Water pollution is the contamination of water by harmful substances and includes physical, chemical, and biological types. Key sources of pollution include domestic waste, industrial effluents, agricultural runoff, and radioactive waste, leading to serious ecological and health impacts. Solutions such as reverse osmosis and electrodialysis are used for water treatment to obtain clean water from contaminated sources.

1. WATER
POLLUITON
Sri.A.DHARMANANDAM

2. WATER POLLUTION
The term water pollution refers to the
contamination of water by foreign substances that
makes water harmful to the life and health of all
living organisms.

3. TYPES OF WATER POLLUTION
• PHYSICAL POLLUTION: It refers to changes in
physical properties of water such as colour,
odour, density, taste, turbidity and
temperature.

4. • CHEMICAL POLLUTION: Presence of non-
biodegradable pesticides, trade wastes,
hazardous gases, changes the acidity, alkalinity
and amounts of dissolved oxygen.

5. • BIOLOGICAL POLLUTION: This refers to
pathogenic contamination of water. It is
caused by pollution of water with excretory
products of birds and warm blooded animals
including human beings.

6. SOURCES OF WATER POLLUTION
• Domestic waste and sewage: About 75% of water pollution is
caused by domestic wastes and sewage. It includes kitchen
wastes, soap detergent, garden waste, human excreta, garbage
etc.
• Industrial effluents: Industries discharge their wastes into nearby
water bodies. These contain toxic chemicals, corrosive acids and
alkalis, metallic wastes, oil, dyes etc.
• Agricultural discharges: Chemical fertilizers and pesticides are
washed away from fields by rain and enter into water bodies
causing pollution and ecological imbalance.
• Toxic metals: Traces of heavy metals such as Hg, Cd, Pb, Ag, Co, Fe
and Cr are toxic to aquatic ecosystem and human health. They
accumulate in the bodies of living organism and cause chronic
diseases.

7. • Organic pollutants: Organic pollutants from pharmaceuticals, drugs,
paper mills, tanneries etc increase the biological oxygen demand of
water bodies.
• River dumping: Certain rivers, which are considered holy and sacred by
people are being polluted tremendously. Dissolving of ashes, throwing
flowers, dumping of human bodies in sacred rivers like Ganga etc have
left the water bodies extremely polluted.
• Oil spillage: A substantial amount of oil released into oceans and seas
will destroy wildlife and the ecosystems that sustain them. The main
causes of oil related water pollution are: loss from storage facilities,
spillage during delivery and deliberate disposal of waste oil to drainage
systems.

8. • Radioactive waste: Radioactive substances are used in
nuclear power plants, industrial, medical and other
scientific processes. They can be found in watches,
luminous clocks, television sets and x-ray machinery. If not
properly disposed of, radioactive waste can result in
serious water pollution incidents.

9. • Marine Dumping: Due to deliberate dumping of waste into
coastal waters a staggering amount of waste enters into the
sea every year.
• Other sources of waste include plastics and other materials
blown or washed from land. It was found that effluents
discharged from a plastic factory contained mercury, which
entered the fish and by eating those fish, all the fishermen
suffered from effects of mercury poisoning.

10. Effects of organic pollutants in water:
• Polynuclear aromatic compound hydrocarbons
when present in water cause carcinogenic
effect
• Presence of aldehydes and phenols impart
foul odour and they are toxic to aquatic life.

11. • Oil spills reduce the dissolved oxygen content
in water.
• Bacteria which decays the protein present in
water releases sulphur and phosphorous
compounds which imparts foul smell.

12. • Tannery wastes from industry such as organic
dyes and inorganic complexes, when discharged
into water changes the water colour to form
intense green or blue colouration.
• Presence of chemicals or microorganism (algae,
fungi etc) imparts foul smell.

13. • Unpleasant taste is caused by the presence of
industrial effluents containing Fe, Mn etc.
• When water is polluted with sewage, it turns
highly turbid.
• Hot water discharged from thermal power plants
increases the temperature of water.

14. WATER TREATMENT
REVERSE OSMOSIS:
• This method is based on the principle of squeezing out water from
saline water instead of removing salts from water.
• Millions of hollow fibres are bundled together and dipped in saline
water, which acts as a semi-permeable memberane.
• When saline water is subjected to high pressure, water is literally
squeezed through the memberane into the hollow fibres.
• 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
fibres

15. ELECTRODYALYSIS:
• When brackish 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 memberane.
• 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.