Critical Control Points Register

Purpose. This register records every drinking water critical control point with its target, alert level, critical limit, monitoring, corrective action and the person responsible, as required by the risk management plan.

1.How the register is used

Each critical control point is a step where control is essential to prevent or remove a hazard. Operators must know the values on this register for their plant. Alert levels trigger operator action; critical limits trigger the response in the linked procedure and notification to the control centre. The register is reviewed monthly against the excursion log and formally each year with the risk management plan.

2.CCP 1: Coagulation, Kialla plant

Coagulation with aluminium sulfate and polymer removes particles and pathogens ahead of filtration. It is monitored by settled water turbidity and coagulant dose against the jar test setpoint, with pH controlled by lime.

• Target: settled water turbidity below 2.0 NTU; pH 6.5 to 7.2
• Alert level: settled turbidity 3.0 NTU for 30 minutes
• Critical limit: settled turbidity above 5.0 NTU for 60 minutes or loss of coagulant dosing
• Corrective action: check dose, pump, pH and raw water; reduce flow; if not restored, divert to waste
• Responsible: shift operator; escalation to Water Treatment Manager

3.CCP 2: Filtration, Kialla plant

Dual media filters remove remaining particles and protozoa. Each filter has an online turbidimeter and a filter-to-waste stage after backwash.

• Target: individual filter turbidity below 0.1 NTU
• Alert level: individual filter turbidity 0.2 NTU for 15 minutes
• Critical limit: individual filter turbidity above 0.5 NTU for 15 minutes, or above 0.3 NTU for 60 minutes
• Corrective action: take filter offline, backwash, filter to waste until below 0.1 NTU; investigate media and underdrain
• Responsible: shift operator; escalation to Water Treatment Manager

4.CCP 3: Disinfection, Kialla plant

Sodium hypochlorite dosing with contact time in the contact tank inactivates bacteria and viruses. Monitored by the online free chlorine analyser at the contact tank outlet and the calculated contact time.

• Target: free chlorine 1.2 mg/L at contact tank outlet with contact time value above the minimum in the risk management plan
• Alert level: free chlorine 0.8 mg/L
• Critical limit: free chlorine below 0.5 mg/L for 10 minutes, or contact time value below the minimum
• Corrective action: switch to standby pump, adjust dose, reduce flow; if not restored in 20 minutes, close plant outlet and apply the Water Quality Incident Response Procedure
• Responsible: shift operator; escalation to Water Treatment Manager and Control Centre

5.CCP 4: Disinfection, bore field

Groundwater is disinfected with hypochlorite before entering the northern towns network. Monitored by an online analyser with an automatic shutdown on low residual.

• Target: free chlorine 1.0 mg/L leaving the bore field
• Alert level: free chlorine 0.7 mg/L
• Critical limit: free chlorine below 0.4 mg/L; automatic pump shutdown at 0.3 mg/L
• Corrective action: check dosing, restart, verify residual by bench test; treat any water supplied below the critical limit as an incident
• Responsible: control centre operator; escalation to Water Treatment Manager

6.CCP 5: Reticulation residual

A free chlorine residual is maintained throughout the network to protect against contamination. Monitored by reservoir outlet analysers and verification sampling.

• Target: free chlorine 0.5 mg/L at reservoir outlets
• Alert level: free chlorine 0.3 mg/L at any reservoir outlet
• Critical limit: free chlorine below 0.2 mg/L at a reservoir outlet or non-detectable residual at a verification site
• Corrective action: booster dosing, flushing, reservoir turnover; resample; apply incident procedure if E. coli detected
• Responsible: control centre operator; escalation to Networks Manager

7.Excursion log and review

Every alert and critical limit event is entered in the excursion log with the time, the value, the action and the outcome. The Control Centre and Water Quality Manager reviews the log monthly and reports to the drinking water quality committee.