Within this project, which was funded by the German Ministry of Education and Research (BMBF), a model illustrating the mechanisms of sulfonate adsorption onto activated carbon was developed. For this, the structural character of the sulfonates having a nonpolar aromatic part and ionic sulfonate groups had to be considered. It turned out that besides the usually dominating van-der-Waals interactions electrostatic interactions occur as well. In the second part of the project a pilot-scale GAC adsorber was operated with a groundwater spiked with five selected sulfonates at practical concentrations. The experimental breakthrough data was compared to the results of a series of rapid small-scale column tests (RSSCTs) and to mathematical model predictions.