Bioanalytical and chemical assessment of the disinfection by-product formation potential: Role of organic matter

• Published in: Water research (Oxford) Vol. 47; no. 14; pp. 5409 - 5421
• Main Authors: Farré, Maria José, Day, Sophie, Neale, Peta A., Stalter, Daniel, Tang, Janet Y.M., Escher, Beate I.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15-09-2013; Elsevier
• Subjects: adverse effects; Animals; Applied sciences; Bacteria; Bioassay; bioassays; Biological Assay; bioluminescence; Bromides - chemistry; bromination; Byproducts; Carbon; chemical analysis; Chemical Fractionation; Chlorination; chlorine; Cytotoxicity; Damage; desalination; detection limit; disinfectants; Disinfectants - analysis; Disinfectants - chemistry; Disinfectants - toxicity; Disinfection; dissolved organic carbon; DNA repair; Drinking Water - analysis; Drinking Water - chemistry; Exact sciences and technology; Formations; fractionation; Genotoxicity; glutathione; Glutathione - chemistry; Halogenation; Halogens; In vitro bioassay; Luminescent Measurements; Molecular Weight; Mutagenicity Tests - methods; Organic carbon; Oxidative Stress; Pollution; Proteins - chemistry; Proteins - metabolism; Rats; reverse osmosis; Size fractionation; stress response; Stresses; surface water; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water Purification - methods; water treatment; Water treatment and pollution; United States; North America; America; Oxidative stress; Organic carbon; Cytotoxicity; In vitro bioassay; Size fractionation; Genotoxicity; Bioluminescence; Organic matter; Chemical analysis; Chlorination; Toxicity; Quantization; Tosylchloramide sodium; Precursor; Dissolved organic carbon; Membrane separation; Detection limit; Bacteria; Oxidation; Repair; Public health; Bioassay; Desalination plant; Chlorine; Reaction product; Disinfection; Secondary pollutant; In vitro; Drinking water treatment plant; In vitro bioassay; Surface water; Reverse osmosis; Conjugation
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2013.06.017

Disinfection by-products (DBP) formed from natural organic matter and disinfectants like chlorine and chloramine may cause adverse health effects. Here, we evaluate how the quantity and quality of natural organic matter and other precursors influence the formation of DBPs during chlorination and chloramination using a comprehensive approach including chemical analysis of regulated and emerging DBPs, total organic halogen quantification, organic matter characterisation and bioanalytical tools. In vitro bioassays allow us to assess the hazard potential of DBPs early in the chain of cellular events, when the DBPs react with their molecular target(s) and activate stress response and defence mechanisms. Given the reactive properties of known DBPs, a suite of bioassays targeting reactive modes of toxic action including genotoxicity and sensitive early warning endpoints such as protein damage and oxidative stress were evaluated in addition to cytotoxicity. Coagulated surface water was collected from three different drinking water treatment plants, along with reverse osmosis permeate from a desalination plant, and DBP formation potential was assessed after chlorination and chloramination. While effects were low or below the limit of detection before disinfection, the observed effects and DBP levels increased after disinfection and were generally higher after chlorination than after chloramination, indicating that chlorination forms higher concentrations of DBPs or more potent DBPs in the studied waters. Bacterial cytotoxicity, assessed using the bioluminescence inhibition assay, and induction of the oxidative stress response were the most sensitive endpoints, followed by genotoxicity. Source waters with higher dissolved organic carbon levels induced increased DBP formation and caused greater effects in the endpoints related to DNA damage repair, glutathione conjugation/protein damage and the Nrf2 oxidative stress response pathway after disinfection. Fractionation studies indicated that all molecular weight fractions of organic carbon contributed to the DBP formation potential, with the humic rich fractions forming the greatest amount of DBPs, while the low molecular weight fractions formed more brominated DBPs due to the high bromide to organic carbon ratio. The presence of higher bromide concentrations also led to a higher fraction of brominated DBPs as well as proportionally higher effects. This study demonstrates how a suite of analytical and bioanalytical tools can be used to effectively characterise the precursors and formation potential of DBPs.
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•DBPs, total organic halogens and effects higher after chlorination than after chloramination.•Mode of action covered cytotoxicity, genotoxicity, protein damage and oxidative stress response.•Bioassays important as <50% of the total halogenated DBPs can be explained by 12 quantified DBPs.•Source water with higher organic matter and/or bromide formed more DBPs and showed higher effects.•All molecular weight precursors of organic carbon contribute to DBP formation potential.