Unit 1 Water Technology
, Types of Impurities and its removal methods
1. Suspended Impurities: Impurity particles like soil sand, organic waste
in water having size of particles grater than 1000A° and visible are
suspended impurities.
Removal Method : Simple filtration or sedimientation or settlement
methods
2. Colloidal: Size of colloidal particles is 10 to 1000A° (10-5 to 10-7 cm
Finely divided organic or inorganic matter of colloidal size makes water
turbid. These are evenly distributed in water and do not get settled down.
These are negatively charged particles.
Removal Method :They are separated by coagulation followed by
sedimentation or ultrafiltration. Coagulents (agents) : FeSO4, alum, pulse
floor, sodium aluminate NaAlO2, aluminium sulphate
3. Dissolved Impurities: Different gases (Oxygen, CO2, NH3, H2S, SO2)
and salts or organic compounds such as sugars, carboxylic acids, urea
etc. Removal Method : Mechanical aeration, chemical treatments,
warming water
4. Biological impurities: These impurities include bacteria (aerobic,
anaerobic, pathogenic types) algae, fungi, other small sized aquatic living
things. Removal Method : Filtration followed by sterilization. This is
acieved by using chemicals such as bleaching powder, sodium
hypochlorite, chlorine, ozone etc. and by physical methods such as
boiling, Ultravio le
, Hardness of Water
❖Definition of Hard water :
The water which does not form lather or foam easily with soap, is known as hard water
Hardness character to water is due to presence of dissolved salts of heavy metals such
as Ca++, Mg ++,, Fe ++, Al +++, etc.
❖Soft water: The water which forms lather or foam easily with soap, is known as soft
water
❖Cause of hardness in water: 1) Dissolution of minerals: When water flows or deposits
in ground salts of heavy metals get dissolved in it
2) Action of dissolved CO2: :
CaCO3 + H2 O + CO2 CaH(CO3)2 MgCO3 H2 O + CO2 MgH(CO3)2
Insoluble Soluble Insoluble Soluble
3) Action of O2: Dissolved oxygen converts insoluble minerals to soluble and hardness
causing salts.
2FeS2 + 2H2 O + 7O2 2FeSO4 + 2H2SO4
Insoluble Soluble
, Types of Hardness of Water
1) Carbonate or Temporary Hardness or alkaline Hardness:
The hardness character to water due to presence of bicarbonates and some
soluble carbonates salts of heavy metals is the temporary hardness. Such
salts are CaH(CO3)2, MgCO3, MgH(CO3)2, FeCO3,
Temporary hardness can be removed by boiling hard water which converts
soluble salts to insoluble salts.
boiling
MgH(CO3)2, Mg(OH)2 +2CO2
boiling
Mg(CO3) Mg(OH)2 +2CO2
CaH(CO3)2, CaCO3 +2CO2
2) Non Carbonate or Permanent Hardness non alkaline hardness : The hardness
character to water due to presence of dissolved salts of heavy metals other
than bicarbonates is known as the permanent hardness. Such salts are CaCl2,
MgCl2, CaSO4 ,
Mg (NO3)2, MgSO4, Ca(NO3)2
These salts can be removed by chemical treatments or membrane filtration
methods such as: sodalinme addition, sodium phosphate addition, sodium
aluminate addition, zeolite treatment, ionexcange methos, Reverse osmosis,
electrodialysis, ultrafiltration etc
, Types of Impurities and its removal methods
1. Suspended Impurities: Impurity particles like soil sand, organic waste
in water having size of particles grater than 1000A° and visible are
suspended impurities.
Removal Method : Simple filtration or sedimientation or settlement
methods
2. Colloidal: Size of colloidal particles is 10 to 1000A° (10-5 to 10-7 cm
Finely divided organic or inorganic matter of colloidal size makes water
turbid. These are evenly distributed in water and do not get settled down.
These are negatively charged particles.
Removal Method :They are separated by coagulation followed by
sedimentation or ultrafiltration. Coagulents (agents) : FeSO4, alum, pulse
floor, sodium aluminate NaAlO2, aluminium sulphate
3. Dissolved Impurities: Different gases (Oxygen, CO2, NH3, H2S, SO2)
and salts or organic compounds such as sugars, carboxylic acids, urea
etc. Removal Method : Mechanical aeration, chemical treatments,
warming water
4. Biological impurities: These impurities include bacteria (aerobic,
anaerobic, pathogenic types) algae, fungi, other small sized aquatic living
things. Removal Method : Filtration followed by sterilization. This is
acieved by using chemicals such as bleaching powder, sodium
hypochlorite, chlorine, ozone etc. and by physical methods such as
boiling, Ultravio le
, Hardness of Water
❖Definition of Hard water :
The water which does not form lather or foam easily with soap, is known as hard water
Hardness character to water is due to presence of dissolved salts of heavy metals such
as Ca++, Mg ++,, Fe ++, Al +++, etc.
❖Soft water: The water which forms lather or foam easily with soap, is known as soft
water
❖Cause of hardness in water: 1) Dissolution of minerals: When water flows or deposits
in ground salts of heavy metals get dissolved in it
2) Action of dissolved CO2: :
CaCO3 + H2 O + CO2 CaH(CO3)2 MgCO3 H2 O + CO2 MgH(CO3)2
Insoluble Soluble Insoluble Soluble
3) Action of O2: Dissolved oxygen converts insoluble minerals to soluble and hardness
causing salts.
2FeS2 + 2H2 O + 7O2 2FeSO4 + 2H2SO4
Insoluble Soluble
, Types of Hardness of Water
1) Carbonate or Temporary Hardness or alkaline Hardness:
The hardness character to water due to presence of bicarbonates and some
soluble carbonates salts of heavy metals is the temporary hardness. Such
salts are CaH(CO3)2, MgCO3, MgH(CO3)2, FeCO3,
Temporary hardness can be removed by boiling hard water which converts
soluble salts to insoluble salts.
boiling
MgH(CO3)2, Mg(OH)2 +2CO2
boiling
Mg(CO3) Mg(OH)2 +2CO2
CaH(CO3)2, CaCO3 +2CO2
2) Non Carbonate or Permanent Hardness non alkaline hardness : The hardness
character to water due to presence of dissolved salts of heavy metals other
than bicarbonates is known as the permanent hardness. Such salts are CaCl2,
MgCl2, CaSO4 ,
Mg (NO3)2, MgSO4, Ca(NO3)2
These salts can be removed by chemical treatments or membrane filtration
methods such as: sodalinme addition, sodium phosphate addition, sodium
aluminate addition, zeolite treatment, ionexcange methos, Reverse osmosis,
electrodialysis, ultrafiltration etc
