Treatment process
Multi-stage flash distillation
Thermal desalination in which heated seawater flashes to steam in a sequence of chambers at successively lower pressure, recovering the latent heat at each stage.
Key facts
- Scale
- Industrial / large scale
- Treatment stage
- Thermal desalination
- Energy
- Roughly 10–25 kWh equivalent per cubic metre when thermal energy is counted, against 3–4 kWh/m³ for seawater RO.
How it works
Seawater is heated then passed through 15–40 flash chambers. At each lower pressure, part of the flow flashes to vapour, which condenses on tubes carrying the incoming feed — preheating it and recovering the heat.
What it removes — and what it does not
| Row | Removes | Does not remove |
|---|---|---|
| 1 | All dissolved salts, producing very low salinity distillate | Volatile compounds |
Trade-offs
- Very high thermal energy demand, viable mainly where waste heat or cheap fuel is available
- Tolerant of poor feedwater quality, unlike membranes
- Long asset life
- Displaced by reverse osmosis in almost all new capacity on cost grounds
Related intelligence
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Sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- NSF International / American National Standards Institute — NSF/ANSI drinking water treatment unit standards. Public but restricted · Publisher terms — public access, reuse not clearly granted
- American Water Works Association — AWWA standards, water audits and utility benchmarking. Public but restricted · Publisher terms — public access, reuse not clearly granted