Physicochemical quality, potentially toxic elements characterization and toxicological risk assessment of industrial effluents in Iju River, Ogun State, Nigeria

Abstract

The study aimed to determine the physicochemical quality, concentration of potentially toxic elements (PTEs) and potential health risks of exposure to industrial effluents in the Iju River. Composite water samples were collected from six stations (effluent before treatment, point of treatment, effluent after treatment, point of discharge, 50 m and 100 m downstream), of the river. Temperature and pH were tested in situ, then the sample was transported to the laboratory for analysis. The physicochemical quality of the samples was carried out using standard methods. PTE levels were estimated using an Atomic Absorption Spectrometer (AAS). The study showed a high concentration of pH (6.45 and 8.89) and turbidity (1.00 - 11.0 NTU) in the effluent before treatment, at the point of treatment and 50 m downstream. Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) were high in all sampling stations (7.54, 89.4, 95.2, 95.1, 85.2, 60.5 mg/L and 95.4, 111, 125, 121, 106, 85.5 mg/L) while dissolved oxygen (DO) was low (2.22, 2.54, 3.25, 4.52, 4.98, 7.56 mg/L) across stations compared to the WHO standards (20.0mg/L, 50.0 mg/L and 13.0-14.0 mg/L) for BOD, COD and DO respectively. The obvious similarity between BOD, COD and DO might be due to the presence of a high level of organic or inorganic matter which is oxygen-demanding. Interestingly, this could be linked to anthropogenic activities. Fe concentration in the stations (except 100 m downstream), and the concentration of Cd at the point of treatment and 50 m downstream were higher (0.004 and 0.005 mg/L) than the WHO standard (0.003 mg/L). Health risk assessment showed that all studied PTEs at the time of investigation have a non-significant hazard effect on exposure. Therefore, the effluent is polluted with organic, inorganic materials, and Cd, and Fe at some of the stations.