Ten tanks
servedasacontrol(onlyStyrofoamcover), 10tankswereplantedwithIrispseudacorus,and10withTypha
angustifolia. Nutrients were added weekly to keep total nitrogen (TN) and total phosphorous (TP)
concentrations at approximately 4mgNL
1
and 0.25mgPL
1
. Total removal of TN an TP from the
treatment with Typhawas relatively low, resulting fromthe limitedincrease inplant biomass during the
experiment. Total removal of TN and TP from the tanks planted with Iris was 277mgNm2
d
1
and
9.32mgPm2
d
1
during the experiment. These valueswere significantlyhigher thanthe values for total
removal from the controltanks, i.e., 54 times higher for TN removal and 10 times higher for TP removal.
Plantuptakeplayedamajor roleintheremovalofnitrogenandphosphorous fromthewaterbyFTWs,i.e.,
74% of TN removal and 60% of TP removal resulted from Iris uptake. These results suggest that FTWs
planted with Iris can be applied in a temperate climate to overcome problems with excessive algae
growth in surface waters.
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