The aim of this work is the performance study of the various stages of groundwater treatment in a pharmaceutical industry. We were particularly interested in the influence of the reverse osmosis on the data processing sequence. The water quality was evaluated in terms of conductivity; the performances of RO treatment were evaluated in terms of rejection of different species in the groundwater. Also, fouling potential of groundwater was investigated. Results indicate that the reverse osmosis process is well adapted for this treatment; the retention is more than 99% for the totality of solutes. The conductivity of water to be treated decreases by 1770 mu s/cm to 15 mu s/cm. To be in agreement with the standards of pharmaceutical industry, a deionizer placed at the exit of the osmosor allows decreasing the conductivity down to 0.5 mu s/cm.