Desalination Technologies

Thermal Technology

Membrane Technology

Concept

• Heating of saline water and collecting the condensed vapor (distillate) to produce pure water.
• Usage: Mainly for seawater desalination.

• Feedwater is pumped through semi-permeable membranes to filter out the dissolved solids.
• Usage: Mainly for brackish water desalination.

Sub-categories (Processes)

Three groups: 

• Multi-Stage Flash Distillation
• Multi-Effect Distillation 
• Vapor Compression Distillation 

Two groups: 

• Electrodialysis / Electrodialysis Reversal (ED/EDR)
• Reverse Osmosis (RO)

Merit

• Ability to reduce the maximum salinity concentration.
• Demands less input electrical energy compared to membrane techniques.

• Environmental Friendly: E.g., ED eliminates the need for chemicals.
• Smaller footprint: Typically require less space than conventional technologies.

Demerits

• Using conventional energy sources like coal etc.
• High costs involved: So, rarely been used for brackish water desalination.
• Subject to corrosion: E.g., MSF plants.

• Susceptible to Fouling.
• Require Regular Maintenance
• Face challenges in Membrane Waste Disposal.
• May not fully remove Total dissolved solids (TDS) or pathogens.

Example

Low Temperature Thermal Desalination (LTTD) plants were established in the Kavaratti, Minicoy and Agatti Islands in the UT of Lakshadweep.

Nemmeli Seawater Desalination Plant, Tamil Nadu, on Reverse Osmosis. (Largest desalination plant in the South Asia)