Small presentation about water desalination: What are the main methods? Where are they used? Are there any drawbacks?

1. Water desalination
Wei-Ting SHIH
Martin Degos

2. Introduction
• Desalination is a process that removes minerals from saline water.
• Salt water is desalinated to produce fresh water suitable for human
consumption or irrigation.
• “At the moment, around 1% of the world's population are dependent on
desalinated water to meet their daily needs, but by 2025, the UN expects
14% of the world's population to be encountering water scarcity”
Christopher Gasson (Global Water Intelligence)

3. Where are they used ?
• Australia
• Many countries in the Middle East:
- The single largest desalination project
is Ras Al-Khair in Saudi Arabia (1,025,000
cubic meters per day)
- Israel  produces 40% of its domestic
water use from seawater desalination

4. Methods
• Distillation
• Multi-stage flash distillation (MSF)
• Multiple-effect distillation (MED|ME)
• Vapor-compression (VC)
• Ion exchange
• Membrane processes
• Electrodialysis reversal (EDR)
• Reverse osmosis (RO)
• Nanofiltration (NF)
• Membrane distillation (MD)
• Forward osmosis (FO)
• Freezing desalination
• Geothermal desalination
• Solar desalination
• Solar humidification-Dehumidification (HDH)
• Multiple-effect humidification (MEH)
• Methane hydrate crystallization
• High grade water recycling
• Seawater greenhouse

5. Multistage flash desalinator
• Multi-stage flash distillation plants produce about 60% of all desalinated
water in the world
• An evaporator consists of several
consecutive stages (evaporating
chambers) maintained at decreasing
pressures from the first stage (hot) to the
last stage (cold).

6. Ion exchange
Ion exchange resin beads

7. Reverse osmosis

8. Energy consumption
Desalination
Method
Multi-stage Flash
Multi-Effect
Distillation
Mechanical Vapor
Compression
Reverse Osmosis(RO)
Electrical energy
(kWh/m3)
4–6 1.5–2.5 7–12 3–5.5
Thermal energy
(kWh/m3)
50–110 60–110 None None
Electrical equivalent
of thermal energy
(kWh/m3)
9.5–19.5 5–8.5 None None
Total equivalent
electrical energy
(kWh/m3)
13.5–25.5 6.5–11 7–12 3–5.5

9. Drawbacks
• Thermohaline circulation