Nearly two billion people are thought to use a source of drinking water contaminated with faeces. Many more drink unsafe water because safety can be compromised during transport, storage and handling. Ensuring safe drinking water for all is a key target of the Sustainable Development Goals (SDG 6.1). As well, water safety is of primary importance for infants and young children who are especially vulnerable to diarrhoea and other water-related diseases.
The WHO Guidelines for Drinking Water Quality recommend testing water for evidence of faecal contamination as a measure of water quality. In many countries, however, data on water quality are difficult to collect and typically available only for piped water supplies. Typically, water testing occurs in laboratories which often poses logistical challenges, from transport of water samples to ensuring that samples are tested within appropriate time frames.
Together with the WHO/UNICEF Joint Monitoring Programme (JMP) for Water Supply, Sanitation and Hygiene, the Multiple Indicator Cluster Surveys (MICS) has developed methods for the direct testing of water in household surveys. This information complements data collected on a household’s main drinking water source – data that are already a core element of MICS surveys. With the potential addition of new questions on the availability of drinking water, these elements will enable MICS surveys to report on the SDG indicator on “safely-managed drinking water”.
Two technical task forces on drinking water quality monitoring were convened by the JMP in 2010 and 2012. Experts agreed that there was great potential to collect water quality information through nationally-representative household surveys and that the primary focus should be on faecal contamination – as indicated by the presence of the bacterium Escherichia coli (E. coli) in a 100 mL sample of water. In some countries, arsenic and fluoride can be prioritised. Water testing should assess the level of risk and take place at both the “point of use” and the “point of service delivery”.
Development of the E. coli field test
An innovative field-based testing approach was developed for use in household surveys and first tested during the MICS5 pilot in Bogra, Bangladesh in 2012. Combining enzyme substrate nutrient plates (Nissui Compact Dry) and field-based membrane filtration, the test provides information on levels of E. coli in 100 mL samples. This is the preferred measure of faecal contamination. The test allows comparison against national and international standards (no E. coli in 100 mL) as well as estimate various risk levels of contamination.
Water samples are collected in households and filtered through a membrane. Any E. coli present in the water are retained on the surface of the membrane. Membranes are then stored in specially designed incubation belts carried by the fieldwork staff, or in electric incubators which encourage the growth of E. coli. After a 24 hour period, colonies of E. coli are detectable by eye and counted.
A range of quality assurance and quality control measures were developed for use in MICS. For example, MICS tests “blanks” – samples known to be free of contamination – to ensure that poor survey testing techniques (e.g. dirty hands or equipment) are not leading to positive tests. Field supervision and oversight by technicians from water quality laboratories can provide training further opportunities to ensure that results are robust.
Experience from MICS surveys during module development
Four nationally representative MICS surveys have incorporated the water quality test in Bangladesh (MICS 2012-2013), Nepal (MICS 2014) and the Republic of Congo (MICS 2014) and Cote d’Ivoire (MICS 2016). The module was also incorporated in the Ghana Living Standards Survey (GLSS 2012-2013). The surveys have demonstrated the feasibility of testing water quality in household surveys and have allowed for refinements to the protocols and procedures. The results also show widespread faecal contamination of drinking water in these settings with higher risk of contamination in certain regions in each country. Further, contamination is more common in water at the “point of use” that at the source, indicating that water quality deteriorates after collection.
Some of the key lessons for future surveys have included: the need for advance planning and preparation for the procurement of water testing supplies; the benefits of engaging national water quality experts, especially for the training of field teams; the advantages of incubation belts as an alternative to electric incubators where electricity is unreliable or not accessible; and testing water in 3-5 households per cluster to reduce the burden on field teams.
Field-test in Belize
A field-test in Belize in late 2015 provided an opportunity to evaluate the performance of the E. coli water quality test. Water quality was measured by field teams in over 250 households and samples were also sent to a national laboratory for comparative testing against reference methods.
The field test also comprehensively examined the performance of the questions that are critical for reporting on the SDG indicator safely managed drinking water. Photos were taken of water sources and compared to the survey responses and a variety of techniques were used to assess whether the respondents easily understood and could answer the questions about availability of drinking water when needed. The results of the study have been summarized and published in a peer-review journal (Khan et al. 2017)
Release and roll out of module in MICS6
The module was released as part of the standard MICS6 tools and has since been integrated in over 40 MICS6 surveys, generating nationally representative data on water quality, often for the first time. The water quality module has also been adapted for use in several non-MICS national surveys including Living Standards Measurement Studies and Demographic and Health Surveys, further demonstrating the value of this new approach.
The MICS6 tools for water quality include a detailed training manual for field teams and a dedicated water quality testing questionnaire. Further information on the water quality module is available on the WHO/UNICEF JMP website (washdata.org).
The WHO/UNICEF JMP and MICS teams continue to refine the module, gather feedback from ongoing surveys and are actively exploring alternative low-cost or rapid test procedures for E. coli in collaboration with UNICEF’s Supply Division.