There are three major mechanisms of

There are three major mechanisms often referred in
the literature regarding the nitrogen removal, viz: (1) bacterial
nitrification and denitrification, (2) uptake by plants,
(3) volatilization of ammonia (DeBusk and Reddy, 1987;
Wathugala et al., 1987; Sundblad and Wittgren, 1989; Abbasi and Ramasamy, 1999; Abbas and Fayyad, 2003). Of these,
bacterial nitrifcation/denitrifcation has have the most dominant
influence on nitrogen removal (Weisner et al., 1994).
In the presence of oxygen the microbial nitrification process
dominates resulting in the formation of NO3
−–N, while the
anoxic conditions in which lower concentration of oxygen/air
along with the presence of higher concentration of NO3
−–N
promotes the microbial denitrification process resulting in
the conversion of NO3
−–N into nitrogen gas, which escapes
from the wastewater, thus ultimately resulting in the removal
of NO3
−–N from the wastewater (Crites and Tchobanoglous,
1998; Davis and Cornwell, 1998; Abbasi and Ramasamy, 1999;
Nebel and Wright, 2000). However, in the present study, the
better removal of NO3
−–N during the second half of the
experiment (11–20 days) observed in experiments I and II
(Tables 3 and 7) could be due to the increased plant uptake
rather than the microbial denitrification. This view is supported
by the increase in the DO content recorded towards
the end of each run (Table 4). The increase in DO might not
support the development of anoxic condition. Therefore, the
removal of NO3
−–N at this stage might be due to uptake by the
plant roots. The reports on the nutrient uptake by the wetland