Water pollution refers to the undesirable change occurring in water which harmfully affect the life activities of man and domesticated species.
# Water Pollutants : The common water pollutants are : Domestic sewage, Industrial effluents, Pesticides, Herbicides, Fertilizers, Bacteria and Viruses, Plankton blooms and Heavy metals like Mercury, Temperature, Silt, Radioactivity, Oils etc.
# Causes of water pollution
(a) Domestic sewage : Domestic sewage consists of human faces, urine, and the dirty used–up water in houses. It contains a large number of bacteria and virus. The sewage is released into the rivers on the banks of which most of the cities are situated.
(b) Industrial effluents : All industrial plants produce some organic and inorganic chemical wastes. Those nonusable chemical are dumped in water as a means of getting rid of them. The industrial wastes include heavy metals (Hg, Cu, lead, zinc etc), Detergents, Petroleum, Acids, Alkalies, Phenols, Carbonates, Alcoholcyanides, Arsenic, Chlorine, etc.
(c) Thermal pollution : Many industries use water for cooling. The resultant warm water is discharged into rivers. This brings about thermal pollution.
(d) Agricultural pollution : The fertilizers used for crops are washed into ponds and rivers.
(e) Pesticides : Pesticides are used to control pests in fields and houses. They include DDT, BHC, endrin etc.
(f) Radioactive wastes : Liquid radioactive wastes are released into the sea around nuclear installations. The oceanic currents carry the radioactive contaminants every where.
(g) Oil pollution : Oil is a source of pollution in sea-water. Oil pollution is due to ship accidents, loading and discharging of oil at the harbour, oil refineries and off-shore oil production. Degree of impurity of after due to organic matter is measured in terms of BOD (Biochemical Oxygen Demand). It is the demand for O2 to decompose organic wastes in liter of water.
(h) Eutrophication : Rich growth of micro-organisms consumes most of the dissolved oxygen, so as to depreve other organisms. It generally occurs at the bottom layers of deep lakes. Addition of excessive plant nutrients intensifies eutrophication. It harmful to fish and other aquatic life.
# Control of water pollution : Pollution control by sewage treatment includes the following steps :
(a) Sedimentation : When sewage is allowed to stand, the suspended particles settle to the bottom. So by sedimentation the suspended particles are removed from sewage.
(b) Dilution : The sewage can be diluted with water. This increases the O2 contents and reduces BOD and CO2.
(c) Storage : The diluted sewage is stored in a pond. This facilitates the growth of micro-organisms. This renders further oxidation of sewage.
(iv) Waste stabilization pond or Oxidation pond : The National Environmental Engineering Research Institute (NEERI) at Nagpur has devised a very economical method for the treatment of industrial and domestic effluents. Domestic and industrial wastes are stored in a dilute condition in shallow ponds called oxidation or stabilization ponds. After a few days micro-organisms and algae flourish. The micro–oranisms decompose the organic wastes by oxidation, and the water is purified. This water is rich in nitrogen, phosphorus, potassium and other nutrients. This water can be used for fish culture, agriculture etc.
# Recycling : Pollution can be prevented to a certain extent by reutilizing the wastes. This is called recycling. e.g., :
(a) The dung of cows and buffalo can be used for the production of energy (gobar gas).
(b) Sewage can be used for irrigation and fish culture after treatment in oxidation pond. Certain pollutants from industrial effluents can be removed by filtrationand selective absorption. Excessive use of pesticides and herbicides should be avoided. At the Government level, legislations should be framed to control water pollution.
Water pollution refers to the undesirable change occurring in water which harmfully affect the life activities of man and domesticated species.
# Water Pollutants : The common water pollutants are : Domestic sewage, Industrial effluents, Pesticides, Herbicides, Fertilizers, Bacteria and Viruses, Plankton blooms and Heavy metals like Mercury, Temperature, Silt, Radioactivity, Oils etc.
# Causes of water pollution
(a) Domestic sewage : Domestic sewage consists of human faces, urine, and the dirty used–up water in houses. It contains a large number of bacteria and virus. The sewage is released into the rivers on the banks of which most of the cities are situated.
(b) Industrial effluents : All industrial plants produce some organic and inorganic chemical wastes. Those nonusable chemical are dumped in water as a means of getting rid of them. The industrial wastes include heavy metals (Hg, Cu, lead, zinc etc), Detergents, Petroleum, Acids, Alkalies, Phenols, Carbonates, Alcoholcyanides, Arsenic, Chlorine, etc.
(c) Thermal pollution : Many industries use water for cooling. The resultant warm water is discharged into rivers. This brings about thermal pollution.
(d) Agricultural pollution : The fertilizers used for crops are washed into ponds and rivers.
(e) Pesticides : Pesticides are used to control pests in fields and houses. They include DDT, BHC, endrin etc.
(f) Radioactive wastes : Liquid radioactive wastes are released into the sea around nuclear installations. The oceanic currents carry the radioactive contaminants every where.
(g) Oil pollution : Oil is a source of pollution in sea-water. Oil pollution is due to ship accidents, loading and discharging of oil at the harbour, oil refineries and off-shore oil production. Degree of impurity of after due to organic matter is measured in terms of BOD (Biochemical Oxygen Demand). It is the demand for O2 to decompose organic wastes in liter of water.
(h) Eutrophication : Rich growth of micro-organisms consumes most of the dissolved oxygen, so as to depreve other organisms. It generally occurs at the bottom layers of deep lakes. Addition of excessive plant nutrients intensifies eutrophication. It harmful to fish and other aquatic life.
# Control of water pollution : Pollution control by sewage treatment includes the following steps :
(a) Sedimentation : When sewage is allowed to stand, the suspended particles settle to the bottom. So by sedimentation the suspended particles are removed from sewage.
(b) Dilution : The sewage can be diluted with water. This increases the O2 contents and reduces BOD and CO2.
(c) Storage : The diluted sewage is stored in a pond. This facilitates the growth of micro-organisms. This renders further oxidation of sewage.
(iv) Waste stabilization pond or Oxidation pond : The National Environmental Engineering Research Institute (NEERI) at Nagpur has devised a very economical method for the treatment of industrial and domestic effluents. Domestic and industrial wastes are stored in a dilute condition in shallow ponds called oxidation or stabilization ponds. After a few days micro-organisms and algae flourish. The micro–oranisms decompose the organic wastes by oxidation, and the water is purified. This water is rich in nitrogen, phosphorus, potassium and other nutrients. This water can be used for fish culture, agriculture etc.
# Recycling : Pollution can be prevented to a certain extent by reutilizing the wastes. This is called recycling. e.g., :
(a) The dung of cows and buffalo can be used for the production of energy (gobar gas).
(b) Sewage can be used for irrigation and fish culture after treatment in oxidation pond. Certain pollutants from industrial effluents can be removed by filtrationand selective absorption. Excessive use of pesticides and herbicides should be avoided. At the Government level, legislations should be framed to control water pollution.