KR100762008B1 - Water-treatment system of improved recovery rate - Google Patents

Abstract

A water treatment system which substantially increases the recovery ratio of contained salts, relieves a concentration polarization phenomenon of a membrane, and increases the treatment capacity at the same time by supplying the retreated concentrated water together with raw water to the membrane apparatus again after retreating a portion of concentrated water passing through a membrane apparatus in a non-filtration type salt recovery apparatus is provided. As a water treatment system for improving the recovery ratio of a membrane apparatus, the water treatment system comprises: a pump that provides a drive force for flowing raw water; a pre-treatment filter for eliminating contaminants contained in raw water; a non-filtration type salt recovery apparatus; and a filtration type membrane apparatus, wherein the water treatment system is constructed in such a structure that the retreated concentrated water together with raw water passing through the pre-treatment filter flow into the membrane apparatus again after retreating a portion of concentrated water passing through the membrane apparatus in the salt recovery apparatus such that the salt concentration of the portion of concentrated water is lowered. The membrane apparatus, as an apparatus for removing salts contained in raw water, includes a laminated structure of a graphite sheet, a polymer membrane containing a carbon-based material, and a spacer, and a minute voltage is applied to the graphite sheet.

Description

Water-treatment System of Improved Recovery Rate

1 is a flow chart of a water treatment apparatus according to one embodiment of the present invention.

The present invention relates to a water treatment apparatus with improved recovery rate, and more particularly, to increase the recovery rate of salts in a membrane facility, by introducing a portion of the concentrated water generated during operation of the membrane facility into a non-filtration type salt recovery device. The present invention relates to a water treatment device that improves the recovery rate of a membrane facility by dropping (TDS: Total dissolved solids) and then flowing the raw water back into the membrane device together with raw water.

Although a water treatment apparatus using a separation membrane facility can selectively separate wastewater using less energy, it is not widely used to spread the membrane separation process due to separation membrane contamination that degrades the performance of the membrane. Membrane contamination is a phenomenon in which suspended solids contained in waste water or substances having a property of being easily adsorbed on the surface of the membrane accumulate on the membrane surface and the pore size, which impedes the flow of fluid and thereby reduces permeability.

In general, one of the problems occurring in the membrane separation process is a decrease in permeability, which can be classified into two types. First, the separation function is impaired due to the decrease of permeability due to the contamination of the membrane and the change of the characteristics of the membrane. Second, the concentration of solute at the membrane surface increases as the solution passes through the membrane due to concentration polarization. It is the case to decrease.

When pressure is applied in the membrane separation process, the solute does not pass through the membrane but the solvent freely passes through the membrane. That is, a high concentration of solute stays in the solution at the boundary of the separation membrane and a relatively low concentration of solute layer exists in the permeate. If the solute is continuously concentrated on the membrane surface, the permeability decreases due to an increase in the osmotic pressure due to the high concentration of the solute layer on the membrane surface. In addition, the membrane selectivity and solvent permeability are affected.

As a result, since the effective permeation pressure is reduced to cause a decrease in transmittance, various methods of preventing concentration polarization should be applied to minimize the decrease in transmittance. In addition, the contamination of the membrane may permanently reduce the permeability of the membrane due to the strong binding and accumulation of contaminants on the membrane surface according to the characteristics of the raw water, and also changes the properties of the membrane to change the separation ability.

Some techniques for solving the above problems are known, and as a technique for removing salt concentration, evaporation, ion exchange resin, electrodialysis, activated carbon adsorption, etc. have been developed and are currently being studied.

However, these methods are expensive and most of the processes are economically expensive to apply to the membrane installation, and there is a limitation in practical use. Also, the techniques focus on the efficient removal of salts rather than increasing the recovery rate of salts.

Therefore, there is an urgent need for a technology capable of efficiently increasing the recovery rate of salts while lowering the cost of the process.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After in-depth research and various experiments, the inventors induced a portion of the concentrated water generated during operation of the membrane facility to a non-filtration salt recovery device to reduce the salt concentration (TDS: Total dissolved solids). By reflowing into the separator together, it was confirmed that the concentration polarization phenomenon could be alleviated and the recovery rate of the salts could be significantly improved, thereby completing the present invention.

Accordingly, the water treatment device according to the present invention is a water treatment device that improves the recovery rate of the membrane facility, a pump for providing a driving force for the flow of raw water, a filter for pretreatment to remove contaminants in the raw water, a non-filtration type salt recovery device, And a filtration separator, wherein a part of the concentrated water that has passed through the separator is combined with the raw water that has passed through the filter for pretreatment after retreatment to reduce the salt concentration (TDS: Total dissolved solids) in the salt recovery apparatus. It is characterized in that it is configured to be re-introduced into the separator device.

According to the present invention, a portion of the concentrated water generated during operation of the membrane facility is led to a non-filtration type salt recovery device to reduce the salt concentration, and then flows back into the membrane device together with the raw water, thereby reducing the concentration polarization phenomenon in the membrane device. The recovery rate of salt can be improved, reducing the load at the time of operating a membrane apparatus, such as suppressing.

The pump acts as a driving source for providing a solution flow in the water treatment device, in addition to the primary pump for supplying the raw water to the pretreatment filter, a high pressure pump for introducing the solution passed through the pretreatment filter into the membrane device, etc. may be used. By installing a flow meter to control the working pressure of the pump can be adjusted the flow of the solution.

The pretreatment filter serves to filter particulate matter or suspended matter of a predetermined size or more, and may select a filter having a porosity of various sizes depending on the intended use. The filter for pretreatment is generally used as a physical filtration member by selecting a material having no chemical reactivity.

The separator device is a device for removing salt in raw water, and in one preferred embodiment, the separator comprises: (i) a graphite sheet, (ii) a polymer separator comprising a carbon-based material, and (iii) a stacked structure of spacers. In addition, a small voltage is applied to the graphite sheet. Specifically, the graphite sheet is used as an electrode member for applying an electric current, and the graphite sheets stacked between the carbon-based polymer separators alternately serve as an anode and a cathode, and a uniform potential difference throughout the separator device is repeatedly. Will occur. The carbon-based polymer membrane serves to filter the organic / inorganic material introduced by adsorbing the ionic material induced according to the polarity due to the potential difference supplied to the membrane. On the other hand, the spacer serves as a passage through which the inflow solution flows between the flat membrane of the laminated structure, and when the spacer having a non-reactive network material between the membrane and the surface of the membrane is inserted, the vortex increases the material transfer Promotes and reduces concentration polarization.

Briefly described the operating principle of the water treatment device according to the present invention.

Raw water containing contaminants is subjected to physical filtration while passing through the pretreatment filter by the driving force of the pump, and then, the salt contained in the filter is filtered through the membrane device. In the process of passing the raw water through the membrane device, the salt is divided into the treated water from which the salt is removed and the concentrated water including the salt of high concentration, among which the treated water is used as the process water for the desired use or purpose, and the concentrated water is separately After the post-treatment process, the contained salt is recovered.

Some of the concentrated water is directed to a non-filtration salt recovery device. The concentrated water induced by the salt recovery device has a low salt concentration (TDS: Total dissolved solids) through a series of salt recovery processes, and then merges with the raw water and flows back into the membrane device to concentrate the concentration of the membrane device. It also reduces polarization and improves the recovery of salts throughout the device.

In the water treatment apparatus according to the present invention, when the non-filtration type salt recovery apparatus is not used, the resolution of the membrane apparatus must be increased to increase the salt recovery rate, and a larger amount of the membrane must be used to improve the resolution. As a result, the processing cost increases. In addition, since a large amount of salt must be treated in one process, the concentration polarization of the salt is deteriorated and the effective pressure is increased, resulting in an increase in load on the membrane facility and a decrease in processing capacity.

The salt recovery device is a device for recovering salt without using a filtration method, and does not require a high level of salt resolution. In other words, the salt recovery device is an auxiliary facility for the membrane device to increase the recovery rate, and serves to lower the total dissolved solids (TDS) to a certain level by reprocessing the concentrated water containing a high concentration of salt through the membrane device. do. Since no filtration method is required, no additional components such as ion exchange resins are required, and some salts are recovered from a highly concentrated solution, which does not require a large amount of energy, thereby achieving high recovery rates at low processing costs. Can be.

As a preferable example of the salt recovery device, there is a non-filtration electrosorption and desorption device based on the application of a small voltage.

The electrosorption and desorption device operates by applying a minute voltage from a DC power supply device through an electrode to adsorb ions to ionic organic / inorganic materials. One or more electrodes having a (+) potential and a (-) potential are placed in the reactor, respectively, and the introduced solution is selectively adsorbed as it passes between the electrodes. When adsorption is saturated on the electrodes, the adsorbed material is desorbed and removed by applying an opposite potential to each electrode.

The minute voltage may be variously selected within a range of 1.2 V or less. If the applied voltage is less than 1.2V, the driving force for adsorbing the ions to the ionic organic / inorganic substance is weak, and efficient salt recovery is not achieved. On the contrary, if the voltage exceeds 1.2V, the phase change or electrolysis of the incoming material is performed. This is undesirable because it may change the properties of the material and may require a large amount of energy, resulting in a problem of low efficiency.

The electrode is preferably an activated carbon electrode. Activated carbon has a high porosity, which is excellent in adsorbing materials, and has excellent resistance to rapid changes in external environment such as temperature and pH, and thus can be used as an excellent adsorbent.

Another example of the non-filtration type salt recovery device is a device for agglomeration and precipitation of salts by adding a predetermined amount of flocculant.

In general, the colloidal components have a negative charge, and due to mutual (-) charge, they collide with each other and exist in the water in a stable dispersed state. Therefore, the stable state of the colloid can be broken down, and they can be brought into contact with each other and aggregated to manipulate the colloid destabilization and aggregate.

Specifically, the neutralization of the charge on the surface of the particles to be aggregated by administering a positively charged flocculant causes the particles that have lost the electrical repulsive force to come into contact with each other and bind by attraction force. Through this binding method, precipitation occurs as the particles grow, and can be separated by collecting the precipitated material.

Therefore, the coagulant may be used without limitation as long as it has a material capable of neutralizing the charge of the colloid to agglomerate and a crosslinking ability to bond the colloid particles to each other. Coagulants which are widely used in general are metal salts, such as aluminum salts, iron salts, which are easily hydrolyzed to form a positively charged hydroxide polymer.

When a metal salt such as aluminum or iron is used as a flocculant, the effect of the flocculant varies greatly depending on the pH of the water. Therefore, in some cases, a substance capable of buffering the pH change of water may be added. That is, since the metal salt is generally a weak acid, when it is administered to water, the pH of the water to be treated is lowered, and when the pH is lower than necessary, the ability of the coagulant is weakened, so that the alkali salt (caustic soda) is maintained. , Slaked lime, calcium carbonate, and the like). Such drugs are called alkali adjuvants (pH regulators).

In the concentrated water discharged from the membrane device, the amount circulated to the salt recovery device may vary depending on the concentration of the concentrated water, the amount of the concentrated water, the specific configuration conditions of the membrane device and the salt recovery device, and the like. It may be 10 to 90% by volume, preferably 30 to 70% by volume.

The operating principle of the water treatment apparatus according to one embodiment of the present invention is further described with reference to FIG. 1, but the scope of the present invention is not limited thereto.

Referring to FIG. 1, raw water stored in the first reservoir is sent to a micro filter which is a filter for pretreatment through a feed pump. In microfilters, it acts as a physical filtration device that filters materials above several microns. The pretreated solution is supplied to the membrane device via a high pressure pump. The separator device includes a laminate structure of a graphite sheet, a polymer separator including a carbon-based material (carbon-based separator), and a spacer, and a minute voltage is applied to the graphite sheet to remove salts.

Most of the salt contained in the solution is filtered while passing through the membrane device, the treated water in which the salt is removed flows into the second reservoir, and the concentrated water containing the salt in a high concentration flows into the third reservoir and dried. The process of recovering salts is carried out through the process.

Part of the concentrated water is introduced into the non-filtration type salt recovery device is subjected to a reprocessing process, during which the salt concentration of the concentrated water is significantly reduced. After the reprocessing process, the concentrated water is combined with the raw water through a high pressure pump and flows back into the membrane device, and most of the salt is recovered while passing through the membrane device.

As an example, when the salt concentration of the raw water discharged from the micro filter is 1000, the treated water passing through the membrane device has a salt concentration of 10 and the concentrated water has a salt concentration of 990. Among them, the concentrated water circulated to the non-filtration salt recovery device is lowered to salt concentration 500 while passing through the salt recovery device, and when mixed with raw water discharged from the micro filter, the membrane concentration is increased to 1300 salt concentration. Flows into.

Although described above with reference to the drawings according to an embodiment of the present invention, those of ordinary skill in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the water treatment apparatus according to the present invention is to re-process a portion of the concentrated water passing through the membrane device in a non-filtration salt recovery device, and then supplied back to the membrane device with the raw water, thereby recovering the contained salt At the same time, the concentration polarization phenomenon of the membrane can be alleviated and treatment capacity can be increased.

Claims (7)

A water treatment device that improves the recovery rate of the membrane facility, which includes a pump providing driving force for the flow of raw water, a pretreatment filter for removing contaminants in the raw water, a non-filtration salt recovery device, and a filtration separation device. And a portion of the concentrated water that has passed through the membrane device is configured to be re-introduced into the membrane device together with the raw water that has passed through the pretreatment filter after the reprocessing to reduce the salt concentration in the salt recovery device. According to claim 1, wherein the separator device is a device for removing the salt in the raw water, comprising a laminated structure of a graphite sheet, a polymer separator comprising a carbon-based material, and a spacer, the minute voltage is applied to the graphite sheet It is comprised, The water treatment apparatus characterized by the above-mentioned. The water treatment apparatus according to claim 1, wherein the salt recovery apparatus is a non-filtration type electrosorption and desorption apparatus based on the application of a small voltage. The water treatment device according to claim 3, wherein the minute voltage is 1.2 V or less. The water treatment apparatus according to claim 3, wherein the salt recovery apparatus uses an activated carbon electrode. The water treatment apparatus according to claim 1, wherein the salt recovery apparatus is an apparatus for agglomeration and precipitation of salts by adding a predetermined amount of flocculant. The water treatment apparatus according to claim 1, wherein the amount of the concentrated water discharged from the separator device circulated to the salt recovery device is 10 to 90% by volume of the discharged concentrated water.

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