Water safety and inequality in access to drinking-water between rich and poor households.

While water and sanitation are now recognized as a human right by the United Nations, monitoring inequality in safe water access poses challenges. This study uses survey data to calculate household socio-economic-status (SES) indices in seven countries where national drinking-water quality surveys are available. These are used to assess inequalities in access as indicated by type of improved water source, use of safe water, and a combination of these. In Bangladesh, arsenic exposure through drinking-water is not significantly related to SES (p = 0.06) among households using tubewells, whereas in Peru, chlorine residual in piped systems varies significantly with SES (p < 0.0001). In Ethiopia, Nicaragua, and Nigeria, many poor households access nonpiped improved sources, which may provide unsafe water, resulting in greater inequality of access to "safe" water compared to "improved" water sources. Concentration indices increased from 0.08 to 0.15, 0.10 to 0.14, and 0.24 to 0.26, respectively, in these countries. There was minimal difference in Jordan and Tajikistan. Although the results are likely to be underestimates as they exclude individual-level inequalities, they show that use of a binary "improved"/"unimproved" categorization masks substantial inequalities. Future international monitoring programmes should take account of inequality in access and safety.

Accuracy of the H2S test: a systematic review of the influence of bacterial density and sample volume.

The presence/absence hydrogen sulphide test (P/A H2S) is widely used as a low-cost alternative faecal indicator test in remote and resource-poor settings. The aim of the paper is to assess how bacterial density and sample volume affect its accuracy. Based on a systematic search, we identified studies that tested water samples (n = 2,034) using both the P/A H2S test and recognised tests for thermotolerant coliforms (TTC) or Escherichia coli. We calculated P/A H2S test specificity and sensitivity against a range of TTC and E. coli densities. For two studies, we compared this with sensitivity and specificity estimates for simulated 100 and 20 ml presence/absence tests. For most of the 19 included studies, as the threshold used to define contamination increased from 1 to 100 cfu/100 ml, P/A H2S test sensitivity increased but specificity decreased. Similarly, the simulation indicated that increasing test volumes from 20 to 100 ml increased sensitivity but reduced specificity. There was potential for bias, for example from lack of blinding during test interpretation, in most of the studies reviewed. In assessing the P/A H2S test as an alternative to standard methods, careful consideration of likely indicator bacteria levels and sample volume is required.

A spatial analysis of pit latrine density and groundwater source contamination.

This study aims to assess the relationship between chemical and microbial contamination of groundwater sources and a range of potential hazards in two peri-urban areas of Kisumu, Kenya where shallow wells and pit latrines are widely used. From 1998 to 2004, 263 samples were taken from 61 groundwater sources and tested for thermotolerant coliforms. Eighteen of these sources were also tested for chemical contaminants, including nitrate, chloride and fluoride. The locations of all water sources, buildings and pit latrines in the study area were surveyed. Local pit latrine densities were calculated using a geographic information system. Ten out 18 samples were above the World Health Organization guideline values for nitrate, 236 out of 263 were positive for thermotolerant coliforms, and all were above the guideline values for fluoride. There was neither a relationship between thermotolerant coliform levels and daily rainfall patterns nor with sanitary risk inspection scores for samples from shallow wells (r = 0.01, p = 0.91, n = 191). The density of pit latrines within a 100-m radius was significantly correlated with nitrate and chloride levels (r = 0.64, p = 0.004 and r = 0.46, p = 0.05, respectively) but not with thermotolerant coliforms (r = 0.22, p = 0.11). These results illustrate both the public health risks associated with shallow groundwater sources, on-site sanitation and high population density. These findings have implications for current policies that promote latrine construction, especially in peri-urban areas of high population density. More comprehensive studies of larger communities should be commissioned to extend this analysis of the links between latrine density and groundwater contamination and so identify the contingent policy risks.

Accounting for water quality in monitoring access to safe drinking-water as part of the Millennium Development Goals: lessons from five countries.

OBJECTIVE: To determine how data on water source quality affect assessments of progress towards the 2015 Millennium Development Goal (MDG) target on access to safe drinking-water. METHODS: Data from five countries on whether drinking-water sources complied with World Health Organization water quality guidelines on contamination with thermotolerant coliform bacteria, arsenic, fluoride and nitrates in 2004 and 2005 were obtained from the Rapid Assessment of Drinking-Water Quality project. These data were used to adjust estimates of the proportion of the population with access to safe drinking-water at the MDG baseline in 1990 and in 2008 made by the Joint Monitoring Programme for Water Supply and Sanitation, which classified all improved sources as safe. FINDINGS: Taking account of data on water source quality resulted in substantially lower estimates of the percentage of the population with access to safe drinking-water in 2008 in four of the five study countries: the absolute reduction was 11% in Ethiopia, 16% in Nicaragua, 15% in Nigeria and 7% in Tajikistan. There was only a slight reduction in Jordan. Microbial contamination was more common than chemical contamination. CONCLUSION: The criterion used by the MDG indicator to determine whether a water source is safe can lead to substantial overestimates of the population with access to safe drinking-water and, consequently, also overestimates the progress made towards the 2015 MDG target. Monitoring drinking-water supplies by recording both access to water sources and their safety would be a substantial improvement.

The H(2)S test versus standard indicator bacteria tests for faecal contamination of water: systematic review and meta-analysis.

OBJECTIVES: To assess the diagnostic accuracy of the H(2)S test for microbiological contamination of domestic water across different settings, as a basis for providing guidance on its use. METHODS: We searched a range of bibliographic and 'grey' literature databases to identify studies that had processed domestic water samples using both the H(2)S test and recognized tests for thermotolerant coliforms or Escherichia coli. We screened 661 study abstracts and identified 51 relevant studies based on 13 853 water samples. For each relevant study, we recorded the level of correspondence between the H(2)S and recognized tests, microbial testing procedures, details of the samples processed and study quality indicators. We conducted a meta-analysis to investigate the impact of testing procedures, study quality and sample characteristics on the diagnostic accuracy of the H(2)S test. RESULTS: H(2)S test implementation varied between studies, and the test's diagnostic accuracy varied significantly and substantially between studies. Little of this variation was explained by testing procedures, study quality or the nature of the samples processed. CONCLUSIONS: Although in widespread use, our findings suggest that the diagnostic accuracy, particularly specificity, of the H(2)S test is variable. Optimal conditions for conducting the test remain unclear. As H(2)S test accuracy is low in a minority of these studies, we recommend that its performance be evaluated relative to standard methods, prior to its operational deployment in a new setting.

Commentary on community-led total sanitation and human rights: should the right to community-wide health be won at the cost of individual rights?

The Millennium Development Goals (MDGs) set out to halve the proportion of the population without access to basic sanitation between 1990 and 2015. The slow pace of progress has lead to a search for innovative responses, including social motivation approaches. One example of this type of approach is 'Community-led Total Sanitation' (CLTS). CLTS represents a major shift for sanitation projects and programmes in recognising the value of stopping open-defecation across the whole community, even when the individual toilets built are not necessarily wholly hygienic. However, recent publications on CLTS document a number of examples of practices which fail to meet basic ethical criteria and infringe human rights. There is a general theme in the CLTS literature encouraging the use of 'shame' or 'social stigma' as a tool for promoting behaviours. There are reported cases where monetary benefits to which individuals are otherwise entitled or the means to practice a livelihood are withheld to create pressures to conform. At the very extreme end of the scale, the investigation and punishment of violence has reportedly been denied if the crime occurred while defecating in the open, violating rights to a remedy and related access to justice. While social mobilisation in general, and CLTS in particular, have drastically and positively changed the way we think about sanitation, they neither need nor benefit from an association with any infringements of human rights.

New approach to produce water free of bacteria, viruses, and halogens in a recyclable system.

The antimicrobial activity of a new cross-linked N-halamine polymer against bacteria and viruses was evaluated. The polymer achieved a 9-log(10) reduction of bacteria (both Escherichia coli and Staphylococcus aureus) in 1.5 h and a 5-log(10) reduction of bacteriophage PRD1 in 3 h. At the same time, the ability of the nonhalogenated polymer to trap halide ions was examined. The polymer was incorporated into a multifiltration system to study the ability to produce water free of bacteria, viruses, and halide ions. The antimicrobial activity, useful lifetime, halide ion level, and recycling possibilities of the system were quantified on a laboratory scale. A design for a large-scale multifiltration system based on this polymer is proposed.

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.

Seasonality of enteric viruses in groundwater-derived public water sources.

We investigated the seasonal prevalence of seven enteric viruses in groundwater-derived public water sources distributed across the dominant aquifers of England. Sampling targeted four periods in the hydrological cycle with typically varying microbial risks, as indicated using a decade of Escherichia coli prevalence data. Viruses were concentrated onsite by filtration of raw groundwater, and extracted nucleic acid (NA) was amplified by qPCR or RT-qPCR. Seven out of eight sources, all aquifers, and 31% of samples were positive for viral NA. The most frequently detected viral NA targets were Hepatitis A virus (17% samples, 63% sites), norovirus GI (14% samples, 38% sites), and Hepatitis E virus (7% samples, 25% sites). Viral NA presence was episodic, being most prevalent and at its highest concentration during November and January, the main groundwater recharge season, with 89% of all positive detects occurring during a rising water table. Seasonal norovirus NA detections matched its seasonal incidence within the population. Viral NA is arriving with groundwater recharge, as opposed to persisting for long-periods within the saturated zone. Neither total coliforms nor E. coli were significant predictors of viral NA presence-absence, and there was limited co-occurrence between viruses. Nevertheless, a source with an absence of E. coli in regularly collected historical data is unlikely to be at risk of viral contamination. To manage potential groundwater viral contamination via risk assessment, larger scale studies are required to understand key risk factors, with the evidence here suggesting viral NA is widespread across a range of typical microbial risk settings.

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.

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 280nm and 360nm, 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 1.3ppb 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 <10 TTC cfu per 100mL, which we consider the current limit of detection. If only sources above this limit were classified, the false-negative error rate was very low at 4%. TLF intensity was very strongly correlated with TTC concentration (ρs=0.80). A higher threshold of 6.9ppb dissolved tryptophan is proposed to indicate heavily contaminated sources (≥100 TTC cfu per 100mL). 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.

Urbanisation effects on groundwater chemical quality: findings focusing on the nitrate problem from 2 African cities reliant on on-site sanitation.

By 2010 Africa's urban population will have grown to over 420 million with on-site sanitation the predominant excreta disposal option. The use of on-site sanitation has important public health benefits but can result in large faecally derived loadings of nitrogen and chloride to groundwater resources. Nitrate is of particular concern, with elevated concentrations linked to potentially serious health problems. N and Cl can derive from natural sources so it is important to quantify the additional impact of human activities. Several authors have used empirical relationships between nitrate and chloride concentrations to assess the extent to which excreta influences groundwater quality. However, these relationships have assumed fixed loadings from excreta. Relationships between N and Cl have been extended here by adding country-specific estimates of average annual per capita nitrogen and chloride content of, and loading from, excreta. The results are compared with groundwater monitoring results from two very different mid-sized African cities (Timbuktu, Mali and Lichinga, Mozambique) where the vast majority of residents use on-site sanitation and are dependent on the subsurface water for drinking purposes. The results illustrate the impact of urbanisation on groundwater quality. They are compared with data from other African cities to allow the calculation of a general nitrate and chloride relationship for unsewered African urban areas. Potential interventions to help arrest rising nitrate levels and so provide a public health benefit are also examined.

Quantitative microbial risk assessment to estimate health risks attributable to water supply: can the technique be applied in developing countries with limited data?

In the 3rd edition of its Guidelines for Drinking-Water Quality (2004) (GDWQ) the World Health Organization (WHO) promotes the use of risk assessment coupled with risk management for the control of water safety in drinking water supplies. Quantitative microbial risk assessment (QMRA) provides a tool for estimating the disease-burden from pathogenic microorganisms in water using information about the distribution and occurrence of the pathogen or an appropriate surrogate. This information may then be used to inform decisions about appropriate management of the water supply system. Although QMRA has been used to estimate disease burden from water supplies in developed countries, the method has not been evaluated in developing countries where relevant data may be scarce. In this paper, we describe a simplified risk assessment procedure to calculate the disease burden from three reference pathogens--pathogenic Escherichia coli, Cryptosporidium parvum and rotavirus--in water supplies in Kampala, Uganda. The study shows how QMRA can be used in countries with limited data, and that the outcome can provide valuable information for the management of water supplies.

Monitoring source and domestic water quality in parallel with sanitary risk identification in northern Mozambique to prioritise protection interventions.

Microbiological water quality monitoring in Niassa province, Northern Mozambique, shows groundwater is not, in general, grossly contaminated though contamination levels are strongly linked to season and to risks observable at the wellhead, especially risks dealing with wellhead hygiene and maintenance. Diarrhea incidence, in general, is greatest in the rainy season suggesting poor wellhead protection as a potential mechanism for well contamination. Comparison of source water and stored water in the home shows that significant deterioration in source water quality can occur once transport and storage in the home is undertaken but that this deterioration is also related to the quality of the source water. This study shows that a structured approach to water quality monitoring, with targeted observations and an examination of the relationships between risk and water quality, is important to identify the priority interventions to be undertaken.

Recreational water quality in the Caspian Sea.

Health-based monitoring of the Caspian Sea in Turkmenistan and Iran suggests that bathers are intermittently subject to increased levels of faecal pollution which may lead to gastrointestinal illness. This is the first co-ordinated monitoring programme of recreational waters in the Caspian region and highlights the need to extend such a programme to all countries bordering the Caspian Sea. The novel approach of monitoring that combines risk assessment (water quality monitoring plus a sanitary survey) and risk management, as applied here, allows the identification of possible sources of pollution and the levels of microbiological risk that bathers are subject to. Hence, this allows suitable management interventions to be identified and implemented in the long-term.

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.

Microbial contamination of two urban sandstone aquifers in the UK.

Development of urban groundwater has historically been constrained by concerns about its quality. Rising urban water tables and overabstraction from rural aquifers in the UK have led to a renewed interest in urban groundwater, particularly the possibility of finding water of acceptable quality at depth. This study assessed the microbial quality of groundwater collected from depth-specific intervals over a 15-month period within the Permo-Triassic Sherwood Sandstone aquifers underlying the cities of Nottingham and Birmingham. Sewage-derived bacteria (thermotolerant coliforms, faecal streptococci and sulphite-reducing clostridia) and viruses (enteroviruses, Norwalk-like viruses, coliphage) were regularly detected to depths of 60 m in the unconfined sandstone and to a depth of 91 m in the confined sandstone. Microbial concentrations varied temporally and spatially but increased frequency of contamination with depth coincided with geological heterogeneities such as fissures and mudstone bands. Significantly, detection of Norwalk-like viruses and Coxsackievirus B4 in groundwater corresponded with seasonal variations in virus discharge to the sewer system. The observation of low levels of sewage-derived microbial contaminants at depth in the Triassic Sandstone aquifer is explained by the movement of infinitesimal proportions of bulk (macroscopic) groundwater flow along preferential pathways (e.g., fissures, bedding planes). The existence of very high microbial populations at source (raw sewage) and their extremely low detection limits at the receptor (multilevel piezometer) enable these statistically extreme (microscopic) flows to be traced. Rapid penetration of microbial contaminants into sandstone aquifers, not previously reported, highlights the vulnerability of sandstone aquifers to microbial contamination.

Challenges to achieving sustainable sanitation in informal settlements of Kigali, Rwanda.

Like most cities in developing countries, Kigali is experiencing rapid urbanisation leading to an increase in the urban population and rapid growth in the size and number of informal settlements. More than 60% of the city's population resides in these settlements, where they experience inadequate and poor quality urban services including sanitation. This article discusses the issues and constraints related to the provision of sustainable sanitation in the informal settlements in Kigali. Two informal settlements (Gatsata and Kimisagara) were selected for the study, which used a mixed method approach for data collection. The research found that residents experienced multiple problems because of poor sanitation and that the main barrier to improved sanitation was cost. Findings from this study can be used by the city authorities in the planning of effective sanitation intervention strategies for communities in informal settlements.

Straw N-halamines: evaluation in single and multistage filtration systems.

New N-halamines (I-Cl and II-Cl) based on cellulose extracted from rice straw have been evaluated in single and multistage filtration systems against bacteria and viruses. Escherichia coli and Staphylococcus aureus were used as examples of Gram-negative and Gram-positive bacteria respectively while PRD1 bacteriophage was used as an example for viruses. II-Cl has achieved 9 log reductions in viable counts against E. coli in 2 h and S. aureus in 1h while it has achieved 7 log reductions against PRD1 in 5 h. The particle size of prepared materials was modified as well as the flow rate through the filtration systems. The antimicrobial activity of modified cellulose was proved to be comparable to some synthetic biocidal polymers from the same type in similar water treatment systems.

Economic assessments of small-scale drinking-water interventions in pursuit of MDG target 7C.

This paper uses an applied rural case study of a safer water intervention in South Africa to illustrate how three levels of economic assessment can be used to understand the impact of the intervention on people's well-being. It is set in the context of Millennium Development Goal 7 which sets a target (7C) for safe drinking-water provision and the challenges of reaching people in remote rural areas with relatively small-scale schemes. The assessment moves from cost efficiency to cost effectiveness to a full social cost-benefit analysis (SCBA) with an associated sensitivity test. In addition to demonstrating techniques of analysis, the paper brings out many of the challenges in understanding how safer drinking-water impacts on people's livelihoods. The SCBA shows the case study intervention is justified economically, though the sensitivity test suggests 'downside' vulnerability.