How to Properly Collect and Store Water Sample for BOD Testing

Oct 23, 2017

How to Properly Collect and Store Water Sample for BOD Testing


Biological Oxygen Demand (BOD) measures the amount of oxygen consumed by microorganisms in decomposing organic matter in stream water. 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. On the other hand, BOD testing determines water quality.



Task 1

TASK 1. Use a BOD bottle to collect the water sample.  Most common sizes are 300 mL and 60 mL.  The bottles should be black to prevent photosynthesis. You can wrap a clear bottle with black electrician's tape if you do not have a bottle with black or brown glass.

Task 2

TASK 2. Use gloves for your protection and the water samples'.  The water samples must be collected in such a way that you can cap the bottle while it is still submerged.  You must be able to reach into the water with both arms and the water be deeper than the sample bottle.

Task 3

TASK 3. Carefully wade into the stream.  Stand, so that you are facing one of the banks.

Task 4

TASK 4.  Remove the cap of the bottle.  Slowly lower the bottle into the water, pointing downstream until the lower lip of the opening is submerged.  Allow the water to fill the bottle gradually.  Slowly turn the bottle upright and fill completely.  Keep the bottle under water and allow it to overflow for 2-3 minutes to ensure that no air bubbles are trapped.

Task 5

TASK 5.  Cap the bottle while it is still submerged.  Lift it out of the water and look around the "collar" of the bottle just below the bottom of the stopper.  If you see an air bubble, pour out the sample and try again.

Task 7

TASK 6.  Water sample should be preserved right after collection to maintain integrity.  When travelling, you can store the water sample in a cooler.  Analyze the water sample in the laboratory as soon as possible.  Refrigerated Incubator is the recommended storage for water sample if you plan to use it hours after the collection to keep it oxygenated and O2 stress-free.


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