This document provides information about water pollution from a lecture on water supply and treatment technology. It defines water pollution and discusses various types of water pollutants including sewage, industrial, agricultural, and physical pollutants. It also describes the sources of water pollution from surface water and groundwater. Finally, it outlines measures to control water pollution including primary, secondary, and tertiary treatment of sewage as well as other methods like effluent treatment, water recycling, enforcement of acts, and monitoring of water quality.

1. Water Supply and
Treatment Technology
(EHT 215)
LECTURER: SIR OAK

2. LECTURE SEVEN
 Water pollution
Learning objective:
Upon completion of this topic; students should be able to:
• describe some health hazards and harmful effects of water
pollution.
• appreciate the various types, sources and effects of water
pollutants.
• mention some methods of water pollution control.

3. Introduction
• The ocean and sea amount to about 97% of the waters of the
earth. Fresh water is made up of 3% . Out of the fresh water
0.8% is accessible to man.
• Out of the 3% fresh water; 75% of which is locked up in the
polar ice caps and in glaciers and quite deep under the
earth’s surface as underground water.
• Remember, Salty water is not suitable for drinking, agriculture
and industrial purposes.
• In addition to household uses, water is vital for agriculture,
industry, fishery and tourism etc.

4. Introduction
• The quality of water used is also being deteriorated as it is getting
more and more polluted.
• The fresh water, which we can use, comes to us from two sources,
namely:
 Surface water : Precipitation (rain or snow) that runs-off into stream, rivers and lakes.
 Ground water : The water bearing layers of soil and rocks are called aquifers.
• In spite of a “good” number of water resources, we have shortage
of usable water.
• There is a need to optimize use of water and also conserve surface
run off of water - increasing population, urbanization and industrialization.

5. GROUP ASSIGNMENT
((((The Task))))
Suggest five (5)
possible means
to optimize
use of water.

6. Water Pollution - Parameters
• A large amount of water is discharged back after domestic and
industrial usage.
• Contamination upon reaching beyond certain allowed
concentrations is termed as pollution and the contaminants are
called the pollutants.
• If the concentration of substances naturally present in water
increases then also the water is said to be polluted.
• Water pollution may be defined as the contamination of
streams, lakes, seas, underground water or oceans by
substances, which are harmful for living beings.

7. Water Pollution – Parameters cont…
Water may be called polluted when the following parameters reach
beyond a specified concentration in water:
1. Physical parameters:
colour and turbidity are visible evidences of polluted water.
offensive odour or a bitter and difference than normal taste also
makes water unfit for drinking.

8. Water Pollution – Parameters cont…
2. Chemical parameters:
These include excess amount of carbonates, sulphates,chlorides,
fluorides, nitrates, and metal ions found in water.
These chemicals form the total dissolved solids, present in water.
3. Biological parameters:
These may cause a reduction in the population of both aquatic
plant and animal lives.
It gives an indirect indication of the amount of pollution in water.

9. Sources of Water Pollution
Fresh water pollution may be classified into two types:
Surface water pollution
Ground water pollution

10. Surface water pollution
• Surface water pollution can be categorized as:
 Point and Non-point sources
 Natural and Anthropogenic sources
• Point sources refer to well-defined sources that emit pollutants or
effluents directly into different water bodies of fresh water. Eg.
domestic and industrial waste.
• Non-point sources of water pollution are scattered or spread over
large areas. Eg. runs off from agriculture farms, construction sites,
abandoned mines, etc.

11. Surface water pollution cont…
• Natural and Anthropogenic Sources
An increase in the concentration of naturally occurring
substances such as siltation (which includes soil, sand and
mineral particles).
Deforestation makes soil loose and flood waters bring silt from
mountains into streams, rivers and lakes.
Anthropogenic sources – domestic, industrial and agricultural
wastes goes into the rivers, lakes, streams and seas.

12. Ground Water Pollution
• When the polluted water seeps into the ground and enters an
aquifer it results into ground water pollution.
• The dumping of raw sewage on soil, seepage pits, storage tanks,
landfills, and septic tanks cause pollution of groundwater.
• The soluble pollutants such as nitrogenous fertilizers are able to
mix with the groundwater.
• Groundwater does not have access to air (in contrast to surface
water) therefore, oxidation of pollutants into harmless products in
groundwater does not occur.

13. Water Pollutants
Water pollutant can be broadly put under the following types:
(i) Sewage Pollutants (Domestic and Municipal Waste)
(ii) Industrial Pollutants
(iii) Agricultural Pollutants
(iv) Physical Pollutants

14. (i) Domestic and Municipal Pollutants
• The sewage contains garbage, soaps, detergents, waste food and
human excreta and is the single largest sources of water pollution.
• Pathogenic microorganisms enter the water system through sewage
making it infected.
• Typhoid, cholera, gastroenteritis, polio, viral hepatitis, and
dysentery are commonly caused by drinking infected water.
• They are responsible for deoxygenation of water-bodies which is
harmful for aquatic life.
• Nitrates and phosphates support growth of algae, commonly called
algal bloom (eutrophication)

15. (ii) Industrial Pollutants
• Many industries discharge their untreated effluents into rivers.
Eg. chromium, arsenic, lead, mercury, etc.
• These pollutants are resistant to breakdown by microorganisms,
therefore makes water unsafe for drinking purposes.
• Mercury may enters the food chain through fish and finally into
the human body.

16. (iii) Agricultural Pollutants
• Manure, fertilizers, pesticides, wastes from farms, slaughterhouse,
poultry farms, and silt are drained as run-off from agricultural lands.
• Large quantities of phosphates and nitrates or manures enrich
nutrients in water bodies leading to eutrophication and consequent
depletion of dissolved oxygen.
• Consumption of water rich in nitrates is bad for human health
especially for small children.
• Toxic pesticide residues enter the human body through drinking
water or through food chain (biomagnification).

17. (iv) Physical Pollutants
(a) Radioactive Wastes:
• Accidental leakage of waste material from uranium mines,
nuclear power plants, research laboratories and hospitals.
• Radioactive materials enter human body through water and
food, and may be accumulated in blood and certain vital organs.
• They cause tumours and cancer.

18. (iv) Physical Pollutants cont…
(b) Thermal Sources: Various industries, nuclear power plants
and thermal plants require water for cooling and the resultant hot
water is often discharged into rivers or lakes.
(c) Sediments : Soil particles carried to streams, lakes or oceans
form the sediments. It introduces a large amount of nutrient
matter into water.
(d) Petroleum Products: Oil spills which floats on the water
surface causes death of marine life and severely affects the
ecosystem of the ocean.

19. Water Pollution Control Measures
• Waste water generated by household activity, industries or
garbage landfills is called sewage.
• Sewage is one of the major causes of water borne diseases
and therefore the treatment of sewage is one of the important
tasks.
• The treatment of sewage is carried out in three stages:
(i) Primary treatment
(ii) Secondary treatment, and
(iii) Tertiary treatment

20. (i) Primary treatment
When the waste water is to be dumped off into a river or flowing
steam, the treatment is carried out by:
 sedimentation: polluted water is allowed to settle so that silt, clay
and other matter settle to be bottom and water is slowly allowed to
move out.
 coagulation: the addition of coagulants to aid fine particles and
colloidal suspension settle to the bottom.
 filtration: suspended particles are filtered by passing the water
through a bed of sand or finely divided coal or through some fibrous
materials.

21. (ii) Secondary or Biological treatment
• This is applicable when the treatment is meant for drinking
purposes.
• Polluted water is allowed to spread over a large bed of stones
and gravel so that the growth of different microorganisms
needing nutrients and oxygen is encouraged
• Over a period of time a fast moving food chain is set up. Eg.
bacteria consume organic matter from the polluted water;
protozoa live on bacteria.
• Secondary treatment involves the following processes:

22. (ii) Secondary or Biological treatment cont…
• Softening : undesirable cations of calcium and magnesium are
removed from hard waters with either lime and soda or by
passing it through cation exchangers to make it soft.
• Aeration: soft water is exposed to air by forcing air through it to
add oxygen to water. The addition of oxygen reduces carbon
dioxide. sulphide etc..

23. (iii) Tertiary treatment
• The tertiary treatment is actually disinfecting water.
• Chlorine is the most commonly used disinfectant used for killing
bacteria.
• Reduce the organic matter in water before passing chlorine gas
to avoid formation of undesirable chlorinated hydrocarbons
(toxic and potentially carcinogenic).
• Other methods of disinfection such as ultraviolet radiation,
ozone gas treatment or reverse osmosis are preferred over
chlorine treatment.

24. In Summary
• During primary treatment a large percentage of suspended
solids and inorganic material is removed from sewage.
• The secondary stage reduces organic material by
accelerating natural biological processes.
• Tertiary treatment is done when water is to be reused. Here
99% of solids are removed and various chemical processes
are used to ensure that water is free from infecting
materials.

25. Other Control Measures for Water Pollution
1. Setting up effluent treatment plans to treat waste.
2. Recycling of water must be encouraged.
3. Industrial wastes must be treated before discharge.
4. Educate Public for preventing water pollution and the consequences of
water pollution.
5. Strict enforcement of water pollution control act.
6. Continuous monitoring of water pollution at different places.
7. Developing economical method of water treatment

26. Thank you