As shown in Table 2, the direct contribution of plants in nutrient
removal (nitrogen and phosphorus constituents) is practically
low, although increasing as the plants reach their full growth
(harvesting events after 2009). Specifically, Table 2 presents the
calculated annual plant uptake. The total plant uptake of nitrogen
and phosphorus for the three years of operation varied between
22.8–69.3 g/m2 and 0.46–2.87 g/m2, respectively, depending on
unit characteristics. These values correspond to 1.3–4.0% and
0.2–1.1% respective removal by plant uptake and subsequent harvesting
of total nitrogen and phosphorus load applied during the
three years, values similar to those reported by Kadlec and Wallace
[6], mainly for HSF and FWS systems. Therefore, plant uptake and
harvesting removes only a small fraction of nutrient influent loading,
especially when the loads are higher than the usual, as in this
study.