Wetting pattern in a hydrophobic soil produced by sewage sludge under 2D flow

Water repellency of soils is a property with significant consequences for agricultural water management, water infiltration, vertical soil-water transport, contaminant transport, and for soil erosion. It is caused by the presence of hydrophobic organic materials on soil grains and aggregate surfaces. Dry soil usually absorbs moisture but hydrophobic soil resists or reduces water infiltration into soil. Water repellency potentially affects wetting front and solutes transport in soil. This research was conducted in hydrophobic soils in order to investigate wetting pattern. The soil was collected from the region in the vicinity of sewage pilot of Fouladshar, Isfahan, Iran. Different amounts of urban sewage sludge including 25, 50, 65 and 80 weight percent were added to hydrophilic soil and S25%, S50%, S65% and S80% were obtained. After almost one year, soil water repellency was determined by using water drop penetration time method. In this procedure Three drops of distilled water from a standard medicine dropper are placed on the smoothed surface of a soil sample, and the time that elapses before the drops are absorbed is determined. In general, soil is considered to be water repellent if the WDPT exceeds 5 s. In this way the following classes were distinguished: wettable or non-water repellent (