AWWA ACE54319

The US Environmental Protection Agency has sponsored research to determine the oxidants and by-products resulting from the electrolysis of salt brine. In an evaluation of analytical methods, it was found that FAC (free available chlorine including C12, HOC& and OCl-) was always a major interference with the common (and frequently used) accepted methods used for measuring chlorine dioxide and ozone. Improved selective methods for measuring chlorine dioxide and ozone were developed and tested at the 0.15 mg/L level using zero-headspace storage devices. The analysis of freshly prepared anolyte liquors shows that FAC is the primary oxidant resulting from salt brine electrolysis. No chlorine dioxide was detected. No ozone was detected. No hydrogen peroxide was detected. The liquors contain a high concentration of chloride ion (9 - 10,000 mg/L) and relatively low concentrations of the inorganic by-products C102-, C103-, and Br03-. Preliminary results show that the concentration of Br03- formed varies depending on the Br- concentration of the salt used for preparing the brine solutions. The formation of chlorate ion (C103-) is not a function of C102 produced but rather a result of FAC decomposition. Likewise, Br03- formation in electrolyzed salt brine solutions does not require the presence of ozone. Oxidant compatibility studies wereperformed. No 03, C102, or H202 were measured in freshly prepared anolyte liquor. Studies show that FAC and ozone react in solution on the millisecond timescale. Includes 15 references, tables.