**3. Extensive processes in the Algerian Sahara**

Groundwater is the main source of water in the Algerian Sahara; the preservation of this precious resource from all types of pollution is essential; to this end, the treatment of wastewater in the Algerian Sahara is a requirement and an inescapable social and environmental issue. The extensive process is used in most of the Saharan areas, it is ecological insofar as it does not use any chemical product to treat wastewater and evacuate it safely to the receiving natural environment [5].

We noted more than 90% of the planned purification stations in the Algerian Sahara have extensive processes, the extensive solutions characterized with a large area and totally or partially dependence on natural purification processes in which the concentration of purifying organisms is low [6]. They do not involve recycling of bacterial liquor. Among these processes we note: lagooning and spreading. They bring into play complex natural self-purification phenomena dependent on climatic conditions. These extensive solutions require large footprint areas, implementation is essential and the quality of construction depends in part on the purification performance. They generally require little electromechanical equipment and are known for their hardiness and ability to adapt to variations in organic and hydraulic loads [7].
