Methods of Fresh Water Generation from Seawater

1. Submerged Type Boiling Evaporator (Steam Evaporator)

   – This method involves a boiling process to evaporate seawater and produce fresh water.

   – The evaporator operates under low pressure.

2. FWG (Fresh Water Generator) [Alfa-Laval]

   – FWG is a type of freshwater generator designed by Alfa-Laval.

   – It utilizes a specific process to generate fresh water from seawater.

3. Flash Evaporator

   – Flash evaporators are used to produce fresh water by flashing seawater into steam and then condensing it back into liquid form.

4. Reverse Osmosis

   – Reverse osmosis is a process that separates saltwater and pure water using a semi-permeable membrane.

   – In natural osmosis, water passes through the membrane from a dilute solution to a concentrated solution.

   – In reverse osmosis, pressure is applied to the concentrated solution, causing water to flow from the concentrated side to the dilute side.

   – Reverse osmosis plants use high-pressure pumps to force seawater through the membrane, leaving behind salts and producing fresh water.

   – The obtained fresh water may require further treatment for potable use.

Treatment of Fresh Water for Potable Use

Potable water treatment plants ensure that the freshwater generated is safe for drinking and cooking. These treatment plants typically include sterilizing and neutralizing units.

(a) Sterilizing (Disinfecting) Units

– Heating: The freshwater is heated to sterilizing temperatures (> 80°C).

– Chlorination: Chlorine gas or sodium hypochlorite is added to the water using a chlorinator to disinfect it.

– UV Sterilization: The freshwater passes through UV light to further sterilize it. This method is used in combination with other sterilizing methods.

(b) Neutralizing Units

– Acid Neutralization: Magnesium and calcium carbonate are added to the water to remove acidity and make it neutral or slightly alkaline. This process improves the taste of the water.