Molecular characterization of low molecular weight dissolved organic matter in water reclamation processes using Orbitrap mass spectrometry

Abstract

Reclaimed water has recently become an important water source for urban use, but the composition of dissolved organic matter (DOM) in reclaimed water has rarely been characterized at the compound level because of its complexity. In this study, the transformation and changes in composition of low molecular weight DOM in water reclamation processes, where secondary effluent of the municipal wastewater treatment plant was further treated by biofiltration, ozonation and chlorination, were investigated by "unknown" screening analysis using Orbitrap mass spectrometry (Orbitrap MS). The intense ions were detected over an m/z range from 100 to 450. In total, 2412 formulae with various heteroatoms were assigned, and formulae with carbon (C), hydrogen (H) and oxygen (O) only and C, H, O and sulfur (S) were the most abundant species. During biofiltration, CHO-only compounds with relatively high hydrogen to carbon (H/C) ratio or with saturated structure were preferentially removed, while CHOS compounds were mostly removed. Ozonation induced the greatest changes in DOM composition. CHOS compounds were mostly decreased after ozonation while ozone selectively removed CHO compounds with relatively unsaturated structure and produced compounds that were more saturated and with a higher degree of oxidation. After chlorination, 168 chlorine-containing formulae, chlorinated disinfection by-products (DBPs), were additionally detected. Candidate DBP precursors were determined by tracking chlorinated DBPs formed via electrophilic substitution, half of which were generated during the ozonation.

The effect of advanced secondary municipal wastewater treatment on the molecular composition of dissolved organic matter

“…DOM was eluted from the cartridges with methanol and eluents were stored in the dark at 4°C until aliquots were poured off for analysis. The extraction procedure retained approximately 60% of DOC, which is similar to previous studies that concentrated wastewater-derived samples via SPE (Gonsior et al, 2011; Phungsai et al, 2016; Tseng et al, 2013; Urai et al, 2014). …”

Particle size dependence of biogenic secondary organic aerosol molecular composition

“…Data analysis was performed as described previously, targeting closed-shell molecular formulas (Tu et al, 2016). We also performed Kendrick mass defect analysis (Herzsprung et al, 2014;Phungsai et al, 2016) and calculated the RDB-O value (ring and double-bond equivalent of each molecular formula minus the number of oxygen atoms in the formula; the maximum RDB-O distribution resides within the range −10 and 10 for hydrophobic CHO species; Herzsprung et al, 2014) as the updated criteria to help filter the unreasonable assigned formulas. After removing background peaks, unreasonable formulas, and redundancies due to isotopic substitution, hundreds of unique molecular formulas remained for each sample.…”

Comparison of Low Molecular Weight Dissolved Organic Matter Compositions in Lake Inba and Kashima River by Orbitrap Mass Spectrometry

“…On the other hand, most of the formulae in river sample were suspected to be sulfophenyl carboxylic acids (SPC) and dialkyl tetralin sulfonate intermediates (DATSI) such as C 10 and DATSI are major coproducts of LAS. These LAS-related chemicals are more easily ionized and found from wastewater effluent [18] and reclaimed water [19,20]. Though most of wastewater in the watershed of Lake Inba is transported outside of the watershed, Kashima River still receives effluent from Jyokaso system which is the possible source of LAS-related compounds.…”

“…However, these conventional approaches are not able to elucidate the molecular compositions of DOM. Recently, non-targeted analysis through ultrahigh resolution mass spectrometry (MS) such as Fourier transform ion cyclotron mass spectrometry (FT-ICR MS) and Orbitrap mass spectrometry (Orbitrap MS) have been applied to analyze DOM in aquatic environments [11][12][13][14][15][16] as well as DOM in drinking water and wastewater effluent [17][18][19][20]. These instruments can resolve complex DOM extracted by solid-phase extraction (SPE) and assign molecular formula to each component based on accurate mass.…”