Page 202 - ro membanes

8.8 CONSTRUCTION COSTS OF GRANULAR MEDIA FILTRATION SYSTEMS 185 TABLE 8.7 Example of Second-Stage Pressure Filters of Two-Stage Filtration System for 50,000 m3/day
(13.2 MGD) Desalination Plant
Component/Parameter
FEED WATER
• Design flow rate, m3/day (MGD) • Turbidity, NTU
• SDI5
DESIGN CHEMICAL DOSAGES
• Ferric Chloride, mg/L
• Polymer, mg/L
• Sulfuric acid, mg/L: Target pH: 6.7
FILTER CELLS
• Number
• Diameter, m (ft)
• Length, m
• Filter vessel area
• Total filter media depth
TOP-LAYER FILTER MEDIA
• Type
• Depth
• Effective size
• Uniformity coefficient
• Specific density, tons/m3
BOTTOM-LAYER FILTER MEDIA
• Type
• Depth
• Effective size
• Uniformity coefficient
• Specific density, tons/m3
FILTER PERFORMANCE PARAMETERS
• Average surface loading rate
• Maximum surface loading rate with 2 units out of service • Filtration cycle
BACKWASH RATE
• Average
• Maximum
Specifications/Design Criteria
120,930 (32 MGD) 0.2e5 (max 10) 4e8 (max 10)
0.0 (0.0e8 mg/L) 0.0 (0.0e0.5 mg/L) 0.0 (0.0e30 mg/L)
10
3.5 (11.5 ft)
12 (39.4 ft)
42 m2 (452 ft2) 1.2 m (4.0 ft)
Sand
0.6 m (3.3 ft) 0.6 mm
1.3
2.65
Garnet
0.6 m (3.3 ft) 0.3 mm
1.3
4.10
12.0 m3/m2 h (4.9 gpm/ft2) 15.0 m3/m2 h (6.1 gpm/ft2) 24e48 h
35 m3/m2 h (14 gpm/sq ft) 60 m3/m2 h ( 25 gpm/sq ft)
pressure filters have relatively lower cost than gravity filters for the same daily volume of pretreated saline source water.
For example, in the case of 50,000 m3/day (13.2 MGD) single-stage gravity filtration system presented in Table 8.4, the plant intake flow is 122,093 m3/day (32.3 MGD). For this flow, the estimated construction cost of this pretreatment system is US$ 8.9 million.