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Choosing When to Sample a Rinse Stream 4 questions
Choosing When to Sample a Rinse Stream
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A workshop checks a dissolved marker in its rinse water. Flow is constant. In this model the concentration is constant within each interval and can change between intervals. A mixed sample over four equal intervals gives their average. The workshop must stay at or below 5 mg/L on average and at or below 9 mg/L in each interval.
| Run | First interval (mg/L) | Second interval (mg/L) | Third interval (mg/L) | Fourth interval (mg/L) |
|---|---|---|---|---|
| P | 4 | 4 | 4 | 4 |
| Q | 1 | 1 | 13 | 1 |
Question 1
Which run meets both limits?
- P only
- Q only
- Both runs
- Neither run
Question 2
Calculate the concentration a single mixed sample reports for each run. Explain why the peak cannot be inferred from that reading.
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A second test collects samples only in the first and fourth intervals. Either unsampled interval could have a higher concentration.
Question 3
Evaluate a claim that first and fourth interval readings of 4 mg/L are enough to establish compliance with the peak limit. Give one possible missed record.
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Question 4
Describe a sampling plan that checks both requirements for a new run. Identify how each limit is checked.
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