Distribution and Survival of Six Kinds of Indicator and Pathogenic Microorganisms in a Full-Scale Constructed Wetlands in China

Removal efficiency and distribution of six kinds of indicator and pathogenic microorganisms in a full scale constructed wetlands in China were analyzed, and die-off rates of the indicator and pathogenic microorganisms in the water and the sediment of the constructed wetlands were determined. The results showed that the constructed wetlands could effectively reduce Escherichia coli by 99.9%, fecal streptococci by 99.8%, total coliforms by 99.8% and fecal coliforms by 99.8%, the Salmonella spp. removal efficiency was relatively low by 97.5% and the C. perfringens removal was the least by 77.2%. On a volume/dry weight basis the number of indicator and pathogenic organisms were two to three orders of magnitude higher in the sediment compared to the water column, which indicated the indicator and pathogenic organisms tend to concentrate in sediments of constructed wetland. The quantity of Salmonella spp. in effluent and sediment and the C. perfringens in sediment were magnitude greater than that of total coliforms, fecal coliforms, fecal streptococci and Escherichia coli. The die-off rates of the indicator and pathogenic microorganisms were quite different and were greater in the water than in the sediment. The die-off rates of fecal streptococci in water column and Salmonella spp in the sediment were highest among the six kinds of indicator and pathogenic microorganisms by 2.2041og₁₀ day^-1 and 0.4141og₁₀ day^-1 respectively, while the die-off rates of C. perfringens in water column and sediment were lowest by 0.4541og₁₀ day^-1 and 0.0151og₁₀ day^-1, respectively.