Container solution eases transfers of water purifiers

Enwa has introduced standard 20-ft contain ers to simplify installation offshore of its desalination system, which purifies water through reverse osmosis (RO). According to the company, the new solution should appeal to vessel operators and to drilling rig contractors in particular, as the latter often need to relocate their RO units quickly to different rigs. An order has already been received from Dolphin Drilling, Aberdeen, for two RO/containers operating at 105 cu m/d.

The compact RO units are claimed to be far smaller than conventional evaporators typically installed on ships, and can also produce fresh water, even when the main engines are not running.

Osmosis is a natural process that involves inducing water to flow from a diluted saline solution through a membrane to a more concentrated salt solution. The concentrated salt solution is also then diluted. Flow of pure water through the membrane continues until the concentration of salt in both solutions is equal. The difference between the water level in the container, on each side of the membrane, is the osmotic pressure. By applying pressure greater than the osmotic pressure to the concentrated salt solution, the process can be reversed. Pure water subsequently passes through the membrane, flowing into the weaker salt solution. Desalinated water is thus obtained through dilution.