Background to Critical Control Points
Critical Control Points (CCP) are an important component of Drinking Water Quality Management Plans (DWQMP) as well Recycled Water Management Plans (RWMP). However, the concept was originally developed in the food industry and has been utilised in these water specific management systems.
The Codex Alimentarius (Latin for Food Code) is a collection of internationally recognised food standards. Hazard Analysis and Critical Control Point (HACCP) System and Guidelines for its Application is one of the standards for food safety. HACCP has seven principles:
conduct a hazard analysis.
determine the CCPs.
establish critical limit(s).
establish a system to monitor control of the CCP.
establish the corrective action to be taken when monitoring indicates that a particular CCP is not under control.
establish procedures for verification to confirm that the HACCP system is working effectively.
establish documentation concerning all procedures and records appropriate to these principles and their application.
In the case of DWQMPs and RWMPs these principles have been incorporated in to the 12 elements of the Australian Drinking Water Guidelines (ADWG) and Guidelines for Water Recycling (AGWR). Table 2.2 in the ADWG shows the correlation between HACCP and the 12 elements. In the ADWG a CCP 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. It also has the following operational requirements:
there is a parameter that can be measured and limits set to determine the effectiveness of the activity
it can be monitored frequently enough to provide control
corrective action can be taken.
The ADWG has a detailed section on CCPs in appendix A1.7. This provides examples and a decision tree for the identification of CCPs, which is similar to the Codex decision tree.
When determining CCPs it is important that too many are not identified. Everything cannot be critical, if it is then there is no prioritisation and the methodology loses its potency. Some things can just be important!
Also, under identification of CCPs is an issue. It is important that the intent of HACCP is considered, which is to focus control at CCPs. The Codex states that where a CCP cannot be identified for a hazard that must be controlled, then the operation should be redesigned. This is not explicitly stated in the ADWG and does lead to some utilities not identifying CCPs that should be CCPs (e.g. currently no online monitoring).
After CCPs have been identified critical limits must be assigned. It is deemed to be the point at which process control is lost and there is uncertainty that the product is safe (i.e. a barrier has been lost for a hazard, whether it is actually unsafe would depend on the hazard being present at an unsafe level). The parameters and monitoring used should be real-time to provide an immediate response. The intent is that operational monitoring can be used to protect consumers, as opposed to verification monitoring (e.g. E. coli), which can take days to get a result. When setting critical limits it is good practice to have a concentration and a time (e.g. >0.5NTU for >15mins). This helps to minimise false alarms due to spikes in instrument readings.
The triggering of a CCP critical limit must have a corrective action to bring the process back under control, this can be shutting the system down. All instances of a CCP being triggered should be recorded and reviewed regularly to ensure that they are working and to identify possible process improvements to prevent instances in the future. Note, the breach of a CCP critical limit is reportable to the regulator in some jurisdictions.