THMs and HAAs formation upon chlorination of several model compounds

This study investigated the chlorine demand and formation of trihalomethanes(mainly chloroform) and haloacetic acids(mainly dichloroacetic acid(DCAA) and trichloroacetic acid(TCAA)) upon chlorination of several algal model compounds,including the pepsin(protein),glutathione(polypeptide) and glucose(sugar).Meanwhile,fluka humic acid was also used for comparison.Results showed that after chlorination,the residual chlorine in the solutions of four model compounds all decreased rapidly at first 2 h,and then stabilized after 6 h.The highest chlorine demand was observed in the solution of glutathione(96 h:7.1 mg·mg-1(calculated as per milligram carbon,similar hereinafter),followed by pepsin(96 h:4.2 mg·mg-1),humic acid(96 h:3.0 mg·mg-1) and glucose(96 h:0.7 mg·mg-1).THMs and HAAs formation also showed the similar transition profile characterized by quick increase at first 2 h followed by an extended slow increase.Based on unit carbon,the humic acid and pepsin showed much higher yields of chloroform(96 h:15.1~55.2 μg·mg-1(calculated as per milligram carbon,similar hereinafter)),DCAA(96 h:15.1~55.2 μg·mg-1) and TCAA(96 h:15.1~55.2 μg·mg-1) than those of gluthione and glucose(chloroform-96 h:2.5~5.1 μg·mg-1;DCAA-96 h:0.6~8.0 μg·mg-1;TCAA-96 h:0.12~3.8 μg·mg-1).However,detailed analysis suggested that the precursor of chloroform and TCAA contained more aromaticity(high SUV254 value),and the opposite was true for DCAA precursor.As for the eutrophic source water containing high level of protein,polypeptide and sugar,special attention should be paid to the health risk derived from DCAA.