Formation of haloacetamides during chlorination of dissolved organic nitrogen aspartic acid.
The stability of haloacetamides (HAcAms) such as dichloroacetamide (DCAcAm) and trichloroacetamide (TCAcAm) was studied under different experimental conditions. The yield of HAcAms during aspartic acid (Asp) chlorination was measured at different molar ratio of chlorine atom to nitrogen atom (Cl/N), pH and dissolved organic carbon (DOC) mainly consisted of humic acid (HA) mixture. Ascorbic acid showed a better capacity to prevent the decay of DCAcAm and TCAcAm than the other two dechlorinating agents, thiosulfate and sodium sulfite. Lower Cl/N favored the DCAcAm formation, implying that breakpoint chlorination might minimize its generation. The pH decrease could lower the concentration of DCAcAm but favored dichloroacetonitrile (DCAN) formation. DCAcAm yield was sensitive to the DOC due to higher chlorine consumption caused by HA mixture. Two possible pathways of DCAcAm formation during Asp chlorination were proposed. Asp was an important precursor of DCAN, DCAcAm and dichloroacetic acid (DCAA), and thus removal of Asp before disinfection may be a method to prevent the formation of DCAcAm, DCAN and DCAA.
Chu
Wen-hai
WH
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, PR China. 1world1water@tongji.edu.cn
Gao
Nai-yun
NY
Deng
Yang
Y
D000081:Acetamides / Q000737:chemistry*; D001224:Aspartic Acid / Q000737:chemistry*; D002244:Carbon / Q000032:analysis; D054879:Halogenation; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D017672:Nitrogen Compounds / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification
D000081:Acetamides; D006812:Humic Substances; D007202:Indicators and Reagents; D017672:Nitrogen Compounds; D014874:Water Pollutants, Chemical; D001224:Aspartic Acid; D002244:Carbon