factors such as nutritional requirements, initial concentrations of
P and N and the plant growth rate with varying temperatures
and in the presence of toxic compounds (Cheng et al., 2002a). However,
the present data showed that nitrifications/denitrification
processes were improved by duckweed mat, may strongly affect
the difference in removal rate between N and P, mainly in DP1.
Al-Nozaily et al. (2000), reported TP removal rates close to
95 mg/m2day for duckweed ponds receiving effluent produced
by a UASB reactor, five times less than what is reported here.
It was concluded that during the studied period, approximately
260 kg of nitrogen and 28.5 kg of phosphorus were recovered by
the duckweed ponds, preventing nutrient overflow to the
environment.