Urban wastewater effects on water flow and solute transport in soils

This article aims mainly to verify the consequences of urban wastewater reuse in irrigation practices on hydrological behavior of soils. Herein the effects on both the hydraulic and dispersive properties of characteristic soils in South Sardinia are illustrated. The study was carried out at the Ente Autonomo del Flumendosa (EAF) laboratory. Ten undisturbed soil monoliths, 120 cm height and 40 cm diameter, were collected from plots, the locations of which were preliminarily individuated through a prior pedological study. An experimental facility was set up and sensors for monitoring both soil water and solute concentrations were inserted horizontally in each column at different depths. A disturbed layer at the soil surface, which expands in depth with time, was observed, characterized by reduced soil porosity, translation of pore size distribution towards narrower pores and consequent drastic decrease of permeability. It will be shown that these changes occurring in the disturbed soil layer, although local by nature, affect the mean hydrological behavior of the whole soil profile.