Appraisement of groundwater quality status within Enugu, Nigeria, using physicochemical evaluation and water quality indices

Abstract

Enugu state is notorious for potable water scarcity which forces residents to depend on polluted water sources. In this study, an appraisement of the quality status of groundwater from some areas within Enugu was conducted. Physicochemical characteristics of groundwater sampled from 15 boreholes that supply domestic water to Aninri, Awgu, Ezeagu, Udi and Oji River Areas of Enugu, Nigeria, were determined. A total of 45 water samples were obtained across both rainy and dry seasons. Standard methods were used to determine the physicochemical parameters and trace metals. The physicochemical results showed values within the WHO safe limits, except sulphate (1670 ± 21.5 mg L−1) in Mpu water samples, and high chloride levels in Ndeaboh and Mpu (18088 ± 29.4 and 1095 ± 23.9 mg L−1 for dry and rainy seasons, respectively). The pH values were predominantly slightly acidic, ranging from 5 to 8.2. Groundwater within Ukaete, Ndeaboh, Oduma and Amankpunato had very high levels of electrical conductivity (2897.80 ± 173.38, 31000 ± 45.9, 1672 ± 9.3 and 1222 ± 8.1) in the dry season, respectively; and 1665.06 ± 326.6, 5410 ± 2.4, 4860 ± 9.4, 1872 ± 19.3 in the rainy season, respectively. The higher chloride values observed, possibly due to a geogenic origin, could also be responsible for the higher values of the electrical conductivity. There were traces of copper and lead in the samples during the dry season; however, lead was not detected in most borehole water samples during the wet season. Fe was the only metal that recorded values above the WHO standard. Traces of copper in the samples may have resulted from corrosion in the copper pipelines, reservoirs or other metallic fittings used in the construction of the boreholes. The water quality index (WQI) of the borehole water examined was above 100 in all except Ogugu Awgu samples, indicating that borehole water was generally not potable and therefore unsuitable for domestic application or drinking. The observed results revealed that the groundwaters from the study area were contaminated with chloride and lead, causing the water parameters to be above standard limits. Lead at any concentration is deemed toxic according to USEPA. There is a need to treat borehole water supplies in the area before its application for domestic use.