Since natural resources are limited, sustainable development concept provides biotechnology for their preservation. In this work, we are interested on application of titration for the determination of hidden concentration. Moreover, the method is reliable and proven with convincing results. In the same context, complexometry is the only traditional titrimetric process applied for the instantaneous and quantitative chemical analysis. By the way, total hardness of water index is often calculated from the sum of calcium and magnesium ions concentration. Noting that, hard water can cause many complications; scaling on water pipes, boilers, eczema. The study areas are located in the Northeast of Algeria (Souk Ahras City), it is made up of 26 municipalities, Mechroha is one of them.

The course of the assay begins with the filling of the graduated burette through the EDTA solution up to scale zero. 100 ml of mineral water to be analyzed is poured in the beaker and heated at 60 °C. At that time, 5 ml of buffer solution are added with 10 drops of NET. The starting color is purple, the EDTA solution is poured drop by drop until the color of the beaker solution changes abruptly (blue turn), then the equivalence of volume  is taken.