Field of the Invention

The invention relates to a membrane filter unit and more particularly to a roll-type filter membrane with higher efficiency and prolonged lifetime due to its structure and design.

Background of the Invention

Pressure driven spiral wound membrane filters are widely used in household water purifiers to provide purified water for consumers. The use of spiral wound membranes is advantageous in that it affords very high quality of water to consumers.

Traditionally, the spiral wound membrane elements are formed by winding a plurality of purification membrane groups around a central perforated treated water tube. The purification membrane group is formed by laminating a mesh-like treated water guiding member, a dualfolded membrane and a mesh-like feed water guiding member inside of the dual-folded membrane. A feed water flow channel is formed along the inner surfaces of the dual-folded membrane and a treated water flow channel is formed between the outside surfaces of the adjacent dual-folded membrane.

When such membrane element is in operation, the feed water enters the feed water flow channel from one end, either side surface or outside surface, of the spiral wound membrane element. Treated water is obtained by passing the feed water through the membrane. The treated water flows along the treated water guiding member and into the central treated water tube through the water collection hole. The remaining water which as not filtered flows along the feed water guiding member and is discharged from another end of the spiral wound membrane element as concentrated water. In such traditional spiral wound membrane elements, the main problems are scaling, fouling, falling rejection, reduction in performance (reduced flow or higher pressure), over the time, impurities accumulate and are likely to easily contaminate the membrane, resulting in shorter lifetime of the membrane element.

CN111185096 A (GREE ELECTRIC APPLIANCESINCOF ZHUHAI, 2020) discloses a composite filter element assembly comprises a bottle body and multiple stages comprising a pretreatment filter element, a fine filtration filter element and a post-treatment filter element assembly; the post-treatment filter element assembly comprises a central pipe made of a water- permeable filter material; fluid sequentially passes through the pretreatment filter element, the fine filtration filter element and the post-treatment filter element assembly to be filtered.

CN205868019 II (Foshan Midea, 2017) discloses RO membrane with high filtration efficiency and rate of recovery.

LIS2016207001 A1 (Parker) discloses a double-pass reverse osmosis (RO) separator module having two stages of RO filtration in a single assembly, including a radially outer RO assembly that surrounds a radially inner RO assembly, wherein each RO assembly includes an RO separation medium.

EP2319611 A1 (Voelker, 2011) discloses an RO device in which a liquid feed and retentive and filtrate connections are provided on the upper part, and flow ducts penetrate the lower part. A fluid e.g., untreated water, flows to a lower side of the membrane via the space.

US4990248 A (Kodak, 1991) discloses a water filter cartridge includes a reverse osmosis membrane permeator spirally wound on a central winding tube and surrounded by an impermeable barrier layer which is, in turn, surrounded by a spirally wound prefilter. A post-filter is placed centrally within the winding tube.

A lot of efforts have been made to improve the lifetime of the spiral wound membrane element. Many of the membrane filter units either use chemicals to solve such problems such as descalants or modify the design of the filtration unit, however most of them have complicated or bulky design or incur high costs for alleviating these problems. Therefore, the present inventors have recognized that there is a need to develop a spiral wound reverse osmosis membrane element with a prolonged lifetime and which is easy to be made, is simple, not complicated and does not incur additional costs as compared to traditional spiral wound membranes.

Summary of the Invention

In accordance with a first aspect is provided a membrane filter unit comprising:

(a) a filter case for housing a membrane;

(b) an inner tube housing a treated water chamber and a hollow core tube, a middle tube housing a waste water chamber and an outer tube housing a feed water chamber, wherein the inner tube, the middle tube and the outer tube are coaxially arranged (c) the hollow core tube having a top opening and a bottom opening and having plurality of water collecting pores on its surface and positioned coaxially inside the case, wherein the top opening is adapted to open into the treated water chamber

(d) the membrane having an inner peripheral surface, a top outer peripheral surface , a bottom outer peripheral surface and a side outer peripheral surface and arranged around the core tube such that the inner peripheral surface of the membrane is spirally wound around the core tube and the side outer peripheral surface is capable of permeation of raw water through its surface; wherein a top cover and a bottom cover are sealingly engaged with the top outer peripheral surface and the bottom outer peripheral surface of the membrane respectively; and wherein the top cover comprises a through central hole adapted for and sealingly fitted to the core tube to facilitate passage of treated water through the core tube into the treated water chamber and at least two bands of plurality of orifices opening into the waste water chamber and arranged around the circumference of the central hole such that the bands are arranged concentrically to the central hole, wherein the top cover (10) of the membrane (3) is capped by a membrane connector (11), the membrane connector comprising a cover plate (11 P) extending upwardly towards center to form a raised enclosure (11 R), wherein the raised enclosure (11 B) sealingly engages with the peripheral hollow tube (4P) and the membrane connector (11) is axially spaced from the top cover (10) to allow passage of water from the at least two bands of plurality of orifices (10P.10D) into the waste water chamber (5A)..

Detailed Description of the Invention

The present invention provides a membrane filter unit and a water treatment device having a membrane filtration unit designed in such a way that the filter membrane has a higher efficiency and prolonged lifetime.

The membrane filter unit of the present invention comprises filter case for housing a membrane; an inner tube housing a treated water chamber and a hollow core tube, a middle tube housing a waste water chamber and an outer tube housing a feed water chamber; the membrane which is spirally wound around the core tube; wherein a top cover and a bottom cover are sealingly engaged with the top outer peripheral surface and the bottom outer peripheral surface of the membrane respectively. The structure and design of the membrane filtration unit is such that it solves the problems of scaling, fouling and results in higher efficiency of the membrane and consequently resulting in prolonged lifetime of the membrane filtration unit.

The present inventors were able to design the membrane filtration unit in such a way that with minimum changes as compared to the traditional design of membrane filtration unit, and therefore minimum added costs, the problems associated with membrane filtration units and as identified above are solved in a simple and easy to industrialize manner.

The present invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being implemented in various ways.

The terms “including”, “comprising”, “containing” or “having” and variations thereof as used herein are meant to encompass the items listed thereafter as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings.

Throughout the description of the present invention, wherever a tube or enclosure is defined by naming the structural components forming it, it shall be understood that the identified structural component means ‘at least a part of’ and that structural component or a particularly identified wall of a structural component need not in its entirety be a part of the enclosure and therefore when such structural component or a particularly identified wall of a structural component is named it should be understood that at least a part or portion of that structural component or a particularly identified wall of a structural component is involved in the formation of a given enclosure.

Throughout the description of the present invention all the physical structural components have inner and outer walls and any reference to inner and outer walls is to be understood in context of the respective structural component. It shall also be understood that unless specified, the inner wall means the wall towards inside of the membrane filter unit or the center of the membrane filter unit and the other wall as the outer wall. A membrane filter unit

The present invention provides a membrane filter unit comprising a filter case for housing a membrane; an inner tube housing a treated water chamber and a hollow core tube, a middle tube housing a waste water chamber and an outer tube housing a feed water chamber, wherein the inner tube, the middle tube and the outer tube are coaxially arranged; the hollow core tube having a top opening and a bottom opening and having plurality of water collecting pores on its surface and positioned coaxially inside the case, wherein the top opening is adapted to open into the treated water chamber; the membrane having an inner peripheral surface, a top outer peripheral surface , a bottom outer peripheral surface and a side outer peripheral surface and arranged around the core tube such that the inner peripheral surface of the membrane is spirally wound around the core tube and the side outer peripheral surface is capable of permeation of raw water through its surface; wherein a top cover and a bottom cover are sealingly engaged with the top outer peripheral surface and the bottom outer peripheral surface of the membrane respectively; and wherein the top cover comprises a through central hole adapted for and sealingly fitted to the core tube to facilitate passage of treated water through the core tube into the treated water chamber and at least two bands of plurality of orifices opening into the waste water chamber and arranged around the circumference of the central hole such that the bands are arranged concentrically to the central hole.

It is preferable that the membrane filter unit is employed in a device and more preferable that the membrane filter unit is employed in water treatment device and most preferably a water purifier.

Filter case

The membrane filter unit of the present invention comprises a filter case for housing a membrane. The filter case preferably comprises a main body having an inner wall and an outer wall, a top cap and a bottom cap.

It is preferable that the top cap of the filter case comprises an inner wall and an outer wall and wherein from the inner wall of the top cap two hollow concentric tubes descend downwardly, a central hollow tube and a peripheral hollow tube each having respective inner walls and outer walls. The main body and the top cap could be attached together by a snap fit or a threaded male and female screw connection. It is however preferable that the main body and cover are molded together.

The filter case is preferably intended to hold the membrane housing and also create chambers enclosed by its structural design.

Though the filter case can be made of any material but it is preferable that it is made of food grade material and more preferable that it is made of plastic and most preferably of either a clear plastic or polypropylene material.

The filter case is preferably designed in a way that prevents leakage through any joints other than the inlet and outlets intended for those purposes.

Hollow core tube

The membrane filter unit also comprises a hollow core tube having a top opening and a bottom opening and having plurality of water collecting pores on its surface and positioned coaxially inside the case, wherein the top opening is adapted to open into the treated water chamber. It is preferable that hollow core tube has top end preferably close to top opening and a bottom end preferably close to the bottom opening. It is further preferable that the top end of the hollow core tube is the end that extends beyond the top cover of the membrane. It is further preferable that the top end of the hollow core tube sealingly engages with the central hollow tube and more preferably outer wall of the top end of the hollow core tube sealingly engages with the central hollow tube to form the inner tube. It is further preferable that outer wall of the top end of the hollow core tube sealingly engages with inner wall of the central hollow tube to form the inner tube.

It is preferable that the hollow core tube has a top end facing the top cap of the filter case and a bottom end facing the bottom cap of the filter case. It is preferred that the hollow core tube engages sealingly with the central hollow tube at its top end such that the top opening of the hollow core tube opens into the central hollow tube.

The hollow core tube is intended to have the membrane of the membrane filter unit spirally wound around it. It is preferable that the inner peripheral surface of the membrane is in contact with the hollow core tube and wound around it. It is preferable that the hollow core tube allow passage of treated water through it to the treated water chamber and consequently through the treated water outlet to outside of the membrane filter unit.

It is preferable that hollow core tube forms a part of the inner tube.

It is preferable that an upwardly protruding docking post is placed at the bottom opening of the hollow core tube to hold the hollow core tube in place.

It is preferable that the hollow core tube is made of food grade material, preferably plastic and more preferably of ABS, PPE, PVC, PPO or PSU.

Filter membrane

The membrane of the membrane filter unit comprises an inner peripheral surface, a top outer peripheral surface, a bottom outer peripheral surface and a side outer peripheral surface; and arranged around the core tube such that the inner peripheral surface of the membrane is spirally wound around the core tube and preferably the side outer peripheral surface is capable of permeation of raw water through its surface.

It is preferable that the membrane could be any spirally wound membrane capable of being wound around the hollow core tube, more preferably the membrane is a separation or a desalination membrane and most preferable a filtration membrane or a reverse osmosis membrane. It is highly preferred that the membrane is a reverse osmosis membrane.

Top cover

A top cover is sealingly engaged with the top outer peripheral surface of the membrane. The top cover comprises a through central hole adapted for and sealingly fitted to the core tube to facilitate passage of treated water through the hollow core tube into the treated water chamber and at least two bands of plurality of orifices opening into the waste water chamber and arranged around the circumference of the central hole such that the bands are arranged concentrically to the central hole.

It is preferable that the top cover downwardly extends to cover a portion of the side outer peripheral surface of the membrane. It is preferable that the top cover sealingly engages with top outer peripheral portion of the membrane such that the two bands of plurality of orifices are sealingly separated from each other.

It is preferable that the orifices in the at least two bands are annular or oval in shape.

It is preferable that the at least two bands of plurality of orifices are a proximal band and a distal band, the proximal band being closer to the core tube and the distal band being further from the core tube.

Bottom cover

A bottom cover is sealingly engaged with the bottom outer peripheral surface of the membrane. It is preferable that the bottom cover of the membrane upwardly extends to cover a portion of the side outer peripheral surface of the membrane and has an upwardly protruding docking post, preferably in the center preferably to hold the core tube in place.

Membrane connector

A membrane connector caps the top cover of the membrane, the membrane connector comprises a cover plate extending upwardly towards center to form a raised enclosure, wherein the raised enclosure preferably sealingly engages with the peripheral hollow tube.

It is preferable that the membrane connector is provided with a through central hole in center of the cover plate for the core tube. It is preferable that the central hole of the membrane connector spans beyond the hollow core tube. It is further preferable that the diameter of central hole of the membrane connector is more than the diameter of the hollow core tube. It is more preferable that the diameter of central hole of the membrane connector is at least 1.01 times, more preferably 1.05 times, more preferably 1.1 times more preferably 1.2 times more preferably 1.5 times more preferably 1.6 times more preferably 1.7 times more preferably 1.8 times more preferably 1.9 times more than the diameter of the hollow core tube.

It is further preferable that the membrane connector further comprises a downward skirting and more preferably the downward skirting extends downwardly to cover at least a portion of the outer side peripheral surface of the membrane. It is preferable that the membrane connector is axially spaced from the top cover to allow passage of water from the at least two bands of plurality of orifices into the waste water chamber.

It is further preferable that the membrane connector is provided with radial beams on its inner surface of the cover plate, preferably that faces the top cover of the membrane and more preferably the radial beams abut against the top cover of the membrane.

It is preferable that the raised enclosure of the membrane connector has an inner wall and an outer wall and preferably the raised enclosure sealingly engages with peripheral hollow tube.

In one embodiment of the present invention the raised enclosure of the membrane connector may form an extension of the wall of peripheral hollow tube to form the middle tube. It is also possible that the inner wall of the raised enclosure forms an extension of the wall of peripheral hollow tube to form the middle tube.

Inner tube, middle tube and the outer tube

The membrane filter unit comprises inner tube, middle tube and outer tube and formed inside the filter case preferably between the inner wall of the filter case and other components positioned within the filter case. The inner tube, the middle tube and the outer tube are preferably coaxially arranged preferably around the central axis of the filter case.

Inner Tube

It is preferable that the inner tube is formed by at least a part of the central hollow tube and at least a part of the hollow core tube preferably sealingly fitted with each other, it is more preferable that central hollow tube is sealingly fitted to at least a part of the portion of hollow core tube which extends beyond the top cover of the membrane. It is more preferable that outer wall of top end of the hollow core tube sealingly engages with the inner wall of the central hollow tube.

Middle Tube

It is preferable that the middle tube is formed by at least a part of the outer wall of the central hollow tube and at least a part of the inner wall of the peripheral hollow tube. It is preferable that at least a part of the peripheral hollow tube of the top cap of the filter case sealingly engages with at least a part of the membrane connector and more preferable that the peripheral hollow tube sealingly engages with the at least a part of raised enclosure of the membrane connector and more preferably with at least a part of outer wall of the raised enclosure. It is preferable that the waste water from the two bands of plurality of orifices pass through the central hole of the membrane connector to arrive at the middle tube.

It is preferable that the middle tube is formed by at least a part of the central hollow tube preferably the outer wall and at least a part of the peripheral hollow tube preferably the inner wall. It is preferable that at least a part of the peripheral hollow tube of the filter case, preferably at least a part of inner wall of the peripheral hollow tube sealingly engages with at least a part of the membrane connector and more preferable that the peripheral hollow tube sealingly engages with the at least a part of raised enclosure of the membrane connector.

In one embodiment of the present invention the raised enclosure of the membrane connector may form an extension of the wall of peripheral hollow tube to form the middle tube. It is also possible that the inner wall of the raised enclosure forms an extension of the wall of peripheral hollow tube to form the middle tube. It is highly preferable that the outer wall of the raised enclosure sealingly engages with the inner wall of the peripheral hollow tube to form wall of the middle tube.

It is preferable that the central hollow tube sealingly engages with the hollow core tube to form a wall of the middle tube. It is more preferable that at least a part of, preferably at least a part of outer wall of the hollow core tube sealingly engages with at least a part of, preferably at least a part of inner wall of central hollow tube to form a wall of the middle tube.

In one embodiment it is possible that at least a part of the outer wall of the end of the hollow core tube forms a wall of the middle tube.

Outer Tube

It is preferable that the outer tube is formed by at least a part of the outer wall of the peripheral hollow tube and at least a part of the inner wall of the main body of filter case. It is further preferable that the outer tube is formed by at least a part of the outer wall of the peripheral hollow tube and at least a part of the inner wall of the main body of filter case, at least a part of the top cap and at least a part of the bottom cap of the filter case. It is more preferable that the outer tube is an enclosure formed between at least a part of outer wall of the peripheral hollow tube of the filter case outer wall, at least a part of inner wall of the main body of the filter case, at least a part of inner wall of the top cap of the filter case which is between the point where peripheral hollow tube descends from the top cap of the filter case and the point where top cap descends downwardly to merge with the main body, and at least a part of the bottom cap of the filter case.

It is preferable that at least a part of the raised enclosure of the membrane connector sealingly engages with the at least a part of peripheral hollow tube to form the outer tube. It is more preferable that at least a part of the inner wall of the peripheral hollow tube sealingly engages with at least a part of outer wall of the membrane connector to form the outer tube.

In one embodiment it is possible that the membrane connector forms sealingly engages with the peripheral hollow tube in such a way that it forms an extension of the peripheral hollow tube such that at least a part of outer wall of raised enclosure is a part of outer tube.

The inner tube houses a treated water chamber, used for collection and finally dispensing of the treated water. The treated water chamber is not an enclosed space but a space that is in fluid connection with the hollow core tube and is preferably formed in the upper part of the inner tube and more preferably in the space above the hollow core tube.

The middle tube houses the waste water chamber which is used to collect the waste water or the discarded water after the feed water is treated and the waste water chamber is used to collect and finally dispense waste water out of the membrane filtration unit. It is preferable that the middle tube itself functions as the waste water chamber. It is further preferable that the middle tube receives waste water from the membrane through the at least two bands of plurality of orifices of the top cover of the membrane. It is preferable that the waste water from the membrane passes through the two bands of plurality of orifices, into the central hole of the membrane connector to be collected and dispensed from the waste water chamber.

The outer tube houses the feed water chamber which is intended to receive feed water, preferably raw water intended for treatment by the membrane filtration unit. The feed water chamber is preferably not an enclosed space within the outer tube but spatially forms the upper portion of the outer tube where the feed water first enters and fills that space before entering the channel or slit formed between the inner wall of main body of the filter case and side outer peripheral surface of the membrane. Flow path of Water

The water flow path in the membrane which is in a kind of L-shaped flow across the membrane wound around the hollow core tube, the feed water enters from the outer surface of the membrane from the outer tube into the membrane and waste water exits through the plurality of orifices of the distal band and the proximal band for collection and consequent dispensing from waste water chamber and the treated water enters into the hollow of the hollow core tube to consequently enter the treated water chamber.

Water purifier

The present invention also provides a water purifier comprising:

(i) an inlet to receive feed water

(ii) a pre-filter unit;

(iii) an electromechanical means;

(iv) membrane filter unit comprising: a) a filter case for housing a membrane; b) an inner tube housing a treated water chamber and a hollow core tube, a middle tube housing a waste water chamber and an outer tube housing a feed water chamber, wherein the inner tube, the middle tube and the outer tube are coaxially arranged; c) the hollow core tube having a top opening and a bottom opening and having plurality of water collecting pores on its surface and positioned coaxially inside the case, wherein the top opening is adapted to open into the treated water chamber; d) the membrane having an inner peripheral surface, a top outer peripheral surface ,a bottom outer peripheral surface and a side outer peripheral surface and arranged around the core tube such that the inner peripheral surface of the membrane is spirally wound around the core tube and the side outer peripheral surface is capable of permeation of raw water through its surface wherein a top cover and a bottom cover are sealingly engaged with the top outer peripheral surface and the bottom outer peripheral surface of the membrane respectively; and wherein the top cover comprises a through central hole adapted for and sealingly fitted to the core tube to facilitate passage of treated water through the core tube into the treated water chamber and at least two bands of plurality of orifices opening into the waste water chamber and arranged around the circumference of the central hole such that the bands are arranged concentrically to the central hole, wherein the top cover (10) of the membrane (3) is capped by a membrane connector (11), the membrane connector comprising a cover plate (11P) extending upwardly towards center to form a raised enclosure (11 R), wherein the raised enclosure (11 B) sealingly engages with the peripheral hollow tube (4P) and the membrane connector (11) is axially spaced from the top cover (10) to allow passage of water from the at least two bands of plurality of orifices (10P.10D) into the waste water chamber (5A)..

(v) an outlet for treated water.

It is preferable that the electromechanical means is a pump positioned upstream of the membrane filtration unit to drive water into the membrane filtration unit.

Figures

Brief description

Figure 1 is a schematic representation of filter unit of first aspect showing flow of water within the filter unit.

Figure 2 is a schematic representation of top cover (10) of the membrane.

Figure 3 is a is a schematic representation of Membrane connector (11)

Figure 4 shows waste water flow path.

Detailed Description

Figure 1 shows a membrane filter unit comprising filter case (2) with main body (2M), a top cap (2C) and a bottom cap (2B) for housing a membrane (3); an inner tube (4) housing a treated water chamber (4A) and a hollow core tube (7), a middle tube (5) housing a waste water chamber (5A) and an outer tube (6) housing a feed water chamber (6A), wherein the inner tube (4), the middle tube (5) and the outer tube (6) are coaxially arranged.

The hollow core tube (7) is shown to have a top opening (7A) and a bottom opening (7B) and having plurality of water collecting pores (8) on its surface and positioned coaxially inside the case (2), wherein the top opening (7A) is adapted to open into the treated water chamber (4A); The membrane (3) is shown having an inner peripheral surface (3A), a top outer peripheral surface (3B), a bottom outer peripheral surface (3C) and a side outer peripheral surface (3D); and arranged around the core tube (7) such that the inner peripheral surface (3A) of the membrane is spirally wound around the core tube (7) and the side outer peripheral surface (3D) is capable of permeation of raw water through its surface.

The top cover (10) and a bottom cover (9) are shown sealingly engaged with the top outer peripheral surface (3B) and the bottom outer peripheral surface (3C) of the membrane (3) respectively.

Figure 2 is a graphical representation of top cover (10), the top cover (10) is shown to comprise a through central hole (10A) adapted for and sealingly fitted to the core tube (7) to facilitate passage of treated water through the core tube (7) into the treated water chamber (4A) and at least two bands of plurality of orifices (10P.10D) opening into the waste water chamber (5A) and arranged around the circumference of the central hole (10A) such that the bands (10P.10D) are arranged concentrically to the central hole (10A).

The figure shows the proximal band (10P) and a distal band (10D), the proximal band (10P) being closer to the core tube and the distal band (10D) being further from the core tube.

Figure 3 shows top view and bottom view of the membrane connector (11), the membrane connector is shown comprising a cover plate (11 P) extending upwardly towards center to form a raised enclosure (11 R) and a downward skirting. The bottom view of the membrane connector (11) shows that the membrane connector (11) is provided with radial beams (11 B) on its inner surface of the cover plate (11 P). Both the views also show a through central hole (11 A) for hollow core tube (7) (not shown in this figure).

Figure 4 shows water flow path in the membrane which is in a kind of L-shaped flow across the membrane wound around the hollow core tube, the feed water is seen entering from the outer surface of the membrane (from the outer tube, not shown) into the membrane and waste water exiting through the plurality of orifices of the distal band (10D) and the proximal band (10P) for collection and consequent dispensing from waste water chamber (5A).

The various features of the present invention referred to in individual sections above apply, as appropriate, to other sections mutatis mutandis. Consequently, features specified in one section may be combined with features specified in other sections as appropriate. Any section headings are added for convenience only and are not intended to limit the disclosure in any way.

Examples

The experiment was conducted to find the performance of the membrane filter unit of the present invention have a reverse osmosis (RO) membrane and compared with a traditional reverse osmosis (RO) membrane filter unit. The parameters considered for the performance were salt rejection efficacy and permeate productivity of the membrane filter unit.

The control system used was a traditional RO water purifier. Both the water purifier systems had a water pump, a 400 RO filter element and 800cc current limiter. The feed water was at 400 TDS and 25°C for both the purifiers. The pressure at the side of feed water of RO filter was 100 psi and the pressure at the side of feed water of RO filter was Opsi. The permeate productivity and RO salt rejection percentage was noted for both as presented by the tables 1 and 2 given below.

T able 1 : Water purifier RO filter unit of the present invention

Table 2: Water purifier with Traditional RO

It is clearly evident from the tables as presented above that both the water purifiers started with 5.3 psi pressure but the pressure falls to only 2.4 for the water purifier RO filter unit of the present invention even at 3571 Liters of water as compared to a fall of 2.0 in the traditional RO water purifier at 3290 Liters, the traditional membrane in fact sees a decline of 3.8 psi only at 638 Liters of pure water as compared to the RO filter unit of the present invention which sees the same decline in pressure at 1224 Liters of water which is close to double of 638 Liters. The RO’s salt rejection recorded with the water purifier RO filter unit of the present invention is very good to begin with at 95% and then increases to 97.7% and then remains constant over 3571 Liters of pure water dispensed from the purifier. On the other hand, the traditional RO water purifier has an initial salt rejection of about 86.1 % which increases to only 93.4% and then remains almost constant over 3290 Liters of pure water dispensed from the purifier. Therefore, overall salt rejection is better in the water purifier having the membrane filter unit of the present invention. Higher salt rejection means more safe water over the lifetime of the membrane filter unit.

Both the RO purifier systems are assumed to start at 100% flow rate. The water purifier RO filter unit of the present invention falls slowly from 71 .7% at 1224 Liters of water to only at 45.2% at 3571 Liter of water (more than double the volume of pure water of 1224 Liters). Whereas the traditional RO falls to 71.7 only at 638 Liters of pure water, and drops to 56.6% at 2142 Liters of water which is way less compared to the water purifier RO filter unit of the present invention and finally falls to 37.7% at 3290 Liters of pure dispensed water. This speedy decay in flow rate indicates faster deterioration of the traditional membrane (Table 2) and slow decline in flow rate of water purifier RO filter unit of the present invention (Table 1) means longer life time of the membrane filter unit.