The results from this study suggest FTWs planted with Iris can
be applied in a temperate climate to overcome problems with
excessive algae growth in surface waters in urban and agricultural
settings. Overall, the FTWs planted with Iris removed 277 mg N
m2 d1 and 9.32 mg P m2 d1 from the water during the growing
season. 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 plant uptake This implies, that by harvesting plant
material, phosphorous can be permanently removed from the
system. Therefore, harvesting should be an integral part of FTW
management practice. Based on our study there is no clear need for
whole-plant harvest, because TN uptake by shoots was four times
higher than root uptake and TP uptake by roots was negative.
Additional research is required to study the removal efficiency of
FTWs over time periods of several years. Furthermore, the
possibilities for the application of harvested plant material as a
marketable product should be studied.