Reverse-Osmosis is a process through which filtered seawater is forced under very high pressure against permeable membranes. The membranes are so fine that they can filter out molecules, including salt and some bacteria, purifying the source water to potable standards.
The process however, is extremely energy intensive. In fact, 4% of Malta's electricity goes towards generating freshwater from seawater. This figure is conservative, as it only takes into account the reverse-osmosis plants operated by the Water Services Corporation (WSC), Malta's only public provider of freshwater, whereas many hotels and some businesses also use reverse-osmosis to turn seawater into potable water.
Reverse-osmosis water comes with a high environmental footprint due to carbon gasses emitted to produce the electricity the technology needs. It is also more expensive to produce than naturally occurring high quality freshwater. Malta however, has little choice in the matter - current freshwater demand from the agricultural, domestic and industrial sectors is well above the amount of freshwater nature can provide in Malta. This has forced the islands to focus strongly on other means of generating freshwater, notably through reverse-osmosis desalination of seawater.
Since reverse-osmosis is an energy-intensive and comparatively expensive method of producing freshwater, it is important to first ensure that our water is being consumed efficiently. It would be a misstep to produce such resource intensive water, only to waste it due to poor management.