Page 288 - ro membanes

12.4 ALTERNATIVE SWRO-MEMBRANE SYSTEMS AND PRETREATMENT 271
Permeate front
Final product
4th stage
1st stage
Seawater
1st stage brine
Soda
2nd stage
2nd
stage acid brine
Permeate
Permeate 3rd stage
3rd Soda stage
brine
Permeate rear
FIGURE 12.11 Ashkelon four-stage SWRO system.
TABLE 12.7
Water-Quality Parameter
Temperature, C pH
Ca2þ, mg/L Mg2þ, mg/L Naþ, mg/L
Kþ, mg/L HCO3, mg/L
SO42, mg/L Cl, mg/L F, mg/L NO3, mg/L B, mg/L Br, mg/L TDS, mg/L
Reverse Osmosis Permeate Water-Quality at Ashkelon Seawater Desalination Plant
4th stage brine
Mediterranean Source Seawater Quality
16e28 8.1 483 1,557 12,200 481 162 3,186
22,599 1.4 0.00 5.3
80 40,679
Freshwater Quality Permeate Finished Water
17e29 18e30 7.5e8.5 8e8.5 0.2e0.5 90e110 0.5e0.8 0.5e0.8 6e30 30e39 1.5e1.8 1.5e1.8 0.6e0.8 45e50 1.0e1.4 1.0e1.8
10e15 10e15 0.1e0.2 0.8e1.0 0.00 0.00 0.2e0.3 0.2e0.3 0.2e0.3 0.2e0.3 20e40 180e220
Actual experience at the desalination plants listed above indicates that the four-stage config- uration provides very reliable performance and it is not as sensitive to changes in source-water quality (salinity, temperature and biofouling potential) as are conventional two-pass RO sys- tems. All of the referenced desalination plants with four-stage RO systems have open intakes