The fate of ammonium in integrated vertical-flow constructed wetlands using stable isotope technique

Abstract

The fate of ammonium (NH4+) was investigated using the 15N tracer stable isotope technique in integrated vertical-flow constructed wetlands (IVCWs). Two types of IVCW systems were built: unplanted IVCWs (control) and planted IVCWs. The results showed that a high NH4+ removal efficiency (95.4%) in the planted IVCWs. Plants not only removed NH4+ by direct uptake (13.6±0.7%) but also improved the NH4+ removal capacity of IVCWs, compared with the control. Besides plant uptake, microbial conversion was the dominant mechanism of NH4+ removal in IVCWs, and a large proportion (75.2-85.6%) of added NH4+ may be permanently removed via anammox and nitrification-denitrification processes in IVCWs.