Modeling of transport and transformation of synthetic wastewater in irrigated soils

Scarcity of fresh water has led to use of low quality waters that were considered unsuitable for irrigation in the past. Mismanagement of irrigation with wastewater poses risks to deterioration of the hydraulic soil properties and pollution of groundwater. In order to study these concerns, synthetic wastewater was poured on steady-state flux one-dimensional aerobic sand columns and the results were analyzed. Four irrigation treatments with different levels of chemical oxygen demand (COD) were performed as a randomized complete block design with three replicates. Soil water content, electrical conductivity, water potential, and hydraulic conductivities were monitored. The CXTFIT code was used to inversely determine degradation constant and the transport parameters of the convective–dispersive equation (CDE). In all treatments the hydraulic transport properties remained constant. Conversely, the first-order kinetics degradation constant decreased in an identical way for all COD treatments. It is also concluded that if a primary treatment removes the solids, which is essential for drip irrigation, domestic wastewater, similar to our synthetic water and without toxic or pathogen elements, poses few risks for groundwater pollution.