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Groundwater dependence and threats in urban Sub-Saharan Africa (SSA)
James Sorensen
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Urban population
• By 2050 the urban population of SSA is projected to increase from 40 to nearly 60% and exceed 1.26 billion (UN, 2011).
Natural woman
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• The rapid growth of many urban areas has overwhelmed the ability of many local authorities to provide basic infrastructure
• 60% of the SSA urban population lives in informal settlements and slums (UN-Habitat, 2010)
Wikimedia
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Threats to urban groundwater
• Impacts of wastewater
- 70% population unconnected to reticulated sewerage network
- 80% wastewater is discharged directly to surface waters or soil (Nyenje et al. 2011)
• Threats: enteric pathogens and chemical waste Kenedy Mayumbelo
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Study site Kabwe, Zambia
• Heavily groundwater dependent• Self-supply wide-spread from shallow wells• Ageing sewer network; restricted to 11%
of properties in informal settlements and slums• >100 water supplies sampled across the city
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Tryptophan – indicator of bacterial quality of water?
• Common indicator – thermotolerant coliforms (TTCs)
• Rapid, reagentless measurement using a fluorimeter
• Measured thermotolerant coliforms and many indicators at >100 water supplies
• What was the best indicator of TTCs?
• Tryptophan! For both presence/absence and number of thermotolerant coliforms
Sorensen et al. (submitted). In-situ tryptophan sensing: a rapid indicator of faecal contamination in drinking water supplies. Water Research.
Abs Present
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Emerging Organic Contaminants
• Unsurprisingly from 40 sites, contaminants most prevalent in shallow hand-dug wells
• Good news - Concentrations were below researched toxic levels
• DEET was widespread, but at low concentrations
• Potential use as a wastewater indicator
Sorensen et al. 2014. Emerging contaminants in urban groundwater sources in Africa. Water Research.
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Do TTCs identify the presence of pathogens?
• Filtered sample collection in field from 40 sites, preservation, assay analysis for suite of pathogens
• Work in progress…
• Opportunistic pathogens in c. 70% of supplies
• Vibrio cholera in >40%
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Conclusions
• Urban populations are growing rapidly in SSA and the majority of this population resides in informal settlements or slums
• Tryptophan-like fluorimeters offer a solution to practitioners for the rapid indication of faecal contamination and potential enteric pathogens
• Emerging contaminants may be posing threats to people and the aquatic environment in SSA and could require future regulation