Wetland Design

Question 1

Wetland Design

Answer 1

• Hydrology
• Soils
• Vegetation

Question 2

Hydrology

Answer 2

•Hydroperiod

• Depends on the type of wetland
• Greater variation increases chemical retention

• Hydraulic loading rate
- Recommended HLR
xx 2.5-5 cm/day surface flow wetlands
xx 6-8 cm/day subsurface flow wetlands

•Detention time

• Optimal detention time 5 - 14 days
• Calculations are not always realistic

Question 3

Soils

Answer 3

• Surface flow wetlands

• Provide structure and nutrition for the plants
• Clay for the liner
• Silt clay or loam soils

• Subsurface flow wetlands

• Support rooted vegetation
• Part of the treatment process
• High permeability, i.e. sand or gravel

see slide 27

Question 4

Vegetation

Answer 4

• Primary role to maintain permeability in the filter and
provide habitat for microorganisms

•Physical functions:
– Transpiration
– Flow resistance
– Particulate trapping

• Chemical processing:
– Submersed litter and stems provide surfaces for microbes
– Affects the oxygen supply in water
– C content of litter energy for denitrifiers

Question 5

Vegetation type

Answer 5

• Surface flow: combination of free floating, emergent, and submerged marcophytes
• Subsurface flow: Emerging macrophytes

see slide 29