Study On The Effectiveness Of Polluted Water Restoration By Submerged Macrophytes

With the worsening of eutrophication of water bodies, aquatic macrophytes restoration technology has been increasingly paid more and more attention. In recent years, different degrees of eutrophication occur in the garden water of Suzhou which characterised by small water areas, small water environmental capacities and low self-purification abilities, resulting in the decline in landscape quality and environmental value. This study, conducted outdoors under natural weather conditions, was mainly to study the ability of Cabamba carolimana Gray, Elodea Canadensis, Ceratophyllum demersum L in different seasons and two different planting spaces(100mm×100mm and 200mm×200mm) for removing ammonia nitrogen, phosphate and other water quality indexes, and the submerged macrophyte that has better effectiveness was selected before the effectiveness of water purification for the selected plant in three different planting spaces(100mm×100mm, 200mm×200mm, 400mm×400mm) and different seasons was studied for selecting suitable planting density. Based on the result of the study, the following main conclusion can be drawn:(1)Three submerged macrophytes have good effectiveness of water purification. They can not only remove nitrogen and phosphate, but also increase dissolved oxygen in the water, improve the turbidity of the water body and remove permanganate index. In the spring and summer, the removal rate of ammonia nitrogen is 72.3%～96.5% and the removal rate of phosphate is 29.4%～95.0% for them. The removal rate of ammonia nitrogen is usually higher than the removal rate of phosphate for them.(2)In the spring and summer tests for Cabamba carolimana Gray and Elodea Canadensis, the specific removal rate of Cabamba carolimana Gray is faster than the latter. For the same species, the smaller planting density is, the faster the specific removal rate will be. The specific removal rate in the spring is faster than that in the summer. Three submerged macrophytes have different abilities of purification. In a word, Cabamba caroliniana Gray is better applied for the restoration of garden water.(3)By removal speed and concentration curve fitting for Cabamba caroliniana Gray, removal speed of total nitrogen, phosphate and total phosphorus is all positively correlated with their concentrations in the spring, that is, with the increase of concentration, its removal speed will increase. But in the summer season, the result is not satisfactory for fitting between the removal of speed and concentration. (4)In the spring, the bigger planting density(100mm×100mm planting space) is, the better purification effectiveness will be, while in the summer and autumn, the smaller planting density (400mm×400mm planting space)is, the better purification effectiveness will be in the seasonal tests for Cabamba caroliniana Gray. It is suggested that 200mm×200mm～300mm×300mm planting space is choosed more suitably. But it may change according to the specific situation.