Page 201 - ro membanes

184 8. GRANULAR MEDIA FILTRATION
TABLE 8.6 Example of First-Stage Gravity 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
• Width, m (ft)
• Length, m
• Filter cell area
• Total filter cell depth
• Total filter media depth
• Water depth above the filter bed
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
127,907 (33.8 MGD) 2e30 (max 50) 8e12 (max 16)
15 (2e40 mg/L)
0.25 (0.25e1.5 mg/L) 8 (0e30 mg/L)
10
4 (13.2 ft)
15 (49.2 ft)
60 m2 (649.44 ft2) 5.4 m (19.7 ft) 1.2 m (5.3 ft)
2.0 m (6.6 ft)
Anthracite 0.6 m (3.3 ft) 1.4 mm
1.4
1.55
Sand
0.6 m (3.3 ft) 0.8 mm
1.4
2.65
8.9 m3/m2 h (3.6 gpm/ft2) 11.1 m3/m2 h (4.5 gpm/ft2) 24e48 h
27 m3/m2 h (11 gpm/ft2) 55 m3/m2 h (23 gpm/ft2)