Urban pollutant removal by a constructed riparian wetland before typhoon damage and after reconstruction

Flood damage as a result of an extreme weather event is always a potential threat to constructed riparian wetlands in subtropical regions, and such damage can significantly impair the pollutant-removing performance of these wetlands The present study compares the pollutant-removal performance of the Hsin-Hai Bridge constructed wetland in the Tan-shui River basin of metropolitan Taipei in September 2000 (before the system was inundated by flood as a result of Typhoon Aere’) and in mid-October 2004 (after reconstruction of the wetland). The study analyses biochemical oxygen demand (BOD), ammonia nitrogen (NH4-N), and total phosphorus (TP) of influents and effluents in each of several compartments and for the system as a whole before the typhoon and after reconstruction. The study finds that performance with respect to BOD and NH4-N was marginally reduced (with no statistical significance) after reconstruction, but that performance with respect to TP was markedly improved (with statistical significance) after reconstruction. The study provides possible explanations for these findings and concludes that wetlands can be successfully reconstructed after extreme flood damage.