The indirect and more important role of the plants is to function
as a carbon supplier for microbe metabolism, offer attachment sites
for microbes on their extended root system and transfer oxygen
through their roots. It is noticeable that the performance improvement
(decrease of effluent concentrations) of BOD5, COD, TKN and
NH4
+-N started almost simultaneously with the first plant growth
(spring–summer 2008) within the bed environment, which took
place about 6–7 months after the beginning of the loadings in
October 2007 (Fig. 2a–d). This trend continued with time and stabilized
as plants reached their full growth. Furthermore, biomass
analyses showed that ammonium (the major portion of TKN)
uptake by plants is favored compared to nitrate uptake (Table 2),
as reported by Kadlec and Wallace [6]. Comparing the two plant
species used (common reeds and cattails; units W1 and W2, respectively),
reeds appear to utilize TKN and TP more than cattails, but
cattails seem to be able to uptake nitrate at a higher rate, simultaneously
with ammonia [41].