3.3 Preventive measures for drinking water quality management (element 3)

Components:

• Preventive measures and multiple barriers

• Critical control points

Prevention is an essential feature of effective drinking water quality management. Preventive measures are those actions, activities and processes used to prevent hazards from occurring or reduce them to acceptable levels.

Hazards may occur or be introduced throughout the water system and preventive measures should be comprehensive, from catchment to consumer. Many preventive measures may control more than one hazard, while, as prescribed by the multiple barrier approach, effective control of some hazards may require more than one preventive measure. Preventive measures should be applied as close to the source as possible, with a focus on prevention in catchments rather than sole reliance on downstream control.

Planning of preventive measures should always be based on system-specific hazard identification and risk assessment. The level of protection to control a hazard should be proportional to the associated risk. Assessment of preventive measures involves:

• identifying existing preventive measures from catchment to consumer for each significant hazard or hazardous event

• evaluating whether the preventive measures, when considered together, are effective in reducing risk to acceptable levels (i.e. residual risk – Section 3.2.3)

• if improvement is required, evaluating alternative and additional preventive measures that could be applied.

If additional measures are required, factors such as level of risk, benefits, effectiveness, cost, community expectations and willingness to pay should be considered. Preventive measures often require considerable expenditure, and decisions about water quality improvements cannot be taken in isolation from other aspects of water supply that compete for limited financial resources. Priorities will need to be established and many improvements may need to be phased in over time.

All preventive measures are important and should be given ongoing attention. However, some can significantly prevent or reduce hazards and are amenable to greater operational control than others. These measures could be considered as critical control points (see Section 3.3.2).

Additional guidance on this element is provided in the Appendix.