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NEET Biology Notes Environmental Issues Water Pollution

NEET Biology Notes Environmental Issues Water Pollution

Water Pollution

Water pollution is the undesirable presence of some foreign organic, inorganic, biological, radiological or physical substances in water.

NEET Biology Notes Environmental Issues Water Pollution 1

Effects of Water Pollution

  • Mercury poisoning is the cause of Minamata disease. This disease was first observed from Minamata city, Japan in 1953, when more than 100 persons died or suffered serious nervous damage from eating fish taken from Minamata Bay.
  • Cadmium poisoning is the cause of itai-itai (ouch-ouch) disease in Japan. This disease is characterised by bone softening.
  •  Nitrate in excess with haemoglobin forms non-functional methaemoglobin that inhibits 02 transport. It is known as methaemoglobinemia or blue-baby syndrome.
  •  Fluoride caused skeletal fluorosis due to excess amount of fluoride in drinking water.
  •  Nutrient the presence of large amounts of nutrients in water also causes excessive growth of planktonic algae, called algae bloom. This causes deterioration of water quality and fish mortality.
  • Biochemical Oxygen Demand (BOD) is the amount of oxygen used for biochemical oxidation by microorganisms in a unit volume of water. Polluted water has higher BOD.
  • Chemical Oxygen Demand (COD) indicates total oxygen requirement of all the 02 consuming pollutant materials present in water.
    It’s value is higher than BOD. Both BOD and COD are used in measurement of polluted water.
  • Terror of Bengal’ Eichhomia crassipes commonly known as water hyacinth, a type of aquatic weed which grows faster than our ability to remove them, is known as terror of Bengal.
  • Eutrophication is the natural aging of a lake by biological enrichment of its water. It is increase in amount of nutrients (organic matter) in water.
  • It leads to organic loading and depletion of oxygen. This phenomenon is called cultural or accelerated eutrophication.

Control of Water Pollution
Water pollution can be controlled or reduced by following methods :

  • Water (prevention and control of pollution), Act 1974 ensures*the quality of water and means to control water pollution.
  •  Effect of acid rain on water pollution can be reduced by the use of low sulphur coal, tall chimneys with scrubbers, catalytic converters.
  •  Sewage contains large amount of human excreta, organic matter and microbes should be first treated in sewage treatment plant.
  • Integrated waste water treatment contains two methods
  • Conventional method filtration, sedimentation, chlorine treatments.
  •  Innovative method marshland is developed with bacteria, algae, fungi and plants. This biota neutralise all pollutants and produces the purified water.

 Soil Pollution

It is alternation in soil caused by removal or addition of substances and factors, which decrease its productivity, quality of plants and ground water.
NEET Biology Notes Environmental Issues Water Pollution 2

  • Agro-Chemicals and Their Effects

Pesticides, herbicides, fungicides, etc., used in enhancing crop production are also toxic to non-target organisms that are important components of ecosystem. The increasing amount of chemical fertilisers can create biological magnification conditions in aquatic and terrestial ecosystems too.

  • Biomagnification

Persistent pesticides such as DDT, have a long life time in the environment. They are fat soluble and generally non-biodegradable, therefore they can get incorporated into the food chain and ultimately deposited in the fatty tissues of animals and humans. The magnification of these pesticides in successive higher trophic levels is known as biological magnification.

  • Organic Farming

It is a cyclic, zero-waste procedure, where waste products from one process are cycled in as nutrients for other processes. This allows the maximum utilisation of resource and increases the efficiency of production.
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