Three technologies run the world's desalination. Reverse Osmosis (RO), Multi-Stage Flash (MSF) and Multiple-Effect Distillation (MED) together produce the overwhelming share of desalinated water worldwide - yet they separate water from salt in fundamentally different ways, at very different plant sizes.
The split - a 2016 example
~65%
Reverse Osmosis
~20%
Multi-Stage Flash
~5%
Multiple-Effect Distillation
Around 2016, global installed capacity was roughly 90 million m3/d, with about 90% from these three technologies. Figures shown as a dated example. Current, plant-level and country-level data are available on request via DESALFACTS.
How the three differ
Reverse Osmosis (RO)
A pressure-driven membrane process: feed water is forced through a semi-permeable membrane that holds back the dissolved salts. Flexible on feed-water quality and on location, and highly scalable - but the membranes are sensitive to fouling, so careful pre-treatment is essential.
Multi-Stage Flash (MSF)
A thermal process: seawater is flashed into steam across successive stages and condensed as pure water. Robust and proven at very large scale - a single MSF train can reach tens of thousands of m3/d. First presented in Germany in 1934 (R. Blaum).
Multiple-Effect Distillation (MED)
A thermal process using several effects at falling pressure and temperature, reusing the heat of condensation. Efficient with low-grade or waste heat, and often paired with power generation.
This is the systematics. The depth is in DESALFACTS.
More than 50 desalination technologies are classified in our CDT-26 scheme. We show the possibilities here; the current figures, the plant-level detail and the full classification are available on request.