D2.3.3.1 Ensure treatment is Turbidity. Customer Improve in place to remove complaints. treatment Poor chemical Aluminium. raw water-derived water quality Iron, constituents that leaving the manganese. could otherwise treatment plant Scour, pig deposit in the Inspection. eg, and flush the – distribution system. distribution precipitation of Ensure treatment is system. floc, iron/ operating manganese effectively so that it precipitation. does not add constituents that could deposit in the distribution system. Ensure a regular cleaning/flushing programme, especially through low-flow and areas, being mindful of D2.3.1.7 and D2.3.2.1. D2.3.3.2 Ensure continuous FAC. Failure to meet FAC throughout requirements Poor Microbiological distribution system. of microbiological quality. DWSNZ:2000, water quality Ensure a regular Turbidity. especially FAC leaving the cleaning/flushing not treatment plant programme, maintained. and in the especially through distribution low-flow and system. areas, being mindful of D2.3.1.7 and D2.3.2.1. D2.3.3.3 Review the zones of Flow. Model flow concern, and put in patterns and Water flows too Pressure. place a plan to FAC low resulting in: increase flows residuals to decay of through these identify the chlorine areas. required changes. Design the colonisation reticulation network of surfaces. on a grid rather than tree model to allow greater flexibility in routing water flows, so reducing areas with little flow. D2.3.3.4 See D2.3.1.5 and Microbiological Failure to meet Review D2.3.1.8. quality. requirements maintenance Poor repair of practices. practices Select materials Turbidity. DWSNZ:2000. allowing that are resistant to Change colonisation. biofilm development construction (smooth) and do not and repair promote biofilm materials. development (some plastics do). Event: DEVELOPMENT OF SEDIMENT OR BIOFILM cont’d
D2.3.3.1 Poor chemical water quality leaving the treatment plant – eg, precipitation of floc, iron/ manganese precipitation. Ensure treatment is in place to remove raw water-derived constituents that could otherwise deposit in the distribution system. Ensure treatment is operating effectively so that it does not add constituents that could deposit in the distribution system. Ensure a regular cleaning/flushing programme, especially through low-flow and areas, being mindful of D2.3.1.7 and D2.3.2.1. Turbidity. Aluminium. Iron, manganese. Inspection. Customer complaints. Improve treatment Scour, pig and flush the distribution system. D2.3.3.2 Poor microbiological water quality leaving the treatment plant and in the distribution system. Ensure continuous FAC throughout distribution system. Ensure a regular cleaning/flushing programme, especially through low-flow and areas, being mindful of D2.3.1.7 and D2.3.2.1. FAC. Microbiological quality. Turbidity. Failure to meet requirements of DWSNZ:2000, especially FAC not maintained. D2.3.3.3 Water flows too low resulting in: decay of chlorine colonisation of surfaces. Review the zones of concern, and put in place a plan to increase flows through these areas. Design the reticulation network on a grid rather than tree model to allow greater flexibility in routing water flows, so reducing areas with little flow. Flow. Pressure. Model flow patterns and FAC residuals to identify the required changes. D2.3.3.4 Poor repair practices allowing colonisation. See D2.3.1.5 and D2.3.1.8. Select materials that are resistant to biofilm development (smooth) and do not promote biofilm development (some plastics do). Microbiological quality. Turbidity. Failure to meet requirements of DWSNZ:2000. Review maintenance practices. Change construction and repair materials. Event: DEVELOPMENT OF SEDIMENT OR BIOFILM cont’d
distribution-operation-feb14-v2.docx