GATE Civil Engineering (CE) 2021 Shift 1 Solved Paper
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Question : 43 of 65
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A water sample is analyzed for coliform organisms by the multiple - the fermentation method. The results of the confirmed test are as follows:
The most probable number (MPN) of coliform organisms for the above results is to be obtained using the following MPN Index.
The MPN of coliform organisms per 100 mL is
|
Sample size (mL) |
Number of positive results out of 5 tubes |
Number of negative results out of 5 tubes |
|
0.01 |
5 |
0 |
|
0.001 |
3 |
2 |
|
0.0001 |
1 |
4 |
|
MPN Index for Various Combinations of Positive Results when Five Tubes used per Dilution of 10.0 mL, 1.0 mL, and 0.1 mL |
|
|
Combination of positive tubes |
MPN Index per 100 mL |
|
0 – 2 – 4 |
11 |
|
1 – 3 – 5 |
19 |
|
4 – 2 – 0 |
22 |
|
5 – 3 – 1 |
110 |
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