Effects Of Microbial Activity On Water Quality And Pollutants Release From Sediment In An Urban Lake

Urban lake is an important component of the urban ecosystem and a determinant factor of the advantages of the different urban regions. Eutrophication of urban lakes became dramatically serious with the development of economy and society due to the special hydrological conditions and location of urban lakes. As a biological species with the smallest body, largest quantity and most widely distributed, microbes played an irreplaceable and important role in water environment. With the selected Huajia Pool as the representative of the eutrophicated urban lakes, this paper did the research on the rule of microbial activity in an urban lake system based on a novel sterilization method of micro-filtration with ultraviolet radiation (MCUR) which was developed by us. To find out the rule of water quality change and provide more theory of water quality control in an urban lake, this study investigated the rule of microbial activity on water quality and sediment pollutant release and the rule of sediment pollutant release based on the simulation experiment. The conclusions were as followed:(1) Microbe activities could decrease the equilibrium concentration of organic matter to about 9.5 percent and cut down the time which the equilibrium concentration needed by nearly 7 days; the microbial activity could remarkably increase the amount of total dissolved phosphorus.(2) Without the influence of sediment and oscillation, nitrification and decomposition of the algae were the two determinant factors of nitrate in aquatic ecosystems. When the amount of algae kept steady, the effect of microbial activity could reduce the nitrogen effectively. However, when a mass of algae died, the decomposition of the algae would increase the amount of nitrogen which led to the deterioration of water quality. Therefore, besides the method of exchange water body, the physical methods of removing algae from water body directly would effectively avoid the occurrence of secondary pollution of algae when the biomass of algae increased rapidly. (3) Microbes could reduce the electric conductivity and regulate the pH value in the water body. The decomposition of the algae would consume the dissolved oxygen under the condition of abundant algae died.(4) Under the static condition, sediments could effectively impact the amount of nitrogen in the overlying water by releasing ammonia and adsorbing nitrate. When the pH value ranged at weak alkaline, it revealed a strong negative correlation between total dissolved nitrogen release and pH value. To regulate pH value of water close to 8.5 would be propitious to reduce the total dissolved nitrogen released from sediments.(5) The effects of sediments on total dissolved phosphorus content in the overlying water could be very remarkable. When the pH value ranged at weak alkaline, the total dissolved phosphorus release processes could decrease the pH value in the water body.(6) Microbial activity could increase the speed of ammonia and organic matter released from sediments and the amount of organic matter. Aquatic microbes (excluding microbes in sediments) could inhibit the releasing of dissolved phosphorus at the sediment and water interface and decrease the releasing of nitrogen simultaneously.