Water is ponded to a depth just below the sand surface. These systems require a septic tank for solids removal. They are expensive and it is difficult to find sand fill material. The pits must be lined, and they are often ugly. Constructed wetlands may include subsurface flow system wetlands, free water surface wetlands or floating aquatic plant systems.
Wetlands require pretreatment by a septic tanks for solids removal.
They are typically a flow through system, and the effluent must be disposed of. In Arizona, wetlands may require supplemental water in summer to keep plants alive. Typical plants used in wetlands are shown on page 3 in the EPA manual. A subsurface flow system wetland is shown on page 16 in the EPA manual. A free water surface wetland is shown on page 32 in the EPA manual.