Simulation of water flow and solute transport in intermittent sand filter

Water and solute transport in intermittent sand filtration was simulated with a modified HYDRUS 1D program. Field trials were performed through a 10 × 10 m infiltration basin located at Dissa agriculture area in the north of Gabes city (south-east Tunisia). Performance of the calibrated model has been statistically evaluated for its ability to predict water flow and solute transport. Comparisons between measured and simulated water content resulted in R² and root mean square error (RMSE) average values of 0.88 and 0.74 cm³ cm⁻³ for the calibration period and of 0.86 and 0.78 cm³ cm⁻³ for the validation period, respectively. Predicted water quality parameters were found to be in best agreement with the measured results. On average, the model predicted COD and NH₄-N concentrations well, with a RMSE of 1.06 and 1.26 mg L⁻¹ respectively. However, it underestimated NO₃-N concentration. Similar corresponding values were computed for the validation period indicating that the model is able to predict water flow and solute transport with a reasonable degree of accuracy.