Basic Wastewater Operator Practice Exam

If collecting a manual flow proportional composite sample totaling 1000 mL, how much sample would be needed for sample #4 with given flows?

1. 246 mL

2. 171 mL

3. 293 mL

4. 284 mL

The correct answer is: 284 mL

To determine the correct volume of sample #4 needed in a manual flow proportional composite sampling scenario, you must consider both the individual flow rates and the total flow over the sampling period. In a flow proportional composite sample, the amount of sample collected from each flow incrementally represents the flow conditions during the sampling period. The volume for each sample would be calculated based on the proportion of the total flow represented by that particular sample. The total sample volume is set at 1000 mL, which means that the sum of the volumes from all individual samples must equal 1000 mL. For sample #4, the specific amount collected would depend on its flow measurement in relation to the other samples and the total flow accumulated. To find the sample volume accurately, the proportion of flow for the given sample must be calculated, often utilizing a formula that considers the total flow contributions from each period or sample. The consistent allocation based on flow rates ensures that the composite sample accurately reflects the characteristics of the wastewater throughout the sampling period. In this case, 284 mL is the precise volume needed for sample #4 based on the calculations for that particular flow condition, making it the appropriate amount to achieve a balanced representation in the composite sample.