Comparative hazard evaluation of enteric bacteria in two surface water sources in Akure, Nigeria

Abstract

Abstract This study was carried out to determine the level of enteric bacteria in two surface water sources (river and stream) commonly used for domestic, recreational and agricultural purposes in Akure, Nigeria. This is to gain a better understanding of the level of faecal pollution of the water sources and the potential health risks associated with usage of the waters for human activities. Water samples were collected from the river and the stream from May to September, 2019 (n = 24). The concentration of enteric bacteria in the water samples was determined using the membrane filtration technique, while the physicochemical characteristics of the water samples were determined using the standard method. Results revealed that the concentration of Escherichia coli ranged from 3.00 to 4.78 log10 cfu/100ml and 3.48 to 5.75 log10 cfu/100ml in water samples from the river and stream respectively; Bifidobacterium ranged from 4.18 to 5.00 log10 cfu/100ml and 3.87 to 4.66 log10 cfu/100ml in water samples from the river and stream respectively; Salmonella ranged from 3.30 to 4.30 log10 cfu/100ml and 2.60 to 4.32 log10 cfu/100ml in water samples from the river and stream respectively. Water temperature ranged from 22.1 to 28.5 °C and 23.64 to 25.56 °C in the river and stream respectively; turbidity ranged from 12.28 to 29.11 NTU and 17.07 to 61.80 NTU in the river and stream respectively. Spearman's rank correlation showed that Salmonella had positive relationship with temperature (r = 0.556) in water samples from the stream whereas Bifidobacterium exhibited a positive relationship with dissolved oxygen (r = 0.557) in water samples from the river. While the stream appeared to have a higher turbidity than the river, the level of enteric bacteria in the river was higher than that in the stream. Based on microbiological water quality categories, the findings from this study demonstrated that the level of enteric bacteria in the river and stream suggests strong faecal pollution that may pose potential risks of diarrheal diseases to humans. Water from these two surface water sources must be treated before use in order to protect human health.