Hospital worn water of the University Private clinics of Kinshasa (Democratic Republic of Congo) was evaluated for ecotoxicological tests. The physicochemical parameters of the effluents of the university private clinics of Kinshasa taken in situ and ex situ test a variation active either with the rise for some, or with the fall for others. On the ecotoxicological level, worn water of the university private clinics has a toxicity against the species halieutics such is the concrete cases Gambusia affinis which were useful to us like indicator of toxicity of these effluents .On the four sites of taking away, it was noted that the rate of survivors decreased of a site with another. The rough concentrations (100ml) of the effluents did not grant less chance to the individuals to survive. The effluents are toxic with a lethal concentration going from 52ml to 100ml. After a test of treatment in UASB of the whole of the effluents of the university private clinics obtained at the various outlets, the effluent has a very low toxicity at the populations of Gambusia affinis. After treatment, this effluent is toxic with a lethal concentration around 100ml.

We proposed to undertake an experimental study on the combined toxicity of Lead and Cadmium in aquatic environment, for describing well the danger which run the alive beings which live there and on which the life depends on it. To achieve our goal, we used as biological material Gambusia affinis, a species sensitive to toxicity in order to check if the combined effects of heavy metals in fact Plomb and Cadmium would be the cause of disturbance in aquatic environment. We proceeded to test each salt individually and to determine the CL50 of them;then, to prepare a solution combined with the concentrations corresponding to the value of ½ CL50 of these two salts tested according to méthode(5). Taking into consideration these results obtained, the constant following is released:The Cadmium tested with the concentration of 0,1 G and its dilutions, is very toxic with a CL50 around 0,003 Mg that the solutions of Lead to the same concentration with a CL50 around 0,006 Mg. The biological tests of laboratory made it possible to prove the toxicity of each salt separately and to confirm the combined toxicity of these two heavy metals, owing to the fact that the combination of their ½ CL50 gives synergistic effects to the populations of Gambusia affinis. This study will precisely allow the scientific community, to the industrialists, and the government to manage our environment well, in order to especially avoid the danger due to the pollution with heavy metals which constitutes today a plague threatening the species of the aquatic environment, water, and the life of the human beings in general, in the mine fields of the DRC being a significant mining country.