Spatial Distribution Characteristics of Microorganisms in Constructed Wetland System with New Matrix and Its Effect on Sewage Purification

With construction waste and straw waste as the new matrix and water dropwort as the test plant, the vertical flow wetland system was constructed. Six months after operation of the wetland, the matrix and water samples at different depths were collected to explore the spatial distribution of microorganisms and soil enzyme and the distribution characteristics of the pollutants at different depths. The results showed that the removal rate of total phosphorus, total nitrogen, ammonium nitrogen, and chemical oxygen demand (CODcr) of the sewage by the constructed wetland selected in this study reached 85.07%, 66.13%, 87.47%, and 89.54%, respectively. In the matrix at the depth of 0-40cm, the removal of nitrogen, phosphorus, and organic matter by the constructed wetland was the most rapid. The number of microorganisms in the matrix showed an apparent stratification. The number of microorganisms in the depth of 0-20cm was the largest, decreasing gradually with the increase of depth. The microbial biomass in the matrix showed a trend of bacteria>fungi>actinomycetes. The functional microorganisms decreased with the increase in the depth of the matrix, that is, nitrification bacteria>ammonia-oxidizing bacteria>denitrification bacteria>inorganic phosphorus bacteria. Ammonia-oxidizing bacteria and nitrification bacteria are mainly distributed in 0-40cm. Denitrifying bacteria and inorganic phosphorus bacteria are mainly distributed in 60-80cm. The spatial variation of soil enzyme activity was consistent with the vertical distribution of microorganisms. The soil enzyme activity has a positive correlation with the removal rate of pollutants.