A flow proportional sample is defined as:

• A. Based on time intervals.
• B. Based on flow.
• C. Based on chemical parameter.
• D. Based on plant staff preference.

Answer: (B)

Flow-proportional sampling collects portions of the sample in proportion to the actual wastewater flow during the collection period. As flow increases, larger sample volumes are taken; as flow decreases, smaller volumes are collected. This weighting ensures the final composite represents the true wastewater characteristics over time, especially when flow changes a lot, such as between day and night or during storms. It provides a representative measure of mass loading because the amount of wastewater (and any pollutants it carries) passing through during high-flow periods contributes more to the sample. This approach is different from time-based or fixed-interval sampling, which can bias results when flow varies, and it isn’t chosen based on a chemical parameter or staff preference.