Physiological Response Of Five Wetland Plants To Sewage And Their Purification Ability

Five species of wetland plants, including Phragmites australis, Lythrum salicaria, Scirpus planiculmis, Scirpus validus and Typha angustata, were selected to grow in sewage. Their biological characteristics were assessed and their capability to remove nutrients, such as chemical oxygen demand (CODcr), total phosphorous (TP) and ammonia nitrogen (NH4+-N) in constructed wetland systems, was analyzed. During the experimental period, the growth characteristics, the microbial in rhizosphere soil and sewage cleaning effect of each plant was evaluated by both physiological and chemical methods.The results demonstrated that (1) The plants cultivated in sewage grew better than those in tap water as measured by plant photosynthesis, chlorophyll fluorescence, plant height, and biomass. There were significant differences between the plants growing in tap water and in sewage as measured by net photosynthetic rate, Fv/Fm, Chlorophyll content (P<0.05) of Typha angustata, Scirpus validus and Phragmites australis (P<0.05). We conclude that the five species grow better in the sewage than in the tap water.(2) The treatment system with wetland plants has higher removal efficiency to CODcr, ammonia nitrogen (NH4+-N), total nitrogen (TN) and total phosphorus (TP) than that without wetland plants(P<0.05). The removal efficiency of5wetland plants were determined that ranged80.2-88.5%,98.4-99.3%,68.8-83.8%,89.7-97.2%for CODcr, NH/-N, TN and TP, respectively. The total phosphorus absorption of5wetland plants were97.3%,97.9%,89.7%,97.3%and97.3%, and the surplus in sewage were2.7%,2.1%,10.3%,2.7%and2.7%for Phragmites australis, Scirpus validus Lythrum salicaria, Scirpus planiculmis and Typha angustata, respectively. There was no retention in soil. The total nitrogen absorption of5wetland plants were77.0%,83.4%,45.0%,46.8%and76.1%, and the surplus in sewage were23.0%,16.2%,31.2%,21.7%and23.9%, and the retention in soil were0%,0.4%,23.8%,31.6%and0%, for Phragmites australis, Scirpus validus Lythrum salicaria, Scirpus planiculmis and Typha angustata, respectively. The results of principal component analysis shows that Phragmites australis, Typha angustata, and Scirpus validus are the better ones among the five wetland plants in experiment of domestic sewage clean, followed by Lythrum salicaria and Scirpus planiculmis.(3) The bacterial abundance and community structure was evaluated by DGGE electrophoresis of16S rRNA gene amplification products. The plants cultivated in sewage which rhizosphere microflora Shannon diversity index and richness are higher than those in tap water. Sequencing of partical16S rRNA genes fragments revealed that total bacterial community composition was dominated by Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, and Uncultured bacterium. The activities of these bacteria might contribute to the nutrient removal in the wetlands.