, and a sampling path 410 for collecting a part of the concentrated water branched from the drainage channel 40 as a sample for water quality inspection. have. The sampling path 410 is branched into a plurality of parts, and each branch path has a pH sensor 411 for measuring the pH value of the concentrated water, a temperature sensor 412 for measuring the temperature of the concentrated water, and the electric conduction of the concentrated water. An electrical conductivity sensor 413 for measuring the rate, a hardness sensor 414 for measuring the calcium hardness of the concentrated water, and a total alkalinity sensor 415 for measuring the total alkalinity of the concentrated water. As the pH sensor 411, the temperature sensor 412, and the electrical conductivity sensor 413, various types used for water quality inspection can be used.

  As the hardness sensor 414, a general colorimetric sensor is used. The colorimetric sensor adds a coloring reagent (for example, 2-hydroxy-1- (2′-hydroxy-4′-sulfo-1′-naphthylazo) -3-naphthoic acid) to the collected concentrated water sample. The color development of the sample is detected as a change in absorbance at a specific absorption wavelength, and the calcium hardness is determined based on the absorbance.

The total alkalinity measured by the total alkalinity sensor 415 is expressed by converting the amount of alkali components contained in the concentrated water as bicarbonate, carbonate, hydroxide, etc. into the amount of calcium carbonate (CaCO ₃ ). This is what is referred to as acid consumption (pH 4.8) in various JIS standards relating to water quality analysis. The general total alkalinity sensor 415 is of a colorimetric type, and this indicates the color development of a sample when a coloring reagent (for example, methyl orange) is added to the collected concentrated water sample. Is detected as a change in absorbance, and the total alkalinity is determined based on the absorbance.

  The drainage control valve 43 is for controlling the amount of concentrated water discarded from the reverse osmosis membrane device 20.

  The control device 50 is for controlling the operation of the water treatment device 2, and is a central control device that controls the operation, a storage device that stores operation programs and various data of the water treatment device 2, and an information input / output device. It is an electronic information processing organization provided with (none of which is shown). The input unit of the input / output device is in communication with the water quality inspection device 42 and receives measurement data from the pH sensor 411, temperature sensor 412, electrical conductivity sensor 413, hardness sensor 414, and total alkalinity sensor 415. Is possible. In addition, an operation panel 51 for manually inputting various data and commands necessary for the operation of the water treatment apparatus 1 is communicated to the input unit. On the other hand, the output side of the input / output device receives measurement data and other information from the water supply control valve 11, the first addition device 12, the second addition device 13, the pressurization pump 22, the drainage control valve 43, and the water quality inspection device 42. A display device 52 for displaying or guiding manual input of required information is in contact, and a required operation signal can be transmitted to each of these units.

  The operation program stored in the storage device includes a calculation program for calculating the Langeria index of the concentrated water and a water quality control program for the concentrated water.

  The Langeria index is a general index for evaluating the tendency of scale generation in water systems. A positive value indicates that calcium carbonate is more likely to precipitate as the absolute value increases, and a negative value increases the absolute value. It shows that calcium carbonate hardly precipitates. When the Langeria index is 0, calcium carbonate is in an equilibrium state where neither precipitation nor dissolution occurs. For this reason, when the Langeria index of the concentrated water is less than 0, it is difficult to generate scale due to calcium carbonate on the membrane surface of the reverse osmosis membrane module 21, and conversely, when it exceeds 0, the reverse osmosis membrane module Thus, the scale of calcium carbonate is likely to be generated on the film surface 21.

The Langeria index (LSI) of the concentrated water is usually obtained by the following equation (1).
LSI = pH-pHs (1)

In Formula (1), pH is a pH value of concentrated water. Further, pHs is a theoretical pH value when the calcium carbonate is in an equilibrium state where the calcium carbonate is not dissolved or precipitated in the concentrated water, and is obtained by the following equation (2).
pHs = 9.3 + A value + B value−C value−D value (2)

  In equation (2), the A value is a correction value determined by the evaporation residue concentration. Since the evaporation residue concentration has a correlation with the electric conductivity, the evaporation residue concentration can be obtained from the electric conductivity using a predetermined conversion formula. The B value is a correction value determined by the water temperature. The C value is a correction value determined by the calcium hardness. The D value is a correction value determined by the total alkalinity.

  As apparent from the equation (1), the Langeria index of the concentrated water decreases as the pH of the concentrated water decreases and increases as the pH increases. Therefore, the Langeria index of concentrated water can be controlled by adjusting the pH of the concentrated water.

  The Langeria index calculation program obtains the A to D values by calculating from the measurement data of each sensor of the water quality test apparatus 42 using a predetermined relational expression or referring to a predetermined numerical table. . Then, pHs is obtained from the obtained A to D values by the equation (2), and the Langeria index is calculated by the equation (1) from the pHs and the actually measured pH by the pH sensor 411. Various numerical tables necessary for calculating the Langeria index can be stored in a storage device.

  On the other hand, the water quality control program is for controlling the Langeria index and the silica concentration of the concentrated water by controlling the first addition device 12, the pressurizing pump 22, and the drainage control valve 43 by a process described later.

  Next, the basic operation of the water treatment apparatus 2 will be described. In the water treatment device 2, when the feed water control valve 11 is opened and raw water is supplied from the raw water supply source to the supply path 10, the scale dispersant is added from the second addition device 13 continuously or at regular intervals. In addition, the pressure is increased by the pressurization pump 22 to the osmotic pressure in the reverse osmosis membrane module 21 and supplied to the reverse osmosis membrane module 21. The raw water supplied under pressure to the reverse osmosis membrane module 21 partially passes through the reverse osmosis membrane (that is, is filtered), and is discharged from the treatment water channel 30 as permeated water from which impurities are removed. On the other hand, the remaining raw water is washed away into the drainage channel 40 as concentrated water in which the concentration of the contaminated components whose permeation is blocked by the reverse osmosis membrane is increased. Part of the concentrated water that has flowed to the drainage channel 40 flows to the circulation path 41 and joins the raw water flowing through the supply path 10. The remaining concentrated water that does not circulate to the circulation path 41 is discarded from the drainage control valve 43.

In the operation of the water treatment apparatus 2, the flow rate of raw water supplied to the reverse osmosis membrane module 21 (F ₁ ), the flow rate of permeate (F ₂ ), and the flow rate of concentrated water discarded from the drainage control valve 43 (F By controlling ₃ ), the recovery rate can be adjusted. The recovery rate here is the ratio (%) of the flow rate (F ₂ ) of the permeated water to the flow rate (F ₁ ) of the raw water supplied to the reverse osmosis membrane module 21 (ie, F ₂ / F ₁ × 100). . In the present embodiment, F ₁ is the flow rate of raw water supplied from the water supply control valve 11.

  Since the water treatment apparatus 2 uses the reverse osmosis membrane element including the specific reverse osmosis membrane in the reverse osmosis membrane module 21 as in the first embodiment, the raw water having the water quality condition described in the first embodiment is supplied. By supplying the reverse osmosis membrane device 20 from the path 10, the recovery rate in the reverse osmosis membrane device 20 is set to a relatively high rate of about 70 to 90%, and high purity permeated water, in particular, the salt removal rate is high. 99% or more of permeate can be efficiently produced.

Next, the operation of the water treatment device 2 will be described more specifically with reference to the operation flowchart shown in FIG. In this water treatment method, first, a sample of raw water is collected and analyzed for the silica concentration of raw water (mgSiO ₂ / L). The silica concentration of the raw water can be measured by a chemical analysis method using a commercially available measuring reagent kit or the like, but can also be measured using a commercially available automatic measuring device.

When the operator starts the water treatment device 2, the operation program displays an information input guide on the display device 52 of the control device 50 in step S1, and waits for the operator to input the raw water silica concentration in step S2. . When the silica concentration of raw water checked by the operator is input from the operation panel 51, the operation program shifts from step S2 to step S3, and calculates the recovery rate to be set in the reverse osmosis membrane device 20. More specifically, the recovery rate at which the silica concentration of the concentrated water can be maintained at 150 mgSiO ₂ / L or less is calculated based on the silica concentration of the input raw water.

Here, when the recovery rate is set high, the concentration rate of the raw water is increased (that is, the concentration of impurities in the concentrated water is increased), and when the recovery rate is set low, the concentration rate of the raw water is decreased (that is, the concentrated water is increased). Contaminant component concentration in the case becomes low). For this reason, when the silica concentration of raw | natural water is known, if the concentration rate of raw | natural water is controlled by adjustment of a recovery rate, the silica concentration of concentrated water can be controlled as a result. For example, when the recovery rate is set to 90%, the concentration rate of raw water is about 10 times. In this case, if the silica concentration of the raw water is, for example, 10 mgSiO ₂ / L, the silica concentration of the concentrated water is maintained 10 times the concentration in the raw water, that is, about 100 mgSiO ₂ / L. This is an appropriate recovery rate for maintaining the silica concentration of concentrated water at 150 mg SiO ₂ / L or less. On the other hand, if the silica concentration of the raw water is 20 mgSiO ₂ / L, for example, the silica concentration of the concentrated water is maintained at about 200 mgSiO ₂ / L, which is 10 times, so the recovery rate of 90% Inappropriate recovery rate for maintaining below 150 mg SiO ₂ / L.

The recovery rate calculated based on the concentration rate of the raw water is an upper limit value capable of maintaining the silica concentration of the concentrated water at 150 mgSiO ₂ / L or less. Such a recovery rate of the upper limit value may not be able to maintain the silica concentration of concentrated water at 150 mgSiO ₂ / L or less when a situation occurs in which the silica concentration temporarily increases in the raw water. The recovery rate is usually preferably set to 90% or less from the viewpoint of avoiding a decrease in the raw water treatment efficiency due to fouling on the membrane surface of the reverse osmosis membrane module 21. Therefore, in consideration of these circumstances, it is preferable that the recovery rate calculated in step S3 is usually set to be smaller than the upper limit value by correcting the upper limit value. Fouling refers to a phenomenon in which suspended substances or organic substances in raw water are deposited or adsorbed on the membrane surface of the reverse osmosis membrane, which can cause a reduction in the amount of permeated water in the reverse osmosis membrane.

In addition, when the silica concentration of concentrated water exceeds 150 mgSiO ₂ / L, since a silica-based scale is easily generated on the membrane surface of the reverse osmosis membrane module 21, the amount of permeate decreases in a relatively short time, and the raw water The processing efficiency decreases.

  Next, the operation program proceeds to step S4. In this step, the display device 52 displays the completion of the initial preparation, and waits for the operator to input an operation start command for the water treatment device 2. Then, when the operator inputs an operation start command through the operation panel 51, the operation program proceeds to step S5 and starts operation of the water treatment device 2.

In step S <b> 5, the operation program first opens the water supply control valve 11 and supplies raw water from the raw water supply source to the supply path 10. Thereby, the water treatment apparatus 2 starts the basic operation described above. In this step, the flow rate of the permeated water (F ₂ ) in the reverse osmosis membrane module 21 and the flow rate of the concentrated water to be discarded (F ₃ ) are pressurized so that the recovery rate calculated in step S3 is achieved. It adjusts by control of the rotation speed of the pump 22, and the opening degree of the drainage control valve 43. Thus, the silica concentration of concentrated water is maintained below 150mgSiO ₂ / L.

  In this step, the flow rate of concentrated water flowing out from the reverse osmosis membrane module 21 with respect to the flow rate of permeated water (B) (D) (that is, the circulation path 41 is adjusted by adjusting the flow rate of concentrated water flowing into the circulation path 41. The ratio D / B of the flow rate before branching to is preferably controlled to be 3 or more, and more preferably 5 or more. When the flow rate ratio D / B is less than 3, since the membrane surface flow velocity on the primary side of the reverse osmosis membrane is low, suspended substances contained in the raw water are easily deposited and scales are easily deposited. May block the desired water permeation performance.

In step S <b> 5, the operation program starts addition of the scale dispersant by the second addition device 13. Here, the operation program refers to the flow rate (F ₁ ) of raw water supplied from the water supply control valve 11 to the supply path 10 and controls the concentration of the scale dispersant in the raw water. It is necessary to set the concentration of the scale dispersant in the raw water so that the generation of scale on the membrane surface of the reverse osmosis membrane module 21 is suppressed, and the concentration is generally set higher. In this embodiment, the silica concentration of the concentrated water is maintained at 150 mg SiO ₂ / L or less, and the Langeveria index of the concentrated water is maintained within a range of 0.3 or less as described later, so that 1 to 5 mg / L It can function effectively only by setting it to a minute amount. As a result, the concentrated water discarded from the drainage control valve 43 suppresses an increase in chemical oxygen demand (COD) due to the scale dispersant, and is unlikely to give an environmental load.

  Furthermore, in step S <b> 5, the operation program activates the water quality inspection device 42 and starts the water quality inspection of the concentrated water sample that is always collected from the drainage path 40 through the sampling path 410.

  In the next step S <b> 6, the operation program determines whether or not the operator has input a stop command for the water treatment apparatus 2 from the operation panel 51. When the operator inputs a stop command, the operation program proceeds to step S7, closes the water supply control valve 11 and stops other devices. Thereby, supply of the raw | natural water to the reverse osmosis membrane apparatus 20 stops, and the water treatment apparatus 2 complete | finishes operation | movement.

  On the other hand, during operation of the water treatment device 2, the operation program calculates a Langeria index (LSI) of the concentrated water in step S8. Here, the pH, temperature, electrical conductivity, hardness, and total alkalinity measured by the pH sensor 411, temperature sensor 412, electrical conductivity sensor 413, hardness sensor 414, and total alkalinity sensor 415 of the water quality inspection device 42, respectively. The above-described A to D values are obtained by referring to a predetermined numerical table from each data, and the Langeria index is calculated from the above-described equations (2) and (1).

  It is determined whether or not the Langeria index calculated in step S8 is in the range of 0 to 0.3 in the next step S9. When it is determined that the Langeria index is out of the above range, the operation program proceeds to step S10, and the control operation of the concentrated water Langeria index is executed.

  Here, when the Langeria index exceeds 0.3, the operation program operates the control valve of the first portion 12 a in the first addition device 12 to inject the acidic chemical into the raw water flowing through the supply path 10. Thereby, the pH of the concentrated water decreases and the Langeria index becomes small. On the other hand, when the Langeria index is less than 0, the operation program operates the control valve of the second portion 12b in the first addition device 12 to inject the alkaline chemical into the raw water flowing through the supply path 10. Thereby, the pH of the concentrated water increases and the Langeria index increases. Thus, since the 1st addition apparatus 12 is equipped with both the 1st site | part 12a for adding an acidic chemical | medical agent, and the 2nd site | part 12b for adding an alkaline chemical | medical agent, the Langelia index of concentrated water is shown. It is possible to quickly and stably control the narrow range described above.

  In addition, since the alkaline chemical | medical agent required for adjustment of a Langeria index is a trace amount, it is hard to change the molar ratio of the calcium ion containing with respect to the sodium ion contained in raw | natural water, and can maintain the said molar ratio in raw | natural water.

  The operation program repeats step S8 and step S9 during operation of the water treatment apparatus 2, that is, unless the operator inputs a stop command from the operation panel 51. When necessary, the operation program executes step S10. Control is performed so that the Langelia index is in the range of 0 to 0.3.

By the operation program as described above, in the water treatment apparatus 2, during operation, the Langeria index of concentrated water is maintained at 0 or more and 0.3 or less, and the silica concentration of concentrated water is maintained at 150 mgSiO ₂ / L or less. The For this reason, since the reverse osmosis membrane module 21 suppresses the generation of calcium carbonate scale and silica scale in the reverse osmosis membrane and can stably maintain the flow rate of permeate for a long period of time, the reverse osmosis membrane The recovery rate in the apparatus 20 can be stably maintained within the above-described relatively high range. Further, the maintenance of the flow rate of the permeated water is not achieved by simply adjusting the pH of the concentrated water to be lowered, but precisely controlling the Langeria index of the concentrated water within a narrow range of 0 or more. Therefore, it can be achieved while suppressing the injection amount of the pH adjuster, particularly the acidic drug, with respect to the raw water. As a result, hydrogen carbonate ions and carbonate ions contained in the raw water are prevented from changing to free carbonic acid (dissolved carbon dioxide gas), and the amount of free carbonic acid permeating the reverse osmosis membrane is reduced to suppress deterioration in the quality of the permeated water. Can do.

About this embodiment, the following changes are possible, for example.
(1) The silica concentration of raw water may be stable depending on the geological circumstances of the water source depending on the type of raw water. In this case, unless there is a circumstance where the silica concentration of the raw water fluctuates due to a seasonal change or the like, the water treatment device 2 is unlikely to measure the silica concentration of the raw water every time it operates and to input the measured value. In such a case, the silica concentration of the raw water input by the operator at the first start-up can be stored in the control device 50, and at the subsequent start-up, the operation program can be operated by omitting steps S1 to S3.

(2) In the above operation explanation, the silica concentration of raw water is measured in advance, and the recovery rate is adjusted so that the silica concentration of concentrated water in the reverse osmosis membrane device 20 is maintained at 150 mgSiO ₂ / L or less based on the measured value. Although it is adjusted, the water quality inspection device 42 is further provided with a sensor for measuring the silica concentration of the concentrated water, and the recovery rate is adjusted so that the measured value of the silica concentration at this sensor is maintained at 150 mgSiO ₂ / L or less. You can also

(3) In the above description of the operation, control is performed so that the Langeria index of the concentrated water in the reverse osmosis membrane device 20 is in the range of 0 to 0.3, but the lower limit of the Langeria index is not provided. You can also. However, in such a case, a relatively large amount of pH adjusting agent (acidic agent) is added to the raw water in order to achieve the required Langeria index in the concentrated water in the reverse osmosis membrane device 20, and as a result In addition, the amount of free carbonic acid that permeates the reverse osmosis membrane increases, and the quality of the permeated water decreases. Therefore, the Langeria index is preferably set to 0 or more, and even if it is set to a negative value, it is preferably limited to about -0.2 to 0.

  In addition, the raw water from a supply source can control the Langelia index | exponent of concentrated water to 0.3 or less by the pH adjustment by addition of an acidic chemical | medical agent from the general water quality except the special case. For this reason, in the supply path | route 10, the 1st addition apparatus 12 which consists only of the 1st site | part 12a for adding an acidic chemical | medical agent can also be normally used.

  On the other hand, in a special case where the pH of the raw water itself from the supply source is in the acidic range, for example, when the raw water is factory effluent and the pH is about 5-6, the concentrated water in the reverse osmosis membrane device 20 Often, the Langeria index is 0.3 or less, especially minus, without adjusting the pH of the raw water. In such a case, in order to improve the quality of the permeated water, the first addition device 12 including only the second portion 12b for adding the alkaline agent is used, and the Langerian index of the concentrated water is added while appropriately adding the alkaline agent to the raw water. Is preferably increased to around 0.3.

(4) The water treatment device 2 is provided with the second portion 12b for adding the alkaline chemical to the first addition device 12, and the pH of the raw water is increased by adding the alkaline chemical to the raw water from there. If the water quality is appropriate, an aeration method (a method of removing free carbonic acid using gas-liquid contact between air and raw water) can be employed as a means for increasing the pH of the raw water.

(5) The water treatment device 2 employs a cross flow method in which a circulation path 41 is provided in the drainage channel 40 of the reverse osmosis membrane device 20 for the purpose of increasing the membrane surface flow velocity on the primary side of the reverse osmosis membrane. However, the present invention can be similarly implemented even when the cross flow method is not adopted.

Examples 1 and 2 and Comparative Examples 1 and 2
Test water having a water quality containing calcium ions (Ca ²⁺ ), magnesium ions (Mg ²⁺ ), sodium ions (Na ⁺ ) and silica at concentrations shown in Table 1 was prepared, and the test water was stored in a tank. For a reverse osmosis membrane module loaded with one reverse osmosis membrane element (model name “TMG20-400” manufactured by Toray Industries, Inc.), test water from the tank under the conditions of an operating pressure of 0.49 MPa, a recovery rate of 75% and a temperature of 25 ° C. Was continuously supplied to purify the test water. The permeate flow rate in the reverse osmosis membrane element at this time was 1000 L / h in both Examples 1 and 2 and Comparative Examples 1 and 2. The water flow to the reverse osmosis membrane module is a cross flow system, and the concentrated water is circulated to the primary side inlet of the reverse osmosis membrane module so that the circulating flow rate in the system is five times the permeate flow rate. It was.

Evaluation of Examples 1 and 2 and Comparative Examples 1 and 2 The electrical conductivity (EC) of permeated water and concentrated water after 24 hours from the start of supplying water was measured, and a reverse osmosis membrane based on the following formula: The salt removal rate in the module was measured. The results are shown in Table 1.
Salt removal rate (%) = (Concentrated water EC−Permeated water EC) / Concentrated water EC × 100

  According to Table 1, when the molar ratio of the contained calcium ion to the contained sodium ion is 1.5 or more in the test water, the salt removal rate exceeds 99%. In each example and each comparative example, the permeate flow rate is the same and the recovery rate is set to be the same. Therefore, when the molar ratio of the test water is 1.5 or more, the reverse osmosis membrane module is used. It can be seen that a high salt removal rate can be achieved without sacrificing water permeation performance and recovery rate.

Examples 3-5
A test water supply adjusted to a water quality having an electrical conductivity of 159 mS / m, a hardness of 414 mg CaCO ₃ / L, a silica concentration of 44 mg SiO ₂ / L, a total alkalinity of 90 mg CaCO ₃ / L and a pH of 7.6 is prepared. Stored in tank. In this feed water, the molar ratio of the contained calcium ion to the contained sodium ion was 9.1. Then, through the supply path extending from the tank, this supply water is continuously applied while being pressurized by a pressure pump to a reverse osmosis membrane module loaded with one reverse osmosis membrane element (model name “TMG20-400” manufactured by Toray Industries, Inc.). Was operated under the conditions of a permeate flow rate of 1000 L / h, a recovery rate of 75%, and a temperature of 25 ° C. The permeate flow rate was controlled by adjusting the number of rotations of the pressure pump. The water flow to the reverse osmosis membrane module was a cross flow system, and a part of the concentrated water was circulated to the supply path so that the circulating flow rate in the system was 5 times the permeate flow rate. During such a feed water treatment operation, a portion of the concentrated water is periodically collected as a sample, the silica concentration of the concentrated water is approximately 135 to 150 mg SiO ₂ / L, and the electrical conductivity of the concentrated water is approximately It confirmed that it was maintained at 510-530 mS / m.

  In the above operation, the pH of the feed water flowing to the reverse osmosis membrane module is adjusted to 6 to 6.6 by adding sulfuric acid to adjust the pH of the concentrated water to about 8 to 9, and in Example 3, the Langeria index ( LSI) was controlled to -0.2, in Example 4, the index was controlled to 0.1, and in Example 5, the index was controlled to 0.3. Further, BWA WATER ADDITIVES trade name “Flocon 260” was added as a scale dispersant to the supplied water so that the concentration was 2.5 mg / L as the stock solution.

Comparative Example 3
The feed water was treated under the same conditions as in Examples 3 to 5, except that the Langeveria index of the concentrated water was controlled to 0.5 by adding sulfuric acid to the feed water.

Comparative Example 4
The feed water was treated under the same conditions as in Examples 3 to 5 except that the Langeria index of concentrated water was not controlled by adding sulfuric acid to the feed water.

Comparative Example 5
Except for the point that the Langerian index of the concentrated water was controlled to 0.2 by adding sulfuric acid to the feed water, and the silica concentration of the concentrated water was increased to about 170 mg SiO ₂ / L by increasing the recovery rate. The feed water was treated under the same conditions as in No. 5.

Comparative Example 6
Except that the scale dispersant was not added to the feed water, the feed water was treated under the same conditions as in Example 5 in which the Langeria index was controlled to 0.3.

Comparative Example 7
The feed water was treated under the same conditions as in Examples 3 to 5, except that the Langeria index was not controlled by the addition of sulfuric acid to the feed water, and the scale dispersant was not added to the feed water.

Evaluation of Examples 3 to 5 and Comparative Examples 3 to 7 In each of Examples 3 to 5 and Comparative Examples 3 to 7, changes in effective pressure of the reverse osmosis membrane element during water treatment operation were measured over time. Then, the water permeation coefficient of the permeated water was calculated from the measured value of the effective pressure, the set value of the permeated water flow rate, and the effective membrane area of the reverse osmosis membrane element when a predetermined time elapsed. In addition, since the water permeation coefficient in the initial state varies somewhat depending on individual differences of the reverse osmosis membrane elements, the numerical value at the time when one hour has elapsed from the start of the water treatment operation is used as the initial value. Moreover, the electrical conductivity of the permeated water was measured after 24 hours from the start of the water treatment operation. The electrical conductivity is an index indicating the quality of the permeated water. The lower the value, the smaller the ionic component (contaminated component) in the permeated water, that is, the better the water quality. The results are shown in Table 2. In Comparative Example 7, since the water permeation coefficient at the time when 120 hours had passed dropped to less than 15% of the initial value, the water treatment operation was stopped at this point. Table 2 shows the Langeria index, the silica concentration, and the electrical conductivity of the concentrated water, and the displayed numerical values are average values during the water treatment operation.

  According to Table 2, in Examples 3-5, the water permeation coefficient at the time of 150 hours passage is maintained at 96-97% of the initial value, and it is based on scale adhesion of a reverse osmosis membrane element compared with comparative examples 3-7. It turns out that obstruction | occlusion is suppressed notably. Moreover, the electrical conductivity of permeated water becomes a numerical value comparable as compared with Comparative Examples 3-7 in Examples 3-5, and it turns out that the permeated water with favorable water quality is obtained. Furthermore, according to Examples 3 to 5, when the Langerian index of the concentrated water is less than 0, the electric conductivity of the permeated water tends to be slightly higher, so the Langerian index of the concentrated water is maintained at 0 or more. It can also be seen that it is preferable.

DESCRIPTION OF SYMBOLS 1, 2 Water treatment apparatus 10 Supply path 12 1st addition apparatus 13 2nd addition apparatus 20 Reverse osmosis membrane apparatus 42 Water quality inspection apparatus 43 Drain control valve 50 Control apparatus

Claims (2)

A water treatment method for producing purified water containing silica and a hardness component and purifying raw water having a molar ratio of calcium ions to sodium ions of 1.5 or more and having a salt removal rate of 99% or more ,
The raw water is supplied to the reverse osmosis membrane device, the recovery rate is set to 70 to 90% to separate the permeated water and the concentrated water, and a part of the concentrated water flowing out from the reverse osmosis membrane device is reversely mixed. Including the step of joining the raw water supplied to the osmosis membrane device and discarding the remaining concentrated water flowing out of the reverse osmosis membrane device ,
In the reverse osmosis membrane device, the surface has a negatively charged skin layer using a cross-linked wholly aromatic polyamide, and the concentration is 500 mg / L, pH 7.0 and temperature 25 under the conditions of an operation pressure of 0.7 MPa and a recovery rate of 15%. The water permeation coefficient when supplying a sodium chloride aqueous solution at 1.3 ° C. is 1.3 × 10 ^{−11 to} 1.7 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ and the salt removal rate is 99% or more of the reverse osmosis membrane is used , and the ratio (D / B) of the flow rate (D) of the concentrated water flowing out from the reverse osmosis membrane device to the flow rate (B) of the permeated water is adjusted to 3 or more .
Water treatment method. 2. The water according to claim 1 , further comprising a step of adding a scale dispersant to the raw water, and maintaining the Langeria index of the concentrated water at 0.3 or less and the silica concentration at 150 mg SiO ₂ / L or less. Processing method.

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