Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) pea... more Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) peaks is associated with the presence and enumeration of faecal indicator bacteria in groundwater. We hypothesise, however, that it is predominantly extracellular material that fluoresces at these wavelengths, not bacterial cells. We quantified total (unfiltered) and extracellular (filtered at < 0.22 µm) TLF and HLF in 140 groundwater sources across a range of urban population densities in Kenya, Malawi, Senegal, and Uganda. Where changes in fluorescence occurred following filtration they were correlated with potential controlling variables. A significant reduction in TLF following filtration (ΔTLF) was observed across the entire dataset, although the majority of the signal remained and thus considered extracellular (median 96.9%). ΔTLF was only significant in more urbanised study areas where TLF was greatest. Beneath Dakar, Senegal, ΔTLF was significantly correlated to total bacterial c...
Journal of Water, Sanitation and Hygiene for Development, 2019
Inadequate hygiene coupled with the conjunctive use of the shallow subsurface as both a source of... more Inadequate hygiene coupled with the conjunctive use of the shallow subsurface as both a source of water and repository of faecal matter pose substantial risks to human health in low-income countries undergoing rapid urbanisation. To evaluate water, sanitation and hygiene (WASH) conditions in a small, rapidly growing town in central Uganda (Lukaya) served primarily by on-site water supply and sanitation facilities, water-point mapping, focus group discussions, sanitary-risk inspections and 386 household surveys were conducted. Household surveys indicate high awareness (82%) of domestic hygiene (e.g. handwashing, boiling water) but limited evidence of practice. WHO Sanitary Risk Surveys and Rapid Participatory Sanitation System Risk Assessments reveal further that community hygiene around water points and sanitation facilities including their maintenance is commonly inadequate. Spot sampling of groundwater quality shows widespread faecal contamination indicated by enumerated thermo-to...
Shallow groundwater is vulnerable to faecal contamination, especially in low-income urban areas w... more Shallow groundwater is vulnerable to faecal contamination, especially in low-income urban areas where use of on-site sanitation facilities is high. This paper explores statistical relationships between potential factors influencing contaminant pathways (i.e., variables) and observed faecal contamination of shallow groundwater, represented by nitrate concentrations and counts of Escherichia coli (i.e., response function) in a small, growing town in Uganda over dry and wet seasons in 2018 and 2019. A statistically significant (p = 0.004) multiple linear regression model from dry-season E. coli counts in 2018 identifies medium sanitary risk levels and modes of construction as significant pathways (p = 0.01). Water source depth (<20 m) and proximity (>10 m) to a pit latrine were also significant (p<0.05) in both hydrogeological formations. No significant linear regression models were established for NO3 during both seasons due to low pH and rapid infiltration velocities; incons...
Two billion people still consume drinking water contaminated with faeces. To improve this situati... more Two billion people still consume drinking water contaminated with faeces. To improve this situation, it has been recognised by UNICEF and the WHO that a more rapid approach to detecting faecally contaminated drinking water is necessary. We have previously demonstrated that fluorescence spectroscopy is a significant real-time indicator of the presence/absence and number of faecal indicator bacteria in drinking waters in low-income countries of the tropics. We have also established its potential as an online indicator of faecal contamination of public water supplies in the UK. Outstanding questions remain, however, over the source of the fluorescence and its uniqueness to faecal-indicator bacteria. To address these, we sampled potable groundwater supplies in Kenya, Malawi, Senegal and Uganda across an urbanisation transect from rural Malawi through to the city of Dakar (Senegal) where pollution sources and pressures vary considerably. We report on whether the fluorescence signal in th...
Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) pea... more Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) peaks is associated with the presence and enumeration of faecal indicator bacteria in groundwater. We hypothesise, however, that it is predominantly extracellular material that fluoresces at these wavelengths, not bacterial cells. We quantified total (unfiltered) and extracellular (filtered at < 0.22 µm) TLF and HLF in 140 groundwater sources across a range of urban population densities in Kenya, Malawi, Senegal, and Uganda. Where changes in fluorescence occurred following filtration they were correlated with potential controlling variables. A significant reduction in TLF following filtration (ΔTLF) was observed across the entire dataset, although the majority of the signal remained and thus considered extracellular (median 96.9%). ΔTLF was only significant in more urbanised study areas where TLF was greatest. Beneath Dakar, Senegal, ΔTLF was significantly correlated to total bacterial c...
Journal of Water, Sanitation and Hygiene for Development, 2019
Inadequate hygiene coupled with the conjunctive use of the shallow subsurface as both a source of... more Inadequate hygiene coupled with the conjunctive use of the shallow subsurface as both a source of water and repository of faecal matter pose substantial risks to human health in low-income countries undergoing rapid urbanisation. To evaluate water, sanitation and hygiene (WASH) conditions in a small, rapidly growing town in central Uganda (Lukaya) served primarily by on-site water supply and sanitation facilities, water-point mapping, focus group discussions, sanitary-risk inspections and 386 household surveys were conducted. Household surveys indicate high awareness (82%) of domestic hygiene (e.g. handwashing, boiling water) but limited evidence of practice. WHO Sanitary Risk Surveys and Rapid Participatory Sanitation System Risk Assessments reveal further that community hygiene around water points and sanitation facilities including their maintenance is commonly inadequate. Spot sampling of groundwater quality shows widespread faecal contamination indicated by enumerated thermo-to...
Shallow groundwater is vulnerable to faecal contamination, especially in low-income urban areas w... more Shallow groundwater is vulnerable to faecal contamination, especially in low-income urban areas where use of on-site sanitation facilities is high. This paper explores statistical relationships between potential factors influencing contaminant pathways (i.e., variables) and observed faecal contamination of shallow groundwater, represented by nitrate concentrations and counts of Escherichia coli (i.e., response function) in a small, growing town in Uganda over dry and wet seasons in 2018 and 2019. A statistically significant (p = 0.004) multiple linear regression model from dry-season E. coli counts in 2018 identifies medium sanitary risk levels and modes of construction as significant pathways (p = 0.01). Water source depth (<20 m) and proximity (>10 m) to a pit latrine were also significant (p<0.05) in both hydrogeological formations. No significant linear regression models were established for NO3 during both seasons due to low pH and rapid infiltration velocities; incons...
Two billion people still consume drinking water contaminated with faeces. To improve this situati... more Two billion people still consume drinking water contaminated with faeces. To improve this situation, it has been recognised by UNICEF and the WHO that a more rapid approach to detecting faecally contaminated drinking water is necessary. We have previously demonstrated that fluorescence spectroscopy is a significant real-time indicator of the presence/absence and number of faecal indicator bacteria in drinking waters in low-income countries of the tropics. We have also established its potential as an online indicator of faecal contamination of public water supplies in the UK. Outstanding questions remain, however, over the source of the fluorescence and its uniqueness to faecal-indicator bacteria. To address these, we sampled potable groundwater supplies in Kenya, Malawi, Senegal and Uganda across an urbanisation transect from rural Malawi through to the city of Dakar (Senegal) where pollution sources and pressures vary considerably. We report on whether the fluorescence signal in th...
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