How to filter salt water…
Whenever we read about the Earth, we call it the Blue Planet due to the abundance of water on it. But the fact is that it is mainly saline water which is not potable. In fact, drinking salt water neither satiates thirst, nor hydrates the body, as well as leads to dehydration and death. Listed below are a few methods to filter salt water and make it potable.
How to Filter Salt water:
Thermal distillation: Compared to normal distillation, it can be carried out on a small scale with comparitively lesser expenditure. Salt water is taken in a saucepan with a domed lid and a small vessel is placed in the middle of the pan. It is kept on fire with the lid upside down (knob right above the smaller vessel collecting the distilled water). The vapour gets condensed on the lid and gets collected in the vessel below. This gets accelerated when cold salt water is added on top of the lid. This process purifies water of all impurities including microorganisms, giving direct potable water.
Solar Distillation: It is similar to the natural evaporation that takes place from the surface of water bodies and the precipitation received in various forms. An equipment called “solar still” is used. A dome of plastic collects evaporation from the sea and condenses it into pure water channelled into reservoirs. This water may be drawn through tube in the reservoir. They may also be designed at home: if an area of 10 square feet is covered, about 1 1/2 gallon of water may be collected per day during summer and half of it during winter.
Reverse osmosis: Osmosis is a process by which water passes from region of lower concentration of salts to the region of higher concentration across a semipermeable membrane. Reverse osmosis helps to push only water molecules through the membrane by applying pressure. The membranes include the combination of a micron-thick layer of polyamide(acts as a filter), with a microporous polysulfone layer. Even most of the biological impurities get separated. The filtration speed is directly dependant on the pore size and the pressure applied. It is highly cost-effective and scalable compared to other filtration methods.
Forward Osmosis: Here a combination of concentrated salt solution, mostly edible sugar is used to draw in water through the osmotic membrane. Hydration bags are placed in seawater in sometime to obtain a sugary drink which helps sustenance beyond hydration for backpackers and seafarers. In order to obtain a pure solution, FO is followed by RO especially for contaminated feed solutions.
Graphene filters: This one-atom thick layer of carbon when oxidized to tiny pores allow only water molecules and block all other molecules including gases. Electrodialysis: Shock electrolysis allows the sodium and chloride ions in the salt solution to pass through the membrane by applying electric current. It can become a one-step purification to desalinate and purify the water if a 0.5 micron filter is kept close by.
Information prepared by Muktha M P