Hydrodynamic mechanism of horizontal subsurface flow constructed wetlands for different inflow configurations

The tracer tests for horizontal subsurface flow constructed wetlands with six inflow configurations including common push flow, more direction inflow, part circumfluence, wave flow, diagonal flow, and more point inflow, were carried out. The hydraulic residence time distribution density curve of the test results were obtained. Four kinds of probability distribution functions (normal distribution, logarithm normal distribution, chi-square distribution, and Rayleigh distribution) were used to analyse the data. It was found that, the logarithm normal distribution function has better results in fitting plot. According to the simulation results on tracer concentration of six kinds of horizontal subsurface flow constructed wetlands with different inflow configuration, the completely stirred tank reactor model (CSTRM) is better to fit part circumfluence inflow configuration, the dispersion and plug flow model (DPFM) is better to fit other five kinds of inflow configuration. Considering tracer concentration folding of more direction inflow and more point inflow constructed wetlands, this study discovers that the dual DPFM is better to simulate their tracer movement in horizontal subsurface flow constructed wetlands.