Unlined cast-iron and steel pipes, which are abundant in the Southern California Water Company-Southwest District distribution system, are known to have water quality problems because of higher disinfectant demands and higher biofilm density. Keeping ahead of the loss of disinfectant residual was labor intensive and costly, so the District conducted a pilot study to investigate alternatives.
by Y. Koby Cohen, Calvin G. Abernathy, and Christopher P. Hill
Several bench-scale studies have documented that an effective corrosion control program may increase disinfectant residuals and improve water quality because fewer corrosion products are formed. So, over a three year period, the District studied the long-term effect of corrosion inhibitors on disinfectant residuals, distribution system hydraulics, and water quality. The study proved that the use of polyphosphate-blend corrosion inhibitors is effective in maintaining residuals and will help limit water lost to and labor spent on flushing. The District is in the process of implementing the program systemwide.
District Disinfectant Demand
Unlined cast-iron and steel pipes, installed between 1930 and the late 1950s, comprise about 53 percent of the 410 miles of water distribution pipelines owned by the District. The remaining pipelines are ductile iron, polyvinyl chloride, and asbestos cement. The large number of unlined
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3 year Independent study proving the benefits of polyphosphate-orthophosphate blends used for corrosion inhibition and the additional benefit of chlorine residual stabilization within a Municipal Water System.
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