1. No matter what the alternative water treatment method selected disinfection will be required:

2. Note that “C” values are those of the effluent of the chlorine contact tank.

3. Osmotic Pressure for water in Gulf of Maine:
Salinity = 30 ppt
Osmotic pressure = 22 atm = 300 psi

4. Water flux through the membrane is the most important design and operational parameter. Next most important is solute exclusion. Some solute will diffuse (by molecular diffusion) through the membrane because there will be a significant gradient of the solute across the membrane.
Water Flux:

5. Operating pressure ranges:
R.O./NF: 80 – 600 psig
MF/UF: – 60 psig

6. Pressure/Energy required for desalination using RO:
Osmotic Pressure for seawater = 350 psig
(seawater salt concentration = 0.5 moles/l or
35 g/l of TDS)
Pressure applied = 600 to 1000 psig
Energy required = 5 kWh/m3 of water

7. Power requirements for Electrodialysis are very feed water TDS dependent.
Feed Water TDS (g/L) Energy (kWh/m3)
15 (brackish) 1.5
35 (seawater) 4
(Voltage generally less than 10 volts)
(Product water = 0.5 g/L)

8. Output of Solar Still:

9. Typical output:
E = 0.3
G = 18 MJ/m2 (5 kwh/m2)
A = 1 m2

10. Slow sand filter design:
Head applied above sand: 3-5 ft.
Depth of sand is also about ft.
Loading rates: gpm/ft2
T: 1-6 months