Water Pollution: Sources

Water Pollution refers to the deterioration of physical (such as color, odor, turbidity, taste, temperature), chemical (such as acidity, alkalinity, salinity, etc.), and biological (presence of bacteria, coliform MPN, algae, etc.) characteristics of water through natural and anthropogenic processes to such an extent that it becomes harmful to human beings, plants, and animal communities.


Natural Sources: It includes soil erosion, eroded and weathered sediments, landslides, coastal and cliff erosion, volcanic eruptions and decay and decomposition of plants and animals.


Anthropogenic Sources: It includes:

Industrial Sources: It includes industrial wastewater that contains chlorides, sulfates, nitrates, mercury, cadmium, arsenic, radioactive substances, etc.

Agricultural Sources: It includes chemical fertilizers, pesticides, insecticides, and herbicides, etc.

Urban Sources: It includes sewage, municipal and domestic garbage, industrial effluents from the industrial units located in the urban centers, fall out of the particulate matter of automobile exhausts, etc.


  • The nature and intensity of water pollution is linked with many factors like wastewater disposal and treatment system, hydrological conditions and self-purification capacity of the streams, characteristics of effluents getting discharged and socio-economic conditions of the communities generating the waste.
  • The water pollution is assessed on the basis of certain parameters: Physical, chemical and biological parameters.
  • Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Dissolved Oxygen (DO) and pH values are important indicators of water quality.

Biological oxygen demand (BOD) is the amount of dissolved oxygen needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.

Chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in the mass of oxygen consumed over volume of solution which in SI units is milligrams per liter (mg/L). A COD test can be used to easily quantify the amount of organics available in water.

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