Safe management of drinking water supplies

With the 2003 edition of the Guidelines for Drinking-water Quality, GDWQ, the WHO recommended a comprehensive risk assessment and risk management approach for the first time, termed Water Safety Plans. With this approach, risks to human health can be systematically identified, assessed and controlled in all processes from catchment to consumer.

WSP is a preventive management system tailored towards water supplies. This approach can be universally applied, irrespective of the type of raw water source used, the size or the complexity of the water supply.

For practical implementation of the WSP-approach, WHO has developed a number of tools, including for example a manual for large water supplies as well as a manual and a field guide for implementation in small community water supplies.

At the European level, the WSP-approach was first taken up through the DIN-EN 15975-2 in 2013. UBA, together with the Water Technology Centre (TZW), developed a manual for implementation of the WSP approach in small-scale water supplies in Germany. The manual complements the die DIN-EN 15975-2 with practical explanations, recommendations, examples and supporting tools.

Developing a WSP can help to identify and remediate weaknesses of the system. The process substantially improves the understanding of the specific water supply system and thus strengthens due diligence and organizational confidence of the water supplying entity. Applying WSP also improves the knowledge of the locally relevant technical rules and their application, and it provides a technically sound basis for decisions on improvements. WSP also improve communication between stakeholders within the water supply, as well as with external stakeholders, particularly competent authorities.

The WSP approach comprises hazard analysis, risk assessment and systematic process control. It is an operational quality management concept which includes the following steps:

1. The first step of the WSP approach is for senior management of the water supply to assemble a team. The WSP-team is responsible for independently developing a WSP and for implementing it in routine operation of the supply. A committed team which is capable of acting and which encompasses the expertise required for a comprehensive risk assessment is presented is a prerequisite for successful WSP implementation.
2. The description of the water supply system is the basis of every WSP. It has to cover the catchment area, abstraction, treatment, storage and the distribution system, including pumping stations and pressure boosting systems.
3. The system assessment consists of a hazard analysis and a risk assessment. In WSP terminology, a hazard is any biological, chemical, physical or radiological agent in the water supply system which may cause harm to public health. Hazardous events in the WSP context are incidents or situations which cause hazards to occur in the drinking-water supply. As part of the risk assessment, the WSP team evaluates the risk caused by every hazardous event identified. The risk comprises the two aspects of likelihood to occur and potential severity of consequences. The key questions for the risk assessment are: "What hazards and hazardous events are significant?" and "What is important and why?"
4. Measures for controlling the risks ensure drinking-water quality and reliability of the water supply. Such measures include all actions, activities and processes which aim at permanently eliminating or reducing risks. In this step, the team also has to check and confirm to what extent the existing measures actually control the risks. This means to answer the question: "Is the chosen measure suitable and effective?" for each measure identified. Should this validation process show that the already existing measures are not sufficient to control the identified initial risk, action for improvement or upgrade needs to be taken, and the team should change, optimise, complement or replace the measures respectively. If the validation even indicates that measures are absent, the team should identify and implement suitable technical, organisational or staffing measures.
5. Operational monitoring comprises regular planned inspections, controls or measurements of selected parameters. It aims at ensuring that the control measures in place have been implemented and are operating effectively as planned. Operational monitoring is NOT the same as testing the ‘end product’ drinking-water in accordance with the requirements of the German Drinking Water Ordinance (TrinkwV 2001), but rather includes parameters which can be easily measured or observed, and for which the measurement results are, if ever possible, instantly available. Its purpose is to show that a measure is working within its operational limits (e.g. turbidity at a filter effluent).
6. Verification is an integral part of a WSP in order to confirm that the limit values and requirements of the German Drinking Water Ordinance, as well as water supply goals, are attained.  Classical end product testing of drinking-water in terms of regular self-control by the water supply utility when the water leaves the waterworks and within the distribution system is verification. This end-product testing should not be mistaken for operational monitoring.
7. It is important that the team documents the results of each WSP step, as well as the underlying considerations. The type and extent of documentation vary, depending on the tasks and the size of the water supply.
8. A WSP is never "completed", but should rather be continually and regularly updated and improved by the team. The aim of this planned, periodic review is to "step back to see the bigger picture" to confirm the validity of the WSP.

The German Drinking Water Ordinance requires that facilities for the treatment and distribution of drinking-water are planned, constructed and operated at minimum in compliance with the generally acknowledged technical rules and standards. Specifically for installations in large buildings, the Drinking Water Ordinance includes the requirement to conduct hazard analyses, which are a core element of WSP, if samples exceed a “technical action level” for Legionella.

In total, approximately 300 technical rules describe what needs to be considered in drinking-water supply – for all steps in the process from establishing drinking-water protection zones to testing water taps for their certification. The DVGW has compiled a selection of technical rules particularly for the operation of small-scale water supplies. The aim of the Technical Safety Management (TSM) of DVGW is to support  water suppliers in meeting their responsibilities and to strengthen their technical self-management.

The die DIN-EN 15975-2 of the DVGW describes central elements of the WSP-approach and deals with risk management under normal operating conditions, integrating it into the set of technical rules, whereas die DIN-EN 15975-1 deals with emergency conditions.

The Federal Environment Agency has completed several projects with partners from water supplies, health agencies and operators of buildings in order to assess the extent to which the WSP approach can be implemented in large and in small-scale water supplies, as well as in buildings in Germany, which prerequisites and potentially support is required, and which benefits it conveys. Thus, UBA is promoting the discussion of this fairly new concept in Germany.

As a WHO Collaborating Centre for Research on Drinking-Water Hygiene, UBA also provides consulting services to stakeholders in other countries on implementing the WSP approach, and it supports the development of training materials, tools and guidance for implementing WSP.

In order to assess European experience with the WSP-approach, UBA, together with the World Health Organization (WHO), the Berlin Centre of Competence for Water (KWB), the International Water Association (IWA), the European Federation of National Associations of Water Services (EUREAU) and the DVGW German Technical and Scientific Association for Gas and Water, organized a „Strategic Workshop on Water Safety Plans (WSP) for Europe“ in Berlin on 12-13 March 2014. Participants from research, water supply utilities and regulation discussed approaches for regulation and implementation in the European context and shared experience in implementation of the WSP approach, the resulting benefits as well as enabling prerequisites and boundary conditions.