Floating treatment wetlands (FTWs) may provide an appealing alternative to the more conventional
(sub) surface
flow wetlands to solve problems associated with eutrophication in urban surface waters,
because they do not claim additional land area. This study examined the contribution of plant uptake to
overall removal capacity of FTWs. A batch mesocosm experiment was performed during the growing
season using thirty 84 L polyethylene tanks covered with 0.28 m2 floating Styrofoam mats. Ten tanks
served as a control (only Styrofoam cover),10 tanks were planted with Iris pseudacorus, and 10 with Typha
angustifolia. Nutrients were added weekly to keep total nitrogen (TN) and total phosphorous (TP)
concentrations at approximately 4 mg N L1 and 0.25 mg P L1. Total removal of TN an TP from the
treatment with Typha was relatively low, resulting from the limited increase in plant biomass during the
experiment. Total removal of TN and TP from the tanks planted with Iris was 277 mg N m2 d1 and
9.32 mg P m2 d1 during the experiment. These values were significantly higher than the values for total
removal from the control tanks, i.e., 54 times higher for TN removal and 10 times higher for TP removal.
Plant uptake played a major role in the removal of nitrogen and phosphorous from the water by FTWs, 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.
Floating treatment wetlands (FTWs) may provide an appealing alternative to the more conventional
(sub) surface
flow wetlands to solve problems associated with eutrophication in urban surface waters,
because they do not claim additional land area. This study examined the contribution of plant uptake to
overall removal capacity of FTWs. A batch mesocosm experiment was performed during the growing
season using thirty 84 L polyethylene tanks covered with 0.28 m2 floating Styrofoam mats. Ten tanks
served as a control (only Styrofoam cover),10 tanks were planted with Iris pseudacorus, and 10 with Typha
angustifolia. Nutrients were added weekly to keep total nitrogen (TN) and total phosphorous (TP)
concentrations at approximately 4 mg N L1 and 0.25 mg P L1. Total removal of TN an TP from the
treatment with Typha was relatively low, resulting from the limited increase in plant biomass during the
experiment. Total removal of TN and TP from the tanks planted with Iris was 277 mg N m2 d1 and
9.32 mg P m2 d1 during the experiment. These values were significantly higher than the values for total
removal from the control tanks, i.e., 54 times higher for TN removal and 10 times higher for TP removal.
Plant uptake played a major role in the removal of nitrogen and phosphorous from the water by FTWs, 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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