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Desalination / Evaporation

1,140 bytes added, 22:46, 12 April 2012

→‎Construction, operations and maintenance

To conserve fuel, a still can be placed on top of a cooking- pot which is used everyday, such as a rice pot. As it boils or simmers, the 'waste' heat is usefully harnessed.

Care should be taken to ensure that all pots are stable and out of reach of young children.

'''Reverse osmosis'''<br>

Reverse osmosis is a technique which plants use to absorb water from the soil and to transport the water up the stem to all parts of the plant. Dilute and more concentrated solutions are separated by a semi-permeable membrane, which acts like a very fine filter. The semi-permeable membrane allows water molecules to pass, but prevents the movement of salt or other dissolved chemical molecules.

If two saline solutions (or water and a saline solution) are separated only by a semi-permeable membrane, there will be a transfer of water through the membrane to the more concentrated saline solution. The passage of water will continue until a stable condition is reached, with the difference of liquid levels across the semi-permeable membrane being referred to as the osmotic pressure. The osmotic pressure varies with temperature and the concentrations of the two solutions.

By applying pressure (in excess of the osmotic pressure) to the salt-water solution, the process can be reversed, and water molecules from the salt-water solution can be forced through to the other side of the semi-permeable membrane.

====Maintenance====

Winona

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