[Comparison of nutrient removal ability between Cyperus alternifolius and Vetiveria zizanioides in constructed wetlands].

In order to compare the nutrient removal ability of Cyperus alternifolius and Vetiveria zizanioides, a 17.0 m2 subsurface flow wetland covered with Cyperus alternifolius and another 13.3 m2 one covered with Vetiveria zizanioides were constructed for piggery wastewater treatment, and the biomass as well as the N, P, Cu and Zn contents in the root and shoot of the plants was measured by the end of each season. The results showed that the below-ground biomass of V. zizanioides was greater than that of C. alternifolius. By the contrary, the above-ground biomass of C. alternifolius was greater than that of V. zizanioides. The annual biomass yield of C. alternifolius was 2.3 times higher than that of V. zizanioides,which was 3406.47 g x m(-2) and 1483.88 g x m(-2), respectively. The N concentration in C. alternifolius tissue was higher than that in V. zizanioides tissue, being 22.69 mg x g(-1) and 15.44 mg x g(-1) respectively, and similarly, the P concentration in C. alternifolius tissue was higher than that in V. zizanioides tissue, being 6.09 mg x g(-1) and 5.47 mg x g(-1) respectively. The Cu and Zn concentrations in C. alternifolius tissue were a little higher than those in V. zizanioides. 68.72 g N x m(-2) and 18.49 g P x m(-2) were removed by harvesting C. alternifolius vegetation, while 8.93 g N x m(-2) and 3.69 g x P m(-2) were removed by harvesting V. zizanioides vegetation. It was concluded that the removals of N, P, Cu and Zn by harvesting vegetation were 4-7 times higher in C. alternifolius wetland than in V. zizanioides wetland.