AWWA MTC61151

The objective of this study was to develop a mechanistic understanding of the rejection of traceorganic compounds by high-pressure membranes, based on an integrated framework of compoundproperties, membrane properties, and operational conditions. High-pressure membranes,encompassing reverse osmosis (RO), low-pressure RO (LPRO), and nanofiltration (NF), may providean effective treatment barrier for representative trace organic compounds. About five RO membranes (e.g., LE-440, XLE-440) and about two NF membrane (e.g., NF-90), provided by several companies, were characterized according to pure waterpermeability (PWP), molecular weight cutoff (MWCO), hydrophobicity (contact angle), and surfacecharge (zeta potential). In bench-scale experiments, solute rejections were determined with pure water(Milli-Q) as well as synthetic feed-waters with adjusted pH and ionic strength.Stirred cell tests were performed as dynamic adsorption tests, with results comparedagainst static (isotherm) adsorption tests to describe solute partitioning into the membrane. Theexperimental approach of bench-scale cross-flow tests with flat-sheet specimens involves determiningrejections from synthetic waters over a range of Jo/k ratios and/or recoveries. It is noteworthy thatrejections of compounds of intermediate hydrophobicity by candidate membranes were observed tobe less than salt rejections reported for these membranes, suggesting that transport of these solutesthrough these membranes is facilitated by solute-membrane interactions. Diffusion cell measurementswere performed using actual membrane specimens to determine "hindered" or "facilitated"diffusion coefficients that, when compared to solute diffusion coefficients in water, describe hinderedor facilitated solute transport through a membrane.Data derived from cross-flow and diffusion cell tests will be used as a basis in formulating asolute transport model, delineating transport by convection versus diffusion. In addition, the role ofhydrogen bonding and the influence of membrane fouling are being further explored. To date, the study observed greater rejection of (negatively) charged compounds than neutral compounds, andgreater rejection of non-polar than polar compounds. Includes 22 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

03/01/2005

Number of Pages:

15

File Size:

1 file , 600 KB