Surface and ground water sources are pinpointed, highlighting the genuine sources of public water supply. In further slides, factors governing the selection of a particular source of supply are pointed out; and finally, the necessity of water to mankind is herein.

1. SOURCES OF WATER
AND NECESSITY OF ITS
TREATMENT
ANTHONY NIMELY CHEA, JR.
2K19/ENE/17

2. SOURCES OF WATER AVAILABLE ON THE EARTH
 Surface Sources
 Ponds and Lakes
Streams and Rivers
 Storage reservoirs
Oceans
Sub-
Subface/Underground
Sources
Springs
Infiltration Galleries
Infiltration Wells
Wells and Tube-wells

3. SURFACE SOURCES OF WATER SUPPLIES
Surface sources are those sources in which the water flows over the
surface of the earth, and is thus directly available for water supplies.
The important of these sources are:
Natural ponds and lakes
Streams and rivers; and
Impounding reservoirs

4. PONDS & LAKES
A natural large size depression formed within the surface of the earth, when
gets filled with water, is called a pond or a lake
Pond - small depression
Lake - larger depression
Flow of water in a lake is like that of a
stream
Quality of water is good and does not need
much purification
Larger and older lakes provide better quality
of water than smaller and newer lakes
Self purification due to sedimentation,
bleaching, bacteria removal, etc. makes
lakes water purer and better
 Lakes are not consider principal source of
water supply
Quantity of water available is small

5. STREAMS & RIVERS
Streams feed their waters to lakes or river
Streams are not suitable for water supply;
however, they can be used for water
supply to small villages
Rivers are the most important sources of
water supply
A river may be perennial or non-perennial
Quantity of river water is sufficient
Quality is generally not reliable
A River water must be properly analysed
and well treated before being supplied to
the public

6. IMPOUNDING RESERVOIRS
A water supply scheme drawing water directly from a river or stream may fail to
satisfy the consumers demands during extremely low flows; while during high flows,
it may again become difficult to carry out its operations due to devastating flood.
 A barrier may be constructed
This barrier must be in the form of a dam
 The pool formed on the upstream side of
the dam
The quality of water is not much different
from that of a natural lake
Three kinds of dams – earth, rock filled and
solid masonry dam

7. SUB-SURFACE OF UNDERGROUND SOURCES
The water which gets stored in ground water reservoir through infiltration is
known as underground water
 The water is generally pure
 It is less likely to contain bacteria
They are rich in dissolve salts, minerals, gases, etc.
It is sometimes brought to the surface by natural processes like springs, and sometimes
may be tapped artificially through wells, tube wells, infiltration galleries, etc.

8. FACTORS GOVERNING THE SELECTION OF A PARTICULAR
SOURCE OF SUPPLY
 The Quantity of Water Available: The quantity of water available at any source must be
sufficient to meet the various demands during the entire design period
The Quality of Water Available: the water available at a source must not be toxic, poisonous
or in any way other way injurious to health. The impurities should as less as possible and
should be such as to remove easily and economically.
 The Distance of the Source of Supply: the source of the water must be as near as possible,
so as to reduce the cost of the project and the number of appurtenances
The General Topography of the Area: the area or land between the source and the city
should not be highly uneven.
The Elevation of the Sources of Supply: the source of the water must be on a high contour,
lying sufficiently higher than the city or town to be supplied with water, so as to make the
gravity flow possible.

9. PURIFICATION/TREATMENT OF WATER
Raw water available must be treated and purified before they can be supplied to the
general public for their domestic, industrial or any other uses
The extend of the treatment depends of the characteristics and quality od the water
available.
The available water must be made safe, good in appearance, and attractive to human
taste and tongue.
The method of treatment and purification depend mostly upon the character of raw water
REMEMBER: All the purification techniques may not be used to treat a particular water.
The treatment will depend on the quality available.

10. METHODS OF PURIFICATION OF WATER
 Screening
 Plain Sedimentation
 Sedimentation aided with Coagulation
 Filtration
 Disinfection
 Aeration
 Softening
 Miscellaneous treatments:
fluoridation, recarbonation, liming, desalination, etc.

11. METHODS OF PURIFICATION
Screening
Most of the big and visible objects,
such as trees, branches, sticks, fish,
vegetation, etc. present in raw water,
are removed by this process

12. METHODS OF PURIFICATION CONT’D
Plain Sedimentation
A process by which coarser suspended
materials can be removed by letting
raw water settle in a sedimentation
basin.

13. METHODS OF PURIFICATION CONT’D
Sedimentation with
Coagulation
A process whereby the
effectiveness of sedimentation
increases by the addition of certain
chemicals to raw water, so as to
form flocs, which carries the
suspended particles as they settle.

14. METHODS OF PURIFICATION CONT’D
Filtration
The process by which finer suspended
particles, which may be avoided even after
chemical coagulation, are be removed. The
particle may be removed by filtering the
water through filters.
Types
Slow Sand filters
Rapid Gravity filters
Pressure filters

15. METHODS OF PURIFICATION CONT’D
Disinfection
The process of removing bacteria from water by the addition of chemical
such as chlorine, etc. This process kills germs and micro-organisms from
water, so as to make it wholesome for drinking.

16. NECESSITY OF WATER TREATMENT
 It is necessary that the water required for the
needs of plants, animals and any other living
things’ be of good quality.
It should not contain unwanted impurities or
harmful chemical compounds or bacteria in it.
The necessity of water treatment is to reliably
supply water to that section of the people for
which it has been designed.
In order to ensure the availability of sufficient
quantity of quality water, it becomes almost
imperative in a modern society, to plan and
build suitable supply scheme
The process shall not only ensure a sufficient
water quantity, but also to render it safe and
wholesome for drinking, cooking, bathing,
washing.
Additionally, a treated water must keep disease
away from its users, thereby promoting better
health; the water must also be safe for
supplying fountain, gardens, and irrigation and
industrial purposes
Besides promoting hygiene and health, it shall
ensure safety against fire by supply efficient
quantity of water to extinguish it

17. REFERENCE
ENVIRONMENTAL ENGINEERING (VOL. I & VOL II)
WATER SUPPLY ENGINEERING
SANTOSH KUMAR GARG (29ND REVISED 2016 EDITION)