Adapting P-k-C* Model in Mediterranean Climate for Organic Removal Performance in Horizontal Treatment Wetlands

The P-k-C* is considered as the most suitable in modeling treatment wetland (TW) performance providing a good compromise between accuracy and computational simplicity to assess the degradation processes for selected pollutants. However, there is a need to test the model in different climate conditions due to its high sensitivity to temperature. This study aims at demonstrating the applicability of P-k-C* model to describe the response of horizontal TWs (H-TWs) for domestic and agro-industrial wastewater treatment, and evaluating key design parameters for the model optimization in Mediterranean semi-arid conditions. In particular, kA20 (m year−1) and θ values were assessed in two H-TWs in Eastern Sicily, characterized by different organic loads and hydraulic and design features. The model was evaluated for simulating BOD5 and COD effluent concentrations at the outlet of the H-TW units. Calibration parameters, kA20 and θ, were found by summing and minimizing the squared differences between measured and modeled data, obtained by simultaneous adjustment of kA20 and θ for all samples (25 < n < 27). The coefficient of determination, R2, the Nash–Sutcliffe efficiency, NSE, and the root mean square error, RMSE, were used as statistical performance measures. Results showed a good reliability of the model to describe water quality response in terms of BOD5 and COD effluent concentrations. Most important finding was that a θ < 1 should be used from practitioners to optimize H-TW design in Mediterranean conditions.