Disinfection by-product minimisation by organic and inorganic precursor removal

A matrix of 18 synthetic waters with variable water quality parameters (alkalinity, natural organic matter (NOM), and halide concentration) was prepared. The DBP formation potential of these 18 samples was examined both before treatment, after enhanced coagulation (EC) and after a sequential treatment using EC followed by either powdered activated carbon (PAC), granular activated carbon (GAC), silver-impregnated activated carbon (SIAC), or MIEX® resin. The study shows that natural organic matter (NOM) concentration is greatly reduced with EC, and further reduced by each secondary treatment. Halide adsorption was not possible with EC or PAC, however, MIEX® and GAC had some halide adsorption capacity. SIAC exhibited the greatest halide removal (average 99% adsorption). Total DBP formation was reduced by EC, and further reduced by each secondary treatment process, however, specific highly brominated DBPs increased in concentration with each successive treatment step in all cases except after SIAC treatment. The more highly brominated DBPs may be of a greater public health concern than their chlorinated counterparts, therefore, in salinity-impacted waters, halide removal is desirable.