Influence on the generation of disinfection byproducts in a tannic acid solution by aluminum ions

Abstract

ABSTRACTAluminum (Al) commonly exists in natural waters, and its salts are often used as coagulants in drinking water treatment. Therefore, associated with the security of drinking water, functions of Al ions (Al3+) on generation of disinfection byproducts (DBPs) should not be ignored. This study focuses on DBPs and the carcinogenic factor of chlorinated water samples after the addition of Al3+ with different Al3+/initial tannic acid molar ratios. The results imply that Al3+ acts as a promoter of haloacetic acids (HAAs) and an inhibitor of trihalomethanes (THMs) when tannic acid is selected as model compound of natural organic matter during chlorination. Depending on the results of size exclusion chromatography and ultraviolet spectrophotometer, an equilibrium system can be assumed between hydrolysis and flocculation in tannic acid solution with Al3+. Furthermore, influences on the equilibrium system for Al3+ addition may result in various effects on generation and distribution ratios of THMs and HAAs during chlorination. Finally, according to the analyses of a fluorescence spectrophotometer, it is demonstrated that the presence of Al3+ helps to increase precursors of DBPs (humic acid-like organics) and then improve the generation of DBPs.