Study On Controlling Eutrophication Of Water With The Eco-engineering Methods

Eutrophication of water is a natural and non-natural phenomenon, which results from excess nutrition accumulation, such as nitrogen and phosphorus in water, leading to excess proliferation of alga, deteriorating water and disordering water function. Therefore, its essence is damaging creature diversity, which leads to the system loss of self-maintenance, self-accommodation ability and system balance stability, finally results in the destruction of water eco-system and farther intensification of environmental issues. These are main problems of eutrophication.In this paper we selected alga that suits to grow under different concentration of nutrition, after selecting seed, domesticating, culturing alga purely in the lab, we gained Hydrodictyon reticulatum and microalga, most of which are Miorocystis and chlorella. We selected Hydrodictyon reticulatum with growing quickly and high capability of growth, to prepare a various of photosensitive substances - chlorophyll and its derivative, which are amicable to the environment. We used photosensitive-oxidation photometry to determine active oxygen (O2-,H2O2,OH and 1O2), and picked photosensitizes according to their efficiency of producing active oxygen. We selected copper chlorophyll and copper sodium chlorophyllin to have experiments of culturing microalga, under the same of illumination and the concentration of nutrition, comparing with copper ion. The results show that under the condition of illumination, a certain quantity of photosensitizer can produce a great quantity of active oxygen, which has strong effect of death; Copper chlorophyll and copper sodium chlorophyllin have very strong influence to growth of microalga. Since copper sodium chlorophyllin is water-sol and copper chlorophyll is oil-sol, adsorption characters of microalga to them are different. A little of copper sodium chlorophyllin adsorbed bymicroalga can accelerate growth of microalga, however, copper chlorophyll can accelerate growth of microalga under low concentration of copper chlorophyll, and restrain growth of microalga and even cause microalga death under high concentration of copper chlorophyll. Under the same conditions of illumination and the concentration of nutrition, copper chlorophyll has advantage of no-repollution, no-poison, better effect, long-time effect of restrain and so on, comparing with copper ion, and the mechanism that copper chlorophyll and copper sodium chlorophyllin have very strong influence to growth of microalga is analyzed in the theory.In this paper the release laws of nitrogen and phosphorus in the sediment of Taihu under different proportion of water and sediment and under the condition of aerobic and anaerobic, the relation between the distribution of granule with different dimension and the concentration of nitrogen, phosphorus and organic matter in the granule with different dimension, and the evolution law of water co-system of Taihu under different degree of sediment dredging were also studied. The results show that the average surface release of nitrogen and phosphorus in the sediment under the small proportion of water and sediment is obvious higher than that under the big proportion of water and sediment; under the same proportion of water and sediment the average surface release of nitrogen and phosphorus in the sediment under the condition of anaerobic is obvious higher than that under the condition of aerobic; most of nitrogen, phosphorus and organic matter exist in the granule with small dimension; the proportion of the granule with small dimension, accumulated in the sediment of the serious contaminative field of Taihu, is big; a proper dredging of sediment is beneficial to the improve the quality of water with eutrophication, but both no-dredging and deep-dredging are not beneficial to the improve the quality of water witheutrophication.On the other hand, on the base of prophase stvdy we further studied on the relation between alga interspecies, and confirmed that Hydrodictyon reticulate can restrain strongly the growth of microalga, and gain...