Assessment of groundwater contamination by effluent discharged PAH at NNPC depot in Osisioma, Abia State, Nigeria

Abstract

This study evaluates the potential deleterious impact of untreated waste water discharged into an unlined pit by the Nigerian National Petroleum Company (NNPC) on the groundwater quality of Umuakpara community in Osisioma, Abia state. Its overarching objective is to assess potential contaminant sources, distribution in groundwater using diverse techniques. Water samples collected from 14 domestic wells in two contrasting seasons (Rainy and Dry) were analyzed for Polynuclear Aromatic Hydrocarbons (PAHs) using Gas chromatography (GC). Vertical Electric Sounding (VES) technique was employed to determine the depth to water table and soil lithological layers required for good understanding of contaminants behavior along groundwater flow path. Pearson product moment correlation coefficient (r) and One-way ANOVA were used to define the interactions of detected PAHs and spatial variation in means of the PAHs components (p < 0.05) respectively. Five (5) priority PAHs were found in groundwater samples which generally measured above the WHO (2011) maximum permissible limit for PAHs in drinking water (0.001 mg/l). However, the levels of individual PAHs in each borehole were found to be lower than the USEPA permissible limit for each PAH. Phenanthrene recorded the highest mean concentration of 0.011214 (0.00106 ± 0.01650) mg/l, while Fluoranthene had the lowest mean concentration between N.D (Not detected) − 0.00216 (0.0004060 ± 0.00027136) mg/l. Significant spatial variability of PAH existed across sampled boreholes whereas strong correlations were noted among the respective PAH components at P < 0.01. Findings ultimately informed the design of a novel Composite Filter for Treatment of Hydrocarbon Contaminated Waters.

Keywords

• Waste
• Groundwater
• Contamination
• Advection
• Polynuclear aromatic hydro carbons