The state of water quality in Nairobi River, Kenya

Abstract

The contribution explores the most serious problem experienced globally as a consequence of environmental pollution mainly by inorganic, organic, and organometallic materials. This study was conducted to assess the physical chemical characteristics and heavy metal content in a section of Nairobi River which passes through various residential facilities. Water samples were taken twice during the dry season (June 2013) and twice during the wet season (November 2013). The water temperature, pH, dissolved oxygen (DO) and total dissolved solids (TDS) were measured in situ. Determination of heavy metals (Pb, Cu, Mn, Fe, Zn and Cr) was carried out using spectroscopic techniques whereas incubation, reactor digestion, gravimetric, amino acid, sulfaver 4, diazotization and titration methods were used to determine the levels of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), Phosphate, sulphate, nitrite, flourides and chlorides respectively. The range observed for pH, temperature, DO, TDS, COD, BOD, TSS, EC, sulphate, fluoride, chloride, nitrite, phosphate, iron, manganese, copper, zinc, lead and chromium was 6.89–7.77, 18.3–25.0°C, 8.10–24.29 mg/L, 176–438 mg/L, 40–730 mg/L,10.93–25.26 mg/L, 131–414 mg/L, 348–881μS/cm, 0–68 mg/L, 0.39–2.87 mg/L, 0.0142–0.886 mg/L, 0.002–0.55 mg/L,0.03–5.96 mg/L, 0.0974–3.1438 mg/L, 0.0092–3.6843 mg/L, < 0.010.1799 mg/L,<0.005–0.0197 mg/L, < 0.05–0.4415 mg/L and < 0.02–0.0846 mg/L respectively. The concentrations of cations and anions were found to be heavily dependent on the various activities taking place along the river with some pollutant concentrations being higher than the recommended WHO levels. Whereas industries have regulations for the content of the effluent, the residential units do not. It is recommended that residential units are advised not to discharge raw sewage directly into the river in order to minimize aquatic and environmental pollution that may be detrimental to natural ecosystems.