Pilot-scale evaluation of blending desalinated seawater into a distribution system

A pilot-scale pipe loop test was conducted to evaluate the effects of desalinated seawater on corrosion, lead release, disinfectant decay, and formation of disinfection by-products in the distribution system. Results indicated that the desalinated blend water did not increase corrosion of unlined cast-iron (UCI) pipes, coated cement-lined pipes, or copper pipes. However, aluminum release from uncoated cement-lined pipes did increase. The blend water also increased lead release from leaded solder. These results agreed with the predictions from corrosion indexes and earlier bench-scale testing. Orthophosphate (1 mg/L) added to mitigate lead release was ineffective. Adding phosphate increased bacterial growth in unlined cast-iron pipes and solder. Although chloramine decay was increased by desalinated water, this effect can be managed by controlling bromide (Br-) levels and either reboosting or preforming chloramine. Desalinated blend water did not increase biological activity. In addition, the blend water decreased the formation of total trihalomethanes (THMs) and haloacetic acids (HAAs) as expected but increased nitrosodimethylamine for unknown reasons.