Unit two

• Water is essential for life. Without water no life. It is the medium in which all living process occur
• Functions of water for human body

  • Dissolve nutrients and distribute them to the cells
  • Regulate body temperature
  • Support body structure
  • Remove waste products from the body
• About 60% - 70% of our body is water
• 97% of the water found in the earth is in the form of ocean and sea water. Not useful for human and domestic use
• Only 1% of water is fresh water which is found in the form of ground water and surface water. That is readily available for irrigation, drinking and other domestic purpose
• The other 2% is locked in the form of ice in the polar region of the world
• Purposes of water apart from body needs

  • Domestic purpose
  • Public purpose
  • Industrial purpose
  • Agricultural purpose
  • Universal solvent
  • Source of energy
  • Transportation
• Sources of water for human uses

  • Ground water (e.g. wells, spring)
  • Surface water (e.g. rivers, streams, lakes)
  • Rain water
• Rain water


  • Primary source of all water in the earth
  • From sanitary point of view rain water may be the purest of all source of water
  • As it falls through the atmosphere, it may pick up various gases, dust, particulate matter
  • May be contaminated during storage, distribution, and handling
  • As it touches the surface
• Surface water


  • When rain water reaches the ground it begins to flow in the form of streams, rivers, or collected as lakes, ponds
  • Water from surface source should be disinfected and treated to remove turbidity, color, and impurities
  • Surface water should never be used as source of water supply without treatment
• Disadvantages of surface water

  • It flows over the earth's crust, therefore it picks up anything in the path
  • Quality and quantity of surface water depend upon the condition of surface or catchment area over it flows
• Ground water


  • Part of water sinks into the ground and reaches the subsoil to varying depth
  • Types of wells: shallow well, deep well, tube well, artesian well
• Essential sanitary facilities of well

  • It should be dug in good soil condition and should be at least 15m away from any possible source of contaminant
  • The site should be at a higher level to prevent entrance of surface water
  • Its wall should be made with bricks and masonry work and plastered with cement
  • There should be a concrete platform around the well, it should have a great slope outside
  • Fencing
  • Have covering
  • Diverting ditch: construct around 15m away from well
• Advantages of ground water

  • Comparatively free from disease causing microorganisms
  • If properly protected and treated immediately after completion of construction, we can be used without further treatment
  • We can be found near family or community
  • Not exposed to evaporation
• Disadvantages of ground water

  • Needs expensive pumping machine
  • May contain excessive dissolving minerals
• Major sources of water contamination

  • Surface rain off (flood) entering into surface water and ground water
  • Pollutant falling into rivers, unprotected wells
  • Infiltration from nearby latrines, cesspools, septic tanks
  • Industrial effluent (e.g. sewage, toxic chemicals)
  • Chemicals from agricultural fields (e.g. herbicides, pesticides, fertilizers)
• Types of water-associated diseases

  • Water borne disease (fecal-oral)
  • Water washed disease
  • Water based disease
  • Water related disease
• Water borne diseases


  • Helminthes disease (e.g. Ascariasis, roundworm, trichuriasis)
  • Bacterial disease (e.g. Typhoid fever, cholera, diarrhea)
  • Protozoal disease (e.g. Amoebic, giardiasis)
  • Viral disease (e.g. Infectious hepatitis A virus, poliomyelitis)
• Water washed diseases


  • Disease linked to lack of water for personal hygiene and cleanliness
  • Dermatological disease (e.g. scabies)
  • Ophthalmic disease (e.g. trachoma and conjunctivitis)
  • Louse borne disease (e.g. louse borne typhus and relapsing fever)
  • Caused by lack of good personal hygiene, unable to wash clothes
  • Quality of water is more important than quantity of water
• Water based diseases


  • Disease caused by infectious agents that are spread by contact with water
  • Essential part of the life cycle of the infectious agent takes place from aquatic animals
  • The number of diseases depends on the pathogenic organism spending part of their life cycle in water or intermediate host which live within the water
  • Infection of man cannot occur by immediate ingestion, or contact with the organism, excreted by sufferer
  • Many of the diseases in this class are caused by worms (e.g. Schistosomiasis, Dracunculosis (guinea worm))
• Prevention strategies for water-associated diseases

  • Avoidance of contact and ingestion of contaminated water
  • Reduction of intermediate host
  • Storage of water from 24-72hr to kill the microorganisms
• Water related diseases


  • Disease transmitted by insects that live close to water
  • Infections are transmitted by mosquitoes, flies and other insects that breed in water
  • Infection with this disease have no relation with human consumption or contact with water (e.g. Malaria, sleeping sickness, yellow fever, onchocerciasis)
• Summary of water associated diseases

  • Water borne disease (fecal-oral): Contaminated water by feces (e.g. Typhoid, Cholera, Diarrhea, Paratyphoid)
  • Water washed disease: Lack of water (e.g. Scabies, Trachoma, Louse borne fever)
  • Water based disease: Penetrating skin and ingestion (e.g. Schistosomiasis, Guinea worm)
  • Water related disease: Biting of insects (e.g. Sleeping sickness, Malaria)
• Objectives of municipal water treatment

  • To remove pathogenic organisms
  • Remove substances which impart color, taste, or odor to water
  • To remove excess or undesirable chemical or minerals from water
  • Regulate essential elements or chemicals
  • To remove excess or undesirable dissolved gases
• Treatment of water in small scale: Boiling

  • One of the most satisfactory methods of disinfecting water at home level
  • After water is brought to the boiling point, it should be kept boiling for at least 15-20 minutes to get reliable results in the destruction of disease producing organisms
  • Effective for all forms of raw water except those containing toxic chemicals
• Treatment of water in small scale: Filtration


  • A process where the suspended matter is separated by passing the water through minute porous material or medium
  • Most important and oldest practice of water purification
  • Started in 1852, value of filtration was witnessed when cholera epidemic struck the citizens of Hamburg in Germany in 1892
  • Objectives: To produce clear and sparkling water (reduce turbidity), Reduce number of microorganisms, To reduce contaminants which cause undesirable taste and odor, To remove any suspended solid from water
  • Example: home-made sand filter
• Treatment of water in small scale: Disinfection


  • Killing of all disease causing microorganisms within the water
  • Methods: Physical (e.g. ultra violet irradiation, boiling), Chemicals (e.g. chlorine, bromine, iodine, ozone)
  • Chlorine or its compounds can be applied to disinfect water at household level either as liquid form or tablet form of chlorine
• Treatment of water in small scale: Aeration

  • It is the treatment process whereby water is brought into intimate contact with air
  • Purposes: Addition of oxygen to oxidize dissolved iron and manganese in water, Removal of carbon dioxide to reduce corrosion, Removal of hydrogen sulfide, methane, and volatile organic compounds that create bad odor and taste to water