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Raul Jimenez
Senior Project Manager
Asked a question 2 years ago

Give a brief explanation about BOD method.

explain the process of conducting BOD test in laboratory.

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Terry Collins
Sustainability consultant
Give a brief explanation about BOD method.

Biological oxygen demand(BOD):

Biological oxygen demand is one of the clinical procedures which is used to determine the amount of dissolved oxygen which is needed by aerobic biological organisms in a body of water to director organic material is present in given water samples and certain temperature for a specific period.

Biological oxygen demand and chemical oxygen demand are different processes.

To assess the quantity of surface water for the biological oxygen demand test and other purposes then it is important to understand the characteristics of dissolved oxygen content in water and wastewater.

Thank you

The Biochemical Oxygen Demand (BOD) is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic organisms in a water body to break the organic materials present in gives water samples at certain temp. Over a specific period of time.

BOD is the amount of O2 needed for the biological decomposition of dissolved organic matter to occur under standard conditions at standard time and temperature.

Temp = 20°C, Time = 5 days

Apparatus:- BOD bottle, Beaker (250ml), Measuring cylinder, Dropper, Stirrer

Reagents:- Manganous sulphate soln, Alkaline potassium iodide soln, 0.025μ Sodium thiosulphate, Starch soln (indicator), conc H2SO4 

BOD is the principle test to give an idea of the biodegradability of any sample & strength of waste. The determination of BOD of water is useful in the design of treatment facilities.

BOD test is among the most imp process in sanitary analysis to determine the polluting power or strength of sewage, polluted water.

Drinking water std for BOD is 0.2mg/L at 20°C


  1. Add 1ml of Manganous sulphate soln to BOD bottle by means of pipette dipping in end of pipette just below surface of water.
  2. Add 1 ml of Alkaline potassium iodide soln to BOD bottle in a same way.
  3. Insert stopper and mix by inverting the bottle several times.
  4. Precipitaes settle & mix again halfway.
  5. Add 1 ml of H2SO4 . Immediately insert stopper and mix as before.
  6. Allow soln to stand at least 5 min.
  7. Withdraw 100ml of soln into flask.
  8. Add about 1 ml of Starch soln & continue until the blue color just disappears.
  9. Record the ml of thiosulphate used.

Hi, biological oxygen demand is an oxidation process. This test is performed in presence of air, therefore it is called the aerobic method.


It is my shirt by placing a water sample for incubation for a period of 5 days around 20 degree Celsius. Then the reduction in oxygen amount consumes the amount of oxygen by aerobic organisms.

After five days biological oxygen demand can be calculated.

Generally, BOD is used for oxidising the natural organic matter and best in water as a cleaning process.

Increase in. BOD value shows harmful water and not suitable for domestic use.