STUDY OF THE VULNERABILITY OF WATER CAPTURED IN DRILLING EQUIPMENT INSTALLED IN WET AND POLLUTED AREAS

This study deals with the vulnerability and risks of groundwater pollution from drilling equipment installed in four districts of Brazzaville, namely; Poto-Poto, Moungali, Ouenzé and Talangaï. This equipment is subject to a humid and relatively polluted soil environment. A statistical study was conducted in the selected study area. This shows that several households (72%) claim not to have carried out hydrogeological studies before the installation of their boreholes, and also that they express their distrust of the potability of these waters (74%). Physicochemical analyzes of the samples taken from 27 selected sites (drilling) were carried out in order to characterize these waters. These analyzes covered thirteen (13) parameters including: hydrogen potential (pH), redox potential (PR), temperature T, total dissolved solids (TDS), electrical conductivity (EC), total iron (Fetot), dissolved oxygen (O2dis.), Nitrates (NO3 - ), chlorides (Cl- ), phosphates (PO4 3- ), complete total alkalinity (TAC), total hardness (THt), bicarbonate ions (HCO3 - ). The application of the ascending hierarchical classification (AHC) has made it possible to identify the relevant parameters describing the quality of this groundwater, to show the spatial variability, to group the boreholes homogeneously within the framework of a possible study of the follow-up temporal and spatial quality of groundwater. The results obtained confirm the doubt of certain populations because they have shown that of the 27 selected sites, only two drilling show an acceptable mineralization. Thus, the reliability of all the drilling installed in these areas is questioned.