The conversion of drinking water disinfection process from free chlorine to mono-chloramine reduces the formation of trihalomethanes (THM), but increases the concentration of nitrogenous disinfection by-products (N-DBP), especially five new haloacetamides (HAcAm) including monochloroacetamide (MCAcAm), dichloroacetamide (DCAcAm), trichloroacetamide (TCAcAm), monobromoacetamide (MBAcAm) and dibromoacetamide (DBAcAm). Among these HAcAms, DCAcAm and TCAcAm are nor-mally present in drinking water at a higher concentration. The hydrolysis characteristics with different pH values and chlorination characteristics under different chlorine dosages of HAcAm were studied by combi-nation with linear free-energy relationship (LFER). Based on the hydrolysis and chlorination characteristics of HAcAm, the reaction pathways of hydrolysis and chlorination for HAcAm were also investigated by de-tection of final product haloacetic acids (HAA). The results indicated that DCAcAm reacted slowly with water in highly acidic condition (pH＝4) but was stable at pH 5 within 7 d reaction time. Acid environment can not cause TCAcAm hydrolysis reaction. Obvious hydrolysis reactions of DCAcAm and TCAcAm were discovered in alkaline conditions, which followed the first order reaction. The water sample containing DCAcAm and TCAcAm could be preserved by adjusting pH to 5. The use of chlorine disinfection and in-crement of chlorine dosage caused the amount of THM and HAA to go up in drinking water, however, it maybe resulted in the decrease of N-DBP such as HAcAm. Trichloroacetic acid (TCAA) was produced rap-idly by TCAcAm hydrolysis at pH 10. For chlorination of TCAcAm, relatively stable Cl-N-TCAcAm was produced from a reaction between TCAcAm and HOCl, then continued to generate TCAA and NHCl2 at a higher concentration of HOCl.

Key words: drinking water, nitrogenous disinfection by-product, haloacetamide, linear free-energy relationship, hydrolysis, chlorination, reaction pathway