Eutrophicated Water Ecological Restoration Engineering

The serious issue of eutrophication, such as the damage of the water ecosystem of rivers,lakes and reservoirs, has been a threat to natural resources and contributed to water pollution. Meanwhile it blocks the construction of harmony society and the refinement of well beings; therefore, restore then clean water for the survival of human beings becomes a focusThe traditional remediation of water bodies, including physical and chemical methods and mechanical control measures, has achieved certain of remarkable results. According to biological control methods and some environmental and ecological measures combined, the paper is written to devote to the study of bioremediation efficiency of applying submerged plants introduced by large cladocera raised in library: A case study in Dishui Lake of Shanghai, China. First of all, due to the salinity of the river, we have made a preliminary study on salinity tolerance ability of Vallisneria natans before ecological restoration project in the D port of Lingang New City. It turns out that the Vallisneria natans boast the salinity tolerance ability. Basically, its maximum limit is 7,at which a seed cannot sprout. The growth of Vallisneria natans , not only the roots but also the leaves, are doomed to be restricted in the degree of 3.5, which provides effective reference to the implement of project.From the study of ecological restoration of the river of the D port, water transparency has been improved by putting the cultured large cladoceras into the river at earlier stage.It guarantees the transplant and survival of the submerged plants, as well as stimulates the growth of the submerged plants, in particular Vallisneria natans; while compared with other water bodies in water quality in the prolonged course of the test, the water quality of the ecological restoration area is inclined to descend in all sorts of nutrient salts rates. The restoration of the submerged plants exerts a great positive influence upon the water quality, which gives evidence of the success of the ecological restoration of the demonstration project.Water quality monitoring at Tai lake indicates that the water quality indices were up to gradesⅠ～Ⅲof state water quality standards for surface water in ecological restoration area. The indices inside and outside the area were significant different (P<0.01) during the experiment. The indices of TN,TP and CODMn were decreased by 67.3%, 50% and 70.8%, while dissolved oxygen (DO) was increased by 85.9%, and the Secchi depth (SD) reached to an average of 1.68 m after restoration. In later period of the project, with the effectively restore of submerged macrophytes in enclosure, water quality factors inside and outside the area which were monitored. Main indices such as Chlorophill a, Nitrogen and phosphorus were decrease significantly comparing to outside water(P<0.01), which indicated the significant effectiveness of submerged macrophytes on improving and maintaining the water environment.