AWWA DSS58691

This slide presentation outlines several processes for operating and maintaining water quality in finished water storage facilities that include: auditing the facility; monitoring; inspecting; cleaning and maintaining; operating; and retrofit and design. Auditing the facility involves reviewing records, drawings and photographs. Monitoring involves sampling in the storage facility because outlet sampling alone is not enough; providing access for sampling; installing sampling lines and taps; evaluating chlorine residual and microbiological quality; and, regulatory monitoring alone is not enough. The presentation lists three inspection types: routine, daily/weekly; periodic, monthly/quarterly; and, comprehensive, 3-5 years. Inspection methods include: visual/video; hatch access; and, float down. Common problems of inspections include: no bug screens on vents and over flows; cathodic protection not working; hatches not locked; presence of lead paint; and, use of non-NSF paints. Maintenance includes: a recommended cleaning interval of 3 to 5 years for covered storage facilities, and once/twice a year for uncovered; tanks painted every 10-15 years. Operations involving water age (moving water through storage): under utilization, no or low flow; short circuiting (stagnant or dead zones). Design and retrofit suggestions from AWWARF Project 255 included: design should achieve good mixing; avoid baffling in most instances; avoid stratification in storage reservoirs; mixing achieved through development of a turbulent jet; and, mixing time in a tank should be less than typical fill time.