How to Perform Desalination

The ocean can provide a source of water for desalination.

There are two major methods of desalination, thermal and membrane. Membrane desalination utilizes either pressure or electrical current. Pressure forces water through a membrane separating salt and other minerals; electrical current attracts salt molecules removing it from the water. These methods of desalination are widely used in commercial factories. Thermal desalination heats water to the point of boiling, creating steam which then condenses into fresh water. Thermal desalination is the easiest method of desalinating water at home.

Things You'll Need

• Shovel
• Black plastic
• Polyurethane plastic (clear)
• Collection bucket
• Rock
• Water
• Heat source

Instructions

1. Build a desalination unit. Dig a pit in the ground and line it with a polythene sheet of black plastic. The pit can be anywhere from 3 to 33 feet in length, depending on how much water you wish to desalinate daily. Place a collection bucket in the center of the pit.

2. Fill the pit with water from your hose or tap. Make sure that the water level stays below the lip of the bucket. Cover the pit with a polythene sheet of clear plastic. Secure the edges of the plastic to the ground around the bucket. Place a rock on top of the plastic, at a location above the collection bucket.

3. Allow water a day to sit under the sun. The solar energy from the sun will cause the base water to evaporate. The evaporating water will be free of salt and minerals. As the evaporated water cools it will condense on the polythene sheet. The condensation will run along the polythene sheet and collect at the point where the rock on top of your plastic sheet. It will naturally drip into the collection bucket. At the end of the day, empty the collection cup into a drinking container. You have completed the desalination process and now have potable water.

Tips & Warnings

• To increase heat within your desalination unit line the bottom with black polythene sheets. Increasing heat will shorten the amount of time water takes to desalinate, allowing you to produce more fresh water in a shorter time frame.

• If you do not wish to build your own desalination unit, mobile units are available for lease or purchase. These units typically utilize reverse osmosis and are widely used by military and other emergency relief agencies.

• Commercial desalination factories result in pollution, excess energy usage and wildlife damage.

References

• Solar De Mer: How to Build a Backyward Desalinator
• Global H2O: Desalination Units
• California Department of Water Resources: Water Use and Efficiency Branch Water Recycling and Desalination