For Level 2 Constructed Wetland, the flow path ratio should be at least?

For Level 2 Constructed Wetland, the flow path ratio should be at least?

• A. 1:1
• B. 3:1 or more
• C. 2:1
• D. 4:2

Answer: (B)

The main idea is that the flow path ratio expresses how far water must travel through the wetland relative to its horizontal footprint. A longer flow path increases hydraulic detention time, giving more opportunity for sedimentation, plant uptake, and microbial treatment, which improves pollutant removal. For Level 2 Constructed Wetlands, design guidance requires a minimum flow path length of three times the width, so the ratio should be at least 3:1. This helps prevent short-circuiting and ensures sufficient contact time with the wetland media and vegetation. Ratios like 1:1 or 2:1 would provide shorter travel distances and less treatment opportunity, while 4:2 is mathematically equivalent to 2:1 and remains below the required minimum. Therefore, three to one or more is the appropriate guideline.

The main idea is that the flow path ratio expresses how far water must travel through the wetland relative to its horizontal footprint. A longer flow path increases hydraulic detention time, giving more opportunity for sedimentation, plant uptake, and microbial treatment, which improves pollutant removal. For Level 2 Constructed Wetlands, design guidance requires a minimum flow path length of three times the width, so the ratio should be at least 3:1. This helps prevent short-circuiting and ensures sufficient contact time with the wetland media and vegetation. Ratios like 1:1 or 2:1 would provide shorter travel distances and less treatment opportunity, while 4:2 is mathematically equivalent to 2:1 and remains below the required minimum. Therefore, three to one or more is the appropriate guideline.