The effluents from the water treatment station of REGIDESO located in Kingabwa (Kinshasa city) are accused of reducing aquatic biodiversity of Matete and N'djili rivers and are responsible of some human diseases. The effects of these effluents on the physico-chemical and biological quality of water of Matete and N’djili rivers were evaluated. The benthic macro-invertebrates and Gambusia affinis were used as biodiversity richness indicator and model system for toxicity assays. The analyses of physicochemical parameters revealed a constant temperature in the stations studied (± 25 °C) and a high value of conductivity in the sites near the effluents discharge location. On the whole of the sites, the bacterial load was reduced to the neighboring sites of the effluents discharge. The pH is slightly acidic depending on the period and the sampling sites. Dissolved oxygen decreases as sampling seasons. 1405 specimens of benthic macro-invertebrates including 499 in the rainy season and 906 in dry season were harvested. The Shannon index value ranges from 0.4 to 2.9 during rainy season and 1.7 to 2.9 during dry season, reflecting the passage of polluted water to moderately pollute in rain season and moderately polluted to slightly pollute in the dry season. The toxicity bioassay revealed that these effluents are toxic (LC50= 0.109%). It is thus desirable to install a monitoring system near of the station of water purification of the REGIDESO N’djili in order to regularly control the dangerosity of the effluents poured in the surrounding watery ecosystems.

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.