ABSTRACT
Constructed wetlands used for the treatment of wastewater have three basic components: emergent aquatic plants, a substrate (generally gravel or sand), and heterotrophic and autotrophic bacteria. This chapter compares plant growth and wastewater treatment in two plastic substrates and in 1-cm-diameter gravel, each of which had different specific surface areas. Three substrates were used: gravel (high specific surface area, low porosity) and two sizes of plastic media (low and medium specific surface area, both with high porosity). Four emergent plant species were evaluated: Typha latifolia, Phragmites australis, Scirpus pungens, and Sagittaria latifolia. All species of plants were grown in the gravel substrate. Removal of TKN and TP was highest in the gravel treatments. Percent removal of TKN (based on a mass balance accounting for evapotranspiration losses in each plant/substrate treatment) for the 5. latifolia and T. latifolia planted in the gravel was significantly (p = 0.05) higher than the P. australis and control.
