Carbonaceous and Nitrogenous Disinfection Byproduct Formation Potential of Microcystis Aeruginosa and Pyrrole Model Compounds
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Disinfection byproducts (DBPs) are toxic compounds that form during the disinfection of drinking water. Harmful algal blooms have been on the rise due to climate change and increasing levels of nutrient influx into surface waters. This study lies at the intersection of these two misfortunes and aims to evaluate the formation of disinfection byproducts when a disinfectant (i.e. chlorine or chloramine) is applied to algal organic matter (AOM) extracted from the cyanobacterium Microcystis aeruginosa . To achieve this, M. aeruginosa was cultured, its extracellular (EOM) and intercellular (IOM) organic matter were separated, and chlorine and chloramine were applied for 5-7 days to evaluate the disinfection byproduct formation potential of the algae’s IOM and EOM. Pyrrole compounds with substituted methyl and carboxylic acid functional groups were evaluated as disinfection byproduct precursors due to their presence in algal pigments. A Gas Chromatography-Mass Spectrometry instrument was used to measure the yield of DBPs listed in EPA methods 551.1 and 521, and a total nitrosamine (TONO) assay was employed to measure the yield of all nitrosamines. The disinfection of AOM with chlorine and chloramine results in a cocktail of regulated (trihalomethanes) and non-regulated (dichloroacetonitrile and N-nitrosodimethylamine) DBPs. Results from EPA Method 521 and TONO analysis show that NDMA constituted the majority of nitrosamines formed in the IOM, but failed to account for the nitrosamines formed in the EOM; Thus, EOM has the potential to form nitrosamines that go unmeasured in EPA 521. The disinfection experiments of model compounds yielded 1,1,1-trichloropropane in addition to the DBPs formed in AOM experiments.