P7.2.1.11 Ensure ClO2 dosing ClO2 residual Low ClO2 Cover open solution is concentration. residual (see channels or Exposure to protected from Appendix). reticulate in sunlight sunlight. pipes. resulting in E. coli or coliforms of detected in ClO2. 100 mL sample of water leaving the treatment plant. P7.2.1.12 Provide staff Analysis Independent Identify staff training for sample records. checks show training needs ClO2 analysis and record monitoring and provide monitoring keeping. inaccuracies. training. samples taken incorrectly or Develop monitoring incorrectly schedule and recorded (see roster. Guide D4). P7.2.1.13 Provide staff Analysis Independent Identify staff training for sample records. checks show training needs Method of analysis and record monitoring and provide ClO2 keeping. inaccuracies. training. measurement incorrect, incorrectly calibrated, or reagents used in analysis have deteriorated. Event: CHLORINE DIOXIDE (ClO2) CONCENTRATION TOO HIGH Possible hazards: Chlorite, chlorate, chlorine dioxide. Level of risk: Low–moderate P7.2.2.1 Routine controller ClO2 ClO2 residual Identify cause and dosing pumps residual concentration of fault and Dosing maintenance. more than 50% of rectify. malfunction its MAV. (see Guide Replacement of Replace P10). controller if Maintenance Frequent repair controller with suspect. log. needed. new unit. Fit an alarm to Maintenance log indicated incorrect not signed off. CIO2 concentration. P7.2.2.2 Regular manual ClO2 ClO2 residual Recalibrate checks on residual concentration controller Dosing calibration of more than 50% of sensor. controller’s controller (see its MAV. sensor Manually DWSNZ:2000 Section incorrectly Calibration monitor and 3.3.4.8). calibrated. schedule not adjust ClO2 signed off. dose rate until recalibration undertaken. Event: CHLORINE DIOXIDE (ClO2) CONCENTRATION TOO HIGH cont’d
P7.2.1.11 Exposure to sunlight resulting in of ClO2. Ensure ClO2 dosing solution is protected from sunlight. ClO2 residual concentration. Low ClO2 residual (see Appendix). E. coli or coliforms detected in 100 mL sample of water leaving the treatment plant. Cover open channels or reticulate in pipes. P7.2.1.12 ClO2 monitoring samples taken incorrectly or incorrectly recorded (see Guide D4). Provide staff training for sample analysis and record keeping. Develop monitoring schedule and roster. Analysis records. Independent checks show monitoring inaccuracies. Identify staff training needs and provide training. P7.2.1.13 Method of ClO2 measurement incorrect, incorrectly calibrated, or reagents used in analysis have deteriorated. Provide staff training for sample analysis and record keeping. Analysis records. Independent checks show monitoring inaccuracies. Identify staff training needs and provide training. Event: CHLORINE DIOXIDE (ClO2) CONCENTRATION TOO HIGH Possible hazards: Chlorite, chlorate, chlorine dioxide. Level of risk: Low–moderate P7.2.2.1 Dosing malfunction (see Guide P10). Routine controller and dosing pumps maintenance. Replacement of controller if suspect. Fit an alarm to indicated incorrect CIO2 concentration. ClO2 residual Maintenance log. ClO2 residual concentration more than 50% of its MAV. Frequent repair needed. Maintenance log not signed off. Identify cause of fault and rectify. Replace controller with new unit. P7.2.2.2 Dosing controller’s sensor incorrectly calibrated. Regular manual checks on calibration of controller (see DWSNZ:2000 Section 3.3.4.8). ClO2 residual ClO2 residual concentration more than 50% of its MAV. Calibration schedule not signed off. Recalibrate controller sensor. Manually monitor and adjust ClO2 dose rate until recalibration undertaken. Event: CHLORINE DIOXIDE (ClO2) CONCENTRATION TOO HIGH cont’d
treatment-chlorine-dioxide-treatment-feb14-v2.docx