SUMMARY
The aim of this study is interested in the influence of clay addition to the coagulation-flocculation process of Djorf-Torba’s water dam situated near Bechar region (South West Algeria).The Jar test trials with aluminum sulphate were conducted on the raw water using lime adjuvant and clay. The operations of floculation-coagulation process were conducted with lime alone, lime +clay (Maghnia clay and Oued Khodir clay) and add clay without lime. The results show that the turbidity value of raw water was decreased with amount of clay adjuvant used alone. Indeed, the obtained results showed that the addition of clay doses in interval 7 - 9 mg/l give significant reductions of turbidity. However, the best amount of clay is 7 mg/l and the yield calculated at this concentration is equal at 96 %, highest value, then it is only 95.3% in the presence of lime alone.