Improving Water Quality

• The water purification process has multiple stages. Developed countries tend to follow the full process but developing countries may use a much reduced programme, depending on resources.
• Process

  1. Screening - Water is passed through mesh screens on leaving the reservoir or borehole. These screens remove debris which come in the raw water from the catchment area.
  2. Coagulation and Flocculation - Coagulation is when coloids and impurities are removed. Aluminium sulphate helps to bind impurities to form particles (floc). Flocculation is adding chemicals (polymers). Particles formed by coagulation are increased in size for effective removal.
  3. Sedimentation - Particles form into a sludge which is removed and water is left to settle.
  4. Filtration - Removes any remaining impurities (bacteria, parasites). Either by sand or a mixture of sand and coal (anthracite).
  5. Disinfection - Vital to ensure water-borne diseases are eliminated. Chlorine or chlorine and ammonia (chloramination). Used in either liquid or gas form.
• Water Purification Process

  1. Screening
  2. Coagulation and Flocculation
  3. Sedimentation
  4. Filtration
  5. Disinfection
• Water Purification Screening

  Water is passed through mesh screens on leaving the reservoir or borehole. These screens remove debris which come in the raw water from the catchment area.
• Water Purification Coagulation and Flocculation

  Coagulation is when coloids and impurities are removed. Aluminium sulphate helps to bind impurities to form particles (floc). Flocculation is adding chemicals (polymers). Particles formed by coagulation are increased in size for effective removal.
• Water Purification Sedimentation

  Particles form into a sludge which is removed and water is left to settle.
• Water Purification Filtration

  Removes any remaining impurities (bacteria, parasites). Either by sand or a mixture of sand and coal (anthracite).
• Water Purification Disinfection

  Vital to ensure water-borne diseases are eliminated. Chlorine or chlorine and ammonia (chloramination). Used in either liquid or gas form.
• Low Income Countries - Boiling Water Processes

  This kills or inactivates most bacteria.
• Low Income Countries - Boiling Water Benefits and Challenges

  • Little technical expertise needed.
  • Reduces diarrhoea.
  • Fuel cost.
  • Long process.
• Low Income Countries - Chlorination Processes

  Using a tablet so the chlorine reacts and disinfects.
• Low Income Countries - Chlorination Benefits and Challenges

  • High cost.
  • Change of dose depending on water quality.
• Low Income Countries - BioSand Filters Processes

  Filters through sand and gravel to filter particles out.
• Low Income Countries - BioSand Filters Benefits and Challenges

  • Need trained technicians.
  • Flow rate and microorganisms need closely monitored.
  • High cost.