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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)

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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