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wat15 Measuring the O2 consumption during cleaning of waste water
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Left:
Waste water is mixed with air during cleaning. This is necessary that microorganisms
like bacteria can eat the substances in the waste water, digest and decompose
them.
Middle:
The more complete bacteria have decomposed the substances in the waste
water the less oxygen they withdraw from the water after its cleaning.
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Keep 6 samples of cleaned waste water in closed vials.
*
Determine the the oxygen in vial 0 directly after
taking the samples.
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Keep the vials 1 - 5 closed to repeat the procedure after 1, 2, 3, 4, 5
days.
Observations
Right:
At the 3. day after taking the samples the oxygen in the right vial is
completely consumed: The white precipitae (of manganese(II)-hydroxide)
is a prove for it.
The
brown
precipitate (of manganese(III)-hydroxide) was formed due to the oxygen
which was dissolved at the first day.