Why Desalination?
Desalination is very significant because of the rapidly increasing rate of consumption of water worldwide. The consumption has exceeded the availability and supply of fresh water. More than two-thirds of the earth is covered by water; 98% of which is oceans and seas. Hence the need to utilize brackish or sea water for the purpose of fulfilling water consumption needs. Industrial units need a constant supply of water for their use. Notable among them is hydro-electric power generation which is a widely used renewable energy form.
The Methods
Methods like Distillation, Ion Exchange and Membrane processes are used for desalination.
Distillation involves evaporation of water by applying heat that is delivered by pre-compressed vapor.
Ion Exchange is the exchange of ions between two solutions and is used to perform separation and purification of water.
The Membrane process makes use of membrane stages and pressure to separate salt from water. This process utilizes technologies like Reverse Osmosis and Nano-filtration to perform the filtration.
Desalination and Power Generation
Hydroelectric power generation requires a regular supply of water to generate power. This adds to the strain on the existing fresh water resources like rivers and lakes which are already burdened with domestic consumption requirements. By desalinating brackish or sea water, the processed water can be utilized to generate power. Desalination and power generation though are considered dual processes which are carried out together in a combined facility due to the high energy requirement for desalination.
There are new desalination processes being developed which are more economic in the use of electricity. One such desalination technique uses a microbial desalination cell for generating electricity besides producing clean water.
The microbial cell has two chambers, one chamber containing wastewater and the other chamber containing sea water. Each chamber contains an electrode and is separated by ionized membranes. Naturally occurring bacteria in the wastewater feed on the organic material producing charged ions which react with the salt content in the brackish or sea water through ion exchange thus producing electricity. The advantage of using this technique is that waste water is transformed into clean water, besides rendering the desalination process energy efficient.
