3.2.5. Plants uptake and biomass production
Hill and Payton (1998) reported that during the cold winter months a translocation of nutrients from stems to rhizomes
occurred which results in an increase of nutrient content in the
wastewater. For that purpose, plant harvesting must be practiced
in order to remove organic matters and nutrients from the system.
Since the aim of this study is to achieve the highest removal of
pollutants, biomass was harvested after 12 months operation for
Canna and P. australis, while Cyprus was not harvested as it was so
short. The dry biomass of P. australis was 3.26 kg/m
2
. This biomass
yield was slightly greater than that reported for the same plant
by Hofmann (1986) and Ennabili et al. (1998). They reported maximum dry biomass of 2–3 kg/m
2
. In addition, the Canna yield in
this study reached 4.83 kg/m
2
compared to 3.125 kg/m
2
obtained
by Dennis Konnerupa et al. (2009) for the same plant. The plants
nitrogen and phosphorus uptake were 68.1 g/m
2
and 32.55 g/m
2
,
for Canna and 48.6 g N/m2
and 28.91 g P/m
2
for Phragmites. This
indicated that Canna was better than Phragmites for nitrogen and
phosphorus uptake. This may be attributed to the fact that Canna
roots were distributed more widely in the bed. The average concentrations of TKN, P and heavy metals as well as the bacterial
counts in the roots of the three different plants under consideration are shown in Table 1. The results indicated that Cyprus is much
better for the removal of nitrogen, phosphorus and heavy metals
from wastewater than Canna and Phragmites. Also, bacterial analysis in the three plants indicated that Canna was more effective
for the removal of microorganisms. However, the residual bacterial counts in the treated effluent slightly exceed the permissible
limits (10
3
MPN/100 ml) stated in National Regulatory Standards
for wastewater reuse in restricted irrigation