Desalination

Safe and readily available water is important for public health, whether it is used for drinking, domestic use, food production, or recreational purposes. Despite the vast quantity of water on Earth, just 2.5% of it is fresh water, and an estimated 800 million people lack a clean source of drinking water, and 1.4 billion people live in areas of high water vulnerability. Desalination of seawater is a vital technology to meet the world’s drinking water needs.

Currently, the main method of desalination of seawater is reverse osmosis but this uses a tremendous amount of energy, and in the process of desalting water in this way, harmful waste is generated, which is usually discharged back into the sea or ocean.

New techniques

 * A nanofiber membrane makes seawater drinkable in minutes and with 99.99% efficiency. Co-axial electrospun nanofiber membranes are fabricated by an alternative nanotechnology, which is electrospinning. It can prevent wetting issues and also improve the long-term stability of the membrane distillation process. Electrospinning uses a vinyl polymer as the sheath and a silica aerogel to produce a membrane with a super-hydrophobic surface. This allows them to produce a filter that had a higher surface roughness and lower thermal conductivity. During tests, stable membrane distillation lasted 30 days and the nanofiber membrane obtained by electrospinning maintained a percentage of 99.99% in the rejection of salt.
 * A method to derive fresh water from seawater, brackish water, or contaminated water is through highly efficient solar evaporation. It can produce enough daily fresh drinking water for a family of four (between 10 and 20 liters) from just one square meter of source water. A photothermal structure sits on the surface of a water source and converts sunlight to heat, focusing energy precisely on the surface to rapidly evaporate the uppermost portion of the liquid. The system operates at 100 percent efficiency for the solar input and draws up to another 170 percent energy from the water and environment.

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Desalination