Assessment of underground water quality in Okobo local government area of Akwa Ibom State, Nigeria

Abstract

The ground water quality of Okobo Local Government Area was investigated. Sixteen boreholes (BHs) water samples were collected from four zones (Okopedi, Ekeya, Ukwong and Okiuso) in Okobo. Standard analytical procedures were used to analyze the physicochemical, bacteriological and heavy metal parameters in the water samples and the results compared to Nigerian standard for drinking water quality (NSDWQ). some physicochemical parameters investigated were within the acceptable limits set by NSDWQ except pH (5.99 ± 0.37), DO (0.31 ± 0.06) mg/L, BOD5 (6.26 ± 0.4) mg/L and Nitrate (62.53 ± 5.96) mg/L. Bacteriological parameter like fecal coliform (128.69 ± 31.40) MPN/100 mL and total coliform (287.63 ± 40.31) MPN/100 mL were also above the limits set by NSDWQ implying organic pollution due to fecal contamination. Heavy metals were also within the acceptable limit except Lead (0.1 ± 0.1) mg/L, Chromium (0.4 ± 0.2) mg/L, and Manganese (0.16 ± 0.2) mg/L which were slightly above acceptable limits in all the zones. Water quality index calculation results grouped the BHs into; BH7 (26–50) very good; BH1, BH3, BH4, BH8, BH11, BH14, and BH16 (51–75) poor; BH2, BH5, BH6, BH9, BH12, BH13 and BH15 (76–100) very poor and BH 10(> 100) unsuitable for drinking. Pearson coefficient correlation, principal component analysis (PCA) and cluster analysis (CA) were used to establish interrelationship among the parameters, common sources of the pollutants and grouping of the BHs affected by these pollutants. PCA extracted six principal components (PCs) from the investigated parameters in the BHs, with sources of pollution either natural mineral or anthropogenic source. CA grouped all the sixteen BHs investigated into three clusters with various levels of contamination from pollutant sources. Consequently, the polluted BHs require treatment using high test hypochlorite (HTH) as the pollutant common to all the BHs is mostly bacterial pollutant; moreover, BHs should be sited 15 m away from septic tank or latrine to reduce contamination from coliform.