Analysis of the Water Flow Patterns in the Vertical Flow Constructed Wetlands

The water flow patterns in the vertical flow constructed wetlands were analyzed with different height of water outlet,based on the tracer experiment by using the theory of the resident time distribution(RDT).The results indicated that the actual flow pattern was between the ideal plug flow and continuous stirred flow.The main difference of the flow pattern under different height of water outlet was the mean resident time and the difference of the dispersion can be neglected.When the water outlet was higher,the mean resident time was longer,and this was favorable to the degradation of the pollutants in the vertical flow constructed wetland.