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.
* WaterPod is a self-cleaning solar desalination system that uses a wick structure to absorb seawater from underneath and transport it to a black fabric placed on top of an aluminum plate. As sunlight passes through the transparent cover, the seawater evaporates from the fabric onto the dome cover.
* Aquastill uses membrane distillation in which pure water is separated from saltwater by means of evaporation through a membrane. The porous membrane used in membrane distillation is typically hydrophobic, which means that it repels water in liquid form. Due to this hydrophobic nature, it only allows gasses to pass through the membrane pores. Water vapour is a gas, so for water to pass through the membrane it must first evaporate into water vapour.
* The Solar Desalination Skylight is a device that uses seawater to create natural ambient light, drinking water, and generates energy from the remaining sea salt. It is the finalist of the Lexus Design Award 2021, a competition dedicated to empowering humans to make good things for the future of humanity and the planet.
* Waterlight is a portable device filled with half a litre of seawater that can generate light for 45 days. This uses ionization of an electrolyte composed of saltwater, which reacts with magnesium and copper plates on the interior of the lamp to produce electricity.

See also:

Desalination