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9. MEMBRANE FILTRATION
Membrane Pretreatment Costs
Upper Cost Bracket Lower Cost Bracket
40,000
30,000 Construction Cost (in US$1,000 ) 20,000 10,000
0 0
40,000 80,000 120,000 160,000 200,000 240,000 280,000 320,000 360,000 400,000
Desalination Plant Intake Flow Rate (m3/day)
FIGURE 9.11
Construction costs of membrane pretreatment systems.
modules for the entire plant. This configuration incorporates 7% of safety factor (2400/ 2251 1⁄4 7%). With one UF train in backwash and one train out of service for cleaning, the plant operating flux will be 122,093m3/day1000L/(8 UF trains120 vesselstwo mod- ules  40 m2/
module  24 h) 1⁄4 66.2 L/m3 h (38.8 gfd), which is within the acceptable range of 50e75 L/ m2 h (30e44 gfd) determined by pilot testing.
9.9 CONSTRUCTION COSTS OF MEMBRANE PRETREATMENT SYSTEM
The construction costs for membrane pretreatment are difficult to determine based on existing projects because of the relatively limited track record of this type of pretreatment compared to granular media filtration and also because of the diversity of membrane prod- ucts and configurations presently available on the market. Therefore, rather than a single cost curve, Fig. 9.11 presents a range of probable year 2017 costs of membrane pretreatment for desalination plants as a function of the plant intake flow rate.
For the example of 50,000 m3/day desalination plant described in the previous section of this chapter, which has an intake flow of 122,093 m3/day (32.3 MGD), the construction cost in US$ of the intake pretreatment system in the year 2017 is estimated in a range of US$9.4e14.9
million (average of US$12.1 million) based on cost curves depicted in Fig. 9.11.