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.
This study aims to improve knowledge on discharges of industrial effluents and their effects on receiving waters. It focuses on the analysis of physicochemical parameters (pH, temperature, COD, BOD5 and SS). Water samples were taken at three industries (cosmetics, pharmaceutical and brewing) in the city of Kinshasa. The results showed high levels for the parameters measured in the majority of the stations. In addition to pH and temperature, the contents of COD, BOD5 and SS of the effluent is much higher than the limit values set by WHO for industrial discharges to receiving waters. This could be major health risks for the population of the study area.
Among the waste treatment methods, anaerobic digestion is an attractive option for the degradation of fermentable household wastes into useful products such as biogas and high quality compost. Therefore, we conducted a comparative experimental study between the anaerobic digestion of fermentable household waste and anaerobic co-digestion of fermentable household waste and septic tank sludge. The experiment was conducted in two tanks of 80 liters. The first tank was filled only with 14 kg of biodegradable household waste and the second was filled with 14 kg of household waste mixed with 4.2 L fresh septic tank sludge in a ratio Volatile Suspended Solids (VSS) of septic tank sludge on Volatile Organic Matter of waste (=MOV) (VSS / MOV = 0.3). The evolution of the COD yields a balance on the degradation of organic matter and biogas production. Anaerobic digestion and anaerobic co-digestion took place at a temperature of 25C° in two stages so that the first step in a 80 L tank, stops at acidogenesis and that the second step (methanogenesis) takes place in another 10 L digester. The results yield that 1.3Nm3 methane are produced from the anaerobic digestion of waste and 1.8 Nm3 methane are produced from co-digestion of waste and faecal sludge.