Integration of desalinated seawater into a distribution system: A corrosion pilot study

A proposed seawater desalination plant for Carlsbad, Calif., will produce treated water that varies from the city—s typical imported surface water supply. A six‐month pilot study was conducted to compare how Carlsbad distribution materials would be affected by the potential corrosion that might arise from conditioned desalinated seawater versus the city—s typical supply. Various distribution and home plumbing appurtenances were evaluated in parallel test systems, including copper pipe, brass service meters, cement‐mortar‐lined pipe, and cast‐iron distribution system gate valves. Corrosion was assessed by analyzing changes in water quality caused by pipe corrosion or passivation, including metal concentration (iron, zinc, lead, copper, and aluminum), calcium, alkalinity, and turbidity changes. Pilot testing demonstrated that conditioned reverse osmosis permeate achieving minimum water quality goals—alkalinity of 45 mg/L as calcium carbonate (CaCO3), hardness of 40 mg/L as CaCO3, and pH of 8.5—was not likely to trigger new corrosion problems in the Carlsbad distribution system.