What is biochemical oxygen demand (BOD) test ? At what stage of Sewage treatment this test is performed? BOD level of three samples of water labelled as A,B and C are 30mg/L, 10mg/L and 500 mg/L respectively. Which sample of water is most polluted?
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1. **Definition of Biochemical Oxygen Demand (BOD)**:
- BOD is a measure of the amount of oxygen that microorganisms will consume while decomposing organic matter in water. It indicates the level of organic pollution in the water. Higher BOD values signify higher levels of organic matter and, consequently, more pollution.
2. **Stage of Sewage Treatment for BOD Test**:
- The BOD test is performed during the **secondary treatment** stage of sewage treatment. This stage, also known as biological treatment, involves the use of microorganisms to break down organic matter present in the sewage.
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CBSE COMPLEMENTARY MATERIAL-MICROBES IN HUMAN WELFARE-SA-II
