The presence of MtBE in groundwaters, due to its past use as an oxygenate additive to "green" gasoline, poses potential threats to human health as a possible carcinogen. As its chemical properties render it very mobile and poorly treatable by means of bioremediation, chemical oxidation, stripping, or carbon adsorption, a new, ex-situ treatment process was recently developed by the US EPA and the University of Cincinnati. The objective of the study was to evaluate the effectiveness of this pump-and-treat technology in actual contaminated groundwater plumes in the field in two different conditions. The technology based on the combination of aerobic degradation and a special filtration medium is simple to operate, easily meets the challenge of producing a highly polished effluent in a cost-effective fashion, compared to other processes.