Correlations between organic matter properties and DBP formation during chloramination

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies

Background:

• Disinfection by-products (DBPs) are formed when disinfectants react with organic matter (OM) in water.
• Chloramination is a common water disinfection method, but it can also lead to DBP formation.
• Understanding the characteristics of OM is crucial for predicting and controlling DBP formation.

Purpose of the Study:

• To analyze the characteristics of isolated organic matter (OM) fractions.
• To correlate these characteristics with the formation of specific disinfection by-products (DBPs) and total organic halogen (TOX) after chloramination.
• To evaluate the predictive power of fluorescence intensity and specific UV absorbance (SUVA) for DBP formation.

Main Methods:

• Organic matter (OM) fractions were isolated from various water sources using XAD-8/4 resins.
• Chloramination was performed by reacting OM isolates with monochloramine under controlled conditions (5 mg/L DOC, pH 7.5, 7 days).
• Fluorescence regional integration (FRI) of excitation-emission matrix (EEM) fluorescence spectroscopy and specific UV absorbance (SUVA) were used to characterize OM fractions.

Main Results:

• Cumulative normalized EEM volumes in regions II and IV (FRI) showed linear relationships with dichloroacetic acid (DCAA), chloroform, dichloroacetonitrile (DCAN), and total organic halogen (TOX) yields.
• Specific UV absorbance (SUVA) values demonstrated strong linear correlations with DCAA, chloroform, DCAN, and TOX yields.
• SUVA did not correlate with cyanogen chloride (CNCl) or chloropicrin (CP) formation.

Conclusions:

• Specific UV absorbance (SUVA) is a strong predictor of DBP and TOX formation during chloramination.
• Fluorescence regional integration (FRI) also provides valuable insights into DBP formation potential.
• A modified model is proposed to simplify chloramination reactions with OM fractions, with FTIR confirming reactivity of ketone groups.