Preferential Halogenation of Algal Organic Matter by Iodine over Chlorine and Bromine: Formation of Disinfection Byproducts and Correlation with Toxicity of Disinfected Waters

Abstract

The increasing occurrence of harmful algal blooms (HABs) in surface waters may increase the input of algal organic matter (AOM) in drinking water. The formation of halogenated disinfection byproducts (DBPs) during combined chlorination and chloramination of AOM and natural organic matter (NOM) in the presence of bromide and iodide and haloform formation during halogenation of model compounds were studied. Results indicated that haloform/halogen consumption ratios of halogens reacting with amino acids (representing proteins present in AOM) follow the order iodine > bromine > chlorine, with ratios for iodine generally 1–2 orders of magnitude greater than those for chlorine (0.19–2.83 vs 0.01–0.16%). This indicates that iodine is a better halogenating agent than chlorine and bromine. In contrast, chlorine or bromine shows higher ratios for phenols (representing the phenolic structure of humic substances present in NOM). Consistent with these observations, chloramination of AOM extracted from Microcystis aeruginosa in the presence of iodide produced 3 times greater iodinated trihalomethanes than those from Suwannee River NOM isolate. Cytotoxicity and genotoxicity of disinfected algal-impacted waters evaluated by Chinese hamster ovary cell bioassays both follow the order chloramination > prechlorination-chloramination > chlorination. This trend is in contrast to additive toxicity calculations based on the concentrations of measured DBPs since some toxic iodinated DBPs were not identified and quantified, suggesting the necessity of experimentally analyzing the toxicity of disinfected waters. During seasonal HAB events, disinfection practices warrant optimization for iodide-enriched waters to reduce the toxicity of finished waters.

Interface Change and Toxicity Risks of Loose Deposits Induced by Boiling in Water with Discoloration

“…6 Even though concentrations of HANs were lower than THMs and HAAs, they are the main origins of the total calculated cytotoxicity and genotoxicity because of their high toxicity indices. 46 Accordingly, the particles lead to a slight increase in the calculated cytotoxicity and genotoxicity owing to the higher HAN formation compared to that of water without particles (Figure S11). Under high residual chlorine (Figure S12), DOM increased first and then decreased with the increase of temperature.…”

“…Evaluating the toxicity changes throughout the boiling process instead of taking a snapshot before and after boiling has been considered to be important for systematically understanding the formation and transformation processes co-occurring during heating/boiling . Even though concentrations of HANs were lower than THMs and HAAs, they are the main origins of the total calculated cytotoxicity and genotoxicity because of their high toxicity indices . Accordingly, the particles lead to a slight increase in the calculated cytotoxicity and genotoxicity owing to the higher HAN formation compared to that of water without particles (Figure S11).…”

Elimination and Redistribution of Intracellular and Extracellular Antibiotic Resistance Genes in Water and Wastewater Disinfection Processes: A Review

“…The chlorination of a heterocyclic NH-group (guanosine and thymine) is much faster than that of an amino group . H-bond is disrupted by the N-chlorination and results in dissociation of the double strand. − The irreversible halogenation by HOCl subsequently occurs in the unpaired bases associated with a disrupted H-bond (i.e., C-chlorination), generating chlorinated products such as 3,5-dichlorocytosine, 5-chlorouracil, and 8-chloroadenine . The reaction of NH 2 Cl and iARGs/eARGs is driven by the trace amount of HOCl formed from the hydrolysis of NH 2 Cl. , In addition, the direct transfer of chlorine from NH 2 Cl to heterocyclic NH-group and amino group in nucleotides was also identified …”

Decomposition of Total Organic Halogen Formed during Chlorination: The Iceberg of Halogenated Disinfection Byproducts Was Previously Underestimated

“…The main precursors of DBPs, natural organic matters, comprise a broad range of molecules and produce a complex mixture of DBPs after reacting with disinfectants. Other precursors including algal organic matters, micropollutants, atmosphere particulate matters, and engineering agents/materials also play a role in DBP formation, which further enhances the complexity of DBP mixtures. − Currently, over 700 DBPs have been structurally characterized. Among them, approximately 100 DBPs have been quantified and subjected to systematic toxicity evaluation. ,− , By using ultrahigh-resolution mass spectrometry, researchers even detected more than 1800 halogen-containing molecules in chlorinated water .…”