Using natural zeolite for contamination reduction of agricultural soil irrigated with treated urban wastewater

Nowadays, due to the global water crisis, reusing treated wastewater is being considered as water resources for different purposes, particularly for agricultural applications. Irrigating soil using urban wastewaters which are not treated properly, however, has negative effect on the soil and its subsequent drained water. Because of that, selective adsorption properties of the natural zeolite were used to improve filtering properties of the soil irrigated with wastewater. The effects of application method, dosage, and particle size of natural zeolite were studied on the EC, pH, BOD5, Na+, Ca2++Mg2+, and nitrate concentration of an urban wastewater by passing it through zeolite-added soil columns. The result shows that by adding zeolite to the soil column, the value of pH, EC, and Na+ of the column outlet were increased, while its Ca2++Mg2+, nitrate concentration, as well as the BOD5 were decreased. BOD5 level of the column effluent in the control, mixed, and layered treated soil with zeolite were lower than BOD5 of used fresh wastewater by 38.42, 54.98, and 71.84%, respectively. However, the nitrate concentration of the column effluent in the control, mixed, and layered treated soil with zeolite were lower than the nitrate content of the fresh wastewater by 12.18, 32.19, and 54.90%, respectively. It can be concluded that application of the natural zeolite into the soil in a layered treatment does more effectively reduce the pollutant transferred to the soil-depth and consequently can improve the quality of drainage water.