D1.2.8 Train staff in calculation Treatment Elevated See of dose rates and in the chemicals. turbidity/ Contingency Chemical use of methods for treatment Plan. Turbidity. optimising treatment chemical from plant operation. incorrect post- chemical Document treatment treatment. dosing. plant dosing procedures (especially calculations of Absence of type and quantity of written materials used), and descriptions those for the reservoir if it of dosing is dosed. procedures. Turbidity more than 0.2 NTU. INTRODUCTION OF CONTAMINATING MATERIAL INTO SERVICE RESERVOIR cont’d D1.2.9 Ensure that there is an Change in Disconnect airgap or other suitable quality. water quality any direct Backflow backflow prevention after rain connections. from drains. Turbidity. device between tank events. Isolate tank, Overflow overflow and sewer or Turbidity dump the construction. stormwater drains. more than water, clean, 0.2 NTU. chlorinate and check the E. coli or coliforms quality before detected in refilling. 100 mL of water. Event: DEVELOPMENT, OR RE-SUSPENSION, OF SEDIMENT WITHIN TANK OR RESERVOIR Possible hazards: Germs; manganese, disinfection by-products (trihalomethanes, haloacetic acids, chloral hydrate). Level of risk: Low–moderate D1.3.1 Avoidance of rapid FAC. Visible slime/ Review drain/fill. sediment. cleaning Sediment/ procedures slime Undertake regular quality. Customers and plant cleaning of reservoirs complain of Turbidity. operation. and (every 1–5 years slime/ Manganese. release. depending on the quality sediment. Isolate tank, of the source water, flow chlorinate and Audit cleaning FAC residual through and degree of check the procedures stagnation in the tank and operation. less than etc). quality. If 0.2 mg/L. there is gross Cleaning procedures E. coli or contamination, need to consider coliforms dump the disinfection of all detected in water, clean equipment, satisfactory 100 ml of and refill training procedures, water. before preferably isolation chlorinating. Turbidity during cleaning, more than minimisation of sediment 0.2 NTU. stir-up if online during cleaning. Maintain chlorine residual. Minimise conditions leading to post-treatment floc formation.
D1.2.8 Chemical from incorrect chemical dosing. Train staff in calculation of dose rates and in the use of methods for optimising treatment plant operation. Document treatment plant dosing procedures (especially calculations of type and quantity of materials used), and those for the reservoir if it is dosed. Treatment chemicals. Turbidity. Elevated turbidity/ treatment chemical post- treatment. Absence of written descriptions of dosing procedures. Turbidity more than 0.2 NTU. See Contingency Plan. INTRODUCTION OF CONTAMINATING MATERIAL INTO SERVICE RESERVOIR cont’d D1.2.9 Backflow from drains. Ensure that there is an airgap or other suitable backflow prevention device between tank overflow and sewer or stormwater drains. quality. Turbidity. Overflow construction. Change in water quality after rain events. Turbidity more than 0.2 NTU. E. coli or coliforms detected in 100 mL of water. Disconnect any direct connections. Isolate tank, dump the water, clean, chlorinate and check the quality before refilling. Event: DEVELOPMENT, OR RE-SUSPENSION, OF SEDIMENT WITHIN TANK OR RESERVOIR Possible hazards: Germs; manganese, disinfection by-products (trihalomethanes, haloacetic acids, chloral hydrate). Level of risk: Low–moderate D1.3.1 Sediment/ slime and release. Avoidance of rapid drain/fill. Undertake regular cleaning of reservoirs (every 1–5 years depending on the quality of the source water, flow through and degree of stagnation in the tank etc). Cleaning procedures need to consider disinfection of all equipment, satisfactory training procedures, preferably isolation during cleaning, minimisation of sediment stir-up if online during cleaning. Maintain chlorine residual. Minimise conditions leading to post-treatment floc formation. FAC. quality. Turbidity. Manganese. Audit cleaning procedures and operation. Visible slime/ sediment. Customers complain of slime/ sediment. FAC residual less than 0.2 mg/L. E. coli or coliforms detected in 100 ml of water. Turbidity more than 0.2 NTU. Review cleaning procedures and plant operation. Isolate tank, chlorinate and check the quality. If there is gross contamination, dump the water, clean and refill before chlorinating.
distribution-post-treatment-storage-feb14-v2.docx