Formation of iodinated disinfection by-products during oxidation of iodide-containing waters with chlorine dioxide

This study was to explore the formation of iodinated disinfection by-products (I-DBPs), including iodoform (CHI₃), iodoacetic acid (IAA) and triiodoacetic acid (TIAA), when iodide-containing artificial synthesized waters and raw waters are in contact with chlorine dioxide (ClO₂). Among the investigated I-DBPs, CHI₃ was the major species during ClO₂ oxidation in artificial synthesized waters. Impact factors were evaluated, including the concentrations of ClO₂, iodide (I^-), dissolved organic carbon (DOC) and pH. Formation of CHI₃, IAA and TIAA followed an increasing and then decreasing pattern with increased ClO₂ or DOC concentration. I-DBPs yield was significantly affected by solution pH. High concentrations of I-DBPs were generated under circumneutral conditions with the maximum formation at pH 8. The increase of I^- concentration can increase I-DBPs yields, but the increment was suppressed when I^- concentration was higher than 50μM. When 100μg/L I^-and ClO₂ (7.5-44.4μM) were spiked to the raw water samples from Yangshupu and Minhang drinking water treatment plant, certain amounts of CHI₃ and IAA were found under pH 7 and the concentrations were strongly correlated with ClO₂ dosage and water qualities, however, no TIAA was detected. Finally, we investigated I-DBPs formation of 18 model compounds, including 4 carboxylic acids, 5 phenols and 8 amino acids, treating with ClO₂ when I^- was present. Results showed that most of these model compounds could form a considerable amount of I-DBPs, especially for propanoic acid, butanoic acid, resorcinol, hydroquinone, alanine, glutamic acid, phenylalanine and serine.