Assessment of water pollution and risks to surface and groundwater resources in Bamako, Mali

Abstract

ABSTRACT: Due to the lack of research on wastewater quality in Mali, a specific monitoring campaign focusing on both chemical pollution (trace elements, heavy metals, nitrates, ammonium) and biological pollution in the cities of Bamako and Koulikoro and the Bani agricultural region was undertaken. Monitoring the water quality of 18 vulnerable areas in the BamakoKoulikoro metropolitan area shows that all of them exceeded the WHO standard for wastewater effluent without surface water treatment on at least three parameters. Parameters requiring priority actions are BOD5, COD, SS and heavy metals. It is further concluded that the run-off is not a significant source of contamination by heavy metals. Rainfall events cause significant volumetric variation, which places the treatment works under stress, particularly in the correction of BOD5 and COD (the main parameters of biological purification). Consequently, an essential intervention would be to separate wastewater sewer networks from the run-off collection system. Finally, the priority is to regulate industrial effluents by imposing treatment and water quality controls on the industries, such as the power plant of Daar-Salam. As for the rest of the Niger River valley, no major risk of water pollution yet exists, thanks to the low rates of population growth and urbanisation. As shown by the water quality monitoring specific anthropogenic pollution problems are regularly observed. Thus water pollution is actually a problem related more to education than it is a technical problem of protecting water resources. However, the very fast population growth, associated with increases in waste production and the development of the Bamako-Koulikoro urban area, will severely worsen the situation. In the short term, if no measures are adopted to treat the effluents, all the water resources could be contaminated. In the near future, industrial effluent must be efficiently controlled and the population educated on the problems and hazards of water pollution. Finally, instead of exploiting the deep aquifer, it seems more profitable to urgently improve the existing infrastructures already in place in terms of water resources, and to develop wastewater treatment facilities. This would ensure that the current resource can be used in the longer term.