P7.2.3.2 Provision of TOC/colour. Elevated Optimise treatment TOC/colour. treatment Natural processes parameters in organic matter Elevated chlorite upstream to reduce upstream present in the formation. levels of organic processes to water being matter in the maximise chlorinated removal of (reduction of organic ClO2 to matter. chlorite). Contingency Plans If an event happens despite preventive and corrective actions you have taken, you may need to consult with the Medical Officer of Health to assess how serious a problem is. ClO2 concentration is lower than minimum effective level Event – A detectable ClO2 residual cannot be obtained in the water Indicators: leaving the treatment plant. In 100 ml samples of leaving the treatment plant, or E. coli coliforms are continually detectable, or is present at E. coli elevated levels (more than 10 per 100 mL). Widespread illness in the community. Follow the actions in Figure 3.2 of the Required DWSNZ:2000. actions: Identify the reason for the failure and rectify. Record cause of system failure and steps taken to correct. Modify your safety plan if necessary. Manager designated responsible for the water supply. Responsibility: ClO2 concentration is higher than maximum acceptable value Event – Knowledge of a major overdose of ClO2 into the water. Indicators: Inability to obtain pink colour from DPD indicator despite high ClO2 dose rates. (NB: This indicates ClO2 levels well in excess of the MAV very high ClO2 levels bleach the pink colour that – normally develops in the presence of ClO2.) Change in the odour or taste of the water. Widespread levels of taste and odour complaints, or illness, in the community.
P7.2.3.2 Natural organic matter present in the water being chlorinated (reduction of ClO2 to chlorite). Provision of treatment processes upstream to reduce levels of organic matter in the TOC/colour. Elevated TOC/colour. Elevated chlorite formation. Optimise treatment parameters in upstream processes to maximise removal of organic matter. Contingency Plans If an event happens despite preventive and corrective actions you have taken, you may need to consult with the Medical Officer of Health to assess how serious a problem is. Event – ClO2 concentration is lower than minimum effective level Indicators: A detectable ClO2 residual cannot be obtained in the water leaving the treatment plant. In 100 ml samples of leaving the treatment plant, E. coli or coliforms are continually detectable, or E. coli is present at elevated levels (more than 10 per 100 mL). Widespread illness in the community. Required actions: Follow the actions in Figure 3.2 of the DWSNZ:2000. Identify the reason for the failure and rectify. Record cause of system failure and steps taken to correct. Modify your safety plan if necessary. Responsibility: Manager designated responsible for the water supply. Event – ClO2 concentration is higher than maximum acceptable value Indicators: Knowledge of a major overdose of ClO2 into the water. Inability to obtain pink colour from DPD indicator despite high ClO2 dose rates. (NB: This indicates ClO2 levels well in excess of the MAV – very high ClO2 levels bleach the pink colour that normally develops in the presence of ClO2.) Change in the odour or taste of the water. Widespread levels of taste and odour complaints, or illness, in the community.
treatment-chlorine-dioxide-treatment-feb14-v2.docx