Correlations between organic matter properties and DBP formation during chloramination

Characteristics, including fluorescence intensity and specific UV absorbance (SUVA), of 16 organic matter (OM) fractions isolated from four OM samples plus a standard were analyzed and correlated with their specific disinfection by-product (DBP) and total organic halogen (TOX) formation after chloramination. These isolates were obtained from various water sources by using XAD-8/4 resins. Chloramination was achieved by adding 20 mg/L monochloramine to a solution containing one OM isolate at 5 mg/L DOC and buffered at pH 7.5 for 7 days. The fluorescence regional integration (FRI) method was used to analyze the fluorescence intensity data obtained from excitation-emission matrix (EEM) fluorescence spectroscopy, in which the EEM figure was divided into five regions and a normalized fluorescence volume was calculated. The cumulative normalized EEM volumes at regions II and IV (Φ_II+IV,n) showed linear relationships with the yields of dichloroacetic acid (DCAA) (R²=0.60), chloroform (R²=0.42), dichloroacetonitrile (DCAN) (R²=0.53), and TOX (R²=0.63). The SUVA values were found to have linear relationships with the yields of DCAA (R²=0.82), chloroform (R²=0.73), DCAN (R²=0.88) and TOX (R²=0.80), but not with the yields of cyanogen chloride (CNCl) and chloropicrin (CP). A modified model is proposed to simplify the reactions involving chloramination of OM fractions. FTIR spectra of OM before and after chloramination partially confirmed that ketone groups were reactive with monochloramine.