State of Play on the Physicochemical Quality of Waters Stored in Concrete Tank Buried Under Wet and Polluted Soil: The Case of the City of Pointe-Noire (CONGO)

The problem of water supply from the public distribution network is still very acute in many cities in developing countries. The intermittent supply of water is forcing some households to build underground tanks of reinforced concrete to store domestic water. This work shows the problem of sustainability of water storage tanks made of concrete, in an aggressive environment but also especially the physicochemical quality of water stored in. The methodological approach chosen is based first of all on the physicochemical analysis of the water stored in these tanks. Indeed, the reliability of tanks, which reflected in their impermeability overlooked external environment, has a direct impact on the quality of stored water and therefore the use that is made daily. In this context, the results of the physicochemical measurements carried out, the comparison of the water coming out of the treatment plant of the National Water Distribution Company (SNDE), made it possible to highlight indices of pollution in the stored waters contained in the buried tanks.. Some samples of stored water, about 42.10%; which poses a public health problem. These results have clearly demonstrated the porous nature of the concrete chosen as the base material used for the construction of said tanks. Thus, anthropogenic pollution is evoked, which is confirmed by the high levels of physicochemical parameters measured in samples RE01, RE02, RE03, RE04, RE04, RE05, RE10, RE11 and RE12. In addition, 57.9% of these stored waters have low mineralization. These are acceptable as drinking water (RE06, RE07, RE08, RE09, RE13, RE14, RE15, RE16, RE17, RE18 and RE19). These waters identified as such must be subject to specific treatment and time monitoring. These results were obtained during dry season. During this period, there is drawdown of ground water. In rainy season, ground water is enhanced and exchanges are more important.