3.3.2 Critical control points

Summary of actions

• Assess preventive measures from catchment to consumer to identify critical control points.

• Establish mechanisms for operational control (see Section 3.4).

• Document the critical control points, critical limits and target criteria.

From among the preventive measures, critical control points should be identified for those hazards that represent a significant risk and require elimination or reduction to assure supply of safe drinking water.

A critical control point is defined as an activity, procedure or process at which control can be applied and which is essential to prevent a hazard or reduce it to an acceptable level.

Not all preventive measures are amenable to selection as critical control points. A critical control point has several operational requirements, including:

• operational parameters that can be measured and for which critical limits can be set to define the operational effectiveness of the activity (e.g. chlorine residuals for disinfection);

• operational parameters that can be monitored frequently enough to reveal any failures in a timely manner (online and continuous monitoring is preferable);

• procedures for corrective action that can be implemented in response to deviation from critical limits.

Critical limits are performance criteria that separate acceptability from unacceptability in terms of hazard control and water safety. They should be chosen carefully and should not be confused with target criteria (see Section 3.4.2). Critical limits may incorporate a numerical value as well as a consideration of time (e.g. failure to provide a minimum chlorine residual for a specified time).

Deviation from critical limits indicates loss of control of the process or activity and should be regarded as representing a potentially unacceptable health risk. Such events should result in immediate notification of the relevant health authority or drinking water regulator. Discussion of target criteria and critical limits is included in Section 3.4.2, and more detailed explanation of critical control points and their requirements is provided in Chapter 9 Section 9.4.3, 9.4.6 and the Appendix.