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Point and Non-Point Sources of Water Pollution

Water Pollution and its Effects

Point and Non-Point Sources of Water Pollution

  • The term `nonpoint source’ (NPS) is defined to mean any source of water pollution that does not meet the definition of ‘point source’.
  • On the other hand, the term ‘point source’ means any discernible, confined and specific source of pollution such as industrial unit, power plant, etc., from which pollutants are discharged or may be discharged.
  • The NPS pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources.
  • As a river runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters and groundwater.

The NPS includes the following:

  • Excess fertilisers, herbicides and insecticides from agricultural lands.
  • Oil, grease and toxic chemicals from urban runoff.
  • Sediments from improperly managed construction sites, etc.
  • Bacteria and nutrients from livestock, animal excreta, etc.

Effects of Water Pollution

Effects on Aquatic Ecosystem

  • Polluted water has less dissolved oxygen. Hence, species which demand higher oxygen cannot survive in polluted water.
  • Polluted water has less DO content due to the following two factors:
  1. Hot water discharged from industries lowers the DO content. Oxygen dissolves more in cold water.
  2. Presence of organic and inorganic wastes in water decreases the dissolved oxygen in water.

Effects on Human Health

  • Polluted water contains pathogens such as viruses, bacteria, protozoa which can cause diseases such as jaundice, cholera, etc.
  • Mercury compounds in wastewater are converted by bacterial action into methylmercury which is consumed by fish which is further consumed by marine animals and even humans.
  • Consumption of methylmercury can cause ‘minamata’ disease (a disease of nervous system).                    Water Pollution and its Effects
  • Cadmium (Cd) present in water bodies can cause ‘itai-itai’ disease, which is also called ‘ouch-ouch’ disease.
  • The itai-itai disease can cause softening of bones and kidney failures.



Environment & Biodiversity

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