JP5768959B2 - 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 containing silica and a hardness component.

  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, since continuous mass production is required, it is necessary to stably maintain the amount of filtrate (permeated water) in the reverse osmosis membrane device. However, the reverse osmosis membrane device highly separates the contaminated components contained in the raw water with the reverse osmosis membrane, and as a result, the concentration of the contaminated components increases on the primary side of the reverse osmosis membrane, that is, on the introduction side of the raw water. Since the concentrated water comes into contact, fouling and scale occur on the primary side, and the amount of permeate tends to gradually decrease. Here, fouling refers to a phenomenon in which suspended substances, organic substances, etc. in raw water are deposited or adsorbed on the membrane surface of the reverse osmosis membrane, and can cause a reduction in the amount of permeated water in the reverse osmosis membrane. On the other hand, scale is a deposit of hardness components such as calcium and silica, which are mainly contained as natural components, in raw water, which causes the permeated water volume in the reverse osmosis membrane to decrease by blocking the pores of the reverse osmosis membrane. obtain.

  Generally, in reverse osmosis membrane devices, increasing the recovery rate, that is, the proportion of permeated water obtained relative to raw water, increases the concentration of contaminated components in concentrated water, and decreases the amount of permeated water due to fouling and scale in a short time. Therefore, by controlling the recovery rate to be low, an increase in the concentration of contaminating components in the concentrated water can be suppressed, and a stable permeated water amount can be maintained for a relatively long period of time. However, in this case, since the amount of permeated water is reduced, the treatment efficiency of raw water (that is, the production efficiency of purified water) is impaired.

  As a countermeasure against such a problem, Patent Document 1 discloses a method of adding an acid so that the pH of the raw water becomes about 5.5 while adding a scale inhibitor to the raw water. However, as described in Patent Document 1, this method has a problem that the quality of the permeated water is deteriorated and cannot be overlooked in the production of purified water.

  Incidentally, in the method described in Patent Document 1, the quality of the permeated water decreases because the excessive addition of acid changes the hydrogen carbonate ions and carbonate ions contained in the raw water into free carbonic acid (dissolved carbon dioxide gas). This is because carbonic acid ions or carbonate ions contained in the raw water change to free carbonic acid (dissolved carbon dioxide gas) due to excessive addition of acid, and the free carbonic acid permeates the reverse osmosis membrane.

Japanese Patent Laid-Open No. 9-206749 (paragraph 0010, paragraph 0013 and paragraph 0045 and paragraph 0050, comparative example 1)

  An object of the present invention is to suppress a decrease in the flow rate of permeated water while suppressing deterioration in the quality of the permeated water in water treatment for purifying raw water containing silica and hardness components using a reverse osmosis membrane device.

The present invention relates to a water treatment apparatus for purifying raw water containing silica and a hardness component. This water treatment apparatus filters raw water from a raw water supply path and raw water from the supply path, and transmits permeated water and concentrated water. A reverse osmosis membrane device for separating the water, a purification device for purifying the permeated water obtained by the reverse osmosis membrane device, and a first adjusting means for adjusting the pH of the raw water provided in the supply path And a second adjusting means for adjusting the recovery rate of the permeated water in the reverse osmosis membrane device, an adding device for adding a scale dispersant to the raw water, and a quality of the concentrated water. A water quality inspection device for inspecting, a computing means for calculating the Langeria index of the concentrated water based on the water quality inspected by the water quality inspection device, and the Langeria index of the concentrated water are maintained at 0.3 or less And the silica concentration is 150m To be maintained below SiO 2 / _L, and a water quality control means for controlling the first adjusting means and the second adjustment means.

  The purification apparatus is usually an ion-recovering apparatus selected from an electric regeneration type ion exchange apparatus, an ion exchange resin mixed bed tower, and a cation exchange resin single bed tower, or a filtration apparatus equipped with a reverse osmosis membrane. In addition, the purification apparatus includes a filtration apparatus equipped with a reverse osmosis membrane, and an electric regenerative ion exchange apparatus, an ion exchange resin mixed bed tower, and a cation exchange resin unit for further purifying the permeated water purified by the filtration apparatus. An ion trapping device selected from among the floor towers may be provided.

  The water quality control means normally controls the first adjustment means so that the Langeria index of the concentrated water is maintained at 0 or more.

  The first adjusting means is, for example, an injection device for injecting a pH adjusting agent into the raw water. The pH adjuster used here is usually at least one of an acidic drug that lowers the pH of raw water and an alkaline drug that increases the pH of raw water.

The present invention according to another aspect relates to a water treatment method for purifying raw water containing silica and a hardness component, and this water treatment method supplies raw water added with a scale dispersant to a reverse osmosis membrane device. And Step 1 for separating permeated water and concentrated water, and Step 2 for purifying the permeated water. In Step 1, the Langeria index of the concentrated water is 0.3 or less, and the silica concentration is 150 mg SiO _2. / L or less.

  In this water treatment method, in step 2, the permeate is usually purified by an ion trapping device selected from an electric regeneration type ion exchange device, an ion exchange resin mixed bed tower and a cation exchange resin single bed tower, Alternatively, the permeated water is purified by a filtration device equipped with a reverse osmosis membrane. Step 2 includes a step of purifying the permeated water using a filtration device equipped with a reverse osmosis membrane, and an electric regenerative ion exchange device, an ion exchange resin mixed bed tower, and a cation exchange resin. And further purifying with an ion trap selected from a single bed column.

  In Step 1, it is usually preferable to maintain the Langeria index of concentrated water at 0 or more.

  In Step 1, the Languel index of concentrated water is usually controlled by adjusting the pH of raw water, and the silica concentration of concentrated water is controlled by adjusting the recovery rate of permeated water in the reverse osmosis membrane device.

  The scale dispersant used in the present invention contains, for example, polycarboxylic acid and phosphonic acid.

In purifying raw water containing silica and a hardness component using a reverse osmosis membrane device, the present invention has a Langeria index of concentrated water in the reverse osmosis membrane device of 0.3 or less and a silica concentration of 150 mg SiO ₂ / L. Since it maintains below, the fall of the flow volume of permeated water can be suppressed, suppressing the water quality fall of permeated water.

1 is a schematic diagram of a water treatment device according to Embodiment 1 of the present invention. FIG. 2 is a detailed view of part A in FIG. 1. The flowchart which shows operation | movement of the said water treatment apparatus. Schematic of the water treatment apparatus which concerns on Embodiment 2 of this invention. Schematic of the water treatment apparatus according to Embodiment 3 of the present invention.

Embodiment 1
A water treatment apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2 (detailed view of part A in FIG. 1). In the figure, the water treatment apparatus 1 is composed of silica (meaning all silicas defined in “44. Silica (SiO ₂ )” in Japanese Industrial Standards JIS K0101: 1998 “Industrial Water Test Method”) and hardness. Raw water containing components (calcium ions and magnesium ions), for example, industrial water, tap water, groundwater (shallow well water, deep well water, spring water or underground water, etc.), surface water (river water or lake water, etc.) or factory effluent or Purified water is produced by purifying the mixed water of these arbitrary combinations, and the raw water supply path 10, the first processing unit 20 for purifying the raw water from the supply path 10, the first A second processing unit 30 and a control device 40 for further purifying purified water from the processing unit 20 are mainly provided.

  The supply path 10 is for supplying raw water from a raw water supply source (not shown) to the first processing unit 20, and includes a water supply control valve 110 and raw water for controlling supply and stop of the raw water. The 1st addition apparatus 120 and the 2nd addition apparatus 130 for adding a chemical | medical agent with respect to are provided in this order.

  The first addition device 120 (an example of a first adjustment unit) is for injecting a pH adjusting agent into the raw water supplied to the first processing unit 20, and includes a first part 121 and a second part 122. I have. The 1st site | part 121 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 122 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 121 and the second part 122 has a pH adjusting agent storage part and an injecting part for injecting the pH adjusting agent from the storage part into the raw water. The injecting part is a pH adjusting agent. It has a control valve for adjusting the injection amount.

  The 2nd addition apparatus 130 is for adding a scale dispersing agent with respect to the raw | natural water supplied to the 1st process part 20, and adds the storage part of a scale dispersing agent, and a scale dispersing agent from a storage part to raw | natural 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 the scale dispersant, in the reverse osmosis membrane module 211 to be described later of the first processing unit 20, it is possible to effectively suppress the calcium carbonate scale from adhering to the membrane surface of the reverse osmosis membrane. 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 1st process part 20 is for purifying by filtering the raw | natural water from the supply path 10, and is mainly provided with the reverse osmosis membrane apparatus 210, the process water channel 220, and the drainage channel 230. FIG.

  The reverse osmosis membrane device 210 includes a reverse osmosis membrane module 211 and a pressure pump 212. The reverse osmosis membrane module 211 includes a single or a plurality of reverse osmosis membrane elements (not shown). The reverse osmosis membrane element that forms the reverse osmosis membrane element is a membrane that can prevent the permeation of fine contaminant components having a molecular weight of several dozens in the raw water. A low nanofiltration membrane (NF membrane) may be used.

  The pressurizing pump 212 can pressurize the raw water from the supply path 10 and supply it to the reverse osmosis membrane module 211. The raw water from the supply path 10 is supplied to the reverse osmosis membrane module 211 in a state of being pressurized to a pressure higher than the osmotic pressure of the reverse osmosis membrane by the pressurizing pump 212, 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 contaminant components have been removed (that is, purified water) and concentrated water having increased contaminant component concentrations.

  The treatment water channel 220 is a route for sending the permeated water generated in the reverse osmosis membrane device 210 to the second treatment unit 30. The drainage channel 230 is a path for discharging the concentrated water generated in the reverse osmosis membrane device 210 from the device, and the circulation path 231, the water quality inspection device 232 and the drainage control valve 233 are arranged in this order from the reverse osmosis membrane device 210 side. I have.

  The circulation path 231 is for circulating a part of the concentrated water from the reverse osmosis membrane apparatus 210 to the supply path 10. The circulation path 231 branches from the drainage path 230 and is between the second addition device 130 and the pressure pump 212. To the supply path 10.

  The water quality inspection device 232 is for measuring the quality of the concentrated water flowing through the drainage channel 230, and a sampling path 240 for collecting a part of the concentrated water branched from the drainage channel 230 as a sample for water quality inspection. have. The sampling path 240 branches into a plurality of parts, and each branch path has a pH sensor 241 for measuring the pH value of the concentrated water, a temperature sensor 242 for measuring the temperature of the concentrated water, and the electrical conduction of the concentrated water. An electrical conductivity sensor 243 for measuring the rate, a hardness sensor 244 for measuring the calcium hardness of the concentrated water, and a total alkalinity sensor 245 for measuring the total alkalinity of the concentrated water. As the pH sensor 241, the temperature sensor 242, and the electrical conductivity sensor 243, various types used for water quality inspection can be used.

  As the hardness sensor 244, 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 245 is expressed by converting the amount of alkali components contained in the concentrated water as bicarbonate, carbonate and hydroxide 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 245 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 sample of concentrated water. Is detected as a change in absorbance, and the total alkalinity is determined based on the absorbance.

  The drainage control valve 233 is for controlling the amount of concentrated water discarded from the reverse osmosis membrane device 210.

  The 2nd process part 30 is for further refine | purifying the permeated water from the treated water path 220, and is provided with the refiner | purifier 310 and the water purification path | route 320. FIG. The purification device 310 is an ion trapping device for trapping and removing ions remaining in the permeated water, and is usually an electric regeneration type ion exchanger, an ion exchange resin mixed bed tower, and a cation exchange resin single bed tower. It was chosen from home.

  The electric regenerative ion exchange apparatus has a desalting chamber and a concentrating chamber formed by alternately arranging a cation exchange membrane and an anion exchange membrane, and the desalting chamber has a mixed bed ion exchanger (resin or resin). Fiber). This electric regenerative ion exchanger can capture and remove both cations and anions remaining in the permeated water in both the cation exchanger and the anion exchanger in the desalination chamber. Yes, since both ion exchangers are electrically regenerated continuously in parallel with the trapping of ions by the cation exchanger and the anion exchanger, the permeated water can be stably purified over a long period of time. . In addition, the concentrated water containing the removed ions generated in the electric regeneration type ion exchange apparatus may be discarded, but a part of the concentrated water to the raw water side of the first processing unit 20 (that is, to the supply path 10) or The entire amount can also be returned.

  The ion-exchange resin mixed-bed tower is a water treatment tower packed with a cation exchange resin and an anion exchange resin that can capture and remove both cations and anions remaining in the permeate. is there.

  The cation exchange resin single-bed tower is a water treatment tower filled with a cation exchange resin and can capture and remove cations remaining in the permeated water. In general, since the skin layer of the reverse osmosis membrane is negatively charged, the residual ions contained in the permeated water treated with the reverse osmosis membrane have a small anion ratio and a high cation ratio. Therefore, the permeated water can be highly purified by selectively removing cations having a large residual ratio using a cation exchange resin single-bed tower that easily suppresses the operating cost.

  The purified water path 320 is a path for sending the permeated water purified by the purification apparatus 310, that is, purified water, a tank for temporarily storing purified water, and various apparatuses using purified water (for example, Semiconductor manufacturing equipment, pharmaceutical manufacturing equipment, steam boiler equipment, etc.)

  The control device 40 is for controlling the operation of the water treatment device 1, and is a central control device that controls the operation, a storage device that stores an operation program and various data of the water treatment device 1, and an information input / output device. It is an electronic information processing organization provided with (none of which is shown). The water quality inspection device 232 communicates with the input unit of the input / output device, and receives measurement data from each of the pH sensor 241, the temperature sensor 242, the electrical conductivity sensor 243, the hardness sensor 244, and the total alkalinity sensor 245. Is possible. In addition, an operation panel 41 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 110, the first addition device 120, the second addition device 130, the pressurization pump 212, the drainage control valve 233, and the water quality inspection device 232. The display device 42 for displaying or guiding manual input of required information and the refining device 310 are in contact with each other, 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 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 concentrated water is less than 0, it is difficult to generate a scale due to calcium carbonate on the membrane surface of the reverse osmosis membrane module 211, and conversely, when it exceeds 0, the reverse osmosis membrane module Scales due to calcium carbonate are likely to be generated on the film surface 211.

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 computer program for the Langeria index calculates the A to D values by calculating from the measurement data of each sensor of the water quality inspection device 232 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 Langeeria index and the silica concentration of the concentrated water by controlling the first addition device 120, the pressurizing pump 212, and the drainage control valve 233 by a process described later.

  Next, the basic operation of the water treatment apparatus 1 will be described. In the water treatment apparatus 1, when the water supply control valve 110 is opened and raw water is supplied from the raw water supply source to the supply path 10, the scale dispersant is added to the raw water continuously or at regular intervals from the second addition device 130. In addition, the pressure is increased by the pressurization pump 212 to the osmotic pressure in the reverse osmosis membrane module 211 and supplied to the reverse osmosis membrane module 211. The raw water supplied under pressure to the reverse osmosis membrane module 211 partially permeates through the reverse osmosis membrane (that is, is filtered), and passes through the second treatment unit 30 from the treatment water channel 220 as permeate from which impurities are removed. Are continuously sent to the refining device 310.

  From the permeated water sent to the purifying device 310, residual ions, that is, ions that permeate the reverse osmosis membrane in the reverse osmosis membrane module 211 are removed, and flow through the water purification path 320 as purified water.

  On the other hand, in the reverse osmosis membrane module 211, the remaining raw water that does not permeate the reverse osmosis membrane is pushed into the drainage channel 230 as concentrated water in which the concentration of contaminant components that are prevented from permeating by the reverse osmosis membrane is increased. Part of the concentrated water that has flowed to the drainage channel 230 flows to the circulation path 231, and merges with the raw water that flows through the supply path 10. Further, the remaining concentrated water that does not circulate to the circulation path 231 is discarded from the drainage control valve 233.

In such an operation of the water treatment apparatus 1, the flow rate of the permeated water from the reverse osmosis membrane module 211 (F ₂ ) and the flow rate of the concentrated water discarded from the drainage control valve 233 (F ₃ ) are controlled. The rate can be adjusted. Here, the recovery rate 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 211 (ie, F ₂ / F ₁ × 100). Say. In the present embodiment, F ₁ is the flow rate of raw water supplied from the water supply control valve 110.

Next, the operation of the water treatment apparatus 1 will be described more specifically with reference to the operation flowchart shown in FIG. Here, first, a sample of raw water is collected, and the silica concentration (mgSiO ₂ / L) of the raw water is analyzed. 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 1, the operation program displays an information input guide on the display device 42 of the control device 40 in step S1, and waits for the operator to input the silica concentration of raw water in step S2. . When the operator inputs the silica concentration of raw water examined in advance from the operation panel 41, the operation program shifts from step S2 to step S3, and calculates the recovery rate to be set in the reverse osmosis membrane device 210. 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 collection 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. Further, 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 211. 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.

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 211, the amount of permeated water 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 42 displays the completion of the initial preparation, and waits for the operator to input an operation start command for the water treatment device 1. Then, when the operator inputs an operation start command through the operation panel 41, the operation program moves to step S5 and starts operation of the water treatment device 1.

In step S <b> 5, the operation program first opens the water supply control valve 110 and flows the raw water from the supply source to the supply path 10. Thereby, the water treatment apparatus 1 starts the basic operation described above. In this step, the flow rate of the permeated water (F ₂ ) in the reverse osmosis membrane module 211 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 212 and the opening degree of the drainage control valve 233. Thus, the silica concentration of concentrated water is maintained below 150mgSiO ₂ / L.

In step S <b> 5, the operation program starts addition of the scale dispersant by the second addition device 130. Here, the operation program refers to the flow rate (F ₁ ) of the raw water supplied from the water supply control valve 110 and controls the concentration of the scale dispersant in the raw water. It is necessary to set the concentration in the raw water so that the scale dispersant is prevented from generating scale on the membrane surface of the reverse osmosis membrane module 211, 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 233 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 232 and starts the water quality inspection of the concentrated water sample that is constantly collected from the drainage channel 230 through the sampling channel 240.

  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 1 from the operation panel 41. When the operator inputs a stop command, the operation program moves to step S7, closes the water supply control valve 110, and stops other devices. Thereby, the supply of raw water to the reverse osmosis membrane device 210 is stopped, and the water treatment device 1 ends its operation.

  On the other hand, during operation of the water treatment apparatus 1, 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 241, temperature sensor 242, electrical conductivity sensor 243, hardness sensor 244, and total alkalinity sensor 245 of the water quality inspection device 232, 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 part 121 in the first addition device 120 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 Langelia index is less than 0, the operation program operates the control valve of the second portion 122 in the first addition device 120 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 120 is equipped with both the 1st site | part 121 for adding an acidic chemical | medical agent, and the 2nd site | part 122 for adding an alkaline chemical | medical agent, the Langelia index of concentrated water is obtained. It is possible to quickly and stably control the narrow range described above.

  The operation program repeats step S8 and step S9 during operation of the water treatment apparatus 1, that is, unless the operator inputs a stop command from the operation panel 41. 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.

According to the operation program as described above, the first processing unit 20 maintains the Langeria index of concentrated water at 0 or more and 0.3 or less and the silica concentration of the concentrated water at 150 mgSiO ₂ / L or less during operation. Is done. For this reason, the reverse osmosis membrane module 211 can suppress the production | generation of a calcium carbonate type scale and a silica type scale in a reverse osmosis membrane, and can maintain the flow volume of permeated water stably over a long period of time. 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. For this reason, in the purification apparatus 310 of the 2nd process part 30, the removal burden of the remaining free carbonic acid is reduced, and the purified water from which the contaminant component was removed highly can be obtained.

Embodiment 2
With reference to FIG. 4, 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 from raw water similar to that of the first embodiment. In the water treatment device 1 of the first embodiment, the second treatment unit 30 is replaced with another second treatment unit 30. The processing unit 50 is changed.

  The second processing unit 50 used in this embodiment mainly includes a filtration device 510 and a third addition device 520. Filtration device 510 includes reverse osmosis membrane device 511, water purification channel 512, and drainage channel 513, and reverse osmosis membrane device 511 is reverse osmosis similar to that used in reverse osmosis membrane device 210 in the first embodiment. A reverse osmosis membrane module 514 provided with a membrane element (not shown) and a pressurizing pump 515 capable of pressurizing the permeated water from the treatment water channel 220 and supplying it to the reverse osmosis membrane module 514 are provided. The permeated water from the treated water channel 220 is supplied to the reverse osmosis membrane module 514 in a state in which the permeated water is pressurized to a pressure higher than the osmotic pressure at the reverse osmosis membrane by the pressure pump 515, thereby reverse osmosis in the reverse osmosis membrane element Part permeates the reverse osmosis membrane element. Thereby, in the reverse osmosis membrane element, the permeated water is converted into permeated water from which residual impurities such as residual ions have been removed (that is, purified water) and concentrated water in which the concentration of residual impurities such as residual ions is increased. To be separated.

  The purified water path 512 is a path for sending purified water from the reverse osmosis membrane device 511, and a tank for temporarily storing purified water, and various devices using purified water (for example, semiconductor manufacturing equipment, pharmaceuticals) Manufacturing equipment and steam boiler equipment).

  The drainage channel 513 communicates between the water supply control valve 110 and the first addition device 120 in the supply route 10 and is a route for circulating the concentrated water generated in the reverse osmosis membrane device 511 to the raw water. Further, the drainage channel 513 includes a circulation channel 516 and a drainage control valve 517 in this order from the reverse osmosis membrane device 511 side. The circulation path 516 is branched from the drainage path 513 and communicates with the treatment water path 220 between the third addition device 520 and the pressure pump 515, and is supplied from the first processing unit 20 to the second processing unit 50. A part of the concentrated water from the reverse osmosis membrane device 511 is circulated with respect to the permeated water. The drainage control valve 517 is for controlling the drainage amount of the concentrated water from the reverse osmosis membrane device 511, and the recovery rate in the reverse osmosis membrane module 514 can be adjusted by this control.

  The third addition device 520 is for adding a chemical to the permeated water flowing through the treatment water channel 220. The agent added here is for ionizing free carbonic acid (dissolved carbon dioxide gas) contained in the permeated water, and can increase the pH of the permeated water, such as sodium hydroxide and potassium hydroxide. An aqueous solution is used.

  Next, operation | movement of the above-mentioned water treatment apparatus 2 is demonstrated. In the water treatment device 2, when the water supply control valve 110 is opened and raw water is supplied from the raw water supply source to the supply path 10, the scale dispersant is added to the raw water continuously or at regular intervals from the second addition device 130. And supplied to the reverse osmosis membrane device 210 of the first processing unit 20. In the reverse osmosis membrane device 210, the raw water from the supply path 10 is pressurized to a pressure higher than the osmotic pressure in the reverse osmosis membrane module 211 by the pressure pump 212 and supplied to the reverse osmosis membrane module 211. The raw water supplied under pressure to the reverse osmosis membrane module 211 partially passes through the reverse osmosis membrane (that is, filtered), and passes through the second treatment unit 50 from the treatment water channel 220 as permeate from which contaminant components have been removed. To the reverse osmosis membrane device 511. At this time, the permeated water is added with the chemical from the third addition device 520 continuously or at regular intervals, and free carbonic acid (dissolved carbon dioxide) is ionized. The amount of the drug added to the permeated water is preferably set so that the pH of the permeated water can be adjusted to 8 or more in order to promote ionization of free carbonic acid.

  The permeated water sent to the reverse osmosis membrane device 511 is pressurized to a pressure higher than the osmotic pressure in the reverse osmosis membrane module 514 by the pressure pump 515 and supplied to the reverse osmosis membrane module 514. The permeated water supplied under pressure to the reverse osmosis membrane module 514 partially passes through the reverse osmosis membrane (that is, is filtered), and residual impurities such as residual ions that have passed through the reverse osmosis membrane module 211. The free carbonic acid-derived ions generated by the addition of the drug from the third addition device 520 and the purified water from which the ions derived from the added drug itself have been removed flow to the water purification path 512.

  On the other hand, in the reverse osmosis membrane module 511, the remaining permeated water that does not permeate the reverse osmosis membrane is pushed into the drainage channel 513 as concentrated water in which the concentration of ions and the like blocked by the reverse osmosis membrane is increased. Part of the concentrated water that has flowed to the drainage channel 513 flows to the circulation channel 516, and merges with the permeated water from the first processing unit 20 that flows through the treatment water channel 220. Further, the remaining concentrated water that does not circulate to the circulation path 516 joins the raw water from the water supply control valve 110 in the supply path 10.

The above-described operation in the water treatment device 2 is controlled by the control device 40 as in the first embodiment. Therefore, the first processing unit 20 is operated so that the Langeveria index of the concentrated water in the reverse osmosis membrane device 210 is maintained at 0.3 or less and the silica concentration is maintained at 150 mgSiO ₂ / L or less. .

Embodiment 3
With reference to FIG. 5, the water treatment apparatus which concerns on Embodiment 3 of this invention is demonstrated. In the figure, the water treatment device 3 is obtained by further adding a third treatment unit 60 to the water treatment device 2 of the second embodiment.

  The 3rd process part 60 is for further refine | purifying the purified water which flows through the purified water path | route 512, and is provided with the refiner | purifier 610 and the purified water path | route 620. FIG. The purification device 610 is an ion trapping device for trapping and removing ions remaining in the permeate, and is usually the same electric regenerative ion exchange as that used in the second processing unit 30 of the second embodiment. It is selected from among an apparatus, an ion exchange resin mixed bed tower and a cation exchange resin single bed tower.

  The purified water path 620 is a path for sending purified water purified by the purification apparatus 610, and a tank for temporarily storing purified water, and various apparatuses (for example, semiconductor manufacturing apparatus, pharmaceuticals) using the purified water. Manufacturing equipment and steam boiler equipment).

  In this water treatment device 3, since ions remaining in the purified water from the water purification path 512 can be further removed in the purification device 610, purified water with higher purity can be obtained.

Other Embodiments (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 in which the silica concentration of the raw water fluctuates due to seasonal changes, the water treatment apparatus 1 of Embodiment 1 needs to measure the silica concentration of the raw water every time it is operated and input the measured value. Is low. In such a case, the supply path 10 and the first processing unit 20 store the silica concentration input by the operator at the first start in the control device 40, and omit the steps S1 to S3 of the operation program at the subsequent start. Can also be operated. The same applies to the water treatment device 2 of the second embodiment and the water treatment device 3 of the third embodiment.

(2) In each of the above-described embodiments, the silica concentration of raw water is measured in advance, and recovery is performed so that the silica concentration of the concentrated water in the first processing unit 20 is maintained at 150 mgSiO ₂ / L or less based on the measured value. Although the rate is adjusted, the water quality inspection device 232 is further provided with a sensor for measuring the silica concentration of the concentrated water, and the recovery rate is maintained so that the measured value of the silica concentration with this sensor is maintained at 150 mgSiO ₂ / L or less. Can also be adjusted.

(3) In each of the above-described embodiments, the concentrated water Langeria index in the first processing unit 20 is controlled to be in the range of 0 or more and 0.3 or less. In the present invention, the lower limit of the Langeria index is set. It can also be made not to provide. However, in such a case, a relatively large amount of pH adjuster (acidic agent) is added to the raw water in order to achieve the required Langeria index in the concentrated water in the first treatment unit 20, and as a result In addition, the amount of free carbonic acid permeating through the reverse osmosis membrane in the reverse osmosis membrane device 210 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 120 which consists only of the 1st site | part 121 for adding an acidic chemical | medical agent can also be normally used.

  On the other hand, when the pH of the raw water itself from the supply source is in the acidic range, for example, when the raw water is a factory wastewater and the pH is about 5 to 6, the concentrated water in the first treatment unit 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 120 including only the second portion 122 for adding the alkaline agent is used, and the Langerian index of the concentrated water is appropriately added while adding the alkaline agent to the raw water. Is preferably increased to around 0.3.

(4) In each of the embodiments described above, the first addition device 120 is provided with the second portion 122 for adding the alkaline chemical, and the alkaline chemical is added to the raw water from there to increase the pH of the raw water. When the raw water quality is appropriate, an aeration method (a method for removing free carbonic acid using gas-liquid contact between air and raw water) can be employed as means for increasing the pH of the raw water.

(5) In each of the above-described embodiments, a cross flow method in which a circulation path 231 is provided in the drainage channel 230 of the first processing unit 20 for the purpose of efficiently using raw water and suppressing the amount of concentrated water discarded. However, the present invention can be similarly implemented even when the cross flow method is not adopted. Moreover, the water treatment apparatus 2 of Embodiment 2 can also be changed in the 2nd process part 50 so that all the concentrated water in the reverse osmosis membrane apparatus 511 may be discarded, without providing the circulation path 516. FIG.

(6) In each of the above-described embodiments, the supply path 10 may further include a water softening device upstream of the first addition device 120 (raw water supply source side). The water softening device removes the hardness component contained in the raw water by exchanging it with a monovalent cation (for example, sodium ion) using a cation exchange resin, and converts the raw water into softened water. is there. In a general water softening device, the calcium hardness of raw water can be reduced to 0.1 mg / L or less.

  As apparent from the above-described equation (2), the Langerian index of the concentrated water in the first processing unit 20 is determined based on the calcium hardness of the raw water, and becomes smaller by reducing the calcium hardness of the raw water. . Therefore, if a water softening device is used, it becomes easier to control the Langeria index of concentrated water within a predetermined range by suppressing the addition of a pH adjuster, particularly an acidic agent, to raw water. It becomes easier to suppress the deterioration of water quality.

<Experimental example>
Experimental Examples 1-3
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. Then, through the supply path extending from the tank, this supply water is continuously pressurized while being pressurized with a pressure pump to a reverse osmosis membrane module loaded with one reverse osmosis membrane element (model name “RE8040-BLF” of Eunjin Chemical Co., Ltd.). 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 this experimental example, the pH of the feed water flowing to the reverse osmosis membrane module is adjusted to about 6 to 6.6 by adding sulfuric acid to adjust the pH of the concentrated water to about 8 to 9, and in Experimental Example 1, the Langeria index ( LSI) was controlled to -0.2, in Experiment 2 the index was controlled to 0.1, and in Experiment 3 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 Experiment Example 1
The feed water was treated under the same conditions as in Experimental Examples 1 to 3 except that the Langeria index of concentrated water was controlled to 0.5 by adding sulfuric acid to the feed water.

Comparative Experiment Example 2
The feed water was treated under the same conditions as in Experimental Examples 1 to 3 except that the Langerian index of the concentrated water was not controlled by adding sulfuric acid to the feed water.

Comparative Experiment Example 3
By adjusting the addition of sulfuric acid to the feed water, the Langeria index of the concentrated water was controlled to 0.2, and the recovery rate was increased to increase the silica concentration of the concentrated water to about 170 mg SiO ₂ / L, The feed water was treated under the same conditions as in Experimental Examples 1 to 3.

Comparative Experiment Example 4
Except that the scale dispersant was not added to the feed water, the feed water was treated under the same conditions as in Experimental Example 3 in which the Langeria index was controlled to 0.3.

Comparative Experiment Example 5
The feed water was treated under the same conditions as in Experimental Examples 1 to 3 except that the Langeria index was not controlled by adding sulfuric acid to the feed water and the scale dispersant was not added to the feed water.

In each of Evaluation Experimental Examples 1 to 3 and Comparative Experimental Examples 1 to 5, the change in effective pressure of the reverse osmosis membrane element during the water treatment operation was 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 1. In Comparative Experimental Example 5, the water permeation coefficient after 120 hours had dropped to less than 15% of the initial value, so the water treatment operation was stopped at this point.

  According to Table 1, in Experimental Examples 1 to 3, the water permeation coefficient after 150 hours was maintained at 96 to 97% of the initial value, and the scale adhesion of the reverse osmosis membrane element compared to Comparative Experimental Examples 1 to 5 It can be seen that obstruction due to is significantly suppressed. In addition, in Experimental Examples 1 to 3, the electrical conductivity of the permeated water is a numerical value comparable to that in Comparative Experimental Examples 1 to 5, and it is understood that permeated water with good water quality is obtained. Furthermore, according to Experimental Examples 1 to 3, since the conductivity of the permeated water tends to be slightly higher when the Langerian index of the concentrated water is less than 0, the Langerian index of the concentrated water is maintained at 0 or more. It can also be seen that it is preferable.

1, 2, 3 Water treatment device 10 Supply path 40 Control device 120 First addition device 130 Second addition device 210 Reverse osmosis membrane device 220 Treatment water channel 230 Drainage channel 232 Water quality inspection device 310, 511, 610 Purification device

Claims (15)

A water treatment device for purifying raw water containing silica and hardness components,
The raw water supply path;
A reverse osmosis membrane device for filtering the raw water from the supply path and separating it into permeated water and concentrated water;
A purification device for purifying the permeated water obtained by the reverse osmosis membrane device;
First adjusting means for adjusting the pH of the raw water provided in the supply path;
A second adjusting means for adjusting the recovery rate of the permeated water in the reverse osmosis membrane device;
An addition device for adding a scale dispersant to the raw water provided in the supply path;
A water quality inspection device for inspecting the quality of the concentrated water;
Based on the water quality inspected by the water quality inspection device, computing means for calculating a Langeria index of the concentrated water;
Water quality for controlling the first adjusting means and the second adjusting means so that the Langeria index is maintained at 0.3 or less and the silica concentration of the concentrated water is maintained at 150 mgSiO ₂ / L or less. Control means;
Water treatment device with   The water treatment apparatus according to claim 1, wherein the purification apparatus is an ion trapping apparatus selected from an electric regeneration type ion exchange apparatus, an ion exchange resin mixed bed tower, and a cation exchange resin single bed tower.   The water treatment apparatus according to claim 1, wherein the purification apparatus is a filtration apparatus including a reverse osmosis membrane.   The purification apparatus includes a filtration apparatus provided with a reverse osmosis membrane, and an electrically regenerative ion exchange apparatus, an ion exchange resin mixed bed tower, and a cation exchange resin for further purifying the permeated water purified by the filtration apparatus. The water treatment apparatus according to claim 1, comprising an ion trapping device selected from a single bed tower.   The water treatment apparatus according to any one of claims 1 to 4, wherein the water quality control unit controls the first adjustment unit so that the Langeria index is maintained at 0 or more.   The water treatment apparatus according to any one of claims 1 to 5, wherein the first adjustment means is an injection apparatus for injecting a pH adjusting agent into the raw water.   The water treatment apparatus according to claim 6, wherein the pH adjuster is at least one of an acidic chemical that lowers the pH of the raw water and an alkaline chemical that increases the pH of the raw water.   The water treatment apparatus according to any one of claims 1 to 7, wherein a material containing polycarboxylic acid and phosphonic acid is used as the scale dispersant. A water treatment method for purifying raw water containing silica and hardness components,
Supplying the raw water to which the scale dispersant has been added to the reverse osmosis membrane device, and separating it into permeated water and concentrated water; and
And step 2 for purifying the permeate.
In step 1, the Langeria index of the concentrated water is maintained at 0.3 or lower, and the silica concentration is maintained at 150 mgSiO ₂ / L or lower.
Water treatment method.   The water treatment according to claim 9, wherein in step 2, the permeated water is purified by an ion trapping device selected from an electric regeneration type ion exchange device, an ion exchange resin mixed bed tower, and a cation exchange resin single bed tower. Method.   The water treatment method according to claim 9, wherein in step 2, the permeated water is purified by a filtration device equipped with a reverse osmosis membrane.   Step 2 includes a step of purifying the permeated water using a filtration device equipped with a reverse osmosis membrane, and an electric regenerative ion exchange device, an ion exchange resin mixed bed tower, and a cation exchange for the permeated water purified by the filtration device. The water treatment method of Claim 9 including the process of further refine | purifying with the ion trapping apparatus selected from the resin single bed towers.   The water treatment method according to any one of claims 9 to 12, wherein, in step 1, the Langeria index is maintained at 0 or more.   In the step 1, the Langerial index is controlled by adjusting the pH of the raw water, and the silica concentration is controlled by adjusting the recovery rate of the permeated water in the reverse osmosis membrane device. The water treatment method in any one of 13 thru | or 13.   The water treatment method according to claim 9, wherein the scale dispersant contains polycarboxylic acid and phosphonic acid.

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