The bioaccumulation of four heavy metals (Zn, Pb, Cu and Cd) in Clarias gariepinus (Burchell, 1822), Chrysichthys nigrodigitatus (Lacepède, 1803), Mormyrops anguilloides (Linnaeus, 1758) and Coptodon rendalli (Boulenger, 1897) fluently fished and sold in Kingabwa district (Kinshasa, Democratic Republic of the Congo). At first, the results of physico-chemical analysis of water of inspected sites (2) revealed that the values of pH and temperature are in the standards as recommended by WHO and FAO, while the conductivity as well as the dissolved total solids in inspected sites are very weak.. Yet, the two sites are polluted by heavy metals. Secondly, the dosage of heavy metals by atomic absorption spectrometry revealed that all tested fish are polluted. However, the Cadmium has not been detected in the muscles of three fish: Clarias gariepinus, Coptodon rendalli and Mormyrops anguloides. Meanwhile, Coptodon rendalli species didn't reveal any presence of Lead in its muscles. The results obtained show that the consumption of these fish can represent a health risk for the exposed populations notably fishers and their family who consume these fish at least once per day. Thus, by formulating the hypothesis that the fisher or his family is the more exposed and while increasing the quantity of fish for example from 0.025 kg/j to 0.5 kg/j, we can note that the coefficient of danger is superior to 1 for the cadmium and then the danger becomes apparent. It is therefore desirable that the Democratic Republic of the Congo authorities can develop a better policy for the management of the interior waters in order to avoid possible health problems linked to the pollutions of these waters.

The access to safe water remains a serious major concern in Africa particularly in rural areas. The aim of this study was to assess the efficiency of pond water treatment consumed by plateau de Batéké population in Bita village using Moringa oleifera seed powder and Vetivera zizanoides root powder. Pond water samples were treated with different concentrations of M. oleifera seeds and V. zizanoides roots as a bio-coagulant. The measurement of physico-chemical parameters in the course of time has permitted to determine the optimum conditions and to evaluate the treatment efficacy. Results revealed that Moringa oleifera seeds are more efficient than Vetivera zizanoides roots. This activity is dose dependent. After one day post-treatment, the rate of turbidity reduction is 93.53% at the concentration of 1.818 g/l. Also, the treatments allowed the reduction of nitrates and nitrites in treated pond water. These results indicate that M. oleifera improve considerably physic-chemical quality of treated pond water. Thus, this approach is ecological and respectful of the environment. It is inexpensive, simple and beneficial for the populations of the rural zones. Moreover, M. oleifera is a plant species particularly easy to cultivate in an intensive way and is adapted to the tropical climate of Africa.