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264 12. REVERSE OSMOSIS SYSTEM DESIGN AND PRETREATMENT
TABLE 12.4 Reverse Osmosis Permeate-Water Quality, Seawater SourcedMediterranean
Sea
Water-Quality Parameter
Temperature, C pH
Ca2þ, mg/L Mg2þ, mg/L Naþ, mg/L
Kþ, mg/L CO32, 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
Permeate Water Quality
Mediterranean Source-Seawater Quality
16e28 8.1 480 1,558 12,200 480 5.6
160
3,190
22,340 1.4 0.00 5.0
80 40,500
Single-Pass SWRO System
17e29 6.3e7.2 1.0e2.0 1.9e2.8 98e196 3.0e5.5 0.0
1.7e2.4
2.9e6.3
169e260 0.7e1.1 0.00 0.9e1.5 0.9e1.3 280e480
Split Partial Two-Pass RO System
18e30 7.9e8.1 0.35e0.45 0.5e1.0 15e34 0.8e1.8 0.0
0.5e0.8
1.4e2.95
25e52 0.5e0.8 0.00 0.4e0.6 0.35e0.6 45e95
systems have been mainly used to upgrade the capacity and improve energy use of existing conventional single-stage SWRO plants.
Sometimes, two-stage SWRO systems are designed to be operated with lower feed pres- sure to the first stage, because of the highly fouling nature of the feed water. Since operation at lower feed pressure allows to reduce fouling of the first-stage/pass elementsdthis config- uration could be beneficial if the pretreatment system is not very robust and the water quality from the SWRO system is of high alluvial organic or particular content.
12.4.5 Hybrid SWRO Systems With Multiple Passes and Stages
The two-pass and two-stage RO system configurations may be combined to achieve an optimum plant design and tailor desalination plant operation to the site-specific water- source water quality conditions and product water-quality goals.
An example of a full-scale two-pass/two-stage SWRO system application is the 170,500 m3/ day Fujairah seawater desalination plant (Sanz et al., 2007). A general treatment process sche- matic of this plant is depicted in Fig. 12.8. The plant uses Gulf of Oman source seawater.