IRON AND MANGANESE IN GROUNDWATER AND THEIR IMPACT ON STRUCTURES:CASE OF A FEW LOCALITIES IN THE TAHOUA REGION (NIGER)

In Niger, some localities in the Tahoua region, groundwater is the main source of drinking water for the population. However, these waters are very loaded with Fe (II) and Mn (II), respectively exceeding the standard set by the WHO (0.3 mg / L and 0.1 mg / L). When these waters are in contact with the oxygen in the air, this degrades their aesthetic and organoleptic quality, but also that of structures and pipes. The objective of this study is to take stock of the presence of iron and manganese in water and their impact on the structures, which may justify the need for the creation of a treatment unit for their removal. Sampling was carried out at the level of the four localities. The pH was measured at the sites, total iron and manganese (II) are measured in the laboratory by colorimetry using a DR3900. The results show that in all the boreholes sampled, the concentration of total Fe varies from 1.231 mg / L to 6.295 mg / L, and that of Mn (II) from 0 mg / L to 0.97 mg / L. All of the structures and pipes that carry this water are completely damaged or blocked by a ferric deposit, identified by the DRX as a very poorly crystallized 2-Line ferrihydrite.