AWWA MTC61073

AWWA MTC61073 Bench-Scale Testing of Seawater Desalination Using Nanofiltration
Conference Proceeding by American Water Works Association, 03/01/2005

Harrison, Catherine J.; Childress, Amy E.; Le Gouellec, Yann A.; Cheng, Robert C.

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The Long Beach Water Department, EEC. The flux and rejection properties of these membraneswere systematically investigated using stirred-cell and bench-scale membrane test units.The water flux and solute rejection of the three membranes under various solutionchemistries are being evaluated using a bench-scale membrane test unit. Prior to each set of experiments, the membranes are compacted at 575 psi (the highestexperimental operating pressure) for 8 hours using DDW. After compaction, the salt solution isadded to the feed reservoir. The solution is recirculated through the system at a low pressure forthe equivalent of two tank volumes to ensure adequate mixing. During this time, the temperature is equilibrated to 15C. The pressure is then increased to the initial operating pressure, and thesystem is allowed to reach equilibrium over 30 min. This time was found to be sufficient for theflux to reach a stable value. The permeate flux, J, is then measured continuously for 20 min usingan electronic balance (Model PB 303-3, Mettler Toledo, Columbus, OH) interfaced with acomputer. The permeate water is returned to the feed tank after each experiment. At the end ofthe 20-min experiment, two 100 mL samples are taken for analysis. This process is repeated forthe remainder of the operating pressures. The temperature is then raised to 20C, and the entireset of experiments is repeated.The temperature range of 15 to 20 C was based on the seasonal range of temperaturesfrom the Pacific Ocean near Long Beach (i.e., 60 to 70 F). The different molarities for the testsof individual salts bracket the anticipated individual salt concentrations in the feed and permeateof Stage 1. Sodium and potassium are measured using flame emission spectrophotometry;calcium and magnesium using flame atomic absorption spectrometry (AAS); boron withinductively coupled plasma spectrophotometry (ICP); sulfate, bromide, and chloride with ionchromatography (IC); and bicarbonate with an alkalinity titration. Includes tables, figures.