Control of drinking water disinfection byproducts with a novel bromide-selective anion exchange resin: Design, mechanism, and performance

In regions where drinking water sources containing elevated bromide levels, the formation of brominated disinfection byproducts (Br-DBPs) is enhanced, which may increase risks of cancer and birth defects. Anion exchange resin (AER) adsorption is a promising approach for reducing precursors of Br-DBPs (e.g., bromide and natural organic matter) due to its strong electrostatic force for reversible ion exchange process. However, high bromide water sources typically have high salinities, and the presence of co-existing ions (e.g., sulfate, nitrate, chloride) can significantly diminish the efficiency of conventional AERs, which use polyacrylic or polystyrene skeletons with trimethyl-ammonium functional groups. This study designed a novel AER with the polystyrene skeleton and tripentyl-ammonium functional group for the selective bromide removal, which resisted interferences from co-existing ions based on ion dehydration and ion-pairing electrostatic interactions. Column experiments with continuous high-bromide water flows demonstrated that the novel AER exhibited up to three times the operating capacity of conventional AERs, achieving reductions of 71.2 %, 44.6 %, and 67.7 % in bromide, dissolved organic carbon, and specific UV absorbance, respectively. Competitive experiments showed that the novel AER's strong sulfate interference resistance enhanced its bromide selectivity. The electrostatic interactions between AER fragments and bromide or sulfate particles were quantitatively evaluated using density functional theory calculations. Treatment with the novel AER led to reductions in total organic bromine, aliphatic Br-DBPs, and cyclic Br-DBPs by 76.7 %, 62.5 %, and 90.5 %, respectively. Notably, cytotoxicity assays using Chinese hamster ovary cells indicated a 39.7 % decrease in overall cytotoxicity of chlorinated drinking water following treatment with the novel AER.