environmentalhealth water
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Environmental HealthDr Paul T Francis, MDCommunity Medicine
College of Medicine, Zawia
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Contents Importance of environmental health
Water purification:
Small quantity Large quantity
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Role of Environment in
Health Health of man depends on the
interaction between Agent, Host and
Environment Epidemiological triad
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Epidemiological triad
Environment
AgentHost
Disease
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Role of Environment in
Health Physical environment includes air,
water, soil, housing etc.
Biological environment includesplants, animals, insects, bacteria etc.
Social environment includes customs,
culture, habits, occupation etc.
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Environment and disease Many of the diseases in man are caused byadverse() environmental factors like
Water pollution, air pollution, soil pollution,poor housing, insect vectors, animal reservoirsetc.
Due to industrialization and urbanization
environmental pollution has increased,resulting in increased morbidity
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Environmental sanitation Environmental sanitation() is notmerely sanitary disposal of excreta
It means clean home, clean farm , cleanbusiness, clean neighborhood and cleancommunity
The purpose of environmental health is tocreate and maintain conditions that willpromote health and prevent disease
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Water andHealth
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Water Many diseases occurring in man aredue to lack of safe drinking water
Common water-borne diseases are: Viral hepatitis E&A, Polio, diarrhea,
typhoid, cholera, amoebiasis etc.
Providing safe drinking water is very
important to prevent diseases in man
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Sources of water supply Rain Surface water
Reservoirs, Ponds, Sea (after desalination)
Rivers
Ground water Shallow well
Deep well Nahr project of Libya
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Purification of water Purification in small scale (small
quantity) e.g. in a house
Boiling, Filtration, Chemical (chlorinetablets, bleaching powder)
Purification of water in large scale(large quantity)
Purification of water for supplying to acity is different from purification on a
small scale
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Purification of water on a
large scale There are two methods of
purification
Slow sand filtration Rapid sand filtration
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Slow sand filtration There are 3 steps
1. Storage
2. Filtration3. Chlorination
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Storage Water is first stored in large tanks for
about 10 days
This will result in impurities settling() down
Some organic material will be oxidized
A great decrease (90%) in the number ofbacteria occurs in the water
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Filtration Large Sand() filters are used tofilter water
The sand filter consists of sand ofdifferent sizes about 1-1.5 mts inthickness
When water flows through the sand
it gets filtered
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Section of sand filter Impurewater
Purewater
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Rapid Sand filtration There are three steps in rapid sand
filtration
1. Mixing with Alum2. Filtration
3. Chlorination
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Rapid sand filtration Mixing with Alum In rapid filtration method water is Notstored Water is mixed with Alum, which will combine
with the impurities )and form big )particles()
The particles of Alum will settle down with theimpurities and are removed
The clear water is filtered using rapidsandfilter
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Disinfection The last step in water purification isdisinfection
Destroys most of the infectiousagents in the water
Chlorination is the most commonly
used method
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Chlorination First the amount of chlorine required todestroy all microbes and organic matter iscalculated. It is the chlorine demand of
water Then chlorine (gas) is added till freechlorine appears in water
Wait for 1 hour for the chlorine to kill allthe bacteria
However some viruses, cysts are notdestroyed
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Residual chlorine 0.5mg of chlorine per liter of wateris added extra to protect against
contamination during distribution ofwater
This is called residual chlorine
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Purification of water on
small scale Boiling Water must be boiled for 5-10minutes
Care must be taken to preventcontamination later
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Chlorination Small quantities of water may bedisinfected with chlorine tablet
0.5g for 20L Bleaching powder can be used to
disinfect wells
2.5gm for 1000L
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Summary Environmental sanitation is important toprevent disease
Water is an important source of infection
Safe drinking water is important toprevent diseases
Water can be purified in small quantities
at home by boiling, chlorination
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Summary Water purification on large scale isdone by 2 methods
1. Slow filtration method Storage,Filtration and Chlorination
2. Rapid filtration method Mixing withAlum, Filtration and Chlorination
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