Over the recent years, activated carbons have been widely used as an active support for the treatment of wastewater. This importance comes from the possibility of making readily structural modifications leading particularly to the enhancement of both porosity and specific surface [5-8]. On the basis of such characteristics, it has attempted in this study to set up a bi-layer filtration bed made of activated carbon and sand dune. This pilot was developed essentially for the purification of domestic wastewater. The efficiency of the resulting filtrating system was assessed from the monitoring of the following parameters: acidity, conductivity, chemical and biochemical demand on oxygen (COD, BOD5).