This work aims to study coagulation process for hard Ghrib Dam (GD) water treatment. Conventional coagulation (CC), enhanced coagulation (EC) and alkaline coagulation (AC) experiments were realized on jar tests. This study demonstrated the effectiveness of GD water treatment by the EC process compared to CC. Indeed, by CC, it has been demonstrated that each of the two coagulants studied (alum and FeCl 3 ) is effective for remarkable reductions in OM of 36% and 47.4%, respectively. However, EC, by slightly acidifying water, gave better removal efficiencies of the studied parameters. Indeed, the best abatement of OM is about 78% when water is treated with ferric chloride at pH 5.5, lowered with nitric acid. The observed disadvantage here is the residual nitrate, which existed in the raw water at only low level. On the other hand, at the same pH, the reduction of the OM is 64% when alum is used as coagulant. In addition, the data collected have led to the conclusion that the physicochemical quality of the GD water has a high salinity and lowering its pH (EC) does not affect it at all. On the other hand, its pH elevation (AC) considerably reduces its total hardness which is 41% with NaOH. Such a performance advantageously positions this total hardness reduction technology among the possible solutions to the problems associated with total hardness.