ABSTRACT
Nitrogen content in the raw septage, which mostly exist in the form of organic nitrogen (OrgN) and NH4+-N, are removed by means of physical and biochemical processes (Vymazal, 2007). The particulate Org-N is physically filtered at the wetland surface with other solids content to form a layer of sludge deposit. Meanwhile, the removal of dissolved Org-N and NH4+-N mainly rely on sequential ammonification-nitrification. Nevertheless, the absence of denitrification due to the dominant aerobic environment results in excessive NO3−-N (Vymazal, 2010). In VFCW system, the microorganisms involved in the biochemical process develop as a biofilm attached on the surface of porous medium (Kadlec and Wallace, 2008), and thus the treatment performance is governed by the flow rate through the wetland bed.
