Claims:1. A process of treating feed water containing undesirable dissolved salts removable by reverse osmosis and providing a treated water stream comprising the steps of :-
a. providing a membrane separation means having a feed side and a permeate side,
b. providing a storage means for storing a portion of treated feed water on the permeate side of the membrane separation means,
c. providing a target instruction means for fetching a target instruction for repeated performance of removing the dissolved salts from the feed water during reverse osmosis cross-flow conditions and cleansing the membrane separation means during forward osmosis reverse flow conditions,
d. performing a first execution as per the said target instruction means of step (c) comprising of :-
i) passing the feed water containing dissolved salts from the feed side of the membrane separation means and across the membrane separation means under reverse osmosis cross-flow conditions controlled by a cross-flow means and thereby changing the membrane separation means to a salt solutes-enriched fouled membrane separation means,
ii) removing from the permeate side of membrane separation means a treated water permeate stream depleted in the dissolved salts through a first outlet means,
iii) removing from the feed side of membrane separation means a dissolved salts-enriched water stream through a second outlet means, and
iv) storing a portion of treated water permeate stream on the permeate side of the fouled membrane separation means in the storage means which is the end of the first performance execution,
e. performing a second execution as per the said target instruction means of step (c) in continuation of termination of first execution step (d) of target instruction means comprising of :-
i) reverse flow of the said stored treated water permeate stream from the storage means on the permeate side of the said fouled membrane separation means and across the said fouled membrane separation means under forward osmosis reverse flow conditions for cleansing the said fouled membrane separation means, or
ii) reverse flow of the said stored treated water permeate stream from the storage means on the permeate side of the said fouled membrane separation means and across the said fouled membrane separation means under forward osmosis reverse flow conditions controlled by a back wash means for cleansing the said fouled membrane separation means, and
iii) removing from the feed side of membrane separation means a salt-solutes-enriched water stream and thereby leaving the fouled membrane separation means clean,
f. repeating the method from step (d) and step (e) of target instruction means to continuously process the feed water to produce treated water stream as per fetched target instruction from step (c) of target instruction means.
2. The process of treating feed water as claimed in claim 1, wherein the target fetching instruction of repeat performance of step (c) of target instruction means of claim 1 includes a loop count value that determines the predetermined number of times the step (d) and step (e) instruction is performed repeatedly until termination.
3. The process of treating feed water as claimed in claim 1, wherein the forward osmosis reverse flow conditions for the reverse flow of the said stored treated water in storage means from permeate side of membrane separation means and across the fouled membrane separation means to the feed side of the membrane separation means is by using a back wash means which is a minimal hydrostatic head of the storage means above the membrane separation means to facilitate reverse flow under natural osmosis.
4. The process of treating feed water as claimed in claim 1, wherein the forward osmosis reverse flow conditions for the reverse flow of the said stored treated water in storage means from permeate side of membrane separation means and across the fouled membrane separation means to the feed side of the membrane separation means is by using a back wash means which is a closure means and arranging the closure means in-between the storage means water and the membrane separation means.

5. The process of treating feed water as claimed in claim 1 &4, wherein the closure means of the back wash means may be a manually operable means, an electromechanically operable means, an electromagnetically operable means, an electrically operable means, or an electronically operable means.
6. The process of treating feed water as claimed in claim 1, 4&5, wherein the forward osmosis reverse flow conditions for the reverse flow of the stored treated water in storage means from permeate side of membrane separation means and across the fouled membrane separation means to the feed side of membrane separation means for the reverse flow is a back wash means which is a pump with a closure means .
7. A reverse osmosis treating system for treating feed water containing dissolved salts removable by reverse osmosis and providing a treated water stream comprising of :-
h. a membrane separation means having a feed side and a permeate side,
i. a storage means for storing all or a portion of treated water stream from the permeate side of the membrane separation means,
j. a first outlet means for removing treated water from the permeate side of the membrane separation means,
k. a second outlet means for removing dissolved salt enriched water stream from the feed side of the membrane separation means.
l. a cross-flow means having pump means and a closure means arranged on the feed side of the membrane separation means along with another closure means arranged on the permeate side of the membrane separation means to control flow of feed water from the feed side of the membrane separation means and across the membrane separation means to the permeate side of the membrane separation means under reverse osmosis cross flow conditions,
m. a back wash means which is by placing the storage means at a hydrostatic head above the membrane separation means with or without at least a closure means arranged on permeate side of membrane separation means to control back-flow of stored portion of treated water stream in the storage means from the permeate side and across the membrane separation means to the feed side of membrane separation means for cleansing the said fouled membrane separation means under forward osmosis reverse flow conditions, and
n. a target instruction means for operating selectively, sequentially and combinedly the said cross-flow means with said pump , the closure means upstream of the membrane separation means and the closure means downstream of the membrane separation means for reverse osmosis cross flow conditions and the said backwash means for forward osmosis reverse flow conditions, thereby controllably treating the feed water and cleansing the membrane separation means, the said arrangement is characterized in
- wherein said cross-flow means with the pump means , the closure means upstream of the membrane separation means and the closure means downstream of the membrane separation means adapted combinedly to enable during switch ON mode of cross-flow means the passing of the contaminated feed water from the feed side of membrane separation means and across the membrane separation means to the permeate side of membrane separation means under reverse osmosis cross flow conditions for generating a treated water permeate stream depleted in the dissolved salts at the permeate side of the membrane separation means and leaving behind on the feed side of the membrane separation means a dissolved salts-enriched water stream and further fouling the membrane separation means into a salt-solutes-enriched fouled membrane separation means due to absorption of dissolved salts from the feed water during its passage across the membrane separation means,
- wherein backwash means with or without closure means adapted to enable during switch OFF mode of cross flow means the passing of the back-flow of a stored portion of the generated treated water permeate stream from the permeate side of the membrane separation means and across the membrane separation means under forward osmosis reverse flow washing conditions and generating a salt-solutes-enriched water stream at the feed side of membrane separation means and leaving the fouled membrane separation means clean due to release of absorbed salts into treated water during water passage across the membrane separation means,
- wherein the operation state of cross flow means is different from the operation state of the backwash means at an instant whereby if one of the two means is in ON state, the other means is in OFF state, and
- wherein the operation state of the closure means upstream of the membrane separation means is same as the operation state of the closure means downstream of the membrane separation means, which is same as the operation state of the cross-flow means wherein if one of the two closure means is in ON state, the other closure means is also in the ON state.
8. The reverse osmosis treating system as claimed in claim 7, wherein the target instruction means is adapted to determine the predetermined number of times, the selective operation of the cross flow means with pump means, the closure means upstream of the membrane separation means and the closure means downstream of the membrane separation means, and thereafter corresponding operation of the backwash means is performed sequentially and alternatively until termination.
9. The reverse osmosis treating system as claimed in claim 7, wherein the closure means for the backwash means may be a manually operable means, an electromechanically operable means, an electromagnetically operable means, an electrically operable means, or an electronically operable means.
10. The reverse osmosis treating system as claimed in claim 7, wherein the backwash means is a hydrostatic head of the storage means above the membrane separation means.
11. The reverse osmosis treating system as claimed in claims 7, wherein the storage means, the membrane separation means and backwash means form a generally U tube arrangement having one long arm and one short arm and such that the storage means is positioned at the remote end of the long arm, the membrane separation means positioned at the other remote end of the short arm and the optional backwash control means arranged therein-between.
12. The reverse osmosis treating system as claimed in claim 7, wherein the backwash means is a pump. , Description:FIELD OF INVENTION:

The invention relates to membrane type water purification system.

BACKGROUND OF INVENTION:

Most current State of the Art water purification systems used in consumer homes, typically consist of the following generic types of “filters”.

The first in the battery of filters is typically a “Sediment filter” which is made up of non woven polymer fibres. These materials are shaped into an annular cylindrical block, through which water flows radially inward. The “sediment” filter blocks can consist of sintered polymer powder as well as other materials. Being the first filter in the line of water flow and disposable, this filter typically has the least cost among the battery of filters making up the water purification system. These filters are also called “dead end” filters which means that all the water passes through the filter.

The second filter in the battery of filters is typically a bound annular block made from Granular or powdered activated carbon. In addition to removing colloidal impurities, both inorganic and microbial, these filters are capable of removing dissolved organic molecules. The granular or powdered activated carbon is treated with silver salts to deposit silver onto the activated carbon granules. This prevents the colonization of the activated carbon media by micro-organisms. Due to the current cost of silver enhanced activated carbon and the cost associated with converting granular activated carbon into a solid annular block, this filter typically costs more than the “sediment” filter. However carbon filters are currently lower in cost compared membrane filters. These filters are also “dead end” filters as all the water passes through the filter.
OBJECT OF INVENTION:

Due to advances in membrane technology, membrane filters have emerged as the most preferred filters for water filtration. Membrane filters are typically classified based on the size of contaminants they can eliminate. This has led to classifications such as nano-filters, ultra-filters and micro-filters. However they are also classified in terms of the physical configuration of the membrane filter. This has resulted in classifications such as the Spiral wound membranes and Hollow Fibre Membranes, with the latter being a more recent development.

However the most popular and the most preferred water purification filter for drinking water purification is the Reverse Osmosis (RO) membrane filter which is typically available in the spiral wound format. This is the only filter capable of preventing dissolved salts (present as ions) from passing through in significant quantities. It also eliminates dissolved organics, viruses and bacteria from the filtered water. RO membrane filters are not “dead-end” but “cross-flow”. In “cross flow” filtration the water passes over the filter, while only a fraction of the input water passes through it. Cross flow filters essentially splits the input water into 2 streams. These are the “pure” water stream made of the “pure” water that passes through it and the “concentrated” water stream which consists of the water that passes over it, which is also called the “reject” water stream. The “pure” water stream has a significantly lower concentration of the dissolved salts, when the filter is a RO membrane filter. Cross flow filtration enhances life of the filter.

The object of the invention is to ensure that the water purification system internal component more specifically the ‘membrane’ is routinely cleaned.

Current Issues with RO Membrane Technology
One of the main disadvantages of the RO membrane technology is that it produces a “reject” water stream which typically consists of 75 % of the input water volume. This water wastage can be reduced by recovering more of the input water as pure water thereby reducing the “reject” stream. If the fraction of the input water recovered as pure water is high, then the salt concentration in the reject stream is also high which accelerates the formation of scale on the outer surface of the membrane. Scale is composed of precipitated salts which are typically Calcium or Magnesium Carbonates. Hence most water purification systems choose to operate at low recovery of pure water (typically 30 % or below) to ensure long life of the RO membrane. However even after operation at low pure water recovery, with use, scale develops on the RO membrane filter which reduces flow of purified water through the filter. This also increases the quantity of water which is rejected by the RO membrane filter. Over time scaling of the RO membrane causes operating pressure to build up which can lead to system failure.

The life of the membrane filter varies with the TDS level of the input water and the pure water recovery level it is operated at. The life can vary from 3 months to over 3 years depending on the above variables. Due to scaling or fouling of the RO membrane element and failure of the other components and filters, water purification systems may require frequent service and replacement of parts. Hence, a system of maintaining the RO membrane element by preventing the formation of scale in these elements would be of considerable value to consumers. An Automatic Membrane Maintenance (AMM) system would also allow for using the RO system at higher water recovery, as scale formation, which is faster at higher pure water recovery, could be prevented. Hence an effective AMM system would allow us to operate the RO system with lower water waste.
DESCRIPTION OF THE DRAWINGS
Figure 1
Parts Part numbers
1 inlet
2 Low pressure switch
3 Pressure reducing valve
4 Sediment filter
5. Silver activated carbon filter
6. Hollow fibre membrane
7. Input TDS measurement
8. RO Pump
9. Solenoid valve 1
10 RO Membrane
11 Flow restrictor
12 Post carbon
13 Output TDS measurement
14 Storage Tank
15 Solenoid valve 2
16 Drain / Reject outlet
17 Product outlet

Figure 2
Parts Part numbers
1. Inlet
2. Low pressure switch
3. Pressure Reducing valve
4. Sediment Filter
5. Silver activated carbon filter
6. Hollow fibre membrane
7. Input TDS measurement
8. RO Pump
9. Solenoid valve 1
10. RO Membrane
11. Flow Restrictor
12. Post Carbon
13. Output TDS measurement
14. Storage Tank
15. Solenoid valve 2
16. Drain /Reject outlet
17. Product Outlet
18. Backwash Pump
19. Check valve
20. Solenoid valve 3

Figure 3
Parts Part Numbers
1. Inlet
2. Low Pressure switch
3. Pressure Reducing valve
4. Sediment Filter
5. Silver activated carbon filter
6. Hollow Fibre membrane
7. Input TDS measurement
8. RO pump
9. Solenoid valve 1
10. R O membrane
11. Flow Restrictor 1
12. TDS Control valve
13. Check valve 1
14. Flow restrictor 2
15. Post carbon
16. Output TDS measurement
17. Storage Tank
18. Solenoid valve 3
19. Drain/ Reject outlet
20. Product outlet

Figure 4
Parts Part number
1 Inlet
2 Low Pressure Switch
3 Pressure Reducing valve
4 Sediment Filter
5 Silver activated carbon filter
6 Hollow Fibre membrane
7 Input TDS measurement
8 R O Pump
9 Solenoid valve 1
10 RO Membrane
11 Flow Restrictor 1
12 TDS control valve
13 Check Valve 1
14 Flow restrictor 2
15 Post Carbon
16 Output TDS measurement
17 Storage Tank
18 Solenoid valve 2
19 Drain/Reject outlet
20 Backwash Pump
21 Check valve 2
22 Solenoid valve 3

Figure 5
Parts Part number
1. Inlet
2. Low Pressure switch
3. Pressure Reducing valve
4. Sediment Filter
5. Silver activated carbon filter
6. Hollow Fibre membrane
7. Input TDS measurement
8. RO Pump
9. Solenoid valve 1
10. RO membrane
11. Flow restrictor
12. Post carbon
13. Output TDS measurement
14. Storage Tank
15. Solenoid valve 2
16. Drain / Reject outlet
17. Product outlet

Figure 6
Parts Part numbers
1. Inlet
2. Low Pressure Switch
3. Pressure Reducing valve
4. Sediment Filter
5. Silver activated carbon filter
6. Hollow fibre membrane
7. Input TDS measurement
8. R O pump
9. Solenoid valve 1
10. RO Membrane
11. Flow restrictor
12. Post Carbon
13. Output TDS measurement
14. Storage Tank
15. Solenoid valve 2
16. Drain/Reject outlet
17. Product outlet
18. Solenoid valve 3

Figure 7
Parts Part Number
1. Inlet
2. Low Pressure Switch
3. Pressure Reducing valve
4. Sediment Filter
5. Silver activated carbon filter
6. Hollow fibre membrane
7. Input TDS measurement
8. RO pump
9. Solenoid valve 1
10. RO membrane
11. Flow restrictor
12. Post carbon
13. Output TDS measurement
14. Storage Tank
15. Solenoid valve 2
16. Drain/Reject outlet
17. Product outlet
18. Solenoid valve 3
19. Backwash pump

Figure 8 (a)
Parts Part Numbers
1. Tap/Supply
2. Pre-filter
3. Pump
4. RO Membrane Casing
5. Throttle Valve
6. Reject
7. Permeate Storage

Figure 8(b)
Parts Part Numbers
1. Tap/Wall Outlet
2. Pre-filter
3. Pump
4. RO Membrane Casing
5. Throttle Valve
6. Reject
7. Permeate for membrane cleaning
8. Permeate Storage

DESCRIPTION OF THE INVENTION

The invention is disclosed with figures 1-7, 8a, 8b.

In this invention we describe an improved RO membrane based water purification system, and a process for operating the same, which significantly enhances life of the RO membrane. We claim that the above system and process has the ability to significantly delay scale formation, and hence fouling of the RO membrane element, even when it is operated under conditions of high input water TDS and Hardness. Its value can also be demonstrated by operation 2 RO membrane based purifiers at high pure water recovery, say above 50 %, one with and the other without the provisions disclosed in this invention. A comparison of the flow rates of the pure water from these 2 systems would demonstrate if the provisions disclosed here are capable of extending the life of the RO membrane element. The system described in this invention also allows the user to operate the water purification system at a higher pure water recovery, without risking damage to the membrane, thereby reducing water waste by around 50 %.

Figure 1 shows a typical RO membrane based water purification system. Water enters the system at (1) and purified water is available at port (17) and the concentrated reject water is discharged at port (16) which is typically placed in the kitchen sink for home use water purification systems. All significant functional parts are shown in the figure and the part names are shown in the legend. In the direction of water flow through the system the first functional part is a low pressure switch (3), followed by a pressure reducing valve (3), which are provided to safeguard the system from very low or very high supply water pressure. Next come the Sediment Filter (4), the Silver enhanced Activated Carbon Filter (5) and the hollow fibre membrane filter (6). This is followed by a port for measuring the input TDS in the water (7). Next in line, typically, is a positive displacement pump, usually called the RO pump (8), which is required to pressurize water to get an acceptable flow rate of purified water through the membrane. The RO pump is followed by a solenoid valve (9) used to start and stop water flow through the membrane element. This is followed by the RO membrane casing, which holds the RO membrane element (10). The RO membrane element in the casing, “splits” the input water stream into a low salt containing stream and a high salt containing stream. The low salt containing stream, which is called the pure water stream or the permeate stream, is typically allowed to collect in a pure water or product water storage tank (14) from where it is dispensed for use. Many purifiers provide another carbon filter in the permeate water line upstream of the storage tank which is often called the “post carbon” (12) and it is expected to impart a natural taste to the product water. Another part often present is an output TDS measurement point (13) which is used to measure and display the TDS level in the output water. Yet another essential part of a RO based water purification system, is a flow restricting or throttling device (11) which is used to ensure adequate positive pressure is maintained in the RO casing to achieve an acceptable permeate flow from the RO system. The output from the flow restricting device is discharged to the sink (16). Optionally yet another solenoid valve (15) can be provided to empty the water storage tank into the sink, on demand. While the above describes a typical RO based home use water purification system, it is possible to construct a system with additional parts for functional benefits or without some of the parts mentioned above.

Typically a RO based water purification cycle is operated by a level sensor placed in the storage tank. When the system is switched on, the level sensor is used to start the system if the storage tank is empty. When the water level in the storage tank reaches the full level, the system is switched off. The system is then switched on only when the level drops below a preset empty level. The gap between the “full” level and the “empty” level should be sufficient to prevent frequent cycling of the purifier.

Figure 2 shows a schematic of a water purification system which is identical to the one described above, but with some additional parts, which embody one of the several possible means of implementing this invention. The additional parts are a pump (18), a check valve (19) and a solenoid valve (20), as shown in figure 2. In use, the “auto-cleaning” system operates after every fill cycle in the following manner. When the system is switched off, upon reaching the full level of the storage tank, the RO pump (8), the valves (20) and (9) are switched off and the backwash pump (18) is switched on. This causes the purified water from the storage tank to flow into the RO membrane from the permeate side. This permeate then displaces the high TDS water from inside the RO casing which exits the system through the flow restrictor (11). The backwash pump is allowed to run for a few minutes to ensure that all the high TDS water from the casing is displaced. This system for cleaning the membrane has been found to enhance membrane life significantly.

Figure 3 shows another water purification system with a few additional parts for feedback control of the TDS level of the output water, using an “Intelligent TDS control system”. The parts are labelled and explained in the legend. Figure 4 shows another water purifier identical to the one shown in figure 3 but with the additional parts which enable the Automatic Membrane maintenance (AMM) system to be implemented in the same. These additional parts are the pump (20), the check valve (21) and the solenoid valve (22). In use, the AMM system is triggered immediately after the storage tank is filled. The pump sends permeate water into the RO casing to clean the membrane system and displace the high TDS water from around the membrane. This results in a significant improvement in membrane life.

Figure 5 shows a schematic of a RO membrane based water purification system, without the essential features of this invention. The system shown in Figure 5 differs from the systems shown in figure 1 and figure 3, in that the storage tank (14) in figure 5 is elevated to a level such that the tank bottom is above the RO membrane casing. The rest of the elements shown in figure 5 are explained in the legend and the preceding text. Figure 6 shows the schematic of a water purification system which is identical to the system shown in Figure 5, but having additional features which represent a possible embodiment of this invention. These features are a tubing through which water can pass, connecting the bottom of the permeate storage tank (14) to the permeate discharge end of the RO membrane casing, and a closure means, such as a solenoid valve (18), which is placed in the above conduit, such that the solenoid valve can be used to control the backwash process. Yet another possible embodiment of the invention is shown in figure 7 wherein a pump (19) is added in the conduit connecting the bottom of the permeate storage tank (14) to the permeate discharge end of the RO membrane casing (10). In operation this feature would allow the use of the pump to backwash the membrane element with permeate.

Yet another preferred embodiment of this invention is shown in Figure 8. Figure 8 (a), shows a schematic of a simple RO based water purification system without the features of this invention. The water purification system shown in figure 8 (a) consists of an inlet water supply port (1), a pre-filtration system (2), a pump or pressurizing device (3), a closure means followed by the RO membrane element (4) which is held within a RO membrane casing. The RO membrane in the casing splits the input stream into two streams, the relative volumes of which are controlled by a throttling means (5), which produces a concentrated salt solution called the “reject” (6) and a permeate or relatively salt depleted solution called the permeate, which is typically collected in a storage tank (7). Figure 8 (b) shows a schematic of a water purification system which is identical to the system shown in figure 8(a) but additionally having features which represent another preferred embodiment of this invention. This additional feature is a permeate holding vessel (7) which is placed at an elevation above the level of the membrane casing. The permeate holding vessel (7) has a inlet port, which is at its bottom end, and a discharge port, which is above the bottom end, preferably near its top end. There is a water conveying conduit connecting the discharge port of the permeate holding vessel (7) to the inlet of the permeate storage tank (8). In operation, the permeate produced by the RO membrane first fills the permeate holding vessel (7), after which it “overflows” out of (7) to fill the permeate storage tank (8). When the RO membrane operation stops, permeate held in the dead volume in (7) is available to the membrane at its permeate discharge end. This dead volume of permeate flows in the reverse direction through the membrane, due to the osmotic gradient thereby cleaning out the membrane of deposited salts. Hence the system schematic shown in figure 8(b) represents a simple implementation of this invention.

The advantages and inventive steps of this invention are detailed below.
In the first aspect, the invention is relating to a improved water purification system and a process for operating the same, where in the water purification system is provided with the following additional parts :-
a. A permeate holding vessel which is substantially above the membrane element
b. A conduit capable of conveying water connecting the above permeate holding vessel to the permeate discharge port of the RO membrane element with or without a closure means
c. An arrangement of the above elements such that the stored permeate is available under a positive pressure to the membrane element on its permeate side, wherein natural or forward osmosis can occur to transport the permeate from the permeate side of the membrane separation means to the feed side of the membrane separation means, when the cross flow reverse osmosis flow is stopped.
In another aspect the invention relates to a process of treating feed water containing undesirable dissolved salts removable by reverse osmosis and providing a treated water stream comprises of various steps. Firstly the system has a membrane separation means having a feed side and a permeate side. A storage means for storing a portion of treated feed water is arranged on the permeate side of the membrane separation means. A target instruction means is arranged for fetching a target instruction for repeated performance of removing the dissolved salts from the feed water during reverse osmosis cross-flow conditions and cleansing the membrane separation means during forward osmosis reverse flow conditions. The process involves the performance of a first execution as per the said target instruction means which is firstly passing the feed water containing dissolved salts from the feed side of the membrane separation means and across the membrane separation means under reverse osmosis cross-flow conditions controlled by a cross-flow means. Due to flow of feed water the membrane separation means is soiled to a salt solutes-enriched fouled membrane separation means.
The process includes removing from the permeate side of membrane separation means a treated water permeate stream depleted in the dissolved salts through a first outlet means and also removing from the feed side of membrane separation means a dissolved salts-enriched water stream through a second outlet means. The process has a step for storing a portion of treated water permeate stream on the permeate side of the fouled membrane separation means in the storage means which is the end of the first performance execution.

Further there is a need to perform a second execution as per the said target instruction means of in continuation of termination of above first execution process of target instruction means which comprises of allowing reverse flow of the said stored treated water permeate stream from the storage means on the permeate side of the said fouled membrane separation means and across the said fouled membrane separation means under forward osmosis reverse flow conditions for cleansing the said fouled membrane separation means, or it may allow the reverse flow of the said stored treated water permeate stream from the storage means on the permeate side of the said fouled membrane separation means and across the said fouled membrane separation means under forward osmosis reverse flow conditions controlled by a back wash means for cleansing the said fouled membrane separation means, and thereafter removing from the feed side of membrane separation means a salt-solutes-enriched water stream. The flow of clean water ensures the fouled membrane separation means is cleaned. The above process comprising of first execution and second executions have to be repeated which is repetition of instruction of target instruction means to continuously process the feed water to produce treated water stream as per fetched target instruction.
In another aspect the invention relates to a process of treating feed water as described above and is such that target fetching instruction of repeat performance of above step of target instruction means of above embodiments includes a loop count value that determines the predetermined number of times the above instruction of first execution and second execution is performed repeatedly until termination.
In another aspect the invention relates to a process of treating feed water as described above to facilitate reverse flow under natural osmosis such that the forward osmosis reverse flow conditions for the reverse flow of the said stored treated water in storage means from permeate side of membrane separation means and across the fouled membrane separation means to the feed side of the membrane separation means is by using a back wash means which is a minimal hydrostatic head of the storage means above the membrane separation means which facilitate the desired reverse flow under natural osmosis.
In another aspect the invention relates to a process of treating feed water as described above is such that the forward osmosis reverse flow conditions for the reverse flow of the said stored treated water in storage means from permeate side of membrane separation means and across the fouled membrane separation means to the feed side of the membrane separation means is by using a back wash means which is a closure means and arranging the closure means in-between the storage means water and the membrane separation means.
In another aspect the invention relates to a process of treating feed water as described above is such that the closure means of the back wash means may be a manually operable means, an electromechanically operable means, an electromagnetically operable means, an electrically operable means, or an electronically operable means.
In another aspect the invention relates to a process of treating feed water as described above is such that the forward osmosis reverse flow conditions for the reverse flow of the stored treated water in storage means from permeate side of membrane separation means and across the fouled membrane separation means to the feed side of membrane separation means for the reverse flow is a back wash means which is a pump with a closure means.

In another aspect the invention beyond process also discloses a system which is a reverse osmosis treating system for treating feed water containing dissolved salts removable by reverse osmosis and providing a treated water stream comprising of :
a. a membrane separation means having a feed side and a permeate side.
b. a storage means which stores all or a portion of treated water stream from the permeate side of the membrane separation means.
c. a first outlet means is provided for removing treated water from the permeate side of the membrane separation means.
d. a second outlet means provided for removing dissolved salt enriched water stream from the feed side of the membrane separation means.
e. a cross-flow means having pump means and a closure means is arranged on the feed side of the membrane separation means along with another closure means arranged on the permeate side of the membrane separation means to control flow of feed water from the feed side of the membrane separation means and across the membrane separation means to the permeate side of the membrane separation means under reverse osmosis cross flow conditions,
f. a back wash means which is achieved by placing the storage means at a hydrostatic head above the membrane separation means with or without at least a closure means arranged on permeate side of membrane separation means to control back-flow of stored portion of treated water stream in the storage means from the permeate side and across the membrane separation means to the feed side of membrane separation means for cleansing the said fouled membrane separation means under forward osmosis reverse flow conditions, and
g. a target instruction means is arranged for operating selectively, sequentially and combinedly the said cross-flow means with said pump, the closure means upstream of the membrane separation means and the closure means downstream of the membrane separation means for reverse osmosis cross flow conditions and the said backwash means for forward osmosis reverse flow conditions, thereby controllably treating the feed water and cleansing the membrane separation means.
The above said arrangement of the system is novel in feature that the said cross-flow means with the pump means, the closure means upstream of the membrane separation means and the closure means downstream of the membrane separation means adapted combinedly to enable during switch ON mode of cross-flow means the passing of the contaminated feed water from the feed side of membrane separation means and across the membrane separation means to the permeate side of membrane separation means under reverse osmosis cross flow conditions for generating a treated water permeate stream depleted in the dissolved salts at the permeate side of the membrane separation means and leaving behind on the feed side of the membrane separation means a dissolved salts-enriched water stream and further fouling the membrane separation means into a salt-solutes-enriched fouled membrane separation means due to absorption of dissolved salts from the feed water during its passage across the membrane separation means.
The arrangement of the above system as per invention is also novel for the reason that the arrangement is such that wherein backwash means with or without closure means is adapted to enable during switch OFF mode of cross flow means the passing of the back-flow of a stored portion of the generated treated water permeate stream from the permeate side of the membrane separation means and across the membrane separation means under forward osmosis reverse flow washing conditions and generating a salt-solutes-enriched water stream at the feed side of membrane separation means and leaving the fouled membrane separation means clean due to release of absorbed salts into treated water during water passage across the membrane separation means.
The arrangement of the above system as per invention is further distinct for the reason that the arrangement is such that and wherein the operation state of cross flow means is different from the operation state of the backwash means at an instant whereby if one of the two means is in ON state, the other means is in OFF state, and wherein the operation state of the closure means upstream of the membrane separation means is same as the operation state of the closure means downstream of the membrane separation means, which is same as the operation state of the cross-flow means wherein if one of the two closure means is in ON state, the other closure means is also in the ON state.
In another aspect the reverse osmosis treating system as described above is such that the target instruction means is adapted to determine the predetermined number of times, the selective operation of the cross flow means with pump means, the closure means upstream of the membrane separation means and the closure means downstream of the membrane separation means, and thereafter corresponding operation of the backwash means is performed sequentially and alternatively until termination.

In another aspect of the above system as per invention, the reverse osmosis treating system as described above is such that the closure means for the backwash means may be a manually operable means, an electromechanically operable means, an electromagnetically operable means, an electrically operable means, or an electronically operable means.

In another aspect of the above system as per invention, the reverse osmosis treating system as described above is such that the backwash means is a hydrostatic head of the storage means above the membrane separation means.

In another aspect of the above system as per invention, the reverse osmosis treating system as described above is such that the storage means, the membrane separation means and backwash means form a generally U tube arrangement having one long arm and one short arm and such that the storage means is positioned at the remote end of the long arm, the membrane separation means positioned at the other remote end of the short arm and the optional backwash control means arranged therein-between.

In another aspect of the system as per invention, the reverse osmosis treating system as described above is such that the backwash means is a pump.
In another aspect, of the invention, it is an improved water purification system and a process for operating the same, where in the water purification system is provided with the following additional parts
(i) a pump is provided whose suction end is operationally connected to the storage tank containing the permeate and whose discharge end is connected to the RO membrane elements permeate discharge port
(ii) a check valve or any other similar valve is provided downstream of the above pump to prevent any back flow into the pump
(iii) a solenoid valve or any such shutoff valve is provided upstream of the post carbon filter or in the absence of the post carbon filter a solenoid or any other shutoff valve is provided in the line conveying pure / permeate water to the storage tank
(iv) a 3-way junction point is provided in the permeate line downstream of the RO membrane element, such that the first of the other 2 ends of the 3-way junction is connected to the check valve from the above mentioned pump, and the other end of the 3-way junction is connected to the inlet of the solenoid or shut-off valve upstream of the post carbon filter

In another aspect of the invention, it is for a process for operating the above water purification system, wherein at the end of each water fill cycle, or within a time period of upto 60 mins from the end of the fill cycle, the following are enacted, to complete the backwash cycle. The end of the fill cycle ensures the switching off the RO pump, closing off the solenoid valve in the inlet line to the RO membrane element,
(i) The solenoid valve placed upstream of the post carbon filter or in the absence of the post carbon filter, the solenoid valve in the pure water discharge line, conveying RO permeate to the storage tank, is closed. This solenoid valve is allowed to remain closed for the duration of the backwash cycle, which can extend from 10 seconds to 1 hour.
(ii) The above mentioned pump with suction end connected to the permeate storage tank and the discharge end connected to the RO permeate discharge port, is switched on, and allowed to run for a period of the backwash cycle which can vary from 10 secs to 1 hour.
(iii) The above components, namely the backwash pump and the solenoid valve are switched off at the end of the back-wash cycle, such that the system is ready for the next fill cycle.
The embodiments and drawings are only sake of understanding and do not limit the scope of invention. All variations and modification as known to skilled persons are well within the scope of this invention.