Hydrochemical and Microbiological Characterization of Groundwater Resources for Drinking Water Safety Assessment in Calabar Metropolis, Nigeria

Abstract

This study assessed the hydrochemical and microbiological characteristics of groundwater resources to determine their suitability for drinking-water consumption in Calabar Metropolis, Nigeria. A cross-sectional research design was adopted, covering Calabar Municipality and Calabar South. From a reported population of 1,055 functional groundwater facilities comprising 1,034 boreholes and 21 hand-dug wells, 290 facilities were selected using stratified and systematic sampling. Groundwater samples were assessed for physical, hydrochemical, heavy-metal and microbiological parameters and compared with stated WHO and NESREA benchmarks. Temperature ranged from 27.2–28.7 °C, electrical conductivity from 198–341 µS/cm, and total dissolved solids from 130–224 mg/L. pH ranged from 6.3–7.1. Iron concentrations ranged from 0.16–0.40 mg/L and exceeded the WHO benchmark stated in the manuscript (0.10 mg/L), while lead reached 0.016 mg/L and exceeded the stated 0.01 mg/L benchmark at some locations. Microbiological results showed total coliform counts of 18–56 CFU/100 mL, fecal coliform counts of 0–24 CFU/100 mL, and Vibrio cholerae counts of 0–13 CFU/100 mL. The reported results indicate microbiological non-compliance at all presented sampling locations. The study concludes that the investigated groundwater sources require appropriate treatment, source protection and regular monitoring before being relied upon for drinking. Because the results tables present 18 location-level observations although the methodology reports 290 sampled facilities, the authors should clarify whether the tabulated values are individual observations, site means, or another aggregation before publication.