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Tel Aviv, Israel

Since first reported on October 2010 (EuroMed 2010, "Desalination for clean water and energy", 3-7 October, Tel Aviv, Israel), the large volume of diverse experimental results recently published on closed circuit desalination (CCD) technology reveal new state-of-theart technology of high recovery; low reverse osmosis (RO) energy in the absence of energy recovery; reduced scaling and fouling with a wide range of operational flux without exceeding membranes' test condition specifications and flexible online control of all principle parameters in desalination processes independent of each other; of unmatched performance characteristics compared with the widely practised conventional plug flow desalination methods. In order to realize the scope and prospects of the new CCD technology on the basis of its performance characteristics which appears to presently meet most, if not all, long-term (20 years) targets of the growing worldwide desalination industry with high cost effectiveness, the present document provides an updated summary of all available results together with a critical evaluation in comparison with conventional Plug Flow technology. The results of this critical comparative study reported herein provide the desalination industry with a new technology ready for immediate application, which addresses essentially all beneficial aspects of RO. © 2012 Desalination Publications. All rights reserved. Source


The performance of the osmotic-pressure RO, FO and PRO processes is analyzed on the basis of a uniformed model with water flux derived from the modified conventional expression J w =β*A*(δπ-δp) where β (<1.0) stands for the FO actual/ideal flux ratio of a given membrane in a defined salinity gradient and also applies to PRO; whereas β=1.0 applies to RO membranes. The β parameter takes account of the detrimental effects on flux in FO and PRO membranes and becomes unity for RO membranes. The uniformed model is explored to evaluate the various aspects of RO, FO and PRO and some of their FO-RO and PRO-RO hybrids, with emphasis on advanced closed circuit desalination RO (CCD) and PRO (CC-PRO) techniques and widespread feed sources such as treated sewage effluent (TSE) and seawater (SW) or seawater brine (SWB) from SWRO desalination plants. The results of this comparative study reveal that the desalination of SW and TSE with CCD proceeds with low energy of near absolute energy conversion efficiency at the ultimate state-of-the-art, unattainable by the conventional techniques practiced today. With regard to FO and PRO, this comparative study reveals that the effectiveness of both processes depends on the actual/ideal flux ratio (β) which manifests membranes' detrimental effects. Moreover, this study also shows that PRO power generation is also a function of the permeation/draw flow ratio (δ) apart from β and the salinity gradient and that operating at high δ (e.g., 40) of high power density (PD) yields low net electric power density (NEPD) which takes into account the power consumption of the auxiliary components in the PRO system. The distinction between PD and NEPD considered in the context of the SW-SE and SWB-TSE salinity gradients suggests that such applications are unlikely to become economically effective for energy generation and the same conclusion is also true for the application of the FO-RO and PRO-RO hybrids for the desalination of TSE which proceeds most effectively by direct CCD with exceptionally high recovery and low energy. © 2016. Source


Brackish Water sources of 6800 and of 4000 μS cm-1 were desalinated in closed circuit by single stage consecutive sequential process with 80% and 88% recovery, respectively, using an apparatus comprising eight modules (8″), each of four elements (ESPA2+), with their inlets and outlets connected in parallel, wherein recycled concentrate mixed with fresh pressurized feed admitted at inlet to modules. The exemplified apparatus, named REIM-I, was operated with fixed permeate flow under variable pressure conditions and the brine in the closed circuit was occasionally replaced by fresh feed through the engagement a side conduit and this without stopping desalination and without any energy loss. The operation of the REIM-I unit is exemplified with 80% recovery of a high salinity (6,800 μS cm-1) feed source at fixed flux of 19 lmh; fixed permeate flow of 24.4 m3 h-1 (586 m3 d-1) of an average 625 μS cm-1 conductivity; a variable pressure range of 11-22 bar with an average of 17.7 bar, and an overall specific energy consumption of 0.82 kWh m-3 with high pressure pump efficiency of ≈55%. The operation of the REIM-I unit is also exemplified with 88% recovery of a medium salinity (4000 μS cm-1) feed source remove off at fixed flux of 27 lmh; fixed permeate flow of 35.0 m3 h-1 (840 m3 d-1) of an average 482 μS cm-1 conductivity; a variable pressure range of 12-21 bar with an average of 16.2 bar, and an overall specific energy consumption of 0.80 kWh m-3 with high pressure pump efficiency of ≈60%. The new technology under review, which enables the attainment of any desired recovery made possible by the constituents of the source in the presence of suitable anti-scaling agents without any loss of brine energy, has been operated commercially for the past two years continuously providing some 400,000 m3 of permeates under 1300 μS cm-1 for irrigation in the dry Negev district of Israel. The application of the new technology for Brackish Water desalination of high recovery and low energy, reported herein for the first time, was recently demonstrated to allow desalination of Mediterranean Water (4.1%) with a record low RO energy (1.85 kWh m-3, 13 lmh flux, and 85% efficiency of high pressure positive displacement pump) which manifests energy saving of ≈30% compared with the reported RO energy consumption of large desalination plants equipped with modern energy recovery means. © 2012 Desalination Publications. All rights reserved. Source


A new method for continuous Brackish Water desalinated by a two-mode consecutive sequential process which incorporates closed circuit and plug flow desalination (PFD) techniques is exemplified with a commercial apparatus (named REIM-II) comprising 10 modules (8″), each of four elements (ESPA2+), with their inlets and outlets connected in parallel, and with recycled concentrate mixed with fresh pressurized feed admitted at inlet to modules. When the salinity of the recycled concentrate inside the closed circuit manifests the desired system recovery level, the apparatus switches from closed circuit to PFD by valve means until the entire brine in the closed circuit replaced by fresh feed, and thereafter, closed circuit desalination (CCD) resumed. CCD in said apparatus experienced most of the time with the same fixed flow rate of feed and permeate under variable pressure conditions; whereas, PFD takes place briefly only after the system attains its desired recovery level at a predefined pressure in order to enable replacement of brine by fresh feed without stopping desalination. Replacement of brine by fresh feed takes place with enhanced feed flow under reduced pressure with a lower momentary recovery in order to expedite the process and minimize brine energy losses. The new method is exemplified by the commercial operation of the REIM-II unit with feed of 6800 μS cm-1 according to conditions as followed: CCD Mode: 35 m3 h-1 flow rate of feed and permeate (≈19 lmh); 36 m3 h-1 flow rate of recycled concentrate; 1.1 bar of module pressure difference (Δp); and 17-25 bar of an effective variable pressure range. Plug Flow Desalination Mode: 45 m3 h-1 flow rate of feed; 16 m3 h-1 flow rate of permeate (≈10 lmh); 29 m3 h-1 flow rate of rejected brine; 0.5 bar of module pressure difference (Δp); and 9 bar average pressure. Overall Performance: 30.7 m3 h-1 average flow rate of permeate; 37.04 m3 h-1 average flow rate of feed; 82.9% recovery; 28.83 kW power consumption; 0.94 kWh m-3 specific energy with 61.5% efficiency of the high pressure pump; 20 min total sequence duration with 65% of the time experienced with CCD, 20% experienced with PFD, and 15% experienced during transitions between cited modes. The commercial REIM-II unit has been operated continuously over the past 20 mo and produced some 400,000 m3 permeates with 88-80% recovery in the respective feed salinity range 5800-8900 μS cm-1. © 2012 Desalination Publications. All rights reserved. Source


Stover R.L.,Desalitech
Desalination and Water Treatment | Year: 2016

Desalination and water reuse using reverse osmosis (RO) are viable new water supply resources; however, traditional RO systems often create excess brine waste, do not fully utilize source water supplies, and consume too much energy. Newly emerging closed-circuit RO processes improve RO performance and reduce its cost by increasing recovery, reducing fouling and scaling, and reducing energy consumption. This performance has been documented in dozens of RO installations in a range of applications. In particular, a closed-circuit RO unit operated on groundwater with a silica concentration of 59 ppm at recovery rates of up to 93.5%, producing brine silica concentrations exceeding 900 ppm. This recovery rate was sustained at neutral pH, with modest anti-scalant dosing and no scaling-related CIP requirements. A traditional RO system operating in feedwater with this concentration of silica would be limited to 76% recovery or less, corresponding to more than 3 times the production rate of brine concentrate. At another site, seawater with a total dissolved solids content of 35,329 ppm was desalinated with 5.5 kWh/1,000 gal (1.45 kWh/m3) of RO pump energy. This represents the lowest energy consumption ever reported for seawater RO at a comparable recovery rate and flux. © 2016 Balaban Desalination Publications. All rights reserved. Source

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