CCD series no 20: high flux low energy upgrade of municipal water supplies with 96% recovery for boiler feed and related applications
AbstractThis study describes the application of closed circuit desalination (CCD) as a first pass for boiler feed supplies with high recovery (96% and low energy (0.34 kWh/m3) from a municipal source (553 mS/cm) comprising the scaling constituents Ca (65 ppm) SO4 (180 ppm) SiO2 (32 ppm) F (1.2 ppm) Ba (0.022 ppm) and Sr (0.295 ppm) in addition to modest amounts of Na (65 ppm) and Cl (18.8 ppm) The 96% recovery trials were performed using a pilot comprised of a single module (8' with three elements (ESPA2 MAX) under fixed flow and variable pressure consecutive sequential CCD conditions at flux of 27.5 lmh and feed temperature of 20.7degC. Under the specified trial conditions, average permeates of 13 mS/cm electric conductivity ~6.5 ppm) are produced with energy consumption of 0.59 kWh/m3 which translates 0.34 kWh/m3 at 25degC and pressurizing means efficiency of 75% The process proceeds at pH 5.0 in the presence of an antiscalant (Hydrex 4192 and 4102) with recycled concentrates of high super saturat.