Students study material

1. WATER TREATMENT
Subject Code: 07AT02
CHEMISTRY FOR BIOLOGIST - II
By
Dr. G. Balakrishnan
Assistant Professor
Department of Chemistry
Vivekananda College
Madurai, Tamil Nadu

2. UNIT- V: POLLUTIONS
Water pollution: Types,
sources,
sewage,
industrial effluents, inorganic
pollutants –
control –
water treatment

3. Desalting or Desalination by Reverse Osmosis
Definition: Reverse Osmosis, commonly referred to as RO, is a
process where you demineralize or deionize water by pushing it
under pressure through a semi-permeable Reverse Osmosis
Membrane.
https://www.fotosearch.com/CSP395/k55466650/

4. REVERSE OSMOSIS
This method is based on the principle of compressing
out water from saline water instead of removing salts from
water.
Millions of hollow fibers are bundled together and
dipped in saline water, which acts as a semi-permeable
membrane.
When saline water is subjected to high pressure, water is
literally compressed through the membrane into the
hollow fibers.
Thus pure and fresh water is collected at the opening
ends of the capillaries while salts and impurities remain
on the outer side of the fibers.

5. Electrodialysis
Definition: Electrodialysis is a process by which electrically
charged membranes are used to separate ions from an
aqueous solution by an electrical potential driving force.
https://glossary.periodni.com/glossary.php?en=electrodialysis

6. ELECTRODYALYSIS
 When salty water passes through ion-exchange membranes under
the influence if electric field, positive and negative ions present in
water get separated.
 The tank is divided into three compartments using anion and
cation exchange membranes.
 On passing current, cations from the middle compartment pass
through cation-permeable membrane while anions pass through
anion-permeable membrane.
 Due to movement of ions into the outer compartments, salt content
of water in the middle compartment decreases.
 Water from the outer compartments is discarded while water in the
middle compartment is collected and subjected to electrodialysis
again and again.

8. Thank you