The Ecological Effect And Influence Factors Of Algae Salvage And Phytoremediation In Eutrophic Water

Eutrophication is becoming more severity day by day. It has currently become one of the main water environment issues. In recent years, people began to study on techniques of water recovery from ecological point, and committed to eliminate the adverse effects of human activities on the lake and reservoir systems. They have done a lot of research work on it. However, it is a formidable mission that will take a long time to recovery the eutrophic water to a self-sustaining condition. It not only involves many technology instruments and recovery measures,but also needs optimization and cooperation so that it can gain a better effect. In this paper, we discussed the ecological effect and influence factors of algae salvage and phytoremediation. It contains the effect of temperature to the algae mineralization, the effect of dredging to algae mineralization, the effect of wastewater volume to phytoremediation by one kind of hydrophytes, the effect of phytoremediation by many kinds of hydrophytes and so on. Therefore, the ecological effect of algae salvage was evaluated, the timing of algae salvage was provided, the advice that about how to choose and collocate the hydrophytes was offered.Through experiments, there were some important conclusions as follow:The algae in the eutrophic water were an enrichment organ of nitrogen and phosphor. The total nitrogen, total phosphor, dissociative phosphor and organic matter content in the algae sample salvaged from Lake Taihu were 98.87g/kg,3.25g/kg,0.21g/kg and 95.65%. In the sediment, the mineralization period of the algae was 10days,13days and 15days at 13℃,23℃and 33℃respectively. The intensity that the algae released N, P to the water enhanced with the temperature rising. But in the different area, the intensity was different evidently. It was proved that algae salvage was an effective way to prolong the food chain and remove nitrogen and phosphor. The growth state of hydrophytes had to do with the proportion of discharging wastewater. Abundant nutriments were supplied to the hydrophytes by nitrogen and phosphor in the wastewater that were beneficial to hydrophytes growth. But, at the same time, if the proportion of discharging wastewater was over size, the excessive stress of hydrophytes would injury the cell membrane of the hydrophytes, stunt the hydrophytes growth even cause death.Although the wastewater were up to the discharging mark, it polluted and impacted the receiving water, increased the content of organic matter,nitrogen and phosphor. The content of organic matter,nitrogen and phosphor in the water increased with the proportion of the wastewater increasing. The chlorophyll content and the algae cells density decreased with the degree of dredge deepening. However, excessive dredge made the chlorophyll content increased greatly, and then brought the system irreversible damage, broke the water system balance, degraded the water quality.It was more stable and less fluctuate that when more kinds of hydrophytes restoring than only one kind. As the proportion of the sediment in the system reduced, the degree of dredge deepened, the contents of COD,nitrogen and phosphor in the water declined. Because the nitrogen and phosphor in the sediment were taken in quantity with the sediment removed, and then endogenous releasing was reduced.The growth of the hydrophytes could be influenced by each other when different kinds of hydrophytes work together. The contents of COD,nitrogen and phosphor in the water were entirely different too. Thereinto, the growth of the waterweed and the myriophyllum spicatum were most stable and faster. Contrast the contents of COD,nitrogen and phosphor in the different water systems. It could be found that it was optimal that using the H.reticulatum to restore eutrophic water first.