Page 194 - ro membanes

Filter cell depth
Filter cell length-to-width ratio
Individual filter cell area
Maximum water depth above filter bed
4.5e7.5/15e25 ft
2:1e4:1 (typically 3:1)
25e100 m2 (270e1100 ft2)
2.5 m/8 ft (should be equal or slightly higher than filter bed headloss, which usually is 1.8e2.4 m/6e8 ft).
Anthracite/pumice layerddepth
Anthracite/pumice layerddepth
Anthracite/pumicedeffective size
Anthracite/ pumiceduniformity coefficient
Anthracitedspecific gravity Anthracitedbulk density Pumicedspecific gravity Pumicedbulk density Bottom Layer: Sand
1.0e1.8 m (2.6e6.0 ft)dfor deep bed filters/high turbidity waters
0.4e0.8 m for shallow bed filtersdused for waters with low turbidity (<5NTU)
and low organic content (TOC < 2 mg/L) 0.8e2 mm (typical 1.2 mm)
1.3e1.7 (preferable < 1.4)
1.5e1.6 tons/m3 0.80e0.85 tons/m3 1.1e1.2 tons/m3 0.40e0.55 tons/m3
0.8e2.0 m for deep bed filters 0.4e0.6 mdfor shallow bed filters 0.4e0.6 mm
<1.4
2.65 tons/m3
1.5e1.9 tons/m3
8.7 PLANNING AND DESIGN CONSIDERATIONS 177
FILTRATION RATE (AT DESALINATION PLANT INTAKE DESIGN FLOW)
With all filters in service 8e10 m3/m2 h (3e4 gpm/ft2) With two filters out of service 15 m3/m2 h (6 gpm/ft2) FILTER MEDIA
Top Layer: Anthracite or Pumice
Sand layerddepth
Sand layerddepth
Sanddeffective size Sandduniformity coefficient Sanddspecific gravity
Sanddbulk density
AireWater Filter Backwash System
Maximum backwash rate Average backwash rate Duration (total air þ water)
55 m3/m2 h (22 gpm/ft2)
40e45 m3/m2 h (16e18 gpm/ft2)
15e30 min (includes filter cell draining & fill up).