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In urban environment, the increase in population generates considerable quantities of waste water which is treated in the purification plants to specialize or reject directly without control in the courts of water case of Bechar river. Because of their various origins (domestic rejections), this water is generally charged in organic, mineral elements and in micro-organisms of which some could be harmful with health and strongly takes part in the degradation of the tablecloths which could be irreversible.

The town of Bechar (Southern Algerian West) which is in an arid Saharan area, knows like all the Algerian cities of the problems of surface and underground pollution the waters, whose main causes are: the discharge of waste water in nature without purification and the absence of the systems of purification and depollution of waste water. The present study is undertaken on the course of Bechar River, carried out in April 2011 revealing a polluting load: (Nitrate 7.94 mg/l, Nitrite 0.6 mg/l, Ammonium 26.60 mg/l, NTK 62.18 mg/l).

In April 2011, of samplings of waste water noted Wi were realized according to the recommendations of WHO. The choice of the sites was fixed according to the direction of flow. The results obtained according to the study analyzes physic-chemical samples of the rejections testify in their majority that a contamination of subterranean water of the tablecloths by waste water of the river according to a process of infiltration which depends on several environmental and climatic factors is extremely probable and which an urban treatment of the rejections is paramount to protect the tablecloth and the ecosystem.