EnvironmentalHealth Water

8/13/2019 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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