Community Medicine

Theme: Environmental sanitation


CONTENTS:

1.    Diseases associated with water suply.

2.    Type of water. Advantages and disadvantages.

3.    Water sources. Its  protection.

4.    Sources of water contamination.

5.    Water sterilization.

INTRODUCTION 

WHO estimates that  40 % of people do not have access to basic sanitation ( that is 2.6 billion people of whom 1.5 billion live in China and India). It is also estimated that 20 % of world wide population do not have access to clean water.

Every day 3 900 children die as a direct result of unsafe water or absence of basic sanitation.

Water-washed diseases ( lack of water for personal hygiene)

·      Diarrheal diseases.

·      Skin diseases ( including scabies)

·      Eye diseases ( including trachoma)


Water-borne diseases ( Carry organism of specific diseases)

·      Typhoid fever.

·      Cholera.

·      Poliomyelitis.

·      Amoebiasis.

·      Hepatitis A,E

Water-related diseases ( water is necessary in the life cycle of a disease vector)

·      Malaria.

·      Schistosomiasis ( bilharzia)

·      Onchocerciasis  ( River blindness )

·      Draculosis  ( guinea worm )

·      Trypanosomiasis ( sleeping sickness)


The water-washed diseases are diseases preventable by washing transsmitted by:

      1.   Faecal-oral route due to lack of washing hands, eating utensils and vegetables.

2.   Lack of personal hygiene( washing the face eye and body )

 
The water-borne diseases are due to dirty water containing the disease organisms themselves.

 

Type of water

1.    Rain water.

Advantages:

·      If collected from iron sheets or tile roofs into gutters and then clean, closed tanks, this is normally the purest natural water.

           Disadvantages:

·      It is very difficult to collect from thatched roofs.

·      Gutters and large tanks are required to store sufficient rain water to last into the dry season.

·      The water is “soft” and does not contain any essential mineral salts. It may not taste very good.

2.    Water that falls on high hills ( upland surface water)

Advantages:

·      The water that collects into streams above where people live is often plentiful and clean and makes very good drinking water.

·      If  it can be piped to people living lower down the hills, the water comes by gravity and no pumping is required.

           Disadvantages:

·      The source must be protected .
If animal grazing or human settlement occurs in the catchment area, the water will be polluted.

 

3.    Water in all other areas  ( such as plains and the coastal belt)

A.  Surface water.

Advantages:

·      Surface water , whether in ponds, lakes, shallow springs, streams or rivers, or in water holes, shallow wells or dams, is the commonest source of water for most people.

·      It is easily accessible, It can be obtained by hands or by simple pumps, and the larger lakes and rivers are permenent all the year round.

           Disadvantages:

·      This water is frecuently and easily polluted as it runs over the ground where humans and animals urinate and defecate, people also wash and bathe in it . It may be, as well, be polluted by chemicals used in agriculture or industry.

B.   Underground water.

             Advantages:

·      It is usually clean and often plentiful and permanent.

·       It may come from a long way away and it not so dependent on local rain .

·      Many rural areas and small towns use this type of water.

              Disadvantages:

·      Water from deep wells and deep springs has usually dissolved a lot of salts and others minerals, making the water salty.

·      This water generally needs pumping from great depths, often to tanks or reservoirs before reaching the user.

C.   Sea water.


Sources of water.

1.  Springs.

How to make it safer?

·      By erecting a fence with a gate around the spring area to keep out animals.

·      By building a ditch to allow water to drain away.

·      By building a stone wall or box around the springs itself, through which a pipe is led.

2.  Wells and boreholes. ( step wells, open wells, tubewells )

      Well water can be made safer by:

·      Fixing a removable cover.

·      Building an outward-sloping apron wall around the well , 0.5-1 meter high. The wall prevents dirty water from running into the well and acts as a shelf  where waterpots can be placed.

·      Building a concrete drainage channel around the outside of the wall.

·      Providing one container to draw water.
( this container with is fixed rope is allowed to rest only on the apron wall, never on the ground.

·      Ensuring that no one use the well for washing.

·      Encouraging the community to set up its own system for keeping the surrounds clean , repairing the well each year, keeping the handpump in good repair and chlorinating the well at regular intervals.

3. Ponds and watering holes. ( water from this sources is dangerous and can spread a variety of diseases, it should not be use for drinking, unless there is not other supply available but:

·      It should be boiled or sterilized before drinking.

·      Any pond used as a water supply  or for washing should not be used for washing or watering animals.

4.  Rivers and streams

Warning:

·      Water should be collected from the river above the village , preferably through a sand filter , infiltration gallery or , in the case of hill communities, a gravity flow system.

·      Bathing, washing and the watering of animals take place only below the village .

 

5.  Water from standpipes or other piped systems.

Water coming from a tap is not always clean . It may come from a dirty source or become contaminated in the pipes.

Tap water can be made safer by:

·  Checking the source is not dirty or contaminated.

·  Checking the pipes to make sure there are not leaks or joins where germs can enter.

·  Keeping the surrounds of a standpipe  ( standpost) clean and well drained.

·  Building a concrete or wooden platform on which to rest buckets.

·  Constructing a fence to keep away animals.

·  Encouraging the community to set up a system for checking source, pipes , tap and surround  and keeping them clean and in good repair.

6.  Rainwater tanks.

 It can be made safer by:

·      Cleaning the tank and entrance pipe before the rainy season.

·      Placing a filter or screen where the water enters the tank to keep out insects, leaves and other dirt.

·      Placing a sealed cover over the tank to keep the water clean and prevent mosquitoes from breeding

·      Ensuring that taps alone are used for withdrawing water.

·      Allowing the first heavy rainfall of the season to run through being used

·      Chlorination.


Source of water contamination.

·      The collecting surfaces for rain water may have leaves, insects or bird and animal faeces  on them.

·      When water runs over the earth, it may become contaminated with human or animal excreta,refuse, fertilizers or industrial waste.

·      Shallow wells may be contaminated by excreta and refuse being washed into them, specially if latrines are nearby

·                          Rivers , lakes or dams may be contaminated by bathing or urinating or defecating in the water.

·      Wells may also be contaminated by the use of dirty containers for drawing water , or by oil from a pump.

·      Even piped water may become contaminated from leaks in the pipes, especially when this pass near foul water or dirty drains.

·                          Water may go bad if it  is stored for too long in a pot or cistern.

·      Water from any source may become contaminated if it is drunk from dirty or communal drinking vesssels.


            Testing water    

When new water supplies are being developed on a large scale, the quality of the water should be tested . The two main methods are:

1.    Bacteriological analysis.

2.    Chemical analysis.

For bacteriological analysis, water  is collected in a sterile 500 ml flask. It must be kept cold (between 4 and 10 oC ) and analysis within 30 hours.

For chemical analysis, 4 or 5 litres are collected in any clean container. Examination for cyanide and pesticides should be done within 24 hour; for fluorides within a week.

 
Water sterilisation

1.    The three pot method.

2.    Filtration.

3.    Disinfection with chlorine or bleach is highly effective.

4.    Boiling ( It is the most effective way of killing germs)

5.    Exposure to sun.

6.    New technologies

·      Water treatment system.

·      Pur water purifier.

References:

· Community Health programme, page 305-322.

· Community Health, second edition, page 170-190.


 

 

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