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    The effects of operating conditions on boron removal from geothermal waters by membrane processes
    (Elsevier Science Bv, 2010) Koseoglu, H.; Harman, B. I.; Yigit, N. O.; Guler, E.; Kabay, N.; Kitis, M.
    The main objective of this work was to determine the optimum operating conditions for boron removal and permeate flux in geothermal waters employing lab-scale tests. A total of 8 different SWRO, BWRO and NF membranes were tested. Permeate boron concentrations as low as 1.0 mg/L were obtained by the BWRO membranes at 20.7 bar (300 psi) pressure and pH 8.0. Using SWRO membranes, permeate boron concentrations of about 0.3-0.7 mg/L were obtained at 48.2 bar (700 psi) pressure and pH 8.0. Increasing pH from 8 to 10.5 significantly increased boron rejections by all membranes. At pH 10.5, permeate boron concentrations as low as 0.04 mg/L were obtained by BWRO membranes. However, at pH 10.5, higher degree of flux reductions was observed due to enhanced scaling. Tested BWRO and SWRO membranes were effective in rejecting silica, sulfate and conductivity. No correlation among boron and salt rejections was found. Results suggested that tested geothermal water may be effectively desalinated by BWRO membranes and used for various types of agricultural irrigation. Such approach may not only provide irrigation water but also may reduce the negative impacts of discharged brackish geothermal waters after use to the receiving water bodies and surrounding agricultural areas. (C) 2010 Elsevier B.V. All rights reserved.
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    Integrated solution for boron removal from seawater using RO process and sorption-membrane filtration hybrid method
    (Elsevier Science Bv, 2011) Guler, E.; Kabay, N.; Yuksel, M.; Yigit, N. O.; Kitis, M.; Bryjak, M.
    The main objective of this work was to investigate the possibility of implementing a new hybrid system which combines reverse osmosis (RO) process with sorption-membrane filtration method. The RO tests were performed using a small-scale seawater reverse osmosis (SWRO) system which was established in Urla Bay, Izmir, Turkey. Dowex (XUS 43594.00) ion exchange resin with a particle size of 0-20 mu m was employed for removal of boron from RO permeates. A submerged-style hollow-fiber module containing two polypropylene membranes (diameter: 1.3 mm, thickness: 200 mu m, pore diameter: 0.4 mu m) and a ZW-1 model submerged ultrafiltration module was used throughout the sorption-membrane filtration hybrid system. Sorption of boron was performed on a fine powdered boron selective ion exchange resin and boron loaded resin was separated by submerged membranes later on. The main advantage of sorption-membrane filtration hybrid process is the opportunity of using very fine particles of the resin, which increases specific surface and results in faster kinetics. Process variables such as resin concentration in the suspension, flow rates of fresh and saturated resins, and permeate have been evaluated in order to determine the efficiency of the hybrid process for boron removal from RO permeate. (C) 2011 Elsevier B.V. All rights reserved.