Desalting

2.  The process of desalination, also called desalting,
involves removing dissolved salts from seawater,
municipal wastewater, and even groundwater
with high mineral content.
 This process makes water fit for human
consumption, irrigation, industrial applications,
and more.
 The by-product of the desalination process is
brine

3. Can we drink salt water?
 Small quantities are not harmful, but it is counterproductive
(it just makes you more thirsty!)
 Eventually, it can be dangerous, ultimately producing fatal
seizures, heart arrhythmias and kidney failure

4. There are several methods which is can be divided
into 1- membrane-based (e.g., reverse osmosis)
and 2- thermal-based (e.g., multistage flash
distillation) methods.
The traditional process of desalination is distillation,
i.e. boiling and re-condensation of seawater to leave
salt and impurities behind.
Currently there are two technologies with more
desalination capacity in the world, multi-stage flash
distillation and reverse osmosis.

5. Natural Desalination: Water Cycle!
Major Stages
1. Evaporation
2. Condensation
3. Precipitation
4. Collection

6. Desalination Technologies
1. Thermal Desalination Processes
 Similar to the Earth’s natural water cycle
 Water is heated, evaporated and collected
 Produces clean water and brine
Example: Multi-Stage Flash Desalination
 Process uses multiple boiling chambers kept at
different atmospheric pressures
 Saltwater enters the system and is boiled and
evaporated in each chamber
 Process produces clean water and brine

7. Desalination Technologies
2. Membrane Desalination Processes
 Saltwater is forced through membrane sheets at high
pressures
 Membrane sheets are designed to catch salt ions
 Process produces clean water and brine
Example: Reverse Osmosis
 Saltwater is forced through a membrane at 600
to 1000 psi
 Multiple layers of membranes remove as many
of the salt ions as possible

9. • Membrane Desalination Processes:-
1. Reverse osmosis:
The reverse osmosis (RO) membrane processes use semipermeable membranes and
applied pressure (on the
membrane feed side) to preferentially induce water permeation through the membrane
while rejecting
salts. Reverse osmosis plant membrane systems typically use less energy than thermal
desalination processes.
2. Electro dialysis membrane :
Electro dialysis utilizes electric potential to move the salts through pairs of charged
membranes, which trap salt in alternating channels. Several variances of electro
dialysis exist such as conventional electro dialysis, electro dialysis.
3. Membrane distillation

10. • Thermal Desalination Processes:-
1. Multi-stage flash distillation :
Water is evaporated and separated from sea water through multi-stage flash distillation,
which is a series of flash evaporations. Each subsequent flash process utilizes energy
released from the condensation of the water vapor from the previous step.
2. Solar distillation :
Solar distillation mimics the natural water cycle, in which the sun heats sea water
enough for evaporation to occur. After evaporation, the water vapor is condensed onto
a cool surface. There are two types of solar desalination. The first type uses
photovoltaic cells to convert solar energy to electrical energy to power desalination.
The second type converts solar energy to heat, is known as solar thermal powered
desalination.
3. Vapor-compression distillation
4. Natural evaporation
5. Vacuum distillation