Permanganate oxidation is used in drinking water treatment for a number of reasons including taste and odor control, disinfection byproduct control, iron and manganese removal, and zebra mussel growth inhibition. Little is understood, however, about how dissolved organic matter (DOM) scavenges permanganate and is chemically-altered by permanganate. We have characterized how permanganate oxidation changes DOM composition for both terrestrial and algal DOM isolates using Fourier Transform-infrared (FT-IR) spectroscopy and Fourier Transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS). Second derivative analyses of the FT-IR spectra revealed shifts to indicate the presence of more oxidized aromatic groups, more aromatic carboxylic acid groups, and conservation of alkene groups for both DOM source types. FT-ICR-MS analysis was performed using positive and negative mode electrospray ionization (ESI), as well as positive and negative mode laser desorption ionization. We find that, if negative mode ESI had been used solely, which is common in FT-ICR-MS characterization of DOM, we would miss important structural information about permanganate oxidation reactions. Using all four ionization types, we observed conservation of lipids and lignin for both DOM source types. We observe shifts in condensed aromatic to partially oxidized polycyclic aromatic components and an increase in the number of aliphatic compounds. We concluded that these polycyclic aromatic components are likely benzoic acids on the basis of proton affinity, because they were ionized most efficiently using positive mode ESI. Condensed aromatics were lost following permanganate oxidation while tannins were conserved in the terrestrial sample; in contrast, in the algal isolate we observed shifts to more oxidized condensed aromatic components and to more oxidized tannin-like components. Our results highlight how multiple ionization techniques and thermodynamic parameters can be used to enhance DOM characterization by FT-ICR-MS and to help us to understand how DOM is altered by permanganate during drinking water treatment.

Dissolved organic matter alterations by permanganate during drinking water treatment

2019 Spring National Meeting

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