Chen(2004)improved the application of traditional constructed wetlands in order to process high-concentration household wastewater. The pilot scale system was designed for two-stage processing, including horizontal bio filters for aeration and subsurface-flow constructed wetlands. The total removal rate for water quality indicators such as biological oxygen demand and suspended solids was above 73% on the average after initial processing. The cost to build a two-stage constructed wetland was one-sixth of a traditional wastewater treatment plant and the yearly operational costs were reduced to one-third.