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

Abstract

Irrigation with treated wastewater was carried out in an experimental site in Castellón (eastern part os Spain). By using water soil samplers at differen depths some physico-chemical parameters (conductivity, pH, major ions, nitrogen species, BOD, COD, and organic matter) were controlled to identify the processes affecting the self-cleaning power of the vadose zone. Modeling of these processes has been carried out by means of the NET-PATH software. two intervals have been considered, the first one from 15 to 180 cm in depth and the second one from 180 a 240 cm, in which ionic exchange processes affecting Na+, Ca2+, Mg2+, and K+, calcete precipitation, and dolomite and gypsum dissolution are active. The main differences between the intervals are modifications of CO2 interchange and the behavior of sodium. As result of the synergic effect of different processes involved there is a good level of purifiction.