Production of Trihalomethanes, Haloacetaldehydes and Haloacetonitriles during Chlorination of Microcystin-LR and Impacts of Pre-Oxidation on Their Formation

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Microcystins (MCs) in drinking water have gained much attention due to their adverse health effects. However, little is known about the impact of pre-oxidation in the formation of disinfection by-products (DBPs) during the downstream chlorination of MCs. The present study examined the formation of both carbonaceous and nitrogenous DBPs from chlorination of MC-LR (the most abundant MC species) and evaluated the impact of permanganate (PM), hydrogen peroxide (H2O2) and chlorine dioxide (ClO2) pre-oxidation on the DBP formation in chlorination. Higher yields of chloroform (CF) (maximum 43.0%) were observed from chlorination of MC-LR than free amino acids which are included in MC-LR structure. Chloral hydrate (CH) and dichloroacetonitrile (DCAN) were also produced from the chlorination of MC-LR, and the latter one was formed probably due to the chlorination of peptide bonds. A high pH favored the production of CF and CH, but inhibited the formation of DCAN. In the presence of bromide, bromo-DBPs could be produced to pose a threat. For example, 0.58 μg/L of tribromoacetaldehyde was produced from the chlorination of MC-LR at Br−= 200 μg/L. PM and ClO2pre-oxidation could both reduce the DBP formation from MC-LR. In contrast, H2O2appeared not to significantly control the DBP formation.



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