PHYSICOCHEMICAL AND MICROBIOLOGICAL QUALITY OF BOREHOLE AND SACHET DRINKING WATER IN PERI-URBAN COMMUNITIES OF SOUTHWEST NIGERIA: IMPLICATIONS FOR PUBLIC HEALTH RISK ASSESSMENT

Abstract

Access to safe drinking water remains a major public health and environmental challenge in many
low- and middle-income countries, particularly in rapidly urbanizing peri-urban communities
where dependence on alternative water sources has increased because of inadequate municipal
water supply. In Southwest Nigeria, borehole and sachet water constitute the primary sources of
potable water for millions of households, educational institutions, and commercial establishments.
However, growing concerns regarding groundwater pollution, inconsistent water treatment
practices, and inadequate regulatory compliance have heightened the risk of physicochemical and
microbiological contamination, with significant implications for human health. This study
assessed the physicochemical and microbiological quality of borehole and sachet drinking water
in selected peri-urban communities of Southwest Nigeria and evaluated the associated public
health risks. A cross-sectional laboratory-based analytical design was adopted. Representative
borehole and sachet water samples were collected using standard sampling protocols and analysed
for key physicochemical parameters, including pH, turbidity, electrical conductivity, total
dissolved solids, total hardness, nitrate, and selected heavy metals, alongside microbiological
indicators comprising total heterotrophic bacteria, total coliforms, faecal coliforms, Escherichia
coli, and Salmonella spp., using internationally accepted analytical methods. Water quality results
were compared with the World Health Organization (WHO) and Nigerian Standard for Drinking
Water Quality guideline values, while health risks associated with chemical exposure were
evaluated using established human health risk assessment models. The findings indicated that
although most physicochemical parameters complied with recommended drinking water
standards, borehole water exhibited significantly higher turbidity, electrical conductivity, total
dissolved solids, hardness, nitrate concentrations, and selected heavy metals than sachet water (p
< 0.05). Microbiological contamination was more prevalent in borehole water, with detectable
levels of total coliforms, faecal coliforms, and Escherichia coli, whereas sachet water
demonstrated comparatively better microbiological quality despite isolated contamination in a
small proportion of samples. Regression analysis further identified poor environmental sanitation,
inadequate borehole maintenance, and proximity to pollution sources as significant predictors of
water quality deterioration.