5.1.1. Audit

In the audit approach to surveillance, assessment activities, including verification testing, are undertaken largely by the supplier, with third-party auditing to verify compliance. It is increasingly common that analytical services are procured from accredited external laboratories. Some authorities are also experimenting with the use of such arrangements for services such as sanitary inspection, sampling and audit reviews.

An audit approach requires the existence of a stable source of expertise and capacity within the surveillance agency in order to:

• review and approve new WSPs;
• undertake or oversee auditing of the implementation of individual WSPs as a programmed routine activity;
• respond to, investigate and provide advice on receipt of reports on significant incidents.

Periodic audit of the implementation of WSPs is required:

• at intervals (the frequency of routine audits will be dependent on factors such as the size of the population served and the nature and quality of source water and treatment facilities);
• following substantial changes to the source, the distribution or storage system or treatment processes;
• following significant incidents.

Periodic audit would normally include the following elements:

• examination of records to ensure that system management is being carried out as described in the WSP;
• ensuring that operational monitoring parameters are kept within operational limits and that compliance is being maintained;
• ensuring that verification programmes are operated by the water supplier (either through in-house expertise or through a third-party arrangement);
• assessment of supporting programmes and of strategies for improving and updating the WSP;
• in some circumstances, sanitary inspection, which may cover the whole of the drinking-water system, including sources, transmission infrastructure, treatment plants, storage reservoirs and distribution systems.

In response to reports of significant incidents, it is necessary to ensure that:

• the event is investigated promptly and appropriately;
• the cause of the event is determined and corrected;
• the incident and corrective action are documented and reported to appropriate authorities;
• the WSP is reassessed to avoid the occurrence of a similar situation.

The implementation of an audit-based approach places responsibility on the drinking-water supplier to provide the surveillance agency with information regarding system performance against agreed indicators. In addition, a programme of announced and unannounced visits by auditors to drinking-water suppliers should be implemented to review documentation and records of operational practice in order to ensure that data submitted are reliable. Such an approach does not necessarily imply that water suppliers are likely to falsify records, but it does provide an important means of reassuring consumers that there is true independent verification of the activities of the water supplier. The surveillance agency will normally retain the authority to undertake some analysis of drinking-water quality to verify performance or enter into a third-party arrangement for such analysis.

5.1.2. Direct assessment

It may be appropriate for the drinking-water supply surveillance agency to carry out independent testing of water supplies. Such an approach often implies that the agency has access to analytical facilities with staff trained to carry out sampling, analysis and sanitary inspection.

Direct assessment also implies that surveillance agencies have the capacity to assess findings and to report to and advise suppliers and communities. A surveillance programme based on direct assessment would normally include:

• specified approaches to large municipality/small municipality/community supplies and individual household supplies;
• sanitary inspections to be carried out by qualified personnel;
• sampling to be carried out by qualified personnel;
• tests to be conducted using suitable methods by accredited laboratories or using approved field testing equipment and qualified personnel;
• procedures on reporting findings and follow-up to ensure that they have been acted on.

For community-managed drinking-water supplies and where the development of in-house verification or third-party arrangements is limited, direct assessment may be used as the principal system of surveillance. This may apply to drinking-water supplies in small towns by small-scale private sector operators or local government. Direct assessment may lead to the identification of requirements to amend or update the WSP, and the process to be followed when undertaking such amendments should be clearly identified.

Where direct assessment is carried out by the surveillance agency, it complements other verification testing of the water supplier. General guidance on verification testing, which is also applicable to surveillance through direct assessment, is provided in section 4.3.

5.2.1. Urban areas in developing countries

Drinking-water supply arrangements in urban areas of developing countries are typically complex. There can often be one or more large piped supplies with household and public connections, in combination with a range of alternative drinking-water supplies, including point sources and vended water. In these situations, the surveillance programme should take account of the different sources of drinking-water and the potential for deterioration in quality during collection, storage and use. Furthermore, the population will vary in terms of socioeconomic status and vulnerability to water-related disease.

In many situations, zoning the urban area on the basis of vulnerability and drinking-water supply arrangements is required. The zoning system should include all populations within the urban area, including informal and periurban settlements, regardless of their legal status, in order to direct resources to where greatest improvements (or benefits) to public health will be achieved. This provides a mechanism to ensure that non-piped drinking-water sources are also included within drinking-water supply surveillance activities.

Experience has shown that zoning can be developed using qualitative and quantitative methods and is useful in identifying vulnerable groups and priority communities where drinking-water supply improvements are required.

5.2.2. Community drinking-water supplies

Small community-managed drinking-water supplies are found in most countries and may be the predominant form of drinking-water supply for large sections of the population. The precise definition of a “community drinking-water supply” will vary, but administration and management arrangements are often what set community supplies apart, especially in developing countries. Community-managed supplies may include simple piped water systems or a range of point sources, such as boreholes with hand pumps, dug wells and protected springs.

The control of water quality and implementation of surveillance programmes for such supplies often face significant constraints. These typically include:

• limited capacity and skills within the community to undertake process control and verification; this may increase the need both for surveillance to assess the state of drinking-water supplies and for surveillance staff to provide training and support to community members;
• the very large number of widely dispersed supplies, which significantly increases overall costs in undertaking surveillance activities.

Experience from both developing and developed countries has shown that surveillance of community-managed drinking-water supplies can be effective when well designed and when the objectives are geared more towards a supportive role to enhance community management than towards enforcement of compliance.

Surveillance of community drinking-water supplies requires a systematic programme of surveys that encompass all aspects of the drinking-water supply to the population as a whole, including sanitary inspection (including catchment inspections) and institutional and community aspects. Surveillance should address variability in source water quality, treatment process efficacy and the quality of distributed or household-treated and household-stored water.

Experience has also shown that the role of surveillance may include health education and health promotion activities to improve healthy behaviour towards management of drinking-water supply and sanitation. Participatory activities can include sanitary inspection by communities and, where appropriate, community-based testing of drinking-water quality using affordable field test kits and other accessible testing resources.

In the evaluation of overall strategies, the principal aim should be to derive overall lessons for improving water safety for all community supplies, rather than relying on monitoring the performance of individual supplies.

Frequent visits to every individual supply may be impractical because of the very large numbers of such supplies and the limitations of resources for such visits. However, surveillance of large numbers of community supplies can be achieved through a rolling programme of visits. Commonly, the aim will be to visit each supply periodically (once every 3–5 years at a minimum) using either stratified random sampling or cluster sampling to select specific supplies to be visited. During each visit, sanitary inspection and water quality analysis will normally be done to provide insight to contamination and its causes.

During each visit, testing of water stored in the home may be undertaken in a sample of households. The objective for such testing is to determine whether contamination occurs primarily at the source or within the home. This will allow evaluation of the need for investment in supply improvement or education on good hygiene practices for household treatment and safe storage. Household testing may also be used to evaluate the impact of a specific hygiene education programme.

5.2.3. Household treatment and storage systems

Where water is handled during storage in households, it may be vulnerable to contamination, and sampling of household-stored water is of interest in independent surveillance. It is often undertaken on a “survey” basis to develop insights into the extent and nature of prevailing problems. Surveillance systems managed by public health authorities for drinking-water supplies using household treatment and household storage containers are therefore recommended.

The principal focus of surveillance of household-based interventions will be assessment of their acceptance and impact through sample surveys so as to evaluate and inform overall strategy development and refinement. Systematic determination of continued, correct and effective use and management is recommended so that deficiencies in use and management can be identified and corrected by those responsible.

5.3.1. Accessibility

From the public health standpoint, the proportion of the population with sustained, reliable access to safe drinking-water is the most important single indicator of the overall success of a drinking-water supply programme.

There are a number of definitions of access (or coverage), many with qualifications regarding safety or adequacy. Sustainable Development Goal (SDG) target 6.1 calls for universal and equitable access to safe and affordable drinking-water for all. The target is monitored using the indicator “proportion of population using safely managed drinking water services”, which is defined as the use of an improved water source that is accessible on premises, available when needed, and free from faecal and priority chemical contamination (WHO & UNICEF, 2017). SDG target 1.4 also references drinking-water, by calling for “all men and women” to have equal access to basic services, including “basic drinking water services”, which are defined as use of an improved water source, provided that collection time is not more than 30 minutes for a round trip, including queuing.

An improved drinking-water source is one that has the potential to deliver safe water by the nature of its construction and design. Improved sources are more likely than unimproved sources to supply drinking-water free from microbiological contamination, although microbiological contamination does occur in all types of water supply, particularly when they are inadequately managed. Improved and unimproved water supply technologies are summarized below:

• Improved drinking-water sources:

  —

  piped supplies (including household and yard connections, public taps and standpipes)

  —

  boreholes and tubewells

  —

  protected dug wells

  —

  protected springs

  —

  rainwater

  —

  water kiosks

  —

  packaged water

  —

  delivered water.

• Unimproved drinking-water sources:

  —

  unprotected dug wells

  —

  unprotected springs

  —

  surface water (rivers, reservoirs, lakes, ponds, streams, canals and irrigation channels).

Determining the proportion of a population with reliable access to drinking-water is an important function of a drinking-water surveillance agency. This task can be facilitated by establishing a common definition for reasonable access, appropriate to the local context, which may describe a minimum quantity of water supplied per person per day, together with a maximum tolerable distance or time to a source (see section 5.3.2).

The global SDG indicators identify different levels of accessibility: the basic service indicator calls for improved water supplies to be located within a 30-minute round trip travel time, including queuing, while the safely managed services indicator requires that the water collection point be located on-premises (i.e. within the household, yard or plot).

5.3.2. Quantity

The quantity of water used by households has an important influence on health. There is a basic human physiological requirement for water to maintain adequate hydration and an additional requirement for food preparation. There is a further requirement for water to support hygiene, both personal and household, which is necessary for health.

Estimates of the volume of water needed for health purposes vary widely. In deriving World Health Organization (WHO) guideline values, it is assumed that the daily per capita consumption of drinking-water is approximately 2 litres for adults, although actual consumption varies according to climate, activity level and diet. Based on currently available data, a minimum volume of 5.3 litres per person per day will provide sufficient water for hydration under most conditions. There is insufficient empirical evidence to define a minimum quantity of water necessary for food preparation or for hygiene. Experience and expert opinion suggest that 20 litres per person per day is often sufficient for drinking, cooking, food hygiene, handwashing and face washing. However other hygiene practices, including bathing and laundry, may not be assured. Further, where demands for water are increased—for example, due to increased hand hygiene in response to outbreaks of disease—20 litres per person per day may be insufficient; in many cases, running water from a tap will be necessary to support sufficient handwashing.

Table 5.1

Summary of water access, adequacy and level of health concern.

The quantity of water collected and used by households is primarily a function of the distance to the water supply or the total collection time required (including queuing). This broadly equates to access level. Four levels of access can be defined, as shown in Table 5.1.

Access level is a useful and easily measured indicator that provides a valid proxy for the quantity of water collected by households and is the preferred indicator for surveillance. Available evidence indicates that health gains accrue from improving access level in three key stages: delivery of water within 1 km or 5–30 minutes of total collection time (“basic access”); water being supplied reliably on-plot, especially when running water is available (“intermediate access”); and water being available within the home through multiple taps (“optimal access”). The first and second categories of access broadly align with the access levels associated with basic and safely managed services, respectively. Although health gains do occur in these two categories, health concerns remain, particularly during outbreaks of disease when enhanced personal hygiene is needed. The volume of water collected may also depend on the continuity, reliability and cost of the water. Therefore, collection of data on these indicators is important.

5.3.3. Continuity

Interruptions to drinking-water supply, as a result of either intermittent sources or engineering inefficiencies, are a major determinant of the quantity and quality of drinking-water available to households. Analysis of data on continuity of supply requires the consideration of several components. Continuity can be classified as follows:

• year-round service from a reliable source with no interruption of flow at the tap or source;
• year-round service with frequent (daily or weekly) interruptions, of which the most common causes are:

  —

  water production that is insufficient to meet demand, requiring rationing of water;

  —

  restricted pumping regimes in pumped systems, whether planned or due to power failure or sporadic failure;

  —

  peak demand exceeding the flow capacity of the transmission mains or the capacity of the reservoir;

  —

  excessive leakage within the distribution system;

  —

  excessive demands on community-managed point sources;

  —

  breakdown of components of point sources (e.g. handpump parts);

• seasonal service variation resulting from source water fluctuation, which typically has three causes:

  —

  natural variation in source water volume during the year, which may be exacerbated by changes in climate (see section 6.1);

  —

  volume limitation because of competition with other uses, such as irrigation;

  —

  periods of high turbidity when the source water may be untreatable;

• combined frequent and seasonal discontinuity.

These classifications reflect broad categories of continuity, which are likely to affect the quantity and quality of water available and thereby public health in different ways. Any interruption of service is likely to result in an increased risk of degradation of water quality, an increased risk of exposure to contaminated water and therefore an increased risk of waterborne disease. Managed discontinuity often results in low supply pressure and a consequent risk of in-pipe recontamination. Other consequences include reduced availability and lower volume use, which adversely affect hygiene. This may be a problem both when the discontinuity is predictable and when it is highly unpredictable. Household water storage may be necessary, and this may lead to an increase in the risk of contamination during such storage and associated handling. Discontinuity often forces users to obtain water from inferior and distant sources. As a consequence, in addition to the obvious reduction in water quality and quantity, time is lost in water collection, and other risks (e.g. to musculoskeletal health) may arise. This applies particularly to women, who disproportionately bear the burden of collecting and hauling water from off-premises sources.

The SDGs do not specify a minimum quantity of water to be available, but the safely managed drinking-water services indicator calls for water to be “available when needed”. For the purposes of global reporting, households are considered to have water available when needed if they report having “sufficient water” or that water is available “most of the time” (i.e. at least 12 hours per day or 4 days per week). However, although this metric is useful for global monitoring, it does not imply that this level of continuity is sufficient to realize public health gains, or that it represents a normative target. The indicators used for SDG monitoring are simplifications and do not capture all aspects of water services that are important from a normative perspective.

5.3.4. Affordability

Affordability, or economic accessibility, implies that individuals or households should be able to purchase water without compromising the purchase of any other basic needs (UNICEF & WHO, 2021). A critical component in assessing affordability is the cost of water paid by individuals and further information related to costs is described in these Guidelines.

The cost of water has an influence on the use of water and selection of water sources. Households with the lowest levels of access to safe water supply frequently pay more for their water than do households connected to a piped water system. The high cost of water may force households to use alternative sources of water of poorer quality that represent a greater risk to health, or to use multiple sources of water, which may have varying quality and therefore also pose a risk to health. Furthermore, high costs of water may reduce the volumes of water used by households, particularly where multiple sources are not available, which in turn may influence hygiene practices and increase risks of disease transmission.

When assessing cost, it is important to collect data on the price at the point of purchase. Where households are connected to the drinking-water supplier, this will be the tariff applied. Where water is purchased from, for example, public standpipes or trucked water, the price at the point of purchase may be very different from the drinking-water supplier tariff. Many alternative water sources (notably vendors) also involve costs, and these costs should also be considered. In addition to recurrent costs, the costs for initial acquisition of a connection for households connected to the drinking-water supplier or where households have their own private point source should be considered.

5.5.1. Interaction with community and consumers

Community participation is a desirable component of surveillance, particularly for community and household drinking-water supplies. As primary beneficiaries of improved drinking-water supplies, community members have a right to take part in decision-making. The community represents a resource that can be drawn upon for local knowledge and experience. They are the people who are likely to first notice problems in the drinking-water supply and therefore can provide an indication of when immediate remedial action is required. Communication strategies should include:

• provision of summary information to consumers (e.g. through annual reports or the Internet);
• establishment and involvement of consumer associations at local, regional and national levels.

In many communities, however, the simple right of access to information will not ensure that individuals are aware of the quality or safety of the water supplied to them. The agencies responsible for surveillance should develop strategies for disseminating and explaining the significance of results obtained.

It may not be feasible for the surveillance agency to provide feedback information directly to the entire community. Thus, it may be appropriate to use community organizations, where these exist, to provide an effective channel for providing feedback information to users. Some local organizations (e.g. local councils and community-based organizations, such as women’s groups, religious groups and schools) have regular meetings in the communities that they serve and can therefore provide a mechanism of relaying important information to a large number of people within the community. Furthermore, by using local organizations, it is often easier to initiate a process of discussion and decision-making within the community concerning water quality. The most important element in working with local organizations is to ensure that the organization selected can access the whole community and can initiate discussion on the results of surveillance (see sections 7.6.1 and 8.7).

5.5.2. Regional use of data

Strategies for regional prioritization are typically of a medium-term nature and have specific data requirements. While the management of information at a national level is aimed at highlighting common or recurrent problems, the objective at a regional level is to assign a degree of priority to individual interventions. It is therefore important to derive a relative measure of health risk. Although this information cannot be used on its own to determine which systems should be given immediate attention (which would also require the analysis of economic, social, environmental and cultural factors), it provides an extremely important tool for determining regional priorities. It should be a declared objective to ensure that remedial action is carried out each year on a predetermined proportion of the systems classified as high risk.

At the regional level, it is also important to monitor the improvement in (or deterioration of) both individual drinking-water supplies and the supplies as a whole. In this context, simple measures, such as the mean sanitary inspection score of all systems, the proportion of systems with given degrees of faecal contamination, the population with different levels of service and the mean cost of domestic consumption, should be calculated yearly and changes monitored.

As shown in Table 7.10 in section 7.4, the aim should be to provide drinking-water that contains no faecal indicator organisms, such as Escherichia coli. However, in many developing and developed countries, a high proportion of household and small community drinking-water systems, in particular, fail to meet requirements for water safety, including the absence of E. coli. In such circumstances, it is important that realistic goals for progressive improvement are agreed upon and implemented. It is practical to classify water quality results in terms of an overall grading for water safety linked to priority for action, as illustrated in Table 5.2.

Grading schemes may be of particular use in community supplies where the frequency of testing is low and reliance on analytical results alone is especially inappropriate. Such schemes will typically take account of both analytical findings and results of the sanitary inspection through matrices such as the one illustrated in Table 5.3.

Table 5.2

Example of categorization of drinking-water systems on the basis of population size and quality rating in order to prioritize actions (see also Table 7.10).

Table 5.3

Example of assessment of priority of remedial actions of community drinking-water supplies based on a grading system of microbial quality and sanitary inspection rating or score.

Combined analysis of sanitary inspection and water quality data can be used to identify the most important causes of and control measures for contamination. This is important to support effective and rational decision-making. For instance, it will be important to know whether on-site or off-site sanitation could be associated with contamination of drinking-water, as the remedial actions required to address either source of contamination will be very different. This analysis may also identify other factors associated with contamination, such as heavy rainfall. As the data will be non-parametric, suitable methods for analysis include chi-square, odds ratios and logistic regression models.

Combined analysis of sanitary inspection and water quality data is especially useful in assessing household water management systems. Microbial water quality data are often limited, and sanitary inspection risk scoring therefore becomes an important consideration in assessing household water systems, their management and priority for remedial actions. An example of a combined system to assess risk and prioritize remedial actions for household water systems is shown in Table 5.4.

Table 5.4

Example of assessment of priority of remedial action for household drinking-water systems based on a grading system of microbial quality and sanitary inspection rating or scores.