Evaluation of Treated Wastewater Quality Changes through the Vadose Zone

Abstract

Due to water challenges in arid and semi-arid regions including water scarcity and increasing demands, wastewater reuse in irrigation is becoming more widely practiced. This paper presents a case study for Sadat City, Egypt, to assess the impacts of using treated wastewater (TWW) in irrigation on soil and evaluating the natural attenuation of the TWW in the vadose zone. A field and laboratory program was conducted to identify the hydraulic properties of the soil and the contaminant concentration in water and soil. Water flow and solute transport are simulated in the vadose zone using HYDRUS 1D for five soil profiles in the study area through 50 years from 1992 to 2042. Six contaminants of concern were selected to simulate (Mg, Cl, Fe, NH₃, NO₃ and Fecal Coliform to study the bio-clogging effect on the soil). Six irrigation scenarios were selected to simulate flow and transport according to thewastewater treatment (primary, secondary, oxidation pond, tertiary treated wastewater, tertiary for double field water duty and irrigation with two year rotation(primary treated wastewater and groundwater)). The results show the concentration of contaminants of concern which will reach to groundwater aquifer after the purification and soil leaching.The results indicate that the concentrations of contaminants of concern were affected sensitively by the initial concentration of soil columns.

Keywords: Wastewater, groundwater, vadose zone, HYDRUS 1D