Desalination Brine as a Source of Iodinated and Brominated DBPs to Aquatic Ecosystems

Abstract

Desalination by reverse osmosis (RO) is an increasingly important source of drinking water in coastal regions facing population growth and water scarcity. Prechlorination of seawater to control membrane biofouling can produce disinfection byproducts (DBPs), yet little is known about their occurrence in finished desalinated water or discharged RO brines. This study quantified 53 DBPs, including trihalomethanes (THMs), iodo-THMs, haloacetonitriles, haloacetamides, haloketones, halonitromethanes, and haloacetaldehydes, using GC–MS at three full-scale U.S. desalination plants (two seawater and one inland brackish groundwater facility). DBPs were detected on both sides of the RO membrane, with 44 compounds in permeate and 45 in brine at total concentrations up to 34.9 and 9.5 μg/L, respectively. Brominated DBPs dominated both matrices, with bromoform the most abundant, indicating that many brominated species readily pass through RO membranes. Low levels of iodinated DBPs were also detected in brine and permeate from one seawater plant. DBPs from all six classes crossed the RO membrane, although permeability varied by compound class, with THMs, haloacetonitriles, and haloketones contributing most to permeate concentrations. At one seawater plant, brines exhibited higher calculated cytotoxicity than permeate, and DBPs detected in source water before chlorination suggested the potential for persistence in coastal environments.