Groundwater Quality Assessment in Crude Oil-Impacted Communities in Ogoniland in the Niger Delta Using the Water Quality Index (WQI)

Abstract

Crude oil pollution has resulted in severe groundwater pollution in Ogoniland in the Niger Delta. There are indications that groundwater pollution extends beyond pollution sites, justifying the need for this comprehensive groundwater quality study. This study assessed the groundwater quality in crude oil-impacted communities in Ogoniland in the Niger Delta using the Water Quality Index (WQI). Forty-two groundwater samples were collected from fourteen wells in Ogoniland and analyzed using standard methods. The physical and chemical water quality parameters which include temperature, electrical conductivity (EC), turbidity, total dissolved solids (TDS), pH, total alkalinity, hardness, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate, sulphate, phosphate, chloride, heavy and essential metals were determined. Total coliform counts were determined using the standard microbiological pollution indicators assessment method. The overall quality of the groundwater samples and their suitability for human consumption were determined using the weighted arithmetic WQI. Nemerow Pollution Index (NPI) was used to identify the polluting parameters in the groundwater. The results obtained showed that the studied groundwater had physical, chemical and microbial contaminations. The WQI results were above 100 (Class E) for all the samples and ranged from 282.76 in S9 to 467.29 in S3, indicating that all the studied samples were unsuitable for drinking. NPI results showed that the parameters that contributed most to the deteriorated groundwater status include turbidity, BOD, COD, phosphate, chloride, cadmium, iron, and total coliform bacterial load. Recommendations include detailed groundwater characterization in Ogoniland and an improved groundwater remediation approach that considers a combination of in-situ and ex-situ groundwater remediation options to ensure effective decontamination of polluted groundwater in Ogoniland.