It was recommended to use the sand dune of N'Goussa region (Ouargla) that has fine grain, uniform, slightly salty, poor in organic matter and alkaline pH with a low lime content, which gives good results in the field of biological filtration at the pilot scale; was chosen as a site for our investigations after washing with distilled water to minimize the maximum chemical properties.
This work was a continuation of the previous series of comparative studies on this material and it has been adapted for purification by slow filtration[9].
The table 2 shown the difference between the N'Goussa sand naturally and washed N'Goussa sand