The Environment and Its Impact on
Community Health
B. Water
By: Maryam Fatima
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Objectives
At the completion of this unit, students will be
able to learn the:
• Definition of safe and wholesome water
• Uses of water
• Daily requirements for one person.
• Sources of water and its pollution.
• Water-borne diseases (viral, Bacterial,
protozoal, worms etc.)
• Water purification at small and large scales.
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Safe water
• Safe water means water that will not harm if
consumed. The most common use of this term
applies to drinking water. To be safe, the water
must have sufficiently low concentration of
harmful contaminants.
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Wholesome water
• Wholesome water is defined as that which is
free from pathogenic agents, free from harmful
chemical substances, pleasant to taste,
colorless and odorless. Use able for domestic
purposes. Water is fit to use for drinking,
cooking, food preparation or washing without
any potential danger to human health.
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Uses of water
All living things, including humans, depend on
water to survive, but water is not only used for
survival. There are four main uses of water:
• Domestic use
• Industrial use
• Public use
• Agriculture use
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Uses of water
1. Domestic use (7%)
• For domestic use 7% water is available for
drinking, cooking, washing, bathing etc.
recommended need of water is
gallon/day/person. But in Lahore , Karachi
available water is 15-20 gallons/day/person.
2. Industrial use (23%)
• Nearly 23 of water is used in industries.
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Uses of water
3. Public purpose
• Water is also required for public cleansing,
maintenance of garden, swimming pools and
other civil activities.
4. Agriculture use (70%)
• Lot of water is required for agriculture use (for
growth of food)
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Daily requirements of water
• The national Academies of Sciences,
Engineering, and Medicine in USA determine
determined that an adequate daily fluid intake is:
• About 15.5 cups (3.7 litters) of fluids a day for
men
• About 11.5 cups (2.7 litters) of
fluids a day for women
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Daily requirements of water
• A daily supply of 150-200 litters per capita is
considered as an adequate supply to meet the
need for all domestic purposes.
• Every day you lose water through your breath,
perspiration, urine and bowel movements. For
your body to function properly, you must
replenish its water supply by consuming
beverages and foods that contain water.
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Surface water
• Surface water refers to all the water bodies
present on the Earth's surface like lake, pond,
stream, river, reservoir, or ocean.
• Surface water mainly originates from rainfall.
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Surface water
• Surface water is used as drinking-water and
other public uses, irrigation uses, and for use by
the thermoelectric-power industry to cool
electricity-generating equipment.
• Surface water is more readily available, but
since it is not filtered.
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Surface water
• It is often contaminated by pollution, microbes
and harmful minerals.
• It must be treated before it is safe to use or
ingest.
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Ground water
• Ground water is located below the surface of
the earth in spaces between rock and soil (open
well, tube well , springs) .
• Groundwater is fresh and naturally
uncontaminated, since the water gets filtered
as it trickles through the sediment.
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Ground water
• However, groundwater is not easily accessible
as it is usually located in deeper parts of the
Earth, often requiring tools or machinery to
access it.
• The largest use for groundwater is to irrigate
crops. 64%
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Water pollution
• Water pollution can be defined as presence of
solid, liquid or gaseous contaminants in such
concentration that may alter the quality of
water and that is harmful to the living
organism.
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Causes of water pollution
The principal sources of water pollution resulting
from exploration and production operations are:
• Domestic waste
• Sewage system
• Solid waste
• Industrial waste
• Acid rain
• Oil industry
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Causes of water pollution
Other causes of water pollution are:
• Religious means
• Death of aquatic organisms
• Rivers are changed into dustbin
• Aquatic plants
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Water purification
• Water purification is the process of removing
undesirable chemicals, biological
contaminants, suspended solids, and gases
from water. The goal is to produce water that is
fit for specific purposes.
• Water purification is done in two methods:
1. Purification at large scale
2. Purification at small scale
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Purification at large scale
It involves three methods that follow one
another.
1. Storage
2. Filtration
3. Disinfection
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1. Storage
• Water is drawn out from the source and stored
in reservoir.
• The reservoir may be natural or artificial.
• As a result of storage, a very considerable
amount of purification takes place.
• This purification occurs in three aspects
i. Physical
ii. Chemical
iii. Biological
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1. Storage
Physical action
• By mere storage, 90% of suspended impurities
settle down in 24 hours due to gravity.
• Water becomes clearer physically.
• This allows penetration of light which further
improves water quality (hence reduces the load
on filter)
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1. Storage
Chemical action
• Certain chemical changes occur during
storage.
• The aerobic bacteria oxidize the organic matter
present in the water with the aid of dissolved
oxygen.
• This results in reduction of free ammonia and
rise in Nitrates occurs.
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1. Storage
Biological action
• This is one of the greatest benefits of storage.
• The pathogenic organisms gradually die out.
• It has been seen that when river water is stored
the total bacterial count drops by as much as
90% in 5 – 7 days.
• The optimum period of storage of river water
is about 10 – 14 days
• If the water is stored for longer periods, algae
might grow which imparts a bad smell and
colour to the water. 24
2. Filtration
• Filtration is the 2nd stage in purification and It
is the oldest and universal method of
purification.
• In this stage, 98 – 99 % of the remaining
bacteria get removed.
• There are two types of filtration:
i. SLOW sand filter (Biological filter)
ii. RAPID sand filter (Mechanical filter)
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SLOW sand filter (Biological filter)
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RAPID sand filter (Mechanical filter)
Steps in purification of water using rapid sand
filter
1. Coagulation
2. Rapid mixing
3. Flocculation
4. Sedimentation
5. Filtration
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3. Disinfection
• The final step in water purification, is
disinfection of the filtered water
Most practical disinfection at the large scale is
chemical disinfection.
• Chlorination
• Ozonization
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Purification at small scale
Purification at small scale or domestic level
include steps:
• Boiling
• Chemical disinfection
• Filtration
• Solar radiation
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Purification at small scale
Boiling
• It is satisfactory method of purifying water for
house hold purposes.
• Water is boiled (preferably for 20 minutes) to kill
the microorganisms and allowed to stand for some
time.
• Boiling also remove temporary hardness by
driving off carbon dioxide & precipitating the
calcium carbonate.
• The taste of water is altered but this is harmless.
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Purification at small scale
Chemical disinfection
Chemical disinfectant includes:
• Bleaching powder
• Chlorine solution
• Chlorine tablets
• Iodine
• High test hypochlorite
• Potassium permanganate
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Purification at small scale
Filtration
• The clear water is decanted off and filtered
through ceramic candles. Ceramic candles have
fine pores which allow only the water to pass
through, but not the suspended particles.
• Ceramic filter involves:
Pasteur chamberland filter
Berkfeld filter
Katadyn filter
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Purification at small scale
Solar radiation
• It involves the exposure of film of water, to
several quartz mercury vapor arc lamps
emitting ultraviolet radiation at a wavelength
of 254 nm.
• Water should be free from turbidity and
colloidal constituents.
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