WO2002076587A1

WO2002076587A1 - Reverse osmosis water purification apparatus for coercive circulation of concentrate

Info

Publication number: WO2002076587A1
Application number: PCT/KR2002/000537
Authority: WO
Inventors: Yong-Chae Jang
Original assignee: Aquatech Asia Co., Ltd.
Priority date: 2001-03-27
Filing date: 2002-03-27
Publication date: 2002-10-03
Also published as: KR20020076197A

Abstract

Disclosed is a reverse osmosis water purification system including means for compulsory circulation of a concentrate stream. The system includes: a reverse osmosis membrane unit having a feed inlet for supplying a feed water stream, a circulating inlet for supplying a circulating water stream, a reverse osmosis membrane for purifying the feed water stream supplied through the feed inlet and the circulating water stream supplied through the circulating inlet, a product outlet for discharging a product water stream purified by the reverse osmosis membrane, and a concentrate outlet for discharging the concentrate stream that has not been purified in the reverse osmosis membrane; and a circulation pump for pressurizing and circulating the concentrate stream discharged to the concentrate outlet to the circulating inlet of the reverse osmosis membrane filter. The apparatus of the present invention is capable of increasing the ratio of product water to feed water, reducing system size and preventing the propagation of germs and bacteria by eliminating the need of a holding tank, and decreasing the quantity of water consumption compared to purified product water.

Description

REVERSE OSMOSIS WATER PURIFICATION APPARATUS FOR

COERCIVE CIRCULATION OF CONCENTRATE

Technical Field

The present invention relates to a water purification system, and more particularly, to a reverse osmosis water purification system including means for compulsorily circulating concentrate water rejected by the reverse osmosis membrane. The water purification system of the present invention can increase the ratio of product water to feed water significantly, thereby reducing the volume of feed water necessary to generate the same amount of purified water compared to the conventional purification system.

Background Art

In recent years, the installation of purification systems providing filtered water has become increasingly popular at households or businesses. With its own purification means, the purification system is generally adapted to purify raw water from a water pipe in an appropriate way and to store the purified water in a water storage tank.

Among the many available types of water purification systems, the reverse osmosis system is one of the most widely used and is commercially available, since it is well known that such a filter system has some advantages over other types of purification systems both in it's efficiency and management. FIG. 1 shows a block diagram of a constitution of a conventional reverse osmosis water purification system. In the figure, reference numeral

10 represents a sediment filter, 20 a boosting pump, 30 a pre-carbon filter, 40 a reverse osmosis membrane filter, 50 a post-carbon filter, and 60 a water storage tank. And, 'D₀' denotes a raw water stream, 'D_F' a feed water stream, 'D_P' a product water stream, and 'D_c' a concentrate stream.

Here, the sediment filter 10 and the pre-carbon filter 30 are often collectively defined as a pre-processor, and the post-carbon filter 50 as a postprocessor. Usually, the sediment filter 10 is directly connected to a feed water pipe

71 at the front end of the purification system, and a product water storage tank 60 is connected to a product water pipe 78 at the rear end. The sediment filter 10 removes relatively large sized particles such as dusts, sands, rust and the like contained in the raw water stream D₀, thereby protecting the reverse osmosis membrane filter 40 from the mechanical damages caused by these particulates. The pre-carbon filter 30 functions to absorb and remove contaminants such as chlorine and organic compounds from the liquid stream.

The boosting pump 20 serves to generate water stream of a desired flow rate and pressure and can be connected either between the sediment filter and pre-carbon filter or after the pre-carbon filter before the reverse osmosis membrane. The reverse osmosis membrane unit 40 functions to separate and remove contaminants such as germs, bacteria, fine particles, and heavy metals from water. By applying reverse osmotic pressure to semipermeable membranes, the system can purify water efficiently in a simple manner. The post-carbon filter50 or other types of post-processor removes impurities such as chlorine, smell or odor still remaining in the product water stream D_P that has passed through the reverse osmosis membrane unit 40. In the conventional purification system, the concentrate stream D_c exiting from the reverse osmosis membrane unit 40 is usually discarded.

FIG. 2 shows a schematic diagram of the parts of the conventional purification system presented in FIG. 1. As shown in the figure, the sediment filter 10, the boosting pump 20, the pre-carbon filter 30, the reverse osmosis membrane filter 40, the post-carbon filter 50, and the water storage tank 60 are integrally contained in the housing of the purification system. The product water purified by the above filter unit is usually retained in the product water storage tank 60 and then is withdrawn, whenever desired.

FIG. 3 shows the structure a commonly used reverse osmosis membrane, which is a spiral wound type. In the figure, reference numeral 43 represents an active layer or a reverse osmosis membrane, 44 a product collection pipe, 45 a permeating spacer, and 46 a feed spacer; and, 'D_F' the feed water stream, 'D_P' the product water stream, and 'D_c' the concentrate stream.

In this example, the reverse osmosis membrane filter is configured in such a manner that the permeating spacer 45 is inserted between the active layers 43 and then sealed. The feed spacer 46 is spread on the outer surface of the active layer 43, and the reverse osmosis membrane filter is spirally wound around the product collection pipe 44 and is mounted in the housing.

The feed water stream D_F supplied in the reverse osmosis membrane flows around the feed spacer 46 that is spread on the outer surface of the active layer 43. A part of the feed water D_F supplied to the reverse osmosis membrane filter passes through the active layer 43 and flows around the permeating spacer 45 in the interior of the active layer 43 such that it is collected by the product collection pipe 44. The water in the product collection pipe 44 is the product water stream D_P. Alternatively, the feed water stream D_F that has not passed through the active layer 43 flows around the feed spacer 46 and is then discharged as the concentrate D_c. In this type of filter unit, the feed spacer

46 activates the formation of turbulence on the surface of the active layer 46, thus reducing the concentration polarization.

As pure water permeates through the reverse osmosis membrane, concentration polarization tends to cause membrane fouling. By causing a larger flow of water to pass across the membrane surface, the effect of the turbulence helps to prevent concentration polarization and extend membrane life. For this reason, the ratio of filtered pure water to concentrate is such that the majority of feed water is sent to drain in the form of concentrate in the conventional reverse osmosis system. Typical membrane recovery (percent of feed which becomes product) is about 25%.

In other words, in the conventional purification system, about three times of the amount of product water obtained is discarded in order to generate enough turbulence of the liquid on the membrane surface to prevent concentration polarization and membrane fouling. FIG. 4 shows a mechanism of water purification by membrane filter unit of FIG. 3. In the figure, reference numeral 42 represents a boundary layer, 43 the active layer (or the reverse osmosis membrane), 44 the product collection pipe, and 46 the feed spacer. 'D_F' means the feed water stream, 'D_P' the product water stream and 'D_c' the concentrate stream. The feed water stream D_F flows in parallel to the active layer 43, and the product water stream D_P flows in a vertical direction to the active layer 43.

Therefore, the solutes contained in the feed water stream D_F are accumulated on the active layer 43, resulting in formation of the boundary layer 42. This formation of the boundary layer 42 is called as the "concentration polarization", and this decreases membrane performance by influencing the flux and the rejection ratio. Therefore, in the conventional purification system, it is necessary for a predetermined amount of D_c to flow across the membrane surface to maintain turbulence to prevent concentration polarization. In current application, this flow is usually discarded to drain in entirety.

Disclosure of Invention

It is an object of the present invention to provide a reverse osmosis water purification system including means for compulsory circulation of concentrate water which is capable of forcibly recirculating a concentrate stream exiting from a reverse osmosis membrane unit such that a volume of waste in relation to the feed water can be decreased.

According to a preferred embodiment of the first feature of the present invention, there is provided a reverse osmosis water purification system including means for compulsory circulation of a concentrate stream which comprises: a reverse osmosis. membrane unit having a feed inlet for supplying a feed water stream, a circulating inlet for supplying a circulating water stream, a reverse osmosis membrane for purifying the feed water stream supplied through the feed inlet and the circulating water stream supplied through the circulating inlet, a product outlet for discharging a product water stream purified by the reverse osmosis membrane, and a concentrate outlet for discharging the concentrate stream that has not been purified in the reverse osmosis membrane; and a circulation pump for pressurizing and circulating the concentrate stream discharged to the concentration outlet to the circulating inlet of the reverse osmosis membrane filter unit.

In the present invention, the majority of the concentrate stream is circulated by the circulation means and the minority of the concentrate is discharged. The cross-flow or turbulence generated by this extra amount of water stream is used to remove the solutes. This prevents solute accumulation on the surface of the membrane and as a result, the concentration polarization is dramatically reduced. In the preferred embodiment of the first feature of the present invention, the concentrate outlet of the reverse osmosis membrane filter unit is connected to a drain restrictor to adjust the quantity of the concentrate stream discharged from the concentrate outlet.

In the preferred embodiment of the first feature of the present invention, the circulation pump is adapted to pressurize and circulate the concentrate stream discharged from the concentrate outlet of the reverse osmosis membrane filter unit and supply the pressurized concentrate stream to the circulating inlet of the reverse osmosis membrane filter unit.

In the preferred embodiment of the first feature of the present invention, the feed inlet of the reverse osmosis membrane filter is connected to a preprocessor such as a sediment filter and/or a pre-carbon filter to first purify the feed water before it enters the membrane unit.

In the preferred embodiment of the first feature of the present invention, the product outlet of the reverse osmosis membrane filter is connected to a postprocessor such as a post-carbon filter to further purify the product water from the product outlet. According to a preferred embodiment of the second feature of the present invention, there is provided a reverse osmosis purification system including means for a compulsory circulation of a concentrate sfream, which comprises: a reverse osmosis membrane filter unit having a feed inlet for supplying a feed water stream, a circulating inlet for supplying a circulating water stream, a reverse osmosis membrane for purifying the feed water sfream supplied through the feed inlet and the circulating water stream supplied through the circulating inlet, a product outlet for discharging a product water stream purified by the reverse osmosis membrane, and a concentrate outlet for discharging the concentrate stream that has not been purified by the reverse osmosis membrane; a circulation pump for pressurizing and circulating the concentrate stream discharged to the concentrate outlet to the circulating inlet of the reverse osmosis membrane filter unit; and a boosting pump for boosting the feed water stream supplied to the feed inlet to supply the boosted feed water stream to the feed inlet of the reverse osmosis membrane filter unit. In the preferred embodiment of the second feature of the present invention, the concenfrate outlet of the reverse osmosis membrane filter unit is connected to a drain restrictor to adjust the quantity of the concentrate stream discharged from the concentrate outlet.

In the preferred embodiment of the second feature of the present invention, the circulation pump is adapted to pressurize and circulate the concentrate stream discharged from the concentrate outlet of the reverse osmosis membrane unit and supply the pressurized concentrate sfream to the circulating inlet of the reverse osmosis membrane filter unit.

In the preferred embodiment of the second feature of the present invention, the feed inlet of the reverse osmosis membrane is connected to preprocessor such as a sediment filter and/or a pre-carbon filter at the inlet to first purify the feed water before it enters the membrane.

In the preferred embodiment of the second feature of the present invention, the product outlet of the reverse osmosis membrane unit is connected to a post-processor such as a post-carbon filter with a result that the product water stream to be discharged to the product outlet is purified once again.

According to a preferred embodiment of the third feature of the present invention, there is provided a reverse osmosis purification system including means for compulsory circulation of a concentrate stream, which comprises: a reverse osmosis membrane filter unit having a feed inlet for supplying feed water, a circulating inlet for supplying circulating water, a reverse osmosis membrane for purifying the feed water supplied through the feed inlet and the circulating water supplied through the circulating inlet, a product outlet for discharging the product water purified by the reverse osmosis membrane, and a concentrate outlet for discharging the concentrate stream that has not been purified by the reverse osmosis membrane; and a dual pump for boosting the feed water stream to the reverse osmosis membrane unit and for pressurizing and circulating the concentrate stream discharged from the concentrate outlet thereby supplying the concentrate stream to the circulating inlet of the reverse osmosis membrane unit .

In the preferred embodiment of the third feature of the present invention, the concentrate outlet of the reverse osmosis membrane filter unit is connected to a drain restrictor to adjust the quantity of the concentrate stream discharged from the concentrate outlet.

In the preferred embodiment of the third feature of the present invention, the dual pump is connected to a pre-processor such as a sediment filter and/or a pre-carbon filter at the inlet to first purify the feed water.

In the preferred embodiment of the third feature of the present invention, the product outlet of the reverse osmosis membrane filter is connected to a postprocessor such as a post-carbon filter to purify the product water that has passed through the membrane unit once again.

Brief Description of the Drawings

Further, the objects and advantages of the present invention can be more fully understood from the following detailed description, taken together with the accompanying drawings, in which:

FIG. 1 shows a block diagram of a constitution of a conventional reverse osmosis water purification system;

FIG. 2 shows the schematic diagram of the parts of the system in FIG.

i;

FIG. 3 shows the structure of the reverse osmosis membrane filter commonly used in the water purification system;

FIG. 4 shows the detailed purification mechanism of the reverse osmosis membrane filter in FIG. 3;

FIG. 5 shows a block diagram of a first feature of the reverse osmosis water purification system of the present invention, which is embodied with one circulation pump;

FIG. 6 shows the schematic arrangement of the parts of the system in FIG. 5;

FIG. 7 shows a block diagram of a second feature of the reverse osmosis water purification system of the present invention, which is embodied with one circulation pump and one boosting pump;

FIG. 8 shows the schematic arrangement of the parts of the system in FIG. 7;

FIG. 9 shows a block diagram of a third feature of the reverse osmosis water purification system of the present invention, which is embodied with one dual pump;

FIG. 10 shows the schematic arrangement of the parts of the system in FIG. 9;

FIG. 11 shows the detailed purification operation of the reverse osmosis membrane filter in FIGS. 5, 7 and 9; FIG. 12 shows one example of the operation mode according to the present invention wherein the reverse osmosis membrane units are arranged in a row.

Best mode for Carrying Out the Invention

Hereinafter, an explanation of the preferred embodiments of the present invention will be discussed with reference to FIGS. 5 to 12.

FIG. 5 shows a block diagram of a reverse osmosis water purification system including means for compulsory circulation of a concenfrate water sfream according to a first embodiment of the present invention, which is embodied with one circulation pump. In the figure, reference numeral 110 represents a sediment filter, 120 a pre-carbon filter, 130 a reverse osmosis membrane unit, 140 a circulation pump, 150 a post-carbon filter, 160 a drain restrictor. And, 'Q₀' denotes a raw water stream, 'Q_F' a feed water stream, 'Q_P' a product water sfream, 'Q_R' a circulating water sfream, 'Q_c' a concentrate water stream, and 'Q_D' a draining water stream.

In this embodiment, the reverse osmosis membrane unit 130 is provided with a feed inlet and a circulating inlet at the one side and with a product outlet and a concenfrate outlet at the other side.

The feed inlet of the reverse osmosis membrane unit 130 is connected to the outlet of the pre-carbon filter 120 through a pipe 163, and the inlet of the pre- carbon filter 120 is connected to the outlet of the sediment filter 110 via a pipe 162. The inlet of the sediment filter 110 is supplied with the raw water via a feed pipe 161.

The product outlet of the reverse osmosis membrane unit 130 is connected to the inlet of the post-carbon filter 150 through a pipe 164, and the outlet of the post-carbon filter 150 is connected to a pipe 168 through which the product water stream is discharged.

On the other hand, the concenfrate outlet of the reverse osmosis membrane unit 130 is connected to the inlet of the circulation pump 140 through a pipe 165, and the outlet of the circulation pump 140 is connected to the circulating inlet of the reverse osmosis membrane filter unit 130 via a pipe 167. The inlet of the drain restrictor 160 is connected to a pipe 166 through which the concentrate stream is adjusted and discharged.

The feed inlet of the reverse osmosis membrane unit 130 is supplied with the feed water stream Q_F from the pre-carbon filter 120, and the circulating inlet thereof is supplied with the circulating water sfream Q_R from the circulation pump 140.

A part of the feed water and circulating water supplied from the reverse osmosis membrane unit 130 is purified through the reverse osmosis membrane and is then discharged as the product water stream Q_P. At that time, the feed water stream that has not been purified is discharged to the concentrate stream Qc. A part of the concenfrate stream Q_c flows through the drain restrictor 160 and is then discharged to the drain water stream Q_D or circulated by the circulation pump 140 in such a manner as to be supplied to the reverse osmosis membrane unit 130.

FIG. 6 shows the schematic arrangement of the parts of the system in FIG. 5. In the figure, reference numeral 130 denotes the reverse osmosis membrane filter, 140 the circulation pump, and 160 the drain restrictor.

As shown, the reverse osmosis membrane unit 130 is provided with two inlets on the top end, with the product outlet on the bottom end, and with the concentrate outlet on the other side of the bottom end. For example, one of the outlet can be placed at the center of the bottom end and the other at the periphery of the bottom. However, relative position of these two outlets is not important as long as they fit comfortably with the housing. The thickness of arrows in the drawing indicates quantities of water flowing in the purification system. Thick arrows mean a large quantity of flow, and thin ones a small quantity. The quantity of product water sfream Q_P is smaller than the sum of the feed water stream Q_F and the circulating water sfream Q_R. And, the quantity of the draining water stream Q_D is smaller than that of the product water sfream Q_P.

In the present invention, the recovery (percent of feed water that permeates through the membrane and becomes product water) can be as high as 80% depending on the TDS level of the feed water.

FIG. 7 shows a block diagram of a reverse osmosis water purification system including means for compulsory circulation of concentrate water according to a second embodiment of the present invention, which is embodied with one circulation pump and one boosting pump. In the figure, reference numeral 210 represents a sediment filter, 220 a pre-carbon filter, 230 a boosting pump, 240 a reverse osmosis membrane unit, 250 a circulation pump, 260 a post-carbon filter, and 270 a drain restrictor. And, 'Q_F' denotes a feed water stream, 'Q_P' a product water stream, 'Q_R' a circulating water sfream, 'Q_c' a concentrate water sfream, and 'Q_D' a draining water sfream.

In this embodiment, the reverse osmosis membrane unit 240 is provided with a feed inlet and a circulating inlet at the one side and with a product outlet and a concenfrate outlet at the other side. The feed inlet of the reverse osmosis membrane unit 240 is connected to the outlet of the boosting pump 230 through a pipe 274, and the inlet of the boosting pump 230 is connected to the outlet of the pre-carbon filter 220 through a pipe 273. The inlet of the pre-carbon filter 220 is connected to the outlet of the sediment filter 210 via a pipe 272. The inlet of the sediment filter 210 is supplied with the raw water via a pipe 271.

The product outlet of the reverse osmosis membrane unit 240 is connected to the inlet of the post-carbon filter 260 through a pipe 275, and the outlet of the post-carbon filter 260 is connected to a pipe 279 through which the product water sfream flows. On the other hand, the concentrate outlet of the reverse osmosis membrane unit 240 is connected to the inlet of the circulation pump 250 through a pipe 276, and the outlet of the circulation pump 250 is connected to the circulating inlet of the reverse osmosis membrane unit 240 via a pipe 278. A part of the concentrate stream discharged from the concentrate outlet of the reverse osmosis membrane unit 240 is supplied to the drain restrictor 160 via a pipe 277 and then drained.

The feed inlet of the reverse osmosis membrane unit 240 is supplied with the feed water sfream Q_F boosted in the boosting pump 230, and the circulating inlet thereof is supplied with the circulating water sfream Q_R from the circulation pump 250.

FIG. 8 shows the schematic anangement of the parts of the system in FIG. 7. In this figure, reference numeral 230 represents the boosting pump, 240 the reverse osmosis membrane filter, 250 the circulation pump, and 270 the drain restrictor.

Again, the feed inlet of the reverse osmosis membrane unit 240 is supplied with the feed water stream Q_F boosted in the boosting pump 230, and the circulating inlet thereof is supplied with the circulating water stream Q_R from the circulation pump 250. Using the boosting pump 230 and the circulation pump 250, the pressure in the water supplied to the reverse osmosis membrane unit 240 can be substantially increased.

FIG. 9 shows a block diagram of a reverse osmosis water purification system including means for compulsory circulation of a concenfrate water sfream according to a third embodiment of the present invention, which is embodied with one dual pump. In the figure, reference numeral 310 represents a sediment filter, 320 a pre-carbon filter, 330 a dual pump, 340 a reverse osmosis membrane unit, 350 a post-carbon filter, and 370 a drain restrictor. And, 'Q_F' denotes a feed water sfream, 'Q_P' a product water stream, 'Q_R' a circulating water sfream, 'Qc' a concentrate water sfream, and 'Q_D' a draining water sfream.

As shown, the reverse osmosis membrane unit 340 is provided with a feed inlet and a circulating inlet at its one side and with a product outlet and a concentrate outlet at its other side.

The dual pump 330 is provided with two inlets at its one side and with two outlets at its other side. The dual pump 330 is comprised of two pumps as a unitary body and it boosts the feed flow and circulates the concentrate.

The feed inlet of the reverse osmosis membrane unit 340 is connected to the one outlet of the dual pump 330 through a pipe 364. And, the circulating inlet of the reverse osmosis membrane unit 340 is connected to the other outlet of the dual pump 330 through a pipe 368.

The one inlet of the dual pump 330 is connected to the outlet of the pre- carbon filter 320 through a pipe 363, and the other inlet of the dual pump 330 is connected to the concentrate outlet of the reverse osmosis membrane unit 340 via a pipe 366. At that time, the concentrate sfream discharged to the concentrate outlet of the reverse osmosis membrane unit 340 is adjusted by means of the drain restrictor 370 and then discharged.

The inlet of the pre-carbon filter 320 is connected to the outlet of the sediment filter 310 via a pipe 362. The inlet of the sediment filter 310 is supplied with the raw water via a pipe 361.

The product outlet of the reverse osmosis membrane unit 340 is connected to the inlet of the post-carbon filter 350 through a pipe 365.

FIG. 10 shows the schematic anangement of the parts of the system in FIG. 9. In this figure, reference numeral 310 represents the sediment filter, 320 the pre-carbon filter, 330 the dual pump, 340 the reverse osmosis membrane unit, and 350 the post-carbon filter.

As shown, one of the dual pump 330 is connected between the outlet of the pre-carbon filter 320 and the feed inlet of the reverse osmosis membrane unit 340, for boosting the feed water sfream. The other side pump of the dual pump 330 is connected between the concentrate outlet of the reverse osmosis membrane unit 340 and the circulating inlet of the reverse osmosis membrane unit 340, for boosting the circulating water sfream.

FIG. 11 shows the detailed purification operation of the reverse osmosis membrane filter that can be used in the systems shown in FIGS. 5, 7 and 9. In the figure, a reference numeral 131 represents a product collection pipe, and 132 an active layer or a reverse osmosis membrane. And, 'Q_F' denotes a feed water sfream, 'Q_P' a product water sfream, 'Q_R' a circulating water sfream, 'Q_c' a concenfrate water sfream, and 'Q_D' a draining water sfream. The feed water stream Q_F passes through the active layer 132 and is discharged to the product water sfream Q_P through the product collection pipe

131. . The feed water stream Q_F that does not pass through the membrane to the product water stream Q_P or the draining water sfream Q_D is circulated as the circulating water sfream Q_R. The circulating water stream Q_R provides the necessary cross flow and turbulence on the membrane surface to prevent the formation of the boundary layer on the active layer 132.

FIG. 12 shows one example of the operation mode according to the present invention. In this diagram, the membrane units are ananged in a row to increase purification capacity. Therefore, each box or the reference numeral 130 represents each separate reverse osmosis membrane unit, 140 the circulation pump, and 160 the drain restrictor. And, 'Q_F' denotes the feed water sfream, 'Q_P' the product water sfream, 'Q_R' the circulating water sfream, 'Q_c' the concenfrate water sfream, and 'Q_D' the draining water stream. Here, the reverse osmosis membrane filter 130 is comprised of n repeating units denoted as 130a to 13 On. The feed inlets Q_Fa to Q_Fn of the 1^st to n^th membrane units 130a to 13 On are connected to a pipe 163 through pipes 163 a to 163n. The concentrate outlets Q_Ca to Q_Cn of the 1^st to n^Λ membrane units 130a to 13 On are connected to the inlet of the circulation pump 140 through series of pipes called 165a to 165n. And, the outlet of the circulation pump 140 is connected through a pipe 167 to the circulating inlets Q_Ra to Q_Rn of the 1^st to n^th reverse osmosis membrane units 130a to 13 On. Therefore, the circulating water stream Q_R discharged through the circulation pump 140 is supplied to the circulating inlets Q_Ra to Qp^ are operated under the same pressure and flow rate. On the other hand, the product outlets Q_Pa to Q_Pn of the 1^st to n^th reverse osmosis membrane units 130a to 130n are connected to a pipe 164 through pipes 164a to 164n, thereby discharging the total product water sfream Q_P. Therefore, the quantity of the product water discharged through the pipe 164 is the sum of the water coming from the product outlets of the 1^st to n^th membrane units of 130a to 130n.

If enough membrane units are connected, a desired quantity of product water can be made at a rate that does not require a water storage tank, and the amount of feed water needed for this process is much less compared to the conventional reverse osmosis water purification. If it is desired, only single unit of membrane can be used in the present purification system.

According to the present invention, the ratio of product water to draining water is about 4: 1, thereby enabling a quantity of draining water to be remarkably reduced. It is one of the characteristics of the present invention that by increasing the recovery rate it is possible to increase the membrane capacity for a fixed feed stream such that the water storage tank may not be required. However, the present purification system also may be provided with a water storage tank if desired. .

Industrial Application

As appreciated from the foregoing, there is provided a reverse osmosis water purification system including means for compulsory circulation of a concentrate sfream which is capable of solving such problems suffered in a conventional reverse osmosis water purification system. Generally, the ratio of the feed water to the product water is 4: 1 in the conventional system. This is why most conventional reverse osmosis water purifiers are accompanied by a storage tank, i.e., under usual municipal water supply condition, the conventional system cannot generate enough water to spend without temporary storage of the water. However, this inevitably causes bigger sized units and requires more space to install. Further, the water retained in the storage tank is likely to be exposed to germs, bacteria and the like; The present invention, however, by increasing the ratio of product water to the feed water, can reduce consumption of feed water and function without a storage tank.

Claims

What Is Claimed Is:

1. A reverse osmosis water purification system including means for compulsory circulation of a concenfrate sfream, said system comprising: a reverse osmosis membrane unit comprised of a feed inlet for supplying a feed water sfream, a circulating inlet for supplying a circulating water sfream, a reverse osmosis membrane for purifying said feed water sfream supplied through said feed inlet and said circulating water stream supplied through said circulating inlet, a product outlet for discharging a product water stream purified by said reverse osmosis membrane, and a concentrate outlet for discharging said concentrate sfream that has not been purified in said reverse osmosis membrane; and a circulation pump for circulating said concentrate sfream discharged to said concenfrate outlet to said circulating inlet of said reverse osmosis membrane unit .

2. The system according to claim 1, wherein said concentrate outlet of said reverse osmosis membrane unit is connected to a drain restrictor to adjust the quantity of said concentrate stream discharged from said concentrate outlet.

3. The system according to claim 1, wherein said circulation pump is adapted to pressurize said concentrate sfream discharged from said concenfrate outlet of said reverse osmosis membrane unit and supply the pressurized concentrate sfream to said circulating inlet of said reverse osmosis membrane unit.

4. The system according to claim 1, wherein said feed inlet of said reverse osmosis membrane unit is connected to a pre-processor.

5. The system according to claim 1 wherein said product outlet of said reverse osmosis membrane unit is connected to a post-processor.

6. A reverse osmosis water purification system including means for compulsory circulation of a concenfrate sfream, said system comprising: a reverse osmosis membrane unit comprised of a feed inlet for supplying a feed water sfream, a circulating inlet for supplying a circulating water stream, a reverse osmosis membrane for purifying said feed water sfream supplied through said feed inlet and said circulating water stream supplied through said circulating inlet, a product outlet for discharging a product water sfream purified by said reverse osmosis membrane, and a concentrate outlet for discharging said concentrate sfream that has not been purified in said reverse osmosis membrane; a circulation pump for pressurizing and circulating said concenfrate sfream discharged to said concenfrate outlet to said circulating inlet of said reverse osmosis membrane filter; and a boosting pump for boosting said feed water sfream supplied to said feed inlet of said reverse osmosis membrane unit.

7. The system according to claim 6, wherein said concentrate outlet of said reverse osmosis membrane unit is connected to a drain restrictor to adjust the quantity of said concentrate stream discharged from said concenfrate outlet.

8. The system according to claim 6, wherein said circulation pump is adapted to pressurize and circulate said concentrate stream discharged from said concentrate outlet of said reverse osmosis membrane unit and supply the pressurized concenfrate sfream to said circulating inlet of said reverse osmosis membrane unit.

9. The system according to claim 6 wherein said inlet of said reverse osmosis membrane unit is connected to a pre-processor.

10. The apparatus according to claim 6, wherein said product outlet of said reverse osmosis membrane unit is connected to a post-processor.

11. A reverse osmosis water purification system including means for compulsory circulation of a concentrate sfream, said system comprising: a reverse osmosis membrane unit comprised of a feed inlet for supplying a feed water sfream, a circulating inlet for supplying a circulating water sfream, a reverse osmosis membrane for purifying said feed water stream supplied through said feed inlet and said circulating water sfream supplied through said circulating inlet, a product outlet for discharging a product water sfream purified by said reverse osmosis membrane, and a concentrate outlet for discharging said concenfrate sfream that has not been purified in said reverse osmosis membrane; and a dual pump for boosting said feed water sfream supplied to said feed inlet and for pressurizing and circulating said concenfrate sfream discharged to said concentrate outlet to said circulating inlet of said reverse osmosis membrane filter.

12. The system according to claim 11, wherein said concenfrate outlet of said reverse osmosis membrane filter is connected to a drain restrictor to adjust the quantity of said concenfrate sfream discharged from said concenfrate outlet.

13. The system according to claim 11, wherein said feed inlet of said reverse osmosis membrane unit is connected to a pre-process.

14. The apparatus according to claim 11, wherein said product outlet of said reverse osmosis membrane unit is connected to a post-processor