Biochemical Oxygen Demand and Coliform

Biochemical Oxygen Demand:
  • It is the amount of dissolved oxygen needed by aerobic biological organisms in a water body to break down organic material present in a given water sample (at certain temperature in a specific time period).
  • It is not a precise quantitative test, although it is widely used as an indication of the organic quality of water.
Significance:
  • BOD directly affects the amount of dissolved oxygen in rivers and streams.
  • The greater the BOD, the more rapidly oxygen is depleted in the stream.
  • This means less oxygen is available to higher forms of aquatic life.
Applications of the BOD Method:
  • To check the aerobic decomposition of environmental chemicals
  • To determine the respiration of soils, sludge, sediment, garbage and liquids
  • To test the toxicity in soils, sludge, sediment, garbage and liquids
  • To determine bio-activity in various environmental compartments
  • To check performance in a sewage treatment plant
  • To determine the respiration rates of living beings
Coliform:
  • Total coliform bacteria are a collection of relatively harmless microorganisms that live in large numbers in the intestines of man and warm- and cold-blooded animals.
  • They aid in the digestion of food.
Faecal coliform:
  • A specific subgroup of this collection is the faecal coliform bacteria, the most common member being Escherichia coli.
  • These organisms may be separated from the total coliform group by their ability to grow at elevated temperatures and are associated only with the faecal material of warm-blooded animals.
Faecal coliform- as a pollutin indicator:
  • The presence of faecal coliform bacteria in aquatic environments indicates that the water has been contaminated with the faecal material of man or other animals.
  • The source water may be contaminated by pathogens or disease producing bacteria or viruses which can also exist in faecal material.
  • Some waterborne pathogenic diseases include typhoid fever, viral and bacterial gastroenteritis and hepatitis A.
  • The presence of faecal contamination is an indicator that a potential health risk exists for individuals exposed to this water.
  • Faecal coliform bacteria may occur in ambient water as a result of the overflow of domestic sewage or non-point sources of human and animal waste.

One comment

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