Occurrence of Polycyclic Aromatic Hydrocarbons in Wastewater Effluents and Stream Water in Delta State, Nigeria

Abstract

Wastewater effluent derived from petrochemical and other industrial processes is one of the sources of polycyclic aromatic hydrocarbons (PAHs) in surface water. In the environment, PAHs may be persistent, bio accumulative and toxic, and are of concern, particularly, to human health. The occurrence of PAHs in industrial wastewater effluents and two streams in Delta State, Nigeria, was studied. The study was undertaken to determine the types and concentrations of PAHs occurring in effluents and stream water and the potential risks posed to the environment. In June 2016, effluent samples were collected from seven different wastewater treatment locations while water samples were obtained from Otu-jeremi and Evwreni Streams. The analytes in the samples were extracted by means of liquid-liquid extraction with a mixture of 1:1 hexane and methylene chloride. Gas chromatography-mass spectrometry was used in the chemical analysis of the extract for PAHs. The result indicated the occurrence of fourteen different PAHs in wastewater effluents with concentrations ranging from 0.002-0.108 mg/L. In stream water, the concentrations of the eleven PAHs detected ranged from 0.002-0.054 mg/L. Measured concentrations of PAHs in stream water were generally lower than those of wastewater effluent. However, concentrations of all the PAHs in stream water exceeded international drinking water quality standards. Levels of PAHs in stream waters above guideline values for drinking water imply potential risks to humans exposed to the waters.