Water purification systems are used to provide high-quality drinking water. Reverse osmosis systems are widely used to deliver purified water in households and commercial beverage systems. Typical arrangements include a storage tank with a bladder in which purified water is stored under pressure. During the purification process, water flowing through a reverse osmosis membrane experiences a pressure drop. With increasing fluid levels in the storage tank, the pressure in a purified water line connecting the reverse osmosis membrane to the storage tank also increases. As a result, the purified water must flow against a “back pressure” resulting in a decrease in flow rate of the purified water. With an almost full tank, less than 10% of the incoming raw water is purified by the reverse osmosis membrane and stored in the storage tank, while over 90% of the water is not used and drained from the system as so-called concentrate.
Some reverse osmosis systems use a number of pumps in order to reduce the water being drained from the system. The pumps can be used to increase the pressure upstream of the reverse osmosis membrane. Other systems use a pump to recycle the concentrate back into the system upstream of the reverse osmosis system. These pumps are driven by electric motors, which increase the overall size, weight, and energy consumption of the reverse osmosis system. As a result, installation of reverse osmosis systems can require significant on-site assembly and a team of technicians due to the size and the weight of the systems.
Atmospheric tanks are also commonly used in reverse osmosis systems to reduce the water waste. Their advantage lies in the fact that the purified water does not have to flow against the increasing back pressure, resulting in fewer variations in the flow rate of the purified water. Their disadvantages lie in the fact that powerful pumps are required to extract water from atmospheric tanks over a wide range of flow rates.
Permeate water produced by reverse osmosis systems have a very low mineral content or a low total dissolved solids (TDS) level. Beverages prepared with the permeate water can lack the taste associated with the minerals. If the permeate water is used for drinking purposes, minerals are often added back into the permeate water downstream of the reverse osmosis membrane. Calcite sticks can be used to re-mineralize permeate water. However, a concentration of minerals achieved with this approach can be variable, and this concentration is not easily adjusted to meet specific TDS concentrations.
Some embodiments of the invention provide a reverse osmosis system including a feed water inlet, a reverse osmosis module coupled to the feed water inlet, and one or more blend valves. The reverse osmosis module can include a permeate outlet, through which permeate water can exit the reverse osmosis module. The blend valve can be coupled to the permeate outlet and the feed water inlet and can be capable of blending the feed water and the permeate water to produce mixed water. The blend valve can be adjusted to achieve a desired TDS level in the mixed water.
Some embodiments of the invention provide a reverse osmosis system including a reverse osmosis module having a reverse osmosis membrane, a boost pump to provide feed water to the reverse osmosis membrane, and a permeate pump to remove permeate water from the reverse osmosis membrane. The boost pump and the permeate pump can be driven by a common motor with two output shafts.
Some embodiments of the invention provide a reverse osmosis system including a reverse osmosis module and a pressure tank coupled to a permeate outlet. The reverse osmosis membrane can be flushed with permeate water after there has been substantially no demand for permeate water, but before an induction time for scaling has elapsed.
Before any embodiments of the invention are explained in detail, it is to be understood that the 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 practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof 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 both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention.
Some embodiments of the invention provide a reverse osmosis system including a feed water inlet, a reverse osmosis module coupled to the feed water inlet, and one or more blend valves. The reverse osmosis module can include a permeate outlet, through which permeate water can exit the reverse osmosis module. The blend valve can be coupled to the permeate outlet and the feed water inlet and can be capable of blending feed water and permeate water to produce mixed water, with a TDS value anywhere between a TDS value of the feed water and TDS value of the permeate TDS. The blend valve or valves can be manually adjusted at system installation until a TDS level of the mixed water (e.g., measured with a handheld TDS sensor) reaches the desired value. Alternatively, TDS sensors can be incorporated within the reverse osmosis system that sense a current TDS level in the mixed water. The blend valve or valves can be controlled to achieve a desired TDS level in the mixed water.
Some embodiments of the invention provide a reverse osmosis system including a reverse osmosis module, a pressure tank coupled to a permeate outlet, and a permeate flush scheme. During the reverse osmosis process, feed water containing minerals and/or dissolved solids can be pressurized and can be fed to a reverse osmosis membrane. Given sufficient feed water pressure, permeate water (mostly free of minerals and dissolved solids) can pass through the membrane, leaving behind the minerals and/or the dissolved solids. As a result, the feed water stream can become more concentrated in dissolved solids, and this stream is known as concentrate. If enough permeate is forced through the membrane, the dissolved solids content of the concentrate can surpass the mineral's solubility limit and thus mineral precipitation can occur. The ratio of the permeate that is forced through the membrane to the feed water supplied to the membrane is known as membrane recovery.
At a given membrane recovery, the precipitation of the minerals and/or dissolved solids may or may not occur instantly, and if it does not occur instantly, the time lag observed can be termed an induction time. The induction time can be increased by adding anti-scaling chemicals, such as, but not limited to, hexametaphosphate and polymeric acrylic acids. Mineral precipitation within the reverse osmosis membrane can be particularly problematic if the flow through the system is stopped (i.e., when there is no water demand) and the minerals either precipitate on the membrane surface or precipitate from the concentrate stream and deposit on the membrane surface, thus reducing the amount of water that can permeate through the membrane.
In order to maximize the permeate recovery of a reverse osmosis system, but to also ensure that scaling does not occur, a flush scheme can be incorporated into the operation of the RO system. The flush scheme can direct water, which can vary in quality between the feed water and the permeate water, upstream from the pressure tank to the reverse osmosis module in order to flush the reverse osmosis membrane with water. The reverse osmosis membrane can be flushed with water after there has been substantially no demand for mixed water or permeate water, but before an induction time for scaling has elapsed. The duration of the flush can be such that the concentration of minerals and dissolved solids present in the feed water and the concentrate are equivalent to the concentrations of minerals and dissolved solids in the water used for flushing. Operationally, this can be determined by measuring the TDS level of the concentrate exiting the membrane module, and noting when the TDS level approaches the TDS level of the water used for flushing and thus ending the flush duration.
A suitable pressure tank 28 can be the accumulator tank described in U.S. Pat. No. 7,013,925 issued to Saveliev et al., the entire contents of which is herein incorporated by reference. The pressure tank 28 can vary in volume. In one embodiment, the pressure tank 28 does not exceed about two gallons, while in another embodiment, the pressure tank 28 does not exceed about six gallons. The pressure tank 28 can store the permeate water. In some embodiments, the pressure tank 28 can store a mixture of the permeate water and the feed water.
The reverse osmosis system 10 of
The third manifold 22 can be equipped with the second valve 36 that can be normally closed and can open during normal operation. The third manifold 22 can also be equipped with a blend port 38. The blend port 38 and the bypass port 35 can be in fluid communication so that a portion of the feed water can bypass the reverse osmosis module 20. The mixture of permeate and feed water leaving the third manifold 22 can be referred to as mixed water. Downstream of the third manifold 22, permeate water or mixed water can flow through the permeate pump 24 before flowing through the fourth manifold 26. The permeate pump 24 can work against an increasing pressure in the pressure tank 28 in order to further support feed water flow through the reverse osmosis module 20. The fourth manifold 26 can be equipped with a second TDS sensor 40, which can measure the TDS level of the permeate water or the mixed water. From the fourth manifold 26, the permeate water or the mixed water can be stored in the pressure tank 28.
In one embodiment, the permeate pump 24 has a shut-off setting of about 90 PSI in order to shut the reverse osmosis system 10 down when the pressure tank 28 is pressurized to about 90 PSI. From the permeate pump 24, the water enters the fourth manifold 26. When the TDS level of the permeate water or mixed water is higher than a maximum setting, the second valve 36 can close while the boost pump 16 is running, forcing all the water to flush through the brine port 45 in order to flush the surface of the reverse osmosis module 20.
From the brine port 45 of the reverse osmosis module 20, the water can pass through a brine water flow control (not shown) and then through a check valve (not shown). The blend port 38 can be equipped with a flow control to regulate the amount of water bypassing the reverse osmosis module 20. A controller 55 can measure the incoming TDS value with the first TDS sensor 34 and the outgoing TDS with the second TDS sensor 40. An ideal mixed water TDS value can be entered into the controller 55 by a technician. The blend port 38 and the brine water flow control can be set during installation to obtain the ideal mixed water and recovery fraction for the local water quality. If the mixed TDS rises above its set point, the reverse osmosis module 20 may be fouling. The first valve 32 can remain open and the second valve 36 can close while the boost pump 16 is running. All the water in the reverse osmosis module 20 can be forced out the brine port 45, flushing the reverse osmosis module 20. In one embodiment, the flush cycle can last for about one minute. If the reverse osmosis system 10 goes into the flush cycle a certain number of times and the permeate TDS is still above its setting, the controller 55 can indicate that an adjustment needs to be made. The technician can make adjustments to the blend port 38 or replace the carbon filter 12 and/or the reverse osmosis module 20.
In one embodiment, the reverse osmosis system 10 only measures the TDS of the mixed water. As a result, the reverse osmosis system 10 can includes the TDS sensor 40.
In some embodiments, a net flow rate through the boost pump 16 can differ significantly from a net flow rate through the permeate pump 24. A volumetric displacement of the boost pump 16 and a volumetric displacement of the permeate pump 24 can be adjusted according to a desired flow rate. For example, the volumetric displacement of the boost pump 16 can be selected to coincide with the net flow rate expected for the feed water stream, and the volumetric displacement of the permeate pump 24 can be selected to coincide with the net flow rate expected for the permeate stream.
The net flow rate through the permeate pump 24 can depend on the feed water characteristics as described above. The net flow rate through the permeate pump 24 can correlate to the membrane recovery of the reverse osmosis module 20. In some embodiments, the volumetric displacement of the boost pump 16 can be substantially equal to the volumetric displacement of the permeate pump 24. In some embodiments, the boost pump 16 and the permeate pump 24 can share a common motor 44, and the motor 44 can drive the boost pump 16 and the permeate pump 24 at substantially equal or different speeds.
The different net flow rates through the boost pump 16 and the permeate pump 24 can compromise the longevity of at least one of the boost pump 16 and the permeate pump 24. Some embodiments can include a bypass, which can recycle at least a portion of the net flow rate through at least one of the boost pump 16 and the permeate pump 24. In one embodiment, the bypass can fluidly connect an outlet of the boost pump 16 and the permeate pump 24 with a respective inlet of the same pump. As a result, a gross flow rate through the boost pump 16 and the permeate pump 24, i.e. the net flow rate plus the recycled portion by the bypass, can be adjusted to the net flow rate of the corresponding other pump. In one embodiment, the gross flow rate through the permeate pump 24 can substantially equal the net flow rate of the boost pump 16. The bypass can be adjusted using gate valves, needle valves, pressure regulators, orifices or other conventional devices. The bypass can be manually operated or by the controller 55.
While the bypass can substantially keep the gross flow rate through the boost pump 16 and the permeate pump 24 equal, the net flow rate of the boost pump 16 and the permeate pump 24 can be substantially different, if a portion of the net flow rate is recycled through the bypass. In one embodiment, the bypass can fluidly connect the pressure tank 28 with the inlet of at least one of the boost pump 16 and the permeate pump 24. As a result, the net flow rate through the boost pump 16 and the permeate pump 24 can be adjusted to fulfill on-demand flow requirements of the reverse osmosis system 10.
The reverse osmosis system 10 of
The reverse osmosis system 10 of
The reverse osmosis system 10 of
The reverse osmosis system 10 of
The reverse osmosis module 20 can be flushed to reduce scaling. This can be achieved in a number of ways. The valves 32, 36 can be changed to normally open valves and can attach to the brine port 45. The normally open valves 32, 36 can be closed while producing the permeate water and can open to purge when the boost pump 16 and the permeate pump 24 are off. This can result in flushing the reverse osmosis module 20 every cycle of the reverse osmosis system 10. A pressure relief valve can be added to the brine port 45 to purge concentrate when the second valve 36 is closed. The water flow can also be limited during a production cycle that is held constant as the pressure tank 28 is filled to pressure.
The plumbing connections of the reverse osmosis system 10 of
In some embodiments, the required inlet water pressure for the reverse osmosis system 10 of
The reverse osmosis system 10 of
In some embodiments, the demands of all the beverage equipment the reverse osmosis system 10 will serve can be averaged together. The reverse osmosis system 10 can serve various types of beverage equipment, such as coffee equipment, fountain equipment, and steamer equipment. Table 1 summarizes performance characteristics of the reverse osmosis system 10 according to one embodiment of the invention.
The reverse osmosis system 10 can include safety devices, such as a pressure switch to guard the reverse osmosis module 20 and plumbing connections from rupture and a temperature probe to guard against high and low temperatures. The temperature limitations of the TDS meter can also be selected and published in a user manual.
The reverse osmosis system 10 of
The reverse osmosis system 10 can still further include a controller 200, a first pressure switch 205, and a second pressure switch 210. The display 55 can connect to the controller 200 and can communicate user input to the controller 200. The controller 200 can operate the boost pump 16, the permeate pump 24, the first valve 32, the second valve 36, and the motor 44 based on signals from the TDS sensor 40, the display 55 (user input), the first pressure switch 205, and the second pressure switch 210. The controller 200 can include control routines to minimize user intervention.
From the feed inlet 30, incoming feed water can flow through the first manual shut-off valve 65 and the pressure regulator 80. If the reverse osmosis system 10 becomes inoperative, the manual shut-off valve 65 can be closed and the feed water can be directed to at least one of the permeate water outlet 100 and the mixture outlet 135. In one embodiment, the pressure regulator 80 can level the incoming feed water pressure to about 50 PSI to prolong the life span of the pre-treatment cartridge 13 and other components of the reverse osmosis system 10, and to ensure consistent blending of the feed water and the permeate water. The minimum incoming feed water pressure can be about 50 PSI, which may become necessary to achieve if the incoming feed water is pre-treated before entering the reverse osmosis system 10. From the pressure regulator 80, the feed water can flow through the first valve 32, the pre-treatment cartridge 13, and the boost pump 16 before entering the reverse osmosis module 20. The first valve 32 can be operated by the controller 200 depending on a detected flow demand of the permeate water. The detected flow demand can correspond to a signal from the second pressure switch 210.
The feed water entering the reverse osmosis module 20 through the feed water inlet 75 can reach the permeate outlet 76 or can exit the reverse osmosis module 20 through the brine port 45. The boost pump 16 can increase the feed water pressure to propel water through the reverse osmosis module 20 in order to increase the ratio of permeate water to concentrate. The flow control 160 can be positioned upstream of the concentrate outlet 165 and can restrict the flow rate through the brine port 45 to further support the production of permeate water. The flow of the concentrate leaving the reverse osmosis system 10 through the brine port 45 can be substantially laminar, in some embodiments. The concentrate outlet 165 can include one or more drain lines. The flow rate through the drain lines can be adjusted to achieve a system recovery fraction that depends on a local water quality.
The permeate water leaving the reverse osmosis module 20 through the permeate outlet 76 can enter the permeate pump 24. The controller 200 can operate the permeate pump 24 based on signals from the first pressure sensor 205, which can measure the pressure of the permeate water leaving the permeate pump 24. The permeate pump 24 can increase the production of the permeate water by lowering a pressure on its upstream side in order to increase the flow rate through the reverse osmosis module 20. The permeate pump 24 can also increase the pressure on its downstream side to facilitate filling of the pressure tank 28.
The second pressure switch 210 can measure the pressure of the permeate water downstream of the permeate pump 24. The signals from the second pressure switch 210 can be used as an indication of the fill level of the pressure tank 28. The permeate water pumped into the pressure tank 28 by the permeate pump 24 can exit through the outlet 42 of the pressure tank 28. From the outlet 42, the permeate water can flow through the second pressure regulator 85 before splitting into two streams. A first stream can flow through the permeate line 86 and can exit the reverse osmosis system 10 through the permeate water outlet 100. The permeate line 86 can include the second check valve 90 and the second manual shut-off valve 95.
A second stream of the permeate water can flow through the blend port 38, which can be fluidly connected to the bypass port 35. In some embodiments, the blend port 38 can include the DBV 105 and the third check valve 110. In some embodiments, the bypass port 35 can include the FBV 115 and the fourth check valve 125. The DBV 105 and the FBV 115 can be adjusted to control the TDS value of the mixture of the feed water and the permeate water. The TDS value of the mixed water can be measured by the TDS sensor 40 upstream of the mixture outlet 135. The third manual shut-off valve 130 can be positioned between the TDS sensor 40 and the mixture outlet 135. The DBV 105 can draw permeate water from the pressure tank 28 to create the mixture of the permeate water and the feed water. The pressure tank 28 can receive the permeate water while delivering the permeate water to the DBV 105. Using the permeate water stored in the pressure tank 28 can increase the flow rate of the mixed water and/or can prolong the time a certain flow rate of the mixed water can be achieved by the reverse osmosis system 10. Even if a requested flow rate of the mixed water can be fulfilled on-demand by the reverse osmosis system 10, the permeate water can be supplied from the pressure tank 28.
If the TDS sensor 40 detects an elevated TDS value, the controller can initiate a flush cycle. During the flush cycle, no permeate water will be produced. The first valve 32 can be closed by the controller 200, while the second valve 36 can be opened. The first check valve 82 can prevent flow back into the permeate pump 24. By opening the second valve 36, the permeate water stored in the pressure tank 28 can flow through the fifth check valve 155 to the feed water inlet 75 of the reverse osmosis module 20 with a high velocity in order to flush away accumulated deposits in the reverse osmosis module 20 and dissolved solids in the water adjacent to the membrane. The flush water together with the solids can exit through the brine port 45. The controller 200 can also initiate the flush cycle based on a regular interval. This regular interval and the duration of the flush cycle can be programmed in the controller 200 by a user or a technician. Table 2 summarizes the duration of the flush cycle proportional to the flow rate through the brine port 45 according to one embodiment of the invention.
The pre-treatment cartridge 13 can act as a scale inhibitor by removing dissolved and/or non-dissolved solids. The pre-treatment cartridge 13 can include an anti-sealant component. In one embodiment, the pro-treatment cartridge 13 can only include an anti-sealant while in other embodiments, the pre-treatment cartridge 13 can include the anti-sealant and/or carbon and/or particle filtration. The reverse osmosis module 20 can include a pre-treatment media. The pre-treatment media can act as a scale inhibitor. In one embodiment, the pre-treatment media can be positioned adjacent to the feed water inlet 75 and be separated from the brine port 45 by a brine seal. For example, the pre-treatment media can be positioned in a cap of the reverse osmosis module 20. The brine seal can prevent the feed water coming through the feed water inlet 75 from reaching the permeate outlet 76 without flowing through the reverse osmosis module 20. The scale pre-treatment media can reduce scaling on the reverse osmosis module 20 and can include hexametaphosphate, in some embodiments. In some embodiments, the pre-treatment media can include nanotechnology material, polyacrylic acids or other anti-sealants.
The reverse osmosis module 20 can include an ultra-slick surface to prevent scale build up. Other measures to prevent scaling on the reverse osmosis module 20 can include placing dimples and/or pleats on the reverse osmosis module 20. The pleats can be aligned with a direction of flow inside the reverse osmosis module 20. In some embodiments, the reverse osmosis module 20 can include sonicators, which can prevent or reduce scaling using ultrasonic waves. In some embodiments, the reverse osmosis module 20 can include nanotechnology material.
Near the feed water inlet 75, the flow rate of the feed water passing through the reverse osmosis membrane 214 can be less than farther away from the feed water inlet 75. As a result, the velocity of the water through the reverse osmosis membrane 214 can be smaller close to the feed water inlet 75 and can increase in the downstream direction. This velocity gradient can be related to the production of permeate water over the length of the reverse osmosis membrane 214. A slow flow velocity through the reverse osmosis membrane 214 can increase scaling. To help prevent or reduce scaling near the feed water inlet 75, the reverse osmosis membrane 214 can enable a higher flow rate to the permeate outlet 76. In one embodiment, the flow rate toward the permeate outlet 76 can be substantially constant over the length of the reverse osmosis module 20.
In one embodiment, a cross section of the feed water inlet 75 can be selected to increase the velocity of the feed water entering the reverse osmosis module 20. As a result, the flow rate to the permeate outlet 76 can increase near the feed water inlet 75. In one embodiment, the cross-sectional area of the feed water inlet 75, the permeate outlet 76, and the brine port 45 can be substantially equal. In another embodiment, the cross-sectional area of the feed water inlet 75, the permeate outlet 76, and the brine port 45 can be substantially different from each other. The brine port 45 can have the smallest cross-sectional area, the feed water inlet 75 can have a medium cross-sectional area, and the permeate outlet 76 can have the largest cross-sectional area.
In some embodiments, the reverse osmosis membrane 214 can be constructed using extruded netting manufactured by DelStar Technologies, Inc. and sold under the brand Naltex®.
After a prolonged period of the reverse osmosis system 10 being idle, the controller 200 can open the second valve 36. In one embodiment, the prolonged period can be less than a scaling induction time of about three hours, and in another embodiment, about one to two hours. The scaling induction time can depend on the TDS level of the feed water. In some embodiments, the scaling induction time can also depend on the scale inhibitor used upstream of the reverse osmosis module 20. With an open second valve 36, the permeate water can flow back through the fourth manifold 26 and the fifth check valve 155 before entering the reverse osmosis module 20 through the feed water inlet 75, as shown in
The incoming permeate water can force the feed water inside the reverse osmosis module 20 to exit through the brine port 45. The controller 200 can close the second valve 36 when substantially the entire reverse osmosis module 20 is filled with permeate water. Flushing the reverse osmosis module 20 with the permeate water can help prevent or reduce scaling on the reverse osmosis module 20 in order to enhance production of permeate water and increase the life span of the reverse osmosis module 20.
The flow path as shown in
If the stored permeate water must be discarded, the pressure tank 28 can be drained by opening the fourth manual shut-off valve 140. The permeate water stored in the pressure tank 28 can then exit through the tank bleed line 145. Draining the pressure tank 28 may be necessary to disinfect the components of the reverse osmosis system 10. A disinfectant can be flushed from the reverse osmosis system 10 before the production of the permeate water is started again.
The display 55 can include buttons to program the controller 200 via user input.
It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein. Various features and advantages of the invention are set forth in the following claims.
This application claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 61/062,611 filed on Jan. 28, 2008, the entire contents of which is incorporated herein by reference.
Number | Date | Country | |
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61062611 | Jan 2008 | US |
Number | Date | Country | |
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Parent | 12361487 | Jan 2009 | US |
Child | 15413265 | US |