Vertical Subsurface Flow CW's: Operation
The wastewater is applied 2 or 4 times a day on the surface of the reed bed by pumping.The wastewater slowly percolates down through the filter material. This allows filtration and contact with the dense microbial populations growing on the surface of the substrate and roots and rhizomes. Water is collected at the bottom of the wetland by a network of drain pipes. Treatment  is a series of cycles with pumping and draining phases and therefore mainly aerobic. See animated GIF's below.
Constructed Wetlands