Long term performance of stormwater wetland systems (2012-2015)

The Bäckaslöv stormwater pond and constructed wetland in Växjö was built in 1994. A comprehensive evaluation of the system in 1995 through 1997 showed high water quality treatment and retention of the system. However, although there is a risk that the long-term performance might not be sufficient, no performance upkeep has been done.

Also in research there is a lack of studies evaluating the performance of constructed stormwater wetlands with an operational age exceeding 10 years.

The aim of this study is to investigate the long term performance of the Bäckaslöv wetland system. By comparing these results with the existing results from the 1990’s, changes of the function can be quantified.

Preliminary results show that the CSW still provides efficient peak flow reduction and, depending on the event characteristics, also volume reduction. It still treated stormwater effectively: removal of Cd, Cu, Pb, Zn, TSS and TP event mean concentrations were between 89 and 96%, whereas mean concentrations of TN were reduced by 59%. The load removal efficiencies were even higher. Comparative analysis of the three monitoring periods based on the load removal efficiency revealed that the CSW, despite the lack of maintenance, performed more efficiently and stably for most pollutants compared to when newly constructed. This underlines the importance of the establishment and maturation of constructed wetland systems.

This project is a collaboration between LTU and the municipality of Växjö.

Godecke-Tobias Blecken och Ahmed Al-Rubaei