In full-scale treatment systems, duckweed ponds form an ecosystemwith
diverse organisms, in which the nutrient dynamics are complex
compared to in vitro or pilot experiments. According to Zimmo
et al. (2004), nitrogen elimination can occur in one of four ways:
incorporation by duckweed biomass, nitrification and denitrification
processes, sedimentation and volatilisation. In the present work, volatilisation
and sedimentation were considered negligible because of the
low pH levels and the lack of sludge formation. Also, minimal ammonia
volatilisation in duckweed ponds has been confirmed by several
authors including Van Der Steen et al. (1988), Zimmoet al. (2004), Caicedo
(2005) and El-Shafai et al. (2007).