Abstract:
ABSTRACT: This study was carried out to investigate the growth and nutrient uptake of two
wetland plants from Lake Tana. Rhizomes of Cyperus papyrus and Phragmites karaka were grown
outdoors in four parallel-aligned horizontal sub-surface flow constructed wetland (HSSFCW) treatment
beds. The treatment beds were irrigated with wastewater sourced from students’ residence from
January 21 to March 20, 2011. The results of the study showed that Cyperus papyrus had higher rate of
biomass accumulation as evidenced by increase in shoot and root weights (83.93 gm) compared to
Phragmites karka. It had also significantly (p < 0.05) higher root total phosphorus and leaf total nitrogen
content than that of Phragmites karka. The mean removal efficiency of the papyrus-planted treatment bed
was 56.37% (NO3-N), 84.04% (PO43-); the phragmites- planted treatment bed was 58.37% (NO3-N),
65.18% (PO4 3- ) and the unplanted (control) treatment bed was 36.13% (NO3-N) and 50.21% (PO4 3-).
Pollutant removal efficiency differences were statistically significant (p < 0.05) between planted and
unplanted treatment beds for PO43- but not for NO3-N. The study also showed that the progressive
increase in the plant density, shoot length and stem diameter was positively correlated with the
nutrient removal efficiency of the treatment beds. The average removal efficiency of the two planted
treatment beds was higher than unplanted bed. The study proved that these macrophytes had the
ability to accumulate high biomass and remove nutrients and therefore have high potential in biological
nutrient removal processes
