A tale of two cities

Across much of Africa, cities are growing quickly. Current projections estimate that by 2050, 60 per cent of the population will be living in urban areas – half of them in slums. Many of these people have little access to services such as clean water and sanitation, and the UN has identified fixing this as a major priority

Real-time inference of thermotolerant coliforms in groundwater

Enteric pathogens are typically inferred from the presence of cultured surrogate indicator organisms such as thermotolerant coliforms (TTCs). Their analysis requires suitable laboratories, specialist trained personnel, and is time-consuming, which can limit sampling resolution, particularly during critical pollution events. Tryptophan-like fluorescence has been demonstrated as a useful indicator of human influence on freshwater resources due to its association with sewage and farm waste. Following recent developments in field-deployable optical sensor technology, portable tryptophan-like fluorimeters are now commercially available. We demonstrate their real-time applicability at potable urban groundwater supplies in the developing world. We sampled over 100 supplies for TTCs, and traditional surrogates, such as turbidity and nutrients, as well as tryptophan-like fluorescence. The intensity of tryptophan-like fluorescence was the most effective predictor of the presence/absence and number of TTCs. These sensors have the potential to be included in real-time pollution alert systems for drinking water supplies throughout the world, as well as mapping enteric pathogen risks in developing regions

A longitudinal study of long-term change in contamination hazards and shallow well quality in two neighbourhoods of Kisumu, Kenya

Sub-Saharan Africa is experiencing rapid urbanisation and many urban residents use groundwater where piped supplies are intermittent or unavailable. This study aimed to investigate long-term changes in groundwater contamination hazards and hand-dug well water quality in two informal settlements in Kisumu city, Kenya. Buildings, pit latrines, and wells were mapped in 1999 and 2013-2014. Sanitary risk inspection and water quality testing were conducted at 51 hand-dug wells in 2002 to 2004 and 2014. Pit latrine density increased between 1999 and 2014, whilst sanitary risk scores for wells increased between 2002 to 2004 and 2014 (n = 37, Z = -1.98, p = 0.048). Nitrate levels dropped from 2004 to 2014 (n = 14, Z = -3.296, p = 0.001), but multivariate analysis suggested high rainfall in 2004 could account for this. Thermotolerant coliform counts dropped between 2004 and 2014, with this reduction significant in one settlement. Hand-dug wells had thus remained an important source of domestic water between 1999 and 2014, but contamination risks increased over this period. Water quality trends were complex, but nitrate levels were related to both sanitary risks and rainfall. Given widespread groundwater use by the urban poor in sub-Saharan Africa, the study protocol could be further refined to monitor contamination in hand-dug wells in similar settings

Socio-economic aspects of domestic groundwater consumption, vending and use in Kisumu, Kenya

Shallow hand-dug wells are commonly used to supplement partial or intermittent piped water coverage in many urban informal settlements in sub-Saharan Africa. Such wells are often microbially contaminated. This study aimed to quantify the amount of such groundwater consumed, identify the socio-economic profile of well owners and consumers, and patterns of domestic water usage in informal settlements in Kisumu, Kenya. Building on a previous study, 51 well owners and 137 well customers were interviewed about well water abstraction, water usage and handling patterns, asset ownership, and service access. An estimated 472m3 of groundwater per day was abstracted in two informal settlements, with most groundwater consumers using this water for purposes other than drinking or cooking. According to an asset index, well owners were significantly wealthier than both the customers purchasing their groundwater and those drinking or cooking with untreated groundwater. This suggests that shallow groundwater sources provide poorer urban households with a substantial volume of water for domestic purposes other than drinking and cooking. Ongoing challenges are thus to raise awareness of the health risks of such water among the minority of consumers who consume untreated groundwater and find means of working with well owners to manage well water quality

A participatory methodology for future scenario analysis of sub-national water and sanitation access: case study of Kisumu, Kenya

This study pilots a participatory methodology for sub-national spatial planning of urban and peri-urban water and sanitation services. Three groups of key informants were presented with evidence on national historic and future service provision trajectories and asked to map water and sanitation access in the city of Kisumu, Kenya, by 2030, assuming current trends continue. Comparison of the groups’ outputs suggests greater certainty among participants regarding service access in Kisumu’s urban core compared to peri-urban areas. We discuss extensions to this preliminary methodology, including the potential benefits of its application to Kenya’s rapidly expanding small towns as suggested by participants

Large-scale survey of seasonal drinking water quality in Malawi using in situ tryptophan-like fluorescence and conventional water quality indicators

Faecally-contaminated drinking water is a risk to human health, with the greatest risks to those living in developing countries. UN Sustainable Development Goal 6 aims to address this issue. Tryptophan-like fluorescence (TLF) shows potential as a rapid method for detecting microbial contamination in drinking water, which could reduce the spread of waterborne diseases. This study is the first to investigate the effectiveness of TLF for a large-scale survey using a randomised, spot-sampling approach. The large-scale survey took place in Malawi, sub-Saharan Africa, in the dry season (n = 183). A subset of sources were revisited at the end of the following wet season (n = 41). The effectiveness of TLF was assessed by comparing TLF results to thermotolerant coliforms (TTC), humic-like fluorescence (HLF), inorganic hydrochemical data and sanitary risk scores. The most prominent differences in microbial water quality were observed between source types, with little variation between districts and seasons. TLF, TTCs, turbidity and sanitary risk scores were all elevated at alternative sources (shallow wells and tap stands) compared to hand-pumped boreholes. In the dry season, 18% of hand-pumped boreholes showed TTC contamination, which increase to 21% in the wet season. Groundwater recharge processes are likely responsible for seasonal variability of inorganic hydrochemistry at hand-pumped boreholes. TLF was able to distinguish no and low WHO risk classes (TTC 0–9 cfu/100 mL) from medium, high and very high risk classes (TTC 10 – >1000 cfu/100 mL). TLF failed to distinguish between no and low risk classes, which limits the use of TLF for assessing water quality to drinking water standards. This dataset indicates that HLF may raise baseline TLF for samples with low TLF values, increasing false positives. Therefore, TLF is better suited as a rapid high-level water quality screening tool to assess moderate and high levels of faecal contamination

Tryptophan-like fluorescence as a high-level screening tool for detecting microbial contamination in drinking water

Regular monitoring of drinking water quality is vital to identify contamination of potable water supplies. Testing for microbial contamination is important to prevent transmission of waterborne disease, but establishing and maintaining a water quality monitoring programme requires sustained labour, consumables and resources. In low resource settings such as developing countries, this can prove difficult, but measuring microbial contamination is listed as a requirement of reaching the UN's Sustainable Development Goal 6 for water and sanitation. A nine-month water quality monitoring programme was conducted in rural Malawi to assess the suitability of tryptophan-like fluorescence (TLF), an emerging method for rapidly detecting microbial contamination, as a drinking water quality monitoring tool. TLF data was compared with thermotolerant coliforms (TTCs, E. coli) and inorganic hydrochemical parameters. A large (n = 235) temporal dataset was collected from five groundwater drinking water sources, with samples collected once or twice weekly depending on the season. The results show that TLF can indicate a broader contamination risk but is not as sensitive to short term variability when compared to other faecal indicators. This is likely due to a broad association of TLF with elevated DOC concentrations from a range of different sources. Elevated TLF may indicate preferential conditions for the persistence of TTCs and/or E. coli, but not necessarily a public health risk from microbial contamination. TLF is therefore a more precautionary risk indicator than microbial culturing techniques and could prove useful as a high-level screening tool for initial risk assessment. For widespread use of TLF to be successful, standardisation of TLF values associated with different levels of risk is required, however, this study highlights the difficulties of equating TLF thresholds to TTCs or E. coli data because of the influence of DOC/HLF on the TLF signal

Tracking pathways for pathogen contamination in urban groundwater supplies in Africa: novel application of qPCR techniques

Low income urban communities across Africa depend on local shallow, often highly contaminated, groundwater sources for drinking and domestic use as well as larger municipal supplies extracting groundwater from deeper within the aquifer system where these are available and affordable. Rapid lateral and vertical pathways in the subsurface, often only active for limited periods e.g. during high water table conditions, can lead to rapid deterioration of groundwater quality. Sanitary risk assessments and quantification of basic water quality indicators such thermotolerant coliforms are often used as part of water point vulnerability assessments in urban and peri-urban water supplies in Africa. While there have been huge advances in the development of polymerase chain reaction (PCR) techniques in recent years for amplifying microbial DNA, these techniques have not been used to date for quantifying specific pathogenic strains of bacteria in groundwaters in Africa. In this paper we present results from a pilot study using qPCR techniques for the first time to quantify the occurrence of 26 specific pathogenic strains in water supplies in Kabwe, Zambia. Pathogen occurrence is assessed in both shallow and deep groundwater points during both the wet and dry season in a vulnerable dolomite aquifer system. Multiple pathogens were revealed within the groundwater system including Vibrio cholera and Salmonella enterica. This technique shows great potential for tracking specific pathogens, fingerprinting sources of pathogens in groundwater sources and assessing rapid shallow pathways in widespread vulnerable settings in Africa, and elsewhere, such as those found in lateritic or karstic terrains

Challenges to Achieving Sustainable Sanitation in Informal Settlements of Kigali, Rwanda

The data was collected by researchers in Kigali with cooperation of the local community leaders. The authors would like to thank the researchers Roger Mugisha and Carine Tuyishime. This research is part of the 3K-SAN project, funded by SPLASH, Swiss Agency for Development and Cooperation (SDC), which is investigating how to catalyse self-sustaining sanitation chains in low-income informal settlements in Kigali (Rwanda), Kampala (Uganda) and Kisumu (Kenya). Self-sustaining sanitation chains are defined here as socio-technological systems that provide continued health and environmental improvement, as required to meet the MDGs, without continued external intervention. This definition includes, but is not limited to, construction, maintenance, and management of the waste through pump-out/collection services, transport, treatment and re-use or disposal.Peer reviewedPublisher PD

Real-time detection of faecally contaminated drinking water with tryptophan-like fluorescence: defining threshold values

We assess the use of fluorescent dissolved organic matter at excitation-emission wavelengths of 280 nm and 360 nm, termed tryptophan-like fluorescence (TLF), as an indicator of faecally contaminated drinking water. A significant logistic regression model was developed using TLF as a predictor of thermotolerant coliforms (TTCs) using data from groundwater- and surface water-derived drinking water sources in India, Malawi, South Africa and Zambia. A TLF threshold of 1.3 ppb dissolved tryptophan was selected to classify TTC contamination. Validation of the TLF threshold indicated a false-negative error rate of 15% and a false-positive error rate of 18%. The threshold was unsuccessful at classifying contaminated sources containing 100 TTC cfu per 100 mL). Current commercially available fluorimeters are easy-to-use, suitable for use online and in remote environments, require neither reagents nor consumables, and crucially provide an instantaneous reading. TLF measurements are not appreciably impaired by common intereferents, such as pH, turbidity and temperature, within typical natural ranges. The technology is a viable option for the real-time screening of faecally contaminated drinking water globally