Abstract:

In order to remove different concentrations of suspended sediment (SS), a serial connected system of emerging plants, floatingleaved plants and submerged plants based on spatial distribution of natural water body was constructed by aquatic marcrophytes, such as Cyperus alternifolius, Acorus tatarinowii, Trapa japonica, Ceratophyllum demersum, Hydrilla verticillata and Vallisneria spiralis. Sandy water then flew through emerging plants, floatingleaved plants and submerged plants. The input SS concentrations were 21.76, 37.04, 45.09 and 71.18 mg/L, and the hydraulic retention time (HRT) of each concentration were 12, 16, 24 and 24 h. The removal rates of SS were 68.1%, 71.7%, 77.5% and 74.0%. The aquatic marcrophytes not only removed the SS, but also greatly improved the transparency of water. The HRT obviously influenced the removal effect. While the HRT was long, no matter how high was the input SS concentration, the removal rate and the net removal per unit time could achieve an ideal level. Placing emerging plants in the region with higher input SS concentration could reduce the SS concentration, and palliate the environmental press of deep water area on submerged plants. Therefore, submerged plants were necessary for the stabilization of the whole ecosystem, which further removed the SS that might not be cleaned by emerging plants, and the resuspension of SS was restrained.

Key words: suspended sediment, aquatic marcrophyte, plant communities, hydrolic retention time (HRT), removal rate