WO2016059691A1 - Production method for purified daily life water and production apparatus for purified daily life water - Google Patents

Abstract

[Problem] The present invention addresses the problem of providing a purified water production method and a water purification apparatus for efficiently removing impurities such as heavy metal ions and arsenic. The present invention also addresses the problem of reducing the size of a central water purification apparatus for supplying purified water to an entire structure such as an apartment or office building. [Solution] This production method for purified daily life water that adds a nucleating agent to raw water and filters same with a membrane means is characterized in that: for said nucleating agent, an aqueous dispersion of ferric hydroxide colloid particles of 5-160 nm weight average particle diameter is used; and the ratio of the mass of iron in the ferric hydroxide colloidal particles with respect to the total mass of iron added to the raw water is at least 0.9.

Description

Method for producing water for daily life and apparatus for producing water for daily life

The present invention relates to water treatment technology.

In recent years, small water purifiers for the purpose of removing residual chlorine (hypochlorous acid), musty odor, turbidity, microorganisms and the like from tap water have become widespread. In these water purifiers, residual chlorine in tap water, activated carbon that removes off-flavors and odors, ceramic filters, microfiltration membranes that remove turbidity and microorganisms, hollow fiber membranes, and the like were used. When such a water purifier is provided in a residence or the like, it is often installed under a kitchen faucet or sink, and tap water has been purified to be suitable for drinking and cooking.

On the other hand, there was a need to use purified tap water in the entire area of buildings such as buildings and hotels, or to purify well water and use it in the entire area of the building. Installing the vessel is cumbersome. Therefore, a water purification system that attaches a large water purification device to an entrance for introducing tap water or the like into a building, purifies the tap water collectively, and supplies the entire building to water has begun to spread. These large water purifiers are also composed of activated carbon, ceramic filters, microfiltration membranes, etc., just like small water purifiers. By passing these, residual chlorine and turbidity in tap water are removed, and a plurality of water purifiers in the building are removed. Supply purified water to the place where it is used. In the present invention, such a large water purifier may be referred to as a central water purifier.

As such a large water purification apparatus, a filtration apparatus using a membrane module is known (for example, Patent Documents 1 to 3). In Patent Document 1, a plurality of membrane modules, an introduction line for introducing a stock solution to the primary side of each of the membrane modules, and a secondary side of each of the membrane modules are connected and filtered by the membrane module. A filtration liquid discharge line for discharging the filtrate, and at the time of backwashing, the flow path of the introduction line communicating with the membrane module to be backwashed is provided in the introduction line in a filtration device that is closed A filtrate supply pump for supplying a filtrate at a predetermined flow rate to the membrane module; a filtrate pump for pumping the filtrate while being provided in the filtrate discharge line; and a filtrate pump for the filtrate discharge line And a flow path between the downstream side of the membrane module and the secondary side of each of the membrane modules, and the membrane module to be backwashed during backwashing. The flow path from the membrane module to be backwashed during backwashing is opened and connected to the primary side of each of the membrane modules and the backwash line through which the filtrate flows as backwashing liquid. A cleaning liquid discharge line through which the backwash liquid that has passed through the membrane module is discharged, pressure detection means for detecting the pressure of the filtrate on the suction side of the filtrate pressure feed pump, and detected by the pressure detection means And a control means for controlling the drive of the filtrate pumping pump based on the pressure.

In Patent Document 2, in a method of operating a membrane separation apparatus having a plurality of membrane modules having a common permeate line, the permeate from other membrane modules is used when backwashing is performed in some membrane modules. There is disclosed a method of operating a membrane separation device, characterized in that it is supplied to the secondary side of the membrane module to be backwashed by the discharge pressure and then pressurized gas is supplied to the secondary side.

Patent Document 3 discloses that in a membrane filtration apparatus including a plurality of membrane modules, a membrane passage that performs backwashing is directly passed with membrane permeated water obtained from another membrane module and backwashed. Equipped with a fluid passage switching mechanism for switching, a compressor and air piping for supplying pressurized air to each membrane module, stops the introduction of raw water into the membrane module performing backwashing, and instead pressurizes from the compressor Introduce air to the primary side of the membrane module for backwashing and introduce permeated water from other membrane modules to the secondary side of the membrane module for backwashing to perform backwashing or backwashing. A membrane filtration device configured to supply pressurized air to the secondary side of a membrane module that performs washing, mix in backwash water, and backwash with a gas-liquid mixed fluid. The main pipe is connected, and the raw water main pipe Branch pipes are branched, the end side of each raw water branch pipe is connected to the raw water inlet of each membrane module, each raw water branch pipe is provided with an open / close valve, and the concentrated water outlet of each membrane module is connected via the pipe The three-way valve is connected to an inflow port of the three-way valve, and each of the three-way valves has two outflow ports. One of the outflow ports is connected to a branch pipe for circulating the concentrated water. Connected to the main pipe, one end of the branch pipe for backwash drainage is connected to the other outflow port of the three-way valve, and the other end of the branch pipe is connected to the main pipe for backwash drainage discharge One end of a branch pipe for extracting permeate is connected to the permeate outlet of the membrane module, and the other end of the branch pipe is connected to a main pipe for extracting permeate, Raw water branch piping The end side of the air branch pipe is connected to the portion between each on-off valve and each membrane module, the upstream end side of each air branch pipe is connected to the air main pipe, and this air main pipe is connected to the compressor. A membrane filtration device characterized by this is disclosed.

Depending on the type of raw water collected by the water purification device, the content of impurities such as heavy metals, arsenic, and fluorine may differ, and it is necessary to efficiently remove impurities. As a method for removing impurities, there is known a method in which impurities are aggregated by using a flocculant to precipitate and separate. For example, Patent Document 4 is a coagulation filtration apparatus for filtering water to be treated, which has flocs formed by adding a flocculant, with a membrane module, and is provided with an addition unit for adding the flocculant to the water to be treated. An aggregating and filtering apparatus comprising: a stirrer that stirs water to be treated with a flocculant added downstream of the adding unit; and the membrane module that is disposed downstream of the agitator. It is disclosed.

A water treatment method using ferric hydroxide colloid is known. For example, in Patent Document 5, a ferrous salt aqueous solution and a positively charged ferric hydroxide colloid solution are added to water to be treated and stirred, and then the pH of the water is adjusted to 6-8. Thus, a water purification method is disclosed, in which an organic substance or an inorganic substance dissolved or dispersed in water is removed by precipitation and a porous membrane. In Patent Document 6, in a wastewater treatment method for reducing COD of wastewater with high COD in which phenols are dissolved, (1) ferrous chloride aqueous solution, ferric chloride aqueous solution, or ferrous chloride in an oxidized state An aqueous solution mixed with ferric chloride or an aqueous solution of ferric hydroxide colloid having an average particle size of 4 nm or more and less than 30 nm is added, or iron is generated by electrolysis of the waste water using iron as an anode. (2) The pH of the waste water is adjusted by mixing an alkaline aqueous solution or an aqueous acid solution to 5 or more and less than 9, and (3) after removing the generated precipitate, (4) with an average particle size of 10 nm or more Disclosed is a method for treating waste water, which comprises adding a ferric hydroxide colloid aqueous solution of less than 20 nm to remove precipitates.

JP 2011-177653 A JP 2001-190935 A Japanese Patent No. 4178178 JP 2004-267842 A JP 2010-247057 A JP 2012-196657 A

In a filtration apparatus using a membrane module as a filtration means, a method of adding a flocculant and precipitating and removing agglomerates requires a coagulation sedimentation tank, which increases the size of the apparatus. However, in order to install a filtration device in a building such as a building or a hotel, it is required to reduce the size of the filtration device. Moreover, when the filtration apparatus which uses a membrane module as a filtration means is used continuously, a foreign material will clog the filtration membrane with which a membrane module is provided, and filtration efficiency will fall. In order not to lower the filtration efficiency of the membrane module of the filtration device, it is necessary to back-wash the membrane module. However, when a conventional flocculant is used, the agglomerates easily block the pores of the filtration membrane, and frequent backwashing is required. In particular, when the coagulation sedimentation layer is not provided, there is a problem that the filtration membrane becomes clogged and the amount of raw water treated is significantly reduced. In addition, conventional flocculants cannot efficiently remove heavy metal ions from raw water containing heavy metal ions.

Patent Documents 5 and 6 disclose a water treatment technique that uses ferric hydroxide colloid and diffuses and filters pores using a porous membrane. However, the pore diffusion / filtration method is a method of performing filtration by a cross flow method with a transmembrane pressure difference of 0.3 atm or less, and has a low raw water treatment capacity. Moreover, since the porous flat membrane is used, there is a problem that the apparatus becomes large in order to increase the raw water treatment amount.

This invention is made | formed in view of the said situation, Comprising: It aims at providing the manufacturing method of domestic water purification which removes impurities, such as heavy metal ion and arsenic efficiently, and the manufacturing apparatus of domestic water purification To do. Another object of the present invention is to reduce the size of a central water purification apparatus that supplies clean water for daily use to the entire building such as a condominium and a building.

The method for producing domestic water for purification according to the present invention is a method for producing domestic water for purification by adding a nucleating agent to raw water and filtering with a membrane means, wherein the nucleating agent has a weight average particle diameter of 5 nm to 160 nm. Using the aqueous dispersion of ferric hydroxide colloidal particles, the ratio of the iron mass of the aqueous ferric hydroxide colloidal particles to the total mass of iron added to the raw water is set to 0.9 or more. It is characterized by that.

The commercially available flocculants are suitable for aggregating colloidal particles of about 100 μm to 1 μm floating in the water to be treated, for example, but agglomerate ionic substances and ionic molecules such as small metal ions. Is difficult. The present inventors used an aqueous dispersion of ferric hydroxide colloidal particles having a weight average particle diameter of 5 nm to 160 nm (hereinafter sometimes simply referred to as “aqueous dispersion of ferric hydroxide”). For example, the inventors have found that the effect of capturing ionic substances and ion molecules such as heavy metal ions having a small particle size is increased, and the present invention has been completed. The aqueous dispersion of ferric hydroxide colloidal particles having a weight average particle diameter of 5 nm to 160 nm used in the present invention adsorbs ionic impurities contained in the raw water by the charge effect due to the potential, It is considered that the particle grows as the center and has an effect of increasing the particle size. Furthermore, an aggregate in which particles centering on a nucleating agent are aggregated may be generated. In the present invention, an aqueous dispersion of ferric hydroxide colloidal particles having such an effect is called a “nucleating agent” and is distinguished from a general flocculant. The general flocculant is intended to agglomerate impurities, to enlarge and precipitate the aggregate, and to remove it, in the method for producing purified water for daily use of the present invention, the flocculating agent formed by the “nucleating agent” It is characterized in that it is filtered directly by membrane means without precipitating the product. In the present invention, if an aqueous dispersion of ferric hydroxide colloidal particles having a weight average particle diameter of 5 nm to 160 nm is used as the nucleating agent, the particle size of the aggregate formed by the “nucleating agent” is controlled, There is an effect of suppressing the blockage of the membrane means. As a result, a certain amount of clean water for daily use can be stably supplied.

The apparatus used in the method for producing domestic purified water according to the present invention includes a raw water supply channel, a raw water supply unit that is disposed in the raw water supply channel, and feeds the raw water, and a plurality of branching the raw water supply channel into at least two or more. A raw water branch path, a membrane module that is arranged in the plurality of raw water branch paths and includes a plurality of membrane means for filtering raw water, a discharge path that is connected to a primary side of the plurality of membrane modules, and the plurality of membrane modules Means for supplying a nucleating agent to the raw water on the primary side of the membrane module. And a separation tank that precipitates and separates agglomerates generated by the addition of a nucleating agent.

According to the present invention, it is possible to provide clean water for daily use from which ionic impurities such as heavy metal ions and arsenic are efficiently removed. Moreover, according to this invention, the water purifier with high backwashing efficiency is obtained. The water purifier of the present invention can be reduced in size.

It is explanatory drawing which illustrates a ferric hydroxide colloid particle typically. It is explanatory drawing which illustrates a ferric hydroxide colloid particle typically. It is explanatory drawing which illustrates the aspect which capture | acquires a heavy metal ion typically. It is explanatory drawing which illustrates typically the aspect which nucleated particle | grains aggregate. It is a figure which shows typically the purified water manufacturing apparatus of one Embodiment of this invention. It is a figure which shows the water flow state of the purified water manufacturing process of the purified water apparatus of embodiment. It is a figure which shows the water flow state of the backwashing process of the water purifier of embodiment. It is a figure which shows the water flow state of the backwashing process of the water purifier of embodiment. It is a graph which shows Cd density | concentration change in the treated water before and behind a filtration process. It is a graph which shows a Cd removal load amount index | exponent. It is a graph which shows the As density | concentration change of the treated water before and behind a filtration process. It is a graph which shows an As removal load amount index. It is a graph which shows the pH dependence of As concentration after a filtration process. It is a graph which shows the pH dependence of Pb density | concentration after a filtration process. It is a graph which shows the relationship between an average particle diameter and a removal rate.

(1) Manufacturing method of domestic water purification The manufacturing method of domestic water purification of this invention is a manufacturing method of domestic water purification which adds a nucleating agent to raw | natural water and filters with a membrane means, As said nucleating agent, Using an aqueous dispersion of ferric hydroxide colloidal particles having a weight average particle diameter of 5 nm to 160 nm, the mass of iron in the aqueous dispersion of ferric hydroxide colloidal particles relative to the total mass of iron added to the raw water The ratio is made 0.9 or more. According to the present invention, ionic impurities such as heavy metal ions having a small particle size contained in the raw water are captured by the nucleating agent and efficiently removed.

First, raw water to be treated by the method for producing water for daily life of the present invention will be described. Examples of the raw water include natural water or tap water. Natural water is fresh water that exists in the natural world such as well water, groundwater, rainwater, rivers, ponds, and lakes. Tap water is purified water supplied from a water purification facility. The raw water to be treated in the present invention does not include industrial wastewater, industrial wastewater and the like. This is because industrial wastewater and industrial wastewater have many types of impurities and have a high concentration of impurities, so that the impurities cannot be removed even by the present invention and are not acceptable as clean water for daily use.

Moreover, according to this invention, the ionic impurity contained in raw | natural water can be removed. The ionic impurities contained in the raw water include heavy metal ions such as iron (Fe ²⁺ , Fe ³⁺ ), cadmium (Cd ²⁺ ), copper (Cu ²⁺ ), lead (Pb ²⁺ ), arsenic (AsO ₄ ^3−, etc.) Metal ions such as aluminum (Al ³⁺ ) can be removed. According to the present invention, both anionic impurities and cationic impurities can be removed.

Next, an aqueous dispersion of ferric hydroxide colloidal particles having a weight average particle diameter of 5 nm to 160 nm used as a nucleating agent in the present invention will be described. The aqueous dispersion of ferric hydroxide colloidal particles having a weight average particle diameter of 5 nm to 160 nm used in the present invention adsorbs ionic impurities contained in the raw water by the charge effect due to electric potential, and the particles are mainly composed of colloidal particles. Are believed to grow and become larger in particle size. Furthermore, the grown particles centering on the nucleating agent may aggregate to form an aggregate. In the present invention, by using a ferric hydroxide colloid particle aqueous dispersion having a weight average particle size of 5 nm to 160 nm as a nucleating agent, an ionic impurity having a small particle size contained in raw water (heavy metal ions, arsenic, Ionic substances such as fluorine) can be efficiently captured. From the viewpoint of controlling the particle size of the grown nucleating agent particles and the aggregates of these nucleating agents, the weight average particle size of the nucleating agent is preferably controlled to 5 nm to 160 nm. By using a nucleating agent having a weight average particle diameter of 5 nm to 160 nm, it is considered that clogging of the membrane means by aggregates is suppressed.

The weight average particle size of the aqueous dispersion of ferric hydroxide is more preferably 10 nm or more, further preferably 15 nm or more, preferably 50 nm or less, more preferably 40 nm or less, and further preferably 25 nm or less. If the weight average particle size becomes too small, the aqueous dispersion of ferric hydroxide may permeate the membrane means. Moreover, when the weight average particle diameter becomes too large, the effect of capturing ionic molecules such as arsenic and heavy metals is reduced. In the present invention, the weight average particle size of the aqueous dispersion of ferric hydroxide is measured by a dynamic light scattering method using, for example, DLS-8000 / 6500 manufactured by Otsuka Electronics Co., Ltd.

As the ferric hydroxide colloidal particle aqueous dispersion, for example, a colloidal particle formed by adsorbing a negatively charged counterion on the outside of a positively charged ferric ion particle is dispersed in water. Can be mentioned. Examples of the counter ion include sulfate ion, hydroxide ion, and chlorine ion.

FIG. 1 is an explanatory view schematically illustrating ferric hydroxide colloidal particles 100 used as a nucleating agent. A layer 102 made of hydroxide ions (OH ⁻ ) as counter ions is formed on the surface of the nucleus 101 made of positively charged iron ions (Fe ³⁺ ). The ferric hydroxide colloidal particles 100 have a high affinity with water and a high stability in water because the layer 102 made of hydroxide ions is formed outside the core 101 made of iron ions. . Further, by adding iron ions (Fe ³⁺ ) for growth around the ferric hydroxide colloidal particles, as shown in FIG. 2, a layer 103 made of iron ions (Fe ³⁺ ), Layers 104 made of hydroxide ions (OH ⁻ ) are alternately formed, and the particle diameter is increased.

FIG. 3 is an explanatory view schematically illustrating an aspect in which ferric hydroxide colloidal particles, which are nucleating agents, capture heavy metal ions (X ⁻ ). On the surface of the nucleus 101 made of positively charged iron ions (Fe ³⁺ ), a layer 102 made of hydroxide ions (OH ⁻ ) as counter ions is formed. Since the layer 102 of hydroxide ions (OH ⁻ ) is negatively charged, it attracts cations (M ⁺ ) and hydrogen ions (H ⁺ ) contained in the nucleating agent and raw water. As a result, a layer 105 made of positively charged cations is formed outside the layer 102 made of hydroxide ions. By the same action, the layer 105 made of cations attracts heavy metal ions (X ⁻ ) and hydroxide ions (OH ⁻ ), and the layer 106 made of anions is formed outside the layer 105 made of cations. Is done. In addition, the electric charge effect by an electric potential becomes weak as it leaves | separates from the nucleus 101 which consists of iron ions. Therefore, positive and negative ions are likely to be mixed in the outer layer. As described above, the nucleating agent grows particles by adsorbing the counter ion around the core of the metal ion. At that time, ionic impurities in the raw water are trapped inside the particles. FIG. 4 shows a mode in which nucleated particles aggregate to form further aggregates.

The aqueous ferric hydroxide colloidal particle dispersion can be prepared, for example, by adding sodium hydroxide to ferric chloride and adjusting the pH to about 2.7 and heating. . The average particle diameter can be controlled by the amount of iron ions added for the growth of trivalent iron ions and hydroxide ions or colloidal particles. The aqueous dispersion of ferric hydroxide colloidal particles preferably has a pH adjusted to 1.5 to 4.0. This is because as the pH increases, the stability of the ferric hydroxide colloid may decrease. If the ferric hydroxide colloidal particle aqueous dispersion contains ferric chloride or other iron ions, the size of the aggregates generated from the raw water by the nucleating agent increases, and the membrane means is used. Since it becomes easy to block, by adjusting the amount of ferric chloride and sodium hydroxide, the aqueous dispersion of ferric hydroxide colloidal particles does not contain ferric chloride-derived iron ions. It is better to do so.

The total iron concentration of the aqueous dispersion of ferric hydroxide colloidal particles used as a nucleating agent (an aqueous dispersion of a nucleating agent prepared in advance for addition to raw water) is determined by the transportability of the nucleating agent and Considering the transportation cost, a high concentration is preferable. That is, the total iron concentration is preferably 1,000 mg / L or more, more preferably 3,000 mg / L or more, and further preferably 4,000 mg / L or more. However, if it exceeds 10,000 mg / L, it is self-aggregated to produce a precipitate, so that it is preferably 10,000 mg / L or less, more preferably 8,000 mg / L or less, and even more preferably 6,000 mg / L or less. The total iron concentration is the total mass (mg) of iron (Fe) contained in 1 L of the aqueous dispersion of ferric hydroxide colloid particles. Total iron concentration is measured by ICP mass spectrometry.

As an aspect of adding the nucleating agent to the raw water, for example, an aspect of adding the nucleating agent to the raw water stored in the raw water tank, an aspect of adding the nucleating agent to the raw water in the raw water supply path for supplying the raw water to the membrane means And so on. From the viewpoint of controlling the particle size of the aggregate formed by the nucleating agent, it is preferable to add the nucleating agent to the raw water immediately before the membrane means. If the aggregate particle size becomes too large, the aggregate may block the pores of the membrane means. In addition, in the aspect which adds a nucleating agent to raw | natural water, it is preferable to filter with a membrane means as it is, without settling and isolate | separating the generated aggregate.

The amount of nucleating agent (aqueous dispersion of ferric hydroxide colloidal particles) added to the raw water exhibits a removal effect as the concentration increases, so that the total iron concentration is preferably 0.05 mg / L or more, 0 .3 mg / L or more is more preferable, and 0.5 mg / L or more is more preferable. The amount of the nucleating agent added to the raw water is preferably 9 mg / L or less, more preferably 6 mg / L or less, and further preferably 4 mg / L or less in terms of total iron concentration. If it is 9 mg / L or less, the manufacturing cost can be reduced and the nucleating agent tank can be downsized. In the case of raw water (for example, tap water) having a low impurity content, the upper limit of the nucleating agent concentration relative to the raw water is preferably 3 mg / L, more preferably 2 mg / L, from the viewpoint of cost reduction. L is more preferable. The addition amount of the nucleating agent is represented by the total mass (mg) of the iron component (Fe) of the nucleating agent (aqueous dispersion of ferric hydroxide colloid particles) added to 1 L of raw water.

In the present invention, the ratio of the mass of iron contained in the aqueous dispersion of ferric hydroxide colloid particles to the total mass of iron added to the raw water is set to 0.9 or more. That is, when an iron-containing aqueous liquid other than the aqueous dispersion of ferric hydroxide colloid particles is added to the raw water, the mass of iron contained in the aqueous dispersion of ferric hydroxide colloid particles is A, Aqueous dispersion of ferric hydroxide colloidal particles relative to the total mass of iron added to the raw water (A + B), where B is the mass of iron contained in the iron-containing aqueous liquid other than the aqueous dispersion of ferric colloidal particles The mass ratio (A / (A + B)) of iron A contained in the product is preferably 0.9 or more, more preferably 0.95 or more, and even more preferably 0.99 or more. . By making the ratio of (A / (A + B)) close to 1, blockage of the membrane means can be suppressed and water purification costs can be reduced. Here, the iron content of the aqueous dispersion of ferric hydroxide colloidal particles (the aqueous dispersion of the nucleating agent prepared in advance for addition to the raw water) includes, for example, the iron content of the colloidal particles themselves and the colloidal particles. The iron content derived from ferric chloride used as a raw material is included. Examples of the iron-containing aqueous liquid other than the aqueous dispersion of ferric hydroxide colloidal particles include a ferrous chloride aqueous solution and a ferric chloride aqueous solution. The iron content contained in the iron-containing aqueous liquid may be adsorbed on the colloidal particles to increase the particle size of the nucleating agent. When giving priority to such an effect, the value of (A / (A + B)) may be set to 0.99 or less, and may be set to 0.98 or less. The iron concentration is measured by ICP mass spectrometry.

Also, the raw water may contain iron ions. In such a case, the mass C of iron contained in the raw water, the mass of iron contained in the aqueous dispersion of ferric hydroxide colloid particles is A, and iron content other than the aqueous dispersion of ferric hydroxide colloid particles is contained. When the mass of iron contained in the aqueous liquid is B, the value of A / (A + B + C) is preferably 0.9 or more, more preferably 0.95 or more, and 0.99 or more. More preferably. By making the ratio of (A / (A + B + C)) close to 1, blockage of the membrane means can be suppressed and water purification costs can be reduced. In some cases, the iron contained in the raw water or the iron contained in the iron-containing aqueous liquid is adsorbed on the colloidal particles to increase the particle size of the nucleating agent. When giving priority to such an effect, the value of (A / (A + B + C)) may be set to 0.99 or less, and may be set to 0.98 or less. The iron concentration is measured by ICP mass spectrometry.

In the method for producing clean water for daily use of the present invention, it is preferable to adjust the pH of raw water before adding the nucleating agent to 4 to 8.5. By adjusting the pH of the raw water to 4 to 8.5, the removal efficiency of arsenic in the raw water can be increased. From this viewpoint, the pH of the raw water is preferably 4.5 or more, more preferably 5 or more, preferably 7.5 or less, more preferably 7 or less, and even more preferably 6.5 or less. The pH may be adjusted by adding an alkali or acid to the raw water. Examples of the alkali include alkali solutions such as sodium hydroxide, potassium hydroxide, and ammonia. Sodium hydroxide or potassium hydroxide is preferable and sodium hydroxide is more preferable because it is inexpensive and easy to handle. Examples of the acid include hydrochloric acid, nitric acid, acetic acid, dilute sulfuric acid, and the like, and hydrochloric acid and dilute sulfuric acid are preferable, and hydrochloric acid is more preferable because it is inexpensive and easy to handle.

The membrane means used in the present invention removes foreign matters such as fine particles and turbidity in raw water and discharges purified water. Examples of the membrane means include filtration membranes such as reverse osmosis membranes (RO membranes), nanofiltration membranes (NF membranes), microfiltration membranes (MF membranes), and ultrafiltration membranes (UF membranes). As a membrane means, a microfiltration membrane (MF membrane) and an ultrafiltration membrane (UF membrane) are preferable from the viewpoint that raw water can be filtered at a relatively low pressure and low cost.

Generally, when the purpose is to remove heavy metal ions or the like in raw water with a membrane means, an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane) is not used as the membrane means. This is because the ultrafiltration membrane (UF membrane) and microfiltration membrane (MF membrane) have larger pore diameters than the heavy metal ions, and the heavy metal ions in the raw water permeate the membrane means. Therefore, when removing heavy metal ions in raw water by a membrane means, it is necessary to use a reverse osmosis membrane (RO membrane) or nanofiltration membrane (NF membrane) having a small pore diameter. However, since reverse osmosis membranes (RO membranes) have high water flow pressures during filtration, it is necessary to increase the performance or size of the raw water supply means. In addition, the power cost during operation may be high, and the amount of water used is also high because waste water is required. Further, when a nanofiltration membrane (NF membrane) is used, the raw water treatment amount decreases because the pore diameter of the membrane means is small. On the other hand, in the present invention, since the nucleating agent captures heavy metal ions to form aggregates having a large particle size, the aggregates capturing heavy metal ions are converted into ultrafiltration membranes (UF membranes) or microfiltrations having large pore sizes. It can be removed with a film (MF film). By using an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane) having a large pore diameter, the amount of raw water treated can be increased.

Moreover, in the method for producing water for daily life of the present invention, it is preferable to use a hollow fiber membrane as the membrane means. As a filtration method, all raw water is filtered through a filtration membrane to make purified water (dead-end filtration method), and raw water is run parallel to the surface of the filtration membrane, Although there is a cross-flow filtration method that discharges both purified water that has been filtered through a filtration membrane, it is preferable to employ a full-volume filtration method that can increase the amount of purified water.

In the water purification method of the present invention, when the weight average particle diameter of the nucleating agent is A (nm) and the pore diameter of the membrane means of the membrane module is B (nm), B / A is 1 to 20 More preferably. When the weight average particle diameter A (nm) of the nucleating agent and the pore diameter B (nm) of the membrane means satisfy the above relationship, the nucleating agent and the aggregate block the pores of the membrane means. And the number of backwashes can be reduced. In this respect, B / A is preferably 2 or more, more preferably 5 or more, and preferably 10 or less, more preferably 7 or less. The pore diameter B (nm) of the membrane means can be determined according to the bubble point method (JIS K 3832).

In the case of an ultrafiltration membrane (UF membrane), the size of the eyes is classified according to the molecular weight cut off using the substance to be separated as an index. That is, classification is performed based on the molecular weight of the marker that can be separated on the target membrane. Representative markers are shown in the table below. The membrane rejection is defined by the ratio of the concentration of the target substance on the permeate side to the concentration of the target substance on the supply liquid side, and the separation performance can be evaluated. Usually, the molecular weight of the target substance having a rejection rate of about 90% is defined as the fractional molecular weight. The pore diameter B (nm) of the membrane means is an approximate curve (Y = 0.1506 × M ^0.3371) where Y is the molecular diameter (nm), and M is the molecular weight. , R ² = 0.9994), and the molecular diameter Y (nm) calculated from this was adopted.

(Refer to JPO Standard Technology Collection: Organic Polymer Porous Material 2-1-3-2. Flux (fractional molecular weight))

In the method for producing domestic clean water of the present invention, the transmembrane pressure difference of the membrane means is preferably more than 0.03 MPa, more preferably 0.04 MPa or more, and further preferably 0.05 MPa or more. Preferably, it is 0.45 MPa or less, more preferably 0.3 MPa or less, further preferably 0.2 MPa or less, and particularly preferably 0.15 MPa or less. By setting the transmembrane differential pressure of the membrane means within the above range, the treatment capacity of raw water can be increased, and a desired amount of clean water for daily life can be ensured. In this case, the pressure on the primary side of the membrane means is preferably 0.08 MPa or more, more preferably 0.13 MPa or more, further preferably 0.15 MPa or more, preferably 0.50 MPa or less, more preferably 0.35 MPa or less. 0.25 MPa or less is more preferable. Further, the pressure on the secondary side of the membrane means is preferably 0.05 MPa or more, more preferably 0.10 MPa or more, further preferably 0.12 MPa or more, preferably 0.30 MPa or less, more preferably 0.25 MPa or less. 0.20 MPa or less is more preferable.

In the method for producing domestic purified water of the present invention, the ratio (V / S, (m / hr)) of the filtration amount V (m ³ ) per hour to the total filtration area S (m ² ) of the membrane means is 0 .05 or more, preferably 0.1 or more, more preferably 0.3 or more, particularly preferably 0.5 or more, and 3.0 or less. Preferably, it is 2.5 or less, more preferably 2.0 or less. When the ratio is 0.05 or more and 3.0 or less, the amount of raw water treated per unit filtration area becomes a desired range. In particular, in the case of a pore diffusion technique using a porous membrane that is a flat membrane, the amount of raw water treated per unit filtration area is extremely small, and in order to increase the amount of raw water treated, the filtration area is increased. The filtration device becomes larger.

A chemical solution may be added to the purified water for domestic use obtained by filtering with a membrane means, if necessary. Although it does not specifically limit as said chemical | medical solution, For example, hypochlorous acid, sodium hypochlorite, hypochlorous acid aqueous solution, etc. can be mentioned. Among these, it is preferable to use a sodium hypochlorite aqueous solution. By adding sodium hypochlorite, it ionizes to hypochlorite ions in water, and part of it reacts with water to form hypochlorous acid. In the clean water for daily use discharged from the water purifier by these sterilizing power, for example, it is possible to prevent the growth of bacteria in the piping from the water purifier to each use location, and the safety of the purified water until the user drinks it. Can be maintained.

When sodium hypochlorite is added to purified water, the chlorine concentration in the obtained purified water is preferably 0.3 mg / L or more in consideration of the relationship between sterilizing power and chlorine removal efficiency in the secondary water purification device. 0.4 mg / L or more is more preferable, 0.5 mg / L or more is more preferable, 0.8 mg / L or less is preferable, and 0.7 mg / L or less is more preferable. By containing chlorine in the purified water in this way, even when the raw water is tap water containing chlorine, even if the chlorine is removed by the purified water manufacturing method of the present invention, chlorine is added to the purified water flowing out from the water purification device. Even when water that does not contain chlorine is used as raw water, chlorine can be added, resulting in excellent hygiene.

The domestic purified water obtained by the production method of the present invention includes domestic water used for cooking, washing, bathing, showering, and drinking water. In particular, the production method of the present invention is suitable for producing drinking water.

(2) Water purification apparatus The water purification apparatus for domestic use of the present invention is an apparatus used in the method for manufacturing water for domestic use of the present invention,
Raw water supply channel,
Raw water supply means that is disposed in the raw water supply path and feeds raw water,
A plurality of raw water branch paths that branch the raw water supply path into at least two or more;
A membrane module that is disposed in the plurality of raw water branches and includes a plurality of membrane means for filtering raw water;
A discharge path connected to a primary side of the plurality of membrane modules;
A plurality of water purification branches connected to the secondary side of the plurality of membrane modules;
A plurality of water purifying branches, and
The primary side of the membrane module is provided with means for supplying a nucleating agent to raw water, and is not provided with a separation tank for precipitating and separating aggregates generated by the addition of the nucleating agent.

In the embodiment in which the nucleating agent is added to the raw water, the nucleating agent contacts the impurity in the raw water, and the nucleating agent captures the impurity. The nucleating agent that has captured the impurity cannot pass through the membrane means, and is removed from the raw water together with the impurity. Means for supplying a nucleating agent comprising an aqueous dispersion of ferric hydroxide colloid particles having a weight average particle diameter of 5 nm to 160 nm is not particularly limited. For example, a tank for storing a nucleating agent, a nucleating agent, and the like. It is comprised from the liquid feeding means which supplies nucleating agent, and a nucleating agent supply path. In addition, the water purifier of this invention does not provide the separation tank which precipitates and isolate | separates the aggregate which generate | occur | produces by addition of a nucleating agent from a viewpoint of reducing in size.

It is preferable that the production apparatus for domestic water purification of the present invention is configured so that the membrane module can be back-washed. This is for removing clogging of the membrane module and supplying clean water stably for a long period of time. Hereinafter, the manufacturing apparatus of this invention is demonstrated based on the aspect of the central water purifier comprised so that back washing | cleaning is possible.

The central water purification apparatus 1 shown in FIG. 5 is disposed in the raw water supply path 3, the raw water supply path 3, a raw water supply means P <b> 1 that feeds the raw water, and a plurality of branches that branch the raw water supply path 3 into at least two or more A raw water branch 5A, 5B, a plurality of membrane modules 9A, 9B that are disposed in the plurality of raw water branches 5A, 5B and filter raw water, and membrane means 9c that filters the raw water included in the membrane modules 9A, 9B. Purified water where the discharge paths 7A and 7B connected to the primary side, the plurality of water purification branch paths 11A and 11B connected to the secondary side of the plurality of membrane modules 9A and 9B, and the plurality of water purification branch paths 11A and 11B merge. The passage 13 is provided with a tank 37 for storing a nucleating agent, and a supply means P3 for supplying the nucleating agent. In the present invention, the side on which raw water is supplied to the membrane means is referred to as the primary side, and the side from which the purified water is discharged from the membrane means is referred to as the secondary side.

The raw water supply path 3 supplies raw water to be subjected to purification treatment such as tap water and natural water. The raw water supply channel 3 is preferably connected to a raw water tank that stores tap water from a water main supplied to a building such as an apartment, an apartment, a building, a hotel, or a plurality of detached houses. It can also be connected directly to the main. The raw water supply path 3 is constituted by a pipe line having a predetermined pipe diameter. The raw water supply path 3 preferably includes an inflow valve (first valve V1) for opening and closing the raw water supply path 3. For example, the inflow valve may be a check valve.

In the raw water supply path 3, raw water supply means P1 for sending raw water is disposed. Examples of the raw water supply means P1 include a vertical multi-stage centrifugal pump, a horizontal multi-stage centrifugal pump, and a positive displacement pump. Among these, it is preferable to use a vertical multistage centrifugal pump as the raw water supply means P1 because the raw water is stably pressurized and fed.

The downstream end of the raw water supply path 3 is connected at the branch point 4 to the upstream ends of the raw water branch paths 5A and 5B that branch the raw water supply path 3 into a plurality. The raw water branch paths 5A and 5B are constituted by pipe lines having a predetermined pipe diameter. The raw water branch paths 5A and 5B include inflow valves (second valve V2 and third valve V3) for opening and closing the raw water branch paths 5A and 5B, respectively. The downstream ends of the raw water branch paths 5A and 5B are connected to membrane modules 9A and 9B that filter the raw water.

The membrane modules 9A and 9B remove foreign matters such as fine particles and turbidity in the raw water, and discharge purified water. The membrane modules 9A and 9B include membrane means 9c for filtering raw water and a cylindrical container 9d for housing the membrane means 9c. In the membrane modules 9A and 9B, the raw water region 9e to which raw water is supplied and the purified water filtered by the membrane means flow into the cylindrical container 9d with the membrane means 9c for filtering the raw water interposed therebetween. It is preferable to provide the purified water region 9f.

The membrane modules 9A and 9B are provided with a raw water inlet 9g and a purified water outlet 9h, and further with a concentrated water outlet 9i for discharging concentrated water. The raw water inlet 9g and the concentrated water outlet 9i are connected to the raw water area 9e of the membrane modules 9A and 9B, and the purified water outlet 9h is connected to the purified water area 9f of the membrane modules 9A and 9B.

The membrane module may be either an external pressure type or an internal pressure type, preferably an internal pressure type. As membrane means, it is preferable to use a hollow fiber membrane comprising an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane).

The water purifier of the present invention has means for supplying a nucleating agent. In the embodiment of FIG. 5, the means for supplying the nucleating agent includes a tank 37 for storing the nucleating agent, a supplying means P3 for supplying the nucleating agent, and a nucleating agent supply path 6. In the embodiment of FIG. 5, the nucleating agent is supplied to the raw water stored in the raw water tank 35. It is also preferable to provide the raw water tank 35 with a stirring function such as stirring by a stirring blade or stirring by a circulation pump. The stirring function can increase the contact efficiency between the nucleating agent and various ions, and can contribute to increasing the particle size of the nucleating agent. In addition, you may make it supply a nucleating agent directly to raw | natural water, for example in raw | natural water supply path 5A, 5B. Examples of the supply unit P3 include a vertical multistage centrifugal pump, a horizontal multistage centrifugal pump, and a positive displacement pump. The nucleating agent supply path 6 is composed of a pipe having a predetermined pipe diameter.

5 has the discharge paths 7A and 7B connected to the primary side of the membrane means 9c included in the membrane modules 9A and 9B. The discharge path is a flow path for discharging the backwash water when the membrane module is mainly backwashed. The said discharge path should just be connected to the upstream of the membrane means 9c with which membrane module 9A, 9B is equipped, for example, the aspect connected to the raw | natural water area | region 9e of membrane module 9A, 9B, it connects with raw | natural water branch 5A, 5B Or a mode of connecting to both the raw water region 9e of the membrane modules 9A and 9B and the raw water branch paths 5A and 5B.

5, one ends of the discharge paths 7A and 7B are connected to the concentrated water discharge ports 9i of the membrane modules 9A and 9B. The discharge passages 7A and 7B are preferably composed of pipe passages having a predetermined pipe diameter, and are provided with valves (fourth valve V4 and fifth valve V5) for opening and closing the respective passages. The discharge paths 7A and 7B may further merge.

The upstream ends of the purified water branch paths 11A and 11B are connected to the downstream side of the membrane modules 9A and 9B. The purified water branch paths 11A and 11B are connected to the purified water discharge port 9h of the membrane modules 9A and 9B. The downstream sides of the purified water branch paths 11A and 11B are formed so that the purified water branch paths 11A and 11B connected at the junction 17 and connected to the plurality of membrane modules communicate with each other. By connecting the purified water branch paths 11 </ b> A and 11 </ b> B, the purified water discharged from one membrane module can be made to flow backward to the other membrane module. The junction 17 is provided with a three-way cock 49 for switching the flow path. Instead of the three-way cock 49, an open / close valve for switching the flow path may be provided on the downstream side of the purified water branch paths 11A and 11B.

The raw water branch 5A and 5B are preferably provided with pressure gauges 14A and 14B for measuring the pressure of the raw water flowing in the raw water branch. Moreover, it is preferable that the pressure gauges 16A and 16B which measure the pressure of the purified water which flows through the inside of the purified water branch are provided in the purified water branches 11A and 11B.

The purified water path 13 is connected to the junction 17 of the purified water branch paths 11A and 11B. The water purification channel 13 is provided with a valve (eighth valve V8) for opening and closing the water purification channel 13. The water purification path 13 is composed of a pipe having a predetermined pipe diameter. It is preferable that the purified water path 13 is provided with a purified water discharge path 19 for discharging purified water. The purified water discharge path 19 is constituted by a pipeline having a predetermined pipe diameter, and includes a valve (a ninth valve V9) for opening and closing the purified water discharge path 19.

5 is preferably provided with a control means 21. The control means 21 preferably includes, for example, an inverter control unit 23, a valve control unit 25, a membrane differential pressure calculation unit 27, a display 29, a manual switch 31, a timer 33, and the like.

It is particularly preferable that the water purifier 1 in FIG. 5 has an inverter control unit 23 that controls the raw water supply means P1. It is preferable to control the raw water pressure supplied by the raw water supply means by controlling the raw water supply means P1 with an inverter. For example, the inverter control unit 23 controls the raw water supply means P1 so that the pressure of the raw water is substantially constant during the production of purified water, and controls the raw water supply means P1 so that the pressure of the raw water pulsates during the reverse cleaning operation. .

The membrane differential pressure calculation unit 27 receives the measurement values of the pressure gauges 14A, 14B, 16A, and 16B, and calculates the transmembrane pressure difference between the primary side and the secondary side of the membrane modules 9A and 9B. For example, the membrane differential pressure calculation unit 27 instructs the valve control unit 25 to switch the valve so as to perform the purified water production operation or the reverse cleaning operation in accordance with the data of the transmembrane differential pressure.

The valve control unit 25 opens and closes the valve based on manual switch operation data, transmembrane pressure data supplied by the membrane pressure calculation unit, time data supplied by a timer, and the like. The valve controller and each valve are preferably connected by wire or wirelessly.

For example, the timer 33 measures the time of the normal filtration operation and the time of the back washing operation, and when each operation time reaches a predetermined time, the water purification manufacturing operation or the back washing operation is performed on the valve control unit 25. Thus, it is possible to instruct switching of the valve.

The indicator 29 can display, for example, the pressure value received from the pressure gauge, the transmembrane pressure difference, the current operation process, and the like.

5 has a chemical tank 41 for adding a chemical solution such as hypochlorous acid or sodium hypochlorite to the purified water, and a pump P2 for feeding the chemical solution. In addition, in FIG. 5, although the purified water obtained by the purified water manufacturing apparatus 1 is shown in figure so that it may be supplied to the water receiving tank 45, the water receiving tank 45 is not necessarily required.

It is also preferable that the raw water tank 35 and the water receiving tank 45 include level meters L1 and L2. For example, based on the water level data of the raw water tank 35 measured by the level meter L1, the valve control unit 25 switches the valve so that the normal filtration operation and the reverse cleaning operation are switched when a certain amount of raw water is processed. You may be instructed.

In the embodiment of FIG. 5, the membrane module is described based on a form having the first membrane module 9A and the second membrane module 9B, but the number of membrane modules is preferably two or more. For example, the aspect which has two or more pairs of membrane module sets which consist of a 1st membrane module and a 2nd membrane module can be mentioned. Since the water purifier of the present invention has a plurality of pairs of membrane module sets each composed of a first membrane module and a second membrane module, the amount of raw water treated can be increased.

In the embodiment of FIG. 5, the purified water obtained from one membrane module in a filtered state is configured to be used as backwash water for another one membrane module to be backwashed. That is, the ratio of the number of membrane modules in a filtered state to the membrane module to be backwashed is 1: 1. However, the purified water obtained from a plurality of membrane modules in a filtered state may be merged and used as backwash water for one membrane module to be backwashed, or 1 in a filtered state. You may comprise so that the purified water obtained from one membrane module may be branched and used as the backwash water of the several membrane module used as the backwash object. However, in the case of membrane module in filtration state: membrane module to be backwashed = multiple: 1, the pressure of backwashing water becomes too high, and there is a risk of damaging the filtration membrane provided in the membrane module to be backwashed. . On the other hand, when the membrane module in the filtered state: the membrane module to be backwashed = 1: many, the pressure of backwashing water is lowered, so that the backwashing efficiency may be lowered. Therefore, it is preferable that the ratio of the number of membrane modules in a filtered state and the number of membrane modules to be backwashed is 1: 1.

The water purification apparatus of the present invention can be suitably used as a central water purification apparatus that can supply purified water to buildings such as apartments, apartments, buildings, hotels, and multiple houses. The amount of purified water supplied from the central water purification apparatus is appropriately set according to the number of supply destinations and the amount of water used. For example, assuming that one central water purification device is installed in one apartment building of 100 to 200 units, the supply amount of purified water of the central water purification device is preferably 3,000 L / hour or more, and 4,000 L / hour. More preferably, 5,000 L / hour or more is more preferred, 8,000 L / hour or less is preferred, 7,000 L / hour or less is more preferred, and 6,000 L / hour or less is more preferred.

Next, a specific example of a method for producing domestic clean water using the production apparatus of FIG. 5 will be described. The water purification method using the water purification apparatus of FIG. 5 supplies raw water in parallel to a plurality of membrane modules having at least a first membrane module and a second membrane module, and filters the raw water through the plurality of membrane modules. The purified water production process for producing purified water and supplying the raw water to one of the first membrane module or the second membrane module and filtering, and at least a part of the obtained purified water as backwash water, the other membrane module And a backwashing step of backwashing the other membrane module by backflowing from the downstream side to the upstream side.

FIG. 6 is a view showing a water flow state of the water purifier 1 of the present invention in the water purification production process. As shown in FIG. 6, in the water purification manufacturing process, the first to third valves V1 to V3 and the eighth valve V8 are released, and the fourth to seventh valves V4 to V7 and the ninth valve V9 are closed. Thus, a raw water treatment line is formed in which the raw water supply path 3, the raw water branch paths 5A and 5B, the purified water branch paths 11A and 11B, and the purified water path 13 communicate with each other through the membrane modules 9A and 9B. The valve opening / closing operation may be automatic control by the valve control unit or may be manually controlled.

The raw water supply means P1 preferably pressurizes the raw water and sends it to the raw water supply path. The pressure of the raw water is preferably set as appropriate according to the allowable pressure of the membrane module to be used. For example, in the case of an ultrafiltration membrane (UF membrane) and a microfiltration membrane (MF membrane), the allowable pressure is about 0.35 MPa, and the pressure Pf of the pressurized raw water is preferably 0.08 MPa or more, 0.13 MPa or more is more preferable, 0.15 MPa or more is more preferable, 0.35 MPa or less is preferable, 0.32 MPa or less is more preferable, and 0.30 MPa or less is more preferable. When the pressure Pf of the pressurized raw water exceeds the allowable pressure, the filtration membrane is easily damaged. Moreover, if the pressure Pf of the pressurized raw water is too low, the flow rate of the raw water is reduced. In the purified water production process, the pressure Pf of the raw water is preferably substantially constant.

The raw water branches at the branch point 4 and is supplied to the first and second membrane modules 9A and 9B through the raw water branch paths 5A and 5B. The raw water is filtered by the first and second membrane modules 9A and 9B. Foreign matter and turbidity contained in the raw water are removed by the membrane module. Impurities contained in the raw water (heavy metal ions, arsenic, fluorine, etc.) are captured by the nucleating agent and removed from the raw water by the membrane means. When the raw water is filtered by the first and second membrane modules 9A and 9B, the fourth and fifth valves V4 and V5 are opened, and the concentrated water is filtered while being discharged from the discharge passages 7A and 7B. A method may be adopted. Moreover, you may employ | adopt the dead end system which closes the 4th and 5th valve | bulb V4, V5, and filters raw | natural water. When the dead end method is adopted, foreign matter accumulates in the reservoirs in the membrane modules 9A and 9B, so the fourth and fifth valves V4 and V5 are occasionally released to discharge the foreign matter. It is preferable to do.

The purified water discharged from the first and second membrane modules 9A and 9B merges at the junction 17 through the purified water branch paths 11A and 11B, and flows out to the purified water path 13, respectively.

Next, the backwash process will be described. In the backwashing process, raw water is supplied to one of the first membrane module or the second membrane module and filtered, and at least a part of the obtained purified water is used as backwash water from the downstream side of the other membrane module. The other membrane module is back-washed by flowing back to the side.

Hereinafter, the case where the first membrane module is operated in the filtration state and the second membrane module is backwashed will be described in detail with reference to FIG. In order to place the first membrane module in the filtration state and the second membrane module in the backwash state, the first and second valves V1, V2, the fifth valve V5, and the eighth valve V8 are released, and the third, fourth, The sixth and seventh valves V3, V4, V6, V7 and the ninth valve V9 are closed. The valve opening / closing operation may be automatic control by the valve control unit or may be manually controlled. By this valve operation, a raw water treatment line is formed in which the raw water supply path 3, the raw water branch path 5A, the purified water branch path 11A, and the purified water path 13 communicate with each other through the membrane module 9A. Further, a backwash line is formed in which the purified water branch path 11B and the discharge path 7B communicate with each other via the second membrane module 9B.

At least a part of the purified water discharged from the first membrane module 9A flows back through the purified water branch 11B as backwash water, and passes from the purified water discharge port 9h downstream of the second membrane module 9B to the second membrane module 9B. invade. The backwash water that has entered the second membrane module 9B passes through the membrane means 9c disposed in the second membrane module 9B, and flows out from the upstream concentrated water discharge port 9i to the discharge path 7B. At this time, the foreign matter adhering to the membrane means 9c of the second membrane module 9B is released and flows out into the discharge path 7B together with the backwash water. The foreign matter adhering to the backwash water and the second membrane module 9B is discharged out of the water purifier from the discharge path 7B connected to the concentrated water discharge port 9i. The foreign matter adhering to the film means 9c includes a nucleating agent adhering to the film means 9c and an aggregate formed by the nucleating agent.

Further, the remaining portion of the purified water discharged from the first membrane module 9A flows out to the purified water channel 13. Thereby, it is possible to continue discharging a certain amount of purified water while backwashing the second membrane module 9B. Note that the eighth valve V8 may be closed and all the purified water discharged from the first membrane module 9A may be backwashed water.

In the above, a line in which the purified water branch path 11B, the second membrane module 9B, and the discharge path 7B communicate with each other is adopted as the backwash line. For example, the purified water branch path 11B, the raw water branch path 5B, and the discharge path 15B However, you may employ | adopt the line connected via the 2nd membrane module 9B.

In the reverse cleaning step, the raw water supply means P1 may supply the raw water to the first membrane module 9A while pulsating the water pressure of the raw water. Supplying the raw water to the first membrane module 9A while pulsating the water pressure of the raw water pulsates the purified water discharged from the first membrane module 9A, that is, the backwash water pressure, so that the reverse of the second membrane module 9B This is because the cleaning efficiency is increased. As a method of pulsating the water pressure of the raw water, for example, it is preferable to continuously change the rotation speed of the raw material supply means P1 by the inverter control unit 23.

Next, the case where the second membrane module 9B is operated in the filtration state and the first membrane module 9A is backwashed will be described with reference to FIG. In order to operate the second membrane module 9B in the filtration state and put the first membrane module 9A in the backwash state, the first, third valves V1, V3, the fourth valve V4, and the eighth valve V8 are released, The second, fifth, sixth, and seventh valves V2, V5, V6, V7, and the ninth valve V9 may be closed to perform the same operation. The valve opening / closing operation may be automatic control by the valve control unit or may be manually controlled. By this valve operation, a raw water treatment line is formed in which the raw water supply path 3, the raw water branch path 5B, the purified water branch path 11B, and the purified water path 13 communicate with each other through the second membrane module 9B. Moreover, the purified water branch path 11A and the discharge path 7A form a backwash line communicating with the first membrane module 9A.

In the above description, the backwash line in which the purified water branch path 11A and the discharge path 7A communicated with each other via the first membrane module 9A is adopted as the backwash line. For example, as the backwash line, the purified water branch path 11A and A line in which the raw water branch 5A and the discharge path 15A communicate with each other via the first membrane module 9A may be adopted.

The method for producing purified water of the present invention in which a nucleating agent is added to raw water and filtered through a membrane module provided with membrane means includes, for example, the following steps, and includes the following steps (2) to (4) as appropriate: It is preferable to carry out switching.
(1) Step of adding a nucleating agent to raw water (2) Purified water production step of filtering raw water through both the first membrane module and the second membrane module (3) The first membrane module is put into a filtered state, and the second membrane module (4) Backwashing process in which the second membrane module is in the filtered state and the first membrane module is in the backwashed state. For example, manual switch operation data, membrane differential pressure calculation This is preferably performed based on differential pressure data supplied by the unit, time data supplied by the timer, and the like.

What is necessary is just to set the operation time of a purified water manufacturing process suitably according to the quality of raw | natural water, a processing speed, etc. Therefore, the time of the water purification production process may vary from several minutes to several hours to several days. The time for the back washing step is, for example, preferably 30 seconds or more, more preferably 1 minute or more, particularly preferably 5 minutes or more, preferably 20 minutes or less, more preferably 10 minutes or less, and particularly preferably 7 minutes or less.

As described above, the present invention has been described based on preferred embodiments, but the present invention is not limited to the above-described embodiments, and the shape, configuration, arrangement, and the like of each embodiment are within the scope of the present invention. Materials, processes, and the like can be changed as appropriate. In addition, the definitions of the configuration, arrangement, material, shape, numerical range, process, and the like shown in each embodiment can be applied independently or in combination of any two or more rules.

Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and all modifications and embodiments without departing from the gist of the present invention are not limited thereto. Included in range.

[Synthesis of nucleating agent (aqueous dispersion of ferric hydroxide colloidal particles)]
Prepare ferric chloride, sodium hydroxide, and water as raw materials, adjust the pH after mixing to around 2.5, and adjust the concentration to 5,000 mg / L in terms of iron concentration. An aqueous dispersion of viscosity was obtained.
[Particle size control of nucleating agent]
The weight average particle diameter of the nucleating agent was proportional to the ratio of ferric chloride and was controlled by the mixing ratio of ferric chloride and sodium hydroxide.
[Flocculant]
As comparative flocculants, the following commercial products were used.
Flocculant 1: Polyglutamic acid-based flocculant Flocculant 2: Polyglutamic acid-based flocculant (including magnetic substance)
Flocculant 3: Inorganic flocculant (mainly Shirasu)
Coagulant 4: Calcium salt type coagulant Coagulant 5: Zeolite type coagulant

[Metal removal test]
(1) Removal test for various metals A nucleating agent (an aqueous dispersion of ferric hydroxide colloid particles having a weight average particle diameter of about 10 nm) was added to 50 mL of raw water in which various metal components were adjusted to predetermined concentrations. . The nucleating agent was added so that the total iron concentration relative to the raw water was 0.6 mg / L. After the nucleating agent was added, the liquid to be treated was stirred for 1 minute to generate aggregates. Thereafter, the liquid to be treated was filtered through a filter membrane (filter paper: Advantec No. 2, pore size: 5 μm), and the removal rate was calculated. The calculated removal rate is shown in Table 2. In the filtration experiment using filter paper, metal components contained in the raw water may be adsorbed on the filter paper. Therefore, the entire removal rate including the filter paper and a blank test without adding the nucleating agent were performed, and the removal rate (only chemicals) excluding the influence of the filter paper was shown. This result shows that the nucleating agent used in the present invention can remove various metals.

(2) Comparative test of nucleating agent and flocculant To 50 mL of raw water adjusted to a metal concentration of 0.02 mg / L, a nucleating agent (an aqueous dispersion of ferric hydroxide colloid particles having a weight average particle diameter of about 10 nm). And flocculants 1-5 were added respectively. The addition amount of the flocculant was set to 0.6 mg / L, and the addition amount of the nucleating agent was set to 0.6 mg / L at the total iron concentration. After adding the nucleating agent and the flocculant, the mixed solution was stirred for 1 minute to generate agglomerates. Thereafter, the liquid to be treated was filtered through a filtration membrane (Advantec No. 2: pore size: 5 μm), and the removal rate and removal load index were calculated. The removal load index is a comprehensive index for determining filtration performance expressed by the concentration difference before and after the filtration process × the treatment amount. As and Cd were used as heavy metals. The heavy metal concentration and the removal load index before and after the filtration treatment are shown in FIGS. The removal rate of heavy metals is shown in Table 3. In a filtration experiment using filter paper, heavy metals contained in raw water may be adsorbed on the filter paper. Therefore, the overall removal rate including the filter paper and the blank test without adding the nucleating agent and the flocculant showed the removal rate (chemicals only) excluding the influence of the filter paper.

Looking at the results of the removal load index indicating the overall heavy metal removal performance, the nucleating agent used in the present invention shows a higher removal performance than the flocculants 1-5.

(3) About the influence of pH The purified water was manufactured using the experimental machine which combined the nucleating agent supply means and the ultrafiltration membrane (UF membrane). That is, in the raw water tank, the raw water whose metal concentration was adjusted to 0.02 mg / L was adjusted to pH 5.5, 6.5, 7.5, and 8.5, respectively. Thereafter, a nucleating agent (an aqueous dispersion of ferric hydroxide colloidal particles having a weight average particle diameter of about 10 nm) is added from the nucleating agent storage tank to a total iron concentration of 0.12 mg / L, 0.36 mg / L. , 0.6 mg / L was added to the raw water, and the liquid to be treated was stirred for 2 minutes to generate aggregates. The liquid to be treated was filtered using a UF membrane (Membrane Tensha, pore size: about 100 nm) under the following conditions.
・ Transmembrane differential pressure = 0.11 MPa
・ Primary pressure = 0.24 MPa
・ Secondary pressure = 0.13 MPa
The ratio of the filtration amount V to the total filtration area S of the membrane means (V / S) = 0.08 m / hr

As the heavy metal, As and Pb were used, and the removal rate was calculated. FIG. 13: is a graph showing the relationship between the pH of raw | natural water and the heavy metal density | concentration in the purified water after a filtration process about As. FIG. 14 is a graph showing the relationship between the pH of raw water and the concentration of heavy metals in purified water after filtration for Pb. From the results of FIG. 13, it can be seen that the removal effect is obtained at pH 8.5, and the removal effect of As is higher when the pH is lower than 8.5. Moreover, it can be seen from the results of FIG. 14 that the effect of removing Pb is higher when the pH is higher than 5.5.

(4) About the weight average particle diameter of the nucleating agent In the raw water whose As concentration was adjusted to 0.02 mg / L, the nucleating agent was added to the total iron concentration of 0.12 mg / L, 0.36 mg / L, 0.6 mg. / L was added, and the liquid to be treated was stirred for 1 minute to generate aggregates. The liquid to be treated was filtered through a filtration membrane (Advantec No. 2: pore size: 5 μm), and the removal rate was calculated. As the nucleating agent, those having a weight average particle size of 15 nm, 25 nm, 50 nm, and 160 nm were used. FIG. 15 is a graph showing the relationship between the As removal rate and the weight average particle size of the nucleating agent. It can be seen that the nucleating agent used in the present invention exhibits a high removal rate for As when the weight average particle diameter is in the range of 15 nm to 160 nm.

The central water purification apparatus of the present invention is small in size, can efficiently remove impurities such as heavy metal ions and arsenic, and has high backwashing efficiency. The central water purification apparatus of this invention is suitable as a water purification apparatus which supplies purified water to the whole building, such as a condominium and a building.

1: Water purification device, 3: Raw water supply path, 5A, 5B: Raw water branch path, 7A, 7B: Discharge path, 9A, 9B: Membrane module, 11A, 11B: Purified water branch path, 13: Clean water path, P1: Raw water supply Means 18: Pressure gauge

Claims (12)

1. A method for producing clean water for daily life, in which a nucleating agent is added to raw water and filtered by a membrane means, wherein water dispersion of colloidal particles of ferric hydroxide having a weight average particle diameter of 5 nm to 160 nm is used as the nucleating agent The ratio of the mass of iron in the aqueous dispersion of ferric hydroxide colloidal particles to the total mass of iron added to the raw water is made 0.9 or more using Method.
2. The method for producing purified water for daily use according to claim 1, wherein the nucleating agent captures ionic impurities contained in raw water to form aggregates, and the aggregates are filtered by a membrane means.
3. The method for producing purified water for daily life according to claim 1 or 2, wherein raw water added with a nucleating agent is directly supplied to a membrane means and filtered.
4. The method for producing domestic purified water according to any one of claims 1 to 3, wherein the raw water is natural water or tap water, and the domestic purified water is drinking water.
5. The method for producing purified water for daily use according to any one of claims 1 to 4, wherein the ionic impurity is a heavy metal ion.
6. The method for producing purified water for daily use according to any one of claims 1 to 5, wherein an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane) is used as the membrane means.
7. The method for producing clean water for daily use according to any one of claims 1 to 6, wherein the amount of the nucleating agent added to the raw water is 0.12 mg / L or more and 9 mg / L or less in terms of total iron concentration.
8. The method for producing clean water for daily use according to any one of claims 1 to 7, wherein the transmembrane pressure difference of the membrane means is more than 0.03 MPa and 0.45 MPa or less.
9. The method for producing water for daily life according to any one of claims 1 to 8, wherein the primary pressure of the membrane means is 0.08 MPa to 0.50 MPa.
10. The method for producing purified water for daily use according to any one of claims 1 to 9, wherein the secondary pressure of the membrane means is 0.05 MPa to 0.30 MPa.
11. The method for producing clean water for daily use according to any one of claims 1 to 10, wherein the filtration method is a total amount filtration method.
12. An apparatus used in the method for producing water for daily life according to any one of claims 1 to 11,
    Raw water supply channel,
    Raw water supply means that is disposed in the raw water supply path and feeds raw water,
    A plurality of raw water branch paths that branch the raw water supply path into at least two or more;
    A membrane module that is disposed in the plurality of raw water branches and includes a plurality of membrane means for filtering raw water;
    A discharge path connected to a primary side of the plurality of membrane modules;
    A plurality of water purification branches connected to the secondary side of the plurality of membrane modules;
    A plurality of water purifying branches, and
    Purifying water for daily use comprising a means for supplying a nucleating agent to the raw water on the primary side of the membrane module, and no separation tank for precipitating and separating aggregates generated by the addition of the nucleating agent. Manufacturing equipment.

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