Soil Aquifer Treatment (SAT) – is a suitable technology for tertiary treatment of waste water. Principal aim is to reuse the water as a source for groundwater recharge and irrigation in agriculture. One example of a large and efficient SAT – system is the Shafdan – SAT site in Israel, south of Tel Aviv. It performs an advanced treatment with effluents coming from the Shafdan waster water treatment plant. These effluents are periodically infiltrated into several basins, follow a flow path through (app. 40 m) vadose soil zone, until reaching the groundwater table. Recovery wells surround the infiltration areas in distances of 500 m – 1.000 m and extract the water after its passage through unsaturated zone and aquifer. The recovered water is pumped to the irrigation facilities at several agricultural sites. During its way through the soil and aquifer the water quality is improved in a variety of ways: DOC is reduced by an order of magnitude, an extensive nitrification process takes place, micropollutants become significantly reduced or disappear completely. Research tasks in the project focused mainly on clarifications, which important processes take part in what extent in the upper soil / sediment layer during percolation and further treatment of infiltrated waste water. Extensive “out door” observations and sampling of seepage water in the subsurface soil at field sites are often practically limited or impossible. As a result we constructed a large scale column facility, which can simulate the conditions of SAT very close to the field site’s reality. Moreover the column facility provided the advantages of a wider range and flexibility for testing variations of operational conditions.