Groundwater Quality Assessment of Boreholes in Onna Local Government Area, Akwa Ibom State, Nigeria

Abstract

The study assessed aspect of water quality of groundwater from different boreholes in Onna Local Government Area, Akwa Ibom State. Water samples were collected from boreholes in the study sites using standard methods. Twenty (20) water quality parameters, in ten (10) study sites, were analysed using spectroscopic and titrimetric methods to determine the water quality index of groundwater in the study sites. Water quality parameters of interest include physicochemical, major ions, nutrients, heavy metals, and microbial indicators. Results indicate variations in pH (4.4–7.16), electrical conductivity (14–102 µS/cm), total dissolved solids (7 – 49 mg/L), Na (58.2 mg/L - 108 mg/L), K (56.4 mg/L - 74.3 mg/L), Ca (8 - 33.6 mg/L), Fe (BDL–4.753 mg/L), Zn (0.002 - 1.063 mg/L) and Mn (0.002–1.063 mg/L), Cl- (3.89 – 28.33), NO3- (1.342 – 2.541mg/L), PO43- (0.014 – 0.041 mg/L), SO42- (0.104 – 6.186 mg/L). Most water samples showed acidic pH and variable levels of salinity, hardness, and microbial contamination, suggesting the influence of geogenic and anthropogenic factors. Elevated Fe and Mn levels in some samples pose health risks, while microbial contamination indicates faecal pollution, necessitating urgent remediation. While some parameters complied with World Health Organisation and Nigerian safety regulatory standards, others exceeded permissible limits. Water Quality Index assessment of the study sites indicates that, with the exception of ONN 2, the water quality of all sample sites is suitable for drinking. However, there is need for continuous and improved groundwater monitoring, as well as point-of-use treatment strategies for contaminated groundwater in Onna LGA, Akwa Ibom State.