Abstract
This study identified the sources of fecal contamination in the groundwater of different land covers. A total of 300 groundwater samples were collected in the Kathmandu Valley, Nepal, in the dry (n = 152) and wet (n = 148) seasons of 2016. Fecal indicator bacteria were initially enumerated, and then fecal contamination sources were identified using human (BacHum), ruminant (BacR), and pig-associated (Pig2Bac) Bacteroidales quantitative polymerase chain reaction assays. Sixty-six percent (197/300) of the tested groundwater samples had Escherichia coli concentrations higher than the World Health Organization threshold for drinking (<1 most probable number/100 mL). The fecal contamination of the groundwater was of human (22%, 55/250), ruminant (11%, 28/250), and pig (3%, 8/250) origin. Deep tube wells were less likely to be positive for E. coli and fecal markers compared to shallow dug wells. The human fecal marker was more likely to be detected in sources from built-up as compared to agricultural areas (Adjusted odds ratio (AOR) = 3.60, p = 0.002). Likewise, the ruminant fecal marker was more likely to be detected in sources from agricultural as compared to built-up areas (AOR = 2.90, p = 0.018). These findings suggest the preparation of mitigation strategies for controlling fecal pollution based on land cover and well types.
Highlights
Fecal pollution in water sources is a major concern for public health
This study provided insights into the distribution and abundance of Fecal indicator bacteria (FIB) in the groundwater sources throughout the entire Kathmandu Valley, and their detection in groundwater indicated unsuitability for drinking purposes
The shallow aquifer sources, mainly shallow dug wells and stone spouts, pose a potentially higher risk to humans compared to tube wells due to the potential presence of pathogens in fecal sources, as indicated by the high prevalence of FIB and fecal markers in these sources
Summary
Fecal pollution in water sources is a major concern for public health. Drinking water sources with fecal contamination may cause outbreaks of illness and economic degradation [1]. Water 2018, 10, 1796 is a major source for domestic water use, and fecal contamination has been widely reported in many developing countries [2,3,4,5,6], and appears to be a persistent problem [7]. Urbanization, likely elevate the fecal contamination of shallow well water, increasing the risk of diarrheal diseases [10]. Urbanization and agriculture can substantially degrade water quality, causing eutrophication and fecal contamination [11,12]. In some agricultural areas in Cambodia, animals have been found to be primary sources of the fecal pollution of water sources [3]
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