Pollutants removal and distribution of microorganisms in a reed wetland of shanghai mengqing park

This project studies a constructed reed wetland located in Mengqing Park, near the downstream of Suzhou Creek, Shanghai. Under hydraulic loading of 60-70 cm/day, the mean treatment efficiency to remove ammonia, biochemical oxygen demand, and suspended solid could reach about 30, 50, and 60%, respectively, in reed wetlands. To clarify the roles of microorganisms on pollutant degradation in reed wetlands, distribution and characterization of heterotrophic bacteria, nitrifying bacteria, and denitrifiers were studied in the water and sediment of the wetland, using the traditional culture-dependent and molecular methods. It was found that heterotrophic bacteria, nitrobacteria, and denitrifying bacteria varied seasonally. The distribution of heterotrophic bacteria and autotrophic bacteria in the inlet of wetland was quite different from that in the outlet areas of the wetland. There were more heterotrophic bacteria and much less nitrobacteria in the inlet sediment than in the outlet. The amount of bacteria in reed rhizospheres ivas larger than that in nonrhizospheres. The good correlation between the removal rate of ammonia and the amount of nitrifying bacteria indicated that nitrobacteria contributed significantly to ammonia removal in the reed wetland. Profile of PCR-SSCP (single-strand conformation polymorphism) also showed that DNA diversity of bacteria in the inlet area was higher than that in the outlet, and the dominant bacteria in the wetland were genus of Bacillus. DNA diversity and similarity suggested that the functional microorganism distribution correlated to the different nutrient level in the wetland. Furthermore, the addition of exogenous microorganism, products to the wetland could help promote the pollutant removal by bioaugmentation.