AWWA WQTC64059

Poseidon Resources Corporation has proposed an ocean desalination plant in Carlsbad, California that would produce up to 50 million gallons per day of potable drinking water for transmission to the City of Carlsbad water supply system. This seawater desalination process would produce treated water that varies in quality from the City of Carlsbad's typical imported, treated surface water supply in several respects. The water quality of the reverse osmosis (RO) permeate would generally contain lower total dissolved solids, calcium concentrations, alkalinity, and disinfection byproduct formation potential, as well as higher concentrations of bromide, sodium, and chloride ions than the imported water supply. The purpose of the corrosion pilot study was to compare corrosion indicators for conditioned desalinated seawater with those of the imported water from the Metropolitan Water District of Southern California (MWD). Two primary scenarios were evaluated over a six-month period for each water source, including contact with typical household plumbing materials (copper pipe and brass water service meters) using a diurnal flow regime representative of household consumption, and contact with typical distribution main materials (cement mortar-lined pipe and gate valves) at a representative, constant flow rate. Three different configurations of pipe systems were constructed to compare the corrosivity of RO permeate and the imported MWD water supply on a variety of distribution system and residential plumbing materials: flow-through systems consisting of new copper pipe and system-harvested residential brass water service meters (brass meters); recirculation systems of new cement mortar-lined steel pipe; and, recirculation systems containing harvested, cast iron distribution system gate valves. Each of the three test system configurations was replicated in four independent pipe testing loops or lengths. Two of the four loops or lengths in each set received conditioned RO permeate and the other two received MWD water. MWD water was acquired from a connection to a potable water line at the site. Due to the inherent imprecision of corrosion processes and corrosion pilot testing, the pilot facility included a duplicate of each pipe loop or test system for each water quality. The paper provides a schematic of the pipe test system layout. Includes 8 references, tables, figures.