Q 6 how to measure bod
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Q 6. How to measure BOD? PowerPoint PPT Presentation


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Q 6. How to measure BOD?. 1. Measure the volume of a sample of water in a dark bottle. Measure its oxygen level by oxygen meter / chemical method. 2. Incubate the water at 20 oC in dark to prevent photosynthesis for 5 days. 3. Measure the oxygen level again.

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Q 6. How to measure BOD?

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Q 6 how to measure bod

Q 6. How to measure BOD?

  • 1. Measure the volume of a sample of water in a dark bottle. Measure its oxygen level by oxygen meter / chemical method.

  • 2. Incubate the water at 20 oC in dark

  • to prevent photosynthesis for 5 days.

  • 3. Measure the oxygen level again.

  • 4. The difference between the 2 oxygen level is BOD.


Bod biological oxgen demand

BOD (Biological oxgen demand)

  • -the amount of oxygen used (0.5) by organism (0.5) in a fixed volume ofwater(0.5) over a specified period of time (~5 days).

  • - indicate the amount of organic

    matter and microorganisms

     indicate the degree of water

    pollution

    BOD high  degree of pollution high

    BOD low  degree of pollution low 

    clean water


Tubifex worms blood worms

Tubifex worms / blood worms

  • - can tolerate to low oxygen level

  • - indicator species of polluted and

    anoxic water

    Mayfly nymph / dragonfly nymph

  • - cannot tolerate to low oxygen level

  • - indicator species of clean water with high oxygen level


Q 6 how to measure bod

Q11

  • (a) Account for the changes in level of

  • (i) dissolve oxygen

  • (ii) ammonium compounds

  • (iii) nitrate compounds

  • in the river water below the

    source of pollution.


Q11 a

Q11 (a)

  • Sequence of events

    1. Point of outfall of sewage

    (organic matter e.g. urea,

    protein, dietary fibre +

    bacteria)

     Organic pollution


Q11 a1

Q11 (a)

  • Sequence of events

  • decomposer (bacteria+fungi)

    2. organic matter -------------------------

    ammonium O2

    3. Ammonium --------------- nitrite  nitrate

    ammonium nitrate

    4. O2 clean water species + polluted species

    Nitrate  algae


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