Assessment of the water quality of lake kongo and rivers in the surroundings of sugar cane plantations in the city of nkayi (republic of Congo)

Background: This article focuses on the assessment of the water quality of Lake Kongo and rivers in the vicinity of the sugar cane plantations in Nkayi in the Republic of Congo. Objective: The physico-chemical study is based on the determination of the contents of the various parameters. The samples taken in the field were subjected to physico-chemical analyzes. The levels were determined by several methods: in situ and in the laboratory. Methods: The results of the chemical analyzes were processed by hydrochemical and statistical methods. Results: The organoleptic parameters reveal contents of the wastewater higher than the WHO standards (MES: 591 mg / l, turbidity: 806.5 NTU in the rainy season and MES: 469 mg / l, turbidity: 463.98 NTU in season dried). The physico-chemical parameters also show levels higher than WHO standards for certain rivers such as Louadi (bicarbonates: 235.5 mg / l), Livouba (calcium: 89.83 mg / l) in the dry season. The pH is basic, greater than 7, only the wastewater gives an acidic pH with 6.09 in the dry season and 6.4 in the rainy season. Regarding undesirable substances, nitrates have levels higher than WHO standards: 67.59 mg / l for Lake Kongo and 72.6 mg / l for the Mintouyou river in the dry season, 51.59 mg / l for wastewater and 55.38 mg / l for the Louadi river in the rainy season. Conclusion: The mineralization of water is mainly caused by the phenomena of dissolution and precipitation of minerals (calcite, dolomite, anhydrite, gypsum and halite). The results obtained by the PCA indicate that the variables which control the salinization of water are Ca2+, Mg2+, Al3+, HCO3-, SO42- and K+. Most of these waters are polluted by a permanent source of pollution which remains to be determined in the future.