Israel lies in an arid region with water shortage. An essential demand for this country is a high percentage of reused waters to cover water demand and protect water resources. Due to the water deficiency a lot of measures have been taken to ensure the water supply. Soil Aquifer Treatment (SAT) on Shafdan site near Tel Aviv is characterised by highly variable hydraulic conditions in the soil due to temporary infiltration of spreaded water. Pretreated wastewater flows in dry-wet cycles in several basins, which are filled
within approx. 1 day. The water in the basins drains away within 12 hours and therefore the water content and moisture tension in the subsurface vary in dependency of the flooding intervals. During percolation, dissolved organic carbon (DOC) is diminished by 90%. The processes responsible for this enormous elimination are still widely unknown. Possibly the aerobic biodegradation could play a role but the proof is lacking. Many parameters of the soil water (redox potential, oxygen concentration, etc.) are
usually influenced by the actual hydraulic conditions in the soil. However, no continuous physical or chemical analyses of Shafdan soil water have been available so far, due to the lack of a sampling technology. Therefore, a sampling procedure was developed in a unique 6 m laboratory column, which allows a representative sampling. The column was filled with soil from Shafdan site. It consists of 6 equal modules (1 m long each). Two samplers (suction probes) were installed in each module of the soil column (= 12 probes). Additionally, tensiometers installed nearly in the same layer can determine current moisture tensions. The resulting values are used for steering the vacuum at the suction probes. The preselected pressure difference between current soil tension value and vacuum pressure at the probes enables constant soil water sampling during all phases of percolating water plume and variable soil water contents. This new method will allow representative sampling in different soil levels and thus help understanding the processes occurring in the subsurface.