Seasonal Performance of Constructed Wetland and Winter Storage Pond for Sewage Treatment in Korea

A pilot study was performed from July 1998 to December 2002 to examine the feasibility of a constructed wetland system for sewage treatment in small communities of Korea. To maintain treatment performance during the winter period, an intermittent-discharge pond was connected to the wetland; its effects were evaluated from December 2001 to April 2003. The subsurface flow (SSF) wetland was satisfactory for treating sewage with good removal efficiency even during the winter period. The wetland effluent concentrations of BOD5 and TSS were often higher in winter than in the growing season, but this was explained by the higher loading rates, rather than lower removal efficiency. The relatively poor-quality wetland effluent was further polished during winter in the pond. The upper layer of the pond water column became remarkably clear immediately after ice melt. Overall, the wetland system was found to be adequate for treating sewage with stable removal efficiency, and the intermittent-discharge pond was found to be effective for further polishing if necessary. Therefore, a wetland and subsequent pond system is recommended as a practical alternative for treating sewage in small communities in Korea, and partial discharge of pond water in March is suggested.