Evaluating the potential of treated municipal wastewater reuse in irrigation and groundwater recharge; 5-year contaminant transport modeling

The use of treated municipal wastewater in agricultural irrigation has become commonplace throughout the world for many years. So far, numerous research has been accomplished on the harms and benefits behind this work. This study was carried out in two parts to investigate the following issues: First, calculating 14 irrigation indices to ensure the appropriateness of using treated municipal wastewater in agricultural land irrigation, and second, conducting soil column experiments along with numerical modeling to predict contaminant transport in soil using HYDRUS-1D software and to investigate the possibility of using treated municipal wastewater in irrigation without harming groundwater resources. The results revealed that although most indices display the suitability of Wastewater for irrigation, some show the opposite. Accordingly, four indices of Magnesium Hazard (mean = 53.3%), Kelly’s Ratio (mean = 1.06 meq / L ), Corrosivity Ratio (mean = 2.3), and Total Hardness (mean = 245.8 mg / L ) are higher than the allowable limit of irrigation standards. Hence, wastewater reuse can cause problems concerning the physicochemical and microbial properties of soil as well as crop production. Finally, hydraulic conductivity ( K = 252.73 cm / day ), porosity ( Φ = 38%), saturated soil water content ( θ s = 0.27), bulk density ( ρ b = 1.81 g / cm 3 ), and longitudinal dispersivity ( D l = 14.81 m ) were given as input data to the model. The transport modeling determined that heavy metals’ mobility in the soil is as follows Ti > Mn > Al > Sb > Sn > Fe = V > Zr > Co . Thus, Ti and Co have the highest and lowest mobility, respectively. As a result, it can be said that Ti has the highest possibility of leaching and contaminating groundwater in the long run due to its high mobility.