Using Multi-Function Constructed Wetland for Urban Stream Restoration

Abstract

In 2007, a 2.8-ha multi-function constructed wetland was successfully built in Pingtung County, Taiwan to improve the water quality of local stream and ecosystem of the surrounding environment. The mean inflow rate was approximately 1,350 m3/day. The major influents of the wetland come from the local drainage ditches and streams mainly containing returned water from upstream farmlands and secondary wastewater from hog farms located in the upper catchment of the wetland. Thus, the influents contain moderate to high concentrations of organics and nutrients. The mean measured hydraulic loading rate, hydraulic retention time, water depth, and total volume of wetland system were 0.1 m/day, 5.5 days, 0.7 m, and 7,800 m3, respectively. In this study, water, sediment, and plant samples were collected and analyzed quarterly for each wetland basin during the two-year investigation period. Results show that more than 77% of total coliforms (TC), 78% of biochemical oxygen demand (BOD), 88% of total nitrogen (TN), and 96% of ammonia nitrogen were removed via the constructed wetland system. Thus, the wetland system has a significant effect on water quality improvement and is able to remove most of the pollutants from the local stream through natural attenuation mechanisms. Except for stream water quality improvement and rehabilitating the natural ecosystem, this wetland also offers more water assessable eco-ponds and eco-gardens for public. This constructed wetland has become one of the most successful multi-function constructed wetlands in Taiwan.