Quick Answer
For desalination in a survival situation, use solar stills, transpiration bags, and sand filtration to remove salt and contaminants from seawater. These techniques can produce drinkable water with minimal equipment. Prioritize water purification to stay hydrated and avoid waterborne illnesses.
Solar Stills: A Reliable Option
Solar stills are an effective method for desalination, especially when sunlight is abundant. To build a solar still, dig a shallow hole and place a container or plastic bag in the center. Pour the seawater around the container, and weigh down the center with a rock. As the sun heats the seawater, water vapor will rise and condense on the underside of the plastic, dripping into the container. This method can produce up to 1 liter of water per hour.
Transpiration Bag: A Lightweight Solution
Transpiration bags, also known as solar stills or bag desalination, are a lightweight and compact option for desalination. To use a transpiration bag, fill the bag with seawater and place it in direct sunlight. Weigh down the center of the bag with a rock, and cover the top with a clear plastic bag or a space blanket. As the sun heats the seawater, water vapor will rise and condense on the underside of the plastic, dripping into a container. This method can produce up to 0.5 liters of water per hour.
Sand Filtration: A Secondary Purification Step
While solar stills and transpiration bags can remove salt from seawater, they may not remove all contaminants. Sand filtration is an effective secondary purification step to remove particulate matter and bacteria. To build a sand filter, dig a shallow hole and place a layer of sand at the bottom. Add a layer of charcoal and another layer of sand on top. Pour the desalinated water through the filter, and collect the filtered water. This method can remove up to 99% of particulate matter and bacteria.
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