Physico-chemical processes in a vadose zone during the infiltration of treated wastewater used for irrigation: application of the NETPATH model

Irrigation with treated wastewater was carried out in an experimental site in Castellon (eastern part of Spain). By using water soil samplers at diffe rent depths some physico-chemical parameters (conductivity, pH, major ions, nitrogen species, BOD, COD, and organic matter) were controlled to identif y the processes affecting the self-cleaning power of the vadose zone. Model ing of these processes has been carried out by means of the NET-PATH softwa re. Two intervals have been considered, the first one from 15 to 180 cm in depth and the second one from 180 to 240 cm, in which ionic exchange proces ses affecting Na+, Ca2+, Mg2+, and K+, calcite precipitation, and dolomite and gypsum dissolution are active. The main differences between the interva ls are modifications of CO2 interchange and the behavior of sodium. As a re sult of the synergic effect of different processes involved there is a good level of purification.