community medicine 3rd year mbbs

1. 1
3/19/2015 1
04/08/2025

2. Community Water Supply
Prof. Dr Riaz Ahmed

3. Today's Session learning objectives
• Water, importance of water & its uses
• What is safe water
• What is community water requirements
• Type & sources of water
• Hydrologic Cycle

4. Water
• Water, a substance composed of the chemical
elements hydrogen and oxygen (H2O)and existing in
gaseous, liquid, and solid states

5. Water-Characteristics
• Plentiful and essential of compounds
• A tasteless and
• Odourless liquid at room temperature
• Should be easily accessible, adequate in quantity ,
• Free from contamination ,safe and readily available
throughout the year

6. Role of Water
• Great role to play in socio-economic development of
human population
• Essential factor in the economic, social and cultural
developing of a community
• Also integrated with other PHC Components

7. Safe and wholesome water
Free from
• Pathogenic agents
• Harmful chemical substances
• Pleasant to the taste i.e. free from colour and
odour and
• Usable for domestic purposes

8. Water requirement
• The basic physiological requirements for
drinking about 2 liters per head per day
• 150-200 liters per capita / day is considered to
meet the needs for all domestic purpose
• The consumption of water, however, depends
upon climate conditions, standard of living
and habits of the people

9. Uses of water
The uses of water in a community are:
• Domestic use, drinking, cooking, washing
and bathing, flushing of toilets, gardening
• Public purpose; cleaning streets, recreational
purpose like swimming pools, public
fountains and ornaments ponds, fire
protection and public parks

10. Uses of water….cont
• Industrial purposes: for processing and cooling
• Agricultural purpose: irrigation
• Power production from hydropower and stream
power
• Carrying away waste from all manner of
establishments and institutions
• Eliminate diseases, promote rural development
and improve quality of life

11. Distribution of Earth’s water

12. Classification of water
• Portable water: used for drinking purposes
• Clean water: all times free from contamination and
safe for human consumption,
• Polluted water: which has suffered impairment of
physical quality through addition of substances
causing turbidity, odor or taste
• Contaminated water: which carries infection due to
the addition of human or animal waste

13. Sources of water supply
In general, water sources must conform to two
criteria:
1. The quantity must be sufficient to meet
present and future requirement
2. The quality of water must be acceptable
• There are three main sources of water

14. Sources of water supply…cont.
1. RAIN
2. SURFACE WATER
• Impounding Reservoirs
• Rivers and streams
• Tanks, Ponds and Lakes
3. GROUND WATER
• Shallow Wells
• Deep Wells
• Springs

15. RAIN WATER
• It is the prime source of all water
• A part of the rain water sinks into the grounds to form
ground water,
• Part of its evaporates back into the atmosphere, and
some runs off to form streams and rivers which flow
ultimately into the sea
• Some of the water in the soil is taken up by the plants
and is evaporated in the turn by leaves (Events spoken
“water cycle”).

16. Characteristics of rain water
• Purest water in nature
• Physically it is clear, bright and sparking
• Chemically it is very soft water contain only
traces of dissolved solids (0.0005 %)
• Free from pathogenic agents

17. Impurities: of rain water
• Rain water tends to become impure as it
passes through the atmosphere
• It picks up suspended impurities from the
atmosphere such as dust, soot and
microorganisms and gases such as carbon
dioxide, nitrogen, oxygen and ammonia.

18. Acid Rain
• Gases sulfur and nitrates oxides
are emitted from power plants
that use fossil fuels
• These gases react with
atmospheric water, forming
dilute solution of sulfuric and
nitric acid
• The precipitation of these acids
(acid rain) has begun to have
serious impacts on surface
water quality and on plants etc

19. Forest Damaged by Acid Rain
Forests, lakes, ponds, and other terrestrial and aquatic environments throughout the world are being severely
damaged by the effects of acid rain Acid rain is caused by the combination of sulfur dioxide and nitrogen compounds
with water in the atmosphere. In addition to chemically burning the leaves of plants,
acid rain poisons lake water, killing most, if not all, the aquatic inhabitants.

20. Surface water

21. Ground water (Shallow well)

22. Ground water (Deep well)

23. Ground water (Spring)

24. Ground water - Rain water percolates in
ground

25. Causes of water scarcity
• Aridity: A permanent shortage of water caused by
dry climate

26. Causes of water scarcity
• Drought: Shortage of water due to a short rainfall or
non flow of surface water

27. Causes of water scarcity
• Desertification: A drying up of the landscape and
degradation of land resources that result from
activities such as deforestation and overgrazing as
well as from drought

28. Causes of water scarcity
• Water stress: Due to increase in number of people
using fixed levels of water runoffs

29. Hydrologic Cycle

30. Hydrologic cycle
• The hydrologic or hydrological cycle involves
the continuous circulation of water in the
Earth-Atmosphere system
• Its motion of the water from the ground to the
atmosphere and back again

31. Stages of the hydrologic cycle
5 major stages involved, the most important are:
• Evaporation
• Transpiration
• Condensation
• Precipitation and
• Runoff

33. Water Pollution

34. Water Pollution
• Contamination of water by foreign matter
such as microorganisms, chemicals,
industrial or other wastes, or sewage
• Deteriorates the quality of the water and
make it unfit for its intended uses

35. Major Pollutants
• The major pollutants are:
• Sewage and other oxygen-
demanding wastes
• Infectious agents

36. Major Pollutants…cont.
• Plant nutrients that can stimulate the growth
of aquatic plants
• Exotic organic chemicals, including pesticides,
various industrial products, surface-active
substances in detergents, and the
decomposition products of other organic
compounds

37. Major Pollutants…cont.
• Petroleum, especially from oil spills
• Inorganic minerals and chemical compounds
• Sediments consisting of soil and mineral particles
washed by storms and floodwater
• Radioactive substances from the wastes

39. Purification of water
Done by two ways:
• Natural methods
• Artificial methods

40. Natural methods
Includes:
• Aeration
• Sedimentation
• Sunlight
• Dilution (make-up water)
• Oxidation
• Aquatic (Plants & Animals)

41. Natural water purification
• Sedimentation

42. • Mass distillation/precipitation

43. Fine sieve filter. Nature uses porous rock for this
cleaning method.

44. Artificial methods
Carried out at:
• Large scale
• Small scale

45. Purification of water at large scale
Done by filtration which may be:
• Slow sand filtration
• Rapid sand filtration
• Desalination

46. Purification of water at large scale…cont.
• The purpose is to produce water is safe and
wholesome depends upon the nature of raw
and desired standards of water quality

47. Purification of water at large scale…cont.
• Ground water i.e. well & springs may need no
treatment other than disinfection

48. Purification of water at large scale…cont.
• Surface water i.e. River water which tends to
be turbid & polluted require purification

49. Purification of water at large scale…cont.
Water supply caries following steps:
• Storage
• Filtration
• Disinfection

50. Storage-Physical
• Water is drawn out from the source and
impounded in natural or artificial reservoirs
• By mere storage considerable quality of water
improves
• About 90% of suspended impurities and
turbidity of water settle down in 24 hours

51. Storage-Chemical
• Certain chemical changes take place during
storage
• The aerobic bacteria oxidize the organic
matter present in water with the aid of oxygen
• As a result the content of free ammonia is
reduced

52. Storage-Biological
• Due to antibiosis and oxidation 90%
pathogenic organism in the first 6-7 days
gradually die out

53. Purification of water at small scale or
domestic level
It is carried out by:
• Boiling
• Chemical disinfection
• Filtration
• Solar radiation

54. What Is Water Quality?

55. Measuring Water Quality: Acceptability
Temperature Turbidity Suspended
Sediment
Width Depth Velocity

57. Measuring Water Quality: Acceptability
• Chlorides
• Hardness
• pH
• Ammonia
• Hydrogen sulphide
• Iron
• Sodium
• Sulphate
• Total dissolved solids
• Zinc
• Manganese
• Dissolved Oxygen
• Copper
• Aluminum

58. Measuring Water Quality: Microbiology
• Coliforms
• Faecal streptococci
• Clostridium Perfringes
• Viruses
• Protozoa
• Helminths
• Free-living organisms
(algae, fungi)

59. Measuring Water Quality: Chemical
• Arsenic
• Cadmium
• Chromium
• Cyanide
• Fluoride
• Lead
• Mercury
• Nitrate & Nitrites
• Selenium
• Pesticides

60. Measuring Water Quality: Chemical
Conductivity; A measure of how much electrical
current water can conduct. It gives a good idea of the
amount of dissolved solids (such as salt, dust)
• Distilled water; low conductance
• Rainwater; higher
• Sea water; extremely high ability of
water to conduct an electrical current

61. Measuring Water Quality: Radiological

63. Thanks