Effects of physical clogging on the performance of a lab-scale vertical subsurface flow constructed wetland system and simulation research

The accumulation of inorganic solids and the corresponding change in performance indicators over time in the top layer of vertical subsurface constructed wetlands (SSF CWs) with a constant contaminant loading rate were studied in laboratory. Concentration of total suspended solids (TSS) in outflow had a significant correlation with that of the inflow at the 0.01 level. Total suspended solids (TSS) reduction rate remained steady during the experimental period (46.4% ± 8%), resulting in a linear relationship between both accumulated solids and effective porosity, and continued operation time (R2 was 0.871 and 0.797, respectively). The infiltration rate declined rapidly during the first 60 days of operation, followed by a fluctuation period of about 80 days, with a descending tendency slowing down in infiltration rate after this point. A significant correlation was observed between accumulated solids and porosity (P < 0.01; Pearson correlation coefficient: −0.776). Porosity also correlated with infiltration rate (P < 0.05), but no direct correlations were observed between the level of accumulated solids and infiltration rate (P = 0.109). Formulas were effectively employed to quantify the relationship among these indicators, with a good fit established between the simulated and the measured values.