Groundwater Quality Assessment and Health Implications Using Hierarchical Cluster Analysis and Associated Descriptive Techniques: A Case Study of Wasinmi District of Ewekoro South-West Nigeria

Current water quality status from groundwater system of two separate sources in Wasinmi community of Ewekoro Local Government Area, South-West Nigeria was investigated in this study with the principal aim of assessing the biogeochemical levels in relation to the general health implications. Inhabitants of this region rely on these water sources for drinking and other purposes. Water samples were collected from 25 boreholes and 25 hand-dug wells at various sampling points across the study area. Standard Analytical and laboratory Methods were employed for all analyses for geochemical and microbiological parameters using principally Inductively Coupled Mass/Optical Emission Spectrometry and Pour Plate Technique; the results were compared with both National and International water quality standards of the World Health Organisation (WHO), National Environmental Standard Regulation Agency (NESREA), the Nigerian Standard for Drinking Water Quality (NSDWQ) and National Food And Drug Administration and Control (NAFDAC). Most quality determinants in the sampled water are within WHO guidelines except BOD, ALK, Cl-, HCO32-, MgCO3-, Zn2+ and Fe3+. The overall ionic dominance pattern for the boreholes and wells followed similar trends namely K+ >Na2+ > Fe3+ >Mn2+ and Cl- >NO3- >NO2-. The sanitary integrity of the two water sources was found to be poor. It was found that the two underground water sources are polluted, having BOD5:NO3- ratio > 4 with values of 178.33 and 162.85 for borehole and well water respectively based on the maximum concentration level. High BOD5, Coliform Count and BOD5:NO3- ratios of groundwater sample indicate organic pollution due to faecal contamination. Multivariate and descriptive statistical approaches [Correlation Analysis, Hierarchical Cluster Analysis (HCA) and Bubble Plot] were used to identify interrelationships between the analyzed geochemical parameters and the pollution sources. Based on the cluster analysis output, identified water sample parameters were classified into 3 differentiable clusters with distinct differences and corresponding peculiarities. The highest Total Coliform Count (TCC), Total Heterotrophic Bacteria Count (THBC), and Faecal Coliform Count (FCC) were all recorded in well water samples with 210. 0 × 102 MPN/100 ml, 12.20×102 cfu/ml and 5.30 x 102 cfu/ml respectively. The high coliform count obtained from the analyzed groundwater samples of the investigated study area implies poor sanitary conditions of the water bodies, and is also an indication of pollution by organic materials. These integrated results imply that water bodies in Wasinmi were polluted and pose potential risk of water related illnesses with accompanied threatening consequences.