Improved solute transport and pollutant degradation model of free water surface constructed wetlands considering significant linear correlation between model parameters.

To unify the structures of solute transport and pollutant degradation models and evaluate the wetland performance conveniently, a pollutant degradation model combining first-order kinetics with the hybrid solute transport model (plug flow with dispersion + continuous stirred-tank reactor, PFD + CSTR) was developed. Orthogonal tests revealed significant correlation between the model parameters, and the original models were optimized via linear substitution of parameters. The improved PFD + CSTR solute transport model exhibited a satisfactory fit with the original model, and the average relative errors of the determination coefficient (R) and correlation coefficient were <5%. The multiple linear regressions between the hydraulic indicators and model parameters were reconstructed and exhibited consistent structures between different stages. The degradation constant k between the original and improved models exhibited high consistency (R = 0.982). Conclusively, the improved models exhibited good consistency with the original models and allowed rapid and accurate performance evaluation.