The most effective means of consistently ensuring the safety of a drinking-water supply is through the use of a comprehensive risk assessment and risk management approach that encompasses all steps in the water supply from catchment to consumer.
Such approaches are termed Water Safety Plans (WSPs). The WSP approach has been developed to organize and systematize a long history of management practices applied to drinking-water and to ensure the applicability of these practices to the management of drinking-water quality.
WSPs represent an evolution of the concept of sanitary surveys and vulnerability assessments that include and encompass the whole of the water supply system and its operation.
The WSP approach draws on many of the principles and concepts from other risk management approaches, in particular the multiple-barrier approach and hazard assessment and critical control points (as used in the food industry).
Water Safety Plans vary in complexity, as appropriate for the situation. In many cases, they will be quite simple, focusing on the key hazards identified for the specific drinking-water supply system. The wide range of examples of control measures given in the following text does not imply that all of these are appropriate in all cases.
WSPs should, by preference, be developed for individual drinking-water systems.
For smaller systems, it may be possible to develop generic Water Safety Plans by a statutory body or accredited third-party organization. In these settings, guidance on household water storage, handling and use may also be required.
Plans dealing with household water should be linked to a hygiene education programme and advice to households in maintaining water safety. A WSP has three key components, which are guided by health based targets and overseen through drinking-water supply surveillance. They are:
- a system assessment to determine whether the drinking-water supply chain (up to the point of consumption) as a whole can deliver water of a quality that meets identified targets. This also includes the assessment of design criteria of new systems.
- identifying control measures in a drinking-water system that will collectively control identified risks and ensure that the health-based targets are met. For each control measure identified, an appropriate means of operational monitoring should be defined that will ensure that any deviation from required performance is rapidly detected in a timely manner.
- management and communication plans describing actions to be taken during normal operation or incident conditions and documenting the system assessment, including upgrade and improvement planning, monitoring and communication plans and supporting programmes.
The primary objectives of a WSP in ensuring good drinking-water supply practice are the prevention or minimization of contamination of source waters, the reduction or removal of contamination through treatment processes and the prevention of contamination during storage, distribution and handling of drinking-water.
These objectives are equally applicable to large piped drinking-water supplies, small community supplies and household systems and are achieved through:
- development of an understanding of the specific system and its capability to supply water that meets water quality targets.
- identification of potential sources of contamination and how they can be controlled.
- validation of control measures employed to control hazards.
- implementation of a system for operational monitoring of the control measures within the water system.
- timely corrective actions to ensure that safe water is consistently supplied.
- undertaking verification of drinking-water quality to ensure that the WSP is being implemented correctly and is achieving the performance required to meet relevant national, regional and local water quality standards or objectives.
Water Safety Plans are a powerful tool for the drinking-water supplier to manage the supply safely. They also assist surveillance by public health authorities. Key benefits for water suppliers implementing WSPs include:
- demonstration of “due diligence”.
- improved compliance.
- rationalizing and documenting existing operational procedures, leading to gains in efficiency, improvement of performance and quicker response to incidents.
- better targeted and justification for long-term capital investments based on risk assessment.
- improved management of existing staff knowledge and identification of critical gaps in skills for staff.
- improved stakeholder relationships.
One of the challenges and responsibilities of water suppliers and regulators is to anticipate, plan for and provide for climate variations and weather extremes. Water Safety Plans are an effective tool to manage such variations and extremes.
Where a defined entity is responsible for a drinking-water supply, its responsibility should include the preparation and implementation of a WSP. This plan should normally be reviewed and agreed upon with the authority responsible for protection of public health to ensure that it will deliver water of a quality consistent with the defined targets.
Where there is no formal service provider, the competent national or regional authority should act as a source of information and guidance on the adequacy of appropriate management of community and individual drinking-water supplies.
This will include defining requirements for operational monitoring and management. Approaches to verification in these circumstances will depend on the capacity of local authorities and communities and should be defined in national policy.
Many water suppliers may face practical challenges in initiating, developing and implementing a Water Safety Plans. These include mistaken perceptions that one prescribed methodology must be followed and that WSP steps must be undertaken with risks managed from source to tap in a defined order.
That developing a WSP always requires external expertise; WSPs supersede, rather than build on, existing good practices and that WSPs are necessarily complicated and are not appropriate for small supplies.