AWWA WQTC62389

Reverse osmosis (RO) and nanofiltration (NF) membrane technologies are becomingincreasingly attractive alternatives to conventional treatment processes for drinking watertreatment because of their ability to provide effective rejection barriers against a broad range ofwater contaminants, and for their adaptability to treat water from sources of lower quality inareas in which other water resources are becoming limited. Furthermore, membrane treatmentplants tend to be more compact than conventional plants, thus making them more economical inhighly populated areas in which minimizing plant layout area becomes critical (Wiesner et al.,1994). However, a broader implementation of RO/NF processes is somewhat inhibited byprevailing problems such as concentration polarization and associated fouling and scaling effectsthat are important factors affecting the cost of RO/NF membrane treatment systems (Braghetta etal., 1998). In order to minimize the risk of these detrimental effects taking place, RO/NFsystems are currently operated at limited pressures so that the permeate flux does not exceed acritical maximum value. Although experimental evidence is available to support this practice,recent results have shown that the concentration polarization layer of Rhodamine-WT(MW=521), used as a surrogate compound for organic water contaminants, could be disrupted atpermeate flux levels significantly higher than that currently considered as critical.Comprehensive investigation is needed to validate this new idea because several factorsincluding solute diffusivity coefficient, permeate flux, and rejection efficiency affectconcentration polarization. The effect that this disruption could have on fouling and the rejectionof chemical contaminants also remains to be elucidated. Based on this background, the primaryobjective of this project is to systematically investigate the influence of operating pressure andshear conditions on concentration polarization and the associated rejection of selectedcontaminants by RO/NF membranes in the absence and presence of foulant surrogates. It isanticipated that information gained from this research will contribute to a better understanding ofthe concentration polarization phenomena and the development of recommendations foroptimum treatment of natural waters with RO/NF membranes with special emphasis inachieving high removal of organic contaminants with minimal risk of the occurrence of fouling. Includes 5 references, figure.

Product Details

Edition:

Vol. - No.

Published:

11/01/2005

Number of Pages:

5

File Size:

1 file , 150 KB