Hydraulic Design of Constructed Wetland

Constructed wetland (CW) design requires determination of the necessary detention time for the desired treatment, associated CW volume/area, loading rates, substrate medium, and water depth. CW substrate is critical toward pollutant removal and adequate plant rooting conditions and directly affects the wetland hydraulics, particularly in the Subsurface Flow systems. Depending on local availability and costs, substrate materials range from relatively inert sands, gravels, and drain rock or aggregate to more reactive materials with internal pore space such as zeolite aggregate. Selection of a suitably permeable substrate in relation to the hydraulic and organic loading is the most critical design parameter of vertical subsurface flow CWs. The inlet control structures for CWs include surface and subsurface manifolds such as perforated pipes, or open trenches oriented perpendicular to the CW flow direction that uniformly distribute the inflow across the entire CW width. Properly designed CWs incorporate a vegetation zone where influent wastewater is introduced to the wetland.