9.3 Biochemical Oxygen Demand Flashcards

1
Q

What is biochemical oxygen demand?

A

BOD is the amount of oxygen used by the aerobic micro-organism in water to decompose the organic matter in the water over a fixed period of time usually 5 days at a fixed temperature usually 20 degrees Celsius.

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2
Q

How is BOD used?

A

As a measure of the quality of water.

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3
Q

What does a low BOD mean?

A

The lower the BOD the less polluted the water.

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4
Q

How can the Winkler method be used?

A

To measure the concentration of dissolved oxygen in a sample of water - involving a redox titration.

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5
Q

What are the equation involved in the Winkler method?

A

2Mn(OH)2 (s) + O2 (aq) —–> 2MnO(OH)2 (s)

MnO(OH)2 (s) + 4H+ (aq) —-> Mn4+ (aq) + 3H20 (l)

Mn4+ (aq) + 2I- (aq) —-> Mn2+ (aq) + I2 (aq)

I2 (aq) + 2S2O32- (aq) —–> S2O62- (aq) + 2I- (aq)

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6
Q

What does the series of moles calculations in the Winkler method result in?

A

The number of moles of oxygen in the sample is 1/4 the number of moles of sodium thiosulfate used in the titration.

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