AMD VARIABLE PRESSURE CO»iT!0«S

BACKGORUNO OF THE INVENTION IN LIGHT OF PRIOR ART

Desalination of salt water solution feed (feed) fay reverse osmosis (RO) can be divided broadly into plug Sow and closed circuit batch techniques of conceptually different principles and operational modes. In plug flow desalination (PFD), a pressurize feed stream at inlet to a pressure vessel with semi-permeable membrane elements in line, a so-called module, splits at its outlet into two streams, one of a high salinity pressunzed concentrate referred to as brine and the ether of a low salinity non-pressurized permeate. PFD is a continuous hydrodynamic process; wherein, permeate recovery depends on the number of lined elements in modules, separation energy of water from feed is depends on the permeation flux created by a fixed applied: pressure greater than the osmotic pressure of said brine, and energy efficiency dependence on the ability to recycle the energy stored in the disposed brine by an energy recovery device (ERD). In simple terns, recovery in PFD depends on the number of lined elements in modules and the energy consumption on the feed source salinity; flux, and efficiency of ERD. PFD is practiced in various modificatas including such with single-stage or multi-stage modules' designs and with partial concentrate recirculation in a dosed or an open circuit. PFD processes, irrespective of their exact mode, are characterized by the flow balance expression and the mass-balanced expression

wherein, Q stands for flow rate, C for total dissolved salt, and the subscript f for

feed, p for permeate and b for brine. PFD desalination recovery (R) is expressed from How rates or concentrations by from.

In contrast with PFD, dosed-eircuit desalination (CCD) is a batch desalination process made continued by consecutive sequential us wherein the entire concentrate is recycled from outlet(s) to inters) of moduie(s) after diluted: with fresh pressurized feed which proceeds with identical flow rates of pressunzed feed {£¾} and permeate {(¾?) and with the increased salinity of the closed circuit. The progression of CCD since inception is well documented in the patent literature starting with the US 4,814,886 by Bratt and the US 4,983,301 by Szucx et ai. patents of similar 1387 priority dates for the making of batch CCD processes continuous by means of .. two relatively large capacity tanks.. " which are alternately engaged with the closed circuit and thereby, enable consecutive sequential closed circuit desalination under fixed pressure conditions without the need to stop the batch process for recharge. After filled with brine at the end of a batch destination sequence, the disengaged tank is separated from fie closed circuit by vafee means, decompressed, fts brine replaced by fresh feed at near atmospheric- pressure, and then sealed, compressed and left on stand-by for the next engagement by a procedure involving hydrostatic compressio^'decompression steps of negligible energy demand/loss which circumvent the need for energy recovery from piessuazed brine flow as sn PFD. While saving; the need for ERD means, the drawback of this approach rest with the need for large volume high pressure tanks which makes this approach of prohibited economic feasibility.

Batch CCD under fixed flow and variable pressure conditions and such a consecutive sequential process wrth two alternating contains was taught first in by Efraty and demonstrated the unique operational principles of this approach on a linear time scale wits each CCD sequence comprises cycles of fixed time duration, defined by unchanged flow rates of feed (-permeate) and cross-flow and in a closed circuit of a fixed intrinsic volume. Each CCD cycle under such condions is dwaderized by fixed inlet and outlet module concentrations, applied pressure requirement, specific energy consumption, and quality of produced permeates, with an overall sequence performance per a defined recovery expressed by the average cycle performance. CCD under fixed flow and variable pressure conditions takes place with fixed flux, module recovery (MR), and sequence recovery (R) operational set-points with flux defined by where

and where

are the identical cumulative volumes of teed and permeate, respectively. R could also be estimated from electric conductivity since where subscript b stands for brine

effluent f for feed, and ρ for average permeate over the entire sequence. CCD sequence recovery (R) under fixed flow and variable pressure conditions is a function of the CCD cycle-number, irrespective of the number of elements per module. Irs a CCD system of fixed operational set-points (e.g., fa, MR and R), CCD cycle time duration is a fixed entity expressed by

and therefore, variations of applied pressure and salinity of constituents during CCD hatch sequences are linear of the time scale and exponential on the recovery scale. A noteworthy difference between fixed pressure variable flow approach taught by either Bratt and/or SEUGZ et al. and the fixed flow variable pressure approach taught by relates to the lower energy consumption prospects of the latter; however, the principle obstacle of these techniques irrespective of their mode of operation arises from the need of two large volume high pressure containers tanks with lines and valve means to enable their alternating actuation which limits such designs only for small scale desalination apparatus. The next stage in the progression of the CCD technology in by Efratv teaches apparatus and method for continuous consecutive sequential CCD under fixed Sow and variable pressure conditions with a single container. According to this invention, a single container of the intrinsic volume of the closed circuit is occasionally engaged; with the closed circuit for concentrate brine replacement by fresh feed for a single cycle duration when the consecutive sequential batch desalination process reaches its designated sequence recovery as manifested by maximum applied pressure and/or electric conductivity (EC! of recycled concentrate; and thereafter, the container is disengaged from the closed circuit, decompressed _. , recharged with fresh feed at near atmospheric pressure, and then, sealed, compressed by one-end connection to the closed circuit and left on stand-by to the next engagement. CCD according to this invention is carried with high energy conversion efficiency without need for ERD, since the compression/decompression steps of the single container take place under hydrostatic conditions with negligible energy losses. The low energy consumption of CCD under fixed flow and variable pressure conditions arises from the combination of average energy consumption along the sequential recovery scale with near absolute energy conversion efficiency, and this approach is unmatched by conventional PFD techniques. This technology is not confined to a specific salt water solution feed source is particularly effective for seawater desalination where energy consumption is an essential economic parameter; however, the application of this technology is limited to relatively small units in light of the volume requirement size of the pressure container to match the intrinsic volume of the closed circuit section of pressure vessels, elements and conduit lines.

Apparatus and method for continuous consecutive sequential CCD under fixed flow and variable pressure conditions without need of a container is described in by Efrafcy and teaches the integration of CCD and PFD for high recovery low energy desalination with the former mode experienced under fixed flow and variable pressure conditions most of the time (>85%) and the latter mode applies for brief brine lush-out of concentrate brine without stepping desalination. The CCD-PFD approach is of particularly relevant for high recovery (88%-97%) low energy desalination of brackish wafer, since requires simple inexpensive apparatus of high cost effectiveness and save both water for reuse and energy.

Another reported aspect of CCD described in by Eftaly teaches a hybrid system comprising a conventional PFD multi-stage BWRO design and a retrofit CCD unit at the brine effluent outlet of the former which utilizes the power stored in the pressurized brine stream for sis further desalination and thereby, lost energy is saved and used to increased the water recovery of y of the entire system. The CCD retrofit is a non-autonomous unit intended for integration with conventional PDF muiti- stage BWRO units in order to iroprove their performance, arid can be viewed as an energy recovery device with saved energy applied for the fciriher desalination of the feed source beyond the feats of the conventional PFD process.

DerJefcR/deterioration of fresh water supply sources in many parte of the vi/ortd as result of rising standards of living, a growing global population, climate changes in large regions worldwide prompted by the progression of the global "green-house effect, and increased marsmade pollution of ground and surface wafer soyrces, created the needs for water treatment and waste water recycling as well as for increased reliance on seawater desalination for fresh water supplement. SWRO is the desalination method of the lowest energy consumption and increased reliance SWRO for fresh water supplement is already evident worldwide by the growing number of such plants of small to mega size production capacity, and this trend is expected to intensify in the future. Desalination of Ocean seawater (35,000 ppm) of 50% recovery at fiux of 13 Imh in large modern SWRQ-PFD desalination plants equipped with advance ERD means proceeds with specific energy (SE) in the range of 2.45 - 3.00 kWh/rn ³ , with energy accounting to 35% ~> 70% of the desalination costs as function of the electricity tariff. By analogy, SWRO-CGD under the same fiux and recover/ conditions using the PCT/1L20Q4/000743 inventive method was shown to proceed only with SE<1.75 kVWm ³ - distinctly lower energy consumption compared with that the of conventional SWRQ-PFD methods; however, said CCD approach with an engaged/disengaged side container is confined to small units under 1,000 m-Vday production capacity .

The present invention hereinafter describes CCD systems of large production capacity under fixed flow and variable pressure conditions where brine placement with fresh feed inside the closed circuit takes place by Pressure Exchange (PE) means.

SUi!MRY OF THE IHVEMTION

The present invention proposes systems comprising one or several batch dosed circuit desalination (CCD) units integrated with pressure exchange (PE) means made of one PE or several PE units with their respective inlets and outlet lines connected In parallel; and conducting lines with valve means to enable a periodic engagement of each said CCD unit with said PE means for brine replacement with fresh feed, while consecutive sequential desalination under fixed flow and variable pressure conditions in said batch CCD unit(s} is continued nonstop with unchanged membrane performance of predetermined fixed flux, cross-flow, and recovery, independent of each other. The method of operation of sad inventive system takes place by the actuation of valve means triggered by signals of on-line monitored data such as of pressure, and electric conductivity; whereby, each batch CCD unit at its designated recovery is engaged with said PE means for brine replacement with fresh feed and thereafter, disengaged when tie entire- closed circuit volume of the said engaged CCD unit is replaced. According to the inventive method, a sequential maximum applied pressure signal per each said batch CCD unit manifesting the attainment of the designated recovery, wi trigger an engagement procedure with the PE means for brine replacement by fresh feed and engagement termination will take place when the monitored displaced brine volume matches the intrinsic volume of said CCD unit. PE means in the Inventive system are either active or idle and can be actuated continuously and alternately when the number of batch CCD units in the system design is also the required number of CCD cycles to attain a designated recovery.

The application of ihe inventive system and method for seawaier desalination will enable for ihe first lime the design of large scale systems for under fixed flow and variable pressure CCD conditions of exceptionally low energy consumption by overcoming ihe volume Imitations of design according to prior art teachings. The application of the inventive system and method for brackish water desalination of high recovery and low energy under fixed How and variable pressure CCD conditions will enable for the first time the design of large scale systems with unchanged membrane performance and flux in contrast with prior art teaching of a similar approach OR the basis of a two-step consecutive sequential process wherein CCD is experience most of the time with brief PFD steps of lower flux apply between batch desalination sequences for concentrate brine replacement with fresh feed - constant flux according to the present invention instead of changing flux in the two-step process of prior art should enable a higher system productivity and a longer membrane durability compared with the former CCD-PFD prior art technique.

BRIEF DESCRIPTION OF DRAWINGS

Fig, 1A: A schematic diagram of an inventive system for continuous closed circuit desalination comprising a batch CCD unit, a pressure exchange (PE) unit, and conducting lines and valve means between CCD and PE, showing an actuation mode where both said units are disengaged.

Fig. IB: A schematic diagram of an inventive system for continuous dosed circuit desalination comprising a batch CCD unit a pressure exchange (PE) unit, and conducting lines and valve means between CCD and ΡΈ, showing an actuation mode where both said units are engaged. Fig.2: A schematic diagram of the inventive system for continuous dosed circuit desalination comprising a batch CCD unit,, a pressure exchange (PE) unit, conducting fines and valve means between CCD and PE during an engagement mode, and RO skids of different plausible configurations such as NNEn {&], :N(2MEn) [B] and, N{3MEn) [C], where MEn stands for a module containing and n elements and N for vertically fed of one, two and three horizontally linked modules, respectively .

Fig. 3: A schematic diagram of multitude pressure exchange (PE) units with their inlets and outlets lines connected in parallel to enable their simultaneous .actuation.

Fig, 4: A schematic diagram of the inventive system for corstinuQus dosed circuit desalmation comprising two batch CCD units, pressure exchange (PE) unls, and the conducting lines and valve means between them, showing an actuation mode where one of the CCD units (RO-1) is disengaged from the PE means white the other unit (RO-2) is .engaged with said PE means undergoing brine replacement with fresh feed, whereby continuous operation of both CCD units under fixed flow and variable pressure conditions is enabled by the alternating engagement of said units the with the PE means.

Fig. 5: A schematic diagram of the inventive system as in Fig. 4; except that both units are supplied with pressurized feed by the same high pressure pump (HP) and the fixed flow variable pressure operation within each CCD unit is created by means of their separate booster pumps (BP).

DETAILED DESCRIPTION OF THE INVENTION

The inventive step of the present invention relates to the use of PE means for brine replacement with fresh pressurized feed in batch CCD units operated consecutive sequentially under fixed flow and variable pressure conditions. Prior art teaching of brine replacement with fresh pressurized feed in said consecutive sequential hatch CCD process through a disengaged/engaged single container (CCD-SC) proceeds with negligible hydrostatic compression^decompression energy losses with theory predicted near absolute energy conversion efficiency which was ultimately confirmed experimentally. PE means comprise mechanical unit of two inlets and outlets wherein a pressurized effluent stream actuates a feed pressurizing devise and the efficiency of such a unit depends on the inlet-ouffet pressure difference of said effluent stream, the hydraulic efficiency of said feed pressurizing device, and the degree of mixing between said brine effluent and feed streams, isobars ERD based of posive displacement principles of conventional PFD plants (e.g., PX, DVVEER, etc.) are noted for their high hydraulic efficiency (93%-9S%); however, the overall energy conversion efficiency of said ERD should be only ~90% or less if account is taken of their inlet-outlet pressure-difference,, mixing, and plausibly mechanical and flow induced pressure losses. Accordingly, the integration of the relatively small size PE means, such as the isobaric-ERD tools, info batch CCD units of fixed low and variable pressure operational mode should enable a design flexibility of large production cost effective units by circumventing the need for large volume side containers; however, this will be done at an expense of a somewhat greater SE (~10%) compared with that of CCD with a side container (CCD-SC). For example, the energy consumption pnaection of the inventive method (CCD-PE) for large scale Ocean seawafer (35,000 ppm) desalination of 50% recovery at 13 Irrib of ~1.92 kWh/m ³ is expected to be 10% higher than that demonstrated for a small scale CCD- SC unit (1.75 kWh/m ³ ) and -22% lower than that of the most efficient SWRO-PX large commercial plant (2.45 kWh/m ³ !) located in Partf (Australia).

An integrated system of a batch CCD unit for fixed flow and variable pressure operation with PE means according to one of the preferred embodiments of the inventive system disclosed schematically in Fig. 1 (AS), shows a single batch CCD unit, a single PE unit, conducting lines in each of said units and those between them, and the valve means and monitoring means whereby said system is actuated continuously under the designated flow and pressure conditions with performance continuously monitored to enable a process control and detection of male functions if occurred. The conducting lines in the drawing are distinguished from each other to facilitate the distinction of their function, with flow direction in lines indicated by arrows. The two-mode actuation of the inventive system; wherein, said CCD and PE units am either disengaged; or engaged, are displayed in Fig. 1A and Fig. 18, respectively. The batch CCD unit in Fig. 1(AB) comprises a RO skid of a single module with a selected number of membrane elements, or of multitude of such modules with their respective inlet and outlet lines connected in parallel; a dosed circuit line for concentrate recycling from outlets) to infers) of said modules) by means of a circulation pump (CP) equipped with a variable frequency drive (½¾) means to enable a selected fixed cross-flow {QCP) in said batch CCD unit; a high pressure feed pump (HP) equipped with a variable frequency drive (Wbf) means with its Inlet line for feed and outlet line for pressurized feed to enable the a selected constant flux under variable pressure conditions irrespective of cross-low; a linefs) for permeate release from said rnodule(s) In said batch CCD unit; and a single PE means with its inlet line of pressurized concentrate brine, inlet line of feed, outlet line of decompressed concentrate brine, and outlet line of pressurized feed. Other features in Fig. 1{AB) include the the connecting lines from said dosed circuit line of said batch CCD unit to the inlet line of pressurized concentrate brine and to the outlet line of pressurized feed of said PE means: actuated valve means |V1 , V2, and one-way check valve (CV)]; a flow/volume monitoring means on inlet line to HP (FHP) and on outlet line off CP(FGP); pressure monitoring means on inle! line (Pin) to module(s) and on out line (Pout) off mcduie(s); and lectric-conductivity monitoring means on permeate outlet line (E _p ), feed inlet line to HP (EXP), brine effluent line off PE {E _B ). and recycled concentrate in the closed circuit line (Ece).

The RO skid design of said hatch CCD unit in the preferred embodiment of the inventive system in Fig. 1(AB) is outlined with further details in Fig. 2{A-C). in said RO skids, the respective inlet and outlet fees of modules are connected in parallel to a single outlet line and a single inlet line which are part of said closed circuit line for concentrate recycling. Identical flow distribuiion to inleffsi and off outlets) of moduie(s) in said RO skids under fixed flow and variable pressure conditions implies an equivalent module performance, irrespective of the number of modules in the design provided thai ail the modules comprise of the same number of elements. Alignment of modules in said RO skids Is possible in trie vertical and/or horizontal configurations displayed in Fig. 2|A-C); wherein., Fig. 2A shows the vertical stacking of H modules of tie UMEn configuration with their respective inlet and outlet lines connected in parallel; Fig, 2B shows the vertical stacking of M taste, each comprises ivvo horizontally linked modules, of the M{2!Ers) configuration with respective Inlet and outlet Sines of all modules connected In parallel: and Fig. 38 shows the vertical stacking of N unite, each comprises three horizontally linked modules, of the N(3MEn) configuration with respective inlet and outlet lines of all modules connected in parallel. The basic MEn unit in said configurations Is of a module design comprising of a pressure vessel with it membrane elements (E) inside, with or without an additional empty volume inside pressure vessels created by spacers which is part of the free intrinsic volume of said module unit and that of the closed circuit of the entire system configuration - the free intrinsic volume of said module unit is an essential structural parameter which defines the fixed cycle duration during a batch CCD process under fixed low and variable pressure conditions.

The method of actuation of he preferred embodiment of the inventive system displayed in Fig. 1{AB) and Fig. 2(A-C) proceeds by a continuous two-mode consecutive sequential process under fixed How and variable pressure conditions according to predetermined set-points of flux, module recovery (MR), arid system recovery (R), or parameters derived from said set points such as fixed pressurized feed flow rate instead of flux, fixed cross-low rate (QCP) instead of MR and maximum

applied pressure (p _max ) instead of R. During said two-mode consecutive sequential process, engagement of batch CCD unit with PE means takes place only part of the time, to enable replacement of brine by fresh pressurized feed at the predefined desired system recovery from the intrinsic closed circuit volume of system. Row through said PE means during engagement is the same as QCP. CCD operation of unchanged flux, MR. and R in a fixed intrinsic volume (½) proceeds by CCD cycles of constant lime duration wherein, recovery is a function of number of CCD cycles, or their cumulative batch sequence time intervals, with periodic engagement between said CCD and PE units to enable complete replacement of concentrate brine by fresh feed is of one CCD cycle duration (WQCP) per a consecutive sequence. It should be pointed out again that the PE means are activated once per sequence for a single CCD cycle time duration remain inactive during the rest of the time, and the frequency of PE means is function of

recovery - declined ^' frequency with increased recovery.

Actuation of the preferred inventive system embodiment displayed in Fig, 1{AB| and Fig. 2 |A-€) takes place by means of operational set-points (e.g. _: flux, MR and R or their derivatives) and on-line monitored data. The control-board actuation of said system relates to CCD and PE enppmentfdisengagernent by the valve means. Inactive PE means is said system (Fig. 1A) implies an opened V1 and a closed V2 valve means; whereas, the activation of the PE means is achieved fay the simultaneous closure of Viand opening of V2 valve means in said system (Fig. 1B). Accordingly, reaching the desired recovery will be manifested by a defined maximum applied pressure signal, or by a defined maximum electric conductivity signal of recycled concentrate (Emax) and each said on-line monitored signals may apply to trigger PE engagement with the batch CCD unit for brine replacement with fresh feed without stopping desalination. The termination of the engagement may proceed after a single CCD cycle duration (WQCP), since the fixed tow rates (HP and CP) in the system remain unchanged. An alternative engagement termination signal may relate to the monitored CP volume during engagement (∑Ycp) with a termination signal prompted when∑Vcp=Vi.

Apart from signals for valve means actuations, the monitoring means cited hereinabove in the preferred embodiment of the inventive system in Fig. 1(A8) also serve for the follow-up of the sequential CCD performance characteristics of pressure, flow rates, and electric conductivity which provide valuable information concerning of the development of fooling an/or scaling conditions in membranes and male function warnings specific system's components, ft should also be pointed out that the reference to a single PE unit in Fig. f AB) and Fig. 2{A-€) is made for clarity and simplicity and that such a preferred embodiment of the inventive system may comprise of many such PE units of a simultaneous actuation mode as long as their respective infet and outset lines are connected in parallel according to the schematic drawing in Fig, 3.

According to the preferred embodiment of the inventive system in Fig. 1{AB) and Fig. 2{A-C), the batch CCD unit operates continuously under fixed flow and variable pressure conditions while the PE unit operates periodically, once during each sequence and remains idle during the rest of the time. The frequency of PE actuation is defined by the number of identical CCD cycles (φ) required to reach a designated sequential recovery (R) with VS¾CP expressing the active period per sequeiioe of said PE unit and (φ-1)*(ν»'Χ3σ4 the nor*-acfrve period of said unit with percent idle firne expressed by 100*{1-1/φ). In CCD umfer fixed Sow and variable pressure conditions, the term φ is defined by the selected R and MR set points, with sequential time period defined by R and the number of CCD cycles experienced during said sequence period determined by MR, or more specically by QCP, wrlh a fester selected cross-flow manifested by a lower MR value, a larger number of CCD cycles (φ) per given R, and a shorter cycle period. The aforementioned dependencies in the context of the inventive system in Fig. 1(AB) and Fig. 2{A-C) of a typical brackish water source {2,000 ppm HaCI) at 20 imh with 75%, 85%, and 85% recovery are illustrated, amongst other, in Example-1 (Table 1). The preferred embodiment of the inventive system in Fig. 1|AB| and Fig. 2{A-C) when applies to seawater CCD of 50% recovery at 13 Imh flux proceeds with few CCD cycles (e.g., 2-4) and a greater actuation frequency of the PE unit(s), with less idle time in between sequence.

The CCD performance effectiveness under fixed flow and variable pressure conditions of the preferred embodiment of the inventive system in Fig. 1fAB) and Fig. 2{A~€) depends on a suitable selection of components with emphasis on the PE and CP units, valve means and an effective control board program. The said PE unit should be of a high hydraulic efficiency (>93%) not affected the changing pressure under constant flow conditions and of a fast starting response when engaged wsih the closed circuit of the batch CCD unit. Said engagement takes place when said batch CCD unit reaches its maximum applied pressure with an unchanged CP cross-flow rate (fixed Gcp) _s under which conditions a fast start of said PE unit is expected, pending a quick response of the actuated valve means in the system. The function of CPwif in Fig. 1(AB) and Fig. 2{A~C) is to maintain a fixed cress-flow rate in said batch CCD unit and this implies enough power to overcome the modules) pressure difference (Δρ) when said batch CCD and PE units are disengaged as well as the to provide a pressure supplement ( Δρ _PE } when both said units are engaged, where Δρ _PE is the pressure loss in said PE unit. The vfd means in said CPwff should be sufficiently responsive to enable a near constant cross-Sow during the engaged/disengaged modes in the inventive system.

Another preferred embodiment of the inventive system in Fig. 4 describes the integration of two batch CCD units with the same pressure exchange means comprised of either one such unit (PE) or multitude of PE units (PEn) with their respective inlets and outlets connected in parallel. The engagement of the CCD units and PE means in said Inventive system is enabled alternately, rather than simultaneously, through the valve means, white desalination is continued nonstop in both CCD units. The features in said batch CCD units, labeled RO-1 and RO-2, are same as already explained hereinabove for the preferred embodiment of the inventive method in Fig. 1{AB) and Fig, 2(A-C). Each batch CCD unit in Fig. 4 is autonomous and can be engaged alternately with said PE means for brine replacement by fresh feed through a concentrate line off its dosed srcut line and valve means, in simple terms, PE means in of tie preferred embodiment in Fig. 4 can fee engaged with either RO-1 or with RO-2, one at a time, through their respective conducting lines and valves means, and remain idle when not engaged. Three operational modes are enabled by valve means actuation (opened closed positions} of the inventive system under review {Fig. 4} as followed: Continuous desalination while PE means are idle (Opened position V11 and V21 ; Closed posticn -> VI 2, ¥13, V22 and ¥23); Continuous desalination with PE means engaged with RO-2 (Opened position -> V11, V22 and V23. Closed position -> Y21 , V12 and VI 3); and Continuous desalination with PE means engaged with RO-1 (Opened position -> V21, V12 and V13. Closed sosion -> V11, V22 and V23). Valve means V13 and V23 can be replaced by one-way check valve means, since the outlet line from said PE means is always under a somewhat reduced pressure (2-3 bare} than that of the recycled concentrate inside said batch CC D units. The actuation mode of the inventive system displayed in Fig. 4 is thai where RO-1 is disengaged and RO-2 engaged with the PE means.

A single unique mode of operation of the preferred embodiment of the inventive system in Fig. 4 exists when both batch CCD unite in the design are of identical configuration and operate identical iwo-eyde CCD consecutive sequences of same fa, module recovery {MR}, recovery (R), sequence time duration (2*Vi/Qcp), and cycle time duration (WQCP). In this event, the inventive system m Fig. 4 is actuated with the PE means operated continuously, half the time with said RO-1 and half the time with said RO-2. Moreover, the entire conducting lines between the CCD units and pressure PE means in Fig. 4 remain under pressure, implying a small pressure difference during the actuation of the valve means in the system and the ability to achieve fast actuation of valves without damage. The monitormg means in the inventive system in Fig. 4, although not cited, are of the same type and located in the same respective positions as revealed for the single batch CCD unit in Fig. 1{AB).

The inventive system in Fig. 4 for the simultaneous actuation of two batch CCD units with the same PE means can operate with one batch CCD unit with idle PE means when not engaged. This option, enabled by valve control means, implies the ability to stop one of the two batch CCD units in the system for maintenance and/or repair while the other is maintained operational.

A modified design of the preferred embodiment of the inventive system in Fig. 4 is revealed in Fig. S; wherein, a single high pressure pump (HP) without vfd means supplies a fixed flow of the feed minimum pressure required by the batch CCD units, with pressure boosting inside the medu!e(s) of RO-1 and RO-2 to enable a fixed permeation flow operation achieved by means of the respective booster pumps 8P1s« and both equipped with vfd means to alow a fixed How control. The monitoring means in the inventive

system in Fig. 5, although not died, are of the same type and located in the same respective positions as revealed for the- single batch CCD unit in F

Systems according to the inventive method may comprise many batch CCD units which engage with the same PE means sequentially , one at a time,, for concentrate brine replacement with feed. Inventive systems with many identical batch CCD units operated under the same conditions, will engage the PE means continuously when the cycle-number (ψ) to reach a designated: recovery(R) is the same as the number of said batch CCD units, in this case, the sequence time duration of each said batch unit is expressed by with cycle lime duration of expressing the sequential periodic engagement with said PE means.

It will be understood to the skilled in the art that the inventive systems of the inventive method pertain to integration between batch CCD unitfs) of fixed flow and variable pressure mode of operation and PE means to enable periodic concentrate brine replacement by feed in said batch CCD unit(s) without stopping desalination, and that the preferred embodiments of the inventive systems in Fig. IfAB), Fig. 2|A-C). Fig. 3 _. . Fig. 4 and Fig, 5 are schematic and simplified and are not to be regarded as limiting the invention but as several examples of many for the diverse implementation of the invention. In practice, systems according to the irwerive method may comprise many additional lines, branches, valves, and other installations and devices as deemed necessary according to specific requirements while still remaining within the scope of tie invention's claims.

It will be understood to the skilled In the art that means for pressurizing feed, boosting feed pressure, recycling of concentrate, pressure exchange, and flow manipulation are comprised of ordinary commercial components such as a pressure pump, a circulation pump, a booster pump, a pressure exchange device, and a valve device, or several such components that are applied simultaneously in parallel, or in line as appropriate. It is further understood that the referred monitoring means in Fig. 1{A8) are typical of all the inventive systems and thai their signals essential for the actuation and control of specie components within said systems as well as for the entire systems. Noteworthy in particular in this context is the fixed: slow operation of HPvfd and CPvfd in the batch CCD unit(s) of the Inventive systems which is made possible through vfd and flow monitoring means and that signals of such monitoring means apply to actuation of said valve means through a programmable control board whereby the entire operation is executed and controlled. ft will be obvious to the ski in the art that the design of the inventive systems is not confined by the number of modules and/or element-number per module andfor the type of modules and elements in each said batch CCD unit, nor by the number of said batch CCD units and/or number of pressure exchange units per inventive system, and therefore, said inventive systems could apply also for large scale desalination of low energy and high recovery of sal water solutions including at the level of seawater.

The inventive systems and methods pertain to the integration of batch CCD unft(s) with pressure exchange means tough conducting lines with valve means into systems exemplified by the preferred embodiments in F¾, 1(AB| _: Fig. 2f A-C). Fig. 4 and Fig. S with monitoring and control means to enable continuous consecutive sequential CCD operation under fixed flow and variable pressure conditions in compliance with predefined operational set-points of lux,, module recovery and sequence recovery, which are independent of each other. The specified mode of operation is intended to enable continuous desalination of tow energy high recovery also in inventive systems of large production capacity and high oost-efectiveness. Skilled in the art will recognize fat the application of pressure exchange means with batch CCD uni's) is non-cfewous in the absence of any pressurized brine flow release during said CCD process as is case of conventional plug flow desalination techniques where pressure exchange means are being used continuously in a different mode.

While the invention has been described hereinabove in respect to particular embodiments, if will be obvious to those versed in the art that changes and modifications may be made without departing form this invention in its broader aspects, therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit of the invention.

EXAMPLE-!

Seawater (35,000 ppm) CCD with operational set-points of 13 imh flux, 33.3% module recovery (MR), and 50% recovery (R), according to the preferred embodiment of the inventive system in Fig. 4; wherein, each batch CCD unit comprises 42 moduiefs) of a specified number of elements per module of eight-section long pressure vessels. Both said CCD units in the system are of identical designs, operate with the same set- posnts, each executes a two-cycle consecutive sequences of 4.0 minute duration with a cycle period of 2.0 minute, and the PE means are operated continuously alternate every 2.0 minute from one CCD unit to the other, and thereby, allow a continuous desalination of both CCD units simultaneously at the same average set-point flux. In simple terms, the PE means in the design (Fig. 4) are operated nonstop and alternately engaged with each CCD unit for 2.0 minute duration. The various design and performance aspects of the exemplified system of the preferred embodiment are summarized in Table 1.

Table-1 : Illustration of the design and performance aspects of systems with 4MEn (n=2-6) batch CCD unit configurations according to the preferred embodiment of the inventive system in Fig. 4, as applied for the desalination of seawater (35,000 ppm) with 50% recovery.

Noteworthy features in Table 1 : Inventive systems of MEn (2-6) module designs; a low energy consumption depending on module design [1.805 - 1.853 kWh/m ³ for MEn(n=3-6), and 1.990 kWh/m ³ for ME2]; permeate of 347-^419 ppm TDS with salinity order manifesting increased concentration polarization of 1.1 1 -^1.34; fixed flux operation with production capacity manifesting the number of elements per module in the design; and maximum production capacity per system of two batch CCD 42*ME6 units (#1) of 6,416 The yelow-backgraund data signifies unadvisabie operational conditions from -the

stand pesint of concentration polarization

EXAMPLE-II

Sail water solution {2,000 ppm NaCi) batch CCD win operational set-points of 20 Imh flux;, a selected module recovery (MR) manifesting a concentration polarization factor of 1.17; and a seieeiej recovery {R} of 75%, or 85%, or 95%, according to the preferred embodiment of the inventive system in Fig. 1; wherein, said batch CCD unit comprises 42 modules of a specified numbe-r of elements per module [42MEn, n=4-8] made of eight-section long pressure vessel, and its operation proceeds by consecutive CCD sequences with periodic concentrate brine replacement by feed achieved by engagement with pressure exchange means for a single cycle duration; and thereafter, said pressure exchange means disengaged and remain idle until the next said engagement, with design and performance aspects said inventive systems summarized in Table 2.

Tabfe~2: lustration of the design and performance aspects according to the preferred embodiment of the inventive system in Fig. 1 with batch CCD unit configuration of 42MEn (n=3-6) as applied to the desalination of a sail water solution of 2,000 ppm NaCI with 75%, 85% and 95% recovery .

Noteworthy features in Table 2: Inventive systems of different module configuration (tvEn; n =4-6); few energy oonsumption as function of recovery (O.400->0.S35 kVYh/rn ³ for 75% ->35% recovery); permeates of 38-→152 ppm IDS with salinity order rnanifesfinp; increased recovery; and inventive systems of fixed operational flux, same concentration polarization factor (1.17), with permeate output proportional to the number of elements per module in thse design of maximum production capacity (4,935 m ³ /eay) exemplified with 42ME6 units (#1.1, #12, and #13).

BENEFITS OF INVENHWE SYSTEMS OVER PRIOR ART

1. Large Scale, Low Energy, Cost-Effective SWRO-CCD Systems

Low cost continuous seawaier closed circuit desalination under fixed flow and variable pressure conditions of low energy consumption and large production capacity is taught hereinabove by the periodic engagement of batch CCD unit(s) with pressure exchange means to enable concentrate brine replacement by feed and thereby, allow a batch process continued on a consecutive sequential basis. The inventive method overcomes the limitations of large intrinsic volume requirements and complex conduit lines and valve means of PCT/IL2002/000636 with two alternating side containers and of PCT/IL2004/000748 with a angle side container, both of confined CCD production capacity and low cost-effectiveness. The preferred embodiment of the inventive systems in Fig.1 and Pig.2 are suitable for large scale consecutive sequential CCD of seawater by a process involving actrve/nacove PE means: whereas, the preferred errtbcolment of the inventive systems in Fig. 4 and Fig. 5, teach the integration of two batch CCD wis with the same PE means of a continuous actuation mode with alternating engagement to each said batch CCD unit for toe same time duration - systems suitable for large scale 9eawater desabnation of low energy high-cost effectiveness.

Example #1 in Table 1 iusirates the performance a single batch CCD unit of 42ME6 configuration for 3,208 m ³ /day ciesaknated seawater of 50% recovery with energy consumption of 1.831 kWh/m ³ end permeates' quality of 347 ppm average TDS; and an integrated inventive system two batch CCD units with the same PE means of 2[42λ4E6] configuration for double production (6,416 mVday) under the same conditions.

2. Large Scale, High Recovery, Coat-Effective BWRO-CCD Systems of Declined Fouling Propensity

Whfe PCT/IL2002/000636 with two artemating side containers and of PCT/lL2004/000748 with a single side oontainer can appfy to tow energy higher recovery desalination of brackish water rJesalinabon with unchanged membranes perforrnance, said techniques are confined to smafl scale production of tow cost-efisctiveness due to their targe intrinsic volume requirements and complex conduit Gnes and valve means. PCT/IL2005V000670 esrninates the needs for a side container of large intrinsic volume and extensive valve means making this technology highly cost effective for brackish water desalination of tow energy and high recovery by a two-step consecutive sequential process wrth CCD under fixed Row and variable pressure conditions experienced most of the time (>85%} with brief periodic PFD steps of tow flux and recovery to enable brine replacement by feed, and the two-step process implies frequent changes of membrane perforrnance. The inventive systems in Fig. 1, Fig. 2, Fig. 4 and Fig. 5 teach large scale consecutive sequential CCD of brackish water of high recovery and tow energy with unchanged membrane performance as previously taught by PCTAL2002/D00636 and PCT/IL2004/000748, but without intrinsic volume imitations on large scale procluction. The advantage of present inventive systems over PCT/IL2005/000670 arises from thev steady unchanged membrane performance during the course of desaanatton, including when brine concentrate is replaced with fresh feed. In reference to large scale desalinate prospects of brackish water by the inventive systems, noteworthy are the projected performance results in Examples #1.1(75%: 0.407 kWh/m ³ ; 38 ppm IDS; 4,935 m ³ /day), #1.2 (85%; 0.473 kWhftn ³ ; 56 ppm TDS; 4,935 m ³ /day), and #1.3 (95%; 0.8C6 kVVhim ³ ; 143 ppm TDS; 4,835 m ³ /day) of Table 2 as applied to a 2,000 ppm NaCI feed source and a single batch CCD unit of 42ME6 configuration according to the preferred embodiment of the inventive systems in R§ , 1 and Fig.2. Twice the production capacity (S.870m ³ /day} is made possibfe when two said batch CCD units of same configurations are operated continuously and simultaneously with the same PE means according the preferred embodiment of the inventive systems in Rg. 4 and Fig. 5. The same conceptual design can be expanded to include 3 said batch CCD units for a system of 14,805 ¾fey, 4 said batch CCD units for a system of 19,740 ³ /day, and inventive system alike.