Column experiments were designed in order to establish stable redox conditions especially iron and sulphate reduction. The columns were filled with a mixture of quartz sand and 0.01 %wt. ferric oxides. An artificial groundwater spiked with nutrients was streamed through the columns continuously. The microbial activity was enhanced by inoculation with soil extracts. After a several weeks the formation of redox zones in a dynamic equilibrium could be observed indicated by the development of redox-specific parameters along the flowpath. Chromium(VI) (0.05 mmol/l) was added to the water after sulphate reduction was observed in the column. The eluent was sampled in distinct time intervals over a period of six months and the breakthrough of Chromium was detected. The mobility of Chromium was dependent on a redox reaction with hexavalent Chromium and
divalent Iron and the precipitation of Chromium(III)hydroxides. The reaction with Fe(II) from the solid phases dominated the first part of the experiment. The Iron reduced continuously by micro-organisms was utilized to reduce Chromium(VI) in a
secound phase of the experiment. The concentration of Chromium in the eluent was less than the primary concentration during the whole experiment.