Element arrangement methodology to improve performance of reverse osmosis and nanofiltration systems

Abstract

An aspect of the present disclosure is directed to methods and systems for enhanced membrane filtration system designs with reduced internal recycle inside the membrane system, while maintaining high recovery, and in some cases design comprise zero internal recycle, which imparts the ability to avoid scaling under supersaturated conditions by reducing residence times inside the system to below scaling induction time.

Description

ELEMENT ARRANGEMENT METHODOLOGY TO IMPROVE PERFORMANCE OF REVERSE OSMOSIS AND NANOFILTRATION SYSTEMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 740,424, filed December 31, 2024, which is fully incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to filtration systems and methods of operating filtration systems.BACKGROUND INFORMATION

[0003] Water filtration systems often include at least one filter membrane for producing permeate from a feed stream. One example of a water filtration system 10 is generally illustrated in FIG. 1.One or more pumps 12 (e.g., high pressure pumps) may be used to supply one or more feed streams 14 (also known as feedwater or feed flow) to the membrane system 10. The membrane system 10 further includes one or more membranes or filters 16. The feed stream 14 may be separated into a permeate flow 18 (e.g., a purified flow) and a concentrate or reject flow 20. A concentrate valve 22 may be provided to adjust the percentage of the feed stream 14 that flows into the permeate flow 18 and / or concentrate or reject flow 20.

[0004] As used herein, recovery is defined as the percentage of membrane system feedwater that emerges from the system as product water or permeate (e.g., recovery is the ratio of permeate flow to feed flow). Membrane system design is based on expected feedwater quality and recovery is defined through initial adjustment of valves on the concentrate stream. Recovery is often fixed at the highest level that maximizes permeate flow while preventing precipitation of super- saturated salts thin the membrane system.

[0005] As used herein, rejection is defined as the percentage of solute concentration removed from system feedwater by the membrane. In reverse osmosis (RO), a high rejection of total dissolvedsolids (TDS) may be important, while in nanofiltration (NF) the solutes of interest may be specific, e.g., low rejection for monovalent salts and high rejection for hardness and organic matter.

[0006] As used herein, passage is defined as the opposite of rejection, passage is the percentage of dissolved constituents (e.g., contaminants) in the feedwater allowed to pass through the membrane.

[0007] As used herein, permeate is defined as the purified product water produced by a membrane system.

[0008] As used herein, flow is defined as the rate of feed water introduced to the membrane element or membrane system, usually measured in gallons per minute (gpm) or cubic meters per hour (m3 / h). Concentrate flow is the rate of flow of non-permeated feedwater that exits the membrane element or membrane system. This concentrate contains most of the dissolved constituents originally carried into the element or into the system from the feed source. It is usually measured in gallons per minute (gpm) or cubic meters per hour (m3 / h).

[0009] As used herein, flux is defined as the rate of permeate transported per unit of membrane area, usually measured in gallons per square foot per day (GFD) or liters per square meter per hour (L / m2h).

[0010] Permeate flux and salt rejection are two performance parameters of which can be used to evaluate filtration system (e.g., reverse osmosis and / or nanofiltration) performance. Under specific reference conditions, flux and rejection are intrinsic properties of membrane performance. The flux and rejection of a membrane system may be influenced by variable parameters including pressure, temperature, recovery, and feed water salt concentration.

[0011] With reference to FIGS. 2-5, various qualitative examples of the impact of each of these parameters is shown when the other three parameters are kept constant. In practice, there is normally an overlap of two or more effects. For example, FIG. 2 illustrates that with increasing effective feed pressure, the permeate TDS decrease while the permeate flux will increase. FIG.3 generally illustrates that in the case of increasing recovery, the permeate flux will decrease and stop if the salt concentration reaches a value where the osmotic pressure of the concentrate is as high as the applied feed pressure. The salt rejection drops with increasing recovery. FIG. 4 generally illustrates that if the temperature increases and all other parameters are kept constant, thepermeate flux and the salt passage will increase. FIG. 5 generally illustrates the impact of the feedwater salt concentration on the permeate flux and the salt rejection.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various aspects and features of the present disclosure will be better understood by reading the following detailed description, taken together with the drawings wherein:

[0013] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the teaching of the present specification and are not intended to limit the scope of what is taught in any way.

[0014] FIG. 1 outlines the basic components of a nanofiltration or reverse osmosis treatment system including a feed stream supplied by an inlet or raw water or feed pump, a high pressure booster pump, a semipermeable membrane separation which produces a concentrate and permeate stream when the concentrate valve is used to throttle to build up feed-concentrate side pressure using the feed pump to generate the filtration pressure.

[0015] FIG. 2 generally shows how permeate flux (permeate flow per unit of membrane surface area) and salt rejection (salt concentration in feed less salt concentration in permeate, divided by salt concentration in the feed) vary with feed pressure.

[0016] FIG. 3 generally shows how permeate flux and salt rejection vary with water recovery (permeate flow divided by feed water flow entering reverse osmosis system).

[0017] FIG.4 generally shows how permeate flux and salt rejection vary with water temperature in the reverse osmosis system.

[0018] FIG. 5 generally shows how permeate flux and salt rejection vary with feed water concentration entering reverse osmosis system.

[0019] FIG.6 generally shows basic components and flow streams of a membrane plant.

[0020] FIG.7 generally illustrates a cross-sectional view of one example of a pressure vessel.

[0021] FIG.8 generally illustrates components of a standard rolled membrane element including feedwater channel spacer (a plastic mesh to create a flow path for feed and concentrate to flow through the membrane element), membrane leaves, glue seal, permeate spacer, and permeate tube. The size of a standard commercial membrane element is 8” diameter by 40” long and this iscommonly denoted as an 8040 element size. The number of membrane leaves in an 8040 element ranges from 15 to over 30 leaves.

[0022] FIG. 9 generally illustrates a cross-sectional of a membrane element permeate tube showing membrane leaf arrangement around the permeate tube.

[0023] FIG. 10 generally illustrates a plurality of filter membranes arranged in series inside a pressure vessel, and one or more pressure vessels arranged in parallel that form a stage.

[0024] FIG. 11 shows how membrane elements may be connected end to end with a coupling between adjacent membranes, then installed into a pressure vessel. While not a limitation of the present disclosure unless specifically claimed as such, up to eight membrane elements are typically installed in one pressure vessel.

[0025] FIG. 12 shows basic components and flow streams of a two-stage membrane plant, each stage has a parallel arrangement of pressure vessels, with the concentrate from the stage one membrane vessels becoming the feed to the stage two membrane vessels, with the ratio of the number of vessels in the first stage to the number of vessels in the second stage membrane vessels is two-to-one, so as to keep the velocity inside the membrane feed spacer channels at the desired level to maintain performance in the membrane.

[0026] FIG. 13 generally illustrates the basic components and flow streams of a single-stage membrane plant with concentrate recycle.

[0027] FIG. 14 generally illustrates the basic components and flow streams of a two-pass membrane plant, each pass can have a parallel arrangement of pressure vessels, with the concentrate from pass one membrane vessels becoming the concentrate of the system while the permeate from pass one becoming the feed to the second pass membrane vessels. The pass two membranes serve as a second membrane purification step to additionally remove contaminants to a lower level. The concentrate from pass two is recycled to pass one to manage water recovery.

[0028] FIG. 15 generally illustrates a comparison of an attached-to-membrane feed spacer of the adhesive-deposition type with spacer element location guided by a stencil versus a traditional diamond mesh feed spacer.

[0029] FIG. 16 generally illustrates print-in-place channel height versus permeate flow rate and crossflow energy savings associated with frictional pressure drop through the feed channel of the resulting membrane element. Permeate flow rate is directly proportional to membrane area, andlower print height allows more membrane area, and hence more permeate flow rate, to be produced inside the same standard element envelope (8” diameter by 40” long, 8040 element). Frictional pressure drop, at the same feed and permeate and flow rate, would generally be reduced for taller print heights. Channel heights reported range from 6 mil to 30 mil.

[0030] FIG.17 generally illustrates a visual comparison of two mesh type spacers, diamond mesh and parallel mesh.

[0031] FIG. 18 generally illustrates one standard industry design from FILTEC which provides guidance on flux, minimum concentrate flow rate per membrane element, maximum element recovery, by water source type and water quality as well as by element size and type. In all cases the elements are standard mesh feed spacer type with standard mesh type element sizes up to 440 ft2.

[0032] FIG. 19 generally illustrates a block flow diagram of one example of the unit operations involved in a full scale commercial RO / NF installation, including raw water supply which can be ground water, surface water, wastewater, and a process stream; pretreatment, which is typically focused on suspended solids removal to prevent clogging RO feed channels, but can also treat for scale formers, dissolved organics and other dissolved materials which could result in fouling including biofouling, and scaling and may include antiscalant, oxidant destruction such as sodium bisulfite, and pH correction; the NF / RO system itself which may have chemical dosing inside its control system including pH adjustment, antiscalant, oxidant destruction; a bypass option that sends RO / NF feed around the RO / NF to blend this bypass feed with the RO / NF permeate to produce a final blended product at the desired quality. Post RO / NF / blending adjustment for pH and other desired product features is also possible, but not explicitly shown.

[0033] FIG. 20 generally illustrates a listing of commercial semi-batch reverse osmosis (SBRO) systems as well as competitive systems used for higher recovery design than standard continuous reverse osmosis systems.DETAILED DESCRIPTION

[0034] The advent of attached-to-membrane (ATM) membrane spacers for rolled membrane elements, has allowed ATM membranes, such as print-in-place (PIP) membranes, to achieve narrower openings between membrane sheets / leaves, thereby allowing significantly improvedpacking density for membrane area into a fixed membrane envelope. Historically, increased packing density generally has resulted in the need for cleaner feed water i.e. higher levels of pretreatment to the RO / NF system to avoid plugging of these narrower feed flow channels, and as such the largest membrane area in a standard 8040 (8” diameter, 40” long) membrane element has typically been capped at 440 ft2 with 28 mil feed spacers. While ATM membrane elements having a channel height of less than 20 mil and an area over 500 ft2 membrane area is possible in the same 8040 membrane envelope, those of ordinary skill in the art do not believe that ATM membrane elements are reliable and can avoid fouling or scaling feeds.

[0035] In studying PIP-type ATM membranes, there are detailed features that can be harnessed, such as the style of membrane feed spacer does not have limitations of typical free feed spacers, such as the need for supporting and bridging structures, to keep the spacer in position. This opens up the flow path significantly versus a typical diamond mesh spacer. Also, since ATM membrane elements do not need supporting cross members, the space or height-creating features can be attached at any desired location to the membrane surface, so as to avoid blocking flow or doubling up on each other, again leading to more open cross-sectional area for feed flow in an ATM membrane element (see, e.g., ATM membrane elements as described in U.S. Patent No. 7,311,831, which is fully incorporated herein by reference).

[0036] FIG. 6 generally illustrates one example of an NF / RO system 600 having a single stage 602. One or more pumps 612 (e.g., high pressure pumps also ref erred to as booster pumps) may be used to supply one or more feed streams 614 (also known as feeds, feedwater, and / or feed flow) to the single stage 602. The single stage 602 may include one or more membrane elements 616 (also referred to as separation layers, membranes and / or filters). The membrane elements 616 may be configured to separate the feed stream 614 into a permeate 618 (e.g., a permeate flow and / or purified flow) and a concentrate 620 (also referred to as a reject flow). A concentrate valve 622 may be provided to adjust the percentage of the feed 614 that flows across the membrane separation layers 616 into the permeate 618 and / or concentrate 620.

[0037] One example of a membrane element 700 consistent with the present disclosure is generally illustrated in FIGS. 7-10. The membrane element 700 may be used in any of the NF / RO systems described herein. The membrane element 700 may include a housing 702 (such as, but not limited to a cylindrical housing) that contains one or more membrane leaves (also referred to as membraneseparation layers and / or a permeate carrier) 704 as well as one or more feed spacers 706 (which create flow channels). The housing 702 (also referred to as a shell) may be constructed from a wrapping, mesh, sleeve, fiberglass, and / or stainless steel. The membrane element 700 may also include one or more anti-telescoping devices and / or end caps 708 (e.g., that seal the membrane element 700 and / or connect the membrane element 700 to piping, not shown), one or more feed inlets 710 that supply the feed to the membrane element 700, and one or more permeate ports 712 (that collects purified water).

[0038] An embodiment of a spiral-wound membrane element 20 consistent with the present disclosure is generally illustrated in FIG 8. The spiral-wound membrane element 20 may be used in any of the NF / RO systems described herein. One example of a spiral- wound membrane element is FILMTEC™ includes thin film composite membranes packed in a spiral-wound configuration. Spiral-wound membrane element 20 may offer many advantages compared to other module designs, such as tubular, plate-and-frame and hollow-fiber module designs for most of the reverse osmosis applications in water treatment. A spiral-wound membrane 20 may offer significantly lower replacement costs, simpler plumbing systems, easier maintenance and greater design freedom than other configurations, making it commonly used for reverse osmosis and nanofiltration membranes in water treatment.

[0039] The construction of a spiral-wound membrane element 20 as well as its installation in a pressure vessel is schematically shown in FIG. 8. A spiral-wound membrane element 20 may contain from one, to more than 30 membrane leaves 22, depending on the element diameter and element type. Each leaf 22 may be made of two membrane sheets 24 glued together back-to-back with a permeate spacer 26 between them. The spiral-wound membrane element 20 may include glue lines 28 about 1.5 in (4 an) wide that seal the inner (permeate) side of the leaf against the outer (feed / concentrate) side. There is a side glue line at the feed end and at the concentrate end of the element, and a closing glue line at the outer diameter of the element 20. The open side of the leaf 22 is connected to and sealed against the perforated central part of the product water tube 30, which collects the permeate from all leaves 22. The leaves 22 are rolled up with a sheet of feed spacer 32 (e.g., but not limited to, a plastic mesh) between each of them, which provides a flow path or channel for the feed and concentrate flow. In operation, the feed water 14 enters the face of the element 20 through the feed spacer channels 32 and exits on the opposite end as concentrate20. A part of the feed water-typically 10-20%-permeates through the membrane 20 into the leaves 22 and exits the permeate water tube 30. As discussed herein, the size of a standard commercial membrane element is 8” diameter by 40” long, and is commonly denoted as an 8040 element size. The number of membrane leaves 22 in an 8040 element ranges from 15 to over 30 leaves 22, but this depends on the length of each leaf 22, where more shorter leaves 22 are utilized, and fewer longer leaves 22 are utilized. Unfolded leaf length range from 2 feet to over 7 feet.

[0040] When elements 20 are used for high permeate production rates, the pressure drop of the permeate flow inside the leaves 22 reduces the efficiency of the element 20. The elements 20 may be selected with a higher number of shorter membrane leaves 22 and thin and consistent glue lines 28. Element 20 productivity may be enhanced by having a high active area while a thick feed spacer 32 reduces fouling and increases cleaning success. A cross-section of a permeate water tube 30 with attached leaves 22 is shown in FIG. 9.

[0041] Referring to FIG. 10, a plurality of membrane elements 616a-616n may be arranged in series to form a pressure vessel 601. Each pressure vessel 601 may include 1 membrane elements 616, 2 membrane elements 616, 3 membrane elements 616, 4 membrane elements 616, 5 membrane elements 616, or more. Within each pressure vessel 601, all of the plurality of membrane elements 616 may be the same. Alternatively, one or more of the plurality of membrane elements 616 within the stage 602 may be different. FIG. 11 generally shows how membrane elements 616a-n may be connected end to end with a coupling 34 between adjacent membrane elements 616a-n, then installed into a pressure vessel 601 (which extends over all of the membrane elements 616a-n). The concentrate of one element 601a may become the feed to an adjacent membrane element 60 In and so on. The permeate tubes 30 may be connected with interconnectors 34 (also called couplers), and the combined total permeate exits the pressure vessel 601 at one side (sometimes at both sides) of the pressure vessel 601. In some examples, up to 8 membrane elements 616 may be installed in one pressure vessel 601.

[0042] Turning now to FIG. 12, one example of a two-stage membrane plant 1200 is generally illustrated. The two-stage membrane plant 1200 includes a first and a second stage 602a, 602n in series. It should be appreciated that a three or more stage membrane plant would include additional stages 602 in series. Each stage 602a, 602n has a parallel arrangement of pressure vessels 601a-601 n, with the concentrate from the first stage 602a becoming the feed to the adjacent, downstream stage 602n.

[0043] The first stage 602a may have more pressure vessels 601a-601n compared to the downstream stages (e.g., second stage 602n) so as to keep the velocity inside the membrane feed spacer channels 32 at the desired level to maintain performance in the membrane element 601. For example, the ratio of the number of pressure vessels 601a-601n in the first stage 602a to the number of pressure vessels 601a-601n in the second stage 602n may be two-to-one.

[0044] FIG. 13 shows an example of a single stage membrane plant 1300 including concentrate recycle. For example, a portion of the concentrate 620 may be recycled to form a concentrate recycle flow 1301 and feed back to an inlet of the stage 602. In one example, the concentrate recycle flow 1301 may be supplied to the high pressure pump 612. A concentrate recycle valve 1302 may be provided to adjust the flow rate of the concentrate recycle flow 1301. The concentrate recycle flow 1301 aids in managing water velocity and water element recovery.

[0045] FIG. 14 shows an example of a two-pass membrane plant 1400 including concentrate recycle. Each pass 602a, 602n (e.g., pass) is arranged in series with another stage 602 and can have a parallel arrangement of pressure vessels 601a-601n therein. The concentrate 620a from the first pass 602a becomes the concentrate 620a of the system 1400 while the permeate 618a from the first pass 602a becomes the feed to the second pass 602n. The second pass 602n may serve as a second membrane purification step to additionally remove contaminants to a lower level. The concentrate 620b from the second stage 602n is recycled 1301 to the first stage 602a to manage water recovery. Optionally, one or more first pass high pressure pumps 612a may supply feed to the inlet of the first pass 602a and one or more second high pressure pumps 612n may supply feed to the inlet of the second pass 602n.

[0046] Historically, increased packing density generally for traditional membranes elements has resulted in the need for cleaner feed water (i.e„ higher levels of pre-treatment to the RO / NF system) to avoid plugging of the resulting narrower feed flow channels which range from nominally 28 to 31 one thousandths of an inch (mil). As a result, the largest membrane area in a standard 8040 (8” diameter, 40” long) membrane element has typically been capped at 440 ft2 with 28 mil feed spacers. Although smaller channel heights (e.g., below 28 mil) are commercially available, a practical minimum feed channel limit for the membrane industry has been a 28 milspacer. As used herein, a standard membrane element is defined as a membrane element having a spacer with a spacer height of at least 28 mil. As used herein, a standard 8040 membrane element is defined as a membrane element having a fixed membrane envelope that is 8” in diameter and 40” long and interchangeable with all industry- standard 8040 membranes, with a maximum membrane area of 440 ft2 and spacers having a spacer height of at least 28 mil.

[0047] The advent of attached-to-membrane (ATM) membrane spacers for membrane elements (e.g., rolled membrane elements), has allowed ATM membrane elements (such as print-in-place (PIP) membrane elements), to achieve narrower openings between membrane sheets (e.g., leaves), thereby allowing significantly improved packing density for membrane area into a fixed membrane envelope.

[0048] FIG. 15 generally shows a comparison of an attached-to-membrane (ATM) feed spacer of the adhesive-deposition type with spacer element location guided by a stencil versus a traditional diamond mesh feed spacer. The attached-to-membrane appears as hemispherical flow disruption islands constructed from translucent adhesives on the membrane sheet with no crossmembers connecting the individual islands, leaving the membrane surface unimpeded to flow. In contrast, the diamond mesh feed spacer has cross-members that lead to feed channel blockage and hydraulic dead spots where low feed flow exists and that result in areas where contaminants can accumulate in the membrane feed flow path.

[0049] FIG. 16 generally shows print-in-place channel height versus permeate flow rate and crossflow energy savings associated with frictional pressure drop through the feed channel of the resulting membrane element. Permeate flow rate is directly proportional to membrane area, and lower height of PIP spacers allows more membrane area, and hence more permeate flow rate, to be produced inside the same standard element envelope (8” diameter by 40” long, 8040 element). Frictional pressure drop, at the same feed and permeate and flow rate, would generally be reduced for taller print heights.

[0050] As used herein, an ATM membrane element may include a membrane element where the spacer is attached directly to the membrane surface without any cross-members connecting the spacers. Examples of ATM membranes are described in U.S. Patent No. 7,311,831, U.S. Publ. No. 2023 / 0093181 Al, as well as U.S. Publ. No. 2022 / 0016809A1, all of which are fully incorporated herein by reference.

[0051] An 8040 ATM membrane element may include as a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 19 mil but ranging from 5 mil to 30 mil where the spacer is attached directly to the membrane surface without any cross-members connecting the spacers. In some examples, an 8040 ATM membrane element may have a fixed membrane envelope or external dimension that is 8” in diameter and 40” long and a minimum membrane area of 520 ft2, for example, a minimum membrane area of 540 ft2, and / or a minimum membrane area of 550 ft2. In addition (or alternatively), an 8040 ATM membrane element may have a fixed membrane envelope or external dimension that is 8” in diameter and 40” long and a spacer height (also referred to as a channel height) ranging from 5 mil to 30 mil, for example, from 6 to 20 mil, from 6 mil to 18 mil, from 8 mil to 20 mil, from 6 mil to 15 mil, from 15 mil to 20 mil, smaller than 18 mil, smaller than 19 mil, and / or smaller than 20 mil. In addition (or alternatively), an 8040 ATM membrane element may have a fixed membrane envelope or external dimension that is 8” in diameter and 40” long where the spacer is attached directly to the membrane surface without any cross-members connecting the spacers.

[0052] An 8040 PIP- ATM membrane may include any of the 8040 membrane elements described herein, with the membrane attached by a printing-type deposition including 3D printing approaches, onto the membrane. Adhesive deposition onto the membrane surface with use of a stencil for placement and shaping of the feed spacer is another way to delivery ATM membranes.

[0053] While it is possible for ATM membranes to have over 500 ft2 membrane area in the 8040 membrane envelope, those of ordinary skill in the art do not believe that ATM membranes having over 500 ft2 membrane area can be reliably used in a reverse osmosis (RO) or nanofiltration (NF) system due to the channel size being less than the current industry minimum of 28 mil feed channel height, as outlined elsewhere in this document (e.g., to avoid fouling or scaling feeds).

[0054] As described herein, the inventor of the present disclosure has recognized that there are detailed features ATM membrane elements that can be harnessed to improve performance in RO and / or NF systems. For example, the style of membrane feed spacers in ATM membrane elements do not have limitations of typical unattached feed spacers (for example those used in traditional membranes such as spiral- wound membranes as shown in FIG. 14 and FIG. 17), such as the need for supporting and bridging structures, to keep the spacer in position. The membrane feed spacersin ATM membrane elements opens up the flow path significantly versus a typical diamond mesh spacer used in traditional spiral-wound membrane elements as shown in FIG. 14 and FIG. 17.

[0055] In particular, FIG. 17 generally illustrates a visual comparison of two mesh type spacers, diamond mesh and parallel mesh. Both have cross-members that block parts of the feed channel, but have significant differences in performance due to specifics of the arrangement of the mesh strands. Diamond mesh feed spacer separate the two adjacent membrane sheets (e.g„ leaves) in a membrane element by a height equal to the additive thickness of its two similarly sized component strands. As a result, the flow path is effectively equal to the height of one strand (i.e. half the mesh height) while the other half of the flow path is filled by the second strand of the diamond mesh. In addition, the resulting feed flow path is not parallel to either strand with the feed flow generally passing through the open space adjacent to each sequential strand along the feed flow direction from inlet to outlet of the membrane element.

[0056] There are pockets or corners in the diamond mesh where low flow occurs and these dead pockets can lead to accumulation of contaminants that lead to membrane surface fouling or blockage. Parallel spacer mesh is produced from square mesh with equal sized strands, where the flow path channel height equals the height of the two strands. Strands in one direction of the square mesh are stretched to create a thinner strand with thickness approximately 30% of its original size, and generally centered at the center height of the original unstretched strand, resembling a ladder with thicker uprights and thinner cross-members. This thinner, stretched strand opens a flow path of nominally 70% of feed channel height, roughly 35% above and below the thinner strand. The membrane feed flows parallel to the unstretched thicker strands and come into contact with the stretched thinner strands, the thinner strands introducing turbulence in the membrane feed flow path while not creating any dead pockets for flow, all of which helps keep the membrane surface cleaner than diamond mesh membranes. Parallel or ladder mesh typically is more effective than diamond mesh, due to its design, but the cross-member does block approximately 30% of the flow path, and reduces effective channel height to 35% albeit with better turbulence.

[0057] Open channel, attached to membrane (ATM) spacers consistent with the present disclosure improve over both types of mesh spacers (diamond and parallel mesh spacers) by removing completely any flow obstructions making the feed channel 100% open to particles, reducing riskof blockage nearly completely. Also, since ATM membrane elements do not need supporting cross members, the space or height-creating features can be attached at any desired location to the membrane surface, so as to avoid blocking flow or doubling up on each other, again leading to more open cross-sectional area for feed flow in a well-designed ATM membrane, e.g. U.S. Patent No. 7,311,831 (incorporated fully herein by reference) and as shown in FIG. 15 and FIG. 16.

[0058] Using these ATM features (including the absence of flow path blocking cross-members), the inventor of the present disclosure has recognized that it is possible to use feed channels and / or feed spacers having a height of less than 20 mil (including all the ranges as described herein), thereby allowing ATM membrane elements to be used in applications reserved typically for larger feed channel which use standard membranes (e.g., such as a standard 8040 membrane element with standard diamond mesh) having an industry typical 28 mil channel or spacer height or taller mesh height. By virtue of the design of diamond mesh spacers (i.e., the RO / NF industry standard feed spacer), the inventor of the present disclosure has recognized that nominally half of the standard diamond mesh channel height (e.g., a 28 thousandths of an inch spacer will have a 14 thousandths of an inch feed flow path channel occlusion crossmember, a 31 thousandths of an inch spacer will have a 15.5 thousandths of an inch feed flow path channel occlusion crossmember, and a 34 thousandths of an inch spacer will have a 17 thousandths of an inch feed flow path channel occlusion crossmember) as described in FIG. 15 and FIG. 17 could be equivalent in open flow path (unimpeded by connecting cross-members) in a well-designed ATM membrane element, because a diamond mesh spacer has two equal size strands stacked up to make the total feed spacer height and hence half of the feed channel is occluded by the one crossmember the feed channel flow path versus zero occlusions for the ATM spacer as outlined in FIG. 15 and FIG. 17 and associated descriptions. Based on this recognition, an ATM membrane element having a 19 mil feed spacer height was compared against 34 mil feed spacer height standard feed spacers with respect to membrane area and minimum concentrate flow rate per element.

[0059] As generally shown in FIG. 18, a standard 8040 membrane element having 365 and 400 ft2, the minimum concentrate flow rate recommended for an element is 10 gpm and the channel height maximum is nominally 34 mil and this translates into an open feed flow channel (i.e., no feed mesh spacer displacement accounted for) of 3.9 feet per minute, determined as 10 gpm concentrate flow divided by cross-sectional open flow area of membrane element. Cross-sectionalopen flow area of a membrane element is determined as edge length of membrane in the flow direction multiplied by channel height. In summary: 10 gpm / (400 ft2 divided by 40 inch length of membrane x 34 mil open feed channel height) = 3.93 feet per minute (fpm) or nominally 4 feet per minute. This translates to 7.3 gpm for a 19 mil, 520 ft2 ATM membrane, i.e. 10 gpm x (19 mil I 34 mil) x (520 ft2 / 400 ft2) = 7.3 gpm. And similarly, this translates to 8.0 gpm for a 19 mil, 520 ft2 ATM membrane i.e. 10 gpm x (19 mil / 34 mil) x (520 ft2 I 365 ft2) = 7.96 or 8 gpm minimum concentrate flow per element. Other examples of open channel velocity include at least 4.0 foot per minute, at least 5.6 foot per minute, at least 6 foot per minute, including all values and ranges therein. The inventor of the present disclosure has recognized the following unexpected benefits and features of using a 19 mil ATM membranes:

[0060] (1) a standard 8040, 34 mil membrane has an area of 365 to 400 ft2, while an 8040 ATM of 19 mil spacer has over 500 ft2 area. Note that 520 to 560 ft2 PIP elements were manufactured to confirm that this membrane area range fits into a standard 8040 envelope. It is possible to have a membrane area of approximately 600 ft2 using a 15 mil ATM spacer in a standard 8040 envelop.

[0061] (2) using spacer total height for feed channel flow area determination, and matching the cross-sectional feed channel area flow velocity minimum (> 4 feet per minute (fpm) as the design equivalence approach to match mass transfer, the 19 mil, 520 ft2 ATM membrane (e.g., but not limited to, a PIP-type ATM membrane) may utilize 7 to less than 10 gpm concentrate flow, e.g., 7.3 to less than 8.0 gpm concentrate flow, versus 10 gpm and 11 gpm for 34 mil, 365 ft2 and 34 mil, 400 ft2 membrane elements respectively.

[0062] The inventor of the present disclosure has recognized that these two features / benefits, along with the recognition that 34 mil standard spacer and less than 20 mil ATM spacers have similar channel openness (typically 34 mil / 2 = 17 mil PIP are equally open due to diamond mesh strands typically being 50% of channel height), allows simultaneously a lower concentrate flow rate minimum per ATM membrane element (e.g., 7 to less than 10 gpm concentrate flow) and higher area ATM membrane elements to be utilized in a RO or NF systems. This results in theability of ATM membrane element systems to achieve higher recovery (e.g., ranging from 1% to over 5% increased recovery) compared to the same system utilizing standard 8040, 34 mil membranes, whilst also avoiding the complexity of going to higher membrane stage counts and / or using concentrate circulation. Recovery equals permeate flow rate per unit of feed flow rate, i.e. the conversion rate of feed to permeate. Recovery in the industry may range from 40% to over 80%. The present disclosure may feature a recovery of at least 85%, for example, at least 87%. at least 88%, including all values and ranges therein as discussed herein.

[0063] Notably, increasing the number of stage counts results in increased pressure drop and higher energy use, and similarly, use of circulation flow (where concentrate is internally recycled back to the front of the membrane system) adds more power use, but also results in reduced permeate quality of the membrane system. The inventor of the present disclosure has recognized that ATM systems would achieve higher recovery with two or three stage designs without concentrate recycle compared to the same system utilizing standard 8040, 34 mil membranes.

[0064] It should be noted that each membrane pressure vessel (e.g., the pressure enclosure containing the membrane elements in a reverse osmosis or nanofiltration system) typically comprises 8 or less membrane elements, and more typically 7 or less membrane elements. Each reverse osmosis or nanofiltration system stage or pass is usually fitted with the same pressure vessels (i.e. the same number of membrane elements per pressure vessel) and generally it is preferred to have the same pressure vessels in all stages and passes of a nanofiltration or reverse osmosis system for mechanical simplicity, but if different, the second stages are usually shorter vessels. The addition of the total number of membrane elements in the vessels of Stage 1 and that of Stage 2 is regarded as the total length of series membrane elements in the system, and is independent of the number of parallel pressure vessels in each stage. For example, a membrane system with 7 long stage 1 pressure vessels and 5 long stage 2 pressure vessels is a 12 long membrane system. Similarly, a membrane system with 6 long stage 1 pressure vessels and 6 long stage 2 pressure vessels is a 12 long membrane system. FIG.12 generally outlines a 2-stage system showing parallel and series arrangement of six pressure vessels.

[0065] 1

[0066] In some examples, the present disclosure features 2-stage membrane systems and methods including a plurality of AMT membrane elements without concentrate recycle, for example, as generally illustrated in FIG. 12. The 2-stage membrane systems may comprise 12 or more (e.g. up to 14) long membrane systems with AMT membrane elements.

[0067] 2

[0068] In other examples, the present disclosure includes retrofit systems and methods. For example, an existing NF or RO system having a plurality of standard membrane elements (e.g., a plurality of standard 8040 membrane elements) may be retrofitted with a plurality of ATM membrane elements (e.g., a plurality of 8040 ATM membrane elements). In some examples, the recycle flow rate may not be adjusted (e.g., increased) and none of the booster pumps which supply feed to the plurality of ATM membrane elements (e.g., plurality of 8040 ATM membrane elements) are changed. Known systems and methods for increasing recovery and production rate in existing RO / NF systems by retrofit include closed-circuit RO (CCRO) and CCNF processes such as U.S. Pat. No. 7,695,614B2 and related technologies as outlined in FIG. 19 (which is fully incorporated herein by reference). These systems usually need the addition of a circulation flow from the concentrate to the feed, in order to ensure suitable hydraulic conditions exist in the final stage membranes while increasing recovery. Such circulation flows raise the average membrane inlet contaminant levels, and negatively impact overall RO / NF system rejection, leading to poorer permeate quality and added capital and operating cost for implementing the circulation flow. These processes could benefit from the current disclosed approach as outlined in more detail in this document under the general nomenclature of semi-batch reverse osmosis (SBRO) systems.

[0069] Using the features described herein of lower concentrate flow rate (nominally 8 gpm), and higher membrane area (e.g., an ATM membrane element with 20 mil spacers or less having over 500 ft2 area), the inventor of the present disclosure has recognized that it is possible to replace one or more standard membrane elements (e.g., but not limited to, standard 8040 membrane elements) in at least the first and other non-final stages of an existing NF / RO system with AMT membrane elements (e.g., 8040 AMT membrane elements), thereby increasing membrane area in those stages. The final stage membrane area and / or pressure vessel count may be adjusted by removing membrane elements and replacing with pipe spools or entire pressure vessels blinded off at theirinlet / outlet ports to fit the reduced concentrate flow going nominally from 13 gpm to 8 gpm per pressure vessel required by improved recovery for the RO / NF system without the need to increase a concentrate recycle stream. If the existing RO or NF system already includes a recycle stream, the recycle flow rate can be reduced by adjusting to the ATM minimum concentrate flow of nominally 8 gpm per membrane element or eliminated using this same approach, as long as the minimum ATM concentrate flow rate is met. By reducing the recycle below prior values, the permeate quality can be improved by over 50% conductivity or dissolved solids in some cases, as the blended feed entering the membrane elements has reduced contaminants from lower recycle flow of concentrated contaminants from the RO concentrate lines, albeit at higher recovery example of over 3%, and may eliminate the need for a second pass RO / NF to upgrade NF / RO permeate if the permeate quality from pass one meets the project goals without a second pass RO / NF step needed, thereby simplifying the overall process.

[0070] The present disclosure also features another method and system to improve overall process recovery by modifying an existing RO / NF system (e.g., any RO or NF system described herein) using the method described herein which involves replacing one or more standard 8040 membrane elements with ATM membrane elements (e.g., 8040 ATM membrane elements) and re-arranging elements in the existing system in a RO / NF system having a preexisting concentrate recycle. The system / method may be operated at the same water recovery (permeate flow / feed flow), but with improved permeate quality, e.g., 10% or more reduced dissolved solids in permeate, than before the modification. This allows for more RO / NF feed to be bypassed around the RO / NF as shown in FIG. 19 with bypass fraction related to blended water quality goals, and since bypass water has no concentrate losses like the NF / RO, bypassing more water thereby increasing overall recovery of blended effluent while maintaining the same NF / RO system recovery. This approach reduces energy proportionally to the increased bypass fraction, but would also save energy proportionally to bypass fraction, for water treated inside the NF / RO, as less water is treated in the RO / NF system where high pressure pump utilization is reduced.

[0071] For systems without recycle, improving permeate quality is more challenging, as the option to simply reduce recycle to the front of the RO / NF system does not exist and may require use of higher rejection membrane elements in the system to achieve improved permeate quality. Such membrane elements remove higher levels of dissolved salts, but generally need higher operationpressures and as such, to be made to work with the existing pump system, would need the system operation to find flow reduction opportunities using ATM membrane elements by using the proposed retrofit technique, enabling improved productivity and improved water recovery nominally 3% or more depending on existing system features with acceptable product quality example within 5% of the existing permeate quality.

[0072] In further examples, the present disclosure includes continuous supersaturated systems and methods focus on reducing or eliminating recycle flow rates to minimize retention time of concentrate inside the new or retrofit systems. The focus is on managing and minimizing and even eliminating recycle in RO / NF system design.

[0073] With reference to “3D-PRINTED FEED SPACERS IN THE WILD” by Kurth, Herrington, Roderick and Weingardt (AMTA 2023, hereinafter “Kurth”), fully incorporated herein by reference, an energy retrofit saving for a brackish water reverse osmosis system is described, but at decreased recovery, and with circulation of concentrate. This represents a typical retrofit when membrane elements are enlarged from 400 ft2 standard mesh membranes to over 500 ft2 per membrane, where the system can operate between energy savings mode (lower permeate flux where permeate flux is permeate flow rate per unit membrane surface area, example gallons per day per foot square of membranes or GFD; lower feed channel pressure drop) and productionincrease mode (permeate flow rate increase), but with a reduced recovery (reduced permeate to feed ratio). The inventor of the present disclosure has discovered that the reduced recovery associated with Kurth is not needed.

[0074] FIG. 18 provides guidelines for design flux range. In particular, the present disclosure may operate at average membrane flux no more than 17.5 GFD, e.g.. average membrane flux no more than 17.4 GFD, e.g., at average membrane flux no more than 16.3 GFD, e.g., at average membrane flux no more than 15.9 GFD, e.g., at average membrane flux no more than 15.5 GFD, e.g., at average membrane flux no more than 15 GFD, e.g., at average membrane flux no more than 14 GFD, including all values and ranges therein.

[0075] As is typical in the industry, if the concentrate flow rate for the 8040 PIP membrane was matched to the original mesh membranes, it appears manual control settings led to a slight drop in production rate for the PIP case, and hence a drop in recovery rate. In contrast, based on a detailed analysis of the crossflow velocity and boundary layer analysis, the inventor of the present inventionhas unexpectedly discovered that ATM membrane spacers (e.g., PIP spacer membranes) can in fact operate at lower concentrate flow rates (nominally 8 gpm versus 12 gpm or more for mesh membranes) and maintain crossflow velocity, as described herein. The inventor of the present disclosure has recognized that this approach is different than industry standard design considerations, where the industry standard design considerations are based on generally holding the minimum concentrate volumetric flow rate per membrane element constant at nominally 13 gpm, regardless of feed channel heights, as shown in FIG.20 which is from a recognized industry guideline from DuPont ™ membranes. The industry standard design considerations are consistent with the fact that it was previously believed that the feed spacers of standard 8040 membranes are of a similar nature and design (e.g., diamond mesh, two-fiber arrangements) in reverse osmosis and nanofiltration membranes and these spacers dominate mass transfer features inside the membranes. The inventor of the present disclosure has unexpectedly discovered that with open channels (such as ATM membranes), mass transfer would follow an analysis of mass transfer boundary development akin to that from hollow fiber inside-out membranes which have open feed channels and no crossmember-supports traversing the feed flow path, and rely more on turbulence promotion related to velocity (Reynolds number) than turbulence promotion from feed flow channel inserts, such as diamond mesh feed spacers.

[0076] The approach of reduced concentrate flow rates when using larger area membranes outlined here can also be valuable in conjunction with semi-batch (SBRO) or closed circuit reverse osmosis (CCRO) systems. SBRO and CCRO systems are part of a family of RO systems that operate non-continuously in a semi-batch mode, where production is interrupted routinely for system flush. Batch operation has been used in RO systems almost as long as RO membranes have been around and operates with a fixed feed volume in a feed tank and only permeate is removed throughout the batch cycle and terminates when the final batch concentration or minimum feed tank level reduction is achieved. Batch differs from semi-batch RO. in that SBRO has raw feed topping off the feed tank throughout the batch run, giving an impression of continuous feed, but still experiencing routine flush steps interrupting production. Over the last twenty years, a number of semi-batch RO processes evolved with batch production cycle times < 1 hour and which focus on enhanced water recovery by operating under the principal of induction time for scale formation. These processes push past the conventional RO scale limit with and without antiscalant, into theinduction time, to improve water recovery. The scale induction time equals the period between when conditions are met for scale formation and when scale actually forms. This is somewhat similar in concept to the elapsed time between adding caustic to raise the pH in a stirred precipitative softening reactor filled with suspended-solids-free, hard water and the time when scale such as calcium carbonate actually forms in the reactor. This elapsed time is usually of the order of minutes, which is the same time range as typical semi-batch RO production run, typically 5 to over 60 minutes. As such, SBRO processes take takes advantage of chemical inertia of nucleate scale formation to raise recovery above that limited by typical continuous operation, scale-limited RO.

[0077] SBRO systems sometimes require removal of membranes from the final stage of the RO / NF system to create working volume to allow practical cycle times for flushing the concentrate, especially smaller systems. Use of larger area membranes, such as attached-to-membrane spacer membranes would increase the non-final stage membrane area nominally 10% to sufficiently counter the loss of final stage membrane area from membranes being removed in the final stage, thereby avoiding excessive system flux that may otherwise have occurred if only standard area membranes were employed.

[0078] Another feature from attached-to-membrane (ATM) spacer membrane elements is that a lower minimum concentrate flow rate is required as was described herein, and so use of these membrane elements in SBRO and SBNF systems can reduce internal concentrate circulation required for improved recovery targeted by the SBRO processes. But if the designer would accept that smaller channels of PIP-type and other ATM membranes would be practical, counter-intuitive to the industry thinking, this concept could further be implemented in even two stage NF / RO systems where it is unusual to be able to achieve high water recovery (nominally over 80%) without concentrate recycle. By significantly reducing or eliminating internal recycle inside the NF / RO and achieving sufficiently high recovery to supersaturate some sparingly soluble salts in the NF / RO concentrate, attached-to-membrane (ATM) spacer membrane elements can enable operation with low residence time of contaminants inside the NF / RO system, these residence time being lower than induction times of the supersaturated salts, thereby enabling continuous supersaturated operation in a non-scaling manner in such NF / RO systems. Unlike semi-batch NF / RO systems, such a continuous supersaturated operation requires less automation, simplerequipment, and can easily be applied to new and existing equipment to avoid scale limitation with ease, enabling a new class of simple, continuously supersaturated high recovery induction-time based NF / RO systems.

[0079] 1. The common belief among those of ordinary skill in the art is that smaller feed channel height are less reliable membrane, with more risk to scaling, plugging and fouling.

[0080] 2. The inventor of the present disclosure has unexpectedly discovered that ATM membrane elements (e.g., PIP-type and stenciled adhesive type ATM membrane elements) have the ability to place feed channel features on the membrane / leaf surface to both enable a more open feed flow path while reducing channel height (e.g., from equal to or greater than 28 mil for standard membrane elements to less than 20 mil for ATM membrane elements).

[0081] 3. The reduced channel height yield reduces concentrate flow rate at the same concentrate velocity. The inventor of the present disclosure has unexpectedly discovered that if the designer related mass transfer to velocity at the membrane surface, equivalent mass transfer can be achieved at lower concentrate flow rates in lower channel height membranes

[0082] 4. Using # 2 and # 3 (and unexpectedly ignoring industry accepted # 1), the inventor of the present disclosure has unexpectedly discovered that a RO / NF system design (new or retrofit) can be developed where the first stage has relatively more membrane area than the second stage (> typical 2:1 area ratio for stage l:stage 2) and produces the bulk of permeate production, and the second stage has less membrane area, producing relatively less than typical permeate proportionally to standard system, with a goal to deliver high recovery while maintaining good crossflow velocity, while avoiding poor permeate quality by avoiding concentrate circulation flow.

[0083] Additional Example Aspects

[0084] It should be appreciated that features from one or more the Examples may be combined with other Examples, unless specifically stated otherwise.

[0085] Example 1: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one attached-to -membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pumps in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a recovery of the refitted RO or NF system at the same or better production rate is increased relative to the existing RO or NF system.

[0086] Example 2 includes the features of Example 1, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

[0087] Example 3 includes the features of Example 1, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane element.

[0088] Example 4 includes the features of Example 3, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0089] Example 5 includes the features of Example 3, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

[0090] Example 6 includes the features of Example 1, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element furtherincludes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0091] Example 7 includes the features of Example 6. wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0092] Example 8: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one attached-to -membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a production rate of the refitted RO or NF system at the same or higher water recovery is increased relative to the existing RO or NF system.

[0093] Example 9 includes the features of Example 8, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

[0094] Example 10 includes the features of Example 8, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0095] Example 11 includes the features of Example 10, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0096] Example 12 includes the features of Example 10, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

[0097] Example 13 includes the features of Example 8, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0098] Example 14 includes the features of Example 13, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0099] Example 15: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one attached-to -membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a flux of the refitted RO or NF system at the same or better production rate is decreased relative to the existing RO or NF system.

[0100] Example 16 includes the features of Example 15. wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

[0101] Example 17 includes the features of Example 15. wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0102] Example 18 includes the features of Example 17, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0103] Example 19 includes the features of Example 17, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

[0104] Example 20 includes the features of Example 15, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0105] Example 21 includes the features of Example 20, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element furtherincludes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0106] Example 22: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one attached-to-membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a permeate quality of the refitted RO or NF system at the same or better production rate is improved relative to the existing RO or NF system.

[0107] Example 23 includes the features of Example 22, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

[0108] Example 24 includes the features of Example 22, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0109] Example 25 includes the features of Example 24, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope orexternal dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0110] Example 26 includes the features of Example 24, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

[0111] Example 27 includes the features of Example 22, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0112] Example 28 includes the features of Example 27, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0113] Example 29: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one attached-to -membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a concentrate hold up volume of the refitted RO or NF system is created for a minimum of 5 minutes production cycle time for a cyclic or semi-batch system at the same or better production rate relative to the existing RO or NF system.

[0114] Example 30 includes the features of Example 29. wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

[0115] Example 31 includes the features of Example 29, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0116] Example 32 includes the features of Example 31, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0117] Example 33 includes the features of Example 31, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

[0118] Example 34 includes the features of Example 29, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0119] Example 35 includes the features of Example 34, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0120] Example 36: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more highpressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long and at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a recovery of the refitted RO or NF system at the same or better production rate is increased relative to the existing RO or NF system.

[0121] Example 38 includes the features of Example 36, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0122] Example 39 includes the features of Example 36, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0123] Example 40 includes the features of Example 36, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

[0124] Example 41 includes the features of Example 40, wherein the at least one ATM membrane element includes at least one stenciled adhesive type ATM membrane elements.

[0125] Example 42 includes the features of Example 41, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope orexternal dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0126] Example 43 includes the features of Example 41, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

[0127] Example 44 includes the features of Example 40, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0128] Example 45 includes the features of Example 44, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0129] Example 46: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a production rate of the refitted RO or NF system at the same or higher water recovery is increased relative to the existing RO or NF system.

[0130] Example 47 includes the features of Example 46, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0131] Example 48 includes the features of Example 46, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0132] Example 49 includes the features of Example 46, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

[0133] Example 50 includes the features of Example 49, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0134] Example 51 includes the features of Example 50, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0135] Example 52 includes the features of Example 49, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

[0136] Example 53 includes the features of Example 49, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0137] Example 54 includes the features of Example 53, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0138] Example 55: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a flux of the refitted RO or NF system at the same or better production rate is decreased relative to the existing RO or NF system.

[0139] Example 56 includes the features of Example 55, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0140] Example 57 includes the features of Example 55, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0141] Example 58 includes the features of Example 55, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

[0142] Example 59 includes the features of Example 58, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0143] Example 60 includes the features of Example 59, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0144] Example 61 includes the features of Example 59. wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

[0145] Example 62 includes the features of Example 58, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0146] Example 63 includes the features of Example 62, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0147] Example 64: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a permeate quality of the refitted RO or NF system at the same or better production rate is increased relative to the existing RO or NF system.

[0148] Example 65 includes the features of Example 64, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0149] Example 66 includes the features of Example 64, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0150] Example 67 includes the features of Example 4, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

[0151] Example 68 includes the features of Example 67, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0152] Example 69 includes the features of Example 68, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0153] Example 70 includes the features of Example 68, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

[0154] Example 71 includes the features of Example 67, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0155] Example 72 includes the features of Example 71 , wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element furtherincludes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0156] Example 73: One aspect of the present disclosure features a method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising: replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a concentrate hold up volume of the refitted RO or NF system is created for a minimum of 5 minutes production cycle time for a cyclic or semi-batch system at the same or better production rate relative to the existing RO or NF system.

[0157] Example 74 includes the features of Example 73, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0158] Example 75 includes the features of Example 73, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

[0159] Example 76 includes the features of Example 73, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

[0160] Example 77 includes the features of Example 76, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

[0161] Example 78 includes the features of Example 77, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

[0162] Example 79 includes the features of Example method of claim 77, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

[0163] Example 80 includes the features of Example 76, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0164] Example 81 includes the features of Example 80, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

[0165] Example 82: One aspect of the present disclosure features a reverse osmosis (RO) or nanofiltration (NF) system comprising:

[0166] a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane area at least 500 ft2 and a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch operating at average membrane flux no more than 16.3 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

[0167] Example 83 includes the features of Example 82, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

[0168] Example 84 includes the features of Example 82, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

[0169] Example 85 includes the features of Example 82, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

[0170] Example 86 includes the features of Example 85, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

[0171] Example 87 includes the features of Example 85, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

[0172] Example 88: One aspect of the present disclosure features a reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes an attached-to-membrane (AMT) spacer membrane element with a membrane area at least 500 ft2 operating at average membrane flux no more than 16.3 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

[0173] Example 89 includes the features of Example 88, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the total number of the plurality of 8” membrane elements.

[0174] Example 90 includes the features of Example 89, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

[0175] Example 91 includes the features of Example 88, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

[0176] Example 92 includes the features of Example 88, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

[0177] Example 93: One aspect of the present disclosure features a reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2 operating at average membrane flux no more than 15.9 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

[0178] Example 94 includes the features of Example 93, wherein the system is able to achieve at least 87% recovery.

[0179] Example 95 includes the features of Example 93, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

[0180] Example 96 includes the features of Example 93, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

[0181] Example 97 includes the features of Example 93, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

[0182] Example 98 includes the features of Example 97, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

[0183] Example 99 includes the features of Example 97, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

[0184] Example 100: One aspect of the present disclosure features a reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2 operating at average membrane flux no more than 17.4 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

[0185] Example 101 includes the features of Example 100, wherein the system is able to achieve at least 88% recovery.

[0186] Example 102 includes the features of Example 100, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

[0187] Example 103 includes the features of Example 102, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

[0188] Example 104 includes the features of Example 100, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

[0189] Example 105 includes the features of Example 104, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

[0190] Example 106 includes the features of Example 104, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

[0191] Example 107: One aspect of the present disclosure features a reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2, a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch, and operating at average membrane flux no more than 17.5 GFD, maintaining at least 6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

[0192] Example 108 includes the features of Example 107, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

[0193] Example 109 includes the features of Example 108, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

[0194] Example 110 includes the features of Example 107, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

[0195] Example 111 includes the features of Example 110, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

[0196] Example 112 includes the features of Example 110, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

[0197] Example 113: One aspect of the present disclosure features a reverse osmosis (RO) or nanofiltration (NF) system comprising:a 14-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2, a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch, and operating at average membrane flux no more than 14 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

[0198] Example 114 includes the features of Example 113, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

[0199] Example 115 includes the features of Example 114, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

[0200] Example 116 includes the features of Example 113, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

[0201] Example 117 includes the features of Example 116, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

[0202] Example 118 includes the features of Example 116, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

[0203] Example 119: One aspect of the present disclosure features a A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 14-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of standard 8” membrane elements, wherein at least one of the plurality of standard 8” membrane elements includes a membrane element with a membrane area at least 500 ft2, a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch, and operating at average membrane flux no more than 15 GFD, maintaining at least 6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

[0204] Example 120 includes the features of Example 119, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

[0205] Example 121 includes the features of Example 120, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

[0206] Example 122 includes the features of Example 119, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

[0207] Example 123 includes the features of Example 122, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

[0208] Example 124 includes the features of Example 122, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

[0209] Example 125: One aspect of the present disclosure features a reverse osmosis (RO) or nanofiltration (NF) system operating in such a manner that a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

[0210] Example 126 includes the features of Example 125, wherein the RO or NF system includes a concentrate recycle.

[0211] Example 127 includes the features of Example 125, wherein the RO or NF system does not include a concentrate recycle.

[0212] Example 128 includes the features of Example 125, wherein the RO or NF system includes at least one attached-to-membrane (ATM) membrane element.

[0213] Example 129 includes the features of Example 128, wherein the RO or NF system includes at least one stenciled adhesive type ATM membrane element.

[0214] Example 130 includes the features of Example 128, wherein the RO or NF system includes a plurality of membrane elements, wherein at least 20% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

[0215] Example 131 includes the features of Example 128, wherein the RO or NF system includes a plurality of membrane elements, wherein at least 80% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

[0216] Example 132: One aspect of the present disclosure features a method of operating a three or fewer stage reverse osmosis (RO) or nanofiltration (NF) system comprising operating in such a manner that a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

[0217] Example 133 includes the features of Example 132, wherein the RO or NF system does not include a concentrate recycle.

[0218] Example 134 includes the features of Example 132, wherein the RO or NF system includes at least one attached-to-membrane (ATM) membrane element.

[0219] Example 135 includes the features of Example 134, wherein the RO or NF system includes at least one stenciled adhesive type ATM membrane element.

[0220] Example 136 includes the features of Example 132, wherein the RO or NF system includes a plurality of membrane elements, wherein at least 20% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

[0221] Example 137 includes the features of Example 136, wherein the RO or NF system includes a plurality of membrane elements, wherein at least 80% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

[0222] Example 138: One aspect of the present disclosure features a new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising:at least one attached-to-membrane (ATM) membrane element,wherein the RO or NF system does not include concentrate recycle;wherein a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

[0223] Example 139: One aspect of the present disclosure features a new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising:three or less stages operating in such a manner that a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

[0224] Example 140: One aspect of the present disclosure features a new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising:two or less stages operating in such a manner that a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

[0225] Example 141: One aspect of the present disclosure features a new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising:operating in such a manner that a concentration of at least one foulant in some portion of the RO or NF system exceeds a critical fouling concentration, but that a retention time of thatfoulant in the RO or NF system is below a time required to foul irreversibly, allowing the RO or NF system to operate in a continuous feed and bleed operation with super-critical fouling in the RO or NF system.

[0226] While the principles of the disclosure have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the disclosure. Other embodiments are contemplated within the scope of the present disclosure in addition to the exemplary embodiments shown and described herein. It will be appreciated by a person skilled in the art that an apparatus may embody any one or more of the features contained herein and that the features may be used in any particular combination or sub-combination. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present disclosure, which is not to be limited except by the claims.

Claims

What is claimed is:

1. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one attached-to-membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pumps in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a recovery of the refitted RO or NF system at the same or better production rate is increased relative to the existing RO or NF system.

2. The method of claim 1, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

3. The method of claim 1 , wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane element.

4. The method of claim 3, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

5. The method of claim 3, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

6. The method of claim 1, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

7. The method of claim 6, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

8. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one attached-to -membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a production rate of the refitted RO or NF system at the same or higher water recovery is increased relative to the existing RO or NF system.

9. The method of claim 8, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

10. The method of claim 8, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

11. The method of claim 10, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

12. The method of claim 10, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

13. The method of claim 8, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

14. The method of claim 13, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

15. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one attached-to-membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a flux of the refitted RO or NF system at the same or better production rate is decreased relative to the existing RO or NF system.

16. The method of claim 15, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

17. The method of claim 15, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

18. The method of claim 17, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

19. The method of claim 17, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

20. The method of claim 15, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

21. The method of claim 20, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

22. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one attached-to -membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a permeate quality of the refitted RO or NF system at the same or better production rate is improved relative to the existing RO or NF system.

23. The method of claim 22, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

24. The method of claim 22, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

25. The method of claim 24, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

26. The method of claim 24, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

27. The method of claim 22, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

28. The method of claim 27, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

29. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one attached-to -membrane (ATM) membrane element while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein a pumping power of each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as a pumping power of the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a concentrate hold up volume of the refitted RO or NF system is created for a minimum of 5 minutes production cycle time for a cyclic or semi-batch system at the same or better production rate relative to the existing RO or NF system.

30. The method of claim 29, wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system.

31. The method of claim 29, wherein the plurality of standard membrane elements include a plurality of standard 8040 membrane elements and wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

32. The method of claim 31, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

33. The method of claim 31, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) or stenciled adhesive type ATM membrane element.

34. The method of claim 29, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

35. The method of claim 34, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

36. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long and at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a recovery of the refitted RO or NF system at the same or better production rate is increased relative to the existing RO or NF system.

38. The method of claim 36, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

39. The method of claim 36, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

40. The method of claim 36, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

41. The method of claim 40, wherein the at least one ATM membrane element includes at least one stenciled adhesive type ATM membrane elements.

42. The method of claim 41, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

43. The method of claim 41, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

44. The method of claim 40, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

45. The method of claim 44, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

46. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a production rate of the refitted RO or NF system at the same or higher water recovery is increased relative to the existing RO or NF system.

47. The method of claim 46, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

48. The method of claim 46, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

49. The method of claim 46, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

50. The method of claim 49, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

51. The method of claim 50, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

52. The method of claim 49, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

53. The method of claim 49, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

54. The method of claim 53, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

55. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a flux of the refitted RO or NF system at the same or better production rate is decreased relative to the existing RO or NF system.

56. The method of claim 55, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

57. The method of claim 55, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

58. The method of claim 55, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

59. The method of claim 58, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

60. The method of claim 59, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

61. The method of claim 59, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

62. The method of claim 58, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

63. The method of claim 62, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

64. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a permeate quality of the refitted RO or NF system at the same or better production rate is increased relative to the existing RO or NF system.

65. The method of claim 64, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

66. The method of claim 64, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

67. The method of claim 64, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

68. The method of claim 67, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

69. The method of claim 68, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

70. The method of claim 68, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

71. The method of claim 67, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

72. The method of claim 71, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

73. A method of retrofitting an existing reverse osmosis (RO) or nanofiltration (NF) membrane system to form a retrofitted RO or NF membrane system, the existing RO or NF membrane system including one or more high pressure booster pumps and one or more stages having at least one pressure vessel, the at least one pressure vessel including plurality of standard membrane elements, the method comprising:replacing at least one of the plurality of standard membrane elements with at least one retrofit membrane element having at least 13.6% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements while maintaining at least 4 foot per minute velocity in a final stage of the retrofitted RO or NF system;wherein a number and size of the plurality of membrane vessels in the retrofitted RO or NF system is the same as the existing RO or NF system;wherein each of the one or more high pressure booster pumps in the retrofitted RO or NF system is the same as the one or more high pressure booster pump in the existing RO or NF system;wherein a concentrate velocity in each stage in the refitted RO or NF system has not been reduced compared to a concentrate velocity in each of the one or more stages in the existing RO or NF system;wherein a concentrate recycle relative to feed of the refitted RO or NF system has not been increased compared to the existing RO or NF system; andwherein a concentrate hold up volume of the refitted RO or NF system is created for a minimum of 5 minutes production cycle time for a cyclic or semi-batch system at the same or better production rate relative to the existing RO or NF system.

74. The method of claim 73, wherein the at least one retrofit membrane element has at least 18% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

75. The method of claim 73, wherein the at least one retrofit membrane element has at least 20% larger membrane surface area compared to surface area of the at least one replaced standard membrane elements.

76. The method of claim 73, wherein the at least one retrofit membrane element includes at least one attached-to-membrane (ATM) membrane element.

77. The method of claim 76, wherein the at least one ATM membrane element includes at least one 8040 ATM membrane elements.

78. The method of claim 77, wherein the at least one 8040 ATM membrane element includes a membrane element having a fixed membrane envelope or external dimension that is 8” in diameter and 40” long, with a minimum membrane area of 500 ft2 and spacers having a spacer height typically less than 20 mil, wherein the spacers are attached directly to a membrane surface without any cross-members connecting the spacers.

79. The method of claim 77, wherein the at least one ATM membrane element includes an 8040 print-in-place (PIP) ATM membrane element.

80. The method of claim 76, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 20% of the total number of the plurality of standard membrane elements with ATM membrane elements.

81. The method of claim 80, wherein replacing the at least one of the plurality of standard membrane elements with at least one ATM membrane element further includes replacing at least 80% of the total number of the plurality of standard membrane elements with ATM membrane elements.

82. A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane area at least 500 ft2 and a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch operating at average membrane flux no more than 16.3 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

83. The RO or NF system of claim 82, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

84. The RO or NF system of claim 82, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

85. The RO or NF system of claim 82, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

86. The RO or NF system of claim 85, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

87. The RO or NF system of claim 85, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

88. A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes an attached-to-membrane (AMT) spacer membrane element with a membrane area at least 500 ft2 operating at average membrane flux no more than 16.3 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

89. The RO or NF system of claim 88, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the total number of the plurality of 8” membrane elements.

90. The RO or NF system of claim 89, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

91. The RO or NF system of claim 88, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

92. The RO or NF system of claim 88, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

93. A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2 operating at average membrane flux no more than 15.9 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

94. The RO or NF system of claim 93, wherein the system is able to achieve at least 87% recovery.

95. The RO or NF system of claim 93, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

96. The RO or NF system of claim 93, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

97. The RO or NF system of claim 93, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

98. The RO or NF system of claim 97, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

99. The RO or NF system of claim 97, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

100. A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2 operating at average membrane flux no more than 17.4 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

101. The RO or NF system of claim 100, wherein the system is able to achieve at least 88% recovery.

102. The RO or NF system of claim 100. wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

103. The RO or NF system of claim 102, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

104. The RO or NF system of claim 100, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

105. The RO or NF system of claim 104, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

106. The RO or NF system of claim 104, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

107. A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 12-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2, a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch, and operating at average membrane flux no more than 17.5 GFD, maintaining at least 6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

108. The RO or NF system of claim 107, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

109. The RO or NF system of claim 108, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

110. The RO or NF system of claim 107, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

111. The RO or NF system of claim 110, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

112. The RO or NF system of claim 110, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

113. A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 14-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of 8” membrane elements, wherein at least one of the plurality of 8” membrane elements includes a membrane element with a membrane area at least 500 ft2, a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch, and operating at average membrane flux no more than 14 GFD, maintaining at least 5.6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

114. The RO or NF system of claim 113. wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

115. The RO or NF system of claim 114, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

116. The RO or NF system of claim 113. wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

117. The RO or NF system of claim 116, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

118. The RO or NF system of claim 116, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

119. A reverse osmosis (RO) or nanofiltration (NF) system comprising:a 14-membrane long, two-stage system wherein each of the pressure vessels includes a plurality of standard 8” membrane elements, wherein at least one of the plurality of standard 8” membrane elements includes a membrane element with a membrane area at least 500 ft2, a feed flow path channel occlusion crossmember below 15.5 thousandths of an inch, and operating at average membrane flux no more than 15 GFD, maintaining at least 6 foot per minute open channel velocity in the final stage, without recycle of concentrate, and able to achieve at least 85% recovery.

120. The RO or NF system of claim 119. wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 20% of the total number of the plurality of 8” membrane elements.

121. The RO or NF system of claim 120, wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes at least 80% of the total number of the plurality of 8” membrane elements.

122. The RO or NF system of claim 119. wherein the at least one of the plurality of 8” membrane elements having a membrane area at least 500 ft2 includes an attached-to-membrane (AMT) spacer membrane element.

123. The RO or NF system of claim 122, wherein the AMT spacer membrane element includes a print-in-place (PIP) ATM membrane element.

124. The RO or NF system of claim 122, wherein the AMT spacer membrane element includes a stenciled adhesive type ATM membrane element.

125. A reverse osmosis (RO) or nanofiltration (NF) system operating in such a manner that a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

126. The RO or NF system of claim 125, wherein the RO or NF system includes a concentrate recycle.

127. The RO or NF system of claim 125, wherein the RO or NF system does not include a concentrate recycle.

128. The RO or NF system of claim 125, wherein the RO or NF system includes at least one attached-to -membrane (ATM) membrane element.

129. The RO or NF system of claim 128, wherein the RO or NF system includes at least one stenciled adhesive type ATM membrane element.

130. The RO or NF system of claim 128, wherein the RO or NF system includes a plurality of membrane elements, wherein at least 20% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

131. The RO or NF system of claim 128. wherein the RO or NF system includes a plurality of membrane elements, wherein at least 80% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

132. A method of operating a three or fewer stage reverse osmosis (RO) or nanofiltration (NF) system comprising operating in such a manner that a concentration of at least one salt in someportion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

133. The method of claim 132, wherein the RO or NF system does not include a concentrate recycle.

134. The method of claim 132, wherein the RO or NF system includes at least one attached-to-membrane (ATM) membrane element.

135. The method of claim 134, wherein the RO or NF system includes at least one stenciled adhesive type ATM membrane element.

136. The method of claim 132, wherein the RO or NF system includes a plurality of membrane elements, wherein at least 20% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

137. The method of claim 136. wherein the RO or NF system includes a plurality of membrane elements, wherein at least 80% of the total membrane elements are attached-to-membrane (ATM) membrane elements.

138. A new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising:at least one attached-to-membrane (ATM) membrane element,wherein the RO or NF system does not include concentrate recycle;wherein a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

139. A new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising: three or less stages operating in such a manner that a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

140. A new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising:two or less stages operating in such a manner that a concentration of at least one salt in some portion of the RO or NF system exceeds a saturation of that salt, but that a retention time of that salt in the RO or NF system is below a precipitation induction time of that salt whether with or without scale inhibitors, allowing the RO or NF system to operate in a continuous feed and bleed operation with supersaturated salt in the RO or NF system.

141. A new or existing reverse osmosis (RO) or nanofiltration (NF) system comprising:operating in such a manner that a concentration of at least one foulant in some portion of the RO or NF system exceeds a critical fouling concentration, but that a retention time of that foulant in the RO or NF system is below a time required to foul irreversibly, allowing the RO or NF system to operate in a continuous feed and bleed operation with super-critical fouling in the RO or NF system.

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