NAMS 2002 Workshop - ICOM 2008

model results with bench-scale studies of seawater desalination using
commercially available NF/RO membranes. We have created a simple analytical
model that estimates full-scale NF/RO system product water quality and specific
energy consumption considering a membrane’s water permeability and TDS
rejection, feed water concentration, total system flux, and concentration
polarization. In addition, we have developed a bench scale NF/RO seawater
desalination simulator for testing real NF/RO membrane performances in the
modeled scenarios.
Model results for single-pass SWRO systems suggest the theoretical minimum
specific energy consumption is not yet realized, the effects of concentration
polarization are non-negligible, and increasing SWRO membrane permeability
beyond that of modern BWRO membranes may yield little benefit. These results
may have important implications and could be used to guide future efforts to
engineer better performing SWRO membranes and modules. These results and
their implications will be discussed in the presentation. Model simulations are
also performed to elucidate the optimal combination of first and second pass
NF/RO membrane rejections for a two-pass system. Simulations consider three
scenarios in which (a) membrane resistance and CP are neglected, (b)
membrane resistance is neglected, CP is considered, and (c) membrane
resistance and CP are considered. These results highlight the important role of
membrane resistance and CP in multi-pass system performance. Finally, three
scenarios have been tested in the laboratory: (a) two-pass NF membrane
followed by a high-rejection BWRO membrane, (b) two-pass seawater NF
(SWNF) membrane followed by another SWNF membrane, and (c) a one-pass
SWRO membrane. All three scenarios give desalination performance that may
have practical value. In this presentation we will present details of our modeling
and experimental results, and discuss the implications for single-pass and multipass
NF/RO seawater systems.
Reference:
1.Sauvet-Goichon, B., Ashkelon desalination plant -- A successful challenge. Desalination, 2007.
203(1-3): p. 75.
2.Lomax, I., Experiences of Dow in the field of seawater reverse osmosis. Desalination, 2008.
224(1-3): p. 111.
3.Harrison, C.J., et al., Bench-scale testing of nanofiltration for seawater desalination. Journal of
Environmental Engineering-Asce, 2007. 133(11): p. 1004-1014.