Membranes brackish water desalination

Figure 3.34 Lime pre-treatment system plus a RO membrane brackish water desalination plant process flow sheet. Source Cabibbo et al.

In the case of clarified feeds and low current densities, membrane lifetime can be as long as seven or 10 years for brackish water desalination or drinking water nitrate removal, respectively. However, if the feed solution is fouling or scaling or the ED separation plant has not been well designed or is not properly conducted, membrane lifetime is no longer than a year. 

Seawater and brackish water desalination membranes operated with 0.5 to 5 wt% salt solutions at pressures of 200-1000 psi. 

Seawater and Brackish-Water Desalination with Membrane Operations... 

Another interesting possibility is the use of pressure-driven membrane processes, in particular MF and UF are becoming standard and very efficient pretreatment options for sea- and brackish-water desalination. Also, for wastewater treatment, MF/UF pretreatment technology can efficiently reduce the highly fouling nature of the feed. 

Another field where membrane contactors are studied in the logic of the process intensification is seawater and brackish-water desalination. The scarcity of... 

Atomic force microscopy (AFM) studies contribute also to the improvement of the NF membranes, especially for desalination of brackish water. AFM characterization of a series of commercial NF and RO membranes of different polymer types for brackish water desalination had not been attempted, so far. Thus, as reported by Hilal [79], it is imperative to study the properties of these membranes and to show that the characteristics obtained from AFM correlate to the process behaviour. This is expected to provide substantial new insights into the influence of NF/RO membrane properties on performance, providing a database for the selection of NF membranes to account for the complexities of brackish water. 

H. Dach, J. Leparc, H. Suty, C. Diawara, A. Jadas-Hecart, A. Lhassani, M. Pontie, Innovative approach for characterization of nanofiltration (NF) and low pressure reverse osmosis (LPRO) membranes for brackish water desalination, Desalination, 2006 (submitted). 

Table 1.1 Development of RO membranes for brackish water desalination.

Reverse osmosis membrane is widely used in seawater and brackish water desalination processes. Compared to traditional distillation, there is no energy-intensive phase change involved in membrane processes. Therefore, desalination with RO membrane is more energy efficient. In addition to the traditional desalination processes, RO membranes have also found wide application in industrial and municipal wastewater treatment, in pure water production for the electronic and pharmaceutical industries, and in the food industries. 

Hon-celluloslc Membranes. Despite an Intensive search for more favorable membrane polymers, cellulose acetate remained the best material for reverse osmosis until 1969 when the first B-9 permeator for brackish water desalination was Introduced by Du Font. Richter and Hoehn ( ) Invented aromatic polyamide asymmetric hollow-fiber... 

As of the end of 1984, the desalination of brackish water accounted for 82% of capacity. This is due to the fact that early reverse osmosis membranes were incapable of single stage seawater desalination and, thus, they were limited to brackish water desalination. Within the last 10 years, significant advances have been made in both the flux and rejection capability of membranes and reverse osmosis is technically able to desalt seawater in a single stage. In the recent past, it has been an effective competitor to the distillation process in seawater desalination. In fact, reverse osmosis is now beginning to replace existing distillation capacity in the Middle East.4... 

While the cellulose acetate membranes are compacted at the moderate pressures required for brackish water desalination, the thin film composite membranes exhibit bo compaction at these pressures and a very low compaction rate at pressures of 1,000 psig. 

N NaCl has been used. Conversely, for brackish water desalination a 0.1 N NaCl/membrane/0.2 N NaCl may be used. The membrane potential is measured using a potentiometer or high impedance voltmeter (more than 2 MQ). In general, the membrane potential is high when the ratio of the concentration of the concentrated side solution to that of the dilute side solution is high and becomes low when salt solutions of high concentration are used. Transport numbers are calculated by Eq. (4.1) when a 1 1 valence electrolyte solution is used and the potentials between the probe electrodes and their ambient solutions are subtracted ... 

Brackish Water Desalination Low-pressure membranes were used by Glueckstern et al. (1986) for brackish water desalination. With a feed water of 6000-6500 mg/1, recovery of 65%, and applied pressure of 14 bars (net driving pressure of 7 bars), a salt rejection of 95% was obtained. An energy saving of 33% was achieved. 

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