Quantitative Microbial Risk Assessment (QMRA) of major drinking water sources at household level incorporating boiling treatment effect

Abstract

This study conducted a quantitative microbial risk assessment (QMRA), incorporating the effect of boiling of water, on major sources of drinking water for households in Afikpo North LGA, Ebonyi State, Nigeria. Water samples were collected from12 drinking water boreholes (n =36), a popular spring water (n= 36) and four popular brands of sachet water (n= 36).The samples were analysed in the laboratory for colonies of microorganisms, coliform organisms, E. coli, Salmonella spp and Giardia lamblia. Data were analysed for specific parameters of the study population (n =1150). The parameters include daily water consumption per person per day (L/person/day), the fraction of thepopulatonexposed to the contaminated drinking water source under consideration, the percentage ofthe population vulnerableto pathogenic infection among the exposed population,the pathogen strike rate in each water source, and the probability that water is boiled before drinking. Quantitative microbial risk assessment was performed for concentrations of E. coli (CFU/L), Salmonella spp (CFU/L), and Giardia lamblia (Cyst/L) in the water samples. From the findings, the risk of diarrhea is significantly highin all the drinking water sources examined. The risk of diarrhea ranged between0.090 and 0.190 for borehole water source, 0.004 and 0.032 for spring water source, 0.039 and 0.125 for sachet water sources. The implication is an urgent need to regualte the operation of water boreholes, protect spring water source, and enforce standards on the processes of production, distribution and storage of sachet water in Afikpo North LGA.